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S A Carlson

Publications and source records attributed to S A Carlson.

24 records · Page 2Linked to original sources
PubMed1996

Lack of constitutive activation or inactivation of the platelet-activating factor receptor by glutamate substitution of alanine 230.

The platelet-activating factor (PAF) receptor (PAFR) is a G protein-coupled receptor (GPCR) that mediates a diverse array of biological responses to PAF. Recently, we provided evidence that the third intracellular domain (3i) of the rat PAFR (rPAFR) is a critical determinant in its coupling to phosphoinositide phospholipase C (PI PLC)-activating G proteins. In the present study, we assessed the potential role of a conserved alanine in the carboxyl-terminal region of 3i of the rPAFR in rPAFR signaling activity. Previous studies with the m5 muscarinic acetylcholine and human PAF receptors revealed that substitution of a carboxyl-terminal alanine was found to impair receptor-mediated PI PLC activation. Here we report the effects of the analogous nonconservative substitution of glutamate for alanine 230 of the rPAFR (rPAFR A230E) on receptor-mediated agonist binding and PI PLC activation following transient expression of the receptor cDNA. BHK cells transfected with a cDNA encoding the rPAFR A230E exhibited PAF-stimulated increases in inositol phosphate (IP) accumulation with no increase in basal levels of IPs. PAF-stimulated IP production in rPAFR transfectants was dependent on the amount of DNA transfected, although PAF provoked a larger increase in IPs in rPAFR transfectants than in rPAFRA230E transfectants in cells transfected with equal amounts of receptor cDNA. This latter finding apparently reflects differences in the transfection efficiency or expression of the wild-type and rPAFR A230E cDNAs because PAF produced indistinguishable effects on IP accumulation in rPAFR and rPAFR A230E transfectants expressing equivalent numbers of receptors. These results provide evidence for a nonconserved role of this conserved alanine in coupling of group I GPCRs to PI PLC-activating G proteins and also suggest that this residue has differential roles in regulating expression and signaling by rat and human PAFRs.

Alanine↗
PubMed1994

Pyogenic sacroiliitis.

This report describes two cases of pyogenic sacroiliitis with remarkably similar histories. The initial diagnosis is often overlooked because of its rarity and poorly localized signs and symptoms. Clinical and radiological findings, as well as treatment measures, are discussed. Familiarity with this type of septic arthritis is essential if prompt and appropriate therapy is to be rendered.

Adult↗
PubMed1986

Prolongation of lidocaine spinal anesthesia with epinephrine and phenylephrine.

The effect of vasoconstrictors on the duration of lidocaine spinal anesthesia is controversial. We conducted a double-blind study of 28 neurologically normal ASA Class I or II patients to determine the effect of vasoconstrictors (epinephrine and phenylephrine) on the duration of lidocaine spinal anesthesia. The patients were randomized into three groups. All patients received 1.2 mg lidocaine per inch body height, mixed with 0.5 ml of test solution. Group 1 patients received lidocaine plus 0.5 ml normal saline; Group 2 patients received lidocaine plus 0.3 mg epinephrine; Group 3 patients received lidocaine plus 5 mg phenylephrine. Segmental sensory blockade was assessed by pinprick at 2-min intervals for the first 20 min and then every 5 min thereafter. Mean highest level was between T-2 and T-3 for all 3 groups. Time from injection to highest sensory level was similar in Groups 1 and 3, 11.6 +/- 3.57 and 12.0 +/- 5.10 min, respectively, but was significantly prolonged in Group 2, 18.1 +/- 4.33 min. Time for regression by two sensory dermatomes were significantly prolonged in both Groups 2 and 3, 102.9 +/- 18.1 and 105.7 +/- 33.1 min, respectively, compared to 78.1 +/- 12.6 min in Group 1. Times for regression to T-12 was also significantly prolonged in both Groups 2 and 3, 153.7 +/- 27.6 and 156.8 +/- 26.7 min, respectively, compared to 117.71 +/- 10.0 min in Group 1. In the doses used in the present study, both epinephrine and phenylephrine significantly prolong the duration of lidocaine spinal anesthesia.

Adolescent↗
PubMed1980

Hypomagnesemia: higher risk using total parenteral nutrition in the treatment of patients with malignancies.

The syndrome of hypomagnesemia in patients receiving total parenteral nutrition (TPN) is well known. To determine particular high-risk groups for the development of this syndrome, 26 consecutive patients on TPN were initially evaluated for serum magnesium (Mg) and followed at regular intervals. Seventeen had a diagnosis of solid tumor or hematologic malignancy (CA); nine had inflammatory bowel disease and/or small bowel fistulae (ID). All met the standard criteria for being malnourished--anergy, low serum albumin, and recent weight loss. During TPN, all patients received an average of 24 mEq of magnesium sulfate per day, and all had satisfactory anabolic response in terms of weight gain and increase in serum albumin. Ten patients had at least one magnesium determination below the lower limits of normal, and four of these developed symptoms of tremor which responded to increased amounts of magnesium in their TPN. Eight of these ten (80%) had a diagnosis of CA, and four of four (100%) of those requiring additional magnesium to alleviate symptoms had CA. None of the patients with ID developed symptomatic hypomagnesemia. We conclude that patients with solid tumor malignancy are more likely to develop hypomagnesemia, possibly because of the increased requirements for magnesium in lymphocytolysis of tumor cells., and they must be carefully monitored to prevent this complication.

Adolescent↗
PubMed1977

Hormonal regulation of membrane phenotype.

Incubation of rat hepatoma cells (HTC) in tissue culture with glucocorticoids alters several membrane properties characteristic of transformed cells, without affecting the growth rate of these cells. Variant cell lines resistant to dexamethasone inhibition of plasminogen activator production have been isolated using an agar-fibrin overlay technique to detect plasminogen activator production by individual colonies of HTC cells. The resistance of dexamethasone is not secondary to abnormal or absent glucocorticoid receptors, but due to a lesion in a later step in hormone action specific for plasminogen activator. These variants should prove useful for the study of the mechanism of steroid action as well as for the analysis of the role of proteases in the hormonal regulation of membrane function.

Carcinoma, Hepatocellular↗