Current concepts for the surgical management of carotid body tumor.

Background: Carotid body tumor (CBT) is a rare lesion of the neuroendocrine system. Chronic hypoxia has long been recognized as an etiology of CBT and other paragangliomas. Recent biogenetic discoveries reveal that mutations in oxygen-sensing genes are another etiology, accounting for approximately 35% of cases, and that these 2 etiologies are probably additive.

Clinical and epidemiologic studies of cleft lip and palate in the Philippines.

Clinical and epidemiologic studies of defined geographic populations can serve as a means of establishing data important for genetic counseling and as a first step in identifying strategies best suited for identification of causes. Under the sponsorship of Operation Smile International, clinical, genetic, and epidemiologic studies were carried out at six sites within the Philippines between 1989 and 1996. Patients who were being evaluated for surgical repair of craniofacial anomalies (primarily clefts of the lip and palate) were briefly examined for the presence of associated anomalies, and a family history was obtained to look for the frequency of cleft lip and palate in siblings.

Speculation on the role of transposable elements in human genetic disease with particular attention to achondroplasia and the fragile X syndrome.

We suggest that mutations for fragile X-positive Martin-Bell syndrome, and perhaps also for achondroplasia, may result from the insertion of transposable elements (TE's). Loss of genetic function could result from either the insertion of TE's within or adjacent to a normal chromosomal gene or, in the case of fragile X, from the loss of genes distal to the site of TE insertion following subsequent TE excision without ligation of the resulting discontinuity. The phenotypically and often cytogenetically normal transmitting males in fragile X pedigrees are interpreted not as "nonpenetrant" transmitters of a fully formed fragile X but rather as transmitters of some or all of the factors necessary for TE insertion at Xq27.

G2 chromosomal radiosensitivity in ataxia telangiectasia lymphocytes.

The peripheral lymphocytes from 7 patients affected with ataxia telangiectasia (AT) were found to be about twice as sensitive to the induction of chromatid-type aberrations by X-rays administered during the G2 phase of the cell cycle as cells from normal controls. Peripheral lymphocytes from 6 AT heterozygotes were no more sensitive than the controls. Using labelling of peripheral lymphocytes with tritiated thymidine, followed by autoradiography, it was determined that cells from affected patients, heterozygotes and normal controls, whether irradiated or not, all had similar percent labeled mitoses (PLM) curves, so the increased induced aberration yields seen in the AT cells is not simply the consequence of a longer than normal G2 phase, nor of G2 delay induced by the radiation.

G0 chromosomal radiosensitivity in ataxia telangiectasia lymphocytes.

Contrary to an earlier report, peripheral lymphocytes from 4 AT patients were not found to exhibit higher yields of unequivocal chromosome type aberrations following irradiation in the G0 phase of the cell cycle, providing that only first post-irradiation metaphases were included in the samples (ensured by 5-bromodeoxyuridine (BrdU) incorporation and differential fluorescence or Giemsa staining). We were able, however, to confirm the earlier-reported increase in chromatid-type aberrations in the G0-irradiated cells. AT lymphocytes were found to experience more cell-cycle delay following G0 irradiation than normal cells.