alpha-synuclein is phosphorylated by members of the Src family of protein-tyrosine kinases.

alpha-Synuclein (alpha-Syn) is implicated in the pathogenesis of Parkinson's Disease, genetically through missense mutations linked to early onset disease and pathologically through its presence in Lewy bodies. alpha-Syn is phosphorylated on serine residues; however, tyrosine phosphorylation of alpha-Syn has not been established (, ). A comparison of the protein sequence between Synuclein family members revealed that all four tyrosine residues of alpha-Syn are conserved in all orthologs and beta-Syn paralogs described to date, suggesting that these residues may be of functional importance (). For this reason, experiments were performed to determine whether alpha-Syn could be phosphorylated on tyrosine residue(s) in human cells. Indeed, alpha-Syn is phosphorylated within 2 min of pervanadate treatment in alpha-Syn-transfected cells. Tyrosine phosphorylation occurs primarily on tyrosine 125 and was inhibited by PP2, a selective inhibitor of Src protein-tyrosine kinase (PTK) family members at concentrations consistent with inhibition of Src function (). Finally, we demonstrate that alpha-Syn can be phosphorylated directly both in cotransfection experiments using c-Src and Fyn expression vectors and in in vitro kinase assays with purified kinases. These data suggest that alpha-Syn can be a target for phosphorylation by the Src family of PTKs.

Liquid chromatographic determination of ivermectin in feed.

An analytical method for determining ivermectin in feed at 0.50-3 ppm is presented. The method is based on liquid chromatographic measurement after sample preparation by adsorption chromatography on alumina and solid-phase extraction. Two complete, final, finished medicated feeds and the corresponding control feeds used in their preparation were analyzed. Recoveries from feeds fortified at 50-150% of the 2 ppm ivermectin use concentration also were determined. Mean recoveries from replicate analyses ranged from 90 to 100%, and coefficients of variation (CVs) were less than 4.5%. No significant interferences were found in control feeds. The pooled distribution of individual analytical results (n = 100) gave a mean recovery of 100%, a recovery range of 90-111%, and an overall CV of 5.5%. Resolution of the total variance into its 2 components gave a within-laboratory CV of 4.1% and a between-laboratory CV of 3.4%. There was no significant difference in recoveries among laboratories, days, concentrations, and feed base or between fortified and medicated feeds (P > 0.2).

Expression of human p140trk receptors in p140trk-deficient, PC12/endothelial cells results in nerve growth factor-induced signal transduction and DNA synthesis.

Nerve growth factor (NGF) regulates proliferation, differentiation, and survival of sympathetic and sensory neurons through the tyrosine kinase activity of its receptor, p140trk. These biological effects of NGF depend upon the signal-mediating function of p140trk substrates which are likely to differ from cell to cell. To define p140trk receptor substrates and the details of signalling by NGF in the hybrid cell PC12EN, we stably transfected cultures with a vector encoding a full-length human p140trk cDNA sequence. Two stably transfected clones, one expressing p140trk with higher affinity (PC12EN-trk3; Kd 57.4 pM, Bmax 9.7 pmole/mg) and one expressing p140trk with a lower affinity (PC12EN-trk1; Kd 392.4 pM, Bmax 5.7 pmole/mg) were generated. Radioreceptor assays indicate that transfected p140trk receptors show slow NGF-dissociation kinetics, are resistant to trypsin or Triton X-100 treatment, are specific for NGF compared to other neurotrophins, and are internalized or downregulated as are native PC12 p140trk receptors. NGF stimulates p140trk tyrosine phosphorylation in a dose- (0.01-10 ng/ml) and time- (5-120 min) dependent manner, and tyrosine phosphorylation was inhibited by 200-1,000 nM K-252a. NGF-induced Erk stimulation for 60 min was assessed using myelin basic protein as a substrate. NGF treatment also led to an increased phosphorylation of p70S6k, SNT, and phospholipase C gamma, demonstrating that the major NGF-stimulated signalling pathways found in other cells are activated in PC12EN-trk cells. Staurosporine (5-50 nM) rapidly and dBcAMP (1 mM) more slowly, but not NGF induced morphological differentiation in PC12EN-trk cells. Rather, NGF treatment in low-serum medium stimulated a 1.3- and 2.3-fold increase in DNA synthesis measured by [3H]thymidine incorporation in PC12EN-trk1 and PC12EN-trk3, respectively. These data highlight the functionality of the transfected p140trk receptors and indicate that these transfected cells may serve as a novel cellular model facilitating the study of the mitogenic properties of NGF signalling and the transducing role of the p140trk receptor substrates.

