ACTH secretion in mouse pituitary tumor cells in culture: Inhibition of CRF-stimulated hormone release by somatostatin

Synthetic corticotropin-releasing factor (CRF) stimulates ACTH secretion in the clonal mouse pituitary cell strain AtT20/D16v (D16) in a dose-dependent manner with a half-maximal effect at 2×10^?9M. A single dose of 5×10^?9M CRF maximally stimulates the rate of ACTH secretion during the initial two hrs of treatment. During the period of maximal CRF stimulation intracellular hormone concentration declines progressively to a nadir at 4 hrs. During the ensuing 24 hrs of incubation intracellular hormone levels in CRF-stimulated cells increase gradually toward control values. Somatostatin (SRIF) inhibits the secretory response to CRF. This action of SRIF is dose-dependent with a half-maximal effect at 1×10^?9M and results in decreased maximal ACTH secretion with little effect on the ED₅₀ for CRF.     

The copolymeric structure of pig skin dermatan sulphate. Isolation and characterization of l-idurono-sulphate-containing oligosaccharides from copolymeric chains

Dermatan sulphate was degraded by testicular hyaluronidase and an oversulphated fraction was isolated by ion-exchange chromatography. This preparation, which contained fairly long segments derived from the non-reducing terminal portion of the molecule, was subjected to periodate oxidation under acidic conditions. The oxidized iduronic acid residues were cleaved by reduction-hydrolysis (Smith-degradation) (Fransson & Carlstedt, 1974) or by alkaline elimination. The oligosaccharides so obtained contained both GlcUA (glucuronic acid) and IdUA-SO(4) (sulphated iduronic acid) residues. Copolymeric oligosaccharides obtained after alkaline elimination were cleaved by chondroitinase-AC into disaccharide and higher oligosaccharides. Since the corresponding oligosaccharides obtained by Smith-degradation were unaffected by this enzyme, it was concluded that the carbohydrate sequences were GalNAc-(IdUA-GalNAc)(n)-GlcUA-GalNAc. The iduronic acid-containing sequences were resistant to digestion with chondroitinase-ABC. It was demonstrated that the presence of unsulphated N-acetylgalactosamine residues in these sequences could be responsible for the observed effect. This information was obtained in an indirect way. Chemically desulphated dermatan sulphate was found to be a poor substrate for the chondroitinase-ABC enzyme. Moreover, digestion with chondroitinase-ABC of chondroitinase-AC-degraded dermatan sulphate released periodate-resistant iduronic acid-containing oligosaccharides. It is concluded that copolymeric sequences of the following structure are present in pig skin dermatan sulphate: [Formula: see text] N-acetylgalactosamine moieties surrounding IdUA-SO(4) residues are unsulphated to a large extent.     

Die Wirkung von Dinactin auf die cyclische Photophosphorylierung,die lichtinduzierte ATP-Pa-Austauschreaktion und den lichtinduzierten Protonentransport in Chloroplasten

Summary Dinactin, an antibiotic forming complexes with K⁺ ions, uncouples phosphorylation in chloroplasts without requiring the presence of a substance increasing the permeability of the membrane for protons. To inhibit photophosphorylation, less Dinactin is necessary in the absence than in the presence of K⁺.When added before the light phase, Dinactin affects the light-triggered ATP-P_i exchange reaction in the same way as it does the complete photophosphorylation. Addition of the antibiotic after the activation by light inhibits the exchange reaction independently of the presence of K⁺, possibly by blocking the energy transfer to ATP.The inhibition of the light-induced proton transport by Dinactin is more pronounced in the presence of K⁺ than of Na⁺ ions. The manner in which changes in the permeability of the chloroplast membrane for K⁺ ions caused by Dinactin may influence photophosphorylation and reactions coupled with it is discussed.

