Unusual ribosomal RNA gene organization in copepods of the genus Calanus.

Ribosomal RNA genes in the nuclear genomes of eukaryotes are generally found in tandemly repeated units encoding 18 S, 5.8 S and 28 S rRNA (in that order). 5 S rRNA genes typically lie outside these units, most often in tandem clusters coding exclusively for 5 S rRNA. Inclusion of 5 S genes within the 18 S-5.8 S-28 S repeat unit is known only for certain protozoa and fungi. Here we report that, in the copepod Calanus finmarchicus, single 5 S genes are included within many or all of the 18 S-5.8 S-28 S repeat units. Sequence analyses of regions cloned from two of these repeat units show that they indeed include 5 S genes (which are distal to 28 S genes) and that these are transcribed from opposite strands.

Microscopical investigation of canine anterior cruciate ligament and patellar tendon: collagen fascicle morphology and architecture.

The collagen structure of the canine anterior cruciate ligament (ACL) and patellar tendon (PT) was examined by using light and scanning electron microscopy. The collagen waviness known as a crimping was found to occur in ACL and PT fascicles. This waviness, seen at the periphery of fascicles, is very smooth, and its amplitude seems to decrease from the periphery toward the fascicular center. It appears as a periodic collapse of the fascicle in two dimensions. Two models of the architectural patterns of the ACL and PT wavy fascicles are presented. The constituent collagen fibrils are either parallel or twisted relative to the fascicle axis, giving rise to planar and helical wave patterns, respectively. There is a distinct difference between the ACL and PT collagen structure. The helical wave pattern occurs in both PT and ACL while the planar waveform is found only in the centrally located ACL fascicles. In addition, there is less variability in fascicular size and density over the PT cross-section than in ACL.

Capillary electrophoretic separation of uncharged polymers using polyelectrolyte engines. Theoretical model.

We recently demonstrated that the molecular mass distribution of an uncharged polymer sample can be analyzed using free-solution capillary electrophoresis of DNA-polymer conjugates. In these conjugates, the DNA is providing the electromotive force while the uncharged polydisperse polymer chains of the sample retard the DNA engine with different amounts of hydrodynamic drag. Here we present a theoretical model of this new analytical method. We show that for the most favourable, diffusion-limited electrophoresis conditions, there is actually an optimal DNA size to achieve the separation of a given polymer sample. Moreover, we demonstrate that the effective friction coefficient of the polymer chains is related to the stiffness of the two polymers of the conjugate, thus offering a method to estimate the persistence length of the uncharged polymer through mobility measurements. Finally, we compare some of our predictions with available experimental results.

Load-bearing role of facets in a lumbar segment under sagittal plane loadings.

In the present work, the load-bearing role of the facet joints in a lumbar I2-3 segment is quantitatively determined by means of a three dimensional nonlinear finite element program. The analysis accounts for both material and geometric nonlinearities and treats the facet articulation as a nonlinear moving contact problem. The disc nucleus is considered as an inviscid incompressible fluid and the annulus as a composite of collagenous fibres embedded in a matrix of ground substance. The spinal ligaments are modelled as a collection of nonlinear axial elements. The loadings consist of axial compression and sagittal plane shears and bending moments, acting alone or combined. The results show that in pure compression, the external axial force is transmitted primarily by the intervertebral disc. The facet joints carry only a small percentage of the force. However, the facet joints carry large forces in extension, whereas in small flexion they carry none. Addition of compression tends to increase these contact forces in extension while it has no effect on them in flexion. In extension, the forces on the facet joints are transmitted by both the articular surfaces and the capsular ligaments. Although in small flexion the facets carry no load, large contact forces are predicted to develop as the segment is flexed beyond 7-8 degrees. These forces are of the same magnitude as those computed under large extension rotation and are oriented nearly in the horizontal plane with negligible component in the axial direction. The horizontal components of the contact forces generated during articulation are often larger than the axial components which directly resist the applied compressive force. The axial components of the contact forces, therefore, grossly underestimate the total forces acting on the facets. The transfer of forces from one facet to the adjacent one occurs through distinct areas in flexion and in extension loadings. That is, on the superior articular surface, the contact area shifts from the upper tip in large flexion to the lower margin in extension. On the inferior articular surface, the contact area shifts from the upper and central regions in large flexion to the lower tip in extension.

