Detecting symptom- and test-coached simulators with the test of memory malingering.

The ability of the Test of Memory Malingering (TOMM; Tombaugh, 1996) to detect feigned-memory impairment was explored. The TOMM was administered to three groups: (a) a control group instructed to perform optimally, (b) a symptom-coached group instructed to feign memory problems after being educated about traumatic brain injury symptomatology, and (c) a test-coached group instructed to feign memory problems after being educated about test-taking strategies to avoid detection. The recommended cutoff scores (Tombaugh, 1996) on Trial 2 and the Retention Trial produced overall classification accuracy rates of 96%, with high levels of sensitivity and specificity. Although the symptom-coached group performed more poorly on the TOMM relative to the test-coached group, the test was equally sensitive in detecting suboptimal effort across the different coaching paradigms.     

Prolonged vitamin C supplementation and recovery from eccentric exercise

We have previously shown that vitamin C supplementation affects recovery from an unaccustomed bout of demanding exercise, with the most pronounced effect being that on plasma interleukin-6 concentration. However, because of the proposed role of interleukin-6 in the regulation of metabolism, it was unclear whether this represented a reduced response to muscle damage or some form of interaction with the metabolic demands of the activity. Therefore, the aim of the present study was to investigate the effect of the same form of supplementation on a bout of exercise that initiated similar muscle damage but had a low metabolic cost. Fourteen male subjects were allocated to either a placebo (P) or a vitamin C (VC) group. The VC group consumed 200 mg of ascorbic acid twice a day for 14 days prior to a bout of exercise and for the 3 days after exercise. The P group consumed identical capsules that contained 200 mg lactose. Subjects performed 30 min of downhill running at a gradient of –18% and recovery was monitored for up to 3 days after exercise. Plasma VC concentrations in the VC group increased following supplementation. Nevertheless, downhill running provoked a similar increase in circulating markers of muscle damage (creatine kinase activity and myoglobin concentration) and muscle soreness in P and VC groups. Similarly, although downhill running increased plasma interleukin-6, there was no effect from VC supplementation. These results suggest that vitamin C supplementation does not affect interleukin-6 concentrations following eccentric exercise that has a low metabolic component.     

Molecular Cloning of a 32-Kilodalton Lipoprotein Component of a Novel Iron-Regulated Staphylococcus epidermidis ABC Transporter

Our previous studies identified two iron-regulated cytoplasmic membrane proteins of 32 and 36 kDa expressed by both Staphylococcus epidermidis and Staphylococcus aureus. In this study we show by Triton X-114 phase partitioning and tritiated palmitic acid labelling that these proteins are lipoproteins which are anchored into the cytoplasmic membrane by their lipid-modified N termini. In common with those of some other gram-positive bacteria, these highly immunogenic lipoproteins were released from the bacterial cell into the culture supernatants, with release being promoted by growth of the bacteria under iron-restricted conditions. Immunoelectron microscopy with a monospecific rabbit antiserum to the 32-kDa S. epidermidis lipoprotein showed that the majority of the antigen was distributed throughout the staphylococcal cell wall. Only minor quantities were detected in the cytoplasmic membrane, and exposure of the lipoprotein on the bacterial surface was minimal. A monoclonal antibody raised to the 32-kDa lipoprotein of S. aureus was used in immunoblotting studies to investigate the conservation of this antigen among a variety of staphylococci. The monoclonal antibody reacted with polypeptides of 32 kDa in S. epidermidis and S. aureus and of 40 kDa in Staphylococcus hominis. No reactivity was detected with Staphylococcus lugdunensis, Staphylococcus cohni, or Staphylococcus haemolyticus. The gene encoding the 32-kDa lipoprotein from S. epidermidis has been isolated from a Lambda Zap II genomic DNA library and found to be a component of an iron-regulated operon encoding a novel ABC-type transporter. The operon contains three genes, designated sitA, -B, and -C, encoding an ATPase, a cytoplasmic membrane protein, and the 32-kDa lipoprotein, respectively. SitC shows significant homology both with a number of bacterial adhesins, including FimA of Streptococcus parasanguis and ScaA of Streptococcus gordonii, and with lipoproteins of a recently described family of ABC transporters with proven or putative metal ion transport functions. Although the solute specificity of this novel transporter has not yet been determined, we speculate that it may be involved in either siderophore- or transferrin-mediated iron uptake in S. epidermidis.     

