PubMed Health⌕ Search

Biomedical subjects

P M Tiidus

Publications and source records attributed to P M Tiidus.

At least 19 recordsLinked to original sources
PubMed2005

Oestrogen influence on myogenic satellite cells following downhill running in male rats: a preliminary study.

AIM: This study examined the effect of oestrogen supplementation in rats on myogenic satellite cell quantities in type I and II muscles following eccentric exercise. METHODS: Gonad intact adult male rats divided into four groups, oestrogen supplemented (25 mg oestrogen pellet) control (EC), oestrogen supplemented, exercised (EE), sham (no oestrogen) control (SC) and sham, exercised (SE). After 1 week of oestrogen exposure the EE and SE animals performed 90 min of intermittent downhill running (5 min running/2 min rest @-13.5 degrees incline and 17 m min(-1) speed). Seventy-two hours later exercised (EE and SE) and control (EC and SC) animals were killed and blood samples taken and soleus and white (superficial) vastus muscles surgically removed. Histochemical sections of soleus and white vastus muscles were examined for myogenic satellite cell content by use of Pax7 antibody and for neutrophil content by use of haematoxylin and eosin (H and E) staining procedures. RESULTS: Downhill running resulted in significant elevations in satellite cells and neutrophils detected in both soleus and white vastus muscle samples (P < 0.01). Interestingly, oestrogen supplementation resulted in significantly greater (P < 0.01) post-exercise elevations in satellite cells detected in both soleus and white vastus muscle samples compared with sham (no oestrogen) rats. Increases in neutrophils were significantly (P < 0.05) attenuated in oestrogen supplemented rats relative to sham in soleus but not in white vastus muscles. CONCLUSIONS: Oestrogen supplementation in male rats may have accentuated the 72 h post-downhill running increase in Pax7 detected myogenic satellite cell number in both soleus and white vastus muscles relative to unsupplemented rats. The mechanisms and physiological consequences of this effect are yet to be determined.

Animals↗
PubMed2002

Differential effect of oestrogen on post-exercise cardiac muscle myeloperoxidase and calpain activities in female rats.

The effects of oestrogen administration on 1 h post-exercise cardiac muscle myeloperoxidase (MPO) and calpain activities were determined in female rats. Rats were ovariectomized and implanted for 2 weeks with either oestrogen (25 mg 17-oestradiol) or placebo pellets or left with ovaries intact. Rats were then run for 1 h at 21 m min-1, 12% grade, killed 1 h post-exercise and cardiac muscle and blood samples were removed. Control animals from each group were killed without prior exercise. Serum oestrogen levels in the order of the highest to lowest were; ovariectomized oestrogen replaced rats > intact ovaries rats > ovariectomized placebo rats. Oestrogen induced significant (P < 0.05) elevations in cardiac MPO activity at rest and at 1 h post-exercise in ovariectomized rats. No significant elevations in cardiac MPO activity were evident in placebo ovariectomized or normal ovary rats at rest or post-exercise. Cardiac calpain activities were similar in all unexercised groups. Ovariectomized placebo and intact ovary rats had significantly (P < 0.05) elevated cardiac calpain activities 1 h post-exercise while calpain activity was not significantly elevated in hearts from ovariectomized oestrogen rats. These results demonstrate that oestrogen supplementation in ovariectomized rats induces elevations in cardiac muscle MPO activities at rest and at 1 h post-exercise. This is opposite to the effect of oestrogen in post-exercise skeletal muscle and implies a greater neutrophil infiltration into cardiac muscle caused by oestrogen. This effect cannot be explained by changes in 1 h post-exercise cardiac muscle calpain activity, the elevation of which was suppressed by oestrogen administration. Oestrogen influences cardiac calpain activity similarly to its effect in skeletal muscle. Thus, oestrogen administration to ovariectomized rats induces elevations in cardiac MPO activity while suppressing cardiac calpain activity.

Animals↗
PubMed2001

Oestrogen and sex influence on muscle damage and inflammation: evidence from animal models.

