Biomedical subjects

J W Nieves

Publications and source records attributed to J W Nieves.

12 recordsLinked to original sources

PubMed2006

Determinants of bone mass and bone size in a large cohort of physically active young adult men.

The determinants of bone mineral density (BMD) at multiple sites were examined in a fit college population. Subjects were 755 males (mean age = 18.7 years) entering the United States Military Academy. A questionnaire assessed exercise frequency and milk, caffeine, and alcohol consumption and tobacco use. Academy staff measured height, weight, and fitness. Calcaneal BMD was measured by peripheral dual-energy x-ray absorptiometry (pDXA). Peripheral-quantitative computed tomography (pQCT) was used to measure tibial mineral content, circumference and cortical thickness. Spine and hip BMD were measured by DXA in a subset (n = 159). Mean BMD at all sites was approximately one standard deviation above young normal (p < 0.05). African Americans had significantly higher hip, spine and heel BMD and greater tibial mineral content and cortical thickness than Caucasians and Asians. In Caucasians (n = 653), weight was a significant determinant of BMD at every skeletal site. Prior exercise levels and milk intake positively related to bone density and size, while caffeine had a negative impact. There was an apparent interaction between milk and exercise in BMD at the heel, spine, hip and tibial mineral content and cortical thickness. Our data confirm the importance of race, body size, milk intake and duration of weekly exercise as determinants of BMD and bone size.

Journal Article↗

PubMed2005

Short-term effects of estrogen, tamoxifen and raloxifene on hemostasis: a randomized-controlled study and review of the literature.

INTRODUCTION: Estrogen therapy (ET), tamoxifen and raloxifene are associated with a two- to three-fold increased risk of venous thrombosis (VT); however, the mechanisms by which each drug increases venous thrombosis propensity are not fully understood. The objectives of this investigation were to compare the effects of these three treatments on hemostasis in a head to head randomized placebo-controlled trial. PATIENTS/METHODS: Ninety-four postmenopausal women were assigned to receive oral estrogen (conjugated equine estrogen [CEE] 0.625 mg, n=23), tamoxifen 20 mg (n=24), raloxifene 60 mg (n=24) or placebo (n=23) daily for 6 months. Blood samples were analyzed for procoagulant factors (prothrombin, factors VII [fVII], VIII [fVIII], IX [fIX] and XI [fXI], D-dimer and von Willebrand factor [vWf]), anticoagulant factors (antithrombin [AT], total and free protein S, protein C and activated protein C [APC] resistance) and fibrinolytic factors (thrombin activatable fibrinolysis inhibitor [TAFI] and plasminogen activator inhibitor-1 [PAI-1]), at baseline and at 6 months of treatment. RESULTS: Estrogen increased factor VII and D-dimer, and decreased antithrombin, total and free protein S and PAI-1. Changes with tamoxifen were distinct from estrogen with increases in factors VIII, IX, vWf and free protein S, and decreases in AT, total protein S, protein C and plasminogen activator inhibitor-1. Raloxifene produced similar effects as tamoxifen, but did not increase factor IX or decrease protein C. CONCLUSIONS: Estrogen, tamoxifen and raloxifene affected hemostasis favoring procoagulation and impairing anticoagulation. The biochemical effects of the selective estrogen receptor modulators (SERMs) were distinct from those of estrogen and differed only subtly from each other.

Biomarkers↗

PubMed2003

Constant mineralization density distribution in cancellous human bone.

