Shortly after administration of 6-methoxy-1,2,3,4-tetrahydro-beta-carboline (6-MeOTHBC) and yohimbine to normal or hypothyroid rats [the latter exhibiting chronically elevated levels of serotonin (5-HT) neuronal activity in the hypothalamus] there was a highly significant increase in hypothalamic noradrenaline (NA) activity and in ACTH release concomittant with a reduction in hypothalamic 5-HT activity (P less than 0.01) and in growth hormone (GH) (P less than 0.01) and in thyroid stimulating hormone (TSH) (P less than 0.01) release from the pituitary. Both compounds caused an increase in hypothalamic dopamine (DA) metabolism and in pituitary prolactin (PRL) release in normal rats (P less than 0.01) but only yohimbine exerted this action in hypothyroid rats. Lower doses of 6-MeOTHBC exerted a relatively specific effect in hypothyroid rats, reducing (P less than 0.01) 5-HT neuronal activity in parallel with pituitary TSH secretion (P less than 0.05). While gross effects of 6-MeOTHBC and yohimbine were similar with respect to their effects on NA and 5-HT status in the hypothalamus, there were quantitative differences. 6-MeOTHBC always caused a greater decrease in 5-HT turnover and a lesser increase in NA turnover than did yohimbine. On the basis of these studies we suggest that the effect of tetrahydro-beta-carboline-related alkaloids on pituitary hormone release may be due to their influence on hypothalamic monoamine status and the subsequent alteration of the hypothalamic-pituitary control system.
The illumination of dark-adapted cells of E. gracilis under non-dividing conditions induced not only the production of chloroplasts but also a rapid breakdown of J3-1,3·glucan, the reserve carbohydrate of this organism. The decrease in ,8-1,3-glucan preceded the synthesis of most of the chlorophyll and was confined to the first 24 hr of illumination, whereas chlorophyll synthesis continued for at least 72 hr.
No significant change occurred in the uptake by the thyroid of male Wistar rats of a standard dose of carrier-free 131I administered intraperitoneally and its retention by the thyroid, as measured by biological and effective half-life, after feeding these rats a powdered pelleted diet containing lithium carbonate (1.1 g per kg of diet) for 7 days. However, continuing this diet for 10 days inhibited thyroid uptake and increased the retention of 131I. Uptake remained suppressed for up to 4 months after lithium treatment and continuing this treatment for 6 months did not result in any significant change in 131I uptake by the thyroid. Lithium treatment for 10 days increased the biological and effective half-life of 131I in the thyroid and this increase continued for the 6 months treatment period. The dose of 131I delivered to the thyroid was significantly lower after 10 days and 1 month of lithium treatment but there was no change in this dose after 2 and 4 months of treatment. However, there was a significant increase after 6 months.
The net uptake and oxidation of glucose by leg muscle, pregnant uterus, and lactating mammary gland, together with the rate of irreversible loss and oxidation of glucose in the whole body of Merino ewes are reported. The ewes were fed on either chaffed oaten hay (OR), chaffed lucerne hay (L), or a mixture of chaffed oaten and lucerne hays (OHL). Measurements were made during five different physiological states: dry (nonpregnant), at 94 and 125 days of pregnancy, and at 20 and 50 days after lambing.
Ovariectomized mice were injected intravaginally with a physiological dose of (9,12,12-2H3)oestradiol (3), and a control group was similarly injected with (11xi,12,12-2H3)oestradiol (4). Gas-liquid chromatography/mass spectrometry (g.l.c./m.s.) analysis of the oestradiols recovered from the vaginae of the two sets of mice showed that the content and distribution of deuterium were the same as in the respective pure trideuterated oestradiols (3) and (4). This proved conclusively that the 9 alpha-hydrogen of oestradiol is not exchanged during residence in and stimulation of the vagina. It therefore appears unlikely that reversible quinone methide formation in oestradiol is the trigger mechanism for stimulation of RNA synthesis, unless a hydrogen transfer relay system permits repetitive removal and replacement of the hydrogen atom at C9 during the oxidation-reduction cycle.
M. aeruginosa is a bloom-forming cyanobacterium which is common in fresh-water lakes. It contains a potent hepatotoxin which when purified has been shown to be a heptapeptide of molecular weight 1019. The toxin was iodinated with 125I using the lactoperoxidase method, the labelled toxin administered intravenously to adult female rats and the half-life and organ distribution measured. The blood half-life after redistribution into extracellular pools was 42 min. The liver and kidneys showed accumulation of 21.7 +/- 1.1 and 5.6 +/- 0.2% of the dose respectively after 30 min. Little accumulation was observed in other organs and tissues. Small-intestinal contents and urine contained 9.4 +/- 6.1 and 2.9 +/- 1.2% of the dose respectively after 120 min. It was concluded that the liver is the main target organ for both accumulation and excretion of the toxin.
