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Biomedical subjects

M Levy

Publications and source records attributed to M Levy.

At least 433 records · Page 24Linked to original sources
PubMed1987

Action mechanism of Escherichia coli DNA photolyase. I. Formation of the enzyme-substrate complex.

Escherichia coli DNA photolyase (photoreactivating enzyme) is a flavoprotein. The enzyme binds to DNA containing pyrimidine dimers in a light-independent step and, upon illumination with 300-600 nm radiation, catalyzes the photosensitized cleavage of the cyclobutane ring thus restoring the integrity of the DNA. We have studied the binding reaction using the techniques of nitrocellulose filter binding and flash photolysis. The enzyme binds to dimer-containing DNA with an association rate constant k1 estimated by two different methods to be 1.4 X 10(6) to 4.2 X 10(6) M-1 S-1. The dissociation of the enzyme from dimer-containing DNA displays biphasic kinetics; for the rapidly dissociating class of complexes k2 = 2-3 X 10(-2) S-1, while for the more slowly dissociating class k2 = 1.3 X 10(-3) to 6 X 10(-4) S-1. The equilibrium association constant KA, as determined by the nitrocellulose filter binding assay and the flash photolysis assay, was 4.7 X 10(7) to 6 X 10(7) M-1, in reasonable agreement with the values predicted from k1 and k2. From the dependence of the association constant on ionic strength we conclude that the enzyme contacts no more than two phosphodiester bonds upon binding; this strongly suggests that the pyrimidine dimer is the main structural determinant of specific photolyase-DNA interaction and that nonspecific ionic interactions do not contribute significantly to substrate binding.

Collodion↗
PubMed1987

Do genetic factors play a role in Berger's disease?

The epidemiology of Berger's disease is poorly defined. We know that the disease occurs worldwide and that there may be an increased occurrence in certain ethnic groups. Whether secondary mesangial IgA deposits should be considered part of the same disease process is unknown. The association of certain HLA antigens with the occurrence of Berger's disease has been demonstrated by several groups. The multiple occurrence of Berger's disease or of Berger's disease and Henoch-Schönlein purpura in the same family has been reported. The preliminary results of a French collaborative study show 43 such families. However, these facts do not demonstrate a familial clustering since the multiple occurrence of cases in a family may occur by chance. The study of affected siblings (sib pair method) from different families may be used nevertheless, in order to understand the possible inheritance of the disease. Previously reported data on HLA haplotypes of affected siblings are combined with unpublished cases. There is an excess of HLA-identical siblings but it is possible that there might have been some bias towards publishing HLA-identical pairs. Further systematic studies on a large number of HLA-typed affected sibling pairs are needed before concluding a linkage between HLA and the disease.

Glomerulonephritis, IGA↗
PubMed1987

Molluscum contagiosum in a horse with granulomatous enteritis.

Widespread cutaneous papules in a yearling Standardbred filly were attributed by light and electron microscopic examination to molluscum contagiosum. Concomitant granulomatous enteritis, suspected clinically due to protein-losing enteropathy, was verified histopathologically. An associated altered altered immune response is suggested as the reason for the widespread poxvirus infection.

Animals↗
PubMed1987

Reduction of asthenopia after accommodative facility training.

Five patients reporting asthenopia secondary to accommodative deficiencies underwent automated accommodative facility training. A matched-subjects, crossover design was used to control for placebo effects. All patients receiving automated accommodative training showed a marked increase in accommodative amplitude along with a concurrent reduction of asthenopia. Decreases of blur and increases of reading time were the most frequently reported changes by patients. This experiment shows the effectiveness of automated accommodative training in reducing asthenopia and improving accommodative facility.

Accommodation, Ocular↗
PubMed1987

Fertility and obstetric history in patients with familial Mediterranean fever on long-term colchicine therapy.

The obstetric histories were examined for 36 women with familial Mediterranean fever (FMF) on long-term colchicine treatment followed for periods ranging between 3 and 12 years. Seven of 28 pregnancies (25%) associated with colchicine therapy ended in miscarriage. Thirteen women (36%) had periods of infertility; these were due to ovulatory dysfunction in six women, to peritoneal adhesions in four and remained unexplained in three women. The rates for miscarriage and infertility are high but are similar to those reported for women with FMF before colchicine therapy was introduced. All 16 infants born to mothers who had taken colchicine during pregnancy were healthy. Currently, we do not advise discontinuation of colchicine before planned pregnancy but recommend amniocentesis for karyotyping and reassurance.

