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Biomedical subjects

M Carey

Publications and source records attributed to M Carey.

At least 55 records · Page 3Linked to original sources
PubMed2000

Oxytocin and vasopressin expression in the ovine testis and epididymis: changes with the onset of spermatogenesis.

Contractions of seminiferous tubules and epididymal duct walls promote spermiation and sperm transfer, and they are thought to be stimulated by the related peptides oxytocin and vasopressin. This study tested the hypothesis that if oxytocin and/or vasopressin play a physiological role in sperm shedding and transport, then local or circulating concentrations of these peptides would increase during puberty. Testes, epididymides, and trunk blood of sheep at stages during the first spermatogenic wave were collected, and radioimmunoassay measured significant increases in testicular and epididymal oxytocin during spermatogenesis. No changes were measured in circulating oxytocin or in local or circulating vasopressin. Localization and synthesis was investigated by immunohistochemistry and Western blot analysis employing antibodies recognizing epitopes of either oxytocin, oxytocin-associated neurophysin, vasopressin, or vasopressin-associated neurophysin. Marked expression of both oxytocin and its associated neurophysin in testicular Leydig and epididymal principal cells was seen, and weak neurophysin immunoreactivity was also identified in Sertoli cells. The intercellular distribution of oxytocin varied between regions of the epididymis, suggesting several roles for oxytocin. Vasopressin synthesis was not apparent in either tissue. These results confirm the presence and development of paracrine oxytocinergic systems in the ram testis and epididymis of ram during puberty while questioning the physiological importance of vasopressin.

Animals↗
PubMed2000

The effects of intracuff lidocaine on endotracheal-tube-induced emergence phenomena after general anesthesia.

UNLABELLED: Coughing during emergence from general anesthesia is a common clinical problem. We sought to determine whether inflating the endotracheal tube cuff with lidocaine would create a reservoir of local anesthetic, which might diffuse across the cuff membrane to anesthetize the mucosa, thus attenuating stimulation during extubation of the trachea. A total of 63 patients undergoing elective surgery were enrolled in a prospective, randomized, double-blinded study. After intubation of the trachea with an endotracheal tube, the cuff of the tube was inflated with either lidocaine 4%, saline, or air. After extubation, a blinded observer noted heart rate, blood pressure, oxygen saturation, end-tidal isoflurane concentration, and the incidence of coughing. Data were analyzed by using analysis of variance, Student's t-test, and the chi(2) test for multiple variables. The groups were demographically comparable. There was no difference in hemodynamic or oxygen saturation data between either group. The incidence of coughing was decreased in the lidocaine group for the time period of 4-8 min postextubation (P < 0.05). We conclude that inflation of the cuff of the endotracheal tube can reduce the incidence of coughing in the initial postextubation period, a finding that may benefit certain patient groups in which this is particularly desirable. IMPLICATIONS: Tracheal intubation with an endotracheal tube is often necessary during anesthesia. After intubation, inflating a cuff around the endotracheal tube maintains a seal. This can result in coughing during emergence from anesthesia. Our study shows that inflating the cuff of an endotracheal tube with lidocaine rather than air can reduce the incidence of postextubation coughing.

Adult↗
PubMed2000

Mechanism for specificity by HMG-1 in enhanceosome assembly.

Assembly of enhanceosomes requires architectural proteins to facilitate the DNA conformational changes accompanying cooperative binding of activators to a regulatory sequence. The architectural protein HMG-1 has been proposed to bind DNA in a sequence-independent manner, yet, paradoxically, it facilitates specific DNA binding reactions in vitro. To investigate the mechanism of specificity we explored the effect of HMG-1 on binding of the Epstein-Barr virus activator ZEBRA to a natural responsive promoter in vitro. DNase I footprinting, mutagenesis, and electrophoretic mobility shift assay reveal that HMG-1 binds cooperatively with ZEBRA to a specific DNA sequence between two adjacent ZEBRA recognition sites. This binding requires a strict alignment between two adjacent ZEBRA sites and both HMG boxes of HMG-1. Our study provides the first demonstration of sequence-dependent binding by a nonspecific HMG-box protein. We hypothesize how a ubiquitous, nonspecific architectural protein can function in a specific context through the use of rudimentary sequence recognition coupled with cooperativity. The observation that an abundant architectural protein can bind DNA cooperatively and specifically has implications towards understanding HMG-1's role in mediating DNA transactions in a variety of enzymological systems.

Animals↗
PubMed2000

Effect of calcium or 25OH vitamin D3 dietary supplementation on bone loss at the hip in men and women over the age of 60.

