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Biomedical subjects

G A Machin

Publications and source records attributed to G A Machin.

At least 55 records · Page 3Linked to original sources
PubMed1991

Fiducial points for three-dimensional computer-assisted reconstruction of serial light microscopic sections of umbilical cord.

Fascicles of human sural (peripheral sensory) nerve were used as external fiducial points (FP) for accurate registration of serial light microscopic sections in three-dimensional reconstruction of human umbilical cord. This paper describes a method for embedding the FPs within the paraffin wax block simultaneously with the specimen to be sectioned. Using a new design of embedding box, the FPs are embedded close to the specimen and are transferred to the slides as part of the tissue sections. Three to four FPs were used to align and scale the serial tissue sections for digitization and computerized reconstruction, using a commercially available software program on IBM-compatible 80386 hardware. A three-dimensional solid surface graphic model of a segment of human umbilical cord was generated.

Histological Techniques↗
PubMed1990

Definitive methods of zygosity determination in twins: relevance to problems in the biology of twinning.

Many studies of embryogenesis and fate of twin pregnancies are invalidated because zygosity is not determined definitively, or is assumed on the basis of inadequate criteria. This paper briefly reviews methods of zygosity determination. It reports published results and a new series of twins in which zygosity was determined by DNA fingerprinting. Implications for methods of prenatal diagnosis of zygosity are discussed in the context of the occasional need for intervention in twin transfusion syndrome or in twins discordant for major malformations. Definitive zygosity and placental anatomy (number of chorions and amnions) is discussed as the firm substrate for studies of normal and abnormal twin development.

British Columbia↗
PubMed1989

Microscopic study of holoprosencephalic facial anomalies in trisomy 13 fetuses.

The cerebral and facial anatomy of four trisomy 13 fetuses was studied in order to delineate the varying degrees of expression of severity of holoprosencephaly. Fetal heads were serially sectioned and analyzed microscopically in the horizontal plane. Examples of cyclopia, cebocephaly, and a proposed new category, premaxillary dysgenesis, were studied. The last category represents the least severe end of the facial spectrum of holoprosencephaly in this series. In this condition, there are deficiencies or clefts within the premaxilla, in contrast to the usual site of clefting between the maxilla and the premaxilla. There is asymmetry of the defects in the anterior midface of all four cases.

Abnormalities, Multiple↗
PubMed1989

Anatomic findings in dicephalic conjoined twins: implications for morphogenesis.

The morphogenesis of conjoined twins is incompletely understood. We therefore conducted a postmortem study of dicephalus dibrachii dipus conjoined twins. The twins were born without pertinent history or prenatal diagnosis at 38 weeks and lived for several hours. External genitalia were female and partly duplicated; a caudal appendage was present in the thoracolumbar region. The heart and liver were shared and exhibited major abnormalities in configuration. Four lungs, three kidneys and adrenal glands, and two spleens were identified; biliary and upper gastrointestinal tracts appeared as mirror images. From these findings, we postulate three major sets of consequences arising from the anatomical disposition of the twin notochords ("paleoaxes"). 1) The degree of convergence/divergence of craniocaudal paleoaxes is variable. Convergences are maximal in the upper thoracic and sacral regions, where duplication of organs in minimal because of interaction aplasia. 2) In the horizontal plane, paleoaxes are sufficiently divergent to produce a degree of twin expression posteriorly, whereas anteriorly they converge to form a single, anterior, midline "neoaxis." Interposed between these zones of paleoaxial and neoaxial expression are areas of variable interaction aplasia. 3) The left twin was in situs solitus; the right twin was in situs inversus in a manner resembling polysplenia.

Abnormalities, Multiple↗
PubMed1989

Maternal malignant melanoma with placental metastasis: a case report with literature review.

Histologic detection of micrometastatic melanoma in the placenta led to the clinical diagnosis in the mother. Metastases were present in the intervillous space and in villous stroma. The infant has survived and has no evidence of disease at one year of age. The mother died of metastatic disease 6 months post-partum. Literature review shows that only 25% of infants with placental metastatic melanoma succumb to the disease. In a review series of 16 cases, there are some maternal clinical factors which seem to have some bearing on the likelihood of fetal metastasis and death from disease. Features that are associated with an unfavorable fetal/infant prognosis are: maternal age less than 30 years, primiparity, leg primary site, disease onset greater than 3 years prior to pregnancy, node-1 metastatic status prior to pregnancy, M4 status in third trimester, birth at greater than 36 weeks' gestation, male sex. Extent of penetration of metastases into the villi does not have prognostic significance.

