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J W Harding

Publications and source records attributed to J W Harding.

At least 127 records · Page 7Linked to original sources
PubMed1985

Characterization of angiotensin binding in the African green monkey.

The observation that there are differences in the characteristics and distribution of angiotensin receptors in the central nervous system of mammalian species led to the analysis of angiotensin binding in a primate model, the African Green monkey. Initial studies using [125I]angiotensin II ([125I]AII) as the radioligand showed binding in peripheral tissues but little binding in the central nervous system. Conversely, binding studies using [125I]AIII as the radioligand indicated more central nervous binding with diminished peripheral binding. Specific binding of [125I]AIII is evident throughout the brain with high binding in the circumventricular organs, striatum, caudate nucleus, olfactory bulb and localized areas of the thalamus and cerebral cortex. This binding was found to possess many of the properties commonly associated with binding to membrane-bound receptors. The specifically bound radioligand extracted from incubations of [125I]AIII and central nervous tissue appears to be a product of the metabolism of [125I]AIII rather than the peptide itself. Binding of [125I]AII does occur in peripheral tissues and to a limited extent in the cerebellum, but to a different receptor from that characterized using [125I]AIII. These results are similar to those seen in the gerbil and raise questions concerning the utilization of the rat as the primary model for studying the biochemistry of the brain-angiotensin system in humans.

Angiotensin II↗
PubMed1985

Characterization of angiotensin II binding sites in African Green monkey uterus.

The observation that there are significant differences in the concentration, affinity, and specificity of both central nervous system (CNS) and peripheral angiotensin receptors among several different mammalian species, including the African Green monkey, led to the detailed analysis of 125I-angiotensin II binding in the uterus of the African Green monkey. The Bmax for angiotensin receptors in uterine tissue from this species is 56.6 +/- 8.7 fmole per mg protein. The Kd for angiotensin II is .601 +/- .108 nM. The specificity of the receptor is similar to that reported for the uterus of the rat and dog. These results indicate that the angiotensin II receptors, although nearly absent from the CNS of the African Green monkey, are found in the uterus and are very similar to uterine receptors previously characterized in the rat and dog and support the use of these species as appropriate models for studying the biochemistry of angiotensin binding in the uterus.

Angiotensin II↗
PubMed1985

Pressor action and dipsogenicity induced by angiotensin II and III in rats.

The primary brain sites responsible for angiotensin-induced pressor action and dipsogenicity in the laboratory rat appear to be located in forebrain circumventricular organs (CVO). Because CVOs have a reduced blood-brain barrier, intracarotid infusion of angiotensin via a brachial arterial catheter results in direct stimulation of these sites. This investigation determined that brachial arterial infusion of angiotensin II (ANG II) into alert free-moving rats resulted in pressor and dipsogenic responses greater than those observed with equivalent doses of angiotensin III (ANG III). However, intracerebroventricular (ICV) injections of ANG II and ANG III yielded equivalent pressor and drinking responses. ICV pretreatment with the specific angiotensin receptor antagonist [Sar1, Ile8]-ANG II significantly reduced ANG II- and ANG III-induced pressor and drinking responses. This inhibition lasted approximately 20 min with recovery at 60-70 min. The results indicate that ICV-administered ANG III is a much more potent ligand than previously determined if the stickiness due to electrical charge of this compound is prevented by appropriate treatment of glassware. The receptor antagonist results encourage the possibility that ANG II and ANG III activate a common central receptor site.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1984

Characterization of angiotensin binding to gerbil brain membranes using [125I]angiotensin III as the radioligand.

The observation that an Angiotensin II (AII)-sensitive species, the gerbil, exhibited little or no [125I]AII binding to brain membranes led to the hypothesis that AII's central action may be mediated by smaller and/or modified fragments of AII. This possibility was assessed, in part, by examining the ability of gerbil brain membranes to specifically bind [125I]desAsp1 AII (AIII), a heptapeptide fragment of AII. Specific binding was evident throughout the gerbil brain with highest binding in the septum (containing the subfornical organ), anterior ventral third ventricular region, hypothalamus (containing the median eminence), and striatum. This binding was found to possess many of the properties commonly associated with binding to membrane bound receptors. The binding within the circumventricular organs had characteristics that set them apart from the other central nervous tissues examined. Both the olfactory bulb and adrenal gland appeared to have two different angiotensin binding sites. It appears that the binding sites within the brain interact with a product of the metabolism of AIII or AII rather than the peptides themselves. The results suggest that [125I]AIII appears to be a better ligand than [125I]AII in the binding assay because it is more readily degraded to another substance.

