Locus determining the human sperm-specific lactate dehydrogenase, LDHC, is syntenic with LDHA

From the data presented in this report, the human LDHC gene locus is assigned to chromosome 11. Three genes determine lactate dehydrogenase (LDH) in man. LDHA and LDHB are expressed in most somatic tissues, while expression of LDHC is confined to the germinal epithelium of the testes. A human LDHC cDNA clone was used as a probe to analyze genomic DNA from rodent/human somatic cell hybrids. The pattern of bands with LDHC hybridization is easily distinguished from the pattern detected by LDHA hybridization, and the LDHC probe is specific for testis mRNA. The structural gene LDHA has been previously assigned to human chromosome 11, while LDHB maps to chromosome 12. Studies of pigeon LDH have shown tight linkage between LDHB and LDHC leading to the expectation that these genes would be syntenic in man. However, the data presented in this paper show conclusively that LDHC is syntenic with LDHA on human chromosome 11. The terminology for LDH genes LDHA, LDHB, and LDHC is equivalent to Ldh1, Ldh2, and Ldh3, respectively.     

Preliminary studies of the effects of bromocriptine on testicular regression and the spring moult in a seasonal breeder, the male blue fox (Alopex lagopus)

Bromocriptine administration in the form of slow-release injections to male blue foxes during March-May abolished the normal spring rise in plasma prolactin concentrations seen in May and June. The spring moult was prevented and the treated animals retained a winter coat of varied quality and maturity until the end of the study in August. Plasma testosterone concentrations fell normally from March until August. Testicular regression was, however, delayed, although there were individual variations in response. Estimation by DNA flow cytometry in early July of the relative numbers of haploid, diploid and tetraploid cells in the testis showed that, in the treated animals, 74-80% of the cells were haploid (maturing germinal cells), 4-6% tetraploid (mainly primary spermatocytes) and the rest diploid cells (somatic cells and the remaining germinal cell types). In the control males, however, no haploid cells were detected and the majority of cells were diploid (93-99%). At castration in August, histological examination revealed various stages of testicular regression in the treated and control animals.     

Covalent labeling of opioid receptors with 3H-D-Ala2-Leu5-enkephalin chloromethyl ketone. I. Binding characteristics in rat brain membranes

The chloromethyl ketone derivative of D-Ala2-Leu5-enkephalin was synthesized in a radioactive form, and the resulting compound (3H-DALECK) was used to label opioid receptors. 3H-DALECK binds with high affinity, specificity and saturability to rat brain membranes. The number of sites labeled is 130 fmoles/mg protein. Unlabeled opioids inhibited the binding of 3H-DALECK; etorphine and DAGO being most potent. A 10-fold preference for mu sites over delta was seen in site-specific competition experiments; while DALECK displayed low affinity for kappa sites of rat brain. DALECK irreversibly blocked a certain population of sites. Approximately 40% of 3H-DALECK binding at 15 min, and 60% at 60 min association time did not dissociate in the presence of a large excess of unlabeled DALECK and was resistant to washing. Autoradiography performed after SDS-PAGE revealed specific alkylation of proteins with molecular weight of 74, 65, 56, 43 and 34 kD. These results demonstrate the applicability of using 3H-DALECK to covalently label opioid receptors.     

Presynaptic control of dopamine metabolism in the nucleus accumbens. Lack of effect of buspirone as demonstrated using in vivo voltammetry

Buspirone is a non-benzodiazepine drug with anxiolytic properties. It has been reported to induce a marked increase in the metabolism of dopamine in the striatum and the nucleus accumbens which is similar to that induced by neuroleptics. It has been suggested that the effect observed in the striatum reflects an action of buspirone on dopaminergic autoreceptors in both terminals and cell bodies. In the present study, presynaptic effects of buspirone on dopaminergic metabolism in the nucleus accumbens were investigated, and they were compared to the effects of the classical neuroleptic, haloperidol. Dopaminergic terminals were isolated by infusion of tetrodotoxin into the median forebrain bundle in order to evaluate the effects of buspirone and haloperidol on presynaptic receptors. Changes in dopamine metabolism were determined by in vivo voltammetry. Buspirone administered after interruption of the impulse flow did not affect dopamine metabolism. In contrast haloperidol treatment led to an increase in metabolism of dopamine. It is concluded that buspirone did not act at the presynaptic level and furthermore on dopaminergic autoreceptors.     

