Classification of pain following spinal cord injury

Pain continues to be a significant management problem in people with spinal cord injuries. Despite this there is little consensus regarding the nature, terminology and definitions of the various types of pain that occur following spinal cord injury. This has led to large variations in the reported incidence and prevalence of pain following spinal cord injury. Treatment studies have been hampered by inconsistent and inaccurate identification of pain types. We believe that both research and management would benefit from an agreed upon classification system which accurately and reliably identifies the types of pain that occur following spinal cord injury. We have reviewed the literature on the classification of pain following spinal cord injury and have developed a classification system which adopts the strengths of previous systems and attempts to avoid the weakness inherent in others. Our proposed classification system of pain following spinal cord injury includes four major divisions: musculoskeletal, visceral, neuropathic and other types of pain. We have divided neuropathic pain on the basis of region into two subdivisions: neuropathic at level and neuropathic below level pain. We have further divided neuropathic at level pain into two categories: radicular and central, to indicate the presumed site of the lesion responsible for pain generation. We believe that our proposed classification system is comprehensive, simple and readily applicable in the clinical and research situation. It is our hope that this proposed classification will contribute to the eventual development of a universal system for the classification of pain following spinal cord injury.

Evidence that tolerance and dependence of guinea pig myenteric neurons to opioids is a function of altered electrogenic sodium-potassium pumping

Ouabain acutely depolarizes most types of cells through inhibition of electrogenic Na+,K+ pumping and is a useful tool with which to study conditions that affect electrogenic pumping. Intracellular recording techniques were used with neurons of the guinea pig myenteric plexus/longitudinal muscle preparation exposed to ouabain. Of 35 S neurons exposed to ouabain (1 microM), 15 were hyperpolarized by 10 +/- 2 mV, 11 were depolarized by 8 +/- 2 mV and the remaining neurons had no change in membrane potential. The nonselective potassium channel antagonist tetraethylammonium chloride (TEA; 0.5 mM) alone evoked modest (<5 mV) and inconsistent changes in the resting membrane potential of S neurons. However, in the presence of TEA, the hyperpolarizing response to 1 microM ouabain was eliminated, and the proportion of cells depolarized by ouabain increased from 31% to 83%. Glibenclamide (10 microM) and 100 nM iberiotoxin did not change the pattern of membrane potential changes induced by 1 microM ouabain. Calcium-free buffer eliminated the hyperpolarization and potentiated the depolarization induced by 1 microM ouabain. Ouabain (5 microM), in either the presence or absence of TEA, induced depolarization in all neurons tested (mean, 15-16 mV), indicating a predominant effect of inhibition of electrogenic pumping. These data suggest that ouabain may directly or indirectly activate myenteric S neuron calcium-sensitive potassium channels as well as inhibit the Na+,K+ pump and that TEA will antagonize the former effect. Chronic exposure (morphine pellets) of guinea pigs to morphine resulted in a partial depolarized state of myenteric neurons, as previously reported. Ouabain (5 microM), either with or without TEA, depolarized neurons from chronically morphine-treated guinea pigs very little (5-6 mV) in comparison with naive neurons (15-16 mV). This supports the conclusion that the depolarized state of morphine-tolerant neurons is associated with a reduction in electrogenic Na+,K+ pumping.

Acute and chronic effects of adriamycin on fatty acid oxidation in isolated cardiac myocytes

