Search PubMed⌕ Search

Biomedical subjects

K J Miller

Publications and source records attributed to K J Miller.

At least 37 records · Page 2Linked to original sources
PubMed1998

Evidence for P2X3 receptors in the developing rat brain.

P2X receptor-mediated responses to the ATP analogue, alpha,beta-methylene ATP, in rat brain cannot be accounted for by the receptor proteins known to be present. Such experiments are often performed on cells from neonates and, since differential developmental regulation of P2X1 and P2X2 receptor messenger RNAs has already been demonstrated, this is likely to be the case for other P2X receptors. This study was designed to address the possible existence of alpha,beta-methylene ATP-sensitive P2X3 receptors in rat brains of various ages using a P2X3 receptor-selective antibody. P2X3 receptor protein was found in discrete regions of the embryonic (E16) and neonatal rat brain (P7 and P14) but was not detectable in adult animals. This is the first demonstration of the presence of these receptors in brains from various ages of rat and the differential expression of these receptors in neonates may account for some reported electrophysiological responses to alpha,beta-methylene ATP.

Age Factors↗
PubMed1998

Effects of Ionic and Osmotic Strength on the Glucosyltransferase of Rhizobium meliloti Responsible for Cyclic beta-(1,2)-Glucan Biosynthesis.

The cyclic beta-(1,2)-glucans of Rhizobium meliloti and Agrobacterium tumefaciens play an important role during hypoosmotic adaptation, and the synthesis of these compounds is osmoregulated. Glucosyltransferase, the enzyme responsible for cyclic beta-(1,2)-glucan biosynthesis, is present constitutively, suggesting that osmotic regulation of the biosynthesis of these glucans occurs through modulation of enzyme activity. In this study, we examined regulation of cyclic glucan biosynthesis in vitro with membrane preparations from R. meliloti. The results show that ionic solutes inhibit glucan synthesis, even when they are present at low concentrations (e.g., 10 mM). In contrast, neutral solutes (glucose, sucrose, and the compatible solutes glycine betaine and trehalose) were found to stimulate glucan synthesis in vitro when they were present at high concentrations (e.g., 1 M). Furthermore, high concentrations of these neutral solutes were shown to compensate for the inhibition of glucosyltransferase activity by ionic solutes. Consistent with their ionic character, the compatible solute potassium glutamate and the osmoprotectant choline chloride inhibited glucosyltransferase activity in vitro. The results suggest that intracellular ion concentrations, intracellular osmolarity, and intracellular concentrations of nonionic compatible solutes all act as important determinants of glucosyltransferase activity in vivo. Additional experiments were performed with an ndvA mutant defective for transport of cyclic glucans and an ndvB mutant that produces a C-terminal truncated glucosyltransferase. Cyclic beta-(1,2)-glucan biosynthesis, although reduced, was found to be osmoregulated in both mutants. These results reveal that NdvA and the C terminus of NdvB are not required for osmotic regulation of cyclic beta-(1,2)-glucan biosynthesis.

Journal Article↗
PubMed1997

Motor unit recruitment and discharge behavior in movements and isometric contractions.

The purpose of this study was to contrast the discharge patterns of the same motor units during movements and during isometric contractions that were produced with comparable torque-time characteristics. Subjects performed elbow flexion and extension movements with predetermined acceleration characteristics. The average acceleration and deceleration profiles for the movements were reproduced in the isometric setting by presenting the kinematic profiles as templates for torque production. Trained subjects were able to match the first agonist (AG1) and antagonist (ANT) electromyographic (EMG) bursts, but tended to produce a smaller second agonist burst (AG2) in the isometric contraction. Twenty-five motor units from triceps brachii were studied. The same motor units (with one exception) were recruited and subsequently discharged in a similar fashion in both the isometric and movement tasks in the AG1 and ANT EMG bursts, with fewer motor unit discharges in the AG2 burst in the isometric contraction. The central control mechanisms appear to be the same for the acceleration phase of movement and isometric contraction, but differ during the deceleration phase.

Adult↗
PubMed1997

Serotonin 5HT2A receptor activation inhibits inducible nitric oxide synthase activity in C6 glioma cells.

