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Biomedical subjects

A Pena

Publications and source records attributed to A Pena.

At least 37 records · Page 2Linked to original sources
PubMed1998

Determination of tetracycline and its major degradation products by liquid chromatography with fluorescence detection.

A liquid chromatographic method of tetracycline and its major degradation products on a C8-reversed phase column with acidic mobile phase and fluorescence detection is described. The quantification limit, measured as the amount of sample that gave a signal ten times the peak-to-peak noise of the baseline, was: 0.25 ng for tetracycline (TC) and epitetracycline (ETC), 25 ng for and 4-epianhydrotetracycline (EATC) and 50 ng for anhydrotetracycline (ATC) of injected standard. By means of this liquid chromatography (LC) assay TC, ETC, EATC and ATC as main degradation products of tetracycline, can be separated and determined with good sensitivity and specificity within 15 min.

Anti-Bacterial Agents↗
PubMed1998

Enthalpy-entropy compensation for the solubility of drugs in solvent mixtures: paracetamol, acetanilide, and nalidixic acid in dioxane-water.

In earlier work, a nonlinear enthalpy-entropy compensation was observed for the solubility of phenacetin in dioxane-water mixtures. This effect had not been earlier reported for the solubility of drugs in solvent mixtures. To gain insight into the compensation effect, the behavior of the apparent thermodynamic magnitudes for the solubility of paracetamol, acetanilide, and nalidixic acid is studied in this work. The solubility of these drugs was measured at several temperatures in dioxane-water mixtures. DSC analysis was performed on the original powders and on the solid phases after equilibration with the solvent mixture. The thermal properties of the solid phases did not show significant changes. The three drugs display a solubility maximum against the cosolvent ratio. The solubility peaks of acetanilide and nalidixic acid shift to a more polar region at the higher temperatures. Nonlinear van't Hoff plots were observed for nalidixic acid whereas acetanilide and paracetamol show linear behavior at the temperature range studied. The apparent enthalpies of solution are endothermic going through a maximum at 50% dioxane. Two different mechanisms, entropy and enthalpy, are suggested to be the driving forces that increase the solubility of the three drugs. Solubility is entropy controlled at the water-rich region (0-50% dioxane) and enthalpy controlled at the dioxane-rich region (50-100% dioxane). The enthalpy-entropy compensation analysis also suggests that two different mechanisms, dependent on cosolvent ratio, are involved in the solubility enhancement of the three drugs. The plots of deltaH versus deltaG are nonlinear, and the slope changes from positive to negative above 50% dioxane. The compensation effect for the thermodynamic magnitudes of transfer from water to the aqueous mixtures can be described by a common empirical nonlinear relationship, with the exception of paracetamol, which follows a separate linear relationship at dioxane ratios above 50%. The results corroborate earlier findings with phenacetin. The similar pattern shown by the drugs studied suggests that the nonlinear enthalpy-entropy compensation effect may be characteristic of the solubility of semipolar drugs in dioxane-water mixtures.

Acetaminophen↗
PubMed1998

Acute myocardial infarction case fatality, incidence and mortality rates in a population registry in Gerona, Spain, 1990-1992. REGICOR Investigators.

BACKGROUND: Community-based registries provide the best approach to assessing the impact of myocardial infarction (MI) in a population. The objective of the present study was to determine MI mortality, incidence, attack rate and 28-day case fatality in the province of Gerona, Spain from 1990 to 1992. METHODS: Standardized methods were used to find, register and classify MI cases in that population (509628 inhabitants) as definite, possible and insufficient-data MI. RESULTS: Of the 1456 cases fulfilling eligibility criteria, 850 (58.4%) were classified as definite MI, 162 (11.1%) as fatal possible MI, 232 (15.9%) as no MI and 160 (11.0%) as fatal insufficient data. The 1990-1992 age-standardized incidence rates (first MI cases only) for definite and fatal possible MI were 140.8 per 100000 men and 20.4 per 100000 women, all aged 35-64 years; attack rates (first and recurrent MI cases) were 182.9 and 24.5, and mortality rates 46.4 and 5.8, respectively. Case fatality at 28 days was 27.4% and 19.9% in men and women, respectively, but women died later over that period. With respect to men, the age-adjusted risk among women of dying within 28 days post-MI was 1.26 (95% confidence interval [CI]: 0.94-1.69). CONCLUSIONS: Myocardial infarction, incidence, mortality rates and case fatality in Gerona are among the lowest in the world. Age-adjusted case fatality within 28 days is only marginally higher in women than in men, but fatal cases occur later within this period in women.

