Induction of tolerance to hypothermia by previous heat shock using human fibroblasts in culture.

The technique of organ preservation is limited by the amount of time which organs can be hypothermically stored. A potential method to effectively extend reliable storage times involves the conditioning of cells to better withstand hypothermia by previous exposure to a less severe stress. Using human fibroblasts in culture, we have demonstrated that such an approach may be feasible. Subjecting human diploid IMR-90 fibroblasts to 5 h 42.5 degrees C heat shock was found to improve cell survival more than 10-fold to subsequent 4 degrees C hypothermic exposure. The prior heat shock resulted in the increased synthesis of heat shock proteins (HSPs), the absolute concentrations of which were measured by an assay which utilized sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting techniques. Both the degree of cold tolerance conferred upon IMR-90 cells and the levels of HSP27 and HSP27 were dependent upon initial heat shock duration. Induced cold tolerance was found to be reversible; longer recovery times at 37 degrees C following heat shock resulted in a loss of this cold-tolerant state as well as a disappearance of HSPs. The fact that the degree of cold tolerance and HSP concentrations showed similar trends with respect to both heat shock time at 42.5 degrees C and subsequent recovery time at 37 degrees C suggests that these proteins may be intimately involved in the induction of cold tolerance.

Microfiltration of recombinant yeast cells using a rotating disk dynamic filtration system.

To develop a highly efficient cell harvest step under time constraint, a novel rotating disk dynamic filtration system was studied on the laboratory scale (0.147-ft.(2) nylon membrane) for concentrating recombinant yeast cells containing an intracellular product. The existing cross-flow microfiltration method yielded pseudo-steady state flux values below 25 LMH (L/m(2). h) even at low membrane loadings (10 L/ft.(2)). By creating high shear rates (up to 120,000(-1)) on the membrane surface using a rotating solid disk, this dynamic filter has demonstrated dramatically improved performance, presumably due to minimal cake buildup and reduced membrane fouling. Among the many factors investigated, disk rotating speed, which determines shear rates and flow patterns, was found to be the most important adjustable parameter. Our experimental results have shown that the flux increases with disk rotating speed, increases with transmembrane pressure at higher cell concentrations, and can be sustained at high levels under constant flux mode. At a certain membrane loading level, there was a critical speed below which it behaved similarly to a flat sheet system with equivalent shear. Average flux greater than 200 LMH has been demonstrated at 37-L/ft.(2) loading at maximum speed to complete sixfold concentration and 15-volume diafiltration for less than 100 min. An order of magnitude improvement over the crossflow microfiltration control was projected for large scale production. This superior performance, however, would be achieved at the expense of additional power input and heat dissipation, especially when cell concentration reaches above 80 g dry cell weight (DCW)/L. Although a positive linear relationship between power input and dynamic flux at a certain concentration factor has been established, high cell density associated with high viscosity impacted adversely on effective average shear rates and, eventually, severe membrane fouling, rather than cake formation, would limit the performance of this novel system.

Pilot-scale harvest of recombinant yeast employing microfiltration: a case study.

In order to develop a cost-effective recovery process for an intracellular product, crossflow microfiltration was studied for the harvest of a recombinant yeast under severe time constraint. It was required to process yeast broth in a short period of time to minimize the risk for product degradation. Preliminary microfiltration studies employing flat sheet membranes showed high throughout with initial fluxes on the order of water fluxes (> 1000 LMH, regime I, < 2 min), followed by a rapid decay towards a low pseudo-steady state flux (20 LMH, regime II, > 2 min). Exploitation of these high fluxes and control of their eventual decline were crucial in establishing a rapid crossflow filtration process. The effect of several parameters, such as initial cell concentration, shear rate, transmembrane pressure, membrane pore size and medium composition on filtration performance were investigated to better understand the flux decline mechanisms. We found that the major contributor to flux decay was reversible fouling by the cake formation on the membrane surface. Within the operating boundaries of our microfiltration system, large-pore membrane (0.65 micron) was much more desirable for harvesting our yeast (10 microns size) without cell leakage than smaller pore ones (0.22 micron and 0.45 micron). Among adjustable operating parameters, feed flow rate (i.e., shear rate) exerted significant impact on average flux, whereas manipulation of transmembrane pressure afforded little improvement. Although initial cell concentration affected adversely the permeation rates, growth medium components, especially soy-peptone, was deemed pivotal in determining the characteristics of cell cake, thus controlling yeast microfiltration.

Proximal placement of the acetabular component in total hip arthroplasty. A long-term follow-up study.

