Aging of bone density in the second metacarpal.

Bone weight, bone and cortical areas, and apparent and true bone densities (W/BV and W/CV) were measured on the second metacarpals of 114 male and 114 female Japanese, aged 30 to 98 years. Measurements were taken from midshaft cross-sections 2 mm thick, using an electron balance and an image analyzing system. The mean values of these variables were greater in men than in women at all ages. Bone area stayed almost unchanged regardless of age. Bone weight and cortical area decreased linearly with advancing age. The respective rates of decrease per decade observed for the these variables were 3.1% and 2.9% in men and 5.5% and 4.8% in women. Apparent bone density decreased gradually with age after the fourth decade in women. While, in men, it stayed almost unchanged or increased slightly until the fifth decade and then, decreased gradually with age. The rate of decrease per decade was accelerated after the fifth decade in women and after the sixth in men, being 10.3% and 8.1% in each gender, respectively. The mean loss of bone was about twice as great in women as in men. In women, significant differences (p less than 0.01) were found in these variables after the seventh decade compared with the preceding age group. However, true bone density (W/CV) stayed almost unchanged regardless of age, being about 2.0 in men and about 1.9 in women. Osteoporosis could be primarily a manifestation of normal aging, including the postmenopausal estrogen deficiency in women, regardless of gender or race.     

Age and sex differences in bone density of the second metacarpal in its midshaft cross-section

On the basis of the midshaft cross-section of the second metacarpal in 102 male and 96 female Japanese, aged 30 to 98 years, age- and sex-related differences of bone mass and density are examined. Bone mass and density are almost always greater in males than in females. Cortical mass and apparent bone density decrease gradually with age after 45 years of age in both sexes. The decreasing rate is about twice as great in females as in males. The sex difference increases gradually with age, especially after the sixth decade. However, true bone density remains almost constant, regardless of age, until the seventh decade in both sexes. The maximum density layer is more deeply located at the radial side than at the ulnar, and also more so in males than in females, corresponding to the differences in cortical thickness. The relative depth of this layer to the bone width is about 15% at the radial side and 12% at the ulnar in males and about 12% and 10% at each side in females, respectively.     

掌骨,近节指骨骨髓腔的测量及其意义

目的 :测量掌、指骨骨髓腔长度 ,观察髓腔形状及变化 ,为掌指关节假体的设计及改进提供参考数据。方法 :2 0只手标本随机分为两组。 10只手从干骺端开始每隔 10mm进行横切 ,测量髓腔的冠状径及矢状径 ;其余纵切 ,测量髓腔长度及髓腔最狭窄处。拍摄 2 0只手标本X光片。测量Swanson假体柄及绞链区长度及宽度。结果 :掌骨骨髓腔形状男女及左右手无差别 ,髓腔长度大约为其全长的 3 /5 ,髓腔的狭窄段在全长中点近侧约 5～ 10mm处。指骨髓腔呈“喇叭型” ,长度同指骨无明显的比例关系。X光片测量结果基本同实际解剖测量相同。Swanson假体两端柄长度约为髓腔长度的 2 /3。绞链区长度稍小于1/2干骺端至掌骨头长度。结论 :掌指骨髓腔在中间较窄 ,两侧较宽 ,存在约 5～ 10mm的狭窄段。中间段髓腔形状五指各不相同。为设计国人掌指关节假体及改进Swanson硅胶假体提供参考数据 ,另外对于选择骨折内固定物及手术操作亦有指导意义     

Spatial variation in osteon population density at the human femoral midshaft: histomorphometric adaptations to habitual load environment

Intracortical remodeling, and the osteons it produces, is one aspect of the bone microstructure that is influenced by and, in turn, can influence its mechanical properties. Previous research examining the spatial distribution of intracortical remodeling density across the femoral midshaft has been limited to either considering only small regions of the cortex or, when looking at the entirety of the cortex, considering only a single individual. This study examined the spatial distribution of all remodeling events (intact osteons, fragmentary osteons, and resorptive bays) across the entirety of the femoral midshaft in a sample of 30 modern cadaveric donors. The sample consisted of 15 males and 15 females, aged 21–97 years at time of death. Using geographic information systems software, the femoral cortex was subdivided radially into thirds and circumferentially into octants, and the spatial location of all remodeling events was marked. Density maps and calculation of osteon population density in cortical regions of interest revealed that remodeling density is typically highest in the periosteal third of the bone, particularly in the lateral and anterolateral regions of the cortex. Due to modeling drift, this area of the midshaft femur has some of the youngest primary tissue, which consequently reveals that the lateral and anterolateral regions of the femoral midshaft have higher remodeling rates than elsewhere in the cortex. This is likely the result of tension/shear forces and/or greater strain magnitudes acting upon the anterolateral femur, which results in a greater amount of microdamage in need of repair than is seen in the medial and posterior regions of the femoral midshaft, which are more subject to compressive forces and/or lesser strain magnitudes.     

