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Biomedical subjects

A Maldonado

Publications and source records attributed to A Maldonado.

At least 73 records · Page 4Linked to original sources
PubMed1993

Respiratory distress syndrome. A suggestive pattern of shunt effect detected by means of macroparticles.

An esophagobronchial fistula developed in a patient who had well-differentiated squamous carcinoma of the lung that was treated with chemotherapy. Because the esophagobronchial fistula could not be surgically repaired, it was isolated with a mechanical stitch above and below it. Forty-eight hours after initiation of enteral nutrition, a perfusion lung scan was performed because of clinical suspicion of pulmonary embolism. Because the scan showed reduced pulmonary radioactivity and accumulation of activity in the kidneys and spine, an arteriovenous shunt was suspected. However, subsequent digital subtraction angiography ruled out this possibility and a recurrence of the esophagobronchial fistula was confirmed with an esophagogram. The unusual extrapulmonary activity could be related to a reversible capillary shunt in the pulmonary vasculature, secondary to acute respiratory distress syndrome.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1992

Effect of diazepam on successive negative contrast in one-way avoidance learning.

The effect of administration of diazepam on successive negative contrast in one-way avoidance learning was examined in rats. Contrast was induced by shifting rats from a large reward, 30 s spent in the safe compartment, to a small reward, 1 s spent in the safe compartment. IP administration of 2 mg/kg diazepam eliminated this negative contrast. Moreover, this effect is dose dependent, with doses of 2 and 2.5 mg/kg, but not 0.5 mg/kg, effective in reliably reducing contrast. These results suggest the existence of similar or common underlying mechanisms in both aversive and appetitive contrast effects; they are discussed in light of the current theories of frustrative nonreward and as a mean of studying the behavioral and biological mechanisms of anxiety.

Animals↗
PubMed1992

Successive negative contrast in one-way avoidance learning in rats.

In three experiments, successive negative contrast was examined in one-way avoidance learning. Reward magnitude in first (pre-shift) and second (post-shift) phases was manipulated by time spent in the safe compartment. Experiment 1 demonstrated that when time in the danger compartment was held constant, a group shifted from a large reward--30 sec spent in the safe compartment--to a small reward--1 sec--showed poor performance and longer response latency than a group conditioned with the small reward in both phases. Experiment 2 replicated this effect with a less intense shock and also demonstrated that a group shifted from large to small reward performed more poorly than a group exposed to large reward--30 sec--in both phases. Finally, Experiment 3 showed that changes in intertrial interval, defined as total time spent in the safe compartment and the danger compartment before the onset of the warning signal, were not responsible for this contrast effect. These results suggest that time spent in a safe place can act as appetitive incentive during one-way avoidance learning.

Animals↗
PubMed1991

Carcinocythemia in a patient with rhabdomyosarcoma.

Solid tumor cells are rarely seen in peripheral blood smears. When this occurs the term carcinocythemia is used. This report describes an 18-year-old female who presented with a painless lump in the labia majora associated with pancytopenia. Tumor cells were identified in the peripheral blood smear and the bone marrow aspirate showed a predominant population of small round vacuolated primitive cells, many of which formed clumps of varying sizes. Biopsies of the vulvar mass and bone marrow were interpreted as alveolar rhabdomyosarcoma. Review of the literature revealed 12 previously reported cases in whom carcinocythemia had been documented; rhabdomyosarcoma was the specific cell type involved in only two of these. The median time between detection of the leukemic phase of the tumor and death was 8.5 weeks, reflecting the fact that carcinocythemia, when it occurs, represents the terminal event of the disease. To our knowledge, our case is the third well documented case of rhabdomyosarcoma in leukemic phase so far reported. The clinical evolution as well as the management of this patient will be described in detail along with a review of the pertinent available literature.

Adolescent↗
PubMed1990

Fast processing of black and white films used in the EM lab.

