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Biomedical subjects

R C Roberts

Publications and source records attributed to R C Roberts.

At least 145 records · Page 8Linked to original sources
PubMed1981

Postnatal maternal effects on growth and fat deposition in mice selected for large and small size.

A crossfostering experiment involving lines of mice selected for large (L) and small (S) 6-week body weight was designed to determine correlated responses in direct genetic and postnatal maternal genetic effects and postnatal litter size effects on fat deposition at 6 weeks of age. The gonadal fat pad was used as an index of adiposity. The L line exceeded the S line in both direct genetic and postnatal maternal genetic effects on weight and percentage (of body weight) of the gonadal fat pad. Postnatal maternal genetic effects were about one-third as large as direct genetic effects. A prenatal line x postnatal line interaction for weight and percentage of gonadal fat was caused by the inability of S line dams to provide sufficient milk to maintain normal development of L line young. Further evidence supporting this hypothesis was the high mortality rate among L line young reared by S line dams when compared with the mortality in all other subgroups. Increasing postnatal litter size reduced weight and percentage of gonadal fat, but this factor was of less importance than direct genetic effects. In general, the relative importance of direct genetic, postnatal maternal genetic and postnatal litter size effects was similar for metric measures of growth (body weight, body length and tail length) and for adiposity (gonadal fat pad weight and percentage). Rate of gonadal fat pad development relative to body weight was higher in line L than in line S. At a constant body weight, however, line L mice had less fat than line S mice.

Adipose Tissue↗
PubMed1980

Human alpha-2-macroglobulin. Studies on the electrophoretic heterogeneity.

Purified alpha-2-macroglobulin may be resolved into as many as five electrophoretic bands on selected polyacrylamide gel systems. The microheterogeneity does not result from prior proteolytic attack but appears to correspond to different conformational states of the inhibitor. Trypsin binding capacity and the extent of subunit cleavage into 120,000 and 70,000 dalton fragments by mild alkaline treatment are related to the proportion of fast and slow electrophoretic forms. Study of proteinase binding after electrophoretic separation by special zymogram techniques confirms that the fastest electrophoretic form has very low binding capacity. No electrophoretic differences conld be observed in alpha-2-macroglobulin derived from cystic fibrosis plasma relative to control alpha-2-macroglobulin. Alpha-2-macroglobulin appears to exist as a simple, slow electrophoretic form in fresh plasma but converts into faster forms upon aging the plasma or during purification. Characterization of the electrophoretic microhetergeneity of alpha-2-macroglobulin preparations should be a prerequisite for the study of its proteinase binding properties.

Cystic Fibrosis↗
PubMed1980

Detection of proteinases in electrophoretograms of complex mixtures.

A simple, sensitive technique for detecting proteolytic enzyme zones on electrophoretograms by making contact print zymograms is described. The method is applicable to electrophoretograms prepared on a variety of support media, immunoelectrophoretograms or isoelectric focusing patterns on various media. The contact print zymograms are prepared by placing unfixed, unstained electrophoretograms in contact with a thin film of casein which has diffused into a layer of agarose supported by a hydrophilic polyester film. After staining the casein film with Coomassie blue, the proteolytic zones are detected as clear zones against a blue background. The method can detect as little as 9 ng of trypsin. The utility of the method is illustrated by detection of the proteinase enzymes in thermophilic actinomycete antigen preparations separated by polyacrylamide electrophoresis, crossed immunoelectrophoresis and isoelectric focusing on agarose and granulated dextran supports.

Actinomycetaceae↗
PubMed1980

Antibody-independent complement consumption by Micropolyspora faeni.

Micropolyspora faeni is an etiologic agent of hypersensitivity pneumonitis, a disease with an ill-defined mechanism of pathogenesis. Many reports have suggested an immunologic mechanism. A number of laboratories have demonstrated a nonantibody-mediated activation of the complement cascade. This study was undertaken to define the pathway of the complement consumption induced by M. faeni. We utilized an extract of M. faeni grown on synthetic media rather than the more common double dialysis extracts. Complement consumption by this extract was easily demonstrable in the absence of detectable antibody, but was inhibited by EDTA and MgEGTA. With the exception f C1, all of the early components of the classical pathway were markedly reduced following incubation of normal human serum with this extract. C1 was poorly consumed. In addition, factor B conversion to B was not inhibited by 10 mM MgEGTA suggests that the alternative pathway may also be affected. The generation of M. faeni-dependent chemotactic factor(s) from serum demonstrates that the complement cascade is being activated rather than inhibited.

Antibodies↗
PubMed1979

Characterization of precipitin response to Micropolyspora faeni in farmer's lung disease by quantitative immunoelectrophoresis.

