L-Arabinose induces synthesis of secreted beta-galactosidase in the filamentous fungus penicillium canescens

The mechanism of induction of secreted beta-galactosidase was studied in the filamentous fungus Penicillium canescens. L-Arabinose and its metabolite L-arabitol induce the synthesis of the enzyme. Apart from beta-galactosidase, L-arabinose induces the synthesis of other extracellular carbohydrolases including alpha-L-arabinofuranosidase. Increasing L-arabinose concentration above 1 mM or addition of other carbon sources results in carbon catabolite repression of the synthesis of the secreted enzymes. The data suggest that arabinofuranosidase can regulate the synthesis of secreted enzymes in P. canescens, thus controlling the level of free L-arabinose.     

Cryptic heterokaryons in Saccharomyces cerevisiae strains: pseudopleiotropic suppression in the multiple marked YPH857 strain

The yeast strain YPH857 carrying multiple genetic markers was shown to segregate clones that had the pleiotropic suppression phenotype. The phenotype was designated Ppsu+. This suppression involves deletion alleles of the TRP1 and HIS3 genes and an insertion in the URA3 gene. Unlike the original YPH857 culture that carries an unidentified mutation of resistance to cycloheximide, the Ppsu+ clones exhibited a decreased level of resistance to this inhibitor of protein synthesis. In addition, they have a lower mating ability and can produce asci on a standard medium for sporulation. A comparative analysis of total DNA from the YPH857 strain and Ppsu+ segregants by Southern blotting provided evidence for the presence of an extraneous nucleus in these segregants. Ppsu+ strains were shown to contain wild-type alleles, apart from deletion and insertional alleles typical for the YPH857 strain. Moreover, they contain the 2 microns DNA of the Scp3 type with deletion of one of the two EcoRI and HpaI recognition sites (whereas the 2 microns DNA of YPH857 belongs to the Scp1 type) and exhibit heterogeneity with respect to the presence of one EcoR1 recognition site in the gene of 5S ribosomal RNA. It was supposed that the "cryptic" nucleus belongs to a strain of low viability and can survive as an unexpressed DNA in a small fraction of cells. Nuclei from the cryptic and YPH857 strains can be fused at a low rate to yield Ppsu+ cells capable of sporulation. In certain cases, a Ppsu+ clone may be heterogeneous: some of its cells contain nuclei in an unfused heterokaryotic state. This assumption has been confirmed by selecting Cyhr colonies with the original YPH857 genome among Ppsu+ clones on the cycloheximide-containing medium.     

Diversity among bacteria isolated from the deep subsurface

Culturable bacteria from the deep subsurface (179 m) at Cerro Negro, New Mexico were isolated and characterized. The average number of viable aerobic bacteria was estimated to be 5×10⁵g^–1 of sediment, but only about 0.1% of these could be recovered on agar medium when incubated under aerobic conditions. Of 158 strains isolated from this depth, 92 were characterized by cellular fatty acid profiles (FAME), 36 by analysis of partial 16S rDNA sequences, and 44 by rep-PCR genome fingerprint analysis using three different sets of oligonucleotide primers (REP, BOX, or ERIC). These analyses showed the majority of isolates (67%) were Gram-positive bacteria and primarily members of genera with a high %G+C DNA. The remaining isolates were -subdivisionProteobacteria (19%) and members of the flavobacteria group (14%). The diversity indices based on these different methods of characterization were very high suggesting this subsurface habitat harbors a highly diverse microbial community.     

Co-activation of RanGTPase and inhibition of GTP dissociation by Ran-GTP binding protein RanBP1.

RCC1 (the regulator of chromosome condensation) stimulates guanine nucleotide dissociation on the Ras-related nuclear protein Ran. Both polypeptides are components of a regulatory pathway that has been implicated in regulating DNA replication, onset of and exit from mitosis, mRNA processing and transport, and import of proteins into the nucleus. In a search for further members of the RCC1-Ran signal pathway, we have identified proteins of 23, 45 and 300 kDa which tightly bind to Ran-GTP but not Ran-GDP. The purified soluble 23 kDa Ran binding protein RanBP1 does not activate RanGTPase, but increases GTP hydrolysis induced by the RanGTPase-activating protein RanGAP1 by an order of magnitude. In the absence of RanGAP, it strongly inhibits RCC1-induced exchange of Ran-bound GTP. In addition, it forms a stable complex with nucleotide-free RCC1-Ran. With these properties, it differs markedly from guanine diphosphate dissociation inhibitors which preferentially prevent the exchange of protein-bound GDP and in some cases were shown to inhibit GAP-induced GTP hydrolysis. RanBP1 is the first member of a new class of proteins regulating the binding and hydrolysis of GTP by Ras-related proteins.     

