Biomedical subjects

K A Jones

Publications and source records attributed to K A Jones.

At least 109 records · Page 6Linked to original sources

PubMed1994

Halothane and pertussis toxin-sensitive G proteins in airway smooth muscle.

We hypothesized that halothane-induced depression of airway smooth muscle (AWSM) contractility is caused, in part, by an effect on pertussis toxin-sensitive guanosine triphosphate (GTP)-binding regulatory proteins (G proteins). To determine the effect of G protein inactivation on the ability of halothane to relax AWSM, isolated strips of canine tracheal smooth muscle were contracted with the muscarinic agonist acetylcholine and relaxed by halothane (0.2 to 1.6 minimum alveolar anesthetic concentration [MAC]). Half of the strips were treated with pertussis toxin 10 micrograms/mL. Because a pertussis toxin-sensitive G protein mediates muscarinic inhibition of adenylyl cyclase, depression of G protein function by halothane might also enhance the relaxing effects of beta-adrenoreceptor agonists. To test this possibility, in another series of experiments, the effect of pretreatment with 1.6 MAC halothane on the ability of isoproterenol to relax strips contracted with acetylcholine was studied; the converse order of drug presentation was also performed. Treatment with pertussis toxin did not affect the ability of halothane to relax AWSM; 1.6 MAC halothane produced a 42% +/- 8% (mean +/- SD) and 38% +/- 8% decrease in force in treated and untreated strips, respectively. Exposure to 1.6 MAC halothane did not significantly affect the dose-response relationship between isoproterenol and force. Conversely, exposure to isoproterenol (0.036 +/- 0.033 micron) did not significantly affect the dose-response relationship between halothane and force. These results do not support the presence of a significant effect of halothane on the function of pertussis toxin-sensitive G proteins.

Acetylcholine↗

PubMed1994

The detailed characterisation of a 400 kb cosmid walk in the BRCA1 region: identification and localisation of 10 genes including a dual-specificity phosphatase.

We have produced a detailed physical and transcriptional map of a 400 kb region within the narrowest flanking markers known to contain the hereditary breast and ovarian susceptibility gene, BRCA1. The approach described here has avoided the problems of chimaerism, instability and rearrangements commonly observed in yeast artificial chromosomes by converting the YAC clones into ordered chromosome 17-specific cosmid contigs and joining these contigs by cosmid end-walking. A detailed long-range restriction map provided a framework for the cosmid contig assembly and further refines existing physical mapping data. We have used a combined approach towards the isolation of the genes housed within these cosmids. This has resulted in the isolation and precise localisation of eight novel genes, including a novel G protein and an endogenous retrovirus related to the HERV-K family, and the previously described dual-specificity VHR phosphatase and MOX1 homeobox genes.

Animals↗

PubMed1993

Inhibition of axonal growth by SNAP-25 antisense oligonucleotides in vitro and in vivo.

Axonal elongation and the transformation of growth cones to synaptic terminals are major steps of brain development and the molecular mechanisms involved form the basis of the correct wiring of the nervous system. The same mechanisms may also contribute to the remodelling of nerve terminals that occurs in the adult brain, as a morphological substrate to memory and learning. We have investigated the function of the nerve terminal protein SNAP-25 (ref. 2) during development. We report here that SNAP-25 is expressed in axonal growth cones during late stages of elongation and that selective inhibition of SNAP-25 expression prevents neurite elongation by rat cortical neurons and PC-12 cells in vitro and by amacrine cells of the developing chick retina in vivo. These results demonstrate that SNAP-25 plays a key role in axonal growth. They also suggest that high levels of SNAP-25 expression in specific areas of the adult brain may contribute to nerve terminal plasticity.

Animals↗

PubMed1993

HIV-1 core promoter lacks a simple initiator element but contains a bipartite activator at the transcription start site.

