Spiral growth in the radially-expanding piloboloid mutants ofPhycomyces blakesleeanus

The growth zone of the sporangiophore of a piloboloid mutant,pil, ofPhycomyces expands radially at an increased rate until the growth zone becomes nearly spherical, in sharp contrast to that of the wild-type sporangiophore which exhibits longitudinal elongation only and is conical. The rotation of thepil sporangiophore reverses its direction from clockwise (CW) to counterclockwise (CCW) during the period of increased radial expansion, and the CCW rotation continues as long as does the radial expansion. The direction of rotation and the time of reversal are correlated with the relative rates of cell-wall expansion in the longitudinal and transverse directions. The CCW rotation of the sporangiophore of this mutant can be explained by the behavior of the microfibrils, as previously proposed to explain the rotation of the wild-type sporangiophore.Abbreviations CW clockwise - CCW counterclockwise — both as viewed from above     

Effect of propranolol on glycerol induced acute renal failure in rats

The effect produced by propranolol, administered for a prolonged period of time and in large doses, on renal function in rats has been studied, as well as the modifications induced by this treatment in an experimental model of acute renal failure, and the effects of a single dose of propranolol given 1 hour before provoking failure. Propranolol, administered chronically, causes sodium and water retention and increases creatinine clearance. Acute renal failure induced by glycerol in rats treated for 7 days with propranolol is less severe than the one produced in untreated animals. In this ARF model, a single dose of propranolol does not seem to have a protective effect.     

Effect of temperature on the kinetics of electron transfer from the tetraheme cytochrome to the primary donor in Rhodopseudomonas viridis.

The kinetics of electron transfer from the third highest potential heme (c-552, Em = +20 mV) to the primary donor (P-960) have been measured by flash absorption spectroscopy in isolated reaction centers of Rhodopseudomonas viridis between 300 K and 7 K. The data are analyzed on the basis of three exponential components with a very fast phase (t1/2 = 120 ns) dominating at high temperature and a very slow one (t1/2 = 1.2 ms) at low temperature. This multiphasic behavior is interpreted in terms of the existence of three states with a temperature-dependent population and a very limited effect of the temperature on the kinetics for each state.     

Cortisol influence on some typical parameters of protein malnutrition in rats (author's transl)

A daily v.s. dose of cortisol administered to rats, induces certain metabolic modifications, which after using the "pair-fed" system have been proven to be at least partially independent of the ingesta decrease originated by cortisol. Both cortisol treatment and experimental proteic malnutrition, originate a decrease in corporal weight, a lessening of the gamma-globulins plasmatic fraction, and an elimination increase in total nitrogen, protein, creatine and creatinine in urine. Cortisol treatment determines an increase in blood red cells number, as well as an increase in total serum proteins, especially albumin, without provoking a lessening in the beta-globulins fraction, as happens in cases of proteic malnutrition.     

A.C. cable theory and its implications on the measurements of the membrane electric parameters

The solution to the a.c. cable equations for a leaky non-inductive coaxial cable is presented. It is shown that the exact solution can be expressed in terms of a simple Ohm's law formulation modified by multiplicative factors. A numerical analysis of these factors shows that the formulation reduces to a simple Ohm's law for the case of infinite impedance terminations, if the voltage is recorded at a distance 0·421/λ from the centre of a midpoint current injection, 1 is the half-length of the cell and A the space constant. The same result applies to the case of external current injection if the voltage is recorded at a distance of 0·581/λ from the centre of the cell segment of length 21. This thus allows an easy and accurate computation of the membrane resistance and capacitance. It is also shown that the accuracy obtained in these computations can be estimated quantitatively. The actual values of the accuracy obtained in a.c. studies of Nitella translucens are presented.     

Limited overlapping roles of P15(INK4b) and P18(INK4c) cell cycle inhibitors in proliferation and tumorigenesis

Entry of quiescent cells into the cell cycle is driven by the cyclin D-dependent kinases Cdk4 and Cdk6. These kinases are negatively regulated by the INK4 cell cycle inhibitors. We report the generation of mice defective in P15(INK4b) and P18(INK4c). Ablation of these genes, either alone or in combination, does not abrogate cell contact inhibition or senescence of mouse embryo fibroblasts in culture. However, loss of P15(INK4b), but not of P18(INK4c), confers proliferative advantage to these cells and makes them more sensitive to transformation by H-ras oncogenes. In vivo, ablation of P15(INK4b) and P18(INK4c) genes results in lymphoproliferative disorders and tumor formation. Mice lacking P18(INK4c) have deregulated epithelial cell growth leading to the formation of cysts, mostly in the cortical region of the kidneys and the mammary epithelium. Loss of both P15(INK4b) and P18(INK4c) does not result in significantly distinct phenotypic manifestations except for the appearance of cysts in additional tissues. These results indicate that P15(INK4b) and P18(IKN4c) are tumor suppressor proteins that act in different cellular lineages and/or pathways with limited compensatory roles.     

