Presence of a unique glycoconjugate on the surface of rat primordial germ cells during migration

This investigation was undertaken to examine the chemical nature of components on the surface of primordial germ cells (PGCs) possibly related to their directed migration during development. To this end, lectins conjugated to horseradish peroxidase were used as specific histochemical probes to characterize the structure of PGC cell surface glycoconjugates and changes in their composition during and after their migration in the rat embryo. A lectin specific for terminal N-acetylgalactosamine (GalNAc) from Dolichos biflorus intensely stained the cell surface and a perinuclear region assumed to be Golgi zone of PGCs only during their migration. With one exception, no other site in the embryo stained with this lectin as migration proceeded. These observations suggest that the GalNAc-containing glycoconjugates on the surface of PGCs may be of functional importance in regulating the guidance and locomotion of these cells during the course of their extensive migration.     

Obligatory biosynthesis of L-tyrosine via the pretyrosine branchlet in coryneform bacteria.

Species of coryneform bacteria (Corynebacterium glutamicum, Brevibacterium flavum, and B. ammoniagenes) utilize pretyrosine [beta-(1-carboxy-4-hydroxy-2,5-cyclohexadien-1-yl) alanine] as an intermediate in L-tyrosine biosynthesis. Pretyrosine is formed from prephenate via the activity of at least one species of aromatic aminotransferase which is significantly greater with prephenate as substrate than with either phenylpyruvate or 4-hydroxyphenylpyruvate. Pretyrosine dehydrogenase, capable of converting pretyrosine to L-tyrosine, has been partially purified from all three species. Each of the three pretyrosine dehydrogenases is catalytically active with either nicotinamide adenine dinucleotide or nicotinamide adenine dinucleotide phosphate as cofactors. The Km values for nicotinamide adenine dinucleotide phosphate in C. glutamicum and B. flavum are 55 microM and 14.2 microM, respectively, and corresponding Km values for nicotinamide adenine dinucleotide are 350 microM and 625 microM, respectively. The molecular weights of pretyrosine dehydrogenase in C. glutamicum and in B. flavum are both about 158,000, compared with 68,000 moleculr weitht in B. ammoniagenes. In all three species the enzyme is not feedback inhibited by L-tyrosine. Results obtained with various auxotropic mutants, which were used to manipulate internal concentrations of L-tyrosine, suggest that pretyrosine dehydrogenase is expressed constitutively. Pretyrosine dehydrogenase is quite sensitive to p-hydroxymercuribenzoic acid, complete inhibition being achieved at 10 to 25 microM concentrations. This inhibition is readily reversed by thiol reagents such as 2-mercaptoethanol. Coryneform organisms, like species of blue-green bacteria, appear to lack the 4-hydroxyphenylpyruvate pa thway of L-tyrosine synthesis altogether. The loss of pretyrosine dehydrogenase in extracts prepared from a tyrosine auxotroph affirms the exclusive role of pretyrosine dehydrogenase in L-tyrosine biosynthesis. Other reports in the literature, in which the presence in these organisms of prephenate dehydrogenase is described, appear to be erroneous.     

DNA base compositions and photoreactivation capabilities of six Hansenula species

The DNA base compositions and photoreactivable sectors of six species of Hansenula were determined. The G+C ratios revealed two groups; the first had values of 38 to 44% and the second had lower values of 32–36%. Hansenula muscicola could not repair the UV-induced damage; whereas, H. dryadoides, H. lynferdii, H. ofunaensis, H. philodendra and H. sydowiorum could do so.     

Reversible dissociation of aspartokinase I/homoserine dehydrogenase I from Escherichia coli K 12. The active species is the tetramer

Dimers of aspartokinase I/homoserine dehydrogenase I from Escherichia coli K 12 have been isolated under very mild conditions. The dimers which cannot be distinguished from the tetramers by their kinetic properties, reassociate in the presence of potassium ions or L-aspartate. The selective sensitivity of aspartokinase I/homoserine dehydrogenase I to mild proteolytic digestion of dimers has been used to probe the reassociation reaction under the conditions of aspartokinase assay. We demonstrate that rapid reassociation occurs and that the protein species present in the assay when dimers are used to test the activity is tetrameric. These results confirm the previously proposed model for the subunit association of aspartokinase I/homoserine dehydrogenase I.     

