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Biomedical subjects

F González

Publications and source records attributed to F González.

At least 55 records · Page 3Linked to original sources
PubMed2002

[Effect of sildenafil citrate on the cortical visual responses].

OBJECTIVE: To study the possible effect of oral sildenafil citrate on the response of cortical visual cells to visual stimulation. METHOD: Multiunit activity was recorded from cortical area V2 of one behaving monkey. Spatio-temporal receptive field maps were obtained by using a reverse cross correlation technique and white noise visual stimulation before and after oral administration of sildenafil citrate. RESULTS: The receptive field maps showed a reduction in response latency after administration of sildenafil citrate. CONCLUSIONS: Since sildenafil citrate is an inhibitor of retinal phosphodiesterase-6, an enhancement on light sensitivity in the photoreceptors is proposed as the cause of the observed reduction in response latency (Arch Soc Esp Oftalmol 2002; 77: 241-246).

Animals↗
PubMed2001

Pregnancy-associated glycoproteins (PAG) detection in milk samples for pregnancy diagnosis in dairy goats.

In ruminants, glycoproteins synthesized in the outer layers of the trophoblast enter the maternal bloodstream. The assay of their concentration in plasma or in serum can be used for pregnancy diagnosis and to indicate feto-placental health status. In this study, concentrations of the pregnancy-associated glycoprotein (PAG) were investigated in the milk of dairy goats. The mean concentrations of PAG in milk were significantly higher in pregnant than in non-pregnant goats throughout the sampling period. Positive milk PAG levels were found in all pregnant animals from Day 32 after breeding, but remained at negative values in nonpregnant ones. This study reports for the first time a pregnancy diagnosis based on milk concentrations of PAG, that could be of great use on the farm.

Animals↗
PubMed2001

Chlorodicyclohexylborane-mediated aldol additions of alpha,alpha'-dioxygenated ketones.

Boron aldol additions of variously O-protected alpha,alpha'-dioxygenated ketones using dicyclohexylboron chloride and a tertiary amine have been investigated. The stereoselectivity of the process was dependent on the protecting group on the alpha-oxygen atoms. Notably, ketones with bulky silyloxy groups gave syn aldols, most likely via Z enolates. This rules out the participation of chelates during the enolization process, at least in the presence of such sterically crowded protecting groups. An alternative explanation is offered.

Journal Article↗
PubMed2001

Comparative study on the selective chalcopyrite bioleaching of a molybdenite concentrate with mesophilic and thermophilic bacteria.

This study evaluates different bioleaching treatments of a molybdenite concentrate using mesophilic and thermophilic bacterial cultures. Further studies on the chemical leaching and the electrochemical behavior of the MoS(2) concentrate were carried out. Bioleaching tests showed a progressive removal of chalcopyrite from the molybdenite concentrate with an increase in temperature. Chemical leaching tests support the idea of an indirect attack of the concentrate. Electrochemical tests indicate that chalcopyrite dissolution is favored when molybdenite is present. Therefore, this type of bioleaching treatment could be applied to purify molybdenite flotation concentrates by selectively dissolving chalcopyrite.

Bacteria↗
PubMed2001

Reproducibility of the parameters of the on-transient cardiopulmonary responses during moderate exercise in patients with chronic obstructive pulmonary disease.

To be clinically useful as indices reflective of altered physiological function consequent to interventions in patients with chronic obstructive pulmonary disease (COPD), the time constant (tau) and steady-state amplitude of the kinetic responses for oxygen uptake (VO2) carbon dioxide output (VCO2) ventilation (VE) and heart rate (HR) have to be appropriately differentiable and reproducible. We therefore assessed the reproducibility of tau and steady state amplitude values in 41 patients with severe COPD [mean (SD)] [forced expiratory volume in 1 s = 41 (7)% predicted], aged 64 (5) years. Of the total, 6 of the patients (15%) did not produce breath-by-breath data of sufficient quality to warrant kinetic analysis. The remaining 35 patients completed two moderate-intensity 10 min square-wave exercise tests separated by 2 h, both before and after an endurance training programme. Tests were conducted on an electromagnetically-braked cycle ergometer at an exercise intensity corresponding to 80% of the estimated lactate threshold (thetaLa) or 50% of peak oxygen uptake if thetaLa was insufficiently differentiable. Breath-by-breath measurements of VO2, VCO2, VE and HR were averaged into 10 s bins and the on-transient response kinetics were estimated using a mono-exponential model. Analysing the pre-training and the post-training test 1 and test 2 comparisons together, the test 1- test 2 differences were not significantly different from 0 for either tau or A. The standard deviation of the test 1- test 2 differences allowed us to define the magnitude of change that would reach statistical significance. For tau, this averaged some 8, 10, 11 and 8 s, for VO2, VCO2, VE and HR, respectively, for a one-tailed paired-comparisons test (i.e. appropriate for assessing hypothesised improvements resulting from an intervention); for a two-tailed comparison, the differences were approximately 2 s greater. The corresponding one-tailed values for A were 100 ml x min(-1), 95 ml x min(-1), 2.5 1 x min(-1) and 4 beats x min(-1), respectively; the two-tailed values were 10%-15% greater. We therefore conclude that both tau and A for moderate-intensity exercise can be reproducibly estimated in patients with COPD when the data set provides a sufficiently large amplitude of response and sufficiently low sample variability to allow appropriate parameter estimation.

