Some red cell antigens in the Hausa population of northern Nigeria

The A, B, O, D, Du, C, c, E, e, M, N, S, s, Kell and Duffy antigens were determined on 190 blood samples from Hausas in the north of Nigeria. The highest gene frequencies in the rhesus system were cDe (0.648) and cde (0.176). Su gene frequency was 0.270. The great majority of subjects were Kell negative (98.9%) and Duffy negative (98.8%). As the MNSs group determinants are carried by glycophorins, which are also receptor sites for Plasmodium falciparum, and the Duffy antigen marks the receptor for P. vivax, the present study provides data of interest in the epidemiology and genetics of malaria.     

Maturation of pig and rat oocytes transplanted into surrogate pig follicles in vitro

Pig oocytes obtained from slaughterhouse material and rat oocytes obtained from PMSG-treated immature females were incubated as isolated oocytes or injected into explanted pig follicles (5–8 mm). Free oocytes of both species, with or without their cumulus investment or gonadotropins during culture, matured at high rates after 30 hr or 9–10 hr of culture, respectively. Gonadotropic stimulation was necessary for maturation of both the native and injected cumulus-intact pig oocytes in follicle culture. Cumulus-free pig oocytes injected into follicle failed to mature in response to gonadotropic stimulation, suggesting an inability to perceive or respond to stimulation. Injected rat oocytes, however, matured irrespective of cumulus investment or gonadotropic stimulation. Their maturation was delayed and reduced at 9 hr. These results in the rat suggest that the pig follicular environment is incapable of regulating rat oocyte maturation but rather presents a permissive or supportive environment for their maturation. The explanted surrogate follicles from the pig or other species may provide a useful model for the study of oocyte-follicle interactions in oocyte maturation within or between species.     

Cytochrome b561 catalyzes transmembrane electron transfer

Purified cytochrome b561 from bovine adrenal medulla chromaffin vesicles has been reconstituted into phosphatidylcholine vesicles by a detergent-dialysis method. When the reconstituted cytochrome-containing vesicles were preloaded with ascorbic acid and cytochrome c was added to the external medium, the internal ascorbic acid was able to reduce the external cytochrome c. This reduction of cytochrome c was dependent on the presence of cytochrome b561 in the membrane and was not due to leakage of ascorbate from the vesicles. These results demonstrate that cytochrome b561 catalyzes a transmembrane electron transfer.     

Some characteristics of monolayers of 1-palmitoyl-2-oleoyl-phosphatidylglycerol with and without dipalmitoylphosphatidylcholine during dynamic compression and expansion

Some properties of monolayers of $\text{1-}\text{palmitoyl}\text{-2-}\text{oleoyl}\text{-sn-}\text{glycero}\text{-3-}\text{phospho}\text{-rac-}\text{glycerol}$ (POPG) alone or of POPG in mixtures with $\text{1,2-}\text{dipalmitoyl}\text{-sn-}\text{glycero}\text{-3-}\text{phosphocholine}$ (DPPC) have been measured near 35°C during dynamic compression and expansion at 3.6 cm²·s^?1. (2) The mean values of minimum surface tension (corresponding to maximum surface pressure) which could be obtained with pure POPG monolayers at high compression ranged from 15 to 18 mN·m^?1 in the presence of Na⁺, Ca²⁺ or low pH (2.0) in the subphase. (3) The presence of Ca²⁺ or low pH in the subphase increased the collapse plateau ratios obtained on cyclic compression. This might represent enhanced respreading into the monolayer of pure POPG from a collapsed form during reexpansion of the surface. (4) Monolayers containing 10% or 30% POPG and 90% or 70% DPPC could be compressed to surface tensions approaching zero. (5) In such mixed monolayers, 10% or 30% POPG did not appear to enhance respreading, as measured by collapse plateau ratios, in the presence of Na⁺ or Ca²⁺ in the subphase.     

Occurrence of an inhibitor of lactic Acid bacteria in green olives

Green olives were found to contain an inhibitor(s) of several species of lactic acid bacteria usually associated with the Spanish-type brined olive fermentation. The inhibitor was demonstrated by the presence of inhibition zones surrounding tissue which had been cut from frozen olives and implanted in a seeded nutritive agar medium. Relative potencies of aqueous extracts of frozen olives were determined by a paper disc assay method. The Mission variety of olive contained the most inhibitor, and the Manzanillo and Ascolano, about 50 and 40% as much as the Mission variety, respectively. Sevillano and Barouni varieties contained comparatively little inhibitor. Effects of the inhibitor on growth rates of lactic acid bacteria were determined by adding various amounts of a concentrated aqueous extract of olives to a nutritive broth medium contained in screw-capped tubes. Of the four species of lactic acid bacteria tested, Leuconostoc mesenteroides was the most sensitive, and Lactobacillus plantarum was the least sensitive; Pediococcus cerevisiae and Lactobacillus brevis were intermediate in sensitivity. Extracts possessed a bactericidal property, as evidenced by their effect on L. mesenteroides. Sodium chloride, especially at concentrations of about 5% and higher, greatly increased the effectiveness of the inhibitor. The inhibitor was ethyl alcohol-soluble and was stable when heated at 100 C in aqueous solution. Potencies of extracts were reduced greatly by adjustment to pH 10, but no appreciable effect was noted by adjustment to pH 0.8.     

