Search PubMed⌕ Search

Biomedical subjects

M Garcia

Publications and source records attributed to M Garcia.

At least 163 records · Page 9Linked to original sources
PubMed1995

What are the origins of ecdysteroids in gastropods?

Terrestrial gastropods contain ecdysteroids, the origins of which are unknown. Whether they are synthesized by the animals or they arise from the diet is an open question. To address this problem, labeled cholesterol and various molecules which are efficiently converted into ecdysone by arthropods were tested as possible ecdysone precursors in Stylommatophra (gastropods). None of these experiments led to ecdysone biosynthesis and although snails and slugs were shown to contain some of the enzymes required for a biosynthetic pathway (i.e., a 3-oxoecdysteroid 3 beta-reductase, a 25-hydroxylase, and a 20-hydroxylase), no 2-hydroxylase and 22-hydroxylase activity could be detected. An endogenous origin would imply that Stylommatophora use a biosynthetic pathway different from that of insects. A dietary origin for ecdysteroids is also possible since, when ingested, these molecules remain in animals for several days and undergo limited metabolic conversion.

Animals↗
PubMed1995

Mivacurium-induced neuromuscular blockade during sevoflurane and halothane anaesthesia in children.

The neuromuscular blocking effects of mivacurium during sevoflurane or halothane anaesthesia was studied in 38 paediatric patients aged 1-12 yr. All received premedication with midazolam, 0.5 mg.kg-1 po and an inhalational induction with up to 3 MAC of either agent in 70% N2O and O2. The ulnar nerve was stimulated at the wrist by a train-of-four stimulus every ten seconds and the force of adduction of the thumb recorded with a Myotrace force transducer. Anaesthesia was maintained with a one MAC end-tidal equivalent of either volatile agent for five minutes before patients received mivacurium (0.2 mg.kg-1) iv. The onset of maximal blockade occurred in 2.4 +/- 1.26 (mean +/- SD) min with halothane and 1.8 +/- 0.54 min with sevoflurane (NS). Four patients failed to achieve 100% block (3 halothane, 1 sevoflurane). The times from injection to 5, 75, and 95% recovery during sevoflurane (9.8 +/- 2.6, 19.5 +/- 4.4, and 24.2 +/- 4.8 min) were greater than during halothane anaesthesia (7.2 +/- 2.2, 15.0 +/- 4.0, 19.2 +/- 4.9 min, respectively (P < 0.005). All patients demonstrated complete spontaneous recovery of neuromuscular function (T1 > 95%, T4/T1 > 75%) during the surgery which lasted 24-63 min. All patients showed clinical signs of full recovery of neuromuscular blockade (i.e., headlift, gag, or cough). Pharmacological reversal was not required. It is concluded that following a single intubating dose of mivacurium, the time to maximum relaxation was not different during halothane and sevoflurane anaesthesia; recovery times to 5, 75 and 95% twitch height were longer during sevoflurane anaesthesia and neuromuscular reversal was not necessary.

Anesthesia Recovery Period↗
PubMed1995

Potentiation of the immobility response elicited by bandaging and clamping in mesencephalic rats.

In earlier work, we showed that adult rats exhibit immobility response (IR) if a clamp is fastened to the skin of the nape of the neck, but not at other areas of the body, and not by bandaging. The present study characterizes IR in adult rats with complete mesencephalic transections. In the mesencephalic rats, the duration of the IR not only increased, but the stimuli capable of eliciting it were more diverse. All head and body areas clamped or bandaged were capable of inducing a profound IR. In contrast, the IR in intact rats was of shorter duration, and was only induced by clamping the neck, or by bandaging the upper or the lower torso. Furthermore, unlike the mesencephalic rats the ability of the bandaging to induce IR is reduced after the first trial and finally disappears. Only clamping the neck was able to persistently induce IR in intact rats. These data support the hypothesis that the IR control system is in the midbrain, hindbrain or spinal cord, and that systems above the mesencephalon modulate the IR. Such modulation appears to involve the ability to discriminate amongst tactile stimuli, and to integrate previous experience.

Animals↗
PubMed1995

Rapid sequestration of DPP IV/CD26 and other cell surface proteins in an autophagic-like compartment in Caco-2 cells treated with forskolin.

