Identification of possible quantitative trait loci responsible for hyperglycaemia after 70% pancreatectomy using a spontaneously diabetogenic rat

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an animal model for obese-type non-insulin-dependent diabetes mellitus (NIDDM) in humans. The OLETF rat exhibits sustained hyperglycaemia after partial pancreatectomy, while the normal control rat does not. This difference is thought to be genetically determined and to be caused by impairment of beta-cell regrowth, a possible event involved in the pathogenesis of NIDDM. Our investigation was designed to identify quantitative trait loci (QTL) responsible for post-pancreatectomy hyperglycaemia by performing a genome-wide scan in an F2 intercross obtained by mating the OLETF and Fischer-344 (F344) rats. We have identified three possible QTL on rat chromosomes (Chrs) 3, 14 and 19 that account for a total of approximately 75% of the genetic variance in the F2. For the QTL on Chr 14, the OLETF allele corresponds with increased glucose levels, as expected. Surprisingly, for the QTL on Chr 19, the F344 allele corresponds with increased glucose levels. The Chr 3 QTL exhibits heterosis, heterozygotes showing significantly higher glucose levels than OLETF or F344 homozygotes. We also found evidence for interaction (epistasis) between the QTL on Chrs 14 and 19.

Cardiomegaly in the juvenile visceral steatosis (JVS) mouse is reduced with acute elevation of heart short-chain acyl-carnitine level after L-carnitine injection

The long-term administration of L-carnitine was very effective in preventing cardiomegaly in juvenile visceral steatosis (JVS) mice, which was confirmed by heart weight as well as the lipid contents in heart tissue. After i.p. injection of L-carnitine, the concentration of free carnitine in heart remained constant, although serum free carnitine level increased up to 80-fold. On the other hand, a significant increase in short-chain acyl-carnitine level in heart was observed. These results suggest that increased levels of short-chain acyl-carnitine, not free carnitine, might be a key compound in the protective effect of L-carnitine administration in JVS mice.

Dynamic changes in serum leptin concentrations during the fetal and neonatal periods

We investigated the dynamics of the leptin concentration throughout the perinatal period. Serum leptin concentrations in venous cord blood at different gestational ages were measured in 20 preterm and 139 term newborns, as well as in 143 pregnant women and 24 term newborns at approximately 6 d of life. Leptin concentrations in preterm newborns (mean 4.6+/-6.9 ng/mL) were lower than those in term newborns (mean 19.6+/-14.3 ng/mL) and tended to increase according to gestational age and birth weight, especially from the late stage of gestation. Leptin concentrations in pregnant women increased from the first trimester and then remained higher than those in non-pregnant women throughout the remainder of pregnancy even after controlling for body mass index. The leptin concentrations of newborns declined rapidly and were extremely low by approximately 6 d of life (mean 1.9+/-1.1 ng/mL). These results suggest that fetuses might produce a part of circulating leptin in their own adipocytes and that the relatively high leptin concentrations at birth and their rapid decline in the early neonatal period might reflect the dramatic changes of the hormonal and nutritional state during the perinatal period.

Both supplementary and presupplementary motor areas are crucial for the temporal organization of multiple movements

Both supplementary and presupplementary motor areas are crucial for the temporal organization of multiple movements. J. Neurophysiol. 80: 3247-3260, 1998. To study the involvement of the supplementary (SMA) and presupplementary (pre-SMA) motor areas in performing sequential multiple movements that are individually separated in time, we injected muscimol, a gamma-aminobutyric acid agonist, bilaterally into the part of each area that represents the forelimb. Two monkeys were trained to perform three different movements, separated by a waiting time, in four or six different orders. First, each series of movements was learned during five trials guided by visual signals that indicated the correct movements. The monkeys subsequently executed the three movements in the memorized order, without the visual signals. After the injection of muscimol (3 microliter, 5 micrograms/microliters in 10 min) into either the SMA or pre-SMA bilaterally, the animals started making errors in performing the sequence of movements correctly from memory. However, when guided with a visual signal, they could select and perform the three movements correctly. The impaired memory-based sequencing of movements worsened progressively with time until the animals could not perform the task. Yet they still could associate the visual signals with the different movements at that stage. In control experiments on two separate monkeys, we found that injections of the same amount of muscimol into either the SMA or pre-SMA did not cause problems with nonsequential reaching movement regardless of whether it was visually triggered or self-initiated. These results support the view that both the SMA and pre-SMA are crucially involved in sequencing multiple movements over time.