Electro-optical studies of conformation and interaction of polynucleotides

Measurements by the technique of electric birefringence with pulsed sinusoidal electric fields on polyriboadenylic acid (poly-A) and polyribouridylic acid (poly-U) indicate that the kinetics of the double-stranded helix formation of poly (A + U) in the presence of Mg²⁺ is second order and consists of two steps: nucleation and propagation of base pairs from nuclei. The nucleation involves approximately 7 base pairs. It seems that the requirement of 7 base pairs to start the formation of a double-stranded helix is not peculiar to poly (A + U) but is associated with double-stranded helices of polynucleotides in general. This implies that it may be associated with spatial requirements of the phosphate-sugar backbone, rather than with the particular bases linked to the backbone. The decline in rate of poly (A + U) formation observed above a critical temperature is the consequence of changes in the poly-A conformation setting in at this critical temperature, rather than resulting from an increase in the reversibility of the base-pair propagation step of double-stranded helix formation. The dominant role of the conformation of poly-A in the double-stranded helix formation of poly (A + U) is further borne out by the pH dependence of the rate which completely parallels the conformation changes known to occur in poly-A as a function of pH. This indirectly suggests that at neutral pH poly-A is a single-stranded helix. The rotary diffusion coefficients attest to the flexibility of this helix, while the stacked nature of the base pairs at low temperatures is revealed by the identical increments in the specific Kerr constant on going from poly-A to poly (A + U) and from poly (A + U) to poly (A + 2U) helices. Results suggest that Mg²⁺ binds to the phosphate part of the backbone. Poly-U binds Mg²⁺ more strongly than poly-A; this difference in binding strength is attributed to differences in conformation (random coil versus helix). It is also borne out by the present results that the degree of order in the structure of poly-U, even at low temperatures and neutral pH, is at best an order of magnitude smaller than that of poly-A under similar conditions. Furthermore, the earlier proposed double-stranded structure of poly-U is called into question. A hairpinlike structure seems to agree with results of this investigation. Finally, the results support the contention that the ion atmosphere polarization is responsible for orientation of polyelectrolytes in the presence of alternating electric fields in the neighborhood of 25 kc./sec. frequency.     

Down-regulation of IL-2 production by activation of T cells through Ly-6A/E

Ly-6A/E molecules are expressed on the surface of T cells and have been shown to function in activation by the capacity of anti-Ly-6A/E mAb to induce T cell hybridomas or normal T cells to produce IL-2. Recent evidence suggests that activation through Ly-6A/E may be linked to the TCR signaling pathway. To further investigate the relationship between Ly-6- and TCR-induced T cell activation, we have examined whether an anti-Ly-6A/E mAb (D7) modulates TCR signaling in vitro. We now report that mAb D7 specifically inhibited IL-2 production by T cells also activated through TCR. Such inhibition was noted for normal T cells stimulated by soluble anti-CD3 or alloantigen and for T hybridomas stimulated by soluble anti-CD3. The ability of D7 to inhibit IL-2 production by T hybridomas was dependent on the nature of the TCR activating signal because IL-2 production was not inhibited when T hybridomas were stimulated with Ag or immobilized anti-CD3. Inhibition of IL-2 production by D7 apparently required cross-linking of the mAb because D7 F(ab')2 fragments were not effective for inhibition of IL-2 production. Similar to its ability to enhance anti-Ly-6A/E-induced activation of T and B cells, IFN-gamma enhanced the D7-induced inhibition of IL-2 production by alloantigen-activated normal T cells. These data further support the notion that Ly-6 and TCR signaling pathways are interrelated.     

G regulatory proteins and muscarinic receptor signal transduction in mucous acini of rat submandibular gland

The involvement of G regulatory proteins in muscarinic receptor signal transduction was examined in electrically permeabilized rat submandibular acinar cells. The guanine nucleotide analog, GTP gamma S, caused the dose dependent hydrolysis of membrane phosphatidylinositol 4,5-bisphosphate to release IP3. This response was insensitive to pertussis toxin treatment and was duplicated by NaF but not by GDP beta S. Enhanced IP3 synthesis was observed with a combination of GTP gamma S and carbachol. Exogenous IP3, as well as carbachol and GTP gamma S, provoked the release of sequestered 45Ca2+ from non-mitochondrial stores. In intact cells, carbachol significantly reduced the level of cyclic AMP induced by the beta-adrenergic agonist, isoproterenol, to 69% of its normal value. Pertussis toxin abolished this inhibitory action of carbachol on cyclic nucleotide levels. These results suggest that muscarinic receptors are coupled to two separate G regulatory proteins in submandibular mucous acini-the pertussis toxin-insensitive Gp of the phosphoinositide transduction pathway associated with elevated cytosolic calcium levels, and the pertussis toxin-sensitive Gi inhibitory protein of the adenylate cyclase complex.