Staurosporine potentiates platelet activating factor stimulated phospholipase C activity in rabbit platelets but does not block desensitization by platelet activating factor

The possible involvement of protein kinase C activation in regulating PAF-stimulated PLC activity was studied in rabbit platelets. PAF (100 nM for 5 seconds) stimulated incorporation of 32P into proteins and caused [3H]InsP3 levels to increase about 260% of control. These responses were compared after platelets were pretreated with either PAF, phorbol 12-myristate 13-acetate (PMA) or staurosporine and also after pretreatments with staurosporine followed by PAF or PMA. Pretreating platelets with staurosporine potentiated PAF-stimulated [3H]InsP3 levels by 54% and blocked protein phosphorylation. Pretreatments with PAF and PMA caused PAF-stimulated [3H]InsP3 levels to decrease to 115 and 136%, respectively. Staurosporine pretreatment blocked the decrease caused by the PMA pretreatment but not that by PAF. This study demonstrates that PAF-stimulated PLC activity is negatively affected by protein kinase C (PKC) activation and that inhibition of PKC activity did not prevent desensitization of PLC by PAF.

Altered expression of platelet surface glycoproteins during storage

Human blood platelets were stored in autologous plasma at 4 degrees C or 22 degrees C and their surface changes were probed with three lectins--wheat germ agglutinin, lentil lectin and concanavalin A. Platelets stored at either temperature for different times showed increased sensitivity to lectins. Lectins which were nonagglutinating to fresh platelets readily agglutinated stored platelets. The platelets stored for 24 h or longer lost their ability to respond to thrombin but demonstrated enhanced aggregation with wheat germ agglutinin. Surface labelling experiments revealed progressive loss of a glycoprotein of Mr 150,000 (GPIb) together with the appearance of components with Mr 69,000, 60,000 and 25,000 respectively. New high molecular weight glycoproteins were detected only in stored platelets. These findings illustrate the usefulness of lectins for the detection of altered expression of surface glycoconjugates which may be a factor in storage related dysfunction of platelets.

The stability of O-antigen plasmid is determined by a chromosomal region of Shigella dysenteriae 1

It is well established that plasmids are involved in the expression of lipopolysaccharide in certain species of Shigella. In Shigella sonnei, both the biosynthesis of oligosaccharide side chains (O antigen), and cell invasiveness are controlled exclusively by a 120 megadalton (MDa) plasmid. In Shigella dysenteriae 1, a 10 kilobase (kb) plasmid is required for O-antigen production. Shigella dysenteriae 1 strains devoid of this plasmid lose the ability to synthesize O antigen. Interestingly, this 10-kb plasmid is not stably maintained in Escherichia coli K-12 strains, where it is lost spontaneously at a high frequency. Our genetic analyses of Shigella dysenteriae 1 strain IDBM11 and its derivatives indicate that the stability of this plasmid is associated with the histidine region of the chromosome which is unique to Shigella dysenteriae. Furthermore, the 10-kb plasmid is stably maintained in wild-type IDBM11 with an intact histidine locus. However, this plasmid is not stable in IDBM11 derivatives (e.g., IDBM11-1 and IDBM11-2), in which the his locus has been substituted with the histidine region of an E. coli K-12 chromosome. The S. dysenteriae IDBM11 strain, and its derivatives (lacking a 10-kb plasmid), displayed an invasive property as demonstrated by their internalization by HeLa cells in an in vitro assay. Thus the 10-kb plasmid of Shigella dysenteriae 1 is required for O-antigen synthesis but not for cell invasion.

A simple ELISA for antigiardial antibody using the membrane fraction of the parasite as antigen

Most existing methods for detecting antigiardia lamblia antibody require the use of cultured Giardia lamblia trophozoites as antigen in immunofluorescent and enzyme-linked immunosorbent assays. However, the maintenance of trophozoite culture systems limits the large-scale use of these antibody detection systems. An antigen extracted from Giardia lamblia by the detergent Triton X-100, when used in an ELISA system, produces specific, objective, quantitative and reproducible results. It is likely that such a test system could be packaged in kit form for large-scale diagnostic and epidemiological application in all parts of the world.

Effect of thyroxine on the hepatic glycogen and glucose-6-phosphatase activity of developing rats

The influence of exogenous thyroxine was studied on the hepatic glycogen content and glucose-6-phosphatase activity of rats of different age groups. The glycogen content and glucose-6-phosphatase activity were found to be decreased in the livers of 5, 15, 30 and 60-day-old rats after thyroxine treatment. In normal rats of 5, 15, 30 and 60-day-old, a gradual rise in both the hepatic glycogen content and glucose-6-phosphatase activity was noted as the age advanced from immature to adult.

Direct-response ultraviolet thermoluminescent dosimeter

An integrating solid-state dosimeter has been developed to detect ultraviolet radiation using the process of "direct" ultraviolet stimulation. This process yields a thermoluminescent signal after an exposure to ultraviolet radiation, without prior exposure to ionizing radiation. Magnesium oxide crystals were found to show a directly stimulated thermoluminescent glow peak at 145 degrees C which can be utilized as a linear, energy-independent ultraviolet dosimeter.

Increase in serum alpha foetoprotein level in hepatic regeneration of the rat. Effects of age and of magnitude of regenerative activity

The effects of variable degrees of liver regeneration induced by two-thirds partial hepatectomy or intoxication with different doses of carbon tetrachloride (CCl4) on increased production of alpha foetoprotein (AFP) have been studied in very young (5-6 weeks) and older (15 weeks and more) rats by counter-immunoelectrophoresis (sensitivity down to 250 ng/ml). In the young animal adequate regeneration following two-thirds hepatectomy as well as 100 myl CCl4 successfully induced large increases in serum AFP levels. Smaller doses as well as a large fatal dose of the toxin, all of which resulted in inadequate regenerative activity, failed to excite AFP synthesis and secretion up to detectable levels. The adult animal did not show detectable AFP with any of these procedures. However, necrosis induced in the regenerating adult liver 24 h following partial hepatectomy did result in the detection of small amounts of protein in the serum. It is concluded that in hepatic regeneration of this species, the age of the animal as well as the magnitude of regenerating activity in the liver are critical in the occurrence of high levels of serum AFP.

Diverse mechanisms of hepatocellular injuries due to chemicals: evidence in rats administered carbon tetrachloride or dimethylnitrosamine

Differences in acute hepatotoxicity of carbon tetrachloride (CCl4) and dimethylnitrosamine (DMN) have been tested in normal foetal, newborn and adult rats, foetal, newborn and adult rats pretreated with phenobarbitone and partially hepatectomized adult rats. While CCl4 is non-toxic to the foetal and newborn liver, DMN induces identical necrosis at all ages. Prior dosing with phenobarbitone augments CCl4 toxicity only in the adult and the newborn but the foetus continues to be resistant. Such pretreatment, on the other hand, significantly reduces the effects of DMN on liver in all animals. Partial hepatectomy makes the liver less susceptible to CCl4 and more so to DMN. Such diversities of hepatic response to the two toxins can be accounted for by the levels of the respective toxifying enzymes in the liver cell in different situations.