Neuropeptide Y (NPY) and peptide YY (PYY) receptors in rat brain

1. Specific binding sites for neuropeptide Y (NPY) and peptide YY (PYY) were investigated in rat brain areas using quantitative receptor autoradiography with 125I-Bolton-Hunter NPY (125I-BH-NPY) and 125I-PYY, radioligands for PP-fold family peptides receptors. 2. There were no differences between localization of 125I-BH-NPY and 125I-PYY binding sites in the rat brain. High densities of the binding sites were present in the anterior olfactory nucleus, lateral septal nucleus, stratum radiatum of the hippocampus, posteromedial cortical amygdaloid nucleus, and area postrema. 3. In cold ligand-saturation experiments done in the presence of increasing concentrations of unlabeled NPY and PYY, 125I-BH-NPY and 125I-PYY binding to the stratum radiatum of the hippocampus, layer I of the somatosensory frontoparietal cortex, molecular layer of the cerebellum, and area postrema was single and of a high affinity. There was a significant difference between the affinities of 125I-BH-NPY (Kd = 0.96 nM) and 125I-PYY binding (Kd = 0.05 nM) to the molecular layer of the cerebellum. The binding of the two radioligands to the other areas examined had the same affinities. 4. When comparing the potency of unlabeled rat pancreatic polypeptide (rPP), a family peptide of NPY and PYY, to inhibit the binding to the areas examined, rPP displaced 125I-BH-NPY and 125I-PYY binding to the area postrema more potently than it did the binding to the stratum radiatum of the hippocampus, layer I of the somatosensory frontoparietal cortex, and molecular layer of the cerebellum. 5. Thus, the quantitative receptor autoradiographic method with 125I-BH-NPY and 125I-PYY revealed differences in binding characteristics of specific NPY and PYY binding sites in different areas of the rat brain. The results provide further evidence for the existence of multiple NPY-PYY receptors in the central nervous system.     

Adenoviruses in lymphocytes of the human gastro-intestinal tract

Objective

Persistent adenoviral shedding in stools is known to occur past convalescence following acute adenoviral infections. We wished to establish the frequency with which adenoviruses may colonize the gut in normal human subjects.

Methods

The presence of adenoviral DNA in intestinal specimens obtained at surgery or autopsy was tested using a nested PCR method. The amplified adenoviral DNA sequences were compared to each other and to known adenoviral species. Lamina propria lymphocytes (LPLs) were isolated from the specimens and the adenoviral copy numbers in the CD4+ and CD8+ fractions were determined by quantitative PCR. Adenoviral gene expression was tested by amplification of adenoviral mRNA.

Results

Intestinal tissue from 21 of 58 donors and LPLs from 21 of 24 donors were positive for the presence of adenoviral DNA. The majority of the sequences could be assigned to adenoviral species E, although species B and C sequences were also common. Multiple sequences were often present in the same sample. Forty-one non-identical sequences were identified from 39 different tissue donors. Quantitative PCR for adenoviral DNA in CD4+ and CD8+ fractions of LPLs showed adenoviral DNA to be present in both cell types and ranged from a few hundred to several million copies per million cells on average. Active adenoviral gene expression as evidenced by the presence of adenoviral messenger RNA in intestinal lymphocytes was demonstrated in 9 of the 11 donors tested.

Conclusion

Adenoviral DNA is highly prevalent in lymphocytes from the gastro-intestinal tract indicating that adenoviruses may be part of the normal gut flora.     

Stimulation of NPY Y2 receptors by PYY3-36 reveals divergent cardiovascular effects of endogenous NPY in rats on different dietary regimens

