Lake Baikal: a unique place to study evolution of sponges and their stress response in an environment nearly unimpaired by anthropogenic perturbation.

Lake Baikal is considered as a unique place to study evolution. In this review, we report on recent data on the evolution of endemic freshwater sponges of this ancient lake. Nucleotide sequence data support the idea that these sponges are of monophyletic origin and evolved from Spongillidae. Baikalian sponges form the dominating biomass in the benthos of the lake. Data on the expression of the biomarker heat shock protein 70, revealed that the endemic sponge species of Lake Baikal are useful as bioindicators to assess the anthropogenic impact on the lake.     

phnE and glpT Genes Enhance Utilization of Organophosphates in Escherichia coli K-12

Wild-type Escherichia coli K-12 strain JA221 grows poorly on low concentrations (≤1 mM) of diisopropyl fluorophosphate and its hydrolysis product, diisopropyl phosphate (DIPP), as sole phosphorus sources. Spontaneous organophosphate utilization (OPU) mutants were isolated that efficiently utilized these alternate sources of phosphate. A genomic library was constructed from one such OPU mutant, and two genes were isolated that conferred the OPU phenotype to strain JA221 upon transformation. These genes were identified as phnE and glpT. The original OPU mutation represented phnE gene activation and corresponded to the same 8-bp unit deletion from the cryptic wild-type E. coli K-12 phnE gene that has been shown previously to result in phnE activation. In comparison, sequence analysis revealed that the observed OPU phenotype conferred by the glpT gene was not the result of a mutation. PCR clones of glpT from both the mutant and the wild type were found to confer the OPU phenotype to JA221 when they were present on the high-copy-number pUC19 plasmid but not when they were present on the low-copy-number pWSK29 plasmid. This suggests that the OPU phenotype associated with the glpT gene is the result of amplification and overproduction of the glpT gene product. Both the active phnE and multicopy glpT genes facilitated effective metabolism of low concentrations of DIPP, whereas only the active phnE gene could confer the ability to break down a chromogenic substrate, 5-bromo-4-chloro-3-indoxyl phosphate-p-toluidine (X-P_i). This result indicates that in E. coli, X-P_i is transported exclusively by the Phn system, whereas DIPP (or its metabolite) may be transported by both Phn and Glp systems.     

Na+/H+-exchange in A6 cells: Polarity and vasopressin regulation

Summary We have analyzed the mechanism of Na⁺-dependent pH_i; recovery from an acid load in A6 cells (an amphibian distal nephron cell line) by using the intracellular pH indicator 27-bis(2-carboxyethyl)5, 6 carboxyfluorescein (BCECF) and single cell microspectrofluorometry. A6 cells were found to express Na⁺/H⁺-exchange activity only on the basolateral membrane: Na⁺/H⁺-exchange activity follows simple saturation kinetics with an apparent K _mfor Na⁺ of approximately 11 mm; it is inhibited in a competitive manner by ethylisopropylamiloride (EIPA). This Na⁺/H⁺-exchange activity is inhibited by pharmacological activation of protein kinase A (PKA) as well as of protein kinase C (PKC). Addition of arginine vasopressin (AVP) either at low (subnanomolar) or at high (micromolar) concentrations inhibits Na⁺/H⁺-exchange activity; AVP stimulates IP₃ production at low concentrations, whereas much higher concentrations are required to stimualte cAMP formation. These findings suggest that in A6 cells (i) Na⁺/H⁺-exchange is located in the basolateral membrane and (ii) PKC activation (heralded by IP₃ turnover) is likely to be the mediator of AVP action at low AVP concentrations.This work was supported by the Swiss National Science Foundation (Grant No. 32-30785.91), the Stiftung für wissenschaftliche Forschung an der Universität Zürich, the Hartmann-Müller Stiftung, the Sandoz-Stiftung, the Roche Research Foundation, and the Geigy Jubiläumsstiftung. Prof. Dr. V. Casavola and Dr. R. Guerra were supported by a research grant, No. 91.02470.CT14 of the Consiglio Nazionale della Ricerche (C.N.R.) We are grateful to Prof. Dr. B.C. Rossier of the Institute of Pharmacology of Lausanne (Switzerland) for the gift of the A6 cells, to H.P. Gaeggeler for the supply of the necessary culture media and to Jutka Forgo for her excellent help in the day-to-day culturing of the A6 cells. The secretarial assistance of D. Rossi is gratefully acknowledged.     

