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Biomedical subjects

W Schaffner

Publications and source records attributed to W Schaffner.

At least 325 records · Page 18Linked to original sources
PubMed1976

Determination of nicotine concentrations in human milk.

A total of 34 samples of human milk from 15 donors was analyzed for nicotine content, using a new method of sample preparation and subsequent quantification by gas chromatography. Nicotine was not found in the six samples of milk from non-smokers. The 28 samples from smokers contained an average of 91 parts per billion (ppb) nicotine (ranging from less than 20 ppb to 512 ppb). While no adverse effects to the infant due to nicotine in human milk have been documented, this method of analysis will allow systematic monitoring of nicotine concentrations in the milk of lactating women. These results should not be used to deter breast-feeding; rather, they offer another reason for mothers to reduce or cease smoking.

Breast Feeding↗
PubMed1976

Molecular analysis of the histone gene cluster of Psammechinus miliaris: I. Fractionation and identification of five individual histone mRNAs.

The electrophoretic separation of labeled "9S" histone mRNAs obtained from cleaving sea urchin polysomes was found at first to be highly unreproducible. It became evident that the secondary structure of the individual mRNAs had a greater effect on their relative electrophoretic mobilities than did their molecular weight differentials. We determined the parameters affecting electrophoretic mobility by the novel method of running the labeled polysomal RNA in slab gels across polyacrylamide and urea gradients. The initially complex and species-specific electrophoretic pattern could then, by a judicious choice of denaturing conditions, be simplified to yield five well defined classes of labeled mRNAs. Using optimal conditions for the separation of the RNA components, five messengers were isolated from Psammechinus embryos by preparative disc electrophoresis, four of which, after two electrophoretic separations, exhibited a unimodal distribution. Each of the mRNAs was translated in vitro, four of the five fractions promoting the synthesis of one major protein. The in vitro products were characterized by comparison of their electrophoretic mobilities with those of known sea urchin histones. It was thus possible to correlate individual mRNAs with specific histones. We propose that the five mRNAs designated a-e in order of decreasing electrophoretic mobility code for the histones H4, H2A, H2B, H3, and H1.

Animals↗
PubMed1976

Molecular analysis of the histone gene cluster of psammechinus miliaris: II. The arrangement of the five histone-coding and spacer sequences.

Histone DNA of Psammechinus miliaris was obtained in an enriched form by buoyant density gradient centrifugation and was cleaved into 6 kb repeat units (Birnstiel et al., 1975a) by the action of the specific endonucleases EcoRI and HindIII. Since it was suspected that the 6 kb unit harbored all five histone-coding sequences, the histone DNA unit was subdivided into five segments with the aim of providing five fragments carrying just one coding sequence each. This was achieved by the combined use of EcoRI Hindll, Hindlll, and Hpa I. A physical map was constructed from the overlaps arising in these restriction experiments. Each of the five segments was shown to hybridize uniquely with just one of the five highly purified histone mRNAs (Gross et al., 1976a). By this procedure, the order of the mRNA sequences on the histone DNA was found to be a, c, d, b, e (Gross et al., 1976a), and hence of the protein coding sequences H4, H2B, H3, H2A, and H1. Further evidence is presented that the 6 kb repeat unit, amplified by means of a Murray lambda vector phage, contains AT-rich DNA sequences which would be expected not to code for histone proteins.

Adenine↗
PubMed1976

Molecular analysis of the histone gene cluster of Psammechinus miliaris: III. Polarity and asymmetry of the histone-coding sequences.

