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Biomedical subjects

M Chavez

Publications and source records attributed to M Chavez.

At least 55 records · Page 3Linked to original sources
PubMed1995

Intraventricular insulin enhances the meal-suppressive efficacy of intraventricular cholecystokinin octapeptide in the baboon.

Chronic intraventricular (IVT) insulin infusion suppresses food intake and body weight in the baboon. It has been hypothesized that one mechanism of this action may be enhancement of the effectiveness of satiety factors that regulate meal size. This hypothesis was supported by prior demonstration of a shift in the meal-suppressive effectiveness of cholecystokinin octapeptide (CCK-8) which was given intravenously. The authors tested the effectiveness of a near threshold dose of CCK-8 (25 ng/kg) given via the lateral ventricles (IVT) prior to a 30-min meal, while baboons were chronically infused with cerebrospinal fluid or insulin (100 microU/day) via the lateral ventricles. IVT CCK-8 infusion resulted in meal size changes of -44 +/- 7% and -75 +/- 9% in the absence and presence of insulin, respectively; this was observed in each of the three animals studied. These results provide further support for the hypothesis that IVT insulin can interact with other, meal-regulatory, peptides.

Animals↗
PubMed1995

A comparison between effects of intraventricular insulin and intraperitoneal lithium chloride on three measures sensitive to emetic agents.

When low doses of insulin are infused directly into the third ventricle, rats reduce their food intake and lose weight. To determine whether these effects could be due to malaise induced by the treatment, the effects of intraventricular insulin were compared to the effects of the emetic agent lithium chloride to condition a taste aversion, to stimulate oxytocin secretion, and to reduce sodium appetite in response to furosemide treatment. For all three of these measures, lithium chloride treatment had a predictable effect compared to controls. Specifically, lithium caused a significant taste aversion, elevated plasma oxytocin, and attenuated sodium appetite. However, lithium did not produce a significant change in food intake or body weight. On the other hand, intraventricular insulin treatment did cause a significant reduction in body weight yet had no effect on these indices of malaise in the rat. These data are consistent with the hypothesis that intraventricular insulin does not reduce food intake and body weight by producing malaise but rather serves as a negative feedback signal of body adiposity to the central nervous system.

Animals↗
PubMed1994

Intraventricular insulin increases dopamine transporter mRNA in rat VTA/substantia nigra.

The hormone insulin can down-regulate the function and synthesis of the re-uptake transporter for norepinephrine (NET) in vivo and in vitro. In the present study we tested whether this action of insulin is generalized to another member of the catecholamine transporter family. We determined the level of dopamine transporter (DAT) mRNA expression in the ventral tegmental area (VTA)/substantia nigra compacta (SNc) of rats which were chronically treated with vehicle or insulin via the third cerebral ventricle (i.c.v.). DAT mRNA was significantly elevated in the VTA/SNc of rats treated with insulin, as compared with levels in vehicle-treated rats. This is in contrast to our previous observation that i.c.v. insulin decreases NET mRNA in the rat locus coeruleus, and suggests that insulin may have differential and specific modulatory effects on CNS catecholaminergic pathways.

Animals↗
PubMed1994

Circulating proteins and iron status in blood as indicators of the nutritional status of 10- to 12-year-old Bolivian boys.

The purpose of the present study was to evaluate the nutritional status of children based on anthropometric measurements, biochemical indicators of protein energy malnutrition as well as hematological variables. The subjects were 93 10- to 12-year-old Bolivian boys: 12 HAHSES, 28 HALSES, 36 LALSES, and 17 LALSES (see Introduction to this Supplement). The overall nutritional status of the boys was evaluated by anthropometric indicators (weight for age [W/A], height for age [H bd, and weight for height [W/H]). The biochemical indicators included proteins total, albumin, prealbumin, orosomucoid and protein C-reactive (for MPE) as well as hematocrit (Ht), hemoglobin (Hb), serum iron, serum ferritin, and transferrin saturation (TS). The prevalence of growth retardation of LSES boys at HA as well as at LA was found to be high when the 3rd percentile was used as the cutoff point. The corresponding prealbumin levels were found to be lower in LSES than in HSES boys at both altitudes. The study shows that LSES boys at both altitudes have significantly lower prealbumin levels than HSES boys. The socioeconomic factor seems to be more critical for the nutritional status of prepubertal boys than altitude. The study also shows that all the boys had hematological parameters within normal range. The HA boys of both SES had higher hemoglobin concentration and hematocrits than the LA boys, a fact that is explained by high-altitude hypoxia. The hematological data do not provide evidence of malnutrition among the boys.

