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Biomedical subjects

C Stevens

Publications and source records attributed to C Stevens.

At least 37 records · Page 2Linked to original sources
PubMed1994

Ganciclovir: treatment of cytomegalovirus in immunocompromised individuals.

Ganciclovir is synthetic antiviral agent that interferes with the CMV DNA synthesis. Administered intravenously, the antiviral drug can effectively stop the CMV herpes virus from replicating in adolescents and adults. CMV does pose a serious threat to immunocompromised individuals. Nursing care of patients receiving ganciclovir should include a complete assessment, predosing laboratory work and a complete drug and allergy history. Proper administration of ganciclovir, observation of side effects, and documentation are the responsibility of the nephrology nurse.

Cytomegalovirus Infections↗
PubMed1993

Validity and reliability of three methods used in the diagnosis of Raynaud's phenomenon. The UK Scleroderma Study Group.

Three different assessment methods for the classification of Raynaud's phenomenon (RP) were compared. These were (i) a previously validated method using colour charts supplemented with a short questionnaire, (ii) answers to a questionnaire based on criteria derived from the consensus opinion of a group of clinicians, and (iii) individual clinician's assessment using standard descriptions based upon the same consensus view. We report the results of a study involving six clinicians and 30 subjects investigating the level of repeatability between the three methods and also the reliability between the six clinicians. There did not exist any overall systematic bias between the six clinicians. Further, agreement between them, as assessed by the kappa statistic, ranged from moderate to good. However, there did exist systematic bias between the results from all three of the classification approaches with agreement between them ranging from only poor to moderate. We conclude that the previously validated colour chart assessment is too insensitive to detect RP. Further, a structured questionnaire based on perceived clinician's opinion could not reproduce clinicians' classification in practice. By contrast, supplying clinicians with standard descriptions did yield a reliable classification system for RP.

Humans↗
PubMed1993

Cellular biology of bone resorption.

Past knowledge and the recent developments on the formation, activation and mode of action of osteoclasts, with particular reference to the regulation of each individual step, have been reviewed. The following conclusions of consensus have emerged. 1. The resorption of bone is the result of successive steps that can be regulated individually. 2. Osteoclast progenitors are formed in bone marrow. This is followed by their vascular dissemination and the generation of resting preosteoclasts and osteoclasts in bone. 3. The exact pathways of differentiation of the osteoclast progenators to mature osteoclasts are debatable, but there is clear evidence that stromal cells support osteoclast generation. 4. Osteoclasts are activated following contact with mineralized bone. This appears to be controlled by osteoblasts that expose mineral to osteoclasts and/or release a factor that activates these cells. 5. Activated osteoclasts dissolve the bone mineral and digest the organic matter of bone by the action of agents secreted in the segregated microcompartments underlying their ruffled borders. The mineral is solubilized by protons generated from CO2 by carbonic anhydrase and secreted by an ATP-driven vacuolar H(+)-K(+)-ATPase located at the ruffled border. The organic matrix of the bone is removed by acid proteinases, particularly cysteine-proteinases that are secreted together with other lysosomal enzymes in the acid environment of the resorption zone. 6. Osteoclastic bone resorption is directly regulated by a polypeptide hormone, calcitonin (CT), and locally, by ionized calcium (Ca2+) generated as a result of osteoclastic bone resorption. 7. There is new evidence that osteoclast activity may also be influenced by the endothelial cells via generation of products including PG, NO and endothelin.

Animals↗
PubMed1993

Osteoclast function and its control.

Bone resorption appears to be dependent on a range of processes. It requires an adequate number of osteoclasts to access bone mineral. These osteoclasts must be activated by a mechanism which is dependent upon prior osteoblastic stimulation. A range of factors then contribute to the formation of a functionally effective resorptive hemivacuole. These entail osteoclast adhesion to the bone surface leading to the formation of a sealing zone. Only then can subsequent processes such as H+ ion transport, enzyme secretion and matrix digestion become effective. Thus, any one process is potentially limiting to resorption and is a potential target for regulation. Long-range regulation takes place through the action of hormones, of which the mode of action of calcitonin has been the subject of recent investigations in isolated osteoclasts. Such studies have shown a possible involvement of distinguishable receptor subtypes, the occupancy of which may activate at least two types of triggering mechanism. It is likely that an eventual influence on motility properties through G protein mediation accounts for the actions of this hormone and of related peptides such as amylin and CGRP at the cellular level. Similar pathways may contribute to shorter range modulation of osteoclast activity by increases in ambient Ca2+. Finally, there is recent evidence for a contribution of endothelial cell-derived product to osteoclast regulation.

