Étude physico-chimique des solutions concentrées en acide phosphorique par voie électrochimique. Propriétés acido-basiques et oxydo-réductrices

Acid–base properties in 1 to 14 M H3PO4 solutions are characterized with a R0(H) acidity function and [Formula: see text], [Formula: see text], [Formula: see text] functions which respectively represent the H+ activity in these media and their ability to give [Formula: see text], [Formula: see text], [Formula: see text] species. The thermodynamic limits of potential and the nature of the ionization equilibrium are studied. H and R acidity levels in phosphoric media are compared to those of sulfuric, hydrochloric, and hydrofluoric acid media. The identity of their R0(H) acidity level for the same value of water activity is shown.

Ribosomal RNA genes of Drosophila melanogaster have a novel chromatin structure

We have examined the chromatin organization of the Drosophila melanogaster ribosomal RNA genes using both micrococcal nuclease and DNase I. Several findings are of interest. First, the transcribed DNA segments of the rRNA repeat unit appear to be packaged into an unstable or "multiphasic" nucleosome structure. Second, the 5' end of the transcription unit is preferentially exposed to nuclease attack. Third, the non-transcribed spacer immediately upstream from the transcription start site has a novel chromatin organization with micrococcal nuclease and DNase I cleavage sites spaced at intervals of about 240 base-pairs. This unusual fragment distribution appears to reflect the underlying sequence organization of the spacer DNA segment, which consists of a series of tandemly repeated 239 base-pair sequence blocks. We have also examined the chromatin structure of the rRNA repeat unit after extraction of nuclei with different concentrations of salt. Our results suggest that the higher order structures may be of importance in determining the novel chromatin organization of the rRNA repeat unit.

The rudimentary locus of Drosophila melanogaster

In the studies reported here, we have examined the molecular organization of the rudimentary gene of Drosophila melanogaster. rudimentary encodes a 220,000 Mr polypeptide catalyzing the first three steps in pyrimidine biosynthesis: carbamyl phosphate synthetase, aspartate transcarbamylase and dihydroorotase. We have determined the direction of transcription of the gene relative to the genetic map of the locus. The 5' end maps to the distal end of the locus (relative to the centromere) and transcription proceeds through the domains encoding dihydroorotase, carbamyl phosphate synthetase and finally aspartate transcarbamylase. The rudimentary transcription unit spans a DNA segment of 13.2 X 10(3) base-pairs and encodes a mature messenger RNA of 7.3 X 10(3) base-pairs. Three intervening sequences have been identified, one of which is over 4 X 10(3) base-pairs in length. Finally, we have compared the DNA sequence organization of the Drosophila rudimentary gene with the corresponding loci of yeast and hamster.

Chromatin fine structure of the histone gene complex of Drosophila melanogaster

We have used salt extractions of nuclei and long agarose gels to dissect the chromatin fine structure of the histone gene repeat of Drosophila melanogaster. Extraction of nuclei with 0.35 M KCl removes many non-histone chromosomal proteins but does not significantly disturb the overall nucleosome arrangement of the repeat unit. After extraction of nuclei with 0.55 M KCl, which also removes histone Hl, the basic arrangement of nucleosome core particles in the repeat unit is not greatly disturbed and the exposed DNA segments near the 5' ends of the histone genes are also retained. Extraction of nuclei with 0.75 M or higher KCl concentrations causes extensive nucleosome sliding and rearrangement with accompanying changes in the nucleoprotein organization of the histone gene complex and loss of the 5' hypersensitive sites. Our results indicate that the histone gene repeat displays a highly organized chromatin structure in vivo.

Intimate association of 5S RNA and tRNA genes in Drosophila melanogaster

In this communication, we report the isolation of seven new recombinants derived from the 5S gene locus of Drosophila melanogaster. These recombinants can be divided into three different classes. There are four clones derived from within the 5S gene cluster, two which contain non-5S sequences representing the 5'flanking segment of the gene array and have a structure similar to 12D8 described by Artavanis-Tsakonas et al. (1977), and finally one (22A8) which is shown to contain a DNA segment that is located adjacent to the 3' end of the 5S gene cluster. Analysis of these recombinants supports the model in which all 5S genes of our D. melanogaster Oregon-R wild type strain are arranged in one uninterrupted cluster and are transcribed in the same direction. Interestingly, the 2.5 kb of non-5S RNA coding sequences on the recombinant derived from the 3' edge of the cluster contains at least four genes coding for tRNAs and one of these is located less than 300 bp downstream from the last 5S transcription unit. These tRNA genes are shown to be functional on the basis of the ability of 22A8 DNA to direct the synthesis of tRNA in an in vitro transcription system.