The degree of mineralization of bone matrix is an important factor in determining the mechanical competence of bone. The remodeling and modeling activities of bone cells together with the time course of mineralization of newly formed bone matrix generate a characteristic bone mineralization density distribution (BMDD). In this study we investigated the biological variance of the BMDD at the micrometer level, applying a quantitative backscattered electron imaging (qBEI) method. We used the mean calcium concentration (Ca(Mean)), the most frequent calcium concentration (Ca(Peak)), and full width at half maximum (Ca(Width)) to characterize the BMDD. In none of the BMDD parameters were statistically significant differences found due to ethnicity (15 African-American vs. 27 Caucasian premenopausal women), skeletal site variance (20 ilium, 24 vertebral body, 13 patella, 13 femoral neck, and 13 femoral head), age (25 to 95 years), or gender. Additionally, the interindividual variance of Ca(Mean) and Ca(Peak), irrespective of biological factors, was found to be remarkably small (SD < 2.1% of means). However, there are significant changes in the BMDD in the case of bone diseases (e.g., osteomalacia) or following clinical treatment (e.g., alendronate). From the lack of intraindividual changes among different skeletal sites we conclude that diagnostic transiliac biopsies can be used to determine the BMDD variables of cancellous bone for the entire skeleton of the patient. In order to quantify deviations from normal mineralization, a reference BMDD for adult humans was calculated using bone samples from 52 individuals. Because we find the BMDD to be essentially constant in healthy adult humans, qBEI provides a sensitive means to detect even small changes in mineralization due to bone disease or therapeutic intervention.

Adult↗

PubMed1998

Comparative assessment of bone mineral measurements using dual X-ray absorptiometry and peripheral quantitative computed tomography.

A measurement of bone mass is the single most important determinant of future fracture. However, controversy exists as to which technique (dual X-ray absorptiometry (DXA) or peripheral quantitative computed tomography (pQCT), and which site of skeletal measurement (axial vs appendicular) provides the best prediction of fracture risk. The aims of this study were: (1) to determine the ability of pQCT to predict bone mass of the lumbar spine, proximal femur, and distal forearm measured using DXA, and (2) to compare the ability of DXA and pQCT to discriminate prevalent fractures in women with established osteoporosis. One hundred and sixty-five women were studied, including 47 with established osteoporosis (vertebral, hip or Colles' fractures) as well as 118 who had bone mass measurements to assess osteoporosis risk. Each subject had bone mass measured by DXA at the lumbar spine and femoral neck, and at the distal radius by both DXA and pQCT. In women with fractures, bone mass, when expressed as a standardized score, was in general lower using DXA compared with the appendicular skeleton measured using pQCT. Bone mass determinations at all sites were significantly correlated with each other. The highest correlation coefficients were observed within the axial skeleton. In women with fractures, the highest odds ratios were observed at skeletal regions measured using DXA. Likewise, the areas under the receiver-operating characteristic (ROC) curves were comparable at all skeletal regions measured using DXA; and were significantly greater than the areas under the ROC curves for pQCT measurements. In summary, the strongest discriminators of prevalent fractures were measurements using DXA. Measurements of bone mass at the appendicular skeleton, using either DXA or pQCT, were poorly associated with axial bone mass. PQCT has the poorer ability to discriminate persons with fractures, and appears to be less sensitive than measurements using DXA.

Absorptiometry, Photon↗

PubMed1998

Calcium potentiates the effect of estrogen and calcitonin on bone mass: review and analysis.

We reviewed published clinical trials that measured bone mass of postmenopausal women from at least one skeletal site to evaluate whether calcium supplementation influenced the efficacy of estrogens and intranasal calcitonin on bone mass change. We compared results of the administration of oral estrogen or nasal calcitonin in conjuction with additional calcium intake either through diet or supplements compared with those of estrogen or calcitonin alone. Of the 31 published estrogen trials analyzed, 20 modified the diet or used a calcium supplement (total 1183 mg/d) and 11 did not (total 563 mg/d). The mean increase in bone mass of the lumbar spine when estrogen was given alone was 1.3%/y (n = 5) compared with 3.3%/y when estrogen was given in conjunction with calcium (n = 14; P = 0.01). The mean increase in bone mass of the femoral neck with estrogen alone (n = 3) was only 0.9%/y compared with 2.4%/y when calcium was given with estrogen (n = 6; P = 0.04). Similarly, forearm bone mass increased 0.4%/y with estrogen alone (n = 7) compared with 2.1%/y when estrogen was given with calcium (n = 12; P = 0.04). Similar results were found when weighted means were calculated. Of the seven published trials evaluating the effects of 200 IU nasal salmon calcitonin, six also used calcium supplements (total 1466 mg/d) whereas one used calcitonin alone (total 627 mg/d). Bone mass of the lumbar spine increased 2.1% with calcitonin plus calcium supplementation compared with -0.2%/y with calcitonin alone. These results suggest that a high calcium intake potentiates the positive effect of estrogen on bone mass at all skeletal sites and perhaps that of calcitonin on bone mass of the spine.

