Biomedical subjects

A Tamarin

Publications and source records attributed to A Tamarin.

At least 19 recordsLinked to original sources

PubMed1987

Spontaneous complete clefting of the palates in a mouse fetus: a study by scanning electron microscopy and serial section reconstruction.

A 15 day mouse fetus having spontaneous complete clefting of the primary and secondary palates was studied in comparison with its normal litter mates and with normal 14 day fetuses. Specimens were studied by scanning electron microscopy at various stages of microdissection, by light microscopy of thin serial sections and by serial section reconstruction of the anterior chondrocranium of the clefted specimen and one of its normal litter mates. Differentiation of tooth and bone tissue was slightly retarded in the clefted fetus but paranasal and oral landmarks, though distorted, were present. The clefted fetus had a smaller angle between cranial base and nasal capsule and a marked discontinuity between the primary and secondary palates. Cell surfaces on the medial edge of the secondary palate in the clefted fetus resembled cell surfaces of oral areas that do not normally fuse, i.e. they are polygonial, flat and bear few surface projections in contrast to the normal 14 day condition where these cells are spindle shaped, convex and have many microvilli. The observations support the concepts that clefting of the secondary palate is consequential to clefting of the primary palate, that maldevelopment of neural crest mesenchyme is not necessarily a contributing factor, that clefting of the primary and secondary palates is associated with a shorter anterior-posterior dimension of the head and that when fusion of palatal shelves fails to occur the cells of the medial edges modulate in the direction of a generalized type of surface epithelium.

Animals↗

PubMed1985

Electron microprobe analysis of human labial gland secretory granules in cystic fibrosis.

X-ray microanalysis of freeze-dried labial gland cryosections revealed that Na concentration was doubled and the Ca/S concentration ratio was decreased in secretory granules of labial glands from patients with cystic fibrosis (CF) when compared with glands from normal subjects. Other results suggested that the decrease in the Ca/S concentration ratio resulted from an increase in S concentration. These findings imply that mucous granules in labial saliva showed a CF-related increase in Na and S content, and such changes would be expected to affect the rheology of the mucus after exocytosis. In contrast with a previous study in human parotid glands, no evidence was found for CF-related changes in cytoplasmic or nuclear Na, K, and Ca concentrations. Significant elemental differences were found between secretory granules and nuclei and cytoplasm of control cells.

Adolescent↗

PubMed1984

Analysis of upper beak defects in chicken embryos following with retinoic acid.

Implanting inert carriers soaked in retinoic acid into the anterior margin of the developing limb of chicken embryos leads to orofacial malformations as well as affecting pattern formation in the limb. Using anion-exchange beads as carriers, and soaking solutions of 1-10 mg/ml retinoic acid, almost 100% of the embryos have malformations of the face. The effects on the treated limbs range from symmetrical patterns of duplicated digits (maximum number of digits being four) to truncations in which no digits were formed at all. Typically, in the malformed faces the upper beak is completely absent, no nostrils are present and the front of the face forms a scalloped rim of tissue above the mouth. By reference to normal beak development, the seven bulges of tissue that make up the rim can be identified as derivatives of the masses of tissue that normally would fuse to form the upper beak. The roof of the mouth consists of three bulges of tissue flanked by widely separated palatal shelves. The defect can thus be classified as severe bilateral clefting of the primary palate. By examining the morphology of the faces of treated embryos, the origin of the defect can be traced to failure of the frontonasal mass to enlarge. Thus, the oronasal fissures are very wide and fusion across them to form the primary palate cannot occur. The way in which retinoic acid brings about the defect is discussed in relation to possible mechanisms involved in the production of cleft palate. The parallel is noted between the associated effects of retinoic acid on beak and limb morphogenesis and the chick mutation cpp, that also affects both face and limbs.

Abnormalities, Drug-Induced↗

PubMed1983

Stage 9 macaque embryos studied by scanning electron microscopy.

Two macaque embryos representing the beginning and the end of stage 9 were studied by scanning electron microscopy. Morphometric evaluation shows that differential growth of head plate elevation, height of the caudal region, width of the head plate and width caudal to the neural groove exceeds embryo elongation, while width of the mid-region, embryonic disc area, width of the embryonic disc, embryo height at the mid-region, length of embryonic disc, and length of the primitive streak undergo relative shrinkage. The head plate becomes topographically subdivided into the three primary segments, while the neural groove narrows, the number of somite pairs increases from one to three, and Hensen's node is obscured. Comparison with relevant rodent studies demonstrates some topographical differences and some cytological similarities.

