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Biomedical subjects

D Rodbard

Publications and source records attributed to D Rodbard.

At least 109 records · Page 6Linked to original sources
PubMed1980

Limited adrenal reserve in paracoccidioidomycosis: cortisol and aldosterone responses to 1-24 ACTH.

Adrenal function in twenty-three patients with paracoccidioidomycosis (South American Blastomycosis) has been assessed by measuring the response to adrenocortical stimulation with 1-24 ACTH. Two patients with overt Addison's disease showed very low basal levels and the complete absence of an increase in either cortisol or aldosterone secretion. Six patients showed probable diminished adrenal reserve in terms of cortisol and three patients showed diminished reserve in terms of aldosterone function. These findings indicate an incidence of significant hypoadrenalism in 44% of hospitalized patients with disseminated paracoccidioidomycosis.

Adolescent↗
PubMed1980

Kinetic analysis of cooperative ligand binding: applications to the insulin receptor.

We have developed a mathematical model for the kinetics of cooperative binding, assuming a linear relationship between the dissociation rate constant kd' and receptor occupancy, and have extensively explored its properties. Under ideal conditions changes in receptor occupancy by the hormone are coupled to changes in its dissociation rate. However, the correlation between receptor occupancy and the apparent dissociation rate can be obscured or even reversed in the presence of minor nonspecific binding, incomplete separation of bound and free ligand, and/or when there is a short lag period between the true onset of dissociation and measurement of "initial" binding. The present model and computer simulation studies suggest ways to reconcile otherwise conflicting observations. These results provide a basis for improved experimental design, to test the ability of this class of cooperative models to describe hormone binding systems.

Allosteric Regulation↗
PubMed1979

Increased insulin binding to erythrocytes in anorexia nervosa: restoration to normal with refeeding.

We studied [125I] insulin binding to circulating cells in patients with anorexia nervosa (eight females), in the basal cachectic state (seven patients) and after weight gain (eight patients) and compared the values to those obtained in 17 normal volunteers (eight females and nine males). Untreated patients showed increased insulin binding to receptors on erythrocytes (mean +/- S.E.M., 12.2 +/- 0.99 per cent of total); after weight gain, these increased levels returned to normal (6.8 +/- 0.42 vs 6.7 +/- 0.63 per cent of total). Increased binding was due to an increased number of receptors per cell, with little or no change in receptor affinity. In five patients (one untreated, four treated), results of [125I] insulin binding to erythrocytes correlated closely (r = 0.982) with results obtained with monocytes. We conclude that in patients with anorexia nervosa, insulin binding to receptors is altered and that the abnormality is corrected by restoration of normal food intake and body weight.

Adolescent↗
PubMed1979

Isolation and characterization of proteoglycans from porcine ovarian follicular fluid.

Monomer proteoglycan was isolated from porcine ovarian follicular fluid by isopycnic CsCl centrifugation in the presence of 4 M guanidine HCl and protease inhibitors. The elution profile of the D1 preparation on Sepharose 2B was similar to that of monomer proteoglycan from bovine nasal cartilage, indicating a similar molecular size. Follicular fluid proteoglycans consist of about 20% protein, 50% dermatan sulfate, and 20% oligosaccharides rich in sialic acid, galactose, mannose, glucosamine, and galactosamine. The amino acid composition of this proteoglycan is significantly different from that of cartilage proteoglycans, with a higher proportion of aspartic acid, threonine, and lysine, and lower amounts of proline and glycine. Alkali-released dermatan sulfate chains are larger on Sepharose 6B (average Mr = 56,000) than chondroitin sulfate chains from cartilage proteoglycans (average Mr = 25,000), and iduronic acid accounts for 9% of total hexuronic acid. Disaccharide units released by chondroitinase ABC consists of 67% 4-sulfated, 22% 6-sulfated, 5% non-sulfated, and 5% disulfated disaccharides. After treatment with 0.05 M NaOH, 1 M NaBH4 at 45 degrees C for 24 h, two major sialic acid-containing oligosaccharides were observed on Sephadex G-25, corresponding to penta- and hexasaccharides. The pentasaccharide contained sialic acid, galactose, glucosamine, and galactosamine in the proportions 1:2:1:1. The galactosamine is O-glycosidically linked to the protein core. This oligosaccharide accounts for approximately 77% of all the sialic acid in the follicular fluid proteoglycans. The hexasaccharide fraction contained sialic acid, galactose, mannose, and glucosamine in the proportions 1:2:1:2. It also contained a small amount of fucose and galactosamine. The linkage of these oligosaccharides to the protein core remains to be determined. The follicular fluid proteoglycans, unlike those from cartilage, do not interact with hyaluronic acid. Digestion with trypsin, chymotrypsin, or plasmin released dermatan sulfate-peptides nearly as small as those released by papain or alkali; in contrast, cartilage proteoglycans were resistant to plasmin and released peptides containing an average of more than four chondroitin sulfate chains after trypsin or chymotrypsin digestion.

