Increase In Tissue Weight Research Articles

Knockout of the Muscle-Specific E3 Ligase MuRF1 Affects Liver Lipid Metabolism upon Dexamethasone Treatment in Mice.

In order to preserve muscle mass during catabolic states, investigators are actively searching for a specific inhibitor of MuRF1, the only known E3 ligase that can target muscle contractile proteins for their degradation. However, what would be the consequences of such inhibitors on other organs, both in the short and long term? Indeed, skeletal muscles can provide amino acids for liver gluconeogenesis, which is a crucial adaptation for maintaining glucose homeostasis upon elevated energy demands (e.g., during prolonged starvation). Comparing 3-month-old wild-type and MuRF1-KO mice, we measured tissue weights, liver glycogen, lipid and protein content, and liver biochemical composition using Fourier transform infrared (FTIR) spectrometry in control animals and in dexamethasone (Dex)-treated animals. Dex induces a catabolic situation with muscle atrophy and lipid deposits in the liver. In response to Dex treatment, liver glycogen, lipid, and protein content increased in wild type (WT) and MuRF1-KO mice. We found that MuRF1 deletion differentially affected organ weights, the liver of KO mice being hypertrophied upon Dex treatment when compared to WT mice. Upon Dex treatment, muscle mass was preserved in MuRF1-KO mice, and by contrast, liver lipid content increased more in these animals than in WT mice. PLS-DA analysis of FTIR showed that the levels of 13 markers were significantly altered in KO vs WT mice, witnessing profound alterations of lipid, protein, and glycogen content in the liver due to the absence of MuRF1. Using Nile red and oil red lipid staining, we also found that both membrane-linked lipids and intracellular lipid droplets were altered due to the absence of MuRF1. Altogether, it seems that when the liver is deprived of the possibility of obtaining amino acids from muscle upon Dex treatment, there is a concomitant increase in tissue weight and anabolic activity.

Bottom culture is a promising strategy for final grow-out of the Portuguese oyster Crassostrea angulata

Almost all the Portuguese oyster Crassostrea angulata in China are grown in nearshore farms using suspended culture. Problems such as overstocking and environmental degradation have occurred in many suspended oyster farms. In this study, two batches of C. angulata, which were pre-grown in suspended culture in Dapeng Cove, South China Sea, were transplanted onto the seabed at the mouth of the bay. The first batch of small-sized C. angulata was deployed on March 16, 2019 (bottom culture A), while the second batch of large-sized oysters was deployed on July 6, 2019 (bottom culture B). Temporal variations in the survival and growth of these oysters were tested against their counterparts that continued growing in suspended culture. Results indicated mortality of oysters in bottom culture A was mainly a result of crab predation, while summer mass mortalities in the suspended culture and bottom culture B were a result of stress from reproduction and high temperatures. Oysters in bottom culture A exhibited smaller but cleaner shells than those in suspended culture. The soft tissue of C. angulata in all treatments continued to increase until August 22. Accelerated increases in tissue weight and condition index (CI) from early July to late August were mainly attributed to gamete formation, while subsequent decreases in tissue weight and CI likely resulted from the spawning activity. Oysters in bottom culture A consistently performed better in terms of tissue growth and CI than those in suspended culture. Individuals in both the suspended culture and bottom culture B exhibited very similar growth patterns after July 6, when overcrowding at the oyster farm was partially resolved. The results of this study indicate that bottom culture is a promising strategy for producing meaty and clean C. angulata within a short duration. This method also provides a feasible solution to the overcrowding problem in suspended oyster farms. Nevertheless, a simple, efficient, and economical method to reduce crab predation in bottom culture is needed.

Endothelial SIRT-1 has a critical role in the maintenance of capillarization in brown adipose tissue

Brown adipose tissue (BAT) has critical roles in thermogenesis and systemic metabolism. Capillary rarefaction was reported to develop in BAT with dietary obesity, and previous studies showed that suppression of vascular endothelial growth factor A (VEGF-A) reduced capillary density in BAT, promoting the functional decline of this organ. Capillarization is regulated through the balance between angiogenesis and vasculogenesis on the one hand and apoptosis of endothelial cells (ECs) on the other; however, the role of EC apoptosis in BAT remained to be explored. In studies testing the role of boysenberry polyphenols (BoyP) in BAT, we found that BoyP decreased EC apoptosis, enhanced capillarization in BAT, and ameliorated dietary BAT dysfunction, which was associated with the upregulation of nicotinamide adenine dinucleotide-dependent protein deacetylase sirtuin 1 (SIRT-1) in ECs. Our studies suggest that EC SIRT-1 would be one of the potential targets of BoyP that contributes to BAT capillarization and function.

