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T Hayden

Publications and source records attributed to T Hayden.

16 recordsLinked to original sources
PubMed2001

Deep trouble.

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Animals↗
PubMed2001

Improved convergence and speed for the distance geometry program APA to determine protein structure.

The alternating projections algorithm (APA) is a program that is based on alternating projections and is designed to determine the three dimensional structure of proteins using distance geometry. The sampling and convergence properties of APA, as tested on bovine pancreatic trypsin inhibitor (BPTI) were previously reported in this journal. The results confirmed the program's earlier success with poly-L-alanine. However, the asymptotic convergence of the alternating projections was slow. We show that after good convergence is first obtained via alternating projections, that a weighted quadratic penalty function then produces the final conformation with better convergence in half the time required by the asymptotic convergence of alternating projections.

Algorithms↗
PubMed1990

Naltrexone normalizes the suppression but not the surge of delta 5-3 beta-hydroxysteroid dehydrogenase activity in Leydig cells of stressed rat fetuses.

Rat fetuses from mothers stressed chronically by immobilization and high intensity illumination beginning on day 14 of gestation have higher than normal levels of delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta HSD) activity in Leydig cells on day 17 of gestation and lower than normal levels on days 18 and 19. Plasma testosterone titers in normal and stressed male fetuses closely parallel the activity of 3 beta HSD in fetal Leydig cells. In the present study quantitative cytochemistry was used to determine whether the stress-induced alterations in 3 beta HSD activity could be prevented by treating the mother with naltrexone, an opioid receptor blocker, before each stress session. Naltrexone normalized 3 beta HSD activity on days 18 and 19 of gestation, suggesting that the stress-induced suppression involves the endogenous opioid system. In contrast, naltrexone did not prevent the elevation in enzyme activity seen on day 17 in stressed fetuses. The persistence of a stress-induced surge on day 17, in spite of naltrexone therapy, suggests that some nonopioid mechanism is operational at that time.

3-Hydroxysteroid Dehydrogenases↗
PubMedDate not supplied

Computed tomographic demonstration of obstruction of the inferior vena cava caused by hepatocellular carcinoma.

A case of hepatocellular carcinoma obstructing the hepatic portion of the inferior vena cava by extrinsic compression demonstrated on computerized tomography is presented. To our knowledge, only one previous case has been reported which demonstrates actual invasion of the inferior vena cava by hepatic tumor. The signs of obstruction include: nonvisualization of the intrahepatic portion of the IVC, dilatation of the infrahepatic IVC with paravertebral venous collaterals and lack of changes in the diameter of the IVC after Valsalva maneuver.

Carcinoma, Hepatocellular↗