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P Silva

Publications and source records attributed to P Silva.

At least 37 records · Page 2Linked to original sources
PubMed2001

Respiratory alkalosis and associated electrolytes in long-term ventilator dependent persons with tetraplegia.

STUDY DESIGN: A pilot case control study of the acid-base and electrolyte status in 30 long-term ventilator-dependent (LTVD) and 30 self ventilating persons with tetraplegia. OBJECTIVES: To assess the extent of respiratory alkalosis and screen for associated hypokalaemia, hypomagnesaemia and/or hypophosphataemia. SETTING: Medically stable persons with tetraplegia under the long-term care of the Southport Spinal Injuries Centre, England. METHODS: Blood gases and electrolytes were sampled from 30 control patients with tetraplegia and from 30 patients having been LTVD for more than 12 months. RESULTS: All the blood gas measurements in the LTVD group lay outside both the reference range and the 95% confidence intervals (CI) of the control group: pH 7.46 (0.06); PCO(2) 3.46 (1.1) kPa; bicarbonate 18.3 (3.8) and base excess -3.2 (2.8) mmol/l; PO(2) 13.8 (2.8) kPa (means and standard deviations). The serum potassium, magnesium, phosphate, and sodium means lay within the reference ranges but the potassium, phosphate and calcium were at or below the 95% CI of the control values. One patient on part-time ventilatory support having less bicarbonate compensation had low serum electrolytes during ventilation. CONCLUSION: There was no evidence of biochemical jeopardy from long-term mechanical hyperventilation although acutely administered hyperventilation has the potential to cause falls in serum potassium, magnesium and phosphate and so caution should be exercised in part-time ventilated persons. The full range of electrolytes should be assayed during stabilisation in LTVD and periodically thereafter. Hyperventilation helps to maintain good oxygenation in LTVD persons with paralysis and normal lungs. SPONSORSHIP: None.

Adolescent↗
PubMed2001

Auxiliary functions in photosynthesis: the role of the FtsH protease.

Oxygenic photosynthesis can be described effectively by using two long-standing models: the Z-scheme and the chemiosmotic hypothesis. However, these models do not reveal the dynamic nature of the thylakoid membrane and the four major complexes that it binds. The composition of the photosynthetic apparatus is continually changing in response to a range of environmental stimuli. In addition, many photosynthetic components have some of the highest turnover rates in Nature. Changes in composition and turnover of photosynthetic components require the degradation of existing and damaged polypeptides and the resynthesis and co-ordinated assembly of new polypeptides and their associated cofactors. This is achieved by several auxiliary functions, including proteolysis, protein targeting and the action of molecular chaperones. Some of the components involved in these functions, such as translocons, chaperones and proteases, have been identified but many of the auxiliary functions of photosynthesis remain uncharacterized. Among the proteases known to be associated with the thylakoids is the zinc metalloprotease FtsH, which might also act as a chaperone. Here we provide an overview of the thylakoid FtsH protease and discuss its role in the maintenance and assembly of the photosynthetic apparatus.

ATP-Dependent Proteases↗
PubMed2001

Maspin expression in myoepithelial tumors of the breast.

Maspin is a mammary inhibitory serine protease that harbors tumor suppressor, tumor invasiveness-suppression and anti-angiogenic properties. It is consistently expressed by mammary myoepithelial cells. However, to the best of our knowledge, no assessment of maspin immunoexpression in myoepithelial cell lesions of the breast has been reported so far. We evaluated maspin expression by immunohistochemistry in five normal breast samples, one sclerosing papilloma (SP), one tubular adenomyoepithelioma (TA), one adenoid cystic carcinoma (ACC), one epithelial-myoepithelial carcinoma of the breast (EMC), and one malignant adenomyoepithelioma (MA). We also compared maspin expression with the expression of other classic myoepithelial markers in myoepithelial and secretory cells, as well as in stromal components of all samples. In normal breast samples, maspin expression was restricted to myoepithelial cell nuclei and cytoplasm. A strong nuclear and cytoplasmic maspin immunoreactivity was observed in the myoepithelial components of SP, TA, ACC, and EMC. In MA, maspin immunoreactivity was confined to the nucleus and cytoplasm of the cells lining tubular-like and papillary structures, as well as in squamous cells. The myoepithelial nature of maspin-positive cells was further confirmed by classic myoepithelial cell markers, including alpha-actin and S-100 protein. No stromal, neural or vascular components were immunostained by maspin. In spite of the small number of myoepithelial lesions here assessed, we suggest that maspin should be used in surgical pathology practice either as an additional marker in immunohistochemical panels defining a myoepithelial histogenesis in odd breast neoplasms, or in those cases in which the definite diagnosis relies on the myoepithelial cell layer identification.

