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N L Cross

Publications and source records attributed to N L Cross.

At least 37 records · Page 2Linked to original sources
PubMed1988

Induction of acrosome reactions by the human zona pellucida.

We have used two approaches to test the ability of the human zona pellucida to induce acrosome reactions in human sperm. First, nonviable human oocytes were incubated for 1 min in a suspension of capacitated sperm (of which fewer than 5% were acrosome-reacted) to allow binding of about 200 sperm per oocyte. Some of the oocytes were fixed immediately, and the remainder were fixed after a further 1-h incubation without free-swimming sperm. As determined by light microscopy, sperm on the zona were only 3 +/- 2% (avg. +/- SD) acrosome-reacted at 1 min, and the incidence increased to 46 +/- 15% during the next hour. Electron microscopy confirmed that most sperm on the zona at 1 min were acrosome-intact. A few sperm were in an early stage of the acrosome reaction. Acrosome reactions occurring on the zona during the subsequent hour appeared to be morphologically normal. Second, treatment of sperm in suspension with acid-disaggregated zonae (2 to 4 zonae/microliter) increased the incidence of acrosome-reacted sperm from 3 +/- 1% to 24 +/- 4%. We conclude that the human zona pellucida, or material intimately associated with it, can induce acrosome reactions in human sperm.

Acrosome↗
PubMed1987

Glycoconjugates of the human sperm surface: distribution and alterations that accompany capacitation in vitro.

We have studied changes in the binding of fluoresceinated lectins to human sperm during in vitro capacitation. We first determined the surface labeling pattern of viable sperm obtained by the swim-up procedure. Sperm were labeled with 100 micrograms/ml FITC-conjugated lectin at 4 degrees C for 30 min. We simultaneously used Hoechst stain 33258 as a supravital stain to help differentiate surface from intracellular lectin labeling. Of 14 lectins studied, six (phytohemagglutinin-E, concanavalin A, Ricinus communis agglutinin-I, and the lectins of wheat germ, Lens culinaris, and Pisum sativum) bound to the entire surface of sperm, sometimes with minor local heterogeneity. Three lectins (from peanut, Maclura pomifera, and soybean) usually bound in a punctate manner, with more label on the tail than on the head. Five lectins (Ulex europaeus, Dolichos biflorus, Helix pomatia, and Vicia villosa lectins, and lectin II of Griffonia simplicifolia) bound very poorly or not at all to the sperm surface. Sperm were also inspected for changes in surface lectin binding patterns after 0, 5, and 23 hr of incubation in a capacitating medium. Two lectins showed reproducible changes. The labeling by Maclura pomifera agglutinin decreased by 5 hr in eight of ten experiments, and among sperm labeled with concanavalin A, the incidence of sperm with a highly fluorescent anterior margin of the sperm head increased by about 3.5-fold between 0 and 5 hr. The labeling pattern of the other lectins did not change.

Fluorescein-5-isothiocyanate↗
PubMed1987

Detection of antisperm antibodies: their localization to human sperm antigens that are transferred to the surface of zona-free hamster oocytes during the sperm penetration assay.

The authors have developed an extension of the sperm penetration assay for detecting serum immunoglobulins to sperm antigens that are transferred to the plasma membrane of a sperm-penetrated hamster oocyte. After the hamster oocytes have been scored for sperm penetration by observing for the presence of swollen sperm heads, they are incubated in serum followed by either a 20-minute treatment with rhodamine-conjugated protein A (which binds to most subclasses of IgA, IgG, and IgM) or a 2-hour incubation in guinea pig serum (complement). Positive fluorescence indicates that the serum contains antibodies to sperm antigens that were transferred to the surface of an oocyte during gamete fusion. Complement-mediated lysis indicates that the immunoglobulin that is bound can also fix complement. The advantages of this assay for detection of serum antisperm antibodies are that it is an extension of a widely used assay, is rapid and requires readily available reagents and equipment, can detect most subclasses of IgA, IgG, and IgM, detects antibodies to those sperm antigens that may be transferred to the oocyte during fertilization, and indicates whether the detected antisperm antibodies can mediate complement-dependent lysis of the fertilized oocyte.

Animals↗
PubMed1987

Normality of single fibre electromyographic jitter: a new approach.

The distribution of jitter values derived from single fibre electromyography (SFEMG) in normal extensor digitorum communis has been found to be skewed. A reciprocal transformation technique is presented which renders the distribution normal. The distribution enables SFEMG changes to be assessed using parametric statistics. The relationship of the new technique to existing methods of analysis of SFEMG is discussed.