The enterocytic differentiation of Caco-2 cells, a human colon adenocarcinoma cell line, is accompanied by the transcriptionally regulated expression of a subset of proteins and their correct sorting towards the cell surface. In the present work we have explored the possibility that post-translational events may interfere with this process by investigating the short term effects of a potent adenylyl cyclase activator, forskolin, on cell surface expression of dipeptidyl peptidase IV. Previous works have shown that this protein is targeted towards the apical domain through either a direct or an indirect route. Domain specific biochemical experiments demonstrate that cell surface expression of neosynthesized dipeptidyl peptidase IV rapidly decreases after a 1 hour forskolin treatment. Both initial basolateral and apical dipeptidyl peptidase IV membrane delivery were altered by forskolin treatment. Decrease of dipeptidyl peptidase IV cell surface expression was not restricted to this protein, since membrane expression of '525' antigen, a basolateral protein and of sucrase-isomaltase, an apically targeted hydrolase, which unlike dipeptidyl peptidase IV mainly follows a direct route to the brush border membrane, also decreases. In addition endocytosis of proteins from the apical and from the basolateral domain was essentially unchanged, suggesting that forskolin's target may be located on the exocytic pathway. Confocal laser scanning microscopy and immuno-electron microscopy studies demonstrate that, within 5 minutes of forskolin treatment, the cell surface proteins studied accumulate in intracellular vesicles which were co-labeled with a polyclonal antibody raised against Lamp-1, a lysosomal membrane marker. Electron microscopy studies show that these vesicles display an autophagic-like morphology. Finally, biochemical experiments indicate that dibutyryl cAMP does not mimick the forskolin effect, thus suggesting that it is a cAMP-independent phenomenon.

Adenocarcinoma↗
PubMed1995

Retropharyngeal abscess after adenoidectomy.

In this paper, we describe a case of retropharyneal abscess with atlantoaxial joint subluxation after an adenoidectomy. This is a rare complication of which the otolaryngologist must be aware because of its potential consequences.

Adenoidectomy↗
PubMed1995

Transfected cathepsin D stimulates high density cancer cell growth by inactivating secreted growth inhibitors.

Cathepsin D, a lysosomal protease, is overexpressed in primary breast cancer and associated with increased risk of metastasis. We have shown previously by transfection in rat tumor cells that overexpression of cathepsin D increased both experimental metastasis in nude mice and in vitro proliferation under low-serum conditions. In this study, we used the transfected cell lines to investigate the mechanism by which cathepsin D prevents density-dependent arrest of cell proliferation. This effect was not associated with a general alteration of cell-substratum or cell-cell adhesiveness. As shown by coculture and conditioned media experiments, control cells reaching saturation density released inhibitory activity that was able to prevent the growth of control or cathepsin D transfectants and decreased the cloning efficiency of normal rat kidney fibroblasts in agar. By contrast, in media from two cathepsin D-transfected cell lines, this inhibitory activity was markedly reduced. Cathepsin D overexpression did not affect cell sensitivity to the inhibitor but modified the secretion of several proteins. The increase in cell density appeared to be due to intracellular maturation of cathepsin D since it was reversed by amine treatment that neutralizes the pH of acidic compartments within the cells. Moreover, the addition of secreted pro-cathepsin D was unable to increase the saturation density of control clones. Finally, the inhibitory factor was partially characterized as a heat-labile, secreted protein. We conclude that cathepsin D overexpression increases the growth of cancer cells to a higher density via an intracellular mechanism, leading to a decreased secretion of growth inhibitor(s).

Animals↗
PubMed1995

Determination of the efficiency of K99-F41 fimbrial antigen vaccine in newborn calves.

Semipurified K99 and F41 fimbrial antigens were used to prepare an oil-emulsified vaccine against bovine enterotoxigenic colibacillosis. Nine Nelore cows about 7 months pregnant were divided into 3 groups (A, B and C) of 3 animals each, which received different doses of vaccine (1,500 HU, 750 HU and 380 HU, respectively) 8 and 2 weeks before delivery, in the neck by the subcutaneous route. As a control (group D), 3 pregnant cows of the same breed were not vaccinated for later challange of their calves. Vaccine efficiency was measured by the serological tests double diffusion and ELISA. Challenge of calves from the vaccinated and from the three control unvaccinated cows was carried out with the virulent Escherichia coli B41 strain (0101, STa+, K99+, F41+). Two of the 3 calves from the unvaccinated cows died within 48 h with acute diarrhea. E. coli B41 was recovered as pure culture from their stools. In contrast, none of the calves born from vaccinated cows presented diarrhea. These data suggest that the antibody transfer to calves through colostrum gave full protection against the challenge. This semipurified fimbrial vaccine against K99-F41-harboring strains is the first oil-emulsified immunogen prepared in Brazil, which was not only efficient, but also had no adverse effects on vaccinated pregnant cows.

