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Biomedical subjects

A R Burdi

Publications and source records attributed to A R Burdi.

At least 19 recordsLinked to original sources
PubMed1994

Patterns of abnormal myogenesis in human cleft palates.

To test the hypothesis that soft palate muscles are abnormal in cleft palate, we compared soft palate morphogenesis in fetuses with cleft palate (n = 4) to age-matched (n = 3) and nonmatched (n = 1) control specimens. The morphologic status of all soft palate and masticatory structures were classified into one of six stages based on the level of histogenesis. At 54 mm crown-rump length (CRL), the levator veli palatini (L), palatopharyngeus (PP), and palatoglossus (PG) in cleft subjects demonstrated mesenchymal condensation into myoblastic fields, lagging behind the control specimens (97 mm CRL), which displayed definitive fields of myoblasts and myotube formation. In the 175 mm and 225 mm cleft and the 170 mm and 192 mm control specimens, muscular morphology was similar and had reached its postnatal appearance for the tensor veli palatini (175 m only) and L, PP, PG (225 mm only). Muscle fiber directions were, however, disoriented and disorganized, especially close to the medial epithelial edge of the cleft. The levator veli palatini, could not be distinguished as a discrete muscle in the cleft specimens, and what we believed to be the PP and PG seemed "normal" at the level of light microscopy, but malpositioned in a superior direction. This preliminary study demonstrates for the first time that early myogenesis in cleft palates differs from normal.

Case-Control Studies↗
PubMed1988

Prenatal pattern emergence in early human facial development.

This report addresses the emergence of proportional patterns in the early development of the human face. Fifty-nine human embryos and fetuses (7 through 26 weeks fertilization age) constituted a "normal" study sample. Midfacial cephalometric analyses were done on projected histologic sections cut frontally through the maxillary deciduous first molar tooth crowns. The midface was divided into three cephalometric zones. Data show that while each zone increases in absolute width, least change is seen in the central facial zone, with greatest change seen in the lateral-most facial zone. This pattern of proportional stability of the central facial zone becomes evident at 9 weeks gestation, at which time the changing embryonic optical axes have converged toward the midline to within several degrees of their position at birth. These data show that the central portion of the postnatal facial T-zone has a clearly recognizable prenatal antecedent as early as the ninth week in fetal life.

Cephalometry↗
PubMed1987

Critical periods in the prenatal morphogenesis of the human lateral pterygoid muscle, the mandibular condyle, the articular disk, and medial articular capsule.

This study was prompted by the renewed clinical interests in understanding the natural history or early morphogenesis of the human temporomandibular joint. Using histologic preparations of 52 representative human embryos and fetuses, each of the major components of the joint was systematically assessed for its changing structure and related to an approximate time scale. The emergence and continued morphogenesis of the joint articular fossa, mandibular condyle, disk, capsule, lateral pterygoid muscle fibers, and both joint cavities occur in regular temporal and spatial pattern. A key observation from this study of embryos and fetuses ranging in age from 32 days to 22 weeks is that each of the component parts of the TMJ progressively emerge with some kind of continuity from a common mass of embryonic mesenchyme interposed between the future temporal bone and mandibular regions. The observations of this study lead to the suggestion that significant developmental disturbances to this common tissue mass or "developmental field" can lead to anomalous morphogenesis of those structures expected to emerge over time from the "developmental field" of the temporomandibular joint. Timing and the identification of a critical time period for the joint are important variables. This study identifies the critical period in the early morphogenesis of TMJ structures as generally falling between the early 7th and 11th prenatal weeks.

Cartilage, Articular↗
PubMed1986

The natural history and pathogenesis of the cranial coronal ring articulations: implications in understanding the pathogenesis of the Crouzon craniostenotic defects.

