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Biomedical subjects

F Wong

Publications and source records attributed to F Wong.

At least 91 records · Page 5Linked to original sources
PubMed1999

Long-term renal sodium handling in patients with cirrhosis treated with transjugular intrahepatic portosystemic shunts for refractory ascites.

PURPOSE: The long-term effects of transjugular intrahepatic portosystemic shunts on renal sodium excretion are not known. We sought to determine these long-term effects, as well as to measure the effects of a sodium load in patients who are free of ascites. SUBJECTS AND METHODS: Ten patients with cirrhosis who had been successfully treated with transjugular intrahepatic portosystemic stent shunt for refractory ascites were studied before the shunt and again at 6 and 14 months after the shunt while on a 22 mmol sodium/day diet. At 14 months they were also studied on a 200 mmol sodium/day diet for 7 days without diuretics. Renal sodium handling, central blood volume, neurohumoral factors, and hepatic function were measured. RESULTS: Sodium balance was negative at 6 months (urinary sodium excretion [mean +/- SD] 51 +/- 11 mmol/day versus 7 +/- 2 mmol/day pre-shunt; P < 0.05), was maintained at 14 months (22 +/- 4 mmol/day; P < 0.05 versus pre-shunt), and was associated with normalization of renin activity and aldosterone levels, but not norepinephrine levels, as well as significantly improved renal hemodynamic measurements. Sodium loading with 200 mmol/day resulted in weight gain associated with increased central blood volume and appropriate renal sodium handling in most but not all patients (urinary sodium excretion 188 +/- 14 mmol/day), despite persistent nonsuppressibility of sympathetic hyperactivity. CONCLUSIONS: In cirrhotic patients with refractory ascites treated with a transjugular intrahepatic portosystemic stent shunt, long-term renal sodium handling is improved. Adequate intravascular filling in ascites-free cirrhotic patients with normal portal pressure permits an improved but not normalized renal response to a sodium load, possibly due to persistently elevated sympathetic activity. Therefore, these patients should increase their sodium intake cautiously.

Adult↗
PubMed1999

Effects of ursodeoxycholic acid on systemic, renal and forearm haemodynamics and sodium homoeostasis in cirrhotic patients with refractory ascites.

Systemic arterial vasodilatation has been implicated in the pathogenesis of sodium retention in cirrhosis. Hydrophobic bile acids, which have vasodilatory actions, may be involved. Ursodeoxycholic acid, a hydrophilic bile acid, could potentially decrease systemic arterial vasodilatation, possibly due to its antioxidant effects, and improve sodium handling in cirrhosis. The effects of ursodeoxycholic acid on systemic, renal and forearm haemodynamics, liver function and renal sodium handling were assessed in vasodilated cirrhotic patients with refractory ascites treated with a transjugular intrahepatic porto-systemic shunt (TIPS). Eight cirrhotic patients with refractory ascites without TIPS placement served as controls for the sodium handling effects of ursodeoxycholic acid. From 1 month post TIPS, seven patients were studied before, after 1 month of treatment with ursodeoxycholic acid (15 mg.day-1.kg-1) and at 1 month follow-up. Lipid peroxidation products were used as indices of its antioxidant effects. Ursodeoxycholic acid caused a significant reduction in sodium excretion in both groups (P<0.05). This, in the post-TIPS patients (urinary sodium excretion: 35+/-8 mmol/day at 1 month versus 93+/-21 mmol/day at baseline, P<0.05), was due to a significant increase in sodium reabsorption proximal to the distal tubule (P<0.05), without any significant changes in systemic, renal or forearm haemodynamics, or in liver function. No significant change in lipid peroxidation products was observed. We conclude that: (i) in cirrhotic patients with refractory ascites, ursodeoxycholic acid causes sodium retention, (ii) the abnormality in sodium handling in the post-TIPS cirrhotic patients appears to be the result of a direct effect on the proximal nephron, suggesting that factors other than systemic vasodilatation also contribute to sodium retention in cirrhosis, (iii) caution should be exercised in administering ursodeoxycholic acid in cirrhotic patients with ascites.