Fragments of histone DNA produced by restriction endonucleases contain 5' and 3' termini with defined topologies relative to the histone-coding sequences. After limited resection with lambda-exonuclease, the 6 kb Hindlll histone DNA fragment (see Schaffner et al., 1976) hybridizes to H4 histone mRNA whether or not the DNA has been denatured. This shown that the coding sequence for the histone H4 is proximal to the 3' terminus of the Hindlll restriction fragment. By contrast, lambda-exonuclease digestion of the 6 kb EcoRI histone DNA fragment drastically reduces hybridization of the H4 mRNA. Hence in this molecule, the H4 DNA sequence is near a 5' terminus of the EcoRI restriction fragment. From these results and those described in the preceding paper (Schaffner et al., 1976), the polarity of the H4 gene is therefore 5' H2B leads to H4 leads to H1 3'. Cloned Psammechinus histone DNA (S. G. Clarkson, H. Smith, W. Schaffner, K. Gross, and M. Birnstiel, manuscript submitted for publication) may be strand-separated by electrophoresis. Highly purified histone mRNAs (Gross et al., 1976) all hybridize almost exclusively to the strand of lesser electrophoretic mobility. It follows that all coding sequences are arranged in tandem within the same DNA strand, and that hence they share the same polarity as the H4 DNA sequences. Transcription therefore proceeds in the gene cluster in the direction H4 leads to H2B leads to H3 leads to H2A leads to H1.

Animals↗
PubMed1976

An outbreak of nosocomial infection due to multiply resistant Serratia marcescens: evidence of interhospital spread.

Interhospital spread appeared to be responsible for a large epidemic of infections due to a strain of Serratia marcescens that was resistant to all currently available parenteral antibiotics. Between April 1, 1973 and January 1, 1975, 210 patients in four geographically separate hospitals in Nashville, Tennessee, were infected with the epidemic strain; 21 patients were bacteremic and eight died. Catheter-associated urinary tract infection accounted for the majority of isolates, and broad-spectrum antibiotic exposure appeared to promote the acquisition of the epidemic strain. The serotype (O1:H7) and phage type (186) of the organism were identical in all four hospitals, but background, sensitive strains of S. marcesens yielded a variety of other serotypes. Carriage on the hands of hospital personnel was implicated as the mode of spread within the hospital and apparently was the mode of transmission between the hospitals. Antibiotic resistance was largely episomally mediated, but resistance to gentamicin, cephalothin, and colistin was not transferable.

Cross Infection↗
PubMed1976

Integration of eukaryotic genes for 5S RNA and histone proteins into a phage lambda receptor.

Highly purified HindIII restriction fragments of Xenopus laevis 5S DNA and of Psammechinus miliaris histone DNA have been covalently inserted into a derivative of phage lambda. This phage, genetically constructed by Murray et al. (1), contains only a single target for HindIII in the cI gene. Viable hybrid molecules were detected as clear plaque-forming phage after transfection of E. coli, the vast majority of which were shown by hybridization to be recombinants of the desired type. The lambdaSam7 mutation has been introduced into one hybrid phage containing histone DNA, thereby substantially increasing the yield of recombinant DNA.

Animals↗
PubMed1976

Medicaid records as a valid data source: the Tennessee experience.

Health care researchers rarely employ Medicaid claim files as a data base, in part because they are designed to serve fiscal and administrative ends. Indeed, some investigators have emphasized the deficiencies in such records. In contrast, we have found Tennessee Medicaid data to be suitable for research. A statewide automated data processing system reduces the occurrence of many of the errors noted by others. Further, analysis of the July 1974 month of payment file illustrates the accuracy and internal consistency of Tennessee Medicaid data. Specimen legend drug results for ambulatory patients suggest investigations of physician prescribing patterns. Evaluation of the Medicaid claims processing system suggests other applications in health care administration and research. In a time when available resources are dwindling, the incisive use of Medicaid claims files offers an attractive alternative to expensive new systems of data collection and analysis.

Aged↗
PubMed1976

Prescribing of chloramphenicol in ambulatory practice. An epidemiologic study among Tennessee Medicaid recipients.

