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Biomedical subjects

J B Long

Publications and source records attributed to J B Long.

At least 55 records · Page 3Linked to original sources
PubMed1988

Spinal subarachnoid injection of somatostatin causes neurological deficits and neuronal injury in rats.

The tetradecapeptide somatostatin produced dose-related neurological deficits following subarachnoid injection in the lumbar spinal cords of rats. Lower pharmacological doses (1.6 and 3.1 nmol, i.t.) of somatostatin caused only transient deficits, while higher doses (6.2-25 nmol, i.t.) caused persistent deficits characterized by motor and sensory impairments in hindlimbs and tail, hindlimb edema, priapism, bladder atony with infarction, and urinary incontinence. Pretreatment with 0.3 nmol of the somatostatin receptor antagonist cyclo[7-aminoheptanoyl-Phe-D-Trp-Lys-Thr(Bzl)] blocked the hindlimb paralytic effects of 3.1 and 6.2 nmol of somatostatin, and significantly improved neurological recovery injection of 12.5 nmol of somatostatin. Higher doses of the antagonist produced hindlimb paralysis by itself. Neuroanatomical evaluations revealed extensive cell loss and necrosis in the lumbosacral spinal cords of rats paralyzed by 25 nmol of somatostatin. Collectively, these results suggest that through interactions with a receptor, somatostatin destroys neurons involved in diverse spinal cord functions.

Animals↗
PubMed1988

Evaluation of naloxone therapy for Escherichia coli sepsis in the baboon.

This study evaluated the effects of naloxone hydrochloride in the treatment of Escherichia coli-induced shock in baboons. The baboons were studied for 12 hours and monitored for survival times. All baboons were intravenously infused for two hours with E coli and treated as follows: group 1, E coli (control); group 2, E coli plus naloxone hydrochloride, 0.5 mg/kg bolus plus 0.5 mg/kg/h for 9.5 hours; and group 3, E coli plus naloxone hydrochloride, 2.0 mg/kg bolus plus 2.0 mg/kg/h for 3.8 hours. Naloxone was administered after arterial pressure had reached the nadir (more than two hours following initiation of E coli infusion). Mean arterial pressure was supported by the lower dose of naloxone; however, sustained leukopenia and neutropenia were not reversed by its infusion. Naloxone prevented the increase in plasma beta-endorphin level and blunted the increase in plasma cortisol level. Despite these effects, naloxone did not prevent multiple-organ disease and did not decrease mortality.

Animals↗
PubMed1988

Chronic administration of morphine and naltrexone up-regulate[3H][D-Ala2,D-leu5]enkephalin binding sites by different mechanisms.

Previous studies have demonstrated that chronic administration of morphine up-regulated the lower affinity binding site for [3H][D-ala2,D-leu5]enkephalin, without producing a detectable alteration in the higher affinity binding site for [3H][D-ala2,D-leu5]enkephalin (Rothman et al., Eur. J. Pharmac. 124: 113-119, 1986). The experiments reported in this paper tested the hypothesis that chronic administration of morphine and naltrexone up-regulated the binding sites for [3H][D-ala2,D-leu5]enkephalin by different mechanisms. Rats were given either morphine or naltrexone chronically. Chronic administration of morphine up-regulated the lower affinity site, while chronic administration of naltrexone up-regulated both the higher and lower affinity binding sites for [3H][D-ala2,D-leu5]enkephalin. Unlike the lower affinity binding site for [3H][D-ala2,D-leu5]enkephalin present in membranes prepared from rats treated with placebo pellets, the lower affinity binding sites which were up-regulated by naltrexone and morphine were partially (naltrexone) or completely (morphine) labile to preincubation for 60 min at 25 degrees C in 50 mM Tris-HCl, pH 7.4, containing 0.4 M NaCl. These data suggest that chronic administration of morphine and naltrexone up-regulate binding sites for [3H][D-ala2,D-leu5]enkephalin through different mechanisms, and that the lower affinity binding sites for [3H][D-ala2, D-leu5]enkephalin which are up-regulated by chronic administration of morphine and naltrexone might differ biochemically from the lower affinity binding sites present in membranes treated with placebo.

