CT and MR imaging of nonaccidental pediatric head trauma.
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Brain Injuries↗
Biomedical subjects
N Petitti
Publications and source records attributed to N Petitti.
The hyperdense middle cerebral artery sign.
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Brain Ischemia↗
Cerebral infarction: time course of signal intensity changes on diffusion-weighted MR images.
OBJECTIVE: The objective of this study was to determine the time course of signal intensity changes on diffusion-weighted MR images after cerebral infarction. MATERIALS AND METHODS: Echoplanar diffusion-weighted MR images were obtained at 1.5 T in 212 patients referred for suspected cerebral infarction over a 6-month period. Of those patients, 85 met strict criteria for inclusion in this study: final clinical diagnosis of stroke, reliable timing of clinical ictus by history, and neurologic symptoms persisting longer than 48 hr after onset. Using adjacent or contralateral normal brain for comparison, diffusion-weighted images were visually analyzed retrospectively to evaluate for abnormalities in signal intensity. Because three patients were scanned on two occasions and five patients had two anatomically separable infarctions, 93 reliably dated brain lesions were analyzed. RESULTS: Diffusion-weighted images showed abnormal findings in 13 (100%) of 13 lesions less than 1 day old, 46 (96%) of 48 lesions 1-4 days old, 16 (94%) of 17 lesions 5-9 days old, three (60%) of five lesions 10-14 days old, and zero (0%) of 10 lesions more than 14 days old. CONCLUSION: Abnormal signal intensity was present on all diffusion-weighted MR studies obtained in patients within 24 hr of acute cerebral infarction and in up to 94% of patients scanned during the first 2 weeks after ictus. The percentage of abnormal diffusion studies declined with time, and no signal intensity abnormality was seen in stroke patients scanned more than 2 weeks after symptom onset.
Aged↗
Duplicate publication and correction.
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Accidents, Traffic↗
Images in clinical medicine. Sand as a foreign body.
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Accidents, Traffic↗
Progesterone attenuation of alpha 1-adrenergic receptor stimulation of phosphoinositol hydrolysis in hypothalamus of estrogen-primed female rats.
These experiments examined whether the previously observed abolition by progesterone (P) of alpha 1-adrenergic potentiation of adenylyl cyclase activity in brain slices of estrogen-primed female rats is attributable to a reduced capacity of alpha 1-adrenoceptors to stimulate phosphoinositol hydrolysis. In preoptic area and hypothalamic slices from ovariectomized (OVX) female rats, both norepinephrine (NE) and the alpha 1-adrenergic agonist phenylephrine (PHE) were robust stimulators of inositol phosphate (IP) formation. The NE response was completely blocked by the alpha 1-adrenergic antagonist prazosin. PHE-induced IP formation in tissue from OVX females exposed for 48 h to estrogen alone was comparable to that in OVX controls. In hypothalamic tissue from OVX rats given estrogen plus P, NE and PHE activation of phosphoinositol hydrolysis was attenuated. Both chlorethylclonidine, an irreversible antagonist of alpha 1b-adrenoceptors, and 5-methylurapidil, an alpha 1a-selective antagonist, reduced NE-induced IP formation regardless of the hormonal condition of the animals. Analysis of PHE competition for [3H]prazosin binding indicated that agonist binding was of high affinity (Ki, 16-30 microM) and was unaffected by hormonal status. Therefore, P abolition of alpha 1-adrenergic augmentation of adenylyl cyclase is correlated with reduced phosphoinositol hydrolysis, but not with changes in alpha 1-adrenoceptor agonist binding affinity. Moreover, both alpha 1a- and alpha 1b-adrenoceptors appear to work together to stimulate this second messenger system in the female rat hypothalamus.
Adenylyl Cyclases↗
Progesterone promotes rapid desensitization of alpha 1-adrenergic receptor augmentation of cAMP formation in rat hypothalamic slices.
We previously demonstrated that norepinephrine (NE) induction of cAMP accumulation in slices of the preoptic area (POA) and middle hypothalamus (MH) is reduced by in vivo administration of progesterone to estradiol-primed rats, apparently by eliminating alpha 1-receptor augmentation of beta-receptor-stimulated cAMP formation. The present studies examined whether in vitro exposure to progesterone would also depress NE-stimulated cAMP synthesis. POA and MH slices from estradiol-primed females were incubated with 20 nM progesterone for 5-30 min prior to addition of 100 microM NE. Pre-incubation of slices with progesterone for as little as 5 min significantly suppressed NE-stimulated cAMP formation by greater than 60%. This effect was estrogen-dependent in that progesterone in vitro did not inhibit NE-stimulated cAMP accumulation in slices from ovariectomized rats not pretreated with estradiol. Isoproterenol, a beta-adrenergic agonist, elevated cAMP to the same extent in slices from estradiol-primed females incubated with and without progesterone in vitro; however, the alpha 1-agonist, phenylephrine, was unable to augment cAMP formation in slices incubated in vitro with progesterone for 5 min prior to drug challenge. To determine whether the rapid effects of progesterone may be exerted at the level of the plasma membrane, we employed progesterone conjugated to bovine serum albumin at carbon 3 (P-3-BSA). Slices from estradiol-primed rats incubated with P-3-BSA for 5 min did not exhibit an alpha 1-receptor augmentation of beta-receptor-stimulated cAMP accumulation. These data indicate that progesterone may have rapid, non-genomic effects on alpha 1-adrenergic receptor coupling to second-messenger systems in the hypothalamus of female rats.
