Non-cardiac nucleic acid composition and protein synthesis rates in hypertension: studies on the spontaneously hypertensive rat (SHR) model

Various studies have shown the involvement of extracardiac tissues in hypertension, including the hepato-intestinal tract, musculo-skeletal system, skin, and the kidney. It was our hypothesis that these perturbations in non-cardiac tissues would also include alterations in protein metabolism. Thus, the reported differences in soleus contractile protein composition may be related to changes in muscle protein synthesis or reduced protein synthetic efficiencies. The aim of the present study was to characterise tissue composition of nucleic acids and rates of protein synthesis in non-cardiac tissues, such as liver, skeletal muscle (i.e., the Type I fibre-predominant soleus and Type II fibre-predominant plantaris), kidney, bone (tibia), skin and the gastrointestinal tract in a genetic model of hypertension (i.e., spontaneously hypertensive rats (SHRs), 15 weeks old) compared to their genetic aged-matched counterparts, i.e., normotensive Wistar-Kyoto (WKY) controls. Rates of protein synthesis were measured in vivo after injection with a flooding dose of L-[4-(3)H]phenylalanine. The results showed changed tissue wet weights (g per organ) for plantaris (+10%, P<0.05), liver (+25%, P<0.01), brain (-9%, P<0.01), jejunum (+39%, P<0.001) and tibia (+17%, P<0.001) in SHRs compared to WKY controls. Protein content (g or mg per organ) was increased in the liver (+32%, P<0. 01) and tibia (+37%, P<0.05). RNA contents (mg per organ) were increased in plantaris (+17%, P<0.01), liver (+22%, P<0.01) and jejunum (+11%, P<0.05). DNA (mg per organ) was increased in plantaris (+16%, P<0.025) and jejunum (+12%, P<0.025). The protein synthetic capacities (i.e., C(s), mg RNA/g protein) were higher in soleus (+41%, P<0.01) and plantaris (+6%, P<0.05) muscles of SHRs compared to WKYs, whereas values were lower in liver (-11%, P<0.01) and kidney (-6%, P<0.01) of SHRs compared to WKYs. The fractional rate of protein synthesis (i.e., k(s), the percentage of the protein pool renewed each day) was not significantly different for any of the tissues, though the rate of protein synthesis per unit RNA (i.e., k(RNA), mg protein/day per mg RNA) was reduced in the soleus (-24%, P<0.05) and the synthesis rate per unit DNA, i.e., k(DNA) (mg protein/day per mg DNA) was increased in the tibia (+31%, P<0.025). This is the first report of significant differences between indices of protein metabolism in extracardiac tissues in hypertension, which may reflect endocrine factors and/or the systemic influence of hypertension per se.     

Effect of early low-intensity exercise on rat hind-limb muscles following acute ischemic stroke

This study examined the effects of daily low-intensity exercise following acute stroke on mass, Type I and II fiber cross-sectional area, and myofibrillar protein content of hind-limb muscles in a rat model. Adult male Sprague-Dawley rats were randomly assigned to 1 of 4 groups (n = 7-9 per group): stroke (occlusion of the right middle cerebral artery [RMCA]), control (sham RMCA procedure), exercise, and stroke-exercise. Beginning 48 hours post-stroke induction/sham operation, rats in the exercise group had 6 sessions of exercise in which they ran on a treadmill at grade 10 for 20 min/day at 10 m/min. At 8 days poststroke, all rats were anesthetized and soleus, plantaris, and gastrocnemius muscles were dissected from both the affected and unaffected sides. After 6 sessions of exercise following acute ischemic stroke, the stroke-exercise group showed the following significant (p < .05) increases compared to the stroke-only group: body weight and dietary intake, muscle weight of affected soleus and both affected and unaffected gastrocnemius muscle, Type I fiber cross-sectional area of affected soleus and both affected and unaffected gastrocnemius muscle, Type II fiber cross-sectional area of the unaffected soleus, both affected and unaffected plantaris and gastrocnemius muscle, Type II fiber distribution of affected gastrocnemius muscle, and myofibrillar protein content of both affected and unaffected soleus muscle. Daily low-intensity exercise following acute stroke attenuates hind-limb muscle atrophy in both affected and unaffected sides. The effects of exercise are more pronounced in the soleus and gastrocnemius as compared to the plantaris muscle.     

