Immunocytochemical localization of lingual lipase in serous cells of the developing rat tongue

The ontogeny of the rat lingual serous and mucous glands was explored by light and electron immune microscopy using the peroxidase-antiperoxidase and streptavidin-gold techniques. Tissues from fetal and neonatal rats from day 18 of gestation through 4 wk after birth were fixed and embedded in paraffin or Epon for light and transmission electron microscopy, respectively. Electron microscopy revealed that the only cells containing lingual lipase were the developing serous cells; secretory granules containing lingual lipase of varying degrees of maturity were seen. Mucous cells did not show immunospecific staining in rats of any age. The neonatal "mixed" lingual glands secrete lingual lipase from serous components immediately after birth to aid in fat digestion.

The embryogenesis and anatomy of Waldeyer's ring

The developmental history of the embryonic germ disk is briefly traced through the bilaminar, trilaminar, and bodyfold stages with emphasis on the pharyngeal arches, pouches, and clefts. This is followed by a discussion of the genesis and adult anatomy of the tonsillar tissues.

Ontogeny of substance P-like immunoreactive fibers in the taste buds and their surrounding epithelium of the circumvallate papillae of the rat. II. Electron microscopic analysis

We studied the ontogeny of the fine structure of substance P-like immunoreactive (SPI) fibers in the extragemmal epithelium and taste buds of the circumvallate papillae in the rat tongue by electron microscopy and by the unlabeled antibody-enzyme method. SPI fibers in the lamina propria first appeared at gestational day 19, and those in the extragemmal epithelium and in the taste buds at day 21. These fibers did not form synaptic contact with underlying cells. In addition, the occurrence of nonimmunoreactive fibers in these areas preceded that of SPI fibers. Our findings suggest that SPI fibers are not primarilly involved in the differentiation of the extragemmal epithelium and taste bud cells.

Congenital hemifacial hyperplasia: an embryologic hypothesis and case report

Congenital hyperplasia is a developmental disorder characterized by marked unilateral asymmetry. The structural disproportions from one side to the other far exceed variations commonly seen in the normal population. Classically, as first described in 1836, the overgrowth of tissue is restricted to one-half of the body, including the extremities. In other cases the hyperplastic enlargement involves segmental areas of the body, such as the hemifacial skeleton and an extremity. A case report is presented, and the clinical characteristics of 192 cases of congenital hyperplasia in the literature are briefly reviewed. Use of the word hyperplasia to describe the condition (rather than hypertrophy) is encouraged. The authors propose a new embryologic hypothesis: asymmetrical development of the neural fold and hyperplasia of the neural crest cells are said to form the basis for the disorder. The rewards, risks, and limitations of reconstructive surgery over a 10-year period are discussed.

The innervation of the primate fungiform papilla--development, distribution and changes following selective ablation

The development of the terminal parts of the chorda tympani nerve, lingual nerve and cranial sympathetics in the macaque fungiform papillae were studied by light- and electron microscopy. Their respective distributions in the intra- and extragemmal compartments of papillae from adult macaques were examined following selective ablation of each nerve. Prior to midgestation, a single bundle of unmyelinated axons which contained numerous axoaxonic synapses passed through the subepithelial connective tissue and ramified in the single nascent chemosensory corpuscle and surrounding non-gustatory epithelium. Following midgestation, additional chemosensory corpuscles appeared, possibly by division of existing corpuscles, myelination of axons was begun, axoaxonic synapses were eliminated, and nerve terminals appeared in the subepithelial connective tissue as free nerve endings and coiled simple nerve endings. In the perinatal period, coiled simple endings, corpuscular receptors and Meissner corpuscles were present in the papilla core. Large numbers of intra-epithelial nerve endings were present in the extragemmal epithelium throughout development. Tonofilament collars ensheathed intra-epithelial axons and 80-100 nm dense core granules, occupying adjacent epithelial cells, appeared to be sequestered near such axons. Experimental selective ablation indicated that the terminal parts of chorda tympani fibers were present only within chemosensory corpuscles. In contrast, lingual nerve endings were present both in the extragemmal epithelium and chemosensory corpuscles and also were the sole supply of corpuscular receptors. Sympathetics appeared to be sparsely distributed in the papilla core. Intra-epithelial axons degenerated within 24 h following transection, while axons with Schwann or lamellar cell sheaths or myelin persisted for at least 3 days.

