Search PubMed⌕ Search

Biomedical subjects

H Herrera

Publications and source records attributed to H Herrera.

18 recordsLinked to original sources
PubMed1997

A prioritization and analysis strategy for environmental surveillance results.

DOE facilities are required to conduct environmental surveillance to verify that facility operations are operated within the approved risk envelope and have not caused undue risk to the public and the environment. Given a reduced budget, a strategy for analyzing environmental surveillance data was developed to set priorities for sampling needs. The radiological and metal data collected at Sandia National Laboratories, New Mexico, were used to demonstrate the analysis strategy. Sampling locations were prioritized for further investigation and the needs for routine sampling. The process of data management, analysis, prioritization, and presentation has been automated through a custom-designed computer tool. Data collected over years can be analyzed and summarized in a short table format for prioritization and decision making.

Cesium Radioisotopes↗
PubMed1997

Role of membrane potential in hypoxic inhibition of L-arginine uptake by lung endothelial cells.

System y+ accounts for the majority of L-arginine transport by pulmonary artery endothelial cells (PAEC). Given that membrane potential is a driving force for transport via system y+, we examined the hypothesis that hypoxia inhibits this transport by decreasing membrane potential. Porcine PAEC or plasma membrane vesicles derived from these cells were exposed to normoxia (room air-5% CO2) or hypoxia (0% O2-95% N2-5% CO2). After exposure, L-[3H]arginine transport and/or accumulation of the lipophilic cation [3H]tetraphenylphosphonium, a quantitative sensor of changes in cell membrane potential, were measured. Hypoxia caused reversible time-dependent decrease in L-arginine transport and membrane potential in PAEC and in plasma membrane vesicles. Comparable decreases in membrane potential and L-arginine transport by PAEC were also observed after depolarization induced by KCl or ouabain. Hyperpolarization, induced by valinomycin, increased membrane potential and L-arginine transport in PAEC and plasma membrane vesicles. Valinomycin also prevented the hypoxia-mediated decreases in membrane potential and L-arginine transport in PAEC. These results indicate that hypoxia-induced plasma membrane depolarization is responsible for reduced L-arginine transport by system y+ in hypoxic porcine PAEC.

Animals↗
PubMed1996

Neurobehavioral test performance among apprentice painters: baseline data.

In the debate on chronic effects of solvent use, it is often difficult to find information on the cerebral health status of subjects before any exposure has occurred. The objective of this study was to obtain baseline data by examination of workers at the beginning of their occupational lives. This study compares the performance of 57 apprentice painters, mean age 16.6 +/- 1.2 years, with that of 62 apprentices, mean age 16.2 +/- years, drawn from other manual trades involving no significant exposure to solvents. Their performances were compared twice over a period of 3 years using a series of behavioral tests chosen from a translated version of the Neurobehavioral Evaluation System (NES). There were no major differences in performance between the apprentices, except for the verbal ability test, which showed lower results for painters. This can be explained by factors such as socioeconomic background, previous schooling, or mother tongue, and raises the question of whether it is appropriate to use such a test to adjust for the influence of premorbid ability in elderly exposed workers.

Adolescent↗
PubMed1995

Hypoxia inhibits L-arginine uptake by pulmonary artery endothelial cells.

