Biomechanical reconstruction of the hip: a randomised study comparing total hip resurfacing and total hip arthroplasty

We have compared the biomechanical nature of the reconstruction of the hip in conventional total hip arthroplasty (THA) and surface replacement arthroplasty (SRA) in a randomised study involving 120 patients undergoing unilateral primary hip replacement. The contralateral hip was used as a control. Post-operatively, the femoral offset was significantly increased with THA (mean 5.1 mm; -2.8 to 11.6) and decreased with SRA (mean -3.3 mm; -8.9 to 8.2). Femoral offset was restored within sd 4 mm in 14 (25%) of those with THA and in 28 (57%) of the patients receiving SRA (p < 0.001). In the THA group, the leg was lengthened by a mean of 2.6 mm (-6.04 to +12.9), whereas it was shortened by a mean of 1.9 mm (-7.1 to +2.05) in the SRA group, compared with the contralateral side. Leg-length inequality was restored within sd 4 mm in 42 (86%) of the SRA and 33 (60%) of the THA patients. The radiological parameters of acetabular reconstruction were similar in both groups. Restoration of the normal proximal femoral anatomy was more precise with SRA. The enhanced stability afforded by the use of a large-diameter femoral head avoided over-lengthening of the limb or increased offset to improve soft-tissue tension as occurs sometimes in THA. In a subgroup of patients with significant pre-operative deformity, restoration of the normal hip anatomy with lower pre-operative femoral offset or significant shortening of the leg was still possible with SRA.

Specific binding of basic fibroblast growth factor to basement membrane-like structures and to purified heparan sulfate proteoglycan of the EHS tumor

The binding of iodinated basic fibroblast growth factor (bFGF) to low-density heparan sulfate proteoglycan purified from the Engelbreth Holm Swarm (EHS) sarcoma was investigated using different techniques. The tumor clearly contained bFGF, the level being comparable to that found in other tissues such as human or bovine brain. 125I bFGF strongly bound to the basement membrane-like matrix of EHS frozen sections as revealed by autoradiography. Iodinated bFGF bound to purified heparan sulfate proteoglycan but not to laminin or collagen type IV, three components isolated from the same tumor. In contrast, acidic fibroblast growth factor (aFGF) displayed negligible binding to heparan sulfate proteoglycan. Binding of bFGF to frozen sections and to purified proteoglycan could be strongly inhibited by heparin and was displaced by an excess of unlabeled factor and completely suppressed after heparitinase and heparinase treatments. Binding was a function of the salt concentration and was abolished at 0.6 M NaCl. Scatchard analysis indicated the affinity site had a Kd of about 30 nM, a value 10-15 higher than that recently reported by Moscatelli (J. Cell. Physiol., 131:123-130, 1987) in the case of the low-affinity binding sites present on the surface of baby hamster kidney (BHK) cells.

Chromium and cobalt ion release following the Durom high carbon content, forged metal-on-metal surface replacement of the hip

We evaluated the concentrations of chromium and cobalt ions in blood after metal-on-metal surface replacement arthroplasty using a wrought-forged, high carbon content chromium-cobalt alloy implant in 64 patients. At one year, mean whole blood ion levels were 1.61 μg/L (0.4 to 5.5) for chromium and 0.67 μg/L (0.23 to 2.09) for cobalt. The pre-operative ion levels, component size, female gender and the inclination of the acetabular component were inversely proportional to the values of chromium and/or cobalt ions at one year postoperatively. Other factors, such as age and level of activity, did not correlate with the levels of metal ions. We found that the levels of the ions in the serum were 1.39 and 1.37 times higher for chromium and cobalt respectively than those in the whole blood.

The levels of metal ions obtained may be specific to the hip resurfacing implant and reflect its manufacturing process.

