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Biomedical subjects

J H Baker

Publications and source records attributed to J H Baker.

At least 37 records · Page 2Linked to original sources
PubMed1986

Peripheral eosinophilia and respiratory symptoms in rubber injection press operators: a case-control study.

To evaluate a suspected association between an outbreak of acute respiratory illness and eosinophilia and employment as a rubber worker, we performed a retrospective review of medical records of rubber workers employed from September 1983 to July 1984 in a plant housing a thermoinjection process. Twenty-five workers met the case definition of a respiratory illness requiring a physician visit. The predominant respiratory illness was acute in onset with cough, chest tightness, and dyspnea. Peripheral eosinophilia, up to 40% of white blood cells in a peripheral smear, was seen in 10 of 18 (56%) cases. Twenty-one of 25 white males with respiratory symptoms were employed in the thermoinjection process (odds ratio = 22, p less than .001). Smoking and employment in this process contributed independently to an increased risk of being a case as determined by a logistic regression analysis. Return to the plant building caused recurrence of symptoms in most cases, and these workers have been transferred or left the company. We conclude that a strong previously unrecognized association exists between employment in this neoprene rubber thermoinjection process and the development of an acute respiratory illness.

Adult↗
PubMed1985

The development of central cores in both fiber types in tenotomized muscle.

Using the histochemical reaction for myosin adenosine triphosphatase (ATPase), a study of the rat soleus muscle following tenotomy was undertaken. It was demonstrated that both type 2A and 2C fibers undergo degenerative changes following tenotomy. All previous studies have stated that only type 1 fibers were affected and developed central core lesions and that type 2 fibers were somehow protected from the degenerative process. The results of this experiment illustrate that central core lesions will develop in all three fiber types (types 1, 2A, and 2C) of the soleus following tenotomy.

Adenosine Triphosphatases↗
PubMed1984

Traumatic cerebral flaccid paraplegia.

Two cases of paraplegia caused by head injuries sustained in recent military conflicts are presented. The underlying pathological disturbances could be related to the CT scan appearances and are discussed in the light of previously reported series. Both cases were remarkable for an early and prolonged paraplegia which was flaccid, rather than spastic, and for the sensory impairment produced.

Adult↗
PubMed1984

Atropine toxicity in acute cervical spinal injury.

A patient with a C.3/C.4 fracture dislocation resulting in an incomplete tetraplegia was treated with Cimetidine 400 mg bd to prevent gastrointestinal bleeding and 0.6 mg of atropine 6 hourly. He developed symptoms of atropine poisoning in the form of hallucinations, confusion and dilated pupils when the total dosage of atropine was 2.8 mg. This is far below the toxic levels normally considered necessary to produce atropine poisoning. The patient recovered. In view of the fact that this combination of drugs may be used in spinal units to prevent gastrointestinal bleeding and bradycardia, this experience is reported.

Adult↗
PubMed1983

Ultrastructural and biochemical changes in rat soleus muscle following tenotomy.

This study was designed to correlate changes in the rate-limiting enzymes of glycogen synthesis (glycogen synthase) and glycogen breakdown (glycogen phosphorylase) with the ultrastructural changes which occur in the soleus muscle following tenotomy. Soleus muscles were removed at 1, 2, 3, 7, 14, 21, and 63 days after tenotomy and were prepared for electron microscopy or frozen for enzyme analysis. In the first 7 days posttenotomy, soleus muscle fibers underwent a series of degenerative changes, while both synthase and phosphorylase activities decreased. Over the next 8 weeks the histological appearance of the soleus muscle eventually returned to normal while synthase and phosphorylase activities increased. We suggest that recovery from tenotomy involves an increase in the energy demands of the muscle, resulting in the increased activity of the key rate-limiting enzymes of muscle glycogen metabolism from the drastically reduced levels observed in the period before recovery begins.

Animals↗
PubMed1983

Bacterial activity associated with the decomposition of woody substrates in a stream sediment.

Ground bark and heartwood from Alnus rubra and Pseudotsuga menziesii were added to a muddy sediment from a small Oregon stream and incubated in situ. Carbon dioxide and methane production rates were increased by all amendments, the biggest increase being shown with A. rubra wood. Except for sediment amended with A. rubra wood, nitrogen fixation rates from all treatments (including the control) were approximately 0.1 nmol/g per h throughout the 6-month study period. Contrary to expectations, neither bark had a noticeable adverse effect on microbial activity, but the A. rubra wood promoted nitrogen fixation. These results help to explain the faster rate of decomposition of A. rubra wood in water compared with that of P. menziesii described in the literature. The uptake kinetics of glucose (V(max)) did not follow the same pattern as gas evolution.

