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PubMed2002

Seasonal variation in lysogeny as depicted by prophage induction in Tampa Bay, Florida.

A seasonal study of the distribution of lysogenic bacteria in Tampa Bay, Florida, was conducted over a 13-month period. Biweekly water samples were collected and either were left unaltered or had the viral population reduced by filtration (pore size, 0.2 micro m) and resuspension in filtered (pore size, 0.2 micro m) water. Virus-reduced and unaltered samples were then treated by adding mitomycin C (0.5 micro g ml(-1)) to induce prophage or were left untreated. In order to test the hypothesis that prophage induction was phosphate limited, additional induction experiments were performed in the presence and absence of phosphate. Induction was assessed as an increase in viral direct counts, relative to those obtained in controls, as detected by epifluorescence microscopy. Induction of prophage was observed in 5 of 25 (20%) unaltered samples which were obtained during or after the month of February, paralleling the results from a previous seasonal study. Induction of prophage was observed in 9 of 25 (36%) of the virus-reduced samples, primarily those obtained in the winter months, which was not observed in a prior seasonal study (P. K. Cochran and J. H. Paul, Appl. Environ. Microbiol. 64:2308-2312, 1998). Induction was noted in the months of lowest bacterial and primary production, suggesting that lysogeny was favored under conditions of poor host growth. Phosphate addition enabled prophage induction in two of nine (22%) experiments. These results indicate that prophage induction may occasionally be phosphate limited or respond to increases in phosphate concentration, suggesting that phosphate concentration may modulate the lysogenic response of natural populations.

Bacteria↗

PubMed1990

Disparate mechanisms of induction of procoagulant activity by live and inactivated bacteria and viruses.

This study describes the dose response, time course, and lymphocyte requirements of procoagulant activity (PCA) induction following stimulation of thioglycolate-elicited BALB/c peritoneal macrophages with live and inactivated bacteria (Bacteroides fragilis, Escherichia coli, and Staphylococcus aureus) and murine hepatitis virus type 3 (MHV-3). Induction of PCA by MHV-3 was significantly more rapid and the maximal PCA achieved was significantly greater than by the three bacterial species studied. In relation to induction of PCA by bacteria, the PCA response was more rapid and of greater magnitude with S. aureus and E. coli than with B. fragilis. MHV-3 induced an augmented PCA response at all concentrations of virus studied in a dose-dependent fashion, whereas higher titers of live bacteria (greater than 10(7) CFU/ml) inhibited PCA, suggesting the production of an inhibitory factor. Significant PCA induction was observed when macrophages were incubated with bacteria or virus in the absence of lymphocytes. At low titers of B. fragilis (10(3) CFU/ml), addition of lymphocytes greatly augmented PCA production, whereas at higher titers (10(7) CFU/ml), the addition of lymphocytes only slightly augmented the PCA response. In contrast, MHV-3 induction of PCA was enhanced by the addition of lymphocytes at all concentrations of virus studied, suggesting a lymphocyte-dependent process. Heat-inactivated bacteria were as effective as live bacteria in inducing PCA, suggesting that induction of PCA by bacteria requires only a bacterial surface component. In contrast, UV-inactivated MHV-3 did not induce PCA, suggesting that viral replication is a necessary step in PCA induction. These results suggest that the cellular and metabolic requirements for induction of PCA differ among viral and bacterial pathogens and may partly explain their differences in pathogenicity.

Animals↗

PubMed1979

Developmental induction of Myxococcus xanthus myxospores.

Myxospore differentiation during the developmental cycle of Myxococcus xanthus is characterized by several distinguishable morphological stages. Two experimentally useful criteria of myxospore induction are the conversion of vegetative rods to optically refractile short rods or ovoids and the development of resistance to sonic lysis. The use of optical refractility as the first morphological criterion of myxospore induction has facilitated an analysis of induction on developmental plates. The time-dependent changes in the cell population from vegetative rods to the final products of development, autolysed cells and myxospores, were determined in liquid suspension by interrupting cells from developmental plates before the first appearance of myxospores. The treatment of cells involved a two-step induction system. The cells were first aerated in buffer at 32 degrees C (preinduction) and then aerated in 1% tryptone (Difco) at 32 degrees C (induction). At early plate times (0 to 18 h) there was little or no response to these treatments. After 18 h, many of the cells undergoing development on plates responded to preinduction in buffer by subsequent induction to myxospores in tryptone medium (intermediate cells). After 32 h, cells induced to myxospores in tryptone medium and did not require preinduction (competent cells). After 36 h, cells begin to undergo differentiation to myxospores on plates. These results indicate that there was a sequence of physiological changes in developing cells that are defined by the differential response of cells to treatment in liquid suspension. The liquid induction system described here provides a means to analyze the regulation of developmental myxospore induction.

