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Biomedical subjects

D Bixler

Publications and source records attributed to D Bixler.

At least 55 records · Page 3Linked to original sources
PubMed1984

Fetal mortality in oral cleft families (VII): Birth intervals.

Birth intervals in sibships of oral cleft probands are analysed to detect prolonged delays between successive pregnancies. Such intervals are useful indicators of undetected fetal mortality. The present study indicates that the average interval for 462 cleft families in Indiana is 30.61 months. The average interval leading to the birth of a cleft child is 33.94 and is significantly greater than the average interval for the entire sample. Although the contraception status of the Indiana population is not known, the significantly greater delay preceding the birth of a cleft child is indicative of a cause other than contraception. This finding is in agreement with the report by Drillien et al. (1966) that abnormal conceptions occur more frequently adjacent to cleft offspring. It is interesting that some increase in the average interval is also noted in the present study immediately following the birth of a cleft child. Such delays occurring both preceding and following the birth of a cleft child (in contrast to smaller intervals for other pregnancies in the same sibships) may indicate excessive fetal wastage due to a combination of genetic and environmental factors.

Birth Intervals↗
PubMed1983

Probable autosomal recessive inheritance of polysplenia, situs inversus and cardiac defects in an Amish family.

We report on an Amish family with five individuals in two generations with complex congenital heart disease. Autopsy findings in one and clinical examination in the others support the diagnosis of polysplenia "syndrome." In a mouse model, this spectrum of situs abnormalities and cardiovascular defects shows recessive inheritance with homozygotes having either situs solitus or situs inversus or ambiguous situs. The parents of the four affected sibs are fourth cousins. We think that the father of these four children is an affected but clinically normal homozygote, that his deceased sister was an affected homozygote, and it seems likely that they too had consanguinous parents.

Abnormalities, Multiple↗
PubMed1983

Fetal mortality in oral cleft families(IV): the "doubling effect".

Fetal mortality data from Lancaster, Penn., Chicago, Ill. and Minneapolis, Minn. are presented which support the authors' earlier findings in Indiana and Montreal that a positive relationship exists between the degree of liability to malformation and the incidence of fetal deaths in probands' sibships. Altogether, the study involved 189 CL sibships, 690 CLP sibships, and 3,416 pregnancies. On the basis of these data, which are derived from families of several different backgrounds of European ancestry, it is generalized that, as we proceed from CL sibships to CLP sibships, there is a doubling effect on fetal mortality. The consistency of this finding in several population samples is impressive. The implications of this observation are discussed with reference to genetic counseling.

Cleft Lip↗
PubMed1983

Fetal mortality and cleft lip with or without cleft palate.

Analysis of fetal mortality in sibships of 406 probands with cleft lip with or without cleft palate (CL(P)) indicates that the incidence of fetal mortality is significantly greater in sibships of probands with bilateral CL(P) than in those of unilateral CL(P). The difference is even greater when fetal mortality in sibships of male probands with unilateral CL(P) is compared with that of female probands with bilateral CL(P). These findings support a multifactorial two-threshold concept in which a lower level of liability results in clefting while a higher level of liability causes fetal mortality.

Cleft Lip↗
PubMed1983

Fetal mortality in oral cleft families: data from Indiana and Montreal.

Analysis of 418 sibships of oral cleft probands from Indiana, and 288 sibships from Montreal indicate that the incidence of fetal mortality is significantly greater in sibships of probands with cleft lip and cleft palate (CLP) as compared to that in sibships of probands with cleft lip (CL) alone. These findings support a multifactorial-two-threshold concept, according to which a lower level of liability results in clefting whereas a higher level of liability causes fetal deaths. They add confirmatory evidence in support of the authors' earlier work, utilizing data from two different sources.

Cleft Lip↗
PubMed1983

Clouston syndrome: an ultrastructural study.

A previously undescribed French-Canadian family affected with Clouston Syndrome (Hypohidrotic Ectodermal Dysplasia) is described. Ultrastructural study of the hair shows disorganization of the hair fibrils with loss of the cuticular cortex. The SEM findings are consistent with the model, suggesting a biochemical defect in the keratin of the integumentary system.

Child↗
PubMed1983

Clinical, laboratory, and genetic investigations of hypophosphatasia: support for autosomal dominant inheritance with homozygous lethality.

This article presents detailed clinical and laboratory investigations of six hypophosphatasia kindreds. Serum alkaline phosphatase and urinary phosphoethanolamine comparisons between the affected population and a normal control population demonstrate these parameters routinely identify the heterozygous individual when age and sex variations are accounted for. Using clinical data from the kindred population and a detailed review of the literature, the type and frequency of clinical findings for both the homozygous and heterozygous genotype are enumerated. The clinical and biochemical phenotypes were subjected to segregation analysis. When the results of these analyses are viewed in light of their mathematical limitations and the genetic precepts of autosomal dominant and recessive inheritance, hypophosphatasia is best described as an autosomal dominant disorder with 85% penetrance and homozygous lethality.

Age Factors↗
PubMed1983

Fetal mortality in oral cleft families (VI): a search for early embryonic and zygotic mortality.