Recent evidence suggests that oestrogen and sex may influence the degree of disruption and post-damage inflammatory response seen in skeletal muscle. Evidence primarily from animal models suggests that oestrogen may be able to attenuate muscle disruption and attenuate or delay muscle leukocyte infiltration after contraction-induced and ischaemia-reperfusion-induced damage. Several potential mechanisms for this effect are discussed, along with the potential for oestrogen to influence the ultimate rate of skeletal muscle recovery from damage.

Animals↗
PubMed2001

Effects of ovariectomy and estrogen on ischemia-reperfusion injury in hindlimbs of female rats.

The effects of estrogen and ovariectomy on indexes of muscle damage after 2 h of complete hindlimb ischemia and 2 h of reperfusion were investigated in female Sprague-Dawley rats. The rats were assigned to one of three experimental groups: ovariectomized with a 17beta-estradiol pellet implant (OE), ovariectomized with a placebo pellet implant (OP), or control with intact ovaries (R). It was hypothesized that following ischemia-reperfusion (I/R), muscle damage indexes [serum creatine kinase (CK) activity, calpain-like activity, inflammatory cell infiltration, and markers of lipid peroxidation (thiobarbituric-reactive substances)] would be lower in the OE and R rats compared with the OP rats due to the protective effects of estrogen. Serum CK activity following I/R was greater (P < 0.01) in the R rats vs. OP rats and similar in the OP and OE rats. Calpain-like activity was greatest in the R rats (P < 0.01) and similar in the OP and OE rats. Neutrophil infiltration was assessed using the myeloperoxidase (MPO) assay and immunohistochemical staining for CD43-positive (CD43+) cells. MPO activity was lower (P < 0.05) in the OE rats compared with any other group and similar in the OP and R rats. The number of CD43+ cells was greater (P < 0.01) in the OP rats compared with the OE and R rats and similar in the OE and R rats. The OE rats had lower (P < 0.05) thiobarbituric-reactive substance content following I/R compared with the R and OP rats. Indexes of muscle damage were consistently attenuated in the OE rats but not in the R rats. A 10-fold difference in serum estrogen content may mediate this. Surprisingly, serum CK activity and muscle calpain-like activity were lower (P < 0.05) in the OP rats compared with the R rats. Increases in serum insulin-like growth factor-1 content (P < 0.05) due to ovariectomy were hypothesized to account for this finding. Thus both ovariectomy and estrogen supplementation have differential effects on indexes of I/R muscle damage.

Animals↗
PubMed2001

Estrogen effect on post-exercise skeletal muscle neutrophil infiltration and calpain activity.

We hypothesized that estrogen administration would attenuate skeletal muscle neutrophil infiltration, indices of muscle membrane disruption, and muscle calpain activity shortly after the termination of exercise. Ovariectomized female rats were implanted with either an estogen pellet (25 mg beta-estradiol) or a placebo pellet. Two weeks postimplant, animals were killed either at rest or 1 h after running exercise (60 min at 21 m x min(-1), 12% grade). The 4 experimental groups (n = 12) used were: unexercised placebo (UP), unexercised estrogen (UE), exercised placebo (EP), and exercised estrogen (EE). Blood samples were analyzed for creatine kinase (CK) activity and estradiol content. Plantaris and gastrocnemius muscles were removed and histochemical determination of neutrophil content or biochemical determination of myeloperoxidase (MPO), glucose-6-phosphate dehydrogenase (G6PD), and calpain-like activity determined. Estrogen supplemented animals had 10-20-fold higher circulating estradiol levels than placebo animals. EP animals had significantly higher (P < 0.05) circulating CK activities than EE or unexercised animals. Muscle neutrophil concentrations were significantly (P < 0.01) elevated in EP and EE groups compared with unexercised controls, with EP muscle neutrophil levels also being over 60% greater (P < 0.05) than in EE animals. EP animals also had higher (P < 0.05) muscle MPO activities than unexercised or EE animals. Muscle G6PD activities were not significantly different between any groups. Muscle caplain-like activities were 80% higher (P < 0.01) in EP animals than EE animals with calpain-like activities in EE animals similar to unexercised groups. These results indicate that estrogen supplementation in ovariectomized rats attenuated 1-h post-exercise serum CK activities, muscle neutrophil infiltration, MPO activities, and calpain-like activities when compared with exercised, unsupplemented animals. This supports the possibility of a relationship between estrogen, calpain dependent production of neutrophil chemo-attractant peptides, and 1-h post-exercise skeletal muscle neutrophil infiltration.

