Immunocytochemical developmental patterns of the thoracolumbar sympathetic chain in the chick and a comparison with its adrenal counterpart.

The immunocytochemical development of the thoracolumbar sympathetic ganglion and its adrenal counterpart was studied in the chick from days 3.5 to 12 of incubation, using antibodies to 17 separate antigens, including antibodies to pan-neuroendocrine markers, catecholamine-synthesizing and proprotein-processing enzymes, and neuropeptides. Some of the antigens studied (Go protein-alpha subunit, thyrosine hydroxylase, and galanin) were strongly expressed from the first days of development, whereas others (chromogranin-A, chromogranin-B, 7B2 protein, and somatostatin) showed a diverse immunoreactive expression at different stages. Three different patterns were found in the development of both adrenal medulla and thoracolumbar sympathetic ganglion. In the first (chromogranin-A and B, Go protein-alpha subunit, tyrosine hydroxylase, HNK-1, and galanin), virtually all medullary and thoracolumbar sympathetic ganglion cells were strongly immunostained from day 4 onward. Except for HNK-1, chromogranin-A and B, there was a steady increase in immunoreactive cells for all the remaining antigens up to day 12. In the second (7B2 protein, proprotein convertase 2, and secretogranin II), full antigenic expression was reached in medullary and thoracolumbar sympathetic ganglion cells by day 10. In the third pattern (proprotein convertase 3, somatostatin, dopamine-beta-hydroxylase, neuron-specific enolase, vasoactive intestinal polypeptide, and met-enkephalin), differences in immunoreactivity were observed between the medullary and thoracolumbar sympathetic ganglion cells.

Development of the human elbow joint.

Many studies have been published on the development of the human elbow joint, but authors disagree on its morphogenetic timetable. Most discrepancies center on the cavitation of the elbow joint (including the humeroradial, humeroulnar, and superior radioulnar joints), and the organization of the tunnel of the ulnar nerve. We summarize our observations on the development of the elbow joint in 49 serially sectioned human embryonic (n = 28) and fetal (n = 21) upper limbs. During week 12, ossification begins in the epiphyses of the elements comprising the elbow joint. At the end of the embryonic period, the shallow groove between the posterior aspect of the medial epicondyle and the olecranon process, begins to be visible. The elbow joint cavity appears in O'Rahilly stage 21 (51 days) at the level of the humeroulnar and humeroradial interzones. Formation of the cavity begins at the medialmost portion of the humeroradial interzone and the lateralmost portion of the humeroulnar interzone. The annular ligament begins to develop in O'Rahilly stage 21 (51 days), and the superior radioulnar joint cavity appears between this ligament and the lateral aspect of the head of the radius during O'Rahilly stage 23 (56 days). We established the morphogenetic timetable of the human elbow joint.

Ectodermal ablation of the third branchial arch in chick embryos and the morphogenesis of the parathyroid III gland.

The parathyroid glands have been classically considered to be derivatives of the third and fourth pharyngeal pouches in most species, including humans. Furthermore, the presence of neural crest-derived cells in the parathyroid glands connective tissue has been apparently established. However, our previous studies have provided a new hypothesis on the origin of these glands in human and chick embryos. To determine the origin of the parathyroid III (P3) gland, ectoderm of the third branchial arch was cauterized in chick embryos at Hamburger and Hamilton's stage 19 (embryonic day 3). Cauterization of the ventral half of the ectoderm was followed by the non-formation, on the same side, of the P3 gland. When the dorsal half of the ectoderm was cauterized, both the right and left P3 glands formed. Our observations suggest that the ectoderm of the ventral half of the third branchial arch is necessary for the organization of the P3 gland.

Development of the human temporomandibular joint.

