Can you elaborate on that? Addressing participants' need for cognition in computer-tailored health behavior interventions

Computer-tailored interventions, which deliver health messages adjusted based on characteristics of the message recipient, can effectively improve a range of health behaviours. Typically, the content of the message is tailored to user demographics, health behaviours and social cognitive factors (e.g., intentions, attitudes, self-efficacy, perceived social support) to increase message relevance, and thus the extent to which the message is read, considered and translated into attitude and behaviour change. Some researchers have suggested that the efficacy of computer-tailored interventions may be further enhanced by adapting messages to suit recipients' need for cognition (NFC) - a personality trait describing how individuals tend to process information. However, the likely impact of doing so, especially when tailored in conjunction with other variables, requires further consideration. It is possible that intervention effects may be reduced in some circumstances due to interactions with other variables (e.g., perceived relevance) that also influence information processing. From a practical point of view, it is also necessary to consider how to optimally operationalise and measure NFC if it is to be a useful tailoring variable. This paper aims to facilitate further research in this area by critically examining these issues based on relevant theories and existing evidence.

Species-specific low plasma glucose in fish is associated with relatively high tissue glucose content and is inversely correlated with cardiac glycogen content

The relationship between plasma glucose concentration and intracellular glucose (liver, heart, brain, gill, gonad, intestine, kidney, spleen, white muscle) was determined in fish species with a range in plasma glucose (Atlantic cod, 5.06 mM; cunner, 3.8 mM; rainbow trout, 3.7 mM; lumpfish, 0.9 mM; short-horned sculpin, 0.6 mM; and winter flounder, 0.6 mM). The ratio of intracellular glucose/plasma glucose was always higher than one in liver for all species consistent with a diffusion gradient from the tissue to the plasma. In all other tissues in Atlantic cod, cunner, and rainbow trout the diffusion gradient was from the plasma to the intracellular space. In short-horned sculpin, the mean ratio in heart and white muscle exceeded one and in winter flounder the ratio was significantly greater than one at 5.97 and 2.92 for heart and muscle, respectively. The presence of an active glucose 6-phosphatase in white muscle could account for elevated amounts of free glucose. The white muscle of all species displayed phosphoenolpyruvate carboxykinase and in winter flounder the activity was as high in white muscle as in liver suggesting that gluconeogenesis may be associated with a relatively high-muscle glucose content. The glycogen content was highest in liver followed by heart with lower amounts in all other tissues. There was an inverse correlation between heart glycogen content and plasma glucose concentration when all species were included. It is contended that in species with low plasma glucose, heart glycogen is accumulated at a slow rate under normoxia, to be called upon under hypoxic conditions when the gradient for inward diffusion is unfavourable for high rates of glucose metabolism.

A systematic review of physical activity-based behaviour change interventions reaching men with prostate cancer

PURPOSE

Men who are survivors of prostate cancer report a variety of psychological and physical factors contributing to a lower quality of life, and physical activity can assist to mitigate these issues. This review aims to provide a summary of physical activity behaviour change trials targeting prostate cancer survivors, assess the feasibility of these interventions and, if possible, identify intervention and study characteristics associated with significant intervention effects.

METHOD

Four databases (PubMed, CINAHL, PsycINFO and EMBASE) were systematically searched for randomised controlled trials containing at least one behavioural outcome relating to physical activity published up until July 2016. Forward and backwards, hand, key author citation searching and known research were also considered.

RESULTS

From a total of 13, 828 titles, the search resulted in 12 studies (6 prostate cancer only and 6 mixed cancer interventions), eight of which found positive results most often related immediately to post-intervention aerobic activity. Factors relating to efficacy were not conclusive due to the heterogeneity of studies and lack of cancer-specific data in mixed cancer trials. Future research focusing on intervention reach, maintenance of intervention effects and resistance training outcomes is needed.

CONCLUSION

There is preliminary evidence to suggest that a variety of physical activity behaviour change interventions targeting men with a history of prostate cancer can be efficacious, at least in the short term. Experimental studies are required to identify key intervention features.

IMPLICATIONS FOR CANCER SURVIVORS

Physical activity interventions can assist prostate cancer survivors in relation to short-term lifestyle change, though more evidence is required to improve the clarity of factors related to efficacy.

Abstract P6-12-06: Effect and moderators of exercise on fatigue in patients with breast cancer: Meta-analysis of individual patient data

Background - Fatigue is one of the most common and disabling complaints in patients with breast cancer and can effectively be reduced by physical exercise, with small to moderate effect sizes. To identify heterogeneity in responses to exercise and to further personalize exercise prescriptions, moderators of exercise effects on fatigue should be investigated. However, most randomized controlled trials (RCTs) are not adequately powered for such analyses. Therefore we conducted meta-analyses using the individual patient data of several exercise RCTs. The aim is to investigate the effect and moderators of physical exercise on cancer-related fatigue in patients with breast cancer.

Methods - Within the Predicting OptimaL cAncer RehabIlitation and Supportive care (POLARIS) consortium, principal investigators of 34 exercise RCTs worldwide have shared their individual patient data. Twenty-two of these RCTs included patients with breast cancer with a total sample size of 3,061. Different questionnaires to assess level of fatigue were used, which was acknowledged by using z-scores in the analysis. A one-step individual patient data meta-analysis, using a linear mixed-effect model adjusted for baseline fatigue, with a random intercept on study (to account for study clustering) was undertaken to investigate effect of exercise on fatigue. The result, a between-group difference in z-scores, corresponds to a Cohen's d effect size. An interaction term was included in the model to assess potential moderators including demographic (age, marital status, education), clinical (body mass index, presence of distant metastasis), intervention-related (intervention timing, delivery mode and duration), and exercise-related (exercise type, frequency, intensity, duration) characteristics.

Results – Exercise significantly reduced fatigue reported by women with breast cancer (β= -0.15, 95% CI -0.21;-0.09). This effect did not differ significantly between patients with different demographic and clinical characteristics (p-valuesinteraction >0.05). Also, neither timing (during or post-treatment) and duration of the intervention, nor exercise-related factors moderated intervention effects on fatigue. Supervised exercise had significantly larger effects on fatigue than unsupervised exercise (βdifference= -0.17, 95%CI -0.28;-0.05). Compared to the control group, supervised exercise significantly improved fatigue (β = -0.21, 95%CI = -0.28;-0.14), while unsupervised exercise did not (β = -0.04, 95%CI = -0.14;0.06).

Conclusion – Exercise significantly reduces fatigue in patients with breast cancer across subgroups formed on the basis of age, marital status, education level, body mass index, and presence of distant metastasis. The effect of exercise is significantly larger when performed under supervision. Hence, exercise, and preferably supervised exercise, represents a viable intervention for the prevention and treatment of fatigue among patients with breast cancer.

Citation Format: van Vulpen JK, Sweegers MG, Kalter J, Peeters PH, Courneya KS, Newton RU, Aaronson NK, Jacobsen PB, Steindorf K, Stuiver MM, Hayes S, Mesters I, Knoop H, Goedendorp M, Mutrie N, Thorsen L, Schmidt M, Sonke GS, Bohus M, James EL, Oldenburg HS, Velthuis MJ, Nollet F, Wenzel J, Wiskemann J, Galvão DA, Chinapaw MJ, Irwin ML, Griffith KA, van Weert E, Daley AJ, McConnachie A, Schulz K-H, Short CE, Plotnikoff RC, Potthoff K, van Beurden M, van Harten WH, Schmitz KH, Winters-Stone KM, Taaffe DR, van Mechelen W, Kersten M-J, Verdonck-de Leeuw IM, Brug J, Buffart LM, May AM. Effect and moderators of exercise on fatigue in patients with breast cancer: Meta-analysis of individual patient data [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-12-06.

Designing more engaging computer-tailored physical activity behaviour change interventions for breast cancer survivors: lessons from the iMove More for Life study

BACKGROUND

Participating in regular physical activity is a recommended cancer recovery strategy for breast cancer survivors. However, tailored support services are not widely available and most survivors are insufficiently active to obtain health benefits. Delivering tailored programs via the Internet offers one promising approach. However, recent evaluations of such programs suggest that major improvements are needed to ensure programs meet the needs of users and are delivered in an engaging way. Understanding participants' experiences with current programs can help to inform the next generation of systems.

PURPOSE

The purposes of this study are to explore breast cancer survivor's perspectives of and experiences using a novel computer-tailored intervention and to describe recommendations for future iterations.

