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Biomedical subjects

A Altamirano

Publications and source records attributed to A Altamirano.

10 recordsLinked to original sources
PubMed2001

Stimulation of human endonuclease III by Y box-binding protein 1 (DNA-binding protein B). Interaction between a base excision repair enzyme and a transcription factor.

Human endonuclease III (hNth1) is a DNA glycosylase/apurinic/apyrimidinic (AP) lyase that initiates base excision repair of pyrimidines modified by reactive oxygen species, ionizing, and ultraviolet radiation. Using duplex 2'-deoxyribose oligonucleotides containing an abasic (AP) site, a thymine glycol, or a 5-hydroxyuracil residue as substrates, we found the AP lyase activity of hNth1 was 7 times slower than its DNA glycosylase activity, similar to results reported for murine and human 8-oxoguanine-DNA glycosylase, which are also members of the endonuclease III family. This difference in rates contrasts with the equality of rates found in Escherichia coli and Saccharomyces cerevisiae endonuclease III homologs. A yeast two-hybrid screen for potential modulators of hNth1 activity revealed interaction with the damage-inducible transcription factor Y box-binding protein 1 (YB-1), also identified as DNA-binding protein B (DbpB). The in vitro addition of His(6)YB-1 to hNth1 increased the rate of DNA glycosylase and AP lyase activity. Analysis revealed that YB-1 affects the steady state equilibrium between the covalent hNth1-AP site Schiff base ES intermediate and the noncovalent ES intermediate containing the AP aldehydic sugar and the epsilon-amino group of the hNth1 active site lysine. This equilibrium may be a checkpoint in modulating hNth1 activity.

Base Pair Mismatch↗
PubMed2000

Isolation and identification of xylitol-producing yeasts from agricultural residues.

Selected yeast strains isolated from corn silage and viticulture residues were screened for their capacities to convert D-xylose into xylitol A conventional TLC was adapted for easy determination of xylose and xylitol in the culture supernatant solutions. This technique is suitable for the first steps of a screening program to select xylitol-producing yeasts from natural environments. Candida tropicalis ASM III (NRRL Y-27290), isolated from corn silage, appears to be a promising strain for xylitol production with a high yield (0.88 g xylitol per g of xylose consumed).

Candida↗
PubMed1991

Testosterone biotransformation by the isolated perfused canine pancreas.

There is strong evidence indicating that the pancreas is under the influence of sex steroid hormones, and that it may even participate in their biosynthesis and metabolism. In the present study, [3H]testosterone was perfused into the isolated canine pancreas, and measured in the effluent with several of its metabolites (5 alpha-dihydrotestosterone, androstenedione, and estradiol). Results show that testosterone is readily transformed by the canine pancreas. The main product found in the effluent is androstenedione. The testis and spleen were also perfused with [3H]testosterone and used as controls. In both cases, this hormone appeared mostly unchanged in the effluent as compared to the pancreatic perfusion (p less than 0.0001). From our data, we conclude that the canine pancreas has the capacity to transform sex steroid hormones, and could be considered an extragonadal site of sex steroid biosynthesis.

Androstenedione↗
PubMed1991

Serum testosterone:dihydrotestosterone ratio and CA 19-9 in the diagnosis of pancreatic cancer.

The testosterone:dihydrotestosterone ratio (T:DHT) and the antigenic marker CA 19-9 were studied in the serum of 21 male patients with pancreatic cancer and 62 controls with other gastrointestinal malignancies or benign pancreatobiliary disease. Specificity of the T:DHT ratio was 98%, significantly better than the specificity of CA 19-9 at both a 37 U/ml cutoff level (61%) and at 100 U/ml (79%). Sensitivity of the T:DHT ratio was 67%, and that of CA 19-9, 71% and 90% at the upper and lower cutoff levels, respectively. False-negative results of the T:DHT ratio were found predominantly in cases of advanced pancreatic cancer, whereas all four stage I patients had an abnormal (less than 5) T:DHT ratio. These results suggest that the T:DHT ratio is a useful marker for pancreatic cancer in males. It can be used alone or in combination with CA 19-9, and should be further evaluated in the differential diagnosis of patients with the early stages of this disease.

Adult↗
PubMed1990

Pancreatic cancer and androgen metabolism: high androstenedione and low testosterone serum levels.

