Sperm penetration in vitro: correlations between parameters of sperm quality and the penetration capactiy

A nonlinear regression analysis was used in order to fit a logistic model to 200 runs of human ejaculated spermatozoa penetrating cervical mucus of good quality. The data revealed excellent correlation between the number of sperm penetrating (sigma penetration, SP) and the motility (r = 0.776) and vitality (r = 0.534) of the spermatozoa. The percentage of abnormal spermatozoa found in the ejaculate was negatively correlated (r = -0.649), while sperm concentration showed a poor correlation with SP (r = 0.327). Furthermore, concentration was shown to have no effect in samples containing over 5 million sperm/ml. The conclusion of this study is that the two major parameters of sperm quality determining the capacity of spermatozoa to penetrate cervical mucus are motility and the presence of normal forms of spermatozoa.

Distribution of [14C]-labelled aflatoxin B1 in mice

The distribution of [14C]-labelled aflatoxin B1 has been studied in mice with the aid of whole-body autoradiography. In addition to the localisation of labelled aflatoxin B1 and/or its metabolities in the liver, bile, kidney, lung and urine an uptake of 14C in the pigment of the Harderian gland and the eye was observed. Uptake of radioactivity was also found in the eyes of the foetuses although their livers did not accumulate radioactivity.

Incorporation of N-acetylglucosamine from UDP-N-acetylglucosamine into proteins and lipid intermediates in microsomal and Golgi membranes from rat liver

Rough and smooth microsomes and Golgi membranes incorporate N-acetylglucosamine from UDP-N-acetylglucosamine into endogenous protein acceptors. A lipid intermediate of the dolichol phosphate type participates in this transfer reaction in the case of both microsomal subfractions, but the nature of lipid glycosylation is different in these two fractions. Glucosamine transfer in Golgi membranes does not appear to involve a lipid intermediate. In contrast to the results obtained under in vivo conditions, no glucosamine label is recovered in nascent ribosomal proteins or on luminal secretory proteins after incubation in vitro. Proteolysis of intact vesicles of the subfractions removes glycosylated dolichol phosphate and protein acceptors to various extents and interferes with transferase activities. This finding suggests the possiblity that glycosylation at the cytoplasmic side of the membrane of the endoplasmic reticulum may involve a system separate from that acting at the luminal side of the same membrane.

Incorporation of galactose from UDP-galactose into microsomal and Golgi membranes of rat liver

Rough and smooth microsomes and Golgi membranes were incubated with UDP[14C]galactose and the incorporation of radioactivity into the lipid extract and into endogenous protein acceptors were measured. Antagonistic pyrophosphatases were inhibited with ATP and interference from beta-galactosidase activity was greatly decreased by carrying out the incubation at pH 7.8. After incubation the particles were centrifuged to remove free oligosaccharide residues. Radioactivity was found in the lipid extract from Golgi membranes but not from rough and smooth microsomes. This radioactivity, however, was not associated with dolichol or retinyl phosphates. The incorporation of radioactivity into proteins of the Golgi fraction was more than double than that of the microsomal fractions. In addition, the transferases in these two types of particles exhibited different properties. Trypsin treatment of intact rough microsomal vesicles, smooth vesicles and Golgi membranes removed about 5, 15 and 50%, respectively, of newly incorporated protein-bound galactose, indicating that the proportion of the newly galactosylated proteins, which are localized at the cytoplasmic surface of the membrane, is lowest in rough microsomes, intermediate in smooth, and highest in Golgi membranes.

Mannosylation of endogenous proteins of rough and smooth endoplasmic reticulum and of Golgi membranes

Mannosylation of the proteins of microsomal and Golgi membranes was investigated both after incubation in vitro of the isolated subfractions with GDP-[14C]mannose and after injection of [3H]mannose into rats followed by separation of these subfractions. Mannosylation of endogenous and added exogenous dolichol phosphate and also of dolichol pyrophosphate-oligosaccharide occurs in all three fractions. It was essential to inhibit antagonistic enzymes during incubation and to centrifuge after incubation. The presence of detergent in the incubation mixture influences the incorporation pattern of the different fractions in very different ways. In a system in vitro predominantly membrane proteins and not secretory proteins are mannosylated. Trypsin treatment of intact vesicles removes components from the outer surface only; such treatment liberates about one third of the radioactive mannose associated with lipid, releases radioactivity from the protein acceptor to the same extent and causes some inactivation of the transferase activities. It appears that a part of the mannosyl transferase system in rough and smooth endoplasmic reticulum and in Golgi membranes is localized at the cytoplasmic side of these membranes. This activity is probably involved in the glycosylation of proteins localized at the cytoplasmic surface of the endoplasmic reticulum.

Glycosyl transfer from nucleotide sugars to C85- and C55-polyprenyl and retinyl phosphates by microsomal subfractions and Golgi membranes of rat liver

The capacity of isolated membrane fractions to catalyse transfer of sugars from sugar nucleotides to alpha-saturated and non-saturated forms of phosphorylated C85 and C55 polyprenols and retinyl phosphate was examined. The amount of endogenous lipid acceptor present for various sugars was also measured. It appears that the types and amounts of polyprenyl phosphates present in rough- and smooth-microsomal fractions and Golgi membranes are different and the individual polyprenyl phosphates exhibit specificity as sugar acceptors.

Distribution of protein-bound sugar residues in microsomal subfractions and Golgi membranes

Liver microsomal subfractions and Golgi membranes free from adsorbed and secretory proteins have a characteristic sugar composition. The ratio of mannose to galactose is largest in rough microsomes, smaller in smooth I microsomes, still smaller in smooth II microsomes, and smallest in Golgi membranes. There is about twice as much glucosamine in Golgi membranes and 3 times as much in smooth II microsomes as in the other microsomal subfractions. Golgi membranes are rich in sialic acid in comparison to rough microsomes and it is present at even higher levels in the two smooth microsomal subfractions. Increasing concentrations of deoxycholate preferentially remove protein-bound mannose and glucosamine, while releasing significantly less galactose. About half of the microsomal mannose and galactose can be liberated from the surface of intact microsomal vesicles by treatment with trypsin. When trypsin is added to permeable vesicles where the inside surface can be also attacked, an additional 20% of the total mannose but no additional galactose is liberated.

Distribution of polychlorinated biphenyls: structural requirements for accumulation in the mouse bronchial mucosa

Autoradiography showed that labelled polychlorinated biphenyls with chlorine in positions 2, 41, 5 and hydrogen in positions 3, 31, 6, 61 in the molecule are accumulated in the mouse bronchial mucosa. Further testing of this observation showed that 2, 21, 4, 51-tetrachlorbiphenyl-14C, but not biphenyl-14C, was taken up in the bronchi of mice.