Comparison between acetylator phenotype and genotype polymorphism of n-acetyltransferase-2 in tuberculosis patients

BACKGROUND

Isoniazid (INH) is one of the most important drugs of antitubercular treatment regime, and in some cases it causes hepatotoxicity. It is metabolized by hepatic N-acetyltransferase-2 (NAT2).

AIM

To compare whether both methods, i.e., genotype NAT2 and phenotype test of measuring serum INH levels, are useful to identify acetylator status of patients on antitubercular treatment (ATT).

METHODS

A total of 251 tuberculosis (TB) patients on standard treatment were followed up to 6 months for this study. NAT2 genotype was assessed by PCR with restriction fragment length polymorphism (RFLP) whereas serum INH levels were measured by fluorometry.

RESULTS

Of the 251 patients, 50 (19.9%) developed ATT-induced hepatotoxicity. By phenotypic estimation, in the hepatotoxicity group, 17/50 (34%) were slow acetylators whereas 33/50 (66%) were fast acetylators. Genotypically, 19/50 (38%) were slow acetylators and 31/50 (62%) fast acetylators. By phenotypic analysis, in non-hepatotoxicity group, 46/201 (22.9%) were slow acetylators and 155/201 (77.1%) fast acetylators. By genotypic analysis, 30/201 (14.9%) were slow acetylators and 171/201 (85%) fast acetylators. Overall, slow acetylators (25.1%) measured phenotypically were not significantly different from slow acetylators (19.5%) measured genotypically.

CONCLUSION

This study suggests that the acetylator status of TB patients can be detected by phenotypic method as efficaciously as by genotypic method. Therefore, phenotypic method can replace genotypic method to determine acetylating status as phenotypic method is simple and inexpensive.

A novel Y332C missense mutation in the intracellular domain of the human growth hormone receptor does not alter STAT5b signaling: redundancy of GHR intracellular tyrosines involved in STAT5b signaling

BACKGROUND

The growth hormone receptor (GHR), upon binding with GH, induces JAK2-mediated phosphorylation of GHR intracellular tyrosines, which then recruit STAT5b. Aberrancies in STAT5b signaling, due to mutations in GHR or STAT5b genes, result in poor responses to GH and severe short stature.

OBJECTIVE

To evaluate and compare the role of a novel Y332C GHR variant identified in a patient with short stature to the other GHR intracellular tyrosines in the GHR-STAT5b signaling process.

RESULTS

Recombinant human GHR constructs carrying Y332C or single Y to F changes for each of the 7 intracellular tyrosines did not alter GH-induced GHR-STAT5b signaling in reconstitution studies. However, GH-induced STAT5b activation was specifically abrogated in an hGHR variant in which all 7 tyrosines were inactivated (MYF). When hGHR variants carrying single intracellular tyrosines were evaluated, STAT5b activation was comparable to that of wild-type hGHR only with variants carrying Y534, Y566 or Y627.

CONCLUSION

We provide evidence that in human GHR, 3 intracellular tyrosines are critical and redundant in the GH-induced STAT5b signaling process. This redundancy may explain why an Y332C variant did not alter STAT5b signaling. Identification of missense variants in human GHR intracellular domain should be interpreted with caution and rigorously analyzed.

Evaluation of the effectiveness of ophthalmic assistants as screeners for glaucoma in North India

AIM

To assess whether ophthalmic assistants are effective in screening people for glaucoma in India.

METHODOLOGY

The study subjects were examined by both trained ophthalmic assistants and an ophthalmologist in both hospital and community settings. Specific tests for the diagnosis of glaucoma suspects included visual field examination using frequency doubling technology perimetry, intraocular pressure measurement (Tonopen), A-scan central anterior chamber depth measurement and dilated optic disc examination. The findings recorded by the ophthalmic assistants were masked to the ophthalmologist to avoid measurement bias.

RESULTS

In the hospital setting, there was a substantial level of agreement between the ophthalmic assistants and the ophthalmologist in the diagnosis of glaucoma suspects (89.29%, k=0.7, 95% confidence interval (CI)=0.54-0.86). The diagnostic accuracy of the ophthalmic assistants in detecting glaucoma suspects was high for sensitivity (95.2%, 95% CI=91.4-97.7%) but lower for specificity at 71.4% (95% CI=60.0-78.7%).In the community setting, there was a moderate level of agreement between the ophthalmic assistants and the ophthalmologist in the diagnosis of glaucoma suspects (78.23%, k=0.50, 95% CI=0.37-0.64). The diagnostic accuracy of the ophthalmic assistants in detecting glaucoma suspects was moderate for sensitivity (82.9, 95% CI=69.7-91.5%) but lower for specificity at 76.8% (95% CI=72.7-79.5%).

