Surrounding Muscle Fibers Research Articles

Growth of Arterioles in Chronically Stimulated Adult Rat Skeletal Muscle

The purpose of this study was to test the hypothesis that capillary growth induced by chronic electrical stimulation of skeletal muscle is accompanied by the growth of small arterioles. Lower limb flexor muscles of Sprague-Dawley rats were stimulated by electrodes implanted in the vicinity of the peroneal nerve at 10 Hz for 8 h/d for 2 and 7 days. Cryostat sections from the proximal, middle, and distal regions of the extensor digitorum longus muscle (EDL) were fluorescently immunolabeled with alpha-smooth muscle actin (alpha SMA) and myosin heavy chain (MHC) to identify mature (alpha SMA and MHC-positive) and immature (alpha SMA-positive, MHC-negative) arterioles. The fluorescent derivative of the lectin Griffonia simplicifolia I (GSI) was used to identify all microvessels, including arterioles, capillaries, and venules. The number of vessels positive for GSI or alpha SMA surrounding muscle fibers was similar in all three muscle regions (proximal, middle, distal). The mean values +/- SEM for GSI-positive vessels from all regions were similar in control (4.3 +/- 0.07) and 2-day stimulated (4.7 +/- 0.08) but higher in 7-day stimulated muscles (6.7 +/- 0.1, p < 0.05), thus confirming the previous findings on capillary growth. A similar increase was found in the number of alpha SMA positive vessels < or = 10 microns outer diameter (1.3 +/- 0.09 versus 0.4 +/- 0.03 around muscle fibers in controls). The density of terminal arterioles (< or = 10 microns) was slightly but not significantly higher after 2 days of stimulation (19.5 +/- 4 versus 15.6 +/- 2 profiles/mm2 in control muscles) and significantly higher after 7 days (33 +/- 7). While a similar increase was observed in the density of preterminal arterioles > 10 microns (17 +/- 3 control, 22 +/- 3 at 2 days and 40 +/- 5 at 7 days), the density of MHC-positive vessels muscles stimulated for 7 days was unchanged. Seven-day stimulated muscle also had a fivefold higher density of microvessel profiles < or = 10 microns that were only partially surrounded by alpha SMA. This considerably exceeds the relative increase in the number of capillaries and thus supports the concept of arteriolar growth by transformation from capillaries. Chronic electrical stimulation results in an early increase in the number of immature (MHG-negative), but not mature (MHC-positive) arterioles, a process that accompanies the increase in capillarization. The great increase in the number of microvessels only partially covered by alpha SMA suggests arteriolization of capillaries as a contributing mechanism in this growth.

HGF/SF Is Present in Normal Adult Skeletal Muscle and Is Capable of Activating Satellite Cells

We have shown that hepatocyte growth factor/scatter factor can stimulate activation and early division of adult satellite cells in culture, and that the action of hepatocyte growth factor/scatter factor is similar to the action of the unidentified satellite cell activator found in extracts of crushed muscle. We now provide new evidence that hepatocyte growth factor/scatter factor is present in uninjured adult rat skeletal muscle and that the activating factor in crushed muscle extract is hepatocyte growth factor/scatter factor. Immunoblots of crushed muscle extract demonstrate the presence of hepatocyte growth factor/scatter factor. Furthermore, crushed muscle extract stimulates the scattering of cultured MDCK cells. Immunolocalization studies with adult rat skeletal muscle show the presence of hepatocyte growth factor/scatter factor in the extracellular matrix surrounding muscle fibers; in addition, the receptor for hepatocyte growth factor/scatter factor, c-met, is localized to putative satellite cells. In muscle from mdx mice, hepatocyte growth factor/scatter factor and c-met are colocalized in activated satellite cells in regions of muscle repair. Moreover, the satellite cell-activating activity of crushed muscle extract is abolished by preincubation with anti-hepatocyte growth factor antibodies. Finally, direct injection of hepatocyte growth factor/scatter factor into uninjured tibialis anterior muscle of 12-month-old rats stimulated satellite cell activation. These experiments demonstrate that hepatocyte growth factor/scatter factor is present in muscle, can be released upon injury, and has the ability to activate quiescent satellite cellsin vivo.

