Brain histamine response to stress in 12 month old rats

The regional brain histamine regulation in response to stress was investigated in 12 month old Sprague-Dawley male rats. Air blast exposure (15 min) induced significant (26.5%) elevation in hypothalamic HA level; midbrain and cortical HA concentrations were not affected. Histamine methyltransferase activity was not altered by stress in any of the brain regions investigated. Plasma corticosterone levels of stressed rats were significantly elevated (6.5 fold). Hence, the response of hypothalamic HA to stress is still evident in 12 month old rats.     

Free radical scavengers vitamins A, C, and E plus magnesium reduce noise trauma

Free radical formation in the cochlea plays a key role in the development of noise-induced hearing loss (NIHL). The amount, distribution, and time course of free radical formation have been defined, including a clinically significant formation of both reactive oxygen species and reactive nitrogen species 7-10 days after noise exposure. Reduction in cochlear blood flow as a result of free radical formation has also been described. Here we report that the antioxidant agents vitamins A, C, and E act in synergy with magnesium to effectively prevent noise-induced trauma. Neither the antioxidant agents nor the magnesium reliably reduced NIHL or sensory cell death with the doses we used when these agents were delivered alone. In combination, however, they were highly effective in reducing both hearing loss and cell death even with treatment initiated just 1 h before noise exposure. This study supports roles for both free radical formation and noise-induced vasoconstriction in the onset and progression of NIHL. Identification of this safe and effective antioxidant intervention that attenuates NIHL provides a compelling rationale for human trials in which free radical scavengers are used to eliminate this single major cause of acquired hearing loss.     

Lack of a Precursor-Product Relationship Between Histamine and Its Metabolites in Brain After Histidine Loading

Abstract: Levels of histamine and its major metabolites in brain, tele -methylhistamine (t-MH) and tele -methylimidazoleacetic acid (t-MIAA), were measured in rat brains up to 12 h after intraperitoneal administration of l -histidine (His), the precursor of histamine. Compared with saline-treated controls, mean levels of histamine were elevated at 1 h (+ 102%) after a 500 mg/kg dose; levels of t-MH did not increase. Following a 1,000 mg/kg dose; levels mean histamine levels were increased for up to 7 h, peaked at 3 h, and returned to control levels within 12 h. In contrast, levels of t-MH showed a small increase only after 3 h; levels of t-MIAA remained unchanged after either dose. Failure of most newly formed histamine to undergo methylation, its major route of metabolism in brain, suggested that histamine was metabolized by another mechanism possibly following nonspecific decarboxylation. To test this hypothesis, other rats were injected with α-fluoromethylhistidine (α-FMHis; 75 mg/kg, i.p.), an irreversible inhibitor of specific histidine decarboxylase. Six hours after rats received α-FMHis, the mean brain histamine level was reduced 30% compared with saline-treated controls. Rats given His (1,000 mg/kg) 3 h after α-FMHis (75 mg/kg) and examined 3 h later had a higher (+112%) mean level of histamine than rats given α-FMHis, followed by saline. Levels of t-MH and t-MIAA did not increase. These results imply that high doses of His distort the simple precursor-product relationship between histamine and its methylated metabolites in brain. The possibility that some His may undergo nonspecific decarboxylation in brain after His loading is discussed. These findings, and other actions of His independent of histamine, raise questions about the validity of using His loading as a specific probe of brain histaminergic function.     

Inhibitors of Histamine Methylation in Brain Promote Formation of Imidazoleacetic Acid, Which Interacts with GABA Receptors

Abstract: In brain, the precursor of imidazoleacetic acid (IAA), a GABA_A agonist but a GABA_C antagonist, is not known. In the periphery, IAA derives from oxidation of histamine. But in brain, histamine is thought to be metabolized solely by histamine methyltransferase (HMT), forming tele -methylhistamine (t-MH) and tele -methylimidazoleacetic acid (t-MIAA). We showed that [³H]histamine (intracerebroventricularly) could be converted to IAA in brains of rats, a process increased by inhibition of HMT. This demonstrated that brain can oxidize histamine and suggested that endogenous histamine might also be oxidized if HMT activity were reduced. We examined, in rat cerebral cortex, effects of the following HMT inhibitors (mg/kg i.p.): metoprine (10), tacrine (10), velnacrine (10, 30), and physostigmine (1, 2). Tacrine was a potent inhibitor ( K _i∼ 22 n M ). To measure histamine in tissue that contained HMT inhibitors, we developed a gas chromatography-mass spectrometry method. After 2 h, all drugs reduced endogenous levels of t-MH and t-MIAA and increased levels of histamine and IAA. Our results show that inhibition of HMT promotes oxidation of histamine in brain, probably by shunting histamine to an alternative metabolic pathway. Formation of IAA provides a novel interaction between histaminergic and GABAergic systems in brain. Accumulation of IAA should be considered when inhibitors of HMT are used to probe brain histamine function.     

Die Theorie der Rhegmatypie

Ohne ZusammenfassungMit 4 Figuren und 2 TabellenDie folgenden Erörterungen wurden im Wesentlichen 1920 niedergeschrieben als Teil einer umfassenderen Studie. Da es späterhin zweckmässiger erschien, die einzelnen Teile gesondert zu veröffentlichen, möge nun auch dieser Abschnitt in gekürzter Form den anderen folgen.     

Fatty acid composition of six freshwater wild cyanobacterial species

Hydroxy, n-saturated, branched, dioic, and unsaturated fatty acids in six freshwater wild cyanobacteria (Chroococcus minutus, Lyngbya ceylanica, Merismopedia glauca, Nodularia sphaerocarpa, Nostoc linckia, and Synechococcus aeruginosus) collected from different lakes and springs of Israel have been identified by gas chromatography-mass spectrometry (GC-MS).     

Sterol compositions of the filamentous nitrogen-fixing terrestrial cyanobacterium Scytonema sp

Thirteen unsaturated sterols were identified by gas chromatography--mass spectrometry using serially-coupled capillary columns from the filamentous nitrogen-fixing terrestrial cyanobacterium Scytonema sp. isolated from the microbial community of cyanobacterial on 'Black Cover' biofilms limestone walls in Jerusalem. The dominant sterols were cholest-5-en-3 beta-ol (18.9%), 3 beta-methoxycholest-5-ene (16.2%) and 3 beta-acetoxycholest-5-ene (11.2%).