Biomedical subjects

J E Novotny

Publications and source records attributed to J E Novotny.

At least 19 recordsLinked to original sources

PubMed2003

Precision and accuracy of joint space width measurements of the medial compartment of the knee using standardized MTP semi-flexed radiographs.

OBJECTIVE: To quantify the precision and accuracy of measurements of joint space width (JSW) and joint space narrowing (JSN) from the medial tibiofemoral compartment of knee radiographs using a simple and easily adaptable protocol. METHODS: Radiographs of a caliper (a surrogate for JSW) were obtained to determine the precision limits of the system under ideal conditions. Bilateral knee radiographs from 10 healthy volunteers were obtained at three different times using the metatarsophalangeal (MTP) semi-flexed view posterior-anterior position without fluoroscopy. A backlit digitizing tablet and three manual methods were used to measure JSW and analyses of precision were performed. The accuracy of measuring change in JSW (a measure of JSN) was estimated from radiographs of cadaver knees that were placed in a servo-hydraulic device that moved the femur relative to the tibia through known intervals. RESULTS: Radiographic measurements of the caliper inter-blade distance were comparable to the resolution limits of the backlit digitizing tablet (0.025 mm). Repeated radiography of healthy subject knees produced JSW standard deviation (SD) measurements of 0.08 mm by the median SD method, and 0.11 mm by repeated measures analysis. The accuracy of JSN measurements in the cadaver knees as a mean difference from the known reference value was 0.09 mm. CONCLUSION: The results indicate a high level of precision in measurements of JSW from MTP semi-flexed view knee radiographs of normal volunteers. Reproducibility was attained through careful subject positioning without fluoroscopy and the use of a backlit digitizing tablet. From the cadaver study we can predict that greater than 0.13 mm of measured JSN represents actual or true change in JSN. This radiographic technique can be used as a primary measure for early knee osteoarthritis (OA) when cartilage thickness is decreasing and limited bony remodeling has occurred.

Arthrography↗

PubMed2001

A numerical solution to calculate internal-external rotation at the glenohumeral joint.

OBJECTIVE: To validate the approach of using angular velocity vectors to quantify internal-external rotation of the humerus. DESIGN: An experimental approach was used to compare predictions of internal-external rotation of the humerus based on angular velocity vectors, and known measurements of internal-external rotation. BACKGROUND: A primary concern associated with description of glenohumeral biomechanics is measurement of internal-external rotation of the humerus. Euler angles are often used, yet they do not address problems such as Codman's paradox and 'gimbal lock'. Previous work has presented a technique that uses angular velocity vectors to quantify internal-external rotation instead of Euler angles. This approach is promising with regard to providing an independent measure of internal-external rotation of the humerus, and requires validation for subsequent use on humans. METHODS: A gimbal with three axes of rotation that simulated the rotational d.o.f. of the humerus relative to the glenoid was developed and used to validate the use of angular velocity vectors to quantify internal-external rotation of the humeral shaft portion of the gimbal. RESULTS: Correlations between calculated and measured rotation values revealed R(2) values of 0.99, slopes at diagonal (1.0), and y-intercepts near zero (-0.6 degrees ).Conclusions. The expression developed here is a valid and useful method for measuring motion of the humerus relative to the glenoid. RELEVANCE: Angular velocity vectors can be used to accurately determine internal-external rotation of the humerus relative to the glenoid, and this may be useful for the development of arthrometers to characterize the glenohumeral joint.

Biomechanical Phenomena↗

PubMed2000

In vivo technique to quantify the internal-external rotation kinematics of the human glenohumeral joint.

Internal and external rotation of the humerus are often related to instability, injury mechanisms, and surgical and rehabilitation outcomes at the glenohumeral joint. The goal of this study was to develop a technique to quantify the internal-external rotation kinematics of the glenohumeral joint in human subjects, including the rotational range of motion, neutral-zone laxity, and flexibility. For both arms of 10 normal subjects, the rotational range of motion of the humerus was assessed at 45 degrees of abduction with 4 Nm of applied moment to produce internal and external rotations about the long axis. The neutral zone was defined as the portion of the rotational range of motion that occurred between +1 and -1 Nm of applied internal-external rotation torque. The flexibility was determined from the slope of the moment-rotation curve from 1 to 4 Nm of applied moment. The repeatability of the device during two trials on the same day and two trials 1 week apart was determined. There were no significant differences between the two same-day and two across-day trials for each outcome measure. The internal-external rotational range of motion was 139.4 degrees (SD 40.5 degrees). The neutral-zone laxity was 77.8 degrees (SD 46.0 degrees). With a linear approximation, the external rotation flexibility (20.1 degrees/Nm [SD 13.7 degrees/Nm]) was four times greater than the internal rotation flexibility (5.8 degrees/Nm [SD 5.1 degrees/Nm]). The changes in the magnitude of the laxity, the ratio between the laxity and the range of motion, or the values for flexibility determined with this technique could be used to describe joint laxity, surgical outcome, and rehabilitation progress.

