Biomedical subjects

J Lincks

Publications and source records attributed to J Lincks.

5 recordsLinked to original sources

PubMed1999

Effect of surface roughness and composition on costochondral chondrocytes is dependent on cell maturation state.

During endochondral bone formation, as occurs in fracture healing, chondrocytes are one of the first cells to see an implant surface. We tested the hypothesis that chemical composition and surface roughness affect chondrocyte differentiation, matrix synthesis, and local factor production and that the nature of the response is dependent on the state of maturation of the cells. To do this, we harvested rat growth zone and resting zone chondrocytes and examined their response to smooth and rough disk surfaces manufactured from either commercially pure titanium or titanium alloy. Profilometry, scanning electron microscopy, Auger spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the surfaces. Average roughness values were 0.22 microm for smooth titanium surfaces, 0.23 microm for smooth titanium alloy surfaces, 4.24 microm for rough titanium surfaces, and 3.20 microm for rough titanium alloy surfaces. Cells were grown on the different disk surfaces until the cultures had reached confluence on plastic. The effect of the surfaces was determined by assaying cell number and [3H]thymidine incorporation as measures of cell proliferation, cell layer and cell alkaline phosphatase specific activity as markers of differentiation, and collagen production and [35S]sulfate incorporation as indicators of extracellular matrix production. In addition, the synthesis of prostaglandin E2 and transforming growth factor-beta were examined to measure changes in local factor synthesis. In growth zone and resting zone cultures, cell number and [3H]thymidine incorporation were decreased on rough surfaces; however, this effect was greater on commercially pure titanium surfaces. Cell layer and cell alkaline phosphatase specific activity were decreased in resting zone cells grown on rough surfaces. Cell alkaline phosphatase specific activity in growth zone cells was decreased on rough surfaces, whereas cell layer alkaline phosphatase specific activity was increased only in growth zone cells grown on rough commercially pure titanium surfaces. Resting zone cell collagen production was decreased only on rough commercially pure titanium, whereas in growth zone cells, collagen production was increased. Increased prostaglandin E2 release into the media was found for growth zone and resting zone cell cultures on the disks with rough surfaces. The observed effect was greater on rough commercially pure titanium. Production of transforming growth factor-beta by resting zones was similarly affected, whereas an increase in its production by growth zone cells was measured only on rough commercially pure titanium. These results indicate that surface roughness affects chondrocyte proliferation, differentiation, matrix synthesis, and local factor production and that these parameters are also affected by chemical composition. Furthermore, the nature and extent of the cell response is dependent on cell maturation. The overriding variable in response to an implant material, however, appears to be roughness of the surface.

Alloys↗

PubMed1998

Response of MG63 osteoblast-like cells to titanium and titanium alloy is dependent on surface roughness and composition.

The success of an implant is determined by its integration into the tissue surrounding the biomaterial. Surface roughness and composition are considered to influence the properties of adherent cells. The aim of this study was to determine the effect of chemical composition and surface roughness of commercially pure titanium (Ti) and Ti-6A1-4V alloy (Ti-A) on MG63 osteoblast-like cells. Unalloyed and alloyed Ti disks were machined and either fine-polished or wet-ground, resulting in smooth (S) and rough (R) finishes, respectively. Standard tissue culture plastic was used as a control. Surface topography and profile were evaluated by cold field emission scanning electron microscopy and profilometry, while chemical composition was determined using Auger electron spectroscopy and Fourier transform infrared spectroscopy. The effect on the cells was evaluated 24 h postconfluence by measuring cell number, [3H]-thymidine incorporation into DNA, cell and cell layer alkaline phosphatase specific activity (ALPase), osteocalcin and collagen production, [35S]-sulfate incorporation into proteoglycan, and prostaglandin E2 (PGE2) and transforming growth factor-beta (TGF-beta) production. When compared to plastic, the number of cells was reduced on the pure Ti surfaces, while it was equivalent on the Ti-A surfaces; [3H]-thymidine incorporation was reduced on all surfaces. The stimulatory effect of surface roughness on ALPase in isolated cells and the cell layer was more pronounced on the rougher surfaces, with enzyme activity on Ti-R being greater than on Ti-A-R. Osteocalcin production was increased only on the Ti-R surface. Collagen production was decreased on Ti surfaces except Ti-R; [35S]-sulfate incorporation was reduced on all surfaces. Surface roughness affected local factor production (TGF-beta, PGE2). The stimulatory effect of the rougher surfaces on PGE2 and TGF-beta was greater on Ti than Ti-A. In summary, cell proliferation, differentiation, protein synthesis and local factor production were affected by surface roughness and composition. Enhanced differentiation of cells grown on rough vs. smooth surfaces for both Ti and Ti-A surfaces was indicated by decreased proliferation and increased ALPase and osteocalcin production. Local factor production was also enhanced on rough surfaces, supporting the contention that these cells are more differentiated. Surface composition also played a role in cell differentiation, since cells cultured on Ti-R surfaces produced more ALPase than those cultured on Ti-A-R. While it is still unknown which material properties induce which cellular responses, this study suggests that surface roughness and composition may play a major role and that the best design for an orthopaedic implant is a pure titanium surface with a rough microtopography.

