Implications from and for food cultures for cardiovascular disease: longevity

A healthy cardiovascular system, with minimal arteriosclerosis, good endothelial function and well-compensated ventricular function has been observed at advanced ages, and linked to a healthy lifestyle. This has consisted of a plant-based diet, low in salt and fat, with monounsaturates as the principal fat. Other healthy lifestyle factors include regular physical activity (farming and traditional dance) and minimal tobacco use. The associated negative risk factors are low homocysteine, healthy cholesterol profile (Total:HDL ratio less than 3.5) and reasonable blood pressures throughout the life cycle. Hormone-dependent cancers including breast, ovary, prostate and colon and osteoporotic complications, such as hip fracture rates, are also less frequent compared to the west. Protective factors may include high anti-oxidant consumption, mainly flavonoids and carotenoids, through a high vegetable (e.g., onions) and soy intake. Related biological observations include low lipid peroxide, high superoxide dismutase activity and high serum hydroxyproline, a marker of bone formation. Dehydroepiandrosterone (DHEA) and its hormonal byproducts testosterone and oestrogen appear to be high in Okinawan serum compared with age-matched Americans, possibly reflecting a slower age-associated decline in the sex hormone axis in Okinawans. This may be linked to better cardiovascular and overall health. Further study is needed to delineate the reasons behind the impressive cardiovascular and overall health of the Okinawans.

The enzymatic formation of novel bile acid primary amides

Bifunctional peptidylglycine alpha-amidating monooxygenase (PAM) catalyzes the copper-, ascorbate-, and O(2)-dependent cleavage of C-terminal glycine-extended peptides and N-acylglycines to the corresponding amides and glyoxylate. The alpha-amidated peptides and the long-chain acylamides are hormones in humans and other mammals. Bile acid glycine conjugates are also substrates for PAM leading to the formation of bile acid amides. The (V(MAX)/K(m))(app) values for the bile acid glycine conjugates are comparable to other known PAM substrates. The highest (V(MAX)/K(m))(app) value, 3.1 +/- 0.12 x 10(5) M(-1) s(-1) for 3-sulfolithocholylglycine, is 6.7-fold higher than that for d-Tyr-Val-Gly, a representative peptide substrate. The time course for O(2) consumption and glyoxylate production indicates that bile acid glycine conjugate amidation is a two-step reaction. The bile acid glycine conjugate is first converted to an N-bile acyl-alpha-hydroxyglycine intermediate which is ultimately dealkylated to the bile acid amide and glyoxylate. The enzymatically produced bile acid amides and the carbinolamide intermediates were characterized by mass spectrometry and two-dimensional (1)H-(13)C heteronuclear multiple quantum coherence NMR.

N-acylglycine amidation: implications for the biosynthesis of fatty acid primary amides

Bifunctional peptidylglycine alpha-amidating enzyme (alpha-AE) catalyzes the O2-dependent conversion of C-terminal glycine-extended prohormones to the active, C-terminal alpha-amidated peptide and glyoxylate. We show that alpha-AE will also catalyze the oxidative cleavage of N-acylglycines, from N-formylglycine to N-arachidonoylglycine. N-Formylglycine is the smallest amide substrate yet reported for alpha-AE. The (V/K)app for N-acylglycine amidation varies approximately 1000-fold, with the (V/K)app increasing as the acyl chain length increases. This effect is largely an effect on the KM,app; the KM,app for N-formylglycine is 23 +/- 0.88 mM, while the KM,app for N-lauroylglycine and longer chain N-acylglycines is in the range of 60-90 microM. For the amidation of N-acetylglycine, N-(tert-butoxycarbonyl)glycine, N-hexanoylglycine, and N-oleoylglycine, the rate of O2 consumption is faster than the rate of glyoxylate production. These results indicate that there must be the initial formation of an oxidized intermediate from the N-acylglycine before glyoxylate is produced. The intermediate is shown to be N-acyl-alpha-hydroxyglycine by two-dimensional 1H-13C heteronuclear multiple quantum coherence (HMQC) NMR.