Effects of stress and beta-funal trexamine pretreatment on morphine analgesia and opioid binding in rats

This study was essentially an in vivo protection experiment designed to test further the hypothesis that stress induces release of endogenous opioids which then act at opioid receptors. Rats that were either subjected to restraint stress for 1 hr or unstressed were injected ICV with either saline or 2.5 micrograms of beta-funaltrexamine (beta-FNA), an irreversible opioid antagonist that alkylates the mu-opioid receptor. Twenty-four hours later, subjects were tested unstressed for morphine analgesia (tail-flick assay) or were sacrificed and opioid binding in brain was determined. [3H]D-Ala2NMePhe4-Gly5(ol)enkephalin (DAGO) served as a specific ligand for mu- opioid receptors, and [3H]-bremazocine as a general ligand for all opioid receptors. Rats injected with saline while stressed were significantly less sensitive to the analgesic action of morphine 24 hr later than were their unstressed counterparts. Beta-FNA pretreatment attenuated morphine analgesia in an insurmountable manner. Animals pretreated with beta-FNA while stressed were significantly more sensitive to the analgesic effect of morphine than were animals that received beta-FNA while unstressed, consistent with the hypothesis that stress induces release of endogenous opioids that would protect opioid receptors from alkylation by beta-FNA. beta-FNA caused small and similar decreases in [3H]-DAGO binding in brain of both stressed and unstressed animals. Stressed rats injected with saline tended to have increased levels of [3H]DAGO and [3H]-bremazocine binding compared to the other groups. This outcome may be relevant to the tolerance to morphine analgesia caused by stress.     

Uterine blood flow during the development and regression of the decidual cell reaction in ovariectomized, steroid-treated mice

Uterine blood flow was assessed in mice by measuring organ uptake of intravenously injected [14C]butanol. In ovariectomized mice, injection of 100 ng oestradiol-17 beta increased blood flow 5-fold over that of untreated controls. The injection of oestradiol-17 beta in progesterone-treated mice also increased uterine blood flow at the time of maximal sensitivity to a decidual stimulus, but not 4 days later. Absolute values of blood flow increased during development of the decidual cell reaction in proportion to the increase in uterine weight, reaching maximal values 96 h after decidual induction. When progesterone injections were stopped 72 h after decidual induction, a rapid decrease in absolute and relative blood flow values preceded the decrease in uterine weight. This decrease in uterine blood flow occurred within 12 h of removing a subcutaneous implant containing progesterone. These results are consistent with the view that increased uterine blood flow during decidual development may be necessary to support the rapid increase in uterine weight at implantation and the subsequent decrease in both relative and absolute uterine blood flow on withdrawal of progesterone may promote decidual regression in the mouse.     

Mutations that increase the mitotic stability of minichromosomes in yeast: characterization of RAR1

Summary In an attempt to identify proteins involved in the initiation of DNA replication, we have isolated a series of Saccharomyces cerevisiae mutants in which the function of putative replication origins is affected. The phenotype of these Rar^- (regulation of autonomous replication) mutants is to increase the mitotic stability of plasmids whose replication is dependent on weak ARS elements. These mutations are generally recessive and complementation analysis shows that mutations in several genes may improve the ability of weak ARS elements to function. One mutation (rar1-1) also confers temperature-sensitive growth, and thus an essential gene is affected. We have determined the DNA sequence of the RAR1 gene, which reveals an open reading frame for a 48.5 kDa protein. The RAR1 gene is linked to rna1 on chromosome XIII.     

Influence of leaf age on photosynthesis, enzyme activity, and metabolite levels in wheat

The rate of photosynthesis under high light (1000 micromole quanta per square meter per second) and at 25°C was measured during development of the third leaf on wheat plants and compared with the activity of several photosynthetic enzymes and the level of metabolites. The rate of photosynthesis reached a maximum the 7th day after leaf emergence and declined thereafter. There was a high and significant correlation between the rate of photosynthesis per leaf area and the activities of the enzymes ribulose 5-phosphate kinase (r = 0.91), ribulose 1,5-bisphosphate (RuBP) carboxylase (r = 0.94), 3-phosphoglycerate (PGA) kinase (r = 0.82), and fructose 1,6-bisphosphatase (r = 0.80) per leaf area. There was not a significant correlation of photosynthesis rate with chlorophyll content. The rate of photosynthesis was strongly correlated with the level of PGA (r = 0.85) and inversely correlated with the level of triose phosphate (dihydroxyacetone phosphate and glyceraldehyde 3-phosphate) (r = 0.92). RuBP levels did not change much during leaf development; therefore photosynthesis rate was not correlated with the level of RuBP. The rate of photosynthesis was at a maximum when the ratio of PGA/triose phosphate was high, and when the ratio of RuBP/PGA was low. Although several enzymes change in parallel with leaf development, the metabolite changes suggest the greatest degree of control may be through RuBP carboxylase. The sucrose content of the leaf was highest under high rates of photosynthesis. There was no evidence that later in leaf development, photosynthesis (measured under high light and at 25°C) was limited by utilization of photosynthate.