Abortion, Spontaneous↗
PubMed1987

Hepatic denervation alters first-phase urinary sodium excretion in dogs with cirrhosis.

Cirrhotic dogs without intrahepatic hypertension (IHH) never retain sodium or expand plasma volume. To test the hypothesis that IHH may cause urinary sodium retention early in cirrhosis, we prepared cirrhotic dogs (chronic biliary obstruction) who underwent simultaneous hepatic denervation with end-side portacaval anastomoses. Such animals, along with appropriate controls and unanesthetized were studied by balance techniques. In the experimental group, plasma volume never increased, and sodium retention did not occur until 2 days prior to the appearance of detectable ascites. In a sham-denervated group, plasma volume increased by 10% and sodium retention occurred on the average 8.4 days prior to ascites. When the portal veins were left intact, the sham-denervated group showed the usual magnitude of plasma volume expansion observed in cirrhotic dogs (18.3%) with a 7-day delay between sodium retention and ascites appearance. Those dogs with hepatic denervation demonstrated a 9.2-day delay with 12.6% expansion of plasma volume. When ascites was mobilized with a peritoneovenous valve, and dogs were subjected to a high salt diet (130 meq/day), denervated dogs excreted the load normally, whereas sham-denervated dogs retained sodium and developed anasarca. We conclude that in cirrhotic dogs with IHH, liver denervation prevents early non-volume-related sodium retention.

Animals↗
PubMed1987

Sodium excretion in dogs with low-grade caval constriction: role of hepatic nerves.

Low-grade thoracic caval constriction will raise intrahepatic pressure without driving fluid from the vascular space as ascites. In eight such dogs where venous pressure was increased by 6.6 cmH2O, sodium balance studies showed a positive cumulative balance of 85 meq and a weight gain of 480 g over a 6-day period in the absence of any change in renal perfusion, glomerular filtration rate, central venous pressure, blood pressure, cardiac output peripheral vascular resistance, or plasma levels of aldosterone. Liver function tests, including bromosulfophthalein disappearance curves, were also normal. In dogs with either sham surgery, or subjected to equivalent venous hypertension of the abdominal vena cava or portal veins, there was a cumulative positive sodium balance of only 21-28 meq over a 2-day period. When the liver was completely denervated prior to performing the thoracic caval constriction, the sodium handling profile reverted to the same pattern as observed in sham controls, i.e., 22 meq cumulative sodium over a 3-day period. When the thoracic caval constriction was tightened to produce ascites, a LeVeen valve was inserted and the ascites mobilized. In response to 130 meq/day sodium diet, denervated dogs excreted the sodium load normally, whereas dogs with intact hepatic nerves retained sodium and developed anasarca. We conclude that intrahepatic baroreceptors may modulate sodium excretion in the presence of intrahepatic hypertension.

Aldosterone↗
PubMed1987

Natriuretic response to volume loading in normal and edematous dogs during lower body positive pressure.

The application of lower body positive pressure with military antishock trousers (MAST) to dogs in a 45 degrees head-up tilt is known to increase cardiac output and blood pressure, and to maintain life. In the present study we used MAST in an attempt to improve the natriuretic response to saline loading in normal and edematous anesthetized dogs. Twelve normal dogs were saline-loaded (7% body weight) in the supine position with and without MAST 4 days apart. The increment in UNaV without MAST was 853.3 +/- 26 mu Eq/min and averaged 870.4 +/- 33 mu Eq/min with MAST (p greater than 0.05). The dogs were then subjected to chronic thoracic caval constriction, and when ascitic were tested again. Now, the increment to acute volume loading was 87.6 +/- 12.1 mu Eq/min without MAST and 92.8 +/- 8.8 mu Eq/min with MAST (p greater than 0.05). The application of lower body positive pressure (60-80 mm Hg legs; 40-60 mm Hg abdomen) is not effective in promoting a natriuretic response to acute volume loading in either normal or edematous dogs with profound disturbances to the Starling forces over an extensive vascular territory.

Animals↗
PubMed1987

Improving cancer patients' pain control through education.

While patient accrual for this study is not yet complete, it appears that the intervention may be helping patients to feel more in control over their pain, take the correct medication dosage and take action to prevent side effects. At this point, the experimental subjects seem much less worried about tolerance to pain medications. The early results suggest some sociodemographic differences in response to pain which, if they persist, should probably be considered as factors in designing patient education programs.

Analgesics, Opioid↗