Analysis by mutagenesis of the ATP binding site of the gamma subunit of skeletal muscle phosphorylase kinase expressed using a baculovirus system.

Active gamma subunit of skeletal muscle phosphorylase kinase has been obtained by expression of the rat soleus cDNA in a baculovirus system. The protein exhibited the expected pH 6.8/8.2 activity ratio of 0.6, and its activity was insensitive to Ca2+ addition, indicating that it was free gamma subunit and not a gamma subunit-calmodulin complex. It was stimulated approximately 2-fold by Ca(2+)-calmodulin addition, demonstrating that it had retained high-affinity calmodulin binding. By site-directed mutagenesis, we have examined the role of six of the amino acids that constitute the consensus ATP binding site of the protein kinase, which in the gamma subunit is represented by the sequence 26Gly.Arg.Gly.Val.Ser.Ser.Val.Val33. Changes were evaluated by the kinetic determination of the dissociation constants of gamma-ATP, gamma-ADP, gamma-AMP.PCP, and gamma-phosphorylase and the maximum catalytic activity. The mutants Ser26-gamma, Ser29-gamma, Phe30-gamma, and Gly31-gamma each exhibited an essentially identical dissociation constant for gamma subunit phosphorylase, indicating that these mutations had not caused a global alteration in the protein structure but were limited to changes in the nucleotide binding site domain. Substitution of either Val33 (by Gly) or Gly28 (by Ser), two of the most conserved residues in all protein kinases, resulted in enzyme with marginally detectable activity. In noted contrast, the Ser26 mutant, which substituted the first glycine of the consensus glycine trio motif, and which is also very highly conserved, retained at least 25% of the enzymatic activity. The Gly31 substitution, which restored a glycine to a position characteristic for most protein kinases, had little overall effect upon the maximum rate of catalysis. Restoration of Ser30 to the more typical phenylalanine, which is present in most protein kinases, had minimal effect on catalysis. These data provide the first direct evaluation of the roles that different residues play within this consensus glycine trio/valine motif of the protein kinases, which up to now have only been surmised to be of importance because of their conservation. Two unexpected findings are that for one residue that is very conserved (Gly26) there is some flexibility of substitution not apparent from the evolutionary conservation and that a second quite conserved residue in protein kinases (equivalent to Gly at position 31) does not produce a protein optimized for nucleotide binding.     

An EPR signal from the "invisible" copper of cytochrome oxidase.

Sulfide is both an inhibitor and a slow reductant of oxidized cytochrome $\text{c}$ oxidase. When the enzyme is exposed to sulfide for short times (one minute or less) and frozen, the resultant electron paramagnetic resonance (EPR) signals show clearly: low spin heme a, low spin heme a₃, the usual “EPR detectable” Cu²⁺ signal (g_⊥ = 2.17, g_⊥ = 2.03), and a new Cu²⁺ signal superimposed on the same region, with (g_⊥ ～ 2.19, g_⊥ = 2.05). This new signal presumably arises because the antiferromagnetic coupling postulated to exist between the iron atom of heme a₃ and this copper is disrupted when heme a₃ is driven to a low spin state by sulfide. The implications of this result with respect to models of the O₂-binding site and redox geometry of oxidase are briefly discussed.     

Inter-rater reliability of physiotherapists using the Action Research Arm Test in chronic stroke

Objectives:The purpose of this study is to establish whether physiotherapists’ ratings are consistent, when using the Action Research Arm Test (ARAT) to score a chronic stroke patient.Methods:This was part of a large project establishing the reliability in chronic stroke. This study used a correlational design comparing the association between physiotherapist scores of the same patient, to establish the ARAT’s inter-rater reliability. The COSMIN checklist was followed to enhance the methodology of the study.Results:Twenty physiotherapists (8 female and 12 male) aged between 25 and 53 years were selected. There were no participant dropouts or withdrawals. The sample size was normally distributed. The physiotherapists appeared representative of the UK physiotherapy population, with the exception of gender. The distribution of scores showed a normal distribution with standard deviation of score of 1.9. The Kendall’s W test showed 0.711 of agreement between the raters. The scores achieved statistical significance showing consistency between physiotherapists’ scores with chronic stroke. Limitations of the study were the use of a small single center convenience sample that may reduce the generalizability of the findings.Conclusions:The ARAT is consistent when scored by physiotherapists in a chronic stroke population. The inter-rater reliability range was (0.70 to 0.90) which is categorized as good.     

