Urinary calcium, sodium, and bone mass of young females

Calcium is an important determinant of peak bone mass in young adults because of its influence on skeletal development during growth. Attainment of maximum peak bone mass requires optimal positive balance between calcium intake and obligatory losses of calcium, primarily in urine and feces. Urinary excretion is an important determinant of calcium retention in the body. Accordingly, the purpose of this study was to evaluate the influence of various nutrients on urinary calcium excretion, and to assess their impact on bone mass of young females, aged 8-13 y, during early puberty. The study was conducted in 381 healthy white females in pubertal stage 2. From each participant we collected basic anthropometric measurements, a 3-d food record, blood, a 24-h urine sample, and bone mass measurements of the total body and forearm by dual X-ray absorptiometry. Urinary sodium was found to be one of the most important determinants of urinary calcium excretion: [urinary calcium (mmol/d) = 0.01154 x urinary sodium (mmol/d) + 0.823], whereas calcium intake had relatively little impact: [urinary calcium (mmol/d) = 0.02252 x calcium intake (mmol/d) + 1.5261]. Urinary calcium was much higher at a calcium intake of approximately 37.5 mmol/d (1500 mg/d), supporting the notion that calcium is a threshold nutrient. Calcium intake had a significant positive influence on the bone mineral content and density of the whole body and radius shaft whereas urinary calcium had a negative influence, presumably by reducing calcium accretion into the skeleton.(ABSTRACT TRUNCATED AT 250 WORDS)     

Aerobic workout and bone mass in females

This cross-sectional study aimed to investigate bone mass in females participating in aerobic workout. Twenty-three females (age 24.1 +/- 2.7 years), participating in aerobic workout for about 3 hours/week, were compared with 23 age-, weight- and height-matched non-active females. Areal bone mineral density (BMD) was measured in total body, head, whole dominant humerus, lumbar spine, right femoral neck, Ward's triangle, trochanter femoris, in specific sites in right femur diaphysis, distal femur, proximal tibia and tibial diaphysis, and bone mineral content (BMC) was measured in the whole dominant arm and right leg, using dual energy X-ray absorptiometry. The aerobic workout group had significantly (P < 0.05-0.01) higher BMD in total body (3.7%), lumbar spine (7.8%), femoral neck (11.6%), Ward's triangle (11.7%), trochanter femoris (9.6%), proximal tibia (6.8%) and tibia diaphysis (5.9%) compared to the non-active controls. There were no differences between the groups concerning BMD of the whole dominant humerus, femoral diaphysis, distal femur and BMC and lean mass of the whole dominant arm and right leg. Leaness of the whole dominant arm and leg was correlated to BMC of the whole dominant arm and right leg in both groups. In young females, aerobic workout containing alternating high and low impact movements for the lower body is associated with a higher bone mass in clinically important sites like the lumbar spine and hip, but muscle strengthening exercises like push-ups and soft-glove boxing are not associated with a higher bone mass in the dominant humerus. It appears that there is a skeletal adaptation to the loads of the activity.     

Cross-validation of fat-free mass estimated from body density against bioelectrical resistance: effects of obesity and gender

The major purpose of this study was to examine whether estimates of body composition from bioelectrical resistance were systematically biased by obesity and/or gender (using hydrodensitometry as a comparison method). We compared fat-free mass (FFM) by bioelectrical resistance (BR) using 5 equations (Lukaski, Kushner, Rising, Khaled, and Segal) to FFM by hydrodensitometry (HD) in 20 lean men, 30 lean women, 33 obese men and 22 obese women. None of the BR equations was successfully cross-validated against FFM by HD in all 4 sub-groups. The Lukaski equation significantly underestimated FFM in all 4 groups by 2.7 to 4.7 kg; the Kushner equation significantly underestimated FFM by 2.0 to 2.9 kg except in obese women; the Rising equation significantly overestimated FFM in obese women (5.3 kg) and men (2.9 kg); the Khaled equation successfully predicted FFM in all groups except obese men; and the Segal equation successfully predicted FFM in all groups except lean men. In some groups, a portion of the discrepancy could be explained by bias originating from body fat. Analysis of our data by forward regression analysis demonstrated that height2/resistance, body weight, gender and suprailiac skinfold thickness provide the most accurate estimates of FFM (R2 = 0.92; SEE = 3.58 kg) that are free of bias originating from gender and body fat. We conclude that the estimation of fat-free mass by BR is significantly influenced by gender and obesity. An alternative equation is proposed for estimating fat-free mass based on measurement of height2/resistance, body weight, gender and suprailiac skinfold thickness.     