Human spermatozoal peptides, liberated during autolysis of the cells, were fractionated by gel-filtration chromatography and thin-layer chromatography. After conjugation to 125I-labelled human serum albumin, all fractions were assayed with rabbit antihuman spermatozoa antiserum. The reactions indicated the presence of a number of antigenic peptides in the spermatozoal autolysate and one of the fractions revealed a significantly higher antibody binding capacity than all other fractions assayed (P less than 0.05). Release of immunogenic peptides during autolysis of the spermatozoal membrane could be important in the aetiology of spermatozoal iso- and autoantibodies.
The fertility obtained with ram semen pellet frozen on dry ice (-79°0) (Lightfoot and Salamon 1970; Salamon and Lightfoot 1970) has stimulated further investigation. Information was also needed on fertility of ram spermatozoa pelleted at a temperature below -79°C (Salamon 1970) and this communication presents the results of two experiments and treatment comparisons for each.
Amitraz, 1, 5-di(2, 4-dimethylphenyl)-3-methyl-1, 3, 5-triazapenta-1, 4-diene, labelled with 14C in the 2-methyl groups was applied to B. microplus larvae by an immersion technique. The chemical penetrated readily but never appeared in large amounts internally due to rapid cleavage to N-2, 4-dimethylphenyl-N'-methylformamidine. The expected complementary cleavage product 2, 4-dimethylformanilide was not produced in equivalent quantity. However, large amounts of polar metabolite(s) were produced. Small quantities of 2, 4-dimethylaniline and an unidentified non-polar metabolite were also produced. Of the identified chemicals only amitraz and N-2, 4-dimethylphenyl-N'-methylformamidine were toxic to larvae. Piperonyl butoxide applied simultaneously with amitraz had only a slight effect on metabolism but had a three-fold synergistic effect. SKF 525-A similarly applied had a negligible effect on both metabolism and toxicity.
The incorporation of [U-HClglucose into the major classes of RNA in mouse embryos cultivated in vitro was studied at stages from eight-cell to the blastocyst. Comparative studies using [5-3H]uridine were also included.
Formaldehyde has been used to protect proteins and lipids from metabolism in the rumen, and the present studies were designed to investigate the metabolism of formaldehyde when given to ruminants as an aldehyde-casein-oil complex. Approximately 60-80% of the consumed formaldehyde was metabolized to carbon dioxide and methane, a further 11-27% was excreted in the faeces, and 5-6% was accounted for in the urine. The amount of radioactivity excreted either in the expired air or faeces appeared to be dependent on the length of the reaction time between the aldehyde and casein prior to feeding. Small amounts of 140 radio� activity were detected in body tissues and milk, but this was not present as formalde� hyde. It is concluded that ruminants effectively metabolize formaldehyde and there is no accumulation of this compound in the carcass or milk.
The effect of administration of low and high doses of pyridoxine on the metabolism of lipids and glycosaminoglycans has been studied in rats fed normal and high fat, high cholesterol diets. Low doses of pyridoxine (0.005 mg/100 g body weight) caused increased concentrations, of cholesterol and triglycerides in the serum and aorta in animals fed normal and high fat, high cholesterol diets. Administration of high doses of pyridoxine (5.0 mg/100 g body weight) caused decrease in the concentration of these lipids in these tissues except in the case of the aorta in the animals fed a normal diet. Low doses of pyridoxine generally caused a decrease in the concentration of many glycosaminoglycan fractions in the aorta in rats fed normal and high fat, high cholesterol diets, whilst high doses caused an increase. The activity of glucosaminephosphate isomerase (glutamine-forming) and UDPglucose dehydrogenase, both key enzymes in the biosynthetic pathway of glycosaminoglycans, decreased in rats given low doses of pyridoxine and increased in rats given high doses. The activity of many enzymes concerned with degradation of glycosaminoglycans--hyaluronoglucosidase, beta-glucuronidase, beta-N-acetylglucosaminidase, aryl sulphatase, and cathepsin D--generally increased in rats fed low doses of the pyridoxine and decreased in those given high doses. The concentration of hepatic 3'-phosphoadenosine-5'-phosphosulphate, and the activity of the sulphate-activating system and of aryl sulphotransferase decreased when the dose of pyridoxine was low and increased when the dose was high.
