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C Pimentel

Publications and source records attributed to C Pimentel.

15 recordsLinked to original sources
PubMed2005

Solution structure of two insect-specific spider toxins and their pharmacological interaction with the insect voltage-gated Na+ channel.

Delta-paluIT1 and delta-paluIT2 are toxins purified from the venom of the spider Paracoelotes luctuosus. Similar in sequence to mu-agatoxins from Agelenopsis aperta, their pharmacological target is the voltage-gated insect sodium channel, of which they alter the inactivation properties in a way similar to alpha-scorpion toxins, but they bind on site 4 in a way similar to beta-scorpion toxins. We determined the solution structure of the two toxins by use of two-dimensional nuclear magnetic resonance (NMR) techniques followed by distance geometry and molecular dynamics. The structures of delta-paluIT1 and delta-paluIT2 belong to the inhibitory cystine knot structural family, i.e. a compact disulfide-bonded core from which four loops emerge. Delta-paluIT1 and delta-paluIT2 contain respectively two- and three-stranded anti-parallel beta-sheets as unique secondary structure. We compare the structure and the electrostatic anisotropy of those peptides to other sodium and calcium channel toxins, analyze the topological juxtaposition of key functional residues, and conclude that the recognition of insect voltage-gated sodium channels by these toxins involves the beta-sheet, in addition to loops I and IV. Besides the position of culprit residues on the molecular surface, difference in dipolar moment orientation is another determinant of receptor binding and biological activity differences. We also demonstrate by electrophysiological experiments on the cloned insect voltage-gated sodium channel, para, heterologuously co-expressed with the tipE subunit in Xenopus laevis oocytes, that delta-paluIT1 and delta-paluIT2 procure an increase of Na+ current. delta-PaluIT1-OH seems to have less effect when the same concentrations are used.

Animals↗
PubMed2001

Influence of insulin-like growth factor-I and its interaction with gonadotropins, estradiol, and fetal calf serum on in vitro maturation and parthenogenic development in equine oocytes.

The effects of insulin-like growth factor-I (IGF-I) and its interaction with gonadotropins, estradiol, and fetal calf serum (FCS) on in vitro maturation (IVM) of equine oocytes were investigated in this study. We also examined the role of IGF-I in the presence or absence of gonadotropins, estradiol, and FCS in parthenogenic cleavage after oocyte activation with calcium ionophore combined with 6-dimethylaminopurine (6-DMAP), using cleavage rate as a measure of cytoplasmic maturation. Only equine cumulus-oocyte complexes with compact cumulus and homogenous ooplasm (n = 817) were used. In experiment 1, oocytes were cultured in TCM-199 supplemented with BSA, antibiotics, and IGF-I at 0 (control), 50, 100, 200 ng/ml, at 39 degrees C in air with 5% CO(2), 95% humidity for 36 or 48 h. In experiment 2, oocytes were cultured with FSH, LH, estradiol, and FCS with IGF-I at the concentration that promoted the highest nuclear maturation rate in experiment 1. In experiment 3, oocytes from the three experimental groups (IGF-I; hormones; and IGF-I + hormones) were chemically activated by exposure to calcium ionophore followed by culture in 6-DMAP. In experiment 1, IGF-I stimulated equine oocyte maturation in a dose-dependent manner with the highest nuclear maturation rate at a concentration of 200 ng/ml. No significant effect of IGF-I on nuclear maturation was observed in experiment 2. In experiment 3, a significant difference in cleavage rate was observed between the hormone + IGF-I group (15 of 33; 45.4%) compared with IGF-I (10 of 36; 27.8%) and hormone (4 of 31; 12.9%) alone (P < 0.05). These results demonstrated that IGF-I has a positive effect on nuclear maturation rate of equine oocytes in vitro. The addition of IGF-I to an IVM medium containing hormones and FCS did not increase nuclear maturation, but resulted in a positive effect on cytoplasmic maturation of equine oocytes measured by parthenogenic cleavage.

