Search PubMed⌕ Search

Biomedical subjects

J C Miller

Publications and source records attributed to J C Miller.

At least 91 records · Page 5Linked to original sources
PubMed1989

Association between inhibition of arachidonic acid release and prevention of calcium loading during ATP depletion in cultured rat cardiac myocytes.

The development of irreversible myocardial ischemic injury is associated with progressive degradation of membrane phospholipids, accumulation of arachidonate and other free fatty acids, and electrolyte derangements, including calcium accumulation. To study the relationship between arachidonate release and calcium loading during adenosine triphosphate (ATP) depletion in cardiac myocytes, the effects of two purported phospholipase inhibitors, mepacrine and U26,384, were evaluated. Cultured neonatal rat ventricular myocytes were pretreated for 90 minutes with 5 to 10 microM U26,384 (a steroidal diamine) or 10 to 50 microM mepacrine (an alkyl acridine) and then treated for 3 hours with 30 microM of the metabolic inhibitor, iodoacetic acid (IAA), with or without an additional dose of drug. IAA treatment resulted in a marked reduction in ATP level and a several-fold increase in free fatty acid radioactivity released from myocytes prelabeled with tritiated arachidonic acid (3H-AA). U26,384 produced substantial inhibition of the increased 3H-AA release, and was effective when given as a single pretreatment dose before IAA exposure or as continuous treatment before and during IAA exposure (for example, with 5 microM U26,384, the percentage of 3H-AA release versus IAA alone was 8% +/- 2% [SEM] [N = 15] for pretreatment only and 13% +/- 4% [N = 10] for continuous treatment). Mepacrine also resulted in significant reduction in 3H-AA release, but was more effective when given as continuous treatment (for example, with 50 microM mepacrine, the percentage of 3H-AA release versus IAA alone was 43% +/- 9% [N = 6] for pretreatment only and 22% +/- 7% [N = 9] for continuous treatment). More detailed analysis showed that U26,384 and mepacrine blocked the IAA-induced redistribution of 3H-AA into free fatty acids from other lipid species. Electron probe x-ray microanalysis of freeze-dried cryosections revealed marked electrolyte derangements in myocytes exposed to IAA, including a 24-fold increase in cellular Ca, a four fold increase in cellular Na, and a seven fold decrease in cellular K, and associated changes in cytoplasm and mitochondria. U26,384 treatment markedly reduced these electrolyte abnormalities, and maintained normal Ca levels in some protocols. Mepacrine treatment was less effective, but did produce normal Ca levels in 50% of myocytes. Prevention of IAA-induced cellular hypercontraction and blebbing also was observed. These data support the hypothesis that reduction of free fatty acid accumulation by inhibition of accelerated phospholipid degradation is associated with protection of myocytes from calcium loading and morphologic damage during inhibition of ene

Adenosine Triphosphate↗
PubMed1988

Ethanolaminephosphotransferase in rat lung: selectivity for endogenous and exogenous diacylglycerol.

Ethanolaminephosphotransferase (EC 2.7.8.1) activity was determined in lung microsomes using diacylglycerols generated endogenously from [14C]glycerol 3-phosphate and different mixtures of fatty acids. Ethanolaminephosphotransferase used endogenously generated dipalmitoylglycerol better than dioleoylglycerol. The apparent Km and the reaction rates for four different endogenously generated mixtures were the same (16 nmol/mg microsomal proteins). The apparent Km values for CDP-ethanolamine were the same (0.26 mm) for endogenously generated dipalmitoylglycerol and dioleoylglycerol. The amount of diacylglycerol generated in microsomes was 2-3-times the apparent Km for diacylglycerol. Dipalmitoylglycerol, supplied exogenously as a Tween 20/phosphatidylglycerol emulsion, was nearly twice as active as dioleoylglycerol. Both dipalmitoylglycerol and dioleoylglycerol were more active as substrates when emulsions were made with phosphatidylglycerol/Tween 20 than with Tween 20 alone. The results suggest that ethanolaminephosphotransferase in lung is relatively nonselective for molecular species of diacylglycerol. In addition, the results suggest that the concentration of diacylglycerol and the physical state in which it is presented to the enzyme can affect the apparent selectivity of ethanolaminephosphotransferase for diacylglycerols.

