Biomedical subjects

S E Brown

Publications and source records attributed to S E Brown.

At least 37 records · Page 2Linked to original sources

PubMed2000

Preliminary X-ray crystallographic and NMR studies on the exonuclease domain of the epsilon subunit of Escherichia coli DNA polymerase III.

The structured core of the N-terminal 3'-5' exonuclease domain of epsilon, the proofreading subunit of Escherichia coli DNA polymerase III, was defined by multidimensional NMR experiments with uniformly (15)N-labeled protein: it comprises residues between Ile-4 and Gln-181. A 185-residue fragment, termed epsilon(1-185), was crystallized by the hanging drop vapor diffusion method in the presence of thymidine-5'-monophosphate, a product inhibitor, and Mn(2+) at pH 5.8. The crystals are tetragonal, with typical dimensions 0.2 mm x 0.2 mm x 1.0 mm, grow over about 2 weeks at 4 degrees C, and diffract X-rays to 2.0 A. The space group was determined to be P4(n)2(1)2 (n = 0, 1, 2, 3), with unit cell dimensions a = 60.8 A, c = 111.4 A.

Catalytic Domain↗

PubMed2000

Endometrial glycodelin-A expression in the luteal phase of stimulated ovarian cycles.

OBJECTIVE: To determine if controlled ovarian hyperstimulation (COH) affects the endometrial expression of glycodelin-A (GdA). DESIGN: Prospective, controlled study. SETTING: Tertiary infertility clinic. PATIENT(S): Fifteen oocyte donors undergoing COH cycles and 19 natural-cycle control patients. INTERVENTION(S): COH, endometrial biopsies. MAIN OUTCOME MEASURE(S): Immunohistochemical scoring of endometrial GdA expression, morphologic endometrial dating, and serum E2, LH, and P4 concentrations. RESULT(S): GdA was detected in all subjects throughout the implantation window period. Immunolocalization was demonstrated in the endometrial glands and not in the stroma or on the surface. A significantly increased proportion of GdA-staining endometrial cells were noted in COH cycle patients as compared with natural-cycling control patients throughout the window of embryo implantation. Both cycle types demonstrated increasing GdA expression throughout the late luteal phase. A significant positive correlation was noted between GdA expression and serum E2 levels (r = 0.5, P<.001) in natural cycles and advanced histology in COH cycles (r = 0.63, P=.01). Neither LH nor P4 were correlated with endometrial GdA expression. CONCLUSION(S): COH cycles have a significantly increased endometrial GdA expression throughout the implantation phase of the luteal cycle when compared with normal menstrual cycles. The increased expression may affect implantation during COH cycles.

Adult↗

PubMed2000

Histochemical localization of endometrial insulin-like growth factor binding protein-1 and -3 during the luteal phase in controlled ovarian hyperstimulation cycles: a controlled study.

OBJECTIVE: To determine if controlled ovarian hyperstimulation (COH) affects the endometrial expression of IGFBP-1 and IGFBP-3. DESIGN: Prospective, controlled study. SETTING: Tertiary infertility clinic. PATIENT(S): Eighteen oocyte donors undergoing COH cycles and 17 natural cycle controls. INTERVENTION(S): Controlled ovarian hyperstimulation, endometrial biopsies. MAIN OUTCOME MEASURE(S): Immunohistochemical scoring of endometrial IGFBP-1 and -3 expression, morphological endometrial dating, and serum estradiol (E(2)), LH, and progesterone (P(4)) concentrations. RESULT(S): No statistically significant difference was observed between natural and stimulated cycles in change in IGFBP-1 or -3 over standardized cycle days throughout the window of embryo implantation (days 17-24). The IGFBP-1 and -3 expression was zero or near zero for both the natural and COH cycles until day 12-13. Both IGFBPs showed increased production throughout the secretory phase. Advanced endometrial histology (>/=1 day) in glands and stroma was noted in COH cycles. Significant positive correlations of E(2) and P(4) were noted with IGFBP-1 and -3 but not with advanced endometrial morphology in the COH cycles. CONCLUSION(S): The COH cycles have no significantly increased endometrial IGFBP-1 or -3 expression throughout the implantation phase of the luteal cycle compared with normal menstrual cycles. Both IGFBPs were absent in the proliferative phase and increased throughout the secretory portion of the embryo implantation window.

