摘要:

AbstractThe sequence of events in the development of the brain in staged human embryos was investigated in much greater detail than in previous studies by listing 100 features in 165 embryos of the first 5 weeks. Using a computerized bubble‐sort algorithm, individual embryos were ranked in ascending order of the features present. This procedure made feasible an appreciation of the slight variation found in the development features. The vast majority of features appeared during either one or two stages (about 2 or 3 days). In general, the soundness of the Carnegie system of embryonic staging was amply confirmed. The rhombencephalon was found to show increasing complexity around stage 13, and the postoptic portion of the diencephalon underwent considerable differentiation by stage 15. The need for similar investigations of other systems of the body is emphasized, and the importance of such studies in assessing the timing of cogenital malformations and in clarifying syndromic clusters is suggeste

ISSN:0002-9106    

DOI:10.1002/aja.1001710302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to estimate the absolute and relative masses of the three types of skeletal muscle fibers in the total hindlimb of the male Sprague‐Dawley rat (Rattus norvegicus). For six rats, total body mass was recorded and the following weights taken from dissection of one hindlimb: 32 individual major muscles or muscle parts, remaining skeletal musculature (small hip muscles and intrinsic foot muscles), bone, inguinal fat pad, and skin. The fibers from the 32 muscles or muscle parts (which constituted 98% of the hindlimb skeletal muscle mass) were classified from histochemistry as fast‐twitch oxidative glycolytic (FOG), fast‐twitch glycolytic (FG), or slow‐twitch oxidative (SO), and their populations were determined. Fiber cross‐sectional areas from the same muscles were measured with a digitizer. Mass of each of the fiber types within muscles and in the total hindlimb was then calculated from fiber‐type population, fiber‐type area, and muscle‐mass data. Skeletal muscle made up 71% of the total hindlimb mass. Of this, 76% was occupied by FG fibers, 19% by FOG fibers, and 5% by SO fibers. Thus, the FG fiber type is clearly the predominant fiber type in the rat hindlimb in terms of muscle mass. Fiber‐type mass data are compared with physiological (blood flow) and biochemical (succinate dehydrogenase activities) data for the muscles taken from previous studies, and it is demonstrated that these functional properties are closely related to the proportions of muscle mass composed of the va

ISSN:0002-9106    

DOI:10.1002/aja.1001710303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe force produced within skeletal muscle fibers is transmitted to the bone via a myotendinous junction. This junctional region was examined by light and electron microscopy in the sartorius muscles of threeRana temporaria. The muscle fibers tapered and inserted at an angle of about 25° with the connective tissue fascia near the bone. The composition of the structures within the last 100 μm of the fiber was analyzed morphometrically. The T‐system, terminal cisternae, and caveolae were the same as in the central region of the muscle fiber. However, the mitochondrial content was higher and the volume of longitudinal sarcoplasmic reticulum was lower than elsewhere in the fiber. The membrane at the end of the fiber had extensive villiform processes interdigitating with the tendon. The surface area of the membrane around the villiform processes was estimated with point‐counting techniques and calculated from the stereological equations appropriate for partially anisotropic structures. The extra membrane involved in the myotendinous junction was about 32 times that of the cross‐sectional area of the fiber. Part of this additional membrane contained specialized adherens junctions through which the contractile proteins of the muscle are anchored to collagen. The increased area at the myotendinous junction presumably provides greater mechanical strength than a flat termination. The high values of membrane capacitance and specific resistance measured electrophysiologically at the end of the fiber also can be attributed to the characteristics of the terminal membrane st

ISSN:0002-9106    

DOI:10.1002/aja.1001710304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractBecause the architectural and biochemical properties of a skeletal muscle dictate its force, velocity, and displacement properties, the major extensors (triceps brachii) and flexors (biceps brachii, brachialis, and brachioradialis) of the elbow in a primate (cynomolgus, monkey) were studied. Functional cross‐sectional areas (CSA) were calculated from muscle mass, mean fiber length (normalized to a 2.20 μm sarcomere length), and angle of fiber pinnation measurements from each muscle. Fiber‐type distributions were determined and used as a gross index of the biochemical capacities of the muscle. The extensor group had a shorter mean fiber length (31 vs. 47 mm), a larger CSA (13 vs. 8 cm2), and a higher overall percentage of slow‐twitch fibers (47 vs. 26%). Consequently, the elbow extensors had a relatively greater potential for force production and force maintenance than the flexors. In contrast, the flexors were designed to optimize their length‐velocity potentials; i.e., they had relatively long fibers and a higher fast‐twitch fiber composition than the extensors. These morphologic differences between antagonistic muscle groups should be considered when evaluating the motor control mechanisms regulating reciprocal movements about