A retrospective review was undertaken of thirty-seven hips (thirty-four patients) that had had a complex cemented total hip arthroplasty. In these hips, circumstances had necessitated that the center of the hip be placed farther proximally, as measured from the interteardrop line, than the anatomical position that is normally used. The mean duration of clinical and roentgenographic follow-up was eleven years (range, seven to seventeen years), and the mean age of the patients was fifty-one years (range, sixteen to seventy-three years). Most of these hips had a major deficiency or defect of the acetabular bone stock, or both. Of the six acetabular components (16 per cent) that became loose and were followed for ten years, only one needed revision. Because this study was aimed specifically at assessment of the acetabular component, if the femoral component alone needed revision, the final clinical rating that was used was the one obtained after the femoral revision. Thirty-one hips (84 per cent) were rated as having a good or excellent result; they had an average Harris hip-rating score of 43 points preoperatively and 93 points postoperatively. Thirty-three of the thirty-seven acetabular components were not substantially displaced laterally as compared with the anatomical location that is normally used. Our findings suggest that, when circumstances dictate, proximal positioning of the acetabular component without lateral displacement can give an acceptable result in cemented total hip-replacement procedures.

Evaluation and treatment of hand and wrist disorders in musicians.

Hand symptoms in musicians reflect a complex, multifactorial etiology. A multidisciplinary approach is required for proper evaluation and treatment. Good results can be achieved in most patients with localized inflammatory and overuse disorders or nerve compression syndromes. Motor control disorders and chronic pain syndromes are associated with poorer results. Early diagnosis appears to improve outcome.

Isolated talocalcaneal arthrodesis. A technique using moldable bone graft.

Combined autogenous iliac-crest bone-grafting and fixation with a pin or screw was used to achieve a fusion of the talocalcaneal joint in forty-one adults (forty-five arthrodeses). At a mean length of follow-up of fifty-seven months (range, thirty to ninety-six months), thirty-seven (90 per cent) of the patients were satisfied with the result. Objectively, the results were excellent after thirty-nine arthrodeses (87 per cent), good or fair after five (11 per cent), and poor after one (2 per cent). There was one non-union and one superficial wound infection. At the time of follow-up, no secondary degenerative changes in the associated joints of the hind part of the foot were identified on roentgenograms. The surgical technique appears to be appropriate and effective in the treatment of arthritis of the talocalcaneal joint in adults.

Tibiotalocalcaneal arthrodesis for arthritis and deformity of the hind part of the foot.

We devised a method for tibiotalocalcaneal arthrodesis to treat deformities or degenerative arthritis, or both, that involve the tibiotalar and talocalcaneal joints. Satisfactory results were obtained in approximately 75 per cent of twenty-one patients; osseous union was radiographically evident in all but three patients. Secondary degenerative changes in the adjacent joints were not evident radiographically during a period of follow-up that ranged from 2.5 to seven years.

Cemented total hip arthroplasty with contemporary techniques. A five-year minimum follow-up study.

A retrospective clinical and roentgenographic review was performed on 251 consecutive cemented total hip arthroplasties (THA) performed from 1978 to 1980 that had been followed a minimum of five years (range, five to seven years). All arthroplasties involved the use of a Harris Design II femoral stem, an intramedullary plug, a cement gun, and pulsatile lavage of both the acetabulum and the femoral canal. At the final follow-up examination, 98% of the patients had excellent results. The average Harris hip score was 47 points preoperative and 97 points postoperative. There were three definitely loose femoral stems, one probably loose, and two possibly loose. There was one loose acetabular component, no revisions or operations were performed. When comparing this series with a similar study, there were statistically improved results in all parameters. Results from this study of cemented THAs using contemporary techniques and prosthetic stem design represent the standard for comparison when evaluating alternative THA systems.

The John Charnley Award paper. Efficacy of using a bone graft substitute to enhance biological fixation of a porous metal femoral component.

The efficacy of using hydroxyapatite/tricalcium phosphate (HAP/TCP) particles to enhance the biological fixation of a canine cementless femoral component with a noninterference fit was evaluated with a custom-designed collarless, wedge-shaped femoral component with titanium fiber metal pads along the anteroposterior surfaces of the stem. A polyethylene acetabular component was cemented into the pelvis. Three groups of dogs were employed: group I (n = 7) had a femoral component with an interference fit; group II (n = 6) had a component with a noninterference fit with uniform voids along the anteroposterior stem surfaces; and group III (n = 6) had a component with a noninterference fit including uniform voids filled with HAP/TCP particles. All dogs were harvested after 12 weeks of unrestricted weight bearing. Cross-section specimens from three different levels from each bone-component composite were evaluated histologically to determine the type and extent of tissue ingrowth and the percentage of peripheral bone or HAP/TCP particles adjacent to the fiber metal pad surfaces. Three other cross-section specimens, adjacent to the histological section levels of the same composites, were assessed for shear strength at the fiber metal-tissue interface and for biochemical composition of the ingrown tissue.