Sea urchin sperm head plasma membranes: characteristics and egg jelly induced Ca2+ and Na+ uptake

Sea urchin sperm respond to egg factors with changes in the ionic permeability of their plasma membrane. It has been previously shown that plasma membranes isolated preferentially from sea urchin sperm flagella respond to egg jelly increasing their Ca2+ and Na+ uptake (Darszon et al. (1984) Eur. J. Biochem. 144, 515-522). However, the egg jelly induced acrosome reaction occurs in the sperm head, and there is evidence for an heterogeneous distribution of plasma membrane components within the various regions of this cell. We here report a method for purifying sperm head membranes using positively charged beads according to Jacobson (1977) Biochim. Biophys. Acta 471, 331-335). Under the transmission electron microscope these membranes appeared homogeneous and apparently free of internal membranes. The yield of the preparation was 0.9% of the total protein in the sperm homogenate. The preparation contained less than 5% of the mitochondrial marker cytochrome oxidase, and 10% of the total DNA/mg protein. Surface labeling with 125I indicated a 2.5-3-fold enrichment in specific activity of the head membranes with respect to whole sperm. The SDS band pattern and the lipid composition of this preparation were different from those of isolated flagellar membranes. Phosphatidylcholine was higher in the head membranes, while phosphatidylserine and phosphatidylethanolamine were lower. The head membranes displayed a 1.7-2.3-fold higher Ca2+-ATPase activity and a 2.5-fold lower Na+/K+-ATPase activity, than the flagellar membranes. These results are consistent with a heterogeneous distribution of membrane components along the sea urchin sperm plasma membranes. Isolated head membranes sonicated in the presence of soybean phospholipid liposomes responded to egg jelly with a species-specific increase in Ca2+ and Na+ uptake. As in whole sperm, Ca2+ uptake was inhibited by the Ca2+ channel blocker nisoldipine. A close analog of this compound, [3H]nitrendipine, binds with high affinity to head membranes in a saturable, reversible manner, showing a Kd and Bmax of 31 nM and 5.3 pmol/mg protein, respectively.     

Improved performance of intensive semicontinuous cultures of Scenedesmus by biomass recirculation

The microscopic green alga, Scenedesmus obliquus, was used in a semicontinuous culture system for the tertiary treatment of urban wastewater, with the simultaneous production of usable biomass. Partial biomass recycling was used to increase the productivity of the system by overcoming the limits imposed by the low maximal growth rate of the alga. The biomass to be recycled was collected by simple gravity settling of the removed culture.The culture system was operated at different dilution rates and its productivity measured at each rate. An evaluation of the crude nutrient composition of the algae produced at each dilution rate was also carried out.The system was found to operate stably at dilution rates of up to 0.8 day(-1) which represents a 20% net increase over the maximum dilution rate allowed under the same conditions in a system without recirculation. The composition of the biomass produced varied little over a range of dilution rates, which may be of relevance to its projected end-use.The study indicated that such a system can exploit available light to the full and should be of particular value for the treatment of low-strength wastes such as we employed.     

Comparative study of G- and C-banded chromosomes of five species of Microtidae

G-banded karyotypes were compared in the following species of Microtidae: Microtus nivalis; M. cabrerae; M. arvalis and Arvicola sapidus. Previous observations on A. sapidus and A. terrestris (Díaz de la Guardia & Pretel, Caryologia 32: 183–189, 1979) were also incorporated in this study. The results show that Robertsonian translocations and pericentric inversions are common mechanisms involved in the karyotypic evolution of this group. Interspecific differences in C-banding patterns were also analyzed. Using the karyograph method (Imai et al., Am. Nat. 121: 477–488, 1983), the evolutionary distances of the karyotypes were estimated, and an attempt was made to establish a presumptive phylogenetic tree.     

The origin of 45,X males.

Maleness in association with the karyotype 45,X is a very rare and hitherto unexplained condition previously described in only four or five patients. This study was carried out to determine whether such males might actually possess Y-chromosomal material. Of the two 45,X males studied, one was found to be a low-grade mosaic with a 46,XY karyotype in less than 3% of fibroblasts; all lymphocytes karyotyped were 45,X. Fibroblast DNA from this individual was found to contain Y-specific repeated sequences in 1%-3% the amount observed in the father, consistent with mosaicism for a 46,XY cell line. No Y-specific repeated sequences were detected in the other patient, in whom all mitoses were 45,X. In neither patient were there detectable amounts of any of the single-copy Y-specific DNA sequences for which we tested. Studies of Xg blood groups and of X-linked restriction fragment length polymorphisms indicated that the single X chromosome was of maternal origin in both 45,X male probands. In contrast to the situation in XX males, we can exclude paternal X-Y interchange as the etiology in the cases described here. Our findings are compatible with mosaicism being the explanation of at least some "45,X" males.     

A deletion map of the human Y chromosome based on DNA hybridization.

