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Biomedical subjects

J M Smith

Publications and source records attributed to J M Smith.

At least 145 records · Page 8Linked to original sources
PubMed1996

Site-specific codon bias in bacteria.

Sequences of the gapA and ompA genes from 10 genera of enterobacteria have been analyzed. There is strong bias in codon usage, but different synonymous codons are preferred at different sites in the same gene. Site-specific preference for unfavored codons is not confined to the first 100 codons and is usually manifest between two codons utilizing the same tRNA. Statistical analyses, based on conclusions reached in an accompanying paper, show that the use of an unfavored codon at a given site in different genera is not due to common descent and must therefore be caused either by sequence-specific mutation or sequence-specific selection. Reasons are given for thinking that sequence-specific mutation cannot be responsible. We are unable to explain the preference between synonymous codons ending in C or T, but synonymous choice between A and G at third sites is largely explained by avoidance of AG-G (where the hyphen indicates the boundary between codons). We also observed that the preferred codon for proline in Enterobacter cloacea has changed from CCG to CCA.

Bacterial Outer Membrane Proteins↗
PubMed1996

Maternal recognition of pregnancy in swine. I. Minimal requirement for exogenous estradiol-17 beta to induce either short or long pseudopregnancy in cycling gilts.

Five experiments were conducted to determine the minimal requirement for estradiol-17 beta (E2) injections to induce either short pseudopregnancy (SPP) or long pseudopregnancy (LPP) in cycling gilts. In experiments 1 through 5, E2 was injected i.m. on combinations of days between 11 and 25 days postestrus. Exogenous E2 on Days 12 and 13 or on Days 12 through 19 was optimal for induction of SPP or LPP, respectively. The duration of E2-induced diestrus was clearly demarcated between SPP (n = 73, duration 23-35 days) and LPP (n = 23, duration > 50 days). A sixth experiment was conducted to determine the minimum dose of intrauterine E2 required to induce SPP, and these gilts received intrauterine infusions of 0, 4, 40, or 400 micrograms E2 per 24 h on Days 12 and 13 postestrus. Pseudopregnancy was induced in 0 of 12, 1 of 4, 1 of 11, and 4 of 7 gilts in the treatment groups, respectively. These data suggest that uterine exposure alone is not sufficient to induce SPP. The present results indicate that the optimal signal for inducing LPP in unmated cycling gilts, and perhaps also for maternal recognition of pregnancy in mated gilts, may occur in two phases with continuous exposure to E2 being required from Day 12 to Days 17-19.

Animals↗
PubMed1996

Why should we do environmental dose reconstructions?

Environmental dose reconstructions are being conducted at many nuclear weapons production and testing sites in the United States. These projects involve reconstructing potential radiation exposures and doses from past releases of radionuclides to people who lived near nuclear facilities where these releases occurred. The results of dose reconstructions can be used as the basis for deciding if epidemiologic studies or other public health activities should be undertaken. In addition, the results of dose reconstruction can be used in other risk assessment activities, such as those associated with environmental restoration and radioactive waste management. For example, the historical inventory of hazardous materials used and potentially released at the site can be used to begin to assess the risk for exposures from current and future activities. The site-specific environmental dosimetry methods developed for dose-reconstruction purposes are applicable to other environmental risk assessments performed for that site. These and other benefits of environmental dose reconstructions are discussed.

Environmental Exposure↗
PubMed1996

Risk of radiation induced skin injuries from arrhythmia ablation procedures.

Catheter guided ablation of cardiac arrhythmias is an effective and safe procedure for the treatment of most supraventricular and selected ventricular tachycardias. Because catheter manipulation is fluoroscopically guided, there is risk of radiation induced injury, especially during prolonged procedures. The Food and Drug Administration has recently issued a bulletin warning of the risks of acute skin injury occurring during fluoroscopically guided procedures that result in an exposure level exceeding 2 Gray units (Gy). This study was performed as an investigation into the risk of radiation induced skin injury during arrhythmia ablation procedures. The amount of radiation exposure for 500 patients who underwent ablation was calculated based upon fluoroscopy times and the entrance dose of radiation (0.02 Gy/min). The mean radiation exposure was 0.93 +/- 0.62 Gy. Although 5.6% of patients (n = 28) received enough radiation exposure to reach the threshold dose (2 Gy) for early transient erythema, no clinical manifestations of acute radiation induced skin injury were observed. No patients achieved the threshold dose for irreversible skin injury. Patients undergoing AV node ablation or modification received significantly less radiation (0.39 +/- 0.40 Gy and 0.79 +/- 0.44 Gy, respectively) than patients undergoing other ablation procedures (0.94-1.45 Gy, P < 0.05). There was no association between the magnitude of radiation exposure and the presence of underlying heart disease. Patients undergoing ablation of accessory pathways were exposed to more radiation if there was a right-sided pathway (1.69 +/- 0.93 Gy) compared to other sites (0.87-1.24 Gy, P < 0.05). This study demonstrates that the risk of significant radiation induced skin injury during arrhythmia ablation procedures is low provided that precautions are taken to minimize radiation exposure.