The craniostenotic birth defects seen in patients with Crouzon syndrome have prompted this developmental study on the system of articulations between the human frontal, sphenoid, and ethmoid bones. The Crouzon facies, including midfacial hypoplasia and exorbitism, have been linked to the premature synostosis of calvarial sutures. However, considerable evidence shows that midfacial positioning is linked to increasing length of the midline cranial base. Thirty-seven typical-for-age (8 to 29 weeks) embryos were histologically prepared, read serially, and three-dimensionally reconstructed to map the so-called coronal ring articulations that continuously join the frontal, sphenoid, and ethmoid bones. A morphologic staging plan was used to show the progressive development of bones and intervening joints. Data show that a coronal ring exists beginning at 8 weeks. Those portions of the ring separating the frontal and sphenoid bones (within the orbit and laterally along the coronal suture) show the typical structure of a five-layered suture. This sutural component of the ring is C-shaped with a cartilaginous bridge between the optic foramina completing the ring. This is the sphenoethmoidal (S-E) synchondrosis of the midline cranial base. It is suggested that this deeply located cartilage joint is the primary site of pathogenesis in the craniostenotic facies and not the coronal sutures which are operated upon. Even though the S-E cartilage would be difficult and potentially morbid to approach surgically, this study would suggest that preoperative computed tomography (CT) of the skull base with special emphasis on the S-E region may provide a better prognosis regarding midface growth effects after surgery. It appears to be the fused S-E synchondrosis and not necessarily the premature closure of the coronal sutures that may tether the midface posteriorly.

Adult↗
PubMed1985

Reexamination of the origin and early development of the human larynx.

The respiratory primordium buds off the primitive foregut and grows caudally, on a lengthening stalk; the cephalic end of the stalk develops into the glottis and infraglottis, and the rest becomes the trachea. Compression by pharyngeal mesoderm cephalic to the respiratory diverticulum obliterates the foregut lumen ventrodorsally as far cranially as the 4th pharyngeal pouches, forming an epithelial lamina with a narrow pharyngoglottic duct along its dorsal border. The mesoderm also raises an epiglottic and two arytenoid swellings in the pharyngeal floor at the level of the 4th pouches; the triangular 'cecum', bounded by these swellings, grows caudally along the ventral border of the epithelial lamina to just above the glottis. Beginning at stage 21, the epithelial lamina separates cephalocaudally, bringing the cecal lumen into continuity with the pharyngoglottic duct to form the laryngeal vestibule; when the separation is complete, the vestibule is continuous with the infraglottic cavity. Meanwhile, bilateral pouches arising from the caudal end of the cecum form the ventricles, the lower lips of which become the vocal folds, and the pharyngeal mesoderm surrounding the laryngeal cavity gives rise to the laryngeal cartilages and intrinsic musculature. The cricoid chondrifies bilaterally from a single center in the ventral arch of a precartilaginous template that encircles the infraglottic cavity, and on meeting forms the dorsal lamina. Each arytenoid chondrifies from a single center, and each half of the thyroid cartilage chondrifies from two. Anlagen for the intrinsic muscles appear during stage 17, sites of individual muscles are recognizable by stage 23, and myofibrils are present by the 12th week.

Cartilage↗
PubMed1985

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.

Child, Preschool↗
PubMed1985

Adipose tissue growth patterns during human gestation: a histometric comparison of buccal and gluteal fat depots.

Morphometric analysis of fat lobule size and number, and fat cell number in middle buccal and gluteal fat depots during the prenatal period was carried out using histological sections from 88 typical-for-age or normal human prenates of both sexes. The sample ranged from 110 to 385 mm Crown-Rump length (or from 14 through 42 gestational weeks). Compared with the buccal fat pad, the gluteal fat was one to four weeks delayed in lobule maturation. In addition to fat maturation differences between buccal and gluteal fat sites, gluteal fat characteristically showed fewer but larger fat lobules than did the buccal fat pad. Conversely there appeared a larger number of fat cells per unit area in the buccal fat than in the gluteal fat. Fat accumulation in human buccal and gluteal fat depots include differences in growth timing and magnitude, but also different developmental patterns. These patterns suggests our hypothesis that while lobule hyperplasia and hypertrophy occur at both sites, gluteal fat lobules grow primarily through lobule hypertrophy whereas the buccal fetal pad grows through lobule hyperplasia.