Isolation and characterization of hnRNA-snRNA-protein complexes from Morris hepatoma cells

Of the RNA labelled after incubation of hepatoma cells with radioactive precursors for 20 and 150 min. 35% and 70%, respectively, can be isolated from nuclei by two consecutive extractions with 0.14 M NaCl at pH 8. The isolated RNA is complexed with nuclear proteins forming structures with sedimentation coefficients of less than 30 S to greater than 100 S. Similar complexes from rat liver isolated under the same experimental conditions show coefficients of 30-40 S. The RNA-associated proteins are similar, on the basis of sodium dodecyl sulphate/polyacrylamide gel electrophoresis, to the respective proteins of other cell types. The presence on these RNP complexes of six discrete small nuclear RNAs (snRNA) has been established. Experiments with a reversible inhibitor of RNA synthesis, D-galactosamine, demonstrated, differences in the turnover of hnRNA and snRNA. The half-lives of the six snRNA species has been determined, varying from 32 h for snRNA species a, b and d, to 22 h for snRNA species e and f and to 13 h for snRNA species c. Treatment of the nuclear extracts with 0.7 M and 1 M NaCl results in dissociation of hnRNA from the 'core' and other polypeptides, whereas snRNA remains complexed with polypeptides of Mr 54 000-59 000. Incubation of the nuclear extracts at 0 C with low doses of pancreatic R Nase (up to 1.5 micrograms/ml), which renders approximately 80% of the hnRNA acid-soluble and cleaves most of the snRNA, results in conversion of the high-molecular-weight hnRNPs to 30-S structures, without disrupting the 30-S RNP. Treatment of the nuclear extracts with higher doses of RNase (3 micrograms/ml) leads to disruption of the 30-S RNP and release of the hnRNA-associated proteins, underlining the importance of hnRNA-protein interaction for the retainment of the hnRNP structures.

Tetracycline-resistant L-forms isolated from an antibiotic-susceptible strain of Listeria monocytogenes

A tetracycline-susceptible strain of Listeria monocytogenes type 4b was converted to stable L-forms by penicillin. L-form variants resistant to tetracycline were then selected from a predominantly tetracycline-susceptible L-form population on plates containing penicillin and increasing concentrations of tetracycline. The origin of tetracycline-resistant L-forms from the parent Listeria strain was confirmed biochemically, by immunofluorescence, and by polyacrylamide gel electrophoresis. Scanning and transmission electron microscopy confirmed the typical L-form structure and the complete lack of cell wall in both L-form strains. The level of [3H]tetracycline uptake was lower in tetracycline-resistant than in susceptible cells.

Evaluation of single-cell classification schemes for computer classification of cervical cells

Three single-cell classification schemes were evaluated and compared with the performance of a cytotechnologist in classifying single cells from routinely prepared cervical smears. All of the single-cell classification schemes were found to approach the performance of the cytotechnologist in distinguishing normal squamous cells from significantly dysplastic or malignant squamous cells. For distinguishing non-squamous cell types from dysplastic or malignant squamous cells, however, all three schemes fell far short of the cytotechnologist's performance in classifying the same cells. Current research aimed at overcoming these difficulties is also described.

Chromatin structure of the histone genes of D. melanogaster

We have examined the chromatin structure of the histone gene repeat of D. melanogaster using an indirect end-labeling technique. Our results show that each DNA segment of the repeat is packaged into a precisely defined and characteristic structure, as follows: the nontranscribed spacers display a "normal" chromatin arrangement, with each nucleosome precisely positioned on the underlying DNA sequence; the 5' ends of all five histone genes are in an exposed configuration, highly sensitive to both micrococcal nuclease and DNAase I; and the genes have an "altered" chromatin structure, as indicated by the weak and irregularly spaced nuclease cuts. This well-defined chromatin arrangement is established early in development and is stably maintained throughout the remainder of the D. melanogaster life cycle.

Chromatin structure of the 5S RNA genes of D. melanogaster

The 5S RNA gene cluster of Drosophia melanogaster is a tandem array of a repeat unit made up of a 135 bp gene plus a 238 bp spacer. The length of the 5S repeat (373 bp) equals the average length of a Drosophila dinucleosome. Digestion of Drosophila nuclei with micrococcal nuclease generates discrete 5S RNA gene subfragments when the purified DNA is further cleaved with a single-cut restruction enzyme. We have mapped four micrococcal nuclease-sensitive sites within the 5S repeat: A1, centered at bp--110 (+1 being the G:C bp at the start of the gene); A1', at bp--80; A2, at bp +80, within the intragenic control region; and B, at --190 bp. These findings suggest that nucleosomes can be positioned on the 5S gene repeat in one of two possible phases, A or B. In the A phase a potential regulatory sequence near the center of the gene is exposed in one of the two linkers of the repeat. In the B phase, in contrast, one of the linkers includes the 5' end of the gene.