CONCLUSION

Ophthalmic assistants can be used for opportunistic case detection of glaucoma suspects in the community. Structured training of the ophthalmic assistants together with enhanced clinical experience would improve their performance in detecting glaucoma suspects in the community.

Pseudothrombocytopenia -- a caveat

Pseudothrombocytopenia is an ex vivo thrombocytopenia, counted by an automated cell counter, but not configured by microscopic examination of a well prepared blood smear. Incidences of pseudothrombocytopenia reported in different studies range from 0.09-0.21%, which could account for 15-30% of all cases of thrombocytopenla. Failure to identify pseudothrombocytopenia has led to a lot of clinical problems like unnecessary platelet transfusion, glucocorticoid therapy and so on. Haematological cell counters count platelets as particles with volume between 2 and 20fl. Thus platelet clumps are counted as leucocytes while fragmented RBCs as platelets. This study found pseudothrombocytopenia due to causes like EDTA blood stored at less than 32 degrees C for more than 2 hours (35%), excess EDTA in sample (10.7%), hyperlipidaemia, auto-immune disease, pregnancy, etc. No apparent cause could be found in 52% of cases. Hence it is emphasised that direct microscopic examination of a well stained blood smear from EDTA-venous blood (within 1hour) and or direct counting under Neubauer chamber with 1% ammonium oxalate (in special cases) is almost mandatory before releasing a report of platelet count. Also factors related to ratio and storage of EDTA-blood, calibration of instruments, proper selection of reagents, supervision of laboratory staff are essential to rule out any error of report including pseudothrombocytopenia.

Molecular simulation of the frictional behavior of polymer-on-polymer sliding

Molecular simulations of the sliding processes of polymer-on-polymer systems were performed to investigate the surface and subsurface deformations and how these affect tribological characteristics of nanometer-scale polymer films. It is shown that a very severe deformation is localized to a band of material about 2.5 nm thick at the interface of the polymer surfaces. Outside of this band, the polymer films experience a uniform shear strain that reaches a finite steady-state value of close to 100%. Only after the polymer films have achieved this steady-state shear strain do the contacting surfaces of the films show significant relative slippage over each other. Because severe deformation is limited to a localized band much thinner than the polymeric films, the thickness of the deformation band is envisaged to be independent of the film thickness and hence frictional forces are expected to be independent of the thickness of the polymer films. A strong dependency of friction on interfacial adhesion, surface roughness, and the shear modulus of the sliding system was observed. Although the simulations showed that frictional forces increase linearly with contact pressure, adhesive forces contribute significantly to the overall friction and must therefore be accounted for in nanometer-scale friction. It is also shown that the coefficient of friction is lower for lower-density polymers as well as for polymers with higher molecular weights.

Diffuse Neutron Scattering from Surfaces and Interfaces

The use of neutron scattering as a tool for exploring surfaces and interfaces has become more prevalent over the last several years, mainly due to the increasing popularity of reflectivity techniques, which study specular reflection from single surfaces or multilayers. Due to intensity limitations, the use of off-specular or grazing-incidence neutron scattering techniques has been much less prevalent. In this paper we shall discuss the origins of magnetic off-specular scattering (e.g., as observed in magnetic multilayers) and the origins of anomalies seen in the X-ray or neutron diffuse scattering from multilayers near Bragg reflections in terms of the Dynamical Theory of Scattering.

Measurement of the interior structure of thin polymer films using grazing incidence diffuse x-ray scattering

A method is developed for calculating the small-angle x-ray scattering originating from within the interior of a thin film under grazing incidence illumination. This offers the possibility of using x-ray scattering to probe how the structure of polymers is modified by confinement. When the diffuse scattering from a thin film is measured over a range of incident angles, it is possible to separate the contributions to scattering from the interfaces and the contribution from the film interior. Using the distorted-wave Born approximation the structure factor, S(q), of the film interior can then be obtained. We apply this method to analyze density fluctuations from within the interior of a silicon supported molten polystyrene (PS) film. Measurements were made as a function of film thickness ranging from one to ten times the polymer radius of gyration (Rg). The compressibility, calculated by extrapolating the measured S(q) to q=0, agrees well with that of bulk PS for thick films, but thinner films exhibit a peak in S(q) near q=0. This peak, which grows with decreasing thickness, is attributed to a decreased interpenetration of chains and a consequent enhanced compressibility.

