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Biomedical subjects

J R Baker

Publications and source records attributed to J R Baker.

At least 325 records · Page 18Linked to original sources
PubMed1978

Biochemical characterization of some species of Trypansoma (Schizotrypanum) from bats (Microchiroptera).

Trypanosoma (Schizotryanum) species isolated from bats (Microchirotera) in Europe and Latin America were examined by determining the buoyant densities of their nuclear and kinetoplastic deoxyribonucleic acid (DNA) and the electrophoretic patterns of six isoenzymes. By these criteria they were separated into three distinct groups -- two from Europe (T. dionisii and T. vespertilionis) and one from America. T. dionisii was also separable by its morphology in vitro. Geographical location and DNA buoyant densities suggested that the American stocks were more closely related to T. cruzi than to the European species, though they differed from it marginally in kinetoplastic DNA density and in being noninfective to mice. Similar stocks studied by other workers have been shown to differ from T. cruzi also in reduced infectivity to, and lack of natural association with, Triatominae, and in antigenic composition. It is therefore proposed that trypanosomes of the subgenus Schizotryanum occuring naturally in Microchiroptera and differing from T. cruzi sensu stricto as outlined above should be treated as a distinct subspecies, T. cruzi marinkellei ssp. nov. T. cruzi sensu stricto thus becomes the nominate subspecies T. cruzi cruze Chagas 1909.

Alanine Transaminase↗
PubMed1977

Development of hemangiosarcomas in B6C3F1 mice fed 2-methyl-1-nitroanthraquinone.

Subcutaneous hemangiosarcomas developed in 97% of 172 B6C3F1 mice of both sexes fed either 0.03% or 0.36% 2-methyl-1-nitroanthraquinone in the diet. There was no significant relationship to dose or sex. In addition similar vascular tumors occurred in the mesentery of 14 mice. 2-Methyl-1-nitroanthraquinone is carcinogenic in B6C3F1 mice when given in food. One of 97 control mice had a splenic hemangiosarcoma.

Animals↗
PubMed1977

The binding of topically applied glucocorticoids to rat skin.

The epidermis of rat skin was shown to be the major site of accumulation of label after the topical application of [3H]-cortisol, [3H]-corticosterone and [3H]-triamcinolone acetonide. However, incubation of the skin in vitro in a way which ensured contact only between the dermal side of the skin and the steroid showed preferential accumulation of label from [3H]-cortisol and [3H]-corticosterone in the epidermis whereas label from [3H]-triamcinolone acetonide appeared evenly spread in the dermis and epidermis. The affinity of corticosterone to soluble proteins in skin homogenates was greater than that of cortisol as measured by displacement binding and correspondingly glucose uptake into the skin in vitro was inhibited for 18 hr after a single application of corticosterone but was not inhibited by cortisol.

Administration, Topical↗
PubMed1977

Skull malformation and cerebellar herniation in captive African lions.

Thickening of the cranial vault with a resulting cerebellar herniation is described in a series of litters of lion cubs, all with the same parents, one of whom was also very mildly affected. This animal, when mated to his daughter, also produced affected cubs. The aetiology of the condition is discussed and it is considered that vitamin A deficiency may have been less important than has been suggested by other authors.

Animals↗
PubMed1977

Renal uptake and metabolism of adrenocorticotrophin analogues in the rat: an autoradiographic study.

Renal resorption of tritiated adrenocorticotrophin analogues was studied in the rat using light microscopic and quantitative electron microscopic autoradiography. The synthetic corticotrophins used were Synacthen (corticotrophin-(1-24)-tetracosapeptide) and C41795-Ba ([D-Ser1,Lys17,Lys18]-corticotrophin-(1-18)-octadecapeptide amide), the tetracosapeptide being tritiated in either the tyrosine residue of position 2 or 23 or the phenylalanine of position 7 and the octadecapeptide in the tyrosine of position 2. Inspection of autoradiographs showed that peptides injected intravenously were resorbed into proximal tubules by endocytosis to produce vesicles whose radiolabel later appeared in lysosomes, a route previously elucidated for other peptides and proteins. The use of two techniques for analysis of electron microscopic autoradiographs, however, suggested that apical tubules also acquire label and are in some way involved in the transfer of resorbed labelled material from endocytotic vesicles to lysosomes. In addition, the autoradiographic analyses revealed that the duration of lysosomal labelling depends upon the position of tritium in the chain. Thus, when the CO2H-terminus of Synacthen was labelled, silver grains were more transiently associated with lysosomes than was the case when the NH2-terminal or core regions were tritiated, indicating a greater resistance of these portions of the peptide to attack by intracellular peptidase. The label from the chemically protected C 41795-Ba was also less readily expelled from the lysosomes of the proximal tubules.

