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Biomedical subjects

M Bansal

Publications and source records attributed to M Bansal.

At least 127 records · Page 7Linked to original sources
PubMed1982

Carcinosarcoma and separate carcinoid tumor of the stomach. A case report with light and electron microscopic studies.

A carcinosarcoma of the cardia of stomach is reported. This is a rare entity which is of further interest because of an associated but distinctly separate carcinoid tumor. The main tumor showed distinct adenocarcinomatous and spindle cell components which collided in many areas. The sarcomatous nature of the spindle cell component was confirmed by ultrastructural studies. We have reviewed the literature and have not found a similar case.

Aged↗
PubMed1982

Small cell anaplastic lung cancer presenting as an ovarian metastasis.

An unusual case of small cell anaplastic carcinoma of the lung, presenting as a pelvic mass, is presented. Histochemical and electron microscopic findings confirmed the diagnosis. The pathologic features and unique clinical characteristics are discussed with comments on the topic of metastatic ovarian tumors.

Adult↗
PubMed1982

Left-handed helices for DNA: studies on poly[d(I-C)].

Earlier, we showed that, for the D form (n = 8 and h = 3.03 A, where n is number of nucleotide units per turn and h is height per nucleotide unit) of poly[d(A-T)], both right- and left-handed double helical models are stereochemically satisfactory and give good agreement with the observed fiber diffraction data. It was also noted that the conformations of the right- and left-handed D-DNA models are very similar to those of the right- and left-handed B-DNA models. This observation was consistent with the D leads to B transition in the solid phase. As a continuation of our earlier studies, we have carried out similar experiments with poly[d(I-C)]. We could obtain a crystalline D-form pattern (n = 8, h = 3.13 A) of the fiber at 75% relative humidity (r.h.); the hydrated (r.h. approximately equal to 95%) form of the same fiber gave the classical B-form pattern (n = 10, h = 3.40 A). In the present report, we show that both right- and left-handed double-helical models are consistent with the fiber diffraction data of poly[d(I-C)] in the D-form. Theoretical energy calculations also suggest that the right- and left-handed B- and D-DNA models are almost equally stable. Hence, we conclude that the right- and left-handed double-helical models of poly[d(I-C)] in a given form (B or D) are equally likely and that the fiber diffraction data do not permit discrimination.

DNA↗
PubMed1981

Role of non-planar peptide unit in regular polypeptide helices. New model for poly-beta-benzyl-L-Aspartate.

The effect of non-planarity of the peptide unit on helical structures stabilized by intrachain hydrogen bonds is discussed. While the present calculations generally agree with those already reported in the literature for right-handed helical structures, it is found that the most stable left-handed structure is a novel helix, called the delta-helix. Its helical parameters are close to these reported for poly-beta-benzyl-L -aspartate. Conformational energy calculations show that poly-beta-benzyl-L -aspartate with the delta-helical structure is considerably more stable than the structure it is generally believed to take up (the omega-helix) by about 15 kcal/mol-residue.

Chemical Phenomena↗
PubMed1980

Conformational flexibility of DNA: polymorphism and handedness.

It is shown that left-handed duplexes are possible for A, B, and D forms of DNA. These duplexes are stereochemically satisfactory and are consistent with the observed x-ray intensity data. On scrutiny the refined right-handed models of B and D DNA by Arnott and coworkers are found to be stereochemically unacceptable. It was possible to formulate a stereochemical guideline for molecular model building based on theory and analysis of single-crystal structure data of dinucleoside monophosphate and higher oligomers. This led to both right- and left-handed DNA duplexes. The right-handed B and D DNA duplexes so obtained are stereochemically superior to earlier models and agree well with the observed x-ray intensity data. The observation that DNA can exist in either handedness for all the polymorphous forms of DNA at once explained A in equilibrium B and B in equilibrium D transitions. Hence it is confirmed that polymorphism of DNA is a reflection on the conformational flexibility inherent in DNA, the same cause that ultimately allows DNA in either handedness. The possibility of various types of right- and left-handed duplexes generated by using dinucleoside monophosphate and trinucleoside diphosphate as repeating units resulted in a variety of models, called RL models. All these models have alternating right and left helical segments and inverted stacking at the bend region as suggested by us earlier. It turns out that the B-Z DNA model of Wang et al. is only an example of RL models.

DNA↗
PubMed1978

A theoretical study of the structures of (Gly-Pro-Leu)n and (Gly-Leu-Pro)n.

