Minimizing creatine kinase variability in rats for neuromuscular research purposes

Rat serum or plasma creatine kinase (CK) activity is widely used to evaluate myopathic processes, to test the myotoxicity of different drugs, or to analyse the benefits of emerging gene therapies in some neuromuscular disorders. However, great variability is found in this determination. The aim of this study has been to control some factors of variation in order to reduce variability and increase the reproducibility of analytical data. 8-10-week-old Wistar-Han rats were used. The study consisted of four sequential phases. Phase I aimed to analyse the effect of ether and isoflurane as anaesthetic drugs. The objective of Phase II was to evaluate bleeding rats via retro-orbital sinus vs. tail vein. Phases III and IV were designed as two separate, repeated measure experiments on two factors: habituation to laboratory handling procedures in Phase III and gender in Phase IV. The repeated factor was the storage temperature of blood sample prior to centrifugation. Ether did not significantly increased the CK value. Using isoflurane, getting rats accustomed to laboratory handling procedures and whole blood refrigeration prior to centrifugation and serum separation resulted in statistically significant reduction in CK value and variability. Male rats showed significantly higher values than female rats. In the light of our findings, CK value and variability in rats may be minimized by choosing tail vein as site of bleeding, getting rats accustomed to laboratory handling procedures and maintaining whole blood refrigerated until centrifugation and serum separation.     

Reciprocal changes in renal ACE/ANG II and ACE2/ANG 1-7 are associated with enhanced collecting duct renin in Goldblatt hypertensive rats

Alterations in the balance between ANG II/ACE and ANG 1-7/ACE2 in ANG II-dependent hypertension could reduce the generation of ANG 1-7 and contribute further to increased intrarenal ANG II. Upregulation of collecting duct (CD) renin may lead to increased ANG II formation during ANG II-dependent hypertension, thus contributing to this imbalance. We measured ANG I, ANG II, and ANG 1-7 contents, angiotensin-converting enzyme (ACE) and ACE2 gene expression, and renin activity in the renal cortex and medulla in the clipped kidneys (CK) and nonclipped kidneys (NCK) of 2K1C rats. After 3 wk of unilateral renal clipping, systolic blood pressure and plasma renin activity increased in 2K1C rats (n = 11) compared with sham rats (n = 9). Renal medullary angiotensin peptide levels were increased in 2K1C rats [ANG I: (CK = 171 ± 4; NCK = 251 ± 8 vs. sham = 55 ± 3 pg/g protein; P < 0.05); ANG II: (CK = 558 ± 79; NCK = 328 ± 18 vs. sham = 94 ± 7 pg/g protein; P < 0.001)]; and ANG 1-7 levels decreased (CK = 18 ± 2; NCK = 19 ± 2 pg/g vs. sham = 63 ± 10 pg/g; P < 0.001). In renal medullas of both kidneys of 2K1C rats, ACE mRNA levels and activity increased but ACE2 decreased. In further studies, we compared renal ACE and ACE2 mRNA levels and their activities from chronic ANG II-infused (n = 6) and sham-operated rats (n = 5). Although the ACE mRNA levels did not differ between ANG II rats and sham rats, the ANG II rats exhibited greater ACE activity and reduced ACE2 mRNA levels and activity. Renal medullary renin activity was similar in the CK and NCK of 2K1C rats but higher compared with sham. Thus, the differential regulation of ACE and ACE2 along with the upregulation of CD renin in both the CK and NCK in 2K1C hypertensive rats indicates that they are independent of perfusion pressure and contribute to the altered content of intrarenal ANG II and ANG 1-7.     

Brain creatine kinase activity in an animal model of mania

There is evidence pointing to dysfunction at the mitochondrial level as an important target for the understanding of the pathophysiology of bipolar disorder (BD). We assessed creatine kinase (CK) activity in rats submitted to an animal model of mania which included the use of lithium and valproate. In the acute treatment, amphetamine (AMPH) or saline was administered to rats for 14 days, and between day 8 and 14, rats were treated with either lithium, valproate or saline. In the maintenance treatment, rats were pretreated with lithium, valproate or saline, and between day 8 and 14, AMPH or saline were administered. In both experiments, locomotor activity was assessed by open-field test and CK activity was evaluated in hippocampus, striatum, cerebellum, whole cortex and prefrontal cortex. Our results showed that mood stabilizers reversed AMPH-induced behavioral effects. Moreover, AMPH (acute treatment) inhibited CK activity in hippocampus, striatum and cortex, but not in cerebellum and prefrontal cortex, and administration of lithium or valproate did not reverse the enzyme inhibition. In the maintenance treatment, AMPH decreased CK activity in saline-pretreated rats in hippocampus, striatum and cortex, but not in cerebellum and prefrontal cortex. AMPH administration in lithium- or valproate-pretreated animals decreased CK activity in hippocampus, striatum and cortex. Our results showed that AMPH inhibited CK activity and that mood stabilizers were not able to reverse and/or prevent the enzyme inhibition. These findings reinforce the hypothesis that mitochondrial dysfunction plays an important role in the pathophysiology of BD.     

