repE--the Dictyostelium homolog of the human xeroderma pigmentosum group E gene is developmentally regulated and contains a leucine zipper motif

We have cloned and characterized the Dictyostelium discoideum repE gene, a homolog of the human xeroderma pigmentosum (XP) group E gene which encodes a UV-damaged DNA binding protein. The repE gene maps to chromosome 4 and it is the first gene identified in Dictyostelium that is homologous to those involved in nucleotide excision repair and their related XP diseases in humans. The predicted protein encodes a leucine zipper motif. The repE gene is not expressed by mitotically dividing cells, and repE mRNA is first detected during the aggregation phase of development when the cells have ceased dividing and replicating genomic DNA. The mRNA level plateaus by the time the developing cells have entered multicellular aggregates and remains at the same steady-state level for the remainder of development. In addition, we have demonstrated that the level of mRNA is very low in developing cells. These observations suggest that repE may play a regulatory role in development. The data indicate that potential developmental roles for XP-related genes can be profitably studied in this system.

Effects of growth-factor-enhanced culture on a chondrocyte-collagen implant for cartilage repair

The effects of incubation and addition of growth factors to a chondrocyte-seeded collagen implant for cartilage repair were studied. Type I collagen matrices seeded with lapine articular chondrocytes and unseeded controls cultured in the presence and absence of fibroblast growth factor and insulin for 2, 6, and 9 weeks were subjected to biomechanical, biochemical, and histological analysis. Aggregate modulus of elasticity of seeded implants decreased by half at 6 weeks, then rose by a factor of 10 above initial values. Permeability of seeded implants and their controls decreased steadily. Glycosaminoglycan content peaked at 6 weeks, coinciding with the greatest number of chondrocytes and mitotic activity in seeded implants. Chondrocytes remained phenotypically stable and metabolically active; they incorporated glycosaminoglycan into the extracellular matrix, and formed an organized pericellular environment despite the predicted resorption of the collagen matrix. Adding fibroblast growth factor and insulin tripled the rate of cell turnover and doubled the glycosaminoglycan content of seeded implants, but had no effect on their material properties. In vitro incubation for 6 weeks in the presence of fibroblast growth factor and insulin creates a metabolically and mitotically active chondrocyte-collagen composite for implantation into articular cartilage defects.

Canine bone response to tyrosine-derived polycarbonates and poly(L-lactic acid)

Tyrosine-derived polycarbonates are a new class of degradable polymers developed for orthopedic applications. In this study the long-term (48 week) in vivo degradation kinetics and host bone response to poly(DTE carbonate) and poly(DTH carbonate) were investigated using a canine bone chamber model. Poly(L-lactic acid) (PLA) served as a control material. Two chambers of each test material were retrieved at 6-, 12-, 24-, and 48-week time points. Tyrosine-derived polycarbonates were found to exhibit degradation kinetics comparable to PLA. Each test material lost approximately 50% of its initial molecular weight (Mw) over the 48-week test period. Poly(DTE carbonate) and poly(DTH carbonate) test chambers were characterized by sustained bone ingrowth throughout the 48 weeks. In contrast, bone ingrowth into the PLA chambers peaked at 24 weeks and dropped by half at the 48-week time point. A fibrous tissue layer was found surrounding the PLA implants at all time points. This fibrous tissue layer was notably absent at the interface between bone and the tyrosine-derived polycarbonates. Histologic sections revealed intimate contact between bone and tyrosine-derived polycarbonates. From a degradation-biocompatibility perspective, the tyrosine-derived polycarbonates appear to be comparable, if not superior, to PLA in this canine bone chamber model.

In vitro fertilization: increased VLA (very late antigen) integrins and fibronectin after acrosome reaction

The pattern of detectable adhesion molecules (AM) on human ejaculated spermatozoa used for in vitro fertilization (IVF) of human oocytes was evaluated. The percentage of spermatozoa with the alpha chains 3, 4, 5, and 6 of the integrins (also called very late antigens, VLA alpha 3, 4, 5, 6), the alpha V and the beta 3 chains, as well as the matrix proteins laminin and fibronectin, were determined by flow cytometry using monoclonal antibodies against integrins and matrix proteins before and after the acrosome reaction. This reaction was induced by the low-temperature method according to P. Sanchez, E. Töpfer-Petersen, R. J. Aitken, and W. B. Schill (1991, Andrologia 23:197-203) and monitored by the binding of FITC-conjugated Pisum sativum agglutinin. Twenty-three of 34 investigated semen samples fertilized at least one oocyte (fertile group) and 11 samples did not induce a pronucleus formation or cleavage of an oocyte (infertile group). Significant differences in the classical semen parameters between both semen sample groups could be shown only for the percentage of progressively motile spermatozoa (p = .046, U test). The spermatozoa of the fertile group showed a significantly higher expression of VLA alpha 3 (p = .045) and fibronectin (p = .048). Additionally, after the loss of the acrosome a significantly higher expression of alpha 4, alpha 5, and alpha 6 chains of integrins (p < .05) was detected in the fertile semen group. In contrast, the inducibility of the acrosome reaction differed only to a nonsignificant extent (p = .094). These data suggest that spermatozoa showing a higher expression of the alpha chains of the integrins after the acrosome reaction have a better fertilization rate in vitro.

