Effect of Annealing on Optical, Electrical and Charge Trapping Properties of TiO2 NPs Arrays.

Glancing angle deposition technique has been carried out to synthesize TiO2 nanoparticles over SiO(x) thin film. The samples were annealed at different temperatures 550 °C and 950 °C. The average grain sizes and surface RMS roughness have been increased from 9 nm, 0.62 nm (as deposited); 21 nm, 2.47 nm (550 °C annealed) to 37 nm, 4.2 nm (950 °C annealed). Fivefold maximum increase in optical absorption has been recorded for the 950 °C annealed sample as compared to that of the as grown. The absorption and photoluminescence peaks show the red shift with an increase in annealing temperature and grain sizes. Transmission electron microscopy (TEM) has been used to investigate phases of nanoparticles. The junction capacitance of the Au/TiO2 NPs device was observed to decrease with an increase in frequency. A minimum change in junction capacitance of 1 pF was calculated for 950 °C annealed device for the variation of frequency from 500 Hz to 1 MHz. The results are used to simulate the capacitance as a function of frequency and voltage characteristic of TiO2 NPs based device in different temperature. Simulated results are exceptionally close to experimental results. The TiO2 NPs based device annealed at 950 °C possessed higher impedance and lower conductance among all three type of devices. The sample annealed at 950 °C showed the maximum capacitance (0.09 pF at 0 V) as well as charge (˜0.6 Coulomb at +8 V) retention compared to that of the 550 °C annealed and as deposited samples.

Neu-Laxova syndrome: a case report.

Neu-Laxova syndrome (NLS) is a rare lethal syndrome found in both consanguinous and non-consanguinous couple. This is characterized by terrible face with unusual craniofacial appearance with exophthalmos, spectrum of central nervous system malformation, like microcaphaly, hypoplastic cerebellum, cleft lip/palate, ichthyosis and oedema. The diagnosis is made on the basis of clinical parameter. We report a 4 hour old male term newborn with IUGR of Neu-Laxova syndrome presented with anencephaly, rudimentary cerebellum, exophthalmos of right eye, bilateral cleft lip and palate and cryptorchidism. Anencephaly and cryptorchidism are two recently reported findings of NLS. We are presenting this case in addition from Bangladesh to lend further support to those two new findings as component of Neu-Laxova syndrome. Outcome of this syndrome is not good. Most of the patients are died of infection within hours to days.

Prevalence of Gingivitis, Plaque accumulation and Decayed, Missing and Filled Teeth among slum population in Bangladesh.

A cross-sectional survey, using cluster sampling technique, of slum population, was done to explore the oral health status and the prevalence of common oral diseases. A close ended questionnaire comprising Decayed, Missing and Filled Teeth (DMFT) Index, Gingival Index (Löe and Silness) and Plaque Index was applied to evaluate and record oral diseases, in both male and female population, covering a wide range of age groups. Clinical examination was carried out in different shum set ups, including slum schools by trained and calibrated examiners. Three thousand nine hundred and four (3904) slum dwellers participated in the survey. Prevalence of Caries was expressed in mean DMFT, recording of gingival status followed the method of Löe and Silness, oral hygiene status was evaluated using Plaque index. Mean decayed component, of the DMFT, was significantly higher than filling and missing component. Both decayed and missing components showed increasing trend, and filling components decreased as the age progressed. Prevalence of gingivitis and plaque accumulation was remarkably high among slum dwellers. Significantly high level of common oral diseases was found among Tongi slum dwellers.

A census of general surgery consultants in England and Wales: implications for the current and future surgical workforce.

