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Biomedical subjects

T J Heath

Publications and source records attributed to T J Heath.

At least 37 records · Page 2Linked to original sources
PubMed1997

Personal and family backgrounds of first-year veterinary science students at the University of Queensland.

OBJECTIVE: To provide information on changes in the social and educational backgrounds of veterinary students over a 10 year period in an effort to determine the extent to which they are representative of the community. METHODS: Questionnaires were completed by first-year veterinary students at The University of Queensland in 1985 and 1986 (152 students), and 1995 and 1996 (154), and the data were analysed using the SAS System for Windows. RESULTS: The gender ratio of first-year veterinary students was 50:50 (male:female) in 1985 and 1986 but 10 years later it had changed to 38:62. In 1985 and 1986 77% had come directly from school, with 43% of the total coming from government schools, 17% from Catholic schools and 34% from other private (independent) schools. A decade later the percentage coming directly from school had decreased to 40%, that from Independent schools increased to 45% and that from cities increased from 53% to 64%. The educational backgrounds of parents varied widely though a high percentage had university degrees; mothers had received less formal education than fathers, and the educational attainments of both parents were higher at the beginning than at the end of the study. More than half (57% initially; 67% 10 years later) the fathers were in professional or managerial occupations, and a similar number (50% initially; 48% 10 years later) of mothers were teachers, nurses or clerks. The number of males from country areas decreased from 26 to 16 over this period. CONCLUSION: These veterinary students differed from the community generally in that progressively more were female, more were from Independent schools, their parents had more formal education and more of their parents were in professional, managerial or clerical occupations.

Adolescent↗
PubMed1996

Tonsils of the soft palate of young pigs: crypt structure and lymphoepithelium.

BACKGROUND: Tonsils of the soft palate are especially important in pigs as the major pharyngeal mucosal-associated lymphoid tissue and as a portal of entry for microorganisms. They play a key role in initiating immune responses against antigens entering tonsillar crypts from the oropharynx. The aim of this study was to describe the architecture of the tonsillar crypst and the morphology of their epithelial surface. METHODS: Tissue taken from the tonsil of the soft palate of freshly-killed pigs was examined using light microscopy, electron microscopy, and three-dimensional reconstruction techniques. RESULTS: Tonsils of the soft palate in pigs are penetrated by numerous crypts which extend into, and branch extensively within, the lymphoid tissue. Stratified squamous non-keratinised epithelium covering the oropharyngeal surface is continuous with that lining the neck of crypts. Lymphoepithelium covers the tonsillar lymphoid tissue within the crypts. It consists of non-keratinised epithelial cells, M cells, goblet cells and many intraepithelial lymphoid cells. M cells have a variable surface morphology: some are covered by relatively regular and well-formed microvilli; others possess very long undulant microvilli emanating from broad membranous folds. CONCLUSIONS: Variations in M cell surface morphology occur and these may reflect alterations of the apical plasmalemma in response to antigenic stimuli. Further investigation will be required to determine molecular specializations of the apical membrane of M cells which may facilitate interactions with antigenic material.

Animals↗
PubMed1996

A longitudinal study of veterinary students and recent graduates. 1. Backgrounds, plans and subsequent employment.

OBJECTIVE: To examine factors that influence career choices by veterinary graduates. DESIGN: Longitudinal study. POPULATION: Students-77 female and 77 males-who began studying veterinary science at The University of Queensland in 1985 and 1986. PROCEDURE: Questionnaires were completed in the first and fifth year of the course, and in the second year after graduation. The data were arranged into an aggregated data set, then analysed using the SAS System for Windows. RESULTS: These students chose veterinary science, in many cases at an early age, because of their attitudes towards animals rather than advice from other people. Most had extensive experience with animals, and many gained this in cities rather than on farms. Between half and two-thirds of them looked forward to a career in private-practice when they were in first year. The proportion planning a career in private practice was highest for those who chose veterinary science before they were 12 years old. One-quarter of those in first year were undecided about what they would do after graduation. When they were surveyed in fifth year, most planned to enter mixed private practice at least initially. In fact, 59% entered mixed practice and 28% small animal practice. there were no significant relationships between prior experience with animals and either career plans or success in the job market. When asked in their second year after graduation, about half planned to continue in private practice over the longer term, and a quarter were undecided. CONCLUSIONS: The decision to study veterinary science is often made at a young age, and is influenced mainly by attitudes towards animals. The career path planned by the majority involves private practice, but for about a quarter the future is unclear, both when they enter the course and after they have worked as veterinarians.