Efficacy in sheep and pharmacokinetics in cattle that led to the selection of eprinomectin as a topical endectocide for cattle.

Eprinomectin (MK-397 or 4"-epi-acetylamino-4"-deoxy-avermectin B1) is a novel avermectin selected for development as a topical endectocide for all cattle, including lactating cows. The initial efficacy assessments were made in sheep to identify subclasses of the avermectin/milbemycins that possessed inherent activity against a spectrum of nematode parasites. This included examination of several hundred analogs each given orally to a single sheep experimentally infected with a range of parasitic nematodes. Representatives of several subclasses, most notably the 4"-epi-amino avermectin B1 subclass, were identified as possessing potent, broad-spectrum activity against the endoparasites, whereas subclasses such as those with a variety of synthetic substitutions at C-4a or oximes at C-5 were among the least potent. Eprinomectin, a member of the 4"-epi-amino subclass, possessed potent activity against the range of nematodes when tested at 0.025 mg kg-1 per os. Milk and plasma concentration profiles were also made for these and other selected avermectin/milbemycins following topical administration to lactating dairy cattle. The molecular structure of each compound had a significant effect on the milk to plasma ratio, but the ratio of each was constant over time, implying an equilibrium between the 2 compartments. Compounds that were saturated at the C-22,23 bond had milk to plasma ratios > or = 1.0, whereas those unsaturated at this bond were generally < or = 1.0. The milk to plasma ratio of eprinomectin was < or = 0.2. Therefore, not only is eprinomectin the most potent broad-spectrum avermectin/milbemycin identified to date, but it also possesses one of the lowest milk partitioning coefficients in this class of antiparasitics.

Evolution of a specific fluorogenic derivatization of ivermectin for bioanalytical applications. A review.

The evolution of the fluorogenic derivatization of ivermectin is traced through a series of continual modifications that have resulted in improvements in speed and sensitivity. Since the original development of this selective analytical technique, the reaction time has been shortened from 24 h at 100 degrees C to < 30 s at room temperature and, through modifications of the derivatization reagent and catalyst, the sensitivity has also been increased 50-fold to 20 pg of analyte with no significant decrease in precision. A procedure is reported, based on the use of fluorescence derivatization, which eliminates the use of solid-phase columns for sample preparation and fluorophore isolation, and is faster and less cumbersome than previous methods. The method was evaluated with cattle and canine plasma samples over the concentration range 1.0-40 ng ml-1 of ivermectin. It has an accuracy of 1.9% (mean relative error) over this concentration range and a precision of 5.6% (RSD) at the 1 ng ml-1 ivermectin concentration level in a 1 ml plasma sample.

Differential utilization of Janus kinase-signal transducer activator of transcription signaling pathways in the stimulation of human natural killer cells by IL-2, IL-12, and IFN-alpha.