Animals↗
PubMed1993

Changes in progesterone and oestrogen receptor mRNA and protein during maternal recognition of pregnancy and luteolysis in ewes.

This study characterized changes in levels of mRNA and protein for endometrial oestrogen receptors (ERs) and progesterone receptors (PRs) during luteolysis and maternal recognition of pregnancy. For cyclic and pregnant ewes, endometrium was collected on days 10, 12, 14, or 16 post-oestrus (4 ewes/day for each status) for the measurement of ER and PR mRNA and protein. The amount of receptor mRNA is expressed in relative units above background, measured from radiographs of dot-blot hybridization of total endometrial RNA with ER and PR cDNAs. At hysterectomy, jugular vein blood samples were collected and assayed for progesterone, total corpus luteum weight was recorded and, in vitro, endometrial oxytocin-stimulated inositol phosphate formation was estimated. In pregnant ewes, plasma progesterone increased gradually between days 10 and 16 (P < 0.01), corpus luteum weight was stable at approximately 0.8 g and oxytocin did not stimulate endometrial formation of inositol phosphates in vitro. In contrast, in cyclic ewes, plasma progesterone decreased from day 10 to day 16 (P < 0.01), corpus luteum weight decreased after day 14 to approximately 0.48 g (P = 0.05) and oxytocin stimulated an increase of approximately 1300% in the endometrial formation of inositol phosphates on day 16. cDNAs specifically hybridized with 1.6 and 3.1 kb transcripts for PR mRNA and a 6.5 kb transcript for ER mRNA. In cyclic ewes, the amount of PR mRNA increased from day 10 to maximum levels on days 14-16. The number of PRs decreased from day 10 (2.25 pmol/mg DNA) to day 12 (0.98 pmol/mg DNA) and then increased from day 14 to day 16 (2.8 pmol/mg DNA). In pregnant ewes, PR mRNA levels were greatest on days 10-12 and decreased by approximately 50% by day 16. In contrast, the number of PRs was relatively unchanged from day 10 to day 16 (1.53 to 1.03 pmol/mg DNA). In cyclic ewes, the amount of ER mRNA was lowest at day 10 and increased fivefold by day 16. The number of ERs remained relatively unchanged from day 10 to day 14 (6.07 pmol/mg DNA) and increased by day 16 (16.12 pmol/mg DNA). In pregnant ewes, ER mRNA decreased by approximately 80% from day 12 to day 16. Similarly, the number of ERs decreased from day 10 to day 16 (5.41 to 2.05 pmol/mg DNA). Correlations between ER mRNA and PR mRNA (r = 0.68), ERs and PRs (r = 0.50) and ER mRNA and ERs (r = 0.50) were high (P < 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Galactose oxidase of Dactylium dendroides. Gene cloning and sequence analysis.

