Search PubMed⌕ Search

Biomedical subjects

R C Roberts

Publications and source records attributed to R C Roberts.

At least 127 records · Page 7Linked to original sources
PubMed1983

Regulation of protein synthesis in rabbit reticulocyte lysates: separation of heme regulated protein kinase into a high and a low molecular weight species.

Protein synthesis in rabbit reticulocyte lysates is regulated by heme. In heme deficiency, a heme regulated protein kinase (HRI) is activated that phosphorylates initiation factor eIF-2. Consequently, eIF-2 is inactivated. Results described in this report show that HRI exists in crude and highly purified preparations in two forms; a high molecular weight component which sediments at a sedimentation co-efficient of 14-15S and a previously described 5.8S component (Ranu, R. S. and London, I. M. (1976) Proc. Natl. Acad. Sci. USA 73, 4349-4353). The 14-15S HRI selfphosphorylates poorly and undergoes dissociation into the 5.8S component via an intermediate of 8.5-9S. The 5.8S HRI, on weight basis, is about 5-10 times more active than the 14-15S HRI. In addition, a phosphoprotein phosphatase has been detected in lysates that dephosphorylates selfphosphorylated HRI. This observation suggests that phosphate on HRI turns over. These findings may be relevant to the mechanism of activation and inactivation of HRI in the absence and presence of heme in situ.

Animals↗
PubMed1983

Isolation and possible relevance of Thermoactinomyces candidus proteinases in farmer's lung disease.

The thermophilic actinomycetes are the most common etiological agents causing hypersensitivity pneumonitis. Antigen preparations of these organisms contain proteolytic activity. Further investigation of the proteinases of the thermophilic actinomycetes was undertaken to determine whether this activity may contribute directly to the pathogenesis of hypersensitivity pneumonitis and pulmonary mycotoxicosis. The presence of proteolytic activity in aerosolized dust from moldy silage was demonstrated, and antibodies to two proteolytic enzymes from Thermoactinomyces candidus were found in the blood of farmer's lung patients who had been sensitized to this organism. These two enzymes were isolated from culture filtrate antigen preparations that had been partially characterized with respect to the proteolytic activities and their interaction with human serum proteinase inhibitors. Both proteinases belonged to the serine class of endopeptidases. Neither proteinase was inhibited by alpha 1-proteinase inhibitor or alpha 1-antichymotrypsin. Both proteinases were inhibited by alpha 2-macroglobulin. One of the proteinases had elastase activity. Inhalation of these proteinases apparently does occur, and they may induce an inflammatory response in the lungs since they are not inhibited by the main proteinase inhibitors protecting the lung.

Antibodies, Fungal↗
PubMed1983

Cheese worker's hypersensitivity pneumonitis.

A patient employed in a plant where blue cheese was manufactured developed hypersensitivity pneumonitis to Pencillium roqueforti. Symptoms of cough, dyspnea, and malaise, and findings of bibasilar crackles, reduced lung volumes, hypoxemia, and bilateral infiltrates on chest roentgenogram, resolved after she left the workplace. Bronchoalveolar lavage revealed a high percentage of lymphocytes. Antibody to P. roqueforti was demonstrated in serum and lavage fluid. To our knowledge this case represents a new occurrence of hypersensitivity lung disease in the cheese manufacturing industry in the United States.

Adult↗
PubMed1983

Cartilage metabolism during growth retardation following irradiation of the head of the neonatal rat.

The heads of 2-day-old male and female rats were irradiated with a single dose of 600 rads X irradiation, a dose which is known to stunt body weight, tibial length, and tail length, in order to ascertain its effects on synthesis by cartilage of sulfated proteoglycans, DNA, chondroprotein, and collagen as determined by utilization of [35S]sulfate, [Me-3H]thymidine, [1-14C]leucine, and [3,4-3H]proline, respectively. Data have been collected at 20-21, 23, 41-45, and 70-71 days of age. In comparison to controls, growth in body weight, tibial length, and tail length was significantly retarded in irradiated rats of both sexes. Although slow catch-up growth was observed with respect to tail length in both sexes and tibial length in females, a significant deficit in body weight in irradiated rats in both sexes remained at 70-71 days. Cartilage metabolism as evidenced by incorporation of the labeled substances showed no significant disturbance just prior to weaning (20-21 days) or after completion of the principal growth surge (70-71 days). Reduced sulfate and thymidine incorporation attributable to a brief period of undernutrition associated with weaning occurred in head-irradiated rats immediately following weaning (23 days). Increased isotope incorporation occurred at 41-45 days of age in cartilage of irradiated rats incubated with labeled sulfate, leucine, and proline; it did not increase with labeled thymidine. We conclude that neonatal head irradiation slows the rate of growth through the age of most rapid postnatal growth in normal rats. The pattern of cartilage metabolism during this time can be the result either of stimulation by a factor other than somatomedin, or selective inhibition of cartilage thymidine incorporation acting in combination with somatomedin.

