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Biomedical subjects

A E Davis

Publications and source records attributed to A E Davis.

At least 127 records · Page 7Linked to original sources
PubMed1981

Delayed expulsion of the nematode Nippostrongylus brasiliensis from rats on a low protein diet: the role of a bone marrow derived component.

Rats on a low protein diet, containing 10% casein as the only source of protein, have an impaired capacity to expel primary infections with the nematode Nippostrongylus brasiliensis and remain susceptible to reinfection. In the present study, the transfer of syngeneic bone marrow cells to rats on a low protein diet reconstituted the expulsion mechanism allowing parasite rejection to occur at the same rate as rats on a sufficient diet. Serum transfer, on the other hand, did not significantly alter the rate of worm expulsion. These results demonstrate that a bone marrow derived component plays an important role in the impaired immunity of rats fed a low protein diet.

Animals↗
PubMed1980

EMG biofeedback in patients with motor disorders: an aid for co-ordinating activity in antagonistic muscle groups.

A computer program was developed to analyse the relative amount of EMG activity in an agonist-antagonist pair of muscles while subjects performed voluntary flexion-extension movements at the wrist to track a visual target. The data were presented to the subjects in the form of a vector display, the angle and length of which was determined from calculation of EMG power in the two muscles. This new approach to EMG biofeedback was evaluated in two hemiplegic patients and three patients with cerebellar incoordination. Over a training period of several weeks, all the subjects were able to modify the pattern of EMG activity in the muscles to reduce the amount of inappropriate coactivation of flexors and extensors and to produce more sustained and regular activation of individual muscle groups.

Adult↗
PubMed1980

The effect of iron deficiency, protein deficiency and dexamethasone on infection, re-infection and treatment of Giardia muris in the mouse.

The association between nutrient deficiencies, steroid administration, anti-flagellate therapy and giardiasis was examined using the Giardia muris/mouse model. Administration of steroids to BALB/c mice resulted in persisting high levels of infection with G. muris, whereas untreated animals were able to eliminate this parasite. In addition, steroid treatment significantly reduced the efficacy of anti-flagellate therapy. Protein-deficient mice eliminated the parasite at the same rate as mice on an optimum diet and also developed strong acquired resistance to re-infection. A similar pattern was observed in iron-deficient mice, except that the number of parasites that became established during the first 2 weeks of infection was significantly reduced. Thus, there was no evidence of synergism between iron and protein deficiency and infection in this model.

Animals↗
PubMed1980

Active site amino acid sequence of human factor D.

Factor D was isolated from human plasma by chromatography on CM-Sephadex C50, Sephadex G-75, and hydroxylapatite. Digestion of reduced, S-carboxymethylated factor D with cyanogen bromide resulted in three peptides which were isolated by chromatography on Sephadex G-75 (superfine) equilibrated in 20% formic acid. NH2-Terminal sequences were determined by automated Edman degradation with a Beckman 890C sequencer using a 0.1 M Quadrol program. The smallest peptide (CNBr III) consisted of the NH2-terminal 14 amino acids. The other two peptides had molecular weights of 17,000 (CNBr I) and 7000 (CNBr II). Overlap of the NH2-terminal sequence of factor D with the NH2-terminal sequence of CNBr I established the order of the peptides. The NH2-terminal 53 residues of factor D are somewhat more homologous with the group-specific protease of rat intestine than with other serine proteases. The NH2-terminal sequence of CNBr II revealed the active site serine of factor D. The typical serine protease active site sequence (Gly-Asp-Ser-Gly-Gly-Pro was found at residues 12-17. The region surrounding the active site serine does not appear to be more highly homologous with any one of the other serine proteases. The structural data obtained point out the similarities between factor D and the other proteases. However, complete definition of the degree of relationship between factor D and other proteases will require determination of the remainder of the primary structure.

Amino Acid Sequence↗
PubMed1979

Neutralization test in influenza: use in individuals without hemagglutination inhibition antibody.

In influenza immunization trials, patients who were seronegative by the hemagglutination inhibition test could be divided into two groups according to preimmunization levels of neutralizing (Neut) and neuraminidase inhibition (NI) antibodies. The group with low levels of Neut and NI antibodies usually developed adequate levels of hemagglutination inhibition antibody after one dose of vaccine, and the group with undetectable Neut and NI antibodies did not.

Antibodies, Viral↗
PubMed1979

Nippostrongylus brasiliensis infection in the rat: effect of iron and protein deficiency on the anthelmintic efficacy of mebendazole, pyrantel, piperazine, and levamisole.

The benzimidazole anthelmintics mebendazole and fenbendazole have been shown to be much less effective against Nippostrongylus brasiliensis infections in the rat on a combined iron and protein deficient diet. In the present experiments it was shown that the anthelmintic efficacy of mebendazole was significantly impaired in the rat on either an iron deficient or a protein deficient diet. Furthermore, iron and protein deficiency reduced the efficacy of the anthelmintics pyrantel and piperazine but not levamisole. The finding that nutritional deficiencies reduce anthelmintic efficacy may well be relevant to worm eradication programmes in iron deficient and protein calorie malnourished populations.

