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Biomedical subjects

D R Singh

Publications and source records attributed to D R Singh.

At least 19 recordsLinked to original sources

Thermal stabilization of metal finishing waste with clay.

Thermal treatment of metal finishing waste with locally available clay, in their varying ratios, was carried out at 850 degrees C and above temperatures. In the presence of 1:1 ratio of waste and clay a solidified product was obtained at 950 degrees C. Measurement of an appreciably high compressive strength, approximately 500 kg cm(-2) and a very small (0.4%) water absorption from the solidified product indicated its stable nature. Toxicity Characteristic Leaching Procedure (TCLP) test of the waste showed nearly 85 to 90% decrease of leaching of Fe, Cu, Ni, Zn, Mn and Cr after thermal treatment compared to their leaching without treatment. No hexavalent chromium (Cr(VI)) was observed from the leachate of the solidified product. This indicates the absence of re-oxidation phenomena of chromium during thermal treatment up to 950 degrees C. X - ray diffraction (XRD) of solidified product indicated the presence of hematite, and aluminum silicate as main phases of the solidified product. Involvement of the above waste metals with these phases during thermal treatment could be the reason for their immobilization.

Aluminum Silicates↗

Effects of pH on Cr-Fe interaction during Cr(VI) removal by metallic iron.

In the present investigation, the effect of pH on Cr-Fe interactions has been studied by carrying out Cr(VI) removal utilising metallic iron from the dichromate solutions of pH 2 to 7 by batch shaking process. Since the presence of ferrous iron in the solution is mainly responsible for Cr(VI) reduction, solubility of iron from the metallic iron was also measured. The maximum Cr(VI) removal efficiency was found at pH 2 but pH 3 was considered to be a suitable solution condition for Cr(VI) removal due to the occurrence of a minimum level of iron in the treated solution. Chemical analysis of Cr(VI)-reacted iron and treated dichromate solutions has indicated the reduction of Cr(VI) to Cr(III) at the metal surface itself at pH 2 and 3 and in the solution at pH 4 and above. A considerable decrease in chromium concentration on the iron surface in the pH range 4 - 7 as compared to pH 2 and 3 was also observed by EDXA analysis. These studies confirmed that after reduction, involvement of Cr(III) with Fe takes place at the metallic iron surface itself at pH 2 and 3 while it reduces with the rise of pH.

Carcinogens, Environmental↗

Retrospective review and long-term follow-up of radical cystectomy in a developing country.

OBJECTIVE: To retrospectively review the clinical data from patients undergoing radical cystectomy for bladder cancer, and to analyse the complications and survival rates associated with this operation in a developing country. PATIENTS AND METHODS: The study comprised 105 patients who underwent radical cystectomy from 1986 to 1993. Data were collected from retrospective reviews of hospital and physician's office records, and by contact with the patients. Metastatic status was evaluated before surgery and tumours staged using the Tumour-Nodes-Metastasis classification. The indication for surgery was histologically confirmed muscle invasion after transurethral resection biopsy, or endoscopically uncontrollable superficial disease. The data were analysed to assess the perioperative complications and long-term survival, with 5-year survival rates determined using Kaplan-Meier survival curves. RESULTS: The complication rate was 27.6%; most of the complications were managed conservatively with good results and re-operation was required in only two patients. There were two deaths (1.9%) at 15-45 days after surgery, but none during surgery. Patients were divided into node-negative and node-positive groups for analysis and 5-year survival rates determined; for node-negative organ-confined disease (< or =pT3A) the survival was 68% and for nonorgan-confined disease (> or =pT3B) 25%. The 5-year survival rate in the presence of nodal metastases was 13% for N1 and none for N2 disease. Six patients developed urethral recurrence, detected on follow-up urethral-wash cytology. Five of these patients underwent urethrectomy, and four of the six survived for 5 years. Pelvic recurrence occurred in five patients (4.7%), none of whom survived for 5 years. CONCLUSION: Radical cystectomy and pelvic lymph node dissection remains the mainstay of treatment in muscle-invasive bladder cancer. This is a relatively safe procedure with minimal morbidity and mortality; 68% of the present patients with organ-confined disease survived 5 years and 12 patients were alive at 10 years, indicating the effectiveness of this operation in selected cases. However, < 29% of patients with nonorgan-confined and nodal metastatic disease survived 5 years, thereby implying the need for more effective adjuvant therapy in these patients. Radical cystectomy is a viable option in developing countries, with 5-year survival rates comparable with most large published series.