[Embryogenesis of the styloglossus muscle in the human embryo. Its relationship with neighboring structures]

Histogenesis of the muscles of the human tongue has been studied from the 15th week in utero onward: however their intrinsic or extrinsic origin is uncertain. The intrinsic musculature has sometimes be questioned (Saban, 1971). The embryogenesis of the styloglossus muscle has been studied in ten 39 to 58 day old human embryos. Its differentiation beyond the first lingual swellings in contact with a branch of the hypoglossus nerve allows its development to be followed outside the territories of the branchial arches. This study showed its progressive development, from day 42 onward, along bundles of the ceratoglossus and basioglossus muscles. The styloglossus muscle penetrates slowly on day 45 in the transverse fibres located behind the tongue. These latter differentiate earlier, independently and at the same time as the geniohyoid and genioglossus muscles, near the neural extensions of the hypoglossus nerve: they are very rapidly intermixed with the fibres of the genioglossus muscle: the other muscular fibres and those of the styloglossus muscle penetrate only later and progressively. In the current state of knowledge of axial neural organization, it can be concluded that the lingual muscles differentiate from the same type of cells recognized and innervated by the neurons of the hypoglossus nerve. The epigenesis of the different muscles is related to the appearance of their various functions.

Ontogeny of substance P-containing fibers in the taste buds and the surrounding epithelium. I. Light microscopic analysis

Ontogeny of the substance P-like immunoreactive (SPI) structures in the circumvallate papillae of the rat taste buds was examined by means of indirect immunofluorescence method. SPI fibers in the lamina propria first appeared at gestational day 20, and their quantity increased up to postnatal day 10. On the other hand, SPI fibers in the epithelium were first seen on gestational day 21 and in the taste buds at postnatal day 2-4. These fibers increased remarkably in number after postnatal day 5 and reaching their maximum at postnatal day 20, and thereafter numbers decreasing slightly.

A morphometric study of normal and abnormal fetal to childhood tongue size

The weight, length, width and thickness of 83 normal tongues from patients aged 25 weeks of gestation to 10.5 years were compared statistically with several measures of body and head size and changes described by linear regression; the relationships between measures were examined by partial and least-squares correlation. Sex differences in tongue size were not evident. The tongue doubles in length, width and thickness between birth and adolescence and grows considerably beyond this period. That the major dimensions of the tongue correlated more with head size than body size implies that local factors affect lingual growth more than generalized somatic ones. The weights of 45 tongues thought to be abnormal in size were compared with those of controls. The volume of normal and abnormal tongues was identical to weight, indicating that density remains constant in a variety of conditions. The tongue was abnormally small in hypoglossia hypodactylia and in cleft lip and palate. Tongue weights were within 1 SD of control means in DiGeorge syndrome or oligohydramnios. The tongue was significantly enlarged when protuberant or in anencephaly, CHARGE association and Crouzon syndrome. Anasarca produced a variable degree of enlargement. Concomitant aberrations in the size of the tongue and mandible occurred frequently, but small tongues were not always associated with small mandibles and large tongues were not always observed with large mandibles. Thus, the association of lingual and craniofacial anomalies seems to develop from a number of diverse factors, in addition to biomechanical ones.

[Structure of the neuromuscular spindles in the tongue of human fetuses]

The dynamics in development of some components--of the neuromuscular spindles in the human fetus and newborn tongues have been studied by means of certain general and neurohistological methods with elements of morphometry. During the whole prenatal period of the human life, there is a certain synchronism in the development of the lingual proper muscles and the neuro-muscular spindles. Certain integration in the development of the neuro-muscular spindles is observed in 4-6-month-old fetuses; in 8-9-month-old fetuses and in newborns it is substituted for heterochronicity. By the time of birth, the muscle spindle contractile elements are supplied with a more differentiated efferent innervation. The latter actively effects the morphological state of the intrafusal muscle fibers and forms a base for functional activity of the tongue.

