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Biomedical subjects

T J Heath

Publications and source records attributed to T J Heath.

At least 55 records · Page 3Linked to original sources
PubMed1990

Pathways of lymph flow from superficial tissues in the legs of horses.

Pathways of peripheral lymph flow from the legs in horses were studied with casts, and with light and electron microscopic techniques. Although lymph nodes in horses occur in large groups, each lymph vessel draining from the periphery appeared to terminate on a single node within a group. The larger branches of each vessel divided either on the node surface or after penetrating into the node, and 25 to 60 terminal afferent vessels entered either the subcapsular, medullary or trabecular sinuses. Numerous initial efferent lymphatics arose either within the medulla, or at its surface, and they often coalesced to form an anastomosing network on the node surface. Almost all of the one to four efferent lymphatics that left the vicinity of the node terminated on other nodes, usually within more centrally placed groups. This arrangement may aid in the amplification and propagation of immune responses initiated in primary nodes.

Animals↗
PubMed1989

Pathways between lymph vessels and sinuses in lymph nodes: a study in horses.

The pathways through which lymph flows from terminal afferent lymphatics to the lymph sinuses, and from the sinuses to initial efferent lymphatics, were studied in horse lymph nodes by using Microfil casts and electron microscopy. Terminal afferent lymphatics are continuous with the subcapsular sinus through oval holes, about 3 microns wide, along their length, and through larger openings near their end. Other terminal afferents penetrate into the node within trabeculae and are supported by processes across the lumen. They connect with trabecular and medullary sinuses through oval or round holes, generally 20-30 microns across. Some of these have processes, similar to the luminal strands of the adjacent sinuses, extending across them, apparently providing reinforcement. Initial efferent lymphatics receive lymph from medullary sinuses through holes which are similar to those in afferent lymphatics, though more common, especially near the origin of the vessel. Initial efferents within the medulla appear to be supported by the luminal strands of the surrounding medullary sinuses. It seems likely that these strands, like the trabeculae which surround the penetrating afferent lymphatics, may help to keep the lymphatic vessels open as the node swells while draining an area of infection.

Animals↗
PubMed1989

Blood vessels within lymph nodes: a comparison between pigs and sheep.

In sheep, most blood vessels enter the lymph nodes at a discrete hilus, which is where the capsule overlies medullary tissue. In pigs, vessels within the node arise from an extensive network of arteries on the surface, and most vessels penetrate the capsule where it overlies diffuse tissue--the counterpart of the sheep medulla. In both species the blood vessels divide extensively as they approach and supply the dense lymphoid tissue which contains lymph nodules. The blood vessels within sheep lymph nodules are surrounded by a thick layer of amorphous material. The dense lymphoid tissue has an abundant network of venules which have smooth muscle cells in their walls. These venules are involved in lymphocyte migration and in pigs they are lined by high endothelium which is similar to that in most other species, while in sheep the endothelium is much lower. Fenestrated capillaries occur in both pig and sheep lymph nodes.

Animals↗
PubMed1989

Fine structure of lymph pathways in nodes from the superficial inguinal lymph centre in the pig.

In the pig lymph node most lymph passes from afferent lymphatics to trabecular sinuses in centrally located dense nodular tissue. The lining of these sinuses is continuous adjacent to the trabecula but it is interrupted by numerous gaps adjacent to the parenchyma. Where the trabeculae end, their associated sinuses are continuous with the many interstitial spaces, up to 10 microns across, in the diffuse tissue. Lymph percolates through these spaces and is directly exposed to large numbers of macrophages with elaborate cytoplasmic veils and to reticular fibres which could be involved in antigen retention. Parts of the diffuse tissue are arranged into sinuses and cords in a manner similar to the medullary tissue in other species and a subcapsular sinus is also present over the diffuse tissue. There are gaps in the lining of these sinuses through which they communicate with the interstices of the parenchyma. Lymph flows from the sinuses in the diffuse tissue into efferent lymph vessels; these are usually in the capsule or along the plane of fusion of adjacent node anlagen.

Animals↗
PubMed1987

Pathways of lymph flow to and from the medulla of lymph nodes in sheep.

Medullary sinuses are continuous with penetrating afferent lymphatics, and with the trabecular and tubular sinuses which penetrate through the cortex. Tubular sinuses are often associated with blood vessels, especially in the deep cortex, and they appear to be important in the transport of lymphocytes. The subcapsular sinus is continuous over the cortex and the medulla, although trabeculae and reticular processes appear to restrict the flow of afferent lymph to the subcapsular sinus over the medulla. Lymph leaves the medulla through up to 100 or more initial efferent lymphatics, some only 60 micron across. Almost all of these arise from sinuses adjacent to the capsule lining the hilus. Some efferents remain associated with the capsule for a short distance whereas others, especially in nodes with a deep hilar depression, leave immediately at an angle of 30-90 degrees.

Animals↗
PubMed1986

Lymph drainage from the mammary gland in sheep.