Bone Density↗

PubMed1997

Resistance to bone resorbing effects of PTH in black women.

Black women have a lower incidence of vertebral and hip fractures than white women, possibly due to differences in skeletal and mineral metabolism. One suggested mechanism is that blacks have decreased skeletal sensitivity to parathyroid hormone (PTH). To test this hypothesis, we infused h(1-34)PTH in healthy premenopausal black (n = 15) and white (n = 18) women over 24 h and measured serum and urine indices of bone turnover and calcium metabolism throughout the infusion. At baseline, the mean 25-hydroxyvitamin D (25(OH)D) concentration was significantly lower in black women (46%). There were also nearly significant trends toward higher PTH and lower urinary calcium and pyridinoline levels in black women. During infusion, there were no racial differences in the mean (1-34)PTH levels achieved or in resultant elevations of serum calcium or 1,25-dihydroxyvitamin D (1,25(OH)2D) levels. Endogenous parathyroid suppression (measured by (1-84)PTH levels) was also similar between blacks and whites. There was an initial decline in urinary calcium/creatinine in both groups with a greater reduction in black women early in the infusion period (p < 0.05 at 8 h). Furthermore, blacks had lower levels of urinary calcium/creatinine throughout the infusion (p < 0.05 group difference). Bone formation markers (carboxy-terminal propeptide of type I procollagen and osteocalcin) decreased within 8 h and continued to decline throughout the infusion with no distinguishable racial differences (p < 0.05 time trend for both). The most dramatic difference between black and white women in response to PTH infusion was represented by the bone resorption markers. Three separate metabolites of bone resorption (cross-linked N-telopeptide of type I collagen, cross-linked C-telopeptide of type I collagen, and free pyridinoline) all showed substantially greater elevations in white (mean peak increments 399, 725, and 43%) compared with black women (mean peak increments 317, 369, and 17%) during the infusion (p < 0.05 group differences for all three variables). These data strongly suggest that blacks have decreased skeletal sensitivity to the acute resorptive effects of increased PTH. This finding indicates that calcium homeostasis may be accomplished in blacks (during times of relative calcium deficiency) by greater conservation of calcium from nonskeletal sources (most likely renal) with relative preservation of skeletal tissue. These differences in calcium economy could account, at least in part, for the increased bone mass and lower incidence of osteoporotic fractures in black women.

Adult↗

PubMed1995

Teenage and current calcium intake are related to bone mineral density of the hip and forearm in women aged 30-39 years.

The relation between diet and bone mineral density in premenopausal women was evaluated in a cross-sectional study of 139 women aged 30-39 years. The population consisted of volunteers recruited in Rockland County, New York, between September 1988 and August 1992. A food frequency questionnaire was used to determine nutrient intake for both the year prior to bone density measurement and for ages 13-17 years. Physical measurements included height, weight, grip strength, and percent body fat. Bone mineral density was measured in the lumbar spine, hip, and forearm. Multiple regression equations were used to relate nutrient intake to bone density while controlling for age, height, weight, and grip strength. There were no relations between lumbar spine or distal forearm bone density and any nutrient studied from either the current or teenage diet. Current dietary calcium intake was modestly related to hip bone density (beta = 0.077; p = 0.074). When fiber intake was added to the multiple regression model, the association between calcium and hip bone density was strengthened (beta = 0.101; p = 0.037); this would be expected, because fiber interferes with calcium absorption. In the teenage diet, phosphorus and calcium intake were related to hip bone density. A higher lifetime calcium intake was associated with a higher hip bone density compared with low lifetime calcium intake. An increase in teenage calcium intake from 800 to 1,200 mg per day is estimated to increase hip bone density by 6 percent.

