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Biomedical subjects

N Maeda

Publications and source records attributed to N Maeda.

At least 307 records · Page 17Linked to original sources
PubMed1996

FK960 N-(4-acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate ameliorates the memory deficits in rats through a novel mechanism of action.

With passive avoidance (PA), Morris water maze (WM) and eight-arm radial maze tasks, we evaluated the memory-enhancing action of FK960 [N-(4-acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate], a compound which we have found through rational drug screening based on our hypothesis that penile erection is a valid predictor of central cholinergic activation. Memory performance in the tasks was impaired in aged (24- to 26-months-old) rats as well as in rats with nucleus basalis magnocellularis lesions. Scopolamine (1 mg/kg i.p.) treatment induced memory impairment in PA and WM; treatment with cysteamine (200 mg/kg s.c.) induced memory impairment in PA but not in WM, whereas fimbria fornix lesioning affected the rats in the opposite manner. FK960 (0.1-10 mg/kg i.p.) ameliorated all the memory impairments except those induced by cysteamine or fimbria fornix lesion, and the dose-response curves were bell shaped with maximal response at 1 to 3.2 mg/kg. The effects of FK960 on the scopolamine-induced memory impairment in the PA and/or WM were abolished by cysteamine (200 mg/kg s.c.), dl-p-chlorophenylalanine methyl ester hydrochloride (150 mg/kg i.p. for 3 days) or raphe lesioning, but not by neonatal 6-hydroxydopamine (35 micrograms/head) treatment. Neurochemical analysis revealed that cysteamine and raphe lesions reduced brain somatostatin and serotonin contents, respectively. The treatment with FK960 (0.32-320 mg/kg p.o.) dose-dependently increased both serotonin and 5-hydroxyindoleacetic acid levels in the brain areas examined and significantly increased hippocampal somatostatin contents at the smaller doses. From these results, we conclude that FK960 ameliorates cognitive dysfunction through an activation of the somatostatinergic-serotonergic link.

Aging↗
PubMed1996

[Health status, social networks and support systems of so called old old in a population-based comparative study of residents ages 69-74 and 75-80].

To analyze the different features of health status, social support and networks of elderly people by age groups, a survey was performed of the social environment and health related issues among residents aged 69-74 and 75-80, the so called old-old, in Takasu, a small farming town in Hokkaido. The results were as follows: 1. The percentage of elderly having some of the symptoms related to dementia, lower scores of ADL, and poorer conditions of eye sight or hearing were significantly higher among the elderly aged 75-80 compared to those aged 69-74. The prevalence of diseases, such as senile cataracts in both sexes, and heart diseases in men were also higher among those aged 75 and over. 2. Although there were no differences in the mean number of hospital admissions or in the percentage of those having been sick in bed for more than 1 week during the previous one year, both the mean number of out-patient visits and percentage having a family physician were significantly higher in the elderly over 75 than under. Deterioration of IADL were prominent in the item on being able to go far away by themselves. 3. Almost 70% of the elderly participated in community-based social activities in Takasu. There were only small differences in social support and network among the different categories of family structure of the elderly. However women over 75 had statistically significantly lower number of the social supports compared to the younger age groups. A significantly smaller percentage of people was able to obtain the emotional or care support from their spouse for in elderly over 75 than for elderly under 75. 4. The results of this study suggest the need to provide more social support and networks for the old-old over 75 years old who tend to have more diseases and to be in poorer health condition, both physically or mentally than younger old.

Aged↗
PubMed1995

Effects of imidazoline antagonists of alpha 2-adrenoceptors on endogenous adrenaline-induced inhibition of insulin release.

We studied the effects of adrenoceptor antagonists and imidazoline derivatives on endogenous adrenaline-induced inhibition of insulin release in anesthetized rats. The intracerebroventricular injection of neostigmine increased plasma levels of catecholamines and glucose but not insulin. Pretreatment with an i.p. injection with phentolamine caused a dose-dependent increase in insulin secretion. When atropine was coadministered with phentolamine, the phentolamine-induced increase in insulin secretion was inhibited. Neither phentolamine nor atropine affected plasma levels of catecholamine. Yohimbine and idazoxan, which are alpha 2-adrenoceptor antagonists, and tolazoline, a non-selective alpha-adrenoceptor antagonist, also reversed adrenaline-induced inhibition of insulin secretion. Phenoxybenzamine, prazosin, propranolol, and antazoline, an imidazoline without alpha 2-adrenoceptor activity, did not affect insulin levels. When agents were preinjected i.p. in rats that were given saline into the third cerebral ventricle, phentolamine and antazoline, but not yohimbine and idazoxan, increased plasma levels of insulin. The results suggest that the inhibition of insulin release induced by adrenaline was reversed by antagonism of alpha 2-adrenoceptors. Phentolamine and antazoline, both of which are imidazoline derivatives, induced insulin secretion independently of the adrenoceptors only under the resting conditions.