Functional consequences of acute collagen degradation studied in crystalloid perfused rat hearts.

The impact of acute collagen disruption by the disulfide donor, 5,5'-dithio-2-nitrobenzoic acid (DTNB) on ventricular properties was tested in rat hearts. Collagen was degraded acutely in 13 isolated, isovolumically contracting rat hearts by perfusion with 1 mM DTNB added to Krebs-Henseleit solution for 1 hour followed by 2-hour perfusion with normal solution. Another 13 hearts were perfused with normal solution for 3 hours (Control). Collagen content was 3.5 +/- 0.5% of ventricular dry weight in control group compared with 2.1 +/- 0.4% in DTNB group (decrease by 40%, p < 0.01). Scanning electron micrographs revealed loss of the delicate collagen network surrounding muscle fibers in DTNB treated hearts. Developed pressure at a fixed volume decreased to 86 +/- 17% of the baseline value after 3-hour perfusion in the control group, whereas in DTNB treated hearts developed pressure fell to 68 +/- 13% (p < 0.01). End-diastolic pressure was set at 5 mmHg at the beginning of the experiment and rose to 15 +/- 8 mmHg in control and 30 +/- 13 mmHg (p < 0.01) in the treated hearts. Concomitantly, wet-to-dry weight ratio increased from 5.63 +/- 0.26 in control to 6.07 +/- 0.11 (p < 0.05) in the DTNB treated hearts. A separate set of experiments on isolated myocytes excluded the possibility of a direct effect of DTNB on myocyte contractile function. These data suggested that with 40% collagen disruption by DTNB there is a significant increase in tissue edema that results in a decrease in chamber capacitance; in addition, there is a significant decrease in systolic performance which reflects the combined effect of edema and loss of collagen.

Myonuclear apoptosis in dystrophic mdx muscle occurs by perforin-mediated cytotoxicity.

Myonuclear apoptosis is an early event in the pathology of dystrophin-deficient muscular dystrophy in the mdx mouse. However, events that initiate apoptosis in muscular dystrophy are unknown, and whether elimination of apoptosis can ameliorate subsequent muscle wasting remains a major question. We have tested the hypothesis that cytotoxic T-lymphocytes initiate myonuclear apoptosis in dystrophic muscle, and examined whether perforin-mediated cytotoxicity plays a role in the pathophysiology of muscular dystrophy. Mdx mice showed muscle invasion by cytotoxic T cells and helper T cells at the onset of histologically detectable muscle fiber pathology. At this time, perforin-expressing cells were also present at elevated concentration. Mdx mice depleted of CD8(+) cells showed a significant reduction of apoptotic myonuclei concentration and a reduction in necrosis, judged by macrophage invasion of muscle fibers. Double-mutant mice, deficient in dystrophin and perforin, showed nearly complete absence of myonuclear apoptosis, and a significant reduction in the concentration of macrophages in the connective tissue surrounding muscle fibers. However, muscle fiber invasion by macrophages was not reduced significantly in double mutant mice. Thus, cytotoxic T-lymphocytes contribute significantly to apoptosis and necrosis in mdx dystrophy, and perforin-mediated killing is primarily responsible for myonuclear apoptosis.

Ultrastructural Study of the Female Reproductive System of Saduria Entomon (Linnaeus, 1758) (Isopoda, Valvifera)

