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Biomedical subjects

A Garcia

Publications and source records attributed to A Garcia.

At least 73 records · Page 4Linked to original sources
PubMed2001

Follow-up of Ascaris lumbricoides and Trichuris trichiura infections in children living in a community treated with ivermectin at 3-monthly intervals.

Ivermectin treatment was administered every 3 months over a 1-year period (April 1993-April 1994) to the whole eligible population of a village in South Cameroon where both Ascaris lumbricoides and Trichuris trichiura were hyper-endemic. A parasitological stool examination was performed before each treatment. Thirty children, aged 5-15 years, were not only found egg-positive for A. lumbricoides and/or T. trichiura before the first treatment but were also each treated and examined in each treatment round. Among these children, the intensity of infection with A. lumbricoides decreased significantly following the first treatment but thereafter remained steady. In contrast, the repeated ivermectin treatments had no significant impact on the intensity of the T. trichiura infections or on the prevalence of infection with T. trichiura or A. lumbricoides among the 30 children.

Adolescent↗
PubMed2001

Hormonal control of growth hormone secretion.

Growth hormone secretion by the somatotroph cells depends upon the interaction between hypothalamic regulatory peptides, target gland hormones and a variety of growth factors acting in a paracrine or autocrine fashion. This review will be focused on recent data regarding the mechanism by which growth hormone-releasing hormone (GHRH) influences somatotroph cell function and the physiological role played by Ghrelin and leptin in the regulation of growth hormone (GH) secretion. It is well established that binding of GHRH to its receptor leads to activation of protein kinase A (PKA). More recently, it was found that GHRH can also activate mitogen-activated protein (MAP) kinase both in pituitary cells and in a cell line overexpressing the GHRH receptor. Whether somatotroph adenomas, either with or without a GS-alpha mutation, have alterations in some of the components of the activation of the MAP kinase pathway remains to be known. The recent isolation of Ghrelin, the endogenous ligand of the growth hormone secretagogue receptor, can be considered a landmark in the GH field, which opens up the possibility of gaining greater insight into our understanding of the mechanisms involved in the regulation of GH secretion and somatic growth. Indeed, preliminary evidences indicate that this peptide exerts a marked stimulatory effect on plasma GH levels in both rats and humans. Finally, it is well known that GH secretion is markedly influenced by nutritional status. Leptin has emerged as an important adipose tissue-generated signal that is involved in the regulation of GH secretion, thus providing an integrated regulatory system of growth and metabolism. Although the effects of leptin on GH secretion in humans remain to be clarified, indirect evidences indicate that it may play an inhibitory role.

Ghrelin↗
PubMed2001

Opposing offspring sex ratio variations with increasing age and weight in mouflon mothers (Ovis musimon).

There are two main theories explaining offspring sex biases in polygynous mammals. Trivers and Willard (1973) argue that mothers with greater reproductive resources should invest in the sex with the greater variance in reproductive success, usually sons. In contrast, because daughters in many polygynous mammals stay with their mother and compete with her for food, Local Resource Competition theory (e.g. Clark, 1978; Silk, 1983) predicts that the mothers with the greatest reproductive resources should invest in daughters. We investigated the strategy of sex allocation of a captive, outdoor population of 139 mouflon mothers, Ovis musimon, kept in a game state. A complex picture emerged in which, despite weight and body condition being correlated with age in female mouflons, mothers lambed more daughters with increasing age but also, within a given age, gave birth to more sons with increasing weight. Results may be useful in game management aimed at increasing the recruitment or quality of males in managed populations.

Age Factors↗
PubMed2001

Calf growth in captive Iberian red deer (Cervus elaphus hispanicus): effects of birth date and hind milk production and composition.

This study examines effects of birth date, hind milk production and its composition, and weight of hind and calf at birth (HBW and CBW, respectively) on calf growth responses born to Iberian hinds (Cervus elaphus hispanicus) and lactating over 34 wk. Males showed daily gains greater than those of females (P = 0.04). Calf birth weight was strongly related to calf gain over a standard (15-wk) lactation (P < 0.01), but HBW did not influence growth or CBW (P > 0.10). After correcting for nutrient supply, birth date did not affect growth, but birth date x total protein yield (TPY), birth date x total fat yield (TFY), and birth date x total lactose yield (TLY) interactions influenced growth (P < 0.001), and early-born calves showed greater growth than those born late for wk 2 to 34 (P < 0.05). Calf birth weight showed the highest correlation with protein-to-fat ratio in milk (P < 0.001), a high correlation with milk protein content (P < 0.05), and a low negative correlation with fat (P < 0.10). Calf gains also showed the highest correlation with protein-to-fat ratio in milk (P < 0.05). Similarly, total milk yield (TMY), TPY, and TFY during lactation affected growth as single factors (P < 0.001). Calves showed not only an overall difference in daily gain between calves born early or late (P = 0.02), but also a greater speed of growth independently of CBW (percentage of weight gained per week, P < 0.001). Early-born calves were heavier at 12 and 18 mo (P < 0.05). Results suggest that selecting hinds of high milk production and nutrient supply and advancing calving date may increase growth of calves and their performance at adulthood.

