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Biomedical subjects

R L Potter

Publications and source records attributed to R L Potter.

At least 19 recordsLinked to original sources
PubMed1991

Connective tissue growth factor: a cysteine-rich mitogen secreted by human vascular endothelial cells is related to the SRC-induced immediate early gene product CEF-10.

Human umbilical vein endothelial (HUVE) cells have been previously reported to express the genes for the A and B chains of PDGF and to secrete PDGF-related factors into culture media. Antihuman PDGF IgG affinity chromatography was used to purify PDGF-related activity from HUVE cell-conditioned media. Immunoblot analysis of the affinity-purified proteins with anti-PDGF IgG and antibodies specific for the A or B chain peptides of PDGF combined with chemotactic and mitogenic assays revealed that the major PDGF immunorelated molecule secreted by HUVE cells is a monomer of approximately 36-38 kD and that less than 10% of the purified biologically active molecules are PDGF A or B chain peptides. Screening of an HUVE cell cDNA library in the expression vector lambda gtl 1 with the anti-PDGF antibody resulted in the cloning and sequencing of a cDNA with an open reading frame encoding a 38-kD cysteine-rich secreted protein which we show to be the major PDGF-related mitogen secreted by human vascular endothelial cells. The protein has a 45% overall homology to the translation product of the v-src-induced CEF-10 mRNA from chick embryo fibroblasts. We have termed this new mitogen connective tissue growth factor.

Amino Acid Sequence↗
PubMed1990

Nucleoside diphosphate kinase from Xenopus oocytes; partial purification and characterization.

We have identified and partially purified a soluble nucleoside diphosphate kinase (NDP kinase) from Xenopus laevis oocytes. The enzyme preparation can catalyze the transfer of phosphate from ATP to all of the major oxy- and deoxynucleotides. It can also catalyze the transfer of a phosphorothioate group from gamma-S-ATP to an acceptor GDP forming gamma-S-GTP. Like NDP kinases from other sources, the catalytic mechanism appears to involve a phosphoenzyme intermediate which can be isolated. Transfer of phosphate from nucleoside triphosphates to protein is rapid, reaching saturation within 1 min following the addition of nucleoside triphosphates. The transfer of phosphate from phosphoprotein intermediate to nucleoside diphosphates is equally fast. While nucleoside diphosphate kinases are generally thought to require magnesium for activity, both the oocyte enzyme preparation and a commercial bovine liver enzyme preparation are only partially inhibited by short (10 min) exposures to 25 mM EDTA. Both enzyme preparations are, however, further inhibited by long incubations with this metal chelator (2 h, 70% inhibition). Zinc enhances the inhibition of NDP kinase by EDTA, but is ineffective on its own. Rapid phosphorylation in the presence of [gamma-32P]ATP and EDTA could be used to identify the phosphoenzyme intermediate in homogenates of Xenopus oocytes and facilitated its isolation. Sodium dodecyl sulfate polyacrylamide gel electrophoresis coupled with autoradiography indicated the presence of only a single phosphorylated species of Mr 21,500 in supernatants of fresh oocyte homogenates. Partial purification of this protein utilizing salt precipitation, hydrophobic-interaction chromatography and an affinity step with Affi-Gel Blue Sepharose resulted in a 100-fold purification and a 29% overall yield of NDP-kinase activity. Size-exclusion chromatography of the purified preparation yielded two peaks containing enzyme activity. They eluted with apparent molecular weights of 45,000 and 70,000, suggesting a native enzyme that is multimeric or associated with other proteins.

Adenosine Triphosphate↗
PubMed1990

Biomedical information, peer review, and conflict of interest as they influence public health.

The peer review process serves a vital role in the publication of biomedical information. When properly functioning, review should focus exclusively on questions of scientific validity and should avoid becoming enmeshed in questions such as "authorization" and "data ownership." We present a case in which the dissenting views of a coinvestigator were suppressed because the principal investigator and grantee institution informed a medical journal that the coinvestigator was not "authorized" to use the data generated by a publicly funded grant and because the editor of a scholarly journal refused to review the dissenting manuscript and to submit that dissent to external reviewers for peer review. The current peer review system, as shown by this case, is unable to embrace dissent within the peer review process and to use dissent to serve scientific truth and the public interest.

Biomedical Research↗
PubMed1989

Role of gamma-aminobutyric acid in antipanic drug efficacy.

All effective pharmacologic agents used to treat panic disorder augment gamma-aminobutyric acid (GABA) transmission. Anxiolytics and antidepressants that lack GABA activity are not effective in panic disorder. To test the hypothesis that GABA activity is a component of antipanic drug efficacy, the authors treated nine medication-free panic disorder subjects with oral baclofen (30 mg/day for 4 weeks) in a double-blind, placebo-controlled crossover trial. Baclofen, a selective GABA agonist, was significantly more effective than placebo in reducing the number of panic attacks and scores on the Hamilton anxiety scale, Zung scale, and Katz-R nervousness subscale. The authors discuss possible mechanisms of antipanic drug efficacy.

