Sex-matched Control Rats Research Articles

Overexpression of the receptor for advanced glycation end-products in the auditory cortex of rats with noise-induced hearing loss

BackgroundThe receptor for advanced glycation end-products (RAGE) is involved in neuroinflammation. This study investigated the changes in RAGE expression following noise-induced hearing loss.MethodsThree-week-old female Sprague–Dawley rats were exposed to 115 dB SPL white noise for 4 h daily for 3 d (noise group, n = 16). In parallel, age and sex-matched control rats were raised under standard conditions without noise exposure (control group, n = 16). After 2 h (noise immediate, n = 8) and 4 wk (noise 4-week, n = 8) of noise exposure, the auditory cortex was harvested and cytoplasmic and nuclear fractions were isolated. The gene expression levels of tumor necrosis factor alpha (TNF-α), interleukin 6 (IL6), interleukin 1 beta (IL1β), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and RAGE were evaluated using real-time reverse transcription polymerase chain reaction. The protein expression levels of nuclear RAGE and cytosolic RAGE were evaluated using western blotting. Additionally, matrix metalloproteinase 9 (MMP9) was pharmacologically inhibited in the noise immediate group, and then nuclear and cytosolic RAGE expression levels were evaluated.ResultsThe noise immediate and noise 4-week groups exhibited increased auditory thresholds at 4, 8, 16, and 32 kHz frequencies. The genes encoding the pro-inflammatory cytokines TNF-α, IL6, IL1β, and NF- κB were increased 3.74, 1.63, 6.42, and 6.23-fold in the noise immediate group, respectively (P = 0.047, 0.043, 0.044, and 0.041). RAGE mRNA expression was elevated 1.42-fold in the noise 4-week group (P = 0.032). Cytosolic RAGE expression was increased 1.76 and 6.99-fold in the noise immediate and noise 4-week groups, respectively (P = 0.04 and 0.03). Nuclear RAGE expression was comparable between the noise and control groups. matrix metalloproteinase 9 (MMP9) inhibition reduced cytosolic RAGE expression in the noise immediate group (P = 0.004).ConclusionsNoise exposure increased the expression of cytosolic RAGE in the auditory cortex and upregulated pro-inflammatory genes, but this response could be alleviated by MMP9 inhibition.

Ion-current-based Proteomic Profiling of the Retina in a Rat Model of Smith-Lemli-Opitz Syndrome

Smith-Lemli-Opitz syndrome (SLOS) is one of the most common recessive human disorders and is characterized by multiple congenital malformations as well as neurosensory and cognitive abnormalities. A rat model of SLOS has been developed that exhibits progressive retinal degeneration and visual dysfunction; however, the molecular events underlying the degeneration and dysfunction remain poorly understood. Here, we employed a well-controlled, ion-current-based approach to compare retinas from the SLOS rat model to retinas from age- and sex-matched control rats (n = 5/group). Retinas were subjected to detergent extraction and subsequent precipitation and on-pellet-digestion procedures and then were analyzed on a long, heated column (75 cm, with small particles) with a 7-h gradient. The high analytical reproducibility of the overall proteomics procedure enabled reliable expression profiling. In total, 1,259 unique protein groups, ~40% of which were membrane proteins, were quantified under highly stringent criteria, including a peptide false discovery rate of 0.4%, with high quality ion-current data (e.g. signal-to-noise ratio ≥ 10) obtained independently from at least two unique peptides for each protein. The ion-current-based strategy showed greater quantitative accuracy and reproducibility over a parallel spectral counting analysis. Statistically significant alterations of 101 proteins were observed; these proteins are implicated in a variety of biological processes, including lipid metabolism, oxidative stress, cell death, proteolysis, visual transduction, and vesicular/membrane transport, consistent with the features of the associated retinal degeneration in the SLOS model. Selected targets were further validated by Western blot analysis and correlative immunohistochemistry. Importantly, although photoreceptor cell death was validated by TUNEL analysis, Western blot and immunohistochemical analyses suggested a caspase-3-independent pathway. In total, these results provide compelling new evidence implicating molecular changes beyond the initial defect in cholesterol biosynthesis in this retinal degeneration model, and they might have broader implications with respect to the pathobiological mechanism underlying SLOS.

