Dietary Methionine and Total Sulfur Amino Acid Restriction in Healthy Adults.

OBJECTIVES: Dietary restriction of methionine (Met) and cysteine (Cys) delays the aging process and aging-related diseases, improves glucose and fat metabolism and reduces oxidative stress in numerous laboratory animal models. Little is known regarding the effects of sulfur amino acid restriction in humans. Thus, our objectives were to determine the impact of feeding diets restricted in Met alone (MetR) or in both Met and Cys (total sulfur amino acids, SAAR) to healthy adults on relevant biomarkers of cardiometabolic disease risk. DESIGN: A controlled feeding study. SETTING AND PARTICIPANTS: We included 20 healthy adults (11 females/9 males) assigned to MetR or SAAR diet groups consisting of three 4-wk feeding periods: Control period; low level restriction period (70% MetR or 50% SAAR); and high level restriction period (90% MetR or 65% SAAR) separated by 3-4-wk washout periods. RESULTS: No adverse effects were associated with either diet and level of restriction and compliance was high in all subjects. SAAR was associated with significant reductions in body weight and plasma levels of total cholesterol, LDL, uric acid, leptin, and insulin, BUN, and IGF-1, and increases in body temperature and plasma FGF-21 after 4 weeks (P<0.05). Fewer changes occurred with MetR including significant reductions in BUN, uric acid and 8-isoprostane and an increase in FGF-21 after 4 weeks (P<0.05). In the 65% SAAR group, plasma Met and Cys levels were significantly reduced by 15% and 13% respectively (P<0.05). CONCLUSION: These results suggest that many of the short-term beneficial effects of SAAR observed in animal models are translatable to humans and support further clinical development of this intervention.

Estimation of compliance with exclusive smoking of very low nicotine content cigarettes using plasma cotinine.

Regulations requiring a reduction of the nicotine content in cigarettes to minimally addictive levels could significantly reduce the public health impact of cigarette smoking. Clinical trials evaluating this strategy are ongoing and methods have been developed to use nicotine biomarkers to estimate compliance with use of very low nicotine content cigarettes (VLNCs). To date, these methods have not considered the potential contribution of nicotine absorption from environmental tobacco smoke (ETS) among research participants. This study used data from 100 randomly selected study completers in ongoing clinical trials of VLNCs (50 randomized to Usual Nicotine Content Cigarettes (UNCs) and 50 to VLNCs) to assess the use of plasma cotinine to estimate compliance. Plasma cotinine and smoking behavior were recorded at baseline after 2 weeks smoking UNC cigarettes, and then after 18 weeks of either continuing smoking UNCs or reducing the nicotine content such that the last 6 weeks comprised smoking VLNCs. Plasma cotinine remained stable (267 ng/ml) in the UNC group but reduced to 93 ng/ml in the VLNC group (p < 0.01). Compliance with smoking VLNCs was first estimated by comparing the cotinine per cigarette on VLNCs with UNCs after allowing for potential compensatory smoking. We found that 29 (58%) of the VLNC group were compliant. Adjusting for potential ETS exposure estimated 32 (64%) to be compliant. This latter group (n = 32) had a mean plasma cotinine on VLNCs of 7 ng/ml (range = 3-16.4 ng/ml). Adjusting for potential ETS exposure may improve identification of participants who plausibly complied with exclusive VLNC use.

Loss of expression of protein kinase C beta is a common phenomenon in human malignant melanoma: a result of transformation or differentiation?

As with most cancers, the aetiology of human cutaneous melanoma is likely to be multifactorial and to include the accumulation of irreversible alterations in an unknown number of genes. Elucidating this molecular progression necessitates both the identification of genetic perturbations at each clinically relevant stage, and the assessment of their impact on the normal melanocyte. The observation that the epidermal melanocyte, in contrast to metastatic melanoma cells, requires activation of the protein kinase C (PKC) pathway to facilitate growth in vitro indicates that one or more isoforms (or substrates) of this large and complex family of proteins are among those that undergo alteration during the development of malignant melanoma. Consequently, a number of studies have investigated the expression of various PKC family members in both melanocyte and melanoma cell lines, without a consensus of opinion as to which isoforms are of biological significance in melanoma development and progression. The present study involved a comprehensive evaluation of the PKC profile in normal melanocytes and in 16 metastatic melanoma cell lines. The results show that the major difference in isoform expression between epidermal melanocytes and melanoma cells is the loss of PKCbeta protein expression in 90% of melanoma cell lines. Examination of PKCbeta in benign and malignant melanocytic lesions revealed that this protein is either downregulated or absent in both naevi and metastatic melanomas. We conjecture that, although the loss of PKCbeta expression is a common phenomenon in malignant melanocytes, it may be related more to a normal process of melanocytic differentiation than to malignant transformation.

