Leucine Supplementation in a Chronically Protein-Restricted Diet Enhances Muscle Weight and Postprandial Protein Synthesis of Skeletal Muscle by Promoting the mTOR Pathway in Adult Rats

Low protein intake causes a decrease in protein deposition in most animal tissues. The purpose of this study was to investigate whether leucine supplementation would increase the synthesis rate of protein and muscle weight in adult rats, which chronically consume only 58.8% of their protein requirements. Thirty-six male Sprague-Dawley rats were assigned to one of three dietary treatments including a 20% casein diet （CON）, a 10% casein ＋ 0.44% alanine diet （R）, and a 10% casein ＋ 0.87% leucine diet （RL）. After a 10 d dietary treatment, plasma amino acid levels were measured after feeding, the gastrocnemius muscles and soleus muscles were harvested and weighed, and the fractional synthesis rate （FSR） and mammalian target of rapamycin （mTOR） signaling proteins in skeletal muscle were measured. Regarding the plasma amino acid level, the RL group had the highest concentration of leucine （P 〈 0.05） and the lowest concentration of isoleucine （P 〈 0.05） among the three groups, and the CON group had a lower concentration of valine （P 〈 0.05） than the R and RL groups. Compared with the R and RE groups, the CON group diet significantly increased （P 〈 0.05） feed intake, protein synthesis rate, and the phosphorylation of eukaryutic initiation factor 4E binding protein 1 （4E-BP1）, and decreased the weight of abdominal adipose. Compared with the R group, the RL group significantly increased in gastrocnemius muscle weight, protein synthesis rate, and phosphorylation of both ribosomal protein $6 kinase 1 （56K1） and 4E-BP1. In conclusion, when protein is chronically restricted in adult rat diets, leucine supplementation moderately improves body weight gain and increases muscle protein synthesis through mTOR activation,

A comprehensive study of long-term skeletal changes after spinal cord injury in adult rats

Spinal cord injury（SCI）-induced bone loss represents the most severe osteoporosis with no effective treatment.Past animal studies have focused primarily on long bones at the acute stage using adolescent rodents. To mimic chronic SCI in human patients, we performed a comprehensive analysis of long-term structural and mechanical changes in axial and appendicular bones in adult rats after SCI. In this experiment, 4-month-old Fischer 344 male rats received a clinically relevant T13 contusion injury. Sixteen weeks later, sublesional femurs, tibiae,and L4 vertebrae, supralesional humeri, and blood were collected from these rats and additional non-surgery rats for micro-computed tomography（m CT）, micro-finite element, histology, and serum biochemical analyses.At trabecular sites, extreme losses of bone structure and mechanical competence were detected in the metaphysis of sublesional long bones after SCI, while the subchondral part of the same bones showed much milder damage. Marked reductions in bone mass and strength were also observed in sublesional L4 vertebrae but not in supralesional humeri. At cortical sites, SCI induced structural and strength damage in both sub- and supralesional long bones. These changes were accompanied by diminished osteoblast number and activity and increased osteoclast number and activity. Taken together, our study revealed site-specific effects of SCI on bone and demonstrated sustained inhibition of bone formation and elevation of bone resorption at the chronic stage of SCI.

Application of Luxol Fast Blue staining in locating the corticospinal tract in adult rats

