Glycosphingolipid fatty acid arrangement in phospholipid bilayers: cholesterol effects

Deuterium wide line NMR spectroscopy was used to study cholesterol effects on the ceramide portions of two glycosphingolipids (GSLs) distributed as minor components in fluid membranes. The common existence of very long fatty acids on GSLs was taken into account by including one glycolipid species with fatty acid chain length matching that of the host matrix, and one longer by 6 carbons. N-stearoyl and N-lignoceroyl galactosyl ceramide with perdeuterated fatty acid (18:0[d35] GalCer and 24:0[d47] GalCer) were prepared by partial synthesis. They were dispersed in bilayer membranes having the 18-carbon-fatty-acid phospholipid, 1-stearoyl-2-oleoyl-phosphatidylcholine (SOPC), as major component. Glycolipid fatty acid chain behavior and arrangement were analyzed using order profiles derived from their 2H-NMR spectra. Cholesterol effects on order parameter profiles for 18:0[d35] GalCer, with chain length equal to that of the host matrix, followed the pattern known for acyl chains of phospholipids. The presence of sterol led to restriction of trans/gauche isomerization along the length of the chain, with the largest absolute increase in order parameters being toward the surface, but somewhat greater relative effect just below the "plateau" region. In cholesterol-containing membranes, order parameter profiles for the long chain species, 24:0[d47] GalCer, showed a characteristic secondary "plateau" associated with carbon atoms C14 to C23, a feature also present in SOPC bilayers without cholesterol and in pure hydrated 24:0[d47] GalCer. Cholesterol-induced ordering effects on the long chain glycolipid were similar to those described for the shorter chain species, but were minimal at the methyl terminus. Within a given membrane,SCD profiles for 1 8:O[d3] GalCer and 24:0[d47] GalCer were quantitatively similar to a membrane depth of C13 to C14. SCD values at C16 and C17 were about 15% and 28% higher, respectively, for the long chain GSL than for its short chain analogue inSOPC/cholesterol (compared to 21 and 31%, respectively, in membranes without cholesterol). Nitroxide spin labels attached rigidly to C16 of the long chain glycolipid gave EPR order parameters that were twice as high as for the same spin label at C16 on the shorter chain glycolipid in both matrices. It would appear that the above factors impose a tendency for the "extra" portion of the 24-carbon chain to cross the bilayer midplane where it may interact with terminal portions of acyl chains in the opposing monolayer; however, steric constraints, and probably collision events associated with lateral diffusion, induce wide orientation fluctuations in the segment involved.

[Effects of pregnant exposure to electromagnetic field emitted by electric blankets on brain catecholamine and behavior in offspring mice]

NIH pregnant mice were exposed to electromagnetic field emitted by electric blankets with 1-1.2kV/m and 0.2-0.4microT for five hours daily during their whole gestational period. Catecholamine (CA) content in the hypothalamus of their newborn offsprings was quantitatively measured with histochemical methods, and their varied behavioral activities were determined with behavioral toxicological methods. Results showed catecholamine content in exposed offsprings decreased significantly not only seven days but also 40 days after delivery as compared with the controls (P < 0.01 and P < 0.05, respectively).

Ribozyme-mediated in vitro cleavage of transcripts arising from the major transforming genes of human papillomavirus type 16

Human papillomaviruses (HPV) have been strongly implicated as important cofactors in the development of several human malignancies, particularly anogenital carcinomas. Products arising from the E6 and E7 open reading frames (ORFs) from HPV-16, a type commonly associated with human cervical carcinoma, are essential for viral transformation. Unfortunately, a highly effective treatment for this infection is not available. To develop a novel treatment for this disease, ribozymes were designed to cleave all transcripts encoding HPV-16 E6 and E7 ORFs in proximity to their translational start sites ("AUG"). Cleavage sites for Rz110 and Rz558 occur immediately 3' to nucleotides 110 and 558 of the viral genomic DNA, respectively. Oligonucleotides corresponding to these ribozymes were synthesized and inserted into a eucaryotic viral vector derived from the nonpathogenic parvovirus, adeno-associated virus. Ribozyme transcription from this vector, termed CWRT7:SVN, is under control of both the highly active Rous sarcoma virus long terminal repeat and bacteriophage T7 promoters. T7 transcripts of the E6 and E7 ribozymes efficiently cleaved their cognate targets in vitro under a variety of conditions, including physiological temperature. These results may provide the basis for the development of a ribozyme-based, gene therapeutic treatment for HPV-associated diseases.