Integrity of the dissociated adult cardiac myocyte: gap junction tearing and the mechanism of plasma membrane resealing

Summary Dissociation of adult cardiac myocytes by collagenase perfusion techniques requires separation of the junctional contacts that link the cells physically, electrically and metabolically in the intact heart. Gap junctions, one of three types of intercellular junction present at the cardiac intercalated disc, are not split into their component membranes when myocytes are dissociated; they are ripped from the plasma membrane of one cell, to be retained by its neighbour. Partitioning of junctions in this way might be expected to constitute a serious threat to the ionic integrity of dissociated myocytes, but in practice, high yields of functionally intact cells, suitable for experimental studies, are routinely obtained. To explain this apparent paradox, repair mechanisms, operating to seal the membrane lesions caused by gap junction tearing, have been hypothesized, but evidence for their existence has previously been lacking. Using freeze-fracture electron microscopy, the present study identifies repair sites as smooth membrane domains that are continuous with the neighbouring plasma membrane, thus forming intact seals. That these structures are not chemically-induced artefacts is demonstrated by their presence in myocytes that were frozen directly from the living state. Subsarcolemmal vesicle clusters, detected in thin sections and freeze-fracture replicas, are associated with the smooth sealing domains. These structures may represent either rounded-up fragments of mechanically disrupted membrane or structures concerned with the synthesis of new lipid. From their freeze-fracture morphology, the sealing domains appear to be lipid-rich and protein-poor. Cytochemical studies using Ruthenium Red, cationized ferritin and lectins show in addition that they have a lower content of negatively-charged membrane components than the neighbouring plasma membrane, and that the carbohydrate residues normally associated with plasma membrane glycolipids and glycoproteins are absent.     

Large-scale molecular and tissue microarray analysis of mesothelin expression in common human carcinomas

The 40-kilodalton processed glycoprotein, mesothelin, is highly expressed in epithelial mesotheliomas and adenocarcinomas of the ovary (serous papillary) and pancreas, but its expression in a large series of other common carcinomas has not been completely explored. In the present study, we used oligonucleotide and tissue microarrays to profile the expression of the mesothelin gene (MSLN) and encoded protein, respectively. Among 150 carcinomas of multiple anatomic sites, we found the highest average expression of MSLN in serous carcinomas of the ovary and adenocarcinomas of the pancreas, consistent with previous reports, as well as measurable but less-striking expression in pulmonary, gastric/esophageal, and colorectal adenocarcinomas. On tissue microarrays containing 621 carcinomas derived from the same and additional sites as those profiled by gene expression, mesothelin immunoreactivity was highest in cancers of the ovary (serous papillary, endometrioid, and undifferentiated) and pancreas, with less frequent staining seen in adenocarcinomas of the endometrium, lung, and stomach/esophagus. Some immunopositivity was observed in 42% of pulmonary adenocarcinomas, including 18% that had >50% of tumor cells that were immunoreactive. Some 14% of breast and 30% of colorectal adenocarcinomas showed immunopositivity, but no case contained >50% tumor cells that were immunoreactive. Mesothelin was either entirely absent or present in <5% of carcinomas of the prostate, bladder/ureter, liver, kidney, and thyroid. Overall, we observed good concordance between the results obtained by oligonucleotide and tissue microarrays. This large study of the MSLN gene and protein expression in common carcinomas provides data for future investigations that evaluate the utility of mesothelin/megakaryocyte potentiating factor as a potential serum tumor marker or target of immunotoxin-based therapy in human cancers.     

A combination of genetic polymorphisms increases the risk of progressive disease in chronic hepatitis C

Background: There is increasing interest in the influence of host genetic factors on hepatic fibrosis, and whether genetic markers can reliably identify subjects at risk of developing severe disease. We hypothesised that hepatitis C virus (HCV) infected subjects with progressive fibrosis, classified using strict criteria based on histology at biopsy in addition to disease duration would be more likely to inherit several genetic polymorphisms associated with disease progression compared with subjects with a low rate of disease progression. Methods: We examined polymorphisms in eight genes that have been reported to have an association with hepatic fibrosis. Results: Associations between polymorphisms in six genes and more rapidly progressing fibrosis were observed, with individual adjusted odds ratios ranging from 2.1 to 4.5. The relationship between rapidly progressing fibrosis and possession of ⩾3, ⩾4, or ⩾5 progression associated alleles was determined and the adjusted odds ratios increased with increasing number of progression associated alleles (9.1, 15.5, and 24.1, respectively). Using logistic regression analysis, a predictive equation was developed and tested using a second cohort of patients with rapidly progressing fibrosis. The predictive equation correctly classified 80% of patients in this second cohort. Conclusions: This approach may allow determination of a genetic profile predictive of rapid disease progression in HCV and identify patients warranting more aggressive therapeutic management.     