This study was designed to determine if acute (in vitro) or chronic (in vivo) adriamycin inhibits cardiac fatty acid oxidation and if so at what sites in the fatty acid oxidation pathway. In addition, the role of L-carnitine in reversing or preventing this effect was examined. We determined the effects of adriamycin in the presence or absence of L-carnitine on the oxidation of the metabolic substrates [1-14C]palmitate. [1(-14)C] octanoate. [1(-14)C]butyrate, [U-14C]glucose, and [2(-14)C]pyruvate in isolated cardiac myocytes. Acute exposure to adriamycin caused a concentration- and time-dependent inhibition of carnitine palmitoyl transferase 1 (CPT 1) dependent long-chain fatty acid, palmitate, oxidation. Chronic exposure to (18 mg/kg) adriamycin inhibited palmitate oxidation 40% to a similar extent seen in vitro with 0.5 mM adriamycin. Acute or chronic administration of L-carnitine completely abolished the adriamycin-induced inhibition of palmitate oxidation. Interestingly, medium- and short-chain fatty acid oxidation, which are independent of CPT 1, were also inhibited acutely by adriamycin and could be reversed by L-carnitine. In isolated rat heart mitochondria, adriamycin significantly decreased oxidation of the CPT 1 dependent substrate palmitoyl-CoA by 50%. However, the oxidation of a non-CPT 1 dependent substrate palmitoylcarnitine was unaffected by adriamycin except at concentrations greater than 1 mM. These data suggest that after in vitro or in vivo administration, adriamycin, inhibits fatty acid oxidation in part secondary to inhibition of CPT 1 and/or depletion of its substrate, L-carnitine, in cardiac tissue. However, these findings also suggest that L-carnitine plays an additional role in fatty acid oxidation independent of CPT 1 or fatty acid chain length.

Chronic morphine treatment of guinea pigs induces nonspecific sensitivity changes in the nucleus tractus solitarius in vitro

Chronic morphine treatment results in the development of an opioid tolerance in guinea pig myenteric S-neurons that is nonspecific among pharmacologically unrelated inhibitory agonists and the concurrent development of a nonspecific super-sensitivity to unrelated excitatory agonists. The purpose of these studies was to extend this model of opioid tolerance in the guinea pig to central neurons, specifically to the medial nucleus tractus solitarius (mnTS), the primary brainstem relay for visceroceptive information. Pharmacological responses of the guinea pig mnTS neurons were examined in an in vitro brainstem slice preparation and compared between chronically morphine-treated animals and untreated controls. The spontaneous activity of guinea pig mnTS neurons was inhibited by gamma-aminobutyric acid (GABA), the GABAA-selective agonist muscimol, 2-chloroadenosine and clonidine and was excited by glutamate and elevations in extracellular potassium. Applied alone, morphine or the GABAA-selective antagonist bicuculline inhibited and excited approximately equal proportions of nucleus tractus solitarius (nTS) neurons. However, when applied in the presence of bicuculline, morphine inhibited most neurons tested. Reduced inhibitory responses to four agonists, i.e., morphine, muscimol, 2-chloroadenosine and clonidine, were observed in mnTS neurons in slices obtained from chronically morphine-treated animals. Increased excitation of these neurons by elevated extracellular potassium was observed. It is concluded that 1) guinea pig nTS neurons respond similarly to nTS neurons from other species in vitro, 2) opioids disinhibit some proportion of guinea pig nTS neurons in vitro through a GABAergic mechanism and 3) the development of opioid tolerance in guinea pig nTS neurons is qualitatively similar to that of guinea pig myenteric S-neurons.

Prophylaxis against Staphylococcus epidermidis vascular graft infection with rifampicin-soaked, gelatin-sealed Dacron

An animal model was used to assess the efficacy of rifampicin-impregnated, gelatin-sealed Dacron in the prevention of vascular graft infections caused by Staphylococcus epidermidis. Under a general anaesthetic an interposition graft was placed into sheep carotid artery. On completion of the operation 1 ml of normal saline containing 10(8) colony forming units (cfu) of a slime-producing S. epidermidis was inoculated directly onto the graft. After 3 weeks the graft was harvested. Swabs were taken of perigraft tissues, and of external and internal aspects of the graft. A 3-5-mm segment of the graft was incubated in broth medium and a second segment was ground for 5 min and incubated in broth medium. The presence of abscess formation and anastomotic disruption was assessed. Ten sheep received a gelatin-sealed Dacron graft (control), while nine received the same graft impregnated with rifampicin at a concentration of 1.2 mg/ml (treated). Eight of 10 control grafts were infected, with 30 of 50 possible cultures positive, compared with four of nine treatment grafts infected (P = 0.13) and 13 of 45 cultures positive (P = 0.004). The control group had four abscesses and two anastomotic disruptions; the treatment group had no abscesses (P = 0.05) or anastomotic disruptions (P = 0.26). Other organisms were isolated from nine of the 12 infected grafts, most commonly Staphylococcus aureus. There was no development of resistance to rifampicin. Rifampicin-impregnated, gelatin-sealed Dacron is successful at reducing the incidence of S. epidermidis vascular graft infection.

