Early experience of a local pathway on the waiting time for MRI in patients presenting to a UK district general hospital with suspected cauda equina syndrome.

AIM: This study evaluated the impact of the Salisbury Protocol for Assessment of Cauda Equina Syndrome (SPACES) on the waiting time for MRI in patients presenting with suspected Cauda Equina Syndrome (sCES) within a UK district general hospital. PATIENTS AND METHODS: All consecutive patients undergoing an MRI scan in our hospital, for sCES, over a 12 month period, prior to and following the introduction of SPACES, were identified. Patient's gender, age, MRI diagnosis, time from MRI request to imaging and outcome were recorded. RESULTS: In the year prior to the introduction of SPACES, 66 patients underwent MRI for sCES, out of which 10.6% had cauda equina compression (CEC), 63.5% had other spinal pathology and 25% had a normal scan. In the year after introduction of SPACES, 160 patients underwent MRI for sCES out of which 6.2% had CEC, 70.7% had other spinal pathology and 23% had a normal scan. Despite the referrals for sCES increasing by more than 2-fold following the introduction of SPACES, the median time from MRI request to scan decreased from 9.1 to 4.2 hours (p = 0.106, Mann-Whitney-U) and the number of patients transferred to the regional hub hospital decreased from 7 to 3. CONCLUSION: Implementation of SPACES for patients with sCES resulted in a substantial reduction in waiting time for MRI and decreased the number of transfers to the regional hub hospital. Based on our early experience, we encourage other centres within the UK to introduce such a pathway locally, to improve the management of patients with sCES.

Bone induction at physiological doses of BMP through localization by clay nanoparticle gels.

Bone Morphogenic Protein 2 (BMP2) can induce ectopic bone. This ability, which first motivated the widespread application of BMP2 in fracture healing and spinal arthrodesis has, more recently, been indicated as one of several serious adverse effects associated with the supra-physiological doses of BMP2 relied upon for clinical efficacy. Key to harnessing BMPs and other agents safely and effectively will be the ability to localize activity at a target site at substantially reduced doses. Clay (Laponite) nanoparticles can self assemble into gels under physiological conditions and bind growth factors for enhanced and localized efficacy. Here we show the ability to localize and enhance the activity of BMP2 to achieve ectopic bone formation at doses within the sub-microgram per ml range of concentrations sufficient to induce differentiation of responsive cell populations in vitro and at approximately 3000 fold lower than those employed in clinical practice.

High concentrations of oxytocin in hypophysial portal plasma.

Hypophysial portal blood was collected from pentobarbital-anesthetized male rats, and the content of oxytocin (OT) was measured by RIA. The concentration of OT in portal plasma was 1.88 +/- 0.48 ng/ml (SEM) and was at least 15 times higher than the concentration of OT in peripheral plasma samples from the same rats. Dilutions of portal plasma produced a displacement curve parallel to those of synthetic OT and posterior lobe extract. The data support a possible role for OT as a hypothalamic-releasing hormone.

Inhibition of corticotropin release during hypothermia: the role of corticotropin-releasing factor, vasopressin, and oxytocin.

To investigate the mechanism by which ACTH secretion is inhibited during hypothermia, hypophysial portal blood was collected from euthermic and hypothermic rats, and the concentrations of corticotropin-releasing factor (CRF), vasopressin (AVP), and oxytocin (OT) were measured by RIA. Whereas CRF levels in portal plasma were not different in the two groups, AVP and OT levels were significantly lower in hypothermic rats. The concentration of AVP and OT in peripheral plasma was also significantly lower in hypothermic rats compared with euthermic controls. The pituitary responsiveness to CRF during hypothermia was tested in vivo and in vitro. In pentobarbital-anesthetized male rats injected iv with 0.1 or 1.0 nmol CRF, the ACTH response was significantly smaller in hypothermic compared with euthermic animals. However, hemipituitaries superfused at 31 C released the same amount of ACTH in response to 1 nM CRF as hemipituitaries superfused at 37 C (31 C, 541 +/- 90 pg; 37 C, 563 +/- 29 pg) despite reduced baseline secretion (31 C, 77 +/- 10 pg/10 min; 37 C, 114 +/- 14 pg/10 min; P less than 0.05). The data suggest that the inhibition of ACTH secretion during hypothermia is mediated by decreased hypothalamic secretion of AVP and OT which in turn decreases the pituitary responsiveness to CRF.

