Detrimental role of endogenous nitric oxide in host defence against Sporothrix schenckii

We earlier demonstrated that nitric oxide (NO) is a fungicidal molecule against Sporothrix schenckii in vitro. In the present study we used mice deficient in inducible nitric oxide synthase (iNOS(-/-)) and C57BL/6 wild-type (WT) mice treated with N omega-nitro-arginine (Nitro-Arg-treated mice), an NOS inhibitor, both defective in the production of reactive nitrogen intermediates, to investigate the role of endogenous NO during systemic sporotrichosis. When inoculated with yeast cells of S. schenckii, WT mice presented T-cell suppression and high tissue fungal dissemination, succumbing to infection. Furthermore, susceptibility of mice seems to be related to apoptosis and high interleukin-10 and tumour necrosis factor-alpha production by spleen cells. In addition, fungicidal activity and NO production by interferon-gamma (IFN-gamma) and lipopolysaccharide-activated macrophages from WT mice were abolished after fungal infection. Strikingly, iNOS(-/-) and Nitro-Arg-treated mice presented fungal resistance, controlling fungal load in tissues and restoring T-cell activity, as well as producing high amounts of IFN-gamma Interestingly, macrophages from these groups of mice presented fungicidal activity after in vitro stimulation with higher doses of IFN-gamma. Herein, these results suggest that although NO was an essential mediator to the in vitro killing of S. schenckii by macrophages, the activation of NO system in vivo contributes to the immunosuppression and cytokine balance during early phases of infection with S. schenckii.

Is dystonic posturing during temporal lobe epileptic seizures the expression of an endogenous anticonvulsant system?

In temporal lobe epilepsy (TLE) seizures, tonic or clonic motor behaviors (TCB) are commonly associated with automatisms, versions, and vocalizations, and frequently occur during secondary generalization. Dystonias are a common finding and appear to be associated with automatisms and head deviation, but have never been directly linked to generalized tonic or clonic behaviors. The objective of the present study was to assess whether dystonias and TCB are coupled in the same seizure or are associated in an antagonistic and exclusive pattern. Ninety-one seizures in 55 patients with TLE due to mesial temporal sclerosis were analyzed. Only patients with postsurgical seizure outcome of Engel class I or II were included. Presence or absence of dystonia and secondary generalization was recorded. Occurrence of dystonia and occurrence of bilateral tonic or clonic behaviors were negatively correlated. Dystonia and TCB may be implicated in exclusive, non-coincidental, or even antagonistic effects or phenomena in TLE seizures. A neural network related to the expression of one behavioral response (e.g., basal ganglia activation and dystonia) might theoretically ""displace"" brain activation or disrupt the synchronism of another network implicated in pathological circuit reverberation and seizure expression. The involvement of basal ganglia in the blockade of convulsive seizures has long been observed in animal models. The question is: Do dystonia and underlying basal ganglia activation represent an attempt of the brain to block imminent secondary generalization? (C) 2007 Elsevier Inc. All rights reserved.

Effects of statins on matrix metalloproteinases and their endogenous inhibitors in human endothelial cells

Statins exert anti-inflammatory effects and downregulate matrix metalloproteinases (MMPs) expression, thus contributing to restore cardiovascular homeostasis in cardiovascular diseases. We aimed at comparing the effects of different statins (simvastatin, atorvastatin, and pravastatin) on MMP-2, MMP-9, tissue inhibitors of metalloproteinases (TIMP)-1, TIMP-2, and MMP-9/TIMP-1 and MMP-2/TIMP-2 ratios released by human umbilical vein endothelial cells (HUVEC) stimulated by phorbol myristate acetate (PMA). HUVECs were incubated with statins (0.1-10 mu M) for 12 h before stimulation with PMA 100 nM. Monolayers were used to perform cell viability assays and the supernatants were collected to determine MMPs and TIMPs levels by gelatin zymography and/or enzyme immunoassay. While treatment with PMA increased MMP-9 and TIMP-1 levels (by 556% and 159%, respectively; both P < 0.05), it exerted no effects on MMP-2 and TIMP-2 levels. Simvastatin and atorvastatin, but not pravastatin, attenuated PMA-induced increases in MMP-9 levels (P < 0.05). Only atorvastatin decreased baseline MMP-2 levels significantly (P < 0.05). We found no effects on TIMP-2 levels. Simvastatin and atorvastatin, but not pravastatin, decreased MMP-9/TIMP-1 ratio significantly (both P < 0.05), whereas atorvastatin and pravastatin, but not simvastatin, decreased MMP-2/TIMP-2 ratio significantly (both P < 0.05). Our data support the notion that statins with different physicochemical features exert variable effects on MMP/TIMP ratios (which reflect net MMP activity). Our results suggest that more lipophilic statins (simvastatin and atorvastatin), but not the hydrophilic statin pravastatin, downregulate net MMP-9 activity. However, atorvastatin and pravastatin may downregulate net MMP-2 activity. The clinical implications of the present findings deserve further investigation.