The in vivo quantification of myocardial performance in rabbits: a model for evaluation of cardiac gene therapy

Evaluating cardiac gene therapy in the intact animal requires an index of cardiac function capable of detecting regional differences in contractility in a load-independent fashion. Potentially load-insensitive measures of ventricular performance were therefore evaluated in 10 open- and closed-chested, anesthetized rabbits. LV transmural pressure and myocardial segment length were measured using micromanometry and sonomicrometry during steady-state and transient inferior vena caval occlusion, over a range of inotropic and loading conditions. For each intervention, segmental stroke work was calculated as the area within the left ventricular transmural pressure-length loops at a given end-diastolic segment length during inferior vena caval occlusion; regression analysis was applied to obtain the linear Frank-Starling relationship. In both open- and closed-chested states, these relationships were highly linear (r = 0.97 +/- 0.1) and reproducible. The slope of the linear relationship between segmental stroke work and end-diastolic segment length increased significantly with calcium and epinephrine infusions (P < 0.05 v control) but was not significantly altered by decreased afterload or increased afterload (P > 0.4). The x-intercept was not significantly altered by changes in intropy or afterload (P > 0.4). These data validate the linear Frank-Starling relationship and the slope, MW, as a load-insensitive index of contractility in the intact rabbit. This study presents a novel approach to the quantification of regional cardiac function in smaller animals.

Determination of delta 9-tetrahydrocannabinol levels in brain tissue using high-performance liquid chromatography with electrochemical detection

delta 9-Tetrahydrocannabinol (delta 9-THC) is the major psychoactive component of cannabis. To assist in investigating the mechanism(s) of action of delta 9-THC, a convenient method for determining its levels in brain tissue is required. We now describe a method for determining nanogram quantities of delta 9-THC in rat brain tissue. The method employs solvent extraction with methanol-hexane-ethyl acetate, followed by analysis using liquid chromatography with electrochemical detection. Overall recoveries were greater than 80%. The relationship between the peak-height ratio for processed standards extracted in the presence of tissue (delta 9-THC/internal standard) and the amount of delta 9-THC added was shown to be linear within the range of concentrations examined. Quantitative measurements of delta 9-THC in different brain regions following the intravenous administration of delta 9-THC are presented as examples of the applications of this method.

Cobalt-permeable non-NMDA receptors in developing chick brainstem auditory nuclei

Kainate, an agonist at non-NMDA glutamate receptors, evoked strong concentration-dependent cobalt accumulation in the chick brain stem auditory nuclei angularis, laminaris (NL) and magnocellularis (NM). This effect could be blocked completely by the AMPA/kainate receptor antagonist CNQX and the AMPA antagonist GYKI 53655 but not by antagonists of NMDA receptors or voltage-sensitive calcium channels. Kainate (30 microM) evoked cobalt uptake from embryonic day (E)9 through E21, with a peak intensity at E15. Before E13, uptake occurred mainly in NL but declined markedly in NM after E15 and ceased in NL by E21. We conclude that calcium-permeable non-NMDA receptors are transiently expressed at the time when mature neuronal number, form and synaptic connectivity are established.

