Search PubMed⌕ Search

Biomedical subjects

G Mendoza

Publications and source records attributed to G Mendoza.

At least 19 recordsLinked to original sources
PubMed2003

Variceal bleeding and portal hypertension: has there been any progress in the last 12 months?

A review of the literature on the management of esophagogastric varices published in the last 12 months shows that the data are still quite conflicting. In the primary and secondary prophylaxis of variceal bleeding, beta-blockers are still the mainstay of pharmacotherapy. Measurement of the hepatic portal venous pressure gradient is considered to be a reliable parameter for successful reduction of portal pressure using medical therapy. However, intolerance of propranolol requiring discontinuation of therapy has been observed in approximately 30 % of patients. Patients' compliance with medication may represent another drawback of medical therapy. The role of endoscopic band ligation in secondary prophylaxis is now indisputable, especially in comparison with sclerotherapy. In the primary prevention of variceal bleeding, band ligation is beginning to have a competitive edge over pharmacological therapy. Acute variceal bleeding is no longer a frequent morbid emergency. Most cases of bleeding can now be managed successfully with band ligation and N-butyl-2-cyanoacrylate obliteration. N-butyl-2-cyanoacrylate has come into increasingly widespread use in the treatment of bleeding gastric fundal varices in which surgery or transjugular intrahepatic portosystemic shunting were previously regarded as the preferred therapies.

Acute Disease↗
PubMed2001

Cerebral perfusion and haemodynamics measured by SPET in symptom-free patients with transient ischaemic attack: clinical implications.

Transient ischaemic attacks (TIAs) are heterogeneous from the clinical, physiopathological, aetiological and prognostic points of view. Single-photon emission tomography (SPET) may influence patient management by helping to define the vascular topography and by suggesting the probable mechanism (embolic or haemodynamic). However, the variables predicting focal regional cerebral blood flow (rCBF) and cerebrovascular reserve (CVR) abnormalities on SPET and their clinical correlation are poorly known. Our objective in this study was to assess the value of rCBF and CVR measured by SPET in a prospective series of 42 patients with recent (within the preceding 30 days) first-ever TIA Two SPET examinations [baseline and post-acetazolamide (ACZ)] were consecutively performed, and region/reference ratios were obtained using an irregular region of interest (ROI) method. Percentages of interhemispheric asymmetry between homologous brain regions were used to identify abnormalities on baseline SPET, and the percentage changes in asymmetry between the baseline and post-ACZ SPET studies were used to identify abnormal responses to the vasodilator stimulus. Mean baseline and test-retest values previously obtained in normals were used as a reference. The relationship of SPET findings with clinical data and results of complementary examinations was assessed. Most patients (98%) had abnormal findings on either baseline (43%), post-ACZ (19%) or both SPET studies (36%). Thus, 33 patients had hypoperfusion on baseline SPET (78.5%, symptom related in 45%). In 23 patients, a poor response to ACZ was found (55%, symptom related in 21.5%). No predictors for rCBF or CVR impairment were found. Most patients with a first-ever TIA episode present focal hypoperfusion on SPET, either with or without correlation with TIA symptoms. Post-ACZ SPET increases the probability of finding cerebrovascular abnormalities, and orients attention towards an haemodynamic compromise. Focal hypoperfusion on SPET should not be viewed as clinically insignificant because it probably reflects previous or ongoing clinical and/or subclinical episodes of cerebral ischaemia.

Acetazolamide↗
PubMed2000

Modulation of A-type potassium channels by a family of calcium sensors.

In the brain and heart, rapidly inactivating (A-type) voltage-gated potassium (Kv) currents operate at subthreshold membrane potentials to control the excitability of neurons and cardiac myocytes. Although pore-forming alpha-subunits of the Kv4, or Shal-related, channel family form A-type currents in heterologous cells, these differ significantly from native A-type currents. Here we describe three Kv channel-interacting proteins (KChIPs) that bind to the cytoplasmic amino termini of Kv4 alpha-subunits. We find that expression of KChIP and Kv4 together reconstitutes several features of native A-type currents by modulating the density, inactivation kinetics and rate of recovery from inactivation of Kv4 channels in heterologous cells. All three KChIPs co-localize and co-immunoprecipitate with brain Kv4 alpha-subunits, and are thus integral components of native Kv4 channel complexes. The KChIPs have four EF-hand-like domains and bind calcium ions. As the activity and density of neuronal A-type currents tightly control responses to excitatory synaptic inputs, these KChIPs may regulate A-type currents, and hence neuronal excitability, in response to changes in intracellular calcium.

