Isolation and characterization of myogenic precursor cells from human cremaster muscle.

Human myogenic precursor cells have been isolated and expanded from a number of skeletal muscles, but alternative donor biopsy sites must be sought after in diseases where muscle damage is widespread. Biopsy sites must be relatively accessible, and the biopsied muscle dispensable. Here, we aimed to histologically characterize the cremaster muscle with regard number of satellite cells and regenerative fibres, and to isolate and characterize human cremaster muscle-derived stem/precursor cells in adult male donors with the objective of characterizing this muscle as a novel source of myogenic precursor cells. Cremaster muscle biopsies (or adjacent non-muscle tissue for negative controls; N = 19) were taken from male patients undergoing routine surgery for urogenital pathology. Myosphere cultures were derived and tested for their in vitro and in vivo myogenic differentiation and muscle regeneration capacities. Cremaster-derived myogenic precursor cells were maintained by myosphere culture and efficiently differentiated to myotubes in adhesion culture. Upon transplantation to an immunocompromised mouse model of cardiotoxin-induced acute muscle damage, human cremaster-derived myogenic precursor cells survived to the transplants and contributed to muscle regeneration. These precursors are a good candidate for cell therapy approaches of skeletal muscle. Due to their location and developmental origin, we propose that they might be best suited for regeneration of the rhabdosphincter in patients undergoing stress urinary incontinence after radical prostatectomy.

Regulation of Vascular Smooth Muscle Cell Stiffness and Adhesion by [Ca2+]i: An Atomic Force Microscopy-Based Study.

The intracellular concentration of calcium ion ([Ca2+]i) is a critical regulator of cell signaling and contractility of vascular smooth muscle cells (VSMCs). In this study, we employed an atomic force microscopy (AFM) nanoindentation-based approach to investigate the role of [Ca2+]i in regulating the cortical elasticity of rat cremaster VSMCs and the ability of rat VSMCs to adhere to fibronectin (Fn) matrix. Elevation of [Ca2+]i by ionomycin treatment increased rat VSMC stiffness and cell adhesion to Fn-biofunctionalized AFM probes, whereas attenuation of [Ca2+]i by 1,2-Bis (2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxymethyl ester) (BAPTA-AM) treatment decreased the mechanical and matrix adhesive properties of VSMCs. Furthermore, we found that ionomycin/BAPTA-AM treatments altered expression of α 5 integrin subunits and α smooth muscle actin in rat VSMCs. These data suggest that [Ca2+]i regulates VSMC elasticity and adhesion to the extracellular matrix by a potential mechanism involving changing dynamics of the integrin-actin cytoskeleton axis.

Normal values of abdominal muscles thickness in healthy children using ultrasonography.

Abdominal muscles are one of the important elements to support the lumbar spine. Evaluation of muscle thickness using ultrasonography (US) is considered to be a source of information from muscles characteristics. The purpose of this study was to demonstrate normal reference data of abdominal muscles thickness and subcutaneous fat in adolescents using US. A random sample of 160 healthy adolescents (80 boys and 80 girls) at the age range of 15-18 years was recruited. Three abdominal muscles including Transversus Abdominis (TA), Internal Oblique (IO), External Oblique (EO) and subcutaneous fat (SF) were bilaterally measured using US. The range of normal values for TA muscle thickness was between 2.31 and 2.57 mm, for IO muscle thickness was between 4.02 and 5.15 mm and for EO muscle thickness was between 2.81 and 3.17 mm. The normal patterns of abdominal muscles were found as IO > EO > TA at both sides. Boys were taller, heavier with greater body mass index (BMI) and had larger abdominal muscles thickness than girls. A weak negative correlation was found between age and muscles size [r = (-0.06) - (-0.23), p < .05], but a significant positive correlation was found between BMI and muscle size (r = 0.21-0.68, p < .05). It seems that abdominal muscles thickness in adolescents followed the same pattern of muscle size in adults. BMI appeared to be the best predictor of muscle thickness. However, further studies are recommended to support the findings of the present study.

HS1 deficiency impairs neutrophil recruitment in vivo and activation of the small GTPases Rac1 and Rap1.

