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Biomedical subjects

R W Taylor

Publications and source records attributed to R W Taylor.

At least 127 records · Page 7Linked to original sources
PubMed1993

Endotracheal intubation and mechanical ventilation in severe asthma.

OBJECTIVE: To determine the occurrence rate of complications and mortality in patients with severe asthma requiring endotracheal intubation and mechanical ventilation. DESIGN: Retrospective review of medical records from September 1982 to July 1988. SETTING: Urban, teaching hospital serving primarily indigent patients. PATIENTS: Fifty-seven adult patients with asthma requiring tracheal intubation and mechanical ventilation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Fifty-seven patients requiring tracheal intubation and mechanical ventilation during 69 hospital admissions were identified. Medication noncompliance and upper respiratory tract infections were recorded as the most frequent precipitating events for exacerbation of asthma. Forty-nine intubations were initiated because of a clinical diagnosis of respiratory distress, but multiple indications were present in 42 admissions. One or more complications occurred in 31 episodes of endotracheal intubation and mechanical ventilation (45%). Death occurred in four (6%) of 69 admissions. Three of the four deaths occurred in patients who had a cardiorespiratory arrest before hospital admission. CONCLUSIONS: While complications occurred in 45% of patients with severe asthma requiring intubation and mechanical ventilation, the mortality rate was low. We conclude that intubation and mechanical ventilation in patients with life-threatening asthma are safe and beneficial interventions.

Adolescent↗
PubMed1992

Measurement of acyl-CoA dehydrogenase activity in cultured skin fibroblasts and blood platelets.

The measurement of acyl-CoA dehydrogenase activity is an essential part of the investigation of patients with suspected defects of fatty acid oxidation, and recently the organometallic oxidant ferricenium hexafluorophosphate has been introduced as an electron acceptor for these assays. However, we show that when medium-chain acyl-CoA dehydrogenase activity was measured in cultured skin fibroblasts and platelets from patients with proven defects of this enzyme, there was considerable residual enzyme activity when this electron acceptor was used. The ferricenium assay is not as specific as the anaerobic ETF-linked assay in the biochemical diagnosis of medium-chain acyl-CoA dehydrogenase deficiency in fibroblasts, and therefore is of limited clinical applicability in its present form.

Acyl-CoA Dehydrogenases↗
PubMed1992

The mouse alpha 1(XII) and human alpha 1(XII)-like collagen genes are localized on mouse chromosome 9 and human chromosome 6.

Type XII collagen is a member of the FACIT (fibril-associated collagens with interrupted triple helices) group of extracellular matrix proteins. Like the other members of this group, collagen types IX and XIV, type XII has alternating triple-helical and non-triple-helical domains. Because of its structure, its association with collagen fibrils, and its distribution in dense connective tissues, type XII is thought possibly to act as a cross-bridge between fibrils and resist shear forces caused by tension. A portion of the ffuse gene was isolated by screening a genomic library with a chicken alpha 1 (XII) cDNA probe, followed by subcloning and sequence analysis. Comparison of exon sequences with the sequence of a mouse cDNA clone allowed the mouse gene to be identified as the alpha 1 (XII) collagen gene. In the mouse, Col12a1 is located on chromosome 9, as determined by linkage analysis using DNA from interspecific backcrosses with Mus spretus. Screening of a human genomic library also allowed the isolation of a human alpha 1(XII)-like gene (CoL12A1). This gene was mapped to chromosome 6 by blot hybridization to DNA from human/hamster hybrid cell lines. This information should prove useful in determining the role of type XII collagen genes as candidate genes in inheritable connective tissue diseases.

Amino Acid Sequence↗
PubMed1992

Chloride ion in intensive care medicine.

