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Biomedical subjects

J A Benson

Publications and source records attributed to J A Benson.

At least 91 records · Page 5Linked to original sources
PubMed1978

A complement fixation test for antibody to the contagious equine metritis organism.

A complement fixation test (CFT) based on that used for brucellosis (Brinley Morgan and others 1971) has been developed for use on the sera of horses exposed to the contagious equine metritis (CEM) organism. None of 50 single samples from horses thought to be unexposed to the CEM organism was positive to the test, although five showed inconclusive reactions. Samples were examined from 41 mares either proved to be infected or from an infected stud. Of these 21 were positive, 11 were inconclusive and nine were negative. The relationship of the CFT to reactions in the other tests used in this condition is discussed--the serum agglutination test (SAT) and antiglobulin test (AGT) (Benson and others 1978). Complement fixing antibodies appear to remain for a longer period in the infected animal, and are therefore more likely to be of use in the diagnosis of the chronic carrier state.

Agglutination Tests↗
PubMed1978

The course of serum antibody development in two ponies experimentally infected with contagious metritis.

Serum agglutination tests, anti-globulin tests, and complement fixation tests were carried out on sera taken over a period of 98 days from two fillies experimentally infected with the contagious equine metritis organism. The pattern, and significance in diagnosis, of these results is discussed. All 3 tests showed positive titres in the acute phase of experimental disease; reactions in the complement fixation test persisted longest.

Agglutination Tests↗
PubMed1978

Axonal adaptations to osmotic and ionic stress in an invertebrate osmoconformer (Mercierella enigmatica Fauvel). I. Ultrastructural and electrophysiological observations on axonal accessibility.

The giant axons in Mercierella are overlaid by narrow glial processes which provide an incomplete covering of the axonal surface. Where more complete covering occurs the intercellular clefts are not sealed by tight junctional complexes. Ionic lanthanum penetrates to the surfaces of axons from sea-water-adapted animals (in normal saline and during initial exposure to hyposmotic saline) and, also, to the surface of hyposmotically adapted axons. A relatively free intercellular access to the axon surfaces is also indicated by the rapid electrical responses of sea-water-adapted axons to hyposmotic dilution and of hyposmotically adapted axons to sodium-deficient saline. The giant axon possesses an unusual ultrastructural specialization: hemidesmosome-like structures (associated with the axon membrane) which are connected to a network of neurofilaments within the axon. Theoretical considerations suggest that these structures could enable the axons to withstand appreciable excesses in intracellular hydrostatic pressure resulting from osmotic imbalance during hyposmotic stress.

Action Potentials↗
PubMed1978

Axonal adaptations to osmotic and ionic stress in an invertebrate osmoconformer (Mercierella enigmatica Fauvel). II. Effects of ionic dilution on the resting and action potentials.

The giant axon of this extreme euryhaline osmoconformer possess an unusual ability to produce action potentials of large amplitude over a wide range of ionic dilution when constant osmotic concentration is maintained by the addition of mannitol to the bathing medium. Ionic dilution under these circumstances causes a decline in the overshoot of the action potential (resulting largely from reduction in [Na+]o) and an appreciable axonal hyperpolarization (primarily as a result of decrease in [K+]O). This hyperpolarization tends to compensate for the reduction in the extent of the overshoot and so maintains the amplitude of the sodium-mediated action potentials during isosmotic dilution of the bathing medium. The axonal hyperpolarization also appears to reduce sodium inactivation so as to maintain a rapid rate of rise of the action potential despite drastic reduction in the ionic concentration of the bathing medium. Prolonged exposure to reduced ionic concentrations appears to induce a ouabain sensitive reduction in intracellular sodium concentration which increases the sodium gradient across the axon membrane during isosmotic dilution of the external medium.

Action Potentials↗
PubMed1978

Axonal adaptation to osmotic and ionic stress in an invertebrate osmoconformer (Mercierella enigmatica Fauvel). III. Adaptations to hyposmotic dilution.