Adenocarcinoma↗
PubMed2001

[Causative agents of bloodstream infections in children with neoplasm, in 5 hospitals of Santiago (1994-1998)].

BACKGROUND: Pediatric patients in treatment for cancer can have fatal bacterial infections. Thus, in the presence of fever or other signs infection, antimicrobials have to be prescribed empirically. AIM: To know the causative agents of bacteremia in children with cancer, their changes with time and between different hospitals and their patterns of susceptibility. MATERIAL AND METHODS: We reviewed the blood cultores of children with cancer in five hospitals of Santiago, from 1994 at 1998. RESULTS: During the study period, 707 agents were isolated. The most frequently isolated species or genus were coagulase negative Staphylococcus (43%), Staphylococcus aureus (16%), Escherichia coli (9%), Klebsiella spp. (8%), Pseudomonas spp. (5%) and Candida spp. (4%). Coagulase negative Staphylococcus was 55% resistant to meticilin and S. aureus was 44% resistant. Enterobacteriaceae had 15% resistance to gentamicin and amikacin, 2% to imipenem, 26% to ceftriaxone, 21% to cefotaxime and 20% to ceftazidime. Among non fermenting agents resistance was 6% for imipenem, 9% for amikacin 10% for ciprofloxacin, 19% for ceftazidime and 22% for cefoperazone. The resistance of Streptococcus spp. (non pneumoniae) to penicillin reached 50% and that of Enterococcus spp. was of 33%. CONCLUSIONS: Treatment for pediatric patients with cancer must be modified and new guidelines including more active medications for patients at risk for bacteremia, should be devised.

Adolescent↗
PubMed2000

Adjunctive thrombus aspiration and mechanical protection from distal embolization in primary percutaneous intervention for acute myocardial infarction.

Primary percutaneous intervention for acute occlusion of a native coronary artery may be complicated by distal embolization of plaque or thrombotic debris, with infarct extension. We tested the clinical application of a new therapeutic strategy combining maximal antiplatelet therapy, with glycoprotein IIb/IIIa inhibition, and adjunctive mechanical protection from distal embolization and direct aspiration of thrombus with a new balloon and catheter system (PercuSurgetrade mark). Successful aspiration of thrombus could be obtained in 7 out of 8 attempted procedures, with inability to negotiate the angulated take-off of the circumflex coronary artery in one patient. The current mechanical characteristics of the device, primarily developed for use in larger saphenous vein grafts, and certain caveats and limitations are discussed. New dedicated systems should be available in the near future for the native coronary circulation. Excellent immediate angiographic results were obtained in all treated patients, without evidence of loss of distal branches and no intraprocedural complications.

Abciximab↗
PubMed1999

Adenotonsillectomy in the very young patient: cost analysis of two methods of postoperative care.

