Biomedical subjects

V Rojas

Publications and source records attributed to V Rojas.

9 recordsLinked to original sources

PubMed2001

Studies on acetate ester production by non-saccharomyces wine yeasts.

A double coupling bioreactor system was used to fast screen yeast strains for the production of acetate esters. Eleven yeast strains were used belonging to the genera Candida, Hanseniaspora, Metschnikowia, Pichia, Schizosaccharomyces and Zygosacharomyces, mainly isolated from grapes and wine, and two wine Saccharomyces cerevisiae strains. The acetate ester forming activities of yeast strains belonging to the genera Hanseniaspora (Hanseniaspora guilliermondii and H. uvarum) and Pichia (Pichia anomala) showed different substrate specificities and were able to produce ethyl acetate, geranyl acetate, isoamyl acetate and 2-phenylethyl acetate. The influence of aeration culture conditions on the formation of acetate esters by non-Saccharomyces wine yeast and S. cerevisiae was examined by growing the yeasts on synthetic microbiological medium. S. cerevisiae produced low levels of acetate esters when the cells were cultured under highly aeration conditions, while, under the same conditions, H. guilliermondii 11104 and P. anomala 10590 were found to be strong producers of 2-phenylethyl acetate and isoamyl acetate, respectively.

Acetates↗

PubMed2000

[Aflatoxins in newly harvested corn in Panama].

Mycotoxins are fungal metabolites that may contaminate foods and feeds, resulting at times in important disease in humans and animals. Thirty-six samples of nine varieties of newly harvested corn (4 samples each variety) were analyzed in search of aflatoxins by thin layer chromatography and high pressure liquid chromatography, and also cultured for the presence of Aspergillus flavus. Of the 36 samples studied, one was contaminated with 1290 ppb aflatoxin B1, which is 258x the concentration suggested by WHO, placed at 5 ppb in food for human consumption. Culture of the 36 samples of corn resulted in growth of 55 colonies of A. flavus from all but two (1 and 6) of the 9 varieties. Of the 55 colonies of A. flavus obtained, 15 (27.3%) were toxigenic. Comments are made on the public health implications of these findings.

Aflatoxins↗

PubMed1999

[High prevalence of undiagnosed primary hyperaldosteronism among patients with essential hypertension].

BACKGROUND: Classically, primary hyperaldosteronism was diagnosed in no more than 1% of patients with hypertension, when hypokalemia was used as the screening test. However, numerous patients with primary hyperaldosteronism do not have hypokalemia and the disease remains undiagnosed. AIM: To assess the prevalence of normokalemic primary hyperaldosteronism among patients classified as having essential hypertension. PATIENTS AND METHODS: One hundred hypertensive patients with a blood pressure over 145/95 were studied. Plasma aldosterone and plasma renin activity were measured in all. A primary hyperaldosteronism was diagnosed when high aldosterone levels (over 16 ng/dl) and low plasma renin activity (below 0.5 ng/ml/h) coexisted in two blood tests or the aldosterone/plasma renin activity ratio was over 50. A probable primary hyperaldosteronism was diagnosed when the ratio was between 25 and 50 and these patients were subjected to a Fludrocortisone test to confirm the diagnosis. A dexametasone suppression test was done to discard glucocorticoid remediable aldosteronism. An adrenal TAC scan was done to all patients with primary hyperaldosteronism. RESULTS: A diagnosis of primary hyperaldosteronism was reached in ten patients. Seven had elevated aldosterone and low plasma renin activity. In three the diagnosis was confirmed with the fludrocortisone test. All ten patients had normal serum potassium levels. Dexametasone suppression test was positive in three patients, that normalized their blood pressure levels. Adrenal TAC scans showed an adenoma in one patient and hyperplasia in another. CONCLUSIONS: Primary hyperaldosteronism is more frequent than previously thought, it is overlooked when hypokalemia is used as the screening test and it can only be diagnosed measuring plasma aldosterone and renin activity.

Aldosterone↗

PubMed1999

[Antimicrobial resistance of different Acinetobacter baumannii biotypes isolated in the northern region of Chile].

BACKGROUND: Acinetobacter baumannii nosocomial outbreaks are common and the microorganism is frequently resistant to multiple antimicrobials. There is little information about Acinetobacter baumannii antimicrobial susceptibility in the northern region of Chile. AIM: To identify different Acinetobacter baumannii biotypes isolated from clinical samples and to determine their antimicrobial susceptibility. MATERIAL AND METHODS: One hundred twenty three Acinetobacter baumannii isolates were studied. The identification and typing of Acinetobacter baumannii was based on phenotypic characteristics. Antimicrobial susceptibility was investigated using agar dilution techniques. RESULTS: Most Acinetobacter baumannii strains were isolated from wounds, urinary and respiratory infections. Seven biotypes were isolated, being biotype 9 the most frequent. Imipenem was the antimicrobial with the higher activity against the microorganism. Amikacin, cefoperazonesulbactam, ampicillinsulbactam and ceftazidime had a moderate activity. There were high resistance levels to ampicillin and older cephalosporins. CONCLUSIONS: Acinetobacter baumannii is emerging as a significant nosocomial pathogen in Chile and shows high resistance rates to multiple antibiotics.