Effect of surface freezing on meniscus relaxation in side chain comb polymers

We have observed a sharp slowing down of the relaxation of the liquid meniscus for poly(n-alkyl acrylate) at temperatures where there are no abrupt changes in bulk viscosity or surface tension. This slowing down is due to the formation of a surface-ordered monolayer above the bulk melting temperatures. X-ray photon correlation spectroscopy measurements reveal that the surface capillary fluctuations are also significantly slower due to the formation of the ordered monolayer for film thicknesses comparable to that of the precursor films. The slowing down of the precursor film dynamics is responsible for slower meniscus relaxation below the surface ordering transition temperature.

Antenatal corticosteroids and neonatal outcomes according to gestational age: a cohort study

OBJECTIVE

To see whether there was any difference in the effect of antenatal corticosteroids on neonatal outcomes according to different gestational ages at birth.

METHODS

This was a prospective cohort study in a geographically defined population (Trent region, UK). All infants admitted for neonatal care, of 23-32 weeks' gestation, born to Trent resident mothers over the 15-year period between 1993 and 2007 were included. Antenatal corticosteroid treatment was given to pregnant women at risk of preterm birth. The primary outcome was survival until discharge from neonatal unit. Secondary outcomes included length of stay on the neonatal unit, duration of artificial respiratory support (mechanical ventilation and continuous positive airway pressure (CPAP)) and chronic lung disease (CLD).

RESULTS

The overall mortality among babies born between 24 and 29 weeks with maternal steroids was lower (n=850 out of 4370; 19.4%) as compared to their counterparts whose mothers did not receive steroids (n=323 out of 920; 35.1%) The gestation-specific mortality figures (%) in the steroid treated group between 24 and 29 weeks' gestation were 61.5, 36.9, 28.5, 17.5, 10.2 and 5.1, respectively, and this was significantly lower than the group without steroid treatment. There was a 9.9% reduction in mortality among babies born at 23 weeks' gestation in the steroid treated group (n=81 out of 102; 79.4%) compared to the non-steroid group (n=75 out of 84; 89.3%), but this did not reach statistical significance (p=0.068). There was no significant effect of antenatal steroid treatment on length of stay, duration of respiratory support and CLD among infants who survived until discharge. There was no trend in survival in the two groups over the 15-year study period.

CONCLUSIONS

Antenatal corticosteroid treatment is associated with improved survival in babies born between 24 and 29 weeks' gestation. This, however, does not lead to any significant improvements in length of stay, duration of respiratory support and CLD among survivors.

Reduced viscosity of the free surface in entangled polymer melt films

By embedding "dilute" gold nanoparticles in single polystyrene thin films as "markers", we probe the local viscosity of the free surface at temperatures far above the glass transition temperature (T(g)). The technique used was x-ray photon correlation spectroscopy with resonance-enhanced x-ray scattering. The results clearly showed the surface viscosity is about 30% lower than the rest of the film. We found that this reduction is strongly associated with chain entanglements at the free surface rather than the reduction in T(g).

Synchrotron studies of lattice distortions and lattice modulations in complex oxides

We review some recent studies of lattice modulations and lattice distortions in single crystals of the layered manganite compound La1.2Sr1.8Mn2O7 and the YBa2Cu3O6+ x cuprate superconductors obtained from X-ray diffuse scattering using synchrotron radiation. These results confirm the existence of a polaronic liquid (with short-range order) in the paramagnetic insulator phase of the manganite compound, and of lattice modulations (with short-range order) in the cuprate compounds, which co exist with superconductivity down to the lowest temperatures.

Expanding the spectrum of mutations in GH1 and GHRHR: genetic screening in a large cohort of patients with congenital isolated growth hormone deficiency

CONTEXT

It is estimated that 3-30% of cases with isolated GH deficiency (IGHD) have a genetic etiology, with a number of mutations being reported in GH1 and GHRHR. The aim of our study was to genetically characterize a cohort of patients with congenital IGHD and analyze their characteristics.