In two experiments 48 prepuberal Merino ewe lambs were injected with oestradiol-17 beta (E2) or saline to study the effect of E2 on their plasma LH levels and on oestrus and ovulation. In the three groups which received 30 (experiment I), 50 and 30 (experiment II) microgram E2 respectively, 27 out of 28 lambs showed an LH response, the corresponding mean LH peaks being 64.3 +/0 22.5, 153.6 +/-33.4 and 91.7 +/- 16.9 ng/ml at mean intervals of 11.1, 11.2 and 10.5 h, respectively, after injection. None of the 20 lambs in the control groups had an LH level higher than 18 ng/ml 12 h after injection. In the three E2 groups, 41.7, 62.5 and 37.5% of animals showed oestrus within 26 h of injection while in the control groups only one animal showed oestrus. Of 13 animals showing oestrus in the E2 groups, 11 failed to ovulate. The mean pre-injection plasma FSH level in experiment I was 102.7 ng/ml, and in four 5--7-month-old lambs over several weeks uas 155.3 ng/ml. Despite these high pre-injection levels of FSH, it appears that the follicles were unable to respond to the LH peak which followed the E2 injection.
Progesterone up to 15.9 mumol/l progressively suppressed prolactin-stimulated fatty acid synthesis in cultured mammary explants from 11-day pseudopregnant rabbits, but did not influence the proportion of fatty acids of medium chain length (C8:0-C12:0). Greater sensitivity to progesterone inhibition was observed at the low end of the ranges of corticosterone (29 nmol/l) and insulin (4.2 nmol/l) concentrations in the culture medium, which suggests an interaction between the hormones. A range of from 0.0001 to 10 mumol/l of 17 beta-estradiol concentrations had no effect on prolactin-stimulated fatty acid synthesis in the presence or absence of progesterone.
Plasma concentrations of LH, FSH and oestradiol-17 beta were measured in blood samples taken at 15 min intervals for 48 h during the follicular phase of four Merino ewes. The amplitude of pulses of LH and the mean concentration of LH were higher at the beginning of the follicular phase, 36-24 h before the preovulatory surge of LH (amplitude 2.4 ng ml-1, mean concentration 3.9 ng ml-1), than at the end, 24-0 h before the preovulatory surge (amplitude 1.2 +/- 0.1 ng ml-1; mean concentration 1.4 +/- 0.1 ng ml-1). There was no change in the inter-pulse interval during this time (mean 74 +/- 5 min). Over the same period, oestradiol levels increased from 7-8 pg ml-1 to a peak of 10-15 pg ml-1. Mean FSH concentrations declined (36-24 h: 3.6 ng ml-1 vs 24-0 h: 1.8 +/- 0.3 ng ml-1) before rising at the time of the preovulatory surge of LH and again 24 h later. It was concluded that the biphasic response of LH to oestrogen that is seen in ovariectomized ewes may also operate during the follicular phase of the oestrous cycle in entire ewes.
The hormonal control of uterine sensitivity in progesterone-treated, ovariectomized mice was investigated by stimulating the deciduoma reaction by various means. Uterine sensitivity reached a peak on day 5 of progesterone treatment and then declined. Oestradiol before and after stimulation significantly increased the weight of the deciduomata induced by crushing, bradykinin, and compound 48/80 and increased uterine sensitivity so that intraluminal peanut oil could induce deciduomata. A single injection of 0·024 fJ-g of oestradiol 8 hr before intraluminal peanut oil also greatly increased uterine receptivity to oil. The dose of oestradiol and the time of injection of oestradiol and progesterone were critical parameters. Surprisingly, the hormonal requirements for uterine sensitivity to intraluminal peanut oil are more stringent than for transferred blastocysts.