IL-2-, IL-12-, and IFN-alpha-mediated signaling pathways were analyzed in primary NK cells and in the NK3.3 cell line. Gel mobility shift and immunoprecipitation analyses revealed that in addition to activating STAT3 (signal transducer and activator of transcription-3) and STAT5, IL-2 induced tyrosine and serine phosphorylation of STAT1 alpha, which formed IFN-gamma-activated sequence-binding complexes by itself and with STAT3. Although IL-2 and IFN-alpha activated STAT1 alpha and STAT5, IL-2 predominantly activated STAT5, while IFN-alpha predominantly activated STAT1 alpha. IL-2 induced less STAT1 alpha activation and IFN-alpha induced greater STAT5 activation in NK3.3 cells compared with preactivated primary NK cells. In NK3.3 cells, IL-2 induced comparable formation of c-fos promoter sis-inducible element IFN-gamma-activated sequence-binding complexes containing STAT3 alone with complexes containing STAT3 and STAT1 alpha, while in preactivated primary NK cells, it preferentially induced complexes containing STAT3 and STAT1 alpha. Thus, signaling in NK3.3 cells is not always identical with that in primary NK cells. In contrast to IL-2 and IFN-alpha, IL-12 induced strong tyrosine phosphorylation of STAT4 and variable weak phosphorylation of STAT3. However, supershift analyses using the c-fos promoter sis-inducible element probe showed that IL-12 activated STAT4, STAT1 alpha, and STAT3, and induced complexes containing STAT4 only, STAT4 with STAT1 alpha, STAT3 with STAT1 alpha, or STAT1 alpha only in preactivated primary NK cells. STAT1 alpha activation by IL-12 correlated with increased phosphorylation of serine, but not tyrosine. Finally, IL-2 induced tyrosine phosphorylation of JAK1 and JAK3, while IL-12 induced phosphorylation of JAK2 and TYK2 in both preactivated primary NK and NK3.3 cells. Differential phosphorylation and consequent differential activation of both separate and overlapping STAT proteins by IL-2, IL-12, and IFN-alpha may provide a molecular basis for the similarities and differences in the actions of these cytokines on NK cells.

Role of protein kinase C alpha in nerve growth factor-induced arachidonic acid release from PC12 cells.

Nerve growth factor (NGF) increases arachidonic acid (AA) release by PC12 pheochromocytoma cells. To explore the role of protein kinase C (PKC) in this action of NGF, PKC was down-regulated by long-term treatment of the cells with phorbol 12-myristate 13-acetate (PMA). Such prolonged exposure to PMA (1 microM) resulted in the inhibition of NGF-induced AA release. Moreover, pretreatment of PC12 cells with the protein kinase inhibitor staurosporine or with calphostin C, a specific inhibitor of PKC, also blocks the increase of AA release induced by NGF. These data, as well as that PMA alone can induce AA release in PC12 cells, suggest that PKC is necessary for NGF-induced AA release. Immunoblot analysis of whole cell lysates by using antibodies against various PKC isoforms revealed that our PC12 cells contained PKCs alpha, delta, epsilon, and zeta. PMA down-regulation depleted PKCs alpha, delta, and epsilon, and partially depleted zeta. To see which isoform was involved in NGF-induced AA release, an isoform-specific PKC inhibitor was used. GO 6976, a compound that inhibits PKCs alpha and beta specifically, blocked NGF-induced AA release. In addition, thymeleatoxin, a specific activator of PKCs alpha, beta, and gamma, induced AA release from PC12 cells in amounts comparable with those seen with NGF. Taken together, these data suggest that PKC alpha plays a role in NGF-induced AA release.

Induction of nerve growth factor responsiveness in C6-2B glioma cells by expression of trkA proto-oncogene.