Locus coeruleus norepinephrine activity mediates sensory-evoked awakenings from sleep

A defining feature of sleep is reduced responsiveness to external stimuli, but the mechanisms mediating sensory-evoked arousal remain unclear. We hypothesized that reduced locus coeruleus (LC) norepinephrine (NE) activity during sleep mediates unresponsiveness, and its action promotes sensory-evoked awakenings. We tested this using electrophysiological, behavioral, pharmacological, and optogenetic techniques alongside auditory stimulation in freely behaving rats. We found that systemic reduction in NE signaling lowered probability of sound-evoked awakenings (SEAs). The level of tonic LC activity during sleep anticipated SEAs. Optogenetic LC activation promoted arousal as evident in sleep-wake transitions, EEG desynchronization, and pupil dilation. Minimal LC excitation before sound presentation increased SEA probability. Optogenetic LC silencing using a soma-targeted anion-conducting channelrhodopsin (stGtACR2) suppressed LC spiking and constricted pupils. Brief periods of LC opto-silencing reduced the probability of SEAs. Thus, LC-NE activity determines the likelihood of sensory-evoked awakenings, and its reduction during sleep constitutes a key factor mediating behavioral unresponsiveness.

Kinematic TKA using navigation: Surgical technique and initial results

BACKGROUND

Kinematic alignment for total knee arthroplasty (TKA) may be one way of improving outcomes. Previous studies have either used patient-specific instrumentation, which adds cost, or standard instrumentation, which provides no intraoperative feedback on resection alignment.

HYPOTHESIS

To determine if computer navigation could reproduce native patient anatomy and simplify ligament balance during TKA whilst giving satisfactory improvements in functional scores at early follow-up.

MATERIALS AND METHODS

Computer navigation was used for kinematic distal femoral and proximal tibial cuts in 100 consecutive and unselected TKAs. Resections were modified only if measured angles fell outside a pre-defined safe range of combined coronal orientation within±3 degrees of neutral and/or independent femoral or tibial cuts within±5 degrees. Pre- and postoperative measurements of the hip-knee-ankle (HKA) angle, the lateral distal femoral angle (LDFA) and the medial proximal tibial angle (MPTA) were taken using long-leg standing radiographs. Clinical evaluation was with the WOMAC and KOOS scales.

RESULTS

Mean follow-up was 2.4 years (range 1.0-3.7, SD 0.8). The mean pre-op LDFA was 2.1 degrees valgus (9.2 valgus to 3.7 varus, SD 2.5) and 1.8 degrees valgus post-op (5.7 valgus to 4.2 varus, SD 2.0) (P=0.41). The mean pre-op MPTA was 3.0 degrees varus (10.6 valgus to 10.2 varus, SD 3.2) and 2.4 degrees varus post-op (4.0 valgus to 6.8 varus, SD 2.2) (P=0.03). The mean WOMAC score improved from 49.4 (29-85, SD 12.8) to 24.7 (0-73, SD 16.5) (P<0.001) and the mean KOOS score from 37.1 (7.2-77.2, SD 13.0) to 65.1 (26.8-100, SD 16) (P<0.001). Five knees (5%) required additional ligament release, four with valgus OA and one with varus OA. Two knees (2%) required lateral retinacular release for patellar tracking.

DISCUSSION

Computer navigation for kinematic TKA provides the operating surgeon with full control and feedback at each step, whilst also allowing partial correction of more extreme anatomy that might be unsuitable for recreation during TKA. This technique helps to preserve ligament isometry and produces satisfactory improvements in functional scores.

LEVEL OF EVIDENCE

IV (retrospective case series review).

A randomised study comparing resection of acetabular bone at resurfacing and total hip replacement

We have undertaken a prospective, randomised study to compare conservation of acetabular bone after total hip replacement and resurfacing arthroplasty of the hip. We randomly assigned 210 hips to one of the two treatment groups. Uncemented, press-fit acetabular components were used for both.

No significant difference was found in the mean diameter of acetabular implant inserted in the groups (54.74 mm for total hip replacement and 54.90 mm for resurfacing arthroplasty). In seven resurfacing procedures (6.8%), the surgeon used a larger size of component in order to match the corresponding diameter of the femoral component.