Postoperative management of the patient younger than 36 months undergoing adenotonsillectomy has been the subject of many debates. Concerns for early postoperative complications such as airway obstruction, emesis, dehydration, and hemorrhage have led many physicians to consider overnight hospitalization following adenotonsillectomy in very young children. Trends in health care management have had increasing focus on cost effective means of treating patients to limit unnecessary expenditure on the part of the patient, physician, and hospital facility. The purpose of this retrospective review was to analyze two methods of early postoperative management in children less than 36 months old undergoing adenotonsillectomy at the Children's Hospital, San Diego from 1992 to 1997. Three hundred and seven cases were reviewed. Same-day discharge was compared with overnight inpatient observation based on the cost analysis of these two methods of postoperative care. Postoperative care was based on length of stay in the recovery room and as an inpatient. Expense of postoperative care was based on cost calculation for the recovery room and overnight hospitalization. Of the 307 patients, 194 went home the day of surgery and 113 were observed overnight in the hospital. Average hospital cost was higher in the outpatient group than in the inpatient group (P < 0.001). This difference reflects longer recovery room stay (350 min) in the outpatient group compared to the inpatient group (108 min) (P < 0.001). Outpatient adenotonsillectomy in the patient under 36 months may be safe; however, prolonged recovery room stays may actually make outpatient surgery less cost-effective than overnight admission. Recovery room costs are significantly higher per unit time than costs of inpatient hospitalization. Further investigation of cost-effective outpatient observation units may improve cost containment in the outpatient surgical setting.

Adenoidectomy↗
PubMed1999

Mode of activation of salt secretion by C-type natriuretic peptide in the shark rectal gland.

We studied the modes of activation of the salt-secreting rectal gland of the spiny dogfish, Squalus acanthias, by the native cardiac peptide CNP. The stimulatory action of CNP in isolated perfused glands is inhibited by 10 mM procaine, presumably by blocking release of vasoactive intestinal peptide (VIP) from nerves. Procaine reduces the slope of the dose-response curve of human CNP and that of shark CNP (each P < 0.0001). CNP increases short-circuit current in cultured rectal gland cells from 4.8 +/- 1.6 to 27.0 +/- 7.8 microA/cm2. It also stimulates the secretion of chloride in isolated perfused glands in the presence of 10 mM procaine from 72 +/- 31 to 652 +/- 173 microeq. h(-1). g(-1). These results suggest that CNP has a direct cellular action not mediated by the neural release of VIP. The residual stimulation of perfused glands in the presence of procaine was almost completely inhibited by staurosporine [10 nM; an inhibitor of protein kinase C (PKC)] from 652 +/- 173 to 237 +/- 61 microeq. h(-1). g(-1). Although CNP stimulates guanylyl cyclase in shark rectal gland, chloride secretion of perfused glands was not elicited by 8-bromoadenosine-cGMP (8-BrcGMP) alone nor by the activator of PKC phorbol ester. The combination of PKC activation and 8-BrcGMP infusion, however, stimulated chloride secretion in perfused glands from 94 +/- 30 to 506 +/- 61 microeq. h(-1). g(-1), a level comparable to that observed in glands blocked with procaine. Several parallel pathways appear to be synergistic in activating chloride secretion stimulated by CNP in the rectal gland.

Animals↗
PubMed1998

Inhibition by the anti-mitotic drug doxorubicin of platelet-activating-factor-induced late eosinophil accumulation in rats.

Platelet-activating factor (PAF) has been shown, in the rat model of pleural inflammation, to induce the generation of an intermediate proteic factor able to cause eosinophil proliferation in vitro. This study was undertaken to investigate the effect of the anti-mitotic compound doxorubicin on PAF-induced eosinophilia in rats, in order to evaluate the contribution of local cell proliferation to this phenomenon. The late eosinophil infiltration caused by another chemoattractant leukotriene B4 was used for comparison. We observed that local treatment with doxorubicin (20 and 40 microg/cavity), given 6 h after PAF (1 microg/cavity), suppressed the eosinophil accumulation within 24 h, whilst only the higher dose was effective when the drug was given 12 h post-PAF. An effect on chemotaxis was ruled out, since local doxorubicin (40 microg/cavity) failed to modify the eosinophil migration noted 24 h after leukotriene B4 (0.5 microg/cavity) and the neutrophil/eosinophil infiltration noted at 6 h after PAF injection. Transfer of the pleural fluids collected 6 h after PAF from donors to recipient rats caused significant eosinophil accumulation in the recipient rats, an effect which was inhibited by the co-administration of doxorubicin (40 microg/cavity). No inhibitory effect was noted when the drug was given 6 h after the pleural fluids were transferred. We also found no change in the number of blood or bone marrow eosinophils after PAF stimulation. We conclude that doxorubicin selectively impaired the late eosinophil accumulation triggered by PAF in the pleural cavity of rats, clearly indicating that local cell proliferation seems to contribute to the development of this inflammatory response.

