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Biomedical subjects

J M Price

Publications and source records attributed to J M Price.

At least 37 records · Page 2Linked to original sources

Learning in the Africanized honey bee: Apis mellifera L.

Several series of experiments are reported that investigate learning in the Africanized honey bee. In the first series, classical conditioning of proboscis extension was studied by confining bees to small metal tubes where they received pairings of an odor with a 3-s feeding of sucrose. After a number of odor-sucrose pairings, the bees began to extend their proboscis to the odor. Controls include Unpaired, Discrimination, and Pseudoconditioning Groups. This technique was used to look at conditioning to a light CS, and to the odors of beeswax, geraniol, citral, and hexanal. The results indicate that acquisition was best when sucrose was paired with the odor of beeswax. Conditioning to the remaining odors was roughly similar, but acquisition did not occur using a light. In a second series of experiments, odors were no longer followed by sucrose feedings and the conditioned response slowly disappeared. With the exception of geraniol as a CS, this extinction effect did not occur if the animals continued to be fed on an unpaired schedule. In a third series of experiments, conditioned inhibition was demonstrated when geraniol was used as conditioned stimuli, but no effect was found when the odors of hexanal, citral and wax were used. In a fourth series of experiments, unrestrained bees flew back and forth from the laboratory to the hive, where they were taught to distinguish targets based on color and odor. With this technique, color and odor discrimination in the Africanized bees was demonstrated. In addition, it was found that more intruder bees visited the experimental station when the stimuli used were olfactory rather than visual.

Animals↗

beta-Amyloid induces cerebrovascular endothelial dysfunction in the rat brain.

beta-Amyloid toxicity plays a central role in the pathology of Alzheimer's disease. Contraction and relaxation responses of pressurized rat posterior cerebral artery were studied before and after in vitro exposure to beta-amyloid. The peptide-induced characteristic features of endothelial dysfunction including enhanced vasoconstriction with serotonin and diminished relaxation to endothelium-dependent vasodilators acetylcholine and bradykinin. Response to the endothelium-independent vasodilator nitroprusside was not affected by beta-Amyloid. beta-amyloid inhibition of acetylcholine-induced vasodilation was prevented by the oxygen radical scavenging enzyme superoxide dismutase. Endothelial destruction and the protective effect of superoxide dismutase was verified by electron microscopy. The results suggest that beta-amyloid peptide produces endothelial dysfunction in cerebral microvessels through reactive oxygen species.

Acetylcholine↗

Beta-amyloid-induced coronary artery vasoactivity and endothelial damage.

Amyloid beta-peptide (A beta) deposition has been associated with coronary heart disease and neurodegenerative diseases. A link between A beta and free radical generation has been explored in neuronal tissue. We report here on the effect of A beta on pressurized segments of coronary resistance arteries and the role of free radicals. A small oscillatory response to A beta (10[-6] M) that consisted of a relaxation followed by constriction and a return to the basal diameter was observed in all vessels. The thromboxane A2 analog U46619 produced a significantly greater constriction compared with the response before treatment with A beta. The presence of the antioxidant enzyme superoxide dismutase (SOD) reduced both the response to A beta alone and the enhanced response to U46619. Vasodilation responses to acetylcholine (10[-9]-10[-5] M) were virtually eliminated at all concentrations by A beta. We confirmed endothelial cell damage by A beta with electron microscopy. The results suggest that A beta deposition in coronary resistance arteries causes endothelial damage that is mediated through superoxide radicals.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

Calcium-activated potassium channel-mediated arteriolar relaxation during endotoxic shock.

