Ventricular activation during sympathetic imbalance and its computational reconstruction

We characterized the epicardial activation sequence during a norepinephrine (NE)-induced ventricular arrhythmia in anesthetized pigs and studied factors that modulated it. Subepicardial NE infusion caused the QRS complex to invert within a single beat (n = 35 animals, 101 observations), and the earliest epicardial activation consistently shifted to the randomly located infusion site (n = 14). This preceded right atrial activation, whereas the total ventricular epicardial activation time increased from 20 +/- 4 to 50 +/- 9 ms (P < 0.01). These events were accompanied by a ventricular tachycardia and a drop in left ventricular pressure, which were fully reversed after the infusion was stopped. Epicardial pacing at the infusion site mimicked all electrical and hemodynamic changes induced by NE. The arrhythmia was prevented by propranolol and abolished by cardiac sympathetic or vagal nerve stimulation. Focal automaticity was computationally reconstructed using a two-dimensional sheet of 256 x 256 resistively coupled ventricular cells, where calcium handling was abnormally high in the central region. We conclude that adrenergic stimulation to a small region of the ventricle elicits triggered automaticity and that computational reconstruction implicates calcium overload. Interventions that reduce spatial inhomogeneities of intracellular calcium may prevent this type of arrhythmia.

In vivo elemental partition analysis using fast neutrons. A tool for testing the efficacy of new clinical interventions

The nutritional status of patients can be evaluated by monitoring changes in body composition, including depletion of protein and muscle; distribution of adipose tissue; and changes in hydration status, and bone or cell mass. Fast neutron activation (for N and P) and neutron inelastic scattering (for C and O) are used to assess in vivo elements characteristic of specific body compartments. Nonbone phosphorus for muscle is measured by the 31P(n,alpha)28Al reaction, and nitrogen for protein via the (n,2n) fast neutron reaction. The carbon-to-oxygen (C/O) ratio is used to measure distribution of fat and lean tissue in the body and to monitor small changes in lean mass and its quality. In addition to evaluating the efficacy of new treatments, the method is used to study the mechanisms of depletion of lean tissue with aging.

ASW: a gene with conserved avian W-linkage and female specific expression in chick embryonic gonad

Vertebrates exhibit a variety of sex determining mechanisms which fall broadly into two classes: environmental or genetic. In birds and mammals sex is determined by a genetic mechanism. In mammals males are the heterogametic sex (XY) with the Y chromosome acting as a dominant determiner of sex due to the action of the testis-determining factor, SRY. In birds females are the heterogametic sex (ZW); however, it is not known whether the W chromosome carries a dominant ovary-determining gene, or whether Z chromosome dosage determines sex. Using an experimental approach, which assumes only that the sex-determining event in birds is accompanied by sex-specific changes in gene expression, we have identified a novel gene, ASW (Avian Sex-specific W-linked). The putative protein for ASW is related to the HIT (histidine triad) family of proteins. ASW shows female-specific expression in genital ridges and maps to the chicken W chromosome. In addition, we show that, with the exception of ratites, ASW is linked to the W chromosome in each of 17 bird species from nine different families of the class Aves.

Comments on "PM(2.5) mortality in long-term prospective cohort studies: cause-effect or statistical association?"

Images

Kallmann syndrome gene (KAL-X) is not mutated in schizophrenia

Kallmann syndrome and schizophrenia share several clinical features, including dysfunctional olfactory ability, hypogonadotrophic hypogonadism, an excess of affected males, and psychiatric presentation. Because of this congruence, it has been proposed that up to 70% of male schizophrenics might have mutations affecting the function or expression of the gene mutated in Kallmann syndrome, KAL-X. We identified and studied 9 unrelated males with schizophrenia (as defined by DSM-IIIR criteria) who also have severe anosmia (first percentile of normal range) and low sex drive (seventh percentile of the normal range), and we sequenced the exons and the intron-exon junctions of the KAL-X gene for each. We found no mutations, and conclude that schizophrenia is rarely, if ever, due to a mutation in the coding sequence or splice junctions of KAL-X.