C6-glioma cells endogenously express both 5HT2A receptors and inducible nitric oxide synthase (iNOS). iNOS can be induced by transcriptional activation to produce nitric oxide (NO) in response to a challenge with lipopolysaccharide (LPS). Experiments were conducted to determine whether 5HT2A receptor activation could modify the production of NO in response to LPS. Incubation of 10 microg/ml LPS with C6-glioma cells for a period of 24 hours resulted in a 2.6 fold increase in nitrite levels, as a measure of NO levels, over vehicle treated controls. Co-incubation with the selective 5HT2A receptor partial agonist (+/-)-2,5-dimethoxy-4-iodoamphetamine (DOI) produced a dose-dependent inhibition of the LPS-induced nitrite levels of 22% with an IC50 of 16 nM. The full agonists serotonin (5HT) and alpha-methyl-5HT produced an inhibition of approximately 30% at a concentration of 1 microM. The inhibitory effect of 1 microM DOI was blocked by the 5HT2A receptor antagonists spiperone and ritanserin (10 nM). Inhibition of protein kinase C (PKC) using 100 nM chelerythrine prevented the DOI-mediated decrease in LPS-induced nitrite levels. Addition of DOI to the cells after 1 hr following the LPS addition did not produce a decrease in nitrite levels indicating iNOS was not modified post-translationally. The data demonstrate that iNOS activity can be modulated by serotonin 5HT2A receptor activation, most likely at the initiation of the induction process, via PKC. We therefore suggest that there may be a link between the serotonergic system and NO-mediated immune responses in the brain.

Brain Neoplasms↗
PubMed1997

The comorbidity of alcoholism and personality disorders in a clinical population: prevalence rates and relation to alcohol typology variables.

This study assessed prevalence rates and overlap among Diagnostic and Statistical Manual of Mental Disorders (3rd ed., revised; DSM-III-R; American Psychiatric Association, 1987) personality disorders in a multisite sample of 366 substance abusers in treatment. In addition, the relation of antisocial personality disorder (APD), borderline personality disorder (BPD), and paranoid personality disorder (PPD) to alcohol typology variables was examined. Structured diagnostic interviews and other measures were administered to participants at least 14 days after entry into treatment. Results indicated high prevalence rates for APD and non-APD disorders. There was extensive overlap between Axis I disorders and personality disorders, and among personality disorders themselves. APD, BPD, and PPD were linked to more severe symptomatology of alcoholism and other clinical problems. However, only APD and BPD satisfied subtyping criteria, after controlling for other comorbidity. Implications for classifying alcoholics by comorbid disorders are discussed.

Adult↗
PubMed1997

Radiolabeling of the rat P2X4 purinoceptor: evidence for allosteric interactions of purinoceptor antagonists and monovalent cations with P2X purinoceptors.

The rat recombinant P2X4 purinoceptor was expressed in CHO-K1 cells, and binding studies were performed using the radioligand [35S]adenosine-5'-O-(3-thio)triphosphate ([35S]ATPgammaS). In 50 mM Tris/1 mM EDTA assay buffer, pH 7.4 at 4 degrees, [35S]ATPgammaS bound with high affinity to the P2X4 purinoceptor (KD = 0.13 nM, Bmax = 151 pmol/mg of protein). The purinoceptor agonists ATP and 2-methylthioadenosine triphosphate possessed nanomolar affinity for the P2X4 purinoceptor, whereas the antagonist suramin possessed much lower affinity (IC50 = 0.5 mM). Cibacron blue was more potent than suramin but produced a biphasic competition curve, whereas d-tubocurarine potentiated binding at concentrations in excess of 10 microM. The complex effects of cibacron blue and d-tubocurarine seemed to be due to an allosteric interaction with the P2X4 purinoceptor because these compounds affected radioligand dissociation, measured after isotopic dilution with unlabeled ATPgammaS. Cibacron blue (1-100 microM) and d-tubocurarine (0.1-1 mM) produced rapid (10 sec to 5 min) decreases or increases, respectively, in the level of [35S]ATPgammaS binding measured immediately after initiation of the dissociation reaction. However, the subsequent rates of radioligand dissociation were not markedly different from those measured in their absence. Monovalent cations produced similar affects on the P2X4 purinoceptor and, like d-tubocurarine, increased [35S]ATPgammaS binding. The actions of d-tubocurarine and sodium were not additive. The findings from this study indicate that [35S]ATPgammaS can be used to label the P2X4 purinoceptor and suggest that this binding can be enhanced by monovalent cations and d-tubocurarine and may be subject to negative allosteric modulation to varying degrees by different purinoceptor antagonists.

