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Biomedical subjects

A Taylor

Publications and source records attributed to A Taylor.

At least 505 records · Page 28Linked to original sources
PubMed1992

Evidence for increased prevalence of SRY mutations in XY females with complete rather than partial gonadal dysgenesis.

The Y chromosome gene SRY (sex-determining region, Y gene) has been equated with the mammalian testis-determining factor. The SRY gene of five subjects with 46,XY complete gonadal dysgenesis (46,XY karyotype, completely female external genitalia, normal Müllerian ducts, and streak gonads) was evaluated for possible mutations in the coding region by using both single-strand conformation polymorphism (SSCP) assay and DNA sequencing. Mutations were identified in three subjects, of which two gave altered SSCP patterns. Two of them were point mutations causing amino acid substitutions, and the third was a single-base deletion causing a frameshift. All three mutations caused alterations in the putative DNA-binding region of the SRY protein. Genomic DNA was obtained from the fathers of two of the three mutant patients: one mutation was demonstrated to be de novo, and the other was inherited. The presence of SRY mutations in three of five patients suggests that the frequency of SRY mutations in XY females is higher than current estimates.

Base Sequence↗
PubMed1992

Effect of macronutrient composition of an energy-restrictive diet on maximal physical performance.

Thirty-six sedentary, mildly obese (30-40% fat), premenopausal women (29-49 yr) were randomly assigned to one of two dietary regimens for an 8-wk double-blind, parallel study of the effect of moderate caloric restriction and macronutrient variation on maximal physical performance. Group 1 (N = 19) consumed 4186 kJ.d-1 (1000 kcal.d-1) with a diet composition of 40% fat, 40% carbohydrate (CHO), and 20% protein. Group 2 (N = 17) also consumed 4186 kJ.d-1 but varied the percent kilojoules to 20% fat, 60% CHO, and 20% protein. Maximal aerobic power was measured using a modified Balke protocol, strength was assessed using isotonic bench and leg press machines and a Cybex 340 isokinetic device during knee flexion and extension, and muscular endurance was taken as the number of sit-ups performed in 1 min. Pre- to post-testing revealed significant (P less than or equal to 0.05) reductions in body weight (group 1, -7.4 kg; group 2, -6.5 kg) within both groups. No significant changes were seen in maximal aerobic power within both groups. Strength measures for both groups showed a trend toward reduction but statistical significance was only evident in right knee extension for group 1 and left knee extension for group 2 (P less than or equal to 0.05). Sit-up number increased nonsignificantly for both groups. Between group differences were not found in any body weight, body composition, or physical performance index. We therefore conclude that in mildly obese women, maximal exercise performance is relatively unimpaired after 8 wk of caloric restriction with either of two diets differing moderately in their macronutrient content.

Adult↗
PubMed1992

Results of the multicenter evaluation of a novel homogeneous immunoassay for digoxin based on the cloned enzyme donor immunoassay technology.

A new CEDIA assay for the measurement of digoxin in serum on random access analyzers was evaluated by twelve laboratories in Europe and the United States. Studies on the analytical range, reproducibility, calibration stability, recovery in controls, interlaboratory comparability, comparability with routine methods, and the effect of various interfering factors have been performed and the results are presented in this paper. The analytical performance was comparable to that of routine methods provided the manual pipetting step for pre-incubation was performed with accurate pipettes. A major advantage of the CEDIA Digoxin assay in terms of convenience is the simple two-point calibration procedure. Moreover, digoxin can be determined within 15 minutes after receiving the samples on random access analyzers like Boehringer Mannheim/Hitachi analysis systems. Thus, the CEDIA Digoxin assay represents an attractive alternative to the measurement of digoxin on dedicated immunochemical assay systems.

Calibration↗
PubMed1992

Radiation dosimetry for technetium-99m-MAG3, technetium-99m-DTPA, and iodine-131-OIH based on human biodistribution studies.