The giant axons of this extreme osmoconformer were adapted, in vitro, to progressive hyposmotic dilution of the bathing medium (from 1024 m-Osmol to concentrations as low as 76.8 m-Osmol). Hyposmotic adaptation is associated with reductions in the intracellular concentrations of both sodium and potassium ions. These reductions do not appear to result from appreciable axonal swelling. The different electrical responses to isosmotic and hyposmotic dilution suggest that reduction in [Na+]1 results from ouabain-dependent sodium extrusion, in response to ionic dilution, and that reduction in [K+]1 is induced by a combination of ionic and osmotic dilution. The reduced level of intracellular potassium achieved during hyposmotic adaptation represents a balance between the necessity to contribute to osmotic equilibration and to maintain a potassium gradient across the axon membrane sufficient to produce appreciable axonal hyperpolarization during dilution of the bathing medium. This hyperpolarization tends to maintain the amplitude of the action potential, by compensating for reduction in overshoot (with decline in E(Na), and by reducing sodium inactivation. This, together with the reduction in [Na+]1, enables overshooting action potentials of relatively large amplitude and rapid rise time to be maintained during more than tenfold dilution of the ionic and osmotic concentration of the bathing medium.

Action Potentials↗
PubMed1978

Endoscopic retrograde cholangiopancreatography in the diagnosis and management of nonalcoholic pancreatitis.

Twenty-eight consecutive patients with idiopathic pancreatitis were studied. Endoscopic retrograde cholangiopancreatography was diagnostic in 21 of 28, while an operation was diagnostic in four of the remaining seven patients. Fifteen of 25 patients had operable disease of the gallbladder, common bile duct, ampulla of Vater or pancreatic duct. Of ten patients who had an operation on the pancreas or biliary tract, or both, for painful attacks of pancreatitis, none had a recurrence in a seven month to three year follow-up study. Two patients had reconstruction of the pancreatic duct for chronic painless steatorrhea, one of whom had marked clinical improvement. Ten of 25 patients had normal biliary tracts with normal or minimally abnormal pancreatic ducts and were treated medically. Visualization of biliary and pancreatic ducts should be attempted by endoscopic retrograde cholangiopancreatography in patients with pancreatitis of unknown cause. Operable lesions were found in 15 of 25 patients, and the postoperative results were excellent.

Acute Disease↗
PubMed1977

Performance of graduates of foreign medical schools on the examinations of the American Board of Internal Medicine.

We investigated the performance of two groups of graduates of foreign medical schools on the 1975 and 1976 certification examinations of the American Board of Internal Medicine. Nearly all their postdoctoral residency training was obtained in the United States. The performance (most of those in this study were born in Asia and Southeast Asia) was much lower than that of graduates of United States medical schools. United States citizens who studied medicine abroad performed no better than alien graduates from foreign medical schools. Approximately half the foreign graduates born in the United States studied in Italy, and 10% in Switzerland, Mexico and Belgium. There were no significant differences in performance associated with the type of postdoctoral training (university, university-affiliated, community or other) undertaken in the United States. A significant inverse relation was observed between the interval from completion of training to first examination and the examination performance.

Analysis of Variance↗
PubMed1975

Simple chronic constipation: pathophysiology and management.

Chronic constipation is not a simple problem. It is often related to fundamental beliefs and habits. Once it has been established that the cause is not an organic disorder, the physician must take pains to explore with the patient other possible causes. Simple, inorganic constipation can usually be traced to poor diet or poor habits. The physician should provide simple explanations of the mechanisms involved in the act of elimination and detailed instructions on appropriate food and water intake and the development of regular habits. Laxatives should be prescribed only if absolutely necessary and if the patient taking them can be carefully observed.

Antacids↗
PubMed1974

Pseudomembranous enterocolitis. Resurgence related to newer antibiotic therapy.

Six patients with pseudomembranous entercolitis were seen at one institution over a six-month period. Clindamycin therapy preceded the diagnosis in all six patients and possibly caused the disease in five cases. Common clinical features included diarrhea, abdominal pain, fever, leukocytosis, radiographic findings of large bowel dilatation with mucosal thickening and a characteristic sigmoidoscopic or gross pathologic demonstration of discrete yellow-white plaques on an otherwise normal mucosa. Complications included toxic megacolon and sigmoid colon perforation. Two of the six patients died. The literature since 1970 is tabulated to clarify the clinical and pathological features of pseudomembranous enterocolitis associated with newer antibiotic therapy. Lincomycin and clindamycin are strongly implicated in the recent resurgence of this formerly rare variety of colitis.

Adult↗