Nerve growth factor prevents apoptotic cell death in injured central cholinergic neurons

Experimental lesions have been widely used to induce neuronal degeneration and to test the ability to trophic molecules to prevent lesion-induced alterations, but these studies have not demonstrated unequivocally that afflicted neurons die as a result of these manipulations. The documentation of neuronal death in the above-described models and the time when it occurs after injury are crucial for the interpretation of trophic effects. In the present study, we combined multiple approaches to investigate the nature of retrograde neuronal changes in cholinergic neurons of the medial septal nucleus (MSN) after complete, unilateral transection of the fimbria-fornix (F-F). Projections neurons of the MSN were prelabeled with the fluorescent tracer Fluoro-gold (FG) 1 week prior to lesion. By counting both FG-labeled and choline acetyltransferase (ChAT)-immunoreactive neurons in the MSN at multiple time points postaxotomy, we differentiated the phenotypic response to injury from the degenerative process and established a critical time between the third and fourth weeks postaxotomy, during which approximately 50% of fluorescent perikarya disappear. Working in the previous time window, we identified dying cells by electron microscopy (EM) and terminal transferase-mediated (TdT) deoxyuridine triphosphate (d-UTP)-biotin nick end labeling (TUNEL) and showed that MSN neurons die via apoptosis, beginning at 16 days postaxotomy. An additional group of animals was allowed to survive for 1 month (i.e., 10 days after cell death has been completed); during this period, animals were treated with intraventricular nerve growth factor (NGF). Quantitative analysis of surviving cholinergic perikarya showed that NGF prevented degeneration of the majority of neurons. In concert, the results of the present study establish that NGF does not merely protect the phenotype but also prevents cell death in lesioned central cholinergic neurons.

Preliminary evidence for neurodegenerative changes in the substantia nigra of Rett syndrome

Rett syndrome (RS), which affects approximately 1 in 10,000 young females, is characterized by cognitive deterioration, ataxia, apraxia, rigidity, and stereotyped hand movements. Neuropathological features include reduction in brain size and hypopigmentation of neurons of the substantia nigra pars compacta (SNpc). Neurochemical and imaging studies support nigrostriatal involvement. The results of our preliminary studies show abnormalities in neurons of the substantia nigra (SN), including decreased numbers of neurons, ubiquitin-stained neuronal inclusion bodies, decreased immunostaining for transmitter markers, and evidence of cell death using terminal deoxynucleotidyl transferase (TDT)-mediated dUTP-biotin nick end labeling (TUNEL), which labels fragmented intranucleosomal DNA. These preliminary data represent the first evidence for cell death in RS.

Neurotrophic strategies for treating Alzheimer's disease: lessons from basic neurobiology and animal models

Because neurotrophic factors can prevent natural and experimental cases of neural cell death and induce and maintain differentiation, they are especially attractive agents for the treatment of neurodegenerative diseases, such as Alzheimer's disease (AD). The present report argues for the specific role of particular families of trophic factors, such as neurotrophins (e.g., nerve growth factor [NGF]) and neurokines (e.g., ciliary neurotrophic factor [CNTF]), for the promotion of the survival and phenotype of subsets of central nervous system (CNS) neurons vulnerable in AD, such as basal forebrain cholinergic neurons and cortical projection neurons. Although there is ample evidence for the therapeutic role of NGF in experimental or natural injury of cholinergic neurons, not enough progress has been made on trophic models involving cortical neurons. Further understanding of the mechanisms of cell death in AD and elucidation of the transduction cascades of trophic factors will undoubtedly refine our current concepts of a neurotrophic treatment for AD.

Food intake and estradiol effects on insulin binding in brain and liver

Three groups of ovariectomized rats were treated for 6 days: 1) estradiol benzoate (100 micrograms/kg) (SC) and fed ad lib; 2) vehicle-injected controls fed the same amount of food as eaten by estradiol-treated rats; 3) vehicle-injected, free-feeding controls. Specific binding of insulin to liver and hypothalamus slices was measured by quantitative film autoradiography. Estradiol-treated rats lost weight (p < 0.001) and had elevated plasma insulin (p < 0.01). Liver insulin binding in rats with estradiol treatment was greater (p < 0.01) than in rats without estradiol, but was less (p < 0.05) than in controls fed the same food levels as consumed by the estradiol-treated rats. Therefore, with equal food intake, estradiol decreased liver insulin binding. Insulin binding in the dorsomedial, ventromedial, and arcuate nuclei of the hypothalamus was unchanged by food intake or estradiol, however. Thus, altered insulin binding in the arcuate, ventromedial, or dorsomedial nuclei of the hypothalamus is probably not involved in the effects of insulin or estradiol on food intake.

