The physiology of sperm recovered from the human cervix: acrosomal status and response to inducers of the acrosome reaction

Cervical mucus was collected from 35 women after artificial insemination. Mucus collections were performed at 1 h, 1 day, 2 days, or 3 days following insemination. Sperm viability was greater than 80% at all recovery times as assessed by exclusion of the supravital dye Hoechst 33258. Virtually 100% of the viable sperm were acrosome-intact at all times as assessed with a fluorescein isothiocyanate-conjugated pea lectin. Sperm were recovered from the mucus after migration into the Biggers, Whittin, and Whittingham medium in vitro. Sperm did not undergo the acrosome reaction in response to human follicular fluid immediately after migration from the mucus but did respond to this agonist after 6 h of incubation in vitro. Sperm recovered at all times after insemination had the same pattern of response to follicular fluid. Sperm that penetrated a column of cervical mucus in vitro also responded to follicular fluid with an increase in acrosome reactions after migration from the mucus and incubation for 6 h in vitro. Unlike the sperm that migrated from cervical mucus, sperm that were separated from semen by Percoll density centrifugation did not undergo the acrosome reaction when challenged with follicular fluid after 6 h but did respond after 24 h incubation. Sperm that migrated from cervical mucus had a similar increase in acrosome reactions after 6 h incubation, regardless of whether the acrosome reaction agonist was follicular fluid or disaggregated human zona pellucida.(ABSTRACT TRUNCATED AT 250 WORDS)     

Novobiocin-resistance sequences from the novobiocin-producing strain Streptomyces niveus

Two distinct DNA sequences expressing novobiocin resistance in Streptomyces lividans were cloned from the novobiocin-producing species Streptomyces niveus. Clone pGL101 (5kb) conferred resistance to 50 micrograms ml-1 novobiocin, whereas clones pGL102 and pGL103, which carry the same 6.5kb insert but in opposite orientations, expressed resistance to 150 micrograms ml-1. The cloned inserts from pGL101 and pGL103 failed to hybridize with each other or with the cloned novobiocin-resistant gyrB sequence from Streptomyces sphaeroides. Both probes hybridized strongly with DNA from the novobiocin-producing species S. niveus and S. sphaeroides but no hybridization (pGL103) or very weak hybridization (pGL101) was detected with DNA from the non-producing species S. lividans, Streptomyces griseus and Streptomyces antibioticus. S. niveus contains at least three novobiocin-resistance determinants with the pGL101 and pGL103 cloned sequences specific for novobiocin-producing strains of Streptomyces.     

The use of two populations of hepatocytes with different triacylglycerol contents as a model to study the accumulation of liver lipid in the laying hen.

(1) A method has been developed to separate hepatocytes, isolated from laying hens, according to their densities, using discontinuous density-gradient centrifugation on Nycodenz. (2) The hepatocytes recovered from the interface of the 5% and 10% Nycodenz layers were rich in triacylglycerol and were termed 'fatty' hepatocytes: 'non-fatty' hepatocytes were obtained from the interface of the 15% and 30% Nycodenz layers and contained less than one-quarter as much triacylglycerol. (3) 'Fatty' hepatocytes incorporated radiolabelled glucose and glycerol into total lipid at more than twice the rate of 'non-fatty' cells: the corresponding increases in the incorporation of radiolabelled choline and valine into phospholipid and protein respectively were smaller and not statistically significant. (4) A higher proportion of glycerol and glucose incorporated into total lipid was found to be phospholipid in the 'non-fatty' hepatocytes. (5) A higher proportion of radiolabelled lipid or protein formed from glycerol or valine respectively was secreted into the medium by the 'non-fatty' hepatocytes. (6) The use of these hepatocytes as a model to study fatty liver syndromes is discussed.