Adrenal Glands↗
PubMed1984

Thymidine incorporation in the olfactory epithelium of mice: early exponential response induced by olfactory neurectomy.

The incorporation of [3]thymidine by the olfactory epithelium rises exponentially immediately after nerve section, reaches a peak 12-fold over control values at day 4, and decreases somewhat less rapidly to near control levels by day 10. The protein content of the epithelium decreased to about 50% of control levels at day 3, then increased linearly, and reached control values by day 10. These data are consistent with a rapid loss of cells from the olfactory epithelium following olfactory nerve section that is coincident with a marked increase in the mitogenic activity of the basal cell population.

Animals↗
PubMed1984

Central angiotensin III-induced dipsogenicity in rats and gerbils.

Previous findings from our laboratory demonstrated [125I]angiotensin II (AII) binding to plasma membranes from rat but not gerbil circumventricular organs (CVOs), the presumed location of brain receptors for angiotensin-induced dipsogenicity. Since members of both species drink to intracranially applied AII, a degradation product of AII was suspected to be the active ligand in gerbils. High specific [125I]angiotensin III (AIII) binding capacity was presently determined in CVOs taken from both rats and gerbils. Nearly identical dose-response curves were obtained for members of each species following the intracerebroventricular injection of AIII; however, rats drank more water than gerbils following the administration of AII. These results were interpreted to suggest that the dipsogenically active ligand in gerbils is AIII or derived from AIII, and that this analogue also contributes to angiotensin-induced drinking in rats. Since the distribution of specific angiotensin binding capacity represented by gerbil closely approximates that seen in non-human primate brain, these findings are of particular relevance and encourage future efforts directed toward understanding the role of AII metabolites in the central control of dipsogenicity.

Angiotensin II↗
PubMed1984

Angiotensin III-induced dipsogenic and pressor responses in rodents.

Subcutaneous injections of [des-Asp1]-angiotensin I [( des-Asp1]-AI), angiotensin II (AII), and angiotensin III (AIII) induced drinking in the laboratory rat and the South American rodent Octodon degus, but not in the gerbil. In a second experiment, pretreatment with captopril, an angiotensin converting enzyme inhibitor, prevented the endogenous conversion of subcutaneously injected [des-Asp1]-AI to AIII and prevented drinking in rats and degus. The pharmacological artifact of hypovolemia caused by angiotensin-induced increases in vascular permeability was not observed in members of these species. In a final experiment blood pressure changes resulting from subcutaneous injections of AII and AIII in rats and gerbils were measured. Significant pressor elevations were seen following the administration of both analogues, although AII was more potent. These results demonstrate that AIII is dipsogenic in rats and degus and serves as a pressor agent in rats and gerbils. No ready explanation is available for the gerbil's relative lack of dipsogenicity to the presently tested angiotensins.

Angiotensin I↗
PubMed1982

Recovery of olfactory function after bilateral bulbectomy.

Mice were trained to discriminate between scented and unscented air. After olfactory bulbs were removed, discrimination was lost, but returned with the formation of synaptic connections between regenerated primary olfactory neurons and the cortex of the forebrain. The acquisition of a second olfactory-mediated task by long-term bulbectomized mice and controls was indistinguishable. The results emphasize the plasticity of the nervous system, correlate the presence of neural connections between olfactory mucosa and forebrain with the recovery of olfactory function, suggest that olfactory-mediated memory resides at least in part outside the olfactory bulbs, and demonstrate that the bulbs are not required for the acquisition of olfactory tasks.

Animals↗
PubMed1982

An evaluation of dipsogenic stimuli in the African green monkey.

Elevations in the concentration of plasma angiotensin II (AII) and decline in plasma aldosterone (Ald) were noted in African Green monkeys at 48 hr of water deprivation but not subsequent to an equivalent duration of food deprivation, compared with nondeprived levels. In a second experiment, drinking was initiated following treatment with AII, hypertonic saline, and the beta-adrenergic stimulator isoproterenol. Concomitant elevations in plasma AII concentrations were measured following isoproterenol injection, but not after AII or hypertonic saline injection, when compared with isotonic saline treatment. Elevations in plasma Ald levels were noted following AII injection. A third experiment evaluated dipsogenic additivity of stimuli by comparing the volumes of water consumed following isoproterenol or hypertonic saline injection with the intake resulting from combined treatment with isoproterenol and hypertonic saline. Additivity was tested under ad lib conditions and following adaptation to a daily water deprivation regimen. The results of the first two experiments generally agree with predictions based on the respective contributions by intracellular dehydration and extracellular fluid volume depletion, to thirst. However, additivity of thirst stimuli was not demonstrated in the third experiment.

