Systematic investigation of metallosis associated with magnetically controlled growing rod implantation for early-onset scoliosis

AIMS

To investigate metallosis in patients with magnetically controlled growing rods (MCGRs) and characterize the metal particle profile of the tissues surrounding the rod.

METHODS

This was a prospective observational study of patients with early onset scoliosis (EOS) treated with MCGRs and undergoing rod exchange who were consecutively recruited between February 2019 and January 2020. Ten patients were recruited (mean age 12 years (SD 1.3); 2 M:8 F). The configurations of the MCGR were studied to reveal the distraction mechanisms, with crucial rod parts being the distractable piston rod and the magnetically driven rotor inside the barrel of the MCGR. Metal-on-metal contact in the form of ring-like wear marks on the piston was found on the distracted portion of the piston immediately outside the barrel opening (BO) through which the piston rod distracts. Biopsies of paraspinal muscles and control tissue samples were taken over and away from the wear marks, respectively. Spectral analyses of the rod alloy and biopsies were performed to reveal the metal constituents and concentrations. Histological analyses of the biopsies were performed with haematoxylin and eosin staining.

RESULTS

Titanium (Ti), vanadium (V), and neodymium (Nd) concentrations in the biopsies taken near the wear marks were found to be significantly higher than those in the control tissue samples. Significantly increased Nd concentrations were also found in the tissues near the barrel of the MCGR. Chronic inflammation was revealed by the histological studies with fibrosis and macrophage infiltration. Black particles were present within the macrophages in the fibrotic tissues.

CONCLUSION

Ti and V were generated mainly at the BO due to metal-on-metal contact, whereas the Nd from the rotor of the MCGR is likely released from the BO during distraction sessions. Phagocytotic immune cells with black particles inside raise concern regarding the long-term implications of metallosis. Cite this article: Bone Joint J 2020;102-B(10):1375-1383.

Rapid manufacturing techniques in the development of an axial blood pump impeller

This paper presents a comparison of manufacturing techniques used in the development of an axial blood pump impeller. In this development process the impeller was designed and its performance was evaluated with the aid of computational fluid dynamics (CFD). Prototypes of those designs where the CFD results show promise were needed in sufficient quantities at a low cost for experimental validation of the CFD results. As the impeller is less than 16 mm in diameter with a maximum blade thickness of about 1.5 mm, innovative manufacturing techniques are explored in this paper to determine the best process for quick fabrication of prototypes that are dimensionally accurate, structurally robust and low in cost. Four rapid prototyping techniques were explored. The completed parts were compared on the basis of manufacturing time, quality and strength of parts obtained, manufacturing cost and also in vitro performances. Based on these studies, it was concluded that selective laser sintering (SLS) is the most appropriate method for the quick production of prototype parts for evaluation of pump performance.

An alternative to a randomised control design for assessing the efficacy and effectiveness of bracing in adolescent idiopathic scoliosis

Randomised controlled trials (RCTs) that assessed the efficacy of bracing for adolescent idiopathic scoliosis have suffered from small sample sizes, low compliance and lack of willingness to participate. The aim of this study was to assess the feasibility of a comprehensive cohort study for evaluating both the efficacy and the effectiveness of bracing in patients with adolescent idiopathic scoliosis. Patients with curves at greater risk of progression were invited to join a randomised controlled trial. Those who declined were given the option to remain in the study and to choose whether they wished to be braced or observed. Of 87 eligible patients (5 boys and 63 girls) identified over one year, 68 (78%) with mean age of 12.5 years (10 to 15) consented to participate, with a mean follow-up of 168 weeks (0 to 290). Of these, 19 (28%) accepted randomisation. Of those who declined randomisation, 18 (37%) chose a brace. Patients who were more satisfied with their image were more likely to choose bracing (Odds Ratio 4.1; 95% confidence interval 1.1 to 15.0; p = 0.035). This comprehensive cohort study design facilitates the assessment of both efficacy and effectiveness of bracing in patients with adolescent idiopathic scoliosis, which is not feasible in a conventional randomised controlled trial.

The effect of excision of the posterior arch of C1 on C1/C2 fusion using transarticular screws

Transarticular screw fixation with autograft is an established procedure for the surgical treatment of atlantoaxial instability. Removal of the posterior arch of C1 may affect the rate of fusion. This study assessed the rate of atlantoaxial fusion using transarticular screws with or without removal of the posterior arch of C1. We reviewed 30 consecutive patients who underwent atlantoaxial fusion with a minimum follow-up of two years. In 25 patients (group A) the posterior arch of C1 was not excised (group A) and in five it was (group B). Fusion was assessed on static and dynamic radiographs. In selected patients CT imaging was also used to assess fusion and the position of the screws. There were 15 men and 15 women with a mean age of 51.2 years (23 to 77) and a mean follow-up of 7.7 years (2 to 11.6). Stable union with a solid fusion or a stable fibrous union was achieved in 29 patients (97%). In Group A, 20 patients (80%) achieved a solid fusion, four (16%) a stable fibrous union and one (4%) a nonunion. In Group B, stable union was achieved in all patients, three having a solid fusion and two a stable fibrous union. There was no statistically significant difference between the status of fusion in the two groups. Complications were noted in 12 patients (40%); these were mainly related to the screws, and included malpositioning and breakage. The presence of an intact or removed posterior arch of C1 did not affect the rate of fusion in patients with atlantoaxial instability undergoing C1/C2 fusion using transarticular screws and autograft.

Replication study of SNP associations for colorectal cancer in Hong Kong Chinese

BACKGROUND

Recent genome-wide association studies of colorectal cancer (CRC) have identified common single-nucleotide polymorphisms (SNPs) mapping to 10 independent loci that confer modest increased risk. These studies have been conducted in European populations and it is unclear whether these observations generalise to populations with different ethnicities and rates of CRC.

METHODS

An association study was performed on 892 CRC cases and 890 controls recruited from the Hong Kong Chinese population, genotyping 32 SNPs, which were either associated with CRC in previous studies or are in close proximity to previously reported risk SNPs.

RESULTS

Twelve of the SNPs showed evidence of an association. The strongest associations were provided by rs10795668 on 10p14, rs4779584 on 15q14 and rs12953717 on 18q21.2. There was significant linear association between CRC risk and the number of independent risk variants possessed by an individual (P=2.29 × 10(-5)).