Airway provocation test with ragweed pollen extract in Chinese asthmatics

As ragweed becomes widespread over China, ragweed pollenosis tends to be more frequent. Incidence of ragweed pollenosis is about 1.04% in Qingdao district. To elucidate ragweed as an allergen in the development of bronchial asthma, ragweed pollen extract inhalation airway provocation tests (APT) were studied in 55 patients with ragweed pollenosis. A single dosage of 9,000 PNU ragweed pollen extract was applied and positive response was defined as more than 35% fall in SGrs at the dose of PT35-Grs. Among 55 patients, positive APTs were found in 27 cases (49%), dual late-phase responses in 11 patients, single late-phase responses in 2 patients in the complicated asthma group. Late-phase responses were related to the increased specific IgE and strong positive skin test response (wheal > 11 mm). The results suggested ragweed pollen was one of the important allergens causing bronchial asthma. There was airway hyperresponsiveness to ragweed pollen in some patients (20%) with ragweed pollenosis without asthmatic symptoms.

Optimization of methods to achieve mRNA-mediated transfection of tumor cells in vitro and in vivo employing cationic liposome vectors

Direct in vivo transfection of tumor nodules in situ via liposome-DNA complexes has been employed as a strategy to accomplish antitumor immunization. To circumvent the potential safety hazards associated with systemic localization of delivered DNA, the utility of mRNA transcript-mediated gene delivery was explored. Capped, polyadenylated mRNA transcripts encoding the firefly luciferase and Escherichia coli lacZ reporter genes were derived by in vitro transcription. Transfection of the human breast cancer cell line MDA-MB-435 in vitro was accomplished employing cationic liposome-mRNA complexes. Evaluation of a panel of cationic liposome preparations demonstrated significant differences in the capacity of the various preparations to accomplish mRNA-mediated transfection. Quantitative evaluation of in vitro transfection demonstrated that target cells could be transfected at a high level of efficiency. The mRNA liposome-complexes were evaluated for in vivo transfection of tumor nodules in human xenografts in athymic nude mice. It could be demonstrated the liposome-mRNA complexes were comparable in efficacy to liposome-DNA complexes in accomplishing in situ tumor transfection. Thus, mRNA may be considered as an alternative to plasmid DNA as a gene transfer vector for genetic immunopotentiation applications.

Molecular mechanism for familial protein C deficiency and thrombosis in protein CVermont (Glu20-->Ala and Val34-->Met)

The role of two protein C gamma-carboxyglutamic acid domain mutations in familial thrombosis, protein CVermont (Bovill, E. G., Tomczak, J. A., Grant, B., Bhushan, F., Pillemer, E., Rainville, I.R., and Long, G. L. (1992) Blood 79, 1456-1465), was investigated. Two single mutations (Glu20-->Ala and Val34-->Met) and the naturally occurring double mutation were created by site-directed mutagenesis and were expressed in human kidney 293 cells. Purified recombinant protein C with the mutation glutamate to alanine at position 20 is defective in the assays of activated partial thromboplastin time, factor Va inactivation, and fibrinolysis. Mutation from valine to methionine at position 34 has only a minor effect. Activation of Glu20 mutants by thrombin-thrombomodulin was not enhanced by phospholipid vesicles and showed a different calcium dependence compared with the wild type, suggesting that Gla20 is important in the interaction of the protein C Gla domain with a phospholipid-mediated site on the thrombomodulin molecule. Glu20-substituted protein C is not inhibited by calcium ion in its interaction with the calcium-dependent monoclonal antibody H-11, suggesting that this mutation has lost the calcium-induced, lipid-independent conformational transition of the protein C Gla domain. These data indicate that the loss of Gla20 causes the major familial dysfunction of protein C to associate with phospholipid as well as to undergo Ca(2+)-dependent, lipid-independent conformational changes and are consistent with the importance of Gla20 in both external and internal Ca2+ binding based upon the x-ray-derived structure of the homologous Gla domain in bovine prothrombin.

