The effects of acceleration on the mechanical impedance response of a primate model exposed to sinusoidal vibration.

Criteria for developing active and passive isolation mechanisms for reducing the effects of whole-body vibration exposure rely on a thorough understanding of the stiffness, damping, and resonance behaviors of the human or human surrogate body. Three Rhesus monkeys were exposed to seated whole-body sinusoidal vibration between 3 and 20 Hz at 0.69 and 3.

[Use of the principle of reverse problems for detecting processes, occurring in cells suspended in culture. II. Distribution of glutathione, SH groups, and optical density in the E. coli cell cycle].

A method was proposed for calculating the content of intracellular components during the cell cycle of an individual cell. The principle of reverse problems was used in the mathematical model proposed. The model allowed us to calculate changes of intracellular parameters of an individual cell from corresponding parameters measured in the whole culture.

[Use of the principle of reverse problems for detecting processes, occurring in cells suspended in culture. I. Distribution in the exponential growth phase of the age component of the cell population by its dynamic characteristics].

A mathematical model of age distribution in the suspension culture was verified. This model used the principle of reverse problems and allowed determination of age distribution from the cell numbers dynamics in the population. The verification was based on the complex non-destructive measurement of the microorganism parameters, which allowed simultaneous determination of the cell population dynamics and the distribution of cells according to their projection areas.

[Diabetogenic properties of Coxsackie A13 and Coxsackie B4 viruses in experimental infection in mice].

Studies of diabetogenic properties of Coxsackie A13 and B4 viruses in mice sensitive to diabetes (males, DBA line) and resistant (males and females F1(CBA X C57BL/6), females DBA/2 using in the latter case the subdiabetogenic doses of alloxan revealed in the infected animals biochemical changes manifested by reduction of glucose tolerance and disorders in the synthesis of immunoreactive insulin. Most marked changes were observed in males of DBA/2 line infected with Coxsackie B4 virus and in males F1 (CBA X C57BL/6) and females DBA/2 infected with Coxsackie A14 virus. With Coxsackie A13 virus such data have been obtained for the first time.

[Experimental diabetes in mice infected with Coxsackie viruses].

The influence of Coxsackie B4 and AI3 viruses on the pancreas of mice (resistant and susceptible to diabetes) was studied. Glucose intolerance and changes in the synthesis of immunoreactive insulin were detected in all the treated groups of animals. Biochemical changes were more prominent in male DBA/2 mice, infected with Coxsackie B4 virus, in FI (CBA X C57Bl/6) hybrids and in female DBA/2 mice infected with Coxsackie AI3 virus and alloxan.

The vertebral cartilaginous endplate of the preadult rhesus monkey (Macaca mulatta). A correlative scanning electron-and light-microscopic study.

The microanatomy of the preadult rhesus monkey (Macaca mulatta) vertebral cartilaginous endplate was investigated with scanning electron microscopy and light microscopy. The plate contains three zones: an outer noncalcified zone adjacent to the intervertebral disc, a middle zone of acellular islands of calcification surrounded by cellular hyaline cartilage, and an inner zone resembling a cartilaginous growth plate. Fibers from the annulus fibrosus pass through an outer zone into the middle zone.

Effect of rotopositioning on the growth and maturation of mandibular bone in immobilized rhesus monkeys.

As part of an ongoing effort to mimic the hypokinesia and hypogravity of spaceflight, the effects of 14 d immobilization and rotopositioning on mandibular bone osteon growth (= radial rate of closure) was assessed in 12 juvenile Rhesus monkeys by tetracycline labeling. The monkeys had been restrained in a supine position and rotated 908 every 30 min through a full 3608 arc for 14 d. Osteon growth was also assessed after the immobilized/rotopositioned animals had been permitted to recover in metabolism cages for periods of 28 and 56 d.

Structural models for human spinal motion segments based on a poroelastic view of the intervertebral disk.

Analytical and finite element models (FEMs) were used to quantify poroelastic material properties for a human intervertebral disk. An axisymmetric FEM based on a poroelastic view of disk constituents was developed for a representative human spinal motion segment (SMS). Creep and steady-state response predicted by FEMs agreed with experimental observations, i.

Poroelastic dynamic structural models of rhesus spinal motion segments.

Finite element models (FEMs) and analytical and experimental models based on poroelastic constitutive laws were developed for rhesus spinal motion segments (SMSs). Long-time creep, transient creep, and impact were studied for SMSs with normal and simulated degenerated discs. The results suggested that long-time creep observed in excised SMSs may be reduced in the in vivo SMS.

Analysis of compressive creep behavior of the vertebral unit subjected to a uniform axial loading using exact parametric solution equations of Kelvin-solid models--Part II. Rhesus monkey intervertebral joints.

