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Biomedical subjects

B J Murphy

Publications and source records attributed to B J Murphy.

At least 73 records · Page 4Linked to original sources
PubMed1990

Identification, characterization, and photoaffinity labeling of the dihydropyridine receptor associated with the L-type calcium channel from bovine adrenal medulla.

The dihydropyridine receptor associated with the L-type Ca2+ channel in adrenal medulla membranes has been identified and characterized. [3H]PN200-110 binds in a stereoselective, saturable manner to a single class of high affinity sites in adrenal medulla membranes, with a Kd of 0.1 nM and a Bmax of 141 fmol/mg of protein. Dihydropyridines inhibited [3H]PN200-110 binding with the rank order (+)-PN200-110 greater than nifedipine greater than nimodipine greater than usoldipine greater than or equal to nitrendipine greater than BayK8644 greater than (-)-PN200-110. [3H] PN200-110 binding was sensitive to divalent cations, as examined by the effects of Ca2+, Mg2+, and the chelators ethylene glycol bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid and EDTA. [3H]PN200-110 binding was modulated by various classes of L-type Ca2+ channel effectors. Benzothiazepines modulated binding of [3H]PN200-110 in a negative or positive manner that was temperature dependent, whereas phenylalkylamines weakly inhibited [3H]PN200-110 binding. Bepridil stimulated [3H] PN200-110 binding, whereas phencyclidine was without effect. The photoaffinity probe [3H]azidopine labeled a single polypeptide that migrated with an apparent molecular weight of 185,000-190,000 in sodium dodecyl sulfate gel electrophoresis. The dihydropyridine receptor was found to bind specifically to wheat germ agglutinin columns. These results demonstrate the presence of a Ca2+ channel blocker complex in adrenal medulla. The drug receptor sites reside on a glycoprotein complex in which a polypeptide analogous to the alpha 1-subunit of the L-type Ca2+ channel from skeletal muscle has been identified.

Adrenal Medulla↗
PubMed1989

The CT appearance of cystic masses of the liver.

The authors here discuss twelve discrete pathologic entities that they found, in a review of over 500 abdominal CT scans, caused the appearance of a cystic lesion in the liver. The CT characteristics of the various lesions are illustrated, differential points in the patients' histories are noted, and gross and microscopic pathology specimens are correlated with the CT appearances to explain the CT findings. Lesions considered include: simple (bile duct) cyst, adult polycystic kidney disease, Caroli disease, pyogenic abscess, echinococcal cyst, amebic abscess, metastasis, biliary cystadenoma and cystadenocarcinoma, hepatocellular carcinoma, cholangiocarcinoma, biloma, and extrapancreatic pseudocyst.

Carcinoma, Hepatocellular↗
PubMed1988

Transcriptional analysis of Bacillus subtilis rRNA-tRNA operons. I. The tRNA gene cluster of rrnB has an internal promoter.

Although the sequence and organization of many Bacillus subtilis tRNA genes are known, primary transcripts from these regions have not been previously analyzed. In this paper, S1 nuclease mapping, S1-type mapping, and Northern analyses were applied to the end of the 23 S rRNA, the 5 S rRNA, and the 21 tRNA genes of B. subtilis operon rrnB. Primary transcripts from the 5 S rRNA and tRNA genes up to approximately 600-800 nucleotides long were observed with S1-type mapping. The presence of discrete bands of processing intermediates indicated preferred processing points within the initial transcript. S1 nuclease mapping delineated a start point for transcription between the second and third tRNA genes. The -10 sequence was within the 37-base pair spacer region between tRNA genes, and the -35 sequence was within the structural gene for the upstream tRNA. Precursors from this region were evident during midexponential growth and two sporulation stages. Thus, in addition to promotion from the rRNA promoters, 19 of the 21 downstream tRNA genes are also under the control of an internal tRNA gene promoter. The accompanying paper (Vold, B. S., Green, C. J., Narasimhan, N., Strem, M., and Hansen, J. N. (1988) J. Biol. Chem. 263, 14485-14490) investigates the minor 5 S rRNA and 16 tRNA genes of another rRNA-tRNA gene set and emphasizes unique promoter elements in that system as well as a potentially unique rRNA processing scheme.