Adult↗

PubMed2000

Modeling the stability of the human glenohumeral joint during external rotation.

An analytical model of the human glenohumeral joint was developed to predict glenohumeral kinematics and investigate how the glenohumeral capsule and articular contact between the humeral head and the glenoid stabilize the joint. This was performed during a simulation of an apprehension clinical exam or the cocked phase of throwing, when the humerus is susceptible to anterior instability or dislocation. Contact between the joint surfaces was modeled using a deformable articular contact method and the capsule was modeled as five elements with the ability to wrap around the surface of the humeral head. Experimental measurements (Novotny et al., Journal of Shoulder and Elbow surgery, 1998, 7, 629-639) provided geometric data from four in vitro specimens and kinematic results to validate model predictions. Material properties were taken from the literature. An equilibrium approach was used with the forces and moments produced by the ligaments and surface contact balanced against those applied externally to the humerus during external rotation of the abducted and extended humerus. The six equilibrium equations were solved for the position and orientation of the humerus. The center of the humeral head translated posteriorly and superiorly with external rotation. Model predictions for translational and rotational ranges of motion were not significantly different from experimental findings; however, at individual moment increments, the model underestimated the external rotation and overestimated the superior-inferior position of the humerus relative to the glenoid. The anterior band of the inferior glenohumeral ligament increased in tension with external rotation, while the axillary pouch and posterior band decreased in tension. Contact area, stress and force increased with external rotation and the contact area moved posteriorly and inferiorly around the rim of the glenoid. The model results provide information on how the relationship between the ligament element tensions and contact forces may act to avoid glenohumeral instability.

Humans↗

PubMed1998

Reliability of axial landmarks for pedicle screw placement in the lower lumbar spine.

STUDY DESIGN: Measurements were made on transverse-plan, computed tomography scans from three different patient groups. OBJECTIVE: To describe the correlation between two previously described pedicle screw entry points to the pedicle axis and the predicted frequency of pedicle breakthrough from the use of a 6.5-mm screw placed parallel to the pedicle axis. SUMMARY OF BACKGROUND DATA: Fluoroscopic assistance improves the accuracy of pedicle screw placement. Whether this is a result of improved accuracy of the starting point or correct directional guidance is unclear. No morphologic studies have been done to assess the accuracy of previously described entry points. METHODS: Computerized digitizing and mathematic superimposition of the images from computed tomography scans of the low lumbar spine were used to quantify facet and pedicle anatomy and the correlation between two previously described entry points and the pedicle axis. RESULTS: The two previously described entry points are significantly medial to the pedicle axis. They are most medial at the L5 pedicle in patients with L4 degenerative spondylolisthesis. CONCLUSIONS: The two previously described entry points for pedicle screws in the low lumbar spine that were studied here are not reliable and tend to direct screw placement medial to the pedicle axis enough to lead to a substantial frequency of pedicle breakthrough for screws parallel to this axis. Surgeons implanting screws should take this tendency into account and use alternative methods to obtain accurate entry to the pedicle.

Adolescent↗

PubMed1998

Kinematics of the glenohumeral joint with Bankart lesion and repair.

