Hepatoprotective Activity of Vitex trifolia against Carbon Tetrachloride-induced Hepatic Damage

Aqueous and ethanol extracts of leaf of Vitex trifolia was investigated for hepatoprotective activity against carbon tetrachloride induced liver damage. To assess the hepatoprotective activity of the extracts, various biochemical parameters viz., total bilirubin, total protein, alanine transaminase, aspartate transaminase and alkaline phosphatase activities were determined. Results of the serum biochemical estimations revealed significant reduction in total bilirubin and serum marker enzymes and increase in total protein in the animals treated with ethanol and aqueous extracts. However significant rise in these serum enzymes and decrease in total protein level was noticed in CCl4 treated group indicating the hepatic damage. The hepatoprotective activity is also supported by histological studies of liver tissue. Histology of the liver tissue treated with ethanol and aqueous extracts showed normal hepatic architecture with few fatty lobules. Hence the present study revealed that Vitex trifolia could afford significant protection against CCl₄ induced hepatocellular injury.     

Pseutarin C,a prothrombin activator from Pseudonaja textilis venom: its structural and functional similarity to mammalian coagulation factor Xa-Va complex

Several snake venoms contain procoagulant proteins that can activate prothrombin. We have purified pseutarin C, a prothrombin activator from the venom of the Australian brown snake (Pseudonaja textilis). It converts prothrombin to thrombin by cleaving both the peptide bonds Arg(274)-Thr(275) and Arg(323)-Ile(324), similar to mammalian factor Xa. It is a protein complex (approximately 250 Kd) consisting of an enzymatic and a non- enzymatic subunit. These subunits were separated by reverse phase HPLC and their interactions with bovine factor Xa and factor Va were studied. The enzymatic subunit of pseutarin C has an approximately 13 fold higher affinity for bovine factor Va (K(d) of 11.4 nM for pseutarin C enzymatic subunit--bovine factor Va interaction as compared to a K(d) of 147.4 nM for the bovine factor Xa-Va interaction). The non-enzymatic component, however, was unable to activate bovine factor Xa. N-terminal sequence analysis of the catalytic subunit of pseutarin C showed approximately 60% homology to mammalian factor Xa and approximately 78% homology to trocarin, a group D prothrombin activator from Tropidechis carinatus venom. Structural information for the non-enzymatic subunit of pseutarin C was obtained by amino terminal sequencing of several internal peptides. The sequence data obtained indicates that the non-enzymatic subunit of pseutarin C has similar domain architecture like the mammalian factor Va and the overall homology is approximately 55%. Thus pseutarin C is the first venom procoagulant protein that is structurally and functionally similar to mammalian factor Xa-Va complex.     

Snake venom glutaminyl cyclase.

Glutaminyl cyclase (QC) catalyzes N-terminal glutamine cyclization of many endocrine peptides and is typically abundant in brain tissue. As three-finger toxins in the venoms of colubrid snakes Boiga dendrophila and Boiga irregularis contain N-terminal pyroglutamate, we searched for QC in venom glands of both snakes. Here we report cDNA sequences of QC from brain and venom gland tissues of Boiga species. We propose that QC expressed in snake venom gland tissue plays a role in the N-terminal pyroglutamate formation of several snake venom toxins, indirectly contributing to venom potency.     

Two parallel prothrombin activator systems in Australian rough-scaled snake, Tropidechis carinatus. Structural comparison of venom prothrombin activator with blood coagulation factor X

It is uncommon for similar pathways/systems to be involved in highly divergent functions within single organisms. Earlier, we have shown that trocarin D, a venom prothrombin activator, from the Australian rough-scaled snake Tropidechis carinatus, is structurally and functionally similar to the blood coagulation factor Xa (FXa). The presence of a haemostatic system in these snakes implies that they have two parallel prothrombin activating systems: one in the plasma, that participates in the life saving process of blood clotting and the other in their venom, where it acts as a toxin. Here, we report the complete cDNA sequence encoding the blood coagulation factor X (FX) from the liver of T. carinatus. Deduced T. carinatus FX sequence shows approximately 80% identity with trocarin D but approximately 50% identity with the mammalian FX. Our present study confirms the presence of two separate genes--one each for FX and trocarin D, that code for similar proteins in T. carinatus snake. These two genes have different expression sites and divergent uses suggesting that snake venom prothrombin activators have probably evolved by the duplication of the liver FX gene and subsequently marked for tissue-specific expression in the venom gland.     

Platelet aggregation and exogenous factors from animal sources

Platelet aggregation plays a crucial role in thrombosis. This review describes exogenous factors isolated from various animal sources, including venoms and the salivary glands that interfere in platelet aggregation. Some of these factors induce platelet aggregation or agglutination, whereas others inhibit platelet aggregation. These proteins range from small molecular weight peptides to large proteins. Some of these proteins exhibit various enzymatic activities, while others are nonenzymatic. These exogenous factors affect platelet aggregation by various mechanisms and thus they have been classified based on their mechanism of action. Many of these proteins have evolved through both convergent and divergent evolution. For example, platelet aggregation inhibitors, which interfere in the interactions between fibrinogen and its receptor, the glycoprotein IIb/IIIa complex, show extreme structural diversity but they share the common functional site of Arg-Gly-Asp (RGD) tripeptide segment. On the other hand, C-type lectin related proteins exhibit diverse biological effects by interacting with different proteins, but share common structural scaffold. Thus the mechanistic and structure-function studies of these exogenous proteins have contributed significantly to the understanding of molecular mechanisms of platelet aggregation and to the development of potent antiplatelet agents, respectively. A number of new exogenous factors have been identified recently and the search is still on for novel factors that interfere with platelet aggregation. Further studies in this area will help in the development of novel strategies for treating cardiovascular and hematological disorders.     

