Physiological basis of the low calcium response in Yersinia pestis.

It is established that duplication in vitro of that amount of Ca2+ (2.5 mM) and Mg2+ (1.5 mM) present in blood permits vegetative growth of Yersinia pestis with repression of virulence factors encoded by the Lcr plasmid (Lcr+); similar simulation of intracellular fluid (no Ca2+ and 20 mM Mg2+) promotes bacteriostasis with induction of these virulence determinants. However, proliferation of yersiniae in mice occurs primarily within necrotic focal lesions (supplied by Ca(2+)-deficient host cell cytoplasm) within visceral organs rather than in Ca(2+)-sufficient blood. The present study addressed this enigma by defining conditions necessary for achieving vegetative growth of Lcr+ yersiniae at 37 degrees C in simulated intracellular fluid. Maximum optical densities were increased by substitution of K+ for Na+ and elimination of Cl-; the combination of Na+ plus L-glutamate was selectively toxic to Lcr+ cells. This phenomenon was attributed in part to the absence of aspartase in Y. pestis (a lesion known to facilitate massive accumulation of L-aspartate via transamination of the oxalacetate pool by L-glutamate). Replacement of L-glutamate by exogenous L-aspartate or alpha-ketoglutarate reversed this toxicity by favoring retention of oxalacetate. Proliferation of Lcr+ cells in a medium containing K+ and L-aspartate but lacking added Ca2+ and Na+ was markedly enhanced by increasing the concentration of fermentable carbohydrate. Accordingly, in the worst-case scenario (i.e., added Na+, Cl-, and L-glutamate), Lcr+ yersiniae underwent restriction of growth after one doubling, and in the best-case scenario (i.e., added K+ and L-aspartate), the organisms completed more than five doublings, thereby achieving full-scale growth. Both of these Ca(2+)-deficient media promoted maximum induction of Mg(2+)-induced V antigen, a virulence factor encoded by the Lcr plasmid.     

Preservation of 5-hydroxytryptamine1A receptor-G protein interactions in the cerebral cortex of patients with Alzheimer's disease.

The coupling of 5-hydroxytryptamine1A (5-HT1A) receptors to guanine nucleotide binding (G) proteins was investigated in membranes prepared from frontal and parietal cortices of control and Alzheimer's disease brains by characterising the effect of guanosine 5'-[beta gamma-imido]diphosphate (Gpp[NH]p) on [3H]8-hydroxy-2-(di-n-propylamino)-tetralin ([3H]8-OH-DPAT) binding parameters. In the absence of guanine nucleotides, [3H]8-OH-DPAT bound to a single high affinity binding site in all membrane types. The number of [3H]8-OH-DPAT binding sites was significantly decreased in the parietal cortex of Alzheimer's disease samples compared with controls, whereas in the frontal cortex the number of binding sites remained unchanged. Gpp[NH]p reduced the [3H]8-OH-DPAT binding affinity and the number of binding sites to the same degree in both regions in control and Alzheimer's disease cases. [3H]8-OH-DPAT binding was inhibited in a concentration dependent manner with an IC50 value of approximately 1 microM in all cases. These results suggest that the 5-HT1A receptor-G protein complex is functionally intact in these regions in Alzheimer's disease brain.     

B cell chronic lymphocytic leukaemia cells have reduced capacity to upregulate expression of MHC class I in response to interferon-gamma

AIMS: An important consideration in the design of a tumour vaccine is the ability of tumour-specific cytotoxic T lymphocytes (CTL) to recognise unmanipulated tumour cells in vivo. To determine whether B-CLL might use an escape strategy, the current studies compared B-CLL and normal B cell MHC class I expression. METHODS: Flow cytometry, TAP allele PCR and MHC class I PCR were used. RESULTS: While baseline expression of MHC class I did not differ, upregulation of MHC class I expression by B-CLL cells in response to IFN-gamma was reduced. No deletions or mutations of TAP 1 or 2 genes were detected. B-CLL cells upregulated TAP protein expression in response to IFN-gamma. Responsiveness of B-CLL MHC class I mRNA to IFN-gamma was not impaired. CONCLUSIONS: The data suggest that MHC class I molecules might be less stable at the cell surface in B-CLL than normal B cells, as a result of the described release of beta(2)m and beta(2)m-free class I heavy chains from the membrane. This relative MHC class I expression defect of B-CLL cells may reduce their susceptibility to CTL lysis in response to immunotherapeutic approaches.     

