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Biomedical subjects

R Schenck

Publications and source records attributed to R Schenck.

4 recordsLinked to original sources
PubMed2001

A low stiffness composite biologically fixed prosthesis.

The current authors addressed the question whether stress-induced adaptive bone remodeling of the proximal femur is a necessary consequence after total hip reconstruction with extensively biologically-fixed femoral components. A novel total hip femoral component was designed to simultaneously achieve stable skeletal fixation, structural durability, and reduced femoral stress shielding. This implant allowed for proximal and distal canal filling, yet was significantly less rigid than all-metallic femoral stems crafted of either cobalt chromium or titanium alloy. A cohort of 366 patients (386 hips) treated at 21 institutions worldwide now have been followed up a mean of 2.4 years postoperatively (range, 3 months-6 years). Two hundred sixty-eight patients have 2 years minimum followup. To date, no femoral implants have failed to achieve bone ingrowth and none have required revision. The implants appear radiographically well-fixed with no progressive radiolucencies or osteolysis. Radiostereometric analysis studies on one subset of patients showed stable initial fixation and minimal stem micromotion. Dual energy xray absorptiometry analysis on another subset of patients revealed excellent periprosthetic bone mineral density retention. Compared with more rigid metal implants, this design shows reduced proximal femoral bone loss secondary to stress-mediated bone resorption.

Absorptiometry, Photon↗
PubMed1981

Bacteriophage T4 alc gene product: general inhibitor of transcription from cytosine-containing DNA.

The alc gene of bacteriophage T4 was originally defined on the basis of mutations which allow late protein synthesis directed by T4 DNA containing cytosine rather than hydroxymethylcytosine. The question remained whether the normal alc gene product (gpalc) also blocks the transcription of early genes from cytosine-containing DNA. Complementation experiments were performed between hydroxymethylcytosine-containing phage which direct gpalc synthesis but carry mutations in a given gene(s) and cytosine-containing phage carrying that gene(s). The required protein would then have to be directed by the cytosine-containing DNA: it is looked for directly on polyacrylamide gels or through its physiological effects or both. For all early proteins examined in this way, no synthesis was observed when 95 to 100% of the hydroxymethylcytosine was substituted by cytosine in the infecting DNA, whereas there was significant synthesis with 75% substitution or less. The results indicate that gpalc is carried in with the infecting DNA or is made very early to block transcription of all cytosine-containing DNA.

Cytosine↗
PubMed1977

[Reactive-periodical variations of vegetative parameters following orthopedic operations (author's transl)].

Continuous examinations during 4-6 weeks following various orthopedic operations of circulatory, retinuous improvement of the factors examined. E.g. frequency of resting pulse showed periodic variations with, in parts, regressive tendencies. In individual cases the maxima and minima of these variations showed considerable differences, but had a peak of frequency at 6-7 days. Similar variations of stabilizations of circulation were seen in 7 amputees of the lower limb, at rest and when learning to walk. Such variations with mainly circaseptan periodicity are unspecific accompanying reactions as part of vegetative adaptation, as known elsewhere. Similar investigations on 15 patients, walking after replacement of the hip joint and before the operation, are reported on. During the first 3-5 postoperative weeks circulatory findings were much worse, but 2 years later the values at rest and when walking were much improved, because of better walking economy.

Amputation, Surgical↗