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Biomedical subjects

R Rudolph

Publications and source records attributed to R Rudolph.

At least 235 records · Page 13Linked to original sources
PubMed1978

The significance of nasal protease inhibitor concentrations in house dust allergy.

In 57 patients with house dust allergy and 20 controls protease inhibitor concentrations in nasal secretions were measured before and after antigen challenge. A correlation was found between low inhibitor levels and long duration of disease. Furthermore, significant differences of inhibitor concentrations could be demonstrated between patients with strong or moderate reactions to antigen provocation, and between patients with isolated rhinitis or a combination of rhinitis and bronchial asthma. The clinical significance of the results will be discussed with special regard to different biochemical mechanisms in the pathophysiology of seasonal and perennial immediate-type rhinitis.

Adolescent↗
PubMed1978

Reconstitution of rabbit muscle aldolase after dissociation and denaturation at alkaline pH.

Tetrameric rabbit muscle aldolase is dissociated to the inactive monomer at strongly alkaline pH (pH greater than or equal to 12). As shown by sedimentation velocity, fluorescence emission, and specific activity, the final profiles of dissociation, denaturation, and deactivation run parallel. Increasing incubation time proves the enzyme to be metastable in the pH range of deactivation. At 10 less than pH less than 12 "hysteresis" of the deactivation-reactivation reaction is observed. Short incubation at pH greater than or equal to 12 leads to high yields of reactivation (greater than or equal to 60%), while irreversibly denatured enzyme protein is the final product after long incubation. The kinetics of reconstitution under essentially irreversible conditions (pH 7.6) can be described by a sequential uni-bimolecular mechanism, assuming partial activity of the isolated subunits. The kinetic constants correspond to those observed for the reactivation after denaturation at acid pH or in 6M guanidine. HCl. Obviously the pH-dependent deactivation and reactivation of aldolase at alkaline pH obeys the general transconformation/association model which has been previously reported to hold for the reconstitution of numerous oligomeric enzymes after denaturation in various denaturants.

Alkalies↗
PubMed1977

Effect of coenzymes and temperature on the process of in vitro refolding and reassociation of lactic dehydrogenase isoenzymes.

Dissociation and deactivation of the H4 and M4 isoenzymes of lactic dehydrogenase in strong denaturants may be reversed with a yield of reactivation up to 100%. The products of reconstitution are indistinguishable from the native enzymes as far as the Michaelis constants and the dissociation constants for substrate and coenzyme as well as spectral and hydrodynamic properties are concerned. The presence of NAD+ and NADH does not affect either the conformational state of the product of reconstitution, or the kinetics of reactivation, using the pure apoenzymes as a reference. At 20 degrees C the kinetics of reactivation for LDH-M4 in the presence and absence of coenzyme may be quantitatively described by a second-order rate equation (k2 = 23.4 +/- 2.6 mM-1S-1) while LDH-H4 is characterized by a uni-bimolecular reaction sequence (k1 = 1.45 +/- 0.45 X 10(-3)-S-1, k2 = 5 +/- 1 mM-1S-1), in agreement with earlier observations (Rudolph, R., et al. (1977), Biochemistry 16, 3384-3390). Regarding the influence of temperature on the rate of reactivation no significant anomalies are detectable within the range of 0-25 degrees C. The (apparent) activation energies, taken from the linear Arrhenius plots, are 58 kcal/mol for the association reaction of LDH-M4, and 41 kcal/mol for the transconformation reaction of LDH-H4.

Animals↗
PubMed1977

Kinetics of reactivation of rabbit muscle aldolase after denaturation and dissociation in various solvent media.

The denaturation of aldolase from rabbit muscle in various solvents leads to significant qualitative and quantitative differences with respect to the structural disintegration of the enzyme. The differences refer to the quaternary structure and to the conformation which is changed only slightly in MgCl2 while in guanidine-HCl or urea at pH approximately 2 the molecule is close to the state of the random coil. Using the enzymic activity as a quantitative measure for the refolding process, the reaction order and the rate constants of the processes of structure formation (vi leads to N*) are found to be identical. This observation suggests a common intermediate D in the process of renaturation after denaturation and dissociation in the different solvent media. D may be considered an intermediate state with a defined number of nucleation centers whose rapid formation is predetermined by the aminoacid sequence. As taken from the first order kinetics in the given range of enzyme concentration, transconformation reactions are rate limiting in the obligatory pathway of refolding. At low enzyme concentrations second order steps gain importance which indicates that the enzymic activity is significantly modified by the formation of the native quaternary structure.