Alphamethrin-impregnated bed nets for malaria and mosquito control in China

A community-based intervention trial was carried out to evaluate the effectiveness of alphamethrin-impregnated bed nets for control of Plasmodium vivax malaria and its vector in an area of moderate endemicity in southern Henan province, central China in 1990. Malaria incidence was significantly lower in the intervention group than in the comparison group (2.03 vs. 3.57 per 100 person-years at risk). The protective efficacy for malaria incidence was 43%. The prevalence of malaria parasitaemia among children under 10 years old in the intervention group was about one-quarter of that in the comparison group (0.93% vs. 3.25% and 0.71% vs. 1.96% after one and 4 months use of impregnated nets, respectively). Alphamethrin-impregnated bed nets had a mass killing effect on vector mosquitoes. The outdoor person-biting density of Anopheles anthropophagus and A. sinensis decreased by 70.3% and 29.3% respectively. The density of these 2 mosquito species found resting inside treated nets was close to zero. No side effect was found among users of impregnated bed nets. Impregnation with alphamethrin was more effective on polyester than on cotton netting and residual effects lasted at least one year. Use of alphamethrin is less expensive than permethrin and deltamethrin.

Agouti protein is an antagonist of the melanocyte-stimulating-hormone receptor

The genetic loci agouti and extension control the relative amounts of eumelanin (brown-black) and phaeomelanin (yellow-red) pigments in mammals: extension encodes the receptor for melanocyte-stimulating hormone (MSH) and agouti encodes a novel 131-amino-acid protein containing a signal sequence. Agouti, which is produced in the hair follicle, acts on follicular melanocytes to inhibit alpha-MSH-induced eumelanin production, resulting in the subterminal band of phaeomelanin often visible in mammalian fur. Here we use partially purified agouti protein to demonstrate that agouti is a high-affinity antagonist of the MSH receptor and blocks alpha-MSH stimulation of adenylyl cyclase, the effector through which alpha-MSH induces eumelanin synthesis. Agouti was also found to be an antagonist of the melanocortin-4 receptor, a related MSH-binding receptor. Consequently, the obesity caused by ectopic expression of agouti in the lethal yellow (Ay) mouse may be due to the inhibition of melanocortin receptor(s) outside the hair follicle.

Receptor-mediated effects of angiotensin II on neurons

Aside from its well-known and numerous actions at peripheral tissues, the octapeptide angiotensin II (ANG II) elicits specific receptor-mediated effects within the central nervous system. In this review we focus on the receptor-mediated actions of ANG II on neurons. The distribution of ANG II receptors in the brain and physiological, electrophysiological, and cellular effects mediated by these receptors are discussed. This is extended to a review of the characteristics of ANG II receptor subtypes on cultured neurons and the cellular and genomic actions mediated by these receptors. Finally, we develop this information into speculative models for the cellular effects mediated by each ANG II receptor subtype in neurons.

Loss of membrane-dependent factor Va cleavage: a mechanistic interpretation of the pathology of protein CVermont

Clinical manifestations of arterial and venous thrombosis in a family with protein C deficiency was associated with two mutations in the light chain of protein C: Glu20-->Ala and Val34-->Met. Further studies showed that the mutation Glu20-->Ala which eliminated a gamma-carboxylation site was exclusively responsible for the anticoagulant defect of activated protein C (APC). Membrane-bound human factor Va is inactivated by APC after two sequential cleavages of the heavy chain at Arg506 and Arg306. Human factor Va inactivation by human recombinant APC (rAPC) and a mutant molecule with an alanine instead of a glutamic acid at position 20 (rAPC(gamma 20A)) was investigated in the presence and absence of phospholipid vesicles. During a 2-hour incubation period of the cofactor with either rAPC or rAPC(gamma 20A). In the absence of a membrane surface, factor Va is cleaved quantitatively at Arg506 and retains approximately 60% of its initial cofactor activity. After a 2-hour incubation period with rAPC membrane-bound factor Va has no cofactor activity, whereas in the presence of a membrane surface and rAPC(gamma 20A) factor Va retains 60% of its initial cofactor activity. The completed loss in factor Va cofactor activity upon incubation of the membrane-bound cofactor with phospholipid vesicles and rAPC is associated with cleavages at Arg506 and Arg306, whereas membrane-bound factor Va cleavage at Arg306 by rAPC(gamma 20A) is impaired, resulting in a cofactor that is cleaved at Arg506. Slow cleavage at Arg306 occurs when membrane-bound factor Va is incubated with rAPC(gamma 20A) and only small amounts of fragments of M(r) = 45,000 and 30,000 are noticed. Our data show that the genetic defect which leads to the absence of a gamma-carboxylation site at Glu20 impairs membrane binding of human APC, which in turn is required for cleavage of factor Va at Arg306 and inactivation of the cofactor. The consequence of impaired membrane-dependent cleavage at Arg306 is manifested in vivo by venous and arterial thrombosis.