ISSN:0002-9106    

DOI:10.1002/aja.1001710305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractAblation of various regions of premigratory trunk neural crest which gives rise to the sympathetic trunks was used to remove sympathetic cardiac innervation. Neuronal uptake of [3H]‐norepinephrine was used as an index of neuronal development in the chick atrium. Following ablation of neural crest over somites 10–15 or 15–20, uptake was significantly decreased in the atrium at 16 and 17 days of development. Ablation of neural crest over somites 5–10 and 20–25 caused no decrease in [3H]‐norepinephrine uptake. Removel of neural crest over somites 5–25 or 10–20 caused approximately equal depletions of [3H]‐norepinephrine uptake in the atrium. Cardiac norepinephrine concentration was significantly depressed following ablation of neural crest over somites 5–25 but not over somites 10–20. Light‐microscopic and histofluorescent preparations confirmed the absence of sympathetic trunks in the region of the normal origin of the sympathetic cardiac nerves following neural crest ablation over somites 10–20. The neural tube and dorsal root ganglia were damaged in the area of the neural‐crest ablation; however, all of these structures were normal cranial and caudal to the lesioned area. Development of most of the embryos as well as the morphology of all of the hearts was normal following the lesion. These results indicate that it is possible to produce sympathetically aneural hearts by neural‐crest ablation; however, sympathetic cardiac nerves account for an insignificant amount of cardiac norepinephrine. The adrenal medulla is the most likely source of cardiac norepinephrine in s

ISSN:0002-9106    

DOI:10.1002/aja.1001710306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractAlternate serial semithin and thin sections of the glutaraldehyde‐fixed interatrial septum and atrioventricular junction of adult rat were examined in light and electron microscopes. The animals were pretreated with a false precursor of catecholamines, i.e., with 5‐OH‐dopamine, in order to differentiate the adrenergic component of the intrinsic nervous system. According to the light microscope data, two kinds of ganglia can be distinguished at the level of the interatrial septum. Those of the first kind are composed of large pale cells with voluminous nuclei. Those of the other kind resemble acinuslike clusters of small osmiophilic cells. Another small ganglion is invariably associated with the distal edge of the bundle of His. At the electron‐microscope level, two types of ganglionic cells are found in the meshes of the peri‐ and intranodal plexus: (1) small neurons (10 μm) with richly developed neuropiles, and (2) large 5‐OH‐dopamine contrasted neurosecretory cells (up to 25 μm) containing electron‐dense vesicles typical of sympathetic neurons. Numerous glomeruli with dendrodendritic and axodendritic connections are also found in the vicinity of the specialized tissue; and, in the nodal interstitium, several clusters of small chromaffin cells (5 μ) and a network of multipolar satellite cells similar to the interstitial cells of Cajal can be distinguished. Our data suggest that the microanatomical and cytological organization of the terminal innervation of the node of Aschoff‐Tawara and of the bundle to His resembles that of the myenteric plexus. The physiological significance of these ultrastructural data for the local control of electrophysiological properties of the atrioventricular junction i

ISSN:0002-9106    

DOI:10.1002/aja.1001710307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractPseudopregnant, pregnant, and ovariectomized rabbits were utilized to study hormonal mediation of uterine epithelial surface negativity and glycocalyx morphology, and to seek local effects of blastocysts at sites of implantation. A loss of surface negativity [polycationic ferritin (PCF) binding] by day 6 of pregnancy or pseudopregnancy was noted, accompanied by alterations in epithelial glycocalyx. Uteri from estrous animals, or ovariectomized animals receiving oil or estradiol injections, bound PCF and exhibited a “globular” glycocalyx. Uteri from day 6 pseudopregnant or pregnant animals, or ovariectomized animals receiving progesterone injections, did not bind PCF or exhibit a globular glycocalyx. Both PCF binding and the globular character of the epithelial glycocalyx were sensitive to neuraminidase and trypsin treatment, suggesting sialoglycoprotein contribution to surface negativity. Implanting blastocysts had no detectable local effect on surface negativity, but did induce local reduction of epithelial glycocalyx at sites of implantation. Results of this study suggest that uterine epithelial glycocalyx alterations during the preimplantation period reflect a general response to prosgesterone stimulation, primarily qualtitative in nature, related to the acquisition of receptivity to ovo‐implant

ISSN:0002-9106    

DOI:10.1002/aja.1001710308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractCorrelated nuclear and cytoplasmic reorganizations during the 14 hr of reactivated meiosisin vivoandin vitrowere examined in the laboratory mouse. Observations of living oocytes by differential interference contrast microscopy, and by fluorescent microscopy with nontoxic mitochondrial and DNA‐specific probes, enabled us to determine that the major cytoplasmic reorganization involved two mitochondrial translocations associated with two stages of nuclear maturation. These observations were confirmed at the fine structural level by parallel transmission electron microscopy. Mitochondria translocate to the perinuclear region during formation of the first metaphase spindle and subsequently disperse during abstriction of the first polar body. Determinations of frequency of maturation in more than 2,900 normal oocytes, and in more than 1,100 oocytes in which germinal vesicle breakdown was reversibly inhibited, indicated that mitochondrial redistributions are a normal and probably necessary feature of reactivated meiosis in the laboratory mouse. We suggest that these two rapid translocations serve to concentrate mitochondria for localized activities that require elevated levels of adenosine triphosphat

ISSN:0002-9106    

DOI:10.1002/aja.1001710309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001710310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001710301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY