Three tests for shared allelic specificities in the B incompatibility factor of Schizophyllum commune

The incompatibility factors of Schizophyllum commune are each composed of two loci. Several authors have suggested that one locus arose as a duplication of the other, implying that the two loci of a factor have at least one allele in common. Three tests for the detection of such shared specificities in one incompatibility factor are presented here. The data indicate that no alleles are shared by the two loci composing this factor.     

Centromeric Regions Control Autonomous Segregation Tendencies in Single-Division Meiosis of Saccharomyces Cerevisiae

We have previously shown that yeast cdc5 or cdc14 homozygotes can be led through a single-division meiosis in which some of the chromosomes segregate reductionally whereas others, within the same cell, segregate equationally. Chromosomes XI tend to segregate reductionally, whereas chromosomes IV tend to segregate equationally. In this report we present experiments with cdc5 homozygous strains, in which the centromeres of one or both chromosomes XI was replaced by the centromeric region from chromosome IV. Analysis of the products of single-division meioses in these strains demonstrates that the choice between reductional or equational segregation is directed by sequences in the vicinity of the centromeres. Although the choice is made separately for each individual chromosome, the analysis also reveals the existence of a system responsible for coordinated segregation of the two chromosomes of a given pair.     

Anti-Cdc25 antibodies inhibit guanyl nucleotide-dependent adenylyl cyclase of Saccharomyces cerevisiae and cross-react with a 150-kilodalton mammalian protein.

The CDC25 gene product of the yeast Saccharomyces cerevisiae has been shown to be a positive regulator of the Ras protein. The high degree of homology between yeast RAS and the mammalian proto-oncogene ras suggests a possible resemblance between the mammalian regulator of Ras and the regulator of the yeast Ras (Cdc25). On the basis of this assumption, we have raised antibodies against the conserved C-terminal domain of the Cdc25 protein in order to identify its mammalian homologs. Anti-Cdc25 antibodies raised against a beta-galactosidase-Cdc25 fusion protein were purified by immunoaffinity chromatography and were shown by immunoblotting to specifically recognize the Cdc25 portion of the antigen and a truncated Cdc25 protein, also expressed in bacteria. These antibodies were shown both by immunoblotting and by immunoprecipitation to recognize the CDC25 gene product in wild-type strains and in strains overexpressing Cdc25. The anti-Cdc25 antibodies potently inhibited the guanyl nucleotide-dependent and, approximately 3-fold less potently, the Mn(2+)-dependent adenylyl cyclase activity in S. cerevisiae. The anti-Cdc25 antibodies do not inhibit cyclase activity in a strain harboring RAS2Val-19 and lacking the CDC25 gene product. These results support the view that Cdc25, Ras2, and Cdc35/Cyr1 proteins are associated in a complex. Using these antibodies, we were able to define the conditions to completely solubilize the Cdc25 protein. The results suggest that the Cdc25 protein is tightly associated with the membrane but is not an intrinsic membrane protein, since only EDTA at pH 12 can solubilize the protein. The anti-Cdc25 antibodies strongly cross-reacted with the C-terminal domain of the Cdc25 yeast homolog, Sdc25. Most interestingly, these antibodies also cross-reacted with mammalian proteins of approximately 150 kDa from various tissues of several species of animals. These interactions were specifically blocked by the beta-galactosidase-Cdc25 fusion protein.     

Development of secondary sexual characters and their relationship to ontogeny and seasonal reproductive period in Hyphessobrycon igneus (Ostariophysi: Characiformes)

Sexual dimorphism in size, anal‐fin shape and coloration of Hyphessobrycon igneus, Characidae, were examined. Males were more frequent at larger body sizes, confirming body size as a sexually dimorphic trait. Anal‐fin shape and the colour of all fins were the same for females and juveniles, differing only in adult males. Likewise, only adult males had bony hooks on fin rays; larger and more sexually mature males had the most numerous and developed hooks and hooks were most developed in degree and number during peak reproductive periods. Fin hooks regressed in number and developmental degree after the reproductive period, but restarted development with the beginning of the new reproductive period without completely disappearing. Results show that bony hooks have a development and regression cycle related to reproductive seasonality.     

Patterns of Urination of a Blind Subterranean Rodent,Spalax ehrenbergi

Urination patterns of blind mole rats of the Spalax ehrenbergi superspecies of Israel were investigated in the laboratory under various conditions in various types of simulated tunnel systems. Behavioral responses to urine in these systems were observed. The results suggest that mole rats do not mark their tunnels or novel areas, either along the tunnel floor by dropping a urine-trail or at the peripheral ends of the tunnel systems. Urination is not a fear response, and the urine does not contain a chemosensory releaser. Intruders respond (e.g. by sniffing, running away, aggressive threat displays etc.) to occupant's urine in a previously occupied system, and some occupants urinate at a border in ‘no-contact’ encounters with a potential intruder. Male and female mole rats seem to use urine to advertise their ownership of resources by placing their sanitation areas in the vicinity of the nest and food store and may advertise their identity and occupancy at borders when there is potential contact with intruders. Likely similarities between urination patterns in the laboratory and in nature are discussed.     

