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Biomedical subjects

H Pérez

Publications and source records attributed to H Pérez.

At least 19 recordsLinked to original sources
PubMed2006

Paraventricular-coerulear interactions: role in hypertension induced by prenatal undernutrition in the rat.

Rats submitted to fetal growth retardation by in utero malnutrition develop hypertension when adult, showing increased hypothalamic mRNA expression for corticotropin-releasing hormone (CRH) and increased central noradrenergic activity. As hypothalamic CRH serves as an excitatory neurotransmitter within the locus coeruleus (LC) and coerulear norepinephrine plays a similar role within the paraventricular nucleus (PVN) of the hypothalamus, we studied, in both normal and prenatally undernourished 40-day-old anesthetized rats, the effects of intra-LC microinjection of CRH and intra-PVN microinjection of the alpha(1)-adrenoceptor antagonist prazosin on multiunit neuronal activity recorded simultaneously from the two nuclei, as well as the effects on systolic pressure. Undernutrition was induced during fetal life by restricting the diet of pregnant mothers to 10 g daily, whereas mothers of control rats received the same diet ad libitum. At day 40 of postnatal life: (i) undernourished rats showed increased neuronal activity in the PVN and LC, as well as increased systolic pressure; (ii) intra-LC CRH stimulated LC and PVN neurons and increased systolic pressure only in normal rats; (iii) intra-PVN prazosin decreased LC and PVN neuronal activity and systolic pressure only in undernourished rats; and (iv) in normal rats, prazosin prevented the stimulatory effect of CRH only in PVN activity; in undernourished rats, prazosin allowed CRH to regain its stimulatory effects. The results point to the existence of an excitatory PVN-LC closed loop, which seems to be hyperactive in prenatally undernourished rats as a consequence of fetal programming; this loop could be responsible, in part, for the hypertension developed by these animals.

Animals↗
PubMed2006

Trypanosomiasis in Venezuelan water buffaloes: association of packed-cell volumes with seroprevalence and current trypanosome infection.

The seroprevalence of trypanosomiasis and the prevalence of current trypanosome infection in water buffaloes from the most important livestock areas of Venezuela were evaluated by IFAT and the microhaematocrit centrifugation technique, respectively. The usefulness of a PCR-based assay for identifying the trypanosome species in the buffaloes was also evaluated. Of the 644 animals investigated, 40 (6.2%) were found infected with trypanosomes by blood centrifugation, and 196 (30.4%) were found positive for anti-trypanosome antibodies, by IFAT. The results of the PCR-based assay indicated that 92.5% of the animals with current infections were infected with Trypanosoma vivax and the rest with T. theileri (the first molecular confirmation of T. theileri in Venezuelan water buffaloes). The national programme to treat and prevent trypanosome infections in the buffaloes does not appear to be meeting with great success, even though it is focused on T. vivax. Although the level of parasitaemia was categorized as low for 28 (70%) of the infections detected (and packed-cell volumes appeared to be unassociated with IFAT result, and uncorrelated, in the infected animals, with level of parasitaemia), the 40 infected buffaloes had a significantly lower mean packed-cell volume than the uninfected animals (P<0.05). Farmers should therefore be made aware of the probability of trypanosome-attributable losses in buffalo productivity.

Animals↗
PubMed2006

[Vascular access for haemodyalisis. Comparative analysis of the mechanical behaviour of native vessels and prosthesis].