INTRODUCTION: This study aimed to describe the composition of the current general surgical consultant body in England and Wales and quantify levels of inequality within it as well as describe future workforce challenges. METHODS: This is an observational study of all general surgical departments in England and Wales. Consultant general surgeons were identified and data regarding their gender, country of undergraduate medical education, subspecialty and private practice were recorded. RESULTS: Of the 2,682 consultant general surgeons in England and Wales identified for this study, just 17% are women, with gender inequality most marked in university teaching hospitals and among certain subspecialties. Almost 40% of consultants did not obtain their primary undergraduate degree in the United Kingdom and there are considerably fewer surgeons who studied abroad in university teaching hospitals. Over 40% of current general surgical consultants have been qualified for more than three decades and there is no equivalent sized group of younger consultants. CONCLUSIONS: There remains considerable gender and racial inequality in the consultant general surgical workforce, with pockets of a lack of diversity within university or teaching hospital surgical departments and some subspecialties. The proportion of surgeons in their fourth decade of clinical practice represents the largest group of current practising consultants, which points towards an impending workforce crisis should senior clinicians seek to reduce activity or consider taking early retirement.

Profile of neonatal candidiasis in tertiary neonatal intensive care unit: A report from a developing country.

BACKGROUND: Systemic candidiasis is an important nosocomial infection in neonatal intensive care units. The objective of this study was to identify the change in the profile of neonatal candidiasis in a tertiary neonatal intensive care unit (NICU) in eastern India in recent times. METHODS: It was a retrospective review of case records from 2014 to 2019 from a tertiary NICU of eastern India. Data of the fungal sepsis, demographic details, risk factors of fungal sepsis and mortality were collected from 103 neonates. RESULTS: One hundred and three neonates had blood culture positive for fungal species of which 91 (88.3%) infants weighed ≥1500 g and 66 (64%) infants were term. There was significant higher incidence of candidiasis among outborn (Relative risk of outborn 18.84, 95% CI 10.74-33.05). Prolonged antibiotic usage (>14 days), meropenem usage (>5 days), central catheterization (>5 days), invasive mechanical ventilation (>5 days), surgical intervention were found in 64 (62.1%), 46 (44.6%), 31(30.0%), 40 (38.8%) and 39 (37.8%) infants. Non albicans candida (NAC) was isolated as the predominant species (82/103, 79.6%). Resistance to both of fluconazole and amphotericin B were found in 19 (18.4%) babies. Presence of NAC infection and resistance to both amphotericin B and fluconazole were independent predictors of candida associated mortality in NICU. CONCLUSION: Neonatal candidiasis is found among outborn infants with higher birth weight and gestational age. NAC species are predominant organisms with resistance to common antifungal drugs.

Isozymic variations in specific and nonspecific esterase and its thermostability in silkworm, Bombyx mori L.

Esterase isozymic variations were documented in the haemolymph of developed multivoltine and bivoltine silkworm breeds during unfavorable seed crop seasons of May - September using á- and â- napthylacetate separately to identify specific and nonspecific esterase having thermotolerant potentiality. Variations existed in the isozyme pattern with three bands (Est-2, 3 and 4) in pure Nistari race and other developed multivoltine and bivoltine breeds. Est-2 and Est-3 were non-specific esterases as they were observed when both á- and â-napthylacetate was used as substrates separately. Est-4 band was observed only with á-napthylacetate as substrate and was therefore confirmed to be specific á-esterase band in the haemolymph of silkworm, Bombyx mori L. Zymograms showed that the non-specific esterase band (Est-3) with R1 of 0.43 and specific á-esterase band (Est-4) with R(f) of 0.32 predominately withstood a temperature of 70 +/- 2 degrees C for a duration of 10 min and were confirmed as thermostable esterases in haemolymph of silkworm, Bombyx mori L. This also categorized the presence of thermostable esterases in developed multivoltine and bivoltine breeds of silkworm, even though the qualitative activity was more in the former than the latter. The qualitative presence of thermostable esterases and their activity could be adopted as an indicative biochemical marker in relation to thermotolerance in silkworm.

Clinical and echocardiographic characteristics associated with evolution of patent ductus arteriosus in preterm neonates: A prospective cohort study.