Age Factors↗
PubMed1996

A longitudinal study of veterinary students and recent graduates. 2. Views of the veterinary profession.

OBJECTIVE: To examine the development of attitudes and opinions relating to the veterinary profession. DESIGN: Longitudinal study. POPULATION: Students, 154 in all, who began studying veterinary science at The University of Queensland in 1985 and 1986. PROCEDURE: Questionnaires were completed in the first and fifth year of the course and in the second year after graduation. The data were analysed using the SAS System for Windows. RESULTS: Few changes in opinion over time were found on the role of the profession, or on the status and prestige of veterinarians. Changes did occur in views on the characteristics of a successful veterinarian, with increases in the perceived importance of interpersonal skills, and of the capacity to work hard, and decreases in the perceived importance of honesty and integrity, dedication and the prevention of cruelty. Attitudes hardened over time in relation to costs of treatment, non-payment of fees and availability out of hours. Individuals changed their opinion on whether to counsel or report an incompetent colleague, but the changes in one direction were approximately equal to those in the opposite direction. CONCLUSIONS: The attitudes and opinions of veterinary graduates result from experiences before and during their veterinary course. In general the perceived importance of interpersonal skills increases during the course, and the level of altruism decreases.

Animal Welfare↗
PubMed1996

A longitudinal study of veterinary students and recent graduates. 3. Perceptions of veterinary education.

OBJECTIVE: To examine the attitudes and opinions on veterinary education at the beginning and end of the veterinary course, and after graduation. DESIGN: Longitudinal study. POPULATION: Students-154 in all-who began studying veterinary science at The University of Queensland in 1985 and 1986. PROCEDURE: Questionnaires were completed in the first and fifth year of the course and in the second year after graduation. The data were analysed using the SAS System for Windows. RESULTS: When they entered the course, the students were looking forward more to learning about animals than about basic sciences. At fifth year and after graduation most believed that more emphasis should have been placed on all facets of their education except the basic sciences. It may be difficult to increase this emphasis without placing undue pressure on the students, although more than half of the fifth year students and graduates agreed that there is much in the curriculum that is not needed by a practising veterinarian. Only one-third or less agreed that veterinarians are well equipped to practise veterinary science immediately they graduate. There was no relationship between the level of agreement with this statement, and the academic grades obtained. CONCLUSIONS: A majority of veterinary graduates do not believe that they are well equipped to practice immediately they graduate. They believe that more emphasis should have been placed on most facets of their education, but, conversely, that there is much in the curriculum that is not needed by a practising veterinarian.

Animals↗
PubMed1996

A longitudinal study of veterinary students and recent graduates. 4. Gender issues.

OBJECTIVE: To study differences in experiences, attitudes and opinions between female and male veterinary students and recent graduates. DESIGN: Longitudinal study. POPULATION: Students-77 males and 77 females-who began studying veterinary science at The University of Queensland in 1985 and 1986. PROCEDURE: Questionnaires were completed in the first and fifth year of the course, and in the second year after graduation. The data were analysed using the SAS System for Windows. RESULTS: Females decided to study veterinary science at a younger age than males and were more influenced by 'a love of animals', the image of veterinarians as portrayed on television, an interest in living things and in the scientific study of disease. Males were more influenced than females in aspects of the workplace: bosses and money. There were no gender differences in their background in relation to farms, or to animals, or in their career plans. However females when in first year expected a lower initial income than males; an expectation that was realised in the first year after graduation. As first year students and also as veterinarians, females had stronger views than males on animal welfare issues, and also felt that the veterinary profession had a lower status relative to other professions. CONCLUSIONS: Significant differences in attitudes and experiences exist between males and females entering the veterinary profession. The situation of females in relation to income and status is consistent with that in other professions, where females have been disadvantaged compared with males.

Age Factors↗
PubMed1995

The epithelium of canine palatine tonsils.