Noncalcium-dependent modulation of in vitro atrial natriuretic factor release by extracellular osmolality.

Recent reports have described modulation of atrial natriuretic factor (ANF) secretion by atrial stretch, increased Na+ concentration, and a variety of hormones and neurotransmitters. One problem in the study of ANF secretion has been the isolation of stimulatory effects from interference due to rhythmic myocardial contraction. To avoid this problem, rat atria were dispersed, the myocytes were suspended in a polyacrylamide gel matrix, and the resulting cell column was perifused with a physiological buffer. The secretion of ANF immunoactivity was markedly stimulated by increases in extracellular osmolality, regardless of the solute (NaCl, KCl, or glucose). This effect did not require extracellular Ca2+, nor could it be mimicked by depolarizing concentrations of K+ in an isotonic medium. Functional viability of this model was demonstrated by significant dose-related increases in ANF release in response to as little as 1 nM epinephrine. The dissociation of ANF secretion from depolarization-induced changes in Ca2+ flux is unusual and may represent an adaptation to the dual roles of the atrial myocyte, contraction and secretion.

Presence of corticotropin releasing factor-like immunoreactivity in hypophysial portal blood.

Hypophysial protal blood was collected from pentobarbital anesthetized male rats, and the content of corticotropin releasing factor-like immunoreactivity (CRF-LI) was measured using an RIA developed for synthetic ovine CRF. The concentration of CRF-LI in portal plasma was 104.9 +/- 9.7 pM. This concentration is in the range which has been shown to stimulate ACTH and beta-endorphin secretion in vitro. These data support the hypothesis that a molecule with the same or similar structure as synthetic ovine CRF is a physiologically significant hypothalamic releasing factor.

High concentrations of epinephrine derived from a central source and of 5-hydroxyindole-3-acetic acid in hypophysial portal plasma.

This study was designed to determine if active secretion of epinephrine (EPI) and/or 5-hydroxytryptamine (5-HT) from the hypothalamus into the hypophysial portal vasculature takes place, in addition to the well-known secretion of dopamine (DA). Hypophysial portal plasma was collected from urethane-anesthetized male rats by stalk cannulation (Porter method) or by periodic aspiration of portal blood (Worthington and Fink method). Portal and peripheral plasma concentrations of EPI, 5-HT, DA and 5-hydroxyindole-3-acetic acid (5-HIAA) were concurrently measured by high performance liquid chromatography with electrochemical detection. Significantly higher concentrations of EPI were found in hypophysial portal than in peripheral plasma. After adrenalectomy (ADX), peripheral plasma levels of EPI were undetectable, whereas portal plasma EPI levels were only slightly attenuated. Although 5-HT levels in portal and peripheral plasma were not different, 5-HIAA levels were 3-fold higher in portal plasma. DA was 10-15 fold higher in portal plasma. All the above differences were found independent of the collection method. The high level of 5-HIAA in portal plasma was not due to conversion of 5-HT to 5-HIAA by monoamine oxidase in plasma. The results indicate that in addition to DA, another amine (EPI) and an amine metabolite (5-HIAA) have a concentration gradient in portal vs peripheral plasma. Moreover, the presence of EPI in portal plasma after ADX is a strong indication that EPI is primarily derived from a central source, suggesting that the amine may have a direct physiological role in the regulation of anterior pituitary function.

Beta-adrenergic binding and secretory responses of the anterior pituitary.

