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Munchausen’s syndrome and related factitious disorders
Published in David Enoch, Basant K. Puri, Hadrian Ball, Uncommon Psychiatric Syndromes, 2020
David Enoch, Basant K. Puri, Hadrian Ball
Reports of laboratory results may themselves be forged. Zittel et al. (2017) have described the first published case of Munchausen’s syndrome by genetics, in which a 42-year-old nurse presented with apparent symptoms of dopa-responsive dystonia, fluctuating signs and, crucially, a three-year-old report from a certified genetics laboratory stating that she had heterozygous mutations in CGH1 and TH, the respective genes encoding cadherin-1 (or CAM 120/80 or epithelial cadherin) and tyrosine hydroxylase (the enzyme catalysing the biosynthesis of L-3,4-dihydroxyphenylalanine from L-tyrosine). This document was in fact forged, and subsequent independent genetic testing did not show a mutation in either CGH1 or TH. The nurse had used her apparent illness to obtain early retirement, and she had been prescribed daily levodopa and pramipexole. Commenting on this case, Oliveira (2017) has pointed out that “[this case] provided an instructive example of how to pay attention to details that we usually take for granted during the busy clinician routine. It would be crucial to check if the patient had a specific motivation, such as pension application or welfare.”
Biogenic amines
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop
Tyrosine hydroxylase catalyzes the rate-limiting step in the formation of the catecholamines, dopamine, norepinephrine, and epinephrine (see Figure 17.1). Deficient activity of the enzyme leads to diagnostic decrease in CSF concentrations of the metabolic catecholamine degradation products, HVA and MPHG (see Table 17.1). The gene TH contains 14 exons and has an open reading frame of 1491 bp [31]. It was mapped to chromosome 11p.15.5, the most distant end of 11p [32].
Adrenergic Agonists
Published in Sahab Uddin, Rashid Mamunur, Advances in Neuropharmacology, 2020
Tyrosine, an essential amino acid, is a precursor of noradrenaline (Fig. 3.1) and is synthesized from phenylalanine, an amino acid obtained from food. Phenylalanine gets oxidized in liver with phenylalanine hydroxylase as enzyme to yield tyrosine which gets taken up by the adrenergic neurons from circulation via an aromatic acid transporter. In the adrenergic neurons, tyrosine hydroxylase aided by tetrahydrobiopterin hydroxylates tyrosine in the cytoplasm to L-dihydroxyphenylalanine (L-DOPA) (Purves et al., 2004; Wevers et al., 1999). Deficiency of tyrosine hydroxylase causes a high depletion in catecholamine synthesis resulting in neurological defects accompanied by a defect in motor coordination and other extrapyramidal clinical features like Parkinson’s disease (Wevers et al., 1999). L-DOPA undergoes decarboxylation in the presence of L-DOPA decarboxylase with pyridoxal phosphate as a cofactor, thereby forming dopamine. A VNT namely VMAT causes dopamine transfer to the synapses (Njus et al., 1986) followed by a conversion to noradrenaline with the assistance by ascorbic acid with dopamine β-hydroxylase as the enzyme. Noradrenaline then moves to the adrenal medulla then undergoing methylation and leads to the synthesis of adrenaline with the aid of phenylethanolamine N-methyl transferase which is invigorated by glucocorticoids (Sharara Chami et al., 2010; Viskupic et al., 1994).
Effect of vitamin D deficiency on spatial contrast sensitivity function
Published in Clinical and Experimental Optometry, 2022
Studies investigating the relation of VD with dopamine have provided robust evidence that VD substantially contributes to the regulation of dopamine physiology. This influence particularly appears in dopaminergic neurons in the nervous system because the VD receptor has been reported to be intensely concentrated in the substantia nigra, where dopaminergic neurons are abundantly available throughout the human brain.27 Tyrosine hydroxylase is a rate-limiting enzyme of dopamine synthesis and Eyles et al. have shown the presence of the VD receptor in tyrosine hydroxylase positive neurons.28 Additionally, an in vitro study has demonstrated the promoter effect of an active form of vitamin D on tyrosine hydroxylase expression in the VD receptor expressing neuroblastoma cells and in the same study it was reported that depletion of VD in the developing brain reverses this effect.29 Pertil et al. have suggested that VD can promote dopaminergic development by influencing glial cell line-derived neurotrophic factor transcription and its C-ret receptor.30
Effects of nepicastat upon dopamine-β-hydroxylase activity and dopamine and norepinephrine levels in the rat left ventricle, kidney, and adrenal gland
Published in Clinical and Experimental Hypertension, 2020
Diogo Nóbrega Catelas, Maria Paula Serrão, Patricio Soares-Da-Silva
When considering the potential therapeutic benefits of DβH inhibitors, it is worthwhile to mention that inhibition of tyrosine hydroxylase (TH), which catalyzes the rate-limiting step in the synthesis of catecholamines, by alpha-methyl-p-tyrosine causes reserpine-like adverse effects as it enters the central nervous system and depletes brain NE and DA; bearing this in mind, alpha-methyl-p-tyrosine is occasionally used as an adjuvant (with phenoxybenzamine) to treat phaeochromocytomas that cannot be removed surgically, but not for the treatment of essential hypertension (35). Considering the use of a peripheral selective DβH or TH inhibitor (in order to avoid central nervous system adverse effects), DβH inhibition has the potential benefit of increasing DA, ultimately leading to augmentation in vasodilation and natriuresis through activation of dopamine receptors (6,14). Though dopamine itself can activate adrenergic receptors, it should be underscored that dopamine effects upon α-adrenoceptors in the vasculature only take place at very high concentrations (36,37).
The impact and toxicity of glyphosate and glyphosate-based herbicides on health and immunity
Published in Journal of Immunotoxicology, 2020
Cindy Peillex, Martin Pelletier
Besides their unconventional use for suicidal purposes, a correlation between exposure to organophosphate pesticides and suicide rates has been suspected (London et al. 2005). Anxiety behaviors were observed in mice exposed intra-nasally to low doses of Glifloglex® (Baier et al. 2017). Likewise, Ait Bali et al. (2017, 2018) showed that mouse chronic (12 weeks) and even sub-chronic (6 weeks) oral exposures to RoundUp® caused anxiety and depression-like behaviors, for instance, decreased grooming time or increased immobility in open-field experiments. The same depression-like behaviors were observed in rat offspring exposed to GBHs in utero and via lactation from dams given slightly-contaminated water (Cattani et al. 2017). The dopamine pathway was found to be altered in mouse brains after chronic exposure to RoundUp® (Ait Bali et al. 2017). In these hosts, there was a decrease in brain levels of tyrosine hydroxylase, the enzyme allowing the production of the dopamine precursor 3,4-dihydroxyphenylalanine (L-DOPA). After chronic or sub-chronic exposure, the brains of treated mice displayed decreased levels of serotonin (Ait Bali et al. 2017). This induced anxiety and depression-like behaviors also seem linked to gut microbiota dysbiosis (Ait Bali et al. 2018). Altogether, these studies suggest a causal effect of GBHs on the induction of anxiety and depression-like behaviors, at least in rodents.