Genetic linkage analysis of hemoglobin variants in 175 families.

Linkage analysis using the LIPED program developed by Ott for the analysis of whole family data was performed on 175 families with variants of the hemoglobin beta- or gamma-chain. Comparison of our results with those in the literature indicate that there is little evidence for linkage with any of the currently used markers, although there is considerable heterogeneity in lod scores between sexes for the Duffy and MNS blood groups. It is suggested that the most successful approach in the future will be to analyze markers known to be localized on chromosomes which have been indicated as likely sites of the beta-chain locus from hybridization studies.     

Interaction of substituted guanidines with the tetrodotoxin-binding component in Electrophorus electricus.

In efforts to understand the molecular properties of ion channels in biomembranes, we have investigated the interaction of substituted guanidines with the Na⁺ channel site in membranes isolated from Electrophorus electricus. This interaction was measured by equilibrium competitive binding studies with [${}^3\text{H}$]tetrodotoxin ([${}^3\text{H}$]TTX); TTX has been shown to bind specifically to the Na⁺ channel in electrically excitable membranes. Although guanidine and small substituted guanidines such as methylguanidine or aminoguanidine competed with [${}^3\text{H}$]TTX for the membrane binding site, the apparent K_I values for these derivatives were nearly seven orders of magnitude higher than the K_d for TTX. On the other hand, the binding of the guanidines was considerably enhanced by introducing a substituent aromatic ring or aliphatic chain. Detailed analysis of the binding of aliphatic guanidines of varying chain length clearly demonstrated the contribution made by hydrophobic interactions. These results suggest that the channel site may include a hydrophobic region in close proximity to the carboxylate previously postulated to be involved in TTX binding.     

Relationship between Nitrate Uptake, Flux, and Reduction and the Accumulation of Reduced Nitrogen in Maize (Zea mays L.): II. EFFECT OF NUTRIENT NITRATE CONCENTRATION

Two maize hybrids were grown under growth chamber conditions on solution or vermiculite medium that contained 2.5, 7.5, or 15 millimolar nitrate. The objectives were to determine: (a) the effect of nitrate supply on N metabolism and growth and (b) the interrelationship between nitrate uptake, flux, and reduction on the accumulation of reduced N and nitrate by the various plant parts and for the whole plant.     

Plasmids controlling exclusion of the K2 killer double-stranded RNA plasmid of yeast

Saccharomyces strains of two types (K₁⁺R₁⁺ and K₂⁺R₂⁺) kill each other and K^?R^?-sensitive strains by secreting protein toxins. K₁ killer strains carry a 1.25 × 10⁶ dalton double-stranded RNA plasmid, [KIL-k₁], while K₂ killers have a 1.0 × 10⁶ dalton double-stranded RNA plasmid, [KIL-k₁]. Mating [KIL-k₁] haploids with [KIL-k₂] haploids yields only [KIL-k₁] diploids, that is, [KIL-k₁] excludes [KIL-k₂]. [EXL], a new non-Mendellan genetic element from a nonkiller strain, excludes [KIL-k₂] but does not exclude [KIL-k₂]. A second new non-Mendelian genetic element, called [NEX], when present prevents [EXL] from excluding [KIL-k₂]. [NEX] does not prevent [KIL-k₁] or [KIL-s₁] (a suppressive mutant of [KIL-k₁]) from excluding [KIL-k₂]. A chromosomal gene, called MKT1, is needed for maintenance of [KIL-k₂] if [NEX] is present. In the absence of [NEX], [KIL-k₂] does not need MKT1. [KIL-k₁] does not need MKT1 even if [NEX] is present. [EXL] replication depends on at least the products of MAK1, MAK3, MAK10and PET18. [NEX]replication depends on MAK3 but is independent of MAK4, MAKE, MAK27 and MKT1.     