Role of Cytoskeleton Proteins in the Morphological Changes During Apoptotic Cell Death of Cerebellar Granule Neurons

Cytoskeleton proteins are substrates for proteases and further apoptotic death. We evaluated the participation of cytoskeleton in morphological changes during cell death induced by two apoptotic conditions, potassium deprivation (K5) and staurosporine, in cerebellar granule neurons (CGC). We found that K5 induced somatic damage, but neurites were relatively preserved, which corresponded to the reorganization of actin and α-tubulin in neurites. Staurosporine (STS) induced an early alteration of neurites with reorganization of cytoskeleton proteins in somas. Caspase inhibitor ZVAD totally inhibited STS-induced α-tubulin reorganization and partially blocked STS-induced actin reorganization. α-tubulin and actin reorganization induced by K5 was affected by ZVAD. Calpain inhibitor (IC1) did not affect α-tubulin or actin reorganization induced by STS, K5 or ionomycin. Neither ZVAD, nor IC1 changed α-tubulin or actin levels upon K5 treatment. STS increased α-tubulin and actin levels, but neither ZVAD nor IC1 changed α-tubulin levels upon STS treatment. In contrast, ZVAD reduced the STS-induced increase of actin. These results suggest that CGC cytoskeleton proteins undergo a differential expression and reorganization depending on the apoptotic condition.     

YphC and YsxC GTPases assist the maturation of the central protuberance,GTPase associated region and functional core of the 50S ribosomal subunit

YphC and YsxC are GTPases in Bacillus subtilis that facilitate the assembly of the 50S ribosomal subunit, however their roles in this process are still uncharacterized. To explore their function, we used strains in which the only copy of the yphC or ysxC genes were under the control of an inducible promoter. Under depletion conditions, they accumulated incomplete ribosomal subunits that we named 45S_YphC and 44.5S_YsxC particles. Quantitative mass spectrometry analysis and the 5–6 Å resolution cryo-EM maps of the 45S_YphC and 44.5S_YsxC particles revealed that the two GTPases participate in the maturation of the central protuberance, GTPase associated region and key RNA helices in the A, P and E functional sites of the 50S subunit. We observed that YphC and YsxC bind specifically to the two immature particles, suggesting that they represent either on-pathway intermediates or that their structure has not significantly diverged from that of the actual substrate. These results describe the nature of these immature particles, a widely used tool to study the assembly process of the ribosome. They also provide the first insights into the function of YphC and YsxC in 50S subunit assembly and are consistent with this process occurring through multiple parallel pathways, as it has been described for the 30S subunit.     

Mascot file parsing and quantification (MFPaQ), a new software to parse, validate, and quantify proteomics data generated by ICAT and SILAC mass spectrometric analyses: application to the proteomics study of membrane proteins from primary human endothelial cells

Proteomics strategies based on nanoflow (nano-) LC-MS/MS allow the identification of hundreds to thousands of proteins in complex mixtures. When combined with protein isotopic labeling, quantitative comparison of the proteome from different samples can be achieved using these approaches. However, bioinformatics analysis of the data remains a bottleneck in large scale quantitative proteomics studies. Here we present a new software named Mascot File Parsing and Quantification (MFPaQ) that easily processes the results of the Mascot search engine and performs protein quantification in the case of isotopic labeling experiments using either the ICAT or SILAC (stable isotope labeling with amino acids in cell culture) method. This new tool provides a convenient interface to retrieve Mascot protein lists; sort them according to Mascot scoring or to user-defined criteria based on the number, the score, and the rank of identified peptides; and to validate the results. Moreover the software extracts quantitative data from raw files obtained by nano-LC-MS/MS, calculates peptide ratios, and generates a non-redundant list of proteins identified in a multisearch experiment with their calculated averaged and normalized ratio. Here we apply this software to the proteomics analysis of membrane proteins from primary human endothelial cells (ECs), a cell type involved in many physiological and pathological processes including chronic inflammatory diseases such as rheumatoid arthritis. We analyzed the EC membrane proteome and set up methods for quantitative analysis of this proteome by ICAT labeling. EC microsomal proteins were fractionated and analyzed by nano-LC-MS/MS, and database searches were performed with Mascot. Data validation and clustering of proteins were performed with MFPaQ, which allowed identification of more than 600 unique proteins. The software was also successfully used in a quantitative differential proteomics analysis of the EC membrane proteome after stimulation with a combination of proinflammatory mediators (tumor necrosis factor-alpha, interferon-gamma, and lymphotoxin alpha/beta) that resulted in the identification of a full spectrum of EC membrane proteins regulated by inflammation.