Muscle atrophy in rats following denervation, casting, inflammation, and tenotomy.

One week after unilateral denervation, tenotomy, casting, or joint inflammation, skeletal muscles of adult female Wistar rats were studied to determine the effect of these processes on muscle weights and fiber diameters of the soleus, the red and white regions of the plantaris, plus muscle weights and protein content of the gastrocnemius. All atrophic processes caused greater weight loss of the soleus than of the plantaris or gastrocnemiums. Within the soleus and plantaris muscles, the type-I fiber atrophy was equal to the type-II fiber atrophy except for the white region of the plantaris following tenotomy, where the wasting of the type-I fiber was greater than that of type II. This study also demonstrated that denervation, tenotomy, casting, and inflammation resulted in a greater loss of myofibrillar proteins (content and absolute amounts) than of sarcoplasmic and stromal proteins. Denervation generally was found to have the greatest effect on the parameters evaluated. The findings are consistent with the hypothesis that slow muscle is more dependent than fast muscle on neuronal control, and that nerve controls muscle through the dual role of impulse activity and axoplasmic flow.     

Prehabilitation and rehabilitation for attenuating hindlimb unweighting effects on skeletal muscle and gait in adult and old rats

OBJECTIVE: To compare the effectiveness of no exercise with prehabilitation (exercise before hindlimb unweighting [HLU]) versus rehabilitation (exercise given after HLU) on gait function and skeletal muscle mass and force. DESIGN: Randomized controlled trial. SETTING: Animal laboratory. ANIMALS: Male-specific, pathogen-free Fisher344/Brown Norway rats (N=149). Groups consisted of adult and old controls, HLU, prehabilitation, rehabilitation, natural cage recovery (reloading), and exercise without HLU. INTERVENTIONS: Ten days of general conditioning exercise were given to 6-month-old adult and 30-month-old old rats before or after a week of HLU. MAIN OUTCOME MEASURES: Gait stride length and width; soleus, plantaris, extensor digitorum longus, and peroneus longus mass and peak contractile force; whole gastrocnemius mass; and total protein concentration for the soleus and gastrocnemius. RESULTS: Muscle mass (approximately 30%) and force (24%-36%) declined with age in all muscles studied. In adult rats declines in muscle mass occurred with HLU in the soleus, plantaris, and gastrocnemius. Prehabilitation did not prevent the loss of muscle mass in adult rats. Rehabilitation and natural recovery effectively restored soleus and gastrocnemius muscle mass in adult rats but not soleus peak force. Old rats had a significant 23% HLU effect only on gastrocnemius mass (control, 1670+/-129 mg; HLU, 1274+/-184 mg). Prehabilitation did not prevent the decline in gastrocnemius mass. Rehabilitation in old rats restored gastrocnemius mass to within 13% of control levels. Prehabilitation was effective for preventing and rehabilitation was effective for restoring soleus contractile force in old rats (control, 114+/-9 mg; HLU, 67+/-22 mg; prehabilitation, 106+/-31 mg; rehabilitation, 120+/-26 mg) compared with recovery without exercise (86+/-29 g). A significant reduction in stride length was observed with aging (136+/-18 mm vs 98+/-10 mm), which decreased further with HLU (78+/-14 mm). Prehabilitation attenuated HLU-related reductions in stride length, and rehabilitation was effective for stride length restoration in old rats. CONCLUSIONS: Exercise, particularly rehabilitation, was more effective for old than young rats. Prehabilitation and rehabilitation diminished some of the detrimental effects of HLU on skeletal muscle mass and force and gait function in old rats.     