Radiation dose estimates were calculated for the renal agents 99mTc-DTPA, 99mTc-MAG3, and 131I-OIH from biodistribution data gathered in groups of healthy human volunteers. Biokinetics were evaluated by Anger camera imaging, blood sampling, and urine collection and counting. Collected data were fit to four- or five-compartmental models using the CONversational Simulation, Analysis, and Modeling (CONSAM) software. Radiation dose estimates were performed using standard MIRD techniques. Average residence times in urinary bladder, kidney, and remainder of the body were used to predict radiation dose equivalents and effective dose equivalents for the three agents. Doses for DTPA and MAG3 were very similar and much lower on a per unit injected activity than OIH. The effective dose equivalents were 3.3 mSv/370 MBq for 99Tc-DTPA, 3.7 mSv/370 MBq for 99mTc-MAG3, and 0.99 mSv/11.1 MBq for 131I-OIH for bladder voiding every 4.8 hr; effective dose equivalents were 2.0 mSv/370 MBq for 99mTc-DTPA, 1.5 mSv/370 MBq for 99mTc-MAG3, and 0.28 mSv/11.1 MBq for 131I-OIH for bladder voiding at 30 min and then every 4.0 hr. Patients should void at the conclusion of the study, as early voiding can reduce the gonadal radiation dose by a factor of 2 to 3.

Humans↗
PubMed1992

Extracorporeal photochemotherapy for cutaneous T-cell lymphoma and other diseases.

Extracorporeal photochemotherapy is an effective method for the treatment of CTCL. It is most effective in the erythrodermic stages of the disease but may also have a place in the treatment of more advanced disease. Phototherapy has also been used in the treatment of other T-cell-mediated diseases. Psoralen plus UVA are known to interact with cellular DNA, proteins, and lipids. The mechanism of action is not completely understood but there is suggestive evidence that cell membrane changes so caused can render the cell susceptible to immune surveillance and destruction.

AIDS-Related Complex↗
PubMed1991

A colourimetric enzyme-linked sandwich assay for the detection of human platelets bound to a fibrinogen-coated surface.

A colourimetric enzyme-linked sandwich assay has been developed to investigate the binding of human platelets to fibrinogen. The presence of platelets bound to fibrinogen-coated plastic can easily be detected and quantitated. Platelets treated with chymotrypsin to expose the fibrinogen receptor, are fixed with paraformaldehyde, and stored frozen. The detection sandwich consists of a mouse monoclonal antibody directed against the human platelet CD9 antigen, and a rabbit anti-mouse immunoglobulin conjugated to the enzyme alkaline phosphatase. The cleavage of the phosphatase substrate p-nitrophenyl phosphate can be monitored colourimetrically. The data presented provide evidence that this method is capable of detecting platelet-fibrinogen binding in a physiologically relevant manner. The binding is inhibited by EDTA or excess fibrinogen. The fibrinogen alpha and gamma chain peptides, RGDS and LGGAKQAGDV, and the snake venom echistatin are also inhibitory with IC50 values of 135 microM, 1.8 mM and 100 nM respectively.

Blood Platelets↗
PubMed1991

Preliminary characterization of a cloned neutral isoelectric form of the human peptidyl prolyl isomerase cyclophilin.

We report the cloning of a neutral isoelectric form of the human peptidyl prolyl isomerase, cyclophilin, its expression in Escherichia coli, and its purification and comparison to bovine thymus cyclophilin. The cloned protein exhibited a pI of approximately 7.8 and formed a simple 1:1 complex with cyclosporin A. This cloned form had a pI similar to that observed for the neutral isoform (pI approximately 7.4) of human splenocyte cyclophilin. The bovine thymus proteins exhibited anomalous behavior on CM-cellulose chromatography but were resolved into alkaline (pI approximately 9.3) isoforms and a new neutral (pI approximately 7.8) isoform by isoelectric focusing gel electrophoresis and ultimately into at least four discrete isoforms by capillary electrophoresis. For cyclosporin A binding we observe a Kd of approximately 160 nM for an electrophoretically heterogeneous preparation of the natural bovine protein and approximately 360 nM for the more homogeneous preparation of the cloned human neutral isoform. Stopped-flow measurements of the activation energies for peptidyl-prolyl isomerase activity indicate the recombinant human protein has an activation enthalpy of 3.67 kcal/mol and an activation entropy of -47.3 cal/K-mol for cis----trans isomerization.

Amino Acid Isomerases↗
PubMed1991

Study of human urinary metabolism of fenfluramine using gas chromatography-mass spectrometry.