Successful surgical removal of a large arteriovenous malformation in a patient with hemophilia: case report

OBJECTIVE AND IMPORTANCE

This is the first reported case of the successful surgical removal of a large arteriovenous malformation (AVM) in a patient with hemophilia A.

CLINICAL PRESENTATION

A 19-year-old male patient was admitted to our department with intracranial hemorrhage. He had previously been diagnosed with hemophilia A and a cerebral AVM. Carotid angiography revealed a large AVM in the right temporal and parietal lobes. The neurological and neuroradiological findings, especially those of single photon emission computed tomography, identified an area of devitalization around the lesion, which was thought to reduce the risk of new deficits resulting from surgical manipulation.

INTERVENTION

We resected the AVM in conjunction with supplemental infusions of Factor VIII before, during, and after the operation. A slight cerebral hemorrhage on the 7th postoperative day was observed despite control with Factor VIII, but the patient was discharged without any new deficits.

CONCLUSION

We evaluated and managed all problems of a patient with multiple complications and achieved a medical cure.

Task-dependent selectivity of movement-related neuronal activity in the primate prefrontal cortex

Task-dependent selectivity of movement-related neuronal activity in the primate prefrontal cortex. J. Neurophysiol. 80: 3392-3397, 1998. We studied movement-related neuronal activity in the dorsolateral prefrontal cortex from the perspective of a general role for the prefrontal cortex in controlling motor behavior to achieve a specific goal according to the requirements of a given task. Monkeys were trained to perform two delayed motor tasks. The first task involved reaching for a target that matched the shape of a cue. The second task involved reaching for a target that matched the location of the cue. A majority (54%) of 175 movement-related prefrontal neurons exhibited preference for either the target shape or the type of task requirements. Sixty-four neurons (36%) were selectively active while reaching for a circle or a triangle. On the other hand, the activity of 59 neurons (34%) depended on whether the task required matching the shape or the location. These properties, characterizing the movement-related neuronal activity in the prefrontal cortex, rarely were found in the arm area of the primary motor cortex. Only 1 of 130 movement-related neurons (0.8%) showed task selectivity, and none showed target-shape selectivity.

A missense mutation of mouse OCTN2, a sodium-dependent carnitine cotransporter, in the juvenile visceral steatosis mouse

Carnitine is an essential cofactor for the mitochondrial beta-oxidation of long-chain fatty acids. The juvenile visceral steatosis (JVS) mouse, an animal model of systemic carnitine deficiency, is inherited in an autosomal recessive manner. Recently, a human OCTN2 gene encoding a sodium-dependent carnitine cotransporter was isolated and mapped to human chromosome 5q31. Since the mouse jvs locus was assigned to the region of chromosome 11 where it is syntenic to human chromosome 5q31, we isolated the mouse octn2 gene and screened for its mutation in the jvs mouse. DNA sequencing analysis disclosed a missense mutation from CTG (Leu) to CGG (Arg) at codon 352 located within the sixth transmembrane domain of octn2. This amino acid replacement possibly causes the conformational change of the protein that leads to dysfunction of the gene product. Hence, we conclude that octn2 is a candidate gene responsible for the JVS mouse.

Mouse placental cells secrete soluble leptin receptor (sOB-R): cAMP inhibits sOB-R production

The aims of this study were to identify whether mouse placenta secretes soluble OB-R (sOB-R) and to find the regulating factor of OB-R expression. Total RNAs were extracted from placenta and decidua, and OB-R expression was assessed by Northern blot analysis. Decidua did not express OB-R mRNA. However, OB-R mRNA expression was detectable in the placenta on day 13 of pregnancy, and then it increased and reached a peak on day 17 of pregnancy. Mouse placental cells from day 12 of pregnancy were cultured and OB-R gene expression was assessed by Northern blot analysis. OB-R mRNA expression was detectable from the second day of culture and reached a peak on the third day of culture. To determine whether placental cells release sOB-R, supernatant of cultured placental cells was subjected to Western blot analysis. sOB-R was detected in the medium by the second day of culture and sOB-R release increased up to the fourth day of culture. Addition of leptin to the medium did not affect expression of OB-R mRNA. However, 8-bromo cAMP inhibited both steady-state levels of OB-R mRNA and the amount of sOB-R protein in the medium in a dose- and time-dependent manner. These results suggest that trophoblast cells differentiate, express, and release sOB-R both in vivo and in vitro and that cAMP is one of several potent regulators of sOB-R secretion by the mouse placenta.

