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Biomedical subjects

J W Holaday

Publications and source records attributed to J W Holaday.

At least 37 records · Page 2Linked to original sources
PubMed1989

Inhibition of lymphocyte proliferation by antibodies to prolactin.

Recent in vivo studies have shown that treatments that decrease circulating prolactin (PRL) in rodents result in significant immunosuppression. Our attempts to demonstrate corresponding direct stimulatory effects of PRL on cultured lymphocytes were unsuccessful. However, antibodies against pituitary PRL potently inhibited both murine and human lymphocyte proliferation in response to both T and B cell mitogens. Further studies using IL 2 and IL 4 responsive cell lines (CTLL-2 and HT-2) demonstrated that the same anti-PRL antibodies inhibited the proliferative response to these cytokine growth factors. Thus, antibodies to PRL appear to block an event occurring in the G1 to GS phase transition of these cell lines, which constitutively express growth factor receptors. The inhibitory activity of anti-PRL antibodies could be adsorbed by addition of purified human PRL or by immobilized PRL on an affinity column. Antibodies to other pituitary hormones were without inhibitory effect on CTLL-2 cell proliferation. Proliferation of lymphocytes in serum-free medium was also potently inhibited by anti-PRL antibodies, suggesting that antibody effects were not due to neutralization of PRL or other factors contained in culture serum supplements. We suggest from these data that a protein with homology to PRL and recognized by these anti-PRL antibodies is produced by lymphocytes and plays a critical role in their progression through the cell cycle.

Animals↗
PubMed1989

Calcium administration increases the mortality of endotoxic shock in rats.

Calcium chloride is administered frequently to critically ill patients to improve cardiac output and BP. However, Ca has been implicated in the pathophysiology of shock and ischemic disorders. To test the hypothesis that Ca may be deleterious to shock outcome, we studied the effects of CaCl and Ca chelator (EGTA) infusions on mean arterial pressure (MAP) responses to endotoxin and 24-h survival in rats. Increasing ionized Ca from 4.1 +/- 0.06 to 4.9 +/- 0.20 and 8.5 +/- 0.52 mg/dl progressively increased endotoxin lethality from 20% to 37% and 80%, respectively. This occurred despite slight improvements in MAP in hypercalcemic rats. Conversely, hypocalcemia (3.6 +/- 0.08 mg/dl) lowered endotoxin-induced mortality to 0 without significant effects on MAP. Ca and EGTA infusions alone were not associated with any mortality. Although Ca administration may improve MAP, it significantly increases mortality associated with endotoxic shock in rats. Based on these observations, we advise caution when using Ca in patients with sepsis.

Animals↗
PubMed1989

Cardiovascular responses to intrathecal vasopressin in conscious and anesthesized rats.

Increases in mean arterial pressure and heart rate have been documented after the intrathecal administration of [Arg8]vasopressin (AVP) in rats. Prior studies in our laboratories with conscious rats indicated that these cardiovascular changes were associated with a marked hindlimb sensorimotor dysfunction. In this study, which represents the first systematic comparison of the effects of intrathecal AVP in conscious and anesthesized rats, we demonstrate that in conscious male Sprague-Dawley rats 1) the motor dysfunction induced by intrathecal AVP is accompanied by a rise in mean arterial pressure that is significantly greater than that produced by an equal intravenous dose of AVP, and 2) both paralytic and pressor effects of intrathecal but not intravenous AVP are blocked by the intrathecal administration of the V1-receptor antagonist d(CH2)5[Tyr(Me)2]AVP (V1-ANT) but are not blocked by intravenous phenoxybenzamine, hexamethonium, or [Sar1, Thr8]angiotensin II, an angiotensin II antagonist. In contrast, in anesthesized rats the arterial pressor response to intrathecal AVP was blocked by intrathecal V1-ANT, intravenous hexamethonium, and intravenous phenoxybenzamine. Furthermore, conscious but not anesthesized rats exhibited a tachyphylaxis to intrathecal AVP. These results indicate that intrathecal AVP produces both the cardiovascular changes and the sensorimotor deficits through interactions with centrally located V1-receptors. In addition, sympathetic catecholaminergic mechanisms mediate the rise in mean arterial pressure produced by intrathecal AVP in anesthesized rats, but they do not in conscious rats.

Animals↗
PubMed1989

Arginine8-vasopressin reduces spinal cord blood flow after spinal subarachnoid injection in rats.