Severe Hyperprolactinemia Promotes Brown Adipose Tissue Whitening and Aggravates High Fat Diet Induced Metabolic Imbalance.

BackgroundThe association of high serum prolactin and increased body weight is positive but controversial, therefore we hypothesized that additional factors such as diets and the impact of prolactin on brown adipose tissue may condition its metabolic effects.MethodsWe used LacDrd2KO females with lifelong severe hyperprolactinemia due dopamine-D2 receptor deletion from lactotropes, and slow onset of metabolic disturbances, and compared them to their respective controls (Drd2 loxP/loxP ). Food intake, and binge eating was evaluated. We then challenged mice with a High Fat (HFD) or a Control Diet (CD) for 8 weeks, beginning at 3 months of age, when no differences in body weight are found between genotypes. At the end of the protocol brown and white adipose tissues were weighed, and thermogenic and lipogenic markers studied, using real time PCR (Ucp1, Cidea, Pgc1a, Lpl, adiponectin, Prlr) or immunohistochemistry (UCP1). Histochemical analysis of brown adipose tissue, and glucose tolerance tests were performed.ResultsHyperprolactinemic mice had increased food intake and binge eating behavior. Metabolic effects induced by a HFD were exacerbated in lacDrd2KO mice. Hyperprolactinemia aggravated HFD-induced body weight gain and glucose intolerance. In brown adipose tissue pronounced cellular whitening as well as decreased expression of the thermogenic markers Ucp1 and Pgc1a were observed in response to high prolactin levels, regardless of the diet, and furthermore, hyperprolactinemia potentiated the decrease in Cidea mRNA expression induced by HFD. In subcutaneous white adipose tissue hyperprolactinemia synergistically increased tissue weight, while decreasing Prlr, Adiponectin and Lpl mRNA levels regardless of the diet.ConclusionsPathological hyperprolactinemia has a strong impact in brown adipose tissue, lowering thermogenic markers and evoking tissue whitening. Furthermore, it modifies lipogenic markers in subcutaneous white adipose, and aggravates HFD-induced glucose intolerance and Cidea decrease. Therefore, severe high prolactin levels may target BAT function, and furthermore represent an adjuvant player in the development of obesity induced by high fat diets.

In-situ microplastic egestion efficiency of the eastern oyster Crassostrea virginica

Microplastics (MP) are a pervasive environmental pollutant that enter coastal water bodies, posing an ingestion risk to marine biota. This study quantified the ability of the Eastern oyster (Crassostrea virginica) to egest MP in-situ in their biodeposits - feces and pseudofeces. Oysters of all sizes were able to egest environmental MP at a mean rate of 1 MP per 1 h through feces, and 1 MP per 2 h through pseudofeces. Smaller C. virginica were more efficient at egesting MP, and efficiency decreased by 0.8% per 1-g increase in tissue weight, with C. virginica of harvestable size being much less efficient. These findings are of relevance to resource managers for C. virginica populations as it further contributes to our understanding of MP accumulation in wild populations and has implications for not just C. virginica but also for their consumers.

Ovariectomy-Induced Hepatic Lipid and Cytochrome P450 Dysmetabolism Precedes Serum Dyslipidemia.

Ovarian hormone deficiency leads to increased body weight, visceral adiposity, fatty liver and disorders associated with menopausal metabolic syndrome. To better understand the underlying mechanisms of these disorders in their early phases of development, we investigated the effect of ovariectomy on lipid and glucose metabolism. Compared to sham-operated controls, ovariectomized Wistar female rats markedly increased whole body and visceral adipose tissue weight (p ˂ 0.05) and exhibited insulin resistance in peripheral tissues. Severe hepatic triglyceride accumulation (p ˂ 0.001) after ovariectomy preceded changes in both serum lipids and glucose intolerance, reflecting alterations in some CYP proteins. Increased CYP2E1 (p ˂ 0.05) and decreased CYP4A (p ˂ 0.001) after ovariectomy reduced fatty acid oxidation and induced hepatic steatosis. Decreased triglyceride metabolism and secretion from the liver contributed to hepatic triglyceride accumulation in response to ovariectomy. In addition, interscapular brown adipose tissue of ovariectomized rats exhibited decreased fatty acid oxidation (p ˂ 0.01), lipogenesis (p ˂ 0.05) and lipolysis (p ˂ 0.05) despite an increase in tissue weight. The results provide evidence that impaired hepatic triglycerides and dysregulation of some CYP450 proteins may have been involved in the development of hepatic steatosis. The low metabolic activity of brown adipose tissue may have contributed to visceral adiposity as well as triglyceride accumulation during the postmenopausal period.