CONCLUSION

These results indicate that some previously reported SNP associations also impact on CRC risk in the Chinese population. Possible reasons for failure of replication for some loci include inadequate study power, differences in allele frequency, linkage disequilibrium structure or effect size between populations. Our results suggest that many associations for CRC are likely to generalise across populations.

Case report: Spinal anesthesia by mini-laminotomy for a patient with ankylosing spondylitis who was difficult to anesthetize

BACKGROUND

Orthopaedic surgeons frequently encounter patients with ankylosing spondylitis who would benefit from various types of lower limb operations; however, some of these patients present challenges for anesthesiologists.

CASE DESCRIPTION

We report the case of a 65-year-old patient with a fractured femoral component 30 years after a cemented THA. The patient had severe tracheal stenosis and ankylosing spondylitis making general endotracheal and conventional neuraxial anesthesia nearly impossible.

LITERATURE REVIEW

Possible alternative anesthetic approaches described in the literature include awake fiberoptic bronchoscopic guided intubation, laryngeal mask airway, and caudal anesthesia.

PURPOSES AND CLINICAL RELEVANCE

We achieved successful anesthesia using spinal laminotomy with the patient under local anesthesia followed by insertion of a spinal catheter and injection of an anesthetic agent. The loosened component was revised to a cementless THA.

Permanent deficits in brain functions caused by long-term ketamine treatment in mice

Ketamine, an injectable anesthetic, is also a popular recreational drug used by young adults worldwide. Ketamine is a non-competitive antagonist of N-methyl-d-aspartate receptor, which plays important roles in synaptic plasticity and neuronal learning. Most previous studies have examined the immediate and short-term effects of ketamine, which include learning and cognitive deficits plus impairment of working memory, whereas little is known about the long-term effects of repeated ketamine injections of common or usual recreational doses. Therefore, we aimed to evaluate the deficits in brain functions with behavioral tests, including wire hang, hot plate and water maze tests, plus examine prefrontal cortex apoptotic markers, including Bax, Bcl-2 and caspase-3, in mice treated with 6 months of daily ketamine administration. In our study, following 6 months of ketamine injection, mice showed significant deterioration in neuromuscular strength and nociception 4 hours post-dose, but learning and working memory were not affected nor was there significant apoptosis in the prefrontal cortex. Our research revealed the important clinical finding that long-term ketamine abuse with usual recreational doses can detrimentally affect neuromuscular strength and nociception as part of measurable, stable and persistent deficits in brain function.

Genital verrucous carcinoma is associated with lichen sclerosus: a retrospective study and review of the literature

BACKGROUND

The association of lichen sclerosus (LS) with genital squamous cell carcinoma is well recognized. However, the relationship between LS and verrucous carcinoma remains unclear.

OBJECTIVE

To evaluate the associations of genital and perianal verrucous carcinomas with LS.

METHODS

We conducted a retrospective study on patients with a genital or perianal verrucous carcinoma and reviewed their histopathology specimens and clinical notes. We also conducted a literature review.

RESULTS

We identified a total of 13 patients (including 6 women and 7 men) with a genital or perianal verrucous carcinoma. All 5 women with vulval verrucous carcinoma had coexisting LS (5/5), and 1 man with penile verrucous carcinoma had coexisting LS (1/3). In contrast, no coexisting LS was found in all 5 cases of perianal verrucous carcinoma (0/5). Half of the cases of verrucous carcinoma with coexisting LS had recurrences (3/6), while no recurrences were found in those without coexisting LS (0/7).

CONCLUSIONS

Our study and review of the literature demonstrate that vulval verrucous carcinoma is strongly associated with LS. In contrast, perianal verrucous carcinoma is not associated with LS. When genital verrucous carcinoma is diagnosed, it is important to consider LS as a potential concomitant diagnosis and offer appropriate treatments and close follow-up to detect recurrence of verrucous carcinoma.

A study on the influence of breathing phases in intensity-modulated radiotherapy of lung tumours using four-dimensional CT

During gated intensity-modulated radiotherapy (IMRT) treatment for patients with inoperable non-small cell lung cancer (NSCLC), the end-expiration (EE) phase of respiratory is more stable, whereas end-inspiration (EI) spares more normal lung tissue. This study compared the relative plan quality based on dosimetric and biological indices of the planning target volume (PTV) and organs at risk (OARs) between EI and EE in gated IMRT. 16 Stage I NSCLC patients, who were scanned by four-dimensional CT, were recruited and re-planned. An IMRT plan of a prescription dose of 60 Gy per respiratory phase was computed using the iPlan treatment planning system. The heart, spinal cord, both lungs and PTV were outlined. The tumour control probability for the PTV and normal tissue complication probability for all OARs in the EE and EI phases were nearly the same; only the normal tissue complication probability of the heart in EE was slightly lower. Conversely, the conformation number of the PTV, V20 of the left lung, V30 of both lungs, Dmax of the heart and spinal cord, V10 of the heart and D5% of the spinal cord were better in EE, whereas D(mean) of the PTV, V20 of the right lung and maximum doses of both lungs were better in EI. No differences reached statistical significance (p<0.05) except Dmax of the spinal cord (p=0.033). Overall, there was no expected clinical impact between EI and EE in the study. However, based on the practicality factor, EI is recommended for patients who can perform breath-hold; otherwise, EE is recommended.

Spinal cord compression secondary to brown tumour in a patient on long-term haemodialysis: a case report

Brown tumours may occur secondary to hyperparathyroidism in patients with chronic renal failure (CRF). Diagnosing a spinal brown tumour causing cord compression requires a high index of suspicion. We report a 65-year-old woman, who had been on haemodialysis for CRF for over 10 years, who presented with leg weakness and back pain over the thoracolumbar junction. She had a brown tumour at T8 causing subacute spinal cord compression. Ambulation was regained after surgical decompression and stabilisation. Adherence to the National Kidney Foundation guidelines in the management of patients with CRF may prevent renal osteodystrophy. Treatment of spinal brown tumour depends on the severity of the neurological deficit. Remineralization is expected after correction of the parathyroid level, thus negating the need for total excision of the parathyroid glands.

