Analysis of physiological variations of piperidine levels in tissues by mass fragmentography

By use of a mass fragmentographic technique the distribution of piperidine in tissues and changes in levels under physiological conditions were examined. Only trace amounts of piperidine existed in the brain of several animal species, although higher concentrations were detected in other species. In the brain of rats and rabbits, some regional differences were seen and high concentrations were found in the striatum. Piperidine levels in the brain and adrenal gland similarly showed the daily and seasonal rhythmic fluctuations.     

Effect of Acute Hypoxia on Ascorbate Content of Plasma, Cerebral Cortex, and Adrenal Gland

Levels of ascorbic acid (AA) in the plasma, brain, and adrenal gland of rats were determined after 15 min of hypoxia (PaO2 less than 25 mm Hg) and following asphyxia. In rabbits, AA plasma levels were followed up to 75 min of reoxygenation following 15 min of hypoxia of the same severity. A significant increase (approximately 70%) in AA levels was found in plasma of rats and rabbits after hypoxia and asphyxia. This increase was found to be transient, with a return to normal levels within 1 h after resumption of normal oxygenation. Pretreatment with dexamethasone reduced the increase in AA level in both rabbits and rats. Adrenalectomy in rats, performed 24 h before the experiment, abolished the response to hypoxia. Ascorbate levels in the cerebral cortex, hypothalamus, and adrenal gland of awake rats subjected to hypoxia or asphyxia were found to be the same as in normoxic rats. Our results suggest that the observed changes in plasma AA levels are probably mediated through adrenocorticotropic hormone and that the adrenal gland is the major source of ascorbate efflux into the circulation during oxygen deprivation.     

Pharmacological basis for the use of nimodipine in central nervous system disorders

Nimodipine, a Ca2+ antagonist with cerebrovasodilatory and anti-ischemic effects, binds to rat, guinea pig, and human brain membranes with high affinity (less than 1 nM). Only at higher concentrations has nimodipine been reported to block the release of some neurotransmitters and hormones from neuronal tissue. Nimodipine has no consistent effect on brain oxygen consumption or cortical ATP or phosphocreatine levels, although the ischemia-induced fall of brain ATP levels in gerbils or the lowering of intracellular brain pH in rabbits with focal cerebral ischemia were antagonized by the drug. In rats and baboons with middle cerebral artery occlusion, nimodipine was found to reduce neurological deficits without an increase in intracranial pressure or brain edema. Electrophysiological studies with nimodipine suggested a direct neuronal action. In rabbit dorsal root ganglion cells, concentrations as low as 20 nM were reported to block inward Ca2+ currents. Recent studies have suggested that nimodipine may also improve memory in brain-damaged or old rats, restore sensorimotor function and abnormal walking patterns of old rats, and accelerate acquisition of associative learning in aging rabbits. Blockade of age-related changes in Ca2+ fluxes in rat hippocampal neurones by nimodipine in vitro pointed to neuronal plasma membrane as the site of nimodipine action. The therapeutic usefulness of nimodipine appears not to be limited to cerebral ischemia, but may include dementia, age-related degenerative diseases, epilepsy, and ethanol intoxication.     

LEVELS OF 5-HYDROXYTRYPTAMINE, DOPAMINE AND NOREPINEPHRINE IN WHOLE BRAIN OF RABBITS IN CHRONIC MANGANESE TOXICITY

Abstract— The levels of 5-Hydroxytryptamine (5-HT), dopamine and norepinephrine were estimated in whole brain of rabbits inoculated intratracheally with manganese dioxide (400 mg). Twenty one and 58 per cent lowering in the concentrations of dopamine and norepinephrine, respectively, were observed as compared to that of controls, the concentration of 5-HT was found to be unaltered.     

