Estimation of cumulative incidence functions when the lifetime distributions are uniformly stochastically ordered.

In the competing risks problem an important role is played by the cumulative incidence function (CIF), whose value at time t is the probability of failure by time t from a particular type of risk in the presence of other risks. Assume that the lifetime distributions of two populations are uniformly stochastically ordered. Since this ordering may not hold for the empiricals due to sampling variability, it is natural to estimate these distributions under this constraint. This will in turn affect the estimation of the CIFs. This article considers this estimation problem. We do not assume that the risk sets in the two populations are related, give consistent estimators of all the CIFs and study the weak convergence of the resulting processes. We also report the results of a simulation study that show that our restricted estimators outperform the unrestricted ones in terms of mean square error. A real life example is used to illustrate our theoretical results.

Protective effect of vitamin E, beta-carotene and N-acetylcysteine from the brain oxidative stress induced in rats by lipopolysaccharide.

The major goal of this study was to examine the ability of several antioxidants namely, vitamin E, beta-carotene and N-acetylcysteine, to protect the brain from oxidative stress induced by lipopolysaccharide (LPS, endotoxin). LPS, a component of the bacterial wall of gram-negative bacteria, has been recognized as one of the most potent bacterial products in the induction of host inflammatory responses and tissue injury and was used in this study to mimic infections. LPS injection resulted in a significant increase in the stress indices, plasma corticosterone and glucose concentration, a significant alteration of the brain oxidative status observed as elevation of the level of malondialdehyde (MDA, index of lipid peroxidation) and reduction of reduced glutathione (GSH), and a disturbance in the brain energy metabolism presented as a reduction in the ATP/ADP ratio and an increase in the mitochondrial/cytosolic hexokinase ratio. However, the activities of brain superoxide dismutase and Na+, K+-ATPase and contents of cholesterol and phospholipids were not altered. Administration of the aforementioned antioxidants prior to LPS injection ameliorated the oxidative stress by reducing levels of MDA, restoring GSH content and normalizing the mitochondrial/cytosolic hexokinase ratio in the brain in addition to lowering levels of plasma corticosterone and glucose. In conclusion, this study showed the increased free radical generation during infections and LPS-induced stress. It also suggests that brain oxidative status and energy is disturbed.

Effect of pretreatment with vitamin E or diazepam on brain metabolism of stressed rats.

The effect of vitamin E (VE) or diazepam (DZ) pretreatment on some carbohydrate metabolic aspects in the brains of stressed rats was studied. DZ and VE were given i.p. at doses of 5 mg/kg body wt for 6 days prior to subjecting the animals to single swimming stress (SSS). Pretreatment of the rats with DZ or VE diminished the stress-induced increases in plasma corticosterone and glucose levels and reversed the decrease due to stress on brain ATP, glucose, glycogen and pyruvate contents. The increase in brain ADP and lactate was brought back to levels which approached the pre-stressed values. Moreover, DZ and VE pretreatments helped in attenuating the stress-induced alteration in brain mitochondrial and cytosolic hexokinase as well as sodium, potassium adenosine triphosphatase (Na+,K(+)-ATPase) activities. The change in these metabolic parameters produced by VE pre-treatment was less than that exhibited by DZ. The effects of VE were explained in light of its antioxidant property in preventing the free radical production and lipid peroxide formation which are important factors in the pathogenesis of stress.

Effect of vitamin C administration in modulating some biochemical changes in arthritic rats.

Two phases of arthritis, acute phase (four days after adjuvant inoculation) and chronic phase (21 or 29 days after adjuvant inoculation) were studied in male rats. The effect of administration of vitamin C in a daily oral dose of 50 mg/kg body wt for four and 21 days starting on the day of adjuvant inoculation and for 7 days starting 21 days after adjuvant inoculation against these phases of arthritis was demonstrated. Results showed that prolonged administration of vitamin C (21 days) increased the lowered serum sulphydryl (SH-groups) to prearthritic values while it decreased the elevated level of blood glutathione (GSH) of arthritic rats. However, neither (four-day) nor seven-day treatment with vitamin C exerted any significant changes in these parameters. The results showed also a slight significant increase in the level of erythrocyte superoxide dismutase activity (SOD) [1.15.1.1] upon seven-day treatment with vitamin C. Meanwhile, four-, 21- or seven-day treatment with vitamin C produced no significant change in the elevated levels of serum ceruloplasmin (Cp) and alpha 2-macroglobulin (alpha 2-M) of arthritic rats. However, 21-day and 7-day administration of vitamin C has improved the lowered A/G ratio in these animals. The improvement in these parameters after prolonged administration of vitamin C was explained in the light of the antioxidant property of this vitamin and suggests a beneficial role for it in the treatment of arthritis.