The concentrations in peripheral plasma of oestradiol-17 p, cortisol and progesterone were determined in 10 sows from 5-6 days prepartum to 4 days post partum. At the same time, the presence and composition of mammary secretion was monitored. Plasma progesterone levels declined from 4·9±0·6flgl-1 (mean±s.e.m.) 12h prepartum to 2·6±0·5flgl-1 at farrowing, and to about 1 flg 1- I by day 1 post partum, although the timing of the fall in plasma progesterone level ranged from day 4 prepartum to the day of parturition in individual sows. Farrowing in all sows was associated with a fall in plasma oestradiol-17P levels, from 0'68±0'07 flgl-' to O'13flgl-' 12h after the start of labour, and with a rise in plasma cortisol level from 14'09±3'74flgl-1 24h prepartum to 43· 66 ± 7· 06 flg 1- I when lactation was becoming established. Mammary secretion was obtained from individual sows up to 3 days prepartum: the onset of lactation was assessed visually by evaluation of the colour and viscosity of secretions against a six-point scale ranging from no secretion to precolostral secretion to mature milk. Lactogenesis was estimated also from the concentrations of lactose, immunoglobulins G, Na + and K + in mammary secretions obtained postnatally. The timing of the first expression from the teats was not correlated with the onset of lactation as measured by changes in milk composition. Further more, there was no relationship between circulating progesterone, oestradiol-17 p or cortisol levels and the day on which secretion was first expressed. We conclude that, in the sow, lactogenesis, as indicated by changes in milk composition, coincides postnatally with decreased plasma concentrations of oestradiol-17 p, cortisol and progesterone. Furthermore, observation of the colour and viscosity of mammary secretion, rather than analysis of its constituents, may determine lactogenesis inaccurately in sows owing to the rapid but variable onset of lactation in this species.
Oestradiol-17 beta (40 micrograms intravenously) failed to elicit a surge in plasma LH levels by 13 h after administration in 64% (16 out of 25) Merino ewes about 30 days post partum in the anoestrous season. LH-RH responsiveness and LH-RH priming effect were significantly greater in these ewes than in similar post-partum (n = 9) and non-parturient ewes (n = 3) not treated with oestradiol. This suggests that the failure of the oestrogen-positive feedback effect on LH release in post-partum ewes is not due to a failure of oestradiol action on the pituitary increasing pituitary responsiveness to LH-RH and LH-RH priming effect, but could be due to inadequate release of LH-RH from the hypothalamus.
The total (bound plus free) concentrations of progesterone, 20 alpha-dihydroprogesterone, oestradiol-17 beta and cortisol were determined in the plasma of sows at three stages during pregnancy and more intensively from 5 days pre-partum to 5 days post-partum. The free fractions of progesterone, oestradiol-17 beta and cortisol were measured in the same samples by a rate dialysis method. Up to day 110 of gestation, the amounts of free hormone in plasma did not fluctuate independently of their total concentrations. During farrowing, the total and free concentrations of progesterone and cortisol varied independently of each other, whereas total and free oestradiol-17 beta declined simultaneously. The initiation of parturition was associated with a decrease in circulating total progesterone, and was accentuated by a decrease in the free fraction (P less than 0.005) so that its active free concentration was only 20% of its day 1 pre-partum value. Total and free cortisol concentrations rose rapidly during labour so that at 12-18 h after birth of the first piglet 30% of that cortisol in maternal plasma was free hormone.
The effects of active immunization against oestradiol-17 beta on the ovarian response to pregnant mare serum gonadotrophin (PMSG) was investigated in Merino ewes. Immunized (79) and control (41) ewes were synchronized with intravaginal sponges, given either 750 or 1500 i.u. PMSG and then mated to rams or inseminated laparoscopically with fresh diluted semen. All control ewes mated naturally exhibited oestrus and 40 out of 41 control ewes ovulated. The ovulation rate was higher in the controls receiving 1500 i.u. PMSG than in those ewes which received 750 i.u. PMSG (10.2 v. 3.3). Immunization against oestradiol-17 beta resulted in antibody titres varying from 100 to more than 100 000 in plasma taken 1-4 days after mating. The ovarian response increased significantly in the lowest titre group (100-1000) in conjunction with stimulation with 1500 i.u. PMSG. In these ewes the ovulation rate increased over controls (16.7 v. 10.2) as did the total ovarian response, which includes follicles greater than 10 mm diameter (22.3 v. 11.1). The total ovarian response was also increased in those ewes given 750 i.u. PMSG which had titres in the 1000-10 000 and 10 000-100 000 range, but this was not accompanied by significant increases in the ovulation rate. In general, the higher titre levels (greater than 1000) were correlated with decreases in the proportion of ewes showing oestrus and ovulating and in the embryo recovery rate. The 1500 i.u. PMSG treatment group with the highest titres (greater than 10 000) also showed a significant drop in the ovulation rate as compared to the 1500 i.u. PMSG controls.
