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G A Machin

Publications and source records attributed to G A Machin.

At least 37 records · Page 2Linked to original sources
PubMed1996

Anatomy of the circle of Willis in three cases of human fetal synophthalmic holoprosencephaly.

In three human fetuses with synophthalmic holoprosencephaly (8, 14, 23 weeks post conceptionem) the circle of Willis was studied using serial histological sections and computer aided three dimensional reconstruction methods. This structure was abnormal in all cases. In two cases the anterior communicating arteries were absent. In all cases the anterior cerebral arteries could not be found. One case showed an incomplete circle with no posterior communicating artery. The results indicate that the malformation of the circle of Willis reflects the malformation of the brain.

Anencephaly↗
PubMed1994

Mirror-image dental fusion and discordance in monozygotic twins.

A pair of monozygotic twins had similar but not identical dental anomalies. One twin had fusion of deciduous mandibular lateral incisor and canine on the left, with normal dentition on the right; the co-twin had right mandibular incisor/canine fusion, with aplasia of the lateral incisor on the left. These findings are discussed in the context of the related phenomena of situs inversus, mirror-imaging in twins, and gradients of severity of anomalies in the four copies of the mandibular developmental dental field.

Anodontia↗
PubMed1994

The enigma of cephalogenesis.

The cascade of developmental events in cephalogenesis is initiated by specific genes being transcribed and translated into polypeptides and proteins that form the structural basis of cells and tissues. These become differentiated into the complex organs of the craniofacies by the actions of signalling transducers, growth factors, and morphogens. Defects of development may be traced back through this sequence to determine the specific etiologic factors responsible for dysmorphogenesis. Molecular biology and embryology are becoming increasingly significant for clinicians.

Embryonic and Fetal Development↗
PubMed1993

Conjoined twins: implications for blastogenesis.

It is difficult to draw sweeping general conclusions about the blastogenesis of CT, principally because so few thoroughly studied cases are reported. It is to be hoped that methods such as painstaking gross or electronic dissection will increase the number of well-documented cases. Nevertheless, the following conclusions can be proposed: 1. Most CT can be classified into a few main anatomic types (or paradigms), and there are also rare transitional types that show gradation between the main types. 2. Most CT have two full notochordal axes (Fig. 5); the ventral organs induced along these axes may be severely disorientated, malformed, or aplastic in the process of being arranged within one body. Reported anatomic types of CT represent those notochordal arrangements that are compatible with reasonably complete embryogenesis. New ventro-lateral axes are formed in many types of CT because of space constriction in the ventral zones. The new structures represent areas of "mutual recognition and organization" rather than "fusion" (Fig. 17). 3. Orientations of the pairs of axes in the embryonic disc can be deduced from the resulting anatomy. Except for dicephalus, the axes are not side by side. Notochords are usually "end-on" or ventro-ventral in orientation (Fig. 5). 4. A single gastrulation event or only partial duplicated gastrulation event seems to occur in dicephalics, despite a full double notochord. 5. The anatomy of diprosopus requires further clarification, particularly in cases with complete crania rather than anencephaly-equivalent. Diprosopus CT offer the best opportunity to study the effects of true forking of the notochord, if this actually occurs. 6. In cephalothoracopagus, thoracopagus, and ischiopagus, remarkably complete new body forms are constructed at right angles to the notochordal axes. The extent of expression of viscera in these types depends on the degree of noncongruity of their ventro-ventral axes (Figs. 4, 11, 15b). 7. Some organs and tissues fail to develop (interaction aplasia) because of conflicting migrational pathways or abnormal concentrations of morphogens in and around the neoaxes. 8. Where the cardiovascular system is discordantly expressed in dicephalus and thoracopagus twins, the right heart is more severely malformed, depending on the degree of interaction of the two embryonic septa transversa. 9. The septum transversum provides mesenchymal components to the heawrt and liver; the epithelial components (derived fro the foregut[s]) may vary in number from the number of mesenchymal septa transversa contributing to the liver of the CT embryo.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Bone marrow transplantation for Niemann-Pick type IA disease.

Bone marrow transplantation has been undertaken with encouraging results as therapy for a wide variety of lysosomal storage diseases. We report a case of Niemann-Pick disease Type IA in which, despite the presence of only mild hypotonia with depressed reflexes, the clinical course of the disease appeared to be only slightly modified by this procedure, which was performed at the earliest practical opportunity. The patient was diagnosed early when asymptomatic, because of a family history of an affected sibling who died at 14 months. He received a bone marrow transplant from an HLA-identical, MLC non-reactive sibling donor, whose leukocyte sphingomyelinase activity was in the homozygote normal range. There was adequate engraftment as evidenced by persistently normal leukocyte sphingomyelinase activities, and there was no evidence of graft-versus-host disease. Visceral storage and neurological impairment were less rapidly progressive than in his untreated sibling but he eventually died at 30 months. Autopsy confirmed that this was essentially due to the effects of the underlying Niemann-Pick disease. We conclude that despite some success in other neurovisceral lysosomal storage disorders, bone marrow transplantation is not likely to be an adequate treatment for Niemann-Pick disease Type IA.

Bone Marrow Transplantation↗
PubMed1992

Germline intronic and exonic mutations in the Wilms' tumour gene (WT1) affecting urogenital development.

Denys-Drash syndrome is a rare human developmental disorder affecting the urogenital system and leading to renal failure, intersex disorders and Wilms' tumour. In this report, four individuals with this syndrome are described carrying germline point mutations in the Wilms' tumour suppressor gene, WT1. Three of these mutations were in the zinc finger domains of WT1. The fourth occurred within intron 9, preventing splicing at one of the alternatively chosen splice donor sites of exon 9 when assayed in vitro. These results provide genetic evidence for distinct functional roles of the WT1 isoforms in urogenital development.

Alternative Splicing↗