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Biomedical subjects

W R Bowen

Publications and source records attributed to W R Bowen.

10 recordsLinked to original sources
PubMed1998

Visualization of bacterial glycocalyx with a scanning electron microscope.

Using a new technique for scanning electron microscopic preparation, bacterial glycocalyx is seen in its natural, highly hydrated state for the first time. Visual images of the glycocalyx obtained from these preparations are a marked departure from the visual images of glycocalyx obtained previously with conventional scanning electron microscopic analysis. The dominating presence of glycocalyx visualized in its naturally hydrated state gives credence to the role of bacterial glycocalyx as a mechanical barrier to host defenses and antibiotics and supports the role of glycocalyx as a significant factor in bacterial virulence.

Animals↗
PubMed1991

Pathogenesis of onychoschizia (lamellar dystrophy).

Onychoschizia or lamellar dystrophy of the nails is common, especially in adult women, but little information is available about its cause. Most theories involve environmental factors, but supportive experimental data are scarce. Therefore we studied the in vitro nail changes produced by several organic solvents, detergents, water, other polar materials, and both acidic and basic solutions. Challenged and control fingernail clippings were examined grossly, microscopically, and by scanning electron microscopy at regular intervals. There was a progressive increase in severity with prolonged wetting and drying. By 3 weeks, scanning electron microscopy demonstrated unattached individual cells in empty spaces in which separation was more prominent. Basic solutions caused some softening, but layering (peeling) was seen only after repeated hydration and dehydration. Although other factors may influence onychoschizia, the typical changes can be produced in normal nails after a 21-day challenge of repeated exposure to water followed by dehydration. These findings suggest a probable cause for the condition and a logical approach to management.

Adult↗
PubMed1990

Nephrotoxic and ototoxic agents.

It is well established that many drugs, such as the aminoglycoside antibiotics and the chemotherapeutic drug cisplatin, are capable of inducing both nephrotoxicity and ototoxicity. The factors that selectively predispose the kidney and inner ear to the toxic effects of these agents as well as the mechanism by which damage is produced are not well defined. The two organs differ greatly in their exposure to these toxic agents. The kidney has an abundant vascular supply and tends to selectively concentrate a number of drugs within the renal cortex or medulla, often to toxic levels. The vascular supply of the inner ear is not as extensive. In addition, the stria vascularis of the cochlea may act as a functional regulator of drug entry into inner ear fluids. The absorption of drugs into perilymph and endolymph is poorly understood. Selective accumulation theories of drug accumulation in the inner ear must be questioned because of the results of recent pharmacokinetic studies, which give contrary data. Drug-induced ototoxicity and nephrotoxicity can be explained on a cellular level. Studies using radiolabeled gentamicin suggest that binding mechanisms of the drug to the plasma membrane of the outer hair cells of the cochlea and vestibular apparatus and to the brush border receptors of the renal proximal convoluted tubules are similar. This suggests the same receptor sites for aminoglycosides occur in otic and renal organs. Calcium channels are implicated because of the reversibility of aminoglycoside-induced changes in the cochlear microphonic by calcium and other divalent cations. Calcium channel blockers, such as verapamil, reduce the nephrotoxicity of a number of drugs that are also ototoxic. Studies are needed to assess potential prevention of ototoxicity by use of these same calcium channel blocking agents. Aminoglycosides concentrate within the lysosomes of renal proximal tubular cells. Possibly, they also may concentrate in lysosomes within the cells of cochlear and vestibular structures. Nephrotoxic heavy metals concentrate within proximal tubular cells and, some, such as lead or bismuth, specifically concentrate within intracytoplasmic or intranuclear inclusion bodies. Studies are necessary to determine if the same metals accumulate within the cochlear and vestibular cells, inclusion bodies, or both. These questions and others must be answered before it can be determined why many nephrotoxic drugs and agents are also ototoxic.

Adolescent↗
PubMed1970

Symbiosis between Euglena and damselfly nymphs is seasonal.

An endosymbiotic association has been demonstrated between Euglena and nymphs of three species of damselfly. The hindgut of the nymphs is inhabited by the euglenoid only during the winter. Symbiotic associations involving green euglenoids and insects are virtually unknown.

Animals↗