Lipid oxidation inhibition capacity of plant extracts and powders in a processed meat model system

A meat model system was used for screening lipid oxidation inhibiting capacity of diverse horticultural plant materials. In the model, heme-containing sarcoplasmic proteins from the meat water-phase were homogenized with linoleic acid and thiobarbituric reactive substances (TBARS) were measured. 23 Plant materials were investigated at three high (50, 100, and 200 ppm) concentrations and five plant extracts were tested at three low (5, 10, and 20 ppm) concentrations over time. In the high concentration sets, summer savory freeze-dried powder, beetroot leaves extracted with 50% ethanol, and an olive polyphenol powder extracted from wastewater, inhibited oxidation the most effectively. After two weeks and at 200 ppm concentration, oxidation was reduced to 17.2%, 16.6% and 13.5% of the blank sample with no added antioxidants respectively. In the low concentration set, spray dried rhubarb juice inhibited oxidation the most after two weeks at 5 ppm where oxidation was reduced to 68.3% of the blank sample with no added antioxidants.

Antioxidant capacity and major phenol compounds of horticultural plant materials not usually used

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Antioxidant properties and phenols in plant materials not usually used were studied.

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Folin-Ciocalteu, FRAP and ABTS measures correlate with different phenol compounds.

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Large differences in antioxidant properties were found between and within species.

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Sea buckthorn and black currant leaves had the highest antioxidant capacity.

Horticultural plant materials not usually used from onion, carrot, beetroot, sea buckthorn, black and red currants as well as a wastewater powder from olive oil production were analyzed for total phenols content (FC), ferric reducing ability of plasma (FRAP), radical scavenging capacity (ABTS), and for major phenolic compounds by HPLC-MS. Antioxidant capacity and phenol content varied significantly between species and cultivars, with extracts of sea buckthorn leaves being superior. In different species, different phenolic compounds were closely associated with FRAP, ABTS and FC. For instance, hydrolysable tannins were major antioxidants in sea buckthorn whereas quercetin was the major antioxidant in onion peel and skin. This study shows that horticultural plant materials usually left in the field or waste materials from processing may have high antioxidant properties, and that extracts of these materials therefore could be of potential interest for development of antioxidant food additives.

A BIM-Info delivery protocol

Today, with many of the technological issues of integrated information management resolved (perhaps excluding the matter of interoperability), defining the content and status of BIM information deliveries remains both a practical and a theoretical problem. New BIM tools and new design processes and procedures have led to a certain confusion of what information is needed for particular BIM uses. This paper seeks to explore and enable a method of defining the content of model information deliverables through a review of 2 key primary specific BIM uses: 3d Design Coordination and Early Energy Appraisal through an analysis of practical application. The scope of this study is limited to a review of information flow within residential projects in a Swedish context and looks at two projects with a view to identify and establish a common definition of the key BIM objects and properties necessary for particular tasks. The key deliverable from this study is the BIM-Info Delivery Protocol (IDP) which attempts to align consultant BIM-information delivery expectations and represents a tangible solution to assist consultants to manage BIM information. Concluding reflections consider the positioning of the IDP relative to the on-going development of IDMs / MVDs and highlight the key constituent parameters of an Information Delivery Specification (IDS).  

Problems and problem attention in the construction sector – understanding the influence of human factors

Problems concerning quality and productivity in the construction sector have been a recurrent issue for many years and seem to remain in spite of various initiatives for resolving them. This situation is a result of human action. From social sciences we know that psychological factors crucially influence action design. Knowledge of this influence seems however to be underestimated in the construction sector, and could represent a missing link between strategies, plans and instructions, and the actions carried out.In order to prospect for new problem solving approaches we undertook a questionnaire-based survey to investigate how individuals in the sector perceive the importance and occurrence of, and attention directed to, different proposed causes of inadequate performance. The design of the questionnaire enabled comparisons of different answers to look beyond the respondents’ overt answers.      The result suggests that (1) the whole problem solving situation, including individual, relational and contextual problem components should be addressed as ‘the problem’; (2) the workforce has the ambition and courage to do what is expected but does not always have adequate information and the ability or resources to do it; (3) mental information distortion might be responsible for affecting the way the world is understood.

Phenols and ascorbic acid in black currants (Ribes nigrum L.): variation due to genotype, location, and year

Black currant berries contain many biochemical compounds with proven or potential human health benefits. We studied the content of total and single polyphenols, ascorbic acid, soluble sugars, and titratable acidity for two advanced selections and three cultivars of black currant at two distant locations in Sweden (south: 56°06'N; north: 65°21'N) over a 3 year period. Regression analyses revealed the effect of genotype to be considerably larger than that of location and year. However, significant effects of location, year, and interactions were also revealed. A principal component analysis nevertheless separated the genotypes. The content of ascorbic acid, total phenols, total anthocyanins, and soluble sugars was highest in berries from the south, whereas the content of phenolic acids and titratable acidity was highest in berries from the north. The results show that selection of cultivars and production sites are important for cultivation of high-quality black currant raw material for health-promoting products.