Cell cycle arrest and apoptosis of melanoma cells by docosahexaenoic acid: association with decreased pRb phosphorylation.

The incidence of cutaneous malignant melanoma is undergoing a dramatic increase in persons with light-color skin in all parts of the world. The prognosis for individuals with advanced disease is dismal due to the lack of effective treatment options. Thus, there is a need for new approaches to control tumor progression. Epidemiological, experimental, and mechanistic data implicate omega-6 polyunsaturated fatty acids (PUFAs) as stimulators and long-chain omega-3 PUFAs as inhibitors of development and progression of a range of human cancers, including melanoma. The aim of this study was to assess the mechanisms by which docosahexaenoic acid (DHA), an omega-3 PUFA, affects human melanoma cells. Exponentially growing melanoma cell lines were exposed in vitro to DHA and then assessed for (a) inhibition of cell growth; (b) expression of cyclins and cyclin-dependent kinase inhibitors in individual cells by flow cytometry and immunocytochemistry using specific monoclonal antibodies to cyclin D1, cyclin E, p21WAF1/CIP1, or p27(KIP1); and (c) expression of total pRb(T) independent of phosphorylation state and hypophosphorylated pRb(P-) in fixed cells by flow cytometry and immunocytochemistry using specific monoclonal antibodies to pRb(T) or pRb(P-), respectively. After treatment with increasing concentrations of DHA, cell growth in a majority of melanoma cell lines (7 of 12) was inhibited, whereas in 5 of 12 cell lines, cell growth was minimally affected. Two melanoma cell lines were examined in detail, one resistant (SK-Mel-29) and one sensitive (SK-Mel-110) to the inhibitory activity of DHA. SK-Mel-29 cells were unaffected by treatment with up to 2 microg/ml DHA whether grown in the absence or presence of 1% fetal bovine serum (FBS). No appreciable change was observed in cell growth, cell cycle distribution, the status of pRb phosphorylation, cyclin D1 expression, or the levels of the cyclin-dependent kinase inhibitors p21 and p27. In contrast, SK-Mel-110 cell growth was inhibited by DHA with the cells accumulating either in G1 or S phase: 0% in SK-Mel-29 versus 13.3 or 41.2% in SK-Mel-110 in the absence or presence of FBS, respectively. In the absence of serum, considerable death occurred by apoptosis. In addition, DHA treatment resulted in increasing numbers of SK-Mel-110 cells (from 12 to >40%) expressing hypophosphorylated pRb, whereas the levels of cyclin D1 and p21 changed little. Expression of p27 in these cells increased >2.5 times when grown in the absence of FBS but not in the presence of 1% FBS. Thus, we show for the first time that DHA inhibits the growth of cultured metastatic melanoma cells. Furthermore, growth inhibition correlates with a quantitative increase in hypophosphorylated pRb in the representative sensitive melanoma cell line SK-Mel-110. Although multiple factors influence pRb phosphorylation, it appears that both cyclin D1 and p21 expression do not change in the presence of DHA, although p27 was strikingly increased in SK-Mel-110 cells in the absence of FBS. The fact that pRb became hypophosphorylated after exposure to DHA suggests a cross-talk mechanism between fatty acid metabolism and the pRb pathway. Determining the mechanism by which PUFAs can inhibit melanoma growth will be an important first step in the rational use of PUFAs as antitumor agents.

Photoinduced refractive-index change in Sm(+2)/Sm(+3) codoped aluminosilicate fiber by irradiation of an Ar-ion laser.

