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Biomedical subjects

J R Siebert

Publications and source records attributed to J R Siebert.

At least 37 records · Page 2Linked to original sources
PubMed1989

Anatomic findings in dicephalic conjoined twins: implications for morphogenesis.

The morphogenesis of conjoined twins is incompletely understood. We therefore conducted a postmortem study of dicephalus dibrachii dipus conjoined twins. The twins were born without pertinent history or prenatal diagnosis at 38 weeks and lived for several hours. External genitalia were female and partly duplicated; a caudal appendage was present in the thoracolumbar region. The heart and liver were shared and exhibited major abnormalities in configuration. Four lungs, three kidneys and adrenal glands, and two spleens were identified; biliary and upper gastrointestinal tracts appeared as mirror images. From these findings, we postulate three major sets of consequences arising from the anatomical disposition of the twin notochords ("paleoaxes"). 1) The degree of convergence/divergence of craniocaudal paleoaxes is variable. Convergences are maximal in the upper thoracic and sacral regions, where duplication of organs in minimal because of interaction aplasia. 2) In the horizontal plane, paleoaxes are sufficiently divergent to produce a degree of twin expression posteriorly, whereas anteriorly they converge to form a single, anterior, midline "neoaxis." Interposed between these zones of paleoaxial and neoaxial expression are areas of variable interaction aplasia. 3) The left twin was in situs solitus; the right twin was in situs inversus in a manner resembling polysplenia.

Abnormalities, Multiple↗
PubMed1989

Megalencephaly in sudden infant death syndrome.

The fresh brain weights of 79 infants with sudden infant death syndrome (SIDS) were tabulated and compared with expected "normal" brain weights. The series included 47 males and 32 females. Their ages ranged from 8 days to 16 months with a median of 2.5 months. The weights of all these brains were above the 50th percentile for age, and 64 of 79 brains (81%) were above the 95th percentile, including 15 (19%) at or above the 99.9th percentile. The ratio of the brain stem plus cerebellum weight to the whole brain weight of 93 formalin-fixed brains from victims of SIDS showed that the cerebrum was disproportionately heavier in most cases. No gross or microscopic evidence of cerebral edema was noted to account for the heavier weight. The significance of these findings is debatable. The increase in brain weight was less obvious in infants younger than 1 month of age but accelerated after that age. The brain weights of infants with SIDS may represent the really "normal" weights, since these patients were not known to be ill prior to death. If the brain weights of SIDS infants are really heavier than "normal," the possibility must be considered that disproportionately rapid growth of the brain during early infancy may be detrimental to the neural control of the cardiorespiratory system.

Brain↗
PubMed1988

Congenital posterolateral diaphragmatic hernia: associated malformations.

Congenital posterolateral diaphragmatic hernia (CDH) is widely regarded as an isolated defect, but this view is incomplete. We reviewed our clinical and autopsy experience and the literature from the past 25 years in order to catalogue the frequency and clinical importance of additional malformations in patients with CDH. The study showed two broad categories of patients. In the larger group of infants (65 of 108, or 60%), CDH was the only severe defect, apart from those normally associated with the presence of abdominal viscera in the thorax. Thirty-six of these patients (55%) survived. A striking finding among infants with isolated CDH, not previously highlighted in the literature, was cryptorchidism which was present in 30% of males. By contrast, 43 patients (40%) had one or more severe extradiaphragmatic malformations; only six of these infants (14%) survived. Defects in morphogenesis were widespread, heterogeneous, and seemingly related to numerous pathogenetic mechanisms. Most often abnormalities involved the heart, brain, genitourinary system, craniofacial region, or limbs. The high incidence of multiple anomalies in some patients with CDH should influence our investigations into causes and mechanisms. Patients with CDH should be evaluated carefully for additional defects--their presence has a significant impact on management and worsens prognosis.

Abnormalities, Multiple↗
PubMed1987

Duplication 7p in a family with t(7;11): association with anomalies of the anterior cranial base.