Sera from 12 patients with farmer's lung disease (FLD) drawn during an acute episode and displaying precipitins to Micropolyspora faeni were analyzed by crossed immunoelectrophoresis with an intermediate gel combined with a rabbit reference precipitate system. Forty-six precipitin arcs were identified in the reference system, and FLD sera reacted with 36 of these antigens. The FLD sera displayed significantly more precipitates and higher precipitin scores when compared with sera from 16 precipitin-positive subjectw who did not have FLD. However, there was overlap between the 2 groups, and neither measurement distinguished the 2 persons who became ill after challenge from one person who did not. Three disease specific antigens were identified that may have special relevance for pathogenesis of disease. Ten exposure-relevant antigens were also identified. We propose that these antigens be important components of a standardized M. faeni antigen preparation.

Chronic Disease↗
PubMed1978

Physical and chemical properties of human plasma alpha2-macroglobulin.

Alpha2-M (alpha2-macroglobulin) was purified from human plasma by two different procedures. As well as having no detectable impurities by the usual criteria for testing the homogeneity of protein preparations, these alpha2M preparations showed a single component, after reduction in urea, of 185000 daltons by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The molecular weight of the alpha2M was found to be 718000 by sedimentation equilibrium experiments using the gravimetrically determined -v of 0.731 ml/g. The interaction of several proteinases with alpha2M was studied by using a novel discontinuous polyacrylamide-gel system, which showed clear separation of the enzyme-complexed alpha2M from the free alpha2M. These studies indicated that urokinase, as well as trypsin, chymotrypsin, plasmin and thrombin forms complexes with alphaM. The cleavage of the 185000-dalton subunit to a 85000-dalton species on interaction of trypsin with alpha2M was demonstrated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis after reduction of the alpha2M-trypsin complex in urea. The amino acid composition, carbohydrate content, absorption coefficient at 280 nm, the specific refractive increment and the sedimentation coefficient for these alpha2M preparations were measured. The stability of the trypsin-binding activity of the alpha2M preparations was also studied under several storage situations.

Amino Acids↗
PubMed1978

Farmer's lung disease among farmers with precipitating antibodies to the thermophilic actinomycetes: a clinical and immunologic study.

Farmers were evaluated for the presence of farmer's lung disease by serologic methods and by clinical histories. From a large farming population screened serologically, 40 of 92 farmers with precipitating antibodies to the thermophilic actinomycetes consented to be evaluated for clinical evidence of farmer's lung disease. Each subject completed a standardized questionnaire which was reviewd by a trained observer. On the basis of the questionnaire and an indepth clinical history, the subjects were grouped into those farmers who had a history of farmer's lung disease (38%), those with no history (50%), or a doubtful group (12%). When these groups were compared for radiologic changes, pulmonary function abnormalities, and immune function, no differences were discernible. None of the parameters tested were useful in predicting which farmer would develop clinical farmer's lung disease. The parameters tested did not provide reliable criteria for differentiating those patients who present without acute symptoms but relate a history of recurrent pulmonary illnesses associated with moldy forage.

Actinomycetales↗
PubMed1977

Immunological studies on an aberrant form of ataxia telangiectasia.

We describe two brothers with ataxia telangiectasia (AT) of which one was unique in that he had no detectable IgG and IgA concentrations in the serum or saliva. The other brother had the more common IgA deficiency in the serum and saliva. Neither patient had a history of undue sinopulmonary infections. In spite of the absence of these immunoglobulins in the sera, there were cells in the bone marrow and peripheral blood that stained with fluorescein-labeled anti-IgG and anit-IgA. Both patients had demonstrable humoral antibody and cell-mediated immune responses to the antigens tested. We also discuss possible pathophysiological mechanisms causing the above defects.

Adult↗
PubMed1977

The antigens of pigeon breeder's disease. II. Isolation and characterization of antigen PDE1.

Antigen PDE1 was purified from pigeon dropping extracts by chromatography on DEAE-cellulose and Bio-Gel A-1.5. It was characterized as a glycoprotein, containing 88% protein and 12% carbohydrate, with a molecular weight of approximately 200,000. PDE1 appears to be derived from pigeon intestinal IgA, showing the typical immunoglobulin structure of heavy and light chains. This antigen represents about 24% of the dry weight of the unfractionated pigeon dropping extract.

Alveolitis, Extrinsic Allergic↗
PubMed1977

System for simplified discontinuous-gradient polyacrylamide-gel electrophoresis.

We describe a modified polyacrylamide gel electrophoresis method with which plasma proteins are excellently resolved in 4 h. We made a three-layer discontinuous gradient gel with concentrations of 80,60, and 45 g of polyacrylamide per liter of tris(hydroxymethyl)aminomethane/ethylenediaminetetraacetic acid/borate buffer, pH 9.2. Time and material needed in the preparation of the gel was greatly decreased, a well-resolved (22-25 bands) pattern was obtained in 1 h, and the gel slabs were easier to remove from the cell than were gels prepared according to the manufacturer's specifications. We saw a marked shift in the higher polymers of haptoglobin type 2-2 toward the cathode in this system, and also a clearly resolved double band of alpha2-macroglobulin in whichthe more anodal band appears to represent alpha2-macroglobulin/protease complex.

Blood Protein Electrophoresis↗