Animals↗
PubMed1982

Comparison of the polypeptide composition of cystic fibrosis plasma with normal plasma by high resolution electrophoresis.

Cystic fibrosis and normal plasma proteins were compared by the method of high resolution two-dimensional electrophoresis in polyacrylamide gels. For the first dimension, samples were treated with urea and dithiothreitol and then subjected to isoelectric focusing in pH gradients of 3.5-10.0 or 5.0-8.0. The second dimension involved sodium dodecyl sulfate electrophoresis into gels of 10-20% polyacrylamide gradients. In one "blind" experiment, an attempt to segregate 12 plasma samples into six cystic fibrosis and six normals based on the polypeptide patterns was unsuccessful. Experiments using known cystic fibrotic and normal plasma samples (three further samples of each), depleted of albumin prior to electrophoresis, also failed to confirm the presence of cystic fibrosis related proteins or peptides. We have not been able to substantiate, by electrophoretic means, changes of sialic acid content of any plasma glycoprotein which might be expected to occur, for example, as a result of the postulated altered sialyltransferase activity in cystic fibrosis liver.

Blood Proteins↗
PubMed1982

Disproportionate growth of organs and body weight following glucocorticoid treatment of the rat fetus.

The effects of pharmacologic doses of dexamethasone, betamethasone, and cortisone given to pregnant rats on gestation days 12 and 13 were studied in mothers and fetuses on gestation day 21. Dexamethasone and betamethasone treatment resulted in a significant decrease in maternal and fetal weight gain, occurrence of cleft palate and omphalocele, and impaired growth of fetal heart, liver, adrenals, kidneys, and skeletal muscle. Cortisone produced fewer developmental defects and less impairment of growth of fetal weight and other organs. Corynebacterium kutscheri infections occurred in pregnant rats treated with dexamethasone but not in rats treated with betamethasone or cortisone. The analogues had widely different effects on organ growth and on the ratios of organ weight to body weight. The findings indicate that proportionate growth of fetal organs and body weight is disturbed by glucocorticoid treatment in rats.

Animals↗
PubMed1982

Comparison of the structure and aspects of the proteinase-binding properties of cystic fibrotic alpha-macroglobulin with normal alpha 2-macroglobulin.

Considerable attention has been focused recently on alpha 2-macroglobulin (alpha 2M), a major endopeptidase inhibitor in blood plasma, as a possible source of the primary defect in cystic fibrosis (CF). We report here studies designed to compare the structure of CF alpha 2M with normal alpha 2M to determine if there is a difference. The physicochemical properties of purified alpha 2M as revealed by various electrophoretic techniques, covalent proteinase binding properties, and primary structural studies on a variety of partial hydrolyzates of CF alpha 2M and normal alpha 2M are compared. These studies were carried out on eight different individual isolates of CF alpha 2M and three age-matched normal alpha 2M preparations and alpha 2M isolated from fetal cord blood. Three properties of CF alpha 2M were studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE): (1) the existence of four identically-sized subunits in the native molecule (10), (2) the cleavage of this subunit into fragments of approximately 100,000 daltons upon interaction with proteinases (10), and (3) the cleavage of an alkaline/heat sensitive bond to produce 120,000 and 60,000 dalton fragments (11). Both CF and normal alpha 2M were cleaved to the extent of 79-87%, CF alpha 2M behaves identically with normal alpha 2M with regard to all these properties. Salvesen and Barrett (24) have demonstrated that varying proportions of several [125I]-labeled proteinases form SDS-stable, non-reducible links to normal alpha 2M. Two of the CF alpha 2M preparations were studied to determine if similar covalent binding of proteinases occurred. The positions of the labeled and % of proteinase bound bands in SDS/reduced PAGE system were identical for normal alpha 2M and CF alpha 2M. These results indicate that CF alpha 2M behaves normally with regard to covalent binding of proteinases. Qualitative comparison of the peptide fragments separated by SDS-PAGE or isoelectric focusing of CF and normal alpha 2M produced by partial proteolysis with trypsin, chymotrypsin or Staphylococcus aureus V-8 proteinase did not reveal any difference unique to CF alpha 2M. The cyanogen bromide fragmentation studies and the cysteine cleavage studies also indicated that no major change in the positions of methionyl residues or cysteinyl/cystinyl residues has occurred in CF alpha 2M. The failure of all these different studies and those reported by others to demonstrate any differences between CF and normal alpha 2M makes it highly unlikely that there is a primary defect in alpha 2M in CF.

