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J Lara

Publications and source records attributed to J Lara.

At least 19 recordsLinked to original sources
PubMed2004

Is Atkins dead (again)?

Despite consistent epidemiological evidence that weight gain is linked to higher fat and lower carbohydrate consumption, supported by animal evidence and the inescapable truth that fat supplies 9 kcal/g compared to 3.75 kcal/g from carbohydrates, low-carbohydrate "Atkins" style diets are heavily promoted for obesity control. The randomised controlled trial evidence is very small. The totality of the evidence continues to show that low-carbohydrate diets are marginally disadvantageous for long-term health and for weight maintenance. People can lose weight equally well on low-carbohydrate ("Atkins-style") diets, and some groups of obese patients tend to lose a little more than on high-carbohydrate groups. This small difference (1-2 kg) may be explained by rapid loss of (glycogen-associated) body water, or by the influence of extraordinary media coverage leading to elevation of expectation and compliance with low-carbohydrate diets in the short term.

Animals↗
PubMed2001

Nutrition and cataract in low-income Mexicans: experience in an Eye camp.

Surgical Eye-camps for cataract treatment of low-income adult Mexicans have been undertaken over the last 10 years. Despite the high prevalence of cataracts among these subjects, no assessment of their nutritional or health status has ever been made. We compare the results obtained for 81 adults (44 men and 37 women) who received treatment in May 1997 with those for a "control" group of age and sex-matched but affluent individuals in Mexico City. alpha-Tocopherol and beta-carotene were assessed and analysed by HPLC and colorimetric procedures, respectively. The plasma tocopherol to cholesterol ratio did not reveal deficiencies of this vitamin, and only 5 patients (2 men and 3 women) had low beta-carotene plasma levels. The patients had high BMI values, with 32% of men and 30% of women overweight, and 2% and 14%, respectively, obese, with higher glucose, cholesterol and triglyceride values reflecting enhanced insulin resistance and lipid abnormalities. The alkaline phosphatase values were elevated suggesting that many of these blind patients are osteomalacic because they now remain indoors. Although it has been suggested that an adequate intake of carotenes and tocopherol are associated with absence of cataract, this appears not to be the case in our study population. Surveys in Mexico have revealed, however, a highly prevalent deficiency of other vitamins such as niacin and riboflavin, both of which have been proved to be protective against cataract. It appears that nutritional deficiencies, obesity, incipient diabetes and lipid disorders co-exist in modern Mexico. We have identified a need for research to aid the design of preventive nutritional approaches at the population level that could be applied in parallel with ongoing surgical treatment.

Adult↗
PubMed1999

Large-conductance Ca2+-activated potassium channels in secretory neurons.

Large-conductance Ca2+-activated K+ channels (BK) are believed to underlie interburst intervals and contribute to the control of hormone release in several secretory cells. In crustacean neurosecretory cells, Ca2+ entry associated with electrical activity could act as a modulator of membrane K+ conductance. Therefore we studied the contribution of BK channels to the macroscopic outward current in the X-organ of crayfish, and their participation in electrophysiological activity, as well as their sensitivity toward intracellular Ca2+, ATP, and voltage, by using the patch-clamp technique. The BK channels had a conductance of 223 pS and rectified inwardly in symmetrical K+. These channels were highly selective to K+ ions; potassium permeability (PK) value was 2.3 x 10(-13) cm(3) s(-1). The BK channels were sensitive to internal Ca2+ concentration, voltage dependent, and activated by intracellular MgATP. Voltage sensitivity (k) was approximately 13 mV, and the half-activation membrane potentials depended on the internal Ca2+ concentration. Calcium ions (0.3-3 microM) applied to the internal membrane surface caused an enhancement of the channel activity. This activation of BK channels by internal calcium had a KD(0) of 0.22 microM and was probably due to the binding of only one or two Ca2+ ions to the channel. Addition of MgATP (0.01-3 mM) to the internal solution increased steady state-open probability. The dissociation constant for MgATP (KD) was 119 microM, and the Hill coefficient (h) was 0.6, according to the Hill analysis. Ca2+-activated K+ currents recorded from whole cells were suppressed by either adding Cd2+ (0.4 mM) or removing Ca2+ ions from the external solution. TEA (1 mM) or charybdotoxin (100 nM) blocked these currents. Our results showed that both BK and K(ATP) channels are present in the same cell. Even when BK and K(ATP) channels were voltage dependent and modulated by internal Ca2+ and ATP, the profile of sensitivity was quite different for each kind of channel. It is tempting to suggest that BK and KATP channels contribute independently to the regulation of spontaneous discharge patterns in crayfish neurosecretory cells.