Kinetics↗

PubMed1979

Suppression of tif-mediated induction of SOS functions in Escherichia coli by an altered dnaB protein.

The tif-1 mutation in the Escherichia coli recA gene is known to cause induction of the various "SOS" functions at high temperature, including massive synthesis of the recA protein, lethal filamentation, elevated mutagenesis, and, in lambda lysogens, induction of prophage. It is shown here that the deoxyribonucleic acid initiation mutation dnaB252 suppresses all these manifestations of tif expression. Induction of lambda by ultraviolet irradiation, however, is not affected by the dnaB252 mutation. No similar suppression of tif is observed with other dnaB mutations affecting deoxyribonucleic acid elongation or with other deoxyribonucleic acid initiation mutations at the dnaA and dnaC loci. The fact that an alteration of the dnaB protein specifically suppresses tif-mediated SOS induction implies a role of the replication apparatus in this process, as has been suggested for ultraviolet induction. The induction of lambda is known to proceed via repressor cleavage, presumably promoted by an activated (protease) form of the recA protein. Since lambda induction is normal after ultraviolet irradiation of the tif-1 dnaB252(lambda) strain, tif-mediated induction in this strain may be blocked in a tif-specific step leading to activation of the recA (tif) protein. It is possible that the recA (tif) mutant protein may be directly involved in the replication complex in processes leading to this activation.

Bacterial Proteins↗

PubMed1996

Characterization of the ZI domains in the Epstein-Barr virus BZLF1 gene promoter: role in phorbol ester induction.

Induction of the Epstein-Barr virus lytic cycle is mediated through the immediate-early BZLF1 gene and the coordinately regulated BRLF1 gene. The BZLF1 gene product, Zta, transactivates its own promoter, as well as the promoters of a number of lytic genes, thereby initiating a cascade of viral gene expression. Previous work identified four related elements (ZIA, ZIB, ZIC, and ZID) and a cyclic AMP response element binding-AP-1 element (ZII) that are involved in the induction of the BZLF1 promoter (Zp) by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) (E. Flemington and S. H. Speck, J. Virol. 64:1217-1226, 1990). Here we report a detailed characterization of TPA induction mediated by the ZI domains. Mutation of individual ZI domains within the context of the intact promoter significantly diminished TPA induction. Cloning of individual ZI domains upstream of a minimal promoter demonstrated that the ZIA, ZIC, and ZID domains, but not the ZIB domain, are TPA responsive. Furthermore, cloning of the ZII domain downstream of the ZI domains significantly augmented TPA induction. The critical regions within the ZIA and ZIC elements involved in binding of cellular factors were identified by using methylation interference and electrophoretic mobility shift analyses of ZI domain mutants. Four specific complexes were observed with the ZIA and ZID domains, all of which could be specifically competed for by either the ZIA or ZID domain. Methylation interference analyses of bound complexes revealed the presence of two overlapping binding sites for cellular factors in the ZIA domain, and functional studies provided evidence that both of these sites are involved in TPA induction. Functional analyses of the ZIC domain revealed that the 5' region of this domain is largely responsible for mediating TPA induction. Binding data correlated well with functional activity and revealed that the ZIC domain binds only a subset of the cellular factors that bind to the ZIA and ZID domains. Analysis of factor binding to the ZIB domain revealed only a single shifted complex, which correlated with the most slowly migrating complex observed with the ZIA and ZID domains. These data provide a direct demonstration of TPA induction mediated by the ZIA, ZIC, and ZID domains and also provide the first evidence that the ZI domains exhibit distinct functional characteristics.

Base Sequence↗

PubMed1993

A branched signaling pathway for nerve growth factor is revealed by Src-, Ras-, and Raf-mediated gene inductions.

