Inhibition of interferon-gamma-mediated activation in mouse macrophages treated with lipoarabinomannan.

Lipoarabinomannan (LAM), purified from the cell walls of Mycobacterium leprae and M. tuberculosis, is a potent inhibitor of interferon-gamma (IFN-gamma) mediated activation of macrophages. The capability of LAM to inhibit IFN-gamma activation of macrophages in vitro was dose dependent and required a 24-h pre-exposure. Defective activation was evident as a block in IFN-gamma-induced cytocidal activity for tumour cell targets and microbicidal capacity for intracellular Toxoplasma gondii. Additionally, LAM treatment blocked the induction of surface Ia antigens on peritoneal macrophages by IFN-gamma. The requirement for pretreatment with LAM was further substantiated by the finding that peritoneal macrophages that were activated in vivo were not affected by LAM treatments and retained full microbicidal function. However, once inhibited by LAM treatment in vitro, macrophages remained fully refractory to IFN-gamma activation for up to 5 days in culture. Inhibition of IFN-gamma activation in macrophages treated with LAM was not overcome by 100-fold increases in the dose of IFN-gamma used or by a constant dose of IFN-gamma in combination with 100-fold increases in the level of endotoxin used to trigger cytotoxic activity. The defect in IFN-gamma unresponsiveness was not due to altered receptor function, as control and LAM-treated macrophages showed similar capacity to bind, internalize, and digest radiolabelled IFN-gamma. Based on the in vitro findings reported here, the inhibition of IFN-gamma-mediated macrophage activation by exposure to LAM may contribute to defective macrophage function observed in lepromatous granulomas and thus constitutes an important aspect of pathogenesis in mycobacterioses.     

Inhibition of lethality in endotoxin-challenged mice treated with zinc chloride.

Zinc chloride protected against lethality in mice undergoing endotoxin shock.     

Experimental tick-borne encephalitis in golden hamsters treated with specific immunotherapy

Efficiency of various protocols of specific immunoglobulin treatment was evaluated in golden hamsters inoculated with two Far Eastern tick-borne encephalitis (TBE) strains. After a low therapeutic dose (0.1 ml) of immunoglobulin, corresponding to total dose (60 ml) per course, all parameters (survival, immunogenicity, pathomorphology of the brain) deteriorated in animals infected with both strains. A higher dose (0.2 ml) corresponding to total dose of 120 ml notably improved all the studied parameters. The efficiency of specific immunoglobulin depends on the clinical and pathogenetic characteristics of TBE, determined by the properties of TBE strains. The results validate therapy and prevention of TBE by high-titer immunoglobulin in adequate total dose, monitored by blood analyses for TBE antigen and evaluations of the time course of IgM antibodies.     

Inhibition of experimental tumor growth in hamsters by small direct currents.

The effect of three electric current levels (3 mamp, 500 micronamp, and 960 mmicronamp) on the growth of A-Mel-4 tumor was evaluated in hamsters as a mode of therapy. Direct current (dc) was applied for one hour a day from the third to sixth posttumor implant day by the introduction of a shielded point electrode directly into the tumor site. Tumor growth was inhibited, and metastases were reduced in the exposed animals. The higher dl levels produced necrosis in the tumors, and in several animals, the implantation site tumor was completely destroyed. These effects were most pronounced with the positive electrode.     

Water intake of Djungarian and Syrian hamsters treated with various dipsogenic stimuli

Djungarian and Syrian hamsters were found to exhibit robust water intake following water deprivation, and in response to hyperosmotic and hypovolumetric challenges to body fluids following injections of hypertonic NaCl and polyethylene glycol, respectively. Water intake was not stimulated following peripheral injections of isoproterenol, serotonin, or angiotensins II or III. Both hypovolema and isoproterenol activated the renin-angiotensin system. This profile of drinking responses in hamsters is similar to that reported previously for mice and degus.     

