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Biomedical subjects

A Goel

Publications and source records attributed to A Goel.

At least 199 records · Page 11Linked to original sources
PubMed1997

Supply-Side Analysis of Growth of Bacillus subtilis on Glucose-Citrate Medium: Feasible Network Alternatives and Yield Optimality.

Our prior work revealed that compared to the case for glucose metabolism, increased carbon yield and nil acid formation result when Bacillus subtilis grows on glucose medium containing citrate. To scrutinize further how citrate addition may alter metabolic flux regulation and the degree that the observed carbon yield corresponds to the maximal value, experimental (by least-squares analysis) and optimal (by linear programming) fluxes and yields were contrasted. Networks with differing reaction routes, directionality constraints, and transhydrogenase activities were examined. To attain an elevated carbon yield, citrate-glucose utilization need not alleviate any stoichiometric constraints that can sometimes interfere with the attainment of network objectives. Rather, the high carbon yield and nil acid formation attained may be linked to restriction of glycolytic capacity, particularly at the level of pyruvate kinase, which is consistent with a hypothesized effect of coupled metal-citrate uptake. Allowing for malic enzyme activity, hexose monophosphate pathway cycling, and transhydrogenase activity may also lead to the flux distributions underlying the high carbon yield observed. Finally, the observed carbon yield corresponded well to the maximum yield provided by all the network alternatives examined. Collectively, these results suggest that (i) the observed carbon yield is essentially equal to the maximal values associated with plausible networks and (ii), as suggested by others, nonoptimal flux regulation may contribute significantly to apparent cellular maintenance requirements.

Journal Article↗
PubMed1997

Splitting of temporalis muscle for basal exposure--technical note.

Splitting of the temporalis muscle to increase the basal exposure in subtemporal approaches is discussed. The temporalis muscle is split vertically in the direction of its insertion at the coronoid process of the mandible up to the zygomatic arch and the split components of the muscle are retracted apart. This simple procedure significantly reduces the obstruction caused by the temporalis muscle during subtemporal surgery. The procedure was employed in six patients with tumors located in the basal temporal, posterior cavernous sinus, and petrous apex region. Zygomatic osteotomy could be avoided in selected patients and the exposure of the infratemporal fossa region could be widened by employing this technique. The function and bulk of the temporalis muscle were effectively preserved.

Humans↗
PubMed1997

Immunohistochemical analysis of human embryos and fetuses: an insight into the mechanism of subversion of antigenic differentiation in neoplasia.

OBJECTIVES: Immunohistochemical identification of intermediate filaments and other cell identity markers is of immense value in diagnostic tumor pathology. However, the literature contains many examples of inappropriate expression of markers by various tumors or coexpression of two or more markers supposedly specific for different cell types. The present study investigated this subversion of antigen differentiation in tumors by using developing tissues as a model. MATERIALS AND METHODS: Twenty-five human embryos and fetuses of 4 to 24 weeks' gestation were studied. An indirect immunoperoxidase method was applied to formalin-fixed, paraffin-embedded sections using a panel of 13 commonly used cell identity markers including intermediate filaments. RESULTS: During early development, vimentin was found to be coexpressed with cytokeratin in surface ectoderm, developing notochord, renal tubule epithelium, and intestinal mucosa. It coexpressed with glial fibrillary acidic protein in developing neuroglial tissue, with S100 in cartilage, and with skeletal muscle markers in myotubules. Hence, vimentin represents immaturity of tissues and is coexpressed with specific cell markers to be eventually replaced by the latter. Transbarrier expression of cytokeratin in smooth muscle was also noted. CONCLUSION: The aberrant expression of antigens in neoplastic tissues, as reported in the literature, simulates the varying expression of antigens in immature tissues during development. Hence, it is proposed that the phenomenon of antigenic subversion in neoplasia is related to the process of maturation and differentiation.