Animals↗
PubMed1995

[Estrogens and breast cancer: from action mechanisms to clinical applications].

The role of estrogens as promoters of breast carcinogenesis has been well established while their action in tumor invasion appears more complex. Breast cancer cells without estrogen receptor (ER) are generally less differentiated and more aggressive than those containing function ER. Moreover the reexpression of ER by transfection in ER-negative cell lines inhibit their metastatic potential. These results suggest a protective role of ER in the metastatic progression of breast cancers. Studies of the underlying mechanisms of this effect may open new therapeutical strategies.

Breast Neoplasms↗
PubMed1994

Inhibition of tumoral cell respiration and growth by nordihydroguaiaretic acid.

The effects of nordihydroguaiaretic acid (NDGA), best known as an inhibitor of lipoxygenase activities, on the culture growth, oxygen consumption, ATP level, viability, and redox state of some electron carriers of intact TA3 and 786A ascites tumor cells have been studied. NDGA inhibited the respiration rate of these two tumor cell lines by preventing electron flow through the respiratory chain. Consequently, ATP levels, cell viability and culture growth rates were decreased. NDGA did not noticeably inhibit electron flow through both cytochrome oxidase and ubiquinone-cytochrome b-c1 complex. Also, the presence of NDGA changed to redox state of NAD(P)+ to a more reduced level, and the redox states of ubiquinone, cytochrome b and cytochromes c + c1 changed to a more oxidized level. These observations suggest that the electron transport in the tumor mitochondria was inhibited by NDGA at the NADH-dehydrogenase-ubiquinone level (energy-conserving site 1). As a consequence, mitochondrial ATP synthesis would be interrupted. This event could be related to the cytotoxic effect of NDGA.

Adenosine Triphosphate↗
PubMed1994

Multiple mechanisms of arachidonic acid release in Chinese hamster ovary cells transfected with cDNA of substance P receptor.

We investigated the release of [3H]arachidonic acid ([3H]AA) and its relationship to the formation of [3H]inositol trisphosphate ([3H]IP3) elicited by substance P (SP) in prelabeled Chinese hamster ovary cells stably expressing the SP receptor. Activation of the SP receptor resulted in a concentration- and time-dependent stimulation of [3H]AA release. Half-maximal release was obtained at 10(-9) M, comparable to that for [3H]IP3 formation reported previously, and the maximal release effected by 0.1 microM SP was 8 to 10-fold above the basal value. Both the [3H]AA release and the [3H]-IP3 accumulation stimulated in the cells by 0.1 microM SP were concentration-dependently blocked with the specific SP receptor antagonist CP-96,345, with IC50 values of 2.5 and 0.4 microM, respectively. The time course of [3H]AA release showed a biphasic pattern: an initial rapid release essentially independent of Ca2+, followed by a sustained release markedly suppressed by removal of extracellular Ca2+ or chelation of intracellular Ca2+ with 1,2-bis(2-aminophenoxyethane)-N,N,N',N'-tetraacetic acid (BAPTA). While pretreatment with pertussis toxin (200 ng/mL, 6 hr) did not block [3H]IP3 formation, it did reduce [3H]AA release by 50% at 1 and 10 min after SP stimulation. Treatment of the cells with a phorbol ester, a protein kinase C activator, augmented the SP-stimulated [H]AA release, and sphingosine, a protein kinase C inhibitor, reversed the phorbol ester-potentiated [3H]AA release, but not the release stimulated by SP alone, suggesting a synergistic effect of protein kinase C on SP-stimulated AA release. These results demonstrate that SP, acting at the SP receptor, stimulates [3H]AA release via mechanisms that are (1) mediated by a pertussis toxin-sensitive G-protein, (2) dependent on extracellular Ca2+, and (3) enhanced by activation of protein kinase C.

Animals↗
PubMed1994

Retinoid-resistant estrogen receptor-negative human breast carcinoma cells transfected with retinoic acid receptor-alpha acquire sensitivity to growth inhibition by retinoids.