Histochemical fiber type alterations secondary to exercise training of reinnervating adult rat muscle

The purpose of this study was to evaluate the effect of exercise training on reinnervating rat muscle histochemistry. Adult female Wistar rats in 5 groups (1 control and 4 experimental) underwent bilateral sciatic nerve crush. The 4 experimental groups were exercised on a motorized treadmill at 35% grade and a speed of 27m/min once (groups J and L) or twice (groups K and M) daily, 5 days/week from the 2nd (groups J and K), and 3rd (groups L and M), to the 6th week after the crush. The exercise sessions lasted 1 hour. The fiber diameter and percent of type I and II fibers (weak and strong myosin ATPase reaction, pH .94) were evaluated in the soleus and superficial and deep regions of the plantaris muscles. Exercise training did not affect the fiber diameters. There was no change in the fiber type distribution in the soleus and superficial region of the plantaris. However, the percent of type II fibers increased significantly (p less than 0.05) in the deep region of the plantaris groups J, K, L and M bu 12%, 7%, 15% and 10%, respectively. This study indicated that exercise did not interfere with reinnervation and that there was an increase in the proportion of fibers with a strong myosin ATPase reaction in the deep region of the plantaris.     

Length and circumference measurements in one-joint and multijoint muscles in rabbits after immobilization

In this article, we compared changes in the length and circumference of the soleus and the plantaris muscles in rabbits. The rabbits were assigned to a nonimmobilized external control group (n = 4), an experimental shortened-position group (n = 10), or an experimental lengthened-position group (n = 9). One hind limb of each animal in the experimental groups was immobilized in a cast for four weeks to put the muscles in either a shortened or lengthened position. The contralateral limb served as an internal control for the animals in the experimental groups. After the immobilization period, the limbs were fixed in situ, the muscles were dissected, and length and circumference measurements were taken. In both experimental conditions, the immobilized soleus muscles were shorter than their contralateral counterparts (p less than .05); the length of the plantaris muscles did not change. The immobilized muscles had decreased circumference values regardless of the immobilization angle. When compared with the control condition, the shortened soleus muscles had a greater decrease in circumference than did the plantaris muscles. More connective tissue was observed in the muscle bellies of the soleus after immobilization than in the plantaris. Similar significant changes (p less than .05) were found in the nonimmobilized limbs of the animals in the experimental groups. Specifically, the soleus muscles demonstrated length and circumference changes, whereas the plantaris muscles showed changes only in circumference. These findings suggest that when a weight-bearing limb is immobilized, adaptations in gross muscle length and circumference are to be expected in the involved and uninvolved limbs. An assessment of similar adaptations in humans should be a part of the evaluation during recovery.     

Synergistic tenotomy: effect on chronically denervated slow and fast muscles of rat.

A study was conducted with chronically denervated adult female Wistar rats to test the hypothesis that synergistic tenotomy of denervated skeletal muscles does not just retard atrophy but produces an increase in muscle weight. The animals were categorized in three groups-denervated exercised (DE), denervated tenotomized (DT), and denervated-tenotomized-exercised (DTE). Mechanical stretch was induced in the DE group by forcing the animals to stand on their hind legs to reach for food and water. In the DT group, mechanical stretch was induced by tenotomy of two synergists in the gastrocnemius-plantaris-soleus complex of each leg of the rat so that either the soleus or the plantaris was left as the only plantar-flexor of the ankle joint in each leg. Mechanical stretch was induced in the DTE group by forcing the animals to stand after the tenotomy of synergists at eight weeks postdenervation. All animals in the three experimental groups, and in the sedentary control group (D) were sacrificed at nine weeks postdenervation; the soleus and plantaris muscles were removed and evaluated for MW, DW and percent of hydration. The slow muscle (soleus) increased in muscle mass in DT (53%), DE (26%), and DTE (17%). The fast muscle (plantaris) increased in weight in DE (18%) and in DTE (24%), but showed no significant changes in DT. Study results confirm the hypothesis that synergistic tenotomy stimulates an increase in muscle weight rather than merely retarding atrophy, and that this phenomenon can take place in the absence of neuronal influences. It is suggested that the increase in denervated muscle mass stimulated by muscle elongation is not a true work hypertrophy associated with significant changes in protein concentrations but only an adaptation to a new muscle length. The purpose of the adaptational changes is to optimize the overlap of actomyosin bridges in anticipation of forceful muscle contraction.     