Amino Acids↗
PubMed1979

The pulse wave arrival time (QKd interval) in normal children.

The interval between the onset of QRS of the electrocardiogram and the arrival of the pulse wave at the brachial artery, as detected by the appearance of Korotkoff sounds at diastolic pressure (QKd), provides a measure of a pulse wave arrival time, i.e., the sum of the pre-ejection period and a pulse transmission time. This measurement has proven useful in the evaluation of cardiovascular disease, thyroid and catecholamine status, and several other conditions in adults. In order to standardize this measurement in children, measurements were obtained on 63 normal children ranging in age from 7 months to 18 years. Because of the dependence of pulse transmission time on the distance of propagation, the QKd interval (in msec) is related to height (H in cm) by the equation: QKd = 56.6 + 0.797H. By use of this equation one can obtain a "height corrected QKd." Correction for pulse rate is not necessary for resting subjects. These normal ranges permit use of the QKd interval for clinical studies in children. These studies also permit measurement of the mean pulse wave velocity for a group of individuals. PWV (m/sec) increases with age according to the equation: PWV = 2.44 + 0.203 A, (A in years) with a correlation coefficient of r = 0.823. This implies progressive loss of functional elasticity of the major arteries throughout childhood.

Adolescent↗
PubMed1979

Radioiodinated nondegradable gonadotropin-releasing hormone analogs: new probes for the investigation of pituitary gonadotropin-releasing hormone receptors.

Studies of pituitary plasma membrane gonadotropin-releasing hormone (GnRH) receptors using [125I]-iodo-GnRH suffer major disadvantages. Only a small (less than 25%) proportion of specific tracer binding is to high affinity sites, with more than 70% bound to low affinity sites (Ka = 1 x 10(6) M-1). [125I]Iodo-GnRH is also inactivated during incubation with pituitary plasma membrane preparations. Two superactive analongs of GnRH, substituted in positions 6 and 10, were used as the labeled ligand to overcome these problems. Both analogs bound to the same high affinity sites as GnRH on bovine pituitary plasma membranes, though the affinity of the analogs was higher than that of the natural decapeptide (Ka = 2.0 x 10(9), 6.0 x 10(9), and 3.0 x 10(8) M-1 for [D-Ser(TBu)6]des-Gly10-GnRH ethylamide, [D-Ala6]des-Gly10-GnRH ethylamide, and GnRH, respectively. The labeled analogs bound to a single class of high affinity sites with less than 15% of the specific binding being to low affinity sites (Ka approximately equal to 1 x 10(6) M-1). The labeled analogs were not inactivated during incubation with the pituitary membrane preparations. Using the analogs as tracer, a single class of high affinity sites (K1 = 4.0 x 10(9) M-1) was also demonstrated on crude 10,800 x g rat pituitary membrane preparations. Use of these analogs as both the labeled and unlabeled ligand offers substantial advantages over GnRH for investigation of GnRH receptors, allowing accurate determination of changes in their numbers and affinities under various physiological conditions.

Animals↗