Spatial fiber type distribution in normal human muscle Histochemical and tensiomyographical evaluation

The variability of fiber type distribution in nine limb muscles was examined with histochemical and tensiomyographical (TMG) methods in two groups of 15 men aged between 17 and 40 years. The aim of this study was to determine the extent to which the relative occurrence of different fiber types and subtypes varies within human limb muscles in function to depth and to predict fiber type proportions with a non-invasive TMG method.The distribution of different fiber types varied within the muscles, as a function of depth, with a predominance of type 2b fibers at the surface and type 1 fibers in deeper regions of the muscle. For all the analyzed muscles the contraction times measured at stimulus intensity 10% of supramaximal stimulus (10% MS) were significantly (p<0.05) shorter than the contraction times measured at 50% of supramaximal stimulus intensity (50% MS). The Pearson's correlation coefficient between percentage of type 1 muscle fibers measured at the surface of the muscle and contraction time at 10% MS, obtained by TMG was statistically significant (r=0.76,P<0.01). Also the Pearson's correlation coefficient between percentage of type 1 muscle fibers measured in the deep region of the muscle and contraction time at 50% MS obtained by TMG was also statistically significant (r=0.90,P<0.001).These findings suggest that the contraction time obtained by TMG may be useful for non-invasive examining of muscle fiber types spatial distribution in humans.     

Characterization of sugar transport in 2-deoxy-d-glucose resistant mutants of yeast

Summary A number of 2-deoxy-d-glucose (2-DOG) resistant mutants exhibiting resistance to glucose repression were isolated from variousSaccharomyces yeast strains. Most of the mutants isolated were observed to have improved maltose uptake ability in the presence of glucose. Fermentation studies indicated that maltose was taken up at a faster rate and glucose taken up at a slower rate in the mutant strains compared to the parental strains, when these sugars were fermented together. When these sugars were fermented separately, only the 2-DOG resistant mutant obtained fromSaccharomyces cerevisiae strain 1190 exhibited alterations in glucose and maltose uptake compared to the parental strain. Kinetic analysis of sugar transport employing radiolabelled glucose and maltose indicated that both glucose and maltose were transported with higher rates in the mutant strain. These results suggested that the high affinity glucose transport system was regulated by glucose repression in the parental strain but was derepressed in the mutant.     

Immunization with AgTRIO,a Protein in Anopheles Saliva,Contributes to Protection against Plasmodium Infection in Mice

1. Download high-res image (116KB)
2. Download full-size image

     

Chemotaxonomic Considerations of the n‐Alkane Composition in Pinus heldreichii,P. nigra,and P. peuce

The n‐alkane composition in the leaf cuticular waxes of natural populations of Bosnian pine (Pinus heldreichii), Austrian pine (P. nigra), and Macedonian pine (P. peuce) was compared for the first time. The range of n‐alkanes was wider in P. nigra (C₁₆ – C₃₃) than in P. heldreichii and P. peuce (C₁₈ – C₃₃). Species also diverged in abundance and range of dominant n‐alkanes (P. heldreichii: C₂₃, C₂₇, and C₂₅; P. nigra: C₂₅, C₂₇, C₂₉, and C₂₃; P. peuce: C₂₉, C₂₅, C₂₇, and C₂₃). Multivariate statistical analyses (PCA, DA, and CA) generally pointed out separation of populations of P. nigra from populations of P. heldreichii and P. peuce (which were, to a greater or lesser extent, separated too). However, position of these species on the basis of n‐alkane composition was in accordance neither with infrageneric classification nor with recent molecular and terpene investigations.     

Power Dissipation in the Cochlea Can Enhance Frequency Selectivity

The cochlear cavity is filled with viscous fluids, and it is partitioned by a viscoelastic structure called the organ of Corti complex. Acoustic energy propagates toward the apex of the cochlea through vibrations of the organ of Corti complex. The dimensions of the vibrating structures range from a few hundred (e.g., the basilar membrane) to a few micrometers (e.g., the stereocilia bundle). Vibrations of microstructures in viscous fluid are subjected to energy dissipation. Because the viscous dissipation is considered to be detrimental to the function of hearing—sound amplification and frequency tuning—the cochlea uses cellular actuators to overcome the dissipation. Compared to extensive investigations on the cellular actuators, the dissipating mechanisms have not been given appropriate attention, and there is little consensus on damping models. For example, many theoretical studies use an inviscid fluid approximation and lump the viscous effect to viscous damping components. Others neglect viscous dissipation in the organ of Corti but consider fluid viscosity. We have developed a computational model of the cochlea that incorporates viscous fluid dynamics, organ of Corti microstructural mechanics, and electrophysiology of the outer hair cells. The model is validated by comparing with existing measurements, such as the viscoelastic response of the tectorial membrane, and the cochlear input impedance. Using the model, we investigated how dissipation components in the cochlea affect its function. We found that the majority of acoustic energy dissipation of the cochlea occurs within the organ of Corti complex, not in the scalar fluids. Our model suggests that an appropriate dissipation can enhance the tuning quality by reducing the spread of energy provided by the outer hair cells’ somatic motility.     