In the present experiments the gut hormone peptide YY3-36 (PYY3-36), which inhibits neuropeptide Y (NPY) release, was used as a tool to study the cardiovascular effects of endogenous NPY under different dietary regimens in rats instrumented with a telemetry transmitter. In a first experiment, rats were placed on a standard chow diet ad libitum and in a second experiment on a high-fat diet ad libitum. After 6 wk, PYY3-36 (300 microg/kg) or vehicle was injected intraperitoneally. In a third experiment, PYY3-36 or vehicle was administered after 14 days of 50% restriction of a standard chow diet. In food-restricted rats, PYY3-36 increased mean arterial pressure (7 +/- 1 mmHg, mean +/- SE, P < 0.001 vs. saline, 1-way repeated-measures ANOVA with Bonferroni t-test) and heart rate (22 +/- 4 beats/min, P < 0.001) during 3 h after administration. Conversely, PYY3-36 did not influence mean arterial pressure (0 +/- 1 mmHg) and heart rate (-8 +/- 5 beats/min) significantly in rats on a high-fat diet. Rats fed standard chow diet ad libitum showed an intermediate response (mean arterial pressure 4 +/- 1 mmHg, P < 0.05, and heart rate 5 +/- 2 beats/min, not significant). Thus, in our studies, divergent cardiovascular responses to PYY3-36 were observed in rats on different dietary regimens. These findings suggest that the cardiovascular effects of PYY3-36 depend on the hypothalamic NPY release, which is increased after chronic food restriction and decreased during a high-fat diet.     

Functional endothelin/sarafotoxin receptors in the rat uterus

Functional receptors for the peptides of the endothelin (ET) and sarafotoxin (SRTX) families were detected in the rat uterus. These receptors specifically bind 125I-SRTX-b (Bmax = 220 fmol/mg protein), as well as ET-1, ET-3 and SRTX-c (IC50's 10, 5, 300 and 780 nM, respectively). Activation of the uterine ET/SRTX receptors induced dose-dependent phosphoinositide (PI) hydrolysis and three typical contractile responses: 1) increase in the muscle tonic tension; 2) increase in frequency of the spontaneous rhythmic contractions; 3) decrease of relaxation in each spontaneous rhythmic cycle. All three effects appeared at doses as low as 0.5-1 nM. Dose responses yield ED50 values of 5.5, 30 and 680 nM for ET-1, SRTX-b and ET-3, respectively. SRTX-c was the least effective peptide in achieving decrease in relaxation. In view of these results, and since the uterine responses to the peptides were almost immediate and reversible, we suggest that the functional ET/SRTX receptor of the rat uterus that is coupled to PI hydrolysis may be of physiological significance.     

PYY preference is a common characteristic of neuropeptide Y receptors expressed in human, rat, and mouse gastrointestinal epithelia

This investigation describes the relative potencies of four peptide agonists, namely, peptide YY (PYY), [Leu3l,Pro34]PYY (Pro34pYY), neuropeptide Y (NPY), and [Leu31,Pro34]NPY (Pro34NPY), as antisecretory agents in human, rat, and mouse gastrointestinal preparations. The inhibition of agonist responses by the Y1-receptor antagonist BIBP 3226 was also tested in each preparation. An unexpectedly pronounced preference for PYY and Pro34PYY was observed in functional studies of two human epithelial lines stably transfected with the rat Y1 receptor (Y1-7 and C1Y1-6). NPY and Pro34NPY were at least an order of magnitude less effective than PYY in these functional studies but were only marginally less potent in displacement binding studies using membrane preparations of the same clonal lines. The orders of agonist potency obtained in Y1-7 and C1Y1-6 epithelia were compared with those obtained from a single human colonic adenocarcinoma cell line (Colony-6, which constitutively expresses Y1 receptors) and also from mucosal preparations of rat and mouse descending colon. Similar peptide orders of potency were obtained in rat and mouse colonic mucosae and Colony-6 epithelia, all of which exhibited PYY preference (although less pronounced than with Y1-7 and C1Y1-6 epithelia) and significant sensitivity to the Y1 receptor antagonist, BIBP 3226. We have compared the pharmacology of these five mammalian epithelial preparations and provide cautionary evidence against the reliance upon agonist concentration-response relationships alone, in the characterization of NPY receptor types.     

