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A Cáceres

Publications and source records attributed to A Cáceres.

At least 37 records · Page 2Linked to original sources
PubMed1996

Heterogeneous distribution and organization of cytoskeletal proteins drive differential modulation of metabolic fluxes.

On the basis of experimental data obtained in vitro, we propose that differential segregation of actin and tubulin in the cytoplasm may be a regulatory mechanism of metabolic fluxes. The results presented point out that the same enzymes may be differentially modulated at different locations in the cytoplasm, depending on the cytoskeletal protein present at that location, its concentration, polymeric status, or geometric arrangement. Essentially, actin or microtubular protein would exert their effect on enzymatic catalysis through displacement of the equilibrium of enzyme oligomers either to active or less active species. The latter was corroborated by mathematical modeling of the dynamic coupling between microtubular protein assembly-disassembly and pyruvate kinase activity. From these results, a precise biochemical meaning can be given to the putative linkage existing between the mechanisms by which cells rearrange their cytoplasmic architecture and the dynamics of biochemical reactions taking place concomitantly.

Actins↗
PubMed1996

MAP-1B/TAU functional redundancy during laminin-enhanced axonal growth.

When cultured cerebellar macroneurons develop attached to a laminin-containing substrate or after the acute addition of laminin to the tissue culture medium, there is an acceleration in the rate and extent of axonal elongation. Furthermore, laminin is capable of inducing axonal formation and microtubule stabilization in neurons arrested at stage II of neuritic development by tau suppression (Caceres and Kosik, 1990; Caceres et al., 1991). Laminin-enhanced or induced axonal extension is paralleled by a selective and dramatic incorporation of phosphorylated MAP-1b into axonal microtubules. Axonal formation in neurons growing in the presence of laminin is prevented by treatment of the cultures with a mixture of MAP-1b and tau antisense oligonucleotides, but not by the single suppression of any one of these MAPs. However, suppression of MAP-1b, but not of tau, greatly reduces the increase in the rate and extent of axonal elongation induced by laminin. No such effects are elicited by MAP-1b antisense oligonucleotides in neurons growing in the absence of laminin, e.g. polylysine alone, where most of the MAP-1b present in the cells is dephosphorylated and not associated with the cytoskeleton. Taken collectively, these data suggest that, with regard to axonal elongation, MAP-1b and tau can be functionally substituted, and that extracellular matrix molecules, such as laminin, affect axonal extension by promoting the in vivo utilization of MAP-1b.

Animals↗
PubMed1995

Neuritogenic effect of estradiol on rat ventromedial hypothalamic neurons co-cultured with homotopic or heterotopic glia.

In sexually segregated cultures of dissociated neurons taken from ventromedial hypothalamus of rat fetuses at embryonic day 16 (E16), it is demonstrated that only neurons from males respond with increased axonal growth to the addition of 17-beta-estradiol 100 nM (E2) to the culture medium. Moreover, this response is contingent upon co-culture with heterotopic glia from a target region (amygdala), whereas in the presence of homotopic glia or in cultures without glia, E2 has no effect. It is concluded that before neurons are exposed to gonadal steroids in utero there is a sexual difference in the response to E2, probably explained by earlier maturation of neurons from males as compared to females. The possibility that the observed axogenic effect may be the consequence of an interaction among E2, cells equipped with specific receptors, and glia-producing trophic factors is discussed.

Animals↗
PubMed1995

Antigonorrhoeal activity of plants used in Guatemala for the treatment of sexually transmitted diseases.

Plants popularly used in Guatemala for the treatment of gonorrhoea were macerated in 50% alcohol and the tincture tested for in vitro activity against Neisseria gonorrhoeae using strains isolated from symptomatic patients and confirmed by standard bacteriological procedures. From 46 plants investigated, 13 (28.3%) showed evident inhibition zones (> 9 mm), seven (15.2%) showed small activity (6.1-8.9 mm) and 26 (56.5%) showed no activity; nine of these plants inhibited five strains of N. gonorrhoea freshly isolated. The most active plants of American origin were: bark of Bixa orellana fruits of Parmentiera edulis, leaf of Diphysa robinioides, Eupatorium odoratum, Gliricidia sepium, Physalis angulata, Piper aduncum and Prosopis juliflora, root of Casimiroa edulis, and whole Clematis dioica.