A morphometric analysis of craniofacial growth and changes in spatial relations during secondary palatal development in human embryos and fetuses

Staged human embryos and fetuses in the Carnegie Embryological Collection were morphometrically analyzed to show craniofacial dimensions and changes in spatial relations, and to identify patterns that would reflect normal developmental events during palatal formation. Normal embryos aged 7-8 weeks postconception (Streeter-O'Rahilly stages 19-23) and fetuses aged 9-10 weeks postconception, in eight groups with mean crown-rump (CR) lengths of 18-49 mm, were studied with cephalometric methods developed for histologic sections. In the 4-week period studied, facial dimensions increased predominantly in the sagittal plane with extensive changes in length (depth) and height, but limited changes in width. Growth of the mandible was more rapid than the nasomaxillary complex, and the length of Meckel's cartilage exceeded the length of the oronasal cavity at the time of horizontal movement of the shelves during stage 23. Simultaneously with shelf elevation, the upper craniofacial complex lifted, and the tongue and Meckel's cartilage extended forward beneath the primary palate. Analysis of spatial relations in the oronasal cavity showed that the palatomaxillary processes became separated from the tongue--mandibular complex as the head extended, and the tongue became positioned forward with growth of Meckel's cartilage. As the head position extended by 35 degrees, the cranial base angulation was unchanged and the primary palate maintained a 90 degrees position to the posterior cranial base. However, the sagittal position of the maxilla relative to the anterior cranial base increased by 20 degrees between stages 19 and 23. In the late embryonic and early fetal periods, the mean cranial base angulation of approximately 128 degrees and the mean maxillary position angulation of approximately 84 degrees were similar to the angulations previously shown to be present later prenatally and post-natally. The results suggest that human patterns of cranial base angulation and maxillary position to the cranial base develop during the late embryonic period when the chondrocranium and Meckel's cartilage form the primary skeleton.

Alphafoetoprotein uptake by cloned cell lines derived from a nickel-induced rat rhabdomyosarcoma

Rat, mouse, pig and chicken alphafoetoproteins (AFP), rat serum albumin and egg albumin, or their fluoresceinated conjugates were added to cultures of several cloned cell lines isolated from a nickel-induced rat rhabdomyosarcoma. The intracellular uptake of assayed proteins was revealed by the indirect immunoperoxidase technique and/or by direct fluorescence microscopy. All the clones examined bound AFP, and all but one internalized the protein. The protein localized in the membrane and the cytoplasm, as well as along straight processes interconnecting cells. Nuclei were always AFP negative. The protein uptake of fluoresceinated conjugates of AFP and serumalbumin was already visible 15 min after incubation and progressed with time to reach a plateau 4-5 h later. Ultrastructural radioautographs of cells incubated with [3H]-AFP (rat) showed protein accumulation in several organelles and particularly in lipid droplets. Parallel to these observations, the intracellular presence of AFP within myofibrillar structures was demonstrated in tongue sections of rat foetuses and neonates. The results presented here provide experimental evidence of the reappearance in cloned cell lines derived from a primary rhabdomyosarcoma of a property pertaining to foetal striated muscle.

A description of the times of appearance and regression of marginal lingual papillae in human fetuses and newborns

Papillae, located along the anterolateral margin of the human tongue, were observed in fetal and newborn stages. The papillae appeared in the prenatal period and attained maximum development in the newborn. They had almost disappeared by the time of weaning. Although morphologically, the papillae may be considered to be a form of the filiform papillae, they differed from the filiform papillae in that they were temporary, localized at the anterolateral margin of the tongue, and larger in size. These papillae are homologous with those in certain land mammals and toothed whales, and may assist in sucking. Our findings on the times of appearance and regression of marginal papillae support this notion.