Animals↗
PubMed2001

Neutrophil response to prolonged exercise in immune-competent and RAG2/gamma c null mice.

The two aims of this study were (i) to compare the effects of prolonged exercise on circulating neutrophil number and muscle myeloperoxidase (MPO) activity between RAG2/gamma c null and immune-competent mice, and (ii) to evaluate the general suitability of the lymphocyte-deficient RAG2/gamma c null strain for use in exercise models of immune regulation. RAG2/gamma c null (male and female) and C57BL/6 (congenic immune-competent, male) mice were assigned to either control (C) or treadmill exercise (EX, 22 m/min, 90 min, 6% grade) groups. EX mice were killed immediately (EX0) or 24 h (EX24) after exercise. RAG2/gamma c null males had significantly (P < 0.05) fewer circulating CD45+ cells and higher %CD45+ neutrophils than did C57BL/6 males, independent of exercise. A significant interaction was observed for the effects of exercise and gender on %CD45+ neutrophils in the blood. At EX24, gastrocnemius (Gastroc) MPO significantly increased in EX mice. Gastroc MPO activity was 44% and 35% higher in RAG2/gamma c null vs. C57BL/6 males, and in female vs. male RAG2/gamma c null mice, respectively. Heart MPO activity did not differ between strains or among treatments. We concluded that the Rag2/gamma c null strain is a suitable model for future investigations on immune regulation following acute exercise stress.

Animals↗
PubMed2000

Estrogen and gender effects on muscle damage, inflammation, and oxidative stress.

Information suggests that there may be gender-based differences in skeletal muscle responses to damaging exercise. Evidence demonstrates that estrogen has strong antioxidant properties and may be an important factor in maintaining postexercise membrane stability and limiting creatine kinase (CK) leakage from damaged muscle in female animals. Research demonstrates effects of estrogen and possible gender differences in other morphological and biochemical indices of postexercise muscle damage and leukocyte invasion. Nevertheless, there are conflicting findings suggesting that in some in vivo exercise models, estrogen administration has limited ability to affect exercise-induced oxidative stress and muscle damage and may cause loss of tissue vitamin C. Gender differences appear to exist in tissue levels of other important antioxidants such as vitamin E and glutathione. More research is needed to fully define the potential for estrogen to influence postexercise muscle damage and the inflammatory response and to determine the mechanisms by which it may operate.

Animals↗
PubMed1999

Estrogen attenuates HSP 72 expression in acutely exercised male rodents.

Estrogen has been shown to reduce post-exercise skeletal muscle damage. Exercise-induced muscle damage may be a factor in the elevated post-exercise expression of heat-shock proteins (HSPs). Thus, the present investigation was conducted in order to examine the influence of estrogen on post-exercise levels of HSP 72 and heat-shock cognate, HSC 73, in male and female rodents. Prior to an acute bout of treadmill running, male and female Sprague-Dawley rats received daily injections of either 40 microg x kg(-1) of beta-estradiol 3-benzoate or olive oil vehicle for 2 weeks. A two- to fourfold reduction in post-exercise HSP 72 content was observed in the heart, liver, lung and red and white vastus muscles of estradiol-treated males compared with their vehicle-injected counterparts (P < 0.05). Compared to the males, the females had significantly lower post-exercise HSP 72 levels which were not affected by estradiol supplementation. Moreover, estradiol administration in male rodents resulted in a HSP response similar to that of females following exercise. Thus, the results of the present investigation suggest that estrogen is the factor responsible for the observed differences in post-exercise HSP 72 levels between males and females.

Animals↗
PubMed1999

Oestrogen attenuates post-exercise myeloperoxidase activity in skeletal muscle of male rats.