Impaired morphological development of the dorsal cochlear nucleus in hamsters treated postnatally with alpha-difluoromethylornithine

The dorsal cochlear nucleus is a highly organized nucleus in the auditory system in which the ramifications of depletion of specific cell types during development can be studied. Granule cells, small interneurons that are located in all layers of the DCN in the adult hamster, proliferate postnatally and are, therefore, potentially vulnerable to anti-mitotic agents that are administered after birth. The present experiments describe the effects of alpha-difluoromethylornithine, a drug that inhibits proliferation of cerebellar granule cells, on the granule cells in the dorsal cochlear nucleus. As in the cerebellum, the density of granule cells in the dorsal cochlear nucleus is reduced after alpha-difluoromethylornithine treatment. In hamsters treated with alpha-difluoromethylornithine (200 or 500 mg/kg subcutaneously (s.c.), twice daily on postnatal days 4-14), the numerical density of granule cells was reduced in the superficial dorsal cochlear nucleus at 15 days; by 40 days this effect was also apparent in the deep layer, suggesting that cells located superficially that would have migrated into the deep dorsal cochlear nucleus had either failed to develop or did not arrive at their final location. This evidence suggests that the cells normally migrate down from the superficial proliferative zone into the deeper layers. In the drug-treated animals, a layer of mixed granule cells and fusiform cells was thinner than in controls probably due to the reduction in interspersed granule cells since the number of fusiform cells was unaffected. There was also a dose-dependent effect on cell growth; fusiform cells were affected at both doses, while giant cells were only affected at the highest dose. Granule cells form a major input to the fusiform cells and their depletion may account for some of the effects on fusiform cell growth. There could also be additional direct actions of alpha-difluoromethylornithine on this population.     

Enhanced sprouting of retinotectal fibers after early superior colliculus lesions in hamsters treated with gangliosides

Summary The effects of exogenous gangliosides on sprouting of optic tract axons was studied in hamsters which, after a right tectal lesion on the day after birth (P1), had an abnormal retinotectal projection from the left eye to the left superior colliculus (SC). Sprouting of these axons was induced by removing the competing input by right eye removal on postnatal day 9 (P9). Intraperitoneal G_M1, given daily and started on P9, significantly stimulated the sprouting response. This was demonstrated by Fink-Heimer silver staining of anterograde axonal degeneration three days after the left eye was removed on P36. Terminal fields in the left SC were, in average, twice as large compared to controls. An estimate of the total number of terminals (silver stained particles) revealed a value of 7.9×10⁶ for G_M1 and 3.2×10⁶ for control hamsters, respectively. Diencephalic structures which also receive collateral input from the sprouting optic tract did not show any alterations in the size of the terminal field due to G_M1-treatment, suggesting that, in vivo, gangliosides fail to initiate sprouting in areas that have not previously been denervated. Unexpectedly, G_M1-treated hamsters also had significantly smaller right SC damage and less left damage near the midline. Subsequent reanalysis of the data based on a lesion-matching procedure indicates that effects on reducing atrophy were independent of the G_M1-enhanced sprouting of retinofugal axons. These findings provide the first direct evidence that exogenous G_M1 stimulates lesion-induced axon sprouting in the mammalian brain.     

CD10/neutral endopeptidase inhibition augments pulmonary neuroendocrine cell hyperplasia in hamsters treated with diethylnitrosamine and hyperoxia.

In previous studies, we demonstrated that pulmonary neuroendocrine cell (PNEC) hyperplasia in hamsters treated with diethylnitrosamine (DEN) plus 65% hyperoxia (DEN/O2) reflects predominantly neuroendocrine cell differentiation. Several peptides implicated in non-neoplastic PNEC hyperplasia are hydrolyzed by CD10/neutral endopeptidase 24.11 (CD10/NEP), an enzyme known to downregulate neurogenic inflammation of the lung by modulating locally effective concentrations of multiple bioactive peptides. In fetal mice, we observed that CD10/NEP inhibition by SCH32615 potentiates cell proliferation and type II cell differentiation in the lung in utero. Further, CD10/NEP messenger RNA levels parallelled relative PNEC numbers in DEN/O2-treated hamster lung, suggesting that the enzyme might mediate spontaneous regression of PNEC hyperplasia. The goals of the present study were: (1) to determine whether CD10/NEP inhibition would alter the extent of PNEC hyperplasia occurring in these hamsters, and (2) to analyze cellular mechanisms potentially involved in altering numbers of PNECs in this model. We administered SCH32615 chronically to a subset of DEN/O2-treated hamsters. Immunostaining of lungs from the CD10/ NEP-inhibited subset demonstrated significant acceleration of the development of PNEC hyperplasia, increased PNEC proliferation, and diminished PNEC apoptosis as compared with animals receiving no SCH32615. These observations indicate that PNEC hyperplasia can occur as a result of multiple cellular processes, including increased neuroendocrine cell differentiation, proliferation, and survival. CD10/NEP modulates PNEC numbers primarily by promoting cell differentiation and proliferation during lung injury, probably via increasing the half-life of bioactive peptides in the lung.     