Adult↗

Cr(VI) removal in acidic aqueous solution using iron-bearing industrial solid wastes and their stabilisation with cement.

In this study, iron-bearing industrial solid wastes iron filings, ETP sludge of steel and red mud of aluminium industries; were used for Cr(VI) removal at pH 3. A complete removal of Cr(VI) was found for initial 10 mg 1(-1) of 100 ml solutions in the presence of 2.5 g iron filings, 8 g ETP sludge and 10 g red mud for up to one hour of shaking at room temperature. After Cr(VI) removal, inclusion of chromium on the reacted iron filing surface was demonstrated by EDAX analysis. Leachability of chromium and iron from the reacted wastes was determined by using Toxicity Characteristics Leaching Procedure (TCLP). This test showed a very low level of leachability of chromium as Cr(III) and iron from the reacted wastes. To minimise their leachability further, Cr(VI)-reacted solid wastes were stabilised with Portland cement in their 3:1 ratio. Leachability tests of stabilised wastes by TCLP indicated a considerable decrease in leachability of chromium and iron compared with the that of reacted wastes alone. To explore the possibility of utilisation in building materials, bricks of cement-mixed Cr(VI)-reacted wastes were made and their comprehensive strength, durability and leachability under immersion conditions were measured.

Aluminum↗

Influence of dissolved oxygen on aqueous Cr(VI) removal by ferrous ion.

Hexavalent chromium [Cr(VI)] is a highly toxic and carcnogenic pollutant, introduced to the environment due to several industrial activities. Ferrous iron (Fe(II)], an important natural reductant of the Cr(VI), and its release from iron-bearing materials is now becoming a viable alternative for transforming Cr(VI) to the relatively non toxic trivalent form of chromium [Cr(III)]. Cr(VI) removal by ferrous ion at different pH is widely discussed in the literature but the influence of dissolved oxygen on the Cr(VI) removal with respect to pH, is still a contradictory subject. In the present study a systematic approach has been made to estimate the Cr(VI) removal by ferrous ion in oxygen-free and oxygen-containing aqueous solutions of pH 3 to 7. Quantitative analysis results suggest that the influence of dissolved oxygen on the Cr(VI) reduction starts at pH 4. Though, its effect appears to be in significant up to pH 6, becomes quite pronounced at pH 7 because nearly 10 to 12% less removal of the Cr(VI) was observed in the presence of the stoichiometric requirement of three equivalents of Fe(II) in oxygenated solution of pH 7. This was evidenced by carrying detailed spectrophotometric absorption measurements of the Cr(VI) in the presence of Fe(II) in its different equivalent ratios in oxygenated and deoxygenated solutions.

Biological Availability↗

Malignant fibrous histiocytoma of the rectum.

Malignant fibrous histiocytoma (MFH) of the gastrointestinal tract is a rare occurrence. We report a case of MFH of the rectum in a 55-year-old man. Ultrasound examination revealed thickening of the rectal wall and the biopsy study indicated MFH. The patient underwent abdominoperineal resection and chemoradiation and is doing well after 46 months. A high index of suspicion for colorectal MFH should be taken into account in order to avoid histological misdiagnosis.

Histiocytoma, Benign Fibrous↗

Lord's procedure: a curative outpatient operation for primary hydrocele.

Surgical procedures for hydrocele carry a significant morbidity rate from haematoma formation. Lord's procedures (n = 26) were performed for primary hydrocele as outpatient operation. Peroperative drain was put in one case (3.85%). Postoperative complications were negligible except scrotal oedema in 3 cases (11.53%), which required no specific treatment. No recurrence was noted till one year of follow-up. It is concluded that Lord's procedure is simple, effective, safe and economical technique.

Adolescent↗

Uncommon craniospinal dysraphism.

The uncommon variants amongst 619 cases of craniospinal dysraphism have been studied between 1987 to 1993. Lateral cervical meningocele is an extremely rare condition as to date only ten cases are traceable in the world literature. Its pathogenesis is discussed in detail. Similarly, this case of lateral frontal encephalocele is the second such example. Orbital meningocele may be congenital or following trauma to the orbital roof. Besides other unusual locations like the vertex, posterior fontanelle and anterior sacral are also encountered. Thus this paper focuses on the aetiology, clinical presentation and management of uncommon types of craniospinal meningo-encephaloceles.

Child↗

Chemical radiosensitization by misonidazole: production and repair of DNA single-strand breaks in Yoshida ascites tumor cells.

