Viability of femoral heads treated with resurfacing arthroplasty

There is a general conception that resurfacing arthroplasty causes femoral head osteonecrosis and subsequent failure of the implant. This study histologically analyzed 25 resurfaced femoral heads up to 12 years postoperatively and found that osteonecrosis was not induced by the procedure.

T-cell co-stimulation through B7RP-1 and ICOS

T-cell activation requires co-stimulation through receptors such as CD28 and antigen-specific signalling through the T-cell antigen receptor. Here we describe a new murine costimulatory receptor-ligand pair. The receptor, which is related to CD28 and is the homologue of the human protein ICOS, is expressed on activated T cells and resting memory T cells. The ligand, which has homology to B7 molecules and is called B7-related protein-1 (B7RP-1), is expressed on B cells and macrophages. ICOS and B7RP-I do not interact with proteins in the CD28-B7 pathway, and B7RP-1 co-stimulates T cells in vitro independently of CD28. Transgenic mice expressing a B7RP-1-Fc fusion protein show lymphoid hyperplasia in the spleen, lymph nodes and Peyer's patches. Presensitized mice treated with B7RP-1-Fc during antigen challenge show enhanced hypersensitivity. Therefore, B7RP-1 exhibits co-stimulatory activities in vitro and in vivo. ICOS and B7RP-1 define a new and distinct receptor-ligand pair that is structurally related to CD28-B7 and is involved in the adaptive immune response.

Evaluation of the Nutrition Education at Primary School (NEAPS) programme

OBJECTIVE

To assess the impact and suitability of a pilot dietary educational programme for primary school pupils. The Nutrition Education at Primary School (NEAPS) programme aimed to build awareness of the benefits of healthy eating, induce positive behaviour change and increase the children's knowledge.

DESIGN

A comparative quasi-experimental study with follow-up after 3 months.

SETTING

Eight primary schools in the Eastern and North Western Health Boards and three control schools in the same board regions.

SUBJECTS

Data were used from 821 Irish school children aged 8-10 years old.

METHODS

The education programme comprised 20 sessions over 10 weeks including circular worksheets, homework assignments and an aerobic exercise regime. At baseline and after 3 months pupils completed food diaries and a validated food pairing questionnaire on food behaviour, knowledge and preferences.

RESULTS

Significant differences were found in the intervention children's behaviour and preference levels after the NEAPS programme (P < 0.01 in both sections). Knowledge levels were very high at baseline and though some individual items improved, average change overall was not significant. Rural children appeared to benefit more in behaviour and preferences from the programme (P <0.01). The NEAPS programme appeared to be less effective in pupils in disadvantaged areas (P < 0.01 for each of the sections: behaviour, preference and knowledge). One hundred and eighty-seven children completed food diaries. The intervention children's consumption of fruit and vegetables increased, and they consumed less salty snacks after the programme. Rural children were confirmed to have healthier diets at baseline.

CONCLUSIONS

Following the NEAPS pilot programme positive changes were seen in the school children's eating behaviour and preferences for healthier foodstuffs. This suggests successful development of a culturally sensitive nutrition education programme for school children aged 8-10 years.

Quantitative structure-activity relationship (QSAR) analysis of surfactants influencing attachment of a Mycobacterium sp. to cellulose acetate and aromatic polyamide reverse osmosis membranes

A series of 23 neutral, anionic, and zwitterionic surfactants were tested at a concentration of 0.1% wt/vol for their influence on attachment of a Mycobacterium sp. to cellulose acetate (CA) and polyamide (PA) reverse osmosis (RO) membranes. Four cell attachment bioassays were used: (1) semiconcurrent addition of surfactant and bacteria to RO coupons (standard assay); (2) surfactant pretreatment of RO membranes (membrane pretreatment assay); (3) surfactant treatment of adsorbed cells (detachment assay); and (4) surfactant pretreatment of mycobacteria (cell pretreatment assay). Seventeen surfactants inhibited attachment to PA membranes, whereas 15 inhibited attachment to CA in standard assays and, in 13 cases, the same surfactant inhibited attachment to both PA and CA. Despite greater cell attachment to PA than CA, surfactants were typically more effective in the former membrane system. More surfactants were effective in impairing cell attachment than in promoting detachment and a number enhanced attachment in membrane pretreatment assays, suggesting surface modification of RO membranes. Cell pretreatment inhibited attachment to CA membranes, suggesting the bacterial surface was also a target for detergent activity. Multivariate regression and cluster analyses indicated that critical micellar concentration (CMC) was positively correlated with Mycobacterium attachment in CA and PA standard assays. Surfactant dipole moment and octanol/water partitioning (LogP) also contributed to detergent activity in the PA system, whereas dipole moment, molecular topology (i.e., connectivity indices), and charge properties influenced activity in the CA system. Influential variables in membrane pretreatment assays included the LogP, topology indices, and charge properties, whereas CMC played a diminished role. Surfactant dipole moment was most influential in CA membrane detachment assays. Increasing system ionic strength by LiBr addition strengthened inhibition of cell attachment to CA membranes by dodecylbenzene sulfonic acid (DBSA) and promoted DBSA adsorption to CA surfaces as indicated by attenuated total reflection Fourier-transform infrared spectrometry. Results indicate that inhibition of bacterial attachment to RO membranes may be maximized by manipulating surfactant molecular structure to optimize surface adsorption behavior.