Adult↗
PubMed1998

High prevalence of cardiovascular risk factors in Gerona, Spain, a province with low myocardial infarction incidence. REGICOR Investigators.

STUDY OBJECTIVE: To establish the prevalence of main cardiovascular risk factors in the province of Gerona, where the incidence of myocardial infarction is known to be low. DESIGN: This was a cross sectional study of prevalence of cardiovascular risk factors conducted on a large random population sample. SETTING: The province of Gerona, Spain. PARTICIPANTS: Two thousand four hundred and four eligible inhabitants of Gerona aged between 25 and 74 years were randomly selected for a multi-stage sample stratified by age and sex. The following were standardly measured: lipids (total cholesterol, high density, low density, lipoprotein (a) and triglycerides), fibrinogen, basal glycaemia, arterial pressure, anthropometric variables, smoking, history of angina (Rose questionnaire), and a medical history questionnaire. Population measurements were standardised for the world population of 24 to 74 years of age. RESULTS: The participation rate was 72.7% (1748). Total mean cholesterol was 5.69 mmol/l in men and 5.61 mmol/l in women and mean high density cholesterol was 1.22 mmol/l and 1.47 mmol/l, respectively. Median lipoprotein (a) was 0.22 g/l. These three lipids increased significantly with age. Mean fibrinogen was 2.92 g/l in men and 3.09 g/l in women, and was higher in smokers. The prevalence of hypertension (systolic arterial tension > or = 140 mm Hg or diastolic > or = 90 mm Hg or drug treatment) was 31.3% in men and 27.7% in women. The proportion of male smokers was 33.8% and female smokers 22.7%. The proportion of female smokers in the 25-34 year age group exceeded that of the remaining age groups for both men and women. CONCLUSIONS: The prevalence of cardiovascular risk factors in Gerona is relatively high for the low myocardial infarction incidence typical of the area, although similar to that of other Spanish areas. The factors that confer sufficient protection to compensate for the effect of the prevalence of these risk factors remain to be elucidated.

Adult↗
PubMed1997

Interaction of family history of atherosclerosis with atherogenic lipid traits in men with non-coronary atherosclerosis.

Family history of atherosclerosis has been recognised as an nonmodifiable cardiovascular risk factor. Lipid levels, together with hypertension and diabetes, appear to have an inheritable component. The aim of the study was to ascertain whether lipoprotein abnormalities of 169 adult patients with non-coronary atherosclerosis were associated with a family history of atherosclerosis. Besides intermediate density lipopoprotein composition and Lp(a) levels, we focused on apo(a) and apo E phenotypes, LDL cholesterol/apo B ratio, VLDL triglyceride/HDL cholesterol ratio, and environmental factors. We found that patients with a family history of atherosclerosis had a higher prevalence of VLDL triglyceride/HDL cholesterol ratio above 1.8 (51.3% vs 34.7%) than patients without. Similarly, there was a significant inverse correlation between both considered ratios (r = -0.24, p < 0.05). The odds ratio of the presence of both abnormal ratios (4.60, 95% CI, 1.41-15.00) and low molecular weight apo(a) isoforms (3.30, 95% CI, 1.05-10.30 and family history of atherosclerosis was independent of smoking and hypertension. Apo(a) isoform size seems to be more important than Lp(a) concentrations in the family history of atherosclerosis risk determination. Subsequent analysis showed that patients with a family history of atherosclerosis had a greater-than-fourfold increased risk of having one or both abnormal ratios reflecting metabolic disturbances which probably constitute a combined trait. Family history of atherosclerosis may constitute a specific lipoprotein-related marker of atherosclerosis. Such a marker often precedes the onset of overt disease and may contribute to identifying patients with an atherogenic lipoprotein profile even in the absence of classical lipid risk factors.

Adult↗
PubMed1997

Extraperitoneal abdominopelvic inflammatory pseudotumor: report of four cases.

We describe four cases of inflammatory pseudotumor seen at our institution in the past 4 years. Four children were each found to have a large extraperitoneal mass on imaging studies, three of which were in the pelvis. Malignant sarcomatous tumors were suspected. Surgical biopsy of each mass, however, revealed inflammatory pseudotumor.

Abdomen↗
PubMed1997

The tethered spinal cord in patients with anorectal malformations.

