Robust and Objective Evaluation of Superficial Punctate Keratopathy in a Murine Dry Eye Model

Purpose

To establish a robust and objective method to evaluate (SPK) superficial punctate keratopathy in a murine dry eye model by developing a reliable photographic system.

Design

Experimental study.

Subjects

A murine dry eye model was generated by exorbital lacrimal gland excision. Sham-operated mice were used as healthy controls. For the sham operation, an incision was made without touching the gland.

Methods

A photographic system was constructed, consisting of an LED lamp and a digital camera fitted with a zoom lens and sharp cut filter. SPK was detected by applying fluorescein solution. To validate the system, SPK was compared between dry eye mice and healthy control mice, and diquafosol (DIQUAS ophthalmic solution 3%; Santen Pharmaceutical Co., Ltd.) or cyclosporine (PAPILOCK Mini ophthalmic solution 0.1%; Santen Pharmaceutical Co., Ltd.) was used to dry eye mice.

Main Outcome Measures

SPK was evaluated using the parameters of fluorescence score and fluorescein-stained area.

Results

The photographs clearly indicated SPK in dry eye mice. A fluorescence score of 0 to 9 could be easily assessed, and the fluorescein-stained area was quantifiable. The fluorescein-stained area correlated with fluorescence score (correlation coefficient: 0.98), with good interobserver reliability (intraclass correlation coefficient: 0.999). The fluorescein-stained area increased significantly in dry eye mice compared with that of healthy controls (P < 0.0001). Both types of therapeutic eye drops decreased the fluorescein-stained area relative to saline-treated mice (P < 0.05 in diquafosol vs. saline; P < 0.01 in cyclosporine vs. saline).

Conclusions

This newly developed system is a robust alternative for quantitative evaluation of SPK in a murine dry eye model.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Prognostic value of cardiac 123I-metaiodobenzylguanidine imaging for predicting cardiac events after transcatheter aortic valve replacement

Background

In patients with aortic valve stenosis (AS), cardiac sympathetic nervous (CSN) dysfunction and its improvement after TAVR have been reported; however, the prognostic impact of CSN function remains unclear. This study investigated the prognostic value of cardiac 123I-metaiodobenzylguanidine (MIBG) imaging for the prediction of cardiac events after transcatheter aortic valve replacement (TAVR).

Methods

This study was a single-center prospective observational study that enrolled patients with AS or failed surgical bioprostheses between July 2017 and May 2019. MIBG scintigraphy was performed before and after TAVR to evaluate the delayed heart–mediastinum ratio (d-H/M). Patients were classified into three pairs of groups based on the baseline and post-TAVR d-H/M (≥2.0 or &lt;2.0) and on the presence of TAVR-related improvement of d-H/M. The study endpoints were major adverse cardiac events (MACE), including all-cause death, myocardial infarction, and hospitalization due to heart failure. The association of d-H/M with MACE following TAVR was based on a Cox proportional hazards ratio model adjusted for multiple prognostic variables.

Results

Of 187 consecutive patients who underwent TAVR, 111 (31 men; median age: 86 years) were evaluated. Over a median follow-up of 366 days, 16 (14.4%) patients had MACE. The incidence of MACE was significantly lower in patients with d-H/M improvement and/or the high post-TAVR d-H/M (≥2.0). Post-TAVR d-H/M had significant impacts on MACE, with an adjusted hazard ratio of 1.326 (95% confidence interval, 0.139–2.515; p=0.027).

Conclusions

Both d-H/M improvement and high post-TAVR d-H/M were associated with better prognosis in patients who underwent TAVR. Cardiac MIBG imaging was useful for predicting cardiac events after TAVR.

Funding Acknowledgement

Type of funding source: None

P932Structural changes in left ventricle after transcatheter aortic valve implantation

Background

Transcatheter aortic valve implantation (TAVI) has improved prognosis and quality of life of patients with severe aortic stenosis (AS) who had been considered inoperable or at high risk for surgical aortic valve replacement reflecting their age, frailty, and comorbidities. However, less is known about changes in cardiac geometry after TAVI procedure, and predictors of them.

Purpose

To clarify changes in cardiac geometry after TAVI, and their predictors.

Methods

We retrospectively analyzed patients with severe AS who underwent TAVI in our institute between May 2016 and June 2018. Of the 117 consecutive patients enrolled to this study, 12 patients died before six-month follow up, and finally 88 patients received follow up exams including echocardiography at six months after TAVI procedure.

Results

The analysis of echocardiographic data at the baseline and the six-month follow up of the 88 patients (age 86.2±4.0 years, male 19.3%, STS-PROM 6.76±3.28%, peak aortic jet velocity 4.67±0.75m/s) revealed that left ventricular end-diastolic volume index (LVEDVi) (from 80.1±20.9ml/m2to 74.2±15.9ml/m2, p=0.011), and left ventricular mass index (LVMi) (from 116.0±32.7g/m2to 93.6±25.6g/m2, p<0.001) had improved in six months after TAVI procedure. The difference of LVEDVi (ΔLVEDVi: six-month LVEDVi–baseline LVEDVi) and the difference of LVMi (ΔLVMi: six-month LVMi – baseline LVMi) were significantly higher in the patients with chronic atrial fibrillation compared to the rest (ΔLVEDVi: +7.7±8.7ml/m2 vs −7.2±18.1ml/m2, p=0.024; ΔLVMi: +7.1±11.5g/m2 vs −25.3±33.5g/m2, p=0.008). In echocardiographic data, ΔLVEDVi and ΔLVMi both had positive correlation between baseline E/e' ratio (ΔLVEDVi: r=0.224, p=0.048; ΔLVMi: r=0.240, p=0.034), and negative correlation between baseline LVEDVi (ΔLVEDVi: r=−0.674, p<0.001; ΔLVMi: r=−0.312, p=0.003), LVMi (ΔLVEDVi: r=−0.422, p<0.001; ΔLVMi: r=−0.699, p<0.001), peak aortic jet velocity (ΔLVEDVi: r=−0.257, p=0.016; ΔLVMi: r=−0.376, p<0.001), and mean transaortic pressure gradient (ΔLVEDVi: r=−0.269, p=0.011; ΔLVMi: r=−0.403, p<0.001).