Adult↗

PubMed2000

Evaluation of outpatient hysteroscopy, saline infusion hysterosonography, and hysterosalpingography in infertile women: a prospective, randomized study.

OBJECTIVE: To compare the diagnostic accuracy, pain scores, and procedure length of outpatient hysteroscopy (OHS), hysterosalpingography (HSG), and saline infusion hysterosonography (SIS) for evaluation of the uterine cavity of infertile women. DESIGN: Prospective, randomized, investigator-blind study. SETTING: Tertiary infertility clinic. PATIENT(S): Forty-six consecutive infertile women. INTERVENTION(S): Outpatient HSG, OHS, and SIS, followed by operative hysteroscopy (HS). MAIN OUTCOME MEASURE(S): Uterine abnormalities, procedure length, and subjective pain. RESULT(S): Fifty-nine percent of infertile subjects were found to have an abnormality on at least one of three outpatient uterine evaluations. When compared with the case of definitive operative HS, 60% of abnormalities were correctly classified by HSG, 72% by OHS, and 52% by SIS (P: NS). When comparing all combinations of 2 outpatient screening tests to operative hysteroscopy, 68% were correctly classified by HSG/OHS, 58% by HSG/SIS, and 64% by OHS/SIS (P: NS). The average time length for the OHS was 9.1 min., which was significantly greater than for both HSG (average, 5.3 min) and SIS (average, 6.1 min.) (P<.0001 for both). HSG and SIS were not statistically different regarding procedure time length. The average pain score (0-10) for SIS was 2.7, compared with 5.8 and 5.3 for HSG and OHS, respectively. Both HSG and OHS mean pain scores were significantly greater than the SIS mean. CONCLUSION(S): OHS, SIS, and HSG were statistically equivalent regarding evaluation of uterine cavity pathology in infertile women.

Adult↗

PubMed2000

Structure and location of a ferritin gene of the yellow fever mosquito Aedes aegypti.

We have isolated and sequenced a genomic clone encoding the 24- and 26-kDa ferritin subunits in the mosquito Aedes aegypti (Rockefeller strain). The A. aegypti gene differs from other known ferritin genes in that it possesses an additional intron and an unusually large second intron. The additional intron is located within the 5' untranslated region, between the CAP site and the start codon. The second intron contains numerous putative transposable elements. In addition, unlike the human and rat ferritin genes, the A. aegypti ferritin gene is a single copy gene, located at 88.3% FLpter on the q-arm of chromosome 1. Primer extension analysis indicates that the A. aegypti ferritin gene has multiple transcriptional start sites. A differential usage of these sites is observed with varied cellular iron concentrations.

5' Untranslated Regions↗

PubMed2000

Does a multi-disciplinary health degree provide a satisfactory post-registration course for nurses? A follow-up survey of health science studies graduates.

The purpose of this investigation was to find out if nurses who had chosen to take a particular post-registration health science studies degree (rather than a nursing degree) were satisfied, retrospectively, with the usefulness of this type of degree to their professional development and career progress. The investigation also examined if these graduates were remaining in nursing, if they were active in nursing research, and the role of their employers in the choice of degree course. Questionnaires were sent to 10 cohorts of nurse graduates from one health science studies course. The idea to study for a degree had usually come from the nurses themselves, and most employers had taken little interest in the course content. The nurses showed a high level of satisfaction with their chosen course and considered that it had significantly improved their job performance. Almost all the graduates had remained in nursing; many had been involved in carrying out research, or hoped to be research-active in future. More than half the respondents had gained a post-graduate qualification or were in the process of studying for one. It is suggested from the evidence gathered that in this case a broad health degree seems to have provided a useful and satisfactory educational experience for nurses.

Adult↗

PubMed1999

NMR structure of the N-terminal domain of E. coli DnaB helicase: implications for structure rearrangements in the helicase hexamer.