The role of calcium-activated potassium (KCa) channels in the in vivo relaxation of arterioles was investigated before endotoxin shock (Pre-ENDT) and during endotoxin shock at 180 min (Post-ENDT). Diameters of 2nd and 3rd order (A2 and A3) arterioles in the left cremaster muscle of male Sprague-Dawley rats anesthetized with pentobarbital sodium were measured using videomicroscopy. Adenosine (ADO) at 534 micrograms intraarterially, topical ADO at 10(-3) M, and the endothelium-dependent agonist topical acetylcholine (ACH) at 10(-4) M significantly dilated both A2 and A3 arterioles Pre-ENDT and Post-ENDT. Topical tetraethylammonium chloride (TEA) at 1 mM blocked ADO (intraarterially and topical)-induced A2 and A3 arteriolar dilations Pre-ENDT and Post-ENDT. Arteriolar dilation to ACH was maintained Pre-ENDT, but was blocked by TEA in A2 and A3 arterioles Post-ENDT. The endothelium-independent agonist sodium nitroprusside (10(-5) M), when topically applied, caused maximal arteriolar dilation Pre-ENDT and Post-ENDT in the presence of TEA. The data show that vascular smooth muscle KCa channels are a significant factor in ADO-induced relaxation of cremaster microvessels and are not significantly affected by ENDT. The results also suggest that the mechanism for endothelium-dependent ACH vasodilation changes from a non-KCa channel-mediated mechanism Pre-ENDT to a KCa-mediated mechanism Post-ENDT.

Acetylcholine↗

Some preliminary studies on the ability of Africanized honey bees (Apis mellifera L.) to tolerate cold temperatures when placed inside a refrigerator.

Cold is often suggested as an ecological mechanism to prevent the migration of Africanized honey bees. The ability of Africanized honey bees to tolerate cold temperatures was investigated. In one study an observation hive was placed inside a refrigerator at 25 degrees C. The study was conceptualized as a choice experiment in which the colony could remain in a cold environment or leave for a warm environment. Analysis indicated that the bees remained at 9 +/- 1 degrees C for 14 days before leaving. In a second series of studies, testing the tolerance to 0 degree C, 280 bees were placed individually in small metal tubes. The data gathered included survival rate, time to regain consciousness, and ability to feed. Analysis indicated that Africanized bees can survive for up to 3 hr. at 0 degree C with few ill effects. At 4 hr., however, the survival rate is low. Limitations of the study, the use of cold as a possible deterrent to honey bee mites, and suggestions for additional research are discussed.

Animals↗

Inhibition of cAMP mediated relaxation in rat coronary vessels by block of Ca++ activated K+ channels.

The hypothesis for this study is that block of calcium activated potassium (KCa) channels inhibits cAMP induced relaxation in pressurized rat coronary resistance arteries. Pressure-diameter experiments with septal arteries (200-270 microns internal diameter at 60 mmHg and maximum dilation) showed significant basal tone over a range of pressure from 40-120 mmHg. The level of tone was increased with the thromboxane A2 analogue 9,11-dideoxy-11 alpha, 9 alpha-epoxy-methanoprostaglandin F2 alpha (U46619) in all experiments. Receptor activation of the cAMP pathway was done with adenosine (ADO) and isoproterenol (ISO). Tetraethylammonium ion (TEA+), 1mM, significantly inhibited relaxation to ADO (10(-6)-10(-3)M) with a maximal inhibition of 75 +/- 7% (as a % of maximum diameter change with the vasodilator alone) at 10(-3)M ADO. TEA+ inhibited ISO (10(-6)M) relaxation by 63 +/- 9%. Direct activation of the cAMP pathway was done with forskolin and 8-bromo-cAMP. TEA+ significantly inhibited forskolin (10(-6)-10(-4)M) induced relaxation with a maximal inhibition of 81.3 +/- 1.2% at 10(-4)M forskolin. TEA+ and iberiotoxin (10(-7)M) significantly inhibited 8- bromo-cAMP (10(-3)M) induced relaxation by 72 +/- 5% and 56 +/- 3% respectively. The effect of TEA+ on relaxation induced by nitroprusside (a cGMP dependent vasodilator) was not significant. The results show that rat coronary resistance arteries possess significant myogenic tone and modulation of Kca channels plays a major role in cAMP mediated relaxation.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

Expression of c-kit receptor and its autophosphorylation in immature rat type A spermatogonia.

