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G Bélanger

Publications and source records attributed to G Bélanger.

18 recordsLinked to original sources
PubMed1989

Mapping of the puh messenger RNAs from Rhodospirillum rubrum. Evidence for tandem promoters.

The mRNA transcripts of Rhodospirillum rubrum gene puh, coding for the H subunit of the photoreaction center, and of genes flanking puh were analyzed by blot hybridization. Open reading frame G115, upstream of structural gene puh, is transcribed as a 2.25-kilobase mRNA. Gene puh itself is transcribed as two mRNAs of 1118 and 1032 nucleotides. Mung bean nuclease protection analysis shows that the puh transcripts have different 5' termini within open reading frame G115 and a unique rho-independent termination signal within open reading frame I2372. The lifetimes of the puh messages, as determined by an oxygen blockade of transcription, were 10 and 12 min for the large and small puh mRNAs, respectively. An expression vector carrying a chloramphenicol acetyltransferase gene was used to select promoters in DNA stretches upstream of the startpoints of each of these transcripts. Chloramphenicol resistance was expressed in Escherichia coli, using as a promoter a 179-nucleotide stretch upstream of the small mRNA startpoint but not from a 124-nucleotide stretch upstream of the large mRNA startpoint. The promoter for the small mRNA, designated Ppuh2, is thought to encompass in its -10 and -35 regions a sigma 70-like RNA polymerase recognition sequence. The region upstream of the large message startpoint contains a sequence similar in its -12 and -24 regions to promoter sequences recognized by the sigma 60 RNA polymerase holoenzyme. This is designated as promoter Ppuh1.Ppuh1 is proposed to be strictly regulated by light intensity and by oxygen tension while Ppuh2 would be less sensitive to these parameters.

Bacterial Proteins↗
PubMed1989

A multimedia medical communication link between a radiology department and an emergency department.

The most critical aspect of a radiologist's work is communicating his findings to the attending physician responsible for the patient's care. This is also the part of the process that is least well organized and the most subject to failure. At the University of Ottawa Medical Communications Research Centre we are investigating technical means to improving communications between radiologists and attending physicians. We first introduce the radiology communication service problem and show why it is essentially a multimedia communication problem. We then briefly describe a multimedia communication system designed and implemented by our research team. The multimedia system consists of several work stations linked by the Hospital's local area network (LAN). Each physician work station comprises a Compaq 386/20-Mhz microcomputer with 16 Mbytes of RAM, a 500-Mbyte image disk, and an image memory that drives a 1,000-line monochrome monitor. The images are digitized using a Konica laser-based film digitizer (2430 by 2000 10-bit pixels for a standard chest radiograph). The multimedia file server manager station is built around a PC-AT compatible with a Northern Telecom Meridian SL-1ST digital PBX and a Meridian Mail digital voice messaging system. This last device is used to store voice data and is linked via the PBX to the workstations' digital telephones. A Sytek 6,000 LAN links all work stations to the file server. All data, image, and graphic information is transmitted via this network, while the twisted pair connections linking the digital PBX to the telephone sets are used for transmitting voice data.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer Communication Networks↗
PubMed1989

Context-dependent enhancements for radiological images.

Many techniques have been proposed to enhance radiographic images and each of them may be optimal depending upon the circumstances. However, the problem confronting the radiologist or the physician is which enhancement to use and how to select the parameters when a specific feature is to be emphasized. At the University of Ottawa, our research work is oriented towards automatic context-dependent enhancements. Our approach attempts to match the three phases involved in viewing a radiograph: getting a global impression, analyzing the objects and the local features, and focusing on the image perturbations. In this article, we report on enhancements to support the first two phases in the case of chest radiographs and on the applicability of gray level reversal transformations.

Emergency Service, Hospital↗
PubMed1988

The structural genes coding for the L and M subunits of Rhodospirillum rubrum photoreaction center.