Gastric protective effect of peripheral PYY through PYY preferring receptors in anesthetized rats

The influence of intravenous peptide YY (PYY) on the gastric injury induced by 45% ethanol was investigated in urethane-anesthetized rats. PYY (25, 75, 125, and 250 pmol x kg(-1) x h(-1)) significantly reduced gastric lesions by 36, 59, 40, and 38%, respectively. Antibody against ratPYY (2 mg/rat) injected intravenously completely prevented the gastroprotective effect of intravenous PYY (75 pmol x kg(-1) x h(-1)), whereas injected intracisternally (460 microg/20 microl), it significantly prevented intracisternal PYY (24 pmol/rat)-induced 58% reduction of ethanol lesions but not that induced by intravenous PYY. Vagotomy did not influence the gastroprotective effect of intravenous PYY. The Y(1)/"PYY-preferring" receptor agonist [Pro(34)]PYY (75 pmol x kg(-1) x h(-1) iv) significantly decreased ethanol-induced gastric lesions by 82%, whereas [Leu(31), Pro(34)]NPY, a Y(1)/Y(3) agonist, and PYY-(3-36), a Y(2) agonist, had no effect. These data indicate that PYY-infused intravenously at doses reported to mimic postprandial peak blood levels prevents ethanol-induced gastric injury through vagal independent pathways and PYY-preferring receptors.     

Recent progress in PYY research--an update report for 8th NPY meeting

PYY(3-36) is a gut regulatory peptide which has recently been found to reduce appetite. Variability of this effect across different experimental conditions has led to confusion and polarization of opinion on its potential as an anti-obesity treatment. This review summarizes recent progress in this area. The basic anorexigenic effect leading to weight loss in rodents has now been confirmed by several groups. Anorexia has also been confirmed in human studies although optimal route and dosing remain to be defined. Gastric bypass causes PYY levels to rise, which may in part mediate the weight loss occurring after this surgery, and levels have been found to be normal or low in obese people. The straightforward ARC model of mechanism, involving inhibition and activation, respectively, of NPY and POMC neurons, is giving way to a more complicated system involving vagal afferent signals. Conclusion: It works, but not how we thought it did.     

NPY receptors in human cancer: a review of current knowledge

Many peptide hormone receptors are over-expressed in human cancer, permitting an in vivo targeting of tumors for diagnostic and therapeutic purposes. NPY receptors are novel and promising candidates in this field. Using in vitro receptor autoradiography, Y1 and Y2 receptors have been found to be expressed in breast carcinomas, adrenal gland and related tumors, renal cell carcinomas, and ovarian cancers in both tumor cells and tumor-associated blood vessels. Pathophysiologically, tumoral NPY receptors may be activated by endogenous NPY released from intratumoral nerve fibers or tumor cells themselves, and mediate NPY effects on tumor cell proliferation and tumoral blood supply. Clinically, tumoral NPY receptors may be targeted with NPY analogs coupled with adequate radionuclides or cytotoxic agents for a scintigraphic tumor imaging and/or tumor therapy.     

Immunocytochemical identification of polypeptide YY (PYY) cells in the human gastrointestinal tract

Various parts of the human gastrointestinal tract were investigated immunocytochemically for the occurrence of polypeptide YY (PYY) and pancreatic polypeptide (PP). PYY-immunoreactive cells were observed in the lower part of the ileum, in the colon and in the rectum, and PP-immunoreactive cells were found in the colon and rectum. Both cell types were of the open type, i.e. they extended from the basal lamina to the gut lumen. PYY-immunoreactive cells were seen to emit cytoplasmic processes to the neighbouring goblet cells. This latter observation suggests that PYY cells may exert a paracrine action on the mucus-secreting goblet cells. Staining of consecutive thin plastic sections and staining of the same section simultaneously for two peptides showed that PYY-immunoreactivity did not occur in PP- or enteroglucagon-immunoreactive cells. On the ultrastructural level PYY-immunoreactivity was localized in basal granulated endocrine cells. These cells contained round or slightly oval electron dense granules with a mean diameter of 150 nm (range 100-300 nm).     