Alkaline Phosphatase↗

PubMed1989

Acoustic analyses of speech changes after maxillectomy and prosthodontic management.

Acoustic speech patterns of five maxillofacial surgery patients were examined before and after prosthodontic reconstruction to determine the effectiveness of a maxillary prosthesis for eliminating (or reducing) nasal resonances. Vowel formant frequencies were measured for /i/ (as in seep) and /u/ (as in in soup). Within-subject, across test-session comparisons were made by using analysis of variance techniques. Prosthodontic restoration significantly reduced the nasal resonances in all patients by either (1) completely eliminating the resonances, (2) reducing the amplitude of the resonances, or (3) changing the frequency of the resonances to more nearby regions of the vowels.

Dentures↗

PubMedDate not supplied

Burn size estimate reliability: a study.

A study was undertaken to assess any differences between physicians' and nurses' estimates of burn size from drawings of 10 hypothetical patients with burns. Patient drawings were sent to the 199 burn facilities that are listed in the American Burn Association's Burn Care Resources in North America 1989-1990. The mailings were randomized between physicians and nurses. In order to have an even distribution, the cover letter asked the individual who received the forms to fill them out himself or herself rather than to pass them on to someone else. Forty-one nurses and 16 doctors (29%) returned the completed forms. The length of experience in burn care for the nurses averaged 9.3 years (range, 2 to 20 years), and the length of experience in burn care for the physicians averaged 14.7 years (range, 1 to 30 years [p = 0.01]). There were significant differences in the estimate of mean burn size between the physicians and nurses for only the two smallest drawings; in these cases, size may have been hard to translate from the patient to the drawing. There were four smaller burn charts (less than 20% body surface area), and in two (50%) of these, there were significant differences in the estimation of the burn size. For the six larger burn charts (greater than 20% body surface area), there were no differences in the size estimates. With regression analysis, no trend was noted that correlated the size estimates with the length of experience in burn care for either the physicians or the nurses. Additionally, the participants were asked to indicate which method of estimating burn size was used in their units. Thirty-five percent use the Rule of Nines, 33% use the Lund & Browder chart, 5.3% use Berkow's method, 3% use other methods, and 1.75% use a combination of the Lund & Browder chart and the Rule of Nines. Twenty-one percent failed to indicate any preferred method. Estimates of burn sizes with the use of standardized burn forms were consistently the same whether estimates were made by physicians or nurses. Sixty-eight percent of the respondents used the Rule of Nines or the Lund & Browder chart to estimate burn size, but 21% of the respondents failed to answer the question about which method is used in their units. In conclusion, there appears to be little variance in estimation of burn size as made by experienced burn nurses and physicians, and use of these estimates in a centralized data bank should be reliable.

Burn Units↗

PubMedDate not supplied

Blood use in the burn unit: a possible role for erythropoietin.

Recently, several of our patients have raised questions concerning the safety of blood transfusions and especially the transmission of human immunodeficiency virus infection. We have noticed a growing reluctance of patients to receive blood transfusions. This prompted us to review the use of blood in our burn unit for 530 patients who were admitted from 1987 to 1989. Our traditional reasons for transfusion have been either an ongoing hemorrhage that leads to hypotension or a hematocrit of less than 30%. For these reasons 131 (24.7%) of the 530 patients reviewed required transfusions. The average number of units transfused in patients who received blood was 10 (range 1 to 69). Three hundred ninety-nine patients (75.3%) did not require transfusions. We undertook a prospective preliminary trial of recombinant erythropoietin in five patients who were admitted to our burn unit over a 2-month period to evaluate whether this agent could lessen the transfusion requirements. Because no definite value is given in the literature as to what level of hematocrit is most appropriate for transfusion, we chose a hematocrit of 20% as our new indication for transfusion. Inclusion into the trial required a total body surface area burn of over 10% that required at least one operation. Five patients met the inclusion criteria. Administration of erythropoietin was started on admission. According to our new criteria for transfusion none of the five patients receiving erythropoietin required the transfusion of blood or blood products. This study would suggest the need for both a prospective clinical trial of erythropoietin and further studies to better define the indications for transfusions in patients with burns.

Adult↗