Dietary supplements that prevent bone loss at the hip and that can be applied safely in the elderly are likely to reduce hip fractures. A daily dietary supplement of 750 mg calcium or 15 microg 25OH vitamin D3 on bone loss at the hip and other sites, bone turnover and calcium-regulating hormones were studied over 4 yr in elderly volunteers using a randomized, double-blind, placebo-controlled trial. Bone mineral density (BMD) was measured by dual x-ray absorptiometry and bone structure by radiographs. Calcium biochemistry and bone turnover markers were measured in blood and urine. The 316 women entering the trial had a mean age of 73.7 yr and the 122 men of 75.9 yr. Baseline median calcium intake was 546 mg/day, and median serum 25OH vitamin D3 was 59 nmol/L. On placebo, loss of BMD at total hip was 2% and femoral medulla expansion was 3% over 4 yr. Calcium reduced bone loss, secondary hyperparathyroidism, and bone turnover. 25OH vitamin D3 was intermediate between placebo and calcium. Fracture rates and drop-out rates were similar among groups, and there were no serious adverse events with either supplement. A calcium supplement of 750 mg/day prevents loss of BMD, reduces femoral medullary expansion, secondary hyperparathyroidism, and high bone turnover. A supplement of 15 microg/day 25OH vitamin D3 is less effective, and because its effects are seen only at low calcium intakes, suggests that its beneficial effect is to reverse calcium insufficiency.

Aged↗
PubMed1999

Cooperative assembly of androgen receptor into a nucleoprotein complex that regulates the prostate-specific antigen enhancer.

Prostate cancer is characterized by elevated serum levels of prostate-specific antigen (PSA). PSA gene expression is controlled by an androgen-responsive transcriptional enhancer. Our study suggests that formation of a nucleoprotein complex, encompassing 170 base pairs of enhancer DNA, mediates androgen-responsive PSA enhancer activity. The complex is assembled by cooperative binding of androgen receptor to at least four tandem, nonconsensus androgen response elements (AREs). Systematic mutagenesis of the AREs demonstrated that they act synergistically to stimulate androgen receptor-responsive gene expression. We discuss a mechanism whereby a combination of high androgen receptor levels in the prostate and low affinity AREs contribute to the cell type specificity and activity of the enhancer.

Gene Expression Regulation↗
PubMed1999

Folding of apocytochrome c in lipid micelles: formation of alpha-helix precedes membrane insertion.

Apocytochrome c, which in aqueous solution is largely unstructured, acquires a highly alpha-helical structure upon interaction with lipid. The alpha-helix content induced in apocytochrome c depends on the lipid system, and this folding process is driven by both electrostatic and hydrophobic lipid-protein interactions. The folding kinetic mechanism of apocytochrome c induced by zwitterionic micelles of lysophosphatidylcholine (L-PC), predominantly driven by hydrophobic lipid-protein interactions, was investigated by fluorescence stopped-flow measurements of Trp 59 and fluorescein-phosphatidylethanolamine-(FPE) labeled micelles, in combination with stopped-flow far-UV circular dichroism. It was found that formation of the alpha-helical structure of apocytochrome c precedes membrane insertion. The unfolded state in solution (U(W)) binds to the micelle surface in a helical conformation (I(S)) and is followed by insertion into the lipid micelle, i.e., formation of the final helical state H(L). Binding of apocytochrome c to the lipid micelle (U(W) --> I(S)) is concurrent with formation of a large fraction (75-100%, depending on lipid concentration) of the alpha-helical structure of the final lipid-inserted state H(L). The highly helical intermediate I(S) is formed on the time scale of 3-12 ms, depending on lipid concentration, and inserts into the lipid micelle (I(S) --> H(L)) in the time range of approximately 200 ms to >1 s, depending on lipid-to-protein ratio. The final lipid-inserted helical state H(L) in L-PC micelles has an alpha-helix content approximately 65% of that of cytochrome c in solution and has no compact stable tertiary structure as revealed by circular dichroism results.

Animals↗
PubMed1999

Activity of aortic chemoreceptors in the anaesthetized rat.

