L-lactate dehydrogenase (LDH) cDNAs encoding for LDH-A4 (muscle) and LDH-B4 (heart) isozymes from caiman (Caiman crocodilus apaporiensis) belonging to the order Crocodilia were sequenced. The phylogenetic relationships of the newly determined cDNA and their deduced protein sequences, as well as the previously published sequences of vertebrate LDH isozymes were analyzed by various phylogenetic tree construction methods. These results indicated that Chelonia is indeed more closely related to Crocodilia. The divergent times between caiman and alligator, Chelonia and Crocodilia, were estimated to be approximately 36, 177 million years, respectively. £`-crystallin/Lactate dehydrogenase B cDNA from caiman (Caiman crocodilus apaporiensis), Pekin duck (Anas platyrhynchos), Muscovy duck (Cairina moschata) and Greylag goose (Anser anser) eye lens were sequenced. Accorcding to cDNA sequences, duck lens £`¡Vcrystallin and heart LDH-B are the products of the same gene. In amino acid sequences, two residues Asn-114 and Phe-118 are well conserved in£`-crystallin/ LDH-B among caiman, Muscovy duck and Greylag goose except in Pekin duck which are replaced by glycine residues. The lens protein composition, LDH activity and£`-crystallin/ LDH B4 protein structure of caiman and three avians were analyzed and compared. The results show no significant differences in conformational or enzymatic properties between Pekin duck £`-crystallin and caiman, Muscovy duck and Greylag goose £`-crystallin. The unique replacement of both Asn-114 and Phe-118 by Gly residues in Pekin duck £`-crystallin amino acid sequence might therefore be due to the selective pressure during the recruitment processes of active enzyme into avian lens£`-crystallins.

The purpose of this study was to compare the concentration of and the time to peak blood lactate following three 90-s cycle ergometer tests--intermittent all-out (Int-A), continuous all-out (Cont-A), and continuous constant (Cont-C), and to compare group peak lactate to blood lactate at individual peak time. Eight fingertip blood samples were drawn between 1 and 12min post-exercise. Subjects were university hockey players (n = 19) and physical education students (n = 19). The two all-out tests had a higher peak concentration than the Cont-C test (P $<$ 0.05). The Int-A test had an earlier peak than the two continuous tests (P $<$ 0.05) but this difference vanished if peak time was measured from the onset of the tests. A number of sampling times had lactate concentrations similar to the individual peak concentration (P $<$ 0.05): (1) 1, 2, 3, and 4min for Int-A; (2) 2, 3, 4, 5, and 6min for Cont-A; (3) 2 and 4min for Cont-C.

Increased glucose metabolism may occur in malignant tumours due to altered gene expression or a response to hypoxia. It has been shown that tumours with high levels of glycolysis, indicated by elevated lactate, are less responsive to radiotherapy. It is not clear whether this effect is caused by lactate itself or rather that high lactate is a surrogate for a radioresistant property such as hypoxia. Furthermore, we are not aware of studies that examine the manipulation of lactate production in tumours to alter radiation response. We propose a novel approach of metabolic targeting of HIF-1 to address these issues. HIF-1 is a major regulator of glycolysis and its inhibition would decrease malignant cell metabolism and could lead to a decrease in lactate production. The goal of this pre-clinical study was to evaluate metabolic targeting as a strategy of enhancing radiation response by inhibiting the HIF-1 transcription factor.

Increased glucose metabolism may occur in malignant tumours due to altered gene expression or a response to hypoxia. It has been shown that tumours with high levels of glycolysis, indicated by elevated lactate, are less responsive to radiotherapy. It is not clear whether this effect is caused by lactate itself or rather that high lactate is a surrogate for a radioresistant property such as hypoxia. Furthermore, we are not aware of studies that examine the manipulation of lactate production in tumours to alter radiation response. We propose a novel approach of metabolic targeting of HIF-1 to address these issues. HIF-1 is a major regulator of glycolysis and its inhibition would decrease malignant cell metabolism and could lead to a decrease in lactate production. The goal of this pre-clinical study was to evaluate metabolic targeting as a strategy of enhancing radiation response by inhibiting the HIF-1 transcription factor.

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The purpose was to compare the blood lactate response and performance of varsity hockey players to recreational players, and to provide a shift by shift analysis of blood lactate accumulation in a simulated ice hockey task. Ten university, varsity players and ten recreational players performed a continuous aerobic treadmill test (VO2max), a 45 s Wingate test, and four trials of the Repeat Sprint Skate (RSS) test. Each RSS test consisted of four repetitions of a 91.4 m skate with repetitions initiated on 30 s intervals. To simulate game, competition, 5 min of recovery separated each RSS test. Results indicated: (1) performance of the varsity players was superior (p < 0.01) to that of the recreational players in the RSS test; (2) four shifts of the RSS test elicited similar peak blood lactate concentrations for the varsity and recreational groups; (3) change in blood lactate following 15 min of passive recovery was similar in the two groups, and (4) there was a significant relationship (&prop; = 0.05) between performance indices in the RSS test and corresponding variables measured in the 45 s Wingate test.

