Allosteric modulation of dopamine D2 receptors by homocysteine

It has been suggested that L-DOPA-induced hyperhomocysteinemia can increase the risk of stroke, heart disease, and dementia and is an additional pathogenetic factor involved in the progression of Parkinson's disease. In Chinese hamster ovary (CHO) cells stably cotransfected with adenosine A(2A) and dopamine D2 receptors, homocysteine selectively decreased the ability of D2 receptor stimulation to internalize adenosine A(2A)-dopamine D2 receptor complexes. Radioligand-binding experiments in the same cell line demonstrated that homocysteine acts as an allosteric D2 receptor antagonist, by selectively reducing the affinity of D2 receptors for agonists but not for antagonists. Mass spectrometric analysis showed that, by means of an arginine (Arg)-thiol electrostatic interaction, homocysteine forms noncovalent complexes with the two Arg-rich epitopes of the third intracellular loop of the D2 receptor, one of them involved in A(2A)-D2 receptor heteromerization. However, homocysteine was unable to prevent or disrupt A(2A)-D2 receptor heteromerization, as demonstrated with Fluorescence Resonance Energy Transfer (FRET) experiments in stably cotransfected HEK cells. The present results could have implications for Parkinson's disease.     

Intracisternal administration of cholecystokinin-8 counteracts the central cardiovascular effects of adrenaline and NPY. A study based on the coexistence of cholecystokinin, phenylethanolamine N-methyltransferase and neuropeptide Y immunoreactivity in neurons of the nucleus tractus solitarius

(1) In the present study the occlusion method was employed to evaluate the overall coexistence of neuropeptide Y and phenylethanolamine-N-methyl transferase, neuropeptide Y and tyrosine hydroxylase as well as cholecystokinin and phenylethanolamine-N-methyl transferase immunoreactivity in nerve cell bodies of the dorsal subnuclei of the nucleus tractus solitarius of the male rat. A high degree of coexistence was established for neuropeptide Y/phenylethanolamine-N-methyl transferase, cholecystokinin/phenylethanolamine-N-methyl transferase and for tyrosine hydroxylase/neuropeptide Y immunoreactivity. (2) Sulfated [¹²I]cholecystokinin-8 was used as radioligand to study the densities of cholecystokinin-8 binding sites in the dorsal medulla oblongata by means of quantitative receptor autoradiography. High densities of binding sites were observed in parts of the nucleus tractus solitarius and in the area postrema. Labeling was also observed in the dorsal motor nucleus of the vagus. (3) In the physiological studies adrenaline (0.15–1.0 nmol), neuropeptide Y (0.075–0.75 nmol) and sulfated cholecystokinin-8 (0.3–3.0 nmol) were administered alone or in combination with neuropeptide Y or adrenaline intracisternally into -chloralose anaesthetized male rats. Especially the hypotensive and bradycardic responses of adrenaline were counteracted in the adrenaline/cholecystokinin co-treated animals, whereas the cardiovascular effects of neuropeptide Y when co-administered with cholecystokinin-8 (0.3 nmol) appeared to be more resistant to the antagonistic effect of cholecystokinin 8. In addition, cholecystokinin-8 further enhanced the neuropeptide Y-induced bradynpnea and increase in the tidal volume.

The present results indicate the existence of neuropeptide Y, adrenaline and cholecystokinin-8 immunoreactivity in the same neurons of the dorsal subnuclei of the nucleus tractus solitarius. Furthermore, binding sites for cholecystokinin-8 seem to at least partly co-distribute with -2 adrenergic and neuropeptide Y binding sites in the nucleus tractus solitarius. In the functional analysis, an antagonistic interaction between cholecystokinin-8 and adrenaline as well as between cholecystokinin and neuropeptide Y is demonstrated opening up the possibility that cholecystokinin peptides act as intrinsic modulators in the putative cholecystokinin/neuropeptide Y/adrenaline synapses in the nucleus tractus solitarius.     

Cerebrospinal nematodiasis in a moose in Norway

A case of cerebrospinal nematodiasis in a young adult moose (Alces alces) from Telemark county, southeastern Norway, is described. The moose was found by bird hunters during January, displaying signs of severe posterior paresis. It was killed and submitted for autopsy. The carcass was emaciated, and there were skin excoriations and subcutaneous edema over both metacarpi. Histopathologic examination revealed traumatic malacia throughout the spinal cord and meningeal accumulations of mononuclear inflammatory cells and eosinophils in brain and spinal cord. Two adult female nematodes were found in sections, respectively, of the subarachnoid and subdural spaces of the thoracic spinal cord. The nematode cross sections were similar with those of the two neurotropic Elaphostrongylus species, E. rangiferi and E. cervi. The moose originated from an area overlapping the grazing area of a large population of wild reindeer (Rangifer tarandus tarandus) living on the mountain plateau of Hardangervidda, suggesting the moose was infected with E. rangiferi from reindeer.     