OBJECTIVE: To review the physiology of the chloride ion and its relationship to various disease states encountered in the ICU. Special emphasis was paid to the renal handling of chloride and its role in the evaluation of the urine and serum anion gaps. Metabolic acidosis and alkalosis are discussed. DATA SOURCES: English-language articles were identified through a search of the MEDLINE and Index Medicus databases. Bibliographies of retrieved articles were examined for relevant articles. STUDY SELECTION: Approximately 125 articles and 25 textbook chapters were reviewed. Those articles most applicable to the ICU were used. Information contained in text chapters was included primarily in the tables. DATA EXTRACTION: All available information was reviewed and analyzed by the authors before inclusion. DATA SYNTHESIS: Guidelines for the evaluation of urine and serum electrolyte concentrations are presented. The use of the urine anion gap is discussed, particularly as it relates to the diagnosis of hyperchloremic metabolic acidosis. Stool chloride provides information relevant to congenital and acquired diarrheas. The evaluation of metabolic acidosis requires the calculation of the serum anion gap. Both normal and increased gap acidoses are discussed, although increased gap acidoses are more commonly encountered in the ICU. Urine chloride is invaluable in defining whether the metabolic alkalosis is sodium-chloride responsive (urine chloride less than 10 mmol/L) or sodium chloride-unresponsive (urine chloride greater than 20 mmol/L). CONCLUSIONS: Measurement of chloride is a valuable tool in the evaluation and treatment of a variety of disorders. Serum chloride is most helpful in assessing both normal and increased anion gap metabolic acidoses, while urine chloride finds utility in the diagnosis of metabolic alkalosis and hyperchloremia metabolic acidosis. The evaluation of any disturbance in chloride homeostasis that defies easy explanation necessitates the measurement of stool electrolytes.

Acid-Base Equilibrium↗
PubMed1992

Pericardiocentesis.

Cardiac tamponade is a life-threatening condition resulting from compression of the cardiac chambers by a pericardial effusion. The principal cause of pericardial effusion is malignant disease of the pericardium, but infectious causes and cardiac trauma are common as well. The patient with cardiac tamponade demonstrates an abnormal pulsus paradoxus, and clinical signs of shock and impending cardiovascular collapse occur with very severe cardiac compression. Relief of the increased intrapericardial pressure is mandatory to establish adequate cardiac output. The definitive treatment of cardiac tamponade is emergent removal of enough pericardial fluid to acutely lower intrapericardial pressure. Echocardiographic guidance may be used if immediately available, but is not required to perform pericardiocentesis in a critical situation. Placement of a pulmonary artery catheter prior to pericardiocentesis is not indicated in cardiac tamponade. Once cardiac output and tissue perfusion have been restored, further drainage procedures such as pericardial catheter placement or surgical drainage are indicated. Therapeutic measures to address the underlying disease process should be initiated after pericardial drainage is accomplished.

Aftercare↗
PubMed1992

Robotic method for the analysis of morphine and codeine in urine.

A totally automated procedure has been developed for the detection and quantitation of morphine and codeine in urine case samples. The samples were initially screened for these drugs by a Syva EMIT Toxicology System (ETS). A Zymate laboratory robotic system confirms positive samples from Syva ETS by performing the hydrolysis, extraction, and derivatization of morphine and codeine. The derivatized morphine and codeine were detected using gas chromatography/mass spectrometry (GC/MS). Enzymatic hydrolysis conditions were experimentally optimized during method development. The automation of these procedures has proven to be reliable and efficient.

Codeine↗
PubMed1992

Occupational exposure to cocaine involving crime lab personnel.

The possibility of exposure to cocaine as a result of analyzing it or handling material contaminated by it has been a major concern of laboratory personnel. Several different work environments and simulated situations were examined to assess the likelihood of this type of exposure occurring. Urine specimens were collected and evaluated for cocaine and benzoylecgonine using the Syva ETS System (EMIT). Each specimen was analyzed for the two substances using gas chromatography/mass spectrometry (GC/MS). Urine specimens of laboratory-management personnel not working with drug samples showed no trace of cocaine or benzoylecgonine. A urinary benzoylecgonine level of 227 ng/mL was found in the specimen from one narcotics criminalist who was working on a routine case of 2 kilos of cocaine hydrochloride in the Narcotics Laboratory. A maximal urinary benzoylecgonine concentration of 1570 ng/mL was determined in the urine specimen from one narcotics criminalist who was sampling a case containing 50 kilos of cocaine hydrochloride over a period of 3 h. Decreasing the levels of airborne cocaine dust appears to minimize the amount of cocaine absorbed by the criminalists. Gloves, face masks, and goggles prove to be effective in minimizing exposure.

