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Biomedical subjects

W G Clark

Publications and source records attributed to W G Clark.

At least 37 records · Page 2Linked to original sources

The genes encoding the small subunit of ribulose-1,5-bisphosphate carboxylase are expressed differentially in petunia leaves.

We have isolated five members of the multigene family encoding the small subunit (rbcS) of ribulose-1,5-bisphosphate carboxylase in petunia and examined their expression in petunia leaves. Of the five rbcS genes, two (ssu11A and ssu8) are expressed at high levels in petunia leaves. Northern analysis using gene specific oligonucleotide probes revealed that ssu11A accounts for 40% of the total rbcS transcripts in petunia leaves while ssu8 accounts for 4 to 5% of the total rbcS transcripts. Structural comparisons of ssu8 and ssu11A revealed that the coding sequence of ssu8 is interrupted by three introns, while the coding sequence of ssu11A is interrupted by two introns. The positions of the first two introns are identical, the third intron in ssu8 is located in a highly conserved region of the protein. The 5' and 3' flanking sequences of ssu11A are highly homologous to the 5' and 3' flanking sequences of ssu8. S1 nuclease mapping was used to locate the start of transcription of ssu8 and ssu11A and showed that ssu8 mRNA leader differs in sequence from the ssu11A mRNA leader.

Amino Acid Sequence↗

The rabbit ear-withdrawal test: a new analgesiometric procedure.

The latency to movement of an ear exposed to radiant heat was prolonged after intravenous administration of morphine to rabbits. The quantification of this response in a relatively inactive species that is especially suited for long term and repeated tests suggests that the rabbit ear-withdrawal test will be useful for screening analgesic/anesthetic compounds.

Analgesia↗

Changes in body temperature after administration of adrenergic and serotonergic agents and related drugs including antidepressants: II.

This survey continues a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published from 1980 to 1984 but data from many earlier papers are also tabulated.

Amphetamines↗

Altered body temperature of rabbits after central injection of beta-endorphin and other peptides.

After injection of 5 micrograms into a lateral cerebral ventricle, 6 of 12 peptides induced mean changes of 0.3 degree C or more in rectal temperature of rabbits. When beta-endorphin was studied further with 1.25-5 micrograms in 10, 23 and 30 degrees C environments, it induced dose-related hypothermia in the cold, hyperthermia in the heat and progressively smaller increases in body temperature with increasing doses at 23 degrees C.

Animals↗

Changes in body temperature after administration of acetylcholine, histamine, morphine, prostaglandins and related agents: II.

This survey continues a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published since 1979, but data from many earlier papers are also tabulated.

Acetylcholine↗

Changes in body temperature after administration of amino acids, peptides, dopamine, neuroleptics and related agents: II.

This survey begins a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published since 1978, but data from many earlier papers are also tabulated.

Amino Acids↗

Analysis of the antipyretic action of alpha-melanocyte-stimulating hormone in rabbits.

alpha-Melanocyte-stimulating hormone (alpha-MSH) or paracetamol was injected into a lateral cerebral ventricle (I.C.V.) of rabbits with elevations in rectal temperature induced by sodium arachidonate (I.C.V.), prostaglandin E2 (I.C.V.) or leucocytic pyrogen (I.V.). alpha-MSH (200 ng) was more effective than paracetamol (0.5 mg) in reducing fever caused by leucocytic pyrogen, but it did not alter hyperthermia induced by sodium arachidonate. In contrast, paracetamol reduced hyperthermic responses to arachidonate by about 70%. Neither alpha-MSH nor paracetamol affected hyperthermic responses to prostaglandin E2. The doses of alpha-MSH and paracetamol used in these experiments did not interfere with thermoregulation in a cold environment (10 degrees C). We conclude (1) that alpha-MSH and paracetamol differ in their central mechanism of antipyresis or (2) that inhibition of arachidonic acid metabolism by paracetamol is not requisite for its antipyretic effect, in which case central release of alpha-MSH may mediate the antipyretic effect of paracetamol.

Acetaminophen↗

Hyperthermic response of the cat to intraventricular injection of the opioid delta-receptor agonist D-Ala2-D-Leu5-enkephalin.

The delta opioid receptor agonist D-Ala2-D-Leu5-enkephalin was injected into the third cerebral ventricle of cats to determine its effects on core temperature for comparison with other peptide and non-peptide opioids that act on a variety of receptors to alter thermoregulation. Like other opioid peptides that have been studied in this species, D-Ala2-D-Leu5-enkephalin (5-25 micrograms) induced a dose-related hyperthermia. This response was undiminished in cats tolerant to morphine and was found to consist of two components. One component of the hyperthermic response was inhibited by pretreatment with low doses of opioid antagonists (25 micrograms naloxone; 5-15 micrograms naltrexone) and may be mediated by the v2-receptor that mediates this response to D-Ala2-Met-enkephalinamide. The other component, which was prevented by 100 micrograms naltrexone but still only partially inhibited by 250 micrograms naloxone, is attributed to delta-receptor stimulation. In tests over a range of environmental temperatures, the hyperthermic response to 10 micrograms D-Ala2-D-Leu5-enkephalin was less in a 4 degrees C environment than at the usual laboratory temperature of 22 degrees C. Responses in 22 and 34 degrees C environments were similar. No increase in respiratory rate occurred to indicate activation of compensatory heat-loss mechanisms so that the hyperthermia was indicative of an increase in the level about which body temperature is regulated.

