Enzymatic reduction of chromium(VI) by human hepatic microsomes

The reduction of chromium(VI) by human hepatic microsomes was investigated. The reduction rates were proportional to the amount of microsomes added and reduction was mediated by an NADPH-dependent enzymatic system which exhibited a Km for chromate of 1.04 +/- 0.18 microM and a Vmax of 5.03 +/- 0.49 nmol/min/mg protein. Relative to incubation under 0% O2, 21% O2 inhibited microsomal Cr(VI) reduction in three individuals by 53, 36 and 37%. Cr(VI) reduction was not inhibited by metyrapone, carbon monoxide, aminopyrine, piperonyl butoxide or chloroform, suggesting that cytochrome P450s did not play a major role. Thallium trichloride (0.13 and 0.26 mM), a known flavoprotein inhibitor, caused a complete inhibition of both Cr(VI) reduction and NADPH:cytochrome P450 (c) reductase activity. A partial inhibition of Cr(VI) reduction was seen in the presence of n-octylamine, which may suggest a possible role for flavin-containing monooxygenase (FMO). Overall, human microsomal Cr(VI) reduction is very different from the P450-mediated microsomal reduction observed in rodents. Specifically, the human system is much less oxygen-sensitive, has a much greater affinity for chromate and is apparently mediated by flavoproteins.     

Effects of propofol on human hepatic microsomal cytochrome P450 activities

1. The potential of propofol to inhibit the activity of major human cytochrome P450 enzymes has been examined in vitro using human liver microsomes. Propofol produced inhibition of CYP1A2 (phenacetin O-deethylation), CYP2C9 (tolbutamide 4'-hydroxylation), CYP2D6 (dextromethorphan O-demethylation) and CYP3A4 (testosterone 6beta-hydroxylation) activities with IC50 = 40, 49, 213 and 32 microM respectively. Ki for propofol against all of these enzymes with the exception of CYP2D6, where propofol showed little inhibitory activity, was 30, 30 and 19 microM respectively for CYPs 1A2, 2C9 and 3A4. 2. Furafylline, sulphaphenazole, quinidine and ketoconazole, known selective inhibitors of CYPs 1A2, 2C9, 2D6 and 3A4 respectively, were much more potent than propofol having IC50 = 0.8, 0.5, 0.2 and 0.1 microM; furafylline and sulphaphenazole yielded Ki = 0.6 and 0.7 microM respectively. 3. The therapeutic blood concentration of propofol (20 microM; 3-4 microg/ml) together with the in vitro Ki estimates for each of the major human P450 enzymes have been used to estimate the extent of cytochrome P450 inhibition, which may be produced in vivo by propofol. This in vitro-in vivo extrapolation indicates that the degree of inhibition of CYP1A2, 2C9 and 3A4 activity which could theoretically be produced in vivo by propofol is relatively low (40-51%); this is considered unlikely to have any pronounced clinical significance. 4. Although propofol has now been used in > 190 million people since its launch in 1986, there are only single reports of possible drug interactions between propofol and either alfentanil or warfarin. Consequently, it is difficult to conclude from either the published literature or the ZENECA safety database whether there is any evidence to indicate that propofol produces clinically significant drug interactions through inhibition of cytochrome P450-related drug metabolism.     

Bleeding classification in clinical trials: observer variability and clinical relevance

To evaluate the bleeding classification in a recent trial on venous thrombosis treatment, a selection of reported bleeding episodes was adjudicated twice by an independent committee and graded by the treating physician and independent clinical experts on the clinical severity and impact on the patient's life. The kappa values for the dichotomy major bleeding versus minor or no bleeding were 0.79 (95% CI, 0.57-1.0) for the agreement between the two members of the adjudication committee and 0.77 (95% CI, 0.52-1.0) for the agreement between both adjudication sessions. The kappa values for the dichotomy major or minor bleeding versus no bleeding were 0.42 and 0.44. The weighted kappa values for the agreement between the treating physician and the independent experts were 0.76 for the clinical severity and 0.79 for the impact on the patient's life (95% CI, 0.63-0.88 and 0.70-0.89). The association between the adjudication result expressed as major bleeding or minor or no bleeding and the clinical grading by the treating physician resulted in an ROC curve with an area under the curve of 0.98 for the clinical severity and 0.99 for the impact on the patient's life. The dichotomy major or minor bleeding versus no bleeding resulted in areas under the curve of 0.70 and 0.66. In conclusion, the applied criteria for major bleeding are reproducible and clinically relevant. The criteria for minor bleeding are not reproducible and are less associated with the observed clinical relevance.     