Neurohumoral control of esophageal epithelial electrolyte transport

The neurohumoral control of epithelial esophageal electrolyte transport was investigated by studying the effect of various hormones and neuroeffector agents on the potential difference (PD) in vivo or on the electrical parameters of electrolyte transport in vitro. The rabbit esophagus, which has no submucosal esophageal glands, demonstrated no effect of pentagastrin, cholecystokinin octapeptide, or synthetic secretin in vivo, and no effect of these hormones or of vasopressin, aldosterone, carbachol, epinephrine, or cAMP in vitro. The rabbit esophagus did respond to metabolic substrates (glucose) in vitro by increasing sodium absorption. In contrast, the opossum esophagus, which contains extensive submucosal glands, had a lower electrical resistance, PD, short-circuit current, and sodium absorption with higher chloride secretion. This esophagus responded to carbachol and epinephrine by sodium and chloride secretion. We believe that only the submucosal glands of the esophagus are under significant neurohumoral control while the sodium transporting function of the stratified squamous epithelium of this organ is important in maintaining its barrier function.     

Changes in Schwann cells and vessels in lead neuropathy.

Transmission electron microscopy (TEM) of peripheral nerve in rats receiving 6% lead carbonate for 4-10 weeks provided evidence of a specific Schwann cell injury, associated with demyelination. Intranuclear inclusions in Schwann cells appeared within 2 weeks of administration of a lead-containing diet. Swelling of Schwann cells and disintegration of their cytoplasm was evident at 4 weeks. Distinctive electron-dense inclusions appeared in both Schwann and endothelial cells during the period of intoxication and were ultrastructurally identical to pathognomonic inclusions of lead poisoning seen in renal tubular epithelial cells. Scanning microscopy (SEM) with electron-probe microanalysis was used to identify the lead-containing deposits. In addition to Schwann cell changes, vessels revealed endothelial cell injury and alteread permeability to macromolecules. Since morphologic changes of Schwann cells precede the development of altered vascular permeability and endoneurial edema, it appears that lead gains access to the endoneurium prior to the development of altered vascular permeability, suggesting that edema and altered endoneurial fluid pressure are epiphenomena that supervene after demyelination occurs. Remyelination, Schwann cell proliferation and formation of onion bulbs are manifestations of persistent toxic injury to myelin-sustaining cells, resulting in chronic demyelination.     

Cytogenetics of primary prostatic adenocarcinoma. Clonality and chromosome instability.

We have examined 62 prostatic adenocarcinomas by conventional cytogenetic analysis. Most were primary cultures harvested in 14 days or less. The most consistent finding was a normal male diploid karyotype, found in 87% of all cells analyzed, and as the exclusive finding in 19 tumors. Nonrandom chromosomal changes included gain of chromosome 7 and loss of the Y chromosome. In addition, clonal gains of chromosomes 8, 12, and 18, and clonal losses of chromosomes 14 and 19 were noted in individual cases. Two structural clonal aberrations, a 9p+ in one case and a t(Y;22) (q11.2;p12) in another, were also seen. Ten of 62 cultures demonstrated chromosome instability, defined herein as nonclonal gain or loss of chromosomes in more than 10% of the metaphases examined from that culture. In those cases with nonclonal numerical aberrations, loss of chromosomes was more common than gain. The distribution of apparently random numeric abnormalities was similar to that of the clonal abnormalities in that the most frequent nonclonal gain was of chromosome 7 and the most frequent nonclonal loss was of the Y chromosome. Apparently random structural aberrations were observed in less than 1% of all analyzed cells. These included a 4p-,del(3)(q13), and t(1;11). The extent of apparently random aneuploidy suggests that chromosome instability characterizes cultured prostatic adenocarcinomas. An increase in the frequency of nonclonal aberrations may be an indicator of tumor origin in a predominantly diploid cell population. The coexistence of clonally aberrant, nonclonally aberrant, and normal diploid cells in culture may reflect heterogeneity of prostate tumors in vivo.