Xyloglucan endotransglycosylases: diversity of genes, enzymes and potential wall-modifying functions

Plant cells are enclosed by walls that define the shapes and sizes of cells and mediate cell-to-cell contact. The dynamics of plant growth, morphogenesis and differentiation require concomitant modifications of the walls. A class of enzymes known as xyloglucan endotransglycosylases have the potential to enzymatically modify wall components, but although their biochemical activity has been defined, the physiological roles of xyloglucan endotransglycosylases remain undefined. Xyloglucan endotransglycosylases are encoded by large gene families, and in an attempt to clarify their physiological role, the diverse regulation of the genes and properties of the proteins are being determined.

Syngeneic stem cell transplantation for HIV-related lymphoma

The treatment of human immunodeficiency virus (HIV)-related lymphoma is beset by a number of therapeutic limitations. High-dose chemotherapy followed by peripheral blood stem cell transplantation (PBSCT) for relapsed disease is one option, but may be compromised by unacceptable treatment-related morbidity and mortality. We describe an HIV-positive male with relapsed immunoblastic non-Hodgkin's lymphoma (NHL) who successfully received salvage chemotherapy followed by a syngeneic PBSCT from his HIV-negative (hepatitis C positive) brother. At 15 months post-transplant he remains in complete remission with low-level HIV viral load, an improved CD4 lymphocyte count and absent anti-hepatitis C antibodies. We believe selected patients with relapsed HIV-related NHL should be considered for high-dose therapy.

In vitro activities of four xyloglucan endotransglycosylases from Arabidopsis

Xyloglucan endotransglycosylases (XETs) are encoded by a gene family in Arabidopsis thaliana. These enzymes modify a major structural component of the plant cell wall, xyloglucan, and therefore may influence plant growth and development. We have produced four Arabidopsis XETs (TCH4, Meri-5, EXGT and XTR9) using the baculovirus/insect cell system and compared their biochemical activities. TCH4, as previously demonstrated, and the other three proteins are capable of carrying out transglycosylation of xyloglucans. The K(m) for XLLGol acceptor oligosaccharide is in the range of 20-40 microM for all the XETs except XTR9, which has a Km of 5 microM and is significantly inhibited by high levels of XLLGol. All four enzymes are most active between pH 6.0 and 6.5. TCH4 and XTR9 have temperature optima of 18 degrees C, whereas Meri-5 and EXGT are most active at 28 and 37 degrees C, respectively. Although the activity levels of three of the XETs are not influenced by the presence of fucose on the xyloglucan polymer, XTR9 has a clear preference for non-fucosylated xyloglucan polymer. The four XETs show a marked preference for XLLGol over either XXFGol or XXXGol as acceptor oligosaccharide. All four XETs are glycosylated; however, only the activities of TCH4 and Meri-5 are affected by the removal of the N-glycan with PNGase F. These four enzymes most likely function solely as transglycosylases because xyloglucan endoglucanase activity was not apparent. Subtle differences in biochemical activities may influence the physiological functions of the distinct XETs in vivo.

Effect of molecular weight, calcium stearate, and sterilization methods on the wear of ultra high molecular weight polyethylene acetabular cups in a hip joint simulator

Orthopaedic surgeons must currently choose from several types of ultra high molecular weight polyethylene acetabular cups that differ in their material properties and in the methods used for their sterilization. Information on the wear resistance of these different cups may help in the selection process. This study included two separate tests for wear run on a hip simulator to investigate the effect of molecular weight, calcium stearate, and sterilization methods on the wear resistance of ultra high molecular weight polyethylene acetabular cups. Test 1 revealed nearly identical wear rates for acetabular cups with molecular weights in two distinct ranges, as well as for cups with molecular weights in the same range but with or without calcium stearate added. In Test 2, cups that were sterilized in air with gamma irradiation exhibited lower rates of wear than those sterilized with ethylene oxide, presumably due to the crosslinking induced by the irradiation. In addition, cups that were irradiated while packed in a partial vacuum to minimize oxygen absorbed in the surface layer initially showed lower rates of wear than those irradiated in air, with the wear rates becoming similar as wear penetrated the more oxidized surface layer and the more crosslinked subsurface region. Because these tests were run a few months after the irradiation, the potential effects of long-term oxidation of any residual free radicals in the irradiated materials could not be taken into account. After artificial aging to accelerate oxidative degradation of the materials, the wear rates could be markedly different. Analyses performed after wear indicated that the irradiated (i.e., crosslinked) cups exhibited a smaller proportion of, as well as shorter, fibrils in the wear debris and an increased crystallinity and melting temperature and that gamma irradiation in the low-oxygen environment reduced the level of oxidation and increased the level of crosslinking in the surface region of the cups.

