A common protein C inhibitor exosite partially controls the heparin induced activation and inhibition of serine proteases

Protein C inhibitor (PCI) maintains hemostasis by inhibiting both procoagulant and anticoagulant serine proteases, and plays important roles in coagulation, fibrinolysis, reproduction, and anti-angiogenesis. The reactive site loop of PCI traps and irreversibly inhibits the proteases like APC (activating protein C), thrombin (FIIa) and factor Xa (FXa). Previous studies on antithrombin (ATIII) had identified Tyr253 and Glu255 as functional exosites that interact and aid in the inhibition of factor IXa and FXa. Presence of exosite in PCI is not known, however a sequence comparison with the PCI from different vertebrate species and ATIII identified Glu239 to be absolutely conserved. PCI residues analogous to ATIII exosite residues were mutated to R238A and E239A. Purified variant PCI in the presence of heparin (10 μg/ml) showed a 2-4 fold decrease in the rate of inhibition of the proteases. However, the stoichiometry of inhibition of FIIa, APC, and FXa by native PCI, R238A and E239A variants were found to be close to 1.0, which also indicated the formation of stable complexes based on SDS-PAGE and western blot analysis with thrombin and APC. Our findings revealed the possible presence of an exosite in PCI that influences the protease inhibition rates.

Protein disulfide isomerase uses thrombin-antithrombin complex as a template to bind its target protein and alter the blood coagulation rates

During inflammation and situations of cellular stress Protein Disulfide Isomerase (PDI) is released in the blood plasma from the platelet and endothelial cells to influence thrombosis. The addition of exogenous PDI makes the environment pro-thrombotic by inducing disulfide bond formation in specific plasma protein targets like vitronectin, factor V, and factor XI. However, the mechanistic details of PDI interaction with its target remain largely unknown. A decrease in the coagulation time was detected in activated partial thromboplastin time (APTT), prothrombin time (PT), and thrombin time (TT) in addition to the purified recombinant PDI (175nM). The coagulation time can be controlled using an activator (quercetin penta sulfate, QPS) or an inhibitor (Quercetin 3-rutinoside, Q3R) of PDI activity. Likewise, the PDI variants that increase the PDI activity (H399R) decrease, and the variant with low activity (C53A) increases the blood coagulation time. An SDS-PAGE and western blot analysis showed that the PDI does not form a stable complex with either thrombin or Antithrombin (ATIII) but it uses the ATIII-thrombin complex as a template to bind and maintain its activity. A complete inhibition of thrombin activity on the formation of ATIII-thrombin-PDI complex, and the complex-bound PDI-catalyzed disulfide bond formation of the target proteins may control the pro- and anti-thrombotic role of PDI.

Naringin binds to protein disulfide isomerase to inhibit its activity and modulate the blood coagulation rates: Implications in controlling thrombosis

Currently used antithrombotic drugs are beset with several drawbacks which necessitates the need for new and cheaper alternatives. Protein disulfide isomerase (PDI) is secreted in the blood plasma in cellular stress conditions and initiates the thrombus formation. A screening of library of natural compounds revealed that naringin had a high binding affinity for the PDI (-8.2 kcal/mol). Recombinant PDI was purified using the affinity chromatography. Incubation of purified PDI (3 μM) with naringin (0-100 μM, pH 7.4, 25 °C) partially modulated its conformation. Consequently, the fluorescence emission spectra of the PDI binding to naringin were assessed using the Stern-Volmer equation, which indicated an association constant of 2.78 × 104 M-1 suggesting an appreciable affinity for the naringin, with a unique binding site. An insulin turbidity assay showed that PDI activity is decreased in the presence of naringin indicating inhibition. Molecular dynamic simulation studies showed the changes in the PDI structure on binding to the naringin. Incubation of naringin (80 μM) in fresh human plasma along with exogenous PDI (175 nM) showed a significant delay in the intrinsic and extrinsic coagulation pathways. We show that naringin is able to modulate the PDI conformation and activity resulting in altered blood coagulation rates.