In Rhodospirillum rubrum, pufL, and pufM, the structural genes coding for the photoreaction center L and M polypeptides, are comprised respectively of 831 and 921 nucleotides. They are separated by a stretch of 12 nucleotides between the TAA stop codon of pufL and the first base of the ATG initiation codon of pufM. The predicted amino acid sequence of the L and M polypeptides, respectively, contain 275 and 305 residues with corresponding molecular weights of 30,473 and 33,978. Their sequences are highly homologous to those of Rhodobacter sphaeroides, Rhodobacter capsulatus, and Rhodopseudomonas viridis. As can be deduced from the crystallographic structure of other photoreaction centers, the regions of greatest similarity are the binding sites of the cofactors involved in the photochemical reaction rather than the protein secondary structure. L and M contain, at conserved positions of their sequences, three main clusters of positively charged residues on the cytoplasmic side of the membrane. This arrangement may be involved in protein orientation during membrane assembly. Evolutionary distance of pufL and pufM, as assessed by substitution frequency analysis, confirms the closeness of the two Rhodobacter species, the other two species being equidistant from one another. Interspecies evolutionary distance is greater for pufL than for pufM.

Bacterial Proteins↗
PubMed1988

Structure and expression of the puf operon messenger RNA in rhodospirillum rubrum.

In Rhodospirillum rubrum, the genes coding for the alpha and beta polypeptides of the B880 antenna (pufA,B) and the L and M polypeptides of the photoreaction center (pufL,M) are clustered on operon puf. In oxygen-limited cells, the puf mRNA is present as species of 2561, 640, and 617 nucleotides. Aerated cells contain only traces of these mRNAs. The large mRNA encodes the alpha,beta, L, and M polypeptides, whereas the small mRNAs encode only alpha and beta. S1 nuclease protection mapping showed these transcripts to have a common 5' end, immediately downstream of a region of dyad symmetry and at 166 nucleotides upstream of the initiation codon of pufB. The 3' termini of the small transcripts are located in the intercistronic region between pufA and pufL, downstream of another region of dyad symmetry. This region is highly conserved in Rhodospirillum rubrum, Rhodobacter capsulatus, and Rhodobacter sphaeroides and shares 61% sequence similarity with the repetitive extragenic palindromic sequences of Escherichia coli. The slightly heterogeneous 3' termini of the large transcript are downstream of a region of dyad symmetry characteristic of rho-independent transcription termination. Following a shift from oxygen-limited to aerated conditions, the pufL,M and the pufA,B mRNAs decayed with respective half-lives of 9 and 20 min. These high relative stabilities, attributed to secondary structure, are in accord with the mole ratio (2:1) of the pufA,B/pufL,M messages. While the differential expression of alpha,beta/L,M congruent to 15 is thought to be due, in part, to this relative stability, the main factor may be a more efficient translation initiation for pufA,B than for pufL,M.

Bacterial Proteins↗
PubMed1986

Molecular cloning and sequence of the B880 holochrome gene from Rhodospirillum rubrum.

Restriction fragments of genomic Rhodospirillum rubrum DNA were selected according to size by electrophoresis followed by hybridization with [32P]mRNA encoding the two B880 holochrome polypeptides. The fragments were cloned into Escherchia coli C600 with plasmid pBR327 as a vector. The clones were selected by colony hybridization with 32P-holochrome-mRNA and counterselected by hybridization with Rs. rubrum ribosomal RNA, a minor contaminant of the mRNA preparation. Chimeric plasmid pRR22 was shown to contain the B880 genes by hybrid selection of B880 holochrome-mRNA. We report a restriction map of its 2.2-kilobase insert and the sequence of a 430 base pair fragment thereof. Genes alpha and beta are nearly contiguous, indicating that they are transcribed as a single operon. The predicted amino acid sequences coincide with the sequences of the alpha and beta polypeptides established in other laboratories, except for additional C-terminal tails of 10 and 13 amino acid residues, respectively. We suggest that these tail sequences may serve, during membrane assembly, to give these intrinsic membrane proteins their peculiar orientation with their C-terminus facing the periplasm and their N terminus facing the cytoplasm. Intraspecific sequence homology between the alpha and beta genes of R. rubrum is low, showing no evolutionary relatedness. This is in contrast to the high interspecific homology between the corresponding sequences of Rs. rubrum and Rhodopseudomonas capsulata B880 genes.

