Roy T Sawyer

Roy T Sawyer
Medical Leech Museum · Archives

PhD (Zoology)

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151
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Introduction
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Publications

Publications (151)
Book
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This three-volume work provides a complete study of this well-known group of animals, dealing with every level of their biological organization, from the molecular to the zoological. The leech, once so prominent in the history of medicine, is again being used widely in modern hospitals, especially in microsurgery. Revival in the use of leeches coin...
Article
Previously enigmatic, ovoid to sac-like fossils of organic, acid resistant substance which are common components of leaf cuticle and megaspore assemblages in limnic and terrestrial palaeoen- vironments are identified as cocoons of clitellates. They have been recorded for a long time by palaeobotanists and palynologists, particularly in the Mesozoic...
Article
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Cell lineages during development of leeches can be ascertained by injection of horseradish peroxidase as a tracer into identified cells at early stages of embryogenesis. The injected embryos continue their normal development, in the course of which horseradish peroxidase is passed on in catalytically active form to the descendants of the injected c...
Article
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The bite of the medicinal leech bleeds for many hours. For decades it has been assumed that the remarkably prolonged bleeding time of a leech bite wound is due to hirudin, a specific anti-thrombin secreted by the leech during feeding. By measuring haematological parameters of blood oozing from a leech bite wound on 15 different occasions in 7 human...
Article
Full-text available
Cellular mechanisms of secretion in exocrine and endocrine glands are technically difficult to study. We present here a model which offers fundamental advantages for studying excitation-secretion coupling at the level of the isolated single cell. The salivary gland of the leech Haementeria ghilianii possesses a unique combination of unusual propert...
Article
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The genus Placobdella (Glossiphoniidae) has a centre of species concentration in North America. The type species P. costata is the only representative in the Palaearctic region. American Placobdella which feed on turtles are represented predominantly by two common species, P. parasitica and P. rugosa, which geographically overlap in eastern USA and...
Article
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A tuberculated species of turtle leech is indigenous to the Great Dismal Swamp and environs of northeastern North Carolina, and differs from other known species of Placobdella. This study of hundreds of specimens for more than a decade documents its unexpected taxonomic complexity. In fact, this seemingly innocuous leech undergoes radical transform...
Article
Full-text available
A tuberculated species of turtle leech is indigenous to the Great Dismal Swamp and environs of northeastern North Carolina, and differs from other known species of Placobdella. This study of hundreds of specimens for more than a decade documents its unexpected taxonomic complexity. In fact, this seemingly innocuous leech undergoes radical transform...
Article
Full-text available
Evidence is presented in this paper for the first time that reproduction without cross-fertilisation can occur in the arhynchobdellid leech Barbronia weberi (Blanchard, 1897). The discovery of "virgin birth" in this invasive Asian species was serendipitous in that a single unmated hatchling reared in isolation to maturity unexpectedly laid viable c...
Article
Full-text available
vidence is presented in this paper for the first time that reproduction without cross-fertilisation can occur in the arhynchobdellid leech Barbronia weberi (Blanchard, 1897). The discovery of “virgin birth” in this invasive Asian species was serendipitous in that a single unmated hatchling reared in isolation to maturity unexpectedly laid viable co...
Article
Full-text available
The terrestrial leech Haemopis septagon Sawyer & Shelley, 1976, is indigenous to the Great Dismal Swamp and environs of northeastern North Carolina and southeastern Virginia, USA. Ever since its discovery in 1895 at Lake Drummond in the Dismal Swamp, this elusive species has been recognized as taxonomically aberrant. For example, it is the only jaw...
Article
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The Okefenokee Swamp, one of the largest freshwater wetlands in the United States, supports more than 100 known taxa of macroinvertebrates, but no leeches have been recorded heretofore. In this paper, we report the discovery of four individuals swimming in open water during a six-week period in midsummer 2017. Based on characteristic slits and pore...
Article
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The jawed leech Philobdella floridana (Verrill, 1874) occurs widely in swamps of the southeastern United States. The discovery of a population of P. floridana in Lake Phelps, an isolated lake in the Albemarle Peninsula in the Outer Banks region of North Carolina, is by far the northernmost record for this species. Description of the Lake Phelps lee...