The gaoA gene, encoding the secreted copper-containing enzyme galactose oxidase, has been isolated from the Deuteromycete fungus Dactylium dendroides. Degenerate oligonucleotide primers were designed from amino acid sequence data for use in the polymerase chain reaction. A 1.4-kilobase DNA fragment amplified from genomic DNA was used to screen a genomic library constructed in ZAP. A strongly hybridizing clone was rescued as a pBluescript derivative, pGAO9, by in vivo excision. The sequence of 3466 nucleotides of pGAO9 insert DNA was determined by progressively designing sequencing primers. The translation product of the single long open reading frame matches the available galactose oxidase peptide sequence data, which represents 42% of the residues in the protein. The mature enzyme has 639 residues, which have been assigned to a 1.7-A electron density map (Ito, N., Phillips, S. E. V., Stevens, C., Ogel, Z. B., McPherson, M. J., Keen, J. N., Yadav, K. D. S., and Knowles, P. F. (1991) Nature 350, 87-90). The gene lacks introns and encodes an mRNA of approximately 2.5 kilobases with three transcription initiation start points at least 324 nucleotides upstream of the translation start site. Multiple ATG codons are present between the transcription initiation region and the start of the mature protein; two in-frame ATGs could encode the initiating Met residue to give proteins with 89 or 41 residue N-terminal leader peptides. The shorter potential leader has N-terminal features characteristic of a secretion signal sequence and may also contain a pro-sequence processed by an enzyme specific for a monobasic (arginine) cleavage site, as proposed for other fungal genes. The codon bias of gaoA is characteristic of other filamentous fungal genes. No significant homologies exist between galactose oxidase and other protein sequences available in data bases.

Amino Acid Sequence↗
PubMed1992

Tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6 expression in inflammatory bowel disease.

The etiology of ulcerative colitis (UC) and Crohn's disease (CD) remains enigmatic. Infiltrating intestinal macrophages are capable of producing the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and interleukin-6 (IL-6). We investigated the presence of IL-6, TNF-alpha and IL-1 beta mRNA transcripts in inflammatory bowel disease (IBD), normal, and other inflammatory intestinal specimens utilizing the polymerase chain reaction (PCR). TNF-alpha mRNA levels did not very between inflammatory bowel disease and control specimens. IL-1 beta mRNA levels were highest in active UC and noninflammatory bowel disease inflammatory specimens while IL-6 mRNA levels were highest in active IBD specimens. Infiltrating T cells, macrophages, and B cells were identified as sources of IL-6 protein in inflammatory bowel disease specimens by immunofluorescent staining. IL-6 transcripts were elevated only in active inflammatory bowel disease specimens, suggesting that IL-6-mediated immune processes are ongoing in the inflammatory mucosal environment of CD and UC.

B-Lymphocytes↗
PubMed1992

Three-dimensional structure of galactose oxidase: an enzyme with a built-in secondary cofactor.

Galactose oxidase is a copper-containing enzyme, which catalyses stereospecific oxidation of primary alcohols. The three-dimensional structure of the enzyme has been determined in this study by X-ray crystallography at high resolution. The molecule is almost entirely composed of beta-structures and consists of three domains. The arrangement of 28 beta-strands in the second domain is of particular interest, having seven four-stranded antiparallel beta-sheets with pseudo-sevenfold symmetry. The copper site has square-pyramidal coordination with two histidines, one tyrosine and one exogenous ligand at the equatorial sites and another tyrosine at the axial site. The most intriguing structural feature is a covalent bond between C epsilon 1 of Tyr-272, which is one of the equatorial ligands, and S gamma of Cys-228. This unexpected thioether bond, and Trp-290 stacked above it, strongly supports the presence of a tyrosine free radical in the enzyme as a 'built-in' secondary cofactor. Calculation of the molecular surface shows a small pocket at the copper site and suggests a substrate-binding model, which can explain the substrate specificity. A model for the catalytic mechanism, involving a tyrosine free radical and basic tryptophan, is also proposed.

Amino Acid Sequence↗
PubMed1992

Reliability of skin involvement measures in scleroderma. The UK Scleroderma Study Group.

Two methods have been proposed to quantify the extent of skin involvement in scleroderma. These are (1) a scoring system which quantifies and summates this severity rating in 17 areas of skin surface and (2) a method estimating the percentage of skin involvement using a shaded manikin. We report on a study comparing the inter-observer reliability of these two approaches using the ratings of six clinicians on 12 patients. Systematic bias between observers was noted with both methods, but inter-observer agreement, as-assessed by the intraclass correlation coefficient (ICC), was higher with the score method. The manikin method resulted in a greater degree of disagreement between the observers, as well as a higher amount of random error, reflecting the difficulty of defining the bounds of abnormal skin. Despite the presence of bias, the score method is the preferred method for assessing the level of skin involvement.

