H-2 histocompatibility antigens of subcellular membranes of mouse liver

Purified fractions of plasma membrane, Golgi apparatus, rough endoplasmic reticulum vesicles, nuclear envelope, and mitochondria were isolated from mouse liver and the distribution of H-2 histocompatibility antigens determined by indirect radioimmunoassay before and after membrane disruptive treatments. Fractions enriched in plasma membrane (surface membrane) revealed H-2 antigens in highest concentration; disruptive treatments were not necessary to reveal H-2 antigens with surface membranes. In contrast, internal membranes did not possess H-2 antigens which were accessible to antibody. Golgi apparatus fractions or some component of these fractions (e.g. secretory vesicles) possessed the antigens but in a latent form where accessibility was provided by simple rupture of the membrane vesicles. With endoplasmic reticulum, detergent solubilization of the membranes was required before H-2 antigen could be detected. Nuclear envelope preparations contained little or no demonstrable H-2 activity. These results were confirmed by several techniques including immunoprecipitation of labelled solubilized membrane components with anti-H-2 serum and subsequent analysis in SDS-PAGE.     

Reproductive and hormonal patterns in the African green monkey (Cercopithecus aethiops).

The results of breeding Cercopithecus aethiops under time-mated laboratory conditions and analysis of total estrogen, progesterone, and LH concentrations in plasma during the menstrual cycle and plasma estrogen and progesterone concentrations during pregnancy indicate that this species is a suitable alternative for the rhesus monkey as a model for investigations of reproductive function in man.     

Effect of thyroidectomy on rhythmic gonadotropin release.

Nonstress blood samples were obtained from intact and thyroidectomized (TE) male rats at 3-hr intervals over a 24-hr period via rapid decapitation. The animals were thyroidectomized when 40 days old and used 6 weeks later. Intact animals showed periodicity in serum LH (P less than 0.01) and prolactin (P less than 0.01). Both gonadotropins began increasing after 8 PM and peak levels occurred at 11 PM. In contrast, 24-hr periodicity was not observed in serum FSH. Corticosterone levels in these same serum samples showed the expected circadian periodicity. After TE, the 24-hr pattern in all gonadotropins was altered significantly. Serum LH increased (P less than 0.01) and circadian periodicity appeared to be absent. FSH and prolactin levels were increased and decreased, respectively (P less than 0.01), with serum prolactin showing a 9-hr phase shift. Prolactin began increasing at 2 AM and reached a peak at 8 AM. Corticosterone in TE animals showed a 24-hr rhythm similar to that of intact rats. These findings confirm our previous observations that nonstress serum LH and prolactin levels fluctuate with a 24-hr periodicity and suggest that the level of, and the phase angle betweeen, these rhythms is markedly influenced by pituitary-thyroid activity.     

Development of a nuclear polyhedrosis virus in midgut cells and penetration of the virus into the hemocoel of the armyworm,Pseudaletia unipuncta

The development of a nuclear polyhedrosis virus (NPV) in larval midgut cells of the armyworm, Pseudaletia unipuncta, is similar to that of other NPV. In the nucleus, the envelopes around the nucleocapsids seem to be derived de novo or from the inner layer of the nuclear envelope wich forms cisternae, blebs, or infoldings. The nucleocapsids are also enveloped by synhymenosis during passage through the nuclear membrane, the cell membrane, or the endoplasmic reticulum membrane. Both enveloped and unenveloped nucleocapsids may enter the cytoplasm through the nuclear pore or budding through the nuclear membrane. From the cytoplasm the virions may enter the hemocoel through the basal cell and basement membranes or through the endoplasmic reticulum, intercellular space, and the basement membrane.     

Purification and properties of phosphofructokinase (EC 2.7.1.11) of Saccharomyces carlsbergensis.