A Sm(+2)/Sm(+3) codoped aluminosilicate glass optical fiber was fabricated by use of modified chemical-vapor deposition in conjunction with an aerosol-delivery technique. A permanent index change of 7.6 x 10(-5) was induced in the fiber by irradiation of 1 W of multiline output from an Ar-ion laser. Bleaching of a broad absorption band of Sm(+2) in the visible range was also observed, and it is believed that photoionization of Sm(+2)? Sm(+3)+e plays an important role in the induced photorefractivity.

Quantitative variation in obesity-related traits and insulin precursors linked to the OB gene region on human chromosome 7.

Despite the evidence that human obesity has strong genetic determinants, efforts at identifying specific genes that influence human obesity have largely been unsuccessful. Using the sibship data obtained from 32 low income Mexican American pedigrees ascertained on a type II diabetic proband and a multipoint variance-components method, we tested for linkage between various obesity-related traits plus associated metabolic traits and 15 markers on human chromosome 7. We found evidence for linkage between markers in the OB gene region and various traits, as follows: D7S514 and extremity skinfolds (LOD = 3.1), human carboxypeptidase A1 (HCPA1) and 32,33-split proinsulin level (LOD = 4.2), and HCPA1 and proinsulin level (LOD = 3.2). A putative susceptibility locus linked to the marker D7S514 explained 56% of the total phenotypic variation in extremity skinfolds. Variation at the HCPA1 locus explained 64% of phenotypic variation in proinsulin level and approximately 73% of phenotypic variation in split proinsulin concentration, respectively. Weaker evidence for linkage to several other obesity-related traits (e.g., waist circumference, body-mass index, fat mass by bioimpedance, etc.) was observed for a genetic location, which is approximately 15 cM telomeric to OB. In conclusion, our study reveals that the OB region plays a significant role in determining the phenotypic variation of both insulin precursors and obesity-related traits, at least in Mexican Americans.

Evidence for linkage of regions on chromosomes 6 and 11 to plasma glucose concentrations in Mexican Americans.

The genetic factors involved in type II diabetes are still unknown. To address this problem, we are creating a 10 to 15 cM genetic map on 444 individuals from 32 Mexican American families ascertained on a type II diabetic proband. Using highly polymorphic microsatellite markers and a multipoint variance components method, we found evidence for linkage of plasma glucose concentration 2 hr after oral glucose administration to two regions on chromosome 11: beta-hemoglobin (HBB) and markers D11S899/D11S1324 near the sulfonylurea receptor (SUR) gene. Iod scores at these two loci were 2.77 and 3.37, respectively. The SUR gene region accounted for 44.7% of the phenotypic variance. Evidence for linkage to fasting glucose concentration was also observed for two loci on chromosome 6, one of which is identical to a proposed susceptibility locus for type I diabetes (D6S290). When diabetics were excluded from the analyses, all Iod scores became zero, suggesting that the observed linkages were with the trait diabetes rather than with normal variation in glucose levels. Results were similar whether all diabetics were included in the analyses or only those who were not under treatment with oral antidiabetic agents or insulin.

Evidence for a major gene for type II diabetes and linkage analyses with selected candidate genes in Mexican-Americans.

We have carried out two independent family studies in low-income Mexican-Americans from San Antonio, Texas. In the first study, probands were ascertained at random without regard to any medical condition (658 examined individuals from 50 families), and in the second study, probands were subjects with type II diabetes identified in a prior epidemiological survey (523 examined individuals from 29 families). Pedigrees ranging in size from 2 to 45 family members (median 11) in the first study and from 2 to 50 family members (median 12) in the second study were examined. Diabetes was diagnosed according to World Health Organization criteria. In both sets of families, segregation analyses revealed support for a major gene with an autosomal dominant mode of inheritance influencing early age of onset of diabetes. Non-Mendelian inheritance was rejected in both data sets. Individuals with the early age of onset allele had a mean age of diabetes onset of 51 years in the first data set and 60 years in the second data set. In the first data set, the major gene accounted for approximately 70% of the phenotypic variance in age of onset of diabetes, and there were no residual family effects once the major gene effect was taken into account. In the second data set, the major gene accounted for approximately 50% of the phenotypic variance, and residual family effects were statistically significant. Linkage analyses were performed with 11 candidate genes, and tight linkage with diabetes was rejected for Rh blood group, glucose transporter 2, fatty acid-binding protein, tumor necrosis factor beta, glucokinase, and lipoprotein lipase. A logarithm of odds (LOD) score of 0.92 at a recombination fraction of 0.05 was observed for insulin receptor substrate 1. This LOD score corresponds to a chi2 of 4.24 (P = 0.039).

