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Biomedical subjects

D Acosta

Publications and source records attributed to D Acosta.

At least 109 records · Page 6Linked to original sources
PubMed1996

Prolonged adverse effects of benzalkonium chloride and sodium dodecyl sulfate in a primary culture system of rabbit corneal epithelial cells.

This investigation was undertaken to determine prolonged adverse effects of benzalkonium chloride (BzCl), a cationic surfactant, and sodium dodecyl sulfate (SDS), an anionic surfactant, after an initial treatment of and subsequent removal from a primary culture system of rabbit corneal epithelial cells. Metabolic integrity and cell growth were evaluated at specified periods after a 1-hr treatment with the surfactants because of their importance in tissue repair. Intracellular calcium ([Ca2+]i) and intracellular pH (pHi) were also measured because of their importance in cellular homeostasis. ATP/ADP ratios were used to assess metabolic integrity, and propidium iodide staining of cells was used to measure relative cell number and cell growth. Digitized fluorescence imaging was used to measure [Ca2+]i with fura-PE3 and pHi with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). BzCl induced a concentration-dependent decrease in ATP/ADP ratios 24 hr after its removal from the cultures, whereas SDS had minimal effects on metabolic integrity throughout the 48-hr postexposure measurement period. The proliferative response of cultures treated with SDS, however, was decreased when compared with BzCl-treated cells. BzCl induced an increase in [Ca2+]i, whereas SDS decreased [Ca2+]i 1-3 hr after removal of surfactants. BzCl produced a sustained decrease in pHi in surviving cells 1-4 hr after its removal, with a return to control values at 24-48 hr. SDS transiently increased pHi 1 hr after its removal and decreased pHi at the 48-hr post-treatment period. In conclusion, the two surfactants in vitro had distinctly different prolonged effects on corneal epithelial cells, which may suggest that BzCl and SDS differentially affect cellular recovery in vivo.

Adenosine Diphosphate↗
PubMed1996

Interactions of intracellular pH and intracellular calcium in primary cultures of rabbit corneal epithelial cells.

Homeostasis of intracellular calcium ([Ca++]i) and pH (pHi) is important in the cell's ability to respond to growth factors, to initiate differentiation and proliferation, and to maintain normal metabolic pathways. Because of the importance of these ions to cellular functions, we investigated the effects of changes of [Ca++]i and pHi on each other in primary cultures of rabbit corneal epithelial cells. Digitized fluorescence imaging was used to measure [Ca++]i with fura-2 and pHi with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Resting pHi in these cells was 7.37 +/- 0.05 (n = 20 cells) and resting [Ca++]i was 129 +/- 10 nM (n = 35 cells) using a nominally bicarbonate-free Krebs Ringer HEPES buffer (KRHB), pH 7.4. On exposure to 20 mM NH4Cl, which rapidly alkalinized cells by 0.45 pH units, an increase in [Ca++]i to 215 +/- 14 nM occurred. Pretreatment of the cells with 100 microM verapamil or exposure to 1 mM ethylene bis-(oxyethylenenitrilo)-tetraacetic acid (EGTA) without extracellular calcium before addition of 20 mM NH4Cl did not abolish the calcium increase, suggesting that the source of the calcium transient was from intracellular calcium stores. On removal of NH4Cl or addition of 20 mM sodium lactate, there were minimal changes in calcium even though pHi decreased. Treatment of CE cells with the calcium ionophores, ionomycin and 4-bromo A23187, increased [Ca++]i, but produced a biphasic change in pHi. Initially, there was an acidification of the cytosol, and then an alkalinization of 0.10 to 0.11 pH units above initial values. When [Ca++]i was decreased by treating the cells with 5 mM EGTA and 20 microM ionomycin, pHi decreased by 0.35 +/- 0.02 units. We conclude that an increase in pHi leads to an increase in [Ca++]i in rabbit corneal epithelial cells; however, a decrease in pHi leads to minor changes in [Ca++]i. The ability of CE cells to maintain proper calcium homeostasis when pHi is decreased may represent an adaptive mechanism to maintain physiological calcium levels during periods of acidification, which occur during prolonged eye closure.