Adrenergic alpha-2 Receptor Agonists↗
PubMed1995

A mouse model for beta 0-thalassemia.

We have used a "plug and socket" targeting technique to generate a mouse model of beta 0-thalassemia in which both the b1 and b2 adult globin genes have been deleted. Mice homozygous for this deletion (Hbbth-3/Hbbth-3) die perinatally, similar to the most severe form of Cooley anemia in humans. Mice heterozygous for the deletion appear normal, but their hematologic indices show characteristics typical of severe thalassemia, including dramatically decreased hematocrit, hemoglobin, red blood cell counts, mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration, as well as dramatically increased reticulocyte counts, serum bilirubin concentrations, and red cell distribution widths. Tissue and organ damage typical of beta-thalassemia, such as bone deformities and splenic enlargement due to increased hematopoiesis, are also seen in the heterozygous animals, as is spontaneous iron overload in the spleen, liver, and kidneys. The mice homozygous for the b1 and b2 deletions should be of great value in developing therapies for the treatment of thalassemias in utero. The heterozygous animals will be useful for studying the pathophysiology of thalassemias and have the potential of generating a model of sickle cell anemia when mated with appropriate transgenic animals.

Animals↗
PubMed1995

Neuroglycan C, a novel membrane-spanning chondroitin sulfate proteoglycan that is restricted to the brain.

Monoclonal antibodies were raised to membrane-bound proteoglycans derived from rat brain, and four monoclonal antibodies that recognized a 150-kDa chondroitin sulfate proteoglycan with a core glycoprotein of 120 kDa were obtained. Immunohistological study revealed that the proteoglycan was associated with developing neurons. We screened rat brain cDNA libraries using the four monoclonal antibodies and isolated overlapping cDNA clones that encoded the entire core protein of 514 amino acids plus a 30-residue signal peptide. The deduced amino acid sequence suggested an integral membrane protein divided into five structurally different domains: an N-terminal domain to which chondroitin sulfate chains might be attached, a basic amino acid cluster consisting of seven arginine and two lysine residues, a cysteine-containing domain, a membrane-spanning segment, and a C-terminal cytoplasmic domain of 95 amino acids. On Northern blots, the cDNA hybridized with a single mRNA of 3.1 kilobases that was detectable in brains of neonatal and adult rats but not in kidney, liver, lung, and muscle of either. The sequence of the proteoglycan did not exhibit significant homology to any other known protein, indicating that the proteoglycan, designated neuroglycan C, is a novel integral membrane proteoglycan.

Aggrecans↗
PubMed1995

A new family of retroviral long terminal repeat elements in the human genome identified by their homologies to an element 5' to the spider monkey haptoglobin gene.

A new family of retroviral long terminal repeats that we name Spm-LTR has been identified as a result of DNA sequence comparisons between the entire GenBank databank and an element, SPHP, located 5' to the haptoglobin gene of spider monkeys. The 18 human Spm-LTR sequences so identified fall into three subtypes. There is no sequence similarity between Spm-LTR elements and any endogenous retroviral LTR sequences previously reported except for general features that define LTRs. However, a previously described repeated sequence (MER-4) forms a portion of the Spm-LTR sequence.

Animals↗
PubMed1995

Gene targeting approaches to complex genetic diseases: atherosclerosis and essential hypertension.

Gene targeting allows precise, predetermined changes to be made in a chosen gene in the mouse genome. To date, targeting has been used most often for generation of animals completely lacking the product of a gene of interest. The resulting "knockout" mice have confirmed some hypotheses, have upset others, but have rarely been uninformative. Models of several human genetic diseases have been produced by targeting--including Gaucher disease, cystic fibrosis, and the fragile X syndrome. These diseases are primarily determined by defects in single genes, and their modes of inheritance are well understood. When the disease under study has a complex etiology with multiple genetic and environmental components, the generation of animal models becomes more difficult but no less valuable. The problems associated with dissecting out the individual genetic factors also increases substantially and the distinction between causation and correlation is often difficult. To prove causation in a complex system requires rigorous adherence to the principle that the experiments must allow detection of the effects of changing only a single variable at one time. Gene targeting experiments, when properly designed, can test the effects of a precise genetic change completely free from the effects of differences in any other genes (linked or unlinked to the test gene). They therefore allow proofs of causation.