The simulation of long-term creep response behavior, observed on 54 Rhesus monkey intervertebral joints subjected to a constant axial compressive stress, is attempted by two- and three-parameter-solid models utilizing the Burns- Kaleps 'exact analysis scheme'. Model parameters identified by the analysis of each specimen's experimental strain data were optimized via a computer program and the mechanical properties (Young's moduli and the viscosity coefficient) appropriate to each model were calculated for individual spinal segments. Simulation results for the two-parameter-solid (one- Kelvin -unit) model demonstrate its general ineptness in predicting the observed strain-time behavior of normal spinal sements .

Analysis of compressive creep behavior of the vertebral unit subjected to a uniform axial loading using exact parametric solution equations of Kelvin-solid models--Part I. Human intervertebral joints.

The creep response phenomena observed on 47 human intervertebral discs subjected to a constant axial compressive stress was analytically studied by two-, three- and four-parameter-solid models employing the Burns- Kaleps 'exact analysis scheme'. The mechanical properties (Young's moduli and viscosity coefficients) associated with each model were calculated for each of the 47 disks, with superior results obtained for the latter two models. Results for the two-parameter-solid model suggest its possible usefulness in simulating creep response that is characteristic of disk degeneration.

Growth and maturation of mandibular bone in otherwise totally immobilized rhesus monkeys.

The effects of 14 days of total postcranial body immobilization (in plaster casts) on the mineralization rate and on the maturation of matrix and mineral moieties in the rhesus jaw were studied by tetracycline labeling and by density gradient methods, respectively. Immobilization did not alter the rates of periosteal and endosteal mineralization in the dense cortical bone from the lingular region of the jaw, but it did impair mineralization in osteonal bone. Osteons that continued to show radial closure did so at a normal rate.

Quantitative histochemistry of rat lumbar vertebrae following spaceflight.

Spaceflight has been shown to cause alterations in bone mineral content, bone growth, and resorption. In this study, the effects of return to gravity immediately and 6 and 29 days following spaceflight on bone of rat vertebral bodies were histochemically analyzed. Immediately postflight, there was no significant change in calcium salt content of the vertebrae, but 6 days later it was significantly decreased (P less than 0.

The scanning electron microscopy of compressed vertebral bodies.

Scanning electron microscopy was used in this study to determine the effects of compression at different rates on the structure of trabecular bone in primate vertebral bodies. Rhesus monkey vertebral bodies were subjected to compressive loads at two different strain rates (8.89 x 10(-1) m/sec and 8.

The effects of hypokinesia in primates on bone strength.

A 14 days ground based primate hypokinesia investigation was conducted to determine what changes, if any, in bone strength may be demonstrated following 2 weeks cast immobilization and at 14 davs after removal from casts. Controlled compressive loads were applied to vertebral bodies excised from control, 2 weeks immobilization and 2 weeks post immobilization Rhesus monkeys. The material properties reported herein are ultimate load, displacement to ultimate load, stiffness and energy to ultimate load.

Active muscle force and moment response of the human arm and shoulder.

This paper is concerned with collection of active muscle force and moment response data of the human arm and the shoulder complex when the arm is subjected to various external forces. The major components of the specially designed and built experimental apparatus for this research are a subject restraint system, a force application device which employs three sonic emitters, and an upper arm cuff with four sonic emitters. The sonic emitters are utilized to determine the direction and the location of the force application on the arm and the orientation of the upper arm with respect to the torso.

Spinal injuries in the F/FB-111 crew escape system.

During the years 1970-75, a larger than expected number of aircrewmen, forced to use the F/FB-111 crew escape module, experienced acute spinal trauma during otherwise uneventful ejection. This trend in the incidence and severity of F/FB-111 aircrew spinal injuries attracted considerable attention and stimulated extensive inquiry concerning the ethiology of the trauma in order to implement appropriate corrective measures. In response to the expressed concerns, an investigation was initiated to analyze the biodynamic pathogenetic mechanism associated with ejection in the F/FB-111 crew escape module.

Identification and classification of vertebral fractures following emergency capsule egress from military aircraft.

This paper deals with systematically classifying the type, level, and severity of traumatic lesions to the spinal column associated with the crew module escape system. Its objectives are to describe characteristic spinal injury encountered in the crew escape module and to shed additional light on the pathomechanics and dynamics of spinal column damage. An analysis of this type is necessary for complete understanding of the clinical, roentgenographic, and pathological findings.

[The role of the pallidum in regulating cortical activity].

Bilateral ablation of the pallidum halves the duration of extinction of conditioned motor food reflexes and contributes to 30 to 50% extinction of the electro-defensive reflexes. Pallidum functional depression by potassium chloride or novacaine leads to a temporary total depression of conditioned motor food reflexes. Depending on the frequency of pallidum stimulation, synchronization or desynchronization of the cortical bioelectrical activity is observed.