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H Bertrand

Publications and source records attributed to H Bertrand.

At least 37 records · Page 2Linked to original sources
PubMed1994

Mutations in the structural gene for cytochrome c result in deficiency of both cytochromes aa3 and c in Neurospora crassa.

The cyt-12-12 mutant of Neurospora crassa is characterized by slow growth and a deficiency of spectrophotometrically-detectable cytochromes aa3 and c. Using a sib-selection procedure we have isolated the cyt-12+ allele from a cosmid library of N. crassa genomic DNA. Characterization of the cyt-12+ allele reveals that it encodes the structural gene for cytochrome c. DNA sequence analysis of the cyt-12-12 allele revealed a mutation in the cytochrome c coding sequence that results in replacement of a glycine residue, which is invariant in the cytochrome c of other species, with an aspartic acid. Genetic analysis confirms that cyt-12-12 is allelic with the previously-characterized cyc-1-1 mutant, which was also shown to affect the single locus encoding cytochrome c in N. crassa. We suggest that the amount of functional cytochrome c present in mitochondria influences the level of cytochrome aa3.

Alleles↗
PubMed1993

Expression of the open reading frames of a senescence-inducing, linear mitochondrial plasmid of Neurospora crassa.

Senescence-prone strains of Neurospora crassa from Aarey, India, harbor a linear mitochondrial plasmid, maranhar, which potentially encodes an RNA polymerase and a DNA polymerase (Court and Bertrand, 1992). To investigate the expression of the open reading frames (ORFs) of this plasmid, the mitochondria of the prototype of the senescence-prone strains, Aarey-1e, were analyzed for the presence of maranhar-specific transcripts and proteins. In addition to several low-abundance and small RNAs, two major large transcripts, each encompassing one of the long ORFs, were identified. The 5'-termini of these two transcripts are identical and coincide with a nucleotide sequence that is located in the terminal inverted repeats of the plasmid and partially resembles the promoter sequences of Neurospora mitochondrial genes. The 3' end of one of the plasmid transcripts also has been mapped. It is located within the DNA spacer between the two convergent ORFs and does not coincide with a conventional transcription-termination or RNA-processing signal. Two novel proteins, which may be the plasmid-encoded DNA and RNA polymerases, are synthesized in the mitochondria of the maranhar-containing strain. Although the termini of the plasmid are linked to terminal protein, a third plasmid-specific polypeptide was not observed. Transcripts encompassing three small ORFs in the maranhar nucleotide sequence also were identified. These RNAs occur in rather low copy numbers, and translation products that might correspond to the small ORFs were not detected in the mitochondria of the plasmid-containing strain.

Amino Acid Sequence↗
PubMed1993

Structure and evolution of a highly repetitive DNA sequence from Brassica napus.

A Hind III family of highly repetitive DNA sequences, canrep (canola repeat), was cloned from the nuclear DNA of canola (Brassica napus cv. Westar). The basic units of this family of repeats consists of 176 bp and are arranged in clusters of tandem direct repeats. Each canrep repeat is composed of three related subrepeats of ca. 60 bp. Each subrepeat contains two inverted repeats of about 23 bp and another unrelated sequence of about 12 bp. Based on the internal structure, a possible scheme for the evolution of canrep is proposed. At least two subfamilies of the canrep sequences are present in the genome, as revealed by sequence analyses. In situ hybridization showed that canrep sequences are mainly clustered at centromeric regions of chromosomes. Northern hybridizations indicate that there are no transcripts related to canrep in the total RNAs extracted from plant seedlings.

Base Sequence↗
PubMed1993

Long-term caloric restriction improves baroreflex sensitivity in aging Fischer 344 rats.

The effects of aging and caloric restriction on mean arterial pressure (MAP), heart rate (HR), and baroreflex sensitivity were determined in young (7-9 months) and old (22-24 months) awake, male Fischer 344 rats which had been either ad libitum fed or calorie restricted (60% of the ad libitum calories). The MAP of young rats was higher than that of old rats. The MAP of old ad libitum fed rats was higher than that of old restricted rats with no effect of diet in young rats. The HR of restricted rats was lower than ad libitum fed rats with no significant age effect. Reflex bradycardia to hypertensive episodes was greater in restricted than in ad libitum fed rats. Reflex tachycardia to hypotensive episodes was greater in young than in old rats and greater in calorie restricted than in ad libitum fed rats. These findings demonstrate that caloric restriction alters the age-associated decline in several hemodynamic parameters.