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Verwendete Abkürzungen ATP Adenosintriphosphat - ADP Adenosindiphosphat - P_a anorganisches Phosphat - PMS Phenazinmethosulfat - DCPIP Dichlorphenolindophenol - FeCy Ferricyanid - DNP Dinitrophenol - FCCP Carbonylcyanid-p-trifluormethoxyphenylhydrazon - SQ 15859 Squibb Compound 15859     

Das Wachstum infiltrierter Keimlinge

Zusammenfassung Werden Keimlinge vonHelianthus annuus undVicia faba mittels einer Wasserstrahlpumpe mit Wasser infiltriert, so führt dies sofort in allen Organen der Pflanze zu einer sehr starken und mitunter völligen Hemmung des Wachstums. Wirkt der Unterdruck in Luft ein, so daß es hernach zu keiner Wasserfüllung der Interzellularen kommt, so unterbleibt jede Wachstumshemmung.Die Frage nach der Kausalbeziehung zwischen Infiltration und Wachstumshemmung konnte nicht geklärt werden, da die nächstiliegende Annahme, Infiltration führe zu einer Atmungshemmung, durch das Experiment nicht bestätigt werden konnte.Es wird darauf hingewiesen, daß die Zufuhr von Wirk- oder Nährstoffen durch Infiltration eine Methode ist, die in wachsenden Organen nur mit großem Vorbehalt angewendet werden darf, da eine im Wachstum weitgehend gehemmte Pflanze sich in einem anomalen Zustand befindet.Mit 8 Textabbildungen.     

The extracellular nuclease of Serratia marcescens: studies on the activity in vitro and effect on transforming DNA in a groundwater aquifer microcosm

A quantitative endonuclease assay, which relies on the introduction of single and double strand breaks into supercoiled plasmid DNA, was used to study the activity of the extracellular nuclease of Serratia marcescens SM6 in buffer and in groundwater. The parallel enzyme concentration-dependent production of relaxed and linear plasmid molecules suggests that the nuclease produces single and double strand breaks in duplex DNA. Bovine serum albumin stimulated the nuclease activity towards DNA and RNA and increased the stability of the enzyme against thermal inactivation. The DNase activity at 4 °C and 50 °C was almost half of that at the optimum temperature (37 °C). The nuclease was active in groundwater, although the specific activity was lower than in buffer. In a groundwater aquifer microcosm, mineral-adsorbed transforming DNA was substantially less accessible to the nuclease than was dissolved DNA. The data suggest that the extracellular nuclease of Serratia marcescens may contribute to DNA turnover in the environment and that adsorption of DNA to minerals provides protection against the nuclease.Abbreviations GW groundwater GWA groundwater aquifer     

Locus Heterogeneity for Waardenburg Syndrome is Predictive of Clinical Subtypes

Waardenburg syndrome (WS) is a dominantly inherited and clinically variable syndrome of deafness, pigmentary changes, and distinctive facial features. Clinically, WS type I (WS1) is differentiated from WS type II (WS2) by the high frequency of dystopia canthorum in the family. In some families, WS is caused by mutations in the PAX3 gene on chromosome 2q. We have typed microsatellite markers within and flanking PAX3 in 41 WS1 kindreds and 26 WS2 kindreds in order to estimate the proportion of families with probable mutations in PAX3 and to study the relationship between phenotypic and genotypic heterogeneity. Evaluation of heterogeneity in location scores obtained by multilocus analysis indicated that WS is linked to PAX3 in 60% of all WS families and in 100% of WS1 families. None of the WS2 families were linked. In those families in which equivocal lod scores (between −2 and +1) were found, PAX3 mutations have been identified in 5 of the 15 WS1 families but in none of the 4 WS2 families. Although preliminary studies do not suggest any association between the phenotype and the molecular pathology in 20 families with known PAX3 mutations and in four patients with chromosomal abnormalities in the vicinity of PAX3, the presence of dystopia in multiple family members is a reliable indicator for identifying families likely to have a defect in PAX3.