Apoptosis and cell proliferation in rat hepatocytes induced by barbiturates.
(73/1949)
To examine the effect on cell population in hepatocytes of phenobarbital (PB) and other barbiturates, PB, allobarbital (ALB), barbital sodium (BS) and barbituric acid (BA) were given orally to male rats for 7 consecutive days. Although there was no apparent change in non-promoting BA, hepatomegaly was induced by PB, BS and ALB, which are promoters of hepatocarcinogenesis. In PB- and BS-treated livers, hepatomegaly was attributable to hepatocyte proliferation and enzyme induction. In ALB-treated liver, it was attributable to enzyme induction. The level of cell proliferation was reduced to less than the control values following withdrawal of PB, ALB and BS. It seemed that the degree of suppression of cell proliferation following withdrawal of these compounds correlated to the degree of cell proliferation (PB>BS>ALB) during treatment. In PB-treated liver, apoptosis was induced during treatment, serving to eliminate the excess of hepatocytes. This suggests that short-term administration of PB neither induced suppression of apoptosis nor disturbed homeostasis of hepatocyte populations. (+info)
Comparative cardiopulmonary effects of carfentanil-xylazine and medetomidine-ketamine used for immobilization of mule deer and mule deer/white-tailed deer hybrids.
(74/1949)
Three mule deer and 4 mule deer/white-tailed deer hybrids were immobilized in a crossover study with carfentanil (10 microg/kg) + xylazine (0.3 mg/kg) (CX), and medetomidine (100 microg/kg) + ketamine (2.5 mg/kg) (MK). The deer were maintained in left lateral recumbency for 1 h with each combination. Deer were immobilized with MK in 230+/-68 s (mean +/- SD) and with CX in 282+/-83 seconds. Systolic, mean and diastolic arterial pressure were significantly higher with MK. Heart rate, PaO2, PaCO2, pH, and base excess were not significantly different between treatments. Base excess and pH increased significantly over time with both treatments. Both treatments produced hypoventilation (PaCO2 > 50 mm Hg) and hypoxemia (PaO2 < 60 mm Hg). PaO2 increased significantly over time with CX. Body temperature was significantly (P<0.05) higher with CX compared to MK. Ventricular premature contractions, atrial premature contractions, and a junctional escape rhythm were noted during CX immobilization. No arrhythmias were noted during MK immobilization. Quality of immobilization was superior with MK, with no observed movement present for the 60 min of immobilization. Movement of the head and limbs occurred in 4 animals immobilized with CX. The major complication observed with both of these treatments was hypoxemia, and supplemental inspired oxygen is recommended during immobilization. Hyperthermia can further complicate immobilization with CX, reinforcing the need for supplemental oxygen. (+info)
D(2), but not D(1) dopamine receptor agonists potentiate cannabinoid-induced sedation in nonhuman primates.
(75/1949)
In primates, CB(1) cannabinoid receptor agonists produce sedation and psychomotor slowing, in contrast to behavioral stimulation produced by high doses of dopamine receptor agonists. To investigate whether dopamine agonists attenuate the sedative effects of a cannabinoid agonist in monkeys, we compared the effects of D(1) or D(2) dopamine receptor agonists on spontaneous behavior in three to six cynomolgus monkeys (Macaca fasicularis) alone and after administration of a low dose of the CB(1) agonist levonantradol. Alone, the CB(1) cannabinoid receptor agonist levonantradol (0.01-0. 3 mg/kg) induced sedation, ptosis, and decreased locomotor and general activity. Alone, D(2)-type dopamine agonists quinelorane (0. 001-1.0 mg/kg; n = 4) or pergolide (0.01-1.0 mg/kg) or a D(1) dopamine agonist 6-chloro-7,8-dihydroxy-1-phenyl-2,3,4, 5-tetrahydro-3-allyl-[1H]-3-benzazepine (0.3-3.0 mg/kg) produced either no effect or promoted hyperactivity. Thirty minutes after administration of a threshold dose of levonantradol (0.03 mg/kg), D(2)-type agonists, but not the D(1) agonist, precipitated marked sedation, ptosis, and decreased general activity and locomotor activity. These data inducate the following: 1) D(2,) but not D(1) dopamine agonists, potentiate sedation in monkeys treated with a CB(1) cannabinoid agonist, at doses of agonists that alone do not produce sedation; 2) the threshold dose for cannabinoid-induced sedation is reduced by D(2) agonists, but not by a D(1) dopamine agonist, differentiating D(1) and D(2) dopamine receptor linkage to cannabinoid receptors; and 3) modulation of D(2) dopamine receptor activity by a nonsedating dose of a cannabinoid agonist has implications for the pathophysiology and treatment of dopamine-related neuropsychiatric disorders and drug addiction. Cannabinoid agonists and D(2) dopamine agonists should be combined with caution. (+info)
Quantitative prediction of metabolic inhibition of midazolam by erythromycin, diltiazem, and verapamil in rats: implication of concentrative uptake of inhibitors into liver.
