Circadian variation in stroke onset: identical temporal pattern in ischemic and hemorrhagic events

Stroke is the culmination of a heterogeneous group of cerebrovascular diseases that is manifested as ischemia or hemorrhage of one or more blood vessels of the brain. The occurrence of many acute cardiovascular events—such as myocardial infarction, sudden cardiac death, pulmonary embolism, critical limb ischemia, and aortic aneurysm rupture—exhibits prominent 24 h patterning, with a major morning peak and secondary early evening peak. The incidence of stroke exhibits the same 24 h pattern. Although ischemic and hemorrhagic strokes are different entities and are characterized by different pathophysiological mechanisms, they share an identical double-peak 24 h pattern. A constellation of endogenous circadian rhythms and exogenous cyclic factors are involved. The staging of the circadian rhythms in vascular tone, coagulative balance, and blood pressure plus temporal patterns in posture, physical activity, emotional stress, and medication effects play central and/or triggering roles. Features of the circadian rhythm of blood pressure, in terms of their chronic and acute effects on cerebral vessels, and of coagulation are especially important. Clinical medicine has been most concerned with the prevention of stroke in the morning, when population-based studies show it is of greatest risk during the 24 h; however, improved protection of at-risk patients against stroke in the early evening, the second most vulnerable time of cerebrovascular accidents, has received relatively little attention thus far.     

Grouping Myxococci (Corallococcus) Strains by Matrix-Assisted Laser Desorption Ionization Time-of-Flight (MALDI TOF) Mass Spectrometry: Comparison with Gene Sequence Phylogenies

Nine Corallococcus isolates and three type strains of Corallococcus species were characterized by Intact Cell Mass Spectrometry using Matrix Assisted Laser Desorption Ionization Time-of-Flight (MALDI-TOF) mass spectrometry. The resulting phenetic clustering was compared to the phylogenetic grouping based upon sequences of two housekeeping genes. The three dendrograms of relatedness resembled each other in that the isolates were highly similar to the type strains of Corallococcus exiguus and Corallococcus coralloides, while Corallococcus macrosporus and Myxococcus xanthus were more distantly related. While certain pairs of organisms were recovered by spectrometry and genes sequence analysis, others were detected by two of the three approaches. The degree of similarity determined by sequence analysis of the two genes was not higher than that revealed by MALDI-TOF analysis. The results show that the spectral profile, consisting of about 25 to 45 masses ranging between 2 and 20 kDa, have indeed taxonomic significance, confirming literature data that ribosomal proteins and certain housekeeping proteins are responsible for the masses obtained. Provided the availability of a database of type strains, MALDI-TOF analysis of unknown strains appears to be a rapid and inexpensive method to taxonomically cluster environmental isolates, expanding the spectrum to strains other than those of medical importance predominantly investigated so far.     

Elimination of inhibitory synapses is a major component of adult ocular dominance plasticity

During development, cortical plasticity is associated with the rearrangement of excitatory connections. While these connections become more stable with age, plasticity can still be induced in the adult cortex. Here we provide evidence that structural plasticity of?inhibitory synapses onto pyramidal neurons is?a major component of plasticity in the adult neocortex. In?vivo two-photon imaging was used to monitor the formation and elimination of fluorescently labeled inhibitory structures on pyramidal neurons. We find that ocular dominance plasticity in the adult visual cortex is associated with rapid inhibitory synapse loss, especially of those present on dendritic spines. This occurs not only with monocular deprivation but also with subsequent restoration of binocular vision. We propose that in the adult visual cortex the experience-induced loss of inhibition may effectively strengthen specific visual inputs with limited need for rearranging the excitatory circuitry.     

Pretreatment with granulocyte colony-stimulating factor reduces myelopoiesis in irradiated mice

The purpose of this study was to investigate effects of the treatment prior to irradiation with granulocyte colony-stimulating factor (G-CSF) on hematopoiesis in B10CBAF1 mice exposed to a sublethal dose of 6.5 Gy of 60Co gamma radiation. G-CSF was administered in a 4-day regimen (3 microg/day); irradiation followed 3 h after the last injection of G-CSF. Such a treatment was found to stimulate granulopoiesis, as shown by increased counts of granulocyte-macrophage progenitor cells (GM-CFC) and of granulocytic cells in the femoral marrow and spleen at the time of irradiation. However, postirradiation counts of GM-CFC and granulocytic cells in the marrow of mice pretreated with G-CSF were reduced up to day 18 after irradiation. Interestingly, the D0 values for marrow GM-CFC determined 1 h after in vivo irradiation were 1.98 Gy for controls and 2.47 Gy for mice pretreated with G-CSF, indicating a decreased radiosensitivity of these cells after drug treatment. The inhibitory effects of the pretreatment with G-CSF on the postirradiation granulopoiesis could be attributed to the phenomenon of "rebound quiescence" which can occur after cessation of the treatment with growth factors. Postirradiation recovery of erythropoiesis in the spleen of mice pretreated with G-CSF exhibited a dramatic increase and compensated for the decreased erythropoiesis in the marrow at the time of irradiation. This complexity of the hematopoietic response should be taken into account when administering G-CSF in preirradiation regimens.     