Electromyography↗
PubMed1987

Immobilization of mammalian eggs on solid substrates by lectins for electron microscopy.

Cumulus-free, zona pellucida invested hamster and mouse eggs were immobilized by adherence of the zonae to glass or plastic substrates to which the lectin, wheatgerm agglutinin, had been attached. This simple method of egg immobilization enabled processing of very small quantities of eggs for both scanning and transmission electron microscopy. Soluble protein in the medium did not affect zona-substrate adhesion, and virtually all of the eggs were retained during dehydration and critical point drying.

Animals↗
PubMed1986

Sperm binding activity of the zona pellucida of immature mouse oocytes.

Immature oocytes taken from ovarian follicles are sometimes used in studies of sperm-zona interaction in species for which it is difficult to obtain ovulated eggs. As yet, however, there has been no quantitative comparison of the sperm binding capacities of immature and ovulated oocytes. We report here that in mice there is no significant difference in the numbers of sperm which bind to the zonae pellucidae of immature and ovulated oocytes in vitro. These results support the use of immature oocytes in studies of sperm-zona interaction. We have also analyzed the sources of variability in sperm binding assays, and we make suggestions for the most efficient design of experiments.

Animals↗
PubMed1985

Isolation and partial characterization of Urechis caupo egg envelopes.

Eggs of Urechis caupo are surrounded by a congruent to 0.9 micrometer thick egg envelope and, attached to that, a peripheral jelly layer about 3 micrometers thick. Before fertilization, the sperm undergoes the acrosome reaction and binds to the egg envelope. As part of a study of the induction of the acrosome reaction and sperm binding in Urechis, we have developed a method to prepare an egg envelope fraction by differential centrifugation. The isolation procedure removes much of the jelly layer, but does not alter the fine structure of the envelope. When a sperm contacts an isolated envelope, it undergoes a normal acrosome reaction and binds to the envelope's outer face. Electrophoresis of the envelope fraction on sodium dodecyl sulphate (SDS)/polyacrylamide gels revealed six major components stained by Coomassie Blue, of which four are stained by the periodic acid-Schiff reagents (PAS). To measure the degree of enrichment of the envelope fraction, envelopes were isolated from eggs that had been externally radio-iodinated; the specific activity of the envelope fraction was 17 +/- 3 times greater than that of intact eggs. The amino acid composition of the envelope fraction is dominated by Gly (19 mole %), Asx (11%), Thr (11%), Ser (8%), Ala (8%) and Glx (8%). The sugars fucose, xylose, mannose, galactose, glucose, N-acetylglucosamine and N-acetylgalactosamine were detected by gas-liquid chromatography. We also investigated whether the egg envelope changes at fertilization. No change was detected in the electrophoretic 125I pattern of externally radio-iodinated eggs, and the envelope fractions prepared from unfertilized and fertilized eggs produced the same Coomassie Blue pattern on SDS/polyacrylamide gels.

Amino Acids↗
PubMed1984

Electrical properties of vertebrate oocyte membranes.

The electrical properties of vertebrate oocyte and egg cell membranes are reviewed. Ion channels of these oocytes generate transcellular currents and action potentials as well as responses to neurotransmitters. Electrical properties change during meiotic maturation and fertilization. Available information about the electrical properties of sperm is also discussed.

Action Potentials↗
PubMed1983

A repeated dose study of the toxicity of inhaled 2-chlorobenzylidene malononitrile (CS) aerosol in three species of laboratory animal.

The repeated dose inhalation toxicity of 2-chlorobenzylidene maloninitrile (CS) was investigated in male mice, rats, and guinea-pigs. Exposure was 1 h X day-1 for 120 days surviving animals being killed approximately 1 year after the start of exposure. Excess mortality was noted in the high dose groups of all three species but at exposure concentrations below 30 micrograms X 1(-1) mortality varied little between the control and test groups. Death during the experiment was related to concentration of exposure rather than total dose (Ct). No case of a dose-response relationship between tumours in a particular site, and total dose of CS was noted.

Aerosols↗
PubMed1983

The pH within the jelly coat of sea urchin eggs.

