Compartmental fasciotomy and isolating a muscle from neighboring muscles interfere with myofascial force transmission within the rat anterior crural compartment

Muscles within the anterior crural compartment (extensor digitorum longus, EDL; tibialis anterior, TA; and extensor hallucis longus, EHL) and within the peroneal compartment were excited simultaneously and maximally. All muscles were kept at constant length with the exception of EDL, for which muscle length was changed by moving its proximal tendon. Active and passive force was measured at proximal as well as distal EDL tendons and at the combined distal tendons of TA and EHL (TA+EHL). In the initial experimental condition, a difference (F(proximal) > F(distal)) in EDL force, amounting to 0-14% of proximal force, was confirmed for most EDL lengths. This is interpreted as a clear proof of extramuscular myofascial force transmission, as no significant EDL length effects could be shown on TA+EHL force. Repeated measurements were confirmed to cause marked changes of both proximal and distal length-force characteristics, such as a shift of the whole ascending limb of the active curve, including optimum length, to higher lengths without decreasing optimum force, and decreasing active force at low lengths (by approximately 57%). Repeated measurements also lowered proximal and distal EDL passive force (by up to 35%). The proximo-distal difference in passive as well as active EDL force was decreased, but persisted. At most lengths, this difference for active force amounted to a constant fraction (14%) of proximal force. TA+EHL force was not affected significantly. Subsequently, acute effects of experimental surgical alterations were studied: The first manipulation was full lateral fasciotomy of the anterior crural compartment that caused a further decrease in active force at the proximal EDL but not at the distal EDL tendon. Passive forces showed no further significant changes. The proximo-distal EDL active force difference decreased to 0-5% of proximal force. After fasciotomy, TA+EHL force increased by 30%. This was interpreted as evidence of increased intramuscular and decreased extramuscular myofascial force transmission. The second manipulation was full isolation of EDL from TA+EHL, but not from extramuscular connective tissues, which caused a further decrease of the EDL proximo-distal force differences, indicating a stiffening effect of the presence of TA+EHL on the extramuscular matrix. For EDL active force the difference was no longer significantly different from zero. In contrast, for EDL passive force the proximo-distal force difference persisted. It is concluded that extramuscular myofascial force transmission is an important feature of the anterior crural compartment. The magnitude of this force transmission requires that it be considered in analysis of muscular function.

Synthesis of new molecules containing head, spacer, and label moieties

We describe the synthesis and characterization of novel molecules containing head with precise shape, spacer, and label moieties. The protocol is based on a Pd(0)-catalyzed cross-coupling reaction between ethynylphenyl/bromide to obtain a rigid head followed by the attachment of a flexible spacer possessing two reactive functional groups on the termini. The final step consists of forming a covalent bond between spacer and label. In addition, monosubstituted soluble labels were synthesized in good yields.

Intermuscular interaction via myofascial force transmission: effects of tibialis anterior and extensor hallucis longus length on force transmission from rat extensor digitorum longus muscle

Force transmission in rat anterior crural compartment, containing tibialis anterior (TA), extensor hallucis longus (EHL) and extensor digitorum longus (EDL) muscles, was investigated. These muscles together with the muscles of the peroneal compartment were excited maximally. Force was measured at both proximal and distal tendons of EDL muscle as well as at the tied distal tendons of TA and EHL muscles (the TA + EHL complex). Effects of TA + EHL complex length and force on proximally and distally measured forces of EDL muscle kept at constant muscle-tendon complex length were assessed. Length changes of EDL muscle were imposed by movement of the proximal force transducer to different positions.Proximal EDL force was unequal to distal EDL force (active as well as passive) over a wide range of EDL muscle-tendon complex lengths. This is an indication that force is also transmitted out of EDL muscle via pathways other than the tendons (i.e. inter- and/or extramuscular myofascial force transmission). At constant low EDL length, distal lengthening of the TA + EHL complex increased proximal EDL force and decreased distal EDL force. At optimum EDL length, TA+EHL active force was linearly related to the difference between proximal and distal EDL active force. These results indicate intermuscular myofascial force transmission between EDL muscle and the TA + EHL complex. The most likely pathway for this transmission is via connections of the intact intermuscular connective tissue network. The length effects of the TA + EHL complex can be understood on the basis of changes in the configuration, and consequently the stiffness, of these connections. Damage to connective tissue of the compartment decreased the proximo-distal EDL force difference, which indicates the importance of an intact connective tissue network for force transmission from muscle fibers to bone.

