The use of "2-octyl cyanoacrylate" as skin adhesive in pediatric and congenital cardiac surgery.

AIM: The aim of this paper was to evaluate the safety and cost-effectiveness of "2-octyl-cyanoacrylate" as skin adhesive in congenital heart surgery. METHODS: From April 2010 to December 2011, we collected data from 300 patients who underwent cardiac surgery for congenital heart disease. We divided our population into 3 groups: group-1 (N.=100):"2-octyl-cyanoacrylate" has been used to replace the intra-dermal suture line; group-2 (N.=100):"2-octyl-cyanoacrylate" has been utilized as a barrier ("add-on measure") in addition to the intra-dermal suture line, group-3 (N.=100) with a standard intra-dermal suture line. RESULTS: Median age of patients was 1.36 years. One-hundred and thirty-nine patients were younger than 12 months and 56 older than 16 years. There were 11 wound dehiscence (3.6%) (2 in group-1 and 9 in group-3, P=0.001) and 1 superficial wound infection (group-1). Six patients (2%) required surgical wound revision (2 in group-1 and 4 in group-3, P=NS). Wound complication was significantly associated to delayed sternal closure (3/12 patients, 25% versus 13/288 patients, 4.5%) (P=0.04). Median cost (intra-/postoperative) for wound treatment was lower in group-1 and 2 (19±5.5 and 23.9±7.4 € respectively) when compared to Group-3 (26.7±3.2) (P<0.0001). CONCLUSION: The use of "2-octyl-cyanoacrylate" proved to be safe and effective; the "add-on measure" strategy provided the best cost-effective solution.

One-and-a-half ventricle repair as a surgical alternative to Fontan revision in an adult.

We report a case of a young man with hypoplastic right ventricle, who presented with recurrent untreatable arrhythmias after a Bjork Fontan procedure in infancy. He underwent one-and-a-half ventricle repair as an alternative surgery to Fontan revision.

One-and-a-half ventricle repair in adult patients: a word of caution.

OBJECTIVES: The "one-and-a-half ventricle repair" (1.5 VR) is applied to several congenital heart diseases with hypoplastic right ventricle (RV), with good functional and clinical results in infants and children, but feasibility in adult population is being explored. MATERIALS AND METHODS: This is a retrospective analysis of medical records of all adult patients undergoing 1 + 1/5 VR between 2000 and 2012. RESULTS: Five patients (M/F = 4/1, mean age of 42.3 years, range 29-66.8) underwent 1 + 1/5 VR. Underlying diagnoses were Ebstein's anomaly (EA) in three, hypoplastic RV and tricuspid valve (TV) in two. Mean TV annulus Z-score was -3.0; mean pulmonary vascular resistance was 1.6 WU/m(2) . Eleven associated procedures were performed simultaneously to 1.5 VR. There were no operative deaths. All patients were discharged home alive and in good clinical condition on anticoagulation regimen. At a mean follow-up of 8.6 ± 5.2 years, there was one cerebral stroke-related death; two patients experienced major complications. Two patients are in NYHA Class I, one is in NYHA Class II, and the last in NYHA Class III on a transplant list. CONCLUSIONS: The one-and-a-half ventricle repair in adult patients is feasible with low mortality. However, advanced age-associated co-morbidities and prolonged chronic RV preoperative dysfunction may jeopardize long-term results when compared to children.

The use fibrinogen/thrombin-coated equine collagen patch in children requiring reoperations for congenital heart disease. A single center clinical experience.

