Hip Pain after Distal Femoral Derotational Osteotomy for a Patient with Patellar Instability: A Case Report

BACKGROUND

Increased torsional deformity of femur is one of the most important factors in recurrent patellofemoral instability. And distal femoral derotational osteotomy is an effective treatment option in patients with increased femoral torsional deformity. However, groin pain is a rare complication after femoral derotational osteotomy.

CASE PRESENTATION

The patient was a 23-year-old female suffering from anterior knee pain and patellar instability in her left leg. Continuous CT scans of the hip, knee, and ankle were performed and the femoral anteversion was 44.99°. Considering the significant enlargement of the femoral internal torsion which may contribute most for dislocation of patella, we did a derotational osteotomy of distal femur. The anterior knee pain and patellar instability were resolved after surgery. The femoral internal torsion angle was corrected to 21.47°. But she developed left hip pain in the groin area which she had never encountered before 1 year after the surgery. We believed that the hip pain was closely related to the surgery. And the imaging and follow-up partly confirmed this.

CONCLUSIONS

The situation of the hip joint should be carefully evaluated before doing derotational osteotomy in recurrent patellofemoral instability and patient should be informed that derotational osteotomy may cause hip pain. Clinical studies are needed to further clarify the impact of derotational osteotomy on the hip.

Proximal external femoral torsion increases lateral femoral shaft bowing: a study based on 3D CT reconstruction models

PURPOSE

Femoral bowing influences the genesis and management of knee osteoarthritis (OA). The aim of this study was to investigate the relationship between the femoral torsion angle (FTA) and femoral bowing angle (FBA) in a southern Chinese population. It was hypothesized that a greater FTA would lead to a greater lateral FBA.

METHODS

A total of 381 lower extremities from 381 osteoarthritic patients (298 women, 83 men; 201 left, 180 right; mean age 66.5 ± 8.9 years) were retrospectively reviewed. Age, sex, body mass index (BMI), side, height, femoral length (FL), hip-knee-ankle angle (HKA) and FTA were set as FBA-related factors. The three-dimensional (3D) FBA, the angle between the anatomical axis of the proximal femur and the anatomical axis of the distal femur in the plane they form, and its projection on the coronal (lateral FBA) and sagittal (anterior FBA) planes were measured on 3D computed tomography (CT) models. The correlation of the 3D, lateral and anterior FBAs with each of the FBA-related factors was explored using multiple linear regression analysis. The correlation between the FBA and FTA was explored and verified after using propensity score matching to control for the other FBA-related factors.

RESULTS

The mean lateral and anterior FBAs were 5.5°, with 53.5% greater than 5°, and 12.7°, with 70.3% greater than 11°, respectively. 3D FBA was positively correlated with age (Std.Co = 0.113, P < 0.05) and HKA (Std.Co = 0.129, P < 0.05). Lateral FBA was positively correlated with age (Std.Co = 0.118, P < 0.05), female sex (Std.Co = 0.206, P < 0.05), HKA (Std.Co = 0.184, P < 0.05) and FL (Std.Co = 0.220, P < 0.05). Anterior FBA was positively correlated with age (Std.Co = 0.108, P < 0.05) and male sex (Std.Co = 0.108, P < 0.05). When the related factors were balanced between the two groups (NS), FTA did not significantly affect 3D FBA or anterior FBA (NS), while FTA was positively correlated with lateral FBA (Std.Co = 0.165, P < 0.05).

CONCLUSION

External torsion of the proximal femur increases the lateral FBA by twisting a partial anterior FBA into a lateral FBA, especially in the female population. If a patient is found to have a large lateral FBA preoperatively, one should be alert to the possibility of a concomitant large FTA, as there are implications for femoral orthopedics, TKA and patellofemoral pressure distribution.

LEVEL OF EVIDENCE

III.

Surgical Transepicondylar Axis Is Not a Reliable Reference when there Was Lateral Femoral Bowing

OBJECTIVE

The surgical transepicondylar axis (sTEA) is believed to be a consistent reference for femoral rotation axis, and the reliability of its orientation seriously affects the accuracy and outcome of total knee arthroplasty (TKA). This study was designed to investigate the relationship between the orientation of sTEA and femoral bowing angle (FBA) and posterior condylar line (PCL) using three-dimensional (3D) computed tomography (CT) reconstruction models to verify its reliability.

