Sustained oscillations and time delays in gene expression of protein Hes1.
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Animals↗
Biomedical subjects
M H Jensen
Publications and source records attributed to M H Jensen.
Thermodynamic formalism of the harmonic measure of diffusion limited aggregates: phase transition.
We study the nature of the phase transition in the multifractal formalism of the harmonic measure of diffusion limited aggregates. Contrary to previous work that relied on random walk simulations or ad hoc models to estimate the low probability events of deep fjord penetration, we employ the method of iterated conformal maps to obtain an accurate computation of the probability of the rarest events. We resolve probabilities as small as 10(-35). We show that the generalized dimensions D(q) are infinite for q<q*, where q* = -0.18+/-0.04. In the language of f(alpha) this means that alpha(max) is finite. We present a converged f(alpha) curve.
Journal Article↗
Release of CFC-11 from disposal of polyurethane foam waste.
The halocarbon CFC-11 has extensively been used as a blowing agent for polyurethane (PUR) insulation foams in home appliances and for residential and industrial construction. Release of CFCs is an important factor in the depletion of the ozone layer. For CFC-11 the future atmospheric concentrations will mainly depend on the continued release from PUR foams. Little is known about rates and time frames of the CFC release from foams especially after treatment and disposal of foam containing waste products. The CFC release is mainly controlled by slow diffusion out through the PUR. From the literature and by reevaluation of an old reported experiment, diffusion coefficients in the range of 0.05-1.7 x 10(-14) m2 s-1 were found reflecting differences in foam properties and experimental designs. Laboratory experiments studying the distribution of CFC in the foam and the short-term releases after shredding showed that about 40% of the CFC is solubilized in the PUR phase, and that up to 10% of the total content will be released within a few weeks if the foam is shredded down to 2-cm sized pieces. For smaller pieces the quick release will be larger. Fifty percent of residual CFC content will be released within 9-300 years from 2-cm pieces based on the range in diffusion coefficients reported. For larger pieces the initial release is insignificant, and the release time frames are much longer than for the shredded foam.
Air Pollutants↗
Hydrogen bonds in polymer folding.
We studied the thermodynamics of a homopolymeric chain with both van der Waals and directed hydrogen bond interaction. The effect of hydrogen bonds is to reduce dramatically the entropy of low-lying states and to give rise to long-range order and to conformations displaying secondary structures. For compact polymers a transition is found between helix-rich states and low-entropy sheet-dominated states. The consequences of this transition for protein folding and, in particular, for the problem of prions are discussed.
Hydrogen Bonding↗
Pathways in two-state protein folding.
Thermodynamic measurements of proteins indicate that the folding to the native state takes place either through stable intermediates or through a two-state process without intermediates. The rather short folding times of proteins indicate that folding is guided through some sequence of contact bindings. We discuss the possibility of reconciling a two-state folding event with a sequential folding process in a schematic model of protein folding. We propose a new dynamical transition temperature that is lower than the temperature at which proteins in equilibrium unfold. This is in qualitative agreement with observations of in vivo protein folding activity quantified by chaperone concentration in Escherichia coli. Finally, we discuss our framework in connection with the unfolding of proteins at low temperatures.
Biophysical Phenomena↗
Production of a highly immunogenic subunit ISCOM vaccine against Bovine Viral Diarrhea Virus.
Bovine Viral Diarrhea Virus (BVDV) is a major pathogen of cattle in most countries. The main reservoir of virus in herds are BVDV persistently infected animals, which arise as a result of infection of the bovine fetus early in gestation. The spread of virus to the unborn fetus may be prevented by vaccination of the dam. We describe in this report the production and initial testing of an inactivated subunit vaccine against BVDV. The vaccine is based on production of antigen in primary bovine cell cultures, extraction of antigens from infected cells with detergent, chromatographic purification, concentration, and insertion of antigens into immune stimulating complexes (ISCOMs). Vaccines based on two different Danish strains of BVDV were injected into calves and the antisera produced were tested for neutralising activity against a panel of Danish BVDV strains. The two vaccines induced different neutralisation responses, which seem to partly complement each other. The implication of these observations for successful vaccination against BVDV is discussed.
Adjuvants, Immunologic↗
Detection of antibodies against porcine parvovirus nonstructural protein NS1 may distinguish between vaccinated and infected pigs.