Adipose Tissue↗
PubMed1984

The chronology of adipose tissue appearance and distribution in the human fetus.

Timing of first appearance and subsequent distribution of adipose tissue were assessed in 488 normal-for-age human fetuses. The sample represented each of the three trimesters of normal pregnancies. Light microscopy showed that adipose tissue first appears and progressively develops from the 14th to 24th week of gestation (100-216 mm crown-rump length) in those areas where it characteristically accumulates after birth. No significant sex differences were found in patterns of early fat deposition. It is suggested that the second trimester of gestation is the critical or key period in fat adipogenesis.

Abdomen↗
PubMed1984

Crown area as an indicator of changing crown size in human pre-natal teeth.

This study deals with correlations of tooth size in human primary teeth. Traditionally, mesiodistal or buccolingual measurements have been used to express crown size. However, in this study, crown area was used as a reference parameter. Graphic reconstructions of 38 histologically prepared human fetuses with Crown-Rump Length (CRL) between 54 and 280 mm were used to obtain linear and area measurements. Based on clinical records and physical examinations, these fetuses were considered typical-for-age, or "normal". Correlation matrices indicated high levels of concordance among all developing deciduous tooth crowns and arch measurements. It was concluded that crown area is a statistically better trait to use in comparison of teeth rather than the traditional mesiodistal measurement.

Body Height↗
PubMed1983

Growth and development of human adipose tissue during early gestation.

805 normal-for-age human embryos and fetuses were used to study early prenatal fat development. The investigation included observations on stages of fat morphogenesis at the light microscopic level and computerized image analyses of fat lobule size and number. The buccal fat pad was selected as a model system for the analyses. Fat tissue differentiates between the 14th and the 16th weeks: there are five morphogenic phases in adipose tissue formation, strongly associated with the formation of blood vessels. Fat lobules are the earliest structures to be identified before typical vacuolated fat cells appear. Concerning fat lobule size and number, we show that after the 23rd week the total number of fat lobules remains approximately constant, while from the 23rd to 29th week the growth of adipose tissue is determined mainly by an increase in size of the lobules. These results suggest that the 14th through the 23rd week is a sensitive period in fat lobule development, and that disturbances of normal adipogenesis during this period may play a role in the etiology of obesity in later life.

Adipose Tissue↗
PubMed1981

Comment on the prune belly syndrome: a 11-week fetus with megacystis.

An 11-week human fetus with megacystis, prostatic dysgenesis, and lateral displacement of the abdominal muscles is described. We suggest that a subtle outflow obstruction of the very early bladder may give rise to both bladder dilation and bladder wall dysgenesis. The bladder dilation may produce abdominal muscle dysplasia or atrophy and almost certainly produces dilation of the prostatic urethra. The dilation of the prostatic urethra disrupts the formation of the prostate.

Abdominal Muscles↗
PubMed1981

Adjacency effects in developmental correlations among tooth organs in human fetuses.

This study explores whether the "distance gradient" model shown for embryonic development and postnatal tooth growth is also characteristic of the fetal period. Histologic data and ratings from 26 human fetuses show that, unlike the embryonic and postnatal periods, changes occurring in two tooth germs are significantly alike, regardless of the number of intervening teeth.

Fetus↗
PubMed1981

Congenital alar field defects: clinical and embryological observations.

Congenital malformations of the nasal ala may occur as isolated unilateral nasal alar defects or as part of more severe facial clefting syndromes. The embryologic significance of the isolated alar deformity seems separate from other craniofacial deformities and justified comment. Clinical examples of isolated nasal alar malformations are correlated with a study of 60 human embryos ranging from seven to 10 weeks gestation. These studies indicate that the nasal and alar developmental fields each have a separate critical time during which cells are most susceptible to altered development.

Female↗