Amino Acid Sequence↗
PubMed2000

Purification and characterization of an adhesin from Pasteurella haemolytica.

We purified an adhesin from Pasteurella. haemolytica by affinity chromatography using glutaraldehyde treated rabbit erythrocytes stroma. The adhesin is a protein of 68 kDa, as determined by SDS-PAGE, and the most abundant amino acids constituting this protein were Gly, Ser, Glx, and Ala, and low concentrations of Cys, Met, and Tyr residues were also found. The N-terminal sequence of the adhesin is ANEVNVYIYKQPYLI. No carbohydrate residues were detected. The adhesin agglutinated rabbit erythrocytes but when the latter were desialylated or pronase treated the agglutinating activity was abolished. The agglutinating activity of the adhesin was inhibited with N-acetyl-D-glucosamine (GlcNAc), and in a lesser degree with N-acetyl-neuraminic acid (NeuAc). GalNAc, N-glycolyl-neuraminic acid, N-deacetylated GlcNAc, or neutral sugars do not modify the activity of the adhesin. The equatorial -OH on C4 and the NH-acetylated group on C2 from GlcNAc, as well as the 4-OH and NH-acetylated group on C5 from NeuAc seem to be responsible for the interaction with the adhesin. The protein is divalent cation-dependent and thermolabile. As for the agglutinating activity, the adhesion of P.haemolytica to tracheal cell-cultures was inhibited by GlcNAc, NeuAc or the purified adhesin, strongly suggesting that the P.haemolytica adhesin plays an important role in infection.

Adhesins, Bacterial↗
PubMed1999

An alternative model for the transmembrane segments of the yeast H+-ATPase.

An alternative topological model for the yeast plasma membrane H(+)-ATPase from K. lactis was deduced by joint prediction, using 11 algorithms for the prediction of transmembrane segments complemented with hydrophobic moment analysis. Similarly to the model currently used in the literature, this alternative model contains 10 transmembrane segments, four in the N-half and six in the C-half of the protein. However, the distribution of the membrane-associated segments on the C-half of the enzyme differs in both models. Nine of the 10 transmembrane segments are highly hydrophobic with low hydrophobic moments, and are probably involved in structural roles. The fifth transmembrane segment is, on the other hand, less hydrophobic, with the highest hydrophobic moment, suggesting that this segment might have a dynamic role in the coupling of the hydrolysis of ATP with the translocation of protons across the membrane. The alignment of the Ca(2+)-ATPase, the Na(+)/K(+)-ATPase and the H(+)-ATPase sequences showed that these proteins have the same topology in the N-half, but important differences were found at the C-half of the enzymes. In contrast with the mammalian ATPases, the fifth transmembrane segment in the H(+)-ATPase appears early in the sequence, giving rise to a shorter cytoplasmic central loop. This alternative model will be useful in the designing of site-directed mutagenesis experiments and contains information for the fitting of the amino acid sequence into the transmembrane region of the three-dimensional model of the ATPase.

Algorithms↗
PubMed1999

New uses of legacy systems: examples in perinatal care.

In this article, new uses of the Perinatal Information System at the Uruguayan Social Security health care facilities are described. The perinatal information system has been in place for over 13 years, with about 40 thousand clinical records on electronic files. A newly created Web interface allows a distributed access to existing perinatal information within the National Social Security Wide Area a Network. Perinatal data is also exported to a management information system, allowing to dynamically answer questions and make managerial decisions, and eventually link these data with other sources. Future steps regarding clinical information systems are outlined.

Humans↗
PubMed1998

Transabdominal intra-amniotic endoscopic assessment of previable premature rupture of membranes.

OBJECTIVE: Our purpose was to describe the endoscopic characteristics of the site of rupture in vivo in patients with spontaneous premature rupture of membranes. STUDY DESIGN: Patients with preterm premature rupture of membranes between 16 and 26 weeks of gestation, without evidence of intra-amniotic infection, and with a normal karyotype underwent transabdominal endoscopic examination of the amniotic cavity. Subsequently, an amniopatch of a combination of platelets and cryoprecipitate to seal the membrane defect was administered. The study was approved by the Institutional Review Board of St. Joseph's Hospital in Tampa, Florida, and all patients gave written informed consent. RESULTS: Four patients underwent endoscopic examination and amniopatch administration; three had spontaneous preterm premature rupture of membranes, and in the other the membranes ruptured after an early amniocentesis. The location of the site of rupture was over the internal os in the 3 cases with spontaneous preterm premature rupture of membranes. This area was normal in the patient with iatrogenic preterm premature rupture of membranes. The longer the time between preterm premature rupture of membranes and fetoscopy, the larger and less defined was the site of rupture. The amniopatch restored amniotic integrity for a maximum of 72 hours. CONCLUSIONS: This is the first in vivo endoscopic visualization of the site of spontaneous rupture of membranes from within the uterine cavity. The defect is located over the internal cervical os in patients with spontaneous preterm premature rupture of membranes. There appear to be time-related changes in the morphologic characteristics of the site of rupture. Endoscopic visualization of the site of rupture has the potential for improving our understanding of spontaneous preterm premature rupture of membranes and in the development of possible therapeutic alternatives.

