Noninvasive determination of ulnar stiffness from mechanical response--in vivo comparison of stiffness and bone mineral content in humans

An approach referred to as Mechanical Response Tissue Analysis (MRTA) has been developed for the noninvasive determination of mechanical properties of the constituents of the intact limb. Of specific interest in the present study is the bending stiffness of the ulna. The point mechanical impedance properties in the low frequency regime, between 60 and 1,600 Hz are used. The procedure requires a proper design of the probe for good contact of the skin at midshaft and proper support of the proximal and distal ends of the forearm to obtain an approximation to "simple support" of the ulna. A seven-parameter model for the mechanical response is then valid, which includes the first mode of anterior-posterior beam bending of the ulna, the damping and spring effect of the soft tissue between probe and bone, and the damping of musculature. A dynamic analyzer (HP3562A) provides in seconds the impedance curve and the pole-zero curve fit. The physical parameters are obtained from a closed-form solution in terms of the curve-fit parameters. The procedure is automated and is robust and analytically reliable at about the five percent level. Some 80 human subjects have been evaluated by this mechanical response system and by the Norland single photon absorptiometer, providing for the first time in vivo, a comparison of elastic bending stiffness (ulna) and bone mineral content (radius). Three functional parameters of potential clinical value are the cross-sectional bending stiffness EI, the axial load capability Pcr (Euler buckling load) and the bone "sufficiency" S, defined as the ratio of Pcr to body weight. The correlation between EI and bone mineral (r = 0.81) is only slightly less than previous in vitro results with both measurements on the same bone (r = 0.89). When sufficiency is taken into consideration, the correlation of Pcr and bone mineral content is improved (r = 0.89). An implication is that "quality" of bone is a factor which is not indicated by bone mineral content but which is indicated by stiffness. Bone mineral is necessary for proper stiffness but not sufficient. Therefore mechanical measurement should provide a new dimension to be used toward a better understanding of the factors related to bone health and disease.     

The influence of level of infection of rats with Nippostrongylus brasiliensis on the haematology and phospholipase activity and mast cell numbers in the small intestine and colon

The haematology and phospholipase activity and mast cell numbers of the small intestine and colon of rats was studied 10 days after infection with various numbers of larvae of N. brasiliensis. A significant reduction in the RBC occurred after infections with 200 and 5000 larvae but not with 1000 larvae. Hb was significantly reduced after infection with 200 larvae and increases in the MCV and MCH indicated the development of a macrocytic anaemia. Reticulocyte count was increased at all levels of infection except after 200 larvae. WBC was increased at all levels of infection except in the 5000 larvae group. Lymphocytes were significantly increased in all groups except those infected with 5000 larvae. Neutrophils increased only at the lower levels of infection. The most marked changes occurred in eosinophil numbers, significant increases occurring with increasing levels of infection. However, after infection with 5000 larvae the numbers were significantly lower than after infection with 200 or 1000 larvae. Phospholipase activity, which is believed to be related to tissue eosinophil levels, was significantly increased at all infection levels in the proximal small intestine. Significant increases in the distal ileum and colon occurred mainly after infection with 1000 and 5000 larvae. Mast cell numbers did not change significantly at any infection level. It is suggested that the pathology observed, here in the form of anaemia, is multifactorial in origin and is largely a function of the immune response, the development and expression of which is dependent on the level of infection, with suppression of immune damage occurring at the high levels of infection when pathogenesis may involve a direct effect of the worms.     

MECHANISM OF ACTION OF β-N-OXALYL-L-α, β-DIAMINOPROPIONIC ACID, THE LATHYRUS SATIVUS NEUROTOXIN

The source of ammonia in the brain tissue of young rats treated with β-N-oxalyl-l -α, β-diaminopropionic acid (ODAP) has been studied. ODAP administration to 12-day-old rats causes a significant increase in the levels of adenylic acid deaminase in the brain. Glutaminase activity also shows an increase under these conditions. An increase in the levels of acid protease and transglutaminase is also observed in the brain of ODAP-treated animals. Glutamate dehydrogenase activity is decreased slightly. Glutamine synthetase enzyme is not affected. Aspartate-α-ketoglutarate transaminase and aspartate-pyruvate transaminase activities are enhanced in the brain tissue of ODAP-treated rats. It is held that protein degradation, especially the cleavage of free and protein-bound amide bonds, may be responsible for excess ammonia liberation in the brain of ODAP-treated young rats.     

Insulin binding to liver nuclei from lean and obese mice is altered by dietary fat.

Insulin binding to the plasma membrane is known to be altered by modifying the membrane composition through dietary treatment. As insulin binding receptors are also present on nuclear membrane, this study was undertaken to investigate if specific binding of insulin to the liver nuclei is altered by diet. 8-wk-old female C57 B 6J lean and ob/ob mice were fed semipurified diets containing 20% (w/w) fat of either high or low polyunsaturated-to-saturated (P/S) fatty acid ratio for 4 wk. Liver nuclei were prepared, insulin binding was measured and nuclear phospholipids were isolated for lipid analysis. Insulin binding was highest in nuclei prepared from lean mice fed a high P/S diet. Specific binding of insulin to nuclei prepared from obese mice was also increased by the high P/S diet, but to a lesser extent compared to lean mice. Feeding a high P/S diet increased polyunsaturated fatty acid content of membrane phospholipids from both lean and ob/ob mice. Obese mice were characterized by higher levels of arachidonic acid and lower levels of linoleic acid in phosphatidylcholine. The present study establishes that insulin binding to liver nuclei is increased by feeding a high P/S diet, and that insulin binding to liver nuclei from obese mice is lower than from lean mice.     