A myriad of gene induction events underlie nerve growth factor (NGF)-induced differentiation of PC12 cells. To dissect the signal transduction pathways which lead to NGF actions, we have assessed the relative roles of NGF receptor, Src, Ras, and Raf activities in mediating specific gene inductions. We have used the PC12 cell line as well as sublines which inducibly express activated forms of either Src, Ras, or Raf or a dominant inhibitory form of Ras (p21N17 Ras) to study the expression of multiple NGF-inducible mRNAs. The NGF induction of NGFI-A, transin, and VGF mRNAs was mimicked by activated forms of Src, Ras, or Raf and was blocked by p21N17 Ras. The NGF induction of SCG10 mRNA was mimicked only by activated Src and Ras and was blocked by p21N17 Ras, while the induction of Thy-1 mRNA was mimicked only by activated Src and was not blocked by p21N17 Ras. The NGF induction of mRNAs for two sodium channel types was neither mimicked by any activated oncoprotein nor blocked by p21N17 Ras. From these and previous results, we suggest a model in which a linear order of NGF receptor, Src, Ras, and Raf activities is used by NGF to elicit gene inductions. These signaling components define branchpoints in the pathway to specific gene induction events, providing a mechanism for generating a host of diverse NGF actions.

Animals↗

PubMed1997

JAK2 is required for induction of the murine DUB-1 gene.

Cytokine receptors activate multiple signal transduction pathways, resulting in the induction of specific target genes. We have recently identified a hematopoietic cell-specific immediate-early gene, DUB-1, that encodes a growth-regulatory deubiquitinating enzyme. The DUB-1 gene contains a 112-bp enhancer element that is specifically induced by the beta c subunit of the interleukin-3 (IL-3) receptor. To investigate the mechanism of DUB-1 induction, we examined the effects of dominant-negative forms of JAK kinases, STAT transcription factors, and Raf-1 in transient transfection assays. In Ba/F3 cells, IL-3 induced a dose-dependent activation of DUB-1-luciferase (luc) and GAS-luc reporter constructs. A dominant-negative form of JAK2 (truncated at amino acid 829) inhibited the induction of DUB-1-luc and GAS-luc by IL-3. A dominant-negative form of STAT5 (truncated at amino acid 650) inhibited the induction of GAS-luc but not DUB-1-luc. A dominant-negative form of Raf-1 inhibited the induction of DUB-1-luc but had no effect on the induction of GAS-luc by IL-3. The requirement for JAK2 in the stimulation of the DUB-1 enhancer was further supported by the suppression of DUB-1 induction in Ba/F3 cells stably expressing the dominant-negative JAK2 polypeptide. We hypothesize that IL-3 activates a JAK2/Raf-1 signaling pathway that is required for DUB-1 induction and is independent of STAT5.

Animals↗

PubMed1997

GABP factors bind to a distal interleukin 2 (IL-2) enhancer and contribute to c-Raf-mediated increase in IL-2 induction.

Triggering of the T-cell receptor-CD3 complex activates two major signal cascades in T lymphocytes, (i) Ca2+-dependent signal cascades and (ii) protein kinase cascades. Both signal cascades contribute to the induction of the interleukin 2 (IL-2) gene during T-cell activation. Prominent protein kinase cascades are those that activate mitogen-activated protein (MAP) kinases. We show here that c-Raf, which is at the helm of the classic MAP-Erk cascade, contributes to IL-2 induction through a distal enhancer element spanning the nucleotides from positions -502 to -413 in front of the transcriptional start site of the IL-2 gene. Induction of this distal IL-2 enhancer differs from induction of the proximal IL-2 promoter-enhancer, since it is induced by phorbol esters alone and independent from Ca2+ signals. In DNA-protein binding studies, we detected the binding of transcription factors GABP alpha and -beta to a dyad symmetry element (DSE) of the distal enhancer, which is formed by palindromic binding sites of Ets-like factors. Introduction of point mutations suppressing GABP binding to the DSE interfered with the induction of the distal enhancer and the entire IL-2 promoter-enhancer, while overexpression of both GABP factors enhanced the IL-2 promoter-enhancer induction. Overexpression of BXB, a constitutive active version of c-Raf, and of further members of the Ras-Raf-Erk signal cascade exerted an increase of GABP-mediated promoter-enhancer induction. In conjunction with previously published data on c-Raf-induced phosphorylation of GABP factors (E. Flory, A. Hoffmeyer, U. Smola, U. R. Rapp, and J. T. Bruder, J. Virol. 70:2260-2268, 1996), these results indicate a contribution of GABP factors to the Raf-mediated enhancement of IL-2 induction during T-cell activation.