Adrenocorticotropic Hormone↗
PubMed1977

A light microscopical study of healing incised dermal wounds in rats, with special reference to eosinophil leucocytes and to the collagenous fibres of the periwound areas.

Incised wounding of rat skin had a significant effect on the number of eosinophils both within the scar and in the adjacent areas. The numbers increased, after the inflammatory phase, to a peak between the 7th and 12th-14th days after wounding and remained elevated for the rest of the 30-day experimental period. In the areas contiguous to wounds, the dense bundles of collagenous fibres characteristic of normal dermis became progressively more dispersed from the 3rd to the 14th day, and then gradually re-aggregated into bundles. The fact that eosinophils, which are known to be collagenolytic, increase in numbers and change in morphology at the same time as newly formed scar collagen is remodelled and fibres around wounds are aggregated indicates a role for these cells in connective tissue metabolism. It is suggested that the dispersion of the collagenous fibres in the areas around wounds which occurs before the rise in eosinophil numbers could be related to the known increase in sulphated glycosaminoglycans around incised wounds.

Animals↗
PubMed1977

Localization in platelets of sodium 51Cr-chromate, 125I-antibody to whole membrane, and 3H-diisopropylfluorophosphate using electron microscopic autoradiography.

Platelets from the rabbit and rat, respectively, were incubated with sodium 51Cr-chromate and 3H-diisopropylfluorophosphate (3H-DFP) in the same manner as for platelet survival studies. A third isotope, 125I, was incorporated into a labeled antibody raised against a partially purified pig platelet membrane fraction. The 51Cr label was found to be concentrated predominantly in the cytoplasm, with a marked degree of association with mitochondria, whereas the tritium label appeared to be largely confined to the periphery of the platelet, particularly in association with the open canalicular system. The 125I-labeled antibody showed a very marked association with the plasma membrane and the open canalicular system, suggesting a membrane-bound affinity.

Animals↗
PubMed1976

Autoradiographic study of the distribution and cellular uptake of (14C) - streptozotocin in the rat.

The distribution and cellular accumulation, in the rat, of three specifically 14C-labelled forms of streptozotocin were investigated. A significant pancreatic accumulation of radioactivity was observed with (3' -methyl-14C)-streptozotocin only. Autoradiographic studies revealed high levels of bound radioactivity in the islet tissue following the administration of (3 -methyl-14C)-streptozotocin whereas much lower levels of radioactivity were detected in the pancreatic tissue following the administration of either (1-14C)-streptozotocin or (2' -14C)-streptozotocin. In the pancreasea, the amount of radioactivity bound to islet tissue was always significantly higher than that bound to acinar tissue. In addition to the islet tissues, the kidney cortex showed a very high level of bound radioactivity after the administration of (3' -methyl-14C)-streptozotocin. The results suggest that streptozotocin is rapidly metabolised by the rat. The apparent specificity for the accumulation of radiolabel from (3' -methyl-14 C)-streptozotocin suggests that a metabolite derived from the methyl bearing ureido side chain of the drug may be specifically involved in the induction of tissue damage and the consequent development of diabetes.

Animals↗
PubMed1976

Comparison of collagenase activity in eosinophil and neutrophil fractions from rat peritoneal exudates.

The collagenase activity had been compared in extracts of eosinophils and of neutrophilss from peritoneal exudates in two groups of rats, one of which had been treated to augment the numbers of eosinophils and the other the numbers of neutrophils. The proportion of granulocytes to other cells in each preparation was increased by differential centrifugation over a continuous gradient. Collagenase was extracted from the fractions in which granulocytes were concentrated and the activity assayed by the radioactive fibril method. There was at least as much collagenase in the eosinophil-enriched extracts as in the neutrophil-enriched extracts. It is postulated that eosinophil collagenase may have a function in the remodelling of newly-synthesised collagen during the post-inflammatory phase of healing, since eosinophil leucocytes appear in significant numbers within the connective tissue during this phase. This suggests a different role for eosinophil collagenase than that for neutrophil collagenase, since neutrophil are present only in the early stages of inflammation, when collagen is being degraded.

Animals↗