Animals↗
Estradiol selectively regulates alpha 1B-noradrenergic receptors in the hypothalamus and preoptic area.
We previously demonstrated that estradiol administered in vivo elevates the number of alpha 1-adrenoceptors in preoptic area (POA) and hypothalamic membranes from ovariectomized female rats and potentiates alpha 1 receptor augmentation of beta-adrenoceptor-stimulated cAMP formation in slices from these brain regions. Present studies examined (1) if estradiol selectively regulates any alpha 1-adrenoceptor subtype, and (2) which alpha 1 receptor subtype mediates the augmentation of cAMP synthesis. Hypothalamic and POA membranes from estradiol-treated rats, when compared to ovariectomized rats, had modestly (30-50%) but significantly elevated numbers of 3H-prazosin (alpha 1) binding sites. Estradiol affected neither the number of alpha 1 receptor sites in frontal cortex nor the affinity of 3H-prazosin binding in any brain region examined. Results of binding studies conducted in the presence of chlorethylclonidine, a selective, irreversible inactivator of the alpha 1B receptor subtype, indicated that the estrogen-dependent increase in total alpha 1 binding sites in POA and hypothalamic membranes was attributable to a selective, five- to sixfold increase in alpha 1B receptor number. Progesterone had no measurable effects on alpha 1 receptor binding. Blockade of alpha 1B receptors with chlorethylclonidine eliminated phenylephrine augmentation of isoproterenol-stimulated cAMP formation in slices, whereas the alpha 1A antagonist 5-methyl-urapadil did not. This suggests that the alpha 1B receptor subtype potentiates cAMP formation. Thus, the increased alpha 1 receptor augmentation of cAMP formation seen in slices from estradiol-treated rats is correlated with increased alpha 1B receptor number.
Animals↗
Protein kinase C and phospholipase C mediate alpha 1- and beta-adrenoceptor intercommunication in rat hypothalamic slices.
These experiments examined the mechanism by which phenylephrine enhances beta-adrenoceptor-stimulated cyclic AMP formation in rat hypothalamic and preoptic area slices. To this end we manipulated phospholipase C. phospholipase A2, and protein kinase C activity in slices and assessed the effects of these manipulations on phenylephrine augmentation of isoproterenol-stimulated cyclic AMP generation. Since previous work indicated that estrogen enhances the alpha 1-component of cyclic AMP formation, we examined slices from both gonadectomized and estrogen-treated animals. The alpha 1-antagonist prazosin eliminated phenylephrine augmentation of the beta-response, suggesting that alpha 1-adrenergic receptors mediate the potentiation of cyclic AMP formation. Inhibition of protein kinase C by H7 attenuated the alpha 1-augmentation of beta-stimulated cyclic AMP formation. Staurosporine, a more potent protein kinase C inhibitor, completely abolished the alpha 1-augmenting response. In addition, phenylephrine potentiation of the isoproterenol response was not observed if protein kinase C was first stimulated directly with a synthetic diacylglycerol (1-oleoyl-2-acetyl-sn-glycerol) or phorbol ester (phorbol 12,13-dibutyrate). Neomycin, an inhibitor of phospholipase C, decreased alpha 1-receptor enhancement of beta-stimulated cyclic AMP formation, whereas quinacrine, an inhibitor of phospholipase A2, did not. The data suggest that the postreceptor mechanism involved in alpha 1-adrenergic receptor potentiation of cyclic AMP generation in hypothalamic and preoptic area slices includes activation of phospholipase C and protein kinase C.
1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
Alpha 1-adrenoceptor augmentation of beta-stimulated cAMP formation is enhanced by estrogen and reduced by progesterone in rat hypothalamic slices.
These experiments examined the influence of estradiol and progesterone given in vivo on norepinephrine (NE) regulation of cAMP synthesis in hypothalamic and preoptic area slices in vitro. Administration of progesterone to estrogen-primed female rats attenuated NE-induced slice cAMP accumulation. This hormone-dependent reduction in NE-stimulated cAMP synthesis was observed in slices incubated with TTX and in slices prepared from hypophysectomized rats, suggesting that progesterone effects on NE receptor activation of cAMP-generating systems are not secondary to the release of neurotransmitters that inhibit adenylyl cyclase or to changes in pituitary hormone secretion. Progesterone suppression of NE-induced cAMP formation could be prevented by incubating slices in the presence of a phorbol ester. In additional studies, the activity of beta-NE receptors was assessed by measuring isoproterenol (ISO)-stimulated cAMP accumulation in the presence of the phosphodiesterase inhibitor RO-20-1724, and the activity of alpha 1 receptors was evaluated by measuring phenylephrine (PHE) augmentation of the ISO response. Estradiol reduced the cAMP response to ISO in both hypothalamic and preoptic area slices, and this effect was not reversed by subsequent progesterone treatment. Estradiol also enhanced PHE augmentation of ISO-stimulated cAMP synthesis. Moreover, administration of progesterone subsequent to estradiol eliminated alpha 1-receptor augmentation of the ISO response. An alpha 1 enhancement of the ISO response is observed if the progestin receptor antagonist RU 38486 is administered before progesterone. Progesterone also abolished PHE potentiation of vasoactive intestinal polypeptide-stimulated cAMP accumulation. In contrast, neither phorbol ester nor muscarinic (carbachol) potentiation of the cAMP response to ISO was affected by progesterone. The data suggest that ovarian steroids regulate the coupling of both alpha 1 and beta receptors to the membrane effector systems that generate intracellular cAMP.