Craniofacial development in the absence of muscle contraction

The muscular dysgenesis (mdg) mutation in mice causes developmental arrest of myogenesis at the myotube stage. Stained and cleared skeletal preparations and histological sections of the heads of mdg/mdg and normal mouse fetuses were compared in order to determine the effects of the mutation on craniofacial morphology. Muscles of mastication were more severely affected than tongue muscles. Mutant crania had more domed vaults and slender zygomatic arches that were displaced dorsally. The posterior part of the dysgenic mandible was bent dorsally and compressed dorsoventrally. These shape changes may be the distorting effects of persistent cervical kyphosis. Measurements of camera lucida tracings indicated that the lengths of the total mandible, the angular cartilage and process, and the condylar cartilage and process were similar between mutant and control mice. However, the widths of the condylar and angular cartilages were greatly decreased in the mutants. Moreover, the cartilages of dysgenic mice showed no size increase between 18 and 20 days of gestation. The diminished cartilages presumably result from the absence of mechanical loading from prenatal muscle function. For both condylar and angular cartilages, normal muscle activity should produce compression along the long axis of the cartilage and bending/shearing perpendicular to the long axis. It is argued that these forces are more important in promoting growth in cartilage width than length, accounting for the selective reduction of widths in the dysgenic mutant.

[Morphometric analysis of differentiation of skeletal muscle fibers of the maxillofacial region during the process of embryonic development]

The skeletal muscle tissue of the lip, tongue, soft palate and masticatory muscles have been morphometrically studied in 70 human fetuses (4-10-month-old). In the muscles mentioned decrease in the nuclear volume and in the nuclear-cytoplasmic ratio is observed. Increase of the muscle fibres in the area of transversal sections is especially intensive during last three months. The labial and glossal fibres reach the greatest thickness. On the 6th month and further, there is an essential difference in number of myons with nuclei in the transversal section of the tongue and lips, as compared with the masticatory muscle and soft palate. In 9-10-month-old fetuses the index on saturation of the glossal and labial muscle fasciculi with capillaries is much greater than that of the soft palate and the masticatory muscle. There exists a statistically important and rather high positive correlation between the area of transversal sections of the muscle fibres, the number of nuclei in them and the density of capillaries in the muscle fasciculi. The relation between histochemical profile of the muscles under investigation and the number of capillaries in them is discussed.

Histological and histochemical study on the development of foliate papillae in guinea pigs

The present work was carried out to study the development of foliate papillae in guinea pigs and the associated changes in the activity of true cholinesterase enzyme. Histological and histochemical differentiation were found to start in the early intrauterine life and were completed before birth. The activity for the true cholinesterase enzyme was detected as early as the 22nd day of gestation while histological differentiation started 2-3 days later. The findings obtained and their possible significance were discussed.

The morphology of the vertical and transverse intrinsic musculature of the tongue in the 15-week human fetus

The attachments, courses and interrelationships of the transverse and vertical intrinsic muscle masses of the tongue were examined in 28 fifteen-week fetal specimens. Observations were made from 30-micron sections cut through the tongue in one of the three standard planes of section. Both sets of muscululature are qualitatively well-developed by this time period in fetal life. The transverse fibers were found to occupy the entire length of the tongue. They attach to the lamina propria of the lateral aspect of the body of the tongue and, in the root, to perimysial and adventitial connective tissue. In addition, some fibers were observed to be confluent with the mm. palatoglossus, tonsilloglossus and pharyngis superior. Medially, transverse fibers were found for the most part to terminate in the dense ventral aspect of the median septum. Vertical fibers are present from a point slightly posterior to the tip of the tongue to the level of the foramen cecum, beyond which they become sparse. All vertical fibers attach superiorly to the dorsal lamina propria. In the free part of the body, their ventral attachment, likewise, is to lamina propria. In the middle part of the tongue and, to a greater extent, in the root (as the inferior and lateral free surface decreases) these fibers attach in either the fascial plane underlying the transverse component or to the perimysium of longitudinally-running muscle bundles.

