Transferrin endocytosis and iron uptake by developing erythroid cells in the chicken (Gallus domesticus)

Summary The mechanism of iron uptake by avian erythroid cells was investigated using cells from 7 and 15-day chicken embryos, and chicken serum transferrin and conalbumin (ovotransferrin) labelled with¹²⁵I and⁵⁹Fe. Endocytosis of the protein was determined by incubation of the cells with Pronase at 4°C to distinguish internalized from surface-bound protein.Iron was taken up by the cells by receptor-mediated endocytosis of transferrin or conalbumin. The receptors had the same affinity for serum transferrin and conalbumin. Endocytosis of diferric transferrin and conalbumin and exocytosis of apo-protein occurred at the same rates, indicating that iron donation to the cells occurred during the process of intracellular cycling of the protein. The recycling time was approximately 4 min. The rate of endocytosis of diferric protein varied with incubation temperature and at each temperature the rate of endocytosis was sufficient to account for the iron accumulated by the cells. These results and experiments with a variety of inhibitors confirmed the role of endocytosis in iron uptake.The mean cell volumes, receptor numbers and iron uptake rates of 7-day embryo cells were approximately twice those of 15-day embryo cells but the protein recycling times were approximately the same. Hence, the level of transferrin receptors is probably the main determinant of the rate of iron uptake during development of chicken erythroid cells.Transferrins from a variety of mammalian species were unable to donate iron to the chicken cells, but toad (Bufo marinus) transferrin could do so at a slow rate. The mechanism of iron uptake by developing chicken erythroid cells appears to be similar to that described for mammalian cells, although receptor numbers and iron uptake rates are lower than those reported for mammalian cells at a similar stage of development.Abbreviations BSS Hanks balanced salt solution - PBS phosphate buffered saline - MCV mean corpuscular volume - CCCP carbonyl cyanide-M-chlorophenyl hydrazone     

Ethnic Comparison of Weight Loss in the Trial of Nonpharmacologic Interventions in the Elderly

Objective: To compare weight loss in blacks and whites in the Trial of Nonpharmacologic Interventions in the Elderly (TONE). Research Methods and Procedures: TONE enrolled 421 overweight white and 164 overweight black adults, 60 to 79 years old, with blood pressure well-controlled on a single, antihypertensive drug. Drug therapy withdrawal was attempted 3 months after randomization to counseling for weight loss, sodium reduction, both weight loss and sodium reduction, or to usual care, with follow-up for 15 to 36 months after enrollment. Statistical procedures included repeated measures analysis of covariance and logistic and proportional hazards regression. Results: In the weight-loss condition, net weight change (in kilograms) was −2.7 in blacks and −5.9 in whites (p < 0.001; ethnic difference, p = 0.0002) at 6 months and −2.0 (p < 0.05) in blacks and −4.9 (p < 0.001) in whites at the end of follow-up (ethnic difference, p = 0.007). In weight/sodium, net weight change was −2.1 (p < 0.01) in blacks and −2.8 (p < 0.001) in whites at 6 months, and −1.9 in blacks and −1.7 in whites at the end of follow-up (p < 0.05; ethnic difference, p > 0.5). Exploratory analyses suggested a more favorable pattern of weight change in blacks than in whites from 6 months onward. There was no ethnic difference in blood pressure outcomes. Discussion: Whites lost more weight than blacks without, but not with, a concurrent focus on sodium reduction.     

Total and Central Obesity among Elderly Hispanics and the Association with Type 2 Diabetes