In situ mechanical behavior of posterior spinal ligaments in the lumbar region. An in vitro study.

The posterior ligaments: ligamentum flavum, articular, interspinous and supraspinous ligaments of twenty five fresh cadaveric intervertebral segments, from T11-T12 to L4-L5, extracted from fourteen spines were tested in tension. A progressive dissection method was used, that is, each segment was tested after first resecting the disk with the ligaments intact and a force-elongation curve obtained. Then one ligament was cut and the test repeated, and so on. The most restrictive ligament was found to be the ligamentum flavum followed by the articular, interspinous, and supraspinous ligaments.

Statistical analysis of knee ligament lengths.

Absolute locations of the main knee ligamentous structures' insertion sites on the femur, the tibia and the patella have been obtained for 30 knees originating from 18 fresh human cadavers. For each knee, the length of ten selected structures was deduced. These length data form the input of the statistical analysis presented in the paper. The correlations between the ligament lengths are presented. A comparison of the lengths from the left and right (laterality) knees of the same specimen is also done and shows no significant difference. The sex difference is also studied and does not seem to be a determinant parameter for the sample investigated. Prediction equations are proposed to estimate the ligament lengths for the knee in extension with respect to the three external parameters: height, weight and femoral condyle width. The menisco-femoral length, the patellar tendon length and the patellar length are not related to the external parameters and predictions are based on mean values. For the other six ligament lengths, the square multiple correlation coefficient with the external parameters ranges between 0.22 and 0.43. The condylar width is the most often used external parameter in these equations while the weight parameter is never present.

Body composition in quadriplegic patients.

The nutritional state of 12 patients with quadriplegia, secondary to spinal cord injury, was assessed by determining body composition with a multiple isotope dilution technique. For comparative purposes, similar measurements were obtained in 25 normal volunteers. The mean duration of quadriplegia was 14.8 +/- 8.5 months. All the patients were hospitalized, receiving a regular hospital diet and all were on a similar rehabilitation program. Because skeletal muscle atrophy is extensive in quadriplegics, we had expected a reduced body size, which was otherwise normal in composition, with a comparable decrease in both the body cell mass (BCM) and the extracellular mass (ECM). Instead, a body composition characteristic of malnutrition was observed in an unexpectedly large percentage (58%) of patients. In the normally nourished individual, the BCM and ECM are approximately equal in size. However, in seven of the 12 quadriplegic patients, the body composition was characteristic of malnutrition, with a BCM (13.5 +/- 1.6 kg) which was reduced relative to the ECM (28.7 +/- 1.9 kg). Their body composition was significantly (p less than 0.05) different from the body composition of both the healthy volunteers and the other five quadriplegic patients, whose body composition was normal (BCM = 22.9 +/- 1.5 kg, ECM = 28.5 +/- 1.6 kg). The nutritional state of the quadriplegic patients correlated significantly with the level of spinal cord injury and not with the duration of quadriplegia.

Pathomechanics and management of scoliosis in Friedreich ataxia patients: preliminary report.

The preliminary results based on a one year study on the evolution and management of scoliosis are presented. Twenty-one patients were followed in the Neuro-Muscular Disease Clinic at Ste-Justine Hospital where standardized spinal radiographs were taken periodically with the Scoliosis Chariot and the Throne. The short period of observation as well as the relatively small number of Friedreich ataxia patients followed requires that these results and the following remarks be interpreted with caution. Pathomechanics -- Between the age groups I (5 - 10 years) and II (10 - 15 years), a substantial increase in the Cobb values occurs. Associated with it, an increase was observed in the thoracic and thoracolumbar projected surface area indices. The relative rotation between the thoracic and lumbar segments was presumed to be the cause of the sudden increase in the Cobb measurements. For the non-ambulatory patients, a decrease in the lumbar lordosis towards a thoraco-lumbar kyphosis as well as a sudden increase in the sacral angle and a drop in the lumbo-sacral angle were associated with the seated posture assumed by the patient. Management -- Prevention of the progression of established curves was our main objective. Careful examination of the spine, depending on the age of the child, in our preliminary study, stimulated early orthopaedic treatment in any curve of 20 degrees or more. There was always concern for curves of 30 degrees or more. In the growing child, bracing was recommended. In the older child, the curve was usually stable after sixteen years of age. Surgery was usually attempted in curves over 40 degrees in the growing child. The same curve was usually stable after the growth period. For the non-ambulatory patients, the present study suggested the prescription of a molded seat with the following characteristics: i) a posterior lumbar support, ii) low thoracic lateral supports and iii) a slight inclination of the seating system. This was presumed to be beneficial in maintaining stability of the spine. Presently, an evaluation of such a device is under investigation.