Drug Evaluation, Preclinical↗
PubMed1994

Neurotrophin-3 enhances neurite outgrowth in cultured hippocampal pyramidal neurons.

Low density dissociated cultures of embryonic rat hippocampal cells were used to study the effects of neurotrophin-3 (NT-3) on neuronal morphogenesis. The results obtained indicate that NT-3 enhances neurite outgrowth and branching; this is a dose-dependent effect, detected in approximately 50% of the neurons, and prevented by K-252a, an inhibitor of the trk family of receptor protein kinases. NT-3 also accelerates the development of neuronal polarity, a phenomenon preceded by a dramatic accumulation of bundles of looped microtubules within axonal growth cones; these microtubule bundles contain tyrosinated, detyrosinated, and acetylated alpha-tubulin. Taken collectively, our data suggest that even though the basic shape of hippocampal neurons may be endogenously determined, critical aspects of their morphological development may be modulated by trophic factors such as NT-3. In addition, our observations suggest that at least some of the neuritogenic effects of NT-3 involve a stimulation of microtubule assembly and/or transport.

Acetylation↗
PubMed1994

Microfilament-associated growth cone component depends upon Tau for its intracellular localization.

We report here a novel intracellular localization and function of Tau proteins in cultured cerebellar neurons. Immunofluorescence staining of detergent-extracted cytoskeletons with antibodies specific for Tau proteins revealed intense labeling of growth cone microtubules. Besides, suppression of Tau by antisense oligonucleotide treatment results in the complete disappearance of antigen 13H9, a specific growth cone component with properties of microfilament- and microtubule-associated protein [Goslin et al., 1989: J. Cell Biol. 109:1621-1631], from its normal intracellular location. This phenomenon is unique to neurite-bearing cells, is not associated with the disappearance of microtubules from growth cones, and is not reversed by taxol, a microtubule-stabilizing agent. In addition, Tau-suppressed neurons display a significant reduction in growth cone area and fillopodial number; on the contrary, fillopodial length increases significantly. The alterations in growth cone morphology are accompanied by considerable changes in the phalloidin staining of assembled actin. Taken together, the present results suggest that in developing neurons Tau proteins participate in mediating interactions between elements of the growth cone cytoskeleton important for maintaining the normal structural organization of this neuritic domain.

Actin Cytoskeleton↗
PubMed1994

Microtubular protein in its polymerized or nonpolymerized states differentially modulates in vitro and intracellular fluxes catalyzed by enzymes of carbon metabolism.

The fluxes through HK/G6PDH and PK/LDH coupled-enzymatic reactions were quantified in the presence of physiological concentrations (1-15 microM) of polymerized or non-polymerized microtubular protein (MTP) from rat brain and in a permeabilized yeast cell system. In vitro enzymatic fluxes were increased by either polymerized or nonpolymerized brain MTP mainly in the lower range of MTP concentration. At fixed MTP concentrations in the flux stimulatory range of HK/G6PDH (1 mg/ml MTP) or PK/LDH (0.4 mg/ml MTP), a hyperbolic and sigmoidal response to NADP and PEP, respectively, was detected. That dependence varied according to the polymeric status of MTP. The specificity of the phenomenon observed in vitro, was tested for the PK/LDH and HK/G6PDH enzymatic couples in the presence of neutral polymers such as glycogen (< or = 10 mg/ml), poly(ethylene glycol) (up to 10% w/w) or G-actin (< or = 1 mg/ml). In permeabilized Saccharomyces cerevisiae cells, the PK-catalyzed flux was sensitive to microtubule disruption by nocodazole (15 micrograms/ml). The HK/G6PDH system was not affected by nocodazole showing values of kinetic parameters close to those obtained in vitro in the presence of polymerized brain MTP. Indirect immunofluorescence with specific antibodies against tubulin allowed to confirm the microtubules disruption in the presence of nocodazole in permeabilized yeast cells under the same conditions in which enzymes were assayed intracellularly. The experimental evidence is in agreement with the observed phenomenon of increase in fluxes in the enzymatic reactions assayed to be specifically induced by MTP either in vitro or in situ. The results presented are discussed in terms of the assembly of large supramolecular structures as a supraregulatory mechanism of synchronization of systemic cellular processes such as metabolic fluxes.

