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Biomedical subjects

I T Thomas

Publications and source records attributed to I T Thomas.

30 records · Page 2Linked to original sources
PubMed1986

Isolated and syndromic cryptophthalmos.

The association between cryptophthalmos and multiple congenital malformations has been well documented over the last century. Numerous authors have described cases as the cryptophthalmos syndrome, but recently reports of cases without cryptophthalmos have led several authors to use the eponymic designation Fraser syndrome. We have seen seven cases of cryptophthalmos syndrome, including three sib pairs. All presented with cryptophthalmos and bilateral renal agenesis in addition to other characteristic associated malformations. A literature review showed 124 cases in which 27 demonstrated isolated cryptophthalmos, while 97 showed a pattern of multiple congenital malformations. We selected four major and eight minor criteria which enabled us to classify 86 of those cases as having cryptophthalmos syndrome with 11 remaining unclassified. Cryptophthalmos demonstrates equal sex distribution, occurrence in sibs, consanguinity in families with more than one affected child, and lack of vertical transmission--strongly suggesting autosomal recessive inheritance. Isolated cryptophthalmos or cryptophthalmos sequence was sporadic in 16 cases and familial in 11. The familial cases occurred in three families and demonstrated vertical transmission. The pathogenesis of this syndrome is unknown. There are similarities to animal models of maternal vitamin A deprivation and defects in programmed cell death. Cryptophthalmos syndrome should be considered in the differential diagnosis of cases with multiple congenital malformations, especially when they are associated with renal agenesis, even in the absence of cryptophthalmos.

Abnormalities, Multiple↗
PubMed1986

The effect of cobalt-chromium-molybdenum powder on collagen formation by fibroblasts in vitro.

Surgical implants frequently become surrounded by fibrous tissue. In order to investigate the mechanisms which cause this fibrosis, fibroblastic cells in culture were exposed to powders of cobalt-chromium-molybdenum alloy simulating the wear debris of metal-on-metal joint replacements. Collagen production during periods of up to 20 d was assayed by measurement of soluble and insoluble hydroxyproline. No stimulation of collagen production was seen with any of the concentrations of metal powder tested. It is therefore suggested that fibrosis around joint replacements is not caused by direct stimulation of fibroblasts by metallic wear debris.

Animals↗
PubMed1986

The in vitro toxicity of cobalt-chrome-molybdenum alloy and its constituent metals.

Cobalt-chrome-molybdenum alloys are widely used in orthopaedic implants. Although they are relatively well tolerated, complications (including loosening and tissue necrosis) still occur and sometimes appear to be due to incomplete biocompatibility of the alloy. To investigate the local effect of the alloy on cells derived from the musculo-skeletal system, primary lines of fibroblastic cells from newborn rats were exposed to powders of cobalt-chrome-molybdenum alloy and its main constituents cobalt, chromium nickel and molybdenum. The toxicity of the metals was determined by counts of total cell number and of abnormal cells at intervals from 2 to 12 d. The alloy was much less toxic than cobalt or nickel and the pattern of toxicity was different for each metal. The results emphasize the difficulty of devising a single tissue culture test of toxicity which will measure the toxicity of any potential implant material.

Animals↗
PubMed1975

Defective neutrophil chemotaxis with variant ichthyosis, hyperimmunoglobulinemia E, and recurrent infections.

Host defense mechanisms were evaluated in a 4-1/2-year-old boy with recurrent pyogenic infections and a unique hyperkeratotic skin disorder. The patient's neutrophils were consistently defective in chemotactic responsiveness but had normal NBT reduction, glucose oxidation, and iodination. Serum concentrations of IgE were markedly elevated and the secondary antibody response was abnormal. No T-cell dysfunction was detected. These findings suggest a relationship between this patient and patients with other syndromes associated with recurrent infections, cutaneous disease, defective chemotaxis, immunodeficiency, and hyperimmunoglobulinemia E.

Chemotaxis↗
PubMedDate not supplied

Teratogens and teratogenesis: general principles of clinical teratology.

Numerous factors hinder our ability to recognize fully human teratogens. Among these are the limitations of animal and epidemiologic studies, the lack of understanding of the mechanisms of action of most teratogens, and the variability in expression of the clinical manifestation. Dose and timing of exposure, interactions with other environmental agents, and host susceptibility influence this variable expressivity. Recent studies suggest the genetic constitution of the mother and the fetus play a central role in the teratogenic response. Techniques currently being developed may help in a near future to identify susceptible individuals and to prevent specific types of drug-induced birth defects.

Abnormalities, Drug-Induced↗
PubMedDate not supplied

The cardiovascular manifestations of genetic disorders of collagen metabolism.

Current research in the biochemistry and molecular genetics of collagen metabolism has produced a sophisticated level of understanding of the mechanisms involved in the pathogenesis of a number of inherited diseases of connective tissue. Nowhere is this better exemplified than in the cardiovascular disorders associated with certain genetic disorders of collagen metabolism. For instance, the life-threatening vascular complications of Ehlers-Danlos syndrome IV, the Sack-Barabas type, appears to be related to a number of defects in the production of Type III procollagen. The large size of the collagen genes and the complexity of the biochemistry of collagen have not made research a simple task. Nevertheless, the location of certain genes is now known with a reasonable degree of accuracy and a few have been cloned in their entirety. The future investigation of these genetic mutations holds great excitement for those engaged in research in this fascinating field.

Cardiovascular Diseases↗
PubMedDate not supplied

The heart in selected congenital malformations. A lesson in pathogenetic relationships.

The application of new knowledge on the pathogenesis of congenital heart defects has increased our understanding of associated, non-cardiac malformations seen in certain syndromes. Defects in the proliferation and migration of neural crest cells are thought to contribute to conotruncal defects. These are seen in association with conditions such as DiGeorge syndrome. CHARGE association, hemifacial microsomia, and Shprintzen syndrome. They also form part of the isotretinoin and thalidomide embryopathies. Their association with conotruncal defects suggests that abnormal migration of neural crest cells may play a role in the pathogenesis of these syndromes.

Abnormalities, Multiple↗