Air Pollution, Indoor↗
PubMed1991

The formation constants of ionomycin with divalent cations in 80% methanol/water.

The protonation constants and complex formation constants of ionomycin have been determined in 80% methanol/water (w/w) at 25.0 degrees C and mu = 0.050 (tetraethylammonium perchlorate). Potentiometric and spectrometric titration techniques give the following values for the mixed-mode protonation constants of ionomycin: log KH1 = 11.94 +/- 0.02 and log KH2 = 6.80 +/- 0.03. Comparison of these values with those for model compounds indicates that KH1 and KH2 refer to equilibria involving the beta-diketone and carboxylic acid moieties, respectively. Titrations of ionomycin with metal ion at fixed values of pH produced changes in the UV-visual absorbance spectra which were analyzed to give conditional complex formation constants, KMI'. The pH dependence of the values of KMI' indicated that 1:1 divalent metal ion-ionomycin (MI) complexes and protonated MHI+ complexes were formed in the pH range studied. The values of log KMI ranged from 5.30 +/- 0.11 for Sr2+ to 10.25 +/- 0.03 for Ni2+. The selectivity pattern and relative affinities (in parentheses) for the formation of the species MI are as follows: Ni2+ (2000) greater than Zn2+ (600) greater than CO2+ (440) greater than Mn2+ (47) greater than Mg2+ (1.00) greater than Ca2+ (0.21) greater than Sr2+ (0.022). Logarithmic values of KMHI, for the reaction MI + H+ in equilibrium MHI+, ranged from 5.9 (Ni2+) to 8.4 (Sr2+). Calculations using the values of the equilibrium constants determined indicate that an appreciable fraction of the complexed ionophore exists as the protonated complex, MHI+, in the pH range of 6.5-8.5.

Cations↗
PubMed1991

Effects of solute concentration on the entrapment of solutes in phospholipid vesicles prepared by freeze-thaw extrusion.

Phospholipid vesicles prepared by the freeze-thaw extrusion method contain internal solute concentrations which are much higher than the external values (entrapment ratios much greater than 1). This concentrating effect is a complex function of the total impermeant solute concentration in the medium used to prepare vesicles, the presence or absence of permeant solutes in the medium and the apparent competitive binding interactions between solutes and phospholipid. Increases in water phase solute concentration during freezing are thought to underlie the concentrating phenomenon, while osmotic pressure driven lysis of vesicles during thawing appears to limit its magnitude. By judicious selection of solute concentration and physical properties, further increases in the entrapment ratio should be obtainable, improving the usefulness of these vesicles as drug delivery vesicles and experimental systems.

Calcium↗
PubMed1991

The use of role-play in teaching medical students obstetrics and gynaecology.

There is a great need to review and critically assess medical education. Role-play has seen increasing use as an educational tool. We investigated its role in a 'conventional speciality', Obstetrics and Gynaecology. This is a part of the medical curriculum where communication skills are particularly important, but difficult to learn in practice. Twenty-one medical students took part in three role-play case studies. An innovation we implemented was the use of 'time outs' which could be called at any time through a session. After the exercise students were required to complete a questionnaire designed to probe their attitudes towards the experience. The results indicate that this technique can be successfully used in teaching a conventional speciality. Unlike some previous studies we also found this to be a satisfactory tool in teaching the factual part of the course. We found the 'time out' innovation to be an important aid. We argue that there is an important niche for role-play in medical education.

Clinical Competence↗
PubMed1991

Biochemical changes in endometrial carcinoma and their correlation to clinical outcome and prognosis.

