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Biomedical subjects

L Hernandez

Publications and source records attributed to L Hernandez.

At least 91 records · Page 5Linked to original sources
PubMed1995

Mechanism of action of bisimidazoacridones, new drugs with potent, selective activity against colon cancer.

Antitumor bisimidazoacridones are bifunctional DNA binders which have recently been shown to selectively target human colon carcinoma cells in vitro and in vivo and appear to be excellent candidates for clinical development. We have studied the mechanism of action of one bisimidazoacridone, WMC26, which is 1,000-10,000 times more toxic to human colon carcinoma cells (HCT116) than to melanoma cells (SKMEL2) in vitro. Plasmid DNA exposed to WMC26 showed enhanced digestion by DNase I at A-T-rich sites, suggesting alterations in DNA conformation upon drug binding. These results led us to investigate whether WMC26 was selectively toxic due to a specific recognition of DNA bends by repair excinucleases, as has been demonstrated with the DNA bisintercalator, ditercalinium. Both prokaryotic and eukaryotic cells with intact repair capacity were shown to be selectively sensitive to WMC26, strongly indicating that excision repair plays a role in its toxicity. Confocal microscopy studies utilizing fluorescence of the WMC26 chromophore showed compound localization in the perinuclear cytoplasmic area, as had been previously noted for ditercalinium, indicating that cytoplasmic DNA could be the target. This irreversible accumulation of compound was gradually followed by vacuolization of the cytoplasm and cell death. Cell cycle analysis of both lines treated with WMC26 or with ditercalinium showed that, while the latter induced HCT116 growth arrest at G1-G0, WMC26 also blocked the cell cycle at G2-M; SKMEL2 cells did not undergo any changes in cell cycle as a result of either treatment. Our data show that WMC26 is 10-100 times more cytotoxic than ditercalinium in vitro. Like ditercalinium, WMC26 appears to exert its toxicity via cytoplasmic elements, through a mechanism involving excision repair processes. However, its highly selective cytotoxicity may stem from additional undefined targets in sensitive colon cancer cells.

Aminoacridines↗
PubMed1995

Sulpiride increases and dopamine decreases intracranial temperature in rats when injected in the lateral hypothalamus: an animal model for the neuroleptic malignant syndrome?

Sulpiride in the perifornical lateral hypothalamus (pfLH) (4, 8 and 16 micrograms/0.5 microliter) increased intracranial temperature (Tic). The hyperthermia started immediately after the injection, peaked 30 min later and lasted for more than 90 min. Sulpiride (12 micrograms) accelerated recovery from hypothermia in anesthetized animals. Forty-five min after sulpiride Tic raised 1.17 +/- 0.06 degrees C. After a control injection the raise was only 0.5 +/- 0.13 degrees C. Locally applied dopamine (DA) (5, 10 and 20 micrograms) 5 min before sulpiride (12 micrograms) attenuated sulpiride hyperthermia. The largest DA dose reduced Tic (-1.21 degrees C) when administered alone. These findings suggest the existence of D2 receptors in the LH involved in thermoregulation. Changes are that D2 receptors in the human LH could be responsible for the neuroleptic malignant syndrome (NMS), and that sulpiride injections in the rat LH could be used as a model for the study of the pathogenesis of this syndrome.

Animals↗
PubMed1995

Chronic food deprivation decreases extracellular dopamine in the nucleus accumbens: implications for a possible neurochemical link between weight loss and drug abuse.

In rats reduced to 80% of normal body weight (n = 9), the basal levels of extracellular dopamine (DA) in the nucleus accumbens (NAC), as determined by microdialysis, decreased significantly to 33% (mean +/- SEM) of their normal baseline (p < 01). Basal extracellular DA did not change significantly over a matching 3-week period in controls (n = 7). No changes were observed in NAC serotonin after weight reduction. These results indicate that parts of the mesolimbic DA system are depressed in underweight rats. The observed decrease in basal DA may be responsible for a variety of behavioral changes observed in undernourished humans and animals including the tendency to eat and gain weight when food becomes available. Given that DA can be released in the NAC when rats self-inject drugs of abuse, the present findings may help explain why animals increase drug intake when they are underweight.

Animals↗
PubMed1995

The role of growth hormone, insulin-like growth factors (IGFs), and IGF-binding proteins in experimental diabetic kidney disease.