Anxiety Disorders↗
PubMed1984

Transition from residency training to academia.

Anxious and depressive reactions during transitions from psychiatry residency to career settings have been reported. The authors describe difficulties encountered in their transition from psychiatry residency to academic psychiatry within the same program. Four stages of transition are described: Termination--a time of separation and grief over losses; Adjustment--a time of ambivalence and uncertainty; Identity Formation--a time of increased productivity and comfort; Consolidation--a time of accomplishment and compatibility of life goals. Women may additionally encounter gender-specific problems in entering a predominantly male profession. The development of supportive relationships within and outside work settings are viewed as the best methods of coping with transitional stress.

Adaptation, Psychological↗
PubMed1983

Regional cell count and respiration in the brain of Rana catesbeiana.

Cell counts were made in three divisions of the bullfrog brain: (1) olfactory lobestelencephalon, (2) diencephalon-mesencephalon, and (3) the hindbrain; average cellular respiration in potassium-enriched Ringer solution and the rate of respiration in sodium-free medium were tested for their possible relationship to the numbers of glia and numbers of neurons in each region. After restoring some of the sodium ions to sodium-free minces, the percent increase in respiration was plotted for each brain segment and compared to the percent of glia per brain division to determine the glial respiratory contribution. Where glial numbers were greater, the potassium-stimulated respiration was greater; where neuronal numbers were greater, the sodium-free respiration was most prominent. The respiration increased most above the sodium-free rate, when sodium ions were added or when the full amount of sodium was present, in the hindbrain, where the glia appear to metabolize more vigorously and the neurons least actively.

Animals↗
PubMed1983

Changes in nucleotide-binding proteins during oocyte maturation in Xenopus laevis.

Photoaffinity nucleotide analogs of ATP and GTP have been used to investigate the purine nucleotide-binding proteins of Xenopus laevis oocytes. These analogs label Xenopus oocyte supernatant proteins in a highly specific manner. The pattern of proteins labeled with these analogs was determined by polyacrylamide gel electrophoresis. A number of changes in this pattern were observed during the time course of progesterone-stimulated maturation in vitro. If one alters the dynamic balance of phosphatase and kinase activities with NaF, these changes are not observed. This photoaffinity approach also provides an assay for the purification of high-affinity nucleotide-binding proteins, including protein kinases, which may be important in the process of oocyte maturation.

Adenosine Triphosphate↗
PubMed1983

Manic-depressive variant syndrome of childhood. Diagnostic and therapeutic considerations.

A case is described of manic-depressive variant syndrome of childhood in a ten-year-old boy. Children with manic-depressive variant syndrome frequently have signs and symptoms of hyperactivity and are often first seen by their pediatrician. The diagnoses of attention deficit disorder, organic mental disorder, borderline personality disorder, and childhood schizophrenia, are discussed with relation to their differentiation from the manic-depressive variant syndrome of childhood. The discussion further describes the early onset of symptoms in this boy and points out how a consideration of this diagnosis might be possible in early childhood, allowing for early inauguration of lithium therapy.

Attention Deficit Disorder with Hyperactivity↗
PubMed1980

The structural domains of cAMP-dependent protein kinase I. Characterization of two sites of proteolytic cleavage and homologies to cAMP-dependent protein kinase II.

The regulatory subunit of cAMP-dependent protein kinase I has been cleaved proteolytically into two structurally independent domains. The larger domain (35K with trypsin or thermolysin and 31K with chymotrypsin) corresponded to the COOH-terminal end of the polypeptide chain and retained the cAMP binding site(s). The smaller domain (11 to 12K with trypsin), corresponding to the NH2-terminal region of the regulatory subunit, contained the region of dimer interaction. In the absence of reducing reagent, the two protomers of the native regulatory subunit and of the smaller domain could be covalently cross-linked by a disulfide bond. In addition to the two major domains, a 15-residue peptide that links the two domains has been isolated and partially characterized. Two major sites on the type I regulatory subunit were susceptible to proteolytic degradation. Site 1, susceptible to cleavage by both trypsin and thermolysin, has the following sequence: LysArg-Arg-Gly-Ala-Ile-Ser-Ala-. Cleavage at this site generated a 35K cAMP-binding fragment. Site 2 contained a chymotryptic cleavage site as well as a secondary tryptic site. The sequence at Site 2 was Val-Arg-Arg-Val-Ile-Ala. Cleavage here generated a 31K cAMP-binding fragment. Both sites contained 2 consecutive basic amino acid residues similar to the corresponding sequence in the type II regulatory subunit; however, in the case of the type I regulatory subunit, the serine at Site 1 does not serve as a site of autophosphorylation. In contrast to the dissociated regulatory subunit, the holoenzyme is partially protected from proteolytic degradation.

Amino Acid Sequence↗