Duplication 7p has been observed in association with several balanced translocations. Of eight previously recorded cases, only one exhibited duplication of the entire short arm of chromosome 7. We report on a newborn infant with multiple congenital anomalies and an abnormal chromosome constitution: 46,XX,-11,+der(11),t(7;11) (p11.1;p15.5)mat. The proposita appeared to possess an isolated duplication of the entire short arm of 7. The patient died at age 4 days because of respiratory complications of meconium aspiration. Clinical and postmortem findings included craniocerebral asymmetry, craniosynostosis of a lambdoid suture, arhinencephaly, hypertelorism, anomalies of the ethmoidal portion of the cranial base, large anterior fontanelle, low set ears, ventricular septal defect (VSD), dysplastic tricuspid and pulmonic valves, hypoplastic genitalia, bilateral dislocated hips, and other minor limb malformations.

Abnormalities, Multiple↗
PubMed1987

Atelencephalic microcephaly: craniofacial anatomy and morphologic comparisons with holoprosencephaly and anencephaly.

This is the first detailed report of the craniofacial anatomy of atelencephaly. Comparisons were made with a control specimen and others with holoprosencephaly, anencephaly, and anencephaly with holoprosencephalic facial features. In the atelencephalic fetus, severe microcephaly, flattened calvaria, and partial synostosis of the metopic suture were apparent. The cranial fossae were much smaller than usual; lesser wings of the sphenoid were folded into a rounded basal mass. Facial features were pronounced, and orbits were hyperteloric, lowset, and rounded. Ethmoidal cartilages, nasal bones, and maxillary structures were distorted and elongated. The secondary palate was displaced inferiorly and cleft. Because major components of the craniofacial complex were generally present, although misshapen, changes in the atelencephalic skull seem to be deformations rather than malformations. Differences in the cranial morphology of associated disorders--holoprosencephaly and anencephaly--can be construed as aberrations of separate developmental fields. Relationships between atelencephaly and these fields are unclear.

Abnormalities, Multiple↗
PubMed1987

Chest size and symmetry in congenital diaphragmatic hernia.

Infants with congenital diaphragmatic hernia have significantly increased chest circumferences. This implies that intrathoracic volumes are increased as well. Forces produced by the herniated abdominal viscera seem to provide the chief impetus for this change. Other factors may also contribute, for thoracic enlargement is asymmetric and not always ipsilateral to the hernia. The contribution of an enlarged chest to respiratory insufficiency, persistence of the fetal circulation, and hyperinflation is not fully understood, but may have relevance in evaluating new approaches to therapy.

Body Height↗
PubMed1986

Prenatal growth of the median face.

The growth and development of the median facial region remain incompletely understood. Data concerning the prenatal size and growth rates of facial components are especially lacking. A group of fetuses and newborn infants with apparently normal craniofacial development and body size was therefore studied at autopsy. The interorbital distance and dimensions of the external nose, philtrum (upper lip), and mouth were determined; the growth of morphogenetically related structures--the ethmoid bone and tongue--was also studied. The slopes of linear regressions of these variables against body length indicated that growth of the median facial region proceeds slowly in the latter half of gestation. The center of the face seems to grow slower than the sides of the face. A multivariate technique, factor analysis, identified and ordered relationships among the variables. The best statistical summary of size in the median face was given by four transversely oriented variables, nose breadth, outer orbital distance, inner canthal distance, and mouth width. Within the region, a secondary cluster was dominated by sagittally oriented variables. The second best summary of median facial relationships was provided by three variables of lingual size and was followed by a group of variables representing ethmoidal size. This pattern of growth may represent the effects of a developmental hierarchy. Growth seems to be coordinated along the major axes of the body, with transverse growth controlled more rigidly than sagittal growth. The statistical independence of the three regions suggests that the controls of growth are also separate.

Biometry↗
PubMed1986

Atelencephalic microcephaly in a 21-week human fetus.

