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Biomedical subjects

R D Clark

Publications and source records attributed to R D Clark.

At least 55 records · Page 3Linked to original sources
PubMed1990

Penile agenesis: a fatal variation of an uncommon lesion.

Two male neonates (46XY karyotype) were born with a triad of penile agenesis associated with imperforate anus and complete absence of the median raphe. Both patients died of renal dysplasia and secondary pulmonary hypoplasia shortly after birth. This triad appears to be secondary to a lack of caudal mesoderm migration during month 1 of gestation, leading to severe developmental defects in the caudal axis. In all reported cases to date this triad of findings has been incompatible with extrauterine life.

Abnormalities, Multiple↗
PubMed1990

Affinity of 2-(tetrahydroisoquinolin-2-ylmethyl)- and 2-(isoindolin-2-ylmethyl)imidazolines for alpha-adrenoceptors. Differential affinity of imidazolines for the [3H]idazoxan-labeled alpha 2-adrenoceptor vs the [3H]yohimbine-labeled site.

A series of 2-(tetrahydroisoquinolin-2-ylmethyl)- and 2-(isoindolin-2-ylmethyl)imidazolines were prepared and tested for alpha 1- and alpha 2-adrenoceptor affinity with radioligand binding. Several compounds, 5-fluoro-(5h), 5-chloro-(5j), 5,8-dimethoxy- (5r), and 5,8-dimethoxy- (5r),1-methyl- (5s) 2-(tetrahydroisoquinolin-2- ylmethyl)imidazoline, were found to be selective alpha 2-adrenoceptor ligands on the basis of displacement of [3H]yohimbine from rat cerebral cortical membranes. One compound, 2-[(8-chloro tetrahydroisoquinolin-2-yl)methyl]imidazoline (5m), showed a 36-fold difference in affinity for the [3H]idazoxan-labeled alpha 2-adrenoceptor relative to the [3H]yohimbine-labeled site, which may be evidence for alpha 2-adrenoceptor subtypes.

Animals↗
PubMed1990

1,9-Alkano-bridged 2,3,4,5-tetrahydro-1H-3-benzazepines with affinity for the alpha 2-adrenoceptor and the 5-HT1A receptor.

A number of 1,9-alkano-bridged 2,3,4,5-tetrahydro-1H-3-benzazepines were prepared and evaluated for 5-HT1A receptor and alpha 2-adrenoceptor affinity by using radioligand receptor binding techniques. Several compounds displayed 5-HT1A receptor affinity comparable to, or greater than, the known 5-HT1A ligand buspirone. The highest affinity 5-HT1A receptor ligands were N-alkyl-, N-allyl-5-chloro-, and 5-methoxy-1,2,3,4,8,9,10,10a-octahydronaphth[1,8-cd]azapines (4c, 4m, 4n), which had pKi values of 7.9-8.1. The S enantiomer of 4c had a higher affinity for the 5-HT1A receptor than the corresponding R isomer (pKi of 8.2 for (S)-4c vs 7.7 for (R)-4c). These compounds had a relatively low affinity for the alpha 2-adrenoceptor (pKi of 7 or less). On the other hand, the closely related 5-chloro-2-methyl-2,3,4,8,9,9a-hexahydro-1H-indeno[1,7-cd]azepine (3b) had high affinity for both the alpha 2-adrenoceptor (pKi = 8.1) and 5-HT1A receptor (pKi = 7.6). These results indicate that the two receptors may share common recognition sites.

Animals↗
PubMed1990

Holoprosencephaly and polydactyly: a possible expression of the hydrolethalus syndrome.

We report two fetuses with hydrocephalus, features of holoprosencephaly, and postaxial polydactyly born to a consanguineous Mexican-American couple. The phenotype is consistent with the hydrolethalus syndrome, although holoprosencephaly has not previously been seen in this condition. We believe other similar cases with a trisomy 13 phenotype but normal chromosomes may also have the hydrolethalus syndrome.

Abnormalities, Multiple↗
PubMed1990

The phenotype of 45,X/46,XY mosaicism: an analysis of 92 prenatally diagnosed cases.

