Stimulation of lens regeneration from the newt dorsal iris when implanted into the blastema of the regenerating limb

Dorsal iris from the eyes of adult Notophthalmus viridescens was transplanted into the blastema of regenerating limbs, subcutaneously in the limb or shoulder region, into the dorsal fin of larval newts and into the hindbrain of larval Ambystoma maculatum. The iris implants into the blastema regenerated lens vesicles or lenses with fibers in 40–75% of the cases. Multiple lenses were found in a few instances. No lenses developed from iris implants into the dorsal fin. Twenty percent of subcutaneous implants of iris formed lenses or lens vesicles, but lens regeneration from implants into the brain occurred only rarely. Denervation of the limb at the time of iris transplantation into the blastema greatly reduced the number of lenses regenerated. Studies on nerve fiber distribution in dorsal fin, subcutaneous areas, and denervated and innervated regenerating limbs, using the Bodian method, showed a general correlation between density of nerve fibers in the implant site and the incidence of lens regeneration from iris implants into that site. These results provide some evidence for a trophic action of nerve fibers on lens regeneration from the iris.     

Skeletal muscle cells from insulin-resistant (non-diabetic) individuals are susceptible to insulin desensitization by palmitate.

We recently demonstrated that in vivo insulin resistance is not retained in cultured skeletal muscle cells. In the present study, we tested the hypothesis that treating cultured skeletal muscle cells with fatty acids has an effect on insulin action which differs between insulin-sensitive and insulin-resistant subjects. Insulin effects were examined in myotubes from 8 normoglycemic non-obese insulin-resistant and 8 carefully matched insulin-sensitive subjects after preincubation with or without palmitate, linoleate, and 2-bromo-palmitate. Insulin-stimulated glycogen synthesis decreased by 27 +/- 5 % after palmitate treatment in myotubes from insulin-resistant, but not from insulin-sensitive subjects (1.50 +/- 0.08-fold over basal vs. 1.81 +/- 0.09-fold, p = 0.042). Despite this observation, we did not find any impairment in the PI 3-kinase/PKB/GSK-3 pathway. Furthermore, insulin action was not affected by linoleate and 2-bromo-palmitate. In conclusion, our data provide preliminary evidence that insulin resistance of skeletal muscle does not necessarily involve primary defects in insulin action, but could represent susceptibility to the desensitizing effect of fatty acids and possibly other environmental or adipose tissue-derived factors.     

Cryptic female choice: frogs reduce clutch size when amplexed by undesired males

In species with internal fertilization, females can 'cryptically' choose (e.g. through sperm selection) which individuals sire their offspring, even when their overt preferences for copulatory partners are overrun by male-male competition and sexual coercion. The experiment presented here reveals that control of paternity after copulation has begun is also possible in species with external fertilization. Females of the hybridogenetic Rana essonae-Rana esculenta (LL-LR) waterfrog complex adjust their clutch size in response to mate type: they release fewer eggs when amplexed by hybrid LR males who--jeopardize successful reproduction--than when amplexed by parental LL males. This reduction in the number of eggs laid can increase a female's residual reproductive value through a second mating in the same breeding season or a larger clutch size in the next year. We argue that cryptic female choice through clutch size adjustment (i) may have evolved more often than previously assumed, and (ii) can arise even where females mate only once during a reproductive period.     

A genetic mechanism of species replacement in European waterfrogs?

Introduced Rana ridibunda currentlyreplace the native waterfrogs R. lessonaeand R. esculenta in several areas ofcentral Europe. The unusual reproductive systemin waterfrogs of the Rana esculentacomplex suggests that this replacement may bedriven by a genetic mechanism: Ranaesculenta, a hybrid between R. ridibundaand R. lessonae, eliminates the lessonae genome from the germline and clonallytransmits the ridibunda genome(hybridogenesis). Hybrids form mixedpopulations with R. lessonae (L-E-system)in which they persist by backcrossing with theparental species. Matings between hybrids areunsuccessful, because their ridibundagenomes contain fixed recessive deleteriousmutations. When introduced into a L-E-system,R. ridibunda can mate with both nativetaxa, producing R. ridibunda offspringwith R. esculenta, and R. esculentaoffspring with R. lessonae (primaryhybridizations). If primary hybrids arehybridogenetic, they produce viable R.ridibunda offspring in matings with otherhybrids, because their clonal genomes areunlikely to share the deleterious allelespresent in the ancient clones. Thus, R.ridibunda will increase in the population atthe expense of both native taxa, eventuallyleaving a pure R. ridibunda population.We provide three lines of evidence for thisprocess from a currently invaded population inSwitzerland: (1) Primary hybridizations takeplace, as roughly 10% of hybrids in thepopulation possess ridibunda genomesderived from the introduced frogs. (2)Hybridogenesis occurs in primary hybrids,although at a low frequency. (3) Many hybrid ×hybrid matings in the population indeed produceviable offspring. Hence, the proposed geneticmechanism appears to contribute to the speciesreplacement, although its importance may belimited.     