INTRODUCTION: The prosthesis nowadays used in the vascular access for haemodialysis have low patency rates, mainly due to the luminal obstruction, determined by the intimal hyperplasia. Several factors have been related to de development of intimal hyperplasia and graft failure. Among them are the differences in the biomechanical properties between the prosthesis and the native vessels. In the searching for vascular prosthesis that overcomes the limitations of the currently used, the cryopreserved vessels (cryografts) appear as an alternative of growing interest. However, it is unknown if the mechanical differences or mismatch between prosthesis and native vessels are lesser when using cryografts. OBJECTIVE: To characterize and compare the biomechanical behaviour of native vessels used in vascular access and cryografts. Additionally, segments of expanded polytetrafluoroethylene (ePTFE) were also evaluated, so as to evaluate the potential biomechanical advantages of the cryografts respect to synthetic prosthesis used in vascular access. METHODS: Segments from human humeral (n = 12), carotid (n = 12) and femoral (n = 12) arteries, and saphenous vein (n = 12), were obtained from 6 multiorgan donors. The humeral arteries were studied in fresh state. The other segments were divided into two groups, and 6 segments from each vessel were studied in fresh state, while the remaining 6 segments were evaluated after 30 days of criopreservation. For the mechanical evaluation the vascular segments and 6 segments of ePTFE were mounted in a circulation mock and submitted to haemodynamic conditions similar to those of the in vivo. Instantaneous pressure (Konigsberg) and diameter (Sonomicrometry) were measured and used to calculate the viscous and elastic indexes, the compliance, distensibility and characteristic impedance. For each mechanical parameter studied, the mismatch between the prosthesis and the native vessel was evaluated. RESULTS: The ePTFE was the prosthesis with the higher mechanical mismatch (p < 0.05). The venous and arterial cryografts showed the least mismatch with native veins and arteries, respectively. The prosthesis with the least mechanical mismatch was different, depending on the native vessel evaluated, and for a native vessel, on the parameter considered. CONCLUSION: The mechanical mismatch between the native vessel and the vascular prosthesis used in a vascular access could be reduced using cryografts.

Adult↗
PubMed2005

Strain characterization of Echinococcus granulosus protoscoleces of cattle origin using the in vitro vesicular development.

The aim of this work was to characterize the strain of protoscoleces of E. granulosus of cattle origin using the in vitro vesicular development. The in vitro development of these samples was compared to samples of sheep origin determined previously by genetic analyses as common sheep strain (G1). There were similarities between sheep and cattle samples not only in the time of microcysts formation, but also in the development process. Vesiculated protoscoleces and protoscoleces with posterior bladders appeared during the first week of incubation. After 14 days of culture, a laminated layer appeared like a fine membrane in one of the extremes of the protoscoleces. In the sheep samples, microcysts were observed between 19 and 20 days. In the cattle samples, microcysts appeared between 20 and 23 days. The coincidence between the development times and physiological characteristics found in the present study may indicate that the parasites from cattle and sheep were of the same strain.

Animals↗
PubMed2003

Chronic pancreatitis associated with systemic lupus erythematosus in a young girl.

Systemic lupus erythematosus (SLE) is an uncommon etiology of pancreatic disease. Up to now, only 3 cases of chronic pancreatitis associated with SLE have been reported in adults. We report the case of a 14-year-old girl with SLE and calcifying chronic pancreatitis. At the age of 4 she was diagnosed with SLE. She presented with several acute exacerbations of SLE that were managed with prednisone and azathioprine. At the age of 9, she was admitted with abdominal pain and elevation of serum amylase and lipase levels; no gallstones were found on ultrasound, and treatment with azathioprine was withdrawn. Thereafter, she developed numerous episodes of acute pancreatitis. Later, an ERCP showed pancreatic calcifications and distortion of the main pancreatic duct, both findings consistent with established chronic pancreatitis. At the age of 14, her condition worsened progressively, and a surgical procedure (corporo-caudal spleno-pancreatectomy) was performed. The pathology specimen showed acinar atrophy and intense fibrosis. After surgery, the patient has remained pain-free and is enjoying a normal life.

Adolescent↗
PubMed2002

Absence of coherence between cervical and lumbar spinal cord dorsal surface potentials in the anaesthetized cat.

Recordings of spontaneous cord dorsum potentials (CDPs) along the longitudinal axis of the spinal cord were made. These recordings were obtained from the surface of the dorsal horn at different points along the spinal cord caudally and cranially in relation to the point giving spontaneous potentials of maximal amplitude. We found two curves (lumbar and cervical) for the longitudinal distribution of the area of the power spectra of these recordings. Each of these curves had a symmetrical decrement on both sides of the position of the point for the maximal area of power. Such points were discovered on the L5-L7 and C3-C4 spinal segments. Spectral analysis of the spontaneous CDPs simultaneously recorded in both regions indicates no evidence of coherence, thus suggesting that the spontaneous CDPs recorded in the lumbar and cervical regions of the pentobarbitone-anaesthetized cat are generated by two independent populations of neurones not functionally interconnected between them.

Action Potentials↗
PubMed2001

Effect of ketamine on spinal cord nociceptive transmission in normal and monoarthritic rats.