Adult↗
PubMed1999

Role of cardiac structural and functional abnormalities in the pathogenesis of hyperdynamic circulation and renal sodium retention in cirrhosis.

The aim of this study was to assess the relationship between subtle cardiovascular abnormalities and abnormal sodium handling in cirrhosis. A total of 35 biopsy-proven patients with cirrhosis with or without ascites and 14 age-matched controls underwent two-dimensional echocardiography and radionuclide angiography for assessment of cardiac volumes, structural changes and systolic and diastolic functions under strict metabolic conditions of a sodium intake of 22 mmol/day. Cardiac output, systemic vascular resistance and pressure/volume relationship (an index of cardiac contractility) were calculated. Eight controls and 14 patients with non-ascitic cirrhosis underwent repeat volume measurements and the pressure/volume relationship was re-evaluated after consuming a diet containing 200 mmol of sodium/day for 7 days. Ascitic cirrhotic patients had significant reductions in (i) cardiac pre-load (end diastolic volume 106+/-9 ml; P<0.05 compared with controls), due to relatively thicker left ventricular wall and septum (P<0.05); (ii) afterload (systemic vascular resistance 992+/-84 dyn.s.cm(-5); P<0. 05 compared with controls) due to systemic arterial vasodilatation; and (iii) reversal of the pressure/volume relationship, indicating contractility dysfunction. Increased cardiac output (6.12+/-0.45 litres/min; P<0.05 compared with controls) was due to a significantly increased heart rate. Pre-ascitic cirrhotic patients had contractile dysfunction, which was accentuated when challenged with a dietary sodium load, associated with renal sodium retention (urinary sodium excretion 162+/-12 mmol/day, compared with 197+/-12 mmol/day in controls; P<0.05). Cardiac output was maintained, since the pre-load was normal or increased, despite a mild degree of ventricular thickening, indicating some diastolic dysfunction. We conclude that: (i) contractile dysfunction is present in cirrhosis and is aggravated by a sodium load; (ii) an increased pre-load in the pre-ascitic patients compensates for the cardiac dysfunction; and (iii) in ascitic patients, a reduced afterload, manifested as systemic arterial vasodilatation, compensates for a reduced pre-load and contractile dysfunction. Cirrhotic cardiomyopathy may well play a pathogenic role in the complications of cirrhosis.

Adult↗
PubMed1998

The cloning of GRK7, a candidate cone opsin kinase, from cone- and rod-dominant mammalian retinas.

PURPOSE: Desensitization in the rod cell of the mammalian retina is initiated when light-activated rhodopsin is phosphorylated by the G protein-coupled receptor kinase (GRK), GRK1, often referred to as rhodopsin kinase. A distinct kinase that specifically phosphorylates cone opsins in a similar manner has not been identified in mammals. To determine the existence of a cone opsin kinase, RNA from the retinas of cone- and rod-dominant mammals was analyzed by PCR. METHODS: RNA prepared from the retinas of two cone-dominant mammals, the thirteen-lined ground squirrel and the eastern chipmunk, and a rod-dominant mammal, the pig, was used to clone a new GRK family member by RT-PCR. The tissue distribution and localization of the kinase in retina were determined by Northern blot hybridization and in situ hybridization. The protein encoded by this cDNA was expressed in human embryonic kidney-293 (HEK-293) cells and compared with bovine GRK1 for its ability to phosphorylate bovine rhodopsin and to undergo autophosphorylation. RESULTS: The cDNA cloned from ground squirrel contains an open reading frame encoding a 548 amino-acid protein. Sequence analysis indicates that this protein is orthologous to GRK7 recently cloned from O. latipes, the medaka fish. Partial cDNA fragments of GRK7 were also cloned from RNA prepared from eastern chipmunk and pig retinas. In situ hybridization demonstrated widespread labeling in the photoreceptor layer of the ground squirrel retina, consistent with expression in cones. Recombinant ground squirrel GRK7 phosphorylates bovine rhodopsin in a light-dependent manner and can be autophosphorylated, similar to bovine GRK1. CONCLUSIONS: These results indicate that cone- and rod-dominant mammals both express GRK7. The presence of this kinase in cones in the ground squirrel and its ability to phosphorylate rhodopsin suggests that it could function in cone cells as a cone opsin kinase.