Animals↗
PubMed1995

COOH-terminal disruption of lipoprotein lipase in mice is lethal in homozygotes, but heterozygotes have elevated triglycerides and impaired enzyme activity.

The role of the enzyme lipoprotein lipase (LPL) in atherosclerosis is uncertain. To generate an animal model of LPL deficiency, we targeted the LPL gene in embryonic stem cells with a vector designed to disrupt the COOH terminus of the protein and used these cells to generate LPL-deficient mice. Germ line transmission of the disrupted LPL allele was achieved with two chimeric males, and offspring from each of these animals were phenotypically identical. Pups homozygous (-/-) for LPL deficiency died within 48 h of birth with extreme elevations of serum triglycerides (13,327 mg/dl) associated with essentially absent LPL enzyme activity in heart and carcass. Newborn heterozygous (+/-) LPL-deficient pups had lower LPL enzyme activity and higher triglycerides (370 versus 121 mg/dl) than wild type (+/+) littermates. Adult heterozygotes had higher triglycerides than wild type mice with ad libitum feeding (236 mg/dl for +/- versus 88 mg/dl for +/+) and after fasting for 4 h (98 mg/dl for +/- versus 51 for +/+) or 12 h (109 mg/dl for +/- versus 56 mg/dl for +/+). Triglycerides were present as very low density lipoprotein particles and chylomicrons, but high density lipoprotein cholesterol levels were not decreased in +/- animals. Plasma heparin-releasable LPL activity was 43% lower in +/- versus +/+ adult animals. LPL activity, mRNA, and protein were lower in the tissues of +/- versus +/+ mice. Homozygous LPL deficiency caused by disruption of the COOH terminus of the enzyme is lethal in mice. Heterozygous LPL deficiency caused by this mutation is associated with mild to moderate hypertriglyceridemia without affecting static HDL cholesterol levels. Heterozygous LPL-deficient mice could be useful for determining if hypertriglyceridemia, independently or in combination with other discrete defects, influences atherosclerosis.

Animals↗
PubMed1995

Thapsigargin-sensitive Ca(2+)-ATPases account for Ca2+ uptake to inositol 1,4,5-trisphosphate-sensitive and caffeine-sensitive Ca2+ stores in adrenal chromaffin cells.

In chromaffin cells of adrenal medulla, heterogeneity of Ca2+ stores has been suggested with respect to the mechanisms of Ca2+ uptake and release. We have examined Ca(2+)-ATPases responsible for loading of Ca2+ stores in these cells for their sensitivity to thapsigargin, a highly selective inhibitor of the SERCA [sarco(endo)plasmic reticulum calcium ATPase] family of intracellular Ca2+ pumps. Using immunostaining, we studied the distribution of Ca(2+)-ATPases, and of receptors for inositol 1,4,5-trisphosphate (InsP3) and ryanodine, in the density-gradient fractions of microsomes from bovine adrenal medulla. In parallel, we examined distribution profiles of ATP-dependent Ca2+ uptake in the same fractions, along with subcellular markers for plasma membranes and endoplasmic reticulum (ER). Two Ca(2+)-ATPase-like proteins (116 and 100 kDa) were detected, consistent with the presence of SERCA 2b and SERCA 3 isoenzymes of Ca2+ pumps. The distribution of these putative Ca(2+)-ATPase iso-enzymes paralleled that of InsP3 and ryanodine receptors. This distribution of ER Ca(2+)-ATPases, as determined immunologically, was consistent with that of thapsigargin-sensitive, but not of thapsigargin-insensitive, ATP-dependent Ca2+ uptake. In contrast, the distribution profile of the thapsigargin-insensitive Ca2+ uptake was strongly correlated to that of plasma membranes, and co-distributed with plasma membrane Ca(2+)-ATPase detected immunologically. In isolated, permeabilized chromaffin cells, InsP3 and caffeine induced Ca2+ release following an ATP-dependent Ca2+ accumulation to the stores. This accumulation was abolished by thapsigargin. Together, these data strongly indicate that the thapsigargin-sensitive, presumably SERCA-type Ca(2+)-ATPases account for Ca2+ uptake to InsP3-sensitive, as well as to caffeine-sensitive, Ca2+ stores in bovine adrenal chromaffin cells.

Adrenal Medulla↗
PubMed1995

Regulation of blood pressure by the type 1A angiotensin II receptor gene.