Antibodies, Monoclonal↗
PubMed1997

Role of proteases in tumor invasion and metastasis.

Cancer remains a major cause of worldwide deaths due to ability of cancer cells to form secondary tumors at other sites by multistep process called metastasis. In order to migrate from their original site, tumor cells have to cross several barriers like basement membranes, interstitial tissues and extracellular matrices, which are composed primarily of collagen, proteoglycans, elastin, laminin and other glycoproteins. Tumor cells over express and secrete proteases which are capable of degrading the components of these barriers and thus facilitate their migration. The classes of proteases which have been implicated in the process of tumor invasion and metastasis include metalloproteases, serine proteases and cathepsins. Cancer cells in general have elevated levels of proteases belonging to more than one class. In some studies, process of invasion has been inhibited by using specific inhibitors of these proteases. Expression of some proteases has been observed only in some specific tumors. These proteases have been proposed to be of diagnostic/prognostic value. However a better understanding of the process of metastasis and tumor invasion is required before proteases can be used as therapeutic targets for blocking the spread of cancer.

Animals↗
PubMed1997

Joint moments in minor limb length discrepancy: a pilot study.

A biomechanical analysis was performed to determine if a minor limb length discrepancy alters lower extremity joint mechanics significantly and in a manner that could contribute to the development of joint abnormalities. Ten healthy subjects with equal limb lengths were recruited. Gait analysis was performed for both left and right sides to determine the maximum moments at the hip, knee, and ankle joints. A minor limb length discrepancy was simulated by adding a shoe lift of 1.25 cm to the left leg. After a period of acclimation, the gait was reanalyzed. Differences for maximum joint moments at the hip, knee, and ankle before and after simulation were nonsignificant. An additional 10 healthy, asymptomatic patients with actual limb length discrepancies ranging from 1 cm to 2 cm were also recruited. Gait analysis for maximum joint moments before and after correction of the limb length discrepancy was performed. Side-to-side differences in joint moments before correction were nonsignificant. After correction of the limb length discrepancy, side-to-side joint moment differences were significantly increased (P = 0.02) and may suggest acute overcompensation to the presence of the corrective shoe lift. Consequently, this study did not find an association between minor limb length discrepancies and predictable changes in lower extremity joint kinetics that might potentially lead to joint abnormalities.

Adolescent↗
PubMed1997

Re-classification of carcinoma cervix uteri by mucin histochemistry.

Biopsies of cervix uteri from 166 patients with benign and malignant lesions (12 normal, 48 inflammatory lesion, 6 adenocarcinoma, 2 adenosquamous carcinoma and 98 from squamous cell carcinomas) were studied histochemically. The stains used were PAS with/without diastase, AB/PAS (pH 2.5) and OR/AB. In inflammatory lesions neutral mucin was predominent which was replaced by sialomucin and sulphomucin in endocervical polyps. In malignant lesions sulphomucin was predominent. Seventeen percent cases of squamous cell carcinomas needed reclassification after mucin staining. Of the fourteen large cell non-keratinizing squamous cell carcinomas, 12 were reclassified as squamous cell carcinoma with mucin secretion and 2 as adenosquamous carcinoma. One case of small cell non-keratinizing squamous cell carcinoma was reclassified as moderately differentiated adenocarcinoma. None of the keratinizing carcinomas had evidence of mucin secretion. Mucin histochemistry should be done routinely on non-keratinizing squamous cell carcinomas to pick up more cases of carcinoma with evidence of mucin secretion which can be missed on routine haematoxylin and eosin stains. Such carcinomas are known to pursue a more aggressive clinical course and have a poorer prognosis than non-mucin secreting type of squamous cell carcinoma.

Adenocarcinoma↗
PubMed1996

Behçet-type vasculopathy in a patient without the diagnostic features of Behçet's disease.