Altitude↗
PubMed1993

Inhibition of an in vivo antigen-specific IgE response by antibodies to CD23.

Immunoglobulin E (IgE) mediates many allergic responses. CD23 is a 45-kilodalton type II transmembrane glycoprotein expressed in many cell types. It is a low-affinity IgE receptor and interacts specifically with CD21, thereby modulating IgE production by B lymphocytes in vitro. In an in vivo model of an allergen-specific IgE response, administration of a rabbit polyclonal antibody to recombinant human truncated CD23 resulted in up to 90 percent inhibition of ovalbumin-specific IgE synthesis. Both Fabs and intact IgG inhibited IgE production in vitro and in vivo. Thus, CD23 participates in the regulation of IgE synthesis in vivo and so could be important in allergic disease.

Amino Acid Sequence↗
PubMed1992

Presence of D-alanine in proteins of normal and Alzheimer human brain.

This report constitutes the first demonstration of the presence of D-alanine in the proteins of the human nervous system. Proteins of the frontal lobe white and gray matter of human brains, both normal and Alzheimer subjects, contain D-alanine at concentrations between 0.50 and 1.28 mumol/g of wet tissue, 50-70-times lower than the concentration of L-alanine. Both white and gray matter of Alzheimer brains contain D-alanine 1.4-times higher than the respective regions of normal brains. The gray matter proteins of Alzheimer brains show a highly significant 8% decrease in total alanine content, when compared with normal brain gray matter proteins. Since Alzheimer's disease is exhibited by deterioration of the gray matter, the occurrence of elevated D-alanine levels in the gray matter of Alzheimer brains is a significant discovery and raises the question whether this enantiomer causes the degeneration of the gray matter proteins in Alzheimer's disease, or whether it is an effect of the disease.

Aged↗
PubMed1992

Area postrema mediation of physiological and behavioral effects of lithium chloride in the rat.

The area postrema (AP), a chemoreceptor trigger zone for nausea and vomiting, has been implicated in taste aversion conditioning with LiCl. In addition to taste aversion acquisition, the present studies indicate that a number of other responses to LiCl administration are eliminated by lesions of the AP. These include a behavioral response, 'lying-on-belly' as well as two physiological responses, delayed stomach emptying and hypothermia. These findings suggest that the area postrema is critically involved in the detection of LiCl and in a wide range of responses to this toxin. They also provide strong evidence that the failure to acquire conditioned taste aversions to LiCl-paired flavors after AP lesions can be attributed to the absence of a significant 'illness' response in lesioned animals.

Animals↗
PubMed1992

Susceptibility and resistance to autoimmunity following neonatal injection of semi-allogeneic spleen cells in rats.

A model of neonatal allotolerance was developed in rats. Brown-Norway (BN) neonates injected with semi-allogeneic (BN x Lewis) F1 hybrid spleen cells express a long-lasting chimerism and exhibit polyclonal B cell activation demonstrated by hyperimmunoglobulinemia affecting mainly IgE and IgG1, anti-laminin and anti-DNA autoantibodies as well as glomerulonephritis and anti-hapten antibodies. These abnormalities are autoregulated although the chimerism persists. In contrast, Lewis (LEW) neonates injected with semi-allogeneic (BN x LEW) F1 hybrid spleen cells exhibit a very short-lasting chimerism and transient activation of B cells, as reflected by increased allo-class II antigen expression, but do not develop an autoimmune disease. The autoimmune syndrome observed in BN rats is similar to that reported in mice during host-versus-graft reaction. Similarities between the drug-induced models of autoimmunity and allogeneic reactions in BN rats are also striking. The susceptibility of BN rats and the resistance of LEW rats to these autoimmune diseases might respectively reflect the involvement of TH2-like or of TH1-like subsets.