Animal Husbandry↗
PubMed2000

Measurement of gamow-teller strength for 176Yb --> 176Lu and the efficiency of a solar neutrino detector

We report a 0 degrees 176Yb(p,n)176Lu measurement at IUCF where we used 120 and 160 MeV protons and the energy dependence method to determine Gamow-Teller (GT) matrix elements relative to the model independent Fermi matrix element. The data show that there is an isolated concentration of GT strength in the low-lying 1(+) states making the proposed Low Energy Neutrino Spectroscopy detector (based on neutrino captures on 176Yb) sensitive to pp and 7Be neutrinos and a promising detector to resolve the solar neutrino problem.

Journal Article↗
PubMed2000

Hantavirus pulmonary syndrome in Panama: identification of novel hantaviruses and their likely reservoirs.

Hantavirus pulmonary syndrome (HPS), a severe respiratory disease with high mortality caused by rodent-borne hantaviruses, has previously been identified in the United States and Canada as well as central and southern South America. In late 1999 and early 2000, an outbreak of acute illness compatible with HPS was reported in Los Santos, Panama, with the death of 3 of the 12 (25%) suspected cases. Hantavirus-specific antibodies were detected in patient sera, and virus RNA was detected by reverse transcriptase-polymerase chain reaction. Sequence analysis of virus genome N-, G1-, and G2-encoding fragments showed this to be a novel hantavirus, Choclo virus. Serologic and virus genetic analyses of rodents trapped in the area showed Oligoryzomys fulvescens to be the likely reservoir for the HPS-associated Choclo virus. In addition, Zygodontomys brevicauda rodents were shown to harbor another genetically unique hantavirus, Calabazo virus.

Animals↗
PubMed2000

A novel role for protein phosphatase 2A in the dopaminergic regulation of Na,K-ATPase.

Stimulation of dopaminergic type 1 (D(1)) receptors increases lung edema clearance by regulating Na,K-ATPase function in the alveolar epithelium. We studied the role of serine/threonine protein phosphatases in the Na,K-ATPase regulation by D(1) agonists in A549 cells. We found that low doses of the type 1/2A protein phosphatase inhibitor okadaic acid as well as SV40 small t antigen transiently transfected into A549 cells prevented the D(1) agonist-induced increase in Na,K-ATPase activity and translocation from intracellular pools to the plasma membrane. This was associated with a rapid and transient increase in protein phosphatase 2A activity. We conclude that D(1) stimulation regulates Na,K-ATPase activity by promoting recruitment of Na,K-ATPases from intracellular pools into the basolateral membranes of A549 cells via a type 2A protein phosphatase.

Antigens, Viral, Tumor↗
PubMed2000

Preliminary evaluation of LATEX/T. b. gambiense and alternative versions of CATT/T. b. gambiense for the serodiagnosis of human african trypanosomiasis of a population at risk in Côte d'Ivoire: considerations for mass-screening.

A study was conducted to compare classical card agglutination test for trypanosomiasis (CATT)/T. b. gambiense with CATT-EDTA and LATEX/T. b. gambiense as alternative field tests for serodiagnosis of Human African Trypanosomiasis. The tests were performed on freshly collected blood in an endemic and a low prevalence area in Côte d'Ivoire. Diagnostic performance of each test was assessed using Quantitative Buffy Coat as the parasitological reference and immune trypanolysis as the serological reference test. According to the parasitological data, CATT-EDTA on 10 microl and LATEX/T. b. gambiense on blood diluted 1:4, detecting all confirmed cases with good specificity (respectively 94.6% and 98.1%) yielded better results than the classical CATT did (one false negative and 92.5% specific). However, when immune trypanolysis data and feasibility are taken into account, the classical CATT remains the test of choice for mass screening under the given field conditions.

