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Biomedical subjects

S Pereira

Publications and source records attributed to S Pereira.

At least 55 records · Page 3Linked to original sources
PubMed1996

Otolaryngologic manifestations of multiple pterygium syndrome.

Escobar Syndrome, or Multiple Pterygium Syndrome (MPS), is a rare syndrome with multiple congenital anomalies involving the head and neck area and limbs. Affected individuals have multiple pterygia, camptodactyly and/or syndactyly as the main features of this syndrome. Patients with MPS have a characteristic facies, including ptosis, antimongoloid slant of the palpebral fissures, hypertelorism, micrognathia, neck pterygia, and a sad flat, emotionless look to the face. We present a case of MPS recently treated at our institution for the purpose of further describing the clinical features of this syndrome, emphasizing the otolaryngologic manifestations. Increased awareness of MPS will facilitate appropriate management of this syndrome.

Abnormalities, Multiple↗
PubMed1996

Liver transplantation for haemophiliacs with hepatitis C cirrhosis.

BACKGROUND: Experience of liver transplantation in haemophiliacs with end stage hepatitis C liver disease is limited and particularly difficult questions are raised when there is also HIV infection. AIMS: This is the first report in Great Britain to describe the operative replacement therapy and initial outcome in four haemophiliacs with end stage HCV cirrhosis. PATIENTS: Two patients had factor VIII, one had factor IX, and one had factor X deficiency. One patient had also contracted HIV infection from factor replacement but had no AIDS defining illnesses. METHODS: Intraoperatively patients were given either factor VIII infusions, factor IX bolus, or fresh frozen plasma, according to formulae devised to calculate exact clotting factor requirements. Baseline preoperative coagulation studies included prothrombin time, activated partial thromboplastin time, fibrinogen concentrations, and factor VIII, IX, and X concentrations. Factor concentrations were then assayed at 12, 24, 48, and 72 hours postoperatively. RESULTS: Postoperatively all patients had coagulation factor concentrations sustained within the normal ranges by 72 hours unsupported (137, 125, 95, 104 IU/dl), representing de novo synthesis by the graft. Transfusion requirements during the operative and immediate post-transplant period were no greater than those of patients without clotting disorders. Two patients had episodes of bleeding postoperatively, one of which was fatal, occurring at the site of a previous untreated subdural bleed. In both instances the bleeding occurred in the presence of normal concentrations of clotting factor. The remaining three patients are at 6, 6, and 12 months post-transplant and remarkably improved clinically with sustained factor concentrations. One patient has evidence of graft dysfunction from HCV recurrence and all have evidence of recurrent viraemia with HCV on polymerase chain reaction studies. CONCLUSIONS: Orthotopic liver transplantation should be considered in haemophiliac patients with end stage liver disease from hepatitis C infection with or without concomitant HIV infection. Their clinical condition is likely to be greatly improved by orthotopic liver transplantation and the haemophilia cured with only a small risk of severe graft dysfunction from recurrent HCV infection.

Adult↗
PubMed1996

[Sympathetic nervous activity in cirrhosis: the relationship between peripheral hemodynamics and renal function changes].

The relationship between the activity of the sympathetic nervous system and the systemic and peripheral hemodynamic and renal function changes and the antinatriuretic activity in a group of 30 cirrhotic patients and 8 healthy subjects (control group) was investigated. Plasma catecholamines (noradrenaline, adrenaline and dopamine), plasma renin activity, plasma aldosterone concentrations, mean arterial pressure, cardiac output, blood volume, right femoral arterial flow (RFAF) and renal function parameters were determined in all the participants. Cyclic GMP urinary excretion (cV-UGMP) was used as an indirect index of systemic nitric oxide production. The plasma concentration of noradrenaline was greater in the patients than in the control group and was directly correlated with other vasopressor and antinatriuretic systems, RFAF, cV-UGMP, the degree of hepatic failure studied by the Pugh score and was inversely correlated with creatinine clearance and urinary sodium excretion. On Cox regression analysis, only the RFAF, creatinine clearance and plasma adrenaline concentration remained independently associated with plasma noradrenaline levels. Furthermore, plasma noradrenaline was significantly higher in patients with greater hyperdynamic circulation. These results indicate that extrasplanchnic vasodilatation substantially contributes to sympathetic nervous hyperactivity which may significantly influence in the renal function changes observed in these patients.

Creatinine↗
PubMed1996

[Arterial hypertension in a patient with cardiac tamponade].

An elevated arterial pressure in cardiac tamponade, although not unusual might postpone the diagnosis of pericardial disease. We reported a case of cardiac tamponade, due to neoplastic infiltration of the pericardium, in which the diagnosis was first suspected by the presence of pulsus paradoxus. The patient presented cardiac tamponade and arterial hypertension simultaneously.

Cardiac Tamponade↗
PubMed1996

RNA binding analysis of yeast REF2 and its two-hybrid interaction with a new gene product, FIR1.