AIM: The aim of this study was to evaluate the efficacy and cost-effectiveness of fibrinogen/thrombin-coated collagen patch (FTCCP)(TachoSil®) during intraoperative hemostasis in patients with congenital heart disease, who required a reoperation during childhood. METHODS: We reviewed data on the intraoperative blood product requirements and hospital costs of children (age <16 years) who underwent a reoperation for treating their congenital heart disease between January 2009 and December 2011. RESULTS: One-hundred and seventeen patients were included. Median age at surgery was 2.1 years (range 3 days-14.1 years). Main causes of intraoperative bleeding were: 1) reinforcement of suture lines (106 patients, 90.6%); 2) lung lesions (5 patients, 4.2%); 3) epicardial lesions (3 patients, 2.6%); and 4) chest wall lesions (3 patients, 2.6%). At logistic regression the amount of packed red blood cells (PRBC) requirement was significantly higher in patients with preoperative cyanosis (P=0.008, OR=3.85) and in patients who required the use of cardiopulmonary bypass (P=0.005, OR=21.19). The use of FTCCP (N.=90 patients) as first line treatment was significantly associated with a lower PRBC requirement (P=0.0003, OR=0.1) which in addition to the avoidance of other hemostatic/sealant agents, leads to lower hospital cost. CONCLUSION: FTCCP is an effective hemostatic agent which can be safely used during the hemostasis of children requiring reoperations for their congenital heart malformations. When used as first line treatment, with specific indications, FTCCP limited the intraoperative PRBC requirement and the use of other hemostatic/sealant agents thus reducing hospital costs.

Efecto de distintos antimicrobianos sobre el crecimiento de Listeria monocytogenes / Effect of different antimicrobial agents on the growth of Listeria monocytogenes

En este estudio se ha evaluado la eficacia de dos ácidos orgánicos contemplados en la lista positiva de aditivos alimentarios, el lactato sódico (E-325) y el diacetato sódico (E-262), sobre el crecimiento de Listeria monocytogenes. Estos aditivos se adicionaron en diferentes concentraciones a un medio de cultivo líquido, determinando el incremento de densidad óptica del medio a 600 nm durante 24 horas a 37 ºC, con respecto al medio sin inocular que se tomó como blanco, realizando la medida cada hora. El incremento de absorbancia se midió con respecto al tiempo, evaluando el crecimiento de la bacteria a través de la interpretación de la tasa máxima de incremento de absorbancia (micro) y el tiempo mínimo requerido para detectar un incremento en la densidad óptica del medio (epsilon). Este último parámetro se puede equiparar al tiempo de latencia o tiempo de adaptación al medio. Así, para el lactato sódico, se observó que ejerce un efecto negativo dosis dependiente sobre el crecimiento de L. monocytogenes, prolongando el tiempo que necesitó la bacteria para adaptarse al medio de cultivo (epsilon), sin afectar a la tasa de crecimiento (micro) una vez que esta comenzó a crecer. El diacetato sódico mostró ser más efectivo que el lactato sódico frente al crecimiento de la bacteria, incrementando el tiempo de adaptación al medio, así como disminuyendo la tasa de crecimiento. Además, el diacetato sódico consiguió inhibir de forma completa el crecimiento de la bacteria a concentraciones iguales o superiores a 0.2%(AU)

The effectiveness of two organic acids included in the positive list for additives, sodium lactate (E-325) and sodium diacetate (E-262), was evaluated against Listeria monocytogenes growth. Different concentrations of these additives were added to the liquid culture medium. The optical density increments at 600 nm was measured for a 24 hours period under 37 0C, using non-inoculated medium as blank. The measurements were taken every hour in sterile 96 wells plates each. After this analysis, a graphical representation of absorbance increment against time was done, extrapolating the maximum absorbance increment rate (micro) and the minimum time required to detect an absorbance increment (epsilon) from the graphic. These two parameters made possible to evaluate the bacterial growth. After the analysis of epsilon and micro for lactate concentrations, a negative effect in bacterial growth was observed, extending epsilon value. Nevertheless, once the bacterial growth started, any effect on micro value was detected. A higher inhibitory effect was observed after the analysis of these parameters for diacetate concentrations, an extension on epsilon value as well as a micro value descent was found. In this way, a total inhibition of growth occurred when diacetate concentration was 0,2% or higher(AU)

[Association between relational and organizational factors and occurrence of musculoskeletal disease in health personnel]. / Associazione fra fattori relazionali e organizzativi e insorgenza di patologia muscolo-scheletrica negli operatori sanitari.