Expression and mechanical modulation of matrix metalloproteinase-1 and -2 genes in facial and cranial sutures

Craniofacial sutures create a soft tissue interface between various calvarial and facial bones. Facial and cranial sutures show differences in their surrounding anatomical structures and local mechanical strain environments. Despite previous attempts to identify the expression of matrix metalloproteinase genes (MMPs) in cranial sutures, little is known regarding whether facial and cranial sutures differ in MMP expression. We have investigated the expression of MMP-1 and MMP-2 in the pre-maxillomaxillary suture (PMS; facial suture) and the frontoparietal suture (FPS; cranial suture) in 32-day-old rats with or without the application of cyclic loading. Expression of MMP-1 and MMP-2 was detected by the reverse transcription/polymerase chain reaction technique. At 32 days of postnatal development (n=6), both MMP-1 and MMP-2 were reproducibly expressed in the facial PMS, in comparison with negligible MMP-1 and MMP-2 expression in the cranial FPS. In six age- and sex-matched control rats, cyclic loading at 4 Hz and 1000 mN was applied to the maxilla for two 20-min episodes within a 12-h interval. In some (but not all) cases, cyclic loading induced marked expression of MMP-1 and MMP-2 in the PMS and FPS in comparison with corresponding non-loaded controls. These data confirm our previous finding that short doses of cyclic loading upregulate MMP-2 expression in craniofacial sutures and suggest the possibility that facial and cranial sutures differ in matrix degradation rates during postnatal development.

Islet neogenesis is stimulated by brief occlusion of the main pancreatic duct

Current models of islet neogenesis either cause substantial pancreatic damage or continuously stimulate the pancreas, making these models unsuitable for the study of early events that occur in the neogenic process. We aimed to develop a method where the initial events that culminate in increased pancreatic endocrine mass can be studied. Ten 12-week-old female Wistar rats were subjected to a midline laparotomy, the pancreas was isolated and the main pancreatic duct was occluded for 60 seconds. The pancreas was released and carefully relocated within the abdomen. Ten age-, strain- and sex-matched control rats were subjected to a sham operation. The animals were killed 56 days post occlusion, and the pancreata excised and fixed for histological analysis. Body, pancreatic and hepatic weights were noted at termination and serum was taken for analysis. The endocrine-to-exocrine ratio was calculated and the number of endocrine cells in each islet from the sectioned pancreata was counted. Occlusion of the main pancreatic duct for 60 seconds results in an increase in endocrine mass by 80% 56 days post occlusion. This constitutes an increase in endocrine units (1-6 cells), and in small (7-30 cells), medium (31-60 cells) and large (> 60 cells) islets by 85%, 96%, 95% and 71% respectively. Brief occlusion of the main pancreatic duct results in an increase in pancreatic endocrine mass. An increase in endocrine units and small islets is indicative of islet neogenesis. Therefore, owing to the briefness of the stimulation, this model can therefore be used to study the initial events that occur during the neogenic process.

Increased density of hippocampal kainate receptors but normal density of NMDA and AMPA receptors in a rat model of prenatal protein malnutrition.

The postnatal development of excitatory amino acid receptor types including kainate, N-methyl-D-aspartate (NMDA), and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) was assessed in the hippocampus, entorhinal cortex, and adjacent neocortex in normal and prenatally protein malnourished rats ages 15, 30, 90, and 220 postnatal days by quantitative autoradiography. Tritiated ligands used to measure binding site density were (3)[H]kainate, (3)[H]MK-801, and (3)[H]AMPA, respectively. Kainate receptors showed statistically significant increases in binding density in stratum lucidum of CA3 (hippocampal mossy fiber zone) in 90- and 220-day-old malnourished rats compared with age- and sex-matched controls but not in 15- or 30-day-old malnourished rats. Compared with previous anatomic studies, these results are mostly in agreement with a significantly decreased hippocampal mossy fiber plexus in 15-, 90-, and 220-day-old rats but not in 30-day-old rats. These results suggested that the increased density of postsynaptic kainate receptors located mainly on proximal apical dendrites of CA3 pyramidal cells may be compensatory to decreased glutamate release due to the reduction in mossy fiber plexus. In contrast, the density of putative NMDA and AMPA receptors quantified in prenatally malnourished rats was comparable to the density quantified in age- and sex-matched control rats, as were all three receptor types in entorhinal cortex and adjacent neocortex. Thus, the selectivity of the compensation of (3)[H]kainate-labeled mossy fiber plexus in adult but not in early postnatal developing malnourished rats may help ensure continued breeding and survival of the species under otherwise adverse environmental conditions.