Adult↗
PubMed1989

Pulmonary thromboembolism from a large hemangioma in a 4-week-old infant.

A female infant with an extensive congenital hemangioma of the left knee region was treated medically for consumption coagulopathy; the hemangioma began to shrink, the coagulopathy improved, and the infant was clinically well when she died suddenly at the age of 4 weeks. The cause of death was a saddle pulmonary thromboembolus which had originated in the hemangioma. This is the first documented case of fatal thromboembolism complicating a conservatively managed extensive neonatal hemangioma. Causes of neonatal thromboembolism are reviewed.

Dexamethasone↗
PubMed1988

Intraabdominal testis with yolk sac tumor in a 2-year-old child.

A case of a large yolk sac tumor in an undescended testicle in a 2-year-old child is presented. No such similar finding has been reported in a young child. Despite the large size of the primary tumor, the high level of serum alpha-fetoprotein and the relatively late clinical presentation, this was a stage I lesion, and the child responded to surgical resection of the tumor and chemotherapy.

Child, Preschool↗
PubMed1987

Autopsy findings in two adult siblings with Coffin-Lowry syndrome.

We describe the major autopsy findings in two adult sibs of the original pedigree of Lowry et al [Am J Dis Child 121:496-500, 1971]. These results support the idea that Coffin-Lowry syndrome is a systemic connective tissue disorder. Visceral neuropathy was also noted as the basis of extensive intestinal diverticular disease.

Abnormalities, Multiple↗
PubMed1987

Fetus with asymmetric parietal encephalocele, and hydrops secondary to laryngeal atresia.

We describe a fetus with an asymmetric, nonmidline, parietal encephalocele that appeared to result from "expulsion" through the center of the membranous bone; the fetus also had laryngeal atresia, which caused pulmonary overdistension (fetal Valsalva maneuver) with consequent hydrops fetalis. A common cause and clear pathogenetic relationship between these anomalies is not apparent.

Abnormalities, Multiple↗
PubMed1987

Acute second trimester EPH (edema/proteinuria/hypertension) gestosis as an indicator of fetal anomaly.

EPH gestosis in the second trimester suggests the likelihood of a number of fetal anomalies; the status of the fetus and risk to mother are such that spontaneous delivery or hysterotomy is usually the outcome, often without a full prenatal investigation. The types of fetal disorders encountered in this clinical setting are listed. Effects of abnormal endocrine environment as well as primary fetal malformations are distinguishable in these fetuses.

Abnormalities, Multiple↗
PubMed1987

Microscopic study of midline determinants in janiceps twins.

The earliest hitherto recorded developmental stage of human cephalothoracopagus (janiceps) twins, at 8 weeks of conceptional age, is described macroscopically and microscopically. The nearly perfect disymmetrical configuration of the 2 faces was compared with previously reported cases, and horizontal sectioning of the entire conceptus allowed detailed histologic description of the internal orientation of most organs and systems. The concept of conflicting facial and vertebral axes was explored to account for shared cerebral, facial, pharyngeal, and esophageal structures, and for aplasia of the pituitary and thymus glands and of the teeth. Critical points of changing axial orientation were identified at the mesencephalon, the Rathke pouch and third branchial arch, and with the hepato-cardio-respiratory complex split between the 2 axes. The caudal components conformed with previously reported cases.

Abdomen↗
PubMed1987

Holoprosencephalic synophthalmia (cyclopia) in an 8 week fetus.

Histopathological examination of an 8-week-old human cyclopic fetus revealed holoprosencephaly, synophthalmia, and malformed midfacial features. The telencephalon was undivided and projected a single median optic stalk partially subdivided into optic vesicles contained in a single orbit. Aberrant midfacial ossification underlay arrhinia and uncleft lips and palate. Maxillary anodontia and mandibular hypodontia prevailed. Postcranial normality was disturbed by pedal postaxial hexadactyly, suggesting trisomy 13. The exceptionally young age of the specimen distinguishes its detailed analysis from the majority of older cyclopic specimens previously reported.

Abnormalities, Multiple↗