Determination of adenosine triphosphate in human semen to estimate the fertilizing potential and to quantify sperm antibodies

The measurement of the ATP content of fresh semen is as accurate as the estimation of sperm motility by conventional methods in discriminating between semen of fertile versus subfertile men. The ATP content of frozen thawed donor semen is correlated with the probability of conception per cycle of insemination. Exact quantification of cytotoxic sperm antibodies in serum is possible with the adenosine-triphosphate-release-cytotoxicity test, since measurement is free of the bias of microscopic examination. The procedure has been simplified by testing only one serum dilution and calculating the ‘sperm toxicity index’.     

Modification of ion transport in lipid bilayer membranes by the insecticides DDT and DDE

In order to elucidate the mechanism of action of organochlorine insecticides on the ion transport in biological membranes, we have studied the effect of DDT and its analog DDE on the structural parameters of phosphatidylethanolamine (PE) planar bilayers. DDT and DDE increase the conductance induced by the hydrophobic ions tetraphenylarsonium (TPhAs⁺) and tetraphenylborate (TPhB^?) in lipid bilayers. Neither DDT nor DDE alters the surface potential of PE monolayers. On the other hand, these organochlorine compounds increase only slightly the electric capacitance of the bilayers. These results are compatible with the hypothesis that these insecticides increase the fluidity of the membrane.     

Biotin transport by a biotin-deficient strain of escherichia coli

Biotin uptake has been investigated using an Escherichia coli biotin requiring auxotroph grown under biotin-deficient conditions. This strain accumulated biotin in the free and bound form. In agreement with a previous report by O. Prakash and M.A. Eisenberg (J. Bacteriol. 120 (1974) 785–791), the biotin entry proved to be an active process which depended on an energy source and was inhibited in the presence of uncouplers. The kinetic parameters have been determined (K_M = 0.05 μM, V_max = 7 pmol/min per mg dry weight). The pool of free biotin could be readily exchanged with external biotin and decreased to a very low level in the absence of an energy source. The use of several biotin analogues revealed that this transport system was quite specific for biotin: slight modifications, for instance in the valeric chain. lowered drastically the affinity for the carrier.     

Membrane function in cystic fibrosis. I. Putrescine transport in normal and cystic fibrosis fibroblasts

Putrescine transport was examined in normal and cystic fibrosis fibroblasts. No differences were observed in accumulation pattern, kinetics of uptake, or efflux between CF and normal cells. In both growing and growth-arrested CF and normal fibroblasts, exogenously supplied putrescine remained unchanged for at least 60 min. Some differences were observed in the response of CF and normal cells to environmental (media) changes.This research was supported by a grant from the Cystic Fibrosis Foundation and by a grant from the National Institutes of Health, Training Grant (GM01316 11 GNC).     

Mg2+ accelerates plastoquinone reduction in chloroplasts

The transient fluorescence quenching induced by the addition of a small amount of an oxidant to illuminated chloroplasts can be used to estimate the rate of electron transported by the oxidant. Using this technique, it is found that the reduction of plastoquinone by the primary acceptor of Photosystem II is sensitive to salt depletion.     

Reproductive morphology of the male Tuatara,Sphenodon punctatus

Over the past decade, studies on reproductive morphology in the Squamata (snakes and lizards) have expanded tremendously. With the accumulation of these studies and revisions of the terminology based on structural similarities and differences, it is imperative to review the work on tuataras to determine whether the structural organization fits the revised terminology of vertebrates. We investigated the morphology of the male reproductive system in the Tuatara, Sphenodon punctatus (Rhynchocephalia), the sister taxon to the Squamata. Previous studies on the Tuatara used a nomenclature for the testicular ducts different from the current terminology for amniotes. The reproductive system in the Tuatara is consistent with reports in the Squamata. Two rete testis tubules exit the testis within a connective tissue sheath similar to that shown in other squamate species and the protherian Echidna. Each rete testis divides into multiple ductuli efferentes that fuse with the epididymis. The epididymis transitions into the ductus deferens where the sperm become more concentrated into spherical bundles. The ductus deferens enters the cloacal urodeum separately from the ureter. An ampulla ureter or ampulla urogenital papilla was not observed, which differs from previous studies of lepidosaurians. Furthermore, a sexual segment of the kidney (SSK) was not observed, consistent with previous studies on the Tuatara.     

Phospholipid dependence of the anion transport system of the human erythrocyte membrane. Studies on reconstituted band 3/lipid vesicles

Band 3 protein extracted from human erythrocyte membranes by Triton X-100 was recombined with the major classes of phospholipid occurring in the erythrocyte membrane. The resulting vesicle systems were characterized with respect to recoveries, phospholipid composition, protein content and vesicle size as well as capacity and activation energy of sulfate transport. Transport was classified into band-3-specific fluxes and unspecific permeability by inhibitors. Transport numbers (sulfate ions per band 3 per minute) served as a measure of functional recovery after reconstitution. The transport properties of band 3 proved to be insensitive to replacement of phosphatidylcholine by phosphatidylethanolamine, while sphingomyelin and phosphatidylserine gradually inactivated band-3-specific anion transport when present at mole fractions exceeding 30 mol%. The activation energy of transport remained unaltered in spite of the decrease in transport numbers. The results, which are discussed in terms of requirements of band 3 protein function with respect to the fluidity and surface charge of its lipid environment, provide a new piece of evidence that the transport function of band 3 protein depends on the properties of its lipid environment just as the catalytic properties of some other membrane enzymes. The well-established species differences in anion transport (Gruber, W. and Deuticke, B. (1973) J. Membrane Biol. 13, 19–36) may to some extent reflect this lipid dependence.     

In vivo and in vitro sugar transport in frog intestine

In the frog intestine, both in vitro and in vivo, experiments were carried out in order to increase knowledge of the mechanism of sugar exit across the basolateral membrane of the enterocyte. The frog intestine was chosen because it lacks crypt cells and, consequently, any external fluid circuit mechanism during sugar transport can be avoided. Therefore, the sugar concentration in the absorbate collected on the serosal side is likely to be similar to that present underneath the basolateral membrane of the enterocyte. Under this condition, cell and absorbate sugar concentrations are similar; yet there is a concomitant net transintestinal sugar transport. Moreover, in in vivo experiments a net transintestinal sugar transport takes place even against a concentration difference. These results suggest that sugar exit across the basolateral membrane is not simply due to a chemically facilitated diffusion.     

A rapid-filtration technique for membrane fragments or immobilized enzymes: measurements of substrate binding or ion fluxes with a few-millisecond time resolution

The construction and use of a filtration system with milliseconds time resolution is described here. This apparatus allows measurements of substrate binding to immobilized enzyme or ion fluxes through membrane vesicles to be performed over a very large time scale, from 10 ms to seconds. The main advantage of this system compared to the widely used quench-flow technique is that it does not require the use of an inhibitor. Following adsorption of the enzyme in an adequately chosen filter, the reaction is allowed to proceed within the filter during a forced filtration of a buffer containing the reactive substrate (or of a washing solution in the case of efflux measurements). The design allows the duration of filtration and buffer flux to be finely and reproducibly controlled. This paper illustrates the use of this rapid-filtration system for time-resolved measurements of calcium binding and transport by sarcoplasmic reticulum Ca-ATPase and of the initial phase of ADP transport by the ADP/ATP carrier of intact mitochondria.