Actins↗
PubMed1993

Plants used in Guatemala for the treatment of dermatophytic infections. 2. Evaluation of antifungal activity of seven American plants.

From 52 plants screened for antifungal activity, 26 (50%) were active against dermatophytes. This paper reports further evaluation of seven American plants against four pathogenic fungi (Aspergillus flavus, Epidermophyton floccosum, Microsporum gypseum and Trichophyton rubrum), the part showing most activity, the best solvent and, in three cases, the minimal inhibitory concentration (MIC) against the fungus in pure culture. Antifungal activity was confirmed in all of the plants, but not all parts; the most active parts were the bark and leaves. The most active species were Byrsonima crassifolia, Cassia grandis, Gliricidia sepium and Malpighia glabra. Diphysa robinioides, Rhizophora mangle and Cassia occidentalis were less active. The most susceptible fungi were E. floccosum and T. rubrum; A. flavus was not susceptible. Ethanol was usually the best solvent and the MIC of C. grandis, C. occidentalis and D. robinioides was 50 micrograms/ml.

Antifungal Agents↗
PubMed1993

Plants used in Guatemala for the treatment of gastrointestinal disorders. 3. Confirmation of activity against enterobacteria of 16 plants.

Ethnobotanical surveys and literature review identified 408 plants used in Guatemala for the treatment of gastrointestinal disorders. The screening of 84 showed that 34 inhibit one or more enterobacteria; 16 of these were selected for further investigation. Extracts were obtained with three solvents of different polarity (n-hexane, acetone and alcohol) and the in vitro activity was demonstrated against enteropathogenic Escherichia coli, Salmonella enteritidis and Shigella flexneri. The activity of nine ethanolic extracts against enterobacteria, particularly Acalypha guatemalensis, Diphysa robinioides, Lippia dulcis, Psidium guajava and Spondias purpurea was confirmed. The plants with antibacterial activity are discussed.

Diarrhea↗
PubMed1992

Time lapse study of neurite growth in hypothalamic dissociated neurons in culture: sex differences and estrogen effects.

Cultures of dissociated hypothalamic cells taken from rat fetuses of 19 days of gestation were studied using time-lapse recording and sequential microphotography from 1 to 5 days in vitro (DIV) and at 7 and 21 DIV. Cultures were seeded with cells taken from fetuses grouped by sex or sexually mixed; experimental cultures were raised in medium containing 17-beta-estradiol 100 nM (E2). Cells were plated on poly-D-lysine-coated coverslips at a culture density of approximately 4,000 cells/cm2. Immunocytochemistry of cell cultures was performed using a Tau monoclonal antibody (clone Tau-1 PC1C6) and a monoclonal antibody against MAP-2 (clone AP-20). Cells started to produce lamellipodia and neuritic processes approximately 4 hr after plating. Forty-eight hours later a few neurons had defined their morphological polarity by the differentiation of an axon-like process that grows faster than the others; at 5 DIV almost all neurons had defined their axons. At this time, monoclonal antibody against MAP-2 clearly stained soma and dendrites, but not axons. Tau immunoreactivity (lots CCA101 and CCA101N from Boeringher Mannheim) was differentially distributed, with a clear predominance in axon and soma. Results on the morphometric analysis of control and E2 treated neurons provide direct evidence for the existence of sex related differences in the neurite outgrowth response of hypothalamic neurons, since cultured neurons taken from female fetuses differentiated axons later and had fewer primary neurites and shorter dendrites than neurons taken from male fetuses or sexually mixed cultures. Also, it was demonstrated in living neurons that E2 effectively enhances outgrowth and elongation in axons. The frequency distribution curves of axonal length for control and E2 treated cultures was unimodal, suggesting that the effect of E2 was a uniform increase in the axonal length of all neurons. The structural differences between neurons from both sexes and the changes induced by E2 may contribute to explain the differences in brain function found between the sexes.

Animals↗
PubMed1992

Amygdala neurons in vitro: neurite growth and effects of estradiol.