Neutrophil extravasation is a critical step of the innate immune system's response to inflammation. This multistep process is tightly regulated by adhesion and signaling molecules in the endothelium and neutrophils. Activation of the ß2 integrin LFA-1 is critical for adhesion of leukocytes to postcapillary venules. This step requires coordinated activation of signaling pathways in chemokine-stimulated neutrophils, including GTPase activation and cytoskeletal remodeling, leading to conformational changes in LFA-1. Hematopoietic cell-specific lyn substrate 1 (HS1) is a cortactin-related and leukocyte-specific actin-binding protein (ABP) that regulates several processes in various immune cells. It has been shown in vitro that HS1 is important for neutrophil chemotaxis and transendothelial migration of NK cells, but its role in neutrophil extravasation in vivo has not been investigated yet. Intravital microscopy of CXCL1-stimulated cremaster venules revealed an increased rolling velocity and reduced neutrophil adhesion and transmigration in HS1 knockout (KO) mice. CXCL1-induced rapid neutrophil arrest in vivo and adhesion under flow conditions in vitro were also reduced significantly. Whereas random motility of neutrophils was unaffected, chemotaxis toward a CXCL1 gradient was reduced in the absence of HS1. Further analysis of the underlying mechanisms demonstrated that HS1 controls CXCL1-induced activation of the small GTPases Ras-related C3 botulinum toxin substrate 1 (Rac1) and Ras-related protein 1 (Rap1), thus supporting LFA-1-mediated neutrophil adhesion. Importantly, with the use of Rac1 KO neutrophils, we could show that Rac1 acts upstream of Rap1. Our results establish HS1 as an important regulator of proper Rac1 and Rap1 activation and neutrophil extravasation.

Fetal Rat Gubernaculum Mesenchymal Cells Adopt Myogenic and Myofibroblast-Like Phenotypes.

PURPOSE: Gubernaculum-cremaster complex development is hormonally regulated and abnormal in a cryptorchid rat model. Using cell tracking techniques and imaging we studied myogenic phenotypes and fates in the fetal rat gubernaculum-cremaster complex. MATERIALS AND METHODS: Embryonic day 17 gubernaculum-cremaster complexes were labeled with CellTracker™ or the DNA synthesis marker EdU (5-ethynyl-2'-deoxyuridine), or immobilized in Matrigel® and grown in culture. Embryonic day 17 to 21 gubernaculum-cremaster complex sections and cells were imaged using wide field and deconvolution immunofluorescence microscopy, and muscle and/or myofibroblast specific antibodies. Deconvolved image stacks were used to create a 3-dimensional model of embryonic day 21 gubernaculum-cremaster complex muscle. RESULTS: PAX7 (paired box 7) positive and myogenin positive muscle precursors were visible in a desmin-rich myogenic zone between muscle layers that elongated and became thicker during development. Gubernaculum-cremaster complex inner mesenchymal cells expressed desmin and αSMA (α smooth muscle actin) at lower levels than in the myogenic zone. After pulse labeling with CellTracker or EdU mesenchymal cells became incorporated into differentiated muscle. Conversely, mesenchymal cells migrated beyond Matrigel immobilized gubernaculum-cremaster complexes, expressed PAX7 and fused to form striated myotubes. Mesenchymal gubernaculum-cremaster complex cell lines proliferated more than 40 passages and showed contractile behavior but did not form striated muscle. Our 3-dimensional gubernaculum-cremaster complex model had 2 orthogonal ventral layers and an arcing inner layer of muscle. CONCLUSIONS: Our data suggest that mesenchymal cells in the peripheral myogenic zone of the fetal gubernaculum-cremaster complex contribute to formation of a distinctively patterned cremaster muscle. Nonmyogenic, desmin and αSMA positive gubernaculum-cremaster complex mesenchymal cells proliferate and have a myofibroblast-like phenotype in culture. Intrinsic mechanical properties of these divergent cell types may facilitate perinatal inversion of the gubernaculum-cremaster complex.

Regional Cell-Specific Transcriptome Mapping Reveals Regulatory Complexity in the Adult Drosophila Midgut.