Lymph from the mammary gland passes through at least three lymph nodes. These are usually the mammary, iliofemoral and medial iliac, although the subiliac, internal inguinal and sacral lymph nodes may also be involved. The iliofemoral, a large, flattened node in the dorsolateral wall of the pelvis, receives lymph from subiliac and popliteal as well as mammary nodes. Afferent lymphatic vessels either enter the subcapsular sinus on the dorsal surface of this node, or penetrate more deeply into the node. Lymphatics carrying mammary lymph enter more caudally than those from the popliteal or subiliac lymph nodes. Evans blue dye, injected into the mammary gland, showed a characteristic distribution within the mammary and iliofemoral nodes. Within the iliofemoral nodes it was present mainly in the caudal part. However, when China ink was used, carbon particles were distributed throughout most of the ipsilateral mammary nodes. In the iliofemoral node the carbon was distributed more widely than the Evans blue; it was found, mostly within macrophages, over the whole length of the node. A similar distribution of carbon was seen when it entered from the popliteal node. It appears likely that, although lymph from the mammary gland shows some preference for the caudal part of the iliofemoral node, constituents of this lymph may mix within the node with lymph from other primary nodes.

Animals↗
PubMed1986

Afferent pathways of lymph flow within the popliteal node in sheep.

Lymph enters the popliteal node in sheep either at the subcapsular sinus, or through terminal afferent lymphatics which pass within trabeculae to medullary sinuses. Lymph from the subcapsular sinus traverses trabecular sinuses and/or a network of tubular sinuses in the cortex before entering the medullary sinuses, which are very extensive. Carbon particles, injected either into an afferent lymphatic or subcutaneously into the leg, were initially found mainly in a circumscribed area of the subcapsular sinus. Within a few hours they were present within macrophages in and around medullary sinuses in a band which extended around virtually the whole medulla. It was concluded that the pathways taken by lymph constituents in the sheep node may differ from those described for mice, rats and rabbits.

Afferent Pathways↗
PubMed1986

Blood vessels of lymph nodes in the pig.

Pig lymph nodes have an unusual arrangement of cortical and medullary tissue, and lack a hilus. The aim of the present study was to describe the pathways by which blood reaches these lymph nodes. Natural or synthetic latex casts were made of blood vessels of superficial inguinal, popliteal and jejunal lymph nodes. Major nodal arteries approach these lymph nodes and give rise to about five branches, most of which remain on the node surface. These branches often wrap around part or all of the node in a claw-like manner and they divide to form a network on its surface. Arteries from this network penetrate the capsule directly to supply the lymphoid parenchyma. Anastomoses are common at all levels between the arteries supplying the nodes and arteriovenous anastomoses occur within the nodes. These may help to maintain and regulate blood flow within the lymph node under different conditions of stimulation.

Animals↗
PubMed1985

Effect of development of the ovine forestomachs on the anatomy of portal vessels and on the intrahepatic distribution of portal blood.

The two main tributaries of the ovine portal vein are the splenic vein, which carries blood mainly from the spleen and forestomachs, and the cranial mesenteric vein. In newborn lambs, these veins are of similar size and they converge at an angle of about 120 degrees. Blood which is carried from the intestines in the cranial mesenteric vein is not completely mixed with that from the splenic vein and it is preferentially distributed to the right side of the liver. As the fore-stomachs develop, the splenic vein becomes relatively larger than the cranial mesenteric and its direction of flow becomes oriented more caudally. Thus in the portal vein of sheep, blood in the cranial mesenteric vein meets a larger volume of blood flowing in almost the opposite direction from the splenic vein. As a result, the extent of mixing of blood in the portal vein of adult sheep is much greater than in young lambs.

Animals↗
PubMed1984

Drainage of lymph from the foreleg to the superficial cervical lymph node in sheep.

The superficial cervical (prescapular) node in sheep is large and readily accessible. It lies medial to the omotransverse muscle and 40 to 60 mm cranial to the ventral end of the scapular spine. Lymph vessels reaching this node from the foreleg all enter its ventral half. These lymphatics can be approached surgically opposite the elbow joint where they lie adjacent to the cephalic vein. Carbon particles infused into a single afferent lymphatic were restricted to a small segment of the ventrocranial quadrant of the node. When Evans' Blue dye, or a suspension of carbon particles, was injected subcutaneously just above the hoof they were carried to the node in two to five afferent lymphatics and were found mainly in the ventrocranial quadrant. A knowledge of the anatomy of the superficial cervical node and its afferent lymphatics may be of value in immunological studies, especially where it is desired to introduce antigen into a known part of a node and to leave the remainder for control observations.

Animals↗
PubMed1979

Lantadene A toxicity in sheep. A model for cholestasis.

Liver injury occurred after sheep were injected intravenously with the triperpene acid lantadene A, the toxic principle of the tropical plant Lantana camara. A single dose of 1--3 mg/kg of the compound caused mild hepatocellular injury characterized by transient rises in serum enzymes, with or without hyperbilirubinaemia. Higher doses resulted in hepatic necrosis. When low doses of the triterpene were given repeatedly over several days a cholestatic syndrome developed which appeared identical with that caused by consumption of the plant. This is a disease model which may be of value in experimental studies of intrahepatic cholestasis. This study provides evidence that lantadene A is hepatotoxic and does not require metabolism in the alimentray tract for toxicity in sheep.

Animals↗