Adolescent↗
PubMed1996

The safety profile of nefazodone.

Comprehensive review of safety data from approximately 3500 patients who received nefazodone in premarketing clinical trials demonstrates the drug to be very well tolerated, with a favorable side effect profile compared with other antidepressant drugs. Nefazodone treatment was associated with fewer side effects than were the control drugs. The incidence of side effects was generally low, and treatment discontinuations for adverse effects were less frequent with nefazodone than with imipramine and comparable with fluoxetine. No late-appearing side effects or toxicity emerged during the long-term treatment (1 year or longer) of several hundred patients. There were no drug-related fatalities and no evidence that nefazodone caused specific organ toxicity, although some cardiovascular side effects were noted (e.g., asymptomatic reduced systolic blood pressure, asymptomatic sinus bradycardia). Experience in 488 elderly patients treated with nefazodone yielded no evidence of increased susceptibility of older patients to nefazodone-associated adverse experiences, including those pertaining to the cardiovascular system. However, treatment should be initiated at a reduced dose in elderly patients because of reduced hepatic clearance of nefazodone in this age group. Final dose range may be similar in healthy younger and older patients. Although nefazodone may interact with some other medications (e.g., increases at steady state in AUC: alprazolam, twofold; triazolam, fourfold), drug-drug interactions involving patients have been clinically minor. On the basis of the inhibition of cytochrome P450 3A4 isoenzyme by nefazodone in vitro, coadministration of terfenadine or astemizole with nefazodone is contraindicated because nefazodone can increase the plasma levels of these two drugs. Extensive clinical experience provides substantial evidence that nefazodone is an extremely safe and effective treatment for depression, with important advantages over existing therapies. Therapeutic benefits include a low incidence of clinically troublesome side effects and lack of unwanted psychic activation, sexual dysfunction, weight change, and the cardiotoxicity of other antidepressants.

Adolescent↗
PubMed1996

Differential distribution of von Willebrand factor in canine vascular endothelium.

OBJECTIVE: To determine whether endothelial cell (EC) von Willebrand factor (vWf) is uniformly distributed in canine blood vessels. DESIGN: Contents of EC vWf from vascular segments was evaluated in Haütchen preparations, using immuno-histochemistry. EC from femoral arteries and veins and jugular veins were grown in culture, and the intracellular content and constitutive release of vWf from these cells were measured. The amount of vWf mRNA in the cultured EC was determined. ANIMALS: Vascular segments for Häutchen preparations and EC for culture were obtained from 5 and 10 clinically normal, mixed-breed dogs, respectively. PROCEDURES: Appropriate vascular segments were removed, fixed; processed for immunohistochemistry, using a monospecific polyclonal antibody to canine vWf, and Haütchen preparations were made. Intracellular and constitutive released vWf was measured, using an ELISA, and vWf mRNA was measured by Northern blot analysis. RESULTS: Intact endothelial linings from femoral veins, jugular veins, vena cava, and pulmonary veins stained more intensely than femoral arteries, carotid arteries, aorta, and pulmonary veins. Constitutive release and intracellular content of vWf in cultured EC from femoral veins was about 30 times higher than that from femoral arterial EC, which was barely detectable. Similar differences were seen in amounts of mRNA. CONCLUSIONS: There is marked diversity in EC vWf in canine vasculature that may result from differences in vWf mRNA. CLINICAL RELEVANCE: Low amounts of vWf in canine systemic arterial EC may contribute to thromboresistance of canine arteries.

Animals↗
PubMed1996

Setting standards of prescribing performance in primary care: use of a consensus group of general practitioners and application of standards to practices in the north of England.

BACKGROUND: There is considerable variation in prescribing, and existing standards against which primary care prescribing is routinely judged consist largely of local or national averages. There is thus a need for more sophisticated standards, which must be widely applicable and have credibility among the general practice profession. AIM: A study aimed to develop a range of criteria of prescribing quality, to set standards of performance for these criteria, and apply these standards to practices. METHOD: A consensus group consisting of eight general practitioners and a resource team was convened to develop and define criteria and set standards of prescribing performance using prescribing analyses and cost (PACT) data. The standards were applied to 1992-93 prescribing data from all 518 practices in the former Northern Regional Health Authority. RESULTS: The group developed criteria and set numeric standards for 13 aspects of prescribing performance in four areas: generic prescribing, prescribing within specific therapeutic groups, drugs of limited clinical value and standards based on prescribing volume. Except for generic prescribing, standards for individual criteria were achieved by between 9% and 34% of practices. For each criterion, a score was allocated based on whether the standard was achieved or not. Total scores showed considerable variation between practices. The distribution of scores was similar between fundholding and non-fundholding practices, and also between dispensing and non-dispensing practices. CONCLUSION: Using a consensus group of general practitioners it is possible to agree criteria and standards of prescribing performance. This novel approach offers a professionally driven method for assessing the quality of prescribing in primary care.