METHODS

This study retrospectively collected lower extremity images of 443 southern Chinese osteoarthritic patients (347 women, 96 men; 234 left, 209 right; mean age 66.5 ± 9.3 years) from August 2016 to June 2018. The hip-knee-ankle angle (HKA) was measured on anteroposterior weight-bearing full lower extremity standing radiographs. Measurements on 3D CT models of the femurs included lateral angle between the femoral mechanical axis and sTEA coronal angle, angle between sTEA and distal joint line (distal condylar axis angle, DCA); angle between sTEA and PCL (sTEA axial angle); angle between anatomical axis of proximal femur and anatomical axis of distal femur in the plane they form (actual FBA) and its projection on the coronal (lateral FBA) and sagittal (anterior FBA) planes. The correlations between sTEA coronal angle, sTEA axial angle and actual FBA, lateral FBA, anterior FBA, HKA, DCA were explored using the Spearman correlation test.

RESULTS

The mean value of actual FBA is (14.4 ± 3.6)°, of lateral FBA is (6.0 ± 4.0)°, and of anterior FBA is (12.7 ± 3.0)°. The mean value of sTEA coronal angle is (88.7 ± 3.6)°, of sTEA axial angle is (2.1 ± 2.8)°. The sTEA coronal angle was positively correlated with actual FBA (r = 0.320, P < 0.01), lateral FBA (r = 0.448, P < 0.01), anterior FBA (r = 0.113, P < 0.05), HKA (r = 0.482, P < 0.01) and DCA (r = 0.486, P < 0.01). The sTEA axial angle was positively correlated with DCA (r = 0.168, P < 0.01), but not significantly correlated with all FBAs and HKA (NS).

CONCLUSION

The sTEA cannot be used as a stable reference when there was an obvious femoral bowing deformity. As the lateral femoral bowing increases, the orientation of sTEA becomes more varus, no matter the knee is varus or valgus.

Prediction of visual function from automatically quantified optical coherence tomography biomarkers in patients with geographic atrophy using machine learning

Geographic atrophy (GA) is a vision-threatening manifestation of age-related macular degeneration (AMD), one of the leading causes of blindness globally. Objective, rapid, reliable, and scalable quantification of GA from optical coherence tomography (OCT) retinal scans is necessary for disease monitoring, prognostic research, and clinical endpoints for therapy development. Such automatically quantified biomarkers on OCT are likely to further elucidate structure-function correlation in GA and thus the pathophysiological mechanisms of disease development and progression. In this work, we aimed to predict visual function with machine-learning applied to automatically acquired quantitative imaging biomarkers in GA. A post-hoc analysis of data from a clinical trial and routine clinical care was conducted. A deep-learning automated segmentation model was applied on OCT scans from 476 eyes (325 patients) with GA. A separate machine learning prediction model (Random Forest) used the resultant quantitative OCT (qOCT) biomarkers to predict cross-sectional visual acuity under standard (VA) and low luminance (LLVA). The primary outcome was regression coefficient (r2) and mean absolute error (MAE) for cross-sectional VA and LLVA in Early Treatment Diabetic Retinopathy Study (ETDRS) letters. OCT parameters were predictive of VA (r2 0.40 MAE 11.7 ETDRS letters) and LLVA (r2 0.25 MAE 12.1). Normalised random forest feature importance, as a measure of the predictive value of the three constituent features of GA; retinal pigment epithelium (RPE)-loss, photoreceptor degeneration (PDR), hypertransmission and their locations, was reported both on voxel-level heatmaps and ETDRS-grid subfields. The foveal region (46.5%) and RPE-loss (31.1%) had greatest predictive importance for VA. For LLVA, however, non-foveal regions (74.5%) and PDR (38.9%) were most important. In conclusion, automated qOCT biomarkers demonstrate predictive significance for VA and LLVA in GA. LLVA is itself predictive of GA progression, implying that the predictive qOCT biomarkers provided by our model are also prognostic.

Slight femoral under-correction versus neutral alignment in total knee arthroplasty with preoperative varus knees: a comparative study

Background

This study aimed to compare the short-term clinical results of slight femoral under-correction with neutral alignment in patients with preoperative varus knees who underwent total knee arthroplasty.

