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Biomedical subjects

S Bravo

Publications and source records attributed to S Bravo.

At least 19 recordsLinked to original sources
PubMed2006

Finding of conjunctival melanocytic pigmented lesions within pterygium.

AIMS: Conjunctival pigmented lesions have characteristic clinical and histopathological appearances. Melanocytic pigmented lesions commonly occur in the conjunctiva, although they have not been previously reported in pterygium, a common lesion which originates from conjunctiva. Our aim was to evaluate the possibility of an association between pterygium and conjunctival melanocytic pigmented lesions. METHODS AND RESULTS: A total of 80 samples of pterygium excised from Ecuadorian patients in 2002 were collected. Clinical data were available regarding age, sex, race and place of residence. Histological sections were evaluated for the presence of melanocytic pigmented lesions. Nine cases of conjunctival melanocytic, pigmented lesions within pterygium were found and were classified according to the histopathological criteria previously published for pigmented lesions of the conjunctiva, as naevi and primary acquired melanosis (PAM) with varying degrees of atypia. Five of the nine cases showed primary acquired melanosis without atypia, while two cases had atypia; one case showed features of compound naevus and one lesion was designated as subepithelial naevus. CONCLUSIONS: Our findings suggest that conjunctival melanocytic, pigmented lesions occasionally occur in pterygium. All surgically removed pterygia should undergo careful histopathological examination.

Adolescent↗
PubMed2005

Kinetics of Bifidobacterium longum ATCC 15707 fermentations: effect of the dilution rate and carbon source.

The effect of the dilution rate on biomass and product synthesis in fermentations of glucose, fructose and a commercial mixture of fructooligosaccharides (FOS) by Bifidobacterium longum ATCC 15707 was studied. Kinetic parameters (maximum specific growth rate, Monod constant, maintenance, and yield coefficients) in the mathematical model of the fermentation were estimated from experimental data. In the FOS mixture fermentations, approximately 12% of the total reducing sugars (mainly fructose) in the feed were not metabolized by the bacterium. In fermentations of fructose and the FOS mixture, biomass concentration increased as the dilution rate increased and, once maximum values were reached [3.90 (D=0.20 h(-1)) and 2.54 g l(-1) (D=0.15 h(-1)), respectively], decreased rapidly as the culture was washed out. Formic acid was detected at low dilution rates in glucose and fructose fermentations. The main products in fermentations of the three carbon sources were lactic and acetic acids. Average values of the molar ratio between acetic and lactic acids of 1.18, 1.21 and 0.83 mol mol(-1) were obtained in glucose, fructose and FOS mixture fermentations, respectively. In batch fermentations carried out without pH control this molar ratio was lower than 1.5 only when fructose was used as the carbon source.

Acetic Acid↗
PubMed2005

Regulation of peroxisome proliferator activated receptor-gamma in rat pituitary.

Peroxisome proliferator activated-receptor gamma (PPARgamma) is a member of the nuclear receptor superfamily and, in addition to its relation with obesity and insulin sensitivity, it has recently been localized in human and mice pituitary, indicating a functional significance of PPARgamma in adenopituitary tumours. In the present study, we localized the PPARgamma mRNA and protein in different cell types of rat pituitary. Moreover, using the real-time polymerase chain reaction, we assessed the mRNA expression of PPARgamma in different physiological and pathological settings known to be associated with alterations in anterior pituitary cell proliferation and/or function. Our experiments have shown that PPARgamma mRNA levels were repressed by oestrogen through an oestrogen receptor-alpha effect. However, PPARgamma protein levels were only modified in males but not in females. On the other hand, PPARgamma mRNA expression was increased in dwarf rats in comparison with Lewis rats. Finally, nutritional, thyroid status or pregnancy did not change PPARgamma expression. Taken together, we provide new data regarding the regulation of pituitary PPARgamma mRNA by hormonal and metabolic status.

Animals↗
PubMed2003

Cellular distribution and regulation of ghrelin messenger ribonucleic acid in the rat pituitary gland.

Ghrelin, a 28-amino-acid acylated peptide, strongly stimulates GH release and food intake. In the present study, we found that ghrelin is expressed in somatotrophs, lactotrophs, and thyrotrophs but not in corticotrophs or gonadotrophs of rat pituitary. Persistent expression of the ghrelin gene is found during postnatal development in male and female rats, although the levels significantly decrease in both cases from pituitaries of 20-d-old rats onward, but at 60 d old, the levels were higher in male than female rats. This sexually dimorphic pattern appears to be mediated by estrogens because ovariectomy, but not orchidectomy, increases pituitary ghrelin mRNA levels. Taking into account that somatotroph cell function is markedly influenced by thyroid hormones, glucocorticoids, GH, and metabolic status, we also assessed such influence. We found that ghrelin mRNA levels decrease in hypothyroid- and glucocorticoid-treated rats, increase in GH-deficient rats (dwarf rats), and remain unaffected by food deprivation. In conclusion, we have defined the specific cell types that express ghrelin in the rat anterior pituitary gland. These data provide direct morphological evidence that ghrelin may well be acting in a paracrine-like fashion in the regulation of anterior pituitary cell function. In addition, we clearly demonstrate that pituitary ghrelin mRNA levels are age and gender dependent. Finally, we show that pituitary ghrelin mRNA levels are influenced by alteration on thyroid hormone, glucocorticoids, and GH levels but not by fasting, which indicates that the regulation of ghrelin gene expression is tissue specific.