BACKGROUND: In preterm infants, persistence of ductus arteriosus is an important medical condition. Functional echocardiography for patent ductus arteriosus (PDA) may guide clinical decision-making regarding treatment requirement strategies. Objectives of the study were to assess the trends of clinical and functional echocardiographic parameters with evolution of ductus arteriosus in babies≤1250 gm of birth weight and to evaluate whether there is any association of these parameters with persistence of ductus. METHODS: In this prospective observational study, recruited babies were assessed serially for clinical events and functional echocardiography. Babies were classified into three groups: without PDA, with PDA but PDA spontaneously closed (within 7 days) and persistent PDA. RESULT: We included 143 infants (Birth weight 1017±179 g, gestational age 30.8±2.7 weeks). Out of 60 babies with PDA, PDA failed to close spontaneously in first week in 32 (53.4 %) infants. PDA Doppler flow pattern on day 3 was found to be one of the most significant markers for future ductus. The highest frequency of growing pattern (37.5%) and pulsatile pattern (59.4%) was seen in persistence ductus group. PDA diameter and LA/Ao ratio were found strongly correlated with all other variables except E/A ratio. CONCLUSION: We noticed persistence of ductus in preterm infants had significant clinical and echocardiographic association. PDA doppler flow pattern on day 3 was found to be a significant marker for future behaviour of ductus. Significant correlation was found among individual functional echocardiographic parameters in babies with PDA. This would guide judicious treatment of PDA in preterm neonates.

Prognostic factors for survival after curative resection of Dukes' B colonic cancer.

AIM: Data on the prognostic factors for survival in patients with locally advanced, node-negative colon cancer are limited. This study aimed to determine which factors might predict survival in patients with Dukes' B (T3 or T4, N0) colon cancer. METHOD: One hundred and eighty (93 male; median age 75 [range, 38-96] years) consecutive patients who had resection of a primary Dukes' B (on final histopathological analysis) colonic cancer between 1998 and 2003 were studied. No patient received neoadjuvant chemotherapy. Multivariate Cox regression modelling was used to assess the prognostic value of variables. Median follow up was 85 (60-125) months. RESULTS: Thirteen (7%) patients had a perforation at presentation. The median distance from tumour to the nearest longitudinal resection margin was 6 (0.3-27) cm. One hundred and twenty-four (69%) patients had a lymph node yield of 12 or more nodes. Actual 5-year survival was 59%. On multivariate regression analysis, tumour perforation (perforation vs no perforation, 5-year survival, 23%vs 61%; hazard ratio (HR), 3.7; 95% confidence interval (CI), 1.6-8.4; P = 0.002), tumour-to-margin distance (< 5 cm vs ≥ 5 cm, 48%vs 65%; HR, 1.7; 95% CI, 1.1-2.7; P = 0.039) and older age (≥ 75 years vs < 75 years, 45%vs 72%; HR, 3; 95% CI, 1.8-5; P < 0.001) were independent significant variables. CONCLUSION: A lymph node yield of 12 or more nodes is not a significant prognostic factor for survival after resection of Dukes' B colonic cancer. Patients with tumour perforation or limited resection have worse prognosis.

Bancroftian elephantiasis in Nilphamari, Bangladesh.

The parasitic nematodes Wuchereria bancrofti, causes a dreadful disease in humans known as lymphatic filariasis, which afflicts more than 250 million people in tropical countries. Twelve districts with about 20 million people are endemic out of 64 districts in Bangladesh affecting more on Northern districts. This study was done in the Nilphamari, Kisorgonj and Sayedpur Thana under Nilphamari district, which is the most endemic for filariasis. In the present study, nineteen unions were investigated. Average 1.34% people were infected with filariasis (0.87% male and 1.81% female) out of 2,32,005 populations in those area. The highest percentage of infected unions was Alam Biditor (1.35%) under Kisorgonj Thana and lowest infected unions was Khatamadhupur (0.21%) under Sayedpur Thana. Among the affected people, 69.48% were poor, 28.88% were middle class and 1.63% was rich. The age group, 26-45 years, showed the highest rate (53.07%) of infection and the age group, 6-15 years, showed the lowest rate (1.92%) of infection. The relationships between infection status of male and female were statistically significant.

Prediction of ductus closure and development of adverse clinical outcome by functional echocardiography in very low birth weight newborn.

