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Biomedical subjects

R E Brown

Publications and source records attributed to R E Brown.

At least 91 records · Page 5Linked to original sources
PubMed1997

Sympathetic and vascular effects of short-term passive smoke exposure in healthy nonsmokers.

BACKGROUND: The physiological effects of cigarette smoking have been widely studied; however, little is known about the effects of acute exposure to sidestream smoke (passive smoking). We examined the effects of sidestream smoke on muscle sympathetic nerve activity (MSNA) and forearm vascular resistance (FVR) at rest and during stressful stimuli, including the cold pressor test (CPT), sustained handgrip (SHG), and mental stress (MS). METHODS AND RESULTS: In 17 healthy nonsmokers, blood pressure (BP), heart rate (HR), forearm blood flow (venous occlusion plethysmography), FVR, and MSNA (obtained through direct intraneural recordings) were measured before and during inhalation of sidestream smoke in one session (n = 16) and before and during vehicle (air) inhalation in another session (n = 17) on a separate day. The order of sessions was randomized between subjects. Responses to CPT, SHG, and MS were measured before and after inhalation of smoke or vehicle (ie, twice during each session). After 15 minutes' exposure to sidestream smoke, plasma nicotine and carboxyhemoglobin levels increased to 0.77 +/- 0.11 ng/mL and 0.36 +/- 0.04% (mean +/- SEM, P < .05), respectively. Sidestream smoke, but not vehicle inhalation, increased resting MSNA from 23 +/- 2 to 28 +/- 2 bursts/min (P < .05). FVR increased with passive smoking, but this increase was not significantly different from the change in FVR with vehicle. Plasma norepinephrine and epinephrine, BP, and HR were not changed significantly by sidestream smoke. The responses of MSNNA, BP, HR, and FVR to the stressful stimuli were not potentiated by sidestream smoke, except for an increased BP response to the CPT (P < .05). CONCLUSIONS: Acute short-term passive (sidestream) smoke exposure elicits a modest increase in MSNA in healthy non-smokers but does not change HR, BP, or FVR.

Adult↗
PubMed1997

Inhibition of activator protein 1 activity and neoplastic transformation by aspirin.

Aspirin, along with its analgesic-antipyretic uses, is now also being considered for prevention of cardiovascular disease, cancer, and treatment of human immunodeficiency virus infection. Although many of aspirin's pharmacological actions are related to its ability to inhibit prostaglandin biosynthesis, some of its beneficial therapeutic effects are not completely understood. Transcription factor activator protein 1 (AP-1) is critical for the induction of neoplastic transformation and induction of multiple genes involved in inflammation and infection. We have used the JB6 mouse epidermal cell lines, a system that has been used extensively as an in vitro model for the study of tumor promotion and anti-tumor promotion, to study the anti-carcinogenesis effect of aspirin at the molecular level. Aspirin and aspirin-like salicylates inhibited the activation of AP-1 in the same dose range as seen for the inhibition of tumor promoter-induced transformation. The inhibition of AP-1 and tumor promoter-induced transformation in JB6 cells occurs through a prostaglandin independent- and an Erk1- or Erk2-independent pathway. The mechanism of AP-1 and transformation inhibition in this cell culture model may involve the elevation of H+ concentration. The inhibition effects on the activation of AP-1 activity by aspirin and aspirin-like salicylates may further explain the anti-carcinogenesis mechanism of action of these drugs.

Animals↗
PubMed1997

Fast increases of AMPA receptor sensitivity following tetanus-induced potentiation in the CA1 region of the rat hippocampus.

Changes in sensitivity of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) subtype of glutamate receptors following the induction of long-term potentiation (LTP) were investigated in rat hippocampal slices. AMPA was ejected into the stratum radiatum of the hippocampal CA1 region by pressure ejection and the response recorded intracellularly. Responses to AMPA exhibited a fast increase (2-3 min) following LTP induction: the time course of this increase paralleled the potentiation of the excitatory postsynaptic current (EPSC). In cases where there was no increase in the slope of intracellularly recorded EPSC following tetanization, no increase of the AMPA responses was observed. These results suggest that increases in postsynaptic AMPA sensitivity can underlie short-term potentiation (STP) and thus, support a postsynaptic locus for both STP and LTP.