Cloning, Molecular↗

PubMed1988

Gene induction by interferons and double-stranded RNA: selective inhibition by 2-aminopurine.

Transcription of several interferon-inducible human genes is also induced by double-stranded RNA. The nature and the mechanism of action of signals generated by interferons and by double-stranded RNA which mediate the induction of these genes are under investigation. Here we report that 2-aminopurine, a known inhibitor of protein kinases, could selectively block this induction process. Induction of mRNAs 561 and 6-16 in HeLaM cells by double-stranded RNA was completely inhibited by 10 mM 2-aminopurine, whereas cellular protein and RNA syntheses as well as the induction of metallothionein mRNA by CdCl2 were unaffected by this inhibitor. In addition, 2-aminopurine blocked the induction of the same two mRNAs and of mRNAs 2-5(A) synthetase, 2A, and 1-8 by alpha interferon and of mRNAs 2A and 1-8 by gamma interferon in HeLaM cells. The observed inhibition was at the level of transcription, and for establishing efficient inhibition, the 2-aminopurine treatment had to begin at early stages of interferon treatment. In GM2767 cells, 2-aminopurine inhibited induction of mRNAs 561 and 6-16 by double-stranded RNA but not by alpha interferon. These results suggest that double-stranded RNA-induced signal 2 is distinct from the interferon-alpha-induced signal 2 (R. K. Tiwari, J. Kusari, and G. C. Sen, EMBO J. 6:3373-3378, 1987) and that 2-aminopurine can block the former but not the latter. Moreover, it appeared that 2-aminopurine could block the production of signal 1 by interferons. This was confirmed by experiments in which we separately tested the effects of 2-aminopurine on signal 1 and signal 2 production by interferons in HeLaM cells. Although no direct experimental evidence is available as yet, our results are consistent with the hypothesis that the functioning of a protein kinase activity may be necessary for transcriptional induction of genes by double-stranded RNA and for gene induction by interferons in those cells in which signal 1 production is needed.

2-Aminopurine↗

PubMed2004

Nebulised salbutamol administered during sputum induction improves bronchoprotection in patients with asthma.

BACKGROUND: Inhalation of hypertonic or even isotonic saline during sputum induction may cause bronchospasm in susceptible patients with asthma, despite premedication with 400 microg inhaled salbutamol delivered by pressurised metered dose inhaler (pMDI). The bronchoprotection afforded by additional inhaled salbutamol administered through the ultrasonic nebuliser during sputum induction was investigated. METHODS: Twenty patients with moderate to severe asthma underwent sputum induction by inhaling saline 4.5% (or 0.9% if post-bronchodilation forced expiratory volume in 1 second (FEV1) <65% predicted) for 10 minutes according to two protocols given 1 week apart in random order. At visit A the patients received 400 microg salbutamol administered through a pMDI+spacer 20 minutes before induction while at visit B the premedication was supplemented by 1500 microg nebulised salbutamol inhaled throughout the induction procedure. Both the investigator and the patients were blind to the nebulised solution used. FEV1 was recorded during sputum induction at 1, 3, 5, and 10 minutes. Sputum cell counts and histamine, tryptase and albumin levels in the supernatants were determined. RESULTS: The mean (SE) maximal reduction in FEV1 over the 10 minute period of sputum induction was 11.7 (2.8)% at visit A, which was significantly greater than at visit B (2.6 (1.2)%; mean difference 9% (95% CI 2.7 to 15.4), p<0.01). Total and differential sputum cell counts as well as albumin, tryptase, and histamine levels did not differ between the two visits. CONCLUSION: The addition of inhaled salbutamol through an ultrasonic nebuliser markedly improves bronchoprotection against saline induced bronchoconstriction in patients with moderate to severe asthma undergoing sputum induction without affecting cell counts and inflammatory markers.

Administration, Inhalation↗

PubMed1990

Induction of long-term potentiation at hippocampal mossy-fiber synapses follows a Hebbian rule.