The influence of nitric oxide on in vivo human skeletal muscle properties

We have investigated the action of exogenous nitric oxide (NO) on the strength and contractile properties of human skeletal muscle working in vivo. Maximum isometric voluntary contraction force (MVC) of the quadriceps was measured and superimposed electrical stimulation was used to estimate the level of activation and 'true maximum force' (TMF). Force-frequency relationships were determined to assess changes in contractile properties of the muscle. Subjects in the experimental group (E, n=10) were measured before and during two separate periods of treatment with different doses of glyceryl trinitrate, a NO donor, delivering 100 (GTN100) or 200 (GTN200) microg h-1 as a trans-dermal patch. A control group (C, n=6) was measured during two similar periods whilst taking an oral placebo. There was a significant increase in strength with GTN200 (MVC: +5. 15%; TMF: +3.87%). There was no change in the strength of group C. There was a trend towards reduced forces at submaximal frequencies with GTN administration but the most notable change was a decline in twitch force (approximately 12%, P < 0.05) with GTN100 treatment and this remained depressed throughout the study. No changes were seen in the contractile properties of the control group C. The present results show that GTN treatment increased maximum voluntary strength but decreased twitch tension. The time course and dose-response characteristics indicate that these are two separate actions of NO on human muscle working in vivo.

The effect of magnitude and frequency of interfragmentary strain on the tissue response to distraction osteogenesis

PURPOSE

Bone regeneration is believed to be partially controlled by the applied local mechanical strain. To test whether the magnitude or frequency of discontinuous traction regulates the tissue response, defined daily strains were applied on mandibular osteotomies using an implanted mechanical distractor.

MATERIALS AND METHODS

Unilateral mandibular osteotomies were performed in skeletally immature rabbits (n = 36). and distraction was done by applying 2,000, 20,000, 200,000, or 300,000 microstrains once or 10 times (2,000, 20,000 microstrains) per day, respectively. Sham-operated animals (n = 6), serving as controls, underwent frame application and osteotomy without distraction. At the end of the distraction process, the newly formed tissue was evaluated histomorphometrically by the use of a well-defined scoring system of bone-forming indices.

RESULTS

The highest bone-forming indices were detected in the osteotomized, nondistracted group and in samples exposed to a physiologic strain (2,000 microstrains). Application of hyperphysiologic strains (200,000 and 300,000 microstrains) resulted in the formation of fibrous tissue and decreased bone-forming indices. Using Kruskal-Wallis tests, a statistically significant relationship was found between the bone-forming indices and the applied strain magnitudes. Scanning and transmission electron microscopic examinations showed osteoblastic differentiation and early mineral deposition in samples distracted up to 20,000 microstrains, whereas higher strain magnitudes led to the formation of fibroblast-like cells surrounded by collagen fibrils and only slight mineralization. Multiple strain applications (10 cycles/d vs 1 cycle/d) did not alter the histomorphometric indices or ultrastructural morphology significantly but increased the amount of newly formed tissue.

CONCLUSIONS

These results suggest that the magnitude and not the frequency of mechanical loading controls the differentiation of bone cells and the subsequent formation of bone tissue.

Serotyping, ribotyping, PCR-mediated ribosomal 16S-23S spacer analysis and arbitrarily primed PCR for epidemiological studies on Legionella pneumophila

Fifty clinical and environmental isolates of Legionella pneumophila were typed serologically and by DNA fingerprinting using arbitrarily primed polymerase chain reaction (AP-PCR). Furthermore, variability in and around ribosomal operons was assessed by conventional ribotyping and PCR-mediated amplification of the spacer region separating the 16S and 23S genes. It appears that serotyping suffers from low resolution capabilities, and ribotyping and spacer PCR display intermediate resolving capabilities, whereas AP-PCR is more discriminating. Results from AP-PCR and both forms of ribotyping analysis correlate with epidemiological and environmental data. It is suggested that AP-PCR typing may be the method of choice for rapidly determining clonality among L. pneumophila isolates.

