Biomedical subjects

E A Stone

Publications and source records attributed to E A Stone.

At least 19 recordsLinked to original sources

PubMed2001

Pharmacological blockade of brain alpha1-adrenoceptors as measured by ex vivo [3H]prazosin binding is correlated with behavioral immobility.

The present studies examined the relationship between the blockade of central alpha1-adrenoceptors, as measured by ex vivo binding of [3H]prazosin in the cerebral cortex and the inhibition of behavioral activation to a mildly novel environment (cage change). It was found that intraventricular (i.v.t.) terazosin, a saline-soluble alpha1-adrenoceptor antagonist, dose dependently inhibited both ex vivo cortical binding and behavioral activation and that there was a highly significant positive correlation between the two with a slope near unity. Prazosin, a nonsaline soluble antagonist which had to be given intraperitoneally (i.p.), was much less potent at blocking both behavioral activity and cortical ex vivo binding, although it blocked ex vivo binding in the lung, indicating that it was effective peripherally but did not readily enter the brain. Despite this, however, the inhibition of cortical binding and behavioral activation that i.p. prazosin did produce were highly correlated with each other and had a slope near unity as with terazosin, whereas the more potent inhibition of lung binding was less well correlated with behavioral inhibition and had a slope significantly less than one. These results confirm our earlier studies, which have shown that alpha1-adrenoceptor activity is essential for gross and fine motor behavior in the mouse and that prazosin, which is used extensively in behavioral research, has difficulty entering the mouse brain.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed2001

Pharmacological evidence for the role of central alpha 1B-adrenoceptors in the motor activity and spontaneous movement of mice.

Central alpha 1-noradrenergic neurotransmission has been shown to be an important complement of dopaminergic transmission in the control of motor activity but the identity of the responsible alpha 1 receptor subtype has not yet been identified. This was investigated in the present experiment by measuring the effects of intraventricular administration of a series of alpha 1 antagonists varying in affinities for the three known receptor subtypes--1a, 1b and 1d--on active behavior in mice in response to a cage change. It was found that the potency of the drugs to block both gross and small movements correlated highly with published affinities for the cloned 1b receptor but not for those of either the cloned 1a or 1d receptors. It is concluded that central alpha 1B receptors are critically involved in the mediation of the (nor)adrenergic influence on active behavior, a finding which has implications for basic and clinical research in both movement and mood disorders.

Adrenergic alpha-Antagonists↗

PubMed2001

Intravenous theophylline--an alternative to temporary pacing in the management of bradycardia secondary to AV nodal block.

OBJECTIVE: To report a case of bradycardia secondary to atrioventricular nodal block (AVNB) successfully treated with intravenous theophylline. Intravenous theophylline was used as an alternative to temporary pacing in a patient with sepsis secondary to thermal injury. CASE SUMMARY: A 79-year-old white woman with significant cardiac history was admitted with 14.5% total body surface area burns after a house fire. Cardiac events included intermittent episodes of sinus bradycardia complicated by the development of second-degree AVNB and periods of sinus arrest. Intravenous theophylline initiation maintained normal sinus rhythm without further episodes of sinus bradycardia or heart block, thus preventing the need for cardiac pacemaker placement. DISCUSSION: This is the first case published in the English-language literature describing the use of intravenous theophylline as an alternative therapy to temporary pacing in a patient with sepsis secondary to thermal injury. Bradyarrhythmic events in sepsis patients have been associated with catecholamine production increasing adenosine formation. High concentrations of adenosine in the areas of the sinoatrial or atrioventricular nodal regions may induce sinus bradycardia or AVNB. Theophylline, an adenosine antagonist, has been identified as a treatment option for such bradyarrhythmic events. CONCLUSIONS: Theophylline, a methylxanthine derivative, may represent an alternative to other pharmacologic therapies and temporary pacing in the treatment of bradycardia secondary to AVNB. These agents may represent a pharmacologic alternative in patients in whom other pharmacologic strategies or cardiac pacemaker insertion may be contraindicated.

