Delwyn G Cooke

Massey University, Palmerston North City, Manawatu-Wanganui, New Zealand

Are you Delwyn G Cooke?

Claim your profile

Publications (11)23.07 Total impact

  • Source
    Delwyn G. Cooke · Leonard F. Blackwell · Simon Brown
    [Show abstract] [Hide abstract]
    ABSTRACT: Excel’s “line chart” has several peculiarities that can yield misleading representations of data. However, in Excel 2010 it is possible to combine “line charts” with “scatter charts” which exacerbates the capacity to be misleading.
    Full-text · Article · Feb 2016
  • [Show abstract] [Hide abstract]
    ABSTRACT: STUDY QUESTION Do the basal body temperature (BBT) shift and the cervical mucus markers for the beginning of the post-ovulatory infertile phase (POIP) of a menstrual cycle agree with the corresponding urinary pregnanediol glucuronide (PdG) threshold value?
    No preview · Article · Dec 2015 · Human Reproduction
  • Simon Brown · Delwyn G Cooke · Leonard F Blackwell
    [Show abstract] [Hide abstract]
    ABSTRACT: Ligand-binding assays, such as immunoassays, are usually analysed using standard curves based on the four-parameter and five-parameter logistic models. An estimate of the uncertainty of an analyte concentration obtained from such curves is needed for confidence intervals or precision profiles. Using a numerical simulation approach, it is shown that the uncertainty of the analyte concentration estimate becomes significant at the extremes of the concentration range and that this is affected significantly by the steepness of the standard curve. We also provide expressions for the coefficient of variation of the analyte concentration estimate from which confidence intervals and the precision profile can be obtained. Using three examples, we show that the expressions perform well.
    No preview · Article · May 2015 · Scandinavian journal of clinical and laboratory investigation
  • Delwyn G Cooke · Leonard F Blackwell
    [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Human milk lysozyme was conjugated with estrone glucuronide to give a monoacylated conjugate, two disubstituted isoforms and one trisubstituted isoform in 99.4% yield. The conjugates were pure and highly inhibited (>98%) by the anti-estrone glucuronide antibody. The clearing curves were biphasic for all four conjugates but a three minute initial rate assay was established and used to measure a normal menstrual cycle profile of estrone glucuronide excretion rates. The marked differences between the hen egg white and human milk lysozyme conjugates shows that near identical tertiary structures do not necessarily imply similar physical, chemical, biochemical and kinetic behaviour.
    No preview · Article · Jan 2015 · Journal of Immunoassay and Immunochemistry
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: What are the characteristics of, and how variable are, individual normal menstrual cycle profiles of excretion rates for the urinary metabolites oestrone glucuronide (E1G) and pregnanediol glucuronide (PdG)? There is a continuum of menstrual cycle profiles that differ from standard textbook profiles but which can be understood simply in terms of growth, atresia and ovulation of ovarian follicles. Point-of-care assays with the Ovarian Monitor pre-coated assay tubes, using urine samples diluted to a constant volume per unit time, give laboratory accurate clinical data for individual menstrual cycles. Lay operators can perform the point-of-care assay system at home to achieve reliable and reproducible results, which can be used for natural family planning. This prospective study involved 62 women, with normal menstrual cycles, recruited from three centres: Palmerston North, New Zealand, Sydney, Australia and Santiago, Chile. The study lasted 3 years. Women collected daily urine samples and determined their E1G and PdG rates with a pre-coated enzyme assay system known as the Ovarian Monitor. For two cycles, the assays were repeated in a study centre and the results were averaged to give 113 individual menstrual cycles for analysis. The cycles were displayed individually in a proprietary database program. The individual normal hormonal profiles were more complex than the classic composite curves for 40% of the cycles. Of 113 ostensibly normal cycles, only 91 were potentially fertile and 22 had some luteal phase defect. The oestrone glucuronide and PdG excretion rates were reliable and informative in the non-invasive elucidation of ovulation and ovarian function for both simple and complex profiles. Daily monitoring revealed the variability of normal menstrual cycle profiles. The LH peaks were variable and ambiguous markers for ovulation. The study consisted of cycles only from women with regular cycles of 20-40 days duration. All the women were intending to avoid a pregnancy during the study thus the limits of the fertile window were not tested. The principles established in this study should apply to cycles of any length. All peaks in oestrone glucuronide excretion should be tested by concurrent measurements of PdG, which gives a positive indication of the fate of the follicle it represents. The Ovarian Monitor provides a useful addition for practitioners of natural family planning. Financial support for this study was obtained from the UNDP/UNFPA/World Bank/WHO Special Programme of Research, Development and Research Training in Human Reproduction (HRP). D.G.C. is currently employed by and holds stock in Manawatu Diagnostics Ltd, a company in the development phase of a potentially competing product. The remaining authors have nothing to declare.