Role for cingulate motor area cells in voluntary movement selection based on reward

Most natural actions are chosen voluntarily from many possible choices. An action is often chosen based on the reward that it is expected to produce. What kind of cellular activity in which area of the cerebral cortex is involved in selecting an action according to the expected reward value? Results of an analysis in monkeys of cellular activity during the performance of reward-based motor selection and the effects of chemical inactivation are presented. We suggest that cells in the rostral cingulate motor area, one of the higher order motor areas in the cortex, play a part in processing the reward information for motor selection.

Selective hippocampal damage to hypoxia after mild closed head injury in the rat

Our previous studies have shown selective neuronal damage in the CA3 region after mild closed head injury (CHI) combined with hypoxia. In the present studies, we examined (1) extracellular concentrations of neuroactive amino acids using in vivo microdialysis technique and (2) neuroactive amino acid binding to their receptors using quantitative autoradiography. Male SD rats were divided into five groups; sham control, mild CHI (sacrificed at 1 h or 24 h after CHI), mild CHI followed by hypoxia (1 h or 24 h). [3H]-Glutamate binding to NMDA receptors, [3H]-muscimol binding to GABAA receptors and [3H]-kainate binding to KA receptors were measured in hippocampus and cortex by quantitative autoradiography. With CHI alone, GLU and TAU levels were transiently increased by 15 min posttrauma. In the CHI with hypoxia, increases in GLU and TAU levels were sustained until 60 min following CHI. GABA level was also increased until 75 min posttrauma Pretreatment of MK-801 significantly diminished the prolonged elevation in GLU and TAU levels. (2) CHI alone did not produce prominent change in the measured receptor binding. When hypoxia was combined with CHI, significant increase in [3H] GLU binding to NMDA receptors and significant decrease in [3H]-muscimol binding to GABAA receptors were observed in CA1 and CA3 at 1 h and 24 h post-insult. These results demonstrate that selective hippocampal damage to hypoxia after mild CHI may be mediated through an increase in NMDA receptor activation and the further release of GLU and that NMDA antagonist may be beneficial in preventing secondary neuronal damage by hypoxia.

Circulating leptin did not associate with the development of the hyperglycemia accompanied by insulin insensitivity in spontaneous noninsulin dependent diabetes mellitus model Otsuka-Long-Evans-Tokushima-Fatty rats

Leptin, the product of the ob gene, has been reported to regulate feeding behavior and energy metabolism. Plasma leptin concentration was strongly correlated with body fat content in humans. It is well known that increased body fat content is accompanied by insulin insensitivity. In order to study the relationship between serum leptin level and metabolic variables, we performed caloric restriction on Otsuka-Long-Evans-Tokushima-Fatty (OLETF) rats, a model of noninsulin dependent diabetes mellitus. The male OLETF rats were allocated at random to three groups: 100% group, and 85% and 70% groups (which consumed 85% and 70% of the amount of food consumed by the 100% group, respectively). A significant correlation between serum leptin level and the body fat content, body weight, triglyceride, and fasting plasma glucose was observed. Using a partial correlation analysis to control for body fat content, however, the correlation between serum leptin and these variables disappeared. No significant changes in serum leptin levels were observed before and after a 1 h hyperinsulinemic euglycemic clamp test. In conclusion, serum leptin was significantly correlated with body fat content rather than fasting plasma glucose, serum insulin and insulin sensitivity. This suggests that circulating leptin per se may not result in hyperinsulinemia and insulin insensitivity in the OLETF rat.

