Clonal population structure of encapsulated Haemophilus influenzae.

Chromosomal genotypes of 2,209 isolates of the six polysaccharide capsule types of Haemophilus influenzae recovered from human hosts worldwide were characterized by an analysis of electrophoretically demonstrable allelic profiles at 17 metabolic enzyme loci. For 222 representative isolates, restriction fragment length polymorphism patterns produced by digestion of cap region DNA were also determined. With few exceptions, isolates belonging to individual phylogenetic lines or groups of allied lineages identified by multilocus enzyme electrophoresis had characteristic cap region restriction fragment length polymorphism patterns and characteristic combinations of cap region patterns and outer membrane protein types. The occurrence of strong associations of characters and the recovery of isolates with identical genetic properties in widely separated geographic regions and over a 40-year period indicated that the population structure of encapsulated H. influenzae is clonal. Recombination of chromosomal genes, including those mediating capsule synthesis, apparently is not a major factor in the short-term evolution of these pathogenic organisms and, therefore, may be of minor clinical significance.     

Using the demand–control model of job strain to predict caregiver burden and caregiver satisfaction in the informal caregivers of heart failure patients

Objectives The demand–control (D–C) model of job strain has generated a considerable body of empirical support in predicting psychological health outcomes in the context of work. This study aimed to extend previous work using the D–C model of job strain to predict caregiver burden and satisfaction in the informal caregivers of patients with heart failure. Design and method Data were gathered from 60 caregiver/patient dyads in a cross‐sectional design. Patients with chronic stable heart failure were recruited from out‐patient clinics. The dependent variables were caregiver burden and satisfaction. Demand and control were measured using both patient‐ and caregiver‐derived measures. Results The D–C model accounted for 15 and 19% of the variance in caregiver burden, after controlling for age, gender and relationship to the patient. Lower control was associated with higher burden. The D–C model did not predict caregiver satisfaction. Conclusion The D–C model was associated with caregiver burden, but not satisfaction in caregivers, with control being the dominant predictor. Research linking the theory and findings from job strain and informal caregiving studies may elucidate both fields of research. Using the demand–control model of job strain to predict caregiver burden and caregiver satisfaction in the informal caregivers of heart failure patients.     

Effects of Creep and Cyclic Loading on the Mechanical Properties and Failure of Human Achilles Tendons

The Achilles tendon is one of the most frequently injured tendons in humans, and yet the mechanisms underlying its injury are not well understood. This study examines the ex vivo mechanical behavior of excised human Achilles tendons to elucidate the relationships between mechanical loading and Achilles tendon injury. Eighteen tendons underwent creep testing at constant stresses from 35 to 75 MPa. Another 25 tendons underwent sinusoidal cyclic loading at 1 Hz between a minimum stress of 10 MPa and maximum stresses of 30–80 MPa. For the creep specimens, there was no significant relationship between applied stress and time to failure, but time to failure decreased exponentially with increasing initial strain (strain when target stress is first reached) and decreasing failure strain. For the cyclically loaded specimens, secant modulus decreased and cyclic energy dissipation increased over time. Time and cycles to failure decreased exponentially with increasing applied stress, increasing initial strain (peak strain from first loading cycle), and decreasing failure strain. For both creep and cyclic loading, initial strain was the best predictor of time or cycles to failure, supporting the hypothesis that strain is the primary mechanical parameter governing tendon damage accumulation and injury. The cyclically loaded specimens failed faster than would be expected if only time-dependent damage occurred, suggesting that repetitive loading also contributes to Achilles tendon injuries. © 2003 Biomedical Engineering Society. PAC2003: 8719Rr     

Intercellular adhesion molecule-3 is the predominant co-stimulatory ligand for leukocyte function antigen-1 on human blood dendritic cells

Dendritic cells (DC) are potent stimulators of primary T lymphocyte responses to foreign antigen. The initial DC-T lymphocyte interaction involves the binding of the adhesion molecule leukocyte function antigen-1 (LFA-1; CD11a/CD18) on the T lymphocyte to an intercellular adhesion molecule (ICAM) on the DC. Although blood and tonsil DC express ICAM-1 (CD54) and ICAM-2 (CD102) on their surface, anti-ICAM-1 and anti-ICAM-2 monoclonal antibodies (mAb) have little inhibitory activity on the DC-stimulated mixed leukocyte reaction (MLR). We therefore examined the expression of the more recently identified LFA-1 ligand, ICAM-3 (CD50), in comparison to ICAM-1 and ICAM-2 on blood DC and sought a functional role for ICAM-3 in DC-mediated T lymphocyte responses. Resting blood DC expressed significantly more ICAM-3 than ICAM-1 or ICAM-2 as assessed by flow cytometry. Treatment of resting DC with interferon-γ led to increased expression of ICAM-1; however, ICAM-2 and ICAM-3 levels remained relatively constant. Solid-phase recombinant chimeric molecules ICAM-1-, ICAM-2- and ICAM-3-Fc were able to co-stimulate CD4⁺ T lymphocyte proliferation in conjunction with suboptimal solid-phase CD3 mAb 64.1. However, the anti-ICAM-3 mAb CAL 3.10 inhibited a DC-stimulated MLR to a greater extent than anti-ICAM-1 or anti-ICAM-2 reagents and appeared to act by blocking the DC ICAM-3- T lymphocyte LFA-1 interaction. As ICAM-3 is the predominant LFA-1 ligand on resting blood DC, we postulate that DC may utilize ICAM-3 for initial DC-T lymphocyte interactions, and that ICAM-1, which is up-regulated upon DC activation, and/or ICAM-2, may contribute to DC migration or later phases of the T lymphocyte activation process.     