Functional mapping of human growth trajectories

Human height is an important trait from biological and social perspectives. Genes have been widely recognized to be involved in human body growth, but their detailed controlling mechanisms are poorly understood. Here, we present a computational model for functional mapping of quantitative trait loci (QTLs) that control trajectories of human height growth through an interactive network. The model integrates mathematical equations of human growth curves into the mixture model-based functional mapping framework, allowing the identification and mapping of individual QTLs responsible for the developmental pattern of human growth. The model was derived on a random sample of subjects from a natural population, for each of which molecular markers within candidate genes or throughout the entire genome are typed and height data from childhood to adulthood are collected. A series of testable hypotheses are formulated about the genetic control of developmental timing and duration at different stages. The model was used to characterize epistatic QTLs for height growth hidden in 548 Japanese girls which is a semi-real data set with simulated the marker genotypes. With an increasing availability of genetic polymorphic data, the model will have great implications for probing the genetic and developmental mechanisms of human body growth and its associated diseases.     

On the alleged presence of non-argyrophile argentaffin cells in the human gastro-intestinal tract

Summary The relationship between the argentaffin and argyrophile cells of the human gastrointestinal tract has been studied, in foetal and adult material, by a technique involving the staining of sections first by an argentaffin method (Gomori-hexamine silver, Schmorl, Diazonium) and subsequently by an argyrophile method (Bodian). A comparison of the cells staining by the two methods shows that all argentaffin cells of the human gastrointestinal tract are also argyrophile and that there is no evidence to support the claim of Hellweg (1952) and of HamPerl (1952) regarding the presence of non-argyrophile argentaffin cells.W. H. O. fellow from the Department of Anatomy, Medical College, Rohtak, India. — I am very grateful to Professor J. D. Boyd and to the World Health Organisation for having made it possible for me to carry out this research at the Anatomy School, Cambridge. I am indebted to Dr. G. A. Gresham and his staff for their very willing cooperation in providing material from surgical resections. My thanks are also due to Mr. J. F. Crane for the photographs and to Mr. J. W. Cash and Mr. R. Smith for helpful discussions on staining techniques.     

Functional coupling reactions of human amylin receptor and nicotinic acetylcholine receptors in rat brain neurons

Human amylin (hAmylin) is co-released with insulin from pancreatic B-cells and the actions of this peptide on its target tissues maintain the cell excitability and glucose homeostasis. Inappropriate control of hAmylin secretion may result in human disease, particularly Alzheimer's disease (AD). It's unknown that which kind of receptor is activated by human amylin, leading to the neurotoxicity in neurons of brain. Nicotinic acetylcholine receptors (nAChRs) are known to play a critical role in a variety of nervous diseases. In the present study, we sought to determine the inter-relationships between these two receptors by examining the actions of hAmylin and nicotine on whole-cell currents and membrane potential in basal forebrain neurons. Whole cell patch-clamp recordings were performed on enzymatically dissociated neurons of the diagonal band of Broca (DBB), a cholinergic basal forebrain nucleus. The results showed that either hAmylin or nicotine individually caused a dose-dependent (1 nmol/L-20 μmol/L) membrane depolarization and an increase in firing frequency of DBB neurons. Application of AC253, an amylin receptor antagonist, blocked the excitatory effects of not only hAmylin but also nicotine; dihydro-β-erythroidine (DHβE), a nAChR antagonist, also blocked the effects of nicotine and hAmylin. These electrophysiological results suggest that hAmylin receptor and nAChRs on DBB neurons are coupled and may function in a co-operative manner to influence the excitability of DBB neurons. This finding is important for us to understand the cause and mechanisms of AD.     

TRH-like immunoreactivity in endocrine cells and neurons in the gastro-intestinal tract of the rat and guinea pig

Summary By use of the indirect immunofluorescence technique, the cellular localization of thyrotropin-releasing hormone (TRH) was studied in the gastrointestinal tract of rats and guinea pigs of different ages. TRH-like immunoreactivity (LI) was observed in many pancreatic islet cells of young rats and guinea pigs but only in single cells of 6-month-old rats. In aged guinea pigs, a reduction in the number of TRH-positive cells was evident; however, numerous strongly fluorescent cells were still present. In the guinea pig, TRH-LI was in addition observed in gastrin cells in the stomach. TRH-positive nerve fibers occurred in the myenteric plexus of the oesophagus, stomach and intestine of the rat, and in the muscle layers of the guinea pig. These results suggest a functional role of TRH both as hormone and neuroactive compound in various portions and sites of the gastro-intestinal tract of the rat and guinea pig