Less calcemic Vitamin D analogs enhance creatine kinase specific activity and modulate responsiveness to gonadal steroids in the vasculature

Vitamin D receptors are widely expressed in the cardiovascular system, in which Vitamin D and its metabolites exert a variety of biological activities such as regulation of cellular proliferation and differentiation, cell calcium transients and cell energy metabolism in vitro. The latter is mediated through the control of the brain type creatine kinase specific activity (CK), which serves to provide a readily available reservoir for ATP generation under increased work-load. In the present study we undertook to assess the role of Vitamin D on energy metabolism in the rat heart and aorta in vivo by using CK, which is a key energy metabolizing enzyme and compare Vitamin D depleted and repleted animals. Vascular tissues from female or male Vitamin D-depleted rats showed 61-80% lower CK activity in the aorta (Ao) and left ventricle of the heart (Lv) than control, Vitamin D-replete rats. Moreover, neither estradiol-17beta (E2) nor dihydrotestosterone (DHT), which increases CK specific activity in Ao and Lv of intact female or male rats, respectively, were able to stimulate CK in Vitamin D-depleted rats. Treatment of intact female rats for 2 weeks or 2 months with the less-calcemic Vitamin D analogs JKF 1624F2-2 (JKF) or QW 1624F2-2 (QW) (Fig. 1), did not significantly affect CK specific activity. However, after pretreatment with these analogs, there was an up regulation of the E2-induced CK response in Ao and Lv. In intact female rats, all Vitamin D analogs also potentiated the in vivo CK response to the SERMs raloxifene (Ral) and tamoxifen (TAM) in Ao and Lv. However the inhibitory effect of Ral or TAM on E2-induced CK activity was lost after pretreatment with Vitamin D analogs. The non-calcemic analog CB 1093 (CB) induced a significant increase in estradiol receptor alpha (ERalpha) protein in both myocardial and aortic tissue from intact and from ovariectomized female rats. Collectively, these results indicate that Vitamin D analogs modulate cell energy homeostasis in vascular tissues through induction of CK and up regulation of the response and sensitivity of CK in vascular tissues to E2 and to SERMs, possibly through via an increase in ERalpha protein in female derived organs. These results corroborate our previous in vitro studies in human vascular cells and further suggest that the Vitamin D system plays an important physiological role in maintaining normal cell energy reservoir in the vasculature.     

