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Biomedical subjects

R S Singh

Publications and source records attributed to R S Singh.

At least 19 recordsLinked to original sources
PubMed2006

Optimization of medium and process parameters for the production of inulinase from a newly isolated Kluyveromyces marxianus YS-1.

A newly isolated strain of Kluyveromyces marxianus YS-1 was used for the production of extra cellular inulinase in a medium containing inulin, meat extract, CaCl2 and sodium dodecyl sulphate (SDS). Fermentation medium pH 6.5, cultivation temperature 30 degrees C and 5% (v/v) inoculum of 12 h-old culture were optimal for enzyme production (30.8 IU/ml) with a fermentation time of 72 h at shake flask level. Raw inulin (2%, w/v) extracted from dahlia tubers by processing at 15 kg/cm2 for 10 min was optimum for bioreactor studies. Maximum enzyme production (55.4 IU/ml) was obtained at an agitation rate of 200 rpm and aeration of 0.75 vvm in a stirred tank reactor with a fermentation time of 60 h.

Bioreactors↗
PubMed2006

Removal of toluene vapour using agro-waste as biofilter media.

Biodegradation of toluene vapour was investigated in a laboratory scale biofilter packed with cylindrical pieces of yellow-gram (Cajanus cajan) stalk. Inlet concentrations and volumetric flow rates of toluene were varied from 2.56 to 34.73 g/m3 and 0.18 to 0.24 m3/h, respectively. The steady state was achieved within seven days and the degradation of toluene followed an exponential behaviour with time. Elimination capacity increased and tended towards a constant value but removal efficiency decreased with increase in inlet toluene loading. Depending upon loading rate, the process was either mass transfer or reaction-controlled.

Air Pollutants↗
PubMed2006

Enhanced adaptive evolution of sperm-expressed genes on the mammalian X chromosome.

Genes on the mammalian X chromosome may be under unique evolutionary pressure due to their hemizygous expression in males. Since any recessive deleterious mutation would immediately be expressed in males and, therefore, efficiently removed from the population, selective constraint could be more pronounced in X-linked genes. Conversely, if a recessive mutation were beneficial, its immediate exposure to selection would be advantageous, and would facilitate adaptive evolution. We tested for positive selection in a total of 86 genes using a maximum likelihood approach, including 40 sperm-expressed and 46 non-sperm, tissue-specific genes. We find evidence to suggest that X-linkage enhances the effects of positive selection in sperm-expressed genes in terms of the number of codons affected, and report a general trend for positively selected genes to reside on the X chromosome rather than on the autosomes. Our data suggest that hemizygous expression in males makes the X chromosome a preferred location for positively selected sperm genes that do not require postmeiotic transcription.

Adaptation, Physiological↗
PubMed2006

Performance evaluation of an agro waste based biofilter treating toluene vapours.

Biodegradation of toluene vapour was investigated for 162 days in a laboratory scale biofilter packed with maize waste. Inlet concentration of toluene was varied from 2.86 to 5.79 g m(-3) and the volumetric flow rate of toluene loaded air from 0.09 to 0.3 m3 h(-1). The media bed height used in the study was 0.63 m. Plug flow behaviour of the bed was confirmed by RTD experiments. The steady state was achieved in 18 days. Depending upon initial loading rates, removal efficiency ranging from 54.5 to 85.3% and elimination capacity ranging from 43.47 to 174.6 g h(-1) m(-3) were observed during steady state operation. The dynamic behaviour of the biofilter was evident from response to change in process conditions. The stability of the biomass was evident from the fast response of the biofilter to shutdown and restart operations. High value of carbon recovery confirms the effective biodegradation in the biofilter. In the startup period, the pressure drop in the bed increased for some time after that it tended towards a constant value.

Air Pollutants↗
PubMed2006

A time-sequence functional analysis of mating behaviour and genital coupling in Drosophila: role of cryptic female choice and male sex-drive in the evolution of male genitalia.

Male genitalia in Drosophila exemplify strikingly rapid and divergent evolution, whereas female genitalia are relatively invariable. Whereas precopulatory and post-copulatory sexual selection has been invoked to explain this trend, the functional significance of genital structures during copulation remains obscure. We used time-sequence analysis to study the functional significance of external genitalic structures during the course of copulation, between D. melanogaster and D. simulans. This functional analysis has provided new information that reveals the importance of male-driven copulatory mechanics and strategies in the rapid diversification of genitalia. The posterior process, which is a recently evolved sexual character and present only in males of the melanogaster clade, plays a crucial role in mounting as well as in genital coupling. Whereas there is ample evidence for precopulatory and/or post-copulatory female choice, we show here that during copulation there is little or no physical female choice, consequently, males determine copulation duration. We also found subtle differences in copulatory mechanics between very closely related species. We propose that variation in male usage of novel genitalic structures and shifts in copulatory behaviour have played an important role in the diversification of genitalia in species of the Drosophila subgroup.