Animals↗
PubMed1997

Phosphatidylcholine acyl unsaturation modulates the decrease in interfacial elasticity induced by cholesterol.

The effect of cholesterol on the interfacial elastic packing interactions of various molecular species of phosphatidylcholines (PCs) has been investigated by using a Langmuir-type film balance and analyzing the elastic area compressibility moduli (Cs(-1)) as a function of average cross-sectional molecular area. Emphasis was on the high surface pressure regions (pi > or = 30 mN/m) which are thought to mimic biomembrane conditions. Increasing levels of cholesterol generally caused the in-plane elasticity of the mixed monolayers to decrease. Yet, the magnitude of the cholesterol-induced changes was markedly dependent upon PC hydrocarbon structure. Among PC species with a saturated sn-1 chain but different sn-2 chain cis unsaturation levels [e.g., myristate (14:0), oleate (18:1delta9(c), linoleate (18:2delta9,12(c), arachidonate (20:4delta5,8,11,14(c), or docosahexenoate (22:6delta4,7,10,13,16,19(c)], the in-plane elasticity moduli of PC species with higher sn-2 unsaturation levels were less affected by high cholesterol mol fractions (e.g., >30 mol %) than were the more saturated PC species. The largest cholesterol-induced decreases in the in-plane elasticity were observed when both chains of PC were saturated (e.g., di-14:0 PC). When both acyl chains were identically unsaturated, the resulting PCs were 20-25% more elastic in the presence of cholesterol than when their sn-1 chains were long and saturated (e.g., palmitate). The mixing of cholesterol with PC was found to diminish the in-plane elasticity of the films beyond what was predicted from the additive behavior of the individual lipid components apportioned by mole and area fraction. Deviations from additivity were greatest for di-14:0 PC and were least for diarachidonoyl PC and didocosahexenoyl PC. In contrast to Cs(-1) analyses, sterol-induced area condensations were relatively unresponsive to subtle structural differences in the PCs at high surface pressures. Cs(-1) versus average area plots also indicated the presence of cholesterol concentration-dependent, low-pressure (<14 mN/m) phase boundaries that became more prominent as PC acyl chain unsaturation increased. Hence, area condensations measured at low surface pressures often do not accurately portray which lipid structural features are important in the lipid-sterol interactions that occur at high membrane-like surface pressures.

Cholesterol↗
PubMed1997

The elephant's respiratory system: adaptations to gravitational stress.

Elephants have had to adapt to gravitational stresses imposed on their very large respiratory structures. We describe some unusual features of the elephant's respiratory system and speculate on their functional significance. A distensible network of collagen fibers fills the pleural space, loosely connects lung to chest wall but appears not to constrain lung-chest wall movements. Myriad spaces within the network and its rich supply of capillaries suggest effective local sources and sinks for pleural fluid that may replace the gravity-dependent flows of smaller mammals. The lung is partitioned into approximately equal to 1 cm3 parenchymal units by a system of thick, elastic septa that ramify throughout the lung from origins on the lung's elastic external capsule. Parenchymal units suspended upon the elastic septal system protect dependent alveoli from compression, thereby reducing the usual gravitational gradient of lung expansion. Intra-pulmonary airways are devoid of cartilage, instead they appear to derive resistance to collapse from tethering forces of the attached septa.

Adaptation, Physiological↗
PubMed1997

Caudal epidural butorphanol plus bupivacaine versus bupivacaine in pediatric outpatient genitourinary procedures.