A Bankart repair is performed to reduce abnormal translations of the humeral head on the glenoid due to a Bankart lesion, a separation of the capsulolabral complex from the glenoid rim. However, this is often accompanied by a loss of rotational range of motion that may lead to decreased function and osteoarthritis. This loss of rotation, coupled to the goal of reducing humeral translations, may be a result of the amount of imbrication of the capsule during repair. To determine the effects of capsular imbrication, we investigated how two Bankart repairs (2.5 and 5.0 mm of capsular imbrication) and a Bankart lesion altered the translations and rotations of the human glenohumeral joint in vitro. Coupled moments were applied to the unconstrained humerus in abduction-adduction, in flexion-extension, and to simulate the cocked phase of throwing. Motion was measured with an electromagnetic system. There were no differences in the kinematics between the intact specimens and those with a Bankart lesion or between normal specimens and the first (2.5 mm) Bankart repair. The first repair significantly reduced external rotation for the cocked phase of throwing compared with the Bankart lesion: from 46.8 +/- 23.6 degrees to 32.4 +/- 14.2 degrees (+/-SD). The second (5.0 mm) Bankart repair produced significantly different posterior translation (-4.7 +/- 3.9 mm) of the humeral head relative to the glenoid compared with normal (5.1 +/- 4.7 mm anterior) and the first repair (6.1 +/- 8.3 mm anterior), as the humerus moved from full flexion to full extension. Differences were also found for all rotations in the cocked phase of throwing. For the second repair, the humerus extended 24.3 degrees and externally rotated 18.6 degrees less than normal and was abducted 15.4 degrees more. These results indicate that both Bankart repairs do little to affect humeral translations with unconstrained moment loading but that rotations are affected during the cocked phase of throwing, with significant losses of external and extension rotations.

Biomechanical Phenomena↗

PubMed1997

Clinical, radiographic, and kinematic results from an adjustable four-pad halovest.

STUDY DESIGN: Charts and radiographs of all patients treated with this halovest at one university hospital were reviewed retrospectively. OBJECTIVES: To describe the outcomes from an adjustable four-pad halovest and to compare them with those from standard halovests, as previously published. SUMMARY OF BACKGROUND DATA: With standard halovests, there can be cervical motion up to 70% of normal values, substantial loads between the halo and vest, and complications of pin loosening, pin infections, and scapular pressure sores. The four-pad vest reduces halovest loads and vest-torso motions. METHODS: The four-pad vest has four independently adjustable pads that completely avoid contact with the scapula, clavicle, and abdomen. Clinical records were analyzed to determine the incidences of halo pin loosening, pressure sores, injury or surgical site nonunion, and loss of cervical alignment. Lateral radiographs were taken with the patient in the upright and supine positions at various times to determine intervertebral rotations (flexion-extension). RESULTS: The clinical results with the four-pad vest were at least as good as those for standard vests. Scapular pressure sores were prevented completely by the absence of vest-scapula contact. Kyphosis did not increase significantly with time. The mean segmental rotations were all 3 degrees or less and showed a smoothly decreasing pattern from C1-C2 to C6-C7. The value at Oc-C1 was opposite to that at C1-C2 and is the subject of further analysis. CONCLUSIONS: The rotations occurring with the four-pad vest are less than or equal to those occurring with standard vests, for overall cervical rotation and for individual motion segment rotations. This is consistent with the smaller halovest forces seen with this vest. Prospective, comparative testing will assess the clinical significance of these findings.

Adult↗

PubMed1995

Resection and adjuvant chemotherapy of pulmonary blastoma: a case report.

BACKGROUND: Pulmonary blastoma is a rare malignancy treated primarily with surgery. Chemotherapy has proven effective in some cases, and has been used in adjuvant fashion in pediatric patients. METHOD: This is a case report of a 40 year-old woman treated with surgical resection, and because of the high risk of recurrence, adjuvant chemotherapy was also given. RESULTS: At the time of this writing, the patient has been in continued remission since surgery in October, 1993. CONCLUSION: This rare entity is difficult to diagnose noninvasively. The limited number of case reports makes therapeutic decisions difficult. To the authors' knowledge, this case is the first reported adult treated with adjuvant chemotherapy. A central registry of cases would be helpful to physicians treating patients with this disease.

Adult↗

PubMed1994

Multidirectional stability of the Graf system.

