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Biomedical subjects

C Wallace

Publications and source records attributed to C Wallace.

At least 55 records · Page 3Linked to original sources
PubMed1993

Ovine anterior pituitary proopiomelanocortin gene expression is not increased by ACTH secretagogues in vitro.

Recent reports have demonstrated that the secretion of ACTH from sheep anterior pituitary primary cultures is markedly stimulated by arginine vasopressin (AVP) but not by CRF, and that AVP-stimulated ACTH secretion is potentiated by CRF. It has also been reported that AVP increases total ACTH content (secreted plus intracellular ACTH), suggesting that AVP stimulates POMC biosynthesis in the ovine anterior pituitary. These observations differ from the rat, in which CRF is the most potent of the ACTH-releasing factors and the only ACTH secretagogue which stimulates POMC gene expression and biosynthesis. The second messenger pathways which mediate CRF- and AVP-stimulated ACTH release (protein kinase A and protein kinase C, respectively) are the same in sheep and rat corticotrophs. The present studies were undertaken to determine if ovine POMC gene expression, unlike the rat POMC gene, is stimulated by AVP via the protein kinase C pathway. A 295 base pair portion of the ovine POMC gene was isolated using polymerase chain reaction and sequenced. Ovine POMC messenger RNA (mRNA) levels were quantitated using this partial complementary DNA clone in a solution hybridization/nuclease protection assay with cytoplasmic RNA from sheep anterior pituitary primary cultures which had been treated with various combinations of ACTH secretagogues or with glucocorticoids for 18 h. Treatment with AVP, alone or with CRF, greatly increased total and secreted ACTH levels; however, the amount of POMC mRNA in these cells was not significantly increased. Treatments which stimulated secretion to a lesser extent and did not alter total ACTH levels (CRF alone, cAMP alone, or with phorbol ester) were associated with a decrease in POMC mRNA levels relative to untreated cells. Glucocorticoid treatment decreased both total ACTH and POMC mRNA levels. Taken together, the data demonstrate a lack of secretagogue-induced stimulation of POMC mRNA levels concomitant with increased total ACTH levels, an unexpected result given the close association between secretion of POMC-derived peptides and POMC gene expression in other mammalian corticotroph systems.

Adrenocorticotropic Hormone↗
PubMed1993

Management of craniomandibular disorders. Part 1: A craniocervical dysfunction index.

A craniocervical dysfunction index has been developed (based on the Helkimo Dysfunction Index) to comprehensively assess craniocervical dysfunction and to objectively monitor the management of patients who present with these clinical problems. The close functional interrelationship of temporomandibular joints, jaw muscles, and cervical joints and muscles is reviewed, and a mechanism is proposed to explain dysfunctional relationships between these structures. This is the first of three papers stemming from a clinical study that investigated craniomandibular disorders and assessed the effect of routine dental management on craniomandibular and craniocervical dysfunction.

Craniomandibular Disorders↗
PubMed1992

Glutamine and macrophage function.

The effects of glutamine concentration on the phagocytosis of an opsonized antigen, the synthesis of RNA, and the production of interleukin-1 (IL-1) by macrophages were investigated in vitro. A minimum A minimum of 0.125 mmol/L glutamine was required for a significant increase in phagocytosis of opsonized sheep erythrocytes, compared with that recorded for macrophages cultured in the absence of glutamine. The synthesis of 3H-RNA by macrophages also required 0.125 mmol/L glutamine in the culture medium before it was significantly increased above the levels of control cultures. A minimum of 0.03 mmol/L glutamine was required for the induction of significant levels of IL-1 by lipopolysaccharide (LPS)-stimulated macrophages. Therefore, recent findings suggesting that decreases in plasma glutamine resulting from major burn injury, sepsis, trauma, and surgery may be partly responsible for the associated impairment of immune function now have a basis in both phagocytosis and in modulation of the synthesis of IL-1 (the first cytokine of the interleukin cascade that leads to specific immunity) by macrophages, in addition to the previously established dependency of lymphocytes on external sources of glutamine for their replication.

