In vitro susceptibility to infection with SIVcpz and HIV-1 is lower in chimpanzee than in human peripheral blood mononuclear cells

This study was undertaken to evaluate and compare the susceptibility of chimpanzee versus human peripheral blood mononuclear cells (PBMCs) to infection with SIVcpz and HIV-1 non-syncitium inducing primary isolates. The results demonstrate clearly that chimpanzee PBMCs have a lower capacity to support viral replication as compared to human PBMCs. There was no experimental evidence that this difference was due to a lower availability of target cells for viral infection (PBMCs positive for CD4 and CCR5 molecules) or to a differential susceptibility to apoptosis (PBMCs positive for CD4 and CD95 molecules). A lower capacity of chimpanzee PBMCs to support SIVcpz and HIV-1 replication in vitro is related to a post-entry barrier to virus replication.     

Sequencing of the GRIK1 gene in patients with juvenile absence epilepsy does not reveal mutations affecting receptor structure

Hereditary factors play a major role in the etiology of juvenile absence epilepsy (JAE) that is a common subtype of idiopathic generalized epilepsy (IGE). Sander et al. [1997: Am J Med Genet 74:416-421] reported an allelic association of JAE with the nine-copy allele of a tetranucleotide repeat polymorphism in the third intron of the kainate-selective GluR5 receptor gene (GRIK1) and supportive evidence for linkage of IGE to GRIK1 in families of JAE probands. These findings suggest that a major genetic determinant of GRIK1 confers susceptibility to JAE. Assuming that the GRIK1 tetranucleotide repeat polymorphism is unlikely to have functional relevance itself, we have sequenced the coding regions and regulatory sequences of the GRIK1 gene in eight JAE patients who carry the nine-repeat allele of the GRIK1 tetranucleotide repeat polymorphism to detect a putative functional GRIK1 mutation that is in linkage disequilibrium with the nine-repeat allele. Seven of them were derived from families showing positive evidence for linkage to GRIK1. Our mutation analysis of coding regions and splice junctions revealed only two silent polymorphisms (A522C and C1173T) out of the five SNPs present in public databases and no mutations affecting protein structure. No significant differences were found in the allele frequencies of the detected polymorphisms between the JAE patients and controls. High levels of sequence conservation were also found in the promoter, in the 5' and both the 3' untranslated regions and in the RNA secondary structure involved in the editing reaction. The results presented indicate that mutations in the coding sequences, in the intron-exon boundaries and in the main regulatory regions of the GRIK1 are not commonly involved in the etiology of JAE.     

Signaling to localized degranulation in neutrophils adherent to immune complexes

The present study demonstrates that the secretion of azurophilic granules occurring during Fc receptor-mediated attachment and spreading of neutrophils is highly localized to the adhering region of the cell. In contrast, the secretion of specific granules occurs in a nonpolarized way. This implies that unique signals are involved in the regulation of azurophilic degranulation. Assembly of actin filaments, as visualized by staining with rhodamine phalloidin, neither hindered nor facilitated degranulation. Further, the azurophilic secretory response remained localized in the presence of cytochalasin B. Release of azurophilic-granule content was inhibited by genistein and erbstatin, inhibitors of tyrosine kinases, and by GF109203X, a protein kinase C (PKC) inhibitor. We could also demonstrate a relative enrichment of syk tyrosine kinase and the PKC isoforms alpha and beta1 in adherent plasma membranes.     

Presence of macrophage migration inhibitory factor in human milk: evidence in the aqueous phase and milk fat globules

Human milk is a source of bioactive substances regulating the development and activity of the newborn immune system. Human milk has been found to contain a number of cytokines, including interleukins, growth factors, and colony stimulating factors. In the present study, we assessed 10 specimens of human milk for the presence of macrophage migration inhibitory factor (MIF), a cytokine recently described in several human reproductive organs and tissues. Using biochemical as well as immunologic techniques, we showed that MIF is abundantly present in human milk, mostly distributed in the lipid layer and in the aqueous phase. Fractionation of the lipid layer showed that MIF is highly concentrated inside milk fat globules. In view of its proinflammatory features, we speculate that milk MIF may protect the newborn against infection and play a role in preserving the functionality of the lactating mammary gland. Furthermore, the localization of MIF in lipid globules suggests a possible strategy for the protection of milk cytokines from the gastric barrier.     