Embryonic development of the head and neck: part 2, the branchial region

The embryology of the branchial (pharyngeal) region is reviewed in terms of the embryonic pharynx, branchial apparatus and derivatives, tongue, larynx, and trachea. Derivatives of the branchial pouches, grooves (clefts), and arches are analyzed in relation to each other and to the first arch syndrome. Other common head and neck defects attributable to abnormal development of the branchial region are also discussed, particularly those defects involving the incomplete degeneration or the abnormal migration of branchial tissues.

Selective inhibition of mandibular growth and induction of cleft palate by diazo-oxo-norleucine (DON) in the rat

A high percentage of cleft palates can be induced in rat fetuses by a single injection of the glutamine analog diazo-oxo-norleucine (DON) on day 15 of gestation. The purpose of this study was to evaluate the effects of DON in vivo on craniofacial growth and spatial relations in order to identify factors that may contribute to the palatal defects. Sprague-Dawley rats in the experimental groups were given a single IP injection of 2.0 mg DON (6 mg/kg maternal body weight) on day 15 and were killed on day 16 or 17. Control fetuses were collected on days 15, 16 and 17. Fetal heads were fixed in Bouin's solution, embedded in Paraplast and serially-sectioned. Midsagittal and coronal sections were projected at 30 X and a series of linear and angular measurements were made. DON had limited effect on growth of the cranial base, nasomaxillary complex, and palatine processes, but dramatically reduced the length of Meckel's cartilage. Treatment with DON delayed shelf elevation approximately 24 hours, and tongue position remained high in the oronasal cavity. Growth retardation in Meckel's cartilage therefore may contribute to delayed shelf movement by retarding downward and forward positioning of the tongue-mandibular complex.

[Remnants of the thyroglossal duct. A histological study]

This study was undertaken in order to find out the frequency of thyroglossal duct remnants and to specify the relationship between this tract the hyoïd bone. The remnants having undergone cystic pathology refer to tracks edged with an epithelial lining which can be various, associated or isolated, types. Thyroïd follicles may be annexed to this track, in or out of its cystic part. The systematic study of 23 hyoïdal and sub hyoïdal regions of adults exempt of any pathologic remnants allows one to find tracks in 13 cases, that is in every other case. This frequency is higher than the one normally described. These remnants always refer to some thyroïd follicle islands and rarely to an epithelial track. Furthermore, we can sometimes observe the frankly intra hyoïdal situation of the thyroid tissue. This last location is discussed according to embryologic data.

Palatal process movement in the rat as demonstrated in frozen sections

During mammalian secondary palate development, movement of the lateral palatine processes from the vertical plane to the horizontal plane involves a complex interaction of the palatine processes and the tongue within a dynamic growing oronasal cavity environment. This study of pre-fixation facial profile photographs and frozen sections was undertaken to evaluate external and internal changes in the oronasal complex during secondary palate elevation without the shrinkage known to be present with routinhistological preparation of embryonic tissues. Frozen sections of Sprague-Dawley rat embryos between 15 and 17 days of (conceptual) age were prepared by hexane quenching and cryostat cutting. The results showed that, during the stages of palate development prior to shelf elevation, the tongue and mandible became positioned beneath the primary palate, and the vertical dimension of the oronasal cavity increased by the lifting of the nasomaxillary complex. The tongue and mandible maintained contact with the primary palate, whereas a space developed above the tongue in the middle and posterior palate regions. As the vertical dimension increased the volume of the palatomaxillary processes increased rapidly, the tongue became squeezed, and the palatine processes bulged medially above the level of the tongue. After shelf elevation extensive contact between the palatine processes was present, and the tongue became flattened. The results of this study support the observations of Lazzaro (1940) that rapid increase in shelf volume owing to increased intercellular volume contributes to movement of the processes above the tongue. But, rapid increase in shelf volume occurred contemporaneously with the time when the tongue and mandible outgrew the oronasal cavity and became positioned beneath the primary palate. Therefore, it would appear that the simultaneous occurrence of a lower and more forward tongue position, and an increased palatomaxillary process volume without change in maxillary width, contributed to the medial movement of the processes above the tongue.