METHODS

Qualitative data from a sub-sample of iMove More for Life study participants were analysed thematically to identify key themes. Participants long-term goals for participating in the program were explored by analysing open-ended data extracted from action plans completed during the intervention (n = 370). Participants negative and positive perceptions of the website and recommendations for improvement were explored using data extracted from open-ended survey items collected at the immediate intervention follow-up (n = 156).

RESULTS

The majority of participants reported multi-faceted goals, consisting of two or more outcomes they hoped to achieve within a year. While clear themes were identified (e.g. 'being satisfied with body weight'), there was considerable variability in the scope of the goal (e.g. desired weight loss ranged from 2 to 30 kg). Participants' perceptions of the website were mixed, but clear indications were provided of how intervention content and structure could be improved.

CONCLUSIONS

This study provides insight into how to better accommodate breast cancer survivors in the future and ultimately design more engaging computer-tailored interventions.

Low levels of extracellular glucose limit cardiac anaerobic metabolism in some species of fish

There is a wide interspecific range in plasma glucose levels in teleosts from less than 0.5 to greater than 10 mmol l^-1 Here we assessed how glucose availability influences glucose metabolism in hearts of Atlantic cod (Gadus morhua), rainbow trout (Oncorhynchus mykiss), lumpfish (Cyclopterus lumpus) and short-horned sculpin (Myoxocephalus scorpius) under normoxic and hypoxic conditions. These species had plasma glucose levels of 5.1, 4.8, 0.9 and 0.5 mmol l^-1, respectively. Rates of glucose metabolism and lactate production were determined in isolated hearts perfused with medium containing physiological levels of glucose. Under normoxic conditions there was no significant difference in rates of either glucose metabolism (average 15 nmol g^-1 min^-1) or lactate production (average 30 nmol g^-1 min^-1) across species. Under hypoxia (12% of air saturation) there were significant increases in rates of glucose metabolism and lactate production in hearts from Atlantic cod (glucose-130; lactate-663 nmol g^-1 min^-1) and rainbow trout (glucose-103; lactate-774 nmol g^-1 min^-1); however, there was no change in rate of glucose metabolism in hearts from either lumpfish or short-horned sculpin and only increases in lactate production to rates much lower than the other species. Furthermore, Atlantic cod hearts perfused with medium containing low non-physiological levels of glucose (0.5 mmol l^-1) had the same rates of glucose metabolism under normoxic and hypoxic treatments. Anaerobic metabolism supported by extracellular glucose is compromised in fish with low levels of plasma glucose, which in turn may decrease performance under oxygen-limiting conditions at the whole-animal level.

High rates of glucose utilization in the gas gland of Atlantic cod (Gadus morhua) are supported by GLUT1 and HK1b

The gas gland of physoclistous fish utilizes glucose to generate lactic acid that leads to the off-loading of oxygen from haemoglobin. This study addresses characteristics of the first two steps in glucose utilization in the gas gland of Atlantic cod (Gadus morhua). Glucose metabolism by isolated gas gland cells was 12- and 170-fold higher, respectively, than that in heart and red blood cells (RBCs) as determined by the production of (3)H2O from [2-(3)H]glucose. In the gas gland, essentially all of the glucose consumed was converted to lactate. Glucose uptake in the gas gland shows a very high dependence upon facilitated transport as evidenced by saturation of uptake of 2-deoxyglucose at a low extracellular concentration and a requirement for high levels of cytochalasin B for uptake inhibition despite the high efficacy of this treatment in heart and RBCs. Glucose transport is via glucose transporter 1 (GLUT1), which is localized to the glandular cells. GLUT1 western blot analysis from whole-tissue lysates displayed a band with a relative molecular mass of 52 kDa, consistent with the deduced amino acid sequence. Levels of 52 kDa GLUT1 in the gas gland were 2.3- and 33-fold higher, respectively, than those in heart and RBCs, respectively. Glucose phosphorylation is catalysed by hexokinase Ib (HKIb), a paralogue that cannot bind to the outer mitochondrial membrane. Transcript levels of HKIb in the gas gland were 52- and 57-fold more abundant, respectively, than those in heart and RBCs. It appears that high levels of GLUT1 protein and an unusual isoform of HKI are both critical for the high rates of glycolysis in gas gland cells.

Extracellular glucose supports lactate production but not aerobic metabolism in cardiomyocytes from both normoglycemic Atlantic cod and low glycemic short-horned sculpin

Fish exhibit a wide range of species-specific blood glucose levels. How this relates to glucose utilization is yet to be fully realized. Here, we assessed glucose transport and metabolism in myocytes isolated from Atlantic cod (Gadus morhua) and short-horned sculpin (Myoxocephalus scorpius), species with blood glucose levels of 3.7 and 0.57 mmol l(-1), respectively. Glucose metabolism was assessed by the production of (3)H2O from [2-(3)H]glucose. Glucose metabolism was 3.5- to 6-fold higher by myocytes from Atlantic cod than by those from short-horned sculpin at the same level of extracellular glucose. In Atlantic cod myocytes, glucose metabolism displayed what appears to be a saturable component with respect to extracellular glucose, and cytochalasin B inhibited glucose metabolism. These features revealed a facilitated glucose diffusion mechanism that accounts for between 30% and 55% of glucose entry at physiological levels of extracellular glucose. Facilitated glucose diffusion appears to be minimal in myocytes for short-horned sculpin. Glucose entry by simple diffusion occurs in both cell types with the same linear relationship between glucose metabolism and extracellular glucose concentration, presumably due to similarities in membrane composition. Oxygen consumption by myocytes incubated in medium containing physiological levels of extracellular glucose (Atlantic cod 5 mmol l(-1), short-horned sculpin 0.5 mmol l(-1)) was similar in the two species and was not decreased by cytochalasin B, suggesting that these cells have the capability of oxidizing alternative on-board metabolic fuels. Cells produced lactate at low rates but glycogen levels did not change during the incubation period. In cells from both species, glucose utilization assessed by both simple chemical analysis of glucose disappearance from the medium and (3)H2O production was half the rate of lactate production and as such extracellular glucose was not available for oxidative metabolism. Overall, extracellular glucose makes only a minor contribution to ATP production but a sustained glycolysis may be necessary to support Ca(2+) transport mechanisms at either the sarcoplasmic reticulum or the sarcolemmal membrane.

Extracellular glucose can fuel metabolism in RBCs from high glycemic Atlantic cod (Gadus morhua) but not low glycemic short-horned sculpin (Myoxocephalus scorpius)

Energy metabolism was assessed in RBCs from Atlantic cod and short-horned sculpin, two species that have markedly different levels of blood glucose. The objective was to determine if the level of extracellular glucose impacts rates of glucose metabolism. Blood glucose level was 2.5 mmol l-1 in Atlantic cod and 0.2 mmol l-1 in short-horned sculpin, respectively. Oxygen consumption, lactate production, and glucose utilization were measured in whole blood and related to g RBC. Glucose utilization was assessed by measuring both glucose disappearance and by the production of 3H2O from [2-3H]-glucose. RBCs from both species have an aerobic based metabolism. In Atlantic cod, extracellular glucose is sufficient to provide the sum of glucosyl equivalents to support both oxidative metabolism and lactate production. In contrast, extracellular glucose can account for only 10% of the metabolic rate in short-horned sculpin RBCs. In both species, about 70% of glucose enters the RBCs via facilitated transport. The difference in rates of extracellular glucose utilization is related to the extremely low levels of blood glucose in short-horned sculpin. In this species energy metabolism by RBCs must be supported by alternative fuels.

How social cognitive theory can help oncology-based health professionals promote physical activity among breast cancer survivors

PURPOSE

The majority of post treatment breast cancer survivors do not engage in physical activity (PA) at the recommended level. The promotion of PA among this group has the potential to dramatically improve quality of life and health outcomes. To maximise effectiveness, programs should be theory-based and address key determinants of PA behaviour. Social Cognitive Theory (SCT) has shown particular promise for developing and guiding PA interventions, but future research regarding how each SCT construct relates to PA among this group is needed. This study aims to explore how core SCT constructs impact on PA participation among post treatment breast cancer survivors, and gain greater insights into how to shape PA program strategies that will be appealing and effective for this group.

METHODS

Post treatment breast cancer survivors were recruited from the Breast Cancer Network Australia's review and survey group. Semi-structured telephone interviews examined PA patterns and SCT constructs and data were analysed thematically.

