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Biomedical subjects

J A Maynard

Publications and source records attributed to J A Maynard.

At least 37 records · Page 2Linked to original sources
PubMed1985

A histologic comparison of continuous and interrupted microarteriorrhaphy.

Interrupted and continuous microsuturing techniques were compared 3 weeks after microarteriorrhaphy in the rat femoral artery using light microscopy, and internal luminal diameter determinations were measured with a Bio Quant II Digitizer. The histologic appearance of the arteries of both groups was similar, with intimal hyperplasia, intimal incorporation of suture projections into the lumen, minimal inflammatory response to suture material, and restoration of the media. No significant difference was demonstrated between internal diameters at the anastomosis site for the continuous (N = 11, mean diameter 804 +/- 60 microns) and interrupted (N = 11, mean diameter 901 +/- 45 microns) groups. However, the experimental arteries in both continuous and interrupted groups were significantly dilated when compared to their controls (513 +/- 41 microns and 621 +/- 44 microns, respectively). This study indicated that interrupted and continuous suture techniques in laboratory microarteriorrhaphy result in similar histologic and morphologic characteristics, and that the repaired vessels were dilated compared to intact vessels.

Animals↗
PubMed1984

The evolution and histopathology of adolescent tibia vara.

This clinical, radiographic, and histologic study clarifies the evolution of the distinct clinical and radiographic disorder known as adolescent tibia vara (Blount's disease). Although previous reports have suggested that the disorder occurs in a limb that has been normally aligned until adolescence, we have found that most children with adolescent tibia vara maintain a mild degree of infantile physiologic genu varum. Then, concurrent with the adolescent growth spurt, certain children with predisposing factors, such as obesity, extreme activity, or rapid growth, injure the posteromedial physis as a result of repetitive trauma due to normal use of a limb already in mild varus. The result is growth suppression, further varus, and a classic radiographic presentation. Histologic examination in two cases suggests injury to the growth plate as demonstrated by fissuring and clefts in the physis as well as fibrovascular and cartilaginous repair tissue at the physeal-metaphyseal junction. Transverse trabeculae, resembling growth arrest lines, were noted in the adjacent metaphysis; however, true bony bridging of the growth plate was not seen. Recommended treatment is corrective osteotomy below the growth plate.

Adolescent↗
PubMed1984

Pseudoachondroplasia: biochemical and histochemical studies of cartilage.

Cartilage from patients with pseudoachondroplasia is characterized by unique inclusions in the cisternae of the endoplasmic reticulum and proteoglycan abnormalities have been suggested in this form of dwarfism. To elucidate the nature of the proteoglycan defect, we determined the amount of the individual glycosaminoglycans present in iliac-crest cartilage of three patients and extracted the proteoglycan monomers from one of the samples. Sections of iliac-crest cartilage and proximal fibular growth plates were examined by electron microscopy and also stained with hematoxylin and eosin, safranin O-fast green, and alcian blue in the presence of increasing concentrations of magnesium chloride (zero to one molar). The chondrocytes of the iliac crest and fibular physes were arranged in clusters more than in columns and contained characteristic endoplasmic reticulum inclusions, which were particularly large in the hypertrophic cells. The cartilage stained very poorly with hematoxylin and eosin and with safranin O-fast green. The alcian-blue stain was abolished from perilacunar areas and from longitudinal septa by magnesium chloride concentrations that were lower than those required by normal tissue. The proteoglycans of iliac-crest cartilage were found to be significantly enriched in keratan sulphate and had a below-normal ratio of chondroitin-4-sulphate to chondroitin-6-sulphate, although the amount of the two isomeric chondroitin sulphates combined was within normal limits. The urinary excretion of glycosaminoglycan by the three patients was normal. Pseudoachondroplasia appears to be a generalized cartilage disorder involving abnormalities of proteoglycans, probably related to the core protein or to enzymes that are responsible for the formation of the glycosaminoglycan chains.(ABSTRACT TRUNCATED AT 250 WORDS)

Achondroplasia↗
PubMed1983

An in situ study of the influence of a sclerosing solution in rabbit medial collateral ligaments and its junction strength.

A double-blind study was conducted to assess the influence of a sclerosing solution on rabbit medial collateral ligaments (MCL) in situ. It was shown that repeated injections of 5% sodium morrhuate into the MCL and its bony attachments significantly increased its bone-ligament-bone junction strength, ligament mass and thickness when compared to saline-injected controls. Morphometric analysis of electron micrographs showed a highly significant corresponding increase of the collagen fibril diameters in the experimental ligament compared against the control MCL. These composite findings suggested that the sclerosing solution had a significant influence on dense connective tissue at the insertion sites. The mechanisms for these changes are uncertain and are the basis for future investigations.

