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Biomedical subjects

J Probst

Publications and source records attributed to J Probst.

At least 19 recordsLinked to original sources
PubMed2002

Surface properties of calcium phosphate particles for self setting bone cements.

Calcium phosphate cements (CPC), consist of multicomponent powder mixtures of calcium orthophosphates with grain sizes in the region of 1-20 microm. Due to the small particle sizes surface properties as the zeta potential and adsorption processes play a significant role during manufacturing and application. In the context of this work zeta potentials of different calcium phosphates, like dicalcium phosphate anhydride (DPCA) tetracalcium phosphate (TTCP) and hydroxyapatite were measured in various organic/aqueous media with different pH values. The results show a strong dependency of the zeta potential on the kind of suspension medium used associated with different milling properties. The addition of sodium phosphate leads to a pH value dependent stabilization of the particles in the liquid phase; the zeta potential of the surface increases from about -15 to -18 mV in water and from -35 to -45 mV in 0.05 mol/l sodium phosphate solution. Besides the interaction of particles with various antibiotics was determined on the basis of the zeta potential of the surface. The substances partly cause a tremendous change of the surface load. This is accompanied by a change of the rheological properties of the cement paste, the morphology of the hardened cement matrix and a significant deterioration of the application-relevant properties as setting time or mechanical strength.

Anti-Bacterial Agents↗
PubMed2000

CAIR-1/BAG-3 forms an EGF-regulated ternary complex with phospholipase C-gamma and Hsp70/Hsc70.

CAIR-1/BAG-3 forms an EGF-regulated ternary complex with Hsp70/Hsc70 and latent phospholipase C-gamma (PLC-gamma). The expression of CAIR-1, CAI stressed-1, was induced in A2058 human melanoma cells by continuous exposure to CAI, an inhibitor of nonvoltage-gated calcium influx. CAIR-1 sequence is identical, save 2 amino acids, to BAG-3 also cloned recently as Bis, a member of the bcl-2-associated athanogene family. We show that CAIR-1/BAG-3 binds to Hsp70/Hsc70 in intact cells and this binding is increased by short term exposure to CAI (P<0.007). CAIR-1/BAG-3 is phosphorylated in vivo in the absence of stimulation. Basal phosphorylation is inhibited by treatment with d-erythrosphingosine (d-ES), a broad inhibitor of the protein kinase C family. CAIR-1/BAG-3 contains several PXXP SH3 binding domains leading to the hypothesis that it is a partner protein of phospholipase C-gamma. PLC-gamma is bound to CAIR-1/BAG-3 in unstimulated cells. It is increased by CAI or d-ES (P=0.05) treatment, and abrogated by EGF (r2=0.99); d-ES treatment blocks the EGF-mediated dissociation. We show that CAIR-1/BAG-3 binds to PLC-gamma and Hsp70/Hsc70 through separate and distinct domains. Hsp70/Hsc70 binds to the BAG domain of BAGs-1 and -3. CAIR-1/BAG-3 from control and EGF-treated cell lysates bound selectively to the SH3 domain of PLC-gamma, but not its N-SH2 or C-SH2 domains. Confirming the SH3 interaction, PLC-gamma was pulled down by CAIR-1/BAG-3 PXXP-GST fusions, but GST-PXXP constructs confronted with lysates from EGF-treated cells did not bind PLC-gamma as was seen in intact cells. Hsp70/Hsc70 was brought down by the PLC-gamma SH3 construct equally from native and EGF-treated cells, but did not bind the PXXP construct under either condition. We propose that CAIR-1/BAG-3 may act as a multifunctional signaling protein linking the Hsp70/Hsc70 pathway with those necessary for activation of the EGF receptor tyrosine kinase signaling pathways.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Effect of carotid body denervation on breathing in neonatal goats.

The objective of the present study was to determine in goats whether carotid body denervation (CBD) at 1-3 days of age causes permanent changes in breathing greater than those that occur after CBD in adult goats. Goats underwent CBD (n = 6) or sham CBD (n = 3) surgery at 1-3 days of age. In addition, one unoperated control animal was studied. Bolus intravenous injections of NaCN 2 days postsurgery verified successful CBD surgery. However, at 3, 11, and 18 mo of age, the CBD goats had regained a NaCN response that did not differ (P > 0.10) from that of intact goats. Intracarotid NaCN injections elicited a hyperpnea in the sham CBD but not the CBD goats. Only one animal exhibited highly irregular breathing [characterized by prolonged (>9-s) apneas] after CBD, and the irregularity disappeared by 3 mo of age. One CBD goat died at 35 days of age, and autopsy revealed that death was associated with pneumonia. After 3 mo of age, there were no statistically significant differences (P > 0.10) between sham and CBD goats in eupneic breathing, hypoxia and CO(2) sensitivity, and the exercise hyperpnea. It is, therefore, concluded that CBD at 1-3 days of age in goats does not appear to affect selected aspects of respiratory control after 3 mo of age, conceivably because of the emergence of other functional chemoreceptors that compensate for the loss of the carotid chemoreceptor.

