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Biomedical subjects

J Paquette

Publications and source records attributed to J Paquette.

13 recordsLinked to original sources
PubMed1992

A reliable method for the use of oligonucleotides as probes in blot-hybridization experiments.

We have developed a ligation and specific-primer radiolabeling method that allows the use of oligonucleotides as probes in blot-hybridization experiments. The major advantage of the protocol is that standard hybridization and washing conditions may be used and yield high signals and low background. The observed increase in the stability and intensity of the hybridization signals appears to result from both increased length and specific radioactivity of the hybridization probe.

Base Sequence↗
PubMed1992

The polar-lethal Ovum mutant gene maps to the distal portion of mouse chromosome 11.

Genome imprinting is the process by which identical alleles at a particular locus may be rendered functionally different depending on the sex of the parent contributing the allele. While several mutations in imprinted genes have been defined, no variants in the regulatory system that gives rise to imprinting have been described. Here we report our genetic analysis of the behavior of the interstrain, polar, embryonic-lethal phenotype known as the "DDK syndrome." We have mapped the interstrain, polar-lethal region of the genome to the distal portion of mouse chromosome 11, near the Xmv-42 locus. We propose that the lethal phenotype is not caused by a standard mutation, but by aberrant imprinting of a gene within this region.

Animals↗
PubMed1992

[Positive results from light therapy].

In their original May 1991 article, (this journal), the authors described the guidelines for, and results of, implementation of artificial light therapy in a Sherbrooke Hospital psychiatric unit for the treatment of seasonal affective disorder. In the present article, the authors describe an evaluation conducted to determine if there were specific aspects relating to the client or the therapy that had a direct influence on the results, and if it was necessary to develop new guidelines or parameters to guide future administration of treatments. They also wanted to obtain a typical portrait of their clients. Eighteen clients were treated on an outpatient basis during the winter of 1990-91. All but two completed their treatment programs and took part in the evaluation. The majority of the clients identified were women (94 per cent); 56 per cent were unmarried; and of those of working age, all were regularly employed except one. The greatest majority of clients had no social activities, 69 per cent had a history of psychiatric problems and 44 per cent were taking anti-depressants. Because of the artificial light therapy, improvement was noted in their level of energy, social activities, sleep, appetite and emotional state.

Adult↗
PubMed1991

[Light therapy].

Since the discovery of a link between seasonal depression and diminishing sunlight, many studies have been initiated. Animal studies have confirmed this link. In 1989, a committee from the psychiatric department of Sherbrooke Hospital was formed to plan, organize and implement artificial light therapy in the general and legal psychiatric unit. Two nurse members of this committee give a description of the treatment, and comment on guidelines and results. They are convinced that a functional structure for light therapy may revolutionize psychiatry.

Humans↗
PubMed1990

The conformation of single-stranded nucleic acids tDNA versus tRNA.

Conformational analyses using the single-strand-specific nuclease from mung bean and restriction endonucleases have been performed on a series of DNA fragments related to the sequence of the yeast initiator tRNA(Met). Mung bean nuclease cleaves DNA fragments exclusively in some, but not all, single-stranded regions as predicted by RNA secondary structural rules. Comparison of cleavage patterns of yeast initiator tRNA(Met), tDNA(Met) (a DNA oligomer having the sequence of tRNA(Met] and the anti-tDNA(Met) (the complement of tDNA(Met] suggests that the conformation of the three molecules is very similar. Furthermore, both tDNA and anti-tDNA are cleaved by HhaI and CfoI restriction endonucleases at two GCG/C sites which would be in double-stranded regions (the acceptor and dihydrouridine stem), if the two molecules adopt the tRNA cloverleaf structure. On the other hand, minor cleavage products show that the core region, i.e. the extra loop area, is slightly more exposed in tDNA and in anti-tDNA than in tRNA. Therefore, we submit that the global conformation of nucleic acids is primarily dictated by the interaction of purine and pyrimidine bases with atoms and functional groups common to both RNA and DNA. In this view the 2'-hydroxyl group, in tRNA at least, is an auxiliary structural feature whose role is limited to fostering local interactions, which increase the stability of a given conformation.

Base Sequence↗
PubMed1990

[The focal study].

Representing a new approach to assessing the quality of nursing care, the focal study provides an effective and systematic method for resolving particular nursing problems. This article summarizes a focal study carried out by two nurses in the psychiatric unit of a major hospital in Sherbrooke, Québec. It addresses problems associated with the use and completion of the nursing history for each client. The methodology used is explained in detail and accompanied by specific examples.

Humans↗
PubMed1989

Structure of the pig pancreatic GP-2: role of intramolecular disulfides in the resistance to proteolysis.

GP-2 is the major membrane glycoprotein characteristic of the pancreatic zymogen granule membrane. When granules are lysed in the presence of DTT, GP-2 becomes completely and specifically degraded. This proteolysis was reproducible with the same characteristics in the purified granule membrane. The protease was purified from this source using hydrophobic interaction chromatography. The proteolytic activity was identified as a 29-kDa protein because, in a reconstituted system containing both the purified GP-2 and the 29-kDa protein, the proteolytic degradation of GP-2 was sensitive to the same spectrum and concentrations of inhibitors or reducing agents as in the membrane. The activity was characteristic of a serine protease. It was also shown that GP-2 only becomes sensitive to proteolytic digestion when its disulfide bonds are reduced, and that DTT does not activate the protease. Seven intramolecular disulfide bonds were identified on GP-2. All of them are located in a 65-kDa tryptic fragment that is very resistant to exogenous proteases under nonreducing conditions. Because of the quite specific degradation of GP-2 under reducing conditions, we believe that the 29-kDa protease must be closely associated with GP-2 on the membrane. This protease could be responsible, in part, for the solubilization of the GP-2 from the membrane into the zymogen granule content and its resulting secretion by the pancreas.