Regulation of angiotensin II type 1 receptor mRNA in neuronal cultures of normotensive and spontaneously hypertensive rat brains by phorbol esters and forskolin

Neuronal cells in primary culture from the brains of normotensive, Wistar-Kyoto (WKY) rats and spontaneously hypertensive (SH) rats express angiotensin II type 1 (AT1) receptors. Treatment of WKY rat brain cultures with a phorbol ester, phorbol 12-myristate 13-acetate (PMA), causes a time- and dose-dependent increase in the levels of an approximately 2.3-kb AT1 receptor mRNA transcript. A maximal stimulation of 4.5-fold in the AT1 receptor mRNA transcript level is observed with 200 nM PMA in 4 h and is blocked by 1 microM staurosporine. Forskolin also increases the AT1 receptor mRNA levels in WKY rat brain neurons in a time- and dose-dependent manner, and a 4.5-fold stimulation is achieved with 50 microM forskolin in 4 h. The stimulatory effects of both PMA and forskolin are completely abolished by coincubation of neuronal cultures with 1 microM actinomycin D. In addition, nuclear run-on assay indicated an increase in the transcription of AT1 receptor mRNA in WKY rat brain neurons treated with either PMA or forskolin. Both PMA and forskolin also stimulate levels of AT1 receptor mRNA in neuronal cultures from brain of the SH rat. The degree of stimulation in these cultures is comparable to that in WKY rat brain neurons. These observations show that although the basal AT1 receptor gene expression is significantly higher in SH rat brain neurons compared with WKY rat brain neurons, the protein kinase C- and protein kinase A-responsive stimulation is not altered. These data suggest a possible involvement of protein kinase C and protein kinase A response elements in AT1 receptor gene expression.

Structure of mouse protein S as determined by PCR amplification and DNA sequencing of cDNA

The cDNA sequence of mouse protein S was derived by conventional PCR amplification from liver mRNA, initially using primers derived from the human cDNA sequence, followed by direct DNA sequencing. Seven overlapping PCR fragments covering all of the mature protein, part of the propeptide, and the 3' noncoding region were generated and sequenced. In some cases primers based upon the human cDNA sequence were ineffective. Subsequent successful amplification with mouse-derived primers to the same regions and comparison of the mouse and human sequences in these regions suggest that the failure of the human primers was due to insufficient degree of heterospecies identity. The mouse protein S cDNA sequence of the coding region shares 82% identity to human. The 3' noncoding region of mouse protein S cDNA has several small deletions and insertions compared to human protein S cDNA. Mature mouse protein S consists of 634 amino acids in a single polypeptide chain and displays domain organization similar to that for other species. The amino acid sequence of mouse protein S is about 80% identical to that of other species. Eleven glutamic acid residues were found in the amino terminal region and are predicted to be sites of gamma-carboxylation. Amino acid residues #80-244 are defined as four cysteine-rich repeat sequences homologous to epidermal growth factor. The remainder of the molecule is homologous to plasma sex steroid binding protein. The mouse protein S contains two potential N-glycosylation sites at positions #458 and 468 and is lacking the putative glycosylation site at #490 found in human protein S.

Fabrication and characterization of glucose sensors based on a microarray H2O2 electrode

A glucose sensor was recently developed by modifying an immobilized GOD (glucose oxidase) membrane and coating Nafion diffusion limiting membrane over an amperometric H2O2 MAE (microarray electrode), which was fabricated by using standard planar processing. The chip of the sensor is 2.5 mm by 15. The MAE is composed of an Ag/AgCl RE (reference electrode), a Pt CE (counter electrode) and two sets of Pt WE (working electrode), each set consists of five bands. Silicon nitride was chosen as the top insulator. Six MAEs different in both width and length of the band were examined and the MAE with the narrowest width (10 microns) of bands exhibits the best electrochemical performances. The glucose sensor based on the MAE B1-2 presents a linear range of 0.5-40 mM glucose at 37 degrees C with a 1/15 M phosphate buffer solution (pH = 7.0) as supporting electrolyte. The sensitivity, background current, response time, CV (coefficient of variation) and long-term stability of the sensor are 7.1 +/- 0.5 nA/mM, 2 +/- 0.5 nA, 30 s, 3.4% and 6 days respectively.