The effects of 2 weeks of oestrogen (40 microg kg BW-1 beta-estradiol 3-benzoate) injection on 24 h post-exercise myeloperoxidase (MPO) activities were determined in plantaris and soleus muscles and liver of sexually mature male and female rats. The treadmill running protocol (45-60 min, at 28 m min-1, 15% grade) induced significant elevations in muscle MPO activities 24 h post-exercise in male rats, while prior oestrogen administration to male rats eliminated the post-exercise elevations in muscle MPO activities. Female rats experienced no significant post-exercise elevations in muscle MPO activities. Hence oestrogen administration to male rats attenuated post-exercise muscle MPO activities to levels found in female animals. Liver MPO activities were not significantly affected by exercise, gender or oestrogen administration. Oestrogen may be a factor in diminishing 24 h post-exercise skeletal muscle leukocyte infiltration and inflammatory response in both male and female muscle.

Animals↗
PubMed1999

Massage and ultrasound as therapeutic modalities in exercise-induced muscle damage.

Although both massage and ultrasound treatment are used in clinical settings to enhance muscle functional recovery following exercise-induced muscle damage, there is a paucity of experimental evidence for their efficacy. Theoretically both massage and ultrasound could affect some physiological factors associated with enhancement of postexercise muscle recovery. However, the actual physiological mechanisms by which massage or ultrasound could influence postexercise muscle damage and repair are unknown. Most experimental evidence suggests that massage has little influence on muscle blood flow, clearance of "noxious" substances, recovery of postexercise muscle strength, or delayed soreness sensation. However, more data is needed before conclusions can be drawn as to the ability of massage to influence postexercise inflammatory response or various other physiological changes that characterize exercise-induced muscle damage and repair. There is even less information on the ability of ultrasound to influence physiological or functional factors associated with postexercise muscle damage. The few experiments that have been done tend to be contradictory and have yet to consider the range of ultrasound treatment parameters for therapeutic effectiveness in treating postexercise damage and influencing repair processes. Much more research is needed to determine whether either treatment modality can have any therapeutic effect on exercise-induced muscle damage and recovery of postexercise muscle function.

Exercise↗
PubMed1999

Gender and exercise influence on tissue antioxidant vitamin status in rats.

Although gender differences in antioxidant status based largely on differing estrogen levels have been postulated, it is not known if other gender based differences in tissue antioxidants exist. This experiment examined whether gender based differences in tissue vitamin C and vitamin E concentration exist, and investigated the possibility of gender based differences in indices of tissue oxidative stress following an acute exercise bout. It was determined that female rats had significantly higher levels of vitamin E in liver and heart tissues than males and that males had significantly more vitamin C in the plantaris muscle than females. However, female rats also had less liver glutathione than males. Acute exercise resulted in significant and equal tissue oxidative stress in both genders as indicated by tissue glutathione status. With some exceptions, tissue vitamin C and vitamin E concentrations were generally unaffected by acute exercise in either gender. Hence, while some gender differences in tissue antioxidant status in rats are evident, these differences do not affect tissue indices of oxidative stress following acute exercise.

Animals↗
PubMed1999

Estrogen and gender do not affect fatigue resistance of extensor digitorum longus muscle in rats.

The effects of estrogen on skeletal muscle fatigue are controversial. To determine the effects of estrogen and gender on rat extensor digitorum longus (EDL) muscle, we either injected 40 microg beta-estradiol 3/benzoate.kg BW(-1) to female rats or sham injected male or female rats for 14 days. Subsequently a 90 min fatigue protocol consisting of electrical stimulation at 10 Hz delivered in 500 ms trains was administered. Force was recorded for a 5 s period at the start of the protocol (0 min) and at 5 min intervals until completion following 90 min of stimulation. After 90 min, EDL force generation at 10 Hz stimulation declined in all groups to between 50-60 % of initial values. However, no significant difference in fatigue rate or final 10 Hz stimulated force was seen between females administered estrogen, sham injected females or males. Hence, estrogen administration and gender did not significantly affect EDL muscle fatigue in this model.

Adolescent↗
PubMed1998

Radical species in inflammation and overtraining.