Behçet's disease is a multisystem inflammatory disorder which may involve the vascular system. The vasculopathy of Behçet's disease is distinctive among the vasculitides in that it involves both arteries and veins, and vessels of all sizes. Most published diagnostic criteria for Behçet's disease include the classic triad of orogenital ulceration and ocular inflammation. In this report, we describe a patient who had a vasculopathy fitting the Behçet's disease type, but who lacked the other characteristic or diagnostic features of Behçet's disease. This case illustrates an unusual presentation and natural history of a complex vasculitic disease.

Adult↗
PubMed1996

Multilayer reconstruction of the middle cranial fossa floor.

Alternative methods of multilayer reconstruction for cranial basal defects are discussed in this report. The reconstruction procedure employs usage of multiple layers of vascularised pedicle flaps which are placed over one another. The extensive vascular supply to the temporalis muscle and its fascial coverings was exploited in fashioning the flaps. The procedure not only provided a compact sealing of the defect, but by virtue of its volume helped in reducing the dead space. The technical issues concerning the harvesting of the flaps and their indications are discussed in this report.

Adult↗
PubMed1996

Surgical management of giant pituitary tumours--a review of 30 cases.

An experience with surgical management of 30 giant pituitary tumours is analysed in this report. The clinical features, anatomical spread and relationship of these tumours with the cavernous sinus and other parasellar and basal forebrain structures is analysed. The problem encountered in the surgical treatment are reviewed. An unusual feature in the management was an intra-operative and post-operative tumour swelling and acute elevation of the intracranial pressure in 5 patients. Despite the technical problems encountered during surgery and in the post-operative period it was observed that a significant resection and adequate decompression of the visual apparatus offered a reasonable opportunity for recovery in vision and a satisfactory outcome. Complete resection of the tumour was not possible in this series. A contralateral subfrontal route was seen to be most suitable for resection of the part of the tumour that invaded the cavernous sinus.

Adenoma↗
PubMed1996

Cadaveric Hands-on Workshop Using a Three-Dimensional High-Definition Television System.

We report the introduction of a three-dimensional high-definition television system in cadaveric microneurosurgical hands-on workshops on skull base technique. The system was found to be a useful means of exact communication between the instructor and the participants and avoided congestion around the instructor's table. The instructions could be refayed to the multiple participants at one time and thus avoided repetitions. More participants could be accommodated in the workshops. The entire proceeding could be recorded three-dimensionally for later use and educational purposes.

Journal Article↗
PubMed1996

Basal extension of craniotomy for subtemporal middle fossa approach.

Resection of the root of the zygomatic arch including the glenoid fossa, and the roof of the external ear and the superior third of the mastoid process was seen to improve the basal exposure of the lateral subtemporal middle fossa approach. The exposure was horizontally wide. The enhanced exposure helped in reducing the extent of brain retraction that was necessary and improved the working space for manipulation of the instruments.

Craniotomy↗
PubMed1996

Occipital falcine meningioma presenting with ipsilateral hemifacial spasm: a case report.

We report a large right occipital falcine meningioma, the main presenting feature of which was ipsilateral hemifacial spasm. The patient was relieved of the hemifacial spasm after the supratentorial tumour was resected. The pathogenesis of hemifacial spasm is reviewed in light of this unusual case and the treatment of hemifacial spasm secondary to a tumour is discussed.

Brain Neoplasms↗
PubMed1996

Intradiploic haematoma behaving as a progressive mass lesion.

A 17-year-old boy presented with a slowly growing right frontal bone swelling over an 8-year period. The swelling resulted in marked proptosis and reduced his visual acuity and eye movements. He was found to have clotting factor VIII deficiency. A chronic intradiploic haematoma as the cause of the swelling was a surprise finding.

Adolescent↗
PubMed1996

Unattached intracranial extra-axial schwannoma.

We describe an intracranial extra-axial petroclival schwannoma which did not arise from any cranial nerve, nor was it attached to brain parenchyma or dura. The possible pathogenesis is discussed.

Adult↗