    Preview · Article · Oct 2013 · Human Reproduction
  • [Show abstract] [Hide abstract]
    ABSTRACT: The UNDP/WHO/World Bank/Special Programme of Research, Development and Research Training in Human Reproduction (Geneva) set up a study to determine whether it is feasible for women to monitor their ovarian activity reliably by home testing. Daily self-monitoring of urinary hormone metabolites for menstrual cycle assessment was evaluated by comparison of results obtained with the Home Ovarian Monitor by untrained users both at home and in study centres. Women collected daily data for urinary estrone glucuronide (E1G) and pregnanediol glucuronide (PdG) for two cycles, then the procedure was repeated in the women's local centre (in Chile, Australia or New Zealand) giving a total of 113 duplicate cycles. The tests were performed without the benefit of replicates or quality controls. The home and centre cycles were normalized and compared to identify assay errors, and the resulting home and centre menstrual cycle profiles were averaged. Reliable mean cycle profiles were obtained with the home and centre excretion rates agreeing to within 36 ± 21 nmol/24 h for E1G and 0.77 ± 0.28 µmol/24 h for baseline PdG values (1-5 µmol/24 h). The cycles had a mean length of 28.1 ± 3.1 days (n = 112; 5th and 95th percentiles: 24 and 35 days, respectively), a mean follicular phase of 14.8 ± 3.1 days (n = 107; 5th and 95th percentiles: 11 and 21 days) and a mean luteal phase length of 13.3 ± 1.5 days (n = 106; 5th and 95th percentiles: 11 and 17 days), calculated from the day of the LH peak. The study confirmed that the Ovarian Monitor pre-coated assay tubes worked well even in the hands of lay users, without standard curves, quality controls or replicates. Point-of-care monitoring to give reliable fertility data is feasible.
    No preview · Article · Nov 2011 · Human Reproduction
  • Delwyn G Cooke · Jan E Binnie · Leonard F Blackwell
    [Show abstract] [Hide abstract]
    ABSTRACT: A direct enzyme linked immunosorbent assay (ELISA) system has been optimized as a reference method for the measurement of first statistically significant rises in estrone glucuronide excretion rates in human urine by analysing samples pre-diluted at the time of the collection by the women subjects to a constant urine production rate of 150 mL/h. Validation was achieved by correlation of the individual menstrual cycle profiles with the corresponding estrone glucuronide excretion rates determined by radioimmunoassay (RIA) on the same urine samples for a total of 221 samples from nine cycles. The pre-dilution procedure removed random variations due to fluctuations in the daily rate of urine excretion and minimized between sample matrix effects. When the ELISA data were correlated with the RIA data, Deming regression gave a slope of 1.20+/-0.03 and an intercept of 4.6+/-1.8 nmol/24h (r=0.944) and a random experimental error of 14.2 nmol/24h. The major difference in the measurements was a proportional error of 20%, which was present in either the ELISA or RIA methods or in both. Comparison of the standard normal variate transformation of the ELISA and RIA data gave hormonal profiles of the individual menstrual cycles (N=9) that overlapped almost perfectly. Statistically significant rises or falls in the magnitude of the excretion rate in one profile were mirrored faithfully in the other.
    No preview · Article · Jul 2007 · Steroids
  • Delwyn G Cooke · Leonard F Blackwell
    [Show abstract] [Hide abstract]
    ABSTRACT: Lysozymes ( from goose (Anser anser) egg white, turkey (Melagris gallopavo) egg white, phage T4 and human milk were compared with hen egg white lysozyme in their ability to clear a suspension of Micrococcus lysodeikticus. All of the lysozymes, except hen egg white lysozyme, catalysed the clearing of the Micrococcus lysodeikticus suspension in a biphasic fashion. Compared to hen egg white lysozyme, the total absorbance or transmission change over 5 and 20 minutes was less in all cases, except for human lysozyme. Human lysozyme was, therefore, a potential alternative, more rapid signal generator for the measurement of urinary estrone glucuronide excretion rates because of its structural similarity to hen egg white lysozyme. The apparent K(M) values for hen egg white lysozyme increased with the enzyme concentration.
