Clustering of insulin resistance, total and central abdominal fat: same genes or same environment?

Obesity, insulin resistance and disturbed glucose metabolism cluster within the Insulin Resistance Syndrome (IRS). Whether this reflects shared genetic or environmental factors detectable in 'normal' populations (not selected for IRS features) is unknown. This study estimated (i) genetic influences on IRS traits and (ii) shared and specific genetic and environmental factors on the relationships between these traits in healthy female twins. Fasting insulin, glucose, total and central fat were measured in 59 monozygotic (MZ) and 51 dizygotic (DZ) female twin pairs aged (+/- SD) 52 +/- 13 years. Body fat was measured by dual-energy X-ray absorptiometry, insulin resistance and secretion by a modified homeostasis model assessment. Using intraclass correlation coefficients and univariate model-fitting analyses, genetic influences were found in total fat, central fat, insulin resistance, fasting glucose and insulin secretion, with genetic factors explaining 64, 57, 59, 75 and 68% of their variance, respectively, using the latter technique. In matched analysis intra-pair differences in total and central fat related to intra-pair differences in insulin resistance (r2 = 0.19, P < 0.001). Multivariate model-fitting showed a close genetic relationship between total and central fat (r = 0.88). The genetic correlation between IR and central fat (0.41) was significantly greater than that for total fat (0.24), suggesting that central fat is not only a predictor of, but shares considerable genetic influence with, insulin resistance. In Cholesky analysis, these genetic influences were separate from those shared between central and total fat. In conclusion, both shared and specific genetic factors regulate components of the IRS in healthy females. However, there were discrete genetic influences on beta-cell insulin secretion, not shared with other IRS components, suggesting that a separate genetic propensity exists for Type 2 diabetes. These findings suggest we may understand the genetic and environmental influences on IRS from the study of the normal population.

Genetic and environmental contributions to the association between quantitative ultrasound and bone mineral density measurements: a twin study.

This study was designed to assess the relative contributions of genetic and environmental factors to the variation and covariation of quantitative ultrasound (QUS) measurements and their relationships to bone mineral density (BMD). Forty-nine monozygotic (MZ) and 44 dizygotic (DZ) female twins between 20 and 83 years of age (53 +/- 13 years, mean +/- SD) were studied. Digital (phalangeal) QUS (speed of sound [SOS]) and calcaneal QUS (broadband ultrasound attenuation [BUA] and velocity of sound [VOS]) were measured using a DBM Sonic 1200 ultrasound densitometer and a CUBA ultrasound densitometer, respectively. Femoral neck (FN), lumbar spine (LS), and total body (TB) BMD were measured using dual-energy X-ray absorptiometry. Familial resemblance and hence heritability (proportion of variance of a trait attributable to genetic factors) were assessed by analysis of variance, univariate, and multivariate model-fitting genetic analyses. In both QUS and BMD parameters, MZ twins were more alike than DZ pairs. Estimates of heritability for age- and weight-adjusted BUA, VOS, and SOS were 0.74, 0.55, and 0.82, respectively. Corresponding indices of heritability for LS, FN, and TB BMD were 0.79, 0.77, and 0.82, respectively. In cross-sectional analysis, both BUA and SOS, but not VOS, were independently associated with BMD measurements. However, analysis based on intrapair differences suggested that only BUA was related to BMD. Bivariate genetic analysis indicated that the genetic correlations between BUA and BMD ranged between 0.43 and 0.51 (p < 0.001), whereas the environmental correlations ranged between 0.20 and 0.28 (p < 0.01). While the genetic correlations within QUS and BMD measurements were significant, factor analysis indicates that common genes affect BMD at different sites. Also, individual QUS measurements appear to be influenced by some common sets of genes rather than by environmental factors. Significant environmental correlations were only found for BMD measurements and ranged between 0.50 and 0.65 (p < 0.001). These data suggest that QUS and BMD measurements are highly heritable traits. While it appears that there is a common set of genes influencing both QUS and BMD measurements, specific genes yet to be identified appear to have greater effects than that of shared genes in each trait.

