Search PubMed⌕ Search

Biomedical subjects

W H Simmons

Publications and source records attributed to W H Simmons.

At least 37 records · Page 2Linked to original sources
PubMed1992

Dipeptidase activities in rat brain synaptosomes can be distinguished on the basis of inhibition by bestatin and amastatin: identification of a kyotorphin (Tyr-Arg)-degrading enzyme.

The neuropeptide kyotorphin (Tyr-Arg) was degraded by rat brain synaptosomes via a synaptic membrane-bound peptidase which was inhibited by bestatin but not by amastatin. The Km for kyotorphin was 8 x 10(-6) M and the Ki for bestatin was 1 x 10(-7) M. The kyotorphin-degrading enzyme was distinguished from at least one other dipeptide-hydrolyzing activity in synaptosomes which was inhibited by both bestatin and amastatin. Gel permeation chromatography of detergent-extracted synaptosomes resulted in the separation of the dipeptide-hydrolyzing activities. A single kyotorphin-degrading enzyme peak was observed which had a M(r) = 52,000. The activity peak could degrade other dipeptides including Phe-Arg, a synaptic membrane-generated metabolic of bradykinin. The kyotorphin-degrading enzyme appears to be novel and can be distinguished from other known dipeptidases on the basis of substrate specificity, subcellular localization, and inhibition profile.

Animals↗
PubMed1991

Tryptase from rat skin: purification and properties.

Tryptase was purified 13,000-fold to apparent homogeneity from rat skin. The two-step procedure involved ammonium sulfate fractionation of the initial extract followed by combined sequential affinity chromatography on agarose-glycyl-glycyl-p-aminobenzamidine and concanavalin A-agarose. The purified enzyme had a specific activity toward N-benzoylarginine ethyl ester (BzArgOEt) of 170 mumol/min mg-1 and was obtained in a yield of 28% as determined by the specific substrate, H-D-Ile-Pro-Arg-p-nitroanilide. Rat skin tryptase was thermal labile, losing 50% of its activity when preincubated for 30 min at 30 degrees C. The presence of NaCl (1 M) improved thermal stability and was necessary for long-term storage. Heparin did not stabilize the enzyme against thermal denaturation, and heparin-agarose failed to bind the enzyme. Rat skin tryptase was inhibited by diisopropylphosphofluoridate, antipain, leupeptin, and aprotinin but not by alpha 1-antitrypsin, ovomucoid, or soybean or lima bean trypsin inhibitors. Substrate specificity studies using a series of tri- and tetrapeptidyl-p-nitroanilide and peptidyl-7-amino-4-methylcoumarin substrates demonstrated the existence of an extended substrate binding site. Rat skin tryptase hydrolyzed [Arg8]vasopressin, neurotensin, and the oxidized B-chain of insulin at the -Arg8-Gly9-NH2, -Arg8-Arg9-, and -Arg22-Gly23-bonds, respectively. No general proteinase activity was observed toward casein, hemoglobin, or azocoll. Rat skin tryptase had a Mr of 145,000 by gel filtration. The subunit Mr was either 34,000 or 30,000 depending on the electrophoretic technique used. Treatment of the enzyme with peptide N-glycosidase F (N-glycanase) decreased the subunit Mr by 4000. The enzyme exhibited multiple isoelectric forms (pI's of 4.5-4.9). Rat skin tryptase was found to be related statistically to other tryptases on the basis of amino acid composition. The N-terminal amino acid sequence was Ile1-Val2-Gly3-Gly4-Gln5-Glu6-Ala7-+ ++Ser8-Gly9-Asn10-Lys11-Trp12-Pro13- Trp14- Gln15-Val16-Ser17-Leu18-Arg19-Val20- --21-Asp-22Thr23-Tyr24-Typ25-, with a putative glycosylation site at residue 21. This sequence was 72-80% homologous with the N-terminus of other tryptases but only 40% homologous with that of bovine trypsin.

Amino Acid Sequence↗
PubMed1990

Aversive properties of bombesin in rats.