Animals↗

PubMed1982

The formation of the primitive choanae and the junction of the primary and secondary palates in the mouse.

This study has followed the development of the primary choanae in the mouse and has shown that they originate at the developmentally strategic position of junction between the primordia of the primary and secondary palates and that this basic anatomic relationship is maintained throughout further development. Involution of the oronasal membrane begins late in the 11th day (stage 19) with the formation of interstitial gaps. The gaps enlarge and coalesce so that a completely patent opening between nasal passage and stomodeum is established by 13 days (stage 21). The membrane consists of two layers of simple squamous epithelium which become separated as involution progresses. The form of the choanal antrum changes from a simple funnel-shaped ellipse early in the 13th day to a complex slitlike opening within the following 24 hours. This coincides with the completion of a definitive primary palate and the enlargement and elevation of the shelves of the secondary palate. The maturation of the incisive papilla and interchoanal columella is related to the final stages of choanal morphogenesis. Thus, by stage 22 (14 days) the shape of the primary choanae and their anatomic relationship to the primary and secondary palates are established, and they remain essentially unchanged in later stages.

Animals↗

PubMed1979

The topography of rat submandibular gland parenchyma as observed with S.E.M.

The parenchymal components of rat submandibular gland were examined by scanning electron microscopy after removal of the stromal connective tissue by acid hydrolysis and/or enzymatic digestion. Secretory acini have polymorphous topographies but usually consist of three to five truncated lobes emanating from a common hilus. They have a mean volume of about 33,000 micrometers3. Myoepithelial cells are associated with the deeper acini of the gland where they cover congruent to 54% of the surface area of their allied acini. Each flattened myoepithelial cell has a central perikaryon that gives rise to four or five broad primary processes that bifurcate two or three times to produce a total complement of 20 to 40 terminal processes per cell, each 0.5 micrometer to 1.7 micrometers wide. The terminal processes of adjacent myoepithelial cells tend to slightly overlap and to attach to each other by desmosomes forming a network over adjacent acini. The components of the duct system are examined and each characterized by salient features as observed with the SEM.

Animals↗

PubMed1979

The leukocytic response in ligated rat submandibular glands.

Within 1 h after ligation of the main excretory duct of the rat submandibular salivary gland neutrophils begin to migrate into the parenchymal epithelium and by 18 h they accumulate, unchanged, within the lumina of acini and intralobular ducts. By 24 h, monocytes become the predominant intraepithelial migrating cell type. These selectively migrate into lumina of convoluted ducts where they phagocytize intraluminal material consisting of secretion products, egested cell debris and neutrophils. By 4 days monocytes laden with phagosomes begin to migrate into the stroma and by 17 days relatively few leukocytes remain within the parenchyma. Changes in ligated gland weight reflect the cytological changes. It is concluded that in experimental obstructive adenitis monocytes play a most important role while neutrophils are adventitious.

Animals↗

PubMed1977

Facial and visceral arch development in the mouse embryo: a study by scanning electron microscopy.

The morphogenesis of the face and visceral arch region were studied by scanning electron microscopy in 63 mouse embryos between 8 and 13 days post coitum. The developmental stages were determined by reference to Theiler's (1971) scheme for the categorization of the normal stages of development. After the cervical fold is formed (stage 12) the mandibular primordium appears (stage 13) followed by the primordia of arches II and III (stage 14 with arch IV forming last (stage 15). Arches II, III and IV regress in reverse order, with no evidence that a cervical sinus pouch is formed. Placodes of the sensory ganglia from cranial nerves 7, 9 and 10 are formed in the first, second and third visceral grooves respectively. Formation of the external auditory meatus and its surrounding tubercles were also observed. Morphogenesis of the upper face is dominated by the midsagittal grove, which extends into the stomatodeum; and by the medial nasal, lateral nasal and maxillary processes. The temporal changes in shape and the interrelationships of the structures mentioned are described in detail.

Animals↗

PubMed1977

The blastomere pattern in echinoderms: cleavages one to four.