Plasmids required for utilization of molecular hydrogen by Alcaligenes eutrophus

Alcaligenes eutrophus and three other hydrogen bacteria exposed to plasmid-curing agents generated autotrophic-minus mutants at high frequency. These mutants were blocked in the metabolism of H₂ as an energy source and had normal levels of enzymes involved in CO₂ fixation. The loss of hydrogenase activity in A. eutrophus was accompanied by the loss or alteration of a plasmid that had molecular weight of approximately 200×10⁶. Mobilization of this plasmid from wild-type A. eutrophus strains into cured hydrogenase-minus derivatives restored hydrogenase function. It is concluded that A. eutrophus contains a large plasmid required for hydrogen metabolism and thereby autotrophic growth.Abbreviations Aut autotrophic - Hup hydrogen uptake - NTG N-methyl-N-nitro-N-nitrosoguanidine - RuBP ribulose bisphosphate - RuMP ribulose monophosphate - Kan kanamycin - Nal nalidixic acid - Rif rifampicin - Tet tetracycline     

Evidence of Spread of the Emerging Infectious Disease, Finch Trichomonosis, by Migrating birds

Finch trichomonosis emerged in Great Britain in 2005 and led to epidemic mortality and a significant population decline of greenfinches, Carduelis chloris and chaffinches, Fringilla coelebs, in the central and western counties of England and Wales in the autumn of 2006. In this article, we show continued epidemic spread of the disease with a pronounced shift in geographical distribution towards eastern England in 2007. This was followed by international spread to southern Fennoscandia where cases were confirmed at multiple sites in the summer of 2008. Sequence data of the ITS1/5.8S/ITS2 ribosomal region and part of the small subunit (SSU) rRNA gene showed no variation between the British and Fennoscandian parasite strains of Trichomonas gallinae. Epidemiological and historical ring return data support bird migration as a plausible mechanism for the observed pattern of disease spread, and suggest the chaffinch as the most likely primary vector. This finding is novel since, although intuitive, confirmed disease spread by migratory birds is very rare and, when it has been recognised, this has generally been for diseases caused by viral pathogens. We believe this to be the first documented case of the spread of a protozoal emerging infectious disease by migrating birds.     

Influence of chitosan structure on the formation and stability of DNA-chitosan polyelectrolyte complexes

The interactions between DNA and chitosans varying in fractional content of acetylated units (FA), degree of polymerization (DP), and degree of ionization were investigated by several techniques, including an ethidium bromide (EtBr) fluorescence assay, gel retardation, atomic force microscopy, and dynamic and electrophoretic light scattering. The charge density of the chitosan and the number of charges per chain were found to be the dominating factors for the structure and stability of DNA-chitosan complexes. All high molecular weight chitosans condensed DNA into physically stable polyplexes; however, the properties of the complexes were strongly dependent on FA, and thereby the charge density of chitosan. By employing fully charged oligomers of constant charge density, it was shown that the complexation of DNA and stability of the polyplexes is governed by the number of cationic residues per chain. A minimum of 6-9 positive charges appeared necessary to provide interaction strength comparable to that of polycations. In contrast, further increase in the number of charges above 9 did not increase the apparent binding affinity as judged from the EtBr displacement assay. The chitosan oligomers exhibited a pH-dependent interaction with DNA, reflecting the number of ionized amino groups. The complexation of DNA and the stability of oligomer-based polyplexes became reduced above pH 7.4. Such pH-dependent dissociation of polyplexes around the physiological pH is highly relevant in gene delivery applications and might be one of the reasons for the high transfection activity of oligomer-based polyplexes observed.     

Thromboxane A2: Effects of airway and vascular smooth muscle

Thromboxane A₂, an unstable compound derived from prostaglandin G₂, weas generated by incubation of arachidonic acid with a suspension of human platelets. The activity of thromboxane A₂ relative to that of prostaglandin H₂ in causing contractions of a number of smooth muscle organs were as follows: rabbit aorta, 7–20; human umbilical artery, 9–60; and guinea pig trachea, 2–12. Intravenous injection of thromboxane A₂ into anaesthetized guniea pigs was followed by a pronouced increase in the tracheal insufflation pressure, potency compared to prostaglandin H₂, 31–45.     

Subjective symptoms among mobile phone users—A consequence of absorption of radiofrequency fields?

In a previous epidemiological study, where we studied the prevalence of subjective symptoms among mobile phone (MP) users, we found as an interesting side finding that the prevalence of many of the subjective symptoms increased with increasing calling time and number of calls per day. In this extrapolative study, we have selected 2402 people from the epidemiological study who used any of the four most common GSM MP. We used the information about the prevalence of symptoms, calling time per day, and number of calls per day and combined it with measurements of the Specific Absorption Rate (SAR). We defined three volumes in the head and measured the maximum SAR averaged over a cube of 1 g tissue (SAR(1g)) in each volume. Two new exposure parameters Specific Absorption per Day (SAD) and Specific Absorption per Call (SAC) have been devised and are obtained as combinations of SAR, calling time per day, and number of calls per day, respectively. The results indicates that SAR values >0.5 W/kg may be an important factor for the prevalence of some of the symptoms, especially in combination with long calling times per day.