Acinetobacter↗

PubMed1994

Altered cortisol response and hippocampal atrophy in pediatric HIV disease.

The hippocampus is a major center for the regulation of the hypothalamic-pituitary-adrenal axis. There is experimental evidence that chronic exposure to high levels of glucocorticoids may be toxic to the hippocampus. We observed elevated mean basal and 60-min cortisol (F) levels in response to adrenocorticotropin stimulation (0.25 mg cortrosyn, i.v. bolus infusion) in 15 children with HIV infection. Furthermore, in eight of the children for whom data was available, in addition to high peripheral cortisol levels, neurologic dysfunction and hippocampal atrophy were noted on CT scan. These preliminary data suggest that in HIV-infected children an altered cortisol secretion may be associated with specific central nervous system damage.

Adolescent↗

PubMed1989

An epitope of the transferrin receptor is exposed on the cell surface of high-grade but not low-grade human lymphomas.

In attempting to identify antigens that are differentially expressed on tumor cells following transformation from follicular small cleaved cell lymphoma (FSC) to immunoblastic lymphoma (IL), we identified a unique epitope of the transferrin receptor (TfR). The epitope is available for binding in aggressive lymphomas but not in indolent lymphomas or normal cells. An immunoglobulin G2a (IgG2a) antibody that binds this epitope, Trump, was produced by screening on tumor cells from a patient who initially had a low-grade lymphoma which subsequently converted to a high-grade lymphoma. Immunoprecipitation and comodulation studies show that Trump binds to the TfR, but blocking studies and immunostaining reveal that the TfR epitope seen by Trump is distinct from the OKT9 and anti-TfR binding sites. The ability of Trump to discriminate a separate population of more highly malignant cells suggests that the expression of the Trump epitope is determined by the state of activation or degree of malignancy of the cell. In addition, it may be possible to use the Trump antibody diagnostically or therapeutically in the management of lymphomas.

Antigen-Antibody Reactions↗

PubMedDate not supplied

[Knowledge, beliefs, and practices related to acute respiratory infections in adults over 65 years old].

Knowledge, beliefs, and practices related to acute respiratory infections (ARIs) in individuals caring for the elderly (over 65 years of age) were evaluated. Home interviews were conducted with 245 persons: 136 lived in urban areas and 109 in rural areas. Mean age was 62 years. All interviewees could read and write. Some 52% of the elderly cared for themselves. A total of 33% smoked. They were generally unaware of the severity of signs and symptoms in ARIs (37% could not mention any). Some 47% did not follow the physician's orders. Self-medication with antibiotics was commonplace. A total of 28% failed to increase liquid intake during the course of ARIs. The results demonstrated insufficient knowledge and management of ARIs in the elderly. An educational program and specific intervention were conducted to improve the situation identified by the study.

Acute Disease↗

PubMedDate not supplied

[Cryptococcus neoformans isolation from the soil in Panama].

Reports of Cryptococcus neoformans isolations from patients in Panama have appeared since 1978, but to our knowledge, thIs is the first report of isolation of this organism from soil samples in the Republic. Of 25 soil samples analyzed, two (25%) yielded the organism on birdseed agar medium. Canavanine-glycine-bromthymol blue medium served to identify the isolates as belonging to C. neorformans var neoformans, and not C. Neoformans var. gattii. Initially, isolates did not have capsules, but upon passage through newborn mice, wide capsules developed. This finding has important public health implications, since non-encapsulated environmental organisms, once in the host, can develop capsules, which significantly contribute to virulence.

Cryptococcus neoformans↗

PubMedDate not supplied

Infectious bronchitis: effect of viral doses and routes on specific lacrimal and serum antibody responses in chickens.

An enzyme-linked immunosorbent assay was used to measure the effect of various infectious bronchitis virus (IBV) (strain H-120) vaccine doses and routes of immunization on specific lacrimal and serum antibody responses. The results of the first trial showed that the maximum dose, 10(6) median embryo infective doses (EID50s), delivered by the ocular route elicited both a systemic and a local antibody response in the vaccinated chickens. Lower doses of vaccinal virus, 10(4) (median dose) and 10(2) (minimum dose) EID50 delivered by the same route did not induce a detectable systemic antibody response. A significant increase of IBV-specific lacrimal IgA was elicited by both the maximum and the median vaccine doses. The low vaccine dose (10(2) EID50) did not induce a detectable increase of lacrimal IgA. In a second trial approximately the same vaccine dose was administered to different chicken groups by ocular instillation, drinking water, spray, and cloaca. The results showed that all routes of vaccination tested, including the cloacal route, resulted in an increase of specific serum antibodies. Higher IgG levels were detected throughout the experimental period after vaccination by the ocular route as compared with vaccination via the drinking water. All routes of vaccination tested resulted in an increase of specific IgA in lacrimal fluid. The vaccine application methods spray, ocular instillation, and drinking water induced similar lacrimal IgA responses.

Aging↗