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Biomedical subjects

S K Clarren

Publications and source records attributed to S K Clarren.

At least 55 records · Page 3Linked to original sources
PubMed1986

The origin of prenatal and postnatal deformities.

Deformities are abnormalities of shape or form caused by abnormal or imbalanced mechanical forces. In prenatal deformation, most infants are intrinsically normal and the deformation results from extrinsic constraining forces. Most prenatal deformities will resolve spontaneously or with the application of counteracting forces. In contrast, postnatal deformities result from either extrinsic pathologic processes, affecting the bones, nervous system, or muscle and resulting in the application of abnormal forces to bone, or normal forces acting on intrinsic diseases of bone. While many postnatal deformities can be contained or corrected by the application of counteracting forces, aggressive physical therapy, casting, or surgery is often required for correction.

Bone Development↗
PubMed1986

Studying alcohol teratogenesis from the perspective of the fetal alcohol syndrome: methodological and statistical issues.

Alcohol is a teratogenic drug and the effects appear to be grossly dose related. The severest effects are observable clinically as the fetal alcohol syndrome and are associated with heavy prenatal alcohol exposure and a history of chronic maternal abuse of alcohol. Hypotheses for subtler behavioral effects associated with lower levels of exposure can be generated from observation of the behavioral effects in FAS. Behavioral effects associated with various levels of prenatal alcohol exposure in humans include poor sucking and poor habituation in the newborn, poorer mental and motor development in infancy, and attentional and reaction time effects at four and seven years of age. Human behavioral teratology studies are necessarily complex due to the large number of covariates that affect behavior, modify the effects of teratogens, and influence interpretation. Challenging problems exist in assessing exposure, outcomes, and covariates. Common to assessment of all these classes of variables are the multiplicity of measurement and the indirect nature of the measurement. Answering specific questions about timing and dose effects demands careful statistical modeling procedures and large, complex data bases. Large data bases and indirect measurement problems suggest factor analytic extensions of current regression methodology, which we have proposed in this paper.

Child, Preschool↗
PubMed1985

Natural history of the fetal alcohol syndrome: a 10-year follow-up of eleven patients.

Of the eleven children who were the first to be diagnosed as having the fetal alcohol syndrome ten years ago, two are now dead, one is lost to follow-up, and the remaining eight continue to be growth deficient and dysmorphic. With menarche, which occurred with normal timing, the female patients developed increased body fat. The mothers were all severe chronic alcoholics. Four of the eight known survivors are of borderline intelligence and have needed some remedial teaching. The other four are severely handicapped intellectually and need complete supervision outside the home. The degree of growth deficiency and intellectual handicap was directly related to the extent of craniofacial abnormalities. New features of the syndrome include dental malalignments, malocclusions, and eustachian tube dysfunction, which may relate embryologically to midface hypoplasia.

Abnormalities, Multiple↗
PubMed1985

Ankylosed teeth as abutments for maxillary protraction: a case report.

It has been recognized that using the maxillary teeth to deliver extraoral force to the maxilla not only results in sutural remodeling but also periodontal remodeling and tooth movement. In patients with severe maxillomandibular malrelationships, the potential for tooth movement often limits the amount and duration of extraoral force and, consequently, affects the success of treatment. This case report describes a technique to intentionally ankylose deciduous teeth in a patient with severe maxillary retrusion. The ankylosed teeth were used as abutments to deliver an anteriorly directed intermittent extraoral force. After 12 months of treatment, the anterior crossbite was nearly corrected. At that point the ankylosed teeth loosened because of root resorption and the treatment was terminated. Cephalometric superimposition demonstrated that the occlusal correction was the result of anterior maxillary movement with little mandibular growth and no movement of the ankylosed teeth. The results suggest that intentionally ankylosed teeth may be used as abutments for extraoral traction in patients with a severe disturbance in maxillary growth.

Acrocephalosyndactylia↗
PubMed1985

Fetal alcohol syndrome: an examination of craniofacial dysmorphology in Macaca nemestrina.

The purpose of this investigation was to evaluate the craniofacial features in nonhuman primate models exposed in utero to moderate and high weekly binge doses of ethanol. While the high-dosed animal did have unusual craniofacial dysmorphology, she did not exhibit the typical facial pattern seen in human fetal alcohol syndrome. The high-dosed specimen displayed a scaphocephalic head shape secondary to synostosis of the sagittal suture. The brain of this monkey was grossly abnormal and microcephalic.

Animals↗
PubMed1984

Measures of alcohol damage in utero in the pigtailed macaque (Macaca nemestrina).

A non-human primate model for the fetal alcohol syndrome (FAS) has been developed in a pilot study on four pigtailed macaques (Macaca nemestrina) receiving ethanol once weekly from 40 days of gestation (2.5 g/kg for three moderate-dose monkeys and 4.1 g/kg for one high-dose monkey). Ethanol and acetaldehyde levels and indices of general health were monitored throughout pregnancy. One pregnancy ended in miscarriage. The three infants born at term were compared to control infants. The infant exposed to the higher ethanol dose showed phenotypic similarities to humans with FAS. Its brain was microcephalic and dysplastic; reflex, motor and cognitive development were retarded. One infant receiving the moderate dose had subtle brain abnormalities; it was hyperkinetic and showed developmental retardation on several behavioral measures. The other moderately dosed infant was normal. A larger study now in progress will comprise six groups of seven monkeys, each group being exposed to 0 (control), 0.3, 0.6, 1.2, 2.5 or 4.1 g/kg of ethanol once weekly throughout gestation. So far, 4.1 g/kg ethanol has been shown to be fetotoxic when given between 8 and 13 days of pregnancy.

