Interaction of protein kinase C with phosphatidylserine. 2. Specificity and regulation.

The roles of specific and nonspecific interactions in the regulation of protein kinase C by lipid have been examined. Binding and activity measurements reveal two mechanisms by which protein kinase C interacts with membranes: (1) a specific binding to the activating lipid phosphatidylserine and (2) a nonspecific binding to nonactivating, acidic lipids. The specific interaction with phosphatidylserine is relatively insensitive to ionic strength, surface charge, and the presence of nonactivating lipids. The two second messengers of the kinase, diacylglycerol and Ca2+, increase markedly the affinity of the kinase for phosphatidylserine. In contrast, the nonspecific interaction is sensitive to ionic strength and surface charge, and is unaffected by diacylglycerol. These results suggest that electrostatic interactions promote the binding of protein kinase C to membranes but the cooperative and selective binding of phosphatidylserine is the dominant driving force in a productive protein-lipid interaction.     

Interaction of protein kinase C with phosphatidylserine. 1. Cooperativity in lipid binding.

The basis for the apparent cooperativity in the activation of protein kinase C by phosphatidylserine has been addressed using proteolytic sensitivity, resonance energy transfer, and enzymatic activity. We show that binding of protein kinase C to detergent-lipid mixed micelles and model membranes is cooperatively regulated by phosphatidylserine. The sigmoidal dependence on phosphatidylserine for binding is indistinguishable from that observed for the activation of the kinase by this lipid [Newton & Koshland (1989) J. Biol. Chem. 264, 14909-14915]. Thus, protein kinase C activity is linearly related to the amount of phosphatidylserine bound. Furthermore, under conditions where protein kinase C is bound to micelles at all lipid concentrations, activation of the enzyme continues to display a sigmoidal dependence on the phosphatidylserine content of the micelle. This indicates that the apparent cooperativity in binding does not arise because protein kinase C senses a higher concentration of phosphatidylserine once recruited to the micelle. Our results reveal that the affinity of protein kinase C for phosphatidylserine increases as more of this lipid binds, supporting the hypothesis that a domain of phosphatidylserine is cooperatively sequestered around the enzyme.     

Interaction of soil moisture and elevated CO2 on the above-ground growth rate, root length density and gas exchange of turves from temperate pasture

Interactions between water availability and elevated atmosphericCO₂ concentrations have the potential to be important factorsin determining future forage supply from temperate pastures.Using large turves from an established pasture, the responseof these communities at 350 or 700 l l^–1 CO₂ to a soilmoisture deficit and to recovery from the deficit in comparisonto turves that were well-watered throughout was measured. Priorto this experiment the turves had been exposed to the CO₂ treatmentsfor 324 d. Net CO₂ exchange continued at elevated CO₂ even when the volumetricsoil moisture content was less than 0.10 m³ m^–3 soil;at the same moisture deficit gas exchange at ambient CO₂ waszero. The additional carbon fixed by the elevated CO₂ turveswas primarily allocated below-ground as shown by the maintenanceof root length density at the same level as in well-wateredturves. When the dry turves were rewatered there was compensatorygrowth at ambient CO₂ so that the above-ground growth rate exceededthat of turves that had not experienced a moisture deficit.At the start of this experiment, the turves that were growingat 700 l I^–1 CO₂ had a greater proportion of legume (principallywhite clover, Trifolium repens L.) in the harvested herbage.There was a trend for the legume content at elevated CO₂ tobe reduced under a soil moisture deficit. The results indicate different strategies in response to soilmoisture deficits depending on the CO₂ concentration. At ambientCO₂, growth stopped, but plants were able to respond stronglyon rewatering; while at elevated CO₂ growth continued (particularlybelow-ground), but no additional growth was evident on rewatering.Ecosystem gas exchange measurements taken at the end of theexperiment (after 429 d of exposure to CO₂) showed 33% moreCO₂ was fixed at elevated CO₂ with only a small (12%) and nonsignificantdownward regulation. Key words: Carbon dioxide, climate change, grassland, gas exchange, soil moisture deficit     

Seasonal changes in moult,body mass and reproductive condition in siskins Carduelis spinus exposed to daylength regimes simulating different latitudes

Birds use change in daylength during the year to time events during their annual cycles. Individual Eurasian siskins Carduelis spinus can breed and winter in widely separated areas in different years. Birds at different latitudes will experience different changes in photoperiod. So how does latitude affect photoperiodic control? Our aim in this study was to find whether Siskins caught from the wild in Britain and exposed to different photoperiodic regimes, typical of widely separated latitudes, would differ in the subsequent timing and duration of their moults and associated processes. Siskins were caught in late February and early March, and initially kept outside on natural photoperiods. From the spring equinox (21 March), they were divided into three groups kept under photoperiodic regimes that simulated latitudes 40°, 55° and 70°N respectively. All three groups showed highly significant subsequent changes in body mass, fat scores and cloacal protuberance size. Moult of the primary feathers started during June – August (mean 9 July), and lasted 61–99 days (mean 75 days). Birds that started to moult late in the season had shorter moult durations. All individuals showed lower mass and fat levels during moult than before or after moult. Crucially, there were no significant differences in the timing of these events between the three photoperiodic groups. Apparently these birds did not use prevailing absolute photoperiod or the prevailing rate of change in photoperiod to time moult‐related seasonal events, but used instead some other feature of the annual photoperiod cycle or some form of interval timer linked to photoperiod.     