1. The induction of long-term potentiation (LTP) at hippocampal mossy-fiber synapses requires an increase in postsynaptic [Ca2+]i but is independent of N-methyl-D-aspartate (NMDA) receptor activation. Voltage-gated Ca2+ channels have been proposed as one alternative source for raising [Ca2+]i during the induction of LTP. We tested the hypothesis that voltage-gated Ca2+ channel activation could mediate the induction of LTP by examining whether 1) the induction of mossy-fiber LTP was dependent on postsynaptic depolarization and 2) depolarization alone, of a magnitude presumably capable of activating Ca2+ channels, was sufficient to induce LTP. 2. Intracellular recordings were made from rat CA3 pyramidal cells in the hippocampal slice preparation under both current- and voltage-clamp conditions. Mossy-fiber postsynaptic potentials and currents were recorded before and after high-frequency stimulation (HFS) in the presence of 20-50 microM D-2-amino-5-phosphonovaleric acid (D-APV), an NMDA-receptor antagonist. 3. Voltage clamping of CA3 neurons between -80 and -100 mV during HFS reversibly blocked the induction of mossy-fiber LTP. Conversely, HFS paired with depolarizing-current steps under current clamp increased the magnitude of LTP compared with controls. These results indicate that mossy-fiber LTP is dependent on postsynaptic depolarization, and presynaptic activation alone was not sufficient to induce mossy-fiber LTP. 4. Depolarizing-current injections, which presumably depolarized CA3 cells to potentials sufficient to activate voltage-gated Ca2+ channels, had no effect on mossy-fiber synaptic responses. These results suggest that synaptic activation, in addition to postsynaptic depolarization, is required for the induction of mossy-fiber LTP. 5. Single mossy-fiber afferent volleys were also paired with depolarizing-current pulses. In the presence of APV, pairing of single-mossy-fiber excitatory postsynaptic potentials (EPSPs) with postsynaptic depolarization did not potentiate synaptic responses, suggesting that some form of HFS is also required for mossy-fiber LTP. In the absence of APV, however, the contamination of mossy-fiber synaptic responses by CA3-recurrent inputs resulted in some potentiation. 6. These results suggest that the induction of mossy-fiber LTP is dependent on both pre- and postsynaptic activity and thus follows a Hebbian rule for synaptic modification. In contrast to that demonstrated at Schaffer-collateral-commissural synapses, however, the induction of mossy-fiber LTP may require HFS in addition to postsynaptic depolarization.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2005

Effect of preeclampsia, magnesium sulfate prophylaxis, and maternal weight on labor induction: a retrospective analysis.

BACKGROUND: Our purposes were to determine the effect of preeclampsia, magnesium sulfate prophylaxis, and maternal weight on labor induction in women with preeclampsia and identify risk factors associated with its failure. METHODS: Fifty-five preeclamptic women and 176 non-preeclamptic women requiring labor induction over an 18-month period were studied retrospectively. Prostaglandin E(2) (dinoprostone) and oxytocin were used for labor induction. Women with rupture of the membranes, spontaneous contraction resulting in cervical change, or an initial cervical examination showing more than 2 cm dilatation and 50% effacement were excluded. Statistics were analyzed with chi(2) test, Fisher's exact test, Student t test, Mann-Whitney U test, and multiple logistic regression. RESULTS: The women with preeclampsia had a significantly higher rate of failed induction than did those without preeclampsia (p = 0.01). However, the women with preeclampsia had a higher mean maternal weight and an increased use of magnesium sulfate, and labor was induced at earlier gestational age than in those without preeclampsia (p < 0.05 for each). Multiple logistic regression showed that the use of magnesium sulfate, higher maternal weight, and unfavorable cervix, but not preeclampsia, were significantly associated with an increased risk of failed induction after correction for known confounding variables. CONCLUSIONS: Although the risk of failed induction is increased in preeclamptic women, preeclampsia is not an independent risk factor for failed induction. The use of magnesium sulfate, higher maternal weight, and unfavorable cervix are independent risk factors for failed induction.

Adult↗

PubMed1999

Type-specific induction of interleukin-8 by adenovirus.

Infection with adenovirus (Ad) causes acute pneumonia in a type-specific fashion because type 7 but not type 5 Ad has been isolated as a causative agent. We postulated that the type specificity of induction of pneumonia may be related to type-specific cytokine induction in lung cells. To test this hypothesis, we infected human fetal lung fibroblasts and the lung epithelial cell line A549 with live type 5 and type 7 Ad. Virus inactivated by irradiation was used as a control. Type 7 but not type 5 Ad induced interleukin (IL)-8 protein production in both cell types in a dose- and time-dependent manner. Inactivated virus had no effect on the production of IL-8 protein. Type 7 but not type 5 virus also stimulated IL-8-specific messenger RNA (mRNA) production in these cells. Because half-life of IL-8 mRNA was prolonged in both type 5- and type 7-infected A549 cells, induction likely involves enhancement of message stability as well as other effects. Virus early gene expression did not consistently correlate with IL-8 message induction and followed induction in fibroblasts. These results suggest that there is type-specific induction of IL-8 production during infection of lung cells with Ad. Induction involves message stabilization and may not require viral gene expression. Because IL-8 is one of the important mediators of lung inflammation, type-specific induction of this and other cytokines may account for the different consequences of lung infection with different types of Ad.