Isolation and characterization of interferon-producing reticuloendothelial cells from mouse epidermis

A homogeneous population of trypsin-resistant epidermal cells has been isolated from newborn ICR mice. These cells are characterized by adherence, receptors for Fc-IgG, ATPase activity, phagocytosis of latex particles and opsonized sheep erythrocytes, and secretion of lysozyme and interferon. The production of interferon by these cells suggests that they may be important in protection against viral infections of the skin as well as in regulation of immune responses. The ultrastructure of these trypsin-resistant epidermal cells shows striking similarity to that of reticuloendothelial cells.     

CTLA-4 expression on antigen-specific cells but not IL-10 secretion is required for oral tolerance

CD4(+) T cells play a vital role in mediating the tolerance induced at mucosal sites following exposure to non-pathogenic stimuli, and further understanding of the precise mechanisms by which these cells prevent aberrant responses is required. We have developed a model using transfer of DO11.10 TCR-transgenic bone marrow into irradiated recipients in which it has been possible to track antigen-specific CD4(+) cells in mesenteric lymph nodes (mLN), Peyer's patches (PP) and lamina propria following primary exposure to antigen. Using this model we have demonstrated initial activation in all three gut-associated lymphoid tissue compartments characterized by increases in the frequency of transgenic cells expressing CD69 and CD25. These cells subsequently enter a state of hyporesponsiveness both locally in the mLN and PP and in the periphery following feeding and challenge. Investigating the role of CTLA-4 either using anti-CTLA-4 mAb or by generating chimeras using DO11.10xCTLA-4(-/-) mice as donors we have clearly shown that antigen-specific cells require the expression of this regulatory molecule for oral tolerance. In contrast, oral tolerance was intact in chimeras generated using DO11.10xIL-10(-/-) cells, indicating that secretion of this cytokine by antigen-specific cells is not required.     

Insulin-like growth factor binding protein-1 (IGFBP-1): a multifunctional role in the human female reproductive tract

Insulin-like growth factor-1 (IGFBP-1) is particularly important in human female reproductive physiology, where it is involved with other factors in a complex system which regulates menstrual cycles, puberty, ovulation, decidualization, implantation and fetal growth. This has implications for clinical obstetrics and gynaecology, where there is evidence for a pathophysiological role for IGFBP-1 in pre-eclampsia, intrauterine growth restriction, polycystic ovarian syndrome and trophoblast and endometrial neoplasms.     

Transformation of rabbit arterial smooth muscle cells with Simian virus 40

Summary In vitro studies were carried out to induce viral transformation of vascular smooth muscle cells. Cultured rabbit arterial smooth muscle cells were infected with simian virus 40 (SV 40), and transformed cultures were produced that exhibit altered morphology, increased growth rate and plating efficiency, growth on semi-solid substrate, and chromosomal abnormalities. Nuclear SV 40 T-antigen was detected in all cells of these cultures. Muscle-specific actin was identified by a specific monoclonal antibody suggesting retention of smooth muscle cell characteristics by the transformed cells. Significant cytoplasmic lipid accumulation occurred in transformed cells incubated with -very low density lipoprotein, as revealed both by chemical analyses and Nile Red lipid staining of the cultures. The transformed smooth muscle cells grow permanently in cell culture. Our investigations show that arterial smooth muscle cells transformed with SV 40 virus exhibit altered phenotypic properties distinct from that of normal arterial smooth muscle cells.     