A genetic dissociation of learning and recall in Caenorhabditis elegans

A learning event can be dissociated into 3 components: acquisition, storage, and recall. When the laboratory wild-type strain of Caenorhabditis elegans (N2 strain) is exposed to benzaldehyde in the absence of food, the worms display a reduction of their attractive response to this volatile odorant. This results from the association between benzaldehyde and a nutrient-deficient environment. Another wild-type isolate, the CB4856 strain, fails to display this decreased response to benzaldehyde after exposure to benzaldehyde in the absence of food. However, like the N2 strain, when tested to isoamyl alcohol after benzaldehyde conditioning, the CB4856 strain displays a decreased isoamyl alcohol response. Therefore, the CB4856 strain does not have an acquisition deficit, but it suffers from a recall deficit specific to benzaldehyde.     

A genetic and clinical study of individuals with nonsyndromic retinopathy consequent upon sequence variants in HGSNAT,the gene associated with Sanfilippo C mucopolysaccharidosis

Pathogenic variants in the gene HGSNAT (heparan‐α‐glucosaminide N‐acetyltransferase) have been reported to underlie two distinct recessive conditions, depending on the specific genotype, mucopolysaccharidosis type IIIC (MPSIIIC)—a severe childhood‐onset lysosomal storage disorder, and adult‐onset nonsyndromic retinitis pigmentosa (RP). Here we describe the largest cohort to‐date of HGSNAT‐associated nonsyndromic RP patients, and describe their retinal phenotype, leukocyte enzymatic activity, and likely pathogenic genotypes. We identified biallelic HGSNAT variants in 17 individuals (15 families) as the likely cause of their RP. None showed any other symptoms of MPSIIIC. All had a mild but significant reduction of HGSNAT enzyme activity in leukocytes. The retinal condition was generally of late‐onset, showing progressive degeneration of a concentric area of paramacular retina, with preservation but reduced electroretinogram responses. Symptoms, electrophysiology, and imaging suggest the rod photoreceptor to be the cell initially compromised. HGSNAT enzymatic testing was useful in resolving diagnostic dilemmas in compatible patients. We identified seven novel sequence variants [p.(Arg239Cys); p.(Ser296Leu); p.(Phe428Cys); p.(Gly248Ala); p.(Gly418Arg), c.1543‐2A>C; c.1708delA], three of which were considered to be retina‐disease‐specific alleles. The most prevalent retina‐disease‐specific allele p.(Ala615Thr) was observed heterozygously or homozygously in 8 and 5 individuals respectively (7 and 4 families). Two siblings in one family, while identical for the HGSNAT locus, but discordant for retinal disease, suggest the influence of trans‐acting genetic or environmental modifying factors.     

Insulin receptors in lizard brain and liver: structural and functional studies of α and β subunits demonstrate evolutionary conservation

Summary Specific insulin receptors are present in the liver and brain of the lizard Anolis carolinesis. In this study, the specific binding of ¹²⁵I-insulin to the receptors showed time, temperature and pH dependency. Specific binding to crude membranes prepared from brain was 1–2% of the total radioactivity added compared to 4–5% in the crude membranes prepared from liver. Solubilization and wheat germ agglutinin purification of the membranes resulted in an increase in the specific binding (per mg of protein) between 6 and 32 times for liver membranes and 13–186 for brain membranes. Binding inhibition of tracer insulin by unlabeled porcine insulin was characteristic for insulin receptors with 50% inhibition for liver crude membranes at 60 ng/ml of porcine insulin and 0.7 ng/ml for purified brain insulin receptors. Chicken insulin was 2- to 3-fold more potent and proinsulin about 100 times less potent than porcine insulin. The -subunits of liver and brain had apparent molecular weights on sodium dodecyl sulfate polyacrylamide gel electrophoresis of 135 kDa and 120 kDa respectively. Apparent molecular weights of subunits were 92 kDa for both tissues. Insulin stimulated phosphorylation of the subunit of both brain and liver receptors. Both tissues demonstrated tyrosine-specific phosphorylation, which was stimulated by insulin, of exogenously added artificial substrates. In addition, purified brain insulin receptor preparations contained an endogenous protein with apparent molecular weight of 105 kDa, whose phosphorylation was stimulated by insulin (10^–7 mol/l). This phosphoprotein was not immunoprecipitated by anti-insulin receptor antibodies. These studies suggest that the structural differences between brain and liver receptors previously demonstrated in the rat are also present in the lizard, which is about 300,000,000 years older than the mammalian species. Thus, there is strong evolutionary conservation of the brain insulin receptor.     

Evaluation of urethral pressure profilometry for the diagnosis of genuine stress incontinence

Summary Given the expense of radiographic imaging facilities and the reproducibility of urethral pressure measurements with microtransducers, the use of urethral pressure profilometry (UPP) has been gaining widespread popularity for the diagnosis of genuine stress incontinence (GSI). However, the clinical usefulness of the technique has not been adequately evaluated against the best available technique, namely videocystourethrography. Using the latter technique as the Gold Standard, the UPP results of 114 normal women and 95 GSI patients have been compared. In order to determine the most diagnostic UPP measure, 25 parameters were examined for each patient. With the use of the Kappa statistic it was found that the area under the stress profile was the most discriminatory of the UPP parameters. Even using this measure, the overlap between normal and GSI is so great as to make accurate diagnosis impossible. It is therefore concluded that UPP is useless for the diagnosis of GSI.