Early renal changes in type I diabetes are characterized by an increase in renal size, glomerular volume, and kidney function, and later by development of mesangial proliferation, accumulation of glomerular extracellular matrix, and increased urinary albumin excretion (UAE). Growth hormone (GH) and insulin-like growth factors (IGFs) have a long and distinguished history in diabetes mellitus, with possible participation in the development of long-term complications. In experimental diabetes in dwarf rats with isolated GH and IGF-I deficiency, a slower and lesser renal and glomerular hypertrophy is observed as compared with diabetic control animals with intact pituitary. Furthermore, diabetic dwarf rats with a diabetes duration of 6 months display a smaller increase in UAE, indicating that GH and IGF-I may be involved in the development of diabetic kidney changes. In line with this, administration of octreotide to streptozotocin (STZ)-diabetic animals with normal pituitary inhibits initial renal growth without affecting blood glucose levels, and 6 months' administration of octreotide to diabetic rats reduces long-term renal/glomerular hypertrophy and UAE. In addition, the initial increase in renal size and function in experimental diabetes is preceded by an increase in renal IGF-I, IGF-binding proteins (IGFBPs), and IGF-II/mannose-6-phosphate receptor (IGF-II/Man-6-P receptor) concentration. Finally, specific changes occur in renal GH-binding protein (GHBP) mRNA, IGF-I receptor mRNA, and IGFBP mRNA expression in long-term diabetes. In conclusion, the knowledge we have today indicates that GH and IGFs, through a complex system consisting of GHBP, IGFs, IGF receptors, and IGFBPs, may be responsible for both early and late renal changes in experimental diabetes.

Animals↗
PubMed1995

Chronic clozapine selectively decreases prefrontal cortex dopamine as shown by simultaneous cortical, accumbens, and striatal microdialysis in freely moving rats.

We used microdialysis to study the acute and chronic effects of clozapine on the metabolism of dopamine (DA) in terminal areas of the mesocortical, mesolimbic, and nigrostriatal systems simultaneously. In the acute experiment, groups of four rats received the following doses: 0 (vehicle), 10, 20, and 40 mg/kg of clozapine subcutaneously, which resulted in a dose-related increase in extracellular DA, 3,4-dihydroxyphenalacetic acid (DOPAC), and homovanillic acid (HVA) in the prefrontal cortex (PFC). In the nucleus accumbens (NAC) and striatum (STR), no significant changes were observed at any dose. In the chronic experiment, six rats received 20 mg/kg of clozapine and a control group received vehicle daily for 30 days. After 30 days of treatment, DA, DOPAC, and HVA were significantly lower in the PFC, and unchanged in the NAC or STR. The 30th clozapine injection failed to increase DA, DOPAC, or HVA in any of the three regions. We conclude that clozapine acted selectively on the mesocortical system, and that this may underlie clozapine's therapeutic, antipsychotic effect.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1995

Triple electrical channels on a triple fluid swivel and its use to monitor intracranial temperature with a thermocouple.

A low-torque, bubble-free and multiple-channel fluid swivel of easy construction was recently described. This paper describes the design, construction and testing of 3 electrical channels added to the original fluid swivel. The new channels were tested monitoring intrahypothalamic temperature (T(hy)) by means of a copper-constantan thermocouple in freely moving rats, before and after a single intraperitoneal (i.p.) amphetamine injection (3 mg/kg). This test showed an increase in T(hy) after the injection and the maintenance of the electrical continuity along the whole testing period, even when the animals were hyperactive. With this improvement the original swivel was transformed in a more versatile device for experiments requiring fluid handlings and electrophysiological manipulations. Electrical stimulation as in kindling or brain self-stimulation, and electrophysiological recordings as in electroencephalography, electromiography, electrocardiography, in vivo voltammetry and even neuronal unit recording, are just examples of the electrophysiological methods that can be combined with drug self-administration and microdialysis using the present device.

Animals↗
PubMed1995

A new non-invasive approach for monitoring respiratory movements of sleeping subjects.

We have developed a minimally intrusive system to monitor respiratory movements of sleeping subjects. This system is based on a pressure transducer which measures the changes in air pressure inside an inflatable mattress on which the subject sleeps. Using a mechanical filter to protect the transducer against the large pressure changes due to sudden movements and subject weight, we can detect the more subtle movements of the subject's chest. This paper discusses the design of the monitoring system, including the design and modelling of the mechanical filter.

Adult↗
PubMed1994

Peptide-linked 1,3-dialkyl-3-acyltriazenes: gastrin receptor directed antineoplastic alkylating agents.