Aversive properties of bombesin were determined in the conditioned place-preference paradigm in rats and compared with the effects on spontaneous behavior. Bombesin induced excessive grooming and/or scratching behavior at doses of 80 ng, 400 ng, and 2.0 micrograms ICV. In the conditioned place-preference paradigm, doses of 400 ng and 2.0 micrograms ICV induced a profound aversion to the environment in which the animals had received peptide treatment. Eighty ng were partially effective, and 16 ng did not induce a significant change in preference. The grooming/scratching behavior was attenuated by pretreatment with 4 mg/kg morphine-sulfate. These results show that bombesin is strongly aversive at doses that induce grooming/scratching behavior. Although the relationship between these different effects is not known, the similarity in their dose-response relationship suggests that they may be mediated by a common mechanism.

Animals↗
PubMed1989

A seasonal pineal peptide rhythm persists in superior cervical ganglionectomized rats.

Neurohypophyseal peptide hormone activity is present in the pineal gland of mammals, and varies over a seasonal cycle. Pineal peptide levels, measured by arginine vasotocin (AVT) radioimmunoassay, increase dramatically for a brief time during August each year. The manner in which this cycle is regulated is as yet unknown. Input to the pineal from sympathetic axons arising in the superior cervical ganglia (SCG) is essential for the generation and regulation of the circadian rhythm in melatonin synthesis, and is the only pathway known to regulate pineal biochemical processes. It was of interest then to determine the impact of the SCG on the seasonal peptide cycle. Levels of pineal arginine vasotocin immunoactivity (iAVT) were monitored during August, 1984, in rats which had been superior cervical ganglionectomized (SCGX), in sham-operated and intact controls (L:D 12:12), and in rats subjected to L:D 22:2. The results indicate that SCGX does not abolish the seasonal cycle, but may influence the timing of the iAVT peak. Inhibition of pineal melatonin synthesis by exposure of rats to L:D 22:2 did not mimic the phase delay seen with SCGX, but did cause a significant increase in the amplitude of the August iAVT activity peak.

Animals↗
PubMed1989

Influence of age on August levels of pineal immunoreactive arginine vasotocin in rats.

The present study was undertaken to evaluate carefully the influence of age on physiological levels of arginine vasotocin-like peptide in rat pineal glands. Glands were collected from male and female rats aged 13, 33, 53, and 73 days on August 4, 12, and 19, 1984. Individual extracts were assayed for arginine vasotocin (AVT) by radioimmunoassay. The results confirm our previous observation that rat pineal AVT immunoactivity (iAVT) increases significantly during August each year; and in this study, each group of rats reached the same peak level of iAVT (700-750 pg/gland) regardless of age or gender. Thus we do not confirm a previously reported decrease in AVT activity with age. In our studies thus far, season of the year is the physiological variable with the most significant influence on pineal AVT activity levels.

Aging↗
PubMed1987

Aminopeptidase P from bovine lung: solubilization, properties, and potential role in bradykinin degradation.

Aminopeptidase P was solubilized from bovine lung by sodium deoxycholate extraction of salt-washed, delipidated lung acetone powders. Hydrolysis of the standard aminopeptidase P substrate, Gly-Pro-Hyp, as well as cleavage of Arg-Pro-Pro and the Arg1-Pro2 bond of bradykinin, co-eluted from a Mono Q anion exchange column and demonstrated identical inhibitory profiles suggesting that all activities were functions of the same enzyme. The metal chelator, 1,10-phenanthroline, completely inhibited activity suggesting that aminopeptidase P is a metallopeptidase. 2-Mercaptoethanol was both a potent and specific inhibitor of the enzyme (at 4 mM). A variety of other peptidase inhibitors showed either no effect or failed to completely inhibit even at high concentrations. The inhibitory profile and substrate specificity differ considerably from previous reports claiming to study the properties of this enzyme. Evidence is provided that aminopeptidase P may have an important role in the pulmonary degradation of the potent vasoactive peptide, bradykinin.

Aminopeptidases↗
PubMed1987

Specific antagonists of the acute behavioral response to centrally-administered vasopressin in mice.