Conclusion

TAVI resulted in reverse remodeling and regression of hypertrophy in left ventricle. And these improvement were grater in patients with more advanced left ventricular remodeling and hypertrophy, and higher severity of AS at the baseline, however, less in patients with chronic atrial fibrillation and worse diastolic dysfunction.

P1221Effect of transcatheter aortic valve implantation on cardiac sympathetic nervous function assessed by 123I-metaiodobenzylguanidine scintigraphy in patients with severe aortic stenosis

Background

Cardiac sympathetic nervous (CSN) function assessed by 123I-metaiodobenzylguanidine (MIBG) scintigraphy is associated with poor prognosis in patients with heart failure.

Purpose

The aim of this study was to investigate the effects of transcatheter aortic valve implantation (TAVI) on CSN function in patients with severe aortic stenosis (AS) using MIBG scintigraphy.

Methods

This was a single-center prospective observational study that enrolled patients between July 2017 and July 2018. Among 77 registered patients who scheduled to undergo TAVI, 35 patients (7 men; mean age: 87 years) were evaluated. The MIBG scintigraphy was performed at baseline and 6 months after TAVI procedure to evaluate the heart-mediastinum ratio (H/M) and washout rate (WR). The MIBG parameter changes were compared with B-type natriuretic peptide (BNP) levels and echocardiographic parameters, including aortic valve area (AVA), peak velocity (Vmax), mean pressure gradient (PG), and left ventricular ejection fraction (LVEF).

Results

All patients successfully underwent TAVI with improved BNP level (388±341 pg/mL vs. 167±118 pg/mL, p<0.001). The AVA, Vmax, mean PG and LVEF improved after TAVI (0.6±0.2 cm2 vs. 1.6±0.5 cm2, p<0.001; 4.6±0.8 m/s vs. 2.1±0.3 m/s, p<0.001; 54±20 mmHg vs. 9±3 mmHg, p<0.001; 58±11% vs. 63±9%, p=0.01, respectively). In the MIBG imaging, the delayed H/M significantly increased (2.5±0.6 vs. 2.6±0.7, p=0.03), and the WR decreased (32±8% vs. 29±8%, p=0.047) after TAVI. There was a correlation between the changes in the MIBG parameters and the change in mean PG from baseline to 6 months (delayed H/M: r=0.391, p=0.02; WR: r=0.347, p=0.04). Multivariate logistic regression analysis showed that baseline mean PG was an independent predictor of improved both delayed H/M and WR (odds ratio=1.062; 95% confidence interval: 1.009–1.137; p=0.042).

Conclusions

TAVI can improve the CSN function in patients with AS. Such CSN improvement was related with hemodynamic changes.

Acknowledgement/Funding

None

Usefulness of an accelerometer-based portable navigation system in total knee arthroplasty

Aims

The aim of this study was to evaluate the effects of using a portable, accelerometer-based surgical navigation system (KneeAlign2) in total knee arthroplasty (TKA) on the alignment of the femoral component, and blood loss.

Patients and Methods

A total of 241 consecutive patients with primary osteoarthritis of the knee were enrolled in this prospective, randomised controlled study. There were 207 women and 34 men. The mean age of the patients was 74.0 years (57 to 89). The KneeAlign2 system was used for distal femoral resection in 121 patients (KA2 group) and a conventional intramedullary femoral guide was used in 120 patients (IM group).

Results

One patient (0.8%) in the KA2 group and 19 in the IM group had an alignment which was > 3° away from the neutral mechanical axis (p < 0.01). The mean deviation from neutral alignment was 1.01° (standard deviation (sd) 1.0°) in the KA2 group and 1.93° (sd 1.7°) in the IM group (p < 0.01). Blood loss was significantly less in the KA2 group compared with the IM group (784 ml (sd 357) versus 1071 ml (sd 310), p < 0.001).

Conclusion

The KneeAlign2 system provides a technically straightforward method for identifying the femoral head and performing an accurate distal femoral resection at TKA with significantly less blood loss compared with a conventional intramedullary guide. Cite this article: Bone Joint J 2017;99-B:1047–52.

Extraordinary carrier multiplication gated by a picosecond electric field pulse

The study of carrier multiplication has become an essential part of many-body physics and materials science as this multiplication directly affects nonlinear transport phenomena, and has a key role in designing efficient solar cells and electroluminescent emitters and highly sensitive photon detectors. Here we show that a 1-MVcm⁻¹ electric field of a terahertz pulse, unlike a DC bias, can generate a substantial number of electron–hole pairs, forming excitons that emit near-infrared luminescence. The bright luminescence associated with carrier multiplication suggests that carriers coherently driven by a strong electric field can efficiently gain enough kinetic energy to induce a series of impact ionizations that can increase the number of carriers by about three orders of magnitude on the picosecond time scale.

Studying carrier multiplication in materials is important to understand their transport properties and interaction with light. Hirori et al. show that intense terahertz pulses can generate electron-hole pairs in GaAs quantum wells that then emit infrared light, contrary to the effect with a DC field.

Real-time terahertz near-field microscope

We report a terahertz near-field microscope with a high dynamic range that can capture images of a 370 x 740 μm2 area at 35 frames per second. We achieve high spatial resolution (14 μm corresponding to λ/30 for a center frequency at 0.7 THz) on a large area by combining two novel techniques: terahertz generation by tilted-pulse-front excitation and electro-optic balanced imaging detection using a thin crystal. To demonstrate the microscope capability, we reveal the field enhancement at the gap position of a dipole antenna after the irradiation of a terahertz pulse.