Deciphering contributions of specific cell types to organ function is experimentally challenging. The Drosophila midgut is a dynamic organ with five morphologically and functionally distinct regions (R1-R5), each composed of multipotent intestinal stem cells (ISCs), progenitor enteroblasts (EBs), enteroendocrine cells (EEs), enterocytes (ECs), and visceral muscle (VM). To characterize cellular specialization and regional function in this organ, we generated RNA-sequencing transcriptomes of all five cell types isolated by FACS from each of the five regions, R1-R5. In doing so, we identify transcriptional diversities among cell types and document regional differences within each cell type that define further specialization. We validate cell-specific and regional Gal4 drivers; demonstrate roles for transporter Smvt and transcription factors GATAe, Sna, and Ptx1 in global and regional ISC regulation, and study the transcriptional response of midgut cells upon infection. The resulting transcriptome database (http://flygutseq.buchonlab.com) will foster studies of regionalization, homeostasis, immunity, and cell-cell interactions.

The method of isolation of the crayfish abdominal stretch receptor maintaining a connection of the sensory neuron to the ventral nerve cord ganglion.

The crayfish stretch receptor consisting of the single mechanoreceptor neurons enveloped by satellite glial cells is the simplest functioning neuroglial preparation. However, during isolation, its axons are usually transected that eliminates afferent regulation and induces complex axotomy-related signaling responses in neurons and satellite glia. We developed new microsurgical method of crayfish stretch receptor isolation, which preserves connections of sensory neurons to the ventral nerve cord ganglion. The stretch receptor may either remain on the abdominal carapace, or be completely isolated. In both cases, it may be either intact, or axotomized. The integrity of axons was confirmed by firing recording from proximal and distal axon points. Normal, necrotic and apoptotic cells were visualized using double fluorochroming with Hoechst 33342 and propidium iodide. The isolated mechanoreceptor neurons maintain regular firing during 8-10 or more hours. Glial cells surrounding non-axotomized neurons demonstrate lower necrosis and apoptosis levels than the axotomized ones. Unlike the existing method, in which the sensory neurons were axotomized, the present method preserves links between the sensory neurons and the ganglion and makes possible to avoid consequences of axotomy in neurons and satellite glia. The present neuroglial preparation may be used as a simple but informative model object in studies of axotomy-induced degeneration and survival of peripheral neurons, the role of glia in neuron injury, the signaling mechanisms of neuroglial interactions, and the effects of diverse physical and chemical factors on neuronal and glial cells.

Development of the annelid axochord: insights into notochord evolution.

The origin of chordates has been debated for more than a century, with one key issue being the emergence of the notochord. In vertebrates, the notochord develops by convergence and extension of the chordamesoderm, a population of midline cells of unique molecular identity. We identify a population of mesodermal cells in a developing invertebrate, the marine annelid Platynereis dumerilii, that converges and extends toward the midline and expresses a notochord-specific combination of genes. These cells differentiate into a longitudinal muscle, the axochord, that is positioned between central nervous system and axial blood vessel and secretes a strong collagenous extracellular matrix. Ancestral state reconstruction suggests that contractile mesodermal midline cells existed in bilaterian ancestors. We propose that these cells, via vacuolization and stiffening, gave rise to the chordate notochord.

An Org-1-Tup transcriptional cascade reveals different types of alary muscles connecting internal organs in Drosophila.

The T-box transcription factor Tbx1 and the LIM-homeodomain transcription factor Islet1 are key components in regulatory circuits that generate myogenic and cardiogenic lineage diversity in chordates. We show here that Org-1 and Tup, the Drosophila orthologs of Tbx1 and Islet1, are co-expressed and required for formation of the heart-associated alary muscles (AMs) in the abdomen. The same holds true for lineage-related muscles in the thorax that have not been described previously, which we name thoracic alary-related muscles (TARMs). Lineage analyses identified the progenitor cell for each AM and TARM. Three-dimensional high-resolution analyses indicate that AMs and TARMs connect the exoskeleton to the aorta/heart and to different regions of the midgut, respectively, and surround-specific tracheal branches, pointing to an architectural role in the internal anatomy of the larva. Org-1 controls tup expression in the AM/TARM lineage by direct binding to two regulatory sites within an AM/TARM-specific cis-regulatory module, tupAME. The contributions of Org-1 and Tup to the specification of Drosophila AMs and TARMs provide new insights into the transcriptional control of Drosophila larval muscle diversification and highlight new parallels with gene regulatory networks involved in the specification of cardiopharyngeal mesodermal derivatives in chordates.

Fiber type characterization of striated muscles related to micturition in female rabbits.