Malignant potential in a Brunner's gland hamartoma

Brunner's gland hamartomas are rare tumours of the duodenum. These lesions have previously been described as being benign, with no malignant potential. A case report is presented of a Brunner's gland hamartoma, whose histology revealed a focus of well marked epithelial dysplasia. This case suggests a dysplastic stage in the natural history of Brunner's gland hamartoma, and questions the malignant potential of these lesions.     

Adrenal status in children with septic shock using low-dose stimulation test.

OBJECTIVES: There is paucity of data on the magnitude of absolute or relative adrenal insufficiency in septic shock, especially in children. We conducted a prospective study to determine the prevalence of adrenal insufficiency in children with septic shock using a low-dose Synacthen (1 microg) stimulation test. DESIGN: Cross-sectional study. SETTING: Pediatric intensive care unit in a tertiary care hospital in northern India. PATIENTS: Children with septic shock. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We performed cortisol estimation at baseline and after low-dose Synacthen (1 microg) stimulation at 30 and 60 mins in children with fluid refractory septic shock admitted to our pediatric intensive care unit. Basal cortisol levels <7 microg/dL and peak cortisol level <18 microg/dL were used to define adrenal insufficiency. An increment of <9 microg/dL after stimulation was used to diagnose relative adrenal insufficiency. As there is lack of consensus on the cutoffs for defining relative adrenal insufficiency using the low-dose adrenocorticotropic hormone test, we evaluated different cutoff values (increment at 30 mins, increment at 60 mins, greater of the two increments) and evaluated their association with the incidence of catecholamine refractory shock and outcomes. Children with sepsis but without septic shock were sampled for baseline cortisol levels as a comparison. Thirty children (15 girls) with septic shock were included; median age (95% confidence interval) was 36.5 (9.39- 58.45) months. Median Pediatric Risk of Mortality score was 22.5 (14.13-24.87). Fifteen (50%) children survived. The median (95% confidence interval) cortisol values at baseline and 30 mins and 60 mins after stimulation were 71 (48.74-120.23) microg/dL, 78.1 (56.9-138.15) microg/dL, and 91 (56.17-166.44) microg/dL, respectively. The median baseline cortisol value in age- and gender-matched children with sepsis was 11.5 microg/dL. None of the children with septic shock fulfilled the criteria for absolute adrenal insufficiency. However, nine (30%) patients had relative adrenal insufficiency (increment in cortisol <9 microg/dL). Of these nine patients, five (56%) died; of the 21 patients with a greater increment in cortisol after stimulation, ten died (p = .69). Compared with patients in septic shock with normal adrenal reserve, those with relative adrenal insufficiency had a higher incidence of catecholamine refractory shock (p = .019) but no difference in mortality rate (p = .69). On the sensitivity and specificity analysis using various cutoffs of increment, the best discrimination for catecholamine refractory shock was obtained with a peak increment <6 microg/dL. CONCLUSIONS: Relative adrenal insufficiency is common in children with septic shock and is associated with catecholamine refractory shock.     

Serial circulating vasopressin levels in children with septic shock.

BACKGROUND: Septic shock is an important cause of death in pediatric intensive care units. Initial evaluations have shown that vasopressin may have a role in catecholamine refractory shock in adults. It is important to determine whether children with septic shock have deficiency of vasopressin. This will help in defining the role of vasopressin in septic shock. DESIGN: Prospective cohort study. SETTING: Pediatric intensive care unit of a tertiary care hospital in north India. PATIENTS: Patients were children with septic shock, and controls were children with sepsis but no shock. STUDY DESIGN: Vasopressin levels in plasma were determined by enzyme-linked immunosorbent assay for children with septic shock at diagnosis (baseline) and thereafter at 24, 48, and 96 hrs to determine the time trends. The baseline vasopressin values for children with septic shock were compared with those for children without shock. RESULTS: The median (95% confidence interval) vasopressin level at baseline in children with septic shock was 116 (63.3-130.7) pg/mL, and in children with sepsis but no shock it was 106 (61.7-131.77) pg/mL. The median value for survivors was 76 (44.6-130.9) pg/mL, and for nonsurvivors, 118 (81.7-259) pg/mL (p = .16). The serial values also did not show any significant changes; the values at 24 hrs (n = 17), 48 hrs (n = 16), and 96 hrs (n = 15) were 105 (76.1-125.9), 105 (41.4-155.5), and 109.5 (54.9-154.8) pg/mL, respectively. CONCLUSIONS: The results of our study suggest that vasopressin levels are elevated in children with septic shock and that serial values up to 96 hrs do not show any decline.