不同因素致亚健康大鼠血液生化、血气电解质指标的影响

目的观察不同因素致亚健康模型大鼠血液生化和血气电解质指标的变化。方法 60只雄性Wistar大鼠随机分为5组,即多因素（MF）组、热水游泳（WS）组、睡眠不足（SD）组、单纯束缚（PC）组和正常对照（C）组,每组12只。采用热水游泳、睡眠剥夺和单纯束缚等单因素或多因素联合建立亚健康大鼠模型,各组造模5d后,处死6只,剩余动物进行恢复性饲养3 d后处死。分别测定造模结束后和恢复3 d时大鼠的血清中的丙氨酸转氨酶（ALT）、天冬氨酸转氨酶（AST）、总蛋白（TP）、白蛋白（ALB）、尿素氮（BUN）、肌酐（CREA）、血糖（GLU）、总胆固醇（TC）、甘油三酯（TG）、肌酸磷酸激酶（CK）、乳酸脱氢酶（LDH）和血气电解质等指标。结果 （1）与正常对照（C）组比,造模5d后MF组的大鼠BUN和TG水平显著降低（P〈0.05,P〈0.01）,同时CREA、AST、CK、CK/AST和LDH水平显著升高（P〈0.01）,WS组的大鼠TC、CK、CK/AST和LDH水平亦升高显著（P〈0.01）,且各模型组的大鼠GLU浓度明显增加（P〈0.01）;恢复3 d后,MF组的大鼠TC、AST、ALT、ALB、BUN、CK、CK/AST和LDH水平均明显高于C组（P〈0.05,P〈0.01）;WS组的大鼠血清AST、CK、CK/AST比值和LDH水平亦显著高于C组（P〈0.01）,SD组的大鼠CK显著高于C组（P〈0.05）;（2）与C组比,造模5d后MF组、SD组和PC组的大鼠PCO2、Hct和Hb均明显升高（P〈0.05,P〈0.01）,WS组Hct和Hb升高显著且Na＋显著降低（P〈0.01）,MF组的大鼠PO2和SO2%均显著降低且K＋明显升高（P〈0.05）,且各造模组的大鼠HCO3-♂的浓度均显著升高（P〈0.05,P〈0.01）;恢复3 d后,除各造模大鼠的血液pH值和PO2均明显下降（P〈0.05,P〈0.01）外,MF组、SD组和PC组的大鼠PCO2升高并伴有SO2%的降低（P〈0.05,P〈0.01）,MF组和WS组Na＋仍明显低于C组（P〈0.05,P〈0.01）,SD组的大鼠K＋和Mg2＋则明显高于C组（P〈0.05,P〈0.01）。结论不同因素诱导的亚健康状态大鼠的血液生化、血气电解质指标均出现了不同程度上的改变,故血液生化和血气电解质指标能有效评估亚健康状态机体血液微环境的改变。     

辽宁地区普通级和SPF级Wistar大鼠血液生化指标检测

目的建立本省、本地区实验动物生理指标数据背景资料,为科学研究和新药安全性评价提供准确、可靠、科学的参考依据。方法普通级、SPF级Wistar大白鼠（6～8周龄）各60只,雌雄各半,腹主动脉采血,用全自动生化分析仪及配套试剂盒检测血液生化指标。结果普通级Wistar大白鼠的ALT、ALP、CHO、CK、CRE雌雄之间差异显著（P〈0．05或P〈0．01）;SPF级Wistar大白鼠的ALB、ALT、ALP、CHO、BUN、CK、AST、GLU、TBIL雌雄之间差异显著（P〈0．05或P〈0．01）;普通级与SPF级Wistar大白鼠的ALT、ALP、TP、BUN、TBIL、CRE、CHO、CK、AST、ALB、GLU差异显著（P〈0．01）。结论本研究的结果证明普通级与SPF级Wistar大白鼠的血液生化指标差异显著,多数生化指标雌雄之间存在显著差异,为应用提供了有价值的参数。     

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.     

大鼠一次性力竭跑台运动模型的建立及动态评价

目的跑台急性运动疲劳动物模型的建立及评价。方法选取清洁级雄性Wistar大鼠24只(8周龄)作为实验对象。采用多级递增负荷跑台运动方案(跑台坡度为0°,负荷分为三级)建立一次性力竭跑台运动动物模型。尾静脉取血,分别测定大鼠在安静、运动30 min、运动90 min、力竭、恢复30 min、恢复90 min各时间点外周血葡萄糖(GLU)、乳酸(LD)、尿素(BU)、丙二醛(MDA)浓度和肌酸激酶(CK)、超氧化物歧化酶(SOD)活性。结果一次性力竭运动过程中大鼠行为能力和运动能力、血液代谢产物及能量物质呈现阶段性的动态变化。外周血LD、BU、MDA浓度及CK活性均较安静时显著性增高(P<0.01,P<0.05);GLU浓度、SOD活性较安静时显著降低(P<0.01,P<0.05)。各指标的变化特征说明大鼠已达到运动疲劳状态。结论建立了大鼠一次性力竭跑台运动模型,并客观动态评价了大鼠在运动疲劳产生、发展、恢复等不同阶段各指标的变化特点及规律。该模型可用于后续运动疲劳机制的相关研究。     

Effect of Ethanol on Nuclear Casein Kinase II Activity in Brain

Casein kinase II (CK II) plays an important role in serine/threonine dependent protein phosphorylation. In brain it is associated with long term potentiation besides its involvement in DNA, RNA and protein metabolism. Ethanol has been shown to induce cognitive impairment and affects DNA, RNA and protein metabolism at various steps. Since CK II is central in all these events, which are specifically affected by ethanol, the role of nuclear CK II is investigated in the present study. Total nuclear casein kinase activity was unaffected while heparin sensitive nuclear casein kinase II activity showed a 30% decrease in the brain from chronic alcohol fed rats. Cytosolic CK II activity was also unaffected. Immunological detection by western analysis using CK II antibodies showed no alteration in the quantity of enzyme. The decrease in nuclear casein kinase II might be responsible for ethanol induced cognitive impairment in the brain.     