Atelencephalic microcephaly, a rare and extreme disorder, is known morphologically by only six cases. Derivatives of the telencephalon are absent or dysplastic, while more caudal structures are normal or mildly deformed. A more extensive form, aprosencephaly, involves structures of the diencephalon and may be associated with holoprosencephalic facies. Extracranial anomalies may be present in both atelencephaly and aprosencephaly. We describe the seventh and youngest specimen, a 21-week female with atelencephaly. Maternal and gestational histories were unremarkable; the fetus was obtained by therapeutic abortion following diagnosis of a severe cranial malformation by ultrasound. A small and depressed, but intact, calvarium covered the brain. The forebrain was rounded and showed fused hemispheres, absent gyri, olfactory bulbs, and tracts. Caudal structures were mildly deformed. An oval mass of bone filled much of the middle cranial fossa. By light microscopy, several dysplastic changes were apparent in the forebrain. Ventricles were not present; small round cells resembling those of the germinal matrix were prominent in the forebrain. Pyramidal tracts were absent at all levels. The process responsible for these changes cannot be established with certainty; the changes are, however, in keeping with previous damage, such as that accepted for other encephaloclastic disorders. The insult in atelencephaly presumably occurs after closure of the rostral neuropore; earlier damage, with more widespread consequences, is possible for aprosencephaly. As with other destructive processes, etiology in atelencephaly and aprosencephaly is most likely heterogeneous.

Brain↗
PubMed1986

Relationships of cardiac and somatic growth in infancy and childhood.

Recent advances at clinical and experimental levels bespeak the need for a more complete understanding of cardiac growth and its relationship to somatic growth. The size of the heart is integral to several physiologic processes, including aerobic and work capacity, athletic performance, and reproduction. Because the morphologic foundations for cardiac size are laid in large part before adulthood, cardiac growth and the factors controlling it are important in achieving optimal cardiovascular fitness. We provide a baseline for normal cardiac growth during the late fetal to adolescent periods. Sexual differences are not evident in this prepubertal population. Heart weight is related to three measures of body and chest size. These relationships follow a hierarchy, whereby heart weight is most closely related to body weight, followed by body length, then chest circumference. The association of heart weight with chest circumference is a secondary one, reflecting more primary relationships between heart weight and body weight and length. Deviations from this normal hierarchy occur in certain environments and disease states.

Body Height↗
PubMed1985

Pathologic features of the CHARGE association: support for involvement of the neural crest.

Defects associated with choanal atresia include coloboma, cardiac anomalies (usually involving the conotruncal region), physical or mental retardation, genital hypoplasia, and abnormalities of the ear. This constellation of defects is known as the "CHARGE" association and may be accompanied by other anomalies. Many of these defects seem to result from abnormalities in the development, migration, or interaction of cells of the cephalic neural crest. The range of variation in neural crest development is substantial, as indicated by the rather large number of malformation complexes and syndromes that are related phenotypically to the CHARGE association. The increasingly unwieldy nature of this collection of malformations demonstrates the need for an expanded classification of the "neurocrestopathies."

Abnormalities, Multiple↗
PubMed1985

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.

Anthropometry↗
PubMed1984

Self-reported physical stress reactions: first- and second-order factors.

Stress Inventory-6, a 72-item self-report questionnaire designed to tap 18 factors of physical stress reactions, was subjected to factor analysis. The instrument was given to 474 students (254 females, 206 males, and 14 who failed to indicate their gender). The final factor solution identified 16 first-order and 4 second-order factors. The first-order solution replicated most of the factors identified in a previous study and defined factors in terms of organ system, muscle group, and simple content. In the second-order solution, Factors I, III, and IV include symptoms that are immediate and direct, appear to be related to arousal of the somatic and sympathetic nervous system, and are marked prominently by cardiorespiratory activity. In contrast, Factor II includes symptoms that are indirect and often delayed consequences of sustained arousal (Fatigue and Lack of Energy, Headaches, Backaches, etc.). A major distinction can be made between stress arousal Factors I and III. Factor III appears to be a simple "fight or flight" arousal pattern characterized by fairly direct manifestations of striated muscle tension as well as cardiorespiratory activity. In contrast, Factor I is a complex arousal pattern characterized by diffuse autonomic arousal, self-directed attention, and possibly low self-esteem. The results of this study draw into question the extent to which popular stress inventories tap a representative sample of stress symptoms. Clinical implications are discussed.

