Unsuccessful treatment of severe pyruvate carboxylase deficiency with triheptanoin.

UNLABELLED: Pyruvate carboxylase (PC) deficiency (OMIM 266150) is an autosomal recessive disorder that usually presents with lactic acidaemia and severe neurological dysfunction, leading to death in infancy. Because the enzyme is involved in gluconeogenesis and anaplerosis of the Krebs cycle, therapeutic strategies have included avoiding fasting and attempts to correct the defect of anaplerosis. Triheptanoin is a triglyceride of C7 fatty acids. The oxidation of odd chain fatty acids leads to the production not only of acetyl-CoA but also of propionyl-CoA, which is an anaplerotic substrate for the Krebs cycle. One infant with PC deficiency has previously been treated with triheptanoin as well as citrate and 2-chloropropionate. We report two further patients with PC deficiency, who were treated with triheptanoin, continuously from 11 and 21 days of age. They were also given citrate, aspartate and dichloroacetate. Triheptanoin did not lead to any clinical or biochemical improvement. The plasma and CSF lactate concentrations remained high with episodes of severe ketoacidosis and lactic acidosis. Both patients had severe hearing loss, roving eye movements, seizures and very limited neurodevelopmental progress; they died at the ages of 7 and 8 months. CONCLUSION: Though triheptanoin did not alter the clinical course in our patients, it was well tolerated. It remains possible that less severely affected patients might benefit from this form of therapy.

An investigation into the potential for upward range expansion in high-montane species on the roof of the world.

Climate warming is occurring in high-mountain areas at a faster rate than the global average. To escape the increasing temperatures, alpine species may shift in distribution upwards, threatening cold-adapted nival plant specialists. However, little is known about the success of seedling emergence and establishment at high altitudes outside the current range, particularly in the highest mountain areas of the Himalayas. We selected four native alpine species occurring around 4000 m a.s.l. and sowed seeds at the natural growing site (GS), at a high elevation site (HS; 5000 m a.s.l.) and at high elevation with soil from the growing site (HS-S) in the Khumbu Valley, north-eastern Nepal. We monitored seedling emergence and establishment for two consecutive years. Seedling emergence and establishment varied between species. Emergence was similar between GS and HS and improved at HS-S. Establishment was low at high elevations with all but one species having high mortality after winter. Seedling emergence of low elevation plants is possible at high elevations in the Everest region, indicating species may be able to shift their distribution range upwards. However, successful establishment may be limited by the soil and high winter mortality at high elevations, although not in all species. Climate warming will potentially lead to upward migration of some Himalayan plant species, leading to altered community composition in high-mountain areas.

Dietary practices in pyridoxine non-responsive homocystinuria: a European survey.

BACKGROUND: Within Europe, the management of pyridoxine (B6) non-responsive homocystinuria (HCU) may vary but there is limited knowledge about treatment practice. AIM: A comparison of dietetic management practices of patients with B6 non-responsive HCU in European centres. METHODS: A cross-sectional audit by questionnaire was completed by 29 inherited metabolic disorder (IMD) centres: (14 UK, 5 Germany, 3 Netherlands, 2 Switzerland, 2 Portugal, 1 France, 1 Norway, 1 Belgium). RESULTS: 181 patients (73% >16 years of age) with HCU were identified. The majority (66%; n=119) were on dietary treatment (1-10 years, 90%; 11-16 years, 82%; and >16 years, 58%) with or without betaine and 34% (n=62) were on betaine alone. The median natural protein intake (g/day) on diet only was, by age: 1-10 years, 12 g; 11-16 years, 11 g; and >16 years, 45 g. With diet and betaine, median natural protein intake (g/day) by age was: 1-10 years, 13 g; 11-16 years, 20 g; and >16 years, 38 g. Fifty-two percent (n=15) of centres allocated natural protein by calculating methionine rather than a protein exchange system. A methionine-free l-amino acid supplement was prescribed for 86% of diet treated patients. Fifty-two percent of centres recommended cystine supplements for low plasma concentrations. Target treatment concentrations for homocystine/homocysteine (free/total) and frequency of biochemical monitoring varied. CONCLUSION: In B6 non-responsive HCU the prescription of dietary restriction by IMD centres declined with age, potentially associated with poor adherence in older patients. Inconsistencies in biochemical monitoring and treatment indicate the need for international consensus guidelines.

Dietary management of urea cycle disorders: UK practice.