Bladder sensation evaluation of a carrageenan-induced chronic prostatitis model using a direct measurement of the bladder mechanosensitive single-unit afferent nerve activity.

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) causes long-standing pain and/or storage symptoms. This study aimed to evaluate the likelihood of deterioration of bladder sensation in a carrageenan-induced CP/CPPS model by direct measurement of the bladder mechanosensitive single-unit afferent nerve activity. In this study, male adult Sprague-Dawley rats were used. They were injected 50 µL of 3% λ-carrageenan or its vehicle (saline) into both lobes of the ventral prostate. Seven days following injection, the pain behavior at the pelvic-perineal area (using von Frey filaments), prostatic blood flow (using a laser blood flowmeter), and histology were examined along with cystometry (under conscious free-moving condition) and mechanosensitive single-unit afferent nerve activity (under urethane anesthesia). The prostate showed increased tissue weight and decreased blood flow and inflammatory cell infiltration in the carrageenan group compared to the control group. Consequently, the threshold of the pain behavior was decreased, and the basal and threshold pressures of the bladder were increased in the carrageenan group. In contrast, no significant differences of bladder histology and other cystometric parameters were found between the groups. Regarding Aδ- or C-fibers, the mechanosensitive afferent nerve activities revealed no differences in either group. The carrageenan-induced CP/CPPS rat model showed edema, ischemia, and inflammatory pain in the prostate, whereas a little change was detected in bladder sensation. These findings, which were evaluated using a direct measurement of the mechanosensitive single-unit afferent nerve activity, suggest that the bladder sensation is unlikely deteriorated in this model.

Seasonal effects to metallothionein responses to metal exposure in a naturalised population of Ruditapes philippinarum in a semi-enclosed estuarine environment

The Manila clam (Ruditapes philippinarum), an invasive species in Northern Europe, can be used as a bioindicator of metal pollution. Seasonal effects on metallothionein (MT) production have not been considered in this species at the northernmost extent of its European distribution. This study assesses the annual seasonal effects on MT and metal concentrations in R. philippinarum from Poole Harbour, UK. R. philippinarum were collected in winter, spring, summer, and autumn throughout 2015, and MT and metal concentrations, as well as biotic and abiotic variables, were quantified. During winter, linear regression analysis showed significant positive relationships between tissue metal and MT concentrations. However, during spring and summer, these relationships were mostly insignificant. MT concentrations during spring had significant positive relationships with tissue and whole weight. Significant positive relationships were also observed between MT and condition index, during summer. During spring and summer, biotic factors seem to override the role of MT as a detoxification mechanism for metal exposure in this species. This is probably due to an increase in MT concentration in spring caused by gametogenesis, associated with increased tissue weight as the gonads expand. A depletion of energy resources, or physical stressors such as heat, may be attributed to the reduced MT production in clams of poor body condition in summer. The evidence from this study suggests that MT may only be a useful biomarker of metal pollution during winter in R. philippinarum in the UK. This verifies the natural variability of MT in this species at high latitudes, and highlights the potential and limits to a widely available bioindicator of metal pollution.

Muscle plasticity related to changes in tubulin and αB-crystallin levels induced by eccentric contraction in rat skeletal muscles.