Effects of Ballota nigra on blood biochemical parameters and insulin in albino rats

Ingestion of aqueous 70% ethanol extract of Ballota nigra (400 mg/kg body weight for 7 days) by albino rats (n=10) was investigated to study its effects on glucose, total cholesterol, triglycerides, aspartate aminotransferase (AST), alanine aminotransferase (ALT), troponin I (TnI), serum creatine kinase (CK), total protein, total bilirubin and blood urea. Ballota nigra extract caused a significant decrease in blood glucose, total serum cholesterol and CK levels. Blood levels of TnI, AST, ALT, triglycerides, total bilirubin, total protein and blood urea were unchanged. The hypoglycemic effect of Ballota nigra extract on albino rats was further investigated by conducting a glucose tolerance test intraperitoneally (IPGTT). Healthy rats that were fasting for 18 hours followed by administration of a dose of 400 mg/kg body weight of the crude extract of Ballota nigra, orally. A significant decrease in blood glucose levels (after 15, 30, and 45 minutes) with a significant increase in serum insulin level (after 15 and 30 minute) was noted. These results suggest that, the crude extract of Ballota nigra have hypoglycemic, insulin-releasing and cholesterol lowering effects in rats.     

Intracellular distribution of creatine kinase isoenzymes in the brains and hearts of rats at different stages of postnatal development]

The total activity and range of the creatine kinase (CK) isozymes have been studied in the homogenate and subcellular fractions (nuclei, mitochondria, cytoplasm) of the rat brain and heart during postnatal ontogenesis. The total activity of CK in the brain and heart of newborn rats was found to be 4 and 2 times less, resp., than in those of adults. The age patterns were established in the activity of cytoplasmic (CK-1, CK-2 and CK-3) and mitochondrial (CK-4) isozymes. During the whole postnatal development the rat brain contains only one cytoplasmic isozyme, CK-1. In the heart of newborn rats, as compared with adults, the content of CK-1 and CK-2 is much higher and that of CK-3 lower. On the 12-15th day of life the range of the CK isozymes approaches that characteristic of adult animals. The activity of CK-4 was found in the brain on the 5-7th day of life and in the heart on 12-15th day. In the range of the CK isozymes in the adult brain the content of mitochondrial CK amounts to 19.3% and in the heart to 16.5%. The data obtained complement the literary ones suggesting the low level of energy-forming processes in the brain and heart cells at the early stages of the rat postnatal development.     

Enzymatic activities in brains of diabetic rats treated with vanadyl sulphate and sodium tungstate

The hypothesis of the present study was that diabetes mellitus might affect brain metabolism. Streptozotocin (STZ)-induced diabetic rats, treated with vanadyl sulphate (V) and sodium tungstate (T) were employed to observe the aspartate aminotransferase (AST), alanine aminotransferase (ALT) and creatine kinase (CK) activities in brain homogenates. Significant increases in AST, ALT and CK activities were found in diabetic brain homogenates against controls, suggesting increments of transamination in brain and/or increases in cell membrane permeability to these enzymes. The increase in brain CK possibly expresses alterations in energy production. The decrease in CK activity caused by V and T treatment in diabetic rats suggests that both agents tend to normalize energy consumption. It is also possible that V and T-induced hypoglycemic effects cause metabolic alterations in brain.     

Effects of moderate pressure overload cardiac hypertrophy on the distribution of creatine kinase isozymes