Aged↗
PubMed2001

Increased activation of protein C, but lower plasma levels of free, activated protein C in uraemic patients: relationship with systemic inflammation and haemostatic activation.

Chronic renal failure (CRF) courses with both systemic inflammatory reaction and haemostatic activation. We explored the relationship of these processes with plasma levels of free, activated protein C (APC) and complexes of APC with its inhibitors in patients with CRF under conservative treatment. Plasma concentrations of inflammatory cytokines [tumour necrosis factor alpha (TNFalpha) and interleukin 8], acute-phase proteins (C-reactive protein, fibrinogen, alpha1-anti-trypsin and von Willebrand factor), and markers of haemostatic activation (thrombin-anti-thrombin complexes, plasmin-anti-plasmin complexes, and fibrin and fibrinogen degradation products) were higher in patients than in controls. Inflammatory and haemostatic markers were significantly and positively correlated. Total plasma APC and APC:alpha1-anti-trypsin (alpha1AT) complexes were 44% and 75% higher in patients than in controls (P = 0.0001), whereas free APC was 20% lower (P < 0.015). No significant difference was observed in APC:protein C inhibitor (PCI) complexes between both groups. The free/total APC ratio was significantly lower in patients than in controls (P < 0.0001). Total plasma APC and APC:alpha1AT were positively correlated with activation markers of haemostasis and acute-phase proteins, whereas free APC was inversely correlated with plasma levels of creatinine, acute-phase proteins and fibrin degradation products (FnDP). Systemic inflammation and activation of haemostasis are interrelated processes in CRF. APC generation was increased in response to elevated thrombin production, but the inflammatory reaction, associated with increased synthesis of alpha1AT, reduced its anticoagulant effect. Lower free plasma APC in CRF may be pathogenically associated with atherothrombosis, a major cause of death in this disease.

Adult↗
PubMed2001

Influence of ruminal distribution on norfloxacin pharmacokinetics in adult sheep.

Norfloxacin (NF) ruminal distribution after intravenous (i.v.), intramuscular (i.m.) and oral (p.o.) administration was determined in order to assess the influence of the rumen on the pharmacokinetic behaviour of NF in sheep. Norfloxacin concentrations in rumen were detected after i.v. and i.m. administrations between 4 and 48 h in all animals studied. The experimental distribution ratios after i.v. and i.m. administration expressed as area under the concentration-time curve ratios AUC(rumen)/AUC(plasma) were 0.24 and 0.39, respectively, and thus lower than corresponding predicted value of 5.06. Apparently, drug persisted in the rumen content longer than in plasma. The experimental mean residence time ratios MRT(rumen)/MRT(plasma) after i.v. and i.m. administrations were 2.33 and 1.66, respectively. After p.o. administration, NF concentrations in the rumen content were extremely high compared with the respective plasma concentrations, resulting in mean peak concentrations ratio C(max-rumen)/C(max-plasma) of 383.66 and AUC(rumen)/AUC(plasma) experimental ratio of 402.32. This value was considerably higher (approximately 79 fold) than the predicted distribution ratio of 5.06. Our results suggest that the limited p.o. bioavailability of NF in ruminants could not be attributed to ruminal degradation.

Administration, Oral↗
PubMed2001

Pharmacokinetic behavior of marbofloxacin after intravenous and intramuscular administrations in adult goats.

The pharmacokinetic behavior of marbofloxacin was studied in goats after single-dose intravenous (i.v.) and intramuscular (i.m.) administrations of 2 mg/kg bodyweight. Drug concentration in plasma was determined by high performance liquid chromatography (HPLC) and the data collected were subjected to compartmental and noncompartmental kinetic analysis. This compound presented a relatively high volume of distribution (Vss=1.31 L/kg), which suggests good tissue penetration, and a total body clearance (Cl) of 0.23 L/kg small middle doth, which is related to a long elimination half-life (t1/2beta=7.18 h and 6.70 h i.v. and i.m., respectively). Pharmacokinetic parameters were not significantly different between both routes of administration. Marbofloxacin was rapidly absorbed after i.m. administration (Tmax=0.9 h) and had high bioavailability (F=100.74%).