Journal Article↗
PubMed1978

Changes in length of sarcomeres following tenotomy of the rat soleus muscle.

Tenotomy of the proximal and distal tendons of the soleus muscle of female Wistar rats was performed and sarcomeric length and muscle fascicle length measured. On the first postoperative day muscle bellies were found shortened and their sarcomeric length considerably reduced. Four weeks following tenotomy, although the muscle bellies remained shortened, sarcomeric length was comparable with that of control muscles. Measurement of muscle fascicle lengths at this time showed that those of experimental muscles were nearly 50% less than those of control muscles. It was concluded from these experiments that a reduction of the number of sarcomeres in series had occurred, thus compensating for the reduced length of the muscle belly.

Animals↗
PubMed1978

Autoradiographic study of the permeability characteristics of the small intestine.

This autoradiographic study demonstrates the distribution of a range of small solutes and macromolecules in the mucosa of the guinea-pig small intestine after intracardiac injection. The substances investigated were: 14C-urea, 3H-mannose, 3H-inulin, and 125I polyvinylpyrrolidone (PVP). Small bowel biopsies were taken at intervals from one to 60 minutes after injection and the tissues processed for autoradiography. Light microscopic examination of the autoradiographs showed that the compartmental distribution depended on the molecular size of the substances being studied. Urea and mannose, as small solutes, were uniformly distributed throughout the intravascular, extravascular, and epithelial compartments. Inulin was evenly distributed in the vessel lumen and extravascular space but there was a considerable drop in concentration in the epithelium. PVP exhibited the most marked gradients, the concentration being greatest in the vascular lumina, lower in the extravascular space, least in the epithelium. Thus there appear to be two barriers to macromolecular passage which are freely permeable to small solutes: the capillary wall and the epithelium. At a light microscopical level it is not possible to observe whether the limiting membrane of each of these barriers is the cell plasmalemmal membrane or the basement membrane. The selectivity of the epithelial barrier is greater than that of the capillary barrier.

Animals↗
PubMed1978

Estimation of bacterial production in fresh waters by the simultaneous measurement of [35S]sulphate and d-[3H]glucose uptake in the dark.

Sulphate uptake in the dark by phytoplankton constitutes a severe limitation to the determination of bacterial heterotrophic production from sulphate-uptake rates. Consequently a modification to the 35S-method has been developed involving size fractionation to separate the algae from the bacteria. Both the whole water sample and the algae-free filtrate are incubated in the dark with trace quantities of [3H]glucose, whereas the filtrate alone is incubated with 35SO4. The experimental determined ratio (whole sample glucose assimilation: filtrate glucose assimilation) is used to correct the measured sulphate uptake (filtrate) and yields an estimate of bacterial sulphate uptake in the whole sample. A potential filtration artefact has been demonstrated in the 35SO4 uptake methodology. Excision of the outer edge of the membrane filter and counting of the inner wetted circle alone eliminated this problem and significantly improved the analytical performance of the method: coefficient of variation approximately 5%, detection limit approximately 2 ng S l-1 h-1. The modified [35SO4]-[3H]-glucose method was applied to samples from an English chalk stream: bacterial sulphate uptake was higher during the spring diatom maximum (10.6 ng S l-1h-1) than 3 weeks later when detritus dominated the seston (4.9 ng S l-1h-1). We estimate the corresponding rates of formation of particulate (bacterial) carbon to be 0.53 and 0.24 microgram C l-1h-1 respectively.

Bacteria↗
PubMed1969

Role of the accompanying anion in the effect of calcium salts on potassium uptake by excised barley roots.

The effect of addition of Ca salts on accumulation of K from 5 mN KCl or K(2)SO(4) solutions was found to depend on whether Ca was added as Cl or SO(4) salt. Chloride as well as K uptake was increased when Ca and Cl concentrations in culture solutions were increased. Pre-treatment of roots with CaCl(2) stimulated subsequent K uptake from K(2)SO(4) solutions as compared to pre-treatment with distilled water but pre-treatment with CaSO(4) did not. The results indicate that addition of Ca salts to KCl or K(2)SO(4) solutions increased anion uptake and the effect of the addition of the Ca salts on K uptake was in part the result of increased anion uptake and not entirely a direct effect of Ca.In contrast, accumulation of Na and K from solutions containing these ions as SO(4) or Cl salts was changed from preferential uptake of Na to preferential uptake of K by addition of either CaCl(2) or CaSO(4). Thus, while Ca salts may influence K accumulation partly as a result of effects on anion uptake, the selectivity for K uptake depends on the presence of Ca and is influenced little by the accompanying anion.

Journal Article↗