Aged↗

PubMed2000

Use of bilateral temporary nephrostomy catheters for emergency treatment of bilateral ureter transection in a cat.

A 2-year-old Himalayan cat was examined because of 4 days of vomiting, lethargy; and anorexia. The cat had undergone hysterectomy and removal of left ovarian remnants 5 days earlier. Results of laboratory testing and excretory urography were consistent with uremia and bilateral ureteral obstruction. Nephrostomy catheters were placed to drain urine and allow time for physiologic diuresis prior to definitive repair. During the next 2 days, the cat's physiologic status improved greatly. The cat underwent exploratory surgery, and both ureters were found to be ligated. The healthy proximal portions of the ureters were implanted into the bladder. Six months after surgery, the cat was doing well, and excretory urography demonstrated that both ureters were patent. Bilateral obstruction of the ureters is a life-threatening condition that can be difficult to correct in cats. Placement of nephrostomy catheters allows time for improvement in the cat's physiologic status prior to the protracted anesthesia time needed for surgical repair of the ureters.

Abdomen↗

PubMed1999

Alpha-1-noradrenergic neurotransmission, corticosterone, and behavioral depression.

BACKGROUND: Impaired brain alpha-1 noradrenergic neurotransmission has been implicated in some of the symptoms of depressive illness but has been difficult to investigate experimentally because of the insensitivity of current animal models of depression. The present experiment addressed this problem by examining the effects of pharmacologic blockade and corticosteroid-induced desensitization of alpha-1 receptors on two newer, more sensitive models in mice: the inhibition of nest-leaving and the tail suspension tests (TST). METHODS: Male mice were administered either prazosin, betaxolol, atipamezole, corticosterone, or repeated restraint stress prior to measurement of either nest-leaving or TST. General behavioral function was assessed in horizontal wire, swim, and latency to escape footshock tests. RESULTS: Prazosin increased depressive behavior in the nest-leaving and TSTs, whereas corticosterone and restraint stress did so only in the more sensitive nest-leaving test. Betaxolol also reduced nest-leaving, suggestive of an alpha-1 beta-1 receptor synergy. The effects of these agents could not be attributed to hypotension, sedation, or general behavioral impairment. CONCLUSIONS: The fact that a reduction in alpha-1 noradrenergic neurotransmission increases depressive behavior, coupled with the fact that this change can result from elevated corticosteroid secretion, provides further support for a role of this factor in depressive illness. As not all alpha-1 functions are reduced in depression, it is likely that only a subgroup or specific locality of alpha-1 receptors are affected.

Adrenergic alpha-Antagonists↗

PubMed1999

Brain alpha 1-adrenergic neurotransmission is necessary for behavioral activation to environmental change in mice.

Terazosin, a water-soluble alpha 1 antagonist that can be administered in high doses intraventricularly was used to study the relationship between brain alpha 1 adrenoceptor neurotransmission and behavioral activation in the mouse. The antagonist was found to produce a dose-dependent, complete inhibition of motor activity and catalepsy which were reversed preferentially by coinfusion of an alpha 1 agonist (phenylephrine) compared to a D1 (SKF38393) or a D2 agonist, (quinpirole). Blockade of central beta-1 (betaxolol), alpha-2 (RX821002) or beta-2 (ICI 118551) adrenoceptors had smaller or non-significant effects. Terazosin's selectivity for alpha 1 receptors versus dopaminergic receptors was verified under the present conditions by showing that the intraventricularly administered antagonist protected striatal and cerebral cortical alpha 1 receptors but not striatal or cortical D1 receptors from in vivo alkylation by N-ethoxycarbonyl-2-ethoxy-1, 2-dihydroxyquinoline. That its effect was due to blockade of brain rather than peripheral receptors was shown by the finding that intraperitoneal doses of terazosin three to 66 times greater than the maximal intraventricular dose produced less behavioral inhibition. Intraventricular terazosin also produced hypothermia and a reduced respiratory rate suggestive of a reduced sympathetic outflow. However, external heat did not affect the inactivity, and captopril, a hypotensive agent, did not mimic it. Terazosin did not impair performance on a horizontal wire test or the ability to make co-ordinated movements in a swim test suggesting that its activity-reducing effect was not due to sedation and may have a motivational or sensory gating component. It is concluded that central alpha 1-noradrenergic neurotransmission is required for behavioral activation to environmental change in the mouse and may operate on sensorimotor and motivational processes.