[The structure of the ovaries, oviducts, fertilization chamber and spermathecae of a mature female of Saduria entomon (L., 1758) is presented at the ultrastructural level. In the ovaries a proximal and a distal part is distinguished. The proximal part is only built of a flattened epithelium lying on a thick basal lamina. In the lumen of this part are previtellogenic and primary vitellogenic oocytes enveloped in follicle cells in which synthetic organelles are absent. Previtellogenic oocytes have large nuclei containing synaptonemal complexes and very large nucleoli with vacuoles of various sizes. Primary vitellogenic oocytes are characterized by intra-oocytic yolk formation inside the elements of the endoplasmic reticulum. The walls of the distal parts of the ovaries and oviducts are built of an epithelium and its surrounding muscle cells. On the lumen side, the oviduct epithelium is covered with a cuticle in which an epicuticle and an endocuticle can be distinguished. The fertilization chamber is built of large cells containing bundles of myofilaments in some areas. Their cytoplasm is rich in mitochondria and glycogen granules. The bundles of myofilaments occurring in the muscle cells of the ovaries, oviducts and the cells of the fertilization chamber are striated. They are characterized by a short sarcomer length (2.6 μm and 3.5 μm) and a high ratio of thin-to-thick filaments. The single epithelium building the spermathecae is separated from the haemocoel only by a basal lamina. The apical surface of the epithelium is covered with a thick intima which does not look like a cuticle., The structure of the ovaries, oviducts, fertilization chamber and spermathecae of a mature female of Saduria entomon (L., 1758) is presented at the ultrastructural level. In the ovaries a proximal and a distal part is distinguished. The proximal part is only built of a flattened epithelium lying on a thick basal lamina. In the lumen of this part are previtellogenic and primary vitellogenic oocytes enveloped in follicle cells in which synthetic organelles are absent. Previtellogenic oocytes have large nuclei containing synaptonemal complexes and very large nucleoli with vacuoles of various sizes. Primary vitellogenic oocytes are characterized by intra-oocytic yolk formation inside the elements of the endoplasmic reticulum. The walls of the distal parts of the ovaries and oviducts are built of an epithelium and its surrounding muscle cells. On the lumen side, the oviduct epithelium is covered with a cuticle in which an epicuticle and an endocuticle can be distinguished. The fertilization chamber is built of large cells containing bundles of myofilaments in some areas. Their cytoplasm is rich in mitochondria and glycogen granules. The bundles of myofilaments occurring in the muscle cells of the ovaries, oviducts and the cells of the fertilization chamber are striated. They are characterized by a short sarcomer length (2.6 μm and 3.5 μm) and a high ratio of thin-to-thick filaments. The single epithelium building the spermathecae is separated from the haemocoel only by a basal lamina. The apical surface of the epithelium is covered with a thick intima which does not look like a cuticle.]

Laminin extraction and disorganization of collagen fibrils in snail muscles by EDTA treatment

Snail muscles were extracted by a solution of EDTA and electron microscopy showed that the extract contained dispersed, depolymerized collagen fibrils and cross-shaped laminin-like structures. The extracts were purified by ultracentrifugation followed by two different procedures which enriched the content of laminin-like structures. The laminin-related molecules displayed unique properties when analyzed by biochemical, immunological and morphological methods. Electrophoretic patterns of the molecular form purified primarily by ion exchange chromatography, resembled EHS-tumor laminin and displayed a cruciform shape when viewed by electron microscopy. Immunohistology, using antiserum obtained against the agarose gel-purified protein, showed that this laminin was primarily located in the extracellular matrix surrounding muscle fibers. Western blots using anti-EHS laminin antibody showed reaction of a 300 kDa subunit of this snail laminin. The protein obtained by another procedure, initially using gel filtration, followed by ion exchange chromatography, also appeared to be a laminin. It had a collapsed cruciform appearance when viewed by electron microscopy. It contained several different subunits, one of which, ca 300 kDa, reacted with anti-EHS-laminin antibody and with anti-snail laminin antibody. In contrast, EHS laminin did not react with the anti-snail laminin antibody. The composite results suggest that at least two different forms of laminin are extractable from snail muscle and that they share molecular properties and immune determinants with mouse tumor laminin.

Abnormal expression of laminin suggests disturbance of sarcolemma-extracellular matrix interaction in Japanese patients with autosomal recessive muscular dystrophy deficient in adhalin.

