Search PubMed⌕ Search

Biomedical subjects

R Rudolph

Publications and source records attributed to R Rudolph.

At least 217 records · Page 12Linked to original sources
PubMed1979

Influence of coenzyme on the refolding and reassociation in vitro of glyceraldehyde-3-phosphate dehydrogenase from yeast.

Kinetic analysis of the reactivation in vitro of glyceraldehyde-3-phosphate dehydrogenase from yeast in the presence of NAD+ suggested that transconformation reactions of inactive monomers and their subsequent association to native tetramers are responsible for the sigmoidal relaxations [R. Rudolph et al. (1977) Eur. J. Biochem. 81, 563-570]. Comparison with the reactivation behaviour in the absence of coenzyme was not feasible at this stage due to the instability of the apoenzyme. In the present study, solvent conditions were established which allowed both apoenzyme and holoenzyme to exhibit high stability. The apoenzyme is stable in phosphate buffer; but if excess NAD+ and phosphate are present (both of which stabilize the enzyme if applied separately), destabilization occurs. Protection of functional groups against oxidation by addition of a reducing agent and by degassing and preventing contact with air, increase the stability. Only partial stabilization can be achieved in the presence of NADH. Comparing the kinetics of reactivation in the presence and absence of coenzymes shows that both oxidized and reduced coenzyme enhance the rate of reactivation significantly, and to the same extent. The kinetic effect of coenzyme binding to the refolding polypeptide chain is discussed in terms of the stabilization of intermediates or end products of reconstitution on the one hand, and acceleration of folding and association reactions, on the other.

Drug Stability↗
PubMed1979

Effects of low concentrations of guanidine . HCl on the reconstitution of lactic dehydrogenase from pig muscle in vitro. Evidence for guanidine binding to the native enzyme.

The presence of low concentrations of guanidine . HCl has a pronounced effect on the overall rate of reactivation of lactic dehydrogenase from pig muscles after preceding dissociation and deactivation in various denaturants. The obseverd attenuation is a function of the amount of guanidine . HCl present during reconstitution. At a given guanidine concentration in the reactivation buffer the yield, but not the rate of reactivation, is influenced by the extent of denaturation caused initially in the process of deactivation and dissociation. As a possible explanation for the influence of guanidine . HCl on the kinetics of reconstitution, binding of the ligand to intermediates of folding and association is considered. This hypothesis is corroborated by the observation that guanidine . HCl in the relevant concentration range does bind to native lactic dehydrogenase without inactivating the enzyme or disrupting its quaternary structure. A kinetic model comprising guanidine binding to both the native enzyme and structured intermediates is proposed to describe the observed effects of guanidine . HCl on the rate of reactivation. In addition, the dissociation constants for guanidine binding to intermediates of reconstitution and to native lactic dehydrogenase are estimated.

Animals↗
PubMed1979

Capsular contraction around silicone mammary prostheses.

Contraction of fibrous capsules is the most common complication of augmentation mammaplasty using silicone implants. This contraction occurs unpredictably with all kinds of implants, and despite various surgical maneuvers to prevent it. Current clinical practices are reviewed. Wound healing around silicone breast implants is similar to that elsewhere in the body. Acute inflammation is followed by collagen synthesis. Breast capsules contain contractile fibroblasts like those found in other contracting scars. Silicones implanted into tissue undergo some detectable changes that at present cannot be related to capsular contraction. The possible roles of physical and chemical characteristics of the silicone implants are discussed. Steroids are widely used to prevent contraction, but much debate exists over whether or not they actually work. Other possible drug treatments are discussed, based on current research.

Animals↗
PubMed1979

Inhibition of myofibroblasts by skin grafts.

The myofibroblast population was studied by electron microscopy in rat wounds healing by (1) contraction of granulation tissue, (2) by coverage with split-skin grafts, and (3) by coverage with full-thickness skin grafts. In all 3 types of wounds, myofibroblasts appeared early and reached a peak number at two weeks after wounding. At this time, 40 to 50 percent of the wound fibroblasts had myofibroblast characteristics. The granulating wounds contracted rapidly and completely, and had long persistence of myofibroblasts. Split-skin grafted wounds contracted less and had a more rapid decrease in myofibroblasts. The wounds covered with full thickness skin grafts had a minimum of contraction with a very rapid decrease in the number of myofibroblasts until by 4 weeks no myofibroblasts were present. Full-thickness skin grafts thus appeared to influence contracting wounds not by preventing the formation of myofibroblasts, but by speeding up completion of their life cycle.

