Relationships betweenOryza species (Poaceae) based on 5S DNA sequences

Relationships between 9Oryza species, covering 6 different genomes, have been studied using hybridization and nucleotide sequence information from the5S Dna locus. Four to five units of the major size class of 5S DNA in each species, 55 units in all, were cloned and sequenced. Both hybridization and sequence data confirmed the basic differences between the A and B, C, D genome species suggested by morphological and cytological data. The 5S DNA units of the A genome species were very similar, as were the ones from the B, C, and D genome-containing species. The 5S DNA ofO. australiensis (E genome) grouped with the B, C, D cluster, while the units ofO. brachyantha (F genome) were quite different and grouped away from all other species. 5S DNA units fromO. minuta, O. latifolia, O. australiensis, andO. brachyantha hybridized strongly, and preferentially, to the genomic DNA from which the units were isolated and hence could be useful as species/genome specific probes. The 5S DNA units fromO. sativa, O. nivara, andO. rufipogon provided A genome-specific probes as they hybridized preferentially to A genome DNA. The units fromO. punctata andO. officinalis displayed weaker preferential hybridization toO. punctata DNA, possibly reflecting their shared genome (C genome).     

Effect of 5 alpha-dihydrotestosterone on sexual receptivity and neural progestin receptors in ovariectomized rats given pulsed estradiol

Experiments were carried out to examine the mechanism whereby 5 alpha-dihydrotestosterone (DHT) antagonizes the stimulatory effects of estrogen plus progesterone (P) on sexual receptivity (lordosis) in the ovariectomized rat. Estradiol (E2; 1 microgram s.c. in 10% ethanol) was administered in a discontinuous (pulsed) treatment regimen thought to mimic phase requirements of estrogen action; two injections of E2 were given either 6 or 12 h apart (first injection, Hour 0). Progesterone (0.5 mg in oil) was injected at Hour 20, and behavioral testing occurred at Hour 24. Dihydrotestosterone (2.5 mg s.c. in 10% ethanol/propylene glycol) inhibited lordosis when it was given before (-12 or -3 h), between (+3, or -3 and +3 h), or after (+8 h) the two E2 injections, but was not effective when given at +20 h. Significant inhibition of E2 + P-induced lordosis was achieved by 2.5 but not 1.0 or 0.2 mg DHT at -3 h, while uterine weights in the same animals were reduced significantly by 2.5 and 1.0 mg DHT. Serum E2 and DHT concentrations peaked rapidly after injection, declining to near baseline by 3 and 12 h, respectively. Induction of cytosolic progestin receptors (cPR) in the preoptic area and medial basal hypothalamus by estrogen was not prevented by DHT when animals were given the two pulsed E2 injections or daily injections of estradiol benzoate, although P was able to override the inhibitory behavioral effects of DHT in the latter but not the former group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distinctions betweenHordeum bulbosum andH. murinum s.l. in seed and herbarium collections

It is sometimes necessary to identify eitherH. bulbosum orH. murinum on the basis of the inflorescence or seeds alone. The majority of taxonomic keys use the presence of swollen basal culms for the former against the annual habit for the latter. Confusion is due to similarities in inflorescences and spikelet morphology. Lodicules which always persist and are present beside the fruit in a mature caryopsis, and other characters such as the awns of the lemmas of the lateral spikelets enable conclusive distinction.     

Formation of hydroxyl radicals in the presence of ferritin and haemosiderin. Is haemosiderin formation a biological protective mechanism?

Horse spleen and human spleen ferritins increase the formation of hydroxyl radicals (OH) at both pH 4.5 and pH 7.4 in reaction mixtures containing ascorbic acid and H2O2. The generation of OH is inhibited by the chelator desferrioxamine. Human spleen haemosiderin also accelerates OH generation in identical reaction mixtures, but is far less effective (on a unit iron basis) than ferritin under all reaction conditions. It is proposed that conversion of ferritin into haemosiderin in iron overload is biologically advantageous in that it decreases the ability of iron to promote oxygen-radical reactions.     