Estimation of the number of full sibling families at an oviposition site using RAPD-PCR markers: applications to the mosquito Aedes aegypti

There are many species in which groups of individuals encountered in the field are known to consist of mixtures of full-sibling families. We describe a statistical technique, based on the use of random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) markers, that allows for the estimation of the number of families contained in these groups. We test the technique on full-sibling families of the mosquito Aedes aegypti, a species that distributes its eggs among several locations. Mixtures of 10 families with 15 individuals per family were analyzed using 40 RAPD-PCR loci amplified by 5 primers. Our analysis accurately estimated the number of families. The technique was accurate when the number of families was small or when family sizes were small and variable.     

Damaging effect of 3H-uridine on tissue culture cells during the logarithmic and stationary phases of growth]

The Chinese hamster fibroblasts entered the stationary phase of growth after 5.5 days of cultivation. The induction of the culture proliferation occurred within the first 4 hrs of cultivation in the fresh nutrient medium. After addition of 3H-uridine in high concentration and with high specific activity (75 micron Cu/M and 23 Cu/mM), in the stationary phase a lesser number of cells with aberrations and a higher mitotic index were noted than in the logarithmic phase. 3H-uridine injured the cells in the stationary phase of growth but to a lesser extent than those in the logarithmic phase, i. e. during the intensive RNA synthesis in cells.     

The role of the structural organization of apoprotein E in cholesterol binding

The ability of some proteins to bind cholesterol was accompanied by a decrease of turbidity of aqueous cholesterol suspensions and correlated with a quantity of arginine residues in them. Maximum clearing of aqueous cholesterol suspensions at the addition of proteins containing equimolar arginine concentrations was observed in the presence of apoproteins E and A-I. Optical rotatory dispersion spectra of apoprotein E, polyarginine and histone H3 have shown the influence of sterol on the secondary structure of apoprotein E only.     

Effect of tetanus toxin on mechanisms by which calcium ions regulate transmitter secretion at the neuromuscular junction

Phrenicodiaphragmal rat preparations were used to study the transmitter secretion by intracellular recording of end plate potentials (EPP) and miniature EPP (MEPP). In tetanus toxin-poisoned terminal, the regulatory effect of the external gradient of Ca2+ was abolished as evidenced by the fact that spontaneous secretion did not differ from that in calcium-free solution in health, as the external concentration of Ca2+ rose from 0 to 20 mM. Calcium ionophore A 23187 in intact terminals activated spontaneous release of the transmitter, but did not affect the poisoned terminal. Ouabain enhanced spontaneous secretion both in health and in poisoning. 4-Aminopyridine (4-AP) did not change the frequency of MEPP, while "giant" MEPPs that reflect spontaneous synchronization of the release of quants occurred both in health and in poisoning. 4-AP potentiated the reactivation effects of rhythmic stimulation of poisoned synapses, particularly with reference to the evoked release and led to the recovery of transmission. It is likely that tetanus toxin fixed by gangliosides of the presynaptic membrane prevents, in this particular case, the functioning of both endo- and exogenous ionophoroses that transport Ca2+ to the "active zones", without affecting their asynchronous supply from the intracellular depots.     

Effect of "immune" RNA on various types of cells interacting in the immune response]

Simultaneous injection of marrow cells previously incubated with "immune" RNA, thymus cells and sheep red cells to X-ray treated mice resulted in a greater accumulation of antibody-forming cells in the spleen, as compared to mice inoculated with intact cells or with those incubated with normal RNA. Preliminary incubation of thymus cells with "immune" RNA did not affect the accumulation of antibody-forming cells. Incubation of peritoneal exudate cells with "immune" or normal RNA failed to influence the mode of accumulation of the antibody-forming cells either.     

Effect of trauma on space-time organization of B-dependent area of the regional lymph node cortex

In the experiment performed on 238 non-inbred white mice it has been demonstrated that after trauma in the concha auricularis population density (PD) of immune-competent cells in the germinative center (GC) and in the crown of the regional lymph node (LN) changes. The PD of small lymphocytes increases, and the PD of mitotically dividing cells, immunoblasts, plasmoblasts, immature and mature plasmocytes decreases sharply in both zones. The increase of small lymphocytes PD in the regional LN after the trauma is obviously connected with intensification of their inflow from the lesion focus. Inhibition of proliferation and differentiation of the immune-competent cells in the GC of the crown is a response to the operation stress. During the posttraumatic period both spectral composition and parameters of the constituents of rhythmical alteration of the cells PD change both in the GC and in the crown. As a rule, displacement of acrophase and decrease in amplitude of the rhythm take place. Total power of the process for various types of immune-competent cells alters unequally. In the spectral composition of the rhythmicity amount of circadian components increases, their power increases, too. This demonstrates an increase of central hormonal effects during the posttraumatic period. After trauma fluctuations of the cells PD of the plasmacytic line, as well as in mitotically dividing cells with a 7-hour's period, which has been revealed in intact animals before the trauma, are preserved. This demonstrates a relative independence of the given synchronizer of rhythmicity at a tissue level from any influence of the higher regulatory center.