Myocardial activities and isozyme distributions of creatine kinase (CK) and lactate dehydrogenase (LDH) were measured in rats with moderate pressure overload hypertrophy. Three weeks after aortic banding, the ratio of left ventricular (LV) weight to body weight increased by 30%. Values for enzyme activity in the hypertrophied LV were compared to values for control rats as well as to the contralateral relatively unaffected right ventricle (RV). In rats with moderate LV hypertrophy, total CK activity was unchanged. The percent MB-CK increased significantly (p less than 0.01) only in the hypertrophied LV, from 13 +/- 1% to 19 +/- 1% of total CK, while the sum of MM and mitochondrial-CK decreased from 86 +/- 3 to 80 +/- 3% (p less than 0.01). LDH activity increased (p less than 0.05) only in the hypertrophied ventricle from a control of 2.90 +/- 0.13 to 3.21 +/- 0.13 IU/mg protein, while the ratio of LDH activity at high to low substrate increased from 0.12 +/- 0.02 to 0.14 +/- 0.02 (p less than 0.05). Thus, the development of moderate pressure overload hypertrophy in the LV is associated with normal levels of total CK, but the percentage of MB-CK increases selectively in the primarily affected ventricle. Also, total LDH and LDH activity at high to low substrate concentration increases significantly in LV hypertrophy.     

Acute and remote biochemical and physiological effects of exhaustive weightlifting exercise

The goal of the work was a study of exhaustive weightlifting exercise effect on prolonged changes in physiological and biochemical variables characterized functional status of skeletal muscles. An exercise gave rise to significant blood lactate concentration increase that was indicative of an anaerobic metabolism to be a predominant mechanism of muscle contraction energy supply. A reduction of m. rectus femoris EMG activity (amplitude and frequency), tonus of tension and an increase in tonus of relaxation were found immediately after exercise. Both EMG amplitude and frequency were increased 1 day post-exercise. However, after 3 days of recovery, EMG amplitude and frequency were decreased again and, in parallel, blood serum creatine kinase (CK) activity was significantly increased. After 9 recovery days, all measured variables with the exception of CK were normalized. A significant reverse correlation was found between blood serum lactate concentration and m. rectus femoris EMG activity at the same time points. Blood serum CK activity and m. rectus femoris EMG and tonus variables were observed to be significantly reversely correlated on the 3rd post-exercise day. Presented data demonstrate that exhaustive exercise-induced muscle injury resulted in phase alterations in electrical activity and tonus which correlated with lactate concentration and CK activity in blood serum.     

Antidepressant Effects of the Ginsenoside Metabolite Compound K,Assessed by Behavioral Despair Test and Chronic Unpredictable Mild Stress Model

Depression is a major social and health problem worldwide. Compound K (CK), an intestinal metabolite of panaxadiol ginsenosides, has been demonstrated to possess significant pharmacological effects on the central nervous system (CNS). Here, we set up this study to investigate the antidepressant effect of CK, and to explore the potential mechanisms underlying this activity. The behavioral despair model and chronic unpredictable mild stress (CUMS) model were established in mice or rats, respectively. Forced swimming test (FST), tail suspension test (TST) and locomotor activity were performed in mice, while the open-field test, food consumption and sucrose preference were assessed in rats. To investigate the underlying mechanism, the levels of endogenous noradrenaline, dopamine (DA), 5-hydroxytryptamine (5-HT) and their metabolites in the prefrontal cortex (PFC) and hippocampus were detected by HPLC coupled with electron detector. The dopamine degradation enzyme (COMT and MAO) expression was measured by western blot. The BDNF and NGF expression were investigated by immunohistochemical staining analysis. The results showed CK (10, 30 mg/kg) intragastric administration for 14 days significantly shorten the immobility time in FST and TST, which could be partially reversed by a D1 receptor antagonist Sch23390. For CUMS rats, CK alleviated the depressant-like behaviors, including decreased food consumption, spontaneous locomotor activity and lower sucrose preference, while WAY-100635, a 5-HT_1A receptor antagonist, could attenuate this effect. In addition, CK increased the levels of 5-HT, DA and their metabolites in the PFC and hippocampus of CUMS rats, and could reverse overexpression of MAO_B in PFC and hippocampus. CK also increased the GSH and GPx activity in the hippocampus and PFC. The IHC results revealed the BDNF and NGF expression were increased in CK-treated rats. The obtained results indicate that CK exhibits antidepressant effects in rodents, which may be due to the regulation of monoamine neurotransmitter concentration, enhancement of antioxidant capacity, as well as increase of neurotrophin expression in the CNS.     

Kinetics of thymic stroma development in the foetal period

The kinetics of thymic epithelial cell development was examined in Wistar strain rats between 13th and 21st days of foetal life. The studies were based on immunocytochemical localisation of cytokeratin 16 (CK 16), Ki67 and on ultrastructural observations of thymus development. Expression of CK16 in individual groups was evaluated using the Micro Image v.4.0 software. In order to monitor changes in CK16 expression in individual days of foetal life, their results were subjected to statistical analysis, demonstrating: (1) correlation between CK16 expression and duration of foetal life, (2) most pronounced CK16 expression on the 16th day of foetal life, (3) typical localisation of CK16-positive cells in individual days of foetal life. The morphological observations suggest that individual subpopulations of epithelial cells differ in their kinetics of proliferative activity.     