STUDY DESIGN: To assess the biomechanical influences of the Graf fixation system on the spine, motion segments were tested. In normal spines, destabilized and restabilized with the Graf system conditions, the range of motion and flexibilities were found under various loading conditions. OBJECTIVES: These results should explain how the Graf Fixation system affects the biomechanical response of a motion segment. METHODS: Motion segments (L2-3) and (L4-5) were subjected to these loading conditions: compressive loading, flexion-extension, lateral bending, and axial rotation moments. During the loading, the main and coupled motions were measured, and flexibilities were computed. The position of the balance point in axial loading was also determined. The motion segments were tested under three conditions: intact, destabilized, and restabilized. The destabilization consisted of a bilateral total laminectomy (pedicle-to-pedicle). Restabilization was affected with the Graf stabilization system, consisting of polyester bands between pedicle screw implants. RESULTS: The total laminectomy significantly changed the balance point location by moving it forward. The restabilized motion segment had a balance point more similar to normal conditions. The mean compressive compliance was significantly less after application of the Graf system compared with destabilization. The range of motion for flexion-extension and axial rotation was significantly reduced for the main motion with the Graf system. For lateral bending, the main and coupled rotations were affected significantly, with lateral bending and flexion-extension motion reduced and axial rotation increased after restabilization. Restabilization decreased the flexibility of the destabilized motion segment for all of the moments. CONCLUSIONS: The Graf fixation system reduced the range of motion and the flexibility values in some loading conditions. These results only assess the immediate stabilization characteristics of this implant system in cadaveric material. Further research should address the fatigue characteristics.

Biomechanical Phenomena↗

PubMed1994

L4-5 isthmic spondylolisthesis. A biomechanical analysis comparing stability in L4-5 and L5-S1 isthmic spondylolisthesis.

The authors have previously reported that the L4-5 isthmic spondylolisthesis lesion often progresses more than the L5-S1 lesion in adult patients. This biomechanical study compares the in vitro stability of the L4-5 isthmic spondylolisthesis lesion compared with the L5-S1 isthmic lesion. The authors also analyzed the role of the L5 iliolumbar ligament as a contributing factor to stability. Six fresh frozen human cadaveric specimens (L4 to the sacrum including the iliolumbar ligamentous complex) were tested by applying 10 Nm flexion-extension moments. Sagittal plane motion was measured with the specimens intact and after sequential transection of the pars interarticulares at L4 and L5 and finally with the iliolumbar ligaments cut at L5-S1. L4-5 and L5-S1 both showed significant increases in rotation with the pars defect compared with normal (L4-5 = +2.0, L5-S1 = +3.2 degrees). Decreased translation of L5-S1 occurred with pars defect at this level. There were no significant differences at the L5-S1 level after sectioning of the iliolumbar ligament. Calculating the percentage difference from normal, L4-5 with a pars defect exhibited significantly greater relative motion compared with L5-S1 with the same defect; 12% more rotation, 33% more shear, and 43% more axial translation. The iliolumbar ligament did not appear to contribute to these differences because there was no significant change in the L5-S1 kinematics after its transection. These results support the hypothesis that L4-5 pars defects are more unstable than L5-S1 lesions. The iliolumbar ligament could not be implicated as the major contributing factor in these differences.

Biomechanical Phenomena↗

PubMed1993

Decompression for degenerative spondylolisthesis and spinal stenosis at L4-5. The effects on facet joint morphology.

Anatomic variations exist in the facet joint orientation, shape, and size at L4-5. This morphology is further modified by degenerative changes in spinal stenosis and degenerative spondylolisthesis. This study explored the morphologic alteration of "pedicle-to-pedicle" decompression on the facet joints in normal patients, spinal stenosis patients, and degenerative spondylolisthesis patients. Using computerized digitization, computed tomographic scan images of the facet joint at L4-5 and the medial border of the pedicle at L5 were superimposed. The facet joint orientation, coronal dimension, percentage, and absolute reduction in coronal dimension after pedicle-to-pedicle decompression, and residual coronal dimension after decompression at L4-5 were measured for the three groups. There is a significantly reduced coronal dimension of the facet joint in degenerative spondylolisthesis patients compared with spinal stenosis and normal patients (P < 0.01). The average reduction of the facet joint coronal dimension is 34% (SD 30%) in degenerative spondylolisthesis, and 36% (SD 25%) in spinal stenosis. The smaller preoperative coronal dimension in degenerative spondylolisthesis leads to a significantly reduced residual coronal dimension in degenerative spondylolisthesis compared with normal patients (5.9 mm [SD 4.3 mm] vs. 9.3 mm [SD 3.5 mm]), respectively. Wide variations in facet joint reduction and residual facet joint coronal dimension exist. The significantly reduced coronal dimension after decompression in degenerative spondylolisthesis may be correlated to a trend to further anterior displacement if it is treated with decompression alone. Case-specific assessment of residual facet joint morphology after decompression in both spinal stenosis and degenerative spondylolisthesis patients should be integrated into decisions about fusion for stability at the L4-5 level.

