Relationship between aerobic endurance training and dynamic cerebral blood flow regulation in humans.

The incidence of orthostatic intolerance is elevated in endurance-trained individuals. We sought to test the hypothesis that aerobic endurance training is associated with an attenuated control of the cerebral vasculature. Endurance trained (ET, n = 13) and age-matched untrained (UT, n = 11) individuals (peak O2 consumption, mean ± SEM; 63 ± 1 vs 42 ± 1 mL/min/kg, P < 0.05) were examined while supine and seated upright. Dynamic cerebral autoregulation (CA) was assessed by calculation of the rate of regulation (RoR) from the arterial blood pressure (ABP) and middle cerebral artery (MCA) mean blood velocity (V mean ) responses to a bilateral thigh cuff release, which evoked a transient hypotension. Cerebral oxygenation (oxyhemoglobin; HbO2 ) was determined with near-infrared spectroscopy. When seated upright, cuff release evoked a greater decrease in ABP (P < 0.001), MCA V mean (P = 0.096) and HbO2 (P < 0.001) in ET compared with UT. However, RoR was similar in ET and UT individuals while seated upright (to 0.193 ± 0.039 vs 0.129 ± 0.029/s, P > 0.05), and there was no significant difference in the relative change in RoR from the supine to upright positions (ΔRoR: -65 ± 7 and -69 ± 7%, for ET and UT, respectively). These findings suggest that aerobic endurance training is not associated with an attenuation in dynamic CA.

Transient acid-impairment of growth ability of oral Streptococcus, Actinomyces, and Lactobacillus: a possible ecological determinant in dental plaque.

INTRODUCTION: Dental plaque pH decreases to about 4 through bacterial fermentation of carbohydrates and this low pH is maintained for from several minutes to about an hour. Repeated acidification causes demineralization of the tooth surface, resulting in caries formation. The acidification also influences plaque bacteria. Severe acidification kills bacteria efficiently, while physiological acidification, the condition occurring in plaque, kills bacteria partially and may impair growth ability. We, therefore, investigated the effects of physiological acidification on representative caries-related bacteria. METHODS: Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguinis, Streptococcus oralis, Lactobacillus paracasei, and Actinomyces naeslundii were used. Effects of physiological acidification at pH 4.0 on cell viability and growth ability, as well as the growth rate of these bacteria at pH 4.0-7.0, were investigated. RESULTS: Mutans streptococci and Lactobacillus grew at pH 4.0 but the growth of S. sanguinis and S. oralis ceased below pH 4.2 and pH 4.2-4.4, respectively. Acidification at pH 4.0 for 1 h killed 43-89%, 45% and 35-76% of S. sanguinis, S. oralis, and Actinomyces, respectively. Furthermore, assessment of bacterial growth curves revealed that the growth ability of the surviving cells of S. sanguinis, S. oralis and Actinomyces was impaired, but it was recovered within 2-5 h after the environmental pH had returned to 7.0. The acidification neither killed nor impaired the growth of mutans streptococci and Lactobacillus. CONCLUSIONS: These results indicate that physiological and transient acidification is not sufficient to kill bacteria, but it causes a temporary acid-impairment of their growth ability, which may function as an ecological determinant for microbial composition in dental plaque.

Reduced angiotensin II levels in the cerebrospinal fluid of patients with amyotrophic lateral sclerosis.