BACKGROUND: There are many methods for myelin staining, mordant, or oil-soluble dye or the special reaction of osmic acid with lipoid is used according to different principles. The commonly used methods are classic Well staining, classic lithium carbonate-haematine staining, fast green staining, silver staining, etc. Luxol Fast Blue can brightly stain myelin sheath, and has certain specificity. The background can be very clean if there is proper differentiation, whereas Luxol Fast Blue is cheap and convenient to operate, thus it is an ideal staining reagent for routine myelin sheath. OBJECTIVE: To show the corticospinal tract of normal adult rats with Luxol Fast Blue staining method. DESIGN: A repetitive measurement design. SETTINGS: Institute of Nuerobiology, Nantong University; Department of Rehabilitation Medicine, Affiliated Hospital of Nantong University. MATERIALS: Six healthy adult male SD rats of clean degree, weighing averagely 300 g, were provided by the experimental animal center of Nantong University. 1 g/L Luxol Fast Blue solution was provided by Sigma Company; Leica CM1900 cryostat microtome by Leica Company; Leica DMR microscope by Leica Company. METHODS: The experiment was carried out in the Staff Room of Human Anatomy, Nantong University in May 2005. The rats were given intraperitoneal injection of combined anesthetic (2 mL/kg), then the chest was open for perfusing saline and phosphate buffer containing formamint via heart. Brain and spinal cord were removed after 1 hour then fixed, then changed to phosphate buffer (pH 7.4) containing 300 g/L saccharu at 4 ℃, and stayed overnight, tissue blocks at pyramid, decussation of pyramid and cervical, thoracic, lumbar and sacral segments of spinal cord were removed to prepare continuous horizontal frozen sections (30 μm) after sedimentation, the sections were dried at room temperature. The corticospinal tract of normal adult rats were shown with Luxol Fast Blue staining method, and observed under Leica DMR microscope. MAIN OUTCOME MEASURES: Positive fibers in Luxol Fast Blue staining. RESULTS: After the Luxol Fast Blue staining, the labeled myelinated nerve fibers were bright blue. They located in the pyramid, decussation of pyramid and the ventral part of posterior funiculus in cervical, thoracic, lumbar and sacral segments of spinal cord. CONCLUSION: Luxol Fast Blue staining method may manifest the distribution of corticospinal tract with clear distinct in adult rats.

Synergistic effects of brain-derived neurotrophic factor and retinoic acid on inducing the differentiation of bone marrow stromal cells into neuron-like cells in adult rats in vitro

BACKGROUND： Under induction of retinoic acid （RA）, bone marrow stromal cells （BMSCs） can differentiate into nerve cells or neuron-like cells, which do not survive for a long time, so those are restricted to an application. Other neurotrophic factors can also differentiate into neuronal cells through inducing BMSCs; especially, brain-derived neurotrophic factor （BDNF） can delay natural death of neurons and play a key role in survival and growth of neurons. The combination of them is beneficial for differentiation of BMSCs. OBJECTIVE： To investigate the effects of BDNF combining with RA on inducing differentiation of BMSCs to nerve cells of adult rats and compare the results between common medium group and single BDNF group. DESIGN： Randomized controlled animal study SETTING： Department of Neurology, Affiliated Hospital of Xuzhou Medical College MATERIALS： The experiment was carried out in the Clinical Neurological Laboratory of Xuzhou Medical College from September 2003 to April 2005. A total of 24 SD rats, of either gender, 2 months old, weighing 130-150 g, were provided by Experimental Animal Center of Xuzhou Medical College [certification： SYXK （su） 2002-0038]. Materials and reagents： low-glucose DMEM medium, bovine serum, BDNF, RA, trypsin, separating medium of lymphocyte, monoclonal antibody of mouse-anti-nestin, neuro-specific enolase, glial fibrillary acidic protein （GFAP） antibody, SABC kit, and diaminobenzidine （DAB） color agent. All these mentioned above were mainly provided by SIGMA Company, GIBCO Company and Boshide Company. METHODS： Bone marrow of SD rats was selected for density gradient centrifugation. BMSCs were undertaken primary culture and subculture; and then, those cells were induced respectively in various mediums in total of 3 groups, including control group （primary culture）, BDNF group （20 μg/L BDNF） and BDNF＋RA group （20 μg/L BDNF plus 20 μg/L RA）. On the 3^rd and the 7^th days after induction, BMSCs were stained immunocytochemically with nestin （sign of nerve stem cells）, neuron-specific enolase （NSE, sign of diagnosing neurons） and GFAP （diagnosing astrocyte）, and evaluated cellular property. MAIN OUTCOME MEASURES ： Induction and differentiation in vitro of BMSCs in 3 groups RESULTS： （1） Induction and differentiation of BMSCs： Seven days after induction, cells having 2 or more apophyses were observed. Soma shaped like angle or erose form, which were similar to neurons and glial cells having strong refraction. （2） Results of immunocytochemical detection： Three days after induction, rate of positive cells in BDNF＋RA group was higher than that in BDNF group and control group [（86.15±4.58）%, （65.43±4.23）%, （4.18±1.09）%, P 〈 0.01]. Seven days after induction, rate of positive cells was lower in BDNF group and BDNF＋RA group than that in both groups at 3 days after induction [（31.12±3.18）%, （29.35±2.69）%, P 〈 0.01]; however, amounts of positive cells of NSE and GFAP were higher than those at 3 days after induction （P 〈 0.01）; meanwhile, the amount in BDNF＋RA group was remarkably higher than that in BDNF group （P 〈 0.01）. CONCLUSION： Combination of BDNF and RA can cooperate differentiation of BMSCs into neurons and astrocyte, and the effect is superior to single usage of BDNF.