Methods

The medical records and imaging data were retrospectively collected from patients who had undergone total knee arthroplasty in our hospital from January 2016 to June 2019. All patients had varus knees preoperatively. Upon 1:1 propensity score matching, 256 patients (256 knees) were chosen and divided into a neutral alignment group (n=128) and an under-correction group (n=128). The patients in the neutral group were treated with the neutral alignment. In the under-correction group, the femoral mechanical axis had a 2° under-correction. The operative time, tourniquet time and the length of hospital stay in the two groups were recorded. The postoperative hip-knee-ankle angle, frontal femoral component angle and frontal tibial component angle were measured. Patient-reported outcome measures were also compared.

Results

The operative time, tourniquet time and the length of hospital stay in the under-correction group were significantly shorter than the neutral alignment group (P<0.05). At the 2-year follow-up, the under-correction group had a larger varus alignment (P<0.05) and a larger frontal femoral component angle (P<0.05), and the frontal tibial component angles of the two groups were comparable. Compared with the neutral alignment group, the slight femoral under-correction group had significantly better patient-reported outcome measures scores (P<0.05).

Conclusion

For varus knees treated with total knee arthroplasty, alignment with a slight femoral under-correction has advantages over the neutral alignment in terms of the shorter operative time and better short-term clinical results.

Level of evidence

III

Accuracy of a Novel 3D-Printed Patient-Specific Intramedullary Guide to Control Femoral Component Rotation in Total Knee Arthroplasty

Objective

Total knee arthroplasty (TKA) is one of the most universal and effective means for treating terminal stage osteoarthritis (OA) of knee. Accurate intramedullary guide of femur is the basis for the distal femoral cuts. Determining the surgical transepicondylar axis (sTEA) is the key to reconstruction of the femoral rotational alignment, because the correct rotational alignment can place the femoral component in the right position, balance the flexion gap so that the inner and outer tension is equal, get stability during the flexion process of the knee, and enhance the quality of life of patients. With the development of three‐dimensional printing (3DP) technology in the medical domain, the application of patient‐specific instrumentation (PSI) in arthroplasty has become more common. The aim of this study was to evaluate the accuracy of a novel 3D‐printed patient‐specific intramedullary guide to control femoral component rotation in TKA.

Methods

Eighty patients (65 females and 15 males) with knee OA were included in this prospective randomized study. The patients were divided into two groups by random number table method, 40 in each group. TKA assisted by PSI (PSI group) and conventional TKA (conventional group) was performed respectively. Clinical outcomes [operation time, postoperative drainage volume, duration of drainage, Hospital for Special Surgery knee score (HSS), American Knee Society knee score (AKS)] and radiological outcomes [hip‐knee‐ankle angle (HKA), posterior condylar angle (PCA), patella transverse axis‐femoral transepicondylar axis angle (PFA), depth of intramedullary guide] were compared between and within the two groups.

Results

PSI group had less postoperative drainage volume but longer operation time than the conventional group (P < 0.05). The AKS and HSS scores after surgery were improved compared with those before surgery in each group (P < 0.05). However, there was no significant difference in the duration of drainage and range of motion (ROM) after surgery between the two groups. For the radiological results, the HKA and PFA were improved after surgery in both groups (P < 0.05).The postoperative PFA and PCA of the PSI group were closer to 0°, which was better than that of the conventional group (P < 0.05). The depth of intramedullary guide in the PSI group was less than the conventional group (P < 0.05). But there was no significant difference in HKA before and after surgery between the two groups as well as the preoperative PFA.

Conclusion

The short‐term clinical efficacy of TKA assisted by PSI was similar to the conventional TKA. Although TKA assisted by PSI spent more time during operation, it could assist in intramedullary guide and align femoral rotation more accurately.

Optical limiting, nonlinear refraction and nonlinear absorption of the associates of Cd0.5Zn0.5S quantum dots and dyes

The optical limiting properties of alloyed Cd_0.5Zn_0.5S quantum dots associated with erythrosine dye are analyzed using 532 nm, 40 ps pulses. We show that joint influence of saturable absorption, reverse saturable absorption and two-photon absorption cause the optical limiting of 532 nm radiation at the pulse energies exceeding 1 mJ. The nonlinear refraction and nonlinear absorption of these quantum dots associated with different organic dyes were studied using 1064 nm and 532 nm radiation. The nonlinear refraction index and nonlinear absorption coefficient of Cd_0.5Zn_0.5S quantum dots were measured at λ = 1064 nm to be 2 × 10^-13 cm² W^-1 and 1.2 × 10^-8 cm W^-1, while the reverse saturable absorption of Cd_0.5Zn_0.5S quantum dots and erythrosine at λ = 532 nm was almost two orders larger. The potential applications of these quantum dots for high-order harmonic generation are discussed.