BACKGROUND: Recent studies suggest that angiotensin II, a major substrate in the renin-angiotensin system, protects neurons through stimulation of its type 2 receptors. However, quite a few clinical studies of angiotensin II levels have shown their relation to disease severity in neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS). AIMS OF THE STUDY: To clarify the significance of angiotensin II in ALS. METHODS: We assayed angiotensin II concentrations in cerebrospinal fluid (CSF) samples from 23 patients with ALS, nine patients with spinocerebellar degeneration (SCD) and 24 control individuals. We evaluated the disability levels of patients with ALS using the Revised ALS Functional Rating Scale (ALSFRS-R) and calculated the disease progression rate (DPR). RESULTS: CSF angiotensin II levels were significantly lower in the ALS group compared with that in the control group (P = 0.00864), and showed a significant positive correlation with scores on the ALSFRS-R, and a significant negative correlation with the DPR. CONCLUSIONS: In the present study, we reveal for the first time that angiotensin II levels in the CSF from patients with ALS are significantly reduced and significantly associated with disease severity and progression rate. These findings suggest that reduced levels of intrathecal angiotensin II may play a role in ALS.

Characterization of dental pulp stem cells of human tooth germs.

In previous studies, human dental pulp stem cells (hDPSCs) were mainly isolated from adults. In this present study, we characterized hDPSCs isolated from an earlier developmental stage to evaluate the potential usage of these cells for tissue-regenerative therapy. hDPSCs isolated at the crown-completed stage showed a higher proliferation rate than those isolated at a later stage. When the cells from either group were cultured in medium promoting differentiation toward cells of the osteo/odontoblastic lineage, both became alkaline-phosphatase-positive, produced calcified matrix, and were also capable of forming dentin-like matrix on scaffolds in vivo. However, during long-term passage, these cells underwent a change in morphology and lost their differentiation ability. The results of a DNA array experiment showed that the expression of several genes, such as WNT16, was markedly changed with an increasing number of passages, which might have caused the loss of their characteristics as hDPSCs.

ATP-sensitive K+ channels in the hypothalamus are essential for the maintenance of glucose homeostasis.

Glucose-responsive (GR) neurons in the hypothalamus are thought to be critical in glucose homeostasis, but it is not known how they function in this context. Kir6.2 is the pore-forming subunit of K(ATP) channels in many cell types, including pancreatic beta-cells and heart. Here we show the complete absence of both functional ATP-sensitive K+ (K(ATP)) channels and glucose responsiveness in the neurons of the ventromedial hypothalamus (VMH) in Kir6.2-/- mice. Although pancreatic alpha-cells were functional in Kir6.2-/-, the mice exhibited a severe defect in glucagon secretion in response to systemic hypoglycemia. In addition, they showed a complete loss of glucagon secretion, together with reduced food intake in response to neuroglycopenia. Thus, our results demonstrate that KATP channels are important in glucose sensing in VMH GR neurons, and are essential for the maintenance of glucose homeostasis.

Distinct nuclear proteins competing for an overlapping sequence of cyclic adenosine monophosphate and negative regulatory elements regulate tissue-specific mouse renin gene expression.

The mouse renin locus (Ren-1d) exhibits specific patterns of tissue expression. It is expressed in kidney but not submandibular gland (SMG). This locus contains a negative regulatory element (NRE) and a cAMP responsive element (CRE) that share an overlapping sequence. In the kidney, CRE binding proteins (CREB) and NRE binding proteins (NREB) compete for binding to this sequence, with the CREB having a greater affinity. In the SMG, CREB is inactivated by an inhibitory protein, permitting NREB to bind to the sequence, thus inhibiting Ren-1d expression. We hypothesize that the competition between NREB and CREB for this sequence governs tissue-specific expression of mouse renin. We speculate that this may be a general paradigm that determines tissue-specific gene expression.

In vivo identification of a negative regulatory element in the mouse renin gene using direct gene transfer.

