Sexual differences in the expression of copper deficiency in rats

The present investigation was undertaken to establish whether the severity of copper deficiency in rats fed diets containing fructose is affected by the presence and type of endogenous sex hormones. Intact and castrated male rats and intact and ovariectomized females were fed from weaning a copper-deficient diet (0.6 ppm) containing 62% fructose for 8 weeks. Regardless of castration, male rats were anemic, exhibited heart hypertrophy, and died of the deficiency. However, castration ameliorated the anemia and delayed the mortality. In contrast, none of the females died of the deficiency. It is suggested that in addition to the sex of the animal, levels of testosterone in the male may also play a role in the severity of copper deficiency.     

Light-Regulated Gravitropism in Seedling Roots of Maize

Red light-induced changes in the gravitropism of roots of Zea mays variety Merit is a very low fluence response with a threshold of 10⁻⁹ moles per square meter and is not reversible by far red light. Blue light also affects root gravitropism but the sensitivity of roots to blue is 50 to 100 times less than to an equal fluence of red. In Z. mays Merit we conclude that phytochrome is the sole pigment associated with light-induced changes in root gravitropism.     

Construction of hybrid Tn501/Tn21 transposases in vivo: identification of a region of transposase conferring specificity of recognition of the 38-bp terminal inverted repeats.

In order to study the transposase enzymes of Class II prokaryotic transposable elements, we have constructed genes encoding hybrid transposase proteins. This was done by recombination in vivo between the tnpA genes of transposons Tn501 and Tn21. These hybrid genes can complement in trans a transposition-defective mutant of Tn501. The structures of the products of this complementation indicate whether the specificity of the hybrid transposase in recognising the 38 bp terminal inverted repeats is that of Tn501 or that of Tn21. The determinant of this specificity is in the N-terminal region of the transposase protein, between amino acids 28 and 216. The predicted amino acid sequences so far determined of transposases from the Class II family reveal an area of homology in this region.     

Surface areas of 1-palmitoyl phosphatidylcholines and their interactions with cholesterol.

The activity of the high-molecular-weight beta-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) obtained from culture filtrates of Botryodiplodia theobromae Pat. was affected by added NaCl in such a way that an initial phase of stimulation was followed by a phase of rapid non-linear decrease in velocity and finally by a phase of slow linear decrease in velocity as the concentration of NaCl was increased. In the presence of 0.014 M-sodium acetate/acetic acid buffer (pH 5.0) there was a slight increase in enzymic activity in the presence of low concentrations of dioxan (up to about 10% dioxan) and a rapid decrease in enzymic activity at higher dioxan concentrations, but both effects were mitigated in the presence of 0.1 M buffer. The order of efficiency of added glucosyl acceptors in beta-glucosidase-catalysed reactions was found to be fructose greater than sucrose greater than glycerol greater than methanol. The enzyme was inactivated by the active-site-directed compound conduritol-B-epoxide; but this inactivation was concentration-dependent, was prevented by 10 mM-glucose, and involved an acidic group with pKa 4.3. A rate equation has been derived on the assumption of a mechanism of action involving a solvent-separated and an intimate glucosyl cation-carboxylate ion-pair intermediate and an alpha-glucosyl enzyme intermediate [Umezurike, G. M. (1981) Biochem. J. 199, 203-209]. Calculations based on the application of the derived rate equation and the calculated kinetic parameters show that the rate equation explains the peculiar properties of beta-glucosidase in the presence of added glucosyl acceptors or of NaCl.     

The relative toxicity of a spore preparation of Bacillus thuringiensis var. israelensis against fourth instar larvae of Aedes aegypti and Toxorhynchites amboinensis: suspension feeding compared with enemas and forced feeding

The toxic effect of a spore preparation of Bacillus thuringiensis var. israelensis Berliner Serotype H-14 (Bti) on 4th instar larvae of Aedes aegypti L. and Toxorhynchites amboinensis (Doleschall) was observed when given either in a suspension feeding test or when injected orally as a forced feeding or via the anus as an enema. The A. aegypti larvae showed the greater sensitivity to Bti both because they greatly concentrate the toxin by filter feeding and they are more sensitive to Bti than are the larvae of T. amboinensis. The latter appeared approximately two-fold less sensitive to Bti than the former after taking into account their greater body weight.

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Résumé La toxicité sur des larves de 4ème stade de A. aegypti et T. amboinensis, d'une préparation de spores de B. thuringiensis var. israelensis Berliner sérotype H-14, a été examinée après: injection orale par alimentation forcée, injection anale comme lavement, — le témoin étant une alimentation à partir d'une suspension de spores.Les larves de A. aegypti ont présenté la plus grande sensibilité au Bti d'une part parce qu'elles concentrent beaucoup la toxine avec leur alimentation par filtration, et parce qu'elles sont plus sensibles sensu stricto au Bti. Même en tenant compte de leur poids plus élevé, T. amboinensis est apparu comme deux fois moins sensible au Bti.