Distribution of an enzyme which acetylates α-melanocyte stimulating hormone in rat brain and pituitary gland and effects of arcuate nucleus lesions

This study describes the distribution of an α-melanocyte stimulating hormone (α-MSH) acetyltransferase (MAT) in rat brain and pituitary gland. Highest activities of MAT were found in the neurointermediate lobe of the pituitary gland with the anterior lobe containing slightly less. Within the brain, lowest MAT activities were measured in the hypothalamus, the region which contained the highest concentrations of α-MSH. Relatively high enzyme activities of MAT were measured in the hippocampus, cortex and cerebellum—regions with very low α-MSH concentrations. The fact that MAT activity levels did not parallel α-MSH concentrations indicates that MAT was not solely localized to α-MSH synthesizing neurons or endocrine cells. Furthermore, arcuate nucleus lesions which depleted brain α-MSH failed to deplete MAT activity. Although MAT was not solely localized to α-MSH synthesizing cells, it may have functional significance for α-MSH acetylation due to compartmentalization with α-MSH in α-MSH synthesizing endocrine cells and neurons. Alternatively a second regionally specific MAT may exist.     

A SENSITIVE RADIOIMMUNOASSAY FOR 7S NERVE GROWTH FACTOR ANTIGENS IN SERUM AND TISSUES

A radioimmunoassay was developed which can measure accurately concentrations of mouse 7S nerve growth factor antigens (NGFA) as low as 3·0 ng/ml in serum or tissue homogenates. Extremely large amounts of presumed nerve growth factor were found in the submaxillary gland; but considerable quantities were also present in mouse serum, kidney, adrenal gland and vas deferens. Heart, spleen, liver and muscle contained less of the presumed nerve growth factor, and only small amounts were recovered from brain. Rat adrenal gland and serum from rats, guinea pigs and man contained much less immunologically reactive material. The level of presumed nerve growth factor in the mouse heart was highest at birth and decreased slowly during maturation. In the mouse submaxillary gland the content of presumed nerve growth factor increased rapidly after 2 weeks of postnatal age, with higher levels found in male animals. Destruction with 6-hydroxydopamine of the sympathetic nerves in the hearts of newborn or adult mice did not significantly alter the amount of presumed nerve growth factor recovered in the heart.     

Cholesterol synthesis in vivo and in vitro in the WHHL rabbit, an animal with defective low density lipoprotein receptors

These studies were undertaken to measure rates of synthesis of digitonin-precipitable sterols in vivo and in vitro in control rabbits (New Zealand (NZ) control) and in homozygous Watanabe heritable hyperlipidemic rabbits (WHHL) that lack receptors for low density lipoproteins (LDL). The plasma cholesterol concentration in NZ control fetuses equaled 79 mg/dl, rose to 315 mg/dl 12 days after birth, and fell to 80 mg/dl in young adult animals. At these same ages, cholesterol concentrations in the WHHL animals equal 315, 625, and 715 mg/dl, respectively. The rate of whole animal sterol synthesis in vivo, expressed as the mumol of [3H]water incorporated into sterols per hr per kg of body weight, was lower in the WHHL animals than in the NZ controls both in the fetuses (108 vs 176) and in the adult animals (48 vs 66). In adult NZ controls the content of newly synthesized sterols (rate of sterol synthesis) per g of tissue was highest in the liver (538 nmol/g per hr), adrenal gland (438), small bowel (371), and ovary (225) while lower rates of synthesis were found in 15 other tissues. In the WHHL rabbits a higher content of [3H]sterols was found only in the adrenal gland (2,215) while synthesis was suppressed in the liver (310), colon, lung, and kidney, and was unchanged in the remaining organs. These findings were confirmed by measurements of rates of sterol synthesis in the same tissues in vitro. When whole organ weight was taken into consideration, the tissues that were the major contributors to whole body sterol synthesis in both types of rabbits were liver, small bowel, skin, and carcass. However, it was the lower rate of synthesis in the liver of the WHHL animals that alone accounted for the lower rate of whole animal sterol synthesis seen in these rabbits. These studies demonstrate that in WHHL animals that lack LDL receptors and that have very high levels of circulating LDL cholesterol, the rate of cholesterol synthesis in nearly all tissues is normal but in the liver is significantly suppressed. Only the adrenal gland manifested enhanced synthesis. Such findings suggest that in the WHHL rabbit where LDL receptor activity is reduced and plasma LDL levels rise, mechanisms other than receptor-mediated LDL uptake may act to deliver cholesterol to the cells of the various organs and to the liver.     