Overwork-induced axonal hypertrophy in the soleus nerve of the rat

Effect of overwork, induced by synergistic tenotomy (bilateral tenotomy of the gastrocnemius and the plantaris muscles) of the soleus muscle, was evaluated on areas of the large myelinated axons (LMA) (greater than 19.5 micron 2), in the soleus nerve (the tibial nerve branch innervating the soleus muscle) of the rat. Three lots (n = 12-16) of young adult male (body weight of 275 to 325 g), Sprague-Dawley rats were used. One lot of 16 animals was kept as normal, while the other two underwent bilateral L4 or L5 spinal nerve sectioning. Six to seven animals each from the normal, L4-, and L5 neurectomized animals underwent bilateral synergistic tenotomy of the soleus so that the soleus was retained as the sole plantar-flexor of the ankle joint. The remaining animals were kept as normal or neurectomized control groups. Thus, the six groups studied were normal control (n = 9); normal synergistically tenotomized (n = 7); L4 neurectomized control (n = 8); L4 neurectomized and synergistically tenotomized (n = 6); L5 neurectomized control (n = 8); and L5 neurectomized and synergistically tenotomized (n = 7). Seven days after surgery, the soleus muscles were used to evaluate the muscle weights. The soleus nerves were evaluated for the number plus areas of the LMA by computerized planimetric procedures. The data revealed a 13.9% (p less than 0.05) increase in areas of the LMA in the L5 neurectomized control group; whereas the L5 neurectomized and synergistically tenotomized group showed a 39.6% (p less than 0.01) increase in areas of the LMA.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of chronic ethanol feeding on rat hepatocytic glutathione. Relationship of cytosolic glutathione to efflux and mitochondrial sequestration.

Chronic ethanol feeding to rats increases the sinusoidal component of hepatic glutathione (GSH) efflux, despite a lower steady-state GSH pool size. In the present studies, no increase of biliary GSH efflux in vivo was found in chronic ethanol-fed cells. Studies were performed on ethanol-fed and pair-fed cells to identify the kinetic parameters of cellular GSH concentration-dependent efflux. The relationship between cytosolic GSH and the rate of efflux was modeled by the Hill equation, revealing a similar Vmax, 0.22 +/- 0.013 vs. 0.20 +/- 0.014 nmol/min per 10(6) cells for ethanol-fed and pair-fed cells, respectively, whereas the Km was significantly decreased (25.3 +/- 2.3 vs. 33.5 +/- 1.4 nmol/10(6) cells) in ethanol-fed cells. The difference in Km was larger when the data were corrected for the increased water content in ethanol-fed cells. We found a direct correlation between mitochondria and cytosolic GSH, revealing that mitochondria from ethanol-fed cells have less GSH at all cytosolic GSH values. The rate of resynthesis in depleted ethanol-fed cells in the presence of methionine and serine was similar to control cells and gamma-glutamylcysteine synthetase remained unaffected by chronic ethanol. However, the reaccumulation of mitochondrial GSH as the cytosolic pool increased was impaired in the ethanol cells. The earliest time change in GSH regulation was a 50% decrease in the mitochondrial GSH at 2 wk.     