Uptake and secretion of technetium pertechnetate by the rat parotid gland

The ability of acinar cells of the rat parotid gland to transport technetium pertechnetate (99mTcO-4) was examined. After intravenous injection, 99mTcO-4 was rapidly detected in parotid saliva. There was an excellent correlation between saliva and plasma 99mTcO-4 levels. The saliva to plasma ratio was always less than 1, consistent with the inability of rat parotid gland duct cells to concentrate the anion. Output of 99mTcO-4 by the parotid gland closely mimicked fluctuations in parotid saliva flow rate. In vitro, enzymatically dispersed parotid acinar cells accumulated 99mTcO-4 from the incubation medium in a biphasic manner. This uptake was partially blocked by 10(-4) M NaI. Cells which had accumulated 99mTcO-4 showed increased radionuclide efflux after exposure to 10(-5) M carbachol.     

Multiple transduction mechanisms are likely involved in calcium-mediated exocrine secretory events in rat parotid cells

The parotid gland of the aged rat provides an example of an altered alpha 1-adrenergic physiologic response (K+ efflux) resulting from a postreceptor perturbation in signal transduction mechanisms (Ito, H., Baum, B. J., Uchida, T., Hoopes, M. T., Bodner, L. & Roth, G. S. (1982) J. Biol. Chem. 257, 9532-9538). This alteration in gland function can be completely circumvented by eliciting K+ efflux via the Ca2+-ionophore, A23187, at several Ca2+ concentrations (ibid.). Since Ca2+ is purported to mediate other secretory events in the rat parotid, we have probed neurotransmitter regulated Ca2+ mobilization and secretory mechanisms in this tissue by employing an aging paradigm. The responses studied were alpha-adrenergic- and muscarinic-cholinergic-mediated K+ efflux, 45Ca2+ release, and amylase secretion. No differences were detected between young (3 months) and old (24 months) cell preparations for any muscarinic-cholinergic agonist-induced response studied. Following alpha-adrenergic stimulation, K+ efflux and 45Ca2+ release from old cell preparations were reduced markedly, while no changes were found for the amylase secretion response. These results suggest that 1) alpha-adrenergic and cholinergic signal transduction mechanisms for K+ efflux and 45Ca2+ release are dissociated in cells of the rat parotid gland, and 2) following alpha 1-adrenergic stimulation, signal transduction likely proceeds by at least two pathways, one which is apparently involved in protein excytosis (intact in cells from old rats) and the other which is apparently involved in K+ efflux and 45Ca2+ release (perturbed in old cells).     

Feedback inhibition of homoserine kinase from radish leaves

Homoserine kinase is a potential control point in the biosynthetic pathway for threonine, isoleucine and methionine. The radish leaf enzyme was tested     

Mounting and receptive behavior in the ovariectomized female rat: Influence of estradiol,dihydrotestosterone, and genital anesthetization

Two experiments were performed with ovariectomized female rats in an attempt to determine whether estradiol and dihydrotestosterone work synergistically in the brain to activate mounting behavior. In Expt 1, performed in Göteborg, it was found that females treated daily with 2 μg estradiol benzoate (EB) combined with 500 μg dihydrotestosterone (DHT) displayed significantly more mounts with pelvic thrusting than other females treated with the oil vehicle, 500 μg DHT, or 2 μg EB. The behavior of rats receiving EB + DHT was indistinguishable from that of yet another group of females which received 200 μg testosterone propionate (TP). In Expt 2, performed in Rotterdam, it was found that ovariectomized female rats treated with either 200 μg TP or 2 μg EB + 200 μg dihydrotestosterone propionate (DHTP) mounted significantly more than females treated with 2 μg EB. Both clitoral size and the growth of cornified papillae on the glans clitoris were stimulated by the administration of TP or EB + DHTP. However, in no group was the frequency of mounting affected by anesthetization of the clitoris and external vagina with lidocaine paste. Lordosis quotients of females treated with EB + DHTP were significantly lower than in rats receiving either EB or TP, again regardless of whether or not the genital region was anesthetized. It is concluded that the effects of DHT on estradiol-induced mounting and receptivity most likely result from the action of this androgen on the brain, and not from the stimulatory effect which DHT may exert on genital sensory receptors.