A new and highly sensitive method for measuring 3-methoxytyramine using HPLC with electrochemical detection. Studies with drugs which alter dopamine metabolism in the brain

3-Methoxytyramine (3-MT) is a minor metabolite of dopamine which is suggested to reflect the turnover and utilization of dopamine. A novel, isocratic HPLC method has been developed which can be used to analyse 3-MT in homogenates of rat brain without the need for additional purification procedures. Furthermore, the coulometric electrochemical detection system is sensitive enough to measure 3 pg of 3-MT (equivalent to 0.6 ng/g tissue wet weight). 3-Methoxytyramine was measured in the striatum and n. accumbens after decapitation and rapid freezing, using 3-methoxy-4-hydroxybenzylamine as the internal standard. The effects of dopaminergic and other drugs on this metabolite were examined using this method. -Methyl-p-tyrosine (200 mg/kg i.v.) produced parallel linear decreases in dopamine and 3-MT in naive rats, but not those pretreated with tranylcypromine (5 mg/kg i.p.). Methamphetamine (0.3–10 mg/kg i.p.) and amphetamine (0.3–10 mg/kg i.p.) both dose-dependently increased 3-MT in naive and tranylcypromine-pretreated rats. In naive animals, 3-MT was not altered by intraperitoneal injection of the dopamine reuptake inhibitors, bupropion (10 mg/kg) and nomifensine (10 mg/kg) or by sibutramine HCl (3 mg/kg), amitriptyline (10 mg/kg), desipramine (10 mg/kg) and zimeldine (10 mg/kg). 3-Methoxy-tyramine was decreased by apomorphine (5 mg/kg i.p.) and also by large doses of the selective D₂ antagonist, BRL 34778 (5 mg/kg i.p.) or -DOPA (50 mg/kg i.p.). The selective D₁ antagonist, SCH 23390 (0.1 or 5 mg/kg i.p.) was without effect. In tranylcypromine-pretreated rats, 3-MT was dose-dependently reduced and increased by apomorphine (0.01–5 mg/kg i.p.) and BRL 34778 (0.1–5 mg/kg i.p.), respectively. The drug SCH 23390 (0.1–5 mg/kg i.p.) produced much smaller increases in 3-MT which were probably mediated through the striatonigral pathway. Overall, the data suggest that measurement of 3-MT, after inhibition of monoamine oxidase, is a useful index of the release and utilization of dopamine. However, after substantial and prolonged depletion of dopamine, levels of 3-MT in naive animals are a better index. Also, the formation of 3-MT in naive rats provides a sensitive method for distinguishing between dopamine releasing agents and reuptake inhibitors.     

Is intrauterine insemination a viable treatment option for women over 43 years old? An analysis by ovarian stimulation protocol and sperm source

PurposeThe aim of this study was to determine how female age at the end of the reproductive spectrum effects success of natural cycle intrauterine insemination (IUI) or IUI in combination with ovarian stimulation.MethodsWe performed a retrospective cohort study of women 43 years of age and older at the time of IUI in a single academic fertility center between January 2011 and March 2018. Primary outcomes were both pregnancies and live births per cycle of IUI. Data are presented as percentage or mean ± SD. Fisher exact and chi-squared analyses were performed.ResultsThere were 9334 IUI cycles conducted during the study period. Of these cycles, 325 IUIs (3.5%) were for women aged 43 years and over at the time of insemination (43.6 ± 0.8, range 43 to 47 years). Analysis of these 325 IUI cycles revealed 5 biochemical pregnancies (1.5%) and only 1 live birth (0.3%). The pregnancy rate did not differ between IUIs using donor sperm (N = 1/49, 2.0%) compared to IUIs with partner sperm (N = 4/276, 1.4%). The pregnancy rate did not differ between IUIs with gonadotropins (N = 2/211, 0.9%), clomiphene or letrozole (N = 2/78, 2.6%), or natural cycle (N = 1/36, 2.8%).ConclusionsThe use of intrauterine inseminations in women 43 years of age and older is an ineffective treatment strategy. This is irrespective of the use of ovarian stimulation or donor sperm. Costly gonadotropin injections did not increase the chance of pregnancy nor did oral medication when compared to natural cycle IUIs.     

Local anaesthetic and antiarrhythmic properties of an aminosteroid: 3alpha-dimethyl-amino-5alpha-androstan-2beta-ol-17-one (Org. NA 13).

1. The aminosteroid Org. NA13 (3alpha-dimethylamino-5alpha-androstan-2beta-ol-17-one) was shown to be a more potent local anaesthetic than lignocaine in rats and guinea-pigs. 2. Experimental arrhythmias induced in mice by chloroform, in rats by aconitine and in dogs by coronary artery ligation were corrected by Org. NA13 at doses from 10 to 50 mg/kg intravenously. 3. In contrast to lignocaine, other local anaesthetics and beta-adrenoceptor blocking drugs, Org. NA 13 did not show any activity against the arrhythmias induced by ouabian in dogs. 4. The acute toxicity in whole animals and myocardial toxicity in the rabbit isolated atrium appeared to be less than that observed with lignocaine.     

Peripheral stimulation in mice induces short-duration analgesia preventable by naloxone.

Peripheral stimulation was applied to mice by mild caudal electrostimulation, by mechanical pressure or by footshock for 30 sec, before testing on a 52 degrees C hot plate. Reaction times to paw lick and to escape from the hot plate were recorded. Analgesia could be elicited and measured by these procedures. It was of short duration, declining in a minute, and was antagonized by low doses of naloxone. The analgesia measured by the escape reaction time could be elicited after multiple caudal electrostimulation as well as in morphine-tolerant mice, and it could still be reversed by naloxone. An opioid link is thus involved in this phenomenon, which also supports the notion of more than one opioid pathway existing in the brain. The short period of analgesic cover afforded in the face of noxious stimuli would permit aversive action to be taken in nature and thus might represent the prime functional role of enkephalins in the brain.     