Myocardial fibrosis associated with aldosterone or angiotensin II administration: attenuation by calcium channel blockade.

Chronic administration of either angiotensin II (Ang II) or aldosterone (ALDO) leads to myocardial fibrosis. Myofibroblasts (myoFb) play a major role in collagen accumulation at sites of tissue repair. Pathophysiologic bases of cardiac fibrosis in such chronic primary or secondary hyperaldosteronism are under investigation. In vitro studies have shown that Ang II and ALDO each increase intracellular calcium and this second messenger is involved in altered fibroblast collagen turnover and growth. In the present study, we tested our hypothesis that calcium channel blockade would attenuate myocardial fibrosis that accompanies administration of either circulating Ang II or ALDO. Five animal groups were studied: (1) untreated age- and sex-matched control rats; (2) intact rats receiving Ang II (75 ng/min) for 2 weeks; (3) rats receiving Ang II plus mibefradil (30 mg/kg/day p.o.), a calcium channel blocker, for 2 weeks; (4) uninephrectomized rats receiving ALDO (0.75 microgram/h) together with a high salt diet for 6 weeks; and (5) uninephrectomized rats receiving ALDO and high salt diet plus mibefradil. Myocardial fibrosis was assessed by hydroxyproline concentration and interstitial and perivascular collagen volume fraction examined by videodensitometry on heart sections stained with collagen-specific picrosirius red. MyoFb were identified by immunohistochemical alpha-smooth muscle actin (SMA) labeling. ACE binding was determined by in vitro quantitative autoradiography. Compared to controls, in rats receiving either Ang II or ALDO we found: (1) myocardial fibrosis, expressed as microscopic scars, and perivascular fibrosis in both right and left ventricles with increased (P<0.05) hydroxyproline concentration and collagen volume fraction; (2) myoFb at sites of fibrosis, where high ACE binding density was also present; and (3) hydroxyproline concentration and collagen volume fraction were significantly (P<0.05) attenuated and the extent of alpha-SMA labeling and ACE binding density were each markedly (P<0.01) reduced in rats receiving either hormone plus mibefradil. This study therefore suggests calcium may modulate fibrous tissue formation in rat models of hyperaldosteronism by altering MyoFb collagen turnover and cell growth. It further is our contention that these findings implicate calcium as a signal used by effector hormones of the RAAS to promote tissue repair and that calcium channel blockade may offer advantage as a cardioprotective strategy in this setting.

Neuropathology and blood flow of nerve, spinal roots and dorsal root ganglia in longstanding diabetic rats.

Vascular perfusion and neuropathologic evaluation of the lumbar spinal roots and dorsal root ganglia (DRG) were studied in rats with longstanding (duration 12-15 months) streptozotocin-induced diabetes and age- and sex-matched control rats. We also undertook nerve conduction studies including F-wave recordings and measured blood flow in sciatic nerve, DRG, and superior cervical ganglion (SCG). Light microscopically, changes of the myelin sheath in the dorsal and ventral roots and vacuolated cells in the DRG were the major findings, being significantly higher in diabetic rats than in control rats. The effects of the diabetic state on myelin splitting were greater in the dorsal than ventral roots. Electron microscopic studies revealed a gradation of changes in myelin from mild separation to severe ballooning of myelin with relative axonal sparing. DRG cells showed vacuoles of all sizes with cristae-like residues, suggestive of mitochondria. These findings suggest that diabetes mellitus has a dual effect: it accelerates the normal age-related degenerative changes in the spinal roots and DRG, and it also has a selective effect on the sensory neuron. Nerve conduction studies showed markedly reduced conduction velocities in the distal nerve segments and prolonged F-wave latency and proximal conduction time despite the shorter conduction pathway in diabetic rats. Blood flow, which was measured using iodo[14C]antipyrine autoradiography, was significantly reduced in the sciatic nerves, DRG, and SCG of diabetic rats. We suggest that the combination of hyperglycemia and ischemia results in oxidative-stress and a predominantly sensory neuropathy.