The objective of this study was to examine the expression and activation of the c-kit receptor, a specific receptor for kit ligand (stem cell factor, steel factor), in rat type A spermatogonia. Testes were obtained from 9-day-old rats, decapsulated, and then subjected to sequential enzymatic digestion. The mixture of testicular cell types was then separated by sedimentation velocity at unit gravity. The isolated type A spermatogonia were characterized by light and electron microscopy. They exhibited spherical nuclei containing several nucleoli and associated chromatin clumps and organelles generally in a perinuclear location similar to that found in the in vivo 9-day-old testis. The synthesis of the c-kit receptor by the spermatogonia was established by hybridization of total RNA with a specific cDNA for mouse c-kit receptor. Two mRNA transcripts migrating at 4.8 kb and 12 kb were observed. Localization of the c-kit receptor in the isolated cells was determined by immunocytochemistry using an antibody to c-kit protein. Specific staining for c-kit receptor was observed in the cytoplasm of the isolated type A spermatogonia. Furthermore, the presence of the c-kit receptor protein in the spermatogonia was confirmed by Western blot analysis using the same antibody. The antibody recognized the c-kit receptor at approximately 160 kDa. In an attempt to determine whether this receptor has a functional significance, we examined the effect of kit ligand on the phosphorylation of the c-kit receptor. The c-kit receptor appeared to be constitutively autophosphorylated on tyrosine at low basal levels, and upon stimulation with kit ligand, the amount of phosphorylated protein increased significantly. These observations indicate that kit ligand induces autophosphorylation of the c-kit receptor, which may lead to the activation of other cellular target proteins responsible for spermatogonial proliferation and/or differentiation.

Animals↗

Characterization of npf mutants identifying developmental genes in Physarum.

In Physarum polycephalum, uninucleate haploid amoebae develop into macroscopic multinucleate plasmodia. Wild-type, sexual development is triggered when two amoebae carrying different alleles of matA fuse to form a zygote which develops into a diploid plasmodium. Mutations in the matA genetic region give rise to apogamic strains in which a single haploid amoeba can develop into a haploid plasmodium. An essential stage in both sexual and apogamic plasmodium formation is an extended cell cycle in uninucleate cells, which ends with the formation of a binucleate cell by mitosis without cytokinesis. Using a 'brute force' screening method, we have isolated mutants blocked in apogamic plasmodium development. Genetic analysis showed that the mutations we have identified were unlinked to matA, unlike mutations previously identified following an enrichment step. Most of the loci revealed by our screen were represented by only one allele, indicating that further screening should lead to the identification of additional genes required for plasmodium development. Phenotypic analysis showed that different mutants were blocked at different stages of plasmodium formation. Some of the mutations blocking apogamic development at an early stage, close to the start of the long cell cycle, failed to block sexual development in zygotes homozygous for the mutation. Since the two modes of plasmodium formation differ only in the initiation of development, these mutations presumably interfere with the initiation process. In the remaining mutants, in which both sexual and apogamic development were blocked, development first became abnormal towards the end of the long cell cycle. This suggested that the wild-type gene products were required by this time and was consistent with previous evidence that many changes in cellular organization and gene expression occur during the long cell cycle. Each of these mutants showed a different terminal phenotype and some aspects of plasmodium development occurred normally although others were blocked, suggesting that development involves multiple pathways rather than a dependent sequence of events. Phenotypic analysis of double mutants supported this conclusion and also revealed epistatic interactions, presumably due to blocks in the same pathway. In several of the mutants, terminally differentiated cells died by an apoptosis-like mechanism; since this was never observed in vegetative cells, it was presumably triggered by the failure of development. Phenotypic analyses of additional mutants will extend our understanding of the pathways involved in plasmodium development.

Animals↗

Arteriolar reactivity of endotoxin-tolerant rats after hemorrhage and reinfusion.

