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M Lee

Publications and source records attributed to M Lee.

At least 919 records · Page 51Linked to original sources
PubMed1987

alpha-DNA-V. Parallel annealing, handedness and conformation of the duplex of the unnatural alpha-hexadeoxyribonucleotide alpha-[d(CpApTpGpCpG)] with its beta-complement beta-[d(GpTpApCpGpC)] deduced from high field 1H-NMR.

The beta-complementary hexamer, beta-d[GTACGC], to the alpha-sequence, alpha-d[CATGCG], was synthesized by the phosphotriester method. The non-exchangeable proton assignments were obtained using 1D- and 2D-NMR techniques, including NOE, COSY and NOESY. The beta-strand exists as a random coil at 21 degrees C; however, at 4 degrees C, it forms an antiparallel self-recognition duplex annealing at positions 1-4. The beta-strand was annealed to the alpha-strand, and confirmation of complete annealing was obtained by detection and assignment of the six base pair imino protons in H2O/D2O solution at 21 degrees C. 1D-NOE experiments of the alpha, beta duplex d[alpha-(CATGCG) X beta-(GTACGC)] reveal that (i) it exists in aqueous solution in a conformation that belongs to the B family, (ii) it is 70 +/- 10% right-handed, (iii) the sugar-base orientations of the beta-strand are anti, and the deoxyribose units exist predominantly in the 2'-endo-3'-exo conformation. NOE measurements of the imino proton signals in the alpha, beta duplex reveal that the duplex exhibits parallel polarity.

Base Composition↗
PubMed1987

Assay for tyrosine hydroxylase by high-performance liquid chromatography with fluorescence detection.

A sensitive assay method for tyrosine hydroxylase in rat brain and adrenal medulla by high-performance liquid chromatography with fluorescence detection is described. L-DOPA formed enzymatically from the substrate L-tyrosine and alpha-methyldopa (internal standard), after clean-up with small cartridges of an activated alumina and a cation exchanger, Toyopak IC-SP M, are converted into the corresponding fluorescent compounds by reaction with 1,2-diphenylethylenediamine. The derivatives are separated by reversed-phase chromatography on TSK gel ODS-120T. The detection limit for L-DOPA formed enzymatically is 2 pmol per assay tube.

Adrenal Medulla↗
PubMed1987

Picrotoxin but not bicuculline antagonizes 5-hydroxytryptamine-induced inhibition of cerebellar Purkinje neurons.

The inhibitory effects of iontophoretically applied serotonin (5-hydroxytryptamine) on Purkinje cells were examined in the presence of the GABA antagonists picrotoxin and bicuculline in in vivo and in vitro cerebellar preparations. Continuous application of the GABA-mediated chloride ionophore antagonist, picrotoxin, at currents that induced significant antagonism of GABA-elicited inhibition of Purkinje cells decreased the inhibitory effects of serotonin significantly in the same neurons. Bicuculline, an antagonist of GABA receptors, exerted different actions on serotonin-mediated inhibition of Purkinje cells. Continuous iontophoretic applications of bicuculline antagonized the inhibitory effects of GABA on Purkinje cells significantly, but failed to induce significant attenuation of serotonin-mediated inhibition. The inhibitory effects of serotonin on Purkinje cells were examined also in the presence of nipecotic acid, an inhibitor of GABA reuptake, and a low Ca2-high Mg2+ medium, which blocks synaptic transmission. Under these circumstances, serotonin-mediated inhibitions were not influenced significantly, indicating that its inhibitory effects do not involve release or reuptake of GABA. These results indicate that there might be a linkage between the actions of serotonin and GABA.

Action Potentials↗
PubMed1987

In vivo production of leukotriene B4 and leukotriene C4 in rabbit colitis. Relationship to inflammation.

Leukotriene B4, a proinflammatory compound, recently has been identified as the major metabolite of arachidonic acid in tissue incubations of human and animal colitis. To determine the relationship of inflammation to the in vivo production of leukotrienes, rabbit colitis was induced by formalin enema followed by intravenous infusion of immune complexes, and serial samples were collected by rectal dialysis. Leukotrienes B4 and C4 were measured by radioimmunoassay after high-pressure liquid chromatography. Prostaglandin E2 was assayed after Sephadex chromatography. Leukotrienes were not detected in control animals. Eicosanoid production progressively increased during development of inflammation and correlated with severity of inflammatory cell infiltration (p less than 0.01). Methylprednisolone decreased prostaglandin E2 but did not significantly reduce leukotrienes or inflammation. These data demonstrate that in vivo production of leukotrienes B4 and C4 correlates with indices of inflammation, consistent with the concept that these eicosanoids contribute to the inflammation of colitis.

Animals↗
PubMed1987

Regional lymph node and pulmonary metastases after local hyperthermia of melanomas in C57BL/6 mice.