A major quantitative trait locus co-localizing with cholecystokinin type A receptor gene influences poor pancreatic proliferation in a spontaneously diabetogenic rat

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an animal model for obese-type, non-insulin-dependent diabetes mellitus (NIDDM) in humans. The OLETF rat has poor capacity for pancreatic proliferation, which may be the critical pathogenetic event in NIDDM development. Our investigation was designed to identify quantitative trait loci (QTLs) responsible for poor pancreatic proliferation by examining compensatory proliferation of the pancreatic remnant after partial pancreatectomy and performing a genome-wide scan in an F2 intercross obtained by mating the OLETF and the Fischer-344 (F344) rats. We identified a highly significant QTL on rat Chromosome 14 with a maximum lod score of 16.7, which accounts for 55% of the total variance. The QTL co-localizes with the gene encoding cholecystokinin type A receptor (CCKAR) which is likely to mediate the trophic effect of cholecystokinin on pancreas and is defective in the OLETF rat.

Identification of a quantitative trait locus influencing plasma insulin levels after 70% pancreatectomy using the OLETF rat

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an animal model for obese-type non-insulin-dependent diabetes mellitus (NIDDM) in humans. The OLETF rat has poor capacity for proliferation of pancreatic beta-cells after partial pancreatectomy, which may be the critical pathogenetic event in NIDDM development. The poor pancreatic beta-cell proliferation in this model is characterized by reduction in beta-cell mass and decrease in insulin content in the remnant pancreas. Our investigation was designed to identify quantitative trait loci (QTLs) responsible for beta-cell mass and plasma insulin levels after partial pancreatectomy by performing a genome-wide scan in an F2 intercross obtained by mating the OLETF and the Fischer-344 (F344) rats. We have identified a suggestive QTL for the plasma insulin levels, near D20Mgh5 on rat chromosome 20, with a maximum lod score of 3.75 which accounts for 20% of the total variance, while no QTLs were detected for beta-cell mass. This chromosome 20 QTL, whose OLETF allele is associated with low plasma insulin levels through acting in an incompletely recessive manner, may affect insulin secretion itself rather than beta-cell proliferation.

Leptin affects pancreatic endocrine functions through the sympathetic nervous system

The effects of leptin on the secretion of insulin and glucagon were examined. In an experiment involving insulin response to an i.v. glucose load in vagotomized rats, the plasma concentrations of insulin were significantly lower in the leptin (20 nmol/kg BW)-treated group than in a control group. However, in intact rats and rats that had undergone both vagotomy and chemical sympathectomy, this suppressive effect of leptin on insulin secretion was not detected. In an experiment involving a hypoglycemia-induced glucagon secretion test in intact rats, an i.v. injection of leptin (20 nmol/kg BW) augmented the plasma glucagon response to hypoglycemia. In the case of sympathectomized rats, however, this stimulative effect of leptin on glucagon secretion was not detected. In an experiment with perfused rat pancreas, the addition of leptin (20 nM) to the perfusate slightly suppressed insulin secretion, but had no effect on basal or glucopenia-induced glucagon secretion. In intact rats infused with leptin (0.31 micromol/day), the expression of uncoupling protein-1 messenger RNA in interscapular brown adipose tissue was increased, whereas no such effect of leptin on the uncoupling protein-1 messenger RNA expression was observed in brown adipose tissue in chemically sympathectomized rats. These findings suggest that leptin might indirectly affect pancreatic endocrine functions, probably through its stimulative effects on the sympathetic nervous system.

Involvement of NMDA and non-NMDA receptors in the neuronal responses of the primary motor cortex to input from the supplementary motor area and somatosensory cortex: studies of task-performing monkeys

The involvement of N-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptors in mediating the excitatory responses of neurons in the primary motor cortex (MI) to electrical stimulation of the supplementary motor area (SMA) and the somatosensory cortex (SI) was examined in monkeys performing a trained motor task. During the task, a total of 109 MI neurons were identified and classified as movement related (91), motor set related (7), or mixed (11). Subsequently, the influence of receptor antagonists on the stimulus-evoked and task-related activities of these neurons was examined. The selective NMDA antagonist D-2-amino-5-phosphonovaleric acid (APV) and the selective non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) were applied iontophoretically through multibarreled micropipettes. One barrel was used for extracellular unit recording. The excitatory response evoked by SI stimulation was suppressed by CNQX in the vast majority (83%) of the motor task related neurons, and only 10% were suppressed by APV. On the other hand, the response evoked by SMA stimulation was suppressed by APV in 56% of the neurons and by CNQX in 54%. APV and CNQX had parallel effects on the stimulus-evoked responses and the task-related neuronal activity. These results indicate that NMDA and non-NMDA receptors are both involved in mediating the excitatory responses of MI neurons to input from the SMA and SI. On the other hand, the data suggest a greater contribution of non-NMDA receptors in response to SI input and greater involvement of NMDA receptors in mediating the response to SMA input, especially among set-related MI neurons.

