Polypeptide translocation machinery of the yeast endoplasmic reticulum

Proteins enter the secretory pathway by two general routes. In one, the complete polypeptide is made in the cytoplasm and held in an incompletely folded state by chaperoning adenosine triphosphatases (ATPases) such as hsp70. InSaccharomyces cerevisiae, fully synthesized secretory precursors engage the endoplasmic reticulum (ER) membrane by interaction with a set of Sec proteins comprising the polypeptide translocation apparatus (Sec61p, Sec62p, Sec63p, Sec71p, Sec72p). Productive interaction requires displacement of hsp70 from the precursor, a reaction that is facilitated by Ydj1p, a homologue of theEscherichia coli DnaJ protein. Both DnaJ and Ydj1p regulate chaperone activity by stimulating the ATPase activity of their respective hsp70 partners (E. coli DnaK andS. cerevisiae Ssa1p, resepectively). In the ER lumen, another hsp70 chaperone, BiP, binds ATP and interacts with the ER membrane via its contact with a peptide loop of Sec63p. This loop represents yet another DnaJ homologue in that it contains a region of 70 residue similarity to the J box, the most conserved region of the DnaJ family of proteins. In the presence of ATP, under conditions in which BiP can bind to Sec63p, the secretory precursor passes from the cytosol into the lumen through a membrane channel formed by Sec61 p. A second route to the membrane pore that is used by many other secretory precursors, particularly in mammalian cells, requires that the polypeptide engage the ER membrane as the nascent chain emerges from the ribosome. Such cotranslational translocation bypasses the need for certain Sec proteins, instead utilizing an alternate set of cytosolic and membrane factors that allows the nascent chain to be inserted directly into the Sec61p channel.     

Antiviral activities of anthraquinones,bianthrones and hypericin derivatives from lichens

The antiviral activities of some naturally occurring anthraquinones bianthrones, and hypericin derivatives were compared by the end-point CPE (viral cytopathic effects) method and plaque assays. Under optimal conditions of exposure to light, hypericin, 7,7-dichlorohypericin and 5,7-dichloroemodin exhibited strong inhibitory activity against HSV-1 (herpes simplex virus type 1) in both assays. Partial inactivation of the virus was shown by emodin, 7-chloroemodin and 7-chloro-1-O-methylemodin; the bianthrones and other anthraquinones were found to be inactive. Antiviral activity appeared to be, positively correlated with increasing substitution of chlorine in the anthraquinone structure. In the absence of light, only hypericin and 7,7-dichlorohypericin displayed detectable activity.     

Dissection of the pheromone-modulated flight of moths using single-pulse response as a template

The upwind flight of male moths to conspecific females is mediated by the chemical and structural characteristics of a pheromone plume. We describe the reaction of maleCadra cautella, the almond moth, to the interception of single pulses of sex pheromone, the smallest structural units of odour plumes. Following loss of a pheromone plume, males cast, that is fly a crosswind course without progressing upwind. The response of casting males to interception of a pulse of 0.25 s duration was, after a delay of 0.21±0.07 s, to turn and briefly fly straighter upwind, resulting in average net upwind displacements of 18 cm in a 50 cm s^–1 wind. Upwind progress in the single-pulse response was the result of steering more upwind and an increase in airspeed, although average ground speed remained unchanged. During the last third of the surge, males turned crosswind, returning to casting flight. These behavioural reactions to pheromone contact and loss support the phasic-tonic model of odour-modulated flight, in which an underlying tonic counterturning rhythm, expressed upon pheromone loss, is briefly overridden by phasic upwind surges, expressed upon interception of the pheromone filament. The surge portion of the cast-surge-cast response was diminished and more crosswind if individual pulses were shorter (0.02 s), probably due to sub-optimal contact with pheromone. The cast-surge-cast response to interception of a single 0.25 s pulse was used as a template to interpret the form of flight tracks in plumes of known structure. The template matched portions of flight tracks of males flying in plumes of low pheromone pulse frequency, thus reflecting the male's pattern of pulse encounter. In plumes ensuring a high frequency of pulse interception, only the upwind surge portion of the template was expressed, resulting in nearly straight upwind flight tracks. Similar nearly straight upwind flight tracks occurred in flights along plumes of low pulse frequency with large volume. Thus flight tracks of maleC. cautella to point sources of pheromone depend on both the frequency and the size of filaments encountered.     

2-Carboxyethylgermanium sesquioxide,a synthetic organogermanium compound,as an inducer of contrasuppressor T cells