The gastrin receptor is expressed in various human cancers, such as the adenocarcinoma of the colon. The peptide hormone gastrin and the C-terminal peptides derived from it act as growth factors for these cancers. The hypothesis for the present work was to use the gastrin receptor as a target for appropriately constructed cytotoxic agents. We developed methods to link tetragastrin and pentagastrin by their N-termini to cytotoxic 1-(2-chloroethyl)-3-benzyl-3-succinoyltriazene. These compounds, CBS-4 and CBS-5, respectively, whose complete structures were determined by multinuclear NMR and mass spectrometry, competed effectively with gastrin in an assay using either guinea pig stomach fundus or the rat acinar tumor cell line AR42J as the source of the receptor. CBS-5 was cytotoxic to AR42J cells but was not toxic to A549 human lung cancer cells, which do not express the receptor.

Alkylating Agents↗
PubMed1994

Testosterone modulates mesolimbic dopaminergic activity in male rats.

Male rats were castrated before puberty. When they were adult, the activity of their mesolimbic dopamine system was tested by ventral striatum microdialysis. Amphetamine injections increased dopamine more in castrated rats than in normal rats. This exaggerated response was attenuated by testosterone replacement therapy. The mechanism by which androgens modulate the activity of the mesolimbic dopamine system is discussed.

Amphetamine↗
PubMed1994

Dopamine increase in the prefrontal cortex correlates with reversal of haloperidol-induced catalepsy in rats.

The mechanism by which forced swimming reverses, haloperidol-induced catalepsy was examined by measuring dopamine (DA) turnover in the nucleus accumbens-ventromedial caudate (NAC-C) and the prefrontal cortex (PFC) in rats. DA and its metabolites 3,4-dihydroxiphenylacetic acid (DOPAC) and homovanillic acid (HVA) were assessed by microdialysis and high pressure liquid chromatography with electrochemical detection (HPLC-ED) after systemic administration of a cataleptic dose of haloperidol (5 mg/kg) or saline. Haloperidol-induced catalepsy was temporarily suppressed by forced swimming. Haloperidol-treated rats showed an increase of DA, DOPAC, and HVA overflow in the PFC and the NAC-C. This increase was greater in the PFC of rats that were forced to swim. Rats that were not treated with haloperidol but were forced to swim (control group) showed an increase of DA, DOPAC, and HVA in the PFC but not in the NAC-C. Zero micrograms, 5 micrograms, 10 micrograms, and 20 micrograms of DA was bilaterally injected in the PFC of cataleptic rats to evaluate the hypothesis that DA in the PFC reverses catalepsy. Haloperidol-induced catalepsy was diminished by bilateral microinjections of 10 micrograms and 20 micrograms but not by 5 micrograms of DA in the PFC. The higher the dose of DA, the longer the decrease of catalepsy. These results suggest that an increase of DA turnover in the PFC might mediate temporal suppression of haloperidol-induced catalepsy. The mechanism by which the mesocortical DA system reduces catalepsy is discussed.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Treatment of experimental Pneumocystis carinii infection by combination of clarithromycin and sulphamethoxazole.

The efficacy of clarithomycin and sulphamethoxazole for treatment of experimental Pneumocystis carinii infection was investigated. Rats were immunosuppressed with dexamethasone and inoculated intratracheally with 5 x 10(6) P. carinii cysts. After 2 weeks, the lung tissues were assayed for P. carinii cyst burden. The combination of clarithromycin and sulphamethoxazole caused a significantly greater reduction in cyst burden than either drug alone. Up to 50% of the rats treated with the combination of clarithromycin and sulphamethoxazole were negative for P. carinii cysts. Equivalent doses of the individual drugs given alone did not produce cures. The combination of clarithromycin and sulphamethoxazole was more than twice as effective as either drug alone. Clarithromycin combined with sulphamethoxazole in treatment of P. carinii infection could be especially useful since clarithromycin monotherapy provides safe and effective treatment against many other pathogens, including several that are associated with AIDS.

Animals↗
PubMed1993

In vivo monitoring of glutamate in the brain by microdialysis and capillary electrophoresis with laser-induced fluorescence detection.

Glutamic acid, an excitatory neurotransmitter, was monitored in vivo in the corpus striatum of freely moving rats by brain microdialysis and capillary electrophoresis with laser-induced fluorescence detection. A procedure to derivatize glutamate in complex matrices was developed. Capillary electrophoresis in 12 microns I.D. capillaries was performed to determine glutamate with a migration time of 195 s. Laser-induced fluorescence detection with 488-nm radiation from an argon ion laser and with colinear geometry was used. An injection of haloperidol decreased the concentration of glutamic acid in the dialysates. These experiments support the hypothesis that dopamine receptor blockade decreases glutamate release. The potential of these techniques for the study of chemicals in biomedical experiments is discussed.

Animals↗
PubMed1993

Colinear laser-induced fluorescence detector for capillary electrophoresis. Analysis of glutamic acid in brain dialysates.

