Galanin and pancreastatin inhibit stimulated insulin secretion in the mouse: comparison of effects

The effects of the two intrapancreatic peptides galanin and pancreastatin on basal and stimulated insulin and glucagon secretion in the mouse were compared. It was found that at 2 min after intravenous injection of galanin or pancreastatin (4.0 nmol/kg), basal plasma glucagon and glucose levels were slightly elevated. Galanin was more potent than pancreastatin to elevate basal plasma glucagon levels: they increased from 60 +/- 15 to 145 +/- 19 pg/ml (p less than 0.01) after galanin compared to from 35 +/- 5 to 55 +/- 8 pg/ml (p less than 0.05) after pancreastatin. Plasma insulin levels were lowered by galanin (p less than 0.05), but not by pancreastatin. CCK-8 (6.3 nmol/kg) or terbutaline (3.6 mumol/kg) markedly increased the plasma insulin levels. Galanin (4.0 nmol/kg) completely abolished the insulin response to CCK-8 (p less than 0.001), but pancreastatin (4.0 nmol/kg) was without effect. Galanin inhibited the insulin response to terbutaline by approximately 60% (p less than 0.01), but pancreastatin inhibited the insulin response to terbutaline by approximately 35% only (p less than 0.05). CCK-8 and terbutaline did both elevate plasma glucagon levels by moderate potencies: neither pancreastatin nor galanin could affect these responses. Thus, in the mouse, galanin and pancreastatin both inhibit basal and stimulated insulin secretion, and stimulate basal glucagon secretion. Galanin is thereby more potent than pancreastatin. The study also showed that galanin potently inhibits insulin secretion stimulated by the octapeptide of cholecystokin and by the beta 2-adrenoceptor agonist terbutaline, and that pancreastatin inhibits terbutaline-induced insulin secretion.     

Resonance Raman spectra of chlorophylls dissolved in liquid crystal matrices. II. Order parameters of chlorophyll a in an MBBA + EBBA liquid crystalline mixture

The molecular ordering of molecules embedded in a uniaxial liquid crystalline system has been considered. In particular, planar Chl a molecules in an MBBA + EBBA mixture have been studied by using polarized resonance Raman spectroscopy. The second- and fourth-rank order parameters and the orientational distribution function of Chl a in the nematic MBBA + EBBA liquid crystalline phase are discussed.     

Degradation of diarylethane structures by Pseudomonas fluorescens biovar I

Pseudomonas fluorescens biovar I was isolated from a pulp mill effluent based on its ability to grow on synthetic media containing 1,2-diarylethane structures as the sole carbon and energy source. Analysis of samples taken from cultures of this strain in benzoin or 4,4-dimethoxybenzoin (anisoin), showed that cleavage between the two aliphatic carbons takes place prior to ring fission. Intermonomeric cleavage was also obtained with crude extracts. Substrates of this reaction were only those 1,2-diarylethane compounds that supported growth of the bacterium. The purification and partial characterization of an enzyme that catalyzes the NADH-dependent reduction of the carbonyl group of benzoin and anisoin is also reported.     

Penicillin-binding proteins of protoplast and sporoplast membranes of Streptomyces griseus strains

Membrane-bound penicillin-binding proteins (PBPs) of two Streptomyces griseus strains that sporulate well in liquid and solid medium have been investigated during the course of their life-cycle. The PBP patterns were analyzed by sodium dodecylsulphate polyacrylamide-gel electrophoresis and fluorography. One strain (No. 45 H) has only a single band (mol wt: 27,000) in early log phase, and two additional PBPs of higher mol wt (69,000 and 80,000) in the late log phase. The other strain (No. 2682) possessed two bands with mol wts 27,000 and 38,000 which did not change during its vegetative phase. In strain No. 2682, a new PBP with a mol wt of 58,000 appeared in spore membranes while one of those (mol wt 38,000) present in mycelial membranes disappeared. Our results suggest that appearance of the new PBP in the spore may be associated with the sporulation process. The major PBP band (mol wt: 27,000) present in all stages of the life cycle of these strains, may be characteristic of S. griseus while the other PBPs reflect certain stages of the life cycle. A new method was developed for the production of spore protoplasts by consecutive enzymatic treatments.Abbreviation PBP penicillin-binding protein     

Miller-Dieker syndrome and monosomy 17p13:a new case

Summary A 12-year-old boy is described with multiple anomalies and a de novo terminal deletion of 17p13. Based on clinical examination, the Miller-Dieker syndrome was diagnosed.     

Construction of transposons encoding genes for β-glucosidase,amylase and polygalacturonatetrans-eliminase fromKlebsiella oxytoca and their expression in a range of gram-negative bacteria

DNA fragments containing theKlebsiella oxytoca genes encoding -glucosidase and amylase were cloned into the kanamycin resistance transposon Tn5. Another DNA fragment containing two genes for polygalacturonatetrans-eliminase was cloned into Tn1721. These newly constructed transposons were then each transposed in vivo onto the broad-host-range plasmid pR751 and conjugally transferred to a variety of Gram-negative bacteria. These were then screened for the newly acquired phenotypes.     