Analysis of Variance↗
PubMed1991

The myocardial ultrastructure in three amphipod species from Lake Baikal.

The heart ultrastructure of several crustacean species has previously been studied. Special interest has been paid to the development of the membrane systems of the cardiac myofiber relative to the different sarcomeric levels. This system seems to give phylogenetic information, but there still remains some uncertainty concerning its reliability. Is it affected by the size of the species, or is there any geographical variation within the different crustacean orders? The aim of this study is to compare the heart ultrastructure of some large amphipids from Lake Baikal(Acanthogammarus albus, Parapallasea puzylli and Poekilogammarus sukaczewi) with smaller amphipods from Europe and Northern America. It is shown that species size and geographical isolation do not seem to affect the membrane systems qualitatively. The isolation and adaptive radiation of the amphipods in Lake Baikal have not brought about any significant changes in the heart ultrastructure which separates them from other amphipod species. These findings support the use of cardiac membrane systems as a phylogenetic tool in the classification of Crustacea.

Actin Cytoskeleton↗
PubMed1990

Modulation of experimental cyclosporine nephrotoxicity by inhibition of thromboxane synthesis.

The clinical usefulness of Cyclosporine is limited by its intrinsic nephrotoxicity. A potential mechanism of CsA-mediated renal injury may involve an alteration in the prostaglandin-thromboxane (PG-TX) cascade. In our studies, pharmacological manipulation of the PG-TX system in normal and nephrotoxic animals was conducted using a specific thromboxane synthetase inhibitor U63,557A, and the cyclooxygenase inhibitor indomethacin. Administration of CsA 50 mg/kg/day for 7 days to Sprague Dawley rats resulted in a 99% increase in urinary thromboxane B2 excretion compared with controls (48.2 +/- 3.1 vs. 24.2 +/- 2.6 ng/24 hr, P less than 0.001), while plasma levels remained unchanged. Glomerular and tubular function was significantly reduced at this time, with a 48% decrease in creatinine clearance (CCr), and a 25% reduction in the fractional excretion of sodium (FeNa) (P less than 0.001). Histological injury included cortical tubular vacuolization and necrosis. Administration of indomethacin 8 mg/kg/day to both normal and CsA-treated rats resulted in a significant reduction in prostanoid excretion. Indomethacin alone had no adverse effect on glomerular function; however, when coadministered with CsA an exaggerated decrease in renal function was observed. CCr in this group fell by a further 27% compared with the CsA-50 group, while FeNa decreased by 76% (P less than 0.001). Histologic injury intensified, with an increase in vacuolization and necrosis. In contrast, coadministration of U63,557A with CsA prevented the rise in urinary TXB2 excretion, improved CCr by 20% (P less than 0.05), and restored FeNa to control levels. The severity of CsA-induced vacuolization was significantly diminished. Selective inhibition of thromboxane production may therefore be valuable in mitigating the clinical nephrotoxicity of CsA.

Animals↗
PubMed1990

Cloning, sequence analysis, and expression of genes encoding xylan-degrading enzymes from the thermophile "Caldocellum saccharolyticum".

A lambda recombinant bacteriophage coding for xylanase and beta-xylosidase activity has been isolated from a genomic library of the extremely thermophilic anaerobe "Caldocellum saccharolyticum." Partial Sau3AI fragments of the lambda recombinant DNA were ligated into pBR322. A recombinant plasmid with an insertion of ca. 7 kilobases of thermophilic DNA expressing both enzymatic activities was isolated. The location of the genes has been established by analyzing deletion derivatives, and the DNA sequence of 6.067 kilobases of the insert has been determined. Five open reading frames (ORFs) were found, one of which (ORF1; Mr 40,455) appears to code for a xylanase (XynA) which also acts on o-nitrophenyl-beta-D-xylopyranoside. Another, ORF5 (Mr 56,365), codes for a beta-xylosidase (XynB). The xynA gene product shows significant homology with the xylanases from the alkalophilic Bacillus sp. strain C125 and Clostridium thermocellum.