Animals↗
PubMed2000

Differences in growth and water relations among Phaseolus vulgaris cultivars in response to induced drought stress.

Relatively little ecophysiological research has been conducted to determine the responses to drought of Phaseolus vulgaris. Four bean cultivars (cvs.) from Brazil, A320, Carioca, Ouro Negro and Xodó were submitted to an imposed water deficit in order to evaluate the importance of some adaptive mechanisms of drought resistance through the analysis of growth parameters, water status, gas exchange and indicators of tolerance mechanisms at the cellular level. During the drought treatment, relative growth rates were more reduced for A320 and Xodó than Carioca and Ouro Negro. A320 closed its stomata very rapidly and complete stomatal closure was obtained at Psi(w)=-0.6 MPa, in contrast to the other cvs. where stomata were fully closed only at Psi(w)=-0.9 MPa. Net assimilation rates were closely related to stomatal conductances. Mechanisms at the cellular level appeared to be mostly important for higher tolerance. Carioca and Ouro Negro, when compared to A320 and Xodó, were characterized by having better drought tolerance mechanisms and higher tissue water retention capacity leading to a better growth under water deficits. The leaf dehydration rates of those cvs. were slow whereas those of the drought sensitive cvs. were rapid. The results were confirmed by the electrolyte leakage test and leaf osmotic potential measurements, which indicated higher membrane resistance and osmotic adjustment in the two tolerant cvs. Carioca and Ouro Negro. It appears from this study that despite being cultivated in the same geographical region, the four cvs. of P. vulgaris displayed somewhat different drought adaptive capacities for prolonged drought during the vegetative phase.

Journal Article↗
PubMed1998

Small bowel motility in primary biliary cirrhosis.

OBJECTIVE: Previous studies have shown small bowel motor activity abnormalities in patients with liver cirrhosis of different etiologies, but motility has not been studied in patients with primary biliary cirrhosis. Our aim was to investigate proximal small bowel motility in these patients. METHODS: Twenty-five female patients presenting clinical, biochemical, serological, and histological findings compatible with primary biliary cirrhosis, 10 female patients with nonalcoholic liver cirrhosis, and 10 normal female controls were studied. Motility of the upper small bowel was measured in the fasted state by means of perfused manometric catheters, connected to external transducers and positioned in the small bowel under fluoroscopy. RESULTS: The average amplitude of contractions was significantly decreased in patients with primary biliary cirrhosis compared with other liver cirrhosis (20.2+/-1.0 vs 32+/-2.9 mm Hg). Also, a significantly increased frequency of cluster of contractions and an increased duration of phase II of the migrating motor complex as seen in liver cirrhosis was observed when compared with normals. CONCLUSION: We conclude that primary biliary cirrhosis patients present motor abnormalities of the small intestine similar to those of patients with liver cirrhosis of other etiologies. In addition, a decrease in the amplitude of small bowel contractions was also found in these patients, suggesting a myogenic involvement.

Adult↗
PubMed1997

Testicular function in asymptomatic chronic alcoholics: relation to ethanol intake.