Palladium-103 versus iodine-125 for ophthalmic plaque radiotherapy

PURPOSE

A dosimetry study comparing the use of I-125 vs. Pd-103 radioactive seeds for ophthalmic plaque brachytherapy.

METHODS AND MATERIALS

Palladium-103 (Pd-103) seeds in ophthalmic plaques were used to treat 15 patients with intraocular malignant melanoma. Computer-aided simulations were performed to evaluate the intraocular dose distribution of I-125 versus Pd-103 ophthalmic plaques (delivering equivalent apex doses). Seven target points were selected. Starting at the outer scleral surface, four were located along the central axis of the plaque: the 1 mm point (the inner sclera), the 6 mm point, the tumors apex, and the opposite eye wall. We also evaluated the fovea, optic nerve, and the lens because they were considered to be critical structures.

RESULTS

These studies demonstrated that the lower energy photons generated by Pd-103 seeds (average 21 KeV) in ophthalmic plaques were more rapidly absorbed in tissue than photons generated by I-125 (average 28 KeV). Therefore, during ophthalmic plaque radiotherapy, Pd-103 photons were found to be more rapidly absorbed within the tumor and less likely to reach most normal ocular structures. On average, the use of Pd-103 decreased the dose to the fovea by 5.7%, to the optic nerve by 8.4%, to the lens by 26%, and to the opposite eye wall by 38.4%.

CONCLUSION

Palladium-103 ophthalmic plaque brachytherapy resulted in slightly more irradiation of the tumor and less radiation to most normal ocular structures.

Interleukin-1 alpha preconditioning reduces myocardial ischemia reperfusion injury

BACKGROUND

Interleukin-1 (IL-1) has been shown to induce superoxide dismutase (SOD) activity and to express heat shock protein (HSP). Since the reperfusion of ischemic heart is associated with the reduction of antioxidative enzymes including SOD and expression of HSP, it was hypothesized that IL-1 could be beneficial against ischemic reperfusion injury.

METHODS AND RESULTS

Rats were injected with recombinant IL-1 alpha (30 micrograms/kg IP); after 48 hours, they were anesthetized and hearts were removed, isolated, and perfused by the Langendorff technique. Myocardial functions were studied by measuring left ventricular developed pressure (LVDP) and its maximum first derivative (LV dP/dt), and cellular injury was studied by estimating creatine kinase (CK) release. Induction of the expression of HSP27 mRNA and HSP27 protein was examined by Western blot analysis and Northern blot analysis, respectively. Antioxidant enzymes were assayed by enzymatic analysis. Our results indicated reduction of ischemic reperfusion injury by IL-1 alpha, as evidenced by better recovery in postischemic ventricular functions (LVDP [mm Hg]: control, 63 +/- 14; IL-1, 102 +/- 11; P < .05), increased coronary flow (mL/min) (control, 2.93 +/- 0.58; IL-1, 5.17 +/- 0.43; P < .03), and reduced creatine kinase release (IU/L) (control, 110 +/- 5.78; IL-1, 81.76 +/- 7.71; P < .01). IL-1 alpha induced the expression of HSP27 mRNA within 2 hours as examined by Northern blot analysis and the expression of HSP27 after 48 hours. In addition, hearts pretreated with IL-1 alpha for 48 hours and then subjected to 30-minute ischemia and 60-minute reperfusion enhanced the activities (nmol/min/mg protein) of Cu/Zn SOD (control, 1.55 +/- 0.22; IL-1 alpha, 2.92 +/- 0.04; P < .004), Mn-SOD (control, 4.54 +/- 0.19; IL-1 alpha, 6.33 +/- 0.09, P < .001), catalase (control, 15.53 +/- 0.37; IL-1 alpha, 21.67 +/- 0.72; P < .002), glutathione peroxidase (control, 17.49 +/- 0.35; IL-1 alpha, 25.87 +/- 0.58; P < .001), and glucose-6-phosphate dehydrogenase (control, 22.71 +/- 0.44; IL-1 alpha, 29.53 +/- 0.48; P < .001).

CONCLUSIONS

The results of this study indicate that low doses of IL-1 alpha can be used as a therapeutic agent to precondition a heart from ischemia reperfusion injury.