A great deal of research has been published on the development of the human temporomandibularjoint (TMJ). However, there is some discordance about its morphological timing. The most controversial aspects concern the moment of the initial organization of the condyle and the squamous part of the temporal bone, the articular disc and capsule and also the cavitation and onset of condylar chondrogenesis. Serial sections of 70 human specimens between weeks 7 and 17 of development were studied by optical microscopy (25 embryos and 45 fetuses). All specimens were obtained from collections of the Institute of Embryology of the Complutense University of Madrid and the Department of Morphological Sciences of the University of Granada. Three phases in the development of the TMJ were identified. The first is the blastematic stage (weeks 7-8 of development), which corresponds with the onset of the organization of the condyle and the articular disc and capsule. During week 8 intramembranous ossification of the temporal squamous bone begins. The second stage is the cavitation stage (weeks 9-11 of development), corresponding to the initial formation of the inferior joint cavity (week 9) and the start condylar chondrogenesis. Week 11 marks the initiation of organization of the superior joint cavity. And the third stage is the maturation stage (after week 12 of development). This work establishes three phases in TMJ development: 1) the blastematic stage (weeks 7-8 of development); 2) the cavitation stage (weeks 9-11 of development); and 3) the maturation stage (after week 12 of development). This study identifies the critical period of TMJ morphogenesis as occurring between weeks 7 and 11 of development.

Development of Meckel's cartilage in the symphyseal region in man.

BACKGROUND: The aim of this work is to clarify the aspects which are at present most controversial about the development of the anterior segments of Meckel's cartilage, such as the role of and determination of the area that is incorporated in the development of the human mandible. METHODS: Light microscope studies were done on 25 embryos and human fetuses from the collection of the Institute of Embryology at the University Complutense of Madrid and the Department of Morphological Science from the University of Granada. Specimen length was between 18 and 125 mm crown-rump. RESULTS: During the embryonic period, Meckel's cartilages were placed in the midline of the mandibular arch but fusion was not observed between them. Ossification of Meckel's cartilage begins at the end of the embryonic period and is completed in the fetal period and the portion that participates in mandibular formation is determined. This segment extends from the mental foramen to near the midline of the mandible. In this region, on the dorsal surface of the symphysis, cartilaginous nodules that originate from Meckel's cartilage are isolated. CONCLUSIONS: The ventral portions of Meckel's cartilage do not fuse in the midline of the mandibular arch. These present endo- and perichondral ossification and the section from the mental foramen to near the midline (mandibular symphysis) participates in mandibular formation. The ventral ends of Meckel's cartilage, i.e., the ends nearest the midline, do not ossify and remain isolated on the dorsal surface of the fetal mandibular symphysis.

Development of the human knee joint ligaments.

BACKGROUND: Many studies have been published on the development of the human knee joint, but scant attention has been given to the development of the knee joint ligaments. The only elements that have received much attention are the cruciate ligaments and their relationships with the synovial membrane. METHODS: We summarize our observations on the development of the knee joint ligaments in 50 serially sectioned human embryonic and fetal lower limbs (26 embryos and 24 fetuses). RESULTS: The patellar ligament begins to form in O'Rahilly stage 20, with the muscle fibers of the quadriceps muscle being attached inferiorly to the tibial tuberosity. The cruciate ligaments (beginning with the posterior) arise from the articular interzone in O'Rahilly stage 21. Subsequently, with the organization of the Wrisberg's meniscofemoral ligament, in week 10 of development, the cruciate ligament system is completed. The lateral collateral ligament begins to form in O'Rahilly stage 23, and from its first appearance it is independent of the knee joint capsule. At this time, development of the tendon of the popliteus muscle begins. The medial collateral ligament begins to develop in week 9 of development as a condensation of the joint capsule. Two weeks later, the intra-articular pad of fat begins to form from mesenchymal tissue below the patella and between the cruciate and the patellar ligaments. With the organization of the suprapatellar bursa in week 14 of development, knee joint development is complete. CONCLUSIONS: The morphogenetic time table of the knee joint ligaments was established.

Development of the human knee joint.

BACKGROUND: Many studies have been published on the development of the human knee joint, but different investigators disagree on its morphogenetic time table. Most discrepancies center on the cavitation of the knee joint and the participation of the superior tibiofibular joint in the joint knee system. METHODS: We summarize our observations of the development of the knee joint in 50 serially sectioned human embryonic and fetal lower limbs (26 embryos and 24 fetuses). RESULTS: The epiphysis of the femur and tibia become condryfied from O'Rahilly stage 18, and ossification begins during the 13th week of development. The patella appears as a dense blastema during O'Rahilly stage 19, becomes condryfied during O'Rahilly stage 22, and begins its ossification during the 14th week of development. The knee joint cavity appears during O'Rahilly stage 22, initially as the femoropatellar joint. This process begins at the periphery of the articular interzone. The superior tibiofibular joint communicates with the lateral meniscotibial joint between 10 and 11 weeks of development and becomes separated from the 13 week on. The menisci arise from the eccentric portions of the articular interzone during O'Rahilly stage 22; however, until week 9 of development, they are not easily distinguishable. CONCLUSIONS: We establish the morphogenetic time table of the human knee joint.