Animals↗
PubMed1988

Cerebral metabolism of plasma [14C]palmitate in awake, adult rat: subcellular localization.

Following intravenous injection of [U-14C]palmitate in awake adult rats, whole brain radioactivity reached a broad maximum between 15-60 min, then declined rapidly to reach a relatively stable level between 4 hr and 20 hr. At 44 hr total radioactivity was 57% of the 4 hr value (p less than 0.05). About 50% of palmitate which entered the brain from the blood was oxidized rapidly, producing 14C-labeled water-soluble components which later left the cytosol. Radioactivity in the cytosolic fraction peaked at 45 min and then declined, coincident with the decline in total brain radioactivity. Membrane fractions were rapidly labeled to levels which remained relatively stable from 1 to 44 hr. Increases in the relative distributions of radioactivity were seen between 1 and 4 hr for the microsomal and mitochondrial fractions, and beyond 4 hr for the synaptic and myelin membrane fractions (p less than 0.05). Radioactivity in membrane fractions was 80-90% lipid, 5-13% water-soluble components and 3-17% protein. The proportion of label in membrane-associated protein increased with time. Proportions of radioactivity in the combined membrane fractions increased from 65% to 76% to 80% at 4, 20 and 44 hr, respectively. The results show that plasma-derived palmitate enters oxidative and synthetic pathways to an equal extent, immediately after entry into the brain. At and after 4 hr, the radiolabel resides predominantly in stable membrane lipids and protein. Brain radioactivity at 4 hr can be used therefore, to examine incorporation of palmitate into lipids in vivo, in different experimental conditions.

Animals↗
PubMed1988

Regional cerebral palmitate incorporation after unilateral auditory deprivation in immature and adult Fischer-344 rats.

Regional cerebral incorporation of intravenously injected [U-14C]palmitate was measured from 1 day to 13 weeks after left cochlear destruction in 11-day- and 3 month-old, awake Fischer-344 rats. In 11-day-old animals, statistically significant left-right differences in incorporation were absent 1 day after cochlear destruction and were found only in parts of the cochlear nucleus and inferior colliculus after 1 week. After 6 to 13 weeks, consistent with functional neuroanatomy of central auditory regions, incorporation was reduced by 6 to 9% in the left cochlear nucleus and left lateral superior olivary nucleus, compared with corresponding right-side regions. The right medial superior olivary nucleus, medial nucleus of the trapezoid body, lateral lemniscus nucleus, inferior colliculus, medial geniculate body, and auditory cortex had 5 to 9% less incorporation than did corresponding left-side regions. Fewer significant differences after chronic auditory deprivation occurred in 3-month-old rats than in 11-day-old rats following cochlear destruction. Reduced incorporation corresponded to reported changes in cell morphology, which also were greater in immature than mature rats following auditory deprivation. The results suggest that the palmitate method can be used to identify long-term regional changes in the turnover of brain lipids after sensory deprivation.

Animals↗
PubMed1988

Enclosed afferent reservoir breathing systems. Description and clinical evaluation.

A new group of breathing systems, namely the Enclosed Afferent Reservoir (EAR) systems, is described. They allow for the selective elimination of alveolar gas in association with both spontaneous and controlled ventilation. A comparison with the Bain system in controlled ventilation demonstrates greater efficiency in eliminating carbon dioxide. A fresh gas flow (VF) of 70 ml kg-1 min-1 using an EAR system gave mild hypocarbia which equated to a VF of 100 ml kg-1 min-1 using the Bain system. Smaller minute volumes of ventilation are required for optimal performance than with the Bain system. The minimum recommended minute volume of ventilation (VI) should equal VF plus anatomical deadspace ventilation (VDanat). The pattern of ventilation appears to have little influence upon the efficiency of carbon dioxide elimination when using an EAR system, whereas the Bain system does appear to be affected.