Angiotensin II type 1 receptor-mediated stimulation of c-fos gene expression in astroglial cultures

Angiotensin II (ANG II) stimulates plasminogen activator inhibitor 1 (PAI-1) gene expression in astroglial cells prepared from rat brains. In this study, we investigated whether c-fos gene expression may be involved in this cellular action of ANG II. Incubation of astroglial cultures with ANG II caused a time- and dose-dependent transient stimulation of the steady-state levels of c-fos mRNA, with a maximal stimulation of 50-fold observed with 100 nM ANG II within 30-45 min. This stimulation was completely abolished by the presence of the type 1 ANG II (AT1) receptor antagonist losartan but not by the type 2 ANG II receptor blocker PD-123177. Depolarization of brain cell cultures with 50 mM K+ also caused a 100-fold increase in c-fos mRNA levels, an effect partially blocked by losartan. These observations show that AT1 receptor activation stimulates expression of the c-fos gene, which may act as a third messenger in the regulation of cellular actions of ANG II, including PAI-1 gene expression in astroglial cells.

Cell lines from grc congenic strains of rats having different susceptibilities to chemical carcinogens

The growth and reproduction complex (grc-) strains of rats have a 70-kilobase deletion in the major histocompatibility complex (MHC)-linked grc-G/C region that is associated with embryonic death, developmental defects, and an increased susceptibility to chemical carcinogens. To study further the effects associated with the deletion, fibroblastic cell lines from grc-, grc+, and grc+/- rat embryos were developed: BIL-derived cell lines are congenic for the MHC and grc, whereas R16-derived cell lines are congenic for the grc alone. In early passages, all cell lines expressed the MHC class I antigen RT1.A, had a diploid chromosome number, and did not display anchorage-independent growth or in vivo tumorigenicity. The grc- cells [median population doubling time (PDT), 47 h] grew more slowly than the grc+ (PDT, 30.5 h) and grc+/- (PDT, 33 h) cells. All cells underwent crisis, but the crisis stage began earlier and lasted longer in the grc- cells. The established grc- cell lines (PDT, 32.5 h) grew faster than the grc+ (PDT, 48.5 h) and grc+/- (PDT, 54 h) cell lines. Two of the three BIL-derived grc- lines that survived crisis became anchorage independent in tissue culture and tumorigenic in histocompatible F1 rats (highly malignant fibrosarcomas) at passages 33 and 48, respectively; by contrast, none of the R16-derived grc- cell lines transformed. None of 8 grc+ or 8 grc+/- cell lines that survived crisis displayed anchorage-independent growth or tumorigenicity under the same conditions up to passage 50. All of the established cell lines, including the two tumorigenic ones, expressed MHC class I antigens. Southern and Northern blot analyses of BIL-derived cell lines before and after crisis showed that they all constitutively expressed H-ras and Rb and that no cell line showed rearrangement, amplification, or overexpression of c-myc, H-ras, Rb, and p53 either before or after crisis. These observations indicate that: (a) the homozygous grc- deletion is necessary but not sufficient for in vitro transformation; (b) another genetic factor(s) required for transformation is linked to, or possibly in, the MHC; and (c) passage through crisis, spontaneous transformation, or carcinogen treatment does not alter the cellular expression of MHC class I antigens or of several oncogenes and tumor suppressor genes.

Tyrosine phosphorylation of P160 BCR by P210 BCR-ABL

It is well established that the chimeric BCR-ABL gene formed by joining parts of the BCR and ABL genes plays a key role in the pathogenesis of Philadelphia (Ph) chromosome-positive leukemias. We report that simultaneous expression of P210 BCR-ABL and P160 BCR in simian COS-1 cells yielded stable complexes of these two proteins, and induced phosphorylation of P160 BCR on tyrosine residues in vivo. Tyrosine phosphorylation of a deletion mutant encoding 553 amino acids of BCR N-terminal sequences was also detected when it was coexpressed with P210 BCR-ABL. We propose that tyrosine phosphorylation of P160 BCR by P210 BCR-ABL and their stable physical interaction may perturb normal BCR functions and that these alterations are directly involved in the pathologic processes found in Ph chromosome-associated leukemias.

