Estimating the heritability of nitrogen and carbon isotopes in the tail hair of beef cattle

BACKGROUND

The natural abundance of nitrogen (δ15N) and carbon (δ13C) isotopes in animal tissues are used to estimate an animal's efficiency in nitrogen utilization, and their feed conversion efficiency, especially in tropical grazing systems with prolonged protein restriction. It is postulated that selection for improving these two characteristics (δ15N and δ13C) would assist the optimisation of the adaptation in ever-changing environments, particularly in response to climate change. The aim of this study was to determine the heritability of δ15N and δ13C in the tail hair of tropically adapted beef cattle to validate their inclusion in genetic breeding programs.

METHODS

In total, 492 steers from two breeds, Brahman (n = 268) and Droughtmaster (n = 224) were used in this study. These steers were managed in two mixed breed contemporary groups across two years (year of weaning): steers weaned in 2019 (n = 250) and 2020 (n = 242). Samples of tail switch hair representing hair segments grown during the dry season were collected and analysed for δ15N and δ13C with isotope-ratio mass spectrometry. Heritability and variance components were estimated in a univariate multibreed (and single breed) animal model in WOMBAT and ASReml using three generations of full pedigree.

RESULTS

The estimated heritability of both traits was significantly different from 0, i.e. 0.43 ± 0.14 and 0.41 ± 0.15 for δ15N and δ13C, respectively. These traits had favourable moderate to high genetic and phenotypic correlations (- 0.78 ± 0.16 and - 0.40 ± 0.04, respectively). The study also provides informative single-breed results in spite of the limited sample size, with estimated heritability values of 0.37 ± 0.19 and 0.19 ± 0.17 for δ15N and δ13C in Brahman, and 0.36 ± 0.21 and 0.46 ± 0.22 for δ15N and δ13C in Droughtmaster, respectively.

CONCLUSIONS

The findings of this study show, for the first time, that the natural abundances of both nitrogen and carbon isotopes in the tail hair in cattle may be moderately heritable. With further research and validation, tail hair isotopes can become a practical tool for the large-scale selection of more efficient cattle.

A Simple and Quick Method for Decalcification Using Mouse Tail as a Model for Preparation of Lymphedema Study

The disadvantage of 10% EDTA decalcification is a long time-consuming. It needs to identify a quick and straightforward decalcification method when the preparation of lymphedema models using mouse tail which was a sample of bone wrapped in other tissues. In the present study, mouse tail samples were decalcified in 10% EDTA at 25, 37, and 42°C, respectively, with continuous shaking (150 rpm/min). The histologic integrity of samples was evaluated by hematoxylin and eosin staining, and the preservation of antigenicity was tested by either immunohistochemistry or immunofluorescence. The decalcification was distinctly accelerated by temperature. Results of hematoxylin and eosin staining were similar among different temperature groups. Immunohistochemistry and immunofluorescence staining revealed almost no signals in samples decalcified at 42°C for 1 week. Clear signals were detected when samples were decalcified at 37 and 25°C.

Grazing high and low: Can we detect horse altitudinal mobility using high-resolution isotope (δ13 C and δ15 N values) time series in tail hair? A case study in the Mongolian Altai

RATIONALE

Carbon and nitrogen stable isotope time series performed in continuously growing tissues (hair, tooth enamel) are commonly used to reconstruct the dietary history of modern and ancient animals. Predicting the effects of altitudinal mobility on animal δ¹³ C and δ¹⁵ N values remains difficult as several variables such as temperature, water availability or soil type can contribute to the isotope composition. Modern references adapted to the region of interest are therefore essential.

METHODS

Between June 2015 and July 2018, six free-ranging domestic horses living in the Mongolian Altaï were fitted with GPS collars. Tail hairs were sampled each year, prepared for sequential C and N isotope analysis using EA-IRMS. Isotopic variations were compared with altitudinal mobility, and Generalized Additive Mixed (GAMMs) models were used to model the effect of geographic and environmental factors on δ¹³ C and δ¹⁵ N values.

RESULTS

Less than half of the pasture changes were linked with a significant isotopic shift while numerous isotopic shifts did not correspond to any altitudinal mobility. Similar patterns of δ¹³ C and δ¹⁵ N variations were observed between the different horses, despite differences in mobility patterns. We propose that water availability as well as seasonal availability of N₂ fixing type plants primarily controlled horse hair δ¹³ C and δ¹⁵ N values, overprinting the influence of altitude.

CONCLUSIONS

Our study shows that altitudinal mobility is not the main factor that drives the variations in horse tail hair δ¹³ C and δ¹⁵ N values and that seasonal change in the animal dietary preference also plays an important role. It is therefore risky to interpret variations in δ¹³ C and δ¹⁵ N values of animal tissues in terms of altitudinal mobility alone, at least in C₃ -dominated environments.

Mercury Concentrations in the Two-Toed Amphiuma (Amphiuma means) and the Lesser Siren (Siren intermedia): Validating Non-lethal Sampling Methods in Southeastern Aquatic Salamanders

The global decline of amphibians is a major conservation issue. Many stressors are recognized for this decline including exposure to environmental contaminants. Mercury (Hg) is an environmental contaminant that bioaccumulates in wildlife and can cause a variety of negative impacts across taxa, including amphibians. Amphiuma and Siren spp. can comprise a large portion of biomass within their respective ecosystems, and thus, likely serve as important predators or prey in wetland communities. However, due to their cryptic nature, little is known about their ecology, diet, and accumulation potential. We sought to validate a nonlethal sampling method to quantify total mercury (THg) in two enigmatic species of aquatic salamanders: the two-toed amphiuma (Amphiuma means) and the lesser siren (Siren intermedia). We examined relationships between THg content in lethal (whole-body) and nonlethal (tail clip) samples. Tail clips were statistically significant predictors of whole-body THg (all p < 0.001), explaining 84-89% of variation in whole-body THg. Average whole-body THg (mg/kg) did not significantly differ between the two species (p = 0.97), and overall, they had similar whole-body THg content (S. intermedia = 0.330 ± 0.04, n = 18; A. means = 0.333 ± 0.07, n = 11). To our knowledge, these data represent the first reported Hg burdens in A. means and S. intermedia.

Dietary Selenomethionine Administration and Its Effects on the American Alligator (Alligator mississippiensis): Oxidative Status and Corticosterone Levels

Selenium (Se) is an essential nutrient which in excess causes toxicity. The disposal of incompletely combusted coal, which often is rich in Se, into aquatic settling basins is increasing the risk of Se exposure worldwide. However, very few studies have looked at the physiological effects of Se exposure on long-lived, top trophic vertebrates, such as the American alligator (Alligator mississippiensis). During a 7-week period, alligators were fed one of three dietary treatments: mice injected with deionized water or mice injected with water containing 1000 or 2000 ppm selenomethionine (SeMet). One week after the last feeding alligators were bled within 3 min of capture for plasma corticosterone (CORT). A few days later, all alligators were euthanized and whole blood and tail tissue were harvested to measure oxidative damage, an antioxidant-associated transcription factor, and antioxidant enzymes [glutathione peroxidase-1 (GPX1), superoxide dismutase-1 (SOD1), and SOD2] by Western blotting. There was a dose-dependent increase in baseline CORT levels in alligators administered SeMet. Except for blood SOD2 levels, SeMet treatment had no effect (p > 0.05 for all) on oxidative status: oxidative damage, GPX1, SOD1, and muscle SOD2 levels were similar among treatments. Our results illustrate that high levels of Se may act as a stressor to crocodilians. Future studies should investigate further the physiological effects of Se accumulation in long-lived, top-trophic vertebrates.