Animals↗
PubMed1997

Regulation of cell spreading during differentiation in the muscarinic M5 receptor tumor-suppressor model.

Activation of the muscarinic receptor in Chinese hamster ovary (CHO) cells results in a reversal of the malignant phenotype for which spreading into a bipolar, fibroblastic morphology is a marker. The process of morphologic change requires multiple events, including alterations in adhesions to substrates and cytoskeletal re-arrangement. In this report, we demonstrate the calcium-dependent involvement of p125FAK in this cellular shape change using an inhibitor of ligand-induced calcium influx, carboxyamido-triazole (CAI). p125FAK becomes tyrosine-phosphorylated after exposure to the agonist carbachol (CC), reaching maximal phosphorylation prior to initiation of cellular shape change at 1 hr into CC exposure (386 +/- 103%). Phosphorylation remained elevated through the shape change (4-12 hr). CHOm5 cell exposure to the Ca2+-mobilizing agents maitotoxin and ionomycin also resulted in p125FAK phosphorylation. Inhibition of Ca2+ influx with CAI, an inhibitor of ligand-induced Ca2+ influx, had little effect on CC-induced phosphorylation but partially inhibited ionomycin-mediated p125FAK phosphorylation. While the intracellular Ca2+ chelator BAPTA failed to prevent CC-induced p125FAK tyrosine phosphorylation, it inhibited phosphorylation due to ionomycin. CC induced Ca2+-independent binding of phosphorylated p125FAK selectively to the C-terminal SH2 domain of phosphatidylinositol-3'-kinase (PI3K). Further, CC, maitotoxin and ionomycin induced in vitro kinase activity of p125FAK for the exogenous substrate poly(Glu4Tyr1). Kinase activity stimulated by all 3 agonists was inhibited by preincubation with either CAI or BAPTA. Our results indicate that increasing intracellular Ca2+ can stimulate both p125FAK autophosphorylation and kinase activity; however, p125FAK phosphorylation in response to CC also may be induced through a Ca2+-independent pathway.

Animals↗
PubMed1996

Identification and molecular characterization of a m5 muscarinic receptor in A2058 human melanoma cells. Coupling to inhibition of adenylyl cyclase and stimulation of phospholipase A2.

We report the identification and biochemical characterization of an endogenous m5 muscarinic acetylcholine receptor (mAChR) in the A2058 human melanoma cell line. This is the first demonstration of a m5AChR outside the central nervous system. The unusual effector coupling of this endogenous m5AChR is presented. The coding region amplified by polymerase chain reaction was identical to the known m5AChR sequence. Binding studies indicated a Kd of 99 +/- 6 pM and a Bmax of 45 +/- 4 fmol/mg membrane protein. This m5AChR coupled to stimulation of arachidonic acid release and to a 50% inhibition of forskolin-stimulated cAMP accumulation. The inhibition of cAMP production was insensitive to pertussis toxin treatment, but was dependent upon extracellular calcium. In contrast to the odd mAChR pattern, no cAMP was produced in response to carbachol (CC) stimulation. Moreover, no release of inositol phosphates could be measured after CC treatment despite the presence of at least 2 phospholipase C isoforms in A2058 cells. CC-stimulated arachidonic acid release (EC50 = 17.8 +/- 0.1 microM) was dependent upon external Ca2+, with marked reduction after coincubation with EGTA, Co2+, or high doses of verapamil (IC50 = 166 microM) or diltiazem (IC50 = 243 microM). Brief exposure to phorbol 12-myristate 13-acetate augmented CC-stimulated arachidonic acid release, whereas prolonged phorbol 12-myristate 13-acetate treatment resulted in down-regulation of release. Activation of the m5AChR resulted in Ca2+ influx that was attenuated by muscarinic antagonism and removal of extracellular Ca2+. A2058 cells exposed to CC had no alteration of cell shape or growth potential in monolayer culture, however, a statistically significant reduction in density-independent growth was observed over the range of CC concentrations from 0.1 to 100 microM. This endogenous m5AChR has a novel signal transduction coupling profile and receptor activation reduces clonogenic potential.

Adenylyl Cyclase Inhibitors↗
PubMed1992

[Quality of life and economical significance].