Right hip adduction deficit and adolescent idiopathic scoliosis

PURPOSE

To determine whether right hip adduction deficit is associated with adolescent idiopathic scoliosis.

METHODS

102 adolescents (mean age, 14 years) with idiopathic scoliosis were prospectively studied. Their spinal curve pattern (according to Lenke's classification), curve severity (by Cobb's angle), and hip adduction ranges of both sides were recorded. Additional factors that may affect hip adduction range including the preferred leg during standing, the presence of hip flexor tightness, and the side of the dominant leg were also assessed.

RESULTS

The mean Cobb's angle was 27 degrees. The difference in hip adduction range between the right and left hips was 5 degrees (p<0.05). Of 102 patients, 64 had an adduction range deficit of the right hip, 4 of the left hip, and 34 had no difference. Patients with >10 degrees of right hip adduction deficit were associated with a higher proportion of left leg dominance than those with less than or equal to 10 degrees of right hip adduction deficit (18% vs 4%).

CONCLUSION

Left leg dominance may play a role in right hip adduction deficit and scoliosis.

Direct internal kyphectomy for severe angular tuberculous kyphosis

We describe a direct internal kyphectomy through a modified costotransversectomy, an extrapleural approach to the kyphus that does not jeopardize already compromised pulmonary function. A curved longitudinal incision is made 6 to 8 cm lateral to the midline. The posterior 5 cm of the two to three crowded ribs at the apex are resected. The segmental intercostal nerves are preserved as a guide into the spinal canal. Two to three pedicles at the apex are resected. The pleura are elevated with blunt dissection leading to the internal kyphus. Removal of the posterior half of the collapsed vertebrae is performed with a high-speed burr; the posterior walls are removed last to avoid forward migration of the dural sac as the decompression progresses. Cortical strut grafting is then performed as far anteriorly as the exposure permits. We treated five patients with paraparesis of healed disease with this approach. Preoperatively the mean kyphosis was 114 degrees. Neurological improvement was obtained in two patients. At a mean followup of 5 years, solid anterior fusion was achieved in four patients. One patient died 5 months after surgery because of chest infection.

Three-dimensional dynamical measurement of upper limb support during paraplegic walking

Functional electrical stimulation (FES) has been employed in paraplegic rehabilitation to resume their walking ability. However, there is less quantitative assessment method of FES walking efficiency and rehabilitation progress. This paper presents a new dynamical measurement of upper limb support force during paraplegic walking, which can be used to calculate the 3-D handle reaction vector (HRV). HRV may provide an assessment of FES-assisted efficiency. With a series of tests, the measurement accuracy, nonlinearity, and crosstalk of the designed system are testified. The force measurement error is found below 1.01%, while nonlinearity and crosstalk are less than 2.90%, and 3.19%, respectively. This means that the implemented walker system is reliable for the measurement of HRV during FES-assisted walking. A clinical trial is performed with a paraplegic subject. With the monitoring of FES-assisted walking, the downward component of HRV is found to decrease, implying the decreasing force generated from lower limb. The decrease slope in downward load curve can indirectly indicate the FES efficiency change during walking. The experiment and clinical trial results show that a 3-D dynamical measurement system is successfully accomplished to indirectly assess FES efficiency of lower limbs using quantitated forces applied by the upper limbs of paraplegic patients.

Expression of insulin-like growth factor binding protein-3 in pterygium tissue

BACKGROUND

Pterygium is a fibrovascular overgrowth from the conjunctiva onto the cornea. The pathogenesis of this common ocular surface disorder is not well understood and the only treatment is surgical removal.

METHODS

DNA microarray analysis of primary pterygium tissue was carried out using uninvolved conjunctiva tissue as a comparison for gene expression levels. Real time polymerase chain reaction (PCR) was used to verify the mRNA level of expression for genes changed in pterygium. Western blot analysis and immunohistochemistry showed protein expression levels and the tissue distribution.

RESULTS

Microarray analysis revealed that mRNA levels of a number of genes were changed in primary pterygium. In particular the gene for insulin-like growth factor binding protein-3, (IGFBP3), which modulates the effects of insulin-like growth factor on cells was significantly decreased. Both the message and protein expression of IGFBP3 in pterygium were decreased compared to normal, uninvolved conjunctiva.

CONCLUSION

Decreased levels of IGFBP3 protein have been strongly correlated with the presence of cancer. Identification of the low level of expression of IGFBP3 in pterygium suggests that the pathway controlling cell proliferation has lost an important control mechanism, which may explain the continued growth of pterygium.

Effect of segmental artery ligation on the blood supply of the thoracic spinal cord during anterior spinal surgery: a quantitative histomorphological fresh cadaver study

STUDY DESIGN

Human cadaver quantitative morphometric analysis of the blood vessels in the spinal cord after ligation of segmental arteries.

OBJECTIVES

To investigate the effect of ligation of segmental arteries on the quantity and density of the blood vessels in the spinal cord.

SUMMARY OF BACKGROUND DATA

Ligation of segmental arteries is often used in the anterior approach for correction scoliosis. However, whether or not segmental artery ligation is liable to deny the spinal cord an adequate blood supply, thus leading to paraplegia, still remains controversial.

METHODS

Eleven fresh cadavers were divided into control, unilateral, and bilateral groups. For the unilateral and bilateral groups, 5 segmental vertebral arteries (T7-T11) were ligated unilaterally and bilaterally, respectively. Then, the number and density of blood vessels at different levels in the 3 groups were measured.

RESULTS

Compared to that of the corresponding level in the control group, the number of blood vessels at T5 to L1 all decreased in the ligation groups. And significant differences were found at T8 (82.80 +/- 16.36), T10 (77.80 +/- 19.80), and T11 (99.20 +/- 14.85) levels, compared to those of the corresponding levels in the control group: T8 (175.80 +/- 8. 31), T9 (176.40 +/- 32. 33), T10 (171.40 +/- 9. 73), and T11 (189.20 +/- 15. 92). Further decrease was found at each corresponding level in the bilateral group, and significant differences were found at T8 (65.80 +/- 15.55), T9 (24.80 +/- 13.43), T10 (0), T11 (0), and T12 (0) levels. Similar results were obtained with regard to the density of blood vessels. Significant differences were found at T11 (1.246 +/- 0.112) and L1 (1.349 +/- 0.109) in the unilateral group, and T9 (0.260 +/- 0.088), T10 (0), T11 (0), T12 (0), and L1 (0.147 +/- 0.117) in the bilateral group compared to those of the corresponding levels in the control group: T9 (1.810 +/- 0.202), T10 (1.833 +/- 0.175), T11 (2.308 +/- 0.335), T12 (2.510 +/- 0.617), and L1 (2.193 +/- 0.033).