Upregulated microRNA-301a in osteosarcoma promotes tumor progression by targeting CDC14A

MicroRNAs (miRs) are associated with tumor progression in various cancers, such as gastric and hepatic carcinomas, and lung cancer. miR-301a is overexpressed and displays oncogenic activity in cancers. We investigated the biological involvement of miR-301a in osteosarcoma (OS). Quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyze expression levels of miR-301a in 24 OS and matched adjacent non-tumor tissues. A miR-301a mimic was transferred into OS cell lines U-2 OS and MG-63 to upregulate miR-301a. The effects of miR-301a were investigated by examining cell proliferation, migration, and the cell cycle. The miR-301 target was predicted by TargetScan and confirmed by western blotting and qRT-PCR. The expression of miR-301a was significantly higher in OS tissues compared with the matched adjacent non-tumor tissues (0.959 ± 0.39 vs 3.9516 ± 1.18). Upregulated miR-301a significantly increased proliferation at 48 and 72 h compared to the negative control (U-2 OS: 2.11 ± 0.21 vs 2.88 ± 0.24; 2.70 ± 0.26 vs 3.71 ± 0.24; MG-63: 2.19 ± 0.20 vs 3.19 ± 0.22; 3.1 ± 0.25 vs 4.01 ± 0.27) and migration capability (U-2 OS: 100 ± 20.19 vs 150.68 ± 32.83; MG-63: 100 ± 17.20 vs 133.35 ± 26.26), and decreased apoptosis in both U-2 OS (10.87 ± 2.53 vs 4.01 ± 2.23) and MG-63 (15.26 ± 2.15 vs 8.25 ± 3.07). The cell cycle studies revealed that miR-301a caused an increase of the G2 population in U-2 OS (38.6 ± 6.58 vs 47.2 ± 7.27) and MG-63 (44.01 ± 5.28 vs 57.9 ± 4.25). Additional experiments indicated that CDC14A was upregulated by miR-301a (0.63 ± 0.06 vs 0.98 ± 0.06; 1.49 ± 0.25 vs 2.99 ± 0.14). Overexpressed miR-301a may increase CDC14A expression and promote cell proliferation and migration in OS cells. Therefore, miR- 301a may be useful for osteosarcoma diagnosis and therapy.

An Arthroscopic Second-Look Study on the Effect of Remnant Preservation on Synovialization of Bone-Patellar Tendon-Bone Allograft in Anterior Cruciate Ligament Reconstruction

PURPOSE

To assess the effects of preserved more anterior cruciate ligament (ACL) remnant on synovial coverage, knee stability, and function after bone patellar-tendon-bone (BPTB) allograft reconstruction through second-look arthroscopy and follow-up study.

METHODS

From June 2007 to February 2009, 51 patients received single bundle BPTB allograft ACL reconstruction and second arthroscopic examination. The patients were divided into 4 types according to the types of ACL remnant: type 1, 18 had bridging between the posterior cruciate ligament and the tibia; type 2, 21 had bridging between the intercondylar notch roof and the tibia; type 3, 4 had bridging between the lateral condyle and the tibia; and type 4, 8 subjects had no ACL remnants. Clinical results were evaluated with the KT-1000 maximum displacement test and Lysholm scale at mean 12.3- and 53.5-month follow-up. Second-look synovium coverage was recorded as follows: covering 25% or less, 25% to 50%, 50% to 75%, and more than 75%.

RESULTS

Mean percentage of synovium coverage, Lysholm scale, and KT-1000 side-to-side difference were poorer in types 3 and 4 than the other 2 types at mean 12.3-month follow-up without statistical differences. The result of the final follow-up was comparable with the first one. Four patients had ruptured grafts and accepted revision surgery. Three of them belonged to types 3 and 4, and 1 patient with sport trauma belonged to type 2. There were other 11 patients with different types of impingement and partial absorption of grafts.