Objective: To report the prevalence of total and central obesity in a representative sample of Puerto Rican and Dominican elders in Massachusetts, to compare them with a neighborhood‐based group of non‐Hispanic white elders, and to examine associations of obesity indices with the presence of type 2 diabetes. Research Methods and Procedures: We examined the prevalence of overweight, obesity, and central obesity in 596 Hispanics of Caribbean origin, ages 60 to 92 years, and 239 non‐Hispanic whites, and tested linear and logistic regression models to determine associations among body mass index (BMI), waist circumference (WC), and diabetes. Results: Obesity (BMI ≥ 30 kg/m²) was prevalent among all ethnic groups, ranging from 17% to 29% for Dominican and Puerto Rican men, respectively, and from 29% to 40% for non‐Hispanic white and Dominican women, respectively. These differences were not statistically significant. Among Hispanic men and women, diabetes was prevalent across all BMI and WC categories but tended to be greatest among those with BMI of 25 to 29 kg/m² (41% to 43%). In contrast, diabetes was most prevalent in the obese group (36% to 45%) of non‐Hispanic whites. Both BMI and WC were associated with the presence of diabetes, but the coefficients were greater for non‐Hispanic whites than for Hispanics. Discussion: Caribbean Hispanics and non‐Hispanic whites living in the same Massachusetts localities had high prevalences of overweight and obesity. Total and central obesity exerted a differential effect on the presence of diabetes among ethnic groups; for Hispanics, diabetes was prevalent even among non‐obese individuals, whereas for non‐Hispanic white women, the prevalence of diabetes was strongly associated with total and central obesity. Additional research is needed to investigate the factors associated with the differential effect of obesity on the prevalence of type 2 diabetes among Hispanic and non‐Hispanic white elders.     

Ethnic Differences in Visceral Adipose Tissue and Type 2 Diabetes: Filipino,African‐American,and White Women

Objective: To compare ethnic differences in visceral adipose tissue (VAT), assessed by computed tomography, and type 2 diabetes risk among 55‐ to 80‐year‐old Filipino, African‐American, and white women without known cardiovascular disease. Research Methods and Procedures: Subjects were participants in the Rancho Bernardo Study (n = 196), the Filipino Women's Health Study (n = 181), and the Health Assessment Study of African‐American Women (n = 193). Glucose and anthropometric measurements were assessed between 1995 and 2002. Results: African‐American women had significantly higher age‐adjusted BMI (29.7 kg/m²) and waist girth (88.1 cm) compared with Filipino (BMI, 25.5 kg/m²; waist girth, 81.9 cm) or white (BMI: 26.0 kg/m²; waist girth: 80.7 cm) women. However, VAT was significantly higher among Filipino (69.1 cm³) compared with white (62.3 cm³; p = 0.037) or African‐American (57.5 cm³, p < 0.001) women. VAT correlated better with BMI (r = 0.69) and waist (r = 0.77) in whites, compared with Filipino (r = 0.42; r = 0.59) or African‐American (r = 0.50; r = 0.56) women. Age‐adjusted type 2 diabetes prevalence was significantly higher in Filipinas (32.1%) than in white (5.8%) or African‐American (12.1%) women. Filipinas had higher type 2 diabetes risk compared with African Americans [adjusted odds ratio, 2.30; 95% confidence interval (CI), 1.09 to 4.86] or whites (adjusted odds ratio, 7.51; 95% CI, 2.51 to 22.5) after adjusting for age, VAT, exercise, education, and alcohol intake. Discussion: VAT was highest among Filipinas despite similar BMI and waist circumference as whites. BMI and waist circumference were weaker estimates of VAT in Filipino and African‐American women than in whites. Type 2 diabetes prevalence was highest among Filipino women at every level of VAT, but VAT did not explain their elevated type 2 diabetes risk.     

Media for the Enhancement of Fluorescent Pigment Production by Pseudomonas Species

By a simple modification, common commercial dehydrated laboratory media can be used for the evaluation of fluorescent pigment excretion by Pseudomonas species. The addition of sufficient sterile egg white or of the iron-binding egg white protein, conalbumin, to bind all the iron in these media converted them to efficient diagnostic media. The amount of egg white found to be satisfactory was 10% of the final medium volume. Its conalbumin equivalent was 1.7 mg of conalbumin per ml of final medium. Such modified media are at least the equivalent of the medium recommended for the evaluation of this important characteristic.     

