Search PubMed⌕ Search

Biomedical subjects

L K Cohen

Publications and source records attributed to L K Cohen.

At least 55 records · Page 3Linked to original sources
PubMed1980

RsaI: a new sequence-specific endonuclease activity from Rhodopseudomonas sphaeroides.

A new type II sequence-specific endonuclease, RsaI, has been identified from Rhodopseudomonas sphaeroides strain 28/5. An RsaI purification scheme that yields enzyme which is free of contaminating exonuclease and phosphatase activities after a single column fractionation has been developed. The enzyme recognized the tetranucleotide sequence 5'-GTAC-3' and cleaved between the T and A, thereby generating flush ends. RsaI should be extremely useful in deoxyribonucleic acid sequencing experiments.

Base Sequence↗
PubMed1979

Intermembrane phospholipid transfer mediated by cell-free extracts of Rhodopseudomonas sphaeroides.

The transfer of phospholipids between two membrane substrates catalyzed by a soluble protein fraction from Rhodopseudomonas sphaeroides has been demonstrated. The assay employs purified intracytoplasmic membrane (ICM) vesicles derived from cells of R. sphaeroides grown on [3H]acetate as the phospholipid donor substrate and phosphatidylcholine (70%)/phosphatidylethanolamine (30%) unilamellar liposomes containing [14C]triolein, a nontransferable marker, as the acceptor substrate for transferred phospholipids. Incubation of these two membrane substrates with a 40 to 80% (NH4)2SO4 protein fraction from R. sphaeroides results in the transfer of tritium-labeled ICM phospholipids to the acceptor membrane substrate. Upon completion of the incubation period, the donor ICM vesicles are quantitatively separated from the acceptor liposomes by precipitation with antibody prepared against whole, purified ICM vesicles. Phospholipid transfer is linear with respect to time and protein concentration, is inhibited by trypsin and heat, and shows an absolute dependence upon the presence of acceptor liposomes and the 40 to 80% (NH4)2SO4 protein fraction. Control experiments indicate that no fusion of the donor and acceptor membrane occurs during the incubation period and that, following prolonged incubation there is no detectable degradation of the labeled lipid components. Preliminary data on the phospholipid specificity of the transfer reaction is also presented.

Biological Transport↗
PubMed1979

Psychosocial aspects of craniofacial disfigurement. A "State of the Art" assessment conducted by the Craniofacial Anomalies Program Branch, The National Institute of Dental Research.

The psychosocial sequelae of craniofacial disfigurement may have as great an impact on the patient as the strictly physical aspects of the problem. Very little systematic work has been focused directly on these effects. The following broad recommendations would constitute initial research steps in this field: Development of satisfactory measures of physical attractiveness and their use in studies to explore the role of craniofacial features in over-all physical attractiveness. The establishment of valid metrics for assessing the severity of craniofacial anomalies through the use of both physiologic and behavioral measures, thus constructing a broader definition of what constitutes a craniofacial handicap. Studies of the relationships among physiologic and behavioral variables using recently developed statistical techniques and computer methods to determine the psychosocial consequences of craniofacial disfigurement. Studies of the process through which persons with various types of malocclusion decide to seek and complete treatment. The studies would include the patients' demographic characteristics, self-perceptions, perceptions of them by others, and the complex patient-clinician interactions during the treatment programs.

Body Image↗
PubMed1979

Characterization of a site-specific restriction endonuclease from Rhodopseudomonas sphaeroides.

A type II restriction endonuclease, RshI, has been partially purified from photoheterotrophically grown Rhodopseudomonas sphaeroides strain 2.4.1. The enzyme preparation, after a single DE-52 column fractionation, is free of 5' exonuclease and phosphatase activities but contains a trace of 3' exonuclease activity. Based upon deoxyribonucleic acid (DNA) sequencing data in the vicinity of the enzyme-promoted cleavage of pBR322 DNA, we have concluded that RshI probably recognizes the palinodromic hexanucleotide sequence 5'-CGATCG-3' and cleaves between the T and C. lambda cI857 DNA contains three RshI sites, two of which lie in the replaceable region. The plasmid pBR322, which carries resistances to ampicillin and tetracycline, contains a single RshI site in the ampicillin resistance determinant. Insertion of DNA into the RshI site of pBR322 results in loss of ampicillin resistance but retention of tetracycline resistance, thereby providing a convenient screening procedure for recombinant plasmids.

Base Sequence↗
PubMed1977

Social sciences research: ethical and policy implications.

Ethical issues are raised about the conduct of social research in the dental field particularly with respect to the use of survey methodology and aggregated data. Problems associated with respondent identifiers, open-ended and probing questioning, privacy of subject-matter, community contamination and burden, group stereotyping, knowledge of law violations, mis-use of data banks, re-use of data, effects of disclosure, and referral for treatment are discussed. The natural and the contrived social experiments are reviewed as well as the issue of needed research on the effects of regulation on science and on the protection of privacy.

Behavioral Research↗
PubMed1976

Toward the formulation of sociodental indicators.

The bases for the construction of sociodental indicators is discussed in the paper, considering several available indexes of oral health status (dental caries, periodontal disease, malocclusion, oral hygiene, and other oral conditions) as well as measures of quality of services. Very little research exists relating any of the above measures to social indicators such as personal life-style or cultural and ecological factors. Such expansion would enable dental indicators to be useful for purposes of policy decisions. Combining any dental indicators or set of indicators with a potential global social health index is discussed in terms of potential problems obscuring dentistry's cost to society. Dentistry, in addition, is offered as a system in microcosm-one which can be useful for purposes of polishing methodology for the social health indicator movement.

Adult↗
PubMed1976

Transactions of an international conference. Worldwide concern: better dental care for more people. An international collaborative study. How the study was designed.

The study originated from the common need felt by the United States Public Health Service and the World Health Organization for objective information about various national dental care delivery systems and their effectiveness in the societies in which they were used. The relationships between consumers, providers and administrators within each system were emphasized rather than the comparison between systems since each operated within a specific biological and ecological environment. Six systems all of which had been in existence for at least twenty years were originally selected for study to encompass those dependent on a majority of government or private enterprise, use or non-use of auxiliaries, differeing systems of financing and of definition of target groups for receipt of services. The countries originally taking part were Australia, the Federal Republic of Germany, Japan, New Zealand, Norway and Bulgaria, though Bulgaria withdrew early in 1975.

Administrative Personnel↗