Mechanism of cadmium uptake by activated sludge

Summary The significance of metabolic activity in cadmium uptake by unacclimated activated sludge was studied. Below 30 mg/l cadmium in solution, biosorption was found to follow the Freundlich isotherm, which is the most common pattern for physico-chemical adsorption. More than 95% of total cadmium uptake was achieved within 5 min metal-sludge contact time. Biosorption increased strongly when the initial cadmium concentration in solution was raised from 10 to 100 mg/l, whereas in the same concentration range the metabolic activity of the sludge, as measured by respiratory activity and extracellular protein production, was very significantly inhibited. The addition of nutrients at low but significant levels failed to increase cadmium uptake in 2 h contact time, while in 24 h the addition of nutrients caused the biosorption to increase by only 5–10% without any significant growth of the biomass. Biosorption was found to increase with temperature between 5° C and 40° C, in correlation with an increase in the metabolic activity of the sludge. Pretreatment of the sludge with metabolic inhibitors (NaN₃ and UV rays) appeared to cause only a very slight decrease (5–10%) of biosorption. These results suggest that metabolic uptake of cadmium was low and that adsorption to the surface of the cells was the major mechanism of uptake.Offprint requests to: S. S. Sofer     

Immunocytochemistry on scrape cytology in breast cancer: will it unearth the weaker positives?

OBJECTIVE: To standardize the technique of immunocytochemical (ICC) assessment of estrogen (ER) and progesterone receptor (PR) status in breast cancer by scrape cytology and to compare the results with immunohistochemistry on paraffin blocks. STUDY DESIGN: ICC assessment for ER and PR was done on scrape smears from tissue samples in 200 cases of primary breast cancer. The results were compared to those obtained from immunohistochemical (IHC) evaluation of formalin-fixed paraffin same tissue samples. RESULTS: ER/PR positivity rates as well as staining scores were compared between the scrape smears and tissue sections. The concordance between cytology and histology was 84% for ER and 90% for PR. Both the positivity rates and the staining intensity scores were higher for cytochemistry than for histochemistry. CONCLUSION: The ICC method on scrape smears is a simple test with rapid turnaround time. The sample required is small, and antigen loss due to fixation and processing is minimal. This new method gives a higher yield of hormone receptor positivity and, when used in conjunction with the IHC method, may improve the pickup rate of ER-positive cases, thereby playing an important role in risk stratification and therapeutic decision making in patients with breast cancer.     

Exploring residues crucial for nitrilase function by site directed mutagenesis to gain better insight into sequence-function relationships

Nitrilases represent a very important class of enzymes having an array of applications. In the present scenario, where the indepth information about nitrilases is limited, the present work is an attempt to shed light on the residues crucial for the nitrilase activity. The nitrilase sequences demonstrating varying degree of identity with P. putida nitrilase were explored. A stretch of residues, fairly conserved throughout the range of higher (96%) to lower (27%) sequence identity among different nitrilases was selected and investigated for the possible functional role in nitrilase enzyme system. Subsequently, the alanine substitution mutants (T48A, W49A, L50A, P51A, G52A, Y53A and P54A) were generated. Substitution of the rationally selected conserved residues altered the substrate recognition ability, catalysis and affected the substrate specificity but had very little impact on enantioselectivity and pattern of nitrile hydrolysis.     

Tissue Specific Roles for the Ribosome Biogenesis Factor Wdr43 in Zebrafish Development

During vertebrate craniofacial development, neural crest cells (NCCs) contribute to most of the craniofacial pharyngeal skeleton. Defects in NCC specification, migration and differentiation resulting in malformations in the craniofacial complex are associated with human craniofacial disorders including Treacher-Collins Syndrome, caused by mutations in TCOF1. It has been hypothesized that perturbed ribosome biogenesis and resulting p53 mediated neuroepithelial apoptosis results in NCC hypoplasia in mouse Tcof1 mutants. However, the underlying mechanisms linking ribosome biogenesis and NCC development remain poorly understood. Here we report a new zebrafish mutant, fantome (fan), which harbors a point mutation and predicted premature stop codon in zebrafish wdr43, the ortholog to yeast UTP5. Although wdr43 mRNA is widely expressed during early zebrafish development, and its deficiency triggers early neural, eye, heart and pharyngeal arch defects, later defects appear fairly restricted to NCC derived craniofacial cartilages. Here we show that the C-terminus of Wdr43, which is absent in fan mutant protein, is both necessary and sufficient to mediate its nucleolar localization and protein interactions in metazoans. We demonstrate that Wdr43 functions in ribosome biogenesis, and that defects observed in fan mutants are mediated by a p53 dependent pathway. Finally, we show that proper localization of a variety of nucleolar proteins, including TCOF1, is dependent on that of WDR43. Together, our findings provide new insight into roles for Wdr43 in development, ribosome biogenesis, and also ribosomopathy-induced craniofacial phenotypes including Treacher-Collins Syndrome.     

Enhancing TB Case Detection: Experience in Offering Upfront Xpert MTB/RIF Testing to Pediatric Presumptive TB and DR TB Cases for Early Rapid Diagnosis of Drug Sensitive and Drug Resistant TB

Background

Diagnosis of pulmonary tuberculosis (PTB) in children is challenging due to difficulties in obtaining good quality sputum specimens as well as the paucibacillary nature of disease. Globally a large proportion of pediatric tuberculosis (TB) cases are diagnosed based only on clinical findings. Xpert MTB/RIF, a highly sensitive and specific rapid tool, offers a promising solution in addressing these challenges. This study presents the results from pediatric groups taking part in a large demonstration study wherein Xpert MTB/RIF testing replaced smear microscopy for all presumptive PTB cases in public health facilities across India.