A characterization of cuprizone-induced giant mouse liver mitochondria

Cuprizone affects the liver of treated mice in a random manner, causing no appreciable change in some cases and inducing the formation of megamito-chondria with altered properties in others. Lack of a full appreciation of this variability may be at the origin of some discrepancies in published work dealing with the properties of cuprizone mouse liver mitochondria (CMLM). CMLM from fully affected livers were remarkably labile and difficult to isolate in a coupled state by homogenization and centrifugation techniques. The integral respiratory chain proteins of CMLM were functionally normal, with the exception of succinic dehydrogenase which showed considerable inhibition. Coupled morphological and functional analysis provided evidence that these properties were independent of CMLM size, a matter which had remained doubtful thus far and bears on the validity of literature reports.Abbreviations MLM mouse liver mitochondria - CMLM cuprizone mouse liver mitochondria - PMS phenazine methosulfate - Mops 4-morphoinopropanesulfonic acid - TMPD tetramethyl-p-phenylenediamine - AA Antimycin A - RCR respiratory control ratio - BSA bovine serum albumin     

Comparison between airborne pollens in Torino and Perugia (Italy) 1982–83–84

Summary By means of two Burkard Volumetric Spore-Traps situated in the center of Torino and Perugia, pollen was sampled between March and August for three years (1982–83–84). The two pollen spectra, with special reference to trees, were compared for pollen levels and duration of season in the two cities. Comments on vegetation in and around Torino and Perugia and meteorological data are compared with the two pollen spectra.      

Chromatin structure and the state of human organism

The state of chromatin in human buccal epithelium cell nuclei upon the influence of sport trainings was investigated. Chromatin state was evaluated in interphase buccal cell nuclei after orcein staining. The heterochromatin granule quantity (HGQ) was estimated in 30 nuclei per sample, and for every donor the mean HGQ value per 30 cells was determined. Donors of masculine sex, aged from 18 to 48 years performed training walks and samples of buccal epithelium were collected. Sportive charges induced the process of chromatin condensation in cell nuclei. After the period of repose (24-48 h) the HGQ decreased to control level therefore the process of chromatin decondensation was observed. The state of chromatin changes in connection with circadian rhythm. Chromatin became more condensed at nighttime and less condensed in the morning. Hormones such as adrenaline, noradrenaline, and hydrocortisone in vitro induced the increase of HGQ.     

The HIV-Tat protein induces chromosome number aberrations by affecting mitosis

To analyze the effects of the HIV-Tat-tubulin interaction, we microinjected HIV-Tat purified protein into Drosophila syncytial embryos. Following the Tat injection, altered timing of the cortical nuclear cycles was observed; specifically, the period between the nuclear envelope breakdown and anaphase initiation was lengthened as was the period between anaphase initiation and the formation of the next nuclear envelope. These two periods correspond to kinetochore alignment at metaphase and to mitosis exit, respectively. We also demonstrated that these two delays are the consequence of damage specifically induced by Tat on kinetochore alignment and on the timing of sister chromatid segregation at anaphase. Furthermore, we show that the expression of Tat in Drosophila larvae brain cells produces a significant percentage of polyploid and aneuploid cells. The results reported here indicate that Tat impairs the mitotic process and that Tat-tubulin interaction appears to be responsible for the observed defects. The presence of polyploid and aneuploid cells is consistent with a delay or arrest in the M phase of a substantial fraction of the cells expressing Tat, suggesting that mitotic spindle checkpoints are overridden following Tat expression.     

The functional response of Ibalia leucospoides (Hymenoptera: Ibaliidae), a parasitoid of Sirex noctilio (Hymenoptera: Siricidae)

We experimentally studied the functional response of the parasitoid Ibalia leucospoides on its host, Sirex noctilio. Our results show a type III functional response, which we suggest in due to a changing probability, in host encounter. We discuss its relevance to the biological control of woodwasp populations in the field.     

Regulation of G0 entry by the Pho80-Pho85 cyclin-CDK complex

Eukaryotic cell proliferation is controlled by growth factors and essential nutrients. In their absence, cells may enter into a quiescent state (G0). In Saccharomyces cerevisiae, the conserved protein kinase A (PKA) and rapamycin-sensitive TOR (TORC1) pathways antagonize G0 entry in response to carbon and/or nitrogen availability primarily by inhibiting the PAS kinase Rim15 function. Here, we show that the phosphate-sensing Pho80-Pho85 cyclin-cyclin-dependent kinase (CDK) complex also participates in Rim15 inhibition through direct phosphorylation, thereby effectively sequestering Rim15 in the cytoplasm via its association with 14-3-3 proteins. Inactivation of either Pho80-Pho85 or TORC1 causes dephosphorylation of the 14-3-3-binding site in Rim15, thus enabling nuclear import of Rim15 and induction of the Rim15-controlled G0 program. Importantly, we also show that Pho80-Pho85 and TORC1 converge on a single amino acid in Rim15. Thus, Rim15 plays a key role in G0 entry through its ability to integrate signaling from the PKA, TORC1, and Pho80-Pho85 pathways.