The purpose of this study was to determine if previously observed differences in ratings of perceived exertion (RPE) at the same intensities during two graded exercise tests (GXT) were the result of changes in blood lactate concentrations (BLC). Thirteen healthy males (25.3 ±53 yrs.) were maximally tested during two protocols (Bruce and Balke 3.0 mph/2.5 % grade changes every 2 minutes). Subjects were randomly assigned to one GXT and completed the second test after 48 hours; both were completed within one week. Ratings of perceived exertion (RPE) were recorded at the end of each 2 minute stage of the Balke and twice per stage during the Bruce protocol. Blood lactate concentrations (BLC) were collected each minute during both protocols.Results: RPE data was first analyzed using two-way ANOVA (protocol x intensity), and a significant interaction was observed with RPEs being higher at each intensity during the Balke protocol. Mean RPE differences were 1.4, 2.8, and 4.5 for 40, 60, 80% of VO2max respectively. The addition of the BLC at each relative exercise intensity as a covariate in the model suggested that BLC accounted for some of the protocol differences in RPE, at 60 and 80% of VOimax.Conclusion: Differences in RPEs between standard GXT protocols reported in previous studies were due, in part, to differences in BLC. / School of Physical Education

The purpose of this study was to examine if measurements of submaximal blood lactate may improve the prediction of VO2max from submaximal exercise tests. Subjects (39 men & 21 women, age 20-44 yrs) completed a branching protocol on a cycle ergometer which consisted of 3 submaximal stages of 4 minutes each followed by a maximal effort. During the last minute of each stage heart rate (HR) was recorded from telemetry and a capillary blood sample was obtained from a finger puncture. Maximal power output was estimated from the extrapolation of the 3 submaximal HRs to age predicted HRmax and blood lactate concentration was measured using a Yellow Springs analyzer (Yellow Springs, OH). Data were analyzed using multiple regression procedures. Estimated maximal power output (238 ± 56 W) was significantly related to measured VOzmaX (p < 0.001, r2= .523). Mean values for ACSM estimated, ACSM-revised and measured VOz.X were not significantly different (3.170 vs. 3.140 vs. 3.260 L/min respectively), however the SEE % for the ACSM and ACSM revised estimated VOz,. were 13.4% and 12.1%, respectively. When the change in power output relative to the change in blood lactate concentrations (po/BL) from stage 1 to stage 2 and the estimated maximal power output from 3 submaximal heart rates were added as independent variables to the regression model with measured VO2,t as the dependent variable, po/BL was significantly correlated with VO X , accounting for 7.6% of the variance in VOz... In conclusion, only the relative change in power output to the relative change in blood lactate measure from stage 1 to _2 were significant in improving the estimation of VO2 during submaximal exercise tests using a branching protocol. Other blood lactate measures did not improve the estimation of VOA,. in this study. / School of Physical Education

Tinamous (Tinamidae) have the smallest heart in relation to body mass compared to any other flying bird today (Bishop 1997). This means that heart size is likely to restrict aerobic metabolism. Tinamous inhabit areas from sea level to 4800 m a.s.l., which means that the high altitude living species, Nothoprocta ornata (NO), is exposed to hypoxia. In this study the activity of the two metabolic enzymes Lactate Dehydrogenase (LDH) and Citrate Synthase (CS) was measured and the ratio between the enzyme activities calculated to examine if the small heart of the tinamous affects their aerobic/anaerobic metabolism. The activity of the two enzymes was measured in the heart and the gastrocnemius muscle in the three species Nothoprocta ornata (NO), Nothoprocta perdicaria (NP) and Gallus gallus (GG). CS activity was significantly higher in the heart compared to the skeletal muscle and LDH activity was significant higher in the skeletal muscle than in the heart in all three species. The LDH/CS ratio was significantly higher in NO’s skeletal muscle than in chickens but there was no significant difference between species in the heart. The higher ratio in NO´s muscle could be a sign of a higher anaerobic metabolism that is used in the muscles to compensate for the small heart NO have. In conclusion, the Tinamous

The purpose of this study was to examine the effects of recovery modes and exercise durations on blood lactate concentrations and subsequent performance in cycling tests. Fourteen male subjects completed six randomly assigned experimental protocols with a combination of three durations and two modes of recovery (passive and active cycling at 45% VO$ sb{ rm 2 max}$). Each protocol consisted of eight bouts of cycling at 120% of VO$ sb{ rm 2 max}$ interspersed with five minute recovery periods. Each protocol terminated with a maximal performance task consisting of a 45s all-out cycling test. Results indicated significantly (p $<$ 0.05) higher blood lactate concentrations in the passive and 60s conditions. Mean power outputs measured in the performance task were significantly (p $<$ 0.05) higher in the active recovery conditions compared to passive recovery. Mean power outputs were lower during the 60s conditions. Since the correlation between blood lactate and mean power output was low (r = -0.24), other factors were influencing subsequent performance.