Amino Acid Sequence↗
PubMed1985

Isolation and partial characterization of the messenger RNA encoding the B880 holochrome protein of Rhodospirillum rubrum.

The B880 holochrome messenger RNA was extracted from cultures of the photosynthetic bacterium Rhodospirillum rubrum. It was purified by chromatography on Sepharose 4B followed by sucrose density gradient centrifugation. The purified fractions were shown to program an Escherichia coli cell-free system into synthesizing both the alpha and the beta polypeptides of the holochrome. The translation products were identified by immunoprecipitation with specific antibodies raised against these polypeptides. The latter are effective competitors with the translation products for antigen-antibody complex formation. The purest mRNA preparations contained approximately 33% holochrome messenger RNA activity. Its most probable size, as determined by agarose gel electrophoresis in the presence of 6 M urea or methylmercuric hydroxide, is approximately 620 nucleotides. Since the combined sizes of the alpha and beta polypeptides add up to only 106 amino acid residues, we conclude that the holochrome mRNA is most probably polycistronic.

Bacterial Proteins↗
PubMed1979

Ribosomes of Physarum polycephalum. Subunits and protein composition.

Ribosomes from Physarum polycephalum were purified. Optimal conditions for preparation and stability of subunits were determined. KCl concentration above 200 mM induced protein dissociation from the subunits. It was observed that dissociated ribosomes were more stable in a low ionic strength buffer than in 200 mM KCl, where the 40 S was preferentially degraded by ribonucleases. Ribosomal proteins were analyzed by two-dimensional gel electrophoresis. The first dimension was carried out at pH 8.6 while the second was run at pH 4.6. The monosome contained sixty seven proteins, of which six were acidic. Two proteins were lost after subunit dissociation. Twenty six basic and two acidic proteins were observed in the 40 S subunit while the largest subunit gave thirty nine spots on the basic part of the gel and three additional spots on the acidic side. Five proteins were shared by 40 S and 60 S.

Electrophoresis, Polyacrylamide Gel↗
PubMed1979

Development of high resolution computed tomography of the spinal cord.

Computed tomography of the spinal cord was a natural development of total body scanning. Much time and effort was spent in order to visualize the spinal cord and the various conditions affecting it. This was achieved by using an EMI CT5005 scanner and a series of step by step modifications and improvements to obtain a very high degree of resolution. The large variety of intraspinal lesions seen at the Montreal Neurological Hospital allowed us, by selecting appropriate cases, to determine the value of CT of the spinal cord.

Humans↗
PubMed1977

Evaluation of the age of subdural hematomas by computerized tomography.

The computerized tomography (CT) scans of 50 patients with surgically proven subdural hematomas were subdivided into three groups on the basis of the attenuation coefficients of the subdural fluid collections: 28% were more dense, 24% isodense, and 48% less dense than the surrounding brain. The 42 patients with the available data were then subdivided into three groups; acute, subacute, and chronic, according to the time interval between trauma or duration of symptoms and date of CT scanning. Subdural hematomas were found to be hyperdense in 100% of acute patients, isodense in 70% of the subacute group, and hypodense in 76% of the chronic group.

Acute Disease↗
PubMedDate not supplied

Brain hemorrhage from intracranial tumor.

Brain hemorrhage from an intracranial tumor was encountered in 7 males and 6 females during a 4-year period. In 5 patients, hemorrhage was responsible for the first signs of a previously unsuspected neoplasm. The intracranial lesion was demonstrated by computed tomography (CT scanning) in each patient. Characteristic CT scan findings included: a neoplastic core (high or low density); small, multifocal clots usually at the margin of the tumor; and, surrounding, often extensive, edema. Enhancement of the tumor tissue with intravenous injection of 60% Hypaque was observed in the 8 patients so studied. The regions which were enhanced had a peripheral distribution corresponding to the site of hemorrhage. Microscopic examination demonstrated 7 glioblastoma multiforme, 1 oligodendroglioma, 4 metastatic carcinomas (including 1 each of bronchogenic carcinoma, melanoma, hypernephroma, and adrenal carcinoma), and 1 hemangiopericytoma. High-grade malignancy and extensive, abnormal vascularity appeared to be predisposing factors.

Adolescent↗