Effect of partial pancreatectomy on beta-cell mass in the remnant pancreas of Wistar fatty rats

Wistar fatty rat, which has been established by transferring the fa gene of Zucker fatty rat to the Wistar Kyoto rat, has many features in common with human NIDDM. It exhibits hyperglycemic obesity with hyperinsulinemia and insulin resistance. It is unclear, however, whether a defect in the beta-cell proliferation is related to the onset of diabetes mellitus together with insulin resistance in this model rat. To determine this, we compared non-fasting plasma glucose levels, insulin content and beta-cell mass in the remnant pancreas of Wistar fatty rats with those in their diabetic-resistant lean counterparts after a 70% partial pancreatectomy. We also examined whether such a defect, if present, could be improved by either phlorizin or nicotinamide. We further investigated if there were any differences in these parameters between the phenotypically identical but genotypically different Wistar lean rats with a gene type of homogeneous Fa/Fa and that of heterogeneous Fa/fa. Male rats, 6 weeks of age, were allocated at random into two groups: 70% pancreatectomy (Px) and sham-pancreatectomy (sham). A sustained hyperglycemia was evident in the Px Wistar fatty rats after surgery, which was accompanied by a reduction of insulin content and beta-cell mass in the remnant pancreas. The changes in insulin content and beta-cell mass were unaffected by restoration of normoglycemia, induced by phlorizin injection. The administration of nicotinamide partially ameliorated the sustained hyperglycemia by a slight but not significant increase in beta-cell mass. No discernible difference in the above parameters was observed between the Wistar lean rats with Fa/Fa and those with Fa/fa. These findings suggest that Wistar fatty rats have a poor capacity for proliferation of pancreatic beta-cells, which causes the onset of overt diabetes along with insulin resistance due to extreme obesity.

A role of nicotinamide-induced increase in pancreatic beta-cell mass on blood glucose control after discontinuation of the treatment in partially pancreatectomized OLETF rats

Otsuka Long-Evans Tokushima Fatty (OLETF) rat, a model of NIDDM, is normoglycemic at a young age. However, they become hyperglycemic, even at a young age as a result of a 70% pancreatectomy, which is associated with insufficient proliferation of beta-cells. Administration of nicotinamide ameliorates the sustained hyperglycemia by increasing beta-cell proliferation. In order to further understand its mode of action, we studied how long nicotinamide is effective, in terms of ameliorating hyperglycemia, as evidenced by an increase in beta-cell mass, after its administration, in partially pancreatectomized OLETF rats. Male rats, 6 weeks of age, were allocated at random to two groups, 70% pancreatectomy (Px) and sham-pancreatectomy (sham). The Px group was divided into three subgroups, based on treatment with either nicotinamide (350 mg/kg), phlorizin (400 mg/kg) or saline, which continued until 4 weeks after surgery, and were sacrificed at 4, 6, or 8 weeks after surgery. A 70% Px resulted in sustained hyperglycemia in the saline-treated Px rats, which was ameliorated by administration of either phlorizin or nicotinamide, showing the non-fasting blood glucose levels reached to or near the levels found in the sham rats. After cessation of phlorizin injection, non-fasting blood glucose level increased rapidly, reaching the level of the saline-treated Px rats at the end of the experiment, whereas after cessation of nicotinamide injection, non-fasting blood glucose increased gradually to a level which was significantly lower than that observed in the saline-treated Px rats. An increased beta-cell mass, 62.7 +/- 7.8% of total beta-cell mass induced by nicotinamide at 4 weeks, decreased gradually, reaching the level of pretreatment, 30.3 +/- 4.0% 4 weeks after cessation of the treatment. The findings in this study suggest that ameliorated hyperglycemia as a result of proliferated beta-cells during the administration of nicotinamide may results in showing beta-cell exhaustion (a majority of beta-cell degranulation) once stopping injection, as compared with phlorizin treated group in this model rat.

