Biomedical subjects
F Wong
Publications and source records attributed to F Wong.
Hyperinsulinemia in preascitic cirrhosis: effects on systemic and renal hemodynamics, sodium homeostasis, forearm blood flow, and sympathetic nervous activity.
Insulin has been shown to be vasodilatory and antinatriuretic and to stimulate sympathetic nervous activity independent of hypoglycemia in healthy normal subjects. It is hypothesized that hyperinsulinemia, which is commonly observed in cirrhosis, may in part be responsible for the systemic vasodilatation, sympathetic activation, and sodium retention in these patients. The aims of this study, in preascitic cirrhotics, were as follows: (1) to document baseline hyperinsulinemia and its effects on sodium handling, forearm and renal circulations, and sympathetic nervous activity; (2) to determine if pharmacological increases in plasma insulin levels would result in an exaggeration of these physiological effects. Seven male, nonobese, well-compensated, preascitic cirrhotic patients were studied, after being maintained on a 150 mmol sodium per day diet for 7 days, firstly at baseline level, followed by increasing doses of insulin from 10 to 1,200 mU/m2/min using the euglycemic clamp technique. Systemic and renal hemodynamics, urinary sodium excretion, plasma norepinephrine, and forearm blood flow (FBF) were measured at the end of baseline and each hyperinsulinemic period. Baseline measurements in the cirrhotics, when compared with our laboratory standards obtained from a comparable group of male healthy normals, showed significant hyperinsulinemia (P=.01), associated with significantly higher FBF (P=.02), and glomerular filtration rate (GFR) (P=.02), as well as significantly reduced urinary volume (P=.04) and fractional excretion of sodium (P=.04). Insulin infusions in the cirrhotics produced no further sodium retention, but further forearm vasodilatation occurred at doses > or = 10 mU/m2/min. In contrast, there was no further renal vasodilatation except at very high pharmacological levels of insulin together with an unchanged GFR, natriuresis, and diuresis. Hyperinsulinemia produced no significant effects on the sympathetic nervous activity. In conclusion, these results suggest that hyperinsulinemia may be implicated in the glomerular hyperfiltration and sodium retaining tendency of preascitic cirrhotic patients with glucose intolerance. The ability of the kidneys to escape from the sodium retaining effects may serve as an in-built physiological regulatory mechanism on sodium homeostasis.
The effect of posture on central blood volume in patients with preascitic cirrhosis on a sodium-restricted diet.
The status of the central blood volume in cirrhosis is controversial. A combination of sodium restriction and upright posture, which redistributes intravascular volume to dependent parts of the body should further aggravate a contracted central blood volume reduction. The aim of this study was to determine the effect of upright posture and sodium restriction on central blood volume (CBV) in preascitic cirrhotic patients, compared with controls. Eight male, preascitic, alcoholic cirrhotic subjects and eight healthy male controls were studied while on a 20-mmol/d sodium diet. Measurements of CBV by radionuclide angiography, and neurohumoral factors were performed on day 7 in both supine and erect positions and cardiac output and systemic vascular resistance (SVR) was calculated. Sodium restriction resulted in less weight loss in the cirrhotic patients (P = .03), with significantly lower plasma renin activity (P = .001). Similar central blood volumes and systemic hemodynamics were observed in both groups in the supine posture. In contrast to the cirrhotic patients, in the control subjects, upright posture resulted in a significant reduction in cardiac output (P = .002) and increase in SVR (P = .005), associated with a decrease in all blood volumes which were significantly less than in the cirrhotic patients. Mean arterial pressure was maintained in both groups in both postures. In conclusion, with sodium restriction, preascitic cirrhotic patients have less intravascular volume contraction than control patients. Erect posture results in redistribution of this relatively expanded intravascular volume to the CBV. Therefore, a low-sodium diet can be safely administered in preascitic cirrhotic patients.
Overexpression of Bcl-2 and mutations in p53 and K-ras in resected human non-small cell lung cancers.
