ANTIOXIDANT-PROOXIDANT BALANCE OF THE KIDNEYS IN RATS OF DIFFERENT AGES UNDER CONDITIONS OF EXPERIMENTAL CRANIOSKELETAL TRAUMA.

OBJECTIVE: The aim: To determine the peculiarities of the antioxidant-prooxidant balance in the kidney of rats of different ages under conditions of experimental cranioskeletal trauma (CST). PATIENTS AND METHODS: Materials and methods: The experiments involved 147 male white Wistar rats of different age groups. The first experimental group included immature animals aged 100-120 days. The second group included sexually mature animals aged 6-8 months. The third group included old animals aged 19-23 months. In all experimental groups, CST was modelled under thiopental-sodium anaesthesia. The control groups of rats was only injected with thiopental-sodium anaesthesia. The animals were withdrawn from the experiments under anaesthesia after 1, 3, 7, 14, 21 and 28 days by total bleeding from the heart. The content of reagents to thiobarbituric acid and catalase activity was determined in a 10 % kidney homogenate extract, and the antioxidant-prooxidant index (API) was calculated from the ratio of these two parameters. RESULTS: Results: As a result of the application of CST in rats of different age groups, a decrease in the value of renal API was observed with a maximum in immature rats - after 7 days, in mature and old rats - after 14 days. By day 28, the index increased in all experimental groups, but did not reach the control level. The degree of decrease in renal API in old rats under the influence of CCT was significantly higher than in other experimental groups. In immature rats, the impairment of renal API after the application of CST was less, indicating higher reserve capacity of the renal antioxidant defence system in this age group of rats. CONCLUSION: Conclusions: Simulation of CST in rats of different age groups is accompanied by a decrease in the value of API, which by day 28 does not reach the control level in any of the experimental groups. The degree of decrease in renal API value statistically significantly increases with increasing age of rats at all times of the post-traumatic period.

ANALYSIS OF THE BLOOD HYPERCOAGULATION RISK IN PATIENTS WITH ISCHEMIC ATHEROTHROMBOTIC STROKE DEPENDING OF THE VDR GENE POLYMORPHISMS.

OBJECTIVE: Aim: of our study was the analysis of the blood hypercoagulation risk in patients with ischemic atherotrombotic stroke depending of the VDR gene polymorphisms. PATIENTS AND METHODS: Materials and Methods: Blood of 170 patients with ischemic atherothrombotic stroke (IATS) and 124 healthy individuals (control group) was used for genotyping. Four polymorphisms (FokI, BsmI, ApaI, TaqI) of gene VDR were examined with PCR-RFLP methodology. Statistical analysis was performed by using SPSS-17.0 program. RESULTS: Results: Among patients with IATS who are carriers of the f/f genotype, FokI polymorphism of VDR gene by high thrombin time and a decrease in the rate of spontaneous fibrinolysis was registered. In individuals with the B/B genotype homozygous for the polymorphic variant, BsmI had significantly lower mean values of prothrombin and thrombin time and increased the rate of spontaneous fibrinolysis. The homozygotes for the A-allele ApaI polymorphism have 2.7 times higher risk of developing blood hypercoagulation than homozygotes for the a-allele was found. CONCLUSION: Conclusions: Biochemical signs of hypercoagulation syndrome among patients with IATS who are carriers of the f/f genotype of the FokI polymorphic variant and among B/B homozygotes of the BsmI polymorphic variant and homozygotes for the A-allele of the AрaI polymorphism of the VDR gene were registered.

A Current Management Strategy for Children with Chronic Viral Hepatitis B, Based on International and National Guidelines.

BACKGROUND: Peculiarities of the course of chronic viral hepatitis B in children cause an important medical and social problem of health care, despite the implementation of modern treatment and prevention protocols. Pathogenetic mechanisms of the development and progression of viral hepatitis B infection, the presence of occult poorly diagnosed form, the impossibility of completely eliminating the virus and the specificity of the immune response in children are still not fully solved scientific problems. MATERIAL AND METHODS: The aim of this review is to examine current strategies for the diagnosis and treatment of chronic hepatitis B in children, based on international and national guidelines. RESULTS: A detailed analysis of modern guidelines on the course and pathogenesis of viral hepatitis B infection confirms the fact that chronic hepatitis B is characterised by a complex interaction between the immune system of the virus and the patient, whose dynamic balance is not only responsible for the various phases of chronic viral hepatitis B infection but also leads to the result of antiviral treatment. CONCLUSION: Despite the introduction of vaccination of children against hepatitis B, the level of viral hepatitis B vaccination of children in Ukraine remains insufficient, which leads to the further spread of the infection. Currently available antiviral drugs can provide functional treatment of viral hepatitis B infection in a limited number of patients, but today's Ukrainian realities have caused a change in approach to the treatment and monitoring of patients, which may negatively affect the implementation of the key goals of the World Health Organization Global Strategy on the prevention, diagnosis and treatment of viral hepatitis.