Theoretical conformation studies have been carried out for the polytripeptides (Gly-Pro-Leu)n and (Gly-Leu-Pro)n and the Fourier transforms of the structures have been calculated. X-ray powder patterns of these polymers had indicated that both these polymers take up coiled-coil triple-helical structures, but in the case of (Gly-Pro-Leu)n it was not clear whether the triple helix is formed by three parallel polypeptide chains or by a single chain folding back on itself (Scatturin et al 1975). Our studies show that both the polytripeptides can take up stereochemically satisfactory triple-helical structures with three parallel chains. There is also very good agreement between the calculated intensity distribution and that of the observed X-ray pattern, in each case.

Amino Acid Sequence↗
PubMed1977

Stereochemical restrictions on the occurrence of amino acid residues in the collagen structure.

The primary structure of collagen is characterized by the repeating tripeptide sequence (Gly-R2-R3)n. The results of theoretical studies, carried out using contact criteria to compute the stereochemically allowed orientations for various side chains at locations 2 and 3, are reported here. It is found that side chains with only gamma-atoms, as in valine, serine and threonine, or with only one delta-methyl group, as in isoleucine, can occur equally well at locations 2 and 3, as is actually the case in collagen. Side chains with two Cdelta-atoms, as in leucine and phenylalanine, can also be accommodated at both positions. However, if they occur as R3, their freedom of orientation is severely restricted in the presence of a proline residue as R2 in a neighbouring chain. If water molecules bound to the chains of the triple helix are assumed to be present, then location 3 is virtually impossible for leucine and phenylalanine residues. Location 2 is, however, unaffected, and their presence as R2 can help to shield the water molecules from disturbance by the solvent medium. This may be the reason for the preferential occurrence of Leu and Phe residues in location 2 in the collagen triplets, although the polypeptides (Gly-Pro-Leu)n and (Gly-Pro-Phe)n form collagen-like structures.

Amino Acid Sequence↗
PubMedDate not supplied

Is antegrade ureteroscopy better than retrograde ureteroscopy for impacted large upper ureteral calculi?

OBJECTIVE: This study was planned to compare the risks and advantages of antegrade and retrograde ureteroscopy for impacted large upper ureteral calculi. PATIENTS AND METHODS: From September 1996 to February 1998, ureteroscopy was offered to 43 patients. Of these, retrograde ureteroscopy was done in 20 patients, while antegrade ureteroscopy was performed in 23 patients. All these patients were followed up to evaluate the immediate and long-term success of the procedure. The incidence and nature of complications were also noted. RESULTS: During retrograde ureteroscopy, complete stone clearance was achieved in 11 patients (55%), while pushback of the whole or fragmented calculus was seen in the rest. These patients with residual calculi were later treated by extracorporeal shockwave lithotripsy (SWL). The stone-free rate at the end of 3 months was 85%. Three patients developed minor ureteroscopy-related complications. Complete stone clearance was achieved in all patients with antegrade ureteroscopy. No intraoperative or postoperative complications were encountered. CONCLUSION: In this series, antegrade ureteroscopy was found to be a safe and effective option for impacted upper ureteral calculi and assured better results than retrograde ureteroscopy.

Female↗
PubMedDate not supplied

Phosphate depletion syndrome: case report with bone and muscle histology findings and review of the literature.

A 44-yr-old woman with a 16-yr history of heavy antacid ingestion was evaluated for severe weight loss, weakness, bone pain, and multiple fractures. Laboratory investigation revealed severe hypophosphatemia with undetectable phosphate in the urine. Serum parathyroid hormone (PTH), 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D levels were normal. Transiliac bone biopsy revealed evidence of mineralization defect compatible with hypophosphatemic osteomalacia. Bone densitometry documented decreased bone density with a low mineral content. Management included withdrawal of antacids and provision of phosphate-supplemented enteral nutrition, which resulted in prompt weight gain and resolution of the clinical and biochemical abnormalities. The pathogenesis, diagnosis and histological features of hypophosphatemic osteomalacia are discussed.

Adult↗
PubMedDate not supplied

Sarcoidosis presenting with large vessel vasculitis and osteosclerosis-related bone and joint pain.

A 34-year-old African-American female diagnosed earlier with idiopathic thrombocytopenic purpura (ITP), lymphadenopathy, splenomegaly, uveitis, and pulmonary nodules, developed a subclavian artery aneurysm, and generalized annular osteosclerotic lesions with disabling arthralgias. Biopsies from bone and lymph node revealed non-caseating granulomas and no evidence of malignancy or infection, confirming the clinical impression of sarcoidosis.