Reactive oxygen species can be important in the initiation of exercise-induced muscle damage and in the initiation and propagation of the subsequent acute muscle inflammatory response. Oxygen radicals generated via the neutrophil respiratory burst are vital in clearing away muscle tissue that has been damaged by exercise and they may also be responsible for propagation of further damage. Intervention by antioxidants to limit the postexercise inflammatory response and its potential to impair optimal muscle function are of interest to serious and recreational sports participants. Although antioxidants have the potential to limit muscle oxidative stress during the postexercise period, direct evidence for their role in this is limited. It is likely that short-term training can protect muscle from subsequent exercise-induced damage and inflammation without necessarily improving muscle antioxidant status. Although muscle antioxidant status may be enhanced by longer term training, diet, or antioxidant administration, the significance of antioxidants in limiting muscle damage during the acute inflammatory response needs to be more clearly defined. It may even be counterproductive to limit neutrophil function during the inflammatory response, since this may inhibit subsequent muscle repair.

Animals↗
PubMed1997

Failure of manual massage to alter limb blood flow: measures by Doppler ultrasound.

The ability of manual massage to alter muscle blood flow through three types of massage treatments in a small (forearm) and a large (quadriceps) muscle mass was tested in 10 healthy individuals. A certified massage therapist administered effleurage, petrissage, and tapotement treatments to the forearm flexors (small muscle mass) and quadriceps (large muscle mass) muscle groups in a counterbalanced manner. Limb blood flow was determined from mean blood velocity (MBV) (pulsed Doppler) and vessel diameter (echo Doppler). MBV values were obtained from the continuous data sets prior to treatment, and at 5, 10, and 20 s and 5 min following the onset of massage. Arterial diameters were measured immediately prior to and following the massage treatments; these values were not different and were averaged for the blood flow calculations. The MBV (e.g., 5.77 +/- 0.4 and 9.73 +/- 0.7 cm.s-1) and blood flows (39.1 +/- 6.4 and 371 +/- 30 ml.min-1) for brachial and femoral arteries, respectively, were not altered by any of the massage treatments in either the forearm or quadriceps muscle groups (P > 0.05). Mild voluntary handgrip (approximately 35% maximal voluntary isometric contraction) and knee extension (15 cm) contractions resulted in peak blood velocities (15.2 +/- 1.2 and 28.1 +/- 3.1 cm.s-1) and blood flow (126 +/- 19 and 1087 +/- 144 ml.min-1) for brachial and femoral arteries, respectively, which were significantly elevated from rest (P < 0.05). The results indicate that manual massage does not elevate muscle blood flow irrespective of massage type or the muscle mass receiving the treatment. Further, the results indicate that if an elevated muscle blood flow is the desired therapeutic effect, then light exercise would be beneficial whereas massage would not.

Adult↗
PubMed1997

Manual massage and recovery of muscle function following exercise: a literature review.

There is currently little scientific evidence that manual massage has any significant impact on the short- or long-term recovery of muscle function following exercise or on the physiological factors associated with the recovery process. In addition, delayed onset muscle soreness may not be affected by massage. Light exercise of the affected muscles is probably more effective than massage in improving muscle blood flow (thereby possibly enhancing healing) and temporarily reducing delayed onset muscle soreness. This paper reviews current scientific evidence on the use of manual massage to affect: 1) muscle damage caused by eccentric muscle action; 2) retention and recovery of muscle strength and performance following "eccentric-mechanical" muscle damage; 3) reduction of delayed onset muscle soreness following "eccentric-mechanical" muscle damage; and 4) recovery of muscle strength and performance following anaerobic exercise. Because manual massage does not appear to have a demonstrated effect on the above, its use in athletic settings for these purposes should be questioned.

Exercise↗
PubMed1996

Elevated catalase activity in red and white muscles of MyoD gene-inactivated mice.

MyoD is a myogenic transcription factor responsible for skeletal muscle differentiation during development. Muscle antioxidant enzyme status was determined in transgenic MyoD deactivated mice. While catalase activity was significantly (P < 0.05) elevated in soleus and extensor digitorum longus muscles from MyoD deactivated mice, superoxide dismutase and glutathione peroxidase activities were not. While this may imply a greater propensity for inherent oxidative stress, soleus glutathione status was similar between MyoD deactivated mouse and control soleus muscles. Catalase activity is localized primarily in peroxisomes. Therefore elevated catalase activity may also indicate the presence of factors associated with peroxisome proliferation in muscles from MyoD gene-inactivated mice.

Animals↗