Timo Hurme

Healing of skeletal muscle injury: an ultrastructural and immunohistochemical study

The healing of gastrocnemius muscle injury induced with a spring-loaded hammer in rats was analysed ultrastructurally and immunohistochemically. The ends of the ruptured myofibers retracted, which resulted in a central blood filled cavity. Central zone (CZ) later becomes occupied by granulation tissue scar. CZ is surrounded by a zone where myofibers are necrotized and phagocytosed by days 2-3. Complete regeneration within the preserved basal lamina (BL) cylinders takes place in 5-7 days. The regeneration of myofibers across the scar follows a pattern different from that within BL cylinders. Thin, often branched, myotubes grow out of the BL cylinders into the granulation tissue, where they extend between fibroblasts and collagen fibrils, in general oriented parallel to the preserved myofibers. The extension of the regenerating myotube seems to take place primarily by local synthesis in the growth cone. Fusing myoblasts provide nuclei, mostly along the sides but also occasionally at the tip of myotubes. Some myoblasts seem to derive from undifferentiated cells in the granulation tissue. By three weeks only a few thin myotubes had extended across the gap between the stumps of the ruptured myofibers. Growing myotubes appear to attach to the surrounding connective tissue by specialized structures, an attachment which evidently transmits contraction force across the gap, allowing use of the injured limb before the healing is complete.

Activation of myogenic precursor cells after muscle injury.

The time and site of satellite cell activation in contusive myofiber rupture with segmental necrosis were studied in rat by labeling the cells in S phase of mitotic cycle with bromodeoxyuridine. The labeled satellite cell nuclei did not appear before phagocytosis of the necrotized debris had started, usually 1 d after the trauma. Most labeled satellite cell nuclei were found in the necrotized part of the ruptured myofibers, whereas very few of them were detected in the surviving part. The proliferation of satellite cells was extensive during the first 4 d in the regeneration zone; thereafter, it declined and only few labeled nuclei were observed on day 7. These results suggest that necrosis alone is not sufficient as a signal for the satellite cell activation, but it is speculated that (growth?) factors released by the macrophages are needed. A great majority of myoblasts derive from local precursor cells, and satellite cells recruited from the surviving part do not significantly contribute to the regeneration. Most myonuclei needed in regenerating myofibers are produced early within the preserved basal lamina cylinders to be later distributed into those parts of myofibers, which extend into connective tissue between the stumps.

Specific and Innervation-Regulated Expression of the Intermediate Filament Protein Nestin at Neuromuscular and Myotendinous Junctions in Skeletal Muscle

The intermediate filament proteins nestin, vimentin, and desmin show a specific temporal expression pattern during the development of myofibers from myogenic precursor cells. Nestin and vimentin are actively expressed during early developmental stages to be later down-regulated, vimentin completely and nestin to minimal levels, whereas desmin expression begins later and is maintained in mature myofibers, in which desmin participates in maintaining structural integrity. In this study we have analyzed the expression levels and distribution pattern of nestin in intact and denervated muscle in rat and in human. Nestin immunoreactivity was specifically and focally localized in the sarcoplasm underneath neuromuscular junctions (NMJs) and in the vicinity of the myotendinous junctions (MTJs), ie, in regions associated with acetylcholine receptors (AChRs). This association prompted us to analyze nestin in neurogenically and myogenically denervated muscle. Immunoblot analysis disclosed a marked overall increase of accumulated nestin protein. Similar to the extrajunctional redistribution of AChRs in denervated myofibers, nestin immunoreactivity extended widely beyond the NMJ region. Re-innervation caused complete reversion of these changes. Our study demonstrates that the expression levels and distribution pattern of nestin are regulated by innervation, ie, signal transduction into myofibers.