To evaluate the effect of ethanol on testicular function in chronic alcoholics without chronic liver disease, we studied 38 asymptomatic chronic alcoholics and 19 age-matched controls. Detailed clinical history, nutritional status, hormonal analysis, and seminal studies were conducted in each case and control. Alcoholic patients had an average of 39 +/- 2 years old (range: 26 to 60) and reported a daily ethanol consumption from 100 to 350 g (mean: 198 +/- 15) over a period of 18.0 +/- 1.2 years. Alcoholics exhibited a significant increase of the luteinizing hormone (p < 0.001) and a decrease of the Free Androgen Index, compared with controls (p < 0.05) that related significantly with the total lifetime dose of ethanol (p < 0.01, both). Seminal studies indicate that 39.4% of alcoholics had significantly reduced their spermatozoa count (p < 0.01), whereas significant morphological abnormalities were observed in 44.7% of the alcoholics (p < 0.01). Spermatozoa motility from alcoholics was also found to be altered in half of the patients (p < 0.01). A significant increase of serum luteinizing hormone, follicle-stimulating hormone, and sex hormone binding globulin levels, and a decrease of Free Androgen Index were observed in alcoholics with morphology and motility abnormalities (p < 0.05, all). In multivariate analysis, the only independent factor that determined the alterations in sperm (count, morphology abnormalities, and motility alterations) was the total lifetime of ethanol intake (p < 0.001, all). We conclude that alcoholics frequently develop a situation of primary hypogonadism related to a lifetime of ethanol consumption.

Adult↗
PubMed1997

[Endoscopic manometry of Oddi's sphincter].

BACKGROUND: Endoscopic manometry is the gold standard for the diagnosis of sphincter of Oddi dysfunction. AIM: To report the results of the first 30 endoscopic manometries of sphincter of Oddi performed in a Gastroenterology Service. PATIENTS AND METHODS: Thirty manometries were performed in 28 patients aged 30 to 70 years old (14 females). The papilla was cannulated with a perfused catheter, measuring pressure with external transducers. RESULTS: Deep cannulation of the papilla was achieved in 88%. Procedure-related complications were not observed in these cases. Normal values were registered in 11 cases with a basal sphincter pressure 15.6 +/- 10.7 mm Hg, contractions with an amplitude of 92.3 +/- 35.7 mm Hg and 6.0 +/- 2.4/min frequency. The clinical suspicion of hypertonic dyskinesis was confirmed in 5 cases with an elevated basal pressure of 43.69 +/- 13.3 mm Hg, an increased frequency of contractions ("tachyoddia") in one, and large spastic contractions of high pressure in other case. In 3 of 5 cases with common bile duct stones, a predominance of retrograde propagation of the contractions was observed with normal pressure. Variable manometric results were observed after endoscopic papillotomy observing a scale from the complete absence of motor activity to normal sphincter function. CONCLUSIONS: Endoscopic manometry is a reasonably safe method, of great importance in the diagnosis of functional disorders of the sphincter of Oddi.

Adult↗
PubMed1994

Late low-dose pure follicle stimulating hormone for ovarian stimulation in intra-uterine insemination cycles.

At present, there is general agreement that ovarian stimulation improves pregnancy rates after intra-uterine insemination (IUI). Also, ovulation induction with gonadotrophins is associated with higher success rates than clomiphene citrate in IUI cycles. However, the drawbacks to the use of gonadotrophin stimulation before IUI include the risks of ovarian hyperstimulation and multiple gestation, and the relative cost of a treatment cycle in a view of the medication costs and the need for increased monitoring by hormone assays and ultrasonographic measurements. In the present prospective randomized trial, the efficacy and safety of ovarian stimulation with clomiphene citrate (50 mg/day for 5 days) and IUI (clomiphene/IUI group) were compared with those of late low-dose pure follicle stimulating hormone (FSH, 75 IU/day from day cycle 7 until the leading follicle reached > 17 mm in diameter) and IUI (FSH/IUI group) in ovulatory women who were infertile because of unexplained infertility (n = 40) or male subfertility (n = 60). The mean length of treatment in the FSH group was 6.4 +/- 2.5 days. Multiple follicular development was seen in 25% of clomiphene-stimulated cycles but only in 8% of those treated with FSH. Pregnancy rate per cycle in clomiphene/IUI and FSH/IUI groups was 4% (4/98) and 13% (12/94) respectively (P = 0.02). All pregnancies obtained were singleton. There were two and one clinical abortions in the clomiphene/IUI (50%) and FSH/IUI (8%) groups respectively. No patient developed ovarian hyperstimulation syndrome. Use of our therapeutic scheme, which proved to be efficacious, safe and economic for ovarian stimulation in IUI cycles, is advocated before the institution of in-vitro fertilization (IVF) or gamete intra-Fallopian transfer (GIFT) therapy in infertile patients with patient Fallopian tubes. This late low-dose technique of administering pure FSH is suitable for use in offices without immediate access to oestradiol results.