Catecholate siderophore esterases Fes,IroD and IroE are required for salmochelins secretion following utilization,but only IroD contributes to virulence of extra‐intestinal pathogenic Escherichia coli

Salmochelins are glucosylated forms of enterobactin (enterochelin) and contribute to the virulence of Salmonella enterica and some extra‐intestinal pathogenic Escherichia coli (ExPEC). Fes, IroD and IroE esterases degrade salmochelins and enterobactin to release iron. We investigated the apparently redundant role of these esterases in virulence and in salmochelin production and utilization of the ExPEC strain χ7122. The ΔiroD, ΔfesΔiroD and ΔfesΔiroDΔiroE mutants displayed attenuated virulence phenotypes in an avian systemic infection model. Growth of ΔfesΔiroD and ΔfesΔiroDΔiroE mutants was severely reduced in the presence of conalbumin, and although enterobactin was produced, no salmochelins were detected in the culture supernatants of these mutants. Elimination of catecholate synthesis via an entA deletion in a ΔfesΔiroDΔiroE restored growth in the presence of conalbumin, but only partially restored the virulence of the strain. Salmochelin production was reestablished by reintroducing active esterases. Intracellular accumulation of cyclic mono‐glucosylated enterobactin was observed in the triple mutant ΔfesΔiroDΔiroE, and deletion of fepC, required for catecholate import into the cytoplasm, restored salmochelin detection in supernatants. These results suggest that in the absence of esterases, cyclic salmochelins are synthesized and secreted, but remain cell‐bound after internalization indicating that esterase‐mediated degradation is required for re‐secretion of catecholate siderophore molecules following their utilization.     

Ethnic differences in body composition and other markers of cardiovascular disease risk: study in matched Haitian and White subjects from Quebec

Objectives: People of African descent may be at greater risk of metabolic syndrome (MS) compared with whites. We examined the associations among MS markers, body composition, and resting metabolic rate (RMR) in black Haitians and in white subjects living in Quebec, Canada. Research Methods and Procedures: Forty randomly selected Haitians were matched with 40 white subjects for age, sex, and BMI. Glycemic status and insulin resistance were assessed based on a 3‐hour glucose tolerance test. Blood lipids, blood pressure, abdominal fat (computed tomography), and waist circumference (WC) were measured. RMR was estimated by indirect calorimetry. Results: Triglycerides were significantly correlated with blood pressure only in Haitians and with the area under the curve for insulin only in whites. Haitians had significantly (p < 0.05) lower triglycerides and higher high‐density lipoprotein‐cholesterol concentrations but higher blood pressure than whites at any given WC value. General linear models showed that Haitians had less visceral adipose tissue than whites for the same WC. RMR was lower among Haitians for any given value of BMI or WC than in whites. Also, WC was more strongly associated with glucose area under the curve and to log‐homeostasis model assessment in white than in Haitian subjects. Discussion: The MS may be ethnospecific in its features and etiology. The standard anthropometric indices of obesity may not be as effective in populations of African descent compared with whites, unless appropriate cut‐off values are defined.     

Insulin Sensitivity in African‐American and White Women: Association With Inflammation

Whether the contribution of inflammation to risk for chronic metabolic disease differs with ethnicity is not known. The objective of this study was to determine: (i) whether ethnic differences exist in markers of inflammation and (ii) whether lower insulin sensitivity among African Americans vs. whites is due to greater inflammatory status. Subjects were African‐American (n = 108) and white (n = 105) women, BMI 27–30 kg/m². Insulin sensitivity was assessed with intravenous glucose tolerance test and minimal modeling; fat distribution with computed tomography; body composition with dual‐energy X‐ray absorptiometry; markers of inflammation (tumor necrosis factor (TNF)‐α, soluble tumor necrosis factor receptor (sTNFR)‐1, sTNFR‐2, C‐reactive protein (CRP), and interleukin (IL)‐6) with enzyme‐linked immunosorbent assay (ELISA). Whites had greater intra‐abdominal adipose tissue (IAAT), insulin sensitivity, and concentrations of TNF‐α, sTNFR‐1, and sTNFR‐2 than African Americans. Greater TNF‐α in whites vs. African Americans was attributed to greater IAAT in whites. Among whites, but not African Americans, CRP was independently and inversely associated with insulin sensitivity, after adjusting for IAAT (r = ?0.29 P < 0.05, and r = ?0.13 P = 0.53, respectively). Insulin sensitivity remained lower in African Americans after adjusting for CRP (P < 0.001). In conclusion, greater IAAT among whites may be associated with greater inflammation. Insulin sensitivity was lower among African Americans, independent of obesity, fat distribution, and inflammation.     