Pelvic and perineal striated muscles are relevant for reproduction and micturition in female mammals. Damage to these muscles is associated with pelvic organ prolapse and stress urinary incontinence. The fiber type composition of skeletal muscle influences the susceptibility for damage and/or regeneration. The aim of the present study was to determine the fiber type composition of a perineal muscle, the bulbospongiosus, and a pelvic muscle, the pubococcygeus. Both muscles were harvested from adult female rabbits (8-10 months old). NADH-TR (nicotinamide adenine dinucleotide tetrazolium reductase) histochemistry was undertaken to identify oxidative and glycolytic muscle fibers. Alkaline (pH 9.4) ATP-ase (actomyosin adenosine triphosphatase) histochemistry was used to classify type I, type IIb or type IIa/IId muscle fibers. Results showed that the content of glycolytic fibers in the bulbospongiosus muscle was higher than that of oxidative fibers. Meanwhile, the opposite was true for the pubococcygeus. In the bulbospongiosus muscle, the content of type IIb muscle fibers was higher than that of type I, but was similar to that of type IIa/IId. In contrast, the content of each fiber type was similar in the pubococcygeus muscle. The relative proportion of fibers in bulbospongiosus and pubococcygeus muscles is consistent with their function during voiding and storage phases of micturition.

Respiration-related control of abdominal motoneurons.

The abdominal muscles form part of the expiratory pump in cooperation with the other expiratory muscles, primarily the internal intercostal and triangularis sterni muscles. The discharge of abdominal muscles is divided into four main patterns: augmenting, plateau, spindle and decrementing. The patterns tend to be species-specific and dependent on the state of the central nervous system. Recent studies suggest that the abdominal muscles are more active than classically thought, even under resting conditions. Expiratory bulbospinal neurons (EBSN) in the caudal ventral respiratory group are the final output pathway to abdominal motoneurons in the spinal cord. Electrophysiological and anatomical studies indicated the excitatory monosynaptic inputs from EBSN to the abdominal motoneurons, although inputs from the propriospinal neurons seemed to be necessary to produce useful motor outputs. Respiration-related sensory modulation of expiratory neurons by vagal afferents that monitor the rate of change of lung volume and the end-expiratory lung volume (EELV) play a crucial role in modulating the drive to the abdominal musculature. Studies using in vitro and in situ preparations of neonatal and juvenile rats show bi-phasic abdominal activity, characterized by bursting at the end of expiration, a silent period during the inspiratory period, and another burst that occurs abruptly after inspiratory termination. Since the abdominal muscles rarely show these post-inspiratory bursts in the adult rat, the organization of the expiratory output pathway must undergo significant development alterations.

[Functional morphology of puffing behavior in pufferfish (Takifugu obscurus)].

As a defensive behavior of escaping from the predators, sudden inflating ("puffing") has been found in all members of the pufferfish sister taxa Diodontidae and Tetraodontidae. However, the mechanism of inflation is largely unknown. To further understand the inflation behavior of Tetraodontidae, morphological dissection, X-ray and staining methods were conducted to investigate morphological variations and functional adaptation during the inflation in Takifugu obscurus. The results indicated that after receiving stimulation, Takifugu obscurus quickly and frequently swallows water or/and air into the flexible but tough sac, which is a distinct portion of the specialized esophagus. For adapting the inflation, the anterior and posterior joints of the sac and the digestive duct are tightened by special musculature; and the structure and arrangement of the skin of the body, as well as the abdomen muscle bundles are particularly modified to be elasticated; more over, even the backbone and the nerve are ready for flexible positioning change. This study provides some important information about the inflation mechanism of the Takifugu obscurus in sucking and expelling water/air during the puffing behavior, which would be helpful to further understand the neural control mechanism of pufferfish inflation.

Gender specific activation patterns of trunk muscles during whole body tilt.