The palatine tonsil is positioned to play a key role in protecting the body against ingested microorganisms. These microorganisms must traverse the tonsillar epithelium to initiate immune reactions, but no information is available from dogs on the structure of this epithelium. In this study, the morphology and ultrastructure of the epithelium of the palatine tonsil of dogs was examined using light and electron microscopy. The epithelium is of two types: reticular and non-reticular. Reticular epithelium, which is invaded by lymphoid cells, is located over the apices of nodules, separated indistinctly by islands of non-reticular squamous epithelium. The reticular epithelium contains M cells which are more abundant towards the periphery of lymphoid nodules. The apical membrane of the M cells forms folds from which microvilli extend into the lumen of the oropharynx. Abluminally, cytoplasmic processes enfold clusters of lymphocytes. Numerous desmosomes secure the marginal plasma membrane and lateral membranous interdigitations to adjacent epithelial cells, thereby maintaining the integrity of the tonsillar epithelium. Epithelial discontinuities, which are few, occupy similar positions to M cells and appear to contain migrating lymphocytes. A fenestrated basement membrane allows cell transport between the intraepithelial passageways of the reticular epithelium and the subepithelial lymphoid tissues.

Animals↗
PubMed1995

Lymph pathways of the medial retropharyngeal lymph node in dogs.

In dogs, lymph drains from tissues throughout the head, including the tonsils, along lymphatic vessels to the facial, parotid, lateral retropharyngeal and mandibular lymph nodes. From the mandibular lymph nodes, lymph may flow to the ipsilateral medial retropharyngeal lymph nodes, or along anastomotic connections to the contralateral node. Afferent lymphatics convey lymph from these nodes to defined areas in the medial retropharyngeal nodes. They divide over the surface of the node, and within trabeculae. Terminal afferent lymphatics are connected to the subcapsular and trabecular sinuses either through circular or oval holes in the vessel wall, or terminate at the sinus where the vessel contains a valve adjacent to the point of entry. The subcapsular sinus surrounds the entire node, and is continuous with an interconnecting network of trabecular and cortical sinuses which convey lymph through the cortex. Connective tissue septa extend through the sinuses and lymph flows freely between adjacent sinuses through holes in the septal walls. Initial efferent lymphatic vessels, which arise from the medullary sinuses between medullary cords, converge towards and unite within the network of medullary trabeculae. Other vessels, which contain valve-like flaps, drain lymph from the subcapsular sinus. Efferent vessels emerge along the hilus and coalesce to form the tracheal trunk. The tracheal trunk has several layers of smooth muscle cells, well developed elastic laminae and connective tissue, surrounding the lymphatic endothelium.

Animals↗
PubMed1995

Intercellular and lymphatic pathways of the canine palatine tonsils.

The palatine tonsils play a key role in initiating immune responses against antigenic material entering the mouth and their lymphatic pathways are important in disseminating immunological information to the lymph nodes and other mucosal surfaces. Scanning and transmission electron microscopy and Mercox casts were used to examine the intercellular and lymphatic pathways of the palatine tonsil in dogs. Intercellular fluid within the intraepithelial passageways of the reticular epithelium flows through pores in the basement membrane and intermingles with that of the subepithelial intercellular spaces. From there, tissue fluid enters initial lymphatics which form a plexus surrounding each follicle. No lymphatic vessels are seen entering or leaving the follicles but intercellular pathways of the follicles are continuous with those of the adjacent initial lymphatics. These pathways appear to provide the only route for lymphocytes leaving the follicles and directly entering the lymphatic pathway. Lymph then flows into sinuses adjacent to, and incompletely surrounding, the base of follicles; or it may enter a network of sinuses between and beneath the lymphoid follicles which convey lymph throughout the parafollicular tissue. Lymphoid cells enter the parafollicular sinuses which may be a major entry site of lymphocytes emigrating from the lymphoid parenchyma. Some lymph may bypass these sinuses by entering septal lymphatic vessels oriented perpendicular to the central connective tissue lamina of the palatine tonsil. All lymph is collected into basal lymphatic vessels where valves prevent retrograde flow. Basal vessels course within the central lamina and converge to form efferent lymphatic vessels which emerge at the caudal region of the palatine tonsil and convey lymph to the medial retropharyngeal lymph node.

Animals↗
PubMed1995

Pathways of blood flow to and through superficial lymph nodes in the dog.

