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M Weinfeld

Publications and source records attributed to M Weinfeld.

62 records · Page 4Linked to original sources
PubMed1986

Photoreversal-dependent release of thymidine and thymidine monophosphate from pyrimidine dimer-containing DNA excision fragments isolated from ultraviolet-damaged human fibroblasts.

To elucidate the enzymatic excision-repair process operative on cyclobutane-type pyrimidine photodimers in human dermal fibroblasts, we have examined excised dimer-containing material recovered in the trichloroacetic acid soluble fraction from far-ultraviolet-irradiated (254 nm, 40 J m-2) and incubated (24 h) cell cultures. The excised DNA photoproducts were found in oligonucleotide fragments with an estimated mean chain length of approximately 3.7 bases. Exposure of these isolated excision fragments, labeled with [3H]thymidine (dT), to a secondary, dimer-photoreversing fluence of far-UV (5.5 kJ m-2) resulted in the release of free dT and thymidine monophosphate (TMP). Photorelease of these two radioactive species was measured by high-performance liquid chromatography, with TMP being detected as the increase in dT following bacterial alkaline phosphatase treatment. These data imply that the photoliberated dT and TMP moieties were attached to the excision fragments solely by the cyclobutane ring of the dimer. No evidence was obtained for the photoliberation of free thymine, thus corroborating a conclusion reached by others that the excision of dimers in human cells is not initiated by scission of an intradimer N-glycosyl bond. The sum of the tritium label recovered in dT plus TMP corresponded to approximately 40% of that disappearing from thymine-containing dimers on photoreversal, suggesting that in about 80% of the isolated excision fragments the dimer is located at one end of the oligonucleotide and contains a break in its internal phosphodiester bond.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Stereospecific removal of methyl phosphotriesters from DNA by an Escherichia coli ada+ extract.

The ada+ gene product, a DNA methyltransferase present in extracts from an Escherichia coli strain constitutive for the adaptive response, removes only half of the methyl phosphotriesters from alkylated DNA. Since DNA phosphotriesters occur in two isomeric configurations (denoted Rp and Sp), we examined whether this reflects a stereospecific mode of repair by the methyltransferase. Analysis by reverse-phase HPLC, phosphorus NMR and circular dichroism established that only triesters in the Sp configuration are acted upon by the E. coli extract.

Alkylating Agents↗
PubMed1985

Stability of coping style 33 years after prolonged exposure to extreme stress.

Respondents who were in hiding or in the armed resistance movement in Nazi occupied Europe are assumed to have had avoidant and confronting coping styles, respectively. Responses to questionnaire items tapping behavior, attitudes and perceptions were examined in the two groups for the persistence of these same traits 33 years after World War II, in a study of randomly selected community sample of Jews. Taken as a whole, but not individually, responses to the questionnaire items suggested that the traits did persist (P less than 0.001). The results highlight the importance of distinguishing individual differences in coping style when studying the long-term effects of prolonged, stressful experiences.

Adaptation, Psychological↗
PubMed1982

Impairment in Holocaust survivors after 33 years: data from an unbiased community sample.

The authors compared the psychiatric status of 135 survivors of the Holocaust with that of control subjects. This study stands apart from most previous reports in that the two groups were generated by a random sample survey of all heads of households in a community (Montreal). Survivors were more likely to have mild psychiatric symptoms regardless of the age at which they experienced the Holocaust. The difference between survivors and controls in levels of mild psychiatric symptoms was greatly amplified in those respondents who perceived a recent increase in anti-Semitism in Montreal.

Anxiety Disorders↗
PubMedDate not supplied

Plasma membrane enrichment with cis-unsaturated fatty acids enhances LDL metabolism in U937 monocytes.

The mechanism by which dietary cis-unsaturated fatty acids lower low density lipoprotein (LDL) cholesterol is unknown. Because cis-unsaturated fatty acids incorporated into cell membranes increase membrane fluidity and, as a result, can alter membrane-dependent cell functions, we examined LDL binding, uptake, and degradation in upregulated U937 monocytes enriched in membrane oleate, a monounsaturated fatty acid, and membrane linoleate, a polyunsaturated fatty acid. The same parameters were also examined in upregulated U937 monocytes enriched in membrane stearate, a saturated fatty acid, and in upregulated, unmodified U937 monocytes. Monocytes enriched in cis-unsaturated fatty acids exhibited augmented LDL binding, internalization, and degradation compared with both stearate-enriched monocytes and unmodified monocytes. The molar potency of linoleate in augmenting LDL metabolism was 50% greater than that of oleate. Enrichment with oleate and linoleate resulted in a decrease in the fatty acyl mole-weighted melting point of the plasma membrane and an increase in plasma membrane fluidity, as indicated by a reduction in the steady-state fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene incorporated into the membrane. Stearate-enriched monocytes exhibited a slight increase in the plasma membrane fatty acyl mole-weighted melting point and essentially no change in plasma membrane fluidity. Thus, one mechanism by which cis-unsaturated fatty acids lower LDL cholesterol may involve alteration in membrane lipid composition and physical properties, thereby leading to an increase in cellular clearance of this atherogenic lipoprotein.

Cell Line↗
PubMedDate not supplied

Lipoprotein(a), fibrin binding, and plasminogen activation.

Lipoprotein(a) (Lp[a]) is a complex plasma lipoprotein in which apolipoprotein (apo) B-100 is covalently linked by a disulfide bridge to a unique apolipoprotein, apo(a). The cDNA of apo(a) has recently been isolated and sequenced, and a remarkable homology to human plasminogen has been noted. In this report, we demonstrate that, like plasminogen, Lp(a) binds to fibrin. In addition, Lp(a) competes with plasminogen and tissue-type plasminogen activator for fibrin binding. As a functional consequence of these binding properties, we show that Lp(a) attenuates the fibrin-dependent enhancement of tissue-type plasminogen activator activity against the native substrate, and does so as an uncompetitive inhibitor (Ki = 15 nM). Finally, we show that in a plasma milieu, Lp(a) attenuates clot lysis induced by tissue-type plasminogen activator. None of these effects was noted with low density lipoprotein free of apo(a). These data suggest that Lp(a) influences the fibrinolytic system and probably does so by virtue of the fibrin binding properties conferred by the kringle repeats of apo(a).

Binding, Competitive↗