Aged↗

PubMed1993

Postoperative spondylolisthesis at L4-5. The role of facet joint morphology.

Thirty-three patients underwent decompression without fusion at the L4-5 level for spinal stenosis or degenerative spondylolisthesis. Using preoperative and 1-year postoperative lateral lumbar spine radiographs, the incidence of postoperative spondylolisthesis of greater than 5% was found to be 58%. Computed tomographic scans were used to analyze the presurgical facet joint morphology and facet joint-pedicle spatial relationship. This allowed calculation of the facet joint orientation for each side; the coronal dimension of each facet joint; the amount of the facet joint coronal dimension removed if a decompression was performed up to the medial border of the L5 pedicle (facet joint reduction); and the residual coronal dimension of facet joint after such a decompression (residual facet joint). The lateral radiographs were analyzed for presurgical disc height and the presence of traction spurs or spondylophytes. A well-maintained disc height was associated with an increase slip (7.47%) compared with those cases with a narrow or complete loss of disc space before surgery (4.84% P < 0.1 trend). Presence of spondylophytes was associated with a reduced tendency to slip. When spondylophytes were controlled for there was a significant relationship between slip of greater than 10% and sagittal facet joint orientation. Although there was a lesser residual facet joint after decompression in the group that slipped these values were not statistically significant. This study suggests that the development of postoperative spondylolisthesis is related to facet joint orientation and dimensions, rather than the absolute amount of joint removed. The stabilizing effects of reduced disc height and spondylophytes were confirmed.

Aged↗

PubMed1993

Clinical validation of functional flexion/extension radiographs of the cervical spine.

The aim of this study was to determine the clinical validity of functional flexion/extension radiographs of the cervical spine in a defined patient population. Sixty-four adults with functional disorders of the cervical spine underwent passive flexion/extension radiographic examinations. The radiographs were analyzed using a computer assisted method to calculate segmental motion parameters, such as rotations, translations, and centers of rotation. The patients were separated into three groups based on their specific functional disorders, and their motion parameters were compared with those of a healthy population. The three groups consisted of patients with degenerative changes, those with radicular syndrome, and those with whiplash trauma. Most of the patients displayed trends toward hypomobile segmental motion. This trend is displayed more substantially in the groups with degeneration and radicular syndrome. Hypomobility in segmental rotation was significant at C6-C7 for the degenerative and radicular groups. The trauma group showed trends toward hypermobility in the upper and middle cervical levels, and the locations of the centers of rotation were shifted in the anterior direction when compared with those of the healthy population.

Adult↗

PubMed1993

Spinal biomechanics.

The lumbar spine is a source of disability due to low back pain (LBP), yet the precise diagnosis is unknown in 80-90 percent of patients. The lifetime prevalence is 75 percent with a cost to the U.S. economy as high as 80 billion dollars. The problem is partly caused by mechanical overloading of the tissues and thus, there is some potential for both primary and secondary prevention. Biomechanical techniques have been effective in improving our understanding of the loading conditions leading to LBP, and in developing techniques for improved diagnosis and more effectual methods of treatment. Much progress has been made through the use of biomechanical models. Most models assume that the external moments are balanced by trunk musculature. Multiple muscle system models, employing agonist and antagonists, now are available to define 3D spine reaction forces. The static indeterminacy is taken care of either by simplification of the model or by linear or nonlinear optimization. Dynamic analysis has shown that vibrational and impact conditions (such as vehicle driving) can excite the natural frequency of the spine and lead to high spinal loadings. In vivo measurements have shown the resonant frequency of the lumbar spine to be 4-5 Hz and many vehicles excite those frequencies. New biomechanical techniques employing electromyography can estimate muscle load and muscle fatigue. Stereo photogrammetric techniques for establishing segmental kinematics have great potential for improving the diagnosis of spinal problems. These techniques are solidly based on prior in-vitro measurements of spinal kinematics. Mechanical fixation techniques, such as pedicle fixation, show great promise in improving the treatment of spinal problems. These have been extensively analyzed by both finite element techniques and in-vitro simulation so as to improve design as well as surgical technique.

Biomechanical Phenomena↗

PubMed1993

Etiology of spondylolisthesis. Assessment of the role played by lumbar facet joint morphology.