Genetic and environmental correlations between bone formation and bone mineral density: a twin study.

Bone mineral density (BMD) and bone turnover are both heritable. Although bone turnover affects bone mass, it is not clear whether these parameters are under common genetic or environmental control. The relative contribution of genetic and environmental factors to the determination of an index of bone turnover, bone specific alkaline phosphatase (BSAP), and the extent of common genetic regulation with BMD, were examined in 97 female twin pairs, aged 50 +/- 15 years (mean +/- SD), consisting of 48 monozygotic (MZ) and 49 dizygotic (DZ) pairs. BSAP was analyzed by radioimmunometric assay. Bone mineral density (BMD) at the lumbar spine (LS) and femoral neck (FN) was measured by dual-energy X-ray absorptiometry. Twin resemblance for variable traits was assessed by intraclass correlation coefficients. Estimates of genetic and environmental components of variance were based on univariate and multivariate genetic models. As expected, BSAP in premenopausal women (9.8 +/- 4.3 microg/L) was significantly lower than in postmenopausal women (13.3 +/- 6.6 microg/L, p < 0.001), but similar to the subgroup of postmenopausal women on hormone replacement therapy (10.8 +/- 2.6 microg/L, p = 0.15). Although BSAP and BMD were correlated in a cross-sectional analysis (r = -0.35, p < 0.001 for LS-BMD; r = -0.16, p = 0.03 for FN-BMD), the intrapair difference in BSAP was not significantly correlated with the intrapair difference in BMD for MZ twin pairs. After adjustment for menopausal status, the intraclass correlation for BSAP was significantly higher in MZ than DZ twins (0.60 +/- 0.09 vs. 0.27 +/- 0.13, p = 0.03). Univariate model-fitting analyses indicated a heritability of 63% for BSAP, and 77% and 72% for lumbar spine and femoral neck BMD, respectively. By multivariate analyses, genes specifically influencing BSAP accounted for 16% of the total genetic variance in LS-BMD and 4% of the total genetic variance in FN-BMD. There was no evidence for shared environmental factors affecting BSAP and BMD. These findings indicate that BSAP and BMD are heritable and negatively correlated. However, the genetic loci influencing BSAP and BMD appear to be largely independent as are any environmental factors.

Bone mass, lean mass, and fat mass: same genes or same environments?

The contributions of genetic and environmental factors to the association among bone mineral density (BMD), lean mass, and fat mass were assessed in the Sydney Twin Study of Osteoporosis (Australia), 1995-1996, in 57 monozygotic and 55 dizygotic female twin pairs of Caucasian background, aged 52.8 (standard deviation, 13) years. In multiple regression analysis, lean mass was a significant determinant of areal BMD; however, fat mass was a principal determinant of volumetric BMD. Univariate model-fitting analyses indicated that 80% and 65% of variance of lean mass and fat mass, respectively, were attributable to genetic factors. The estimated heritability of BMD for lumbar spine, femoral neck, and total body BMD was 78%, 76%, and 79%, respectively. Multivariate analyses suggested that, while the association between lean mass and fat mass was attributable mainly to environmental factors (re = 0.53, p < 0.01), the association among the three BMD sites was attributable to both genetic and environmental factors (rg = 0.64-0.75, p < 0.001; re = 0.57-0.70, p < 0.001). Furthermore, genetic factors that affect lean mass or fat mass have minor effects on BMD. It is concluded that lean mass and fat mass, as well as bone density, are under strong genetic regulation. However, the associations between BMD and fat mass or between lean mass and fat mass appear to be mediated mainly via environmental influences.

Sensitive reversed-phase high-performance liquid chromatographic method for the determination of atevirdine and its N-desethyl metabolite in human saliva or cerebrospinal fluid using solid-phase extraction.

