The pattern of testosterone replacement influences the recovery of the stimulatory effect of clonidine on growth hormone (GH) secretion in orchidectomized rats

It has previously been described that the growth hormone (GH) releasing effect of clonidine (CLO), an agonist of ₂-adrenoreceptors, disappears after orchidectomy and is restored by testosterone replacement when started immediately after orchidectomy. In the present experiments, the effects of CLO on GH release was analysed in long-term (LTO; 12 weeks) and short-term (STO; 2 weeks) orchidectomized rats. In the first experiment, LTO males were implanted with silastic capsules containing testosterone 10 weeks after orchidectomy and killed 2 weeks later, 15 min after injection of CLO (150 μg/kg) or vehicle. In the second experiment, adult males were implanted with testosterone at the moment of orchidectomy and decapitated 2 or 12 weeks later, 15 min after vehicle or CLO administration. In addition, in order to evaluate the effects of orchidectomy and androgen replacement on ₂ agonists GH release further, prepubertal males (21-days-old) implanted with testosterone or 5--androstane-3-, 17β diol (-diol) at the moment of orchidectomy were killed 2 weeks later, 15 min after ketamine-xylazine (an ₂ agonist) administration. Finally, 10-day-old males (orchidectomized 72 h before) were decapitated 15 min after CLO or vehicle administration. Our results show that: (a) LTO and STO abolished the stimulatory effect of clonidine on GH secretion; (b) orchidectomy also abolished the stimulatory effect of clonidine in neonatal rats and that of xylazine in prepubertal males; (c) testosterone implanted at the moment of orchidectomy prevented the loss of the CLO effect in LTO and STO, but testosterone-delayed administration in LTO was unable to restore the effectiveness of CLO inducing GH release. We conclude that orchidectomy at all ages tested abolishes GH secretion induced by ₂ agonists, which suggests that the functionality of -adrenergic receptors involved in the control of GH secretion is critically dependent on a permanent exposure to testosterone in males.     

Through-bond correlation of adenine H2 and H8 protons in unlabeled DNA fragments by HMBC spectroscopy

Summary A new application of the HMBC experiment is presented that provides a useful means to discriminate between H2 and H8 proton resonances, to assign the base proton resonances to the various residue types and, most importantly, to correlate the H2 and H8 protons for adenine or inosine residues in natural abundance ¹³C fragments. The utility of this experiment is demonstrated for an unlabeled DNA 20-mer. Thanks to the obtained results, preliminary conclusions could be drawn regarding the molecular conformations of the non-canonical G/I-A base pairs in the hairpin formed by this fragment.     

Purification and partial characterization of an acidic ribosomal protein kinase from maize

Phosphorylation and dephosphorylation of ribosomal proteins have been suggested to participate in the regulation of protein synthesis in eukaryotic organisms. The present research focuses on the purification and partial characterization of a protein kinase from maize ribosomes that specifically phosphorylates acidic ribosomal proteins. Ribosomes purified from maize axes were used as the enzyme source. Purification of ribosomes was performed by centrifugation through a 0.5 M sucrose, 0.8 M KCl cushion. A protein kinase activity present in this fraction was released by extraction with 1.5 M KCl and further purified by diethylaminoethyl cellulose column chromatography. A peak containing protein kinase activity was eluted around 400 m M KCl. Analysis of this fraction by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed one band of 38 kDa molecular mass, which cross-reacted in a western blot with antibodies raised against proteins from the large ribosomal subunit. This enzyme specifically phosphorylates one of the acidic ribosomal proteins (P₂). Its activity is inhibited by Ca²⁺ and Zn²⁺ and is activated by Mg²⁺, polylysine and spermine. The relevance of this protein kinase in reinitiating the protein synthesis process during germination is discussed.     

