Transcriptional cofactor dyxin mediates hypertrophic response in the heart during angiotensin II-induced hypertension.

Dyxin is a LIM-domain containing transcriptional regulator protein shown to play a role in a hypertrophic response in the heart. Here, the effect of adenoviral dyxin overexpression was studied on cardiac function and gene expression in the normal heart and in angiotensin II (Ang II)-induced hypertension in rats. The adenovirus-mediated intramyocardial gene transfer of dyxin (1.5x109 infectious units/animal) was performed into the left ventricle (LV) of Sprague-Dawley rats with and without the Ang II (33 µg/kg/h) infusion, administered via osmotic minipumps for 1 and 2 weeks. Echocardiography was used to assess the structural and functional changes. Dyxin expression and localization in the heart was analyzed with quantitative RT-PCR and immunohistochemistry, respectively. In the normal rat heart, the adenoviral overexpression of dyxin did not alter LV function in normal hearts as assessed by echocardiography. Dyxin was found to be localized in the cardiomyocytes as shown by the immunohistochemical staining. In Ang II-induced hypertrophy, echocardiographic data revealed a significant increase in the posterior wall diameter both in systole (21%, P<0.05) and diastole (21%, P<0.01) as well as in the diameter of the interventricular septum in systole (19%, P<0.05) in the dyxin-injected group compared with the LacZ-injected animals after two weeks of Ang II infusion. Interestingly, a significant decrease in the levels of both atrial natriuretic peptide (ANP) mRNA (55%, P<0.01) and B-type natriuretic peptide (BNP) mRNA (68%, P<0.05) was observed in the dyxin-injected group compared with the LacZ control group after one week of Ang II infusion. These results indicate that dyxin overexpression was deteriorative against pressure overload by inducing structural changes in the LV in rats. Interestingly, simultaneous adenoviral overexpression of dyxin suppressed the Ang II-induced changes of ANP and BNP genes suggesting that dyxin might have a role as a regulator of the cardiac hypertrophic gene program.

Tumour necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor Fn14 during cardiac remodelling in rats.

AIM: Accumulating evidence supports the concept that proinflammatory cytokines play an essential role in the failing heart. We examined the concomitant tumour necrosis factor-like weak inducer of apoptosis (TWEAK)/Fn14 expression in myocytes in vitro as well as in vivo in cardiac remodelling. METHODS: We assessed TWEAK and its receptor Fn14 expression in response to angiotensin (Ang) II, myocardial infarction (MI) as well as to local adenovirus-mediated p38 gene transfer in vivo. The effect of various hypertrophic factors and mechanical stretch was studied in neonatal rat ventricular myocyte cell culture. RESULTS: Ang II increased Fn14 levels from 6 h to 2 weeks, the greatest increase in mRNA levels being observed at 6 h (6.3-fold, P < 0.001) and protein levels at 12 h (4.9-fold, P < 0.01). TWEAK mRNA and protein levels remained almost unchanged during Ang II infusion. Likewise, a rapid and sustained elevation of Fn14 mRNA and protein levels in the left ventricle was observed after experimental MI. Moreover, local p38 gene transfer increased Fn14 mRNA and protein but not TWEAK levels. Fn14 immunoreactive cells were mainly proliferating non-myocytes in the inflammation area while TWEAK immunoreactivity localized to cardiomyocytes and endothelial cells of the coronary arteries. Hypertrophic agonists and lipopolysaccharide increased Fn14 but not TWEAK gene expression in neonatal rat myocytes, while mechanical stretch upregulated Fn14 and downregulated TWEAK gene expression. CONCLUSIONS: In conclusion, the cardiac TWEAK/Fn14 pathway is modified in response to myocardial injury, inflammation and pressure overload. Furthermore, our findings underscore the importance of Fn14 as a mediator of TWEAK/Fn14 signalling in the heart and a potential target for therapeutic interventions.