Apoptosis: clinical relevance and pharmacological manipulation

Apoptosis, often synonymously used with the term 'programmed cell death', is an active, genetically controlled process that removes unwanted or damaged cells. Suppression, overexpression or mutation of a number of genes which orchestrate the apoptotic process are associated with disease. The diseases in which apoptosis has been implicated can be grouped into 2 broad groups: those in which there is increased cell survival (i.e. associated with inhibition of apoptosis) and those in which there is excess cell death (where apoptosis is overactive). Diseases in which there is an excessive accumulation of cells include cancer, autoimmune disorders and viral infections. Deprivation of trophic factors is known to induce apoptosis in cells dependent on them for survival. This fact has been exploited in the use of antiandrogens or antiestrogens in the management of prostate or breast cancer. Haemopoietic growth factors like granulocyte-macrophage colony stimulating factor (GM-CSF) or interleukin-3 prevent apoptosis in target cells and modulation of levels of these factors has been tried in the prevention of chemotherapy-induced myelosuppression. Until recently, it was thought that cytotoxic drugs killed target cells directly by interfering with some life-maintaining function. However, of late, it has been shown that exposure to several cytotoxic drugs with disparate mechanisms of action induces apoptosis in both malignant and normal cells. Physiological regulation of cell death is essential for the removal of potentially autoreactive lymphocytes during development and the removal of excess cells after the completion of an immune response. Recent work has clearly demonstrated that dysregulation of apoptosis may underlie the pathogenesis of autoimmune diseases by allowing abnormal autoreactive lymphocytes to survive. AIDS and neurodegenerative disorders like Alzheimer's or Parkinson's disease represent the most widely studied group of disorders where an excess of apoptosis has been implicated. Amyotrophic lateral sclerosis, retinitis pigmentosa, epilepsy and alcoholic brain damage are other neurological disorders in which apoptosis has been implicated. Apoptosis has been reported to occur in conditions characterised by ischaemia, e.g. myocardial infarction and stroke. The liver is a site where apoptosis occurs normally. This process has also been implicated in a number of liver disorders including obstructive jaundice. Hepatic damage due to toxins and drugs is also associated with apoptosis in hepatocytes. Apoptosis has also been identified as a key phenomenon in some diseases of the kidney, i.e. polycystic kidney, as well as in disorders of the pancreas like alcohol-induced pancreatitis and diabetes.     

Awakening, clinical recovery, and psychomotor effects after desflurane and propofol anesthesia

We compared postanesthetic and residual recovery of desflurane versus propofol anesthesia. Twenty volunteers were anesthetized for 1 h at 1-wk intervals with either propofol (induction) plus desflurane (1.25 minimum alveolar anesthetic concentration) in O2 (PD), propofol plus desflurane in N2O-O2 (PDN), propofol plus propofol infusion with N2O-O2 (PPN), or desflurane (induction) plus desflurane in O2 (DD). Awakening and clinical recovery were measured. Psychomotor skills (attention, coordination, reactive skills, and memory) were tested before and 1,3,5, and 7 h after anesthesia. Awakening was fastest in Group PDN. At 1 h after anesthesia, the subjects given desflurane for maintenance (PD, PDN, and DD) performed significantly (P < 0.05-0.01) better in several psychomotor tests compared with those whose anesthesia was maintained with propofol (PPN). However, subjects met criteria for home readiness as fast after PPN as after PDN anesthesia (mean times +/- SE until fitness for discharge were 126 +/- 20, 81 +/- 14, 70 +/- 7, and 106 +/- 14 min after PD, PDN, PPN, and DD, respectively). Awakening and early psychomotor recovery for as long as 1 h after anesthesia is faster after desflurane than after propofol, but there was no difference in time to home readiness or in residual effects thereafter between propofol and desflurane with N2O in O2.     