Contribution of extrasynaptic N-methyl-d-aspartate and adenosine A1 receptors in the generation of dendritic glutamate-mediated plateau potentials

Thin basal dendrites can strongly influence neuronal output via generation of dendritic spikes. It was recently postulated that glial processes actively support dendritic spikes by either ceasing glutamate uptake or by actively releasing glutamate and adenosine triphosphate (ATP). We used calcium imaging to study the role of NR2C/D-containing N-methyl-d-aspartate (NMDA) receptors and adenosine A1 receptors in the generation of dendritic NMDA spikes and plateau potentials in basal dendrites of layer 5 pyramidal neurons in the mouse prefrontal cortex. We found that NR2C/D glutamate receptor subunits contribute to the amplitude of synaptically evoked NMDA spikes. Dendritic calcium signals associated with glutamate-evoked dendritic plateau potentials were significantly shortened upon application of the NR2C/D receptor antagonist PPDA, suggesting that NR2C/D receptors prolong the duration of calcium influx during dendritic spiking. In contrast to NR2C/D receptors, adenosine A1 receptors act to abbreviate dendritic and somatic signals via the activation of dendritic K⁺ current. This current is characterized as a slow-activating outward-rectifying voltage- and adenosine-gated current, insensitive to 4-aminopyridine but sensitive to TEA. Our data support the hypothesis that the release of glutamate and ATP from neurons or glia contribute to initiation, maintenance and termination of local dendritic glutamate-mediated regenerative potentials.     

Development of c‐kit immunopositive interstitial cells of Cajal in the human stomach

Interstitial cells of Cajal (ICC) include several types of specialized cells within the musculature of the gastrointestinal tract (GIT). Some types of ICC act as pacemakers in the GIT musculature, whereas others are implicated in the modulation of enteric neurotransmission. Kit immunohistochemistry reliably identifies the location of these cells and provides information on changes in ICC distribution and density. Human stomach specimens were obtained from 7 embryos and 28 foetuses without gastrointestinal disorders. The specimens were 7–27 weeks of gestational age, and both sexes are represented in the sample. The specimens were exposed to anti‐c‐kit antibodies to investigate ICC differentiation. Enteric plexuses were immunohistochemically examined by using anti‐neuron specific enolase and the differentiation of smooth muscle cells (SMC) was studied with anti‐α smooth muscle actin and anti‐desmin antibodies. By week 7, c‐kit‐immunopositive precursors formed a layer in the outer stomach wall around myenteric plexus elements. Between 9 and 11 weeks some of these precursors differentiated into ICC. ICC at the myenteric plexus level differentiated first, followed by those within the muscle layer: between SMC, at the circular and longitudinal layers, and within connective tissue septa enveloping muscle bundles. In the fourth month, all subtypes of c‐kit‐immunoreactivity ICC which are necessary for the generation of slow waves and their transfer to SMC have been developed. These results may help elucidate the origin of ICC and the aetiology and pathogenesis of stomach motility disorders in neonates and young children that are associated with absence or decreased number of these cells.     

Carriage and Genetic Diversity of Methicillin-Resistant Staphylococcus aureus among Patients and Healthcare Workers in a Serbian University Hospital

ObjectivesThere is a paucity of data on methicillin-resistant Staphylococcus aureus (MRSA) epidemiology among Balkan countries. The aim of our study was to determine the prevalence of nasal and pharyngeal carriages and diversity of MRSA among patients and healthcare workers (HCWs) in the major referral centre in Serbia, and to evaluate performance of three different media for MRSA screening.MethodsNasal and pharyngeal swabs were obtained from 195 patients and 105 HCWs in Emergency Department (ED), Surgical Department (SD) and Medical Department (MD). After broth enrichment, samples were inoculated onto MRSA-ID, ORSA and oxacillin-MSA and incubated for 24/48 hours. Characterisation of isolated MRSA strains was determined by MLVA, spa, SCCmec and agr typing, PVL genes detection and antimicrobial susceptibility.ResultsMRSA carriage prevalence was 11.8% in patients and 7.6% in HCWs. Introduction of pharyngeal swabs in screening procedure increased MRSA carriage rate by over 30%. Variable found to be independently associated with an increased risk for MRSA carriage was ED (odd ratio (OR) = 4.45, 95% confidence interval (CI) 1.78-11.14). A higher risk of multidrug-resistant MRSA carriage was observed among patients (OR = 22; 95% CI 1.92-251.54). CC5-MRSA-SCCmecI was the dominant clone among patients and HCWs in ED and MD, while high genetic diversity of community-associated MRSA (CA-MRSA) was shown in SD especially among HCWs. MRSA-ID was superior to the other tested media with a sensitivity/specificity of 95.2% and 99.6% after 48 hours of incubation.ConclusionsThese results indicate high MRSA carriage rate in the hospital and emergence of CA-MRSA through HCWs in these settings. MRSA-ID was the optimal available choice for MRSA screening.