Characterization and partial purification of <Emphasis Type="Italic">Candida albicans</Emphasis> Secretory IL-12 Inhibitory Factor

Background  

We have previously shown that supernatant from Candida albicans (CA) culture contains a Secretory Interleukin (IL)-12 Inhibitory Factor (CA-SIIF), which inhibits IL-12 production by human monocytes. However, the effect of CA-SIIF on secretion of other cytokines by monocytes is unknown, and detailed characterization of this factor has not been performed.     

Benzene and the risk of non-Hodgkin lymphoma: A review and meta-analysis of the literature

Benzene, an accepted leukemogen, has been suggested to cause other hemato- and lymphopoietic cancers. Here we review the published literature for non-Hodgkin lymphoma (NHL) and occupational exposure to benzene. Six cohorts, sixteen case–control studies and two studies of other designs were identified through keyword searches of bibliographic databases. Twenty-two of twenty-four studies found no association between NHL and ever exposed to benzene compared to never; a random-effects meta-analysis gave a pooled risk estimate of 1.11 (95% confidence interval 0.94–1.30). Our finding of no effect agrees with one of two previous meta-analyses. The other meta-analysis examined if high benzene exposure increased NHL risk but a lack of consistent exposure categories within the same metric should have precluded pooling risks by exposure level. Instead, we reviewed whether dose–response relationships existed. The best available data came from six studies where exposure was estimated from historical measurements and on the whole, no trends in risks of NHL with rising cumulative, average, peak, or duration of benzene exposure were found. NHL is a heterogeneous group of malignancies and although less well-studied, benzene was not associated with any NHL subtype. In conclusion, benzene at either low or high doses does not increase the risk of NHL.     

Morphological and Molecular Identification of Spirometra Tapeworms (Cestoda: Diphyllobothriidae) from Carnivorous Mammals in the Serengeti and Selous Ecosystems of Tanzania

Spirometra tapeworms (Cestoda: Diphyllobothriidae) collected from carnivorous mammals in Tanzania were identified by the DNA sequence analysis of the mitochondrial cytochrome c oxidase subunit 1 (cox1) and internal transcribed spacer 1 (ITS1), and by morphological characteristics. A total of 15 adult worms were collected from stool samples and carcasses of Panthera leo, Panthera pardus, and Crocuta crocuta in the Serengeti and Selous ecosystems of Tanzania. Three Spirometra species: S. theileri, S. ranarum and S. erinaceieuropaei were identified based on morphological features. Partial cox1 sequences (400 bp) of 10 specimens were revealed. Eight specimens showed 99.5% similarity with Spirometra theileri ({"type":"entrez-nucleotide","attrs":{"text":"MK955901","term_id":"1796114604","term_text":"MK955901"}}MK955901), 1 specimen showed 99.5% similarity with the Korean S. erinaceieuropaei and 1 specimen had 99.5% similarity with Myanmar S. ranarum. Sequence homology estimates for the ITS1 region of S. theileri were 89.8% with S. erinaceieuropaei, 82.5% with S. decipiens, and 78.3% with S. ranarum; and 94.4% homology was observed between S. decipiens and S. ranarum. Phylogenetic analyses were performed with 4 species of Spirometra and 2 species of Dibothriocephalus (=Diphyllobothrium). By both ML and BI methods, cox1 and ITS1 gave well supported, congruent trees topology of S. erinaceieuropaei and S. theileri with S. decipiens and S. ranarum forming a clade. The Dibothriocephalus species were sisters of each other and collectively forming successive outgroups. Our findings confirmed that 3 Spirometra species (S. theileri, S. ranarum, and S. erinaceieuropaei) are distributed in the Serengeti and Selous ecosystems of Tanzania.     

Thorium induced testicular changes in rats.

Daily intraperitoneal administration of thorium nitrate produced progressive morphological and biochemical alterations with the increase in thorium concentration in rat testis. The degenerative changes in the seminiferous tubules increased with the duration of treatment and after 90 days calcification occurred in about 25% of the tubules and in the connective tissue of the tunica albuginea. The activity of adenosine triphosphatase and alkaline phosphatase increased markedly as a result of thorium administration. An attempt has been made to interrelate histopathological and enzymatic changes and the metal concentration in the testicular tissue.