Liposome encapsulation attenuates hemoglobin-induced vasoconstriction in rabbit arterial segments

Rudolph, Alan S., Anthony Sulpizio, Paul Hieble, VictorMacdonald, Mark Chavez, and Giora Feuerstein. Liposomeencapsulation attenuates hemoglobin-induced vasoconstriction in rabbitarterial segments. J. Appl. Physiol.82(6): 1826-1835, 1997.Free hemoglobin (Hb) induces a potentvasoconstrictor response that may limit its therapeutic application asa red blood cell replacement. We have investigated whetherencapsulation of stroma-free Hb (SFHb) or cross-linked Hb (-Hb)in liposomes modulates Hb vasoactivity in isolated blood vessels.Relaxation of rabbit thoracic vessels was measured before and afterexposure to acellular SFHb, -Hb, and liposome-encapsulated SFHbor -Hb. SFHb and -Hb caused significant inhibition ofcarbachol-induced relaxation at 0.5 mg/dl, whereas encapsulationinhibited vessel relaxation at 30- to 60-fold higher Hb concentrations.The contractile response of rabbit ear arterial segments to electricalstimulation in the presence of acellular -Hb resulted in a 150%increase (EC₁₅₀) in contractileamplitude at 0.23 mg/dl, whereas theEC₁₅₀ for encapsulated -Hbwas 13.7 mg/dl. Mechanistic studies of the vasoconstrictor activity ofHb demonstrated that acellular -Hb had no effect onnorepinephrine release in the rabbit ear artery. In addition, neitheracellular nor encapsulated -Hb preparations inhibited endothelialnitric oxide (NO) synthase activity isolated from bovine pulmonaryartery. However, inhibition of vessel relaxation by acellular orencapsulated -Hb was reversed by the NO donor S-nitrosylpenacillamine, implicatingHb-NO binding as a possible mechanism for the vasoconstrictor response.In vitro stopped-flow kinetic studies of Hb-NO binding showed similarrates of reaction for conversion of oxyhemoglobin to methemoglobin(metHb; <2 ms), followed by rapid conversion of metHb to NO-Hb (300 ms) for both acellular and encapsulated -Hb, demonstrating thatliposome encapsulation does not retard NO-Hb binding. The attenuatedvasoactivity of encapsulated Hb may, therefore, result from the limitedaccess of encapsulated Hb to NO imposed by the physical size of theliposome and reduced penetration of Hb across the vascular endothelium.

     

Vertical Divergence of Cultured Microfungal Communities Through the Depth in Different Soil Formations at Nahal Nizzana,Western Negev Desert,Israel

We examined the depth-wise distribution of microfungi through 0–50-cm crusted sandy and playa profiles at the Nizzana research site, the Negev desert, Israel. A total of 188 species from 77 genera was isolated using the soil dilution plate method. Density of microfungal isolates sharply decreased with depth highly positively correlating with organic matter content at the sandy profiles. High load of solar radiation (at the surface) as well as strongly limited aeration, water infiltration, and increased salinity (at the playa depth) led to dominance of melanin-containing species with large, multicellular conidia both in the topsoil of all profiles and in the deep playa layers, while at 1–30 cm, species producing light-colored small one-celled conidia mostly prevailed. In that way, the above vertical variations resemble differences in the composition of topsoil microfungal communities found between the sites located in the Negev desert and in the Mediterranean region of Israel.     

Nuclear and mitochondr1al DNA synthesis during yeast sporulation

Nuclear and mitochondrial DNA synthesis during sporulation of Saccharomyces cerevisiae has been studied in a wild-type (aα) strain and 3 sporulation deficient strains. We find that in a strain carrying a dominant mutation which prevents sporulation, nuclear DNA synthesis is initiated but not completed; mitochondrial DNA synthesis, on the other hand, does take place. In aa and αα diploids no initiation of nuclear DNA synthesis is seen to occur, and only a very low level of mitochondrial DNA synthesis is observed. We conclude that mitochondrial DNA synthesis in sporulation medium is uncoupled from nuclear DNA synthesis. In addition, the steps at which the sporulation process is arrested in aa and αα cells and in the dominant mutant can be ordered in time as being before and after the initiation of nuclear DNA synthesis.     

Elevated recombination and pairing structures during meiotic arrest in yeast of the nuclear division mutant cdc5

Summary A diploid strain of yeast, homozygous for the mutation cdc5-1, undergoes a normal meiosis at 25° C. At the nonpermissive temperature of 34° C, meiosis is arrested at the first meiotic division, after premeiotic DNA replication and recombination commitment have taken place. Haploidisation commitment does not occur at 34° C. Electron microscopy reveals that synaptons (synaptonemal complexes) are formed and the stage of arrest is characterised by a prevalence of modified synaptons, which consist of paired lateral elements lacking the central elements. Prolonged incubation at this stage of arrest results in unusually high recombination levels, perhaps related to the synaptonal structures observed.Temperature shift-up experiments (transfers of cells from 25° C to 34° C at various times during meiosis) reveal that the CDC5 function is required for both the first and the second divisions of meiosis.