RESULTS

Eight post treatment breast cancer survivors participated in the study. Changes in activity level since diagnosis were common; in most cases this reflected a decline in PA. Key social cognitive and environmental influences on PA were described under the following themes: knowledge, outcome expectations, self-efficacy and personal, behavioural and environment facilitators and inhibitors.

CONCLUSION

The results of this study demonstrate the utility of SCT for guiding PA programs. Insight into how social cognitive factors may influence PA behaviour in this group is offered and direction for how oncology-based health professionals can promote PA among breast cancer survivors is provided.

Glucose uptake and metabolism by RBCs from fish with different extracellular glucose levels

The aim of the study was to assess if mechanisms of glucose trafficking by red blood cells (RBCs) relates to species specific extracellular glucose levels. Atlantic cod (Gadus morhua), Atlantic salmon (Salmo salar), cunner (Tautogolabrus adspersus), and short-horned sculpin (Myoxocephalus scorpius) had plasma glucose levels of 4 mmol l-1, 4.1 mmol l-1, 1.95 mmol l-1, and 0.73 mmol l-1, respectively. Glucose uptake by isolated RBCs was measured by the initial incorporation of [6-14C]-glucose and steady state glucose metabolism was determined by the production of 3H2O from [2-3H]-glucose. Saturation kinetics of glucose uptake and inhibition of both glucose uptake and metabolism by cytochalasin B and phloretin revealed that Atlantic cod, cunner, and sculpin RBCs all had a facilitated transport component to glucose trafficking. RBCs from Atlantic salmon showed a linear relationship between glucose uptake and extracellular glucose level but exhibited clear inhibition of glucose metabolism by cytochalasin B and phloretin suggesting a component of facilitated glucose transport that is more elusive to detect. The production of 3H2O was linear for at least 6 hr and as such presents a rigorous approach to measuring glycolytic rate. Steady state rates of glucose metabolism were achieved at extracellular levels of approximately 1 mmol l-1 glucose for RBCs from all species showing that within species normal extracellular glucose level is not a primary determinant of basal level of glycolysis. At physiological levels of extracellular glucose the ratio of initial glucose uptake to glucose metabolism was 1.5 to 4 for all RBCs suggesting that there is scope to increase metabolic rate without alteration of the basal glucose uptake capacity.

Expression analysis of glycerol synthesis-related liver transcripts in rainbow smelt (Osmerus mordax) exposed to a controlled decrease in temperature

Rainbow smelt (Osmerus mordax) accumulate high glycerol levels to avoid freezing at subzero temperatures. Glyceroneogenesis is activated by low temperature and occurs in liver via a branch in glycolysis and gluconeogenesis. In this study, carbohydrate and liver transcript levels of 21 genes potentially associated with glycerol production were assessed during a controlled warm to cold transition. Smelt were held at 8°C (warm smelt; non-glycerol accumulating) or subjected to a controlled decrease in water temperature from 8° to 0°C (cold smelt; glycerol accumulating) and sampled at the end of the temperature decrease and 1 mo later. In cold smelt compared with warm smelt, liver glycogen levels were lower and phosphoglucomutase transcript levels were higher. Plasma glycerol levels were higher and increased over time in cold smelt; in cold smelt, liver phosphofructokinase and pyruvate dehydrogenase kinase transcript levels increased over time. These findings imply that glycerol production is being fueled by glycogen degradation and inhibition of pyruvate oxidation serves to channel metabolic flux toward glycerol as opposed to complete glycolysis. Plasma glucose and liver glucose-6-phosphatase transcript levels were higher. Lipoprotein lipase transcript levels were higher, suggesting enhanced lipid breakdown to fuel energy metabolism. Glutamine synthetase transcript levels were higher, perhaps to store nitrogen for biosynthesis in spring.

Osmotic pressure-adaptive responses in the eye tissues of rainbow smelt (Osmerus mordax)

PURPOSE

The rainbow smelt (Osmerus mordax), is a teleost fish, which avoids freezing by becoming virtually isosmotic with seawater. The effects that such massive changes in osmolarity have on both its visual system and its highly evolved and specialized circulation are not known. New knowledge about the osmotic adaptation of the rainbow smelt eye is highly relevant to the adaptation and survival of this species and to its ability to feed as a visual predator in the face of environmental pressures. Moreover, the molecular physiologic response of the smelt to osmotic stress might provide valuable insights into understanding and managing mammalian pathological hyperosmolarity conditions, such as diabetes. We undertook the present study to provide an initial assessment of gene expression in ocular vasculature during osmotic adaptation in rainbow smelt.

METHODS

Immunohistochemistry with species cross reactive antibodies was used to assess blood vessel protein expression in paraffin sections. Western blotting was used to further verify antibody specificity for orthologs of mammalian blood vessel proteins in rainbow smelt. Thermal hysteresis and the analysis of glycerol concentrations in vitreous fluid were used to assess the physiologic adaptive properties of cold stressed eyes.

RESULTS

Glycerol levels and osmotic pressure were significantly increased in the vitreal fluid of smelt maintained at <0.5 °C versus those maintained at 8-10 °C. Compared to the 8-10 °C adapted specimens, the rete mirabile blood vessels and connecting regions of the endothelial linings of the choroidal vessels of the <0.5 °C adapted specimens showed a higher expression level of Tubedown (Tbdn) protein, a marker of the endothelial transcellular permeability pathway. Expression of the zonula occludens protein ZO-1, a marker of the endothelial paracellular permeability pathway showed a reciprocal expression pattern and was downregulated in rete mirabile blood vessels and connecting regions in the endothelial linings of choroidal vessels in <0.5 °C adapted specimens. Smelt orthologs of the mammalian Tbdn and zoluna occludens protein 1 (ZO-1) proteins were also detected by western blotting using anti-mammalian antibodies raised against the same epitopes as those used for immunohistochemistry.

CONCLUSIONS

This work provides the first evidence that molecules known to play a role in ocular vascular homeostasis are expressed and may be differentially regulated during anti-freezing cold adaptation in smelt eyes. We propose a hypothesis that in a state of cold-induced hyperosmolarity, changes in ZO-1 expression are associated with the passage of small solutes from the plasma space to ocular fluid, while changes in Tbdn expression regulate the passage of proteins between the ocular fluid and plasma space. This work also provides fundamental insight into the mechanisms underlying the adaptation of the blood-retinal barrier to metabolically relevant compounds such as glycerol.

Glycerol loss to water exceeds glycerol catabolism via glycerol kinase in freeze-resistant rainbow smelt (Osmerus mordax)

Rainbow smelt accumulate high amounts of glycerol in winter. In smelt, there is a predictable profile of plasma glycerol levels that starts to increase in November (<5 μmol/ml), peaks in mid-February (>200 μmol/ml), and thereafter decreases to reach the initial levels in the beginning of May. The aim of this study was to investigate the respective role of the two main mechanisms that might be involved in glycerol clearance from mid-February: 1) breakdown of glycerol to glycerol-3-phosphate through the action of the glycerol kinase (GK) and 2) direct loss toward the environment. Over the entire glycerol cycle, loss to water represents a daily loss of ∼10% of the total glycerol content of fish. GK activities were very low in all tissues investigated and likely have a minor quantitative role in the glycerol cycle. These results suggest that glycerol levels are dictated by the rate of glycerol synthesis (accelerated and deactivated during the accumulation and decrease stages, respectively). Although not important in glycerol clearance, GK in liver might have an important metabolic function for other purposes, such as gluconeogenesis, as evidenced by the significant increase of activity at the end of the cycle.

Seasonal changes in hepatic gene expression reveal modulation of multiple processes in rainbow smelt (Osmerus mordax)

Rainbow smelt (Osmerus mordax) are freeze-resistant fish that accumulate glycerol and produce an antifreeze protein during winter. Quantitative reverse transcription PCR (qPCR) and subtractive hybridization studies have previously revealed five genes in rainbow smelt liver to be differentially regulated in winter in comparison with the fall when water temperatures are warmer. In order to further define the suite of processes that are regulated seasonally, we undertook a large-scale analysis of gene expression by hybridization of smelt cDNA to the salmonid 16K cGRASP microarray. In total, 69 genes were identified as up-regulated and 14 genes as down-regulated under winter conditions. A subset of these genes was examined for differential regulation by qPCR in the individual cDNA samples that were pooled for microarray analysis. Ten of the 15 genes tested showed significant change in the same direction as microarray results, whereas one showed significant change in the opposite direction. Fructose-bisphosphate aldolase B and the cytosolic NAD-dependent glycerol-3-phosphate dehydrogenase were among the most highly up-regulated genes, a result supporting a metabolic focus on glycerol synthesis during winter. Modulation of other processes, including endoplasmic reticulum stress, lipid metabolism and transport, and protein synthesis, was also suggested by the qPCR analysis of array-identified genes. The 15 genes were subsequently examined by qPCR for seasonal variation in expression over five sampling times between October and March, and ten showed significant variation in expression over the sampling period. Taken together, these results provide new understanding of the biochemical adaptations of vertebrates to an extremely low seasonal temperature.