Expression of acidic fibroblast growth factor mRNA in the developing and adult rat brain

We have localized acidic fibroblast growth factor (aFGF) mRNA in the developing and adult rat brain using in situ hybridization histochemistry. Prenatally, hybridization to aFGF mRNA was observed throughout the brain, with the strongest signal associated with cells of the developing cortical plate. Postnatally, labeling was localized to specific neuronal populations. In the hippocampus, labeling of the pyramidal cell layer and dentate granule cells was observed and became progressively more intense with maturation. Labeling was also observed in both the external and internal granule cell layers of the developing cerebellum. Pyramidal cells of the neocortex as well as neurons of the substantia nigra and locus ceruleus also express aFGF. This pattern persists into adulthood, although the intensity of the labeling is significantly reduced in the adult brain. These patterns of hybridization correlate with specific developmental events and suggest that aFGF plays a significant role in both central nervous system development and neuronal viability in the adult brain.

Hippocampal adenosine A1 receptors are decreased in Alzheimer's disease

Previous studies showed that adenosine receptors of the temporal and frontal cortices were not affected in Alzheimer's disease (AD). Here, we assessed the specific binding of [3H]cyclohexyladenosine to adenosine1 (A1) receptors in hippocampus from AD subjects and age-matched controls. By both particulate membrane and in vitro autoradiographic receptor binding methods we demonstrate that A1 receptors are significantly reduced by 40-60% in AD subjects. Scatchard analysis showed that maximum binding capacity (Bmax) was affected and there was no evidence for a change in the affinity of the receptor for the ligand (Kd). Receptor autoradiography revealed that although several regions including CA1, CA3 and deep layer of the subiculum were affected, the loss in A1 receptors was most prominent in the molecular layer of the dentate gyrus. In view of previous evidence indicating that these receptors are associated with the perforant pathway and dendritic fields of the CA1 and CA3 regions, our findings suggest loss of the presynaptic A1 receptors on axon terminals of extrinsic pathways including the perforant path and intrinsic pyramidal neurons which release glutamate.

Localization of 3H-prazosin binding sites in the supraoptic and paraventricular nuclei of the human hypothalamus

Using 3H-prazosin, we have examined the distribution of alpha 1-adrenergic receptors in the supraoptic and paraventricular nuclei of the human hypothalamus. Our studies show that binding sites for 3H-prazosin in human hypothalamus possess pharmacological characteristics similar to those of rat brain. Autoradiographic studies revealed discrete localization of 3H-prazosin to the paraventricular and supraoptic nuclei.

Identification of a subpopulation of neuropeptide Y-containing locus coeruleus neurons that project to the entorhinal cortex

A fundamental question important to the understanding of the neurochemical organization of the central nervous system focuses on the relationships between the differential phenotypic expression of multiple neurotransmitter markers in individual neuronal populations and the factors that regulate their expression. The first approach in studying this phenomenon is the determination of specific relationships between neurochemically distinct neuronal subpopulations and their efferent targets. The pontine nucleus locus coeruleus (LC) provides a useful model for addressing this question since the projections of LC neurons are topographically organized and several neuropeptides are expressed along with noradrenergic markers in subsets of these neurons. In these studies, we have focused on defining the efferent targets of LC neurons that contain neuropeptide tyrosine (NPY)-like immunoreactivity. This has been accomplished by injecting the retrograde fluorescent tracer fluorogold into specific cortical and hippocampal targets in adult rats and identifying the proportion of retrogradely labeled LC neurons that are positive for NPY-like immunoreactivity. In agreement with other investigators, no preferential cortical projections of NPY-positive LC neurons were observed. However, when fluorogold injections included or were limited to the entorhinal cortex, a discrete cluster of round or ovoid neurons in the dorsomedial portion of the LC approximately 9.8 mm posterior to bregma were found to contain NPY-like immunoreactivity. This observation demonstrates that some topographic organization of NPY-containing LC neurons does exist. In fact, these data indicate that morphologic and topographic organization exists even within neurochemically distinct subsets of neuronal populations.

Insulin binding in the hypothalamus of lean and genetically obese Zucker rats

Recent reports have suggested that the obesity and hyperphagia of the genetically obese Zucker rat may be related to defective insulin action or binding in the hypothalamus. We used quantitative autoradiography to determine if insulin binding is altered in specific hypothalamic nuclei associated with food intake. Insulin binding was measured in the arcuate (ARC), dorsomedial (DMN), and ventromedial (VMN) hypothalamic nuclei of 3-4-month-old lean (Fa/Fa) and genetically obese (fa/fa) Zucker rats. A consistently reproducible 15% increase in the total specific binding of 0.1 nM [125I]-insulin was found in the ARC of the obese genotype. A slight increase in insulin binding in the DMN was also found. No difference in specific insulin binding was found between genotypes in the VMN. Nonlinear least squares analysis of competitive binding studies showed that the Kd of the ARC insulin binding site was 33% higher in the lean rats than in the obese rats, indicating an increased affinity for insulin. No difference in site number (Bmax) was found in the ARC, DMN or VMN, and no evidence was found for reduced insulin binding in the hypothalamus of the obese (fa/fa) genotype. The results suggest that hyperphagia and obesity of the obese (fa/fa) Zucker rat genotype may be associated with increased insulin binding in the arcuate nucleus.