2-Carboxyethylgermanium sesquioxide (Ge-132), a synthesized organogermanium compound with immunomodulaing activities, was shown to be an inducer of anti-suppressor T cells in normal mice. The suppressor cell activity of T6S cells, a clone of burn-induced CD8⁺ IL-4-producing suppressor T cells, was clearly inhibited when a mixed lymphocyte-tumor cell reaction of the clone was conducted with splenic mononuclear cells from mice treated orally with a 100 mg/kg dose of Ge-132. The activity of anti-suppressor cells was demonstrated in spleens of mice 2 days after treatment with Ge-132 and reached its peak on day 3. The anti-suppressor cells induced by the compound were of a contrasuppressor T cell-linage, because they were characterized as CD4⁺ CD28⁺ TCR/⁺ Vicia villosa lectin-adherent T cells. These cells produced IFN- but did not produce IL-2, IL-4, IL-6 or IL-10 in their culture fluids. CD4⁺ anti-suppressor T cells induced by Ge-132 may be different from other subsets of CD4⁺ T cells because Th1 and Th2 cells generated in our laboratory did not adhere toVicia villosa lectin-coated petri dishes, and each produced specific cytokines. Th1 cells produced IFN- and IL-2 while Th2 cells produce IL-4 and IL-10 in vitro. These results suggest that Ge-132 may be useful as an inducer of contrasuppressor T cells in immunocompromised individuals bearing suppressor T cells. To eliminate suppressor T cells from immunocompromised hosts may result in improved resistance from various opportunistic infections.     

Cl−/HCO 3 − exchanger is operative in isolated enterocytes from rat jejunum

Enterocytes isolated from rat jejunum were tested for the existence of a Cl^–/HCO ₃ ^– exchange, previously evidenced in basolateral membrane vesicles but not in brush border. Cells were found to retain functional integrity and transport capabilities long enough to allow Cl^– fluxes to be measured. Both efflux and uptake experiments indicate that a Cl^–/HCO ₃ ^– antiport, inhibited by 4,4-diisothiocyanostilbene-2-2-disulfonic acid (DIDS), is functional under resting conditions.     

The use of cyclophosphamide as an enhancer of the vaccine against foot-and-mouth disease

The immunization of biungulate animals with killed foot-and-mouth disease virus (FMDV) requires periodic vaccinations due to a low vaccine immunogenicity. Therefore, FMDV antigens need to be combined with adjuvants such as aluminum hydroxide, saponin or oil emulsions. Animal handling for periodic inoculations, and the repeated doses of vaccines that have to be administered increase the commercialization costs. Moreover, the use of adjuvants may induce adverse effects.In the present work we show that it is possible to increase the life span of neutralizing antibodies in serum when a single dose of cyclophosphamide (Cy) is administered four days before vaccination with aluminum hydroxidesaponin FMDV vaccine.     

Frederick Pavy (1829-1911) and his opposition to the glycogenic theory of Claude Bernard

For more than 50 years the Guy's Hospital physician Frederick Pavy (1829-1911) attempted to discredit the theory of his erstwhile teacher, Claude Bernard, that liver glycogen was broken down to supply sugar to the systemic circulation. His opposition was driven by his clinical perceptions and was based on two assumptions: the first was that the kidney was a simple filter through which small molecules would diffuse, so that sugar had to be prevented from reaching the systemic circulation. For Pavy, the liver was the barrier. The second was teleological: he could not believe that nature would operate in what he saw as a defective way, i.e. converting sugar into glycogen and then back again. At the beginning of his long working life Pavy regarded himself as a physiologist and was critical of the stagnancy of English physiology which was kept afloat by amateurs like himself in whatever time they could spare from busy private practice. At the end he came to see his own view of carbohydrate metabolism as symbolic of the schism between responsible clinicians (himself) and irresponsible daydreaming physiologists (his opponents).     

Some citrus chitinases also possess chitosanase activities

Several acidic chitinase and chitosanase isoforms were found in 4-week-old nonembryogenic sweet orange (Valencia [Citrus sinensis (L.) Osbeck]) callus tissue. Two isoforms (designated A1-CF1 and A1-CF2) were purified to homogeneity using HPLC size exclusion, anion exchange, and chromatofocusing techniques. Both hydrolase isoforms exhibited activity with either colloidal chitin or solubilized shrimp shell chitosan. Specific activities for the purified isoforms could not be calculated because of the lack of protein and contamination of ampholytes. However, the specific activities for chitinase and chitosanase after anion exchange were respectively 404 nmol GlcNAc per min per mg protein and 2,475 nmol GlcN per min per mg protein. The M_r for both enzymes was 30,500. The homogeneous proteins cross-reacted in western blots with antiserum against a basic class I potato leaf chitinase.     

Cyclophosphamide-impaired regulation of hepatic heme metabolism

Summary Im male rats hepatic cytochromes b₅ and P-450 were reduced at different times after treatment with cyclophosphamide (CP) (200 mg/kg i.p. for 3 days). In contrast, microsomal heme did not change until 48 h after the last dose of CP, leading to accumulation of heme in a non-cytochromal form. Parallel to the above changes the heme metabolism showed derangement: -aminolaevulinate synthase, the rate-limiting enzyme in heme synthesis, was depressed and heme oxygenase, the enzyme which catalyzes the oxidative degradation of heme, was increased.     

Pineal-related changes in cyclic AMP levels of rat medial basal hypothalamus

Summary Pinealectomy (Px) in adult male rats resulted in increased cyclic AMP accumulation by medial basal hypothalamic (MBH) explants 3 and 7 days after surgery. 24 h after superior cervical ganglionectomy (Gx) an augmented MBH cyclic AMP accumulation was observed. The effects of Px and Gx were additive, as revealed in animals subjected to Gx 3 days after Px.This study was supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (N^o 6638) and from the Fundación Alberto J. Roemmers, Argentina.