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N L Cross

Publications and source records attributed to N L Cross.

44 records · Page 3Linked to original sources
PubMed1978

Normal penetration of rabbit spermatozoa through a trypsin- and acrosin-resistant zona pellucida.

Exposure of rabbit ova to wheat germ agglutinin (WGA) at a concentration of 50 microgram/ml for 30-45 min rendered the zona pellucida at least 10 times more resistant to digestion by 1 mg trypsin/ml, and also more resistant to acrosin. Nevertheless, the zonas of WGA-treated eggs were penetrated by spermatozoa as readily as those of untreated eggs in the same oviduct. These results suggest that penetration of spermatozoa through the zona pellucida may not require the agency of a trypsin-like enzyme acting as a primary zona lysin. The validity of the general belief that a lysin in necessary for zona penetration is considered briefly in relation to the mode of penetration and structural organization of the mammalian sperm head.

Acrosin↗
PubMed1973

Appearance and distribution of ferritin in mouse peritoneal macrophages in vitro after uptake of heterologous erythrocytes.

Mouse peritoneal macrophages have been studied in vitro after ingestion of treated rat, rabbit, or sheep erythrocytes. Under light microscopy, phagocytic vacuoles persist up to 24 h. Macrophages lose benzidine reactivity about 5 h after red cell ingestion, and they become prussian blue positive at 2 days. Ultrastructural studies show little or no ferritin in control macrophages not fed erythrocytes. In contrast, after red cell ingestion, ferritin is widely distributed in the cytoplasmic matrix and in some cytoplasmic granules by 48 h. The Golgi complex, pinocytic vacuoles, endoplasmic reticulum, nuclei, and mitochondria do not contain ferritin. Between 2 and 4 days, ferritin in cytoplasmic granules increases, concomitant with decrease in the ferritin in the cytoplasmic matrix. Evidence is presented suggesting that ferritin in the cytoplasmic matrix is translocated into cytoplasmic granules by autophagy. Polyacrylamide gel studies on macrophages after uptake of red blood cells labeled with radioiron confirm that macrophages produce radiolabeled ferritin by 4 days.

Animals↗
PubMedDate not supplied

Prostasome fraction of human seminal plasma prevents sperm from becoming acrosomally responsive to the agonist progesterone.

Seminal plasma prevents human sperm from becoming acrosomally responsive. These experiments tested the idea that the inhibitory activity of seminal plasma is contained in the particulate prostasome fraction. Most of the inhibitory activity was sedimentable (105,000 g, 2 h) and the majority of the recovered activity was in the prostasome fraction. The recovery of inhibitory activity in the prostasome fraction (42% of the activity in unfractionated seminal plasma) was similar to the recovery of cholesterol in that fraction (41%), consistent with cholesterol's role as the major inhibitor in seminal plasma. To test whether components of the prostasome fraction bind to sperm, the prostasome fraction was made fluorescent with fluorescein isothiocyanate or with the acetoxymethyl ester of 2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein. No labeled material was seen to bind to sperm, suggesting that exchange of cholesterol between prostasomes and sperm takes place through the aqueous phase or at the time of vesicle-sperm collision.

Acrosome↗
PubMedDate not supplied

A modified and improved assay for sperm amidase activity.

An assay for sperm amidase activity has been modified so that many samples can be measured rapidly, making it more suitable for use in a clinical setting. The modified assay gave the same results (P greater than 0.05) as its lengthier parent assay (Kennedy et al, 1989). The measured enzyme activity was proportional to the number of sperm assayed over the range tested (3.5 x 10(5) to 2.1 x 10(6) sperm). The within-assay coefficient of variation was 7.8 +/- 1.8% (average +/- SE, n = 12), and the between-assay coefficient of variation was 7.2 +/- 1.2% (n = 3). The sensitivity was 7.6 microIU/well.

Acrosin↗
PubMedDate not supplied

Phosphatidylcholine enhances the acrosomal responsiveness of human sperm.

Supplementing bovine serum albumin-containing medium with phosphatidylcholine (PC) accelerated the in vitro development of human sperm acrosomal responsiveness. Responsiveness was assessed by exposing the sperm to progesterone. The maximum effect was produced by incubation with 100 micrograms PC/ml, which resulted in 40% (23-56%) (mean, 95% confidence limits) of the sperm becoming responsive to progesterone at 24 hours, compared to 23% (10-40%) of control sperm. Enhancement was apparent after as little as 6 hours of incubation in vitro, and the number of responsive sperm was still increasing at the last time point tested (30 hours). PC had no apparent ill effects; it did not alter the percentage of motile sperm or the percentage of sperm stained with the supravital stain, Hoechst 33258. Enhanced responsiveness required prolonged incubation in PC, because PC was not effective when it was only applied at the same time as progesterone. Lysophosphatidylcholine did not enhance acrosomal responsiveness when used at concentrations from 10 ng/ml to 100 micrograms/ml, indicating that the effect of PC was not due to trace amounts of lysophosphatidylcholine. PC also increased the response of sperm to the Ca2+/H(+)-exchanging ionophore, ionomycin, suggesting that PC modifies an event that is coincident with or subsequent to the rise in intracellular free Ca2+ that is triggered by progesterone.

Acrosome↗