Mechanism of failure in hips with an uncemented, all polyethylene socket

The outcome of 32 patients with 33 primary total hip replacements performed using noncemented uncoated polyethylene acetabular cups (RM cup) with cemented titanium alloy monoblock stems (STH-2 stem) was reviewed. At a mean followup of 6.3 years (range, 6 months-10 years), the failure rate was 57%, more than 14 times higher than the rate typically seen with cemented polyethylene acetabular cups used with the STH stem. Failure was characterized by rapidly progressive acetabular or femoral osteolytic lesions that resulted in extensive bone loss, often in patients who had no symptoms. In addition to the debris that typically is generated by a metal on plastic bearing couple, an abundance of polyethylene particles of submicron size were produced at the cup-bone interface. Tissues retrieved from areas of osteolysis revealed the presence of intracellular submicron polyethylene particles in macrophages. It is recommended that patients with no symptoms who have RM noncemented, uncoated acetabular cups be followed up yearly and undergo early revision surgery when faced with osteolysis to prevent extensive bone loss.

Reduction in choline acetyltransferase immunoreactivity but not muscarinic-m2 receptor immunoreactivity in the brainstem of SIDS infants

The cholinergic neurotransmitter system is vital for several brainstem functions including cardiorespiratory control and central chemosensitivity. This study has examined aspects of the cholinergic neurotransmitter system in the brainstem of sudden infant death syndrome (SIDS) and control infants. The cellular localisation and the optical density of the immunoreactivity of the cholinergic enzyme choline acetyltransferase (CHAT-IR) and the muscarinic acetylcholine receptor m2 (m2-IR) in the medulla was described in 14 SIDS and 9 control cases. There was a reduction in the number of CHAT-IR neurons in the hypoglossal nucleus (control: 71.2+/-8.3% vs SIDS: 46.1+/-5.3%) and the dorsal motor nucleus of the vagus (DMV) (control: 77.2+/-5.0% vs SIDS: 52.5+/-7.4%) and reduced optical density of CHAT-IR in the hypoglossal nucleus (control: 0.20+/-0.01 vs SIDS; 0.14+/-0.02) in SIDS infants. In contrast there were no changes in the optical density of m2-IR in the hypoglossal nucleus, the DMV, or the arcuate nucleus. Hypoplasia of the arcuate nucleus was observed in one SIDS infant. These results suggest that there is a specific defect in some cholinergic motor neurons in the medulla of SIDS infants. This could lead to abnormal control of cardiovascular and respiratory function and airway patency and may be one of the contributing factors in the etiology of SIDS.

Development of an extremely wear-resistant ultra high molecular weight polyethylene for total hip replacements

Osteolysis induced by ultra high molecular weight polyethylene wear debris is one of the primary factors limiting the lifespan of total hip replacements. Crosslinking polyethylene is known to improve its wear resistance in certain industrial applications, and crosslinked polyethylene acetabular cups have shown improved wear resistance in two clinical studies. In the present study, crosslinked polyethylene cups were produced by two methods. Chemically crosslinked cups were produced by mixing a peroxide with ultra high molecular weight polyethylene powder and then molding the cups directly to shape. Radiation-crosslinked cups were produced by exposing conventional extruded ultra high molecular weight polyethylene bar stock to gamma radiation at various doses from 3.3 to 100 Mrad (1 Mrad = 10 kGy), remelting the bars to extinguish residual free radicals (i.e., to minimize long-term oxidation), and then machining the cups by conventional techniques. In hip-joint simulator tests lasting as long as 5 million cycles, both types of cross-linked cups exhibited dramatically improved resistance to wear. Artificial aging of the cups by heating for 30 days in air at 80 degrees C induced oxidation of the chemically crosslinked cups. However, a chemically crosslinked cup that was aged 2.7 years at room temperature had very little oxidation. Thus, whether substantial oxidation of chemically crosslinked polyethylene would occur at body temperature remains unclear. The radiation-crosslinked remelted cups exhibited excellent resistance to oxidation. Because crosslinking can reduce the ultimate tensile strength, fatigue strength, and elongation to failure of ultra high molecular weight polyethylene, the optimal crosslinking dose provides a balance between these physical properties and the wear resistance of the implant and might substantially reduce the incidence of wear-induced osteolysis with total hip replacements.