DBA/2J mouse contains two renin gene loci (Ren1d and Ren2d). Ren2d but not Ren1d is expressed in submandibular gland (SMG) while both are expressed in the kidney. Based on vitro studies, we have postulated that a negative regulatory element (NRE) in the renin gene promoter is involved in its tissue-specific expression. In this study, we examined the molecular mechanism at the in vivo level using direct gene transfer. Fragments of the Ren1d or Ren2d promoter were fused to a chloramphenicol acetyltransferase (CAT) gene expression vector. These constructs complexed in fusogenic liposomes were injected directly into the mouse SMG or intraarterially into the mouse kidney via the renal artery. The vector containing the CAT exhibited readily detectable in vivo expressions in both SMG and kidney. In the SMG, Ren1d fragment containing the NRE abolished CAT expression while deletion of the NRE restored CAT expression. The homologous fragment from the Ren2d promoter did not inhibit CAT expression while deletion of the 150-bp insertion resulted in the inhibition. Cotransfection of Ren1d construct with Ren1d-NRE oligonucleotides as transcriptional factor decoy restored CAT expression. Contrary to the SMG, transfection with Ren1d fragment-CAT construct or Ren2d fragment-CAT construct into the kidney resulted in similar levels of CAT expression. Interestingly, human c-myc NRE oligonucleotides which share homology with Ren1d-NRE competed effectively with these oligonucleotides for the regulation of Ren1d gene expression in vivo. This NRE sequence is also homologous to silencer elements found in multiple mammalian genes, suggesting the presence of a family of NRE/NRE binding proteins regulating expression of diverse genes.

Expression of the AT2 receptor developmentally programs extracellular signal-regulated kinase activity and influences fetal vascular growth.

Angiotensin II type 2 (AT2) receptor is abundantly expressed in vascular smooth muscle cells (VSMC) of the fetal vasculature during late gestation (embryonic day 15-20), during which the blood vessels undergo remodeling. To examine directly the influence of AT2 receptor expression in the developmental biology of VSMC, we studied cultures of VSMC from fetal and postnatal wild-type (Agtr2(+)) and AT2 receptor null (Agtr2(-)) mice. Consistent with in vivo data, AT2 receptor binding in cultured Agtr2(+) VSMC increased by age, peaking at embryonic day 20, and decreased dramatically after birth. Angiotensin II-induced growth in Agtr2(+) VSMC (embryonic day 20) was increased by the AT2 receptor blocker PD123319, indicating that the AT2 receptors are functional and exert an antigrowth effect in Agtr2(+) VSMC. Growth of VSMC in response to serum decreased age dependently and was higher in Agtr2(-) than in Agtr2(+), inversely correlating with AT2 receptor expression. However, serum-induced growth in Agtr2(+) and Agtr2(-) VSMC and the exaggerated Agtr2(-) VSMC growth was maintained even in the presence of PD123319 or losartan, an AT1 receptor blocker. Moreover, Agtr2(-) VSMC showed greater growth responses to platelet-derived growth factor and basic fibroblast growth factor, indicating that Agtr2(-) cells exhibit a generalized exaggerated growth phenotype. We studied the mechanism responsible for this phenotype and observed that extracellular signal-regulated kinase (ERK) activity was higher in Agtr2(-) VSMC at baseline and also in response to serum. ERK kinase inhibitor PD98059 inhibited both growth and ERK phosphorylation dose-dependently, while the regression lines between growth and ERK phosphorylation were identical in Agtr2(+) and Agtr2(-) VSMC, suggesting that increased ERK activity in Agtr2(-) VSMC is pivotal in the growth enhancement. Furthermore, the difference in ERK phosphorylation between Agtr2(+) and Agtr2(-) was abolished by vanadate but not by okadaic acid, implicating tyrosine phosphatase in the difference in ERK activity. These results suggest that the AT2 receptor expression during the fetal vasculogenesis influences the growth phenotype of VSMC via the modulation of ERK cascade.

Cardiac-specific overexpression of angiotensin II AT2 receptor causes attenuated response to AT1 receptor-mediated pressor and chronotropic effects.