Gender specific differences as evidenced in both anthropometric data and physical performance of healthy persons have been broadly demonstrated. Recently advancements in surface electromyography (SEMG) have shown possible differences in men's and women's muscle coordination patterns. However, quantitative information about gender related muscle co-ordination patterns are rare. This investigation was carried out to both verify if trunk muscle SEMG amplitude-force relationship differs between men and women and refine techniques of measurement and data analysis using SEMG. Thirty-one healthy volunteers (16 women, 15 men) were investigated during whole body tilt at angles from 5 degrees to 90 degrees (from quasi vertical to horizontal position). Subjects had to maintain body in body axis while their lower body was fixed and the upper body remained unsupported. SEMG was taken from five different trunk muscles of both sides simultaneously. At corresponding tilt angles women exhibited higher amplitude levels of their abdominal muscles in comparison to men, who were characterized by higher back muscle amplitudes. Abdominal muscles showed a non-linear SEMG amplitude-force relationship but differed between genders with more linearity in women. Back muscles showed a linear amplitude-force relationship with no differences between genders. Women were characterized by higher levels of co-contraction of all investigated muscles. The data are in accordance with histological investigations, which already proved specific fiber distribution patterns in both abdominal and back muscles and gender related differences in relative area of Type 1 fibers of back muscles. The observed differences in SEMG-force relationship for the abdominal muscles remain hypothetical because of lack of histological information.

Neuromuscular junction in abdominal muscles of Drosophila melanogaster during adulthood and aging.

The neuromuscular junction (NMJ) of Drosophila melanogaster has been established as a productive model for the study of synaptogenesis, synaptic plasticity, vesicle recycling, and other synaptic functions in embryos and larvae. It also has potential for the study of long-term plasticity during adult life and degenerative processes associated with aging. Here we provide a detailed description of the morphology and ultrastructure of the NMJ on abdominal dorsal longitudinal muscles throughout adult life from eclosion to senescence. In contrast to the case in the larva, the predominant type of terminals in these muscles in the adult fly consists of only two or three branches with tightly packed synaptic boutons. We observed qualitative and quantitative changes as mean bouton size increased gradually during adulthood, and the largest boutons were present in the old fly. The length of nerve branches first increased and thereafter decreased gradually during most of adult life. Branch diameter also decreased progressively, but branch number did not change. The subsynaptic reticulum became progressively thinner, and "naked" boutons were found in old flies. Ultrastructural traits gave indications of an age-associated increment in autophagy, larger synaptic vesicles, and impaired endocytosis. We propose that NMJ aging in the fly correlates with impaired endocytosis and membrane dynamics. This view finds a functional correlate in flies carrying a temperature-sensitive mutation in shibire that reversible blocks endocytosis; age significantly reduces the time required for complete paralysis and increases the time of recovery, thus confirming the age-dependent alteration in vesicle dynamics.

Myoblast-acellular skeletal muscle matrix constructs guarantee a long-term repair of experimental full-thickness abdominal wall defects.

To obtain a valuable treatment of congenital muscle defect, cell-matrix constructs composed of satellite cell-derived myoblasts (XY karyotype) seeded on muscle acellular matrices were used to repair a previously created full-thickness defect of abdominal wall of 18 1-month-old female Lewis rats. Acellular abdominal matrices, obtained by a detergent-enzymatic method, were positive for both basic fibroblast growth factor and transforming growth factor-beta, and were able to support in vitro cell adhesion. All animals survived the surgery, without signs of infection or implant rejection, and were humanely killed at 1, 3, or 9 months after surgery. The implants appeared well preserved, were integrated in the host tissue, and maintained their original dimension and thickness until 9 months. Vesicular acetylcholine transporter was expressed on the surface of muscle fibers from 1 month postsurgery. Finally, implanted male myoblasts were present inside the patches until 9 months, as demonstrated by the expression of SrY mRNA and by the presence of Y chromosome probe signal. These results allow us to conclude that cell-matrix constructs could represent a promising approach to the repair of muscle defects, because they are repopulated in vivo by skeletal muscle cells and nervous elements and maintain their structural integrity over the long term.

Interspecies implantation and mitochondria fate of panda-rabbit cloned embryos.

Somatic cell nuclei of giant pandas can dedifferentiate in enucleated rabbit ooplasm, and the reconstructed eggs can develop to blastocysts. In order to observe whether these interspecies cloned embryos can implant in the uterus of an animal other than the panda, we transferred approximately 2300 panda-rabbit cloned embryos into 100 synchronized rabbit recipients, and none became pregnant. In another approach, we cotransferred both panda-rabbit and cat-rabbit interspecies cloned embryos into the oviducts of 21 cat recipients. Fourteen recipients exhibited estrus within 35 days; five recipients exhibited estrus 43-48 days after embryo transfer; and the other two recipients died of pneumonia, one of which was found to be pregnant with six early fetuses when an autopsy was performed. Microsatellite DNA analysis of these early fetuses confirmed that two were from giant panda-rabbit cloned embryos. The results demonstrated that panda-rabbit cloned embryos can implant in the uterus of a third species, the domestic cat. By using mitochondrial-specific probes of panda and rabbit, we found that mitochondria from both panda somatic cells and rabbit ooplasm coexisted in early blastocysts, but mitochondria from rabbit ooplasm decreased, and those from panda donor cells dominated in early fetuses after implantation. Our results reveal that mitochondria from donor cells may substitute those from recipient oocytes in postimplanted, interspecies cloned embryos.