The genomes of 27 individuals (19 XX males, two XX hermaphrodites, and six persons with microscopically detectable anomalies of the Y chromosome) were analyzed by hybridization for the presence or absence of 23 Y-specific DNA restriction fragments. Y-specific DNA was detected in 12 of the XX males and in all six individuals with microscopic anomalies. The results are consistent with each of these individuals carrying a single contiguous portion of the Y chromosome; that is, the results suggest a deletion map of the Y chromosome, in which each of the 23 Y-specific restriction fragments tested can be assigned to one of seven intervals. We have established the polarity of this map with respect to the long and short arms of the Y chromosome. On the short arm, there is a large cluster of sequences homologous to the X chromosome. The testis determinant(s) map to one of the intervals on the short arm.     

Interactions and quantitative analysis of immunoregulatory cells in the chicken thymus

Step-wise dilution of chicken thymus cell suspensions has been used to sequentially reveal suppressor, effector, and helper cells in these suspensions. The cells were tested either alone or in autologous mixture combinations with peripheral blood lymphocytes (PBL) as a source of effector cells. The assays studied were graft-vs-host reaction (GvHR) and mixed lymphocyte (MLR) reaction, spontaneous cellular cytotoxicity and antibody-dependent cell-mediated cytotoxicity, and mitogen responsiveness to Con A, PHA, and PWM. When tested alone, high numbers of thymus cells (1 X 10(7) gave weak or low responses, with the exception of GvHR, which was high. When this number of thymocytes was mixed with a strongly responding PBL effector population, there was marked suppression of the latter. Nonspecific crowding was excluded as a cause for the decreased responsiveness, and the data therefore demonstrated the presence of suppressor cells in the thymus. With gradual reduction of the thymus cell number in the mixtures, the suppressor activity was lost, but concomitant with this was the appearance of, or a gradual increase in, thymus effector cells giving good responses. Further dilutions of the thymus (to, e.g., 1 X 10(5) cells) depleted the suspension of effector cells, but helper cells capable of markedly amplifying the effector potential of PBL were revealed. The suppressor/helper function of the thymus was not only dependent on the absolute numbers of thymus cells present, but also on the degree of inherent responsiveness of the effector PBL. If the response of PBL alone was strong, a thymus suspension containing both helper and suppressor cells (e.g., 1 X 10(6) cells) caused suppression of the PBL; if the PBL alone were weak, this same thymus cell suspension caused enhancement. The outcome of an immune response is therefore dependent not only on the presence or absence of particular cell types, but also on the ratios between these cells. An imbalance in these ratios in vivo may underlie diseases of immunologic origin, e.g., autoimmunity.     

Cell length in a wee dnaA mutant of Escherichia coli.

The cell length of the short siblings of dividing pairs formed in the absence of replication by two strains of Escherichia coli, OV-25-9 [dnaA46 wee(Am)] and OV-25-10 [dnaA46 wee(AM) supF] was measured. In the presence of Wee, the length of these cells increased to those values expected for newborn wild-type cells growing under similar conditions. In its absence, cell length remained at values near the minimum unit length possible for newborn cells. Our results show that both cell elongation and the action of Wee are independent of DNA replication, being compatible with the role proposed for Wee in coordination between cell elongation and division.     

The origin and ultrastructural characteristics of corticotropin-releasing factor (CRF)-immunoreactive nerve fibers in the posterior pituitary of the rat

Summary A fine network of corticotropin-releasing factor (CRF)-immunopositive fibers was found in the posterior lobe of the pituitary of the rat. The intermediate and distal lobes were free of CRF-immunoreactivity. Varicose, terminal-like axons were frequently observed around capillary vessels. Surgical isolation of the paraventricular nuclei resulted in a complete disappearance of CRF-immunoreactive fibers from the posterior lobe. CRF-immunopositive fibers show the general characteristics of peptidergic axons. These ultrastructural observations support the idea that CRF is secreted into capillary vessels.     

Purification and characterization of 2-enoyl-CoA reductase from bovine liver.

Mitochondrial 2-enoyl-CoA reductase from bovine liver was purified and characterized. A simple three-step purification was developed, involving ion-exchange chromatography to separate the bulk of the NADPH-dependent 2,4-dienoyl-CoA reductase, followed by chromatography on Blue Sepharose and adenosine 2',5'-bisphosphate-Sepharose. Homogeneous enzyme with a subunit Mr of 35 500 is obtained in 35% yield. The Mr of the native enzyme, determined by three different methods, yielded values that suggest that the enzyme is dimeric. NADPH is required as cofactor, and cannot be replaced by NADH. The activity of the purified enzyme towards 2-trans-double bonds in 2-monoene and 2,4-diene structures was investigated. 2-Enoyl-CoA reductase reduced the double bonds in a series of 2-trans-monoenoyl-CoA esters with different chain lengths, but did not exhibit significant activity towards 2-trans-double bonds of 2,4-dienoyl-CoA esters. This result is discussed in the light of analogous observations with enoyl-CoA hydratase.     

Evidence for a rate-limiting role of cysteinesulfinate decarboxylase activity in taurine biosynthesis in vivo

The relationship between activities of enzymes involved in cysteine oxidation and the apparent conversion of cysteine to taurine in vivo were investigated in the rat and cat. Both hepatic cysteinesulfinate decarboxylase activity and the oxidation in vivo of cysteine to taurine were lower in the kitten than in the adult female rat and lower in the latter than in the young male rat. Our data support the hypothesis that cysteinesulfinate decarboxylase plays a rate-limiting role in taurine biosynthesis.