Sodium bicarbonate solution as an anti-erosive agent against simulated endogenous erosion

This study investigated whether sodium bicarbonate solution, applied on enamel previously exposed to a simulated intrinsic acid, can control dental erosion. Volunteers wore palatal devices containing enamel slabs, which were exposed twice daily extra-orally to hydrochloric acid (0.01 M, pH 2) for 2 min. Immediately afterwards, the palatal devices were re-inserted in the mouth and volunteers rinsed their oral cavity with a sodium bicarbonate solution or deionized water for 60 s. After the washout period, the palatal devices were refilled with a new set of specimens and participants were crossed over to receive the alternate rinse solution. The surface loss and surface microhardness (SMH) of specimens were assessed. The surface loss of eroded enamel rinsed with a sodium bicarbonate solution was significantly lower than the surface loss of eroded enamel rinsed with deionized water. There were no differences between treatments with sodium bicarbonate and deionized water for SMH measurements. Regardless of the solution used as an oral rinse, eroded enamel showed lower SMH than uneroded specimens. Rinsing with a sodium bicarbonate solution after simulated endogenous erosive challenge controlled enamel surface loss but did not alter the microhardness.

Interferon-gamma enhances cytotoxic T lymphocyte recognition of endogenous peptide in keratinocytes without lowering the requirement for surface peptide

Keratinocytes expressing the human papillomavirus (HPV) type 16 E7 protein, as a transgene driven by the K14 promoter, form a murine model of HPV-mediated epithelial cancers in humans. Our previous studies have shown that K14E7 transgenic skin grafts onto syngeneic mice are not susceptible to immune destruction despite the demonstrated presence of a strong, systemic CTL response directed against the E7 protein. Consistent with this finding, we now show that cultured, E7 transgenic keratinocytes (KC) express comparable endogenous levels of E7 protein to a range of CTL-sensitive E7-expressing cell lines but are not susceptible to CTL-mediated lysis in vitro . E7 transgenic and non-transgenic KC are susceptible to conventional mechanisms of CTL-mediated lysis, including perforin and Fas/FasL interaction when an excess of exogenous peptide is provided. The concentration of exogenous peptide required to render a cell susceptible to lysis was similar between KC and other conventional CTL targets (e.g. EL-4), despite large differences in H-2D(b) expression at the cell surface. Furthermore, exposure of KC to IFN-gamma increased H-2D(b) expression, but did not substantially alter the exogenous peptide concentration required to sensitize cells for half maximal lysis. In contrast, the lytic sensitivity of transgenic KC expressing endogenous E7 is modestly improved by exposure to IFN-gamma. Thus, failure of CTL to eliminate KC expressing endogenous E7, and by inference squamous tumours expressing E7, may reflect the need for a sustained, local inflammatory environment during the immune effector phase.

The human zoo: Endogenous retroviruses in the human genome

The main focus of the human genome sequencing project has been gene discovery, but a great additional benefit is that it offers the chance to examine the large proportion of the genome that does not contain human genes. The nature of this ‘noncoding’ DNA is poorly understood, both as an evolutionary question (how did it get there?) and in the functional sense (what is it doing now?). Much of the noncoding DNA is derived from retroviruses that have inserted their DNA into the genome. The availability of complete genomic sequences will revolutionize studies of the number and location of endogenous retroviruses, their role in genome evolution, and their contribution to human disease.