With resurfacing arthroplasty, conservation of bone is clearly advantageous on the femoral side. Our study has shown that, with a specific design of acetabular implant and by following a careful surgical technique, removal of bone on the acetabular side is comparable with that of total hip replacement.

Metal ion release from bearing wear and corrosion with 28 mm and large-diameter metal-on-metal bearing articulations: a follow-up study

We have updated our previous randomised controlled trial comparing release of chromium (Cr) and cobalt (Co) ions and included levels of titanium (Ti) ions. We have compared the findings from 28 mm metal-on-metal total hip replacement, performed using titanium CLS/Spotorno femoral components and titanium AlloFit acetabular components with Metasul bearings, with Durom hip resurfacing using a Metasul articulation or bearing and a titanium plasma-sprayed coating for fixation of the acetabular component. Although significantly higher blood ion levels of Cr and Co were observed at three months in the resurfaced group than in total hip replacement, no significant difference was found at two years post-operatively for Cr, 1.58 microg/L and 1.62 microg/L respectively (p = 0.819) and for Co, 0.67 microg/L and 0.94 microg/L respectively (p = 0.207). A steady state was reached at one year in the resurfaced group and after three months in the total hip replacement group. Interestingly, Ti, which is not part of the bearing surfaces with its release resulting from metal corrosion, had significantly elevated ion levels after implantation in both groups. The hip resurfacing group had significantly higher Ti levels than the total hip replacement group for all periods of follow-up. At two years the mean blood levels of Ti ions were 1.87 microg/L in hip resurfacing and and 1.30 microg/L in total hip replacement (p = 0.001). The study confirms even with different bearing diameters and clearances, hip replacement and 28 mm metal-on-metal total hip replacement produced similar Cr and Co metal ion levels in this randomised controlled trial study design, but apart from wear on bearing surfaces, passive corrosion of exposed metallic surfaces is a factor which influences ion concentrations. Ti plasma spray coating the acetabular components for hip resurfacing produces significantly higher release of Ti than Ti grit-blasted surfaces in total hip replacement.

E. coli RNA polymerase, deleted in the C-terminal part of its alpha-subunit, interacts differently with the cAMP-CRP complex at the lacP1 and at the galP1 promoter

A deletion of the C-terminal part of the alpha-subunit of RNA polymerase is known to affect differently promoters activated by CRP depending on the location of the CRP binding site at the promoter. When the CRP binding site is located at -61.5, as at lacP1 (a type I promoter), activation is strongly impaired while it is not significantly affected at galP1 where CRP binds 41.5 bp upstream of the start of the message (type II promoter). We have investigated the differences in the architecture of the corresponding open complexes by comparing the positioning of holoenzymes reconstituted respectively with native or with truncated alpha-subunits (containing the first 235 or 256 residues of a) at two 'up' promoter mutants of the lacP1 and galP1 promoters (respectively lacUV5 and gal9A16C). First, the affinity of wild-type RNA polymerase for both promoters is increased by the presence of CRP and cAMP. By contrast, holoenzymes reconstituted with truncated alpha-subunits, show cooperative binding at the galP1 promoter only. Second, footprinting data confirm these observations and indicate that the truncated holoenzymes are unable to recognize regions of the promoter upstream from position -40. The absence of contacts between the truncated enzymes and CRP at the lacP1 promoter can explain the deficiency in activation. At the galP1 promoter, where the CRP site is closer to the initiation site, protein-protein contacts can still occur with the truncated polymerases, showing that the C-terminal part of the alpha-subunit is not involved in activation.

Joint perception after hip or knee replacement surgery

INTRODUCTION

Knee and hip arthroplasties are recognized as being effective. However, subjects with a prosthetic joint rarely report returned sensation comparable to their native joint.