Retinoids mediate their actions via RARs (retinoic acid receptors) and RXRs (retinoid X receptors). Each class of these nuclear retinoid receptors is further subdivided into three species, namely alpha, beta, and gamma. Recent studies demonstrate that estrogen receptor (ER)-positive human breast carcinoma (HBC) cell lines and tumor samples exhibit significantly higher levels of RAR alpha than their ER-negative counterparts. ER-positive HBC cell lines are sensitive to, and ER-negative cell lines are resistant to, growth inhibitory effects of retinoic acid (RA). We previously demonstrated that the expression of functional ERs in an established ER-negative cell line resulted in higher levels of RAR alpha and sensitivity to growth inhibition by RA. To further investigate the major role of RAR alpha in retinoid-mediated inhibition of growth, we transfected RAR alpha cDNA in two RA-resistant ER-negative HBC cell lines. Analyses of different clonal populations of RAR alpha transfectants from each cell line revealed growth inhibition by retinoids. Utilizing RAR- and RXR-class selective retinoids, we further demonstrated that only the RAR alpha-selective retinoids mediated the growth inhibition in these cells, while the RXR-selective retinoids were biologically inert. We thus provide evidence that the molecular mechanisms of retinoid inhibition of HBC proliferation predominantly involve RAR alpha.

Base Sequence↗
PubMed1994

Anti-proliferative and anti-estrogenic effects of ICI 164,384 and ICI 182,780 in 4-OH-tamoxifen-resistant human breast-cancer cells.

The effects of the anti-estrogens 4-hydroxytamoxifen (OHTam), ICI 164,384 and ICI 182,780 were tested on the MCF-7/LCC2 breast-carcinoma cell line, which grows significantly in the presence of OHTam and serves as a model for studying anti-estrogen resistance of estrogen-receptor-positive breast cancer. Cell proliferation and cathepsin-D secretion were strongly inhibited by either ICI 182,780 or ICI 164,384 alone or ICI 164,384 in combination with 17-beta-estradiol (E2) or OHTam. ICI 164,384 alone did not affect the cathepsin-D and pS2 mRNA levels, but antagonized the stimulatory effects of E2 or OHTam on these 2 mRNAs. OHTam was more effective than E2 in increasing cathepsin-D mRNA levels, supporting the idea that anti-estrogen-resistant breast cancer continues to overexpress cathepsin-D. These data show that the steroidal anti-estrogens ICI 164,384 and ICI 182,780 retain their ability to inhibit cell proliferation and the estrogen-responsiveness of cathepsin-D and pS2 genes in the OHTam-resistant MCF-7/LCC2 cell lines. These pure anti-estrogens may thus be efficient second-line treatments of some Tamoxifen-resistant tumors.

Antineoplastic Agents↗
PubMed1994

A single intravenous high dose of cholic acid to a pregnant ewe does not affect fetal well-being.

Cardiovascular variables of both mother and fetus and total bile acid levels were monitored in amniotic fluid and in maternal and fetal plasma after the administration of a single intravenous high dose (29 mg) of cholic acid to a pregnant ewe. We observed the diffusion of significant quantities of cholic acids from the mother to the fetus and amniotic fluid. Nevertheless, cardiovascular parameters (heart rate, blood pressure, PO2, PCO2 and pH) were not affected, neither did intra-amniotic pressure show significant changes compared with the initial experimental conditions. It is concluded that an acute increase in maternal plasma levels of bile acids does not produce important adverse effects in either the mother animal or the fetus and consequently, if bile acids should be deemed responsible for any deleterious effect observed in a preterm fetus in intrahepatic cholestasis, this should be considered as the consequence of a chronic process.

Animals↗
PubMed1994

Localization of changes in immediate early genes in brain in relation to hydromineral balance: intravenous angiotensin II.

Immediate early genes, detected by Fos- and Jun-like immunoreactivity (FLI, JLI), were induced in discrete regions of the rat brain by intravenous infusion of angiotensin II (Ang II) at dipsogenic doses. The regions included subfornical organ (SFO), organum vasculosum laminae terminalis (OVLT), median preoptic nucleus (MnPO), supraoptic nucleus (SON), and the magnocellular part of the paraventricular hypothalamus (PVH). These responses were sustained for up to 6 h of infusion. In SFO, FLI was induced preferentially in the posterior part, while JLI occurred in more central regions. Cerebroventricular (ICV) injection of the Ang II type 1 receptor (AT-1) antagonist, losartan potassium, completely prevented the FLI induced by Ang II in these brain regions. ICV injection of the Ang II type 2 receptor (AT-2) antagonist, PD 123319, did not reduce Ang II-induced FLI in SFO, OVLT and MnPO, but markedly attenuated the activation in SON and PVH. To determine whether SFO is the primary site for transduction of the circulating Ang II signal, electrolytic lesions were made in or rostral to the SFO. Rats with complete lesions showed a complete absence of Ang-induced FLI in SON and PVH. The data are discussed in terms of functional mapping of the brain regions activated by circulating Ang II and neural circuitry for water intake, including the possible role of AT-2 receptors in PVH and SON.

Angiotensin II↗