Adenosine Triphosphate↗
PubMed1998

Diencephalic and mesencephalic structures related to the optic nerve organization in tench (Tinca tinca L., 1758). A study using fluoro-gold.

The location of several diencephalic and mesencephalic structures in the teleost fish, Tinca tinca, which have not been described previously, was made possible by injecting Fluoro-Gold, as an anterograde and retrograde tracer, into the optic nerve. In the pretectal area, we found the tractus opticus accessorius and the nucleus opticus dorsolateralis. We have made some specifications about the location and nomenclature of the branches belonging to the optic tracts and two nuclei also related to the visual system (the nucleus commissura posterior and the nucleus pretectalis periventricularis pars dorsalis). This study also presents the retinal projections to the optic tectum and the glial cells in the injected optic nerve of the tench. The laminar nucleus and Edinger-Westphal nucleus are also identified and described in relation to the ciliary pathway.

Animals↗
PubMed1996

Adenine nucleotides and intracellular Ca2+ regulate a voltage-dependent and glucose-sensitive potassium channel in neurosecretory cells.

Effects of membrane potential, intracellular Ca2+ and adenine nucleotides on glucose-sensitive channels from X organ (XO) neurons of the crayfish were studied in excised inside-out patches. Glucose- sensitive channels were selective to K+ ions; the unitary conductance was 112 pS in symmetrical K+, and the K+ permeability (PK) was 1.3 x 10(-13) cm x s(-1). An inward rectification was observed when intracellular K+ was reduced. Using a quasi-physiological K+ gradient, a non-linear K+ current/voltage relationship was found showing an outward rectification and a slope conductance of 51 pS. The open-state probability (Po) increased with membrane depolarization as a result of an enhancement of the mean open time and a shortening of the longer period of closures. In quasi-physio- logical K+ concentrations, the channel was activated from a threshold of about -60 mV, and the activation midpoint was -2 mV. Po decreased noticeably at 50 microM internal adenosine 5'-triphosphate (ATP), and single-channel activity was totally abolished at 1 mM ATP. Hill analysis shows that this inhibition was the result of simultaneous binding of two ATP molecules to the channel, and the half-blocking concentration of ATP was 174 microM. Internal application of 5'-adenylylimidodiphosphate (AMP-PNP) as well as glibenclamide also decreased Po. By contrast, the application of internal ADP (0.1 to 2 mM) activated this channel. An optimal range of internal free Ca2+ ions (0.1 to 10 microM) was required for the activation of this channel. The glucose--sensitive K+ channel of XO neurons could be considered as a subtype of ATP-sensitive K+ channel, contributing substantially to macroscopic outward current.

Adenine Nucleotides↗
PubMed1996

Respirator cartridge service-life: exposure to mixtures.

Expressions associated with a previously developed procedure to assess respirator cartridge service-life were modified to address the cartridge breakthrough properties of each of individual compounds comprising systems with more than two components. These were applied to specific ternary and quaternary test mixtures. Experimental breakthrough data were collected for (1) acetone/cyclohexane/toluene, (2) ethyl acetate/cyclohexane/toluene, (3) cyclohexane/toluene/ m-xylene, (4) ethyl acetate/cyclohexane/toluene/m-xylene, and (5) acetone/ cyclohexane/toluene/ m-xylene. Data indicate that as an exposure experiment proceeds, a compound that is adsorbed relatively weakly by the carbon bed may be displaced by a more strongly adsorbed component, which may result in a breakthrough concentration for displaced compounds that exceeds the challenge concentration in the mixture. The approach described accounts for the displacement phenomenon and can predict the ratio of the number of displaced molecules to the corresponding number of displacing molecules. Experimental data for each multicomponent system were used to determine values of three parameters (k', tau, and A(m)) for each compound in each challenge system. The value of k' characterizes the rate of adsorption of a compound under applicable experimental conditions, tau indicates the capacity of the charcoal, and A(m) describes the effectiveness of a compound in displacing a previously adsorbed compound. Parameter values were applied to calculate complete breakthrough curves for each compound of each mixture. Calculated curves were compared with corresponding experimental data; reasonable agreement justifies simplifying assumptions incorporated into the application of the approach to mixtures of more than two compounds. The time-dependence of the weight of each compound adsorbed by the carbon was calculated. The service-life of respirator cartridges exposed to multicomponent mixtures depends on the challenge concentration of each component of the system and is significantly influenced by the displacement effect. The adsorption capacity of the carbon and the breakthrough time for weakly adsorbed compounds are decreased significantly by exposure to mixtures.