Under physiological conditions, L-arginine transport by porcine pulmonary artery endothelial cells (PAEC) is mediated by system y+, a sodium-independent transport system that accounts for 60 +/- 5% of L-arginine transport, and system Bo,+, a sodium-dependent system that accounts for 40 +/- 5% of transport. Because NO production is dependent on intracellular L-arginine content and intracellular L-arginine content depends on transport of extracellular L-arginine, we examined the effect of hypoxia on L-arginine transport and intracellular L-arginine content in PAEC. Exposure of passage 3-7 PAEC in monolayer culture to 0% O2 for 4 h decreased L-arginine transport via system y+ from 120 +/- 10 to 81 +/- 23 (in pmol.mg protein-1.30 s-1) (P < 0.001), whereas 20-h exposures decreased transport from 122 +/- 17 to 84 +/- 18 (P < 0.001) in system y+ and from 104 +/- 19 to 90 +/- 26 (P < 0.05) in system Bo,+. Exposure to 5% O2 for 3-5 wk decreased L-arginine transport via system y+ from 128 +/- 15 to 73 +/- 13 (P < 0.001) and via system Bo,+, from 105 +/- 25 to 65 +/- 13 (P < 0.001). Kinetic studies revealed that hypoxia decreased the maximal transport velocity but not the apparent Michaelis constant for both system y+ and system Bo,+, and the decreases in transport were not reversible after return to normoxia for up to 24 h. Long-term exposure, i.e., 3-5 wk, to 5% O2 also resulted in decreases in intracellular L-arginine content (0.75 +/- 0.10 vs. 0.49 +/- 0.09 nmol/10(6) cells, P < 0.05) which did not reverse after return to normoxia for 24 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Therapeutic tumor-specific cell cycle block induced by methionine starvation in vivo.

The ability to induce a specific cell cycle block selectively in the tumor could have many uses in chemotherapy. In the present study we have achieved this goal of inducing a tumor-specific cell cycle block in vivo by depriving Yoshida sarcoma-bearing nude mice of dietary methionine. Further, we demonstrate that methionine depletion also causes the tumor to eventually regress. The antitumor effect of methionine depletion resulted in the extended survival of the tumor-bearing mice. The mice on the methionine-deprived diets maintained their body weight for the time period studied, indicating that tumor regression was not a function of body weight loss. The data reported here support future experiments utilizing methionine depletion as a target for tumor-selective cell cycle-dependent therapy.

Animals↗
PubMed1993

Expression of the biochemical defect of methionine dependence in fresh patient tumors in primary histoculture.

Methionine dependence is a metabolic defect that occurs in many human tumor cell lines but not normal in unestablished cell strains. Methionine-dependent tumor cell lines are unable to proliferate and arrest in the late S/G2 phase of the cell cycle when methionine is replaced by its immediate precursor homocysteine in the culture medium (MET-HCY+ medium). However, it is not known whether methionine dependence occurs in fresh patient tumors as it does in cell lines. In order to determine whether methionine dependence occurs in fresh patient tumors as well as whether methionine dependence occurs in fresh patient tumors as well as in cell lines we took advantage of the technique of sponge-gel-supported histoculture to grow tumors directly from surgery. We then measured nuclear DNA content by image analysis to determine the cell cycle position in MET-HCY+ compared to MET+HCY- medium in 21 human patient tumors. Human tumor cell lines found to be methionine dependent by cell count were used as positive controls and were found to have marked reduction of cells in G1 compared to total cells in the cell cycle in MET-HCY+ medium with respect to the G1: total cell ratio in MET+HCY- medium. Therefore late cell cycle arrest was used as a marker of methionine dependence for histocultured patient tumors. We found that 5 human tumors of 21, including tumors of the colon, breast, ovary, prostate, and a melanoma, were methionine dependent based on cell cycle analysis. These data on fresh human tumors indicate that methionine dependence may frequently occur in the cancer patient population. Implications for potential therapy based on methionine dependence are discussed.

Cell Count↗
PubMed1992

Occupational exposure of truck drivers to dust and polynuclear aromatic hydrocarbons: a pilot study in Geneva, Switzerland.