LIVER CIRRHOSIS WITH CRYPTOGENIC GENESES. CLINICAL CASE.

The article presents clinical observation of a patient with cryptogenic cirrhosis of the liver, a chronic diffuse progressive liver disease, which is manifested by structural rearrange¬ment of its parenchyma. Cryptogenic cirrhosis is cirrhosis of uncertain etiology that lacks definitive clinical and histological criteria for a specific disease. Cryptogenic cirrhosis accounts for nearly 5% to 30% of cases of cirrhosis and nearly 10% of liver transplants. The problem of cirrhosis of the liver is extremely relevant, because this pathology is observed mainly in young and able-bodied people. In addition, it takes the first place among the causes of mortality from diseases of the digestive system. To clarify the diagnosis, laboratory and instrumental diagnostic methods of investigation were performed. Due to severe thrombocytopenia and minor leukopenia, myelodysplastic syndrome was suspected. Metabolic disorders that can be considered as probable in the occurrence of the above-mentioned changes in the liver parenchyma had been ruled out.

Impact of MMP-9 Genetic Polymorphism and Concentration on the Development of Coronary Artery Disease in Ukrainian Population.

Coronary artery disease (CAD) is one of the leading causes of death in Europe. It is known that atherosclerosis is the primary risk factor of CAD development. MMP-9 is involved in all stages of atherosclerosis and thus may contribute to CAD emergence. To investigate the influence of MMP-9 on the (CAD) development 25 patients with intact coronary arteries (CA), 40 patients with acute coronary syndrome (ACS), and 63 patients with chronic coronary syndrome (CCS) were enrolled in the study. Real-time PCR was carried out for genotyping on the rs17567-polymorphic locus, and ELISA study was performed to measure the MMP-9 plasma concentration. It was found the lower risk of MI occurrence for AG-carriers (P a =0.023; ORa = 0.299, 95% CI = 0.106-0.848) in Ukrainian population.

WAYS OF OPTIMIZING THE DIAGNOSTICS OF FOOD ALLERGIES IN CHILDREN BASED ON THE CLINICAL AND IMMUNOLOGICAL CRITERIA.

OBJECTIVE: The aim of the research was to investigate the spectrum of food sensitization, followed by the determination of the main clinical criteria and immunological markers of food allergy in children with gastroduodenal pathology and atopic dermatitis. PATIENTS AND METHODS: Materials and methods: We conducted a comprehensive clinical and immunological examination of 120 children aged from 6 to 15 years with gastroduodenal pathology (group 1; n = 64) and atopic dermatitis (group 2; n = 56), who had a history of adverse allergic reactions to food. The control group consisted of 22 apparently healthy children. RESULTS: Results: In the group of children with gastroduodenal pathology, the spectrum of the most common significant food allergens was represented by legumes, the reaction to which was observed in 25 (39.1%) subjects, eggs (25.0%) and fish (23.4%), which were found in every fourth child. Among patients with atopic dermatitis, the leading positions were occupied by fruits, which were registered in 20 (35.7%) children, nuts - in 15 (26.8%), honey and vegetables - in 11 (19.6%) children, respectively. The study of immunological status in comparison with the control group revealed reliable increases in pro-inflammatory T-helper-2 cytokines - interleukin-4 and chemokine TARC/CCL-17 and a simultaneous decrease in anti-inflammatory interleukin-10 in children of the 1st and 2nd groups who had gastrointestinal and skin manifestations of allergic reactions when eating food products. CONCLUSION: Conclusions: The study of peculiarities of adverse reactions to food in the examined children allowed us to identify specific clinical criteria and immunological markers of food allergy, which had certain features depending on the skin or gastrointestinal manifestations.