The results of a longitudinal study of the blastomere pattern in six embryos during the first four cleavages are reported. At each cleavage stage optical sections through an embryo, taken at vertical intervals of 5 or 10 micron, were recorded on 35 mm film: digitization of the blastomere contours and computer analysis allow calculation of the center, radius, surface area and volume of each blastomere. The subjective impression of exquisite regularity seen in normal echinoderm blastulae acquires a quantitative dimension from the present study. For example, the individual angles formed by the various quartets of blastomeres depart from right angles by at most a few degrees. The egg volume was found to be conserved up to the fourth cleavage. At the 16-cell stage, unlike the earlier stages, the blastomere positions cannot be ascribed solely to the position and orientation of the respective cleavage planes. Finally, a few features of a formal model of these early cleavages are sketched.

Animals↗

PubMed1976

A longitudinal study of parotid secretory kinematics by cinemicrography and computer analysis.

The kinematic responses of parotid gland acini to isoproterenol were studied in vitro by time-lapse cinemicrography. It was shown that once secretion begins, granule depletion accelerates to a maximum rate in 8-10 min, continues at a steady rate for 5-8 min and then slows, depletion becoming essentially complete 25-30 min after stimulation. The continuum of morphologic change manifested by the acinar lumen during secretion was quantified by computer analysis of sequential cine-frames representing a time resolution of 0.1 min. Interpretation of seventh-order and eleventh-order polynominal non-linear least squares trend curves shows that the lumen enlarges from an initial cross-sectional area of approximately 96 mum2 at 14.9 min. The shape of these curves suggests that after an initial partial enlargement the lumen shrinks (or remains steady) before climbing to the maximum. The basic pattern resembles distortion curves characteristic of two-phase viscoelastic compliance systems. It is also shown that luminal plasma membranes undergo a very active ebb and flow during the egestive phase of secretion.

Animals↗

PubMed1976

The structure and formation of the byssus attachment plaque in Mytilus.

The byssus attachment plaque and the tissues responsible for its formation were studied in M. californianus by light microscopy and by transmission and scanning electron microscopy. It was shown that the plaque consists of at least three phases which ultrastructurally resemble three secretions considered to be collagen, mucoid material and polyphenol. The mucoid and polyphenol appear to mix as a colloidal suspension in which the latter is the continuous phase and forms the definitive bonding surface. Plaque collagen represents an extension of thread material into the cementing substance. Stimulated secretion within the ducts and distal depression of the mussel's foot shows a continuum of increasing heterogeneity from the inner toward the outer regions. This reflects the distribution of exocrine cell apices wherein exocytosis of polyphenol granules predominate deeply, mucous granules superficially and collagen granules in between. It is proposed that the morphology of the plaque conforms to theoretical physical-chemical requirements for adhesion under water.

Adhesiveness↗

PubMed1976

Three-dimensional anatomy of the 8-day mouse concepts: a study by scanning electron microscopy.

The three-dimensional anatomy of the 8-day mouse concepts was studied by scanning electron microscopy aided by microdissection within the microscope specimen chamber. Attention was given to the relationship of the extra-embryonic membranes and their subtended compartments and particular emphasis was placed on the 'inverted' condition of the embryo at this stage of development. The main points brought forth in this study are: (1) the five basic brain segments are discernible on the basis of surface contour; (2) the cervical fold, extending from the ventrum of the metencephalon to the somatopleure, forms a partition which separates the branchial region from the rest of the amniotic space; (3) the procephalic membrane bifurcates in a vertical plane to form the splanchnopeure and somatopleure lateral to the forebrain, and it bifurcates horizontally to form the dorsal and ventral coverings of the pericardial coelom; (4) the anttrum of the pericardial-peritoneal canal opens into the lateral coelom posterior to the cervical fold; (5) the midgut of the embryo is delineated laterally by longitudinal grooves connecting the foregut and hindgut antra; (6) embryonic ectoderm in the neural-fold region is formed by a single layer of pseudostratified columnar cells; (7) the allantois is hollow near its base and the inner surface is formed by a discontinuous layer of squamous cells; (8) blood islands in the extra-embryonic mesoderm form a ring of bulges around the middle of the exocoel. Other structures such as the ectoplacental cavity, the ectoplacental cone and the parietal capsule are also described.

Animals↗

PubMed1975