The exposure to dust and polynuclear aromatic hydrocarbons (PAH) of 15 truck drivers from Geneva, Switzerland, was measured. The drivers were divided between "long-distance" drivers and "local" drivers and between smokers and nonsmokers and were compared with a control group of 6 office workers who were also divided into smokers and nonsmokers. Dust was measured on 1 workday both by a direct-reading instrument and by sampling. The local drivers showed higher exposure to dust (0.3 mg/m3) and PAH than the long-distance drivers (0.1 mg/m3), who showed no difference with the control group. This observation may be due to the fact that the local drivers spend more time in more polluted areas, such as streets with heavy traffic and construction sites, than do the long-distance drivers. Smoking does not influence exposure to dust and PAH of professional truck drivers, as measured in this study, probably because the ventilation rate of the truck cabins is relatively high even during cold days (11-15 r/h). The distribution of dust concentrations was shown in some cases to be quite different from the expected log-normal distribution. The contribution of diesel exhaust to these exposures could not be estimated since no specific tracer was used. However, the relatively low level of dust exposure dose not support the hypothesis that present day levels of diesel exhaust particulates play a significant role in the excess occurrence of lung cancer observed in professional truck drivers.

Air Pollutants, Occupational↗
PubMed1990

Secretory glycoproteins of the rat subcommissural organ are N-linked complex-type glycoproteins. Demonstration by combined use of lectins and specific glycosidases, and by the administration of Tunicamycin.

Two experimental protocols were used to investigate the secretory glycoproteins of the subcommissural organ (SCO). Protocol I: Lectins, specific exoglycosidases and immunocytochemistry were sequentially applied to the same section or to adjacent semithin sections of the rat SCO fixed in Bouin's fluid and embedded in methacrylate. Lectins used: concanavalin A (con A), wheat germ agglutinin, Limulus polyphemus agglutinin, Ricinus communis agglutinin and Arachis hypogeae agglutinin. Glycosidases used: neuroaminidase, beta-galactosidase, alpha-mannosidase, alpha-glucosidase and beta-N-acetyl-glucosaminidase. For immunocytochemistry an antiserum against bovine Reissner's fiber (AFRU) was used. Lectins and glycosidases were used in sequences that allowed the cleaved sugar residue to be identified as well as that appearing exposed as a terminal residue. This approach led to the following conclusions: (1) the terminal sugar chain of the secreted glycoproteins has the sequence sialic acid-galactose-glucosamine-; (2) the con A-binding material present in the rough endoplasmic reticulum corresponds to mannose; (3) the apical secretory granules and Reissner's fibers displayed a strong con A affinity after removing sialic acid, thus indicating the presence of internal mannosyl residues in the secreted material; (4) after removing most of the sugar moieties the secretory material continued to be strongly immunoreactive with AFRU. Protocol II: Rats were injected into the lateral ventricle with Tunica-mycin and killed 12, 24, 50 and 60 h after the injection. The SCO of rats from the last two groups showed a complete absence of con A binding sites. The results from the two experiments confirm that the secretory glycoproteins of the rat SCO are N-linked complex-type glycoproteins with the conformation previously suggested (Rodríguez et al. 1986).

Animals↗
PubMed1989

A general native-state method for determination of proliferation capacity of human normal and tumor tissues in vitro.

An important need in cancer research and treatment is a physiological means in vitro by which to assess the proliferation capacity of human tumors and corresponding normal tissue for comparison. We have recently developed a native-state, three-dimensional, gel-supported primary culture system that allows every type of human cancer to grow in vitro at more than 90% frequency, with maintenance of tissue architecture, tumor-stromal interaction, and differentiated functions. Here we demonstrate that the native-state culture system allows proliferation indices to be determined for all solid cancer types explanted directly from surgery into long-term culture. Normal tissues also proliferate readily in this system. The degree of resolution of measurement of cell proliferation by histological autoradiography within the cultured tissues is greatly enhanced with the use of epi-illumination polarization microscopy. The histological status of the cultured tissues can be assessed simultaneously with the proliferation status. Carcinomas generally have areas of high epithelial proliferation with quiescent stromal cells. Sarcomas have high proliferation of cells of mesenchymal organ. Normal tissues can also proliferate at high rates. An image analysis system has been developed to automate proliferation determination. The high-resolution physiological means described here to measure the proliferation capacity of tissues will be important in further understanding of the deregulation of cell proliferation in cancer as well as in cancer prognosis and treatment.