Allograft of developing metanephroi into omenta of cyclosporine-treated adult rats after preservation

To evaluate the animal models and the effect on organogenesis and function of embryonic metanephroi allografted into cyclosporine-treated aduld rats after their preservation in histidine-tryptophan-ketoglutarate (HTK) solution.Methods Whole metanephroi preserved in HTK for 3 days from embryonic day 16 and 17 (E16,E17) of Sprague-Dawley (SD) rats were grouped and allografted into the omenta of cyclosporine-treated SD adult rats which had one kidney resected.E16 metanephroi implanted directly into omenta were used as controls.3 to 4 weeks after implantation,metanephroi allografted in host rats were removed for histopathological and electronic microscopy (EM) examination or anastomosed for renal function measurement 8 weeks later.Results 3 to 4 weeks post-implantation,E16 and E17 metanephroi had formed mature nephrons and collecting ducts with few lympocytic infiltration.EM examination showed they had cellular ultrastructure of normal nephrons and collecting ducts.E16 and E17 metanephroi allografted after preservation for 3 days had no significantly different values of wet weight (P=0.346,P=0.705),urine volume (P=0.396,P=0.687),and creatinine clearances (P=0.469,P=0.543) from those of E16 metanephroi implanted directly.Conclusion E16 and E17 metanephroi allografted into cyclosporine-treated adult rats undergo growth and differentiation and exhibit excretory function after preservation in HTK solution for 3 days.9 refs,1 tabs.

EXPERIMENTAL STUDY IN DIFFERENT EXPRESSION AND ORGANIZATION OF COLLAGEN IN SKIN WOUNDS OF ADULT AND FETAL RATS

Objective To observe the spatial and temporal distribution of collagen in fetal and adult rats wounds. Methods The organization of collagen deposition in fetal and adult rats skin wounds were observed by using van Gieson stain. The methods of immunohistochemistry and in situ hybridization were applied to examine collagen type Ⅰ and Ⅲ peptide and mRNA localization at serial time point during wound healing. Results Collagen type Ⅰ and Ⅲ were present in wounds of both fetal and adult rats, but the timing and pattern of collagen deposition varied. In the fetus, collagen wes detected by 48h postwounding (PW), but uns not present in the adult wounds until 5d PW. N in situ hybridization, signals in the area of the fetal wound were clearly greater and with increased number of cells as compered to that in the adjacent unwounded tissue. Adult rat wounds had evidence in increased signals of procollagen type Ⅰ and Ⅲ production by wound fibroblasts on day 5. Collagen deposited and wes arranged in reticular pattern as that of the nounal in fetal wounds. While in the adult wound, collagen deposited in the fashion of course bundles. bundles Conclusion Fetal rat wounds appeared to produce collagen mainly by an increased number offibroblasts in the area of the wound. In contrast, adult rat wounds underwent fibroblast migration and induction of procollagen mRNA synthesis. Our results Suggest that the deposition of collagen type Ⅰ and Ⅲ is regulated by their gene expression. Chllagen type Ⅲ plays an important role in the arrangement of collagen depoition.