A sensitive reversed-phase high-performance liquid chromatographic method for the determination of atevirdine and its primary metabolite in human saliva or cerebrospinal fluid using solid-phase extraction is described. Samples mixed with internal standard and sodium phosphate buffer were applied to an activated C18 solid-phase extraction column. The reconstituted eluate was injected onto a Zorbax RX C8 column utilizing a mobile phase of 100 mM ammonium acetate (pH 4.0)-isopropyl alcohol-acetonitrile (55:20:25, v/v/v). Fluorescence detection was employed with excitation at 295 nm and emission at 456 nm. Quantitation was achieved using peak-height ratios. The detection response curve was linear from 2 to 850 nM for atevirdine in both human saliva and cerebrospinal fluid and from 2 to 250 nM for the metabolite in human saliva. The method was utilized to analyze cerebrospinal fluid and saliva samples from clinical studies.

Structure-based design of nonpeptidic HIV protease inhibitors: the sulfonamide-substituted cyclooctylpyramones.

Recently, cyclooctylpyranone derivatives with m-carboxamide substituents (e.g. 2c) were identified as potent, nonpeptidic HIV protease inhibitors, but these compounds lacked significant antiviral activity in cell culture. Substitution of a sulfonamide group at the meta position, however, produces compounds with excellent HIV protease binding affinity and antiviral activity. Guided by an iterative structure-based drug design process, we have prepared and evaluated a number of these derivatives, which are readily available via a seven-step synthesis. A few of the most potent compounds were further evaluated for such characteristics as pharmacokinetics and toxicity in rats and dogs. From this work, the p-cyanophenyl sulfonamide derivative 35k emerged as a promising inhibitor, was selected for further development, and entered phase I clinical trials.

Influence of handedness on calcaneal ultrasound: implications for assessment of osteoporosis and study design.

Calcaneal ultrasound has been increasingly studied for its potential in the assessment of osteoporotic fracture risk. The accuracy of such an assessment is, in part, dependent on the reproducibility of the measurement. This study examines the impact of handedness on ultrasound measurements [broadband ultrasound attenuation (BUA) and velocity of sound (VOS)] in the calcaneus. Two hundred and sixty-four subjects (57 men and 297 women) aged 51.1 +/- 13.6 years (mean +/- SD) were studied. For each subject, calcaneal ultrasound measurements were performed on both heels with a McCue CUBA ultrasound densitometer. Right-handed dominance (94.7%) was determined by structured interview. In men, BUA measurements were significantly higher on the dominant side: mean difference 4.1 +/- 1.5 dB/MHz (mean +/- SD; p = 0.009), equivalent to 4.2 +/- 1.5% and more than 4 times the average rate of annual change in BUA. The difference between sides was greater in young (< 50 years) than old men (> 50 years). Among the women, the difference was not statistically significant (0.7 +/- 0.9 dB/MHz; p = 0.4); however, it was significant in younger women (20-30 years) (99 +/- 4 vs 90 +/- 4 dB/MHz, p = 0.01). By contrast VOS did not differ between sides in either men or women irrespective of age. Within-subject standard deviation of BUA was 9.8 dB/MHz for men and 8.6 dB/ MHz for women and the component due to right and left difference was 8.4 dB/MHz for men and 6.9 dB/MHz for women. This variability of BUA between right and left heels could increase the false-positive rate by up to 28% for a cut-off of 2 SD below the mean. These data indicate that variation between left and right heel measurements of BUA is higher than that of random error measurements, particularly in men and younger, presumably more physically active subjects. Although VOS measurements were not side dependent, in the smaller number of studies examining VOS and fracture risk, VOS appears to have a weaker predictive power than BUA. Clinical and epidemiological studies involving calcaneal BUA measurements should standardize the side measured to either the dominant or non-dominant heel, to reduce within-subject variation and increase their power.

Brain stem auditory-evoked response in relation to neonatal glucose metabolism.