Aging↗
PubMed1993

Hyperactive recombination in the mitochondrial DNA of the natural death nuclear mutant of Neurospora crassa.

In Neurospora crassa, a recessive mutant allele of a nuclear gene, nd (natural death), causes rapid degeneration of the mitochondrial DNA, a process that is manifested phenotypically as an accelerated form of senescence in growing and stationary mycelia. To examine the mechanisms that are involved in the degradation of the mitochondrial chromosome, several mitochondrial DNA restriction fragments unique to the natural-death mutant were cloned and characterized through restriction, hybridization, and nucleotide sequence analyses. All of the cloned DNA pieces contained one to four rearrangements that were generated by unequal crossing-over between direct repeats of several different nucleotide sequences that occur in pairs and are dispersed throughout the mitochondrial chromosome of wild-type Neurospora strains. The most abundant repeats, a family of GC-rich sequences that includes the so-called PstI palindromes, were not involved in the generation of deletions in the nd mutant. The implication of these results is that the nd allele hyperactivates a general system for homologous recombination in the mitochondria of N. crassa. Therefore, the nd+ allele either codes for a component of the complex of proteins that catalyzes recombination, and possibly repair and replication, of the mitochondrial chromosome or specifies a regulatory factor that controls the synthesis or activity of at least one enzyme or ancillary factor that is affiliated with mitochondrial DNA metabolism.

Base Sequence↗
PubMed1992

Genetic organization and structural features of maranhar, a senescence-inducing linear mitochondrial plasmid of Neurospora crassa.

The nucleotide sequence of maranhar, a senescence-inducing linear mitochondrial plasmid of Neurospora crassa, was determined. The termini of the 7-kb plasmid are 349-bp inverted repeats (TIRs). Each DNA strand contains a long open reading frame (ORF) which begins within the TIR and extends toward the centre of the plasmid. ORF-1 codes for a single-subunit RNA polymerase that is not closely related to that encoded by another Neurospora plasmid, kalilo. The ORF-2 product may be a B-type DNA polymerase resembling those encoded by terminal protein-linked linear genetic elements, including linear mitochondrial plasmids and linear bacteriophages. A separate coding sequence for the terminal protein could not be identified; however, the DNA polymerase of maranhar has an amino-terminal extension with features that are also present in the terminal proteins of linear bacteriophages. The N-terminal extensions of the DNA polymerases of other linear mitochondrial plasmids contain similar features, suggesting that the terminal proteins of linear plasmids may be comprised, at least in part, of these cryptic domains. The terminal protein-DNA bond of maranhar is resistant to mild alkaline hydrolysis, indicating that it might involve a tyrosine or a lysine residue. Although maranhar and the senescence-inducing kalilo plasmid of N. intermedia are structurally similar, and integrate into mitochondrial DNA by a mechanism thus far unique to these two plasmids, they are not closely related to each other and they do not have any nucleotide sequence features, or ORFs, that distinguish them clearly from mitochondrial plasmids which are not associated with senescence and most of which are apparently non-integrative.

Amino Acid Sequence↗
PubMed1992

A deletion derivative of the kalilo senescence plasmid forms hairpin and duplex DNA structures in the mitochondria of Neurospora.

A novel deletion derivative, delta kal, of the kalilo senescence plasmid from Neurospora intermedia, was recovered from a culture treated with chloramphenicol. The deletion derivative exists in mitochondria as two different, equally abundant forms: a 2.8 kb duplex DNA molecule (delta kal-2.8) and a 1.4 kb hairpin form (delta kal-1.4). The delta kal-2.8 plasmid contains the 1366 bp terminal inverted repeats and a partially duplicated 102 bp segment of the unique sequence of the 8.6 kb kalilo plasmid. In contrast, the delta kal-1.4 hairpin plasmid appears to result from the folding of single strands that are generated during the replication of delta kal-2.8. Both forms of delta kal have covalently linked terminal proteins. Sequence analysis suggests that delta kal was generated either by slippage of the tip of a growing strand during the replication of kalilo, or by illegitimate recombination between two copies of the plasmid at non-homologous palindromic sequences that might form cruciform structures. In either case, the deletion process was mediated at least in part by an inverted repeat of 5 bp in the unique region of kalilo. Since the terminal segments of kalilo DNA that are implicated in plasmid integration might also form cruciform structures, it is possible, but improbable, that the process that generated the first delta kal molecule is related to that which mediates integration of the plasmid into mitochondrial DNA.