Analysis of Variance↗
PubMed1991

Novel thioether bond revealed by a 1.7 A crystal structure of galactose oxidase.

Galactose oxidase is an extracellular enzyme secreted by the fungus Dactylium dendroides. It is monomeric, with a relative molecular mass of 68,000, catalyses the stereospecific oxidation of a broad range of primary alcohol substrates and possesses a unique mononuclear copper site essential for catalysing a two-electron transfer reaction during the oxidation of primary alcohols to corresponding aldehydes. Recent evidence arguing against a Cu(III)-Cu(I) couple implies the existence of a second redox-active site proposed to involve pyrroloquinoline quinone or a tyrosine radical. We now report the crystal structure of galactose oxidase at 1.7 A resolution. This reveals a unique structural feature at the copper site with a novel thioether bond linking Cys 228 and Tyr 272 in a stacking interaction with Trp 290. We propose that these molecular components stabilize the protein free-radical species essential for catalysis and thus provide a 'built-in' secondary cofactor. This feature may represent a new mechanism for mediating electron transfer in metalloenzymes in the absence of exogenous cofactors.

Binding Sites↗
PubMed1991

The role of interleukin-6 in mitogenic T-cell activation: detection of interleukin-2 heteronuclear RNA by polymerase chain reaction.

It has been documented that interleukin-6 (IL-6) supports the proliferation of purified, anti-CD3-stimulated murine T cells. We found that stimulation of human peripheral blood mononuclear cells (PBMCs) with anti-CD3 induced a significant accumulation of IL-6 mRNA, indicating that antigen-mediated T-cell activation may involve IL-6 release from accessory cells. Phytohemagglutinin (PHA) had little effect upon IL-6 gene expression. In keeping with these findings, anti-IL-6 reduced but did not abolish anti-CD3-mediated proliferation of PBMCs, but had no significant effect upon PHA-stimulated proliferation. The addition of recombinant (r) IL-6 enhanced the proliferation of anti-CD3-stimulated PBMCs and increased the accumulation of IL-2 mRNA in PHA-stimulated PBMCs during the first 5 hr of culture. Nuclear run-off experiments did not reveal significant changes in IL-2 transcription in PHA plus rIL-6-treated PBMCs attempting to assume that IL-6 mediates stabilization of IL-2 mRNA. However, monitoring of partially spliced IL-2 mRNA by polymerase chain reaction revealed a clear increase in IL-2 heteronuclear RNA. Thus IL-6 increases the rate of IL-2 transcription which was not detectable by conventional in vitro transcription assays. We conclude that anti-CD3 triggers T-cell proliferation through a process that is partially but not entirely dependent upon release of IL-6. IL-6, in turn, supports IL-2 transcription. Insofar as anti-CD3 mimics antigen-triggered activation of the T-cell receptor complex, IL-6 appears to support the early immune response by augmenting antigen-triggered IL-2 gene expression.

Antibodies, Monoclonal↗
PubMed1991

Localization of calcitonin gene-related peptide in human esophageal Langerhans cells.

Previously undescribed calcitonin gene-related peptide-immunoreactive intraepithelial cells were seen in specimens of esophageal mucosa obtained by biopsy or surgical resection from 14 individuals. These calcitonin gene-related peptide-immunoreactive cells were sparsely seen in normal mucosa but increased markedly in esophagitis. They were inaccessible to routine histological stains, but osmication showed them as dendritic forms resembling Langerhans cells of the skin. Their cytological identity was determined with immunocytochemical tests for human antigenic markers such as Ia, HLA-DR, and OKT6 for Langerhans cells, Leu-M5 and Leu-M3 for intraepithelial macrophages, CD3 and TCR-1 for T-lymphocytes, Leu-14 for B-lymphocytes, S-100 for Merkel cells, and chromogranin for amine precursor uptake and decarboxylation cells. Double localization showed that calcitonin gene-related peptide immunoreactivity colocalized with Ia, HLA-DR, and OKT6 but not with the other markers. These studies show that intraepithelial Langerhans cells in the esophageal mucosa contain calcitonin gene-related peptide, which may serve as an immunomodulator.