Purification and properties of cyclic-3',5'-GMP-dependent protein kinase from the nematode Ascaris suum

A cyclic-3',5'-GMP-dependent protein kinase was purified 7400-fold from the reproductive tract of female ascarids to a specific activity of 718 nmol min-1 mg-1 (histone as substrate). The yield of the preparation was 25%. The enzyme protein obtained was homogeneous as judged by isoelectrofocusing and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The native enzyme behaved as a dimer of two 82-kDa subunits in gel permeation chromatography on Superose 12. The protein kinase was inactive in the absence of cyclic purine nucleotides. Half-maximum velocity was obtained in the presence of 18 nM cGMP, whereas 400-fold higher concentrations of cAMP were required for the same activity. The enzyme underwent autophosphorylation in first-order kinetics (rate constant 0.054 min-1), leading to maximum incorporation of 0.96 phosphate per subunit. The autophosphorylation led to a 4-fold increase in Vmax, while the Km remained almost unchanged. In an extract from the reproductive tract, cGMP-stimulated phosphorylation was primarily observed in five proteins (molecular masses of 66, 60, 43, 30, and 25 kDa). These proteins also incorporated phosphate when isolated reproductive tracts were incubated in the presence of [32P]phosphate. The phosphate content in cellular proteins was enhanced when the incubation was performed in the presence of 10(-4) M of either octyl-cAMP or octyl-cGMP. In addition to the proteins mentioned above, however, six more electrophoretic bands containing radioactive phosphate were identified after in situ labeling of reproductive tracts with radioactive phosphate.     

High-Affinity Transport of Choline-O-Sulfate and Its Use as a Compatible Solute in Bacillus subtilis

We report here that the naturally occurring choline ester choline-O-sulfate serves as an effective compatible solute for Bacillus subtilis, and we have identified a high-affinity ATP-binding cassette (ABC) transport system responsible for its uptake. The osmoprotective effect of this trimethylammonium compound closely matches that of the potent and widely employed osmoprotectant glycine betaine. Growth experiments with a set of B. subtilis strains carrying defined mutations in the glycine betaine uptake systems OpuA, OpuC, and OpuD and in the high-affinity choline transporter OpuB revealed that choline-O-sulfate was specifically acquired from the environment via OpuC. Competition experiments demonstrated that choline-O-sulfate functioned as an effective competitive inhibitor for OpuC-mediated glycine betaine uptake, with a K_i of approximately 4 μM. Uptake studies with [1,2-dimethyl-¹⁴C]choline-O-sulfate showed that its transport was stimulated by high osmolality, and kinetic analysis revealed that OpuC has high affinity for choline-O-sulfate, with a K_m value of 4 ± 1 μM and a maximum rate of transport (V_max) of 54 ± 3 nmol/min · mg of protein in cells grown in minimal medium with 0.4 M NaCl. Growth studies utilizing a B. subtilis mutant defective in the choline to glycine betaine synthesis pathway and natural abundance ¹³C nuclear magnetic resonance spectroscopy of whole-cell extracts from the wild-type strain demonstrated that choline-O-sulfate was accumulated in the cytoplasm and was not hydrolyzed to choline by B. subtilis. In contrast, the osmoprotective effect of acetylcholine for B. subtilis is dependent on its biotransformation into glycine betaine. Choline-O-sulfate was not used as the sole carbon, nitrogen, or sulfur source, and our findings thus characterize this choline ester as an effective compatible solute and metabolically inert stress compound for B. subtilis. OpuC mediates the efficient transport not only of glycine betaine and choline-O-sulfate but also of carnitine, crotonobetaine, and γ-butyrobetaine (R. Kappes and E. Bremer, Microbiology 144:83–90, 1998). Thus, our data underscore its crucial role in the acquisition of a variety of osmoprotectants from the environment by B. subtilis.     

Note on the diet of the jaguar in central Brazil

Diet of the jaguar Panthera onca in the Cerrado, central Brazil, was investigated based on a sample of genetically identified jaguar scats. At least nine prey species were observed in 35 scat samples. Giant anteaters Myrmecophaga tridactyla contributed more than 75 % of biomass to the observed diet. Tapirs Tapirus terrestris and peccaries Tayassu pecari and Pecari tajacu contributed approximately 6 % to jaguar diet each, and small mammals contributed least to the jaguar diet. At 0.121, dietary niche breadth was narrower than reported in most other studies. Due to their physical characteristics and abundance, giant anteaters are likely the most profitable prey for jaguars in Emas National Park, and as an important prey, they should be included in jaguar conservation efforts.     

The CMT4B disease‐causing proteins MTMR2 and MTMR13/SBF2 regulate AKT signalling

Charcot‐Marie‐Tooth disease type 4B is caused by mutations in the genes encoding either the lipid phosphatase myotubularin‐related protein‐2 (MTMR2) or its regulatory binding partner MTMR13/SBF2. Mtmr2 dephosphorylates PI‐3‐P and PI‐3,5‐P2 to form phosphatidylinositol and PI‐5‐P, respectively, while Mtmr13/Sbf2 is an enzymatically inactive member of the myotubularin protein family. We have found altered levels of the critical signalling protein AKT in mouse mutants for Mtmr2 and Mtmr13/Sbf2. Thus, we analysed the influence of Mtmr2 and Mtmr13/Sbf2 on signalling processes. We found that overexpression of Mtmr2 prevents the degradation of the epidermal growth factor receptor (EGFR) and leads to sustained Akt activation whereas Erk activation is not affected. Mtmr13/Sbf2 counteracts the blockage of EGFR degradation without affecting prolonged Akt activation. Our data indicate that Mtmr2 and Mtmr13/Sbf2 play critical roles in the sorting and modulation of cellular signalling which are likely to be disturbed in CMT4B.     

Cycloheximide resistance in Chinese hamster cells. II. Induction of Chm resistance in Chinese hamster cells by N-nitrosomethylurea.

Mutant Chinese hamster ovarian (CHO) cells with a resistance to 7-10(-7) and 8-10(-7) M cycloheximide (CHM) were induced at mutation rates of 1.9-5.2-10(-3) and 1.6-1.8-10(-3) respectively after treatment with N-nitrosomethylurea (NMU) at 100 mug/ml. The induced mutation rates differed by two orders of magnitude from the spontaneous rate of mutation to CHM resistance.