Involvement of the cystathionine pathway in the biosynthesis of glutathione by isolated rat hepatocytes

The ability of l-methionine to support glutathione biosynthesis has been investigated in isolated rat hepatocytes under conditions of normal and depleted glutathione status. The addition of l-[³⁵S]methionine or [l-[³⁵S]homocysteine to incubation media containing hepatocytes results in the incorporation of ³⁵S into intracellular glutathione. Additionally both l-methionine and l-homocysteine are capable of supporting the resynthesis of glutathione in isolated hepatocytes after prior depletion with diethyl maleate. The inclusion in the incubation medium of 1 mm propargylglycine, which is an irreversible inhibitor of the terminal enzyme of the cystathionine pathway, substantially blocks the incorporation of ³⁵S from methionine and l-homocysteine into cellular glutathione. Propargylglycine treatment of hepatocytes in the presence of [³⁵S]methionine is shown to result in the intracellular accumulation of [³⁵S]cystathionine. These results strongly support the conclusion that in rat hepatocytes the cystathionine pathway enables methionine to provide a significant source of l-cysteine for the support of glutathione biosynthesis, under both normal and glutathione-depleted conditions.     

Effects of vinblastine, oncodazole, procarbazine, chlorambucil, and bleomycin in vivo on colchicine binding activity of tubulin.

Five chemotherapeutic agents which inhibit mitosis caused an $\text{in vivo}$ effect on the colchicine bound to the isolated tubulin from mouse lymphoma L5178Y cells. These effects were examined over a time course of 4, 12, 24, 48, and 72 hours after a single administration of each drug. Vinblastine, oncodazole, and bleomycin decreased the amount of colchicine bound per mg protein; procarbazine and chloroambucil increased the amount bound. All of the drugs except procarbazine required more than 4 hours to cause an effect on colchicine binding and in the case of bleomycin and oncodazole some recovery occurred after 48 hours. The mitotic index was affected by 4 hours by all drugs: procarbazine, chlorambucil and bleomycin caused a decrease; vinblastine and oncodazole, an increase.     

Brachiopod tentacles: Ultrastructure and functional significance of the connective tissue and myoepithelial cells in Terebratalia

Summary The fine structure of the tentacles of the articulate brachiopod Terebratalia transversa has been studied by light and electron microscopy. The epidermis consists of a simple epithelium that is ciliated in frontal and paired latero-frontal or latero-abfrontal longitudinal tracts. Bundles of unsheathed nerve fibers extend longitudinally between the bases of the frontal epidermal cells and appear to end on the connective tissue cylinder; no myoneural junctions were found. The acellular connective tissue cylinder in each tentacle is composed of orthogonal arrays of collagen fibrils embedded in an amorphous matrix. Baffles of parallel crimped collagen fibrils traverse the connective tissue cylinder in regions where it buckles during flexion of the tentacle.The tentacular peritoneum consists of four cell types: 1) common peritoneal cells that line the lateral walls of the coelomic canal, 2) striated and 3) smooth myoepithelial cells that extend along the frontal and abfrontal sides of the coelomic canal, and 4) squamous smooth myoepithelial cells that comprise the tentacular blood channel.Experimental manipulations of a tentacle indicate that its movements are effected by the interaction of the tentacular contractile apparatus and the resilience of the supportive connective tissue cylinder. The frontal contractile bundle is composed of a central group of striated fibers and two lateral groups of smooth fibers which function to flex the tentacle and to hold it down, respectively. The small abfrontal group of smooth myoepithelial cells effects the re-extension of the tentacle, in conjunction with the passive resiliency of the connective tissue cylinder and the concomitant relaxation of the frontal contractile bundle.The authors wish to express their appreciation to Professor Robert L. Fernald for his advice and encouragement throughout the course of this study. Some of the work was conducted at the Friday Harbor Laboratories of the University of Washington. The authors are indebted to the Director, Professor A.O.D. Willows, for use of the facilities. Part of this study was supported by NIH Developmental Biology Training Grant No. 5-T01-HD00266 and NSF grant BMS 7507689     

Diaminopimelic Acid Synthesis in Cultures of an Escherichia coli Double Auxotroph: Effects of Cultural Conditions

The metabolic response to L-lysine of Escherichia coli ATCC 13002, a lysine-histidine double auxotroph, has been examined in a synthetic medium containing sucrose. In shaken cultures largest amounts of extracellular DAP were produced with an initial lysine concentration of 7·5 mg/1 and in static cultures of 2·5 mg/1. Considerably smaller amounts of DAP accumulated under stationary conditions. In cultures shaken for 20 and 43 h there was an overall decrease in the yields of DAP, expressed in terms of cell biomass and of sucrose consumed, as the initial concentration of lysine was increased from 0·75 mg/1 in steps up to 25 mg/1. The regulatory effect of lysine on DAP production was also observed when lysine was supplied to cultures at a constant rate employing diffusion capsules.