Adrenergic and endothelium-dependent arteriolar reactivity are greatly reduced in hemorrhagic shock. However, development of tolerance to endotoxin may prevent the decrease. The reactivity of cremaster muscle arterioles was tested in pentobarbital-anesthetized endotoxin-tolerant (ENDT-T) and nontolerant control rats. Tolerance was developed by sublethal intraperitoneal injections of Escherichia coli endotoxin for 4 days (n = 9). Controls received saline (n = 9). Mean arterial pressure (MAP), arteriolar diameter-response curves to topical norepinephrine (NE) (10-9M to 10-3M) and responses to 10-3M acetylcholine (ACh) were obtained as follows 1) at control, 2) following hemorrhage to 40 mmHg. 3) after uptake of 25% of bled volume with the remainder infused, and 4) at 240 min post-hemorrhage. The A1, A2, and A3 arterioles were constricted following hemorrhage in the ENDT-T group and in the saline group. After reinfusion and in late shock, vessel diameters remained constricted. MAP increased to control levels (106 +/- 5 and 101 +/- 4 mmHg, respectively) following re-infusion in both groups but in late shock it decreased until death in the nontolerant group and decreased only minimally (96 +/- 4 mmHg) in the ENDT-T group. The nontolerant group NE ED50 increased from pre-hemorrhage to late shock (p < .05). The ENDT-T group ED50 was unchanged. The bleeding volumes of the two groups were not different. The survival time of the nontolerant group was 234 +/- 36 min, whereas the ENDT-T group all survived and were sacrificed at 427 +/- 30 min. The response to endothelium-dependent ACH vasodilation in late shock was significantly reduced in the saline group but was unchanged in the ENDT-T group. Alpha 1 receptor activity was maintained in both groups. Alpha 2 receptor activity was attenuated pre-hemorrhage and at 240 min post-hemorrhage in ENDT-T rats. In late shock, alpha 2 receptor activity was attenuated in nontolerant rats. The development of endotoxin tolerance prevents the loss of arteriolar responsiveness to NE and ACh. ENDT-T rats have attenuated alpha 2 receptor activity but not alpha 1 receptor activity.

Acetylcholine↗

In vitro femoral arterial responses to vasoconstrictor and vasodilator agents in endotoxin shock.

The hypothesis for this study is that the decreased arterial response to catecholamines may be due to the effect of endotoxemia on vessel tone. One control ring was taken from one femoral artery of a Wistar rat and after endotoxin (ENDT) infusion (i.v. 6 mg/kg-1 hr.), one ring was removed from the contralateral artery. The post-ENDT rings were tested in four groups which were determined by the mean arterial pressure (MAP) levels at the time of dissection: 100 mmHg (120 min), 80 mmHg (270 min), 60 mmHg (300 min) or 40 mmHg (330 min). KCl, phenylephrine (PHE) and arginine-vasopressin (AVP) dose-response curves (DR) were obtained at a preload of 500 mg which allowed the maximum response in control rings. When compared at 500 mg preload the maximal active response to all agonists post-ENDT was decreased by about 50%. By increasing the preload on the ENDT rings to 800 mg, the active tension became 2.49 times the active tension of the control rings. Length-tension experiments also showed a greater response for post-ENDT rings and a greater preload at maximum response but the ring circumference was the same. In contrast the in vivo femoral artery diameters at 90 min post-ENDT (100 mmHg) were 82.6% of control. Endothelium-dependent relaxation by acetylcholine (ACh) was abolished by ENDT but endothelium-independent relaxation to nitroprusside (NP) was not affected. It is concluded that the resting tone and active tension of femoral artery smooth muscle is increased by ENDT and the decreased in vivo responsiveness to vasoconstrictor agonists may be the result of vessel constriction due to loss of endothelium. The results also suggest that in vitro comparison of vessels in studies of endotoxin shock be done at the same muscle length rather than at the same preload.

Acetylcholine↗

Amplitude enhancement is seen in the cochlear nerve but not at, or before, the afferent synapse.

The amplitude of the cochlear nerve compound action potential (CAP) produced by a moderate intensity tonal stimulus (S2) can be enhanced when S2 is preceded by a low intensity S1 of the same frequency. The presence of S1 had no observable influence on the threshold of the CAP to S2. Enhancement was not observed in the cochlear microphonics or summating potentials. Deactivation of the contralateral olivocochlear bundle did not influence enhancement. Tetrodotoxin (TTX) was applied to the round window to block cochlear nerve spike activity, resulting in a residual EPSP-like potential, as described in the guinea pig by Dolan et al. (1989). Kainic acid, in turn, eliminated this EPSP-like response. Even though some differences were found in the responses of the gerbil and their guinea pig preparation to TTX and kainic acid, enhancement was not observed in this residual potential. When enhancement was observed at the level of the CAP, it was observed at brainstem levels. It is suggested that enhancement originates within the cochlear nerve axons.