Vasopressin and related peptides cause behavioral excitation after intracerebroventricular injection in mice. This behavioral excitation is characterized by excessive scratching and grooming behavior in the unrestrained animal and enhanced escape-directed activity in stressful situations. These effects of vasopressin were found to be blocked by the administration of analogs which act as competitive antagonists of the pressor-activity of vasopressin. The potencies of these analogs in suppressing the behavioral effect paralleled the pressor antagonist potencies. The antagonists did not cause the characteristic behavioral alterations by themselves, nor did they block grooming and/or scratching behavior induced by the structurally-unrelated substances, mescaline, bombesin and substance P. It is suggested that these antagonists provide useful tools for studying the role of endogenous vasopressin in behavior.

Animals↗
PubMed1987

Partial characterization of a renin-releasing factor from plasma and hypothalamus.

Previous studies have indicated that administration of the serotonin releaser p-chloroamphetamine HCl produces a dose-dependent increase in renin secretion through a blood-borne renin-releasing factor. The present studies were designed to partially characterize this renin-releasing factor using an in vitro kidney slice method for the bioassay of renin-releasing activity. Plasma from p-chloroamphetamine-treated, nephrectomized rats was used to obtain the renin-releasing factor, which was fractionated by ultrafiltration into fractions of molecular weight ranges of 1000 to 5000, 5000 to 10,000, and 10,000 to 20,000. The molecular weight ranges of the renin-releasing factor was determined to be between 5000 and 10,000. Since previous studies have shown that lesions in the hypothalamus prevent the effect of p-chloroamphetamine on renin secretion, we tested whether a hypothalamic extract can release renin from kidney slices. Addition of extracts of boiled rat hypothalamic tissue to the kidney slices caused an increase in renin release. Addition of cerebellar extracts produced a smaller increase in renin release, whereas addition of pituitary extracts had no effect. Fractionation by ultrafiltration of bovine hypothalamic extract revealed that the fraction with a molecular weight range of 5000 to 10,000 possessed the highest renin-releasing ability. The 1000 to 5000 (molecular weight) fraction possessed a sizeable renin-releasing activity, but the 10,000 to 20,000 fraction had no renin-releasing activity. Both bovine hypothalamus fractions (molecular weights between 1000-5000 and 5000-10,000) and plasma fraction lost their renin-releasing activity after digestion with pronase, suggesting that the renin-releasing factor or factors are peptides. These results suggest that a renin-releasing factor originate in the hypothalamus.

Animals↗
PubMed1986

Correlations of serotonin and its metabolites in individual rat pineal glands over light:dark cycles and after acute light exposure.

Profiles of pineal indolealkylamines were estimated by high performance liquid chromatography and were correlated in individual glands of male rats sacrificed over several light:dark cycles and after acute exposure to light at night. A significant and positive correlation of 5HIAA vs 5HT in individual glands over both normal and experimental lighting conditions suggested that oxidative deamination is not a major factor in photic regulation of pineal 5HT levels and that the formation of 5HIAA is dependent on substrate availability. Regression analysis of other indole constituents revealed that there was a positive and significant correlation between 5HT vs N-acetylserotonin, but not between 5HT vs melatonin and N-acetylserotonin vs melatonin in individual glands during the dark phase of a light:dark cycle. We propose that this effect may be related to a pulsatile release of melatonin into the blood stream and is the result of sampling glands at different stages in the storage/release of melatonin.

Animals↗
PubMed1986

A V1-like receptor mediates vasopressin-induced flank marking behavior in hamster hypothalamus.

A vasopressin-sensitive mechanism within the medial preoptic area-anterior hypothalamus (MPOA-AH) appears to be essential for expression of a complex behavior involved in olfactory communication in Golden hamsters called flank marking. The present study investigated whether the induction of flank marking by arginine-vasopressin (AVP) within the MPOA-AH is mediated by a receptor that is more similar to the vasopressor (V1) or the antidiurectic (V2) AVP receptor. Adult male hamsters were anesthetized and implanted with a 26 gauge guide cannula stereotaxically aimed at the MPOA-AH and then microinjected with analogs of vasopressin, oxytocin, and selective V1 and V2 antagonists. Hamsters were tested for flank-marking behavior during a 5 or 10 min observation period following the injection of peptide in a vehicle of 100 nl of saline. None of the 15 analogs of AVP and oxytocin produced more flank marking than the 50.8 +/- 16.2 and 76.8 +/- 4.4 (mean +/- SEM; n = 4) flank marks observed following injection of AVP at the 1 or 10 ng dose, respectively. The number of flank marks produced by each analog was found to be highly related to the pressor activity of that analog at both the 1 ng (rho = +0.74, p less than 0.01) and 10 ng (rho = +0.82, p less than 0.01) doses. In contrast, no statistically reliable relationship between flank marking and the antidiuretic activity of these analogs was found at either dose (1 ng: rho = +0.07, p greater than 0.05; 10 ng: rho = +0.10, p greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Motor hypoactivity induced by neurotensin and related peptides in mice.