Relationship between food availability, glycerol and glycogen levels in low-temperature challenged rainbow smelt Osmerus mordax

Rainbow smelt Osmerus modax accumulate glycerol in winter that serves as an antifreeze. Fish were held at 8 degrees C, or subjected to a decrease in water temperature to -1 degrees C over a 19 day period, and subsequently maintained at -1 degrees C from 15 January to 11 May 2004. Starved fish did not survive the challenge of temperature decrease, with death ensuing above the typical freeze point for marine teleosts (-0.8 degrees C). A decrease in temperature activates the glycerol accumulation mechanism at about 5 degrees C with peak plasma levels exceeding 300 micromol ml(-1). Glycerol levels begin to decrease in late February even at water temperatures below -1 degrees C, suggesting either an inherent circannual or photoperiod trigger, possibly in association with sufficiently high levels of antifreeze protein. Glycogen levels in liver did not change significantly in starved fish maintained at 8 degrees C. However, liver glycogen was depleted in fish subjected to the low-temperature challenge and at a faster rate in starved than in fed fish. Stored glycogen in liver and other tissues can account for only a small amount of the total glycerol production, suggesting a strong requirement for food during accelerated glycerol production. Liver glycogen levels increased in April and May in association with the decrease in glycerol. Levels of glycerol in liver, kidney, spleen, gill, intestine, heart, muscle and brain follow the same pattern as that in plasma. During the early part of the glycerol accumulation phase, all tissues except for liver have lower levels of glycerol in the intracellular space than the levels in plasma. In liver, glycerol is in equilibrium between the two compartments.

Sequence of Atlantic cod (Gadus morhua) GLUT4, GLUT2 and GPDH:developmental stage expression, tissue expression and relationship to starvation-induced changes in blood glucose

cDNAs of putative glucose transporters, GLUT4 and GLUT2, were cloned from Atlantic cod (Gadus morhua). The GLUT4 cDNA encodes a 503 amino acid and the GLUT2 cDNA a 506 amino acid protein. Phylogenetic analysis, amino acid sequence alignment, and tissue distribution support categorizing them as homologues of mammalian GLUT4 and 2. GLUT4 clusters with GLUT4s from fish and other vertebrates. It shows 84% amino acid identity to GLUT4 from coho salmon and brown trout and 65% identity with other vertebrates. It is most highly expressed in heart, strongly expressed in red and white skeletal muscle and present at lower levels in gill, gonad, intestine, and kidney. GLUT2 clusters with GLUT2 from rainbow trout and other vertebrates. It shows 75% amino acid identity with rainbow trout and 62% identity with chicken GLUT2. In Atlantic cod, GLUT2 is most highly expressed in liver with lower levels noted in intestine and kidney.

Food deprivation for 2 months was used as a vehicle to monitor GLUT expression at different blood glucose levels. Starvation resulted in a decrease in blood glucose and liver glycogen that recovered following 20 days of re-feeding. GLUT4 expression in heart was decreased with starvation and increased with re-feeding. GLUT4 mRNA level in heart correlated with blood glucose. It is suggested that this relationship is related to insulin responsiveness. GLUT4 expression in white muscle increased with starvation and decreased with re-feeding. It is proposed that this is due to the necessity to maintain high levels of the glucose transporter protein in the face of starvation-associated proteolysis. GLUT2 expression in liver correlated with blood glucose, consistent with higher rates of glucose transport from liver to blood in the fed state than in the food-deprived state.

Glycerol-3-phosphate dehydrogenase (GPDH) cDNA was also cloned. It encodes a 351 amino acid protein, which is 73-90% identical to GPDH from numerous other fish species. GPDH is ubiquitously expressed. Expression in heart decreased with starvation and increased with refeeding, whereas expression in liver did not change with starvation.

In other studies, gene expression was monitored at nine time points from fertilization of eggs to larval development. GLUT4 is detectable in fertilized eggs and is fully expressed by the halfway to hatching point. GLUT2 is not evident at fertilization, is detectable at halfway to hatching, and fully expressed at hatching. GPDH expression was evident from fertilization.

Clinical efficacy and safety of dexmedetomidine and buprenorphine, butorphanol or diazepam for canine hip radiography

OBJECTIVES

To investigate the usefulness of dexmedetomidine for restraint and sedation during hip radiographic examination of hip-extended or stress-radiography views when combined with either buprenorphine, butorphanol or diazepam.

METHODS

One hundred and twenty-seven client-owned clinically healthy golden retrievers or rottweilers were enrolled in a clinical trial that compared hip-extended and PennHIP methods for diagnosing hip dysplasia and were randomly allocated to receive dexmedetomidine or medetomidine in combination with buprenorphine, butorphanol or diazepam. Subjective assessments were made for response to pain, response to noise, palpebral reflex, muscle tone and overall quality of sedation; non-invasive physiological variables were also recorded.

RESULTS

Overall quality of sedation was graded as good or excellent for dogs administered with a combination of butorphanol or diazepam. However, more dogs that received a combination involving buprenorphine had overall a relatively poorer quality of sedation and required additional administration of buprenorphine before the radiographic procedure could commence. Once sedated, clinically sufficient muscle relaxation accompanied by a very low proportion of dogs responding to pain or noise stimuli were observed in all treatment groups. Heart and respiratory rate, and procedure and recovery times were similar for all treatment groups, and no adverse events were observed during the study.

CLINICAL SIGNIFICANCE

Dexmedetomidine sedative protocols, particularly in combination with butorphanol and diazepam, can be used effectively and safely in dogs for radiographic procedures.

Accelerated hepatic glycerol synthesis in rainbow smelt (Osmerus mordax) is fuelled directly by glucose and alanine: a 1H and 13C nuclear magnetic resonance study

At seawater temperatures below 1 degrees C, rainbow smelt (Osmerus mordax) accumulate plasma levels of glycerol up to 400 mM. Aspects of the synthesis of glycerol in liver and its regulation were previously investigated, but the pathways leading to glycerol synthesis remained unconfirmed. Here, we report nuclear magnetic resonance (NMR) studies which elucidate, in more detail, the fuel sources for rapid glycerol synthesis in rainbow smelt. Initial NMR analysis of liver homogenates from fish held at cold (-1 degrees C) temperatures and from fish transferred from 8 degrees C to -1 degrees C showed elevated glycerol, whereas those from fish held at 8 degrees C had far lower glycerol levels. These results confirm a temperature-responsive glycerol synthesis and show that NMR is a suitable approach to investigate the phenomenon. Further studies with fish held at low temperature and injected with labelled L-[2,3-(13)C(2)] alanine or D-[U-(13)C(6)]glucose revealed conversion of both alanine and glucose to glycerol. (13)C spectra showed satellites ((1)J(CC)=41.1 Hz) about the glycerol resonances indicating intact incorporation of a (13)C-(13)C unit in liver glycerol of fish injected with L-[2,3-(13)C(2)]alanine and a (13)C-(13)C-(13)C unit in liver glycerol of fish injected with D[U-(13)C(6)]glucose. Thus, glycerol can be efficiently produced directly from amino acid precursors by glyceroneogenesis, which is an abbreviated gluconeogenesis process leading to glycerol through dihydroxyacetone phosphate (DHAP). Glucose can also be metabolised to glycerol via an abbreviated form of glycolysis that similarly leads to glycerol through DHAP.