Body composition characteristics are associated with the bone density of the proximal femur end in middle- and old-aged women and men

OBJECTIVES: In the present study the associations between bone density of the proximal femur end and weight status, fat distribution patterns (FDI) and body composition parameters i.e. amount of body fat and lean body mass were tested in a sample of old aged women and men. METHODS: In 77 healthy women ranging in age from 60 to 92 years (x=71.8 years) and 62 healthy men ranging in age from 60 to 86 years (x=71.5 years) the bone mineral density (BMD of the proximal femur end and the body composition parameters absolute fat mass, relative fat mass, lean body mass and bone mineral content were estimated by dual energy X-ray absorptiometry. Additionally, the weight status (body mass index, BMI) and the FDI were calculated. The bone density of the proximal femur end was correlated with the absolute fat mass and the lean body mass as well as with the BMI and the FDI. RESULTS: BMD correlated in females significantly positively with parameters of body composition, in males no significant correlations between fat mass (absolute and relative) and BMD as well as BMD/stature was found. Furthermore, it was shown that the weight status (BMI; r(2)=0.13, P<0.0003 in males and r(2)=0.27, P<0.000 in females), and the lean body mass (r(2)=0.21, P<0.001 in males, r(2)=0.36, P<0.004 in females) were associated significantly positively with the BMD of the proximal femur end in both sexes. The absolute fat mass had a significant impact on BMD in the female subsample only (r(2)=0.24, P<0.000). CONCLUSIONS: A lower weight status and a low amount of lean body mass, indicating not only lack of biomechanical forces of the proximal femur end, but also a lack of physical activity can be assumed to be associated increased bone loss and the development of osteoporosis in both sexes. An association between low amount of fat tissue and decreased BMD was especially found in women and may be due to the reduced conversion rates from androgens to estrogens in a low amount of fat tissue.     

Relationships among microstructural properties of bone at the human midshaft femur

Mineralization density and collagen fibre orientation are two aspects of a bone's microstructural organization that influence its mechanical properties. Previous studies by our group have demonstrated a distinctly non-random, though highly variable, spatial distribution of these two variables in the human femoral cortex. In this study of 37 specimens, these variables are examined relative to one another in order to determine whether regions of bone demonstrating higher or lower mineralization density also demonstrate a prevalence of either transversely or longitudinally oriented collagen fibres. An analysis of rank-transformed collagen fibre orientation (as determined by circularly polarized light) and mineralization density (as determined by backscattered electron microscopy) data sets demonstrated that areas of low mineralization density (predominantly in the anterior-lateral cortex) tended to correspond to regions of higher proportions of longitudinally oriented collagen fibres. Conversely, areas of higher mineralization density (postero-medially) tended to correspond to regions of higher proportions of transversely oriented collagen fibres. High variability in the sample led to generally low correlations between the two data sets, however. A second analysis focused only on the orientation of collagen fibres within poorly mineralized bone (representing bone that was newly formed). This analysis demonstrated a lower proportion of transverse collagen fibres in newly formed bone with age, along with some significant regional differences in the prevalence of collagen fibres of either orientation. Again high variability characterized the sample. These results are discussed relative to the hypothesized forces experienced at the midshaft femur.     

Pseudoepiphyses or notches in the non-epiphyseal end of metacarpal bones in healthy children

Longitudinal series of hand x-rays from healthy white children (116 boys, 118 girls) of Fels growth studies were investigated. Notchings of the nonepiphyseal end of the first, second and fifth metacarpal bones were found in every child. Beginning from infancy or early childhood, the notchings follow a sequence of developmental stages (obtuse-angle; acute-angle; cleft: underlying, edge-to-edge, overjutting; and fusion) until they disappear one to one and one-half years before onset of puberty. The notching intensity in the second and the fifth metacarpal bones was rated. A moderate degree of association in notching intensity was demonstrated between brothers and sisters.     

Correlation of hand bone mineral density with the metacarpal cortical index and carpo:metacarpal ratio in patients with rheumatoid arthritis

This study proposed an assessment of the correlation of hand bone mineral density measured by dual energy x-ray absorbtiometry (DXA) with the carpo:metacarpal (C:MC) ratio and metacarpal cortical index (CI) in patients with rheumatoid arthritis (RA). The correlation of total hand BMD, CI and C:MC ratio with BMD at other sites, the Health Assessment Questionnaire (HAQ) and Larsen scores were also examined. The hand and axial BMD of 30 female patients were also compared with 29 age-matched healthy female controls. Total hand BMD values of patients were significantly lower than the control group. There was no significant difference between groups in axial measurements. CI correlated moderately with the second metacap (II.MC) midshaft and total hand BMD. The C:MC ratio correlated with II.MC midshaft and total hand BMD. Total hand BMD correlated moderately with the AP spine (L2-L4) and femoral neck BMD. Larsen scores showed weak negative correlation with II.MC midshaft BMD and CI. Grip strength correlated weakly only with total hand BMD. The results indicated that CI may reflect cortical bone mass of the hand accurately and did not predict bone density of the spine or hip in patients with RA. The C:MC ratio is a useful method for evaluating progression of wrist involvement and may be related to the loss of hand bone mineral density associated with disease process.     