Variation of plasma protein parameters in four free-ranging reindeer herds and in captive reindeer under defined feeding conditions.

Plasma total protein (TP), albumin (ALB) and globulin (GLOB) concentrations and albumin/globulin ratio (A/G) were analysed from blood samples collected from free-ranging reindeer (Rangifer tarandus tarandus) herds at varying times of year. The same parameters were followed in nine captive reindeer with varying protein and energy intake. Variation in the blood constituents of free-ranging reindeer was analysed in relation to different extrinsic and intrinsic factors and compared to findings from captive animals, allowing the analysis of effects of protein and energy intake. There was large overall variation in TP, ALB, GLOB and A/G ratio in the free-ranging animals, ranging between 36-110 g/L, 18-59 g/L, 17-59 g/L and 0.5-2.1. The variation between months and years was significant for all variables except the A/G ratio, where no year effect was noted. Increase in live body mass was associated with a small significant increase and pregnancy with a small significant decrease in all dependent variables, except for the A/G ratio. Age did not have a significant effect on any of the blood constituents when body mass was included in the same model. In captive animals, feeding lichens with low protein content was related to a significant decline in TP, ALB and GLOB, but not in the A/G ratio, whereas feeding commercial ration increased plasma TP, ALB and GLOB significantly. Extrinsic factors such as season and year explained majority of variation in the blood constituents of free-ranging reindeer, whereas body mass, pregnancy and age had only a minor influence. It is concluded that plasma TP and ALB, and to a lesser extent GLOB and A/G ratio may serve as nutritional biomarkers of reindeer.

Endocrinology of pregnancy and early pregnancy detection by reproductive hormones in reindeer (Rangifer tarandus tarandus).

The endocrinology was studied throughout pregnancy in reindeer (Rangifer tarandus tarandus) located in Oulu, Finland (65 degrees N, 25 degrees E) with 13 captive, semi domestic adult females. Blood samples were analyzed for plasma progesterone (P4), estradiol (E2) and estrone sulphate (E1SO4), 15-ketodihydro-PGF2alpha (PG-metabolite) and pregnancy associated glycoproteins (PAG). The mean plasma P4 concentration peaked twice during gestation: at around 24 and three weeks prior to calving. In pregnant females the plasma PAG concentration increased over basal concentrations 21-30 days after the estimated day of conception and peaked at the time of calving. The concentrations of E2 and E1SO4 remained low until 60 days before calving when a rapid increase was found for both hormones. The mean plasma concentration of PG-metabolite increased throughout pregnancy to a maximum at parturition. The estimated mean (range) gestation length was 216 (212-220) days. Judged from measures on reproductive organs collected from 86 free-ranging, semi-domestic female reindeer of unknown age presented for slaughter at Roros, Norway (63 degrees N, 11 degrees E) in the second week of December 1999, it was concluded that the breeding season lasted from early September until the end of November. The results also showed that plasma PAG concentration could provide a tool for detection of pregnancy in reindeer.

The effect of blood sampling method on indicators of physiological stress in reindeer (Rangifer tarandus tarandus).

The effects of manual blood sampling and remote blood sampling using automatic blood sampling equipment (ABSE) on plasma cortisol and catecholamine concentrations were studied on eight adult female reindeer (Rangifer tarandus tarandus). Contemporary body temperatures and heart rates were also recorded to determine their utility as other possible stress indicators. The animals were blood sampled once every hour with ABSE on 9-10 May and then by manual blood sampling on 13-14 May. Animals were also fitted with equipment to record heart rate and body temperature. Heart rate and body temperature were also recorded continuously without blood sampling on 17-18 May in undisturbed control conditions. Plasma cortisol concentrations were five-to-six fold greater during manual blood sampling compared to sampling with ABSE (F(1,3) = 13.34, P < 0.05). Plasma noradrenaline concentrations were significantly higher (F(1,3) = 22.98, P < 0.05) during manual blood sampling compared to sampling with ABSE, whereas plasma adrenaline concentrations did not differ. Heart rate was higher during manual blood sampling compared to control values. Body temperature was significantly higher during manual sampling compared to values recorded without blood sampling (F(1,4)= 31.65, P < 0.01). In conclusion, plasma cortisol concentration provides an excellent indicator of handling stress in reindeer. The use of ABSE for blood sampling enables measurements of plasma cortisol levels close to basal concentrations that may be used for reference values in studies where indicators of physiological stress are required.