PATIENTS AND METHODS

A total of 224 patients (190 pedigrees) with IGHD and a eutopic posterior pituitary were screened for mutations in GH1 and GHRHR. To explore the possibility of an association of GH1 abnormalities with multiple pituitary hormone deficiencies, we have screened 62 patients with either multiple pituitary hormone deficiencies (42 pedigrees), or IGHD with an ectopic posterior pituitary (21 pedigrees).

RESULTS

Mutations in GH1 and GHRHR were identified in 41 patients from 21 pedigrees (11.1%), with a higher prevalence in familial cases (38.6%). These included previously described and novel mutations in GH1 (C182X, G120V, R178H, IVS3+4nt, a>t) and GHRHR (W273S, R94L, R162W). Autosomal dominant, type II IGHD was the commonest form (52.4%), followed by type IB (42.8%) and type IA (4.8%). Patients with type II IGHD had highly variable phenotypes. There was no difference in the endocrinology or magnetic resonance imaging appearance between patients with and without mutations, although those with mutations presented with more significant growth failure (height, -4.7 +/- 1.6 SDS vs. -3.4 +/- 1.7 SDS) (P = 0.001). There was no apparent difference between patients with mutations in GH1 and GHRHR.

CONCLUSIONS

IGHD patients with severe growth failure and a positive family history should be screened for genetic mutations; the evolving endocrinopathy observed in some of these patients suggests the need for long-term follow-up.

Long term follow-up of very low birthweight infants from a neonatal volume versus pressure mechanical ventilation trial

BACKGROUND

A previous randomised trial showed volume controlled ventilation (VCV) was efficacious in ventilating very preterm and extremely low birthweight babies.

OBJECTIVE

To compare long term survival, pulmonary morbidities and gross neurodevelopmental outcomes of babies randomised to either VCV or pressure limited ventilation (PLV) for treatment of respiratory distress syndrome.

DESIGN/METHODS

Masked evaluation of health status, including frequency of respiratory illness, use of medications, hospital admissions, and gross neurodevelopmental status were obtained using a structured parental questionnaire and verification from medical records.

RESULTS

94 of 109 children (86%) survived to discharge. Three died after discharge (2 VCV, 1 PLV). Modality of ventilation did not affect overall mortality; seven VCV children died (12%) versus 11 PLV (21%) (OR 0.5 (95% CI 0.1 to 1.4), p = 0.13). Respiratory abnormalities were present in 32 (37%), and 26 (30%) required hospital readmission. There was no significant difference in readmission rates between the two groups: VC 13/45 (29%) and PLV 19/40 (47%) (OR 0.4 (0.1 to 1.1), p = 0.07). Modality of ventilation did not affect frequency of respiratory illness: VC 12 (27%) and PLV 14 (35%) (OR 0.46 (0.1 to 1.1), p = 0.09). However, significantly fewer VCV children (13%, n = 6) compared to PLV children (32%, n = 13) required treatment with inhaled steroids/bronchodilators (OR 0.3 (0.1 to 0.9), p = 0.04). Nine children had severe neurodevelopmental disability (cerebral palsy, blindness, deafness) (9.8%; 3 VCV, 6 PLV 6) (OR 0.4 (0.09 to 1.7)).

CONCLUSIONS

The efficacy of VCV in very preterm and low birth babies appears to be maintained on longer term evaluation.

Effect of predominant methanogenic flora on outcome of lactose hydrogen breath test in controls and irritable bowel syndrome patients of north India

The relationship between methanogenic flora and hydrogen (H(2)) production is considered to be a possible confounding factor in the interpretation of hydrogen breath tests (H(2)BT). Therefore, the present study was conducted prospectively and included 154 IBS patients (fulfilling Rome II criteria) and 286 age-and-sex-matched apparently healthy controls. Each subject underwent H(2)BT after overnight fasting using 25 g lactose. Methane and H(2) were measured using an SC Microlyser from Quintron, USA, at baseline and every 30 min for a total of 4 h. Subjects with fasting methane concentration <10 ppm were labeled as low methane producers (LMP) and >10 ppm as predominant methane producers (PMP). A rise >20 ppm over base line in hydrogen concentration was taken as +ve hydrogen breath test. IBS and control groups included 66.78% and 67.53% males, respectively. Mean age in the two groups were 48.52 +/- 30.54 years (range 15-68 years) and 45.67 +/- 30.54 years (range 15-78 years), respectively. Hydrogen breath test was +ve in 77/154 (50%) IBS patients and in 142/286 (49.65%) in controls (P > 0.05). It was also observed that the hydrogen breath test was -ve due to PMP in 5/77 (6.49%) of IBS patients and in 29/154 (20.14%) in controls. PMP affected lactose hydrogen breath tests in 6.49-20.14% subjects. This effect is more apparent in apparently healthy subjects as compared to patients with IBS.

