Role of catecholamines in hypotensive response to dieting.

The effect of dieting on blood pressure and catecholamine metabolism was assessed in 11 normotensive obese women by providing first a weight-maintenance regimen high in carbohydrate and then a low-energy diet. All dietary constituents other than carbohydrate were maintained constant throughout the 18-day study. The low-carbohydrate diet led within 48 hours to a 41% fall in the urinary output of 4-hydroxy-3-methoxy mandelate and a significant fall in systolic and diastolic blood pressure. Plasma noradrenaline concentrations also fell and the hypotensive effect of the diet continued despite a maintained total body sodium. Thus the fall in blood pressure appeared to be mediated by changes in catecholamine metabolism independent of sodium intake. This may explain both the usefulness of weight reduction in hypertensive patients and the fainting that occurs in some normotensive obese subjects taking slimming regimens low in carbohydrate.     

Trypsin-induced ATPase Activity in Potato Mitochondria

Potato mitochondria (Solanum tuberosum var. Russet Burbank), which readily phosphorylate ADP in oxidative phosphorylation, show low levels of ATPase activity which is stimulated neither by Mg²⁺, 2,4-dinitrophenol, incubation with respiratory substrates, nor disruption by sonication or treatment with Triton X-100, individually or in concert. Treatment of disrupted potato mitochondria with trypsin stimulates Mg²⁺-dependent, oligomycin-sensitive ATPase activity 10- to 15-fold, suggesting the presence of an ATPase inhibitor protein. Trypsin-induced ATPase activity was unaffected by uncoupler. Oligomycin-sensitive ATPase activity decreases as exposure to trypsin is increased. Incubation at alkaline pH or heating at 60 C for 2 minutes also activates ATPase of sonicated potato mitochondria. Disruption of cauliflower (Brassica oleracea), red sweet potato (Ipomoea batatas), and carrot (Daucus carota) mitochondria increases ATPase activity, which is further enhanced by treatment with trypsin. The significance of the tight association of the inhibitor protein and ATPase in potato mitochondria is not clear.     

Structural and membrane modifying porperties of suzukacillin, a peptide antibiotic related to alamethicin. Part B. Pore formation in black lipid films.

Suzukacillin, a polypeptide consisting of presumably 23 amino acids and 1 phenylalaninol, is produced by a Trichoderma viride strain No. 1037 and it can be isolated from the culture medium. It shows membrane-modifying properties similar to those of alamethicin. Discrete condustance fluctuations indicate the formation of oligomer pores of varying diameter. On the basis of voltage jump relaxation experiments evidence is given that the dimer is the nucleation state from which pore formation starts and the oligomer disappears. According to the voltage-current characteristics, voltage-dependent and voltage-independent conductances are observed. A slow process is involved, which can be interpreted as a change in the equilibrium distribution between different conformations of the suzukacillin monomer at the membrane interphase. This change results from its interaction with the lipid matrix. Differences in experimental observations between suzukacillin and alamethicin are attributed to the relatively larger alpha-helix and higher number of aliphatic side chains of the suzukacillin monomer and to a more intense interaction with the lipid membrane. This leads to a higher probability of forming dimers from monomers and to the occurrence of "inactivation".     

Structural and membrane modifying properties of suzukacillin,a peptide antibiotic related to alamethicin: Part B. Pore formation in black lipid films

Suzukacillin, a polypeptide consisting of presumably 23 amino acids and 1 phenylalaninol, is produced by a Trichoderma viride strain No. 1037 and it can be isolated from the culture medium. It shows membrane-modifying properties similar to those of alamethicin. Discrete conductance fluctuations indicate the formation of oligomer pores of varying diameter. On the basis of voltage jump relaxation experiments evidence is given that the dimer is the nucleation state from which pore formation tion starts and the oligomer disappears. According to the voltage-current characteristics, voltage-dependent and voltage-independent conductances are observed. A slow process is involved, which can be interpreted as a change in the equilibrium distribution between different conformations of the suzukacillin monomer at the membrane interphase. This change results from its interaction with the lipid matrix. Differences in experimental observations between suzukacillin and alamethicin are attributed to the relatively larger α-helix and higher number of aliphatic side chains of the suzukacillin monomer and to a more intense interaction with the lipid membrane. This leads to a higher probability of forming dimers from monomers and to the occurrence of “inactivation”.     

Electrophoretic studies of several hydrolytic enzymes in relation to the cold tolerance of alfalfa.