Gonadectomy and reduced physical activity: effects on skeletal muscle

OBJECTIVES: To examine the effects of testosterone (TST) loss on skeletal muscle contractile function and the potential interactive effects of TST loss and physical inactivity. DESIGN: Randomized control trial. ANIMALS: Forty-eight male rats (age, 6mo) were placed into control (Con) or gonadectomized (Orx) groups. INTERVENTION: Two weeks after Orx or sham surgery, half the Con and Orx rats were hind-limb unloaded (HLU) to reduce muscle activity for 2 weeks. Subsequently, in situ contractile function tests were performed on the soleus (SOL), plantaris (PLAN), peroneus longus (PER), and extensor digitorum longus (EDL). These 4 muscles and gastrocnemius (GAST) then were removed, weighed, sectioned, and stained with adenosine triphosphatase for fiber typing and fiber area measures. MAIN OUTCOME MEASURES: Peak tetanic tension (P(0)), time to peak twitch contraction (TPT), half relaxation time (RT(1/2)), muscle mass, fiber area, and specific tension (ratio of P(0)/muscle mass). RESULTS: Body weight and muscle mass were similar in the Con and Orx groups. The ratio of P(0) to muscle mass was significantly (p <.05) reduced with Orx in SOL (20%), PLAN (18%), PER (28%), and EDL (20%). TPT and RT(1/2) were significantly faster after Orx in PLAN, PER, and EDL. HLU significantly reduced muscle mass in SOL, PLAN, and GAST in Orx and intact groups. HLU also caused a significant decline in SOL and PLAN P(0). The loss in P(0) in the Orx-HLU rats was no greater than the decline in P(0) with HLU alone. CONCLUSIONS: Gonadectomy results in a loss of P(0) regardless of muscle fiber type or function, it is likely to speed up TPT and RT(1/2), and it does not exacerbate HLU-related atrophy and P(0) loss. Findings may have implications for men with reduced TST levels, as in aging, for instance.     

Pathogenesis of Postprandial Hyperlipemia in Rats Fed Ethanol-Containing Diets

To study the mechanism of the increase in serum lipoproteins which occurs in rats fed alcohol chronically, and especially to assess the role of the intestine, the effects of acute and chronic ethanol administration on lymph and plasma lipids were compared in rats with and without intestinal lymph fistulae. In rats not previously given alcohol, the administration of one dose of a diet containing ethanol (3 g/kg) produced a significant increase in lymph flow, lipid output, and incorporation of dietary fat into lymph lipids when compared with the effects of a control diet containing isocaloric carbohydrate. However, no hyperlipemia developed after ethanol. By contrast, previous feeding of ethanol for several weeks modified the acute effects of ethanol on both lymph and serum lipids. Compared with control animals pair-fed with isocaloric carbohydrate-containing diets, rats which had been fed a diet with 36% of total calories as ethanol for 3-4 wk developed postprandial hyperlipemia when given a single dose of the ethanol-containing or even the ethanol-free diet. This was associated with an increased incorporation of labeled dietary fat and of intravenously injected [(3)H]lysine into plasma lipoproteins of d < 1.006. However, postprandial lymph flow and lipid output were not higher in rats fed alcohol chronically than in their pair-fed controls. Moreover, when rats with lymph fistulae were given intravenous (i.v.) infusions of lymph lipids (to substitute for the diverted intestinal lymph), the ethanol-fed animals still developed hyperlipemia. Incorporation of i.v. lysine into d < 1.006 plasma lipoproteins also remained significantly increased. Thus, under these conditions, alcoholic hyperlipemia does not result from changes in intestinal lymph lipids. Two main factors appear to be involved; the acute effects of ethanol on hepatic lipid metabolism and the development of an increased capacity for lipoprotein synthesis during chronic ethanol feeding. The latter most likely occurs in the liver and it is postulated that it is linked to the associated changes in the hepatic endoplasmic reticulum.     

Acute effects of ethanol on protein synthesis in different muscles and muscle protein fractions of the rat

1. The effects of a single dose of ethanol (75 mmol/kg body weight) on rates of muscle protein synthesis were examined in young rats. Fractional rates of protein synthesis were measured in the soleus, plantaris, gastrocnemius, diaphragm and stomach by the large 'flooding-dose' technique. 2. After 150 min, the fractional synthesis rates of all muscles were reduced by 15-35%. Skeletal muscles containing a predominance of anaerobic (fast-twitch, type II) fibres showed greater changes when compared with skeletal muscles with a predominance of aerobic (slow-twitch, type I) fibres. 3. Gastrocnemius muscles were separated into sarcoplasmic, stromal and myofibrillar protein fractions. Protein synthesis was reduced similarly in all fractions by ethanol treatment, by approximately 30%. 4. As skeletal muscle mass comprises 40% of body weight, the responses have important physiological implications and may also be responsible for the muscle atrophy observed in alcoholic patients.     