Analysis of Advanced Glycation Endproducts in Rat Tail Collagen and Correlation to Tendon Stiffening

Methylglyoxal is a major 1,2-dicarbonyl compound in vivo and leads to nonenzymatic protein modifications, known as advanced glycation endproducts. Especially long-lived proteins like collagen are prone to changes of the mechanical or biological function, respectively, by accumulation of Maillard-derived modifications. Specifically, the resulting nonenzymatic cross-link structures in parallel to the natural maturation process of collagen fibrils lead to complications with age or during disease. A novel lysine-lysine amide cross-link derived from methylglyoxal, 2,15-diamino-8-methyl-9-oxo-7,10-diaza-1,16-hexadecanedioic acid, named MOLA, was synthesized and identified in vitro and in vivo. Tail tendons of young, adult, and old rats (3, 12, and 22 months) were enzymatically digested prior to analysis of acid-labile glycation products via liquid chromatography-tandem mass spectrometry (LC-MS/MS). As a result, nine monovalent amino acid modifications, mostly originating from methylglyoxal (36 μmol/mol leucine-equivalents in total), and four glycation cross-links (0.72 μmol/mol glucosepane, 0.24 μmol/mol DODIC (3-deoxyglucosone-derived imidazoline cross-link), 0.04 μmol/mol MODIC (methylglyoxal-derived imidazoline cross-link), 0.34 μmol/mol MOLA) were quantitated in senescent tendon collagen. The results correlated with increased tail tendon breaking time from 10 to 190 min and indicate that methylglyoxal is a major player in the aging process of connective tissue.

Effects of maturation and advanced glycation on tensile mechanics of collagen fibrils from rat tail and Achilles tendons

Connective tissues are ubiquitous throughout the body and consequently affect the function of many organs. In load bearing connective tissues like tendon, the mechanical functionality is provided almost exclusively by collagen fibrils that in turn are stabilized by covalent cross-links. Functionally distinct tendons display different cross-link patterns, which also change with maturation, but these differences have not been studied in detail at the fibril level. In the present study, a custom built nanomechanical test platform was designed and fabricated to measure tensile mechanics of individual fibrils from rat tendons. The influence of animal maturity (4 vs. 16 week old rats) and functionally different tendons (tail vs. Achilles tendons) were examined. Additionally the effect of methylglyoxal (MG) treatment in vitro to form advanced glycation end products (AGEs) was investigated. Age and tissue type had no significant effect on fibril mechanics, but MG treatment increased strength and stiffness without inducing brittleness and gave rise to a distinct three-phase mechanical response corroborating that previously reported in human patellar tendon fibrils. That age and tissue had little mechanical effect, tentatively suggest that variations in enzymatic cross-links may play a minor role after initial tissue formation.

STATEMENT OF SIGNIFICANCE

Tendons are connective tissues that connect muscle to bone and carry some of the greatest mechanical loads in the body, which makes them common sites of injury. A tendon is essentially a biological rope formed by thin strands called fibrils made of the protein collagen. Tendon function relies on the strength of these fibrils, which in turn depends on naturally occurring cross-links between collagen molecules, but the mechanical influence of these cross-links have not been measured before. It is believed that beneficial cross-linking occurs with maturation while additional cross-linking with aging may lead to brittleness, but this study provides evidence that maturation has little effect on mechanical function and that age-related cross-linking does not result in brittle collagen fibrils.

A protocol to correct for intra- and interspecific variation in tail hair growth to align isotope signatures of segmentally cut tail hair to a common time line

RATIONALE

In recent years, segmental stable isotope analysis of hair has been a focus of research in animal dietary ecology and migration. To correctly assign tail hair segments to seasons or even Julian dates, information on tail hair growth rates is a key parameter, but is lacking for most species.

METHODS

We (a) reviewed the literature on tail hair growth rates in mammals; b) made own measurements of three captive equid species; (c) measured δ(2)H, δ(13)C and δ(15)N values in sequentially cut tail hairs of three sympatric, free-ranging equids from the Mongolian Gobi, using isotope ratio mass spectrometry (IRMS); and (d) collected environmental background data on seasonal variation by measuring δ(2)H values in precipitation by IRMS and by compiling pasture productivity measured by remote sensing via the normalized difference vegetation index (NDVI).

RESULTS

Tail hair growth rates showed significant inter- and intra-specific variation making temporal alignment problematic. In the Mongolian Gobi, high seasonal variation of δ(2)H values in precipitation results in winter lows and summer highs of δ(2)H values of available water sources. In water-dependent equids, this seasonality is reflected in the isotope signatures of sequentially cut tails hairs.

CONCLUSIONS

In regions which are subject to strong seasonal patterns we suggest identifying key isotopes which show strong seasonal variation in the environment and can be expected to be reflected in the animal tissue. The known interval between the maxima and minima of these isotope values can then be used to correctly temporally align the segmental stable isotope signature for each individual animal.

Isotopic niche variation in a higher trophic level ectotherm: highlighting the role of succulent plants in desert food webs

Stable isotope analysis of animal tissues allows description of isotopic niches, whose axes in an n-dimensional space are the isotopic ratios, compared to a standard, of different isotope systems (e.g. δ¹³C, δ¹⁵N). Isotopic niches are informative about where an animal, population or species lives and about what it consumes. Here we describe inter- and intrapopulation isotopic niche (bidimensional δ¹³C-δ¹⁵N space) of the Orange-throated whiptail (Aspidoscelis hyperythra), an arthropodivorous small lizard, in ten localities of Baja California Sur (Mexico). These localities range from extreme arid to subtropical conditions. Between 13 and 20 individuals were sampled at each locality and 1 cm of tail-tip was collected for isotope analysis. As expected, interpopulation niche width variation was much larger than intrapopulation one. Besides, isotopic variation was not related to age, sex or individual size of lizards. This suggests geographic variation of the isotopic niche was related to changes in the basal resources that fuel the trophic web at each locality. The position of Bayesian isotope ellipses in the δ-space indicated that whiptails in more arid localities were enriched in ¹³C, suggesting most of the carbon they ingested came from CAM succulent plants (cacti, agaves) and in minor degree in C₄ grasses. Contrarily, whiptails in subtropical areas were depleted in ¹³C, as they received more carbon from C₃ scrubs and trees. Localities closer to sea-level tended to be enriched in ¹⁵N, but a clear influence of marine subsidies was detected only at individual level. The study contributes to identify the origin and pathways through which energy flows across the trophic webs of North American deserts.

Introduction of correlative light and airSEM™ microscopy imaging for tissue research under ambient conditions

A complete fingerprint of a tissue sample requires a detailed description of its cellular and extracellular components while minimizing artifacts. We introduce the application of a novel scanning electron microscope (airSEM™) in conjunction with light microscopy for functional analysis of tissue preparations at nanometric resolution (<10 nm) and under ambient conditions. Our metal-staining protocols enable easy and detailed visualization of tissues and their extracellular scaffolds. A multimodality imaging setup, featuring airSEM™ and a light microscope on the same platform, provides a convenient and easy-to-use system for obtaining structural and functional correlative data. The airSEM™ imaging station complements other existing imaging solutions and shows great potential for studies of complex biological systems.