We investigated expression of Bcl-2, mutations in p53, and K-ras oncogene in 51 resected human non-small cell lung cancers. The studies were designed to test for the possibility of cooperativity between these oncogenes and p53 in the pathogenesis of lung cancer. An inverse relationship was found between expression of Bcl-2 and mutant p53 by immunohistochemistry (P < 0.01; Fisher exact test), suggesting that either Bcl-2 overexpression or mutations in p53 may fulfill a critical function in the pathogenesis of human non-small cell lung cancers. Tumors that harbored K-ras codon 12 mutations seldom had p53 mutations or overexpressed Bcl-2. Statistical analysis of these data showed that mutations in p53 and K-ras or overexpression of Bcl-2 and mutations in K-ras occurred at a frequency that could be explained only by chance [P > 0.1 in each case (Fisher exact tests)]. This suggests that cooperativity between mutant K-ras and mutant p53 or mutant K-ras and overexpressed Bcl-2 is not a common mechanism in the pathogenesis of human non-small cell lung cancers.
Altered cAMP levels in retinas from transgenic mice expressing a rhodopsin mutant.
Transgenic mice expressing the rhodopsin mutant Pro347Ser (Serine 6) display retinal degeneration through apoptosis that is characteristic of the disease retinitis pigmentosa. By 5 weeks after birth, these mice have lost approximately 35% of their photoreceptor cells. Retinas from these mice showed higher levels of cAMP compared to the levels in retinas of normal mice. Our studies provide evidence that elevated cAMP is common to the apoptotic process that occurs in retinitis pigmentosa. In addition, in vitro studies demonstrate no differences in the ability of the mutant and the wild-type rhodopsin to activate transducin, the rod cell G protein, to be phosphorylated by rhodopsin kinase or to bind arrestin. Mutants of rhodopsin, including Pro347Ser, are mistargeted to the rod inner segment, raising the possibility that rhodopsin triggers apoptosis through activation of signaling pathways not normally under its control.
Transjugular intrahepatic portosystemic stent shunt: effects on hemodynamics and sodium homeostasis in cirrhosis and refractory ascites.
OBJECTIVE: To assess the effects of transjugular intrahepatic portosystemic shunt (TIPS) on systemic and renal hemodynamics, neurohumoral factors, and sodium homeostasis in patients with cirrhosis and refractory ascites. DESIGN: Prospective study with 1-year follow-up. SETTING: Tertiary referral center and university-affiliated hospital. PATIENTS: 7 patients with cirrhosis and refractory ascites had metabolic studies done while receiving a 22 mmol/d sodium, 1 L/d fluid diet. INTERVENTION: TIPS insertion. MEASUREMENTS: Urinary sodium excretion, systemic and renal hemodynamics, hormonal profile, and central blood volume were measured before, at day 1 after, and at 1 month after TIPS insertion. RESULTS: Immediately after TIPS insertion, mean corrected sinusoid pressure decreased from 18.2 +/- 2.2 mm Hg to 7.7 +/- 1.3 mm Hg (P < 0.001); mean cardiac output increased from 6.83 +/- 0.68 L/min to 8.62 L/min (P = 0.005); and mean systemic vascular resistance decreased from 1018 +/- 103 dyne.s.cm-5 to 762 +/- 46 dyne.s.cm-5 (P = 0.011). Mean plasma renin activity, serum aldosterone levels, and 24-hour urinary sodium excretion (5.8 +/- 0.7 mmol/d before TIPS insertion compared with 6.0 +/- 1.8 mmol/d 1 day after insertion) were unchanged; mean elevated plasma norepinephrine levels significantly increased. By 1 month after insertion, mean proximal tubular reabsorption of sodium had decreased, and this had led to a mean natriuresis of 15.1 +/- 3.1 mmol/d (P = 0.02 compared with baseline), which was associated with a decrease in plasma renin activity and aldosterone levels to within the normal range. CONCLUSIONS: Our results suggest that natriuresis associated with TIPS is delayed and occurs in the presence of increased systemic vasodilatation at 1 month after insertion and that TIPS insertion should not be done in any patients with refractory ascites without careful attention to cardiac and renal status. However, in carefully selected patients, TIPS is a safe and effective means of managing refractory ascites.