CONCLUSIONS

This study suggests that the more levels the ligation encompasses, the higher the risk of spinal cord damage. Therefore, caution should be taken when several segmental arteries are to be ligated in the clinical setting. What is more, bilateral ligation, which is worse than unilateral ligation, can lead to a significant decrease in the number and density of blood vessels of the spinal.

A prospective comparison of the coronal deformity correction in thoracic scoliosis using four different instrumentations and the fulcrum-bending radiograph

STUDY DESIGN

A prospective study on comparing coronal deformity correction in thoracic scoliosis using four different instrumentations.

OBJECTIVES

To compare the ability of four different instrumentation systems in correcting thoracic scoliosis based on the curve flexibility as reviewed by the fulcrum-bending radiograph.

SUMMARY OF BACKGROUND DATA

The fulcrum-bending radiograph has been shown to be able to accurately reflect the flexibility of thoracic curves, and the fulcrum bending correction index (FBCI) predicts the amount of correction achieved by current surgical techniques. By recruiting curves of known flexibility, the efficacy of the different instrumentations in correcting coronal deformity can be truly compared.

METHODS

A consecutive series of 127 patients with idiopathic scoliosis were treated by one of four implants: CD-Horizon (CD-H), Moss Miami (MM), TSRH, and ISOLA. All surgeries were performed by the same group of surgeons using the respective recommended techniques. FBCI was used to compare the correction achieved by these implants.

RESULTS

The mean FBCI/correction rate was 101.0%/57.9% in the TSRH group, 103.5%/58.5% in ISOLA, 109.1%/67.6% in CD-H, and 100.2%/62.7% in the MM group. The correction rate was significantly (P < 0.05) higher in the CD-H group than those in the TSRH and ISOLA groups, while the differences in the FBCI between the four implants were not statistically significant.

CONCLUSIONS

When curve flexibility is taken into account, despite differences in material and design of four commonly used instrumentations, their ability to correct thoracic scoliosis is the same. Future studies describing surgical correction results should be based on the FBCI.

Pyoderma gangrenosum in a thoracotomy wound associated with a pulmonary cavitating lesion

We present a patient with both pyoderma gangrenosum in a thoracotomy wound and a pulmonary cavitating lesion with the histological features of Wegener's granulomatosis. An ulcer with blue undermined edges developed in our patient's thoracotomy scar after a lobectomy was carried out for the cavitating lung lesion and c Antineutrophil Cytoplasmic Antibodies (cANCA), which is highly specific for active Wegener's granulomatosis but was negative at the time of her skin lesion. This suggests that our patient had cutaneous pyoderma gangrenosum rather than cutaneous Wegener's granulomatosis, although the two conditions may occasionally have similar clinical and histological features.

Isokinetic and isometric lifting capacity of Chinese in relation to the physical demand of job

The aim of the study was to formulate normative data for the lifting capacities of a normal Chinese population, in order to establish a basic foundation for further studies and to investigate the relationship between individual attributes including age, gender, height, weight, job physical demand and each type of lifting capacity. Isokinetic and isometric lifting strength at low, waist and shoulder assessment levels were measured using the LIDO Workset II based on a sample of 93 normal Chinese adults (63 men and 30 women) between the ages of 21-51. The 50th percentile score for adult Chinese female's lifting strength was 17.71% lower than the American female while the adult Chinese male's lifting strength was 14.94% lower than the American male. Lifting forces were higher in the 20-40 year age group. The isometric work mode had considerable impact on the lifting capacities, with shoulder level having the highest lifting capacities. The gender and body weight had a significant positive correlation to lifting capacity while job physical demand had a moderate correlation. Age and body heights were weakly correlated to lifting capacity.

Numerical investigation of the effect of blade geometry on blood trauma in a centrifugal blood pump

Fluid dynamic forces in centrifugal blood pump impellers are of key importance in destruction of red blood cells (RBCs) because high rotational speed leads to strong interaction between the impeller and the RBCs. In this paper, three-dimensional models of five different blade geometries are investigated numerically using the commercial software CFX-TASCflow, and the streaklines of RBCs are obtained using the Lagrangian particle tracking method. In reality, RBCs pass through the pump along complicated paths resulting in a highly irregular loading condition for each RBC. In order to enable the prediction of blood damage under the action of these complex-loading conditions, a cumulative damage model for RBCs was adopted in this paper. The numerically simulated percent hemoglobin (%HB) released as RBCs traversed the impeller and volute was examined. It was observed that the residence time of particles in the blade passage is a critical factor in determining hemolytic effects. This, in turn, is a function of the blade geometry. In addition, it was observed that the volute profile is an important influence on the computed HB% released.

A computational study of the effects of inlet guide vanes on the performance of a centrifugal blood pump

This article presents computational studies on the effects of inlet guide vanes (IGVs) on the flow pattern and shear stress in a centrifugal blood pump. The effect of IGVs is to introduce a pre-swirl to fluid particles entering the impeller with the intention that the fluid particles will travel along the blade profile. Currently, most commercial centrifugal blood pumps employ straight radial impeller blades that are not hydrodynamically ideal for a good flow pattern within the blade passage. Flow separation and formation of vortices within the blade passage are believed to increase the degree of hemolysis and thrombosis. These are causes for blood clotting that will lead to malfunctioning of ventricular assist devices. Four IGVs of different geometrical profiles have been numerically investigated using a commercial software program CFX-Tascflow. The pump is operated at 2,000 rpm, and the results revealed that the relative flow patterns in the blade passage have been dramatically altered. The size of the vortices was reduced, and the pressure contours indicated a gradual rise from the impeller leading edge to the trailing edge. However, inclusion of IGV causes a drop in the pressure head generated. Higher frictional losses are incurred as fluid particles passed through the IGV. In addition, the IGV modifies the inlet velocity triangles, and this also contributes to a drop in the pressure head generated that is consistent with Euler's pump theory. The change in the flow patterns and the gradual variation of the pressure contours have led to lower shear stress within the blade passages as compared to the case without IGVs.