The human immunodeficiency virus type 1 (HIV-1) core promoter region, extending approximately from nucleotides -40 to +80 relative to the transcription start site, contains a complex array of putative regulatory elements, including a TATA box, an initiator element, an element between the TATA box and start site, binding sites for LBP/UBP, the TAR element, and others. However, because of this elaborate architecture, the precise boundaries and functional roles for the individual regulatory elements have not been defined. To facilitate a detailed analysis of the HIV-1 core promoter, we employed in vitro transcription assays to identify the simplest control elements that activate RNA synthesis in the context of a synthetic, heterologous promoter. Because mutations at the start site previously were shown to diminish transcription, we anticipated finding an initiator as a basic regulator. However, we have demonstrated that the HIV-1 core promoter lacks an initiator that is functionally analogous to those found in the terminal transferase and adenovirus major late promoters. In its place, we identified two elements between -6 and +30, both of which appear to be necessary for significant transcriptional activation. Unlike a strong initiator, the activity of these elements was dependent on the presence of a TATA box and on their position relative to TATA. We have called the region containing these two elements the HIV-1 SSR to distinguish it from the simple transcriptional initiator elements found in other genes.

Base Sequence↗

PubMed1993

Biological actions of oncogenes.

Cancer, in many cases, results from multistep genetic mutation. Certain genes can have a predisposed susceptibility to mutations that lead to cancer because of chromosome location or their importance in the control of cell cycles. Mutations that deregulate the expression or activity of enzymes involved in the biochemical pathways of growth and differentiation or that suppress the expression of negative cell cycle control factors result in activation of oncogenesis. The study of oncogenes and tumor suppressor genes has greatly influenced our understanding of the molecular origins of cancer. We focus here on the normal biological action of proto-oncogenes compared with the transforming activities of oncogenes and tumor suppressor genes, and we discuss possible mechanisms of oncogenic transformation.

Animals↗

PubMed1993

Tat and the HIV-1 promoter.

The HIV-1 Tat protein enhances the formation of productive RNA polymerase II elongation complexes, potentially acting through a positive-acting, DRB-sensitive elongation factor. Tat is usually recruited to the HIV-1 promoter through the Tat trans-activation response element RNA stem-loop structure; however, recent data suggest that in certain cell types it can be directed instead through upstream enhancer elements. New studies also reveal that the response element overlaps a novel motif that promotes the assembly of abortive elongation complexes in the absence of Tat.

Amino Acid Sequence↗

PubMed1993

A versatile, computer-controlled, closed-loop system for continuous infusion of muscle relaxants.

A computer-controlled, closed-loop system for continuous infusion of muscle relaxants that allows the operator to choose either atracurium besylate or vecuronium bromide to provide any desired target level of neuromuscular blockade is described. This new system offers certain advantages over computer-controlled systems described previously for continuous infusion of muscle relaxants--that is, the option to choose either of two muscle relaxants to be infused and the inclusion of monitors to provide feedback about the dosage needed to produce a target level of neuromuscular blockade. The clinical performance of this system was tested in 36 patients who were 18 to 65 years old, were classified in American Society of Anesthesiologists physical status 1 or 2, and were undergoing elective orthopedic, abdominal, or thoracic procedures. In all patients, the control algorithm rapidly induced the target level of neuromuscular blockade and maintained that level of blockade at steady state with minimal oscillation. We conclude that the automatic feedback control system described can induce and precisely maintain any predetermined target level of neuromuscular blockade.

Adolescent↗

PubMed1993

Factors influencing the direct actions of volatile anesthetics on airway smooth muscle.

BACKGROUND: The authors hypothesized that the ability of volatile anesthetics to relax airway smooth muscle (AWSM) depends on: 1) the agonist used to produce muscle contraction, 2) the preexisting level of contraction, and 3) the volatile anesthetic used. METHODS: To test the first hypothesis, isolated strips of canine trachealis muscle were precontracted with acetylcholine (ACh), McN-A-343 (McN, another muscarinic agonist), 5-hydroxytryptamine (5HT, a different receptor agonist), or potassium chloride (KCl, which induces contraction by cell depolarization) to 50% of maximal force, then exposed to halothane (0.2-1.6 MAC). To test the second and third hypotheses, other strips were precontracted to 25, 50, 75, and 100% of maximal force with ACh, or to 10, 30, or 50% of maximal force with KCl, and were then exposed to halothane or isoflurane (0.2-1.6 MAC). RESULTS: For AWSM contracted to 50% of maximal force, the amount of relaxation produced by halothane depended on the agonist used to elicit contraction in the following manner: 5HT = McN > ACh; the muscles contracted with KCL did not relax. For ACh-induced contractions, the absolute amount of relaxation produced by halothane did not depend on the level of precontraction. In muscles contracted with KCl, the volatile anesthetics caused significant relaxation only in muscles contracted to 10% of maximal force. Overall, halothane had a significantly greater relaxing effect as compared with isoflurane during ACh-mediated contractions; the effects of the two agents did not differ significantly during KCl-mediated contractions. CONCLUSIONS: When canine AWSM tone is increased by contractile agonists in vitro, the absolute amount of relaxation produced by halothane depends on the agonist used to elicit contraction, but not the degree of precontraction. In addition, there are small but significant differences between the effects of halothane and isoflurane on ACh-mediated contractions.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗

PubMed1993

The hLEF/TCF-1 alpha HMG protein contains a context-dependent transcriptional activation domain that induces the TCR alpha enhancer in T cells.

hLEF/TCF-1 alpha is a lymphoid cell-specific HMG protein that activates the distal enhancer of the gene encoding the alpha-subunit of the T-cell receptor (TCR alpha). We have shown previously that transcriptional activation by hLEF is highly dependent on the context of its binding site within the TCR alpha enhancer. Here, we demonstrate that hLEF contains a potent transcriptional activation domain that is separate from the HMG motif and is preferentially active in T cells. We find that hLEF/GAL4 fusion proteins can activate a GAL4-substituted TCR alpha enhancer up to 50-fold in T-cell lines and are as active as GAL4/VP16 in this context. Unlike GAL4/VP16, however, hLEF/GAL4 could not activate heterologous promoters bearing only GAL4 DNA-binding sites. Thus, activation by hLEF/GAL4, like that noted previously for the native hLEF activator, was strongly influenced by the context of its DNA-binding site within the TCR alpha enhancer. Inspection of enhancer mutants suggests that trans-activation by hLEF/GAL4 is especially dependent on TCF-2, a distinct T-cell-enriched protein that binds to sequences flanking the hLEF-binding site in the enhancer. Analysis of small deletion or clustered amino acid substitution mutants in the hLEF-coding sequences identified a minimal activation region between amino acids 80 and 256 that appears to be bipartite in structure. The hLEF activation domain is not notably acid or glutamine-rich but is proline-rich and includes a motif rich in tyrosine and serine residues. We conclude that sequences outside of the hLEF HMG box mediate cell- and context-specific activation of the TCR alpha enhancer and may facilitate interactions between hLEF and other T-cell-specific factors recruited to the enhancer.

Amino Acid Sequence↗

PubMed1993

Localization of the retinoid X receptor alpha gene (RXRA) to chromosome 9q34.

The retinoid X receptor alpha is one of a number of retinoic acid receptors which are members of the steroid/thyroid hormone superfamily. Localization of RXRA was achieved using the polymerase chain reaction on a panel of somatic cell hybrids. A cosmid clone was isolated using the RXRA PCR product, and this was used to further localize the gene by fluorescence in situ hybridization to chromosome 9q34 distal to the dopamine beta hydroxylase gene (DBH). This mapping position was confirmed by PCR on a panel of translocation hybrids.

Animals↗

PubMed1993

Halothane alters cytosolic calcium transient in tracheal smooth muscle.

Halothane is a potent bronchodilator that attenuates vagally mediated constriction of canine airways, in part by a direct action on the smooth muscle cell. In tracheal smooth muscle, acetylcholine (ACh) produces a transient peak increase in cytosolic ionized calcium concentration ([Ca2+]i), which declines to a sustained plateau concentration that is higher than that of the unstimulated muscle, and a sustained increase in force. The transient peak [Ca2+]i is caused primarily by Ca2+ release from the sarcoplasmic reticulum (SR), whereas the plateau [Ca2+]i is caused primarily by influx of extracellular Ca2+ across the plasma membrane. This study was conducted to investigate the effects of halothane on the 1) transient peak [Ca2+]i during force development (i.e., developed force) and 2) plateau [Ca2+]i during force maintenance (i.e., sustained force) induced by ACh in isolated strips of canine tracheal smooth muscle. Changes in [Ca2+]i were measured with the photoprotein, aequorin. In muscle strips contracted after incubation with 1.1 (n = 5) or 1.5 (n = 5) minimum alveolar concentration (MAC) halothane, halothane significantly attenuated the transient peak aequorin luminescence (AL) and developed force and significantly prolonged the time necessary to reach peak AL and developed force; these effects were not dose dependent. In muscle strips (n = 3) contracted with ACh, addition of halothane caused a reduction in sustained force but no decrease in plateau AL.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMed1993

Severe HELLP syndrome presenting with acute gum bleeding following toothbrushing at 38 weeks' gestation.