BACKGROUND: There is no published data describing UK dietary management of urea cycle disorders (UCD). The present study describes dietary practices in UK inherited metabolic disorder (IMD) centres. METHODS: Cross-sectional data from 16 IMD centres were collected by a questionnaire describing the management of UCD patients on prescribed protein-restricted diets. RESULTS: One hundred and seventy-five patients [N-acetylglutamate synthase deficiency, n = 3; carbamoyl phosphate synthase deficiency (CPS), n = 8; ornithine transcarbamoylase deficiency (OTC), n = 75; citrullinaemia, n = 41; argininosuccinic aciduria (ASA), n = 36; arginase deficiency, n = 12] were reported; 70% (n = 123) aged 0-16 years; 30% (n = 52) >16 years. Prescribed median protein intake decreased with age (0-6 months: 2 g kg(-1) day(-1); 7-12 months: 1.6 g kg(-1) day(-1); 1-10 years: 1.3 g kg(-1) day(-1); 11-16 years: 0.9 g kg(-1) day(-1) and >16 years: 0.8 g kg(-1) day(-1)) with little variation between disorders. Adult protein prescription ranged 0.4-1.2 g kg(-1) day(-1) (40-60 g day(-1)). In the previous 2 years, 30% (n = 53) were given essential amino acid supplements (EAAs) (CPS, n = 2; OTC, n = 20; citrullinaemia, n = 15; ASA, n = 7; arginase deficiency, n = 9). EAAs were prescribed for low plasma quantitative essential amino acids (n = 13 centres); inadequate natural protein intake (n = 11) and poor metabolic control (n = 9). From diagnosis, one centre prescribed EAAs for all patients and one centre for severe defects only. Only 3% (n = 6) were given branch chain amino acid supplements. Enteral feeding tubes were used by 25% (n = 44) for feeds and 3% (n = 6) for medications. Oral energy supplements were prescribed in 17% (n = 30) of cases. CONCLUSIONS: In the UK, protein restriction based on World Health Organization 'safe intakes of protein', is the principle dietary treatment for UCD. EAA supplements are prescribed mainly on clinical need. Multicentre collaborative research is required to define optimal dietary treatments.

Postpartum nutrition affects the insulin-like growth factor system in dominant follicles and plasma of anestrous beef cows.

Effects of nutrition on insulin-like growth factor-I (IGF-I), IGF binding proteins (IGFBP), and insulin in plasma and dominant follicles were evaluated at day 72 and 56 (Exp. 1, n = 12 and Exp. 2, n = 28, respectively) postpartum in anovulatory primiparous beef cows. Cows were stratified based on body condition score at calving and randomly assigned to nutritional treatments: maintain (M), 2.27 kg of a 40 % CP supplement per day and ad libitum hay; or gain (G), ad libitum access to a 50 % concentrate diet and ad libitum hay. Blood samples were collected twice weekly starting 30 days postpartum. Ovarian follicles were evaluated using ultrasonography commencing 42 (Exp. 1) or 30 (Exp. 2) days postpartum. Body weight and condition score were greater (P < 0.05) for cows of G than M groups and postpartum interval to luteal function was longer for cows of the M than G group. Insulin and IGF-I concentrations in follicular fluid (FF) and plasma were greater (P < 0.05) for cows of the G than M group at follicular aspiration. Plasma and FF IGFBP4 and IGFBP5 concentrations were greater (P <  0.05) in Exp. 2, and IGFBP5 was greater in Exp. 1 for cows of the G than M group. Treatment did not affect FF steroid concentrations or granulosal cell CYP19A1, PAPPA, IGFBP4, and IGFBP5 mRNA abundance. These results indicate concentrations of IGF-I, insulin, IGFBP4, and IGFBP5 in FF and plasma are affected by nutritional intake and may be related to follicular function.

Ethics commentary: subjects of knowledge and control in field primatology.

Our primate kin are routinely displaced from their habitats, hunted for meat, captured for trade, housed in zoos, made to perform for our entertainment, and used as subjects in biomedical testing. They are also the subjects of research inquiries by field primatologists. In this article, we place primate field studies on a continuum of human and alloprimate relationships as a heuristic device to explore the unifying ethical implications of such inter-relationships, as well as address specific ethical challenges arising from common research protocols "in the field" (e.g. risks associated with habituation, disease transmission, invasive collection of biological samples, etc.). Additionally, we question the widespread deployment of conservation- and/or local economic development-based justifications for field-based primatological pursuits. Informed by decades of combined fieldwork experience in Indonesia and the Democratic Republic of Congo, we demonstrate the process by which the adherence to a particular ethical calculus can lead to unregulated and ethically problematic research agendas. In conclusion, we offer several suggestions to consider in the establishment of a formalized code of ethics for field primatology.

