Analysis of the Drosophila female sterile mutation fs(1) 1304 by pole cell transplantation experiments

The Drosophila melanogaster mutant fs(1)1304 is an ovary autonomous female sterile mutant that causes abnormal morphology of the egg. Vitellogenesis proceeds at an abnormally slow rate in homozygous females. We have used pole cell transplantation to construct germ line mosaics in order to determine whether the 1304 defect depends upon the genotype of the germ line cells (oocyte or nurse cells) or the somatic line (follicle cells). We have found that the germ line is the primary target tissue where the mutant gene is expressed.     

Comparison of health problems related to work and environmental measurements in two office buildings with different ventilation systems.

A cross sectional survey investigating "building sickness" was carried out in two buildings with similar populations of office workers but differing ventilation systems, one being fully air conditioned with humidification and the other naturally ventilated. The prevalence of symptoms related to work was assessed by a questionnaire administered by a doctor. A stratified, randomly selected sample of workers was seen (84% response). Building sickness includes several distinct syndromes related to work, most of which were significantly more common in the air conditioned building than the naturally ventilated building--namely, rhinitis (28% v 5%), nasal blockage and dry throat (35% v 9%), lethargy (36% v 13%), and headache (31% v 15%). The prevalence of work related asthma and humidifier fever was low and did not differ significantly between the two buildings. An environmental assessment of the offices was performed to attempt to identify possible factors responsible for the differences in the prevalence of disease. Globe temperature, dry bulb temperature, relative humidity, moisture content, air velocity, positive and negative ions, and carbon monoxide, ozone, and formaldehyde concentrations were all measured. None of these factors differed between the buildings, suggesting that building sickness is caused by other factors.     

A new,strikingly patterned Calathea (Marantaceae) from Ecuador

Calathea libbyana from Napo Province, Ecuador, is described. It belongs to the dimorphic-bracted species-group ofCalathea seriesComosae. It is in cultivation under the cultivar name ‘Windows’, which refers to its distinctive leaf pattern with pale, semi-translucent markings.     

Proteolytic processing and compartmentalization of the primary translation products of mammalian apolipoprotein mRNAs

The steps involved in the initial assembly of apolipoproteins and lipids into supramolecular arrays (nascent lipoprotein particles) are largely unknown. Examination of the proteolytic processing and compartmentalization of the primary translation products of apolipoprotein mRNAs represents one approach to deciphering the molecular details of lipoprotein assembly. The structures of the primary translation products of seven mammalian apolipoprotein mRNAs has been determined in the past several years. The organization of apolipoprotein signal peptides is typical of eukaryotic prepeptides, although an unusual degree of sequence conservation is present among the signal segments of apo AI, AIV, and E. For those apolipoprotein sequences studied in detail, SRP-dependent cotranslational translocation and proteolytic processing appears to be highly efficient and results in sequestration of the processed protein within the lumen of the endoplasmic reticulum (ER). However the mechanism by which these lipid-binding proteins avoid arrest during their translocation through the lipid bilayer of the ER membrane remains obscure. The two principal human HDL apolipoproteins undergo novel extracellular post-translational proteolytic processing, which results in removal of nonhomologous propeptides. The proteases responsible for proapo AI and AII processing appear to be different. The processing of these proapolipoproteins provides a potential series of steps for regulating the ordered assembly of HDL constituents.     

Differentiation properties of pure populations of human dystrophic muscle cells

The interpretation of the majority of studies of Duchenne muscular dystrophy (DMD) has been complicated by the heterogeneous composition of the cultures used. In addition to muscle cells, muscle tissue contains adipocytes and fibroblasts and the proportion of these cell types varies, especially in disease states. To overcome this problem we developed culture conditions which permitted isolation and characterization of pure populations of clonally derived human muscle cells [1, 2]. Here we report the successful application of these methods to muscle cells from biopsies of individuals with diagnosed DMD. The normal and mutant human muscle cells were used in experiments of muscle differentiation in the same manner as cell lines. Frozen-stored cells were thawed, plated in a series of replicate plates, and allowed to differentiate under similar culture conditions. Yet, in contrast with cell lines, the cells were karyotypically normal, not altered by adaptation to long-term culture, and had a finite lifespan. We have systematically analysed specific properties of the normal and DMD muscle cells which differentiated in culture. The kinetics and extent of myoblast fusion, myotube morphology, and the accumulation and distribution of membrane acetylcholine receptors were monitored. In addition, the isozyme composition of creatine kinase and its intracellular and extracellular distribution were determined. Our results indicate that DMD muscle cells are fully capable of initiating myogenesis in culture and do not differ from normal muscle in several important parameters of differentiation.     