The tridecapeptide neurotensin (NT) induces a variety of behavioral changes in animals. The present study characterizes the behavioral hypoactivity observed after intracerebroventricular (ICV) injection in mice. At doses higher than 25 ng, NT induced a reduction of general motor activity and increases in immobility which lasted for about one hour. The NT-related amphibian skin peptide xenopsin was about 70-fold more potent than NT itself. After repeated NT-injections, tolerance developed within 2-4 days and disappeared within 2-4 days after cessation of the treatment. The motor hypoactivity induced by NT was not attenuated by pretreatment with naloxone (5 mg/kg, SC). Furthermore, amphetamine-induced locomotor activity was not blocked by NT or xenopsin. These results suggest that the NT-effect is not mediated by a stimulation of opioid mechanisms or attenuation of dopamine-mediated events.

Amphetamine↗
PubMed1985

Pineal ultrastructure and indole profiles spanning the summer rise in arginine vasotocin immunoactivity.

A correlative radioimmunological-biochemical-ultrastructural study of the rat pineal gland was undertaken during the summer months when pineal arginine vasotocin (AVT) immunoactivity increases up to 200-fold. RIA confirmed a rapid rise in AVT activity during mid-August regardless of the time of day sampled. Pineal indoles were separated by HPLC and measured using electrochemical detection. Serotonin (5-HT) and 5-hydroxyindoleacetic acid levels were consistently elevated in daytime samples, and there was a significant trend for increased day and nighttime levels of 5-HT from July to September. Mid-dark levels of melatonin also exhibited a significant increase over the sample period. Nighttime levels of N-acetylserotonin mirrored fluctuations in 5-HT in the preceding photoperiod. Ultrastructural components implicated in peptide/protein and/or indole biosynthesis were quantified by stereological morphometry. The greatest amounts of rough endoplasmic reticulum stacks, lipid droplets, and annulate lamellae-like bodies coincided with peak AVT activity. Dense-cored vesicles and synaptic ribbons were consistently more frequent during the dark period. The number of dense-cored vesicles and nucleolar size tended to be greatest before and after the peak in AVT immunoactivity. These observations are consistent with the hypotheses that endoplasmic reticulum and lipid are functionally related to the synthesis and/or storage of peptide/protein factors and that numerical changes in synaptic ribbons and dense-cored vesicles are more closely related to day/night differences in indole metabolism.

5-Hydroxytryptophan↗
PubMed1984

Factors involved in the inactivation of vasopressin after intracerebroventricular injection in mice.

Behavioral excitation induced by intracerebroventricularly administered vasopressin in mice is very short-lasting, suggesting a half-life of the injected peptide of only a few minutes. The results of the present study suggest that vasopressin and related peptides are too hydrophilic to penetrate lipid membranes readily by passive diffusion and that passive diffusion from the extracellular space into cells or the bloodstream is an unlikely mechanism of inactivation. Pharmacological desensitization (tachyphylaxis) occurs after higher doses, but does not seem to be the major factor responsible for the short duration of action. Some deaminoanalogs of vasopressin, however, show a prolonged action, suggesting that degradation by (an) aminopeptidase(s) is a major route of inactivation. These results also suggest that vasopressin-degrading aminopeptidases are accessible from the extracellular space.

Animals↗
PubMed1984

Hypothermia induced by centrally administered vasopressin in rats. A structure-activity study.