Base Sequence↗
PubMed1991

Stripping out pus in lactational mastitis: a means of preventing breast abscess.

OBJECTIVE: To determine whether manual stripping of pus from the breasts of women with lactational mastitis is effective in preventing the formation of breast abscesses. DESIGN: Case series (chart review). SETTING: Family practice in Montreal. PATIENTS: All (475) charts of patients with lactational mastitis were reviewed; 61 women were excluded because they already had a breast abscess. Most of the patients had been referred. OUTCOME MEASURES: Abscess formation, length of illness after treatment, rate of recurrence of mastitis, illness in the mother or infant within the 6 weeks after the mastitis and continuance of breast-feeding. MAIN RESULTS: The duration of symptoms before treatment was 1 to 56 (mean 5.3) days. In 9% of the cases both breasts were affected, and in 23% at least one episode of mastitis had previously occurred. The stripping technique was applied to all the patients. Pus was removed in 210 women; the remaining women were considered to have cellulitis. Only four patients (less than 1%) had breast abscesses. The mean length of illness after treatment was 7.2 days. The rate of recurrence was 14%. In all, 6% of the mothers and 9% of the infants became ill in the 6 weeks after the mastitis. Most (92%) of the patients continued to breast-feed. CONCLUSIONS: The rate of abscess formation was considerably lower than the rates reported in the literature. Therefore, manual stripping of pus from the infected breasts of lactating women appears to be effective in preventing breast abscesses.

Abscess↗
PubMed1991

The kalilo linear senescence-inducing plasmid of Neurospora is an invertron and encodes DNA and RNA polymerases.

The nucleotide sequence of kalilo, a linear plasmid that induces senescence in Neurospora by integrating into the mitochondrial chromosome, reveals structural and genetic features germane to the unique properties of this element. Prominent features include: (1) very long perfect terminal inverted repeats of nucleotide sequences which are devoid of obvious genetic functions, but are unusually GC-rich near both ends of the linear DNA; (2) small imperfect palindromes that are situated at the termini of the plasmid and are cognate with the active sites for plasmid integration into mtDNA; (3) two large, non-overlapping open-reading frames, ORF-1 and ORF-2, which are located on opposite strands of the plasmid and potentially encode RNA and DNA polymerases, respectively, and (4) a set of imperfect palindromes that coincide with similar structures that have been detected at more or less identical locations in the nucleotide sequences of other linear mitochondrial plasmids. The nucleotide sequence does not reveal a distinct gene that codes for the protein that is attached to the ends of the plasmid. However, a 335-amino acid, cryptic, N-terminal domain of the putative DNA polymerase might function as the terminal protein. Although the plasmid has been co-purified with nuclei and mitochondria, its nucleotide composition and codon usage indicate that it is a mitochondrial genetic element.

Amino Acid Sequence↗
PubMed1991

A new senescence-inducing mitochondrial linear plasmid in field-isolated Neurospora crassa strains from India.