STUDY OBJECTIVE: To investigate the efficacy of adding butorphanol to bupivacaine administered in the caudal epidural space in children undergoing genitourinary (GU) procedures. DESIGN: Randomized, double-blinded, controlled study. SETTING: University affiliated pediatric hospital. PATIENTS: 200 ASA physical status I and II male patients between 6 months and 10 years of age. INTERVENTIONS: Patients were randomized to receive either 0.25% bupivacaine with 1:200,000 epinephrine alone (Group 1) or 0.25% bupivacaine with 1:200,000 epinephrine plus 30 micrograms/kg butorphanol (Group 2) administered via the caudal epidural space prior to surgical incision. MEASUREMENTS AND MAIN RESULTS: Patients were evaluated postoperatively until discharge. Measurements included requirement of additional analgesic, sedation, pain/ comfort scores, and a 24-hour analgesic follow-up. Significantly fewer patients in the butorphanol group required rescue morphine sulfate in the postanesthesia care unit (p < or = 0.001). The total number of morphine doses administered to Group 2 was significantly less than Group 1 (p < or = 0.001). 52% of patients in Group 1 compared with 28% in Group 2 required administration of additional analgesics following discharge from the hospital (p < or = 0.003), with 23% of Group 1 requiring a codeine compound compared with 8% in Group 2 (p < 0.03). CONCLUSIONS: The addition of 30 micrograms/kg butorphanol to 0.25% bupivacaine with epinephrine via the caudal epidural space is a safe, effective means to increase duration of analgesia following GU procedures.

Ambulatory Surgical Procedures↗
PubMed1997

Cost analysis of once-daily ISMN versus twice-daily ISMN or transdermal patch for nitrate prophylaxis.

OBJECTIVE: To compare the costs and outcomes of treating exercise-induced angina with once- or twice-daily isosorbide mononitrate (ISMN) or transdermal patch. METHOD: A decision-analytic model was designed based on published literature showing compliance and increasing symptoms and estimates from physicians on treatment patterns and worsening symptoms. RESULTS: Data show that patients are more compliant with once-daily ISMN (Imdur, Astra Hässle, Mölndal, Sweden) and patch regimens than with twice-daily dose. Based upon the assumption that more compliant patients are better controlled, the model found that fewer medical care resources were consumed by patients treated with the once-daily and the patch regimens. The unit cost of the twice-daily ISMN regimen is 40% of the unit cost of the once-daily. Annual costs of treating an exercise-induced angina patient are 248 pounds for Imdur compared to 250 pounds for the twice-daily ISMN and 299 pounds for the transdermal patch. CONCLUSION: Unit prices alone are not good indicators for estimating medical management costs.

Administration, Cutaneous↗
PubMed1997

Magnetic resonance imaging of severe frostbite injuries.

Frostbite injury causes damage by direct ice crystal formation at the cellular level with cellular dehydration and microvascular occlusion. Acute treatment is well defined with rapid tissue rewarming. Definitive surgical therapy is usually delayed until a clear level of demarcation is seen. Technium (Tc)-99 bone scanning has become the standard imaging study employed within the first several days to assess tissue perfusion and viability. We present 2 patients with severe frostbite injury in which magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) were compared to Tc-99 bone scans. MRI/MRA appears to be superior to bone scanning by allowing direct visualization of occluded vessels, imaging of surrounding tissues, and by showing a more clear-cut line of demarcation of ischemic tissue. MRI/MRA may also allow early intervention in cases of severe frostbite, thus preventing secondary infection and increased cost.

Adult↗
PubMed1997

Reconstruction of a sagittal band and extensor tendon centralization using a palmaris longus tendon graft.

A technique of delayed extensor tendon reconstruction and centralization using a palmaris longus tendon graft is presented. The tendon graft is woven through the base of the proximal phalanx and up and over the reconstructed extensor tendon to simulate the natural sagittal bands. As described, the technique allows gliding of the extensor tendon while maintaining its vitally important central location.

Accidents, Traffic↗
PubMed1997

The avian respiratory system: a unique model for studies of respiratory toxicosis and for monitoring air quality.

There are many distinct differences (morphologic, physiologic, and mechanical) between the bird's lung-air-sac respiratory system and the mammalian bronchoalveolar lung. In this paper, we review the physiology of the avian respiratory system with attention to those mechanisms that may lead to significantly different results, relative to those in mammals, following exposure to toxic gases and airborne particulates. We suggest that these differences can be productively exploited to further our understanding of the basic mechanisms of inhalant toxicology (gases and particulates). The large mass-specific gas uptake by the avian respiratory system, at rest and especially during exercise, could be exploited as a sensitive monitor of air quality. Birds have much to offer in our understanding of respiratory toxicology, but that expectation can only be realized by investigating, in a wide variety of avian taxa, the pathophysiologic interactions of a broad range of inhaled toxicants on the bird's unique respiratory system.

Aerosols↗
PubMed1997

Cost-effectiveness of newer antidepressants compared with tricyclic antidepressants in managed care settings.

BACKGROUND: Our aim was to determine the cost-effectiveness of newer antidepressants compared with tricyclic antidepressants in managed care organization settings. METHOD: We employed cost-utility analysis based on a clinical decision analysis model derived from published medical literature and physician judgment. The model, which represents ideal primary care practice, compares treatment with nefazodone to treatment with either imipramine or fluoxetine or to a step approach involving initial treatment with imipramine followed by nefazodone for treatment failures. The outcome measures were lifetime medical costs, quality-adjusted life years (QALYs), and costs per QALY gained. RESULTS: The base case analysis found that nefazodone treatment had $16,669 in medical costs, compared with $15,348 for imipramine, $16,061 for the imipramine step approach, and $16,998 for fluoxetine. QALYs were greatest for nefazodone (14.64), compared with 14.32 for imipramine, 14.40 for the step approach, and 14.58 for fluoxetine. The cost-effectiveness ratio comparing nefazodone with imipramine was $4065 per QALY gained. The cost-effectiveness ratio comparing nefazodone with the step approach was $2555 per QALY gained. There were only minor differences in costs and outcomes between nefazodone and fluoxetine, with nefazodone resulting in $329 fewer costs and 0.06 more QALYs. The cost-effectiveness ratios comparing fluoxetine with imipramine and with the step approach were $6346 per QALY gained and $5206 per QALY gained, respectively. In the sensitivity analyses, the cost-effectiveness ratios comparing nefazodone and imipramine ranged from $2572 to $5841 per QALY gained. The model was most sensitive to assumptions about treatment compliance rates. CONCLUSION: The findings suggest that nefazodone is a cost- effective treatment compared with imipramine or fluoxetine treatment for major depression. Fluoxetine is cost-effective compared with imipramine treatment, but is estimated to have slightly more medical costs and less effectiveness compared with nefazodone. The basic findings and conclusions do not change even after modifying key model parameters.

Antidepressive Agents↗
PubMed1996

Cannabinoid modulation of rat pup ultrasonic vocalizations.

The present study investigated the effects of the cannabinoid receptor agonist CP 55,940 (1-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl) phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol) and the cannabinoid receptor antagonist SR 141716A (N-(piperidin-l-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-me thyl-1 H-pyrazole-3-carboxamide hydrochloride) on ultrasonic vocalizations, body temperature and activity in 11-13-day-old rat pups. Testing occurred in a 5-min session 30 min following drug administration. CP 55,940 produced a dose-dependent decrease in ultrasonic vocalizations, with a 1000-micrograms/kg dose causing an almost complete inhibition of calls. Doses of 100 and 1000 micrograms/kg of CP 55,940, but not 10 micrograms/kg, caused significant hypothermia in the pups and the 1000 micrograms/kg dose also inhibited activity. The cannabinoid receptor antagonist SR 141716A (20 mg/kg) reversed the effects of 1000 micrograms/kg CP 55,940 on ultrasonic vocalizations and body temperature, but the benzodiazepine receptor antagonist flumazenil (20 mg/kg), the dopamine D1 receptor antagonist SCH 23390 (0.5 mg/kg) and the opioid receptor antagonist naloxone (1 mg/kg) did not. When administered alone, SR 141716A (20 mg/kg) increased pup ultrasonic vocalizations without affecting body temperature or activity. These results indicate that cannabinoids modulate ultrasonic vocalization production in rat pups in a manner that is independent of hypothermia. The increase in ultrasonic vocalizations produced by SR 141716A is one of the first reported behavioural effects of this drug and suggests that the endogenous cannabinoid ligand anandamide may be involved in the regulation of ultrasonic vocalizations.

Analysis of Variance↗
PubMed1996

Histamine H3 receptor-mediated depression of synaptic transmission in the dentate gyrus of the rat in vitro.

1. The effects of histamine on excitatory synaptic transmission in the dentate gyrus region of rat hippocampal slices were examined using extracellular and whole-cell patch-clamp recording techniques. The GABAA receptor antagonist picrotoxin (50 microM) was present in the bath in all experiments. 2. Histamine (0.7-70 microM) reversibly depressed field excitatory postsynaptic potentials (fEPSPs) or excitatory postsynaptic currents (EPSCs) recorded intracellularly by up to 30%. The presynaptic fibre volley and EPSC reversal potential were unaffected by histamine, as were responses following pressure ejection of the glutamate receptor agonist S-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (S-AMPA) into the slice. 3. Histamine (7 microM) depressed equally the AMPA and N-methyl-D-aspartate (NMDA) components of the dual-component EPSC, recorded at -40 mV. 4. In addition to depressing synaptic transmission, histamine also reduced the magnitude of paired-pulse depression (PPD; 40 ms interpulse interval) of the medial perforant path EPSC. 5. Histamine depressed medial perforant path EPSCs more strongly than lateral perforant path EPSCs. Paired-pulse facilitation (PPF; 40 ms interpulse interval) in the lateral perforant path was enhanced by histamine. 6. The effects of histamine on synaptic transmission and PPD were mimicked by the selective H3 receptor agonist R-alpha-methylhistamine (0.1-10 microM) but not by the selective H2 receptor agonist dimaprit (10 microM). Similarly, the H3 receptor antagonist thioperamide (10 microM) blocked the effect of histamine whereas the H1 antagonist mepyramine (1 microM) and the H2 receptor antagonist cimetidine (50 microM) were ineffective. 7. Histamine actions on synaptic transmission and PPD were not occluded by application of the metabotropic glutamate agonist L-2-amino-4-phosphonobutyrate (AP4). 8. The results indicate that histamine depresses synaptic transmission in the dentate gyrus by binding to histamine H3 receptors located on perforant path terminals. The mechanism by which histamine depresses transmission is independent of that used by class III metabotropic glutamate receptors.

Animals↗
PubMed1996

Cholesterol-induced interfacial area condensations of galactosylceramides and sphingomyelins with identical acyl chains.

The interfacial interactions occurring between cholesterol and either galactosylceramides (GalCers) or sphingomyelins (SMs) with identical acyl chains have been investigated using Langmuir film balance techniques. Included among the synthesized GalCers and SMs were species containing palmitoyl (16:0), stearoyl (18:0), oleoyl [18:1 delta 9(c)], nervonoyl [24:1 delta 15(c)], or linoleoyl [18:2 delta 9,12(c)] acyl residues. The cholesterol-induced condensations in the average molecular areas of the monolayers were determined by classic mean molecular area vs composition plots as well as by expressing the changes in terms of sphingolipid cross-sectional area reduction over the surface pressure range from 1 to 40 mN/m (at 1 mN/m intervals). The results show that, at surface pressures approximating bilayer conditions (30 mN/m), acyl heterogeneity in naturally occurring SMs (bovine of egg SM) enhanced the area condensation induced by cholesterol compared with their predominant molecular species (e.g. 18:0 SM in bovine SM; 16:0 SM in egg SM). Nonetheless, cholesterol always had a greater condensing effect on SM compared to GalCer when these sphingolipids were acyl chain matched and in similar phase states (prior to mixing with cholesterol). Also, the cholesterol-induced area changes for a given sphingolipid type (e.g. SM or GalCer) were similar whether the acyl chains were saturated, cis-delta 9-monounsaturated, or cis-delta 9,12-diunsaturated if the sphingolipids were in similar phase states (prior to mixing with cholesterol) and compared at equivalent surface pressures. These results indicate that, under conditions were hydrocarbon structure is matched, the sphingolipid head group plays a dominant role in determining the extent to which cholesterol reduces sphingolipid cross-sectional area. Despite the larger cholesterol-induced area condensations observed in SMs compared to those in GalCers, the molecular-packing densities showed that equimolar GalCer-cholesterol films were generally packed as tight as or slightly tighter than those of the SM-cholesterol films. The results are discussed in terms of a molecular model for sphingolipid-cholesterol interactions. Our findings also do only raise questions as to whether cholesterol-induced condensation data provide a reliable measure of the affinity, i.e. interaction strength, between cholesterol and different lipids but also provide insight regarding the stability of sterol/sphingolipid 1-1 rich microdomains thought to exist in caveolae and other cell membrane regions.

Animals↗
PubMed1996

Topical lidocaine for postoperative analgesia following myringotomy and tube placement.

One of the most frequently performed surgical procedures in pediatrics is myringotomy and tube placement. Analgesia is often difficult to achieve and children may be uncontrollable, distressing both parents and nursing staff. We designed this investigation to determine if topical lidocaine instilled in the ear canal after myringotomy and tube placement could improve postoperative analgesia. This prospective, randomized, double-blind clinical trial compared topical 4% lidocaine combined with antibiotic drops to placebo and antibiotic drops placed in the external auditory canal following completion of myringotomy and tube placement. One hundred twenty-two ASA class I or II patients were enrolled and completed this investigation. Primary outcome measure was relief of pain based on pain scores and the need for acetaminophen. Patients who received 4% lidocaine with gentamicin had better pain scores (2.81; P = 0.002) than those receiving placebo (4.77). Twenty-seven patients (45%) in the control group received acetaminophen for treatment of postoperative pain compared to eight (13%) in the lidocaine group (P < 0.001). No reports or complaints of vertigo or tinnitus were noted in any patient. The application of 4% lidocaine in antibiotic drops significantly improves postoperative analgesia in patients undergoing myringotomy and tube insertion under general anesthesia. Utilizing this technique should help improve analgesia, specifically in the early postoperative period, and decrease the presence of stress following surgery.

Administration, Topical↗
PubMed1996

Ondansetron decreases postoperative vomiting in pediatric patients undergoing tonsillectomy and adenoidectomy.

One of the most frequently performed pediatric surgical procedures is tonsillectomy and adenoidectomy. Nausea and vomiting and the inability to tolerate oral fluids lead to unplanned hospitalizations. Despite treatment with metoclopramide and droperidol, nausea and vomiting continue to be high after this procedure. We designed this investigation to compare currently utilized antiemetics to ondansetron, a new serotonin antagonist, in hopes of decreasing the occurrence of nausea and vomiting in patients undergoing tonsillectomy and adenoidectomy. This prospective, randomized, double-blinded clinical trial compared ondansetron, droperidol, and placebo administered at the induction of general anesthesia and the incidence of vomiting postoperatively. One-hundred sixty-five children between the ages of 2 and 12 years undergoing ambulatory adenotonsillectomy were enrolled and completed this investigation. The primary outcome measure was the elimination of vomiting during the 24-h investigative period following surgery. Both ondansetron and droperidol significantly lowered the incidence of postoperative emesis after tonsillectomy and adenoidectomy (P < 0.012) compared to placebo. Ondansetron was significantly more effective than droperidol in reducing emesis after discharge (P < 0.025). Both ondansetron and droperidol are effective in decreasing emesis when given before surgical incision in pediatric patients undergoing tonsillectomy and adenoidectomy. Ondansetron's antiemetic effect persists for up to 24 h following surgery with significant reductions in emesis. Ondansetron's effectiveness in eliminating vomiting without sedation or other side effects suggests that it should be considered as part of the standard management in pediatric patients undergoing tonsillectomy and adenoidectomy.

Adenoidectomy↗