Scanning and transmission electron microscopic study of visceral and parietal peritoneal regions in the rat.

The visceral peritoneum of intraabdominal organs (spleen, stomach, liver, small intestine), omentum majus and the parietal peritoneum of the anterior abdominal wall and the diaphragm were studied in adult Wistar rats by combined scanning and transmission electron microscopy (SEM, TEM). In general, the peritoneal surface consisted of a mesothelium composed of cubic, flat or intermediate cell types delimited by a basal lamina. Cubic mesothelial cells predominated in parenchymal organs (spleen, liver) and were characterized by prominent and indentated nuclei, a cytoplasm richly supplied with organelles, a dense microvillous coat, basal invaginations and elaborate intercellular contacts. Flat mesothelial cells were observed in the intestinal, omental and parietal peritoneum (tendinous diaphragm, abdominal wall) and showed elongated nuclei, scant cytoplasm, a poorly developed organelle apparatus and sparsely distributed microvilli. An intermediate mesothelial cell type was described within the gastric peritoneum characterized by a central cytoplasmic protrusion at the nuclear region containing most of the cytoplasmic organelles and by thin finger-like cytoplasmic processes. The submesothelial connective tissue layer was composed of collagen fiber bundles, fibroblasts and free cells (macrophages, granulocytes, mast cells) and contained blood and lymphatic vessels. In the spleen, elastic fibers formed a membranous structure with intercalated smooth muscle cells. Mesothelial openings were observed as tunnel-like invaginations within the hepatic peritoneum and as clusters of peritoneal stomata within the parietal peritoneum of the anterior abdominal wall and the muscular diaphragm. The round or oval openings of the peritoneal stomata were frequently occluded by overlapping adjacent mesothelial cells and their microvillous coat or obstructed by cellular material. At the side of the peritoneal stomata the mesothelial cell layer was interrupted to allow a direct access to the underlying submesothelial lymphatic system. The mesothelium and lymphatic endothelium shared a common basal lamina. The endothelial cells were discontinuous and displayed valve-like plasmalemmatic interdigitations facilitating an intercellular transport of fluids and corpuscular elements from the peritoneal cavity to the submesothelial lymphatic lacunae. The findings underline the morphological heterogeneity of the peritoneum in visceral and parietal regions, suggesting different functional implications, and further support the presence of extra-diaphragmatic peritoneal stomata.

Influence of polyglactin-coating on functional and morphological parameters of polypropylene-mesh modifications for abdominal wall repair.

Regarding oversized mechanical properties of most of the currently available materials a new mesh was developed (ETHICON, Norderstedt, Germany) and exactly adopted to the physiology of the human abdominal wall by reducing the amount of polypropylene (weight of <30 g/m2; mesh A). The consecutive increase of pores size as well as the use of multifilaments led to a pronounced increase of flexibility. To improve the handling during operation the initial stiffness of this low-weight large pores mesh was increased by strengthening with different amounts of absorbable polyglactin (combination of glycolide and lactide) in various forms: by coating (mesh B), adding multifilament polyglactin filaments (mesh C, Vypro) or both (mesh D), respectively. To test the consequences of the different supplementary techniques all mesh variants are implanted in a rat model. Over implantation intervals of 3, 7, 14, 21 and 90 days we measured the tensile strength, the resulting stiffness and surveyed the tissue response, particularly in regard to the extent of inflammation and to the induced fibrosis. The results proved a sufficient mechanical stability of the material reduced and pure polypropylene mesh A without restriction of the mobility of the abdominal wall compared with a group that had simple laparotomy and closure. The histological analysis of the interface showed a minor inflammatory reaction and a dense vascularisation. The addition of polyglactin multifilaments (mesh C) reduces the number of macrophages and granulocytes as indicators for acute inflammation, showing generally a scar formation limited merely to the perifilamentary region. The abdominal wall compliance remained unchanged compared with mesh A. The coating of the polypropylene with polyglactin (mesh B and D) appeared to change the tissue reaction remarkably, favouring the formation of a connective tissue capsule around the whole mesh. The mechanical testing revealed an apparent protrusion with an increase of curvature of the artificial abdominal wall at rising intraabdominal pressures. The entire coating of the polypropylene surface with polyglactin induces an all embedding scar plate, filling out the pores and forming a tissue capsule. The complex interaction of tissue and implanted biomaterials with their distinct alterations of the tissue response confirms the necessity of in vivo experiments even after 'minor' modifications. Whereas the addition of polyglactin filaments appears to be favourable, the coating of polypropylene with polyglactin seems to hinder the incorporation of the mesh.