Wide variations occur in the arrangement of the blood vessels of the superficial lymph nodes in dogs. These vessels were studied using Microfil and Mercox casts, scanning and transmission electron microscopy, and the dye Alcian blue. Most nodes receive some arteries at a hilus, but this varies from a single indentation to one or more grooves and in some cases is a smooth and flattened area. Some nodes have no identifiable hilus and arteries enter at many different points. Most nodes that receive arteries at a hilus also receive additional vessels, some of which are derived from a network at the capsule; some of these enter by crossing the subcapsular sinus. In both cortex and medulla, some capillaries are within lymph sinuses, or adjacent to them. Within the cortex, networks of arterioles, capillaries and venules occur near subcapsular and trabecular sinuses, and around nodules, but the nodules themselves are relatively avascular. Some medullary capillaries are fenestrated, but all other capillaries have a complete endothelial lining, with basement membrane and pericytes. All venules, except those in the deep cortex, have a low endothelial lining. Although the distribution of vessels within the nodes follows a general pattern in dogs, the variation in the pattern of supply is such that it is not possible to ascribe any particular pattern to superficial nodes in general, or even to the nodes of a particular lymph centre. This contrasts with the commonly accepted description which implies that all blood vessels to all lymph nodes pass through a well defined hilus.

Animals↗
PubMed1995

Lymphatic drainage from the tonsil of the soft palate in pigs.

The tonsil of the soft palate, the predominant lymphoid tissue of the oropharynx in pigs, is important especially in initiating immune responses against antigenic material entering the mouth. The aim of this work was to describe the lymphatic pathways from the tonsils of the soft palate of pigs through lymph nodes of the head to the bloodstream. This was achieved by gross dissection, and by using Evans' Blue dye and Microfil casts. Efferent lymphatic vessels from the tonsil coalesce to form vessels which convey lymph to the primary nodes, the mandibular and medial retropharyngeal, and thence to the bloodstream, along two distinct pathways. In the superficial pathway, lymph flows through the mandibular lymph node, along lymphatic vessels closely associated with the linguofacial vein, to the ventral superficial cervical node (middle group) and the accessory mandibular node. Most efferent vessels from the accessory mandibular node enter the ventral superficial cervical node, but some may directly join the lymphatic vessels emanating from the ventral superficial cervical node. These vessels convey lymph to the dorsal superficial cervical node and thence, via the efferent lymphatics, to the circulatory system. In the deep pathway, lymph is conveyed directly to the medial retropharyngeal node and then to the tracheal trunk, as in other domestic animals. As the vessels from the tonsils course over the surface of the pharynx, the muscular movements of swallowing may help propel lymph towards the primary nodes and the bloodstream.

Animals↗
PubMed1994

The arrangement of gut-associated lymphoid tissues and lymph pathways in the koala (Phascolarctos cinereus).

Gut-associated lymphoid tissues are poorly developed in koalas. They comprise paired caecocolic lymphoid patches, and a few small mesenteric lymph nodes. The patches lie opposite one another in the lateral gut wall at the junction of the ileum, caecum and proximal colon. The lymphoid parenchyma of the patches consists of a layer of nodules and internodular parenchyma in the submucosa. Apoptosis is common in the nodules. The mucosa and lymphoid tissue of each patch is continuous over a caecocolic recess, formed by the coalescence of laminae which extend along the large intestine. Lymph sinuses between and beneath the lymphoid nodules are continuous with efferent lymph vessels in the submucosa. These then enter 2-4 small lymph nodes at the root of the mesentery. The paucity of lymphoid tissue associated with the gut may be related to germicidal activity in the Eucalypt leaves eaten by the koala.

Animals↗
PubMed1992

Pathways of lymph flow through intestinal lymph nodes in the horse.

In the horse, several thousand lymph nodes receive lymph from the intestine, part of which is very large and contains microorganisms that enable the animal to utilize refractory dietary constituents such as cellulose. The aim of this study was to describe the pathways by which lymph is delivered into, traverses, and is drained from these lymph nodes. These pathways were studied with either Microfil or methacrylate casting materials and with light and electron microscopy. The afferent lymphatic vessel delivering lymph into one of the nodes divides over the capsular surface and within trabeculae into terminal branches, and these are continuous with the subcapsular and trabecular sinuses through rounded holes up to 30 microns across. Lymph is conveyed from the subcapsular and trabecular sinuses through the cortex by four types of sinuses: trabecular sinuses, cortical tubular sinuses, tubule-like sinuses with a network of stellate cell processes, and sinuses between cortical cords. It is conveyed through the medulla by sinuses both within and between medullary cords. Lymph is drained from these sinuses by initial efferent lymphatics of three types: those between medullary cords, those within the subcapsular sinus overlying medullary or cortical cords, and those within trabeculae. All three types are continuous with surrounding sinuses through holes 5-30 microns across. These three alternative routes for lymph drainage may ensure adequate lymph flow during different intranodal conditions that may exist when the node is responding to microorganisms or other foreign materials.