Aging↗
PubMed2001

Localization of growth hormone receptors in rat and human thyroid cells.

Growth hormone (GH) exerts its multiple actions by binding to a specific receptor (GHR) widely distributed in the organism. It is well established that, in acromegaly, the thyroid gland is larger than normal and that GH increases triiodothyronin concentrations and decreases those of tetraiodothyronin (thyroxine). The aim of the present study was to analyze the presence of GHR and its mRNA in rat and human thyroid gland by Western blot, in situ hybridization techniques, and immunohistochemistry. A band of the expected size for GHR was shown in rat and human thyroid by Western blot. GHR immunoreactivity was found in virtually all follicles. The signal was mainly localized in the cytoplasm, although a nuclear positivity was also found. In situ hybridization techniques demonstrated the presence of GHR messenger RNA in the thyroid gland (cytoplasm of the follicular cells). These results provide direct morphological evidence that GHR is localized in the thyroid gland of mammals and opens up the possibility that GH regulates thyroid cell function directly or via local autocrine or paracrine production of insulin-like growth factor I.

Animals↗
PubMed2001

Zymomonas mobilis CP4 fed-batch fermentations of glucose-fructose mixtures to ethanol and sorbitol.

Zymomonas mobilis CP4 fed-batch fermentations of glucose-fructose mixtures were carried out at different operational conditions (aeration, feed rate and substrate concentration) to test their effects on the system productivity. In these fermentations, the main products were ethanol and sorbitol. Kinetic parameters were calculated using the experimental data. However, parameters in the sorbitol synthesis rate were estimated from data recorded in different experiments in order to avoid the effect of the simultaneous cell growth and ethanol synthesis. In this case, the crude cell extract was used as source of the enzyme responsible for the sorbitol synthesis. The highest degree of conversion of fructose into sorbitol obtained with the extract was equal to 71% in a sugar mixture with an initial concentration of 200 g/l. Results obtained in the fed-batch fermentations showed that aeration of the culture has a positive effect on the final biomass concentration. However, final ethanol concentration is lower under aerated conditions. The best sugar yields to biomass and ethanol were 0.032 and 0.411 g/g, respectively. On the other hand, the highest sorbitol yield in the fed-batch fermentations was 0.148 g/g.

Biomass↗
PubMed2000

Effect of feeding strategy on Zymomonas mobilis CP4 fed-batch fermentations and mathematical modeling of the system.

In this work, the effect of the feeding strategy in Zymomonas mobilis CP4 fed-batch fermentations on the final biomass and ethanol concentrations was studied. Highest glucose yields to biomass (0.018 g/g) and to ethanol (0.188 g/g) were obtained in fed-batch fermentations carried out using different feeding rates with a glucose concentration in the feed equal to 100 g/l. Lower values (0.0102 g biomass/g glucose and 0.085 g ethanol/ g glucose) were obtained when glucose accumulated to levels higher than 60 g/l. On the other hand, the highest biomass (5 g/l) and ethanol (39 g/l) concentrations were obtained using a glucose concentration in the feed equal to 220 g/l and exponentially varied feeding rates. Experimental data were used to validate the mathematical model of the system. The prediction errors of the model are 0.39, 14.36 and 3.24 g/l for the biomass, glucose and ethanol concentrations, respectively. Due to the complex relationship for describing the specific growth rate, a fed-batch culture in which glucose concentration is constant would not optimize the process.

Ethanol↗
PubMed1998

Evaluation of a new ambulatory blood pressure device.