The metabolism of 5 alpha-dihydrotestosterone by adult sheep blood was investigated. Erythrocytes contain 3 alpha- and 3 beta-hydroxysteroid dehydrogenase activities. The mean rate of reduction of 5 alpha-dihydrotestosterone by erythrocytes established in 15-min incubations was 0.66 +/- 0.36 (s.d.) mumol ml-1 erythrocytes h-1 and at equilibrium after a 60-min incubation, 90.6 +/- 5.1% of the substrate was reduced. The reduction of 5 alpha-dihydrotestosterone was shown to be dependent upon extracellular glucose and the intracellular cofactor NADPH. The proportion of the two reduction products was determined at equilibrium after separation by paper partition, chromatography and favoured 5 alpha-androstane-3 alpha, 17 beta-diol (96.0%) to 5 alpha-androstane-3 beta, 17 beta-diol (4.0%). The identities and proportions of the two products were confirmed by recrystallization procedures. The fact that erythrocytes can significantly metabolize the androgen 5 alpha-dihydrotestosterone is evidence for the recognition of blood as a major component of steroid endocrine homeostasis in sheep.
A field experiment was conducted to examine the effect of anti-oestradiol-17B antibody titre on the oestrous and ovulatory responses of ewes to low (600 i.u.) or high (1200 i.u.) doses of pregnant mare's serum gonadotrophin (PMSG). Merino ewes were treated with intravaginal sponges and were subsequently used as vehicle-treated controls or were immunized to produce reciprocal anti-oestradiol-17B antibody titres less than 1000 or greater than 1000. Ewes were then treated with PMSG and the incidence of oestrus and ovulation, ovulation rate, and yield of embryos recorded. Treatment of immune ewes with 1200 i.u. PMSG resulted in both a higher proportion of ewes ovulating and a higher ovulation rate than in immune ewes treated with 600 i.u. (86% v. 67% and 13.4 v. 6.0 respectively). As anti-oestradiol-17B titres increased there was a reduction in the proportion of ewes exhibiting oestrus. The proportion of ewes ovulating decreased as antibody increased in ewes treated with 600 i.u. PMSG but not in those treated with 1200 i.u., suggesting an increased positive feedback of oestradiol with high PMSG doses. Fertilization rates were highest at the lower PMSG dose (68% v. 42%) and increased with increasing titre. Overall, there was no increase in ovulation rate or in yield of embryos over control values from either low (less than 1000) or high (greater than 1000) antibody titres.
A survey was made, during 1970 and 1971, of organochlorine pesticide residues in the fatty tissues of 12 mammal, 4 bird, 10 reptile, and 6 fish species collected from areas defined as undeveloped and developed of both the arid and tropical zones of the Northern Territory. Pooled samples were taken of most species. Where possible, each species was sampled from each of the four areas.
Between October 1974 and May 1976, 57 596 mosquitoes, 169 957 Culicoides, 5923 Lasiohelea and 1043 phlebotomines were collected for virus isolation at Beatrice Hill (lat. 12 degrees 39'S.,long. 131 degrees 20'E.) in the Northern Territory of Australia. A total of 94 viruses belonging to 22 different serological groupings was isolated. The following species of insect yielded viruses which were identified and those viruses marked with an asterisk represent a new record of insect host: Culex annulirostris: Ross River, Kokobera, Barmah Forest, Corriparta, Eubenangee*, Wongorr; Anopheles amictus: Mapputta*; An bancroftii: bovine ephemeral fever*; An farauti: Eubenangee*; An annulipes: Mapputta; Culicoides marksi: Barmah Forest*, Belmont, Eubenangee*, Wallal, Warrego, Leanyer*, Parker's Farm*, Humpty Doo*; C. peregrinus: Beatrice Hill*; C. oxystoma: Bunyip Creek*, Marrakai*; C. pallidothorax: Wongorr*; C. histrio: Thimiri*; Lasiohelea spp.: Humpty Doo*. Pools of mixed species of Culicoides yielded bluetongue, Belmont, CSIRO Village, Warrego and Facey's Paddock viruses. Filter-passing agents not yet identified, were isolated from Cx annulirostris and An bancroftii. As well as providing new locality records for all but one of the 22 viruses isolated, the study yielded five new viruses (bluetongue serotype 20, CSIRO Village, Marrakai, Beatrice Hill and Humpty Doo viruses) and a new record for Thimiri virus which had not been recorded previously in Australia nor had it been isolated from an arthropod. Nine of the viruses isolated occur in more than one family of Diptera.
