Differential scanning calorimetric study of the complexes of modified myosin subfragment 1 with ADP and vanadate or beryllium fluoride

Summary The effects of various modifications of rabbit skeletal myosin subfragment 1 on thermal denaturation of subfragment 1 in ternary complexes with Mg-ADP and orthovanadate (V_i) or beryllium fluoride (BeF_x) have been studied by differential scanning calorimetry. It has been shown that specific modifications of SH₁ group of Cys-707 by different sulfhydryl reagents, trinitrophenylation of Lys-83, and reductive methylation of lysine residues promote the decomposition of the S1·ADP·V_i complex and change the character of structural transitions of the subfragment 1 molecule induced by the formation of this complex, but they have much less or no influence on subfragment 1 thermal stability in the S1·ADP·BeF_x complex. Thus, the differential scanning calorimetric studies on modified subfragment 1 preparations reveal a significant difference between S1·ADP·V_i and S1·ADP·BeF_x complexes. It is suggested that S1·ADP·V_i and S1·ADP·BeF_x complexes represent structural analogues of different transition states of the ATPase cycle, namely the intermediate states S1^**·ADP·P_i and S1^*·ATP, respectively. It is also proposed that during formation of the S1·ADP·V_i complex the region containing both Cys-707 and Lys-83 plays an important role in the spread of conformational changes from the active site of subfragment 1 ATPase throughout the structure of the entire subfragment 1 molecule. In such a case, the effects of reductive methylation of lysine residues on the subfragment 1 structure in the S1·ADP·V_i complex are related to the modification of Lys-83.     

Dynamic imaging of the lungs using x-ray phase contrast

High quality real-time imaging of lungs in vivo presents considerable challenges. We demonstrate here that phase contrast x-ray imaging is capable of dynamically imaging the lungs. It retains many of the advantages of simple x-ray imaging, whilst also being able to map weakly absorbing soft tissues based on refractive index differences. Preliminary results reported herein show that this novel imaging technique can identify and locate airway liquid and allows lung aeration in newborn rabbit pups to be dynamically visualized.     

Osteosarcomatosis

A review of the 690 cases of osteosarcoma in the radiographic file of the Armed Forces Institute of Pathology revealed 29 cases of "osteosarcomatosis" (multiple skeletal sites of osteosarcoma). Fifteen of these patients were 18 years old and under and manifested rapidly appearing, usually symmetric, sclerotic metaphyseal lesions. The remaining 14 patients were more than 18 years old and had fewer, asymmetric sclerotic lesions. In most patients (28 of 29), a radiographically dominant skeletal tumor was seen. Pulmonary metastases occurred in the majority of patients and were detected at the same time as the bone lesions. These 29 patients were studied with regard to demographic data and skeletal distribution and radiographic appearance of their lesions. As a result of the findings, a metastatic origin from a primary dominant osteosarcoma is favored over a multifocal origin as the basis for osteosarcomatosis. Osteosarcomatosis is more commonly encountered in the mature skeleton than has been previously recognized.     

Increased muscle stiffness after anterior cruciate ligament reconstruction – memory on injury?

Residual impairment of knee function was tested in 25 patients 6 to 12 months after successful unilateral reconstruction of the anterior cruciate ligament. The control group comprised 25 healthy individuals. Jumping onto one foot from a height of 20 cm was taken as a prototype of similar everyday activities. We measured maximum flexion of the knee during the landing phase of the jump, and the degree of knee flexion at the time of maximum deceleration of the knee against gravity during jumping using the three-dimensional optical motion analysis system-ELITE. In the group of patients, measured parametres were significantly smaller on the operated side than on the unaffected side. These two measured values were significantly smaller on both legs in group of patients as compared to the values in the control group. The results of our study indicate that functional disturbance persisted for 6 to 12 months after anterior cruciate reconstruction. This may be due to the changed muscle activation pattern of the knee causing increased stiffness of knee muscles. It seems that re-programming of the central nervous system occurred in order to protect the injured lower extremities from another injury.     

The axial load teardrop fracture. A biomechanical, clinical and roentgenographic analysis

The anteroinferior cervical vertebral body corner fracture was originally described by Schneider and Cann as the "teardrop" fracture. This report analyzes the biomechanical, clinical, and roentgenographic features of 55 such fractures obtained from the National Football Head and Neck Injury Registry. Teardrop fractures resulting from tackle football characteristically occurred in players attempting to make a tackle in which initial contact was made with the top or crown of the helmet. There were two fracture patterns associated with the anteroinferior corner (teardrop) fracture fragment: 1) the isolated fracture, which is usually not associated with permanent neurologic sequelae; and 2) the three-part, two-plane fracture in which there is an associated sagittal vertebral body fracture as well as fracture of the posterior neural arch. This latter pattern was almost always associated with permanent neurologic sequelae, specifically quadriplegia. Axial loading of the cervical spine was clearly identified as a mechanism of injury for both fracture patterns. Roentgenographic examination must include both anteroposterior and lateral views with computed tomography or tomography as necessary to determine the presence of the sagittal vertebral body fracture and the integrity of the posterior neural arch.