Induction of the human sperm acrosome reaction with mannose-containing neoglycoprotein ligands

In the interest of classifying cases of male factor infertility, we have paid particular attention to the sugar ligand binding properties of the human sperm surface and the functional capacity of the acrosome for exocytosis--key parameters for assessing sperm fertilizing ability. Zona recognition and binding involve the interactions of sperm surface mannose receptors (lectins) with mannose ligands on the zona pellucida. Sperm surface mannose lectins can be visualized by their ability to bind a synthetic model zona ligand, fluorescein isothiocyanate (FITC)-conjugated mannosylated bovine serum albumin (BSA) (Man-FITC-BSA). We now report that Man-FITC-BSA biologically also mimics the effects of solubilized authentic human zonae, in that binding of Man-FITC-BSA results in a time-dependent receptor aggregation and the induction of acrosome exocytosis in capacitated sperm populations from fertile donors. In our assay, the addition of mM amounts of mannose monosaccharide to Man-FITC-BSA increases the number of polyvalent mannose ligands bound by individual spermatozoa and increases the rate of the acrosome reactions induced by Man-FITC-BSA, thereby increasing specimen processing efficiency. We conclude that exposure of human spermatozoa to polyvalent mannose ligands + D-mannose monosaccharide offers a new, convenient and readily available system to study sperm capacity for induced acrosome loss.     

Calcium channel blockers inhibit the antidipsogenic effect of central injections of zinc in rats

Previous data from our laboratory have indicated that acute third ventricle injections of Zn2+ elicit a significant antidipsogenic response in rats in three different situations; dehydration, and central angiotensinergic or cholineric stimulation. In the present study we analyzed whether this response depends on voltage-dependent calcium channels. Dehydrated (14 h of water deprivation, overnight) animals received 2-microliters i.c.v. injections of zinc acetate (Zn(Ac)2; 300 pmol/rat) after pretreatment with the voltage-dependent calcium channel blockers gadolinium (Gd3+; 0.03, 3.0 and 30 pmol/rat) or verapamil (VER; 0.027, 0.05 and 0.11 pmol/rat). Both blockers reserved the antidipsogenic effect of third ventricle injections of Zn2+ in a dose-dependent manner. After 120 min, animals pretreated with saline receiving Zn(Ac)2 drank 3.10 +/- 0.57 ml/100 g body weight while those pretreated with Gd3+ at the highest dose displayed a water intake of 5.45 +/- 0.41 ml/100 body weight (P < 0.01). Animals pretreated with the vehicle of VER receiving Zn(Ac)2 drank 3.15 +/- 0.45 ml/100 g while animals pretreated with VER at the highest dose receiving Zn(Ac)2 drank 6.16 +/- 0.62 ml/100 g (P < 0.01). The antidipsogenic effect of Zn(Ac)2 seems to be specific since the metal (same dose and injection procedures) did not modify food intake in rats after 24 h of food deprivation. It is suggested that Zn2+ exerts its antidipsogenic effect by activation of mechanism(s) depending on the functional integrity of voltage-dependent calcium channels.     

Hemodynamic and cerebral blood flow effects of cocaine, cocaethylene and benzoylecgonine in conscious and anesthetized fetal lambs

Yeast artificial chromosome (YAC) clones propagate large segments of exogenous DNA in a host organism with well-developed classical and molecular genetics. Most extant YAC clones are from libraries created in a single yeast host (AB1380). The application of techniques allowing the manipulation and/or restructuring of these cloned DNA segments often requires a change in the yeast genetic background to introduce desirable genetic markers. Transfer methods in current use require extremely high yeast transformation efficiencies or require access to equipment for yeast tetrad analysis. We have developed an alternative method for moving YAC clones from one yeast strain to another, taking advantage of the properties of kar1 mutants altered in a gene required for normal karyogamy (nuclear fusion) during mating. Transfer by this method requires generally accessible methods, including yeast cell culture, replica plating, and pulsed-field gel electrophoresis. We present data demonstrating efficient transfer of nine different YACs from their original host (AB1380) to a kar1 recipient strain (YPH925) with genetic markers that facilitate the use of existing homologous recombination-based modification methods. The enhanced ability to transfer clones to this new host will accelerate the pace of refinement and fine-structure mapping of the YAC contigs currently under construction and facilitate gene manipulation on YACs for subsequent functional analysis.     

The embryology of the common marmoset (Callithrix jacchus)

Earlier studies have noted the unusual placental anatomy of marmosets and the high frequency of biovular, synchorial twinning. The maintenance of a captive colony of Callithrix jacchus has enabled further studies to be made of embryonic development in this species. Thirty-six embryos from seventeen pregnancies were examined in detail and assigned to horizons on the basis of Streeter's classification of external form and internal structure. The specimens represented tha major part of the embryonic period and, with few exceptions, the structural development of the marmoset closely resembled that of the other primates that have been described. Marmoset embryos of a given horizon were consistently shorter than those of man. The timing of morphogenesis in C. jacchus was different from that observed in man and other primates. There was a considerable delay in early embryogenesis in the marmoset, although subsequent to stage XI, development proceeded at approximately the same rate as other primates. The available evidence suggested that this anomaly was not due to delayed implantation or embryonic diapause but to a generally slower rate of early development. The evolution of synchorial twinning is considered as a possible reason for this mode of development.     

Chronic myelopathy associated with human herpesvirus-6

Human herpesvirus-6 (HHV-6) is implicated in a variety of neurologic diseases. We report a previously healthy elderly woman with progressive spastic paraparesis. At autopsy the spinal cord showed widespread demyelination, axonal loss, and chronic inflammation. HHV-6 DNA was amplified, using polymerase chain reaction, from spinal cord tissue, and glial cells were immunoreactive with an HHV-6 antibody. These findings suggest that HHV-6 may cause myelopathy.     

Fluorometric studies of recovery metabolism of rat fast- and slow-twitch muscles

Recovery metabolism of fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles of the rat has been investigated using fluorometric monitoring of reduction of nicotinamide adenine dinucleotide (NAD). In both EDL and SOL, groups of twitch contractions produced a decrease in fluorescence (oxidation of NADH) which returned to the resting base line after contraction ceased. These responses proceeded more quickly in EDL than SOL and were abolished by anoxia. A 1-s tetanus of SOL produced an initial reduction which could be abolished with iodoacetate followed by a prolonged oxidation which could be blocked by anoxia. The fluorescence of EDL was decreased immediately following a 1-s tetanus but then rapidly increased well beyond the resting level of reduction and persisted throughout the recovery period. This reduction was largely depressed by iodoacetate. The results indicate marked differences in the recovery metabolism of these muscles, consistent with predominantly mitochondrial oxidative activity in the slow-twitch muscles and predominantly glycolytic activity in the fast-twitch muscles.