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Biomedical subjects

R O Howard

Publications and source records attributed to R O Howard.

At least 19 recordsLinked to original sources
PubMed1997

Functional MR imaging during odor stimulation: preliminary data.

PURPOSE: To determine the locations and extent of activation in areas of the brain at functional magnetic resonance (MR) imaging with olfactory stimulation and to determine whether accommodation or amplification of brain activation occurs with sequential olfactory stimulation. MATERIALS AND METHODS: Five adult men with normal senses of smell underwent multisection, gradient-echo, echo-planar imaging according to a blood-oxygen-level-dependent experimental paradigm. Odorants that nearly exclusively stimulate the olfactory system and odorants that stimulate the olfactory and trigeminal nerves were compared by using repetitive imaging procedures. RESULTS: Activation with olfactory nerve-mediated odorants was demonstrated in the orbitofrontal cortex (Brodmann area 11) with a right-sided predominance. Mild cerebellar stimulation was also observed. With repeated testing, overall activation with olfactory nerve-mediated odorants declined. Odorants that also stimulated the trigeminal nerve produced additional cingulate, temporal, cerebellar, and occipital activation. Activation with combined trigeminal and olfactory system odors increased more than sixfold with repeated testing. CONCLUSION: Olfactory nerve-mediated and combined olfactory and trigeminal nerve-mediated odorants activate different regions of the brain. Orbitofrontal stimulation spreads to all parts of the brain when a trigeminal component is added. Habituation (deactivation) occurs with repeated testing of olfactory nerve-mediated odorants, while, paradoxically, activation increases with repeated exposure to odors that also stimulate the trigeminal nerve.

Adult↗
PubMed1996

Multiple changes in oncogenes and tumor suppressor genes in human retinoblastoma.

PURPOSE: To present data to support the hypothesis that human retinoblastoma tumors form by a multistep process. METHODS: Survey of the karyotype of 90 human retinoblastomas, with emphasis on changes in chromosomal regions known to contain oncogenes and tumor suppressor genes. CONCLUSION: The data support the hypothesis that retinoblastoma occurs after multiple and often varied steps, similar to other human malignancies.

Chromosome Banding↗
PubMed1981

Unusual mosaicism of de novo structural abnormalities and ocular anomalies in a male with 13 trisomy syndrome.

A body with the 13 trisomy syndrome was found to have a unique form of mosaicism in which each of the two cell lines had different structural rearrangements. The predominant cell line was partially trisomic for the distal portion of the long arm of chromosome 13, while the minor cell line was trisomic for all of the long arm of 13. The patient is also unusual because he had congenital glaucoma and was still alive at 10 years.

Child↗
PubMed1981

Classification of chromosomal eye syndromes.

Human chromosome disease arises from a change in the number or structure of one or more chromosomes. The multiple genes represented in the duplicated or deleted chromosomes are not usually defective and any systemic abnormalities can be attributed to a change in gene dosage. Banding techniques are now commonly used to identify each chromosome and the specific chromosome duplication and deletion and structural rearrangements can now be identified unambiguously. Most ocular abnormalities have occurred in patients with chromosomal defects. Major ocular abnormalities, such as anophthalmia, cyclopia, retinoblastoma, microphthalmia, corneal opacities, coloboma, cataracts, intraocular cartilage, retinal dysplasia and absent optic nerves; and, minor abnormalities, such as ptosis, abnormal eyelid fissures, and Brushfield spots are present in individuals with abnormal chromosomes. The chromosome errors are usually present in all somatic tissues. consequently, multiple tissue abnormalities would be expected in most patients with chromosome abnormalities. Mental retardation is very common in those patients with abnormalities of autosomes. Therefore, it is unlikely that an isolated single clinical or histopathological ocular abnormality will be the result of a chromosome error. However, if the individual has multiple systemic abnormalities, then a chromosome error can be considered reasonably. Any chromosome disorder can be identified correctly by an appropriate banding chromosome determination on the affected individuals. With the possible exception of the association of 13q 14- and retinoblastoma, there does not appear to be any pathognomonic ocular abnormalities that occur in individuals with chromosome errors.

Adolescent↗
PubMed1980

Retinal anomalies in trisomy 18.

The eyes of three patients with trisomy 18, the second most common human autosomal trisomy, were examined histopathologically. In the posterior retina transmission and scanning electron microscopic examinations reveal cytological details characteristic of immature neural retinas. We are able to confirm the report that the posterior retinal pigment epithelium in trisomy 18 has a paucity of mature melanosomes and, in fact, resembles human albino retinal pigment epithelium. The asociation of hypopigmentation and retinal immaturity suggests pigmentation plays a role in the control of the maturation of the neural retina.

Chromosomes, Human, 16-18↗
PubMed1979

Unilateral cryptophthalmia.

Two patients had the variable clinical features of unilateral cryptophthalmia. A 5-month-old boy had isolated unilateral cryptophthalmia: a small boney orbit, deformed optic canal, and a small amorphous mass with no normal intraocular tissue representing the globe. No extraocular muscles or optic nerve were identified by B-scan ultrasound or by computed axial tomography x-ray techniques. The second patient, a 13-year-old girl, had unilateral cryptophthalmia, and numerous systemic abnormalities including a head circumference less than the third percentile, severe mental retardation, hypoplasia of the left side of the head, and a left facial cleft deformity. She also had contractures of hips, knees and ankles, and bilateral spasticity and jerky movements. The left boney orbit was contracted and deformed and contained a small amorphous tissue with no ocular detail, as revealed by B-scan and computed tomography scan.

