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Biomedical subjects

R D Roberts

Publications and source records attributed to R D Roberts.

At least 19 recordsLinked to original sources
PubMed2000

Monoalleleic transcription of the insulin-like growth factor-II gene (Igf2) in chick embryos.

A polymorphism in the igf2 gene of chickens was identified using NlaIII (GenBank accession number AF218827). In some embryos, the igf2 alleles were expressed monoallelically from either maternal or paternal alleles. These data demonstrate that genomic imprinting is not confined to mammalian vertebrates and suggest that genomic imprinting evolved at an early stage of vertebrate evolution. The observations that the igf2 gene is imprinted in a minority of embryos suggest that the imprinting in birds is unrelated to embryonic growth. Genome imprinting may provide opportunities for evolution of genes in a nonexpressed state. In poultry breeding, the presence of imprinted genes may make a major contribution to unequal performance in reciprocal matings between commercial lines.

Alleles↗
PubMed1999

Mitogenic effects of fibroblast growth factors on chicken granulosa and theca cells in vitro.

We have investigated the role that fibroblast growth factors (FGFs) may play in the rapid growth of preovulatory ovarian follicles in chickens. Granulosa and theca cells, dissected from the follicles of laying hens, were cultured in vitro and treated with FGF-1, FGF-2, FGF-5, and FGF-7. The synthesis of DNA by cultured cells was measured by incorporation of [(3)H]thymidine, which was added to the cultures. FGF-1 and -2 increased the synthesis of DNA in a dose-dependent manner in both cell types; however, FGF-5 and -7 had no effect in this respect. When genistein, a tyrosine kinase inhibitor, was added to these cultures, the synthesis of DNA due to FGF-2 was abolished. Treatment of cells with the glycosaminoglycans heparan sulphate and chondroitin sulphate had no effect on FGF-2-induced mitogenesis, while heparin inhibited it. Addition of a glycosaminoglycan antagonist, hexadimethrine bromide, to FGF-2-treated cultures inhibited DNA synthesis due to FGF-2, although not completely. Our data show that FGF-1 and FGF-2 are mitogenic for chicken granulosa and theca cells, and indicate that the actions of FGF-2 may be mediated via both tyrosine-kinase-type and glycosaminoglycan-type receptors on the surface of these cells.

Animals↗
PubMed1998

Emotional intelligence: in search of an elusive construct.

The view that emotional intelligence should be included within the traditional cognitive abilities framework was explored in 3 studies (total N = 530) by investigating the relations among measures of emotional intelligence, traditional human cognitive abilities, and personality. The studies suggest that the status of the emotional intelligence construct is limited by measurement properties of its tests. Measures based on consensual scoring exhibited low reliability. Self-report measures had salient loadings on well-established personality factors, indicating a lack of divergent validity. These data provide controvertible evidence for the existence of a separate Emotion Perception factor that (perhaps) represents the ability to monitor another individual's emotions. This factor is narrower than that postulated within current models of emotional intelligence.

Adolescent↗
PubMed1994

Insulin-like growth factor-I in the ovary of the laying hen: gene expression and biological actions on granulosa and thecal cells.

Concentrations of insulin-like growth factor-I (IGF-I) were measured in granulosa and thecal tissue dissected from the three largest follicles in the ovaries of laying hens. The higher concentration was found in extracts of granulosa (0.82 +/- 0.01 pmol/g wet wt) and theca (0.36 +/- 0.02), both of which were greater than that in liver extracts (0.25 +/- 0.01). RNA was extracted from these tissues, and by using reverse transcription and the polymerase chain reaction with primers specific for chicken IGF-I, both granulosa and thecal tissue were shown to express chicken IGF-I mRNA. Granulosa and thecal cell cultures were established and used to measure IGF binding sites and the response to exogenous IGF peptides in terms of DNA synthesis. Both cell types bound [125I]IGF-I, which was displaced by IGF-I, IGF-II, and insulin in descending order of potency, characteristic of a type-I IGF receptor. Treatment of granulosa and thecal cell cultures with IGF-I resulted in a dose-dependent increase in [3H]thymidine incorporation into DNA by both cell types. LH, but not FSH, stimulated DNA synthesis in cultured granulosa cells but not in cultured thecal cells. This effect was enhanced in granulosa cells by the addition of IGF-I to the culture medium. These data are consistent with an autocrine or paracrine role for IGF-I within the developing ovarian follicle of the domestic hen.

Animals↗
PubMed1994

Physician financial relationships in the new regulatory environment.

In recent months, physicians have been under scrutiny by the federal government with respect to their financial relationships with both drug manufacturers and home care companies. This heightened scrutiny can be attributed, in part, to the attention that has been placed on health care fraud and abuse in this country as a major cause of rising health care costs. Federal investigators currently are examining physician financial relationships in light of the Medicare/Medicaid antikickback statute to determine whether certain payments made to physicians are intended as inducements to refer patients or to prescribe certain products. "Health Law" is a regular feature of Physician Executive contributed by Epstein Becker & Green. Mark Lutes of the law firm's Washington, D.C., offices serves as column editor.

Drug Industry↗
PubMed1991

The power of health care value-adding partnerships: meeting competition through cooperation.

Given the hypercompetitive health care industry, proposing cooperation as a means to survive and prosper appears radical. This article develops a case for the formation of a health care value-adding partnership as a viable, if not preferred, alternative to the integrated health care system owned and controlled by a single entity. The conceptual and the practical aspects of obtaining voluntary cooperation are addressed, and examples of successful value-adding partnerships are presented.

