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Biomedical subjects

F Carvalho

Publications and source records attributed to F Carvalho.

15 recordsLinked to original sources
PubMed1995

Electrically-evoked release of taurine in the rat vas deferens: evidence for a purinoceptor-mediated effect.

Release of taurine evoked by electrical stimulation (2700 pulses; 5 Hz; 10 mA unless stated otherwise) and its dependence on noradrenaline and ATP was studied in isolated, perifused rat vas deferens. Outflow of noradrenaline was also measured in some experiments. The basal outflow of taurine averaged 3.90 +/- 0.32 nmol/g tissue per min. Electrical stimulation increased the outflow to about 4 times basal values. The electrically-evoked overflow averaged 128.0 +/- 11.7 nmol/g. An increase in current strength to 40 mA increased the evoked overflow by about 50%. At either current strength, the evoked overflow of taurine (and noradrenaline) was abolished by tetrodotoxin. Ca(2+)-deprivation blocked the overflow of taurine elicited by 10 mA and increased the overflow elicited by 40 mA pulses (but abolished noradrenaline overflow under either condition). Neither prazosin nor pretreatment of the rats with reserpine reduced electrically-evoked overflow of taurine (although reserpine pretreatment abolished evoked noradrenaline overflow). Tyramine (100 mumols/l; 9 min) caused an overflow of taurine 36% of that caused by electrical stimulation (but an overflow of noradrenaline 3 times higher than that evoked by electrical stimulation). Exogenous noradrenaline (9 min) caused a concentration-dependent overflow of taurine with a maximal effect at 162 mumol/l, amounting to 33% of the electrically-evoked overflow. alpha,beta-Methylene ATP (19 mumols/l) elicited an overflow of taurine that faded despite continued exposure to the drug and amounted to 62% of the response to electrical stimulation. Thirty minutes after the start of application of alpha,beta-methylene ATP, electrically-evoked overflow of taurine was greatly reduced. Suramin (100 mumols/l) also reduced taurine overflow in response to electrical stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1994

Do invading leucocytes contribute to the decrease in glutathione concentrations indicating oxidative stress in exercised muscle, or are they important for its recovery?

Mice were subjected to one session of strenuous running exercise and their soleus muscles were examined in respect of changes in ultrastructure and to their concentration of reduced glutathione [GSH] which are indicators of oxidative stress. It was hypothesized that invading leucocytes contributed to oxidative stress and they were functionally inhibited in one experimental group by the administration of colchicine. Exercise led to an immediate decrease in [GSH] of about 60%, which slowly recovered during 96 h after exercise. With the administration of colchicine after exercise, [GSH] was higher than in the untreated exercise group 48 h after exercise, indicating an inhibition of the ability of leucocytes to produce oxidative stress. However, at 96 h after exercise, [GSH] was lower in the treated exercise group than in the untreated group. The morphological evaluation of the percentage of affected fibres showed that the invasion of leucocytes increased muscle fibre damage. The results suggested that invading leucocytes enhanced production of reactive species of oxygen that may have participated in inducing muscle damage. However, inhibition of leucocyte invasion did not permit their scavenger action of removing cell debris, which appeared to produce even more oxidative stress in the muscle.

Animals↗
PubMed1994

Bioavailability of residues of diazepam and its metabolites.

The present study was performed to determine the metabolic fate of the residues of diazepam and its metabolites in an in vivo model and using two different animal species, guinea pigs and rats, successively. Guinea pigs were orally dosed with diazepam at 100 mg/kg bw and 10 mg/kg bw. After 2 h the animals were sacrificed and their livers were removed. Rats were fed these livers and sacrificed 8 h later after having ingested the portion given. Blood, kidney, and liver of rats were collected to quantify drug residues. Oxazepam and demethyldiazepam were identified by HPLC-UV in liver and kidney rat extracts and also in some blood samples. Temazepam was only found in liver from rats that had eaten guinea pig liver dosed at the highest level. The identity of demethyldiazepam was confirmed in rat liver extracts by GC-MS. This study demonstrates the bioavailability of diazepam metabolites in a second animal (rat simulating a consumer) following a diazepam administration to a first animal (guinea pigs simulating a target animal). Residue concentrations were reduced from 9.7 and 243 micrograms in consumed guinea pig liver to 3.75 and 455 ng/g in rat liver for parent drug and oxazepam, the lowest and highest residues found, respectively.

Animals↗
PubMed1993

Endothelium-derived oxidative stress may contribute to exercise-induced muscle damage.

In exercise-induced muscle damage, oxidative stress derived from the liberation of reactive oxygen species (ROS) is assumed to be of etiological importance. Xanthine oxidase (XO) located in capillary endothelium is one of the possible sources for ROS, mainly investigated so far under conditions of ischemia/reperfusion. XO can be inhibited by allopurinol. To investigate the contribution of XO for the oxidative stress-induced development of muscle damage, mice were subjected to a single bout of exhaustive running exercise. Another exercised group received allopurinol. The reduced form of glutathione (GSH) was measured to estimate the amount of oxidative stress in soleus muscle, and the same muscle was examined in the light and electron microscope at different periods of time (0, 48, 96 h) after exercise. While exercise alone resulted in a marked reduction of GSH indicative for oxidative stress, which only recovered at 96 h, the administration of allopurinal to exercised animals induced a complete recovery already at 48 h after exercise. Muscle damage was more pronounced in the exercised animals which had not been treated with allopurinol. It is concluded that endothelium-derived ROS contribute reasonably to oxidative stress to exercised muscle and to fiber and capillary damage.

