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T J Hebert

Publications and source records attributed to T J Hebert.

8 recordsLinked to original sources
PubMed1995

Androgenic-anabolic steroids modify beta-endorphin immunoreactivity in the rat brain.

Immunocytochemical localization of beta-endorphin in the brains of intact and castrated male rats was conducted after the administration of high levels of androgenic-anabolic steroids (AAS; 14 daily injections of sesame oil or a cocktail of 2 mg/kg testosterone cypionate, 2 mg/kg nandrolone decanoate, and 1 mg/kg boldenone undecylenate) at doses commonly self-administered by athletes who are considered 'heavy abusers'. In normal intact oil-treated males, cytoplasmic immunoreactivity was prevalent throughout the arcuate nucleus while intense fiber tract immunoreactivity was most prevalent in the bed nucleus of the stria terminalis and the paraventricular hypothalamic nucleus. Administration of AAS significantly decreased the number of neurons exhibiting cytoplasmic immunoreactivity only in the rostral region of the arcuate nucleus. AAS treatment had no effect on beta-endorphin immunoreactivity in the middle or caudal aspects of the arcuate nucleus.

Animals↗
PubMed1995

Inhibition of lordosis in female hamsters and rats by 8-OH-DPAT treatment.

In the present experiments, the ability of the 5-HT1A agonist, 8-OH-DPAT, to inhibit lordosis was determined in ovariectomized hamsters and rats under various hormonal conditions. Systemic administration of 8-OH-DPAT (0.25 mg/kg) significantly inhibited lordosis duration in ovariectomized hamsters treated on 3 consecutive wk with estradiol benzoate (3 or 10 micrograms) and progesterone (500 micrograms). Similarly, systemic administration of 8-OH-DPAT (0.25 mg/kg) significantly inhibited lordosis frequency in ovariectomized rats treated on 3 consecutive wk with estradiol benzoate (0.25, 0.5, or 25 micrograms for 3 days) and progesterone (500 micrograms), although females treated with the higher doses of estrogen were slightly less inhibited on the second and third wk of testing. Results indicate that the 5-HT1A agonist, 8-OH-DPAT, effectively inhibited lordosis in female hamsters, as well as female rats, under varied hormonal conditions.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1994

Effects of hormonal treatment and history on scopolamine inhibition of lordosis.

The muscarinic receptor blocker, scopolamine, inhibits the display of lordosis behavior in female rats but its effectiveness depends on hormonal conditions. In these experiments, systemic administration of scopolamine (0.031-4 mg/kg) inhibited lordosis in ovariectomized rats brought into receptivity by treatment with a low dose of estradiol benzoate (EB, 0.25 micrograms for 3 days) with progesterone (P, 500 micrograms for 1 day), or a high dose of EB (25 micrograms for 3 days) with and without P. However, the effectiveness of scopolamine was reduced at the high dose of EB and with the addition of P. Furthermore, scopolamine failed to inhibit lordosis in females treated on a second week with the high dose of EB with or without P, unless an interval of at least 3 weeks separated the two sets of steroid treatments. The reduced effectiveness of scopolamine cannot be explained by peripheral mechanisms because its inhibitory effect on lordosis also was reduced following repeated hormonal exposure even when scopolamine was infused directly into the lateral ventricles.

Acetylcholine↗
PubMed1992

The effect of estrogen treatment on scopolamine inhibition of lordosis.

Previous evidence indicates that the cholinergic muscarinic antagonist, scopolamine, inhibits lordosis in female rats. In the experiments reported here, the effects of various doses and repeated administrations of estrogen on the scopolamine inhibition of lordosis were examined. In the first experiment, intraperitoneal injections of scopolamine (1 mg/rat) completely inhibited lordosis in ovariectomized rats primed with low doses of estradiol benzoate (0.25 or 0.5 micrograms for 3 days) and progesterone (500 micrograms). However, scopolamine was significantly less effective in inhibiting lordosis in females primed with a higher dose of estradiol benzoate (25 micrograms for 3 days) and progesterone (500 micrograms). When hormone priming was repeated on subsequent weeks, scopolamine continued to inhibit lordosis in females that received 0.25 micrograms estradiol benzoate but was less effective in females primed with 0.5 micrograms. Scopolamine failed to inhibit lordosis in females treated with 25 micrograms estradiol benzoate on these later tests. In the second experiment, various doses of scopolamine (1, 2, or 4 mg/rat) were administered intraperitoneally to females primed with the highest dose of estradiol benzoate (25 micrograms) and progesterone (500 micrograms). Lordosis was inhibited equally by all scopolamine doses during the first week. As in the first experiment, scopolamine failed to inhibit lordosis at all doses on subsequent weeks of testing. These results indicate that the ability of scopolamine to inhibit lordosis is reduced by increasing the dose or the number of estrogen exposures. Because higher doses of scopolamine failed to restore its inhibitory effect on lordosis an upregulation of muscarinic receptors by estrogen cannot account for the reduced effectiveness of scopolamine.

Animals↗
PubMedDate not supplied

Maximum likelihood preprocessing for improved filtered back-projection reconstructions.

OBJECTIVE: Based upon theoretical consideration and experimental investigation, we propose a model-based maximum likelihood (ML) preprocessing approach to the filtered back-projection (FBP) algorithm for application to single photon emission CT (SPECT). MATERIALS AND METHODS: In this approach, we optimally removed Poisson noise and an average blur from the projection images and then applied the FBP algorithm for reconstruction. RESULTS: The average blur was due to the combined effect of the geometric response of the imaging system, septal penetration, scatter, and patient motion. We evaluated this preprocessing approach to FBP reconstruction on SPECT physical phantom and patient studies. Preliminary results were encouraging. CONCLUSION: The advantages of the proposed approach are that statistical noise is accurately modeled, removal of both blur and noise is optimal in the ML sense, and further improvement in this method may be achieved through more accurate modeling of blur in the projection images.

Aged↗