Dystrophin is associated with several novel sarcolemmal proteins, including a laminin-binding extracellular glycoprotein of 156 kD (alpha-dystroglycan) and a transmembrane glycoprotein of 50 kD (adhalin). Deficiency of adhalin characterizes a severe autosomal recessive muscular dystrophy prevalent in Arabs. Here we report for the first time two mongoloid (Japanese) patients with autosomal recessive muscular dystrophy deficient in adhalin. Interestingly, adhalin was not completely absent and was faintly detectable in a patchy distribution along the sarcolemma in our patients. Although the M and B2 subunits of laminin were preserved, the B1 subunit was greatly reduced in the basal lamina surrounding muscle fibers. Our results raise a possibility that the deficiency of adhalin may be associated with the disturbance of sarcolemma-extracellular matrix interaction leading to sarcolemmal instability.

Autoradiographic delineation of skeletal muscle alpha 1-adrenergic receptor distribution

We used light microscopic autoradiography to quantify the distribution of alpha 1-adrenergic receptors in vessels and muscle fibers of slow-twitch (type I), fast-twitch (types IIa and IIb), and mixed fiber muscles of the rat hindquarter. Frozen cross sections of soleus, vastus lateralis, and gastrocnemius muscles were incubated under equilibrium binding conditions with 10-200 pM [3H]prazosin with or without 10(-5) M phentolamine. Because of the low concentration of bound radioligand, specific binding could not be detected with scintillation spectrometry in whole tissue sections scraped from slides. However, quantitative autoradiographic analysis after extended intervals of emulsion exposure revealed a low but significant level of specific binding in muscle fibers. No difference in alpha 1-receptor density was observed among types I, IIa, and IIb fibers. Small blood vessels had a much greater alpha 1-receptor density than muscle fibers. Resistance arterioles (20-100 microns diam) and small arteries (100-500 microns diam) contained 5.8 +/- 0.9 and 31.6 +/- 7.6 (+/- SE) times more binding sites per unit section area, respectively, than did surrounding muscle fibers (both P less than 0.001). Ratios of specific grain densities in fibers and blood vessels did not vary with radioligand concentration, indicating that observed grain densities reflected differences in receptor concentration rather than radioligand affinity by fiber and vessel receptors. The densities of vascular alpha 1-receptors did not vary in slow- and fast-twitch muscles, but resistance arterioles were six and eight times more numerous in soleus than in gastrocnemius and vastus muscles, respectively (both P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Rectal atresia: Transanal, end-to-end, rectorectal anastomosis: A simplified, rational approach to management

Transanal, end-to-end, rectorectal anastomosis (TERA) is a new technique for the surgical correction of rectal atresia. Hitherto performed abdominoperineal or sacroperineal procedures entailed major traumatizing surgery with an inherent risk of complications. The rationale of TERA is based on three factors: (1) the anorectal canal distal to the atresia is normally developed, as are the sphincteric muscles surrounding it; (2) the anorectum can be preoperatively dilated to allow a transanal anastomosis of good size; and (3) the atretic segment can be effectively “intussuscepted” into the anal canal, almost up to the anal verge, by an oversized metal bougie passed through the sigmoid colostomy. A midline sagittal incision over the metal bougie exposes the rectal pouch, which is mobilized from the surrounding muscle fibers, and a direct, end-to-end anastomosis is performed. This technique has been successfully used in two cases of rectal atresia having a gap between the two pouches.

Pathogenesis of hemorrhage induced by bilitoxin, a hemorrhagic toxin isolated from the venom of the common cantil ( Agkistrodon bilineatus bilineatus)

The pathogenesis of hemorrhage induced by the i.m. injection of the hemorrhagic toxin, bilitoxin, was studied using light and electron microscopy. White mice were injected with sublethal doses of the toxin, and tissue samples were obtained at 5 and 30 min, and 1, 3 and 24 hr after the injection. There was a good correlation between amount of toxin injected and amount of hemorrhage observed. Microscopically, hemorrhage was visible in all parts of the connective tissue surrounding muscle cells just 5 min after injection and fibrin was present both intravascularly and extravascularly. At later time periods the hemorrhage was more extensive and there was more fibrin. Many vessels were plugged with platelets. At 30 min after the injection, muscle cells appeared to be damaged having either delta lesions or disrupted myofibrils. Electron microscopy revealed damaged capillaries with ruptured endothelial cells, disrupted basal lamina and intact intercellular junctions. Thus, this hemorrhagic toxin acts rapidly to disrupt the capillary endothelium without damaging the intercellular junctions, and it also appears to damage skeletal muscle cells.

