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Biomedical subjects

M A Taylor

Publications and source records attributed to M A Taylor.

At least 19 recordsLinked to original sources
PubMed1992

Carboxyl-terminal processing of the D1 protein and photoactivation of water-splitting in photosystem II. Partial purification and characterization of the processing enzyme from Scenedesmus obliquus and Pisum sativum.

The D1 polypeptide of photosystem II (PSII) is synthesized as a precursor that is processed by cleavage at the carboxyl terminus during assembly of the active PSII complex. A mutant of the green alga Scenedesmus obliquus, LF-1, inactive in water-splitting, lacks the D1 processing activity but assembles otherwise normal PSII complexes containing the precursor D1 molecule. We have isolated and partially purified a soluble protease from sonicated thylakoids of both wild-type S. obliquus and Pisum sativum which will process the precursor D1 molecule in PSII-enriched membranes from the LF-1 mutant to the mature size. After processing (but not before), photoactivation of these PSII membranes in the presence of manganese restores water-splitting to levels seen after photoactivation of PSII membranes from dark-grown, wild-type, cells. The protease is unable to process D1 in intact thylakoids from the LF-1 mutant but processes D1 if present during sonication of the thylakoids, indicating that processing of the carboxyl-terminal extension of D1 occurs in the lumen of the thylakoid. The processing protease from both S. obliquus and P. sativum is a single subunit enzyme of native molecular mass 33-35 kDa. Processing rate is optimal at pH 6.5. Processing in vitro is evident within 5 min and is markedly inhibited by millimolar concentrations of divalent cations (Cu, Zn greater than Mn greater than Ca, Mg) but not by any known inhibitors of the major classes of proteases. The protease is inactive against the precursors of other thylakoidal proteins and is thus distinct from the thylakoidal amino-terminal processing enzyme involved in the removal of transit peptides from cytoplasmically-synthesised proteins imported into the thylakoid lumen.

Algal Proteins↗
PubMed1992

Elongational flow studies on DNA in aqueous solution and stress-induced scission of the double helix.

Elongational flow techniques are used to investigate the birefringent response and flow-induced molecular scission of monodisperse phage-DNA samples in aqueous solution. A 4-roll mill apparatus was used to characterize the solutions at low stain rates, epsilon less than or equal to 300 s-1, and the opposed jets apparatus used to study fracture of the DNA molecules at strain rates up to 15 x 10(3) s-1. The molecular weight values were measured before and after fracture in elongational flow using the high-resolution technique of pulsed field gel electrophoresis (PFGE). The birefringent response incorporates both rigid and flexible components. The birefringence is nonlocalized and rises gradually to a plateau value, similar to rigid-rod behavior. In addition a certain minimum value in the strain rate is necessary, an onset value epsilon 0, before the signal appears, indicating a flexible component. This behavior is consistent with a hinged-rod model and is similar to that observed for the protein collagen molecule at elevated temperature. We propose that this type of behavior is likely for multistrand rope-like macromolecules where localized separation or partial untwisting of the intertwined chains occurs, creating temporary hinges, in accordance with biochemical evidence for sequence-specific sites of flexibility. Results are presented on the entanglement effects at high concentrations. We have calculated rotational diffusion rates as a function of concentration and molecular weight. Using PFGE to measure the molecular weight profiles, our fracture studies at high strain rates demonstrate chain halving and quartering in accordance with the predictions of the thermally activated barrier to scission theory for single-chain polymers.

DNA, Viral↗
PubMed1992

Expression and sequence analysis of cDNAs induced during the early stages of tuberisation in different organs of the potato plant (Solanum tuberosum L.).

cDNA clones of two genes (TUB8 and TUB13) which show a 25-30-fold increase in transcript in the stolon tip during the early stages of tuberisation, have been isolated by differential screening. These genes are also expressed in leaves, stems and roots and the expression pattern in these organs changes on tuberisation. Southern analysis shows homologous sequences in the non-tuberising wild type potato species Solanum brevidens and in Lycopersicon esculentum (tomato). Sequence analysis reveals a high degree of similarity between the TUB13 cDNA, and a human S-adenosylmethionine decarboxylase gene. The predicted TUB8 peptide sequence shows several repeats of alanine, glutamate and proline which suggests a structural role for the encoded protein.

Adenosylmethionine Decarboxylase↗
PubMed1992

Fabrication of bolus compensators used in the treatment of irregular tissue surfaces in radiation therapy.

Radiation treatment involving irregular surfaces of facial topography often causes difficulties for the radiation oncologists. The isodose curves normally used become skewed, thereby making treatment planning more complex. A simple and useful technique is presented describing the use of dental materials to make a bolus compensator to aid in radiation therapy of nonplanar surfaces. This technique will allow the radiation oncologist to treat these patients in a most efficient manner. The materials needed are readily available to the dentist and are easily handled.

Equipment Design↗
PubMed1992

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) methods for the detection of anthelmintic resistance in nematodes of veterinary importance.

Methods have been described to assist in the detection of anthelmintic resistance in strongylid nematodes of ruminants, horses and pigs. Two tests are recommended, an in vivo test, the faecal egg count reduction test for use in infected animals, and an in vitro test, the egg hatch test for detection of benzimidazole resistance in nematodes that hatch shortly after embryonation. Anaerobic storage for submission of faecal samples from the field for use in the in vitro test is of value and the procedure is described. The tests should enable comparable data to be obtained in surveys in all parts of the world.

Animals↗
PubMed1992

Active papain renatured and processed from insoluble recombinant propapain expressed in Escherichia coli.