Quantifying the backscattering of second harmonic generation in tissues with confocal multiphoton microscopy

The backward second harmonic generation (SHG) in mouse tissues is studied with a confocal multiphoton microscopy system. The total backward collected SHG (B-SHG) consists of the backward generated SHG and the backward-scattered forward-generated SHG (BS-SHG), which can be modeled by a Gaussian and a uniform distribution, respectively, at the confocal pinhole plane. By varying the pinhole size with a series of collection fibers, the proportion of the BS-SHG to the B-SHG and the proportion of BS-SHG to the forward generated SHG can be obtained. The approach is first validated by Monte Carlo simulation. It is then applied to two types of mouse tissues: mouse tail tendon and Achilles tendon. It is found that the BS-SHG contributes less to the B-SHG for the tail tendon than Achilles tendon with thicknesses of ~300 μm. With the thickness of the Achilles tendon tissue increased to 1000 μm but the focal plane kept at the same depth, as high as ~10% of the total forward SHG is backscattered and collected. The results indicate that BS-SHG may not be the major source of B-SHG in the tail tendon, but it may be the major source in the Achilles tendon. These methods and results provide a noninvasive method and supporting information for investigating the generation mechanism of SHG and help with optimizing backward SHG microscopy and spectroscopy measurements.

Visualizing molecular polar order in tissues via electromechanical coupling

Electron microscopy (EM) and atomic force microscopy (AFM) techniques have long been used to characterize collagen fibril ordering and alignment in connective tissues. These techniques, however, are unable to map collagen fibril polarity, i.e., the polar orientation that is directed from the amine to the carboxyl termini. Using a voltage modulated AFM-based technique called piezoresponse force microscopy (PFM), we show it is possible to visualize both the alignment of collagen fibrils within a tissue and the polar orientation of the fibrils with minimal sample preparation. We demonstrate the technique on rat tail tendon and porcine eye tissues in ambient conditions. In each sample, fibrils are arranged into domains whereby neighboring domains exhibit opposite polarizations, which in some cases extend to the individual fibrillar level. Uniform polarity has not been observed in any of the tissues studied. Evidence of anti-parallel ordering of the amine to carboxyl polarity in bundles of fibrils or in individual fibrils is found in all tissues, which has relevance for understanding mechanical and biofunctional properties and the formation of connective tissues. The technique can be applied to any biological material containing piezoelectric biopolymers or polysaccharides.

Structural origins of chiral second-order optical nonlinearity in collagen: amide I band

The molecular basis of nonlinear optical (NLO) chiral effects in the amide I region of type I collagen was investigated using sum-frequency generation vibrational spectroscopy; chiral and achiral tensor elements were separated using different input/output beam polarization conditions. Spectra were obtained from native rat tail tendon (RTT) collagen and from cholesteric liquid crystal-like (LC) type I collagen films. Although RTT and LC collagen both possess long-range order, LC collagen lacks the complex hierarchical organization of RTT collagen. Their spectra were compared to assess the role of such organization in NLO chirality. No significant differences were observed between RTT and LC with respect to chiral or achiral spectra. These findings suggest that amide I NLO chiral effects in type I collagen assemblies arise predominantly from the chiral organization of amide chromophores within individual collagen molecules, rather than from supramolecular structures. The study suggests that sum-frequency generation vibrational spectroscopy may be uniquely valuable in exploring fundamental aspects of chiral nonlinearity in complex macromolecular structures.

Regressing amphibian tail as a model for the cadherin/beta-catenin complex disruption and glycosylation alteration during epithelial apoptosis

Epidermis is one of the many tissues that are resorbed during metamorphosis in the regressing tail of amphibian tadpoles. Apoptotic mechanisms play an important role in this process. In this study, loss of intercellular contacts and alterations in plasma membrane glycosylation were observed during apoptosis. The cadherin/beta-catenin complex represents one of the major adhesive systems in multiple epithelial tissues. Here, we analysed the fate of cadherin/beta-catenin complex and alterations of plasma membrane glycoconjugate compositions in apoptotic epithelial cells. Our results showed that the cadherin molecules were cleaved into extracellular and beta-catenin associated cytosolic domains by an intracellular mechanism. However, the extracellular domains were probably removed completely by matrix metalloproteinases. Lectin histochemistry studies suggested that mannose and alpha(2-->6) linked (but not alpha(2-->3) linked) sialic acids were major sugar motifs in plasma membranes of apoptotic tadpole epithelial cells. Although previous studies indicated reduced levels of sialic acid residues during apoptosis, elevated Sambucus nigra agglutinin (SNA) reactivity might be due to the degradation of high molecular weight glycoproteins (probably including cadherin) that masked the SNA-binding residues of the plasma membrane prior to apoptosis.

Evaluation of tail biopsy collection in laboratory mice (Mus musculus): vertebral ossification, DNA quantity, and acute behavioral responses

A preferred method to genotype genetically engineered mice is through collection of distal tail tissue (tail biopsy) followed by DNA isolation. Currently, general or local anesthesia (or both) is recommended for biopsy after 3 wk of age, the time after which tail vertebrae are considered to be ossified. Our objective was to rigorously evaluate vertebral development, DNA content, and acute behavioral responses at different ages by harvesting tail biopsies of different lengths. We evaluated laboratory mice from 5 inbred strains and 1 outbred stock at each of 12 ages (3 to 42 d of age). Biopsies of 5-, 10-, and 15-mm lengths were obtained. Vertebrae were graded according to level of ossification by using complementary modalities of high-resolution microradiography, microcomputed tomography, and histology. Vertebral development progressed at different rates among the strains, with mature tail vertebrae containing endplates detectable in the tail of some strains by 10 d of age. Within the distal 2 mm of tail, end plates were not identified before 21 d of age. DNA yield (DNA weight/tissue weight) was greatest from the 5-mm biopsy harvest. Acute behavioral responses to biopsy varied by age and strain, and these differences were associated with vertebral maturation. Vertebral development progressed most rapidly in C57BL/6 mice, which also demonstrated the highest response rate to biopsy, whereas BALB/c mice had slower vertebral development and were less responsive. These findings support the collection of minimal lengths of tail tissue from mice at ages younger than 17 d, unless anesthesia or analgesia is provided.

[Establishing the method of collagen-gel droplet embedded culture drug sensitivity test with rat tail collagen]

OBJECTIVE

To explore the clinical application of collagen-gel droplet embedded-culture drug sensitivity test (CD-DST) in the malignant tumors.

METHODS

CD-DST was established with rat tail collagen. Three pancreatic cancer cell lines, surgical resection specimens including 15 cases of pancreatic cancer and 10 cases of gastrointestinal cancer were examined using CD-DST.

RESULTS

The overall achievement ratio of CD-DST for clinical tumor specimens was 80% (20/25). In vitro chemosensitivities of pancreatic carcinoma cells to 5-FU, gemcitabine and oxaliplatin were lower than those of gastrointestinal carcinoma.

CONCLUSIONS

CD-DST with rat tail collagen is a valuable chemosensitivity testing method for malignant tumors. It can be used to realize individualized anticancer chemotherapy.

Increased Proteolysis of Collagen in an In Vitro Tensile Overload Tendon Model

Presently, there is a lack of fundamental understanding regarding changes in collagen's molecular state due to mechanical damage. The bovine tail tendon (BTT; steers approximately 30 months) was characterized and used as an in vitro model for investigating the effect of tensile mechanical overload on collagen susceptibility to proteolysis by acetyltrypsin and alpha-chymotrypsin. Two strain rates with a 1000-fold difference (0.01 and 10 s(-1)) were used, since molecular mechanisms that determine mechanical behavior were presumed to be strain rate dependent. First, it was determined that the BTTs were normal but immature tendons. Water content and collagen content (approx. 60% of wet weight and 80% of dry weight, respectively) and mechanical properties were all within the expected range. The collagen crosslinking was dominated by the intermediate crosslink hydroxylysinonorleucine. Second, tensile overload damage significantly enhanced proteolysis by acetyltrypsin and, to a lesser degree, by alpha-chymotrypsin. Interestingly, proteolysis by acetyltrypsin was greatest for specimens ruptured at 0.01 s(-1) and seemed to occur throughout the specimen. Understanding damage is important for insight into injuries (as in sports and trauma) and for better understanding of collagen fiber stability, durability, and damage mechanisms, aiding in the development of durable tissue-based products for mechanically demanding surgical applications.

