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Biomedical subjects

R Bechtold

Publications and source records attributed to R Bechtold.

11 recordsLinked to original sources
PubMed1998

Expression of human activin C protein in insect larvae infected with a recombinant baculovirus.

In order to generate dimeric recombinant transforming growth factor-beta (TGF-beta) proteins, expensive eucaryotic cell systems, such as CHO cells, are usually used. An alternative represents the expression of such proteins in insects using a baculovirus expression system. In this study, recombinant human activin C protein was expressed in Noctuidae larvae. On SDS-PAGE, the expressed protein has a size of about 15 kD under reducing conditions and of about 20 kD under non-reducing conditions. This suggests that activin C is expressed as a dimer and disulfide bridges can be formed. Compared with expression in eucaryotic cell culture systems, expression in insect larvae presents a rapid and low cost method, without the need for expensive tissue culture scale-ups or special equipment.

3T3 Cells↗
PubMed1997

A study of caloric restriction and cardiovascular aging in cynomolgus monkeys (Macaca fascicularis): a potential model for aging research.

Caloric restriction has been demonstrated to retard aging processes and extend maximal life span in rodents, and is currently being evaluated in several nonhuman primate trials. We initiated a study in 32 adult cynomolgus monkeys to evaluate the effect of caloric restriction on parameters contributing to atherosclerosis extent. Following pretrial determinations, at which time a baseline measure of ad libitum (ad lib) dietary intake was assessed, animals were randomized to an ad lib fed group (control) or a caloric restriction group (30% reduction from baseline intake). The animals are being evaluated for glycated proteins, insulin, glucose, insulin sensitivity measures, and specific measures of body fat composition by CT scans (e.g., intra-abdominal fat) over specified intervals. The results from the first year of observation demonstrate a significant diet effect on body weight, and specifically intra-abdominal fat. Further, insulin sensitivity has been significantly increased after 1 year of caloric restriction compared to the ad lib fed group. These studies indicate that caloric restriction has a marked effect on a pathologic fat depot, and this change is associated significantly with an improvement in peripheral tissue insulin sensitivity.

Aging↗
PubMed1993

Ultrasonographic diagnosis of varicoceles.

OBJECTIVE: To assess the ability of color duplex scrotal ultrasonography to detect subclinical varicoceles and confirm the diagnosis of clinical varicoceles. DESIGN: Physical examination, color duplex scrotal ultrasonography and internal spermatic venography was performed on 64 testicular units in 33 men. SETTING: Male fertility center. PATIENTS: Two hundred sixty-two consecutive men being evaluated for male factor infertility of whom 33 agreed to undergo venography. MAIN OUTCOME MEASURES: Ultrasonographic measurement of scrotal vein diameter of patients in the supine and upright position, before and during valsalva maneuver, and scrotal vein blood flow reversal with valsalva maneuver was compared with the findings of varicocele by physical examination and venography. RESULTS: The best predictor of a varicocele was internal spermatic vein diameter, and the best overall performance of ultrasonography was achieved with the patient at rest in the supine position. The best cutoff point for venous diameter for a clinical varicocele was 3.6 mm and 2.7 mm for a subclinical varicocele, but the overall accuracy was only 63%. CONCLUSIONS: Confirmatory studies are needed to support the ultrasonographic diagnosis of varicoceles before considering surgical repair.

Humans↗
PubMed1992

Kinesin is bound with high affinity to squid axon organelles that move to the plus-end of microtubules.

This paper addresses the question of whether microtubule-directed transport of vesicular organelles depends on the presence of a pool of cytosolic factors, including soluble motor proteins and accessory factors. Earlier studies with squid axon organelles (Schroer et al., 1988) suggested that the presence of cytosol induces a > 20-fold increase in the number of organelles moving per unit time on microtubules in vitro. These earlier studies, however, did not consider that cytosol might nonspecifically increase the numbers of moving organelles, i.e., by blocking adsorption of organelles to the coverglass. Here we report that treatment of the coverglass with casein, in the absence of cytosol, blocks adsorption of organelles to the coverglass and results in vigorous movement of vesicular organelles in the complete absence of soluble proteins. This technical improvement makes it possible, for the first time, to perform quantitative studies of organelle movement in the absence of cytosol. These new studies show that organelle movement activity (numbers of moving organelles/min/micron microtubule) of unextracted organelles is not increased by cytosol. Unextracted organelles move in single directions, approximately two thirds toward the plus-end and one third toward the minus-end of microtubules. Extraction of organelles with 600 mM KI completely inhibits minus-end, but not plus-end directed organelle movement. Upon addition of cytosol, minus-end directed movement of KI organelles is restored, while plus--end directed movement is unaffected. Biochemical studies indicate that KI-extracted organelles attach to microtubules in the presence of AMP-PNP and copurify with tightly bound kinesin. The bound kinesin is not extracted from organelles by 1 M KI, 1 M NaCl or carbonate (pH 11.3). These results suggest that kinesin is irreversibly bound to organelles that move to the plus-end of microtubules and that the presence of soluble kinesin and accessory factors is not required for movement of plus-end organelles in squid axons.

Animals↗
PubMed1990

MRI findings of sciatic endometriosis.