Glycerol production in rainbow smelt (Osmerus mordax) may be triggered by low temperature alone and is associated with the activation of glycerol-3-phosphate dehydrogenase and glycerol-3-phosphatase

Rainbow smelt (Osmerus mordax) accumulate high levels of glycerol in winter that serves as an antifreeze. Fish were subjected to controlled decreases in water temperature and levels of plasma glycerol, liver metabolites and liver enzymes were determined in order to identify control mechanisms for the initiation of glycerol synthesis. In two separate experiments, decreases in temperature from 8 degrees C to 0 degrees C over a period of 10-11 days resulted in increases in plasma glycerol from levels of less than 4 mmol l(-1) to approximate mean levels of 40 (first experiment) and 150 mmol l(-1) (second experiment). In a third experiment, decreases in temperature to -1 degrees C resulted in plasma glycerol levels approaching 500 mmol l(-1). The accumulation of glycerol could be driven in either December or March, thus eliminating decreasing photoperiod as a necessary cue for glycerol accumulation. Glycerol accumulation in plasma was associated with changes in metabolites in liver leading to increases in the mass action ratio across the reactions catalyzed by glycerol-3-phosphate dehydrogenase (GPDH) and glycerol-3-phosphatase (G3Pase). The maximal, in vitro activity of GPDH, increased twofold in association with a sharp increase in plasma glycerol level. The metabolite levels and enzyme activities provide complementary evidence that GPDH is a regulatory site in the low temperature triggered synthesis of glycerol. Indirect evidence, based on calculated rates of in vivo glycerol production by liver, suggests that G3Pase is a potential rate-limiting step. As well, transient increases in glyceraldehyde-3-phosphate dehydrogenase and alanine aminotransferase suggest that these sites are components of a suite of responses, in rainbow smelt liver, induced by low temperature.

Seasonal freeze resistance of rainbow smelt (Osmerus mordax) is generated by differential expression of glycerol-3-phosphate dehydrogenase, phosphoenolpyruvate carboxykinase, and antifreeze protein genes

In winter, rainbow smelt (Osmerus mordax) accumulate glycerol and produce an antifreeze protein (AFP), which both contribute to freeze resistance. The role of differential gene expression in the seasonal pattern of these adaptations was investigated. First, cDNAs encoding smelt and Atlantic salmon (Salmo salar) phosphoenolpyruvate carboxykinase (PEPCK) and smelt glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were cloned so that all sequences required for expression analysis would be available. Using quantitative PCR, expression of beta actin in rainbow smelt liver was compared with that of GAPDH in order to determine its validity as a reference gene. Then, levels of glycerol-3-phosphate dehydrogenase (GPDH), PEPCK, and AFP relative to beta actin were measured in smelt liver over a fall-winter-spring interval. Levels of GPDH mRNA increased in the fall just before plasma glycerol accumulation, implying a driving role in glycerol synthesis. GPDH mRNA levels then declined during winter, well in advance of serum glycerol, suggesting the possibility of GPDH enzyme or glycerol conservation in smelt during the winter months. PEPCK mRNA levels rose in parallel with serum glycerol in the fall, consistent with an increasing requirement for amino acids as metabolic precursors, remained elevated for much of the winter, and then declined in advance of the decline in plasma glycerol. AFP mRNA was elevated at the onset of fall sampling in October and remained elevated until April, implying separate regulation from GPDH and PEPCK. Thus, winter freezing point depression in smelt appears to result from a seasonal cycle of GPDH gene expression, with an ensuing increase in the expression of PEPCK, and a similar but independent cycle of AFP gene expression.

A comparison of propofol infusion and propofol/isoflurane anaesthesia in dexmedetomidine premedicated dogs

The effects of propofol infusion were compared with propofol/isoflurane anaesthesia in six beagles premedicated with 10 microg/kg intramuscular (i.m.) dexmedetomidine. The suitability of a cold pressor test (CPT) as a stress stimulus in dogs was also studied. Each dog received isoflurane (end tidal 1.0%, induction with propofol) with and without CPT; propofol (200 microg/kg/min, induction with propofol) with and without CPT; premedication alone with and without CPT in a randomized block study in six separate sessions. Heart rate and arterial blood pressures and gases were monitored. Plasma catecholamine, beta-endorphin and cortisol concentrations were measured. Recovery profile was observed. Blood pressures stayed within normal reference range but the dogs were bradycardic (mean heart rate < 70 bpm). PaCO2 concentration during anaesthesia was higher in the propofol group (mean > 57 mmHg) when compared with isoflurane (mean < 52 mmHg). Recovery times were longer with propofol than when compared with the other treatments. The mean extubation times were 8 +/- 3.4 and 23 +/- 6.3 min after propofol/isoflurane and propofol anaesthesia, respectively. The endocrine stress response was similar in all treatments except for lower adrenaline level after propofol infusion at the end of the recovery period. Cold pressor test produced variable responses and was not a reliable stress stimulus in the present study. Propofol/isoflurane anaesthesia was considered more useful than propofol infusion because of milder degree of respiratory depression and faster recovery.

Assessing the efficacy of perioperative carprofen administration in dogs undergoing surgical repair of a ruptured cranial cruciate ligament

Twenty-one otherwise healthy dogs that presented for surgical repair of a ruptured cranial cruciate ligament were blindly and randomly given either carprofen (2.2 mg/kg body weight, orally) or a placebo beginning 12 hours preoperatively and continuing every 12 hours for a total of three doses. The patients were assessed for postoperative pain using a subjective pain score and given oxymorphone (0.1 mg/kg body weight, intramuscularly) every four hours if the pain score was 2 or greater. Blood samples were also collected to determine serum cortisol levels. There was a significant increase in serum cortisol levels in the immediate postoperative period in both the placebo group and the carprofen group (p less than 0.05). There was no significant difference in the percentage of increase in serum cortisol levels between the two groups. No correlation was evident between the serum cortisol levels and the corresponding pain scores in either group. This subjective method of assessing postoperative pain was not accurate and should not be relied upon for determination of postoperative analgesic administration. Perioperative oral administration of carprofen did not appear to be effective in controlling postoperative pain in these patients.

Detomidine-propofol anesthesia for abdominal surgery in horses

OBJECTIVE

To evaluate propofol for induction and maintenance of anesthesia, after detomidine premedication, in horses undergoing abdominal surgery for creation of an experimental intestinal adhesion model.

STUDY DESIGN

Prospective study.

ANIMALS

Twelve horses (424 +/- 81 kg) from 1 to 20 years of age (5 females, 7 males).

METHODS

Horses were premedicated with detomidine (0.015 mg/kg i.v.) 20 to 25 minutes before induction, and a propofol bolus (2 mg/kg i.v.) was administered for induction. Propofol infusion (0.2 mg/kg/min i.v.) was used to maintain anesthesia. The infusion rate was adjusted to maintain an acceptable anesthetic plane as determined by muscle relaxation, occular signs, response to surgery, and cardiopulmonary responses. Oxygen (15 L/min) was insufflated through an endotracheal tube as necessary to maintain the SpO2 greater than 90%. Systolic (SAP), mean (MAP), and diastolic (DAP) arterial pressures, heart rate (HR), electrocardiogram (ECG), respiratory rate (RR), SpO2 (via pulse oximetry), and nasal temperature were recorded at 15 minute intervals, before premedication and after induction of anesthesia. Arterial blood gas samples were collected at the same times. Objective data are reported as mean (+/-SD); subjective data are reported as medians (range).

RESULTS

Propofol (2.0 mg/kg i.v.) induced anesthesia (mean bolus time, 85 sec) within 24 sec (+/-22 sec) after the bolus was completed. Induction was good in 10 horses; 2 horses showed signs of excitement and these two inductions were not smooth. Propofol infusion (0.18 mg/kg/min +/- 0.04) was used to maintain anesthesia for 61 +/- 19 minutes with the horses in dorsal recumbency. Mean SAP, DAP, and MAP increased significantly over time from 131 to 148, 89 to 101, and 105 to 121 mm Hg, respectively. Mean HR varied over time from 43 to 45 beats/min, whereas mean RR increased significantly over anesthesia time from 4 to 6 breaths/min. Mean arterial pH decreased from a baseline of 7.41 +/- 0.07 to 7.30 +/- 0.05 at 15 minutes of anesthesia, then increased towards baseline values. Mean PaCO2 values increased during anesthesia, ranging from 47 to 61 mm Hg whereas PaO2 values decreased from baseline (97 +/- 20 mm Hg), ranging from 42 to 57 mm Hg. Muscle relaxation was good and no horses moved during surgery: Recovery was good in 9 horses and acceptable in 3; mean recovery time was 67 +/- 29 minutes with 2.4 +/- 2.4 attempts necessary for the horses to stand.

CONCLUSIONS

Detomidine-propofol anesthesia in horses in dorsal recumbency was associated with little cardiovascular depression, but hypoxemia and respiratory depression occurred and some excitement was seen on induction.

CLINICAL RELEVANCE

Detomidine-propofol anesthesia is not recommended for surgical procedures in horses if dorsal recumbency is necessary and supplemental oxygen is not available (eg, field anesthesia).