CONCLUSIONS

Although lack of statistical power, follow-up study and second-look arthroscopy showed that preserved type 3 and 4 ACL remnant caused poorer synovium coverage and might lead to earlier failure when using BPTB allograft. Early minor laxity at 12.3-month follow-up seemed to be not progressive at the final follow-up.

LEVEL OF EVIDENCE

Level III, case-control study.

Estimated medical cost reductions for paliperidone palmitate vs placebo in a randomized, double-blind relapse-prevention trial of patients with schizoaffective disorder

OBJECTIVE

The objective of this economic model was to estimate the difference in medical costs among patients treated with paliperidone palmitate once-monthly injectable antipsychotic (PP1M) vs placebo, based on clinical event rates reported in the 15-month randomized, double-blind, placebo-controlled, parallel-group study of paliperidone palmitate evaluating time to relapse in subjects with schizoaffective disorder.

RESEARCH DESIGN AND METHODS

Rates of psychotic, depressive, and/or manic relapses and serious and non-serious treatment-emergent adverse events (TEAEs) were obtained from the long-term paliperidone palmitate vs placebo relapse prevention study. The total annual medical cost for a relapse from a US payer perspective was obtained from published literature and the costs for serious and non-serious TEAEs were based on Common Procedure Terminology codes. Total annual medical cost differences for patients treated with PP1M vs placebo were then estimated. Additionally, one-way and Monte Carlo sensitivity analyses were conducted.

RESULTS

Lower rates of relapse (-18.3%) and serious TEAEs (-3.9%) were associated with use of PP1M vs placebo as reported in the long-term paliperidone palmitate vs placebo relapse prevention study. As a result of the reduction in these clinical event rates, the total annual medical cost was reduced by $7140 per patient treated with PP1M vs placebo. One-way sensitivity analysis showed that variations in relapse rates had the greatest impact on the estimated medical cost differences (range: -$9786, -$4670). Of the 10,000 random cycles of Monte Carlo simulations, 100% showed a medical cost difference <$0 (reduction) for patients using PPIM vs placebo. The average total annual medical differences per patient were -$8321 for PP1M monotherapy and -$6031 for PPIM adjunctive therapy.

CONCLUSIONS

Use of PP1M for treatment of patients with schizoaffective disorder was associated with a significantly lower rate of relapse and a reduction in medical costs compared to placebo. Further evaluation in the real-world setting is warranted.

Incidence of tardive dyskinesia: a comparison of long-acting injectable and oral paliperidone clinical trial databases

BACKGROUND

To assess the tardive dyskinesia (TD) rate in studies of once-monthly long-acting injectable (LAI) paliperidone palmitate (PP) and once-daily oral paliperidone extended release (Pali ER).

METHODS

Completed schizophrenia and bipolar studies for PP and Pali ER (≥ 6 month duration with retrievable patient-level data) were included in this post hoc analysis. Schooler-Kane research criteria were applied using Abnormal Involuntary Movement Scale (AIMS) scores to categorise probable (qualifying AIMS scores persisting for ≥ 3 months) and persistent TD (score persisting ≥ 6 months). Spontaneously reported TD adverse events (AEs) were also summarised. Impact of exposure duration on dyskinesia (defined as AIMS total score ≥ 3) was assessed by summarising the monthly dyskinesia rate.

RESULTS

In the schizophrenia studies, TD rates for PP (four studies, N = 1689) vs. Pali ER (five studies, N = 2054), were: spontaneously reported AE, 0.18% (PP) vs. 0.10% (Pali ER); probable TD, 0.12% (PP) vs. 0.19% (Pali ER) and persistent TD, 0.12% (PP) vs. 0.05% (Pali ER). In the only bipolar study identified [Pali ER (N = 614)], TD rate was zero (spontaneously reported AE reporting, probable and persistent TD assessments). Dyskinesia rate was higher within the first month of treatment with both PP (13.1%) and Pali ER (11.7%) and steadily decreased over time (months 6-7: PP: 5.4%; Pali ER: 6.4%). Mean exposure: PP, 279.6 days; Pali ER, 187.2 days.

CONCLUSIONS

Risk of TD with paliperidone was low (< 0.2%), regardless of the formulation (oral or LAI), in this clinical trial dataset. Longer cumulative exposure does not appear to increase the risk of dyskinesias.