Angiotensin (Ang) II has two major receptor isoforms, AT1 and AT2. Currently, AT1 antagonists are undergoing clinical trials in patients with cardiovascular diseases. Treatment with AT1 antagonists causes elevation of plasma Ang II which selectively binds to AT2 and exerts as yet undefined effects. Cardiac AT2 level is low in adult hearts, whereas its distribution ratio is increased during cardiac remodeling and its action is enhanced by application of AT1 antagonists. Although in AT2 knock-out mice sensitivity to the pressor action of Ang II was increased, underlying mechanisms remain undefined. Here, we report the unexpected finding that cardiac-specific overexpression of the AT2 gene using alpha-myosin heavy chain promoter resulted in decreased sensitivity to AT1-mediated pressor and chronotropic actions. AT2 protein undetectable in the hearts of wild-type mice was overexpressed in atria and ventricles of the AT2 transgenic (TG) mice and the proportions of AT2 relative to AT1 were 41% in atria and 45% in ventricles. No obvious morphological change was observed in the myocardium and there was no significant difference in cardiac development or heart to body weight ratio between wild-type and TG mice. Infusion of Ang II to AT2 TG mice caused a significantly attenuated increase in blood pressure response and the change was completely blocked by pretreatment with AT2 antagonist. This decreased sensitivity to Ang II-induced pressor action was mainly due to the AT2-mediated strong negative chronotropic effect and exerted by circulating Ang II in a physiological range that did not stimulate catecholamine release. Isolated hearts of AT2 transgenic mice perfused using a Langendorff apparatus also showed decreased chronotropic responses to Ang II with no effects on left ventricular dp/dt max values, and Ang II-induced activity of mitogen-activated protein kinase was inhibited in left ventricles in the transgenic mice. Although transient outward K+ current recorded in cardiomyocytes from AT2 TG mice was not influenced by AT2 activation, this study suggested that overexpression of AT2 decreases the sensitivity of pacemaker cells to Ang II. Our results demonstrate that stimulation of cardia AT2 exerts a novel antipressor action by inhibiting AT1-mediated chronotropic effects, and that application of AT1 antagonists to patients with cardiovascular diseases has beneficial pharmacotherapeutic effects of stimulating cardiac AT2.

Relationship between oxygenation in inactive biceps brachii muscle and hyperventilation during leg cycling.

Inactive forearm muscle oxygenation has been reported to begin decreasing from the respiratory compensation point (RCP) during ramp leg cycling. From the RCP, hyperventilation occurs with a decrease in arterial CO2 pressure (PaCO2). The aim of this study was to determine which of these two factors, hyperventilation or decrease in PaCO2, is related to a decrease in inactive biceps brachii muscle oxygenation during leg cycling. Each subject (n = 7) performed a 6-min two-step leg cycling. The exercise intensity in the first step (3 min) was halfway between the ventilatory threshold and RCP (170+/-21 watts), while that in the second step (3 min) was halfway between the RCP and peak oxygen uptake (240+/-28 watts). The amount of hyperventilation and PaCO2 were calculated from gas parameters. The average cross correlation function in seven subjects between inactive muscle oxygenation and amount of hyperventilation showed a negative peak at the time shift of zero (r = -0.72, p<0.001), while that between inactive muscle oxygenation and calculated PaCO2 showed no peak near the time shift of zero. Thus, we concluded that decrease in oxygenation in inactive arm muscle is closely coupled with increase in the amount of hyperventilation.

Species-specificity of a panel of prion protein antibodies for the immunohistochemical study of animal and human prion diseases.