Terahertz conductivity of localized photoinduced carriers in a Mott insulator YTiO(3) at low excitation density, contrasted with the metallic nature in a band semiconductor Si

We performed optical-pump terahertz-probe measurements of a Mott insulator YTiO(3) and a band semiconductor Si using a laser diode (1.47 eV) and a femtosecond-pulse laser (1.55 eV). Both samples possess long energy-relaxation times (1.5 ms for YTiO(3) and 15 µs for Si); therefore, it is possible to extract terahertz complex conductivities of photoinduced carriers under equilibrium. We observed highly contrasting behaviour-Drude conductivity in Si and localized conductivity possibly obeying the Jonscher law in YTiO(3). The carrier number at the highest carrier-concentration layer in YTiO(3) is estimated to be 0.015 per Ti site. Anisotropic conductivity of YTiO(3) is determined. Our study indicates that localized carriers might play an important role in the incipient formation of photoinduced metallic phases in Mott insulators. In addition, this study shows that the transfer-matrix method is effective for extracting an optical constant of a sample with a spatially inhomogeneous carrier distribution.

Evaluation of the flexion gap by axial radiography of the distal femur

The shape of the flexion gap in 20 normal knees was evaluated by axial radiography of the distal femur, and the results compared with those obtained in a previous study by MRI. The observed asymmetry was reduced by 29% using radiography, with a mean value of 3.6° (1.5° to 6.3°) compared with that obtained by MRI of 5.1° (2.6° to 9.5°), a mean discrepancy of 1.49°. The results obtained by radiography and MRI showed a strong correlation (r = 0.78).

Axial radiography is acceptable for the evaluation of the flexion gap and is less expensive and more comfortable to perform than MRI. Additionally, no metallic artefact occurs when the radiological method is used for assessment after arthroplasty.

The flexion gap in normal knees

Varus and valgus joint laxity of the normal living knee in flexion was assessed using MRI. Twenty knees were flexed to 90° and were imaged in neutral and under a varus-valgus stress in an open MRI system. The configuration of the tibiofemoral joint gap was studied in slices which crossed the epicondyles of the femur.

When a varus stress was applied, the lateral joint gap opened by 6.7 ± 1.9 mm (mean ± sd; 2.1 to 9.2) whereas the medial joint gap opened by only by a mean of 2.1 ± 1.1 mm (0.2 to 4.2). These discrepancies indicate that the tibiofemoral flexion gap in the normal knee is not rectangular and that the lateral joint gap is significantly lax. These results may be useful for adequate soft-tissue balancing and bone resection in total knee arthroplasty and reconstruction surgery on ligaments.

Kinematics of the patella in deep flexion. Analysis with magnetic resonance imaging

BACKGROUND

Little information is available on the kinematics of the normal knee in deep flexion. The purpose of this study was to use magnetic resonance imaging to analyze the patellofemoral articulation in deep flexion.

METHODS

Axial scans were made of the patellofemoral joint of twenty healthy Japanese volunteers with the knee in approximately 90 degrees of flexion, in maximum active flexion (mean [and standard deviation], 140 degrees +/- 10 degrees ), and in maximum passive flexion (mean, 156 degrees +/- 5 degrees ). A fat-suppressed, three-dimensional, fast low-angle shot sequence was used to visualize the articular cartilage. The patellofemoral contact area was determined on sequential images and was reconstructed three-dimensionally.

RESULTS

At 90 degrees of flexion, the contact area on the patella was continuous over the medial and lateral facets in fourteen knees and was located in the proximal half of the articular surface. At maximum active and passive flexion, the odd facet engaged in fifteen and eighteen knees, respectively. At maximum passive flexion, the contact area of the lateral facet moved distally and decreased significantly (p = 0.0002). From 90 degrees of flexion to maximum active flexion, the mean total contact area remained constant (3.43 +/- 0.70 and 3.62 +/- 0.72 cm (2), respectively); it then decreased significantly in maximum passive flexion (2.96 +/- 0.78 cm (2), p = 0.04).

CONCLUSIONS

The contact area on the patella was divided into two parts (the odd and lateral facets) and moved distally in deep knee flexion. The size of the contact area on the lateral facet significantly decreased in maximum passive flexion.

Anthropometry of the proximal tibia to design a total knee prosthesis for the Japanese population

Anthropometric data on proximal tibiae of 100 knees in 80 Japanese patients undergoing total knee arthroplasty were obtained. Anterior-posterior (AP) and medial-lateral (ML) lengths of the tibia were measured on computed tomography scans and intraoperatively on tibial resection surfaces. A special small component is unnecessary, and size variation should focus on ML length of 65 to 75 mm because this includes 90% of women's knees. AP-to-ML ratio had a negative correlation with ML length, indicating that small knees were longer in the AP direction. Most prostheses had AP mismatch up to 5 mm for small women's knees. These data could provide the basis for designing the optimal tibial component for most of the Asian-Pacific population.

Bone anatomy and rotational alignment in total knee arthroplasty

The purpose of the current study was to investigate the bone anatomy in determining the rotational alignment in total knee arthroplasty using computed tomography. Axial images of 109 knees in 83 patients with varus osteoarthritis who had total knee arthroplasty were analyzed. On the images of the distal femur and the proximal tibia, a baseline for the anteroposterior axis of each component was drawn based on the epicondylar axis for the femur and the medial (1/3) of the tibial tuberosity for the tibia. The angle between these two lines was analyzed as the rotational mismatch between the components when they were aligned to the anatomic landmarks of each bone. Fifty-four knees (49.5%) had an angle of 5 degrees or greater and 13 knees (11.9%) had an angle of 10 degrees or greater. There was a tendency to align the tibial component in external rotation relative to the femoral component. The results indicated that the landmarks of each bone were the intrinsic cause of the rotational mismatch in knees with varus osteoarthritis. Surgeons doing total knee arthroplasties should be aware of this and check the rotational mismatch between the components. When it is present, the tibial component should be realigned to match the femoral component rotation to minimize problems caused by the mismatch.