Animals↗
PubMed1988

beta-FNA binds irreversibly to the opiate receptor complex: in vivo and in vitro evidence.

beta-Funaltrexamine (beta-FNA) is an alkylating derivative of naltrexone. Considerable data support its use as an irreversible mu receptor antagonist. However, pretreatment of rats with beta-FNA attenuates the ability of delta antagonists and naloxone to reverse delta receptor-mediated physiological effects, suggesting that physically adjacent mu and delta receptors interact in vivo. The purpose of this study was to determine which opiate receptor subtype is altered by i.c.v. injections of beta-FNA, as well as by in vitro incubations with beta-FNA, and then to examine the hypothesis that pretreatment of rats with beta-FNA increases the IC50 for naloxone at the altered binding site. The results demonstrate that beta-FNA alters the conformation of the opiate receptor complex, as evidenced by a decrease in the Bmax of the lower affinity [3H]D-Ala2-D-Leu5-enkephalin binding site and a doubling of the naloxone IC50 for displacing [3H]D-Ala3-D-Leu5-enkephalin from this site. [3H]D-Ala2-MePhe4,Gly-ol5-enkephalin binding sites were not detectably altered by i.c.v. injections of beta-FNA. These data collectively support the concept of coupling among opioid receptor subtypes.

Animals↗
PubMed1988

Neurological dysfunction after intrathecal injection of dynorphin A (1-13) in the rat. I. Injection procedures modify pharmacological responses.

In rats, the spinal subarachnoid injection of the kappa opioid agonist Dynorphin A (Dyn A)(1-13) and the delta opioid receptor antagonist ICI 174864 produced dose-related flaccid paralysis of hindlimbs and tail that were influenced appreciably by injection procedures. When injected through indwelling intrathecal (i.t.) catheters terminating at L1 to L2, both peptides were significantly more potent producing paralysis 1 day, rather than 10 to 14 days, after i.t. catheterization. Other rats received direct subarachnoid injections of these peptides through 30-gauge needles placed in the L4 to L5 intervertebral space. In naive, uncatheterized and acutely catheterized rats, direct intervertebral injection of these peptides, as well as D-Ala2-Dyn A (1-13) amide (a metabolically stable analog of Dyn A (1-13), produced hindlimb paralysis with potencies comparable to those recorded after injections through acutely implanted catheters. In contrast, chronically catheterized rats showed significantly reduced responsivity to direct intervertebral injections of all three of these peptides. Loss of hindlimb motor function was associated with loss of nociceptive responsiveness. Elevations in tail-flick latencies were only seen with doses of Dyn A (1-13) which produced motor dysfunction, and were not blocked or reversed by high doses of the opioid antagonist naloxone. These results indicate that: 1) indwelling i.t. catheters induce spinal cord alterations which complicate their experimental usefulness, 2) Dyn A (1-13) does not alter responsiveness to thermal nociceptive stimuli through opioid mechanism and 3) Dyn A (1-13) causes parallel disruptions of spinal cord motor and nociceptive function.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Neurological dysfunction after intrathecal injection of dynorphin A (1-13) in the rat. II. Nonopioid mechanisms mediate loss of motor, sensory and autonomic function.

The kappa opioid agonist dynorphin A (Dyn A) (1-13) produced dose-related neurological deficits after subarachnoid injection in the lumbar spinal cords of rats. Whereas the neurological dysfunctions produced by low doses of Dyn A (1-13) were transient, higher doses caused persistent deficits, characterized by motor and nociceptive impairment in hindlimbs and tail, hindlimb edema, priapism, bladder infarction and atony and urinary incontinence. These deficits appeared to result from nonopioid actions of Dyn A (1-13), as they were: 1) not blocked by the opioid antagonists naloxone or WIN 44,441-3; 2) shared by Dyn A (3-13), which lacks opioid activity; and 3) not produced or altered by the selective kappa opioid agonist U 50,488. Coinjection of a combination of peptidase inhibitors, shown previously to enhance the actions of Dyn A fragments in vitro, significantly increased the paralytic actions of Dyn A (1-13). The peptidase inhibitors did not by themselves cause neurological dysfunction, and they did not alter the paralytic potency of the peptidase-resistant delta opioid antagonist ICI 174864. These findings indicate that Dyn A effects were: 1) limited appreciably by its rapid enzymatic degradation after injection and 2) most likely the result of actions of the intact peptide rather than proteolytic products generated after injection. Neuroanatomical evaluations revealed extensive neuronal and axonal injury in the lumbosacral spinal cords of rats injected with 25 nmol of Dyn A (1-13). Collectively, these results indicate that Dyn A (1-13) acts through nonopioid mechanisms to cause the injury and death of neurons involved in diverse spinal cord functions.