Monoclonal antibodies to the prion protein (PrP) have been of critical importance in the neuropathological characterization of PrP-related disease in men and animals. To determine the influence of species-specific amino-acid substitutions recognized by monoclonal antibodies, and to investigate the immunohistochemical reactivity of the latter, analyses were carried out on brain sections of cattle with bovine spongiform encephalopathy, sheep with scrapie, mice infected with scrapie, and human beings with Creutzfeldt-Jakob disease (CJD) or Gerstmann-Sträussler-Sheinker disease (GSS). Immunoreactivity varied between the antibodies, probably as the result of differences in the amino-acid sequence of the prion protein in the various species. Some monoclonal antibodies against mouse recombinant PrP gave strong signals with bovine, ovine and human PrP(Sc), in addition to murine PrP(Sc), even though the amino-acid sequences determined by the antibody epitope are not fully identical with the amino-acid sequences proper to the species. On the other hand, in certain regions of the PrP sequence, when the species-specificity of the antibodies is defined by one amino-acid substitution, the antibodies revealed no reactivity with other animal species. In the region corresponding to positions 134-159 of murine PrP, immunohistochemical reactivity or species-specificity recognized by the antibodies may be determined by one amino acid corresponding to position 144 of murine PrP. Not all epitopes recognized by a monoclonal antibody play an important role in antigen-antibody reactions in immunohistochemistry. The presence of the core epitope is therefore vital in understanding antibody binding ability.

Interferon-gamma induces AT(2) receptor expression in fibroblasts by Jak/STAT pathway and interferon regulatory factor-1.

The expression of angiotensin II type 2 (AT(2)) receptor is closely associated with cell growth, differentiation, and/or injury. We examined the effect of interferon (IFN)-gamma on AT(2) receptor expression in mouse fibroblast R3T3 cells and demonstrated that IFN-gamma treatment increased the expression of AT(2) receptor mRNA as well as its binding. Interferon regulatory factor (IRF)-1 was induced in mouse fibroblast R3T3 cells after IFN-gamma stimulation, and electrophoretic mobility shift assay showed an increase in IRF-1 binding with the IRF-specific binding sequence in the AT(2) receptor gene promoter region after IFN-gamma stimulation. The IRF-1 gene promoter contains an IFN-gamma-activated sequence (GAS) motif for possible binding of signal transducer(s) and activator(s) of transcription (STAT). Indeed, in R3T3 cells, IFN-gamma treatment resulted in rapid activation of Janus kinase (Jak) 1, Jak2, and STAT1 via tyrosine phosphorylation. Electrophoretic mobility shift assay with the GAS probe revealed increased STAT1 binding to the IRF-1 gene promoter in response to IFN-gamma stimulation. Transfection of GAS-binding oligonucleotides inhibited the effect of IFN-gamma on IRF-1 production, resulting in the AT(2) receptor trans-activation. Taken together, our data show that IFN-gamma upregulates AT(2) receptor expression in R3T3 cells via the activation of the intracellular Jak/STAT pathway and production of IRF-1.

Prion protein interconversions and the transmissible spongiform encephalopathies.

Autocatalytic changes in the conformation and aggregation state of prion protein appear to be fundamental to transmissible spongiform encephalopathies or prion diseases. Here we review the considerable progress that has been made in describing the normal properties of prion protein and the changes that occur during these devastating neurodegenerative diseases.

Deletion of c-myb exon 9 induced by insertion of repeats.

A simple repeat was found to be inserted into exon 9 of the c-myb gene in three out of 20 bovine T lymphomas. The repeat was composed of multiple copies of a 12-nucleotide motif and had no significant homology to the sequences reported so far. Tumor cells containing the repeat expressed two kinds of c-myb mRNA: (1) are that included the repetitive sequence in exon 9, and (2) are that lacked the whole sequence of exon 9. Transfection of an expression vector containing exon and intron sequences and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of the mRNA demonstrated that the insertion of the repeat enhanced exon skipping of the transfected minigene. These observations imply that the insertion of the repeat may enhance exon skipping of the c-myb pre-mRNA. Although the transcription-activating activity by the c-Myb with the repeat was low, that by the c-Myb without exon 9 was three- to eightfold higher than the wild-type c-Myb. These data suggest that insertion of the 12-nucleotide repeat in codon 359 may result in c-Myb proteins having high- and low-transcription-activating activity.

Secondary abnormality of carnitine biosynthesis results from carnitine reabsorptional system defect in juvenile visceral steatosis mice.