Anesthesia, General↗
PubMed1988

Inhibition of the release of arachidonic acid prevents the development of sarcolemmal membrane defects in cultured rat myocardial cells during adenosine triphosphate depletion.

Previous studies have suggested that phospholipid degradation is closely associated with the development of sarcolemmal membrane injury. This study was initiated to characterize the effects of synthetic inhibitors of phospholipase activities using a cultured myocardial cell model in which arachidonic acid is liberated after treatment with the metabolic inhibitor, iodoacetate. Pretreatment with a steroidal diamine (U26,384) blocked the degradation of labeled phosphatidylcholine and the release of arachidonic acid in cultured myocardial cells during ATP depletion. Inhibition of phospholipid degradation by U26,384 prevented the development of sarcolemmal membrane defects and the release of creatine kinase from the cultured myocardial cells during ATP depletion. Pretreatment with U26,384 had no significant effect on the extent of ATP depletion after iodoacetate treatment, which indicates that the activity of this compound could not be simply ascribed to a sparing effect on ATP concentration. These results support the hypothesis that the development of sarcolemmal membrane injury and the associated loss of cell viability are causally related to progressive phospholipid degradation. In addition, these studies indicate that the release of arachidonic acid during ATP depletion is associated with the net loss of the phosphatidylcholine molecule.

Adenosine Triphosphate↗
PubMed1987

Rapid chromosomal assignment of multiple genomic clones in tomato using primary trisomics.

In order to rapidly assign relatively large numbers of tomato genomic clones to specific chromosomes, we have developed the following approach: groups of five to eight clones from a single copy tomato library are pooled, nick-translated, and utilized as probes against Southern blots consisting of a panel of trisomic DNAs. Since the trisomic DNAs are digested with the same enzyme used to produce the genomic library (PstI), each hybridizing band can be related to a specific genomic clone and the relative intensities of the bands can be used to assign each to a specific chromosome. With this technique, we have assigned 52 clones to specific chromosomes and verified the assignment of 21 out of 23 by genetic mapping in a segregating F2 population. In addition to selecting clones according to chromosome, the idea of using multiple clones or "molecular darts" may have broader applications, such as screening for differences between the genomes of nearly isogenic lines.

Chromosome Mapping↗
PubMed1987

Differential localization of alkaline phosphatase in barrier tissues of the frog and rat nervous systems: a cytochemical and biochemical study.

We investigated the localization of alkaline phosphatase (AP) in the peripheral and central nervous systems of the frog (Rana pipiens) and rat. In the frog sciatic nerve, AP reaction product was seen as a precipitate within caveolae and vesicular profiles of perineurial cells, and frequently filled the extracellular space. In the rat peripheral nerve, AP reaction product appeared as small tufts on the cell surfaces and within vesicular profiles of endoneurial blood vessels. AP reaction product was not detected in the rat perineurium or in endoneurial blood vessels of the frog. In the frog central nervous system, AP reaction product was detected in the arachnoid membrane adjacent to the subarachnoid space, but not in the cerebral or pial vessels, whereas in the rat it was detected in the outer arachnoid membrane and in the cerebral and pial blood vessels. Biochemical analysis indicated a sevenfold higher AP activity in the frog perineurium over the endoneurium, whereas in the rat, threefold more activity was measured in the endoneurium over the perineurium. Levamisole, an AP inhibitor, decreased the enzyme activity by 95% in rat tissues, and by 70% in frog tissues and in plasma from both animals. Similar decrements were observed cytochemically. This study suggests that: (1) the distribution of AP varies between species, but that it is always present in at least one component of the blood-brain and blood-nerve barriers, (2) because barrier tissues of the nervous system have enzymatic activity, they may biochemically modify the adjacent environment, (3) vesicular profiles and caveolae in the blood vessels and perineurium may function as microenvironments for enzymatic activity, and (4) in the rat and frog, different isozymes of AP may be present.