Abdomen↗
PubMed1998

11C-methionine PET for differential diagnosis of low-grade gliomas.

Management of low-grade gliomas continues to be a challenging task, because CT and MRI do not always differentiate from nontumoral lesions. Furthermore, tumor extent and aggressiveness often remain unclear because of a lack of contrast enhancement. Previous studies indicated that large neutral amino acid tracers accumulate in most brain tumors, including low-grade gliomas, probably because of changes of endothelial and blood-brain barrier function. We describe 11C-methionine uptake measured with PET in a series of 196 consecutive patients, most of whom were studied because of suspected low-grade gliomas. Uptake in the most active lesion area, relative to contralateral side, was significantly different among high-grade gliomas, low-grade gliomas, and chronic or subacute nontumoral lesions, and this difference was independent from contrast enhancement in CT or MRI. Corticosteroids had no significant effect on methionine uptake in low-grade gliomas but reduced uptake moderately in high-grade gliomas. Differentiation between gliomas and nontumoral lesions by a simple threshold was correct in 79%. Recurrent or residual tumors had a higher uptake than primary gliomas. In conclusion, the high sensitivity of 11C-methionine uptake for functional endothelial or blood-brain barrier changes suggests that this tracer is particularly useful for evaluation and follow-up of low-grade gliomas.

Adult↗
PubMed1997

Prognosis of stroke patients requiring mechanical ventilation in a neurological critical care unit.

BACKGROUND AND PURPOSE: Intubation and mechanical ventilation are sometimes necessary during treatment of acute stroke. Indications include neurological deterioration, pulmonary complications, and elective intubation for procedures and surgery. Prognosis in severe stroke patients requiring mechanical ventilation has often been reported to be poor. This study was performed to prospectively assess the prognosis of stroke patients who require ventilation in a neurological intensive care unit and to determine factors that may influence outcome. METHODS: Analysis was made of 124 consecutive stroke patients who required mechanical ventilation over a 2-year period. We determined the survival rate at 1 year after admission. Initial clinical data, history of previous diseases, and indication for intubation were analyzed for prognostic significance by univariate and multiple logistic regression analysis. RESULTS: The 1-year survival rate was 33.1% (n = 41). Sixty-five patients (52%) died in the neurological intensive care unit. Among 17 variables analyzed, seven were found to significantly influence 2-month fatality in the univariate analysis: age greater than 65 years, atrial fibrillation, bilateral absence of pupillary light reflex, bilateral absence of corneal reflex, bilateral Babinski's sign, infratentorial stroke, and Glasgow Coma Scale (GCS) score less than 10. Independent predictors of death at 2 months were age greater than 65 years (P = .03), GCS score less than 10 (P = .01), and intubation performed because of coma or acute respiratory failure (P = .04). CONCLUSIONS: Overall prognosis of ventilated patients with severe stroke is better than previously reported. Older patients comatose on admission who need to be intubated because of neurological or respiratory deterioration have the poorest prognosis. We conclude that intubation and mechanical ventilation of severe stroke patients should be performed in a timely manner, before irreversible damage occurs.

Activities of Daily Living↗
PubMed1996

[Reversible cerebral MRI findings in acute microangiopathic hemolytic anemia].

A case of acute microangiopathic hemolytic anemia in a 29-year-old primiparous patient is presented. Following an unsuspicuous pregnancy and uncomplicated delivery, the patient developed upper abdominal symptoms and transient psychopathologic abnormalities 2 days after delivery. Because of a series of generalized tonic-clonic seizures and respiratory distress she was admitted to the Neuro ICU. Focal neurological symptoms were absent, and CSF analysis was normal. Laboratory findings indicated hemolytic anemia with fragmented erythrocytes in smear specimens, thrombocytopenia, reticulocytosis, marked elevation of liver and pancreatic enzymes, and microhematuria. T2-weighted MR scans of the brain discluded multiple ischemic lesions of the cerebral white and gray matter, caudate nucleus and pons, displaying a hemodynamic pattern. Specific treatment included administration of corticosteroids, repeated plasmapheresis with substitution by fresh frozen plasma and antithrombin III. A control MR performed on the 3rd day of treatment demonstrated the absence of nearly all abnormal findings previously obtained. During a 3-week clinical course the patient showed full recovery, including normalization of hematologic and neuroradiologic findings. This case demonstrates ischemic cerebral lesions in acute microangiopathic hemolytic anemia to be potentially reversible if specific treatment is provided.