Emergency presentation and socioeconomic status in colon cancer

BACKGROUND

Emergency presentation affects up to every fourth patient with colon cancer, and is associated with worse outcomes. The aim of this study was to investigate any association between socioeconomic status (SES) and mode of presentation in colon cancer.

MATERIALS AND METHODS

Individually attained data on civil status, education and income were linked to quality registries for colon cancer in two large Swedish regions 1997-2006 (n = 12 293) and analyzed by logistic regression, adjusting for age, sex, stage, region and socioeconomic variables.

RESULTS

The frequency of emergency presentation was 23%; 27.8% among patients above the age of 80, and 20.0% among patients aged 70-79 (p < 0.001). There was no difference between men and women (22.6% vs. 23.8%; p = 0.1). Among patients with stage IV colon cancer, 34.6% presented as emergencies. Odds ratio for an emergency presentation in unmarried patients was 1.24 (96% CI 1.04-1.48), and for unmarried patients above the age of 80, OR was 1.45 (95% CI 0.98-2.13). Among patients below the age of 70 with compulsory education only, OR was 1.22 (95% CI 0.98-1.48). For patients within the lowest income quartile (Q1), OR was 1.24 (95% CI 1.04-1.49). This was most pronounced in men (OR 1.34; 95% CI 1.40-1.72), in patients below the age of 70 (OR 1.36; 95% CI 1.02-1.82), and above the age of 80 (OR 1.41; 95% CI 1.00-1.98).

CONCLUSION

Emergency presentation of colon cancer is consistently associated with socioeconomic factors, and this must be considered in efforts aimed at reducing the overall frequency of emergency cases.

An optimized method for analysis of phenolic compounds in buds, leaves, and fruits of black currant ( Ribes nigrum L.)

Although the fruits are the economic driver for the black currant industry, the buds and leaves are excellent sources of beneficial phenolic compounds that may contribute to the future value of the crop. In this study, extraction of phenolic compounds for different parts of the black currant plant was optimized, and an efficient method for their separation by HPLC was developed. This allowed the simultaneous quantification of a range of hydroxycinnamic acids, flavan-3-ols, flavonols, and anthocyanins by DAD following their identification by HPLC-ESI-MS(n). A total of 23 compounds were detected in the buds, 22 of which were found in fruit and leaves. To the best of our knowledge, this is the first report of flavonol glycosides of quercetin, myricetin, isorhamnetin, and kaempferol along with hydroxycinnamic acids such as neo-chlorogenic acid and chlorogenic acid in the buds. Additionally, we provide the first evidence of kaempferol-3-O-rutinoside in black currant leaves. This approach offers avenues for superior combined compositional identification and cultivar selection targeted at the generation of polyphenol-rich products derived from the whole crop and not just the fruit.

Effects of Plantago major L. leaf extracts on oral epithelial cells in a scratch assay

ETHNOPHARMACOLOGICAL RELEVANCE

The present study was undertaken to evaluate the effects from different leaf extracts of the traditional medicinal herb Plantago major L. (plantain) on cell proliferation and migration in vitro, as a test for potential wound healing properties.

MATERIALS AND METHODS

Water and ethanol-based extracts were prepared from Plantago major fresh and dried leaves, and tested in vitro in a scratch assay with oral epithelial cells.

RESULTS

The scratch assay produced reliable results after 18 h. Most of the tested extracts increased the proliferation/migration of the oral epithelial cells compared to the negative control. A concentration of 1.0 mg/mL (on dry weight basis) appears to be optimal regardless of type of extract, and among the alternatives, 0.1 mg/mL was always better than 10 mg/mL. Ethanol-based extracts with a concentration of 10 mg/mL had very detrimental effects on cell proliferation/migration. At the other two concentrations, ethanol-based extracts had the most beneficial effect, followed by water extracts of fresh leaves, ethanol plus water extracts of dried leaves and, finally, water extracts of dried leaves.

CONCLUSIONS

This study suggests that both the water extracts and the more polyphenol-rich ethanol-based extracts of Plantago major leaves have medicinal properties. Further research is, however, needed to determine what compounds are responsible for the wound healing effects.

Emergency presentation of colon cancer is most frequent during summer

AIM

The frequency of emergency colon cancer (ECC) was determined using a reproducible definition of 'emergency' to analyse the impact of mode of presentation on long-term prognosis and to search for risk factors for an emergency presentation.