Use of intravenous tranexamic acid in total knee arthroplasty: a meta-analysis of randomized controlled trials

OBJECTIVE

The effect of tranexamic acid (TA) on patients receiving total knee arthroplasty (TKA) has been reported in many small clinical trials. But single trials are not sufficient enough to clarify the effectiveness and safety of TA. So, we carried out a meta-analysis of randomized controlled trials to investigate the efficacy and safety of the intravenous use of TA in TKA.

METHODS

Literatures were retrieved in Cochrane Library, OVID, PubMed, EMBASE, CNKI and Wanfang Data. All the related literatures were checked by two independent investigators and only the high quality randomized controlled trials were enrolled. Relevant data were analyzed using RevMan 5.1 to compare the difference of blood loss, transfusion and complications between TA group and control group.

RESULTS

There were 353 related literatures and only 22 randomized controlled trials met the inclusion criteria. The use of TA in TKA significantly reduced total blood loss by a mean of 435.41 ml (95% CI 300.62-570.21, P less than 0.01), post-operative blood loss by a mean of 406.69 ml (95% CI 333.16-480.22, P less than 0.01). TA also significantly lowered the transfusion rate (risk difference 0.30, 95% CI 0.21-0.39, P less than 0.01) and transfusion volume (mean difference 0.95 unit, 95% CI 0.53-1.37, P less than 0.01). The risks between TA group and control group in developing deep vein thrombosis and pulmonary embolism were not statistically significant.

CONCLUSION

TA is beneficial for patients undergoing TKA, which can significantly reduce total blood loss, postoperative blood loss, transfusion rate, and transfusion volume. Meanwhile TA is recommended to reduce deep vein thrombosis and pulmonary embolism following TKA.

Genome of the bacterium Streptococcus pneumoniae strain R6

Streptococcus pneumoniae is among the most significant causes of bacterial disease in humans. Here we report the 2,038,615-bp genomic sequence of the gram-positive bacterium S. pneumoniae R6. Because the R6 strain is avirulent and, more importantly, because it is readily transformed with DNA from homologous species and many heterologous species, it is the principal platform for investigation of the biology of this important pathogen. It is also used as a primary vehicle for genomics-based development of antibiotics for gram-positive bacteria. In our analysis of the genome, we identified a large number of new uncharacterized genes predicted to encode proteins that either reside on the surface of the cell or are secreted. Among those proteins there may be new targets for vaccine and antibiotic development.

Chip-based genotyping by mass spectrometry

Silicon chips with immobilized target DNAs were used for accurate genotyping by mass spectrometry. Genomic DNAs were amplified with PCR, and the amplified products were covalently attached to chip wells via N-succinimidyl (4-iodoacetyl)aminobenzoate (SIAB) chemistry. Primer annealing, extension, and termination were performed on a 1-microl scale directly in the chip wells in parallel. Diagnostic products thus generated were detected in situ by using matrix-assisted laser desorption ionization mass spectrometry. This miniaturized method has the potential for accurate, high-throughput, low-cost identification of genetic variations.

Sequencing exons 5 to 8 of the p53 gene by MALDI-TOF mass spectrometry

Matrix-assisted laser desorption ionization time of flight mass spectrometry was used to sequence exons 5 to 8 of the human p53 gene. A single tube procedure was established for target amplification and mass spectrometric (MS) sequencing. The MS sequencing scheme is designed for high throughput and parallel sample processing, and is amenable to full automation. Reliable sequencing data were obtained using fmol sample amounts. The high resolution and accuracy of MS sequencing was demonstrated by direct sequencing of a heterozygous template.

Sequencing double-stranded DNA by strand displacement

Duplex probes with five base single-stranded overhangs can capture dsDNA targets from type IIS restriction nuclease digests. Ligation generates a predesigned nick site, where DNA polymerase can generate sequencing ladders by strand displacement or nick translation in the presence of trace amounts of dideoxynucleotides. This allows dsDNA targets to be captured from mixtures and directly sequenced without subcloning, purification or denaturation.

A strategy for rapid and efficient DNA sequencing by mass spectrometry

Two methods of solid-phase Sanger DNA sequencing followed by detection with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry are demonstrated. In one method, sequencing ladders generated on an immobilized synthetic template were resolved up to the 63-mer including the primer. Detection sensitivity and resolution were sufficient for sequence analysis in the given range. This approach is particularly suitable for comparative (diagnostic) DNA sequencing. A second method that has the potential for high throughput de novo DNA sequencing is also presented; it uses immobilized duplex probes with five-base single-stranded overhangs to capture an unknown DNA template serving as primers for Sanger DNA sequencing. The power of mass spectrometry is demonstrated not only by its very high speed, but also by its ability to identify sequences that are not readable using gel electrophoresis.