[Reassessment of a combination of cerebrospinal fluid scintigraphy and nasal pledget counts in patients with suspected rhinorrhea]

A combination study of cerebrospinal fluid scintigraphy and nasal pledget counts was performed using 37 MBq of 111In-DTPA in 12 patients with suspected rhinorrhea. A pledget was inserted and dwelled in each nasal cavity for 6 hours, with the patient prone during at least 30 minutes. A total of 18 studies was implemented and nasal pledget counting method successfully diagnosed all of CSF rhinorrhea. Diagnosis was possible when pledget counts were greater than 1 kcpm. In patients with persistent, intermittent and occult/no nasal discharge, rhinorrhea was found in 100% (5/5), 60% (3/5), 25% (2/8), respectively. Two cases only exhibited positive scintigraphy. MRI or CT cisternography should be first performed in patients with persistent discharge, but in patients with intermittent/occult discharge pledget counting method might take priority of other diagnostic modalities. In conclusion, nasal pledget counting method is a simple and useful tool for detecting rhinorrhea.

Ovarian hormone-induced beta-cell hypertrophy contributes to the homeostatic control of beta-cell mass in OLETF female rat, a model of Type II diabetes

A sexual dimorphism regarding the incidence of diabetes mellitus in OLETF rat, a model of Type II diabetes, has been reported. As a result, the effects of ovarian hormones on beta cells per se was examined by comparing the capacity of beta-cell proliferation and changes in blood glucose and plasma insulin concentrations after a 70% pancreatectomy. All female animals were randomly assigned to two protocols. The rats involved in protocol I received either a 70% pancreatectomy (Px) or a sham pancreatectomy (sham) at 6 weeks of age, along with their diabetes-resistant counterparts, female LETO rats, which served as normal controls. The rats belonging to protocol II were given an ovariectomy (Ox) at 5 weeks of age, and one week later, they were subjected to either Px or the sham operation, with/without hormone (estradiol, 50 microg/kg; testosterone, 1 mg/kg) replacement. The findings indicate that the capacity for compensatory growth of beta cells after Px was affected by both sex hormonal and genetic components, since a 70% Px resulted in sustained hyperglycaemia within the first week after surgery, but was ameliorated by an increase in beta-cell mass thereafter in the non-Ox Px OLETF rats. The Ox also caused a decline in beta-cell mass which could be improved by replacement with ovarian hormones. Not only endogenous but also replacement ovarian hormones, led to a beneficial effect on beta cells per se in OLETF female rats. This was reflected by an increased beta-cell mass accompanied by a parallel increase in plasma immunoreactive insulin concentration. The effects of ovarian hormones, however, contributed to the beta-cell hypertrophy rather than expansion of the beta-cell population to achieve glucose homeostasis, as evidenced by an increased area of individual beta-cell after Px rather than an increased BrdU-labelling index for the beta cells. The present study suggests that ovarian hormone-induced beta-cell hypertrophy may typically occur, to compensate for changes in functional demand as the results of a 70% Px in female OLETF rats.

Leptin receptor signal transduction: OBRa and OBRb of fa type

We report herein the characterization of activities of signal transduction for three types of leptin receptors (OBRs) from rats, the OBRa, OBRb, and OBRb with fa mutation (OBRb-fa), by measurement of the levels of tyrosine phosphorylation of STAT3 (signal transducers and activators of transcription 3) and MAPK (mitogen-activated protein kinase), which are induced by leptin stimulation of CHO cells stably expressing the OBR (CHO-OBRb, CHO-OBRa, or CHO-OBRb-fa cells). As the result of leptin stimulation, enhanced levels of tyrosine phosphorylation of STAT3 and MAPK were detected in CHO-OBRb cells. In CHO-OBRb-fa cells, enhancement levels for both were lower than those in CHO-OBRb cells. In CHO-OBRa cells, only the phosphorylation of MAPK was detected. These data suggest that these reduced signaling activities cause obesity in fa/fa rats and that OBRa, which has been generally thought to be inactive at signaling, actually transmits signals through the MAPK pathway.