Agglutination Tests↗
PubMed2000

Finite-temperature properties of Pb(Zr1-xTi(x))O3 alloys from first principles

A first-principles-derived approach is developed to study finite-temperature properties of Pb(Zr1-xTix)O3 (PZT) solid solutions near the morphotropic phase boundary (MPB). Structural and piezoelectric predictions are in excellent agreement with experimental data and direct first-principles results. A low-temperature monoclinic phase is confirmed to exist, and is demonstrated to act as a bridge between the well-known tetragonal and rhombohedral phases delimiting the MPB. A successful explanation for the large piezoelectricity found in PZT ceramics is also provided.

Journal Article↗
PubMed2000

Protein phosphatase 2A and phosphatidylinositol 3-kinase regulate the activity of Sp1-responsive promoters.

The transcription factor Sp1 regulates the activity of a large number of eukaryotic gene promoters, including early SV40 and human immunodeficiency virus type 1 (HIV-1). Here, we report that expression of SV40 small tumor antigen (small t) in quiescent CV-1 cells transactivates two Sp1-responsive promoters, including a deletion mutant of HIV-1 LTR, through specific inhibition of endogenous AC and ABalphaC forms of protein phosphatase 2A (PP2A). Expression of a small t mutant, lacking the PP2A-binding domain, failed to transactivate Sp1. Overexpression of the B56alpha, B56beta, and B56gamma1 regulatory PP2A subunits strongly inhibited the ability of small t, but not the phosphatase inhibitor, okadaic acid, to enhance Sp1-driven gene expression. Using inhibitors and co-expression of kinase-deficient mutants, we also show that functional phosphatidylinositol 3-kinase (PI 3-kinase) and atypical protein kinase C zeta are required for small t-induced Sp1-dependent promoter transcriptional activation. Moreover, two inhibitors of PI 3-kinase, wortmannin and LY294002, inhibit the initiation of SV40 DNA replication in quiescent CV-1 cells. Taken together, these results suggest that PP2A and PI 3-kinase contribute to the ability of small t to regulate Sp1 activity, stimulate early SV40 DNA replication, and enhance the transformation of resting cells during SV40 infection.

Animals↗
PubMed2000

Identification of an ApoA-I ligand domain that interacts with high-affinity binding sites on HepG2 cells.

We have previously described the presence of two (high- and low-affinity) HDL binding sites on the hepatoma cell line (HepG2) (R. Barbaras, X. Collet, H. Chap, and B. Perret (1994) Biochemistry 33, 2335-2340]. Moreover, apoA-I, the major HDL apolipoprotein, interacts with these two binding sites, while lipid-free apoA-I binds only to the high-affinity sites. Using tryptic HDL fragments and HepG2 cell monolayers as an "affinity matrix," we identified an apoA-I peptide of 16 amino acids, spanning between residues 62 and 77, as a ligand domain. The corresponding synthetic peptide displays high-affinity (K(d) approximately 10(-7) M) and low-capacity (B(max) 8 pmol/mg of cell protein) binding components. Competition experiments with this peptide, using (125)I-labeled free apoA-I as a ligand, show that this binding corresponds to the high-affinity binding sites already described. In conclusion, we identified the apoA-I 62-77 region as a specific high-affinity ligand domain of HDL on HepG2 cells.

Amino Acid Sequence↗
PubMed2000

Relation between natural killer cells and neoplastic cells in serous fluids.

Natural killer (NK) cells are capable of lysing certain tumor cells in vitro. We investigated whether the percentage of NK cells (NK%) in serous effusions has any relation with the presence of malignant cells. Fresh effusions were routinely processed, and a portion of them was submitted for lymphocyte immunophenotyping, using a flow cytometer. Fifty-one fluids (15 peritoneal, 36 pleural), from 47 patients were analyzed. Thirty-two cases were negative and 19 were positive for neoplastic cells: there were 13 adenocarcinomas, 2 malignant mesotheliomas (MM), 3 malignant lymphomas (ML), and 1 rhabdomyosarcoma (R). Negative cases showed an average NK% of 5.09% (1-16%). Effusions positive for adenocarcinoma had an average NK% of 22.08% (12-33%) (P < 0.001). MM, ML, and R had a low NK%, with an average of 3.01% (0-5%). Investigation of the NK% could be useful in cytologically doubtful cases and in the differential diagnosis between MM and adenocarcinoma.

Adenocarcinoma↗