Adolescent↗

PubMed1993

Dietary risk factors for the incidence and recurrence of colorectal adenomatous polyps. A case-control study.

OBJECTIVE: To investigate the association of dietary factors with the incidence and recurrence of colorectal adenomatous polyps. DESIGN: Two case-control studies. SETTING: Three university-based colonoscopy practices in New York City. PATIENTS: For the incidence study, 286 patients with pathologically confirmed incident adenomatous polyps (162 men and 124 women) were compared with 480 controls (210 men and 270 women) with no current or previous neoplasia. For the recurrence study, 186 patients with recurrent polyps (130 men and 56 women) were compared with 330 controls (187 men and 143 women). These patients had a history of polyps but no current neoplasia. MEASUREMENTS: Structured interviews using the Block food frequency questionnaire were conducted on all participants and were compared over quartiles of crude nutrient intake of total and saturated fat; fiber; protein; carbohydrates; carotene; vitamins A, C, and E; and various food groups. Data were adjusted for age, Quetelet index, and caloric intake by multiple logistic regression for men and women separately. RESULTS: For incident polyps, elevated adjusted odds ratios (high to low quartile) for women were found for saturated fat (odds ratio, 2.3; 95% CI, 0.9 to 5.8) and the ratio of red meat to chicken and fish intake (odds ratio, 1.9; CI, 1.0 to 3.6). Protective associations were observed for fish and chicken (odds ratio, 0.6; CI, 0.3 to 1.2) and vitamin A intake (odds ratio, 0.4; CI, 0.2 to 0.9). Among women, recurrent polyps showed an association with total dietary fat (odds ratio, 4.4; CI, 1.0 to 19.5), saturated fat (odds ratio, 3.8; CI, 1.0 to 14.9; P = 0.15 for the trend), and total fiber (odds ratio, 0.2; CI, 0.1 to 0.5; P = 0.01) and a borderline association with carbohydrates (odds ratio, 0.3; CI, 0.1 to 1.3; P = 0.10). No consistent relations were observed for men, although increased caloric intake increased the risk for incidence and recurrence in both men and women. CONCLUSIONS: These findings are consistent with previously described relations between diet and the incidence of colon cancer and suggest that, at least in women, dietary modification may be warranted in patients diagnosed with polyps.

Adult↗

PubMed1992

Comparative assessment of bone mineral density of the forearm using single photon and dual X-ray absorptiometry.

Forearm bone mineral density (BMD) was measured at proximal and distal sites by 125I single photon absorptiometry (SPA) and by dual energy X-ray absorptiometry (DXA) in 67 consecutive subjects, aged 18-75 years. Correlations and regression equations between these two techniques were determined. All forearm measurements were significantly correlated with each other (r = 0.599-0.926; P < or = 0.0001). Although SPA and DXA correct for fat in different ways, we found similar correlation and regression equations in women with body mass index measurements above and below the mean. In addition, forearm measurements by both techniques were moderately correlated with vertebral spine and hip BMD. We conclude that overall, SPA forearm measurements in a population can be calibrated to DXA measurements if necessary, and that DXA forearm measurements are as predictive of the remainder of the skeleton as SPA measurements.

Absorptiometry, Photon↗

PubMed1992

A case-control study of hip fracture: evaluation of selected dietary variables and teenage physical activity.