Economic Recession and Emergence of an HIV-1 Outbreak among Drug Injectors in Athens Metropolitan Area: A Longitudinal Study

Background

During 2011, a dramatic increase (1600%) of reported HIV-1 infections among injecting drug users (IDUs) was noted in Athens, Greece. We herein assess the potential causal pathways associated with this outbreak.

Methods

Our study employed high resolution HIV-1 phylogenetic and phylogeographic analyses. We examined also longitudinal data of ecological variables such as the annual growth of gross domestic product (GDP) of Greece in association with HIV-1 and HCV sentinel prevalence in IDUs, unemployment and homelessness rates and HIV transmission networks in Athens IDUs before and during economic recession (2008–2012).

Results

IDU isolates sampled in 2011 and 2012 suggested transmission networks in 94.6% and 92.7% of the cases in striking contrast with the sporadic networking (5%) during 1998–2009. The geographic origin of most HIV-1 isolates was consistent with the recently documented migratory waves in Greece. The decline in GDP was inversely correlated with annual prevalence rates of HIV and HCV and with unemployment and homelessness rates in IDUs (all p<0.001). The slope of anti-HCV prevalence in the sentinel populations of IDUs and in “new” drug injectors was found 120 and 1.9-fold (p = 0.007, p = 0.08 respectively) higher in 2008–2012 (economic recession) compared with 2002–2006. The median (25th, 75th) size of transmission networks were 34 (12, 58) and 2 (2, 2) (p = 0.057) in 2008–2012 and 1998–2007, respectively. The coverage of harm reduction services was low throughout the study period.

Conclusions

Scaling-up harm reduction services and addressing social and structural factors related to the current economic crisis should be urgently considered in environments where HIV-1 outbreaks may occur.     

Sizeable acquired subglottic cyst in a baby with Williams–Beuren syndrome: Association or coincidence?

We describe a case of an acquired subglottic cyst presented with persistent stridor and voice hoarsening in a baby diagnosed with Williams–Beuren syndrome that was born premature and required intubation during neonatal period. We also comment on whether this is a coincidence or there can be an association between impaired elastogenesis, a feature of patients with the syndrome and the formation of a subglottic cyst.     

Perinatal physiology in cloned and normal calves: hematologic and biochemical profiles

Although a majority of clones are born normal and apparently healthy, mortality rates of nearly 30% are described in many reports. Such losses are a major limitation of cloning technology and represent substantial economic investment as well as justifiable animal health and welfare concerns. Prospective, controlled studies are needed to understand fully the causes of neonatal mortality in clones and to develop preventive and therapeutic strategies to minimize losses. We report here the findings of studies on the hematologic and biochemical profiles of cloned and control calves in the immediate 48-h postpartum period. Cloned calves were similar to control calves for a majority of parameters studied including blood gases, concentrations of plasma proteins, minerals and electrolytes, and white blood cell, neutrophil, lymphocyte, and platelet counts. The most notable differences between clones and controls in this study were reduced red- and white-blood cell counts in clones at birth and 1 h of age. As a group, plasma electrolyte concentrations were more variable in clones, and the variability tended to be shifted either higher (sodium, chloride) or lower (potassium, bicarbonate) than in controls. Previously, we noted differences in carbohydrate parameters, the length of time required for clones to make the neonatal adaptation to life ex utero, and morphology of the cloned placenta. Taken together, our findings suggest that cloned calves experience greater difficulty adjusting to life ex utero and that further research is warranted to determine the nature of the relationship between the physiological differences noted here in clones at birth and concomitant abnormal placental morphology.     