Intestinal amyloidosis in hamsters with visceral leishmaniasis.

Thirty hamsters about 10 weeks old were inoculated intraperitoneally with Leishmania donovani amastigotes and were serially killed after 15, 30, 45, 60, 75 and 85-90 days. Both the small and large intestines were examined grossly, and the histopathology was assessed by light and electron microscopy. The lamina propria and the submucosa of the whole length of the intestinal tract showed a progressive deposition of amyloid, selectively identified by optical and ultrastructural techniques. The presence of amyloid fibrils in the cytoplasm of plasma cells suggests that appearance of intestinal amyloidosis during visceral leishmaniasis may be the result of a pathological dysfunction of these cells. In addition to these deposits, the presence of inflammatory infiltrates containing lymphocytes, plasmocytes and macrophages confirmed the establishment of leishmaniasis. In the end-stages of the infection both vacuolar degeneration of the epithelial cells lining the lumen of the intestine and a moderate hyperplasia of lymphatic nodules was observed.     

Inability of immune cells treated with anti-thymocyte serum to confer on hamsters resistance to cutaneous infection with Treponema pertenue.

The mechanism by which hamsters acquire resistance to yaws or frambesia is poorly understood. This investigation has shown that immune lymphoid cells (spleen and lymph node) could confer on hamsters resistance to infection with Treponema pertenue. Treatment of these immune cells with a specific antithymocyte serum (ATS) inhibited the transfer of resistance. Twenty-one days after infection, recipients of immune cells treated with ATS had cutaneous lesions, in contrast to recipients of immune cells treated with normal rabbit serum. Treatment of immune cells with ATS, however, did not completely abolish resistance to treponemal infection. The weight and number of treponemes in the lymph nodes of recipients were significantly lower than those infused with normal cells treated with ATS or normal rabbit serum. The specificity of the ATS was demonstrated by its failure to inhibit functional antibody-producing cells and its high cytotoxic activity for thymocytes. These results present direct evidence that ATS-sensitive cells are involved in resistance to frambesial infection.     

Inhibition of antibody responses by cells from mice treated with picryl sulphonic acid.

Cells from mice inoculated with picryl sulphonic acid (PSA cells), which contain suppressor T cells for contact sensitivity to picryl chloride, were examined for their ability to alter antibody responses of normal mice. These cells did not influence antibody or plaque-forming cell (PFC) production accompanying contact sensitivity reactions produced by painting with picryl chloride but reduced IgG antibody and indirect PFC responses to conjugates of trinitrophenyl (TNP) bovine serum albumin and ovalbumin. IgG responses to TNP or new antigenic determinants of TNP-mouse serum albumin were not affected by PSA cells. The PSA cells required several weeks to produce reductions of responses and only reduced responses to optimal doses of antigen. When the injection of antigen was delayed until several weeks after the injection of PSA cells rapid reductions of responses were found but these were short-lived. The inhibition was specific for TNP proteins although responses to hapten and carrier were reduced. Evidence is presented to show that the inhibition was mediated by an adherent macrophage-like cell rather than a T cell. The inhibitory activity was resistant to irradiation and anti-theta treatment but was removed by glutaraldehyde treatment and cotton wool filtration.     

Inhibition of pancreatic hepatocyte induction in hamsters treated sequentially with ethionine, a protein-free diet and then methionine by prior N-nitrosobis-(2-oxopropyl)amine administration

A 100% yield of pancreatic hepatocytes was induced in pancreas tissues of female hamsters treated with twice-repeated sequential administrations of DL-ethionine (ethionine) together with a protein-free diet and then L-methionine (methionine) for 10 weeks. The cells were also found in 40% of hamsters receiving 20 mg/kg body weight of the pancreatic carcinogen, N-nitrosobis(2-oxopropyl)amine (BOP) given twice at the peak of pancreatic regeneration stimulated by methionine after ethionine-induced cell damage. However, BOP at doses of 30, 70, and 100 mg/kg body weight administered before the occurrence of pancreatic regeneration dose-dependently inhibited their appearance, with reduction of the yield to 40%, 25%, and 8.3% respectively, and BOP per se did not induce any development of pancreatic hepatocytes. Stein iodine staining revealed bile pigments in the induced hamster pancreatic eosinophilic cell populations.     