Aldosterone↗
PubMed1981

The distribution of angiotensin II binding sites in rodent brain.

The distribution of specific angiotensin II (AII) binding capacity of several brain regions, pituitary, and adrenals was determined in 6 rodent species namely rats, mice, hamsters, kangaroo rats, gerbils and degus. Rats and mice had similar distributions with the highest levels of binding observed in the area postrema, septum and superior colliculi. Low levels were seen in the cortex, cerebellum, striatum and hippocampus. Other areas had intermediate levels. The distribution of AII binding in gerbils and degus was strikingly different from rats and mice. In these species, little or no binding could be detected in the brain. Additionally, the level of binding in degu adrenals was extremely low when compared to the binding observed in the adrenals of the other species. The distribution of AII binding sites in hamsters and kangaroo rats, although similar in some ways to rats and mice, had several major differences. Both had much higher levels of specific binding in cerebellum, striatum, and the hippocampus areas which had low levels of AII binding in rats an mice. Hamsters were the only species to exhibit significant specific binding in the cortex. The kangaroo rats had an unusual distribution of receptors with an apparent lack of specific binding in midbrain and area postrema.

Angiotensin II↗
PubMed1981

The Na+,K+-ATPase: a plausible trigger for voltage-independent release of cytoplasmic neurotransmitters.

A comparison was made between the releasability of eight neurotransmitters from eight regions of mouse brain in response to either 60 mM-K+ or 20 microM-ouabain, a specific inhibitor of the Na+,K+-ATPase. With few exceptions, all transmitters were released by either or both agents from each brain region examined. Potassium was superior in releasing the biogenic amines and acetylcholine, while the putative amino acid transmitters were generally releasable by both agents. Measurements of tissue depolarization using [3H]-tetraphenylphosphonium uptake indicated that 60 mM-K+ is capable of depolarizing brain tissue above the threshold necessary for initiating an action potential, but 20 microM-ouabain is not. The pattern of release by ouabain coupled with its failure to depolarize brain tissue at 20 microM suggests that inhibition of the Na+,K+-ATPase is capable of releasing cytoplasmic neurotransmitters in a voltage-independent manner.

Acetylcholine↗
PubMed1979

The subcellular distribution of carnosine, carnosine synthetase, and carnosinase in mouse olfactory tissues.

The dipeptide, carnosine, its synthetic enzyme, carnosine synthetase, and its degradative enzyme, carnosinase, appear to be localized in the cytosol of mouse olfactory bulb and epithelium. Mouse olfactory bulbs and epithelium were prelabeled in vivo with [3H]carnosine following intranasal irrigation with [3H]beta-alanine. [3H]carnosine co-distributed in olfactory bulb with lactate dehydrogenase with only 10% in the crude mitochondrial fraction. Similar results were also seen with endogenous carnosine distribution. Over 70% of the carnosine present in the crude mitochondrial fraction was localized in synaptosomes following sucrose gradient centrifugation. However, further fractionation of vesicle containing fractions from osmotically lysed crude mitochondrial fractions indicated that [3H]carnosine was not associated with vesicles. Nearly 70% of all the [3H]carnosine present in olfactory epithelium was soluble with most of the remainder in the crude nuclear fraction. The enzymes carnosine synthetase and carnosinase were clearly soluble in olfactory epithelium with 98% and 85% of the activity in the cytosol. Less than 2% was found in the crude mitochondrial fraction. In olfactory bulb both enzymes also appeared soluble.

Animals↗
PubMed1979

Effects of intranasal irrigation with mitotic inhibitors on olfactory behavior and biochemistry in mice.