Amino Acid Sequence↗
PubMed1990

Identifying subclasses of patients with rheumatoid arthritis through cluster analysis.

Nonhierarchical cluster analysis was used to classify 92 patients with rheumatoid arthritis drawn from a community rheumatology practice into 5 groups on the basis of biochemical measures and disease indices. The major differentiating variables were the number of active joints, number of damaged joints, overall disease activity, extraarticular complications, and history of joint surgery. Although the 5 subclasses were equivalent on measures of psychological functioning, they differed systematically on such health outcome measures as mobility, physical activity, and dexterity. Relationships between the taxonomy produced through cluster analysis and conventional classifications are discussed, and directions for further investigation are noted.

Adult↗
PubMed1989

Autoregulation of the ccd operon in the F plasmid.

Mini-F sequences, including the promoter and portions of the ccd region, were inserted upstream of lacZ in promoterless lacZ vectors, and beta-galactosidase specific activities were measured. The results showed that the H (ccdA), G (ccdB) and D genes, together with a promoter, comprise an operon. Ccd operon expression was shown to be regulated at the level of transcription by the G gene product, probably in concert with the H gene product. Thus expression is autoregulated. Expression of the D gene was largely dependent on the ccd promoter, although low levels of transcription from another promoter within the ccd coding region were detected.

Escherichia coli↗
PubMed1989

The pathogenesis of pseudohyperaldosteronism from carbenoxolone.

Carbenoxolone is a derivative of glycyrrhetinic acid used for the treatment of peptic ulcer and gastritis, with salt and water retention a very common side-effect. To investigate this drug-induced pseudohyperaldosteronism we have studied 6 male volunteers before, during and after treatment with carbenoxolone for 7 days. Serum, urinary and sweat electrolytes values were consistent with a mineralocorticoid-like effect of drug administration. PRA was suppressed, and plasma cortisol and aldosterone progressively decreased over treatment. We have also determined by radioreceptor assay the plasma levels of factors which bind to mineralocorticoid receptors in rat kidney cytosol. The levels of these factors were decreased significantly at day 3 of treatment, suggesting a local renal effect of carbenoxolone to amplify endogenous steroid action. At day 7 the radioreceptor assay values were still decreased but significantly higher than at day 3, suggesting in addition a direct mineralocorticoid effect of the drug. We conclude that the drug is initially effective by amplifying the effect of endogenous steroids, and then when the plasma concentrations of the drug or its metabolites reach a higher plasma concentration, there may also be in addition a direct mineralocorticoid-like effect.

Adult↗
PubMed1989

Immunolocalization of renal mineralocorticoid receptors with an antiserum against a peptide deduced from the complementary deoxyribonucleic acid sequence.

We have synthesized three peptides corresponding to putative antigenic regions in the immunogenic domain, hinge region, and carboxy-terminus of the protein. A rabbit immunized with a peptide derived from the hinge region of the receptor produced an antiserum which showed 50% displacement with 20 pg peptide at a final serum dilution of 1:35,000. When the antiserum was immunopurified and applied to sections of intact rat and human kidney it stained cells lining segments corresponding to distal tubule, connecting piece, and initial cortical collecting duct, consistent with the known sites of mineralocorticoid action. In both human (formaldehyde-fixed) and rat (Bouin's solution) there was ample evidence for both nuclear and cytoplasmic staining. The thymus, in which previously we have found [3H]aldosterone binding to be below detection limits, showed little or no staining. Western blot analyses demonstrated that the polyclonal antibody recognized an epitope of the expected molecular size. The availability of antibodies to the mineralocorticoid receptor should, thus, facilitate investigation of the steroid specificity-conferring mechanism which allows mineralocorticoids, but not glucocorticoids, access to the nonselective receptor in the kidney.

Amino Acid Sequence↗