INTRODUCTION AND OBJECTIVES: Even if work musculo-skeletal disorders represent a serious and commonly observed health problem among health care workers, few data are available about physical therapists. This study aims to compare the musculoskeletal disorders prevalence over two different health care populations and MATERIALS AND METHODS: Two populations have been studied: (i) 100 nurses working in the teaching hospital Azienda Policlinico di Modena and (ii) 100 physical therapists working in different hospitals in Modena and Reggio Emilia. The ergonomic risk assessment has been made according to the Ergo Web questionnaire. A self-reported questionnaire [partly built according to Outil de Repérage et d'Evaluation des Gestes (OREGE) method] has been used to collect data about physiological factors, musculo-skeletal symptoms of the upper limb and spine, stress indexes and psychosocial indexes. RESULTS: The two populations are comparable as far as the data of physiological and working anamnesis. The physical therapists have an higher prevalence of neck pain (p<0.01), whereas the nurses have an higher prevalence of low back pain (p<0.01). Furthermore, the physical therapists have an higher index of pain (involving prevalence, number of occurrences and intensity of the disorder) of right upper limb too. The nurses have higher working strain (p=0.00), attention need at work (p=0.00), poor autonomy (p<0.01) indexes than physical therapists. The indexes' analysis shows that musculo-skeletal disorders are associated to stress and psychosocial factors in both populations.

Surgical outcome for congenital heart malformations in the adult age: a multicentric European study.

Congenital heart diseases are currently treated in the pediatric age. However, a conspicuous number of patients requires treatment in the adult age. This study has been undertaken by members of the European Congenital Heart Surgeons Association with the aim of evaluating the impact of cardiac surgery in this particular age group. We have collected data from 1,247 patients who underwent 1,287 operations during a 5-year period between January 1, 1997 and December 31, 2001. Patients were divided into three groups: (1) palliative procedures (4.4%), operation performed to improve patients' clinical status without restoring normal anatomy or physiology; (2) repair (79.3%), operation performed to achieve an anatomic or physiologic repair with separation of the pulmonary from the systemic circulation (included in this group are also Fontan-type repair and one and a half ventricle repair); (3) reoperation (16.3%), all the reoperations performed after repair (either anatomic or physiologic). Hospital mortality (within 30 days) was 2.4% (range, 0% to 15.3% in different centers). Kaplan-Meier estimates shows a 94% survival at 4 years, which is higher for repair (95%) as compared with reoperations (92%) or palliations (88%). Surgery for congenital heart disease in the adult age is a safe, beneficial, and low-risk treatment that modifies patients' natural history by improving their clinical status.

Surgical treatment of complete A-V canal defects in children before 3 months of age.