Photoreceptor apoptosis in animal models. Implications for retinitis pigmentosa research.
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Transjugular intrahepatic portosystemic shunt: is it the ultimate solution for refractory ascites?
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Small cell carcinoma of the cervix treated with concurrent radiotherapy, cisplatin, and etoposide.
A multimodality regimen of four cycles of cisplatin and etoposide with concurrent locoregional radiotherapy (XRT) has been, since May 1988, the standard therapy for women with small cell carcinoma of the cervix (SCCC). Prophylactic cranial irradiation was to be used in all but primary progressors. All 11 patients (median age 47; 4 with pure SCCC and 7 with mixed histology) seen by us were treated with this regimen. Only 1 patient progressed while on treatment. The 3-year overall and failure-free survivals were 28%. Four patients remain alive in first remission; the remaining 7 died (2 from toxicity, 5 from cancer). Although not statistically significant due to the small numbers, it appeared that the chance of long-term survival depended both on the amount of the cancer as indicated by the FIGO stage and size of the primary and also the performance status. The toxicity was significant with 70% experiencing severe neutropenia and 40% being admitted for control of emesis. This regimen is only appropriate for those women in whom all of the apparent tumor can be encompassed within a radiation field and who, in addition, have a performance status of 0 or 1. For the remainder it does not offer any chance of long-term survival and its toxicity renders it antipalliative.
Pattern of sodium handling and its consequences in patients with preascitic cirrhosis.
BACKGROUND/AIMS: The initial abnormalities in the renal sodium handling in patients with cirrhosis before developing ascites remain unknown. The aim of this study is to further characterize sodium metabolism and the effects of sodium loading in preascitic cirrhosis. METHODS: Eight male, preascitic patients with cirrhosis and 6 volunteers had their daily urinary sodium excretion level measured while on a strictly metabolically controlled diet, first consisting of 20 mmol then of 200 mmol sodium per day each for 7 days. Central blood volume, plasma norepinephrine, and atrial natriuretic factor levels were measured during each diet. RESULTS: Preascitic patients with cirrhosis had significantly less daily urinary sodium excretion on both diets. Volume expansion in the patients with cirrhosis was indicated by significantly greater weight gain and higher atrial natriuretic factor levels for each diet. Patients with cirrhosis had central blood volume expansion (1725 +/- 54 mL/m2) compared with controls (1495 +/- 81 mL/m2; P = 0.03) on a low-sodium diet. This increased significantly in the controls (1864 +/- 164 mL/m2; P = 0.04) on a high-sodium diet, associated with suppression of plasma norepinephrine, but not in the patients with cirrhosis (1679 +/- 107 mL/m2; P > 0.05). CONCLUSIONS: Failure of further central blood volume expansion in the patients with cirrhosis on high-sodium diet in the presence of significant weight gain suggests maldistribution away from the effective arterial blood volume. This study provides further reasons why preascitic patients with cirrhosis might benefit from sodium restriction.
The effect of misoprostol on indomethacin-induced renal dysfunction in well-compensated cirrhosis.
BACKGROUND/AIMS: Indomethacin has been shown to have adverse effects on renal function in patients with well-compensated alcoholic cirrhosis. The aim of this study was to determine whether an oral prostaglandin E1 analogue, misoprostol, could prevent this indomethacin-induced renal dysfunction. METHODS: Six patients with well-compensated alcoholic cirrhosis were studied. Renal hemodynamics and tubular function were assessed by clearance techniques before and after an oral dose of (i) 50 mg of indomethacin alone (I50), and (ii) a combination of I50 and 200 micrograms of misoprostol. RESULTS: I50 produced a significant reduction in glomerular filtration rate, a fall in effective renal plasma flow and an increase in renal vascular resistance. Two hundred micrograms of misoprostol was able to abolish the deleterious renal effects of indomethacin totally, yielding an increase in glomerular filtration rate and effective renal plasma flow and a decrease in renal vascular resistance as well as an increase in urinary volume and urinary sodium excretion. These beneficial effects were maximal in the hour immediately following medication, but were only transient, and this may be a limiting factor in its clinical use. CONCLUSIONS: If the beneficial renal effects of misoprostol could be confirmed after chronic administration, then the vasodilatory, natriuretic and diuretic potential of 200 micrograms of misoprostol could be of potential therapeutic value in patients with well-compensated alcoholic cirrhosis who require non-steroidal anti-inflammatory drug therapy.