OBJECTIVE: To evaluate the role of functional echocardiography for prediction of patent ductus arteriosus (PDA) closure and development of adverse outcome in very low birth weight newborn. METHODS AND STUDY DESIGN: Functional echocardiography was done in 143 neonates with birth weight less than 1250 g on day 3. Nine echocardiographic parameters were analyzed for babies with PDA for prediction of spontaneous closure and development of one or more adverse outcomes (bronchopulmonary dysplasia, necrotizing enterocolitis≥stage 2 and intraventricular hemorrhage > grade 2) during hospital stay. RESULT: The mean (±SD) birthweight and gestational age of the cohort were 1017 (±17) g and 30.8 (±2.7) weeks. PDA was found in 60 (41.9%) babies on day 3 among the recruited babies. Binary logistic regression model showed strong prediction ability of early (day 3) functional echocardiography markers in predicting future spontaneous closure of PDA and development of one or more adverse clinical outcome. In multivariate analysis, abnormal flow pattern (growing or pulsatile) was found to have increased risk for persistence of PDA (adjusted OR 22.9, CI 1.97-269) in comparison to PDA with closing/bidirectional pattern. CONCLUSION: Early functional echocardiography, especially the flow pattern, is useful for prediction of PDA closure. Adverse clinical outcome prediction is possible with functional echocardiography markers when combined with gestational age and PDA closure status.

Salt Intake Behaviors among Type 2 Diabetic Patients of a Tertiary Level Hospital in Dhaka City.

Hypertension and diabetes co-exist frequently. Therefore, salt intake behavior, a risk factor of hypertension, in diabetic patients plays an important role in determining their cardiovascular outcome. The purpose of this study was to assess the knowledge and behaviors of health risks associated with a salt intake in adults with type 2 diabetes. This cross-sectional study was conducted among the type 2 diabetic in-patients of Bangladesh Institute of Health Sciences General Hospital, Dhaka, Bangladesh from October to December 2016. Data were collected from 131 respondents through interview using WHO STEPS module of salt with adaptation to local context like on amount of added salt while taking meal. Information on blood pressure, body mass index and relevant co-morbidities were also collected. About half of the respondents were women (56.5%). Mean age of the respondents was 54.3±14.4 years. More than six in 10 of them (62.6%) took added salt while taking meal; and 40.5% took processed foods with high salt. The mean amount of added salt intake among the users was 4.4±1.6gm per day having no significant difference between men and women. Though 47.3% of the respondents believed that lowering salt in meal is very important and 77.9% of them believed that excess salt or salty sauce can cause health problems. Salt intake behavior is poor in patients with type 2 diabetes even having regular contacts with doctors and other health professionals. Appropriate measures can be taken to increase awareness, change their attitude and behavior regarding salt consumption.

Eastern Indian 3800-million-year-old crust and early mantle differentiation.

Samarium-neodymium data for nine granitic and tonalite gneisses occurring as remnants within the Singhbhum granite batholith in eastern India define an isochron of age 3775 +/- 89 x 10(6) years with an initial (143)Nd/(144)Nd ratio of 0.50798 +/- 0.00007. This age contrasts with the rubidium-strontium age of 3200 x 10(6) years for the same suite of rocks. On the basis of the new samarium-neodynium data, field data, and petrologic data, a scheme of evolution is proposed for the Archean crust in eastern India. The isotopic data provide evidence that parts of the earth's mantle were already differentiated with respect to the chondritic samarium-neodymium ratio 3800 x l0(6) years ago.

Morbidity and mortality after closure of loop ileostomy.

BACKGROUND: A temporary loop ileostomy is commonly used to protect low pelvic anastomoses. Closure is associated with morbidity and mortality. This study investigated patterns of complications after loop ileostomy closure and factors associated with morbidity and mortality. METHOD: A review was performed of patients who underwent loop ileostomy closure between 1999 and 2005. RESULTS: Three hundred and twenty-five patients underwent closure of loop ileostomy. Reasons for primary surgery were: anterior resection for cancer (n = 160, 49%), ileal pouch-anal anastomosis (n = 114, 35%), diverticular disease (n = 25, 8%), Crohn's colitis (n = 4, 1%) and other conditions (n = 22, 7%). Overall mortality was 2.5% (n = 8) and morbidity was 22.8% (n = 74). Thirty-two patients (10%) developed small bowel obstruction, of whom seven required operative intervention. Overall, the re-operation rate in this series was 28 patients (8.6%). Thirteen (4%) patients had an anastomotic leak of whom 12 patients had re-operation. Preoperative anaemia was significantly associated with leakage (Hb < 11 g/dl; n = 65, P = 0.033). The leakage rate was lower after a stapled anastomosis than a hand-sutured anastomosis (4/203 vs 9/122; P = 0.039). Hypo-albuminaemia (albumin < 34 g/l) was significantly associated with mortality (n = 46, P < 0.001). CONCLUSIONS: Loop ileostomy closure is associated with morbidity and mortality. Anaemia and hypo-albuminaemia may be associated with poor outcome.