Influence of previously ingested wheat on fasting breath hydrogen in celiac patients

The excretion of hydrogen in breath commonly persists, despite an overnight fast. Although the elevation of hydrogen concentration above the fasting value after the administration of a test sugar is evidence of malabsorption, the level of the fasting value itself in untreated celiac patients is unknown. Therefore, we studied the fasting breath hydrogen (FBH(2)) concentration in 40 healthy controls, 35 subjects with functional bowel disorders, and 30 patients of untreated celiac disease with and without bread or wheat diet one day before the test. The fasting level of hydrogen concentration in untreated celiac patients (28.7 +/- 19.5 ppm) was significantly higher than those in healthy volunteers (9.5 +/- 3.4 ppm) and subjects with functional bowel disorders (10.6 +/- 4.5 ppm). The percentage of patients with elevated H(2) fasting levels in untreated celiac disease (82.5%) was significantly higher than that in healthy controls (10%) and subjects with functional bowel disorders (17.1%). In 30 celiac patients, studied with and without wheat-free diet one day before the test, the fasting hydrogen levels decreased from 28.7 +/- 19.5 ppm to 10.6 +/- 3.5 ppm, and becoming normal in all patients of celiac disease. Our results show that the patients of untreated celiac disease should be instructed not to eat things made up of wheat one day before hydrogen breath testing so that the normal fasting hydrogen concentration can be obtained and false-negative hydrogen breath test results can be avoided.

The effect of two levels of pressure support ventilation on tidal volume delivery and minute ventilation in preterm infants

OBJECTIVE

To study the effect of different levels of pressure support ventilation (PSV) on respiratory parameters in preterm infants during the weaning phase of mechanical ventilation.

DESIGN/METHODS

In this quasi-experimental crossover study, a total of 19 154 breaths were analysed from 10 ventilated infants of <32 weeks' gestation. Breath-to-breath data on minute ventilation, tidal volume, respiratory rate, peak inspiratory pressure and mean airway pressure were collected during three study epochs: synchronised intermittent mandatory ventilation (SIMV) alone, SIMV with partial PSV (PS(min)), and SIMV with full PSV (PS(max)). PS(min) was set to provide an exhaled tidal volume (V(Te)) between 2.5-4 ml/kg and PS(max) 5-8 ml/kg V(Te). Statistical analyses were performed using analysis of variance (ANOVA) for repeated measures.

RESULTS

The addition of full PSV (PS(max)) was associated with a significant increase in total minute ventilation as compared with SIMV alone (392 ml/kg/min vs 270 ml/kg/min, respectively; p<0.05). This difference in minute ventilation was still present when PS(min) was used (332 ml/kg/min as compared with 270 ml/kg/min in SIMV; p<0.05). There was also a concomitant decrease in the respiratory rate with both PS(max) (59 breaths per minute) and PS(min) (65 breaths per minute) compared with SIMV alone (72 breaths per min) (p<0.05).

CONCLUSIONS

Pressure support ventilation increases total minute ventilation and stabilises breathing in proportion to the level of pressure support used. This may be advantageous and provide a useful ventilation strategy for use during weaning stages of mechanical ventilation in preterm infants.

Complex dynamics in polymer nanocomposites

Polymer nanocomposites offer the potential to create a new type of hybrid material with unique thermal, optical, or electrical properties. Understanding their structure, phase behavior, and dynamics is crucial for realizing such potentials. In this work we provide an experimental insight into the dynamics of such composites in terms of the temperature, wave vector, and volume fraction of nanoparticles, using multispeckle synchrotron x-ray photon correlation spectroscopy measurements on gold nanoparticles embedded in polymethylmethacrylate. Detailed analysis of the intermediate scattering functions reveals possible existence of an intrinsic length scale for dynamic heterogeneity in polymer nanocomposites similar to that seen in other soft materials like colloidal gels and glasses.