Biomedical subjects

G Chambers

Publications and source records attributed to G Chambers.

At least 19 recordsLinked to original sources

PubMed2006

The in vitro effects of piroxicam and meloxicam on canine cell lines.

OBJECTIVES: To analyse the direct antiproliferative effects of both piroxicam and meloxicam at a variety of concentrations on a series of canine cancer cell lines and the mechanism of cell death. METHODS: The in vitro effects of piroxicam and meloxicam at various concentrations on canine cell cultures (Madin-Darby canine kidney cells, osteosarcoma, mammary carcinoma, and lymphoma) were assessed with respect to proliferation inhibition and apoptosis induction. Western blot analysis of cyclooxygenase-1 and cyclooxygenase-2 expression was performed on all cell lines. RESULTS: All cell lines used in this study were cyclooxygenase-1 and cyclooxygenase-2 positive apart from Madin-Darby canine kidney cells which were negative for both cyclooxygenase-1 and cyclooxygenase-2. Both meloxicam and piroxicam were able to inhibit proliferation in cell lines in a dose-dependent manner. However, the drug concentration required for a given effect was cell line dependent. CLINICAL SIGNIFICANCE: The results suggest that significant inhibition of proliferation and induction of apoptosis would only occur when drug concentrations were in excess of those that can be achieved in vivo following maximum recommended dose rates. It is possible, however, that local or topical treatment or altered dosing regimens may offer alternative approaches to the use of these drugs as antineoplastic agents.

Animals↗

PubMed2005

Temperature-induced nucleation of poly(p-phenylene vinylene-co-2,5-dioctyloxy-m-phenylene vinylene) crystallization by HiPco single-walled carbon nanotubes.

Hybrid systems of the conjugated organic polymer poly(p-phenylene vinylene-co-2,5-dioctyloxy-m-phenylene vinylene)(PmPV) and HiPco single-walled carbon nanotubes (SWNTs) are explored using spectroscopic and thermal techniques to determine specific interactions. Vibrational spectroscopy indicates a weak interaction, and this is further elucidated using differential scanning calorimetry (DSC), confocal laser scanning microscopy, temperature-dependent Raman spectroscopy, and temperature-dependent infrared spectroscopy of the raw materials and the composite. An endothermic transition is observed in the DSC of both the polymer and the 0.1% HiPco composite in the region of 50 degrees C. Also observed in the DSC of the composite is a double-peaked endotherm at -39 and -49 degrees C, which does not appear in the polymer. The Raman spectroscopy of the polymer upon increasing the temperature to 60 degrees C shows a diminished cis-vinylene mode at 1575 cm(-1), with an increase in relative intensity of the trans-vinylene mode at 1630 cm(-1). Partially irreversible change in isomerization suggests increased order in the polymer. This change in the polymer is also manifest in the Raman composite spectrum upon increase of the temperature to 60 degrees C, where the spectrum becomes abruptly dominated by nanotubes. Raman spectroscopy of the composite shows no change at -35 degrees C; however, infrared absorption measurements suggest that the transition at -35 degrees C derives from the polymer side chains. Here the composite at -35 degrees C shows a change in the absorbance of the polymer side chain aryl-oxide linkage at 1250 cm(-1) and alkyl-oxide stretch at 1050 cm(-1). Infrared spectra thus suggest that the transitions in the lower temperature region around -35 degrees C are side chain-induced, while Raman spectra suggest that the transition at 60 degrees C is backbone-induced. Furthermore, temperature cycling induces an irreversible decrease in the mean fluorescence intensity of the polymer, coupled with a further reduction in the mean fluorescence intensity of the composite. This suggests that an increase in crystallization of the composite is supported and enhanced by an increase in ordering of the polymer. Implications are discussed.

Journal Article↗

PubMed2003

Sequence variants of bovine papillomavirus E5 detected in equine sarcoids.

The equine sarcoid, one of the most common dermatological lesions in equids, is a benign, locally invasive dermal fibroblastic lesion. Previous studies have suggested an association with two bovine papilloma virus (BPV) types, BPV-1 and BPV-2. In the present study, we examined sarcoids from horses from two geographical areas, Switzerland and the UK, for the major transforming gene of BPV, E5. We detected BPV DNA for the E5 open reading frame and viral E5 RNA transcripts in most sarcoids. Sequence analysis of the E5 open reading frame of sarcoid-associated BPV detected several unique DNA sequence variants, three of which resulted in sarcoid specific amino acid sequence variations. It is unclear if these sequence variants contribute to the unique clinical presentation of the sarcoid. However, our work provides further evidence of the association between BPV and sarcoid development and the direct involvement of the virus in the pathogenesis of sarcoids.