Animals↗
PubMed2001

Pharmacokinetic behaviour of phenylglyoxal bis(guanylhydrazone) (PGBG) after intravenous administration in rabbits.

Phenylglyoxal bis(guanylhydrazone) (PGBG) is a synthesized analogue of methylglyoxal bis(guanylhydrazone) (MGBG), which has demonstrated anti-parasitic activity in rabbits. The pharmacokinetic behaviour of PGBG after intravenous administration (10 mg/kg bodyweight) was studied in five rabbits. Plasma concentrations of PGBG were measured by high-performance liquid chromatography. Plasma PGBG concentrations decreased rapidly and were not detectable beyond 90 min after treatment. The mean [+/- standard deviation (SD)] volume of distribution at steady state (Vdss) was 2.19 +/- 0.47 l/kg and the mean plasma clearance value (Cl) was 29.99 +/- 3.98 ml/min kg. This drug is rapidly eliminated from the body in rabbits, having a short elimination half-life (0.93 h) and mean residence time (1.21 h).

Animals↗
PubMed2001

Epidemiological relationship of human and swine Streptococcus suis isolates.

Two cases of meningitis due to Streptococcus suis in humans are reported here. A butcher and an abattoir worker were referred to a health centre in Castellón (Spain) with fever and symptoms of meningitis. After adequate treatment, a slight hipoacusia persisted as sequelae in both cases. Colonies of S. suis group R, serotype 2 and phenotype MRP+EF+ were isolated from cerebroespinal fluid. Epidemiological studies showed that both workers had in common the handling of pork meat of slaughtered healthy pigs from three closed farms. A study of the tonsils from apparently healthy, slaughtered pigs was carried out. A total of 234 tonsillar samples were obtained and 81 strains of S. suis were isolated from them. Serotype 2 appeared to be the most frequent (50.6%), and the analysis for phenotype showed a high percentage of tonsillar strains with the phenotype MRP+EF+ (35.9%). The humans and 28 tonsillar swine strains showed a similar profile (S. suis group R, serotype 2 and phenotype MRP+EF+). A total of 26 of the swine isolates were analysed by ribotyping using EcoRI. The human strains showed the same six-band hybridization pattern that shared five bands with the pattern most frequently shown by most of the tonsillar N. suis group R, serotype 2 and phenotype MRP+EF+ strains, differing only in the lightest, faintest band which was slightly less anodical in human (> or = 1.8 kb) than in swine (approximately 1.8 kb). From these results, both groups of strains, humans and porcine, showed differences; how can these differences in the pattern of ribotyping be explained if they should have the same origin? Is it possible that they have undergone an adaptation to the new host or perhaps the modification is due to other unknown causes? Further studies in this area are required in order to answer these questions.

Abattoirs↗
PubMed2001

Effect of angiotensin-converting enzyme inhibition on renal filtration surface area in hypertensive rats.

BACKGROUND: Angiotensin-converting enzyme (ACE) inhibitor treatment leads to protective effects on the cellular structure of the glomerulus and the kidney. The aim of this study was to determine whether ACE inhibition increases renal filtration surface area in the spontaneously hypertensive rat (SHR). METHODS: SHR were treated with the ACE inhibitor perindopril at a high dose (3 mg/kg/day) or a low dose (0.1 mg/kg/day) during the period of hypertension development, from 7 to 14 weeks of age. Some animals were treated concomitantly with the bradykinin B2 receptor antagonist, S16118. Tail-cuff systolic blood pressure and body weights were measured twice weekly. At termination of treatment, glomerular number and volume, length, and surface area of glomerular capillaries and renal filtration surface area were estimated using unbiased stereological techniques. RESULTS: There were significant dose-related reductions in blood pressure with high- and low-dose perindopril treatment. Neither low- nor high-dose perindopril treatment had any effect on glomerular number or size or glomerular capillary length and surface area. Hence, there was no significant difference in total renal filtration surface area between any of the experimental groups (8721 +/- 610 mm2 in untreated SHR and 7879 +/- 338 mm2 and 8767 +/- 437 mm2 in the low and high dose perindopril-treated groups, respectively). Coadministration of the bradykinin antagonist did not affect any of the glomerular parameters. CONCLUSIONS: ACE inhibition during the period of hypertension development does not lead to an enhanced glomerular capillary growth or increases in total renal filtration surface area in this model.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2001

Rotavirus-associated medical visits and hospitalizations in South America: a prospective study at three large sentinel hospitals.