Adolescent↗
PubMed1981

Regional differences in the effects of glucocorticoids on maturation of the fetal skeleton of the rat.

The effects of glucocorticoids on fetal growth and development in the rat were investigated. Pregnant rats were injected subcutaneously on gestational days 12 and 13 with betamethasone (0.18 or 0.42 mg), with dexamethasone (0.12 or 0.24 mg), or with physiological saline. Fetuses at day 21 of gestation were weighed, cleared, and stained for calcification with Alizarin Red S. Fetal weight was significantly reduced at both dose levels of each steroid; a greater reduction occurred with the higher dose. Retardation of growth and of calcification of bones in the axial skeleton occurred at both doses; there was greater retardation with the high dose. In the appendicular skeleton there was enhanced calcification of some bones with the low dose, and a retardation of calcification with the high dose of each steroid. The present findings show that different regions of the fetal skeleton may respond discordantly to the effect of glucocorticoids depending on the dose.

Animals↗
PubMed1981

Skin testing in farmers' lung disease.

Intradermal skin tests with a culture filtrate antigen of Micropolyspora faeni grown on a synthetic medium were performed on patients with farmers' lung disease (FLD) and well farmers with and without antibodies to a panel of FLD antigens. Seventy-five percent of the FLD patients, 79% of the well farmers with M. faeni antibody, and 5% of well farmers without M. faeni antibody had a 2+ or greater intradermal immediate skin-test reaction. Prausnitz-Küstner (P-K) reactions were positive using serum of M. faeni immediate skin test-positive FLD patients. IgG-rich fractions from a staphylococcal protein A-Sepharose column of such serum contained the sensitizing factor whereas IgG-depleted fractions did not. M. faeni-specific IgE could not be detected in serum by a polystyrene radioimmunoassay. Positive late-onset (6-hr) skin tests occurred only in FLD patients and farmers with precipitating antibody. Biopsy specimens of the 6-hr reactions revealed a generalized dermal and perivascular polymorphonuclear infiltrate with deposits of immunoglobulin and complement about blood vessels. The skin-sensitizing factor noted in FLD patients and well farmers with antibody is not disease specific. This factor appears to be associated with the IgG-rich fraction of serum, and its role in the pathogenesis of FLD is unclear.

Enzyme-Linked Immunosorbent Assay↗
PubMed1981

Characterization of synthetic medium antigens of Micropolyspora faeni and Thermoactinomyces candidus.

A synthetic (Syn) medium was developed for growth of Micropolyspora faeni and Thermoactinomyces candidus, and optimum conditions for culture filtrate antigen production were found to be 3 days for T. candidus and 9 to 12 days for M. faeni. Appearance of proteolytic activity in the culture fluid supernatant coincided with a decrease in precipitating antigen content, protein content, and number of proteins on polyacrylamide gel electrophoresis (PAGE), probably as a result of proteolysis. The results suggest that protein content, number protein bands on PAGE, and proteolytic activity are predictive of precipitating antigen content. Antigens prepared in Syn medium were compared to those produced by the double-dialysis procedure and found to contain adequate amounts of antigenic material of sufficient quality to warrant clinical studies of their usefulness in the diagnosis of hypersensitivity pneumonitis.

Animals↗
PubMed1981

Angiotensin-converting enzyme in farmer's lung.

Serum levels of angiotensin-converting enzyme were measured in a group of patients with farmer's lung and a group of precipitin-positive subjects with no history of farmer's lung. The levels did not differ significantly from control subjects matched for age and smoking history. The mean serum level of angiotensin-converting enzyme in a group of acutely ill patients with farmer's lung was significantly reduced. An acute challenge of three patients with Micropolyspora faeni did not produce an increase in serum levels of angiotensin-converting enzyme. These studies suggest that an increased serum level of angiotensin-converting enzyme can be a diagnostic aid in making a differential diagnosis between sarcoidosis and farmer's lung.

Antigens, Bacterial↗