We undertook an international survey of prenatally diagnosed 45,X/46,XY mosaicism to ascertain the phenotypic spectrum of this condition. Ninety-two cases were obtained by means of a questionnaire sent to over 730 cytogenetic laboratories. Seventy-six cases (75 males and 1 female) had physical examinations after delivery or termination of pregnancy. Among these, there were four significant genital anomalies: three hypospadias and one female with clitoromegaly. Gonadal histology was abnormal in three (27%) of 11 cases, all of whom had normal male external genitalia. Other anomalies were noted in five cases: one cystic hygroma in a male, two cardiac anomalies, one spina bifida with multiple other defects, and one intrauterine growth retardation. There was no relationship between the percent mosaicism and the presence or degree of abnormalities. We conclude that 95% of 45,X/46,XY fetuses will have normal male genitalia, although there will also be a significant risk (27%) for abnormal gonadal histology. Long-term follow-up studies of prenatally diagnosed cases of 45,X/46,XY mosaicism are needed to study, without ascertainment bias, stature, pubertal development, tumor risk, and fertility.

Female↗
PubMed1989

Expanded phenotype and ethnicity in Setleis syndrome.

Setleis syndrome, an autosomal recessive disorder characterized by "coarse" face, temporal cutis aplasia, double upper eyelashes, absent lower eyelashes, chronic conjunctivitis, and prominent thick lips, was reported previously in 8 Puerto Rican children. We report on 3 unrelated children (one mentally retarded) with Setleis syndrome who are not of Puerto Rican descent. Two of our patients had imperforate anus, which has not previously been reported. The evolution of the phenotype over time is illustrated.

Abnormalities, Multiple↗
PubMed1989

Apparent Fryns syndrome in a boy with a tandem duplication of 1q24-31.2.

We report on a newborn boy with manifestations of Fryns syndrome who also had a mosaic tandem duplication of chromosome 1q24-31.2. The child had a diaphragmatic hernia, cleft palate, hypoplastic and absent digits, micrognathia, long philtrum, thin upper lip, and anteverted nose. The baby died at age 5 hours. An autopsy demonstrated absent right middle lobe of the lung, bilateral renal cysts, hypoplastic renal arteries, urethral stricture, hydronephrosis, and aortic coarctation. The brain was abnormal with absent olfactory tracts and cerebral and cerebellar heterotopias. This is the first report of a chromosome anomaly in a child with Fryns phenotype. It suggests that the gene for Fryns syndrome may be located in the region 1q24-31.2.

Abnormalities, Multiple↗
PubMed1989

Conceiving a fetus for bone marrow donation: an ethical problem in prenatal diagnosis.

We present a family who sought prenatal diagnosis in order to bear a healthy child to serve as an HLA-identical bone marrow donor for their son affected with Wiskott-Aldrich syndrome. They intended to abort HLA-incompatible fetuses who would have been unsuitable bone marrow donors. This case led us to conclude that prenatal diagnosis should not be used to benefit a third party or facilitate the conception or abortion of a fetus for the purpose of generating an organ for transplantation. The limits of parental autonomy and physician responsibility are discussed.

Aborted Fetus↗
PubMed1989

Autosomal dominant transmission of isolated congenital vertical talus.

We report vertical transmission of isolated congenital vertical talus through three generations of a Honduran family. Five of nine affected family members were examined and the diagnosis was confirmed radiographically. There was incomplete penetrance in one clinically unaffected woman with two affected children. Bilateral and unilateral involvement was seen with a wide range of severity. Based on this family and on cases reviewed from the literature, we propose that isolated congenital vertical talus can be inherited as an autosomal dominant trait with variable expression and incomplete penetrance.

Child↗
PubMed1988

A combinatorial method for grouping cases with multiple malformations.

A combinatorial method is described for grouping cases with multiple malformations for the purpose of identifying previously undescribed syndromes. This method includes ways of carrying out 'tight' or 'loose' grouping, of allowing for variability of reporting of physical features by different observers, and of minimising the number of 'spurious' groups. Evaluation using a test data set of known dysmorphic syndromes showed that the method provides a feasible and useful means of grouping undiagnosed cases.

Abnormalities, Multiple↗
PubMed1987

Proteus syndrome: an expanded phenotype.

We report on 11 new cases of Proteus syndrome to illustrate the broad range of the phenotype in this hamartomatous dysplasia. The cardinal manifestations of this sporadic disorder are hemihypertrophy, macrodactyly, exostoses, scoliosis, cavernous hemangiomas, lipomas, linear sebaceous nevi, and deeply rugated soles of the feet. Intelligence is usually normal. The differential diagnosis includes Klippel-Trenaunay-Weber and partial lipodystrophy syndromes.

Adolescent↗