Endogenous endothelin-1 limits exercise-induced vasodilation in hypertensive humans

Essential hypertension is a common disorder, associated with increased endothelin-l-mediated vasoconstrictor tone at rest. We hypothesized that increased vasoconstrictor activity of endothelin-1 might explain why the normal decrease in peripheral vascular resistance in response to exercise is attenuated in hypertensive patients. Therefore, we investigated the effect of endothelin A (ETA) receptor blockade on the vasodilator response to handgrip exercise. Forearm blood flow responses to handgrip exercise (15%, 30%, and 45% of maximum voluntary contraction) were assessed in hypertensive patients and matched normotensive subjects, before and after intra-arterial infusions of the ETA receptor antagonist BQ-123; a control dilator, hydralazine; and placebo (saline). Preinfusion (baseline) vasodilation in response to exercise was significantly attenuated at each workload in hypertensive patients compared with normotensive subjects. Intra-arterial infusions of hydralazine and saline did not increase the vasodilator response to exercise in either hypertensives or normotensives at any workload. The vasodilator response to exercise was markedly enhanced after BQ-123 at the 2 higher workloads in hypertensives (157 +/- 48%, P < 0.01; 203 &PLUSMN; 58%, P < 0.01) but not in normotensives. This suggests that the impaired vasodilator response to exercise in hypertensive patients is, at least in part, a functional limitation caused by endogenous ETA receptor-mediated vasoconstriction. Treatment with endothelin receptor antagonists may, therefore, increase exercise capacity in essential hypertension.

Coexistence of stability and mobility in postural control: evidence from postural compensation for respiration

This study evaluated the extent to which movement of the lower limbs and pelvis may compensate for the disturbance to posture that results from respiratory movement of the thorax and abdomen. Motion of the neck, pelvis, leg and centre of pressure (COP) were recorded with high resolution in conjunction with electromyographic activity (EMG) of flexor and extensor muscles of the trunk and hip. Respiration was measured from ribcage motion. Subjects breathed quietly, and with increased volume due to hypercapnoca (as a result of breathing with increased dead-space) and a voluntary increase in respiration. Additional recordings were made during apnoea. The relationship between respiration and other parameters was measured from the correlation between data in the frequency domain (i.e. coherence) and from time-locked averages triggered from respiration. In quiet standing, small angular displacements (similar to0.5degrees) of the trunk and leg were identified in raw data. Correspondingly, there were peaks in the power spectra of the angular movements and EMG. While body movement and EMG were coherent with respiration (>0.5), the coherence between respiration and COP displacement was low (

The first strand transfer reaction of HIV-1 reverse transcription is more efficient in infected cells than in cell-free natural endogenous reverse transcription reactions

Background: In the presence of dNTPs, intact HIV-1 virions are capable of reverse transcribing at least part of their genome, a process known as natural endogenous reverse transcription (NERT). PCR analysis of virion DNA produced by NERT revealed that the first strand transfer reaction (1stST) was inefficient in intact virions, with minus strand (-) strong stop DNA (ssDNA) copy numbers up to 200 times higher than post-1stST products measured using primers in U3 and U5. This was in marked contrast to the efficiency of 1stST observed in single-round cell infection assays, in which (-) ssDNA and U3-U5 copy numbers were indistinguishable. Objectives: To investigate the reasons for the discrepancy in first strand transfer efficiency between intact cell-free virus and the infection process. Study design: Alterations of both NERT reactions and the conditions of cell infection were used to test whether uncoating and/or entry play a role in the discrepancy in first strand transfer efficiency. Results and Conclusions: The difference in 1stST efficiency could not be attributed simply to viral uncoating, since addition of very low concentrations of detergent to NERT reactions removed the viral envelope without disrupting the reverse transcription complex, and these conditions resulted in no improvement in 1stST efficiency. Virus pseudotyped with surface glycoproteins from either vesicular stomatitis virus or amphotrophic murine leukaemia virus also showed low levels of 1stST in low detergent NERT assays and equivalent levels of (-) ssDNA and 1stST in single-round infections of cells, demonstrating that the gp120-mediated infection process did not select for virions capable of carrying out 1stST. These data indicate that a post-entry event or factor may be involved in efficient HIV-1 reverse transcription in vivo. (C) 2002 Elsevier Science B.V. All rights reserved.