Development of smooth muscle: ultrastructural study of the chick embryo gizzard.

The growth and differentiation of smooth muscle in the chicken gizzard were studied by electron microscopy from the 10th day in ovo to 6 months after hatching; during this period the organ grows 1000-fold in weight. At the earliest stage studied, smooth muscle cells, interstitial cells, and fibroblasts are immature but can already be clearly distinguished. The structural components of muscle cells develop in a characteristic sequence. Mitochondria are more abundant in immature muscle cells (8% in 14 days embryos and 7% in 19 days embryos) than in the adult (5%). Caveolae are virtually absent in the 11 day embryo; they become more common at the end of embryonic life, but continue to increase in relative frequency after hatching. Gap junctions appear around the 16th day in ovo as minute aggregates of connexons, which then grow in size, probably by addition of new connexons. In the earliest stages studied, myofilaments occupy 25% of the cell profile and are assembled into bundles accompanied by dense bodies and surrounded by loosely arranged intermediate filaments. By contrast, membrane-bound dense bands are scarce until the latter part of embryonic life, an observation suggesting that myofilament formation and alignment is not a process initiated near the cell membrane or directed by the cell membrane, and that only late in development bundles of myofilaments become extensively anchored to dense bands over the entire cell surface: at that time myofilaments occupy more than 75% of the cell volume. The muscle cells increase about four-fold in volume over the period studied; the 1000-fold increase in muscle volume is mainly accounted for by an increase in muscle cell number. Mitoses are found in the gizzard musculature at all embryonic ages with a peak at 17-19 days; they occur in muscle cells with a high degree of differentiation. These cells divide at a stage when they are packed with myofilaments and form junctions with neighbouring cells: the mitotic process affects the middle portion of the cell, which takes up an ovoid shape and eventually divides, whereas the remaining portions of the cell do not differ in appearance from the surrounding muscle cells. At all stages of development the population of muscle cells has a uniform appearance (apart from the cells in mitosis), and the growth and differentiation seem to proceed at the same pace in all the cells. There are no undifferentiated cells left behind in the tissue for later development.

Glycogen synthesis from lactate in a chronically active muscle

In response to neural overactivity (pseudomyotonia), gastrocnemius muscle fibers from C57Bl/6Jdy2J/dy2J mice have different metabolic profiles compared with normal mice. A population of fibers in the fast-twitch superficial region of the dy2J gastrocnemius stores unusually high amounts of glycogen, leading to an increased glycogen storage in the whole muscle. The dy2J muscle also contains twice as much lactate as normal muscle. A [14C]lactate intraperitoneal injection leads to preferential 14C incorporation into glycogen in the dy2J muscle compared with normal muscle. To determine whether skeletal muscles were incorporating lactate into glycogen without body organ (liver, kidney) input, gastrocnemius muscles were bathed in 10 mM [14C]lactate with intact neural and arterial supply but with impeded venous return. The contralateral gastrocnemius serves as a control for body organ input. By using this in situ procedure, we demonstrate that under conditions of high lactate both normal and dy2J muscle can directly synthesize glycogen from lactate. In this case, normal whole muscle incorporates [14C] lactate into glycogen at a higher rate than dy2J whole muscle. Autoradiography, however, suggests that the high-glycogen-containing muscle fibers in the dy2J muscle incorporate lactate into glycogen at nearly four times the rate of normal or surrounding muscle fibers.