OBJECTIVES: Surgical repair of complete A-V canal defects (CAVCD) is a well established procedure which is currently performed in infancy. The aim of this study is to evaluate surgical results of correction in early infancy in comparison to older age. METHODS: From January 1985 to March 2001, 119 consecutive patients (age range 27 days to 83 months, mean 6.7 months) underwent repair of CAVCD in our Institution. Forms with unbalanced ventricles in association with Fallot's tetralogy or heterotaxia were excluded from this series. Fifty-eight patients (49%) underwent correction before 3 months of age (Group A), and 61 patients (51%) after 3 months (Group B). Surgical repair was accomplished with a double patch technique in 100 patients (84%). Associated surgical lesions were treated simultaneously in 48 patients (40%). RESULTS: There were 11 operative deaths (<30 days) (two in Group A (3.4%) and nine in Group B (15%)) (P = 0.05). The remaining patients were discharged home in good haemodynamic condition. Reoperation for postoperative left A-V incompetence occurred in five patients in Group A and in eight patients in Group B. There were eight late deaths (three in Group A and five in Group B), of which four were non-cardiac related. At a mean follow-up time of 80 months (range 2-184 months) 100 patients are asymptomatic and well, and free from oral medication. Echocardiographic examination showed absent or mild residual left A-V valve incompetence in 91 patients (49 in Group A and 42 in Group B) and moderate left A-V valve incompetence in nine patients (four in Group A and five in Group B). Kaplan-Meier survival estimates at 10 years were 90% for Group A and 75% for Group B. Kaplan-Meier freedom from reoperation at 10 years was 89% for Group A and 84% for Group B. CONCLUSIONS: Our data demonstrate that repair of CAVCD under 3 months of age is the ideal approach to this malformation with a lower mortality rate at operation compared to older patients. Logistic analysis showed that an operative age >3 months is, compared to an age < or =3 months, an incremental risk factor for hospital mortality with an odds ratio of 4.8 (95% confidence limit 1-23.5) (P = 0.05). In the long term, freedom from reoperation for left A-V valve incompetence is higher when compared to children repaired at an older age.

Surgical treatment of complex cardiac anomalies: the 'one and one half ventricle repair'.

OBJECTIVE: One and one half ventricle repair is a surgical option for congenital cardiac anomalies characterised by right ventricle (RV) hypoplasia and/or dysplasia. METHODS: From March 1994 to March 2001, eight patients (mean age 9.1 years, range 7 months to 35 years) with hypoplastic and/or dysplastic RV underwent correction of their intracardiac anomaly in association with a BCPS (one and one half ventricle repair). Preoperative diagnoses included: Ebstein's anomaly of tricuspid valve (TV) in two, inlet ventricular septal defect (VSD) in association with straddling/overriding TV in two patients, pulmonary atresia-intact ventricular septum in one, tertralogy of Fallot in association with complete atrioventricular canal defect in one, truncus arteriosus in one and heterotaxy syndrome with VSD and anomalous systemic venous return in one. Four patients underwent previous surgery which included: main pulmonary artery (MPA) banding in two patients, pulmonary valvotomy, central shunt and right ventricular outflow tract reconstruction in one, pulmonary artery separation from truncus arteriosus and modified Blalock-Taussig shunt in one, and MPA closure in one. Two patients underwent a bidirectional cavo-pulmonary shunt before the one and a one half ventricle repair. Associated cardiac lesions were treated simultaneously. RESULTS: There were no hospital deaths. All the patients were discharged home in good clinical conditions. There were no late deaths or reoperations. At mean follow-up of 29.8 months (range 8 months to 7.3 years) all the patients are alive and in good general conditions. MPA percutaneous balloon dilation was performed in two patients at 33 and 4 months, respectively, both after MPA reconstruction (which was previously ligated) and dilation of the left pulmonary artery branch in one patient, repeated twice at 10 and 14 months from repair, for a hypoplastic left pulmonary artery after truncus arteriosus repair. CONCLUSIONS: Surgical treatment of congenital cardiac anomalies in the presence of a hypoplastic and or a dysplastic RV by means of one and one half ventricle repair has the advantage of reducing the surgical risk for biventricular repair, and compared to the Fontan circulation, it maintains a low right atrium pressure, a pulsatile pulmonary blood flow and improves the systemic oxygen saturation. Short and medium-term results are promising. Longer follow-up is needed, to prove the efficacy of such a repair, in the long term.

Surgical treatment of complex cardiac anomalies: the 'one and one half ventricle repair'.