What is the most relevant standard of success in assisted reproduction? The importance of informed choice

Whilst there is a need to emphasize the birth rates of healthy infants when reporting success rates following infertility treatment, is 'the singleton term gestation per cycle started' the most appropriate measure? Although there are many ways to measure the efficacy of medical intervention, none of these exclude from the 'successes' those in whom complications have occurred. The safe delivery of healthy twins at term, while possibly not the ideal outcome, should still be regarded as a treatment success. Although multiple pregnancy, in particular high order multiple pregnancy, continues to be a major problem associated with assisted reproductive treatments and also with ovulation induction, appropriate counselling concerning the risks of twin and triplet pregnancies will allow couples to make informed choices and allow clinicians to continue to individualize treatment plans.     

Diacylglycerol acyltransferases: Potential roles as pharmacological targets

Triglyceride (TG) synthesis occurs in many cell-types, but only the adipocyte is specialised for TG storage. The increased incidence of obesity and its attendant pathologies have increased interest in pharmacological strategies aimed at inhibition of triglyceride synthesis. In the liver this would also appear to offer the advantages of the prevention of steatosis and/or dyslipidaemia. The two major enzymes that have DGAT activity appear to have specialised functions, that are most evident in triglyceride-secreting tissues. The presence of triglyceride in non-adipose cells can lead to (through lipolysis), or be a marker for, undesirable complications such as insulin resistance, or can be indicative of simultaneously high capacities for triglyceride synthesis, lipolysis and oxidation of fatty acids as in highly aerobic, trained muscle. Consequently, inhibition of triglyceride synthesis may not be a straightforward strategy, either in terms of its achievement pharmacologically or in its anticipated outcomes. The metabolic complexities of triglyceride synthesis, with particular reference to the diacylglycerol acyltransferases (DGATs) are considered in this short review.     

Membrane stabilising properties of the selective 5-HT2 receptor agonist, (+/-)-DOI.

The effects of (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), a selective 5-HT2 receptor agonist, on nerve conduction in the isolated frog sciatic nerve trunk were examined. Compound action potential amplitude was concentration dependently decreased by (+/-)-DOI (EC50 = 1.2 mM), an effect that was not altered by the presence of ketanserin and with a similar potency to lignocaine. (+/-)-propranolol and disopyramide. The results indicate that (+/-)-DOI has membrane stabilising properties, in addition to its reported 5-HT2 agonist actions.     

Recurrent triploid digynic conceptions and mature ovarian teratomas: Are they different manifestations of the same genetic defect?

Miscarriages affect 15% of clinically recognized pregnancies. Recurrent miscarriage (RM) is defined by the occurrence of at least two consecutive pregnancy losses and affects 1%‐5% of couples trying to conceive. In an attempt to categorize patients with RM and identify the mechanisms leading to their miscarriages, we first used flow cytometry to assess the ploidy of 93 products of conception (POCs) from 53 patients with RM (≥3 miscarriages). We identified a single patient with four triploid POCs. We then used fluorescent in situ hybridization to confirm the triploidies and fluorescent microsatellite genotyping with distal and pericentromeric markers to determine their parental origin and the mechanisms leading to their formation. We found that all four triploidies were digynic and due to a failure in meiosis II (MII), suggesting a genetic predisposition. Upon further investigation into the family, we found a remarkable history of ovarian cysts and dysfunctions on the maternal side. Notably, one maternal cousin had a mature ovarian teratoma that we analyzed and found an identical mechanism at its origin, a failure in MII. The identification of two patients in the same family with two different manifestations—digynic triploid conceptions and mature ovarian teratomas, both resulting from the failure of MII—suggests an inherited genetic susceptibility toward an error in MII segregating in the family that may manifest in the form of a triploid digynic miscarriage or a mature ovarian teratoma. Our findings may facilitate the future identification of causative mutations for MII defects.     

Measurement of 3-methoxytyramine by in vivo voltammetry: evidence for differences in central dopamine function in BALB/c and CBA mice

Differential pulse voltammetry (DPV) combined with carbon fibre electrodes allows selective detection of electroactive dopamine and serotonin metabolites in vivo. While usually employed in rats, we have now applied this in vivo technique in two inbred strains of mice: BALB/c and CBA. Three distinct oxidation peaks were recorded in vivo in the striatum of either BALB/c or CBA mice with a small shoulder occurring after the third peak at approximately +400 mV. Pargyline (150 mg/kg i.p.) potentiated this voltammetric shoulder into an easily measurable peak (Peak 4). In addition, Peak 4 was 2–3 times larger in BALB/c than in CBA mice. Homovanillic acid (HVA) and 3-methoxytyramine (3-MT), both catabolites of dopamine, oxidised at approximately +400 mV in vitro. Brain tissue levels of HVA and 3-MT, measured by high-performance liquid chromatography (HPLC) with electrochemical detection, demonstrated that pargyline treatment reduced striatal HVA, but increased 3-MT. These results support the view that Peak 4 recorded in the striatum of pargyline-treated mice in vivo is due to the oxidation of extracellular 3-MT. Thus, Peak 4 may be a useful index of dopamine release in situations where dopamine itself cannot be detected. Local infusion of KCl (2 μl, 0.1 M) further increased the size of Peak 4 in the striatum of both BALB/c and CBA mice. However, the increase was approx. 3 times greater in BALB/c mice, supporting previous evidence of greater dopaminergic function of BALB/c compared with CBA mice. In addition these two inbred strains of mice provide model systems for investigating the comparative functional roles of nigrostriatal pathways.