Overexpression of cdk4/cyclin D1 induces apoptosis in PC12 cells in the presence of trophic support

The induction of apoptosis by cell cycle regulator molecules under conditions optimal for exponential growth was examined in rat pheochromocytoma PC12 cells by overexpression of cyclins and cyclin-dependent kinases (cdks). By flow cytometry and by immunofluorescence, only cells overexpressing cdk4 or cyclin D1 underwent apoptosis, which was not associated with G1-arrest. Cdk4 kinase activity was significantly higher in cdk4-, or cyclin D1-expressing cells. Furthermore, induction of apoptosis by cdk4 was abrogated by co-transfection of p16(INK4), or dominant negative cdk4. These results suggest that upregulation of cdk4 kinase activity is a primary and critical mediator of apoptosis in PC12 cells under physiological conditions.

Effects of posterior cruciate ligament resection on the tibiofemoral joint gap

The effect of posterior cruciate ligament resection on the tibiofemoral joint gap was analyzed in 30 patients with varus osteoarthritis of thee knee who underwent total knee replacement. The medial soft tissue was released and the bone cut was made without preserving the bone segment of the tibia to which the posterior cruciate ligament was attached. Then the medial and lateral joint gaps in full extension and 90 degrees flexion were measured before and after the posterior cruciate ligament was resected using a tensioning device. After the resection, the flexion gap significantly increased in the medial and the lateral sides (4.8 +/- 0.4 and 4.5 +/- 0.4 mm, respectively, mean +/- standard error) compared with those seen in the extension gap (0.9 +/- 0.2 and 0.8 +/- 0.2 mm). There was no significant difference between the changes in the medial and lateral gaps. The mean value of the flexion gap was 2 mm smaller than the extension gap before the resection and 1.7 mm larger after the sacrifice. Overall, posterior cruciate ligament resection resulted in an increase in the flexion gap and made space for approximately 3-mm thicker polyethylene. The flexion gap can be controlled selectively with posterior cruciate ligament release.

Total hip arthroplasty with a modified cementing technique using hydroxyapatite granules

Results of total hip arthroplasties with a modified cementing technique using hydroxyapatite were evaluated. Femoral and acetabular components were inserted with cement after hydroxyapatite granules (phi = 100-300 microm). The study group comprised 268 hips in 232 patients. The diagnosis was osteoarthritis in 197 patients. After a mean follow-up of 10.3 years, 5 patients died and 30 patients were lost to follow-up, leaving 218 hips (197 patients; mean age, 58.2 years) for evaluation. Three hips were revised because aseptic (1) and septic (2) loosening of acetabular components. Six other sockets were defined as radiologically loose, and no femoral component was loose. Osteolysis was identified in 2 femora and 0 acetabula. The overall loosening rate was 3.2% for acetabular components and 0% for femoral components. These results show that the loosening rate of cemented total hip arthroplasty components, especially the acetabulum, is reduced markedly with this modified cementing technique.

Constituents and pH changes in protein rich hyaluronan solution affect the biotribological properties of artificial articular joints

The relationship between the coefficient of friction and pH value or protein constituents of lubricating fluid, together with viscosity, were studied within a bearing surface model for artificial joint, ultra-high molecular weight polyethylene (UHMWPE) against stainless steel (SUS), using a mechanical spectrometer. Four lubricants were tested in this study: sodium hyaluronate (HA), HA with albumin, HA with gamma-globulin, and HA with (L)alpha-dipalmitoyl phosphatidylcholine ((L)alpha-DPPC). The coefficient of friction between UHMWPE and SUS in HA with albumin or HA with gamma-globulin varied from 0.035 to 0.070 depending on angular velocity and pH. The coefficient of friction in HA or HA with (L)alpha-DPPC varied from 0.023 to 0.045 depending on angular velocity and pH. The variation in pH for HA with albumin had a large effect on the coefficient of friction at low range of angular velocity with viscosity independence. The variation in pH for HA with gamma-globulin had a large effect on the coefficient of friction with viscosity dependence at high angular velocity. The addition of (L)alpha-DPPC showed a small effect on the coefficient of friction at low angular velocity. This study confirms that the presence of albumin in the lubricant promotes pH dependence and viscosity independence of the tribological properties at low speed while the presence of globulin promotes pH and viscosity independence at low speed and promotes pH and viscosity dependence at high speed in the lubrication of UHMWPE against SUS. This study supports the clinical hypothesis that the effect of constituents and pH changes in periprosthetic fluid for the lubrication is a clue toward resolving many complications after total joint replacement.

Gamma-irradiated cross-linked polyethylene in total hip replacements--analysis of retrieved sockets after long-term implantation

The purpose of this study was to evaluate the mechanical and chemical characteristics of gamma-irradiated, cross-linked polyethylene after long-term service in vivo. Two gamma-irradiated ultra high molecular weight polyethylene (RCH 1000, molecular weight: 10(6)) total hip replacement sockets were retrieved at 15 and 16 years after implantation. Mechanical and chemical characteristics of the sockets were evaluated in comparison with nonirradiated sockets. Significant surface oxidation occurred in the nonirradiated sockets; up to 75% of that seen in the irradiated ones. The mechanical properties of the irradiated sockets were not subject to increased deterioration in the presence of high free radical content. The cross-link was stable and was retained for a long period both in vivo and in ambient air. These data indicate that gamma-irradiated polyethylene was not subject to increased oxidative degradation during long-term service in vivo and confirmed the usefulness of this material as an articulating surface in total hip replacement.

Tibiofemoral movement 3: full flexion in the living knee studied by MRI

We studied active flexion from 90 degrees to 133 degrees and passive flexion to 162 degrees using MRI in 20 unloaded knees in Japanese subjects. Flexion over this arc is accompanied by backward movement of the medial femoral condyle of 4.0 mm and by backward movement laterally of 15 mm, i.e., by internal rotation of the tibia. At 162 degrees the lateral femoral condyle lies posterior to the tibia.