Animals↗

PubMed2003

Association of bovine papillomavirus with the equine sarcoid.

The equine sarcoid, a locally aggressive, fibroblastic skin tumour, is the most common dermatological neoplasm reported in horses; there is no consistently effective therapy. It is widely accepted that bovine papillomavirus (BPV) types 1 and 2 are associated with the pathogenesis of sarcoid disease. Most sarcoids appear to contain detectable viral DNA and RNA and are also known to express the BPV types 1 and 2 major transforming protein, E5, but appear not to produce infectious virions. While the mode of transmission of infection has not been elucidated, viral gene expression, in particular of E5, may contribute to virus persistence and disease pathogenesis by downregulating MHC class I expression. Here, the pathology and epidemiology of the sarcoid and its association with BPV is reviewed; the transforming functions of the BPV oncoproteins and their possible role in sarcoid pathogenesis are discussed; and the practical implications of BPV infection for diagnostic and therapeutic purposes are considered.

Animals↗

PubMed2001

Sodium influx blockade and hypoxic damage to CA1 pyramidal neurons in rat hippocampal slices.

We studied the effects of lidocaine and tetrodotoxin (TTX) on hypoxic changes in CA1 pyramidal neurons to examine the ionic basis of neuronal damage. Lidocaine (10 and 100 microM) and TTX (6 and 63 nM) delayed and attenuated the hypoxic depolarization and improved recovery of the resting and action potentials after 10 min of hypoxia. Lidocaine (10 and 100 microM) and TTX (63 nM) reduced the number of morphologically damaged CA1 cells and improved protein synthesis measured after 10 min hypoxia. Lidocaine (10 microM) attenuated the increase in intracellular sodium (181 vs. 218%) and the depolarization (-21 vs. -1 mV) during hypoxia but did not significantly attenuate the changes in ATP, potassium, or calcium measured at 10 min of hypoxia. Lidocaine (100 microM) attenuated the changes in membrane potential, sodium, potassium, ATP, and calcium during hypoxia. TTX (63 nM) attenuated the changes in membrane potential (-36 vs. -1 mV), sodium (179 vs. 226%), potassium (78 vs. 50%), and ATP (24 vs. 11%) but did not significantly attenuate the increase in calcium during hypoxia. These data indicate that the primary blockade of sodium channels can secondarily alter other cellular parameters. The hypoxic depolarization and the increase in intracellular sodium appear to be important triggers of hypoxic damage independent of their effect on cytosolic calcium; a treatment that selectively blocked sodium influx (lidocaine 10 microM) improved recovery. Our data indicate that selective blockade of sodium channels with a low concentration of lidocaine or TTX improves recovery after hypoxia by attenuating the rise in cellular sodium and the hypoxic depolarization. This blockade improves the resting and action potentials, histologic state, and protein synthesis of CA1 pyramidal neurons after 10 min of hypoxia to rat hippocampal slices. A higher concentration of lidocaine, which also improved ATP, potassium, and calcium concentrations during hypoxia was more potent. In conclusion, the depolarization and increased sodium concentration during hypoxia account for a portion of the neuronal damage after hypoxia independent of changes in calcium.

Adenosine Triphosphate↗

PubMed2000

Proteomics: a new approach to the study of disease.

The global analysis of cellular proteins has recently been termed proteomics and is a key area of research that is developing in the post-genome era. Proteomics uses a combination of sophisticated techniques including two-dimensional (2D) gel electrophoresis, image analysis, mass spectrometry, amino acid sequencing, and bio-informatics to resolve comprehensively, to quantify, and to characterize proteins. The application of proteomics provides major opportunities to elucidate disease mechanisms and to identify new diagnostic markers and therapeutic targets. This review aims to explain briefly the background to proteomics and then to outline proteomic techniques. Applications to the study of human disease conditions ranging from cancer to infectious diseases are reviewed. Finally, possible future advances are briefly considered, especially those which may lead to faster sample throughput and increased sensitivity for the detection of individual proteins.