The metabolism of (+/-)fenfluramine, 1-(m-trifluoromethylphenyl)-2-N-ethylpropane, an anoretic agent, was investigated in humans. The analysis method was based on the use of ion-exchange resin extraction, solid-phase purification on the Bond Elut1M C8 cartridge, gradient elution high-performance liquid chromatography, enzymic hydrolysis of conjugates, further purification by Bond Elut C8 cartridge, derivatisation and capillary column gas chromatography-mass spectrometry (GC-MS). After administration of a 1 mg kg-1 oral dose, four metabolites plus unchanged fenfluramine were recovered in the 0-24 h urine from human volunteers and characterised by GC-MS. In the conjugated form, fenfluramine, norfenfluramine and m-trifluoromethylhippuric acid were detected by GC-MS. In the aglycone form, the major metabolite, 1-(m-trifluoromethylphenyl)-1,2-propane diol (fenfluramine diol), was monitored using GC-MS. The mass spectral characteristics of the m-trifluoromethylhippuric acid methyl ester, 1-(m-trifluoromethylphenyl)-1,2-propane ditrifluoracetate derivatives and the norfenfluramine and fenfluramine free base obtained under electron-impact ionization are presented. The metabolism of fenfluramine is discussed including a metabolic pathway in man accounting for the formation of its biotransformation products.

Biotransformation↗
PubMed1991

Effects of aging in vitro on intracellular proteolysis in cultured rabbit lens epithelial cells in the presence and absence of serum.

Alterations in proteolytic capabilities have been associated with abnormalities in the aged eye lens, but in vivo tests of this hypothesis have been difficult to pursue. To simulate aging, we cultured cells from an 8-yr-old rabbit to early (population-doubling level 20 to 30) and late (population-doubling level greater than 125) passage. Long-lived (t1/2 greater than 10 h) and short-lived (t1/2 less than 10 h) intracellular proteins were labeled with [3H]leucine, and the ability of the cells to mount a proteolytic response to the stress of serum withdrawal was determined. For early passage cells, the average t1/2 of long-lived proteins in the presence and absence of serum was 62 and 39 h, respectively. For late-passage cells, the average t1/2 of long-lived proteins in the presence and absence of serum was 58 and 43 h, respectively. The net increase in intracellular proteolysis in the absence of serum was 59 and 35% for early and late-passage cells, respectively. Thus, in vitro-aged rabbit lens epithelial cells amount only 60% the proteolytic response to serum removal shown in "younger" cells. The enhanced ability of early passage cells to respond to serum removal seems to involve lower homeostatic levels of proteolysis in the presence of serum and greater enhancement of proteolysis in the absence of serum. Less than 2% of the protein is in the pool of short-lived proteins. Rates of proteolysis of short-lived proteins in the presence and absence of serum were indistinguishable. With respect to basal proteolytic rates in the presence of serum and ability to mount a proteolytic response upon serum withdrawal, these rabbit lens epithelial cells are similar to bovine lens epithelial cells and fibroblasts.

Animals↗
PubMed1991

Time course of creatine kinase release after termination of sustained ventricular dysrhythmias.

Differentiation between primary and secondary (caused by acute myocardial infarction) ventricular fibrillation has important therapeutic and prognostic implications. The diagnosis of myocardial infarction is based on clinical, ECG, and creatine kinase MB isoenzyme (MBCK) activity. Enzymatic criteria might not be able to confirm the diagnosis of myocardial infarction after recent cardioversion. The routine use of electrophysiologic studies involving the induction and termination of ventricular dysrhythmias provides a setting in which enzyme release as a result of cardioversion alone can be examined. Therefore a systematic investigation of the magnitude and time course of creatine kinase (CK) and MBCK release was performed after termination of ventricular dysrhythmias in 57 patients undergoing electrophysiologic studies. Of patients requiring external cardioversion, only 50% had an elevation in CK and MBCK activity. Elevation when present corrected with the number of shocks and cumulative energy delivered. The magnitude of MBCK release exceeded 10% of the total CK activity in 9% of observations. Pace-termination of ventricular tachycardia did not result in enzyme release. Arrhythmia characteristics, coronary artery disease, and left ventricular function did not affect the magnitude of the time course of enzyme release. These data suggest that cardioversion with multiple shocks may result in a component of MBCK release, and thus a false positive diagnosis of primary acute myocardial infarction may be made by relying exclusively on the enzyme release pattern.

Clinical Enzyme Tests↗
PubMed1991

Evidence for ATP and ubiquitin dependent degradation of proteins in cultured bovine lens epithelial cells.