Calcitonin Gene-Related Peptide↗
PubMed1991

The effects of the intestinal glucosidase inhibitor acarbose on cholesterogenesis in corpulent rats.

1. Groups of lean and obese LA/N-cp and obese Type II diabetic SHR/N-cp rats were fed semisynthetic diets with or without the alpha-glucosidase inhibitor acarbose (ACB, 100 mg/kg diet, p.o.) from 8 until 15 weeks of age, and measures of fasting serum total cholesterol (TC), insulin (INS), and hepatic HMG-CoA synthase activity determined at the end of the study. 2. ACB was without marked effect on mean food intake in either strain or either phenotype, and resulted in less weight gain and decreased adipose mass in obese LA/N-cp rats. INS was greater in the obese than the lean phenotype of both strains, and ACB resulted in greater reductions in INS in obese LA/N-cp than in obese LA/N-cp rats. 3. Serum TC concentrations were greater in the obese than in the lean phenotype of both strains, and ACB resulted in decreases in TC in both strains and in lower beta:alpha lipoprotein cholesterol ratios in obese LA/N-cp rats. Liver HMG Co-A synthase activity was greater in lean than obese rats and ACB resulted in normalization of enzyme activity in obese LA/N-cp but not SHR/N-cp rats. 4. These results confirm the hypercholesterolemia which occurs in the obese phenotype of the corpulent rat strains, and indicates that ACB may bring about significant reductions in body weight and fatness, TC, and in improved beta:alpha lipoprotein ratios and HMG-CoA synthase activity in obesity.(ABSTRACT TRUNCATED AT 250 WORDS)

Acarbose↗
PubMed1991

Crohn's disease associated with autoimmune neutropenia.

We report a 29-year-old woman with a 20-year history of Crohn's disease and neutropenia. Because of repeated complications of Crohn's disease, she has undergone three intestinal resections and also has had recurrent skin abscesses, sinusitis, and pneumonia. Persistent neutropenia has been noted throughout the course of her disease, and antineutrophil antibodies have been detected in her serum and that of her younger brother, who also has Crohn's disease and neutropenia. We discuss autoimmune neutropenia in the context of other autoimmune manifestations of Crohn's disease and speculate as to its possible contributory role in the pathogenesis of Crohn's disease.

Adult↗
PubMed1991

The effects of immunosuppressive agents on in vitro production of human immunoglobulins.

We have evaluated the effects of CsA, methylprednisolone (MP), 6-mercaptopurine (6-MP), and FK506 on T cell-dependent and T cell-independent immunoglobulin production. FK506 and 6-MP were potent inhibitors of IgG and IgM production by PWM-stimulated peripheral blood mononuclear cells, which depend on the presence of T cells. CsA was less effective in this system and MP actually enhanced IgG and IgM production. In order to assess the direct effects of these various immunosuppressive agents on B cells, we utilized human B cell lines representing different stages of B cell differentiation. The B cell lines CESS and SKW6.4 exhibit increased production of IgG and IgM, respectively, in response to interleukin-6. These cells represent activated, but not fully differentiated, B cells. CsA inhibited IL-6-induced IgG production by CESS cells by 64% at 100 ng/ml and 6-MP inhibited this response by 82% at 250 ng/ml. Neither CsA nor 6-MP effectively inhibited IL-6-induced IgM production by SKW6.4 cells. MP at 250 ng/ml inhibited IL-6-induced IgG production by 89%, but enhanced IL-6-induced IgM production more than two-fold. FK506 did not inhibit IL-6-induced IgG or IgM production, suggesting that it has no direct effect on the ability of B cells to respond to this differentiation factor. These experiments clearly demonstrate that CsA, MP and 6-MP have direct inhibitory effects on the response of human B cells to IL-6. In contrast, FK506 has no direct effect on these B cells lines, but is more potent than the other agents at inhibiting T cell-dependent immunoglobulin production.

Anti-Bacterial Agents↗