Modifications of the envelope of Chlamydia psittaci during its developmental cycle: freeze-fracture study of complementary replicas

Examination of complementary replicas obtained by freeze-fracture of Chlamydia psittaci revealed, at the level of the plasma membrane, a progressive differentiation of "crate-like formations," which likely correspond to transmembranal pores. Recognition of "early" and "late" stages observed in the intermediate bodies permitted detailed study of the developmental cycle of this chlamydia.

[An ultrastructural study of the transformation of elementary bodies of Rickettsiella into initial bodies (author's transl)]

An intermediate stage between the elementary and the initial bodies of the Rickettsietta genus is defined as the beginning of an intracellular cycle. It is characterized by several structural changes in the dense elementary body: the cytoplasm becomes less electron-dense; thus, the nucleoid and the ribosomes are visible. The inner layer of the cell-wall becomes progressively clearer and the trilamellar structure of the inner and outer membranes appears distinctly. 'preinitial body' is proposed as name of this stage of development.

[Experimental infection of an invertebrate cell line with a mollicute-like procaryote inducing the "lethargy of coleoptera" (author's transl)]

In vitro multiplication of a pathogenic intravacuolar mollicute-like procaryote from Melolontha melolontha L. was experimentally obtained in an insect cell line. The elongated and pleomorphic forms observed in the insect-host are reproduced in cell cultures. A third peculiar giant form is missing, showing that it does not play any role in the multiplication of the germ. The intrinsic potentialities of the germ are maintained during the successive passages, as proved by reinfection of the insect and by immunology. The original syndrome including the giant form is reproduced in the insect. The immunserum prepared from the wild germ isolated by density gradient is positive with the in vitro mollicute. The germs are intravacuolar, both in the cultured cells and in the insect host. Clearly the microorganism multiplies within the vacuoles. A cytopathogenic effect is noticed in the cultured cells overcrowed with germs. The germs become extracellular when they are released in the culture medium by disaggregation of the cell membranes. It seems that this work shows the first model of an intravacuolar mollicute-like procaryote experimentally multiplied in cultivated cells.

[Familial nephropathy with retinitis pigmentosa and peripheral dysostosis]

The paper reports two siblings, 6 and 3 3/4 years old, with a congenital nephropathy (nephronophthisis), retinitis pigmentosa, heart failure and peripheral dysostosis. The severe histological changes of the kidneys with tubular atrophy and interstitial fibrosis caused the death of the older sister at the age of 7 years. The symptoms of our patients are discussed in comparison to the syndrome described by MAINZER et al.

[Cytochemical and freeze-etching studies of the ultrastructure of a Rickettsiella in a crustacean (author's transl)]

Several characteristics of the intracellular cycle of Ricketsiella are elucidated, particularly regarding the envelope and the cytoplasm of dense forms (elementary bodies) as well as the proteinic inclusions of giant bodies. Cleavage faces have been displayed by freeze-etching, both at the level of cell wall and of plasma membrane. Their characteristics approach those of Gram-negative bacteria and are pratically common to all the stages. Appearance and significance of a polysaccharidic cement joining the outer membrane of the cell wall to the inner membrane (plasma membrane) in the dense forms are discussed. The arrangement of ribosomes and the structure of the nucleoid are described. A 6 nm lattice periodical structure is shown in the proteinic inclusion. Significance of these data for a classification of Rickettsiella and chlamydias is discussed.

High resolution analysis of cervical cells--a progress report

This paper presents preliminary results of research toward the development of a high resolution analysis stage for a dual resolution image processing-based prescreening device for cervical cytology. Experiments using both manual and automatic methods for cell segmentation are described. In both cases, 1500 cervical cells were analyzed and classified as normal or abnormal (dysplastic or malignant) using a minimum Mahalanobis distance classifier with eight subclasses of normal cells, and five subclasses of abnormal cells. With manual segmentation, false positive and false negative error rates of 2.98 and 7.73% were obtained. Similar experiments using automatic cell segmentation methods yielded false positive and false negative error rates of 3.90 and 11.56%, respectively. In both cases, independent training and testing data were used.

Cytology of transitional cell carcinoma in situ of urinary bladder with extensive prostatic involvement

Cytologic differences in the urine of 6 patients with transitional cell carcinoma in situ (CIS) of the urinary bladder with and without prostatic duct involvement are described. In the former group, there was an admixture of CIS cells along with many bizarre malignant cells which increased with time and showed malignant criteria indicative of changes more than CIS alone.