Adolescent↗
PubMed1984

Left ventricular hypoplasia in congenital diaphragmatic hernia.

Quantitative anatomic study of the hearts of eight infants with left-sided congenital diaphragmatic hernia (CDH) has revealed significantly decreased cardiac mass, due to hypoplasia of the left atrium and ventricle and interventricular septum. These morphologic deficiencies may be a result of compression of mediastinal structures by herniated abdominal viscera during prenatal life. Left ventricular hypoplasia is likely to be an important factor in the pathogenesis of cardiac insufficiency in patients with left CDH.

Female↗
PubMed1982

Cyclopia: an anatomic and histologic study of two specimens.

The craniofacial complex of two neonatal, human, cyclopic specimens was studied in detail. Both specimens exhibited a single ocular opening and one had a prominent probosics positioned in the midline directly superior to the ocular aperture. No external nasal development was noted in the other specimen. The most remarkable finding was the lack of development of all skeletal derivatives of the ethmoidal cartilage(cribriform plate, perpendicular plate, superior and middle nasal conchae, medial orbital walls, and nasal septal cartilage) in both specimens. Since these bones normally form the medial, lateral, and superior walls of the nasal passage, this cavity was also absent. The two posterior halves of the maxillae were directed superiorly, medially, and with the vomer merged in the midline as a thick mass of bone. As a result the right and left alveolar portions of the maxillae were joined superiorly in the midline. With the absence of the nasal cavity, the right and left medial pterygoid plates merged medially with the palatal and pyramidal processes of the palatine bone to obstruct the junction between the oropharynx and nasopharynx(choanal atresia). The role of the skeletal parts of the ethmoid during maxillofacial growth and development is discussed.

Abnormalities, Multiple↗
PubMed1982

Parasitic conjoined twins, two cases, and their relation to limb morphogenesis.

Reports of parasitic conjoined twins have appeared rarely in the scientific literature and only one study has included a detailed description of the parasitic extremities. We report here two specimens consisting for the most part of normal hosts with ectopic legs attached to the thorax (case 1, thoracoparasitus) or the abdomen (case 2, gastroparasitus). These two specimens are in agreement with several others reported in the literature in having no sign of vertebral columns. These specimens also exhibit a marked decrease in innervation (case 1) or complete absence of somatic nerves (case 2). This finding is in complete contradiction with the idea of the dependence of limb skeletal structure upon peripheral nerves. The hypothesis is presented that this type of parasitic twin may result from duplication of the Wolffian ridge.

Bone and Bones↗
PubMed1982

Determinants in the morphogenesis of muscle tendon insertions.

The factors that normally determine the location and insertion of a muscle were explored in human experiments of nature with early problems in morphogenesis. Monozygotic conjoined twins for whom there could be no genetic determinants for muscle attachments at the sites of juncture served as one model; these attachments had to follow general principles of morphogenesis. A second type of problem involved absence of bone that presumably antedated muscle and tendon development (e.g., genetically determined radial aplasia). A third category included mechanical alteration of early limb position that may have occurred prior to the development of muscle attachments (e.g., early amnion rupture sequence). The dissection findings from all three types imply a general hierachy of muscle tendon attachments. Tendons appear to attach preferentially to bone. In the absence of the bone to which they would normally attach, they will attach to the next closest bone. If no such bone is available, tendons may attach to other tendons; and if no tendons is available, occasionally they will attach to the fascia of another muscle. If there is no connective tissue attachment site, there will be no muscle, implying a need for function in the development and preservation of muscle.

Abnormalities, Multiple↗