Propofol anesthesia

Although questions may still remain regarding the use of this unique sedative-hypnotic drug with anesthetic properties in high-risk patients, our studies have provided cardiopulmonary and neurological evidence of the efficacy and safety of propofol when used as an anesthetic under normal and selected impaired conditions in the dog. 1. Propofol can be safely and effectively used for the induction and maintenance of anesthesia in normal healthy dogs. Propofol is also a reliable and safe anesthetic agent when used during induced cardiovascular and pulmonary-impaired conditions without surgery. The propofol requirements to induce the safe and prompt induction of anesthesia prior to inhalant anesthesia with and without surgery have been determined. 2. The favorable recovery profile associated with propofol offers advantages over traditional anesthetics in clinical situations in which rapid recovery is important. Also, propofol compatibility with a large variety of preanesthetics may increase its use as a safe and reliable i.v. anesthetic for the induction and maintenance of general anesthesia and sedation in small animal veterinary practice. Although propofol has proven to be a valuable adjuvant during short ambulatory procedures, its use for the maintenance of general anesthesia has been questioned for surgery lasting more than 1 hour because of increased cost and marginal differences in recovery times compared with those of standard inhalant or balanced anesthetic techniques. When propofol is used for the maintenance of anesthesia in combination with a sedative/analgesic, the quality of anesthesia is improved as well as the ease with which the practitioner can titrate propofol; therefore, practitioners are able to use i.v. anesthetic techniques more effectively in their clinical practices. 3. Propofol can induce significant depression of respiratory function, characterized by a reduction in the rate of respiration. Potent alpha 2 sedative/analgesics (e.g., xylazine, medetomidine) or opioids (e.g., oxymorphone, butorphanol) increase the probability of respiratory depression during anesthesia. Appropriate consideration of dose reduction and speed of administration of propofol reduces the degree of depression. Cardiovascular changes induced by propofol administration consist of a slight decrease in arterial blood pressures (systolic, mean, diastolic) without a compensatory increase in heart rate. Selective premedicants markedly modify this characteristic response. 4. When coupled with subjective responses to painful stimuli, EEG responses during propofol anesthesia provide clear evidence that satisfactory anesthesia has been achieved in experimental dogs. When propofol is used as the only anesthetic agent, a higher dose is required to induce an equipotent level of CNS depression compared with the situation when dogs are premedicated. 5. The propofol induction dose requirement should be appropriately decreased by 20% to 80% when propofol is administered in combination with sedative or analgesic agents as part of a balanced technique as well as in elderly and debilitated patients. As a general recommendation, the dose of propofol should always be carefully titrated against the needs and responses of the individual patient, as there is considerable variability in anesthetic requirements among patients. Because propofol does not have marked analgesic effects and its metabolism is rapid, the use of local anesthetics, nonsteroidal anti-inflammatory agents, and opioids to provide postoperative analgesia improves the quality of recovery after propofol anesthesia. 6. The cardiovascular depressant effects of propofol are well tolerated in healthy animals, but these effects may be more problematic in high-risk patients with intrinsic cardiac disease as well as in those with systemic disease. In hypovolemic patients and those with limited cardiac reserve, even small induction doses of propofol (0.75-1.5 mg/kg i.v.) can produce profound hypotens

The use of propofol as an induction agent for halothane and isoflurane anesthesia in dogs

Cardiovascular, pulmonary, and quantitative electroencephalographic parameters were assessed in 12 anesthetized dogs to determine the compatibility of the injectable anesthetic propofol with halothane and isoflurane. No cases of apnea were observed during induction of anesthesia. An adequate level of anesthesia was established in each protocol as judged by both the lack of response to mechanical noxious stimuli (i.e., tail clamping) and evidence of reduction in total amplitude of brain wave activity. The initial propofol-mediated decrease in arterial blood pressure continued during either halothane (52.4%) or isoflurane (38%) anesthesia without a simultaneous increase in heart rate. The results of this study suggest that propofol, in combination with inhalant agents, can be used effectively and safely for canine anesthesia in veterinary practice.

Evaluation of selected cardiopulmonary and cerebral responses during medetomidine, propofol, and halothane anesthesia for laparoscopy in dogs

OBJECTIVES

To compare the dose-sparing effect of medetomidine on the propofol induction dose and concentration of halothane for maintenance of anesthesia during laparoscopy and to provide guidelines for effective and safe use of these anesthetics in dogs to ensure desirable perioperative analgesia.

ANIMALS

14 purpose-bred dogs.

PROCEDURE

Cardiopulmonary and electroencephalographic responses were determined during 2 anesthesia protocols in dogs scheduled for laparoscopy. Fifteen minutes before anesthesia induction, all dogs received atropine sulfate (0.02 mg/kg of body weight, i.m.). Seven dogs were then given propofol (6.6 mg/kg, i.v.); anesthesia was maintained with halothane in oxygen. The other dogs were given medetomidine hydrochloride (10 micrograms/kg, i.m.) 5 minutes after administration of atropine sulfate; anesthesia was then induced by administration of propofol (2.8 mg/kg, i.v.) and was maintained with halothane in oxygen.

RESULTS

The halothane concentration required for laparoscopy was lower in dogs given medetomidine. Anesthetic requirements were significantly increased during abdominal manipulation in both groups. Total amplitude of the electroencephalograph in medetomidine-treated dogs was not significantly lower than that in dogs not given medetomidine. Pulmonary responses were stable throughout all procedures. The primary cardiovascular response was an increase in blood pressure associated with the medetomidine-atropine preanesthetic combination. Significant differences in total amplitude or frequency shifts (spectral edge) of brain wave activity were not associated with surgical stimulation.

CONCLUSION

Lack of neurologic changes during laparoscopy supports the efficacy of either medetomidine-propofol-halothane or propofol-halothane combinations at higher concentrations to provide desirable analgesia and anesthesia in this group of dogs.

The use of propofol for induction of anaesthesia in dogs premeditated with acepromazine, butorphanol and acepromazine-butorphanol

Cardiovascular, pulmonary and anaesthetic-analgesic responses were evaluated in 18 male and female dogs to determine the effect of the injectable anaesthetic propofol used in conjuction with acepromazine and butorphanol. The dogs were randomly divided into three groups. Dogs in Group A were premeditated with 0.1 mg/kg of intramuscular acepromazine followed by an induction dose of 4.4 mg/kg of intravenous propofol; Group B received 0.2 mg/kg of intramuscular butorphanol and 4.4 mg/kg of intravenous propofol; dogs in Group AB were administered a premeditation combination of 0.1 mg/kg of intramuscular acepromazine and 0.2 mg/kg of intramuscular butorphanol, followed by induction with 3.3 mg/kg of intravenous propofol. The induction dose of propofol was given over a period of 30-60 seconds to determine responses and duration of anaesthesia. Observations recorded in the dogs included heart and respiratory rates, indirect arterial blood pressures (systolic, diastolic and mean), cardiac rhythm, end-tidal CO, tension, oxygen saturation, induction time, duration of anaesthesia, recovery time and adverse reactions. The depth of anaesthesia was assessed by the response to mechanical noxious stimuli (tail clamping), the degree of muscle relaxation and the strength of reflexes. Significant respiratory depression was seen after propofol induction in both groups receiving butorphanol with or without acepromazine. The incidence of apnea was 4/6 dogs in Group B, and 5/6 dogs in Group AB. The incidence of apnea was also correlated to the rate of propofol administration. Propofol-mediated decreases in arterial blood pressure were observed in all three groups. Moderate bradycardia (minimum value > 55 beats/min) was observed in both Groups B and AB. There were no cardiac dysrhythmias noted in any of the 18 dogs. The anaesthetic duration and recovery times were longer in dogs premeditated with acepromazine/butorphanol.

Differences in quantitated electroencephalographic variables during surgical stimulation of horses anesthetized with isoflurane

The effects of noxious surgical stimulation on the electroencephalogram (EEG) in 15 horses anesthetized with isoflurane were evaluated during orthopedic (group 1) and soft tissue (group 2) procedures. The quantitative EEG variables theta/delta ratio (T/D), alpha/delta ratio (A/D), beta/delta ratio (B/D), median power frequency (MED), and 80% spectral edge frequency (SEF 80) recorded during Surgeries at 1.7% end-tidal concentration of isoflurane (ET(iso)) were compared with values from five nonstimulated control horses anesthetized at 1,7% ET(iso). The EEG variables T/D, A/D, MED, and SEF 80 from surgically stimulated horses were significantly higher compared with controls. These differences in measured EEG variables were accompanied by a significantly lower relative power in the delta frequency band and a concomitant significantly higher alpha activity. Because the A/D ratio, MED, and SEF 80 in surgically stimulated horses were significantly higher than in nonstimulated control horses these measured EEG variables may provide a valuable tool for identification of nociceptive transmission in isoflurane anesthetized horses.