Vascular Density at the Myotendinous Junction of the Rat Gastrocnemius Muscle After Immobilization and Remobilization

Muscle injuries often occur at or near the myotendinous junction. Immobilization decreases the tensile strength of the myotendinous junction and predisposes it to strain injury. However, there are no data available on whether physical training or remobilization can lower the susceptibility of the myotendinous junction to strain injuries. We investigated the effects of three different remobilization programs (8 weeks) after immobilization (3 weeks) by evaluating the vascular density at the myo tendinous junction of the rat gastrocnemius muscle. The myotendinous junctions had a portal system vas cularity, or capillary-arteriole-capillary system, which probably protects the blood supply against pathologic conditions. The vascular density at the myotendinous junction decreased about 30% after immobilization (P< 0.001). After free cage remobilization for 8 weeks, the mean vascular density returned to the level of the con trols. After progressively increasing running programs the vascular density was slightly higher in the immobi lized myotendinous junction and about 50% higher than controls in the contralateral myotendinous junction (P < 0.001). The capacity of the vascular bed of the rat myo tendinous junction to recover from immobilization atro phy seems to be good. Progressively increasing physi cal training improves the process of revascularization and probably protects an injured and immobilized muscle from reinjury.

Transected myofibres may remain permanently divided in two parts

During regeneration of transected myofibres a scar is formed between their stumps. Myofibres restore their tendon-muscle-tendon continuity and contractile function by attaching to the scar with new myotendinous junctions. The scar contracts with time, and thereby the stumps are pulled close to each other. During early regeneration, myoblasts and myotubes can fuse with the surviving parts of the transected myofibres. However, it is not known whether it is possible that the opposite stumps could eventually fuse to reunite the divided parts of the transected fibres. In this study, we show in rat that even after 12 months the stumps remain attached to the separating scar by myotendinous junctions without showing definite fusion of the stumps. We conclude that transected myofibres probably remain permanently divided in two consecutive tendon-muscle-tendon units.

Clinical findings in prepubertal girls with inguinal hernia with special reference to the diagnosis of androgen insensitivity syndrome.

Objective. Complete androgen insensitivity syndrome (CAIS) is a rare disease. However, there is a higher rate of CAIS in girls with inguinal hernia. The aim of this study was to estimate the incidence of CAIS in girls with inguinal hernia and to find a proper screening test for CAIS in these girls. Material and methods. A total of 109 consecutive girls attending the University Hospitals of Turku and Tampere, Finland, for inguinal hernia repair between January 2003 and December 2007 participated in the study. After induction of anaesthesia, vaginal length was measured with a small, lubricated Hegar dilator. During hernia repair, tension was placed on the round ligament to identify the contents of the hernial sac. The karyotype of all patients was measured, with identification of the Y-chromosome from a buccal mucosa swab sample. Vaginal length measurements were plotted against age and standards for vaginal length in prepuberty were established. Results. Four patients were found to have very short vaginas, with one CAIS patient confirmed as having a 46XY karyotype from the verification of the Y-chromosome from buccal mucosa. The other three patients with abnormal vaginal length were karyotypically normal XX girls and had visible ovaries, fallopian tubes or round ligament, which suggests an error in the measurements. Unlike all the other operated girls, the CAIS patient lacked a round ligament. Conclusions. The incidence of CAIS in girls undergoing hernia repair was 1%. The CAIS patient had a significantly shorter vagina than girls with normal karyotype. Vaginal length is a useful additional clinical tool in screening girls for karyotyping CAIS, especially if abnormalities in the round ligament and contents of the hernial sac are suspected. It is recommended that ovaries and fallopian tubes are searched for if the round ligament is not found to be normal during the hernia operation. If no ovaries or fallopian tubes are found, consent for karyotyping should be sought in cases where the vaginal length is <4 cm in girls older than 4 years and <3 cm in younger girls.

NICE Guidelines Cannot Be Recommended for Imaging Studies in Children Younger Than 3 Years with Urinary Tract Infection

INTRODUCTION We assessed the possible consequences of applying the National Institute of Health and Clinical Excellence (NICE) guidelines for imaging studies of children younger than 3 years with urinary tract infection (UTI) to clinical practice, in terms of altered diagnoses and treatment. MATERIAL AND METHODS In a retrospective cohort of 672 patients with UTI, we evaluated indications for and results of renal and bladder ultrasonography, voiding cystourethrography (VCUG), dimercaptosuccinic acid scintigraphy, UTI recurrence, antimicrobial prophylaxis (AMP), antireflux procedures, and other urological procedures. RESULTS There were a total 125 patients with vesicoureteral reflux (VUR), of whom 59 patients (47%) would have been missed, had the NICE guidelines being applied. These included 20 of the 64 patients (31%) with dilating VUR and 13 of the 30 patients (43%) who underwent antireflux procedures. A VCUG would have been avoided in 184 patients (74%) with no VUR in VCUG. CONCLUSION Based on the results in this cohort of 672 patients, we cannot recommend the use of the NICE guidelines for imaging studies in children younger than 3 years with UTI.