Recent diet, teenage physical activity and teenage calcium consumption were examined as risk factors for hip fracture in a case-control study. Cases were 161 white women admitted to one of 30 participating hospitals with a first hip fracture. Controls included 168 white women from general and orthopedic surgical services frequency-matched to cases by age group and hospital. Information on exposure to possible risk factors was obtained by in-person interview. No association was found between recent intake of calcium, phosphorus, protein, vitamin C or caffeine and hip fracture. Also, teenage calcium intake and milk drinking were not related to hip fracture risk. Recreational activities in adolescence and early adulthood appeared to afford protection against hip fracture. The highest quartile of recreational activity (greater than or equal to 4 times/week) was associated with an odds ratio of 0.24 (95% confidence interval 0.08-0.75) relative to the lowest quartile (less than 1 time/week).

Adolescent↗

PubMed1991

Cancer rates after the Three Mile Island nuclear accident and proximity of residence to the plant.

BACKGROUND: In the light of a possible link between stress and cancer promotion or progression, and of previously reported distress in residents near the Three Mile Island (TMI) nuclear power plant, we attempted to evaluate the impact of the March 1979 accident on community cancer rates. METHODS: Proximity of residence to the plant, which related to distress in previous studies, was taken as a possible indicator of accident stress; the postaccident pattern in cancer rates was examined in 69 "study tracts" within a 10-mile radius of TMI, in relation to residential proximity. RESULTS: A modest association was found between postaccident cancer rates and proximity (OR = 1.4; 95% CI = 1.3, 1.6). After adjusting for a gradient in cancer risk prior to the accident, the odds ratio contrasting those closest to the plant with those living farther out was 1.2 (95% CI = 1.0, 1.4). A postaccident increase in cancer rates near the Three Mile Island plant was notable in 1982, persisted for another year, and then declined. Radiation emissions, as modeled mathematically, did not account for the observed increase. CONCLUSION: Interpretation in terms of accident stress is limited by the lack of an individual measure of stress and by uncertainty about whether stress has a biological effect on cancer in humans. An alternative mechanism for the cancer increase near the plant is through changes in care-seeking and diagnostic practice arising from postaccident concern.

Bias↗

PubMed1990

Cancer near the Three Mile Island nuclear plant: radiation emissions.

As a public charge, cancers among the 159,684 residents living within a 10-mile (16-km) radius of the Three Mile Island nuclear plant were studied relative to releases of radiation during the March 28, 1979, accident as well as to routine plant emissions. The principal cancers considered were leukemia and childhood malignancies. Estimates of the emissions delivered to small geographic study tracts were derived from mathematical dispersion models which accounted for modifying factors such as wind and terrain; the model of accident emissions was validated by readings from off-site dosimeters. Incident cancers among area residents for the period 1975-1985 (n = 5,493) were identified by a review of the records at all local and regional hospitals; preaccident and postaccident trends in cancer rates were examined. For accident emissions, the authors failed to find definite effects of exposure on the cancer types and population subgroups thought to be most susceptible to radiation. No associations were seen for leukemia in adults or for childhood cancers as a group. For leukemia in children, the odds ratio was raised, but cases were few (n = 4), and the estimate was highly variable. Moreover, rates of childhood leukemia in the Three Mile Island area are low compared with national and regional rates. For exposure to routine emissions, the odds ratios were raised for childhood cancers as a whole and for childhood leukemia, but confidence intervals were wide and included 1.0. For leukemia in adults, there was a negative trend. Trends for two types of cancer ran counter to expectation. Non-Hodgkin's lymphoma showed raised risks relative to both accident and routine emissions; lung cancer (adjusted only indirectly for smoking) showed raised risks relative to accident emissions, routine emissions, and background gamma radiation. Overall, the pattern of results does not provide convincing evidence that radiation releases from the Three Mile Island nuclear facility influenced cancer risk during the limited period of follow-up.

Adolescent↗