Experimental assessment of the influence of atmospheric pollutants on respiratory disease

Asthma is a chronic respiratory disease characterized by inflammation, episodes of usually reversible airways obstruction, and bronchial hyperresponsiveness. The disease has significant health, societal and economic consequences. Experimental assessment methods, including controlled human exposure studies, human and animal dosimetry, as well as animal and in vitro toxicology, can shed light on how air pollutants may cause and/or worsen asthma. A brief summary background on selected classes of air pollutants is provided and selected experimental studies that exemplify novel approaches or suggest new hypotheses are highlighted. Possible directions for future research about the effects of particles, pesticides, ambient air toxicants, and pollutant mixtures on asthma, are also outlined.

Localization of a protein-DNA interface by random mutagenesis

The type I restriction and modification enzymes do not possess obvious DNA-binding motifs within their target recognition domains (TRDs) of 150-180 amino acids. To identify residues involved in DNA recognition, changes were made in the amino-TRD of EcoKI by random mutagenesis. Most of the 101 substitutions affecting 79 residues had no effect on the phenotype. Changes at only seven positions caused the loss of restriction and modification activities. The seven residues identified by mutation are not randomly distributed throughout the primary sequence of the TRD: five are within the interval between residues 80 and 110. Sequence analyses have led to the suggestion that the TRDs of type I restriction enzymes include a tertiary structure similar to the TRD of the HhaI methyltransferase, and to a model for a DNA-protein interface in EcoKI. In this model, the residues within the interval identified by the five mutations are close to the protein-DNA interface. Three additional residues close to the DNA in the model were changed; each substitution impaired both activities. Proteins from twelve mutants were purified: six from mutants with partial or wild-type activity and six from mutants lacking activity. There is a strong correlation between phenotype and DNA-binding affinity, as determined by fluorescence anisotropy.

An immunochemical analysis of mdm2 expression in human breast cancer and the identification of a growth-regulated cross-reacting species p170

mdm2 is a 491 amino acid nuclear protein which is involved in complex interactions with important cell-cycle and stress-response regulators including p53, Rb and E2F. Recent data implicate mdm2 in the regulation of both p53 activity and level, and burgeoning data suggest that mdm2 may be involved in human epithelial tumourigenesis, including breast cancer. In this study the expression of mdm2 protein has been investigated in a series of 54 human breast carcinomas using immunoblotting methods. Overexpression of the predominant p90 mdm2 isoform is common in breast cancer (54 per cent) and this is not frequently a consequence of gene amplification. There is no relationship between p90 expression and either p53 protein expression or p53 mutational status. Additional mdm2 immunoreactive species of differing mobilities are identifiable, greatly complicating the analysis. For example, a p170 form is seen in many breast cancer samples (44 per cent) using 2A10 but is not identified by 3G5. This 2A10 immunoreactive species, which is almost certainly not an mdm2 isoform, is a growth-regulated protein, being undetectable in resting peripheral blood lymphocytes and rising to high levels after PHA stimulation. In contrast to mdm2 (p90), p170 is not induced by DNA damage caused by UV light. p170 is identifiable in mdm2 null cells by immunoblotting and is detected as a nuclear protein. While mdm2 immunostaining studies are increasing, this report highlights the complexity of mdm2 analysis in vivo and emphasizes the need to correlate immunohistological and biochemical assays since, in some mdm2 (p90) negative tumours, nuclear immunoreactivity may be identified as a consequence of cross-reacting species such as p170.

Progressive proptosis in a neonate

Images

Health risk profile of prostitutes in Dublin

This study examined the health risk profile of prostitutes in Dublin. Clinical records of all 150 new prostitutes who attended a drop-in clinic for prostitutes in Dublin city during the period 1991-1997 were reviewed. Variables examined included: age, use of injectable drugs, human immunodeficiency virus (HIV) status, hepatitis B and C status, presence of sexually transmitted disease (STD), cervical cytology. Results showed the mean age of the women was 32 years. Among those tested, 2.5% were HIV positive, 5% were hepatitis B positive, 8% were hepatitis C positive and 25% had an STD. Almost 8% were injecting drug users (IDU) with higher prevalences of HIV, hepatitis B and C compared with non-IDU (P < 0.001). The clinic has been successful in providing a health-care facility for the specific health needs of this patient cohort.