Anemia, Hypochromic↗
PubMed1979

Complement-dependent histaminase release from human granulocytes.

The role of particle-bound complement proteins in the induction of noncytotoxic enzyme release from human granulocytes was investigated with the use of sera genetically deficient in complement and highly purified complement components. Release of histaminase, one of two important histamine catabolizing enzymes, and beta-glucuronidase from polymorphonuclear leukocytes was solely dependent on particle-bound C3b (the larger cleavage product of the third component of complement) when fluid-phase complement was excluded. The extent of enzyme release was a function of particle-bound C3b input, was reduced by exposing the particles to C3b inactivator, and was blocked by fluid-phase C3b. Phagocytosis of the C3b-coated particles was not required for enzyme release from neutrophils. In contrast, phagocytosis of "opsonized" particles was required for noncytotoxic release of histaminase and arylsulfatase from eosinophils; other proteins, as well as C3b, were able to opsonize particles for induction of enzyme release from eosinophils. These studies suggest a dual role for complement (particularly C3) in modulating vascular permeability phenomena, i.e., release of vasoactive mediators by the action of C3a and C5a, and release of the corresponding enzymes that inactivate the mediators by C3b.

Amine Oxidase (Copper-Containing)↗
PubMed1979

Properdin factor D: effects on thrombin-induced platelet aggregation.

Factor D, when preincubated with platelet suspensions, at concentrations as low as 1.2 micrograms/ml, inhibited thrombin-induced platelet aggregation. No inhibition of collagen or arachidonic acid-induced platelet aggregation was found. Inhibition occurred, but to a lesser extent, when thrombin and factor D were added to platelets at the same time. No inhibition occurred when factor D was added after thrombin. Thrombin was able to overcome inhibition by factor D by increasing its concentration. Diisopropyl-phosphorofluoridate-inactivated factor D also inhibited thrombin-induced platelet aggregation so that enzymatic activity of factor D was not required for inhibition. Factor D absorbed with hirudin coupled to Sepharose 6B showed no decrease in inhibitory capacity. 125I-Factor D bound to platelets in a manner suggesting an equilibrium reaction similar to thrombin. At low factor D input, binding was linear, whereas at higher input, binding began to approach saturation. Binding of 125I-labeled thrombin to platelets was inhibited by factor D. Analysis of these data show that factor D does not alter the total number of thrombin molecules which bind to the platelet surface at saturation. However, the dissociation constant for thrombin is altered from 2.78 to 6.90 nM in the presence of factor D (20 micrograms/ml). Factor D is thus a competitive inhibitor of thrombin binding, although the affinity of factor D for the platelet thrombin receptor is much less than that of thrombin. These phenomena occur at physiologic concentrations of factor D. Therefore, factor D may function in vivo as an inhibitor of platelet aggregation.

Binding, Competitive↗
PubMed1978

Histopathology in giardiasis: a correlation with diarrhoea.

There is controversy both in regard to the severity of small bowel mucosal damage attributable to giardiasis and to the causal relationship of these changes to the associated diarrhoea. In this series of 17 consecutive patients with giardiasis, small bowel histology and diarrhoea were independently assessed and compared. Disaccharidase assays were performed in 16 of these patients and a repeat biopsy obtained in seven cases. On histological examination the villous architecture varied from normal to sub-total villous atrophy. When these changes were compared with the severity of diarrhoea, a direct correlation was obtained, the more severe symptoms being associated with the more severe villous changes. Repeat biopsy after treatment demonstrated improvement in the histology which correlated with improvement in diarrhoea. Lactase activity was low in all patients with moderate or severe diarrhoea as well as in some patients with mild diarrhoea, two of whom had normal histology. This series demonstrates the occurrence of a spectrum of mucosal changes in giardiasis and supports the concept that these changes mediate the diarrhoea associated with this gut parasite.

Adolescent↗
PubMed1978

Community mental health ideology: a problematic model for rural areas.

The prevailing model for mental health services is found to be inappropriate with respect to many of the needs of rural communities. Special problems of rural areas are identified, and suggestions are offered for revision of mental health concepts and practice that might result in a better fit between professional ideology and rural reality.

Community Mental Health Services↗
PubMed1978

Suppression of rejection of Nippostrongylus brasiliensis in iron and protein deficient rats: effect of syngeneic lymphocyte transfer.

Rejection of Nippostrongylus brasiliensis is impaired in iron and protein deficient rats and this suggests that iron and protein deficiency directly or indirectly suppresses the immune response. The site of the immunological defect in deficient rats was investigated using the technique of cellular transfer of resistance. The functional activity of immune mesenteric lymph node cells obtained from iron and protein deficient donors was not depressed as measured by their capacity to cause parasite rejection in nutritionally sufficient recipients. In contrast, immune lymph node cells obtained from either sufficient or deficient donors did not result in parasite rejection in iron and protein deficient recipients. These results indicate that there is no permanent defect of lymphocyte function in iron and protein deficient rats and suggest that either some other component of the rejection mechanism is defective, or that lymphocyte function is blocked in an iron and protein deficient environment.

Animals↗