Imprecise control of glucose homeostasis is a hallmark of neonatal glucose metabolism. A relatively wide range of glucose concentrations is considered 'euglycemic' (2.22-6.94 mmol/l, 40-125 mg/dl) in the neonatal period. We investigated the effects of a wide range of glucose concentrations on brain stem conduction time (BCT) I-V interpeak latency or prolonged wave V latency. Neonates were assessed by brain stem auditory-evoked response followed immediately by heelstick sampling to determine the blood glucose concentration. Twenty-seven appropriate for gestational age (AGA) term neonates (birth weight 3,245 +/- 766 g, mean +/- SD; gestational age 39 +/- 2 weeks) were studied 3.1 +/- 3.7 days after birth. Twenty-three AGA preterm neonates (birth weight 2,175 +/- 477 g; gestational age 35 +/- 1 weeks) were studied 6.0 +/- 7.2 days after birth. Brain stem conduction time wave I-V interpeak latency and wave V latency were determined in two trials using a Grason-Stadler ABR screener at a 60-decibel stimulation level in the right ear. Neonates were studied between 33 and 40 weeks gestational age. Although the blood glucose concentration ranged from 1.38 to 6.83 mmol/1 (25-123 mg/dl), there was no correlation between either brain stem conduction time wave I-V interpeak latency or wave V latency and blood glucose concentration. We conclude that alterations in glucose concentration within the generally accepted neonatal euglycemic range do not effect the functional status of the brain stem auditory pathway. We suggest that the data can be interpreted to affirm that tighter clinical control of glucose homeostasis is probably not required in the neonatal period.

Screening for osteoporosis: what is the role of heel ultrasound?

Could focused population screening detect osteoporosis earlier and improve the management of this major health care problem? Quantitative ultrasound of the calcaneus is currently being proposed as a suitable screening technique. Correlations between quantitative ultrasound of the calcaneus and dual energy x-ray absorptiometry of bone mineral density of the spine and proximal femur are not high enough to reliably predict bone mineral density at the lumbar spine or proximal femur from the ultrasound results. Some ongoing longitudinal studies suggest that quantitative ultrasound may none the less detect individuals at increased risk of fracture, but its use for mass screening for osteoporosis would be premature.

Yeast TATA binding protein interaction with DNA: fluorescence determination of oligomeric state, equilibrium binding, on-rate, and dissociation kinetics.

A combination of steady-state, stopped-flow, and time-resolved fluorescence of intrinsic tryptophan and extrinsically labeled fluorescent DNA is utilized to examine the interaction of yeast TATA binding protein (TBP) with DNA. TBP is composed of two structural domains, the carboxy domain (residues 61-240), which is responsible for DNA binding and initiation of basal level transcription, and an amino terminal domain (residues 1-60), whose function is currently unknown. The steady-state fluorescence emission spectrum of the single tryptophan in the amino terminal domain of TBP undergoes a huge (30-40 nm) red-shift upon interaction with stoichiometric amounts of TATA box containing DNA. From time-resolved tryptophan fluorescence anisotropy studies, we demonstrate that, in the absence of DNA, the protein exists as a multimer in solution and it contains (at least) two primary conformations, one with the amino terminus associated tightly with the protein(s) in a hydrophobic environment and one with the amino terminus decoupled away from the rest of the protein and solvent-exposed. Upon binding DNA, the protein dissociates into a monomeric complex, upon which only the solvent-exposed amino terminus conformation remains. Kinetic and equilibrium binding studies were performed on TATA box containing DNA which was extrinsically labeled with a fluorescent probe Rhodamine-X at the 5'-end. This "fluorescent" DNA allowed for the collection of quantitative spectroscopic binding, kinetic on-rate, and kinetic off-rate data at physiological concentrations. Global analysis of equilibrium binding studies performed from 500 pM to 50 nM DNA reveals a single dissociation constant (Kd) of approximately 5 nM. Global analysis of stopped-flow anisotropy on-rate experiments, with millisecond timing resolution and TBP concentrations ranging from 20 to 600 nM (20 nM DNA), can be perfectly described by a single second-order rate constant of 1.66 x 10(5) M(-1) s(-1). These measurements represent the very first stopped-flow anisotropy study of a protein/DNA interaction. Stopped-flow anisotropy off-rate experiments reveal a single exponential k(off) of 4.3 x 10(-2) min-1 (1/k(off) = 23 min) From the ratio of on-rate to off-rate, a predicted Kd of 4.3 nM is obtained, revealing that the kinetic and equilibrium studies are internally consistent. Deletion of the amino terminal domain of TBP decreases the k(on) of TBP approximately 45-fold and eliminates classic second-order behavior.