Tibiofemoral movement 3: full flexion in the living knee studied by MRI

We studied active flexion from 90° to 133° and passive flexion to 162° using MRI in 20 unloaded knees in Japanese subjects. Flexion over this arc is accompanied by backward movement of the medial femoral condyle of 4.0 mm and by backward movement laterally of 15 mm, i.e., by internal rotation of the tibia. At 162° the lateral femoral condyle lies posterior to the tibia.

Wear of high-dose gamma-irradiated polyethylene in total hip replacements

Between 1971 and 1978, 62 patients underwent total hip replacements (THRs) with high-dose (100 Mrad) gamma-irradiated polyethylene sockets. After a mean follow-up of 17. 3 years (range, 6-23 years), 28 hips in 26 patients were available for radiographic wear measurement. Twenty-three THRs with non-irradiated sockets were used as controls, although all these hips had loosened within 13 years. The rate of linear wear in irradiated sockets was significantly lower throughout the follow-up period (less than 2 years, 0.16 and 0. 38 mm/year; 2-6 years, 0.05 and 0.29 mm/year; more than 6 years, 0. 05 and 0.28 mm/year, respectively; mean, P < 0.0001). This result has demonstrated that high-dose gamma-irradiated, cross-linked polyethylene is a promising articulating material for THRs.

Hydroxyapatite granules interposed at bone-cement interface in total hip replacements: histological study of retrieved specimens

The effect of hydroxyapatite (HA) granules interposed between bone and polymethylmethacrylate (PMMA) bone cement in total hip replacement was histologically evaluated. The technique consisted of smearing 2-5 g of HA granules (straight phi = 100-300 microm) onto the bone surface just before cementing. Four specimens containing well-fixed bone-cement interface were retrieved at 1, 2, 6, and 10 years postoperatively and examined with back-scattered electron microscopy and light microscopy. The majority of HA granules were incorporated into remodeled trabeculae, and highly convoluted bone-cement interface was maintained up to 10 years. The presence of active remodeling in the adjacent bone was observed. There were no significant inflammatory or foreign body reactions against interposed HA granules. In one specimen retrieved from a patient with rheumatoid arthritis, bone formation around HA granules was limited after 1 year. These results have provided histological evidence for the significantly reduced incidence of radiolucent lines in total hip replacement with this cementing technique, reported elsewhere.

Histologic and mechanical evaluation of impacted morcellized cancellous allografts in rabbits: comparison with hydroxyapatite granules

The bioactivity and mechanical properties of morcellized allografts and hydroxyapatite (HA) granules were evaluated in a rabbit model. Allografts were replaced by viable trabecular structures within 8 weeks. The yield strength and stiffness of allografts were within normal cancellous bone levels by 3 weeks and were maintained afterward. The amount of newly formed bone around HA granules was comparable to that around allografts. The yield strength and stiffness of HA granules were significantly higher than those of allografts at 3 and 12 weeks. Allografts offer the advantage of being replaced by host-bone without significant deterioration in mechanical properties over the course of remodeling. HA granules can also be used for a bone substitute given their bioactivity in bone conduction and superiority in mechanical properties to allografts.

Effect of particles and interface conditions on fibrous tissue interposition between bone and implant. A particle challenge model in rabbit

Interposed fibrous tissue at bone-implant interfaces was quantitatively measured in the presence or absence of polyethylene (PE) or alumina particles. Three different conditions of the interface were designed by implanting a pre-polymerized polymethylmethacrylate (PMMA) plug (plug group), a doughy PMMA (injection group) and a hydroxyapatite (HA) plug (HA group) in the hole drilled at the intercondylar notch of rabbit knees. PE (170+/-18 microm) or alumina particles (88+/-26 microm) were repeatedly administered into the knee joints at one month intervals (six times). All animals were sacrificed seven months after the implantation. The bone-implant interface was histomorphometrically examined using undecalcified ground sections. In the plug group, the PE particles significantly increased the extent of the interposed fibrous tissue (p < 0.05), while the alumina particles showed no effect. In contrast, both particles showed no significant effects in the injection and the HA groups. These results indicate that both particle characteristics and conditions of the bone-implant interface affected particle-induced fibrous tissue interposition. The loose PMMA plug with PE particles induced the greatest amount of fibrous tissue interposition.

Localization of laminin-5, HD1/plectin, and BP230 in the submandibular glands of developing and adult mice

We studied the distributions of laminin-5 and hemidesmosome components, HD1/plectin and BP230, in the submandibular glands of adult and developing mice. In adult mice, laminin-5 was expressed in the basement membranes of both the myoepithelial cells and excretory ducts. The former expression was predictable because laminin-5 is a ligand for hemidesmosomes, which appear in myoepithelial cells and stratified epithelium. However, the latter expression pattern suggested that the non-stratified epithelium of the excretory duct might also be associated with hemidesmosomes. During fetal development, laminin-5 was found in the basement membrane of developing ducts but not epithelial end buds in which future lobules are formed by epithelial branching. The expression of HD1/plectin but not BP230 was noted in the developing duct at early embryonic stages, indicating the presence of type II hemidesmosomes. Expression of BP230 appeared in the excretory duct epithelium at around the day of birth. At this stage, the typical hemidesmosome was observed in the duct epithelium. Our results suggest that laminin-5 is involved in duct development rather than epithelial branching. The results also suggest that the developing duct epithelium interacts with laminin-5 through the type II hemidesmosome, which later matures into a typical hemidesmosome upon the onset of expression of BP230.