Article
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The alien Asian leech Barbronia weberi (Blanchard, 1897) was discovered in two widely separate localities in coastal North Carolina, USA, during an eco-systematic study of the Erpobdellidae of this region. Both populations display key external characteristics of this easily recognizable species, most significantly two accessory pores on the venter...
Article
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RESUMO O uso de sanguessugas medicinais para sangrar pacientes foi uma parcela importante da prática médica ao longo de grande parte do século XIX. No início desse século, a demanda por sanguessugas na Inglaterra, por essa época muito caras, resultou no esgotamento das suas fontes internas, mas a importação de França foi impedida pelas Guerras Napo...
Article
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Anuário do CEHA 2015, N.º 7, pp 283-322. Centro de Estudos de Historia do Atlantico, Funchal, Madeira ABSTRACT The use of medicinal leeches to bleed patients was a major part of medical practice throughout much of the 19th century. By the beginning of that century demand for leeches in England, by then very expensive, resulted in exhaustion of its...
Article
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In the nineteenth century the medicinal leech Hirudo medicinalis evolved into a lucrative commodity in great demand throughout the western world. In less than a century its trade became big business by any measure, involving tens of millions of animals shipped to every inhabited continent. In this context Ireland is particularly instructive in that...
Article
Full-text available
The apparent absence of the medicinal leech Hirudo medicinalis Linnaeus, 1758, in Ireland has been noted for over 150 years. Furthermore, not a single native Irish specimen has been preserved to prove its existence. The status of the Irish medicinal leech has been subject to several retrospective interpretations which need to be put into perspectiv...
Article
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An appeal in The Muskerry News of Blarney, Ireland, for information leading to the existence of the medicinal leech Hirudo medicinalis in Blarney Lake or adjacent waters. This was the last location where the medicinal leech was reported to exist, in the 1840s.
Article
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This article focuses on the chronological sequence of events which affected the people of Gum Neck, a remote fishing village on the Alligator River, Tyrrell County, NC, just south of the Albemarle Sound. This is the first detailed account of the upheaval experienced by the people, especially those who fought, on both side, but also those who were e...
Article
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The Influenza Pandemic of 1918-19 swept the entire world with awesome virulence, killing far more than the Great War itself. In spite of its wake of over 50 million deaths worldwide, including 550,000 in the United States and 13,703 in North Carolina, this disease totally disappeared as quickly as it came. Even today surprisingly little is known ab...
Article
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A new genus, Desserobdella, is described to accommodate the leech Clepsine picta Verrill, 1872 which feeds exclusively on amphibians of northern and central North America. This leech belongs to the subfamily Glossiphoniinae and therefore deposits cocoons directly onto the substrate. The genus Desserobdella n.gen. has the following diagnostic charac...
Article
The geologically ancient Tidewater region of southeastern Virginia and northeastern North Carolina rests precariously atop millions of years of erosion from the nearby Appalachian Mountains. An immense wetland at near sea level, it is host to every conceivable body of fresh water, ranging from brooding swamps and large hidden lakes to sluggish blac...
Book
Full-text available
The geologically ancient tidewater region of southeastern Virginia and northeastern North Carolina rests precariously atop millions of years of erosion from the nearby Appalachian Mountains. An immense wetland at near sea level, it is host to every conceivable body of fresh water, ranging from brooding swamps and large hidden lakes to sluggish blac...
Article
Full-text available
Military aspects of the Civil War in the Albemarle region of North Carolina have been the subject of several excellent recent publications. However, little has been written about how the Civil War affected civilian populations in this region. Toward this end we now look closer at a representative community on the Albemarle peninsula. Gum Neck, the...
Article
Full-text available
This is a documented account of a once-thriving community, now extinct, in the fishing and agricultural community on the Alligator River, Albemarle Peninsula, North Carolina. In the Depression years of the 1930s Up Road was divided naturally into northern and southern sections. The northern part was primarily confined to established farms. The sout...