Dynamics of human lumbar intervertebral joints. Experimental and finite-element investigations.

To improve our understanding of the dynamic characteristics of the human lumbar spine, both experimental and finite-element methods are required. The experimental methods included measurement of the axial steady state response, resonant frequencies, and damping of seven lumbar motion segments under an upper-body mass of 40 kg. The influence of the presence of posterior elements and different magnitudes of compression preload on the response was also studied. To supplement the measurements, linear and nonlinear, axisymmetric, and three-dimensional finite-element models of a L2-L3 disc-vertebra unit were developed to predict the free and forced-vibration responses. The step and harmonic loadings in the axial direction were considered for the forced-vibration analysis. The effect of the presence of the body mass and compression preloads were also examined. The results of experimental and finite-element studies were in good agreement with each other. They indicated that the system resonant frequencies are reduced considerably with the addition of a body mass of 40 kg and increase significantly (P less than .005) as the compression preload increases. The compliance at both low and resonant frequencies decreases with increasing compression preload. Under preloads of not more than 680 N, removal of the facet joints tends to decrease slightly the segmental resonant frequencies irrespective of the magnitude of compression preload (P less than .1). The finite-element model studies show quasi-static response under harmonic loads with periods much larger than the fundamental period of the segment and under step loads with slow rising times. Under a step load without the body mass, the nucleus pressure varies with both location and time and reaches a maximum of about 2.5 times that under equivalent static load. The addition of a 40-kg mass, in this case, renders a single degree-of-freedom response, with the pressure remaining nearly constant with location inside the nucleus. The stresses and strains throughout the segment in this case increase approximately twofold in comparison with equivalent static values. Partial or complete removal of the disc nucleus considerably decreases the resonant frequency and increases the corresponding segmental response amplitude (ie, compliance). The results indicate that the most vulnerable element under axial vibration loads is the cancellous bone adjacent to the nucleus space. Fatigue fracture of bone as a cumulative trauma and the subsequent loss of nucleus content likely initiates or accelerate the segmental degenerative processes. The annulus fibers do not appear to be vulnerable to rupture when the segment is subjected to pure axial vibration.

Degeneration of the human lumbar spine ligaments. An ultrastructural study.

The fine structural alterations in human lumbar spine ligaments were studied in tissue samples obtained from 8 young patients operated upon for idiopathic scoliosis and from 10 adult patients operated upon for herniated discs. The ultrastructure of the scoliotic ligaments was found to be normal. The majority of cells encountered were the fibroblastic-like cells. The collagen-proteoglycans interaction was similar to that described in other normal soft tissues. However, two forms of degenerative changes were demonstrated in posterior ligaments of patients with herniated discs. Metaplasia of ligamentous tissue into fibrocartilage was a common finding. The fibroblasts were replaced by chondrocytes. A few cells which had suffered necrosis were found. Alterations in the collagen-proteoglycans arrangement were also evidenced. This form of degeneration resembled that commonly associated with wear and tear phenomena. A second form of degeneration due to ageing was found to coexist with the aforementioned alterations.

Structural and in vivo mechanical characterization of canine patellar cartilage: a closed chondromalacia patellae model.