Prolonged consumption of moderate doses of alcohol and in vitro gastro-duodenal and ileal contractility in the rat

Abstract. The effects of chronic feeding with moderate doses of ethanol (3% vol/vol in drinking water for 8 weeks), which do not induce tolerance, dependence and withdrawal, on the contractility of gastric, duodenal and ileal strips from rats were investigated. Only 50% of ethanol-treated specimens (as compared to 100% of saccharose-fed controls) exhibited antral phasic contractions (frequency decreased by 31% and 27% in the antrum and duodenum, respectively; P < 0.03 vs. controls). The depolarizing agent potassium chloride (KG, 80 mm) produced less peak active tension in the fundus of ethanol-fed rats ( P < 0.01). In alcoholic rats the sensitivity of the antrum to acetyl-choline was fourfold less than that of control specimens. It is concluded that, in the rat, moderate doses of ethanol given chronically impair both spontaneous and tonic contractility of the stomach and duodenal muscle without affecting ileal contraction. It is possible that motility defects in the gut exposed to ethanol concentrations which do not cause tolerance, dependence or withdrawal in the rat may be due to a local rather than a systemic effect on the smooth muscle.     

Vitamin D Deficiency, hypocalcemia, and increased skeletal muscle degradation in rats.

The myopathy associated with vitamin D deficiency was examined in vitamin D-deficient and vitamin D-supplemented rats. When compared with either vitamin D-supplemented ad lib. or pair-fed rats, weight gain and muscle mass were decreased in vitamin D-deficient hypocalcemic animals. With the exception of a modest decrease in muscle creatine phosphate levels, muscle composition was unchanged by vitamin D deficiency. Muscle protein turnover rates were determined in both in vivo and in vitro studies and demonstrated that myofibrillar protein degradation was increased in vitamin D deficiency. Normal growth rates could be maintained be feeding the rats vitamin D-deficient diets containing 1.6% calcium, which maintained plasma calcium within the normal range. In addition to its role in maintaining plasma calcium, vitamin D-supplemented rats had significantly higher levels of the anabolic hormone insulin. Vitamin D supplementation may affect muscle protein turnover by preventing hypocalcemia, as well as directly stimulating insulin secretion, rather than by a direct effect within skeletal muscle.     

Proteinuria in passive Heymann nephritis is associated with lipid peroxidation and formation of adducts on type IV collagen.

Passive Heymann nephritis (PHN) is a model of human membranous nephropathy that is characterized by formation of granular subepithelial immune deposits in the glomerular capillary wall which results in complement activation. This is causally related to damage of the filtration barrier and subsequent proteinuria. The local accumulation of injurious reactive oxygen species (ROS) is a major effector mechanism in PHN. ROS may induce tissue damage by initiating lipid peroxidation (LPO). In turn, this leads to adduct formation between breakdown products of LPO with structural proteins, such as formation of malondialdehyde (MDA) or 4-hydroxynonenal-lysine adducts. To examine the role of LPO in the development of proteinuria we have localized MDA and 4-hydroxynonenal-lysine adducts in glomeruli of PHN rats by immunofluorescence microscopy, using specific monoclonal antibodies. By immunogold electron microscopy, MDA adducts were localized to cytoplasmic vesicles and cell membranes of glomerular epithelial cells, to the glomerular basement membrane (GBM), and also to immune deposits. Type IV collagen was specifically identified as being modified by MDA adducts, using a variety of techniques. Collagenase pretreatment of GBM extracts indicated that the NC-1 domain of type IV collagen was a site of adduct formation. When LPO was inhibited by pretreatment of PHN rats with the antioxidant probucol, proteinuria was reduced by approximately 85%, and glomerular immunostaining for dialdehyde adducts was markedly reduced, even though the formation of immune deposits was not affected. By contrast, lowering of the serum cholesterol levels had no influence on the development of proteinuria. These findings are consistent with the premise that ROS-induced glomerular injury in PHN involves LPO and that this results not only in damage of cell membranes but in modification of type IV collagen in the GBM as well. The close temporal correlation of the occurrence of LPO with proteinuria and the ability of probucol to inhibit proteinuria support a causal role for LPO in the the alteration of the glomerular permselectivity which results in proteinuria.     