For the first time the pro-form of a recombinant cysteine proteinase has been expressed at a high level in Escherichia coli. This inactive precursor can subsequently be processed to yield active enzyme. Sufficient protein can be produced using this system for X-ray crystallographic structure studies of engineered proteinases. A cDNA clone encoding propapain, a precursor of the papaya proteinase, papain, was expressed in E. coli using a T7 polymerase expression system. Insoluble recombinant protein was solubilized in 6 M guanidine hydrochloride and 10 mM dithiothreitol, at pH 8.6. A protein-glutathione mixed disulphide was formed by dilution into oxidized glutathione and 6 M GuHCl, also at pH 8.6. Final refolding and disulphide bond formation was induced by dilution into 3 mM cysteine at pH 8.6. Renatured propapain was processed to active papain at pH 4.0 in the presence of excess cysteine. Final processing could be inhibited by the specific cysteine proteinase inhibitors E64 and leupeptin, but not by pepstatin, PMSF or EDTA. This indicates that final processing was due to a cysteine proteinase and suggests that an autocatalytic event is required for papain maturation.

Amino Acid Sequence↗
PubMed1979

Differential EEG patterns in affective disorder and schizophrenia.

We analyzed the EEGs of 27 schizophrenic patients and 132 patients with affective disorder who received diagnoses according to rigorous research criteria. The proportion of abnormal EEGs was twice as great among schizophrenics as among affectives, and when the groups were compared for localized cortical differences, schizophrenics had more temporal abnormalities and affectives more parieto/occipital abnormalities. There was also a trend toward different hemispheric lateralization for the two groups, with a reversal of the relative proportions of left- and right-sided abnormalities. These differences were unrelated to age, sex, severity of illness, or past or present drug administration. These findings are complementary to those of other workers, lend support to the validity of our diagnostic research criteria, and provide additional evidence for neurophysiological differences between schizophrenics and patients with affective disorder.

Adult↗
PubMed1979

Unipolar mania revisited.

In a more sophisticated replication of an earlier study (Abrams and Taylor 1974), we examined 77 manic patients, of whom 29 had never suffered a depressive illness, and had two or more manic attacks. These unipolar manics were similar to the 48 bipolar manics for a wide variety of clinical, phenomenological, historical, laboratory and demographic variables, generally supporting our earlier findings. However, the present sample showed a striking excess of males among the unipolar manics, as well as an increased morbid risk for unipolar depression in first-degree relatives. Although not readily explainable, these differences suggest that it is premature to equate unipolar mania with classical bipolar illness. Further studies of unipolar mania are in progress.

Adult↗
PubMed1979

Lateralized neuropsychological dysfunction in affective disorder and schizophrenia.

The authors compared the cognitive functioning of 22 schizophrenic patients, 105 patients with affective disorder, and 99 age-matched normal control subjects. Results of an aphasia screening test indicated that the schizophrenic patients made more total errors and more dominant temporal/temporoparietal errors than patients with affective disorders and that patients in both groups made more errors than controls. Patient sex, age, drug treatment received at test time, previous neuroleptic drug treatment, and severity of illness did not account for the differences. These findings support the validity of the authors' diagnostic research criteria and confirm prior reports of differences in dominant hemisphere dysfunction between schizophrenic patients and patients with affective disease.

Adult↗
PubMed1979

Implications of rubella susceptibility in young adults.

Rubella history and antibody titre were determined for 457 medical, graduate, and physician assistant students. Eighteen per cent were estimated at risk for rubella. There were no male-female differences. Health-profession students did not differ in rubella immune status from the general population. History was not helpful in assessing immune status. Approximately one-half of persons with low antibody titres had considered themselves immune, while one-half with moderate to high antibody titres had considered themselves at risk. Less than one-half of students with low antibody titres available themselves of immunization which was recommended and offered. With a high percentage of adult females at risk for rubella even in a health-motivated population and with poor follow-up on recommended immunization, current immunization practices must be improved if congenital rubella syndrome is to be further reduced. Mass inoculation of school age males and prepubertal school age females without prior determination of rubella antibody titres is suggested as a cost-effective means of decreasing incidence of congenital rubella syndrome.

Adult↗
PubMed1979

Catatonia and mania: patterns of cerebral dysfunction.

We performed a factor analysis on research data from 55 consecutive hospitalized psychiatric patients who showed one or more of eight catatonic motor features. Two factors were extracted, accounting for 32% of the variance. Factor 1 (mutism, negativism, stupor) corresponded to the clinical syndrome of negativistic stupor and was unrelated to diagnosis, sex, age at onset, family history, or treatment response. Factor 2 (mutism, stereotypy, catalepsy, automatic obedience) corresponded to the classical description of catatonia, was associated with a research diagnosis of mania, and tended (p less than 0.10) to predict a favorable treatment response. We suggest that the two factors may reflect different forms of cerebral dysfunction which, in the case of Factor 2, may provide clues as to the nature of the morbid process in mania. Republication is now in progress in a different sample.

Adult↗
PubMed1978

Prevalence of pathogenic yeasts and humoral antibodies to candida in diabetic patients.

The prevalence of oral yeasts and humoral precipitating antibodies to candida was estimated in 204 unselected diabetic patients (172 outpatients and 32 inpatients). Yeasts, mainly Candida albicans, were isolated from the mouths of 41% of the outpatients and precipitins were found in 17.5% although none of the patients had clinically overt candidiasis. The extent of oral yeast colonisation and incidence of antibodies was not related to their antidiabetic treatment or to the duration of their diabetes. It was, however, related to the blood glucose and urine sugar levels at the time they were sampled, the highest incidence being among the diabetic inpatients with high blood glucose levels at the time of sampling and the lowest among outpatients with normal blood glucose levels at the time of sampling. There was no such correlation when diabetic control over the previous 12-month period was considered.

Antibodies, Fungal↗