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Biomedical subjects

M A Harrison

Publications and source records attributed to M A Harrison.

At least 19 recordsLinked to original sources
PubMed1992

Protein phosphorylation and Mg2+ influence light harvesting and electron transport in chloroplast thylakoid membrane material containing only the chlorophyll-a/b-binding light-harvesting complex of photosystem II and photosystem I.

A material containing only photosystem I (PSI) and the chlorophyll-a/b-binding light-harvesting complex of PSII (LHC-II) has been isolated from the chloroplast thylakoid membrane by solubilization with Triton X-100. Fluorescence spectroscopy shows that, within the material, LHC-II is coupled to PSI for excitation-energy transfer and that this coupling is decreased by the presence of Mg2+, which also decreased PSI electron transport specifically at limiting light intensity. Inclusion of phosphorylated LHC-II within the material did not alter its structure, but gave decreased energy transfer to PSI and inhibition of electron transport which was independent of light intensity, implying effects of phosphorylation on both light harvesting and directly on electron transport. Inclusion of Mg2+ within the phosphorylated material gave decreased energy transfer, but slightly increased PSI electron transport. A cation-induced direct promotion of PSI electron transport was also observed in isolated PSI particles. The PSI/LHC-II material represents a model system for examining protein interactions during light-state adaptations and the possibility that LHC-II can contribute to the antenna of PSI in light state 2 in vivo is discussed.

Chlorophyll↗
PubMed1992

Benesh Movement Notation. A tool to record observational assessment.

This article describes the introduction into physiotherapy practice of Benesh Movement Notation, a method for recording observations of patients' posture and movement sequences. Assessments of the technique show it to be a reliable and practical tool for clinical use.

Documentation↗
PubMed1991

Photosynthetic electron transport controls nitrogen assimilation in cyanobacteria by means of posttranslational modification of the glnB gene product.

A glnB gene is identified in the cyanobacterium Synechococcus sp. PCC 7942, and its gene product is found to be covalently modified as a result of imbalance in electron transfer in photosynthesis, where photosystem II is favored over photosystem I. The gene was cloned and sequenced and found to encode a polypeptide of 112 amino acid residues, whose sequence shows a high degree of similarity to the Escherichia coli regulatory protein, PII. In E. coli, PII is involved in signal transduction in transcriptional and post-translational regulation of nitrogen assimilation. Increase in ammonium ion concentration is shown to decrease covalent modification of the Synechococcus PII protein, as in enteric bacteria. We therefore propose that the photosynthetic electron transport chain may regulate the pathway of nitrogen assimilation in cyanobacteria by means of posttranslational, covalent modification of the glnB gene product. The existence of the glnB gene in different strains of cyanobacteria is demonstrated and its implications are discussed.

Amino Acid Sequence↗
PubMed1991

Cyanobacterial thylakoid membrane proteins are reversibly phosphorylated under plastoquinone-reducing conditions in vitro.

Reversible, light-dependent protein phosphorylation was observed in isolated thylakoid membranes of the cyanobacterium Synechococcus 6301. A polypeptide of 15 kDa in particular was phosphorylated under plastoquinone-reducing conditions and was not phosphorylated under plastoquinone-oxidising conditions. Phosphorylation and dephosphorylation reactions involving this and several other membrane polypeptides showed sensitivity to inhibitors of protein kinases and phosphatases. Changes in phosphorylation state correlated with changes in low temperature fluorescence emission characteristic of changes in excitation energy distribution between the photosystems. The 15 kDa phosphopolypeptide is likely to be involved directly in light state adaptations in cyanobacteria.

Cyanobacteria↗
PubMed1990

Modification of a glnB-like gene product by photosynthetic electron transport in the cyanobacterium Synechococcus 6301.

Covalent modification of a 13 kDa soluble-phase protein occurs during adaptation of cells of the cyanobacterium Synechococcus 6301 (mutant AN112) to light specifically absorbed by photosystem II. This adaptation is accompanied by functional changes indicative of altered excitation energy distribution between the photosystems. The 13 kDa protein is identified by solid-phase N-terminal sequencing as a protein related to PII, the glnB gene product of E. coli. In E. coli, the PII protein undergoes uridylylation and acts as a regular of glutamine synthetase at both the post-translational and transcriptional levels. The implications of modification of a transcriptional regulator by photosynthetic electron transport are discussed.

Amino Acid Sequence↗
PubMed1990

Occupational asthma and specific IgE to a diazonium salt intermediate used in the polymer industry.

This study describes sensitization to a diazonium salt intermediate, diazonium tetrafluoroborate (DTFB), produced during the manufacture of a fluorine polymer precursor. Most of the workers exposed to DTFB powder complained of respiratory and mucosal irritation. However, some of these individuals had symptoms typical of occupational asthma. Clinical and immunologic studies, including bronchial provocation testing and specific IgE measurements, were performed on two individuals with asthmatic symptoms associated with exposure to DTFB. These studies confirmed a diagnosis of occupational asthma. In an investigation of 43 other exposed workers in two separate factories handling the diazonium compound, specific IgE antibodies to DTFB-human serum albumin conjugate were found in 20% of individuals. There was a good correlation between specific IgE and exposure-related respiratory symptoms, which suggests an IgE-mediated pathogenesis. DTFB-human serum albumin conjugates were characterized by electrophoretic techniques, and it was found that conjugates prepared at pH 10 elicited optimum IgE binding in RAST. In vitro cross-linking of albumin by DTFB was demonstrated but had no effect on RAST binding. Our findings on the effect of pH and polymerization on IgE binding support proposed mechanisms for in vivo conjugation and provide information on the antigenic determinants important in IgE recognition of hapten-carrier protein conjugates.