Function of the rat salivary glands after exposure to inorganic mercury

In spite of many studies on the toxicity of mercury, very little is known about the effects of mercury on the function of exocrine glands. In the present paper selected functions of Sprague-Dawley rat salivary glands were studied after the exposure of the animals to inorganic mercury at two different doses; 3.25 mg/kg body weight given during 25 days and 7.0 mg/kg body weight given during 27 days. The function of the salivary glands was estimated by saliva secretion rate, secretion of electrolytes, proteins and biosynthesis of glycoproteins. The function was compared between mercury exposed rats and age and sex matched control rats that were given injections with equal volumes of 0.154 mol/l NaCl on the same time schedule. In the present study we report that no significant effect on saliva secretion rate, concentrations of salivary constituents or biosynthesis of glycoproteins in the salivary glands could be observed in rats as a result of mercury exposure at two levels that gave 30 or 60 times higher serum mercury concentrations than in the majority of the Swedish population.

Persistence of metabolic consequences in the progeny of rats fed a HC formula in their early postnatal life

First-generation (1-) male and female rat pups were either reared artificially on a high-carbohydrate (HC) or a high-fat (HF) formula or nursed by mother (MF) from day 4 and weaned onto a stock diet on day 24. 1-HC rats compared with sex-matched control rats (1-HF and 1-MF) were hyperinsulinemic and mildly obese by day 60. We investigated the effect of maternal hyperinsulinemia on the second generation (2-) by intragroup breeding. The 2-HC male and female rats were hyperinsulinemic on day 45, had significantly increased growth rate from approximately day 60 onward, and became obese as evidenced by increased adipose tissue mass due to hypertrophy on day 100. The lipogenic capacity of liver and adipose tissues was significantly higher in the 2-HC than in control rats. Thus the metabolic changes that occurred in the first-generation rats fed a HC formula during early postnatal life not only persisted into their adult life but were also passed on to the next generation.

Reduction of heparan sulphate-associated anionic sites in the glomerular basement membrane of rats with streptozotocin-induced diabetic nephropathy.

Heparan sulphate-associated anionic sites in the glomerular basement membrane were studied in rats 8 months after induction of diabetes by streptozotocin and in age- adn sex-matched control rats, employing the cationic dye cuprolinic blue. Morphometric analysis at the ultrastructural level was performed using a computerized image processor. The heparan sulphate specificity of the cuprolinic blue staining was demonstrated by glycosaminoglycan-degrading enzymes, showing that pretreatment of the sections with heparitinase abolished all staining, whereas chondroitinase ABC had no effect. The majority of anionic sites (74% in diabetic and 81% in control rats) were found within the lamina rara externa of the glomerular basement membrane. A minority of anionic sites were scattered throughout the lamina densa and lamina rara interna, and were significantly smaller than those in the lamina rara externa of the glomerular basement membrane (p<0.001 and p<0.01 for diabetic and control rats, respectively). Diabetic rats progressively developed albuminuria reaching 40.3 (32.2-62.0) mg/24 h after 8 months in contrast to the control animals (0.8 (0.2-0.9) mg/24 h, p<0.002). At the same time, the number of heparan sulphate anionic sites and the total anionic site surface (number of anionic sites x mean anionic site surface) in the lamina rara externa of the glomerular basement membrane was reduced by 19% (p<0.021) and by 26% (p<0.02), respectively. Number and total anionic site surface in the remaining part of the glomerular basement membrane (lamina densa and lamina rara interna) were not significantly changed. We conclude that in streptozotocin-diabetic rats with an increased urinary albumin excretion, a reduced heparan sulphate charge barrier/density is found at the lamina rara externa of the glomerular basement membrane.

Effects of diabetes, insulin treatment, and osmolality on contractility of isolated rat resistance arteries.