Adenosine Triphosphate↗
PubMed1996

Affinity chromatography with immunochemical detection applied to the analysis of human methionyl granulocyte colony stimulating factor in serum.

An on-line, automated, HPLC method was developed for the separation and detection of recombinant human methionyl granulocyte colony stimulating factor (GCSF) and GCSF modified with poly(ethylene glycol) (PEG-GCSF) in rat serum. The automated method consists of an initial immunoaffinity chromatography step, a microbore reverse phase separation, and postcolumn immunochemical detection. Calibration curves were constructed with a lower limit of 1.5 ng of GCSF (80 fmol) and 7.5 ng of PEG-GCSF in 120 microL of rat serum. In vivo serum samples from rats dosed with PEG-GCSF were also analyzed. The development of the method is discussed as well as its general application to the detection of metabolites of recombinant proteins in body fluids.

Animals↗
PubMed1996

On criterion weighting in the DSM-IV.

Differential weighting of illness signs and symptoms has surfaced recurrently in psychiatric nosology. Six alternately weighted algorithms for diagnosing alcohol dependence in accordance with the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994), based on statistical, unit, rational and random criterion weighting systems, were used to predict an array of concurrent validators and 6-month drinking outcomes in a regional clinical sample of 365 participants. Comparable predictive efficiency across all algorithms, including the randomly weighted versus statistical best-fit model, was observed. Further analyses and geometric modeling suggested that this was due to the extremely high internal consistency of the DSM-IV criteria. An alternative strategy that favors factorially complex, less homogeneous criteria was used to develop an experimental DSM-IV algorithm from an array of 39 candidate criteria. This algorithm had extremely low internal consistency, high difficulty, and complex factor loadings. Differential weighting of its criteria produced a good range of efficiencies, predictive power for rational models exceeding the random weight model, and a best-fit algorithm with substantial surplus predictive power. These results illustrate an emerging conflict in nosology between 2 opposing trends: a press for the promulgation of criterion arrays with high internal consistency and a clear desire to assign some criteria extra weight for prognosis or decision making. Both cannot be had in the same algorithm. An alternative approach emphasizing diagnostic criteria with complex structures can satisfy the multiple demands of brevity, validity, and weighting performance.

Adult↗
PubMed1996

Osmoadaptation by rhizosphere bacteria.

The osmolality of rhizosphere soil water is expected to be elevated in relation to bulk-soil water osmolality as a result of the exclusion of solutes by plant roots during water uptake, the release of plant root exudates, and the production of exopolymers by plant roots and rhizobacteria. In contrast, the osmolality of water within highly hydrated bulk soil is low (less than 50 Osm/kg); thus the ability to adapt to elevated osmolality is likely to be important for successful rhizosphere colonization by rhizobacteria. The present review focuses on the osmoadaptive responses of three gram-negative rhizobacterial genera: Rhizobium, Azospirillum, and Pseudomonas. Specifically, we examine the compatible solutes and osmoprotectants utilized by various species within these genera. The adaptation of rhizobacteria to hypoosmotic environments is also examined in the present review. In particular, we focus on the biosynthesis and accumulation of periplasmic glucans by rhizobacteria. Finally, the relationship between rhizobacterial osmoadaptation and selected plant-microbe interactions is considered.

Adaptation, Biological↗
PubMed1996

Motor-unit behavior in humans during fatiguing arm movements.

1. The activity of 40 triceps brachii motor units was recorded from the dominant arms of 9 healthy adult volunteers (age 27.8 +/- 4.4 yr, mean +/- SD) during a fatigue task that included both isometric and anisometric contractions. The fatigue task lasted 8.3 min and consisted of 50 extension and 50 flexion movements of the elbow. Each movement (40 degrees in 0.8s) was separated by an isometric contraction. A constant load resisting extension of 17.7 +/- 3.0% of maximal voluntary contractions (MVC) was applied throughout the task. This paradigm enabled the direct contrast of motor-unit discharge behavior during the different types of fatiguing contractions. 2. Motor-unit behavior was examined to determine the relative contribution of two mechanisms for optimizing force production under fatiguing conditions: recruitment of motor units and modulation of motor-unit discharge following recruitment. Threshold torques for motor-unit recruitment thresholds were determined by ramp-and-hold isometric contractions. Motor-unit discharge was evaluated during the fatigue task by contrasting the number of motor-unit potentials (spikes) per contraction for concentric eccentric, and isometric contractions. 3. The fatigue task resulted in a 30 +/- 12% decline in the mean MVC of elbow extension. Recruitment of nine new motor units (23%) was evident during the fatiguing extension movements, often within five to seven movements (i.e., within 25-35 s). Each newly recruited motor unit had the largest recruitment threshold torque in that experiment. 4. Analysis of the motor units that were active from the beginning of the fatigue task revealed that the mean number of motor-unit spikes per contraction increased, or remained constant as fatigue ensued, yet for the majority of motor units it increased or remained constant. None of the newly recruited motor units demonstrated decreased number of mean spikes per contraction after recruitment. Further, concurrently active motor units displayed different discharge behavior in two-thirds of the subjects. It is proposed that if the neural drive to the muscle is distributed uniformly upon the motoneuron pool, peripheral feedback from the exercising muscle may modulate specific motoneuron discharge levels during fatigue.