Breast Neoplasms↗
PubMed1986

Light- and electron-microscopic immunocytochemistry and lectin histochemistry of the subcommissural organ: evidence for processing of the secretory material.

The subcommissural organ (SCO) of the rat was investigated by use of histochemical and immunocytochemical methods at the light- and electron-microscopic levels. Consecutive thin methacrylate sections were stained with the pseudoisocyanin (Psi), immunoperoxidase (IMC; employing an antiserum against Reissner's fiber, AFRU), periodic acid-Schiff (PAS) and periodic acid-silver methenamine (SM) techniques, and reacted with six types of lectins. Psi, SM, concanavalin A (Con A) and IMC were also used for double and triple sequential staining of the same section. Increasing dilutions of AFRU (from 1:1000 to 1:200 000) were used for immunostaining of serial paraffin sections. In addition, ultrastructural localization of (i) Con A-binding sites and (ii) immunoreactive secretory material was performed. Some of these procedures were also applied to the ophidian and canine SCO. Con A-positive, Psi-positive and immunoreactive materials coexisted within the same cisternae of the rough endoplasmic reticulum. The Golgi apparatus lacked Con A-positive and immunoreactive substances. Apical secretory granules and secreted material lying on the surface of the SCO showed (i) the highest affinity for AFRU, but were (ii) Con A-negative, and (iii) wheat-germ agglutinin-, PAS- and SM-positive. Reissner's fiber displayed a low affinity for AFRU. It is suggested that the SCO secretes N-linked glycoproteins, the carbohydrate and protein moieties of which undergo (i) a maturation process before being released, and (ii) some kind of modification(s) after their release into the ventricle. The perivascular secretory cells of the dog SCO might secrete a material different from that secreted by the ependymal cells.

Animals↗
PubMed1982

Reflexivity and countertransference in a psychiatric cultural consultation clinic.

A Mexican-American woman who complained of persistent head pain and a bothersome "voice" was seen by a team consisting of a psychiatrist, social scientists, and spiritualist healers in a Cultural Consultation Clinic of a Psychiatric Consultation Liaison Service. This single case is analyzed to provide an understanding of the interpretive dimensions of psychiatric practice. It is argued that a hermeneutic analysis of clinical phenomena focuses attention on three distinct aspects of interpretation: on the interpretation by clinicians and clients of the discourse of the other in terms of their own clinical models; on the influence of deeply embedded personal meanings on this interpretive process; and on the role of the observer in clinical ethnography. It is argued that to sustain a hermeneutic analysis of psychiatric practice, an account of transference and countertransference in terms of interpretation theory will have to be developed.

Adult↗
PubMed1981

Metastatic carcinoma to testicle.

Metastatic carcinoma to the testicular, epididymis, and their tunics is unusual and adenocarcinoma of the small bowel is extremely rare. The combination of primary adenocarcinoma of the jejunum with metastasis to the tunica vaginalis of the testis has not been reported previously. An unusual case of a sacral mass in a twenty-seven-year-old black man is presented and the literature reviewed.

Adenocarcinoma↗
PubMedDate not supplied

Regret.

Explore the source record for details and available documents.

Consumer Behavior↗
PubMedDate not supplied

Extensive liver metastasis from human colon cancer in nude and scid mice after orthotopic onplantation of histologically-intact human colon carcinoma tissue.

Clinically-relevant animal models of human cancer are greatly needed for the study of human cancer biology and the development of new cancer therapeutics and diagnostics. We report here that by orthotopically transplanting histologically-intact human colon cancer to the colon of the immunodeficient nude and scid mouse mutants that extensive local growth and liver metastases occur consistently even after extensive in vivo orthotopic passage. We demonstrate that the liver metastases arise by hematogenous spread. The models described in this report for human colon cancer should prove useful for individual cancer patients as well as for basic and applied studies to develop improved treatment.

Animals↗