Article
The Hirudinea have a number of arthropod-like characters, including a true haemocoel and compound eyes. This ‘arthropodization’ may have bearing on the origin of the arthropod phylum Uniramia. Certain traits shared by Clitellata and Uniramia are interpreted as primitive and compatible with the view that a monophyletic link exists between these two...
Article
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Every few generations some 'Act of God' happens without warning, but with such devastation as to change lives forever.Such an event took place on the Alligator River, Tyrrell County, North Carolina, on September 15-16, 1933. For the remote fishing and farming community of Gum Neck there was virtually no warning whatsoever that 'one of the most trag...
Article
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This article is an unique, previously undocumented history of the construction of the Alligator-Pungo Canal, a little known segment of the inland waterway canal, between the Albemarle Sound (Alligator River) and the Pamlico Sounds in tidewater eastern North Carolina. The inland waterway system started as a war defensive canal first proposed when th...
Book
Full-text available
Biographical sketch of Carrie Virginia Jones (1896-1969) of Gum Neck, Tyrrell County, North Carolina. This is a very remote fishing village on the Alligator River, in the tidewater region near the Albemarle Sound. Copies have been deposited with the North Carolina Collection, Joyner Library, East Carolina University, Greenville, NC, and with the Ty...
Article
Full-text available
This article is a documented account of how World War I affected the people of a remote fishing and farming community on the Alligator River, near the Albemarle Sound, North Carolina. By way of background, the author begins by saying: "One of my earliest memories as a little boy in Gum Neck in the mid-1940s was walking with my grandmother, Carrie W...
Article
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A detailed account of the background behind the recent revival of the use of medicinal leeches, Hirudo medicinalis, in modern plastic and reconstructive surgery.
Article
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Biography of Calvin Doss Weatherly from the remote fishing and farming community on the Alligator River, near Albemarle Sound, North Carolina. He was killed on a merchant convoy vessel in the Mediterranean during World War II when his ship was torpedoed by a German U-boat. The story of his naval experiences and details of his death were unknown to...
Article
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Biography of Dr Edward Warren (1828-1893), Surgeon General of the State of North Carolina during the U. S. Civil War. He was born in Tyrrell County, North Carolina, and died in exile in Paris. He wrote "An Epitome of Practical Surgery for Field and Hospital." After the Civil War he went to Baltimore but did not thrive, and became Chief Surgeon on t...
Article
Full-text available
The medicinal leech Hirudo medicinalis Linnaeus, 1758 is genotype of the genus Hirudo and constitutes the taxonomic basis for the family Hirudinidae and even the class Hirudinea. In spite of its unique taxonomic significance, H. medicinalis has never been characterized in terms of criteria currently accepted for the Hirudinea. As part of a broader...
Article
Full-text available
Hirudo medicinalis, the four-inch-long leech that was once used for bloodletting, is finding new work in hospitals. Revival of the medical use of leeches in modern plastic and reconstructive surgery, including story of the leech farm (Biopharm) in Wales. Case studies.
Article
Johann Friedrich Dieffenbach (1792-1847) regularly and successfully utilised leeches in sophisticated plastic surgery in Berlin in the 1820s and 1830s, well before anaesthesia, antisepsis and antibiotics. Inexplicably, it took nearly another 150 years before the use of leeches in this context was revived.
Article
Full-text available
Johann Friedrich Dieffenbach (1792-1847) regularly and successfully utilised leeches in sophisticated plastic surgery in Berlin in the 1820s and 1830s, well before anaesthesia, antisepsis and antibiotics. Inexplicably, it took nearly another 150 years before the use of leeches in this context was revived. (C) 2000 The British Association of Plastic...
Article
Full-text available
Despite technological advances, the humble leech is again being used in certain areas of surgery. Its bloodsucking ability is used after some critical microsurgical operations for re-establishing blood circulation.
Article
Selected antihaemostatic parameters associated with the bite of the Asian medicinal leechHirudo nipponia were investigated in human volunteers. This study confirms earlier work onHirudo medicinalis, in that the wound from a leech bite bleeds for hours even though blood coagulates normally after about 15 min. The whole blood clotting time forH. nipp...