Speckle contrast diffuse correlation tomography of cerebral blood flow in perinatal disease model of neonatal piglets

We adapted and tested an innovative noncontact speckle contrast diffuse correlation tomography (scDCT) system for 3D imaging of cerebral blood flow (CBF) variations in perinatal disease models utilizing neonatal piglets, which closely resemble human neonates. CBF variations were concurrently measured by the scDCT and an established diffuse correlation spectroscopy (DCS) during global ischemia, intraventricular hemorrhage, and asphyxia; significant correlations were observed. Moreover, CBF variations associated reasonably with vital pathophysiological changes. In contrast to DCS measurements of mixed signals from local scalp, skull and brain, scDCT generates 3D images of CBF distributions at prescribed depths within the head, thus enabling specific determination of regional cerebral ischemia. With further optimization and validation in animals and human neonates, scDCT has the potential to be a noninvasive imaging tool for both basic neuroscience research in laboratories and clinical applications in neonatal intensive care units.     

Factors associated with suicide risk among Chinese adults: A prospective cohort study of 0.5 million individuals

BackgroundSuicide is a leading cause of death in China and accounts for about one-sixth of all suicides worldwide. The objective of this study was to examine the recent distribution of suicide and risk factors for death by suicide. Identifying underlying risk factors could benefit development of evidence-based prevention and intervention programs.Methods and findingsWe conducted a prospective study, the China Kadoorie Biobank, of 512,715 individuals (41% men, mean age 52 years) from 10 (5 urban, 5 rural) areas which are diverse across China in geographic locations, social economic developmental stages, and prevalence of disease patterns. After the baseline measurements of risk factors during 2004 to 2008, participants were followed up for suicide outcomes including suicide and possible suicide deaths. Risk factors, such as sociodemographic factors and physical and mental health status, were assessed by semistructured interviews and self-report questionnaires. Suicide and possible suicide deaths were identified through linkage to the local death registries using ICD-10 codes. We conducted Cox regression to calculate hazard ratios (HRs) for suicide and for possible suicide in sensitivity analyses.During an average follow-up period of 9.9 years, 520 (101 per 100,000) people died from suicide (51.3% male), and 79.8% of them lived in rural areas. Sociodemographic factors associated with increased suicide risk were male gender (adjusted hazard ratios [aHR] = 1.6 [95% CI 1.4 to 2.0], p < 0.001), older age (1.3 [1.2 to 1.5] by each 10-yr increase, p < 0.001), rural residence (2.6 [2.1 to 3.3], p < 0.001), and single status (1.7 [1.4 to 2.2], p < 0.001). Increased hazards were found for family-related stressful life events (aHR = 1.8 [1.2 to 1.9], p < 0.001) and for major physical illnesses (1.5 [1.3 to 1.9], p < 0.001). There were strong associations of suicide with a history of lifetime mental disorders (aHR = 9.6 [5.9 to 15.6], p < 0.001) and lifetime schizophrenia-spectrum disorders (11.0 [7.1 to 17.0], p < 0.001). Links between suicide risk and depressive disorders (aHR = 2.6 [1.4 to 4.8], p = 0.002) and generalized anxiety disorders (2.6 [1.0 to 7.1], p = 0.056) in the last 12 months, and sleep disorders (1.4 [1.2 to 1.7], p < 0.001) in the past month were also found. All HRs were adjusted for sociodemographic factors including gender, age, residence, single status, education, and income. The associations with possible suicide deaths were mostly similar to those with suicide deaths, although there was no clear link between possible suicide deaths and psychiatric factors such as depression and generalized anxiety disorders. A limitation of the study is that there is likely underreporting of mental disorders due to the use of self-report information for some diagnostic categories.ConclusionsIn this study, we observed that a range of sociodemographic, lifestyle, stressful life events, physical, and mental health factors were associated with suicide in China. High-risk groups identified were elderly men in rural settings and individuals with mental disorders. These findings could form the basis of targeted approaches to reduce suicide mortality in China.

In a prospective cohort study, Rongqin Yu, Yiping Chen and colleagues investigate factors related to death by suicide among Chinese adults.     

Lectin histochemistry of the embryonic heart: fucose-specific lectin binding sites in developing rats and chicks

Glycoconjugates, particularly their sugar side chains, play important roles in embryonic development. Changes in cell-surface-associated glycoconjugates are known to affect cell differentiation, cellular interactions, and other developmental phenomena during embryogenesis. The embryonic heart goes through a series of complicated morphologic events during development. Of particular interest is morphogenesis of the outflow tract. This region of the embryonic heart originates from more than one cell population and undergoes a complex process of septation during formation of the great vessels. Histochemical analysis with a series of fucose-specific lectins conjugated to horseradish peroxidase has revealed the presence of a fucosylated glycoconjugate in the outflow tract of the developing heart. The results reveal further that the expression of the fucosylated glycoconjugate is stage-dependent and thus probably genetically regulated. The timing and distribution of staining with the lectin OFA suggest that this fucosylated glycoconjugate may play a role in directing the migration of neural crest cells into the heart and subsequent formation of the conus septum.