HYPOTHESIS

Joint perception by patients following hip joint replacement is better than following knee replacement and in both cases this perception is directly related to the clinical results measured with currently validated scores.

PATIENTS AND METHODS

Patient joint perception in prosthetic reconstruction was evaluated in 347 patients, 46 who underwent unicompartmental knee arthroplasty (UKA), 119 tricompartmental knee arthroplasty (TKA), 93 hip resurfacing (HR), and 89 total hip arthroplasty (THA). The subjects' joint perception, their satisfaction, and the WOMAC clinical score were recorded and compared.

RESULTS

Joint perception was significantly worse for knee arthroplasties (TKA and UKA) compared to hip arthroplasties (THA or HR) (P<0.001). The WOMAC score was also significantly less favorable for knee arthroplasties than for hip arthroplasties (P<0.0001). However, there was no significant difference for the clinical scores between TKA and UKA as well as between HR and THA. Joint perception was strongly correlated with the WOMAC score for all groups (R(2)=0.951).

DISCUSSION

No difference was found after more conservative surgeries such as HR or UKA compared to traditional arthroplasty procedures (THA or TKA). Demonstrating inferior results in comparison to the hip, knee arthroplasties deserve particular attention and can still be improved. The assessment of joint perception used in this study can be considered a valuable clinical tool that is strongly correlated to validated, but more complex to apply, clinical scores.

Upstream curved sequences influence the initiation of transcription at the Escherichia coli galactose operon

The two overlapping promoters that control mRNA synthesis at the galactose operon contain three phased stretches of adenine residues, located around positions -84.5, -74 and -63, with respect ot the start of the P1 promoter. As a result, the corresponding DNA sequence is bent, an anomaly that is relieved by the addition of small concentrations of drugs like distamycin A or netropsin. By abortive initiation assays performed on several DNA fragments derived from the wild-type promoter or from various mutants we show that the curved sequence increases the strength of the P1 promoter. In the absence of cyclic AMP (cAMP) and of the corresponding receptor protein (CRP), the upstream curved sequences enhance the rate of isomerization from the closed to the open complex at P1. This effect is abolished when distamycin A is bound in the bent region. In the presence of cAMP-CRP, a more drastic change is observed: activation of the gal P1 promoter takes place at a different formal step, depending whether the upstream curved sequence is present or not (enhancement of the rate of conversion from a closed to an open complex instead of an increase in the affinity of the enzyme during closed complex formation). These data, together with previous results obtained with other mutants of the gal control region, suggest that several closed complexes corresponding to different nucleoprotein arrangements are formed during open complex formation at gal P1, in the presence of CRP.

A prospective randomized clinical trial comparing metal-on-metal total hip arthroplasty and metal-on-metal total hip resurfacing in patients less than 65 years old

The purpose of this prospective randomised study is to compare the early clinical results of the metal-on-metal hip resurfacing to metal-on-metal THA. Two hundred and ten hips were randomised between August 2003 and January 2006 (191 subjects). One hundred and two hips were implanted with an uncemented titanium tapered stem, and an uncemented titanium acetabular component and 28 mm metal-on-metal bearing (THA group) and 103 hips received a hybrid metal-on-metal surface replacement arthroplasty (SRA group). No significant difference was found with the WOMAC or Merle dAubign-Postel scales. However, a significantly higher activity level was found in the SRA group (UCLA score 6.3 versus 7.1, p= 0.037) and a greater percentage of the SRA patients returned to heavy or moderate activities at one - year postoperatively (72% versus 39%, p=0.007). No patient in either group presented with thigh pain one year after surgery. Both techniques present similar complication rates (0.15). This study supports the theory of better functional recovery in the short-term favouring the SRA when compared to THA. The clear benefit of surface replacement arthroplasty over THA is proximal femoral bone preservation. However, the long term survivorship of the SRA will determine the real value of the theoretical advantage.