This contribution to the Symposium concerns four topics which have been addressed in our laboratory over the past five years. First, the responses to a controlled light environment of Merino ewes and rams have been compared with those of two British breeds. The endocrinological patterns were similar in all breeds but cyclic ovarian activity and ram libido were different. While showing a degree of entrainment to photoperiod, the breeding patterns were much less rigidly controlled in the Merinos than in the others. Second, the effectiveness of establishment of a cervical reservoir of spermatozoa, in ewes in which oestrus and ovulation have been controlled, has been re-examined. This is highly dependent on the time of insemination relative to that of the release of LH. Maximum numbers are found when ewes are inseminated shortly after the LH peak, i.e. some 6-10 h after the onset of oestrus. Third, the quantitative and temporal endocrinological and behavioural events following standard, progestagen-PMSG treatment have been quantified. Contrary to earlier expressed beliefs, these events are remarkably predictable provided an intensive system of mating or detection of oestrus is used. The onset of oestrus in treated anoestrous crossbred ewes has a normal distribution, with a range of 24 h, centred around a mean of 33 h after withdrawal of a 30 mg Cronolone intravaginal sponge and injection of 500 i.u. PMSG. This period of time is dose-dependent. The LH peak occurs 4.5 +/- 0.7 h later and the times of onset of oestrus and of LH release are highly correlated (r = 0.93). Ovulation is some 24 h later again. Fourth, differences in the response of ewes to different batches of PMSG have been defined. While the three commercial preparations studied regularly induced ovulation in anoestrous ewes at doses of 250 i.u. and above, the quantitative responses varied greatly. One preparation would not induce multiple ovulation, even at high doses. There are differences in steroidogenesis and in pregnancy rates, associated with dose of PMSG and the consequent ovulation rate: the ideal would be for every ewe to shed two or three ova. A higher ovulation rate is acceptable, as early embryonic mortality generally reduces the litter size. This is particularly important in deep anoestrus. However, this does not solve the problem of breeding in early lactation.
Bovine ephemeral fever is an important viral disease of cattle in Australia. The disease occurred each year, principally in summer and autumn, between 1981 and 1985. Queensland and the northern half of New South Wales were areas of greatest activity with only sporadic cases being reported from the Northern Territory and the northern third of Western Australia. Since 1981, the disease has been endemic in an extensive area of eastern Australia and has tended to occur in widely scattered outbreaks rather than the north-south advancing wave form of the epidemics of 1936-37, 1967-68, 1970-71 and 1972-74. The southernmost outbreaks between 1981 and 1985 were well within the limits of these earlier epidemics. The pattern of disease appears to have become seasonally endemic rather than periodically endemic in the northern two-thirds of eastern Australia. Ephemeral fever was not recorded in Victoria, Tasmania, South Australia or the southern part of Western Australia between 1981 and 1985. The disease was most frequently reported in cattle under 3 years of age, but also occurred in older cattle.
The in vitro incorporation of [3H]thymidine has been examined in thin slices of sheep skin. Most of the radioactivity (88%) was incorporated into the bulb cells of the wool follicles, and the technique is therefore suitable for the study of some aspects of wool follicle DNA synthesis. The effect of mimosine and a number of related 4(1H)-pyridones on [3H]thymidine incorporation into sheep skin slices was examined. Mimosine was shown to inhibit the incorporation at a concentration of 0-2 mM. At this concentration, the incorporation of [3H]uridine or [14C]leucine was not affected. The inhibition of [3H]thymidine incorporation was time dependent, 2 h of incubation being required for maximal inhibition of DNA synthesis, and was readily reversible by removal of mimosine from the incubation medium. The 3-hydroxyl-4-oxo function of the pyridone ring appears to be directly involved in DNA synthesis inhibition. The amino acid side chain is not a toxophoric centre, but changes in its polarity have been shown to affect the inhibitory activity. The results suggest that the primary action of mimosine on the inhibition of wool biosynthesis in vivo is the inhibition of follicle bulb cell DNA synthesis and consequently of cell division.
Mice fed a diet containing 1% (w/w) 3-hydroxy-4(1H)-pyridone (DHP) developed goitre even with a diet high in iodine whereas mimosine (0.5% w/w) did not produce goitre even with a low-iodine diet. Thyroid enlargement was apparent (measured morphometrically) by the 7th week and was advanced by the 11th week. Histologically the goitre was hyperplastic in type. No marked histological changes were found in other organs of mice fed DHP or any organs of mice fed mimosine, except for some atrophy of hair follicles. A single intragastric dose of DHP inhibited the uptake of 125I by the thyroid in the rat but an equivalent dose of mimosine did not. Evidence is presented that the inhibition occurs at the iodine binding step, as with methyl thiouracil, rather than at the iodide trapping step, as with thiocyanate. Chronic treatment of mice with DHP, as with 6-methyl thiouracil, increased the avidity of the thyroid in taking up 125I. The major conjugated form of DHP in mammals, DHP-3-O-glucuronide, was almost as effective a goitrogen as the unconjugated compound when given by mouth but considerably less active than the free form in the blood stream. It was concluded that DHP is a potent antithyroid compound of the thiouracil type with low general toxicity, since mammals can tolerate a level of intake sufficient to produce goitre in spite of iodine supplementation.
