Mediation of serotonin-induced analgesia by the 5HT2 receptor in the pentobarbital anesthetized mouse model

Serotonin can induce analgesia when injected directly into the brain, but analgesia after peripheral administration has been more difficult to show. The pentobarbital anesthetized mouse (PAM) model, developed to alleviate some of the problems involved in the measurement of tail flick latency, was used to assess the action of peripherally administered serotonin. Mice were anesthetized with about 65 mg/kg of sodium pentobarbital IP and their tail flick latencies measured while they were in stage III anesthesia. In these anesthetized mice, IP serotonin induced a significant analgesia that was much more robust than that found in awake mice. The analgesic effect was dose-dependent from 0.25 mg/kg to 10 mg/kg but was not blocked by the antiopiate naltrexone. Of several psychotropic agents tested, only amitriptyline, mianserin, and trazodone had significant effects on analgesia in the PAM model. The analgesic effect of serotonin was reproduced by the 5HT2 agonist DOI and totally blocked by the 5HT2 antagonist NPP. These results show the utility of the PAM model in studying nonopiate analgesia and suggest that the analgesic action of serotonin is mediated primarily through the 5HT2 receptor.     

��-Synuclein Expression in Rat Substantia Nigra Suppresses Phospholipase D2 Toxicity and Nigral Neurodegeneration

We present genetic evidence that an in vivo role of α-synuclein (α-syn) is to inhibit phospholipase D2 (PLD2), an enzyme that is believed to participate in vesicle trafficking, membrane signaling, and both endo- and exocytosis. Overexpression of PLD2 in rat substantia nigra pars compacta (SNc) caused severe neurodegeneration of dopamine (DA) neurons, loss of striatal DA, and an associated ipsilateral amphetamine-induced rotational asymmetry. Coexpression of human wild type α-syn suppressed PLD2 neurodegeneration, DA loss, and amphetamine-induced rotational asymmetry. However, an α-syn mutant defective for inhibition of PLD2 in vitro also failed to inhibit PLD toxicity in vivo. Further, reduction of PLD2 activity in SNc, either by siRNA knockdown of PLD2 or overexpression of α-syn, both produced an unusual contralateral amphetamine-induced rotational asymmetry, opposite to that seen with overexpression of PLD2, suggesting that PLD2 and α-syn were both involved in DA release or reuptake. Finally, α-syn coimmunoprecipitated with PLD2 from extracts prepared from striatal tissues. Taken together, our data demonstrate that α-syn is an inhibitor of PLD2 in vivo, and confirm earlier reports that α-syn inhibits PLD2 in vitro. Our data also demonstrate that it is possible to use viral-mediated gene transfer to study gene interactions in vivo.     

In Vivo Toxicity of Intravenously Administered Silica and Silicon Nanoparticles

Both silicon and silica nanoparticles (SiNPs and SiO₂NPs, respectively) are currently considered to be promising carriers for targeted drug delivery. However, the available data on their in vivo toxicity are limited. The present study was aimed at investigation of SiNP and SiO₂NP (mean diameter 10 and 13 nm, respectively) toxicity using both morphological and functional criteria. Hematological and biochemical parameters were assessed in Sprague-Dawley rats 5, 21 and 60 days after administration of NPs. Inner ear function was determined using otoacoustic emission testing at 21 and 60 days after infusion of NPs. Furthermore, the histological structure of liver, spleen and kidney samples was analyzed. Intravenous infusion of SiNPs or SiO₂NPs (7 mg/kg) was not associated with significant changes in hemodynamic parameters. Hearing function remained unchanged over the entire observation period. Both inter- and intragroup changes in blood counts and biochemical markers were non-significant. Histological findings included the appearance of foreign body-type granulomas in the liver and spleen as well as microgranulation in the liver after administration of NPs. The number of granulomas was significantly lower after administration of SiNPs compared with SiO₂NPs. In conclusion, both tested types of NPs are relatively biocompatible nanomaterials, at least when considering acute toxicity.     

