Release of plasma atrial natriuretic peptide after volume expansion is not related to pituitary-adrenal axis diurnal variation in normal subjects

The existence of a circadian rhythm of atrial natriuretic peptide (ANP) in humans is controversial. We studied the plasma ANP response to isotonic blood volume expansion in the morning and in the afternoon and its relationship with adrenocorticotropic hormone (ACTH)-cortisol diurnal variation in seven normal subjects. Basal plasma ANP level was similar in the morning (19.6 ± 2.4 pg/ml) and in the afternoon (21.8 ± 4.8 pg/ml). The ANP peak obtained with saline infusion (0.9% NaCl, 12 ml/kg) in the morning (49.4 ± 8 pg/ml) did not differ from that obtained in the afternoon (60.3 ± 10.1 pg/ml). There was no correlation between the individual mean cortisol and ACTH levels and the ANP peak obtained with saline infusion. These data indicate no diurnal variation in plasma ANP secretion induced by blood volume expansion and no relationship between plasma ANP peak and ACTH-cortisol diurnal variation

Circadian time-dependent effects of fencamfamine on inhibition of dopamine uptake and release in rat striatal slices

Fencamfamine (FCF) is a central stimulant that facilitates central dopaminergic transmission through inhibition of dopamine uptake and enhanced release of the transmitter. We evaluated the changes in the inhibition of uptake and the release of striatal [3H]-dopamine at 9:00 and 21:00 h, times corresponding to maximal and minimal behavioral responses to FCF, respectively. Adult male Wistar rats (200-250 g) maintained on a 12-h light/12-h dark cycle (lights on at 7:00 h) were used. In the behavioral experiments the rats (N = 8 for each group) received FCF (3.5 mg/kg, ip) or saline at 9:00 or 21:00 h. Fifteen minutes after treatment the duration of activity (sniffing, rearing and locomotion) was recorded for 120 min. The basal motor activity was higher (28.6 ± 4.2 vs 8.4 ± 3.5 s) after saline administration at 21:00 h than at 9:00 h. FCF at a single dose significantly enhanced the basal motor activity (38.3 ± 4.5 vs 8.4 ± 3.5 s) and increased the duration of exploratory activity (38.3 ± 4.5 vs 32.1 ± 4.6 s) during the light, but not the dark phase. Two other groups of rats (N = 6 for each group) were decapitated at 9:00 and 21:00 h and striata were dissected for dopamine uptake and release assays. The inhibition of uptake and release of [3H]-dopamine were higher at 9:00 than at 21:00 h, suggesting that uptake inhibition and the release properties of FCF undergo daily variation. These data suggest that the circadian time-dependent effects of FCF might be related to a higher susceptibility of dopamine presynaptic terminals to the action of FCF during the light phase which corresponds to the rats' resting period

Monosodium glutamate (MSG)-obese rats develop glucose intolerance and insulin resistance to peripheral glucose uptake

Different levels of insulin sensitivity have been described in several animal models of obesity as well as in humans. Monosodium glutamate (MSG)-obese mice were considered not to be insulin resistant from data obtained in oral glucose tolerance tests. To reevaluate insulin resistance by the intravenous glucose tolerance test (IVGTT) and by the clamp technique, newborn male Wistar rats (N = 20) were injected 5 times, every other day, with 4 g/kg MSG (N = 10) or saline (control; N = 10) during the first 10 days of age. At 3 months, the IVGTT was performed by injecting glucose (0.75 g/kg) through the jugular vein into freely moving rats. During euglycemic clamping plasma insulin levels were increased by infusing 3 mU . kg-1 . min-1 of regular insulin until a steady-state plateau was achieved. The basal blood glucose concentration did not differ between the two experimental groups. After the glucose load, increased values of glycemia (P<0.001) in MSG-obese rats occurred at minute 4 and from minute 16 to minute 32. These results indicate impaired glucose tolerance. Basal plasma insulin levels were 39.9 ± 4 µU/ml in control and 66.4 ± 5.3 µU/ml in MSG-obese rats. The mean post-glucose area increase of insulin was 111% higher in MSG-obese than in control rats. When insulinemia was clamped at 102 or 133 µU/ml in control and MSG rats, respectively, the corresponding glucose infusion rate necessary to maintain euglycemia was 17.3 ± 0.8 mg . kg-1 . min-1 for control rats while 2.1 ± 0.3 mg . kg-1 . min-1 was sufficient for MSG-obese rats. The 2-h integrated area for total glucose metabolized, in mg . min . dl-1, was 13.7 ± 2.3 vs 3.3 ± 0.5 for control and MSG rats, respectively. These data demonstrate that MSG-obese rats develop insulin resistance to peripheral glucose uptake

