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T Calhoun

Publications and source records attributed to T Calhoun.

18 recordsLinked to original sources
PubMed2006

Highly purified CD44+ prostate cancer cells from xenograft human tumors are enriched in tumorigenic and metastatic progenitor cells.

CD44 is a multifunctional protein involved in cell adhesion and signaling. The role of CD44 in prostate cancer (PCa) development and progression is controversial with studies showing both tumor-promoting and tumor-inhibiting effects. Most of these studies have used bulk-cultured PCa cells or PCa tissues to carry out correlative or overexpression experiments. The key experiment using prospectively purified cells has not been carried out. Here we use FACS to obtain homogeneous CD44(+) and CD44(-) tumor cell populations from multiple PCa cell cultures as well as four xenograft tumors to compare their in vitro and in vivo tumor-associated properties. Our results reveal that the CD44(+) PCa cells are more proliferative, clonogenic, tumorigenic, and metastatic than the isogenic CD44(-) PCa cells. Subsequent molecular studies demonstrate that the CD44(+) PCa cells possess certain intrinsic properties of progenitor cells. First, BrdU pulse-chase experiments reveal that CD44(+) cells colocalize with a population of intermediate label-retaining cells. Second, CD44(+) PCa cells express higher mRNA levels of several 'stemness' genes including Oct-3/4, Bmi, beta-catenin, and SMO. Third, CD44(+) PCa cells can generate CD44(-) cells in vitro and in vivo. Fourth, CD44(+) PCa cells, which are AR(-), can differentiate into AR(+) tumor cells. Finally, a very small percentage of CD44(+) PCa cells appear to undergo asymmetric cell division in clonal analyses. Altogether, our results suggest that the CD44(+) PCa cell population is enriched in tumorigenic and metastatic progenitor cells.

Animals↗
PubMed2000

Postnatal development of nitric oxide synthase expression in the mouse superior colliculus.

Since nitric oxide has a role in the refinement of the retinal projection to the superior colliculus (SC), we studied the onset of neuronal nitric oxide synthase (nNOS) expression in the mouse SC in order to compare its development with that of the refinement process. Sections from animals at ages P1, P5, P8, P11, P15, and P21 and adults were examined with nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry or immunocytochemistry using an antibody directed against nNOS. At all ages there was a wedge of labeled neurons in the dorsolateral periaqueductal gray extending into the deep layers of the SC. At P1 there was also a single superficial band of labeled neurons within the region that will become the intermediate gray layer (IGL). By P5, labeled neurons were also seen in what will become the superficial gray layer. There was a ventral to dorsal progression in nNOS expression with substantial changes in the numbers of labeled neurons in the different laminae between P5 and adulthood. The number of labeled neurons in the IGL peaked at P15, whereas in the superficial layers the numbers continued to increase through P21 and then declined in adults. At all ages these neurons represented a variety of morphological cell types. The onset of nNOS expression in the different laminae is earlier than has been reported in studies using NADPHd as a marker for nNOS. The temporal and spatial patterns of nNOS expression reported here match more closely the time course of pathway refinement in the SC, providing additional evidence for the involvement of nitric oxide in this process.

Animals↗
PubMed2000

Variables associated with adolescent alcohol use: a multiethnic comparison.

The authors examined the influence of sociodemographic variables on the frequency and intensity of alcohol use among a nationally representative sample of Black, Hispanic, and White adolescents who had participated in the 1991 National Household Survey on Drug Abuse (U.S. Department of Health and Human Services, 1993). The sample consisted of 8,756 U.S. adolescents aged 12 to 18 years. The authors found that (a) approximately 19% of the respondents had used alcohol in the last 30 days: (b) among the respondents who had used alcohol, 21% had consumed 1 or more drinks per drinking episode; and (c) there were important similarities as well as important differences in variables that promoted alcohol use among Black. Hispanic, and White adolescents.

Adolescent↗
PubMed1993

Peer review and risk management.

As physicians and other health-care providers are experiencing an increased number of lawsuits, external pressures also are being exerted by various third-party payers and peer review organizations. An overview of some of the problems that may arise and methods for responding is presented. Knowledge of the processes involved by peer groups will help in risk management concerns as well. A new approach to quality assurance by the federal government is also described, the Health Care Quality Improvement Initiative.

Peer Review, Health Care↗
PubMed1988

The application of preoperative radiation therapy for unresectable malignancies.

Preoperative radiation therapy is one of the major indications for the use of ionizing radiation in the treatment of malignant disease. The preoperative application of radiation treatment is given with the intention of reducing the size of bulky cancers, thus converting unresectable tumors into resectable ones. Other benefits are reduction in the risk of locoregional recurrence and in the risk of blood-borne dissemination of malignant cells promoted during surgical resection.This paper presents and discusses three cases of unresectable intrapelvic tumors initially treated by radiation therapy with the primary goal of palliation. These three cases included rectal, cecal, and uterine carcinoma. In each case, a preoperative radiation dose of 4500 to 5000 cGy was delivered. Evaluations during and after the completion of the radiation treatments revealed that the tumor responded remarkably well to the treatment, which encouraged the surgical intervention; at surgery, minimal tumor was found. These three patients are alive to date without apparent evidence of disease.

Aged↗
PubMed1980

Pancreatic abscess: a major complication of cystogastrostomy.

Twelve cases of pancreatic abscess, managed at two hospitals in the District of Columbia, are analyzed. Forty-two percent of cases followed acute pancreatitis and infected pancreatic pseudocysts without previous surgical intervention. In 58 percent of the patients, pancreatic abscess was a complication of internal drainage of pancreatic pseudocysts. A discussion of management problems is presented.

Abscess↗
PubMed1979

Traumatic diaphragmatic hernias: analysis of six cases.

During three years, from January 1975 through December 1977, the authors saw six cases of traumatic left diaphragmatic hernias, all of whom survived. All were males aged 17 to 56 years, with an average age of 30 years. Four (67 percent) of the cases resulted from blunt abdominal trauma while two (33 percent) were due to stab wounds of the left lower chest. Admitting chest x-ray findings were diagnostic for all acute hernias due to blunt trauma and for all hernias presenting with a delayed interval. Digital exploration of all penetrating lower chest wounds is recommended by some authors if exploratory laparotomy is not contemplated. Our preferred approach for the repair of the hernias includes (1) laparotomy for all acute cases, (2) thoracotomy for delayed cases, and (3) separate abdominal thoracic incisions whenever a combined approach is considered necessary. The repair should be carried out in two layers with nonabsorbable sutures.

Abdominal Injuries↗
PubMed1975

Colostomy. Intraperitoneal or extraperitoneal closure?

Forty-three patients who underwent intraperitoneal closure of colostomy are reported on. Complication rates of 4.6 per cent for wound infection and 4.6 per cent for fecal fistulas appear significantly lower than the 10 to 21 per cent complication rates reported for colostomy closure using other technics.

Colonic Diseases↗
PubMed1975

Granular cell myoblastoma: another unusual esophageal lesion.

The case is presented of a 48-year-old woman with esophageal granular cell myoblastoma who was treated by local excision. A review of the literature is also included. So far as we can determine, this is the thirteenth such case reported.

Esophageal Neoplasms↗