Experiments with capillary electrophoresis using a laser-induced fluorescence detector with a colinear optical arrangement demonstrated several important points. First, increasing the numerical aperture of the microscope objective that is used simultaneously for focusing the excitation laser light as well as collection of emitted fluorescence enhances the signal used for the measurement of the emitted fluorescence and at the same time decreases the noise of interfering light. Second, detection of fluorescein-labelled amphetamine was performed at high-picomolar (10(-10) M) levels. Third, the signal-to-noise ratio of 280 found at the above-mentioned picomolar concentrations indicates that the measurement of low-picomolar concentrations (10(-12) M) of this compound in biological samples should be possible. Fourth, narrow-bore capillaries (5-10 microm internal diameter) were used to detect the neurotransmitters glutamic acid and aspartic acid as their naphthalene-2,3-dicarboxaldehyde derivatives in brain dialysates obtained from a freely moving rat. A mathematical model was developed to explain the relationship between numerical aperture, working distance, magnification of the lens, noise due to laser scattering and signal due to fluorescence. The model correctly predicted the observed values of photomultiplier tube current due to both laser scattering and fluorescence. The potential of the application of capillary electrophoresis with laser-induced fluorescence detection in the neurosciences is discussed.

Animals↗
PubMed1993

Flexible intravenous microdialysis probe for blood sampling in freely moving rats.

A flexible intravenous microdialysis probe was constructed from Silastic tubing (0.5 mm ID and 1.0 mm OD), with a cellulose hollow fiber tip 0.2 mm in diameter and 25 mm long with a 6,000 mol wt cut off. In vitro tests showed relative recovery rates of 39.1 +/- 1.9% for epinephrine. In vivo tests in freely moving rats, 36 h and 7 days after surgery, showed stable amounts of epinephrine and glucose. After intraperitoneal injections of 2-deoxy-D-glucose, circulating levels of epinephrine and glucose increased significantly. Similar results were obtained several days after implantation of the probe. We conclude that in situations where prolonged blood sampling is necessary, the flexible microdialysis probe provides a reliable means of accessing circulating levels of neuroactive compounds, nutrients, metabolites, and drugs.

Animals↗
PubMed1992

Coupling of microdialysis with capillary electrophoresis: a new approach to the study of drug transfer between two compartments of the body in freely moving rats.

The feasibility of in vivo microdialysis and capillary electrophoresis for pharmacokinetic studies was tested. Microdialysis probes were inserted in the jugular vein and brain of rats. After an intraperitoneal injection of phenobarbital, microdialysis was performed in the brain and the blood simultaneously in each rat under freely moving conditions. Capillary electrophoresis with ultraviolet absorption was used to measure phenobarbital in blood and brain dialysates. The time course of phenobarbital in the blood and in the extracellular space of the brain was followed. The results demonstrated that microdialysis can be used for pharmacokinetic studies in freely moving animals. Capillary electrophoresis has the potential to improve the time resolution of microdialysis. Other advantages of microdialysis and capillary electrophoresis for pharmacokinetic studies are discussed.

Animals↗
PubMed1992

Reversal by nickel(II) of inhibitory effects of some scavengers of active oxygen species upon hydroxylation of 2'-deoxyguanosine in vitro.

Effects of ethanol (EtOH), mannitol (Man), L-histidine (His) and glutathione (GSH) on the oxidation of 2'-deoxyguanosine (dG) to its 8-hydroxy derivative (8-OH-dG) with H2O2 plus L-ascorbic acid (Ascb) in the absence and presence of Ni(II) were investigated in order to unveil the nature of active oxygen species involved in that oxidation. In the absence of Ni(II), production of 8-OH-dG was inhibited by His much greater than GSH greater than or equal to GSSG (oxidized glutathione) much greater than EtOH, but not by Man. The latter tended to enhance the production of 8-OH-dG. In the presence of Ni(II), the inhibition by His, GSH and GSSG, but not EtOH, was prevented. The results indicate involvement of a 'crypto-hydroxyl' radical as the dG oxidizing species in both the absence and presence of Ni(II). Also, the results provide evidence that Ni(II) complexes with His, GSH and GSSG may lack antioxidant capacity. Moreover, the Ni(II) complex with His was found capable of enhancing 8-OH-dG production by the Ascb+H2O2 system to a greater extent than Ni(II) alone. Likewise, although to a lesser extent, the formation of 8-OH-dG was enhanced by the combination of Ni(II) and Man which do not form complexes at pH 7.4. Since His is a major Ni(II) carrier in animal tissues, the dG oxidation enhancing capacity of the Ni(II) complex with His may contribute to the toxic and carcinogenic effects of Ni(II).

Ascorbic Acid↗