Adenoviruses, Human↗

PubMed2001

Differential induction of TNF-alpha and MnSOD by endotoxin: role of reactive oxygen species and NADPH oxidase.

Endotoxin (lipopolysaccharide [LPS]) is known to induce the production of tumor necrosis factor (TNF)-alpha and the induction of manganese superoxide dismutase (MnSOD). We have recently demonstrated that induction of TNF-alpha and MnSOD by LPS is mediated through different signal transduction pathways. In the current study, we investigated the role of reactive oxygen species (ROS) in the induction of TNF-alpha and MnSOD messenger RNAs (mRNAs) in human monocytes. Hypoxia (1% O2) inhibited the production of superoxide (O2-) and the induction of MnSOD, but not TNF-alpha, mRNA. Diphenylene iodonium (DPI), a potent inhibitor of the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, had no effect on LPS induction of MnSOD mRNA, whereas it markedly inhibited LPS-induced O2- production. Neither hypoxia nor DPI had any effect on LPS activation of nuclear factor (NF)-kappaB. These results suggest that (1) ROS is important in the induction of MnSOD, but not TNF-alpha, mRNA by LPS, (2) ROS from sources other than NADPH oxidase is involved in LPS induction of MnSOD mRNA, and (3) ROS-mediated LPS induction of MnSOD mRNA is independent of NF-kappaB activation.

Anti-Bacterial Agents↗

PubMed1988

Fentanyl pretreatment modifies anaesthetic induction with etomidate.

Haemodynamic changes and side-effects of induction of anaesthesia with etomidate were evaluated in 60 ASA Class I or II patients. The objective was to find an optimal pre-induction dose of fentanyl which eliminated haemodynamic changes and side-effects during induction and intubation without introducing other problems. Patients were randomly assigned to four groups according to the pretreatment dose of fentanyl (Group I = 2 ml normal saline; Group II = 100 micrograms of fentanyl; Group III = 250 micrograms of fentanyl; Group IV = 500 micrograms of fentanyl) administered intravenously five minutes prior to induction of anaesthesia with etomidate, 0.3 mg/kg. There was an increasing incidence of apnoea (53, 87, 87 and 100% in Groups I-IV respectively) and a decreasing incidence of myoclonus (60, 33, 13 and 0% in Groups I-IV respectively) and injection pain (53, 13, 7 and 0% in Groups I-IV respectively), P less than 0.002 chi-square test for linear trends, with increasing fentanyl dosage. The incidences of postoperative nausea and vomiting were similar in the four groups. There were also significant linear regression relationships (P less than 0.01 ANOVA for linear regression) between increasing doses of fentanyl administered before etomidate and the prevention of increases in systolic blood pressure and heart rate during the induction-intubation sequence. The data demonstrate that increasing pre-induction doses of fentanyl are more effective at minimising side-effects and preventing increases in systolic arterial blood pressure and heart rate but also increase the incidence of apnoea during induction. The results suggest that 500 micrograms of fentanyl is an ideal pretreatment dose in fit patients prior to anaesthetic induction with etomidate.

Adult↗

PubMed1988

Induction using fentanyl to suppress the intubation response in the cardiac patient: what is the optimal dose?