Biomarkers↗

PubMed2000

Differential fall in ATP accounts for effects of temperature on hypoxic damage in rat hippocampal slices.

Intracellular recordings, ATP and cytosolic calcium measurements from CA1 pyramidal cells in rat hippocampal slices were used to examine the mechanisms by which temperature alters hypoxic damage. Hypothermia (34 degrees C) preserved ATP (1.7 vs. 0.8 nM/mg) and improved electrophysiologic recovery of the CA1 neurons after hypoxia; 58% of the neurons subjected to 10 min of hypoxia (34 degrees C) recovered their resting and action potentials, while none of the neurons at 37 degrees C recovered. Increasing the glucose concentration from 4 to 6 mM during normothermic hypoxia improved ATP (1.3 vs. 0.8 nM/mg) and mimicked the effects of hypothermia; 67% of the neurons recovered their resting and action potentials. Hypothermia attenuated the membrane potential changes and the increase in intracellular Ca(2+) (212 vs. 384 nM) induced by hypoxia. Changing the glucose concentration in the artificial cerebrospinal fluid primarily affects ATP levels during hypoxia. Decreasing the glucose concentration from 4 to 2 mM during hypothermic hypoxia worsened ATP, cytosolic Ca(2+), and electrophysiologic recovery. Ten percent of the neurons subjected to 4 min of hypoxia at 40 degrees C recovered their resting and action potentials; this compared with 60% of the neurons subjected to 4 min of normothermic hypoxia. None of the neurons subjected to 10 min of hypoxia at 40 degrees C recovered their resting and action potentials. Hyperthermia (40 degrees C) worsens the electrophysiologic changes and induced a greater increase in intracellular Ca(2+) (538 vs. 384 nM) during hypoxia. Increasing the glucose concentration from 4 to 8 mM during 10 min of hyperthermic hypoxia improved ATP (1.4 vs. 0.6 nM/mg), Ca(2+) (267 vs. 538 nM), and electrophysiologic recovery (90 vs. 0%). Our results indicate that the changes in electrophysiologic recovery with temperature are primarily due to changes in ATP and that the changes in depolarization and Ca(2+) are secondary to these ATP changes. Both primary and secondary changes are important for explaining the improved electrophysiologic recovery with hypothermia.

Adenosine Triphosphate↗

PubMed1999

High density lipoprotein (HDL), and not albumin, is the major palmitate binding protein in New Zealand long-finned (Anguilla dieffenbachii) and short-finned eel (Anguilla australis schmidtii) plasma.

Plasma from two members of the teleost Anguillidae family, the New Zealand long-finned (Anguilla dieffenbachii) and short-finned eels (Anguilla australis schmidtii), were examined. Agarose gel electrophoresis showed both species had a major anionic diffuse protein band migrating at approximately the same position as human albumin, and autoradiography showed this protein bound [14C]palmitic acid, but not 63Ni2+. Cellulose acetate electrophoresis followed by Oil Red O staining suggested that this band was a lipoprotein. Two-dimensional electrophoresis of plasma showed the absence of a significant albumin band at approx. 65 kDa, and that the palmitate binding band appeared to be composed of at least three proteins, with the major protein running at 30 kDa. N-Terminal sequencing of the palmitate binding band indicated major sequences of DAPAPP(S)QLED- for long-finned eel and DAPAPPSQLEHV- for short-finned eel, confirming their identities as apo-AI, the major apolipoprotein of high density lipoprotein (HDL). When ultracentrifugation was used to separate the lipoproteins of each species, the anionic palmitate binding protein was found solely in the lipoprotein fractions. There was no evidence of albumin in plasma from either eel, and it appears that in its absence HDL takes on the role of fatty acid transport.

Anguilla↗

PubMed1999

Detection of immunoglobulin light chain mRNA by in situ hybridisation using biotinylated tyramine signal amplification.

A highly sensitive method for the light microscopic in situ hybridisation of immunoglobulin light chain mRNA in formalin fixed, paraffin wax embedded sections is reported. This method is based on signal amplification using horseradish peroxidase catalysed deposition of biotinylated tyramine at the sites of hybridisation. kappa and lambda light chain immunoglobulin mRNA in situ hybridisation was performed with fluorescein isothiocyanate conjugated oligonucleotide probe cocktails. The hybridisation signal was detected using a biotinylated tyramine signal amplification procedure with streptavidinbiotin-horseradish peroxidase complex as the final layer. Peroxidase was demonstrated using 3,3'-diaminobenzidine. The biotinylated tyramine signal amplification method resulted in the sensitive detection of immunonoglobulin light chain mRNA, with the whole procedure being completed in one day. Moreover, the use of peroxidase as the final reporter molecule also allowed haemamatoxylin to be used as counterstain, thereby permitting the evaluation of cellular morphology.