The effects of systemically and intrathecally administered ketamine on spinal wind-up of normal and monoarthritic rats were studied by using C-fiber reflex responses evoked by repetitive (0.6 Hz) electric stimulation. Both systemic and intrathecal ketamine induced dose-dependent depression of wind-up activity in normal rats, as revealed by the dose-related inhibitory effects of the drug. At the same intraperitoneal doses, ketamine produced a greater inhibitory effect on wind-up activity of monoarthritic rats, compared to normal animals. The intrathecal administration of ketamine also produced wind-up inhibition, the efficacy being higher in the monoarthritic rats. Results indicate that ketamine depresses spinal wind-up, specially in rats submitted to chronic pain, probably due to its antagonistic properties on dorsal horn NMDA receptors, which play a crucial role in the maintenance of chronic pain.

Animals↗
PubMed2000

Tribenzylphosphine oxide.

The title compound, (C(6)H(5)CH(2))(3)PO, is an organic tertiary phosphine oxide. The molecule has threefold symmetry, with the P-O bond along the threefold axis. Main dimensions include P-O 1.488 (4), P-C 1.823 (3) A and O-P-C 114.7 (1) degrees. The crystals were accidentally obtained when preparing complexes of nickel(II) with dibenzylphosphine.

Journal Article↗
PubMed2000

Chagas' disease of the cervix uteri in a patient with acquired immunodeficiency syndrome.

A 27-year-old woman with the acquired immunodeficiency syndrome and endocervical Chagas' disease is reported. The patient was a cocaine addict, and her sexual partner was also human immunodeficiency virus (HIV)-positive. Her past medical history included a son who died 3 days after birth due to congenital Chagas' disease. Seven years later, through a cervical biopsy, a reactivation of Chagas' disease was diagnosed. Giant cells with typical amastigotes were seen; they strongly stained with antibodies against Trypanosoma cruzi. The patient died 5 months later of an acute chagasic myocardiopathy. To our knowledge, this is the first report of this parasitosis in the cervix uteri.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Profilin in Phaseolus vulgaris is encoded by two genes (only one expressed in root nodules) but multiple isoforms are generated in vivo by phosphorylation on tyrosine residues.

Actin-binding proteins such as profilins participate in the restructuration of the actin cytoskeleton in plant cells. Profilins are ubiquitous actin-, polyproline-, and inositol phospholipid-binding proteins, which in plants are encoded by multigene families. By 2D-PAGE and immunoblotting, we detected as much as five profilin isoforms in crude extracts from nodules of Phaseolus vulgaris. However, by immunoprecipitation and gel electrophoresis of in vitro translation products from nodule RNA, only the most basic isoform of those found in nodule extracts, was detected. Furthermore, a bean profilin cDNA probe hybridised to genomic DNA digested with different restriction enzymes, showed either a single or two bands. These data indicate that profilin in P. vulgaris is encoded by only two genes. In root nodules only one gene is expressed, and a single profilin transcript gives rise to multiple profilin isoforms by post-translational modifications of the protein. By in vivo 32P-labelling and immunoprecipitation with both, antiprofilin and antiphosphotyrosine-specific antibodies, we found that profilin is phosphorylated on tyrosine residues. Since chemical (TLC) and immunological analyses, as well as plant tyrosine phosphatase (AtPTP1) treatments of profilin indicated that tyrosine residues were phosphorylated, we concluded that tyrosine kinases must exist in plants. This finding will focus research on tyrosine kinases/tyrosine phosphatases that could participate in novel regulatory functions/pathways, involving not only this multifunctional cytoskeletal protein, but other plant proteins.

Blotting, Western↗
PubMed1999

Apolipoprotein E polymorphism in elderly Chilean people with Alzheimer's disease.

As a part of the WHO Age-Associated Dementia Project, Chile has been participating in a cross-national survey on dementia frequency and determinants since 1989. In the present study, apolipoprotein E (ApoE) polymorphism genotypes have been compared in 95 patients with Alzheimer's disease (AD) (mean age 80.7; 95% CI 79.2-82.2, range 66-97) and 187 healthy people (mean age 78.2; 95% CI 77.2-79.2, range 65-93). Isoelectric focusing and immunoblotting with anti-human ApoE polyclonal antibody were used to determine the distribution of ApoE genotypes. Dementia was diagnosed according to DSM-III-R and ICD-10 clinical criteria. The diagnosis of probable or possible AD was made according to the NINCDS-ADRDA criteria. The ApoE allele frequencies in healthy people were calculated to be epsilon2 = 0.07, epsilon3 = 0.74 and epsilon4 = 0.19. In the probable AD disease group, the frequencies were epsilon2 = 0.08, epsilon3 = 0.52 and epsilon4 = 0.40. The odds ratio (OR) for epsilon4 carriers compared with non-epsilon4 carriers was estimated to be 2.9 (95% CI 1.7-5.1). Taking the genotype epsilon3/epsilon3 as the reference group, the OR for the epsilon4/epsilon4 genotype was estimated to be 12.8 (95% CI 3.9-47.6) and for epsilon3/epsilon4 subjects it was 2.4 (1.3-4.5). These results support the association between ApoE epsilon4 allele with late-onset AD in a Chilean population.