1. It has been widely accepted that the rat aortic depressor nerve contains only baroreceptors. However, the experiments which have provided these negative data have employed whole aortic nerve recording. In the present study, the technical difficulties associated with recording single fibres in vivo, from the rat aortic nerve (diameter 25-50 microm), have been surmounted using a small tip, glass suction electrode technique. 2. Upon switching from normocapnic hyperoxia to hypercapnic hypoxia, irregularly firing units (n = 13) appeared and these were significantly excited by intravenous injections of sodium cyanide (20 microg) but not by rises in arterial blood pressure induced by methoxamine (an alpha1-adrenoreceptor agonist; 10 microg). Inhalation of 100 % oxygen rapidly and reversibly silenced, or profoundly reduced, ongoing activity. 3. Intravenous injection of phenylbiguanide (PBG; a 5-HT3 receptor agonist; 8 microg) strongly stimulated the chemoreceptors and was followed by a period of chemodepression (3-21 s). In contrast none of the single fibre baroreceptors recorded (n = 15) were excited by PBG but all significantly increased their discharge in response to the increases in arterial blood pressure associated with methoxamine and cyanide. Both the excitatory and inhibitory effects of PBG on the chemoreceptor fibres were abolished by ondansetron (a 5-HT3 receptor antagonist: 1 mg kg-1 i.v.; n = 5 animals) whilst the chemoexcitatory action of cyanide was preserved. 4. It is concluded that there are chemoreceptor afferents contained in the aortic nerve of the Sprague-Dawley rat. The 5-HT3 receptor appears not to be a pre-requisite for aortic body chemoexcitation.

Anesthesia↗
PubMed1999

Transanal repair of rectocele corrects obstructed defecation if it is not associated with anismus.

PURPOSE: Rectocele is often associated with anorectal symptoms. Various surgical techniques have been described to repair the rectocele. The surgical results are variable. This study evaluated the results of transanal repair of rectocele, with particular emphasis on the impact of concomitant anismus on postoperative functional outcome. METHODS: Fifty-nine consecutive females who underwent transanal repair of rectocele for obstructed defecation were prospectively reviewed. All 59 patients were parous with a median parity of 2 (range, 1-6) and a median age of 58 (range, 46-68) years. The median length of follow-up was 19 (range, 6-40) months. Anismus was detected by anorectal physiology and defecography. The functional outcome was assessed by a standard questionnaire, physical examination, anorectal manometry, neurophysiology, and defecography. The quality-of-life index was obtained using a visual analog scale (from 1-10, with 10 being the best). RESULTS: The functional outcome of transanal repair of rectocele was superior in patients without anismus. Forty (93 percent) of the 43 patients without anismus showed improved evacuation after repair compared with 6 (38 percent) of the 16 patients with anismus (P<0.05). The quality-of-life index improved (9 vs. 4) if anismus was not present (P<0.05). There were minimal complications. Hemorrhage requiring blood transfusion (2 units) occurred in one patient and urinary retention in another. CONCLUSION: Transanal repair of rectocele is safe and, in the absence of anismus, effectively corrects obstructed defecation.

Aged↗
PubMed1999

A mechanism for hormone-independent prostate cancer through modulation of androgen receptor signaling by the HER-2/neu tyrosine kinase.

Prostate cancer progresses from a hormone-sensitive, androgen-dependent stage to a hormone-refractory, androgen-independent tumor. The androgen receptor pathway functions in these androgen-independent tumors despite anti-androgen therapy. In our LAPC-4 prostate cancer model, androgen-independent sublines expressed higher levels of the HER-2/neu receptor tyrosine kinase than their androgen-dependent counterparts. Forced overexpression of HER-2/neu in androgen-dependent prostate cancer cells allowed ligand-independent growth. HER-2/neu activated the androgen receptor pathway in the absence of ligand and synergized with low levels of androgen to 'superactivate' the pathway. By modulating the response to low doses of androgen, a tyrosine kinase receptor can restore androgen receptor function to prostate cancer cells, a finding directly related to the clinical progression of prostate cancer.

Androgens↗
PubMed1999

Clinical reactogenicity of intradermal bacille Calmette-Guérin vaccination.

Clinical, microbiological, and immunologic responses were evaluated in volunteers vaccinated intradermally with bacille Calmette-Guérin (BCG). Most volunteers (98%) developed ulcerative lesions that drained for a mean +/- SE of 4.3 +/- 0.29 weeks. Mycobacterial DNA was detected by a polymerase chain reaction-based amplification technique in biopsy specimens from BCG ulcers 2 weeks after vaccination and in blood specimens 3 days after vaccination. Mycobacteria were cultured from ulcer drainage 2 months after vaccination, demonstrating a prolonged potential risk of contact spread of the vaccine strain. The duration of ulcer drainage was inversely correlated with prevaccination lymphoproliferative (r = -0.515; P < .002) and interferon gamma (r = -0.841; P < .002) responses specific to mycobacteria and directly correlated with postvaccination increases in lymphoproliferative (r = 0.498; P < .002) and interferon gamma (r = 0.688; P < .02) responses specific to mycobacteria. These results demonstrate the clinical reactogenicity of BCG and the potential risk of contact spread of the vaccine strain and suggest that clinical reactogenicity is a trade-off for the induction of protective mycobacterial immunity.