Cells that lack the high affinity receptor component (trkA) for nerve growth factor (NGF) are unresponsive to NGF. We investigated whether C6-2B cells, a rat glioma derived cell line, express trkA and, as a consequence, are responsive to NGF. In these cells, NGF (100 ng/ml) failed to induce the mRNA encoding for c-fos protooncogene and the low affinity NGF receptor p75NGFR, two NGF-responsive genes. In contrast, both mRNAs were induced in PC12 cells by NGF. Using a RNase protection assay with a cRNA probe for rat trkA, the expected trkA RNA protected fragment was detected in PC12 but not in C6-2B glioma cells, indicating that C6-2B cells either do not express the gene or express it only in low amounts. Cross-linking of 125I-labeled NGF to PC12 cells identified two major bands with an apparent molecular weight of 158 kDa and 100 kDa corresponding to trkA and p75NGFR, respectively. In contrast, only the 100 kDa band could be detected in C6-2B cells by cross-linking analysis. In C6-2B cells stably transfected with the rat trkA cDNA, NGF increased c-fos mRNA, induced tyrosine phosphorylation of gp140trk, and SNT (suc-associated neurotrophic factor-induced tyrosine-phosphorylated target), and caused morphological changes within 72 h. All of these effects of NGF were blocked by the protein kinase inhibitor K-252a suggesting that NGF signal transduction was restored by trkA expression. Most important, in C6trk+ cells, NGF was a weaker (2-fold) inducer of [3H]thymidine incorporation when compared to bFGF (5-fold), suggesting that expression of trkA fails to confer to NGF a strong mitogenic effect. Our findings indicate that C6-2B glioma cells do not possess high affinity NGF receptor and thus are unresponsive to NGF and that expression of trkA in neuroectoderm derived cells elicits some of the NGF responses characteristic of neuronal cells.

Renal artery stenosis after renal transplantation: the impact of the hypogastric artery anastomosis.

A review of 402 renal allotransplants performed during a 5-year period revealed 25 cases of transplant renal artery stenosis in 377 evaluable patients. To our knowledge this is the first large study of this transplant complication in which all patients received cyclosporine immunotherapy. The incidence of transplant renal artery stenosis was 6.6%. The mean internal from transplantation to onset of transplant renal artery stenosis was 11 months. No significant differences in atherosclerotic risk factors were detected between the groups with and without transplant renal artery stenosis. The incidence of acute allograft rejection was not increased in the stenosis group. There was no difference in the incidence of transplant renal artery stenosis following end-to-end (hypogastric artery) or end-to-side (common or external iliac artery) arterial anastomoses. Among patients having end-to-end hypogastric artery anastomoses the incidence of transplant renal artery stenosis was significantly greater (p < 0.01) when endarterectomy was required to render the hypogastric artery suitable for use. Percutaneous transluminal angioplasty was performed in 20 patients and open repair was performed in 18. After percutaneous transluminal angioplasty of hypogastric artery anastomoses, more additional procedures were required and there was a higher allograft loss rate when compared to percutaneous transluminal angioplasty of the external iliac artery. These data suggest that treatment of transplant renal artery stenosis in patients with end-to-end hypogastric artery anastomosis is more difficult and results in a higher morbidity rate than treatment in the external iliac artery group.

Differential effects of 6-hydroxydopamine-induced ablation of peripheral and central adrenergic axons on C-1300 murine neuroblastoma tumor growth and catecholamine concentration in the A/J mouse.

The relationship between 6-hydroxydopamine (6-OHDA)-induced ablation of central and peripheral adrenergic neurons and in situ C-1300 murine neuroblastoma (MNB) tumor growth and catecholamine concentration were investigated. Destruction of central and/or peripheral adrenergic neurons was produced by the intracerebral and/or s.c. administration of 6-OHDA to neonatal A/J mice. Disaggregated MNB cells (1 x 10(6)) were implanted s.c. into each mouse 3 weeks after treatment with 6-OHDA or diluent. Tumor onset time (the time interval between implantation of MNB cells and detection of palpable tumor), tumor weight, tumor weight to body weight ratio, tumor growth rate constant and tissue catecholamine concentrations were determined. Central axotomy caused a significant increase in tumor onset time and decrease in tumor weight when compared to controls. However, neither the tumor weight to body weight ratio or tumor growth rate constant were significantly lowered. In contrast, a reduction in all tumor growth parameters was produced by peripheral axotomy, which differed significantly from centrally axotomized and control animals. The catecholamine concentration of MNB tumors excised from control and 6-OHDA-treated mice 8 days after tumor onset were determined. Norepinephrine and dopamine levels were elevated above controls in MNB tumors obtained from mice that had been either peripherally or peripherally and centrally axotomized; whereas, no change in tumor catecholamine concentrations was noted in centrally axotomized mice. This investigation has demonstrated that ablation of central as well as peripheral adrenergic innervation exerts an inhibitory effect on MNB tumor growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of nerve growth factor on C-1300 murine neuroblastoma tumor growth and catecholamine content in neonatally sympathectomized mice.