Detection and determination of glyceraldehyde-derived pyridinium-type advanced glycation end product in streptozotocin-induced diabetic rats

GLAP, glyceraldehyde-derived pyridinium-type advanced glycation end product (AGE), formed by glyceraldehyde-related glycation, was identified in the plasma protein and the tail tendon collagen of streptozotocin (STZ)-induced diabetic rats. It was detected in the plasma protein and the collagen in diabetic rats by LC-MS and LC-MS/MS analysis, but was not detected in normal rats. In addition, GLAP was formed from glyceraldehyde-3-phosphate (GA3P) with lysine as well as glyceraldehyde (GLA) with lysine in vitro. Accordingly, it is suggested that an increase in the GLAP level reflects an increase in the GLA level and the GA3P level. GLAP might be a biomarker for reduced activity of the glyceraldehyde-related enzymes in the metabolic diseases such as diabetic complications.

Fasting increases delta15N-values in the uric acid of Anolis carolinensis and Uta stansburiana as measured by nondestructive sampling

Previous studies suggest that a nutritional/energetic state may be determined from the delta(15)N-values of an animal's tissues. It has been hypothesized that if an animal is in a negative nutritional/energetic balance, (15)N will be retained by the tissues preferentially and (14)N preferentially excreted. Over time, this should cause enrichment of the delta(15)N-values of the tissues. Tests of this hypothesis have met with mixed results. To date, these studies have focused on endotherms. Few studies have considered the effects of fasting on the (15)N/(14)N ratios of substrates from ectotherms. We hypothesized that the delta(15)N-values of tail tissue and uric acid of fasted lizards would increase over time, while that of the fed lizards would remain the same. We fasted five side-blotched lizards (Uta stansburiana) and five green anoles (Anolis carolinensis) for 14 days. At the same time we fed six side-blotched and four green anoles ad libitum. All lizards were given water ad libitum. During this period, we collected uric acid from each lizard daily and tail tissue on the first day of the study and on the last day of the study. We found the the delta(15)N-values of uric acid of fasted lizards at the end of the study were (15)N-enriched compared with that of the control lizards in both species, probably due to a shift in amino acid source pools during fasting. However, we found no difference between treatment and controls in the delta(15)N-values of the tails.

A chemical and genetic approach to the mode of action of fumagillin

Previous mode of action studies identified methionine aminopeptidase 2 (MetAP-2) as the target of the antiangiogenic natural product fumagillin and its drug candidate analog, TNP-470. We report here that TNP-470-mediated MetAP-2 inhibition blocks noncanonical Wnt signaling, which plays a critical role in development, cell differentiation, and tumorigenesis. Consistent with this finding, antisense MetAP-2 morpholino oligonucleotide injection in zebrafish embryos phenocopies gastrulation defects seen in noncanonical Wnt5 loss-of-function zebrafish mutants. MetAP-2 inhibition or depletion blocks signaling downstream of the Wnt receptor Frizzled, but upstream of Calmodulin-dependent Kinase II, RhoA, and c-Jun N-terminal Kinase. Moreover, we demonstrate that TNP-470 does not block the canonical Wnt/beta-catenin pathway. Thus, TNP-470 selectively regulates noncanonical over canonical Wnt signaling and provides a unique means to explore and dissect the biological systems mediated by these pathways.

A novel Xenopus laevis larval keratin gene, xlk2: its gene structure and expression during regeneration and metamorphosis of limb and tail

A novel cytokeratin (CK) gene, xlk2, was cloned from a cDNA library prepared from regenerating limbs of Xenopus larvae. The deduced amino acid sequence indicated that its product, XLK2, is a 48 kDa type I (acidic) CK and has a high similarity to CK13, 15, and 19 with the highest homology (58%) to mouse CK15. The gene of xlk2 exclusively expressed in basal cells of the bi-layered larval epidermis, but not in other cells in larvae and not in other periods of life. Its expression was down-regulated during spontaneous and thyroid hormone-induced metamorphosis. The basal cells of the apical epidermal cap (AEC) formed on the regenerate of larval limbs terminated the expression of xlk2, whereas those of the adjacent normal epidermis continued to express it. The AEC-basal cells did not re-express the gene in the regenerate. In contrast, the basal cells of the tail regenerate also once terminated the expression of xlk2, but was able to re-express xlk2 later, supporting a notion that the "de-differentiated" basal cells of the tail epidermal regenerate re-differentiate into larval normal epidermal cells.

Preparation of ready-to-use, stockable and reconstituted collagen

Collagen is a widely used material in biomedical applications. Although processes that prepare collagen and collagen-based materials that show suitable properties after extraction exist, a ready-to-use, easily stockable, with tailored collagen concentration has not yet been developed. Using rat tail tendons, acid soluble collagen solutions were prepared by two different methods. To improve cell viability of pure collagen films, solutions with physiological pH were also prepared by mixing with NaOH solution. Specimens in the form of thin sheets were then fabricated by solvent evaporation. Next, IR spectroscopy, tensile testing techniques as well as human fibroblast cell morphology and cytotoxicity were used to validate the significant variations in the processes. The results demonstrated that, during the synthesis of collagen stock solution, lyophilization and mechanical blending had little effect on the final properties and therefore offers a method for obtaining solutions with a more homogeneous and modifiable collagen concentration and longer storage time. Neutralizing the stock solution with aqueous NaOH prior to solvent evaporation provided films that had lower mechanical properties but significantly improved biological performance.

Detection of testosterone, nandrolone and precursors in horse hair

Growing interest among several horse-breeder associations has initiated the development of a screening procedure to test for anabolic agents in hair, which has the advantage over blood and urine specimens of allowing long-term detection. An analytical method was established to monitor in tails or manes several anabolic substances available as veterinary medicines or as so-called nutritional supplements (clenbuterol, different esters or prohormones of nandrolone and testosterone). The analytical procedure to detect steroids in hair samples consists of the following steps: decontamination of the hair strand or segment with methanol/water (1:1), milling, extraction of the hair material in an ultrasonic bath using methanol, purification by liquid-liquid extraction (n-pentane/methanol, 25:1) and HPLC cleanup, derivatisation of the relevant LC fractions with MSTFA, and measurement using GC-MS/MS technique. The first objective of our study was the detection of exogenous nandrolone (nortestosterone, NT) in the horse hair; therefore nandrolone-associated compounds [nandrolone dodecanoate administered intramuscularly (i.m.) and a mixture of 4-estrenediol and 4-estrenedione, transdermal] were administered to four geldings. The highest concentrations of NT following i.m. treatment were measured after 10 days in a 2-cm hair segment (up to 18 pg/mg); NT was detectable for up to 120 days and in some cases up to 330 days in tail hair (limit of detection 0.3 pg/mg). Following transdermal application, nandrolone as well as the administered prohormones were identified in tail and mane until the latest sampling at 3 months. Furthermore, untreated stallions (128) were investigated to estimate the range of endogenous levels of NT and testosterone (T) in hair. Maximum values of 3 pg/mg (NT) and 1 pg/mg (T) were quantified originating from endogenous formation in the male horse. Additionally, a possible relationship between steroid concentrations in hair specimens and the age of stallions was appraised. NT and T were not detected in hair samples of control geldings. Following nandrolone treatment of geldings, highest values in hair exceeded the endogenous amount detected in untreated stallions. Therefore comparison of concentrations measured in control samples with the estimated endogenous levels could give a clue to exogenous application in cases of abnormally high amounts of NT or T. The possibility of the evaluation of threshold values is discussed as a means to verify an exogenous administration of NT and T in hair samples. Furthermore, the detection of a synthetic substance in hair, e. g. the parent steroid ester by itself, would be unequivocal proof of an exogenous origin of NT or T and the previous medication of the stallion.