Continuity of Patient Care↗
PubMed1989

The RHJ/Le rhino mutant: description of a unique murine model of autoimmunity.

The BALB/c HuDI-hrrh rhino mutant, which is no longer available, was an unusual murine model with prominent hepatic inflammation and fibrosis. The current report describes the early appearance of hepatic portal tract inflammation and antinuclear antibodies in the RHJ/Le mouse, a related rhino mutant which is distributed from a commercial source. All homozygous RHJ/Le rhino (hrrh hrrh) mice examined serially from 2 to 18 months of age developed inflammation of hepatic portal tracts. In 81 per cent of mice, portal and central veins were infiltrated with mononuclear cells. Focal infiltrates were found in salivary, Harderian and lacrimal glands and in the pancreas. Isolated animals had myositis involving skeletal muscle and myocardium. Heterogeneous antinuclear antibodies were detected in sera from 100 per cent of rhino mice and antibodies to DNA were present in 28 per cent of mice aged 6 months. Homozygous HRS/J hairless (hr/hr) and BALB/c controls failed to show consistent abnormalities in exocrine glands or liver. We conclude that the RHJ/Le rhino mutant spontaneously develops antinuclear antibodies and mononuclear cell infiltration in liver and exocrine glands. These animals provide unique opportunities to examine inflammatory lesions localized to specific target organs in an animal model of autoimmunity.

Animals↗
PubMed1988

Improving the quality and quantity of whole blood supply: limits to voluntary arrangements.

The inadvertent transmission of AIDS virus through contaminated whole blood has shaken the viability of the American voluntary blood supply system. For the first time since the voluntary donor system replaced the commercial blood system, there are widespread doubts about the ability of blood suppliers to meet the nation's increasing health care demands. This paper presents a framework for analyzing blood collection. First, we critique the existing literature on blood collection, arguing that its focus on donor motivation is difficult to integrate with policy analysis. We then present a specific model of the individual's decision to donate blood as a comparison of the costs and benefits of donating. The current system of collecting whole blood relies on donors receiving only altruistic benefits. We explore the limits of this approach to dealing with the quantity and quality problems presented by the AIDS virus. Alternative approaches to blood collection which allow personal benefits--such as donor designation or monetary payments--may be necessary to supply the nation's blood demands in the future.

Acquired Immunodeficiency Syndrome↗
PubMed1986

The pathophysiology and response to steroid therapy in sarcoidosis.

Fourteen patients with early sarcoidosis were prospectively studied over a period of 12-24 months. After baseline physiologic measurements they were treated with 40 mg of prednisone daily for 8 weeks and the measurements were repeated. Thereafter, the steroid dosage was reduced to 0-10 mg every other day and the measurements were repeated between the 12th and 24th month. Relatively normal lung volumes (VC, FRC, RV, TLC) and low DLCO increased with 8-week intensive steroid treatment and fell to below the pretreatment levels when the steroid was either tapered or stopped. The Vmax50-air, Vmax50-He, FEF25-75, upstream conductance (Gus) increased during intensive treatment whereas the RL fell and the FEV1/FVC ratio did not change. The CC/TLC, CV/VC, delta N2, CLdyn/CLst, delta Vmax50 were abnormal in many patients and did not change after 8 weeks of steroid treatment. We concluded that the obstructive defect is common in early sarcoidosis, predominantly in small airways and patchy in nature; the functional derangement is always improved by intensive and adequate steroid therapy and worsened when the drug is tapered or stopped.

Humans↗
PubMed1983

Low-melting phenytoin prodrugs as alternative oral delivery modes for phenytoin: a model for other high-melting sparingly water-soluble drugs.

Phenytoin is a high-melting, weakly acidic, and sparingly water-soluble drug. Because of these physicochemical properties, phenytoin is subject to erratic bioavailability in a variety of dosage forms both in its acidic as well as sodium salt forms. A homologous series of 3-acyloxymethyl derivatives of phenytoin (acetyl through decanoyl) were synthesized and various physicochemical properties measured. The prodrugs were more readily soluble in various metabolizable glycerol esters such as tributyrin, trioctanoin, and triolein than phenytoin. The solubility of the prodrugs in the various organic vehicles studies was closely correlated to the melting point of the prodrug: the lower the melting point the greater the solubility. The cleavage rates of the prodrugs in plasma and tissue homogenates followed a parabolic relationship with chain length. The prodrug, 3-pentanoyloxymethyl-5,5-diphenylhydantoin when administered in tributyrin gave superior oral phenytoin bioavailability in rats when compared with sodium phenytoin administered as an aqueous solution.

Administration, Oral↗
PubMed1983

Effects of sarcoid and steroids on angiotensin-converting enzyme.

Serum angiotensin-converting enzyme (ACE) has been claimed to be a useful guide in the treatment of pulmonary sarcoidosis. We reviewed the clinical course of 36 patients with sarcoidosis who had ACE levels determined on 2 or more occasions during the course of treatment with prednisone for a total of 55 paired observations. There was a clinical deterioration in 13 instances. Of these 13, there was a rise in ACE level in only 7. There was a clinical improvement in 19 instances. Of these 19, only 12 had a fall in ACE level. There was a negative correlation (r = -0.80) between changes in steroid dose and serum ACE level. Of 23 instances where steroids were increased, there was a fall in ACE level. Thus, ACE levels were not useful for following disease activity in patients during a change in medication.

Adrenal Cortex Hormones↗