Adult↗
PubMed1996

Motor unit activity during human single joint movements.

1. To explore the neural control of single joint movements in humans, the activity of 47 motor units in triceps brachii muscle was recorded during elbow flexion and extension movements. Movements were performed with different but changing deceleration magnitudes, while the acceleration magnitude was kept constant, to determine the relationship between motor unit activity and the acceleration and deceleration characteristics of single joint movements. 2. The number of motor unit action potentials was found to vary with the magnitude of the movement deceleration. In addition the duration of the discharge of a motor unit was found to parallel the duration of the acceleration phase of the movement, when the acceleration duration was varied while acceleration magnitude was kept constant. 3. Approximately half of the recorded motor units in triceps brachii were active both in the initiation and in the termination of the extension movements. However, motor units were identified that participated in specific phases of the movement (i.e., either during the 1st agonist or 2nd agonist burst of muscle activity) depending on the magnitude of the acceleration or deceleration. 4. During flexion movements, when the triceps muscle served as an antagonist, approximately half of the motor units were recruited only when the magnitude of the flexion deceleration was large. Further, this deceleration magnitude was larger than that evident during the extension movements in which the motor unit discharged. 5. The findings of this study demonstrate that the nervous system activates the same motor units whether the muscle is functioning as an agonist or antagonist so as to control the characteristics of acceleration and deceleration of single joint movements.

Acceleration↗
PubMed1995

DSM-III, DSM-IV and ICD-10 as severity scales for drug dependence.

The construct of illness severity serves many scientific and clinical functions. This study tested the performance as severity scales of three systems for diagnosing drug dependence--DSM-III, DSM-IV and ICD-10--in a multisite regional sample of 370 clinical subjects. Both lifetime and current severity of four drug problems--alcohol, cannabis, cocaine and opiate dependence--was studied in three stages: (a) item difficulty and internal consistency analysis; (b) probabilistic modeling of distribution behavior; and (c) concurrent validation against a set of independent measures. All three systems, for most drugs correlated with most test variables, had good to excellent concurrent validity. Unexpectedly, DSM-III showed in some instances better item behavior, composite score behavior and concurrent validity than the other systems, though DSM-IV and ICD-10 are based on slimmer generic algorithms, and may represent a good balance between simplicity and concurrent validity. Results suggest that the design of future diagnostic algorithms start at the item level and strive for moderate levels of both internal consistency and difficulty. Composite score distributions can then be modeled in field research, and necessary item corrections can be made before the algorithm is widely promulgated.

Adult↗
PubMed1995

The use of ketorolac in lumbar spine surgery: a cost-benefit analysis.

The use of ketorolac was studied in patients undergoing lumbar laminectomy and those receiving lumbar fusion with or without instrumentation. Laminectomy patients in the ketorolac group used significantly less narcotic analgesic than did those in the narcotic treatment group. Ketorolac patients in both surgical categories experienced better pain control than narcotic group patients did. Laminectomy ketorolac patients experienced less sedation than did those in the narcotic group, and a similar trend was noted for fusion patients. A significant improvement in postoperative ambulation was demonstrated in the fusion ketorolac group. Postoperative total drug costs were significantly greater in both ketorolac treatment groups. A one-half day decrease in hospitalization was noted for laminectomy ketorolac patients. The overall annual financial impact of the use of ketorolac in lumbar spine patients is a net savings of $211,095.

Adult↗
PubMed1995

Synthesis of glycerophosphorylated cyclic (1,2)-beta-glucans in Rhizobium meliloti strain 1021 after osmotic shock.