A comparison of transporter gene expression in three species of Peronospora plant pathogens during host infection

Protein transporters move essential metabolites across membranes in all living organisms. Downy mildew causing plant pathogens are biotrophic oomycetes that transport essential nutrients from their hosts to grow. Little is known about the functions and gene expression levels of membrane transporters produced by downy mildew causing pathogens during infection of their hosts. Approximately 170-190 nonredundant transporter genes were identified in the genomes of Peronospora belbahrii, Peronospora effusa, and Peronospora tabacina, which are specialized pathogens of basil, spinach, and tobacco, respectively. The largest groups of transporter genes in each species belonged to the major facilitator superfamily, mitochondrial carriers (MC), and the drug/metabolite transporter group. Gene expression of putative Peronospora transporters was measured using RNA sequencing data at two time points following inoculation onto leaves of their hosts. There were 16 transporter genes, seven of which were MCs, expressed in each Peronospora species that were among the top 45 most highly expressed transporter genes 5-7 days after inoculation. Gene transcripts encoding the ADP/ATP translocase and the mitochondrial phosphate carrier protein were the most abundant mRNAs detected in each Peronospora species. This study found a number of Peronospora genes that are likely critical for pathogenesis and which might serve as future targets for control of these devastating plant pathogens.

Mannose 2, 3, 4, 5, 6-O-pentasulfate (MPS): a partial activator of human heparin cofactor II with anticoagulation potential

Thromboembolic diseases are a major cause of mortality in human and the currently available anticoagulants are associated with various drawbacks, therefore the search for anticoagulants that have better safety profile is highly desirable. Compounds that are part of the dietary routine can be modified to possibly increase their anticoagulant potential. We show mannose 2,3,4,5,6-O-pentasulfate (MPS) as a synthetically modified form of mannose that has appreciable anticoagulation properties. An in silico study identified that mannose in sulfated form can bind effectively to the heparin-binding site of antithrombin (ATIII) and heparin cofactor II (HCII). Mannose was sulfated using a simple sulfation strategy-involving triethylamine-sulfur trioxide adduct. HCII and ATIII were purified from human plasma and the binding analysis using fluorometer and isothermal calorimetry showed that MPS binds at a unique site. A thrombin inhibition analysis using the chromogenic substrate showed that MPS partially enhances the activity of HCII. Further an assessment of in vitro blood coagulation assays using human plasma showed that the activated partial thromboplastin time (APTT) and prothrombin time (PT) were prolonged in the presence of MPS. A molecular dynamics simulation analysis of the HCII-MPS complex showed fluctuations in a N-terminal loop and the cofactor binding site of HCII. The results indicate that MPS is a promising lead due to its effect on the in vitro coagulation rate.Communicated by Ramaswamy H. Sarma.

Comparison of patients' assessment of urinary flow strength with uroflowmetry

OBJECTIVE

The objective of the study was to compare patients' self-assessment of urinary flow strength with uroflowmetry.

METHODS

The study was set in the routine uroflow clinic of the urology department. All patients had symptoms of bladder outlet obstruction. They answered 2 questions and a multiple-choice pictorial representation of flow trajectory. Patients were encouraged to provide 3 flows with at least one volume over 150 ml. The maximum flow rate Qmax was compared with the subjective evaluations.

RESULTS

Qmax was normally distributed. Answers to the questions did separate patients significantly (p < 0.001). However, overlap between groups was large; the group who answered that their flow was poor included many false positives. Pictorial assessment showed low correlation with Qmax, again with a high false-positive rate.

CONCLUSION

Patients' self-assessment of strength of stream is unreliable as a measure of Qmax and therefore of obstruction. Resection of prostate on history alone is not recommended.

Bladder transection revisited

OBJECTIVE

To ascertain the safety and effectiveness of bladder transection for the treatment of enuresis and urinary frequency.

PATIENTS AND METHODS

Twelve patients who had an open bladder transection performed at the Victoria Infirmary, Glasgow, were followed up for a mean of 37 months.