Animals↗
PubMed1988

Neurologic deficits and neuronal injury in rats resulting from nonopioid actions of the delta opioid receptor antagonist ICI 174864.

The delta opioid receptor antagonist ICI 174864 produces postural abnormalities and barrel rolling after i.c.v. injection and hindlimb and tail flaccidity after spinal subarachnoid injection in rats. These effects appear to result from nonopioid characteristics of ICI 174864 because they are neither shared nor blocked by other opioid antagonists (naloxone, ICI 154129 and WIN 44,441-3) and are produced by two compounds (ICI 174644 and ICI 178173) that are structurally related to ICI 174864 but lack its delta antagonist properties. Barrel rolling and hindlimb paralysis are also produced by dynorphin A-related peptides; however, rats failed to demonstrate tolerance or cross-tolerance to the hindlimb paralytic actions of ICI 174864 or dynorphin A (1-13) after 7 days of continuous spinal intrathecal infusion of either of these compounds. Whereas hindlimb responses to low doses of ICI 174864 (1.6-6.2 nmol intrathecally) were usually transient, higher doses (6.2-25 nmol intrathecally) produced persistent hindlimb motor dysfunction, altered nociception, priapism, hindlimb edema, bladder infarction and atony and urinary incontinence. Neuronal and axonal changes in the lumbosacral spinal cords of rats with persistent and transient neurologic deficits provided direct evidence of the neuropathologic actions of ICI 174864 (3.1 and 6.2 nmol) and ICI 174644 (25 nmol). These results indicate that 1) use of ICI 174864 as a selective delta opioid receptor antagonist is potentially compromised by its nonopioid neuropathologic actions and 2) ICI 174864 and dynorphin A-related peptides are unique among opioid agonists and antagonists in sharing barrel rolling and hindlimb paralytic effects. A similar mechanism of action may underlie the shared nonopioid actions of these peptides.

Animals↗
PubMed1988

Ventral hernia following abdominal aortic reconstruction.

An unexpectedly high frequency of ventral incisional hernia in our aortic reconstruction patients prompted us to review a recent three year period. Of 76 aortic reconstruction patients, 66 were evaluable for at least one year following their aortic procedure. In these 66 patients, ventral incisional hernias occurred in 14 (21.2%). Of statistical significance (P less than .01) was that ten of the 14 hernias occurred in the 27 aneurysm patients (37%) and four occurred in the 39 occlusive disease patients (10%). Though a comparison group of aneurysm patients is not available in the literature, the incidence of hernia in our occlusive disease population is consistent with the literature experience when careful long-term follow-up is employed. These observations may represent another manifestation of previously reported differences between aortic aneurysm and occlusive atherosclerotic populations.

Aorta, Abdominal↗
PubMed1987

Intrathecal dynorphin A1-13 and dynorphin A3-13 reduce rat spinal cord blood flow by non-opioid mechanisms.

Radiolabeled microspheres were used to examine the effects of paralytic intrathecal doses of dynorphin A (Dyn A1-13) and Dyn A3-13 on rat brain and spinal cord blood flows and cardiac output. Dyn A1-13 produced significant dose-related reductions in blood flow to lumbosacral and thoracic spinal cord without altering cardiac output and blood flow to brain and cervical spinal cord. Naloxone failed to block these effects. Dyn A3-13, which lacks opioid activity, also significantly reduced blood flow in lumbosacral spinal cord. Thus, the paralytic effects of Dyn A in the rat may involve reductions in spinal cord resulting from non-opioid actions of Dyn A.