Reduction of insulin binding in the arcuate nucleus of the rat hypothalamus after 6-hydroxydopamine treatment

Insulin receptors are present in the hypothalamus, but the cell types bearing them are unknown. In order to test the hypothesis that some insulin receptors in the hypothalamus are associated with catecholamine terminals, rats were injected with 50 micrograms or 75 micrograms doses (intracerebroventricular) of 6-hydroxydopamine (6-OHDA). Control rats received vehicle only. The animals were sacrificed 7 days after injection, and catecholamine and indolamine levels in the hypothalamus were measured by high performance liquid chromatography with electrochemical detection. Localization of specific binding sites for [125I]-insulin in the arcuate (ARC), dorsomedial (DMN) and ventromedial (VMN) nuclei were determined by quantitative film autoradiography. Treatment with 6-OHDA resulted in a 70% reduction in hypothalamic norepinephrine content as compared to vehicle-treated controls (P less than 0.01). A slight depletion of epinephrine, dopamine and indolamines was also detected. Computerized image analysis of the autoradiograms was used to determine radioactivity bound (DPM/mm2) in each nucleus. Highest binding was in the ARC and DMN, with much lower binding in the VMN. Insulin binding in the ARC of the 6-OHDA-treated group was decreased by 25% compared to controls (P less than 0.01). No significant change in insulin binding was observed in the DMN or VMN. The 6-OHDA treatment had no significant effect on weight gain or on plasma insulin levels. The reduction of insulin binding in the ARC after 6-OHDA treatment supports the hypothesis that some insulin binding sites are located on catecholamine terminals in the arcuate nucleus.

Localization and measurement of neurotransmitter receptors in rat and human brain by quantitative autoradiography

Receptors for neurotransmitters can be visualized and characterized using in vitro tissue slice binding techniques and quantitative autoradiography. In this article, the general methods used in studies of this type are outlined and specific application to the study of catecholamine and neuropeptide receptors in rat and human brain tissue are described. Receptor autoradiography is used to examine regulation of dopamine receptor density in response to denervation and replacement of dopamine using brain transplants. Morphological and pharmacological aspects of vasopressin receptor ontogeny in the rat brain are examined. Finally, autoradiographic data on catecholamine receptor localization and characterization in the human hypothalamus, locus coeruleus, and frontal cortex are presented and discussed with reference to their applications in the study of neuropsychiatric disorders such as schizophrenia and senile dementia of the Alzheimer's type.

Characterization of insulin-like growth factor I receptors in the median eminence of the brain and their modulation by food restriction

High affinity binding sites for 125I-labeled [Thr59]insulin-like growth factor I (IGF-I) were measured in rat median eminence by in vitro autoradiography with slide-mounted sections of frozen rat brain. Specific binding of 0.1 nM iodo-[Thr59]IGF-I to brain slices reached maximum by 12 h at 4 C and was unchanged at 24 h. Densitometry by computer digital image analysis of autoradiographic images indicated that specific binding of iodo-[Thr59]IGF-I to the median eminence was reversible. The specificity of binding was evaluated with competition of iodo-[Thr59]IGF-I with unlabeled [Thr59]IGF-I, rat IGF-II (multiplication-stimulating activity), and porcine insulin. All were recognized by the binding site, but the rank order of potency was [Thr59]IGF-I greater than IGF-II greater than insulin. Somatostatin was completely ineffective. Further, an antibody against the rat IGF-II receptor did not block binding of iodo-[Thr59]IGF-I to the median eminence. Fourteen days of food restriction (75% of food intake of controls) resulted in significant weight loss and reduction of plasma immunoreactive IGF-I in six food-restricted rats (0.9 +/- 0.1 U/ml) compared with values in six controls (2.6 +/- 0.5 U/ml; P less than 0.001). Binding of 125I-labeled [Thr59]IGF-I in the median eminence was significantly increased in the food-restricted rats, primarily due to an increase in the concentration of iodo-[Thr59]IGF-I-binding sites in the median eminence; the affinity (Kd) of binding was unchanged. The results indicate that the median eminence has type I IGF-I receptors, which become more numerous under metabolic conditions associated with decreased caloric intake and lowered plasma IGF-I levels.