Consequences of following the new American Academy of Pediatrics guidelines for imaging children with urinary tract infection

Abstract Objective.Urinary tract infections (UTIs) and vesicoureteral reflux (VUR) are assumed to predispose children to renal damage. Awareness of the significance of VUR and the possibility of reducing UTI recurrence and renal damage has warranted guidelines on which patients should undergo imaging after UTI. An authoritative guideline has been issued by the American Academy of Pediatrics (AAP). This study assessed the applicability of the AAP guidelines to a subpopulation of patients with UTI, 2–24-month-old children with febrile UTI. Materials and methods. The records of 394 children aged 2–24 months with their first UTI were reviewed. Data were recorded on the indications for renal and bladder ultrasonography (RBUS) and voiding cystourethrography (VCUG) according to the AAP guidelines, RBUS results, VCUG results, use of antimicrobial prophylaxis, antireflux procedures and other urological treatment, and UTI recurrence. Results.An indication for RBUS was seen in 344 patients. RBUS results were abnormal in 87, including 53 with urinary tract dilatation. An unnecessary RBUS would have been avoided in 43 patients. Seven patients with an abnormal RBUS would not have undergone RBUS. An indication for VCUG was seen in 126 patients. VCUG was performed in 206 patients; VUR was found in 72 patients, including 36 with high-grade VUR. An unnecessary VCUG would have been avoided in 82 patients. High-grade VUR would have been missed in six patients. Five patients would not have undergone surgery. Conclusion. The AAP guidelines for imaging studies in children aged 2–24 months with febrile UTI seem applicable to clinical practice.

Factors Associated with Abnormal Imaging and Infection Recurrence after a First Febrile Urinary Tract Infection in Children

Introduction We determined factors associated with abnormal imaging and recurrent infections after a first febrile urinary tract infection (UTI) in children younger than 3 years. Materials and Methods We retrospectively reviewed the records of all patients treated at our institute during the years 2000–2009, for a first febrile UTI in children younger than 3 years, who underwent ultrasonography and voiding cystourethrography. We evaluated data regarding factors potentially associated with abnormal ultrasonography and voiding cystourethrography results and recurrence of infections, and formulated a risk score system to assess risk of reflux and high‐grade reflux. Results There were 282 patients. The only factor predicting abnormal ultrasonogram was non‐Escherichia coli infection. Risk factors for vesicoureteral reflux included abnormal ultrasonogram, atypical infection, non‐E. coli infection and infection recurrence. Patients with no identified risk factors for vesicoureteral reflux were unlikely to have high‐grade reflux. Higher risk scores were associated with a higher risk for reflux. Non‐E. coli infection was the only statistically significant predictor of infection recurrence. Conclusion All children younger than 3 years with first febrile UTI should undergo ultrasonography. Thereafter, patients with no predictive factors for vesicoureteral reflux may be followed up without further imaging. A non‐E. coli infection is associated with reflux and infection recurrence.

Accuracy of ultrasonography in predicting vesicoureteral reflux in children: A meta-analysis

Abstract Objective: The aim of this study was to assess the existing evidence on the accuracy of renal and bladder ultrasonography in predicting vesicoureteral reflux in children with first urinary tract infection. Materials and methods: The CENTRAL, MEDLINE, Embase and Web of Science data sources were searched. A random effects meta-analysis was conducted. Results: Fourteen studies, involving 3544 participants, fulfilled the inclusion criteria. The risk of bias and concern regarding applicability were considered high in four studies. The pooled sensitivity was 0.37 [95% confidence interval (CI) 0.34 to 0.40], specificity 0.81 (95% CI 0.80 to 0.83), positive likelihood ratio 2.0 (95% CI 1.61 to 2.50), negative likelihood ratio 0.75 (95% CI 0.65 to 0.86), diagnostic odds ratio 3.03 (95% CI 2.10 to 4.37) and area under the curve 0.72. Conclusion: There is no evidence that renal and bladder ultrasonography should be recommended as a test to predict a vesicoureteral reflux in children with their first urinary tract infection.