Increased DNA adducts in Barrett's esophagus and reflux-related esophageal malignancies

BACKGROUND: DNA adduct formation can initiate carcinogenic processes. AIM: To examine the pre-malignant condition of Barrett's esophagus by measuring the DNA adducts. METHODS: DNA adducts were measured in the proximal and distal esophagus of patients with Barrett's esophagus (n = 9), patients with adenocarcinoma in the distal esophagus/esophagogastric junction (n = 28), and in control group of patients (n = 8) using the 32-P-postlabeling method. The average levels of DNA adducts are expressed as mean adducts/10(9) nucleotides + standard error of the mean. RESULTS. The average DNA adduct levels in the distal esophagus were significantly higher in both the Barrett's esophagus (24.5 +/- 7.9) and the adenocarcinoma (12.0 + 3.0) than in the control patients (0.1 +/- 0.08), P < 0.001. In the proximal esophagus, the DNA adduct levels were approximately equal in the Barrett's esophagus (7.0 +/- 1.0) and in the adenocarcinoma group (6.4 +/- 0.65). However, the levels in the proximal esophagus in both groups were significantly higher than in the control group (2.1 +/- 0.67), P < 0.05. CONCLUSIONS: Patients with Barrett's esophagus and patients with esophageal/esophagogastric junction adenocarcinoma had significantly more DNA adducts than the control group. These results support the current concept of the carcinogenic potential of chronic gastroesophageal reflux, and the pre-malignant condition of Barrett's esophagus.     

Strenuous exercise-induced alterations of muscle fiber cross-sectional area and fiber-type distribution in steroid myopathy rats

OBJECTIVE: To investigate the effect of exercise intensity on the muscle histopathology in steroid myopathy rats. DESIGN: Eight-week-old male Wistar rats (n=40) were divided into four groups: a control group (n=4), steroid-only group (n=12), moderate exercise + steroid group (n=12), and a high-intensity exercise + steroid group (n=12). Five weeks after triamcinolone injection, the soleus muscle (SOL) and extensor digitorum longus muscle (EDL) were removed and stained for adenosine triphosphatase (ATPase). The muscle fiber area and fiber type distribution of each fiber type were measured. RESULTS: In the high-intensity exercise group, the type I fibers in the SOL and the type IIb fibers in the EDL showed significant atrophy. In the fiber distribution of the SOL, type I fibers decreased in the steroid-only group and high-intensity exercise group as compared with the control, whereas there was a significant increase in the moderate exercise group vs. the steroid-only group. In the EDL, type I fibers were significantly greater in the moderate- and high-intensity exercise groups, whereas type IIb fibers significantly decreased in the moderate-exercise group as compared with the steroid-only group. CONCLUSIONS: In rats with steroid myopathy, high-intensity exercise caused changes such as muscle atrophy. The fiber type distribution of the SOL changed from type II fibers to type I fibers in the moderate exercise group. Intensive exercise, however, resulted in transformation from type I to type II in the fiber type distribution. For the EDL, no significant fiber type changes were observed with high-intensity exercise when compared with moderate exercise.     

Effect of ethanol on fluoroquinolone efficacy in a rat model of pneumococcal pneumonia