Acetates↗
PubMed1995

Calretinin-like immunoreactivity in the optic tectum of the tench (Tinca tinca L.).

The distribution of calretinin-like immunopositive cells and fibers in the optic tectum of the tench (Tinca tinca) was studied by using a polyclonal antibody and the avidin-biotin-peroxidase technique. A clear laminated pattern of calretinin-like immunoreactivity was observed. The stratum periventriculare demonstrated a large number of strongly labeled cells whereas in the strata album centrale and griseum centrale, and at the boundary between the strata griseum centrale and fibrosum et griseum superficiale, some scarce, weakly immunostained cells were observed. No immunoreactive cells were seen in the strata fibrosum et griseum superficiale, opticum and marginale. Cells belonging to neuronal types X and XIV, previously characterized using Golgi impregnation, were found to be calretinin-like immunoreactive. Most calretinin-like immunopositive fibers were found in the strata fibrosum et griseum superficiale and opticum with a distribution pattern similar to retinotectal axons in these layers. In agreement with previous biochemical studies, our data suggest that, by contrast to all other classes of vertebrates, instead of calretinin and calbindin D-28k, only one protein is present in teleosts. Nevertheless, the calretinin-like immunostaining pattern in the teleost optic tectum was more complex than that previously described for calbindin D-28k. When compared to the calretinin-immunostaining in the rat superior colliculus, it is evident the presence in both amniotes and anamniotes of calretinin-immunopositive retinotectal axons. However, the distribution patterns of intrinsic calretinin-immunoreactive cells were different.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Calbindin D-28K distribution in the retina of the developing trout (Salmo fario L.).

The appearance of calbindin D-28K, a calcium-binding protein, during development of the trout retina was studied by immunohistochemistry. The first calbindin immunoreactive cells appear in the inner nuclear layer at the equator of the embryonic retina at the stage 227 degrees C (around embryonic day 15). Just before hatching, stage 440 degrees C (around embryonic day 30) cells located in the ganglion cell layer and inner nuclear layer, expressed calbindin. This pattern of immunoreactivity was conserved in post-embryonic retinae (alevins 15 days old). In adult retinae the ganglion cells showed a faint immunoreaction; the amacrine cells are markedly fewer and their immunoreaction declined; and the bipolar cells expressed calbindin for the first time. The results obtained in the present work attending to the expression of calbindin, generally conforms with the vitreal to scleral progression of differentiation of the teleost retina. Ganglion, amacrine and bipolar cells undergo further maturation after beginning calbindin expression.

Animals↗
PubMed1992

Carcinosarcoma of the submandibular salivary gland. Immunohistochemical findings.

Carcinosarcomas of the salivary glands are rare lesions that generally have been associated with benign mixed tumors. The authors report a case of a submandibular gland lesion, which occurred in a 64-year-old man, that was composed of intermingled ductal type adenocarcinoma and osteogenic sarcoma with a large component of osteoclast-like giant cells. The local recurrence of the tumor was entirely sarcomatous with no epithelial component observed. There was no histologic evidence of a preexisting or coexisting pleomorphic adenoma. Immunohistochemical studies confirmed two separate populations of tumor cells, corresponding to the histologic growth pattern. The authors review the literature and discuss histogenetic implications of distinction between de novo carcinosarcoma and carcinosarcoma in association with pleomorphic adenoma.

Carcinoma, Intraductal, Noninfiltrating↗
PubMed1992

DNA stainability in aneuploid breast tumors: comparison of four DNA fluorochromes differing in binding properties.