Retropsoas positioned bowel: incidence and clinical relevance

PURPOSE: Our goal was to assess the incidence of retropsoas positioned large or small bowel in the population and to examine factors predisposing to its formation. METHOD: The presence of retropsoas positioned bowel was retrospectively studied in 1,852 abdominal CT examinations of 1,055 men and 797 women, 648 younger and 1,204 older than 50 years. All examinations were considered normal or demonstrated findings that were unrelated to the position of the bowel. RESULTS: Retropsoas positioned colon (RPC) was observed in 51 (2.8%) cases for the ascending and 45 (2.3%) for the descending colon. RPC appeared more frequently in younger (< 50 years) than older patients and in individuals with decreased amount of retroperitoneal fat. Retropsoas position of small bowel loops was observed in 11 (0.6%) patients, all exhibiting paucity of retroperitoneal fat. CONCLUSION: Because of its prevalence, retropsoas positioned bowel should be considered when performing percutaneous diskectomy or other interventional procedures in the posterior retroperitoneum.     

Metabolism of psychotropic drugs: pharmacological and clinical relevance

Cytochrome P-450 (CYP) catalyzes phase I metabolic reactions of psychotropic drugs. The main isoenzymes responsible for their biotransformation are CYP1A2, CYP2D6, CYP3A4 and these of the subfamily CYP2C. The majority of metabolites of psychotropic drugs are biologically active. Some of them retain pharmacological properties of parent compounds (eg. selective serotonin reuptake inhibitors, risperidone, carbamazepine, benzodiazepines), but others display quite different (eg. amitriptyline, buspirone) or even opposite (trazodone) profiles. They are present in vivo in concentrations high enough to contribute to pharmacological and clinical effects of the administrated drugs. Active metabolites of psychotropics are also characterized by pharmacokinetic properties different from their parent compounds, e.g. half-life time, plasma protein binding, blood-brain-barrier penetration, the cerebrospinal fluid (CSF) protein binding and tissue binding. These properties lead, in turn, to differences in the brain/plasma and the CSF/plasma concentration ratios between a drug and its metabolites. Therefore studies relating a pharmacological or therapeutic response of psychotropic drug to its plasma concentrations should not disregard the presence of its active metabolites, considering their distinct pharmacological and pharmacokinetic properties. With regard to a low therapeutic index of psychotropics, interindividual differences in the rate of their metabolism, genetic polymorphism of their main metabolic pathways and metabolic interactions in clinical drug combinations, the phenotyping of patients at the beginning of therapy and a control of drug concentrations (and its active metabolites) at a steady state and during coadministration of another drug, may increase the efficiency and safety of the pharmacotherapy of psychiatric disorders.     

Hydroxyethyl starch antibodies in humans: incidence and clinical relevance

Hydroxyethyl starch (HES) is a plasma expander used for perioperative i.v. fluid management, as well as for resuscitation from trauma and shock. HES is very well tolerated, and the incidence of anaphylactic reactions is lower than with dextran or gelatin. Dextran anaphylaxis is caused by circulating dextran-reactive antibodies (ABs) of the immunoglobin G (IgG) class found in most adults. Histamine release from mast cells induces adverse reactions after gelatin infusion. The cause of adverse reactions due to HES is not yet clear. To investigate AB formation due to HES, we collected sera of 1004 patients at least 14 days after starch administration. Using a highly sensitive enzyme-linked immunoabsorbent assay technique, we found one patient with a low 1:10 titer of HES-reactive ABs (immunoglobin M [IgM] class). Despite repeated HES infusions, no clinical reaction could be detected in this patient. On the basis of a binomial distribution, a one-tailed confidence interval (99%) was used to calculate the percentage of the occurrence of ABs in general with maximum of 33 in 10,000 persons (IgM) and 23 in 10,000 persons (IgG). We suggest that HES-reactive ABs are extremely rare and that they do not necessarily induce anaphylaxis. Other mechanisms may be responsible for adverse reactions due to HES. Implications: The frequency of antibody formation due to hydroxyethyl starch, a commonly used plasma expander, was prospectively investigated in 1004 patients. Only one patient showed transient antibody formation, which was not harmful to the patient. This low antigenicity could explain the excellent tolerance of hydroxyethyl starch compared with other plasma expanders.     