Because low molecular weight factors isolated from sea urchin egg jelly increase sperm motility and respiration, but only at a pH less than 7.4, H. Ohtake (J. Exp. Zool. 198, 303-312, 1976) suggested that the pH within the jelly experienced by a sperm swimming to the egg might be 6.5-7.0. With a pH microelectrode, the pH in the jelly coat of single eggs of Strongylocentrotus purpuratus and Lytechinus pictus was measured and found to be not significantly different from the pH of seawater, 8.0; it thus does not seem likely that these low molecular weight factors are important in maintaining sperm motility or respiration during fertilization.

Acrosome↗
PubMed1983

Studies of the voltage-dependent polyspermy block using cross-species fertilization of amphibians.

Fertilization of frog eggs by frog sperm is inhibited if the egg's membrane potential is positive (N.L. Cross and R.P. Elinson, 1980, Dev. Biol. 75, 187-198); however, fertilization of salamander eggs by salamander sperm does not depend on membrane potential (M. Charbonneau, M. Moreau, B. Picheral, J.P. Vilain, and P. Guerrier, 1983, Dev. Biol. 98, 304-318). Since salamander sperm can fertilize frog eggs, we have investigated whether this cross-fertilization is voltage dependent. If, during insemination with Notophthalmus sperm, Xenopus eggs were voltage clamped between +7 and +20 mV, fertilization proceeded in 7/10 (70%) of the clamped eggs, compared to 38/48 (79%) of the neighboring eggs. In control experiments in which voltage-clamped Xenopus eggs were inseminated with Xenopus sperm, fertilization proceeded in only 1/10 (10%) of the clamped eggs, compared to 59/60 (98%) of the neighbors. Similar results were obtained with cross-fertilization experiments between Notophthalmus sperm and Rana eggs. These experiments indicate that the voltage dependence of fertilization depends on the species of sperm.

Amphibians↗
PubMed1983

Casualties from terrorist bombings.

The physical factors responsible for injury following an explosion in a room or building are: direct exposure to overpressure; blast-induced whole body displacement; impact of blast-energized debris; burns from flash and hot gases. The patterns of injury seen in the casualties from four terrorist bombings are described to illustrate the types and severity of particular wounds. The most common fatal injury is brain damage; 'blast lung' is uncommon in civilian terrorist bombings; flash burns, fractures, serious soft-tissue damage, and eardrum injuries are seen in people close to the bomb, who usually require hospital admission; many others taken to hospital can be treated for injury by debris and released. The environment and its internal structure and the position of the occupants of the space can influence the type and severity of injuries.

Barotrauma↗
PubMed1983

Isolation and electrophoretic characterization of the plasma membrane of sea-urchin sperm.

A subcellular fraction containing plasma membranes was isolated from flagella of the sperm of Strongylocentrotus purpuratus by differential centrifugation, and analysed by sodium dodecyl sulphate/polyacrylamide gel electrophoresis. Coomassie Blue staining revealed nine major bands and 14 minor species. Five bands of apparent molecular weights approximately 200 X 10(3), 149 X 10(3), 120 X 10(3), 75 X 10(3) and 59 X 10(3) also stained with periodic acid-Schiff's reagent and so are probably glycoproteins. These five components are externally exposed, as determined by lactoperoxidase-catalysed radio-iodination. Isolation of membranes from radio-iodinated sperm results in an enrichment of about tenfold in the specific activity of 125I. Comparison of the electrophoretic patterns of labelled sperm and of the membranes isolated from 125I-labelled sperm suggests that no major labelled proteins are lost during the isolation procedure, and so to this extent the membrane fraction is representative of the entire sperm plasma membrane.

Animals↗
PubMed1981

A low volume burn resuscitation regimen: assessment of performance by probit analysis.

The findings are presented of a 10-year retrospective review of burn admissions to the Wessex Regional Burn Centre, where a low volume colloid resuscitation regimen is employed. An analysis of mortality probability has been conducted using probit analysis, and the areas of burn injury associated with a 50 per cent mortality probability (LA50) were determined for four different age groups. LA50 values obtained were 0-14 years 59 per cent body surface area (BSA) burn, 15-44 years 70 per cent BSA burn, 45-64 years 38 per cent burn, 65 years and over 17 per cent BSA burn. The figures obtained parallel closely those reported from another large burn centre in the United Kingdom where a widely different fluid regimen is used. The results of this analysis suggest that wide variations in fluid resuscitation regimens, particularly with regard to volume, do little to affect the mortality associated with burn injury as assessed by probit analysis.

Adolescent↗