METHOD

All patients with colon cancer treated at one Swedish GDH between 1996 and 2005 (N = 604) were eligible. Patients admitted through the emergency room, operated on within three days and with an emergency condition confirmed at surgery were classified as ECC. Survival was analysed by Kaplan-Meier estimates and risk of death by Cox regression.

RESULTS

The rate of ECC was 97/585 (17%). Patients with ECC were older (median 77 vs 74, P = 0.02), they had more stage III and IV cancers (65%vs 47%; χ(2) = 9.4, P < 0.001) and had a cancer located in the caecum less often (20%vs 33%, χ(2) = 4.3 P = 0.04). ECC were most frequent between June and August (36%), whereas elective cases were evenly distributed throughout the year (χ(2) = 7.8; P = 0.049), Crude 5-year survival was 18% in ECC and 38% in the elective group (P < 0.001). The hazard ratio for death within five years in ECC, with 30-day mortality excluded and adjusted for age and sex was 2.25 (95% CI; 1.42-3.55).

CONCLUSION

Emergency presentation of colon cancer is an independent and adverse risk factor for long-term survival. The causes of a seasonal variation need to be clarified.

Joint Regression and Association Modeling of Longitudinal Ordinal Data

We propose models for longitudinal, or otherwise clustered, ordinal data. The association between subunit responses is characterized by dependence ratios (Ekholm, Smith, and McDonald, 1995, Biometrika 82, 847-854), which are extended from the binary to the multicategory case. The joint probabilities of the subunit responses are expressed as explicit functions of the marginal means and the dependence ratios of all orders, obtaining a computational advantage for likelihood-based inference. Equal emphasis is put on finding regression models for the univariate cumulative probabilities, and on deriving the dependence ratios from meaningful association-generating mechanisms. A data set on the effects of treatment with Fluvoxamine, which has been analyzed in parts before (Molenberghs, Kenward, and Lesaffre, 1997, Biometrika 84, 33-44), is analyzed in its entirety. Selection models are used for studying the sensitivity of the results to drop-out.

Extra- and Intracellular pH in the Brain During Ischaemia, Related to Tissue Lactate Content in Normo- and Hypercapnic rats

The objective of the present study was to assess the relationship between the amount of lactate accumulated during complete ischaemia and the ensuing changes in extra- and intracellular pH (pHe and pHi, respectively). The preischaemic plasma glucose concentration of anaesthetized rats was varied by administration of glucose or insulin, pHe was determined in neocortex with ion-sensitive microelectrodes, and tissue lactate and CO2 contents were measured, tissue CO2 tension being known from separate experiments. The experiments were carried out in both normocapnic [arterial CO2 tension (PaCO2) approximately 40 mm Hg] and hypercapnic (PaCO2 approximately 80 mm Hg) animals. Irrespective of the preischaemic CO2 tension, DeltapHe was linearly related to tissue lactate content. Depending on the preischaemic glucose concentration, DeltapHe varied from <0.4 to >1.4 units. The results thus fail to confirm previous results that the changes in pHe describe two plateau functions (DeltapHe approximately 0.5 and 1.1, respectively), with a transition zone at tissue lactate contents of 17 - 20 mmol kg-1. Changes in pHi given in this study are based on the assumption of a uniform intracellular space. The pHi changed from a normal value of approximately 7.0 to 6.5, 6.1 and 5.8 at tissue lactate contents of 10, 20 and 30 mmol kg-1. The intrinsic (non-bicarbonate) buffer capacity, derived from these figures, was 23 mmol kg-1 pH-1. Some differences in pH and in HCO3- concentration between extra- and intracellular fluids persisted in the ischaemic tissue. These differences were probably caused by a persisting membrane potential in the ischaemic cells.

Chronic hyperbaric exposure activates proinflammatory mediators in humans

Decompression illness (DCI) is an illness affecting divers subjected to reductions in ambient pressure. Besides a mechanical explanation to DCI, an inflammatory mechanism has been suggested. In this study, levels of interleukin (IL)-8, IL-6, IL-1 receptor antagonist (IL-1ra), secretory leukocyte protease inhibitor (SLPI), and neutrophil gelatinase-associated lipocalcin (NGAL) were measured in divers before and after a 2-mo period of daily diving. The divers were military conscripts and completed their diving period with no clinical symptoms of DCI. We found no change in IL-6 and IL1-ra but did find an increase in IL-8 and NGAL together with a decrease in SLPI levels. The findings suggest an inflammatory activation. This activation is not severe because no changes in IL-6 or IL-1ra were found. The increase in NGAL and IL-8 levels were interpreted as a sign of leukocyte activation. The decreased SLPI levels suggest an influence on the inflammatory defense mechanism. All in all, the findings of this study show a compensated activation of the inflammatory defense mechanism without loss of homeostasis of the inflammatory system.