An open-label, multicentre, randomized comparative study of efficacy, safety and tolerability of the 5 plant - extract BNO 1012 in the Delayed Antibiotic Prescription Method in children, aged 6 to 11 years with acute viral and post-viral rhinosinusitis.

Acute rhinosinusitis (ARS) can be characterized as bacterial (ABRS) and require antibiotic therapy only in 0.5-5% of cases. In most cases, the disease is in a viral and post-viral form, which requires pathogenetic and symptomatic treatment. The study objective was to determine the efficacy of BNO 1012 extract in the technology of delayed antibiotic prescribing in children with acute rhinosinusitis. METHODS: 292 children aged 6 to 11 years with ARS were randomized in the multicenter, comparative study. They received an extract of five medicinal plants in addition to standard symptomatic therapy or standard therapy only. EVALUATION CRITERIA: reduction of the sinusitis severity according to a 4-point medical assessment scale (nasal congestion, severity of anterior and posterior rhinorrhea) at each visit, dynamics of self-scoring of rhinorrhea and headache (according to a 10-point visual analogue scale), "therapeutic benefit" in days, frequency of antibiotic prescriptions due to the use of an extract of five plants. RESULTS: The use of the 5-plant extract BNO 1012 in addition to the standard symptomatic treatment of acute rhinosinusitis provides a clinically significant, adequate reduction in the severity of rhinorrhea, nasal congestion and post-nasal drip, assessed by a physician at V2 (p < 0.005). Significant differences are noted in the patient's self-scoring of rhinorrhea on the second or third day in viral RS, and from the fourth to the eighth day in post-viral RS. Symptoms of similar intensity in control group were observed at V3. Thus, in the first week of treatment, the treatment group compared to the control one showed a "therapeutic benefit" of three days. The use of BNO 1012 in patients with acute rhinosinusitis can 1.81-fold reduce the prescription of antibacterial drugs. CONCLUSION: The combination of five medicinal plants is effective for the treatment of acute rhinosinusitis in children aged 6 to 11 years. Its use provides a significant "therapeutic benefit" when administered in addition to standard symptomatic therapy, reducing the need for antibiotic use.

THE ASSOCIASON OF VITAMIN D RECEPTOR GENE (VDR) POLYMORPHISMS WITH HIGH BLOOD PRESSURE IN STROKE PATIENTS OF UKRAINIAN POPULATION.

OBJECTIVE: The aim: To study the association of the polymorphisms VDR gene with high blood pressure in stroke patients in the Ukrainian population. PATIENTS AND METHODS: Materials and methods: Venous blood of 170 patients with atherothrombotic ischemic stroke (AIS) and 124 healthy individuals (control group) was used for genotyping. Four polymorphisms (FokI, BsmI, ApaI, TaqI) of gene VDR were examined with PCR-RFLP methodology. Statistical analysis was performed by using SPSS-17.0 program. RESULTS: Results: The correlation of genotypes of polymorphic variants of FokI, BsmI, ApaI and TaqI of the VDR gene with the development of ischemic atherothrombotic stroke in individuals with normal and high blood pressure was detected. Statistical analysis of the obtained data revealed that among carriers of genotypes F/F, b/b, a/a, a/A, and T/T patients with AI have statistically significantly higher incidence of hypertension than patients in the control group. CONCLUSION: Conclusions: It was found that persons with genotypes F/F, b/b, a/a, a/A, and T/T showed a statistically significant relationship between hypertension and the development of IAS. The application of logistic regression has made it possible to establish that the risk of IAS in people with normal blood pressure and genotype F/f is 3.2 times higher than in normotensive homozygotes for the F-allele.

The association of aрai-polymorphism of vitamin D receptor gene (VDR) with development of generalized parodontitis in Ukrainian population.