The role of GABAA receptors in the subsensitivity of Purkinje neurons to GABA in genetic epilepsy prone rats

The GABA receptor subtype mediating responses of cerebellar Purkinje neurons to the neurotransmitter was evaluated and compared in GEPR-9 vs. nonepileptic, genetic control GEPR-NE rats. Quantitative analysis of responses to microiontophoretically applied GABA, muscimol and baclofen indicated that the inhibitory action of GABA on cerebellar Purkinje neurons was mediated by GABAA receptors since muscimol produced responses similar to those of GABA and baclofen was without substantial electrophysiological action. In addition, Purkinje neurons in GEPR-9 animals showed a similar reduced sensitivity to both GABA and muscimol. Radioligand binding studies using the GABAA receptor selective ligand, [3H]muscimol, and the benzodiazepine receptor selective ligand, [3H]flunitrazepam, were conducted on cerebellar and cortical homogenates from GEPR 9, GEPR-NE and Sprague-Dawley rats. No differences in the Kd or Bmax for these ligands among the three groups studied were observed. The lack of significant changes in the Kd and Bmax for these two ligands in the cerebellum suggests that the mechanism for the observed subsensitivity to GABA in the GEPR 9 rat lies beyond the level of the receptor, perhaps at the signal transduction process for GABA mediated inhibitory responses.

Overexpression of NGF within the heart of transgenic mice causes hyperinnervation, cardiac enlargement, and hyperplasia of ectopic cells

Nerve growth factor (NGF) supports the survival of developing sympathetic and a subpopulation of sensory neurons. In the adult it participates in maintenance of the neurotransmitter phenotype of responsive neurons. The amount of NGF synthesized by a given target tissue determines its final innervation density; those developing neurons that fail to receive sufficient NGF undergo apoptosis. In order to examine the ramifications of this principle in the context of a specific target organ, a transgenic mouse model was developed in which NGF expression was increased in developing and adult cardiac tissue by placing a NGF minigene under the transcriptional control of the cardiac-specific alpha-myosin heavy chain promoter. Transgenic mice developed cardiac enlargement secondary to both an increase in myocardial mass and the presence of an abundant ectopic cell population. Immunohistochemical analyses with the neural marker S-100 revealed staining of a subpopulation of ectopic cells, suggesting their derivation from the neural crest. Whereas immunostaining for the neuronal-specific protein neuron-specific enolase demonstrated labeling of another subpopulation of ectopic cells within the heart. Measurements of cardiac tissue catecholamine levels revealed a marked elevation in transgenic mice, consistent with sympathetic hyperinnervation. Analysis of mediastinal sympathetic ganglia revealed increases in both the size and the number of neurons. In this model, increased expression of NGF produced hyperinnervation of the heart, pathological cardiac growth, and the recruitment and/or expansion of an ectopic, neural crest-derived cell type.

Adaptive supersensitivity and the Na+/K+ pump in the guinea pig vas deferens: time course of the decline in the alpha 2 subunit

Adaptive supersensitivity in the guinea pig vas deferens has been shown previously to be associated with decreases in transmembrane potential, Na+/K+-ATPase activity, [3H]ouabain binding sites, and density of the alpha 2 subunit of the pump. One of several procedures that induce adaptive supersensitivity in the guinea pig vas deferens is neurotransmitter depletion by chronic administration of reserpine. Guinea pigs were treated with reserpine (1.0 mg/kg/day, intraperitoneally) for 2, 5, or 8 days. Tissues were homogenized and the concentration of the alpha 2 subunit was quantified by use of the selective antibody McB2, slot blot analysis, enhanced chemiluminescence, and densitometric analysis. As reported previously, the concentration of the alpha 2 protein was reduced 41% after 5 days of pretreatment. The reduction was maintained at 8 days (37%). However, there was no change from control after 2 days of pretreatment with reserpine. Thus, the time course of the decline in the alpha 2 subunit is similar to that of the appearance of supersensitivity, depolarization, and the declines in Na+/K+-ATPase and [3H]ouabain binding established earlier. Based upon results in the literature for several different tissues and species, membrane depolarization and decreases in Na+/K+ pump sites may represent widely occurring adaptive mechanisms.