OBJECTIVE: One and one half ventricle repair is a surgical option for congenital cardiac anomalies characterised by right ventricle (RV) hypoplasia and/or dysplasia. METHODS: From March 1994 to March 2001, eight patients (mean age 9.1 years, range 7 months to 35 years) with hypoplastic and/or dysplastic RV underwent correction of their intracardiac anomaly in association with a BCPS (one and one half ventricle repair). Preoperative diagnoses included: Ebstein's anomaly of tricuspid valve (TV) in two, inlet ventricular septal defect (VSD) in association with straddling/overriding TV in two patients, pulmonary atresia-intact ventricular septum in one, tertralogy of Fallot in association with complete atrioventricular canal defect in one, truncus arteriosus in one and heterotaxy syndrome with VSD and anomalous systemic venous return in one. Four patients underwent previous surgery which included: main pulmonary artery (MPA) banding in two patients, pulmonary valvotomy, central shunt and right ventricular outflow tract reconstruction in one, pulmonary artery separation from truncus arteriosus and modified Blalock-Taussig shunt in one, and MPA closure in one. Two patients underwent a bidirectional cavo-pulmonary shunt before the one and a one half ventricle repair. Associated cardiac lesions were treated simultaneously. RESULTS: There were no hospital deaths. All the patients were discharged home in good clinical conditions. There were no late deaths or reoperations. At mean follow-up of 29.8 months (range 8 months to 7.3 years) all the patients are alive and in good general conditions. MPA percutaneous balloon dilation was performed in two patients at 33 and 4 months, respectively, both after MPA reconstruction (which was previously ligated) and dilation of the left pulmonary artery branch in one patient, repeated twice at 10 and 14 months from repair, for a hypoplastic left pulmonary artery after truncus arteriosus repair. CONCLUSIONS: Surgical treatment of congenital cardiac anomalies in the presence of a hypoplastic and or a dysplastic RV by means of one and one half ventricle repair has the advantage of reducing the surgical risk for biventricular repair, and compared to the Fontan circulation, it maintains a low right atrium pressure, a pulsatile pulmonary blood flow and improves the systemic oxygen saturation. Short and medium-term results are promising. Longer follow-up is needed, to prove the efficacy of such a repair, in the long term.

Arterial switch operation after left ventricular retraining in the adult.

Retraining the morphological left ventricle in transposition of the great arteries has been successfully reported in infancy, while older age seems to be a contraindication. A 23-year-old woman with ¿S,D,D¿ transposition of the great arteries and ventricular septal defect developed severe right systemic ventricular dysfunction 22 years after Mustard procedure and ventricular septal defect closure. Hemodynamic investigation revealed moderate pulmonary hypertension and preserved left ventricular function. A pulmonary artery band was applied to obtain a left-right ventricular pressure ratio of 0.91. Her postoperative course was characterized by biventricular failure, treated effectively with inotropic support. Six months later, she underwent a Mustard baffle takedown and arterial switch procedure. Her postoperative course was uneventful. She was discharged home on postoperative day 15. At 24-months follow-up, she is in excellent clinical condition; echocardiographic evaluation shows good left ventricular function (ejection fraction: 0.69) with left ventricular volume within normal limits (70 ml/m2). Our experience demonstrates that, despite adult age, a staged arterial switch operation can be performed successfully in selected patients when left ventricular function is preserved.

Repair of congenital mitral valve dysplasia in infants and children: is it always possible?