BACKGROUND: DnaB is the primary replicative helicase in Escherichia coli. Native DnaB is a hexamer of identical subunits, each consisting of a larger C-terminal domain and a smaller N-terminal domain. Electron-microscopy data show hexamers with C6 or C3 symmetry, indicating large domain movements and reversible pairwise association. RESULTS: The three-dimensional structure of the N-terminal domain of E. coli DnaB was determined by nuclear magnetic resonance (NMR) spectroscopy. Structural similarity was found with the primary dimerisation domain of a topoisomerase, the gyrase A subunit from E. coli. A monomer-dimer equilibrium was observed for the isolated N-terminal domain of DnaB. A dimer model with C2 symmetry was derived from intermolecular nuclear Overhauser effects, which is consistent with all available NMR data. CONCLUSIONS: The monomer-dimer equilibrium observed for the N-terminal domain of DnaB is likely to be of functional significance for helicase activity, by participating in the switch between C6 and C3 symmetry of the helicase hexamer.

Amino Acid Sequence↗

PubMed1999

Vertebrate exon trapping methods: implications for transcript mapping with mosquito DNA.

Exon trapping methods have played an important role in the development of transcript maps. In one in vivo vertebrate method, exons in a genomic DNA clone are transcribed, and they are recovered without any a priori information on the nature of the expressed transcript. The only requirement is that the genomic DNA clone contains exons separated by intervening introns that are removed by splicing during mRNA transcription and that the splice donor and acceptor site sequences follow those used by vertebrates. It is not known whether invertebrate splice donor and acceptor sites from genes that contain short introns will be processed correctly using an in vivo vertebrate exon trapping method. In this report, an analysis of mosquito splice sites using software designed to identify exons in genomic DNA sequence suggested that the vertebrate exon trapping method could recognize mosquito introns and exons. When a mosquito genomic DNA clone containing the D7 gene was tested experimentally, this method failed to recognize and process small introns (< 63 bp) faithfully. In spite of this failure, exons and exon fragments were recovered. The implications of these findings and their application to map-based positional cloning in mosquito genomics is discussed.

Animals↗

PubMed1999

Cellulose and calcium lower the incidence of chemically-induced colon tumors in rats.

In a 30-week preliminary study and a follow-up 22-week study (2 x 2 factorial), dimethylhydrazine (DMH) injections effectively induced colon tumors in Fischer-344 rats. How this incidence of colon tumors might be affected by cellulose (preliminary study) or by calcium and folic acid (follow-up study) was examined. Cellulose in the diet appeared to provide some protection against DMH-induced colon tumors, but the protective effect of calcium was more evident; normal levels of calcium (500 mg per 100 g diet), but not of folic acid (0.1 mg per 100 g diet), provided protection against colon tumors. The effect due to calcium was observed whether viewed in terms of total number of tumors (p < 0.01) or number of tumors per tumor-bearing rat (p < 0.01).

Adenocarcinoma↗

PubMed1999

Change in riverine epilithic extracellular enzyme activity in response to fish farm effluent.

Extracellular aminopeptidase and phosphatase activity was measured at the surfaces of submerged stones collected from a river upstream and downstream of a fish farm discharge. Aminopeptidase activity was largely indifferent to the discharge. Phosphatase activity, in contrast, was depressed downstream of the outfall. Thus, there was no evidence of enhanced epilithic extracellular enzyme activity to facilitate biopurification downstream of the fish farm discharge.

Aminopeptidases↗

PubMed1999

Fluorescence in situ hybridization landmarks for chromosomes of culicoides variipennis (Diptera: Ceratopogonidae).

Because the three chromosomes of Culicoides variipennis (Coquillett) are morphologically indistinguishable, physical landmarks were needed so that the chromosomes can be identified uniquely and oriented unambiguously before initiating the construction of a physical map based on FISH (fluorescence in situ hybridization). When repetitive sequence clones p1887 and K8.1a8 were labeled with digoxigenin and probe K8a.2G2 was labeled with biotin-11-dUTP and digoxigenin, the 3 chromosomes could be differentiated unambiguously when visualized with specific band-pass filters. This provided the basis for C. variipennis FISH landmark probes that enabled the identification and orientation of all 3 pairs of chromosomes. Using this multicolor FISH labeling strategy, probes that provide unique landmarks for the C. variipennis FISH physical map have been found and may be used in all FISH reactions where an unknown probe is placed to metaphase chromosomes of C. variipennis. A physical map of the C. variipennis genome will provide the foundation for map-based positional cloning of the gene(s) that control vector competence for the bluetongue viruses.

Animals↗

PubMed1999

First-generation physical map of the Culicoides variipennis (Diptera: Ceratopogonidae) genome.