The in situ C-1300 murine neuroblastoma (MNB) tumor model was used to investigate the influence of exogenously administered nerve growth factor (NGF) on tumor growth and tissue catecholamine concentration in mice sympathectomized with 6-hydroxy-dopamine (6-OHDA) on postnatal days 4-10. Mice were implanted with 1 x 10(6) disaggregated MNB cells 3 days after termination of 6-OHDA administration. NGF (12-15 micrograms/mouse/day) treatment was initiated at the time of MNB cell implantation and continued until sacrifice of the animal. The time interval between tumor cell implantation and detection of palpable tumor (tumor onset time), transverse tumor diameter, tumor weight, tumor weight to body weight ratio, and tumor catecholamine concentration were determined. Neonatal sympathectomy caused a decrease in myocardial norepinephrine concentration of 88% compared with vehicle-treated animals as well as a significant reduction in total body and organ weight. Average body, brain, heart, and spleen weights were decreased 31%, 16%, 25%, and 42%, respectively, below control values. The daily injection of NGF, from the time of MNB tumor implantation to sacrifice, did not prevent these effects of chemical sympathectomy from being expressed. Tumor onset time following implantation of MNB cells was significantly increased in neonatally sympathectomized mice and was not altered by treatment with NGF. In contrast, the decrease in MNB tumor growth rate observed in sympathectomized mice was reversed by administration of NGF. Mean tumor weight and mean tumor to body weight ratio were 89% and 115% of comparable control values, respectively, in sympathectomized mice receiving exogenous NGF.(ABSTRACT TRUNCATED AT 250 WORDS)

Nerve growth factor stimulation of arachidonic acid release from PC12 cells: independence from phosphoinositide turnover.

The effect of nerve growth factor on the metabolism of arachidonic acid and the hydrolysis of phosphatidylinositol in PC12 cells was examined. Addition of nerve growth factor to PC12 cells isotopically labeled with [3H]arachidonic acid caused an increased release of radioactivity. In a similar manner, treatment of PC12 cells prelabeled with [3H]inositol increased inositol monophosphate accumulation in the presence of LiCl. Stimulation of [3H]arachidonic acid release by nerve growth factor was concentration dependent, attaining a maximum at 0.5 nM. Concentrations of nerve growth factor above 0.5 nM caused less than maximal stimulation. In contrast, nerve growth factor-stimulated accumulation of [3H]inositol monophosphate exhibited a sigmoidal dose-response curve with an apparent maximum at 8 nM. Increased accumulation of [3H]inositol monophosphate could be detected as early as 60 s after nerve growth factor addition, whereas nerve growth factor-stimulated release of [3H]arachidonic acid was not observed until 5 min after nerve growth factor treatment. The nerve growth factor-stimulated release of [3H]arachidonic acid was independent of extracellular calcium concentration. Increased [3H]inositol monophosphate accumulation elicited by nerve growth factor was dependent on the presence of extracellular calcium. These results suggest that the increased metabolism of arachidonic acid and the enhanced hydrolysis of phosphatidylinositol are separately regulated by nerve growth factor.

Determination of ivermectin in medicated swine feeds at the 2 ppm concentration level.

An analytical method has been developed that is applicable to the determination of Ivermectin in medicated feeds at the 2 ppm concentration level. It is based upon liquid chromatographic analysis with a reverse-phase column and ultraviolet detection. After the drug is extracted from the feed into methanol, an analytical sample is prepared by the consecutive use of column chromatography on alumina and solid-phase extraction on Sep-Pak C18 and silica cartridges. This procedure has been applied to the concentration range 0.50-3.0 ppm of Ivermectin in feed with an accuracy of +/- 2% mean relative error and a precision of +/- 2% relative standard deviation at the 2 ppm concentration level.

Influence of host age and tumor load on the growth and catecholamine content of C-1300 murine neuroblastoma in situ.