A good healing result is, of itself, not a measure of life-quality, but only a factor within a complex of values. Throughout time, its significance corresponds to the degree of evolution of the medical profession, and especially that of preservation and reconstructive surgery. Subjective perception, satisfaction with treatment, preservation or impairment of physical abilities, illness in the broadest sense, and finally terminal despair or even death are criteria of the value termed life quality. A key function of the rehabilitation process lies in the confrontation with its result, only the acceptance of a deficient state leads to the regaining of life-quality, this may necessitate a reappraisal of values (delcredere). To secure life-quality after injury is not only a question of financing the individual case, but a matter of economical significance in view of the reclaiming of resources once the injured are reintegrated. This reclamation will be the greater, the more quickly and thoroughly rehabilitation is accomplished. Rehabilitation, in turn, depends upon the adequate development of treatment possibilities, including hospital structures within which performance standards must be conveyed.

Costs and Cost Analysis↗
PubMed1991

[Intra-operative complications in arthroscopic operations. Results of a re-arthroscopy study].

The overall complication rate of arthroscopy and arthroscopic procedure is very low. Iatrogenic arthroscopic joint lesions, especially the alteration of articular cartilage does occur, but there is no idea of proportions and importance of these lesions. Persistent pain and swelling after arthroscopic procedure lead to repeat arthroscopy and therefore to a check of diagnosis and treatment. From 1. 1. 1987-30. 6. 1990 we carried out 239 second-look arthroscopies of knee joint, 121 after diagnostic arthroscopy and arthroscopic procedure. In 34% we had to revise the first diagnosis. After arthroscopic procedure we saw in more than 50% unsatisfactory results. The most important reason for persistent symptoms after arthroscopic meniscectomy were cartilage lesions.

Arthroscopy↗
PubMed1990

[Partial causality in case of physician liability].

The specific theories about causality related to the different branches of law do have importance in the politics of rules. In civil law and physician liability law as well the theory of adequacy is valid. This theory selects only certain conditions as legally effective out of the abundance of all existing conditions. In physician liability law it typically happens, that indifferent chains of cause and effect coincide, what matters is to distinguish one from another and according to conditions to determine the partial causality which has to be attributes to the physician. The example of the untreated peri-lunar luxation and subsequent lunar necrosis illustrates the legally effective problematic nature of two causes.

Germany↗
PubMed1990

[Sequelae and evaluation after distal radius fractures].

The sequela of fractures of the distal radius show the same variety as the fracture models themselves, depending on conservative or operative repositioning. The most frequent disadvantages are deviation of the bone axis, depression of the basis of the radius, steps in the cartilage plain and rough deformity. Most important are the arthrotic changes in the joint, such as entrapment and compression neuropathies. The sequela of fractures in children, adults and the aged differ. The purpose of the expert appraisal is not only to assess the damages after fracture but also to give new proposals for further therapy.

Diagnostic Imaging↗
PubMed1989

[Technics of primary and secondary amputation of the foot].

Maintenance therapy of the traumatized foot by partial amputation, in contrast to lower-leg amputation with subsequent artificial leg adjustment, should always be attempted if there is any possibility of shaping a stump that is independent of the prosthesis. As in former years, the disarticulation technique is performed; however, today the technique has been modified to obtain more functional results and to conserve tissue, which may mean that transosseous amputation is practicable. The quality of the soft-tissue flap and stability are the determining factors in the quality of the stump. These prerequisites mean that the operative technique must be adapted to the requirements of the patients; the soft tissue must be preserved and procedures used that will permit reconstructive procedures later.

Amputation, Surgical↗
PubMed1989

[Resection of the coracoacromial ligament. A simple surgical procedure for decompression of the subacromial space].

Resection of the coracoacromial ligament is a simple method for decompression of the subacromial space. The operation can be performed under arthroscopic control or by means of a small incision above the ligament. 61 patients were operated on by this method during the period between July 1987 and August 1988. 37 patients were questioned regarding the results. In 40% of these there was an alleviation of pain, 48% had an improved motility and 67% would again agree to the operation that appeared indicated (in the patients referred for surgery) both in the impingement syndrome and in antiquated ruptures of the rotator cuffs.

Acromion↗
PubMed1987

[Synergistic joint diagnosis].

Many methods are useful in the diagnosis of diseases of the joints. Noninvasive methods deserve preference; invasive techniques such as arthrography and arthroscopy are second choice, after noninvasive methods have been applied. The synergic combination of the two last-named methods has proved successful. Arthrography, performed before arthroscopy in the operation theatre, supplements arthroscopy findings and extends the diagnostic value of the arthroscopic findings, in a similar manner as the combination of computed tomography and arthrography.

Arthrography↗