Biomedical subjects

S Dwarakanath

Publications and source records attributed to S Dwarakanath.

10 recordsLinked to original sources

PubMed2006

Spontaneous spinal extradural hematomas.

We review three patients who presented with acute spontaneous spinal extradural hematomas (SSEH). We discuss the presentation, imaging and management strategies. All three patients were adult women with thoracic SSEH. All had motor weakness prior to surgery. One patient recovered completely, one partially recovered and one did not recover. SSEH, although rare, should be considered in cases of acute onset paraparesis. The diagnostic modality of choice is magnetic resonance imaging. Favourable outcome is related to aetiology, interval between the ictus and presentation, and the severity of the neurological deficits. Emergent surgical drainage is the treatment of choice.

Acute Disease↗

PubMed2006

Aplasia cutis congenita of the scalp: therapeutic modalities.

Agenesis of scalp is an uncommon but well-recognized clinical entity. Congenital scalp and skull defects can be either obvious or occult; over 300 cases have been reported in literature. Aplasia cutis congenita (ACC) is recognized as a heterogeneous disorder, all characterized by focal absence of the epidermis, dermis and sometimes the calvarium and/or dura. We present a case of ACC in an infant whose mother was exposed to a teratogenic drug (Methimazole--an antithyroid drug) during pregnancy. This case report is presented to highlight the steps to successful management. Definitive full thickness scalp cover at the earliest avoids secondary infection, eschar formation and exsanguination.

Ectodermal Dysplasia↗

PubMed2005

Endoscopic assisted excision of a retroclival arachnoid cyst presenting as hysterical breathlessness.

BACKGROUND: Arachnoid cysts are benign developmental cysts occurring most commonly in the middle fossa. Posterior fossa arachnoid cysts are less common, with retroclival arachnoid cysts especially in the pediatric age group being rare. PATIENTS AND METHODS: We present a case of a retroclival interpeduncular farachnoid cyst in a 10-year-old boy who presented with left-sided ptosis and episodes of hysterical breathlessness. RESULTS: The surgical treatment involved endoscopic assisted microsurgical excision of the cyst and the child made an uneventful and complete recovery with complete cessation of breathlessness. The clinical presentation, etiopathogenesis, imaging characteristics and treatment modalities are discussed and the relevant literature reviewed.

Arachnoid Cysts↗

PubMed2004

Primary plasma cell granuloma of petrous bone.

Plasma cell granulomas are rare intracranial lesions that can mimic a variety of intracranial tumours. As they are usually benign lesions, their identification assumes importance. We report a case of plasma cell granuloma in a 52-year-old man presenting with features of left sided V, VII and bilateral VIII nerve involvement who underwent subtotal excision of the lesion. The relevant literature is reviewed.

Bone Diseases↗

PubMed1997

Dynamics simulation of the interaction between the novel intercalator diethidium cation and B-form DNA.

Previous research has described the interaction between the novel molecule diethidium (2,7-diamino 9-[2,7 diamino 10-N-phenanthridium] 10-N-phenanthridium) (Figure 1) and B-form DNA. Our goal is the elucidation of diethidium as the first member of a novel class of drugs which are potential pharmaceutical agents. This class of potential drug molecules differs from previously known intercalators in the following ways: a) Its structure, that of two perpendicular planes, each known to have excellent intercalation properties, is novel b) Unlike known bis-intercalators, the linker region length in diethidium is zero c) The geometry of the drug matches the geometry of the space available in the major groove d) The drug is shown to cause some vectorial disruption of DNA. For this paper, we have performed a series of 200 picosecond dynamics simulations on the complex formed between diethidium in the major groove and a dodecarner of double-stranded B-form DNA, CGCGAATTCGCG, and have shown that this complex has a intricate interaction. The DNA dodecamer is found to be in an intermediate A-B state, but, even in simulations as long as 1 nanosecond, the drug does not back-out or otherwise leave the intercalation site. The drug is found to be mobile within the intercalation site on timescales longer than 1 nanoscale. The mobility of the drug within the intercalation site has been predicted by our previous energy minimization studies.

Computer Simulation↗

PubMed1996

Site-specific adducts derived from the binding of anti-5-methylchrysene diol epoxide enantiomers to DNA: synthesis and characteristics.

The direct synthesis and characterization of site-specific adducts derived from the binding of (+)-1R,2S-dihydroxy-3S,4R-epoxide-1,2,3,4-tetrahydro-5-methylchrysene and the (-)-1S,2R,3R,4S-enantiomer [(+)- and (-)-5-MeCDE, respectively], to the N2-guanine residues in the oligonucleotide d(CCATCGCTACC) are described. The spectroscopic characteristics of the 5-MeCDE-modified oligonucleotides are discussed, and it is shown that their CD characteristics can be used to distinguish between the trans-addition products of the binding of the (+)- and (-)-enantiomers of 5-MeCDE (C4 position). The 11-mer duplexes with the normal complementary strands are destabilized by the site-specific, covalently bound 5-MeCDE residues: the melting points, Tm, are 5-10 degrees lower than in the case of the unmodified duplex. Stereoselective exonuclease enzyme digestion patterns of the single-stranded (+)- and (-)-trans-5-MeCDE-modified oligonucleotides (Mao et al, 1993, Biochemistry, 32, 11785-11793) were used to probe the orientations of the covalently bound 5-MeCDE residues relative to the modified guanine and the 5'-3' strand polarity; the aromatic residues are positioned either on the 5'-side [(+)-5-MeCDE], or the 3'-side [(-)-5-MeCDE adduct] of the modified guanine residues. The electrophoretic mobilities of the (+)-5-MeCDE-modified 11-mer duplexes in native polyacrylamide gels are slower than those of unmodified and modified duplexes containing the stereoisomeric (-)-5-MeCDE-N2-dG lesions. This indicates that the lesions derived from the tumorigenic (+)-5-MeCDE induce greater degrees of bending or local flexibility than the non-tumorigenic (-)-5- MeCDE enantiomer. These differences in the orientational and structural characteristics are similar to those observed with analogous DNA adducts derived from the tumorigenic (+)-7R,8S-dihydroxy-9S,10R-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene and the non-tumorigenic 7S,8R,9R,10S-enantiomer, respectively. The adducts derived from BPDE and 5-MeCDE enantiomers thus display similar characteristics that depend primarily on the PAH diol epoxide enantiomer stereochemistry. This direct synthesis approach can be used to generate milligram quantities of site-specific 5-MeCDE-modified oligonucleotides that are suitable for NMR studies (Cosman, et al., 1995, Biochemistry, 34, 6247-6260).