The humoral antibody response against the nonstructural protein NS1 and the structural protein VP2 of porcine parvovirus (PPV) was evaluated by immuno-peroxidase test (IPT) and enzyme linked immuno sorbent assay (ELISA) using recombinant PPV antigens. The coding sequence for NS1 and VP2 was inserted into the baculovirus. Autographa californica nuclear polyhedrosis virus (AcNPV) genome resulting in two recombinant baculoviruses AcNPV-NS1 and AcNPV-VP2, respectively. Sf9 cells (Spodoptora frugidiperda) inoculated with AcNPV-NS1 producing recombinant nonstructural protein (rNS1) and AcNPV-VP2 producing recombinant virion protein (rVP2) were used in IPT and ELISA to analyse serum antibodies. Pigs vaccinated with an inactivated whole virus vaccine and experimentally infected pigs were studied. Significant titers against rVP2 were obtained in both vaccinated and infected pigs. Specific antibodies against rNS1 could only be detected in infected pigs and NS1 may in this way allow the specific detection of infected animals. Analysis of serum samples collected up to 18 days post infection (p.i.) from four pigs experimentally infected with PPV showed that antibodies against rNS1 and rVP2 could in all cases be detected on day 9 p.i. Two individual pigs were inoculated twice with PPV and the antibody response was followed 89 days after second inoculation. Serum antibodies against both rVP2 and rNS1 could be detected for this period of time.
Animals↗
Evolution as a self-organized critical phenomenon.
We present a simple mathematical model of biological macroevolution. The model describes an ecology of adapting, interacting species. The environment of any given species is affected by other evolving species; hence, it is not constant in time. The ecology as a whole evolves to a "self-organized critical" state where periods of stasis alternate with avalanches of causally connected evolutionary changes. This characteristic behavior of natural history, known as "punctuated equilibrium," thus finds a theoretical explanation as a self-organized critical phenomenon. The evolutionary behavior of single species is intermittent. Also, large bursts of apparently simultaneous evolutionary activity require no external cause. Extinctions of all sizes, including mass extinctions, may be a simple consequence of ecosystem dynamics. Our results are compared with data from the fossil record.
Adaptation, Biological↗
Synthesis and characterization of Desulfovibrio gigas rubredoxin and rubredoxin fragments.
The 52-residue Desulfovibrio gigas rubredoxin peptide chain has been synthesized and a procedure for chain folding around iron(II) developed. The folded, stable synthetic rubredoxin can be subjected to purification, and reversibly oxidized and reduced. Ultraviolet/visible absorption and CD spectra of both forms show all the same features as native D. gigas rubredoxin, and the symmetric and asymmetric Fe-S stretching bands in the resonance Raman spectrum can be identified. In addition, the matrix-assisted laser desorption mass spectrum of a peptide sample exposed to trace amounts of iron is dominated by a peak at 5735Da very close to the value for the calculated molecular mass. Details in the ultraviolet/visible bandshape and mass spectrum, however, indicate remaining impurities. In comparison, a previously synthesized 25-residue rubredoxin fragment with the non-conserved positions 13-35 and 51-52 omitted and Val5-Glu50 anchored via glycine folds gives the correct molecular mass and ultraviolet/visible spectrum, but is much more labile than the 52-residue protein. This shows that non-conserved residues are crucial in protein folding and that chemical metalloprotein synthesis offers alternative prospects to microbiological protein engineering.
Circular Dichroism↗
Denitrification, dissimilatory reduction of nitrate to ammonium, and nitrification in a bioturbated estuarine sediment as measured with N and microsensor techniques.