Recombinant cosmids labeled with biotin-11-dUTP or digoxigenin by nick translation were used as in situ hybridization probes to metaphase chromosomes of Culicoides variipennis (Coquillett). Paired fluorescent signals were detected on each arm of sister chromatids and were ordered along the 3 chromosomes. Thirty-three unique probes were mapped to the 3 chromosomes of C. variipennis (2n = 6): 7 to chromosome 1, 20 to chromosome 2, and 6 to chromosome 3. This work represents the first stage in generating a physical map of the genome of C. variipennis.

Animals↗

PubMed1999

FISH landmarks for barley chromosomes (Hordeum vulgare L.).

Barley metaphase chromosomes (2n = 14) can be identified by fluorescence in situ hybridization (FISH) and digital imaging microscopy using heterologous 18S rDNA and 5S rDNA probe sequences. When these sequences are used together, FISH landmark signals were seen so that all 7 chromosomes were uniquely identified and unambiguously oriented. The chromosomal location of the landmark signals was determined by FISH to a barley trisomic series using the 18S and 5S probes labeled with different fluorophores. The utility of these FISH landmarks for barley physical mapping was also demonstrated when an Amy-2 cDNA clone and a BAC clone were hybridized with the FISH landmark probes.

Aedes↗

PubMed1998

Intensive lifestyle changes for reversal of coronary heart disease.

CONTEXT: The Lifestyle Heart Trial demonstrated that intensive lifestyle changes may lead to regression of coronary atherosclerosis after 1 year. OBJECTIVES: To determine the feasibility of patients to sustain intensive lifestyle changes for a total of 5 years and the effects of these lifestyle changes (without lipid-lowering drugs) on coronary heart disease. DESIGN: Randomized controlled trial conducted from 1986 to 1992 using a randomized invitational design. PATIENTS: Forty-eight patients with moderate to severe coronary heart disease were randomized to an intensive lifestyle change group or to a usual-care control group, and 35 completed the 5-year follow-up quantitative coronary arteriography. SETTING: Two tertiary care university medical centers. INTERVENTION: Intensive lifestyle changes (10% fat whole foods vegetarian diet, aerobic exercise, stress management training, smoking cessation, group psychosocial support) for 5 years. MAIN OUTCOME MEASURES: Adherence to intensive lifestyle changes, changes in coronary artery percent diameter stenosis, and cardiac events. RESULTS: Experimental group patients (20 [71%] of 28 patients completed 5-year follow-up) made and maintained comprehensive lifestyle changes for 5 years, whereas control group patients (15 [75%] of 20 patients completed 5-year follow-up) made more moderate changes. In the experimental group, the average percent diameter stenosis at baseline decreased 1.75 absolute percentage points after 1 year (a 4.5% relative improvement) and by 3.1 absolute percentage points after 5 years (a 7.9% relative improvement). In contrast, the average percent diameter stenosis in the control group increased by 2.3 percentage points after 1 year (a 5.4% relative worsening) and by 11.8 percentage points after 5 years (a 27.7% relative worsening) (P=.001 between groups. Twenty-five cardiac events occurred in 28 experimental group patients vs 45 events in 20 control group patients during the 5-year follow-up (risk ratio for any event for the control group, 2.47 [95% confidence interval, 1.48-4.20]). CONCLUSIONS: More regression of coronary atherosclerosis occurred after 5 years than after 1 year in the experimental group. In contrast, in the control group, coronary atherosclerosis continued to progress and more than twice as many cardiac events occurred.

Aged↗

PubMed1998

Cloning and expression of the human galanin receptor GalR2.

Galanin is a peptide hormone which modulates a wide variety of physiological processes, including secretion, muscle contraction, cognitive function, the reproductive axis, and feeding. Two galanin receptor subtypes, GalR1 and GalR2, have been cloned; however, for GalR2 only the rat sequence has been reported in the literature. Our cloning of human GalR2 reveals its amino acid sequence to be 85% identical to rat GalR2 and 39% identical to human GalR1. Binding of [125I]galanin to the human GalR2 receptor transiently expressed in COS-7 cells was saturable (Kd = 0.24 nM +/- 0.06 nM) with a receptor density of 383 +/- 66 fmol/mg protein. Human galanin(1-30) bound with high affinity to the human GalR2 receptor, with a Ki value of 0.86 +/- 0.12 nM. With the identification of a second galanin receptor subtype, the specific functions of human galanin receptor subtypes can now begin to be addressed.