A procedure for the purification of phosphofructokinase from brewer's yeast (Saccharomyces carlsbergensis) is reported. Treatments with organic solvents and heat were avoided and chromatographic and filtration techniques in the presence of phenylmethane sulfonyl fluoride were mainly used. The purified enzyme is homogeneous in disc gel electrophoresis and according to sedimentation velocity and equilibrium measurements in the ultracentrifuge. The isoelectric point determined by focusing was 5.3. Absorption spectra, fluorescence spectra and circular dichroism spectrum are given. The molecular weight of the purified enzyme determined by gel filtration was 720 000, in agreement with that of the enzyme in the raw extract. This confirms the results of sedimentation velocity experiments which gave a value of SO20, W equals 19.4. Alkaline treatment leads to a dissociation of the native enzyme, yielding an inactive species with a molecular weight of 360 000. In 6M guanidine hydrochloride the enzyme dissociates into subunits with a mean molecular weight of 90 000 as obtained by ultracentrifugation analysis. This suggests a structure composed of 8 monomers. The specific activity of the enzyme was 116 U/mg under optimum conditions. The enzyme activity was proportional to the enzyme concentration in the range of 6 times 10- minus 12 M to 3 times 10- minus 7 M. The Michaelis constants and Hill coefficients for fructose 6-phosphate and AMP, the pH optima, and the stability properties of the enzyme are reported. Furthermore, the activation energy is given and it is shown that under saturating conditions, a straight Arrhenius plot obtains, whereas the plot is discontinuous at high ATP concentrations and at pH 7.6.     

Subunit structure of 6-phosphofructokinase from brewers' yeast.

An analysis of 6-phosphofructokinase from brewers' yeast in the presence of sodium dodecylsulfate reveals the occurrence of four components with the following molecular weights: alpha = 140000, beta = 130000, and alpha' = 92000, beta' = 87000. It was found that the alpha- and beta-components can be converted to the alpha' and beta' components by treatment of the native preparation with hyaluronidase. A comparison of the molecular weight obtained by ultracentrifugation and gel filtration with the results obtained by dodecylsulfate electrophoresis after treatment with hyaluronidase reveals that the alpha' and beta' components are the smallest molecular structures obtained upon dissociation of the native enzyme. The mechanism of action of hyaluronidase suggests a desensitization of the alpha and beta components of the enzyme towards dodecylsulfate. Thus, in the absence of hyaluronidase treatment; only an apparent molecular weight for the alpha and beta component is obtained. The analysis indicates that the native enzyme might be composed of four different subunits with an alpha, beta, alpha' and beta' configuration. It is not excluded that the native enzyme consists only of alpha- and beta-chains.     

Allosteric interactions of the membrane-bound acetylcholine reception: kinetic studies with alpha-bungarotoxin.

The specific and irreversible reaction of a snake neurotoxin, α-bungarotoxin, with the acetylcholine receptor of electroplax membrane preparations from $\text{Electrophorus electricus}$ proceeds by an initial fast phase followed by a slower one. The fraction of the reaction in the fast phase increases with increasing initial toxin concentrations, while the fraction going slowly decreases correspondingly. Both phases are affected by compounds which initiate or inhibit nerve impulse transmissions. The time course of the reaction can be fitted to the sum of two exponentials. The dependence on initial toxin concentration of the two exponentials, and of the fraction of reaction governed by the exponentials, can be fitted to a minimum reaction mechanism which involves at least two types of toxin binding sites with different dissociation constants and ligand-induced conversion of one type of site into the other. The mechanism is consistent with our previous data which showed that activators and inhibitors of membrane electrical potential changes occupy separate sites, only half of which interact. This type of mechanism has been seen in a number of allosteric regulatory enzymes.     

Ultrastructure of the Bacterial Symbiotes in the Pharyngeal Diverticulum of Dacus oleae (Gmelin) (Trypetidae; Diptera)

Abstract The ultrastructure of the bacterial symbiotes in the pharyngeal diverticula of adult olive flies [Dacus oleae (Gmelin)] was examined. The diverticulum was an extension of the foregut formed by a row of epithelial cells bounded by an inner layer of cuticle. Towards the hemolymph, the epithelial cells showed an infolding of their basement membrane while adjacent to the cuticular lining, the cells contained a zone of extensive membrane proliferation. The diverticula were packed with bacterial rods which possessed elongate filamentous and short catenulate appendages. The function of these appendages is unknown. They did not resemble fimbriae (pili), flagella or prosthecae described from other bacteria.