Animals↗
PubMed2005

Ultrasound crack detection in a simulated human tooth.

OBJECTIVE: Currently, diagnosis of cracked teeth generally depends upon the overall clinical assessment, or on exclusion of other clinical possibilities, not primarily on the direct identification of cracks themselves. Owing to its short wavelength in hard tissues and associated high resolution, ultrasound has the potential to allow detection of cracks within tooth structure. However, ultrasound detection of dental cracks has not previously been achieved. The purpose was to determine if an ultrasound imaging system was capable of imaging cracks in simulated tooth structure. METHODS: A complete ultrasound system including a novel transducer made of PLZT-98, a novel gallium-indium alloy coupling agent, and customized electronic and digital signal processing (DSP) algorithms was developed for the specific application of optimizing crack detection within teeth. A simulated tooth with a known and uniform internal structure and acoustic properties similar to those of natural enamel and dentin was designed to model a human tooth with a crack located in dentin deep to the dentino-enamel junction (DEJ). The distance between the DEJ and a crack of the simulated tooth were calculated. RESULTS: The system unequivocally distinguished between areas with and without a simulated crack. CONCLUSION: A unique ultrasound dental crack detection system using a novel transducer; a novel coupling agent; and customized electronic and digital signal processing (DSP) algorithms has been validated in a simulated tooth.

Algorithms↗
PubMed2003

Validation of two air quality models for Indian mining conditions.

All major mining activity particularly opencast mining contributes to the problem of suspended particulate matter (SPM) directly or indirectly. Therefore, assessment and prediction are required to prevent and minimize the deterioration of SPM due to various opencast mining operations. Determination of emission rate of SPM for these activities and validation of air quality models are the first and foremost concern. In view of the above, the study was taken up for determination of emission rate for SPM to calculate emission rate of various opencast mining activities and validation of commonly used two air quality models for Indian mining conditions. To achieve the objectives, eight coal and three iron ore mining sites were selected to generate site specific emission data by considering type of mining, method of working, geographical location, accessibility and above all resource availability. The study covers various mining activities and locations including drilling, overburden loading and unloading, coal/mineral loading and unloading, coal handling or screening plant, exposed overburden dump, stock yard, workshop, exposed pit surface, transport road and haul road. Validation of the study was carried out through Fugitive Dust Model (FDM) and Point, Area and Line sources model (PAL2) by assigning the measured emission rate for each mining activity, meteorological data and other details of the respective mine as an input to the models. Both the models were run separately for the same set of input data for each mine to get the predicted SPM concentration at three receptor locations for each mine. The receptor locations were selected such a way that at the same places the actual filed measurement were carried out for SPM concentration. Statistical analysis was carried out to assess the performance of the models based on a set measured and predicted SPM concentration data. The value of coefficient of correlation for PAL2 and FDM was calculated to be 0.990-0.994 and 0.966-0.997, respectively, which shows a fairly good agreement between measured and predicted values of SPM concentration. The average index of agreement values for PAL2 and FDM was found to be 0.665 and 0.752, respectively, which represents that the prediction by PAL2 and FDM models are accurate by 66.5 and 75.2%, respectively. These indicate that FDM model is more suited for Indian mining conditions.

Air Pollution, Indoor↗
PubMed2003

Imaging of human tooth enamel using ultrasound.

This paper reports the results of a complete circumferential scan of a human tooth and its underlying dentino-enamel junction using ultrasound at frequencies in the 10-MHz range. The imagery shows clearly a two-dimensional contour of the dentinoenamel junction with a depth and lateral resolution of approximately 100 microm and 750 microm, respectively. The resulting sonograph is compared with an optical micrograph of the same tooth to verify the accuracy of the ultrasonic technique. The results are a significant step toward the biolocation of submillimeter size features within the tooth volume.

Dental Enamel↗
PubMed2001

Monitoring of bacteria growth using a wireless, remote query resonant-circuit sensor: application to environmental sensing.

A new technique is presented for in-vivo remote query measurement of the complex permittivity spectra of a biological culture solution. A sensor comprised of a printed inductor-capacitor resonant-circuit is placed within the culture solution of interest, with the impedance spectrum of the sensor measured using a remotely located loop antenna; the complex permittivity spectra of the culture is calculated from the measured impedance spectrum. The remote query nature of the sensor platform enables, for example, the in-vivo real-time monitoring of bacteria or yeast growth from within sealed opaque containers. The wireless monitoring technique does not require a specific alignment between sensor and antenna. Results are presented for studies conducted on laboratory strains of Bacillus subtilis, Escherichia coli JM109, Pseudomonas putida and Saccharomyces cerevisiae.

Bacteria↗
PubMed2001

In vitro regeneration of Hypericum patulum Thunb.--a medicinal plant.