The aims of this study were to find the prevalence of tethered cord in patients with anorectal malformations; to determine if the presence of tethered cord relates to the severity of the anorectal defect, and to certain symptoms, signs, radiologic findings, and associated anomalies; and finally to determine whether tethered cord impacted on a patient's functional prognosis and whether surgical untethering improved the patient. The authors studied 934 patients with anorectal malformations, 111 of whom had magnetic resonance imaging (MRI) of the spine. We compared patients with and without tethered cord by using parametric and nonparametric statistical tests. Tethered cord occurred in 24% of the patients. The prevalence varied according to the type of anorectal defect from 43% in the complex group to 11% in patients with rectovestibular fistula. Patients with tethered cord had a lateral sacral ratio lower than that of patients without tethered cord (0.410 versus 0.702). Tethered cord was present in 90% of patients with myelodysplasia, 60% of patients with a presacral mass, 57% of patients with sacral hemivertebrae, and 56% of patients with a single kidney. The greater number of associated anomalies a patient had, the greater the risk of having tethered cord (P < .05 for all differences). The authors noted differences between patients with and without tethered cord in the presence of voluntary bowel movements (46% versus 70%), fecal soiling (91% versus 63%), constipation (21% versus 43%), and urinary incontinence (86% versus 42%). The data indicate that patients with tethered cord have a worse functional prognosis than patients without tethered cord. However, the incontinence in our patients was also predictable based on the type of anorectal defect and the character of the sacrum irrespective of the presence of tethered cord. Eighteen patients underwent surgical untethering of the cord, and none had any significant change in bowel or urinary function postoperatively. No patient with tethered cord experienced incontinence that could be attributed to the cord defect alone. This study suggests that tethered cord occurs more frequently in patients with severe anorectal defects, sacral hypodevelopment, myelodysplasia, presacral mass, sacral hemivertebrae, or a single kidney, or in those with an anorectal defect with poor functional prognosis. At present no solid evidence supports the concept that tethered cord by itself affects the functional prognosis of patients with anorectal malformations. Also, there is no good evidence demonstrating that surgical untethering improves the prognosis.

Abnormalities, Multiple↗
PubMed1991

Growth-associated gene expression is not constant in cells traversing G-1 after exiting mitosis.

Analysis of gene expression following stimulation of growth-arrested cells has been the main approach for identification of growth-associated genes. Since the activation of these gene sequences is dependent on both the stimulatory agent and the state of quiescence of the cell, the activation and role of the same genes may be entirely different in non-growth arrested, actively proliferating cells. We have addressed the question of growth-associated gene expression during active growth by analyzing gene expression during G-1 of cells which have just exited mitosis without first leaving the cell cycle. We were able to isolate, by a non-inductive, drug free system, a population of highly synchronized Swiss 3T3 cells within mitosis (greater than 90%) in numbers sufficient to determine the pattern of expression of a large number of representative growth-associated genes. Our results show that after replating the mitotic cells into conditioned medium: (1) growth-associated gene expression is not constant during G-1 of actively proliferating cells, and (2) while a number of genes (e.g., JE, c-myc, ODC, p53, and histone) exhibited patterns of expression similar to that reported in the quiescent systems, others (e.g., nur-77, vimentin, calcyclin) exhibited patterns which were completely different. From these results, we can begin to construct a temporal map of G-1 progression during active growth.

Animals↗
PubMed1991

Augmented-pressure colostogram in imperforate anus with fistula.

Most newborns with imperforate anus, except for those with very low varieties, undergo a diverting colostomy performed in the postnatal period, with definitive surgical repair at a later age. Accurate demonstration of the anatomy of any associated fistula between the rectum and urogenital tract is essential for optimal surgical management. An augmented-pressure distal segment colostogram is recommended prior to definitive repair, both to confirm the level of rectal atresia and to define any associated fistulous communication. We report a case of high imperforate anus with rectourethral fistula in which the fistulous tract was not identified on the conventional contrast colostogram but was readily delineated when an augmented-pressure modification of the technique was utilized. The technical aspects of augmented-pressure colostography are presented.

Anus, Imperforate↗
PubMed1991

A potential role for c-jun in cell cycle progression through late G1 and S.