Animals↗
PubMed1983

Legg-Calvé-Perthes disease. Histochemical and ultrastructural observations of the epiphyseal cartilage and physis.

UNLABELLED: Biopsy specimens of the lateral aspect of the femoral head and neck were obtained from five children with Legg-Calvé-Perthes disease and were studied using histochemistry and electron microscopy. Beneath the normal articular cartilage there was a thick zone of hyaline (epiphyseal) cartilage containing sharply demarcated areas of hypercellular and fibrillated cartilage with prominent blood vessels. The fibrillated cartilage was strongly positive to alcian blue, weakly positive to periodic acid-Schiff, and positive to aniline blue. The interterritorial matrix in the hypercellular areas was weakly positive to both alcian blue and periodic acid-Schiff. Ultrastructural examination of these areas revealed many irregularly oriented large collagen fibrils and variable amounts of proteoglycan granules. These results suggest that in the fibrillar areas there are: (1) a high proteoglycan content, (2) a decrease in structural glycoproteins, and (3) a different size of collagen fibrils from that of normal epiphyseal cartilage. The hypercellular areas had a decrease in proteoglycans, glycoproteins, and collagen. The lateral physeal margin was often irregular, with a marked reduction of collagen and proteoglycan granules, and contained numerous large lipid inclusions. CLINICAL RELEVANCE: The abnormal areas in the epiphyseal cartilage of patients with Legg-Calvé-Perthes disease have different histochemical and structural properties from normal cartilage and from fibrocartilage. This suggests that the disease could be a localized expression of a generalized, transient disorder of epiphyseal cartilage that is responsible for delayed skeletal maturation. The cartilage lesions are similar to those seen in the vertebral plates in patients with juvenile kyphosis. Whether the epiphyseal cartilage abnormalities are primary or are secondary to ischemia remains uncertain; however, it appears that the collapse and necrosis of the femoral head could result from the breakdown and disorganization of the matrix of the epiphyseal cartilage, followed by abnormal ossification.

Cartilage, Articular↗
PubMed1981

Histochemistry and ultrastructure of the growth plate in metaphyseal dysostosis: further observations on the structure of the cartilage matrix.

The metaphyseal dysostosis growth plate matrix was examined by alcian blue-magnesium chloride histochemistry and electron microscopy. The metaphyseal dysostosis matrix is uniformly alcian blue positive at all molarities of MgCl2 up to 1.0 M. In normal growth plates, the vertical septa become alcian blue negative at 0.5 to 0.6 M MgCl2. At 1.0 MgCl2, metaphyseal dysostosis plates are weakly periodic acid-Schiff (PAS) positive compared to intense PAS reactions in normal growth plates. The histochemical findings correlate well with the decreased collagen content of the matrix as seen by electron microscopy, resulting in a relative increase in proteoglycan granules. The findings indicate that the previously described cellular defect seen in metaphyseal dysostosis chondrocytes is related to an abnormal cartilage matrix that mineralizes poorly and is not easily degraded.

Adolescent↗
PubMed1981

Legg-Calvé-Perthes disease in dogs: a comparison to human Legg-Culvé-Perthes disease.

The femoral heads of 12 dogs with naturally occurring Legg-Calvé-Perthes disease were studied by light and electron microscopic techniques. In the early stages of the disease, the bony capital femoral epiphysis was necrotic, but the articular cartilage and growth plate cartilage were not affected. By the early stages of repair, the femoral head had collapsed. the articular cartilage was thickened and furrowed at the sites of collapse, and the chondrocytes appeared more metabolically active. Sites of bone resorption were associated with osteoclasts and macrophages. In some specimens there were areas of necrosis in the metaphysis which interrupted normal enchondral ossification in the growth plate. By the final stages of repair, the epiphysis was almost completely revascularized with the exception of the central proximal segment. In some areas, repair tissue had penetrated into the deeper layers of the articular cartilage. The flattening of the femoral head in Legg-Calvé-Perthes disease appears to be the result of several processes: mechanical collapse, asymmetric growth, and disturbed enchondral ossification at the growth plate.

Animals↗
PubMed1980

Synovial sarcoma: an electron microscopic study of monophasic and biphasic forms.