Serum androstenedione and testosterone levels were measured in 39 male patients with pancreatic cancer, and compared with the values obtained from 37 male patients with chronic pancreatitis or benign obstructive jaundice, and with those from 36 male patients with other gastrointestinal malignancies. Mean androstenedione values were significantly higher in the pancreatic cancer patients when compared to both control groups, and mean testosterone levels were significantly lower. The testosterone/androstenedione ratio was calculated and was also found to be significantly lower in the patients with pancreatic cancer. There was no difference in this ratio or in the androstenedione or testosterone levels when comparing both control groups. In two patients with stage I pancreatic cancer, serum androstenedione and testosterone levels were significantly altered, and returned to normal values after successful resection. These results confirm previous findings indicating that there is significant derangement in the androgen profile of patients with pancreatic cancer.

Aged↗
PubMed1989

Adverse reactions to furazolidone and other drugs. A comparative review.

Furazolidone is a synthetic nitrofuran with a broad spectrum of antimicrobial action and has been widely used in the treatment of gastrointestinal infections. This article reviews the adverse reactions to furazolidone reported in the world literature. Of 10,443 adults and children who were treated with the drug, approximately 8.3% (864) experienced such reactions. Because some of these patients had more than 1 adverse reaction, 1178 reactions were reported in these studies. Nausea with vomiting, the commonest adverse reaction, was reported by 51% of the 864 patients who experienced adverse reactions. The authors compare the adverse reactions to furazolidone with those reported for other antimicrobial and antiprotozoal drugs that are frequently used to treat gastrointestinal infections.

Adult↗
PubMed1987

Low serum testosterone/dihydrotestosterone ratio in patients with pancreatic carcinoma.

Serum testosterone, its metabolite 5 alpha-dihydrotestosterone, and the testosterone/dihydrotestosterone ratio were investigated in 22 male patients with proven pancreatic cancer, and compared with values from male patients with chronic pancreatitis (n = 21) and with nonpancreatic gastrointestinal tumors (n = 19). Testosterone and the testosterone/dihydrotestosterone ratio were significantly lower (p less than 0.001) in the pancreatic cancer group when they were compared with the other two groups. There was no significant difference in the dihydrotestosterone values between cancer groups. A testosterone/dihydrotestosterone ratio of less than 5 clearly distinguished most of the patients (20/22) with cancer of the pancreas from those with other tumors or chronic pancreatitis. The results suggest an alteration in the serum androgen profile in these patients. Therefore, the testosterone/dihydrotestosterone ratio could be a useful marker in the diagnosis of pancreatic carcinoma in male patients.

Dihydrotestosterone↗
PubMed1985

Self-priming effect of luteinizing hormone-human chorionic gonadotropin (hCG) upon the biphasic testicular response to exogenous hCG. I. Serum testosterone profile.

The present study was conducted to investigate whether the early (2-8 h) testicular response to a single dose of exogenous hCG depends on previous exposure to LH activity. Four different groups of subjects were studied: 1) four normal adult men [Tanner stage-G5 (T-G5)] and one late pubertal subject (T-G4); 2) normal prepubertal (T-G1) and early- and midpubertal boys (T-G2 and T-G3) (n = 4-6 each); 3) five patients with hypogonadotropic hypogonadism (HH); and 4) two patients with the complete form of the androgen insensitivity syndrome. Each subject received an im injection of hCG (40 IU/kg) on day 1 and blood samples were drawn before and 1-8, 24, 48, and 72 h after injection. At 96 h, a second dose of hCG was given (80 IU/kg) and blood samples were obtained at the same times as after the first hCG dose. Serum testosterone (T) was measured by RIA. The first dose of hCG evoked a biphasic response of serum T in groups T-G2 to T-G5 as well as in the two patients with the complete form of the androgen insensitivity syndrome. The early peak was at 2-7 h, whereas the late T peak was at 48-72 h after injection. In T-G1 children and in patients with HH, the early response did not occur [T-G1, from 129 +/- 43 (SEM) to 288 +/- 127 pg/ml (P greater than 0.05); HH, 79 +/- 18 to 107 +/- 12 (P greater than 0.05) pg/ml], and the late peak was attenuated as compared with the pubertal boys. There were not significant differences in the responses of the T-G1 and the HH groups. After the second dose, all groups had biphasic T responses, although they varied in magnitude. These results demonstrate that previous exposure to LH activity is an obligatory prerequisite for the early peak of the hCG-mediated biphasic testicular response, and that a single dose of hCG has a priming effect that is sufficient to ensure a biphasic response to a second dose of hCG given 96 h later.

Adolescent↗