Drug Prescriptions↗
PubMed1996

Influences on prescribing in non-fundholding general practices.

BACKGROUND: The experience from general practice fundholding suggests that financial incentives may influence prescribing; guidelines and hospital prescribing are two other suggested influences. AIM: A study was undertaken to establish general practitioners' attitudes to a financial prescribing incentive scheme, the presence and use of guidelines, and the influence of prescribing initiated within secondary care. METHOD: A postal questionnaire survey of non-fundholding general practices in the former Northern Region was conducted. RESULTS: Practices' thinking and subsequent decisions about the incentive prescribing scheme were most often influenced by discussions within the practice (45%). Those practices that achieved their savings under the incentive scheme were less likely than those not achieving savings to feel that the target was not achievable, the time scale was unacceptable, and that the philosophy behind the scheme was unacceptable. Forty-five per cent of practices received advice from neither a medical nor a pharmaceutical adviser; 27% of practices received advice from both, 12% from a medical adviser only and 16% from a pharmaceutical adviser only. Of the practices that tried to make their target savings, 91% intended to increase generic prescribing; fewer than one-third of practices mentioned any other measure. Prescribing guidelines were reported by a minority of practices, although reported rates of use were high when these were present. Clinical guidelines for three conditions, asthma, diabetes and hypertension, were present in more than 50% of practices; 25% of practices had no clinical guidelines. Hospital prescribing was reported as 'always' or 'usually' influencing prescribing for diabetes by 57% of respondents, ischaemic heart disease by 55%, peptic ulceration by 49%, asthma by 42% and hypertension by 39%. CONCLUSIONS: General practitioner prescribing is influenced by a complex web of factors, with no single factor pre-eminent. To understand this area further, there is a need to take each of these areas and ascertain the match between doctors' perceptions and actual practice.

Attitude of Health Personnel↗
PubMed1995

Mutant U5A cells are complemented by an interferon-alpha beta receptor subunit generated by alternative processing of a new member of a cytokine receptor gene cluster.

The cellular receptor for the alpha/beta interferons contains at least two components that interact with interferon. The ifnar1 component is well characterized and a putative ifnar2 cDNA has recently been identified. We have cloned the gene for ifnar2 and show that it produces four different transcripts encoding three different polypeptides that are generated by exon skipping, alternative splicing and differential use of polyadenylation sites. One polypeptide is likely to be secreted and two are transmembrane proteins with identical extracellular and transmembrane domains but divergent cytoplasmic tails of 67 and 251 amino acids. A mutant cell line U5A, completely defective in IFN-alpha beta binding and response, has been isolated and characterized. Expression in U5A cells of the polypeptide with the long cytoplasmic domain reconstitutes a functional receptor that restores normal interferon binding, activation of the JAK/STAT signal transduction pathway, interferon-inducible gene expression and antiviral response. The IFNAR2 gene maps at 0.5 kb from the CRFB4 gene, establishing that together IFNAR2, CRFB4, IFNAR1 and AF1 form a cluster of class II cytokine receptor genes on human chromosome 21.

Alternative Splicing↗
PubMed1995

The major evolutionary transitions.

There is no theoretical reason to expect evolutionary lineages to increase in complexity with time, and no empirical evidence that they do so. Nevertheless, eukaryotic cells are more complex than prokaryotic ones, animals and plants are more complex than protists, and so on. This increase in complexity may have been achieved as a result of a series of major evolutionary transitions. These involved changes in the way information is stored and transmitted.

Animals↗
PubMed1995

Enzymatic synthesis of guanine nucleotides labeled with 15N at the 2-amino group of the purine ring.

GMP and dGMP labeled with 15N at the 2-amino group of the purine ring was obtained enzymatically from NH4Cl (> 99 at.% 15N) and from IMP or dIMP, respectively, by several reactions involving IMP-dehydrogenase, GMP-synthetase, adenylate kinase, and creatine kinase. The first three enzymes were obtained by overexpression in Escherichia coli of the corresponding genes. The isotope content of the primary amino group of guanine determined by mass spectrometry after acid hydrolysis of nucleotides was found higher than 98 at.% 15N. The proton NMR spectrum of [15N]GMP in solution in the absence of nitrogen decoupling showed a doublet with a coupling constant of 92 Hz. When nitrogen decoupling was used during the acquisition time, the doublet was replaced by a single peak at 6.47 ppm, indicating that the corresponding proton is bound to 15N.