     

Electrochemical characteristics of platinum electrodes coated with cytochrome b5-phospholipid monolayers

Platinum electrodes can be coated with cytochrome b5-phospholipid monolayers by the Langmuir-Blodgett technique. Cyclic voltammetry of a series of dyes shows that the coated electrodes become selective for certain electroactive species. The electron transfer reactions of negatively charged species are inhibited at the modified electrode, whereas positively charged species show enhanced reactivity compared with that at a bare metal electrode.     

Effect of growth temperature on the lipids, outer membrane proteins, and lipopolysaccharides of Pseudomonas aeruginosa PAO.

Growth of Pseudomonas aeruginosa PAO1 at 15 to 45 degrees C in tryptic soy broth resulted in changes in the lipids, lipopolysaccharides (LPSs), and outer membrane proteins of the cells. Cells grown at 15 degrees C contained, relative to those cultivated at 45 degrees C, increased levels of the phospholipid fatty acids hexadecenoate and octadecenoate and reduced levels of the corresponding saturated fatty acids. Furthermore, the lipid A fatty acids also showed thermoadaptation with decreases in dodecanoic and hexadecanoic acids and increases in the level of 3-hydroxydecanoate and 2-hydroxdodecanoate as the growth temperature decreased. In addition, LPS extracted from cells cultivated at the lower temperatures contained a higher content of long-chain S-form molecules than that isolated from cells grown at higher temperatures. On the other hand, the percentage of LPS cores substituted with side-chain material decreased from 37.6 mol% at 45 degrees C to 19.3 mol% at 15 degrees C. The outer membrane protein profiles indicated that at low growth temperatures there was an increase in a polypeptide with an apparent molecular weight of 43,000 and decreases in the content of 21,000 (protein H1)- and 27,500-molecular-weight proteins.     

Microflora associated with the internal surfaces of rubber and stainless steel milk transfer pipeline

Sterile sections of rubber and stainless steel milk transfer pipeline were inserted sequentially into a milking installation and soiled with fresh raw milk over a period of 5 d. The resultant adherent microbial population was removed and the generic composition of mesophilic and psychotropic types was determined. In all cases Acinetobacter spp. were found to predominate (59.5-75.6%). The generic composition of the raw milk used to soil the milking unit (with inserted pipe section) was determined once during each 5-d soiling period. In general the milk was found to contain a mixed flora in which Gram-positive organisms predominated.     

Modulation of the membrane potential of the Schwann cell of the squid giant nerve fiber

1. The involvement of second messengers and of other chemical mediators, in the modulation of the membrane potential of the Schwann cell of the giant nerve fiber of the Tropical squid Sepioteuthis sepioidea is described. 2. The involvement of the cyclic nucleotide adenosine 3', 5' monophosphate (cAMP) in mediating the actions of the nicotinic Ach receptors of the Schwann cells is suggested. 3. The presence of octopaminergic receptors in the Schwann cells, mediating their actions through the activation of adenylate cyclase, is also described. 3. Receptors for vasoactive intestinal peptide (VIP) are also present on the Schwann cells, and their actions are mediated via a second messenger system that does not involve the activation of adenylate cyclase. 5. The three independent receptor systems referred above are able to interact in a complex way, which involves both their direct actions on the Schwann cell membrane potential and modulatory effects between the systems.     

Construction of a synthetic Holliday junction analog and characterization of its interaction with a Saccharomyces cerevisiae endonuclease that cleaves Holliday junctions

We describe the construction and characterization of an oligonucleotide Holliday junction analog and characterize its interaction with a Saccharomyces cerevisiae endonuclease that cleaves Holliday junctions. A Holliday junction analog containing four duplex arms and 54 base pairs was constructed by annealing four unique synthetic oligonucleotides. Mixing curve analysis showed that the complex contained a 1:1:1:1 mol ratio of the four unique sequence strands. In addition, a linear duplex with a sequence identical to two of the junction arms was also constructed for use as a control fragment. High resolution gel exclusion chromatography was used to purify and characterize the synthetic junction. The synthetic Holliday junction was found to be a specific inhibitor of a S. cerevisiae enzyme that catalyzes the cleavage of Holliday junctions. Under standard cleavage conditions, 50% inhibition was observed at a synthetic Holliday junction to substrate ratio of 7/1, whereas no inhibition by linear duplex was observed at molar ratios in excess of 150/1. Kinetic analysis showed that Holliday junction was a competitive inhibitor of the reaction and had an apparent Ki = 2.5 nM, although the mode of inhibition was complex. The synthetic Holliday junction was not a substrate for the enzyme, but was found to form a specific complex with the enzyme as evidenced by polyacrylamide gel electrophoresis DNA binding assays.