A sensitive and inexpensive high-performance liquid chromatographic assay for tyrosine hydroxylase

We describe a highly sensitive assay method for tyrosine hydroxylase (TH) using high-performance liquid chromatography with amperometric determination. This assay method could be applicable to any tissues with low enzyme activity, such as rat cerebellum. We also describe the kinetic properties of TH in rat cerebral cortex.     

Fluorescence assay of tyrosine hydroxylase activity in tissue homogenate

Zusammenfassung Es wird eine Fluoreszenzmethode zur Bestimmung der Tyrosin-Hydroxylase-Aktivität von Homogenat beschrieben, die auf der Spektrofluorometrie der DOPA-Bildung beruht. Die Tyrosin-Hydroxylase-Aktivität von Homogenat der Nebenniere und des Gehirns (Nucleus caudatus) wurde mit dieser Methode gemessen.     

A thin-layer chromatographic assay for measuring pineal hydroxyindole-O-methyltransferase activity

Summary A thin-layer chromatographic procedure for measuring pineal HIOMT activity is described, based on the methylation of NAS to melationin. The method enalbes simple and accurate determination in small alipuots from a single pineal organ homogenate.     

A thin-layer chromatographic assay for measuring pineal hydroxyindole-O-methyltransferase activity

A thin-layer chromatographic procedure for measuring pineal HIOMT activity is described, based on the methylation of NAS to melatonin. The method enables simple and accurate determination in small aliquots from a single pineal organ homogenate.     

An inexpensive and sensitive method for measuring and classifying activity in small animals

Summary A vibration-sensitive device which is useful in the quantification of activity in small animals is described. In addition to measurement ot total energy expenditure for activity, this transducer also allows identification of types of activity (sleeping, eating, active movement).     

Tyrosine hydroxylase activity and tyrosine titers during cockroach metamorphosis

Summary Tyrosine hydroxylation (TH) to dopa in vivo in nymphs and pharate adults ofPeriplaneta americana was very low, but increased over 30-fold beginning at ecdysis. Free tyrosine increased in pharate, adults and peaked at ecdysis, whereas TH activity peaked 6 h later. Both TH activity and tyrosine titers declined the next 24 h as the cuticle tanned. TH appears to regulate tanning substrate biosynthesis in cockroaches.Contribution No. 81-294-j, Department of Entomology, Kansas Agricultural Experiment Station, Manhattan KS. Research supported in part by National Science Foundation grant No. PCM-8003859. I wish to thank Dr. M.A.J. Al-Izzi for assistance with the enzyme analyses.     

A sensitive protein assay method using micro-titer plates

Summary A commercially available protein-assay, based on the reaction between bicinchoninic acid (4,4-dicarboxy-2,2-biquinoline) and copper was adapted for use in microtiter plates. The assay is sensitive between 10 m/ml and several mg/ml, and it uses only 10 l of sample material. The results obtained with the method were in accordance with other protein determination methods. The assay was shown to be reproducible, reliable and insensitive to non-ionic detergents.Acknowledgments. The authors are grateful to Miss Barbara Moser who skillfully performed a number of these experiments. This research was supported by the Swiss National Science Foundation, Grant No 3.300–0.82, to U.B.     

The effect of high phenylalanine concentration on the formation of DOPA from phenylalanine and tyrosine by tyrosine hydroxylase

Zusammenfassung Auf der Basis gegenseitiger Hemmung von Phenylalanin konnte die enzymatische Bildung des DOPA über Phenylalanin und Tyrosin mittels Tyrosinhydroxylase untersucht werden. Eine 70%ige Hemmung der enzymatischen DOPA-Bildung ergab sich im Fall der dreissigfachen Konzentration des Phenylalanin. Die Möglichkeit einer Hemmung der Norepinephrin-Bildung in Phenylketonurie wird diskutiert.     

Subcellular distribution of tyrosine hydroxylase and monoamine oxidase in the bovine caudate nucleus

Zusammenfassung Die subzelluläre Lokalisation von Tyrosin-Hydroxylase und Monoaminoxydase im Nucleus caudatus des Rindergehirns wurde untersucht. Tyrosin-Hydroxylase fand sich grösstenteils in den Synaptosomen, den Mikrosomen und dem Zytoplasma. Eine bedeutende Aktivität von Monoaminoxydase war in den Mitochondrien vorhanden.     