We assessed the OSCILL-IT ambulatory blood pressure (BP) recorder (FIGI sr1, Rome, Italy) according to the performance criteria set out by the British Hypertension Society (BHS) protocol. The OSCILL-IT is a portable, noninvasive recorder that uses a process that correlates systolic, mean, and diastolic areas, identified on the oscillations, to the cuff absolute pressure. According to the recommendations of BHS, a large heterogeneous population (100 subjects: 52 men aged from 19 to 79--median 44 and 48 women from 19 to 74--median 54) was recruited in order to assess accuracy and to analyze, in addition, the effects of observer agreement and BP level on the observer-device differences. With reference to BP level, we suggest also a new graphic approach. Four sets of sequential, same arm, comparative BP measurements were obtained, performed by the OSCILL-IT recorder and two skilled clinicians using a mercury column, for each subject. We used a linear combination for the statistical evaluations. We confirmed the observer agreement through the frequency distribution of BP as a function of the observer and through the differences between observers. We compared OSCILL-IT with sphygmomanometric readings: the differences were not significant. A visual inspection, with the addition of regression lines, showed that there were no variations in differences at the changing of BP level. The difference between observers and OSCILL-IT was 0.2 +/- 5.3 mm Hg and 0.2 +/- 5.8 mm Hg both for systolic BP (SBP) and diastolic BP (DBP). The level of agreement, according to BHS criteria, showed that 64% of all systolic and 70% of all diastolic readings obtained by the OSCILL-IT were within 5 mm Hg of the sphygmomanometric determinations. Therefore, the grade is C for SBP, even if 93% of SBP and 95% of DBP obtained by the OSCILL-IT were within 10 mm Hg of the sphygmomanometric determinations. These analyses demonstrate that the OSCILL-IT satisfies the accuracy parameters and the additional linear regression yields graphics more immediate.

Adult↗
PubMed1996

Analysis of blood pressure rhythms for drug efficacy evaluation.

This study analyzes some methods of evaluating the effects of antihypertensive drugs on blood pressure circadian rhythm. We reviewed four different approaches: hourly averages, trough-to-peak ratio, cosinor method, and Fourier series applied to the same data to prove the time course of the effects of isradipine administered once daily. A total of 141 patients of both sexes (mean age 53 years, range 30-76) with mild to moderate essential hypertension were enrolled in this multicenter trial after a 2-week placebo run-in. Treatment with isradipine SRO 5 mg/day administered between 8 and 9 AM was started. Each patient underwent ambulatory BP monitoring at the time of entry and after 6 weeks of treatment. Calculation of hourly averages showed decreases after 4 AM, and from about 8-9 AM, when the drug was administered, and the decreases practically did not vary until about 10 PM. Subsequently, the decreases became smaller and indicated reduced drug activity. However, this hypothesis no longer held after 4 AM. The trough-to-peak ratio was calculated including hourly averages after the dose divided by the lowest hourly average. Both systolic and diastolic blood pressure showed constant reduction from 3 PM (time of peak) to 11 PM. However, after 11 PM, higher trough-to-peak ratios paradoxically occurred due to a major reduction obtained with placebo, and the negative percentages just before the next dose cannot be attributed to treatment. Applying the cosinor method, maximal values were greatly underestimated, nocturnal values were overestimated, and the absolute maximum occurred in proximity to the minimum relating to postprandial dip. The generalized cosinor model, known as Fourier partial series, was always curtailed to the third harmonic. Fourier analysis was able to describe the daily trend of BP both before and after isradipine administration. We used statistical tests to determine if the differences described by the models were significant. The tests indicated significant mean level reductions after therapy and no appreciable amplitude and phase-related variations. The nocturnal and periawakening intervals, in which BP changed linearly, oscillated between 3 and 4 hours. Within these intervals BP rose by 13-16 mm Hg or fell by 14-19 mm Hg. The intervals, ranges, and speed differences were tested and were never significant. The medication tested was effective only at the mean level, the variables used to characterize the time course of its effect remaining unchanged. There was no significant phase shift of the curves, and BP rhythm was preserved.

Adult↗
PubMed1993

Characterization of Chilean hazel nut sweet cookies.

A series of studies were carried out to test the effect of the incorporation of Chilean hazel nut flour in sweet cookies at the levels of 0%, 5%, 10%, 15% and 20%. The proximate chemical analysis of the different flour mixtures showed a regular increase from 7.2 to 12.2%, 14.5% to 18.8% and 1% to 2.2%, respectively, decreasing at the same time with the percentages of water and carbohydrates. Chemical amino acid scores of leucine and threonine in wheat flour improved with the incorporation of Chilean hazel nut flour. The farinographic evaluation made to the different blends showed several changes occurred with the incorporation of Chilean hazel nut flour to wheat flour. These included increase in water absorption, decrease in dough developing time and weakening of the dough. Sensory characteristics such as appearance, texture, flavor and also acceptability improved with the incorporation of Chilean hazel nut flour into the cookie formulas.

Amino Acids↗
PubMed1991

Histologic basis for increased extraocular muscle enhancement in gadolinium-enhanced MR imaging.