Variants in the Adiponectin Gene and Serum Adiponectin: The Coronary Artery Development in Young Adults (CARDIA) Study

Circulating adiponectin is involved in the atherosclerotic process and has been associated with cardiovascular disease as well as obesity, insulin resistance, metabolic syndrome, and type 2 diabetes. The adiponectin gene (ADIPOQ) encodes the circulating protein adiponectin and affects its expression. Only a small proportion of all known ADIPOQ polymorphisms have been investigated in relation to circulating adiponectin concentrations. Using data from 3,355 African‐American and white men and women aged 33–45 at the year 15 examination from the Coronary Artery Development in Young Adults (CARDIA) Study the association between 10 single‐nucleotide polymorphisms (SNPs) within ADIPOQ and serum adiponectin was examined using linear regression. SNPs were chosen based on a tagSNP approach. Models were stratified by self‐reported race to control for population stratification, and Bonferroni corrected for multiple comparisons. ADIPOQ SNPs rs17300539 (P < 0.0001), rs182052 (P = 0.0013), rs822393 (P = 0.0005), rs9882205 (P = 0.0001), and rs3774261 (P = 0.0001) were strongly associated with serum adiponectin concentrations in whites. In general, there was a dose‐response relationship of adjusted mean adiponectin concentrations across genotypes. Only one SNP, rs17300539 was marginally associated with serum adiponectin concentrations (P = 0.0087) in African Americans. Significant interactions were found between waist and rs182052 (P = 0.0029) and between rs9882505 and smoking (P = 0.001) in whites. Many ADIPOQ SNPs have not yet been examined, and additional studies are needed to determine whether these may be functional variants.     

Binge Eating and Eating‐Related Cognitions and Behavior in Ethnically Diverse Obese Women

Objective: To examine binge eating and eating‐related cognitions and behavior in a sample of ethnically diverse women who are severely obese and seeking bariatric surgery. Research Methods and Procedures: Female bariatric surgery candidates (62 African Americans, 18 Latinas, 130 whites) completed questionnaires on binge eating and eating‐related cognitions and behavior and completed a structured clinical interview to confirm binge‐eating disorder diagnosis. Results: Ethnic minorities and whites did not differ in rates of binge‐eating disorder (26.3%), binges per week (M = 0.95), or dietary restraint. Ethnic minorities reported less disinhibition, and there was a trend to report less hunger awareness than whites. After controlling for BMI and education, ethnicity accounted for significant variance in disinhibition (4%; p < 0.01). Ethnic minorities were younger, became overweight at a later age, and were overweight for fewer years than whites. Discussion: Results suggest that ethnicity exerts an important influence on disinhibition and that ethnic differences are not caused by BMI or education. Findings point to the need to continue to investigate the role of ethnicity, binge eating, and disinhibition in severely obese women, so that culturally appropriate services can be provided.     

Cut‐off Point of BMI and Obesity‐Related Comorbidities and Mortality in Middle‐Aged Koreans

Objective: The need for a lower BMI to classify overweight in Asian populations has been controversial. Using both disease and mortality outcomes, we investigated whether lower BMI cut‐off points are appropriate for identifying increased health risk in Koreans. Research Methods and Procedures: We conducted a cohort study among 773, 915 men and women from 30 to 59 years old with 8‐ to 10‐year follow‐up periods. Primary outcomes were change of obesity prevalence, obesity‐related disease incidence, and all‐cause mortality. Results: Prevalence of overweight (BMI of 25.0‐29.9) has steadily increased (1.3% annually), whereas obesity (BMI ≥ 30) showed a lower prevalence and only a slight increase (0.1%‐0.2% annually). Our study revealed that dose‐response relationships exist between obesity and related disease incidences (hypertension, type 2 diabetes, and hypercholesterolemia) beginning at lower BMI levels than previously reported. Compared with those in the healthy weight range, Koreans with a BMI ≥ 25 were not at greater risk of hypertension, type 2 diabetes, or hypercholesterolemia than has been reported for whites in similar studies. Obesity‐related all‐cause mortality also did not seem so different from that of whites. Discussion: Our findings did not support the use of a lower BMI cut‐off point for defining overweight in Koreans compared with whites for the purpose of identifying different risks. However, populations with BMI ≥ 25 are rapidly increasing and have substantial risks of diseases. To preempt the rapid increases in obesity and related health problems that are occurring in Western countries, Korea should consider using a BMI of 25 as an action point for obesity prevention and control interventions.     