Animals↗
PubMed1992

A specific sequence with a bulged guanosine residue(s) in a stem-bulge-stem structure of Rev-responsive element RNA is required for trans activation by human immunodeficiency virus type 1 Rev.

We demonstrate that both the in vitro RNA binding and in vivo trans activation functions of human immunodeficiency virus type 1 Rev regulatory protein Rev require the presence of a 9-nucleotide 5'-CACUAUGGG-3' RNA motif on its cognate target, the Rev-responsive element RNA. For optimal Rev recognition, this sequence must be presented as a stem-bulge-stem structure and must contain at least two G's, one of which must be unpaired, and include some or all of the CACUAU sequence upstream of the three G's. Distal mutations which result in the base pairing of the G's eliminate the Rev response. The first G is crucial, but changes at the other G's are tolerated if at least one G is unpaired. The secondary structure or the three-dimensional orientation of the B1 and B2 stem-loops of the Rev-responsive element are not relevant as long as the 5'-CACUAUGGG-3' sequence is preserved, with at least one bulged G residue.

Base Sequence↗
PubMed1991

Diffuse bile duct tumors: guidelines for management.

The majority of patients with bile duct cancer have small focal adenocarcinomas localized to the upper, middle, or lower third of the bile duct. In contrast, a small subgroup of patients have been identified with bile duct tumors that are diffuse, involving multiple segments of the extrahepatic biliary tract. Among 186 patients with documented bile duct cancer treated at the UCLA Medical Center between 1954 and 1988, 13 patients (7%) had diffuse lesions. Patients with diffuse tumors had markedly poorer survival rates than did those with focal lesions. As diffuse tumors are not amenable to resection, surgical management consists primarily of establishing suitable biliary drainage. All patients with bile duct cancer should undergo careful intraoperative evaluation to exclude a diffuse lesion before tumor resection.

Adult↗
PubMed1991

Gastrointestinal complications after cardiac transplantation: a spectrum of diseases.

Cardiac transplantation has become an accepted treatment modality for end-stage cardiac failure. The gastrointestinal (GI) tract represents a potential source of posttransplant morbidity and mortality. To define the scope of this problem, records of all patients undergoing cardiac transplantation at UCLA between January 1984 and July 1989 were reviewed. In all, there were 120 patients (90 males and 30 females) with a mean age of 45.4 yr. Among them, there were 61 patients (51%) who developed a total of 112 posttransplant GI complications. Of the entire 120 patients, 41 (34%) developed minor complications and 20 (17%) sustained major GI morbidity. Eighteen patients (15%) underwent either endoscopy or surgical intervention. These data suggest that most cardiac transplant recipients will experience some form of GI complication, although most are minor and can be managed conservatively. However, when major, life-threatening complications occur, evaluation and intervention should proceed expeditiously. The gastroenterologist and GI surgeon should play complimentary roles in the care of these complicated patients.

Adolescent↗
PubMed1984

Centruroides exilicauda envenomation in Arizona.

A retrospective survey of 1,135 telephone calls during 1980 and 1981, reporting scorpion envenomation to the Arizona Poison and Drug Information Center, was reviewed. Of these, 438 calls identified Centruroides exilicauda as the offending scorpion on the basis of description of the arthropod and consistency of physical findings and clinical course. Envenomation by C exilicauda occurred primarily in adults during the summer and early fall months of the year. Although most patients (92%) were treated at home with conservative therapy, 8% of patients either came to or were referred to a medical facility. Children younger than 5 years were frequently brought or were referred to either emergency care or inpatient hospital care. We conclude on the basis of this series that despite the historical reputation of lethality associated with envenomation by C exilicauda, most envenomations by this scorpion are relatively minor. The other important observation was that children younger than 5 years appear to be particularly prone to severe toxicity.

Adolescent↗
PubMedDate not supplied

Frequency of twinning in two Costa Rican ethnic groups: an update.

