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Biomedical subjects

M S Levy

Publications and source records attributed to M S Levy.

At least 37 records · Page 2Linked to original sources
PubMed1993

Effect of mutations in SOS genes on UV-induced precise excision of Tn10 in Escherichia coli.

UV treatment increases the frequency of Tn10 precise excision from different sites of the Escherichia coli chromosome. UV induction of Tn10 excision is not evidenced in a lexA3 (ind-) mutant carrying either a recA+ or a recA730 allele. High levels of RecA synthesized by a recA+ gene not repressible by LexA do not relieve the non-inducibility of Tn10 excision in a lexA3 (ind-) background. This indicates that the expression of an SOS gene different from recA is necessary for the induction of Tn10 excision. In contrast to UV induction of point mutations, this induction does not depend on a functional umuC gene since umuC::Tn5 mutants show increased levels of Tn10 excision from leu, thr or gal after irradiation. MucAB+ plasmid pKM101 which renders cells more UV-mutable for point mutations decreases UV-induced Tn10 excision. These results show that UV-induced Tn10 precise excision requires SOS induction and that it involves a pathway different from point mutagenesis.

Bacterial Proteins↗
PubMed1993

In vitro evaluation of an implantable force transducer (IFT) in a patellar tendon model.

A new implantable transducer has been developed for in situ evaluation of ligament and tendon forces. Unlike previous devices, this sensor is placed within the specimen, minimizing measurement errors due to impingement on surrounding soft tissues and bone. In this study, we present the sensor design details as well as test results from initial in vitro trials in the goat patellar tendon model. Device performance and influence of the device on the specimen were evaluated under several loading conditions. In all cases, device output had a strong correlation with induced tissue load. Significant variations in device performance were only noted at high tissue deformation rates. More extensive investigations will be conducted to assess how changes in transducer design might alter performance characteristics.

Animals↗
PubMed1992

Primary and coupled motions in the intact and the ACL-deficient knee: an in vitro study in the goat model.

Quadrupeds are commonly used as animal models to study healing of anterior cruciate ligament (ACL) reconstructions. While rabbits, dogs, goats, and sheep have been used, goats and sheep are increasingly being employed because of the larger joint size that facilitates surgery, ease of availability, and lower expense to maintain in the farm environment. In spite of this, little is known about the function of the ACL in controlling primary and coupled motions in the quadruped. We report here on the measurements of these motions in goats, with the application of anterior-posterior forces, varus-valgus moments, and internal-external moments in the intact and ACL-deficient knee. Sectioning the ACL caused significant increases in primary anterior translation, and in varus-valgus and internal rotations. The increases in anterior translation were similar in amount and dependence on flexion angle to those seen in human knees. The increase in varus averaged 7 degrees and did not depend on flexion angle, whereas the increase in valgus was significant only in the flexed knee. The increases in internal tibial rotation were greatest in extension, whereas the increases in external rotation were small and independent of flexion angle. When the ACL was cut, coupled internal rotation increased with an anterior force as well as a valgus moment. Large increases were seen in coupled anterior translation with the application of varus and valgus moments, whereas smaller increases were seen with internal and external moments. These findings demonstrate that the ACL restrains multiple motions in the goat knee. This study also provides baseline data for future studies of ACL reconstruction.

Animals↗
PubMed1992

The correlation between anterior-posterior translation and cross-sectional area of anterior cruciate ligament reconstructions.

Total anterior-posterior translation is commonly used to assess the integrity of the cruciate ligaments and the success of reconstructive surgery. The purpose of this study was to determine, after surgical reconstruction of the anterior cruciate ligament with a biological graft, if total anterior-posterior translation correlated with graft length, cross-sectional area, or mechanical properties. These factors were investigated by analyzing data from three previous studies. These studies involved replacement of the anterior cruciate ligament in cynomolgus monkeys and goats, with free and vascularized patellar tendon autografts and both patellar tendon and anterior cruciate ligament allografts. Data were available at time periods of 6 and 12 months after surgery. We found statistically significant inverse correlations between the amount of anterior-posterior translation and cross-sectional area of a graft at the time of sacrifice. The Pearson correlation coefficients ranged from -0.966 (p < 0.002) to -0.830 (p < 0.05). We hypothesize that these correlations result from the following mechanism: the increased anterior translation reflects a slack graft; a slack graft is stress shielded by other structures about the knee; the reduced in vivo stresses on the graft modulate cellular metabolism in a way that over time produces a small cross-sectional area.