Biochemical changes in arthritic rats under the influence of vitamin E.

Two phases of adjuvant arthritis, acute phase (4 days after adjuvant inoculation) and chronic phase (21 and 29 days after adjuvant inoculation) were studied in male rats. The effect of administration of vitamin E in a daily oral dose of 147 mg/kg body wt. for one week against these phases of arthritis were demonstrated before and after adjuvant inoculation. Results showed that administration of the vitamin before and after adjuvant inoculation increased the lowered serum-SH group in arthritic rats so that their level was restored to pre-arthritic values especially in chronic treated group. Meanwhile, these treatments produced no change in the increased level of blood GSH or erythrocyte SOD activity of arthritic rats. The results showed also that administration of vitamin E before adjuvant inoculation increased significantly the level of alpha 2-M while it did not alter the increased serum Cp in acute phase. However, administration of the vitamin after adjuvant inoculation failed to exert any change in these parameters. In the meantime, these treatments tended to increase the lowered A/G of arthritic rats in different phases especially in acute one. These observations suggest that antioxidants such as vitamin E may be beneficial for arthritis.

Study of contact activation in endemic hepatosplenomegaly.

Factors of the contact activation complex--FXII, FXI, high-molecular-weight kininogen (HMWK) and prekallikrein (PK) as well as D-dimer were measured in 68 schistosomal patients with and without co-existing chronic hepatitis B virus infection (HBV). Fifty-four cases had mixed hepatosplenic schistosomiasis and HBV infection whereas 14 were suffering from hepatosplenic (HS) schistosomiasis alone. A group of twelve age-matched, healthy individuals served as controls. All coagulation parameters were significantly reduced in both disease groups compared to the healthy controls. The decreased activity of the contact proteins could be attributed to decreased hepatic synthesis, consumption due to disseminated intravascular coagulation (DIC) and to the effect of endotoxins. In mixed schistosomiasis and HBV infections, however, the levels of the contact activation factors were not significantly different from those obtained in patients with HS alone. This apparently paradoxical finding does not, however, exclude a role for co-existing HBV infection in speeding up complications in hepatosplenic schistosomiasis.

The Bouveret syndrome: an unusual cause of hematemesis.

Gallstones are usually silent. Less commonly, patients with cholelithiasis develop symptoms and/or complications; biliary fistula occurs in 3% to 5% of the cases. When a large stone is passed and occludes the duodenum, gastric outlet obstruction (the Bouveret syndrome) may result. In reported cases, the stones are usually larger than 2.5 cm. The usual presenting symptoms are those of bowel obstruction: abdominal pain, nausea, and vomiting. Less commonly, the patients experience melena and, rarely, hematemesis. We describe a patient who had the largest stone reported to cause hematemesis rather than bowel obstruction and to be diagnosed endoscopically. The 5 X 4 X 3 cm stone was extracted surgically. Endoscopic diagnosis and extraction of stones up to 3 cm in size has been reported, avoiding the need for surgery.

Papillary cystadenocarcinoma of the bile ducts resulting in hemobilia.

Cystadenocarcinoma is a rare tumor of the intrahepatic and a very rare tumor of the extrahepatic biliary system. In the reported cases, abdominal swelling is the most common presenting symptom, followed by right upper quadrant mass. Melena was the initial presenting symptom in the present case. Bleeding into the second part of the duodenum was observed only during the third diagnostic esophagogastroduodenoscopy. Hemobilia was suspected because of abnormal liver enzymes and a mass in the left lobe of the liver on computerized tomography. At laparotomy, we suspected that the mass was a hemangioma. Cystadenocarcinoma diagnosis was made only by histopathological examination.

Lipid pattern in Bilharzial hepatic fiprosis.

Plasma total lipid phosphorus, individual phospholipid fractions, free and esterified cholesterol, triglycerides and nonesterified fatty acids were fractionated by thin-layer chromatography and determined in bilharzial hepatic fibrosis patients (57 cases) and normal controls (25 cases). Significant diminutions were encountered in the total and the individual phospholipids, especially the lysolecithin fraction in the 3 groups of patients studied. Total and esterified cholesterol and triglycerides showed significant decreases, especially in moderate and late cases. NEFA, on the other hand, did not reveal any change from normal level in either moderate, late or mixed cases. Such findings may be attributed to malabsorption, lack of energy, insufficiency of required precursors as well as impaired synthesis by the liver.