DIASTOLIC OPENING OF THE AORTIC VALVE (AV) IN A CASE OF AORTIC INSUFFICIENCY DUE TO AV FENESTRATION

A patient with severe aortic insufficiency due to fenestration of the non-coronary aortic valve leaflet is described. A preoperative echocardiogram demonstrated early closure of the mitral valve and early diastolic separation of the aortic valve leaflets. These findings disappeared after partial surgical correction and subsequent hemodynamic improvement. Premature opening of the aortic valve is common in severe aortic insufficiency.     

Method for Lyophilizing Brain Proteolipid Preparation That Increases Subsequent Solubilization by Detergent

Abstract: A frozen mixture of solubilized brain proteolipid proteins in chloroform-methanol is not sublimable in a vacuum. However, when 7 to 10 volumes of benzene were added to a chloroform-methanol solution containing 5 mg of proteolipid protein per ml, the proteolipid proteins remained in solution for a while and the frozen mixture was easily sublimated at 2 mm Hg. Before the addition of benzene, higher concentrations of protein required the acidification of the medium to avoid precipitation of proteolipid proteins. In contrast to what happens when proteolipid proteins are obtained by the evaporation of the organic mixture at room temperature, the protein obtained by lyophilization was soluble in aqueous solutions of ionic and nonionic detergents. Sodium dodecyl sulfate at 0.6 to 0.7% concentration completely solubilized the proteolipid protein obtained by lyophilization. With the nonionic detergents Lubrol WX and Triton X-100, a solubilization between 50 and 65% was achieved. Sodium deoxycholate was practically ineffective. Triton X-100 showed selectivity in solubilizing certain proteins. The role of lipids in the solubilization of proteolipid proteins with detergents is discussed.     

Role of H-2 antigens in the host response to methylcholanthrene-induced tumors

H-2 loss variant sublines of a sarcoma (M-AS), induced by methylcholanthrene in an (A × A.SW)F₁ mouse, were used to study the role of the MHC products in the recognition of MC-TSTA. The two reciprocal variant sublines (M-A and M-S) were found to express the TSTA of the original tumor as shown by cross-reactions in graft rejection experiments performed in (A × A.SW)F₁ mice. In the A/Sn and A.SW mice the presence of the reciprocal parental H-2 antigens on the immunizing cells decreased the response against the tumor antigens. An admixture of lymphocytes derived from hyperimmune mice inhibited the outgrowth of the tumor cells. The growth inhibition was mediated by T cells and was H-2 restricted. Cells derived from hyperimmune syngeneic mice inhibited the outgrowth of the variant subline used for immunization but had no effect on the reciprocal variant subline.     

Zoogeographical distribution of Southeast Asian freshwater Calanoida

This paper reviews the systematic status and geographical distribution of 30 odd species of freshwater calanoid copepods in Southeast Asia. Three regions are delineated based on the diversity and abundance of these organisms; Region I being the Southasiatic element, Region II the attenuated belt of copepods and Region III rich in endemic species. The implication of a north-south diminishing of copepod species to inland fisheries is postulated.     

Conformational properties of the N-terminal residues of S-peptide. I. The ribonuclease S′ system

The contribution of the 1–6 N-terminal sequence to the conformational properties of the S-peptide (the 1–20 sequence of ribonuclease A) was assessed by determining in the ribonuclease S′ system the helical content and the binding capability of synthetic [Orn¹⁰]-S-peptide analogs, in which lysine¹, glutamic² and threonine³ were progressively deleted, alanine⁴ and alanine⁵were alternatively replaced by serine, and alanine⁶ was substituted by serine or proline. Both the deletion of the three N-terminal residues and the alanine⁶/proline replacement produces the loss of the helical structure up to lysine⁷. No or minor effects are found in all other cases. From the comparison of the binding data, the energy for the conformational stabilization of the N-terminal region was calculated to amount to 1.4 kcal/mol. The results are discussed in comparison with the known x-ray data of the enzyme, with some predictive rules of secondary structure which were applied to this region and with the known phylogenetic variance of the residues in this region.