Polymerization of Several Proteins by Ca2+-Independent Transglutaminase Derived from Microorganisms

α_s1-Casein and soybean globulins were polymerized and gelatinized by Ca²⁺-independent transglutaminase that was isolated from the culture filtrate of a microorganism thought to belong to Streptoverticillium sp. of actinomycetes. This enzyme polymerized such albumins as bovine serum albumin, human serum albumin and conalbumin in the presence of dithiothreitol. Rabbit myosin was polymerized by the present emzyme but actin was not. An RP-HPLC analysis after enzymic digestion of the polymerized a_sl -casein showed existence of the £-(y-Glu)Lys bond. Thus, it was confirmed that the polymerization was formed by a catalytic reaction of the transglutaminase.     

Association of ALOX5AP with ischemic stroke: a population-based case-control study

Arachidonate 5-lipoxygenase activating protein (ALOX5AP) has been reported to demonstrate linkage and association with ischemic stroke and myocardial infarction. However, replication studies have been conflicting and to date, a significant proportion of blacks have not been studied. We prospectively recruited cases of ischemic stroke from all 16 hospitals in the Greater Cincinnati/Northern Kentucky region and demographically matched them to stroke-free population-based controls. Single nucleotide polymorphisms (SNPs) were selected based on association with ischemic stroke in prior studies. Allelic, genotypic and haplotypic association testing was performed using HAPLOVIEW. Multiple logistic regression was used to control for the presence of traditional risk factors including hypertension, diabetes, hypercholesterolemia and smoking. A total of 357 cases and 482 controls were genotyped. The SNPs, rs9579646 and rs4769874 were found to be significantly associated at both allelic (P = 0.019 and P < 10⁻⁴, respectively) and genotypic level with ischemic stroke among whites after correction for multiple testing. Haplotype association was identified with ischemic stroke as well as ischemic stroke subtypes among whites. Although an overall haplotype association with ischemic stroke was identified among blacks no evidence of association among individual haplotypes, alleles or genotypes were observed. Allele frequencies for the SNPs examined were markedly different among whites and blacks. In conclusion, we report significant association of variants of ALOX5AP with ischemic stroke and ischemic stroke subtypes among whites. No significant association was identified among blacks.     

Waist Circumference,BMI, and Visceral Adipose Tissue in White Women and Women of African Descent

Although waist circumference (WC) is a marker of visceral adipose tissue (VAT), WC cut‐points are based on BMI category. We compared WC‐BMI and WC‐VAT relationships in blacks and whites. Combining data from five studies, BMI and WC were measured in 1,409 premenopausal women (148 white South Africans, 607 African‐Americans, 186 black South Africans, 445 West Africans, 23 black Africans living in United States). In three of five studies, participants had VAT measured by computerized tomography (n = 456). Compared to whites, blacks had higher BMI (29.6 ± 7.6 (mean ± s.d.) vs. 27.6 ± 6.6 kg/m², P = 0.001), similar WC (92 ± 16 vs. 90 ± 15 cm, P = 0.27) and lower VAT (64 ± 42 vs. 101 ± 59 cm², P < 0.001). The WC‐BMI relationship did not differ by race (blacks: β (s.e.) WC = 0.42 (.01), whites: β (s.e.) WC = 0.40 (0.01), P = 0.73). The WC‐VAT relationship was different in blacks and whites (blacks: β (s.e.) WC = 1.38 (0.11), whites: β (s.e.) WC = 3.18 (0.21), P < 0.001). Whites had a greater increase in VAT per unit increase in WC. WC‐BMI and WC‐VAT relationships did not differ among black populations. As WC‐BMI relationship did not differ by race, the same BMI‐based WC guidelines may be appropriate for black and white women. However, if WC is defined by VAT, race‐specific WC thresholds are required.     

