Sweat Chlorides in Salt-Deprived Cystic Fibrosis Heterozygotes

Sweat chlorides of 10 sets of parents of children with cystic fibrosis and 11 controls were studied in an attempt to develop a test for the diagnosis of cystic fibrosis heterozygotes by subjecting both the parents and controls to a low sodium diet and comparing sweat chloride values as the diet progressed. It was hoped that the sweat chloride levels of the parents, the heterozygotes, would remain stationary throughout the diet, since their children, the homozygotes, reveal this finding under similar conditions of salt deprivation. The sweat chloride levels of the controls, because of effects of aldosterone, were expected to decrease steadily from the commencement of the diet to its termination.A decrease in sweat chloride values of similar magnitude was found in both parents and controls as the diet continued. It is concluded that the study of sweat electrolyte levels in salt-deprived subjects is of no value in the diagnosis of cystic fibrosis heterozygotes.     

Antioxidant Activity of 5-Hydroxytryptophan, 5-Hydroxyindole, and Dopa Against Microsomal Lipid Peroxidation and Its Dependence on Vitamin E

The antioxidant capacity of 5-hydroxy-tryptophan. 5-hydroxy-indole. and DOPA (3,4-dihydroxy-phenyI-alanine) was tested in the Fe-induced lipid peroxidation of liver microsomes of normal- and vitamin E-deficient rats, using ascorbate as a reductant. Lipid peroxidation was monitored as low-level chemilu-minescence, indicative of generation of electronically-excited states arising from the recombination of secondary lipid peroxyl radicals.     

Classical plant taxonomic ambiguities extend to the molecular level

Summary The molecular evolution of cytochrome c from angiosperms is compared to that from vertebrates. On the basis of a cladistic analysis from 26 plant species, compared to that from 27 vertebrate species, we find that although the vertebrate sequences yield reasonably well-defined minimal trees that are congruent with the biological tree, the plant sequences yield multiple minimal trees that are not only highly incongruent with each other, but none of which is congruent with any reasonably biological tree. That is, the plant sequence set is much more homoplastic than that of the animal. However, as judged by the relative rate test, the extent of divergence, and degree of functional constraint, cytochrome c evolution in plants does not appear to differ from that of vertebrates.     

Evaluation of a method to measure conjugal transfer of recombinant DNA in soil slurries

Release of recombinant microbes into the environment necessitates an evaluation of their ability to transfer genetic material. The present report evaluates a method to detect conjugal DNA plasmid transfer in soil slurries under various environmental conditions. DonorPseudomonas cepacia containing pR388::Tn1721 andP. cepacia recipient cultures were coincubated in soil slurries containing autoclaved or natural soil and treated with one or more of 14 experimental conditions. Conjugal mating frequency (transconjugants per initial donor) ranged from 4.8×10^–1 to 1.9×10^–7. Highest numbers of transconjugants, 1.5×10⁷ colony forming units/ml soil slurry, were observed following incubation at 35°C with an enriched nutrient supplement added to the soil. Low numbers of transconjugants, 10³ colony forming units/ml soil slurry, were observed when mating pairs were subjected to low nutrient or pH stress even though initial donor and recipient populations were maintained at high levels. This test system provides a simple way to estimate effects of changing environmental factors on plasmid transfer rates and on the survival of recombinant microorganisms. By use of soil collected from sites proposed to receive genetically engineered microorganisms, preliminary risk assessments can be obtained regarding the potential for gene transfer and microorganism survival with this soil slurry test system.     

Comparability of two tests of olfactory functioning

In the first of two comparisons, 50 patients who came to theConnecticut Chemosensory Clinical Research Center (CCCRC) withvarious chemosensory complaints were evaluated by a dual threshold/odoridentification test administered in the CCCRC and by the self-administeredUniversity of Pennsylvania Smell Identification Test (UPSIT).Agreement between tests proved high, with a correlation coefficientof 0.92. The UPSIT correlated better with the odor identificationcomponent than with the threshold component of the CCCRC test.This disparity stemmed largely from limitations in the reliabilityof the threshold component. An increase in the stringency ofthe criterion for determination of threshold increased the reliabilityof this component and, in a second comparison with a total of58 patients and controls, the correlation between the UPSITand CCCRC test increased. With the more stringent criterion,the correlation equalled 0.96. ²Present address: International Flavors and Fragrances, Researchand Development, Union Beach, NJ 07735, USA     

The use of amphipathic maleimides to study membrane-associated proteins

A series of amphiphilic polymethylenecarboxymaleimides has been synthesized for use as sulfhydryl reagents applicable to membrane proteins. Physical properties of the compounds which are relevant to their proposed mode of action have been determined. By comparing rates of reaction in aqueous and aprotic solvents, the compounds have been shown to react exclusively with the thiolate ion. The effects of the reagents on three membrane-associated proteins are reported, and in two cases a comparative study has been made of the effects on the proteins in the absence of membranes. A mechanism is proposed whereby the reagents are anchored at the lipid/water interface by the negatively charged carboxyl group, thus siting the reactive maleimide in a plane whose depth is defined by the length of the reagent. Supporting evidence for this model is provided by the inability of the reagents to traverse membranes, and variation of their inhibitory potency with chain length when the proteins are embedded in the membrane, but not when extracted into solution. As examples of general use of the reagents to probe sulfhydryl groups in membrane proteins, the reagents have been used to (a) determine the depths in the membrane at which two populations of sulfhydryl groups occur in the mitochondrial phosphate transporter; (b) locate a single sulfhydryl associated with the active site ofD--hydroxybutyrate dehydrogenase in the inner mitochondrial membrane; (c) examine sulfhydryl groups in theD-3-glyceraldehyde phosphate dehydrogenase associated with the human red blood cell membrane.     

Lipid composition and food quality of some freshwater phytoplankton for cladoceran zooplankters

The nutritional value of several planktonic algae was testedby means of feeding trials with three cladoceran zooplankters.The algae were monocultures and included two blue-greens, fourgreens and four flagellates with a size range of 5–48µm. The specific growth rates of the zooplankters werechosen as the measure of the nutritional value of the algae.The three cladocerans showed large differences in growth ratein the different algae, but the two cryptomonads were withoutdoubt best suited as food for all. The fatty acid compositionfor the cryptomonads were different from the other algae. Theycontained high percentages of the polyunsaturated fatty acids20:5æ3 (EPA) and 22:6æ3 (DHA), which also are commonin fish. It is suggested that the lipid composition is a probablefactor determining the nutritional quality of the algae.