RESULTS

Of the 12 patients, three were 'cured', seven were better, two were no better and none were worse than before the operation. All six patients with preoperative enuresis were cured of this by the procedure.

CONCLUSIONS

Bladder transection remains a useful procedure in selected patients and avoids the problems associated with enterocystoplasty.

Amphotericin versus sodium stibogluconate in first-line treatment of Indian kala-azar

Patients do not always respond to treatment of visceral leishmaniasis with pentavalent antimony, and the drug has toxic effects. Amphotericin B might be useful as an alternative first-line treatment for the disease. We compared the efficacy of amphotericin and sodium stibogluconate in a prospective randomised trial in 80 uncomplicated and parasitologically confirmed cases of Indian kala-azar. None of the patients had received an antileishmanial agent before. Sodium stibogluconate was given at 20 mg/kg in two divided doses daily for 40 days, and amphotericin in fourteen doses of 0.5 mg/kg infused in 5% dextrose on alternate days. All 40 patients randomised to amphotericin were cured; of the 40 patients assigned to sodium stibogluconate, 28 (70%) showed initial cure and 25 (62.5%) showed definitive cure (p < 0.001). With amphotericin, there was quicker abatement of fever and more complete spleen regression with no serious adverse effects. Amphotericin is effective in the first-line treatment of Indian kala-azar and superior to antimony therapy.

Renal thoracic ectopia. A case report

We report a case that presented with an opacity on chest X-ray that was found to be an abnormal ectopic kidney. Renal ectopia is rare and usually does not require treatment.

Management of renal stab wounds by arteriographic embolisation

A 26 year old man was admitted with multiple stab wounds to his chest, abdomen and right loin. He was noted to have a large haemothorax, a tender abdomen and frank haematuria. At laparotomy, there was a small non expanding retroperitoneal haematoma that was not explored, and no visceral damage. Post operatively he continued to have haematuria. IVP and ultrasound showed perirenal haematoma and clot in the upper pole calyces but was otherwise normal. Renal arteriography demonstrated a pseudo-aneurysm in the right mid region, feeding an arteriovenous fistula (Figure 1). Selective renal artery embolisation with spring occlusion coils was performed which occluded the branch supplying the false aneurysm and fistula (Figure 2). He had no further haematuria. At six month follow up he remained well, normotensive and with no haematuria. Isotope renogram showed 30% loss of function at the upper pole.

Amphotericin versus pentamidine in antimony-unresponsive kala-azar

We compared the efficacy of amphotericin B and pentamidine isethionate in a prospective randomised trial in 120 uncomplicated and parasitologically confirmed cases of antimony-unresponsive kala-azar. Doses were twenty intramuscular injections of pentamidine 4 mg/kg on alternate days or fourteen definitive doses of amphotericin 0.5 mg/kg infused in 5% dextrose on alternate days. 48 (80%) patients given pentamidine showed initial cure and 46 (77%) showed definitive cure compared with 60 (100%) and 59 (98%) cases, respectively, on amphotericin (p < 0.001). Amphotericin also brought about quicker abatement of fever and more complete spleen regression.

Hypertension associated with increased renin concentrations in nephroblastoma

An infant with severe hypertension who had a nephroblastoma which was secreting active renin is described. Nephroblastoma must be included in the differential diagnosis of hypertension associated with increased renin concentrations, even in the absence of an abdominal mass.