Biotinylation↗

PubMed1999

Thiopental attenuates hypoxic changes of electrophysiology, biochemistry, and morphology in rat hippocampal slice CA1 pyramidal cells.

BACKGROUND AND PURPOSE: Thiopental has been shown to protect against cerebral ischemic damage; however, it has undesirable side effects. We have examined how thiopental alters histological, physiological, and biochemical changes during and after hypoxia. These experiments should enable the discovery of agents that share some of the beneficial effects of thiopental. METHODS: We made intracellular recordings and measured ATP, sodium, potassium, and calcium concentrations from CA1 pyramidal cells in rat hippocampal slices subjected to 10 minutes of hypoxia with and without 600 micromol/L thiopental. RESULTS: Thiopental delayed the time until complete depolarization (21+/-3 versus 11+/-2 minutes for treated versus untreated slices, respectively) and attenuated the level of depolarization at 10 minutes of hypoxia (-33+/-6 versus -12+/-5 mV). There was improved recovery of the resting potential after 10 minutes of hypoxia in slices treated with thiopental (89% versus 31% recovery). Thiopental attenuated the changes in sodium (140% versus 193% of prehypoxic concentration), potassium (62% versus 46%), and calcium (111% versus 197%) during 10 minutes of hypoxia. There was only a small effect on ATP (18% versus 8%). The percentage of cells showing clear histological damage was decreased by thiopental (45% versus 71%), and thiopental improved protein synthesis after hypoxia (75% versus 20%). CONCLUSIONS: Thiopental attenuates neuronal depolarization, an increase in cellular sodium and calcium concentrations, and a decrease in cellular potassium and ATP concentrations during hypoxia. These effects may explain the reduced histological, protein synthetic, and electrophysiological damage to CA1 pyramidal cells after hypoxia with thiopental.

Action Potentials↗

PubMed1998

The albumins of Chinook salmon (Oncorhynchus tshawytscha) and brown trout (Salmo trutta) appear to lack a propeptide.

Plasma samples from two members of the Salmonidae family, the chinook salmon (Oncorhynchus tshawytscha) and brown trout (Salmo trutta), were examined. Albumin, initially identified as the predominant anionic palmitate-binding band on agarose gel electrophoresis of plasma, was purified from both species by DEAE-ion exchange chromatography. Albumin has a plasma concentration of approximately 15 mg/ml in both species. Like other fish species, neither trout nor salmon albumin binds nickel; a characteristic of many mammalian albumins. Salmon and trout albumins have molecular masses of 65 and 67 kDa, respectively, indicating some sequence differences. However, N-terminal sequencing of the first 15 residues of both these proteins indicated identical sequences of 1QNQICTIFTEAKEDG15-. This showed that the mature N-terminal sequence (SQAQNQICTIFTEAKEDG-) predicted from the cDNA of Atlantic salmon albumin is in fact incorrect, with the actual N-terminus for salmonids starting three amino acids later than that predicted. Examination of the Atlantic salmon cDNA sequence suggested that salmonid albumin is unique, in lacking a propeptide. No proalbumin convertase site (RXYR/XYRR) is present and it appears that the salmonid albumin precursor is cleaved only by the signal peptidase, between -1 Ala and +1 Gln, to produce mature albumin. This site has a preferrred motif for the signal peptidase of -1 Ala and -3 Ser, as well as -2 Gln. Thus, salmonid albumin possesses a 21-residue prepeptide, but no propeptide.

Amino Acid Sequence↗

PubMed1998

Etomidate does not alter recovery after anoxia of evoked population spikes recorded from the CA1 region of rat hippocampal slices.

