Cigarette smoke increases the penetration of asbestos fibers into airway walls.

For study of the penetration of asbestos fibers into airway walls, guinea pigs were given amosite asbestos by intratracheal instillation. Half of the animals were also exposed to cigarette smoke. Animals were sacrificed at 1 week and 1 month, and numbers of fibers in airway walls were counted in histologic sections. In both smoke-exposed and nonexposed groups, numbers of fibers per square millimeter of airway wall increased from 1 week to 1 month in the respiratory bronchioles. At each time period, smoke-exposed animals had significantly higher numbers of fibers in the airway walls, compared with nonexposed animals. It is concluded that 1) continued transport of fibers into interstitial tissues may be the reason that asbestosis can progress after cessation of exposure; 2) cigarette smoke increases the penetration of fibers into airway walls. This effect may play a role in the increased incidence of disease seen in smoking, compared with nonsmoking, asbestos workers.     

Frequency of meiotic trisomy depends on involved chromosome and mode of ascertainment

Although maternal meiotic errors predominate in most studies of nonmosaic trisomy, studies of trisomy ascertained through confined placental mosaicism (CPM) have shown a high rate of somatic errors. However, origin of trisomy of many of the chromosomes involved in CPM has not been evaluated previously in cases ascertained through spontaneous abortions (SAs). Therefore, it was impossible to determine if the relative lack of meiotic errors in trisomy-CPM cases was a characteristic of the specific chromosome involved or due simply to ascertainment through a mosaic state. In the present study, parental and meiotic/somatic stages of origin of trisomy were determined in 89 SAs involving trisomy of chromosomes 2, 4 to 10, 12, 15, 17, and 20. Comparisons were then made to origin of trisomy in cases of confined and generalized trisomy mosaicism. Although somatic errors are generally more common in mosaic cases, this depends on the specific chromosome involved. The results suggest that there are chromosome-specific differences in the relative frequency of somatic chromosome gain or loss and/or the ability of an early somatic loss of one chromosome from a trisomic conceptus to "rescue" the pregnancy. As mean maternal age was less in the somatic than meiotic origin cases (P < 0.01), the age distribution of the study population should also influence the probability of detecting a somatic error. No phenotypic differences were apparent when cases were subdivided based on either parent or stage of origin of the trisomy.     

Principles of radiographic exposure a new approach

Radiographic technique charts have traditionally been established by the empirical method. A precisely calculated chart based on the effective energy of the spectrum and the output of the equipment will give more consistent results of density and contrast as well as repeatability of these results from patient to patient. A better understanding of patient attenuation and screen energy sensitivity will enable the radiographer to logically adjust technical factors to change density or contrast scales as required.     

Conversion of isoaspartyl peptides to normal peptides: implications for the cellular repair of damaged proteins.

The hypothesis that cellular protein carboxyl-methylation reactions recognize altered aspartyl residues as part of a protein repair pathway has been tested in an in vitro system using tetragastrin (Trp-Met-Asp-Phe-NH2) as a model sequence. The L-isoaspartyl form of tetragastrin, where the phenylalanine residue is linked to the side-chain carboxyl group of the aspartate residue ([iso-Asp3]tetragastrin), is a substrate for the erythrocyte protein carboxyl methyltransferases, while the normal form is not. The enzymatically produced alpha-methyl ester of [iso-Asp3]tetragastrin, [iso-Asp(OMe)3]tetragastrin, is unstable at pH 7.4 and 37 degrees C and spontaneously demethylates with a half-time of 41 min to an intermediate L-succinimide form ([Asu3]tetragastrin) that, in turn, spontaneously hydrolyzes with a half time of 116 min to give a mixture of normal tetragastrin (20%) and [iso-Asp3]tetragastrin (80%). This sequence of enzymatic and nonenzymatic reactions can be coupled in a single reaction mixture; the [iso-Asp3]tetragastrin that is produced upon succinimide hydrolysis can reenter the reaction sequence by enzymatic methylation, and the net result of the process is the conversion of the isomerized peptide to the normal peptide. The efficiency of this "repair" reaction is limited by a side reaction of racemization at the alpha-carbon of the succinimide (half-time = 580 min). In a 24-hr time period, normal L-aspartyl-containing tetragastrin is obtained in about 50% yield from the coupled reaction mixture; other products include [D-iso-Asp3]tetragastrin and [D-Asp3]tetragastrin. The versatile chemistry of succinimide peptides suggests that methylated L-isoaspartyl sites (and possibly methylated D-aspartyl sites) in cellular polypeptides can eventually yield "repaired" normal L-aspartyl sites through succinimide intermediates.     

Surgery in the nineties

The population of the United States is aging, and by 2020 it is estimated that 16 per cent of U.S. citizens will be over 65 years of age. Little has been published about the results of surgery in nonagenarians but mortality rates of 45 per cent are reported. Given recent improvements in perioperative care we reviewed the experience with major general surgical operative procedures in nonagenarians. We reviewed the charts of patients greater than or equal to 90 years of age who underwent general surgical procedures at UCLA Medical Center since 1986. No patients were excluded. Thirty-two patients were identified. Most (87.5%) patients had significant premorbid conditions. The most common diagnoses were cancer (12), incarcerated hernia (seven), trauma (three), colonic volvulus (two), and cholecystitis (two). Overall perioperative mortality was 9.4 per cent (3 of 32). Twenty-two surgeries (69%) were performed on an emergency basis, and all three deaths were in this group (13.6%). Overall morbidity rate was 57 per cent. Mean intensive care unit stay was 4.8 days. Most patients were discharged home. Our findings support the perioperative safety of elective general surgery in nonagenarians (0% mortality and 20% morbidity). We also found an acceptable risk (13.6% mortality and 68% morbidity) for emergency procedures despite significant comorbid conditions. Most of the patients had acceptable functional outcomes.     

Leiomyoma of the esophagus associated with bronchial obstruction owing to inflammatory pseudotumor in a child

Although relatively common in adults, leiomyoma of the esophagus is a rare disorder in children. A single case report describes the coexistence of both esophageal and bronchial leiomyoma in a child. The authors describe the diagnostic and treatment challenges encountered in a 2-year-old boy with coexisting inflammatory pseudotumor and esophageal leiomyoma presenting as massive atelectasis.