Effect of intrauterine growth retardation on postnatal weight change in preterm infants.

To investigate the cause or causes of early postnatal weight change, we measured total body water and fluid and energy balances in 14 preterm infants who were appropriate in size for gestational age (AGA) and in 5 weight-matched, preterm, small-for-gestational-age (SGA) infants. On the first day of life, AGA and SGA infants had the same weight and total body water content. At 6 +/- 2 days (mean +/- SD), AGA infants had had significant weight loss (94 +/- 45 gm) and body water loss (67 +/- 80 ml), whereas weight and total body water content in the SGA infants at the same age (5 +/- 1 days) did not differ from the values at birth. Loss of weight and total body water in AGA infants was accompanied by a greater diuresis than in SGA infants at the same amount of fluid intake. At the end of week 1, AGA and SGA infants had the same total energy expenditure (184 +/- 33 vs 171 +/- 17 kJ.kg-1 x day-1); energy intake, which had exceeded total energy expenditure from the third day of life and beyond, already provided 188 +/- 46 (AGA) or 209 +/- 109 kJ.kg-1 x day-1 (SGA), respectively, for energy storage. Nitrogen balance was positive. Subsequent weight gain occurred at the same rate in AGA and SGA infants; both total body water and solids increased. Energy intake, total energy expenditure, and the amount of energy stored (measured during stable weight gain on a regimen of full enteral feedings) had significantly increased compared with week 1, but both groups maintained similar energy storage.(ABSTRACT TRUNCATED AT 250 WORDS)

Orbital arteriovenous malformation with secondary capillary angiomatosis treated by embolization with silastic liquid.

A 19-year-old Caucasian man developed signs of an orbital arteriovenous malformation, which was biopsied and then treated by embolization with a rapidly polymerizing silastic liquid. The biopsy from the initial specimen showed arteries and veins that were malformed with irregular elasticas and muscularis thicknesses, but the most curious feature was a secondary endothelial cell proliferation of such proportions as to simulate in various fields a capillary hemangioma of childhood. Approximately 50% of the bulk of the tumor was the result of the secondary endothelial cell proliferation, which we presume occurred in response to the irritative circumstances of increased intracapillary pressure from the high blood flow between the abnormal arteries and veins. Four years after the tumor was treated with the silastic liquid, it recurred and was again removed surgically. On this occasion, the histopathologic study of the tissues demonstrated a persistent secondary capillary angiomatosis, as well as chronic inflammatory reaction and granulomatous response surrounding the entrapped fragments of the polymerized silastic liquid.

Histopathologic examination of a globe containing an intraocular implant.

A patient had both cataracts removed and a Copeland pseudophakos was implanted in one eye. Both globes were retained at autopsy for histopathologic study. The globe containing the implant did not show evidence of acute or chronic inflammation of the anterior segment, nor did it display signs suggesting secondary glaucoma. Some erosion of the iris pigment epithelium was present. In general, the globe appeared to tolerate the implant.

Pulsating metastatic tumor of the orbit.