Effects of NGF and TrkA on GAP-43^+ nerve regeneration in rat autotransplanted splenic tissue

Objective:To study the time-course of the regeneration of GAP-43+ nerve, and the effects of NGF and TrkA on this process. Methods: Adult Wistar rats underwent splenectomy and splenic autotransplantation, or sham-operation. On day 7, 14, 30, 60, 90, 120, and 180 after surgery, the density of GAP-43+ nerve fibers in spleen tissues were measured with the immunohistochemistry followed by computer image analysis. The expressions of GAP-43, NGF and TrkA were determined with in situ hybrdization, and their mRNA levels were detected with RT-PCR and image analysis qualification. Results: (1) The GAP-43+ nerve fibers began their regeneration on 30 d after operation and extended from greater omentum into splenic autotransplants. Density of the nerve fibers gradually became greater and almost normal 180 d after operation. (2) In splenic autografts, the mRNA expression of GAP-43, NGF and TrkA appeared on day 30 after the operation, gradually reached the peak on day 90. Conclusion: The renascent GAP-43+ nerve fibers may come from the greater omentum packaging the splenic autografts and NGF and TrkA can promote the nerval regeneration in the autotransplant spleen tissues.

Effects of intra-gastric beta-casomorphin-7 on somatostatin and gastrin gene expression in rat gastric mucosa

AIM： To investigate the in vivo effect of beta-casomorphin-7on the regulation of gastric somatostatin and gastrin messenger RNA in rat gastric mucosa.METHODS： Somatostatin and gastrin mRNA were quantified by RT-PCR and in situ hybridization （ISH）in 24 rats. The rats were divided into three treatment groups： basal diet ＋ physiological saline （n = 8）, basal diet ＋ beta-casomorphin-7 （7.5 × 10^-7 mol） （n = 8）,and basal diet ＋ poly-Gly-7 （containing equal mol of N with 7.5 × 10^-7 mol beta-casomorphin-7） （n = 8）.After oral administration for 30 days, rats were killed by exsanguinations.RESULTS： After intra-gastric administration of betacasomorphin-7 for 30 d, gastrin mRNA increased by 52.8% （P 〈 0.05, n = 8）, and somatostatin mRNA levels decreased by 30.7% compared with the controls （P 〈0.01, n = 8）. No significant differences in the expression of the two genes were observed in the poly-Gly-treated group, although gastrin mRNA expression was elevated by 35.6% as against the control group （P = 0.15, n =8）. The long-term oral administration of a casomorphin solution significantly decreased the even gray of D-cells,but did not lower the number of D-cells both in the antrum and fundus. Interestingly, the number of G-cells increased in the antrum and fundus, but its average density was augmented only in the antrum.CONCLUSION： Beta-casomorphin-7 is capable of modulating gene expression of the regulatory peptides from G and D cells. Data from in situ hybridization studies indicate that beta-casomorphin-7 affects gastrin gene expression indirectly by means of the paracrine action of somatostatin, and depends on its intrinsic molecular function.

Expression of type-Ⅰ collagen and matrix metalloproteinase-9 mRNA in bone of castrated adult female rats:effects of estrogen

Abstract Objectives To elucidate the molecular changes of bone collagen during the development of postmenopausal osteoporosis and to investigate the molecular effects of estrogen replacement. Methods An adult ovariotomy rat model was used. Type Ⅰ collagen and matrix metalloproteinase 9 (MMP 9) expressions in bone tissues of rats treated by sham surgery (SH), bilateral ovariotomy (OVX) and OVX with estradiol (OVX E2) were analysed at mRNA level by using dot blot technique. The distribution of mRNA of these two genes in bone tissues was studied by in situ hybridization. Results The expression levels of both type Ⅰ collagen and MMP 9 in bone tissues of OVX rats were higher than those of SH group, while treated with estradiol, the expression of both genes declined to some degree. In situ hybridization showed that type Ⅰ collagen mRNA located in osteoblasts, whereas MMP 9 was mainly expressed in osteoclasts, some lining cells on bone surface, and some mononuclear cells in bone marrow. Conclusions The reduction of high bone turnover in osteoporotic bone tissues induced by estrogen replacement may result from alterations in gene expression related to bone formation and bone resorption. These alterations are consistent with the changes observed previously by histomorphometry and biochemical markers of bone metabolism on OVX animals and postmenopausal osteoporosis.