Base Sequence↗
PubMed1988

Clinical experience with the CO2 laser during carpal tunnel decompression.

Scar tissue formation along the cut edges of the transverse carpal ligament has been found to be among the primary causes for persistent median nerve compression following carpal tunnel release with the steel scalpel. Since laser surgery has been shown to be effective in reducing incisional inflammatory reactions, hypertrophic scarring, and postoperative pain and edema, in achieving better hemostasis, the application of the carbon dioxide laser may be a more efficient surgical tool than the steel scalpel for carpal tunnel release. In 46 cases of carpal tunnel syndrome, the carbon dioxide laser was utilized to vaporize the transverse carpal ligament and seal its edges. The patients were then reevaluated at 1 week, 2 weeks, 6 months, 1 year, and 2 years. No intraoperative complications were encountered. Patients reported minimal postoperative pain, rapid return of sensibility, decreased paresthesia, and increased motor function. After 2 years, there have been no recurrent symptoms of median nerve compression in these patients.

Carpal Tunnel Syndrome↗
PubMed1988

Traumatic adrenal hemorrhage: radiologic findings.

Four patients with traumatic hemorrhage in the right adrenal gland were examined with computed tomography (CT) and ultrasound (US) (initial US studies in three patients; follow-up study at least 1 month after the trauma in all patients). CT showed an enlarged inhomogeneous gland of normal to increased attenuation. This finding was associated with stranding of the periadrenal fat and stranding of the subcutaneous fat of the right flank, which corresponded to the site of trauma. US showed an enlarged, hyperechoic mass with a bright central echo that became cystic on follow-up examinations. Magnetic resonance imaging, performed in one patient, showed an enlarged gland that was isointense with liver on T1-weighted images and had increased signal intensity on T2-weighted images. Stranding of the periadrenal and subcutaneous fat of the right flank was present on T2-weighted images and appeared as streaky areas of increased signal intensity.

Adolescent↗
PubMed1987

Subcellular distribution and isolation of the Ca2+ antagonist receptor associated with the voltage regulated Ca2+ channel from rabbit heart muscle.

The Ca2+ antagonist binding sites associated with the voltage dependent calcium channel in rabbit myocardium were found to distribute with the sarcolemmal Na+ + K+ ATPase and adenylate cyclase activities during subcellular fractionation on sucrose-density gradients. The equilibrium dissociation constants (KD) for the binding of [3H]nitrendipine and [3H]verapamil were 0.31 +/- 0.04 nM and 4.1 +/- 0.5 nM respectively, and displayed an average density of 0.55 +/- 0.05 pmol/mg and 0.4 +/- 0.03 pmol/mg protein respectively for the most enriched membrane fraction. The Ca2+ antagonist binding sites were solubilized from the membranes with the detergent 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonate, and specific binding sites for [3H]PN200-110, [3H]verapamil and [3H]diltiazem were isolated on a wheat-germ lectin column. The binding sites for [3H]PN200-110 were enriched about 2,500 fold as compared with the original homogenate and displayed a density of 28.5 +/- 8 pmole/mg protein in the isolated fraction. Sodium dodecyl sulfate gel electrophoresis of the isolated drug binding proteins indicated enrichment of proteins of Mr 170,000, 140,000, 130,000, 100,000 and 53,000. The isolated receptor contained an intrinsic kinase activity that phosphorylated glycoproteins of Mr 170,000 and 53,000. Exogenously added cAMP-kinase stimulated phosphorylation of the 170,000, 100,000, 53,000 and 28,000 Mr glycoproteins in the receptor fraction. The results of this study indicate that the binding sites for [3H]nitrendipine, [3H]PN200-110, [3H]verapamil and [3H]diltiazem residue on glycoprotein(s) which are of sarcolemmal origin, and co-purify together on wheat germ lectin columns. The polypeptide composition of the Ca2+ antagonist binding sites from cardiac muscle appears to be very similar to that of the dihydropyridine receptor in skeletal muscle.