Lichen sclerosus. A review

Lichen sclerosus is a chronic inflammatory skin condition that can cause substantial physical and psychological morbidity. It most commonly affects women in the anogenital region, but may affect any area of skin in either sex at any age. Not only does it cause itching and soreness, but also urinary and sexual problems. There is an increased risk of developing squamous cell carcinoma in the genital area in both female and male sufferers, thus long term follow-up may be justified. The aetiology of Lichen sclerosus is unknown but genetic factors play a role, and chronic infection had been postulated but not proven. The association with autoimmune disease is also well recognized. The mainstay of treatment for genital lichen sclerosus is potent topical steroid. Surgery may be required only to relieve the effect of scarring. Current research to understand the pathogenesis of disease may allow us to target specific intervention in the future.

Quantification of mouse glial cell-line derived neurotrophic factor family receptor alpha 2 alternatively spliced isoforms by real time detection PCR using SYBR Green I

Neurturin (NTN) belongs to the glial cell-line derived neurotrophic factor (GDNF) family of growth factors. Both NTN and GDNF have been shown to potently prevent the degeneration of dopaminergic neuron in vitro and in vivo. The GDNF family receptor alpha 2 (GFR alpha-2) is the preferred receptor for NTN. In addition to the known full-length isoform (GFR alpha-2a), we have previously reported the isolation of two novel alternatively spliced isoforms (GFR alpha-2b and GFR alpha-2c). All three isoforms are expressed in all mammalian tissues examined, including human fetal brain. However, the expression levels of these isoforms have yet to be quantified. In this report, we have developed a real time polymerase chain reaction (PCR) detection method using SYBR Green I to detect the expression levels of the three splice variants (GFR alpha-2a, GFR alpha-2b and GFR alpha-2c). Of the three isoforms, GFR alpha-2a was found to be the most abundant receptor expressed in the whole murine brain. The real time PCR detection method using SYBR Green I developed in this report can be used to unambiguously quantitate expression levels of the GFR alpha-2 isoforms and can be extended to the quantitation of other alternatively spliced isoforms.

Effect of stimulation parameters on intraoperative spinal cord evoked potential monitoring

The purpose of this study was to investigate the effects of the stimulus parameters on spinal cord evoked potential (SCEP) and to recommend a practical epidural stimulation protocol for intraoperative spinal cord monitoring. This prospective study compared the latencies and amplitudes of SCEP obtained on epidural stimulation of 30 patients with scoliosis under anesthesia using different stimulus pulse duration and stimulation rates. SCEP was found to be undetectable with shorter stimulus duration (<0.05 ms). The SCEP latencies did not show any significant difference among different stimulation parameters. However, the SCEP amplitude showed significant changes with differing stimulus durations. The SCEP amplitudes were found to significantly decrease when the pulse durations become shorter than 0.2 ms. Stimulus parameters showed significant effects on SCEP amplitude but not latency. Stimulus rates in the range of 21 to 61 Hz are equivalent for quick and reliable detection of SCEP. Considering the short latency of SCEP, a pulse duration of 0.2 ms is recommended for SCEP using epidural stimulation.

Evaluation of various evoked potential techniques for spinal cord monitoring during scoliosis surgery

STUDY DESIGN

This prospective study compared the outcomes of different evoked potential (EP) techniques for intraoperative spinal cord monitoring.

OBJECTIVES

To evaluate the reliability of different EP techniques administered during scoliosis surgery.

SUMMARY OF BACKGROUND DATA

A number of different methods of intraoperative spinal cord monitoring are available. Because each has its own advantages and limitations, multimodal spinal cord monitoring has been proposed to improve monitoring reliability.

MATERIALS AND METHODS

Cortical somatosensory-evoked potential (CSEP), cortical motor-evoked potential (CMEP), spinal somatosensory-evoked potential (SSEP), and spinal cord-evoked potential (SCEP) were applied simultaneously to 30 patients undergoing surgical correction for spinal deformity. The presence of the EP waveforms and their reproducibilities over separate tests were compared. In addition, the monitoring outcomes were evaluated with the clinical results.

RESULTS

Of the 30 patients, CSEP waveforms were successfully recorded in 28 cases (93%), SCEP in 25 cases (83%), CMEP in 24 cases (80%), and SSEP in 21 cases (70%). Latencies of each EP technique showed no significant variability. However, amplitudes showed significant differences between different techniques. SCEP and CMEP showed clearer waveforms of greater amplitude that could be detected faster than CSEP and SSEP waveforms. SCEP and SSEP waveforms were more easily influenced by the surgical procedure.

CONCLUSION

CSEP and CMEP are recommended for routine monitoring, so that both ascending and descending tracts are monitored. If adequate signals for either of these proposed monitoring methods cannot be easily obtained, SSEP can substitute for CSEP, whereas SCEP can substitute for CMEP.

Back muscle contraction patterns of patients with low back pain before and after rehabilitation treatment: an electromyographic evaluation

The aims of this study were to conduct a comparative investigation of muscle function between patients with low back pain (LBP) and healthy persons, and to determine whether intensive rehabilitation can change back muscle contraction synergy. Twenty healthy persons and 20 patients with chronic LBP were asked to perform symmetrical and asymmetric tasks. The patients with LBP were tested in the weeks immediately before and after 12 weeks of LBP rehabilitation. Tasks include "carrying" weights up and down and with a 45 degrees left rotation. Eight-channel surface electromyographic electrodes were placed on the surface of paraspinal muscles over the lumbar region. Correlations between the right and left corresponding muscles and between values before and after treatment were determined. Lifting capacity for patients with LBP were also measured before and after treatment. Results from electromyographic profiles showed that the muscle activity strategies varied between healthy persons and patients with LBP. The correlation coefficients for spinal muscles have shown very reproducible intrasubject muscle contraction synergies. Unbalanced electromyographic patterns found in patients with LBP given symmetrical tasks were not affected by rehabilitation treatment.