Our studies demonstrated that beta-adrenergic agonists stimulate the release of GH from rat anterior pituitary (AP) cells in vitro. Concentration-response experiments with beta-adrenergic agonists demonstrated that beta 2-adrenergic receptors mediated this phasic GH release, while having no apparent effect on PRL or LH release. The ACTH response to beta-adrenergic agonists was equivocal. Half-maximal stimulation of GH release occurred at 14 +/- 2 (+/-SE) nM isoproterenol, 160 +/- 30 nM epinephrine, and over 1 microM l-norepinephrine (n = 4). Direct binding studies in membrane particulates of rat AP confirmed receptors of the beta 2-subtype. Iodocyanopindolol binding to beta-adrenergic receptors of rat AP yielded a dissociation constant of 4.6 +/- 0.1 pM and a maximal capacity of 1.9 +/- 0.4 fmol/mg protein (n = 3). In contrast, porcine AP contained beta 1-adrenergic receptors. These results support the hypothesis that the endogenous beta 2-adrenergic agonist l-epinephrine may be a GH-releasing factor of physiological significance in the rat.

Effects of synthetic corticotropin-releasing factor and dopamine on the release of immunoreactive beta-endorphin/beta-lipotropin and alpha-melanocyte-stimulating hormone from human fetal pituitaries in vitro.

The effects of synthetic corticotropin-releasing factor (CRF) and dopamine on immunoreactive beta-endorphin/beta-lipotropin (i beta-END/LPH) and alpha MSH release were studied in superfused human fetal pituitary glands. CRF (20 ng) stimulated the release of i beta-END/LPH in four anterior hemipituitaries from fetuses older than 20 weeks in gestation. There was no effect on three anterior hemipituitaries from fetuses of 19-20 weeks gestation. CRF had no effect on i beta-END/LPH or alpha MSH secretion from neurointermediate lobes regardless of fetal age. Dopamine (10(-6) M) had no effect on i beta-END/LPH or alpha MSH secretion from either anterior or neurointermediate lobes. The data suggest that anterior pituitary responsiveness to CRF develops at about 20 weeks gestation and that fetal neurointermediate lobe secretion of peptides is not regulated by CRF.

Supersensitive endocrine response to physostigmine in dopamine-depleted rats: a model of depression?

Depressed patients exhibit an abnormal "supersensitive" increase in the plasma concentration of several pituitary hormones following intravenous injection of the acetyl cholinesterase inhibitor physostigmine (PHY). In the present study, we examined the effects of PHY treatments on the plasma concentrations of prolactin (PRL) and adrenocorticotrophic hormone (ACTH) in the rat. Physostigmine (0-0.6 mg/kg, s.c.) produced a dose-dependent increase in PRL and ACTH immunoreactivity in unoperated animals. Neurotoxin-induced depletion of brain dopamine (DA) or norepinephrine (NE) did not significantly alter baseline plasma PRL or ACTH values. Following depletion of brain DA, but not NE, animals exhibited a "supersensitive" increase in plasma ACTH values, which was evidenced by a sixfold left shift in the dose-response properties of PHY. These results suggest that there are intriguing parallels between the abnormal endocrine response to PHY demonstrated by depressed patients and that demonstrated by rats following depletion of central nervous system (CNS) DA levels.

Hyperventilation-induced cerebral ischemia in panic disorder and effect of nimodipine.

Basilar artery blood flow was measured by transcranial Doppler ultrasonography before and during hyperventilation in nine patients with panic disorder and nine normal comparison subjects. The hyperventilation-induced decrease in basilar artery blood flow was significantly greater in patients with panic attacks than in comparison subjects. Two patients with decreases in basilar flow greater than 80% were successfully treated with nimodipine, a centrally active calcium channel blocker.

Differences in IgG subclass do not effect immune complex-enhanced T cell activation despite differential binding to antigen presenting cells.