Animals↗
PubMed1977

Malignant melanomas in a Duroc boar.

A Duroc boar had 2 malignant melanomas of the skin, with metastases into several lymph nodes, lungs, liver, and spleen. All tumors had these characteristics: invasion of lymph and blood vessels, necrosis, numerous giant cells containing granules, heavily pigmented as well as lightly pigmented and unpigmented melanocytes, few anaplastic features, and few mitotic figures. In the skin tumors, there was neither intraepithelial growth nor junctional activity.

Animals↗
PubMed1977

Intracutaneous cornifying epithelioma ("keratoacanthoma") of dogs and keratoacanthoma of man.

The intracutaneous cornifying epithelioma ("keratoacanthoma") of dogs was compared with keratoacanthoma of man based on findings in the literature and in house studies. The two tumors differ at the following points: epithelium of origin, rate of growth, infiltration, spontaneous involution, breed predisposition (Norwegian Elkhound, generalized form), occurrence in dogs at a younger or middle age. The development of this tumor in dogs seems to be comparable with the development of so-called keratoacanthoma in Mastomys natalensis, which is virus-induced. Further investigations have been initiated to uncover the possible virus nature of the intracutaneous cornifying epthelioma (so-called keratoacanthoma) in dogs.

Animals↗
PubMed1977

The life cycle of the myofibroblast.

Myofibroblasts in pig granulating wounds have an identifiable life cycle that parallels the eight week span of contraction of the wounds. As seen by electron microscopy, fibroblasts with a contractile appearance became prominent within one week after wounding and persisted for 12 weeks, after which time they were not visible. Large tangled filaments, measuring 120 Angstrom units are prominent in fibroblasts in late contracted wounds and may be actin. Such filaments could preserve fibroblasts in a contracted state and allow time for the reorganization of collagen into a fixed rigid scar.

Animals↗
PubMed1976

Equilibrium studies on the refolding and reactivation of rabbit-muscle aldolase after acid dissociation.

Dissociation, denaturation, and deactivation of aldolase from rabbit muscle in the acid pH range have been investigated using sedimentation analysis, fluorescence, circular dichroism, and activity tests. Under comparable experimental conditions the pH-dependent profiles of deactivation and denaturation parallel the dissociation of the enzyme. In the range of dissociation at pH4-5tetramers and monomers are in equilibrium. Intrinsic chromophores and far-ultraviolet circular dichroism suggest the transition to be a complex multistep process. At pH approximately 2.3 the enzyme is split into its fully inactive monomers which still contain some residual secondary structure. After reassociation under optimum conditions (0.2 M phosphate buffer pH 7.6, 1 mM EDTA, 0.1 mM dithiothreitol, 0 degrees C, enzyme concentration 0.4-59 mug/ml) up to 95% enzymic activity is recovered which belongs to a renatured tetrameric species indistinguishable from the native enzyme by all available biochemical and physicochemical criteria.

Animals↗
PubMed1976

Kinetics of refolding and reactivation of rabbit-muscle aldolase after acid dissociation.

Tetrameric rabbit muscle aldolase has been dissociated to the monomer at pH 2.3 and fully reassociated and reactivated at pH 7.6 Kinetics of reactivation and refolding were followed by slow and fast kinetic techniques after neutralization of the acidic enzyme solutions by dilution or rapid mixing. Rate constants (k), reaction orders (n), and activation evergies (E) were calculated from measurements on the time, concentration, and temperature dependence of the reactions. The experimental results prove reactivation at high enzyme concentration (c greater than 4mug/ml) to obey first-order kinetics; at lower concentrations a transition to a higher reaction order is observed. Because of concentration-dependent deactivation at low enzyme concentrations reactivation measurements could not be extended below c approximately o.5 mug/ml. In the accessible concentration range incomplete separation of reassociation and transconformation processes as well as intrinsic residual activity of the isolated subunits lead to an average value of n = 1.40 +/- 0.18. Renaturation as monitored by protein fluorescnce is a multi-step process composed of a fast increase in flurescence emission (first-order rate constant k approximately 15 s-1) and a slow concentration-dependent decrease which parallels the recovery of enzyme activity (n = 1.46 +/- 0.12). The activation energy of both processes is of the order of E = 12-16 Kcal/mol (50-67 kJ/mol). Reassociation is a prerequisite of full catalytic function and native fluorescence.

Animals↗