无菌兔、SPF兔和普通兔脏器系数的比较

目的对普通级新西兰兔进行剖宫产,获得无菌兔,比较无菌兔、SPF兔和普通级兔的脏器系数。方法采取剖宫产手术获得无菌兔,在无菌隔离器内人工哺乳饲养。用电子天平和刻度尺测量无菌兔、SPF兔和普通兔心、肝、脾、肺、肾、肾上腺、胸腺、脑等脏器的脏器重量和长度,计算脏器系数。结果经检测无菌兔符合国家标准;无菌级、SPF级和普通级新西兰兔在左颌下腺、右颌下腺、心脏、肺、胆囊、脾脏、左肾上腺、右肾上腺、子宫＋卵巢、左睾丸、胃长、蚓突长度、盲肠长度、盲肠总重、盲肠干重、胃总重、胃干重等17项指标差异显著（P〈0.05）;脑、肝脏、左肾、右肾、胰脏、右睾丸、胃宽、小肠长度、直肠长度、大肠长度等10项指标差异不显著（P〉0.05）。结论不同等级微生物环境对新西兰兔脏器系数有显著影响。     

Brain and ring gland cyclic AMP and cyclic GMP levels during initiation and termination of pupal diapause in flesh flies

Brain and ring gland concentrations of cyclic AMP were much higher shortly after pupariation in long day (non-diapause destined) flesh flies than in short day (destined for pupal diapause) flies. This difference was most striking in the ring gland (6 times higher in long day flies). Cholera toxin elevated brain-ring gland cAMP four-fold, thus accounting for its efficacy in averting diapause. No differences in cyclic GMP levels were detected between long and short day flies at pupariation. At diapause termination cAMP and cGMP concentrations in the brain and ring gland and cAMP in whole body homogenates changed only slightly, but whole body concentrations of cGMP rose markedly.     

An investigation of the route and progression of Encephalitozoon cuniculi infection in adult rabbits.

Rabbits infected either orally or intratracheally with cell culture-grown Encephalitozoon cuniculi were monitored regularly for serum antibody levels and E. cuniculi in the urine. Their responses were compared with intravenously inoculated and uninoculated control rabbits. All rabbits receiving E. cuniculi developed serum antibodies, generally within 3 weeks, and excreted E. cuniculi by 6 weeks. In the acute stage of infection, the organs most affected were lung, kidney and liver; the brain and gut were unaffected. However, during chronic infection, the brain, kidney, and heart were the only organs found to be involved. Antibody levels were very high at this stage. Thus both the oral and tracheal routes may be normal routes of infection with E. cuniculi in adult rabbits.     

Spinal Morphine Administration Reduces the Fatty Acid Contents in Spinal Cord and Brain by Increasing Oxidative Stress

It is well known that oxidative stress damages bimolecules such as DNA and lipids. No study is available on the morphine-induced oxidative damage and fatty acids changes in brain and spinal tissues. The aim of this work was to determine the effects of morphine on the concentrations and compositions of fatty acid in spinal cord segments and brain tissues in rabbits as well as lipid peroxidation (LP) and glutathione (GSH) levels in cortex brain. Twelve New Zealand albino rabbits were used and they were randomly assigned to two groups of 6 rabbits each. First group used as control although morphine administrated to rats in second group. Cortex brain and (cervical, thoracic, lumbar) samples were taken. The fatty acids between n:18.0 and 21.0 were present in spinal cord sections and n:10 fatty acids in control animals were present in the brain tissues. Compared to n:20.0–24.0 fatty acids in spinal cord sections and 8.0 fatty acids in the brain tissues of drug administered animals. The concentration and composition of the fatty acid methyl esters in spinal cord and brain tissues was decreased by morphine treatments. LP levels in the cortex brain were increased although GSH levels were decreased by the morphine administration. In conclusion, unsaturated fatty acids contents in brain and spinal cord sections and GSH were reduced by administrating spinal morphine although oxidative stress as LP increased. The inhibition oxidative damage may be a useful strategy for the development of a new protection for morphine administration as well as opiate abuse.     