Improved cerebral resuscitation from cardiac arrest in dogs with mild hypothermia plus blood flow promotion

BACKGROUND AND PURPOSE

In past studies, cerebral outcome after normothermic cardiac arrest of 10 or 12.5 minutes in dogs was improved but not normalized by resuscitative (postarrest) treatment with either mild hypothermia or hypertension plus hemodilution. We hypothesized that a multifaceted combination treatment would achieve complete cerebral recovery.

METHODS

With our established dog outcome model, normothermic ventricular fibrillation of 11 minutes (without blood flow) was followed by controlled reperfusion (with brief normothermic cardiopulmonary bypass simulating low flow and low PaO2 of external cardiopulmonary resuscitation) and defibrillation at < 2 minutes. Controlled ventilation was provided to 20 hours and intensive care to 96 hours. Control group 1 (n = 8) was kept normothermic (37.5 degrees C), normotensive, and hypocapnic throughout. Experimental group 2 (n = 8) received mild resuscitative hypothermia (34 degrees C) from about 10 minutes to 12 hours (by external and peritoneal cooling) plus cerebral blood flow promotion with induced moderate hypertension, mild hemodilution, and normocapnia.

RESULTS

All 16 dogs in the protocol survived. At 96 hours, all 8 dogs in control group 1 achieved overall performance categories 3 (severe disability) or 4 (coma). In group 2, 6 of 8 dogs achieved overall performance category 1 (normal); 1 dog achieved category 2 (moderate disability), and 1 dog achieved category 3 (P < .001). Final neurological deficit scores (0% [normal] to 100% [brain death]) at 96 hours were 38 +/- 10% (22% to 45%) in group 1 versus 8 +/- 9% (0% to 27%) in group 2 (P < .001). Total brain histopathologic damage scores were 138 +/- 22 (110 to 176) in group 1 versus 43 +/- 9 (32 to 56) in group 2 (P < .001). Regional scores showed similar group differences.

CONCLUSIONS

After normothermic cardiac arrest of 11 minutes in dogs, resuscitative mild hypothermia plus cerebral blood flow promotion can achieve functional recovery with the least histological brain damage yet observed with the same model and comparable insults.

Effect of annealing temperature on the degradation of reinforcing fibers for absorbable implants

Calcium phosphate fibers designed for reinforcement of bioabsorbable fracture fixation devices were evaluated for their properties upon annealing. The composition of these fibers were 54% PO4, 27% Ca, 12% ZnO, 2.5% NaPO3, and 4.5% Fe2O3, and they were either not annealed, annealed at 250 degrees C, or annealed at 420 degrees C. Chemical degradation, mass loss, and morphology upon degradation were studied. Chemical degradation was performed in Tris-buffered HCl, while mass loss and morphologic studies were performed in both physiologic and nonphysiologic solutions. The results showed that degradation rates for fibers were inversely proportional to the annealing temperature. Mass loss analysis of fibers immersed in the two physiologic solutions (calf serum and simulated body fluid) revealed little change in fiber diameter up to 60 days. Morphologic examination revealed little change in fibers immersed in the two physiologic solutions until 60 days, after which thin shells were found to be peeling off the outer coating of the fiber. Samples in tris-buffered HCl revealed a dramatic difference in mode of degradation among the three fibers. Fibers not annealed and those annealed at lower temperatures underwent a delaminating type of degradation that appeared to destroy the overall integrity of the fiber, whereas fibers annealed at 420 degrees C underwent crater-like deterioration in which the overall alignment of the fiber remained intact. It is therefore concluded that annealing fibers at higher temperatures also undergo a mode of degradation that allows them to maintain their structural integrity. Although annealing fibers close to glass transition temperature may produce an initially weaker fiber, chemical and physical degradation occur much slower, making these fibers most suitable for reinforcement of biodegradable implants.