Adenylate Kinase↗
PubMed1995

Cloning, expression, and purification of an anti-desipramine single chain antibody in NS/O myeloma cells.

Drug-specific monoclonal antibodies and their antigen-binding Fab fragments reverse acute desipramine toxicity in a rat experimental model by inducing a redistribution of drug from cardiac tissue into serum and extracellular fluid. In order to investigate the use of smaller recombinant antibody fragments such as single chain Fv (sFv) as an antidote, an efficient murine NS/O myeloma expression system was developed. The variable light (VL) and variable heavy (VH) domains of a murine anti-desipramine monoclonal antibody were cloned and sequenced. A 270 amino acid VH-(Gly4Ser)3-VL sFv was prepared by overlapping polymerase chain reaction (PCR) amplification of VH with heavy chain leader peptide, VL, and the linker. This construct was subcloned into a mammalian expression vector which utilizes the SR alpha promoter, a hybrid promoter consisting of the SV40 early promoter with portions of the human T-cell leukemia virus type I long terminal repeat and also containing the Escherichia cloi xanthine-guanine phosphoribosyltransferase gene for selection. NS/O myeloma cells were transfected by electroporation. Stable recombinant NS/O clones were screened for expression of sFv using reverse transcriptase-PCR to detect mRNA and an enzyme-linked immunosorbent assay (ELISA) to detect sFv. Secreted sFv from clones capable of growth to a cell density of 2-4 x 10(6) viable cells/mL was purified in a single step using a desipramine affinity column resulting in 12-39 mg/L of purified sFv. Affinity-purified sFv had comparable desipramine binding activity to Fab when evaluated by competitive ELISA.

Amino Acid Sequence↗
PubMed1995

Characterization of recombinant soluble human transforming growth factor-beta receptor type II (rhTGF-beta sRII).

Recombinant human transforming growth factor soluble receptor Type II (rhTGF-beta sRII) corresponding to the 159 amino acid extracellular domain of hTGF-beta RII has been expressed in insect cells using the baculovirus expression system or in a mouse myeloma cell line. N-terminal sequence analysis of the purified protein revealed the removal of the 23 amino acid signal peptide. In SDS-PAGE, the rhTGF-beta sRII resolves into multiple bands due to N-linked glycosylation. Recombinant hTGF-beta sRII is a TGF-beta antagonist and will inhibit the biological activities of TGF-beta 1, TGF-beta 3, and TGF-beta 5 on TGF-beta-responsive cell lines, such as murine HT-2 or human TF-1 with an ED50 of approximately 0.3 micrograms/mL. However, hTGF-beta sRII does not inhibit TGF-beta 2 bioactivities in these cell lines, suggesting that hTGF-beta RII has low affinity for TGF-beta 2. Polyclonal antibodies to hTGF-beta sRII have been produced in goats and purified on Protein-G affinity columns. This antibody can inhibit TGF-beta 1,2,3,5-dependent bioactivities on human cell lines such as TF-1. Additionally, this antibody has species cross-reactivity and will also inhibit TGF-beta-dependent bioactivities on murine cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Heparin levels to guide thromboembolism prophylaxis during pregnancy.

OBJECTIVE: Our purpose was to determine the dose of heparin required in pregnant women to achieve the same heparin levels as standard doses of 5000 units given subcutaneously every 12 hours in the nonpregnant population. STUDY DESIGN: Fourteen pregnant women placed on heparin prophylaxis for a history of thromboembolism had blood drawn for 64 anti-Xa level determinations in the second and third trimesters. Heparin doses were adjusted in an attempt to achieve a midinterval or peak level of 0.05 to 0.25 U/ml, which corresponds to the range seen in nonpregnant patients given standard doses of 5000 units subcutaneously every 12 hours. RESULTS: A standard heparin dose of 5000 units given subcutaneously every 12 hours was inadequate to achieve the desired range in this pregnant population. In five of nine second-trimester pregnancies 7500 units given subcutaneously every 12 hours was inadequate to attain this range. In six of 13 third-trimester pregnancies, > 10,000 units subcutaneously every 12 hours was needed. CONCLUSIONS: Heparin requirements may increase and are highly variable in patients during pregnancy. Until appropriate clinical outcomes trials can determine optimal dosing, measuring anti-Xa activity may be useful to guide therapy.

Antibodies↗