Although spider silk has been studied for a number of years the structures of the proteins involved have yet to be definitely determined. X-ray diffraction and solid-state nuclear magnetic resonance (NMR) were used to study major ampullate (dragline) silk from Nephila clavipes. The silk was studied in its natural state, in the supercontracted state and in the restretched state following supercontraction. The natural silk structure is dominated by beta-sheets aligned parallel to the fiber axis. Supercontraction is characterized by randomizing of the orientation of the beta-sheet. When the fiber is restretched alignment is regained. However, the same reorientation was observed for wetting of minor ampullate silk which does not supercontract. Thus, the reorientation of beta-sheets alone cannot explain the supercontraction in dragline silk. Cocoon silk showed very little beta-sheet orientation in the natural state and there were no changes upon wetting. NMR and X-ray diffraction data are consistent with the beta-sheets arising from the poly-alanine sequences known to be present in the proteins of major ampullate silk as has been proposed previously.

Amino Acid Sequence↗

PubMedDate not supplied

Gauze vs. plastic for peripheral intravenous dressings: testing a new technology.

The authors conducted a randomized, prospective, controlled trial of three different dressings for peripheral intravenous catheters in 301 acutely ill medical inpatients. Catheters were dressed with dry clean gauze or one of two brands of transparent plastic. The gauze dressings remained in place significantly longer (47 hours median) than either Uniflex (39 hours) of Tegaderm (32 hours) transparent plastic dressings (p = 0.026). Catheters were removed for complications (inflammation, mechanical failure, or infiltration) in 35% of the gauze group, compared with 58% of the Uniflex group and 48% of the Tegaderm group (p = 0.015). Not only were inflamed venipuncture sites seen less often with gauze, inflammation occurred later (p = 0.002) and with lesser severity. Dry gauze dressings resulted in longer catheter life, lower complication rates, and less expense than transparent plastic dressings for peripheral intravenous catheters.

Catheters, Indwelling↗

PubMedDate not supplied

Herbicide residues in air-cured burley tobacco.

Explore the source record for details and available documents.

Amides↗

PubMedDate not supplied

Maternal and neonatal neutralizing antibody titers to selected enteroviruses.

Neutralizing antibody titers were determined at term for 98 matched mothers' serum and neonatal cord blood pairs, to coxsackieviruses B2, B3, B4 and B5 and to echovirus 11. The reciprocal of the geometric mean titers of maternal sera were, respectively, 15.3, 18.1, 53.5, 14.1 and 11.4. The geometric mean titers of cord sera were statistically lower for coxsackie B5 and echovirus 11 (P less than 0.031 and p less than 0.005, respectively) than those in maternal sera. The percentage of neonates born with antibody titers less than 1:10 to coxsackieviruses B2, B3, B4 and B5 and echovirus 11 ere 49, 37, 17, 53 and 69%. Thus a large percentage of neonates in our community are born with low titers of enterovirus-neutralizing antibody, which for some infants may be disproportionately lower than maternal titers to selected enteroviruses. Commercially available immune serum globulin contains high titers of antibody to these enteroviruses and may be a useful means of passive antibody acquisition in susceptible neonates at risk for enterovirus infections. However, a single dose of immune serum globulin intramuscularly produced little change in circulating neutralizing antibodies to coxsackie B4 and echovirus 11 in seven neonates.

Adult↗

PubMedDate not supplied

Chronic calcitonin administration and renal calcium transport in the rat.

1. While calcitonin (CT) has now been clearly demonstrated to be a renal Ca2+-conserving hormone and may share similar transport mechanisms with parathyroid hormone (PTH), the effect of prolonged CT exposure on renal Ca2+ transport has not been evaluated. 2. Consequently, a submaximal and maximal Ca2+-conserving concentration of human CT was infused into groups of anaesthetized acutely thyroparathyroidectomized rats that had been treated with twice daily subcutaneous human (h) CT at a low or high dose or vehicle for 12 days. 3. The maximal hCT infusion (10 microg bolus and per hour) produced a marked inhibitory effect on renal Ca2+ excretion in vehicle-treated rats, with the fractional excretion rate of Ca2+ being reduced from 4.49+/-0.31 to 139+/-0.23% (P<0.001). However, in rats pretreated with high concentrations of hormone (0.25 microg hCT) twice daily for 12 days, marked Ca2+ conservation was measured (fractional excretion 1.09+/-0.18%), which was not altered by the additional intravenous administration of maximal hCT. 4. Renal Mg2+ transport was similarly altered by hCT administration, without any evidence that prolonged CT inhibited renal Mg2+ transport. The increase in glomerular filtration rate caused by hCT also appeared to persist with repeated hormone administration. The fractional excretion of Na+ and PO4 was significantly increased by high- but not low-dose hCT treatment and was not altered by the addition of a maximal hormone dose at day 12. 5. The present study failed to demonstrate any down-regulation of the response to prolonged hCT administration when renal Ca2+ and Mg2+ transport was measured. If renal escape does occur with CT, as has been suggested but not proven with PTH, other mechanisms, such as hormone production or release, may be responsible.

Animals↗

PubMedDate not supplied

Phenotypic and functional analysis of expanded natural killer cell subpopulations in Hodgkin's disease patients treated with lymphoid irradiation.

We have evaluated the immunophenotype and function of presumptive NK cells taken from Hodgkin's disease patients before and after mantle/para-aortic lymphoid irradiation. We find that the lymphoid irradiation appears to induce a relatively stable, generalized expansion of the entire NK cell compartment rather than an increase in any specific NK cell subset. Flow cytometric cell sorting and functional NK cell assays based on immunophenotype demonstrate no significant changes in the phenotypic proportions of individual NK cell subsets and no significant changes in the lytic activity or cytotoxicity spectrum of these NK cells. These changes in the NK cell compartment may play a role in the long-term immunosuppression of these patients.

Cytotoxicity Tests, Immunologic↗