Biomedical subjects
Publications and source records attributed to J Landry.
The specialty of emergency medicine has grown rapidly, partially as a result of federal programs providing insurance coverage for large numbers of formerly uninsured individuals. The specialty grew and flourished as a response to improving economic circumstances. Today, however, changes in federal reimbursement policies threaten the future viability of emergency medicine.
A procedure for quantitation of tryptophan in feedstuffs is described. It is based on barytic hydrolysis of material at 125 degrees C for 16 h, acidification of hydrolysate to pH 3 with HCl, high-performance liquid chromatography on Nova Pak C18 (Waters Assoc.), and spectrophotometric determination of tryptophan at 280 nm. The recovery of tryptophan from lysozyme added to samples ranges from 98.7 to 100%.
Supraventricular tachyarrhythmia (SVT) is a common complication of coronary artery bypass grafting. Four hundred twenty-four cases of coronary artery bypass grafting were retrospectively reviewed and 64 patients (15%) were identified who had clinically significant SVT. Sixty randomly selected arrhythmia-free patients served as controls. The arrhythmia group differed from the control group in age (62 +/- 8 years vs 57 +/- 8 years p less than 0.0001), radiographic cardiomegaly (19 of 64 patients with arrhythmia vs 6 of 60 control subjects, p less than 0.01), and echocardiographic left atrial enlargement (16 of 38 vs 6 of 37 control subjects, p less than 0.025). No significant differences existed regarding sex of the patient, prior myocardial infarction, reduced ejection fraction, history of congestive heart failure, occurrence of perioperative myocardial infarction or pericarditis, or pump time. The relative risk of SVT developing in patients 60 years or older was 1.91; in patients 60 years or older with cardiomegaly, 2.39; in patients 60 years or older with left atrial enlargement, 3.29; and in patients 60 years or older with cardiomegaly and left atrial enlargement, 3.47. Thus, it may be possible to select patients at relatively higher risk of having SVT who could especially benefit from preventive measures.
Hyperthermia-induced cell inactivation, thermotolerance development, and heat shock protein synthesis were characterized in a Chinese hamster cell line and its two derivatives, respectively, deficient in glycolysis and respiration. No difference was found in the intrinsic thermosensitivity of the cells or in their ability to respond to heat by developing thermotolerance and synthesizing the heat shock proteins. The results indicate that the direct thermal inactivation of either respiration or glycolysis is not an obligatory rate-limiting event in hyperthermic cell killing and that thermotolerance and heat shock proteins are not triggered exclusively as a consequence of damages induced directly by heat in energy metabolism nor do they result specifically in an increased thermostability of respiration or glycolysis. It is concluded that if energy metabolism is involved somehow in the induction by heat of cell death, thermotolerance, and heat shock protein synthesis, it is due to a heat-induced alteration that indirectly causes changes in the cellular energy status rather than to a direct interaction of heat with energy production.
Rat hepatoma cells become refractory to the induction of heat shock proteins and highly resistant to severe hyperthermia when incubated in Ca2+-free medium. The Ca2+-depleted cells synthesize polypeptides identified as the glucose-regulated proteins, but these proteins do not appear to be directly involved in the inhibition of the heat shock response. The results suggest that a Ca2+-dependent metabolic process is involved in the generation of the heat shock signal and/or mediates a step in the subsequent cascade of events that leads to the induction of heat shock protein synthesis and cell death.
Liver cells isolated from newborn rats and seeded on a non-adherent plastic substratum were found to spontaneously re-aggregate and to form, within a few days, spheroidal aggregates that eventually reached a plateaued diameter of 150-175 micron. Analyses on frozen sections from these spheroids by immunofluorescence microscopy using antibodies to various cytoskeletal elements and extracellular matrix components revealed a sorting out and a histotypic reorganization of three major cell types. A first type consisted of cells that segregated out on the aggregate surface forming a monolayer cell lining; a second type was identified as hepatocytes that regrouped in small islands often defining a central lumen; and a third group of cells reorganized into bile duct-like structures. This intercellular organization in the aggregates was paralleled by the accumulation of extracellular matrix components (laminin, fibronectin, and collagen) and their deposition following a specific pattern around each cell population structure. Determinations of albumin secretion and tyrosine aminotransferase induction by dexamethasone and glucagon at various times after the initiation of the cultures revealed a maintenance of the hepatocyte-differentiated functions for at least up to 2 mo at the levels measured at 3-5 d. It is concluded that cells dispersed as single cells from newborn rat liver conserve in part the necessary information to reconstruct a proper three-dimensional cyto-architecture and that the microenvironment so generated most likely represents a basic requirement for the optimal functioning of these differentiated cells.