Combining regression and association modelling for longitudinal data on bacterial carriage

A longitudinal data set, from the Finnish Otitis Media (FinOM) Studies, reporting carriage or non-carriage of Streptococcus pneumoniae at 2, 3, 4, 5, 6, 9, 12, 15 and 18 months of age of 329 children living in Tampere, Finland, is analysed. A logistic regression model on five time varying explanatory variables is fitted. The temporal association between presence at different ages is measured by dependence ratios and the structure of these is shown to be well described by a model indicating that roughly 10 per cent of the children are not susceptible to the bacteria, while for those that are susceptible, carriage status at a future observation age is conditionally independent of past observed statuses, given the present status. The dependence ratios between carriage at adjacent observation ages decay exponentially with age. Maximum likelihood estimates are obtained for the parameters of the full model, which is the combination of the marginal logistic regression and the association models. The parameter estimates of the full model, strengthened by non-testable Markov assumptions, are used for assessing the median duration of carriage and the acquisition rate as functions of age.

Association models for a multivariate binary response

Models for a multivariate binary response are parameterized by univariate marginal probabilities and dependence ratios of all orders. The w-order dependence ratio is the joint success probability of w binary responses divided by the joint success probability assuming independence. This parameterization supports likelihood-based inference for both regression parameters, relating marginal probabilities to explanatory variables, and association model parameters, relating dependence ratios to simple and meaningful mechanisms. Five types of association models are proposed, where responses are (1) independent given a necessary factor for the possibility of a success, (2) independent given a latent binary factor, (3) independent given a latent beta distributed variable, (4) follow a Markov chain, and (5) follow one of two first-order Markov chains depending on the realization of a binary latent factor. These models are illustrated by reanalyzing three data sets, foremost a set of binary time series on auranofin therapy against arthritis. Likelihood-based approaches are contrasted with approaches based on generalized estimating equations. Association models specified by dependence ratios are contrasted with other models for a multivariate binary response that are specified by odds ratios or correlation coefficients.

Cytokine response after acute hyperbaric exposure in the rat

Intravascular gas has earlier been shown to activate leukocytes and platelets, enhance cell adhesion, and promote secretion of vasoactive substances from platelets. Since decompression is known to release gas bubbles in the bloodstream, the present study was undertaken to investigate the effect of a standardized decompression trauma on inflammatory mediators. Two series of experiments were performed in which male Wistar rats were subjected to a sublethal decompression trauma using a dry pressure chamber. Postdive measurements of cytokine levels were performed to look for signs of an inflammatory reaction. All animals subjected to a decompression trauma showed postdive signs of mild to severe decompression illness (DCI) and measurements of interleukin-6 (IL-6) indicated a postdive increase in the majority of these animals. Our finding of a postdive increase in IL-6 suggests that an inflammatory response, probably created by a blood-gas interface, may be a factor in the process leading to DCI.

Measurement by ICP-MS of lead in plasma and whole blood of lead workers and controls

OBJECTIVES

To test a simple procedure for preparing samples for measurement of lead in blood plasma (P-Pb) and whole blood (B-Pb) by inductively coupled plasma mass spectrometry (ICP-MS), to measure P-Pb and B-Pb in lead workers and controls, and to evaluate any differences in the relation between B-Pb and P-Pb between people.

METHODS

P-Pb and B-Pb were measured by ICP-MS in 43 male lead smelter workers and seven controls without occupational exposure to lead. For analysis, plasma and whole blood were diluted 1 in 4 and 1 in 9, respectively, with a diluted ammonia solution containing Triton-X 100 and EDTA. The samples were handled under routine laboratory conditions, without clean room facilities.

RESULTS

P-Pb was measured with good precision (CV = 5%) even at concentrations present in the controls. Freeze storage of the samples had no effect on the results. The detection limit was 0.015 microgram/l. The P-Pb was 0.15 (range 0.1-0.3) microgram/l in controls and 1.2 (0.3-3.6) micrograms/l in lead workers, although the corresponding B-Pbs were 40 (24-59) micrograms/l and 281 (60-530) micrograms/l (1 microgram Pb/I = 4.8 nmol/l). B-Pb was closely associated with P-Pb (r = 0.90). The association was evidently non-linear; the ratio B-Pb/P-Pb decreased with increasing P-Pb.