The regulation of human MMP-13 by licofelone, an inhibitor of cyclo-oxygenases and 5-lipoxygenase, in human osteoarthritic chondrocytes is mediated by the inhibition of the p38 MAP kinase signalling pathway

BACKGROUND

MMP-13 is one of the most important metalloproteases (MMP) involved in osteoarthritis. Licofelone, a novel dual inhibitor of cyclo-oxygenases (COX) and 5-lipoxygenase (5-LOX), can modulate MMP-13 production in human osteoarthritis chondrocytes.

OBJECTIVE

To evaluate the impact of licofelone on MMP-13 expression/production, promoter, and major MAP kinase signalling pathways and transcription factors.

METHODS

Human osteoarthritis chondrocytes were stimulated by interleukin 1beta (IL1beta) and treated with or without: licofelone (0.3, 1, or 3 mug/ml); NS-398 (10 muM; a specific COX-2 inhibitor); or BayX-1005 (10 muM; a specific 5-LOX inhibitor). MMP-13 synthesis was determined by specific enzyme linked immunosorbent assay, and expression by real time polymerase chain reaction. The effect of licofelone on the MMP-13 promoter was studied through transient transfection; dexamethasone (10(-7) M) was used as comparison. The effect on IL1beta induced MMP-13 signalling pathways was determined using specific ELISA for phosphorylated MAP kinases and transcription factors.

RESULTS

Licofelone dose dependently inhibited the IL1beta stimulated production and expression of MMP-13. NS-398 and BayX-1005 had very little effect. Licofelone also inhibited MMP-13 transcription on each of the promoter constructs used. The licofelone inhibition was comparable to that obtained with dexamethasone. Licofelone had no effect on phosphorylated p44/42 or JNK1/2; however, it decreased phosphorylated c-jun and inhibited phosphorylated p38, CREB, and AP-1 activity.

CONCLUSIONS

Licofelone inhibited MMP-13 production under proinflammatory conditions on human osteoarthritis chondrocytes, through inhibition of the p38/AP-1 pathway and the transcription factor CREB. This may explain some of the mechanisms whereby licofelone exerts its positive effect on osteoarthritic changes.

DNA curvature controls termination of plus strand DNA synthesis at the centre of HIV-1 genome

In vivo and in vitro, reverse transcriptase (RT) from human immunodeficiency virus type 1 (HIV-1) terminates plus strand synthesis at the centre of the viral genome. The central termination sequence (CTS) contains curved DNA fragments located upstream of each terminator site. Two different models, relying either on the A-tract or general sequence roll assumptions, were used to predict the extent and the direction of this curvature as well as to design mutants, which abolished it. Straightening of each curved element abolished termination at the site located immediately downstream from the curvature. When synthesis was performed on the other strand and in the opposite direction, the two curved elements C1 and C2 associated with the two termination sites Ter1 and Ter2, led again to termination of DNA synthesis. Therefore, termination occurred as a nascent bent duplex was synthesized within the template primer binding cleft of RT, even when putative strand-specific motifs have been removed by the inversion. Computation of DNA paths upstream of other known arrest sites suggested that this feature was of general relevance for termination. At the CTS, termination occurred more precisely at the 3' end of an AnTm motif (n + m = 7). The possible structures, adopted by this motif, are discussed and confronted with the present crystallographic and biochemical data obtained on HIV-1 RT-DNA interactions and on HIV-1 RT processivity.

Metal-on-metal hip resurfacing compared with 28-mm diameter metal-on-metal total hip replacement: a randomised study with six to nine years' follow-up