Accumulation in “normal” lungs of live tumorigenic cells during sub-cutaneous growth of weakly and highly metastasizing tumors and their In vitro sensitivity to growth regulation by normal fibroblasts

The main purposes of the study were: (I) in vivo comparison of accumulation of live tumorigenic cells (LTC) in macroscopcally normal lungs of animals bearing 6 s.c. Syrian hamster sarcomas differing in spontaneous metastasizing activity (SMA); (2) in vitro examination of the sensitivity of these cell strains to the growth-regulating signals of normal fibroblasts. Cell strains used differed in SMA from very weak (WM) to extremely high (HM). The numbers of LTC doses in “normal” lung tissue of tumorbearing animals were determined in s.c. transplantation tests by titrating single-cell suspensions prepared from the lung tissues of 5 tumor-bearing animals, for each cell strain, every 5 days during 30 days of s.c. tumor growth, until the appearance of the first spontaneous lung metastases. The sensitivity of WM and HM cells to growth-regulating signals of normal hamster embryo fibroblasts (HEFs) was examined by in vitro co-culturing during 6 days with daily determination of ³H-TdR incorporation in the WM and HM cells grown with or without contact with HEFs. The data presented demonstrate (I) the surprisingly similar efficiency in the occupation of macroscopically normal lung tissues by live tumorigenic cells of WM and HM strains, disseminating spontaneously from the s.c. tumors; (2) the significantly lower sensitivity of HM cells, in contrast to WM, to growth inhibition by contact with HEFs and especially their marked ability to usurp the growth-stimulating signals of normal HEFs. © 1994 Wiley-Liss, Inc.     

A mouse model for Sorsby fundus dystrophy

PURPOSE: Sorsby fundus dystrophy (SFD) is a rare, late-onset macular dystrophy caused by mutations in the tissue inhibitor of metalloproteinases-3 (TIMP3) gene. The known mutations introduce potentially unpaired cysteine residues in the C terminus of the protein and result in the formation of higher-molecular-weight protein complexes of as yet unknown composition and functional consequences in the pathologic course of SFD. To facilitate in vivo investigation of mutant TIMP3, the authors generated a knock-in mouse carrying a disease-related Ser156Cys mutation in the orthologous murine Timp3 gene. METHODS: Site-directed mutagenesis and homologous recombination in embryonic stem (ES) cells was used to generate mutant ES cells carrying the Timp3(S156C) allele. Chimeric animals were obtained, of which two displayed germline transmission of the mutated allele. Molecular genetic, biochemical, electron microscopic, and electrodiagnostic techniques were used for characterization. RESULTS: At 8 months of age, knock-in mice showed abnormalities in the inner aspect of Bruch's membrane and in the organization of the adjacent basal microvilli of the retinal pigment epithelium (RPE). Changes resembling those in the mutant animals were also present to some extent in normal littermates, but only at an advanced age of 30 months. Long-term electrodiagnostic recordings indicated normal retinal function throughout life. The biochemical characteristics of the mutant protein appear similar in humans and knock-in mice, suggesting common molecular pathways in the two species. The localization of the mutant protein in the eye is normal, although there is evidence of increased Timp3 levels in Bruch's membrane of mutant animals. CONCLUSIONS: The knock-in mice display early features of age-related changes in Bruch's membrane and the RPE that may represent the primary clinical manifestations of SFD. In addition, our immunolabeling studies and biochemical data support a model proposing that site-specific excess rather than absence or deficiency of functional Timp3 may be the primary consequence of the known Timp3 mutations.     

Genetic characterization of hantaviruses transmitted by the Korean field mouse (Apodemus peninsulae), Far East Russia

In an epizootiologic survey of 122 rodents captured in Vladivostok, Russia, antibodies positive for hantavirus were found in Apodemus peninsulae (4/70), A. agrarius (1/39), and Clethrionomys rufocanus (1/8). The hantavirus sequences identified in two seropositive A. peninsulae and two patients with hemorrhagic fever with renal syndrome (HFRS) from the Primorye region of Far East Russia were designated as Solovey and Primorye, respectively. The nucleotide sequences of the Solovey, Primorye, and Amur (obtained through GenBank) sequences were closely related (>92% identity). Solovey and Primorye sequences shared 84% nucleotide identity with the prototype Hantaan 76-118. Phylogenetic analysis also indicated a close relationship between Solovey, Primorye, Amur, and other viruses identified in Russia, China, and Korea. Our findings suggest that the Korean field mouse (A. peninsulae) is the reservoir for a hantavirus that causes HFRS over a vast area of east Asia, including Far East Russia.