The effects of local tumor hyperthermia on regional lymph node metastases are inconclusive. We studied the effects of hyperthermia on the incidence of popliteal, femoral, and abdominal lymph node metastases in C57BL/6 mice with primary B16 melanomas (F10 variant) growing subcutaneously in the left foot. Tumors were heated to 42.3, 43.5, and 44.2 degrees C for 90 minutes either 7 days after inoculation of 5 X 10(4) viable cells (microscopic tumor = mic) or when the tumors were approximately 3 mm in diameter (macroscopic tumor = mac). Femoral lymph node metastases occurred in 0/21 control animals and in 8/22 (36%), 11/19 (58%), and 11/17 (65%) animals whose primary tumors were heated to 42.3, 43.5, and 44.2 degrees C, respectively. For all three treatments, the increase in metastases as compared to controls was statistically significant (p less than 0.004, Fisher's exact test). The incidence of abdominal lymph node metastasis was slightly higher in the treated groups than controls. Twenty of 21 (95%) control mice developed popliteal lymph node metastases and hyperthermia-induced increases could not be demonstrated. Fifteen of 21 control mice killed 3 weeks after amputation of tumor-containing leg had pulmonary metastases with an average of 6 +/- 4 (standard deviation) lesions per affected mouse. Pulmonary metastases occurred in 22/22 (100%), 17/19 (89%), and 13/17 (76%) of mice whose tumors were heated to 42.3, 43.5, and 44.2 degrees C, respectively. The numbers of metastases for affected mice were significantly increased compared to controls for tumors heated to 43.5 and 44.2 degrees C (28 +/- 43, 43 +/- 52, 119 +/- 121, p greater than 0.02, p less than 0.006, p less than 0.002, for two sample T-test). While 0/8 mic tumors were cured 5/9 mac tumors heated to 44.2 degrees C disappeared (p less than 0.03, Fisher's exact test) and there was a growth delay in the remaining mice. Mic tumors, heated to 43.5 degrees C, had an accelerated onset of growth while mac tumors heated to this temperature had a slight growth delay. Growth of both mic and mac primary tumors heated to 42.3 degrees C was similar to controls. These results show that therapeutic and subtherapeutic local hyperthermia increases metastases to regional lymph nodes and to lungs even when primary tumor growth rate is partially or totally controlled.

Animals↗
PubMed1987

Adrenalectomy and steroid treatment in obese (ob/ob) and diabetic (db/db) mice.

Adrenalectomy in young obese (ob/ob) and the diabetic (db/db) mouse slowed body weight gain. Treatment of adrenalectomized ob/ob mice with cortisone or deoxycorticosterone acetate (DOCA) significantly increased weight gain in a dose-related manner. Cortisone had no effect on weight gain on lean mice and treatment with dehydroepiandrosterone sulfate was without effect on either ob/ob or lean mice. The increment in body weight of adrenalectomized ob/ob mice treated with corticosterone and DOCA was associated with an increase in body weight and an increase in food intake. When adrenalectomy was performed at twenty-three days of age (five days before weaning), animals carrying the (db/db) genotype remained lighter than their normal littermates. These data document the importance of the adrenal gland and its steroids for the development and maintenance of many features of the obese or diabetes mouse.

Adrenal Glands↗
PubMed1987

Sequence dependent conformation and local geometry of the conserved branch site sequence element d(TpApCpTpApApC), essential for yeast mRNA splicing, deduced from high resolution 1H-NMR.

The conserved sequence element and branch site splice signal d(TpApCpTpApApC) has been synthesized by a solid phase procedure. All the non-exchangeable protons have been assigned using a combination of one-dimensional and two-dimensional 1H-NMR analytical procedures. On the basis of the low NOE intensities in the 1D-NOE and NOESY experiments, the heptamer exists in solution as a random coil. The deoxyribose rings towards the 5' terminus exist predominantly in the S form (2'-endo-3'-exo) while residues on or adjacent to the 2' branch site in the eventual lariat structure [A(6) of TACTAAC] show more N-character (3'endo-2'-exo). In addition unique propeller twisting at contiguous AT base pairs in the consensus 5'-splice site occurs in the region in which there is partial complementarity with the branch splice signal TACTAAC. These subtle structural features, if carried over to the corresponding RNA, may have significance either as a recognition signals or for stereochemical reasons in the formation of the lariat intermediate in the maturation process of mRNA.

Base Sequence↗
PubMed1987

Structure and conformation of the duplex consensus 5'-splice site d[(CpApGpGpTpApApGpT).(ApCpTpTpApCpCpTpG)] deduced from high field 1H-NMR of the non-exchangeable and imino protons.