Is there an excess in maternal transmission of NIDDM?

Family studies have demonstrated that there is a strong genetic component to the aetiology of non-insulin-dependent diabetes mellitus (NIDDM), although the mode of inheritance is unknown. A number of recent family history studies, including one in Mexican Americans, have suggested that there is an excess of maternal transmission of NIDDM. Family history studies are subject to various types of bias, however, and the potential for bias in many of these studies has not been thoroughly evaluated. We therefore tested the hypothesis that diabetes is more likely to be transmitted from mothers than from fathers using data collected from a large family study of low-income Mexican Americans in San Antonio, Texas. The parents and offspring from 318 different nuclear families attended our medical clinic, where they received a 2-h oral glucose test. Diabetes was diagnosed on the basis of World Health Organization criteria. The sibships were classified into diabetic sibships (at least one sibling in the sibship was diabetic; n = 54) and non-diabetic siblings (no diabetic siblings; n = 264). The prevalence of diabetes among mothers of diabetic siblings was 61.4% (27 of 44) compared to 64.3% (18 of 28) among fathers of diabetic siblings (rate ratio = 0.95; 95% confidence interval; 0.51-1.84). For the non-diabetic sibships, the prevalence of diabetes was 31.7% (78 of 246) and 28.9% (37 of 128) among mothers and fathers, respectively (rate ratio = 1.09; 95% confidence interval: 0.73-1.67). These data provide no evidence for an excess maternal transmission of diabetes in Mexican Americans.

The influence of response bias on segregation and linkage analysis.

Response bias in epidemiologic studies can occur if affected individuals are more (or less) likely to participate in a survey than their unaffected counterparts. To examine the effect of response bias in the context of a family study, we conducted segregation and linkage analysis in all 1,000 individuals in the Problem 2 data set, and in two different 65% samples: one sample consisting of 648 randomly selected individuals, and the other sample nonrandomly constructed so that individuals with high levels of Q1 were oversampled. In this simulation the ability to detect major genes for Q1-Q4 in segregation analysis and to link these putative major genes to genetic markers in linkage analysis was not markedly different between the 65% random and the 65% enriched samples.

Linearly and nonlinearly chirped Bragg gratings fabricated on curved fibers.

We can introduce chirping, or a variation in the periodicity of a Bragg grating, into an optical fiber by writing gratings on curved optical fibers. By precisely specifying the curvature, we can obtain linear, quadratic, and square-root chirped gratings. Experimental and numerical verifications of the relationships between curvature and grating characteristics are presented.

NIDDM in Mexican-American families. Heterogeneity by age of onset.

OBJECTIVE: Heredity has long been known as a risk factor for non-insulin-dependent diabetes mellitus (NIDDM), but the mode of inheritance of NIDDM remains unclear. We examined the distribution of diabetes in 29 Mexican-American families ascertained on a diabetic proband. RESEARCH DESIGN AND METHODS: Probands represented a random sample of diabetic Mexican Americans residing in low-income neighborhoods from San Antonio, TX. A total of 375 family members of these diabetic probands were examined, and diabetes was diagnosed according to the World Health Organization plasma glucose criteria. RESULTS: The prevalence of diabetes decreased from 28.2% in first-degree relatives of the probands to 13.3% in second-degree relatives to 11.1% in third-degree relatives. When compared with Mexican Americans with no parental history of diabetes, this represents an excess of diabetes of 2.0-, 1.3-, and 1.1-fold in first-, second-, and third-degree relatives, respectively. Five of the 29 probands (17%) had an age of diabetes onset < 40 years. In the first-degree relatives of these early-onset probands, diabetes prevalence was 47.0% (16 of 34) compared with only 24.1% (34 of 141) in the first-degree relatives of the 24 late-onset probands. After adjustment for age, this excess represented a fivefold increase in the odds of diabetes among relatives of the early-onset probands compared with relatives of the late-onset probands (P < 0.001). Moreover, the 16 affected family members of the early-onset probands had a mean age of diabetes onset of 42.7 years compared with 49.9 years for the 34 affected members of the late-onset probands, although this difference was not statistically significant (P = 0.13). CONCLUSIONS: NIDDM may be genetically heterogeneous in this Mexican-American population, with family members of early-onset diabetes patients being at higher risk for NIDDM than family members of late-onset diabetes patients.