Mice were trained to find buried food pellets or amyl acetate-scented sugar cubes. After training, the mice were intranasally irrigated with saline or one of several mitotic inhibitors--hydroxyurea (10 mM), ethidium bromide (2 mM), cytosine arabinoside (10 mM), or colchicine (0.25 mM). The behavioral testing was continued daily. By day 6 the colchicine animals had completely lost their ability to find sugar cubes. By day 8 all the ethidium bromide animals had lost their ability to find food pellets although 20% could still find the sugar cubes. The hydroxyurea animals exhibited a less dramatic and temporary deficit in olfactory capabilities which peaked near day 8. Cytosine arabinoside had no effect on olfactory-mediated behavior. The testing was terminated at 21 days. Two days later the animals were killed, olfactory tissue removed and assayed for thymidine incorporation into macromolecules, and the chemoreceptor marker, carnosine synthetase. All groups had a reduction in thymidine incorporation (33-25%). The ethidium bromide and colchicine groups exhibited a dramatic decrease in carnosine synthetase activity (ethidium bromide--olfactory bulb = 8% control, epithelium = 2%; colchicine--olfactory bulb = 10%, epithelium, 108%). These data are consistent with the notion that a functional mitotic process is necessary for continued olfactory capabilities and that in interruption in the normal mitotic process results in a decrease in olfactory chemoreceptor neurons and a loss in function.

Administration, Intranasal↗
PubMed1978

Denervation of the primary olfactory pathway in mice. V. Long-term effect of intranasal ZnSO4 irrigation on behavior, biochemistry and morphology.

Intranasal irrigation of mice with 0.17 M ZnSO4 solution results in the immediate and total loss of the ability to find a buried food pellet. This anosmia persists for 6 weeks in at least 80% of the treated mice and for 4 months in half of the animals. This marked behavioral effect is matched by a long-term reduction of the levels of carnosine synthesis and transport in the primary olfactory pathway. These biochemical parameters are virtually undetectable at two weeks after treatment and even at one year after treatment do not exceed 5-10% of average control values. Light microscopic observations of tissues of the primary olfactory pathway at various times after treatment are consistent with these observations and indicate a substantial destruction of the olfactory epithelium with subsequent atrophy of the olfactory bulb. At very long intervals after treatment, some receptor regeneration is apparent with accompanying reinnervation of the olfactory bulb. Estimates from microscopy and biochemistry suggest that much less than 10% of the normal complement of functioning receptor cells is adequate to give apparently normal food-finding behavior.

Alanine↗
PubMed1977

Immunocytochemistry of the olfactory marker protein.

The olfactory marker protein has been localized, by means of immunohistochemical techniques in the primary olfactory neurons of mice. The olfactory marker protein is not present in the staminal cells of the olfactory neuroepithelium, and the protein may be regarded as indicative of the functional stage of the neurons. Our data indicate that the olfactory marker protein is present in the synaptic terminals of the olfactory neurons at the level of the olfactory bulb glomeruli. The postsynaptic profiles of both mitral and periglomerular cells are negative.

Animals↗
PubMed1975

Role of glycerol 3-phosphate dehydrogenase in glyceride metabolism. Effect of diet on enzyme activities in chicken liver.

1. The metabolic role of hepatic NAD-linked glycerol 3-phosphate dehydrogenase (EC 1.1.1.8) was investigated vis-a-vis glyceride synthesis, glyceride degradation and the maintainence of the NAD redox state. 2. Five-week-old chickens were placed on five dietary regimes: a control group, a group on an increased-carbohydrate-lowered-fat diet, a group on a high-fat-lowered-carbohydrate diet, a starved group and a starved-refed group. In each group the specific activity (mumol/min per g wet wt. of tissue) of hepatic glycerol 3-phosphate dehydrogenase was compared with the activities of the beta-oxoacyl-(acyl-carrier protein) reductase component of fatty acid synthetase, glycerol kinase (EC 2.7.1.30) and lactate dehydrogenase (EC 1.1.1.27). 3. During starvation, the activities of glycerol 3-phosphate dehydrogenase, glycerol kinase and lactate dehydrogenase rose significantly. After re-feeding these activities returned to near normal. All three activities rose slightly on the high-fat diet. Lactate dehydrogenase activity rose slightly, whereas those of the other two enzymes fell slightly on the increased-carbohydrate-lowered-fat diet. 4. The activity of the beta-oxoacyl-(acyl-carrier protein) reductase component of fatty acid synthetase, a lipid-synthesizing enzyme, contrasted strikingly with the other three enzyme activities. Its activity was slightly elevated on the increased-carbohydrate diet and significantly diminished on the high-fat diet and during starvation. 5. The changes in activity of the chicken liver isoenzyme of glycerol 3-phosphate dehydrogenase in response to dietary stresses suggest that the enzyme has an important metabolic role other than or in addition to glyceride biosynthesis.

Animals↗