Individually coded telemetry: a tool for studying heart rate and behaviour in reindeer calves.

The aim of the study was to test the performance of a silver wire modified version of the coded telemetric heart rate monitor Polar Vantage NV (PVNV) and to measure heart rate (HR) in a group of captive reindeer calves during different behaviour. The technical performance of PVNV HR monitors was tested in cold conditions (-30 degrees C) using a pulse generator and the correlation between generated pulse and PVNV values was high (r=0.9957). The accuracy was tested by comparing the HR obtained with the PVNV monitor with the standard ECG, and the correlation was significant (r=0.9965). Both circadian HR and HR related to behavioural pattern were recorded. A circadian rhythm was observed in the HR in reindeer with a minimum during night and early morning hours and maximum at noon and during the afternoon, the average HR of the reindeer calves studied being 42.5 beats/min in February. The behaviour was recorded by focal individual observations and the data was synchronized with the output of the HR monitors. Running differed from all other behavioural categories in HR. Inter-individual differences were seen expressing individual responses to external and internal stimuli. The silver wire modified Polar Vantage NV provides a suitable and reliable tool for measuring heart rate in reindeer, also in natural conditions.

Plasma urea, creatinine, and urea: creatinine ratio in reindeer (Rangifer tarandus tarandus) and in Svalbard reindeer (Rangifer tarandus platyrhynchus) during defined feeding conditions and in the field.

Variation in plasma urea and creatinine concentration and plasma urea:creatinine ratio (U:C) were studied in semidomestic free-ranging reindeer (Rangifer tarandus tarandus) on the Norwegian mainland, in wild Svalbard reindeer (Rangifer tarandus platyrhynchus), and in captive reindeer maintained either on a lichen-based diet or a protein-rich concentrate to investigate whether these parameters could be used as indicators of the nutritional status of reindeer. In the mainland animals, plasma creatinine concentration was high in winter and early spring and decreased by two-thirds toward the summer. The overall range in mean plasma creatinine concentration (+/-SE) was from 90+/-1.26 to 280+/-2.88 micromol/L. Mean plasma urea concentration (+/-SE) varied from 2.46+/-0.10 in winter up to 17.44+/-0.29 mmol/L in summer and autumn. Month of sampling explained 65% and 90% of the variation in plasma urea and creatinine concentrations, respectively, indicating that seasonality in the diet had the greatest influence on these parameters. Reindeer given lichens as the only feed showed an increase in plasma creatinine and a decrease in plasma urea concentration. Food restriction caused a temporary elevation in urea level but had no significant effect on plasma creatinine concentration. The slight effect of energy intake on urea and creatinine levels was supported by the fact that severe undernutrition in the Svalbard reindeer population had only a small effect on plasma urea and creatinine levels. Protein-rich pellet feed increased plasma urea from around 3 mmol/L to above 10 mmol/L and reduced creatinine concentrations to less than 100 micromol/L, suggesting that the protein content of forage is an important determinant of these blood parameters. Mean U:C ratio (+/-SE) in plasma varied from 8.9+/-0.28 to 120.8+/-1.88. Ratios above 20 appeared when protein intake was low and energy intake was restricted or when protein intake was high. Low ratios occurred when protein intake was low but energy intake adequate. Plasma urea and creatinine concentrations and the U:C ratio showed complex dynamics that were affected by both season and the protein and feed intake. We conclude that they appear to be difficult to interpret as single measures of nutritional status of reindeer.