Effects of plant size on photosynthesis and water relations in the desert shrub Prosopis glandulosa (Fabaceae)

The Jornada del Muerto basin of the Chihuahuan Desert of southern New Mexico, USA, has undergone a marked transition of plant communities. Shrubs such as mesquite (Prosopis glandulosa) have greatly increased or now dominate in areas that were previously dominated by perennial grasses. The replacement of grasses by shrubs requires an establishment phase where small shrubs must compete directly with similar-sized grass plants. This is followed by a phase in which large, established shrubs sequester nutrients and water within their biomass and alter soil resources directly under their canopy, creating “islands” of fertility. We hypothesized that these two phases were associated with shrubs having different physiological response capacities related to their age or size and the resource structure of the environment. As a corollary, we hypothesized that responses of small shrubs would be more tightly coupled to variation in soil moisture availability compared to large shrubs. To test these hypotheses, we studied gas exchange and water relations of small (establishing) and large (established) shrubs growing in the Jornada del Muerto as a function of varying soil moisture during the season. The small shrubs had greater net assimilation, stomatal conductance, transpiration, and xylem water potential than large shrubs following high summer rainfall in July, and highest seasonal soil moisture at 0.3 m. High rates of carbon assimilation and water use would be an advantage for small shrubs competing with grasses when shallow soil moisture was plentiful. Large shrubs had greater net assimilation and water-use efficiency, and lower xylem water potential than small shrubs following a dry period in September, when soil moisture at 0.3 m was lowest. Low xylem water potentials and high water-use efficiency would allow large shrubs to continue acquiring and conserving water as soil moisture is depleted. Although the study provides evidence of differences in physiological responses of different-sized shrubs, there was not support for the hypothesis that small shrubs are more closely coupled to variation in soil moisture availability than large shrubs. Small shrubs may actually be less coupled to soil moisture than large shrubs, and thus avoid conditions when continued transpiration could not be matched by equivalent water uptake.     

PATTERNS IN LEAF MORPHOLOGY AND PHOTOSYNTHESIS IN SHOOTS OF SASSAFRAS ALBIDUM (LAURACEAE)

Trees of Sassafras albidum (Nuttall) Nees. display leaves that fall into discrete categories of form. Unlobed leaves, with undissected margins, predominate at proximal and distal nodes of shoots, while lobed leaves are most common at intermediate nodes. In this study we investigated the hypothesis that shoots of sassafras respond to environmental changes over the growing season by generating predictable nodal patterns for leaf morphology and physiology. We recorded leaf shape category and measured leaf surface area, node number, chlorophyll content, nitrogen content, and photosynthesis in four trees. Over 1,000 measurements of photosynthesis were made in situ, using the LI-Cor LI 6200 portable photosynthesis system. The two trees growing under heavy shade had few lobed leaves (2.0% and 18.8%) and often had negative carbon balance, with positive net photosynthesis occurring during sun flecks. The two trees growing in more open conditions had many more lobed leaves (56.3% and 61.0%) and higher, less variable net photosynthetic rates. As indicated by chlorophyll and nitrogen contents, the highest leaf photosynthetic rates occurred at intermediate nodes (nodes six to nine), and this was shifted distally along the shoot during the growing season. Leaves at intermediate nodes also had the largest surface areas and the greatest frequency of lobing. In comparative experiments with models, lobing was shown to enhance free-convectional heat loss relative to unlobed leaves of the same surface area. Due to their large surface area, these leaves also have the highest rates of whole leaf photosynthesis. Under conditions of equivalent photosynthetically active radiation, lobed leaves had higher rates of net photosynthesis than did unlobed leaves. We conclude that shoots of sassafras produce groups of leaves with predictably different morphological and physiological specializations.     

Effect of parvalbumin and S-100 protein on protein synthesis in rabbit reticulocyte lysate.

The effect of two high affinity Ca+ binding acidic proteins, parvalbumin and S-100 protein on protein synthesis in rabbit reticulocyte lysates (RRL), was investigated. Nuclease-treated RRL, supplemented with yeast mRNA, and 3H-leucine were incubated at 37 degrees C, and incorporation of 3H-leucine into protein was determined for 24 min. At 20 micrograms/100 microliters lysate concentration, both parvalbumin and S-100 protein caused a marked inhibition of protein synthesis compared with the control lysate. At a lower concentration parvalbumin was less inhibitory than histone H1; the effect of S-100 protein was not significant. The combined inhibitory effect of parvalbumin and H1 was not additive probably due to strong interaction between them as was evidenced by the enhanced absorbance of parvalbumin-H1 mixture. Spectrophotometric profiles of parvalbumin-tRNA mixture indicated that, unlike H1, parvalbumin did not inhibit protein synthesis by binding with nucleic acids. These results suggest an important role for parvalbumin in translational regulation.