Serum and tissue CEA in colorectal cancer: clinical relevance

PURPOSE: This article is an analysis of the information derived from the determination of tumor-tissue concentration of CEA in patients with colorectal cancer. To ascertain the relationship between tumor marker content with the histologic aspects and serologic levels of CEA of this neoplam. MATERIALS AND METHODS: 136 patients with colorectal adenocarcinoma and 41 with colorectal benign processes are analyzed and followed during an average time of 27 months. The CEA of the serum were obtained preoperatively and postoperatively and measured by radioimmunoassay (RIA). Tissular CEA levels were determined with RIA. The histological characteristics are analyzed (Dukes classification, grade of differentiation, index of atypia, microscopic vascular and lymphatic involvement. RESULTS: 1) The cut off point of the tissular CEA with the best sensitivity and specificity for the diagnosis of normal mucosa is 386 ng/mg and for tumoral tissue is 1160 ng/mg. 2) There is no correlation between tissue and serologic CEA value. 3) The tissular level of CEA have a significant statistical correlation with Dukes stage (p < 0.003); other histological characteristics were no significative. 4) There are significant statistical correlations between serologic CEA and relapse but no with survival rates. CONCLUSIONS: 1) Serologic CEA levels depend on numerous factors. 2) There aren't correlations between preoperative serologic levels and tissular CEA levels. 3) Tissular CEA do not predict what patients will have an elevated serologic CEA level in relapse.     

Mediators in polytrauma--pathophysiological significance and clinical relevance

Multiple trauma induces an inflammatory response syndrome of the whole body that is triggered by (a) hemorrhage inducing an ischemia/reperfusion (I/R) syndrome and (b) fractures or organ contusions inducing tissue-repair processes. I/R injury generates oxyradical/proteolytic metabolites and adhesion molecules, while tissue and endothelial injury directly stimulate complement, coagulation and kinin pathways. Membrane-derived phospholipase A2 and lipid mediators potentiate cellular interactions and increase microvascular permeability. The tissue-repair process mediates macrophage/monocyte and T-cell activation which releases pro- and anti-inflammatory cytokines. Mediator action follows a "three-level model", proposing that depending on the degree of traumatic injury cellular and humoral responses may spread from a cellular to an organ and then a systemic level. The systemic response can result in a severe immunological dys-homeostasis that potentially hazards the survival of the trauma patient by uncontrollable cellular dysfunction, appearing clinically as multiple organ-dysfunction syndrome. Blood-mediator concentrations often parallel the inflammatory process; initially, high levels of cytokines are followed by severe organ dysfunction. However, interpretation of these data remains difficult due to distinct beneficial or detrimental effects of mediators on the different levels of inflammation and missing prognostic threshold values, indicating a risk of adverse effects. Future studies must determine pro- and anti-inflammatory mediators directly, during the intensive care therapy, and evaluate their clinical relevance prospectively for the different levels of inflammation at local and systemic sites.     

Superantigens: structure and relevance to human disease

Superantigens are a class of immunostimulatory molecules produced by bacteria and viruses. Their potent immune effects are due to their unique ability to bind to the major histocompatibility complex (MHC) outside the antigen-binding cleft and to stimulate T cells in a T-cell receptor (TCR) Vbeta-specific manner. Structural studies have revealed the binding sites involved in the MHC/superantigen/TCR complex. The bacterial superantigens are responsible for a number of syndromes, including food poisoning and toxic shock syndrome, but their effects may be not only acute but also chronic and complex. Recent evidence suggests that superantigens may be relevant to the pathogenesis of autoimmune and immunodeficiency disorders. To illustrate the detrimental effects of superantigens on disease outcome, evidence demonstrating the modulation of experimental allergic encephalomyelitis, an animal model for multiple sclerosis, by superantigen, as well as the potential role of superantigens in HIV pathogenesis of AIDS, will be presented. The information presented may provide valuable insight into the role of superantigens in autoimmunity and HIV infection.     