Kodak black and white film emulsions 4489, 4162, 2415, TMAX-100, TMAX-400, MPD-4 and RPC-651 can be developed in less than 10 minutes on a film processor, quickly printed on resin coated paper and dried with auto-processor and dryer. Adjustments to the ASA (ISO) to compensate for increased contrast with auto-processing are described.

Microscopy, Electron↗
PubMed1989

[Uncomplicated acute male and female gonorrhea: treatment with a single oral dose of epicillin-probenecid].

We treated 142 patients with acute uncomplicated gonorrhea with a single oral dose of epiciline-probenecid. All cases were confirmed by culture on Thayer Martin medium at the first day and they were all laboratory tested seven days after treatment. At the control time the patients were asked about drug tolerance. All isolated strains were tested for beta-lactamase producing capacity and susceptibility to epiciline and penicillin. All patients who were culture positive seven days after treatment were considered to be treatment failures. The treatment was effective in 94.4% and we detected 8 Neisseria gonorrhoeae strains resistant to penicillin (5.6%); seven of these were PPNG strains. Tolerance to the drug was excellent in 90% of all cases; 9% presented minor adverse reactions for a short period of time. Therefore, the combination of epiciline-probenecid is a valid alternative for routine treatment of acute uncomplicated gonorrhea.

Acute Disease↗
PubMed1989

Zinc in adult human serum in Spain.

Zinc levels in serum taken from 1,166 healthy, adult volunteers, from 16 to 70-year-olds living in 10 different districts of the Province of Granada (Spain), have been measured by atomic absorption spectrophotometry. The zinc levels ranged from 80 micrograms to 130 micrograms/100 ml. There were no significant differences with regard to age. The overall results showed higher zinc levels for males than for females but this did not appear when the values for each individual district were analysed separately.

Adolescent↗
PubMed1988

Vertical jumping and signaled avoidance.

This paper reports an experiment intended to demonstrate that the vertical jumping response can be learned using a signaled-avoidance technique. A photoelectric cell system was used to record the response. Twenty female rats, divided equally into two groups, were exposed to intertrial intervals of either 15 or 40 s. Subjects had to achieve three successive criteria of acquisition: 3, 5, and 10 consecutive avoidance responses. Results showed that both groups learned the avoidance response, requiring increasingly larger numbers of trials as the acquisition criteria increased. No significant effect of intertrial interval was observed.

Journal Article↗
PubMed1987

Identification of penicillinase producing Neisseria gonorrhoeae in Chile during clinical and microbiological study of gonococcal susceptibility to antimicrobial agents.

The first penicillinase producing isolates of Neisseria gonorrhoeae (PPNG) identified in Chile were discovered during a clinical and microbiological study to compare the efficacy of penicillin (4.8 MIU aqueous procaine penicillin G plus 1 g oral probenecid) and tetracycline (1.5 g followed by 500 mg four times daily for four days) treatment regimens for acute uncomplicated gonorrhoea. Penicillin treatment was effective in 93.1% (282) of 303 patients, whereas tetracycline was effective in 98.3% (233) of 237 patients. Six of the penicillin treatment failures were attributable to PPNG strains. In all, 21 PPNG strains were identified during the study. They were genetically identical, having a wild type auxotype, a WII/III serotype (serovar Bajk), and carrying cryptic and transfer plasmids and an Asian type penicillinase producing plasmid. In addition, 674 non-PPNG isolates were tested for their susceptibility to eight antimicrobials. Over 95% were sensitivie to 1 mg/l of penicillin, ampicillin, cefotaxime, cefuroxime, and erythromycin, over 90% were sensitive to 1 mg/l of tetracycline and 2 mg/l of thiamphenicol, and all were sensitive to spectinomycin. Of 226 non-PPNG isolates characterised for plasmid content and auxotype, 90% (205) were either wild type or proline requiring, 67% (153) carried only the cryptic plasmid, and a further 31% (71) carried both cryptic and transfer plasmids. Unusually, three of four isolates lacking the cryptic plasmid carried only the transfer plasmid.