This study examined the role of facet joint morphology in the etiology of both degenerative spondylolisthesis and isthmic spondylolysis. To this end, the axial facet joint morphology of the lower lumbar spine in a normal population and in populations of patients with spinal stenosis or degenerative spondylolisthesis at L4-5 and in patients with isthmic spondylolysis at the L5 level were characterized. Computed tomographic scans were digitized, defining the axial morphology of the normal facet joint at five stations from proximal to distal within the joint. Assessments were made of facet joint orientation, transverse articular dimension, depth of the articular surface, and shape of the articular surface at levels L3-4, L4-5, and L5-S1. There was a gradually more coronal orientation from proximal to distal among the stations at each level, and a maximal transverse articular dimension at the level of the superior endplate of the caudad vertebra. Minimal error in the recording process at this level. In addition to the maximal joint dimension, made this level the most representative of the overall morphology and most useful for further studies. At the L4-5 level, a significantly more sagittal facet orientation was found in the degenerative spondylolisthesis group when compared to both the normal population and spinal stenosis groups (P < 0.01). At L5-S1, the only significant morphologic difference between the normal population and the patients with isthmic spondylolysis was reduced transverse articular dimension. These results support the hypothesis that patients developing degenerative spondylolisthesis are predisposed to this by a developmental sagittal orientation of the L4-5 facet joints.

Adult↗

PubMed1991

In vivo flexion/extension of the normal cervical spine.

Twenty-two women (age range 25-49 years, average 30.9 years) and twenty-two men (age range 23-42 years, average 31.6 years), all healthy and asymptomatic, underwent passive flexion/extension examinations of the cervical spine. Functional x-rays were taken and analyzed using a computer-assisted method that quantified intervertebral rotations, translations, and locations of the centers of rotation for each level C1-C2-C6-C7. The aim of the study was to establish values for these parameters for a normal population as related to age and gender. In the process, a statistically significant difference was found in the average value of rotation between male and female groups at the C5-C6 level. A new parameter, the ratio between translation and rotation, was also established and may prove useful for clinical diagnoses. This parameter has a smaller error associated with it than do pure translations and may aid the clinician by helping to account for the large variation in rotatory ranges of motion within the population. This translation/rotation ratio indicated highly significant differences in the lower segments of the cervical spine between gender groups.

Adult↗

PubMed1991

Clinical validation of functional flexion-extension roentgenograms of the lumbar spine.

The purpose of this study was to determine the clinical validity of functional flexion-extension roentgenograms of the lumbar spine in a defined patient population. One hundred and one adults with low-back pain or functional disorders underwent passive functional flexion-extension examinations. Their roentgenograms were analyzed using a computer-assisted method to determine segmental motion parameters such as rotation and translation of the lumbar vertebrae. The patient population was broken down into five groups with similar pathologies or physical conditions, and their motion parameters compared to a normal population and to each other. It was found that all of the patient groups exhibited significantly hypomobile motion, spread equally among all levels, in comparison to the normal population, except for the group of high-performance athletes, who had significant hypermobility. The uniform spread of hypomobility limits the ability to distinguish with any confidence between the four pathologic groups by their motion. Thus, we believe that the analysis of the segmental motion of the lumbar spine using passive flexion-extension roentgenograms does not aid in differentiating the underlying pathologic condition of patients with low-back pain, and that no useful information can be derived form this procedure, especially in relation to the need for surgical intervention.

Adult↗

PubMed1985

Studies of the purine analog associated modulation of human erythrocyte acid phosphatase activity.

The activity of the human erythrocyte acid phosphatase is modulated by a series of structural analogs of purine. The unsubstituted purine base does not affect the enzyme activity. Addition of a substituent at the number six position usually generates an analog which activates the enzyme while similar substitutions at the two position usually generate an inhibitor. Pyrimidines are generally ineffective as modulators while several modifications of the imidazole ring of the purine analogs do not abolish the modulator activity of the purine analog. The level of response to all active analogs is isozyme specific. Differences in apparent relative affinities among the modulators are noted. The modulators with a positive effect on enzyme activity, are effective in the presence of methanol which is more effective than H2O as a phosphate acceptor. These analogs act by enhancing the rate of transfer of phosphate to H2O, while decreasing the rate of transfer to methanol. The results suggest that the purine analogs may act by altering the rate of hydrolysis of the phosphoenzyme intermediate by H2O or may change the rate-limiting step in the catalytic mechanism.

Acid Phosphatase↗