The aim of this study was to evaluate whether or not the differences in chromatin structure between diploid stromal cells or lymphocytes, which are often used as DNA ploidy standard, and aneuploid breast tumor cells can significantly affect the estimates of the DNA index of these tumors. To this end, the DNA content estimates of 34 aneuploid breast tumors, differing in size, degree of differentiation, and presence or absence of estrogen and progesterone receptors and metastases, were compared using four common DNA fluorochromes: DAPI, Hoechst 33342, propidium iodide, and acridine orange. These dyes differ in their mode of interaction with DNA (binding to minor groove or intercalation) and for each of them binding to DNA is restricted to a different degree by nuclear proteins. It was expected, therefore, that if differences in chromatin structure play a role in DNA content estimates, the DNA index of the measured tumors may vary depending on the dye. The cell nuclei were isolated from the tumors using a detergent-based procedure and stained with each of the dyes and the DNA index was estimated using peripheral blood lymphocytes as a DNA content standard. For each of the tumors, the DNA index estimates with all four dyes correlated very well. When the results obtained with individual dyes were compared in pairs, the correlation coefficients (r) of DNA indices were all above 0.96 (correlation at p less than 0.001). The best concordance was seen between specimens stained with Hoechst 33342 and DAPI (r = 0.99), and the least between those stained with Hoechst 33342 and propidium iodide (r = 0.96). The data indicate that DNA content analysis of unfixed nuclei, utilizing the above fluorochromes, is not significantly biased by differences in chromatin structure of the measured cells.

Acridine Orange↗
PubMed1992

Parvalbumin immunoreactive neurons and fibres in the teleost cerebellum.

The distribution of parvalbumin- (PV) immunopositive cell bodies and fibres in the cerebellum of two species of freshwater teleosts (Salmo gairdneri and Barbus meridonalis) was studied using a monoclonal antibody and the avidin-biotin immunoperoxidase technique. A clear laminated pattern of PV immunoreactivity was observed. After PV-immunostaining, Purkinje cells were strongly labelled in their cell bodies, the initial segments of the axons and the dendritic trees. In the molecular layer, only the dendritic branches of the Purkinje cells were PV-positive. In the granule cell layer, extensive axonal plexuses and scattered cell bodies were observed. Most of the immunopositive perikarya were unequivocally identified as displaced Purkinje cells, whereas a reduced number of smaller neurons with unstained dendrites was also found. Eurydendroid cells, the efferent neurons of the teleost cerebellum, were negative; however, they were impinged upon by numerous PV-positive boutons, corresponding to terminals of Purkinje cell axons. Parallel fibres and climbing fibres, as well as stellate cells and granule cells were negative. Basket cells (or deep stellate cells) whose existence in the teleost cerebellum is discussed, were also not observed. The immunoreactivity distribution pattern for PV in the teleost cerebellum differs from previous observations on the localization of this protein in the cerebellum of amniotes.

Animals↗
PubMed1992

Calbindin D-28k-positive neurons in the rat olfactory bulb. An immunohistochemical study.

We have studied the distribution of calbindin D-28k immunoreactivity in the rat olfactory bulb using specific monoclonal antibodies and the avidin-biotin-immunoperoxidase method. The largest number of positive neurons was located in the periglomerular layer. These neurons were identified as periglomerular cells; they have been described also by other authors as calbindin-positive elements. Close to these neurons, a second population of nerve cells was identified as superficial short-axon neurons. The remaining layers showed a smaller number of stained elements. Other labeled neurons were located along the external border of the external plexiform layer; the scarce neurons marking its internal border were identified as van Gehuchten cells. No immunoreactive structures were found in the mitral cell layer, although we observed another population of immuno-stained short-axon cells at its internal border. Some reactive structures, identified by us as horizontal and vertical cells of Cajal, were located in the boundary zone between the internal plexiform layer and the granule layer. In the white matter, we found a neuronal type characterized by its large size and oriented arborization of varicose dendrites.

Animals↗
PubMed1992

Distribution of calbindin D-28K and parvalbumin immunoreactivities in the nucleus olfactorius anterior of the rat.

The distributions of calbindin D-28K (CaBP) and parvalbumin (PV) in the rat nucleus olfactorius anterior (NOA) were described using monoclonal antibodies and the avidin-biotin-peroxidase method. The NOA showed a high immunoreactivity for CaBP, with a rostrocaudal increase in the positive neurons and fibres. Pars externa (NOAe) was the only subdivision which showed a low CaBP immunostaining. PV-positive elements were less abundant than those CaBP immunostained. The main difference in the distributions for both proteins was observed in the pars medialis which was practically PV negative. PV- and CaBP-stained neurons showed similar morphologies in the subdivisions where they were present. In NOAe, we observed a characteristic PV- and CaBP-positive neuronal type, with an oriented dendritic pattern. Transition areas were clearly observable in both CaBP- and PV-labelled sections.