Biomechanical and histological evaluation of a laparoscopic stapled gastropexy technique in dogs

The biochemical holding strength and histological characteristics of a laparoscopic stapled gastropexy (LG) adhesion were compared with that of an incisional gastropexy (IG) adhesion. An LG was performed in 14 dogs and an IG was performed in six dogs. During the LG procedure, the abdomen was insufflated with carbon dioxide and three cannulae were placed in the caudal aspect of the right side of the abdomen. A 35 mm laparoscopic stapler was used to staple the gastric antrum to the adjacent right lateral abdominal wall. The IG procedure was performed through ventral midline celiotomy. A 35 mm IG was made by apposing the gastric antrum to the adjacent right lateral abdominal wall with two continuous rows of suture. Half of each group of dogs was euthanatized at 7 and 30 days after surgery. The mean tensile load to failure at 7 days was 44.86 +/- 18.54 N for the LG group and 85.33 +/- 23.59 N for the IG group (P < .05). At 30 days the values were 72.39 +/- 18.01 N for the LG group and 71.17 +/-12.11 N for the IG group (P = .41). The gastropexy adhesions in the 7-day postoperative group contained variable amounts of fibrin, hemorrhage, mononuclear cell inflammation, loose fibrovascular tissue, and mature collagenous connective tissue. Adhesions in the 7-day postoperative group were divided subjectively into three histological subgroups based on the relative amounts of mature connective tissue within the adhesion. The LG and IG adhesions were randomly distributed among these subgroups (P = 1.0). Adhesions in the 30-day postoperative group contained well-organized fibrous connective tissue. No difference in the amount of connective tissue could be detected histologically in the LG or IG adhesions. Complications with the LG procedure included stomach perforation (2 cases), splenic puncture (2 cases), and subcutaneous emphysema (4 cases).

Quantitative electroencephalographic evaluation to determine the quality of analgesia during anesthesia of horses for arthroscopic surgery

We compared the anesthetic combination of detomidine, ketamine, and halothane in control horses not undergoing apparently painful procedures with that in horses during arthroscopic surgery. The effectiveness of this regimen in suppressing neurologic response to surgery was, thus, evaluated. In this study, significant differences were not observed in electroencephalographic total amplitude, spectral edge, or beta-to-delta frequency ratio between surgically treated and nonsurgically treated (control) horses. On the basis of its attenuation of encephalographic responses, we conclude that detomidine (20 micrograms/kg of body weight, IV) and ketamine (2.2 mg/kg, IV) induction of anesthesia followed by maintenance with halothane is an effective regimen for control of pain in horses during arthroscopic surgery. The insignificant frequency changes observed without any other signs of inadequate anesthesia or pain may indicate a surgical stress response. We hypothesize that brain activity monitoring may give an earlier index to initiation of surgically induced stress than do hormonal responses, because endocrine alterations are not as rapidly perceived as is the electroencephalogram. Analysis of spectral edge frequency changes could be used to evaluate anesthetic regimens to find those that cause the least stress to the CNS during surgery in horses. Differences in species responses to an anesthetic agent or the regimen's effectiveness in prevention of pain during surgery may be identified by adoption of the study model. Evaluation of cardiopulmonary variables during anesthesia, with and without surgery, did not reveal any alterations that would be relevant to CNS responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of medetomidine administration on intracranial pressure and cardiovascular variables of isoflurane-anesthetized dogs

Intracranial pressure and cardiovascular variables after IV administration of medetomidine (0.03 mg/kg of body weight) were evaluated in 6 healthy, mixed-breed dogs anesthetized with 1.3% end-tidal isoflurane concentration and mechanically ventilated to normocapnia (PaCO2, 35 to 45 mm of Hg). Baseline values were determined for intracranial pressure, heart rate, arterial blood pressure, cardiac output, mean pulmonary artery pressure, pulmonary capillary wedge pressure, central venous pressure, end-tidal CO2 tension and isoflurance concentration, arterial pH and CO2 and O2 tensions, and core body temperature. Cerebral perfusion pressure, cardiac index, systemic and pulmonary vascular resistances, plasma HCO3- concentration, and base excess were calculated. Intracranial pressure was measured, using a calibrated, fiberoptic transducer placed within the brain parenchyma and secured to the calvarium by means of a subarachnoid bolt. Cardiac output was determined by thermodilution. End-tidal CO2 tension and isoflurane concentration were determined, using an infrared gas analyzer. Administration of medetomidine did not change intracranial pressure, but was associated with significant (P < 0.05) decreases in values for heart rate, cardiac index, end-tidal CO2, and HCO3- and with significant increases in systolic, mean, and diastolic pressure; pulmonary artery pressure; systemic vascular resistance; central venous pressure; and pulmonary capillary wedge pressure.

Electroencephalography of detomidine-ketamine-halothane and detomidine-ketamine-isoflurane anesthetized horses during orthopedic surgery. A comparison

This study was done to compare the electroencephalographic (EEG) response evoked by orthopedic surgery in halothane- and isoflurane-anesthetized horses. Eight horses scheduled for bilateral arthroscopic surgery of the stifle were premedicated with detomidine (20 micrograms/kg) intravenously and five minutes later induced to anesthesia with ketamine (2.2 mg/kg) intravenously. Anesthesia was maintained with either halothane or isoflurane. Assignment of inhalation anesthetic was done randomly. The multiple of minimal alveolar concentration (MAC) of halothane required for anesthesia was significantly higher than the multiple of MAC of isoflurane (p < .05) required. Total amplitude of the EEG with halothane was smaller than with isoflurane (p < .05), but 13.0 to 32.0 Hz high frequency/0.0 to 3.9 Hz low frequency (beta/delta) ratio was greater for halothane (p < .05). Arterial partial pressure of oxygen (PaO2) was significantly (p < .05) higher with isoflurane than with halothane. The differences in EEG frequency shift observed suggest that isoflurane provided better analgesia than halothane for this group of horses.

Reduction of isoflurane anesthetic requirement by medetomidine and its restoration by atipamezole in dogs

The isoflurane-sparing effect of the alpha 2-adrenergic agonist medetomidine (30 micrograms/kg of body weight, IV) was tested in 7 dogs, using a blinded, randomized-block study design. The baseline minimal alveolar concentration (MAC) of isoflurane was 1.18 vol% (95% confidence interval [0.97,1.39]). Medetomidine significantly (P < 0.003) reduced isoflurane MAC by 47.2%. Atipamezole (0.3 mg/kg, IV), an alpha 2-adrenergic antagonist, completely reversed the effect of medetomidine on isoflurane MAC. Atipamezole alone did not significantly alter isoflurane MAC. After medetomidine administration, marked bradycardia developed in all dogs and persisted for more than 2 hours. Mean arterial blood pressure increased acutely, but later decreased, and hypotension persisted for more than 2 hours. Atipamezole reversed the bradycardic and hypotensive effects of medetomidine. Results of this study indicate that medetomidine may be useful in clinical cases in which isoflurane MAC-reduction is desirable and that atipamezole might be used to reverse desirable and undesirable effects of medetomidine during isoflurane anesthesia.

Advantages and guidelines for using halothane

Halothane is a frequently used agent. Its cost is inexpensive. Halothane is a safe and effective anesthetic agent if used properly. Proper usage includes adjusting the concentration administered to produce adequate anesthesia for the procedure without excess depression of cardiac, respiratory, and neurologic function. Proper monitoring of the patient indicates the adjustments needed in concentration or needed medications or procedures to increase safe usage. Potent tranquilizers, sedatives, and analgesics used as preanesthetics during halothane anesthesia or the early postanesthetic period may produce profound changes in anesthetic concentrations required or physiologic responses to the combined medications.

The case for high gas flows

High gas flows provide a higher margin of safety and fewer physiologic complications for extended anesthetic periods. The veterinarian should consider personnel, anesthetic, and monitoring equipment and the surgical procedure requiring anesthesia before making a final decision on which flow rates are appropriate.