Disaccharidase levels in normal epithelium of the small intestine of rats with iron-deficiency anemia

Iron-deficiency anemia is the nutritional deficiency most frequently occurring throughout the world, which manifests as a complex systemic disease involving all cells, affecting enzyme activities and modifying protein synthesis. In view of these considerations, the objective of the present study was to determine the effects of iron-deficiency anemia on disaccharidases and on the epithelial morphokinetics of the jejunal mucosa. Newly weaned male Wistar rats were divided into 4 groups of 10 animals each: C6w received a standard ration containing 36 mg elemental iron per kg ration for 6 weeks; E6w received an iron-poor ration (5-8 mg/kg ration) for 6 weeks; C10w received an iron-rich ration (36 mg/kg ration) for 10 weeks; E10w received an iron-poor ration for 6 weeks and then an iron-rich ration (36 mg/kg) for an additional 4 weeks. Jejunal fragments were used to measure disaccharidase content and to study cell proliferation. The following results were obtained: 1) a significant reduction (P<0.001) of animal weight, hemoglobin (Hb), serum iron and total iron-binding capacity (TIBC) in group E6w as compared to C6w; reversal of the alterations in Hb, serum iron and TIBC with iron repletion (E10w = C10w); animal weights continued to be significantly different in groups E10w and C10w. 2) Sucrase and maltase levels were unchanged; total and specific lactase levels were significantly lower in group E6w and this reduction was reversed by iron repletion (E10w = C10w). 3) The cell proliferation parameters did not differ between groups. On the basis of these results, we conclude that lactase production was influenced by iron deficiency and that this fact was not related to changes in cell population and proliferation in the intestinal mucosa

Vitamin D receptor alleles and bone mineral density in a normal premenopausal Brazilian female population

Studies on the association between vitamin D receptor (VDR) polymorphism and bone mineral density (BMD) in different populations have produced conflicting results probably due to ethnic differences in the populations studied. The Brazilian population is characterized by a very broad genetic background and a high degree of miscegenation. Of an initial group of 164, we studied 127 women from the city of São Paulo, aged 20 to 47 years (median, 31 years), with normal menses, a normal diet and no history of diseases or use of any medication that could alter BMD. VDR genotype was assessed by PCR amplification followed by BsmI digestion of DNA isolated from peripheral leukocytes. BMD was measured using dual energy X-ray absorptiometry (Lunar DPX) at the lumbar site (L2-L4) and femoral neck. Most of the women (77.6%) were considered to be of predominantly European ancestry (20.6% of them reported also native American ancestry), 12.8% were of African-Brazilian ancestry and 9.6% of Asian ancestry, 41.0% (52) were classified as bb, 48.8% (62) as Bb and 10.2% (13) as BB. The BB, Bb and bb groups did not differ in age, height, weight, body mass index or age at menarche. Lumbar spine BMD was significantly higher in the bb group (1.22 ± 0.16 g/cm²) than in the BB group (1.08 ± 0.14; P<0.05), and the Bb group presented an intermediate value (1.17 ± 0.15). Femoral neck BMD was higher in the bb group (0.99 ± 0.11 g/cm²) compared to Bb (0.93 ± 0.12) and BB (0.90 ± 0.09) (P<0.05). These data indicate that there is a significant correlation between the VDR BsmI genotype and BMD in healthy Brazilian premenopausal females.

Normal median near nerve potential

In routine studies of sensory nerve conduction, only fibers e7 µm in diameter are analyzed. The late components which originate from thinner fibers are not detected. This explains why a normal sensory action potential (SAP) may be recorded in patients with peripheral neuropathies and sensory loss. In the present study we investigated the late component of the median SAP with a near nerve needle electrode technique in 14 normal volunteers (7 men and 7 women), aged 34.5 ± 14.8 years. The stimulus consisted of rectangular pulses of 0.2-ms duration at a frequency of 1 Hz with an intensity at least 6 times greater than the threshold value for the main component. Five hundred to 2000 sweep averagings were performed. The duration of analysis was 40 or 50 ms and the wave analysis frequency was 200 (-6 dB/oct) to 3000 Hz (-12 dB/oct). We used an apparatus with a two-channel amplifier system, 200 MW or more of entry impedance and a noise level of 0.7 µVrms or less. The main component mean amplitude, conduction velocity and latency and the late component mean amplitude, conduction velocity and latency were respectively (mean ± SD): 26.5 ± 5.42 µV, 56.8 ± 5.42 m/s, 3.01 ± 0.31 ms, 0.12 ± 0.04 µV, 16.4 ± 2.95 m/s and 10.6 ± 2.48 ms. More sophisticated equipment has an internal noise of 0.6 µVrms. These data demonstrate that the technique can now be employed to study thin fiber neuropathies, like in leprosy, using commercial electromyographs, even in non-academic practices