CONCLUSIONS

By means of ICP-MS and a simple dilution procedure, P-Pb may be measured accurately and with good precision down to concentrations present in controls. Contamination of blood at sampling and analysis is no major problem. With increasing P-Pb, the percentage of lead in plasma increases. In studies of lead toxicity, P-Pb should be considered as a complement to current indicators of lead exposure and risk.

Depression after surgery for acoustic neuroma

The purpose of this study was to establish the frequency and pattern of depressive disorders after surgery for acoustic neuroma, and to look for associations. Twenty seven patients with acoustic neuroma underwent thorough psychiatric assessment before surgery and at three and 12 months after surgery. Three patients had a depressive disorder in the preoperative assessment. Of the remaining 24 patients, nine (38%) had a depressive disorder at the three month check up. Deterioration of hearing was the only postoperative detriment associated with a depressive disorder (P = 0·024). All nine patients with a depressive disorder were women (P = 0·001), giving them a 69% incidence. None of the patients without preoperative depression required inpatient treatment for depressive disorder, but three patients out of nine still had a depressive disorder 12 months after surgery.

Influence of hyperglycemia and of hypercapnia on cellular calcium transients during reversible brain ischemia

The object of the study was to find out how preischemic hyperglycemia (in normocapnic animals) or excessive hypercapnia (in normoglycemic animals) affect the calcium transient during ischemia, as this can be assessed by measurements of the extracellular calcium concentration ([Ca2+]e). To that extent, normocapnic-normoglycemic control animals were compared with animals with induced hyperglycemia or hypercapnia, all being subjected to 10 min of forebrain ischemia, the [Ca2+]e and d.c. potential being measured with ion-sensitive glass microelectrodes. Hyperglycemia and hypercapnia delayed the loss of ion homeostasis following induction of ischemia. Furthermore, both hyperglycemia and hypercapnia reduced the delay of Ca2+ extrusion upon recirculation. As a result, both hyperglycemia and hypercapnia significantly reduced the ischemic calcium transient, as this was assessed by calculating the duration of maximal calcium load of cells. The results make it less likely that aggravation of brain damage by hyperglycemia or excessive hypercapnia is related to a further derangement of cell calcium homeostasis.

Coupling of energy failure and dissipative K+ flux during ischemia: role of preischemic plasma glucose concentration

The present experiments were undertaken to assess the influence of preischemic hypo- or hyperglycemia on the coupling among changes in extracellular K+ concentration (K+e) and in cellular energy state, as the latter is reflected in the tissue concentrations of phosphocreatine (PCr), Cr, ATP, ADP, and AMP, and in the calculated free ADP (ADPf) concentrations. The questions posed were whether the final release of K+ was delayed because the extra glucose accumulated by hyperglycemic animals produced enough ATP to continue supporting Na(+)-K(+)-driven ATPase activity, and whether the additional acidosis altered the ionic transients. As expected, preischemic hypoglycemia shortened and hyperglycemia prolonged the phase before K+e rapidly increased. This was reflected in corresponding changes in tissue ATP content. Thus, hypoglycemia shortened and hyperglycemia prolonged the time before the fall in ATP concentration accelerated. When tissue was frozen at the moment of depolarization, the tissue contents of ATP were similar in hypo-, normo-, and hyperglycemic groups, approximately 30% of control. This suggests that hyperglycemia retards loss of ion homeostasis by leading to production of additional ATP. However, hyperglycemia did not reduce the rate at which the PCr concentration fell, and the ATP/ADPf ratio decreased. There were marked differences in the amount of lactate accumulated between the groups. Thus, massive depolarization in hypoglycemic groups occurred at a tissue lactate content of approximately 4 mM kg-1. This corresponds to a decrease in intracellular pH (pHi) from approximately 7.0 to approximately 6.9. In the hyperglycemic groups, depolarization occurred at a lactate content of about 12 mm kg-1, corresponding to a pHi of approximately 6.4.(ABSTRACT TRUNCATED AT 250 WORDS)

Coupling of cellular energy state and ion homeostasis during recovery following brain ischemia