Eighty patients undergoing coronary artery surgery were randomly allocated to receive either 0, 2, 5, 10 or 15 micrograms/kg of fentanyl with induction of anaesthesia. Heart rate and blood pressure were measured before induction, after induction, and after intubation. The effects of fentanyl dose on both heart rate and mean arterial pressure (MAP) were evaluated in terms of both the mean and group responses. At all doses of fentanyl, mean heart rate increased after induction and rose further on intubation. The mean increase after induction was minimal at doses of 5 micrograms/kg and greater. The increase in heart rate after intubation was more difficult to block but with a fentanyl dose of 15 micrograms/kg, 87% of patients had heart rates below 100 bpm. As a group, the percentage of patients in whom the postintubation heart rate remained below 100 bpm increased progressively with the fentanyl dose. In contrast, mean MAP fell at all dose levels after induction, the mean fall being about 30 mmHg at 5 micrograms/kg and greater. Mean MAP exceeded pre-induction values after intubation with 0 and 2 micrograms/kg, and progressive attenuation of the MAP rise was found as the dose of fentanyl increased. The percentage of patients who did not exceed their preinduction MAP rose progressively with increasing dose of fentanyl with an ED50 of 3.7 micrograms/kg. If a minimal fall in mean MAP after induction with no rise above preinduction MAP is the sole criterion, a fentanyl dose of about 3 micrograms/kg is recommended. If heart rate is to be kept below 100 bpm, a dose of at least 10 micrograms/kg should be used.2+ dose or greater will cause the MAP to fall in some patients to less

Blood Pressure↗

PubMed1994

A comparison of three induction agents in paediatric anaesthesia--cardiovascular effects and recovery.

We studied 30 children undergoing circumcision randomly allocated to receive either thiopentone 4 mg.kg-1, propofol 2.5 mg.kg-1 or midazolam 0.5 mg.kg-1 (n = 10) IV over 30 seconds at induction of anaesthesia. Blood pressure and pulse rate during the first 15 minutes of induction were recorded by a Finapres 2300e and a Cardiocap CM-104, and changes from preinduction baseline compared between the three induction agents and the two recording instruments. Postoperatively, blood levels of the induction agents were measured and recovery from anaesthesia was assessed by clinical criteria, mood and sedation scores and psychomotor performance. The Cardiocap data revealed no statistically significant haemodynamic differences between the three induction agents. Finapres data demonstrated that propofol caused a greater decrease in mean arterial pressure when compared to thiopentone at one minute (P = 0.01) and the MAP remained significantly lower than midazolam at five minutes (P = 0.02), illustrating an advantage of continuous over intermittent non-invasive blood pressure monitoring. The midazolam group took longer to identify themselves compared to both the propofol (P = 0.005) and the thiopentone groups (P = 0.02), but there was no difference in the groups in time to eye-opening. Psychomotor performance on awakening was significantly worse in the midazolam group compared to the propofol (P < 0.03) and thiopentone groups (P < 0.02). Most children had recovered to 80% of their best, practised, unmedicated, preoperative performance four hours after awakening, irrespective of the induction agent administered. Drug blood levels correlated weakly with both methods of psychomotor assessment (r > or = 0.6). Of the three induction agents, thiopentone caused the least haemodynamic perturbation on induction, and anaesthesia induced with midazolam caused the greatest psychomotor impairment on awakening. Within one hour patients in all drug groups were equally awake, co-operative and co-ordinated.

Affect↗

PubMed2006

Identifying conditions for inducible protein production in E. coli: combining a fed-batch and multiple induction approach.

BACKGROUND: In the interest of generating large amounts of recombinant protein, inducible systems have been studied to maximize both the growth of the culture and the production of foreign proteins. Even though thermo-inducible systems were developed in the late 1970's, the number of studies that focus on strategies for the implementation at bioreactor scale is limited. In this work, the bacteriophage lambda PL promoter is once again investigated as an inducible element but for the production of green fluorescent protein (GFP). Culture temperature, induction point, induction duration and number of inductions were considered as factors to maximize GFP production in a 20-L bioreactor. RESULTS: It was found that cultures carried out at 37 degrees C resulted in a growth-associated production of GFP without the need of an induction at 42 degrees C. Specific production was similar to what was achieved when separating the growth and production phases. Shake flask cultures were used to screen for desirable operating conditions. It was found that multiple inductions increased the production of GFP. Induction decreased the growth rate and substrate yield coefficients; therefore, two time domains (before and after induction) having different kinetic parameters were created to fit a model to the data collected. CONCLUSION: Based on two batch runs and the simulation of culture dynamics, a pre-defined feeding and induction strategy was developed to increase the volumetric yield of a temperature regulated expression system and was successfully implemented in a 20-L bioreactor. An overall cell density of 5.95 g DW l(-1) was achieved without detriment to the cell specific production of GFP; however, the production of GFP was underestimated in the simulations due to a significant contribution of non-growth associated product formation under limiting nutrient conditions.

Journal Article↗