Efficient preparation of short DNA sequence ladders potentially suitable for MALDI-TOF DNA sequencing

Duplex probes with five-base single-stranded overhangs were developed for positional sequencing by hybridization [Broude et al., Proc Natl Acad Sci USA 91:3072-3076, 1994]. The partially duplex probes can be employed to capture single-stranded oligonucleotide targets and form primer-template complexes. Recently we showed that partially duplex probes can prime Sanger sequencing reactions on immobilized, but non-ligated long single-stranded targets (approximately 500 nucleotide) [Fu et al., Proc Natl Acad Sci, in press]. Here immobilized, non-ligated partially duplex probes were used to capture and sequence short single-stranded targets. This strategy is capable of rapidly preparing large numbers of samples for future mass spectrometric DNA sequencing.

A DNA sequencing strategy that requires only five bases of known terminal sequence for priming

We have previously reported an enhanced version of sequencing by hybridization (SBH), termed positional SBH (PSBH). PSBH uses partially duplex probes containing single-stranded 3' overhangs, instead of simple single-stranded probes. Stacking interactions between the duplex probe and a single-stranded target allow us to reduce the probe sizes required to 5-base single-stranded overhangs. Here we demonstrate the use of PSBH to capture relatively long single-stranded DNA targets and perform standard solid-state Sanger sequencing on these primer-template complexes without ligation. Our results indicate that only 5 bases of known terminal sequence are required for priming. In addition, the partially duplex probes have the ability to capture their specific target from a mixture of five single-stranded targets with different 3'-terminal sequences. This indicates the potential utility of the PSBH approach to sequence mixtures of DNA targets without prior purification.

Activity of the hammerhead ribozyme upon inversion of the stereocenters for the guanosine 2'-hydroxyls

Two guanosine 2'-hydroxyls in the hammerhead RNA complex at positions G5 and G8 are critical for efficient cleavage by this RNA catalyst. These two functional groups are likely involved in the binding of the metal cofactor, or they are involved in specific interresidue hydrogen-bonding interactions. The importance of the stereochemical positioning of both critical 2'-hydroxyls was investigated by comparing the cleavage rates of three arabinosylguanine-substituted complexes (in which the positions of specific guanosine 2'-hydroxyls were stereochemically altered by inverting the C2' stereocenter) with that of the native complex, as well as with the rates of the dG- and dFG-substituted complexes [in which the 2'-hydroxyls are absent as the result of substitution by 2'-deoxyguanosine (dG) or 2'-deoxy-2'-fluoroguanosine (dFG)]. The G5araG and G8araG complexes exhibit dramatically different cleavage rates. The G5araG complex is essentially inactive, at least 10(5)-fold slower than the native complex. RNA cleavage by this analogue ribozyme is also 1000-fold slower than cleavage by either the G5dG or the G5dFG ribozyme, both of which lack the 2'-hydroxyl at G5. By comparison, catlytic efficiency of the G8araG complex as expressed by kcat/Km is comparable with that of the native complex and some 2 orders of magnitude more active than either the G8dG or the G8dFG complex.

Importance of specific guanosine N7-nitrogens and purine amino groups for efficient cleavage by a hammerhead ribozyme

Seven modified hammerhead ribozyme/substrate complexes have been prepared in which individual purine nitrogens, the guanine N7-, the guanine N2-, or the adenine N6-nitrogen, have been excised. The modified complexes were chemically synthesized with the substitution of a single 7-deazaguanosine (c7G), inosine (I), or nebularine (purine riboside, P) base analogue as appropriate for residues G5, G8, G12, A13, A14, or A15. Two of the base analogues, c7G5 and C7G8, occur in a 19-mer ribozyme, while the remaining three residues are present in a 24-mer substrate. Under stoichiometric conditions, four of the complexes, G5c7G, G8c7G, G12c7G, and A14P, are cleaved with relatively little change in rate when compared with the native complex. Two complexes, A13P and A15P, are cleaved some 6-8-fold slower than the native complex, while the G12I complex is reduced in rate by 50-fold. Steady-state kinetic analyses indicate that the cleavage efficiencies, as measured by kcat/KM values, for the G5c7G, G8c7G, and G12c7G complexes are only marginally reduced relative to the native complex. The values for the A13P, A14P, and A15P complexes are reduced by 25-, 15-, and 60-fold, respectively. These reductions in cleavage efficiency are primarily a result of lower kcat values. By comparison, the kcat/KM value for the G12I complex is decreased 450-fold relative to the native complex and is characterized by an 8-fold increase in KM and a kcat value that is reduced nearly 60-fold. These results indicate that the N2-amino group of G12 in the hammerhead ribozyme/substrate complex is critical for efficient cleavage activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Importance of specific adenosine N7-nitrogens for efficient cleavage by a hammerhead ribozyme. A model for magnesium binding