Arginine8-vasopressin (AVP) causes hindlimb paralysis, loss of nociceptive responsiveness and increased arterial pressure after spinal subarachnoid injection in rats. In these experiments, the effects of paralytic intrathecal doses of AVP on rat brain and spinal cord blood flow, vascular resistance and cardiac output were measured using radiolabeled microspheres. Ten minutes after injection, AVP (10-100 pmol) elevated mean arterial pressures significantly, increased vascular resistances in thoracic and lumbosacral spinal cord and reduced blood flow to the lumbosacral spinal cord without altering cardiac output, total peripheral resistance and blood flow to brain and other spinal cord regions. Lumbosacral blood flows remained significantly reduced 30 min after injection of 100 pmol of AVP, and recovered to pretreatment base-line levels by 60 min postinjection. Lactic acid concentrations were elevated significantly in spinal cerebrospinal fluid samples removed 5 to 15 min after AVP injection (100 pmol). The selective AVP V1 receptor antagonist [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid), 2-(O-methyl)tyrosine] arg8-vasopressin, which previously blocked the effects of AVP on hindlimb motor and nociceptive function, in these experiments also blocked the AVP-induced increases in arterial pressure and reductions in lumbosacral perfusion. Intravenous infusion of the vasodilators papaverine and nifedipine failed to block AVP-induced hindlimb paralysis. Nifedipine, however, did accelerate subsequent recovery of hindlimb motor function, although it did not alter the lumbosacral blood flow reductions measured at 10 and 30 min after AVP injection. These findings indicate that AVP has significant vascular effects in the rat spinal cord that are associated with ischemia and neurological dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Cysteamine produces dose-related bidirectional immunomodulatory effects in mice.

The sulfhydryl reducing agent, cysteamine, is known to functionally inactive prolactin and other neurohormones that have been recently shown to play a role as immunomodulators. Cysteamine was administered to mice to evaluate its effects upon immune organ size and mitogen-induced lymphocyte proliferative responses in relation to corresponding effects on the immunomodulatory hormones, prolactin and corticosterone. The lowest dose of cysteamine, 12.5 mg/kg given once per day for 3 consecutive days, produced significant elevations of both concanavalin A-(Con A) and lipopolysaccharide-induced blastogenesis. Serum prolactin levels were also significantly elevated with 12.5 mg/kg cysteamine. By contrast, at 300 and 400 mg/kg, cysteamine significantly reduced Con A and lipopolysaccharide-induced proliferation. This suppression of mitogen-induced proliferative responses was accompanied by marked atrophy of the thymus. Levels of both prolactin and corticosterone in the serum were significantly reduced at 400 mg/kg cysteamine. A positive correlation was observed between serum prolactin levels and Con A-induced proliferation as well as between serum prolactin and corticosterone levels in cysteamine-treated mice. The immunomodulatory effects of cysteamine were not limited to correlative effects on neuroendocrine parameters. A similar pattern of effects was observed following in vitro administration of cysteamine. Low concentrations in vitro (0.1 mM) stimulated Con A-induced proliferation of normal mouse splenocytes, and higher concentrations in vitro (2.0 mM) suppressed proliferation. These studies indicate that, depending upon the dose, cysteamine has bidirectional effects on mitogen-induced proliferation of lymphocytes; these effects are correlated with cysteamine-related alterations in the neuroendocrine status of the animal but may also be observed with direct addition of the drug to stimulated lymphocytes in culture.

Animals↗
PubMed1988

TRH fails to antagonize the acute paralytic effects of intrathecal dynorphin A and substance P antagonists in the rat.

Thyrotropin releasing hormone (TRH), which has been shown to improve neurologic recovery following cervical contusive spinal injury in cats, has also recently been reported to prevent the neuronal damage produced by the intrathecal (i.t.) administration of the substance P antagonist, spantide. Spantide and other substance P antagonists share with dynorphin A (DYN A)-related peptides the ability to produce an acute hindlimb paralysis after i.t. administration in the rat. By virtue of this effect, DYN A has been implicated in the secondary injury mechanisms that follow spinal trauma. Since TRH was shown to reduce the degree of histopathological injury caused by i.t. spantide, we investigated the ability of TRH to prevent or ameliorate the acute hindlimb paralysis produced by the i.t. injection of the substance P antagonists, (D-Arg1,D-Trp7,9,Leu11)-substance P (spantide) and (D-Arg1,D-Pro2,D-Trp7,9,Leu11)-substance P, and DYN A in rats. In this study, TRH failed to improve motor function or survival following i.t. injections of substance P antagonists or DYN A.

Animals↗
PubMed1988

Hindlimb paralytic effects of prodynorphin-derived peptides following spinal subarachnoid injection in rats.

