Non-Tuberculous Chest Disease Found in a Mass X-Ray Survey in Vancouver,B.C

In 1964, 219,085 persons were examined during a tuberculosis survey in Vancouver, B.C. One hundred and fifteen new cases of tuberculosis and 929 cases of significant non-tuberculous lung disease were found. In a four-month follow-up of the non-tuberculous cases it was found that of the 742 patients who had named a physician when examined 26.6% had not made contact with him. Of those who did contact the physician, the follow-up was considered “poor” in only 30 patients (2.1%). Seventeen patients had died in the four-month interval and 81 who could not be located after the initial survey were considered “lost”. Rates were determined for 37 diagnoses per 1000 patients screened. The most common diagnosis was localized pulmonary fibrosis (1.69/1000). Carcinoma was found in 0.30/1000 and solitary lung density in 0.17/1000 population screened.     

Summer Internships: 12 Years' Experience with Undergraduate Medical Students in Summer Employment in Various Areas of Preventive Medicine

Twelve years'' experience in providing summer employment for students in official health agencies in British Columbia is reviewed and a two-week orientation course given prior to employment in 1964 is described. In the program, which provides experience in teaching, research and community service, a total of 43 students have been employed. Students seeking this type of employment and accepted for it tend to have high academic standing. They prefer employment in or near Vancouver irrespective of their original home location. Two main employers have been available: specialized agencies in metropolitan Vancouver, or “rural” health units. Students serving in health units showed a strong tendency to enter general practice after graduation. Urban experience tended to lead to specialization.     

Randomised controlled trial comparing oral and intravenous rehydration therapy in children with diarrhoea.

OBJECTIVE--To determine the effectiveness of oral rehydration in children with moderate dehydration caused by gastroenteritis, and to compare the complications of oral and intravenous treatment. DESIGN--Randomised controlled trial. SETTING--Emergency department and infectious diseases ward in a large urban teaching hospital. PATIENTS--111 children aged 3-36 months who had been previously healthy, had had diarrhoea for seven days or less, had clinical signs of dehydration, and were not in shock. Six children were withdrawn because the diagnosis was incorrect (four in oral group, two in intravenous group) and one (oral group) was withdrawn at her parents'' request. INTERVENTIONS--Oral rehydration fluid was given by mouth or nasogastric tube, or both to 52 children. The remaining 52 received intravenous rehydration fluids but were allowed to drink. MAIN OUTCOME MEASURES--Success or failure of rehydration. Number of times child vomited or passed stool after starting treatment. Time taken to rehydrate. RESULTS--Oral treatment failed in two children (failure rate 3.8%, upper 95% confidence limit 11.6%) and intravenous treatment in none. Vomiting was more common in the oral group (p less than 0.01): 26 of 50 children (52%) in the oral group and 11 of 50 (22%) in the intravenous group vomited during rehydration. There was no significant difference between the two treatment groups in the number of stools passed during rehydration (p = 0.09). None of the children had serious complications of treatment. CONCLUSION--Rehydration by mouth or nasogastric tube is a safe and effective treatment for moderately dehydrated children with gastroenteritis.     

Slipped-strand mispairing: a major mechanism for DNA sequence evolution

Simple repetitive DNA sequences are a widespread and abundant feature of genomic DNA. The following several features characterize such sequences: (1) they typically consist of a variety of repeated motifs of 1-10 bases--but may include much larger repeats as well; (2) larger repeat units often include shorter ones within them; (3) long polypyrimidine and poly-CA tracts are often found; and (4) tandem arrangements of closely related motifs are often found. We propose that slipped-strand mispairing events, in concert with unequal crossing- over, can readily account for all of these features. The frequent occurrence of long tandem repeats of particular motifs (polypyrimidine and poly-CA tracts) appears to result from nonrandom patterns of nucleotide substitution. We argue that the intrahelical process of slipped-strand mispairing is much more likely to be the major factor in the initial expansion of short repeated motifs and that, after initial expansion, simple tandem repeats may be predisposed to further expansion by unequal crossing-over or other interhelical events because of their propensity to mispair. Evidence is presented that single-base repeats (the shortest possible motifs) are represented by longer runs in mammalian introns than would be expected on a random basis, supporting the idea that SSM may be a ubiquitous force in the evolution of the eukaryotic genome. Simple repetitive sequences may therefore represent a natural ground state of DNA unselected for coding functions.      