Amino Acid Sequence↗
PubMed1998

Lipopolysaccharide induces the antiapoptotic molecules, A1 and A20, in microvascular endothelial cells.

The effect of lipopolysaccharide (LPS) on endothelial cells is a key component of the inflammatory response seen in Gram-negative sepsis. LPS does not cause death of cultured human endothelial cells. However, when the expression of new proteins is inhibited by cycloheximide, microvascular endothelial cells in culture undergo apoptosis. This finding suggests that LPS induces apoptotic and antiapoptotic pathways, with the antiapoptotic response being dependent on the synthesis of new proteins. Concurrent activation of apoptotic and antiapoptotic pathways has previously been documented for tumor necrosis factor (TNF). In the case of TNF, the antiapoptotic signal has been attributed to at least two cytoprotective proteins: the Bcl-2 homologue, A1, and the zinc-finger protein, A20. In this study, we demonstrate that both these molecules are induced in microvascular endothelial cells by LPS. Enforced overexpression of either A1 or A20 inhibits LPS and cycloheximide-initiated apoptosis. Induction of A1 and A20 does not require synthesis of intermediary proteins, but is dependent on the presence of soluble CD14. In addition, we show that inhibition of signaling by the transcription factor, NF-kappaB, blocks accumulation of A1 and A20 mRNA. Taken together, our findings suggest that LPS directly induces expression of the cytoprotective proteins, A1 and A20, via a CD14-dependent pathway requiring activation of NF-kappaB.

Apoptosis↗
PubMed1998

Lipopolysaccharide mediates endothelial apoptosis by a FADD-dependent pathway.

Endothelial cells play a pivotal role in the inflammatory process by coordinating the recruitment of inflammatory cells to sites of tissue injury. Lipopolysaccharide (LPS) activates many of the proinflammatory and procoagulant responses of endothelial cells, and endothelial injury is thought to play a crucial role in the pathogenesis of septic shock due to Gram-negative bacteria. The receptor used by LPS to signal endothelial responses has not been identified. It is also not known how LPS induces endothelial injury/death. In this study, we demonstrate that LPS mediates endothelial apoptosis by a FADD-dependent pathway. FADD is a death domain-containing protein that binds to certain members of the tumor necrosis factor receptor family, namely TNFR1, Fas, and DR3. However, none of these receptors appear to be involved in LPS-mediated death, suggesting that LPS may utilize a novel death domain-containing protein to transduce a death signal.

Adaptor Proteins, Signal Transducing↗
PubMed1998

A tacrolimus-related immunosuppressant with biochemical properties distinct from those of tacrolimus.