Formation of strand-breaks in DNA and its repair in Yoshida ascites tumor cells exposed to gamma radiation (100-400 Gy) in presence and absence of misonidazole (10 mM) were studied. The methodology involved pre-labelling of cellular DNA by 3H-thymidine during cell proliferation in rats, irradiation of cells in vitro and analysing sedimentation profile of DNA by ultracentrifugation in alkaline sucrose density gradients. Irradiation under euoxic conditions resulted in formation of about 1.5 times greater number of strand breaks as compared to those formed during irradiation under hypoxic conditions. Misonidazole (10 mM) by its presence along with the cells during irradiation under hypoxic conditions caused a 3-fold increase in the number of single strand breaks, but under euoxic conditions of irradiation the presence of misonidazole did not enhance the strand break formation. Incubation of cells irradiated in absence of misonidazole for 1 hr in tissue culture medium at 37 degrees C resulted in repair of substantial fraction of the strand breaks while there was no repair of the DNA strand breaks in cells irradiated in the presence of the chemical.

Animals↗

Surface ultra-architecture of supraependymal elements in the vicinity of the area postrema of rhesus monkeys.

The caudal part of the fourth ventricle in adult rhesus monkeys, of both sexes, revealed the area postrema (AP) to be composed of bilateral spindle-shaped elevations located ventromedial to the gracile tubercles. Supraependymal (SE) elements, comprised of SE cells and/or fibre processes could be seen near the medial margin of a narrow oligociliated strip separating the nonciliated AP from the profusely ciliated vagal triangle (VT). In general, these consisted of multilobed ganglion-like cell clusters interconnected by fasciculated fibre processes with varicosities along their lengths. Thinner processes radiating from the cell clusters and varicosities traversed towards the VT for short distances and often appeared to penetrate the underlying ependyma. The thicker fibre processes which exhibited a fasciculated configuration extended between raised nodule-like areas in the ventricular floor. The majority of such areas exhibited an uneven surface due to the presence of numerous membranous folds over them. Near the periphery of nodular areas as well as along the fasciculated fibre processes interconnecting them, a few bouton-like protrusions were discernible. The SE elements observed in the caudal portion of the fourth ventricular floor are suggestive of comprising some integrative pathways between the ventricular cerebrospinal fluid and subependymal functional centres in the vicinity of the AP, a circumventricular organ having diverse functions.

Animals↗

Scanning and transmission electron microscopy of the ependyma of the fourth ventricle in the monkey brain.

The ependymal structure of the fourth ventricle floor of adult rhesus monkeys was investigated using both scanning and transmission electron microscopy. Each half of the floor exhibited dense ciliation which decreased towards the median sulcus. The area postrema and the facial colliculus lacked cilia and were covered with non-ciliated ependymal cells. Along the entire length of the median sulcus supraependymal globular protrusions were seen. Over the rostral and middle thirds of the sulcus these protrusions exhibited interwoven ridges. At the former situation they were closely approximated but at the latter they were on the surface of non-ciliated nodules which were lying amongst sparsely ciliated cells. In the caudal third these protrusions presented smoother surfaces without any structural details over them. Transmission electron microscopy through the upper two thirds of the median sulcus revealed these surface protrusions to be non-ciliated cells having long and profuse network of interwoven microvilli over their luminal surface. These cell bodies exhibited well-defined supranuclear Golgi complexes, vesiculated rough and smooth surfaced endoplasmic reticulum, free ribosomes and polyribosomes, few electron dense granules, network of microtubules and light and dense multivesiculated bodies. These features suggested a secretory and/or absorptive role, rather that autophagy to these surface specialization.

Animals↗

Ontogeny of alpha-foetoprotein in human foetal brain.

Alpha-foetoprotein (AFP) was found to be present in human foetal brain during early embryonic life. Antigenically and electrophoretically foetal brain AFP is similar to that found in human foetal serum. Like serum AFP it did not bind oestradiol. Developmental profile of the proteins in foetal brain was distinct from that observed in foetal serum, amniotic fluid and maternal serum compartments. Peak levels of brain AFP were obtained in foetuses in the 20th week of gestation. These levels decreased rapidly and no AFP could be detected in foetal brains derived from the third trimester of pregnancy. The origin of AFP and its possible role in foetal brain development is discussed.

Brain↗

Surface fine structure of the ependymal lining of the rat fourth ventricle.

The floor of the rat brain fourth ventricle has been divided into five zones to study the surface ultrastructure of the ependymal cells. Regional variations in the form of dense ciliation, sparse ciliation, central tufts of cilia, solitary cilia, pores, clavate and filiform microvilli have been observed.

Animals↗