Cardiopulmonary and anesthetic effects of propofol in wild turkeys

OBJECTIVE: To determine safety, anesthetic variables, and cardiopulmonary effects of i.v. infusion of propofol for induction and maintenance of anesthesia in wild turkeys. ANIMALS: 10 healthy, adult wild turkeys. PROCEDURE: Anesthesia was induced by i.v. administration of propofol (5 mg/kg of body weight) over 20 seconds and was maintained for 30 minutes by constant i.v. infusion of propofol at a rate of 0.5 mg/kg/min. Heart and respiratory rates, arterial blood pressures, and arterial blood gas tensions were obtained prior to propofol administration (baseline values) and again at 1, 2, 3, 4, 5, 10, 15, 20, 25, and 30 minutes after induction of anesthesia. All birds were intubated immediately after induction of anesthesia, and end-tidal CO2 concentration was determined at the same time intervals. Supplemental oxygen was not provided. RESULTS: Apnea was observed for 10 to 30 seconds after propofol administration, which induced a decrease in heart rate; however, the changes were not significant. Compared with baseline values, respiratory rate was significantly decreased at 4 minutes after administration of propofol and thereafter. Systolic, mean, and diastolic pressures decreased over the infusion period, but the changes were not significant. Mean arterial blood pressure decreased by 30% after 15 minutes of anesthesia; end-tidal CO2 concentration increased from baseline values after 30 minutes; PO2 was significantly decreased at 5 minutes after induction and thereafter; PCO2 was significantly (P < 0.05) increased after 15 minutes of anesthesia; and arterial oxygen saturation was significantly (P < 0.05) decreased at the end of anesthesia. Two male turkeys developed severe transient hypoxemia, 1 at 5 and the other at 15 minutes after induction. Time to standing after discontinuation of propofol infusion was 11 +/- 6 minutes. Recovery was smooth and unremarkable. CONCLUSION: Propofol is an effective agent for i.v. induction and maintenance of anesthesia in wild turkeys, and is useful for short procedures or where the use of inhalational agents is contraindicated.     

The clinical relevance of biomechanics

Most neurologists are familiar with biomechanics but may be unsure of the relevance of this field to their practice. Actually those involved in musculoskeletal problems are undoubtedly using biomechanical principles. This article is limited to the spine, but the basic principles of biomechanics are applicable to other parts of the body. In this article, we describe the spine and trunk as a biomechanical organ, the biomechanical principles behind back injuries and their importance, the role of biomechanical issues in pain, the utility of clinical tests based on biomechanical principles, the effects of aging, and the future directions in spine biomechanical research.     

Awakening propofol concentration with and without blood-effect site equilibration after short-term and long-term administration of propofol and fentanyl anesthesia

The stage at which breast cancer is diagnosed is an important determinant of prognosis. In contrast to the many investigations of the relationship between alcohol consumption and the risk of developing breast cancer, few have examined how alcohol consumption may affect the stage of this cancer at diagnosis. This article examines the relationship between alcohol intake and breast cancer stage and assesses consumption in relation to the volume of drinks consumed per week and the patterns of consumption 1 year prior to the breast cancer diagnosis. A total of 1191 women, aged 40 to 84 years, with newly diagnosed breast cancer were identified through the population-based Metropolitan Detroit Cancer Surveillance System, a participant of the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute. Of these, 1011 (85%) were interviewed 2 to 4 months following diagnosis. The analyses for this article were limited to 920 cases with local and regional stage disease. The bivariate analysis showed that frequent drinkers were more likely than abstainers or infrequent drinkers to present with regional disease. Logistic regression showed that frequent drinkers were 1.45 times more likely than infrequent drinkers to be diagnosed with later stage breast cancer (95% CI: 1.01-2.10; p = 05). The association between alcohol consumption and disease stage may be due to the relationship between heavy consumption and other unhealthy behaviors. In addition, women who drink more frequently may have less awareness of and access to cancer screening services. Heavy exposure to alcohol may also contribute to accelerated tumor growth once breast cancer is present.     