Prevalence and characteristics of human and bovine verotoxigenic Escherichia coli strains isolated in Galicia (north-western Spain)

An epidemiological study was carried out to determine the incidence and the serotypes of verotoxigenic Escherichia coli (VTEC) that cause infections in Galicia (north-western Spain). Although, VTEC strains were isolated from 55 (14%) of the 387 calves sampled and the majority of bovine VTEC strains belonged to serotypes (026:H11 or H-, 091:H21, O103:H2, 0105:H18, O111:H-O113:H21, O126:H-, O128:H- and O157:H7 or H-) previously associated with human haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS) in other countries, VTEC are not a common cause of human infections in Spain. Thus, VTEC (O26:H11 and O86:H10) were isolated from only 3 (0.6%) of the 482 children with diarrhoea investigated. We examined the 69 (3 humans and 66 bovines) VTEC strains that were initially isolated as E. coli producing a toxin cytotoxic to Vero and HeLa cells by polymerase chain reaction (PCR) using specific primers for VT1, VT2 and eae genes. PCR showed that 38 (55%) of VTEC strains carried VT1 genes. 18 (26%) possessed VT2 genes, and 10 (14%) carried both VT1 and VT2 genes. Three (one human and two bovine) strains which were formerly VTEC had lost the ability to produce verotoxins upon subculture and became negative for VT1 and VT2 by PCR. In total 35 (51%) of 69 VTEC strains, including the two human VT1+ strains of serotype O26:H11, were positive for eae sequences when tested by PCR. Presence of the eae gene was significantly more frequent (100%; 21/21) among VTEC strains with serotypes (O26:H11, O111:H-, O157:H-and O157:H7) considered as enterohaemorrhagic E. coli (EHEC) than among VTEC strains with non-EHEC serotypes (29%; 14/48) (p < 0.001). Results obtained in this study indicate that cattle may be an important source of VTEC involved in human disease. However, severe clinical syndromes caused by VTEC, such as HC and HUS, are uncommon in Spain, in comparison with North America and the UK. In any case, VTEC disease can appear on the scene very suddenly, as occurred in the UK and North America in the 1980s.

Sleepiness of civil airline pilots during two consecutive night flights of extended duration

Sleepiness of civil airline pilots was studied in a two-crew cockpit during two consecutive night flights of about 10 h duration each. Sleepiness was assessed by EEG recordings and subjective ratings during hourly recurrent short experimental phases. On the second night flight, the alertness component that is related to the preceding sleep showed a modification due to reduced quality and quantity of sleep between flights. The daytime sleep during layover was not sufficient to maintain the same alertness level as observed during the initial flight. This result is in coincidence with investigations in shift workers starting a period of night shifts. It is concluded that improvements such as the introduction of a nap schedule should be considered to alleviate spontaneous sleepiness in the cockpit.

Specific gene probe for detection of biotyped and serotyped Listeria strains

A total of 284 strains of Listeria, including all known serovars and biovars together with Listeria grayi and Listeria murrayi, were biotyped and serotyped. Biotyping and serotyping could be done in 2 days. A gene probe encoding a delayed hypersensitivity factor (DTH) was used in the detection of pathogenic biotypes and serotypes of the tested strains. The gene was found in all 117 tested Listeria monocytogenes strains of serogroups 1/2a, 1/2b, 1/2c, 3a, 3b, 3c, 4c, 4d, 4e, 4ab, and 7. It was also present in Listeria ivanovii. Of 78 L. monocytogenes strains of serogroup 4b, 77 strains contained the gene, whereas it was absent in all 10 tested L. monocytogenes strains of serogroup 4a. Furthermore, the gene was absent in Listeria seeligeri, L. grayi, L. murrayi, and L. innocua of serogroups 3c, 4b, and 6a and in L. welshimeri of serogroups 1/2b, 3b, 6a, and 6b. Since L. monocytogenes and L. ivanovii are the only two biotypes of the genus Listeria considered pathogens, the data obtained indicate that the DNA probe tested may be a useful tool in the detection of virulent Listeria isolates in clinical, environmental, and food samples.