    No preview · Article · Apr 2007 · Journal of Immunoassay and Immunochemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: Three structurally characterized estrone glucuronide-lysozyme conjugates, E1 (a 60:40 mixture acylated at K3 and K97), E3 (acylated at K33), and E5 (acylated at both K33 and K97) were isolated and purified using a combination of cation-exchange chromatography on S-sepaharose in 7M urea and hydrophobic interaction chromatography on butyl sepharose. Urea was essential to separate the conjugates into six chromatographically homogeneous fractions. In the absence of urea, complex mixtures of lysozyme and the six conjugate fractions were always encountered. The E1, E3, and E5 conjugates were highly inhibited by a sheep polyclonal anti-estrone glucuronide antibody only after the hydrophobic interaction chromatography step. The high level of inhibition enabled all three conjugates to be utilized as signal generators in homogenous enzyme immunoassays for urinary estrone glucuronide. Despite the apparently higher affinity of E3 for the antibody, both E1 and E3 gave standard curves that were indistinguishable provided that 1.7-fold more antiserum was used for E1. Both E1 and E3 yielded menstrual cycle urinary data that agreed with that provided by the Ovarian Monitor pre-coated assay tubes. Although, the menstrual cycle pattern was similar for the three signal generators, the E1G excretion rates yielded by E5 as the signal generator were only 60% of the reference values. Despite structural differences, there was no advantage gained in separating E1 and E3, but higher substituted conjugates such as E5 need removal for best assay performance.
    No preview · Article · Feb 2003 · Journal of Immunoassay and Immunochemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: Application of time series analysis to a database containing serial pregnanediol data from 113 complete ovulatory menstrual cycles contributed by 83 women of proven fertility and 68 cycles for which pregnanediol values were available over the ovulatory period, detected the first statistically significant risk in pregnanediol excretion for all cycles for which a baseline was available (n = 170). However, even at the 99% confidence level, for 22% of cycles a rise was observed before the presumed day of ovulation. Therefore, a threshold value for pregnanediol was sought from the database as a better marker for the end of fertility. A value of 1.4 mg per 24 h was not reached before day 2 after the pre-ovulatory estrogen peak day for 96% of the cycles. In the remaining 4% of cycles it was reached one day after the total estrogen peak day. The validity of this threshold was confirmed in extensive studies using the Ovarian Monitor where the equivalent is 6.3 mumol per 24 h of pregnanediol glucuronide and measurements are performed on timed urine specimens with a minimum collection time of three hours. These studies were as follows: 1) a World Health Organization study on the use of the Ovarian Monitor as a fertility self test in the home (108 cycles), 2) a multicenter study on returning fertility during breast feeding conducted by Family Health International (73 women), and 3) the general application of the Ovarian Monitor for pregnancy achievement and avoidance during the past ten years (over 250,000 PdG assays performed in ten countries). With rare exceptions, the use of these threshold values is applicable for all women provided correction is made for urine volume.
    No preview · Article · Feb 1998 · Steroids
  • [Show abstract] [Hide abstract]
    ABSTRACT: Estrone glucuronide conjugates of hen egg white lysozyme were prepared by both the mixed-anhydride and active-ester coupling procedures. Both methods gave good yields of conjugate but the active-ester procedure gave a more diverse range of products consistent with a greater acylating ability. Unreacted lysozyme which was present in all cases was removed by a combination of cation-exchange chromatography on a Pharmacia Mono-S column and hydrophobic-interaction chromatography on an Alkyl Superose column. The conjugate families were more hydrophobic than native lysozyme. The chromatographic behaviour of the reaction mixtures on Mono S columns under non-denaturing conditions was complex as a result of hydrophobic effects and only at pH values above 7.0 did the conjugates elute in the order of their overall charges. At pH values below 6.0 the conjugates, although less charged than lysozyme, eluted last on salt gradients. In contrast when denaturing 7 M urea buffers were used the conjugates eluted in the order of their electrostatic charges and reproducible patterns were obtained which served as an excellent analytical system for lysozyme-steroid glucuronide conjugates. The purified conjugate material from the active-ester reaction gave over 90% inhibition of the lytic activity in the presence of an estrone glucuronide antibody. When used in a homogeneous enzyme immunoassay system the levels of urinary estrone glucuronide encountered in a normal menstrual cycle were easily measured.
    No preview · Article · Jan 1995 · Journal of chromatography. B, Biomedical applications

Publication Stats

67 Citations
23.07 Total Impact Points


  • 1995-2015
    • Massey University
      • • Institute of Molecular BioSciences
      • • Institute of Fundamental Sciences
      Palmerston North City, Manawatu-Wanganui, New Zealand