Localization of binding sites for insulin-like growth factor-I (IGF-I) in the rat brain by quantitative autoradiography

In vitro quantitative autoradiography was used to localize IGF-I binding sites in rat brain. Slide-mounted sections of frozen rat brain were incubated in 0.01 nM 125I[Thr59]IGF-I, alone or mixed with 10 nM unlabeled [Thr59]IGF-I or insulin, for 22 h at 4 degrees C and apposed to LKB Ultrofilm. Measurement of labeled [Thr59]IGF-I binding by computer digital image analysis of the autoradiographic images indicated that high affinity IGF-I binding sites are widely distributed at discrete anatomical regions of the brain microarchitecture. The highest concentration of specific binding sites was in the choroid plexus of the lateral and third ventricles. Unlabeled porcine insulin was less potent than unlabeled IGF-I in competing for binding sites on brain slices. Regions of the olfactory, visual, and auditory, as well as visceral and somatic sensory systems were labeled, in particular the glomerular layer of the olfactory bulb, the anterior olfactory nucleus, accessory olfactory bulb, primary olfactory cortex, lateral-dorsal geniculate, superior colliculus, medial geniculate, and the spinal trigeminal nucleus. High concentrations of IGF-I-specific binding sites were present throughout the thalamus and the hippocampus, (dentate gyrus, Ca1, Ca2, Ca3). The hypothalamus had moderate binding in the paraventricular, supraoptic, and suprachiasmatic nucleus. Highest binding in the hypothalamus was in the median eminence. The arcuate nucleus showed very low specific binding, approaching the levels found in optic chiasm and white matter regions. Layers II and VI of the cerebral cortex also had moderate IGF-I binding. The results suggest that the development and functions of brain sensory and neuroendocrine pathways may be regulated by IGF-I.

Distribution of neurotransmitter binding sites in the cat median eminence

Receptor autoradiography was used to determine the distribution of binding sites for monoaminergic and cholinergic neurotransmitters in the cat median eminence. Results showed that binding sites were differentially distributed in that [3H]-p-aminoclonidine (an alpha-2-adrenergic ligand) and [3H]pyrilamine (an H1-histaminergic ligand) binding were concentrated in the medial region of the external layer of the median eminence while [3H]lysergic acid diethylamide (a serotonergic ligand) and [3H] quinuclidinyl benzilate (a muscarinic cholinergic ligand) binding were concentrated within the lateral region of the external layer. These patterns are coincident with the differential distribution of hypophysiotropic hormones in the median eminence, suggesting that monoamines and acetylcholine may regulate the release of these hormones at the level of the median eminence.

Identification of binding sites for an insulin-like growth factor (IGF-I) in the median eminence of the rat brain by quantitative autoradiography

The microanatomical location of IGF-I binding in the rat brain was determined by in vitro autoradiography with slide-mounted sections of frozen brain. Sections incubated in 0.1 nM [125I]-iodo-IGF-I produced a dense grain concentration in regions of the autoradiographic image corresponding to the external palisade zone of the median eminence; other hypothalamic regions were not so heavily labeled. This reaction was significantly reduced in the presence of 100 nM IGF-I. Measurement of binding by computer digital image analysis of autoradiographic images showed that specific binding for IGF-I in the median eminence was 41.3 +/- 8 X 10(-3) fmol/mm2 (mean +/- SEM); nonspecific binding was 11.9 +/- 1.8 X 10(-3) fmol/mm2. In contrast, specific binding to other hypothalamic regions was uniformly lower. In a separate experiment, 1000 nM unlabeled insulin was added. Without insulin, specific binding was 23 +/- 0.9 X 10(-3) fmol/mm2; nonspecific binding was 8 +/- 0.5 X 10(-3) fmol/mm2. In the presence of 1000 nM unlabeled insulin, specific binding for [125I]-iodo-IGF-I was 23 +/- 1 X 10(-3) fmol/mm2. The results suggest that a high concentration of receptors for an IGF-I-like molecule is present in the median eminence.

Localization of neuronal histamine in rat brain

Antisera to histamine were generated by immunization of albino guinea pigs with a complex of histamine and methylated-bovine serum albumin. Characterization of the antisera and preliminary mapping of histaminergic neurons were conducted on brain tissue from normal and experimentally manipulated rats. Using immunofluorescence, histamine-like immunoreactive cell bodies were revealed in the lateral hypothalamus, and fibers were stained in the hypothalamus, cortex, amygdala and hippocampus.