Base Sequence↗

PubMed1994

A neural network approach to the early detection of cancer.

Early detection of some cancers (especially of the colon) may be achieved by nuclear magnetic resonance (NMR) spectroscopy applied to whole blood samples. Analysis by conventional Fourier signal processing techniques of the data so obtained has proved to be unreliable because of noise within the associated spectrum. This paper describes a neural network approach to analysis of the NMR data. At the present time, this method has proved to be highly reliable in differentiating between patients with an without colon cancer.

Colonic Neoplasms↗

PubMed1991

Histopathology of the donor gallbladder removed at orthotopic liver transplantation: correlation with graft function.

The histopathology of 50 consecutive donor gallbladders removed during orthotopic liver transplantation was reviewed and correlated with graft function. Multiple sections of the gallbladders were examined for the presence of mucosal congestion, hemorrhage, and necrosis, without prior knowledge of the clinical outcome. Each pathologic feature was graded as absent (0), involving less than 10% (1+), 10% to 50% (2+), or more than 50% (3+) of the histologically examined mucosa. Graft function was determined by two transplant surgeons, a poor diagnosis being worsening of liver function tests associated with declining mental status and resulting in immediate retransplantation or early postoperative death; all others were categorized as good. Of 39 patients with good graft function, 18 had normal donor gallbladders, 11 had congestion only, and 10 had hemorrhage and/or necrosis. Of 11 patients with poor graft function, eight had hemorrhage and/or necrosis (2+ in seven), three had congestion only, and none had a normal gallbladder mucosa. Congestion alone was found to be a poor predictor of graft damage. Presence of any grade of hemorrhage and/or necrosis in donor gallbladders as related to poor liver graft function had a sensitivity of 73%, a specificity of 74%, a positive predictive value of 44%, and a negative predictive value of 91%. When hemorrhage and/or necrosis of 2+ severity was separately grouped and correlated with poor graft function, the specificity rose to 97% and the positive predictive value to 88%, and the negative predictive value was similar at 90%. We conclude that donor gallbladders often show mucosal abnormalities consisting of varying degrees of congestion, hemorrhage, and necrosis. The finding of hemorrhage and/or necrosis affecting more than 10% of the mucosa appears to be a specific lesion of ischemic damage that correlates highly with poor liver graft function.

Gallbladder↗

PubMed1987

S-100 protein positivity in breast carcinomas: a potential pitfall in diagnostic immunohistochemistry.

S-100 protein, originally isolated from neural tissues, has also been identified in various normal and neoplastic cells, including malignant melanomas. A systematic immunohistochemical investigation of this antigen was performed on formalin-fixed paraffin-embedded samples of benign and malignant breast tissues with use of the avidin-biotin-peroxidase complex immunoperoxidase technique and a polyclonal antiserum that recognizes both the alpha and beta subunits of S-100 protein. In benign breast tissue, S-100 protein was present in both epithelial and myoepithelial cells of terminal ducts and lobules; the staining was cytoplasmic and sometimes nuclear. Of 100 randomly selected invasive breast carcinomas, 48 per cent contained S-100 protein-positive tumor cells. Lobular and medullary carcinomas (60 per cent and 80 per cent, respectively) were more frequently positive than ductal carcinomas (45 per cent). Dendritic cells, most likely Langerhans' cells, were present in some carcinomas and were also positive for S-100. There was no relationship of S-100 positivity to histologic differentiation, recurrence interval, or the expression of various tumor markers. The presence of S-100 protein positivity in metastatic breast carcinomas may lead to the erroneous diagnosis of malignant melanoma. Our observations underscore the importance of testing for a broad panel of tumor markers rather than relying on single antigens in evaluating metastatic malignancies of undetermined origin.

Adenocarcinoma, Mucinous↗

PubMedDate not supplied

Spontaneous subdural empyema in falciparum malaria: a case study.

CLINICAL HISTORY: Malaria is one of the most common diseases in the tropical countries. Cerebral malaria is usually a diffuse symmetric encephalopathy with focal signs being unusual. METHODS: We present a three-year old girl lapsing into unconsciousness following a seizure while undergoing treatment for malaria. Imaging revealed a large heterogenous density, left hemispheric acute subdural haematoma with brain herniation. Investigations revealed anaemia, thrombocytopenia and positive peripheral blood smear for falciparum malaria. RESULTS: Treatment involved surgical evacuation of the clot and the associated subdural empyema, intravenous quinine and antibiotics. CONCLUSION: This is the second case report of spontaneous subdural empyema in complicated falciparum malaria and highlights a rare but surgically manageable complication.

Child, Preschool↗