Comparison of neurologic responses to the use of medetomidine as a sole agent or preanesthetic in laboratory beagles

Different dose regimens of medetomidine (a potent alpha 2-adrenergic agonist), adding up to a combined dose of 80 micrograms/kg, were administered to laboratory beagles to determine physiologic responses including neurologic. The study was intended to determine EEG responses where sufficient sedative and analgesic effects are reached with medetomidine and in contrast its effects when used with ketamine or halothane. Cardiopulmonary responses were very similar in each dose regimen, showing the characteristic properties of single doses of 80 micrograms/kg of medetomidine. Effective sedative and analgesic duration seemed to be a function of when the largest dose was administered. Adequate additional sedative and analgesic could be gained from injections at doses of half of the initial one. The potent sedative and analgesic effects of medetomidine confirmed by neurologic evaluation supports its potential use as a premedication to general anesthesia in dogs. In this study, 2 different doses of medetomidine were also tested as premedication to both ketamine HCI and halothane anesthesia. Neorologic responses were determined at the same time cardiopulmonary parameters, anesthetic quality, and dose requirements were recorded. Medetomidine was found to have favorable qualities in conjunction with these anesthetics. Cardiopulmonary parameters remained satisfactory in both groups as preanesthetic medication prior to halothane, but no additional benefits could be seen from doses of 40 micrograms/kg medetomidine compared to 20 micrograms/kg, except a significant 30% reduction in halothane requirement. The positive chronotropic and inotropic properties of ketamine restored the medetomidine-induced bradycardia and produced a short anesthetic period of 15 to 30 min depending on the dose of medetomidine. The quality of anesthesia was better when 40 micrograms/kg medetomidine was used, but recovery was quicker with 20 micrograms/kg medetomidine. Medetomidine significantly reduced cerebral activity as demonstrated by recordings of total amplitude and frequency evaluation of the EEG with compressed spectral analysis. This analytical method was effective in confirming clinical signs of sedation, analgesia, and anesthesia in canine subjects.

Effects of anticholinergic treatment on the cardiac and respiratory systems in dogs sedated with medetomidine

Alpha 2-adrenergic agonists are often used for sedation and, or, analgesia in dogs, but they are often associated with bradycardia and in some animals with atrioventricular heart block. In this study, atropine or glycopyrrolate either helped to maintain the heart rates or were effective in increasing reduced heart rates of dogs treated with medetomidine. In the process, however, cardiac dysrhythmias often developed. These dysrhythmias were predominantly associated with the combined responses to the medetomidine and the anticholinergic agent because there were no significant changes in respiratory function. A reduced blood oxygen content or increased blood carbon dioxide can contribute to cardiac irritability. Atropine and glycopyrrolate were more effective in preventing bradycardia and had less undesirable side effects when they were given before the administration of medetomidine.

Electroencephalographic power spectrum analysis as a monitor of anesthetic depth in horses

Electroencephalographic (EEG) power spectrum analysis was performed in 18 conscious, adult horses for evaluation as control values for EEG data obtained during anesthesia. Computer-processed total amplitudes for the frequency range 0 to 32 Hz were mainly between 400 and 600 microV, with 80% spectral edge frequency between 16.6 and 32.5 Hz. The highest electrical activity was in the delta band (41.3 +/- 4.4% of total amplitude); there was a less pronounced activity in the beta (34.2 +/- 5.2%), theta (13.6 +/- 1.5%), and alpha (10.0 +/- 1.0%) bands. The applicability of EEG power spectrum analysis as a guide to depth of anesthesia was evaluated in four horses by comparing simultaneously recorded EEG data and clinical signs of anesthesia. Global changes in cerebrocortical electrical activity were detected with a single, monopolar (left frontoatlanto-occipital) EEG lead. Increasing depth of halothane anesthesia was accompanied by a pronounced shift in EEG activity from beta to theta and delta frequency bands, a decrease in 80% spectral edge frequency from 21.5 +/- 2.4 Hz to 12.6 +/- 2.2 Hz, a reduction in the beta/delta ratio of fractional amplitudes from 2.37 +/- 0.84 to 0.49 +/- 0.04, and a slight inconsistent increase in total amplitude from 96.1 +/- 37.3 microV to 185.5 +/- 53 microV. These results show that changes in the clinical signs of anesthetic depth in horses can be described numerically by use of EEG power spectrum analysis.

Treatment of low arterial oxygen tension in anesthetized horses with clenbuterol

Clenbuterol (0.8 microgram/kg intravenously) was administered to 10 anesthetized horses with an abnormally low PaO2 (less than 90 mm Hg) despite controlled ventilation with an oxygen-rich gas mixture. Results were compared with those from 10 controls to which no clenbuterol was given and in which conventional methods to increase PaO2 were ongoing. Horses treated with clenbuterol had higher PaO2 values for at least 90 minutes. Clenbuterol was associated with increased heart rate and profuse sweating. Clenbuterol can be administered intravenously to increase the PaO2 of mechanically ventilated horses that have low arterial oxygen tension while under inhalation anesthesia. Further studies are warranted to define more precisely the circumstances under which clenbuterol may be used safely.

Cardiac dysrhythmias during anesthesia for cervical decompression in the dog

In a retrospective study, the risk for cardiac dysrhythmias was evaluated in dogs undergoing ventral decompression and/or fenestration of the cervical spine (CERV) and compared with that for dogs undergoing dorsal laminectomy for decompression of the thoracic or lumbar spine (TL). The dogs in the CERV subset (48 dogs) tended to be heavier and older than the dogs in the TL subset (111 dogs). There was no apparent bias detected in treatment before anesthesia and surgery. The risk for dysrhythmias was 2.5 times greater in the CERV subset, compared with that in the TL subset (P less than 0.01). The risk for ventricular premature contraction was 3.5 times higher in the CERV group (P less than 0.05). Bradycardia was found in 6 dogs from the CERV subset and was not found in any dogs from the TL subset. A logistic model was derived from the data and may be used to evaluate the risk for dysrhythmias in similar patients undergoing similar surgery and anesthesia. This model uses age, preoperative heart rate, and site of surgery (CERV or TL) to estimate the risk.

Isoflurane anesthesia for equine colic surgery. Comparison with halothane anesthesia

Isoflurane was compared with halothane as an anesthetic agent for emergency colic surgery in a series of 38 juvenile and adult horses. After presurgical stabilization with fluids and supportive medications, anesthesia was induced by intravenous xylazine and/or diazepam followed by ketamine. Anesthesia was maintained with isoflurane or halothane in oxygen with controlled ventilation. Heart rates (HR), arterial blood gases, mean arterial pressures (MAP), rate pressure products (RPP), requirements for cardiovascular support medications, and recovery times to standing were compared using nonparametric methods. Cardiopulmonary responses to isoflurane and halothane anesthesia were generally comparable although some temporal differences were observed. Higher HR (p less than 0.02) and lower PaCO2 levels (p less than 0.01) were identified during the course of isoflurane anesthesia. Recovery times to standing were significantly shorter (0.02 less than p less than 0.05) after isoflurane than halothane anesthesia.

Anesthetic and supportive management during experimental pulsatile flow perfusion studies in calves

The purpose of this study was to determine the factors influencing successful experimental cardiopulmonary bypass studies using pulsatile flow perfusion and the medications and methodology necessary to produce successful bypass in calves. In six calves showing no cardiopulmonary pathology prior to bypass procedures, successful anesthesia and surgical intervention was accomplished. Animals were maintained on 5 hours of pulsatile flow bypass perfusion. Successful recovery from the procedures was accomplished. In two calves with pre-existing pulmonary pathology, anesthetic and surgical intervention was accomplished with the utilization of extensive anesthetic management and cardiac supportive medications until the animals could be initiated into 5 hours of pulsatile flow bypass perfusion, in spite of major pulmonary dysfunction. In these two animals, attempts to resuscitate upon termination of pulsatile flow perfusion were unsuccessful due to pre-existing excessive lesions in the lungs. This study shows a contrast between complete success of a pulsatile flow system in normal subjects versus the ultimate failure in experimental animals with pre-existing pulmonary pathology. The inability of experimental calves with a diseased lung to resume spontaneous cardiopulmonary function after the challenges of thoracic intervention indicates the unsuitability of animals with marked pre-existing pulmonary disease status for use in cardiopulmonary bypass studies.

Preanesthetic medications in ruminants and swine

The use of preanesthetic agents alone or in various combinations in food animals is complex. In addition to considering the pharmacokinetics and dynamics of the medications, one must give additional consideration to the animals's temperament, its physical condition, and its environment. Also, the potential of residues from meat and milk products of animals treated with preanesthetic agents must be considered.