Effect of sample numbers on the kinetic data analysis of MR contrast agents

The Monte Carlo simulation method is used to determine the uncertainties of the estimated are and mean transit time (MTT) of a regional cerebral concentration-time curve of a bolus injected paramagnetic contrast agent. Many factors contribute to these uncertainties. This study concentrates on the error propagation from the sample noise at different sample time points along the concentration-time curve. The uncertainties of area and MTT were determined as a function of the sample noise and the number of sample time points. For example, the percentage standard deviations (uncertainties) of both area and MTT are less than 12% with five samples whose signal-to-noise ratios are greater than 50.

Inhibition of phosphorylation of p160 BCR within p210 BCR-ABL complexes during early stages of phorbol ester-induced differentiation of K562 cells

The kinase activity of the BCR-ABL gene product is known to be down-regulated in K562 cells treated with low concentrations of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). The reduction of BCR-ABL kinase activity is followed by the loss of cell proliferation and progression to a more differentiated state. We have previously demonstrated that K562 cells possess protein complexes that contain p210 BCR-ABL and p160 BCR (M. L. Campbell, W. J. Li, and R. B. Arlinghaus, Oncogene, 5: 773-776, 1990). We performed experiments to determine whether BCR-ABL/BCR complexes were disrupted prior to alterations in cell growth and differentiation effects in TPA-treated K562 cells. Our results indicate that BCR-ABL/BCR complexes disappeared at precisely the same time after TPA treatment as the loss of autophosphorylation activity exhibited by total p210 BCR-ABL, which occurred 16-19 h after TPA treatment. The loss of kinase activity preceded the loss of p210 BCR by more than 24 h. A degraded form of p210 BCR-ABL (about 175 kilodaltons) accounted for the residual autophosphorylation activity seen during the later phases of kinase inactivation following TPA treatment, and this form was preferentially sequestered within BCR-ABL/BCR complexes. This altered BCR-ABL protein, although able to autophosphorylate, had reduced ability to phosphorylate p160 BCR. We conclude that 15 nM TPA treatment of K562 cells initiates effects that simultaneously interfere with the phosphorylation of p160 BCR in BCR-ABL complexes and inactivates the autophosphorylation activity of the full length BCR-ABL protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of central angiotensin responses by angiotensin type-1 receptor antibody

Angiotensin type-1 receptor subtypes (AT1) are implicated in the physiological actions of angiotensin II in the brain. In the present study we used an AT1 receptor antibody and a polymerase chain reaction--synthesized AT1 receptor complementary DNA to show that the hypothalamus expresses significantly higher levels of AT1 receptor messenger RNA and protein compared with the brain stem. Intracerebroventricular injections of AT1-specific antibody blocks the dipsogenic and blood pressure responses induced by centrally injected angiotensin II. These results demonstrate the expression of AT1 receptor gene in the brain and that the AT1 receptor antibody is able to inhibit the physiological responses of angiotensin II mediated by the brain.

Angiotensin II type 1 receptor mRNA levels in the brains of normotensive and spontaneously hypertensive rats

The type 1 angiotensin II (AII) receptor (AT1-R) has been implicated in the physiological actions mediated by AII in the brain. In view of the reported hyperactivity of the brain AII system in the spontaneously hypertensive rat (SHR), we compared the expression of AT1-R mRNAs in the brains of normotensive [Wistar Kyoto (WKY)] and SHR animals. Northern blot analysis showed about three- and approximately 20-fold increases in the levels of AT1-R mRNAs from the hypothalamus and brainstem areas, respectively, of the SHR compared with the WKY rat brain. This was attributable to greater levels of both AT1A- and AT1B-R mRNA subtypes in these areas from the SHR. These observations suggest that increased AII receptor levels in SHR brain may, in part, be a result of increased expression of the AT1-R gene.

Induction of differential heat shock gene expression in heart, lung, liver, brain and kidney by a sympathomimetic drug, amphetamine

Amphetamine, a sympathomimetic drug, can elevate the body temperature by causing enhancement of endogenous lipolysis. This study was designed to examine whether this drug could induce the expression of the genes of heat shock proteins (HSP) in different tissues. Subcutaneous administration of amphetamine (10 mg/kg wt) to the rats increased the rectal temperature of the rats to 42 degrees C within 60 min. After 3 hr rats were sacrificed; and heart, lung, liver, kidney and brain tissue were removed to examine the induction of mRNAs for HSPs by Northern blot analysis using cDNA probes of 27 kDa, 70 kDa and 89 kDa HSPs. The results of this study indicate striking regional and cell type differences in the pattern of induction of the HSP mRNAs by amphetamine suggesting that different organs and cell types respond differently to amphetamine.