We describe a case of hemolysis, elevated liver enzymes and low platelet count (HELLP syndrome) at 38 weeks' gestation. This condition was diagnosed when the patient presented with acute, persistent gum bleeding after toothbrushing. Her platelet count was 26,000/mm3. Bleeding gums have rarely led to the diagnosis of this syndrome; this case appears to be the most severe description of this clinical presentation following toothbrushing yet presented in the literature. Although the patient had been hospitalized 48 hours earlier with nonspecific viral-like symptoms, she was discharged after being treated with intravenous hydration. Reexamination of laboratory studies obtained at the time of her first presentation revealed thrombocytopenia. The diagnosis of this syndrome could possibly have been made at that time. This case emphasizes the importance of maintaining a low threshold of suspicion for this syndrome.

Acute Disease↗

PubMed1992

Muscarinic M3 receptors inhibit a leak conductance in rat corticocallosal neurons.

Acetylcholine, acting on muscarinic receptors, has a powerful modulatory effect on neurons in the cerebral cortex. Recent evidence that cortical tissue contains at least four different muscarinic receptor subtypes having different pharmacological properties indicates the value of new investigations of the receptor subtypes that mediate electrophysiological responses. Here we studied the ionic nature and pharmacology of the depolarizing response to acetylcholine in identified corticocallosal neurons in primary culture. This response is the result of a non-rectifying 'leak' K+ conductance which is reduced in the presence of acetylcholine. The relative sensitivity of this conductance change to the antagonists pirenzepine and 4-DAMP suggests that it is mediated by the M3 subtype of muscarinic receptor.

Acetylcholine↗

PubMed1992

Method of intraoperative monitoring of neuromuscular function and residual blockade in the recovery room.

We evaluated the method used intraoperatively to assess the degree of neuromuscular blockade prior to pharmacologic reversal to determine its role in preventing residual blockade in the postanesthesia care unit (PACU). We studied 38 patients who received a nondepolarizing muscle relaxant during general anesthesia for carotid endarterectomy or thoracotomy. The anesthesiologist assessed the degree of neuromuscular blockade intraoperatively prior to pharmacologic reversal either by the standard method of visually counting the number of evoked thumb twitches elicited by supramaximal train-of-four stimulation of the ulnar nerve (i.e., thumb train-of-four count), or by an alternative method such as 1) visually counting the number of evoked orbicularis oculi muscle twitches elicited by supramaximal train-of-four stimulation of the facial nerve, or 2) observing the patient for clinical evidence of partial recovery (e.g., swallowing or attempts to breathe). Residual blockade in the PACU was defined as 1) a train-of-four ratio less than 0.70 (measured by a mechanomyograph), or 2) the inability of the patient to perform clinical tests of neuromuscular function (e.g., a sustained head lift for 5 seconds) and evidence of neuromuscular weakness that was resolved following administration of edrophonium. Five of the 22 patients (23%) in whom one of the alternative methods was used had residual blockade in the PACU; none of the 16 patients with a thumb train-of-four count of 3 or 4 before pharmacologic reversal of NMB had residual blockade in the PACU (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia Recovery Period↗

PubMed1991

Both NMDA and non-NMDA subtypes of glutamate receptors are concentrated at synapses on cerebral cortical neurons in culture.

N-methyl-D-aspartate (NMDA) and non-NMDA receptors play a key role in synaptic transmission and plasticity in the vertebrate central nervous system. Previous studies have suggested that although both receptor types are present at synapses, the NMDA receptors may be relatively uniformly distributed. We have combined iontophoretic mapping of NMDA and non-NMDA receptors with immunohistochemical localization of synaptic vesicles along dendrites of single neocortical neurons to determine the relationship between NMDA and non-NMDA receptor distribution and the location of synapses. We find that when corrections for glutamate diffusion are made, NMDA responses are concentrated at focal "hot spots" that coincide with non-NMDA hot spots and that there is an excellent correlation between these hot spots and synapses.