Alkylation↗
PubMed1989

Epigenetic and genetic factors affect transgene methylation imprinting.

In some lines of transgenic mice, the methylation of MspI sites within or adjacent to the transgene locus is affected by the sex of the parent from which the transgene is inherited. These differences are consistent with a role for DNA methylation in genome imprinting. In a previous report, we noted that in one such line, all offspring of females exhibited hypermethylation of the transgene while only some offspring of males carried a hypomethylated transgene. In this report, we provide evidence that this phenomenon is controlled by at least two factors, one of which acts in cis and is dependent on the transgene locus, and one of which acts in trans and is supplied by the maternal genome. We also provide evidence that there are genetic differences between inbred mouse strains in the trans-acting factor.

Animals↗
PubMed1988

In vitro stability of pancreatic zymogen granules: roles of pH and calcium.

Purified preparations of pancreatic zymogen granules have the peculiar property of lysing instantaneously at neutral pH, a property clearly irreconcilable with the cytoplasmic pH of the acinar cell. Two important factors known for regulating the stability of secretory granules are calcium and pH. Fluorescence microscopy of acinar cells in the presence of weak bases showed that zymogen granules have an acidic pH. In vivo, abolition of the delta pH by NH4Cl did not induce any lysis of the granules. In vitro, with purified granules, an acidic intragranular pH was measured. This delta pH was produced by a Donnan potential. The importance for granule stability of keeping the intragranular pH acidic has been confirmed in vitro by addition of K+ and nigericin to the suspension medium. These conditions produced alkalinization of the granule matrix and caused instantaneous solubilization of the granules. Concentrations of 15 mM total, and 10 mM free calcium were measured in purified granules. The importance of intragranular Ca2+ was evaluated by means of the ionophore A23187 which induced calcium efflux and granule lysis. The lysis induced by the calcium ionophore was in direct relation with the calcium efflux, since addition of Ca2+ to the medium, at concentrations corresponding to that measured in the granule, relieved the effect. The role of calcium-binding sites on the cytoplasmic surface of the granules was investigated with Ca2+, EGTA, and La3+. Calcium did not have any damaging effects; EGTA induced a slight lysis, while lanthanum yielded a strong and spontaneous lysis at micromolar concentrations. In addition to calcium-binding sites, La3+ would bind to specific sites on the granule that would be directly coupled to maintenance of its stability. These findings suggest that the intragranular acidic pH and calcium are both important for the in vitro stability of the zymogen granule and that purified granules have lost, in the course of purification, some cytoplasmic factors that in vivo, control the permeability of the membrane to protons, and chloride more particularly. Calcium-binding sites and other specific sites probed with La3+, presumably on proteins at the surface of the granule, are also believed to have key roles in preserving the integrity of the membrane and the resulting stability of the granule.

Animals↗
PubMed1987

Site-directed protection of RNA during nuclease digestion.

We report the use of oligodeoxynucleotides to block the nucleolytic hydrolysis of single-stranded regions of RNA. Using complementary oligomers, the hydrolysis of the CCA terminus of methionine initiator tRNA could be prevented. This method can be useful in the production of specific single-stranded fragments of RNA, which are necessary in recombinant RNA technology.

Base Sequence↗
PubMed1986

Reducing conditions induce a total degradation of the major zymogen granule membrane protein in both its membranous and its soluble form. Immunochemical quantitation of the two forms.

The major protein of the pig pancreatic zymogen granule membrane is an integral glycoprotein of 92 X 10(3) daltons (Da) which amounts to 25% of the total proteins of this membrane. When zymogen granule membranes were prepared in presence of 5 mM dithiothreitol (DTT), this glycoprotein specifically vanished from the membrane preparation. During membrane purification two other fractions were produced out of the purified granules: a soluble fraction of zymogens referred to as granule content and a dense pellet. The possibility that DTT could release the 92-kDa protein from the membrane to these other fractions has been rejected. Altogether, addition of DTT during the lysis of the granules induced a total degradation of the 92-kDa protein. This hydrolysis could be inhibited by phenylmethylsulfonyl fluoride but not by N-alpha-p-tosyl-L-lysine chloromethyl ketone or L-1-tosylamide-2-phenylethylchloromethyl ketone. In the course of these experiments, using gel filtration of the granule content, it was found that the 92-kDa protein was also present in the granule content in the form of an aggregate of 300 kDa. A protease was present in this aggregate and could hydrolyse the 92-kDa protein upon addition of DTT. From immunoblotting studies and rocket immunoelectrophoresis, it was found that the soluble 92-kDa protein was antigenically similar to the membrane protein and that 44% of the immunoreactive glycoprotein of the granule was soluble in the content. A cross-reacting fragment of 65 kDa has been observed in all the fractions, yet at different levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