Five modified hammerhead ribozyme/substrate complexes have been prepared in which individual adenosine N7-nitrogens have been excised. The modified complexes were chemically synthesized with the substitution of a single 7-deazaadenosine (c7A) base analogue for residues A11, A14, A26, A27, or A28. Two of the base analogues, c7A11 and c7A14, occur in a 19-mer ribozyme, while the remaining three residues, c7A26, c7A27, and c7A28, are present in a 24-mer substrate. Under stoichiometric conditions, four of the complexes are cleaved with relatively little change in rate when compared with that of the native complex. However, the relative rate for the c7A11 complex is some 35-fold slower than that of the native complex. Steady-state kinetic analyses indicate that the cleavage efficiencies, as measured by kcat/KM, for the c7A14, c7A26, c7A27, and c7A28 complexes are reduced 18-fold, 10-fold, 34-fold, and 16-fold, respectively. These reductions in cleavage efficiency are primarily a result of lower kcat values. By comparison, the cleavage efficiency of the c7A11 complex is reduced more than 200-fold relative to that of the native complex, again primarily as a result of a lower kcat value. The results suggest that the N7-nitrogen of A11 in the hammerhead ribozyme/substrate complex is critical for efficient cleavage activity. The results of the present work, in combination with those from previous reports, indicate that five critical functional groups are located within the tetrameric sequence G10A11U12G13. A preliminary model for the binding of a single magnesium cofactor to this portion of the sequence is proposed.(ABSTRACT TRUNCATED AT 250 WORDS)

Importance of specific purine amino and hydroxyl groups for efficient cleavage by a hammerhead ribozyme

Eight modified ribozymes of 19 residues have been prepared with individual purine amino or hydroxyl groups excised. The modified ribozymes were chemically synthesized with the substitution of a single 2'-deoxyadenosine, 2'-deoxyguanosine, inosine, or purine riboside for residues G10, A11, G13, or A14. Five of the modified ribozymes cleaved the 24-mer substrate with little change in rate as monitored by simple first-order kinetics. However, deletion of the 2-amino group at G10 (replacement with inosine) or deletion of either of the 2'-hydroxyls at G10 or G13 (replacement with 2'-deoxyguanosine) resulted in ribozymes with a drastic decrease in cleavage efficiency. Increasing the concentration of the Mg2+ cofactor from 10 mM to 50 mM significantly enhanced cleavage efficiency by these three derivatives. Steady-state kinetic assays for these three ribozymes indicated that the modifications result in both an increase in Km and a decrease in kcat. These results suggest that the exocyclic amino group at-G10 and the hydroxyls at G10 and G13 are important both for ribozyme-substrate binding and for the Mg(2+)-catalyzed cleavage reaction.

Lead poisoning: cause for alarm

Lead (Pb) is everywhere in our environment and all children are exposed to lead to some degree. The Center for Disease Control (CDC) has recently declared that a blood lead level of 25 micrograms/dL and an erythrocyte protophoryrin of 35 micrograms/dL or above indicate an excessive absorption of lead in children and constitutes grounds for intervention. A study reported that about 780,000 (4%) of American children age 6 months to 5 years had blood lead levels of 30 micrograms/dL or higher. If the current level of 25 micrograms/dL had been used as a criterion in this study, the number of children involved would be much higher. It has been clearly stated by the American Academy of Pediatrics that ideally, all pre-school children should be screened for lead absorption by means of the erythrocyte protophoryrin test. The following is a review of lead poisoning in children and the serious consequences which may follow if it is not recognized early.