The present experiments were undertaken to explore the relationship between recovery of cerebral energy state following transient ischemia, and resumption of Na+/K+ transport, as this is reflected in changes in extracellular K+ concentration ([K+]c). Cerebral energy state was evaluated by measurements of cerebral cortical concentrations of phosphocreatine (PCr), ATP, ADP, and AMP at the end of 15 min of severe, incomplete ischemia, as well as after 2 and 5 min of recirculation. Derivation of intracellular pH (pHi) allowed calculation of 'free' ADP (ADPf) and AMP (AMPf) concentrations. Changes in [K+]e were measured by an ion-sensitive microelectrode. The results showed that tissue ATP concentration, which was close to zero after 15 min of ischemia, rose to 30% of control after 2 min, and to 60% of control after 5 min of recirculation. However, since the adenine nucleotide pool was reduced by the ischemia the latter value represents extensive or complete phosphorylation of that pool, as reflected in a normalized ATP/ADPf ratio. During recirculation, the concentration of pyruvate rose, but the lactate content remained unchanged, suggesting that the substrate for oxidative metabolism was exogenous glucose. Resumption of Na+/K+ transport, as reflected in the [K+]e began after 2-3 min, and a normal [K+]e was attained within 5 min. The results demonstrate that transport of Na+ and K+ is resumed at tissue ATP concentrations which are only 30-40% of control. It is discussed whether this reflects relatively extensive rephosphorylation of the remaining adenine nucleotide pool, or if compartmentation of adenine nucleotides exists during recirculation.

A technique for brain temperature control during ischemia, suitable for measurements with ion-sensitive microelectrodes

A technique is described for maintaining rat brain temperature constant during ischemia, a technique that also allows measurements with, and calibration of, ion-sensitive microelectrodes under defined temperature conditions. The brain temperature is controlled by a stream of air of defined temperature and humidity, which is perfused through a box enclosing the animal's head. A device for calibration of ion-sensitive microelectrodes is temperature controlled by similar principles. The air stream is delivered by a heater/humidifier that is standard in many commercial respirators/ventilators. When the relative humidity of the air stream is greater than 98%, the neocortical temperature can be maintained within less than 0.5 degrees C during 15 min of ischemia. The biological applicability of the technique is discussed.

Changes of labile metabolites during anoxia in moderately hypo- and hyperthermic rats: correlation to membrane fluxes of K+

The objective of this study was to assess the influence of temperature on the coupling among energy failure, depolarization, and ionic fluxes during anoxia. To that end, we induced anoxia by cardiac arrest in anesthetized rats maintained at a body temperature of either 34 degrees C or 40 degrees C, measured extracellular K+ concentration (K+e), and froze the neocortex through the exposed dura for measurements of phosphocreatine (PCr), creatine (Cr), ATP, ADP, and AMP, glucose, glycogen, pyruvate and lactate content after ischemic intervals of maximally 130 s. Free ADP (ADPf) concentrations were derived from the creatine kinase equilibrium. Hypothermia reduced the initial rate of rise in K+e, and delayed the terminal depolarization; however, both hypo- and hyperthermic animals showed massive loss of ion homeostasis at a K+e of 10-15 mM. The initial rate of rise in K+e did not correlate to changes in ATP, or ATP/ADPf ratio, suggesting that temperature changes per se may control the degree of activation of K+ conductances. The results clearly showed that, in both hyper- and hypothermic subjects, energy failure preceded the sudden activation of membrane conductances for ions. The results indicate that temperature primarily influences membrane permeability to ions like K+e (and Na+), and that cerebral energy state is secondarily affected. It is proposed that the higher rate of rise of K+e at high temperatures accelerates ATP hydrolysis primarily by enhancing metabolic rate in glial cells.

Coupling among changes in energy metabolism, acid-base homeostasis, and ion fluxes in ischemia

This article attempts correlating changes in cellular energy metabolism, acid-base alterations, and ion homeostasis in ischemia and other conditions. It is emphasized that loss of ion homeostasis, with thermodynamically downhill fluxes of K+, Ca2+, Na+, Cl-, and H+, occurs because energy production fails and (or) ion conductances are increased. In ischemia, energy failure is the leading event but, in hypoglycemia, activation of ion conductances is what precipitates energy failure. The initial event is a rise in K+ e, at least in part caused by activation of K+ conductances modulated by Ca2+ or ATP/ADP ratio. Secondarily, this leads to release of excitatory amino acids and massive activation of unspecific cation (and anion) conductances. Production of H+ occurs in states characterized by energy failure (ischemia and hypoxia) or by alkalosis (hypocapnia and ammonia accumulation). H+ equilibrates between intra- and extra-cellular fluid via nonionic diffusion of lactic acid, and transmembrane fluxes of H+ or HCO3- via ion channels. Since the relationship between lactate and either pHi or pHe is linear, there are no abrupt pH shifts explaining why hyperglycemia worsens ischemic damage. The reversible insults seem to induce a sustained stimulation of H+ extrusion from cells giving rise to intracellular alkalosis and extracellular acidosis.