Adrenergic alpha-Agonists↗

PubMed1998

Diagnosis and surgical management of obstructive ureteral calculi in cats: 11 cases (1993-1996).

OBJECTIVE: To evaluate diagnostic methods, surgical treatment, perioperative management, and renal function of cats with obstructive calcium oxalate ureteroliths. DESIGN: Retrospective case series. ANIMALS: 11 cats that underwent surgery for removal of calcium oxalate ureteroliths. PROCEDURE: Medical records were reviewed, and the following information was recorded: signalment; results of physical examination, clinicopathologic analyses, and abdominal imaging; surgical procedure; postoperative management; and results of ureterolith quantitative analysis. RESULTS: Ureteroliths in the proximal portion of the ureter were removed from 5 cats (pyelotomy, 1 cat; unilateral ureterotomy, 2 cats; bilateral ureterotomies, 2 cats). Calculi in the middle and distal part of the ureter were removed by partial ureterectomy and ureteroneocystostomy (6 cats). Ten cats recovered from surgery and were discharged from the hospital. One cat died from unknown causes 4 months after surgery, and 1 cat had a nephrectomy elsewhere 5 weeks after ureterolith removal. Eight cats were evaluated 12 to 20 months after surgery. Of these, 2 cats that were markedly azotemic before surgery improved after surgery, and 2 cats developed nephroliths after surgery. Also, of 5 cats that had nephroliths that were not removed at the time of surgery, 4 still had visible nephroliths. One cat had recurrent ureteral obstruction from a ureterolith and persistent urinary tract infection. Ureteroliths or ultrasonographic evidence of ureteral obstruction were not detected in other cats. CLINICAL IMPLICATIONS: A combination of microsurgical techniques and intensive postoperative care is necessary to minimize morbidity of cats after removal of a ureterolith. Renal function may improve or stabilize after removal of the ureteral obstruction.

Animals↗

PubMed1998

Neuroanatomical patterns of Fos-like immunoreactivity induced by naltrexone in food-restricted and ad libitum fed rats.

Chronic food restriction produces a variety of adaptive changes in physiology and behavior aimed at the preservation of energy homeostasis. The brain opioid system may be involved in the adaptation to food restriction since regional levels of opioid peptides, precursor mRNA, and receptor binding have previously been observed. In the present study, c-Fos immunohistochemistry was used to localize cells that are released from opioid-mediated inhibition by naltrexone under conditions of food restriction and ad libitum feeding. In the majority of hypothalamic and forebrain areas examined, Fos-like immunoreactivity (FLI) was higher in food-restricted rats regardless of injection treatment. This may reflect the persistent stress of underfeeding or the synchronizing effect of afternoon feeding on spontaneous c-fos mRNA expression in food-restricted rats. In two brain regions, bed nucleus of the stria terminalis (BNST) and central amygdala (CEA), naltrexone increased FLI in ad libitum fed rats, exclusively. This result suggests the presence of tonic opioid secretion under basal conditions that is suppressed by food restriction. Interestingly, work in other laboratories indicates that anorectic agents consistently increase FLI in BNST and CEA. In three brain regions--lateral (LH), dorsomedial (DMH) and arcuate hypothalamus (ARC)--naltrexone increased FLI in food-restricted rats, exclusively. This result suggests the presence of opioid secretion that is unique to the state of food restriction. The hypothalamic pattern of FLI is discussed in terms of NPY-opioid interactions that result from the ARC response to changes in circulating insulin, corticosterone and leptin levels during food restriction.

Adaptation, Physiological↗

PubMed1997

Greater behavioral effects of stress in immature as compared to mature male mice.