OBJECTIVE: Introduction: At present, it is believed that the genetic component is important in the pathogenesis of periodontitis. One of the candidate genes that are of major importance in the development of the disease is the vitamin D receptor gene (VDR). The association of its genetic polymorphisms, in particular Apal, with periodontitis in different populations of the world is proved. The aim: To study the association of the Apal-polymorphism VDR gene with the development of generalized periodontitis in the Ukrainian population. PATIENTS AND METHODS: Materials and methods: Patient genotypes were determined by polymerase chain reaction with subsequent analysis of restriction fragment length (PCR-RFLP) from buccal epithelium 116 patients with generalized periodontitis (GP) and 67 individuals of control group. Statistical analysis was performed by using SPSS-17,0 program. RESULTS: Results: As a result of the performed studies, it was shown that in the group of patients with GP, the ratio of homozygous for the main allele (a/a), heterozygote (a/A) and homozygote for the minor allele (A/A) was 26 (22,4%), 62 (53,4%), 28 (24,2%), and in control group - 25 (37,3%), 27 (40,3%), 15 (22,4%), respectively. The distribution of genotypes in the comparison groups was not statistically significant (P = 0,084). By the method of binary logistic regression in the framework of the additive inheritance model (a/A vs a/a), a reliable relationship of the genotype with the Apal-polymorphism of the VDR gene was established with the development of generalized periodontitis (Р=0,029). It was shown that in heterozygotes (a/A) the risk of GP in 2,208 (95% CI = 1,084-4,496) times is higher than in homozygotes of the main allele (a/a). After adjusting for age, sex, smoking habit, BMI, the reliability of these results was maintained (P = 0,030). CONCLUSION: Conclusions: The ApaI-polymorphism of the VDR gene is associated with the development of generalized periodontitis in the Ukrainian population.

Modern approaches to treatment of pseudomonas aeruginosa ventilator-associated pneumonia (literature review).

OBJECTIVE: Introduction: Nowadays anti-microbial therapy of ventilator-associated pneumonia caused by is one of the most topical issue as a consequence of widespread multiresistant strains of causative agent and their biological peculiarity of actively formation of resistance to new antibacterial drugs. The aim is to describe modern approaches to therapy of ventilator-associated pneumonia causative agent of which is presented by Pseudomonas aureginosa . PATIENTS AND METHODS: Materials and methods: An analysis and summing up of results of scientific investigations described in medical publications concerning the issues of therapy of ventilatorassociated pneumonia caused by Pseudomonas aureginosa was done. CONCLUSION: Conclusions: Despite the development of modern approaches to anti-microbial therapy of ventilator-associated pneumonia caused by Pseudomonas aeruginosa, which are also concerned with such controversial issues as correct choice of antibacterial drug, its optimal dose, and duration of this therapy, the problem of treatment of hospital-acquired infections of respiratory airways caused by Pseudomonas aeruginosa has been discussable yet and requires the further study.

Vaccination coverage rates and the incidence of vaccine preventable diseases among children in sumy region of Ukraine.

OBJECTIVE: Introduction: Routine immunization contributes immensely to decline the incidence of vaccine preventable diseases among children. Statistical data shown the sharply decrease the vaccination coverage rates in Sumy region of Ukraine. The aim: Assess routine immunization uptake and its effect on the incidence of vaccine preventable diseases among children in Sumy region of Ukraine. RESULTS: Review: During some years, only 50-60 % of Sumy region children had received all recommended vaccines, which is far below World Health Organization target of 80 %. This has led to an increase of morbidity associated with some infectious diseases. Outbreaks of measles were registered in 2006 and 2012, when were ill 9346 and 7931 children respectively. Massive measles outbreak ongoing nowadays. Total number infected have already exceeded 35,000 cases. CONCLUSION: Conclusions: RI uptake in Ukraine is still below World Health Organization target. The main reason for the ongoing measles outbreak was low vaccination coverage for routine immunization antigens as a result of which collective immunity decreased to a critical level. Strict monitoring of the implementation of the immunization schedule by medical institutions at all levels are recommended to improve vaccination status of Ukrainian children.

Peculiarities of crohn's disease in children - the way from diagnosis verification to the development of complications (clinical case).

OBJECTIVE: Introduction: Despite increasing frequency of inflammatory diseases of the intestine in the children worldwide, verification of Crohn's disease (CD) diagnosis in pediatric practice has not studied yet and it is difficult for clinician to determine the stage of the disease. The aim of our study was to analyze clinical case of Crohn's disease (CD) in a child based on literature data and own monitoring. PATIENTS AND METHODS: Materials and methods: 13 year old patient was involved in our examination who took complex lab and instrumental investigation, which allows verifying inflammatory intestinal pathology such as Crohn's disease. Clinical case of the disease demonstrates that clinical symptomatic picture, difficulties of differential diagnostics and the absence of effective interaction between relatives of the patient and doctor can't give the possibility to make correct diagnosis in pediatric practice and it can lead to complications of the development of disablement. CONCLUSION: Conclusions: Crohn's disease is a serious inflammatory intestinal disease that requires an interdisciplinary diagnostic approach for the successful verification of the diagnosis.