BACKGROUND: Etomidate is an anesthetic agent that reduces the cerebral metabolic rate and causes minimal cardiovascular depression. Its ability to improve recovery after anoxia or ischemia is equivocal. An in vitro neuronal preparation was used to examine the action of etomidate on electrophysiologic and biochemical parameters during and after anoxia. METHODS: The Schaffer collateral pathway was stimulated, and a postsynaptic evoked population spike was recorded from the CA1 pyramidal cell layer of rat hippocampal slices. Etomidate or propylene glycol, its solvent, was present 15 min before, during, and 10 min after anoxia. Adenosine triphosphate, sodium, and potassium concentrations were measured at the end of anoxia in tissue treated with etomidate, propylene glycol, or with no added drugs. RESULTS: Etomidate did not alter recovery after 6 min of anoxia. The population spikes from untreated slices recovered to 32% of their preanoxic amplitude, and slices treated with 0.5, 3, and 30 microg/ml etomidate recovered to 24%, 35%, and 13%, respectively. Slices treated with propylene glycol, equivalent to that in 3 and 30 microg/ml etomidate, recovered to 46% and 12%, respectively, and this was not significantly different from untreated slices. Etomidate did not attenuate the decrease in adenosine triphosphate concentrations during anoxia. The increase in sodium and the decrease in potassium during anoxia were significantly attenuated by 30 but not by 3 microg/ml etomidate. CONCLUSIONS: A range of etomidate concentrations did not significantly alter recovery of the evoked population spike after anoxia in rat hippocampal slices. A high concentration of etomidate did attenuate the increase in sodium and the decrease in potassium during anoxia.

Adenosine Triphosphate↗

PubMed1997

Nitrous oxide impairs electrophysiologic recovery after severe hypoxia in rat hippocampal slices.

BACKGROUND: Research has suggested that nitrous oxide may be harmful to ischemic neurons; however, the evidence for this is equivocal. The authors used rat hippocampal slices to examine the effects of nitrous oxide on neuronal hypoxic damage. METHODS: The evoked population spike (PS) was recorded from hippocampal CA1 pyramidal cells before, during, and after hypoxia. Control groups received nitrogen concentrations equal to nitrous oxide throughout the experiments. Biochemical measurements were made from dissected CA1 regions under experimental conditions that matched the electrophysiology studies. RESULTS: Recovery of the PS after hypoxia was 18 +/- 7% in slices treated with 50% nitrous oxide before and during 3.5 min of hypoxia; this compares with 41 +/- 9% (P < 0.05) in nitrogen-treated slices. Slices treated with nitrous oxide (95%) only during hypoxia (6 min) also demonstrated significantly less recovery of the PS than did slices treated with nitrogen. There was no significant difference in recovery if nitrous oxide was discontinued after the hypoxic period. Adenosine triphosphate concentrations after 3.5 min of hypoxia in slices treated with nitrous oxide decreased to the same extent as in nitrogen-treated slices (47% vs. 50%). Calcium influx increased during 10 min of hypoxia in untreated slices, but nitrous oxide did not significantly increase calcium influx during hypoxia. The sodium concentrations increased and potassium concentrations decreased during hypoxia; nitrous oxide did not significantly alter these changes. CONCLUSIONS: Nitrous oxide impaired electrophysiologic recovery of hippocampal slices after severe hypoxia. Nitrous oxide did not cause significant changes in the biochemical parameters examined.

Anesthetics, Inhalation↗

PubMed1997

The effect of isoflurane on biochemical changes during and electrophysiological recovery after anoxia in rat hippocampal slices.

It is unclear whether isoflurane protects against neuronal damage. This study examines the extent and mechanism by which isoflurane might affect anoxic neuronal damage. The size of the evoked postsynaptic population spike recorded from the CA 1 pyramidal cell layer of the rat hippocampal slice 60 min after anoxia was compared with its preanoxic, preisoflurane level. Intracellular adenosine triphosphate (ATP), sodium, and potassium levels were measured in the dentate and CA 1 regions at the end of the anoxic period in similarly treated slices. Isoflurane increased the latency and reduced the amplitude of the evoked response before anoxia. Isoflurane (2%) did not significantly improve recovery of the evoked response after 5 min of anoxia (untreated slices = 6 +/- 2% (mean +/- SEM), isoflurane = 17 +/- 7%); 1.5% isoflurane also did not significantly improve recovery after 4 min of anoxia (untreated = 30 +/- 8% vs. 1.5% isoflurane = 47 +/- 12%). Isoflurane did not significantly attenuate the decrease in ATP levels in either the dentate or CA 1 regions of the hippocampal slice during 4 or 7 min of anoxia; however, there was a significant improvement in ATP levels after 10 min of anoxia in both regions of isoflurane-treated preparations (1.0 +/- 0.1 vs. 1.4 +/- 0.1, CA 1; 1.3 +/- 0.1 vs. 2.0 +/- 0.2 nM/mg dry weight, dentate). Sodium concentrations increased and potassium concentrations decreased during anoxia. Isoflurane did not significantly attenuate the changes in these ions during anoxia. In conclusion, isoflurane does not significantly improve recovery of CA 1 pyramidal cells during anoxia nor does it attenuate the anoxic changes in ATP, sodium, and potassium after 4 or 7 min of anoxia. With a more prolonged period of anoxia (10 min) isoflurane reduces the decrease in ATP levels.