A 47-year-old white man in apparent good health had diplopia and swelling of the right upper eyelid. Ocular examination showed proptosis of the right eye, together with a large, pulsatile, collapsible mass simulating a vascular neoplasm and involving the right temple as well as the right upper outer quadrant of the orbit. Biopsy of the orbital tumor disclosed a clear-cell carcinoma compatible with a renal primary tumor; subsequent laboratory examination revealed the offending tumor in the left kidney. Renal carcinomas may metastasize to the globe or to the orbit before the primary tumor is recognized. Pulsatile exophthalmos acquired in middle life associated with significant bone destruction represents a constellation of findings most consistent with a metastatic tumor, probably renal carcinoma, caused by the exceedingly rich vascularization of these metastatic deposits.

Leiomyoma and leiomyosarcoma of the orbit.

Comparison of the clinical and pathologic features of two orbital leiomyomas, two leiomysarcomas, and one embryonal rhabdomyosarcoma showed the leiomyomas occurred in young individuals and the leiomyosarcomas in older patients. The histopathologic diagnosis rested on the intense cytoplasmic eosinophilia and nostriated longitudinal cytoplasmic filaments demonstrated by means of the trichrome stain. The leiomyosarcomas disseminated 15 months and seven years after their orbital presentations. The treatment of both leiomyoma and leiomyosarcoma is surgical. Leiomyomas are encapsulated growths that may have small satellite nodules projecting from the main tumor mass; thus, a margin of normal tissue should also be excised, lest a small lobulation be left behind to serve as the seed for a late recurrence. Once the diagnosis of leiomyosarcoma has been made, and no evidence of metastasis has been found after a thorough systemic evaluation, the orbit should be exenterated, because the tumor is unencapsulated and liable to widespread dissemination. Rhabdomyosarcoma has a much more fulminant course than leiomyosarcoma, and especially more so than that of leiomyoma of childhood. The histopathologic diagnosis of a malignant smooth muscle tumor in a child should always be questioned, since embryonal rhabdomyosarcoma is a much more likely diagnosis.

Sector hamartoma of the iris.

A 15-year old girl with a jet black-pigmented lesion on the anterior surface of the upper nasal quadrant of her iris was followed up for 12 years, during which interval growth of the lesion was documented. Histopathological evaluation of the excised segment of the iris revealed a pigment epithelial proliferation originating from posterior pigment epithelium. Additionally, there was a band of spindle shaped smooth muscle cells in the posterior stroma and a zone of plump melanocytes in the anterior stroma beneath the proliferating pigment epithelial cells. This combination of abnormalities is thought to represent a benign hamartomatous maldevelopment of the involved sector of the iris rather than a true neoplasm. Such an elaborate dysgenesis is unlike the more modest melanocytic hamartomas of the iris associated with the phakomatoses.

Kaposi's sarcoma of the conjunctiva.

A 75-year-old man with known Kaposi's sarcoma of three-years' duration developed chronic hemorrhagic thickening of the conjunctiva. Biopsy demonstrated histopathologically that the conjunctiva thickening represented sarcoma involvement. Although surgically untenable, the conjunctival lesion responds satisfactorily to radiotherapy.

Electron microscopic diagnosis of medulloepithelioma.

A 20-month-old boy with a ciliary body tumor presented with two white flocculi floating in the anterior chamber of his left eye. This material was examined by electron microscopy. Both the clinical appearance of the tumor and the ultrastructural findings suggested the diagnosis of medulloepithelioma. The flocculi contained tumor cells forming lumina and displaying neuronal-type cilia, neurotubules, and a complex band of apical desmonosomal junctions. Since the last finding is not present in retinoblastoma rosettes in the absence of fleurette differentiation, it distinguishes medulloepithelioma from retinoblastoma. The electron microscopic diagnosis has permitted a trial period of conservative cryotherapy directed at the tumor and the associated glaucoma. The electron microscopic characteristics of the tumor favor the neuroepitheliomatous and neuroblastic differentiation of medulloepithelioma rather than ependymal differentiation.