Bone density profiles and osteoporosis incidence in Irish females

1725 Irish females aged 15-70+ were included in this analysis to establish the group bone mineral density (BMD) profiles. Each subject was screened for 27 risk factors by questionnaire. Subjects were segregated into normal (N) and non-normal (NN) subgroups on the basis of the questionnaire. BMD of lumbar spine and hip were measured by dual energy X ray absorptiometry (DEXA). A substantial difference in BMD at all sites was observed between subgroups even following adjustment for body mass index and years of exposure to oestrogen. In the subgroup designated as non-normal 42%, 54%, 72% and 69% of those studied had spinal BMD levels > 2SD below mean peak at 55-59, 60-64, 65-69 and 70+ respectively. In comparison, similar age cohorts in the subgroup designated normal were 26%, 46%, 44% and 68% respectively. A marked difference was also observed in the younger age groups (15-34) where the percentage of individuals with spinal BMD levels > 2SD below mean peak was < 1.9% for N and 18.8% for NN. The results of this study suggest that the use of a questionnaire may be a valuable low cost screening tool in the younger groups.     

Histomorphometric, physical, and mechanical effects of spaceflight and insulin-like growth factor-I on rat long bones

Pituitary adenylate cyclase activating peptide and vasoactive intestinal peptide belong to the same neuropeptide family. Both peptides are present in nerve fibers in the gastric wall and are thought to be involved in the regulation of inflammatory processes. Experimental ulcers were induced in the rat gastric mucosa by local application of acetic acid. During the healing process we examined the PACAP and VIP innervation by means of immunohistochemistry and in situ hybridization. The ulcer area was examined from day 1 to day 15 after ulcer induction. There was a marked depletion of PACAP in nerve fibers at the ulcer margin from day 1 and onwards. On day 10 and day 15, PACAP-immunoreactive nerve fibers could again be visualized at the ulcer margin. In contrast, VIP immunoreactive nerve fibers were present at the ulcer margin at all time points studied. From day 10 following ulcer induction PACAP- and VIP- immunoreactive nerve fibers were increased in frequency in the smooth muscle beneath the ulcer. An upregulation of VIP and PACAP mRNA was also demonstrated in the myenteric ganglia adjacent to ulcer. The present results indicate that neuronal PACAP and VIP react differently to the inflammation at the ulcer margin but similarly in the smooth muscle during the ulcer healing.     

Total body water volumes for adult males and females estimated from simple anthropometric measurements

Individual total body water volumes for 458 adult males and 265 adult females obtained from dilution studies, together with their height, weight, and age have been selected from the literature. These values were used to derive total body water prediction equations for adults of any age. The equations that gave the best fit were for males: formula (see text) and for females: formula (see text). Numerous other linear regression equations to predict total body water from anthropometric measurements have been reported in the literature. Most apply only to restricted age groups. These, and the equations from the present study were tested on completely independent data. In all cases the equations from the present study gave the best overall results, though for women one equation designed for a specific age group, gave for that age group a marginally better fit.     