Sustained hypertension in Dahl rats. Negative correlation of agonist response to blood pressure

The perfused mesenteric vasculature of Dahl salt-sensitive rats on a high salt diet for 5 days (prehypertensive or early hypertensive) is selectively supersensitive to norepinephrine. The present goal was to determine whether that supersensitivity was maintained as hypertension developed. Littermates of salt-sensitive and salt-resistant rats (Dahl Brookhaven strain) were followed on low or high salt for up to 6 weeks. Systolic blood pressure was elevated in the salt-sensitive, high salt rats after 3 or 6 weeks but not after 5 days of the diet. The perfused mesenteric vascular beds from salt-sensitive rats were supersensitive to norepinephrine and nerve stimulation but not to potassium chloride when the rats had been maintained for 5 days or 3 weeks on the high salt diet. However, responses to norepinephrine declined after 6 weeks of the high salt diet. To determine whether sustained high blood pressure has a negative effect on mesenteric vascular responses, we conducted additional experiments with perfused mesenteric vascular beds from salt-sensitive Brookhaven (high salt, 5 weeks) and Rapp (high salt, 6 weeks) animals. Both groups exhibited significant negative correlations between in vivo systolic pressure and maximal responses of mesenteric vessels to norepinephrine and potassium chloride. We suggest that sustained hypertension in Dahl rats has a negative effect on the contractility of the mesenteric arterial system that, by 5 to 6 weeks, masks the initial supersensitivity to norepinephrine. No effects of any diet on the dilating responses of the mesenteric vessels to acetylcholine were observed in any group.

Molecular cloning and characterization of a novel transglutaminase cDNA from a human prostate cDNA library

The primary sequence of a cDNA encoding a novel transglutaminase from a human prostate cDNA library is reported. The sequence is compared to other known transglutaminases in a multiple alignment. The deduced peptide sequence is 51% identical to a rat prostate transglutaminase.

Functional distribution and role of alpha-1 adrenoceptor subtypes in the mesenteric vasculature of the rat

Because alpha-1 adrenoceptor subtypes are distributed differentially in different arteries, experiments were conducted to determine the functional contribution of these subtypes in conduit vs. resistance vessels. Concentration- or dose-response curves for norepinephrine were obtained from aortic rings, superior mesenteric artery rings or the isolated perfused mesenteric vasculature from male Sprague-Dawley rats. Frequency-response curves to transmural electrical stimulation were obtained from the latter two preparations. The effects of 5-methylurapidil (5-MU), an alpha-1a adrenoceptor antagonist, and chloroethyl-clonidine (CEC), an alpha-1b adrenoceptor antagonist, on contractile responses were determined. In artery rings, 5-MU (30 nM) had no effect on the EC50 of norepinephrine but reduced the maximum response of the mesenteric artery rings by nearly 25%. In the perfused mesenteric vasculature, however, 5-MU (30 nM) shifted the ED50 for norepinephrine about 40-fold while reducing the maximum response by 30%. 5-MU depressed the frequency-response curve in the perfused mesenteric vasculature by nearly 80%, but did not alter the response of artery rings. In aorta, pretreatment with CEC (10 microM) shifted the concentration-response curve of norepinephrine by 800-fold without effecting the maximum. In mesenteric artery rings and perfused mesenteric vasculature, CEC reduced the slope and maximum response of both frequency-response and norepinephrine dose-response curves. Responses to norepinephrine (10 microM) in the perfused mesentery were abolished by 5-MU and reduced only 25% by nifedipine. These data suggest that the density or role of alpha-1a adrenoceptors may be greater in resistance vessels than in conduit vessels.