Chile↗
PubMed1985

Inhibition of uracil-DNA glycosylase increases SCEs in BrdU-treated and visible light-irradiated cells.

We have approached the study of the ability of different types of lesions produced by DNA-damaging agents to develop sister-chromatid exchanges (SCEs) by analyzing SCE levels observed in Allium cepa L cells with BrdU-substituted DNA and exposed to visible light (VL), an irradiation which produces uracil residues in DNA after debromination of bromouracil and enhances SCE levels but only above a certain dose. We have partially purified an uracil-DNA glycosylase activity from A. cepa L root meristem cells, which removes uracil from DNA, the first step in the excision repair of this lesion. This enzyme was inhibited in vitro by 6-amino-uracil and uracil but not by thymine. When cells exposed to VL, at a dose that did not produce per se an SCE increase, were immediately post-treated with these inhibitors of uracil-DNA glycosylase, a significant increase in SCE levels was obtained. Moreover, SCE levels in irradiated cells dropped to control level when a short holding time (less than 15 min) elapsed between exposure to VL and the beginning of post-treatment with the inhibitor. Thus, our results (1) showed that inhibitors of uracil-DNA glycosylase enhanced SCE levels in cells with unifilarly BrdU-substituted DNA exposed to visible light; (2) pointed to uracils and/or to some products of their repair as lesions responsible for SCE formation under our experimental conditions; and (3) indicated the existence of a very rapid repair of SCE-inducing lesions produced by visible light irradiation of cells with unifilarly BrdU-containing DNA.

Allium↗
PubMed1979

[67Ga]citrate scintiscanning in active inflammatory bowel disease.

Twenty-five hospitalized patients were studied prospectively with [67Ga]citrate (GA) abdominal scintillation scanning in an attempt to define its role in the evaluation of patients with active inflammatory bowel disease (IBD). There were nine patients with ulcerative colitis (UC), seven with Crohn's disease (CD), and nine controls. In four patients, two with UC and two with CD, a tissue/plasma radioactivity ratio was obtained and compared to normals. All the UC patients had positive GA scans and only one of seven of the CD patients had a positive scan. There were no false positive scans. Scans performed after a 3- or 5-day delay were more accurate than 6-hr scans alone. Well-delineated colinic radioactivity 6 hr after injection which persists for 3 to 5 days indicates the presence of UC in patients with IBD, while a negative scan is more consistent with active CD. Colonic uptake at 6 hr which clears by 48 or 72 hr is not indicative of UC. This procedure aided in following the course of UC, delineating the extent of disease, and in differentiating active CD from an intraabdominal abscess. Tissues from UC patients had increased tissue/plasma ratioactivity ratios while tissues from CD patients had normal or decreased ratios which were consistent with the imaging data.

Adolescent↗
PubMed1978

An in vitro study of certain properties of a glass ionomer cement.

A glass ionomer cement was tested for its release of fluoride, effect on solubility of enamel, bond to enamel, and ability to seal the cavity. It was comparable to silicate cement in its release of fluoride and its effect on solubility of enamel. The strength of the bond of the cement to tooth structure was similar to polycarboxylate cement, and it appeared to be quite effective in sealing cavities.

Acrylic Resins↗
PubMed1977

The insufflation of freon in vitreoretinal surgery.

Among the various gases recommended for intravitreal injection, sulfur hexafluoride (SF6) and octafluorocyclobutane (C4F8) are the most commonly used. The purpose of the injection is to restore the vitreous chamber after drainage of subretinal fluid or after vitrectomy. Some of the fluorinated hydrocarbons which belong to the group known as Freon (a registered trademark) have previously been used in the animal with the same end in view. Of these, Freon-12 and Freon-114 were selected on account of their physical properties, the fact that they remain in the vitreous cavity for 4-14 days, their availability and their innocuousness, and used in humans as an adjunct to vitreoretinal surgery. The results are compared to those obtained with other halogenated gases.

Animals↗