Ag presentation to CD4 T cells is a critical event in the generation of protective immunity. IgG, in the form of IgG-pathogen (Ag) complexes, is capable of mediating FcgammaR-dependent Ag presentation, and thereby enhanced T cell activation. Therefore, it is important to understand the ability of the individual human IgG subclasses to function in enhanced T cell activation. We hypothesized that increased delivery of Ag to monocyte FcgammaR by high affinity human IgG subclasses, IgG1 and IgG3, would lead to increased Ag presentation, as compared to low affinity IgG subclasses, IgG2 and IgG4. To create immune complexes, we linked biotinylated IgG subclasses to biotinylated Ag via an avidin bridge, and examined T cell responses to them. Although IgG2- and IgG4-Ag complexes bound to monocytes at significantly lower levels than those made with IgG1 and IgG3, we observed no significant difference in the ability of the four human IgG subclasses to mediate enhanced T cell activation. Studies suggest the explanation for this dichotomy lies within the first 24 h of Ag processing, and that processing efficiency may vary with IgG subclass. They also suggest the existence of a highly efficient, and selective processing pathway, which is dependent on IgG subclass, and can compensate for low level production and FcgammaR binding of IgG2- and IgG4-Ag complexes.

Vasopressin and oxytocin: hypothalamic modulators of the stress response: a review.

ACTH secretion is primarily controlled by hypothalamic secretion of corticotropin releasing factor (CRF) into pituitary portal blood. However arginine vasopressin (AVP) and oxytocin (OT) can modulate the actions of CRF and at times may be important mediators of stress-induced ACTH secretion. The relative contributions of CRF, AVP, and OT to the control of ACTH secretion vary with different types of stress. In general, AVP stimulates ACTH secretion in all species studied. OT also stimulates ACTH release in rats but is inhibitory in primates. The involvement of AVP and OT in the control of ACTH secretion may have important implications for physiological and pathological conditions associated with activation of the hypothalamo--hypophysial--adrenal cortical axis.

Immunoneutralization of oxytocin attenuates stress-induced corticotropin secretion in the rat.

Recent studies have demonstrated that oxytocin (OT) is released during certain stresses and that OT can potentiate the activity of CRF in vitro. To better define the role of OT during stress, the effect of injections of anti-OT antiserum on stress-induced corticotropin (ACTH) secretion was studied in vivo. A dose of antiserum which completely neutralized the increase in plasma OT levels during tail-hang stress caused a 59% decrease in plasma ACTH concentrations (P less than 0.005). The data support a physiologic role for OT in the regulation of ACTH secretion.

Beta-adrenergic control of atrial natriuretic factor secretion from dispersed rat atrial myocytes.

Adrenergic control of atrial natriuretic factor (ANF) secretion was studied using perifused, dispersed atrial myocytes. ANF secretion was stimulated by as little as 1 nM epinephrine (EPI) or the beta-adrenergic agonist isoproterenol (ISO). The response to EPI was completely blocked by equimolar propranolol but not by phenoxybenzamine suggesting that, at least in this system, the adrenergic control of ANF secretion is mediated by beta-adrenergic receptors.

Oxytocin inhibits ACTH and peripheral catecholamine secretion in the urethane-anesthetized rat.

