Effects of training at simulated altitude on performance and muscle metabolic capacity in competitive road cyclists

Differences between the effects of training at sea level and at simulated altitude on performance and muscle structural and biochemical properties were investigated in 8 competitive cyclists who trained for 3-4 weeks, 4-5 sessions/week, each session consisting of cycling for 60-90 min continuously and 45-60 min intermittently. Four subjects, the altitude group (AG), trained in a hypobaric chamber (574 torr = 2300 m above sea level), and the other four at sea level (SLG). Before and after training work capacity was tested both at simulated altitude (574 torr) and at sea level, by an incremental cycle ergometer test until exhaustion. Work capacity was expressed as total amount of work performed. Venous blood samples were taken during the tests. Leg muscle biopsies were taken at rest before and after the training period. AG exhibited an increase of 33% in both sea level and altitude performance, while SLG increased 22% at sea level and 14% at altitude. Blood lactate concentration at a given submaximal load at altitude was significantly more reduced by training in AG than SLG. Muscle phosphofructokinase (PFK) activity decreased with training in AG but increased in SLG. All AG subjects showed increases in capillary density. In conclusion, work capacity at altitude was increased more by training at altitude than at sea level. Work capacity at sea level was at least as much improved by altitude as by sea level training. The improved work capacity by training at altitude was paralleled by decreased exercise blood lactate concentration, increased capillarization and decreased glycolytic capacity in leg muscle.     

Angina pectoris-like pain provoked by intravenous adenosine in healthy volunteers.

In a study to characterise the chest pain induced by adenosine this agent was given as a bolus into a peripheral vein to six healthy volunteers (five men) aged 30-44. On the first day the maximum tolerable dose was determined in each case. On the second day three doses of adenosine (one third, two thirds, and the full maximum tolerable dose) and three doses of saline were given single blind in randomised order. Thereafter aminophylline 5 mg/kg was given and the procedure repeated in a different randomised order. On the third day between two thirds and the full maximum tolerable dose was given followed by 10 mg dipyridamole intravenously and a second injection of the same dose of adenosine. Heart rate and atrioventricular blocks were recorded by electrocardiography. One minute after each dose of adenosine the chest pain was scored. The maximum tolerable dose of adenosine ranged from 10.6 to 37.1 mg. All subjects experienced uneasy central chest pain provoking anxiety. The pain radiated to the shoulders, ulnar aspect of the arms, epigastric area, back, and into the throat. The pain began about 20 seconds after the injection and lasted 10-15 seconds. Increasing the dose of adenosine increased the intensity of the pain. Administration of aminophylline reduced the pain significantly. Second degree heart block was recorded in five of the six subjects during the time that the pain was experienced. After aminophylline no block was observed. Dipyridamole increased the intensity of pain. The duration of second degree heart block increased in four of the subjects, and in two of these third degree heart block occurred. These findings suggest that adenosine released from the myocardium during ischaemia induces angina pectoris by stimulating theophylline sensitive receptors.     

The immunofluorescent demonstration of cathepsin B1 in tissue sections

Summary A direct immunohistochemical method of high specificity is presented for the demonstration of sites of cathepsin B1. Antisera were raised in rabbits against pure enzyme preparations. The specific antibodies were subsequently isolated and labelled according to methods previously published. Sections from tissues specially rich in this enzyme like liver, kidney, intestinal epithelia and the active macrophages of talcum granulomas were studied. The results suggest a localization of this enzyme mainly to lysosomal organelles and phagocytic vacuoles, which are known from chemical data to contain this enzyme. The prerequisite for a positive tissue reaction is that the enzyme must be present in a form available for antigen-antibody interaction.     

Studies on the histochemical “leucine aminopeptidase” reaction

Summary A correlative chemical and histochemical study on the leucyl--naphthyl-amide-splitting activity is presented.In the first part comparison is made between homogenates and smears of strain L cells and ELD ascites tumor cells. It was concluded that only the available enzyme activity could be visualized by histochemical means. The growing tumor cells appeared to have more activity available than the strain L cells. The intensity of the histochemical LNAse reaction bore no correlation to the total enzymatic activity extractable. Most of the available activity seemed to reside in lysosome-like structures. Cell damage by repeated freezing and thawing increased the amount of activity available to substrate interaction.In the second part a comparison is made between chemical and histochemical results in four types of progressively growing transplanted or induced mouse tumors. Chemical data showed the occurrence of a mixed pattern of LNA-splitting enzymes, among which the previously described metal-dependent group constituted the main component in the tumor cells. In all cases and types of tumors a positive histochemical LNAse reaction was noticed both in growing tumor cells as well as in different parts of the stromal compartment. The intracellular reaction in tumor cells seemed confined mainly to lysosomal-like bodies. A positive stromal reaction seemed associated with the destructive (cytolytic and collagenolytic) activity at the tumor periphery. The stromal LNAse reaction was probably due to enzymes partly different from the intracellular ones. Additional enzymatic terms, including a chymotrypsin-like and/or a carboxypeptidase activity, may originate from various host cells. These contributions may be greatly increased by accumulation of inflammatory host cells as previously noted by Hess and Mottet.     