The effect of sexual maturity on behavioral effects of stress was examined in male mice. Immature (4-week-old) or mature (8-week-old) animals were subjected to either social stress (exposure to an isolated adult male) or restraint stress for 5 days and examined for body weight, food intake, or plus-maze behavior. Social stress reduced food intake, body weight, and open-arm entries in 4-week-old but not 8-week-old mice. Restraint reduced body weight in 4-week-old but not 8-week-old mice. It is concluded that immature male mice show greater behavioral disturbances after stress than their mature counterparts. The findings are in agreement with much anecdotal evidence that children are more vulnerable to stress than adults.

Aging↗

PubMed1997

Activation of fos in mouse amygdala by local infusion of norepinephrine or atipamezole.

Norepinephrine (NE) is known to activate a number of immediate-early genes (IEGs) in the brain which may be involved in prolonged changes in neuronal function. To investigate the function of these genes it would be useful to have a model system in which they are induced in specific populations of cells in specific brain regions without systemic drug administration which can affect multiple sites. In the present paper we have shown that local infusions of NE or of the alpha2-adrenoceptor antagonist, atipamezole, in the mouse amygdala produces localized expression of fos. The expression of fos was blocked by a cocktail of an alpha1-(prazosin) and beta1-adrenoceptor (betaxolol) blocker but not by a selective 5-HT1A blocker (WAY100135). Prazosin and betaxolol did not have a nonspecific reducing action on fos expression. It is concluded that localized expression of fos after NE infusion in the mouse amygdala represents a model system for further studies of the role of IEG expression in central noradrenergic function.

Adrenergic alpha-Antagonists↗

PubMed1996

Vestibulovaginal stenosis in dogs: 18 cases (1987-1995).

OBJECTIVE: To evaluate vestibulovaginal stenosis in dogs. DESIGN: Retrospective study. ANIMALS: 18 dogs with vestibulovaginal stenosis diagnosed between January 1987 and June 1995. PROCEDURE: Signalment, results of physical examination, and diagnostic testing, treatment, and outcome were analyzed. RESULTS: Mean age at initial examination was 4.6 years. Problems reported by the owners included signs of chronic urinary tract infection (6 dogs), urinary incontinence (4), failure to mate (4), signs of chronic vaginitis (2), and inappropriate urination (1). One dog did not have evidence of a clinical problem. Vestibulovaginal stenosis was detected by means of digital vaginal examination (18/18 dogs), vaginoscopy (17/17 dogs), and positive-contrast vaginography (9/10 dogs). Bacteria were isolated from the urine of 11 of 15 dogs. Twelve of 18 dogs were treated. Manual dilation (4 dogs) and T-shaped vaginoplasty (4) were less successful than vaginectomy (2) or resection of the stenotic area (3). Four of 6 dogs with signs of recurrent urinary tract infection underwent surgical correction, and none of these dogs subsequently had urinary tract infection. Three of 4 dogs with urinary incontinence responded to medical or surgical treatment for sphincter incompetence or for ectopic ureters. CLINICAL IMPLICATIONS: Surgical correction of vestibulovaginal stenosis is indicated in dogs that have mating difficulties or signs of recurrent urinary tract infection or chronic vaginitis, but stenosis is probably an incidental finding in most dogs with urinary incontinence. Vaginectomy and vaginal resection and anastomosis are the preferred surgical options.

Anastomosis, Surgical↗

PubMed1996

Unilateral nephrectomy in dogs with renal disease: 30 cases (1985-1994).