Effect of stimulus pulse duration on intraoperative somatosensory evoked potential (SEP) monitoring

The effect of the stimulus duration on the amplitude and latency of intraoperative somatosensory evoked potential (SEP) was studied in 30 patients with idiopathic scoliosis undergoing surgery. Constant current square-wave electrical stimulation was applied to the posterior tibial nerve at a rate of 5.1 Hz. The effects of both the pulse duration and the stimulus current density on the intraoperative SEP were evaluated. Amplitudes and latencies of SEP were analyzed by one-way parametric analysis of variance. SEP signal recording was found to be difficult if the stimulus duration was less than 0.05 ms. The stimulus duration had no significant effect on the latencies of the SEP, but the amplitude of the SEP showed significant changes with differing stimulus durations. The SEP amplitudes were found with significant increases in pulse durations less than 0.3 ms. Stimulus pulse duration has a significant effect on SEP amplitude, and this should be taken into consideration during intraoperative SEP monitoring. A pulse duration of 0.3 ms is recommended for SEP using posterior tibial nerve stimulation.

The effects of concomitant phenytoin administration on the steady-state pharmacokinetics of quetiapine

Quetiapine fumarate ('Seroquel') is a newly introduced atypical antipsychotic with demonstrated efficacy in the treatment of positive and negative symptoms of schizophrenia. It is extensively metabolized, predominantly by cytochrome P450 3A4. Therefore, concurrent administration of drugs that induce or inhibit this enzyme may affect quetiapine pharmacokinetics. This study demonstrated that the potent cytochrome P450 enzyme-inducer phenytoin did indeed have a marked effect on the metabolism of quetiapine, resulting in a 5-fold increase in clearance when administered concomitantly to patients with DSM-IV-diagnosed schizophrenia, schizoaffective disorder, or bipolar disorder. These results indicate that dosage adjustment of quetiapine may be necessary when the two drugs are given concurrently and that caution may be required when administering other drugs that inhibit or induce cytochromes, particularly P450 3A4.

Single-dose pharmacokinetics of quetiapine in subjects with renal or hepatic impairment

1. The atypical antipsychotic quetiapine ('Seroquel') provides equivalent efficacy to the typical antipsychotics chlorpromazine and haloperidol in the short-term treatment of schizophrenia. Moreover, the incidence of extrapyramidal symptoms associated with quetiapine treatment is equivalent to that observed with placebo treatment, which may lead to increased patient compliance with quetiapine compared with typical antipsychotics. 2. This report presents the results from two small studies aimed at determining the pharmacokinetics of quetiapine in nonpsychotic subjects with renal or hepatic impairment. Equal numbers of impaired subjects and healthy control subjects were administered a single, 25 mg dose of quetiapine, and plasma concentrations were determined up to 48 hr after dosing. 3. No clinically significant differences were found when the pharmacokinetic parameters for subjects with renal or hepatic impairment were compared with those for healthy control subjects. The results indicate that dosage adjustment of quetiapine may be unnecessary in psychotic patients with decreased renal function. 4. In subjects with hepatic impairment related to alcoholic cirrhosis, the results suggest that no change is needed in the recommended quetiapine starting dose (25 mg). However, because of a noted inter-subject variability in the clearance of quetiapine in the cirrhotic group, it is recommended that dose escalation be performed with caution in patients with hepatic impairment. 5. The single dose of quetiapine 25 mg generally was well tolerated in nonpsychotic subjects in good health or with either renal or hepatic impairments. Quetiapine also had no effect on the endogenous creatinine clearance of renally impaired or healthy control subjects.

Variability of somatosensory-evoked potentials in different stages of scoliosis surgery

STUDY DESIGN

A comparison of the latencies and amplitudes of the somatosensory-evoked potential in different stages of scoliosis surgery.

OBJECTIVES

To investigate the normal variability of the somatosensory-evoked potential at different stages of scoliosis surgery and to improve the reliability of spinal cord monitoring.

SUMMARY OF BACKGROUND DATA

False alarms in intra-operative spinal cord monitoring have been reported when the somatosensory-evoked potential measured before skin incision was used as the reference baseline value. However, the normal variability during different stages of surgery and the specificity of somatosensory-evoked potential is not well documented.

METHODS

The somatosensory-evoked potential of 90 patients who underwent surgical correction for idiopathic scoliosis was monitored intraoperatively, with stimuli applied to the posterior tibial nerve. The amplitudes and latencies of the somatosensory-evoked potential were recorded over Cz'-Fz and Cv-Fz. The values of latencies and amplitudes and their percentage variabilities were analyzed.

RESULTS

The values of latencies and their percentage variabilities did not differ significantly from each other in different stages of surgery. The values of amplitudes between different stages showed statistically significant differences. In particular, the amplitude of the somatosensory-evoked potential was found to be significantly decreased after exposure of the spine when compared with the amplitude before skin incision.

CONCLUSION

Some variability in latencies and amplitudes between different stages of scoliosis surgery is normal. These results suggest that the somatosensory-evoked potential when the spine is exposed may be used as the reference baseline to determine whether somatosensory-evoked potentials are subnormal at the subsequent stages of surgery.

Understanding the influence of temperature change and cosolvent addition on conversion rate of enzymatic suspension reactions based on regime analysis

It is a commonly held belief that enzymatic conversions of substrate in aqueous suspensions can be speeded up by raising the temperature or adding organic solvents to promote dissolution of the substrate. To quantify the impact of such changes, we studied the alpha-chymotrypsin-catalyzed hydrolysis of dimethyl benzylmethylmalonate as a model system. It was found that, upon addition of organic cosolvents, longer process times were actually required, even though the substrate solubility increased severalfold as expected. Upon raising the temperature from 25 degrees C to 37 degrees C, on the other hand, both the substrate solubility, the substrate dissolution rate, and the enzymatic reaction rate increased, leading to shorter process times. A dissolution-reaction model incorporating the kinetics of enzyme deactivation could be developed. A simple relation for the prediction of the overall process time was established by evaluating the time constants for the subprocesses: substrate dissolution; enzymatic conversion; and enzyme deactivation. Using regime analysis, rules of thumb for the optimization of an enzymatic suspension reaction were derived.