The transfer of phosphoglycerol moieties from phosphatidylglycerol to the cyclic (1,2)-beta-glucans in growing cultures of Rhizobium meliloti strain 1021 was investigated using pulse-chase experiments with [3H]glycerol and/or [14C]glucose. No transfer occurred when cells were grown and pulse-chased in a medium containing 0.4 M NaCl. However, radiolabelled glycerophosphorylated cyclic (1,2)-beta-glucans could be detected within 30 min after transfer of these cultures to a low-osmolarity medium. Conversely, when low-osmolarity cultures were shifted to a high-osmolarity medium containing 0.4 M NaCl or 0.8 M sucrose, the transfer of phosphoglycerol substituents to the cyclic (1,2)-beta-glucans was inhibited. Further experiments revealed that the transfer of phosphoglycerol substituents to the cyclic (1,2)-beta-glucans occurs within the periplasmic compartment.

Cell Membrane↗
PubMed1995

Identification of a PutP proline permease gene homolog from Staphylococcus aureus by expression cloning of the high-affinity proline transport system in Escherichia coli.

The important food-borne pathogen Staphylococcus aureus is distinguished by its ability to grow at low water activity values. Previous work in our laboratory and by others has revealed that proline accumulation via transport is an important osmoregulatory strategy employed by this bacterium. Furthermore, proline uptake by this bacterium has been shown to be mediated by two distinct transport systems: a high-affinity system and a low-affinity system (J.-H. Bae, and K. J. Miller, Appl. Environ. Microbiol. 58:471-475, 1992; D. E. Townsend and B. J. Wilkinson, J. Bacteriol. 174:2702-2710, 1992). In the present study, we report the cloning of the high-affinity proline transport system of S. aureus by functional expression in an Escherichia coli host. The sequence of the staphylococcal proline permease gene was predicted to encode a protein of 497 amino acids which shares 49% identity with the PutP high-affinity proline permease of E. coli. Analysis of hydropathy also indicated a common overall structure for these proteins.

Amino Acid Sequence↗
PubMed1995

Effect of Phosphate Limitation on Synthesis of Periplasmic Cyclic (beta)-(1,2)-Glucans.

Rhizobium meliloti and Agrobacterium tumefaciens synthesize periplasmic cyclic (beta)-(1,2)-glucans during adaptation to hypoosmotic environments. It also appears that these glucans provide important functions during the interactions of these bacteria with plant hosts. A large fraction of these glucans may become modified with anionic substituents such as phosphoglycerol or succinic acid; however, the role(s) of these substituents is unknown. In this study, we show that growth of these bacteria in phosphate-limited media leads to a dramatic reduction in the levels of phosphoglycerol substituents present on the periplasmic cyclic (beta)-(1,2)-glucans. Under these growth conditions, R. meliloti 1021 was found to synthesize anionic cyclic (beta)-(1,2)-glucans containing only succinic acid substituents. Similar results were obtained with R. meliloti 7154 (an exoH mutant which lacks the ability to succinylate its high-molecular-weight exopolysaccharide), revealing that succinylation of the cyclic (beta)-(1,2)-glucans is mediated by an enzyme system distinct from that involved in the succinylation of exopolysaccharide. In contrast, when A. tumefaciens C58 was grown in a phosphate-limited medium, it was found to synthesize only neutral cyclic (beta)-(1,2)-glucans.

Journal Article↗
PubMed1995

A novel cyclic beta-1,2-glucan mutant of Rhizobium meliloti.

The periplasmic cyclic beta-1,2-glucans produced by bacteria within the Rhizobiaceae family provide functions during hypo-osmotic adaptation and plant infection. In Rhizobium meliloti, these molecules are highly modified with phosphoglycerol and succinyl substituents, and it is possible that the anionic character of these glucans is important for their functions. In the present study, we have used a thin-layer chromatographic screening method to identify a novel R. meliloti mutant specifically blocked in its ability to transfer phosphoglycerol substituents to the cyclic beta-1,2-glucan backbone. Further analysis revealed that the cyclic glucans produced by this mutant contained elevated levels of succinyl substituents. As a result, the overall anionic charge on the cyclic beta-1,2-glucans was found to be similar to that of wild-type cells. Despite this difference in cyclic beta-1,2-glucan structure, the mutant was shown to effectively nodulate alfalfa and to grow as well as wild-type cells in hypo-osmotic media.

Base Sequence↗