Adenosine Triphosphate↗

PubMed1995

The importance of sodium for anoxic transmission damage in rat hippocampal slices: mechanisms of protection by lidocaine.

1. The effect of sodium influx on anoxic damage was investigated in rat hippocampal slices. Previous experiments demonstrated that a concentration of tetrodotoxin which blocks neuronal transmission protects against anoxic damage. In this study we examined low concentrations of lidocaine (lignocaine; which do not block neuronal transmission), for their effect on recovery of the evoked population spike recorded from the CA1 pyramidal cell layer. 2. Recovery of the population spike, measured 60 min after a 5 min anoxic period, was 4 +/- 2% of its preanoxic, predrug level. Lidocaine concentrations of 10, 50, and 100 microM significantly improved recovery to 56 +/- 12, 80 +/- 7 and 70 +/- 14%, respectively. 3. Lidocaine (10 microM) did not alter the size of the evoked response before anoxia and had no significant effect on potassium levels or calcium influx during anoxia. It did, however, reduce cellular sodium levels (146 +/- 7 vs. 202 +/- 12 nmol mg-1) and preserve ATP levels (2.17 +/- 0.07 vs. 1.78 +/- 0.07 nmol mg-1) during anoxia. All values were measured at the end of 5 min of anoxia except those for Ca2+ influx which were measured during 10 min of anoxia. 4. High concentrations of lidocaine (100 microM) did not improve recovery significantly over that observed with 10 microM. They also had no significantly greater effects on sodium levels than 10 microM lidocaine (137 +/- 12 vs. 146 +/- 7 nmol mg-1); however, 100 microM lidocaine significantly improved potassium (202 +/- 18 vs. 145 +/- 6 nmol mg-1) and ATP (2.57 +/- 0.06 vs. 2.17 +/- 0.07 nmol mg-1) levels, while reducing calcium influx (7.76 +/- 0.12 vs. 9.24 +/- 0.39 nmol mg-1 (10 min)-1) when compared with 10 microM lidocaine. 5. We conclude that sodium influx and ATP depletion are of major importance in anoxic damage since 10 microM lidocaine reduced these changes during anoxia and improved recovery of the population spike. In addition, our results indicate that the properties of the sodium channel are altered during anoxia, since sodium influx is blocked by a concentration of lidocaine that does not affect the population spike in the preanoxic period.

Adenosine Triphosphate↗

PubMed1995

Propofol reduces neuronal transmission damage and attenuates the changes in calcium, potassium, and sodium during hyperthermic anoxia in the rat hippocampal slice.