The material basis for reduced mechanical properties in oim mice bones

Osteogenesis imperfecta (OI), a heritable disease caused by molecular defects in type I collagen, is characterized by skeletal deformities and brittle bones. The heterozygous and homozygous oim mice (oim/+ and oim/oim) exhibit mild and severe OI phenotypes, respectively, serving as controlled animal models of this disease. In the current study, bone geometry, mechanics, and material properties of 1-year-old mice were evaluated to determine factors that influence the severity of phenotype in OI. The oim/oim mice exhibited significantly smaller body size, femur length, and moment of area compared with oim/+ and wild-type (+/+) controls. The oim/oim femur mechanical properties of failure torque and stiffness were 40% and 30%, respectively, of the +/+ values, and 53% and 36% of the oim/+ values. Collagen content was reduced by 20% in the oim/oim compared with +/+ bone and tended to be intermediate to these values for the oim/+. Mineral content was not significantly different between the oim/oim and +/+ bones. However, the oim/oim ash content was significantly reduced compared with that of the oim/+. Mineral carbonate content was reduced by 23% in the oim/oim bone compared with controls. Mineral crystallinity was reduced in the oim/oim and oim/+ bone compared with controls. Overall, for the majority of parameters examined (geometrical, mechanical, and material), the oim/+ values were intermediate to those of the oim/oim and +/+, a finding that parallels the phenotypes of the mice. This provides evidence that specific material properties, such as mineral crystallinity and collagen content, are indicative and possibly predictive of bone fragility in this mouse model, and by analogy in human OI.     

Relative predispositional effects and mode of inheritance of HLA-DRB1 alleles among community-based Caucasian females with rheumatoid arthritis

This review addresses two questions. First, why does clozapine apparently occupy low levels of dopamine D2 receptors in patients, in contrast to all other antipsychotic drugs which occupy 70-80% of brain dopamine D2 receptors? Second, what is the receptor basis of action of antipsychotic drugs which elicit low levels of Parkinsonism? Antipsychotic doses of clozapine occupy between 0% and 50% of D2 receptors, as measured in patients by a variety of radioligands. It has recently been found, however, that the percent occupancy of a receptor by a drug depends on the radioligand used to measure that receptor. Based on this new finding, this review concludes that clozapine clinically occupies high levels of D2 receptors in the absence of any radioligand. This occupancy is estimated to be of the order of 70-80% in the dopamine-rich region of the human striatum, and even higher in the limbic D2-containing regions which are low in endogenous synaptic dopamine. This conclusion arises from two different approaches. One approach is to relate the reported clozapine occupancies in the human striatum with the dissociation constants of the various radioligands at the D2 receptor. This relation extrapolates to approximately 70-80% occupancy by clozapine when clozapine competes with endogenous dopamine at the D2 receptor. The second approach is to calculate the D2 occupancy of each antipsychotic drug, using the average spinal fluid concentration and the correct dissociation constant of the antipsychotic, thereby revealing that all antipsychotic drugs, including clozapine, occupy approximately 70-80% of dopamine D2 receptors in the human striatum, and possibly higher in the limbic regions. As determined by the new dissociation constants, antipsychotic drugs which elicit Parkinsonism (trifluperazine, chlorpromazine, raclopride, haloperidol, fluphenazine, risperidone) bind more tightly than dopamine to D2, while those antipsychotic drugs which elicit little or no Parkinsonism (melperone, seroquel, perlapine, clozapine, remoxipride, molindone, sulpiride, olanzapine, sertindole) bind more loosely than dopamine to D2 receptors. Compared to the tightly bound antipsychotic drugs, the more loosely bound antipsychotics generally require higher clinical doses, require fewer days for clinical adjustment, but may dissociate from the D2 receptor more rapidly and could lead to clinical relapse somewhat earlier than that found with the traditional tightly bound antipsychotic drugs.     

Scaling of the limb long bones to body mass in terrestrial mammals

In their normal state, RPE cell are strongly adherent to Bruch's membrane. Certain pathological conditions such as retinal detachment cause an injury-type response (probably augmented or induced by the local accumulation of a variety of substances which modulate cell behaviour) in which RPE begin to dissociate from the membrane. This RPE-Bruch's membrane separation may be mediated by proteins with counter-adhesive properties and proteolytic enzymes, partly derived from the RPE themselves. Concomitant with the RPE disassociation, the cells begin to lose tertiary differentiation characteristics and gain macrophage-like features. When the "free" RPE arrive at the surface of the neuroretina, they may attach to or create a provisional matrix. Some of the cells adopt a fibroblast-like phenotype. This phenotype is similar to that of the dermal fibroblast during cutaneous wound repair and the fibroblastic RPE synthesise the types of matrix components found in healing skin wounds. Many of these molecules in turn further modulate the activities of the cells via several families of cell surface receptors, while the RPE continue to remodel the new matrix with a range of proteolytic enzymes. The resulting tissue (or membrane) has many of the features of a contractile scar and is the hallmark of the condition known as proliferative vitreoretinopathy (PVR). Thus the development of PVR, and the resulting tractional distortion of the neuroretina, appears to be dependent on RPE-matrix interactions. The interactions present a number of potential therapeutic targets for the management of the disorder.     