The effects of osmolality, diabetes, and insulin-treatment on microvascular contractility were examined in mesenteric resistance arteries (internal diameter approximately 250 microns) isolated from streptozotocin-induced diabetic rats, streptozotocin-induced diabetic rats treated with 1-3 U insulin/day during the week before being killed, and age- and sex-matched control rats. Vessels were mounted in a microvascular myograph for isometric tension recording and responses were generated in physiological salt solutions with varying amounts of glucose or mannitol added. The passive response (expressed as the diameter the vessels would maintain if relaxed and exposed to a transmural pressure of 100 mmHg), the maximal response to noradrenaline, and the response produced by partial depolarization with 50 mmol/l potassium were not dependent on glucose or mannitol concentrations of the bathing medium; also, these responses were not dissimilar in vessels from the three groups of rats tested. The sensitivity to noradrenaline, however, was inversely related to the concentration of glucose (P < 0.01) and mannitol (P < 0.01) of the bathing medium without significant differences in slopes of regression lines between rat groups. Moreover, vessels from streptozotocin-induced diabetic rats were less sensitive to noradrenaline than were vessels from control rats; vessels from insulin-treated streptozotocin-induced diabetic animals had the lowest sensitivity to noradrenaline. These data suggest that osmolality, diabetes, and insulin-treatment independently affect microvascular sensitivity to the endogenous neurotransmitter, noradrenaline.

Reduction of heparan sulphate-associated anionic sites in the glomerular basement membrane of rats with streptozotocin-induced diabetic nephropathy

Heparan sulphate-associated anionic sites in the glomerular basement membrane were studied in rats 8 months after induction of diabetes by streptozotocin and in age- and sex-matched control rats, employing the cationic dye cuprolinic blue. Morphometric analysis at the ultrastructural level was performed using a computerized image processor. The heparan sulphate specificity of the cuprolinic blue staining was demonstrated by glycosaminoglycan-degrading enzymes, showing that pretreatment of the sections with heparitinase abolished all staining, whereas chondroitinase ABC had no effect. The majority of anionic sites (74% in diabetic and 81% in control rats) were found within the lamina rara externa of the glomerular basement membrane. A minority of anionic sites were scattered throughout the lamina densa and lamina rara interna, and were significantly smaller than those in the lamina rara externa of the glomerular basement membrane (p<0.001 and p<0.01 for diabetic and control rats, respectively). Diabetic rats progressively developed albuminuria reaching 40.3 (32.2–62.0) mg/24 h after 8 months in contrast to the control animals (0.8 (0.2–0.9) mg/24 h, p<0.002). At the same time, the number of heparan sulphate anionic sites and the total anionic site surface (number of anionic sites × mean anionic site surface) in the lamina rara externa of the glomerular basement membrane was reduced by 19% (p<0.021) and by 26% (p<0.02), respectively. Number and total anionic site surface in the remaining part of the glomerular basement membrane (lamina densa and lamina rara interna) were not significantly changed. We conclude that in streptozotocin-diabetic rats with an increased urinary albumin excretion, a reduced heparan sulphate charge barrier/density is found at the lamina rara externa of the glomerular basement membrane.

Toward novel antirejection strategies: In vivo immunosuppressive properties of CTLA4Ig

Allograft rejection is a process that depends on T cell receptor-ligand interaction and costimulatory signals generated when accessory molecules binds to their ligands, such as CD28 to the B7 molecules. We investigated the possibility that B7 blockade in vivo by the soluble CD28 receptor homolog CTLA4Ig modulates rejection process in a rat model of kidney allograft. Lewis rats orthotopically transplanted with MHC incompatible kidney from Brown-Norway rats were given an intraperitoneal injection of CTLA4Ig (0.2 or 0.5 mg/day) or a nonspecific immunoglobulin for seven days, starting the day of transplant. While control rats rejected the graft within 10 days, all animals given CTLA4Ig had a prolonged kidney allograft survival, independently from the dose of the fusion protein employed. Actually, at the dose of 0.2 mg/day kidney grafts survived 36 to 50 days (median 44 days), while with the highest dose graft survival was 40 to 60 days (median 50 days). In all CTLA4Ig-treated rats renal grafts were well functioning as documented by serum creatinine concentrations comparable to age- and sex-matched control rats 30 days after transplant. At this time in vitro mixed lymphocyte culture (MLR) experiments showed a significant reduction of proliferation of peripheral blood lymphocytes from CTLA4Ig-treated rats when challenged with BN but not third party Wistar Furth lymphocytes. We have also shown that combining a short course of CTLA4Ig (0.2 mg/day) with a dose of cyclosporine (CsA) low enough to fail to inhibit graft rejection allowed indefinite engraftment of kidney allograft without the need of continuous immunosuppression.(ABSTRACT TRUNCATED AT 250 WORDS)