Adult↗
PubMedDate not supplied

Palliative care education and training during residency: a survey among residents at a tertiary care hospital.

BACKGROUND: Palliative care is the active total care of patients in advanced and incurable stages of cancer. More than 70% of all cancer patients in India require palliative care for relief of pain, other symptoms and psychosocial distress. The need for education and training in palliative care has been emphasized by the World Health Organization (WHO) during the past 15 years. This survey aimed to assess the awareness, clinical knowledge, and education and training aspects of palliative care among the clinical residents of a tertiary care hospital. METHODS: During January and February 1999, a total of 100 residents were asked to respond to a questionnaire on palliative care education and training during residency. The questionnaire consisted of 10 questions (each question with 3 different responses). Awareness regarding palliative care was assessed by 3 questions; clinical knowledge by 4 questions; and education and training obtained during residency by 3 questions. Comparisons were made using the Chi-square test between the oncology and non-oncology resident groups. RESULTS: Forty-nine residents (23 oncology and 26 non-oncology) responded to the survey. Awareness that palliative care involves active total care was lacking in 8 (16%) residents. The cost of palliative care in India was considered high by 17 (65%) non-oncology residents and 21 (43%) of the whole group. Hospice, as the right place for palliative care, was chosen by 14 (61%) oncology and 3 (11.5%) non-oncology residents (p = 0.0003). In the whole group, 21 (43%) believed that palliative care could be provided on an outpatient basis. Pain, depression and cachexia were identified as the most distressing symptoms of patients with incurable cancer. Seventeen (83%) oncology and 4 (15%) non-oncology residents (p = 0.000) knew how to use the WHO step-ladder for cancer pain relief. All oncology residents and 10 (38%) non-oncology residents preferred the oral route for providing medications for pain relief (p = 0.0001). The didactic education and training imparted during residency was considered as 'not enough' by 39% of oncology and 62% of non-oncology residents (51% overall). The confidence to deliver quality palliative care was lacking in 43% and 58% of oncology and non-oncology residents, respectively. CONCLUSION: Clinicians in India need to be provided focused skills and training for them to be able deliver quality palliative care to the large number of patients with incurable cancer. The cost of palliative care and the optimum place to deliver it, the symptoms of advanced cancer, pain relief and symptom control methods and quality of life in end-stage cancer patients are some aspects that should be an integral part of clinical residency programmes.

Cachexia↗
PubMedDate not supplied

Structural features of B-DNA dodecamer crystal structures: influence of crystal packing versus base sequence.

We have analyzed the set of inter and intra base pair parameters for each dinucleotide step in single crystal structures of dodecamers, solved at high and medium resolution and all crystallized in P2(1)2(1)2(1) space group. The objective was to identify whether all the structures which have either the Drew-Dickerson (DD) sequence d[CGCGAATTCGCG] with some base modification or related sequence (non-DD), would display the same sequence dependent structural variability about its palindromic sequence, despite the molecule being bent at one end because of similar crystal lattice packing effect. Most of the local doublet parameters for base pairs steps G2-C3 and G10-C11 positions, symmetrically situated about the lateral two-fold, were significantly correlated between themselves. In non-DD sequences, significant correlations between these positional parameters were absent. The different range of local step parameter values at each sequence position contributed to the gross feature of smooth helix axis bending in all structures. The base pair parameters in some of the positions, for medium resolution DD sequence, were quite unlike the high-resolution set and encompassed a higher range of values. Twist and slide are the two main parameters that show wider conformational range for the middle region of non-DD sequence structures in comparison to DD sequence structures. On the contrary, the minor and major groove features bear good resemblance between DD and non-DD sequence crystal structure datasets. The sugar-phosphate backbone torsion angles are similar in all structures, in sharp contrast to base pair parameter variation for high and low resolution DD and non-DD sequence structures, consisting of unusual (epsilon = g-, xi = t) BII conformation at the 10th position of the dodecamer sequence. Thus examining DD and non-DD sequence structures packed in the same crystal lattice arrangement, we infer that inter and intra base pair parameters are as symmetrically equivalent in its value as the symmetry related step for the palindromic DD sequence about lateral two-fold axis. This feature would lead us to agree with the conclusion that DNA conformation is not substantially affected by end-to-end or lateral inter-molecular interaction due to crystal lattice packing effect. Non-DD sequence structures acquire step parameter values which reflect the altered sequence at each of the dodecamer sequence position in the orthorhombic lattice while showing similar gross features of DD sequence structures.

Base Sequence↗