Peritoneal cooling for mild cerebral hypothermia after cardiac arrest in dogs

After normothermic cardiac arrest in dogs, we found that mild hypothermia (34 degrees C) of 1-2 h reduced brain damage, providing that hypothermia was achieved within 15 min of reperfusion. A clinically feasible rapid brain-cooling method is needed. As head-neck surface cooling alone in dogs was found to be too slow (0.1 degrees C/min), we reviewed peritoneal cooling in the Introduction and Discussion sections. PRELIMINARY EXPERIMENTS WITHOUT CARDIAC ARREST: In 5 dogs with spontaneous circulation and IPPV, 2 L of Ringer's solution at 10 degrees C were instilled into the peritoneal cavity, left for 5 min, and drained. Brain (tympanic membrane) temperature (Tty) decreased by a mean of 0.3 degrees C/min (12 min to 34 degrees C). Core (pulmonary artery) temperature (Tpa) decreased by a mean of 0.8 degrees C/min (5 min to 34 degrees C). COOLING AFTER CARDIAC ARREST: In our reproducible dog model of normothermic ventricular fibrillation cardiac arrest of 11 min (no flow), brief low-flow normothermic cardiopulmonary bypass (CPB) was used for reperfusion and restoration of spontaneous circulation (ROSC) within 2 min. In 24 dogs, mild hypothermia was induced by head-neck surface cooling with ice bags, starting with reperfusion, plus peritoneal lavage as above, starting with ROSC. All 24 dogs were resuscitated. Initial head-neck surface cooling alone over 2 min decreased Tty by only 0.15 degrees C/min. Subsequent additional peritoneal lavage decreased Tty by a mean of 0.3 degrees C/min (11 min to 34 degrees C); and Tpa 0.6 degrees C/min (7 min to 34 degrees C). There were no significant physiologic effects. We conclude that peritoneal instillation of cold Ringer's solution is more rapidly effective than other non-intravascular cooling methods reported previously. Peritoneal cooling should be tried in patients during CPR.

Microcapsules through polymer complexation. Part 3: Encapsulation and culture of human Burkitt lymphoma cells in vitro

Methacrylic acid (MAA) based polyelectrolytes were complexed with protonated or quaternized dimethylaminoethyl methacrylate (DMAEMA) containing polyelectrolytes to form microcapsules in vitro. Anchorage independent human Burkitt lymphoma (Raji) cells were successfully cultured in the presence of dissolved MAA containing polymer. Capsule morphology was investigated by light microscopy and by scanning electron microscopy (SEM). Capsules based on quaternized DMAEMA containing polymer were found to be more stable than capsules containing protonated DMAEMA functionality. Raji cells were successfully encapsulated in both systems and divided to confluence; thereafter sufficient pressure was exerted to burst open the capsules. Cells released from these capsules appeared to suffer no discernible trauma and were successfully isolated and subcultured to confluence.

The clinical impact of tissue engineering

Four generations of surgical implant development will be discernible by the end of this century: 1. A first generation of industrial materials (materials originally fabricated for industrial applications other than medical devices) in ad hoc devices that had little impact on the practices of medicine and surgery. 2. Industrial materials in bioengineered devices to effect the replacement of damaged structures. While these devices returned function to millions of people, formed the basis for a new industry, and forever changed the practices of medicine and surgery, their components have proved less than ideal. 3. Bioengineered materials fabricated specifically for medical device use-that are meant to be bioactive rather than inert-and that promise to improve the performance of some devices. 4. Tissue engineering, which while yet to be utilized in widely marketed devices, promises to usher in revolutionary changes at least as dramatic as those caused by the second-generation bioengineered devices. Fourth-generation technologies will focus on repair and regeneration rather than reconstruction and replacement; they will emphasize therapeutic prevention of disease and early intervention. The minimally invasive nature of these new technologies will cause medical practitioners to partially displace surgeons, and fewer hospital beds and operating rooms will be needed. While such technology may involve high startup costs, in the long run the total costs of care should decline because of more efficient, less expensive procedures.

[Directional coronary atherectomy: effect of vessel size on primary results and long-term results]