The importance of graft blood flow and peripheral outflow resistance for early patency in infrainguinal arterial reconstructions

BACKGROUND

At present, the importance of functional parameters as determinants for graft patency is under debate. Therefore, in our institution a prospective study was undertaken to evaluate the influence of graft blood flow as well as the currently applied methods for outflow resistance measurement on early (< or = 30 days) graft outcome.

PATIENT AND METHODS

101 arterial revascularisations with infrageniculate graft insertion were entered into this study. After having verified the morphological integrity of the reconstruction, during temporary inflow occlusion total outflow resistance (TOR) was determined as a pressure/flow relationship by perfusion of the graft with saline (flow rates 25, 50, 100, 150 ml/min before and after papaverine) while simultaneously recording pressure generated at the distal anastomosis. In addition, after restoration of blood flow, flow index (FI) was calculated in an analogous way from the TBF through the graft and the respective mean distal anastomotic pressure. Graft patency at 30 days was determined by Duplex ultrasound.

RESULTS

Functional parameters were found to be unable to differentiate between patent and failed reconstructions during the 30 day period: The mean TORaveraged values amounted to 722.5 (SD = 310) in patent and 735.9 (SD = 228.1) mPRU in occluded bypasses (T-value = 0.1681; n.s.). The corresponding figures were 176.8 (SD = 94.2) and 196.4 (SD = 93.6) ml/min for TBF (T-value = 0.7342; n.s.) and were 0.53 (SD = 0.34) and 0.45 (SD = 0.25) PRU for FI (T-value = 0.8905; n.s.). Using multiple logistic regression analysis functional parameters showed no influence on graft patency while graft length and the necessity for intraoperative graft modification emerged to be significant determinants of early graft outcome (R2 adjusted = 0.46; p = 0.006).

CONCLUSION

The results of our study suggest that neither blood flow nor the presently used methods to assess outflow resistance are relevant prognostic factors for early (< or = 30 days) graft performance.

Recombinant human erythropoietin in anemia of prematurity

OBJECTIVE

To evaluate safety and efficacy of recombinant human erythropoietin (r-HuEPO)in reducing the need for red cell transfusions in anemia of prematurity.

METHODS

forty -two preterm infants (gestational age <32 weeks) were randomly assigned to a "treatment" group (r-HuEPO 400 units/kg every alternate day * 10 doses) or "no treatment" (control) group. All infants on enteral feeds received oral iron 3 mg/kg/day, graded up to 6 mg/kg/day.

RESULTS

Higher reticulocyte counts in week 2 and 3 and higher hemoglobin levels in week 4 were noted after treatment with r-HuEPO. Despite stumulated erythropoiesis, the frequency of transfusions could not be reduced with r-HuEPO therapy.Overall, Phlebotomy losses, frequency and volume of redcell transfusions were significantly more in neonates with birthweight <1000 grams compared with those with birthweight >1000 grams (p<0.05). Associated side effects of r-HuEPO such as neutropenia,sepsis, hypertension or increased risk of late death did not occur.

CONCLUSION

r-HuEPO therapy was safe without any side effects. Inability of r-HuEPO therapy to minimize red cell transfusions for anemia of prematurity may be explained by a relatively strict red-cell transfusion policy and the desired degree of treatment effect.

Co- and/or post-translational modifications are critical for TCH4 XET activity

TCH4 encodes a xyloglucan endotransglycosylase (XET) of Arabidopsis thaliana. XETs endolytically cleave and religate xyloglucan polymers; xyloglucan is one of the primary structural components of the plant cell wall. Therefore, XET function may affect cell shape and plant morphogenesis. To gain insight into the biochemical function of TCH4, we defined structural requirements for optimal XET activity. Recombinant baculoviruses were designed to produce distinct forms of TCH4. TCH4 protein engineered to be synthesized in the cytosol and thus lack normal co- and post-translational modifications is virtually inactive. TCH4 proteins, with and without a polyhistidine tag, that harbor an intact N-terminus are directed to the secretory pathway. Thus, as predicted, the N-terminal region of TCH4 functions as a signal peptide. TCH4 is shown to have at least one disulfide bond as monitored by a mobility shift in SDS-PAGE in the presence of dithiothreitol (DTT). This disulfide bond(s) is essential for full XET activity. TCH4 is glycosylated in vivo; glycosidases that remove N-linked glycosylation eliminated 98% of the XET activity. Thus, co- and/or post-translational modifications are critical for optimal TCH4 XET activity. Furthermore, using site-specific mutagenesis, we demonstrated that the first glutamate residue of the conserved DEIDFEFL motif (E97) is essential for activity. A change to glutamine at this position resulted in an inactive protein; a change to aspartic acid caused protein mislocalization. These data support the hypothesis that, in analogy to Bacillus beta-glucanases, this region may be the active site of XET enzymes.