Fibrosis and myocardial ACE: Possible substrate and independence from circulating angiotensin II

In order to determine the relation between myocardial fibrosis and (1) angiotensin converting enzyme (ACE) binding density, (2) receptor binding of ACE-related peptides, angiotensin II (AngII) and bradykinin (BK), and (3) the regulation of myocardial ACE by circulating Ang II, we used in vitro quantitative autoradiography to localize and assess ACE ([ 125I]351A), AngII receptor ( 125I[Sar 1, IIe 8]AngII), and BK receptor ([ 125I]Tyr 8) binding densities in the rat myocardium. The experimental groups were (1) AngII (9 μg/h subcutaneously) or aldosterone (0.75 μg/h subcutaneously in uninephrectomized rats on a high-sodium diet) administered by implanted minipump to chronically increase or decrease circulating AngII, respectively, (2) unoperated, untreated age- and sex-matched control rats, and (3) age- and sex-matched uninephrectomized control rats on a high-sodium diet. In the same heart studied at 2, 4, and 6 weeks of hormone treatment, serial sections were assessed for myocardial (hematoxylin and eosin) and fibrillar collagen (picrosirius red) morphology. The authors found that (1) marked ACE binding was coincident with sites of fibrous tissue that appeared in both ventricles as either a perivascular fibrosis of intramyocardial coronary arterioles or microscopic scarring in response to AngII or aldosterone infusion, (2) ACE binding was independent of circulating AngII, (3) BK, not AngII, receptor binding density was markedly increased at fibrous tissue sites, and (4) high-density ACE and BK receptor binding were anatomically coincident. Thus, in these experimental models, ACE is related to fibrous tissue formation where it may use BK, not angiotensin I, as a substrate, and its binding density is independent of circulating AngII.

Influence of Orotic Acid on Multistage Hepatocarcinogenesis in the Rat: Resistance of Hepatocytes from Nodules to the Mitoinhibitory Effects of Orotic Acid

This study was designed to determine whether hepatocytes from hepatic nodules are resistant to the mitoinhibitory effects of orotic acid. Hepatic nodules were initiated in Fischer 344 male rats with 1,2-dimethylhydrazine.2HCl (100 mg/kg ip) given 16 hr after two thirds partial hepatectomy and promoted by feeding a diet containing 1% orotic acid. Eight to 9 months later, when persistent nodules had developed, the rats were taken off the orotic acid diet and maintained on a semisynthetic basal diet for 2 to 5 weeks. The effect of orotic acid on the DNA synthesis in the hepatocytes isolated from hepatic nodules and from the surrounding nonnodular liver and from the age- and sex-matched control rats was studied. The results indicated that a dose of orotic acid (120 microM) that almost completely inhibited the transforming growth factor-alpha-induced DNA synthesis in hepatocytes from nonnodular surrounding liver and from age- and and sex-matched control liver could not inhibit the DNA synthesis in hepatocytes from hepatic nodules. These results are consistent with the postulate that orotic acid may promote liver carcinogenesis by a differential mitoinhibition of normal hepatocytes while permitting the initiated hepatocytes to respond to growth stimuli and form hepatic nodules. However, it needs to be determined whether differential mitoinhibition of normal hepatocytes is the mechanism by which orotic acid promotes liver carcinogenesis.