OBJECTIVES: Surgical management of congenital malformation of the mitral valve (MV) in the pediatric age group remains a therapeutic challenge for the wide spectrum of the morphological abnormalities and the high incidence of associated cardiac anomalies. We reviewed our experience so as to assess whether MV conservative surgery is always advisable and its results are superior to MV replacement. METHODS: Thirty-four consecutive children (20 male and 14 female) with a mean age of 5.9 years (range 45 days-18 years) treated surgically for congenital MV disease between January 1987 and June 1999. Four patients (11.7%) were under 12 months of age, while 21 patients (62%) were younger than 5 years. Twenty-two patients presented with MV incompetence (or prevalent incompetence), while 12 presented with stenosis (or prevalent stenosis). Associated cardiac lesions were present in 22 patients (62.8%). RESULTS: Mitral valve reconstruction was possible in all. There were no operative deaths. Three patients required reoperation for MV restenosis (a re-repair in one and MV replacement with mechanical prosthesis in two) 4 months, 27 months and 5.6 years after repair with no operative deaths. There was only one late death for prosthetic valve thrombosis. Follow-up data reveal that the 33 surviving patients are asymptomatic and well 4 months-12 years (mean 72 months) after surgery. At 12 years, actuarial survival and freedom from reoperation are 96.8 and 85.9%, respectively. Echocardiography performed in all of them shows no or mild incompetence or stenosis in 26 (78%), while residual moderate MV incompetence persists in six. CONCLUSIONS: Our experience indicates that MV reconstructive procedures in infants and children with congenital MV dysplasia may be effective and reliable with low mortality and low incidence of reoperation rate. Mitral valve repair should always be attempted, especially in infants, despite the frequent severity of MV dysplasia, to avoid the drawbacks of the currently available prostheses.

Surgical closure of apical ventricular septal defects through a right ventricular apical infundibulotomy.

BACKGROUND: We present a new understanding of the anatomic position of apical ventricular septal defects and its surgical relevance. These defects occur between the left ventricular apex and the infundibular apex, rather than between the left and right ventricular apices. Often a sizable apical recess, the infundibular apex lies anteriorly and inferiorly to the moderator band and is the most leftward part of the right ventricle. METHODS: Four patients (2 boys and 2 girls) with a mean age of 109 days (range, 48 to 217 days) underwent patch closure through an apical infundibulotomy, which allowed complete visualization of the muscular apical ventricular septal defect. RESULTS: There were no early or late deaths at operation. No significant residual shunt at ventricular level was detected by postoperative two-dimensional and Doppler echocardiography. Intraoperative comparison of right atrial and pulmonary arterial blood samples showed a difference of less than 5%. At a mean follow-up of 18 months, all the patients are asymptomatic and growing well. CONCLUSIONS: The successful outcome of these 4 patients indicates that surgical closure of apical ventricular septal defects can be achieved safely and completely in early infancy through a limited right ventricular apical infundibulotomy. Long-term follow-up of these and similar patients is needed to provide further evaluation of this approach.

Straddling tricuspid valve as a sign of ventriculoatrial malalignment: A morphometric study of 19 postmortem cases.

BACKGROUND: Straddling tricuspid valve, despite extensive investigation, remains an incompletely understood form of complex congenital heart disease. METHODS: A morphometric study of 19 postmortem cases of straddling tricuspid valve was performed, and the results were compared with 32 normal control heart specimens. RESULTS: In straddling tricuspid valve, marked malalignment of the ventricles was always found relative to the atria. The angle between the ventricular septum and the atrial septum in the short-axis projection averaged 61 degrees +/- 24 degrees, the normal ventriculoatrial septal angle averaging 5 degrees +/- 2 degrees (P <. 001). The right ventricular sinus (inflow tract) was significantly smaller than the left (P <.01). A ventricular septal defect was present in 79%: atrioventricular canal type in 42%, atrioventricular canal type confluent with a conoventricular defect in 26%, and a conoventricular defect in 11%. When the straddling tricuspid valve adhered to the crest of the muscular ventricular septum (n = 4 cases, 21%), the 2 salient findings were (1) an intact ventricular septum and (2) double-outlet right atrium. The nonstraddling part of the tricuspid valve opened into the small right ventricle. The straddling part of the tricuspid valve opened into the larger left ventricle. The mitral valve also opened into the left ventricle. Hence hearts with double-outlet right atrium had 3 atrioventricular valves. Congenital mitral stenosis was present in 26% of this series. CONCLUSION: Straddling tricuspid valve was always characterized by marked ventriculoatrial malalignment, indicated by an abnormally large ventriculoatrial septal angle, best seen in the short-axis projection.

Changes in fiber composition of soleus muscle during rat hindlimb suspension.