The brain is a target organ after acute exposure to depleted uranium

The health effects of depleted uranium (DU) are mainly caused by its chemical toxicity. Although the kidneys are the main target organs for uranium toxicity, uranium can also reach the brain. In this paper, the central effects of acute exposure to DU were studied in relation to health parameters and the sleep-wake cycle of adult rats. Animals were injected intraperitoneally with 144+/-10 microg DU kg-1 as nitrate. Three days after injection, the amounts of uranium in the kidneys represented 2.6 microg of DU g-1 of tissue, considered as a sub-nephrotoxic dosage. The central effect of uranium could be seen through a decrease in food intake as early as the first day after exposure and shorter paradoxical sleep 3 days after acute DU exposure (-18% of controls). With a lower dosage of DU (70+/-8 microg DU kg-1), no significant effect was observed on the sleep-wake cycle. The present study intends to illustrate the fact that the brain is a target organ, as are the kidneys, after acute exposure to a moderate dosage of DU. The mechanisms by which uranium causes these early neurophysiological perturbations shall be discussed.

Thermal denaturation of UV-irradiated wet rat tail tendon collagen

The thermal helix-coil transition of UV irradiated collagen in rat tail tendon has been investigated by differential scanning calorimetry. During UVB irradiation the tendons were immersed in water to keep the collagen fibers in a fully hydrated condition at all times. UV irradiation induced changes in collagen which caused both stabilization and destabilization of the triple helix in fibers. The helix-coil transition for non-irradiated collagen occurred near 64 degrees C, for irradiated 1 and 3 h at 66 and 67 degrees C, respectively. After irradiating for longer times (20-66 h) the helix-coil transition peak occurred at much lower temperatures. The peak was very broad and suggested that collagen was reduced by UV to different polypeptides of different molecular weight and different lower thermal stabilities. It was caused by the disruption of a network of hydrogen-bonded water molecules surrounding the collagen macromolecule.

Functional relationships among selenium concentrations in the diet, target tissues, and nondestructive tissue samples of two species of snakes

Nondestructive sampling methods, such as removal of feathers for contaminant analysis, are desirable in ecological monitoring programs that seek to minimize the impacts of harvesting organisms. Although many reptiles are declining worldwide, nondestructive sampling techniques seldom have been employed for assessing contaminant exposure in these organisms. In this study, we examined the utility of nondestructive tissue sampling for assessing Se exposure in reptiles. We describe the functional relationships among dietary Se concentrations, target tissue Se concentrations, and Se concentrations in nondestructive tissue samples (blood and tail tissue biopsy) in two species of snakes that had been exposed to Se under very different experimental protocols. Using nonlinear regression, we found strong positive correlations (r2 > 0.92) in all comparisons among Se concentrations in nondestructive tissues, diet, and target tissues. Moreover, equations describing these relationships can be used to estimate concentrations of Se in diet and target organs, from known concentrations of Se in nondestructive tissue samples. Although the current paucity of toxicity data on reptiles precludes tests of our models, we demonstrate how the equations describing these relationships might be used to make predictions about Se accumulation in target organs for risk assessment. Future studies on reptiles that examine these relationships under different Se exposure conditions, and those that document physiological responses of reptiles to various concentrations of Se, will help to refine our models and test their efficacy for predicting health risk.

Impact of collagen structure on matrix trafficking by human fibroblasts

Biodegradation of collagen biomaterial matrices and the deposition of new collagen extracellular matrix (ECM) are critical to the integration of in vitro bioengineered materials and tissues in vivo. In previous studies, we observed significant impact of collagen matrix structure on primary lung fibroblast behavior in vitro. In the present work, to begin to understand the mechanistic basis for our previous observation, the response of human fibroblasts (IMR-90) to the structural state of collagen matrices was studied with respect to cell proliferation, cell morphology, beta-galactosidase level, and transcript content for collagen (Col-1), matrix metalloproteinases (MMP-1, MMP-2), tissue inhibitors of matrix metalloproteinase (TIMP-1 and TIMP-2). Collagen digestion was assessed quantitatively by uptake of collagen-coated fluorescent beads incorporated in the preformed collagen matrix. Transcript levels related to the deposition of new ECM proteins varied as a function of the structure of the collagen matrix presented to the cells. Col-1 expression was 2-fold higher and expression for MMP-1, MMP-2, TIMP-1, and TIMP-2 increased for cells when grown on 156 microg/cm2 denatured collagen compared with cells grown on tissue culture (TC) plastic. On 156 microg/cm2 nondenatured (native) collagen, Col-1 expression was decreased by half and MMP-2 was increased by 2.5-fold compared with cells grown on TC plastic. On 78 microg/cm2 denatured collagen, Col-1 expression was 80% whereas the MMPs and TIMPs were increased by 1.25- to 2-fold compared with cells grown on TC plastic. On 78 microg/cm2 nondenatured collagen expression of all 5 transcripts was reduced 60-90% of the levels determined for the cells grown on TC plastic. Cell viability, based on cell morphology and beta-galactosidase activity, was improved on the denatured collagen. A higher level of collagen matrix incorporation was observed for cells grown on denatured collagen than on nondenatured collagen or TC plastic. These data suggest that tissue engineering matrices incorporating denatured collagen may promote more active remodeling toward new ECM in comparison to cells grown on nondenatured collagen or cells grown on TC plastic.

Strain-Rate Sensitive Mechanical Properties of Tendon Fascicles From Mice With Genetically Engineered Alterations in Collagen and Decorin

Tendons have complex mechanical behaviors that are nonlinear and time dependent. It is widely held that these behaviors are provided by the tissue’s composition and structure. It is generally thought that type I collagen provides the primary elastic strength to tendon while proteoglycans, such as decorin, play a role in failure and viscoelastic properties. This study sought to quantify such structure-function relationships by comparing tendon mechanical properties between normal mice and mice genetically engineered for altered type I collagen content and absence of decorin. Uniaxial tensile ramp to failure experiments were performed on tail tendon fascicles at two strain rates, 0.5%/s and 50%/s. Mutations in type I collagen led to reduced failure load and stiffness with no changes in failure stress, modulus or strain rate sensitivity. Fascicles without decorin had similar elastic properties to normal fascicles, but reduced strain rate sensitivity. Fascicles from immature mice, with increased decorin content compared to adult fascicles, had inferior elastic properties but higher strain rate sensitivity. These results showed that tendon viscoelasticity is affected by decorin content but not by collagen alterations. This study provides quantitative evidence for structure-function relationships in tendon, including the role of proteoglycan in viscoelasticity.