Normal and transformed chick embryo cells and their respective ethidium bromide-treated derivatives that are devoid of a functional respiratory chain were comparatively evaluated for their responses to hyperthermia treatment. No significant difference was found between the control and the respiration-deficient cells. The cells have a similar intrinsic thermosensitivity as judged by their capacity to form colonies after treatment at supraoptimal temperatures, and heat triggers in both cases an equal production of heat shock proteins and a strong induction of thermotolerance. In addition, sodium arsenite, carbonyl cyanide m-chlorophenylhydrazone, oligomycin, and antimycin A induce a similar heat shock protein response in the control and the treated cells. Based on these results, it is concluded that the inhibition by heat of the mitochondrial energy production does not constitute an obligatory rate-limiting event in hyperthermic cell killing and that the intracellular signal triggering development of thermotolerance or heat shock protein production does not obligatorily originate from damages to the respiratory chain. Moreover, the results indicate that the modifications responsible for the increased heat resistance of thermotolerant cells may not, or do not necessarily, involve a stabilization of the mitochondrial energy production.
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Unreduced zein chromatographed on Sephadex G 200 in 8 M urea, on G 100 in 1.5 or 2.5% sodium dodecyl sulfate (SDS) and on hydroxypropylated G 100 in 70% ethanol was resolved into two minor fractions A and B and two major ones D and M irrespective of the medium. The quantitative importance of the fraction M was dependent on the isolation conditions of zein. It decreased from 53% of the proteins contained in ethanolic extract and chromatographed as they were extracted, to 40% of the purified zein. The molecular weight values obtained from SDS-polyacrylamide gel electrophoresis and amino acid compositional data indicated that fractions D and M, as isolated from purified zein in the presence of ethanol, represented respectively dimeric and monomeric forms of a mixture of Mr 22 000 and 24 000 polypeptides with threonine or phenylalanine as NH2-terminal residue. Electrophoretic analysis of selectively carbamylated fraction M on starch gel at pH 3.5 revealed that zein subunits comprised several polypeptides differing in the number and the nature of basic amino acids. At least one of these polypeptides contained one lysyl residue.
The subunits present as monomers in unreduced zein and isolated as fraction M by gel filtration, were chromatographed on sulfoethyl-cellulose. Three major subfractions were detected and characterized. Each of them, submitted to electrophoresis at pH 3.5, migrated as a single band corresponding to each of the three major electrophoretic forms seen in fraction M at the same pH. The presence of lysine in some polypeptides, suggested by amino acid composition data, was confirmed by electrophoretic analysis of carbamylated subfractions at pH 3.5. At pH 8.9 each subfractions was further resolved into three cationic bands in starch gel and three (or more) anionic bands in polyacrylamide gel. The same fractionation was also obtained by submitting the major electroforms of fraction M, as isolated at pH 3.5, to isoelectric focusing. Based on these observations, the most probable distributions of basic amino acids in subunits detected by electrophoresis at pH 8.9 were specified and compared to those recently published for several zein clones. The presence per polypeptide chain of three carboxyl groups and occasionally of one lysine would be a feature of zein originating from maize hybrid Inra 260.
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We recently demonstrated that heat treatments, capable of triggering thermotolerance development in MH-7777 cells, also induce a transiently increased synthesis of a small set of polypeptides, a phenomenon similar to the heat-shock-protein (HSP) induction demonstrated in various organisms. A close temporal relationship was also found between HSP synthesis and thermotolerance development, and the degradation kinetics of the newly synthesized HSPs very closely paralleled the decay of the thermotolerant state. In the present study, we extended our analysis to determine whether various experimental conditions known to affect thermotolerance development (duration and temperature of the conditioning treatment, step-down heating, ethanol exposure) will also influence HSP synthesis and, conversely, whether agents known to induce (sodium arsenite) or to impair (cycloheximide) HSP production will similarly affect thermotolerance. The results suggested that the expression of HSP and thermotolerance in MH-7777 cells are most likely regulated by some interrelated mechanisms, but indicated that HSP synthesis is neither a sufficient or necessary condition for thermotolerance development.