Animals↗
PubMed1987

Effects of adrenalectomy and hypophysectomy on postictal seizure protection.

Endogenous opioid systems activated by seizures appear to contribute to the postictal inhibition of subsequent seizure activity. In consideration of the possible postictal anticonvulsant actions of endogenous opioids of peripheral origin, we examined whether intact adrenal or pituitary sources of these opioids are necessary for the progressive decline in convulsion intensity and duration normally recorded during a series of 6 intermittent maximal electroshocks (MES). Adrenalectomy did not alter the progressive seizure protection associated with repeated MES. Hypophysectomy, in contrast, increased convulsion duration and abolished progressive reductions in convulsion severity. These data indicate that: adrenal secretions do not substantially contribute to postictal protective mechanisms, and endogenous opioids of pituitary origin may be involved in postictal protective mechanisms.

Adrenal Glands↗
PubMed1987

NGF effects on developing forebrain cholinergic neurons are regionally specific.

Nerve growth factor (NGF) has been shown to have an effect on neurons in the central nervous system (CNS). A number of observations suggest that NGF acts as a trophic factor for cholinergic neurons of the basal forebrain and the caudate-putamen. We sought to further characterize the CNS actions of NGF by examining its effect on choline acetyltransferase (ChAT) activity in the cell bodies and fibers of developing neurons of the septum and caudate-putamen. ChAT activity was increased after even a single NGF injection. Interestingly, the magnitude of the effect of multiple NGF injections suggested that repeated treatments may augment NGF actions on these neurons. The time-course of the response to NGF was followed after a single injection on postnatal day (PD) 2. NGF treatment produced long-lasting increases in ChAT activity in septum, hippocampus and caudate-putamen. The response in cell body regions (septum, caudate-putamen) was characterized by an initial lag period of approximately 24 hr, a rapid rise to maximum values, a plateau phase and a return to baseline. The response in hippocampus was delayed by 48 hr relative to that in septum, indicating that NGF actions on ChAT were first registered in septal cell bodies. Finally, developmental events were shown to have a regionally specific influence on the response of neurons to NGF. For though the septal response to a single NGF injection was undiminished well into the third postnatal week, little or no response was detected in caudate-putamen at that time. In highlighting the potency and regional specificity of NGF effects, these observations provide additional, support for the hypothesis that NGF is a trophic factor for CNS cholinergic neurons.

Animals↗
PubMed1987

Intracerebroventricular administration of superFIT and its enantiomer to rats: evidence for in vivo acylation of [3H]DADL binding sites.

SuperFIT is an high affinity acylating ligand derived from fentanyl. Previous studies suggested that a selective acylation of delta receptors (J. Med. Chem. 29:1087-1093, 1986) resulted from exposure of membranes to this and structurally related compounds. We report in this preliminary study that intracerebroventricular administration of either superFIT or its enantiomer 18 to 24 hours prior to sacrifice decreased the subsequent binding of [3H]DADL to both its higher and lower affinity binding sites.

Acylation↗
PubMed1986

Endogenous opioids in spinal cord injury: a critical evaluation.