Long-term influence of adjuvant therapy on natural killer cell activity in breast cancer

Summary Unstimulated IFN- and IL2-stimulated (NK) cell activities were investigated in patients with breast cancer who had received either local radiotherapy alone or adjuvant chemotherapeutic treatment with CMF combined with radiotherapy 12 to 18 months previously. When tested against the primarily NK-sensitive K562 cell line, patients who had received adjuvant chemotherapeutic treatment with CMF were shown to have a significantly decreased unstimulated and IFN-stimulated NK cell activity, as compared to both patients after radiotherapy only (P<0.002) and P<0.005, respectively) and healthy control persons (P<0.05). The former group of patients also had a significantly decreased IFN-stimulated NK cell activity, when tested against the primarily NK-insensitive Chang hepatoma cell line, as compared to patients after radiotherapy only (P<0.005) and healthy controls (P<0.05). Moreover, patients after radiotherapy only proved to have a significantly increased unstimulated (P<0.01) and IFN-stimulated NK cell activity (K562: P<0.05; Chang hepatoma cell line: P<0.05), as compared to healthy control individuals. In contrast, no difference in IL2-stimulated NK cell activity was detected. The investigation for the expression of CD3 and/or Leu 19 antigens as phenotypic markers of cells with non-MHC restricted cytotoxicity showed a significantly lower percentage of cells with the CD3+ phenotype in patients with breast cancer, irrespective of the chosen post-operative treatment, as compared to healthy controls (P<0.01). Finally, patients with breast cancer who had received radiotherapy only had a significant trend towards an increased percentage of CD³+/Leu 19+ PMNC, as compared to both patients after CMF treatment (P<0.05) and healthy controls (P<0.025). We conclude that patients with breast cancer vary on a long-term basis in their NK activity and in the phenotype of their PMNC depending on their post-operative adjuvant management.Abbreviations NK natural killer cells - IFN interferon - IL 2 interleukin 2 - CMF cyclophosphamide, methotrexate, fluorouracil - ER oestrogen receptor - PMNC peripheral blood mononuclear cells - MHC major histocompatibility complex - CTL cytotoxic T lymphocytes     

Pyruvate decarboxylation in astrocytes and in neurons in primary cultures in the presence and the absence of ammonia

Oxidative decarboxylation of [1-¹⁴C]pyruvate was studied in primary cultures of neurons and of astrocytes. The rate of this process, which is a measure of carbon flow into the tricarboxylic acid (TCA) cycle and which is inhibited by its end product, acetyl CoA, was determined under conditions which would either elevate or reduce the components of the malate-aspartate shuttle (MAS). Addition of aspartate (1 mM) was found to stimulate pyruvate decarboxylation in astrocytes whereas addition of glutamate (or glutamine) had no effect. Since aspartate is a precursor for extramitochondrial malate, and thus intramitochondrial oxaloacetate, whereas glutamate and glutamine are not, this suggests that an increase in oxaloacetate level stimulates TCA cycle activity. Conversely, a reduction of the glutamate content by 3 mM ammonia, which might reduce exchange between glutamate and aspartate across the mitochondrial membrane, suppressed pyruvate decarboxylation. This effect was abolished by addition of glutamate or glutamine or exposure to methionine sulfoximine (MSO). These findings suggest that impairment of MAS activity by removal of MAS constituents decreases TCA cycle activity whereas replenishment of these compounds restores the activity of the TCA cycle. No corresponding effects were observed in neurons.     

Interactions of piperidine derivatives with the nicotinic cholinergic receptor complex from Torpedo electric organ

The interactions of eight piperidine derivatives with nicotinic receptor complexes fromTorpedo californica electric organ were studied using [¹²⁵I]alpha-bungarotoxin ([¹²⁵I]BGT) as a probe for the acetylcholine binding site and [³H]perhydrohistrionicotoxin ([³H]H₁₂-HTX) as a probe for a site associated with the receptor-gated ion channel.Cis- andtrans-2-methyl-6-n-undecanyl piperidines (MUP), major constituents of fire ant venom, had a high-affinity for [³H]H₁₂-HTX binding sites (K_i=0.08–0.24 M), but had no affect on receptor binding. MUP affinity for [³H]H₁₂-HTX binding sites was approximately doubled in the presence of 1 M carbamylcholine. Introduction of a 2-hydroxyl group to the undecanyl side channel had little effect on activity of the alkaloid. The analog 2,6- (but not 3,5-) dimethylpiperidine was a moderately active inhibitor of [³H]H₁₂-HTX binding (K _i-8.8 M). 2-Methylpiperidine was considerably less active (K _i=600 M), although it was more potent than either 3- or 4-methylpiperidine. The affinities of 2,6-dimethylpiperidine and 2-methylpiperidine for [³H]H₁₂-HTX binding sites were decreased in the presence of 1 M carbamylcholine. Carbamylcholine affinity for the receptor was increased by up to 7 fold in the presence of 10 and 32 M MUP, but was decreased in the presence of 2,6-dimethylpiperidine and 2-methylpiperidine. Thecis- andtrans-isomers of MUP were equipotent in producing each of its effects. In these actions, MUP resembles a variety of other compounds derived from 2,6-disubstituted piperidines, including histrionicotoxins, gephyrotoxins and pumiliotoxins. These studies establish the importance of alkyl substitutions in theortho position of the piperidine ring in conferring ion channel specificity, and the importance of substantial alkyl side chains in conferring the ability of channel blockers to stabilize the nicotinic receptor complex in high affinity, desensitized conformations.     

Production and purification of Escherichia coli fimbrial antigen F165

Abstract The production of fimbrial antigen F165 by Escherichia coli strains was found to be dependent on the composition of the culture medium and was repressed in the presence of alanine or high levels of glucose, in anaerobic conditions or at growth temperatures of lower than 37°C. Optimal F165 production was found on a minimal medium containing 1% (w/v) casamino acids (MD-1). F165 antigen was isolated from bacteria by mechanical shearing, precipitated with ammonium sulfate, and purified by deoxycholate treatment and gel filtration on Superose 12. The purified fimbriae retained their native morphology as observed by electron microscopy and consisted of two separate protein subunits with apparent molecular weights of 17 500 and 19 000 on sodium dodecyl sulfate-polyacrylamide gels.