Hepatic epithelial cells become thermotolerant when conditioned with a 30 minute heat-treatment at 43 degrees C. The effect reaches a full amplitude after a 4-8 hour period at 37 degrees C and lasts for more than one day at a level corresponding to a 50-fold increase in cellular thermoresistance. During the development period, electrophoretic patterns of proteins from cells incubated in presence of 35S-methionine reveal an increased synthesis of a small set of proteins with molecular weights of 107, 89, 70, 68 and 27KD. The maximal synthesis of the induced proteins occurs concomitantly with the maximal increase of cell thermotolerance and has returned to normal when thermotolerance levels off. The induction of specific protein synthesis is also observed in other liver epithelial cells of normal and cancerous origins and in freshly isolated hepatocytes. It is suggested that the accumulation of these proteins in the cells plays a role in the process leading to a thermotolerant state.
Based on biological observations and the basic physical properties of tri-dimensional structures, a mathematical expression is derived to relate the growth rate of multicellular spheroids to some easily measurable parameters. This model involves properties both of the individual cells and of the spheroid structure, such as the cell doubling time in monolayer, the rate of cell shedding from the spheroid and the depth of the external rim of cycling cells. The derived growth equation predicts a linear expansion of the spheroid diameter with time. The calculated growth rate for a number of spheroid cell types is in good agreement with experimental data. The model provides a simple and practical view of growth control in spheroids, and is further adapted to include parameters presumably responsible for the growth saturation in large spheroids.
Morris hepatoma 7777 cells, heat conditioned at 43 degrees for 0.5 hr, become gradually thermoresistant during an incubation at 37 degrees as judged by their ability to form colonies following a second heat challenge. Pulse incorporation of [35S]methionine into proteins at various times after the conditioning treatment and subsequent fractionation of the proteins by polyacrylamide gel electrophoresis indicate that the gradual putative modifications occurring at the cellular level and leading to the thermotolerance state are accompanied by an elevated synthesis above the normal level of a small set of polypeptides with apparent molecular weights of 27,000, 65,000, 68,000, 70,000, 89,000, and 107,000. Both thermotolerance development and protein induction are completed after a 6- to 8-hr period. At the end of this period, thermotolerance is at its maximum level and heat shock protein synthesis is returned to normal. This acquired thermal resistance eventually disappears between 60 and 80 hr following conditioning treatment. In a parallel manner, the heat shock-induced proteins synthesized during the first 4 hr following the conditioning treatment are maintained in the cells at a high level for several hr but become undetectable by 82 hr. The results provide strong circumstantial evidence that heat shock proteins are involved in the acquisition, maintenance, and decay of thermotolerance.
During the growth of EMT6/Ro mammary tumor multicell spheroids, a large number of cells are shed into the suspension medium. The rate of cell shedding was 218 cells per square millimeter of spheroid surface per hour, or up to 1.5% of the total spheroid cell content per hour. Shed cells had a clonogenic capacity equal to that of exponential monolayer cultures and were further characterized by volume distribution, mitotic index, flow cytofluorometry, and autoradiography. The results indicated that cells are released from the spheroid surface at mitosis, presumably due to a loosening of the cell-to-cell attachment during this cycle phase. These mitotic cells, when placed in monolayer culture, attached and grew synchronously with a cell cycle time of about 13 hours. Shed cells kept in suspension culture had a similar cell cycle time, but these cells reaggregated immediately after mitosis. The results indicated that cell shedding and reaggregation both occur near the time of mitosis and are intrinsic factors regulating the initiation and subsequent growth of multicell spheroids. Although these studies were done with spheroids cultured in vitro, shedding of mitotic cells may play an important role in the in vivo process of metastasis.
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