Two cultivars of alfalfa (Medicago sativa L.), cold-tolerant Vernal and cold-sensitive Sonora, were grown under summer, winter, and dehardening environments to determine the characteristics and relationships of several hydrolytic enzymes to cold tolerance.Soluble enzymatic proteins, extracted from lyophilized crown and root tissues with three different solvents, were separated by polyacrylamide disc-gel electrophoresis and evaluated on the basis of equal dry weights of tissue and equal quantities of protein.Gels assayed for amylases, acid phosphatases, esterases, leucine aminopeptidases, and adenosine triphosphatases exhibited mainly quantitative differences in isoenzymes depending upon extractant, cultivar, and environmental differences. The qualitative differences detected were generally due to differential solubilities of isoenzymes in the three extractants and, to a lesser extent, were related to environmental, cultivar, or stability differences.While activities of esterases, acid phosphatases, and leucine aminopeptidases increased in winter samples, as soluble protein increased, only slight decreases in these enzymes occurred during dehardening. Conversely, activities of amylases were slightly lower in winter samples than in the other samples, and adenosine triphosphatase activity decreased in the most coldtolerant sample.The measured levels of total nonstructural carbohydrate, total soluble sugar, and starch indicated differences between cultivars in starch-sugar conversion. Further, the differential heat stabilities of the isoamylases also provided some information as to the nature of “protected activity” of diastatic enzymes.Differential cryostabilities of peptidases and adenosine triphosphatases detected between cultivars and environments also demonstrated the influence of the extraction medium in maintaining enzyme activity, and these observations may be important to an understanding of cold tolerance in alfalfa. The obvious speculations regarding enzyme stability and the factors involved as related to the cold tolerance of alfalfa require further examination.     

On the carbon and sulphur metabolism in the meromictic Lake Faro (Sicily)

The processes of photosynthesis, chemosynthesis and sulphate reduction were quantitatively studied in the brackish meromitic lake Faro (Sicily) with the aid of C¹⁴ and S³⁵. The layer of “red water” was situated at the depht of the chemocline (13–14 m), where the average concentration of H₂S was 10 mg/l. The total biomass of bacterioplankton consisted in this layer mostly of a brown Chlorobium which reached a wet weight of 30 g/m³. The production of photosynthesis in this layer was 30–60 µg C/l/day. The microbial population in the “red water” was found adapted to an extremely low light intensity and to show a light optimum at the depth µg 9m where only 2,5% of outside light penetrates. The photoautotrophic microflora is consumed by infusoria found in mass in the “red water” layer. An active H₂S-production was found in the water column in the upper part of the H₂S-zone and in the bottom sediments. The data are discussed from the view point of the trophology of meromitic basins.     

Sterically hindered disulfide bridges in cystine diketopiperazine, cysteinyl-cysteine disulfide and derivatives.

L-Cystine diketopiperazine (1), L-cysteinyl-cysteine disulfide -HCl (2), L-cysteinyl-cysteine disulfide methyl ester -HCl (3), and t-butyloxycarbonyl-L-cysteinyl-cysteine disulfide methyl ester (4) are investigated by CD, ultraviolet, 13C NMR, infrared and laser Raman spectroscopy. The temperature dependence of the 13C NMR signals of 1 reveals an exceptionally high energy barrier of deltaGNo. = 15.8 +/- 0.2 kcal/mol for the reversible change in helicity of the inherently dissymmetric disulfide bridge of 1. The P-helical diastereomer predominates in dimethyl-sulfoxide at 25 degrees C, with 80-85% of the molecules having this configuration. The Cotton effects of 1 are larger and show smaller temperature coefficients than the conformationally more mobile cystine compounds 2 and 3. After dissolving crystals of 1 in 95% ethanol there is a time-dependent decrease of the ellipticity of the negative Cotton effect at 225 nm, indicating a conformational change in going from crystal to solution. Besides 1, 2 and 3 are at present the only known examples of cystine derivatives with C-S-S-C torsional angles around 90 degrees, which do not exhibit optical activity in the long wavelength disulfide absorption, as is predicted for 1 from the Linderberg-Michl model. At 305 nm a new weak Cotton effect was discovered for 1. The solvent dependence of the CD spectra is discussed and the infrared and Raman spectra are assigned.     

ZAKβ antagonizes and ameliorates the cardiac hypertrophic and apoptotic effects induced by ZAKα

ZAK (sterile alpha motif and leucine zipper containing kinase AZK), a serine/threonine kinase with multiple biochemical functions, has been associated with various cell processes, including cell proliferation, cell differentiation, and cardiac hypertrophy. In our previous reports, we found that the activation of ZAKα signaling was critical for cardiac hypertrophy. In this study, we show that the expression of ZAKα activated apoptosis through both a FAS‐dependent pathway and a mitochondria‐dependent pathway by subsequently inducing caspase‐3. ZAKβ, an isoform of ZAKα, is dramatically expressed during cardiac hypertrophy and apoptosis. The interaction between ZAKα and ZAKβ was demonstrated here using immunoprecipitation. The results show that ZAKβ has the ability to diminish the expression level of ZAKα. These findings reveal an inherent regulatory role of ZAKβ to antagonize ZAKα and to subsequently downregulate the cardiac hypertrophy and apoptosis induced by ZAKα.     

How honeybee queen attendants become ordinary workers

Honeybee queen attendants disperse queen pheromones to supplement pheromone dispersal by direct queen-worker contacts. With time they lose their dispersal function exponentially due mainly to volatilization of queen pheromones carried on their bodies. The elimination of those airborne pheromones together with the air while ventilating the hive is balanced by pheromone release by the queen. This equilibrium results in a certain level of queen pheromones in the broodnest. The change of the pheromone level (for example, due to loss of the colony of its queen) can serve as a signal to alter the behaviour of the workers and the state of the colony.