Article
Full-text available
Selected antihaemostatic parameters associated with the bite of the Asian medicinal leechHirudo nipponia were investigated in human volunteers. This study confirms earlier work onHirudo medicinalis, in that the wound from a leech bite bleeds for hours even though blood coagulates normally after about 15 min. The whole blood clotting time forH. nipp...
Article
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An article on local entrepreneurs, giving background to establishment of Biopharm Leeches and the Medical Leech Museum.
Conference Paper
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The author takes a reflective look at medical history and what we can learn from it. Focus is on the history of the medicinal leech and the significance, if any, of bloodletting through the ages. Other bloodsucking animals, such as mosquitoes, fleas, ticks and flies, may have something to tell us about drug discovery.
Article
The blood-sucking leech, Haementeria ghilianii, has evolved a number of agents that attenuate haemostasis. Recently we have isolated a potent inhibitor of factor XIIIa, tridegin, in the salivary glands which is almost certainly involved in feeding. Addition of purified natural tridegin to plasma, prior to clotting with thrombin, results in clots th...
Article
Full-text available
1. Crude salivary gland extract of the giant Amazon leech, Haementeria ghilianii, contains an inhibitor of plasma factor XIIIa. 2. The inhibitory agent was purified to homogeneity by anion-exchange, cation-exchange, gel-filtration and reverse-phase chromatography to yield a single band on SDS/PAGE with an apparent molecular mass of 7.3 kDa. It has...
Article
Full-text available
Tridegin is a potent inhibitor of factor XIIIa from the leech, Haementeria ghilianii, which inhibits protein cross-linking. It modifies plasmin-mediated fibrin degradation as shown by the absence of D-dimer and approximately halves the time for fibrinolysis. Plasma clots formed in the presence of Tridegin lyse more rapidly when either streptokinase...
Article
A polypeptide derived from leeches of the species Hirudinaria manillensis has the following amino acid sequence: ( * See Patent for Chemical Structure * ) Cys Val Gly Ser A20sn Val Cys Gly Glu G25ly Asp Asn Cys Asn 30D Gln Leu Ser Ser S35er Gly Asn Gln Cys V40al E Gly Glu Gly T45hr Pro F Pro Gln S50er Gln Thr Glu Gly A55sp Phe Glu Glu Ile P60ro Asp...
Article
The inhibitor is protein derived leech tissue or leech secretions (for example, from Hirudo medicinalis), which is capable of binding to native collagen, in such a way that substantially no cleavage breakdown products of coilagen molecules occur on SDS-PAGE. The protein substantially inhibits collagen-induced platelet aggregation or adhesion, has a...
Article
Tridegin is a new inhibitor of plasma Factor XIIIa, and isolated from the salivary glands of the giant Amazon leech Haementeria ghilianii. Studies showed that clots formed in the presence of Tridegin are more susceptible to fibrinolytic enzymes. Such clots lyse in approximately half the time required for fully cross-linked clots. Complete inhibitio...
Article
Tridegin is a new inhibitor of plasma Factor XIIIa, isolated from the salivary glands of the giant Amazon leech Haementeria ghilianii. The IC50 is in the nanomolar range. It is the most potent inhibitor of Factor XIIIa described to date.
Conference Paper
Full-text available
Leech hyaluronidase has been purified. It is specific for hyaluronic acid as its substrate, in sharp contrast to lack of specficity for mucopolysaccharides exhibited by mammalian testicular hyaluronidase. Leech hyaluronidase has excellent thermostability: At 50 C it loses no activity for 40 min and retains significant activity after several hours....
Article
Full-text available
Calin from the saliva of the medicinal leech, Hirudo medicinalis, is a potent inhibitor of collagen mediated platelet adhesion and activation. In addition to inhibition of the direct platelet-collagen interaction, we presently demonstrate that binding of von Willebrand to coated collagen can be prevented by Calin, both under static and flow conditi...
Article
Full-text available
Interaction between exposed collagen and platelets and/or von Willebrand factor is believed to be one of the initiating events for thrombus formation at sites of damaged endothelium. Interference with this mechanism may provide an anti-thrombotic potential. Calin, a product from the saliva of the leech Hirudo medicinalis, was tested in vitro and fo...