BACKGROUND: Propofol reduces cerebral blood flow, cerebral metabolic rate for oxygen, and intracranial pressure and is being increasingly used in neuroanesthesia. In vivo studies have yielded conflicting results on its ability to protect against ischemic brain damage. In the current study, an in vitro model was used to examine the mechanism of propofol's action on anoxic neuronal transmission damage. METHODS: A presynaptic pathway was stimulated in the rat hippocampal slice to elicit a postsynaptic population spike in the CA1 region. The effects of propofol (20 micrograms/ml), its solvent intralipid or no drug, on the population spike before, during, and 60 min after anoxia at 37 degrees C or 39 degrees C were examined. Intracellular adenosine triphosphate (ATP), Na, and K were measured in dissected CA1 regions at 37 degrees C and 39 degrees C after 5 min of anoxia; 45Ca influx was measured after 10 min of anoxia. RESULTS: Propofol did not improve recovery after 5, 6, or 7 min of anoxia at 37 degrees C. Recovery of the population spike after 6 min of anoxia at 37 degrees C was 62 +/- 11% with propofol, 35 +/- 15% with intralipid, and 44 +/- 10% in untreated tissue (NS). After 5 min of anoxia at 39 degrees C, there was significantly better recovery of the population spike with propofol (76 +/- 12%) than with intralipid (11 +/- 6%) or no drug (13; +/- 5%). Propofol, but not intralipid, reduced the population spike amplitude before anoxia. At 37 degrees C, anoxia caused significant changes in ATP (62% of normoxic concentration), Ca (115%), Na (138%), and K (68%). Both propofol and intralipid significantly attenuated the changes in ATP (78% and 82% of normoxic concentration) and Ca (104% and 103%). Na changes were attenuated by propofol (95%) but not intralipid; K concentration was not affected by either drug. At 39 degrees C, for most parameters, anoxia caused more marked changes: ATP was 23% of normoxic concentration, Ca 116%, Na 185%, and K 48%. Both propofol and intralipid attenuated the decrease in ATP (56% of normoxic); propofol, but not intralipid, significantly attenuated the changes in Ca (100%), Na (141%), and K (63%). CONCLUSIONS: Propofol improved electrophysiologic recovery from anoxia during hyperthermia but not normothermia. At 37 degrees C propofol attenuated the changes in ATP, Na, and Ca, however, this did not result in improved recovery. At 39 degrees C the changes in ATP, Na, and K caused by anoxia were greater than at 37 degrees C; this could explain why electrophysiologic damage was worsened. Improved recovery with propofol at 39 degrees C may be explained by its attenuation of the changes in Ca, Na, and K at this temperature. The decrease in ATP was attenuated by both propofol and intralipid and therefore cannot explain the improved recovery.

Adenosine Triphosphate↗

PubMed1994

Anoxia reduces depolarization induced calcium uptake in the rat hippocampal slice.

Veratridine-induced depolarization caused a large increase in Ca uptake in the rat hippocampal slice (30.2 vs. 9.0 nM/mg dry weight). This uptake was reduced to 18.4 nM/mg when veratridine was combined with anoxia. When compared with veratridine exposure alone, the combination of anoxia and veratridine increased intracellular Na (460 vs. 380 microM/g), decreased intracellular K (30 vs. 40 microM/g) and decreased ATP levels (0.1 vs. 0.8 nM/mg). The changes in Na, K, and ATP should enhance net Ca uptake, yet Ca uptake was reduced. This suggests an effect of anoxia to block Ca channels. In summary anoxia attenuates depolarization-induced Ca uptake. This may represent a mechanism by which neurons are partially protected against anoxic damage which could be more severe if depolarization-induced Ca uptake was not limited.

Adenosine Triphosphate↗

PubMed1992

The barbiturate thiopental reduces ATP levels during anoxia but improves electrophysiological recovery and ionic homeostasis in the rat hippocampal slice.

The barbiturate anesthetic thiopental enhances recovery of the evoked population spike recorded from rat hippocampal slices after short periods of anoxia. Thiopental reduces changes in sodium, potassium and calcium but enhances the fall in ATP levels during anoxia. The postsynaptic population spike recorded from the CA1 pyramidal cell region of the slices treated with thiopental (600 microM) recovered to 67% of the preanoxic amplitude after 3.5 min of anoxia. There was less recovery (24%) when a lower concentration of thiopental (250 microM) was used. Untreated slices recovered to only 10% of their preanoxic amplitude after 3.5 min of anoxia. Other studies have demonstrated that maintaining ATP levels during anoxia may be an important mechanism of protection. In contrast to those studies, thiopental was protective although it enhanced the fall of ATP levels after 3.5 min of anoxia in the CA1 region and after 3.5 and 5 min in the dentate region. Thus enhanced recovery of the population spike with thiopental is not due to its preservation of ATP levels. This result allows a clear separation of improved ATP levels during anoxia from other mechanisms of protection. We therefore looked for other mechanisms of protection. Sodium and potassium levels were measured after 10 min of anoxia. In untreated tissue, sodium levels in the slice rose and potassium levels fell significantly. In thiopental-treated tissue, changes in sodium and potassium caused by anoxia and by veratridine under normoxic conditions were significantly reduced. During anoxia calcium-45 uptake increases; thiopental significantly reduces this uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