The anatomy of m. genioglossus in the 15-week human fetus

The attachments, course, and interrelationships of M. genioglossus were examined in 28 fifteen-week human fetal specimens. Observations were made from histologic sections of the tongue cut in one of the three standard planes of section. The anterior-most genioglossal fibers insert near the tip of the tongue at the level of the anterior extent of the median septum. Within the central mass of the tongue, some fibers of this muscle characteristically decussate across midline, a limited number below the level of the septum and a considerably larger number above it. Posteriorly, a few of the most posterior and inferior fibers of M. genioglossus could be traced to an attachment on the thickened perichondrium on the superior edge of the hyoid anlage. In other respects, the disposition of genioglossal fibers at this stage of development resembles closely that description generally given for the adult structure.

Papillary projections at the lingual margin in the striped dolphin, Stenella coeruleoalba, with special reference to their development and regression

Papillary projections along the anterolateral margin of the tongue were observed in fetal and young stages of the striped dolphin, Stenella coeruleoalba. Papillary projections appear in the prenatal period and attain maximum development in the early postnatal period. They almost disappear by weaning. Vestigial eminences remain at the corresponding region, but they completely disappear in the adult. The papillary projections observed differ markedly from the lingual papillae of the general mammalian tongue as they are temporary, localized at the anterolateral margin and large in size. The projections were also present in young individuals of some other dolphins. No taste buds could be seen on the projections in any of the stages of all specimens observed. Such projections may have important mechanical functions during suckling in these mammals.

Mechanism for the origin and the evolutionary significance of heterochronia

Using material on the evolution of the fundus of the oral cavity in amphibians, four principles were established for the origin of heterochronia: efficiency of ontogenesis; adaptability of an earlier (than in ancestors) beginning for functioning of traits; loss of the adaptive significance of a trait at a previous stage, but a preservation of it at a subsequent stage; and, a prolongation of the adaptive significance of a trait at later stages. The origin of heterochronia is associated with changes in the succession of the functioning of genes, with reorganization of systems of morphogenetic correlations, and with change in the traits themselves that undergo heterochronia. The uniqueness of heterochronia as an adaptation consists of an increase in the evolutionary flexibility of specific stages of ontogenesis.

Palate development after fetal tongue removal in cortisone-treated mice

Morphological studies of cortisone-induced cleft palate have shown retardation in the rotation of palatine shelves from a sagittal to a transverse plane. Cortisone also reduces fetal muscular movements, which may explain why displacement of the tongue from between the palatine shelves is delayed. Previous work with extrauterine development of control fetuses demonstrated that fetal membranes and tongue were major obstacles to shelf rotation. Thus, removal of these obstacles might permit rotation and fusion of palatine shelves in cortisone-treated fetuses. In the present experiment, fetuses from cortisone-treated strain CD-1 mice were released from uterus and membranes and allowed to develop for eight hours in a fluid medium with the umbilical cord left intact. Compared to 4% fusion in utero, there was palatal fusion in 20% of fetuses released from membranes. When the fetal tongue was removed during extrauterine development, the frequency of fusions increased to 61%. Fusion appeared normal by the criteria applicable through light microscopy. Thus, cortisone induces cleft palate primarily through interference with shelf rotation. The palatine shelves of treated fetuses retain their ability to fuse when they can come in contact during the normal time for palate closure.

Effects of craniofacial structures on mouse palatal closure in vitro

Heads of Swiss-Webster mouse fetuses of four ages spanning days 12-13 of gestation, were partially dissected by removing the brain (B), tongue (T) and mandible (M) alone or in combination (BT, BM, BTM). Preparations were suspended in a gassed, circulating culture system such that palatal closure must take place against gravity. Closure occurred earlier than in vivo and required the posterior half of the mandible be intact and the tongue removed.

