Antibodies to egg yolk in blood serum of rabbits and cattle and cervical mucus of cattle inseminated artificially.

Serum titers to egg yolk were induced in 6 rabbits by intravaginal deposition of an egg-yolk citrate extender used for artificial insemination of cattle. There was no effect of the low serum titers to egg yolk on fertility of the inseminated rabbits. Titers to egg-yolk semen extender were found in 3% of 59 cows of normal fertility compared to 29% of 14 repeat breeder cows of low fertility, all previously inseminated with semen diluted with egg yolk-citrate extender. Four of 6 cervical mucus samples (67%) from the repeat breeder cows had high titers to egg yolk, but only one also had a positive titer in blood serum.     

Changes during development in transport processes of the blood-brain barrier

The permeability of the blood-brain barrier to several classes of compounds was studied in rats between the ages of 15 days and 9 weeks. ¹⁴C-labelled test substances were injected simultaneously with two reference isotopes, ³H₂O and ^113mIn-labelled EDTA, into the common carotid artery followed by decapitation 10 s later.There was evidence that a monocarboxylic acid transport system in 15 to 23 day-old rats had a capacity at least six times greater than that present in adult animals. l-Lactate and acetate showed the highest permeability. At all ages there was a constant ratio between l-lactate and (−)d-3-hydroxybutyrate values. d-Glucose permeability increased with age, while that of several amino acids tested was the same in young and adults rats.     

Hyphal walls of isolated lichen fungi

The hyphal walls of three mycobionts, isolated from the lichens Xanthoria parietina, Tornabenia intricata and Sarcogyne sp. were investigated by two techniques: microautoradiography of fungal colonies exposed to radioactive carbohydrate precursors; and binding, in vivo, of fluorescein conjugated lectins to hyphal walls of such colonies.N-[³H] acetylglucosamine was readily incorporated into tips, young hyphal walls and septa of the three mycobionts and the free-living fungus Trichoderma viride, but not into Phytophthora citrophthora, indicating that chitin is a major component of the mycobionts' hyphal walls. All three mycobionts, but neither of the free-living fungi, incorporated [³H] mannose and [³H] mannitol into their hyphal walls.Fluorescein-conjugated wheat germ agglutinin was bound to the hyphal walls of the three mycobionts and T. viride, but not to the walls of P. citrophthora; the binding pattern was similar to the grain pattern obtained in autoradiographs after short N-[³H] acetylglucosamine labelling. As wheat germ agglutinin binds specifically to chitin oligomers, the lectin binding tests further confirmed that chitin is a mycobiont hyphal wall component.Binding characteristics of several fluorescein-conjugated lectins to the three mycobionts indicated that this technique can yield useful information concerning the chemical composition of hyphal wall surfaces.List of abbreviations FITC fluorescein isothiocyanate - WGA wheat germ agglutinin - TCA trichloroacetic acid - PNA peanut agglutinin - LA lotus agglutinin - Glc NAc N-acetylglucosamine - ConA concanavalin A - SBA soybean agglutinin - WBA waxbean agglutinin Part of an M.Sc. thesis submitted by A. Braun to the Department of Botany, Tel Aviv University.     

Dissociation of small-intestinal sucrase - isomaltase complex into enzymatically active subunits.

1. The sucrase - isomaltase complex from rabbit small intestine dissociated into its subunits upon reaction with citraconic anhydride. They can recombine after deacylation under mild acidic conditions. 2. When citraconylated, the subunits could be separated and isolated in a catalytically active form. 3. The previously reported procedure for separation of the subunits by alkaline treatment at pH 9.6 is apparently not due to contaminating degradative enzymes (possibly still present at undetectable levels in the isolated sucrase - isomaltase complex) but to the action of alkali.     

Attachment of lipoprotein to murein (peptidoglycan) of Escherichia coli in the presence and absence of penicillin FL 1060.

In vivo studies on the attachment of lipoprotein to the murein (peptidoglycan) of Escherichia coli showed that it takes several generations of growth until the amount of lipoprotein on newly made murein is equilibrated. The technique used involves degradation of the sodium dodecyl sulfate-insoluble murein-lipoprotein complex (sacculus, rigid layer) with lysozyme and separation of the labeled products on paper. No lipoprotein was found on murein subunits incorporated during a pulse of [3H]diaminopimelate for 1 min in logarithmically growing cells at 37 C. Even after one doubling of the cell mass, only 4 to 8% of the labeled murein was isolated as bound to lipoprotein. With uniformly labeled murein, 30% remains bound to lipoprotein after lysozyme treatment, corresponding to three murein subunits. Therefore it can be concluded that during pulse labeling either no lipoprotein is incorporated into the newly synthesized murein or no murein subunits are inserted into existing murein around lipoprotein attachment sites. Longer pulse and pulse-chase experiments argue for the latter interpretation. It is therefore concluded that incorporation of murein subunits into the growing murein polymer is not at all a random process. Instead, quite large areas of murein, on which lipoprotein is situated, seem to be preserved. Under the influence of penicillin FL 1060 murein synthesis is 50% inhibited. The rate of lipoprotein attachment is less affected so that increasing amounts of lipoprotein become attached during spheroplast formation. By the time the stationary growth phase has been reached, the lipoprotein content of the murein has doubled. Diaminopimelate auxotrophic mutants require, in the presence of penicillin FL 1060, more diaminopimelate for full growth than in the absence of penicillin FL 1060. This finding and the fact that murein synthesis is always inhibited by 50% over a wide range of penicillin concentration (1 to 1,000 mug/ml) point to the inhibition of an enzymatic step of murein synthesis which can be partially bypassed by a second enzyme, less efficient but resistant to penicillin FL 1060.     

The effect of divalent cations on bovine spermatozoal adenylate cyclase activity.

The effect of divalent cations on bovine sperm adenylate cyclase activity was studied. Mn2+, Co2+, Cd2+, Zn2+, Mg2+ and Ca2+ were found to satisfy the divalent cation requirement for catalysis of the bovine sperm adenylate cyclase. These divalent cations in excess of the amount necessary for the formation of the metal-ATP substrate complex were found to stimulate the enzyme activity to various degrees. The magnitude of stimulation at saturating concentrations of the divalent cations was strikingly greater with M2+ than with either Ca2+, Mg2+, Zn2+, Cd2+ or Co2+. The apparent Km was lowest for Zm2+ (0.1 - 0.2 mM) than for any of the other divalent cations tested (1.2 - 2.3 mM). The enzyme stimulation by Mn2+ was decreased by the simultaneous addition of Co2+, Cd2+, Ni2+ and particularly Zn2+ and Cu2+. The antagonism between Mn2+ and Cu2+ or Zn2+ appeared to have both competitive and non-competitive features. The inhibitory effect of Cu2+ on Mn2+-stimulated adenylate cyclase activity was prevented by 2,3-dimercaptopropanol, but not by dithiothreitol, L-ergothioneine, EDTA, EGTA or D-penicillamine. Ca2+ at concentrations of 1-5 mM was found to act synergistically with Mg2+, Zn2+, Co2+ and Mn2+ in stimulating sperm adenylate cyclase activity. The Ca2+ augmentation of the stimulatory effect of Zn2+, Co2+, Mg2+ and Mn2+ appeared to be specific.