We used the model of eccentric contraction of the hindlimb muscle by Ochi etal. to examine the role of eccentric contraction in muscle plasticity. This model aims to focus on stimulated skeletal muscle responses by measuring tissue weights and tracing the quantities of αB-crystallin and tubulin. The medial gastrocnemius muscle (GCM) responded to electrically induced eccentric contraction (EIEC) with significant increases in tissue weight (p < 0.01) and the ratio of tissue weight to body weight (p < 0.05); however, there was a decrease in soleus muscle weight after EIEC. EIEC in the GCM caused contractile-induced sustenance of the traced proteins, but the soleus muscle exhibited a remarkable decrease in α-tubulin and a 19% decrease in αB-crystallin. EIEC caused fast-to-slow myosin heavy chain (MHC) isoform type-oriented shift within both the GCM and soleus muscle. These results have shown that different MHC isoform type-expressing slow and fast muscles commonly undergo fast-to-slow type MHC isoform transformation. This suggests that different levels of EIEC affected each of the slow and fast muscles to induce different quantitative changes in the expression of αB-crystallin and α-tubulin.

1-(2-Hydroxy-2-methyl-3-phenoxypropanoyl)indoline-4-carbonitrile Derivatives as Potent and Tissue Selective Androgen Receptor Modulators

We present a novel series of selective androgen receptor modulators (SARMs) which shows excellent biological activity and physical properties. 1-(2-Hydroxy-2-methyl-3-phenoxypropanoyl)-indoline-4-carbonitriles showed potent binding to the androgen receptor (AR) and activated AR-mediated transcription in vitro. Representative compounds demonstrated diminished activity in promoting the intramolecular interaction between the AR carboxyl (C) and amino (N) termini. This N/C-termini interaction is a biomarker assay for the undesired androgenic responses in vivo. In orchidectomized rats, daily administration of a lead compound from this series showed anabolic activity by increasing levator ani muscle weight. Importantly, minimal androgenic effects (increased tissue weights) were observed in the prostate and seminal vesicles, along with minimal repression of circulating luteinizing hormone (LH) levels and no change in the lipid and triglyceride levels. This lead compound completed a two week rat toxicology study, and was well tolerated at doses up to 100 mg/kg/day, the highest dose tested, for 14 consecutive days.

Stress hormones mediate predator-induced phenotypic plasticity in amphibian tadpoles

Amphibian tadpoles display extensive anti-predator phenotypic plasticity, reducing locomotory activity and, with chronic predator exposure, developing relatively smaller trunks and larger tails. In many vertebrates, predator exposure alters activity of the neuroendocrine stress axis. We investigated predator-induced effects on stress hormone production and the mechanistic link to anti-predator defences in Rana sylvatica tadpoles. Whole-body corticosterone (CORT) content was positively correlated with predator biomass in natural ponds. Exposure to caged predators in mesocosms caused a reduction in CORT by 4 hours, but increased CORT after 4 days. Tadpoles chronically exposed to exogenous CORT developed larger tails relative to their trunks, matching morphological changes induced by predator chemical cue; this predator effect was blocked by the corticosteroid biosynthesis inhibitor metyrapone. Tadpole tail explants treated in vitro with CORT increased tissue weight, suggesting that CORT acts directly on the tail. Short-term treatment of tadpoles with CORT increased predation mortality, likely due to increased locomotory activity. However, long-term CORT treatment enhanced survivorship, likely due to induced morphology. Our findings support the hypothesis that tadpole physiological and behavioural/morphological responses to predation are causally interrelated. Tadpoles initially suppress CORT and behaviour to avoid capture, but increase CORT with longer exposure, inducing adaptive phenotypic changes.

Selective Ablation of ERα in Uterine Epithelia Alters Uterine Estrogen Responses.