Insulin resistance and impaired baroreflex gain during pregnancy

Pregnancy decreases baroreflex gain, but the underlying mechanism is unclear. Insulin resistance, which has been associated with reduced transport of insulin into the brain, is a consistent feature of many conditions exhibiting impaired baroreflex gain, including pregnancy. Therefore, using conscious pregnant and nonpregnant rabbits, we tested the novel hypothesis that the pregnancy-induced impairment in baroreflex gain is due to insulin resistance and reduced brain insulin. Baroreflex gain was determined by quantifying changes in heart rate in response to stepwise steady-state changes in arterial pressure, secondary to infusion of nitroprusside and phenylephrine. We found that insulin sensitivity and baroreflex gain were strongly correlated in nonpregnant and term pregnant rabbits (r2 = 0.59). The decrease in insulin sensitivity and in baroreflex gain exhibited similar time courses throughout pregnancy, reaching significantly lower levels at 3 wk of gestation and remaining reduced at 4 wk (term is 31 days). Treatment of rabbits with the insulin-sensitizing drug rosiglitazone during pregnancy almost completely normalized baroreflex gain. Finally, pregnancy significantly lowered cerebrospinal fluid insulin concentrations. These data identify insulin resistance as a mechanism underlying pregnancy-induced baroreflex impairment and suggest, for the first time in any condition, that decreased brain insulin concentrations may be the link between reductions in peripheral insulin sensitivity and baroreflex gain.     

Alpha-endorphin, gamma-endorphin and their des-tyrosine fragments in rat pituitary and brain tissue

Enkephalins, endorphins and related peptides were determined in pituitary and brain tissue of rats which were killed by decapitation or microwave irradiation. The tissues were heated in 1M acetic acid prior to homogenization and the levels of the various peptides were measured by means of a combination of HPLC and radioimmunoassays. Enkephalin levels in pituitary and brain of irradiation-killed rats were much higher as compared to those in tissue of rats sacrificed by decapitation. Similar data were obtained with respect to pituitary levels of γ-endorphin, des-Tyr-γ-endorphin and des- Tyr-α-endorphin. However, brain levels of α- and γ-endorphin and their respective des-Tyr-fragments were not different with the two methods of sacrifice used. The concentrations of β-endorphin in the pituitary gland were similar in rats killed by microwave irradiation and decapitation, but irradiation showed higher β-endorphin levels in the brain than decapitation. These results suggest that β-endorphin fragments like α- and γ-endorphin and des-Tyr-α- and des-Tyr-γ-endorphin are endogenous peptides in the rat pituitary gland and the brain.     

Daily changes in peripheral plasma progesterone concentrations in pregnant and pseudopregnant rabbits

Peripheral levels of plasma progesterone were found to be similar in pregnant New Zealand White and Dutch-belted rabbits. In early gestation progesterone concentrations rose rapidly, remained relatively constant and declined slowly during the latter third of pregnancy. Among pseudopregnant rabbits progesterone levels rose rapidly until day 11 and declined rapidly thereafter until day 19 at which time baseline values were obtained.     

TRH-related peptides in the rabbit prostate complex during development.