Mercury toxicity in the aquatic oligochaete Sparganophilus pearsei. II: Autotomy as a novel form of protection

Aquatic oligochaetes are commonly used for toxicity testing and for assessment of sediment impairment; some species can be relatively tolerant of sediment contaminants. However, there have been few studies of tolerance mechanisms; most work has focused on behavioral changes. The aquatic oligochaete worm, Sparganophilus pearsei, can be extremely tolerant to mercury in sediments depending on its prior history of exposure. Three S. pearsei populations, differing in their history of mercury exposure and in their tolerance to mercury, were assessed to determine tolerance mechanisms. In mercury-contaminated sediments, tolerant worms accumulated this contaminant in their caudal segments (i.e., their tails), which were then jettisoned via the process of autotomy, thus providing a mechanism of detoxification. This detoxification process appears to require a certain level of tolerance and may represent a novel exposure route for other organisms via feeding on discarded tails or release of accumulated contaminants as the tails decompose. Measurements of tissue mercury concentrations as contaminant body residues for this species (CBRs) are compared to other aquatic invertebrates.

Cyclosporin A inhibits thyroid hormone-induced shortening of the tadpole tail through membrane permeability transition

Regression of the tadpole tail through muscule cell apoptosis is one of the most spectacular events in amphibian metamorphosis. Accumulated evidence has shown that mitochondrial membrane permeability transition (MPT) plays a crucial role in apoptosis. Previously we reported that cyclosporin A (CsA) suppressed 3,5,3'-triiodothyronine (T(3))-induced mitochondrial swelling, which was coupled with cytochrome c (Cyt.c) release through MPT [Comp. Biochem. Phys. 130 (2001) 411-418]. To further clarify the mechanism of tadpole metamorphosis, the present study investigates the effect of CsA on T(3) induced tadpole tail shortening. A low concentration of T(3) (5 x 10(-8) M) was found to induce a shortening of stage X Rana rugosa tadpole tails, accompanied by an increase in caspase-3- and -9 like protease activity, as well as an increase in DNA-fragmentation and ladder formation, while CsA was seen to suppress the effects of T(3). The stage X tadpole tail was found to express Bax mRNA and this expression was not affected by T(3) treatment. CsA, on the other hand, proved to have a slightly supressive effection on Bax expression. 20 microM T(3) as well as 50 microM Ca(2+) induced swelling in mitochondria isolated from the liver of R. rugosa resulting in the release of apoptosis related substances, and the released fraction activated cytosolic caspase-3 and -9 in the presence of dATP. This result indicated that Cyt.c might be released from mitochondria by treatment with T(3) through both direct and indirect action of T(3). From these results and other data it was concluded that mitochondrial MPT plays an important role in T(3)-induced apoptosis in the tadpole tail, resulting in tail shortening, and CsA was seen to suppress the effects of T(3).

[Cytotoxic effects of lead on the endocrine and exocrine sexual function of pubescent male and female rats. Demonstration of apoptotic activity]

This study deals with the impact of chronic exposure to lead on male and female fertility in rats. Male and female rats (3 months old) were fed on commercial tablets (SICO, Sfax). For drinking, some rats were given distilled water (T = controls), the other ones were given distilled water enriched with lead acetate, either 3 (P1 group) or 6 mg ml-1 (P2 group), for 15, 30, 45, 60 or 90 days. In male rats, absolute and relative weights of testis, epididymis, prostate and seminal vesicles were found to significantly decrease at day 15 in the P2 group and at day 45 in the P1 group. However, at day 60, these absolute and relative weights returned to control values. Lead-induced pathological changes in spermatogenesis were observed at day 15 by histological study: arrest of cell germ maturation, changes in the Sertoli cells, and presence of apoptotic cells revealed by borated toluidine blue in the testis. Presence of lead deposits was observed after histochemical staining using sodium rhodizonate. Serum testosterone level was found to be lowered at day 15 in both (P1) and (P2) groups, to display a peak at day 60, then to return to controls values, in spite of the continuation of the treatment. In female rats, absolute and relative weights of ovary and uterus were found unchanged. The vaginal smears practiced in females revealed the oestrus phase in all groups. Exposed females were mated with control males, and fecundity was assessed 15 days later by counting the number of pregnancies and the number of concepti per pregnancy. Fertility was found to be reduced in females of P1 and P2 groups as compared to control females (T group). Lead level in blood was found to be poorly correlated with the level of poisoning, whereas lead accumulation in tail was found to be dose-dependent. Therefore, lead accumulation in tail appears as a more reliable biomarker of exposure to lead. In summary, our study shows that chronic exposure to lead causes a double sexual disorder in rats: first, disorder deals with the hormonal function, which is affected at the early stages of poisoning, but is rapidly corrected; second, disorder deals with the genital tract, affecting the testis and the ovary, resulting in a reduced fertility in both P1 and P2 females, in spite of the presence of a normal oestrus. The cytotoxic effect of lead in males seems to be related to an apoptotic process.

Comparative analysis of the structure and thermal stability of sea urchin peristome and rat tail tendon collagen

We have purified collagen from two distinct sources; the vertebrate, rat tail tendon and an invertebrate, sea urchin adult tissue, the peristome. The collagenous nature of the purification products was confirmed by amino acid compositional analysis. Both preparations had high contents of glycine and proline residues and hydroxyproline was also present. The total pyrrolidine (proline+hydroxyproline) content decreased from 17.9 mole% in rat tail collagen to 12.9 mole% in peristome collagen. Distinctly different circular dichroic spectra were measured for these collagens. Analyses of spectra, measured as a function of temperature, revealed distinct thermal denaturation profiles. The melting temperature for rat tail collagen was 38.5 degrees C, while the corresponding value for peristome collagen was significantly lower at 27 degrees C. A similar thermal denaturation profile was obtained for rat tail collagen in digestion experiments using a 41-kDa gelatinase activity, isolated from sea urchin eggs. These results identify structural differences between a typical, vertebrate type I fibrillar collagen and an echinoderm collagen which serves as a constituent of a mutable connective tissue. These differences may relate to the functional roles played by collagen in these distinctly different tissues.

Viscoelastic properties of collagen: synchrotron radiation investigations and structural model

Collagen type I is the most abundant structural protein in tendon, skin and bone, and largely determines the mechanical behaviour of these connective tissues. To obtain a better understanding of the relationship between structure and mechanical properties, tensile tests and synchrotron X-ray scattering have been carried out simultaneously, correlating the mechanical behaviour with changes in the microstructure. Because intermolecular cross-links are thought to have a great influence on the mechanical behaviour of collagen, we also carried out experiments using cross-link-deficient tail-tendon collagen from rats fed with beta-APN, in addition to normal controls. The load-elongation curve of tendon collagen has a characteristic shape with, initially, an increasing slope, corresponding to an increasing stiffness, followed by yielding and then fracture. Cross-link-deficient collagen produces a quite different curve with a marked plateau appearing in some cases, where the length of the tendon increases at constant stress. With the use of in situ X-ray diffraction, it was possible to measure simultaneously the elongation of the collagen fibrils inside the tendon and of the tendon as a whole. The overall strain of the tendon was always larger than the strain in the individual fibrils, which demonstrates that some deformation is taking place in the matrix between fibrils. Moreover, the ratio of fibril strain to tendon strain was dependent on the applied strain rate. When the speed of deformation was increased, this ratio increased in normal collagen but generally decreased in cross-link-deficient collagen, correlating to the appearance of a plateau in the force-elongation curve indicating creep. We proposed a simple structural model, which describes the tendon at a hierarchical level, where fibrils and interfibrillar matrix act as coupled viscoelastic systems. All qualitative features of the strain-rate dependence of both normal and cross-link-deficient collagen can be reproduced within this model. This complements earlier models that considered the next smallest level of hierarchy, describing the deformation of collagen fibrils in terms of changes in their molecular packing.