Vasopressin and related peptides cause short-lasting hypothermia when injected into the lateral ventricle of the rat. In the present study, the structure-activity relationships for the induction of this effect were examined. For the agonist peptides studies, the structural requirements were found to be similar to those required to cause peripheral vasoconstriction ant to induce behavioral excitation in mice. However, an antagonist of the pressor and behavioral effects of vasopressin was ineffective in antagonizing the hypothermic response. Moreover, this analog and another pressor antagonist themselves caused hypothermia. Comparison with the structure-activity relationships for other effects on the central nervous system strongly suggests that the hypothermic response is unrelated to the effects of vasopressin on consolidation of memory, development of tolerance to drugs, and mechanisms of reinforcement.

Animals↗
PubMed1984

Effects of catecholamine-related mammalian alkaloids on spontaneous and vasopressin-induced behavior in mice.

Heterocyclic catechol derivatives (tetrahydroisoquinoline alkaloids) are known to be formed endogenously via condensation of the catecholamines with carbonyl compounds. In this study, the effects of a variety of representative simple isoquinolines, benzyl isoquinolines, bicyclic isoquinoline-derived alkaloids (pavines and isopavines), an aporphine and berberine were investigated after intracerebroventricular injection in mice. Most (thirteen) of the alkaloids studied were found to induce significant alterations in three behavioral parameters (immobility, grooming and scratching behavior). In addition, the stereotypic scratching behavior elicited by central injection of arginine-vasopressin (AVP) was significantly antagonized by only one of these, 6-O-methyl-tetrahydropapaveroline (6-O-methyl-THP). To a lesser extent, (-)THP and the pavine, (+/-)bisnorargemonine, were also effective. That this rather specific effect did not involve opioid receptors was indicated by the failure of naloxone to reverse the antagonism by 6-O-methyl-THP.

Alkaloids↗
PubMed1984

Pineal arginine vasotocin activity increases 200-fold during August in adult rats and hamsters.

In a previous study, measurements of arginine vasotocin-immunoactivity (iAVT) in immature rats over a period of 14 months, led to the discovery of a significant yearly variation, with peak levels of iAVT in August. In the present study, iAVT was measured in pineals obtained from mature male and female rats and hamsters once or twice weekly from July until early September 1982. For all groups, mean pineal AVT-immunoactivity was less that 7 pg/gland in early July, but then increased significantly by August 11-13. For hamsters, maximum values of 1,272 +/- 49 (mean +/- S.E.: n = 3) and 1,065 +/- 62 pg/gland were recorded for males and females, respectively. For rats, peak values measured were 940 +/- 12 pg/gland for males and 1,040 +/- 34 for females. The AVT-activity levels then decreased to less than 100 pg/gland by early September. Thus, a dramatic August elevation of pineal iAVT is characteristic of hamsters as well as rats, and of mature as well as immature animals.

Animals↗
PubMed1983

Minireview. Peptides and the blood-brain barrier.

Most neuropeptides are known to occur both in the central nervous system and in blood. This, as well as the occurrence of central nervous peptide effects after peripheral administration, show the importance of studying the relationships between the peptides in the two compartments. For many peptides, such as the enkephalins, TRH, somatostatin and MIF-1, poor penetration of the blood-brain barrier was shown. In other cases, including beta-endorphin and angiotensin, peptides are rapidly degraded during or just after their entry into brain or cerebrospinal fluid. Some peptides, such as insulin, delta-sleep-inducing peptide, and the lipotropin-derived peptides, enter the cerebrospinal fluid to a slight or moderate extent in the intact form. Many peptide hormones, such as insulin, calcitonin and angiotensin, act directly on receptors in the circumventricular organs, where the blood-brain barrier is absent. Oxytocin, vasopressin, MSH, and an MSH-analog alter the properties of the blood-brain barrier, which may result in altered nutritient supply to the brain. In conclusion, the diffusion of most peptides across the brain vascular endothelium seems to be severely restricted. There are, however, several alternative routes for peripheral peptides to act on the central nervous system. The blood-brain barrier is a major obstacle for the development of pharmaceutically useful peptides, as in the case of synthetic enkephalin-analogs.

Adrenocorticotropic Hormone↗