Animals↗

PubMed1991

Hyperkinetic borderline hypertension in Tecumseh, Michigan.

Of 691 healthy (untreated) villagers of Tecumseh, Michigan (average age 32.6 years), 99 had a clinical blood pressure exceeding 140/90 mmHg. Thirty-seven per cent of these borderline hypertensives had increased heart rate, cardiac index, forearm blood flow and plasma norepinephrine. These subjects had elevated self-determined home blood pressure (average of 14 measurements). The present hyperkinetic borderlines had elevated blood pressure at 5, 8, 21 and 23 years of age and their parents also had higher blood pressure. The prevalence of high blood pressure in Tecumseh, its long history, elevated blood pressure readings outside the physician's office and family background of hypertension, suggests that the hyperkinetic state is a significant clinical condition. Previous studies on hospital-based populations proved that the hyperkinetic state is caused by an excessive autonomic drive. The association of the hyperkinetic state with elevated norepinephrine in this study suggests that a sympathetic hyperactivity is present in a large proportion of unselected subjects with mild blood pressure elevation.

Adult↗

PubMed1991

Two distinct nuclear transcription factors recognize loop and bulge residues of the HIV-1 TAR RNA hairpin.

Transcriptional activation by the HIV-1 Tat protein requires specific residues in the hexanucleotide loop and trinucleotide bulge of the TAR RNA stem-loop structure found in the 5'-untranslated leader of all viral transcripts. Tat directly contacts residue U22 in the bulge and is thought to act in concert with cellular factors bound to the loop. We find that HeLa nuclear extracts contain two specific TAR RNA-binding proteins, designated TRP-1 and TRP-2, which compete for binding to the upper portion of the TAR hairpin. Analysis of point mutants in TAR RNA reveals that TRP-1 contacts residues in the loop that are important for trans-activation, whereas TRP-2 contacts the bulge, including the same residue (U22) that is required for the Tat-TAR interaction. Glycerol gradient sedimentation and UV cross-linking experiments indicate that TRP-1 is a large heteromeric complex containing a 185-kD RNA-binding protein, whereas TRP-2 activity derives from a family of 110- to 70-kD proteins. Interestingly, both TRP-1 and TRP-2 promote TAR-dependent transcription in vitro in the presence of Tat, although mixing experiments indicate that each of the three proteins must bind independently to TAR RNA. These findings suggest that the TAR element is recognized by two different nuclear RNA-binding proteins that affect transcriptional regulation by Tat.

Base Sequence↗

PubMed1991

A thymus-specific member of the HMG protein family regulates the human T cell receptor C alpha enhancer.

The human T cell-specific transcription factor TCF-1 alpha plays a key role in the tissue-specific activation of the T cell receptor (TCR) C alpha enhancer and binds to pyrimidine-rich elements (5'-PyCTTTG-3') present in a variety of other T cell-specific control regions. Using amino acid sequence information derived from the DNA affinity-purified protein, we have now isolated cDNA clones encoding TCF-1 alpha. The TCF-1 alpha cDNA contains a single 68-amino-acid domain that is homologous to a region conserved among high-mobility group (HMG) and nonhistone chromosomal proteins. Expression of full-length and mutant cDNA clones in bacteria reveal that the single HMG motif, which is predicted to contain two extended alpha-helical segments, is sufficient to direct the sequence-specific binding of TCF-1 alpha to DNA. Northern blot experiments demonstrate further that TCF-1 alpha mRNA is highly tissue specific, found primarily in the thymus or T cell lines. The immature CEM T cell line expresses relatively low levels of TCF-1 alpha mRNA, which are increased upon activation of these cells by phorbol esters. Interestingly, the cloned TCF-1 alpha protein is a potent transcriptional activator of the human TCR alpha enhancer in nonlymphoid cell lines, whereas the activity of the endogenous protein in T cell lines is strongly dependent on an additional T cell-specific protein that interacts with the core enhancer. TCF-1 alpha is currently unique among the newly emerging family of DNA-binding regulatory proteins that share the HMG motif in that it is a highly tissue-specific RNA polymerase II transcription factor.

Amino Acid Sequence↗