Innervation regulates the metamorphic fates of larval abdominal muscles in the moth, Manduca sexta.

With the onset of metamorphosis, the abdominal muscles of the moth, Manduca sexta, follow one of three developmental fates: maintenance, respecification, or death. The maintained muscles retain their larval size and morphology throughout adult development. The respecified and dying muscles dedifferentiate, which involves regression, nuclear degeneration, and myofibril breakdown. Nuclei in both dying and respecified muscles also proliferate. The amount of nuclear degeneration is greater in the dying muscle fibers, and the amount of nuclear proliferation is greater in the respecified muscles. Four to ten days after pupation, the sizes of the respecified muscles stabilize while the dying muscles are lost. During regression, a subset of the respecified muscle fibers die. The surviving respecified muscle fibers grow and differentiate during the last half of adult development. In respecified muscles, denervation triggers an increased amount of nuclear degeneration and a decreased amount of nuclear proliferation. As a result, denervated respecified fibers experience increased muscle regression including an increased loss of muscle fibers and sometimes muscle death. Surviving respecified fibers still grow and differentiate yet are only 5 to 12% of the control size. Denervation triggers dedifferentiation in maintained muscles, resulting in fiber loss and occasionally muscle death. The percentage of fibers which dedifferentiate varies between different muscles. Denervation also triggers nuclear proliferation, with the amount of nuclear proliferation correlated with the extent of dedifferentiation of the individual muscle fibers. The dedifferentiated maintained fibers subsequently undergo differentiation in the absence of muscle growth.

Tissue response to polypropylene meshes used in the repair of abdominal wall defects.

The degree of integration of biomaterials used in the repair of abdominal wall defects seems to depend upon the structure of the prosthesis. Several polypropylene (PP) prostheses are currently available which differ in the number of PP filaments, the type of weave and the porosity. The aim of this study was to evaluate the integration, adhesion formation and resistance to traction of three types of PP prostheses (Marlex, Trelex and Prolene) used in the partial or total repair of abdominal wall defects. Abdominal wall defects (7 x 5 cm) were created in 54 New Zealand rabbits involving all the tissue layers (total substitutions (TS); n = 27) or all layers excluding the parietal peritoneum (partial substitutions (PS); n = 27). The defects were repaired with PP monofilament prostheses of different weave (1 mm porosity) (Marlex, n = 18; Trelex, n = 18) or bifilament (2 mm porosity) (Prolene; n = 18). They were placed in contact on one side with subcutaneous tissue and on the other with abdominal viscera or parietal peritoneum. Animals were killed at 30, 60 and 90 days and samples of prosthesis and scar tissue processed for light and scanning microscopy. The adhesion formation with viscera was evaluated. Resistance to traction was measured with a tensiometer using strips including the prosthesis and anchorage tissue. Adhesions were detected in all the TS and in four PS. Microscopic analysis revealed total integration of the TS samples by fibrous and disorganized tissue. Prostheses used for PS were integrated by white adipose tissue with the exception of the areas around the mesh nodes and anchorage zones. The foreign body reaction could be seen as a moderate accumulation of white blood cells. Tensiometric analysis showed an increase in resistance to traction with time (P < 0.001) in each type of prosthesis, but no differences were detected (P > 0.001) between them. We concluded that: (a) the formation of adhesions was almost inhibited when the parietal peritoneum was left intact; (b) in both TS and PS, polypropylene prostheses integrated completely although the composition of the scar tissue was seem to differ; and (c) resistance to traction was similar in both TS and PS.