When the level of c-jun mRNA was analyzed in WI-38 human fibroblasts exciting short- and long-term quiescence, two peaks of c-jun mRNA accumulation were found. The first occurred one hour after stimulation and lasted three to five hours, whereas the second occurred at the G1/S border and was coupled to the time of entry to S phase rather than to the time of stimulation. The early peak is well documented and in agreement with the proposed role of c-Jun/AP-1 in mediating cellular responses to receptor-generated signals. The later peak, however, has not been previously reported. Additional follow-up studies showed that late G1/S expression was not solely a phenomenon of cells existing a quiescent state, nor was it restricted only to human cells. Gel retardation studies confirmed that there is AP-1 specific DNA binding activity in nuclear extracts isolated in late G1 and S phase, and that this AP-1 binding activity is due to the presence of Jun protein. An anti-Fos antibody was able to significantly decrease AB-1 binding activity in early G1 extracts, but had no effect on extracts isolated in late G1 and S phase, indicating that the complexes observed in late G1 and S phase are clearly different from those seen in early G1. These studies are among the first to suggest a functional dissociation of c-Jun from c-Fos. Our results identify a new, previously unreported role for c-Jun/AP-1 in regulation of cell cycle progression and mammalian cell growth.

Animals↗
PubMed1984

A multicenter clinical study of cefoperazone.

Thirty-five adult and 11 pediatric patients in nine Philippine hospitals were treated with cefoperazone for various moderate to severe infections. Adults received 1 to 8 gm/day and children received 0.450 to 4 gm/day in two divided doses, for a mean period of eight to nine days (ranges, 5 to 11 days for children and 5 to 30 days for adults). The efficacy rate (cured and improved) was 90.90% for pediatric patients and 85.72% for adult patients. In a group of patients shifted from other antibiotic regimens, efficacy rates were 100% for pediatric patients and 85% for adult patients treated with cefoperazone. No follow-up cultures were obtained from patients from whom 26 pathogens were isolated, but correlations between the isolates and clinical efficacy showed that cefoperazone had an efficacy rate of 92.3%.

Adolescent↗
PubMed1983

Computed tomography of traumatic serosanguineous cysts.

Two patients developed traumatic peripelvic serosanguineous cysts, following pelvic fracture. A serosanguineous cyst develops when shearing forces cause separation of the skin and subcutaneous fat from the deep fascia and muscle. The space thus created is filled with serious fluid and blood, and clinically presents as soft cystic masses, appearing usually within a day or so, or rarely, after several weeks or months. Most of these lesions resolve spontaneously, or following aspiration; however, some may persist, necessitating surgical resection. Computed tomography is the modality of choice for detection and, in those cysts requiring surgery, it is helpful in revealing the exact size and location of these lesions.

Adult↗
PubMed1981

Postcibal gastroesophageal reflux in children.

The effect of eating on childhood gastroesophageal reflux (GER) is unclear. Twenty-eight asymptomatic children and 28 children with symptoms of GER were fed apple juice or milk-formula and observed for 3 hr postcibal. Distal esophageal pH was monitored continuously during this interval and used to quantitate the frequency and duration of GER. A period of frequent GER occurred for up to 2 hr after apple juice feedings in asymptomatic children, whereas symptomatic patients had frequent GER for longer periods. Compared to apple juice feedings, milk-formula feedings resulted in a decreased esophageal acidity for the first 2 hr. However, the type of feeding did not affect GER seen in asymptomatic children more than 2 hr postcibal. The frequency and duration of postcibal GER were not reduced by the upright position in either group. Effective medical treatment of symptomatic children did not eliminate the frequent GER within 2 hr of apple juice feedings, whereas the Nissen fundoplication usually eliminated all GER. The absence of GER episodes following apple juice correlated with the inability of most children to burp or vomit following antireflux surgery. Therefore, frequent GER for up to 2 hr after clear liquid meals is probably physiologic in children. The effective control of vomiting by medical or surgical therapy correlated best with a decrease in GER more than 2 hr postcibal.

Child, Preschool↗
PubMed1975

Interaction of ethidium bromide with the transport system for monovalent cations in yeast.

Ethidium was found to be taken up by yeast cells in a process that, at certain concentrations has the main following characteristics: a) a substrate is required; b) it presents cooperative kinetics, with n, according to the Hill equation approximately 3; c) ethidium can be concentrated more than 100-fold; d) the uptake is inhibited by Ca2+; e) the uptake of the dye is inhibited by monovalent cations with a selectivity pattern similar to that observed in their transport by yeast; f) ethidium inhibits the uptake of K+, and, at concentrations up to about 250 muM produces a competitive inhibition on the uptake of Rb+; and g) ethidium produces the same effects as K+ on respiration and the extrusion of H+. It is concluded that ethidium is taken up by yeast cells in a selective way by the same transport system normally employed for monovalent cation uptake.

Binding, Competitive↗