A protocol was developed for high frequency plant regeneration in H. patulum by shoot-tip culture. H. patulum plants were collected from a wild source growing at high altitude in the eastern Himalayas. Multiple buds were initiated from shoot-tips cultured on Murashige and Skoog's medium supplemented with BAP, kinetin. Addition of thiamin HCI, Ca-pantothenate and biotin enhanced multiple shoot formation. Upon transfer to phytohormone free liquid medium following a brief exposure to auxin, root formation occurred from the micro shoots . Rooted plants were hardened and transferred to soil. Regeneration potentiality was found to be constant throughout the year in long term cultures.

Adenine↗
PubMed2000

Aliphatics from Peristrophe bicalyculata.

The isolation and spectral data of the new 14-methyl-tritriacont-14-en-15-ol (1) and 35-hydroxynonatriacontanal (2) from the aerial parts of Peristrophe bicalyculata are reported.

Alcohols↗
PubMed2000

Sex gene pool evolution and speciation: a new paradigm.

In this paper, we review the literature on the growing body of data demonstrating the rapid evolution of sex and reproduction related (SRR) genes and show how a paradigm shift to the study of SRR genes can provide new approaches to solving some of the old problems in evolutionary biology. The argument is based on (1) the growing scope and importance of sexual selection in evolution, (2) the growing number of case studies showing rapid evolution of sexual traits in a wide variety of taxa, (3) the faster rate of DNA sequence divergence in genes affecting sexual function and fertility, (4) the evidence for the involvement of novel traits/genes in sexual functions, and (5) a proposed sex/non-sex dichotomy of the gene pool affecting viability versus fertility. It is argued that the adoption of the sex/non-sex dichotomy of genes/traits can provide new perspectives on such problems as species concepts, modes (allopatric/sympatric) of speciation, Haldane's rule, reinforcement, and the founder effect. It is proposed that the evolutionary study of genes affecting viability versus fertility is the key to understanding the genetic basis of speciation.

Animals↗
PubMed2000

A biogeographic genetic approach for testing the role of reinforcement: the case of Drosophila pseudoobscura and D. persimilis.

The role of reinforcement in speciation can be explained by two distinct models. In model I, two diverged populations hybridize and produce fertile hybrids that successfully backcross (hybridization with gene flow). In model II, two populations hybridize but succeeding backcrosses are unproductive (hybridization without gene flow). Using Drosophila persimilis and D. pseudoobscura, we have tested model I by comparing the extent of heterospecific introgression in sympatric versus allopatric populations. We show that certain expectations of this particular model of reinforcement, which is based on hybridization and gene flow between divergent populations after secondary contact, are not realized in these two species. The evidence consists of the similarity of genetic distances as well as proportions of unique/rare alleles between sympatric and allopatric heterospecific populations and a negative correlation between genetic distance and geographical distance between heterospecific populations, which suggests ecological differentiation. This approach in quantifying differential gene flow has important consequences to studies that compare sympatric and allopatric isolation using genetic distance. Following model I, one would expect a pattern of higher prezygotic isolation in sympatric species compared to allopatric species of the same genetic distance simply as a result of an underestimation of genetic distance due to introgression between sympatric populations. We suggest more parsimonious explanations such as reinforcement without genetic exchange (model II) and ecological differentiation, which require high levels of preexisting reproductive isolation between populations.

Animals↗
PubMed1999

Tension pneumocephalus after excision of posterior mediastinal mass.

Although paraplegia after a posterolateral thoracotomy has been described as a serious complication, the occurrence of tension pneumocephalus after excision of posterior mediastinal mass has also been reported as another life-threatening complication. We report one such case.

Adult↗
PubMed1999

Purulent pericarditis: clinical profile and outcome following surgical drainage and intensive care in children in Chandigarh.

Purulent pericarditis, though rare in developed countries, is not uncommon in developing countries. However, the type of pericardial drainage required and the risk of subsequent constrictive pericarditis has not been clearly defined. Thirty children between the ages of 3 months and 12 years with a diagnosis of purulent pericarditis were studied retrospectively. Pericardial effusion was confirmed in all by echocardiography and the diagnosis of bacterial pericarditis was based on aspiration of purulent fluid with leucocytosis and high proteins. Purulent pericarditis was a part of the disseminated sepsis in 25 (83%) children. Fever was present in all, hepatomegaly in 28 and breathlessness in 25, whereas muffled heart sounds, raised JVP and pericardial rub were found in only 18, 16 and 7, respectively. The ECG was abnormal in only 16 children. Staphylococcus aureus was the causative organism in 24 (96%). Open surgical drainage was done in 26 children, 23 of whom underwent anterior pericardiectomy. Two children died of disseminated sepsis. None of the 21 who returned for follow-up for periods of between 4 and 24 months had any long-term sequelae.

Child↗