Segregation of secondary metabolite biosynthesis in hybrids of Fusarium fujikuroi and Fusarium proliferatum

Fusarium fujikuroi and Fusarium proliferatum are two phylogenetically closely related species of the Gibberella fujikuroi species complex (GFC). In some cases, strains of these species can cross and produce a few ascospores. In this study, we analyzed 26 single ascospore isolates of an interspecific cross between F. fujikuroi C1995 and F. proliferatum D4854 for their ability to produce four secondary metabolites: gibberellins (GAs), the mycotoxins fusarin C and fumonisin B(1), and a family of red polyketides, the fusarubins. Both parental strains contain the biosynthetic genes for all four metabolites, but differ in their ability to produce these metabolites under certain conditions. F. fujikuroi C1995 produces GAs and fusarins, while F. proliferatum D4854 produces fumonisins and fusarubins. The segregation amongst the progeny of these traits is not the expected 1:1 Mendelian ratio. Only eight, six, three and three progeny, respectively, produce GAs, fusarins, fumonisin B(1) and fusarubins in amounts similar to those synthesized by the producing parental strain. Beside the eight highly GA(3)-producing progeny, some of the progeny produce small amounts of GAs, predominantly GA(1), although these strains contain the GA gene cluster of the non-GA-producing F. proliferatum parental strain. Some progeny had recombinant secondary metabolite profiles under the conditions examined indicating that interspecific crosses can yield secondary metabolite production profiles that are atypical of the parent species.     

Genome‐wide association study of body morphological traits in Sudanese goats

Long‐term selection of goats for a certain production system and/or different environmental conditions will be reflected in the body morphology of the animals under selection. To investigate the variation contributing to different morphological traits and to identify genomic regions that are associated with body morphological traits in Sudanese goats, we genotyped 96 females belonging to four Sudanese goat breeds with the SNP52 BeadChip. After quality control of the data, the genome‐wide association study was performed using 95 goats and 24 027 informative single nucleotide polymorphisms (SNPs). Bicoastal diameter was significantly associated (LOD = 6.32) with snp10185‐scaffold1365‐620922 on chromosome 2. The minor allele has an additive effect, increasing the bicoastal diameter by 2.6 cm. A second significant association was found between body length and snp56482‐scaffold89‐467312 on chromosome 3 (LOD = 5.65). The minor allele is associated with increased body length. Additionally, five regions were suggestive for cannon bone, head width, rump length and withers height (LOD > 5). Only one gene (CNTNAP5) is located within the 1‐Mb region surrounding the significant SNP for bicoastal diameter on chromosome 2. The body length QTL on chromosome 3 harbors 49 genes. Further research is required to validate the observed associations and to prioritize candidate genes.     

Early carotid atherosclerosis in overweight non-diabetic individuals is associated with subclinical chronic inflammation independent of underlying insulin resistance.

Overweight in children and young adults is an increasing problem in Western industrialized countries with potential impact on cardiovascular morbidity. Whether early arterial wall thickening in these subjects mainly results from the often associated insulin resistance syndrome or from increased subclinical chronic inflammation probably triggered by adipose tissue is still under discussion. We therefore determined insulin sensitivity index (ISI) by performing an euglycaemic hyperinsulinaemic glucose clamp (insulin infusion rate 1 mU/kg/min) and high-sensitivity C-reactive protein (hsCRP) levels in relation to the intima-media thickness (IMT) at the common carotid artery (high resolution ultrasound; 13 MHz) in 81 young (age 33 +/- 1 years), moderately overweight subjects. To reduce the number of confounding variables, subjects with disturbances in glucose metabolism (75 g oral glucose tolerance test) and hypertension were excluded. As expected, higher BMI was positively correlated with increased IMT (r = 0.358; p = 0.001). After multiple regression analysis, hsCRP levels independently correlated to IMT (r = 0.251; p = 0.03), even after adjusting for age, sex, BMI, ISI, LDL cholesterol and smoking as cofactors. However, taking all above listed factors into account, glucose-clamp assessed insulin sensitivity was not correlated with IMT. Thus, overweight might trigger inflammatory mechanisms leading to vascular wall hypertrophy independent of the insulin resistance syndrome already early in life.     

Genetic diversity of Nubian ibex in comparison to other ibex and domesticated goat species

Capra nubiana is a wild ibex species that is in danger of extinction. This study aimed at assessing the genetic diversity and population structure of Nubian ibex (Capra nubiana, n?=?8) in comparison to Alpine ibex (Capra ibex, n?=?8), Bezoar ibex (Capra aegagrus, n?=?4), and domesticated Taggar goats (Capra aegagrus hircus, n?=?24). All animals were genotyped with the 50K goat SNP chip. Since commercial SNP chips are not designed for wild species, data analysis was done in two ways: (1) using all callable SNPs (33,698) and (2) with a reduced set of SNPs segregating within three out of four populations (662). Using these two sets of SNPs, the observed heterozygosity in Nubian ibex ranged from 0.02 to 0.44, in Alpine ibex from 0.01 to 0.38, and in Bezoar ibex from 0.13 to 0.38, when analyzing 33,698 or 662 SNPs, respectively. In domesticated Taggar goats, the values for the observed heterozygosity using all 33,698 callable SNPs and the reduced set of 662 SNPs were similar (0.40–0.41). Pairwise F_ST values for the differentiation between species ranged from 0.17–0.35 (Bezoar ibex vs. Taggar goats) to 0.47–0.91 (Bezoar vs. Alpine ibex), and was 0.33–0.90 between Bezoar and Nubian ibex, respectively, to the two sets of SNPs. The analysis of molecular variance among all animals revealed that 74–78% can be explained by differences between species, while the residual 22–26% result from differences among individuals, respectively. Cluster analysis of Nei’s genetic distance allowed to detected two distinct clusters comprising Nubian and Alpine ibex on one hand and Taggar goats and Bezoar ibex on the other hand, and clear separation of all four breeds. Principal component (PC) analysis confirmed and further refined the clusters. SNPs that contributed most to PC1 allowed us to identify genomic regions accounting for the distances between species. These regions contain known milk protein genes. The identification of milk protein genes as contributors to the differentiation between species provides insights into the domestication of wild Capra breeds.