This investigation compared the effect of ethanol on fluoroquinolone antibiotic efficacy and pharmacodynamics in an ethanol-fed rat model of pneumococcal pneumonia. Male Sprague-Dawley rats received a liquid diet containing 36% of total calories as ethanol. Paired controls (pair-fed controls) were fed a liquid diet without ethanol or received rat chow. Diets began 7 days before and continued for 10 days after transtracheal infections with 10 times the 50% lethal dose of type 3 Streptococcus pneumoniae. Beginning 18 h after infection, the rats received once daily subcutaneous phosphate-buffered saline, levofloxacin, moxifloxacin, or trovafloxacin at 50 or 100 mg/kg of body weight. White blood cell counts were determined, blood samples were collected for culture, and mortality was recorded. Additional rats were killed on day 5 for pharmacodynamic studies and quantitative cultures of bronchoalveolar lavage fluid. Bacteremia occurred by day 3 in 20 of 22 untreated rats. All 22 untreated rats died by day 9. Moxifloxacin treatment was effective in all diet groups at both the 50- and 100-mg/kg doses. In contrast, 50-mg/kg doses of levofloxacin and trovafloxacin improved survival in ethanol-fed rats but were ineffective in chow-fed rats. High-dose trovafloxacin at 100 mg/kg was associated with increased mortality in pair-fed rats. The free-fraction area under the concentration-time curve/MIC ratio exceeded 50 with all antibiotics in the ethanol group but dropped below 30 with levofloxacin and trovafloxacin in the pair- and chow-fed rats, with higher mortality. Achievement of adequate antibiotic-free fraction area under the concentration-time curve/MIC ratios helps overcome ethanol-induced immune defects induced in experimental pneumococcal pneumonia.     

热应激预处理对离心运动大鼠骨骼肌自由基代谢的影响

背景:研究表明热预处理能够提高肌肉抗损伤的能力,但具体的机制尚不清楚。目的:观察热应激预处理对离心运动大鼠骨骼肌超氧化物歧化酶活性及丙二醛含量的影响。方法:雄性Wistar大鼠随机分为对照组、离心运动组、预热应激+离心运动组。热应激温度为43℃,时间约35min。采用-16°下坡跑台跑做大负荷间歇性离心运动,跑速为26.8m/min,运动5min,间歇1min,共进行10组。分别于运动前1h、运动后1,24,48h取大鼠腓肠肌,采用硫代巴比妥酸法测定大鼠丙二醛含量,黄嘌呤氧化酶法测定超氧化物歧化酶活性。结果与结论:与对照组比较,离心运动组大鼠腓肠肌丙二醛含量显著增高(P<0.05),并随运动后时间的延长逐渐升高,超氧化物歧化酶活性随运动后时间的延长显著降低(P<0.05)。与离心运动组比较,预热应激+离心运动组大鼠腓肠肌超氧化物歧化酶活性显著增高(P<0.05),丙二醛含量显著降低(P<0.05)。说明热应激预处理可增强骨骼肌超氧化物歧化酶活性,降低丙二醛含量,对离心运动损伤有保护作用。     

Chronic ethanol administration to rats decreases receptor-operated mobilization of intracellular ionic calcium in cultured hepatocytes and inhibits 1,4,5-inositol trisphosphate production: relevance to impaired liver regeneration.

We tested the hypothesis that ethanol impairs liver regeneration by abrogating receptor-mediated elevation of cytosolic free calcium ([Ca2+]i). In rats fed for 16 weeks with ethanol, hepatocellular proliferation induced by partial hepatectomy was greatly impaired. Similarly, EGF-induced DNA synthesis was reduced in cultured hepatocytes from ethanol-fed rats. There was no change in the number or affinity of EGF receptors on hepatocytes from ethanol-fed rats. Despite this, EGF-mediated production of inositol 1,4,5-trisphosphate (Ins[1,4,5]P3) was lower in hepatocytes from ethanol-fed rats, and the EGF-induced [Ca2+]i transient appeared to be abrogated. When vasopressin or phenylephrine were used as cell surface receptor ligands, hepatocytes cultured from ethanol-fed rats exhibited major reductions in Ins(1,4,5)P3 synthesis. This was associated with greatly truncated [Ca2+]i transients. These changes were not due to an effect on the Ins(1,4,5)P3 receptor on the endoplasmic reticulum or to a decrease in the size of the Ins(1,4,5)P3-mobilizable intracellular Ca+2 store. Further, mobilization of the same Ca2+ store by 2,5-di-tert-butylhydroquinone or thapsigargin restored the ability of hepatocytes from ethanol-fed rats to proliferate when exposed to EGF. It is concluded that chronic ethanol consumption inhibits liver regeneration by a mechanism that is, at least partly, the result of impaired receptor-operated [Ca2+]i signaling due to reduced generation of Ins(1,4,5)P3.