Myoglobin content and citrate synthase activity in different parts of the normal human heart

Myoglobin (Mb) content and citrate synthase (CS) activity were determined in myocardial samples from nine human brain-dead organ donors with normal hearts. Six regions of each heart were analyzed: right and left atria, right ventricle, left ventricular subepicardium, subendocardium, and anterior papillary muscle. The Mb content was similar, whereas the CS activity was higher in the left than in the right heart at both atrial and ventricular levels. Mb content and CS activity were higher in ventricles than in atria. The subendocardial layer and papillary muscle of the left ventricle had a higher Mb content than the subepicardial layer, whereas CS activity was similar in these three locations. The results suggested a closer relationship between CS activity (oxidative potential) and work load than between Mb content and work load. Mb content may, instead, be related to intramuscular oxygen tension (PO2) on the basis of a comparison between our Mb data and those of others on regional variations in myocardial PO2.     

Local temperatures inferred from plant communities suggest strong spatial buffering of climate warming across Northern Europe

Recent studies from mountainous areas of small spatial extent (<2500 km²) suggest that fine‐grained thermal variability over tens or hundreds of metres exceeds much of the climate warming expected for the coming decades. Such variability in temperature provides buffering to mitigate climate‐change impacts. Is this local spatial buffering restricted to topographically complex terrains? To answer this, we here study fine‐grained thermal variability across a 2500‐km wide latitudinal gradient in Northern Europe encompassing a large array of topographic complexities. We first combined plant community data, Ellenberg temperature indicator values, locally measured temperatures (LmT) and globally interpolated temperatures (GiT) in a modelling framework to infer biologically relevant temperature conditions from plant assemblages within <1000‐m² units (community‐inferred temperatures: CiT). We then assessed: (1) CiT range (thermal variability) within 1‐km² units; (2) the relationship between CiT range and topographically and geographically derived predictors at 1‐km resolution; and (3) whether spatial turnover in CiT is greater than spatial turnover in GiT within 100‐km² units. Ellenberg temperature indicator values in combination with plant assemblages explained 46–72% of variation in LmT and 92–96% of variation in GiT during the growing season (June, July, August). Growing‐season CiT range within 1‐km² units peaked at 60–65°N and increased with terrain roughness, averaging 1.97 °C (SD = 0.84 °C) and 2.68 °C (SD = 1.26 °C) within the flattest and roughest units respectively. Complex interactions between topography‐related variables and latitude explained 35% of variation in growing‐season CiT range when accounting for sampling effort and residual spatial autocorrelation. Spatial turnover in growing‐season CiT within 100‐km² units was, on average, 1.8 times greater (0.32 °C km^?1) than spatial turnover in growing‐season GiT (0.18 °C km^?1). We conclude that thermal variability within 1‐km² units strongly increases local spatial buffering of future climate warming across Northern Europe, even in the flattest terrains.     

Detecting early kidney damage in horses with colic by measuring matrix metalloproteinase -9 and -2, other enzymes,urinary glucose and total proteins

Background  

The aim of the study was to investigate urine matrix metalloproteinase (MMP-2 and -9) activity, alkaline phosphatase/creatinine (U-AP/Cr) and gamma-glutamyl-transpeptidase/creatinine (U-GGT/Cr) ratios, glucose concentration, and urine protein/creatinine (U-Prot/Cr) ratio and to compare data with plasma MMP-2 and -9 activity, cystatin-C and creatinine concentrations in colic horses and healthy controls. Horses with surgical colic (n = 5) were compared to healthy stallions (n = 7) that came for castration. Blood and urine samples were collected. MMP gelatinolytic activity was measured by zymography.     

Electroporation in combination with a plasmid vector containing SV40 enhancer elements results in increased and persistent gene expression in mouse muscle

Gene transfer into muscle upon injection of plasmid DNA is feasible but occurs with low frequency. However, by using electroporation after injection of plasmid DNA into mouse muscle it has been demonstrated that gene expression can be increased more than 150-fold. In this communication, we have used this technique in combination with plasmids containing a tandem repeat of three 72-bp DNA elements from the SV40 enhancer to study gene expression. Our results show that the combination of electroporation and a plasmid vector carrying these DNA elements results in increased and more persistent gene expression of the luciferase reporter gene in BALB/c mouse muscle. At 14 days after gene delivery, the gene expression was 16-fold higher in muscles injected and electroporated with the plasmid carrying the SV40 enhancers than with control plasmid. We have also studied the effects of the vehicle in which the plasmid was delivered, and the DNase inhibitor aurintricarboxylic acid (ATA), on gene expression. By combining ATA with 150 mM sodium phosphate buffer we were able to obtain a 2-fold increase in gene expression compared to delivery of the plasmid in physiological saline. These results are of importance for the development of efficient delivery techniques for naked DNA.