Complement pores in erythrocyte membranes: Analysis of C8/C9 binding required for functional membrane damage

The number of membrane-bound terminal complement proteins (C5b-9) required to generate a functional pore in the human erythrocyte membrane ghost has been determined. Resealed erythrocyte ghost membranes (ghosts) were treated with human complement proteins C5b6, C7, ¹³¹I-C8, and ¹²⁵I-C9 under non-lytic conditions. Following C5b-9 assembly, sucrose-permeant ghosts were separated from C5b-9 ghosts that remained impermeant to sucrose by centrifugation over density barriers formed of 43% (w/v) sucrose. Analysis of ¹³¹I-C8 and ¹²⁵I-C9 bound to sucrose-permeant and sucrose-impermeant subpopulations of C5b-9 ghosts revealed: 1. Sucrose-permeant C5b-9 ghosts show increased uptake of both ¹³¹I-C8 and ¹²⁵I-C9 as compared to ghosts that remain impermeant to sucrose. Ghosts with less than 300 molecules ¹³¹I-C8 bound remain impermeant to sucrose, irrespective of the total C9 input, or, the multiplicity of C9 uptake by membrane C5b-8. 2. In the presence of excess ¹²⁵I-C9, the ratio of ¹²⁵I-C9/¹³¹I-C8 bound to membrane C5b67 is 3.2 ± 0.8 (mean ± 2 S.D.), suggesting an average stoichiometry of 3 C9 per C5b-8. Under these conditions, the ratio of ¹²⁵I-C9/¹³¹I-C8 bound to sucrose-permeant ghosts (3.3 ± 0.7) does not significantly differ from the ratio bound to sucrose-impermeant ghosts (2.9 ± 0.6). 3. With limiting C9 input, the threshold of total C5b-8 uptake required for sucrose permeability increases significantly above 300 per cell when the ratio of bound ¹²⁵I-C9/¹³¹I-C8 is decreased below unity. In the complete absence of C9, 11 700 C5b-8 complexes are bound to sucrose-permeant ghosts. It is concluded that more than 300 C5b-9 complexes must bind to the human erythrocyte to form a sucrose-permeant lesion. Although the binding of one C9 per C5b-8 is critical to the pore-forming activity of these proteins, the binding of additional molecules of C9 to each complex (C9/C8 > 1) does not significantly alter the threshold of total C5b-9 uptake required for lesion formation.     

Susceptibilities of Algae and Legionella pneumophila to Cooling Tower Biocides

Nine algal strains and nine Legionella pneumophila strains were tested in laboratory culture for their susceptibility to inhibition by a variety of commercially available microbiocides. The responses ranged from ineffective to effective at 1/100 the manufacturers' recommended pulse doses. Tests were also performed to determine whether the action of the microbiocide was bacteriostatic or bacteriocidal.     

Stage specificity of selenium-mediated inhibition of mouse mammary tumorigenesis

The experiments reported herein examined the inhibitory role of selenium in chemical carcinogen-induced mouse mammary tumorigenesis. The results from four different experiments are presented herein and are summarized briefly. First, the results demonstrated that relatively low doses of dietary selenium (0.5–2.0 ppm) inhibited 7,12-dimethylbenzanthracene (DBMA)-induced mouse mammary tumorigenesis. At 2 ppm Se, the mammary tumor incidence was reduced from 56 to 15%. Second, the results suggested that the later stages of mammary tumorigenesis (preneoplastic to neoplastic transformation and tumor growth) are not as sensitive to selenium-mediated inhibition as the early stages, i.e., the induction and/or expression of mammary preneoplastic lesions. Finally, the results demonstrated that selenium markedly inhibited mammary tumorigenesis (from 42 to 8%) even when the mice were exposed to selenium only after the carcinogen treatments had been concluded. The results from these experiments are discussed from the viewpoint that selenium-mediated inhibition is a result of a direct block of DNA synthesis.     

Status of reduced glutathione in primary cultures of rat hepatocytes and the effect on conjugation of benzo[a]pyrene-7,8-dihydrodiol-9,10-oxide

The intracellular level of reduced glutathione (GSH) and GSH conjugation have been investigated in primary cell cultures of hepatocytes isolated from control rats, phenobarbitone (PB) and 3-methylcholanthrene (MC) treated rats. The data demonstrate that in all cell cultures the GSH concentrations show a triphasic pattern: (i) within 1 h of culture an initial marked decrease to 50% of the levels found in fresh hepatocytes; (ii) recovery of GSH concentrations to above the levels observed in fresh cells. This occurs after 6 h in culture with control cells and after 10-24 h with cells from either PB or MC treated rats and was most prominent in cells from PB-treated rats. (iii) A slow decline to between 30 and 40 nmol GSH/mg protein from 24 to 96 h in culture. Synthesis of GSH was slower in cultured cells from PB treated rats and this was confirmed by the resynthesis rates when diethylmaleate (DEM) was used to deplete GSH. The formation of GSH conjugates with racemic 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) was measured in control cells in suspension and after 3 and 24 h in culture. Despite the decrease in GSH concentrations observed between 1 and 4 h after culture, the conjugation rates were not decreased.