Photodynamic sensitizers assay: rapid and sensitive iodometric measurement

A rapid, sensitive and simple spectrophotometric method for the detection of¹O₂ produced by photodynamic photosensitizers in slightly acid and air-saturated aqueous solutions has been developed. The method is based on the reaction of¹O₂ (produced by photodynamic processes) with I^– in the presence of ammonium molybdate as a catalyst. The reaction product I₃ ^–, proportional to¹O₂, is followed spectrophotometrically at 355 nm. Several ways of avoiding interference with other oxidizing compounds, either present before or produced during the irradiation, are described.The method could be used to measure the efficiency of water-soluble photodynamic photosensitizers.     

Influence of castration and testosterone replacement on hypothalamic tyrosine hydroxylase activity in the rat

Summary Hypothalamic tyrosine hydroxylase (TH) activity of castrate rats is modulated by testosterone propionate (TP) in vivo. Kinetic studies revealed that bothV _max andK _m were virtually unaltered for substrate tyrosine in the presence of an excess of DMPH₄ cofactor. TP replacement to castrate rats increased theK _m for added DMPH₄ cofactor, whileV _max decreased. These results suggest that TP decreases TH activity of castrate rats by inhibiting the enzymereduced pteridine cofactor complex.     

Influence of castration and testosterone replacement on hypothalamic tyrosine hydroxylase activity in the rat.

Hypothalamic tyrosine hydroxylase (TH) activity of castrate rats is modulated by testosterone propionate (TP) in vivo. Kinetic studies revealed that both Vmax and Km were virtually unaltered for substrate tyrosine in the presence of an excess of DMPH4 cofactor. TP replacement to castrate rats increased the Km for added DMPH4 cofactor, while Vmax decreased. These results suggest that TP decreases TH activity of castrate rats by inhibiting the enzyme-reduced pteridine cofactor complex.     

A simple,sturdy, and inexpensive stimulus generator for nerves and muscles

Zusammenfassung Es wird ein einfaches und preiswertes Reizgerät zur Nerven- und Muskelreizung mit Rechteckimpulsen von 0.9 msec Dauer beschrieben (Frequenz 0.7 bis 100 Hz und Intensität 0 bis 10 Volt).Synchron mit jedem Impuls, oder bei den höheren Frequenzen bei Impulsserien, wird ein Kontakt geschlossen, der über einen Ausgang zur Reizmarkierung verwendet werden kann.     

Hypothalamic tyrosine hydroxylase activity, plasma gonadotropin and prolactin levels after aminooxyacetic acid in ovariectomized rats

Plasma concentrations of gonadotropin, prolactin and hypothalamic tyrosine hydroxylase (TH) activity were measured in ovariectomized rats treated with aminooxyacetic acid (AOAA), a drug which elevates brain GABA levels. Hypothalamic TH activity was significantly increased with a significant decrease in prolactin (Prl) release. Plasma levels of gonadotropins were not modified by AOAA. These results support an inhibitory action of GABA on Prl release possibly mediated through hypothalamic dopamine.     

Hypothalamic tyrosine hydroxylase activity,plasma gonadotropin and prolactin levels after aminooxyacetic acid in ovariectomized rats

Summary Plasma concentrations of gonadotropin, prolactin and hypothalamic tyrosine hydroxylase (TH) activity were measured in ovariectomized rats treated with aminooxyacetic acid (AOAA), a drug which elevates brain GABA levels. Hypothalamic TH activity was significantly increased with a significant decrease in prolactin (Prl) release. Plasma levels of gonadotropins were not modified by AOAA. These results support an inhibitory action of GABA on Prl release possibly mediated through hypothalamic dopamine.Supported by grants from Indian Council of Medical Research (ICMR), New Delhi. RIA kits for the estimation of LH, FSH and Prl were kindly supplied by Dr A.F. Parlow, NIAMDD-NIH, Bethesda, Maryland, USA. GNB is a UGC research fellow.