Race and the response to adrenergic blockade with carvedilol in patients with chronic heart failure

BACKGROUND: The benefits of angiotensin-converting-enzyme inhibitors and beta-blockers may be smaller in black patients than in patients of other races, but it is unknown whether race influences the response to carvedilol in patients with chronic heart failure. METHODS: In the U.S. Carvedilol Heart Failure Trials Program, 217 black and 877 nonblack patients (in New York Heart Association class II, III, or IV and with a left ventricular ejection fraction of no more than 0.35) were randomly assigned to receive placebo or carvedilol (at doses of 6.25 to 50 mg twice daily) for up to 15 months. The effects of carvedilol on ejection fraction, clinical status, and major clinical events were retrospectively compared between black and nonblack patients. RESULTS: As compared with placebo, carvedilol lowered the risk of death from any cause or hospitalization for any reason by 48 percent in black patients and by 30 percent in nonblack patients. Carvedilol reduced the risk of worsening heart failure (heart failure leading to death, hospitalization, or a sustained increase in medication) by 54 percent in black patients and by 51 percent in nonblack patients. The ratios of the relative risks associated with carvedilol for these two outcome variables in black as compared with nonblack patients were 0.74 (95 percent confidence interval, 0.42 to 1.34) and 0.94 (95 percent confidence interval, 0.43 to 2.05), respectively. Carvedilol also improved functional class, ejection fraction, and the patients' and physicians' global assessments in both the black patients and the nonblack patients. For all these measures of outcome and clinical status, carvedilol was superior to placebo within each racial cohort (P<0.05 in all analyses), and there was no significant interaction between race and treatment (P> 0.05 in all analyses). CONCLUSIONS: The benefit of carvedilol was apparent and of similar magnitude in both black and nonblack patients with heart failure.     

Enterococcal prosthetic valve infective endocarditis: report of 45 episodes from the International Collaboration on Endocarditis-merged database

Enterococcal prosthetic valve infective endocarditis (PVE) is an incompletely understood disease. In the present study, patients with enterococcal PVE were compared to patients with enterococcal native valve endocarditis (NVE) and other types of PVE to determine differences in basic clinical characteristics and outcomes using a large multicenter, international database of patients with definite endocarditis. Forty-five of 159 (29%) cases of definite enterococcal endocarditis were PVE. Patients with enterococcal PVE were demographically similar to patients with enterococcal NVE but had more intracardiac abscesses (20% vs. 6%; p=0.009), fewer valve vegetations (51% vs. 79%; p<0.001), and fewer cases of new valvular regurgitation (12% vs. 45%; p=0.01). Patients with either enterococcal PVE or NVE were elderly (median age, 73 vs. 69; p=0.06). Rates of in-hospital mortality, surgical intervention, heart failure, peripheral embolization, and stroke were similar in both groups. Patients with enterococcal PVE were also demographically similar to patients with other types of PVE, but mortality may be lower (14% vs. 26%; p=0.08). Notably, 93% of patients with enterococcal PVE came from European centers, as compared with only 79% of patients with enterococcal NVE (p=0.03). Thus, patients with enterococcal PVE have higher rates of myocardial abscess formation and lower rates of new regurgitation compared to patients with enterococcal NVE, but there are no differences between the groups with regard to surgical or mortality rates. In contrast, though patients with enterococcal PVE and patients with other types of PVE share similar characteristics, mortality is higher in the latter group. Importantly, the prevalence of enterococcal PVE was higher in the European centers in this study.     

An investigation into the relationship between salivary cortisol,stress, anxiety and depression

This study examined the relationship between indices of self-reported emotional distress and absolute versus change in cortisol levels. Fifty-four women attending a diagnostic breast clinic completed scales measuring stress, anxiety and depression and provided five saliva samples over the course of a single day for the measurement of cortisol. No significant relationships were evident between absolute cortisol levels and the distress measures. Analysis of the change in cortisol levels revealed a non-linear interaction effect between stress and anxiety and time of day. There was a non-linear relation between time of day and cortisol levels, but the extent of the non-linearity was dependent upon levels of stress and anxiety, not depression. A relationship was apparent between indices of distress and change in cortisol levels, but not absolute levels of the hormone.