Alkaline Phosphatase↗
PubMed1987

Use of an in vitro tuberization system to study tuber protein gene expression.

Nodal cuttings from micropropagated potato plantlets give rise to microtubers when placed on Murashige and Skoog medium containing 6% sucrose and 2.5 mg/liter kinetin and incubated in the dark at 19 degrees C. Microtubers produced from the cultivar Superior were shown to contain the same characteristic group of proteins as field-grown tubers. As with field-grown tubers, the 40,000-dalton major tuber glycoprotein, patatin, accumulated to high levels in microtubers, reaching 3.7 +/- 0.2 mg/g fresh weight after 90 d. Also in agreement with field-grown plants, stems and leaves of micropropagated plantlets did not contain detectable levels of patatin, but small amounts of an electrophoretically distinct form accumulated transiently in roots. Patatin mRNA is readily detectable in developing microtubers 15 d after transfer of the cuttings to inductive medium. Patatin mRNA was also present in roots, but as with field-grown plants, was 50- to 100-fold less abundant and could be distinguished from that in tubers by primer extension. Microtuber development and patatin accumulation were inhibited by gibberellic acid.

Gene Expression Regulation↗
PubMed1987

Utilization of plasma fatty acid in rat brain: distribution of [14C]palmitate between oxidative and synthetic pathways.

Radioactivity within individual brain compartments was determined from 5 min to 44 h after intravenous injection of [14C]palmitate into awake Fischer-344 rats, aged 21 days or 3 months. Total radioactivity peaked broadly between 15 min and 1 h after injection, declined rapidly between 1 and 2 h, and then more slowly. In 3-month-old rats, the lipid and protein brain fractions were maximally labeled within 15 min after [14C]palmitate injection, then retained approximately constant label for up to 2 days. Radioactivity in the aqueous brain fraction comprised mainly radioactive glutamate and glutamine, and peaked at 45 min, when it comprised 48% of total brain radioactivity, then decreased to 27% of the total at 4 h, 15% at 20 h, and 10% at 44 h. Percent distribution of radioactivity within the different brain compartments, 4 h after intravenous injection of [14C]palmitate, was similar in 21-day-old and 3-month-old rats, despite higher net brain uptake in the younger animals. The results indicate that about 50% of plasma [14C]palmitate that enters the brain of adult rats is incorporated rapidly into stable protein and lipid compartments. The remaining [14C]palmitate enters the aqueous fraction after beta-oxidation, and is slowly lost. At 4 h after injection, 73% of brain radioactivity is within the stable brain compartments; this fraction increases to 86% by 20 h.

Aging↗
PubMed1986

Dissociated effects of misoprostol on gastric acid secretion and mucosal blood flow.

Misoprostol, a synthetic prostaglandin analog, has been reported to inhibit gastric acid secretion and to protect the gastric mucosa from the effects of aspirin and aspirin plus hemorrhagic shock. This study examined the effect of misoprostol on basal gastric corpus mucosal blood flow (MBF), and on pentagastrin-stimulated gastric acid output and MBF. Gastric corpus MBF in ml/min/100 g was measured by hydrogen gas clearance in fasted, anesthetized rats. Acid output in mueq/min was determined by a continuous gastric perfusion technique. For the basal study, vehicle or misoprostol in doses of 50 and 1000 micrograms/kg was administered intragastrically in separate groups of rats. For the pentagastrin-stimulation study, vehicle or misoprostol, 1000 micrograms/kg, was infused intravenously after gastric acid output was stimulated to plateau by intravenous pentagastrin, 20 micrograms/kg/hr. The results showed that misoprostol had no effect on basal gastric corpus MBF. During pentagastrin stimulation, misoprostol decreased acid secretion but did not decrease gastric corpus MBF. We speculate that this dissociated effect of misoprostol on stimulated gastric acid secretion and corpus MBF may be of therapeutic importance if it can be confirmed in human studies.

