Biomedical subjects
N Spritz
Publications and source records attributed to N Spritz.
Oversight of physicians' conduct by state licensing agencies. Lessons from New York's Libby Zion case.
The unexplained and highly publicized death of an 18-year-old woman in a New York Hospital in 1984 became the focus for debate throughout the country concerning working conditions and supervision of house officers. It also led to charges by the State of New York of gross negligence against her resident physicians. The residents were exonerated of all charges by a review panel with lay and physician representation after testimony of expert witnesses. Although the Commissioner of Health concurred with this verdict, residents were charged with gross negligence by the Board of Regents, a lay panel. Fundamental contrasts in the way the two panels made their judgments supports the importance of peer review in disciplining physicians in matters of medical judgment. Analysis of the actions by New York State against the residents also underscores the importance of other principles in the oversight of physician behavior that are applicable to all jurisdictions: resolution of charges without undo delay, an equitable and consistent standard for the administration of sanctions, and adherence to a clearly defined standard for the level of culpability required for disciplinary action. Both the structure of the review process and its application in this instance led to violations of each of these principles.
Effects of coronary risk reduction on mortality.
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Appraisal of alcohol consumption as a causative factor in liver disease and atherosclerosis.
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Review of the evidence linking alcohol consumption with liver disease and atherosclerotic disease.
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Nerve disease in diabetes mellitus.
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Protein kinases associated with peripheral nerve myelin. 1. Phosphorylation of endogenous myelin proteins and exogenous substrates.
When highly purified myelin from rat sciatic nerve was incubated with [gamma-32P]ATP, protein components of the membrane were phosphorylated indicating the presence of both the substrate (receptor protein) and an endogenous kinase in the membrane. Polyacrylamide gel electrophoresis of the phosphorylated membrane proteins followed by scintillation counting of gel slices and autoradiography showed that the polypeptides of molecular weights 28000, 23000 and 19000 were phosphorylated, and 32P from [gamma-32P]ATP having been incorporated into serine residues of the substrate proteins. Phosphorylation of purified myelin was Mg2+-dependent, was optimal at pH 6.5 and was not stimulated by adenosine 3',5'-monophosphate. We found that proteins other than those in myelin, such as phosvitin, casein, protamine and histones, can also act as a substrate for the membrane associated kinase. Muscle protein kinase inhibitor had no effect on the endogenous phosphorylation of myelin proteins or on the phosphorylation of phosvitin by peripheral nerve myelin protein kinase. However, the phosphorylation of histone by peripheral nerve myelin protein kinase was inhibited by the protein kinase inhibitor. After washing the membrane with 150 mM KCl the protein kinase that utilizes histone as substrate was found in the supernatant. In contrast, the endogenous phosphorylation of membrane proteins or the phosphorylation of phosvitin by the membrane associated kinase was not affected by washing. From these findings we conclude that at least two protein kinase systems exist in purified peripheral nerve myelin. One system is not inhibited by muscle kinase inhibitor, is tightly bound to the membrane and utilizes as its receptor proteins either exogenous phosvitin or endogenous membrane proteins. The second system is inhibited by muscle kinase inhibitor, is removable from the membrane and utilizes histones as its receptor proteins.
Metabolism of peripheral nerve myelin in experimental diabetes.
Previous in vitro studies of the metabolism of the peripheral nerve have been based on incorporation of radioactive precursor into components isolated from whole nerve. In this study we have determined incorporation secifically into myelin components of peripheral nerve by isolating myelin after incubating whole nerves with lipid or protein precursors and by determining the specific activity of the components of that membrane. The effect of diabetes on such incorporation was also studied. In the rat, in vitro incorporation of DL-[1-14C]leucine into protein components of myelin was decreased by 30-88% in diabetic animals as compared to controls. The major polypeptide constituent of rat sciatic nerve myelin (mol st 28,000; 58.5% of total mass of proteins) was not labeled in either the diabetic or the control group. In diabetes incorporation rate into a polypeptide of mol wt 23,000, which constitutes 21% of total mass, was approximately one half that of controls. In polypeptides of mol wt 38,000-49,000, which are heavily labeled in normal animals, but constitute only about 5% of total mass of proteins, depression of incorporation was e-en more marked in the diabetics. While these marked differences in incorporation between diabetic and control animals were observed, the amount of protein and its distribution among the constituent polypeptides was the same in both groups. In young rats made diabetic with streptozotocin and young rabbits made diabetic with alloxan, there was a lower rate of incorporation of the lipid precursors, [1-14C]sodium acetate or [3H]water, into myelin components. In older animals of both species incorporation in the controls was considerably lower than in the yount animals, and the effect of diabetes was no longer apparent. In nondiabetic animals, the in vitro addition of insulin (10-7 M) stimulated incorporation of DL-[1-14C]leucine into myelin proteins 1.6-3.1 times that of controls. This stimulation by insulin in vitro was not seen in diabetic animals. In animals in which diabetes had spontaneously recovered, however, incorporation rate in the in vitro experiments approached that of controls and were significantly above that in animals whose diabetes persisted. Since myelin is the palsma membrane of the Schwann cell, these studies provide evidence that the Schwann cell is affected by insulin and that some aspects of the metabolism of myelin are altered in insulin-deficient states.
Decrease in myelin content of rabbit sciatic nerve with aging and diabetes.
Previous studies of the amount of peripheral nerve myelin have been based on histologic examination. In this study, myelin content was measured directly after quantitative isolation from sciatic nerve. There was a decrease in the amount of myelin beginning at nine months, the time of maximal myelin content in normal rabbits, and beginning at six months, the amount was decreased in diabetic as compared with control animals. Composition of myelin isolated from young (age three to four months) and old (age nine to thirteen months) rabbit sciatic nerves was also determined and is similar to that of other species. Although the composition was not affected by diabetes, with aging there was a significant decrease in the amount of cholesterol and an increase in glycolipid.