Aged↗
PubMed1998

Locus coeruleus-mediated inhibition of chemosensory responses in the rat nucleus tractus solitarius is mediated by alpha2-adrenoreceptors.

It is known that electrical and L-glutamate stimulation of the locus coeruleus (LC) reduce the multiunit activity evoked in the nucleus of the tractus solitarius (NTS) by cyanoboro-hydride. In the present study, rats anaesthetised with urethane were microinjected with noradrenergic antagonists into the NTS, to test whether the inhibitory effects of LC stimulation on cyanide-evoked discharge in the NTS were mediated by noradrenaline. Microinjection of yohimbine into the NTS (0.2, 0.6, 1.8, 5.4 nmol) induced dose-dependent reduction of the inhibitory effect of LC stimulation on NTS neurones, while prazosin produced no effect. The results indicate that LC-induced inhibition of the cyanide-evoked discharge in the NTS is mediated by endogenous noradrenaline release acting on alpha2-adrenoreceptors.

Adrenergic alpha-2 Receptor Antagonists↗
PubMed1998

Prenatal protein restriction alters synaptic mechanisms of callosal connections in the rat visual cortex.

Mild prenatal protein malnutrition, induced by reduction of the casein content of the maternal diet from 25 to 8%, calorically compensated by the addition of excess carbohydrates, leads to so-called "hidden" malnutrition in the rat. This form of malnutrition results in normal body and brain weights of pups at birth, but in significant alterations of their central nervous system neurochemical profiles. Since severe forms of prenatal malnutrition induce morpho-functional deficits on callosal interhemispheric communication together with brain neurochemical disturbances, we evaluated, in rats born from mothers submitted to an 8% casein diet, the potassium-induced release of [3H]-noradrenaline in visual cortex slices, as well as functional properties of callosal-cortical synapses by determining cerebral cortical excitability to callosal inputs and fatigability and temporal summation of transcallosal evoked responses. Rats born from mothers submitted to a 25% casein diet served as controls. At birth prenatally malnourished pups had significantly higher cortical percent net noradrenaline release (14.79 +/- 1.11) than controls (9.14 +/- 1.26). At 45-50 days of age, rehabilitated previously malnourished rats showed, when compared to controls; (i) significantly reduced percent net noradrenaline release in the visual cortex (4.50 +/- 0.52 vs 11.31 +/- 1.14); (ii) decreased cortical excitability to callosal inputs as revealed by significantly increased chronaxie (607.2 +/- 82.8 microseconds vs 351.3 +/- 47.7 microseconds); (iii) enhanced fatigability of transcallosal evoked responses as revealed by significantly decreased stimulus frequency required to fatigate the responses (4.9 +/- 0.8 Hz vs 9.2 +/- 1.3 Hz); and (iv) decreased ability of callosal-cortical synapses to perform temporal summation, as revealed by significantly reduced percent response increment to double-shock (54.2 +/- 6.2 vs 83.0 +/- 11.0, for a 3.2-ms interstimulus time interval). These changes, resulting from mild prenatal protein restriction, are discussed in relationship to developmental processes leading to the formation of synaptic contacts between callosal axons and their appropriate cortical target during perinatal age.

Animals↗
PubMed1998

Prenatal malnutrition-induced functional alterations in callosal connections and in interhemispheric asymmetry in rats are prevented by reduction of noradrenaline synthesis during gestation.