Allopurinol↗
PubMed1990

[Evaluation of cardiac manifestations in hypothyroidism: documentation of reversibility].

PURPOSE: To detect the cardiac manifestations due to the state of hypothyroidism and reversibility after euthyroidism. PATIENTS AND METHODS: Thirteen patients with documented primary hypothyroidism were evaluated through the echocardiography and other noninvasive techniques. A new evaluation was performed six months after thyroid hormone therapy. RESULTS: Most of the changes were reversed after the patients became euthyroid. The main finding was the echocardiographic measurement of the velocity of circumferential fiber shortening that showed a significant positive linear correlation with serum thyroid hormones. CONCLUSION: These data demonstrate the existence of a hypothyroid cardiomyopathy.

Adolescent↗
PubMed1989

Uptake inhibitors do not change the effect of imidazoline alpha 2-adrenoceptor agonists on transmitter release evoked by single pulse stimulation in mouse vas deferens.

The present study was undertaken to compare the presynaptic interaction of neuronal noradrenaline uptake inhibitors with imidazoline and phenylethylamine alpha 2-adrenoceptor agonists under two different conditions: at low and high noradrenaline concentrations in the biophase. Isolated mouse vasa deferentia were stimulated with trains of 7 pulses given at 0.2 Hz and the inhibition by the alpha 2-adrenoceptor agonists clonidine, alpha-methylnoradrenaline, and UK-14,304 of twitch responses was measured in the absence and in the presence of either cocaine (12 mumol/l) or desipramine (40 nmol/l). The effects were determined for the first (equivalent to single pulse stimulation) and the last stimulus of each train. Both uptake inhibitors antagonized the presynaptic inhibitory effects of imidazolines (clonidine and UK-14,304) on the last twitch; the effects on the first twitch remained unchanged. In contrast, the uptake inhibitors potentiated the inhibitory effect of the phenylethylamine (alpha-methylnoradrenaline) on both the first and the last twitches. These results support the view that the concentration of noradrenaline in the biophase plays a decisive role in the inhibition by alpha 2-adrenoceptor agonists of the electrically evoked release of noradrenaline. Agonists that are not substrates of neuronal uptake (i.e., clonidine, UK-14,304) become less effective when noradrenaline is present in the biophase while substrates of neuronal uptake (i.e., alpha-methylnoradrenaline) do not. The results argue against the hypothesis that uptake inhibitors interact directly with presynaptic alpha 2-adrenoceptors or act at some link between uptake and receptor sites.

Adrenergic alpha-Agonists↗
PubMed1986

[Value of aspiration biopsy of subcutaneous fat in amyloidosis].

Fine-needle aspiration of subcutaneous fat (FNAF) was performed in 24 patients, 12 with previously diagnosed amyloidosis presenting with proteinuria or nephrotic syndrome, and 12 presenting a nephrotic syndrome without amyloidosis on renal biopsy. FNAF was positive in 10 of 12 patients with amyloidosis (sensitivity: 83%) and negative in 12 of 12 patients with non-amyloid nephrotic syndrome (specificity: 100%). Considering a 2.5 to 10% prevalence of amyloidosis in adult patients with proteinuria or nephrotic syndrome, a positive FNAF is diagnostic of amyloidosis, and a negative FNAF rules out the diagnosis with a probability of 98 to 99%. FNAF is a simple and safe method which can be useful in patients who cannot undergo a renal biopsy.

Adipose Tissue↗
PubMed1985

Interstitial foam cells in the nephrotic syndrome belong to the monocyte/macrophage lineage.

Interstitial foam cells are occasionally seen in patients with the nephrotic syndrome. In a group of patients with the nephrotic syndrome we were able to demonstrate that these cells express markers characteristic of the monocyte/macrophage lineage. Their presence was related to the previous duration of proteinuria, but they had no apparent influence on the subsequent evolution of renal function. The mechanisms leading to their presence are unknown.

Adult↗
PubMed1984

Lead and cadmium concentrations in the hair of fishermen from the Subae River basin, Brazil.

Previous studies have shown heavy pollution by lead and cadmium in the Subae River basin, State of Bahia, Brazil, caused by a lead smelter. Concentrations of these metals were determined in scalp hair of fishermen from three riverside towns and from a reference town. Increased levels for both metals were associated with increasing proximity to the smelter. Mean concentrations of lead and cadmium were higher among fishermen with straight hair than among those with curly hair. The effects of hair washing, hair type, and color and age on metal concentrations in fishermen's hair were studied.

Absorption↗