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Biomedical subjects

E Epstein

Publications and source records attributed to E Epstein.

At least 217 records · Page 12Linked to original sources
PubMed1971

Lateral transport of ions into the xylem of corn roots: I. Kinetics and energetics.

A technique is described for study of the kinetics of lateral transport of ions across single roots of corn, Zea mays, in short term experiments under steady state conditions. The kinetics of chloride transfer to the vessels reflected the kinetics of absorption of chloride by the root cells. Efflux from the root vacuoles contributed to only a small extent to transport of chloride into the exudate. Lateral transport of chloride was inhibited by bromide at chloride concentrations in the ranges of both mechanisms 1 and 2 in a manner implicating competition. The uncoupler carbonylcyanide m-chlorophenylhydrazone used at 1 mum caused transfer of chloride to cease almost immediately at both low and high concentrations of chloride. Oligomycin depressed transport of chloride to the vessels within 10 to 15 minutes after application at 2 micrograms per milliliter. Inhibition by oligomycin was 75% at 0.5 mm chloride and 55% at 5 mm.It is concluded that lateral transport of chloride across corn roots is mediated by the dual mechanisms of ion absorption which reside in the plasmalemma. Transfer of chloride is inhibited by bromide and depends upon ATP as energy source. Chloride moves from the plasmalemma, the site of carriermediated absorption, to the xylem vessels by way of the symplasm. There is no evidence in these experiments that lateral transport of chloride in corn roots is governed by diffusion at any concentrations of chloride used in these experiments.

Journal Article↗
PubMed1971

Lateral Transport of Ions into the Xylem of Corn Roots: II. Evaluation of a Stelar Pump.

When an excised corn (Zea mays) root pretreated with chloride was exposed for 10 minutes to pulse labeling with (30)Cl and then transferred to unlabeled chloride, the activity in the xylem exudate reached a maximum about 4 minutes after pulse labeling was discontinued and then declined sharply. The rate at which labeled chloride was transported across the root into the xylem and basipetally therein was on the order of 75 to 250 centimeters per hour. Consequently, symplasmic movement of chloride in corn roots is fast and may not be rate-limiting in transfer from the root surface to the xylem. Experiments on pulse labeling with (22)Na gave similar results. A large fraction of the absorbed (22)Na was not translocated into the exudate but was tightly sequestered in a cell compartment, probably the vacuole.Electron probe analysis was used to reveal the pattern of potassium distribution in cross sections taken 10 to 11 millimeters from the tip. The cytoplasm and vacuoles of the xylem parenchyma cells accumulated potassium to a much greater extent than cortical and other stelar cells. Ultrastructural studies showed that the cytoplasm of the xylem parenchyma cells contains numerous membrane systems. It was concluded that the xylem parenchyma cells secrete ions from the symplasm into the conducting vessels, and it was suggested that this secretion is driven across the plasmalemma by a carrier-mediated transport.

Journal Article↗
PubMed1971

Dermatologic radiotherapy--R.I.P.

A questionnaire returned by nearly 3,000 dermatologists indicates that about 75 percent of them have discontinued completely the use of x-ray therapy in acne. An additional 11 percent use it in less than 10 percent of their patients who have this disease."Hazards" constituted the greatest deterrent to the use of ionizing radiation. Yet the assumption that it can cause skin cancers, in the absence of radiodermatitis, is not proved and its importance as an additive energy to solar radiation is considered to be limited. About one-third of the respondents expressed belief that better treatments were available for this condition. An equal number were concerned with public resistance to this therapeutic agent, which, however, seems to be more apparent than real. Probably the major roadblock was posed by the dermatologic training centers where teaching was withheld despite a rule of the American Board of Dermatology favoring it. Other factors mentioned with some frequency included ineffectiveness of radiotherapy, lack of equipment, and fiscal and medicolegal considerations. This study indicates that dermatologic radiation therapy is passing into oblivion.

Acne Vulgaris↗
PubMed1971

Triamcinolone-procaine in the treatment of zoster and postzoster neuralgia.

Twenty-four patients with herpes zoster were treated with injections of 2 percent procaine hydrochloride containing 2 mg of triamcinolone per ml. The treatments were given subcutaneously under the cutaneous lesions and in areas of pain. The results were excellent in 22 patients. There was one failure-postzoster neuralgia in an 82-year-old woman. Of 12 patients with postherpetic neuralgia, eight had improvement of 70 to 90 percent and three had complete relief. There were no significant complications in either group.

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