Amyloid precursor protein mRNA stability is controlled by a 29-base element in the 3'-untranslated region

In the accompanying paper (Zaidi, S. H. E., Denman, R., and Malter, J. S. (1994) J. Biol. Chem. 269, 24000-24006) we demonstrate that in tumor and normal cells, multiple cytosolic proteins interact with a 29-base sequence in the 3'-untranslated region of amyloid precursor protein (APP) mRNA. These data suggested that APP gene expression may be modulated by regulated APP mRNA decay. We have investigated this prediction by measuring the decay rates of APP mRNA in resting and mitogen-treated peripheral blood mononuclear cells and H4 and K562 tumor cell lines. In resting peripheral blood mononuclear cells, APP mRNA decayed with a half-life of 4 h. Under these conditions, the activity of APP mRNA-binding proteins was not detectable. After activation, binding protein activities were induced, and APP mRNA decay was blocked with a half-life of > 12 h. In log phase neuronal or lymphoid tumor cell lines, binding activity was constitutively present and APP mRNA displayed a half-life of > 12 h. Protein synthesis inhibition by cycloheximide had no effect on APP mRNA decay in normal or tumor cells. Transfected wild type or mutant APP mRNAs that lacked the 29-base region were stable (t1/2 > 10 h) in K562 tumor cells. Therefore, we conclude that the 29-base region functions in cis to destabilize APP mRNA in resting, normal cells. Upon activation APP mRNA-binding proteins are induced, interact with the 29-base region, and likely participate in stabilization of the mRNA.

Multiple proteins interact at a unique cis-element in the 3'-untranslated region of amyloid precursor protein mRNA

Growing evidence suggests that Alzheimer's disease results from dysregulated production and deposition of beta-amyloid in the central nervous system. beta-Amyloid is derived from proteolytic processing of one of multiple amyloid precursor protein (APP) isoforms. The production of APP in many somatic tissues and tumor cell lines provides a more accessible model to study the regulation of APP gene expression. Recent data suggest that APP mRNAs accumulate in activated lymphocytes and neuronal tumor lines. We are interested in defining the contribution of alterations in stability to changes in steady-state APP mRNA levels in these model systems. Herein we demonstrate by mobility shift assay that the 3'-untranslated region of APP RNAs which contain a contiguous 29-base region interacts in vitro with multiple mRNA-binding proteins found in cytosolic lysates prepared from normal and transformed human cells. UV cross-linking of radiolabeled APP RNAs to cytosolic protein extracts followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis identified six distinct RNA-protein complexes of 42, 47, 65, 73, 84, and 104 kDa. Competition assays with APP, AU-rich, or irrelevant RNAs demonstrated that binding was specific and in some cases preferential for AU- or U-rich sequences by which we tentatively place the binding site of the proteins along the 29-base region. APP mRNA-binding proteins were constitutively active in all tumor lines examined as well as at diminished levels in whole human brain cytosolic lysates. The core element is AU-rich and highly conserved between human and some murine APP mRNAs. In the accompanying paper (Zaidi, S. H. E. and Malter, J. S. (1994) J. Biol. Chem. 269, 24007-24013) we show that this 29-base element in the 3'-untranslated region regulates the stability of APP mRNA. Cumulatively these data suggest that steady-state APP mRNA levels are modulated by cytosolic protein-RNA interactions.

Pattern of leucocyte acid phosphatase reaction in T-cell lymphoblastic leukaemia

Acid phosphatase (AP) reaction is a specific cytochemical marker for T-cell lymphoblastic leukaemia (T-ALL). Twenty six cases of ALL were diagnosed as T-ALL employing cytochemical profiles including AP and sheep red blood cell rosettes. Three district patterns of AP reaction were observed. On one end of the spectrum, 100% of the positive blasts showed the classical dot-like reaction while on the other 100% showed a scattered reaction. Between the two a mixed pattern was observed with 30-80% of the positive blasts showing the dot-like reaction while the rest showed scattered pattern. Dot-like pattern showed L1 morphology, high counts and low SRBC rosettes while scattered showed L2 morphology, low counts and high SRBC rosettes. The pattern observed in our series differs from the dot-like reaction observed in T-ALL in the western series. We recommend that this pattern must be borne in mind when employing AP reaction for T-ALL diagnosis (JPMA 42: 151, 1992).

Unilateral proptosis in E.N.T. practice

Seventeen cases of unilateral proptosis aged 11-54 years are presented. The proptosis was due to mucormycosis in 7, ethmoid polyposis in 4, malignancy in 4, and one each due to Ringert's tumour and fibrous dysplasia. Surgery was performed in all cases with the aim of total extirpation of disease and orbital repositioning. The surgical approaches included transverse maxillary osteotomy, transantral ethmoidectomy, modified lateral rhinotomy, and orbital decompression. There was one fatality, and two recurrences. Three cases showed satisfactory and eleven excellent results.

A study of H2 receptor antagonists in the treatment of chronic intractable pharyngitis

In a controlled study of 75 patients suffering from chronic pharyngitis: 30 were treated with H2-receptor antagonist, 30 with H1-receptor antagonist, local decongestants and antiseptic gargles: and 15 treated with alum, salt or Dispirin gargles acted as controls. Best response was obtained with the first mode of treatment, raising the possibility of role of the H2-receptors in causing chronic pharyngitis. The difference was highly significant (P less than 0.001).