Endometriosis is a rare cause of sciatic mononeuropathy. We report a woman with cyclic, menstruation-related hip pain associated with right leg weakness and sensory loss. Examination and electrodiagnostic studies suggested sciatic nerve dysfunction. Magnetic resonance imaging (MRI) revealed abnormal signal consistent with endometriotic tissue in the region of the right sciatic nerve. The abnormal signal partially regressed after treatment of the endometriosis. This case further illustrates the utility of MRI in the assessment of rare pelvic disorders.

Adult↗
PubMed1986

The abnormal nephrogram.

Recognition of qualitative abnormalities in the nephrogram may be as important as the recognition of structural abnormalities for the detection of renal disease.

Angiography↗
PubMed1985

Structure of an electron transfer complex. II. Chemical modification of carboxyl groups of cytochrome c peroxidase in presence and absence of cytochrome c.

Cytochrome c peroxidase forms an electron transfer complex with cytochrome c. The complex is governed by ionic bonds between side chain amino groups of cytochrome c and carboxyl groups of peroxidase. To localize the binding site for cytochrome c on the peroxidase, we have used the method of differential chemical modification. By this method the chemical reactivity of carboxyl groups (toward carbodiimide/aminoethane sulfonate) was compared in free and in complexed peroxidase. When ferricytochrome c was bound to cytochrome c peroxidase, acidic residues 33, 34, 35, 37, 221, 224, and 1 to 3 carboxyls at the C terminus became less reactive by a factor of approximately 4, relative to the remaining 39 carboxylates of peroxidase. Of the less reactive residues those in the 30-40 region and the 221/224 pair are on opposite sides of the surface area which contains the heme propionates. We, therefore, propose that the binding site for cytochrome c on cytochrome c peroxidase spans the area where one heme edge comes close to the molecular surface. The results are in very good agreement with chemical cross-linking studies (Waldmeyer, B., and Bosshard, H.R. (1985) J. Biol. Chem. 260, 5184-5190); they also support a hypothetical model predicted on the basis of the known crystal structures of cytochrome c and peroxidase (Poulos, T.L., and Kraut, J. (1980) J. Biol. Chem. 255, 10322-10330).

Binding Sites↗
PubMed1983

Pelvic lipomatosis with ureteral encasement and recurrent thrombophlebitis.

Multiple complications occurred in a patient with severe pelvic lipomatosis and recurrent superficial thrombophlebitis. Distal ureteral and rectal encasement by lipomatous infiltration caused obstructive uropathy and rectal deformity without substantial compromise of renal or gastrointestinal function. Clinical evidence suggests an association between pelvic lipomatosis and recurrent superficial thrombophlebitis.

Humans↗
PubMed1982

The cytochrome c peroxidase.cytochrome c electron transfer complex. Experimental support of a hypothetical model.

A hypothetical model of the cytochrome c peroxidase.cytochrome c complex (Poulos, T. L., and Kraut, J. (1980) J. Biol. Chem. 255, 10322-10330) predicts charge interactions between aspartic acid residues of the peroxidase having a spatial distribution that is complementary to the distribution of essential and highly conserved residues of cytochrome c. In a first attempt to test this model, carboxyl groups of cytochrome c peroxidase have been modified with a water-soluble carbodiimide, either alone or in combination with a nucleophile. Modification led to the loss of up to 90% of the ferrocytochrome c peroxidase activity. At least 4-5 carboxyl groups out of a total of 48, but none of the heme carboxyls, were modified in a derivative with 14% residual activity. In the peroxidase.cytochrome c complex the rate of peroxidase inactivation is slowed and approximately 2 carboxyl groups are protected from chemical modification. In the presence of the carbodiimide, cytochrome c and peroxidase were cross-linked to form a covalent 1:1 complex and the linkage sites were preliminarily characterized. Cross-linking occurred to carboxyl groups of the NH2-terminal fragment 1-119 and of fragment 172-229. The four crucial aspartates of the hypothetical model are located in these same two sequence regions.

Animals↗
PubMedDate not supplied

Directional electron transfer in ruthenium-modified horse heart cytochrome c.

Cytochrome c can be modified by [(NH3)5RuII/III-] specifically at the imidazole moiety of histidine 33, and we have recently discussed the thermodynamics and kinetics of electron transfer within this modified protein. X-ray crystal structures of the oxidized and reduced forms of tuna cytochrome c indicate that the separation between the haem group of cytochrome c and the ruthenium label is 12-16 A. Internal electron transfer from the [(NH3)5RuII-] centre to the Fe(III) haem centre occurs with a rate constant k congruent to 53 s-1 (25 degrees C) (delta H = 3.5 kcal mol-1, delta S = -39 EU), as measured by pulse radiolysis. The measured unimolecular rate constant, k congruent to 53 s-1, is on the same timescale as a number of conformational changes that occur within the cytochrome c molecule. These results raise the question of whether electron transfer or protein conformational change is the rate limiting step in this process. We describe here an experiment that probes this intramolecular electron transfer step further. It involves reversing the direction of electron transfer by changing the redox potential of the ruthenium label. Electron transfer in the new ruthenium-cytochrome c derivative described here is from haem(II) to the Ru(III) label, whereas in (NH3)5Ru-cytochrome c the electron transfer is from Ru(II) to haem(III). Intramolecular electron transfer from haem(II) to Ru(III) in the new ruthenium-cytochrome c described here proceeds much slower (greater than 10(5) times) than the electron transfer from Ru(II) to haem(III) in the (NH3)5Ru-cytochrome c. We therefore conclude that electron transfer in cytochrome c is directional, with the protein envelope presumably involved in this directionality.

Animals↗