Ammonium Chloride↗
PubMed1996

[Medullary carcinoma of the thyroid gland. Prognostic factors].

OBJECTIVE: To analyze the clinical features and possible prognostic factors involved in the clinical course of a series of 26 patients with the diagnosis of thyroid medullar carcinoma (TMC). MATERIALS AND METHODS: An analysis was made of the variables age, sex, clinical course to diagnosis, paraneoplastic manifestations (flush, diarrhoea), clinical type (sporadic, non-associated, familial MEN IIa associated TMC, familial MEN IIb associated TMC), histologic uni or multicentricity, and stage of disease as possible predictive factors for the evolution. RESULTS: The most remarkable prognostic factor was tumoral stage. The likelihood of a patient diagnosed with stage I or II being free of metastatic disease was 1, 0.66 and 0.33 at 15, 16 and 17 years, respectively. In contrast, those patients in stage III at diagnosis had a likelihood of being free from metastasis 5 years after diagnosis and therapy of 0. With regard to sex, a better clinical course was observed among males than among females, statistically significant at 3 and 5, but not at 10 years. No statistical significance was reached with the other possible prognostic factors investigated. CONCLUSION: Given the obvious influence of tumoral stage of disease on prognosis, an early access to medical attention is desirable for diagnosis and treatment of TMC, as well as an early detection of family cases by a screening test.

Adolescent↗
PubMed1995

Comparison of ketoconazole- and fluconazole-induced hepatotoxicity in a primary culture system of rat hepatocytes.

Ketoconazole (KT) and fluconazole (FLU) are azole antifungal agents with a broad spectrum of activity against both superficial and systemic mycoses. KT is also an anticancer agent in the treatment of advanced prostate cancer. In many clinical and retrospective studies, KT has been reported to cause liver damage, i.e. chemical hepatitis. Histologic analysis of KT induced hepatotoxicity shows massive centrilobular necrosis in which the hepatotoxicity was not thought to be mediated through an immunoallergic mechanism. According to the medical literature, the pattern of hepatic injury appears to be primarily of the hepatocellular type. Because of the documented reports of KT and FLU hepatotoxicity, a cytotoxicity comparison of KT and FLU was implemented. The objective of this comparison was to evaluate the cytotoxicity of these azoles such that future mechanistic investigations of hepatotoxicity could be performed. The relative hepatotoxicity of KT and FLU was evaluated using primary cultures of postnatal rat hepatocytes. Cytotoxicity was evaluated by measuring the leakage of the cytosolic enzyme, lactate dehydrogenase (LDH), into the medium; by assessing mitochondrial reduction of 3-(4,5-dimethythiazol-2yl)-2,5-diphenyl tetrazolium bromide (MTT); by assessing lysosomal uptake of neutral red (NR); and by gross morphology (phase contrast microscopy). The cultures were exposed to various concentrations of KT (56-188 microM) for 0.5-4 h and to various concentrations of FLU (50 microM to 1.0 mM) for 0.5-6 h. There was a significant increase (P < 0.05) in LDH leakage and a large decrease in MTT reduction and lysosomal uptake of NR at 4 h for KT. One millimolar FLU had minimal effects on the LDH leakage and MTT reduction. These results demonstrate that KT is a more potent cytotoxicant than FLU; and its toxicity was expressed in a dose- and time-dependent manner.

Analysis of Variance↗
PubMed1995

Mitochondrial Ca2+ overload in primary cultures of rat renal cortical epithelial cells by cytotoxic concentrations of cyclosporine: a digitized fluorescence imaging study.