Dissociated cell cultures from embryonic rat medial amygdala were studied using sequential photography and immunocytochemical staining for cytoskeletal proteins and substance P (sP). Cultures were seeded with cells taken from fetuses grouped by sex; experimental cultures were raised in medium containing 17-beta-estradiol (E2). Forty-eight hours after plating a few neurons begin to define their morphological polarity by the differentiation of an axon-like process; at 5 days in vitro (DIV) almost all neurons had developed an axon. Tapering, daughter branch ratio and branch power coefficient coincided with identification of dendrites which could be confirmed by retrospective analysis of immunocytochemically stained cultures: at 5 DIV MAP-2 was restricted to dendrites whereas Tau immunoreactivity was differentially localized with a clear predominance in the axon. At 21 DIV neuronal shape parameters were strikingly like those of amygdaloid neurons in vivo. It was demonstrated in living neurons that E2 increased total dendritic length and that this is due to increased ramification of third or higher order dendritic segments whose individual lengths are not different from controls. Densitometric measurement of MAP-2 stained neurons showed a highly significant increase of immunoreactive material in cells grown in the presence of E2; readings for alpha-tubulin were not different between controls and E2 treated cultures. The effect of E2 on dendritic length was just as manifest in sP-positive as in sP-negative neurons. No sexual differences in morphological parameters, growth characteristics or effects of E2 were found in neurons taken from female fetuses versus neurons from male fetuses. The significance of these results for the generation of sexual differences in the amygdala in vivo is discussed and contrasted with reported results on the effects of E2 in cultures of different neural regions.

Amygdala↗
PubMed1992

Pharmacologic properties of Moringa oleifera. 2: Screening for antispasmodic, antiinflammatory and diuretic activity.

Hot water infusions of flowers, leaves, roots, seeds and stalks or bark of Moringa oleifera were screened to detect three pharmacologic activities in experimental models in rats. The antispasmodic activity was demonstrated using isolated duodenum, oral anti-inflammatory activity by carrageenan-induced hindpaw edema and oral diuretic activity by urine output in metabolic cages. The seed infusion showed a significant inhibition of acetylcholine-induced contraction with an ED50 of 65.6 mg/ml bath concentration, inhibition of carrageenan-induced edema at 1000 mg/kg and diuretic activity at 1000 mg/kg. Some activity was also demonstrated in the roots. All doses expressed here are as equivalents of dried starting plant material.

Animals↗
PubMed1991

Ethnobotanical survey of the medicinal flora used by the Caribs of Guatemala.

An ethnobotanical survey was conducted among the Carib population of Guatemala in 1988-1989. In general terms, the sample surveyed possessed a relatively good standard of living. Results indicated that health services were utilized by the population, and that domestic medicine, mainly plants (96.9%) was used by 15% of the population. One hundred and nineteen plants used for medicinal purposes were collected, of which 102 (85.7%) could be identified; a list of these together with the information provided for each plant is presented. The most frequently reported plants used as medicine are: Acalypha arvensis, Cassia alata, Cymbopogon citratus, Melampodium divaricatum. Momordica charantia, Neurolaena lobata, Ocimum basilicum, Petiveria alliacea and Solanum nigrescens. Most of these plants are found in the region, but some are brought from the Highlands or outside of the country, such as Malva parviflora, Matricaria chamomilla, Peumus boldus, Pimpinella anisum, Rosmarinus officinalis and Tagetes lucida. This survey demonstrated that the Carib population of Guatemala has survived in a transcultural environment of African and native Amerindian beliefs.

Female↗
PubMed1991

Pharmacological properties of Moringa oleifera. 1: Preliminary screening for antimicrobial activity.

The antimicrobial activities of Moringa oleifera leaves, roots, bark and seeds were investigated in vitro against bacteria, yeast, dermatophytes and helminths pathogenic to man. By a disk-diffusion method, it was demonstrated that the fresh leaf juice and aqueous extracts from the seeds inhibit the growth of Pseudomonas aeruginosa and Staphylococcus aureus and that extraction temperatures above 56 degrees C inhibited this activity. No activity was demonstrated against four other pathogenic Gram-positive and Gram-negative bacteria and Candida albicans. By a dilution method, no activity was demonstrated against six pathogenic dermatophytes. A method was standardized for studying the effect of aqueous extracts on Ascaris lumbricoides eggs, but no activity was exhibited by any part of the tree in contrast to Chenopodium ambrosioides leaf extracts.

Animals↗