Identification of mammalian GFRalpha-2 splice isoforms

Neurturin (NTN) belongs to a structurally related family of bioactive molecules which include glial cell-line derived neutrotrophic factor (GDNF) and perserphin (PSP). NTN exerts its effects through a multicomponent receptor system which include a receptor (GFRalpha-2) and the proto-oncogene c-RET. We report here the identification of three splice isoforms of the GFRalpha-2 receptors (GFRalpha-2a, GFRalpha-2b and GFRalpha-2c) by reverse transcription-PCR (RT-PCR). GFRalpha-2b is a novel splice variant. All three isoforms were found to be expressed in various adult murine tissues as well as in the brain of the newborn human. The identity of these isoforms were further confirmed by the isolation of the gene and the characterisation of the splice junctions.

Sequence effect of irinotecan (CPT-11) and topoisomerase II inhibitors in vivo

The DNA topoisomerases I and II are the target of several clinically important antineoplastic agents which produce DNA cleavage by stabilization of the covalent DNA-protein bond with resultant cell death after DNA synthesis is attempted. Depletion of the target topoisomerase and reciprocal changes in the other occur with drug treatment.

PURPOSE AND METHODS

To develop empiric treatment regimens of combinations and sequences of agents directed against topoisomerase I (irinotecan/CPT-11) and II (etoposide and doxorubicin), in vivo studies were performed in mice bearing the EMT-6 mammary tumor to assess efficacy, host tolerance and the resultant biochemical changes in topoisomerase mRNA and protein.

RESULTS

At 24 h after therapy, depletion of the target topoisomerase mRNA and protein with reciprocal increases in the alternate topoisomerase mRNA and, to a lesser extent, protein were noted. No therapeutic antagonism was found with any combination or sequence of agents, and therapeutic antagonism was noted with concurrent irinotecan/etoposide and sequential doxorubicin/irinotecan. Depletion of target topoisomerases by combined therapy beyond a threshold necessary for therapeutic efficacy produced no additional benefit.

CONCLUSIONS

Antineoplastic therapy with combinations of topoisomerase I and II agents is feasible and may produce therapeutic synergy. The appropriate sequence may depend on the particular agents used. The rationale for such therapy, that topoisomerases I and II may have reciprocal and compensatory interactions, is supported by the biochemical data.

Structural requirements for a specificity switch and for maintenance of affinity using mutational analysis of a phage-displayed anti-arsonate antibody of Fab heavy chain first complementarity-determining region

We previously showed that a single mutation at heavy (H) position 35 of Abs specific for p-azophenylarsonate (Ars) resulted in acquisition of binding to the structurally related hapten p-azophenylsulfonate (Sulf). To explore the sequence and structural diversity of the H chain first complementarity-determining region (HCDR1) in modulating affinity and specificity, positions 30-36 in Ab 36-65 were randomly mutated and expressed as Fab in a bacteriophage display vector. Ab 36-65 is germline encoded, lacking somatic mutations. Following affinity selection on Sulf resins, 55 mutant Fab were isolated, revealing seven unique HCDR1 sequences containing different amino acids at position H:35. All Fab bound Sulf, but not Ars. Site-directed mutagenesis in a variety of HCDR1 sequence contexts indicates that H:35 is critical for hapten specificity, independent of the sequence of the remainder of HCDR1. At H:35, Asn is required for Ars specificity, consistent with the x-ray crystal structure of the somatically mutated anti-Ars Ab 36-71, while Sulf binding occurs with at least seven different H:35 residues. All Sulf-binding clones selected following phage display contained H:Gly33, observed previously for Ars-binding Abs that use the same germline V(H) sequence. Site-directed mutagenesis at H:33 indicates that Gly plays an essential structural role in HCDR1 for both Sulf- and Ars-specific Abs.

Cloning of a novel murine isoform of the glial cell line-derived neurotrophic factor receptor

We report here the cloning of a novel form of the murine glial cell line-derived neurotrophic factor (GDNF) receptor. Northern blot analyses of various mouse tissues, including whole brain, demonstrated the existence of multiple transcripts of GDNF receptor. Screening of an adult mouse liver cDNA library yielded two isoforms of the receptor. One of the forms (alpha) shows a high degree of homology with other mammalian GDNFR-alpha and the other novel form (beta) is identical to the alpha form except for a deletion of five amino acids. These two forms do not share high sequence homologies with the recently isolated neurturin receptor. Both the alpha and beta forms are expressed in various murine tissues but not in muscle.

Differences in sequence-specific expression of two anti-arsonate Fabs in E. coli

Monoclonal antibodies are potentially useful therapeutic agents and can now be produced in hosts such as bacteria. However, it has been found that bacterial expression of some antibody-combining site fragments is greatly diminished. We compared two homologous anti-arsonate antibodies, 36-65 and 36-71, to address the question of why the former but not the latter expresses well as Fab in E. coli. These antibodies are both derived from the same variable region germline genes but differ in affinity due to somatic mutations present in 36-71. To investigate the poor expression of 36-71 Fab, we examined several factors, such as cellular toxicity, induction with isopropylthio-beta-D-galactoside, and growth of transformed bacteria at lower temperatures (30 degrees C), as well as the possibility of E. coli strain-related expression of Fab. However, none of these factors made a significant difference to Fab expression. We next localized a significant portion of the defect in Fab expression to the heavy chain by swapping the heavy and light chains from the two antibodies to construct hybrid Fabs. We used site-directed mutagenesis to engineer amino acids into the variable regions of antibody 36-71, to reproduce those found in 36-65 which is expressed well in E. coli. The defect in expression is due to residues located in the complementarity-determining regions, as mutations of heavy chain framework residues to those present in 36-65 do not enhance expression of 36-71 Fab in E. coli.