Adolescent↗
PubMed1999

A near-native state on the slow refolding pathway of hen lysozyme.

The refolding of four disulfide lysozyme (at pH 5.2, 20 degrees C) involves parallel pathways, which have been proposed to merge at a near-native state. This species contains stable structure in the alpha- and beta-domains but lacks a functional active site. Although previous experiments have demonstrated that the near-native state is populated on the fast refolding pathway, its relevance to slow refolding molecules could not be directly determined from previous experiments. In this paper, we describe experiments that investigate the effect of added salts on the refolding pathway of lysozyme at pH 5.2, 20 degrees C. We show, using stopped flow tryptophan fluorescence, inhibitor binding, and circular dichroism (CD), that the rate of formation of native lysozyme on the slow refolding track is significantly reduced in solutions of high ionic strength in a manner dependent on the position of the anion in the Hofmeister series. By contrast, the rate of evolution of hydrogen exchange (HX) protection monitored by electrospray ionization mass spectrometry (ESI MS) is unchanged under the refolding conditions studied. The data show, therefore, that at high ionic strengths beta-domain stabilization and native state formation on the slow refolding pathway become kinetically decoupled such that the near-native state becomes significantly populated. Thus, by changing the energy landscape with the addition of salts new insights into the relevance of intermediate states in lysozyme refolding are revealed.

Animals↗
PubMed1999

The Burch colposuspension for recurrent urinary stress incontinence following retropubic continence surgery.

OBJECTIVE: To evaluate the Burch colposuspension with Cherney incision in women with recurrent urinary stress incontinence after retropubic continence surgery. DESIGN: A retrospective review. PARTICIPANTS: All 53 women had recurrent urinary stress incontinence after retropubic continence surgery with an average of 2.1 (range 1-5) previous failed continence procedures per woman. MAIN OUTCOME MEASURES: Subjective and objective success rates and complications including detrusor instability, voiding difficulties and genital prolapse. RESULTS: Forty-seven women (89%) had no or occasional (< one episode per week) stress or urge incontinence. One woman had persistent stress incontinence and five urge incontinence. Forty-two women (80%) rated their surgery as being highly successful and 38 women (72%) had no urinary leakage due to genuine stress incontinence or detrusor instability on repeat urodynamic evaluation. Three women (6%) developed de novo detrusor instability post-operatively. Two women (4%) had voiding difficulties post-operatively that necessitated the use of intermittent self-catheterisation for at least four months. The median length of follow up was nine months (4-72). In 39 women (73%), marked retropubic fibrosis was found at the time of surgery. CONCLUSIONS: Marked retropubic fibrosis should be expected in women with recurrent stress incontinence after retropubic continence surgery. The Burch colposuspension with the assistance of the Cherney incision and sharp dissection of retropubic fibrosis is an effective and safe procedure for women with this condition.

Adult↗
PubMed1999

Predictors of large esophageal varices in patients with cirrhosis.

OBJECTIVE: Recent guidelines recommend that all cirrhotics undergo screening upper endoscopy to identify those patients at risk for bleeding from varices. However, this practice may not be cost effective as large esophageal varices are seen only in 9-36% of these patients. The aim of this study was to determine whether clinical variables were predictive of the presence of large esophageal varices. METHODS: This is a retrospective analysis of cirrhotics who had a screening upper endoscopy during an evaluation for liver transplantation at three different centers and who had not previously bled from varices. A multivariate model was derived on the combined cohort using logistic regression. Three hundred forty-six patients were eligible for the study. RESULTS: The prevalence of large esophageal varices was 20%. On multivariate analysis, splenomegaly detected by computed tomographic scan (odds ratio: 4.3; 95% confidence interval: 1.6-11.5) or by physical examination (odds ratio: 2.0; 95% confidence interval: 1.1-3.8), and low platelet count were independent predictors of large esophageal varices. On the basis of these variables, cirrhotics were stratified into high- and low-risk groups for the presence of large esophageal varices. Patients with a platelet count of > or = 88,000/mm3 (median value) and no splenomegaly by physical examination had a risk of large esophageal varices of 7.2%. Those with splenomegaly or platelet count < 88,000/mm3 had a risk of large esophageal varices of 28% (p < 0.0001). CONCLUSIONS: Our data show that clinical predictors could be used to stratify cirrhotic patients for the risk of large esophageal varices and such stratification could be used to improve the cost effectiveness of screening endoscopy.

