Opiate receptor subtypes in the regulation of thyrotropin and prolactin secretion in the rat

In the present study both MR 2034 (kappa-agonist) and DAMME (mu-agonist) decreased thyrotropin (TSH) secretion stimulated by cold in the rat when infused into the 3rd ventricle. After infusion into the posterior hypothalamus (PH), a small dose of MR 2034 increased the TSH response to cold whereas other doses did not. The stimulatory (at PH) but not the inhibitory (at 3rd ventricle) effect of MR 2034 was antagonized by naloxone. DAMME had no statistically significant effect at this location. Both the mu- and kappa-agonist stimulated prolactin secretion when infused into the 3rd ventricle, but DAMME was more effective than MR 2034. Furthermore, the stimulatory effect of DAMME, but not that of MR 2034, on prolactin secretion was antagonized by naloxone.     

Effects of some putative amino acid neurotransmitters on the stimulated TSH secretion in male rats

The importance of several amino acids (glycine, L-glutamic acid, L-serine, taurine and beta-alanine) in the regulation of the stimulated secretion of TSH was studied in male rats using both peripheral and central administration of the amino acids. Glycine (10-200 mg/kg i.p.), L-glutamic acid (10-500 mg/kg i.p.) and L-serine (500 mg/kg i.p.) decreased significantly the cold-induced TSH secretion whereas beta-alanine (1-500 mg/kg i.p.) and taurine (10-100 mg/kg i.p.) were not effective. The effect of L-glutamic acid (100 mg i.p.) was partially antagonized by bicuculline (1 mg/kg i.p.) but not by picrotoxin (1 or 2 mg/kg i.p.). Only glycine (50 and 100 mg/kg i.p.) inhibited the TRH-stimulated TSH secretion. When the intracerebroventricular route was used, L-serine (50 micrograms/rat) decreased the TSH could response whereas glycine and L-glutamic acid (1-50 micrograms/rat) had no clear effect. We conclude that glycine, glutamate and serine inhibit the cold-induced TSH secretion in the male rat. The action of serine and glycine is possibly mediated through the periventricular hypothalamus and the anterior pituitary, respectively. The inhibition caused by glutamate seems to be partially mediated through the bicuculline-sensitive GABA receptors in the hypothalamus. Taurine and beta-alanine play no role in the control of rat TSH secretion.     

The Agrobacterium rhizogenes rolB and rolC promoters are expressed in pericycle cells competent to serve as root initials in transgenic hybrid aspen

Expression of the Agrobacterium rhizogenes rolB and rolC promoters was studied in transgenic hybrid aspen ( Populus tremula L. × P. tremuloides Michx.) lines containing a chimeric fusion of either the rolB or the rolC promoter and the reporter gene uidA . The resultant GUS activity was monitored by histochemical analysis in aerial tissues as well as in developing roots. Both the rolC and rolB promoters were shown to be expressed in the phloem and in the root tips, which is similar to the expression pattern previously described for annual plants. However, a strong expression of the rolB promoter in the rays of the phloem and the cambial zone of the stem, and of the rolC promoter in groups of pericycle cells prior to and during lateral root initiation was unique for hybrid aspen. In both stem and root tissues, the expression of the rolB and rolC promoters was localised primarily in a subset of cells competent to form adventitious or lateral roots, suggesting that these cells might serve as the target for A. rhizogencs infection. The biological significance of the cell-specific rol gene expression in establishing the hairy root disease is discussed.     

PIRIN2 stabilizes cysteine protease XCP2 and increases susceptibility to the vascular pathogen Ralstonia solanacearum in Arabidopsis

PIRIN (PRN) is a member of the functionally diverse cupin protein superfamily. There are four members of the Arabidopsis thaliana PRN family, but the roles of these proteins are largely unknown. Here we describe a function of the Arabidopsis PIRIN2 (PRN2) that is related to susceptibility to the bacterial plant pathogen Ralstonia solanacearum. Two prn2 mutant alleles displayed decreased disease development and bacterial growth in response to R.  solanacearum infection. We elucidated the underlying molecular mechanism by analyzing PRN2 interactions with the papain‐like cysteine proteases (PLCPs) XCP2, RD21A, and RD21B, all of which bound to PRN2 in yeast two‐hybrid assays and in Arabidopsis protoplast co‐immunoprecipitation assays. We show that XCP2 is stabilized by PRN2 through inhibition of its autolysis on the basis of PLCP activity profiling assays and enzymatic assays with recombinant protein. The stabilization of XCP2 by PRN2 was also confirmed in planta. Like prn2 mutants, an xcp2 single knockout mutant and xcp2 prn2 double knockout mutant displayed decreased susceptibility to R. solanacearum, suggesting that stabilization of XCP2 by PRN2 underlies susceptibility to R. solanacearum in Arabidopsis.     

Time relationships and reversal by two indoleamines of the pinealectomy-inhibited thyrotropin secretion in male rats

Time relationships and mediators of the inhibitory effect of pinealectomy on cold-induced TSH secretion were studied in male Sprague-Dawley rats. Pinealectomy but not sham operation significantly reduced the TSH cold-response (30 min at +4 degrees C) in 6-8 week-old rats on the 3rd postoperative day. Longer postoperative periods resulted in gradual attenuation of the effect of pinealectomy. Pinealectomy did not modify basal TSH levels on the 3rd or 7th postoperative day. Melatonin, arginine vasotocin and crude pineal extracts failed to antagonise the suppressed cold-response in pinealectomised rats. 5-Hydroxytryptamine and 6-methoxy-tetrahydro-beta-carboline, however, antagonised partially but significantly the pinealectomy-induced reduction in TSH cold-response. Although transient, the suppression of cold-stimulated TSH secretion by pinealectomy may be caused by lack of two pineal indoleamines 5-hydroxytryptamine and/or 6-methoxy-tetrahydro-beta-carboline.     

Comparison of Methods for Inhibiting Bacterial Activity in Sediment

Dilute formaldehyde was the most suitable treatment to inhibit sediment bacteria, since bacterial activity remained low during long-term incubations and the chemical changes in the sediment were minimal. The inhibiting effects of HgCl₂, autoclaving, and gamma radiation were diminished during longer incubations; these treatments also caused increases in dissolved nutrients.