Glossal double fissures in pre- and post-natal human specimens

Glossal double fissures were found in a similar proportion of both pre- and post-natal tongue specimens. The condition was found in both sexes and in subjects of Negro, Caucasian and mixed ethnic origins. In cross-section, the area bounded by the fissures varied from raised to flat or depressed. Histologic analysis suggested that the double fissure appearance was a reflection of the topography of the subjacent muscle bundles and that true fissuring, when present, was probably a secondary phenomenon akin to acquired plication.

Sebaceous choristoma of the thyroglossal duct

The presence of sebaceous glands within the oral mucosa is not uncommon. Such Fordyce granules are frequently seen on the buccal mucosa and lips, as well as in the retromolar area, gingiva, and palate. Whereas sebaceous elements are rarely encountered on the tongue, three cases of ectopic sebaceous glands have been reported in association with apparently patent thyroglossal ducts. An interesting case of a previously unreported sebaceous choristoma of the thyroglossal duct is described.

The role of the mandible in mouse palatal development revisited

Growth changes associated with formation of the secondary palate were studied in H-Velaz mouse embryos by morphometric measurement of medial sagittal sections of the heads between days 13 and 15 of embryonic development. Horizontalization of the palatine processes depends primarily on the length of the mandible and is effected by a shift of palatine process material into the supralingual space. The administration of 7.5 mg cortisone acetate im to the female on day 12, of 0.5 mg 6-aminonicotinamide im on day 14, or amniocentesis on day 14 significantly retards growth of the embryo in general and of the mandible in particular without significantly affecting deflexion of the skull base. The different spatial conditions created by disproportion between deflexion of the base and the length of the mandible cause irregularities in the course of horizontalization which lead, as a rule, to cleft palate.

Developmental changes in the protein profile of cornifying lingual epithelium

Epithelia from the tongue dorsum of 14- to 21-day embryos, 21-day embryos, 3-week-old, and adult rats were separated from their connective tissues by incubation in balanced salt solution containing EDTA. Aliquots from total extracts of these tissues were electrophoresed on sodium dodecyl sulfate-polyacrylamide gels. Scans of gels stained with fast green (FG) revealed more than 20 peaks. Ten major peaks ranging from apparent molecular weights (MW) of 120,000 to 14,000 daltons comprised about 70% of the total protein on each gel. This report focuses primarily on two pairs of peaks, arbitrarily numbered 2 and 3 (MWs 71,000 and 69,000) and 9 and 10 (MWs 17,500 and 14,000). Peaks 9 and 10 predominated in the 15-day embryos where they comprised about 30% of the total protein. As development proceeded, there was a gradual shift in the protein profile in favor of peaks 2 and 3 until on the 20th day the relative amounts of these peaks reached a maximum and peaks 9 and 10 decreased in relative amounts. The protein profile on the 20th fetal day resembled that of the 3-week-old rats and the adults. The rise in the relative amounts of peaks 2 and 3 coincided with the morphologic appearance of large numbers of tonofilaments and the onset of cornification. When the gel was stained by a procedure specific for sulfhydryl groups, peaks 9 and 10 were especially reactive after the 18th day; plainmetric analysis revealed that these had twice the relative affinity for this stain than for FG whereas other peaks had equal or less affinity. The incorporation of [3H]cystine into peaks 9 and 10 was relatively greater than into the other proteins.

The applied anatomy of thyroglossal tract remnants

Recurrences after surgery for thyroglossal cysts and fistulas were common until, in 1920, Sistrunk described his technique for removing the whole thyroglossal tract. Since that time there has been considerable argument concerning the exact path taken by the tract particularly in relation to the hyoid bone. In an attempt to elucidate this problem, studies have been made of embryos at varying stages of development, of serially step-sectioned adult larynges and of surgical specimens. These studies suggest that the thyroglossal tract occupies a constant and embryologically predictable position in relation to the hyoid bone and they support the rationale of Sistrunk's procedure.