We characterized the L-carnitine transport system which is defective in the kidney of juvenile visceral steatosis (JVS) mice by using kidney slices and carnitine-related compounds, and evaluated the influence of the transport defect on the biosynthetic pathway of carnitine. The JVS mouse transport system defect, calculated as the difference in the transport activity between control and JVS mice, was simulated in control by gamma-butyrobetaine (gamma-BB) and acetyl L-carnitine. gamma-BB hydroxylase activity in the liver of JVS mice was double that of control mice, but the hepatic level of gamma-BB in JVS mice was lower than in control mice, suggesting that the conversion of gamma-BB to carnitine is not activated in the liver of JVS mice. JVS mice showed higher fractional excretions not only of L-carnitine but also of gamma-BB and acetyl L-carnitine than control mice, indicating disturbed reabsorption of gamma-BB and acetyl L-carnitine. The disturbed reabsorption of gamma-BB in JVS mice is consistent with the fact that the amount of urinary gamma-BB in JVS mice was four times that of control. The sum of the concentrations of L-carnitine, acetyl L-carnitine and gamma-BB in the urine of JVS mice was not significantly different from that of the control, suggesting no remarkable increase of biosynthesis of gamma-BB and carnitine in JVS mice. All these findings suggest that the carnitine transport system plays a role in the transport of gamma-BB and that carnitine deficiency is aggravated by the disturbed reabsorption of gamma-BB in the kidney.

Abnormal gene expression and regulation in the liver of jvs mice with systemic carnitine deficiency.

Carnitine-deficient jvs mice expressed reduced levels of a group of genes which are preferentially expressed in the liver, including urea cycle enzyme genes (Biochim. Biophys. Acta 1138, 167-171, 1992). The expression of alpha-fetoprotein and aldolase A was elevated, indicating that the liver of jvs mice is undifferentiated or dedifferentiated (FEBS Lett. 311, 63-66, 1992). Studies of the hormone signal transduction pathway showed that serum cortisol and plasma glucagon levels of jvs mice were 2 and 3 times higher, respectively, than those of normal mice, and that the hormone binding activity of glucocorticoid receptor (GR) in the cytosol of jvs liver was 50% of normal mice, which reflected the amount of receptor protein in the cytosol. On the other hand, GR protein accumulated in the nuclear fraction in jvs mice. Exogenously administrated dexamethasone induced carbamoyl phosphate synthetase (CPS) and tyrosine aminotransferase (TAT) mRNAs in jvs mice, indicating that CPS and TAT genes in jvs mice are responsive to induction by glucocorticoid and cAMP. Analysis of transacting factors by gel retardation assay revealed that HNF-1, COUP-TF and SP-1 were detected at almost the same level in the hepatic nuclear fraction of jvs mice as in normal littermates, and C/EBP and CREB were a little higher in jvs mice, suggesting that these factors are probably not targets of jvs mutation causing abnormal gene expression in the liver. On the other hand, AP-1 binding activity was much higher in jvs mice from an early age, preceding the abnormal expression of urea cycle enzyme, and carnitine administration normalized AP-1 binding activity. We suggest that elevated AP-1 binding induced by carnitine deficiency is closely connected with the abnormal gene expression in the liver.

Abnormal expression of urea cycle enzyme genes in juvenile visceral steatosis (jvs) mice.