Animals↗
PubMed1979

Contractile fibroblasts in chronic alcoholic cirrhosis.

Contractile fibroblasts were sought via electron microscopy in liver tissue from 12 patients with chronic alcoholic cirrhosis, and from 3 noncirrhotic patients. In 9 of the 12 cirrhotic livers, contractile fibroblasts (myofibroblasts) were seen containing the classic features of 60-80 A microfilament bundles with electron-dense bodies along with prominent microtubules. The remaining three cirrhotic liver specimens had fibroblasts containing microfilament bundles but without electron-dense bodies. Myofibroblasts were not found in any of the noncirrhotic livers. Just as in other types of scars, myofibroblasts are probably the active contractile force in the scarring and fibrosis which characterize chronic alcoholic cirrhosis.

Adult↗
PubMed1979

Location of the force of wound contraction.

Contractile fibroblasts were found on electron microscopy to be distributed throughout the substance of contracting pig and rat wounds. The force of wound contraction is probably caused by these cells contracting and pulling on each other and on the surrounding stroma. This evidence suggests that the pull theory of wound contraction is correct.

Animals↗
PubMed1979

Experimental skin necrosis produced by adriamycin.

Skin ulceration caused by extravasation of Adriamycin follows a severely protracted course accompanied by considerable morbidity. To develop an animal model of Adriamycin ulceration, we compared intradermal injection of Adriamycin to injection beneath the panniculus carnosus with varying drug volumes and concentrations. Injections beneath the rat panniculus carnosus caused only irregular ulcerative lesions. Intradermal injection produced predictable, uniform skin necrosis and ulceration. Both increasing volume and increasing concentration of Adriamycin caused proportionate increases in skin ulcer size and in time required for healing. A critical concentration range for Adriamycin necrosis is 0.010--0.020 mg/ml, suggesting that the drug would have to be greatly diluted to reduce clinical skin ulceration. Adriamycin-induced skin necrosis heals at a slower rate than surgically created skin defects of similar size, indicating a reduced rate of wound contraction. Removal of the necrotic skin allows faster healing, although still slower than normal, due to removal of splinting effect. Histology shows early skin necrosis, with acute inflammation developing after 1 week. Epidermal hypertrophy is present at the edges of the necrosis. The small vessels remain patent. Multiple small vesicles of unknown etiology are seen in the necrotic dermis.

Animals↗
PubMed1979

Ultrastructure of doxorubicin (adriamycin)-induced skin ulcers in rats.

Skin necrosis was produced in 24 male Fischer 344 rats by intradermal injection of 0.5 ml of doxorubicin (Adriamycin) at a concentration of 2 mg/ml. The resulting wounds healed slowly over 6 to 7 weeks with the reduced contraction rate paralleling the prolonged morbidity of doxorubicin ulcers in humans. Electron microscopy showed bizarre rough endoplasmic reticulum, double-walled vacuoles, and swollen mitochondria from 1 through 12 weeks after injury. Myofibroblasts with 60- to 80-A microfilaments with electron-dense bodies, intercellular connections, and prominent microtubules were seen from 4 through 12 weeks after injury. Although the appearance of myofibroblasts was delayed, their structure was normal. The delayed contraction of doxorubicin-induced skin ulcers thus appears due to persistent nonspecific cellular damage at the nuclear level rather than to specific derangement of myofibroblast function.

Animals↗
PubMed1979

[Cholestasis diagnostics. Experiences with the percutaneous transhepatic cholangiography (PTC) using the Chiba needle (author's transl)].

We were successfull in doing a percutaneous transhepatic cholangiography (PTC) using the Chiba needle in 29 out of our 32 first cases including 19 out of 20 icteric and 10 out of 12 unicteric patients. Already when getting familiarized with the procedure the PTC seems to be superior as compared to the endoscopic retrograde cholangiography (ERC) in regard to results, risks, inconvenience to the patient, costs and technical skill. In this way the cholestasis diagnostics could be improved also in smaller hospitals missing the personnel and instrumental requirements to do the ERC procedure.