Voluntary oral morphine self-administration in rats: effect of haloperidol or ondansetron

Rats were exposed to increasing concentrations of morphine hydrochloride (up to 0.4 mg/ml) in 5% w/v sucrose solution as their sole source of drinking water. Physical dependence was established as determined by the precipitation of withdrawal behaviour following administration of 1 mg/kg IP naloxone hydrochloride on day 23. The choice between either a 5% w/v sucrose solution or a 5% w/v sucrose solution containing 0.4 mg/ml morphine hydrochloride 4 days following withdrawal resulted in rats being categorized into two groups based on their respective consumption of the morphine-containing solution. The amount of morphine solution voluntarily consumed by approximately half the rats were sufficiently high as to lead to a relapse into physical dependence to morphine. The high preference for morphine shown by these rats could not be attributed to the taste of the morphine solution. Naive rats or rats exposed to a 5% w/v sucrose solution for 23 days failed to consume significant quantities of the morphine-containing solution when provided with a choice. The administration of either an IM slow-release formulation of 70.5 mg/kg haloperidol decanoate (= 50 mg/kg haloperidol) or 10 micrograms/kg IP ondansetron hydrochloride daily did not alter morphine ingestion in the high morphine-preferring rats.

Dietary fish oil administration retards blood pressure development and influences vascular properties in the spontaneously hypertensive rat (SHR) but not in the stroke prone-spontaneously hypertensive rat (SHR-SP)

In the present study, we compared the blood pressure in the SHR-SP and in the spontaneously hypertensive rat (SHR) after dietary administration of fish oil from 4 to 17 weeks of age. The retarding influence of dietary fish oils on the development of hypertension was prominent in the SHR (26 mmHg) and not evident in the SHR-SP (8 mmHg). The enhanced development of blood pressure in both the SHR and the SHR-SP is characterised by an elevated maximum contraction in the mesenteric vascular bed to sympathetic nerve stimulation and to injected noradrenaline. In SHR, but not SHR-SP, this maximum contraction was significantly attenuated by dietary fish oil. Likewise, acetylcholine mediated relaxation of the isolated aorta was enhanced in preparations from the SHR but not the SHR-SP. These physiological changes were also associated with a change in the total n-3 polyunsaturated fatty acids (PUFAs) content in vascular tissue, which were inversely proportional to the prevailing blood pressure values seen in all three strains of rat receiving dietary fish oils. Platelet activated thromboxane production was equally depressed in WKY (Wistar Kyoto), SHR and SHR-SP rats. The results indicate that the blood pressure lowering effect of fish oil when administered during the period of development of hypertension is much greater in the SHR than it is in the SHR-SP. Furthermore the lowering of blood pressure by fish oil administration is related to a restoration of normal vascular contraction and normal vascular relaxation, but not related to a suppression of serum thromboxane production.

Functional ontogeny of pulmonary vascular DA1 dopamine receptors in the isolated perfused rabbit lung

Using an in situ isolated salt-perfused rabbit lung preparation, we investigated the functional ontogeny of pulmonary vascular dopamine receptors. In rabbits from 1 to 23 d of age, we measured pulmonary vascular vasodilatory responses to the peripheral vascular dopamine receptor (DA1) agonist, fenoldopam, and sodium nitroprusside during prostaglandin F2 alpha-induced pulmonary vasoconstriction. In separate experiments, the lungs were pretreated with the DA1 receptor blocker, SCH 23390, before prostaglandin F2 alpha, fenoldopam, and sodium nitroprusside. Lungs from rabbits at one of 6 age groups (n = 6-8 per group) were ventilated and perfused. After a stabilization period, prostaglandin F2 alpha was infused into the pulmonary inflow catheter in a concentration range to yield a sustained rise in mean pulmonary artery pressure (4.9 +/- 0.2 mm Hg). Fenoldopam was injected into the pulmonary artery at doses of 0.01, 0.1, 1.0, and 10 micrograms/g after a recovery period, sodium nitroprusside (0.2 micrograms/g) was injected into the pulmonary artery, and the resultant changes in vascular pressure were recorded. Across all age groups, with and without DA1 receptor blockade, sodium nitroprusside-induced vasodilation was similar (-2.7 +/- 0.2 mm Hg) and was considered reference vasodilation. The fenoldopam vasodilation response was considered a percentage of the sodium nitroprusside reference. Response to fenoldopam varied significantly (p < 0.05 by analysis of variance) across the six age groups, with a maximum at 3-5 d of age. Pretreatment with SCH 23390, a selective DA1-blocking agent, significantly attenuated fenoldopam vasodilation in all but the youngest animals (age 0-2 d), in which no blockade effect was noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Coma in the pediatric patient: evaluation and management

