An implantable transducer for measuring tension in an anterior cruciate ligament graft.

The goal of this study was to develop a new implantable transducer for measuring anterior cruciate ligament (ACL) graft tension postoperatively in patients who have undergone ACL reconstructive surgery. A unique approach was taken of integrating the transducer into a femoral fixation device. To devise a practical in vivo calibration protocol for the fixation device transducer (FDT), several hypotheses were investigated: (1) The use of a cable versus the actual graft as the means for applying load to the FDT during calibration has no significant effect on the accuracy of the FDT tension measurements; (2) the number of flexion angles at which the device is calibrated has no significant effect on the accuracy of the FDT measurements; (3) the friction between the graft and femoral tunnel has no significant effect on measurement accuracy. To provide data for testing these hypotheses, the FDT was first calibrated with both a cable and a graft over the full range of flexion. Then graft tension was measured simultaneously with both the FDT on the femoral side and load cells, which were connected to the graft on the tibial side, as five cadaver knees were loaded externally. Measurements were made with both standard and overdrilled tunnels. The error in the FDT tension measurements was the difference between the graft tension measured by the FDT and the load cells. Results of the statistical analyses showed that neither the means of applying the calibration load, the number of flexion angles used for calibration, nor the tunnel size had a significant effect on the accuracy of the FDT. Thus a cable may be used instead of the graft to transmit loads to the FDT during calibration, thus simplifying the procedure. Accurate calibration requires data from just three flexion angles of 0, 45, and 90 deg and a curve fit to obtain a calibration curve over a continuous range of flexion within the limits of this angle group. Since friction did not adversely affect the measurement accuracy of the FDT, the femoral tunnel can be drilled to match the diameter of the graft and does not need to be overdrilled. Following these procedures, the error in measuring graft tension with the FDT averages less than 10 percent relative to a full-scale load of 257 N.     

Three-dimensional structure of unstained, frozen-hydrated extended tails of bacteriophage T4

Unsupported, unstained frozen-hydrated extended tails of bacteriophage T4 have been studied by cryo-electron microscopy. Their three-dimensional structure has been reconstructed after correlation and averaging of the information from different particles. While the reconstructions of hydrated tails show all the features found by conventional electron microscopy, they are characterized by an open structure. Individual subunits constituting the axial repeat cannot be outlined unambiguously, as the density connectivity is sensitive to the phase-contrast transfer function effects. In order to minimize these effects, we found that the best data set for three-dimensional reconstruction is composed of layer-lines corrected for the phase-contrast transfer function and an uncorrected equator.     

THE HORMONAL INTEGRATION OF SEXUAL REPRODUCTION IN OEDOGONIUM

Rawitscher -Kunkel , Erika , and L. Machlis . (U. California, Berkeley.) The hormonal integration of sexual reproduction in Oedogonium. Amer. Jour. Bot. 49 (2) : 177–183. Illus. 1962.—Sexual reproduction in a heterothallic, nannandrous species of Oedogonium was investigated cytologically and physiologically. Several new observations are reported. Oogonial mother cells release a substance which attracts androspores to them. The androspores, when attached to the oogonial mother cells, grow in well-defined directions apparently in response to a hormone originating in the oogonial mother cells. An oogonial mother cell divides into an oogonium and a suffultory cell only after the attached androspores complete their development into dwarf males, each bearing an antheridium. Presumably the developing dwarf males provide a chemical stimulus for the division of the oogonial mother cell. During development, the oogonia become enveloped in a massive gel which also encases the antheridia cut off at the apical ends of the dwarf male plants. The gel appears to function as a sperm trap, preventing the dissemination of the sperm into the surrounding liquid. The sperm are attracted to the protoplasmic papilla which briefly protrudes through the oogonial pore indicating the operation of a second chemotactic agent.     

Testing for Validity and Reliability in Cross-Cultural Research

A set of procedures is offered for assessing interraler reliability and certain aspects of validity of codes in cross-cultural studies. The method assumes that at least two independent raters have coded more than one trait. Each trait coded by one rater is correlated with each trait coded by a second, and all the codings by a single rater are intercorrelated with each other. The results are presented in a multitrait-multi-rater matrix. From this matrix it is possible to determine the interrater reliability and discriminant validity of trails in addition to a higher order concept based on pairs of traits.     

A severe autosomal recessive acromesomelic dysplasia,the Hunter-Thompson type,and comparison with the Grebe type

Summary Two siblings with a short-limb dwarfing condition which we call acromesomelic dysplasia, Hunter-Thompson type are reported. Abnormalities are limited to the limbs and limb joints in this severe form of dwarfism. The middle and distal segments of the limbs are most affected. The lower limbs are more affected than the upper. We are aware of one previously published case of this entity reported by A. G. W. Hunter and M. W. Thompson in 1976. Dislocations of the elbows and ankles were present in all three patients and dislocations of the hips and knees in two. One of the siblings who did not have hip and knee dislocations clinically resembled Grebe chondrodysplasia, another severe acromesomelic dwarfing condition. However, radiological analysis suggests that while acromesomelic dysplasia, Hunter-Thompson type and Grebe chondrodysplasia are related, they are not identical. Grebe chondrodysplasia has been established as an autosomal recessive trait. It appears probable that the entity we describe has the same mode of genetic transmission.