Hepatocellular carcinoma in Karachi

The present study defines the clinical presentation and examines possible aetiological factors in the occurrence of hepatocellular carcinoma in Karachi, Pakistan. Histologically proven cases of hepatocellular carcinoma (n = 366) were seen over 16 years. The maximum frequency occurred in the age range 51-60 years (range: 8-98 years), and the male to female ratio was 2.5:1. The place of birth, place of longest stay and various addictions did not have any association with the occurrence of liver carcinoma. Only three cases had a history of liver cancer in their immediate relatives. The main presenting features were right hypochondrial mass (85%) and pain (79%). The liver size did not correlate with the duration of illness. alpha-Fetoprotein titres were more than 200 ng/mL in 62% of cases. Using a reverse passive haemagglutination assay method, HBsAg and anti-HBc positivity were 32% and 60%, respectively. Antigen figures rose to 60% when radio-immunoassay was used; 41% of cases were anti-delta positive (EIA). Aflatoxin contamination varied between 10% and 17% in various localities of Karachi, suggesting an association of liver cancer with HBsAg and aflatoxins. Histopathologically 73% were trabecular, and 2.5% were mixed hepatocholangiocarcinomas. Follow-up was available in 45% of cases. All except two (1.2%) died within 6 months.

Anthropological study of the mastoid air cell system in Pakistani races

This is an anthropological study of the development of the mastoid process in the four ethnic groups of Pakistani races: Turko-Iranian, Indo-Aryan, Scytho-Dravidian, and Aryo-Dravidian. Cephalometric studies have established that the majority of Pakistanis are brachio to ultra-brachiocephalic (Cephalic Index 82-x). Radiological evaluation of normal mastoids and their planimetric measurements show that the mastoid process is smaller (Av: 10.24 sq.cm. +/- 0.8) than the Caucasian Western races (Av: 12-15 sq.cm.). Neither combined approach tympanoplasty, nor mastoid obliteration technique may be required, nor technically possible in a small mastoid. Natural epithelization of a small 'peanut size' mastoidectomy cavity does not justify these procedures. A modified radical mastoidectomy and tympanoplasty reconstruction provides a satisfactory result in chronic discharging ears.

Noise levels and the sources of noise pollution in Karachi

The menace of noise is a by-product of civilization and its hazards are well known. Noise levels were measured in Karachi, at different places and at different times of the night and day, using an Amplaid noise meter. The leg for Karachi came to 80 dB (A), the General Noise Index x (G.N.I.) to 460, and the noise pollution level (N.P.L.) to 99 dB (A). These values are significantly higher (P less than 0.01) than the available international data. The sources of noise production were indentified as, the road traffic, human activity, industrial and civil works, mechanical and engineering workshops. The most noticeable sources of noise pollution in Karachi, are the autorickshaws, trail motor bikes and the fag horns of public transport (JPMA 39-62, 1989).

Assessment of occupational benzene exposure in petrol filling stations at Rangoon

An occupational health survey was conducted on workers, who inhale petrol fumes which contain low concentrations of benzene, at petrol filling stations in the city of Rangoon, Burma. To evaluate the exposure to benzene, urinary phenol (which is a principal metabolite of absorbed benzene) was measured in workers at petrol filling stations and in a control group of healthy male adults. The survey revealed that the urinary phenol content of workers exposed to petrol fumes was significantly higher than that of workers who were not exposed.

High aspect-ratio holographic photoresist gratings

Holographic gratings with periods as small as 700 nm, rectangular profiles with linewidths of <120 nm, and depths of 1.2 microm (aspect ratio of 10) have been formed using positive photoresist on Si substrates and visible laser exposure (488 nm). Similar aspect ratios have been achieved at a 400-nm period using 334-nm exposing radiation. A simple exposure and development model, which accounts for the large aspect ratios and predicts the grating fabrication limits, is presented.

Spirometry and flow-volume curves in healthy, normal Pakistanis

Previous studies have indicated that lung volumes in healthy, normal Pakistani adults are smaller than measurements reported in comparable healthy European populations; in order to confirm these findings and to examine the relationship of maximal expiratory flow rates to lung volumes, we studied 250 non-smoking healthy subjects (116 men and 114 women) between the ages of 18 and 65 years. The population sample was drawn from urban and rural areas of Pakistan, with low levels of air pollution. The results indicate that the forced vital capacity (FVC) and forced expired volume in 1 second (FEV1) were lower in the Pakistani population compared to European populations and North American populations of European descent. These data are in conformity with previous studies; however, in Pakistani men the effects of age on FVC and FEV1 were slight so that, after the fourth decade, the FVC and FEV1 values are very comparable between the European and Pakistani populations. Amongst Pakistani women, on the other hand, FVC and FEV1 remained lower than in their European counterparts throughout adult life. Maximal expiratory flow rates amongst the men did not correlate with age, and these values were very similar to those reported in age-matched European populations. In women, however, there was a significant correlation of maximal flow rates with age and height, and the maximal expiratory flows were decreased compared to European populations. These data indicate that in Pakistani men pulmonary mechanics may be different to their European counterparts, allowing for higher maximal expiratory flows at any given lung volume.

Experimental bagassosis: role of infection

The pathological lesions of bagassosis have been reproduced in guinea pigs given bagasse fibers along with low doses of actinomycete spores. In the early stages, interstitial infiltration with lymphocytes and macrophages as seen in humans was noted. Later, small interstitial bagasse granulomas composed of foreign body giant cells, fibroblasts, and lymphocytes developed, some of which had a laminated appearance. Lymph node changes consistent with an immunological reaction were observed. Actinomycetes alone showed occasional areas of pneumonitis and bagasse alone small granulomas consisting of foreign body giant cells and bagasse fibers. Finally, the combined effect of dust and actinomycetes produced interstitial fibrosis composed of thick reticulin fibers and occasional collagen fibers, which persisted to the end of the experiment. Bagasse alone and actinomycetes alone produced only thin reticulin fibers. It has been suggested that bagassosis is due to the synergistic action of bagasse fibers and Micropolyspora faeni and that in the pathogenesis of the syndrome an immunological component may be involved.