A total of 219 hips in 192 patients aged between 18 and 65 years were randomised to 28-mm metal-on-metal uncemented total hip replacements (THRs, 107 hips) or hybrid hip resurfacing (HR, 112 hips). At a mean follow-up of eight years (6.6 to 9.3) there was no significant difference between the THR and HR groups regarding rate of revision (4.0% (4 of 99) vs 5.8% (6 of 104), p = 0.569) or re-operation rates without revision (5.1% (5 of 99) vs 2.9% (3 of 104), p = 0.428). In the THR group one recurrent dislocation, two late deep infections and one peri-prosthetic fracture required revision, whereas in the HR group five patients underwent revision for femoral head loosening and one for adverse reaction to metal debris. The mean University of California, Los Angeles activity scores were significantly higher in HR (7.5 (sd 1.7) vs 6.9 (sd 1.7), p = 0.035), but similar mean Western Ontario and McMaster Universities Osteoarthritis Index scores were obtained (5.8 (sd 9.5) in HR vs 5.1 (sd 8.9) in THR, p = 0.615) at the last follow-up. Osteolysis was found in 30 of 81 THR patients (37.4%), mostly in the proximal femur, compared with two of 83 HR patients (2.4%) (p < 0.001). At five years the mean metal ion levels were < 2.5 μg/l for cobalt and chromium in both groups; only titanium was significantly higher in the HR group (p = 0.001). Although revision rates and functional scores were similar in both groups at mid-term, long-term survival analysis is necessary to determine whether one procedure is more advantageous than the other.

Excellent results of large-diameter ceramic-on-ceramic bearings in total hip arthroplasty

Aims

This study reports the mid-term results of total hip arthroplasty (THA) performed using a monoblock acetabular component with a large-diameter head (LDH) ceramic-on-ceramic (CoC) bearing.

Patients and Methods

Of the 276 hips (246 patients) included in this study, 264 (96%) were reviewed at a mean of 67 months (48 to 79) postoperatively. Procedures were performed with a mini posterior approach. Clinical and radiological outcomes were recorded at regular intervals. A noise assessment questionnaire was completed at last follow-up.

Results

There were four re-operations (1%) including one early revision for insufficient primary fixation (0.4%). No hip dislocation was reported. The mean University of California, Los Angeles (UCLA) activity score, 12-Item Short-Form Health Survey (SF-12) Mental Component Summary (MCS) score, SF-12 Physical Component Summary (PCS) score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and Forgotten Joint Score (FJS) were 6.6 (2 to 10), 52.8 (25.5 to 65.7), 53.0 (27.2 to 66.5), 7.7 (0 to 63), and 88.5 (23 to 100), respectively. No signs of loosening or osteolysis were observed on radiological review. The incidence of squeaking was 23% (n = 51/225). Squeaking was significantly associated with larger head diameter (p < 0.001), younger age (p < 0.001), higher SF-12 PCS (p < 0.001), and UCLA scores (p < 0.001). Squeaking did not affect patient satisfaction, with 100% of the squeaking hips satisfied with the surgery.

Conclusion

LDH CoC THAs have demonstrated excellent functional outcomes at medium-term follow-up, with very low revision rate and no dislocations. The high incidence of squeaking did not affect patient satisfaction or function. LDH CoC with a monoblock acetabular component has the potential to provide long term implant survivorship with unrestricted activity, while avoiding implant impingement, liner fracture at insertion, and hip instability. Cite this article: Bone Joint J 2018;100-B:1434–41.

Combination of PI3K and MEK inhibitors yields durable remission in PDX models of PIK3CA-mutated metaplastic breast cancers

Background

Metaplastic breast cancer (MBC) is a rare form of breast cancer characterized by an aggressive clinical presentation, with a poor response to standard chemotherapy. MBCs are typically triple-negative breast cancers (TNBCs), frequently with alterations to genes of the PI3K-AKT-mTOR and RTK-MAPK signaling pathways. The objective of this study was to determine the response to PI3K and MAPK pathway inhibitors in patient-derived xenografts (PDXs) of MBCs with targetable alterations.

