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Biomedical subjects

S Alexiou

Publications and source records attributed to S Alexiou.

16 recordsLinked to original sources
PubMed2002

Electromyographic changes of agonist and antagonist calf muscles during maximum isometric induced fatigue.

The purpose of this study was to examine electromyographic changes of the agonist and antagonist muscles during fatigue. Nine healthy, untrained subjects exerted a maximum voluntary heel lifting contraction with their dominant limb. The EMG activity over the soleus and the tibialis anterior muscles was recorded during the contraction. The results showed that the torque output during heel lifting and the soleus EMG activity decreased, whereas the tibialis anterior EMG revealed a small but non-significant decrease. However, the ratio of the tibialis anterior to the soleus EMG increased significantly at the end of the fatigue protocol, a fact that reveals that the decrease rate of the antagonist's activity was significantly lower than the decrease rate of the agonist activity. It is concluded that during a maximal fatigue protocol, both the agonist and antagonist muscle activity may decline, however, the slower rate of antagonist's activity decrease relative to the agonist's activity is a finding that requires further investigation. This finding may reflect a higher level of agonist and antagonist muscle co-activation and probably a relatively higher opposing torque from the antagonist muscles at the end of the fatigue session.

Adult↗
PubMed2000

Genetic heterogeneity of HIV-1 in Greece.

The aim of this study was to detect and determine the genetic variation of HIV-1 in Greece and to analyze the phylogenetic relationships and transmission dynamics of identified variants. Eighty-six blood samples from HIV-1 seroconverted patients of different risk groups were collected from the AIDS clinic, AHEPA Hospital, Thessaloniki, Greece. Retroviral DNA was extracted from uncultured peripheral blood mononuclear cells. HIV-1 DNA sequences encoding a 500-bp fragment of the gp120 C2-C3 region were amplified from each study subject, and they were genetically subtyped by heteroduplex mobility assay and DNA sequencing. Genetic distances and phylogenetic relationships of DNA sequences were estimated using PHYLIP software. Our results revealed that 82 out of 86 (95.3%) subjects carried subtype B sequences, while four (4.7%) carried subtype A sequences. Subtype A in Greek individuals not having traveled abroad was documented. An average of intrasubtype B genetic divergence of 15% was noted. Our findings demonstrate the presence of at least two genetic subtypes of HIV-1 in northern Greece--subtype B and subtype A. The predominant subtype is subtype B, which was transmitted into Greece by multiple sources. Our observations lend support to the argument that the distribution of HIV-1 subtypes is determined by founder effects or other processes rather than any tropism for particular cell types or mode of transmission.

Adult↗
PubMed2000

HIV-1 co-receptor CCR5 and CCR2 mutations among Greeks.

The frequency of CCR5 and CCR2 alleles in human immunodeficiency virus (HIV)-positive and HIV-negative populations of Northern Greece was investigated. The frequency of the CCR5Delta32 allele among the HIV-negative subjects was 0.052, while it was approximately two-fold lower among the seropositives, suggesting that the heterozygous genotype confers a partial resistance to the HIV infection. No significant difference in CCR2 allele frequency between the two groups was observed.

Alleles↗
PubMed1999

Hydrogen Balmer-alpha broadening in dense plasmas.

This work presents a theoretical analysis of experimental results for the hydrogen Balmer-alpha line in dense plasmas, with electron densities between 2x10(18) and 9x10(18) e/cm(3) A simulation of both electrons and ions is employed to produce reliable theoretical widths. These results are essentially in agreement with standard theory results and, for the most part, disagree with the experimental results. Consequently, either mechanisms not accounted for in the theoretical results (such as quadrupoles) are more important than previously thought at these densities, or else there is a problem in the experimental data (such as a possible reabsorption, which is not ruled out by the experimental data).

Journal Article↗
PubMed1999

Line shape measurement and isolated line width calculations: quantal versus semiclassical methods.

In a recent paper Griem, Ralchencko, Bray [Phys. Rev. E 56, 7186 (1998)] perform quantum-mechanical calculations of the line width of the B III 2s-2p transition and find agreement with previous quantum-mechanical results. The quantum-mechanical widths are a factor approximately 2 smaller than those measured in a recent experiment where the full width at half maximum for the B III 2s-2p transition was measured in a plasma with a measured electron temperature and density of 10 eV and 2 x 10(18) cm(-3). The quantum-mechanical results also disagree with a nonperturbative semiclassical calculation. We will illustrate that Griem, Ralchencko, and Bray are incorrect in stating that the experimental results are in error and that the semiclassical calculations are inapplicable.

Letter↗
PubMed1995

Influenza surveillance in N. Greece during 1983-1993.

Following the WHO programme to monitor influenza, the National Influenza Centre for N. Greece presents the results of a laboratory surveillance during 1983-93. Influenza viruses were isolated every year except for 1986-87 and 1987-88 seasons. Type A viruses predominated in 1983-84, 1985-86, 1988-89 and 1989-90. Type B viruses were prevalent in 1990-91 and 1992-93. Both types of A and B viruses circulated concurrently in the community during the winters of 1984-85 and 1991-92. Seroconversions (CF tests) occurred each year against A, B or both types of influenza viruses. In 1986-87 and 1987-88 when no viruses were recovered, there were seroconversions to B viruses, suggesting influenza B activity in the area. Serological surveys by haemagglutination inhibition (HI) tests were also conducted in 1986-87 and 1988-89. The patterns of the isolated strains were similar to those recorded worldwide at the same time. There have been however differences in the virulence of the viruses and the duration of influenza seasons in this part of the world during 1983-93.

Antibodies, Viral↗
PubMed1995

Renal transplantation in asymptomatic carriers of hepatitis B surface antigen.

The aim of the present study was: (a) to assess the effect of HBsAg on the survival of both renal grafts and patients, and (b) to determine the outcome of HBV chronic infection after renal transplantation. Fourteen patients seropositive for HBsAg but asymptomatic before renal transplantation (group A) were included in the study. The results were compared to those of 14 transplanted patients (group B) seronegative for HBsAg with similar age and immunosuppressive treatment. Four patients received a graft from a living-related donor and 10 patients from a cadaver donor in each group. Eight of 14 patients of group A showed, after renal transplantation, chronic hepatitis, which was not observed in any of the group B patients (p < 0.01). The rate of acute rejection episodes was significantly greater (p < 0.05) in group B than in group A. The graft survival was found to be similar in both groups at the 1st year, but significantly less (p < 0.01) in group B than in group A at the 5th year after transplantation. The survival of patients was found to be significantly less in group A than in group B at the 1st (p < 0.05) and 5th years (p < 0.01) after transplantation. In 2 patients of group A and 1 of group B anti-HCV was found, while HDAg plus anti-HD was found in 1 patient of group B. The HBV-DNA was found in 4 of 8 alive patients of group A.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