Cyclosporine (CsA) has been reported to disrupt Ca2+ efflux from mitochondria, which suggests that CsA interference with Ca2+ homeostasis may be related to its nephrotoxicity. Therefore, the purpose of this study was (1) to determine intracellular free Ca2+ concentration ([Ca2+]i) and mitochondrial free Ca2+ concentration ([Ca2+]m) after primary cultures of rat renal cortical epithelial cells were exposed to cytotoxic concentrations of CsA; and (2) to explore the role of disruption of intracellular and mitochondrial Ca2+ homeostasis in CsA-induced cytotoxicity. [Ca2+]i in single kidney cells was examined by digitized fluorescence imaging (DFI) of the Ca2+ fluorescent probe, fura-2, and [Ca2+]m in single cells was observed by DFI of fura-2 entrapped in mitochondria after selective permeabilization of plasma membrane and other non-mitochondrial organelles by digitonin. Mitochondrial membrane potential (delta psi) in single kidney cells was examined by rhodamine 123 (Rh-123) with DFI. Intracellular ATP in kidney cells was determined by a HPLC method. CsA resulted in an elevation in [Ca2+]i and [Ca2+]m, dissipation of delta psi and depletion of ATP in a dose- and time-dependent manner. The elevation of [Ca2+]i and [Ca2+]m and depletion of ATP preceded CsA-induced cytotoxicity in kidney cells as measured by lactate dehydrogenase (LDH) leakage. We conclude that CsA-induced alterations in mitochondrial Ca2+ homeostasis and a subsequent loss of energy supply may play a key role in CsA-induced cytotoxicity in primary cultures of rat renal cortical epithelial cells.

Adenosine Triphosphate↗
PubMed1995

Effect of glutathione depletion and oxidative stress on the in vitro cytotoxicity of velnacrine maleate.

Velnacrine maleate (Mentane) is an aminoacridine drug developed for the treatment of Alzheimer's disease. Although velnacrine maleate has not been observed to cause prominent cytotoxicity in in vitro hepatocyte cultures, this drug was associated with elevated serum levels of hepatic enzymes in clinical trials. The purpose of the present study was to manipulate cultures of rat hepatocytes in an attempt to elicit a cytotoxic response from this drug and to better understand the in vitro mechanisms of action. Cytotoxicity was evaluated by measuring lactate dehydrogenase (LDH) leakage, neutral red (NR) uptake, and 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction. Preliminary studies with fluorescent probes did not indicate a role for calcium influx or the formation of reactive oxygen species in the cytotoxicity of velnacrine maleate. However, depletion of cellular glutathione (GSH) by diamide (DA) pretreatment resulted in a cytotoxic response at concentrations of velnacrine maleate (1 and 10 micrograms/ml) which were approximately 25-fold lower than those in the absence of DA. Similarly, pretreatment with velnacrine maleate enhanced the cytotoxicity of DA. Pre-exposure of cells to a mixture of DA and t-butyl hydroperoxide (t-BHP) at non-toxic concentrations resulted in significant cytotoxicity of the hepatocyte cultures by velnacrine maleate. Results from these studies indicate that oxidative stress and GSH depletion may enhance Alzheimer patients' susceptibility to the hepatotoxic potential of aminoacridine drugs.

Alzheimer Disease↗
PubMed1994

Cytotoxicity potential of surfactant mixtures evaluated by primary cultures of rabbit corneal epithelial cells.

The use of in vitro cytotoxicity assays as potential alternatives in assessing ocular irritation of surfactant mixtures was evaluated in a primary culture system of rabbit corneal epithelial cells. Two groups of surfactant mixtures, each with the same surfactant components in varying proportions, were studied. Cytotoxicity was determined by lactate dehydrogenase (LDH) enzyme leakage and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) dye reduction in the cell culture system. There was a good correlation between the cytotoxicity in vitro and the reported Draize eye irritation data within each group of the surfactant mixtures studied.

Animal Testing Alternatives↗