The renin-angiotensin system plays a critical role in sodium and fluid homeostasis. Genetic or acquired alterations in the expression of components of this system are strongly implicated in the pathogenesis of hypertension. To specifically examine the physiological and genetic functions of the type 1A receptor for angiotensin II, we have disrupted the mouse gene encoding this receptor in embryonic stem cells by gene targeting. Agtr1A(-/-) mice were born in expected numbers, and the histomorphology of their kidneys, heart, and vasculature was normal. AT1 receptor-specific angiotensin II binding was not detected in the kidneys of homozygous Agtr1A(-/-) mutant animals, and Agtr1A(+/-) heterozygotes exhibited a reduction in renal AT1 receptor-specific binding to approximately 50% of wild-type [Agtr1A(+/+)] levels. Pressor responses to infused angiotensin II were virtually absent in Agtr1A(-/-) mice and were qualitatively altered in Agtr1A(+/-) heterozygotes. Compared with wild-type controls, systolic blood pressure measured by tail cuff sphygmomanometer was reduced by 12 mmHg (1 mmHg = 133 Pa) in Agtr1A(+/-) mice and by 24 mmHg in Agtr1A(-/-) mice. Similar differences in blood pressure between the groups were seen when intraarterial pressures were measured by carotid cannulation. These studies demonstrate that type 1A angiotensin II receptor function is required for vascular and hemodynamic responses to angiotensin II and that altered expression of the Agtr1A gene has marked effects on blood pressures.

Angiotensin II↗
PubMed1995

Genetic control of blood pressure and the angiotensinogen locus.

Variants of the human angiotensinogen gene have been linked in some studies to increased circulating angiotensinogen levels and essential hypertension. To test for direct causality between genotypes at the angiotensinogen locus and blood pressures, we have studied mice carrying zero, one, two, three, or four functional copies of the murine wild-type angiotensinogen gene (Agt) at its normal chromosomal location. Plasma angiotensinogen levels increase progressively, although not linearly, from zero in the zero-copy animals to 145% of normal in the four-copy animals. Mice of all genotypes are normal at birth, but most zero-copy animals die before weaning. The kidneys of the zero-copy animals show pathological changes as adults, but the kidneys are normal in the other genotypes. One adult zero-copy male tested was fertile. The blood pressures of the one-copy through four-copy animals show significant and almost linear increases of approximately 8 mmHg per gene copy despite their normal compensatory mechanisms being intact. These results establish a direct causal relationship between Agt genotypes and blood pressures.

Aging↗
PubMed1995

Mice deficient in cystathionine beta-synthase: animal models for mild and severe homocyst(e)inemia.

Studies by various investigators have indicated that elevated levels of plasma homocyst(e)ine are strongly associated with the occurrence of occlusive vascular diseases. With the eventual aim of determining whether or not elevated plasma homocyst(e)ine concentrations are directly causative of cardiovascular diseases, we have generated mice that are moderately and severely homocyst(e)inemic. Homologous recombination in mouse embryonic stem cells was used to inactivate the cystathionine beta-synthase [L-serine hydrolyase (adding homocysteine), EC 4.2.1.22] gene. Homozygous mutants completely lacking cystathionine beta-synthase were born at the expected frequency from matings of heterozygotes, but they suffered from severe growth retardation and a majority of them died within 5 weeks after birth. Histological examination showed that the hepatocytes of homozygotes were enlarged, multinucleated, and filled with microvesicular lipid droplets. Plasma homocyst(e)ine levels of the homozygotes were approximately 40 times normal. These mice, therefore, represent a model for severe homocyst(e)inemia resulting from the complete lack of cystathionine beta-synthase. Heterozygous mutants have approximately 50% reduction in cystathionine beta-synthase mRNA and enzyme activity in the liver and have twice normal plasma homocyst(e)ine levels. Thus, the heterozygous mutants are promising for studying the in vivo role of elevated levels of homocyst(e)ine in the etiology of cardiovascular diseases.

Amino Acid Metabolism, Inborn Errors↗
PubMed1995

Mild dyslipidemia in mice following targeted inactivation of the hepatic lipase gene.

In order to gain better understanding of the function of hepatic lipase (HL) in vivo, we have generated mice that lack HL using gene targeting in embryonic stem cells. No mRNA for HL was detected in the liver of homozygous mutants, and no HL activity was detected in their plasma. Total cholesterol levels in plasma of mutant mice were increased by about 30% compared with wild type animals. Plasma phospholipids and high density lipoprotein (HDL) cholesterol were also increased, but plasma levels of triglycerides were not altered. Analysis of density fractions of plasma lipoproteins revealed that HDL1 (d = 1.02-1.04) was increased in homozygous mutants fed regular chow. In response to a diet containing high fat and high cholesterol, HDL cholesterol was doubled in the mutants, but was slightly decreased in the wild type mice. These results clearly demonstrate the importance of HL in HDL remodeling and metabolism in vivo. Various earlier studies suggested a role of HL in metabolism of triglyceride-rich particles, but the mutant mice appear to have no impairment in clearing them; the mutants clear exogenously introduced chylomicrons from plasma at a normal rate, and they tolerate acute fat loading as well as normal animals unless the loading is extreme. These differences may reflect species differences. However, it is also possible that the consequence of absence of HL as in our mutants is different from the consequence when nonfunctional HL protein is present as in the human HL-deficient patients and in rats treated with HL antibodies. We hypothesize that absence of HL in mutant mice allows other lipases to bind to the sites in the liver normally occupied by HL and facilitate the clearance of triglyceride-rich particles in these mice.