Viscosity of gums in vitro and their ability to reduce postprandial hyperglycemia in normal subjects

Experiments were carried out in vitro with three viscous polysaccharides (guar gum, pectin, and carboxymethylcellulose (CMC)) of similar initial viscosity submitted to conditions that mimic events occurring in the stomach and duodenum, and their viscosity in these situations was compared to their actions on postprandial hyperglycemia in normal human subjects. Guar gum showed greater viscosity than the other gums during acidification and/or alkalinization and also showed larger effects on plasma glucose levels (35% reduction in maximum rise in plasma glucose) and on the total area under the curve of plasma glucose (control: 20,314 ± 1007 mg dl-1 180 min-1 vs guar gum: 18,277 ± 699 mg dl-1 180 min-1, P<0.01). Pectin, which showed a marked reduction in viscosity at 37oC and after events mimicking those that occur in the stomach and duodenum, did not have a significant effect on postprandial hyperglycemia. The performance of viscosity and the glycemia response to CMC were at an intermediate level between guar gum and pectin. In conclusion, these data suggest that temperature, the process of acidification, alkalinization and exposure to intestinal ions induce different viscosity changes in gums having similar initial viscosity, establishing a direct relationship between a minor decrease of gum viscosity in vitro and a reduction of postprandial hyperglycemia

Cell lineage relationship in the stomach of normal and genetically manipulated mice

The oxyntic mucosa of the mouse stomach is lined with a heterogeneous population of cells that form numerous short pits continuous with long tubular glands. Tritiated thymidine radioautography has made it possible to pinpoint the origin of all cell types and to follow the differentiation/migration of different cell lineages along the pit-gland unit. The proliferating multipotent stem cells functionally anchored in the upper glandular region, the isthmus, give rise to three main lineage precursors: 1) pre-pit cells, which migrate upward to the pit while differentiating into mucus-producing pit cells; 2) pre-neck cells, which migrate downward to the glandular neck while differentiating into mucus-producing neck cells that, by approaching the glandular base, gradually change their phenotype into pepsinogen- and intrinsic factor-producing zymogenic cells; 3) pre-parietal cells, which differentiate into acid-producing parietal cells in the isthmus and then undergo bipolar migration towards the pit and the glandular base. Thus, parietal cells are the only cells that complete their differentiation in the isthmus and then migrate to be scattered throughout the pit-gland unit. To determine whether parietal cells play a role in controlling decisions about cell fate within the pit-gland unit, the gastric epithelium has been examined in transgenic mice expressing the H,K-ATPase ß-subunit-1035 to +24/simian virus 40 large T antigen fusion gene. The blockade in parietal cell differentiation in these mice produces an amplification of lineage precursors, a marked depletion of zymogenic cells and an increase in pit cell census. Ablation of parietal cells in another transgenic mouse model expressing the H,K-ATPase ß-subunit-1035 to +24/diphtheria toxin fragment A fusion gene also produces amplification of lineage precursors, and similar effects on zymogenic and pit cell census. These findings strongly suggest that parietal cells produce regulatory signals that control the cellular differentiation program of both pit and zymogenic cell lineages, and would hopefully improve our ability to identify the cellular pathways leading to malignant transformation

Differences between remaining ability and loss of capacity in maximum aerobic impairment

In the evaluation of exercise intolerance of patients with respiratory diseases the American Medical Association (AMA) and the American Thoracic Society (ATS) have proposed similar classifications for rating aerobic impairment using maximum oxygen uptake (VO2max) normalized for total body weight (ml min-1 kg-1). However, subjects with the same VO2max weight-corrected values may have considerably different losses of aerobic performance (VO2max expressed as % predicted). We have proposed a new, specific method for rating loss of aerobic capacity (VO2max, % predicted) and we have compared the two classifications in a prospective study involving 75 silicotic claimants. Logistic regression analysis showed that the disagreement between rating systems (higher dysfunction by the AMA/ATS classification) was associated with age >50 years (P<0.005) and overweight (P = 0.04). Interestingly, clinical (dyspnea score) and spirometric (FEV1) normality were only associated with the VO2max, % predicted, normal values (P<0.01); therefore, in older and obese subjects the AMA/ATS classification tended to overestimate the aerobic dysfunction. We conclude that in the evaluation of aerobic impairment in patients with respiratory diseases, the loss of aerobic capacity (VO2max, % predicted) should be used instead of the traditional method (remaining aerobic ability, VO2max, in ml min-1 kg-1).