The mouse uterus is a sensitive biological system in which to assess the mechanisms of estrogen response. Biological, biochemical and genomic events initiated by estrogens have been well-characterized and described, allowing assessment of chemicals with suspected estrogenic activity by comparison to the signature responses of proven estrogens. Some of these responses include binding to the estrogen receptor alpha (ERα), which is abundant in uterine cells, interaction with estrogen responsive enhancer DNA sequences (EREs) resulting in regulation of estrogen responsive transcripts, proliferation of the uterine epithelial cells, and increased tissue weight. Uterine tissue is comprised of several cell types, including myometrial cells on the outer margins, epithelial cells lining the inner lumen (luminal epithelium) and glands (glandular epithelium), with stromal cells in the middle compartment. All of these cell types express ERα; earlier studies using tissue recombination have suggested that estrogen-dependent epithelial cell proliferation relies on estrogen-induced stromal growth factors, such as IGF1 or EGF, which then impact the epithelial cells. We have developed a conditional knockout of ERα selective to the uterine epithelial cells (UtEpiαERKO) by intercrossing Wnt7acre and floxed ERα lines. Resulting females have uteri with all cell types present, but are infertile. Mammary glands are fully developed, reflecting normal ERα function in mammary tissue. Examination of the uteri by immunohistochemistry indicates selective ablation of ERα protein only in luminal and glandular epithelia. The administration of estrogen for 24 hours results in epithelial proliferation, with increased markers for S phase as well as M phase. Estrogen also increased the uterine weight after 3 days, but the increase was diminished in comparison to the increase seen in WT animals (4.3-fold for WT, 3.0-fold for the conditional knockout), and was inhibited by co-administration of the ER antagonist, ICI 182,780, indicating the effect is ER-mediated. Interestingly, after 3 days of estrogen treatment epithelial cells of the UtEpiαERKO had gross indications of apoptosis (blebbing) that was confirmed by increased terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) levels. The apoptosis inhibitory protein transcript, Birc1, is increased by E2 in WT but not UtEpiαERKO uteri. No increase in the epithelial-specific estrogen-responsive lactoferrin transcript was seen in the UtEpiαERKO, whereas this transcript was increased 17-fold in WT animals, supporting the epithelial specific ablation of hormone-dependent gene responses. These results demonstrate that in adult animals ERα remaining in other cells is sufficient to initiate the epithelial proliferation. Additionally, epithelial ERα is necessary to elicit a full uterine physiological response to estrogen, including water imbibition, uterine weight increase, gene regulation, inhibition of apoptosis and the hyperplasia of the endometrial tissues. (platform)

Changes in α-glucosidase activities along the jejunal-ileal axis of normal rats by the α-glucosidase inhibitor miglitol

Miglitol, an α-glucosidase inhibitor that inhibits postprandial hyperglycemia by delaying carbohydrate digestion and absorption along the jejunal-ileal axis, has recently been approved for use in patients with type 2 diabetes mellitus. Miglitol treatment may lead to increased α-glucosidase activities toward the ileum because carbohydrate flow toward the ileum increases. However, it is not yet known if miglitol treatment alters the α-glucosidase activities along the jejunal-ileal axis. In this study, we examined the effects of miglitol supplementation for 3 or 7 days on α-glucosidase activities along the jejunal-ileal axis of Wistar rats. Supplementation with miglitol for 3 or 7 days in rats increased tissue weights of the lower jejunum and ileum, but did not alter tissue weights of the upper jejunum and cecum or the contents of the cecum. Furthermore, supplementation with miglitol for 7 days reduced the activities of isomaltase and maltase in the upper jejunum and increased the activities of sucrase, isomaltase, and maltase in the lower jejunum and ileum. These results suggest that the delay in carbohydrate digestion and absorption along the jejunal-ileal axis by miglitol supplementation in rats is associated with increased α-glucosidase activities toward the ileum.

Pancreatic mass, cellularity, and α-amylase and trypsin activity in feedlot steers fed increasing amounts of a high-moisture-corn based diet

Twenty-four yearling beef steers (initial BW = 467 ± 3.6 kg), predominately of Angus breeding, were used in a randomized complete block design to determine the effect of dietary intake on pancreatic cellularity, mass, and α-amylase and trypsin activity. Steers were individually fed a high-moisture corn-based diet at 1.25, 1.50, 1.75, and 2.00% of BW (DM basis) using Calan gates. After 28 d on treatment, the heaviest steer from each dietary treatment was slaughtered per wk and pancreata collected. Average daily gain (kg) and pancreatic weight (g) increased linearly (P ≤ 0.01) with increasing DM intake. Pancreatic DNA and RNA concentration and content, and RNA:DNA and protein:DNA did not differ (P &gt; 0.05) between treatments. This suggests that the observed increase in tissue weight was due to increases in both cell size and number. Total pancreatic α-amylase activity (kU pancreas-1) increased linearly (P = 0.04) with increasing DM intake. These data indicate that total pancreatic α-amylase activity (kU pancreas-1) linearly increases with increasing intake of a high-moisture corn-based finishing diet and that dietary intake-dependent changes in total pancreatic α-amylase activity are primarily due to changes in pancreatic weight rather than changes in the concentration of pancreatic α-amylase activity (U g-1 pancreas). Key words: Beef cattle, pancreas, α-amylase, trypsin, feed intake