Grouped mice breed well in a warm environment but poorly in the cold. This could be the result of temperature-induced changes in behaviour. In order to test this, female mice were exposed to 4, 21, and 33°C in cages equipped with four box shelters arranged on either side of a narrow alley.
In rodents, second and subsequent pregnancies can result either from post-partum or from post-weaning matiugs. If pregnancy results from a post-partum matiug, the gestation period overlaps with the lactation period of the previous reproductive cycle. There is some evidence that under these conditions, the viability and growth of both the suckiug and the unborn litter are affected (McCarthy 1965), although other authors could find little or no evidence of this (Krehbiel 1941; Bruce and East 1956).
The effects of maintaining mice for 10 generations at 34°C were measured by comparing the reproductive productivity, growth rate, oxygen consumption, hair growth, density of the subepidermal capillary net, and frequency of the pink-eye gene in mice selected for productivity at 34°C (R95), the same mice moved to 21°C (L95), controls at 21°C (R70), and offspring of crosses between R95 and R70 mice and an unrelated stock (Wild) kept at 21°C (W95 and W70)_
Groups of mice comprising two males only, two males plus two females, two males plus six females, or two males plus 14 females were housed in pens at 4, 21 or 33°C. The pens were partitioned into two territories connected by a small hole and each subdivision was equipped with two box shelters on either side of an open area containing food, water and woodwool.At all group sizes, the mice at 4 and 21°C sought shelter more frequently than those at 33°C. In addition, those at low temperatures tended to crowd into one of the nesting boxes, while those at 33°C distributed themselves fairly evenly between the four shelters. At all temperatures the males shared the whole of the territory available to them, but at 33°C they were found in the same shelter at the same time only once out of 40 occasions; those at 4 and 21°C were found together on more than 25 occasions. More woodwool and more urination sites were found in the shelters at 4 and 21 than at 33°C, but temperature had little effect on the amounts of food and faeces in the shelters. Hence, it appears that contact between the individual and its companions in male-female groups is, as in all-female groups, inversely related to temperature. It also seems that contact between males in such groups is markedly reduced at high temperatures.
Oestrous cycle frequency was measured in mice housed singly, in mice housed in groups, and in grouped females in olfactory and tactile contact with a male. The animals were kept at 4,21, or 33°0. When the mice were housed singly, all groups had between 2·2 and 3·5 cycles in the 16 days period of observation. The small differences between the groups were not significant. Grouping (15 mice per cage) caused a significant reduction in oestrous frequency at all three temperatures, but the differences between the temperature groups were not significant. Introduction of a caged male into the group of females had no effect on oestrous frequency at 4 and 21 °0. At 33°0 frequency increased and the difference between the temperature groups became significant. When the males were released into the cages of grouped females the incidence of pregnancy in the group at 33°0 was seven times greater than that at 4 or 21 °0.
Seven available inbred strains of mice-A, C57, SWR, C3H, 101, CBA, and DBA-were examined for differences in the shape of their spermatozoal heads. The two most extreme strains with respect to spermatozoal head shape were found to be SWR and C57. The Fl and F2 progenies derived from crossing C57 and SWR strains were found to be roughly intermediate between the parent inbred strains. Spermatozoal head shape for these preliminary investigations was calculated as outlined by Penrose (1953). Discriminant analysis was then carried out on F2 data and a linear discriminant function was obtained whereby 13 characteristics of the spermatozoal head were combined into one "super-character" or discriminant score. The numerical value of the discriminant score was taken as an estimate of spermatozoal head shape for each spermatozoon measured. 4nalyses of variance carried out on the discriminant scores for each generation revealed that intrastrain variation was not significant in the SWR strain and reached only low levels of significance in the C57 strain. The Fl males were found to be more variable than the inbred males. A large portion of the variability between the Fl males was shown to arise from "maternal effects". The F2 males were found to be much more variable than the Fl males and an estimate of heritability was approximately 0 -9. A minimal estimate of the number of "effective factors" operating to distinguish the two inbred parent strains was found to be two. The within-male variance was found not to differ significantly from generation to generation. The implications of these results are discussed.
