In vivo spectroscopy: a novel approach for simultaneously estimating nitric oxide and hemodynamic parameters in the rat brain

Nitric oxide (NO) is a versatile molecule involved in a wide range of biological processes. Under physiological conditions, NO reacts with oxyhemoglobin (OxyHb) to form methemoglobin (MetHb) at a very high rate. Microdialysis studies have used hemoglobin solutions as a trapping method to quantify NO in vivo. The methodology described here uses the microcapillary network with endogenous OxyHb instead of microdialysis probe with exogenous OxyHb for monitoring MetHb as an indirect index of NO levels by in vivo spectroscopy using optical fibers. This new method has been validated in rat cerebral cortex by the infusion of NO or well-known drug-induced changes in NO concentration (NMDA agonists and a NO-synthase inhibitor) and by comparing results with simultaneous voltammetric recordings. Results indicate that this spectroscopy technique is able to record large increases in MetHb levels and to detect reductions of its basal levels. In addition, data show that similar changes and kinetics can be observed with both techniques. Thus, intravascular MetHb can be used as an indirect index of NO levels. It is proposed that in vivo spectroscopy may be a useful tool to gain insight into the roles of NO in hemodynamic parameters and in other physiological processes such as the regulation of the mitochondrial respiratory chain.     

Prevalence of dementia in several regions of the world: analysis of epidemiologic studies from 1994 to 2000

OBJECTIVE: To analyse the prevalence studies of dementia from 1994 to 2000. METHODS: The papers were searched on Medline and Lilacs and the inclusion criteria were: to be an original study, that estimated dementia prevalence and investigated community samples. RESULTS: thirty-eight studies were evaluated from all continents. The mean age-specific prevalence rates of dementia were 1,17% for the 65-69 years group, and 54,83% over 95 years. The results were strongly influenced by age. Dementia prevalence rates were higher on women on 75% of the papers reviewed. The Alzheimer's disease/vascular dementia ratio was higher in South America and lower in Asia. DISCUSSION: Methodological advances were found, specially regarding the homogeneity of diagnostic criteria. The effect of age on the rates of dementia prevalence was pronounced, up to 90 years of age.     

Reversible posterior encephalopathy syndrome: case report

The posterior reversible leukoencephalopathy syndrome (PRES) is a recently proposed cliniconeuroradiologic entity.The most common causes of PRES are hypertensive encephalopathy, eclampsia, cyclosporin A neurotoxicity and the uremic encephalopathies.Most patients are markedly hypertensive at presentation, although some have only mildly elevated or even normal blood pressure. Symptoms may include headache, nausea, vomiting, altered mental status, seizures,stupor, and visual disturbances. On CT and MR studies, edema has been reported in a relatively symmetrical pattern, typically in the subcortical white matter and occasionally in the cortex of the occipital and parietal lobes. These often striking imaging findings usually are resolved on follow-up studies obtained after appropriate therapy. Diffusion-weighted images would not show hyperintense signal because of the presence of interstitial rather than cytotoxic edema. We report a case of PRES due to hypertensive encephalopathy studied by CT and MRI.     

Cellular mechanism underlying LPS-induced inhibition of in vitro L-leucine transport across rabbit jejunum

Lipopolysaccharide (LPS) is a known causative agent of sepsis. In previous studies, we have shown that it reduces L-leucine mediated transport across the rabbit jejunum by about 30%. In this study, the mechanism(s) of LPS inhibition on amino acid transport were analysed in detail. LPS did not inhibit L-leucine transport across brush border membrane vesicles, suggesting the need for an intracellular step. The inhibitory effect of LPS was not altered by the addition of protein kinase A (PKA) inhibitor (IP(20), 10(-7) M) or an analog of cAMP (DB-cAMP, 3 x 10(-4) M), indicating that the PKA signal transduction pathway was not involved in the LPS effect. However, the inhibitory effect of LPS was suppressed by trifluoroperazine (10(-7) M), a Ca(2+)/calmodulin inhibitor and staurosporine (10(-7) M), an protein kinase C (PKC) inhibitor. Likewise, LPS inhibition disappeared in media without calcium. These results suggest that LPS could inhibit the intestinal uptake of L-leucine across the small intestine in vitro by intracellular processes related to calcium, involving PKC and calmodulin protein.     

Evidence for changes in brain enkephalin contents associated to male rat sexual activity

Indirect evidence suggests that ejaculation might activate endogenous opioid systems, which exert an inhibitory influence on male rat sexual behaviour. The objective of the present study was to search for putative long-term changes in the contents of immunoreactive (IR) Met-enkephalin (IR-Met), Leu-enkephalin (IR-Leu) and opioid octapeptide Met--Arg(6)--Gly(7)--Leu(8) (IR-Oct) in specific brain areas, after the execution of different amounts of sexual activity. Additionally, basal contents of these enkephalins were compared between sexually active (SA) and persistent sexually inactive (SI) rats. Immunoreactivity to enkephalins was determined by radioimmunoanalysis, in the frontal cortex, the hypothalamus and midbrain of SA and SI rats, as well as 24 or 48 h after males had one ejaculation or copulated to exhaustion. Twenty-four hours after sexual activity, there was a generalised increase in enkephalin contents that returned to control values at the 48 h measurement in all brain areas, but the hypothalamus, where IR-Met and IR-Oct remained elevated. No differences in the magnitude of the changes were found between rats that ejaculated once and sexually satiated males. IR-Oct concentration in the hypothalamus of SI rats appeared significantly higher than in SA animals, with no differences in IR-Met and IR-Leu. Results give direct evidence of the activation of endogenous opioid systems by male rat sexual activity. The occurrence of long lasting increases in the contents of IR-Met and IR-Oct in the hypothalamus of rats that copulated was detected. Finally, an intrinsically elevated octapeptide concentration in the hypothalamus of SI rats was found.     

Influence of infection related factors on neuropsychological performance of HIV seropositive subjects

There are no definitive risk factors which predict the development of neuropsychological deficits associated to HIV infection, and, taking into account that neuropsychological impairment is a risk factor of early death in all stages of HIV infection, there is a pressing need to determine those factors, either related or foreign to HIV, which help to explain the existing intragroup differences and that may also be associated with the development and progression of the dysfunction. The aim of this work is to revise those factors related with the infection that can influence neuropsychological functioning of the seropositive patients, such as antiretroviral treatments, immunological impairment, viral load and the advance of the infection. Identification of these risk factors will help us to outline characteristics of the seropositive subjects who are neuropsychologically more vulnerable, in order to detect them early with a view to preventing the manifestation of neuropsychological disturbances, and offer quick, suitable treatment.