Animals↗

Variation of levels of mRNA coding for antenna and reaction center polypeptides in Rhodopseudomonas capsulata in response to changes in oxygen concentration.

The effect of oxygen tension on the transcription of genes coding for the photosynthetic apparatus of Rhodopseudomonas capsulata was determined by the Southern hybridization technique. Restriction endonuclease digests of the R-prime plasmid pRPS404 and a subcloned fragment thereof served as DNA probes for genetically defined regions. The results showed that transcripts corresponding to the genes for certain pigment-binding polypeptides increase in amount by about 40-fold after a drop in oxygen tension. Transcripts hybridizing to genes involved in bacteriochlorophyll biosynthesis increase to a much lesser extent, and several genes involved in carotenoid biosynthesis are not affected by pO2.

Bacterial Proteins↗

Evidence against involvement of beta-endorphin in thermoregulation in the cat.

In the cat naloxone has little, if any, effect on temperature under usual laboratory conditions and does not reduce febrile responses to leukocytic pyrogen. Hence, endogenous opioid peptides that are antagonized by naloxone are not essential for induction of fever or for maintenance of normal temperature in the absence of appreciable thermal stress. The purpose of this study was to assess the contribution of such endogenous opioids to thermoregulation in cats exposed to more severe thermal and non-thermal stresses. Changes in temperature of unanesthetized cats were determined after third cerebral ventricular injections of large doses (100, 250 micrograms) of naloxone or saline vehicle. Naloxone had no appreciable effect on the temperature of cats acutely exposed to hot (34 degrees C) or cold (4 degrees C) environments, either before or after tolerance to morphine had been induced by progressively greater daily or twice-daily intraventricular doses of 10-70 micrograms morphine sulfate. Naloxone also did not significantly affect the temperature of cats subjected to neck-restraint or forced to stand on a small platform if they were to avoid contact with ice water. These results provide no indication that an endogenous opioid peptide, such as beta-endorphin, that is antagonized by naloxone contributes appreciably to thermoregulation in cats. They do not rule out the possibility that endogenous opioids, such as Met-enkephalin, that are not readily antagonized by naloxone are important for normal thermoregulation.

Animals↗

Effects of morphine on body temperature of squirrel monkeys of various ages.

Increased sensitivity to certain drugs is believed to contribute to dysthermia in the elderly. To learn whether the temperature-altering effects of an opiate are increased in aged primates, injections of morphine sulfate (0.5-4 mg/kg) were given SC in randomly assigned order to squirrel monkeys ranging in age from 3.5 to over 17 years. Hyperthermia was the predominant response with no clear relationship to age, although hypothermic and biphasic responses also occurred, most commonly after the highest dose. Lateral cerebral ventricular injections of 0.625 and 1.25 micrograms morphine sulfate evoked hyperthermia in monkeys over 8 years of age but did not affect the temperature of animals less than 5 years old. Doses of 2.5 and 5 micrograms usually elicited hyperthermia regardless of age, but 10 micrograms induced hypothermia in a majority of monkeys. Naloxone was given intraventricularly to several monkeys to limit the degree of hypothermia after high doses of morphine given peripherally or centrally. Thus in these primates, as in other species such as the rat, lower doses of morphine usually evoked hyperthermia, but sufficiently high doses caused body temperature to fall. Unlike the case in the squirrel monkey with diazepam and with endogenous substances such as leukocytic pyrogen and taurine, there was not a strong or consistent relationship between age and morphine-induced temperature changes.

Aging↗

Alignment of genetic and restriction maps of the photosynthesis region of the Rhodopseudomonas capsulata chromosome by a conjugation-mediated marker rescue technique.

The restriction map of a 46-kilobase fragment of the Rhodopseudomonas capsulata chromosome was aligned with the genetic map of the photosynthesis region of that chromosome by a marker rescue technique. Marker rescue was effected by mobilization of vectors bearing fragments of R. capsulata DNA from Escherichia coli to a set of R. capsulata mutants. Plasmids pDPT51 and pDPT55 were constructed to mediate the intergeneric mobilization of pBR322 derivatives, and a mutant of R. capsulata with improved intergeneric recipient activity was isolated. Four previously unmapped genes affecting bacteriochlorophyll synthesis and two genes affecting photochemical reaction center synthesis have been located by marker rescue. Some of the fragments of R. capsulata DNA are capable of vector-independent complementation, implying that promoters are located on these fragments. Other fragments complement only in one orientation of insertion in the vector, implying transcription from promotors on the vectors and thereby fixing the direction of transcription for those fragments. Still other fragments of DNA show rescue only via recombination between homologous plasmid-borne DNA fragments and chromosomal mutations. The physical dimensions of the genetic map are 3.0 megadaltons per map unit, which agrees with previous estimates based on the size of the R. capsulata gene transfer agent.

Bacterial Proteins↗

Anorexia nervosa.

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Adolescent↗