Acoustic Stimulation↗

On the relation between social information processing and socially competent behavior in early school-aged children.

This article tested the hypotheses that (1) children's behavioral competence is a function of patterns of social information processing; (2) processing correlates of behavior occur at each of 5 steps of processing within each of 3 social situations; (3) measures at each step uniquely increment each other in predicting behavior; (4) the relation between processing and behavior is stronger within than across domains; and (5) processing patterns are more sophisticated among older than younger children and the processing-behavior relation is stronger among older than younger children. Videorecorded stimuli were used to assess processing patterns (encoding, interpretational errors and bias, response generation, response evaluation, and enactment skill) in 3 domains (peer group entry, response to provocation, and response to authority directive) in 259 first-, second-, and third-grade boys and girls (ages 6-9 years). Ratings of behavioral competence in each domain were made by peers and teachers. Findings generally supported hypotheses, with the magnitude of relations being modest.

Age Factors↗

Inhibition of adenosine-induced coronary vasodilation by block of large-conductance Ca(2+)-activated K+ channels.

The aim of the present study was to investigate the contribution of large-conductance calcium-activated potassium (large-conductance KCa) channels to adenosine (Ado)- and nitroprusside-mediated relaxation in small coronary arteries. Canine subepicardial arteries (170 +/- 23 microns at 120 mmHg) were studied as in vitro pressurized vessels. Pressure-diameter experiments showed myogenic tone over a physiological range of pressures. Tone was increased with the thromboxane A2 analogue 9,11-dideoxy-11 alpha,9 alpha-epoxy-methanoprostaglandin F2 alpha (U-46619). Tetraethylammonium (TEA+; 1 mM) significantly inhibited Ado-induced [and by implication, adenosine 3',5'-cyclic monophosphate (cAMP)-induced] relaxations at Ado concentrations ranging from 0.1 to 10 microM with maximal inhibition (61 +/- 8%) at 1 microM Ado. The large-conductance KCa-channel blocker iberiotoxin (IbTX; 0.01-0.1 microM) inhibited Ado-mediated relaxation in a concentration-dependent manner. Inhibition by IbTX increased with increasing vessel pressure (i.e., 45 +/- 12% at 40 mmHg and 83 +/- 20% at 120 mmHg). TEA+ had a minimal effect (8 +/- 3%) on relaxation induced by nitroprusside. Similar results were found with acetylcholine and bradykinin. These results suggest that (in dog coronary arteries with diameter < 200 microns) large-conductance KCa-channel modulation may play a major role in cAMP-mediated relaxation but is not significant in guanosine 3',5'-cyclic monophosphate-mediated relaxation.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

Attenuation of arteriolar alpha 2-adrenoceptor sensitivity during endotoxemia.

It is well documented that adrenergic responses after endotoxin (ENDT) administration are greatly reduced. The hypothesis of this study is that either alpha 1- or alpha 2-receptor activity is attenuated and the other receptor type is minimally affected during ENDT shock. Reactivity of the arterioles of left cremaster muscles of male Wistar rats anesthetized with pentobarbital sodium was studied using videomicroscopy. Femoral mean arterial pressure and first-, second-, third-, and fourth-order arteriolar diameters were measured. In group I, the decreases in arteriolar diameter and half-maximal effective dose (ED50) values with increasing phenylephrine concentration (alpha 1-adrenergic receptor agonist) were similar in all four branching orders before and after ENDT. In group II, the decreases in arteriolar diameter with increasing clonidine concentrations (alpha 2-adrenergic receptor agonist) were effectively attenuated by ENDT, and ED50 values were increased above control in all four branching orders. In group III, idazoxan (alpha 2-receptor antagonist) effectively blocked the vasoconstrictor effects of clonidine but did not affect the responses to phenylephrine before or after ENDT in all four arteriolar orders. In group IV, prazosin (alpha 1-adrenergic receptor antagonist) blocked the vasoconstrictor effects of phenylephrine before and after the administration of ENDT. However, vasoconstriction due to clonidine post-ENDT even at maximal dosage (10(-3) M), was greatly attenuated in all four branching orders as in group II. It is concluded that during endotoxemia the reduced adrenergic vasoconstrictor response of cremaster muscle arterioles is the result of attenuated activity of alpha 2-adrenergic receptors with minimal if any effects on alpha 1-adrenergic receptor activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

In vitro reconstitution of a functional peripheral-type benzodiazepine receptor from mouse Leydig tumor cells.

