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N Kass

Publications and source records attributed to N Kass.

27 records · Page 2Linked to original sources
PubMed1978

Site specificity and variability in the mutator and antimutator effects of phage T4 gene 43 mutants.

Spontaneous, 2-aminopurine- and 5-bromouracil-induced mutations at six rII nonsense codons were studied in phage T4 strains possessing wild-type and mutant gene 43 alleles. The mutation pathways studied included interconversions and reversions of nonsense codons. The tsCB87 allele, which specifies an antimutator DNA polymerase, reduced base-analogue-induced mutation frequencies along all pathways. However, GC base pairs were less affected than AT base pairs. The frequency of spontaneous UAA leads to UAG conversions was also reduced by tsCB87, but that of spontaneous UAA leads to UAG UGA conversions was often increased. Mutation in the presence of the mutator allele tsL56 was increased along all pathways, with no preference for either AT or GC base pairs. Mutation frequencies in the presence of the two mutant DNA polymerases were highly variable. A strong correlation was found between 2-aminopurine-induced mutation frequencies in ts+ tsCB87 phage along the reversion and UAA changed to UAG (but not UAA changed to UGA) pathways.

2-Aminopurine↗
PubMed1977

Repressor and int synthesis of bacteriophage lambda in the E. coli host mutant ER437.

Analysis of lambda phage infection of the host mutant ER437 by SDS polyacrylamide gel electrophoresis and autoradiography has revealed altered expression of repressor and integration function (Int). We show that in this host Int as well as repressor synthesis is not dependent upon the lambdacIII gene product in the usual manner, nor is their synthesis turned off in the normal way.

Autoradiography↗
PubMedDate not supplied

Chicken infectious anemia virus infection in Israeli commercial flocks: virus amplification, clinical signs, performance, and antibody status.

The impact of chicken infectious anemia virus (CIAV) infection on commercial chicken flocks in Israel was examined by analyzing flocks with or without typical CIAV signs, signs of other diseases, or apparently healthy flocks. In 23 flocks (broilers and layers) of ages up to 8 wk, typical signs of CIAV infection (stunting, gangrenous dermatitis, and secondary bacterial infections) were recorded. When permitted by flock owners, in several cases among these 23 flocks the morbidity, mortality, and performance parameters were recorded; the presence of CIAV was detected by polymerase chain reaction (PCR); and the antibody status of parents and broilers was measured. In addition, total mortality, number of birds sold, total kilograms of meat sold, density (kg/m2), mean age at slaughter, daily growth rate in grams, total kilogram of food consumed, food conversion rate, and the European Index were calculated. We also surveyed flocks affected by other diseases, such as tumors, respiratory diseases, or coccidiosis, and flocks with no apparent clinical signs. The latter flocks were negative by CIAV-PCR, indicating that typical CIAV clinical signs are associated with one-step PCR-CIAV amplification. However, a small amount of CIAV might still be present in these flocks, acting to induce the subclinical effects of CIAV infection. These data indicate a link between the presence of virus sequences and typical CIAV signs and strengthen the concept that CIAV infection has a negative economic impact on the chicken industry.

Animals↗
PubMedDate not supplied

The influence of reovirus sigma C protein diversity on vaccination efficiency.

Avian reovirus (ARV) is a disease agent that causes economic losses in the poultry industry. The available vaccines do not confer full protection. One possible reason is the existence in the field of many virulent serotypes with no cross protection. Several ARV strains have been isolated in Israel in the last few years. In this study, we investigated the diversity of the sigma C protein of ARV because this is the most variable protein in the virus and it induces the production of neutralizing antibodies. Sigma C from two virulent isolates was sequenced, cloned, and expressed. The protein sequence differed from the attenuated vaccine strain (strain 1133) but was similar to a U.S. virulent strain (strain 1733). Those differences led to a change in the antigenic index of the protein, mainly at three sites. Sera of infected birds in a field trial and of birds in a controlled experiment vaccinated with the recombinant sigma C protein showed high titers in enzyme-linked immunosorbent assay to the recombinant protein and lower titers to the attenuated vaccine strain. This means that sigma C can be used as a diagnostic tool for the detection of antibodies relevant for protection and in the future as a subunit vaccine. The results of this study highlight the need to reconsider vaccinations against ARV in terms of the strains to be used and of the method of identifying protective antibodies transferred to progeny.

Amino Acid Sequence↗
PubMedDate not supplied

Prior episode of sexually transmitted disease and subsequent sexual risk-reduction practices. A need for improved risk-reduction interventions.

Persons with a history of a sexual transmitted disease (STD) are at increased risk for infection with human immunodeficiency virus (HIV). The extent to which women with a previous history of a STD report currently practicing protective behaviors against STD transmission is examined. Specifically, whether having experienced one or more previous episodes of an STD was related to current STD/HIV preventive practices was studied. Of the study group, 36% had at least one prior STD episode. Results of bivariate analysis show no relationship between previous STDs and current STD/HIV preventive practices: 47% of women with no previous STD episode, 64% of women with 1 previous episode, and 46% of women with 2 or more previous STD episodes reported currently practicing moderate to high levels of STD/HIV prevention methods. To adjust for potentially confounding variables, logistic regression analyses were also performed. The logistic regression model included age, alcohol use with sex, drug use with sex, marital status, and perceived risk of becoming infected with an STD in the next year. Results from the logistic regression analyses also showed no relationship between prior STD episode and current level of preventive practices against STD/HIV. Variables found to be significantly associated with level of STD/HIV preventive practices were marital status, age, and drug use with sex. These findings suggest that greater advantage should be taken of the opportunities presented when women are diagnosed with an STD to teach individuals at risk of acquiring STDs or HIV to practice risk-reduction behaviors.

Adolescent↗
PubMedDate not supplied

Contraceptive and sexual practices among single women with an unplanned pregnancy: partner influences.

Data from an urban obstetrics clinic on 291 unmarried women with a current unplanned pregnancy show that women with only one partner in the past year are older and are more likely to use the most effective contraceptive methods than are women who have more than one partner. Women with only one partner are also more likely to be solely responsible for decision-making about the choice of contraceptive methods, and are not as likely to use drugs in conjunction with sex. However, women with one partner are also less likely than others to use condoms or to protect in some other way against sexually transmitted diseases or the human immunodeficiency virus.

Adolescent↗