Four biochemical parameters, soluble oestradiol (REC) progesterone (RP) receptors, 17B oestradiol and isocitric dehydrogenase enzymes were studied to evaluate hormone sensitivity in 51 patients with endometrial carcinoma. Samples of tumours were taken before and after 7 to 14 days of oral medroxyprogesterone acetate (MPA) treatment for histological and biochemical analysis. Hormone sensitivity assessed by a decrease in receptor concentration after MPA in REC rich (p less than 0.005) and RP rich (p less than 0.02) tumours was 65% and 63% respectively. Induction of isocitric dehydrogenase enzyme with MPA was highly significant in REC rich (p less than 0.0001) and RP rich (p less than 0.001) tumours, as was the induction of 17B oestradiol dehydrogenase in REC rich (p less than 0.01) and RP rich (p less than 0.005), confirming progestogen sensitivity. Post MPA dehydrogenase enzyme levels predicted survival more accurately than pre MPA receptor status of the tumours.

Adenocarcinoma↗
PubMed1990

General features in the stoichiometry and stability of ionophore A23187-cation complexes in homogeneous solution.

Existing literature describing the stoichiometry and stability of complexes between A23187 and divalent cations in solution has been extended to include additional transition series cations, the heavy-metal cations Cd2+ and Pb2+, plus seven lanthanide series trivalent cations. Stability constants of 1:1 complexes between the ionophore and the divalent cations vary by 6.2 orders of magnitude between Cu2+ and Ba2+ which are the strongest and weakest complexes, respectively. Considering alkaline-earth and first-series transition cations together, the pattern of stability constants obeys the extended Irving-Williams series as is seen with many nonionophorous liganding agents. Cd2+ and Pb2+ are bound with an affinity similar to those of Mn2+ and Zn2+, whereas the lanthanides are bound with little selectivity and slightly higher stability. Titration of the ionophore in the 10(-5) M concentration range with di- and trivalent cations gives rise first to complexes of stoichiometry MA2 and subsequently to MA as the metal concentration is increased. The second stepwise stability constants for formation of the MA2 species exceeds the first constant by approximately 10-fold. With lanthanides, heavy metals, and transition-metal cations, OH-, at near physiological concentrations, competes significantly with free ionophore for binding to the 1:1 complexes. This competition is not apparent when Ca2+ or Mg2+ are the central cations. Possible implications of the 1:1 complex selectivity pattern, the ionophore-hydroxide competitive binding equilibria, and potential ternary complexes involving 1:1 ionophore:cation complexes and other anions present in biological systems are discussed with respect to the ionophore's transport selectivity and biological actions.

Biological Transport↗
PubMed1990

Factors affecting solute entrapment in phospholipid vesicles prepared by the freeze-thaw extrusion method: a possible general method for improving the efficiency of entrapment.

It is often assumed that the internal solute concentrations of phospholipid vesicles are equal to those in the medium in which they were prepared, particularly when freeze-thaw cycles are employed during the procedure. Conditions are reported here which when used to prepare vesicles by the polycarbonate filter extrusion method, produce approximately 12- and approximately 7-fold higher internal concentrations of Ca2+ and sucrose, respectively, than exist in the external medium. Formation of these large gradients is dependent upon the use of freeze-thaw cycles during preparation, on the presence of tetraethylammonium perchlorate in the medium, and is independent of media pH across the region of pH 5-9. Gradient formation is antagonized by high concentrations of an impermeant solute (NaCl). It is proposed that gradients form because solutes are concentrated by exclusion from ice during freezing but that they are normally dissipated by osmotic lysis during thawing. The presence of a permeant solute such as tetraethylammonium perchlorate provides an alternative mechanism to balance osmotic pressure, thereby preserving the gradients of impermeable species.

Calcium↗
PubMed1990

Effect of perilesional injection of alpha-interferon on cervical intraepithelial neoplasia and associated human papillomavirus infection.