Hispanic and Asian pubertal girls have higher android/gynoid fat ratio than whites

Objective: To examine differences in body size, composition, and distribution of body fat among Hispanic, white, and Asian adolescents. Research Methods and Procedures: This included cross‐sectional data from the baseline sample of the Adequate Calcium Today trial. Participants included 180 Asian, 234 Hispanic, and 325 white girls 11.8 ± 0.05 years of age from Arizona, California, Hawaii, Indiana, Ohio, and Nevada. Anthropometric and DXA measurements (Lunar Prodigy) were standardized across sites. Tanner pubertal stage was self‐selected from line drawings. Physical activity was assessed by a validated questionnaire. Comparisons between ethnic groups were examined using contrasts in the context of a general linear model. Results: Controlling for pubertal stage and study site only, Asians weighed less than Hispanics and were shorter than Hispanics and whites. Controlling for pubertal stage, height, weight, and study site, Asians had shorter leg lengths, smaller waist circumference, longer trunk lengths, more lean mass, less total fat mass, and less gynoid fat mass than Hispanics and whites; Asians had larger bitrochanteric width than whites; Asians had smaller DXA‐derived android fat mass than Hispanics; and whites had smaller mean android/gynoid fat ratio than Hispanics. However, whites had a smaller android/gynoid fat ratio than both Asians and Hispanics in a model that adjusted for ethnicity, pubertal stage, bitrochanteric width, waist circumference, trunk length, log of physical activity, and study site, which explained 77% of the variation. Discussion: Ethnic differences in fat distribution are partially explained by differences in skeletal dimensions.     

Genetic studies of low-abundance human plasma proteins

Summary Genetic variation in the C1R subcomponent of the first complement component C1 was investigated in U.S. whites by isoelectric focusing and immunoblotting. In addition to the previously described two alleles, the products of a new and rare third allele designated C1R ^*3 were detected. The expression of the new allele is consistent with autosomal codominant inheritance, which is confirmed by family data. The frequencies of the C1R ^*1, C1R ^*2 and C1R ^*3 alleles in 201 randomly selected U.S. whites are: 0.908, 0.090, and 0.002, respectively.     

Hypertension and Type 2 Diabetes Comorbidity in Adults in the United States: Risk of Overall and Regional Adiposity

Objective: To evaluate the impact of generalized, abdominal, and truncal fat deposits on the risk of hypertension and/or diabetes and to determine whether ethnic differences in these fat patterns are independently associated with increased risk for the hypertension–diabetes comorbidity (HDC). Research Methods and Procedures: Data (n = 7075) from the Third U.S. National Health and Nutrition Examination Survey were used for this investigation. To assess risks of hypertension and/or diabetes that were due to different fat patterns, odds ratios of men and women with various cut‐points of adiposities were compared with normal subjects in logistic regression models, adjusting for age, smoking, and alcohol intake. To evaluate the contribution of ethnic differences in obesity to the risks of HDC, we compared blacks and Hispanics with whites. Results: Generalized and abdominal obesities were independently associated with increased risk of hypertension, diabetes and HDC in white, black, and Hispanic men and women. The risk of HDC due to generalized, truncal, and abdominal obesities tended to be higher in whites than blacks and Hispanics. In men, the contribution of black and Hispanic ethnicities to the increased risk of HDC due to the various obesity phenotypes was ～73% and ～61%, respectively. The corresponding values for black and Hispanic women were ～115% and ～125%, respectively. Conclusions: In addition to advocating behavioral lifestyles to curb the epidemic of obesity among at‐risk populations in the United States, there is also the need for primary health care practitioners to craft their advice to the degree and type of obesity in these at‐risk groups.     