Degradation of endogenous lens proteins has been difficult to show under physiological conditions using lens tissue preparations. In contrast, active proteolytic systems in cultured bovine lens epithelial (BLE) cells have been demonstrated previously. BLE cells also contain ubiquitin, a 76 amino-acid polypeptide which is conjugated to proteins in an ATP/Mg(2+)-dependent process prior to their cytosolic proteolysis. In this study, we show that histone H2A, alpha-crystallin, and actin are conjugated to ubiquitin, resulting in higher molecular mass species, which are detected by anti-ubiquitin antibodies. These proteins are also degraded in cell-free assays containing BLE cell supernatants under physiological conditions in an ATP/Mg(2+)-dependent manner. Observation of 125I-labeled proteolytic fragments was made after SDS polyacrylamide gel electrophoresis of the assays. Quantitation of trichloroacetic acid-soluble radiolabeled fragments generated in the presence of ATP/Mg2+ revealed that, with BLE cell supernatant, 25% of the histone H2A was degraded in 3 hr. Proteolysis of alpha-crystallin and actin amounted to 2.3% and 2.9%, respectively. The requirement of ATP/Mg2+ for proteolysis and the observation of ubiquitin conjugation to the same proteins is consistent with the presence of a ubiquitin-dependent proteolytic pathway in BLE cells. Additionally, in this study the BLE cell proteases were even more active on some substrates than the reticulocyte ubiquitin/ATP-dependent proteolytic system.

Actins↗
PubMed1991

Evaluation of mRNA levels by the polymerase chain reaction in small cardiac tissue samples.

Doxurubicin is an effective and widely used chemotherapeutic agent. However, use of this drug is often limited by its cardiotoxic side effects. We have observed that an early event accompanying doxorubicin cardiomyopathy is a selective decrease in levels of muscle gene transcripts in cardiac tissue (Ito et al., Proc. Natl. Acad. Sci. USA 87: 4275-4279). Since this decrease precedes ultrastructural evidence of cardiac damage, measurements of muscle transcripts might assist in the clinical evaluation of doxorubicin cardiotoxicity. We have therefore assessed the utility of the polymerase chain reaction in the measurement of mRNA in control and doxorubicin-treated animals. These measurements were performed on small tissue samples that simulate endomyocardial biopsies. We measured cardiac alpha-actin transcripts as a fraction of ferritin heavy chain transcripts using the method described by Chelly et al. (Nature 333: 858-860, 1988). 0.5 micrograms of total RNA, an amount equivalent to that obtainable from a typical endomyocardial biopsy, was efficiently co-amplified with cardiac alpha-actin and ferritin heavy chain specific primers. The cardiac alpha-actin/ferritin heavy chain ratio calculated from the PCR results correlated well (R = 0.981) with results obtained using Northern blot analysis of 10 micrograms RNA. The correlation was maintained over a wide range of cardiac alpha-actin transcript abundance. These results show that mRNA from cardiac tissue can be estimated by the polymerase chain reaction, even from a small, endomyocardial biopsy-sized sample.

Actins↗
PubMed1991

Reduction of unique noise in the psychophysics of hearing by Group Operating Characteristic analysis.

Group Operating Characteristic (GOC) analysis can be used to reduce the effects of unique noise on data from psychophysical experiments on hearing. Unique noise can come from physiological sources such as heartbeat and breathing and from other internal sources such as criterion variability, inattention, and faulty memory. The theory of GOC analysis is described and applied to the results of frequency discrimination experiments with human, pigeon, and simulated observers. The method yields relatively unattenuated measures of sensitivity, recovers Receiver Operating Characteristic curves from noisy choice data, and estimates the relative magnitudes of unique and common noise.

Animals↗
PubMed1991

The utility of 99mTc-mercaptoacetyltriglycine in captopril renography.

99mTc-Mercaptoacetyltriglycine (MAG3) is a new 99mTc renal radiopharmaceutical with properties similar to orthoiodohippurate (OIH). 99mTc-MAG3 is highly protein bound and is efficiently extracted by the proximal tubules. While the clearance is only 50 to 65% that of OIH, the plasma concentration is higher and the rates at which the two tracers appear in the urine are almost identical. Studies comparing 99mTc-MAG3 and OIH in animals with renovascular hypertension (RVH) show comparable results. Preliminary studies comparing 99mTc-MAG3 renography with angiography in hypertensive patients show promising results and suggest 99mTc-MAG3 will probably have a sensitivity and specificity for detecting RVH similar to OIH. The optimal criteria for defining an abnormal study still need to be determined and then applied in a prospective study.

Animals↗