Seven cases of synovial sarcoma were studied by electron microscopy. The 4 cases of the monophasic spindle type contained elongated cells arranged in sheets and cords; ultrastructurally the cells contained many cytoplasmic processes and were scattered in an amorphous matrix. The monophasic spindle type demonstrates ultrastructural characteristics that are unique and serve to differentiate it from the biphasic pattern and from fibrosarcoma. Three cases of the biphasic variety demonstrated cytologic characteristics of a true glandular epithelium and a malignant spindle cell stroma. The epithelial nature of the biphasic variety is a feature that raises doubt whether synovium is the stem cell.

Adolescent↗
PubMed1979

Localization of acid and alkaline phosphatase activities in the blood vessels of normotensive and hypertensive rats.

Samples of aortae and caudal arteries from normotensive and hypertensive rats were studied for cytochemical and biochemical determinations of acid and alkaline phosphatase activities. Cytochemical examination revealed an increased amount of acid phosphatase reaction product in hypertensive samples, with extensive localization to the extracellular matrix. Alkaline phosphatase activity was localized to the plasma membrane of fibroblasts and vascular smooth muscle cells and to the extracellular matrix. Biochemical assays of enzyme activities supported the cytochemical findings, showing increased activity in aortae from hypertensive rats.

Acid Phosphatase↗
PubMed1978

Sheathing of collagen fibrils in human intervertebral discs.

In 25 human intervertebral discs studied by electron microscopy, sheathing collagen-like fibrils by electron-dense cylinders was observed. The sheaths consisted of layers of dense granules 3 to 12 times the diameter of the enclosed collagen-like fibrils, and they appeared to be more frequent in older discs.

Adult↗
PubMed1977

An ultrastructure investigation of intrafusal muscle fibers in myotonic dystrophy.

Ultrastructure features of muscle spindles from two patients with myotonic dystrophy are described. Intrafusal muscle fibers exhibit extensive splitting with nuclear bag fibers affected more so than nuclear chain fibers. No sensory endings are present on nuclear chain fibers nor on one nuclear bag fiber throughout the equatorial and myotube regions. Small motor end plates are evident on various segments of split intrafusal fibers in the polar region and some of these extend into the myotube region. Satellite cells are numerous on both nuclear bag and nuclear chain fibers. These frequently occupy the cleft space between segments of split intrafusal fibers. The myotonic dystrophy muscle spindle ultrastructure features seem to closely resemble the appearance of developing mammalian muscle spindles as illustrated with opossum fetal tissue.

Adult↗
PubMed1977

The ultrastructure of the growth plate in slipped capital femoral epiphysis.

Core biopsy specimens of the proximal femoral growth plate from three patients with slipped capital femoral epiphysis were studied by light and electron microscopy. In the resting zone, the cartilage matrix was composed of large, densely packed collagen fibrils. The cartilage matrix in the zones of chondrocyte hypertrophy where the slippage occurred contained only scattered fine collagen fibrils in a homogeneous ground substance. The change in composition of cartilage matrix in the distal region of the epiphyseal plate may predispose that region to slippage.

Adolescent↗
PubMed1976

Elastic fibers in human intervertebral discs.

Although previous studies failed to demonstrate elastic fibers in intervertebral discs, electron microscopy of twenty human intervertebral discs obtained at autopsy and operation revealed characteristic elastic fibers in both the annulus fibrosus and the nucleus pulposus. Their contribution to the mechanical properties of the intervertebral disc remains to be determined.

Adolescent↗
PubMed1975

The influence of physical activity on ligaments and tendons.

Using either a bone-ligament-bone or a muscle-tendon-bone preparation, numerous investigators have demonstrated that the usual site of separation is in the transitional zone between the ligament (or tendon) and bone; hence, the term junction strength or load at separation is used to describe functional changes in these preparations. Junction strength is decreased with inactivity (immobilization) and increased with chronic activity (training) provided that the exercise program is of an endurance nature. Training also increases junction strength in thyroidectomized and hypophysectomized rats. Besides in junction strength, training results in heavier ligaments and higher ligament weight/length ratios. However, water content, collagen concentrations/dry weight or collagen concentration per weight/length unit are not significantly influenced by repeated bouts of exercise. Although immobilization is associated with lower elastic stiffness values (kg/mm), training appears to have little influence on this measure in normal animals. Rats and dogs with surgically repaired ligaments are weaker and the strength results are markedly lower if the leg is immobilized. Exercise training improves the repair strength of ligaments but does not result in normal values twelve weeks after the surgery. Exogenous administration of ICSH or testosterone results in higher repair strength whereas TSH, thyroxine, ACTH and growth hormone decreases this measure. It was concluded that the mechanical stress produced by chronic exercise is an important determination of the strength of repaired ligaments and of the junctions between ligaments (or tendons) and bones.

Achilles Tendon↗