Development of the sympathoadrenal system in the chick embryo: an immunocytochemical study with antibodies to pan-neuroendocrine markers, catecholamine-synthesizing enzymes, proprotein-processing enzymes, and neuropeptides.

BACKGROUND: The adrenal chromaffin cells synthesize, store and secrete a complex mixture containing amines, structural proteins, enzymes, and neurohormonal polypeptides. Most of the studies dealing with the development of the avian sympathoadrenal system have been based on antibodies recognizing signal molecules like HNK-1, NC-1, and N-CAM. METHODS: The development of the chick sympathoadrenal system was studied from 3 1/2 to 21 days of incubation, both morphologically and immunocytochemically, using antibodies to 17 separate antigens, including antibodies to pan-neuroendocrine markers, catecholamine synthesizing enzymes, proprotein-processing enzymes, and neuropeptides. RESULTS: Some of the antigens studied were heavily expressed from the first days of development, e.g., chromogranin-A, chromogranin-B, Go protein-alpha subunit, tyrosine hydroxylase, and galanin, while for others a strong heterogeneity both in number of immunoreactive cells and intensity of immunostaining was recorded at the different stages, e.g., dopamine-beta-hydroxylase,, 7B2 protein, proprotein convertase 2, somatostatin, met-enkephalin, secretogranin II, proprotein convertase 3, neuropeptide Y, phenyl-N-methyl transferase, and neuron-specific enolase. The first immunoreactivities to appear at day 3 1/2 were those for HNK-1, tyrosine hydroxylase, chromogranin-A, and chromogranin-B. Except for HNK-1, immunoreactivity for all the remaining antigens showed a steady increase up to the hatching. CONCLUSIONS: Three expression patterns were found, in the developmental adrenal-gland: defining early permanent markers (chromogranin-A, chromogranin-B, Go protein-alpha subunit, tyrosine hydroxylase, and galanin), others that show a progressively increased expression until the day 10 of development (dopamine-beta-hydroxylase, 7B2 protein, proprotein convertase 2, somatostatin, met-enkephalin), and late-appearing antigens (secretogranin II, proprotein convertase 3, neuropeptide Y, phenyl-N-methyl transferase, and neuron-specific enolase).

Development of the human wrist joint ligaments.

BACKGROUND: Many studies have been published on the development of the human wrist joint, but scant attention has been given to the development of the wrist joint ligaments. Moreover, traditional description of wrist anatomy usually depict only the superficial capsular fibers of the wrist joint. The only ligamentous structure to receive much attention is the articular disc of the wrist joint, which has been described as a fibrocartilaginous structure extending from the medial edge of the lower end of the radius to the ulnar styloid process. METHODS: In the present report, we synthesize our observations in the wrist joint ligaments in 35 serially sectioned human embryonic and fetal hands (16 embryos and 19 fetuses). RESULTS: The interosseous intercarpal ligaments are organized from the mesenchyme, which, until O'Rahilly's stage 23, fills the intercarpal spaces. These ligaments are not individually distinguishable until the 9th week of development. The collateral ligaments begin to form in O'Rahillys's stage 22 and are completely formed by the end of week 10. The palmar radiocarpal and ulnocarpal ligaments (beginning with the palmar radiocarpal ligament) begin to form in O'Rahilly's stage 23 and are fully developed by the end of week 10. At this time, development of the dorsal radiocarpal ligament begins; this process is completed by the end of week 13. The articular disc which is initially formed of a single element, first appears in O'Rahilly's stage 23 and its organization is completed at week 10 of development. CONCLUSIONS: We establish the morphogenetic time-table of the wrist joint ligaments. Our descriptive findings may help explain carpal motion and the origin of wrist injuries.

Grafts of the third branchial arch in chick embryos.