Chronic reduction of gravitational load in the rear limbs of rats to simulate the influence of near-zero gravity in skeletal muscles has been shown previously to elicit atrophy in the soleus muscle. Use of this model by the present investigation indicates that soleus atrophy was characterized by a decline in the number of fibers in groups that contained the slow isoenzyme of myosin and which were classified as type I from intensity of staining to myofibrillar actomyosin adenosinetriphosphatase (ATPase) and to NADH tetrazolium reductase. Furthermore total fiber number was not changed, whereas fibers containing the intermediate isoenzyme and those classified as type IIa increased. There results could be explained by either a change in the composition within existing fibers or a simultaneous loss of slow fibers and de novo synthesis of intermediate and fast fibers. Evidence for transformation included an absence of embryonic or neonatal myosin in muscles from suspended rats and the constant fiber number that was unchanged by 4 wk of suspension. Furthermore although fiber areas of both groups of type I and IIa fibers declined during suspension, variability of the fiber areas within each group did not increase.

Influences of inactivity and indomethacin on soleus phosphatidylethanolamine and size.

Results of previous investigations indicate that muscular prostaglandins (PG) E2 and F2 alpha are biosynthesized during changes in muscular activity and stimulate protein degradation and synthesis, respectively. The results of the present investigation demonstrates a reduction by indomethacin of soleus hypertrophy, which occurred during a one week recovery period following rat hindlimb suspension. While this hypertrophic model evoked significant, rapid increases in soleus myosin and weight in control groups, continuous systemic release of indomethacin (3.5 mg/Kg/day) reduced the gain in soleus weight, Type I and II hypertrophy. Body weights of all groups were not significantly different. Additional analysis found a selective reduction in phosphatidylethanolamine (PE) during soleus atrophy and hypertrophy which were elicited by hindlimb suspension and recovery from suspension, respectively. Indomethacin enhanced PE recovery. Data from previous and present studies support a hypothesis that a change in soleus activity elicits PE catabolism, changes in cytosolic and muscular calcium, in calcium-dependent phospholipase activity, in PG biosynthesis, and in soleus size.

The influence of rat suspension-hypokinesia on the gastrocnemius muscle.

Hind-limb hypokinesia was induced in rats by the Morey method to characterize the response of the gastrocnemius muscle. A comparison of rats suspended for 2 weeks with weight, sex, and litter-matched control rats indicate no difference in gastrocnemius wet weight, contraction, or one-half relaxation times, but less contractile function as indicated by lowered dP/dt. Myosin ATPase staining identified uniform Type I (slow-twitch) and II (fast-twitch) atrophy in the muscles from 4 of 10 rats suspended for 2 weeks and 1 of 12 rats suspended for 4 weeks; muscles from three other rats of the 4-week group displayed greater Type I atrophy. Other histochemical changes were characteristic of a neuropathy. These data together with recently acquired soleus data (29) indicate the Morey model, like space flight, evokes greater changes in the Type I or slow twitch fibers of the gastrocnemius and soleus muscles.

Influence of suspension hypokinesia on rat soleus muscle.

Hindlimb hypokinesia was induced in rats by the Morey method to characterize the response of the soleus muscle. Rats suspended for 1-4 wk exhibited continuous and significant declines in soleus mass, function, and contractile duration. Soleus speeding was in part explained by an alteration in fiber type. The normal incidence of 70-90% type I fibers in the soleus muscle was reduced after 4 wk of suspension to 50% or less in 9 of 11 rats. A significant decline in type I myosin isozyme content occurred without a change in that of type II. Other observed histochemical changes were characteristic of denervation. Consistent with soleus atrophy, there was a significant increase in lysosomal (acid) protease activity. One week of recovery after a 2-wk suspension was characterized by a return to values not significantly different from control for muscle wet weights, peak contraction force, one-half relaxation time, and type I myosin. Persistent differences from control were observed in maximal rate of tension development, contraction time, and denervation-like changes.