Coma in the pediatric patient is a medical emergency and must be dealt with in a rapid, organized way. Basic life support needs, evaluation of history, and physical examination are all of paramount importance and evaluation of these three critical areas must proceed simultaneously. Specific diagnoses must be treated appropriately, but there are key general principals to coma management that must be dealt with sequentially. The outcome in childhood coma is substantially better than adult coma, and in many cases is determined by speed and appropriateness of intervention.

Identification of a nonendothelial cell thromboxane-like constrictor response and its interaction with the renin-angiotensin system in the aorta of spontaneously hypertensive rats

Aortic ring preparations from spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKY) rats were treated with N omega-nitro-L-arginine (NOLA, 10(-4) M). This produced a sustained contraction in preparations from SHR but not WKY rats. A similar contraction in aortic ring preparations from the SHR was produced with methylene blue (10(-5) M) and NG-monomethyl-L-arginine (10(-5) M). The NOLA-induced contraction was reversed with indomethacin (8 x 10(-6) M), ridogrel (10(-5) M) and SQ 29548 (10(-6) M) thus confirming the involvement of thromboxane A2/prostaglandin H2 processes. Subsequent experiments demonstrated that the thromboxane-like contraction was not dependent upon the presence of endothelial cells and occurred in preparations from young, prehypertensive (5 week) and older (17 week) SHRs. The thromboxane-like contraction was markedly suppressed with chronic captopril treatment and reinstated 4 weeks after withdrawal from captopril. The addition of saralasin (10(-6) M) or captopril (10(-6) M) to aortic ring preparations did not suppress the thromboxane-like contractions. The foregoing findings support the presence of a nonendothelial cell thromboxane-like constrictor agent in the aorta of the SHR that is revealed after impairment of nitric oxide production. The activity of the thromboxane-like constrictor process is not tightly linked to prevailing blood pressure, but is reduced with chronic in vivo inhibition of the angiotensin-converting enzyme.

Aneurysm of the membranous ventricular septum producing subpulmonic outflow tract obstruction

The authors report the case of a 31-year-old asymptomatic male who, following investigations for cardiac murmur, was found to have congenitally corrected (status solitus of the atria, left looping of the ventricles, leftward aorta in relation to the pulmonary artery [S,L,L]) transposition of the great vessels with significant right-sided ventricular outflow tract obstruction due to a large aneurysm of the membranous ventricular septum. Diagnosis was made with transesophageal echocardiography and confirmed during corrective surgery. The authors review the literature with regard to aneurysms of the membranous ventricular septum and their association with congenital heart disease, and they discuss the use of noninvasive tests aiding the diagnosis.

Ion-pair extraction and liquid chromatographic analysis of morphine in rat brain and plasma

A highly efficient and reproducible two-step liquid-liquid ion-pair extraction technique for the isolation of morphine from biological samples is described. A rapid normal phase high-performance liquid chromatographic procedure coupled with amperometric electrochemical detection has also been developed for subsequent quantification of morphine. Extraction involves the disruption of brain tissue or plasma in methanol, centrifugation, evaporation and reconstitution in ethyl acetate containing 10 mM di-(2-ethylhexyl) phosphoric acid, a liquid cation-exchanger, and back-extraction into 170 mM orthophosphoric acid. An acidic eluent consisting of acetonitrile-76 mM orthophosphoric acid-ammonia buffer (pH 3.0) (15:85, v/v) in combination with a strong cation-exchange column allows complete separation of morphine and the internal standard, nalbuphine. The limit of detection for morphine is 1.3 ng on-column.