Determination of mechanical properties of impacted human morsellized cancellous allografts for revision joint arthroplasty

This paper deals with the characterization of mechanical properties of impacted morsellized cancellous allograft (IMCA) produced by dynamic compaction of allograft femoral heads ground by commercially available bone mills, i.e. rotating rasp and reciprocating type bone mills. Various ranges and profiles of particle size in the graft aggregates were obtained using these bone mills, and the effect of number of compaction as well as the distribution of particle sizes on the mechanical properties of IMCA under quasistatic compression and shear loading conditions was discussed. The morsellized cancellous allograft prepared by the reciprocating type bone mill showed a broad distribution of particle sizes, and gave IMCA superior mechanical properties to the graft with a more uniform size distribution, or prepared by the rotating rasp type bone mills. The increase of number of compaction also improved the mechanical properties of IMCA in compression.

Anteroposterior and rotational movement of femur during knee flexion

This study was designed to analyze anteroposterior and rotational movement of femoral condyles during knee flexion from 15 degrees to 90 degrees using magnetic resonance imaging. After a pilot study, scans were made in 10 healthy male Japanese volunteers. When centers of the circular profiles of posterior femoral condyles were used as reference points, the medial and lateral femoral condyles displaced posteriorly 1.9 +/- 0.8 mm and 2.3 +/- 0.5 mm, respectively (mean +/- standard error). Duplicate examinations on two separate occasions revealed the accuracy of this procedure was in the range of 1 to 2 mm. These results have confirmed that femoral rollback occurs in the unloaded normal knee during flexion from 15 degrees to 90 degrees, but its magnitude is small (2 mm). The results obtained in this in vivo measurement of anteroposterior movement of the femoral condyles have relevance for total knee replacement design.

Significant role of laminin-1 in branching morphogenesis of mouse salivary epithelium cultured in basement membrane matrix

Mouse submandibular epithelium shows branching morphogenesis in mesenchyme-free conditions when covered with a basement membrane matrix (Matrigel) in medium supplemented with epidermal growth factor. In the present study, the role of laminin-1 (LN1), a major glycoprotein of Matrigel, in this culture system was defined. When the epithelium was cultured in a LN1-nidogen gel, the epithelium showed much branching, comparable to that observed with Matrigel. By electron microscopy, only a felt-like matrix was formed on the epithelial surface in the LN1-nidogen gel cultures, while an organized basal lamina structure was formed on the epithelial surface in direct or transfilter recombination cultures with mesenchyme. Next, the epithelium covered with Matrigel was cultured in medium containing either biologically active peptides from LN1, IKVAV-including peptide (2097-2108), AG10 (2183-2194), AG32 (2370-2381) or AG73 (2719-2730) from the alpha1 chain, or YIGSR-including peptide (926-933) from the beta1 chain. Only AG73 (RKRLQVQLSIRT from the alpha1 chain carboxyl-terminal globular domain) inhibited the epithelial branching in Matrigel. These results suggest that LN1-nidogen can support the branching morphogenesis of submandibular epithelium even if LN1-nidogen is not assembled into an intact basal lamina, and that the AG73 sequence is an important site on LN1, which interacts with submandibular epithelial cells.

Wideband deep penetration of photon-number fluctuations into the quantum regime in series-coupled light-emitting diodes

Experimental results on the squeezing of photon-number fluctuations of series-coupled LED's driven by a constant-voltage source are presented that illustrate the advantage of series-coupled LED's, namely, a greater squeezing capability than that of a single LED driven through an equivalent series resistor. We discuss the microscopic origin of the deep squeezing on the basis of quantum-mechanical Langevin equations.

Measurements of zeta potentials of particulate biomaterials in protein-rich hyaluronan solution with changes in pH and protein constituents

This study was undertaken to determine the zeta potentials of particulate biomaterials in three types of protein-rich hyaluronan solution with changes in pH; a microelectrophoretic method was used. For the purpose of determining the pH value of synovial fluid in various inflammatory conditions, we collected synovial fluid samples from joints with osteoarthritis (OA), rheumatoid arthritis (RA), and those undergoing revisions arthroplasties. The mean values of the pH in the synovial fluid from joints with OA, RA, and revision arthroplasty were shown to be 7.9, 7.5, and 8.1, respectively. The pH-zeta potential curves obtained differed, depending on the biomaterial and the medium. Addition of gamma-globulin to the medium reduced the absolute value of the zeta potentials of some of the biomaterials. The findings of this study suggest that the electrophoretic behaviors of the particulate biomaterials tested in this study are affected by the protein constituents of and pH changes in protein-rich synovial fluid. The values we obtained will be useful as reference standards and will also aid in the study of the surface phenomena of biomaterials.

The EGF system in fetal development

Immunohistochemical localization of the epidermal growth factor receptor (EGFR) disclosed a wide distribution of this protein in diverse fetal tissues. This review focuses on some of the vast work on the expression and operation of the EGFR and its principal ligands in fetal organogenesis.

Laminin alpha1 chain G domain peptide, RKRLQVQLSIRT, inhibits epithelial branching morphogenesis of cultured embryonic mouse submandibular gland

Active sequences from the laminin alpha1 and alpha2 chain carboxyl-terminal globular domains (G domain) have been identified by screening overlapping synthetic peptides in a number of biological assays (Nomizu et al. [1995] J. Biol. Chem. 270:20583-20590; Nomizu et al. [1996] FEBS Lett. 396:37-42). We have tested the activity of these peptides in submandibular gland explants of embryonic day 13 mice to determine the functional sites involved in organ development. The laminin alpha1 chain peptide, RKRLQVQLSIRT (residues 2719-2730 and designated AG-73), significantly inhibited epithelial branching morphogenesis. In contrast, other cell adhesive laminin alpha1 chain peptides including the AASIKVAVSADR and NRWHSIYITRFG failed to inhibit the branching. MG-73, a homologue of AG-73 from the laminin alpha2 chain, did not inhibit the branching. The alpha2 chain peptide had no effect, which may be due to the low levels of this laminin chain in day 13 mice. Laminin alpha2 chain-specific monoclonal antibodies strongly reacted with the basement membranes of developed acini but only weakly stained embryonic day 13 submandibular epithelium. The expression of E-cadherin and alpha6 integrin, as detected by immunofluorescence, were unchanged in both AG-73 and control scramble peptide-treated epithelial cells of the explants. In contrast, immunostaining of nidogen/entactin showed that explants treated with AG-73 for 3 days had a discontinuous basement membrane. Explants treated for 3 days with control peptide showed a normal basement membrane. These results suggest that the region containing the AG-73 sequence of the laminin alpha1 chain is crucial for development of submandibular gland at early embryonic stages. The discontinuous basement membrane in AG-73-treated explants may indicate an important role for this region in basement membrane assembly.