Analysis of Variance↗
PubMed1992

Location-dependent variations in the material properties of the anterior cruciate ligament.

Our recent anterior drawer studies in human cadaveric knees [Guan and Butler, Adv. Bioengng 17, 5 (1990); Guan et al., Trans. orthop. Res. Soc. 16, 589 (1991)] have suggested that anterior bundles of the anterior cruciate ligament (ACL) develop higher load-related material properties than posterior bundles. This was confirmed when we reevaluated the axial failure data for these bundle-bone specimens from an earlier study [Butler et al., J. Biomechanics 19, 425-432 (1986)]. The purpose of this study was to determine, in a larger data set, if anteromedial and anterolateral bundles of the anterior cruciate ligament exhibit significantly larger load-related material properties than the posterior ligament bundles. Seven ACL-bone units from seven donors (the three tissues from the original study plus four new ones) were subdivided into three subunits, preserving the bone insertions. The subunits were failed in tension at a constant strain rate (100% s-1) and four material properties were compared within and between donors. The anterior bundles developed significantly larger moduli, maximum stresses, and strain energy densities to maximum stress than the posterior subunits. Moduli for the anterior vs posterior subunits averaged 284 MPa vs 155 MPa, maximum stresses averaged 38 MPa vs 15 MPa, and strain energy densities averaged 2.7 N m cc-1 vs 1.1 N m cc-1, respectively. No significant differences were found, however, among strains to maximum stress or between any of the other properties for the two anterior subunits. These results are important to the design of ligament replacements and suggest new experiments designed to distinguish in vivo force levels in these ACL bands, a possible reason for the material differences.

Adult↗
PubMed1991

Effects of gamma irradiation on the initial mechanical and material properties of goat bone-patellar tendon-bone allografts.

The effects of 60Co gamma irradiation on the initial mechanical properties of the composite bone-patellar tendon-bone unit (CU) and the tendon midsubstance (TM) were studied. Frozen specimens were exposed to either 2 or 3 Mrad of gamma irradiation. Paired frozen specimens served as intraanimal controls. Treatment effects on the CU were assessed using four mechanical parameters. Effects on the TM were assessed using four material parameters measured using an optical surface-strain analysis system. The maximum force and strain energy to maximum force of the composite unit were significantly reduced 27% and 40%, respectively, after 3 Mrad of irradiation (p less than .05). Mechanical properties of the CU were not significantly altered, however, following 2 Mrad of irradiation. Based on individual paired contrasts between treatment and control, significant differences were also found in the material properties of the tendon midsubstance. The maximum stress, maximum strain, and strain energy density to maximum stress were significantly reduced following 3 Mrad, but not 2 Mrad, of irradiation. The results provide important "time zero" material property data, which will be useful for later anterior cruciate ligament reconstruction studies using irradiated allograft patellar tendons in the goat model and other animal models as well.

Analysis of Variance↗
PubMed1991

RecA-dependent increased precise excision of Tn10 in Salmonella typhimurium.

UV irradiation induced the precise excision of Tn10 inserted in met, trp or srl in a Salmonella typhimurium strain; mitomycin C was also found to induce the frequency of precise excision of Tn10 from srl or met. Precise excision of Tn10 was not increased by either UV or mitomycin C in a recA mutant. Similarly, a recA mutant derived from a uvrD strain showed a drastic reduction in the high spontaneous levels of precise excision of Tn10 of this strain. These results indicate that recA is involved in the increased precise excision of Tn10. In contrast to point mutations excision of Tn10 was found to be UV inducible in a top mutant.

Chromosome Deletion↗
PubMed1990

Individualized care for the treatment of alcoholism.