Dynorphin A-(1-17) acts through non-opioid mechanisms to produce dose-related neurological deficits following injection into the lumbar spinal subarachnoid space in rats. Hindlimb motor function was examined following subarachnoid injection of dynorphin A fragments and other opioid peptides derived from prodynorphin to establish: (1) which portion(s) of the dynorphin A molecule cause hindlimb motor dysfunction, and (2) whether these paralytic actions are shared by other opioids (dynorphin B, alpha-neo-endorphin, and beta-neo-endorphin) derived from the same promolecule. To minimize the influence of enzymatic inactivation on relative bioactivities, peptides were coinjected with a combination of peptidase inhibitors previously shown to enhance the actions of dynorphin A fragments in vitro. Dynorphin A-(1-17) and -(2-17) produced dose-related neurological deficits with equal potencies and durations. Although without effect when injected alone, dynorphin A-(1-8), -(1-7) and -(3-8) caused transient motor dysfunction when co-injected with peptidase inhibitors. In contrast, dynorphin A-(1-6), -(1-5) and -(6-17) did not disrupt hindlimb motor function with or without peptidase inhibition. Dynorphin B, alpha-neo-endorphin and beta-neo-endorphin also caused hindlimb dysfunction which was potentiated by peptidase inhibition. These deficits appeared to result from non-opioid actions of these three peptides, since they were not blocked by the opioid antagonist naloxone. Thus, the paralytic effects of dynorphin A: (1) result from non-opioid actions involving the 3-7 or 3-8 positions of the molecule, and (2) are shared by other prodynorphin-derived opioid peptides.

Animals↗
PubMed1988

Morphine-induced immunomodulation is not related to serum morphine concentrations.

Morphine pellets produced atrophy of the spleen and thymus and affected mitogen-induced lymphocyte proliferation in mice as characterized by marked suppression of concanavalin A-induced blastogenesis at 48 h, and mild stimulation at 120 h. Morphine blood levels in these animals indicated that changes in the immunomodulatory effects of morphine over time were not related to dramatic shifts in circulating morphine. Enclosure of the pellet in nylon mesh did not alter blood levels or morphine-induced immunomodulation.

Animals↗
PubMed1988

Suppression of macrophage activation and T-lymphocyte function in hypoprolactinemic mice.

The effects of prolactin on lactation and reproductive organs are well known. However, the other possible target organs and physiological consequences of altered levels of circulating prolactin remain poorly understood. In this study, mice were treated with bromocryptine, a dopamine receptor agonist that inhibits pituitary prolactin secretion. Bromocryptine treatment prevented T-cell-dependent induction of macrophage tumoricidal activity after the intraperitoneal injection of Listeria monocytogenes or Mycobacterium bovis. Coincident treatment with ovine prolactin reversed this effect. Of the multiple events leading to macrophage activation in vivo, the production by T-lymphocytes of gamma-interferon was the most impaired in bromocryptine-treated mice. Lymphocyte proliferation after stimulation with mitogens in vitro was also depressed in spleens of bromocryptine-treated mice, and coadministration of prolactin also reversed this effect. Bromocryptine treatment also reduced the number of deaths resulting from inoculation of mice with Listeria; exogenous prolactin significantly reversed this effect. The critical influence of pituitary prolactin release on maintenance of lymphocyte function and on lymphokine-dependent macrophage activation suggests that, in mice, lymphocytes are an important target tissue for circulating prolactin.

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

Evidence for a role of endorphins in the cardiovascular pathophysiology of primate shock.

Using the opiate receptor antagonist naloxone, we tested the hypothesis that endorphins act on opiate receptors to cause cardiovascular depression in primate shock. Mean arterial pressure (MAP), cardiac output, and left ventricular contractility (LV dP/dtmax) were measured in 34 anesthetized cynomolgus monkeys. Hemorrhagic shock was induced by bleeding into a heparinized reservoir to achieve (t = 0) and maintain MAP at 45 mm Hg. At t = 60 min, the reservoir was clamped and the animals were treated with 2 mg/kg plus 2 mg/kg.h naloxone (n = 5) or 0.9% NaCl as a control (n = 5). There were no significant differences in the cardiovascular responses to naloxone and saline when acid-base balance and core body temperature were not controlled. Pressor responses to naloxone, however, were present in proportion to arterial pH and body temperature. When these factors were controlled, naloxone (n = 6) significantly increased MAP and LV dP/dtmax by 48% and 83%, respectively, whereas saline (n = 6) had no significant effect. Blood was reinfused at t = 120 min, and survival rate at 72 h was significantly (p = .01) higher with naloxone (3/6) than saline controls (0/6). In the endotoxic shock model, cynomolgus monkeys were treated with 2 mg/kg plus 2 mg/kg.h naloxone (n = 6) or 0.9% NaCl (n = 6) when MAP reached 75 mm Hg or its nadir 60 to 90 min after Escherichia coli endotoxin, 5 mg/kg iv. Naloxone significantly increased MAP and LV dP/dtmax by 24% and 22%, respectively, whereas saline had no effect. Survival rate at 48 h was significantly (p = .01) higher with naloxone (6/6) than saline (1/6). Plasma beta-endorphin and beta-lipotropin concentrations rose three to five-fold in both shock models and were not affected by treatment. We conclude that endorphins are activated in primate shock and act on opiate receptors to contribute to the cardiovascular depression found with hemorrhage and endotoxemia.

Acidosis↗
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↗