Synthesis of Multifunctional Spirocyclic Azetidines and Their Application in Drug Discovery.

The synthesis of multifunctional spirocycles was achieved from common cyclic carboxylic acids (cyclobutane carboxylate, cyclopentane carboxylate, l-proline, etc.). The whole sequence included only two chemical steps-synthesis of azetidinones, and reduction into azetidines. The obtained spirocyclic amino acids were incorporated into a structure of the known anesthetic drug Bupivacaine. The obtained analogues were more active and less toxic than the original drug. We believe that this discovery will lead to a wide use of spirocyclic building blocks in drug discovery in the near future.

[Role of c+70g single nucleotide polymorphism of endothelin receptor a gene in the development of ischemic atherothrombotic stroke].

INTRODUCTION: Endothelial dysfunction is the basic pathogenic development mechanism of ischemic atherothrombotic stroke (IAS). One of the reasons for changes of endothelin structure and properties and its receptor can be genetic polymorphism of their genes. AIM: Study of C+70G polymorphic variant associations of endothelin receptor A gene (EDNRA) with IAS development became the goal of research. MATERIAL AND METHODS: Venous blood of 170 patients with IAS and 124 persons without cerebrovascular pathology was used for the research. The groups did not differ in the ratio of two sexes (P = 0,294 for the ?2-test), but the average age of the first group (76,7 ± 0,93 years) was significantly higher than that of the second one (P < 0,001). Determination of allelic variant of EDNRA gene by C+70G polymorphism was carried out using method of polymerase chain reaction with further analysis of restriction fragment length. RESULTS: As a result of the conducted genotyping, it has been discovered that homozygote correlation by the main allele (CC), heterozygotes (CG) and homozygotes by minor allele (GG) does not differ authentically in patients with IAS and control group (24.1 %, 57.6 %, 8.2 % against 29.0 %, 50.0 %, 21.0 %; ? = 0.426). It is shown that association of the studied genetic marker with the scope of brain damage, localization of atherothrombotic process, course severity, recurrence and neurological manifestations of IAS. CONCLUSIONS: There is no association between the C+70G polymorphism of the EDNRA gene and the development of IAS and its clinical characteristics.

Accuracy of oximetry with thermistor (OxiFlow) for diagnosis of obstructive sleep apnea and hypopnea.

OBJECTIVES: To evaluate the diagnostic accuracy for obstructive sleep apnea and hypopnea (OSAH) of the OxiFlow (OF) device which combines oximetry with recording of thermistor airflow. DESIGN & SETTING: Patients scheduled for overnight diagnostic polysomnography (PSG) were studied with OF either simultaneously during laboratory PSG (L-OF, n=86), at home on a separate night (H-OF, n=66), or both (n=55). PATIENTS: 97 patients with suspected OSAH, of whom 40 had OSAH defined as an apnea-hypopnea index (AHI) of more than 15 events per hour of sleep on PSG. INTERVENTIONS: NA. MEASUREMENTS & RESULTS: The automated respiratory disturbance index (RDI) generated by the OF software considerably underestimated the AHI by PSG for both L-OF and H-OF. Altering the parameters for hypopnea identification by the software did not improve this. Visual inspection of the computerized OF tracings added considerable diagnostic information, but a manual count of RDI during visual review overestimated AHI. For the identification of cases vs. non-cases of OSAH, receiver operating characteristic area-under-the-curve statistics ranged from 0.77-0.90 for L-OF and from 0.71-0.77 for H-OF. Combining automated analysis with subsequent visual inspection of OF tracings yielded an overall sensitivity of 86% and specificity of 74% for the diagnosis of OSAH during H-OF recordings. Analysis of potential technician time saved indicated a benefit from the use of OF. CONCLUSIONS: OF has diagnostic utility for the identification of OSAH. However, because of hardware and software limitations, it is unclear whether this device is superior to oximetry alone.

Changes in obstructive sleep apnea characteristics through the night.