Adult↗
PubMed1995

Monitoring the effacement of the uterine cervix by transperineal sonography: a new perspective.

The objective of this study is to monitor the process of effacement of the uterine cervix and demonstrate that transperineal sonography is the appropriate technique for this purpose. Eighty-six patients with normal, term pregnancies were studied at the beginning of labor. Transperineal sonography was performed in transverse and longitudinal planes. After the initial examination, patients were reexamined several times during a 1 to 4 hour period. We observed a progressive shortening of the canal and the synchronous opening of a funnel-shaped internal cervical os. When the funneling process reached the lower end of the cervix, both orifices fused, completing the process of effacement. The dilatation of the external os, which remained stationary during initial phase, increases very quickly once the effacement has been completed. Transperineal sonography efficiently imaged the changes described here.

Cervix Uteri↗
PubMed1994

Multiple astrocyte transcripts encode nigral trophic factors in rat and human.

The recent discovery of glial cell line-derived neurotrophic factor (GDNF) identified a novel trophin that selectively increases survival of substantia nigra dopaminergic neurons, which degenerate in Parkinson's disease. Our previous studies indicated that GDNF RNA can be amplified from cultured rat nigral type 1 astrocytes and from rat striatum in vivo, implying local as well as target trophic support. The current study establishes the regional pattern of GDNF RNA expression in adult human brain. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed the highest expression of GDNF mRNA in the human caudate, with low levels in the putamen and no detectable message in the nigra, suggesting that GDNF is a target-derived factor in humans. We also report the isolation of two additional GDNF-related cDNAs, termed astrocyte-derived trophic factors (ATF), which apparently result from differential RNA processing. Sequence analysis of rat ATF-1 revealed a 78-bp deletion corresponding to a loss of 26 amino acids within the prepro region of the predicted GDNF protein. The RNA processing events responsible for ATF-1 formation in rat brain are conserved in humans; we report the isolation of a full-length human ATF-1 homologue. We identified a second alternative transcript, human ATF-2; the transcript encodes a protein which differs in its first 18 amino acids from the predicted mature GDNF and ATF-1 proteins and shares the terminal 115 residues with the other two forms. To begin assessing the biologic significance of multiple transcript expression we characterized the actions of COS-expressed GDNF and ATF-1 cDNAs.(ABSTRACT TRUNCATED AT 250 WORDS)

Activating Transcription Factor 1↗
PubMed1994

Hepatic myelopathy: a rare complication of portacaval shunt.

Myelopathy is a rare complication of chronic liver disease associated with extensive portal-systemic shunt of blood. Its main clinical feature is a spastic paraparesis without sensory or sphincteric impairment. We describe 3 patients who presented hepatic myelopathy following the performance of a portacaval shunt.

Adult↗
PubMed1992

Frequent semen collection and sperm reserves of the male Angora goat (Capra hircus).

Semen was collected from six mature and sexually rested Angora bucks at one-hour intervals five times a day on each of 5 consecutive days in the breeding season. There was a marked decline in semen volume (P less than 0.001), sperm concentration (P less than 0.05) and number of spermatozoa (P less than 0.001) on consecutive days. Successive ejaculates within days differed only in number of spermatozoa (P less than 0.001). The following year at the beginning of the breeding season, the weights of testes and epididymides and the reserves of spermatozoa in these parts were examined after slaughter of the six bucks. The mean number of spermatozoa in the paired testes, capita, corpora and caudae of the epididymides were (22.8 +/- 1.24) x 10(9), (9.4 +/- 1.19) x 10(9), (3.4 +/- 0.22) x 10(9) and (35.0 +/- 2.21) x 10(9), respectively. Epididymal reserves of spermatozoa were correlated with testicular weight (r = 0.50, P = 0.01) and number of spermatozoa in the testes (r = 0.42, P = 0.07), but not with epididymal weight. The daily production of spermatozoa per animal in the breeding season was estimated to be 4.0-6.4 x 10(9).

Animals↗