BACKGROUND: Tacrolimus (FK506) is an immunosuppressive drug 50-100 times more potent than cyclosporine (CsA), the current mainstay of organ transplant rejection therapy. Despite being chemically unrelated, CsA and tacrolimus exert their immunosuppressive effects through the inhibition of calcineurin (CaN), a critical signaling molecule during T-lymphocyte activation. Although numerous clinical studies have proven the therapeutic efficacy of drugs within this class, tacrolimus and CsA also have a strikingly similar profile of unwanted side effects. METHOD: Our objective has been to identify a less toxic immunosuppressant through the modification of ascomycin (FK520). Quantitative in vitro immunosuppression and toxicity assays have demonstrated (see the accompanying article, p. 18) that we achieved our goal with L-732,531 (indolyl-ascomycin; indolyl-ASC), a 32-O-(1-hydroxyethylindol-5-yl) ascomycin derivative with an improved therapeutic index relative to tacrolimus. RESULTS: We report that the attributes of indolyl-ASC may result from its distinctive biochemical properties. In contrast to tacrolimus, indolyl-ASC binds poorly to FK506 binding protein 12 (FKBP12), the major cytosolic receptor for tacrolimus and related compounds. However, the stability of the interaction between the FKBP12-indolyl-ASC complex and CaN is much greater than that of the FKBP12-tacrolimus complex. These distinguishing properties of indolyl-ASC result in the potent inhibition of CaN within T lymphocytes but may lower the accumulation of the drug at sites of toxicity. CONCLUSIONS: Indolyl-ASC may define those properties needed to increase the therapeutic efficacy of a macrolactam immunoregulant for treating both human autoimmune disease and organ transplant rejection.

Base Sequence↗
PubMed1998

A tacrolimus-related immunosuppressant with reduced toxicity.

BACKGROUND: Tacrolimus (FK506) has potent immunosuppressive properties reflecting its ability to block the transcription of lymphokine genes in activated T cells through formation of a complex with FK506 binding protein-12, which inhibits the phosphatase activity of calcineurin. The clinical usefulness of tacrolimus is limited, however, by severe adverse effects, including neurotoxicity and nephrotoxicity. Although this toxicity, like immunosuppression, appears mechanistically related to the calcineurin inhibitory action of the drug, a large chemistry effort has been devoted to search for tacrolimus analogs with reduced toxicity but preserved immunosuppressive activity that might have enhanced therapeutic utility. METHODS: Here, we report on the identification of such an analog, which was synthetically derived from ascomycin (ASC), the C21 ethyl analog of tacrolimus, by introducing an indole group at the C32 position. The profile of biological activity of indolyl-ASC was characterized in rodent models of immunosuppression and toxicity. RESULTS: Indolyl-ASC was found to exhibit an immunosuppressive potency equivalent to that of tacrolimus in T-cell activation in vitro and in murine transplant models, even though indolyl-ASC bound about 10 times less to intracellular FK506 binding protein-12 than tacrolimus or ASC. Further evaluation of indolyl-ASC revealed that it is threefold less potent than tacrolimus in inducing hypothermia, a response that may reflect neurotoxicity, and in causing gastrointestinal transit alterations in mice. Moreover, indolyl-ASC was at least twofold less nephrotoxic than tacrolimus upon 3-week oral treatment in rats. CONCLUSIONS: Altogether, these data indicate a modest but definite improvement in the therapeutic index for indolyl-ASC compared with tacrolimus in rodent models.

Animals↗
PubMed1998

Papillary serous and clear cell carcinoma limited to endometrial curettings in FIGO stage 1a and 1b endometrial adenocarcinoma: treatment implications.

OBJECTIVE: The aim of this study was to review the significance of papillary serous and clear cell carcinoma in Stage 1a and 1b adenocarcinoma of the endometrium where this histological subtype is confined to the endometrial curettings and is absent in the hysterectomy specimen. METHODS AND MATERIALS: Three hundred twenty patients with Stage 1a or 1b adenocarcinoma of the endometrium without lymphovascular space invasion or evidence of FIGO Grade 3 histology demonstrated in the hysterectomy specimen were referred to the British Columbia Cancer Agency, Vancouver Clinic, between January 1992 and July 1995. These charts were retrospectively reviewed. RESULTS: On pathology review, eight patients were found to have evidence of papillary serous or clear cell carcinoma confined to the uterine curettings. Five patients also had Grade 1 or 2 endometrioid adenocarcinoma without lymphovascular space involvement seen in the hysterectomy specimen. All patients were managed expectantly. None of these 8 have recurred with a median follow-up of 3 years. CONCLUSION: A clinical dilemma arises when there is evidence of papillary serous or clear cell carcinoma limited to the endometrial curettings where there is no associated adverse pathological features seen in the hysterectomy specimen. In our series of patients treated expectantly, it appears that a small bulk of aggressive disease seen only in the curettage specimen does not adversely impact disease-free survival.