Regulation of proliferation of rat cartilage and bone by sex steroid hormones

We have demonstrated previously that 17β-estradiol (E₂) stimulates proliferation of skeletal tissues, both in vivo and in vitro, as measured by increased DNA synthesis and creatine kinase (CK) specific activity. The effect of E₂ on bone is sex specific. E₂ is active only in females and androgens only in males. By contrast, in cartilage of both sexes, dihydrotestosterone (DHT) as well as E₂ stimulates CK specific activity and DNA synthesis. In bone, we find that sex steroids stimulate skeletal cell proliferation in gonadectomized as well as in immature rats. Ovariectomized (OVX) rats, between 1 and 4 weeks after surgery, show stimulation of CK by E₂. The basal activity and response of CK changes with the varying endogenous levels of E₂ in cycling rats, in which the highest basal activity is at proestrus and estrus and the highest response is in diestrus. In rats of all ages tested, both the basal and stimulated specific activity of CK is higher in diaphysis and epiphysis than in the uterus, or in the adipose tissue adjacent to the uterus, which has a response similar to that of the uterus itself. The effect of E₂ in vivo, and in chrondroblasts and osteoblasts in vitro, is inhibited by high levels of the antiestrogen tamoxifen which, by itself, in similar high concentrations, shows stimulatory effects. In addition to the sex steroids, skeletal cells are also stimulated by secosteroid and peptide calciotrophic hormones. The interactions of the sex steroids and the other calciotrophic hormones. These results provide the first steps towards understanding the regulation of bone cell proliferation and growth by the concerted action of a variety of hormones and growth factors.     

Age-related changes in rat thymic epithelial cells

We investigated age-related changes in immunocytochemical localisation of cytokeratin 16 (CK16) in thymuses of female Wistar rats at various stages of adult life (months 1, 3, 6, 12). Within the 1 st month of life, distribution of CK typical for individual subsets of thymic epithelial cells (TEC) was observed. The most numerous CK16+ TEC were observed in the outer region of medulla, in the outer cells of Hassall's corpuscles and in the superficial epithelial layer neighbouring the connective tissue of the capsule, septa and vessels of the thymus. In the 3rd month of life, increased intensity of CK16 reaction in superficial TEC was accompanied by increased numbers of CK 16+ TEC in the outer region of the medulla. Age-related alterations in the distribution of the studied markers were evident beginning from the 6th month of life and involved increased expression of CK16 in the superficial layer of TEC, which at the interface with the septa formed stratified epithelium. In parallel, decreased numbers of CK16+ TEC were observed in the outer region of the medulla. Changes in CK16+ TEC distribution of a similar type developed in 12-month old rats and they probably reflected altered functions of some TEC populations and decreased or increased biological activity of other TEC populations.     

Effect of denervation on the distribution and developmental transition of phosphoglycerate mutase and creatine phosphokinase isozymes in rat muscles of different fiber-type composition

Phosphoglycerate mutase (PGM) and creatine phosphokinase (CK) occur as three isozymes (types MM, MB and BB) in mammals and these exhibit similar transitions during skeletal muscle development. To study the influence of innervation on this transition and on the maintenance of the isozyme phenotype in mature muscle, we have determined the changes produced by sciatic neurectomy in neonatal and adult rat hindlimb muscles. In 40-day-old rats, denervation decreased both PGM and CK activity, the effect being more pronounced in the fast-twitch extensorum digitorum longus (EDL) and gastrocnemius muscles than in the slow-twitch soleus muscle. It also produced a progressive increase in the proportion of MB- and BB-PGM isozymes in EDL and gastrocnemius but not in soleus, and an increase of MB- and BB-CK isozymes in all three muscles. In 5-day-old rats, denervation prevented the developmental increase of PGM and CK activity in all three muscles. Denervation also prevented the normal decrease in the relative amounts of the MB and BB isozymes of both enzymes which occur during postnatal muscle development. These results can be explained by the different effects of denervation upon slow and fast muscles, and by the distinct distribution of PGM and CK isozymes in rat type I and II muscle fibers.