cagA-Positive Helicobacter pylori Populations in China and The Netherlands Are Distinct

The aim of this research was to study whether and to what extent Chinese cagA-positive Helicobacter pylori isolates differ from those in The Netherlands. Analysis of random amplified polymorphic DNA (RAPD)-PCR-assessed DNA fingerprints of chromosomal DNA of 24 cagA-positive H. pylori isolates from Dutch (n = 12) and Chinese (n = 10) patients yielded the absence of clustering. Based on comparison of the sequence of a 243-nucleotide part of cagA, the Dutch (group I) and Chinese (group II) H. pylori isolates formed two separate branches with high confidence limits in the phylogenetic tree. These two clusters were not observed when the sequence of a 240-bp part of glmM was used in the comparison. The number of nonsynonymous substitutions was much higher in cagA than in glmM, indicating positive selection. The average levels of divergence of cagA at the nucleotide and protein levels between group I and II isolates were found to be high, 13.3 and 17.9%, respectively. Possibly, the pathogenicity island (PAI) that has been integrated into the chromosome of the ancestor of H. pylori now circulating in China contained a different cagA than the PAI that has been integrated into the chromosome of the ancestor of H. pylori now circulating in The Netherlands. We conclude that in China and The Netherlands, two distinct cagA-positive H. pylori populations are circulating.     

Expression of a novel combination of fast and slow troponin T isoforms in rabbit extraocular muscles

Summary The properties of extraocular muscles (EOMs) are quite different from those of the trunk and limb. Here we show that there is a novel pattern of troponin T (TnT) expression in EOMs which most likely contributes to the fine control of ocular movement and may reflect their innervation by cranial motoneurons. Three regions of the muscle were analysed to distinguish the TnT isoforms present in the fast singly-innervated fibres from those in the multiply-innervated fibres. More than 95% of the TnT in the singly-innervated fibres is TnT_3f, which exhibits the most graded response to changes in calcium concentration during activation (Schachatet al., J. molec. Biol. 198, 551–4). In multiply-innervated fibres, which exhibit tonic contractures, the slow troponin T TnT_2s is expressed. While neither TnT_3f nor TnT_2s is unique to EOM, this pattern is unusual in two respects: first, both TnT_3f and TnT_2s are minor components of the trunk and limb musculature, and second, most muscles express several fast and both slow TnT species. Although EOM occupies a highly specialized physiological niche, its unusual physiology is not reflected in the presence of new TnT isoforms but in the expression of a different ratio of the known species of TnT.     

Knowledge,attitudes and practices towards HIV positive and AIDS patients among public service dentists in Nairobi

The purpose of this study was to assess the knowledge, practices and attitudes towards HIV Positive/AIDS patients among 112 dentists from public institutions in Nairobi using a self-administered questionnaire. 94(83.9%) responded. Over 74% had managed HIV positive/AIDS patients. In general, respondents' knowledge and preventive measures against HIV infection were satisfactory. 8.5% did not find use of protective eye wear absolutely necessary. 33% used protective covers routinely. 52.1% advocated for the screening of all suspected cases of AIDS before treatment. 27.7% felt that HIV positive health workers and those with AIDS should not be allowed to treat patients. 53.2% felt that they should be given the right to decide on treating HIV Positive/AIDS patients. 10.6% supported the idea that AIDS patients be isolated from uninfected individuals. It is concluded that a substantial number of dentists were wanting in their attitudes towards HIV positive/AIDS patients.     

L-carnitine: metabolism, functions and value in pathology]