Rising tumour marker during chemotherapy in a patient with an extra-gonadal germ cell tumour--prolonged survival after tumour excision

A 28-year-old white male presented with a palpable abdominal mass and a grossly elevated beta human chorionic gonadotrophin. He refused investigations to establish the pathology and was treated with cisplatin combination chemotherapy. After an initial fall in his marker, it rose while he was on chemotherapy. The tumour was resected which confirmed the presence of a retroperitoneal germ cell tumour (extra-gonadal). He received further adjuvant chemotherapy and is subsequently clear of disease after being off treatment for more than 5 years. Total resection is not usually considered possible in patients with persistent positive markers after induction chemotherapy. This case shows that surgery should be considered as the results of salvage chemotherapy are poor in these patients.

E1A-mediated inhibition of myogenesis correlates with a direct physical interaction of E1A12S and basic helix-loop-helix proteins

The observation that adenovirus E1A gene products can inhibit differentiation of skeletal myocytes suggested that E1A may interfere with the activity of myogenic basic helix-loop-helix (bHLH) transcription factors. We have examined the ability of E1A to mediate repression of the muscle-specific creatine kinase (MCK) gene. Both the E1A12S and E1A13S products repressed MCK transcription in a concentration-dependent fashion. In contrast, amino-terminal deletion mutants (d2-36 and d15-35) of E1A12S were defective for repression. E1A12S also repressed expression of a promoter containing a multimer of the MCK high-affinity E box (the consensus site for myogenic bHLH protein binding) that was dependent, in C3H10T1/2 cells, on coexpression of a myogenin bHLH-VP16 fusion protein. A series of coprecipitation experiments with glutathione S-transferase fusion and in vitro-translated proteins demonstrated that E1A12S, but not amino-terminal E1A deletion mutants, could bind to full-length myogenin and E12 and to deletion mutants of myogenin and E12 that spare the bHLH domains. Thus, the bHLH domains of myogenin and E12, and the high-affinity E box, are targets for E1A-mediated repression of the MCK enhancer, and domains of E1A required for repression of muscle-specific gene transcription also mediate binding to bHLH proteins. We conclude that E1A mediates repression of muscle-specific gene transcription through its amino-terminal domain and propose that this may involve a direct physical interaction between E1A and the bHLH region of myogenic determination proteins.

Adaptive supersensitivity in the guinea pig vas deferens is associated with a reduction in the abundance of the alpha 2 subunit isoform of Na+/K(+)-ATPase

Adaptive supersensitivity has been demonstrated previously in the guinea pig vas deferens after chronic treatment with reserpine, postganglionic denervation, or preganglionic denervation. The magnitude of the change in sensitivity was similar regardless of the method of induction; the underlying mechanism was identified as a partial depolarization secondary to reduced activity of the Na+/K+ pump. Experiments were conducted to quantitatively determine whether the identified losses in Na+/K(+)-ATPase activity and [3H]ouabain binding were due to reductions in the levels of specific protein subunits of the sodium pump. Electrophoretic separation and quantification of the abundance of alpha subunit isoforms were accomplished using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and slot blot analysis. Supersensitivity was induced in the guinea pig vas deferens through pretreatment with reserpine (1.0 mg/kg/day x 5 days). The abundance of the alpha 2 subunit isoform was reduced by 41% in tissue homogenates obtained from animals treated with reserpine, compared with untreated controls. In contrast, there was no significant alteration in the alpha 1 subunit isoform (a protein similar in size to that previously identified in vascular smooth muscle as a "truncated" form of the protein). These data suggest that the adaptation of the guinea pig vas deferens after a chronic reduction in net stimulus is mediated through a change in a specific cellular protein. This evidence supports the assignment of the alpha 2 subunit isoform as the specific protein responsible for the development of nonspecific adaptive supersensitivity in the guinea pig vas deferens.