Fatty acid oxidation and the regulation of malonyl-CoA in human muscle.

Questions concerning whether malonyl-CoA is regulated in human muscle and whether malonyl-CoA modulates fatty acid oxidation are still unanswered. To address these questions, whole-body fatty acid oxidation and the concentration of malonyl-CoA, citrate, and malate were determined in the vastus lateralis muscle of 16 healthy nonobese Swedish men during a sequential euglycemic-hyperinsulinemic clamp. Insulin was infused at rates of 0.25 and 1.0 mU x kg(-1) x min(-1), and glucose was infused at rates of 2.0 +/- 0.2 and 8.1 +/- 0.7 mg x kg(-1) x min(-1), respectively. During the low-dose insulin infusion, whole-body fatty acid oxidation, as determined by indirect calorimetry, decreased by 22% from a basal rate of 0.94 +/- 0.06 to 0.74 +/- 0.07 mg x kg(-1) x min(-1) (P = 0.005), but no increase in malonyl-CoA was observed. In contrast, during the high-dose insulin infusion, malonyl-CoA increased from 0.20 +/- 0.01 to 0.24 +/- 0.01 nmol/g (P < 0.001), and whole-body fatty acid oxidation decreased by an additional 41% to 0.44 +/- 0.06 mg x kg(-1) x min(-1) (P < 0.001). The increase in malonyl-CoA was associated with 30-50% increases in the concentrations of citrate (102 +/- 6 vs. 137 +/- 7 nmol/g, P < 0.001), an allosteric activator of the rate-limiting enzyme in the malonyl-CoA formation, acetyl-CoA carboxylase, and malate (80 +/- 6 vs. 126 +/- 9 nmol/g, P = 0.002), an antiporter for citrate efflux from the mitochondria. Significant correlations were observed between the concentration of malonyl-CoA and both glucose utilization (r = 0.53, P = 0.002) and the sum of the concentrations of citrate and malate (r = 0.52, P < 0.001), a proposed index of the cytosolic concentration of citrate. In addition, an inverse correlation between malonyl-CoA concentration and fatty acid oxidation was observed (r = -0.32, P = 0.03). The results indicate that an infusion of insulin and glucose at a high rate leads to increases in the concentration of malonyl-CoA in skeletal muscle and to decreases in whole-body and, presumably, muscle fatty acid oxidation. Furthermore, they suggest that the increase in malonyl-CoA in this situation is due, at least in part, to an increase in the cytosolic concentration of citrate. Because cytosolic citrate is also an inhibitor of phosphofructokinase, an attractive hypothesis is that changes in its concentration are part of an autoregulatory mechanism by which glucose modulates its own use and the use of fatty acids as fuels for skeletal muscle.

Diet-induced muscle insulin resistance in rats is ameliorated by acute dietary lipid withdrawal or a single bout of exercise: parallel relationship between insulin stimulation of glucose uptake and suppression of long-chain fatty acyl-CoA.

