Biomedical subjects
Publications and source records attributed to A Fontaine.
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T7 endonuclease preferentially cleaves purified supercoiled pBR322 and colE1 plasmids at the single-stranded regions exposed when palindromic sequences assume cruciform structures (Panayotatos, N., and Wells, R.D. (1981) Nature 289, 466-470). In vivo, however, induction of nuclease synthesis off a cloned gene caused complete degradation of the bacterial DNA but not of the plasmid vector; presumably, single-stranded regions (cruciforms?) on the genome effectively complete for the nuclease with similar sites on the plasmid (Panayotatos, N., and Fontaine, A. (1985) J. Biol. Chem. 260, 3173-3177). To overcome this competition, we introduced on the plasmid the naturally occurring colE1 palindrome which forms a more stable cruciform in vitro. In addition, we increased the target size (and the T7 endonuclease gene dosage) by raising the copy number of the plasmid 5-fold. Induction of the endonuclease encoded by this new plasmid (pLAT75) resulted not only in degradation of genomic DNA but also in intracellular nicking and linearization of the plasmid. The cleavage site in vivo was mapped at the colE1 palindrome and coincided with the site cleaved specifically in vitro by either T7 or S1 endonuclease only when this palindrome assumes the cruciform structure. These results indicate that cruciform structures exist intracellularly and demonstrate the usefulness of endonucleases as probes of DNA topology in vivo.
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The study of some characteristics (clinical and sociodemographic) of a population of adolescent clients and the modes of reception and therapeutic modalities which have been proposed for them introduces a discussion on: the contributions and the limits of so-called informal modes of reception and assigning to treatment, as well as the value of taking into consideration the ways the adolescents relate to their environment; the necessity for rapid agreement and the diversity of the observed evolutions which justify both the need for adequate identification of immediate movement and for a dynamic perspective; and, after considering the adequacy of the gathered information for our way of thinking and practicing, the pertinence of an epidemiological evaluation and its utility for clinicians.
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A plasmid carrying the bacteriophage T7.3 endonuclease gene under the control of the lacUV5 promoter could be maintained in the transcriptionally active state only in recA+ strains. In recA- strains, endonuclease induction resulted in extensive degradation of the genomic DNA and cell death. In sharp contrast, the plasmid DNA remained intact in the supercoiled form. In recA+ strains, the recA protein levels were increased and the SOS functions of the host were activated, as shown by measurements of recA protein synthesis and prophage induction. These results indicate that in normal undisrupted and non-irradiated cells, enzymatic nucleolytic damage can induce the SOS response and can be controlled by the DNA repair system of the host. In addition, the higher sensitivity of the genomic DNA to the single-strand-specific endonuclease relative to the plasmid suggests that the two molecules differ in their physiological states and most likely in their degree of single-stranded content.
For the last two decades the most common method of radiographic study of the venous system of the lower limbs has been ascending phlebography, by injection of contrast material in a superficial vein on the dorsum of the foot. We report our own experience with another approach, using a large field technique on recumbent patients, with elevation of the limbs, thus taking advantage of gravity. The contrast injection is usually made in a more distal superficial vein of the foot after a tiny cut-down. Excellent results are consistently obtained in demonstrating all the deep veins, including the iliac vessels. The same principles may be applied to upper limb phlebography.