Specific insulin and proinsulin in normal glucose tolerant first-degree relatives of NIDDM patients

In order to identify early abnormalities in non-insulin-dependent diabetes mellitus (NIDDM) we determined insulin (using an assay that does not cross-react with proinsulin) and proinsulin concentrations. The proinsulin/insulin ratio was used as an indicator of abnormal ß-cell function. The ratio of the first 30-min increase in insulin to glucose concentrations following the oral glucose tolerance test (OGTT; I30-0/G30-0) was taken as an indicator of insulin secretion. Insulin resistance (R) was evaluated by the homeostasis model assessment (HOMA) method. True insulin and proinsulin were measured during a 75-g OGTT in 35 individuals: 20 with normal glucose tolerance (NGT) and without diabetes among their first-degree relatives (FDR) served as controls, and 15 with NGT who were FDR of patients with NIDDM. The FDR group presented higher insulin (414 pmol/l vs 195 pmol/l; P = 0.04) and proinsulin levels (19.6 pmol/l vs 12.3 pmol/l; P = 0.03) post-glucose load than the control group. When these groups were stratified according to BMI, the obese FDR (N = 8) showed higher fasting and post-glucose insulin levels than the obese NGT (N = 9) (fasting: 64.8 pmol/l vs 7.8 pmol/l; P = 0.04, and 60 min post-glucose: 480.6 pmol/l vs 192 pmol/l; P = 0.01). Also, values for HOMA (R) were higher in the obese FDR compared to obese NGT (2.53 vs 0.30; P = 0.075). These results show that FDR of NIDDM patients have true hyperinsulinemia (which is not a consequence of cross-reactivity with proinsulin) and hyperproinsulinemia and no dysfunction of a qualitative nature in ß-cells.

Diagnosing dementia and normal aging: clinical relevance of brain ratios and cognitive performance in a Brazilian sample

The main objective of the present study was to evaluate the diagnostic value (clinical application) of brain measures and cognitive function. Alzheimer and multiinfarct patients (N = 30) and normal subjects over the age of 50 (N = 40) were submitted to a medical, neurological and cognitive investigation. The cognitive tests applied were Mini-Mental, word span, digit span, logical memory, spatial recognition span, Boston naming test, praxis, and calculation tests. The brain ratios calculated were the ventricle-brain, bifrontal, bicaudate, third ventricle, and suprasellar cistern measures. These data were obtained from a brain computer tomography scan, and the cutoff values from receiver operating characteristic curves. We analyzed the diagnostic parameters provided by these ratios and compared them to those obtained by cognitive evaluation. The sensitivity and specificity of cognitive tests were higher than brain measures, although dementia patients presented higher ratios, showing poorer cognitive performances than normal individuals. Normal controls over the age of 70 presented higher measures than younger groups, but similar cognitive performance. We found diffuse losses of tissue from the central nervous system related to distribution of cerebrospinal fluid in dementia patients. The likelihood of case identification by functional impairment was higher than when changes of the structure of the central nervous system were used. Cognitive evaluation still seems to be the best method to screen individuals from the community, especially for developing countries, where the cost of brain imaging precludes its use for screening and initial assessment of dementia.

Uptake of NO-releasing drugs by the P2 nucleoside transporter in trypanosomes

Nitric oxide (NO·) has been identified as a principal regulatory molecule of the immune system and the major cytotoxic mediator of activated immune cells. NO· can also react rapidly with a variety of biological species, particularly with the superoxide radical anion O2·- at almost diffusion-limited rates to form peroxynitrite anion (ONOO-). ONOO- and its proton-catalyzed decomposition products are capable of oxidizing a great diversity of biomolecules and can act as a source of toxic hydroxyl radicals. As a consequence, a strategy for the development of molecules with potential trypanocidal activities could be developed to increase the concentration of nitric oxide in the parasites through NO·-releasing compounds. In this way, the rate of formation of peroxynitrite from NO· and O2·- would be faster than the rate of dismutation of superoxide radicals by superoxide dismutases which constitute the primary antioxidant enzymatic defense system in trypanosomes. The adenosine transport systems of parasitic protozoa, which are also in certain cases implicated in the selective uptake of active drugs such as melarsoprol or pentamidine, could be exploited to specifically target these NO·-releasing compounds inside the parasites. In this work, we present the synthesis, characterization and biological evaluation of a series of molecules that contain both a group which would specifically target these drugs inside the parasites via the purine transporter, and an NO·-donor group that would exert a specific pharmacological effect by increasing NO level, and thus the peroxynitrite concentration inside the parasite.