Animals↗
PubMed1987

A calmodulin dependent protein kinase activity associated with rabbit heart sarcolemma.

Sarcolemmal vesicles prepared from rabbit heart muscle by differential and discontinuous sucrose density gradient centrifugation, exhibited high marker enzyme activities: Na+ + K+ ATPase 22 microMol Pi x mg-1 x h-1, Adenylate cyclase 500 pmole cAMP x mg-1 x min-1, calcium antagonist receptors 0.7 pmoles x mg-1. Calmodulin in the presence of calcium and gamma-ATP32 stimulated rapidly and specifically the 32P incorporation into two membrane proteins of 54 and 44 kDa. Calmodulin stimulated the phosphorylation of the 44 kDa to a greater extent (17.9 pmol 32P x mg-1 protein) than the 54 kDa protein (1.3 pmoles 32P x mg-1 protein). Removal of endogenous calmodulin from the membrane by EGTA extraction resulted in a 2.5 fold increase in calmodulin dependent 32P incorporation into the two proteins in the presence of exogenous calmodulin. It is suggested that the calmodulin dependent protein kinase activity in heart sarcolemma may mediate the effects of calmodulin in the regulation of Ca2+ transport across the membrane.

Adenosine Triphosphate↗
PubMed1987

Innocuous pneumatosis intestinalis of the right colon in renal transplant recipients. Report of three cases.

Three cases of innocuous pneumatosis intestinalis (IPI) of the right colon occurred in a series of 218 renal transplant recipients over a five-year period. Each of the three transplants was in the right iliac fossa. Clinically, these patients had little or no gastrointestinal symptoms and had normal physical examinations of the abdomen. One of the patients had a generalized herpes simplex type 2 (HSV II) infection. Cystic or linear lucencies were present within the bowel wall, associated with varying degrees of localized colonic distention. The condition (IPI) did not warrant surgical intervention or reduction of immunosuppressive therapy. The pneumatosis resolved over a period of several weeks without sequelae or recurrence.

Adult↗
PubMed1986

Neurogenic hyperacute ascites in mice.

Four groups of mice were subjected to controlled fatal head trauma and then evaluated for the presence of ascites (neurogenic hyperacute ascites, NHA). The animals died virtually instantaneously and without evidence of maintained pain or suffering. The volume of ascites was determined in one group of animals. Two of the traumatized groups were pretreated, one with the beta-blocker propranolol and the other with the alpha-blocker phentolamine. A fifth, non-traumatized, group which was killed with either inhalation served as a control group. Two more groups of non-traumatized mice were administered either the alpha-adrenergic agonist methoxamine hydrochloride or the beta-agonist isoethrane mesylate before killing by ether inhalation, and then evaluated for ascites. Transudative ascitic fluid was found in 87-100% of untreated traumatized mice and in no control animals. Pretreatment with phentolamine had no effect on the prevalence of ascites. Pretreatment with propranolol produced a significant decrease in the prevalence of ascites compared with trauma alone (P less than 0.001). Isoethrane (beta-agonist) administration caused ascites in 100% of the treated animals. Methoxamine (alpha-agonist) administration did not cause ascites. A previously undescribed consequence of acute brain trauma is described (NHA) which appears to be mediated by beta-sympathetic activity of central origin. NHA is inhibited by beta-blockade and can be simulated with beta-agonist administration.

Acute Disease↗
PubMed1986

Effect of low levels of fluoride in solution on enamel demineralization in vitro.