Seed germination ecology and salt stress response in eight Mediterranean populations of Sarcopoterium spinosum (L.) Spach

This study aims to deepen the analysis of seed germination ecology and salinity tolerance of Sarcopoterium spinosum (Rosaceae). Germination tests were conducted to evaluate the effect of the fruit’s spongy tissue and the intraspecific variability in seed germination among eight populations of the species on responses to light and total darkness, constant and alternating temperatures, salt stress and germination recovery. The effect of the presence of the spongy tissue varied among populations, with significant results for seed germination. For all populations, optimum germination temperatures were observed in the range of 10–20°C, indicating that S. spinosum and its germination in the field might occur preferably in the period between autumn and early spring. The high water availability due to rainfall during this period could be a considerable advantage for the seed germination of this species. Seeds of S. spinosum showed the ability to germinate in up to 250 mM NaCl in the substrate, and their ability to recover after salt exposure may be interpreted as adaptation to the coastal habitats in which they generally grow. These results give this species a halo-tolerant character. Great inter-population variability is detected in this study in several aspects, which indicated that the Mediterranean populations of S. spinosum differ considerably and are adapted to their local conditions. This study provides new information about S. spinosum seed ecology, which could help to preserve and apply effective conservation measures for this species, which in several areas of its distribution range is endangered.     

Gene expression and integrated stress response in HepG2/C3A cells cultured in amino acid deficient medium

The integrated stress response (ISR), a defense mechanism cells employ when under stress (e.g., amino acid deprivation), causes suppression of global protein synthesis along with the paradoxical increased expression of a host of proteins that are useful in combating various stresses. Genes that were similarly differentially expressed under conditions of either leucine- or cysteine-depletion were identified. Many of the genes known to contain an amino acid response element and to be induced in response to eIF2α phosphorylation and ATF4 heterodimer binding (ATF3, C/EBPβ, SLC7A1, SLC7A11, and TRIB3), as well as others shown to be induced downstream of eIF2α phosphorylation (C/EBPγ, CARS, SARS, CLCN3, CBX4, and PPP1R15A) were among the upregulated genes. Evidence for the induction of the ISR in these cells also included the increased phosphorylation of eIF2α and increased protein abundance of ATF4, ATF3, and ASNS in cysteine- and leucine-depleted cells. Based on genes highly differentially expressed in both leucine- and cysteine-deficient cells, a list of 67 downregulated and 53 upregulated genes is suggested as likely targets of essential amino acid deprivation in mammalian cells.     

Computer, Simulated Evaluation of Possible Mechanisms for Sequestering Metal Ion Activity in Plant Vacuoles: II. Zinc

Various mechanisms have been suggested for sequestering Zn ion activity in vacuoles of Zn-tolerant plants. One of these mechanisms, complexation in the vacuole with organic acids, has received some support in the recent literature. However, the lack of experimental evidence for anticipated vacuolar compartmentation and concerning the nature of metal-ligand species occurring in the vacuole has been criticized. In this study we have used computer modeling of chemical equilibria to predict the metalligand species in vacuoles of tobacco (Nicotiana tabacum) cultured cells. Results of this thermodynamic evaluation support the conclusion that citrate in the concentration range encountered in tobacco cultured cells exposed to 300 or 2000 μm Zn has high potential for forming soluble complexes with Zn, over the entire probable range of vacuolar pH 4 to 7. Complexation of Zn with oxalate is also predicted, especially in cells exposed to high Zn levels. Malate, though the most abundant acid present, showed little potential for competing with other ligands for Zn. Overall, results suggest that vacuolar sequestration of Zn by high levels of vacuolar citrate may be a central mechanism in the accumulation of Zn in plants exposed to either low or high levels of this metal.