Article
A fossil worm-like organism, ca. 0.5 mm long, showing cuticle, gut and setae. is contained in the solid part of the wall of a clitellate cocoon from the Early Cretaceous (Barremian). It is interpreted as having been entrapped and embedded in the intitially viscous cocoon secretion which solidified and thus prevented decay. Size, shape, posture, and...
Article
Novel hirudin variants isolated from the leech Hirudinaria manillensis, a leech more specialized for mammalian parasitism, are described. Isolation of antithrombin polypeptides was performed by ion-exchange chromatographies followed by an affinity chromatography step on immobilized thrombin. The major active component, antithrombin polypeptide peak...
Conference Paper
Full-text available
Calin, from the saliva of the medical leech Hirudo medicinalis, shows a dose-dependent inhibition of 1) the binding of human platelets to collagen; 2) the binding of human von Willebrand factor to collagen; 3) in vitro platelet aggregation; and 4) platelet adhesion to collagen in a Sakariassen flow chamber. This in vivo study shows antithrombotic e...
Conference Paper
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We conclude that Calin, isolated from the saliva of the medicinal leech Hirudo medicinalis, is a specific inhibitor of platelet collagen interaction which may therefore be a useful tool to study contribution of platelet adhesion to collagen and extracellular matrix both in vitro and in vivo.
Article
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The bite of the North American leech Macrobdella decora results in much less prolonged bleeding in fish (8 min; control = 1 min) and amphibians (11.5 min; control = 1.5 min) than in mammals (humans) (73 min; control = 6 min). Coagulation of blood flowing from leech bite wounds is initially prolonged in frogs (4.3 min; control = 2 min) and humans (5...
Article
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Fossils in leaf litter from Spitzbergen were originally treated as seeds and palynomorphs with netted wall structures. In this paper they are reinterpreted as the cocoons of clitellates (leeches and oligochaetes).
Article
The jawed leech, Hirudinaria manillensis is closely related to Hirudo medicinalis, both belonging to the same family Arhynchobdellida. From Hirudo, two potent peptide inhibitors, hirudin (a thrombin inhibitor) and eglin (an elastase/chymotrypsin inhibitor) have been characterised in detail. During our studies to isolate thrombin inhibitor from the...
Article
Full-text available
Prolongation of haemostatic parameters in the host achieved by hatchlingHirudo medicinalis differs quantitatively but not qualitatively from those achieved by adult leeches. The duration and the rate of blood loss from the bite wounds, the gain in body weight of leeches and the duration of feeding each increase with successive feeding episodes. The...
Article
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In this paper the effectiveness of the so-called American medicinal leech Macrobdella decora in overcoming human haemostasis is compared to that of the European medicinal leach Hirudo medicinalis. Thrombin-clotting times indicated that M. decora prevents coagulation of human blood by means of anti-thrombin activity. Our findings suggest that its ro...
Chapter
Full-text available
A summary of recent advances in new pharmacaologically active substances from leeches, mosquitoes, ticks, fleas,vampire bats, flies and other bloodsucking animals. The conclusion is that this is a new potentially useful area for discovering new cardiovascular drugs. 13 pages, 2 tables
Article
The giant Amazon leech Haementeria ghilianii feeds by inserting an exceedingly long tubular proboscis (up to 10 cm) deep into its mammalian host. The wound from its bite is not associated with prolonged bleeding because all antihaemostatic factors, including the fibrinogenolytic enzyme hementin, appear to be secreted exclusively into the lumen of t...
Article
The saliva of the medicinal leech, Hirudo medicinalis, contains a potent, hitherto unsuspected, inhibitor of collagen-mediated platelet adhesion/aggregation. Calin, of molecular size approximately 65,000 (reduced), has a rapid (1-10 min) effect on collagen which is reflected in its ability to suppress collagen-induced platelet aggregation, as well...
Article
The leech Hirudinaria manillensis belongs to the same family as the medicinal leech Hirudo medicinalis, which has been widely used for the study of hirudin, a specific thrombin inhibitor. A similar inhibitor has now been isolated from the heads of the Hirudinaria leech by acetone/acid extraction and further purified to near homogeneity by ion excha...