Animals↗
PubMed1992

A theoretical model for respirator cartridge service life for binary systems: application to acetone/styrene mixtures.

A theoretical model, developed previously to assess respirator cartridge service life, was applied to various acetone/styrene binary assault systems. Experimental data, collected for several binary mixtures differing only with respect to the concentration of each of the two compounds, were interpreted in terms of the model. Styrene concentrations varied from 228 to 1578 ppm; the range of acetone concentrations was 92-985 ppm. The specific influence of the compound assault concentrations on respirator cartridge service life was carefully characterized, as break-through curves were generated for both acetone and styrene for each of several different binary systems. Specifically, experimental data for each system were used to determine values of the following theoretical parameters: k'1, tau 1, k'2, tau 2, and Am. These parameters were employed with the theory to generate complete theoretical breakthrough curves and to determine the time-dependence of the weight of each compound adsorbed by the respirator cartridge carbon bed. An interesting phenomenon observed for the acetone/styrene systems was the displacement (from the carbon) of previously adsorbed acetone molecules by styrene molecules. Acetone breakthrough was observed first in each of the systems studied. Following the onset of this breakthrough, the acetone breakthrough concentration was enhanced by the displacement of acetone from the carbon bed by the adsorption of styrene. The theoretical model accurately predicts both this enhancement and the associated breakthrough characteristics of styrene. In addition, the theory is capable of predicting the ratio of the number of displaced acetone molecules to the corresponding number of displacing styrene molecules. For these studies, this ratio ranged from 0.3 to 0.7. The service life of respirator cartridges exposed to acetone/styrene mixtures depends on the assault concentration of each compound and is significantly influenced (shortened) by the displacement phenomenon.

Acetone↗
PubMed1992

An atlas of the brain of the tench (Tinca tinca L., 1758; Cyprinidae, Teleostei).

This report provides an atlas of the tench brain in the transverse plane. The brain atlas is based on paraffin-embedded brains which are serially sectioned and stained with cresyl violet. It consists of drawings and photographs at several levels throughout the main divisions of the tench brain. The brain of the tench shows important variations in the shape, extension and boundaries of different brain areas and nuclei in comparison with those previously described in the brain of other teleosts.

Anatomy, Artistic↗
PubMed1992

Distribution of enkephalin-like immunoreactivity in the central nervous system of the rainbow trout: an immunocytochemical study.

The distribution of enkephalin-like immunoreactive (ELI) cell bodies and fibres in the brain of the teleost Salmo gairdneri L. was demonstrated with the indirect peroxidase-antiperoxidase immunocytochemical technique using a highly specific antiserum. In the telencephalon, ELI cell bodies were located in the area ventralis. In the diencephalon, they were found in the nucleus ventromedialis of the thalamus, nucleus lateralis tuberis, nucleus recessus lateralis, and nucleus recessus posterioris. In the mesencephalic tegmentum, ELI cell bodies were found in the nucleus of the rostral mesencephalic tegmentum, and in a group of neurons which was located dorsal to the nucleus of the rostral mesencephalic tegmentum. In the medial torus semicircularis, small numbers of immunoreactive cell bodies were found. In the cerebellum, numerous cell bodies were observed in the granule cell layer and at the border between the granular and molecular layer. ELI cell bodies were also seen in the nucleus tegmenti dorsalis lateralis and nucleus fasciculi solitarii. ELI fibres were widely distributed in the rainbow trout brain. The highest density of immunoreactive fibres was found in the area ventralis telencephali, the mesencephalic tegmentum, the stratum opticum of the optic tectum, the central gray of the brainstem, the caudal part of the fasciculi solitarii and the dorsal horn of the spinal cord. In the stratum fibrosum et griseum superficiale, stratum griseum centrale and stratum album centrale of the optic tectum, a moderate number of immunoreactive fibres was observed. In the olfactory bulb only a few immunoreactive fibres were present. No effect in the labelling was found after colchicine injections. These results provide the first complete mapping of the ELI in a fish brain. It is clear that enkephalins show a similar distribution pattern in Salmo gairdneri to that in other vertebrates; however, the number of ELI cell bodies in the fish brain is smaller than in land vertebrates. The distribution of enkephalins in specific hypothalamic nuclei, visual areas, and in the brainstem of the rainbow trout brain, suggests that these peptides are involved in the modulation of neuroendocrine and as well in visual and somatosensory functions.

Animals↗