The OECD Program to Validate the Rat Hershberger Bioassay to Screen Compoundsfor in Vivo Androgen and Antiandrogen Responses. Phase 1: Use of a Potent Agonistand a Potent Antagonist to Test the Standardized Protocol

The Organisation for Economic Cooperation and Development (OECD) has completed phase 1 of the Hershberger validation intended to identify in vivo activity of suspected androgens and anti-androgens. Seventeen laboratories from 7 countries participated in phase 1, and results were collated and evaluated by the OECD with the support of an international committee of experts. Five androgen-responsive tissues (ventral prostate, paired seminal vesicles and coagulating glands, levator ani and bulbocavernosus muscles, glans penis, and paired Cowper’s or bulbourethral glands) were evaluated. The standardized protocols used selected doses of a reference androgen, testosterone propionate (TP), and an antiandrogen, flutamide (FLU). All laboratories successfully detected TP-stimulated increases in androgen-responsive tissue weight and decreases in TP-stimulated tissue weights when FLU was co-administered. The standardized protocols performed well under a variety of conditions (e.g., strain, diet, housing protocol, bedding). There was good agreement among laboratories with regard to the TP doses inducing significant increases in tissue weights and the FLU doses decreasing TP-stimulated tissue weights. Several additional procedures (e.g., weighing of the dorsolateral prostate and fixation of tissues before weighing) and serum component measurements (e.g., luteinizing hormone) were also included by some laboratories to assess their potential utility. The results indicated that the OECD Hershberger protocol was robust, reproducible, and transferable across laboratories. Based on this phase 1 validation study, the protocols have been refined, and the next phase of the OECD validation program will test the protocol with selected doses of weak androgen agonists, androgen antagonists, a 5α-reductase inhibitor, and chemicals having no androgenic activity.

Extracellular fluid volume expansion and third space sequestration at the site of small bowel anastomoses.

Intestinal surgery is usually associated with the parenteral administration of sodium and water, sometimes in amounts considerably in excess of excretory capacity. We have studied the effect of this situation on the water content of the gut at and 5 cm from a single-layer end-to-end anastomosis in the rabbit. Water content was measured by desiccation. One group of animals (group 1) did not receive intravenous therapy. The second group (group 2) received 5 ml kg-1 h-1 of Hartmann's solution during the operative period and thereafter to a total volume of 200 ml by 48 h. In group 1 there was a 5-10 per cent increase in tissue weight both at the anastomotic site and at 5 cm (P less than 0.01, Mann-Whitney U test) on the first 3 days. Thereafter, water content at the anastomosis persisted, but resolved in normal gut. In group 2 a further 5 per cent increase in weight over group 1 occurred (P less than 0.01), persistent at the anastomotic site over 5 days, though resolving elsewhere after 2 days. Extracellular fluid volume expansion exaggerates an anatomical third space present in the region of an anastomosis. At the suture line, oedema so induced is persistent and could be deleterious.

Oedema at the site of small-bowel anastomoses.

Abstract The change in water content of bowel tissue in the area of an end-to-end anastomosis was estimated by a desiccation technique. Significant oedema, sufficient to cause 5-10 per cent increase in tissue weight, could be demonstrated at the anastomotic site up to 96 hours after operation, when compared with control tissue. However, up to 48 hours the anastomoses were neither more nor less oedematous than the remainder of the bowel. After that time the oedema of the unanastomosed bowel began to decrease. It is concluded that the degree of oedema demonstrated, if applied to the human case, could only provok obstruction of a stoma already of critical size.

Leptin Induces Vascular Smooth Muscle Cell Hypertrophy through Angiotensin II- and Endothelin-1-Dependent Mechanisms and Mediates Stretch-Induced Hypertrophy