Tissue PCO2 in brain ischemia related to lactate content in normo- and hypercapnic rats

The amount of lactate formed during ischemia determines the rise in tissue PCO2 (PtCO2). Conflicting results exist on the relationship between lactate and PtCO2. The objective of this study was to settle this issue. We varied the preischemic plasma glucose concentration of normo- and hypercapnic rats, assessed tissue lactate and total CO2 contents, and determined the PCO2/lactate relationship over the lactate range 2-40 mmol kg-1. The results showed that whatever the equilibration time, the PCO2/lactate relationship was linear. The results obtained could be reproduced by a theoretical buffer system that mimics the buffering behavior of intracellular fluid. Our results bear on the question of whether compartmentation of H+ occurs during ischemia, with glial cells becoming more acid than neurons. A discontinuous PCO2/lactate relationship, with a constant PCO2 above a certain lactate content, would support this contention. Since our results demonstrate a linear relationship between lactate and PCO2 over the lactate range 2-40 mmol kg-1, they considerably weaken any argument for gross compartmentation of H+.

Perturbation of cellular energy state in complete ischemia: relationship to dissipative ion fluxes

Loss of cellular ion homeostasis during anoxia, with rapid downhill fluxes of K+, Ca2+, Na+ and Cl-, is preceded by a slow rise in extracellular K+ concentration (Ke+), probably reflecting early activation of a K+ conductance. It has been proposed that this conductance is activated by either a rise in intracellular calcium concentration (Cai2+), or by a fall in ATP concentration. In a previous study from this laboratory (Folbergrová et al. 1990) we explored whether the early activation of a K+ conductance could be triggered by a rise in Cai2+. To that end, labile metabolites and phosphorylase a, a calcium sensitive enzyme, were measured after 15, 30, 60 and 120 s of complete ischemia ("anoxia"). In the present study, we investigated whether brief anoxia is accompanied by changes in ATP/ADP ratio, or in the phosphate potential, which could cause activation of a K+ conductance. To provide information on this issue, we added a group with 45 s of anoxia to the previously reported groups, and derived changes in intracellular pH (pHi). This allowed calculations of the free concentrations of ADP (ADPf) and AMP (AMPf) from the creatine kinase and adenylate kinase equilibria, and hence the derivation of ATP/ADPf ratios. In performing these calculations we initially assumed that the free intracellular Mg2+ concentration remained unchanged at 1 mM. However we also explored how a change in Mgi2+ of the type described by Brooks and Bachelard (1989) influenced the calculation. The results showed that ADPf must have risen to 150-200% of control within 15 s, and to 330-350% of control within 45 s of anoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms versus models for analyzing data that contain misclassification errors

Espeland and Hui (1987, Biometrics 43, 1001-1012) propose a methodology for analysing epidemiologic data contaminated by misclassification. They explicate their algorithm by a data set concerning cervical cancer and circumcision. We reanalyse these data using a conditional independence assumption different from theirs, and reach radically different conclusions. Espeland and Hui's methodology is a form of correlation analysis. We propose an alternative methodology based on the logic of regression analysis.

Extracellular pH in the brain during ischemia: relationship to the severity of lactic acidosis

On the basis of data showing a bimodal distribution of values for extracellular pH (pHe), and a discontinuous delta PCO2/delta lactate relationship, Kraig et al. (1986) proposed that H+ is grossly compartmentalized between neurons and glia in the ischemic brain. We measured delta pHe during ischemia, varying ischemic lactate contents between 9 and 38 mmol kg-1. No bimodal distribution was found, but delta pHe varied linearly with lactate content. Because we have also failed to record a discontinuous delta PCO2/delta lactate relationship, we conclude that major compartmentation of H+ does not occur during ischemia.

Tissue lactate content and tissue PCO2 in complete brain ischaemia: implications for compartmentation of H+

It has recently been proposed by Kraig et al. that H+ is compartmentalized during complete ischaemia, with glial cells of hyperglycemic animals becoming excessively acidic (pH approximately 5.2), compared to neurons (pH approximately 6.2). In part, the evidence for that is a discontinuous delta PCO2/delta lactate relationship, with PCO2 precipitously increasing to a constant value at tissue lactate contents exceeding 20 mmol kg-1. Since the previous study was performed in hypercapnic animals, and encompassed only a small number of animals, we studied the relationship between ischaemic tissue lactate content and tissue PCO2 over the lactate range 8-49 mmol kg-1. Tissue glucose content was varied by glucose injection and ischaemia was induced by decapitation. Tissue PCO2 was measured in vitro at 37 degrees C on excised tissue samples. The results showed a continuous rise in tissue PCO2 over the entire range of lactate concentrations measured, with maximal values around 300 mm Hg. The results thus fail to reveal a discontinuous delta PCO2/delta lactate relationship, with PCO2 increasing to a constant value. The implication of the results for the hypothesis of pH compartmentation is discussed.