OBJECTIVE: To evaluate indications for and complications, efficacy, and effects on renal function of unilateral nephrectomy in dogs with renal disease, and to evaluate the role that scintigraphy had in the decision to excise a kidney. DESIGN: Retrospective case series. ANIMALS: 30 dogs with renal disease that underwent unilateral nephrectomy. A comparison group of 12 dogs with renal calculi that underwent renal scintigraphy but not nephrectomy was included. RESULTS: Indications for nephrectomy included renal or ureteral calculi (n = 10), renal mass (8), chronic pyelonephritis (5), perirenal mass (3), severe hydronephrosis and hydroureter (3), and renal hypoplasia with ureteral ectopia (1). None of the dogs were azotemic before surgery. Renal scintigraphy apparently influenced the decision to perform nephrectomy, because in 14 of 16 dogs that underwent nephrectomy, the affected kidney contributed < or = 33% of the total glomerular filtration rate, but in 6 of 8 comparison dogs that underwent nephrotomy, the affected kidney contributed > 33% of total glomerular filtration rate. Complications of nephrectomy included oliguria (5) and organ laceration (2). Mean +/- SD final serum creatinine concentration for 16 dogs alive at least 6 months after nephrectomy was 2.2 +/- 1.8 mg/dl. Three dogs had chronic renal failure of undetermined cause at the time of death. Nephrectomy did not completely resolve the underlying disease in 13 dogs. Renal function was evaluated in 6 dogs 2 to 3.5 years after nephrectomy and was impaired in 4. None of the dogs were anemic, azotemic, proteinuric, or hypertensive. Survival time varied depending on the underlying disease. CLINICAL IMPLICATIONS: Multiple factors contributed to the decision to perform nephrectomy. Unilateral nephrectomy resulted in few serious complications and was not detrimental to the remaining kidney, but did not always resolve the underlying disease.

Animals↗

PubMed1996

Delayed arousal from anesthesia: a further similarity between stress and beta-1 adrenoceptor blockade.

The present studies investigated the role of beta adrenergic receptors in mediating arousal from anesthesia and the effects of stress on this process. In support of previous findings by others, it was found that blockade of beta-1 and beta-2 receptors by propranolol delayed arousal from halothane anesthesia and that this effect was attributable to blockade of beta-1 receptors because it was duplicated by betaxolol but not by ICI 118,551. Restraint stress also produced a delay in arousal from both halothane and hexobarbital anesthesia. This effect, which was observed at 0.5 but not 24 h after the stress, could not be explained by a stress-induced alteration in the metabolism of the anesthetic, as no difference in brain concentration of hexobarbital was found between stressed and control mice. The parallel effects of beta-1 blockade and stress further supports the hypothesis that stress produces an impairment in function at either the beta-1 receptor or some process coupled to this receptor.

Adrenergic beta-1 Receptor Antagonists↗

PubMed1996

The role of cerebral noradrenergic systems in the Fos response to interleukin-1.

Peripheral administration of interleukin-1 (IL-1) has been shown to activate induction of Fos in the brain, but the mechanism is not known. Because cerebral noradrenergic systems have been implicated in Fos induction, we studied the IL-1-induced appearance of Fos in mice pretreated with 6-hydroxydopamine (6-OHDA) which depleted cerebral norepinephrine (NE) by more than 90%, but did not significantly alter dopamine. Intraperitoneally injected IL-1 beta increased Fos in several brain regions, but most obviously in the hypothalamic paraventricular nucleus (PVN). Pretreatment with 6-OHDA substantially reduced the IL-1-induced Fos increase in the PVN which was no longer statistically significant. When the 6-OHDA treatment was preceded by administration of desmethylimipramine which prevents NE depletion, IL-1 treatment increased Fos in the PVN, suggesting that the effect of 6-OHDA was indeed related to the depletion of NE. These results suggest that the noradrenergic innervation of the PVN is involved in the IL-1-induced induction of Fos in the PVN. By contrast with previous experiments is rats, the IL-1-induced increase in plasma corticosterone was not significantly altered by the 6-OHDA pretreatment in mice.

Adrenergic Uptake Inhibitors↗

PubMed1996

Blockade of effect of stress on risk assessment behavior in mice by a beta-1 adrenoceptor antagonist.