The novel peptide, pyroglutamylglutamylprolineamide (pGlu-Glu-ProNH2), has recently been isolated and characterized from the rabbit prostate complex. The tripeptide is present in high concentrations in the prostate complex and semen, together with a 40-50 residue polypeptide which contains a TRH-immunoreactive fragment at its C-terminus. The present study investigates changes in the levels of these TRH-related peptides in rabbits aged 11 weeks, 4 months, 7 months, 13 months and 2 years. For each age group the peptides were extracted from the prostate complex, separated by gel exclusion chromatography, and located by TRH radioimmunoassay. The TRH-immunoreactive fragment was released from the polypeptide by trypsin digestion prior to radioimmunoassay. Very low concentrations of TRH-immunoreactive peptides were present at 11 weeks of age, but considerable levels of both peptides were found in all the other age groups. Anion exchange chromatography, under conditions which resolve TRH and pGlu-Glu-ProNH2, showed that the majority of the low molecular weight TRH immunoreactivity co-eluted with synthetic pGlu-Glu-ProNH2. The remaining TRH immunoreactivity, which had not bound to the anion resin, also failed to bind to a cation exchange column at pH 2.0, indicating that it was not authentic TRH. Dissection of the prostate complex into its four constitutive regions (vesicular gland, coagulating gland, prostate and bulbourethral gland) followed by extraction, chromatography and TRH radioimmunoassay of each region showed that the TRH-related peptides were located in the prostate.     

Tissue accumulation of cadmium as a function of blood concentration

We have provided data relating Cd concentration in tissue to about a 40-fold range in blood Cd concentration. Osmotic pumps containing cadmium chloride were subcutaneously implanted in male New Zealand white rabbits. The pumps continuously delivered either 0.15 or 1.5 mg Cd/d. Blood and plasma levels of Cd were measured weekly throughout the study. After 28 d, the rabbits were killed and tissue concentrations of Cd determined by atomic absorption spectrophotometry. Less than 10% of the total Cd in the blood was carried in the plasma, the remainder was associated with the blood cells, where it was bound mainly to metallothionein. We found the blood and tissue levels of Cd were correlated for each tissue we investigated. There was a wide range in affinity of the tissues for Cd; liver and kidney had the highest Cd uptake, whereas brain affinity was about 500 times less than liver.     

BRAIN CONCENTRATIONS OF BIOGENIC AMINES AND THEIR METABOLITES IN TWO TYPES OF PYROGEN-INDUCED FEVER IN RABBITS

The effects of two bacterial pyrogens (gonococcus vaccine and E. coli lipopolysaccharide) on brain and CSF concentrations of the biogenic amines and their major metabolites were compared in rabbits. Both pyrogens induced a similar fever, but only the lipopolysaccharide elicited marked biochemical alterations. The main changes observed were: a decrease in the concentrations of acid metabolites of dopamine during the upward course of the first peak of fever; a decrease in the hypothalamic concentrations of noradrenaline at the second peak of fever; a general increase in the metabolites of biogenic amines around the second peak and during the fall of fever. The results led to the conclusion that no significant correlation exists between body temperature and brain amine levels in rabbits. The alterations observed could be a consequence of the fever itself when considered in terms of trauma to the organism.     

Distribution of peptidase activity in teleost and rat tissues

Peptides play important roles in cell regulation and signaling in many tissues. The actions of peptides are regulated by peptidases. Although the activity of these enzymes has been thoroughly characterized in mammals, little is known about their presence or function in fish. In the present study, we compared the activity of several peptidases in selected tissues (pituitary gland, different brain areas, kidney and gills) of the gilthead sea bream and rainbow trout with that found in similar rat tissues (lungs studied in place of gills). Soluble puromycin-sensitive aminopeptidase showed the highest values in the pituitary gland of the sea bream, whereas the membrane-bound form was found to be more active in the trout kidney. Very high levels of activity of aminopeptidase N were detected in trout and sea bream plasma. In contrast, the highest levels of activity of aminopeptidase B were found in rat tissues, with the exception of the gills of the trout. Aminopeptidase N levels tended to be higher in sea bream tissues with respect to those of trout. In contrast, the level of activity of aminopeptidase B was found to be consistently much higher in trout tissues than in those of the sea bream. Prolyl endopeptidase activity was principally detected in the pituitary gland and in the brain areas of teleosts. These differences between species could be related to different mechanisms of osmoregulation in saltwater- and in freshwater-adapted fish.