Chronic high-fat feeding in rats induces profound whole-body insulin resistance, mainly due to effects in oxidative skeletal muscle. The mechanisms of this reaction remain unclear, but local lipid availability has been implicated. The aim of this study was to examine the influence of three short-term physiological manipulations intended to lower muscle lipid availability on insulin sensitivity in high-fat-fed rats. Adult male Wistar rats fed a high-fat diet for 3 weeks were divided into four groups the day before the study: one group was fed the normal daily high-fat meal (FM); another group was fed an isocaloric low-fat high-glucose meal (GM); a third group was fasted overnight (NM); and a fourth group underwent a single bout of exercise (2-h swim), then were fed the normal high-fat meal (EX). In vivo insulin action was assessed using the hyperinsulinemic glucose clamp (plasma insulin 745 pmol/l, glucose 7.2 mmol/l). Prior exercise, a single low-fat meal, or fasting all significantly increased insulin-stimulated glucose utilization, estimated at either the whole-body level (P < 0.01 vs. FM) or in red quadriceps muscle (EX 18.2, GM 28.1, and NM 19.3 vs. FM 12.6 +/- 1.1 micromol x 100 g(-1) x min(-1); P < 0.05), as well as increased insulin suppressibility of muscle total long-chain fatty acyl-CoA (LC-CoA), the metabolically available form of fatty acid (EX 24.0, GM 15.5, and NM 30.6 vs. FM 45.4 nmol/g; P < 0.05). There was a strong inverse correlation between glucose uptake and LC-CoA in red quadriceps during the clamp (r = -0.7, P = 0.001). Muscle triglyceride was significantly reduced by short-term dietary lipid withdrawal (GM -22 and NM -24% vs. FM; P < 0.01), but not prior exercise. We concluded that muscle insulin resistance induced by high-fat feeding is readily ameliorated by three independent, short-term physiological manipulations. The data suggest that insulin resistance is an important factor in the elevated muscle lipid availability induced by chronic high-fat feeding.

Long-term exposure of beta-INS cells to high glucose concentrations increases anaplerosis, lipogenesis, and lipogenic gene expression.

Chronic exposure of pancreatic beta-cells to high glucose has pleiotropic action on beta-cell function. In particular, it induces key glycolytic genes, promotes glycogen deposition, and causes beta-cell proliferation and altered insulin secretion characterized by sensitization to low glucose. Postglycolytic events, in particular, anaplerosis and lipid signaling, are thought to be implicated in beta-cell activation by glucose. To understand the biochemical nature of the beta-cell adaptive process to hyperglycemia, we studied the regulation by glucose of lipogenic genes in the beta-cell line INS-1. A 3-day exposure of cells to elevated glucose (5-25 mmol/l) increased the enzymatic activities of fatty acid synthase 3-fold, acetyl-CoA carboxylase 30-fold, and malic enzyme 1.3-fold. Pyruvate carboxylase and citrate lyase expression remained constant. Similar observations were made at the protein and mRNA levels except for malic enzyme mRNA, which did not vary. Metabolic gene expression changes were associated with chronically elevated levels of citrate, malate, malonyl-CoA, and conversion of glucose carbon into lipids, even in cells that were subsequently exposed to low glucose. Similarly, fatty acid oxidation was suppressed and phospholipid and triglyceride synthesis was enhanced independently of the external glucose concentration in cells preexposed to high glucose. The results suggest that a coordinated induction of glycolytic and lipogenic genes in conjunction with glycogen and triglyceride deposition, as well as increased anaplerosis and altered lipid partitioning, contribute to the adaptive process to hyperglycemia and glucose sensitization of the beta-cell.

Dynamic matrix composition in engineered cartilage with stochastic supplementation of growth factors.

Dynamic extracellular matrix (ECM) synthesis is explored in a hypothesized engineered cartilage construct. Growth (alpha) and decay (beta) rate parameters are developed from a previous engineered cartilage model. The presented mathematical model was constructed from the parameterized experimental data using a deterministic and stochastic examination of ECM synthesis based on a negative feedback control mechanism. A growth factor supplementation is incorporated in a probabilistic mathematical approach. The growth factor component modified an initial deterministic model through a Gaussian white noise fluctuation. As the primary constituents of ECM, the mathematical tool is intended to characterize the probable steady state distribution of glycosaminoglycan (GAG) and collagen molecules as well as mean mass accumulation at homeostasis. Computer simulation of the models is applied to reported data from four similar chondrocyte-polymer construct culture systems. The range in rate ratios reflect the differing nature of GAG and collagen synthesis (alphaGAG/betaGAG = 4.2 to 148.6; alphacollagen/betacollagen = 8.1 to 2590.4). This technique reduced the influencing synthesis factors to a few key descriptive parameters. Additional anabolic and catabolic factors may further be built into the models.