Impaired postural compensation for respiration in people with recurrent low back pain

This study evaluated the degree to which the disturbance to posture from respiration is compensated for in healthy normals and whether this is different in people with recurrent low back pain (LBP), and to compare the changes when respiratory demand is increased. Angular displacement of the lumbar spine and hips, and motion of the centre of pressure (COP), were recorded with high resolution and respiratory phase was recorded from ribcage motion. With subjects standing in a relaxed posture, recordings were made during quiet breathing, while breathing with increased dead-space to induce hypercapnoea, and while subjects voluntarily increased their respiration to match ribcage expansion that was induced in the hypercapnoea condition. The relationship between respiration and the movement parameters was measured from the coherence between breathing and COP and angular motion at the frequency of respiration, and from averages triggered from the respiratory data. Small angular changes in the lumbopelvic and hip angles were evident at the frequency of respiration in both groups. However, in quiet standing, the LBP subjects had a greater displacement of their COP that was associated with respiration than the control subjects. The LBP group had a trend for less hip motion. There were no changes in the movement parameters when respiratory demand increased involuntarily via hypercapnoea, but when respiration increased voluntarily, the amplitude of motion and the displacement of the COP increased in both groups. The present data suggest that the postural compensation to respiration counteracts at least part of the disturbance to posture caused by respiration and that this compensation may be less effective in people with LBP.

Endogenous angiotensin II modulates nNOS expression in renovascular hypertension

Nitric oxide (NO) influences renal blood flow mainly as a result of neuronal nitric oxide synthase (nNOS). Nevertheless, it is unclear how nNOS expression is modulated by endogenous angiotensin II, an inhibitor of NO function. We tested the hypothesis that the angiotensin II AT1 receptor and oxidative stress mediated by NADPH oxidase contribute to the modulation of renal nNOS expression in two-kidney, one-clip (2K1C) hypertensive rats. Experiments were performed on male Wistar rats (150 to 170 g body weight) divided into 2K1C (N = 19) and sham-operated (N = 19) groups. nNOS expression in kidneys of 2K1C hypertensive rats (N = 9) was compared by Western blotting to that of 2K1C rats treated with low doses of the AT1 antagonist losartan (10 mg·kg-1·day-1; N = 5) or the superoxide scavenger tempol (0.2 mmol·kg-1·day-1; N = 5), which still remain hypertensive. After 28 days, nNOS expression was significantly increased by 1.7-fold in the clipped kidneys of 2K1C rats and by 3-fold in the non-clipped kidneys of 2K1C rats compared with sham rats, but was normalized by losartan. With tempol treatment, nNOS expression increased 2-fold in the clipped kidneys and 1.4-fold in the non-clipped kidneys compared with sham rats. The changes in nNOS expression were not followed by changes in the enzyme activity, as measured indirectly by the cGMP method. In conclusion, AT1 receptors and oxidative stress seem to be primary stimuli for increased nNOS expression, but this up-regulation does not result in higher enzyme activity.

On the concept of endogenous volatility

Most financial and economic time-series display a strong volatility around their trends. The difficulty in explaining this volatility has led economists to interpret it as exogenous, i.e., as the result of forces that lie outside the scope of the assumed economic relations. Consequently, it becomes hard or impossible to formulate short-run forecasts on asset prices or on values of macroeconomic variables. However, many random looking economic and financial series may, in fact, be subject to deterministic irregular behavior, which can be measured and modelled. We address the notion of endogenous volatility and exemplify the concept with a simple business-cycles model.