Time-frequency and time-varying analysis for assessing the dynamic responses of cardiovascular control

Time-frequency or time-variant methods have been extensively applied in the study of the heart-rate variability (HRV) signal. In fact, the frequency content of HRV signal has a strong correlation with the control system assessing heart rate. In particular, the power related to the low-frequency (LF) and high-frequency (HF) components have been demonstrated to correlate to the action of sympathetic and parasympathetic branches of the autonomic nervous system. However, the analysis is restricted to stationary conditions, unless time-frequency methods are employed for detecting dynamic changes that may occur during physiological and pathological conditions.This article reviews the most diffused tools for time-frequency analysis, starting from linear decomposition of the signal (including short-time Fourier transform and wavelet and wavelet packet decomposition), to quadratic time-frequency distributions (including Wigner-Ville transform and Cohen's class of distributions), and finally to adaptive or time-variant autoregressive (AR) models, in both the mono- and bivariate forms. In the past few years, these approaches have been applied in several studies related to cardiovascular responses during nonstationary pathophysiological events. Among them, we will recall and discuss myocardial ischemia (spontaneous or induced), drug infusion, rest-tilt maneuver and syncope, neurophysiological, and sleep investigations.     

Biomedical signal processing and modeling in cardiovascular systems

This article revisits the subject of short-term heart-rate and arterial-pressure variability from the perspective of model structures that can be useful in defining signal processing algorithms. We draw a general scheme of the oscillation sources and interactions that contribute to cardiovascular control mechanisms and highlight the elements that were considered in different modeling works.The origin, superposition, and interaction of respiratory high-frequency (HF) and vasomotor low-frequency (LF) rhythms is presented as the integration of supraspinal and spinal circuits, vasomotor activity, and pressure control loops. We analyze in detail the necessity of considering all relevant interactions for the algorithms designed to estimate the baroreflex sensitivity. We also pinpoint the components of cardiorespiratory coupling in relation to the analysis of data from the acoustic quantification of the left ventricular volume. Finally, we analyze the tendency to produce complex behaviors even in extremely simplified systems involving interactions between oscillatory mechanisms.     

Identification of Echinococcus granulosus eggs

OBJECTIVE: The purpose of this QMP-LS patterns-of-practice survey was to determine quality assurance (QA) processes used in Ontario for purchased and in-house culture media, and compliance with recommended practices. METHODS: QMP-LS required laboratories to submit copies of media QC records for August to October 1998. Target media were blood agar, chocolate agar, MacConkey agar, sorbitol MacConkey agar (SMAC), Campylobacter agar, and selective media for pathogenic Neisseria spp. Procedures for acquisition and maintenance of QC stock cultures, media-type specific QC strains, time and temperature of incubation, and the test inoculum were required. Data were captured and analysed using Microsoft Excel. RESULTS: Marked variability and inadequacy of media QC records of 124 participating laboratories was noted. 12/124 prepared media in-house, most did not comply with NCCLS QA recommendations. Those purchasing prepared media frequently did not comply with NCCLS recommendations. In-house QC was not performed by 9% for chocolate agar, 87% for MacConkey agar without crystal violet, and 53% for SMAC agar. Recommended ATCC strains were used by less than half of participants. Time and temperature of incubation of the QC plates were not always appropriate. Only 65/117 laboratories used a correct inoculum to test the sensitivity and selectivity of media for pathogenic Neisseriae. Physical characteristics of prepared media were rarely recorded. Most laboratories were not aware of their supplier's QC protocols. DISCUSSION: Few Ontario laboratories comply with the NCCLS recommendations for QA of culture media. Major compliance failures were not performing QC at all, inappropriate choice of QC bacterial strains, and inoculum used. Incomplete record keeping was common and methods for maintaining stock cultures were sub-optimal. External quality assessment of this important parameter of microbiology practice needs to be undertaken on an ongoing basis.