Cisplatin therapy in recurrent childhood brain tumors

Twenty-two patients with brain tumors were initially treated with surgery, radiation therapy, and/or adjuvant chemotherapy. Histologic diagnosis included 11 gliomas, seven ependymomas, one dysgerminoma, one teratocarcinoma, one pinealoma, and one small cell tumor. At recurrence, documented on computerized tomographic scan, cisplatin (60 mg/m2/day iv X 2) was given every 3-4 weeks. Seventeen patients received two or more courses and were considered to be evaluable for response. Response parameters included change in the size of tumor on computerized tomographic scan and/or in clinical findings. Four patients had complete response, five had partial response, four had stable disease, and four had disease progression. Toxic effects were manageable. The number of patients with grade 3-4 toxic reactions, by category, were: thrombocytic, ten; leukocytic, four; renal, five; metabolic, four; gastrointestinal, none; and neurologic, seven. Two of the 14 patients tested had grade 3-4 ototoxicity. Acute fluid retention with decreased serum electrolytes and serious but reversible changes in the mental status, which were experienced in earlier patients, decreased in severity with increasing experience of the investigator. In summary, cisplatin appears to be active in a spectrum of brain tumors and should be studied further for therapeutic efficacy.

Emblica officinalis Gaertn and serum cholesterol level in experimental rabbits

Twelve albino rabbits of either sex weighing 1.0-1.25 kg were fed a standard laboratory diet of green grass and sattu (roasted Bengal gram). After a 2-week run-in period their serum cholesterol levels were estimated. All animals were now fed 0.5 g cholesterol and 1.0 g clarified butter daily and were not divided into 3 groups of 4 animals each. While all received the standard cholesterol-rich diet, Group A animals received no additional substances, animals in Group B were each fed 10 mg vitamin C daily, while those in Group C were each given 1.0 g fresh Amla (Emblica officinalis Gaertn). Mean serum cholesterol levels in all three groups rose to significantly higher levels by the end of the second week. There was a further rise by the end of the third and fourth weeks in Groups A and B. However, animals in Group C (i.e. those given Amla) showed significantly lower mean serum cholesterol levels at the end of the second week than their counterparts in Groups A and B. At the end of the third and fourth weeks the differences were even more pronounced.

Autoimmune disorders complicating adolescent Hodgkin's disease

Four adolescents with Hodgkin's disease also developed autoimmune diseases. There were two idiopathic thrombocytopenic purpura (ITP), one polymyositis, and one scleroderma. The first two patients developed ITP in the absence of a spleen, and with their Hodgkin's disease in remission. The first patient with Hodgkin's disease has been continuously free of cancer for over five years. The second patient was a 17-year-old male whoe Hodgkin's disease recurred, but whose disease was in remission at the time the ITP occurred. The polymyositis occurred in an 18-year-old youth when he was in his initial remission for his Hodgkin's disease, but his disease subsequently recurred two years later. This youth presented with Coombs positive autoimmune hemolytic anemia. The polymyositis did not respond to therapy, and he is left with severe muscle wasting and weakness; however, the polymyositis is now quiescent. The scleroderma occurred in an 18-year-old female who had been continuously free of Hodgkin's disease for eight years. The scleroderma did not respond to drug therapy and she now has moderate skin changes, but remains in continuous remission of her Hodgkin's disease. Although there are a few reports of Hodgkin's disease and concurrent autoimmune disorders, physicians dealing with cancer in adolescents should be aware of this association.

Effect of different host plants on growth and development of epilachna beetle

An experiment was conducted to study the effect of four different host plants viz., teasel gourd, bitter gourd, sponge gourd, and yard long bean on the growth and development of Epilachna dodecastigma Wied under laboratory condition. The number of eggs laid by female beetle was significantly highest feeding on teasel gourd leaves and lowest on yardlong bean leaves. Egg hatching was faster on yardlong bean and delayed on bitter gourd. The host plant, such as sponge gourd produced the large sized larvae, while large pupa and adult were developed by feeding teasel leaves. The smallest larvae, pupae, and adults were found on the consumption of yardlong bean leaves. Highest larval duration was found on sponge gourd followed by bitter gourd and yardlong bean. Both larval and adult food consumption was highest on teasel gourd and lowest on yardlong bean. Considering the biological characteristics and leaf consumption, the plant teasel gourd appeared to be the best host plant for E. dodecastigma. Key Words: Host plant, growth and development, Epilachna dodecastigma, leaf consumption. DOI: 10.3329/bjar.v34i3.3965 Bangladesh J. Agril. Res. 34(3) : 403-410, September 2009