Although L-carnitine is not considered as an essential nutrient, endogenous synthesis may fail to ensure adequate L-carnitine levels in neonates, especially those born prematurely. Free L-carnitine is found in many foods, mainly those from animal sources. Absorption of free L-carnitine is virtually complete. Lysine and methionine are necessary ingredients for the biosynthesis of L-carnitine. All tissues in the body can produce deoxy-carnitine but, in humans, the enzyme that enables hydroxylation of deoxy-carnitine to carnitine is found only in the liver, brain and kidneys. Complex exchanges of carnitine and its precursors occur between tissues. Muscles take up carnitine from the bloodstream and contain most of the body carnitine stores. L-carnitine and L-carnitine esters are eliminated mainly through the kidneys, which may play a central role in the homeostasis of this compound. Thyroid hormones adrenocorticotrophin (ACTH), and diet all influence urinary excretion of L-carnitine. Free L-carnitine can be assayed in plasma and urine and is occasionally measured in muscle biopsy specimens. Plasma L-carnitine levels may not accurately reflect L-carnitine body stores. L-carnitine ensures transfer of fatty acids to the mitochondria where they undergo oxidation. This process is associated with production of short-chain acylcarnitine which exit from the mitochondria or peroxisomes. L-carnitine ensures regeneration of coenzyme A and is thus involved in energy metabolism. L-carnitine also ensures elimination of xenobiotic substances. Carnitine deficiencies are common. Currently, these deficiencies are classified into two groups. In deficiencies with myopathy, only the muscles are deficient in L-carnitine, perhaps as a result of a primary anomaly of the L-carnitine transport system in muscles. In systemic deficiencies, L-carnitine levels are low in the plasma and in all body tissues. Systemic L-carnitine deficiencies are usually the result of a variety of disease states including deficient intake in premature infants or long-term parenteral nutrition; renal failure; organic acidemias; and Reye's syndrome. Modifications in L-carnitine metabolism have also been reported in patients with diabetes mellitus, malignancies, myocardial ischemia, and alcohol abuse. A large number of supplementation trials have been carried out.     

The effect of caffeine ingestion on physical performance after prolonged exercise

Summary The purpose of this study was to determine the effect of caffeine ingestion on physical performance after prolonged endurance exercise. Twenty three trained male volunteers participated in a 40-km march and were divided into two groups, matched for caffeine clearance rate and aerobic capacity. The experimental group ingested, prior to the march, a caffeinated drink at a dose of 5 mg·kg⁻¹ body mass and at the 3rd and 5th h of marching an additional drink at a dose of 2.5 mg·kg⁻¹ body mass. The control group ingested a drink of equal volume at the same times. Upon termination of the march each subject performed a cycle ergometer test at an intensity of 90% maximal oxygen consumption. Time to exhaustion and rate of perceived exertion (RPE) were recorded. Blood samples were drawn predrink, at the 3rd and 5th h of marching and immediately after the cycle ergometer test, and were analysed for caffeine, free fatty acids (FFA), lactate and glucose levels. Plasma FFA levels increased during the march (p<0.05), with no significant difference between groups. Lactate levels increased in the experimental group (p<0.05), with no significant change in the control group. Glucose levels did not change significantly in either group. After the cycle ergometer test, lactate levels were significantly higher in the experimental, as compared to the control group (3.77±0.33 vs 2.52±0.35 mmol·l⁻¹, respectively). There was no significant difference between treatments in the time to exhaustion on the cycle ergometer, but RPE was different (p<0.05). Under the conditions of this study, the results do not indicate caffeine ingestion as an ergogenic aid which will postpone exhaustion following prolonged endurance exercise. This work was presented, in part, at the Canadian Association of Sports Sciences Annual Meeting, October 1987, Lake Louise, Alberta, Canada     

Molecular determinants of human uveal melanoma invasion and metastasis

The molecular analysis of cancer has benefited tremendously from the sequencing of the human genome integrated with the science of bioinformatics. Microarray analysis technology has the potential to classify tumors based on the differential expression of genes. In the current study, a collaborative, multidisciplinary approach was utilized to study the molecular determinants of human uveal melanoma invasion and metastasis. Uveal melanoma is considered the most common primary intraocular cancer in adults, resulting in the death of approximately 50% of patients affected. Unfortunately, at the time of diagnosis, many patients already harbor microscopic metastases, thus underscoring a critical need to identify prognostic markers indicative of metastatic potential. The investigative strategy consisted of isolating highly invasive vs. poorly invasive uveal melanoma cells from a heterogeneous tumor derived from cells that had metastasized from the eye to the liver. The heterogeneous tissue explant MUM-2 led to the derivation of two clonal cell lines: MUM-2B and MUM-2C. Further morphological and functional analyses revealed that the MUM-2B cells were epithelioid, interconverted (expressing mesenchymal and epithelial phenotypes) highly invasive, and demonstrated vasculogenic mimicry. The MUM-2C cells were spindle-like, expressed only a vimentin mesenchymal phenotype, poorly invasive, and were incapable of vasculogenic mimicry. The molecular analysis of the MUM-2B vs. the MUM-2C clones resulted in the differential expression of 210 known genes. Overall, the molecular signature of the MUM-2B cells resembled that of multiple phenotypes – similar to a pluripotent, embryonic-like genotype. Validation of select genes that were upregulated and down-regulated was conducted by semiquantitative RT-PCR measurement. This study provides a molecular profile that will hopefully lead to the development of new molecular targets for therapeutic intervention and possible diagnostic markers to predict the clinical outcome of patients with uveal melanoma. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of tyrphostin AG-556 on intimal thickening in a mouse model of arterial injury