The parathyroid glands have been classically considered derivatives of the third and fourth pharyngeal pouches in most species, including humans. The presence of neural crest-derived cells in parathyroid glands connective tissue has apparently been established. However, our previous studies have provided a new hypothesis on the origin of these glands in human and chick embryos. To determine the true origin of the third parathyroid (parathyroid III) gland in the chick embryo, pieces of the third branchial arch from donor chick embryos at Hamburger and Hamilton's stage 19 (embryonic day 3) were grafted to host chick embryos at the same stage of development. Starting from Hamburger and Hamilton's stage 27 (embryonic day 5), a structure identified as the parathyroid III appeared in the ectodermal (epipharyngeal) placode of the third branchial arch graft, from which it subsequently became separated at Hamburger and Hamilton's stage 28 (embryonic day 5.5) and continued to develop and mature. Our findings suggest the conclusion that the parathyroid III gland begins to develop from the epipharyngeal placode, so that this gland, from our point of view, could be considered ectodermal in nature.

Development of the human submandibular salivary gland.

The development and morphogenetic timetable of the submandibular gland was studied in 37 human embryos and human fetuses. The medial paralingual groove constituted the anlage of the submandibular gland: Its anterior three-quarters gave rise to Wharton's duct, and its posterior quarter to the submandibular gland proper. The sublingual process of the submandibular gland originated from a lateral ectodermal bud of the anlage of the submandibular gland, in the posterior quarter of the medial paralingual groove.

Developmental differences in the ossification process of the human corpus and ramus mandibulae.

A correlation was sought between the organization of the dental crest and the ossification of the corpus mandibulae in 14 human embryos and 13 human fetuses. The different types of ossification between the corpus and the ramus mandibulae suggest that the cartilago mandibularis (meckeliensis) guides the formation of the mandibula, while the dental crest acts as a coorganizer. In the area of the foramen mentale, the lamina dentalis begins to invaginate (to give rise to the dental crest), and at this level intramembranous ossification of the corpus mandibulae commences. These findings, together with the presence of the cartilago mandibularis before the appearance of the dental crest, and the fact that the former is seen along the entire length of the mandibula (from the symphysis mandibulae to the capsula otica), support the hypothesis that the dental crest, rather than the cartilago mandibularis, acts as the coorganizer in the corpus mandibulae.

Relationships between the parotid gland and the facial nerve during human development.

A correlation was sought between the organization of the parotid gland and the formation of the large vessels and nerves that passed through the glands of 12 human embryos and 12 human fetuses. There was no evidence that the gland became a bilobate structure as a result of the course of the facial nerve, whose interglandular branches were surrounded during development by the multidirectional ramifications of the expanding parotid anlage.

Histogenesis of the spleen in the human embryo in O'Rahilly's stages 17 to 23.

A histological study of the spleen in 30 human embryos in O'Rahilly's stages 17-23 revealed that the splenic anlage is composed of mesenchymal elements. Furthermore, the spleen is formed by a cytoreticulum containing a number of cells similar in appearance to lymphoid elements. No evidence of a celomocapsular separation is seen in this period.

Origin of the ultimobranchial body and its colonizing cells in human embryos.

The early development of the ultimobranchial body and its colonizing cells was studied in human embryos (O'Rahilly's stages 14 and 15). In our studies we have obtained evidence that permits us to propose a new hypothesis on the origin of both the ultimobranchial body and its colonizing cells. Based on our interpretation of the morphogenetic features in human development, we think that the ultimobranchial body derives from the fifth endodermal pharyngeal pouch, which is colonized, from O'Rahilly's stage 14 on, by cellular material of ectodermal placodial nature that originates in the most caudal portion of the epicardiac branchial placode.

Morphogenesis of the ultimobranchial body and its colonizing cells in the chick embryo.

The development of the ultimobranchial body and its colonizing cells was studied in chick embryos in Hamburger-Hamilton's stages 21 to 46. The most significant observations included the following: 1.-The ultimobranchial body is a separate morphological entity with particular characteristics distinguishing it from the fourth pharyngeal pouch in all developmental stages. 2.-The fifth pharyngeobranchial ducts disappear in Hamburger-Hamilton's stage 27. 3.-From Hamburger-Hamilton's stage 27 on, the left ultimobranchial body is in contact with the caudal end of the left parathyroid IV primordium. 4.-The group made up of the ultimobranchial body and its colonizing cells at no time fuses with the thyroid gland.