Animals↗
PubMed1998

Whole blood serotonin relates to violence in an epidemiological study.

BACKGROUND: Clinical and animal studies suggest that brain serotonergic systems may regulate aggressive behavior; however, the serotonin/violence hypothesis has not been assessed at the epidemiological level. For study of an epidemiological sample we examined blood serotonin, because certain physiological and behavioral findings suggested that it might serve as an analog marker for serotonergic function. METHODS: Whole blood serotonin was measured in a representative birth cohort of 781 21-year-old women (47%) and men (53%). Violence was measured using cumulative court conviction records and participants' self-reports. Potential intervening factors addressed were: gender, age, diurnal variation, diet, psychiatric medications, illicit drug history, season of phlebotomy, plasma tryptophan, platelet count, body mass, suicide attempts, psychiatric diagnoses, alcohol, tobacco, socioeconomic status, IQ, and overall criminal offending. RESULTS: Whole blood serotonin related to violence among men but not women. Violent men's mean blood serotonin level was 0.48 SD above the male population norm and 0.56 SD above the mean of nonviolent men. The finding was specific to violence, as opposed to general crime, and it was robust across two different methods of measuring violence. Together, the intervening variables accounted for 25% of the relation between blood serotonin and violence. CONCLUSIONS: To our knowledge, this is the first demonstration that an index of serotonergic function is related to violence in the general population.

Adult↗
PubMed1998

First sexual intercourse: age, coercion, and later regrets reported by a birth cohort.

OBJECTIVES: To investigate how age at first sexual intercourse is related to the reported circumstances and to determine how these corresponded to views in early adulthood about its timing. DESIGN: Cross sectional study within a birth cohort using a questionnaire presented by computer. SETTING: Dunedin, New Zealand in 1993-4. SUBJECTS: 477 men and 458 women enrolled in the Dunedin Multidisciplinary Health and Development Study, comprising 92% of survivors of the cohort. RESULTS: The median age at first intercourse was 17 years for men and 16 years for women. Only one man (0.2%) but 30 (7%) women reported being forced to have intercourse on the first occasion. For women, there were increasing rates of coercion with younger age at first intercourse. More men than women reported that they and their partner were equally willing (77% (316/413) v 53% (222/419)). Mutual willingness of both partners was greater for those who reported that it was also the first time for their partner. Timing of first intercourse was considered about right by 49% (200/411) of men and 38% (148/388) of women. Many women (54% (211/388) reported that they should have waited longer, and this rose to 70% (90/129) for women reporting intercourse before age 16. CONCLUSIONS: Most women regretted having sexual intercourse before age 16. First intercourse at younger ages is associated with risks that are shared unequally between men and women. This information is important to young people themselves.

Adult↗
PubMed1998

Combined liver-kidney transplantation in patients with cirrhosis and renal failure: effect of a positive cross-match and benefits of combined transplantation.

Patients with renal failure after liver transplantation have a particularly poor prognosis. Therefore, in the setting of end-stage renal disease requiring dialysis or severe renal insufficiency that will not improve after liver replacement, combined liver-kidney transplantation (LKT) is the preferred approach. We have adopted a policy of LKT in patients with end-stage liver disease and renal insufficiency undergoing dialysis or with a creatinine clearance less than 35 mL/min and evidence of chronic renal dysfunction. Since 1991, we have performed 208 orthotopic liver transplantations. Fourteen patients (8%) have undergone combined LKT, including 6 patients undergoing hemodialysis. Cytotoxic cross-matches (modified Amos technique and antihuman globulin method) were performed on 13 of 14 patients and were positive in 3 patients. Two patients died less than 4 months after LKT and 12 patients are alive and well. Graft survival censored for patient death was 100% for liver allografts and 93% for renal allografts, with a mean follow-up of 39 +/- 24 months. The most recent serum creatinine level in the patients with the 11 functioning grafts was 1.1 +/- 0.6 mg/dL. Biopsy-proven acute rejection occurred in 50% of simultaneous liver allografts. By contrast, only a single episode (6%) of renal allograft dysfunction was attributable to acute rejection. All rejection episodes occurred in the first 90 days after transplantation and were steroid sensitive. Three of 14 combined procedures were performed in the setting of a positive cytotoxic cross-match. In 2 recent patients, the results were confirmed by positive cross-matches to the donor's T and B cells by flow cytometry. Flow cytometric cross-matches reverted to negative 1 hour after liver transplantation and several hours before the administration of antithymocyte globulin. The cross-matches remained negative on postoperative days 1 and 7. Presently, all 3 patients with a positive cross-match enjoy normal hepatic and renal function at 631, 706, and 2275 days follow-up. Renal scans were performed in 4 LKT recipients not previously undergoing hemodialysis and indicated varying and unpredictable degrees of function in the native and transplanted kidneys. In conclusion, combined LKT can be performed safely and is associated with a low rate of acute rejection, even in the setting of a positive cross-match. Predicting which patients with renal insufficiency will benefit from LKT remains challenging; however, these results suggest that LKT should be encouraged in patients with evidence of irreversible renal insufficiency who require liver transplantation.