Racial Differences in Urinary F2‐Isoprostane Levels and the Cross‐Sectional Association With bmi

Levels of four urinary F₂‐isoprostanes (F₂‐IsoPs) were examined in a large sample of the Insulin Resistance Atherosclerosis Study (IRAS) multiethnic cohort: 237 African Americans (AAs), 342 non‐Hispanic whites (NHWs), and 275 Hispanic whites (HWs). F₂‐IsoP isomers — iPF2a‐III, 2,3‐dinor‐iPF2a‐III, iPF2a‐VI, and 8,12‐iso‐iPF2a‐VI — were measured in 854 urine samples using liquid chromatography with tandem mass spectrometry detection. In AAs, levels of all four F₂‐IsoPs were lower compared with NHWs and HWs (P values <0.05). When stratified by BMI, this gap was not observed among participants with normal BMI but appeared among overweight participants and increased among obese participants. Examining the slopes of the associations between BMI and F₂‐IsoPs showed no association between these variables among AAs (P values >0.2), and positive associations among whites (P values <0.05). Taking into account that positive cross‐sectional associations between systemic F₂‐IsoP levels and BMI have been consistently demonstrated in many study populations, the lack of such an association among AAs reveals a new facet of racial/ethnic differences in obesity‐related risk profiles.     

Vanadyl(IV) conalbumin. I. Metal binding site configurations

Electron paramagnetic resonance (epr) and ultraviolet difference spectroscopy of vanadyl conalbumin indicate a binding capacity of two vanadyl ions, VO²⁺, per protein molecule in the pH 8–11 range; the binding capacity drops in the pH 6–8 range with an apparent pK_a′ = 6.6. Iron-saturated conalbumin does not bind vanadyl ions, which suggests common binding sites for iron and vanadium. Ultraviolet difference spectroscopy indicates 2–3 tyrosines are involved in the binding of each metal ion; pH titrations show that three protons are released per vanadyl ion bound by conalbumin. Room and liquid nitrogen temperature X-band (ca. 9.2–9.5 gHz) epr spectra show that the vanadyl ion binds in three magnetically distinct environments (A, B, and C) that arise from interconvertible metal site configurations. These configurations are probably examples of conformational substrates of the protein. Q-band (ca 34 gHz) epr spectra resolve the spectral features more clearly and show that two configurations (A and B) have axially symmetric epr parameters but angles of noncoincidence of 12° and 8°, respectively, between the z components of the g and nuclear hyperfine tensors. The third (C) configuration has rhombic magnetic symmetry and a 6° angle of noncoincidence. These observations demonstrate that the metal sites are of low symmetry and are flexible in their geometry about the metal.The isotropic g and nuclear hyperfine tensor values and the line widths used in computer-simulated epr spectra are consistent with four oxygen or three oxygen and one nitrogen donor atoms binding equatorially to the VO²⁺ group. The apparent stability constant indicates that vanadyl ion binds to conalbumin approximately twelve orders of magnitude more weakly than iron to human serotransferrin but still sufficiently strongly to overcome hydrolysis.     

Larger Amounts of Visceral Adipose Tissue in Asian Americans

Objective: Excess visceral adipose tissue (VAT) is recognized as an important risk factor for the development of coronary heart disease and type 2 diabetes. Several studies have reported less VAT in African Americans compared with whites. As little is known about the levels of VAT in Asians, we compared whole‐body VAT in Asian Americans with European Americans. Research Methods and Procedures: VAT was measured using whole‐body multislice magnetic resonance imaging in 54 women (18 Asian Americans, 36 European Americans) and 53 men (19 Asian Americans, 34 European Americans) with body mass index (measured in kilograms per square meter) < 30. Data were analyzed by multiple regression modeling. Results: Asian American women had higher log‐transformed VAT compared with European American women (p < 0.05), after adjusting for age and total body fat. There was a significant age by race interaction such that race differences in VAT were most evident over the age of 30 years. No differences in VAT could be detected between Asian American and European American men, even after adjusting for potential covariates, including total adiposity. %Discussion: These data are the first to demonstrate higher amounts of VAT in healthy Asian Americans, a finding that suggests normative VAT values or standards derived from whites may not be applicable to Asians.