A hypothesis concerning the detection of early embryonic and zygotic mortality in oral cleft families is presented. It is suggested that probands from solitary pregnancies are the result of a higher liability to clefting which eliminated potential siblings prior to the conception of the proband. A positive association between the degree of liability to clefting and fetal mortality has already been established by the authors' previous work. In sibships of solitary probands, such liability is assumed to have caused early embryonic and zygotic mortality which eliminated potential siblings and recognizable fetal loss. This hypothesis can be tested by an examination of the sex-ratios in probands from solitary pregnancies and those from multiple pregnancies. For CL(P), a decrease in the proportion of males would be expected in probands from solitary pregnancies in comparison to those from multiple pregnancies. For CP, however, an increase in the proportion of males in solitary probands is expected in comparison to those from multiple pregnancies. This hypothesis is applied to 613 CL(P) probands and 317 CP probands from Indiana. Although the expected decrease (for CL(P)) and increase (for CP) in the proportion of males in solitary probands is not quite significant, the trends are in the expected directions. It is suggested that the hypothesis should be tested further with additional data on oral clefts and other similar anomalies.

Cleft Lip↗
PubMed1983

Stickler syndrome: a cephalometric study of the face.

A lateral roentgencephalometric study to compare the facial morphology of 21 affected and 18 normal members of 8 families with the Stickler syndrome (SS) was undertaken. The affected individuals exhibited two or more of the following four clinical symptoms: (a) flat midface, (b) cleft palate, (c) eye problems, and (d) arthropathy. The diagnostic facial features of the affected individuals as a group were found to be markedly shortened cranial base length, midfacial depth and height, maxillary depth, and mandibular depth, but significantly larger total and lower facial height dimensions. Facial morphology is highly characteristic for the Stickler syndrome. An application of two discriminant function equations (each based on four cephalometric measurements) to our data correctly identified 84.6 to 89.7% of the affected and normal SS family members. These discriminant function equations should be of considerable aid in the clinical diagnosis of the SS patient prior to the onset of symptoms.

Abnormalities, Multiple↗
PubMed1982

Lethal and mild hypophosphatasia in half-sibs.

This report concerns a family showing both the lethal and mild form of hypophosphatasia in half-sibs. In addition, several other paternal family members with the mild form are documented. The lethal form is characterized by extremely low to absent alkaline phosphatase activity in serum with hypomineralization of the skeleton, whereas mildly affected individuals have enzyme levels intermediate between normal and lethal states. On the basis of this pedigree and because the mildly affected individuals have both biochemical abnormalities and the clinical phenotype of premature tooth loss, we prefer to designate hypophosphatasia as a dominant trait affecting both osteogenesis and cementogenesis which has mild clinical expression in the heterozygote but lethality in the homozygote. This situation resembles the dominantly inherited enzymopathy acute intermittent porphyria.

Adult↗
PubMed1982

Radiographic hand abnormalities in fifteen cases of Crouzon syndrome.

Fifteen patients with Crouzon syndrome were evaluated for abnormalities of hand bone length via metacarpophalangeal pattern profile analysis. Data from this group were compared to that from a normal control sample. A discriminant function, utilizing Z scores based on the lengths of three hand bones, was derived and distinguished between the two samples at a rate of 88.3%. The discriminant variables selected in the function represented hand bones that are prominently involved in ACS type V and ACPS type II, syndromes that feature craniofacial abnormalities not unlike those in Crouzon syndrome. The possibility of a common developmental mechanism affecting the hand skeleton in all three of these different conditions is raised.

Craniofacial Dysostosis↗
PubMed1982

Fetal mortality associated with cleft lip and cleft palate.

Analysis of 1,516 pregnancies in sibships of probands with cleft lip with or without cleft palate [CL(P)], and 774 pregnancies in those of probands with isolated cleft palate (CP) indicated that fetal mortality significantly increases with liability to clefting. These data are compatible with the multifactorial two-threshold model, according to which a lower threshold level of liability results in a cleft formation whereas a higher level of liability causes a fetal death.

Cleft Lip↗
PubMed1981

A clinical, genetic, and ultrastructural study of snow-capped teeth: amelogenesis imperfecta, hypomaturation type.

Snow-capped teeth (SCT) is a rare form of amelogenesis imperfecta, hypomaturation type. It has been alluded to on numerous occasions but, to our knowledge, no pedigree or clinical-histopathologic data have been published. In this report, two families are described. Scanning electron microscopic (SEM) studies of unetched teeth from affected persons revealed numerous defects of the enamel surface. After etching with 10 percent hydrochloric acid for 21/2 minutes to remove the outer prismless layer of enamel, SEM features of the enamel prism were essentially identical to those of normal teeth. These findings suggest that the structural defect in SCT is confined to the outer prismless enamel layer and that the bulk of the enamel is normal. The genetic analysis supports the concept that SCT is inherited in an X-linked recessive fashion and not as an autosomal dominant trait, as previously reported.

Adolescent↗
PubMed1981

Cleft palate: a genetic and epidemiologic investigation.

An examination of kindred histories of 561 Danish probands who have non-syndromic CP has indicated that neither a multifactorial-threshold model nor a single major locus model is completely compatible with the data. This suggests etiologic heterogeneity for CP, which was tested with kindred data. As recommended by Smith (1976), at attempt to define partially this heterogeneity within the CP phenotype was undertaken by grouping and comparing the kindred data. It is both reasonable and heuristic to propose that CP,, as defined in this investigation, is composed of three groups: (1) Syndromic CP; (2) Familial CP, which appears to have an autosomal dominant component to its etiology, and (3) Non-familial CP which, by demonstrating an increasing frequency of CP and a maternal age effect, appears to be related to environmental factors which may cause CP or other malformations.

Abnormalities, Multiple↗