Several field-collected strains of Neurospora crassa from the vicinity or Aarey, Bombay, India, are prone to precocious senescence and death. Analysis of one strain, Aarely-1e, demonstrated that the genetic determinants for the predisposition to senescence are maternally inherited. The senescence-prone strains contain a 7-kb, linear, mitochondrial DNA plasmid, maranhar, which is not present in long-lived isolates from the same geographical location. The maranhar plasmid has inverted terminal repeats with protein covalently bound at the 5' termini. Molecular hybridization experiments have demonstrated no substantial DNA sequence homology between the plasmid and the normal mitochondrial (mtDNA) and nuclear genomes of long-lived strains of N. crassa. Integrated maranhar sequences were detected in the mtDNAs of two cultures derived from Aarey-1e, and mtDNAs with the insertion sequences accumulated during subculturing. Nucleotide sequence analysis of cloned fragments of the two insertion sequences demonstrates that they are flanked by long inverted repeats of mtDNA. The senescence syndrome of the maranhar strains, and the mode of integration of the plasmid, are reminiscent of those seen in the kalilo strains of N. intermedia. Nonetheless, there is no detectable nucleotide sequence homology between the maranhar and kalilo plasmids.

Base Sequence↗
PubMed1991

[Gazeous necrosis of the liver due to hepatic artery thrombosis after liver transplantation].

An emergency liver transplantation was performed in a 22 year-old female for fulminant hepatitis. The donor had had splenectomy with portal vein thrombosis which was diagnosed and removed during portoscopy. Nineteen days later, abdominal pain with shock and hepatic failure occurred. X-rays showed pneumoperitoneum and aeric images in the liver area. Laparotomy disclosed massive liver necrosis with gaz under the Glisson's capsula. The hepatic artery was thrombosed. In spite of emergency retransplantation, the patient died 8 days later, due to systemic aspergillosis. Thrombosis of hepatic artery was particular by the importance of gaz-forming infection, and emphasizes the role of rejection. The discovery of portal thrombosis allows to outline the precautions necessary in case of splenectomized donors. The severeness of aspergillosis is underscored.

Adult↗
PubMed1989

Partially N-desulfated heparin as a non-anticoagulant heparin: some physico-chemical and biological properties.

A partially N-desulfated preparation of heparin (UFH) obtained by thermally inactivating heparinic acid for 24 hours at 50 degrees C (TIHA) was examined for its physico-chemical and biological properties in vitro and in vivo. TIHA has a molecular weight of 14,700 and 27% remaining N-sulfate groups (UFH = 17,500; 100% N-sulfate groups). TIHA has no anticoagulant activity measurable by conventional amidolytic or clotting tests. However, in a rabbit stasis-induced thrombosis model and using two different thrombogenic stimuli (Feiba and PCC(Konyne)/RVV), TIHA afforded a dose-dependent (1.0-2.5 mg/kg) protection sufficient to impair thrombosis (UFH: fully effective at 0.13 mg/kg). TIHA did not produce any bleeding at supramaximal antithrombotic dosage in a rat tail bleeding and a rabbit ear blood loss model and it did not augment ADP-induced aggregation of platelets. In contrast, a completely N-desulfated derivative of UFH (Inoue and Nagasawa, Carbohydr. Res. 46, 87-95, 1976) also lacking measurable in vitro activity was completely inactive in vivo. The results in this study suggest that TIHA may be considered as a non-anticoagulant heparin still retaining antithrombotic activity and also with lower haemorrhagic effect than UFH.

Adenosine Diphosphate↗
PubMed1989

Linear kalilo DNA is a Neurospora mitochondrial plasmid that integrates into the mitochondrial DNA.

The linear autonomous form of kalilo DNA (previously called AR-kalDNA) is shown to be resident within mitochondria rather than nuclei, as had been suggested by previous experiments. This form has been renamed mtAR-kalDNA, to signify its mitochondrial location. Experiments are described that illustrate the inheritance and somatic transmission patterns of the mitochondrial kalilo plasmid and the mitochondrial inserted form of kalilo DNA (mtIS-kalDNA). Progeny of a cross with a pre-senescent subculture as the female parent inherited mtAR-kalDNA only; mtIS-kalDNA was not transmitted sexually. During somatic propagation of the ascospore cultures, novel kalilo DNA inserts appeared and most of them persisted until death. We propose that these inserts originated from de novo integration of mtAR-kalDNA into the mitochondrial DNA. In two of the ascopore-derived series analyzed, the first inserts detected were seen only transiently and inserts appearing subsequent to the transient inserts were retained until death. We propose that these enduring inserts originated either from rearrangements of the transient inserts or from novel integration events, either from mtAR-kalDNA or from transposition of the transient inserts.

Blotting, Southern↗