The influence of ovariectomy on ob gene expression in rats

Ovarian steroid hormones exert major influences on eating behaviour and body weight regulation of female rats. Ovariectomy (OVX) results in an increase in food intake and a concomitant increase in body weight, while estradiol (E2) replacement reverses these effects. In this study, we examined the influence of OVX on obese (ob) gene expression in rat adipose tissues and serum leptin concentration. Female Wistar rats, 10 weeks old, were divided into three groups: sham-operated control rats receiving corn oil (group 1, n = 4), ovariectomized rats receiving corn oil (group 2, n = 5), and ovariectomized rats receiving 17beta-E2 (10 microg/kg/day) replacement (group 3, n = 4). After 4 weeks, the rats and food consumption were weighed and serum E2 and leptin levels were measured by radioimmunoassays. Furthermore, the expression levels of ob mRNA obtained from the bilateral perimetric fat pads were estimated by Northern blot analysis. The mean weight and food consumption in group 2 were significantly (p < 0.01) heavier than those in group 1. But there were no significant differences between group 1 and group 3. The expression levels of ob mRNA in group 2 were lower than those in group 1, however, the levels of group 3 were restored to the level of group 1. On the other hand, no significant differences among the 3 groups as to serum levels of leptin were observed. The data herein clearly indicate that ovarian steroid hormones may be one of the factors involved in the regulation of ob gene.

Characteristics of cardiac hypertrophy in the juvenile visceral steatosis mouse with systemic carnitine deficiency

The juvenile visceral steatosis (JVS) mouse exhibits hereditary systemic carnitine deficiency and develops cardiac hypertrophy. The aim of this study was to clarify the characteristics of cardiac hypertrophy in the JVS mouse. Total carnitine content in IVS mouse heart was about 10% of that of control mouse heart at 4 and 8 weeks of age. The heart weight/body weight ratio was bigger in JVS mice than that in control mice at 2 weeks of age, and this difference in ratio increased with age. The wall areas of both ventricles and septum in JVS mice were larger than those of the control mice at 2 and 8 weeks. The myocyte diameter in both ventricular walls and septum in JVS mice was longer than that of the control mice. On electron microscopy, the percent of mitochondria in the myocyte was 66% in JVS mice, and 37% in control mice. The percent of lipid fraction in JVS mice was six-fold higher than that in control mice. Total content of adenine nucleotides in JVS mouse heart was about 60% of that in control mouse heart. Adenylate energy charge in JVS mouse heart was 63 and 45% of that in the control mouse heart at 4 and 8 weeks, respectively. Overall, the cardiac enlargement observed in this animal model could be accounted for by a proportional increase in the myocyte diameter in the ventricles and septum, accompanied by an increase in mitochondria. Furthermore, this cellular growth is associated with decreases in the levels of ATP and ADP, and adenylate energy charge.

[GAD antibody in IDDM]

Glutamic acid decarboxylase (GAD) catalyzes the formation of gamma-aminobutyric acid (GABA), which is a major transmitter in the central nervous system. Two forms of GAD (GAD65 and GAD67) are known to be expressed in human tissues and GAD65 is predominantly expressed in pancreatic beta-cells. Recent findings revealed that GAD functions as an autoantigen in human autoimmunity, especially in insulin-dependent diabetes mellitus (IDDM). GAD is a key antigen for the development of autoimmunity against beta-cells and the production of GADAb precedes other autoantibodies such as IAA and ICA512/IA-2Ab prior to the clinical onset of IDDM. At onset, GADAb is detected in 50-80% of patients using RIA or RBA method. Factors that influence the positivities and titers of GADAb at onset, such as onset age, sex, presence of autoimmunity against thyroid, HLA type, have been reported. After onset, GADAb titer decreased more slowly than that of ICA512/IA-2Ab. These findings suggest that autoantibodies against beta-cells, such as GADAb, may develop independently. The presence of GADAb in relatives of IDDM patients and NIDDM patients predicts the development of beta-cell destruction in combination with other anti-islet autoantibodies.