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Biomedical subjects

R L Summitt

Publications and source records attributed to R L Summitt.

At least 19 recordsLinked to original sources
PubMed1979

Duplication 6q syndrome.

Duplication (partial trisomy) of the long arm of chromosome 6 has been described in 5 children [Robertson et al, 1975, Chen et al, 1976, Clark, 1977]. We wish to report here an additional case due to a familial translocation in which the proband's karyotype is 46,XX,der(3),rcp(3;6)(p25;q21)mat. The phenotypes of the 6 children with duplication 6q are strikingly similar. Each child has duplication involving approximately the distal 1/3 to 1/2 of the long arm of chromosome 6. Distinctive features present in all 6 children include microcephaly, acrocephaly, prominent forehead, flat facial profile, depressed nasal bridge, flat malar areas, "carp" mouth, micrognathia and mental retardation. The phenotype of the duplication 6q syndrome is distinctive enough to be clinically recognizable.

Abnormalities, Multiple↗
PubMed1979

Disturbances of rapid-eye-movement sleep in 3 brothers with Pelizaeus-Merzbacher disease.

The electrophysiological features of 3 brothers with the classic form of Pelizaeus-Merzbacher disease (PMD) were studied. Two consecutive overnight polygraphic sleep recordings indicated a gross distortion of rapid-eye-movement (REM) sleep for all patients. A lower than normal percentage of REM sleep in these patients was consistent with their retarded intellectual development, which supports current thinking that REM sleep may be a sensitive index of brain function integrity. Non-rapid-eye-movement (NREM) sleep, in contrast to reported findings in 1 patient with PMD, was uniformly characterized by distinct stages in which the electroencephalograms contained frequent vertex waves and spindles. Tests of peripheral nerve conduction velocity, acoustic brainstem reflexes, and visual and auditory evoked potentials did not indicate any abnormalities, nor did electroencephalograms obtained during wakefulness. One patient did have epileptiform spikes and spike waves recorded during an all-night EEG, an unusual finding in a child with cerebral white matter disease.

Adolescent↗
PubMed1978

Genetically determined sex-reversal in 46,XY humans.

Evidence is presented for the existence of a gene, probably on the X chromosome, which prevents testis differentiation when present in 46,XY human embryos. Affected 46,XY women are not completely normal because of premature ovarian involution, as a result of which they have "streak gonads" similiar to those of 45,X women.

Disorders of Sex Development↗
PubMed1978

Minor chromosome variations and selected heteromorphisms in 200 unclassifiable mentally retarded patients and 200 normal controls.

Lymphocyte chromosome preparations from 200 mentally retarded children and 200 normal adult controls were analyzed by G-, Q-, and C-banding techniques for minor chromosome variations (G and Q) and selected heteromorphisms (G and C). Minor variations scored included inv(9), prominent or decreased short arms and/or satellites on acrocentric chromosomes, and 17 ph. C heteromorphisms analyzed included those involving 1qh, 9zh, and 16zh regions. Length variations of Yq were scored on G-banded karyo types. No significant differences in frequencies of scored minor variations or heteromorphisms were noted between the retarded and control populations.

Child↗
PubMed1978

The Dubowitz syndrome.

The Dubowitz syndrome is an autosomal recessive condition of intrauterine growth retardation, postnatal growth retardation, microcephaly, characteristic facial appearance, high-pitched hoarse voice, and borderline intelligence or mild mental retardation. Cleft palate may occur as well as hypospadias, cryptorchidism in affected males, and mild limb defects. The 13 cases reported in the European literature and eight personally examined patients are reviewed.

Abnormalities, Multiple↗
PubMed1978

Autosomal syndromes.

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Abnormalities, Multiple↗
PubMed1977

Delineation of Robertsonian translocations in man by means of chromosome banding.

Robertsonian translocations from thirteen unrelated individuals were studied by G, Q and C banding, and by autoradiography. Each of three D-D translocations involved chromosomes 13 and 14, all four D-G translocations involved chromosomes 14 and 21, and five of six G-G translocations involved two chromsomes 21 while the sixth involved 21 and 22. Two centromeres were noted in a single 21-21 translocation chromosome by C banding. Autoradiogrpahy was much less useful in identifying the chromosomes involved in the thirteen translocations. G and Q banding were consistently accurate.

Autoradiography↗
PubMed1977

A cytogenetic survey of 200 unclassifiable mentally retarded children with congenital anomalies and 200 normal controls.

A cytogenetic survey was carried out on 200 patients with mental retardation and multiple congenital anomalies, and on 200 normal adult controls. Patients with a known syndrome were excluded from the survey. Chromosome analyses were carried out on 'blind-coded' slides using the ASG banding technique as the routine stain. After the initial analyses (at least 15 cells per person) the slides were decoded, destained and reused for C and Q band polymorphism studies. Five major chromosome abnormalities were detected in the patient group during the survey. They included three patients with de novo, apparently balanced, reciprocal translocations, karyotypes 46,XY,rcp(3;16)(q21;p12); 46,XX,rcp(5;8)(p15;q22); and 46,XX,rcp(5;12)(p11;q24); one with karyotype 47,XX,+mar and one with karyotype 46,XX,der(13),t(13;?)(q34;?). One additional patient whose karyotype in lymphocytes was 46,XX,inv(9)(p11;q13) was found to have a mosaic karyotype 46,XX,inv(9)(p11;q13)/46,XX,inv(9) (p11;q13), der(12),t(12;?)p13;?) in cultured skin fibroblasts. None of the 200 controls had a major chromosome abnormality. From the combined results of this and previous surveys it is now apparent that about 6.2% of the unclassifiable mentally retarded patients with three or more congenital anomalies and about 0.7% of the controls reveal major chromosome abnormalities.

Abnormalities, Multiple↗
PubMed1977

Tissue limited mosaicism for unbalanced autosomal translocation in a child with congenital anomalies and mental retardation.

We studied a patient with a sporadic mental retardation/multiple congenital anomalies syndrome. Chromosome analysis showed a 46,XX, inv(9)(p 11;q13) karyotype in all lymphocytes. Fibroblasts from two separate skin biopsies revealed a mosaic karyotype. Some 22.5% of fibroblasts had a karyotype like that of the lymphocytes, while 77.5% of fibroblasts had a karyotype 46,XX,inv(9)(p11;q13),der(12),t(12;?)(P13;?). The data in this case emphasize the drawbacks of confining cytogenetic analysis to lymphocytes.

Abnormalities, Multiple↗
PubMed1977

Apparently balanced de novo translocations in patients with abnormal phenotypes: report of 6 cases.

Six patients have been ascertained because of abnormal phenotypes but with apparently balanced de novo translocations. Five of them were mentally retarded with multiple congenital anomalies. The sixth patient had normal mental development but revealed ambiguous genitalia and multiple congenital anomalies. No syndromal diagnosis was possible in any of the six cases. The appearance of apparently balanced reciprocal translocations in association with abnormal phenotype may be coincidental, or the two may be causally related. If the latter is true, the causal relationship may be based upon: 1) a submicroscopic chromosomal loss, 2) position effect, or 3) a mutation at the site of the break in one or both translocated chromosomes.

Abnormalities, Multiple↗