Animals↗
PubMed1984

Isolated tibial hemimelia in sibs: an autosomal-recessive disorder?

Isolated tibial hemimelia is generally considered to occur sporadically. We report on isolated tibial hemimelia in two sibs born to phenotypically normal parents and review a similar case from the literature. These cases suggest autosomal-recessive inheritance. Whether isolated tibial hemimelia represents a discrete syndrome or an expression of a disorder with wider phenotypic variability remains unclear.

Child, Preschool↗
PubMed1983

Neuropathologic findings in the spinal cords of 10 infants with arthrogryposis.

The lumbosacral cord segments of 10 infants with varying clinical forms of neurogenic arthrogryposis were compared with similar spinal cord segments from an infant with congenital contractures secondary to uterine constraint, 8 infants with Werdnig-Hoffman syndrome, and 11 age-matched controls. Neuronal numbers, sizes, and distribution were measured within the anterior horns. In addition to the classical reduction in the numbers of alpha motor neurons in both pathologic states, this study found the smaller neurons of the anterior horn were absent or diminished in Werdnig-Hoffman syndrome, while those cells were present in increased numbers with abnormal histology in all the patients with arthrogryposis. In 5 of the patients with arthrogryposis, the pathologic pattern was consistent throughout each cord segment; in 5 others, normal alpha neurons were retained and unequally distributed in the anterior horn segments. This unequal distribution predicted the muscle group involvement and suggested the mechanism for intrauterine joint fixation in these patients. The pathologic changes in the patients with arthrogryposis appear to be unique in spite of the heterogeneity of etiology and the clinical presentation.

Anterior Horn Cells↗
PubMed1983

Autosomal recessive eye and brain anomalies: Warburg syndrome.

Two siblings are reported who appear to have an autosomal recessive disorder of eye and central nervous system anomalies. The findings in fourteen previously described and similarly affected patients are summarized. Ocular anomalies include microphthalmos, megalocornea, the Peter anomaly, cataract, coloboma, persistent hyperplastic primary vitreous, and retinal detachment with retinal dysplasia. Central nervous system malformations include agyria-pachygyria, cerebellar dysplasia, encephalocele, Dandy-Walker cyst, and hydrocephalus. We suggest that this disorder be known as Warburg syndrome.

Brain↗
PubMed1983

A spectrum of gyral anomalies in Miller-Dieker (lissencephaly) syndrome.

Four unrelated patients who had the clinical appearance of Miller-Dieker syndrome, also called lissencephaly syndrome, were studied. All four had a typical clinical course with failure to thrive, severe psychomotor retardation, opisthotonos, seizures, and death early in life. None of these children had lissencephaly, the anticipated central feature of this disorder. One of the four had pachygyria, one had polymicrogyria, and two had both pachygyria and polymicrogyria. The brain weights were normal to decreased. The ventricles were dilated in all cases. The cerebral cortex was thickened in each, with decreased white matter and diminution or distortion of the cellular layers, and there were neuroglial heterotopias. The corpus callosum was partially absent in one and thinned in three. The neuropathy found in these children with Miller-Dieker syndrome suggests a spectrum of gyral anomalies resulting from a single type of embryonic error.

Agenesis of Corpus Callosum↗
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

Neuroanatomic examination of spina bifida aperta and the Arnold-Chiari malformation in a 130-day human fetus.

A 130-day human female fetus with the Arnold-Chiari malformation and thoracolumbar myeloschisis revealed evidence of neuroectodermal-mesodermal spatial dyssynchrony. The rhombencephalon and the cervico-medullary junction appear most affected. The phylogenetic and ontogenetic development of the transition zone between brain and spinal cord is reviewed. It is hypothesized that the etiologic event responsible for the Arnold-Chiari malformation is the caudal "displacement" of the site of initial fusion of the neural folds. This is believed to result in the posterior displacement of the cervico-medullary junction and myeloschisis (the Arnold-Chiari malformation, type II).

Arnold-Chiari Malformation↗
PubMed1982

Fetal alcohol syndrome: a new primate model for binge drinking and its relevance to human ethanol teratogenesis.

Ethanol was administered nasogastrically to four gravid pigtailed macaques (Macaca nemestrina) weekly from 40 days after conception to term. Three animals received 2.5 gm/kg and one received 4.1 gm/kg per dose. One animal aborted after the first dose of 2.5 gm/kg ethanol. Serum ethanol and acetaldehyde were measured after each dose in the other three animals, who carried to term. After delivery the infants were assessed for growth, dysmorphic features, and neurologic and psychological development over six months and were compared with 10 age- and sex-matched controls. Complete autopsies with neuropathologic examinations were performed. The animal exposed to the high dose had neurologic, developmental, and facial anomalies similar to those seen in human fetal alcohol syndrome. One of the animals exposed to the more moderate dosage was similarly but less severely affected. The study demonstrates that a model for binge drinking and fetal alcohol syndrome can be developed in a primate. The model should be useful in exploring the mechanisms of teratogenesis and in determining the median effective dose for the production of the various anomalies seen in fetal alcohol syndrome.

Alcohol Drinking↗