The purpose of this project was to study the relationship between the structure of the patellar cartilage and its response to static compressive loading with a closed chondromalacia patellae model. An animal model was used to induce degeneration of the patella that was monitored quantitatively and qualitatively as a function of time. Ten adult mongrel dogs had their left patellofemoral groove replaced by a customized metallic implant covered with a thin film of polyethylene for periods of 3 months (five dogs) and 6 months (five dogs). An indenter was designed to perform mechanical indentation testing on the patellar cartilage in situ. The animals were anesthetized and the response of patellar cartilage to a static compressive load of 4.5 MPa was monitored for 20 min and its relaxation after load removal for 20 min. Indentation tests were performed every 3 months of the implantation period. At the end of the implantation period, the patellae were processed for histology, and sections were stained with Safranin-O indicative of the proteoglycans content. Macroscopically, no apparent degeneration or fibrillation of the patellar surfaces was observed after 3 or 6 months of implantation. However, the patellar surface showed a change in coloration after 6 months. A 17 +/- 3% and 37 +/- 8% deformation of the cartilage were calculated for the 3-month and 6-month specimens, respectively. Histologically, a progressive loss of proteoglycans was observed in the matrix as a function of implantation time. These results indicated that an increase in cartilage compliance is associated with an intrinsic remodeling of the cartilage matrix and that these changes might occur without external signs of degeneration and can be quantified.

Long term follow-up of intravesical Bacillus Calmette-Guerin for the treatment of bladder transitional cell carcinoma.

OBJECTIVE: To review the long-term follow-up, in terms of recurrence and progression, of transitional cell carcinoma of the bladder treated with intravesical BCG with the following indications: CIS, Ta and T1. MATERIALS AND METHODS: Ninety-two patients who had received complete course of BCG between 1987 and 1993 were included in the study and followed for an average of 59 months (range 12 to 102). RESULTS: The recurrence and progression were looked at. Patients treated with BCG for Carcinoma in situ, 11 of 19 (53%) remained tumor-free after 1 or 2 courses of BCG for the duration of the follow-up (mean 4.9 years, range 1.5 to 8.5 years). For patients treated for recurring tumors, 17 of 50 (34%) had no recurrences after 1 or 2 courses of BCG with the same follow-up. When facing multiple tumors, 10 of 23 (43%) patients did not experience recurrences. Therefore, in the 92 patients treated, 38 presented no recurrences after 1 or 2 courses of BCG, for a success rate of 41%. In terms of progression, of the 19 patients treated with BCG for CIS, 4 (21%) went on to develop muscle invasive disease. Of the 50 patients treated for recurrent tumors, 2 (4%) eventually developed lamina propria invasion (initial lesion was a Ta tumor), 4 (8%) carcinoma in situ and 7 (14%) muscle invasive disease, for an overall progression rate of 26% in this group. Of the 25 patients treated for multiple tumors, 1 (4%) developed CIS and 3 (12%) presented with muscle invasive disease, for an overall progression rate of 16% for the duration of the follow-up. Therefore, 21 of 92 (23%) patients had progression of their disease following BCG therapy. No prognostic factors for recurrence or progression could be identified in these tumors. CONCLUSION: When indications warrant its use, BCG is effective in reducing recurrences and limiting progression in TCC of the bladder. Recurrence within 2 years of treatment is, however, a sign of poor prognosis and other therapeutic options should be sought.

Modelling of a composite prosthesis for quasi-cylindrical ligaments.

A prosthesis for a cruciate ligament of the knee involves the problem of implanting a short and small spring for which the load-deformation response cannot be duplicated by any single man-made material. This work presents a model of the elastic behavior of a two material composite prosthesis made of high-strength fibers spirally wound around a soft elastic core. At each end of the core, the fibers are attached to a pulling device. Under a tension load, the fibers exert a pressure on the core which deforms radially, permitting the elongation of the prosthesis. This allows the achievement of large deformation while both the fibers and the core remain in the elastic domain. The high strength of the spring is provided by the high yield strength of the fibers. The results show the influence of the design variables on the deformation of the prosthesis.

Load elongation behavior of the canine anterior cruciate ligament.

This paper describes the results of an investigation on the mechanical properties of canine anterior cruciate ligaments. A total of 38 ligaments were tested. It is shown that the completely reversible (elastic) range of strain is limited to 14 percent elongation, corresponding to an applied load of 200 N. Within this range each specimen was tested at different strain rates varying from 0.12 percent/s to 220 percent/s and it is demonstrated that the mechanical behavior of the ligaments is not sensitive to strain rate in the range investigated. After completion of tests in the reversible range, of strain ten ligaments were frozen and similar tests were performed after thawing. It is shown that freezing produces alterations of the mechanical properties. The ligaments become more rigid than when they are tested in fresh conditions. From room temperature up to 45C, the load-elongation relationship is not significantly dependent upon test temperature.

Vasectomy and prostate cancer in Québec, Canada.