Relations between age, mineral density and mechanical properties of human femoral compacta

Relations between mineralisation and mechanical properties have been investigated in human femoral compacta. Evidence of age-related changes in physical properties of bone, independent of mineral density, is provided by significant (P less than 0.05) partial correlation between ultimate tensile stress and age. However, 75 per cent of variance in ultimate tensile stress, and 85 per cent of variance in ultimate compressive stress could be accounted for by variation in mineral density.     

A high sucrose diet decreases the mechanical strength of bones in growing rats

High sucrose diets alter mineral metabolism in humans and animals. We examined the effect of a high sucrose diet on bone growth, composition and mechanical strength in growing rats. Weanling Wistar rats received a high sucrose (43 g/100 g) diet (9 males, 11 females). In the control diet (8 males, 8 females), sucrose was replaced with potato starch, providing an equal energy value. At the onset of the experiment, bones were marked by tetracycline. After 5 wk, the tibias and femurs were weighed, and maximum breaking strengths were determined. Tibias were cut at the tibia-fibular junction; the widths of the bone at the start of the experiment, the periosteal bone formation during the experiment, the widths of the medullary cavity and the final bone width were determined from tetracycline lines. Bone ash weight, Ca and P contents were determined. The breaking strengths of both bones were significantly lower in the sucrose-fed groups of both sexes. In females, the weight of both bones and the final width of the tibias were significantly lower in the sucrose-fed group. The Ca concentration in both bones and the P concentration in tibias were significantly lower in the sucrose-fed group. It was concluded that the metabolic interference induced by sucrose was the reason for the differences. The alterations were more pronounced in females, but independent of body weight.     

Structure,mechanical and tribological characteristics of powdered antifriction materials copper-nickel-calcium fluoride

Translated from Poroshkovaya Metallurgiya, No. 11 (347), pp. 55–59, November, 1991.     

Peak bone mass development of females: can young adult women improve their peak bone mass?

The purpose of this review is to summarize the effects of calcium intake on peak bone mass (PBM) accrual by premenopausal females during their 20s and possibly 30s. Prospective studies are highlighted because of the value of investigating the same subjects for one or more years. Results of cross-sectional studies are also summarized. Findings from both prospective and cross-sectional investigations suggest a positive benefit of adequate or supplemented calcium intakes on bone mineral content (BMC) in females during the third (20s) and fourth (30s) decades of life. PBM of subjects was found to be increased or maintained in comparison to PBM of controls in the five intervention studies that used calcium supplementation or the addition of calcium-rich foods. The results of cross-sectional studies, including a meta-analysis of approximately 20 such studies, also support the benefit to PBM of adequate calcium intakes. In summary, sufficient consumption of calcium during the various stages of the early life cycle, when combined with overall sound nutrition, regular physical activity, and possibly pregnancy, lactation, and child-rearing, may contribute to PBM accrual of women during the early adult decades.     

西藏尕尔穷铜金矿床岩体地球化学特征

对班公湖-怒江缝合带西段尕尔穷中型铜金矿岩体进行了野外地质调查、岩相学研究及全岩地球化学分析.石英闪长岩和花岗斑岩均富集Rb,Ba,Th,U等大离子亲石元素,亏损Nb,Ta,Zr,Hf等高场强元素;Rb/Sr远大于1,具负铌和弱负铕异常,轻重稀土分馏不明显,花岗斑岩明显亏损Sr和Ti元素.研究认为,石英闪长岩为岛弧环境的钙碱性重熔型中酸性岩体,花岗斑岩为陆-陆碰撞钙碱性重熔型酸性岩体.     