Animals↗
Progesterone depression of norepinephrine-stimulated cAMP accumulation in hypothalamic slices.
The present experiments examined the effects of progesterone on adrenergic receptor coupling to adenylate cyclase in hypothalamic and preoptic area slices by monitoring norepinephrine (NE)-stimulated increases in cAMP accumulation. Progesterone treatment of estrogen-primed rats decreased NE-induced slice cAMP accumulation. The reduced cAMP response was estrogen-dependent since it was not demonstrable in slices from rats exposed to progesterone without prior estrogen priming. Neither generalized increases in phosphodiesterase activity nor decreases in the catalytic activity of adenylate cyclase could account for the reduced ability of NE to stimulate cAMP accumulation in hypothalamic slices. Moreover, the cAMP response to two other activators of adenylate cyclase, adenosine and vasoactive intestinal peptide, was not decreased in slices from rats treated with estrogen plus progesterone. Selective adrenergic agonists and antagonists were employed to determine which adrenergic receptors mediate cAMP accumulation in progesterone-exposed slices. Slice cAMP levels were elevated by the beta receptor agonist isoproterenol but not by alpha 1 (phenylephrine) or alpha 2 (clonidine) agonists. However, clonidine potentiated the effect of isoproterenol on slice cAMP formation whereas phenylephrine did not. Likewise, NE-stimulated cAMP accumulation was completely antagonized only by a combination of both beta (propranolol) and alpha 2 (yohimbine) antagonists. The data suggest that in slices from estrogen plus progesterone-treated rats, alpha 2 receptors contribute significantly to NE stimulation of cAMP accumulation. The overall depression of the cAMP response to NE in progesterone-exposed slices may involve a decrease of alpha 1 receptor facilitation of cAMP synthesis.
Animals↗
Mediation of norepinephrine-stimulated cyclic AMP accumulation by adrenergic receptors in hypothalamic and preoptic area slices: effects of estradiol.
Adrenergic receptor agonists and antagonists were employed to establish (a) which receptor subtypes mediate the cyclic AMP response to norepinephrine in hypothalamic and preoptic area slices from gonadectomized female rats and (b) which receptor subtypes might be modulated by the steroid hormone estradiol. Slice cyclic AMP levels were elevated by the beta receptor agonist isoproterenol, but not by alpha 1 (phenylephrine, methoxamine) or alpha 2 (clonidine) agonists. However, the alpha agonist phenylephrine potentiated the effect of the beta agonist isoproterenol on slice cyclic AMP accumulation. In slices from rats given no hormone treatment, the beta antagonist propranolol inhibited norepinephrine-stimulated cyclic AMP production, while the alpha 1 antagonist prazosin was without effect. In contrast, the cyclic AMP response to norepinephrine in slices from estradiol-treated rats was blocked more effectively by prazosin than by propranolol. Estradiol treatment also attenuated the production of cyclic AMP by the beta agonist isoproterenol. The data suggest (a) that norepinephrine induction of cyclic AMP accumulation in hypothalamic and preoptic area slices is mediated by beta receptors and potentiated by alpha receptor activation and (b) that estradiol depresses beta and increases alpha 1 receptor function in slices from brain regions associated with reproductive physiology.
1-Methyl-3-isobutylxanthine↗
Norepinephrine-stimulated cyclic AMP accumulation in rat hypothalamic slices: effects of estrous cycle and ovarian steroids.
Hypothalamic slices prepared from female rats in various hormonal conditions were incubated in vitro in the presence or absence of 10 microM norepinephrine (NE), and cyclic AMP content was measured. Slices from animals in late diestrus or with exogenous estrogen treatment responded to NE with marked elevations of cyclic AMP in all but the posterior hypothalamus. Slices from rats sacrificed in late proestrus or following estrogen plus progestin administration showed little or no NE-stimulated cyclic AMP accumulation.
Animals↗
Mucopolysaccharidosis III (Sanfilippo syndrome) type B: cranial imaging in two cases.
We present the imaging findings in two patients with mucopolysaccharidosis III (Sanfilippo syndrome) type B, both with arachnoid cysts. We postulate that the deposition of glycosaminoglycans in the meninges may impair CSF flow and explain the development of arachnoid cysts also noted in patients with other forms of mucopolysaccharidoses.
Arachnoid Cysts↗