Differential effects of classical and atypical antipsychotic drugs on A9 and A10 dopamine neurons.

Prolonged treatment with classical antipsychotic drugs decreased the number of spontaneously active dopamine neurons in both the substantia nigra (A9) and the ventral tegmental area (A10) of the rat brain. In contrast, treatment with atypical antipsychotic drugs selectively decreased the number of A10 dopamine neurons. Related drugs lacking antipsychotic efficacy failed to decrease dopamine activity. These findings suggest that the inability of atypical antipsychotic drugs to decrease A9 dopamine neuronal activity may be related to their lower potential for causing tardive dyskinesia and that the inactivation of A10 neurons may be involved in the delayed onset of therapeutic effects during treatment.

Lysergic acid diethylamide (LSD) and lisuride: differentiation of their neuropharmacological actions.

The nonhallucinogenic ergot derivative lisuride exerts many pharmacological effects that are similar to those of its hallucinogenic congener, lysergic acid diethylamide (LSD). Animals trained to discriminate between the presence of one drug and the other can be used to differentiate the actions of these compounds on a neuronal level. The discriminative stimulus effect of LSD (the LSD cue) is similar to that of the serotonin agonist quipazine, whereas the lisuride cue is similar to that of the dopamine agonist apomorphine. These data support the hypothesis that serotonin is intricately involved in the hallucinogenic effects of LSD.

DARPP-32: regulator of the efficacy of dopaminergic neurotransmission.

Dopaminergic neurons exert a major modulatory effect on the forebrain. Dopamine and adenosine 3',5'-monophosphate-regulated phosphoprotein (32 kilodaltons) (DARPP-32), which is enriched in all neurons that receive a dopaminergic input, is converted in response to dopamine into a potent protein phosphatase inhibitor. Mice generated to contain a targeted disruption of the DARPP-32 gene showed profound deficits in their molecular, electrophysiological, and behavioral responses to dopamine, drugs of abuse, and antipsychotic medication. The results show that DARPP-32 plays a central role in regulating the efficacy of dopaminergic neurotransmission.

Dopamine D3 receptor mutant mice exhibit increased behavioral sensitivity to concurrent stimulation of D1 and D2 receptors.

The dopamine D3 receptor is expressed primarily in regions of the brain that are thought to influence motivation and motor functions. To specify in vivo D3 receptor function, we generated mutant mice lacking this receptor. Our analysis indicates that in a novel environment, D3 mutant mice are transiently more active than wild-type mice, an effect not associated with anxiety state. Moreover, D3 mutant mice exhibit enhanced behavioral sensitivity to combined injections of D1 and D2 class receptor agonists, cocaine and amphetamine. However, the combined electrophysiological effects of the same D1 and D2 agonists on single neurons within the nucleus accumbens were not altered by the D3 receptor mutation. We conclude that one function of the D3 receptor is to modulate behaviors by inhibiting the cooperative effects of postsynaptic D1 and other D2 class receptors at systems level.

Loss of autoreceptor functions in mice lacking the dopamine transporter.

Autoreceptors provide an important inhibitory feedback mechanism for dopamine neurons by altering neuronal functions in response to changes in extracellular levels of dopamine. Elevated dopamine may be a component of several neuropsychiatric disorders. However, evidence concerning the state of autoreceptors in such conditions has remained elusive. The function of dopamine autoreceptors was assessed in mice lacking the dopamine transporter (DAT). Genetic deletion of the DAT gene in mice results in a persistent elevation in levels of extracellular dopamine. Direct assessment of impulse-, synthesis- and release-regulating autoreceptors in these mice reveals a nearly complete loss of function. These findings may provide insight into the neurochemical consequences of hyperdopaminergia.

Clearance of atrial natriuretic factor by lung, liver, and kidney in human subjects and the dog.