Methods

We compared survival between triple-negative MBCs and other histological subtypes, in a clinical cohort of 323 TNBC patients. PDX models were established from primary breast tumors classified as MBC. PI3K-AKT-mTOR and RTK-MAPK pathway alterations were detected by targeted next-generation sequencing (NGS) and analyses of copy number alterations. Activation of the PI3K-AKT-mTOR and RTK-MAPK signaling pathways was analyzed with reverse-phase protein arrays (RPPA). PDXs carrying an activating mutation of PIK3CA and genomic changes to the RTK-MAPK signaling pathways were treated with a combination consisting of a PI3K inhibitor and a MEK inhibitor.

Results

In our clinical cohort, the patients with MBC had a worse prognosis than those with other histological subtypes. We established nine metaplastic TNBC PDXs. Three had a pathogenic mutation of PIK3CA and additional alterations to genes associated with RTK-MAPK signaling. The MBC PDXs expressed typical EMT and stem cell genes and were of the mesenchymal or mesenchymal stem-like TNBC subtypes. On histological analysis, MBC PDXs presented squamous or chondroid differentiation. RPPA analysis showed activation of the PI3K-AKT-mTOR and RTK-MAPK signaling pathways. In vivo, the combination of PI3K and MAPK inhibitors displayed marked antitumor activity in PDXs carrying genomic alterations of PIK3CA, AKT1, BRAF, and FGFR4.

Conclusion

The treatment of metaplastic breast cancer PDXs by activation of the PI3K-AKT-mTOR and RTK-MAPK pathways at the genomic and protein levels with a combination of PI3K and MEK inhibitors resulted in tumor regression in mutated models and may therefore be of interest for therapeutic purposes.

Transcription activation by cAMP receptor protein (CRP) at the Escherichia coli gal P1 promoter. Crucial role for the spacing between the CRP binding site and the -10 region

The cAMP-CRP complex activates the initiation of transcription at the Escherichia coli gal P1 promoter, and the activation efficiency is highly sensitive to the location of the complex on this promoter region. Moving the CRP binding site by one base pair toward the start of transcription significantly decreases the extent of activation in vivo and actually turns the cAMP-CRP complex into an inhibitor in in vitro experiments. A structural analysis of open complexes formed on the two promoter fragments at 37 degrees C has revealed three elements crucial for an optimal activation process: a strong upstream anchorage of RNA polymerase, a cooperative binding of CRP and RNA polymerase, and an accurate orientation of the two promoter regions located upstream and downstream of the CRP binding site. Furthermore, structural analysis of polymerase promoter complexes at lower temperatures suggests that RNA polymerase initially recognizes the upstream region of the gal P1 promoter and subsequently interacts with sequences from the -10 to +20 region to yield the final open complex structure. The involvement of CRP in these sequential events has been examined.

CAV-2 Vector Development and Gene Transfer in the Central and Peripheral Nervous Systems

The options available for genetic modification of cells of the central nervous system (CNS) have greatly increased in the last decade. The current panoply of viral and nonviral vectors provides multifunctional platforms to deliver expression cassettes to many structures and nuclei. These cassettes can replace defective genes, modify a given pathway perturbed by diseases, or express proteins that can be selectively activated by drugs or light to extinguish or excite neurons. This review focuses on the use of canine adenovirus type 2 (CAV-2) vectors for gene transfer to neurons in the brain, spinal cord, and peripheral nervous system. We discuss (1) recent advances in vector production, (2) why CAV-2 vectors preferentially transduce neurons, (3) the mechanism underlying their widespread distribution via retrograde axonal transport, (4) how CAV-2 vectors have been used to address structure/function, and (5) their therapeutic applications.