Variation in the frequency of twinning among human populations has been presumed to reflect genetic differences. It has been commonly reported that populations of African ancestry have the highest, those of Asian ancestry the lowest, and those of European and Middle-Eastern ancestry intermediate frequencies of twinning. Populations from the Americas have been reported to have intermediate twinning frequencies, presumably reflecting their admixture. In this context, Madrigal (1994. Am J Hum Biol 6:215-218) reported virtually identical (and high) twinning frequencies in two Costa Rican ethnic groups, one of African, the other of Euro-Amerindian ancestry. These frequencies were interpreted in light of frequent inter-ethnic unions, and it was predicted that the two groups would not differ substantially in gene frequencies of several blood enzyme systems. This paper reports the gene frequencies of both groups for such systems. The samples differ significantly for systems that have clearly different frequencies in African and European populations. Given that the groups are actually different in gene frequencies and not homogenous as predicted earlier, the conclusion that twinning frequencies are similar as a result of a similar genetic make up can be questioned. The results challenge the assumption that if populations have similar twinning frequencies it is because they are genetically similar and argue for a stronger environmental component for twinning frequencies.

Costa Rica↗
PubMedDate not supplied

Transient overconsumption of novel foods by deafferentated rats: effects of novel diet composition.

We recently demonstrated that capsaicin-treated rats consume more of an unfamiliar high-fat diet than vehicle-treated controls, but only on initial exposure (Chavez et al, 1997). We hypothesized that negative feedback signals carried by capsaicin-sensitive visceral afferents are critical for the regulation of intake of novel foods, but redundant pathways take over during subsequent exposures. To examine the role of nutrient content of the novel diet, rats were systemically treated with capsaicin (n = 15) or vehicle (n = 10), and exposed to 1) a fat/olestra diet that was isocaloric with chow; 2) a readily accepted fat-free cake; and 3) pure corn oil. Each 3-h feeding trial was preceded by 24-h food deprivation. Treated rats did not overconsume familiar chow, but did consume 50% more than controls of both the fat/olestra diet and the corn oil on first exposure; this suggests that capsaicin eliminated visceral afferents that normally carry satiety signals. However, the effect with the fat/olestra mixture was due primarily to depressed intake by controls, unlike the pure fat diets; this apparent neophobic response was blunted in treated rats. Because treated rats failed to overconsume the fat-free cakes, the neural system damaged by capsaicin appears to be linked to energy or fat sensory mechanisms, and possibly to hedonic responsiveness.

Animal Feed↗
PubMedDate not supplied

[Epidemic dermatits by Paederus irritans in Piura, Perú at 1999, related to El Niño phenomenon].

The phenomen El Niño that affected Peru at 1998, made possible the growth of copious vegetation in traditionally dry places. On this way, Paederus irritans, dipterous of the order Coleoptera that produces dermatitis when croushed on the skin, found substract that allowed the natural growth of its population. The coming of occasional rains on the months of February to April 1999, attacked the habitat of this insect, that looked for urban areas, exposing seriously the general population of Piura on north Perú to the contact. During February and May 1,451 cases of dermatitis caused by Paederus irritans, called latigazo because of its linear and eritematous characteristic lesions on the skin, were notified at Piura. The more affected body areas were head (56.6%) and neck (30.9%), but there were also cases of conjunctivitis and genital injuries, because of hands contamination.

Adolescent↗
PubMedDate not supplied

[Acute pancreatitis: use of a new prognostic stage system].

The spectrum of clinical severity of acute pancreatitis varies widely, but the most important is to predict high risk patients, so that, a number of classification systems have been proposed with the main focus is on laboratory findings. The purpose of this paper was to validate the Rabeneck Clinical prognostic staging system (using clinical features and comorbid illness) which classified in three stages: I, II and III. We conducted a retrospective study in 51 patients admitted to Hospital Arzobispo Loayza, from 1988 to 1994. 42 (82.4%) were female and 9 (17.6%) male. The average age was 40.3 years. The range hospital stay was 3 to 41 days. Ultrasonographically we found some alterations in pancreas texture about 84.4% and gallbladder stones in 57.7%. The mortality rates according to Rabeneck system were stage I: O of 44 (0%); stage II: 1 of 4 (25%); stage III 2 of 3 (66.7%) In conclusion the new prognostic staging system is easy to use, simple and require no additional laboratory test, so that utility to our institutional situation.

Acquired Immunodeficiency Syndrome↗