Previous reports have indicated that calcium is necessary to support active sodium transport by the toad bladder, and may be required as well in the action of vasopressin on both toad bladder and frog skin. The structure and function of the toad bladder has been studied in the absence of calcium, and a reinterpretation of the previous findings now appears possible. When calcium is withdrawn from the bathing medium, epithelial cells detach from one another and eventually from their supporting tissue. The short-circuit current (the conventional means of determining active sodium transport) falls to zero, and vasopressin fails to exert its usual effect on short-circuit current and water permeability. However, employing an indirect method for the estimation of sodium transport (oxygen consumption), it is possible to show that vasopressin exerts its usual effect on Q(oo2) when sodium is present in the bathing medium. Hence, it appears that the epithelial cells maintain active sodium transport when calcium is rigorously excluded from the bathing medium, and continue to respond to vasopressin. The failure of conventional techniques to show this can be attributed to the structural alterations in the epithelial layer in the absence of calcium. These findings may provide a model for the physiologic action of calcium in epithelia such as the renal tubule.

Animals↗

PubMed1965

[Balancing of the occlusion of the natural dentition according to Jankelson's method].

Explore the source record for details and available documents.

Humans↗

PubMed1965

Roentgenologic examination of the small bowel--an improved technique.

IN EXAMINATION OF THE SMALL INTESTINE, SHORTENED TRANSIT TIME AND IMPROVED QUALITY WERE ACHIEVED BY USING THE FOLLOWING ITEMS OF REGIMEN: 1, No laxative; 2, nothing by mouth for 8 hours before examination; 3, 600 ml of micropulverized barium sulfate; 4, patient to lie in right decubitus position for at least one hour between films; and 5, ingestion of 200 ml of cool tap water a half hour after the start of the examination.

Humans↗

PubMedDate not supplied

Reducing cancer risk among Native American adolescents.

BACKGROUND: This article discusses the development, implementation, and preliminary testing of an intervention to reduce cancer risks through tobacco use prevention and dietary modification among Native American youth in the Northeastern United States. METHODS: The intervention outcome study includes a research design and outcome measurement instruments. In collaboration with Native American communities, reservations, and organizations in the Northeastern United States, implementation of the design quantifies the separate and combined effects of a tobacco use prevention and a dietary modification intervention. RESULTS: Native American youths in the tobacco prevention intervention and in the combined tobacco and dietary intervention increased their knowledge of tobacco facts and their awareness of the motives of tobacco advertising, and showed higher ratings for an ability to resist peer pressure and to refuse offers of tobacco use between pretest and posttest. Youths in the combined intervention were significantly less apt to report smoking of any kind. Youths in the tobacco use prevention-only condition reported significantly less smoking than their counterparts in the dietary modification-only condition and control condition on 4 of 8 measurement items. As for dietary variables, pretest to posttest measurement scores showed that, after receiving the curriculum, youths in the dietary modification intervention and in the combined intervention improved their knowledge of the health implications of consuming dietary fat, fiber, fruits, and vegetables. Youths in the dietary modification and combined intervention also improved their scores of knowledge related to cancer risk-reducing nutritional practices, cultural dietary habits, and healthy food choices available for Native American cultures. Youths in the dietary modification-only condition report significantly increasing their consumption of complex carbohydrates and significantly decreasing their fat intake between pretest and posttest occasions. CONCLUSIONS: Data from this longitudinal study suggest the value of the FACETS curriculum for helping Native American youth reduce their risks for cancer associated with tobacco use and dietary preference and consumption patterns. In particular, results indicate the enhanced effects of the combined tobacco use prevention and dietary modification intervention for preventing tobacco use and for improving youths' knowledge and attitudes with regard to tobacco use and diet. Further, the study demonstrates the value of collaborating with Native American organizations to design a cancer risk-reducing curriculum and to implement tests of that curriculum.

Adolescent↗

PubMedDate not supplied

Site-directed mutagenesis for quantitation of base-base interactions at defined sites.

Two alkylation products implicated in initiation of carcinogenesis are O6-alkylguanine (m6G) and O4-alkylthymine (m4T). We have used site-specific insertion of these derivatives into oligonucleotides and measured the kinetic constants of various pairings, using both prokaryotic and eukaryotic polymerases for replication. Preliminary data are also reported for another carcinogen product, N2,3-ethenodeoxyguanosine ( epsilon G). The immediate neighbor bases play an important role in determining the frequency of specific changed basepairing and subsequent elongation of the annealed primer. However, both m4T and m6G prefer to form a type of G.T pairing which would lead to the transitions: G.C----A.T or T.A----C.G. The enzymes were the Klenow fragment of E. coli DNA polymerase I (Kf), engineered 3'----5' exonuclease-free Kf (exo-free Kf), polymerase alpha-primase complex from Drosophila melanogaster or calf thymus, and human immunodeficient virus-I reverse transcriptase (HIV-I RT). All enzymes led to approximately the same frequency of transitions. It is postulated that the mutation frequency at a given site is primarily a function of the structure of the sequence around the target site.

Animals↗