Adult↗
PubMed1998

Messenger ribonucleic acid encoding monocyte chemoattractant protein-1 is expressed by the ovine corpus luteum in response to prostaglandin F2alpha.

To investigate expression of monocyte chemoattractant protein-1 (MCP-1) in the ovine corpus luteum, a partial cDNA was produced by reverse transcription-polymerase chain reaction. This cDNA was 89% identical to that reported for bovine MCP-1 mRNA. In experiment 1, steady-state concentrations of mRNA encoding MCP-1 were measured in pools of luteal tissue collected on Days 3, 6, 9, 12, and 15 of the estrous cycle (estrus = O; n = 4/day). There were no differences in mRNA concentrations for MCP-1 among any of the days studied (p = 0.43). In experiment 2, midluteal-phase corpora lutea were collected from ewes at 0 (untreated), 2, 4, 8, and 16 h after administration of a luteolytic dose of prostaglandin F2alpha (PGF2alpha; n = 4/time point). Concentrations of MCP-1 mRNA were undetectable in untreated controls, were detectable at 2 h post-treatment, had increased 4 and 8 h after administration of PGF2alpha when compared to those at 2 h (p < 0.05), and were decreased 16 h after administration of PGF2alpha when compared to those at 4 h (p < 0.05). In situ hybridization for MCP-1 mRNA combined with immunocytochemical labeling of tissue inhibitor of metalloproteinase-1 (TIMP-1) in large luteal cells was used to determine whether the steroidogenic cells that have PGF2alpha receptors express MCP-1 mRNA in response to PGF2alpha. Messenger RNA encoding MCP-1 and TIMP-1 were not colocalized, indicating that MCP-1 was not expressed by large steroidogenic luteal cells during luteolysis.

Animals↗
PubMed1997

Transport mechanisms that mediate the secretion of chloride by the rectal gland of Squalus acanthias.

The rectal gland of Squalus acanthias secretes chloride by a mechanism that has been termed "secondary active transport" because it depends on the activity of Na-K-ATPase. As currently described, chloride enters the cell across the basolateral cell membrane via the 2 chloride: sodium: potassium cotransporter. The energy for this electroneutral uphill movement of chloride and potassium is provided by the gradient for sodium directed into the cell. Present in the basolateral cell membrane is Na-K-ATPase that maintains the gradient for sodium. A potassium conductance, present as well in the basolateral cell membrane, recirculates the potassium. Chloride exits the cell across the luminal membrane via CFTR, the chloride conductance. This mechanism is widely distributed throughout vertebrates. This report reviews the experimental observations that led to the current definition of the mechanism of chloride transport in the rectal gland.

Animals↗
PubMed1997

The (in)stability of adolescent fears.

This study examined change in different types of fear in a longitudinal study of a birth cohort from age 13-15 yr. When viewed cross-sectionally there were few differences in the frequency and content of fears reported at these ages with the exception of an increase in social fears at age 15. When viewed longitudinally, however, few adolescents who reported fears at age 13 continued to report fears 2 yr later. Implications for developmental theories of fear and phobia are discussed.