We determined human and canine plasma clearance of atrial natriuretic factor (ANF) by lung, liver, and kidney from arteriovenous differences in plasma ANF and measured organ plasma flow. Human subjects had lower plasma ANF concentrations in the pulmonary vein or the pulmonary capillary wedge position when compared with the pulmonary artery, and both sites yielded pulmonary ANF extraction ratios of 24%. Canine lung ANF extraction was 19 +/- 3% and pulmonary ANF clearance was 328 +/- 78 ml/min per m2 vs. 357 +/- 53 ml/min per m2 in man. Hepatic plasma ANF clearance was 216 +/- 26 ml/min with an extraction ratio of 30 +/- 3% in humans and 199 +/- 89 ml/min and 36 +/- 6% in the dog. Renal plasma ANF clearance in human subjects was 78 +/- 12 ml/min per kidney and correlated well with each kidney's creatinine clearance (r = 0.58, P less than 0.05). The mean renal ANF extraction ratio was 35 +/- 4% in human subjects and 42 +/- 6% in the dog. These data quantitate the specific organ ANF clearances by lung, liver, and kidney in human subjects and in dogs and provide a rationale for elevated plasma ANF levels in cirrhosis, renal failure, and diseases accompanied by reduced perfusion of these organs. These findings support the conclusion that plasma ANF concentrations are dependent upon both the stimuli for ANF secretion as well as the specific organ clearances of ANF.

Randomised controlled trial of essential fatty acid supplementation in phenylketonuria.

OBJECTIVE: The long-chain polyunsaturated fatty acids (LC-PUFA) status of children with PKU is often compromised. LC-PUFA, which are important fatty acids in the development of the CNS, can be synthesised endogenously from the parent essential fatty acids (EFA) provided dietary intakes are adequate. This study was designed to assess the biochemical effect over a 20-week period of a phe-free protein substitute that has been supplemented with a balanced blend of n-3 and n-6 EFAs on LC-PUFA status of children with PKU. DESIGN, SETTING AND SUBJECTS: Fifty three community-living children aged 1-10 years diagnosed with PKU in the newborn period were recruited from seven tertiary centres in the UK and France and randomised to a fat-free control formula or the EFA-supplemented test-treatment formula in an open, prospective study. Forty four children completed the study (20 controls, 24 test-treatments). Fatty acid status was assessed at entry and 20-weeks follow-up. Three day dietary diaries were recorded at 20 weeks' follow-up. The safety, efficacy and palatability of the test-treatment formula were also assessed. RESULTS: The test-treatment group had significantly higher intakes of fat and EFA than the control group. There was a significant between group difference (P=0.04) in increases in median docosahexaenoic acid (DHA) concentrations in erythrocyte phospholipids, which increased by 19% in the test-treatment group and by 0.5% in the control group over the study period. Growth and phe control were satisfactory in all subjects. CONCLUSIONS: Supplementing the diets of children with PKU with a balanced blend of n-6 and n-3 EFA improves DHA status without compromising AA status.

Enhanced vulnerability to cocaine self-administration is associated with elevated impulse activity of midbrain dopamine neurons.

Individual differences in responding to a novel environment predict behavioral and neurochemical responses to psychostimulant drugs. Rats with a high locomotor response to a novel environment (HRs) exhibit enhanced self-administration (SA) behavior, sensitization, and basal or drug-induced dopamine release in the nucleus accumbens compared with rats with a low response to the novel context (LRs). In this study, we determined whether such differences in vulnerability to drug addiction might be related to differences in dopamine (DA) neuron activity. Rats were divided into HRs and LRs according to their response to a novel environment and then tested for acquisition of cocaine SA. HRs rapidly acquired cocaine SA (175 microg/kg per infusion), whereas LRs did not. Differences in cocaine SA were not caused by differences in exploratory behavior or sampling because these behaviors did not differ in HRs and LRs self-administering a saline solution. In a separate experiment, we used extracellular single-unit recordings and found that HRs exhibit higher basal firing rates and bursting activity of DA neurons in the ventral tegmental area and, to a lesser extent, in the substantia nigra pars compacta. The greater activity of midbrain DA cells in HRs was accompanied by reduced sensitivity to the inhibitory effects of a DA D2-class receptor agonist, indicating possible subsensitivity of impulse-regulating DA autoreceptors. These results demonstrate that differences in the basal activity of DA neurons may be critically involved in determining individual vulnerability to drugs of abuse.

Analyzing mechanism(s) of hallucinogenic drug action with drug discrimination procedures.