Article
This international conference held in Charleston, South Carolina, brought together key researchers and clinicians from 12 countries who contributed 45 papers. The focus was the scientific understanding of the underlying haematology of the leech in microsurgery and as potential drug discovery. The conference started with the discovery of 120-year-ol...
Article
Full-text available
Biological observations were made on the antihaemostatic activity in the saliva of the giant Amazon leech Haementeria ghilianii. Particular emphasis was placed on determining where the fibrino(geno)lytic enzyme hementin is produced and secreted in the salivary gland complex. Hungry third-fed Amazon leeches produce about 650 units of hementin, with...
Chapter
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A survey of the freshwater and terrestrial leeches collected at the Nam Cat Tien reserve in Vietnam was conducted. Most of the leeches belonged to Hirudinaria similis and Hirudinaria javanica, the so-called buffalo leeches.
Article
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"Secretions from bloodsucking animals are to cardiovascular diseases what penicillin was to infectious diseases"
Article
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The fibrinolytic enzyme Hementin from the giant Amazon leech Haementeria ghilianii is able to break down the platelet-fibrinogen-platelet crosslinks faster than it is able to incoagulate plasma. Hementin has a unique cleavage site between the D and E domains of fibrinogen. Hementin has potential as an agent for deaggregation of platelets within pla...
Article
Full-text available
The fibrinogenolytic enzyme Hementin from the giant Amazon leech Haementeria ghilianii is a unique tool for studying fibrinogen-platelet interaction. Hementin's ability to deaggregate platelet aggregates suggests it should be studied further as a possible thrombolytic agent, particularly on platelet-rich thrombi.
Article
Full-text available
Personal account of the expedition to discover the giant Amazon leech Haementeria ghilianii in the swamps of French Guiana in Amazonian South America.
Article
The effects of triethyltin (TET) have been examined using intracellular electrophysiological recording techniques from identified neurons of the leech (Hirudo medicinalis) CNS and from salivary glands of the giant Amazon leech (Haementeria ghilianii). TET, at concentrations as low as 10(-5) M, caused a reversible neuronal membrane depolarisation ac...
Conference Paper
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The giant leech salivary cells of the Amazon leech Haementeria ghilianii are a useful model for analysing calcium ion channel related effects of compounds on excitable membranes.
Chapter
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A summary of known terrestrial leeches of the United States, with a brief account of terrestrialism in leeches generally. The true terrestrial, borrowing leeches have distinctive morphology, including large body size, firmness of body, prolonged head region and reduction of caudal sucker. In the United States there are two species of terrestrial le...
Article
Full-text available
Leech hyaluronidase (Orgelase) was studied as a potential skin penetration enhancer using human cadaver skin. Results showed there was a twenty-fold increase in flux of metronidazole through the skin compared to controls. Conclusion that leech hyaluronidase has potential as a skin penetration enhancer in vivo.
Article
Leech hyaluronidase is not inhibited by heparin in vitro, whereas mammalian testicular hyaluronidase is inhibited. It is proposed that in a clinical context involving using spreading factors such as hyaluronidase in cardiac or other procedures that leech hyaluronidase would be superior.
Article
Full-text available
Both leech hyaluronidase and bovine testicular hyaluronidase use an arginine residue for substrate binding. However, in addition to the different mechanisms of action of these enzymes they also exhibit distinct substrate specificities. Therefore, although arginine residues are important for substrate binding they appear not to influence substrate s...
Article
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Summary 1. Each salivary gland cell of Haementeria extends a single process, or ductule, anteriorly into the proboscis; secretory products are released at the ductule ending. Some ductules secrete into the lumen of the proboscis and others at the outer surface of its tip, more than 5 cm from the gland in large leeches. 2. Depolarization of a gland-...
Article
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Interest in hirudin as a potential pharmaceutical drug has again put pressure on the endangered medicinal leech. One solution is to manufacture it by means of recombinant DNA technology. However, there remains a need for native hirudin as a standard. Toward this end a leech farm has been set up in Wales to produce native hirudin.