The product of the REF2 gene is required for optimal levels of endonucleolytic cleavage at the 3' ends of yeast mRNA, prior to the addition of a poly(A) tail. To test the role of the previously demonstrated nonspecific affinity of REF2 for RNA in this process, we have identified RNA binding mutants in vitro and tested them for function within the cell. One REF2 variant, with an internal deletion of 82 amino acids (269-350), displays a 10-fold reduction in RNA binding, yet still retains full levels of processing activity in vivo. Conversely, a series of carboxyl-terminal deletions that maintain full RNA binding capability have progressively decreasing activity. These results rule out a major role for the central RNA binding domain of REF2 in mRNA 3' end processing and demonstrate the importance of the carboxyl-terminal region. To ask if the stimulatory role of REF2 depends on interactions with other proteins, we used a two-hybrid screen to identify a new protein termed FIR1 (Factor Interacting with REF) encoded on chromosome V. FIR1 interacts with two independent regions of REF2, one of which (amino acids 268-345) overlaps the RNA binding domain and is dispensible for REF2 function, whereas the other (amino acids 391-533) is located within the critical carboxyl-terminus. As with REF2, FIR1 has a small but detectable role in influencing the efficiency of poly(A) site use. Yeast strains containing a disrupted FIR1 gene are slightly less efficient in the use of cryptic poly(A) sites located within the lacZ portion of an ACT1-lacZ reporter construct. Likewise, a double delta ref2, delta fir1 mutant is more defective in processing of a reporter CYC1 poly(A) site than delta ref2 alone. This synergistic response provides additional support for the interaction of FIR1 with REF2 in vivo, and suggests that a number of gene products may be involved in regulating the cleavage reaction in yeast.

Amino Acid Sequence↗
PubMed1995

A mutation in the ATP binding domain of rho alters its RNA binding properties and uncouples ATP hydrolysis from helicase activity.

The Escherichia coli mutant rho201 was originally isolated in a genetic screen for defects in rho-dependent termination. Cloning and sequencing of this gene reveals a single phenylalanine to cysteine mutation at residue 232 in the ATP binding domain of the protein. This mutation significantly alters its RNA binding properties so that it binds trp t', RNA 100-fold weaker than the wild type protein, with a Kd of approximately 1.3 nM. Rho201 binds nonspecific RNA only 3-4-fold less tightly than it binds trp t', while the wild type differential for these same RNAs is 10-20-fold. Curiously, rho201 displays increased secondary site RNA activation, with a Km for ribo(C)10 of 0.6 microM, compared to the wild type value of 3-4 microM. Although rho201 and the wild type protein hydrolyze ATP similarly with poly(C), or trp t' RNA, as cofactors, rho201 has a higher ATPase activity when activated by nonspecific RNA. Physically, rho201 displays an abnormal conformation detectable by mild trypsin digestion. Despite effective ATP hydrolysis, the rho201 mutant is a poor RNA:DNA helicase and terminates inefficiently on trp t'. The single F232C mutation thus appears to uncouple the protein's ATPase activity from its helicase function, so rho can no longer harness available energy for use in subsequent reactions.

Adenosine Triphosphate↗
PubMed1995

Analysis of E. coli rho factor: mutations affecting secondary-site interactions.

To define and differentiate primary and secondary RNA binding sites within the linear sequence of the rho protein, we investigated two mutant alleles, rho-115 and rhosuA1. They were first identified as defective in transcription termination in vivo, and later demonstrated to be defective in their interactions with RNA at the primary and secondary sites, respectively. Sequencing of rhosuA1 revealed a single lysine to glutamic acid residue change at position 352 (KE352), while rho-115 carries two mutations, glycine99 to valine (GV99) and a proline235 to histidine (PH235). Proteins carrying single mutations at each of these three positions were purified and their characteristics compared to the wild-type protein. We found both KE352 and GV99 to be defective in secondary-site RNA activation, with Km values for r(C)10 of 100 microM and approximately 650 microM, respectively, compared to the wild-type value of 4 microM. These observed secondary-site defects correlated with decreased helicase and ATPase activities, as well as a loss of transcription termination activity in vitro. By contrast, PH235 was very efficient at interacting with r(C)10 at the secondary site, with a measured Km of 0.5 microM, and displayed the characteristics of a hyperactive rho, as judged by its ATPase, helicase and termination capabilities. Our results show that mutations at three very different locations in the polypeptide can affect secondary-site activation by RNA, and that these interactions play a pivotal role in ATP hydrolysis, helicase activity and transcription termination.

Adenosine Triphosphatases↗
PubMed1995

A pre-operative mydriatic regime using a single application of tropicamide Novel Ophthalmic Delivery System and guttae phenylephrine 10%.

