Presenilin 1 regulates the processing of beta-amyloid precursor protein C-terminal fragments and the generation of amyloid beta-protein in endoplasmic reticulum and Golgi

Progressive cerebral deposition of the amyloid beta-protein (Abeta) is believed to play a pivotal role in the pathogenesis of Alzheimer's disease (AD). The highly amyloidogenic 42-residue form of Abeta (Abeta42) is the first species to be deposited in both sporadic and familial AD. Mutations in two familial AD-linked genes, presenilins 1 (PS1) and 2 (PS2), selectively increase the production of Abeta42 in cultured cells and the brains of transgenic mice, and gene deletion of PS1 shows that it is required for normal gamma-secretase cleavage of the beta-amyloid precursor protein (APP) to generate Abeta. To establish the subcellular localization of the PS1 regulation of APP processing to Abeta, fibroblasts from PS1 wild-type (wt) or knockout (KO) embryos as well as Chinese hamster ovary (CHO) cells stably transfected with wt or mutant PS1 were subjected to subcellular fractionation on discontinuous Iodixanol gradients. APP C-terminal fragments (CTF) were markedly increased in both endoplasmic reticulum- (ER-) and Golgi-rich fractions of fibroblasts from KO mice; moreover, similar increases were documented directly in KO brain tissue. No change in the subcellular distribution of full-length APP was detectable in fibroblasts lacking PS1. In CHO cells, a small portion of APP, principally the N-glycosylated isoform, formed complexes with PS1 in both ER- and Golgi-rich fractions, as detected by coimmunoprecipitation. When the same fractions were analyzed by enzyme-linked immunosorbent assays for Abetatotal and Abeta42, Abeta42 was the major Abeta species in the ER fraction (Abeta42:Abetatotal ratio 0.5-1.0), whereas absolute levels of both Abeta42 and Abeta40 were higher in the Golgi fraction and the Abeta42:Abetatoal ratio was 0.05-0.16 there. Mutant PS1 significantly increased Abeta42 levels in the Golgi fraction. Our results indicate PS1 and APP can interact in the ER and Golgi, where PS1 is required for proper gamma-secretase processing of APP CTFs, and that PS1 mutations augment Abeta42 levels principally in Golgi-like vesicles.     

Induction cisplatin/vinblastine and irradiation vs. irradiation in unresectable squamous cell lung cancer: failure patterns by cell type in RTOG 88-08/ECOG 4588. Radiation Therapy Oncology Group. Eastern Cooperative Oncology Group

PURPOSE: To analyze disease failure patterns by pretreatment characteristics and treatment groups in a prospective randomized trial. METHODS AND MATERIALS: Patients with medically inoperable Stage II, unresectable IIIA and IIIB nonsmall cell lung cancer with KPS > or =70 and weight loss < or =5% were randomized to one of three treatment groups: standard radiation therapy with 60 Gy at 2.0 Gy per day (STD RT), induction chemotherapy with cisplatin 100 mg/m2 days 1 and 29 with vinblastine 5 mg/m2 weekly for 5 weeks followed by 60 Gy at 2.0 Gy per day (CT + RT), or hyperfractionated radiation therapy with 69.6 Gy at 1.2 Gy b.i.d. (HFX RT). Of 490 patients enrolled, 458 were evaluable. Minimum and median periods of observation for this analysis were 4 years and 6 years, respectively. RESULTS: Pretreatment characteristics were equally distributed. Toxicities were previously reported. Median survival rates were 11.4, 13.6, and 12.3 months for STD RT, CT + RT, and HFX RT, respectively (log rank p = 0.05, Wilcoxon p = 0.04). Survivals were 20, 31, and 24% at 2 years, and 4, 11, and 9% at 4 years in the STD RT, CT + RT, and HFX RT groups, respectively. There were no differences in local tumor control rates among the treatments. Patterns of first failure showed less distant metastasis (DM) (other than brain) for CT + RT compared to the RT alone arms (p = 0.04). Within squamous cell carcinoma (SCC), DM (other than brain) rates were 43%, 16%, and 38% in SCC for STD RT, CT + RT, and HFX RT, respectively (p = 0.0015). Patients with peripheral/chest wall lesions were significantly more likely to fail first in the thorax when treated on STD RT compared to CT + RT and HFX RT (p = 0.009). Survival rates were similar among the treatment arms for patients with squamous cell carcinoma. Among patients with nonsquamous cell carcinoma, failure patterns did not differ by treatment group, but survival was significantly better in those who were treated by induction chemotherapy (p = 0.04). CONCLUSION: Patients with squamous cell carcinoma treated on the CT + RT arm had a significant reduction of first DM other than brain, but there was difference in survival. Survival favored CT + RT in nonsquamous carcinoma despite similar failure patterns. Reasons for improved survival with CT + RT in NSCLC are not yet available.     