Antibody Formation↗
PubMed1989

Development of a three-channel, 24-h ambulatory esophageal pressure monitor.

We have developed a three-channel ambulatory esophageal pressure monitor and tested it with a series of 24-h studies. The monitor is a battery-operated, microprocessor-based device that measures pressures from three transducers positioned in the esophagus, stores the data in its memory, and transfers the data to an IBM PC computer system at the end of the recording period. Programs on the PC then analyze the data and identify contractile events, categorizing them according to specific parameters. Other programs display the pressure waveforms on the PC and allow visual inspection of the entire recordings or, alternatively, of particular events of interest. The system detects contractile abnormalities in patients with intermittent, noncardiac chest pains. We tested the system on ten normal subjects and found a relatively high incidence of what are usually considered "abnormal" contractions.

Esophagus↗
PubMed1988

The Geriatric Mental State (GMS) used in the community: replication studies of the computerized diagnosis AGECAT.

Three studies are reported using the Geriatric Mental State in one of its community forms on a total of 647 subjects aged over 65 and living in their own homes. The concordance between the computer diagnosis AGECAT and psychiatrists' diagnosis is at least as good in these replication samples as in the original studies (Copeland et al. 1986). AGECAT has been shown to be useful for epidemiological surveys and as a diagnostic guide for non-medical interviewers.

Diagnosis, Computer-Assisted↗
PubMed1987

Airborne aflatoxin in corn processing facilities in Georgia.

Problems affecting the health of agricultural workers in processing facilities where grains are contaminated with aflatoxin have been noted previously. Airborne particulates produced during processing are reported to produce various carcinomas when inhaled by factory workers. Two corn processing plants within Georgia were surveyed during the fall of 1984 and 1985 with utilization of an Andersen 6-stage air sampler, a high-volume air sampler and a slit sampler. No airborne aflatoxin was found; however, 10% of settled dust samples were contaminated with aflatoxin. The average particles were found to be globular in shape with an effective diameter between 2 to 3 microns. Only 30% of the bulk corn samples contained aflatoxin, which was present at low levels (0.15 to 8 ppb).

Aflatoxins↗
PubMed1986

Evaluation of particulate air samplers for airborne aflatoxin B1.

Five air samplers (Millipore, all-glass impinger, centrifugal, Andersen, and absorbent cotton) were evaluated for their ability to collect airborne grain particles contaminated with aflatoxin B1. Corn dust containing 100 micrograms aflatoxin B1/g was aerosolized within a containment system. Each device sampled 100 I air, thus exchanging the air in the chamber two times. Aflatoxin B1 was extracted from all sampling matrices and was detected and quantitated with thin-layer chromatography and scanning fluorodensitometry. The highest efficiency was obtained with the Millipore sampler, while the efficiencies of the centrifugal and the cotton samplers were almost identical. Efficiency of an Andersen was less, with no toxin recovered from an all-glass impinger. Measurement of particle size was accomplished with the Andersen sampler.

Aerosols↗
PubMed1985

Selective and differential medium for detecting Clostridium botulinum.

A selective and differential growth medium was developed for detection of Clostridium botulinum types A, B, and F. The medium consisted of peptone-glucose-yeast extract agar supplemented with cycloserine, 250 micrograms/ml; sulfamethoxazole, 76 micrograms/ml; and trimethoprim, 4 micrograms/ml as selective inhibitors and various types and levels of botulinal antibodies for type differentiation in the immunodiffusion reaction. Growth of proteolytic types of C. botulinum were not affected by the incorporation of the selective agents, but some nonproteolytic types were suppressed. Cross-reactions between types A and B were visually distinguishable, whereas cross-reactions between type F and Clostridium sporogenes did not occur at the optimum antibody titer. Optimum antibody titer varied with toxin type. The proposed selective differential medium should be valuable in isolating and typing of proteolytic C. botulinum types A, B, and F from samples containing mixed microbial populations.

Antitoxins↗
PubMed1975

Fibroxanthosarcoma of bone.

A tumour arising from the body of the eighth thoracic vertebra is believed to be the first recordedexample of a primary fibroxanthosarcoma of bone. Apart from the absence of a demonstrable storiform pattern, the histology conformed to that of fibroxanthosarcoma of the soft tissues. Ultrastructural studies showed that asteroid-like bodies seen in the cytoplasm of some tumour cells consisted of aggregated centrioles surrounded by cytoplasmic vacuoles. The finding of Langerhans cell granules in some tumour cells supported their identification as histiocytes. These granules have not previously been recorded in the fibrous histiocytoma group of tumours.

Aged↗