Amino Acid Sequence↗

PubMed1997

Characterization of a pretranscriptional pathway for induction by phenobarbital of cytochrome P450 3A23 in primary cultures of adult rat hepatocytes.

Our laboratory has proposed that phenobarbital (PB), a typical lipophilic agent that induces some members of the supergene family of liver microsomal cytochromes P450 (e.g., CYP2B1/2 and CYP3A23), acts through a complex process inhibitable by the presence of growth hormone (GH), the absence of some components of the extracellular matrix, or a disrupted cytoskeleton. To verify that these manipulations of the culture environment block specific steps in the PB induction pathway rather than simply exerting nonspecific or toxic effects on CYP2B1/2 gene transcription, we have now examined PB induction of CYP3A23, a gene known to also be transcriptionally activated by dexamethasone (DEX) through a "nonclassical" pathway apparently involving the glucocorticoid receptor. We found that in primary cultures of adult rat hepatocytes treated with PB, induction of CYP3A23 mRNA, just as we reported for induction of CYP2B1/2 mRNA, required the use of Matrigel (a reconstituted basement membrane) and was blocked by the presence of cytoskeletal inhibitors (colchicine or cytochalasins) or of physiologic concentrations of GH in the culture medium. Moreover, PB induction of CYP3A23 and of CYP2B1/2 mRNAs was greatly diminished by inhibitors of cAMP-dependent protein kinase (PKA). In striking contrast, induction of CYP3A23 mRNA by DEX was unaffected by any of these alterations of the culture conditions that block its induction by PB. We conclude that the effects of extracellular matrix, GH, disruption of the cytoskeleton, and activation of cAMP-dependent protein kinase, pharmacologically define multiple, pretranscriptional steps in the pathway(s) for PB induction of liver cytochromes P450.

Animals↗

PubMed1997

Kinetic control of the dissociation pathway of calmodulin-peptide complexes.

The mechanism of dissociation reactions induced by calcium chelators has been studied for complexes of Drosophila calmodulin with target peptides, including four derived from the skeletal muscle myosin light chain kinase target sequence. Reactions were monitored by fluorescence stopped-flow techniques using a variety of intrinsic probes and the indicator Quin2. For most of the complexes, apparently biphasic kinetics were observed in several fluorescence parameters. The absence of any obvious relationship between dissociation rates and peptide affinities implies kinetic control of the dissociation pathway. A general mechanism for calcium and peptide dissociation was formulated and used in numerical simulation of the experimental data. Unexpectedly, the rate of the slowest step decreases with increasing [peptide]/[calmodulin] ratio. Numerical simulation shows this step could contain a substantial contribution from a reversible relaxation process (involving the species Ca2-calmodulin-peptide), convolved with the following step (loss of C-terminal calcium ions). The results indicate the potentially key kinetic role of the partially calcium-saturated intermediate species. They show that subtle changes in the peptide sequence can have significant effects on both the dissociation rates and also the dissociation pathway. Both effects could contribute to the variety of regulatory behavior shown by calmodulin with different target enzymes.

Aminoquinolines↗

PubMed1997

Mechanisms of alcohol impairment of recovery from mechanically denuded areas made within cultured rat hepatocytes.

The effect of ethanol on the ability of a denuded hepatocyte cell surface to recover is unknown. We therefore determined the effect of ethanol on the rate of renewal of mechanical wounds made in near-confluent monolayers of primary cultures of rat hepatocytes. We found that ethanol exerted a dose-dependent effect to impair rat hepatocyte recovery and that at least 12 hours of exposure to ethanol was required to induce this impairment. The effect of ethanol to impair recovery of denuded areas of epithelium was not seen in two established renal tubular epithelial cell lines. Ethanol impairment of rat hepatocyte recovery could be blocked by an alcohol dehydrogenase inhibitor (4-methyl pyrazole) and potentiated by an inhibitor of aldehyde dehydrogenase (pargyline). The effect of ethanol to inhibit rat hepatocyte recovery of denuded areas was not associated with any change in hepatocyte cell surface expression of the beta1 integrin subunit as determined by flow cytometry. These results suggest that acetaldehyde is responsible for ethanol inhibition of hepatocyte recovery from mechanical injury and that this impairment occurs independent of cell surface expression of the beta1 integrin subunit.

Animals↗