Some of the advantages of using drug discrimination (DD) procedure to analyze the mechanisms of action of hallucinogenic and related drugs were illustrated by reviewing research with lysergic acid diethylamide (LSD). Because they ensure that drug-induced alterations in interoceptive "state" become biologically meaningful "cues," these procedures are reliable, robust, sensitive and specific. With reference to LSD, many DD experiments suggest: (1) that while hallucinogens substitute for (mimic) LSD (in rats), such substitution does not predict hallucinogenic potency (in humans) but does predict similarities in mechanism(s) of action; (2) the behavioral (in vivo) effects of LSD, unlike those of some of its congeners, are mediated primarily by central, serotonergic (5-HT) neuronal mechanism although LSD may also have (secondary) dopamine (DA) agonist properties; (3) both the locus and the nature of these LSD-5-HT interactions are unclear: cells arising from B-7, B-8 and B-9 regions of the dorsal-medial raphe may be involved; pretreatment with agents that deplete 5-HT and increase the stereospecific binding of 3H-LSD in vitro (p-chlorophenylalanine; 5,7-dihydroxytryptamine) enhance sensitivity to LSD in vivo.

Enhanced reactivity and vulnerability to cocaine following methylphenidate treatment in adolescent rats.

Treatment of attention deficit hyperactivity disorder with the psychostimulant drug methylphenidate (MP) has increased dramatically among schoolchildren. We tested whether repeated exposure to moderate doses of MP (5 and 10 mg/kg IP for 5 or 7 days) in adolescent rats increased reactivity to cocaine measured by motor responses (ambulations and rearing) to a cocaine challenge in adulthood. We later tested whether repeated exposure to a low dose of MP (2 mg/kg IP for 7 days) enhanced the psychomotor effects of cocaine, measured by different challenge doses (0-30 mg/kg) as well as to the reinforcing effects of cocaine, measured by self-administration of low-dose infusion (75 microg/kg, IV). We found that exposure to moderate doses of MP enhanced psychomotor responses to cocaine but exposure to a low dose only increased cocaine self-administration. These results suggest that adolescent exposure to low doses of MP in rats may increase the incentive value of low reinforcers, thereby rendering adult rats more susceptible to cocaine self-administration.

Dopamine receptor antagonists fail to prevent induction of cocaine sensitization.

We investigated the ability of dopamine D1 and D2 class receptor antagonists to prevent the induction of behavioral sensitization to cocaine. The D2 receptor antagonist eticlopride failed to prevent the induction of cocaine sensitization. An intermediate dose of the D1 receptor antagonist SCH 23390 (0.1 mg/kg) appeared to prevent the induction of cocaine sensitization when tested after 3 days of withdrawal, but sensitization was clearly evident after 10 days of withdrawal. High doses of SCH 23390 alone produced supersensitivity to the behavioral effects of cocaine and to the inhibitory effects of D1 receptor agonists on nucleus accumbens neurons. Co-administration of eticlopride and SCH 23390 also failed to prevent the induction of cocaine sensitization. SCH 23390, but not eticlopride, prevented the expression of cocaine sensitization. We conclude that dopamine receptors are either not involved in the induction of cocaine sensitization or that redundant mechanisms exist to produce the same neuroadaptations.

Effects of tiaspirone (BMY-13859) and a chemical congener (BMY-13980) on A9 and A10 dopamine neurons in the rat.

Two new potential antipsychotic drugs, BMY-13980 and BMY-13859 were compared for the ability to influence the electrophysiological activity of dopaminergic neurons in the substantia nigra zona compacta (A9 DA cells) and ventral tegmental area (A10 DA cells) in the brain of the rat. Both drugs reversed the rate-suppressant effects of the DA agonist apomorphine on DA cells in A10 to a greater extent than DA cells in A9; BMY-13980 was particularly selective in this regard. These results indicate that both drugs may exert DA antagonist effects which are suggestive of antipsychotic potential. In other experiments, the effects of chronic (28 days) treatment with BMY-13980 and BMY-13859 on the neuronal activity of DA were evaluated. Both compounds caused a significant decrease in the number of spontaneously active DA neurons in A10 recorded per electrode track, an effect previously demonstrated to be associated with antipsychotic efficacy. The drug BMY-13859, but not BMY-13980, also significantly decreased the number of spontaneously active DA cells/track in A9, an effect which may predict the liability of potential antipsychotic drugs for causing extrapyramidal motor dysfunction, including tardive dyskinesia. Thus, these experiments indicate that both BMY-13980 and BMY-13859 exert effects which may predict potential antipsychotic efficacy in clinical trials and that BMY-13980 may be less likely to cause extrapyramidal side effects.