Through a discussion of several case vignettes, the author emphasizes the utilization of an individually tailored treatment approach when working with people experiencing problems related to alcohol consumption. Patients may achieve abstinence without believing in the disease concept of alcoholism, and attending Alcoholics Anonymous meetings need not always be a part of the treatment. Furthermore, for some patients, controlled drinking may be as desirable an outcome as abstinence. The importance of entertaining a multiplicity of perspectives when conducting clinical work with such patients is discussed.

Adult↗
PubMed1990

Surface strain variation in human patellar tendon and knee cruciate ligaments.

Local surface strains in bone-fascicle-bone subunits from human patellar tendon and anterior and posterior cruciate ligaments were measured between markers using low-speed photography during low rate subfailure testing. A simple stress-strain relationship of the power form was found to describe the bone-to-bone responses up to four percent strain for all three tissue types examined. The regional material behavior were best fit using an inverted strain-stress relationship, however. The power model, fitted to the experimental data, conformed to the expected stress-strain relationship better than either the quadratic or cubic models. With few exceptions, for a given stress, the strains near the proximal and distal bone ends were not significantly different from each other, but were significantly higher than the strains in the tissue midregions. Local strain patterns generally varied among subunits from the same tissue.

Adult↗
PubMed1988

The Special Treatment Team: an inpatient approach to the mentally ill alcoholic patient.

We review the problems unique to the diagnosis and treatment of patients who suffer both major mental illness and alcohol/drug abuse. We describe the experience and the approach evolved in the Special Treatment Team, a State Hospital unit that has specialized in this work. We discuss in detail the assessment and stabilization of such patients, including psychosocial and pharmacologic strategies, giving special attention to the problem of the unmotivated patient. Several case vignettes illustrate our approach.

Alcoholism↗
PubMedDate not supplied

The disease controversy and psychotherapy with alcoholics.

This article discusses conducting psychotherapy with alcoholics in light of the controversy about whether alcoholism is a disease. The belief that alcoholism is a disease forces many clinicians to offer abstinence from alcohol as the only option for alcoholics who seek treatment. From this perspective, the alcoholic must be helped to accept the idea that he or she has a disease and that to recover from this problem, drinking must stop. Others maintain that alcoholism may not be a disease and view alcoholic drinking as maladaptive behavior. From this vantage point, helping the patient to control or to moderate drinking might be considered. These two distinct paradigms lead to divergent treatment goals, which leaves the clinician in a quandary about how best to treat an individual who experiences a drinking problem. To resolve this dilemma, it is suggested that the clinician who works with alcoholics entertain a multiplicity of perspectives and should not be blinded by any one paradigm. While control of alcohol intake must take place if such patients are to improve their functioning, the author argues that recovery can occur either by abstinence or through moderating drinking.

Alcohol Drinking↗
PubMedDate not supplied

Two-bundle posterior cruciate ligament reconstruction. An in vitro analysis of graft placement and tension.

This study had two purposes: first, to determine how femoral attachment location affects the load sharing between the two bundles of a Y-type posterior cruciate ligament reconstruction, and second, to determine how the bundles, separately and in combination, control posterior tibial translation throughout the full range of knee flexion. One and two-bundle reconstructions were performed in 12 cadaveric knees. The one-bundle reconstructions were attached within the femoral posterior cruciate ligament footprint at one of three locations, high and shallow (S1), mid and shallow (S2), or mid and deep (D). The two-bundle reconstructions comprised an S1 bundle with either an S2 or a D bundle. Posterior translation and bundle tension were measured as the knee was flexed from full extension to 1,200 of flexion while a posterior force of either 50 or 100 N was applied to the proximal tibia. The shallow one-bundle reconstruction restored posterior translation to within 2 mm of that of the intact knee over the entire range of knee flexion. The deep reconstruction did not control abnormal posterior translation above 45 degrees. The tension in the shallow bundles increased with knee flexion, and the deep bundle tension remained nearly constant throughout knee flexion. Both two-bundle reconstructions controlled posterior translation, but with different load-sharing characteristics. The S1-S2 configuration resisted posterior tibial translation as both bundles became taut in flexion. In contrast, the S1-D configuration resisted posterior translation in a reciprocal fashion with the D bundle tension being the greatest in extension and the S1 bundle tension being the greatest tension in flexion.

Aged↗