During the 1-year period from July 1973 through June 1974, 1761 chloramphenicol prescriptions were written for 992 outpatients in the Tennessee Medicaid program. Sxi percent (250 of 3409) of participating physicians prescribed chloramphenicol; 20 physicians wrote 55% of the prescription. Both family practice and rural location were independently associated with increased rates of prescribing chloramphenicol for outpatients. Among rural family practitioners, 21% prescribed chloramphenicol. Physicians graduating since 1955 were as likely to have prescribed chloramphenicol as were earlier graduates. Almost half the adult patients received 6 grams or less, while 2 received more than 250 grams. Approximately half of the prescriptions were for treatment of upper respiratory infections. Most prescriptions were interdicted by good medical practice. Analysis of the prescribing of chloramphenicol (and perhaps other drugs) in ambulatory practice will help identify those physicians most in need or remedial medical education.

Adolescent↗
PubMed1975

Microbiol growth in lipid emulsions used in parenteral nutrition.

Parenteral nutrition via central venous catheterization is associated with serious risks, especially that of sepsis. Lipid emulsion (Intralipid[Sweden]), which may be administered peripherally, was evaluated for its potential to support microbial growth. Washed cultures of Staphylococcus aureus, Candida albicans, and three species of Gram-negative rods were all capable of multiplying in the emulsion at room temperature. Variations in inoculum size did not affect the growth rate. Studies comparing the emulsion to amino acid-glucose solutions (total parenteral nutrition [TPN])confirmed other reports that TPN inhibits the growth of certain bacteria but merely retards fungal multiplication. When human serum was added to the lipid emulsion in an attempt to simulate in vivo conditions at the catheter tip, Escherichia coli was inhibited while the growth of S aureus and C albicians was unaltered.

Amino Acids↗
PubMed1975

Epidemic keratoconjunctivitis: a community outbreak of mixed adenovirus type 8 and type 19 infection.

During the fall and winter of 1973, 145 cases of epidemic keratoconjunctivitis were diagnosed in Nashville, Tennessee. Of the 74 cases studied virologically and/or serologically, 62% were caused by adenovirus type 8, and 28% were caused by adenovirus 19. Whereas adenovirus type 8 was isolated only from conjunctival scrapings, adenovirus type 19 was isolated from nose and throat swabs as well as from conjunctivae. The two viruses produced clinically indistinguishable eye disease and household secondary attack rates that were not statistically different. Regardless of etiology, the secondary attack rate in households was significantly higher among the contacts of those patients who had severe disease for greater than 28 days than among the contacts of patients who had milder disease of shorter duration.

Adenoviridae↗
PubMed1975

Gestational exposure to rubella vaccinees: a population surveillance study.

Over a two-year period an attempt was made to identify instances of transmission of rubella vaccine virus from rubella vaccinees to pregnant women in Nashville-Davidson County, Tennessee. Approximately 24,000 children were immunized in a mass campaign at the outset of the study. Several prospective surveillance methods of 11,635 women and their new babies were employed. Attempts were made to recover rubella virus from throat swabs of 10,951 newborns. No rubella vaccine virus was recovered. Wild rubella virus was isolated from a single infant with the congenital rubella syndrome whose mother had natural rubella during the first month of pregnancy. Rubella virus was not isolated from the products of 240 abortions. There were no seroconversions among 3990 women who had paired sera available for study. Clinical and serologic follow-ups of infants judged to be a high risk because of intimate maternal exposure to vaccine virus revealed no late manifestations of congenital rubella infection. A history of close maternal contact with vaccinees during the three months before and the three months following conception was not associated with an increased incidence of congenital anomalies or clinical features seen with congenital rubella infection. Thus, no evidence of vaccine virus transmission was found, providing further evidence of the safety of rubella vaccine under field conditions. A seroepidemiologic study of 8824 pregnant women revealed the expected decline in rubella susceptibility with increasing age. When age was controlled, the variables of race, parity, and educational achievement produced no major influence on immunity.

Antibodies, Viral↗