Compression of the DNA minor groove is responsible for termination of DNA synthesis by HIV-1 reverse transcriptase

HIV-1 reverse transcriptase (RT) generally terminates plus strand DNA synthesis at the centre of the viral genome. The central termination sequence (CTS) contains two termination sites which are located at the 3' end of AnTm motifs. These motifs generate a global curvature of the DNA helix which correlates with termination of DNA synthesis. Here, we have characterized HIV-1 RT termination sites on different DNA sequences. Again, they are located at the 3' end of A-tracts. Using hydroxyl radicals as a probe of the width of the DNA helix, we have shown that RT termination sites are always located a few base-pairs downstream of a compressed minor groove. Mutations which relieve these compressions also abolish the termination events. The replacement of the adenine tracts by 2,6-diaminopurine tracts has a similar effect. Moreover, no termination site is observed on DNA sequences containing phased GC-tracts which curve the DNA helix but compress the major groove. The compression of the DNA minor groove and not necessarily the curved trajectory of the DNA is, therefore, responsible for termination of DNA synthesis at the CTS by HIV-1 RT. This conclusion is consistent with interpretation of other biochemical data on the processivity of HIV-1 RT, based on the structure of a DNA-enzyme complex.

The endogenous opioid spinorphin blocks fMet-Leu-Phe-induced neutrophil chemotaxis by acting as a specific antagonist at the N-formylpeptide receptor subtype FPR

Spinorphin is an endogenous heptapeptide (leucylvalylvalyltyrosylprolyltryptophylthreonine), first isolated from bovine spinal cord, whose sequence matches a conserved region of beta-hemoglobin. Also referred to as LVV-hemorphin-4 and a member of the nonclassical opioid hemorphin family, spinorphin inhibits enkephalin-degrading enzymes and is analgesic. Recently, spinorphin was reported to block neutrophil activation induced by the chemotactic N-formylpeptide N-formylmethionylleucylphenylalanine (fMLF), suggesting a potential role as an endogenous negative regulator of inflammation. Here we use both gain- and loss-of-function genetic tests to identify the specific mechanism of spinorphin action on neutrophils. Spinorphin induced calcium flux in normal mouse neutrophils, but was inactive in neutrophils from mice genetically deficient in the fMLF receptor subtype FPR (N-formylpeptide receptor). Consistent with this, spinorphin induced calcium flux in human embryonic kidney 293 cells transfected with mouse FPR, but had no effect on cells expressing the closely related fMLF receptor subtype FPR2. Despite acting as a calcium-mobilizing agonist at FPR, spinorphin was a weak chemotactic agonist and effectively blocked neutrophil chemotaxis induced by fMLF at concentrations selective for FPR. Spinorphin did not affect mouse neutrophil chemotaxis induced by concentrations of fMLF that selectively activate FPR2. Thus, spinorphin blocks fMLF-induced neutrophil chemotaxis by acting as a specific antagonist at the fMLF receptor subtype FPR.

Resurfacing arthroplasty of the hip in osteopetrosis

A 34-year-old woman with a benign form of osteopetrosis developed osteoarthritis of the hip. In order to avoid the difficulties associated with inserting the femoral component of a conventional total hip arthroplasty, a hybrid metal-on-metal resurfacing was performed. There were several technical challenges associated with the procedure, including the sizing of the component, press-fit fixation of the acetabular component and femoral head preparation, as well as trying to avoid a fracture. No surgical complication occurred. After more than a year following surgery, the patient showed excellent clinical function and remained satisfied with the outcome. We conclude that the hybrid metal-on-metal resurfacing arthroplasty represents a valuable option for the treatment of patients with osteopetrosis and secondary hip osteoarthritis.

CRP fixes the rotational orientation of covalently closed DNA molecules

Five minicircles of 284 bp were constructed with a reporter sequence located approximately opposite a CRP binding site. The spacing between the center of the CRP site and this sequence is varied within 1.2 helical turns. The reactivity of the reference sequence to DNAse I was determined on the minicircles and on the corresponding fragments, in both the absence and presence of CRP. A rigorous mathematical analysis of the data shows that in the absence of CRP no preferred rotational orientation of the DNA is observed. In contrast, binding of CRP fixes, in a phase-dependent manner, the rotational orientation of the reporter sequence in the minicircles. This result illustrates the transmission at a distance along the DNA molecule of a structural modification. Such effects modulate the extent of synergy between activators and polymerases during the initiation of transcription.