Adrenergic beta-Antagonists↗
PubMed1999

Multiple layers of cooperativity regulate enhanceosome-responsive RNA polymerase II transcription complex assembly.

Two coordinate forms of transcriptional synergy mediate eukaryotic gene regulation: the greater-than-additive transcriptional response to multiple promoter-bound activators, and the sigmoidal response to increasing activator concentration. The mechanism underlying the sigmoidal response has not been elucidated but is almost certainly founded on the cooperative binding of activators and the general machinery to DNA. Here we explore that mechanism by using highly purified transcription factor preparations and a strong Epstein-Barr virus promoter, BHLF-1, regulated by the virally encoded activator ZEBRA. We demonstrate that two layers of cooperative binding govern transcription complex assembly. First, the architectural proteins HMG-1 and -2 mediate cooperative formation of an enhanceosome containing ZEBRA and cellular Sp1. This enhanceosome then recruits transcription factor IIA (TFIIA) and TFIID to the promoter to form the DA complex. The DA complex, however, stimulates assembly of the enhanceosome itself such that the entire reaction can occur in a highly concerted manner. The data reveal the importance of reciprocal cooperative interactions among activators and the general machinery in eukaryotic gene regulation.

Allosteric Regulation↗
PubMed1999

Adaptive mechanisms in the elasmobranch hindbrain

The suppression of self-generated electrosensory noise (reafference) and other predictable signals in the elasmobranch medulla is accomplished in part by an adaptive filter mechanism, which now appears to represent a more universal form of the modifiable efference copy mechanism discovered by Bell. It also exists in the gymnotid electrosensory lateral lobe and mechanosensory lateral line nucleus in other teleosts. In the skate dorsal nucleus, motor corollary discharge, proprioceptive and descending electrosensory signals all contribute in an independent and additive fashion to a cancellation input to the projection neurons that suppresses their response to reafference. The form of the cancellation signal is quite stable and apparently well-preserved between bouts of a particular behavior, but it can also be modified within minutes to match changes in the form of the reafference associated with that behavior. Motor corollary discharge, proprioceptive and electrosensory inputs are each relayed to the dorsal nucleus from granule cells of the vestibulolateral cerebellum. Direct evidence from intracellular studies and direct electrical stimulation of the parallel fiber projection support an adaptive filter model that places a principal site of the filter's plasticity at the synapses between parallel fibers and projection neurons.

Journal Article↗
PubMed1998

Transcription factor IIA derepresses TATA-binding protein (TBP)-associated factor inhibition of TBP-DNA binding.

The interaction of the general transcription factor (TF) IIA with TFIID is required for transcription activation in vitro. TFIID consists of the TATA-binding protein (TBP) and TBP associated factors (TAFIIs). TFIIA binds directly to TBP and stabilizes its interaction with TATA-containing DNA. In this work, we present evidence that TAFIIs inhibit TBP-DNA and TBP-TFIIA binding, and that TFIIA stimulates transcription, in part, by overcoming this TAFII-mediated inhibition of TBP-DNA binding. TFIIA mutants modestly compromised for interaction with TBP were found to be significantly more defective in forming complexes with TFIID. Subtle changes in the stability or conformation of the TFIIA-TBP complex resulted in a failure of TFIIA to overcome TAFII-mediated inhibition of TBP-DNA binding and transcription function. Inhibition of TBP-DNA binding by TAFIIs could be partially relieved by limited proteolysis of TFIID. Proteolysis significantly stimulated TFIIA-TFIID-TATA binding in both electrophoresis mobility shift assay and DNase I footprinting but had little effect on complexes formed with TBP. Recombinant TAFII250 inhibits TBP-DNA binding, whereas preincubation of TFIIA with TBP prevents this inhibition. Thus, TFIIA competes with TAFII250 for access to TBP and alters the TATA binding properties of the resulting complex. Transcriptional activation by Zta was enhanced by temperature shift inactivation of TAFII250 in the ts13 cell line, suggesting that TAFII250 has transcriptional inhibitory activity in vivo. Together, these results suggest that TAFIIs may regulate transcription initiation by inhibiting TBP-TFIIA and TBP-DNA complex formation.

DNA↗
PubMed1998

Transcription: TRF walks the walk but can it talk the talk?

The TBP-related factor TRF binds to a TATA box promoter sequence and mediates basal transcription in vitro. A central question is: does TRF function in vivo to transduce the effects of activators in a tissue-specific fashion?

Amino Acid Sequence↗