(76/1949)
To evaluate the degree of drug-drug interaction concerning metabolic inhibition in the liver quantitatively, we tried to predict the plasma concentration increasing ratio (R) of midazolam (MDZ) by erythromycin (EM), diltiazem (DLZ), or verapamil (VER) in rats. MDZ was administered through the portal vein at the steady state of plasma concentration of these inhibitors. The R values in the area under the plasma concentration curve of MDZ in the presence of EM, DLZ, and VER were 2.02, 1.64, and 1.30, respectively. The liver to plasma unbound concentration ratios of EM, DLZ, and VER at the steady state after infusion were 20.8, 1.02, and 3.01, respectively, suggesting concentrative uptake of EM and VER into the liver. The predicted R value in the presence of EM calculated by use of plasma unbound concentration was 1.03, whereas the value calculated with liver unbound concentration was 1.61, which was very close to the observed value. These findings indicated the need to consider the concentrative uptake of inhibitors into the liver for the quantitative prediction of metabolic inhibition. However, the predicted values in the presence of DLZ or VER calculated by use of liver unbound concentration were still underestimated. This result may be due to the metabolic inhibition by the metabolites of both inhibitors. Therefore, when predicting the degree of metabolic inhibition quantitatively, the inhibitory effect by coadministered drugs and the disposition of these metabolites in the liver must also be considered. (+info)
The metabolism of clomethiazole in gerbils and the neuroprotective and sedative activity of the metabolites.
(77/1949)
A single dose of clomethiazole (600 micromol kg(-1) i.p.) has previously been shown to be neuroprotective in the gerbil model of global ischaemia. In gerbils, clomethiazole (600 micromol kg(-1)) injection produced a rapid appearance (peak within 5 min) of drug in plasma and brain and similar clearance (plasma t(1/2): 40 min) from both tissues. The peak brain concentration (226+/-56 nmol g(-1)) was 40% higher than plasma. One major metabolite, 5-(1-hydroxyethyl-2-chloro)-4-methylthiazole (NLA-715) and two minor metabolites 5-(1-hydroxyethyl)-4-methylthiazole (NLA-272) and 5-acetyl-4-methylthiazole (NLA-511) were detected in plasma and brain. Evidence suggested that clomethiazole is metabolized directly to both NLA-715 and NLA-272. Injection of NLA-715, NLA-272 or NLA-511 (each at 600 micromol kg(-1)) produced brain concentrations respectively 2.2, 38 and 92 times greater than seen after clomethiazole (600 micromol kg(-1)). Clomethiazole (600 micromol kg(-1)) injected 60 min after a 5 min bilateral carotid artery occlusion in gerbils attenuated the ischaemia-induced degeneration of the hippocampus by approximately 70%. The metabolites were not neuroprotective at this dose. In mice, clomethiazole (600 micromol kg(-1)) produced peak plasma and brain concentrations approximately 100% higher than in gerbils, drug concentrations in several brain regions were similar but 35% higher than plasma. Clomethiazole (ED(50): 180 micromol kg(-1)) and NLA-715 (ED(50): 240 micromol kg(-1)) inhibited spontaneous locomotor activity. The other metabolites were not sedative (ED(50) >600 micromol kg(-1)). These data suggest that the neuroprotective action of clomethiazole results from an action of the parent compound and that NLA-715 contributes to the sedative activity of the drug. British Journal of Pharmacology (2000) 129, 95 - 100 (+info)
Sedation and analgesia.
(78/1949)
Sedation is a process of soothing. The concept of the ideal level of sedation is controversial and has changed over the last decade. A shift from deep sedation, often enhanced by muscle relaxants that completely detaches the patient from their environment, to light sedation rendering the patient sleepy but easily arousable has been widely accepted. This change in attitude has been brought about by sophisticated modes of ventilation allowing the ventilator to synchronize with the patient's own breathing pattern. In addition, the increasingly recognised adverse effects of over-sedation have contributed to the reduction in the depth of sedation. (+info)
Physiological role of gap-junctional hemichannels. Extracellular calcium-dependent isosmotic volume regulation.
(79/1949)
Hemichannels in the overlapping regions of apposing cells plasma membranes join to form gap junctions and provide an intercellular communication pathway. Hemichannels are also present in the nonjunctional regions of individual cells and their activity is gated by several agents, including calcium. However, their physiological roles are unknown. Using techniques of atomic force microscopy (AFM), fluorescent dye uptake assay, and laser confocal immunofluorescence imaging, we have examined the extracellular calcium-dependent modulation of cell volume. In response to a change in the extracellular physiological calcium concentration (1.8 to +info)
Sedation for intractable distress of a dying patient: acute palliative care and the principle of double effect.
(80/1949)
Shortly before his death in 1995, Kenneth B. Schwartz, a cancer patient at Massachusetts General Hospital (MGH), founded the Kenneth B. Schwartz Center at MGH. The Schwartz Center is a nonprofit organization dedicated to supporting and advancing compassionate health care delivery, which provides hope to the patient, support to caregivers, and encourages the healing process. The Center sponsors the Schwartz Center Rounds, a monthly multidisciplinary forum where caregivers reflect on important psychosocial issues faced by patients, their families, and their caregivers, and gain insight and support from fellow staff members. The case presented is of a young man dying of recurrent epithelioid hemangioendothelioma, distressed with stridor and severe pain, whose poorly controlled symptoms were successfully treated with an infusion of propofol, titrated to provide effective comfort in the last few hours of the patient's life. The tenet of double effect, which allows aggressive treatment of suffering in spite of foreseeable but unintended consequences, is reviewed. The patient's parents were invited and contributed to the Rounds, providing compelling testimony to the power of the presence of clinicians at the time of death and the importance of open communication about difficult ethical issues. (+info)