Biomedical subjects

Kamal Thapar

Publications and source records attributed to Kamal Thapar.

4 recordsLinked to original sources

PubMed2002

Pituitary surgery: transsphenoidal approach.

THE TRANSSPHENOIDAL APPROACH for sellar tumors has evolved significantly since it was described initially during the first decade of the 20th century. The approach currently incorporates technological advancements and refinements in patient selection, operative technique, and postoperative care. Although many of these innovations are considered indispensable, the operative technique, as performed by contemporary neurosurgeons, is not standardized. This variability is a reflection of surgeon's preference, the lessons of experience, and the bias inherent in neurosurgical training. The methods and preferences described herein embody the distillation of an experience gained from 3900 transsphenoidal operations.

Cerebrospinal Fluid Otorrhea↗

PubMed2000

Octreotide Effect on Growth Hormone and Somatostatin Subtype 2 Receptor mRNAs of the Human Pituitary Somatotroph Adenomas.

Octreotide, a somatostatin analog used to treat acromegalic patients harboring a pituitary tumor, acts via somatostatin subtype 2 receptor (SSTR2) and causes significant decrease of circulating GH levels and sometimes mild to moderate tumor shrinkage. To further elucidate the mechanism of octreotide action, we studied GH and SSTR2 mRNAs by in situ hybridization in densely and sparsely granulated somatotroph adenomas removed by surgery from 14 treated and 14 untreated patients. Only in densely granulated adenomas were the GH and SSTR2 mRNA signals mildly decreased relative to untreated matched adenomas. The decrease of GH mRNA in densely granulated somatotroph adenomas suggests that they may have a more favorable response to octreotide therapy than sparsely granulated tumors.

Journal Article↗

PubMed1996

Assessment of Mitotic Activity in Pituitary Adenomas and Carcinomas.

Assessment of mitotic activity represents one of the oldest and most routinely used histopathologic methods of evaluating the biological aggressiveness of human tumors. In the case of pituitary tumors, however, the relevance of this approach as a means of gauging tumor behavior remains ill-defined. In this article, the relationship between the mitotic index and biological aggressiveness of pituitary tumors was evaluated in a series of 54 pituitary adenomas and 6 primary pituitary carcinomas. All tumors were fully classified by immunohistochemistry and electron microscopy; adenomas were further stratified on the basis of their invasion status, the latter being defined as gross, operatively, or radiologically apparent infiltration of dura or bone. Mitotic figures were present in 11 tumors, 10 being either invasive adenomas or pituitary carcinomas. A significant association between the presence of mitotic figures and tumor behavior was noted, as evidenced by progressive increments in the proportion of cases expressing mitotic figures in the categories of noninvasive adenoma, invasive adenoma, and pituitary carcinoma (3.9, 21.4, and 66.7%, respectively; Fisher's exact test, two-tailed, p < 0.001). The mitotic index, however, appeared to be a less informative parameter, being extremely low in all cases (mean = 0.016% +/- 0.005 [+/- SEMI). Although the mean mitotic index in pituitary carcinomas (0.09% +/- 0.035) was significantly higher than the mean mitotic index of either noninvasive adenomas (0.002% +/- 0.002) or invasive adenomas (0.013% +/- 0.005), no practical threshold value capable of distinguishing these three groups was evident. Comparison of the mitotic index with Ki-67 derived growth fractions in these tumors revealed a significant but weak linear correlation (r = 0.41, p < 0.01). These data suggest that when, mitotic figures are present, they do provide some indication of the behavior and invasive potential of pituitary tumors. For routine diagnostic purposes, however, the discriminating power of this parameter is somewhat limited, being superseded by alternative and more informative methods of growth fraction determination such as that provided by the Ki-67 immunolabeling.

Journal Article↗

PubMed1996

The Pituitary in Isolated ACTH Deficiency: A Histologic, Immunocytochemical, and In Situ Hybridization Study.

A 74-year-old man presented in a near terminal state with progressive generalized muscular weakness, gastrointestinal disturbances, and lethargy. Investigations revealed hypotension, hyponatremia, hypoglycemia, and low plasma cortisol concentration accompanied by undetectable plasma adrenocorticotropic hormone (ACTH) level. The patient died shortly after admission to hospital, with adrenocortical failure being the provisional cause of death. Autopsy disclosed profound bilateral atrophy of adrenal cortices with evidence of a mild focal inflammatory reaction. The pituitary gland appeared normal on both gross and histologic examinations. There was no histologic evidence of inflammation, fibrosis, or adenohypophysial cell hyperplasia. By immunocytochemistry, no ACTH and B-endorphin immunoreactive cells were identified in the adenohypophysis. In situ hybridization (ISH) for pro-opiomelanocortin (POMC) mRNA yielded conclusively negative results. The case presented here was regarded as isolated ACTH deficiency. Although the remaining pituitary functions were not assessed, clinical and morphologic findings strongly support the supposition that aside from ACTH deficiency, secretory function of other pituitary hormones was preserved. This is the first case in which the pituitary was studied by immunocytochemistry and ISH. The possible pathogenetic mechanisms accounting for the isolated ACTH deficiency are discussed.

Journal Article↗