Wear and osteolysis in total joint replacements

This presentation summarizes the results of our recent studies on the pathogenesis of osteolysis around total joint arthroplasties. First, interface tissues with adjacent bone were retrieved and histopathologically investigated with reference to the cells on the bone surface. Secondly, polyethylene particles were extracted with the tissue digestion method and characterized with scanning electron microscopy. Finally, an animal model for osteolysis was created and various interface conditions were compared concerning their resistance to particle migration. Histopathological examinations demonstrated that active bone formation, regarded as a repair process, was the commonest feature, even in revised cases. They also highlighted the role played by macrophages, not as cells producing inflammatory mediators which could activate osteoclasts, but as cells primarily responsible for the bone loss in osteolytic lesions. Among the particle species present, only polyethylene particles were shown to play a significant role in macrophage recruitment and subsequent osteolysis. A quantitative extraction of polyethylene particles showed a significant difference in the "number" of particles between osteolysis positive and negative cases whereas the "sizes" of particles were similar in these two groups. The critical number of particles for osteolysis was around 1 x 10(10) particles/g tissue and the cellular reaction against phagocytosable particles accumulated over this concentration may be the prerequisite for progression of osteolysis. The animal model for osteolysis indicated that the progression of osteolysis depends on the integrity of the bone-implant interface. We suggest that the solid fixation of the prosthesis performed by current techniques (e.g., improved cementing technique, hydroxyapatite coating) is beneficial for preventing particle migration and subsequent osteolysis.

CLINICAL RELEVANCE

Osteolysis induced by particulate wear debris from implant materials has been recognized as the major cause of long-term failure in total joint replacements. However, the development of preventive measures for this phenomenon has not been successful because the mechanism in which wear particles cause osteolysis is not quite clear. On the basis of results obtained in this study, we believe that the basic strategy for addressing the problem of osteolysis is to reduce the "number" of accumulated wear particles in the interface tissues. This could be achieved either by improving the materials or the geometry of the articulating counterface. Another possibility is to increase the integrity of the bone-implant interface to prevent particle migration. It is important to note that pre-clinical testing of materials and prosthetic designs should include an analysis of the characteristics of the particle generated (e.g., size and number). The widespread bone formation, even in revised cases, is encouraging in view of "conservative treatment" of aseptic loosening. Assuming that bone loss in aseptic loosening is not a remorseless process, some form of intervention, whether mechanical or pharmacological, might be possible to tip the balance more in favour of bone formation than resorption. A comprehensive understanding of the bone reactions in osteolysis, including the basic mechanisms of bone loss, shown in this study, are decisive for the development of preventive measures that may minimize the clinical impact of this phenomenon.

Expression of epidermal growth factor receptor in fetal mouse submandibular gland detected by a biotinyltyramide-based catalyzed signal amplification method

Branching morphogenesis of the fetal mouse submandibular gland (SMG) can be modulated in vitro by stimulation or inhibition of the epidermal growth factor receptor (EGFR). Because the mRNAs for EGF and EGFR are detectable in RNA of SMG rudiments isolated directly from fetuses, the EGF system probably operates physiologically as a regulator of SMG morphogenesis. However, neither EGFR protein nor its precise cellular localization has been characterized in the fetal SMG. Here we show EGFR protein in fetal mouse SMG by immunoprecipitation, affinity labeling, ligand-induced autophosphorylation, and immunohistochemistry. SMGs from E16 fetuses (day of vaginal plug = E0) were labeled with [35S]-cysteine/methionine and homogenized. After addition of specific antibody to EGFR, the immunoprecipitate was isolated, resolved by polyacrylamide gel electrophoresis, and detected by autoradiography. A single band of 170 kD was detected, corresponding to the EGFR protein. Affinity labeling with [125I]-EGF of the membrane fraction of E18 SMG also revealed a prominent band at 170 kD, showing that this EGFR protein can bind specifically to its ligand. Incubation of SMG membranes from E18 fetuses with EGF in the presence of [gamma-32P]-ATP, followed by immunoprecipitation with anti-phosphotyrosine antibody also showed a single band at 170 kD, demonstrating autophosphorylation of the EGFR in response to binding of its ligand. Immunohistochemical localization of the cellular sites of EGFR in the fetal SMG required use of a catalyzed signal amplification procedure, with biotinyltyramide as the amplifying agent. EGFR was localized predominantly, if not exclusively, in cell membranes of epithelial cells of the rudiment, whereas staining of mesenchymal cells was equivocal. Staining was strongest on duct cells, and weak on cells of the end-pieces. These findings clearly show that a functional EGFR protein is expressed in fetal SMG chiefly, if not exclusively, on epithelial cells.

Number of polyethylene particles and osteolysis in total joint replacements. A quantitative study using a tissue-digestion method

Our aim was to analyse the influence of the size, shape and number of particles on the pathogenesis of osteolysis. We obtained peri-implant tissues from 18 patients having revision surgery for aseptically loosened Freeman total knee replacements (10), Charnley total hip replacements (3) and Imperial College/London Hospital double-cup surface hip replacements (5). The size and shape of the polyethylene particles were characterised using SEM and their concentration was calculated. The results were analysed with reference to the presence of radiological osteolysis. The concentration of polyethylene particles in 6 areas with osteolysis was significantly higher than that in 12 areas without osteolysis. There were no significant differences between the size and shape of the particles in these two groups. We conclude that the most critical factor in the pathogenesis of osteolysis is the concentration of polyethylene particles accumulated in the tissue.