Reconstruction of femur length from markers of its proximal end

Length of femur and stature are of forensic and anthropological significance. Bony markers such as the head and neck of the femur can be of use in determining the femoral length when only a fragment of the proximal femur is available. A total of 171 South Indian unpaired femora, devoid of gross pathology and grouped by genders and sides, were used to measure the neck-shaft angle, neck length, intertrochanteric apical axis length, maximum vertical diameter of the femur head, and maximum femur length. The data were statistically analyzed for regression. Length of femur significantly correlated with the other dimensions. Simple (linear) regression equations of the length of femur against the neck-shaft angle, neck length, intertrochanteric apical axis length, and maximum vertical diameter of the head have been derived. The equations seem to be robust and can be used for different populations. © 1996 Wiley-Liss, Inc.     

Aging of medical school faculty and the end of mandatory retirement.

In anticipation of the end of mandatory retirement for tenured professors in 1994 (mandatory retirement ended for other academics in 1986), the author analyzed the demographics of medical school faculty, using 25 years of data taken in mid-1989 from the Faculty Roster of the Association of American Medical Colleges. The annual growth rate of the number of full-time faculty dropped from well over 10% before 1972 to about 1.5% after 1982, while the mean age of the faculty increased from under 42 years to over 45 in 1988. Retirement patterns changed little after the minimum mandatory retirement age was raised in 1982 from 65 to 70 (for tenured professors). Only about 2.5% of all faculty separations in 1984-1987 occurred at or after age 70, and only 5.5% did even in the tenure tracks of the 20 largest private medical schools. Since such a small proportion of openings is created each year by mandatory retirement, uncapping will have little effect on the age or turnover of medical faculty.     

Aging as a consequence of intracellular water volume and density

Aging is the result of a gradual failure of physiological and/or biochemical pathways that culminates with the death of the organism. Until now, the causative factors of aging are elusive, despite the increasing number of theories that try to explain how aging initiates. Interestingly, aging cells show an increase in intracellular water volume, but this fact is barely explored in aging studies. All cells have a crowded cytoplasm, where the high concentration and proximity of macromolecules create an environment that excludes many small molecules, including water. In this crowded environment, water can be found in two states termed low density water (LDW), which shows low reactivity and has an ice-like structure, and high density water (HDW) that has a disorganized structure and is highly reactive. LDW predominates in a macromolecular crowded environment, while HDW is found only in microenvironments within cytoplasm. In this sense, we hypothesized that the failure in the water homeostasis mechanisms with time changes the equilibrium between LDW and HDW, increasing the concentration of intracellular HDW. Being reactive, HDW leads to the generation of reactive oxygen species and disturbs the crowded cytoplasm environment, resulting in a diminished efficiency of metabolic reactions. Noteworthy, the cell becomes less prone to repair damage when the concentration of HDW increases with time, resulting in aging and finally death. Interestingly, some biological mechanisms (e.g., anhydrobiosis) reduce the concentration of intracellular water and prolong the life of cells and/or organisms. In this sense, anhydrobiosis and related biological mechanisms could be used as a platform to study new anti-aging therapies.     

Starting at the end

From the time when I entered immunology - in January 1965 at the Salk Institute for Biological Studies in La Jolla, California in the laboratories of Edwin (Ed) Lennox and Melvin (Mel) Cohn - my love has always been B lymphocytes and antibodies. I began my studies at the end of the developmental pathway of these B cells, with plasma cells. After more than 40 years in immunology, I have moved "backwards" over mature B cells, immature B cells, precursor B cells and lymphocyte progenitors to pluripotent hematopoietic stem cells. Initially it was an intellectual exercise to trace the unknown progenitor of known B-lineage cells; now it has become an experimental approach - to de- and re-differentiate B-lineage cells to earlier differentiation stages and to other lineages of hematopoietic cells.     

Telomere end processing: unexpected complexity at the end game

Most human cells lack telomerase, the enzyme that elongates telomeres. The resulting telomere erosion eventually limits cell proliferation and tissue renewal, thereby impacting age-dependent pathologies. In this issue of Genes & Development, a technical tour-de-force by Chow and colleagues (pp. 1167-1178) reveals a highly choreographed sequence of events that processes newly replicated chromosome ends into mature telomeres. This sheds new light on an underappreciated contribution to telomere dynamics that may be as important as telomerase in dictating the correlation between life span and telomere length.     

Caregiving at the end of life

Meeting the demands of chronic illness and disease states is challenging, at best. Too often, the chronicity of the illness hastens death. The physical, psychological, and sociological changes that accompany the death of an individual require attention and forethought if the life transition is to be made with elegance and grace. This article addresses the caregiving demands for the professional and familial/social support surrounding the chronically ill individual at the end of life. Focus is placed on the preparation of advance directives-legal documents that set clear boundaries for honoring the wishes of the patient.