Septicemia due to Streptococcus mitis in neutropenic patients with acute leukemia

Eight neutropenic patients with acute lymphocytic or nonlymphocytic leukemia had septicemia due to different strains of Streptococcus mitis (St. mitis), a microorganism not commonly recognized as a special pathogen in leukemic patients. Four of the patients had been treated with high-dose cytosine arabinoside as part of the cytostatic regimen, six had a central venous line and four patients had oral lesions prior to the infection. Selective gut decontamination consisted of co-trimoxazole/colistin in five patients and quinolones in three patients. The first three patients died, either due to interstitial pneumonia with the adult respiratory distress syndrome (ARDS), or due to infection-triggered disseminated intravascular coagulation despite prompt empiric antibiotic therapy including vancomycin. The other patients improved after empiric supplementation of penicillin G (30 Mega/day) to the antibiotic regimen. Beginning ARDS in two of these patients dramatically responded to high-dose steroids. We conclude that St. mitis is a major pathogen in neutropenic leukemic patients. Infection appears to occur independently of acute leukemic cell type, regimen of selective gut decontamination, venous access, visible oral lesions or treatment with high-dose cytosine arabinoside. The clinical course of our patients raises questions about the value of commonly recommended empiric antibiotic regimens, which were clearly ineffective to control infections with St. mitis in this patient group. Our data indicate that immediate antibiotic therapy with penicillin G is indicated and may be life-saving for suspected St. mitis infections in neutropenic leukemic patients.     

PCSK6 VNTR Polymorphism Is Associated with Degree of Handedness but Not Direction of Handedness

Although the left and right human cerebral hemispheres differ both functionally and anatomically, the mechanisms that underlie the establishment of these hemispheric specializations, as well as their physiological and behavioral implications, remain largely unknown. Since cerebral asymmetry is strongly correlated with handedness, and handedness is assumed to be influenced by a number of genetic and environmental factors, we performed an association study of LRRTM1 rs6733871 and a number of polymorphisms in PCSK6 and different aspects of handedness assessed with the Edinburgh handedness inventory in a sample of unrelated healthy adults (n = 1113). An intronic 33bp variable-number tandem repeat (VNTR) polymorphism in PCSK6 (rs10523972) shows a significant association (significance threshold: p<0.0025, adjusted for multiple comparisons) with a handedness category comparison (P = 0.0005) and degree of handedness (P = 0.001). These results provide further evidence for the role of PCSK6 as candidate for involvement in the biological mechanisms that underlie the establishment of normal brain lateralization and thus handedness and support the assumption that the degree of handedness, instead the direction, may be the more appropriate indicator of cerebral organization.     

Transesterification with Candida Cylindracea Lipase in a Biphasic Aqueous-Organic System. Dependence of the Enantiomeric Ratio and the Reaction Rate on the Proportions of Water and Cyclohexane

18 September 1989

A transesterification reaction between 1-phenyl ethyl butyrate and 1-heptanol was carried out with Candida cylindracea lipase. The reaction was studied, with respect to the reaction rate and the enantiomeric ratio at different proportions of water and cyclohexane. A significantly lower reaction rate was observed for incubations with less than 0.5% water compared with those at a higher water content. Transesterification dominated over hydrolysis as the main reaction even at 70% water and a dramatic increase of the enantioselectivity was observed at this high water content. It is proposed that these effects depend on the mechanism of lipase catalysis at the interface of emulsion droplets. This interface binding gives 1-heptanol a positional preference compared with water for nucleophilic attack of the acyl enzyme and may, in addition, induce an optimal conformation for high enantioselectivity of the enzyme.     

A review of the biology and ecology of the Robber Crab, Birgus latro (Linnaeus, 1767) (Anomura: Coenobitidae)

Birgus latro (L.) is the largest terrestrial hermit crab in the world. The species is widely distributed on remote Indo-Pacific islands of the tropics, but it is rapidly declining and is currently classified as data deficient on the IUCN red list. This review provides a synopsis of both published and unpublished data on the biology and ecology of B. latro. It highlights the lack of robust biological information on the species’ basic biology, particularly in the juvenile and reproductive phases, while behavioural ecology studies are few and report conflicting data between populations. Population studies indicate that B. latro may have limited recruitment events throughout its range, emphasising the need for more systematic research to clearly identify factors that influence successful recruitment events. The review highlights the paucity of substantiated peer reviewed studies on this species and emphasises the need for further systematic research.     