Effect of Diabetes on Fast Response to Norepinephrine in Rat Aorta

The fast and slow components of the mechanical response to 1 microM norepinephrine (NE) were measured in aortic rings isolated from eight spontaneously diabetic rats, six streptozocin-induced diabetic (STZ-D) rats, six STZ-D rats treated with 2.5 U insulin/day during the 4 days before being killed, and six age- and sex-matched control rats. The total contraction to NE (i.e., the sum of fast and slow components) was similar in the four groups: spontaneously diabetic, 16.53 +/- 1.72 mN; STZ-D, 15.68 +/- 1.41 mN; insulin-treated, 16.17 +/- 2.05 mN; and control, 15.27 +/- 0.96 mN (NS). The fast component, measured graphically in a total contraction in 1.35 mM Ca, was greater in spontaneously diabetic (12.61 +/- 1.07 mN, P less than 0.05) and STZ-D (12.25 +/- 0.89 mN, P less than 0.05) rats compared with control (9.14 +/- 0.74 mN) or insulin-treated (8.58 +/- 1.23 mN) rats. The same increase of the fast component was detectable after 3 min of incubation in Ca-free medium + 2 mM EGTA (control 6.54 +/- 0.47 mN, spontaneously diabetic 9.07 +/- 0.76 mN, P less than 0.05; STZ-D 8.82 +/- 0.72 mN, P less than 0.05), and it was also abolished by insulin treatment (insulin-treated 6.29 +/- 0.36 mN). We conclude that the diabetic state increases the fast component of NE-induced contraction either in the absence or presence of Ca in the medium. This suggests that such an increase depends on a larger release of Ca from intracellular stores.

Expression of N-acetylglucosaminyltransferase III in hepatic nodules generated by different models of rat liver carcinogenesis

Our earlier studies revealed that N-acetylglucosaminyltransferase III (GnTase III), which catalyzes the insertion of a bisecting N-acetylglucosamine (bi-Gn) in the complex-type N-linked glycans of cellular glycoproteins, is present in hepatic nodules promoted by the orotic acid model. Neither the bi-Gn residues nor the activity of GnTase III is detectable in normal livers and in the surrounding non-nodular liver of the rat. The present study was designed to find out whether an expression of activity of GnTase III is a phenotypic property characteristic of hepatic nodules or simply unique to nodules produced by the orotic acid model. Fischer male 344 rats were initiated with two different carcinogens namely 1,2-dimethyl-hydrazine or diethylnitrosamine and promoted by other models such as the resistant hepatocyte model and the choline deficient diet model, in addition to the orotic acid model. The hepatic nodules generated by these three different models and hepatocellular carcinomas exhibited significant levels of activity of GnTase III while non-nodular surrounding liver, regenerating liver after 2/3 partial hepatectomy or livers of age and sex matched control rats, had no detectable activity. The detection of the activity of GnTase III in nodules and in cancer is in agreement with the presence of bi-Gn residues reported in gamma-glutamyltranspeptidase of cancer tissues of rats. These results are consistent with the conclusion that the expression of GnTase III is activated during hepatocarcinogenesis and is not related to any particular initiator or promoter.

Effects of irradiation on cortical bone and their time-related changes. A biomechanical and histomorphological study.

The effects of high-dose irradiation on the biomechanical and morphological properties of cortical bone and their time-related changes were studied in male Sprague-Dawley rats. A single fraction of 3500 rads was applied to the middle part of the right thigh. Age and sex-matched control rats that did not receive radiation were used for comparison. Two weeks after irradiation, the animals had lost weight and disappearance of bone cells, shrunken osteocytes, and significantly decreased bone-turnover activities were noted. The bone marrow showed reduced hematopoietic elements and sinusoids with increased fat. No change in the torsional strength and geometric properties of bone was noted at this time. Six to ten weeks after irradiation, histopathological abnormalities of the bone persisted, and there was an accelerated resorption process. However, significant increases in the strength and cortical area of bone appeared only in the non-irradiated, contralateral femur. On the irradiated side, decreased cortical area and increased porosity of bone were found at fourteen to eighteen weeks when compared with the control rats. Other histomorphological properties, such as bone porosity, osteocyte count, and periosteal new-bone formation, appeared to recover eighteen weeks after irradiation, as they became similar to the values for the age-matched normal control rats.