BACKGROUND: Knowledge of the impact of rotavirus-associated disease on the health care systems of South America can aid in defining strategies for diagnosis, management and prevention. Up to date information on the impact of rotavirus disease in South America is scarce. AIM: To determine prospectively the impact of rotavirus disease as a cause of medical visits and hospitalizations at three large sentinel pediatric hospitals in Argentina, Chile and Venezuela. METHODS: A 2-year prospective surveillance for rotavirus-associated medical visits and hospitalizations was conducted during 1997 through 1998 at three large sentinel public hospitals, one each in Argentina, Chile and Venezuela. A common surveillance protocol was implemented at the three sites, and a representative number of nonbloody diarrhea stool samples from children <36 months of age were tested for rotavirus by enzyme-linked immunosorbent assay. RESULTS: For our target age group, acute diarrhea-associated medical visits/hospitalizations represented 41%/2%, 5%/6% and 9%/13% of all medical visits/all hospitalizations at the Argentinean, Chilean and Venezuelan sites, respectively (P < 0.001 for difference among the three sites). Rotavirus detection rates among a total of 5,801/1,256 medical visit/hospitalization diarrhea stool samples tested were 39%/71% in Argentina, 34%/47% in Chile and 29%/38% in Venezuela (P < 0.01 by chi square for difference among the three sites). Rotavirus was associated with a mean of 1.5, 1.8 and 3% of total medical visits and 1.6, 2.8 and 5% of hospitalizations among children <36 months of age at the Argentinean, Chilean and Venezuelan sites, respectively. Seasonality was evident for medical visits at all three sites (although less striking in Chile) with peak activity occurring between November and May. Rotavirus-associated hospitalizations had a marked peak in Venezuela, represented largely by short stays, but not in Argentina and Chile. CONCLUSIONS: Rotavirus was a significant cause of medical visits at all three sentinel sites. Rotavirus caused less hospitalizations than previously reported in Argentina and Chile. On the basis of our findings we estimate that approximately 106,000/ 21,000, 48,000/8,000 and 98,000/31,000 rotavirus-associated medical visits/hospitalizations occur yearly in Argentina, Chile and Venezuela, respectively.

Argentina↗
PubMed2001

[Restless legs syndrome: a clinical study in adult general population and in uremic patients].

BACKGROUND: The restless legs syndrome (RLS) is a movement disorder characterized by an imperative urge to move the legs, associated with paraesthesias, motor restlessness and worsening of symptoms at night with at least partial relief by activity. Its prevalence ranges between 2-15% of general adult population and 20-30% of uremic patients. AIM: To evaluate the frequency and the clinical features of RLS in a sample of general adult population and in uremic patients, in Chile, correlating it with biochemical parameters. METHOD: 100 relatives of outpatients and 166 uremic patients undergoing chronic haemodialysis were interviewed assessing the presence and severity of RLS according to current diagnostic criteria. Biochemical parameters assessed were hematocrit, serum ferritin, phosphate, intact parathyroid hormone (iPTH) levels. RESULTS: 13% of the general population sample was affected, 15% of them were severe. Forty three cases were found among uremic patients (25.9%) (p < 0.01 vs general population), 60% of them were severe and women were affected with higher frequency (p < 0.05) and severity (p < 0.01). Four patients presented RLS even during hemodialysis. No correlation was found with biochemical parameters. Most RLS cases had not been diagnosed previously. CONCLUSIONS: In our population RLS is common and undetected. It is especially prevalent and severe in uremic patients: we found no evidence that anaemia, iron deficiency or iPTH level play a major pathogenic role. Our findings emphasize the need of greater medical awareness of RLS because available therapy may improve the quality of life.

Adolescent↗
PubMed2001

Local effect of the corpus luteum on ovarian follicular functional and morphological features in the goat.

Ovaries of unilaterally ovulated goats (n=21) were used to study follicular morphological features (proportion and degree of atresia, oestradiol production in vitro and progesterone production of granulosa cells in culture). Follicles were dissected out and classified as small (1-2 mm), medium (2-4 mm) and large (>4 mm). Morphological and physiological features were compared in each size class between ovaries bearing and not bearing corpora lutea (CLO and NCLO, respectively). Within the same size class, there was no difference in proportion or in degree of atresia, between CLO and NCLO. A significant effect of follicular size on oestradiol production in vitro was detected, but no effect of the corpus luteum was found. Finally, progesterone production of granulosa cells in culture was significantly higher in CLO than in NCLO after 24 h (p < 0.05) and also after 90 h (p < 0.01) of culture. This higher progesterone production by CLO granulosa cells in culture could be explained by local influence of the corpus luteum stimulating the steroidogenic activity but not aromatase activity. Further studies are needed to clarify possible factors and pathways for this local effect of the corpus luteum upon follicular physiology.

Animals↗