Various cardiovascular pathologies are associated with vascular smooth muscle cell (VSMC) hypertrophy and elevated plasma leptin levels. We used the rat portal vein (RPV) cultured for three days to investigate the effect of mechanical stretch on autocrine secretion of leptin and the effect of exogenous leptin (3.1 nM) on VSMC. Stretching the RPV significantly up-regulated leptin production by greater than 100-fold and leptin receptor expression by up to 10-fold. In addition, stretch increased tissue weight by 23 +/- 1.3 and 30 +/- 1% (P < 0.05), respectively, in the absence or presence of leptin, although this was significantly attenuated by an antileptin antibody (166 ng/ml). Unstretched RPV weight decreased by 7.5 +/- 1.8% in the absence of leptin, whereas in the presence of leptin, weight increased by 6.5 +/- 1.8% (P < 0.05). VSMC size and [3H]leucine incorporation rates were significantly increased by leptin in stretched and unstretched tissues. Leptin-induced hypertrophy was associated with significant extracellular signal-regulated kinase (ERK1/2) activation as well as increased expression of angiotensinogen, the angiotensin type 1 receptor as well as preproendothelin-1, and the endothelin type A receptor, whereas ERK inhibition or inhibition of either the angiotensin II or endothelin-1 systems at both the synthesis and receptor levels blocked the hypertrophic response. The effects of leptin were also completely blocked by the cholesterol-chelating agent methyl-beta-cyclodextrin. Therefore, our study demonstrates stretch-dependent leptin release and a direct hypertrophic effect of leptin on RPV, the latter likely dependent on intact cholesterol-rich membrane microdomains and locally produced paracrine factors.

The Relaxin Gene‐Knockout Mouse: A Model of Progressive Fibrosis

Relaxin is well known for its actions on collagen remodeling. To improve our understanding of the physiologic role(s) of relaxin, the relaxin gene-knockout (RLX-KO) mouse was established by our group and subsequently phenotyped. Pregnant RLX-KO mice underwent inadequate development of the pubic symphysis as well as the mammary glands and nipples compared to wild-type mice, thus preventing lactation. Later studies showed that these deficiencies were associated with increased collagen, primarily in the nipple and vagina. Analysis of male RLX-KO mice also demonstrated inadequate reproductive tract development. The testis, epididymis, and prostate of RLX-KO mice showed delayed tissue maturation and growth associated with increased collagen deposition. In nonreproductive tissues, an age-related increase in interstitial collagen (fibrosis) was also detected in the lung, heart, and kidneys of RLX-KO mice and was associated with organ dysfunction. From 6-9 months of age and onwards, all organs of RLX-KO mice, particularly male mice, underwent progressive increases in tissue weight and collagen content (all P < .05) compared with wild-type animals. The increased fibrosis contributed to bronchiole epithelium thickening and alveolar congestion (lung), atrial hypertrophy and increased ventricular chamber stiffness (heart) in addition to glomerulosclerosis (kidney). Treatment of RLX-KO mice with recombinant human relaxin in early and developed stages of fibrosis caused the reversal of collagen deposition in the lung, heart, and kidneys. Together, these findings suggest that relaxin is a naturally occurring inhibitor of collagen deposition during normal development, aging, and pregnancy and can be used to prevent the progression of fibrosis.

Macroscopic, microscopic and biochemical characterisation of spontaneous colitis in a transgenic mouse, deficient in the multiple drug resistance 1a gene.

1 A novel animal model of spontaneous colonic inflammation, the multiple drug-resistant (mdr1) a(-/-) mouse, was identified by Panwala and colleagues in 1998. The aim of our study was to further characterise this model, specifically by measuring cytokines that have been implicated in inflammatory bowel disease (IBD) (IL-8 and IFN-gamma) in the colon/rectum of mdr1a(-/-) mice, and by determining the sensitivity of these, together with the macroscopic, microscopic and disease signs of colitis, to dexamethasone (0.05, 0.3 and 2 mg kg(-1) subcutaneously (s.c.) daily for 7 days). 2 All mdr1a(-/-) mice had microscopic evidence of inflammation in the caecum and colon/rectum, while control mice with the same genetic background did not. Significant increases in colon/rectum and caecal weights and also in cytokine levels (both IFN-gamma and IL-8) in homogenised colon/rectum were observed in mdr1a(-/-) mice compared to mdr1a(+/+) mice. 3 Dexamethasone reduced the increases in tissue weights and also microscopic grading of colitis severity, but had no effect on IFN-gamma or IL-8. 4 This study supports the similarity of the gastrointestinal inflammation present in mdr1a(-/-) mice to that of human IBD, in particular Crohn's disease. This has been demonstrated at the macroscopic and microscopic levels, and was supported further by elevations in colonic levels of IFN-gamma and IL-8 and the disease signs observed. The incidence of colitis was much higher than previously reported, with all mice having microscopic evidence of colitis. The limited variance between animals in the parameters measured suggests that this model is reproducible.