Two inbred strains of mice and the reciprocal Fl hybrids between them were reared in a temperate or in a hot humid environment. There was an age-related environmental effect on the rate of increase in body weight. Between 2 and 5 weeks the rate· of weight gain was more rapid in the heat but at all other ages weight gain was more rapid in the temperate conditions. Periods of rapid growth were associated with low intra-strain variation in body weight.
Rate of passage of digesta, lumen diameter, and rates of absorption of water, sodium, and potassium w~re calculated from wet weight, dry weight, and sodium and potassium content of digesta in segments of the large intestine of six sheep given 800 g lucerne chaff per day.
This study examined the effects of hypoglucagonaemia and hyperglucagonaemia on the incorporation of 14C from [2-(14)C]propionate into plasma glucose of sheep in vivo. The sheep were adult ewes fed a maintenance diet of lucerne pellets delivered in equal aliquots hourly. The irreversible loss of glucose was determined by the continuous infusion of [6-(3)H]glucose. During the control period (the hour immediately preceding infusion of hormones) 63 +/- 2% of the propionate was converted to glucose, accounting for 30 +/- 2% of glucose production. Glucagon deficiency, induced by infusion of somatostatin (100 micrograms/h), did not affect gluconeogenesis and the irreversible loss of glucose significantly. However, glucagon infusion at 11.5 +/- 0.6 micrograms/h significantly increased the irreversible loss of glucose, with the greatest increase occurring in the first 15 min of infusion. The 14C specific radioactivity of glucose and the fraction of glucose derived from propionate decreased significantly during glucagon infusion. The data are consistent with glucagon have a marked glycogenolytic effect initially, but little or no selective effect in promoting the utilization of propionate for glucose synthesis in vivo in sheep.
Daily intramuscular injections (20 f-Lgjday) of oestradiol-3, 17,8 dipropionate
in adult male rats depressed body growth and reduced the weight of the testes and
seminal vesicles between 4 and 8 days of treatment.
Previous studies have shown an increase in RNA at the shoot apex of L. temulentum following floral induction, detectable chemically 2 days after induction, and by histochemical means after 1 day. Here, a transient increase in the incorporation of 32P, applied to leaves, into nucleic acids at the apex is shown to occur at about the time when the long-day stimulus is estimated to reach the shoot apex. The increased 32p incorporation due to the long-day exposure occurs throughout the apex, and is not confined to the summit region. Most of the 32p was incorporated into RNA.
Oxygen uptakes, growth rates, and reproductive productivities of hairless and naked mice were compared with those of their normal sibs. Mice of all genotypes were acclimatized to 33°0 from birth, or from weaning, or as adults. Oontrols were kept at 2PO.
Ruminal microorganisms were labelled using [35S]sulphate during growth on a sulphur-deficient medium_ More than 99% of the 35S incorporated by the cells was in the organic sulphur fraction_ The labelled microorganisms were then infused into the abomasum of six sheep which were each fed 775 g of a ration containing 2 -1 % nitrogen and 0 -17% sulphur_
Twelve mature ewes from a flock selected for high clean fleece weight (Fleece Plus) and twelve from a flock selected for low clean fleece weight (Fleece Minus) were randomly divided between two dietary treatments: 500 or 1100 g per day of chaffed lucerne hay.
Ten, 2-year-old Merino ewes from a flock selectively bred for high clean fleece weight (Fleece Plus) and ten from a flock bred for low clean fleece weight (Fleece Minus) were randomly divided between two dietary treatments: 600 or 1100 g/day of pelleted lucerne hay. After 14 weeks, each ewe received an intravenous injection of L-[35Sjcystine (66�4.uCi). Venous blood samples were collected at 15 specified times until 8 h after the injections, and wool fibres were plucked until 65-75 days after the injections. Protein-free filtrates prepared from blood plasma were bulked within sample times for ewes from the same flock and dietary treatment. Equations relating the specific radioactivity of free cystine isolated from the bulked filtrates to time after injection contained three exponential terms. The entry rate and pool size of cystine estimated from these equations were greater in Fleece Minus than in Fleece Plus ewes (by 25 and 44 % respectively for entry rate and pool size). Both traits were also higher in ewes offered 1100 g lucerne/day than in those offered 600 g/day (58�7 v. 33�9 mg/h for entry rate and 19�2 v. 11� 8 mg for pool size). The concentration offree cystine in plasma was greater in ewes offered 1100 g lucerne/day (3�0 v. 2�1 mg/I; P < O� 05), and greater in Fleece Minus ewes (3�0 v. 2�1 mg/I; P < 0�05).