Effects of sodium status on the venous response to noradrenaline infusion in pre-ascitic cirrhosis.
1. This study assesses the effects of sodium status on venous responsiveness to noradrenaline and the neurohumoral profile in pre-ascitic cirrhotic patients. Eight cirrhotic patients and ten control subjects were studied after both a low (20 mmol/day) and a high (200 mmol/day) sodium diet. Venous responsiveness to increasing doses of noradrenaline in a dorsal hand vein and various plasma hormone levels were measured. Maximal response (Rmax.) and the dose of noradrenaline that yielded 50% of Rmax. (ED50) were then calculated. 2. A significantly smaller dorsal hand vein diameter was observed in the control subjects on a low sodium (2.23 +/- 0.14 mm) compared with a high sodium (2.57 +/- 0.15 mm; P = 0.04) diet, but not in the cirrhotic patients. Rmax. was not significantly different in either group on both diets. With low sodium intake, ED50 was similar in the two groups. However, on high sodium intake, control subjects had a significantly higher ED50 (34.4 +/- 7.4 ng/min) than the cirrhotic patients (5.03 +/- 0.86 ng/min; P < 0.003). Plasma noradrenaline in the control subjects fell significantly with the change from a low (1.29 +/- 0.11 nmol/l) to a high (0.68 +/- 0.09 nmol/l; P < 0.001) sodium diet, but remained elevated in the cirrhotic patients. Cirrhotic patients had significantly higher atrial natriuretic factor levels and lower plasma renin activity than the control subjects on both diets. 3. In conclusion, pre-ascitic cirrhotic patients show no evidence of venodilatation. Their sympathetic nervous activity is not suppressible by volume expansion. Relative hyper-responsiveness of the peripheral venous circulation to adrenergic stimulation with high sodium intake is present.
Randomized trial of epirubicin and cisplatin chemotherapy followed by pelvic radiation in locally advanced cervical cancer. Cervical Cancer Study Group of the Asian Oceanian Clinical Oncology Association.
PURPOSE: Pelvic radiation is standard treatment for women with stage IIb to IVa cervical cancer, but treatment results are disappointing, particularly for women with bulky tumors. We investigated the role of primary chemotherapy followed by pelvic radiotherapy in a randomized trial. PATIENTS AND METHODS: Two hundred sixty patients with stage IIb and IVa cervical cancer received either standard pelvic radiotherapy or primary chemotherapy with cisplatin 60 mg/m2 and epirubicin 110 mg/m2 administered at 3-week intervals for three cycles, followed by pelvic radiotherapy. RESULTS: Ninety-nine patients have relapsed with a median follow-up duration of 1.3 years; in 62 patients, the first site of progressive disease was the pelvis. Patients who received primary chemotherapy had a significantly higher pelvic failure rate than those who received radiotherapy alone (P < .003). Seventy-six patients have died, and those who received primary chemotherapy had significantly inferior survival compared with those who received radiotherapy alone (P = .02). Tumor response following chemotherapy was observed in 63%. After radiotherapy, tumor response occurred in 72% of those who received combined modality treatment, compared with 92% of those who received radiotherapy alone. CONCLUSION: Primary chemotherapy with epirubicin and cisplatin, although resulting in tumor response in a significant proportion of patients, is accompanied by an inferior local control rate and survival compared with standard pelvic radiotherapy alone.
Site-directed mutagenesis using thermostable enzymes.
The two-primer method for site-directed mutagenesis facilitates the mutation of targets in double-stranded DNA. We have encountered difficulties using the original method for the mutagenesis of DNA cloned into pBluescript vectors, which is possibly due to the presence of regions of secondary structure that cannot be efficiently copied by the enzymes used. We report a modification of the two-primer method using the thermostable VentR DNA polymerase and Thermus aquaticus ligase, allowing an increase in reaction temperatures. The modified method is functional with the pBluescript family of vectors.