The complementary consensus donor exon intron junction d(ApCpTpTpApCpCpTpG) has been synthesized by a solid phase procedure. The non-exchangeable proton assignments were obtained using one- and two-dimensional NMR techniques including NOE, COSY, NOESY and 1H-1H-INADEQUATE. The non self-complementary nonamer exists as a random coil form in aqueous buffer at 21 degrees C as evidenced by the temperature variable 1H-NMR and NOE measurements. The nonamer was annealed to the primary consensus donor junction d(CpApGpGpTpApApGpT) and confirmation of complete annealing was obtained by detection and assignment of base pair imino protons in D2O/H2O mixtures. Application of one- and two-dimensional NMR techniques permitted the complete assignment of all the non-exchangeable protons in the duplex nonamer. These data, together with determination of vicinal coupling constants in the individual deoxyribose moieties, permits the following conclusions on the structure and conformation of the consensus donor junction: (i) it exists in aqueous solution in a conformation that belongs to the B family (ii) the sugar-base orientations are anti (iii) the deoxyribose units exist predominantly in the S conformation (2'-endo-3'-exo) (iv) the contiguous A.T base pairs d[T(5)-A(6)-A(7)].d[T(12)-T(13)-A(14)], two positions removed downstream from the splice site (5'-CAG decreases GTAAGT-3'), are uniquely propeller twisted. The propeller twisting occurs in the region in which there is partial complementarity with the branch site splice signal TACTAAC. The cross-correlation rates were used to derive the interproton distances between adjacent AH2 protons of 4.00 A in the T(5)-A(6).T(13)-A(14) step and of 3.87 A in the A(6)-A(7).T(12)-T(13) step. This structural and conformational feature if carried over into the primary RNA transcripts may serve as a recognition signal for this critical site in the genome.

DNA↗
PubMed1987

Structure and conformation of the branch core triribonucleotide containing 2'-5' and 3'-5' phosphodiester linkages (A 2'p5'G 3'p5'C) i solution, essential for yeast mRNA splicing, deduced from 1H-NMR.

The non-exchangeable 1H-NMR signals of the branch core trinucleotide of the lariat branch site (A2'p5'G3'p5'C, 1) and its derivatives 2 and 3 are completely assigned using one- and two-dimensional NMR techniques including NOE, COSY, NOESY, 1H-1H INADEQUATE and 2D-J-resolved spectroscopy. From the vicinal coupling constants in the individual ribose rings, NOE data and T1 measurements, the following properties of the trimers are deduced. (i) The unique stacking behavior of the trimers is S2'N3'N, and the sugar rings exist predominantly in the N-conformation (3'-endo-2'-exo). (ii) The sugar-base orientations appear to be anti. (iii) The branched trimers exist in solution as single-stranded right-handed conformations resembling A-RNA with stacking between the adenine and guanine residues in aqueous solution at 21 degrees C and pH 7.2. (iv) The calculated values for the torsion angles epsilon t and gamma+ for the trimers are 201-203 degrees and 71-86%, respectively, while the percent beta t values are higher for the guanine (87-92%) than the cytosine residues (73-77%). The computer generated depiction of the triribonucleotide 1 is also shown. These subtle structural features may act as recognition signals for this critical lariat branch site which is essential for the second step in yeast mRNA splicing.

Carbohydrate Conformation↗
PubMed1987

Hepatic amyloidosis in an i.v. drug abuser detected by bone scintigraphy.

A case of diffuse hepatic uptake of Tc-99m MDP in an intravenous drug abuser with biopsy-proven hepatic amyloidosis is presented. The association of parenteral drug addiction and amyloidosis, as well as current concepts regarding hepatic uptake of bone seeking radiopharmaceuticals in amyloidosis and its potential clinical implications are discussed.

Adult↗
PubMed1987

Comparison of EMIT versus bioassay to evaluate inactivation of tobramycin by piperacillin.

We evaluated and compared the sensitivity of enzyme multiplied immunoassay (EMIT) and bioassay techniques in detecting the degree of inactivation of tobramycin by piperacillin in serum specimens. Specimens were prepared to contain initial tobramycin concentrations of 10 micrograms/ml and piperacillin concentrations of 62.5, 125.0, 250.0, and 500 micrograms/ml. The samples were stored at room temperature (25 degrees C), in the refrigerator (4 degrees C), and in the freezer (-10 degrees C) for up to 7 days. Tobramycin concentrations were determined by the two assay methods at the conclusion of 1, 3, and 6 h and 1, 3, 5, and 7 days of storage. The percentage of tobramycin activity as measured by EMIT and bioassay differed throughout the study period. Statistical analysis revealed that the assay method was the only significant variable to contribute to the variability observed in the differences of tobramycin concentration. Our results suggest that the bioassay technique is more sensitive than the EMIT assay for detecting the degree of inactivation of tobramycin by piperacillin. The EMIT assay overestimates tobramycin concentrations, which may be due to measurement of active and inactive tobramycin.

Analysis of Variance↗