Tropicamide Novel Ophthalmic Delivery System (NODS) and guttae (g.) phenylephrine 10% was applied once, 2 hours before cataract surgery, as an alternative to our standard pre-operative regime of g. cyclopentolate 1% and g. phenylephrine 10% used four times before surgery. The two treatment groups were compared using a randomised, prospective, observer-masked study design. The horizontal pupil diameter was significantly smaller using the new regime but the per-operative decrease in diameter was not significantly different, suggesting that surgical miosis was not influenced by reducing the number of mydriatic applications. There was no difference in the subjective grading of the pupil, suggesting that adequate mydriasis suitable for cataract surgery was obtained using the alternative regime. No major complications were documented in relation to the use of NODS. We discuss why less intensive mydriasis is likely to be as efficacious and describe its potential advantages.

Aged↗
PubMed1994

5-azacytidine produces differential undercondensation of alpha, beta and classical human satellite DNAs.

Fluorescence in situ hybridization employing human alphoid, beta and classical satellite DNA probes was performed on 5-azacytidine treated and untreated chromosomes obtained from human lymphocytes. The individual used in this study presented a polymorphism of constitutive heterochromatin of chromosomes 1 and 9 as revealed by in situ digestion with the restriction endonuclease Alul. Neither the alphoid nor the beta satellite DNA domains were susceptible to condensation-inhibition by 5-azacytidine. Only the classical satellite localized on chromosome 9 was affected. The constitutive heterochromatin size polymorphism was shown to depend mainly on variations of the classical satellite DNA domain. Therefore, condensation-inhibition, as a phenomenon which may modify the natural folding of the chromatin fibre, regionally affects human constitutive heterochromatin and seems to be dependent on the heterochromatic family.

Azacitidine↗
PubMed1994

Assessment of Yqh translocations.

Two initially presumed Yqh translocations, one to Xp and another to 21p, were assessed by conventional banding procedures, 5-azacytidine treatment, electron microscopy, and fluorescence in situ hybridisation. While the Yqh nature of the heterochromatic block from Xp was confirmed, this was not the case with the 21ph+ variant. In conclusion, conventional banding techniques are insufficient to diagnose Y;G translocations.

Azacitidine↗
PubMed1994

An extra band within the human 9qh+ region that behaves like the surrounding constitutive heterochromatin.

An extra variant G band in a human 9qh+ region was analysed in normally condensed and 5-azacytidine undercondensed chromosomes. Fluorescence in situ hybridisation showed that specific, classical, alphoid and beta satellite DNA was not present. Nevertheless, this extra band behaves like the surrounding heterochromatin because (1) its chromatin fibres showed condensation inhibition after 5-azacytidine treatment, as confirmed by electron microscopy, and (2) it was not affected by in situ digestion with the restriction endonucleases AluI and Sau3A. These results suggest that this variant band may correspond to euchromatin that has become inactivated by a position effect.

5-Methylcytosine↗
PubMed1994

[The risk of diabetes mellitus in relatives of diabetics treated with insulin].

The objective of this study was to compare the risk of diabetes mellitus in the relatives of type 1 (defined as cases diagnosed before 40 years and beginning insulin less than two years later) and in those of type 2 diabetics, treated with insulin. A random sample of 303 patients was obtained from responders to a postal survey sent to all 2800 diabetics living in the Oporto self county and identified as users of insulin the injection pen. After selecting those who completed the questions for sex, age, dates of diabetes diagnosis and of first insulin prescription, we were left with 192 index cases. They provided data concerning sex; age, and presence of diabetes for 1370 relatives (parents, siblings, offspring and spouses). The risk of diabetes (unspecified type) in family members was significantly lower in relatives of type 1 diabetics (OR = 0.31, CI 95%:0.19-0.48, p < 0.0005). This family risk was lower when the index case was a male (OR = 0.24, CI 95%:0.12-0.47 vs OR = 0.39, CI 95%:0.21-0.74) or for female relatives (OR = 0.22, CI 95%:0.11-0.42 vs OR = 0.43, CI 95%:0.22.-0.82). After adjustment for confounders applying logistic regression to each family stratum, the risk remained significantly lower for parents (OR = 0.35, CI 95%:0.17-0.71) and siblings of type 1 diabetics compared to similar relatives of type 2 cases (OR = 0.84, CI 95%:0.06-10.6) but was not significantly different for the offspring (OR = 0.68, CI 95%:0.11-4.17) or the spouses (OR = 0.84, CI 95%:0.06-10.6).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Frequency of sister chromatid exchanges in humans at 14-16 week foetal stage and at birth.

In order to identify transplacental induced mutagenicity in humans the baseline frequency of sister chromatid exchanges (SCEs) in amniotic fluid cells (8.56 +/- 0.28 per cell) from 14 to 16-week-old foetuses as well as in peripheral blood lymphocytes (7.96 +/- 0.26 per cell) from newborns was determined. A group of twelve patients who were analysed both at 14-16 weeks gestation and at birth showed no SCE variations. These results suggest that foetal amniocytes and T lymphocytes from newborns present a similar sensitivity to the mutagenic activity of the thymidine analogue 5-bromodeoxyuridine employed in the sister chromatid differentiation.

Adult↗