Identification of 3,4-didehydroretinal isomers in the Xenopus tadpole tail fin containing photosensitive melanophores

It is well characterized that melanophores in the tail fin of Xenopus laevis tadpoles are directly photosensitive. In order to better understand the mechanism underlying this direct photosensitivity, we performed a retinal analysis of the tail fins and eyes of Xenopus tadpoles at stages 51-56 using high performance liquid chromatography (HPLC). Following the extraction of retinoids by the formaldehyde method, a fraction containing retinal and/or 3,4-didehydroretinal isomers from the first HPLC analysis were collected. These isomers were then reduced by sodium borohydride to convert retinal and/or 3,4-didehydroretinal isomers into the corresponding retinol isomers to prepare for a second HPLC analysis. Peaks of 11-cis and all-trans 3,4-didehydroretinol were detected in the eyes and tail fins containing melanophores, but they were not detected in the tail fins without melanophores. The amounts of 11-cis and all-trans 3,4-didehydroretinol were 27.5 and 5.7 fmol/fin, respectively, and the total quantity of 3,4-didehydroretinal was calculated at approximately 5 x 10(6) molecules/melanophore. These results strongly suggest the presence of 11-cis and all-trans 3,4-didehydroretinal in melanophores of the tadpole tail fin, which probably function as the chromophore of photoreceptive molecules.

Effects of collagen IV and laminin on the reconstruction of human oral mucosa

To investigate the effects of basement membrane proteins on the reconstruction of mucosa equivalent, oral mucosa substitute were cultured on (1) type I collagen gels, (2) type IV collagen-coated type I collagen gels, (3) laminin-coated type I collagen gels, and (4) type I collagen gels containing both type IV collagen and laminin. H/E and PAS staining showed that the characteristics of the oral mucosa were preserved under all the experimental conditions. However, the basal keratinocytes appeared cuboidal when the type I collagen gels were coated with type IV collagen plus laminin. The expression of the differentiation markers was similar, but weak staining of filaggrin, K13, and involucrin was observed with the type IV collagen plus laminin coating. Furthermore, electron microscopy revealed that the size of the basal keratinocytes was relatively small and uniform when both type IV collagen and laminin were used. These findings suggested that these two major basement membrane proteins are important in the process of differentiation in mucosal keratinocytes.

Nondestructive indices of trace element exposure in squamate reptiles

Compared with birds, mammals, fish, and even amphibians, very little is known about the effects of contaminants on reptiles. Recent evidence that many reptile populations may be declining has stimulated demand for toxicological studies of reptiles as well as development of nondestructive sampling techniques useful for assessing and monitoring contaminant exposure. The current study experimentally evaluated the utility of shed skins, tail clips, and blood samples as nondestructive indices of trace element exposure in banded water snakes, Nerodia fasciata. For 13.5 months, snakes were either fed fish from a coal ash-contaminated site or uncontaminated food from a reference site. Snakes fed contaminated prey accumulated As, Cd, Se, Sr, and V in various organs (i.e. liver, kidney, and/or gonads). Moreover, non-parametric discriminant function analysis revealed that snakes could be placed in two groups that reliably reflected their experimental diet based upon Se, Sr, and As concentrations in tail clips, blood, and/or shed skins. We suggest that nondestructive sampling techniques, particularly analyses of blood and tail clips, may be easily applied in evaluations of contaminant exposure in the field and laboratory and may prevent excessive destructive sampling of potentially threatened reptile species.

Tailflick escape behavior in larval and juvenile lobsters (Homarus americanus) and crayfish (Cherax destructor)

We examined the escape behavior of larvae and postlarvae of the American lobster (Homarus americanus) and of adult immature (stage ADI) crayfish (Cherax destructor). Responses to standardized water jet stimuli delivered through a pipette were observed and analyzed. Lobster larvae did not respond to stimuli within 60 ms, indicating that they do not have functional giant fibers. The first movement by lobster larvae in response to water jet stimuli was a hyperextension of the abdomen. Larval escape responses also showed very little habituation. Postlarval lobsters and ADI crayfish showed the same range of responses as adult animals. Displacement efficiency of tailflicks exhibited by the different animals and stages was examined and related to the morphology of the animals. A separate behavior from tailflicking by larval lobsters in response to water jet stimuli was also observed. Here, the abdomen was hyperextended and the thoracic appendages were promoted. We termed this behavior a "starburst" response. The features of the tailflicking behavior suggest that it evolved to make the larvae difficult prey to handle for small, slower moving predators, and possibly to allow them to ride the bow waves of faster moving predators.

DNA detection in hair of transgenic mice--a simple technique minimizing the distress on the animals

The breeding of transgenic animals requires that each individual offspring be analysed for integration of transgenic deoxyribonucleic acid (DNA), unless exclusively homozygous animals are mated. The standard protocol for identification of transgenic animals (Hogan et al. 1994) is based on tissue samples and preparation of chromosomal DNA including proteinase K digestion and phenol/chloroform extraction. The procedure described here represents a much simpler and faster method to screen offspring for the transgene DNA. It is based on the use of hair bulbs as sample material, which can be directly used for polymerase chain reaction (PCR) after alkaline lysis. This protocol allows large numbers of animals to be easily screened in a minimum amount of time. A unique advantage though, is the reduction of the distress caused to the animals. With respect to the 3Rs (Replacement, Reduction, Refinement), and because of technical advantages this method may replace ear or tail clipping.

Thermal helix-coil transition in UV irradiated collagen from rat tail tendon

The thermal helix-coil transition in UV irradiated collagen solution, collagen film and pieces of rat tail tendon (RTT) were compared. Their thermal stability's were determined by differential scanning calorimeter (DSC) and by viscometric measurements. The denaturation temperatures of collagen solution, film and pieces of RTT were different. The helix-coil transition occur near 40 degrees C in collagen solution, near 112 degrees C in collagen film, and near 101 degrees C in pieces of RTT. After UV irradiation the thermal helix-coil transition of collagen samples were changed. These changes depend on the degree of hydratation.

Overexpression of vascular endothelin-1 and endothelin-A receptors in a fructose-induced hypertensive rat model

OBJECTIVE

To examine the temporal relationship between hyperinsulinemia and hypertension in the fructose-hypertensive rat model and to study the function of endothelin-1 (ET-1) in fructose-induced hypertension.

DESIGN

Since ET-1 induces insulin resistance in conscious rats, we tested the hypothesis that both hyperinsulinemia and hypertension developed in the fructose-hypertensive rat model might be the sequelae of an elevated tissue content of ET-1 and ET(A) receptors.

MATERIALS AND METHODS

Systolic hypertension was induced within 3 weeks in male Sprague-Dawley rats fed on a fructose-rich diet. After continual monitoring of blood pressure and plasma insulin concentrations, the animals were killed at the end of experiment to determine plasma levels of ET-1, the contractile response of aortic rings to ET-1, and ET-1 and ET(A) receptor gene expressions. In a separate experiment, BQ-610 was administered to lower the effect of ET-1 in rats with fructose-induced hypertension.