Distinct morphological characteristics of touch, temperature, and mechanical nociceptive neurons in the crotaline trigeminal ganglia

Intrasomal recording and horseradish peroxidase injection techniques were employed in vivo to determine the morphological characteristics of touch, temperature, and mechanical nociceptive neurons in the trigeminal ganglia of crotaline snakes. The touch neurons, with a peripheral axon conducting at the A-beta range, could be subdivided into tactile and vibrotactile neurons according to their response properties, but there were no morphological differences between them. These neurons exhibited a large and oval soma and possessed a set of large stem, peripheral, and central axons which were all myelinated and equal in diameter with a constriction at the bifurcation. The temperature neurons, which conducted peripherally at the A-delta range, were physiologically separated into thermosensitive and thermo-mechanosensitive neurons, which were also morphologically indistinguishable. The temperature neurons had a round soma of medium size and a set of medium axons with varied axonal bifurcation patterns. All axons of these neurons were myelinated, but the central axon was thinner than the stem and peripheral axons. The mechanical nociceptive neurons, which had a peripheral axon conducting at the A-delta range, were morphologically heterogeneous based on their conduction velocities. The neurons conducting at the fast A-delta range were morphologically similar to the temperature neurons in the ganglion excepting their thinner central axons, whereas those at the slow A-delta range had a thinner myelinated stem axon that gave rise to a thinner myelinated peripheral axon and an unmyelinated stem axon with a bifurcation of either a triangular expansion at the bifurcating point or a central axon arising straightforwardly from the constant stem and peripheral axons. This study revealed that distinct morphological characteristics do exist for the touch and temperature neurons and the subtypes of mechanical nociceptive neurons in the trigeminal ganglion, but not for the subfunctional types of touch neurons or temperature neurons.     

Bone mineral density in thyroxine treated females with or without a previous history of thyrotoxicosis

Alterations in lipid metabolism characterized in major part by a decrease in lipoprotein lipase (LPL) activity in adipose tissue are a central feature of cachexia from chronic infection or malignancy. These metabolic derangements may be mediated in large part through endogenous host proteins produced in response to various pathological stimuli. Differentiation factor/leukaemia inhibitory factor (D-factor) is a cytokine whose functions overlap those of tumour necrosis factor-alpha (TNF), IL-6 and IL-1. Recombinant murine D-factor produced a dose- and time-dependent inhibition of heparin-releasable LPL activity in differentiated 3T3-L1 adipocytes. Although 2-10 fold less potent than recombinant murine TNF, D-factor inhibited LPL activity at concentrations of 1-10 ng/ml. When added together, D-factor and TNF produced a synergistic inhibition of LPL activity. Interleukin 6 (IL-6) was 100-fold less potent than D-factor; 0.1 ng/ml of D-factor or 10 ng/ml of IL-6 caused a 50% inhibition of LPL activity. D-factor and TNF increased IL-6 production in 3T3-L1 cells. Ten ng/ml of D-factor or 1.0 ng/ml of TNF stimulated the release of < 1 ng/ml of IL-6 and inhibited LPL activity to 11 +/- 3% and 3 +/- 2% of control, respectively, whereas 50 ng/ml of recombinant IL-6 was required to decrease LPL activity to 24 +/- 19% of control. TNF produced a marked decrease in LPL mRNA, whereas D-factor had minimal or no effect at doses which inhibited LPL activity almost completely. Western blot analysis of cell extracts showed that TNF caused a greater decrease in LPL protein production than D-factor.2+ with TNF, may contribute to the manifestations of cachexia.     

Bone mineral density and survival of elements and element portions in the bones of the Crow Creek massacre victims

The interpretation of archaeologically-derived skeletal series is dependent on the elements and portions of elements preserved for examination. Bone and bone portion survival is affected by factors, both intrinsic and extrinsic to the elements themselves, that influence deterioration and preservation. Among the intrinsic variables, the density of the element and element portion are particularly important with respect to the degree of preservation. Recently reported bone mineral density values from a contemporary human sample are compared to the survival of prehistoric limb bones of the Crow Creek specimens, a fourteenth-century massacre skeletal series. The contemporary density values are positively correlated with Crow Creek element and element portion survival. Two calculations of bone mineral density, however, are more closely related to preservation than a third. Such density information has implications for assessing minimum number of elements and individuals and documenting taphonomic processes.