Prenatal malnutrition results in increased concentration and release of central noradrenaline, a neurotransmitter that is an important regulator of normal regressive events such as axonal pruning and synaptic elimination. This suggests that some of the functional disturbances in brain induced by prenatal malnutrition could be due at least in part to increased noradrenaline activity that may enhance regressive events during early stages of development. To test this hypothesis we studied whether chronic administration of alpha-methyl-p-tyrosine, an inhibitor of tyrosine hydroxylase, to rats during gestation might prevent long-term deleterious effects of prenatal malnutrition on functional properties of interhemispheric connections of the visual cortex, and on asymmetry of visual evoked responses. The experiments were conducted on normal and malnourished rats 45-50 d of age. Prenatal malnutrition was induced by restricting the food consumption of pregnant rats to 40%, from d 8 postconception to parturition. At birth, prenatally malnourished rats had significantly greater whole-brain noradrenaline concentration as well as significantly enhanced noradrenaline release in the visual cortex. At 45-50 d of age, the malnourished group had a significantly smaller cortical area, exhibiting transcallosal evoked responses; in addition, the amplitude of these responses was significantly smaller. Malnourished rats showed a significant reduction of the normal interhemispheric asymmetry of visual evoked responses. The addition of 0.3% alpha-methyl-p-tyrosine to the diet of malnourished pregnant rats during the last 2 wk of gestation prevented functional disorders induced in the offspring by prenatal malnutrition on interhemispheric connectivity of visual areas and on interhemispheric bioelectrical asymmetry, probably by reducing the elevated brain noradrenaline activity and thereby restoring the normal trophic role of this neurotransmitter.

Animals↗
PubMed1998

Allopregnanolone-induced modification of presynaptic basal and K+-induced [3H]-norepinephrine efflux from rat cortical slices during the estrous cycle.

Superfused frontal slices of cerebral cortex were preloaded with [3H]-norepinephrine ([3H]NE). Basal [3H]NE efflux and K+-induced [3H]NE release were studied during the estrous cycle and in the presence of neurosteroids. Basal [3H]NE efflux showed estrous cycle-related variations, with lowest values found during estrus and diestrus II. Allopregnanolone (10(-9) M) potentiated basal [3H]NE efflux from the 1st minute of its application; the effect of the steroid was still present after 20 min. This effect was also dependent upon the estrous cycle, since basal [3H]NE efflux was mainly increased during estrus diestrus I, and to a lesser degree only during proestrus. During diestrus II and after ovariectomy, basal [3H]NE efflux was no longer affected by the neurosteroid. In the presence of yohimbine (10(-6) M), the effect of allopregnanolone on basal efflux was potentiated only during the first 3 min but vanished thereafter. Allopregnanolone (10(-9) M) potentiated the K+-induced [3H]NE release during estrus, but pregnenolone (10(-9) M) was ineffective, suggesting specificity of the neurosteroid. Yohimbine (10(-6) M) also potentiated K+-induced [3H]NE release. When applied simultaneously with allopregnanolone (10(-9) M), a potentiating effect on [3H]NE release was observed. The present results suggest that allopregnanolone is a neurosteroid able to modulate norepinephrine release in the cerebral cortex in an estrous cycle-dependent manner, and that the effect could involve noradrenergic alpha-2 receptors.

Adrenergic alpha-2 Receptor Antagonists↗
PubMed1997

Bradykinin B1 receptors in human umbilical vein.

The present study was undertaken to demonstrate the presence of bradykinin B1 receptors mediating contraction of human umbilical vein. The bradykinin B1 receptor selective agonist, des-Arg9-bradykinin, produced a dose-dependent contractile response of human umbilical vein rings. Furthermore, des-Arga-bradykinin-mediated response increased in a time-dependent manner in vitro. The maximal response to des-Arg9-bradykinin, expressed as percentage of the maximum elicited by serotonin, was: 10 +/- 2 at 15 min, 55 +/- 5 at 120 min and 80 +/- 3 at 300 min. Des-Arg9-bradykinin-mediated contractions were inhibited by the specific bradykinin B1 receptor antagonist des-Arg9-[Leu8]bradykinin which produced parallel shifts in the dose-response curve to the selective bradykinin B1 receptor agonist. Schild regression analysis of data established a pA2 value of 6.16 +/- 0.06. Kinin-induced contraction was not modified by pre-treatment with indomethacin (10 microM), a cyclo-oxygenase inhibitor. On the other hand, continuous exposure to the anti-inflammatory steroid dexamethasone (100 microM) or to the protein synthesis inhibitor cycloheximide (70 microM) largely prevented the sensitization to des-Arg9-bradykinin in incubated human umbilical vein rings. These results confirm the presence of bradykinin B1 receptors which mediate contraction in isolated human umbilical vein. These responses are up-regulated in a time- and protein synthesis-dependent process.

Anti-Inflammatory Agents↗