It was our impression that the respiratory parameters in obstructive sleep apnea (OSA) worsened as the night progressed. To confirm this, we review polysomnographic studies from 66 patients with apnea-hypopnea indices (AHI) of 40 to 125 events per hour, dividing bed time into equal quartiles. As the night progressed, the mean apnea duration (MAD) increased from 27.2 s to 34.6 s (p < 0.0001), mainly from increases during NREM sleep. The proportion of time spent in apnea increased from 54 to 71% (p < 0.0001) due to increases in both MAD and the proportion of REM sleep (from 2.8 to 14.7% of the total sleep time). The AHI did not change significantly between quartiles. Even though preapneic oxygen saturation did not change and apnea duration increased as the night progressed, the end-apneic saturation did not decrease, hence the rate of oxygen desaturation decreased. Also, it was found that patients with an AHI greater than 65 events per hour increased their proportion of time spent in apnea significantly more than those with an AHI smaller than 65, as the night progressed. In the patients with an AHI greater than 85, this was due to both an increase in MAD and AHI. In conclusion, in patients with an AHI greater than 40 events per hour, the severity of apnea increased as the night progressed due to lengthening of MAD, increased proportion of REM sleep, and in the most severe patients, also an increase in AHI. Even though the exact pathophysiologic mechanisms for the observed changes are unknown, a decrease in respiratory muscle effort with consequent decrease in oxygen consumption may explain both the lengthening of the apneas and the decrease in the rate of oxygen desaturation.

Mechanisms of apnea termination in obstructive sleep apnea. Role of chemoreceptor and mechanoreceptor stimuli.

Previous work from our laboratory has indicated that mechanoreceptor feedback from the respiratory muscles may play an important role in arousal and apnea termination in obstructive sleep apnea (OSA). Other studies have pointed to a prominent role for chemoreceptor stimuli. We postulated that mechanoreceptor stimuli from the respiratory system are the primary determinant of apnea termination, and that chemoreceptor stimuli exert their effect indirectly through stimulation of ventilation and thus proprioceptive feedback. To test this, we measured the diaphragmatic tension-time index (TTdi) during obstructive sleep apneas in seven male subjects with severe untreated OSA. We compared the maximal TTdi values at end-apnea during administration of air, O2, and CO2. We reasoned that if mechanoreceptor stimuli mediate apnea termination, changing the degree of chemoreceptor stimulation during apneas should not alter the level of respiratory effort at end-apnea. O2 administration produced a significant increase in end-apneic arterial oxygen saturation (SaO2) and increased apnea duration. CO2 administration led to an increase in pre- and postapneic end-tidal carbon dioxide pressure (PETCO2), and tended to shorten apneas. However, the mean value for maximal end-apneic TTdi was 0.12 +/- 0.01 (SEM) during room air breathing and was unaltered by O2 (0.12 +/- 0.01) or CO2 (0.11 +/- 0.01) administration. The consistency of end-apneic TTdi values despite the varying chemical drive supports the hypothesis that apnea termination in OSA is mediated by mechanoreceptor feedback from the respiratory system, most likely from the respiratory muscles. The influence of chemoreceptor information may be mediated indirectly through an effect on ventilatory effort.

Influence of weight bearing on the adaptations of rat plantaris to ablation of its synergists.

The present study was designed to determine the contribution of weight bearing to the adaptations of the plantaris (PL) to synergist removal. PL from female rats were exposed to 28 days of a simultaneous condition of synergist ablation and hindlimb suspension. At 28 days, contractile responses and morphological measures were obtained and compared with muscles that either had synergists intact or were weight bearing or a combination of both. Synergist ablation prolonged PL maximum isometric twitch tension (Pt), time to peak tension (12%), and one-half relaxation time (12%); increased Pt (26%), maximum isometric tetanic tension (Po, 44%), fatigue resistance (FI, 42%), and fast fiber cross-sectional area (FT CSA, 20%); and decreased Pt/Po (13%) over nonablation counterparts. Suspension decreased PL Pt (26%), Po (26%), rest length (16%), FT CSA (31%), and slow-twitch fiber (ST) number (24%) but increased FI (75%) over weight-bearing counterparts. PL from weight-bearing animals were heavier than from suspended animals, and the extent of this response was greatest after synergist removal. Whole muscle and ST CSA and ST area contribution were greater only in weight-bearing synergist ablation muscles. Daily weight bearing (4 h) in synergist ablation hindlimb suspension groups caused PL weights and ST expressions to be halfway between 24-h suspension and 24-h weight-bearing groups. Our results suggest that weight bearing is not essential to the induction of several adaptations associated with synergist ablation but is required to cause the large muscle mass and ST expression characteristic of this model.