Alveolar epithelial fluid transport: basic mechanisms and clinical relevance

New evidence indicates that alveolar fluid clearance is driven by active sodium transport across the alveolar epithelium. Several in vivo as well as some in vitro studies indicate that vectorial sodium transport drives fluid clearance across the alveolar epithelium. This transport process can be upregulated by both catecholamine-dependent and catecholamine-independent mechanisms. Water transport appears to move across the alveolar epithelium primarily via transcellular water channels, recently termed aquaporins. Under some conditions, net alveolar fluid clearance continues even in the presence of acute lung injury. It is now possible to study the rate and mechanisms of alveolar fluid clearance in patients with either hydrostatic or increased permeability pulmonary edema. In addition, it may be possible to increase the rate of alveolar fluid clearance and hence the resolution of pulmonary edema in some patients, using aerosolized beta-adrenergic agonist therapy.     

Cardiorespiratory and anesthetic effects of propofol and thiopental in dogs

OBJECTIVE: To compare cardiorespiratory and anesthesia effects of IV administered propofol and thiopental in dogs. ANIMALS: 6 healthy mixed-breed dogs. PROCEDURE: Each dog was anesthetized with isoflurane, then a thermistor catheter was inserted in the pulmonary artery. After a minimum of 2.5 hours of recovery, a catheter was placed in a cephalic vein for administration of lactated Ringer's solution and drugs. Propofol (8 mg/kg of body weight) or thiopental (19.4 mg/kg) was administered to each dog in a randomized crossover design study. All dogs were intubated and allowed to breathe 100% oxygen spontaneously. Heart rate and rhythm; systolic, diastolic, and mean arterial blood pressures; respiratory rate; end-tidal carbon dioxide concentration; tidal volume; and reflexes (toe web pinch, palpebral response, and jaw tone) were measured before and every 2 minutes for the first 10 minutes, then at 15, 30, and 60 minutes after drug administration. Cardiac output was determined at 0, 2, 6, 10, 15, 30, and 60 minutes, and blood samples were collected at 0, 2, 10, and 30 minutes. Time to endotracheal extubation, head lift, and ability to sit sternally and walk unaided were recorded. RESULTS: 3 of 6 dogs in each group were apneic after drug administration. Reflexes were decreased similarly for both anesthetic agents, but were not completely lost. Time to sternal position and walking unaided were significantly shorter in response to propofol. CONCLUSION: Anesthesia was rapid; however, respiratory depression and apnea were major adverse effects associated with propofol and thiopental. Propofol has the advantage of inducing rapid, coordinated anesthesia recovery.     

Long-term follow-up of the clinical relevance of short outer dynein arms in human nasal cilia

A high-performance liquid chromatographic (HPLC) procedure for quantitating ketoprofen in isopropyl myristate (IPM), a compound widely used as a receptor medium in drug diffusion studies of topical aqueous-based formulations, is developed. Previously reported HPLC assays for ketoprofen in IPM have employed relatively complex and tedious methods for purifying the IPM prior to injection onto the HPLC column. The present assay method utilizes a direct injection of the IPM-based sample onto a new reversed-phase ODS column and employs ultraviolet detection at 265 nm. Propyl paraben is employed as the internal standard. The mobile phase consists of acetonitrile-methanol-water (36:54:10, v/v/v) at a flow rate of 1.2 mL/min. The calibration curves are linear (correlation coefficient r > or = 0.988) over concentration ranges of 0.625-10 micrograms/mL and 6.25-100 micrograms/mL. The within-day and between-day precision exhibit coefficients of variation of 1.3-3.3%, and the accuracy (reported as relative error of the mean) varies from -1.9% to 0.6%. The retention times for ketoprofen and propyl paraben are approximately 2.3 and 3.3 min, respectively. The total run time per sample is approximately 7 min. The minimum quantitatable concentration is approximately 0.625 microgram/mL. The assay is stability-indicating, rapid, reproducible, sensitive, and readily adaptable for assaying other non-steroidal anti-inflammatory drugs.