Alleles↗
PubMed1995

Comparison of methods for detecting keratoconus using videokeratography.

BACKGROUND: The detection of keratoconus patterns on videokeratography is important for screening candidates for refractive surgery and for studying the genetic basis of keratoconus. OBJECTIVE: We compared three quantitative approaches to identifying keratoconus from videokeratographic information to examine the limitations and capabilities of each test and to determine their suitability for use in the clinical setting. METHODS: Videokeratographs typical of clinically diagnosed keratoconus (n = 44) and of various non-keratoconus conditions (n = 132, including normal, with-the-rule astigmatism, contact lens-induced corneal warpage, photorefractive keratectomy, keratoplasty, and pellucid marginal degeneration) were selected. Three methods for detecting keratoconus were used: keratometry (average Simulated Keratometry [SimK] readings > 45.7 diopters [D]); the modified Rabinowitz-McDonnell test (central corneal power > 47.2 D and/or Inferosuperior Asymmetry [I-S] value > 1.4 D); and an expert system classifier (classification based on discriminant analysis and classification tree with eight topographic indexes). Sensitivity and specificity were calculated for each test. RESULTS: Sensitivities were 84% for keratometry, 96% for the modified Rabinowitz-McDonnell test, and 98% for the expert system classifier. Specificities for the three methods were 86%, 85%, and 99%, respectively. In terms of sensitivity, the expert system classifier was significantly better than keratometry (P = .04). In terms of specificity, the expert system classifier was significantly better than either of the other methods (P = .001). CONCLUSIONS: For screening candidates for refractive surgery, where high sensitivity is needed, either the modified Rabinowitz-McDonnell test or the expert system classifier is suitable. For diagnosing keratoconus, where high specificity is more useful, the expert system classifier is more appropriate than the other two methods.

Cornea↗
PubMed1995

Exencephaly and hydrocephaly in mice with targeted modification of the apolipoprotein B (Apob) gene.

Apolipoprotein B (apoB) is a key structural component of several lipoproteins. These lipoproteins transport cholesterol, lipids, and vitamin E in the circulation. Humans that produce truncated forms of apoB have low plasma concentrations of apoB, beta-lipoproteins, cholesterol, and often vitamin E. This condition has been modeled in mice by targeted modification of the apoB gene. Homozygous transgenic mice display all of the hallmarks of the human disorder. Unexpectedly, approximately 30% of the perinatal homozygotes are exencephalic and of those that have closed neural tubes, approximately 30% are hydrocephalic. The latter condition has also been noted in a relatively small proportion of the heterozygous mice. Vital staining of gestational day 9 (GD9) homozygous offspring has illustrated a striking pattern of excessive cell death involving the alar plate of the hindbrain. Histological and scanning electron microscopic analyses have confirmed this finding. We speculate that varying degrees of affect, as noted among GD 9 and 10 embryos, lead to the spectrum of malformations, including hydrocephaly, present in term fetuses. Analysis of vitamin E deficiency as a possible causative factor has illustrated that homozygous fetuses, indeed, show this deficiency. Amelioration of the defects through alpha-tocopherol supplementation of the maternal diet has been explored. Further analyses of this transgenic mutant promise to provide significant information relative to the role of deficiency of vitamin E and other apoB dependent compounds in dysmorphogenesis.

Animals↗
PubMed1995

Hepatic failure in a case of multiple myeloma-associated amyloidosis (kappa-AL)

We report a case of kappa-AL amyloidosis which rapidly developed hepatic failure in a 79-year-old Japanese female who was admitted to our hospital because of abdominal distension and loss of appetite. Laboratory examination revealed a marked deterioration of liver function with cholestasis and monoclonal gammapathy. At the time that the diagnosis of IgG-kappa type multiple myeloma was made, jaundice was advanced, with continuous gastrointestinal bleeding. The patient died of hepatic failure 2 weeks after admission. Needle biopsy of the liver revealed a diffuse, massive deposition of amyloid protein.

Aged↗