Physiological responses of rat plantaris motor units to overload induced by surgical removal of its synergists.

1. Rat plantaris muscles were subjected to chronic overload by the surgical removal of the soleus and most of the gastrocnemius muscles. Twelve to 16 wk later whole muscle and motor unit (ventral root dissection technique) contractile properties as well as histochemistry were determined. 2. Motor units were categorized as fast, fatigable (FF), fast, intermediate fatigue-resistant (FI), fast, fatigue-resistant (FR), and slow (S) based on contractile characteristics. Muscle fibers were identified as type I and type II according to myofibrillar ATPase staining. 3. Whole muscles demonstrated increases in wet weight, tetanic force, proportion of type I fibers, and mean cross-sectional areas of both type I and II fibers, as a result of chronic overload. 4. Tetanic tension increased by the same relative magnitude in all motor units whereas twitch tension remained unchanged. A significant change in the proportions of the motor unit types occurred in overloaded muscles, such that the latter contained higher proportions of FF and S units, and lower proportions of FI and FR units, than normal muscles. 5. The fatigue profile of a composite constructed from a summation of motor unit responses revealed that the overloaded plantaris displayed fatigue resistance similar to that of the normal plantaris for a given absolute force output. 6. Glycogen-depleted fibers of hypertrophied single motor units demonstrated uniform myofibrillar ATPase and SDH staining characteristics suggesting that metabolic adaptations among fibers of the same unit were similar after 12-16 wk of overload. 7. The finding that overload caused a uniform increase in the tetanic strength of all motor units, whereas alterations in fatigue resistance varied in degree and direction among unit types, demonstrate that these two properties are not controlled in parallel in this model. The smallest units maintain or even increase their fatigue resistance during the hypertrophic process, whereas high threshold units actually decrease in fatigue resistance.

Contractile and electromyographic characteristics of rat plantaris motor unit types during fatigue in situ.

1. The ventral root dissection technique was used to obtain contractile and electromyogram (e.m.g.) characteristics of ninety-five plantaris motor units in situ in pentobarbitone-anaesthetized rats (n = 20). 2. Motor units demonstrated a wide spectrum of sizes, contractile speeds, and fatigue indices, and were categorized in the same manner as cat hind-limb motor units. Fast-fatigable (f.f.) and fast-intermediate fatigue resistant (f.i.) motor units constituted 20.2 and 25.5% of the motor unit population but together generated over 75% of the cumulative tetanic force. Fast-fatigue resistant (f.r.) and slow motor units composed 43.6 and 10.6% of the population while producing less than 25% of the aggregate tetanic force. 3. Only f.f. and a portion of f.i. motor units demonstrated extensive e.m.g. amplitude reductions during a standard fatigue test. Mean percentage e.m.g. decrease (from the first spike of the first burst to the last spike of the last burst) was 74.0 +/- 27.7% for f.f. units and 28.3 +/- 31.0% (mean +/- S.D.) for f.i. motor units. Relationships between percentage e.m.g. decline and motor unit size (tetanic force) showed significant (P less than 0.01) positive correlations in f.f. (r = 0.71) and f.i. (r = 0.69) motor units. 4. Backward extrapolation of the time course of the force-e.m.g. relationship during the fatigue test revealed that declines in e.m.g. may explain 15, 21 and 66% of the force losses in f.r., f.i. and f.f. motor units. Slow motor units were fatigue resistant and demonstrated a mean e.m.g. decline of 4.3 +/- 6.2%. 5. Indirectly stimulated whole muscle was more fatigable than a composite constructed from motor unit data because of more severe e.m.g. amplitude reductions in the former. 6. The motor unit mechanical and electrical responses during the fatigue test do not summate linearly during whole muscle contractile activity. This is most likely due to the presence, during whole muscle activity, of metabolic changes during the fatigue regimen which influence neuromuscular propagation of excitation, which are not as severe during single motor unit activity.