Nitrogen and oxygen transformations were studied in a bioturbated (reworked by animals) estuarine sediment (Norsminde Fjord, Denmark) by using a combination of N isotope (NO(3)), specific inhibitor (C(2)H(2)), and microsensor (N(2)O and O(2)) techniques in a continuous-flow core system. The estuarine water was NO(3) rich (125 to 600 muM), and NO(3) was consistently taken up by the sediment on the four occasions studied. Total NO(3) uptake (3.6 to 34.0 mmol of N m day) corresponded closely to N(2) production (denitrification) during the experimental steady state, which indicated that dissimilatory, as well as assimilatory, NO(3) reduction to NH(4) was insignificant. When C(2)H(2) was applied in the flow system, denitrification measured as N(2)O production was often less (58 to 100%) than the NO(3) uptake because of incomplete inhibition of N(2)O reduction. The NO(3) formed by nitrification and not immediately denitrified but released to the overlying water, uncoupled nitrification, was calculated both from NO(3) dilution and from changes in NO(3) uptake before and after C(2)H(2) addition. These two approaches gave similar results, with rates ranging between 0 and 8.1 mmol of N m day on the four occasions. Attempts to measure total nitrification activity by the difference between NH(4) fluxes before and after C(2)H(2) addition failed because of non-steady-state NH(4) fluxes. The vertical distribution of denitrification and oxygen consumption was studied by use of N(2)O and O(2) microelectrodes. The N(2)O profiles measured during the experimental steady state were often irregularly shaped, and the buildup of N(2)O after C(2)H(2) was added was much too fast to be described by a simple diffusion model. Only bioturbation by a dense population of infauna could explain these observations. This was corroborated by the relationship between diffusive and total fluxes, which showed that only 19 to 36 and 29 to 62% of the total O(2) uptake and denitrification, respectively, were due to diffusion-reaction processes at the regular sediment surface, excluding animal burrows.
Journal Article↗
A novel subunit ISCOM vaccine against bovine virus diarrhoea virus.
The preparation and preliminary testing of a subunit ISCOM (immunostimulating complex) vaccine against bovine virus diarrhoea virus (BVDV) is described. Vaccination of calves with this vaccine yields high neutralising titres against a panel of Danish BVDV field isolates. The serological difference between virus isolates and vaccine strain selection is discussed.
Animals↗
[Nursing. Risk of lawsuit guides all nursing activities. Interview by Dorte Schmidt].
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Jurisprudence↗
Thyroid cancer: a computer-assisted review of 5287 cases.
Retrospective computer analysis of all reportable cases of thyroid cancer for the Rocky Mountain Cancer Data Systems between 1973 and 1983 was undertaken. Follow-up data were available for periods of 5 to 10 years. All major histologic findings are reviewed with regard to distribution, prognostic factors, mortality rates, and some treatment modalities. Interesting observations determined by this study include: (1) the significantly greater mortality rates seen in patients with thyroid cancer after 50 years; (2) the lack of increased mortality rates in young patients with differentiated cancer; (3) the poorer prognosis of male patients of equivalent age to female patients in all histologic types of cancer in the first 5 years; (4) the lack of sexual difference in influencing mortality rates after the first 5 years in differentiated cancers and lack of sex as a prognostic indicator in undifferentiated cancers; (5) the excellent prognosis of patients with localized differentiated and medullary cancers and a better-than-expected prognosis in the undifferentiated group; (6) the clear need for combined therapy (surgery and irradiation) in regional medullary cancer; (7) the observation that localized thyroid lymphoma had a higher mortality rate than had regional thyroid lymphoma; and (8) a significantly higher mortality rate in patients older than 79 years with differentiated cancer.
Adenocarcinoma↗
[Adenosine, magnesium and the cardiovascular system].
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Adenosine↗
The influence of theophylline and phenobarbital on rat brain 5'-nucleotidase.
Xanthines and barbiturates have opposing effects on cerebral function and metabolism. Since the xanthine theophylline is known to inhibit the enzyme 5'-nucleotidase, and thus endogenic adenosine release, an in vitro experiment was conducted on the assumption that theophylline and phenobarbital may have an opposing effect on 5'-nucleotidase activity. This assumption was confirmed. The hypothesis that barbiturates in general cause an increase in endogenic adenosine release seems compatible with the known functional and metabolic effects of barbiturates. Furthermore, accepting the hypothesis that cellular hypoxic-anoxic survival may ultimately depend on salvage of adenine nucleotides, this may even explain the dichotomy in the effect of barbiturates when used for protection of a hypoxic-anoxic insult.
5'-Nucleotidase↗
[Peroperative cholangiography in elective cholecystectomy].
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Adult↗
A fatal case of malignant hyperthermia following isoflurane anaesthesia.
To date, only two cases of malignant hyperthermia following isoflurane anaesthesia have been reported, neither of which were fatal. This case describes a very malignant form of hyperthermia after isoflurane, in which the laboratory values were grossly abnormal, and with multi-organ failure and death finally supervening.
Adult↗