COMT Gene Polymorphism Is Associated with Declarative Memory in Adulthood and Old Age

Variation in memory performance is to a large extent explained by genes. In the prefrontal cortex, the catechol O-methyltransferase (COMT) gene is essential in the metabolic degradation of dopamine, a neurotransmitter implicated in cognitive functions. The present study examined the effect of a polymorphism in the COMT gene on individual differences and changes in memory in adulthood and old age. Tests assessing episodic and semantic memory were administered to 286 men (initially aged 35-85 years) from a random sample of the population (i.e., the Betula prospective cohort study) at two occasions followed over a 5-year period. Carriers of the Met/Met genotype (with low enzyme activity) performed better on episodic and semantic memory, as compared to carriers of the Val allele (with higher enzyme activity). Division of episodic memory into its recall and recognition components showed that the difference was specific to episodic recall, not recognition tasks; an effect that was observed across three age groups (middle-age, young-old, and old-old adults) and over a 5-year period. The COMT gene is a plausible candidate gene for memory functioning in adulthood and old age.     

A nonlinear model of the arterial vessels within a limb segment

The relationship between the arterial blood pressure and the volume of the arteries within a segment of an extremity is nonlinear. The present paper shows how the flow and volume pulsations of the arteries within a limb segment can be simulated taking this property into account. An electrical model was constructed comprising one resistor and two voltage dependent ‘capacitors’, the latter corresponding to the pressure dependent elasticity, or compliance, of the arteries. Adequate simulations were obtained over a wide pressure range, which is impossible with linear models. The nonlinear, i.e. pressure dependent, relationship between the volume and pressure of arteries, observed under static conditions, must also be taken into consideration when studying pulsatile events with models whether mathematical or physical.     

Hypergammaglobulinemia and autoantibody induction mechanisms in viral infections

Polyclonal hypergammaglobulinemia is a characteristic of chronic inflammatory conditions, including persisting viral infections and autoimmune diseases. Here we have studied hypergammaglobulinemia in mice infected with lymphocytic choriomeningitis virus (LCMV), which induces nonspecific immunoglobulins as a result of switching natural IgM specificities to IgG. The process is dependent on help from CD4+ T cells that specifically recognize LCMV peptides presented by B cells on major histocompatibility complex class II molecules. Thus, hypergammaglobulinemia may arise when specific helper T cells recognize B cells that have processed viral antigens irrespective of the B cell receptor specificity. This nonspecific B cell activation may contribute to antibody-mediated autoimmunity.     

Immunization with recombinant protein: conditions for cytotoxic T cell and/or antibody induction

Safe vaccines should optimally induce both cell-mediated and humoral immunity. Recently, it has been shown that protective cytotoxic T cells (CTLs) can be induced not only with live vaccines, but also with recombinant viral proteins. This report shows in C57BL/6 (H-2^b) mice that the recombinant nucleoprotein (N) of vesicular stomatitis virus (VSV) induced protective CTLs but no neutralizing antibodies in mice, whereas the recombinant glycoprotein (G) of VSV alone induced neutralizing antibodies but no CTLs. If the N and G of VSV were coinjected, both CTLs and a long-lasting neutralizing IgG response was measurable, demonstrating that mixed vaccines can be used to induce protective CTLs and antibodies with an efficiency comparable to live virus. In an attempt to define optimal conditions for CTL priming, the intravenous, intraperitoneal and subcutanous route of injection were compared. Intravenous injection of recombinant VSV-N induced up to 30 times higher responses than the latter two routes. Finally, we tried to define conditions inducing only CTLs and no antibodies binding to the native protein form, or vice versa, only antibodies and no CTLs. Intravenous injection of boiled VSV-N induced a CTL response but no antibodies specific for the native VSV-N, whereas VSV-N injected subcutanously in incomplete Freund's adjuvant induced high amounts of anti-VSV-N antibodies but virtually no CTLs. The conditions defined here permit vaccines to be designed which would function along selected and defined immunological effector pathways.     