Juvenile visceral steatosis (jvs) mice from the C3H-H-2 degrees strain have markedly low levels of all the hepatic urea cycle enzymes (Imamura et al. (1990) FEBS Lett. 260, 119-121). The steady state levels of messenger RNA for the four urea cycle enzymes examined and also for albumin and serine dehydratase were severely reduced in the liver. The levels of mRNA for other liver-specific enzymes including aldolase B and phospho enol pyruvate carboxykinase did not vary significantly from normal littermates. As for extrahepatic expression of the urea cycle enzymes, only argininosuccinate synthetase in the kidney was decreased. Nuclear run-on experiments showed reduced transcription of the corresponding genes, which mostly accounts for the low mRNA levels. Furthermore, the time-course of mRNA accumulation from 5 days of age showed that the developmental induction of hepatic carbamyl phosphate synthetase and argininosuccinate synthetase mRNAs was strongly suppressed. These results suggest that jvs affects not only the regulation of the tissue-specific expression of the urea cycle enzymes but also the regulation of their developmental induction.

Primary defect of juvenile visceral steatosis (jvs) mouse with systemic carnitine deficiency is probably in renal carnitine transport system.

We investigated the reabsorptional system for carnitine in the kidney to elucidate the mechanism of carnitine deficiency in juvenile visceral steatosis (jvs) mice. Jvs mice had a higher rate of carnitine excretion at 10 days after birth than the controls, in spite of having no pathological acylcarnitine excretion in the urine. In an experiment to assay the uptake of carnitine using kidney slices, homozygous mutants showed significantly lower rates of Na-dependent carnitine uptake than controls. Heterozygous mice showed values of transport activity intermediate between homozygous mutants and homozygous controls. Scatchard plots (transport activity versus transport activity/carnitine concentration) revealed that the homozygous mutants had a defect in the high affinity site (Km = 58 microM) in the Na-dependent carnitine transport system in the kidney. These results indicate that the primary defect of jvs mice is most probably related to the system for reabsorption of carnitine in the kidney.

Importance of ornithine transcarbamylase (OTC) deficiency in small intestine for urinary orotic acid excretion: analysis of OTC-deficient spf-ash mice with OTC transgene.

We report the effect of the ornithine transcarbamylase (OTC) transgene composed of 1.3 kb of the 5' flanking region of the rat OTC gene fused to rat OTC cDNA on urinary orotic acid excretion in OTC-deficient spf-ash (sparse-fur with abnormal skin and hair) mice during overnight-starvation and nitrogen loading. During starvation, spf-ash mice with about 6% and 2% of control levels of OTC activity in the liver and small intestine excreted a large amount of orotic acid in the urine. Transgenic spf-ash mice with about 10% and 30% of the control OTC activities in the liver and small intestine did not excrete more than the normal level of orotic acid. Accidental parasitization of transgenic spf-ash mice with ticks (Myocoptes musculinus) resulted in decrease of the OTC activities in the liver and small intestine to the levels in spf-ash mice, and increased excretion of orotic acid. During extermination of the ticks, the mice showed varied levels of OTC activity and orotic acid excretion. On nitrogen loading, transgenic spf-ash mice as well as spf-ash mice excreted larger amounts of orotic acid, while control mice showed no increase in its excretion. The levels of urinary orotic acid were inversely correlated to the logarithms of the OTC activities in the liver and small intestine, the correlation being significantly higher with intestinal OTC than with hepatic OTC activity. These results suggest that the level of OTC activity in the small intestine is important for production of orotic acid.

Altered expression of carnitine palmitoyltransferase II in liver, muscle, and heart of mouse strain with juvenile visceral steatosis.

We conducted a quantitative study of the effect of carnitine deficiency on the mRNA level of carnitine palmitoyltransferase II in the liver, muscle and heart of mice with juvenile visceral steatosis, a strain that is systematically deficient in carnitine. The amount of carnitine palmitoyltransferase II mRNA was increased in liver and muscle of homozygotes, as compared with heterozygotes and normal controls, at 2, 4, and 8 wk of age. The mRNA levels of this enzyme were normalized after carnitine administration. The mRNA level of carnitine palmitoyltransferase II in the heart was increased only at 8 wk, and was not affected by carnitine administration. These results suggest that carnitine displays some effect on the mRNA level of the carnitine palmitoyltransferase II gene in liver and muscle, probably through fatty acid metabolic change.