Animals↗
PubMed1991

Pathways of lymph flow from the intestine of the horse.

The intestine of horses differs from that of most other domestic animals in having a huge ascending colon and cecum, which together act as a large fermentation vat. The lymph drainage from this intestine occurs through a complex network of lymph vessels and lymph nodes, of which there are several thousand. The pathways taken by lymph through these vessels and nodes were studied by tracing injections of dye, by examining Microfil casts, and with light and transmission electron microscopy. Lymph vessels transporting lymph from the intestinal wall generally terminate on a single node within a group of primary nodes. Efferent lymphatics form networks in the immediate vicinity of groups of nodes. In these networks, the vessels branch, anastomose, entwine amongst one another, and sometimes form recirculating loops. Usually 2-9 lymphatic vessels course away from these networks to secondary or higher-order nodes in both local and more central locations. Vessels reaching these nodes generally terminate on more than one node within each group. This pattern of lymph distribution is repeated as lymph passes through a succession of five or more nodes before flowing into the cisterna chyli. The complexity of the lymph pathways, it is suggested, would promote the mixing of lymph from different parts of the intestine and from different nodes, thus collating, integrating, and potentiating the immunological responses of these nodes. The walls of lymphatic vessels are well endowed with smooth muscle cells and elastic fibres, suggesting that intrinsic contractility of these vessels is a major mechanism in the propulsion of lymph from the intestine of the horse.

Animals↗
PubMed1991

Effects of the adjuvant DEAE-dextran and Staphylococcus aureus on the lymph pathways and filtering capacity of popliteal lymph nodes in sheep.

The effects of subcutaneous injections of the adjuvant DEAE-dextran and, or killed Staphylococcus aureus on the structure of the lymph pathways of popliteal lymph nodes in sheep were examined using light and electron microscopy and Microfil casts. Dextran with or without killed S aureus caused significant changes in the lymph pathways both within the node and outside it. However, killed S aureus alone did not. The changes included anastomoses among afferent lymph vessels and between afferent and efferent lymph vessels; proliferation of vessels around the node; joining of parts of the capsule and trabeculae to adjacent parenchyma with loss of parts of the subcapsular and trabecular sinuses; enlargement of medullary sinuses; and reduction of the number of reticular processes in sinuses throughout the node. These changes were accompanied by a reduced ability of the node to filter chicken red blood cells labelled with chromium-51 which were injected into an afferent lymph vessel.

Animals↗
PubMed1991

Topography of the major superficial lymph nodes and their efferent lymph pathways in the koala (Phascolarctos cinereus).

The koala has an inguinoaxillary lymph trunk on either side of the ventral midline, and this carries efferent lymph from the superficial inguinal lymph node directly to the deep axillary lymph node. The superficial lymph nodes are large and soft compared with those of the domestic species, and each lymph centre usually contains only one or two large lymph nodes. Koalas have a rostral mandibular lymph node which has not been described in other species, but lack popliteal and subiliac lymph nodes. The superficial lymph nodes which are readily palpable in the live koala are the facial, rostral mandibular, mandibular, superficial axillary and superficial inguinal. All superficial lymph pathways terminate at the confluence of the common jugular and subclavian veins.

Animals↗
PubMed1991

Relationships between lymphoid nodules and lymph sinuses in lymph nodes: a study in horses.

Secondary lymphoid nodules in lymph nodes of the horse are surrounded by a network of lymph sinuses, including the subcapsular sinus and its extensions around tabeculae, tubular and tubule-like sinuses deeper in the cortex, and sinuses between cord-like projections of cortical tissue. The precise role of this close association between sinuses and nodules in the transport of immune complexes, cells and cytokines is not known.

Animals↗