Minimal to mild enhancement of skeletal muscles is normally seen on gadolinium-enhanced magnetic resonance images. The enhancement of the extraocular muscles is much more intense than that of other skeletal muscles. The authors investigated the structural features of extraocular muscles that contribute to this increased enhancement. After comparing samples of extraocular muscle and quadriceps muscle, the authors concluded that the rich vascularity and the prominence of extravascular space most probably cause extraocular muscles to demonstrate intense enhancement on gadolinium-enhanced images.

Gadolinium DTPA↗
PubMed1991

Developing spinal column: gadolinium-enhanced MR imaging.

Enhancement characteristics of the normally developing spinal column were examined in magnetic resonance (MR) images obtained in 58 children aged 7 days to 9 years. With a 1.5-T imager, short-repetition-time spin-echo images were obtained before and after the administration of 0.1 mmol/kg gadopentetate dimeglumine. Enhancement of normal bone marrow was seen in all patients aged less than 7 years; it was marked only in patients aged less than 2 years. Enhancement of normal cartilage, seen in all patients aged less than 1 1/2 years, may be the most striking feature of enhanced MR images of the infant spine. Enhancement of both bone marrow and cartilage in children appears to be due to the unusual prominence of vasculature, associated with permeability of the capillary endothelium and a plentiful extravascular space. Although marked and diffuse enhancement of vertebral bodies in adults is often thought to indicate a pathologic marrow state, caution must be used before the same criteria are applied to children.

Age Factors↗
PubMed1991

Evolution of the infant spinal column: evaluation with MR imaging.

The appearance of the normal lumbar spinal column was examined in spinal magnetic resonance images obtained in 50 pediatric patients aged 2 years or less. The ossification centers of the developing vertebral bodies, the cartilage, and the disks were studied with a 1.5-T imager by using both short- and long-repetition-time spin-echo sequences. Many of the structures of the spine were noted to undergo dynamic changes in appearance, both in signal intensity and in morphologic characteristics, with growth. The vertebrae and cartilage, especially, transform markedly in infancy and proceed through three characteristic stages of evolution. Stage I, from birth to 1 month of age, is characterized by markedly hypointense ossification centers and hyperintense, prominent cartilage. Stage II, from approximately 1 to 6 months of age, is characterized by increasing signal intensity in the ossification centers, progressing from the endplates in, and decreasing prominence of the cartilage, Stage III, from approximately 7 months of age on, is characterized by increasingly rectangular and centrally intense vertebral bodies and diminishing cartilage. The variability of the signal intensities, with that of muscle used as the standard, and morphologic characteristics of different components of the spine at different stages of development can create significant confusion. Careful analysis, however, permits one to follow the evolution of the lumbar spine and to date it on the basis of its appearance.

Cartilage↗
PubMed1990

Low dose rate radiotherapy for transplantable gliosarcoma in the rat brain.

Interstitial brachytherapy with low energy radionuclides is becoming widely used in conjunction with external beam radiotherapy in the treatment of primary malignant gliomas of the brain. Few radiobiological studies have been carried out with low dose rate brachytherapy for brain tumors. Since we have recently developed a non-invasive low dose rate radiotherapy model for the treatment of transplantable 9L gliosarcoma growing in the rat brain, we carried out a series of radiobiological studies to determine the dose rate effect on the tumor and normal brain tissue. Using TCD50 (the radiation dose to control 50% tumor control) as the endpoints, we obtained the results indicating that the tumor control rate was highly dependent on the dose rate and the total dose delivered to the tumor. The TCD50 of dose rates ranging from 100 cGy/min, 120 cGy/hr, and 40 cGy/hr were 25 Gy, 80 Gy, and 100 Gy, respectively. The normal tissue effects were most pronounced with high dose rate irradiation (100 cGy/min). The LD50 for high dose rate irradiation to the whole brain was 29 Gy. In contrast, the majority of animals treated with low dose rate radio-therapy behaved quite normal up to a year follow-up. The late histopathological changes of the irradiated brain usually consisted of vascular and white matter necrosis, although the extent of such changes showed a considerable individual variation within the long-term survivors.

Animals↗
PubMed1989

Effects of intratumoral injection of I-125 iododeoxyuridine on Ehrlich ascites carcinoma.

Intratumoral injection of I-125 iododeoxyuridine (IUdR), saline solution, and oil suspension was investigated using Ehrlich ascites tumors in the thighs of mice. The oil suspension was more effective in tumor growth delay than was the saline solution. Single injection of the oil suspension at the dose of 12.5 microCi resulted in 21.5 days growth delay, whereas 50 microCi of the saline solution resulted in 11.5 days growth delay relative to control growth delay. At 40 days after treatment, higher radioactivities were observed in the tumor and the skin of the mice treated with the oil suspension, which represented the prolongation of I-125 IUdR oil suspension within the tumor. No normal tissue toxicities were observed.

Animals↗