Quantification of mycoparasitism by the nematode-trapping fungus Arthrobotrys oligospora on Rhizoctonia solani and the influence of nutrient levels

Abstract The influence of nutrient level, type of carbon source and nitrogen concentration on the parasitism of Arthrobotrys oligospora on Rhizoctonia solani were investigated by quantification of coiling frequency. Changes in coiling frequency were also compared with changes in hyphal density and colony radial growth rate. Increasing concentrations of corn meal agar gave increasing coiling frequency up to a concentration of half the recomended strength. At higher concentrations the coiling frequency was constant, although the hyphal density of both fungi increased over the whole concentration range. Coiling frequency was positively correlated with the probability of hyphal encounter, calculated as the product of the hyphal densities of the two fungi, except at high CMA concentrations. Amongst several carbohydrates tested, glucose resulted in the highest, and sucrose the lowest, coiling frequency. The effect of the different carbohydrates on coiling frequency was not correlated with the hyphal densities of the fungi. Addition of a nitrogen source, NaNO₃, removed the differences in coiling frequency between glucose and sucrose and increased coiling frequencies on both sugars.     

A new balancing act: The many roles of melatonin and serotonin in plant growth and development

Melatonin and serotonin are indoleamines first identified as neurotransmitters in vertebrates; they have now been found to be ubiquitously present across all forms of life. Both melatonin and serotonin were discovered in plants several years after their discovery in mammals, but their presence has now been confirmed in almost all plant families. The mechanisms of action of melatonin and serotonin are still poorly defined. Melatonin and serotonin possess important roles in plant growth and development, including functions in chronoregulation and modulation of reproductive development, control of root and shoot organogenesis, maintenance of plant tissues, delay of senescence, and responses to biotic and abiotic stresses. This review focuses on the roles of melatonin and serotonin as a novel class of plant growth regulators. Their roles in reproductive and vegetative plant growth will be examined including an overview of current hypotheses and knowledge regarding their mechanisms of action in specific responses.     

Tools for conservation of Balsamorhiza deltoidea and Balsamorhiza sagittata: Karrikin and thidiazuron-induced growth

Wildfires are having both devastating and regenerative impacts on the ecosystems in the Pacific Northwest of North America. Balsamorhiza sagittata and B. deltoidea (balsamroot) are ecologically important species in this region, and B. sagittata populations are increasing, while B. deltoidea is critically imperiled. The aim of this research was to establish in vitro protocols for germination and regeneration of Balsamorhiza spp. to enable conservation efforts. It was hypothesized that karrikins, which are plant growth regulators released from burning plants during wildfires, would induce seed germination in Balsamorhiza spp. Three karrikins (KAR₁, KAR₂, and KAR₁₁) were tested for the ability to enhance germination in these species at two levels (5 or 10 μM). KAR₂ had the strongest positive effect on germination and induced 47% and 60% germination, respectively, in B. sagittata seeds compared to 14% germination obtained in the control (water agar media). In B. deltoidea, KAR₂ treatment resulted in a germination rate of 73.1% and 100%, compared to 69% in the control. A germplasm collection of seedlings of both species was established for conservation and regeneration experiments. Thidiazuron treatment (10 μM) induced formation of embryo-like structures in seedlings of both B. sagittata and B. deltoidea, with regenerants originating from the crown of seedlings. The present study provides in vitro methods for conservation and mass propagation of Balsamorhiza species.

     

Genome differentiation in Magonoliaceae as revealed from meiotic pairing in interspecific and intergeneric hybrids

The cross compatibility within and between Yulania Spach and Michelia L.(Magnoliaceae) is relatively good and various such hybrids,obtained by conventional artificial hybridization,are available.The aim of the present study was to determine the extent of genome differentiation between the species involved in these crosses through the observation of chromosome pairing during meiosis in pollen mother cells (PMCs) of the hybrids.Chromosome pairing behavior was studied in five species (2n =38) and two interspecific hybrids of Michelia,eight species (2n =38,76 and 114) and 10 interspecific hybrids of Yulania,and three intergeneric hybrids between Michelia and Yulania.The results showed that chromosome pairing was normal with bivalent formation in diploid parental species and in interspecific hybrids.In addition to bivalents,multivalents were encountered in polyploid parental species and polyploid interspecific hybrids.In the intergeneric hybrids between a tetraploid Yulania and two diploid Michelia,19 chromosomes,most likely originating from Michelia,were unable to synapse from zygotene to metaphase I.Meiotic chromosome pairing indicated a high degree of homology between species within Michelia and Yulania and less homology between the genomes of these two genera.The differentiation of morphological characters and the distinctness of natural distribution also support the conclusion that these two genera are likely independent monophyletic groups.This suggests that the two genera were split at early evolution of Magnoliaceae and the overlapping characteristics in external morphology and internal structures of the two genera may be the result of parallel evolution or ancient common ancestry.