Alprostadil↗
PubMed1986

Incorporation of plasma palmitate into the brain of the rat during development.

Jpalm, the rate of incorporation of plasma palmitate into brain, was determined in awake Fischer-344 rats at 15, 20, 25 and 38 days of age, by a modification of the method of Kimes et al. [14C]palmitate was injected intravenously and plasma-specific activity of unesterified palmitate was followed until the animals were killed at 4 h, when radioactivity was determined by quantitative autoradiography in 45 individual brain regions. Jpalm was calculated as the 4 h brain radioactivity divided by integrated plasma palmitate-specific activity to 4 h. Jpalm rose between 15 and 20 days of age in gray and white matter regions, then declined 4-5-fold in gray matter and 7-10-fold in white matter by 38 days and reached adult levels by 3 months. The white/gray ratio for Jpalm declined significantly between 20 and 38 days, and between 38 days and 3 months of age, consistent with a lower rate of turnover of white matter lipids in the mature brain. The results support the use of the Jpalm technique to measure brain lipid synthesis and turnover. They show that Jpalm corresponds to the time course of myelination during development of the rat brain, when there are parallel changes in the rates of palmitate incorporation into gray and white matter regions.

Aging↗
PubMed1986

Development of specificity and stereoselectivity of rat brain dopamine receptors.

Prenatal exposure to the neuroleptic haloperidol has been reported to produce an enduring decrement in the number of dopamine D2 receptors in rat striatum and a persistent diminution of a dopamine dependent behavior, stereotypy. The ontogeny of rat brain dopamine binding sites has been studied in terms of the kinetic properties and phenotypic specificity in rat fetal brain through early postnatal development. Sites showing some properties of the D2 binding site can be found prior to gestational day (GD) 18, can be labeled with [3H]dopamine or [3H]spiroperidol and can be displaced with dopaminergic agonists and antagonists. Saturation kinetics for specific [3H]spiroperidol has previously been found to occur on or about GD 18. It is of interest that the critical period for the prenatal effect of haloperidol to reduce striatal D2 binding sites, GD's 15-18, coincides with the period during which dopamine binding sites lack true specificity, but can be labeled with dopaminergic ligands. In these experiments the development of stereoselectivity of brain dopamine binding sites has been examined. When rat mothers were given either the neuroleptic (+)-butaclamol or its therapeutically inactive isomer (-)-butaclamol during the critical period GD's 15-18, the number of [3H]spiroperidol binding sites in striata of offspring was significantly reduced by both stereoisomers. This is in marked contrast to the postnatal treatment effect by a neuroleptic in which upregulation of striatal D2 binding sites occurs only by treatment with the therapeutically active isomer (+)-butaclamol. In vitro studies of the direct effect of the stereoisomers of butaclamol indicate that the recognition sites detected during fetal brain development with [3H]spiroperidol do not distinguish between the isomers of butaclamol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Prenatal neuroleptic exposure alters postnatal striatal cholinergic activity in the rat.

Previous studies in our laboratory have shown that prenatal exposure to a neuroleptic during a critical period of gestation in the rat results in a marked deficit in the number of striatal dopamine-binding sites and in a diminution of dopamine agonist-induced stereotyped behavior. In the present studies, we examined the effect of prenatal neuroleptic exposure on biochemical parameters of cholinergic activity to determine whether the balance between striatal dopaminergic and cholinergic activity might be altered. The number of muscarinic cholinergic-binding sites and the specific activity of choline acetyltransferase were found to be significantly increased by prenatal treatment with the neuroleptics haloperidol or (+)-butaclamol. From the present studies and previous observations made in our laboratory, it is concluded that the ability of a neuroleptic to affect the number of muscarinic cholinergic receptors in postnatal life may be a result of the phenotypically undifferentiated state of the developing dopamine-binding site. Our findings of increased striatal cholinergic activity accompanied by a marked decrease in dopaminergic activity may have implications for an increased vulnerability to extrapyramidal motor disturbances during postnatal development.

Animals↗