Polymyositis Associated With AIDS Retrovirus

Two homosexual men were initially seen with polymyositis as the only manifestation of the acquired immunodeficiency syndrome (AIDS) retrovirus infection. They developed AIDS-related complex a few weeks later and typical AIDS two to six months after onset of muscle weakness. By use of anti-human T-cell lymphotropic virus type III antiserum and monoclonal antibodies to lymphocyte subsets in an immunofluorescence technique, viral antigens were found in the OKT4-positive lymphoid cells surrounding muscle fibers and invading the endomysia septa. We concluded that an initial infection with the AIDS retrovirus can be associated with polymyositis, which may be the first clinical manifestation of an impending AIDS-related complex or AIDS.

Polymyositis associated with AIDS retrovirus

Two homosexual men were initially seen with polymyositis as the only manifestation of the acquired immunodeficiency syndrome (AIDS) retrovirus infection. They developed AIDS-related complex a few weeks later and typical AIDS two to six months after onset of muscle weakness. By use of anti-human T-cell lymphotropic virus type III antiserum and monoclonal antibodies to lymphocyte subsets in an immunofluorescence technique, viral antigens were found in the OKT4-positive lymphoid cells surrounding muscle fibers and invading the endomysia septa. We concluded that an initial infection with the AIDS retrovirus can be associated with polymyositis, which may be the first clinical manifestation of an impending AIDS-related complex or AIDS. (<i>JAMA</i>1986;256:2381-2383)

Polymyositis in an immunodeficiency disease in monkeys induced by a type D retrovirus.

Fifty percent of primates with acquired immunodeficiency caused by a well-characterized type D retrovirus (SAIDS D) developed clinical, laboratory, and histologic features of polymyositis. By use of specific antisera and immunochemical techniques, we found the virus in the lymphoid cells surrounding muscle fibers and invading the endomysia septa. SAIDS D virus was isolated from the involved muscles and infected myotubes of normal muscle in tissue culture. These results suggest that retroviruses, a group of viruses increasingly associated with human diseases, can cause polymyositis with immunodeficiency in nonhuman primates and could play a role in human polymyositis.

Analysis of macrophages, activated cells and T cell subsets in inflammatory myopathies using monoclonal antibodies.

The availability of monoclonal antibodies which react with lymphocytes and cells of the MPS permits the construction of panels of reagents for immunophenotypic analysis of infiltrating cells in IM. We used immunohistochemical methods to immunophenotype inflammatory cells in muscle biopsies of patients with PM, DM and IBM. The cases of PM and IBM contained an intense MPS cell infiltrate in perivascular and endomysial areas, closely surrounding muscle fibers and occasionally included within the muscle fiber itself; an infiltrate of Leu-6+ cells with a morphology consistent with MPS cells in perivascular and endomysial distribution and occasionally closely apposed to muscle fiber membranes; lymphocytes and MPS cells expressing the IL2-R, and approximately equal numbers of T cells of helper-inducer and suppressor-cytotoxic phenotypes. DM cases had fewer MPS cells and relatively more B cells than T cells.

Histopathologic classification of uterine choriocarcinoma.

Histopathologic features of uterine choriocarcinoma were studied to establish new criteria for grading malignancy of the disease. Thirteen items of histopathologic findings concerning the degree of differentiation and the forms of masses of trophoblasts (Trs), the manner of Tr invasion, and host response of surrounding tissues were studied with relationship to prognosis in 70 patients with uterine lesions (alive, 49; dead, 21). Chi-square test results were examined for each item in relation to prognosis of the patients. Four items were thought to have significance and were selected as criteria: (1) island formation; (2) massive proliferation of intermediate-type Trs; (3) rectangular infiltration of Trs to surrounding muscle fibers; and (4) atypia of Trs at the end-point of tumor invasion. A discriminant analysis was carried out (under the standardization of tumor extension and the historical staging of treatment). From the results obtained in discriminant analysis, scores were given to the four items that existed in the specimen. New criteria for grading malignancy are proposed based on scoring these four items. The algebraic sum of the scores had a possible range of +4 to -16. Patients with scores of -9 and above had a low-grade malignancy with a mortality rate of 7%. Patients with scores of -10 and lower had a mortality of 69% and were classified as having tumors of high-grade malignancy.