Oxytocin (OT) generally has a stimulatory effect on ACTH secretion both in vitro and in vivo. As part of a study of ACTH-releasing factors in hypophysial portal blood, the effects of i.v. OT administration on plasma ACTH levels were tested in urethane-anesthetized rats. Surprisingly, i.v. injection of 10 micrograms OT lowered plasma ACTH levels by about 35% (P less than 0.01). It was reasoned that this paradoxical inhibition of ACTH secretion by OT might be mediated by inhibition of the unusually high rate of peripheral catecholamine secretion in this model. Measurement of plasma catecholamines before and after i.v. administration of 10 micrograms OT revealed a 53% inhibition of EPI (P less than 0.01) and 43% inhibition of NE (P less than 0.05). Administration of the beta-adrenergic antagonist propranolol (400 micrograms) 15 min before the beginning of the experiment completely blocked the inhibitory effects of OT on ACTH secretion and in fact unmasked the stimulatory effects of OT normally seen in conscious animals and in vitro. Superfused bisected adrenal glands exposed to 10(-6) M OT for 10 min secreted more than 30% less EPI and NE than control adrenals suggesting that the inhibition of EPI and NE secretion by OT in vivo occurs, at least in part, directly at the level of the adrenal. The data support the hypothesis that peripheral catecholamines may at times be directly involved in the control of ACTH secretion and also suggest that OT, which has recently been identified in the adrenal medulla, may have important paracrine functions in the regulation of adrenal catecholamine secretion.

An antiserum to atrial natriuretic factor (ANF) cross-reacts with neurophysins in the hypothalamo-neurohypophysial system of rat brain.

The distribution of atrial natriuretic factor (ANF)-like reactivity was examined in rat brain and heart by immunohistochemistry. Immunostaining in heart was confined to atrial myocytes. In the hypothalamus, ANF-absorbable immunoreactivity was observed in magnocellular perikarya of the paraventricular and supraoptic nuclei, and in their projections to the neural lobe of the pituitary gland. No staining was seen in the preoptic or arcuate hypothalamic nuclei or in brain stem nuclei as previously reported by other investigators. The patterns of reactivity for ANF reported here is similar to that observed for neurophysins (NPs). Comparison of sequence data between rat ANF-28 and bovine NPs revealed three regions of 3 amino acid homology between these hypothalamic peptides. Preabsorption of the ANF antiserum with Affigel-coupled bovine NP I also resulted in complete elimination of all "ANF-immunoreactivity" in both atrium and hypothalamus. Cross-reactivity of the ANF antiserum with bovine NP I and II was further confirmed by Western blot analysis. Our findings suggest that ANF antisera can cross-react with NPs if they are directed against the shared antigenic epitopes; complete elimination of staining by preabsorption of the antibody with the immunogen, therefore, does not guarantee authenticity of localization. These observations may have relevance to an earlier study which reported on the existence of ANF-immunoreactivity in oxytocin neurons of the hypothalamus.

Hypothalamic epinephrine is released into hypophysial portal blood during stress.

The hypothalamic secretion of epinephrine (EPI), norepinephrine (NE), and dopamine (DA) into hypophysial portal blood was studied in adrenalectomized rats subjected to heat stress. Portal plasma EPI levels were increased 3-fold by heat stress whereas portal plasma concentrations of NE and DA were not altered by stress. These data suggest that EPI of hypothalamic origin may be involved directly in the modulation of anterior pituitary secretion during stress.

Effect of the serotonin reuptake inhibitor fluoxetine on corticotropin-releasing factor and vasopressin secretion into hypophysial portal blood.

The relative role of corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) in mediating serotonin-induced ACTH secretion was studied using the serotonin reuptake inhibitor fluoxetine. Fluoxetine caused a significant increase in ACTH and AVP concentrations in peripheral plasma as well as a significant increase in CRF and AVP concentrations in hypophysial portal plasma. The data suggest that increased secretion of ACTH induced by fluoxetine is mediated, at least in part, by an increase in the hypothalamic secretion of both CRF and AVP.

Dissociation of oxytocin, vasopressin and corticotropin secretion during different types of stress.

Oxytocin (OT), vasopressin (AVP), and corticotropin (ACTH) levels were measured in peripheral plasma of male rats subjected to one of three models of stress: restraint, cold, or ether. ACTH secretion was increased in all three groups compared to unstressed controls. OT secretion was increased in rats subjected to restraint or ether but not cold. AVP secretion was increased only by ether stress. The data suggest that the hypothalamic and neurohypophysial contribution to the control of ACTH secretion may vary in response to different types of stress.