The present investigation measured the association between vasectomy and prostate cancer (PC) in the male population of Québec, Canada. The Québec Health Insurance Board and the Québec Cancer Registry were our principal sources of information. Lung cancer cases and the male population of Québec served as controls for comparative purposes. Within a retrospective design, our preliminary results indicate an association between vasectomy and PC. Among the 1925-39 birth cohort of individuals diagnosed with PC in 1990--93, the global odds ratio was 2.6 (95% CI=1.7--4.3) while it was compared with lung cancer as the control group. This risk increased with the length of time between vasectomy and the diagnosis of cancer. An historical design indicated strong cohesion of the results. Besides, the risk does not vary when we control for the place of residence of the individuals. Vasectomy seems to increase the risk of PC at least 10 years after the operation, but we cannot exclude the impact of a possible detection bias among vasectomized individuals.

Computer-aided design in wheelchair seating.

This paper describes the integration of computer-aided design (CAD) with the design and fabrication of wheelchair seats. The use of CAD during the design phase permits personal seating for adult and pediatric clientele through a series of standard manufactured seating components. The advent of CAD has permitted the creation of databases of detailed 3-D wheelchair structures that are commercially available, in addition to most standard modular seating components. Direct on-screen manipulation of these components on any selected wheelchair structure is through user-friendly software. When using CAD, structural and physical limitations can be foreseen and taken into consideration during the routine initial fitting on an adjustable simulation fitting chair. The end product is a dimensioned drawing of the seating arrangement as it is positioned in the wheelchair structure. The seating components are manufactured from this drawing. The CAD system permits seating specialists to simulate a client's seating arrangement on the wheelchair in order to determine a functional position before the fabrication phase. Essentially, the CAD software is used as a simulation tool for creating functional seating units. It is also a design tool that allows access through a database to dimensional information about commercial seating products and seating products developed through the use of the CAD system.

Design methodology for a multifunctional hand prosthesis.

The first part of this paper reviews different approaches to define the motion of the fingers and the thumb in order to obtain prehension. The last part presents the design of a hand prosthesis based on a new plane of action for the thumb and on proposed design specifications and functional characteristics. The design methodology consists of two steps: the morphology design of the hand prosthesis and the 4-bar mechanism design for each finger. A 3-D computer-aided design (CAD) interactive program was used as a design tool to obtain the hand morphology. This CAD technique was also used to check the geometry, the relative motions of the fingers, and the possibility of interference for the proposed model with two prehension patterns (tridigital and lateral). It is noted that identical flexion angles of the finger joints were obtained for these two prehension patterns, the difference being in the inclination angle of the thumb's plane of flexion. This finding greatly simplified the design of the internal mechanisms of the fingers. CAD was a powerful tool in the design process of this hand prosthesis and will be more and more useful in the future.

Demonstration of renal varices using technetium-99m red blood cells in the investigation of recurrent macroscopic hematuria.

A case of severe, recurrent, macroscopic hematuria in which the diagnosis of renal vein varices was suggested by Tc-99m red blood cell blood pool imaging is described. Current diagnostic modalities are discussed and an integrated use of this test is proposed.

In vitro fatigue testing of prosthetic ligaments: a new concept.

A cruciate ligament fatigue/wear testing system TTF600 was developed at Ecole Poly-technique in order to reproduce a little better the loading conditions and environment in which they perform. This machine was designed to subject the ligaments to simultaneous tension, bending and torsion. The amplitude of each loading can be adjusted separately. This allows to better define the effect of each loading mode on the viability of a prosthetic device. Six devices can be tested simultaneously in a liquid environment at 37 degrees C. The loading conditions and the behaviour of the prosthesis are monitored by computer.

The irradiation effect on the initial mechanical properties of meniscal grafts.

In this study, the effect of sterilization was investigated on the mechanical properties of rabbit's meniscal grafts. The processes of freezing and irradiation were carried out and their effects upon the elastic and viscoelastic properties measured using a tensile testing machine and an indentation test. It was found that gamma irradiation, at dosages commonly used for sterilizing grafts, had a significant adverse influence on the elastic and viscous response of the grafts. Freezing led also to a small significant decrease in elastic stiffness but no change in failure strength. It is concluded that irradiation sterilization is unsuitable for clinical use and other techniques should be used whenever possible.