Abnormalities, Multiple↗
PubMed1979

Premature cataracts associated with generalized lentigo.

Generalized lentigo (leopard syndrome) is an autosomal dominant trait characterized by lentigo, sensorineural deafness, retarded growth (below 25%), ocular hypertelorism, mandibular prognathism, pectus carinatum or excavatum, dorsal kyphosis, winging of the scapulae, valvular pulmonary artery stenosis, electrocardiographic conduction defects, and genitourinary defects. Ocular evaluations of patients with generalized lentigo have revealed the appearance of multiple small white punctate and comma-shaped opacities in the cortex and nuclci of the lenses of affected patients. On the basis of age of the patients examined, it would seem that the corneal opacities first appear in the third decade. Although the opacities may be extensive, the lens opacities do not appear to impair visual function until approximately twenty years after they first appear.

Adolescent↗
PubMed1978

Ophthalmic features of chromosome deletion 4p- (Wolf-Hirschhorn syndrome).

By using the Giemsa banding technique we identified three patients with chromosome deletion 4p-. All had anterior segment anomalies, exotropia, blepharoptosis, antimongoloid palpebral fissures, hypertelorism, and disk abnormalities. One patient (Case 1) had Rieger's anomaly. Some clinical features in patients with 4p- are similar to those in patients with chromosome deletion 5p-, cri-du-chat syndrome, although 4p- individuals do not have the distinctive cry. The ocular features which distinguish 4p- from other deletions include normal tearing, some degree of blepharoptosis, and the preponderance of anterior segment signs.

Abnormalities, Multiple↗
PubMed1978

Human retinal dysplasia.

We studied the ultrastructure of the four types of dysplastic rosettes and compared them with retinoblastoma rosettes. Dysplastic rosettes have morphologic characteristics intermediate between the normal photoreceptor layer and retino-blastoma rosettes; Müller cells contribute to the formation of dysplastic but not neoplastic rosettes. Abnormality in the relationship between the retina and the retinal pigment epithelium is frequent in cases with spontaneously occurring retinal dsyplasia and is consistent with previous observations that the retinal pigment epithelium influences the development of retinal morphology and function. We believe the normal developmental sequence of cell death and disappearance of necrotic cells may have gone awry in retinal dysplasia.

Abnormalities, Multiple↗
PubMed1977

Ocular findings in triploidy.

We studied the abnormal ocular and systemic findings in one case of true triploidy and two cases of triploid mosaicism. A liveborn triploid child 69,XXY, had abnormalities including cebocephaly, a single midline nostril, incomplete cleft palate, transverse palmar creases, partial syndactyly, and ambiguous genitalia. Ocular abnormalities included hypotelorism, blepharophimosis, microcornia, iris coloboma, cataract, persistent hyaloid vasculature, retinal dysplasia, and optic atrophy. A 16-year-old girl with triploid mosaicism had congenital left facial and body hemiatrophy, both growth and mental retardation, left-sided grand mal seizures, incontinentia pigmenti of both legs, partial syndactyly, and generalized weakness. Results of her ocular examination were within normal limits. A 13-year-old boy with triploid mosaicism exhibited both growth and mental retardation, truncal obesity, and required a brace to support his back. Ocular findings included synophrys, bilateral blepharoptosis, and abnormal results of Schirmer tear test. Studies indicate a wide spectrum of ocular and systemic abnormalities occur that are presumably associated with the chromosome error.

Abnormalities, Multiple↗
PubMed1977

Chromosomal abnormalities associated with cyclopia and synophthalmia.

At the present time, essentially all known facts concerning cyclopia are consistent with some chromosomal disease, including clinical features of the pregnancy (fetal wastage, prematurity, intrauterine growth retardation, maternal age factor, complications of pregnancy), the generalized developmental abnormalities, specific ocular dysgenesis, by the high incidence of chromosomal abnormality already demonstrated, and the possibility of error in those cases of cyclopia with normal chromosomes. Even if chromosomal aberrations represent only one group of several different etiologic factors leading to cyclopia, at the present time chromosomal errors would seem to be the most common cause of cyclopia now recognized. Further studies will establish or disprove a chromosomal error in those instances which are now considered to be the result of an environmental factor alone or those with apparent familial patterns of inheritance. This apparent diverse origin of cyclopia can be clarified if future cyclopic specimens are carefully investigated. The evaluation should include a careful gross and microscopic examination of all organs, including the eye, and chromosome banding studies of all organs, including the eye, and chromosome banding studies of at least two cyclopic tissues. Then the presence or absence of multiple causative factors can be better evaluated.

Abnormalities, Multiple↗
PubMed1976

Russell-Silver dwarfism.

A case of Russell-Silver dwarfism is described with intrauterine dwarfism, craniofacial disproportion, congenital asymmetry of the body, triangular face, retro- and micrognathia and short incurved fifth fingers. This child has numerous ocular abnormalities including microphthalmia, tunica vasculosa lentis, chronic angle closure glaucoma and retinal degeneration with detachment. The glaucoma was controlled with miotic therapy following an iridectomy.

Cataract↗