Previous studies have shown that acute stress impairs risk assessment behavior in mice. The present study was undertaken to determine the role of beta adrenoceptors, which are known to be stimulated by stress, in this effect. Mice were treated with either a beta-1 antagonist, betaxolol, a beta-2 antagonist, ICI 118551, an alpha-1 antagonist, prazosin, or an alpha-2 antagonist, yohimbine, and 30 min later were subjected to a 1-h session of restraint stress. Thirty minutes after the stress the animals were tested for the entry latency, number of headpokes prior to entry, and the path of entry into a white open field from a small dark box. In agreement with previous findings, stress was found to markedly reduce risk assessment behaviors as reflected by a reduced entry latency, a reduced number of headpokes and a changed entry path from wall hugging to central entry. Betaxolol was found to prevent all of the above effects of stress dose dependently, whereas ICI 118551, prazosin, and yohimbine had no reversal effects. It is concluded that beta-1 receptor activation and possibly brain glycogen depletion is involved in the effects of stress on risk assessment behavior.

Adrenergic beta-1 Receptor Antagonists↗

PubMed1996

Partial cystectomy for urinary bladder neoplasia: surgical technique and outcome in 11 dogs.

Partial cystectomy was performed in 11 dogs with bladder neoplasia (10 with transitional cell carcinoma and one with rhabdomyosarcoma). Between 40 and 70 per cent of the bladder was excised during the partial cystectomies. In eight dogs, all the grossly visible tumour was excised but on histopathological examination of the excised tissue, neoplastic tissue was found to extend to the surgical margins in four of these dogs. A ureteral stoma was excised with the tumour in four dogs necessitating ureteral reimplantation; one dog had both ureteral stomas excised and bilateral ureteral reimplantation. The bladder incision dehisced in two dogs, necessitating a second surgery. Six dogs were pollakiuric after surgery. Pollakiuria resolved within two months in four dogs and persisted in two dogs. None was incontinent. Local tumour recurrence was suspected in nine dogs based on imaging studies and confirmed in five dogs during post mortem examination. Five dogs were euthanased two to seven months after surgery. Six dogs survived at least one year, two of these dogs remain alive at 17 and 27 months after surgery. It is concluded that partial cystectomy may provide local control of bladder neoplasia.

Animals↗

PubMed1995

Adrenoceptor antagonists block c-fos response to stress in the mouse brain.

The present study examined the role of monoaminergic systems in mediating the c-fos response to stress in the mouse brain. Mice were pretreated with various monoamine receptor antagonists prior to immobilization stress and were assayed for c-fos immunohistochemically throughout the brain. It was found that the alpha-1 adrenergic antagonist, prazosin significantly reduced the response in 10/12 telencephalic, 2/6 diencephalic and 4/5 brainstem regions and that the beta-1 adrenergic antagonist, betaxolol reduced it in 6/12 telencephalic, 1/6 diencephalic and 015 brainstem regions. The effects of these drugs were not due to nonspecific depressions of neuronal activity as several brain regions with high fos responses were unaffected. Nor were they due to sedation as the drugs did not affect rotorod performance. Neither the brta-2 adrenergic blocker, ICI118,551, the D1/D2 receptor blocker, fluphenazine, the 5HT1A antagonist, WAY 100135, nor the 5HT2 antagonist, ketanserin, produced a clear pattern of effects on the response. It is concluded that of the monoaminergic systems, the noradrenergic is the one most involved in the central fos response to immobilization stress in the mouse brain and that the response is mediated by a mixture of alpha-1 and beta-1 receptors.

Adrenergic Antagonists↗

PubMed1995

Pneumocystectomy in a Midas cichlid.

A pet Midas cichlid with a 2-year history of a distended abdomen and inadequate buoyancy control was found, radiographically, to have an abnormally large swim bladder. A recirculating anesthesic machine was constructed, and the fish was anesthetized with tricaine methanesulfonate prior to removing a portion of the swim bladder. The entire procedure lasted 71 minutes. Buoyancy problems in pet fishes are common. Causes include subcutaneous air accumulation, infectious disease of the swim bladder inner ear disease, and gastroenteritis. Reduction of the volume of the swim bladder improved this fish's ability to maintain a normal posture in the aquarium.

Air Sacs↗