Based upon evidence that opioid antagonists improve neurological outcome following either traumatic or ischemic spinal cord injury, endogenous opioids have been implicated in the pathophysiology of these disorders. Naloxone improved both spinal cord perfusion and neurological function following traumatic spinal cord injury in cats, and was subsequently observed to improve neurological outcome following ischemic spinal cord injury in rabbits. Using several opioid antagonists with varied selectivities for different types of opioid receptors, it was suggested that kappa opioid receptors are involved in both these models of spinal cord injury. In addition, spinal cord trauma in rats is associated with increased concentrations of the endogenous kappa agonist dynorphin A, and increased kappa opioid receptor binding capacity localized to the injury site. Furthermore, dynorphin A induces hindlimb and tail flaccidity following intrathecal injection in rats. Thus, the pathophysiological effects of endogenous opioids in spinal cord injury have been proposed to involve dynorphin A interactions with kappa opioid receptors. However, disparities between the actions of intrathecally injected dynorphin A in rats and the presumed actions of endogenous dynorphin A in cat and rabbit spinal cord injury have been revealed in recent experiments. Paralysis resulting from intrathecal dynorphin A is not altered by opioid receptor antagonists or TRH, produced by non-opioid dynorphin A fragments but not by other selective kappa opioid agonists, and associated with non-opioid mediated reductions in spinal cord blood flow. Furthermore, despite reports of endogenous opioid changes following rat spinal cord trauma, in contrast to cats and rabbits, naloxone failed to improve neurological outcome following traumatic rat spinal cord injury. Thus, the specific endogenous opioids and opioid receptor types involved in spinal cord injury remain to be resolved, and do not appear to be universal among different models of spinal cord injury in different species. Additionally, dynorphin A may participate in spinal cord injury mechanisms in the rat through non-opioid actions.

Animals↗
PubMed1986

Intrathecal dynorphin A (1-13) and (3-13) reduce spinal cord blood flow by non-opioid mechanisms.

Dynorphin A (Dyn A)-related peptides have been implicated in the pathophysiology of spinal cord injury in part because their intrathecal (i.t.) injection causes hindlimb paralysis. The effects of paralytic doses of i.t. Dyn A (1-13) and Dyn A (3-13) on spinal cord blood flow and cardiac output were examined in rats using radiolabeled microspheres. Both Dyn A (1-13) and Dyn A (3-13) significantly reduced blood flow in lumbosacral spinal cord without altering cardiac output. Pretreatment with naloxone failed to block these reductions in blood flow. Thus, the paralytic effects of Dyn A may result from non-opioid actions of Dyn A to reduce spinal cord perfusion.

Animals↗
PubMed1986

Effects of naloxone and thyrotropin-releasing hormone on plasma catecholamines, corticosterone, and arterial pressure in normal and endotoxemic rats.

To investigate the possible involvement of the adrenal cortex and medulla in the cardiovascular effects of naloxone and thyrotropin-releasing hormone (TRH) in endotoxic shock, plasma epinephrine, norepinephrine, dopamine, and corticosterone were measured along with hemodynamic variables during naloxone and TRH treatment of normal and endotoxemic rats. In the absence of endotoxemia, naloxone (3 mg/kg, iv) did not significantly alter mean arterial pressure or plasma catecholamine or corticosterone levels. In contrast, following TRH administration (4 mg/kg, iv), an increase in mean arterial pressure was associated with significant increases in plasma epinephrine, norepinephrine, and corticosterone. TRH also produced a transient increase in plasma glucose levels. Endotoxic shock was associated with marked increases in plasma catecholamine levels, with epinephrine levels showing the greatest change, and significant though less pronounced increases in corticosterone. Both naloxone and TRH significantly elevated mean arterial pressures of endotoxemic rats, although neither of these compounds significantly altered the plasma catecholamine and corticosterone responses to endotoxin. Naloxone and TRH also failed to alter endotoxin-induced changes in plasma glucose levels. These results indicate that the cardiovascular effects of naloxone and TRH in endotoxic shock do not simply arise from an enhancement of adrenal catecholamine or corticosterone secretion.

Animals↗
PubMed1986

Selective surgical management of perforated duodenal ulcer.

In an effort to clarify the preoperative indications and factors predisposing to an increased operative morbidity for "definitive" ulcer procedures, the medical records of 114 patients with perforated duodenal ulcers were reviewed. One hundred nine patients underwent operation, with 55 patients treated with ulcer closure (Group 1) and 54 underwent a "definitive" operation (Group 2). Thirty-two complications developed in 27 patients (25%), with major infectious complications occurring in 9 per cent and 7.5 percent in the simple ulcer closure and definitive surgery groups, respectively. This study demonstrates that preoperative shock, operation delayed greater than 48 hours, and patient age greater than 60 years were significant factors increasing morbidity. The importance of peritoneal soilage and positive cultures are unreliable in predicting subsequent clinical infection and do not contraindicate definitive surgical management.

Adolescent↗