NUMBER OF POLYETHYLENE PARTICLES AND OSTEOLYSIS IN TOTAL JOINT REPLACEMENTS

Our aim was to analyse the influence of the size, shape and number of particles on the pathogenesis of osteolysis. We obtained peri-implant tissues from 18 patients having revision surgery for aseptically loosened Freeman total knee replacements (10), Charnley total hip replacements (3) and Imperial College/London Hospital double-cup surface hip replacements (5). The size and shape of the polyethylene particles were characterised using SEM and their concentration was calculated. The results were analysed with reference to the presence of radiological osteolysis.

The concentration of polyethylene particles in 6 areas with osteolysis was significantly higher than that in 12 areas without osteolysis. There were no significant differences between the size and shape of the particles in these two groups.

We conclude that the most critical factor in the pathogenesis of osteolysis is the concentration of polyethylene particles accumulated in the tissue.

Wear particulate species and bone loss in failed total joint arthroplasties

The aim of this study was to evaluate the relative contribution of polyethylene, metal, and polymethylmethacrylate (cement) particles to the overall bone loss in aseptic loosening. Twenty-four interface tissues with adjacent bone were obtained during 17 revision total joint arthroplasties (11 hips and six knees). Osteoclasts and macrophages were identified immunohistochemically on the bone surface. The length of the bone surface in contact with these cell types was measured and analyzed with reference to the particulate species present within the fibrous interface. The presence of abundant polyethylene particles significantly increased the proportion of the bone surface in contact with macrophages but did not have a significant influence on that of osteoclasts. Osteoclastic bone resorption was significantly more extensive in the presence of metal particles. In contrast, the presence of cement particles did not have a significant influence on macrophage or osteoclast coverage of the bone surface. These results highlight the significance of polyethylene particles in macrophage recruitment and subsequent osteolysis and suggest a different mechanism of bone loss related to metal, namely mediation through osteoclastic activities. The relative contribution of cement particles was negligible and needs reevaluation in light of evidence provided by others.

Nitric oxide synthase is expressed in human macrophages during foreign body inflammation

Although nitric oxide (NO) is a well documented effector molecule in rodent macrophages, its significance in human mononuclear phagocytic cells has been controversial. The foreign body inflammatory reaction around loosened joint replacement implants leads to formation of an osteolytic granulomatous pseudo-synovial membrane rich in activated macrophages. We studied 13 specimens of interface membrane tissue collected from revision surgery of aseptically loosened hip and knee prostheses for the presence of inducible NO synthase (iNOS). The presence of iNOS was demonstrated immunohistochemically in 10 of these specimens. Within the tissue this enzyme was confined to macrophages and vascular endothelial cells. iNOS activity was demonstrated biochemically by measuring the calcium-independent generation of citrulline from L-arginine, and the presence of iNOS mRNA was demonstrated using reverse transcriptase polymerase chain reaction. NO synthesis in the interface tissue may be an important factor in the maintenance of the inflammatory and osteolytic processes.

Importance of nidogen binding to laminin gamma1 for branching epithelial morphogenesis of the submandibular gland

Epithelial-mesenchymal interactions are major driving forces for the development of most solid organs. The importance of these interactions was first shown for the embryonic submandibular gland more than 40 years ago. We here present evidence that interactions between two basement membrane components, nidogen (entactin) and laminin gamma1 chain, could be important for epithelial-mesenchymal interactions in this gland. Nidogen mRNA was detected by in situ hybridization in the mesenchyme, and yet the protein was detected in epithelial and endothelial basement membranes. The role of nidogen-laminin interactions for epithelial morphogenesis was studied by applying antibodies to submandibular gland organ cultures. Antibodies reacting strongly with the nidogen-binding site of laminin gamma1 chain drastically perturbed branching epithelial morphogenesis. Electron microscopy of the epithelial-mesenchymal interface showed that blocking antibodies disrupted the formation of the basement membrane. Epidermal growth factor was shown to increase the expression of nidogen in mesenchyme, and could counteract the effect of the blocking antibodies. We suggest that nidogen could be an important mesenchymal factor for submandibular gland development.

Substructures of the acinar basement membrane of rat submandibular gland as shown by alcian blue staining and cryo-fixation followed by freeze-substitution

The ultrastructure of the epithelial basement membrane was studied in the acinar cells of adult rat submandibular glands after: (i) immersion fixation in 0.1 M sodium cacodylate buffer (CB, pH 7.2) containing 2.5% glutaraldehyde (GA) and alcian blue (0.5%) in conjunction with microwave irradiation, (ii) perfusion fixation with 2.5% GA in CB, (iii) rapid freezing followed by freeze-substitution (RF-FS) with 1% GA in acetone, and (iv) RF-FS with 2% OsO4 in acetone. The specimens were post-fixed with 1% OsO4 in CB after methods (i) and (ii) but not (iii) and (iv). Fixed specimens were embedded in epoxy resin and the ultrathin sections were cut, stained with both lead and uranium, and observed under a transmission electron microscope. Various substructural components could be seen in the acinar basement membrane. In the specimens processed by method (iv), a clear meshwork structure could be found just beneath the basal plasma membrane. This meshwork could not be seen in the specimens processed by method (iii) but thin filaments of approximately 100 nm in length extending from the epithelial base toward the connective tissue space were evident. By methods (i) and (ii), an electron dense 30-75 nm layer could be seen subjacent to basal cell membranes. By method (ii), particularly, thick threads connecting this layer to collagen fibres in the connective tissue were stained with alcian blue. Lamina lucida was not identified.