Adolescent↗
PubMed1997

Good teeth, bad teeth and fear of the dentist.

Studies of dental fear and oral disease suggest that conditioning processes are important in the acquisition of dental fear. At this time, however, definitive conclusions are premature as all research on the etiology of dental fear has been retrospective in design, with most confined to analogue or clinic samples. This study redressed these limitations by prospectively investigating the relationship between oral health (i.e. caries experience) at age 5 and 15 yr and the report of dental fear at age 18 in a large, unselected birth cohort. Caries experience at age 5 was not related to the development of dental fear in late adolescence. In contrast, caries experience at age 15 was significantly, and specifically, related to the report of dental fear at age 18. A ratio of caries severity at age 15, indicating the extent of multi-surface involvement, was inversely related to dental fear at age 18. This intriguing finding suggests that relatively brief dental treatment occasioned by low levels of dental disease may result in the incubation of dental fear in some individuals and that longer episodes of treatment may facilitate fear habituation. Theoretical and practical implications of these findings are discussed.

Adolescent↗
PubMed1997

Role of guanylyl cyclase receptors for CNP in salt secretion by shark rectal gland.

The role of C-type natriuretic peptide (CNP) and its guanylyl cyclase-linked receptors in mediating salt secretion by the rectal gland of the spiny dogfish shark (Squalus acanthias) was investigated using HS-142-1, a competitive inhibitor of the binding of natriuretic peptides to their guanylyl cyclase receptors. CNP binds to receptors and activates guanylyl cyclase in rectal gland membranes in a way that is inhibited by HS-142-1. Guanylyl cyclase activation in rectal gland membranes is far more sensitive to CNP than to atrial natriuretic peptide, whereas the reverse is true for membranes derived from mammalian (rabbit) renal collecting duct cells. HS-142-1 inhibited the stimulatory effect of CNP on ouabain-inhibitable oxygen consumption by rectal gland tubules. In explanted rectal glands continuously perfused with blood from intact donor sharks, HS-142-1 inhibited the increase in salt secretion normally provoked by infusing isotonic saline solutions into the donor animal. These results strongly support the view that CNP released into the systemic circulation in response to volume expansion mediates the secretion of chloride by the rectal gland via receptors linked to guanylyl cyclase.

Adenylyl Cyclases↗
PubMed1997

Impaired potassium-stimulated aldosterone production: a possible explanation for normokalemic glucocorticoid-remediable aldosteronism.

Unlike other forms of primary aldosteronism, recent prospective studies have paradoxically revealed that glucocorticoid-remediable aldosteronism (GRA) is usually characterized by normal potassium (K+) levels. To evaluate this paradox we studied 10 GRA subjects and 14 healthy controls in two protocols: 1) the renal K+ excretory response to acute oral administration of 50 mmol K+ chloride and to fludrocortisone, 0.2 mg p.o. q12 h x 4 doses; and 2) the aldosterone response to administration of 50 mmol K+ chloride. The K+ excretion rate (KER) in GRA subjects (n = 6) at baseline (45.6 +/- 8.3 microEq/min), after K+ (134 +/- 34.2 microEq/min), and after fludrocortisone (100 +/- 35.0 microEq/min) was not significantly different than that seen in the control (n = 8) subjects (54.9 +/- 19.0, 154 +/- 35.5, 112 +/- 45.8 microEq/min, respectively). Thus the renal kaliuretic response to K+ ingestion and exogenous mineralocorticoid is normal in GRA. Serum aldosterone increased from 5.0 +/- 3.8 at baseline to a maximum of 13.1 +/- 6.6 ng/dL 60 min after K+ ingestion in control subjects (n = 7), but failed to increase in GRA subjects (n = 14), going from 8.7 +/- 3.8 (baseline) to 8.8 +/- 5.4 ng/dL at 60 min (P = 0.004 vs. control). The blunted aldosterone response to K+ in GRA in association with the sharp diurnal decline in aldosterone in this ACTH-regulated syndrome probably results in a milder degree of hyperaldosteronism compared with other forms of primary aldosteronism, thereby producing volume expansion with minimal renal K+ wasting.

Adult↗