Chorionic Gonadotropin↗
PubMed1991

Immunobiochemical evidence for the loss of sperm specific histones during male pronucleus formation in monospermic zygotes of sea urchins.

To obtain information on the remodeling of sperm chromatin during male pronuclei formation, we have followed the sperm specific histones (SpH) that form the nucleosomal core by Western immunoblot analysis with polyclonal antibodies directed against the core SpH. The results obtained indicate that the complete set of SpH is absent from zygote chromatin at the beginning of the first S phase. The disappearance of SpH is not coincidental for the five histone classes: SpH4 and SpH3 are lost 5-15 min post insemination (p.i.), SpH2B and SpH2A disappear 20-40 min p.i., and SpH1 is progressively diminished up to 30 min p.i. This order of sperm chromatin remodeling is not affected by the inhibition of protein synthesis by emetine, indicating that the factor(s) responsible for SpH disappearance are present in unfertilized eggs. The lost SpH's are not replaced by newly synthesized CS variants, since the basic proteins synthesized de novo during male pronuclei formation are not incorporated into chromatin remaining in the cytoplasm. These newly synthesized proteins are different from the CS variants as judged by their electrophoretic migration.

Animals↗
PubMed1990

[Tumor markers in liver metastases of colorectal carcinoma].

Colorectal cancer is a potentially curable tumour when diagnosed in the early stages. In order to improve the results obtained up to now, we propose application of a diagnostic program among patients who undergo curative resection for colorectal adenocarcinoma, which would consist of using a panel of tumor markers, in combination with endoscopic, histologic and ultrasonographic diagnostic methods. For this study we studied 105 patients, divided into two groups: A) Group 1: 30 control patients. B) Group 2: 75 patients diagnosed as having colorectal cancer. We performed the preoperative determination of a series of tumor markers (CEA, CA 19.9, GGT and PHI), endoscopy/biopsy and hepatic ultrasonography on these patients. Our results suggest that the design of the preoperative diagnostic program makes early detection of hepatic metastases possible. The tumor marker panel combination provided a visible increase in sensitivity for detecting hepatic metastases.

Adenocarcinoma↗
PubMed1980

Chronic administration of cannabidiol to healthy volunteers and epileptic patients.

In phase 1 of the study, 3 mg/kg daily of cannabidiol (CBD) was given for 30 days to 8 health human volunteers. Another 8 volunteers received the same number of identical capsules containing glucose as placebo in a double-blind setting. Neurological and physical examinations, blood and urine analysis, ECG and EEG were performed at weekly intervals. In phase 2 of the study, 15 patients suffering from secondary generalized epilepsy with temporal focus were randomly divided into two groups. Each patient received, in a double-blind procedure, 200-300 mg daily of CBD or placebo. The drugs were administered for along as 4 1/2 months. Clinical and laboratory examinations, EEG and ECG were performed at 15- or 30-day intervals. Throughout the experiment the patients continued to take the antiepileptic drugs prescribed before the experiment, although these drugs no longer controlled the signs of the disease. All patients and volunteers tolerated CBD very well and no signs of toxicity or serious side effects were detected on examination. 4 of the 8 CBD subjects remained almost free of convulsive crises throughout the experiment and 3 other patients demonstrated partial improvement in their clinical condition. CBD was ineffective in 1 patient. The clinical condition of 7 placebo patients remained unchanged whereas the condition of 1 patient clearly improved. The potential use of CBD as an antiepileptic drug and its possible potentiating effect on other antiepileptic drugs are discussed.

Adult↗