Oxidative stress may explain how hypertension is maintained by normal levels of angiotensin II

It is well known that essential hypertension evolves in most patients with "near normal" levels of plasma renin activity. However, these levels appear to be responsible for the high levels of arterial pressure because they are normalized by the administration of angiotensin II converting inhibitors or angiotensin receptor antagonist. In experimental animals, hypertension can be induced by the continuous intravenous infusion of small doses of angiotensin II that are not sufficient to evoke an immediate pressor response. However, this condition resembles the characteristics of essential hypertension because the high levels of blood pressure exist with normal plasma levels of angiotensin II. It is suggested that small amounts of angiotensin whose plasma levels are inappropriate for the existing size of extracellular volume stimulate oxidative stress which binds nitric oxide forming peroxynitrite. The latter compound oxidizes arachidonic acid producing isoprostaglandin F2a (an isoprostane) which is characterized by a strong antinatriuretic vasoconstrictor renal effect. In this chain of reactions the vasoconstrictor effects derived from oxygen quenching of nitric oxide and increased isoprostane synthesis could explain how hypertension is maintained with normal plasma levels of renin.

Crotoxin, the major toxin from the rattlesnake Crotalus durissus terrificus, inhibits ³H-choline uptake in guinea pig ileum

We examined the effect of crotoxin, the neurotoxic complex from the venom of the South American rattlesnake Crotalus durissus terrificus, on the uptake of ³H-choline in minces of smooth muscle myenteric plexus from guinea pig ileum. In the concentration range used (0.03-1 µM) and up to 10 min of treatment, crotoxin decreased ³H-choline uptake by 50-75% compared to control. This inhibition was time dependent and did not seem to be associated with the disruption of the neuronal membrane, because at least for the first 20 min of tissue exposure to the toxin (up to 1 µM) the levels of lactate dehydrogenase (LDH) released into the supernatant were similar to those of controls. Higher concentrations of crotoxin or more extensive incubation times with this toxin resulted in elevation of LDH activity detected in the assay supernatant. The inhibitory effect of crotoxin on ³H-choline uptake seems to be associated with its phospholipase activity since the equimolar substitution of Sr2+ for Ca2+ in the incubation medium or the modification of the toxin with p-bromophenacyl bromide substantially decreased this effect. Our results show that crotoxin inhibits ³H-choline uptake with high affinity (EC25 = 10 ± 5 nM). We suggest that this inhibition could explain, at least in part, the blocking effect of crotoxin on neurotransmission.

Immunophenotype of normal and leukemic bone marrow B-precursors in a Brazilian population. A comparative analysis by quantitative fluorescence cytometry

The distinction between normal and leukemic bone marrow (BM) B-precursors is essential for the diagnosis and treatment monitoring of acute lymphoblastic leukemia (ALL). In order to evaluate the potential use of quantitative fluorescence cytometry (QFC) for this distinction, we studied 21 normal individuals and 40 patients with CD10+ ALL. We characterized the age-related changes of the CD10, CD19, TdT, CD34 and CD79a densities in normal and leukemic BM. Compared to normal adults, the B-precursors from normal children expressed significantly lower values of CD34-specific antibody binding capacity (SABC) (median value of 86.6 vs 160.2 arbitrary units (a.u.) in children and adults, respectively). No significant age-related difference was observed in the expression of the other markers in the normal BM, or in any of the markers in the leukemic BM. Based on the literature, we set the cut-off value for the normal CD10 expression at 45 x 10³ a.u. for both age groups. For the remaining markers we established the cut-off values based on the minimum-maximum values in the normal BM in each age group. The expression of CD10 was higher than the cut-off in 30 ALL cases and in 18 of them there was a concomitant aberrant expression of other markers. In 9 of the 10 CD10+ ALL with normal CD10 SABC values, the expression of at least one other marker was aberrant. In conclusion, the distinction between normal and leukemic cells by QFC was possible in 38/40 CD10+ ALL cases.