Decreased CP-1 (NF-Y) activity results in transcriptional down-regulation of topoisomerase IIalpha in a doxorubicin-resistant variant of human multiple myeloma RPMI 8226

Decreased topoisomerase II (Topo II) activity results in resistance to antineoplastic agents targeting this enzyme. Dox1V derived from human multiple myeloma RPMI 8226 demonstrated a 4-fold resistance to doxorubicin in the absence of MDR1 overexpression or topo II mutations (Futscher B.W., Foley N., Gleason-Guzman M., Meltzer P.S., Sullivan D.M., and Dalton W.S., Int'l. J. Cancer, 66: 520-5, 1996.). Consistent with its drug resistant phenotype, a 2- to 3-fold decrease in topo II expression was identified. To investigate the molecular basis for decreased topo II expression in Dox1V, a semi-quantitative analysis of Topo II activity, protein level and mRNA transcript were performed. The results demonstrated that reduced Topo II activity is due to a decreased mRNA level. Southern blot and sequencing experiments revealed wild-type sequence of the topo II promoter in the drug resistant cells. Transient gene expression assays demonstrated that topo II is transcriptionally down-regulated in Dox1V independent of the promoter sequence of the endogenous alleles. Instead, the activity of a ubiquitous transcription factor CP-1 (NF-Y) interacting with the topo II promoter is decreased. The decrease in CP-1/NF-Y activity in Dox1V is correlated well with the decrease in topo II transcriptional activity, transcript level, Topo II protein and enzyme activity. Therefore, transcriptional down-regulation resulted from a reduced CP-1/NF-Y activity is responsible for decreased topo II expression in Dox1V cells.

Modulation of antibody affinity by an engineered amino acid substitution

The crystal model of the complex of the somatically mutated anti-p-azophenylarsonate (Ars) Ab 36-71 F(ab) with phenylarsonate reveals that six residues (Asn35, Trp47, Tyr50, Ser99, and Tyr106 in the H chain and Arg96 in the L chain) contact hapten. Further study of this model suggested that H chain Phe108, which forms the base of the combining cavity, also affects Ars binding. We predicted that Trp with a bulkier aromatic side chain might be accommodated in this position and increase Ars affinity. The substitution of Phe by Trp using in vitro mutagenesis at position 108 enhanced affinity 10-fold in the germline-encoded Ab 36-65. However, the same mutation in Ab 36-71 abolished the binding. Phe108 was then mutated to different amino acids in both Abs. The results indicated that except for the Trp substitution in 36-65, all other substitutions at position 108 decrease or abolish Ars binding in both Abs. It was shown previously that the 200-fold difference in affinity between 36-65 and 36-71 could be reproduced by changing only three VH amino acids. Because the mutation of Phe108 to Trp has never been observed during in vivo affinity maturation, we constructed mutants of 36-65 in which Trp108 was combined with one or more of the "favorable" mutations of 36-71, to determine whether the mutations were additive. The results indicate that it is possible to maintain an affinity significantly higher than wild-type by such combined mutations. Thus, the failure to observe Trp108 in vivo is not due to structural idiosyncrasy, but may simply be due to codon usage at Phe108 in the germline sequence. Such limited "adaptability" of a germline sequence indicates that it is possible to achieve higher affinity Abs through protein engineering via routes that are constrained during in vivo selection.

Modulation of antibody affinity by an engineered amino acid substitution

The crystal model of the complex of the somatically mutated anti-p-azophenylarsonate (Ars) Ab 36-71 F(ab) with phenylarsonate reveals that six residues (Asn35, Trp47, Tyr50, Ser99, and Tyr106 in the H chain and Arg96 in the L chain) contact hapten. Further study of this model suggested that H chain Phe108, which forms the base of the combining cavity, also affects Ars binding. We predicted that Trp with a bulkier aromatic side chain might be accommodated in this position and increase Ars affinity. The substitution of Phe by Trp using in vitro mutagenesis at position 108 enhanced affinity 10-fold in the germline-encoded Ab 36-65. However, the same mutation in Ab 36-71 abolished the binding. Phe108 was then mutated to different amino acids in both Abs. The results indicated that except for the Trp substitution in 36-65, all other substitutions at position 108 decrease or abolish Ars binding in both Abs. It was shown previously that the 200-fold difference in affinity between 36-65 and 36-71 could be reproduced by changing only three VH amino acids. Because the mutation of Phe108 to Trp has never been observed during in vivo affinity maturation, we constructed mutants of 36-65 in which Trp108 was combined with one or more of the "favorable" mutations of 36-71, to determine whether the mutations were additive. The results indicate that it is possible to maintain an affinity significantly higher than wild-type by such combined mutations. Thus, the failure to observe Trp108 in vivo is not due to structural idiosyncrasy, but may simply be due to codon usage at Phe108 in the germline sequence. Such limited "adaptability" of a germline sequence indicates that it is possible to achieve higher affinity Abs through protein engineering via routes that are constrained during in vivo selection.

Biosynthesis of glycosylphosphatidylinositol-anchored human placental alkaline phosphatase: evidence for a phospholipase C-sensitive precursor and its post-attachment conversion into a phospholipase C-resistant form

Previous studies have shown that some cells (e.g. SKG3a) express human placental alkaline phosphatase (AP) in a form which can be released from the membrane by bacterial PtdIns-specific phospholipase C (PI-PLC) while others (e.g. HeLa) are relatively resistant to this enzyme. Chemical and enzymic degradation studies have suggested that the PI-PLC resistance of AP is due to inositol acylation of its glycosylphosphatidylinositol (GPI) anchor. In order to identify the biosynthetic origin of PI-PLC resistance we determined the PI-PLC sensitivity of AP in 35S-labelled cells (10 min pulse; 0-60 min chase) by Triton X-114 phase separation. At the beginning of the chase period, the majority of the AP synthesized was hydrophilic, indicating that it had not acquired a GPI anchor. The concentration of hydrophilic AP species decreased with a t1/2 of 30-60 min but was not processed to an endoglycosidase H-resistant species or secreted into the medium. In both SKG3a and HeLa cells all of the hydrophobic, GPI-anchored AP detectable at the beginning of the chase was PI-PLC sensitive. PI-PLC-resistant species of AP were only observed in HeLa cells and these only appeared after about 30 min. The delayed appearance of PI-PLC resistance was unexpected as previous studies have suggested that candidate GPI-anchor precursors are PI-PLC-resistant as a result of inositol acylation. This work reveals unanticipated complexities in the biosynthesis of AP and its GPI anchor.