Characterization of Klebsiella granulomatis pathogenic to silkworm, Bombyx mori L.

Bacterial disease of silkworm causes significant reduction of silk production leading to huge economic loss. This study aims to isolate bacteria from diseased silkworm and to determine its pathogenicity and antibiotic resistance. A strain of Klebsiella granulomatis has been isolated from silkworm haemolymph which was later identified on the basis of biochemical tests and 16S rRNA gene sequencing. The optimum culture condition of K. granulomatis was determined at pH 7.0 and 37 °C temperature. The strain was resistant to most of the antibiotics used in this study except azithromycin, gentamycin and ciprofloxacin. The strain is capable to reproduce flacherrie like symptoms with high mortality rate when re-injected into healthy silkworm. Treatment with low dose of ciprofloxacin was found to be effective to prevent flacherrie induced by the isolated K. granulomatis strain.

Mechanism of action of amphotericin B on Leishmania donovani promastigotes.

The growth of Leishmania donovani promastigotes in a liquid medium was completely inhibited by amphotericin B at a concentration of 0.3 microgram ml-1 (0.3 microM). Continuous release of small molecules that absorb at 260 nm and 280 nm was observed after contact with the drug. Uptake of [U-14C]glucose was inhibited in cells treated with the drug. An immediate release of isotopic glucose and its metabolites from preloaded cells could be demonstrated after incubation with amphotericin B (0.4 microM). Inhibition of respiration by the drug was a comparatively slower process. All the above effects could be effectively prevented in the presence of either cholesterol or ergosterol. The primary site of action of amphotericin B on L. donovani promastigote cells appears to be membrane sterols that result in a loss of the permeability barrier to small metabolites. An interesting biochemical similarity, thus, emerges between flagellated protozoa and fungi.

Hydrolysis of phosphoproteins and inositol phosphates by cell surface phosphatase of Leishmania donovani.

Leishmania donovani promastigotes contain intense tartrate-resistant cell surface acid phosphatase (ACP1) which blocks superoxide anion production by activated human neutrophils [A.T. Remaley et al. (1984) J. Biol. Chem, 259, 11173-11175]. An extensively purified preparation of ACP1 dephosphorylates several phosphoproteins which are phosphorylated at serine residues; these include: pyruvate kinase (Km 1.6 microM; Vmax 71.4 U (mg protein)-1), phosphorylase kinase (Km 0.076 microM; Vmax 5.4 U (mg protein)-1) and histones (Km 4.86 microM; Vmax 2.2 U (mg protein)-1). However, the specific activity of the leishmanial phosphatase on these phosphoproteins is very low as compared to other phosphoprotein phosphatases. The phosphatase activity of ACP1 was also low on phosphohistone phosphorylated at tyrosine residues. Phosphatidylinositol-4,5-diphosphate (PIP2) and inositoltriphosphate (IP3) were also tested as ACP1 substrates. PIP2 was hydrolyzed rapidly by ACP1. The rate of hydrolysis of PIP2 was higher at pH 6.8 (Km 2.35 microM; Vmax 107 X 10(3) U (mg protein)-1) than at pH 5.5 (Km 4.16 microM; Vmax 71 X 10(3) U (mg protein)-1). 32P-labeled IP3 was also a substrate for ACP1; the hydrolysis products consisted of a mixture of inositoldiphosphate and inositolmonophosphate. ACP1 and ten other phosphatases were tested for their ability to dephosphorylate proteins and to inhibit O2- production by stimulated human neutrophils. There was no correlation between the protein phosphatase activity of the acid- and alkaline phosphatases and their ability to block neutrophil O2- production. The results indicate that ACP1 probably blocks the production of reduced oxygen intermediates by a mechanism that does not involve dephosphorylation of phosphoproteins; however, the possibility that the parasite's phosphatase affects phagocyte metabolism by degrading PIP2 or IP3 should be considered.