The prosobranch Fusitriton oregonensis exhibits an unusual form of sperm polymorphism. The viable, eupyrene sperm are attached in groups of about fifty to worm-shaped, apyrene, carrier sperm. There is a second apyrene sperm, which is lancet-shaped and has a different internal organization than the carrier, but does not transport eupyrene sperm. The eupyrene sperm are filiform (185 microns long), with a conical acrosome, elongate nucleus and midpiece. They contain large stores of glycogen in the principal piece, together with an unusually high proportion of protein. The latter is due to a complex interconnecting system of fibres that supports the tail internally. A distinct annulus is located, characteristically, at the junction between midpiece and principal piece. The carrier sperm has a core of about 112 axonemes that arise from basal bodies in the anterior end and extend through its entire length of 36 microns. The basal bodies have unstriated rootlets that are embedded in a granular cap. Large membrane-bound "yolk bodies" are arranged along the length of the carrier sperm, on either side of the median axonemal core. Dense bodies, which may be indigestible residues formed from the degeneration of the nucleus, are excreted by exocytosis. Individual carrier sperm are capable of "corkscrew" propulsion, resembling that of spirochaetes. The lancet sperm is three times as long as the carrier. The sixteen or so axonemes, which are arranged peripherally like a cage enclosing the cytoplasm, originate from a dense centriolar plate in the anterior end. The cytoplasm is filled with secretions including small yolk granules, dense bodies (also excreted), clear vesicles, and a membranated granular secretion that resembles mucus. The possible functions of the lancet and carrier sperm are discussed.
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In the last 10 years, 605 celiomesenteric arteriographic examinations were done at Hôtel-Dieu de Montréal, including 236 for suspected pancreatic disease. Sixty patients with histologic proof of malignant neoplasm had a positive arteriographic examination while 136 had benign disease of the pancreas and 40 others had extra-pancreatic disease. In this series, the sensitivity of arteriography was 88.3% and the specificity 92.6%. In the last 5 years the sensitivity of superselective arteriography was 100%. These results were better than those obtained with noninvasive techniques obtained with noninvasive techniques such as computerized axial tomography, ultrasonography and duodenography. The authors conclude that arteriography and particularly superselective arteriography is an excellent method for evaluating patients with suspected pancreatic cancer.
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Rigorous alkaline hydrolysis of the two primary (cholic and chenodeoxycholic) and of the two preponderant secondary (deoxycholic and lithocholic) bile acids found in bile led to excellent recoveries. Such was not the case with 11 different keto bile acid standards. Recoveries for a number of standards were unacceptably low and a variety of artefactural products were tentatively identified by gas-liquid chromatography. Keto bile acids bearing a keto gropu on C-3 were particularly vulnerable. In view of thee findings, quantitative and qualitative data reported on biological specimens submitted to saponification in ethanol, methanol, or even in water are of questionable significance.
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The prevalence and type of plasma lipoprotein abnormalities were determined in 114 French-Canadian patients with angiographically proven peripheral vascular disease (PVD). The severity of atherosclerosis was positively correlated with plasma triglyceride concentration, especially in the younger patients (r = 0.29, P less than 0.05), and (not significantly) with plasma cholesterol concentration. Of the risk factors believed to predispose individuals to atherosclerosis, cigarette smoking was the most frequently found in the PVD patients (72.8%), especially among the men. Combination of two or more risk factors was the rule. Findings were compared with those in 114 patients who had undergone coronary angiography for suspected coronary heart disease (CHD). The CHD patients were, on average, younger by 10 years. Hyperlipidemia was present in 58.8% of CHD patients, compared with 43.9% of PVD patients. A far higher proportion of CHD patients showed the type II plasma lipoprotein pattern (24.6% v. 7.9%), although the type IV pattern was more common in both groups (31.6% and 28.9%, respectively). A high proportion of all patients (56.1% with PVD and 41.2% with CHD) showed a normal lipoprotein pattern on paper electrophoresis.
Mammography is a basic examination which must never be dissociated from the clinical background. A statistical blind study of 330 cases shows that only well definite syndroms are reliable. The presence of absence of a single sign has no value. Difficulties arise in the diagnosis of suspect nodule in a dense dystrophic breast. Hydratation of the connecting tissue is a fundamental concept for analysis of mammographic pictures. The densities change according to hormonal influence, growth of dystrophy and specific signs of fibrillary or hyalin fibrosis. A histological study of serial cuts of the breast shows that the must reliable signs are found in the center of the nodule ande immediately around it. As in the histological study, serial cuts are indispensable in X-ray examination. Tomography improves the examination of dystrophies.