The effect of low levels of fluoride in solution on in vitro enamel demineralization has been studied. Extracted human teeth were exposed to 0.1 M lactate solutions (at pH 4.3) which were partially saturated with respect to enamel mineral and which contained between 0.004 and 1 ppm fluoride. Enamel demineralization was monitored using SEM and polarized light microscopy. It was observed that, in the absence of fluoride, rapid enamel demineralization occurred, resulting in the formation of cavitations within 72 hours. Using the same demineralizing medium containing as little as 0.024 and 0.054 ppm fluoride, we observed a remarkable protection of the enamel surface. Subsurface enamel demineralization was, however, observed under these conditions as well as in a solution containing 0.154 ppm fluoride. When the demineralizing solution containing 1 ppm fluoride was used, no mineral loss was detected. The observed inhibition of enamel demineralization was also shown to be associated with a significant uptake of fluoride by the enamel mineral. These observations have been noted to correlate with an increase in solution supersaturation with respect to fluoridated apatitic species. The results obtained were found to be consistent with a proposed hypothesis that the net rate of enamel demineralization will be reduced in a demineralizing medium supersaturated with respect to less soluble fluoridated phases, due to the enhancement of the precipitation rate of fluoridated apatitic phases relative to the rate of dissolution of the original enamel surface.

Dental Caries↗
PubMed1985

Potentially conflicting metabolic demands of diving and exercise in seals.

Metabolic replacement rates (Ra) for glucose and free fatty acids (FFA) were determined during rest, exercise, and diving conditions in the gray seal using bolus injections of radiotracers. In the exercise experiments the seal swam at a metabolic rate elevated twofold over resting Ra for glucose and FFA while resting were similar to values found in terrestrial mammals and other marine mammal species. During exercise periods glucose turnover increased slightly while FFA turnover changes were variable. However, the energetic demands of exercise could not be met by the increase in the replacement rates of glucose or FFA even if both were completely oxidized. Under diving conditions the tracer pool displayed radically different specific activity curves indicative of the changes in perfusion and metabolic rate associated with a strong dive response. Since the radiotracer curves during exercise and diving differed qualitatively and quantitatively, it is possible that similar studies on freely diving animals can be used to assess the role of the diving response during underwater swimming in nature.

Animals↗
PubMed1985

Importance of high pKA acids in cariogenic potential of plaque.

Through the use of computer simulation, it is shown that anions of high pKA acids (e.g., acetic, propionic, butyric), present in resting plaque fluid, act as effective buffers during the production of stronger acids (e.g., lactic) by oral micro-organisms. Using reported organic acid compositions for plaque, obtained from caries-resistant and caries-susceptible individuals, analyzed at various times following sucrose exposure, it is shown that the calculated pH values of the aqueous phase of plaque describe typical Stephan curves. Furthermore, it is shown that for higher acid anion contents in resting plaque, a higher degree of saturation of the aqueous plaque phase with respect to enamel is maintained during acid production, resulting in a lower demineralization potential of plaque. Enamel demineralization experiments conducted in vitro confirmed the significance of the results of the computer simulations, thus providing evidence for a correlation between the known metabolic activity of plaque (organic acid composition), physical chemistry of plaque, and caries susceptibility.

Acetates↗
PubMed1984

Hypoxic coordinate regulation of mitochondrial enzymes in mammalian cells.

The effect of hypoxic exposure on various mitochondrial enzymes and on cell mitochondrial genomic content was studied in two types of mammalian cells. Hypoxia depressed the activity of six enzymes to the same degree. The kinetics of depression and of recovery during reexposure to normoxia were statistically similar for three marker enzymes. Despite the global and symmetrical decrease in enzyme activities, mitochondrial DNA remained constant. This suggests either symmetrical loss of mitochondrial enzymes from all mitochondria or complete loss of enzymes from a subpopulation of mitochondria with retention of an intact mitochondrial genome.

Aerobiosis↗
PubMed1984

Coordinate regulation of glycolysis by hypoxia in mammalian cells.

The impact of hypoxic exposure on the activities of all 11 glycolytic enzymes was studied in cell culture into mammalian cells-mouse lung macrophages and L8 rat skeletal muscle cells. During hypoxic exposure, the measured activity of all glycolytic enzymes increased, establishing coordinate regulation. Three nonglycolytic cytoplasmic enzymes showed no change in activity under the same conditions, suggesting a specific mechanism. Hypoxia appears to increase the activities of all glycolytic enzymes whether rate-limiting or not, presumably increasing adenosine triphosphate availability despite decreased O2 supply.

Animals↗