Cell and tissue reactions of turbot Scophthalmus maximus (L.) to Tetramicra brevifilum gen. n., sp. n. (Microspora)

Abstract. Tetramicra brevifilum gen, n. sp, n. is described from the connective tissues throughout the body musculature of turbot Scophthalmus maximus (L.). Uninucleate spores (4.8·2 μm) are characterized by a large posterior vacuole, electron dense inclusion bodies in cytoplasm and nucleus and short filaments with 3–5 coils (50 μm extruded). Sporogony is apansporoblastic and tetrasporoblastic, within a host vacuole. Features of the xenoma (2 mm diameter) include a microvillous surface layer with microtubules and microfilaments and a reticulate nucleus with numerous nucleoli. Adherence between adjacent xenomas results in composite cysts of various sizes and shapes depending on site, being dendritic in the myomeres, arms extending between the fibres. Effects on the host, other than eventual destruction of the host cell, include displacement of muscle fibres in myomeres with loss of attachment to myocommata. Breakdown of the xenoma with release of spores into the connective tissue matrix was associated with a localized necrosis affecting surrounding muscle fibres, with leucocyte infiltration and collagen deposition. Spores phagocytosed by macrophages were destroyed in vacuoles, some with multi‐laminate walls. Experimental infections established by intramuscular injection at marked sites remained localized, which suggested that xenomas afford sufficient scope for spore production without the need of secondary invasion. The swimming efficiency of turbot would be impaired in severe infections leading to lowered growth rates and increased mortality in wild populations due to predation and starvation. Feeding hierarchies exist in turbot and the disease could prove significant in farming conditions.

MUSCLE ULTRASTRUCTURE IN REYE'S SYNDROME (RS): EVIDENCE FOR A MYOPATHY

Biochemical studies have shown elevation of muscle creatine phosphokinase (Roe et al., Ped. 55:119, 1975) and excessive urinary nitrogen losses up to 0.64 g/kg/day (Snodgrass and DeLong, N. Eng. J. Med. 294:855, 1976) in RS, suggest ing skeletal muscle injury. We report electronmicroscopy of muscle biopsies obtained from 15 RS cases on the day of admission and at followup 4 days to 23 weeks later. A myopathy of variable severity was present in each case acutely. In severely affected specimens about 1/40 muscle cells were necrotic with dissolution of the sarcolemma,loss of striations and dispersion of myofilaments, producing a homogenous matrix which contained vesicular fragments of sarcoplasmic reticulum, autophagic vacuoles and spherical mitochondria with expanded matrix and frequently ruptured outer membranes. Surrounding muscle cells were abnormal, displaying glycogen loss, ribosome disorganization, dilation of sarcoplasmic reticulum and intramyo-fibrillar edema. There were 2 populations of mitochondria in muscle cells: Individual mitochondria demonstrated extreme matrix expansion suggestive of that seen in brain and liver in RS, but the majority of muscle cell mitochondria demonstrated only slight matrix expansion. Muscle cell triglyceride was increased and many cells contained myelin figures. Inflammation was absent but influenza virus was isolated from 3 of 5 biopsies in which cultivation was attempted. These studies confirm the existence of a myopathy in RS. The relationship between the myopathy of RS and post-influenzal myopathy of childhood should be investigated.

Pseudomalignant myositis ossificans: A Pathological study of eight cases

Eight cases of pseudomalignant myositis ossificans are presented. There was a male predominance and four patients were under 20 years of age. There was no history of trauma, but there was evidence of mild local or general inflammation with positive roentgenograms in two cases. Histologically there was active fibroblastic proliferation, appearing to develop essentially in fibrin deposits with metaplasia leading to the formation of an unusual osteoid. The newly formed mass was surrounded by bone and compressed the surrounding muscle fibers, which were either atrophic or trapped therein. The histological criteria distinguishing this disorder from other forms of myositis ossificans are discussed, and comparisons are drawn with nodular fasciitis and proliferative myositis. An association with the latter was observed in one case. This nontumourous growth must be distinguished from osteogenic sarcoma of soft tissue. The differential diagnosis is based on careful histological criteria, which must be supported by clinical and radiological data.