RESULTS

Compared with control rats given normal chow, the fructose-fed rats developed systolic hypertension after 3 weeks of the diet (127+/-3.7 versus 110+/-5.5 mmHg, P < 0.01) and hyperinsulinemia both before (1 07.1+/-32.5 versus 48.5+/-14.3 pmol/l, P < 0.005) and after (96.6+/-63.7 versus 50.4+/-5.6 pmol/l, P< 0.05) they became hypertensive. Although plasma ET-1 levels did not differ between the rat groups, aortic ring contraction-concentration curves, indicating vessel contractility in response to ET-1, were significantly greater in these rats than in controls (F1,72 = 12.34, P< 0.00077). Messenger RNA extracted from the tail arteries and blotted with both ET-1 and ET(A) probes showed that fructose-fed rats had greater ET-1 and ET(A)-receptor gene expression than control rats. Concomitant administration of BQ-610 to rats fed on a fructose diet significantly reduced the hypertension. Conclusions These findings suggest that elevated vascular expression of ET-1 and ET(A) receptor genes may mediate the development of hypertension and hyperinsulinemia in rats fed a fructose-rich diet

Genomic DNA from mice: a comparison of recovery methods and tissue sources

Our aim is to identify an extraction method and the source of mouse tissue(s) that could allow a high-resolution genomic scan from a living mouse. We compared and optimized two methods for yield, purity of DNA, and their use in the polymerase chain reaction (PCR) of DNA extracted from different mouse tissues. In addition to whole blood, tissue samples from the brain, liver, testis, and tail were included in this study. The Rapid Method (RM) is preferable for the whole blood samples and testis and brain tissue samples because it is quicker, less toxic, and more cost-effective than the proteinase K method (PM). For liver the PM produced higher yields of DNA with less degradation than the RM. For tail tip, the PM produced a higher yield of DNA, but the RM resulted in a higher yield of PCR product. From a living mouse, a tail snip generated a sufficient amount of DNA for several hundred PCRs but not a complete genomic scan. We suggest that the RM can be used to extract genomic DNA for a complete genomic scan which requires either testicular tissues or repeated blood samples from the suborbital sinus over several months without sacrificing the animal.

Characterization of a metalloproteinase: a late stage specific gelatinase activity in the sea urchin embryo

We have partially purified and characterized an 87 kDa gelatinase activity expressed in later stage sea urchin embryos. Cleavage activity was specific for gelatin and no cleavage of sea urchin peristome type I collagen, bovine serum albumin or casein was detected. Magnesium and Zn2+ inhibited the gelatinase and Ca2+ protected against inhibition. Ethylenediamine tetracetic acid, ethylenebisoxyethylenenitriol tetraacetic acid and 1,10-phenanthroline were inhibitory, suggesting that the gelatinase is a Ca(2+)- and Zn(2+)-dependent metalloproteinase. No inhibition was detected with serine or cysteine protease inhibitors and the vertebrate matrix metalloproteinase (MMP) inhibitor, Batimastat, was also ineffective. The vertebrate MMP activator p-aminophenylmercuric acetate was without effect. These results allow us to identify both similarities and differences between echinoderm and vertebrate gelatinases.

Light-sensitive response in melanophores of Xenopus laevis: II.Rho is involved in light-induced melanin aggregation

Melanophores of the isolated tail fin of the Xenopus tadpole aggregate melanin granules in response to light. This aggregation was found to be inhibited by subcutaneous injection of exoenzyme C3 of Clostridium botulinum. A 26 kDa protein in homogenate obtained from the Xenopus tail fin was ADP-ribosylated by exoenzyme C3. This reaction was inhibited effectively by a monoclonal antibody, anti-Rho mab A5. raised against the small GTP-binding protein Rho. The extent of ADP-ribosylation depended on light and guanine nucleotide. Incubation under illumination partly reduced ADP-ribosylation and the reduction was restored by addition of guanine nucleotide during incubation. These findings suggest that Rho is involved in the photo-sensitive melanophore response as a signal transducer linking photo-stimuli to melanin granule translocation with Xenopus melanophores.

Molecular analysis of a RAPD marker (B20) reveals two microsatellites and differential mRNA expression in Penaeus vannamei

We previously reported a population-specific DNA fragment (B20) in Penaeus vannamei shrimp, fragment found using the randomly amplified polymorphic DNA (RAPD) procedure, that was present in Population 2 but not in Populations 1 and 4. The specific objectives of this study were to clone and sequence this genetic marker, determine if all or part of this cloned sequence could be found in any of the other populations in which this marker could not be amplified, and examine if this marker represents a functional gene by examining the steady-state levels of mRNA expression using Northern blot hybridization. Sequence information of the 1259-bp B20 clone revealed two microsatellites and two candidate open reading frames. Although the entire B20 sequence could only be amplified in Population 2 (from Ecuador), Population 3 (a hybrid of Populations 1 and 2), and a few individuals from wild Ecuadorian shrimp samples, portions of the B20 DNA could be amplified in individuals from Populations 1, 2, 3, candidate Population 4, and wild Ecuadorian samples. These microsatellites vary in size between populations and families. Northern blot hybridization analysis using radiolabeled B20 probe detected two mRNA transcripts of approximately 1.5 and 2.0 kb. Expression data throughout development indicated that these transcripts were present at low levels in nauplii from two of the three crosses examined using broodstocks of Population 1. Higher levels were observed in postlarvae (PL) 6, PL8, and PL10 in one of the three crosses. Individuals from all crosses showed higher levels of expression in the juvenile tail muscle. The mRNA transcript levels were undetected in zoea 3, PL2, and PL4 stages of development and broodstock tail muscle. The levels of expression of B20 mRNA transcripts varied significantly between Populations 1, 2, 3, 4, and wild Ecuadorian individuals as well as between families and within individuals representative of seven families from Population 1. In summary, the B20 clone revealed the presence of two microsatellites that vary in size between populations. These microsatellites will be useful for estimating genetic diversity within and between populations, identifying family-specific markers, and mapping loci responsible for economically important traits in penaeid shrimp. The mRNA levels detected by the B20 clone showed differential expression during development, and the pattern of expression was influenced by the genetic background of the parental crosses used.

The use of ubiquitin as a marker of thyroxine-induced apoptosis in cultured Rana catesbeiana tail tips

Cultured Rana catesbeiana tadpole tail tips were used in combination with a fluoroimmunoassay to determine the levels of ubiquitin--a protein marker of programmed cell death in other systems--during the tissue regression induced by thyroxine (T4). After a 3-day pretreatment with the hormone, tail tips cultured in T4 showed significant increases in ubiquitin levels by 48 hr. Tail tips taken from tadpoles that had been immersed in T4 for 6 days showed a parallel increase in ubiquitin levels, demonstrating the same change in vivo. Treatment of cultured tail tips with the protein kinase C inhibitor, H-7, blocks both regression and the rise in ubiquitin seen in tips treated with T4 alone. Treatment of cultured tips with T4 and either cycloheximide or actinomycin D inhibits regression compared to T4 alone; however, the rise in ubiquitin is only blocked by cycloheximide, suggesting that ubiquitin is being made from RNA that was synthesized during the pretreatment period or earlier. These results suggest that ubiquitin will serve as a good molecular marker of tissue regression in the T4-treated tadpole tail and that it will be productive to consider tissue regression during amphibian metamorphosis as a specific case of programmed cell death or apoptosis.

Molecular markers of differentiation in Caenorhabditis elegans obtained by promoter trapping

Differentiation of specific cell types during animal development can be detected by monitoring expression of appropriate genes. For this study, six different beta-galactosidase expression patterns which can be used as differentiation markers in the nematode Caenorhabditis elegans are described. An earlier promoter trap screen identified pools of recombinant plasmids which gave patterns of beta-galactosidase expression when used to transform C. elegans. Each recombinant plasmid contained a random fragment of C. elegans genomic DNA fused upstream of a promoterless lacZ gene. Six of these pools were chosen, and individual pattern-producing plasmids within these pools were identified. The expression patterns have been characterized more thoroughly than in the original screen, thereby providing molecular markers for differentiation of several cell types. Many of the expression patterns involve more than one cell type. The genomic origin of the inserts of active plasmids were determined through localization on the physical genome map.