Adenocarcinoma↗
PubMed1998

Role of indium-111 labelled platelet scintigraphy in the management of thrombocytopenic patients with malignant neoplasms.

This study was done to investigate the role of indium-111 labelled platelet scintigraphy in the treatment of thrombocytopenia in patients with malignant neoplasms. The study involved 20 consecutive patients with thrombocytopenia associated with malignant neoplasms of hematological disorders and without evidence of underproduction of megakaryocytes due to chemotherapy or bone marrow infiltration by the malignancy. Splenic sequestration of platelets was evaluated by measuring splenic uptake of 111In-labelled platelets, and findings were correlated with the outcome of splenectomy and medication. Of the 20 patients, 13 had splenic sequestration of platelets. Seven of the 13 patients underwent splenectomy; six of these seven patients experienced a complete response. The other six patients received medication only and showed no response. Of the seven patients without splenic sequestration of platelets, five received medication, and four of them responded to it. 111In-labelled platelet scintigraphy has a role in selecting appropriate therapy and predicting its efficacy in patients with thrombocytopenia associated with malignant neoplasms.

Adult↗
PubMed1998

The renal sympathetic and renin-angiotensin response to lower body negative pressure in well-compensated cirrhosis.

BACKGROUND & AIMS: Certain antinatriuretic hormonal systems may be involved in the subclinical sodium handling abnormality in preascitic cirrhosis. The aims of this study were to determine the following in preascitic cirrhosis: (1) basal activity of the renal sympathetic and renin-angiotensin systems and (2) the relationship between the response of these systems to lower body negative pressure and sodium excretion. METHODS: Seven preascitic cirrhotic patients and 9 age- and sex-matched controls were studied on a 150 mmol sodium per day diet. Systemic and renal hemodynamics, renal neurohormonal secretion rates, and sodium excretion were assessed before, during increasing levels of, and after lower body negative pressure, each for 30 minutes. RESULTS: Both groups responded with a significant decrease in central venous pressure (P < 0.01) that remained higher in the cirrhotics than in the controls throughout the study. Cirrhotics showed significant increases compared with controls in renal renin and angiotensin II secretion rates at -20 mm Hg of lower body negative pressure, which was associated with significant renal sodium retention (96 +/- 17 micromol/min vs. 218 +/- 21 micromol/min at baseline, P < 0.05), but there was no change in renal sympathetic activity. CONCLUSIONS: In preascitic cirrhosis, sodium retention occurs in response to lower body negative pressure, which was associated with increased renal renin-angiotensin activity. Stimulation of the intrarenal renin-angiotensin system may be the initial renal pathophysiological change causing sodium retention in cirrhosis.

Adaptation, Physiological↗
PubMed1998

Nonunion of pelvic fractures.

Nonunion of the pelvic bones is uncommon. It may be under-diagnosed because of the difficulty in visualization of the fracture and interpretation with conventional radiography. The authors report four cases of nonunion involving the pelvic bones. Nonunion of the posterior ilium was occult in two patients and was not apparent on routine radiographs. The two patients with nonunion of the anterior iliac crest had major displacement caused by muscle pull. Pain on weight-bearing and awkward gait were common symptoms. All patients required surgical management for symptomatic relief.

Accidents, Traffic↗
PubMed1998

Fatal myocardial infarction associated with bromocriptine for postpartum lactation suppression.

Bromocriptine (Parlodel) has attracted widespread controversy for its use for postpartum lactation suppression because of recent reports of cerebral and cardiovascular complications. This case describes a maternal death in which bromocriptine therapy may have triggered myocardial infarction in a patient with asymptomatic coronary artery disease. We suggest its use with caution, especially in patients with identifiable risk factors of coronary artery disease or arteriovascular disease.

Adult↗