CYTOPLASMIC FILAMENTS IN DEVELOPING AND ADULT VERTEBRATE SMOOTH MUSCLE

An extensive study of adult and developing smooth muscle has revealed the widespread occurrence of a distinct filament with an average diameter of about 100 A (termed the 100 A filament). Unlike that of myofilaments, their appearance in longitudinal section is uniform, but in transverse section they have a round profile, occasionally exhibiting a less electron-opaque core. The 100 A filaments are almost invariably preserved under a variety of fixation procedures, whereas myofilaments, particularly the thicker filaments, are preserved inconsistently. The 100 A filaments appear to be randomly oriented throughout the cytoplasm, either singly or in small groups, although they are sometimes concentrated in the juxtanuclear region of the smooth muscle cells. The intimate association of 100 A filaments with dark bodies, in both developing and adult smooth muscle cells, may indicate that these filaments either play a role in dark body formation or, at least, constitute a part of the dark body. The 100 A filaments are conspicuous in developing smooth muscle cells and occasionally form networks or clusters; they appear to decrease in relative number as maturation proceeds, but considerable numbers are still present in adult tissue.     

Epidemiology and Heritability of Major Depressive Disorder,Stratified by Age of Onset,Sex, and Illness Course in Generation Scotland: Scottish Family Health Study (GS:SFHS)

The heritability of Major Depressive Disorder (MDD) has been estimated at 37% based largely on twin studies that rely on contested assumptions. More recently, the heritability of MDD has been estimated on large populations from registries such as the Swedish, Finnish, and Chinese cohorts. Family-based designs utilise a number of different relationships and provide an alternative means of estimating heritability. Generation Scotland: Scottish Family Health Study (GS:SFHS) is a large (n = 20,198), family-based population study designed to identify the genetic determinants of common diseases, including Major Depressive Disorder. Two thousand seven hundred and six individuals were SCID diagnosed with MDD, 13.5% of the cohort, from which we inferred a population prevalence of 12.2% (95% credible interval: 11.4% to 13.1%). Increased risk of MDD was associated with being female, unemployed due to a disability, current smokers, former drinkers, and living in areas of greater social deprivation. The heritability of MDD in GS:SFHS was between 28% and 44%, estimated from a pedigree model. The genetic correlation of MDD between sexes, age of onset, and illness course were examined and showed strong genetic correlations. The genetic correlation between males and females with MDD was 0.75 (0.43 to 0.99); between earlier (≤ age 40) and later (> age 40) onset was 0.85 (0.66 to 0.98); and between single and recurrent episodic illness course was 0.87 (0.72 to 0.98). We found that the heritability of recurrent MDD illness course was significantly greater than the heritability of single MDD illness course. The study confirms a moderate genetic contribution to depression, with a small contribution of the common family environment (variance proportion = 0.07, CI: 0.01 to 0.15), and supports the relationship of MDD with previously identified risk factors. This study did not find robust support for genetic differences in MDD due to sex, age of onset, or illness course. However, we found an intriguing difference in heritability between recurrent and single MDD illness course. These findings establish GS:SFHS as a valuable cohort for the genetic investigation of MDD.     

The effect of divalent cations on the mode of action of DNase I. The initial reaction products produced from covalently closed circular DNA

The effect of different divalent metal ions on the hydrolysis of DNA by DNase I was studied with an assay which distinguishes between cleavage of one or both strands of the DNA substrate during initial encounters between enzyme and DNA. Using covalently closed superhelical SV40(I) DNA as substrate, initial reaction products consisting of relaxed circles or unit-length linears are resolved by electrophoresis of radioactively labeled DNA in agarose gels. Only in the presence of a transition metal ion, such as Mn2+ or Co2+, and only under certain reaction conditions, is DNase I able to cut both DNA strands at or near the same point, generating unit-length linears. This ability to cut both DNA strands is inhibited by such factors as temperature decrease, the addition of a monovalent ion or another divalent cation which is not a transition metal ion, or a reduction in the number of superhelical turns in the DNA substrate. All of these factors lead to a winding of the duplex helix and antagonize the unwinding of the duplex promoted by transition metal ion binding. Transition metal ions may thus convert the DNA substrate locally to a form in which DNase I can introduce breaks into both strands. In the presence of Mg2+, DNase I introduces single strand nicks into SV40(I), generating exclusively the covalently open, relaxed circular SV40(II) as the initial product of the reaction. In the presence of Mn2+, DNase I generates as initial products a mixture of SV40(II) and unit-length SV40 linear DNA molecules, formed by two nicks in opposite strands at or near the same point in the duplex. These circular SV40(II) molecules consist of two types. A minority class is indistinguishable from the nicked SV40(II) produced by DNase I in the presence of Mg2+. The majority class consists of molecules containing a gap in one of the two strands, the mean length of the gap being 11 nucleotides. The SV40(L) molecules produced in the presence of Mn2+ appear to have single strand extensions at one or both ends.     

Metabolically Protective Cytokines Adiponectin and Fibroblast Growth Factor-21 Are Increased by Acute Overfeeding in Healthy Humans

Context

Circulating levels of metabolically protective and adverse cytokines are altered in obese humans and rodent models. However, it is not clear whether these cytokines are altered rapidly in response to over-nutrition, or as a later consequence of the obese state.

Methods

Forty sedentary healthy individuals were examined prior to and at 3 and 28 days of high fat overfeeding (+1250 kCal/day, 45% fat). Insulin sensitivity (hyperinsulinaemic-euglycaemic clamp), adiposity, serum levels of adiponectin and fibroblast growth factor-21 (FGF21), fatty acid binding protein-4 (FABP4), lipocalin-2 and plasminogen activator factor-1 (PAI1) were assessed. Statistics were performed by repeated measures ANOVA.

Results

Overfeeding increased weight, body fat and liver fat, fasting glucose, insulin and reduced insulin sensitivity by clamp (all P <0.05). Metabolically protective cytokines, adiponectin and FGF21 were increased at day 3 of overfeeding (P ≤0.001) and adiponectin was also elevated at day 28 (P=0.001). FABP4, lipocalin-2 and PAI-1 were not changed by overfeeding at either time point.

Conclusion

Metabolically protective cytokines, adiponectin and FGF-21, were increased by over nutrition and weight gain in healthy humans, despite increases in insulin resistance. We speculate that this was in attempt to maintain glucose homeostasis in a state of nutritional excess. PAI-I, FABP4 and lipocalin 2 were not altered by overfeeding suggesting that changes in these cytokines may be a later consequence of the obese state. Clinical trial registration: www.clinicaltrials.gov (NCT00562393)