材料参数与镍钛形状记忆合金的本构关系

在Ｔａｎａｋａ模型基础上，我们讨论了形状记忆合金热力学特性的本构关系。特别注意了桓温拉伸过程和强迫回复过程。本构方程的材料参数，即弹性模量Ｄ，变化张量Ω，热力弹性张量均以镍钛合金实验测试值来确定。在不同的应力－应变－温度关系试验中发现Ｄ和Ω与温度之间有很强的相关性。     

Characterization of DEAE-dextran by means of light scattering and combined size-exclusion chromatography/low-angle laser light scattering/viscometry

Ten DEAE (2-(diethylamino)ethyl) dextran samples were investigated by means of static and dynamic light scattering, viscometry and size-exclusion chromatography (SEC) in combination with on-line small-angle laser light scattering (LALLS) and viscometry (VISC). In dilute solution the behavior of DEAE-dextran was compared with that of unsubstituted dextran and the molecular weight M dependences of the radius of gyration R_g, hydrodynamic radius R_h, intrinsic viscosity [η], second virial coefficient A₂ and z-average diffusion coefficient D _z were determined. The relationships for DEAE-dextran dissolved in a 0,8 molar sodium nitrate solution were nearly the same as for dextran dissolved in water with 0,05 wt.-% sodium azide and gave the same exponents. The molecular weight dependence of the intrinsic viscosity cannot be described by a Kuhn-Mark-Houwink relationship with a constant exponent. The slope in the plot of log [η] versus log M decreases with increasing molecular weight which indicates the occurrence of branching. By means of SEC/LALLS/VISC measurements the molecular weight distributions were determined. The distributions were calculated (1) directly from the light scattering signal, (2) from a calibration line obtained by light scattering data of a DEAE-dextran sample with a broad distribution and (3) from the intrinsic viscosity distribution obtained by the on-line viscosity/refractive index detector in combination with the [η]-M relationship. In order to get the correct molecular-weight dependence of the intrinsic viscosity it is necessary to determine the molecular weight distribution directly by LALLS (technique 1) and to combine this with the appropriate intrinsic viscosity data from the viscometer. Only the third technique, which is an extension of technique 1, gave satisfactory results over the whole molecular weight region observed.     

Comparison of GB virus C, HIV, and HCV infection markers in hemophiliacs exposed to non-inactivated or inactivated factor concentrates.

BACKGROUND: Until the mandatory introduction of viral inactivation techniques of blood plasma products in the early 1980s many recipients of these products were infected with various viral pathogens. OBJECTIVES: To determine the rate of transmission of GB virus C/hepatitis G virus (GBV-C/HGV) HCV, and HIV through non-virus-inactivated clotting factor concentrates in hemophiliacs, as well as the relation between amount of administered clotting factor and risk for GBV-C/HGV infection. STUDY DESIGN: In this cross-sectional study, we determined retrospectively the rates of infection markers for GBV-C/HGV, HCV, and HIV in a German cohort of hemophiliacs treated with documented amounts of non-virus-inactivated clotting factor concentrates (group A) and in a second group of hemophiliacs who were treated exclusively with virus-inactivated clotting factor (group B). The presence of anti-virus antibodies was determined by ELISA. Viral RNA was detected by RT-PCR. Markers for viral infections were compared to amounts of administered non-virus-inactivated clotting factor. RESULTS: Among hemophiliacs treated with documented amounts of non-virus-inactivated clotting factor the prevalence for GBV-C/HGV, HCV, and HIV was 40.3%, 98.6%, and 56.3%, respectively. In contrast to HIV, the rate of GBV-C/HGV infections did not increase with increasing amounts of consumed non-inactivated clotting factor. Even in the subgroup of heavily treated hemophiliacs the rate of GBV-C/HGV infection markers did not exceed 45%. CONCLUSIONS: The amount of non-virus-inactivated clotting factor is not predictive for the risk of GBV-C/HGV infection in hemophiliacs. Despite repeated parenteral exposure more than 55% of hemophiliacs were not infected with GBV-C/HGV. Our findings indicate a high frequency of host factors preventing parenteral transmission of GBV-C/HGV.