Acid-base changes during complete brain ischemia

We examined the proposal that preischemic hyperglycemia causes exaggerated brain damage by decreasing intracellular or extracellular pH to below a specified threshold value. We also provide a critical appraisal of two related hypotheses. The first is that hyperglycemia enhances brain damage by causing excessive intraglial acidosis; the second, that the critical degree of acidosis is reached not during the ischemia but when recirculation is instituted. The following conclusions are drawn. First, the evidence is inconclusive in favor of marked compartmentation of H+ during ischemia, based on a discontinuous delta lactate/delta PCO2 relation and on direct intracellular pH measurements. In fact, results obtained with identical techniques in normoglycemic animals suggest that the acid compartment assumed to be glia is very small and may be of another origin. Second, although recirculation may give rise to a further increase in either extracellular or intracellular acidosis under certain conditions, this acidosis is not a prerequisite for increased tissue damage or infarction. Third, a critical appraisal of reports supports the contention that enhanced damage is triggered below a specified threshold pH value. In complete or near-complete ischemia, this value corresponds to a tissue lactate content of 17-20 mM.kg-1 wet wt. No correlation exists between subthreshold values for delta lactate and the severity of tissue damage. Furthermore, hyperglycemia cannot be expected to enhance damage if conditions prevent lactate from reaching threshold values or if they uncouple changes in lactate and pH.

Phosphorylase alpha and labile metabolites during anoxia: correlation to membrane fluxes of K+ and Ca2+

The objective of the present study was to explore mechanisms responsible for activation of ion conductances in the initial phases of brain ischemia, particularly for the early release of K+ that precedes massive cell depolarization, and rapid downhill fluxes of K+, Na+, Cl-, and Ca2+. As it has been speculated that a K+ conductance can be activated either by an increase in the free cytosolic calcium concentration (Ca2+i) or by a fall in ATP concentration, the question arises whether the early increase in extracellular K+ concentration (K+e) is preceded by a rise in Ca2+i and/or a fall in ATP content. In the present experiments, ischemia was induced in rats by cardiac arrest, the time courses of the rise in K+e and cellular depolarization were determined by microelectrodes, and the tissue was frozen in situ through the exposed dura for measurements of levels of labile metabolites. including adenine nucleotides and cyclic AMP (cAMP), after ischemic periods of 15, 30, 60, and 120 s. Conversion of phosphorylase b to a was assessed, because it depends, among other things, on changes in Ca2+i. The K+e value rose within a few seconds following induction of ischemia, but massive depolarization (which is accompanied by influx of calcium) did not occur until after approximately 65 s. Activation of phosphorylase was observed already after 15 s and before glycogenolysis had begun. At that time, 3',5'-cAMP concentrations were unchanged, and total 5'-AMP concentrations were only moderately increased. The results demonstrate that a K+ conductance is activated at a time when the overall ATP concentration remains at 95% of control values.(ABSTRACT TRUNCATED AT 250 WORDS)

Sensibility threshold in depressive and nondepressive patients with chronic orofacial pain

Sensibility threshold was measured in patients with depressive and nondepressive psychiatric disorders, where both groups were suffering from chronic orofacial pain. The control patients had no pain and no signs of mental disturbance. Patients with major depressive disorders had a significantly lower sensibility threshold than patients with milder depressive disorders, while patients with milder depressive disorders had a significantly lower sensibility threshold than patients with nondepressive mental disorders. The controls had the highest sensibility threshold. Plasma, beta-endorphin, cortisol and prolactin levels were also measured. The depressed patients were found to have a lower serum beta-endorphin level than the nondepressive patients and the controls, although the difference was not statistically significant.

A pseudo-Markov model for series of neuronal spike events

Spike trains of spontaneous neuronal activity in the rabbit brain are submitted to statistical analyses based on the following pseudo-Markov model. The nerve cell is supposed to alternate between a bursting and a resting state. The numbers of consecutive spikes within each state are assumed to be independent integer-valued random variables with discrete probability distributions. Given the state, the interspike intervals are independent real-valued random variables. The two state semi-Markov model is obtained as a special case when the discrete distributions are geometrical. Statistical second-order properties of recorded spike trains are compared with those predicted by the model on the basis of known first-order properties. For that purpose, serial correlation coefficients and intensity functions for spike trains produced by the model are computed. A comparison between observed and predicted results for the spontaneous activity of 17 brain cells yields a good fit in eight cells and discloses some salient features of the statistical structure in the activity of six other cells. By making it feasible to compute theoretical correlograms, the model may advance the understanding of empirical correlograms. The possibilities for integrating this statistical model of spike trains with a model of the mechanism of spike train production are discussed.