The complete sequence of the coding region of the ATM gene reveals similarity to cell cycle regulators in different species

Ataxia-telangiectasia (A-T) is an autosomal recessive disorderinvolving cerebellar degeneration, immunodeficiency, radiationsensitivity, and cancer predisposition. A-T heterozygotes aremoderately cancer prone. The A-T gene, designated ATM, was recentlyidentified in our laboratory by positional cloning, and a partialcDNA clone was found to encode a polypeptide with a PI-3 kinasedomain. We report here the molecular cloning of a cDNA contigspanning the complete open reading frame of the ATM gene. Thepredicted protein of 3056 amino acids shows significant sequencesimilarities to several large proteins in yeast, Drosophilaand mammals, all of which share the PI-3 kinase domain. Manyof these proteins are involved in the detection of DNA damageand the control of cell cycle progression. Mutations in theirgenes confer a variety of phenotypes with features similar tothose observed in human A-T cells. The complete sequence ofthe ATM gene product provides useful clues to the function ofthis protein, and furthers understanding of the pleiotropicnature of the A-T mutations.     

Predominance of null mutations in ataxia-telangiectasia

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder involving cerebellar degeneration, immunodeficiency, chromosomal instability, radiosensitivity and cancer predisposition. The responsible gene, ATM, was recently identified by positional cloning and found to encode a putative 350 kDa protein with a Pl 3-kinase-like domain, presumably involved in mediating cell cycle arrest in response to radiation-induced DNA damage. The nature and location of A-T mutations should provide insight into the function of the ATM protein and the molecular basis of this pleiotropic disease. Of 44 A-T mutations identified by us to date, 39 (89%) are expected to inactivate the ATM protein by truncating it, by abolishing correct initiation or termination of translation, or by deleting large segments. Additional mutations are four smaller in-frame deletions and insertions, and one substitution of a highly conserved amino acid at the Pl 3-kinase domain. The emerging profile of mutations causing A-T is thus dominated by those expected to completely inactivate the ATM protein. ATM mutations with milder effects may result in phenotypes related, but not identical, to A-T.      

Current controversies in the management of minor pediatric head injuries

Each year hundreds of thousands of children receive care in emergency departments after head injury. Minor head injuries account for a majority of these injuries. The prevalence, morbidity, and costs associated with pediatric minor head injuries make it an important topic. We review the management of pediatric minor head injury, emphasizing current areas of controversy, including criteria for neuroimaging, indications for hospitalization, the role of anticonvulsant therapy, and the long-term neurobehavioral sequelae of pediatric minor head injury.     

Maintenance therapy for prevention of recurrent peptic ulcers

Peptic ulcer disease is a chronic, relapsing disease. Successful healing of duodenal and gastric ulcers with antacids, cimetidine, ranitidine, famotidine, or sucralfate is frequently followed by ulcer recurrence. The need for long-term, low-dose maintenance therapy is based on disease severity, ulcer history, complications, therapeutic intervention, response to treatment, and potential risk factors. Comparison of ulcer maintenance trials requires consideration of important factors such as frequency of endoscopy, duration of follow-up period, and the method used to calculate ulcer recurrence rates. Clinical trials indicate that chronic treatment with low-dose cimetidine, ranitidine, famotidine, and probably sucralfate decreases the frequency of duodenal ulcer recurrence and that ranitidine may be superior to cimetidine. Preliminary studies indicate that higher doses of these same medications may be required to prevent gastric ulcer recurrence. Long-term maintenance therapy with these agents must be continuous in order to prevent relapses, but treatment should be limited to one year because of unknown consequences beyond this period.     

Effect of levamisole on cell sensitivity in rats with experimental Heymann's nephritis

The development of cell-sensitization to renal antigen in rats with experimental Heymann's glomerulonephritis and the effect of levamisole on cell sensitivity have been studied. Morphologic changes in GN rats appeared after 14 days and were most pronounced on days 21-28, with focal proliferation of glomerular cells, an increase of mesangium, a focal increase of the basal membrane material. After day 49 the changes improved slightly and were still the same on day 147 when a location of IgG to the glomerular basal membrane was detected. In every GN rat, cell-sensitivity to renal antigen was revealed from day 21 of the experiment till its end. Levamisole treatment decreased renal morphologic changes and abolished cell-sensitivity to renal antigen. The possible mechanisms of preventing the development of cell-sensitization in rats treated with levamisole are discussed.