Transjugular intrahepatic portosystemic shunt for refractory ascites: tipping the sodium balance.
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Anatomy of C7 lateral mass and projection of pedicle axis on its posterior aspect.
A specimen study focused on the measurements of C7 lateral mass and pedicle as well as the projection of pedicle axis on the posterior aspect of the lateral mass was done, based on 56 whole clean, dry, well-preserved spines of skeletally mature adults, 32 males and 24 females. Lateral mass widths averaged 11.7 mm. Lateral mass heights averaged 14.8 mm. The average thickness of the lateral mass was 6.8 mm. The average pedicle widths were 6.2 mm, and the average heights were 7.0 mm. Small, but statistically significant differences were found between the averages of the aforementioned dimensions in the male and female groups. The angulation between pedicle axis and the posterior aspect of the lateral mass averaged 107.0 degrees in the transverse plane and 76.2 degrees in the sagittal plane, respectively. Differences in angulations were not significant when compared according to side or sex of group. Distances from the projection point of pedicle axis to a line passing through the mid-line of the transverse process ranged from 2 mm superior to the line to 4.5 mm inferior, with an average 1.2 mm inferior on right side and 0.3 mm inferior on the left. Distances from the pedicular axial projection point to the outer margin of the lateral mass ranged from 0.0 mm to 5.4 mm, with an average 2.4 mm on the right side and 2.9 mm on the left side. Differences of distance related to left or right side were statistically significant, whereas the distances when related to the sex of the group were not.(ABSTRACT TRUNCATED AT 250 WORDS)
The dose-dependent effect of misoprostol on indomethacin-induced renal dysfunction in well compensated cirrhosis.
Misoprostol (200 micrograms) has been shown to acutely counteract the indomethacin-induced renal dysfunction in well compensated cirrhotic patients. The aim of this study was to determine if the prophylactic value of misoprostol was dose-dependent. Parameters of renal hemodynamics and tubular sodium and water handling were assessed by clearance techniques in 26 well compensated cirrhotic patients before and after an oral combination of 50 mg of indomethacin and various doses of misoprostol. The 200-micrograms dose was able to totally abolish the deleterious renal effects of indomethacin, whereas the 800-micrograms dose resulted in significant worsening of renal hemodynamics and sodium retention. These changes were maximal in the hour immediately after medications and slowly returned toward base-line levels thereafter. These results suggest that the renal protective effects of misoprostol is dose-dependent. However, until this apparent ability of 200 micrograms of misoprostol to prevent the adverse effects of indomethacin on renal function is confirmed with chronic frequent dosing, it would be prudent to avoid nonsteroidal anti-inflammatory therapy in patients with cirrhosis.
Hepatic and portal vein thrombosis in cirrhosis: possible role in development of parenchymal extinction and portal hypertension.
Obliterative lesions in portal veins (PVs) and hepatic veins (HVs) of all sizes are known to occur in cirrhotic livers. PV lesions have generally been attributed to thrombosis, but the pathogenesis of the HV (veno-occlusive) lesions is unknown. We have studied 61 cirrhotic livers removed at transplantation to clarify the prevalence, distribution, and pathogenesis of venous lesions, as well as the association of these lesions with other morphological features and clinical morbidity. Intimal fibrosis that is highly suggestive of healed HV or PV thrombosis was found in at least 70% and 36% of livers, respectively. The distribution of HV lesions was patchy and largely confined to veins between 0.1 and 3 mm in diameter, suggesting multifocal origin in small veins. PV lesions were more uniform throughout the liver, suggesting origin in large veins with propagation to the small veins. HV lesions were associated with regions of confluent fibrosis (focal parenchymal extinction), and PV lesions were associated with regional variation in the size of cirrhotic nodules and a history of bleeding varices. These observations suggest that thrombosis of medium and large PVs and HVs is a frequent occurrence in cirrhosis, and that these events are important in causing progression of cirrhosis.