BACKGROUND: Inflammation has been shown to play an important role in promoting the response to arterial injury and proinflammatory cytokines, such as tumor necrosis factor (TNF) alpha, are candidate mediators. AG-556 is a tyrosine kinase inhibitor proven to be effective in a model of multiple sclerosis-like syndrome in mice due to its immunomodulating effect. In the current study, we investigated the effect of the tyrphostin AG-556 on neointimal thickening and cytokine profile in a model of arterial injury in the mouse. METHODS: Injury was induced by external cuff placement on the left femoral artery of wild-type C57BL/6 mice. AG-556 dissolved in DMSO was injected intraperitoneally daily to the injured mice in a dosage of 2 mg/mouse. Control mice received DMSO injections. Histological analysis was carried out to assess neointimal formation. Splenocytes were cultured in the absence and presence of a mitogen for evaluation of thymidine incorporation and cytokine production. RESULTS: AG-556 treatment significantly attenuated intimal thickening (43,000+/-17,000 microm2; n=11) when compared to DMSO administration (286,000+/-127,000 microm2; n=10; P<0.05). Basal interferon-gamma production by splenocytes from AG-556-treated mice was increased by approximately 20-fold in comparison with levels in DMSO-treated animals, whereas Con-A induced secretion of the cytokine was similar between both groups. Levels of TNF-alpha, IL-4 and IL-10 in the culture supernatant from treated and non-treated animals did not differ significantly. CONCLUSION: The tyrosine kinase inhibitor AG-556 may have a role in the reduction of intimal thickening. The effect could be mediated via an immune modulating effect involving a significant increase in the smooth muscle cell inhibitory cytokine IFN-gamma.     

Origin and filiation of human plasmacytoid dendritic cells

Human plasmacytoid dendritic cells represent a rare population of leukocytes which produce high amounts of type I interferon in response to certain viruses. Although those cells were first described in 1958, there are still unsolved issues related to their origin and function. Recently, a leukemic counterpart of plasmacytoid dendritic cells was identified. Molecular approaches using either normal or leukemic plasmacytoid dendritic cells provide some new insights into the controversial lymphoid origin of those cells. The need for specific markers is still a critical aspect for the identification of plasmacytoid dendritic cells, whatever stage of differentiation, in normal as well as in pathological conditions. Hopefully, novel markers will allow delineation of the relationships between dendritic cells at different stages of differentiation/maturation along the myeloid and lymphoid lineages.     

The phosphatidylinositol 3-kinase/protein kinase B signaling pathway is activated by lipoteichoic acid and plays a role in Kupffer cell production of interleukin-6 (IL-6) and IL-10

Sepsis caused by gram-positive bacteria lacking lipopolysaccharide (LPS) has become a major and increasing cause of mortality in intensive-care units. We have recently demonstrated that the gram-positive-specific bacterial cell wall component lipoteichoic acid (LTA) stimulates the release of the proinflammatory cytokines in Kupffer cells in culture. In the present study, we have started to assess the signal transduction events by which LTA induces the production of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and the anti-inflammatory cytokine IL-10 in rat Kupffer cells. LTA was found to trigger phosphorylation of mitogen-activated protein kinases (MAPK) (p38 MAPK and ERK 1/2) and protein kinase B (PKB). Compared to LPS, LTA was more potent in inducing PKB phosphorylation after 40 min, although we found that the cytokine responses were similar. For both bacterial molecules, blocking phosphatidylinositol 3-kinase (PI3-K; Ly294002) or Janus kinase 2 (JAK-2; AG490) particularly affected the induction of IL-6 and IL-10 release, whereas TNF-alpha levels were strongly reduced by inhibition of Src family tyrosine kinases (PP2). All three cytokines were reduced by inhibition of p38 MAPK (SB202190) or the broad-range tyrosine kinase inhibitor genistein, whereas IL-6 release was particularly blocked by inhibition of ERK 1/2 (PD98059). Divergences in the regulatory pathways controlling TNF-alpha, IL-10, and IL-6 production in Kupffer cells following LPS or LTA stimulation may create a basis for understanding how the balance between pro- and anti-inflammatory cytokines is regulated in the liver following infections by gram-positive or gram-negative bacteria.