Interrelationships between water and cellular metabolism inArtemia cysts

Cysts of the crustaceanArtemia are a useful model for studies on intracellular water because they are capable of essentially complete and reversible desiccation. We have used a variety of techniques on this system, the present work being an attempt to estimate the density of intracellular water (ρ_w). The density of individual cysts was evaluated from sedimentation velocity. Heptane displacement methods were used to determine the volume of a known mass of cysts, from which the density was calculated. The two methods produce comparable results. It was shown that the densities and water contents of large masses of cysts accurately reflect those of individual cysts. Cyst densities (ρ_c) were determined over the entire range of water content from 0 to 0.63 weight fraction of water (W _f), and temperature dependence was measured for 0.61W _f over 2–41°C. The following refer to 25°C. No marked change was detected in ρ_c until the water content exceeded 0.15W _f, at which ρ_c decreased as a linear function of Wf to maximum water content. However, the cyst does not behave ideally in the sense that the densities of the nonaqueous components and added water are not additive as a function ofW _f. The partial specific volume of water in cysts at maximum hydration was estimated to be 3% larger than that of pure water. These observations are compared with density measurements on other systems, and with previous findings on the physical properties of water in this system.     

Sex-related differences in first-stage impedance cardiographic variables

Impedance cardiography (ZCG), a noninvasive technique used to determine stroke volume and ventricular performance, is currently being utilized more extensively in psychophysiological research and may also prove a useful tool in the control of hypertension. To date, most studies employing ZCG have tested male subjects or patients. However, women and men differ on two important parameters used to calculate stroke volume: thoracic impedance (Zo), and the first derivative of change in impedance over time (dZ/dt_min). Examination of the clinical records of 19 females and 19 males, all nonmedicated, indicated that women had higher Zo levels (F(1, 36)=46.2,p<.0001) and higher dZ/dt_min levels (F(1, 36)=51.8, p<.0001), although calculated stroke volume indexes did not differ. A second sample of 10 women and 8 men, all healthy and nonmedicated, confirmed these findings. The differences in Zo are not due entirely to sex differences in height, weight, percent body fat, and subscapula skin-fold thickness, although these factors differ across sexes. It is important for researchers and clinicians utilizing ZCG with female subjects to be aware of these differences.     

An analysis of proton fluxes coupled to electron transport and ATP synthesis in chloroplast thylakoids

Electron transport, phosphorylation and internal proton concentration were measured in illuminated spinach chloroplast thylakoid membranes under a number of conditions. Regardless of the procedure used to vary these parameters, the data fit a simple chemiosmotic model. Protons from Photosystem II did not appear to be utilized differently from those derived from Photosystem I. The maximal phosphorylation efficiency ($\text{P}\text{e}{}_2$) for photophosphorylation in washed thylakoids under oxidizing conditions is likely to be $\text{4}\text{3}$. This value is consistent with a proton-to-electron-pair ratio of 4 for electron flow through both photosystems and a proton-to-ATP ratio of 3 for the chloroplast proton-ATPase.     

Inhibition of phosphate transport in human erythrocytes by water-soluble carbodiimides

Phosphate entry into human erythrocytes is irreversibly inhibited by treatment of the cells with the water-soluble carbodiimides 1-ethy1-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and 1-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide metho-p-toluene sulfonate (CMC) in the absence of added nucleophile. EDC is the more potent inhibitor (40% inhibition, 2 mM EDC, 5 min, 37°C, 50% hematocrit, pH 6.9), while more than 20 mM CMC is required to give the same inhibition under identical conditions. EDC inhibition is temperature-dependent, being complete in 5 min at 37°C, and sensitive to extracellular pH. At pH 6.9 only 50% of transport is rapidly inhibited by EDC, but at alkaline pH over 80% of transport is inhibited. Inhibition is not prevented by modification of membrane sulfhydryl groups but is decreased in the presence of 4,4′-dinitrostilbene-2,2′-disulfonic acid (DNDS), a reversible competitive inhibitor of anion transport. EDC treatment leads to crosslinking of erythrocyte membrane proteins, but differences between the time course of this action and inhibition of transport indicate that most transport inhibition is not due to crosslinking of membrane proteins.     

Substrate Degradation and Pressure Tolerance of Free-Living and Attached Bacterial Populations in the Intestines of Shallow-Water Fish

This report compares recovery of non-O1 Vibrio cholerae strains from seven California coastal sites during the winter and summer of 1983. A total of 41 identified and 27 presumptive nn-O1 V. cholerae strains were recovered from six of seven coastal sites in the summer. A 5-to 56-fold increase in the numbers of organisms isolated from different sites occurred in the summer months, when water temperatures were 1.9 to 5.1 degrees C higher. At the three sites where the highest levels of non-O1 V. cholerae were found, pollution, as measured by the total number of coliforms, exceeded the legal limit (less than 1,000 coliforms per 100 ml.).     

Effect of Monensin on Growth and Methanogenesis of Methanobacterium formicicum

Monensin inhibited methanogenesis from formate but not from H₂-CO₂ by resting-cell suspensions of Methanobacterium formicicum. The antibiotic severely inhibited growth on formate. The lag phase of H₂-CO₂-grown cultures was prolonged by monensin, but these cultures recovered from the initial inhibition. The recovery did not result from the development of a monensin-resistant population or inactivation of the antibiotic.     

Ribosyl-diphthamide: Confirmation of structure by fast atom bombardment mass spectrometry

Diphtheria toxin inactivates protein synthesis elongation factor 2 by attaching ADP-ribose to an unusual post-translational amino acid derivative, diphthamide, in the factor. Previously, we prepared ribosyl-diphthamide from the ADP-ribosyl-factor and proposed on the basis of NMR spectral analysis that it is 1-α-d-ribofuranosyl-2-[3-carboxyamido-3-(trimethylammonio)propyl]histidine [N. J. Oppenheimer, and J. W. Bodley, (1981) J. Biol. Chem.256, 8579–8581 and op. cit.]. Now, using fast atom bomardment mass spectrometry, the intact cation of ribosyl-diphthamide has been observed in the gas phase. The theoretical mass of the structure proposed for ribosyl-diphthamide uniquely agrees with the observed mass of the inact cation of the compound to within 2 ppm. Collisional activation decomposition mass spectral analysis provided additional structural confirmation. Thus, although the compound has not been synthesized, all available evidence appears uniquely consistent with the structure of ribosyl-diphthamide previously proposed.     

Chromosomal transplantation

Dissociated cells of middle-to-late blastulae were exposed to 0.1 mg colchicine/ml and achieved 92% metaphase arrest. These cells contained a haploid set of Bombina maxima (Anura:Discoglossidae) chromosomes. When transplanted into the enucleated eggs of B. orientalis, some donor cells stimulated development to the late blastula and middle gastrula stages. — Most (17/20) of the embryos resulting from chromosomal transplantation were nonmosaic aneuploids. A high percentage of recipient egg enucleation (93%), the ratio of long-to-short chromosomes, and the presence of species-specific marker chromosomes proved that chromosomes were transplanted from the donor cells. Therefore, metaphase chromosomes lacking intact spindle apparatuses were injected into and incorporated by amphibian eggs. These chromosomes were replicated in all cells of the resulting embryos. The aneuploidy of these embryos is explained by an inability of the recipient egg to locate and replicate many transplanted chromosomes (44%) before first cleavage.