Complete sequences of the rRNA genes of Drosophila melanogaster

In this, the first of three papers, we present the sequence of the ribosomal RNA (rRNA) genes of Drosophila melanogaster. The gene regions of D. melanogaster rDNA encode four individual rRNAs: 18S (1,995 nt), 5.8S (123 nt), 2S (30 nt), and 28S (3,945 nt). The ribosomal DNA (rDNA) repeat of D. melanogaster is AT rich (65.9% overall), with the spacers being particularly AT rich. Analysis of DNA simplicity reveals that, in contrast to the intergenic spacer (IGS) and the external transcribed spacer (ETS), most of the rRNA gene regions have been refractory to the action of slippage-like events, with the exception of the 28S rRNA gene expansion segments. It would seem that the 28S rRNA can accommodate the products of slippage-like events without loss of activity. In the following two papers we analyze the effects of sequence divergence on the evolution of (1) the 28S gene "expansion segments" and (2) the 28S and 18S rRNA secondary structures among eukaryotic species, respectively. Our detailed analyses reveal, in addition to unequal crossing-over, (1) the involvement of slippage and biased mutation in the evolution of the rDNA multigene family and (2) the molecular coevolution of both expansion segments and the nucleotides involved with compensatory changes required to maintain secondary structures of RNA.      

Modulation of alcohol dehydrogenase isoenzyme levels in Zymomonas mobilis by iron and zinc.

Zymomonas mobilis is an unusual microorganism which utilizes both iron-containing alcohol dehydrogenase (ADHII) and zinc-containing alcohol dehydrogenase (ADHI) isoenzymes during fermentative growth. This organism is obligately ethanologenic, and alcohol dehydrogenase activity is essential. The activities of ADHI and ADHII were altered by supplementing growth medium with iron or zinc salts and by iron starvation. Growth under iron-limiting conditions (chelators, minimal medium) reduced ADHII activity but did not prevent the synthesis of the ADHII protein. The inactive form of this enzyme appeared quite stable, was not renatured by iron addition, and persisted in the cell. The iron-induced increase in ADHII activity required de novo synthesis which was blocked by antibiotic additions. The ability of Z. mobilis to synthesize ADHII and ADHI may be advantageous in nature.     

Expression of Zymomonas mobilis adhB (encoding alcohol dehydrogenase II) and adhB-lacZ operon fusions in recombinant Z. mobilis.

The Zymomonas mobilis alcohol dehydrogenase II gene (adhB) was overexpressed 7- to 14-fold on a recombinant plasmid, accompanied by a small decrease in growth rate. A fragment containing the truncated gene with promoter reduced expression from the chromosomal gene as measured immunologically and enzymatically, consistent with the presence of a trans-active regulatory factor and positive regulatory control. Both the complete gene and the promoter fragment increased pyruvate decarboxylase and glucokinase activities, with no effect on alcohol dehydrogenase I or eight glycolytic enzymes. Tandem promoters from adhB expressed beta-galactosidase at higher levels than did either promoter alone in operon fusions. Addition of 50 microM zinc sulfate in minimal medium reduced the expression of adhB and of the operon fusions. Abundant but inactive alcohol dehydrogenase II was produced in iron-limited cells. This inactive enzyme did not form intracellular aggregates, and no morphological changes were apparent by transmission electron microscopy.     

The distribution of blood group antigens in rodent epithelia

Summary The pattern of distribution of antigens cross-reacting with antibodies to human blood group antigens A and B and two precursor molecules was examined by immunofluorescence in the epidermis, oral mucosa and forestomach of rats and mice. Staining for blood group antigen A was negative. In all epithelia examined, blood group antigen B was present at the surface of basal and parabasal cells, and the H antigen at the surface of spinous cells. N-acetyllactosamine was present on the cell membranes in the upper spinous and granular cell layers of epidermis and forestomach epithelium and was not expressed in the oral epithelia except for a limited area in the dorsal tongue epithelium.Thus, the expression of antigen varies both regionally and, as earlier shown in human epithelium, with the stage of maturation of cells within a given epithelium. The observed sequence of expression of these antigens during maturation differs from that of human epithelia, but the present study provides a basis for further experimental studies of the role of cell surface antigens in epithelial homeostasis and maturation.     

Connective tissue influences on patterns of epithelial architecture and keratinization in skin and oral mucosa of the adult mouse

Summary Epithelial-mesenchymal interactions play an important role during embryogenesis but it is uncertain whether such interactions influence the maintenance of epithelial structure in the adult. To examine this problem, separated epithelial and connective tissue components of skin and mucosae from various regions of adult mice were homoor heterotypically recombined and transplanted to histocompatible hosts. The patterns of tissue architecture and keratinization of the resultant epithelia were examined for changes indicative of mesenchymal influences on the epithelial phenotype. Each type of epithelium, in some recombinations, fully conserved its normal pattern of phenotypic expression indicating that subepithelial connective tissue from all regions is permissive and that regionally-specific connective tissue influences are not necessary for conservation of epithelial specificity. In other recombinations, however, the epithelium acquired features of tissue architecture or keratinization typical of the epithelium normally associated with the connective tissue component, indicating directive influ ences from the connective tissue. The patterns of epithelial response observed suggest that there may be separate connective tissue influences on epithelial architecture and cytodifferentiation and that there is a regionally-related variation in the competence of epithelia to respond to these influences.Supported by NIH NIDR 2 R01 DE05190