A collagen peptide motif activates tyrosine kinase-dependent calcium signalling pathways in human osteoblast-like cells

A collagen peptide motif (DGEA) which is a putative alpha 2 beta 1 integrin binding site was examined for its ability to activate Ca2+ signalling pathways in the human osteoblast-like cell line SaOS-2. We show that these cells express both alpha 2 beta 1 integrin subunits (by immunocytochemistry) and that an anti-beta 1 monoclonal antibody (DF5) mobilizes Ca2+ in these cells. DGEA elevated intracellular Ca2+ in fura-2-loaded cells, in a concentration- and sequence-dependent fashion, with an EC50 of 250 microM. The tyrosine kinase inhibitor herbimycin A reduced the number of cells responding to DGEA and to transforming growth factor alpha. Thrombin also stimulated a rise in intracellular Ca2+, but the number of cells responding was not reduced by herbimycin A. The DGEA response was dependent on extracellular Ca2+, but was not due to Ca2+ influx, since it was blocked by thapsigargin and not by lanthanum. Using three different anti-alpha 2 monoclonal antibodies, we were unable to show that the DGEA-induced Ca2+ signal was mediated by the alpha 2 beta 1 integrin. In summary, the DGEA collagen motif does appear to activate receptor-mediated Ca2+ signalling events in SaOS-2 cells, in a divalent cation-dependent manner, but we were unable to demonstrate a role for alpha 2 beta 1 integrin in this response.     

Analysis of Salmonella serovars in Taiwan by the phase induction method

Major strides in the molecular biology of essential hypertension are currently underway. This has tended to obscure the fact that a number of inherited disorders associated with low blood pressure exist and that these diseases may have milder and underrecognized phenotypes that contribute importantly to blood pressure variation in the general population. This review highlights some of the gene products that, if abnormal, could cause hypotension in some individuals. Diseases due to abnormalities in the catecholamine enzymes are discussed in detail. It is likely that genetic abnormalities with hypotensive phenotypes will be as interesting and diverse as those that give rise to hypertensive disorders.     

Herpes labialis in skiers: randomized clinical trial of acyclovir cream versus placebo

Five cases of prenatally detected neck masses that had a potential for airway obstruction at birth are described. The various options for management of the airway are discussed, including using maternal-fetal circulation until intubation, rigid bronchoscopy, tracheotomy, cyst aspiration, or extracorporeal membrane oxygen support. Congenital abnormalities involving the fetal face or neck are extremely rare. With technical advances in ultrasonography, these masses were first noted on prenatal ultrasound in the late 1970s. Before that period, they were detected at delivery. These masses are solid or cystic and may cause asphyxia because of airway obstruction at the time of delivery. The survivability of these neonates without immediate intervention at birth is 0% to 20%. If a neck mass is detected in the fetus by prenatal ultrasonography, then a strategic plan for these types of cases should be developed early in the prenatal period. The airway management plan should be tailored for each individual case. Coordination and the expertise of an obstetrician, neonatologist, anesthesiologist, and pediatric otolaryngologist are needed to manage these complex situations.     

Clinician-educators in academic medical centers: a two-part challenge

Between 1967 and 1996, > 18,700 strains of Yersinia species, excluding Yersinia pestis, were recovered in Belgium from a variety of gastrointestinal and extraintestinal sites in patients. Full identification and serotyping were performed by the two Belgian reference laboratories. Yersinia enterocolitica serogroup O:3 predominated (79.4% of strains), followed by serogroup O:9 (11.1%). The remaining 9.5% of isolates belonged to serogroups and related species generally considered nonpathogenic. Acute enterocolitis was the most common clinical form of Y. enterocolitica infection, affecting primarily children younger than 5 years of age. Since 1967, there was a steady increase in isolations every year, with 305 cases in 1975 and up to 1,469 in 1986. From 1987 on, there was a clear decrease in the number of reported cases, although the number of participating laboratories and culture techniques remained constant. This significant decrease in the occurrence of Y. enterocolitica infections may be explained by changes in the slaughtering procedures and eating habits of the population.     

The 40-kDa subunit of DNA fragmentation factor induces DNA fragmentation and chromatin condensation during apoptosis

We report here the reconstitution of a pathway that leads to the apoptotic changes in nuclei by using recombinant DNA fragmentation factor (DFF), a heterodimeric protein of 40 and 45 kDa. Coexpression of DFF40 and DFF45 is required to generate recombinant DFF, which becomes activated when DFF45 is cleaved by caspase-3. The cleaved fragments of DFF45 dissociate from the DFF40, the active component of DFF. Purified DFF40 exhibited an intrinsic DNase activity that was markedly stimulated by chromatin-associated proteins histone H1 and high mobility group proteins. DFF40 also triggered chromatin condensation when incubated with nuclei. These data suggest that DFF40 is sufficient to trigger both DNA fragmentation and chromatin condensation during apoptosis.