Cholangiography↗
PubMed1978

Refolding and reactivation of liver alcohol dehydrogenase after dissociation and denaturation in 6M guanidine hydrochloride.

Horse-liver alcohol dehydrogenase has been dissociated and denatured by 6 M guanidinium hydrochloride. Removal of the denaturant under optimum conditions of the solvent leads to partial reactivation. The concentrations of the enzyme, as well as the coenzyme (NAD+), and Zn2+, affect the reactivation significantly, since high concentrations promote the formation of inactive aggregation products. Analyzing the kinetics of reactivation and reassociation, conditions far from equilibrium of dissociation-association provide maximum yields (approximately 70%). The sigmoidal kinetic traces suggest a superposition of first-order transconformation and second-order association reactions; the latter are corroborated by the concentration dependence of the reactivation reaction. The coenzyme, NAD+, has no influence on the kinetics of reactivation. Addition of Zn2+ leads to a significant decrease of the rate and yield of reactivation. The process of renaturation, as reflected by the regain of native fluorescence shows complex kinetics: rapid relaxations are followed by slower first-order and second-order processes which parallel reactivation.

Alcohol Oxidoreductases↗
PubMed1978

Effect of zinc(II) on the refolding and reactivation of liver alcohol dehydrogenase.

Horse-liver alcohol dehydrogenase requires Zn2+ for enzymatic activity. Reactivation experiments after dissociation and denaturation of the enzyme in 6 M guanidinium hydrochloride and subsequent separation of zinc prove that the effect of the metal on the rate and yield of reconstitution is complex. In the absence of Zn2+ no reactivation is detectable, while excess of Zn2+ leads to inactive aggregates. Optimum reactivation yields are obtained at 10 muM Zn2+ after short incubation in the denaturant; increasing zinc concentration causes a decrease of the rate of reactivation. The refolding of the zinc-free enzyme is characterized by consecutive first-order processes which may be separated from second-order dimer formation. Addition of 10 muM Zn2+ during refolding may be used to block side reactions competing with the reconstitution. The transition from sigmoidal kinetics to second-order profiles by adding Zn2+ after completion of the aforementioned first-order process corroborates the proposed uni-bimolecular reactivation mechanism which implies the involvement of inactive monomers. These gain their enzymatic function as a consequence of dimerization. The effect of Zn2+ may be explained by a side reaction in the overall reaction scheme of reactivation and renaturation which allows the kinetic measurements to be quantitatively described.

Alcohol Oxidoreductases↗
PubMed1978

Silicon identification in prosthesis-associated fibrous capsules.

The use of correlated microscopic techniques, including the scanning electron microscopic modes of backscattered electron imaging and energy dispersive x-ray analysis, aid in defining the process of dispersion of silicon-containing material around silicone rubber (polydimethylsiloxane) prosthetic devices.

Breast↗
PubMed1978

Spatial orientation of microtubules in contractile fibroblasts in vivo.

Contracting fibrous tissues from skin wounds in pigs, and scars around silicone implants in humans, contained fibroblasts that had multiple bundles of 60--80 A microfilaments with electron-dense bodies, features typical of contractile fibroblasts both in vivo (myofibroblasts) and in vitro. These in vivo fibroblasts contained many 220 A diameter microtubules, which paralleled plasma membrane in these myofibroblasts strongly suggests a bracing or scaffolding function.

Animals↗
PubMed1978

Myofibroblasts and free silicon around breast implants.

Fibrous tissue capsules, from around silicone breast implants, were examined by light microscopy, and by transmission and scanning electron microscopy, the latter combined with energy dispersive X-ray analysis. Contractile fibroblasts (myofibroblasts) were found in most of these fibrous capsules, and especially in those recently formed or manipulated. The element silicon was positively identified by X-ray analysis in half the tissue specimens. This material was found only around gel-filled implants. In the specimens studied, the clinical hardness of the breast was unrelated to the presence of silicon in the capsule.

Breast↗