The peripheral-type benzodiazepine receptor (PBR) was identified and characterized by its high affinity for two distinct classes of compounds, the benzodiazepines (BZs) and the isoquinolines (IQs). An M(r) 18,000 IQ-binding protein has been identified as the PBR. In this report we isolated and sequenced a 626-base pair cDNA, specifying an open reading frame of 169 amino acid residues with a predicted molecular weight of 18,843, from MA-10 mouse tumor Leydig cells [i.e., mouse peripheral-type benzodiazepine receptor (mPBR)]. Expression of mPBR cDNA in simian virus 40-transformed 3T3 fibroblasts resulted in an increase in the density of both BZ and IQ binding sites. To examine whether the increased drug binding was due to the M(r) 18,000 PBR protein alone or to other constitutively expressed components of the receptor, an in vitro system was developed using recombinant mPBR protein. The mPBR cDNA was inserted in the pMAL-c2 vector downstream from the malE gene, which encodes maltose-binding protein (MBP). Transfection of the recombinant pMAL-c2 in Escherichia coli provided high levels of expression of the MBP-mPBR fusion protein. Purified MBP-mPBR recombinant fusion protein incorporated into liposomes, but not MBP alone, was able to bind IQs but not BZs. Addition of MA-10 mitochondrial extracts to the liposomes resulted in the restoration of BZ binding. The protein responsible for this effect was then purified and identified as the M(r) 34,000 voltage-dependent anion channel protein, which by itself does not express any BZ and IQ binding. These results provide strong evidence that PBR is not a single protein receptor but a multimeric complex in which the IQ binding site is on the M(r) 18,000 subunit and expression of the BZ binding site requires both the M(r) 18,000 and 34,000 voltage-dependent anion channel subunits.

3T3 Cells↗

Characterization of colonic transit of nondisintegrating tablets in healthy subjects.

The transit of pharmaceutical dosage forms through the colon has been shown to be highly variable. The amount of fiber in the diet is known to alter gastrointestinal transit; however, the dietary intake of the subjects in previous studies was not adequately controlled. Using the technique of gamma scintigraphy, we have therefore characterized the variability in the colonic transit of nondisintegrating tablets, by strictly controlling the dietary fiber intake of the subjects. Eight healthy male subjects followed a diet containing 25 g dietary fiber per day, for six days prior to dosing. Each subject received five 6-mm nondisintegrating tablets on three consecutive days. Mouth-to-anus transit times exhibited a high degree of variability. Regional differences in colonic transit were evident. Tablet stasis appeared to occur mainly in the ascending colon and hepatic flexure. Despite the diets of the volunteers being identical, colonic transit was still observed to be highly variable, which suggests that this variability is intrinsic.

Adult↗

The effect of meal composition on the gastrocolonic response: implications for drug delivery to the colon.

The response of the colon to eating, the gastrocolonic response (GCR), may have important implications for the design of drug dosage forms for selective delivery to the colon. Therefore, the effect of meal composition on the GCR and its relation to the transit of nondisintegrating tablets has been investigated. Eight healthy male volunteers each received 5 x 6-mm radiolabeled nondisintegrating tablets, and the transit was followed using a gamma camera. When the tablets reached the ileocolonic region, each volunteer received a test meal (1000 kcal) containing 70% carbohydrate, 15% fat, and 15% protein. The subsequent movement of the tablets was then monitored. The study was repeated using a 70% fat meal and a 70% protein meal, so that the effects of a high-carbohydrate, a high-fat, and a high-protein meal on the GCR could be compared. The incidence of GCRs was similar after all meals. Thus, there appeared to be no effect of meal composition on the movement of the tablets into the colon. This implies that the ingestion of food may not necessarily stimulate the passage of material across the ileocecal junction and that other factors may also be involved.

Adult↗