Structural characterization of the galactoxylomannan of Cryptococcus neoformans Cap67

The galactoxylomannan (GalXM) obtained from the culture supernatant of an acapsular mutant of Cryptococcus neoformans Cap67 was purified by Concanavalin A affinity, ion-exchange, and gel-filtration chromatographies. The structure of GalXM was determined by methylation analysis and by 1D and 2D NMR spectroscopic studies of the intact polysaccharide and of the oligosaccharide fragments generated by Smith degradation and by acetolysis. GalXM is a complex polysaccharide with an alpha-(1-->6) -galactan backbone. The polysaccharide is branched at c-3 of alternate Gal units of the backbone. C-3 is the point of attachment of the oligosaccharide side chains comprised of alpha-D-Man- (1-->3)-alpha-D-Man-(1-->4)- beta-D-Gal-substituted with zero to three terminal beta-Xyl residues as shown in the following structure: [formula: see text].

The restriction-modification genes of Escherichia coli K-12 may not be selfish: they do not resist loss and are readily replaced by alleles conferring different specificities

Type II restriction and modification (R-M) genes have been described as selfish because they have been shown to impose selection for the maintenance of the plasmid that encodes them. In our experiments, the type I R-M system EcoKI does not behave in the same way. The genes specifying EcoKI are, however, normally residents of the chromosome and therefore our analyses were extended to monitor the deletion of chromosomal genes rather than loss of plasmid vector. If EcoKI were to behave in the same way as the plasmid-encoded type II R-M systems, the loss of the relevant chromosomal genes by mutation or recombination should lead to cell death because the cell would become deficient in modification enzyme and the bacterial chromosome would be vulnerable to the restriction endonuclease. Our data contradict this prediction; they reveal that functional type I R-M genes in the chromosome are readily replaced by mutant alleles and by alleles encoding a type I R-M system of different specificity. The acquisition of allelic genes conferring a new sequence specificity, but not the loss of the resident genes, is dependent on the product of an unlinked gene, one predicted [Prakash-Cheng, A., Chung, S. S. & Ryu, J. (1993) Mol. Gen. Genet. 241, 491-496] to be relevant to control of expression of the genes that encode EcoKI. Our evidence suggests that not all R-M systems are evolving as "selfish" units; rather, the diversity and distribution of the family of type I enzymes we have investigated require an alternative selective pressure.

Clinical application of the Ottawa ankle rules for the use of radiography in acute ankle injuries: an independent site assessment

OBJECTIVE

Previous studies show that the clinical criteria known as the Ottawa ankle rules (OAR), used for determining the need for radiographs of the ankle when a fracture is suspected, have a sensitivity of 100%, a specificity of 50%, and an overall reduction in radiographs of the ankle of 28%. The purpose of this study was to further assess the clinical usefulness of the OAR when implemented in an emergency department of a level 1 trauma center.

SUBJECTS AND METHODS

Over a 1-year period, all patients who were between 18 and 55 years old and who presented to the emergency department with blunt ankle trauma were examined by emergency department clinicians who used the OAR to determine the need for ordering ankle radiographs.

RESULTS

Of 926 patients with blunt ankle trauma, 759 met OAR criteria for ordering radiographs of the ankle. Of these patients, 152 were found to have a fracture. Another 167 of the patients were determined not to need ankle radiographs. Through either telephone contact or medical records review. 152 (91%) of these 167 patients were successfully followed up for the purpose of detecting any missed fractures. Two missed fractures were discovered, but only one required plaster immobilization. Based on these numbers, overall sensitivity using the OAR was 99% (confidence interval, 95-100%), and specificity was 22%. We found an overall 16% reduction in the number of ankle films ordered.

CONCLUSION

When implemented at a level 1 trauma center, the OAR can adequately screen for ankle fractures.

Sensory-perceptual abnormalities in autism: a case for more research?

Sensory-perceptual abnormalities in people with autism are discussed from two perspectives: published firsthand accounts and existing psychological research evidence. A range of abnormalities, including hyper- and hyposensitivity, sensory distortion and overload, and multichannel receptivity and processing difficulties, are described in firsthand accounts and frequently portrayed as central to the autistic experience. A number of dangers are inherent in uncritically accepting these accounts at face value and in any wider generalization to the autistic population as a whole. Evidence from clinical studies suggests that unusual sensory responses are present in a majority of autistic children, that they are manifested very early in development, and that they may be linked with other aspects of autistic behavior. In addition, experimental studies using a range of indices have found evidence of unusual responses to sensory stimuli in autistic subjects. However the clinical and experimental research to date suffers from serious methodological limitations and more systematic investigation is warranted. Key issues for future psychological research in the area are identified.