Continuous-wave oscillation of thulium-sensitized holmium-doped silica fiber laser.

We have observed oscillation in a Tm(3+) and Ho(3+) codoped silica fiber from the (5)I(7) ? (5)I(8) transition of Ho(3+) in the 2-microm region, by pumping the fiber laser into a Tm(3+) absorption between 800 and 830 nm. By a change in the cavity length, the laser was tunable between 2.037 and 2.096 microm. When the laser was pumped with a Ti:sapphire laser at 820 nm, an absorbed threshold power extracted power of 214mW, a slope efficiency of 4.2%,and maximum extracted power of 12.5 mW were measured.

Broadband superfluorescent emission of the (3)H(4) ? (3)H(6) transition in a Tm-doped multicomponent silicate fiber.

We report the observation of amplified spontaneous emission in the (3)H(4) ? (3)H(6) transition of Tm(+3) in a Ta(2)O(5)-doped multicomponent silicate fiber. The evolutions of the spectral shape, output power, and center wavelength were measured as a function of fiber length and pump power in the previously unstudied high-power range, where saturation effects dominate. An output power of 1 mW has been achieved at 1.91 microm with a bandwidth of 77 nm.

Simple prism-based scheme for fabricating Bragg gratings in optical fibers.

A modified prism-based method for fabricating Bragg gratings in optical fibers is introduced. We have made an optical fiber Bragg grating at 799.67 nm by using a 45 degrees right-angle prism and a frequency-doubled argon-ion laser at 244 nm. The advantage of this method is ease of alignment.

Mutagenic peroxides in diethyl ether.

Concentration of water-saturated commercial samples of diethyl ether by a stream of nitrogen yielded an aqueous residue mutagenic in S. typhimurium strains TA100 and TA102, but not TA1535. Reverse phase high-performance liquid chromatography resolved the mixture into 4 UV absorbing peaks, each of which was positive for peroxide and mutagenic in strain TA100 and TA102. One of these was identified as H2O2 based on HPLC retention time and sensitivity to decomposition by catalase, and another as 1-ethoxyethylhydroperoxide, based on its 1H-NMR spectrum. The mutagenic peroxides appeared to be stable in water between pH 3 and 6, but unstable above pH 7; they were less stable in methanol, acetonitrile, and least stable in chloroform, in which they partially decomposed after 24 h at 20 degrees C. Generalization of the results suggests that adverse effects observed in vitro and in vivo with chemicals containing ether linkages that actually have been caused by contaminant peroxides and reactive oxygen compounds.

Ultraviolet-light photosensitivity in Er(3+)-Ge-doped optical fiber.

Light-induced refractive-index change in Er(3+)-Ge-doped optical fiber is reported for the first time to the authors' knowledge. Evidence of the change is observed when UV light (lambda = 249 nm) irradiates one arm of an unbalanced Mach-Zehnder interferometer made from Er(3+)-Ge-doped fiber. From a measurement of the change in the spectral response of the interferometer with UV exposure, the change in fiber core index as a function of wavelength is determined. The equilibrium change in core index is found to vary between 2.3 x 10(-5) and 3.7 x 10(-5) over the measured wavelength region of 800 to 1700 nm. Also for the first time to our knowledge, fused couplers made of Er(3+)-doped fiber are reported. These identical fiber couplers are used in a novel all-fiber unbalanced Mach-Zehnder interferometer.