The influence of host age and tumor load on survival time, tumor growth parameters and biochemical differentiation, as characterized by tumor catecholamine content, were investigated. A/J mice were implanted with tumor loads of 10(4), 10(5) and 10(6) disaggregated C-1300 murine neuroblastoma (MNB) cells at 1, 7, 14, 21 and 56 days of age. Studies performed in mice between 7 and 56 days of age demonstrated that MNB tumorigenicity, tumor growth rate, host survival and catecholamine content were independent of host age and tumor load whereas, tumor onset time was influenced by both factors. In contrast to older animals, tumor onset time and catecholamine content were decreased and tumor growth rate increased in 1-day-old mice. This difference may be due to the presence of endogenous growth factor(s) that modulate cell proliferation in the immediate post-natal period.

Effects of chemical sympathectomy in neonatal and adult mice on C-1300 neuroblastoma tumor growth and catecholamine content.

The in situ C-1300 murine neuroblastoma (MNB) tumor model was used to investigate the influence of 6-hydroxydopamine (6HD)-induced sympathectomy on tumor growth and catecholamine concentration. One week (adult) and 3 weeks (neonatal) after sympathectomy, mice were implanted with 10(6) disaggregated MNB cells. The time interval between implantation of MNB cells and detection of palpable tumor (tumor onset time), transverse tumor diameter, tumor weight, tumor weight to body weight ratio, and tumor catecholamine concentration were determined. Sympathectomy following 6HD administration was confirmed by analysis of catecholamine concentrations in the heart and spleen by high-pressure liquid chromatography. Treatment of adult animals with 6HD reduced the mean heart and spleen norepinephrine (NE) concentrations to less than 20% of controls (vehicle treated). Neonatal sympathectomy decreased the average heart and spleen NE concentrations to less than 10% of comparable control mice. Whole brain NE and dopamine concentrations were not altered by treatment with 6HD in either age group. Tumor onset time following implantation of MNB cells was significantly increased in animals sympathectomized as either neonates or as adults. In contrast, MNB tumor growth rate following tumor onset was significantly inhibited in animals sympathectomized as neonates but not as adults. The catecholamine concentrations of tumors removed from control and sympathectomized mice 8 days after tumor onset were determined. Tumor NE and dopamine concentrations were increased 9.09 +/- 2.8- (SE) and 7.03 +/- 1.8-fold, respectively, in mice sympathectomized as neonates. There were no significant differences in the NE and dopamine concentrations of tumors obtained from sympathectomized and control adult mice. Pretreatment with desmethylimipramine prior to 6HD administration prevented destruction of sympathetic neurons, inhibition of tumor growth rate, and the increase in tumor catecholamine concentration observed in neonatally sympathectomized mice. These data suggest that the influence of chemical sympathectomy on MNB tumor growth and biochemical differentiation, as defined by catecholamine content, are age dependent.

Pharmacokinetic studies of ivermectin: effects of formulation.

Studies are reported which describe the effects of formulation, animal species, and route of administration on the pharmacokinetics of ivermectin. Biological half-life t1/2 increases in the order: swine (0.5 day) less than dogs (1.8 day) less than cattle approximately equal to sheep (2.8 day). Formulation modifications, based upon the solubility properties of the drug, have been directed towards the development of a nonaqueous injectable formulation for cattle and an aqueous vehicle for horses. Bioavailability following subcutaneous injection in cattle can be regulated by control of injection solvent composition: a vehicle composed of a mixed aqueous-organic solvent exhibits pharmacokinetic properties (i.e., Cp, t1/2, AUC, and F) intermediate between those furnished by an aqueous formulation and via a purely nonaqueous solvent. The longer apparent biological half-life from this latter vehicle (t1/2 = 8.3 days) confirms that a slow absorption process dominates the pharmacokinetics in the nonaqueous injectable product to produce an effective controlled-release formulation. These bioavailability results illustrate the increase in the concentration of an organic solvent and a concomitant decrease in surfactant concentration in a micellar aqueous system for prolonged drug delivery via injection.