In this controlled prospective study, 14 patients with cervical intraepithelial neoplasia (CIN) were observed for one month to exclude spontaneous regression, and then seven patients were treated twice-weekly with perilesional injections of alpha-interferon. Both groups were monitored colposcopically, and advised to use the contraceptive sheath. Cervical smears and biopsies for histology and viral studies were taken before and after the study. There was an improvement of six out of seven of the study group, with two complete cures. Koilocytosis disappeared if it had been present initially, as did human papillomavirus (HPV) 16. By contrast, three control cases showed improvement, but there were no cures, and one case deteriorated; Koilocytosis (2 cases) did not change; HPV 16 disappeared in two controls and appeared in one. A new focus of dysplasia appeared in a part of the transformation zone not being treated with alpha-interferon in one of the study cases, illustrating the advisability of treating the whole transformation zone in CIN.

Cervix Uteri↗
PubMed1988

Modes of spontaneous chromosomal mutation and karyotype evolution in ants with reference to the minimum interaction hypothesis.

Aspects of chromosomal mutation and karyotype evolution in ants are discussed with reference to recently accumulated karyological data, and to detailed karyotype analyses of several species or species complexes with low chromosome number and unusual chromosomal mutations (the complexes of Myrmecia pilosula (Smith) (n = 1, 5 or 9 to 16); M. piliventris Smith (n = 2, 3-4, 17 or 32), and Ponera scabra Wheeler (n = 3 or 4, 2n = 7 or 8). Translocations and Robertsonian polymorphisms are confirmed to be non-randomly distributed among ants -the former are found at high frequencies in species with low chromosome numbers (n less than or equal to 12), while the latter predominate in those with high numbers (n greater than 12). This situation is consistent with the minimum interaction hypothesis of Imai et al. (1986), under which translocations are expected to occur most frequently in low-numbered karyotypes, and that the resulting genetic risks are minimized by increases in chromosome and/or arm numbers through centric fission and pericentric inversion. Centric fusion is considered to be a transient event in karyotype evolution, resulting from telomere instability in acrocentric chromosomes.

Animals↗
PubMed1987

Equilibria between ionophore A23187 and divalent cations: stability of 1:1 complexes in solutions of 80% methanol/water.

The cation complexation equilibria between ionophore A23187 and several alkaline earth and first transition series divalent cations have been investigated. Absorption and fluorescence spectroscopy were used to monitor the reactions which were studied in solutions of 80% methanol/water, at 25 degrees C, and under conditions of controlled ionic strength and pH. Titration of the ionophore with divalent cations results first in formation of the dimeric species MA2 and subsequently in the formation of MA+ by disproportionation of the first product. With Zn2+, Ni2+, and Co2+ (above pH approximately 6), a third species is detected which is postulated to be MA.OH. The existence of this species with Mn2+ and alkaline earth cations is uncertain. For formation of MA2, the second stepwise stability constant is similar to or exceeds the first value with all cations studied. However, it is possible to isolate the first reaction and determine accurate stability constants by working at an ionophore concentration of 3 X 10(-8) M or less and by employing pH values which preclude interference by the mixed ionophore/hydroxide species. Under these conditions, the relationship between log KMA' and pH is linear and displays a slope of 1.0. pH-independent stability constants were calculated by using pH-dependent stability constants and the known value of the ionophore's protonation constant in this solvent. The logarithms of the values obtained ranged from 7.54 +/- 0.06 for Ni2+ to 3.60 +/- 0.06 for Ba2+. The selectivity sequence and relative affinities (in parentheses) for the species MA+ are as follows: Ni2+ (977) greater than Co2+ (331) greater than Zn2+ (174) greater than Mn2+ (34) greater than Mg2+ (1.00) approximately equal to Ca2+ (0.89) greater than Sr2+ (0.20) greater than Ba2+ (0.11). Data are discussed in comparison to other studies on the complexation properties of A23187 and in terms of their significance to interpreting the transport properties of this ionophore.

Calcimycin↗