Of 325 consecutive patients undergoing DCA, 263 patients with 277 stenoses were successfully treated with DCA alone and had angiographic follow-up 3-6 months later. Depending upon the initial reference diameter (RD) patients were divided into two subgroups: group I (n = 159) with a RD > 3 mm and group II (n = 104) showing a RD < or = 3 mm. In contrast to other series DCA was predominantly performed with 7F atherectomy devices using balloon inflation pressures of approximately 5 atm. Angiographic data including the minimal luminal diameter (MLD), percentage of stenosis (%D) and reference diameter (RD) were assessed by quantitative computer-assisted analysis before (pre), after (post) DCA and at a 3-6 months angiographic follow-up (FU). The percentage of diameter stenosis pre/post/FU in group I was 59.9 +/- 12.6%/18.4 +/- 12.8%/29.8 +/- 17.6%, and in group II 55.6 +/- 10.8%/17.8 +/- 12.3%/33.7 +/- 16.1% with a net gain at FU of 1.0 +/- 0.89 mm for group I and 0.86 +/- 0.66 mm for group II. Based on an angiographic restenosis criterion of at least 50% diameter obstruction at FU and or recurrence of symptoms warranting interventional re-treatment of the target lesion, the incidence of restenosis in group I was 20.6% and in group II 28.0% (p: n.s.). There was no significant difference between the two groups concerning complications. Our data show that DCA leads to a satisfying long-term result.(ABSTRACT TRUNCATED AT 250 WORDS)

Formation of a calcium phosphate-rich layer on absorbable calcium carbonate bone graft substitutes

The use of natural coral as a bone graft substitute is common in Europe. However, the bone-coral bonding mechanism remains elusive. A rat subcutaneous model was used to demonstrate changes at the surface of resorbable calcium carbonate in the form of natural coral. Histological results indicated in vivo formation of a calcium phosphate (CaP)-rich layer on the surface of the coral confirmed by backscattered electron imaging and X-ray microanalysis. There appears to be a combination solution-mediated dissolution/cell-mediated degradation of the natural coral with subsequent surface conversion or precipitation. The end result is a CaP-rich layer on the coral. Though this layer has been observed previously, it was originally thought to be a histological artifact. This result is similar, however, to what is seen with Bioglass and glass ceramics and may also explain the good bonding of bone to hydroxyapatite. The fact that this layer is also present on natural coral after implantation in soft tissue sites may explain the intimate bone apposition observed when natural coral is placed in bony sites.

Accuracy of reported family history of heart disease: the impact of 'don't know' responses

BACKGROUND

Usual 'Yes/No' definitions of a family history of heart disease do not allow for 'Don't know' responses. In some families, misclassification of family history may result if these are not considered.

AIMS

To study the accuracy of family history reporting and the impact of 'Don't know' responses.

METHODS

We compared reported family history of coronary heart disease (CHD) and cancer among 360 deceased relatives of 59 probands with 'gold standard' diagnoses recorded on official death certificates.

RESULTS

For first degree relatives, sensitivity of reporting was 81% for CHD, 86% for any heart disease and 60% for cancer, while for second degree relatives, sensitivity was 73%, 69% and 90%, respectively. When 'Don't know' responses were classified as 'No', sensitivity in first degree relatives was not affected, but in second degree relatives, it fell to 49%, 41% and 60%, respectively. Specificities were unchanged. These data show that in families where information beyond first degree relatives is considered, failing to account for 'Don't know' responses is likely to lead to misclassification of family history of CHD.

Effect of surface plasma treatment on the chemical, physical, morphological, and mechanical properties of totally absorbable bone internal fixation devices

The purpose of this work was threefold: to enhance the adhesion between the reinforced absorbable calcium phosphate (CaP) fibers and the absorbable polyglycolide acid (PGA) matrix, to improve the hydrolytic degradation of the CaP fibers, and preliminarily to evaluate the cytotoxicity of the plasma treated surface of CaP fibers. A CH4 plasma treatment was used to achieve these goals. The microbond method was used to evaluate the effects of the plasma treatment on the interfacial shear strength between the PGA matrix and CaP fibers. The treatment increased the mean interfacial shear strength of the CaP/PGA composite system by 30%. AFM data showed that CH4-treated CaP fibers had considerable microscopic surface roughness, which facilitated mechanical interlocking between the reinforced CaP fibers and PGA matrix. The untreated and plasma-treated fibers were also subjected to in vitro hydrolytic degradation in a phosphate buffer solution of pH 7.44 at 37 degrees C for up to 15 h. CH4 plasma treatment resulted in a considerable lower polar term of the surface energy and a significantly higher disperse term in water media. This change in the proportion of surface energy terms may reduce the capillary wicking phenomena of water through the CaP fiber/PGA matrix interface. The CaP fiber dissolution studies revealed that both CH4 and Parylene plasma polymer coatings appeared to reduce the solubility of CaP fibers, and that the magnitude of reduction was higher in an acidic than a physiologic pH environment. A preliminary cytotoxicity test revealed that both CH4 and Parylene plasma-treated CaP fibers were noncytotoxic. Additional research should be done to determine the optimum plasma conditions and the possible use of other plasma gases to improve the interfacial shear stress of the composite and the dissolution properties of CaP fibers.