Methods

The study covered a population of 8.8 million across 18 programmatic sub-district level tuberculosis units (TU), with one Xpert MTB/RIF platform established at each study TU. Pediatric presumptive PTB cases (both TB and Drug Resistant TB (DR-TB)) accessing any public health facilities in study area were prospectively enrolled and tested on Xpert MTB/RIF following a standardized diagnostic algorithm.

Results

4,600 pediatric presumptive pulmonary TB cases were enrolled. 590 (12.8%, CI 11.8–13.8) pediatric PTB were diagnosed. Overall 10.4% (CI 9.5–11.2) of presumptive PTB cases had positive results by Xpert MTB/RIF, compared with 4.8% (CI 4.2–5.4) who had smear-positive results. Upfront Xpert MTB/RIF testing of presumptive PTB and presumptive DR-TB cases resulted in diagnosis of 79 and 12 rifampicin resistance cases, respectively. Positive predictive value (PPV) for rifampicin resistance detection was high (98%, CI 90.1–99.9), with no statistically significant variation with respect to past history of treatment.

Conclusion

Upfront access to Xpert MTB/RIF testing in pediatric presumptive PTB cases was associated with a two-fold increase in bacteriologically-confirmed PTB, and increased detection of rifampicin-resistant TB cases under routine operational conditions across India. These results suggest that routine Xpert MTB/RIF testing is a promising solution to present-day challenges in the diagnosis of PTB in pediatric patients.     

Scrape cell-block technique for fine needle aspiration cytology smears

An inconclusive diagnosis on fine needle aspiration cytology (FNAC) may be due to poor spreading and presence of thick tissue fragments despite aspiration of adequate material. Repeat aspiration may not be possible especially when aspirates of deep seated organs have been obtained by image guided techniques. We have resorted to a 'scrape cell-block' (SCB) technique in such cases. In this technique the cellular material on the slides which had already been fixed and stained, was carefully removed by scraping following destaining and then processed as a cell block. SCB interpretation was then compared with the smear diagnosis and histological diagnosis, wherever available. A total of 27 cases were studied. In 12 cases SCB slides added information to the FNAC smears. In 14 cases SCB did not offer any additional information. SCB was inconclusive in one case. Final histological correlation was available in eight cases and the SCB diagnosis was confirmed in six cases, whereas in two cases SCB failed to identify the tumour. Immunocytochemistry (ICC) was done in one case. SCB is a useful technique to make the best use of the available material when reaspiration is difficult.     

Discovery of pyrazole carboxylic acids as potent inhibitors of rat long chain L-2-hydroxy acid oxidase

Long chain L-2-hydroxy acid oxidase 2 (Hao2) is a peroxisomal enzyme expressed in the kidney and the liver. Hao2 was identified as a candidate gene for blood pressure (BP) quantitative trait locus (QTL) but the identity of its physiological substrate and its role in vivo remains largely unknown. To define a pharmacological role of this gene product, we report the development of selective inhibitors of Hao2. We identified pyrazole carboxylic acid hits 1 and 2 from screening of a compound library. Lead optimization of these hits led to the discovery of 15-XV and 15-XXXII as potent and selective inhibitors of rat Hao2. This report details the structure activity relationship of the pyrazole carboxylic acids as specific inhibitors of Hao2.     

Flux of certain radionuclides in the blood-clam Anadara granosa Linneaus under environmental conditions

The flux of fission product nuclides, caesium-137. cerium-144. and ruthenium-106, in the Bombay harbour ecosystem has been measured over a period of six years (1970–1976). during which the input of controlled low level radioactive waste was gradually reduced by more than 20 times. Of the various pelagic and benthic species studied, the arcid clam Anadara granosa Linn, showed a specific affinity for all three radionuclides; sequence of the degree of bio-accumulation was Ce ? Ru > Cs. Furthermore, the concentration of these nuclides in the tissues varied with the levels in the sedimentary material, which in turn was related to the inputs, maintaining some kind of equilibrium. On reaching maximum accumulation the levels of all three nuclides in the clam population decreased exponentially with time although the radioactivity was still available especially in the sediment. This decrease of radioactivity is defined as an ‘ecological loss rate’. The ecological half-time for cerium-144 and ruthenium-106 was about 3.6 times longer, and that of caesium-137 significantly shorter, than their respective physical half-lives. The ecological half-times of all three radionuclides were predominantly influenced by the environment rather than by the biological half-lives. This indicates that the biological half-lives of these nuclides were much shorter than their respective ecological half-lives. The biological half-time of caesium-137 was biphasic; the short-lived component had a half-time of about three days and the long-lived component had one of about 15 days.The bio-accumulation of an activation product nuclide cobalt-60 in A. granosa increased with the time of exposure and reached a level significantly higher than that of caesium-137, but was independent of the ambient concentrations and temperature. Thus the species was found to maintain the tissue concentration of fission product nuclides, cerium-144, ruthenium-106, and caesium-137 through adjusting physiological flux rates, in equilibrium with the changing levels of radionuclides in the environmental matrices, but not of the activation product nuclide cobalt-60.