Species differences in mutagenicity testing. II. Sister-chromatid exchange and micronucleus induction in rats, mice and Chinese hamsters treated with cyclophosphamide

Comparative investigations of sister-chromatid exchange (SCE)and micronucleus induction in the bone marrow of rats, miceand Chinese hamsters with the cytostatic alkylating mutagencyclophosphamide (CP) revealed remarkable species differencesin their mutagenic responses. With both test systems the sensitivitiesof the three species can be ranked into the order rat > mouse> Chinese hamster. More explicit results were obtained withthe SCE test than with the micronucleus test within the samedose range. This may be due to the influence of species-relateddifferences in the cytotoxic response to CP in the micronucleustest. These results show that clearly different mutagenic responsesin different test species may be obtained in standard assayseven with a compound which is metabolized in a very similarmanner in all animal species.     

Experimental cryptosporidiosis in hamsters.

A new laboratory animal model for experimental cryptosporidiosis is described. Adult immunosuppressed hamsters were infected per os with 0.5 x 10(5) and 1 x 10(5) Cryptosporidium oocysts of calf origin. The mean numbers of oocysts shed per gram of feces per day and the patterns of infection are described. The susceptibility to Cryptosporidium infection, the total number of oocysts shed (a thousand times the infective dose), and the ease of handling in laboratory conditions make hamsters a good animal model for cryptosporidiosis.     

Inhibition of progesterone production in human luteinized granulosa cells treated with LXR agonists

Progesterone production by luteal cells is dependent on the supply of cholesterol by lipoproteins. The aim of this study was to determine whether the liver X receptors (LXRs) contribute to cholesterol homeostasis and progesterone secretion in human luteinized granulosa cells. Cells were isolated from follicular aspirates of patients undergoing in vitro fertilization. Luteinization was induced by a 7-day treatment with human chorionic gonadotrophin. LXR beta was expressed at higher levels than LXR alpha in granulosa cells and its expression was increased during luteinization. Treatment of luteinized granulosa cells by LXR agonists induced a significant time- and dose-dependent reduction in progesterone secretion (50% reductions after a 7-day treatment with 1-microM of either GW3965 or T0901317). mRNA levels of steroidogenic genes including steroidogenic acute regulatory protein and P450 side-chain cleavage were only moderately affected by LXR activation, with a significant reduction that was observed at 10 microM agonist concentration. Cellular cholesterol was markedly reduced after treatment with LXR agonists as a result of an increased cholesterol efflux that was related to the induction of LXR target genes (ABCA1, ABCG1, apo E, PLTP). Our study identifies LXRs as new, key actors contributing to regulation of cholesterol metabolism and steroidogenesis in luteinized granulosa cells.     

Altered retinotectal topography in hamsters with neonatal tectal slits.

Alterations in normal retinotectal topography by mechanical disruption of fiber passage during development was studied in Syrian hamsters using both neuroanatomical and electrophysiological techniques. The mechanical block to fiber passage was created with a medial to lateral slit across the superior colliculus on the day of birth. At maturity, topographically aberrant projections were found in areas of residual scar tissue. These aberrant projections were synaptically functional, producing neurons with mutiple, spatially separated visual receptive fields.No evidence was found for an orderly compression of the retinotopic map in the tectum consequent to the transitory blockage of fiber passage.     

Inhibition of Cryptosporidium infection in mice treated with a cyclodextrin inclusion complex with diloxanide furoate

The efficacies of diloxanide furoate, beta-cyclodextrin and a cyclodextrin inclusion complex against Cryptosporidium parvum were evaluated in a suckling murine model. Efficacy was established by numbers of oocysts recovered from the intestinal tract of mice on day 7 postinfection. The level of infection in treated mice was significantly lower than in control mice and, surprisingly, the most efficacious treatment was beta-cyclodextrin, an excipient used in pharmaceutical technology.     

Testicular amyloidosis in hamsters experimentally infected with Leishmania donovani.

Thirty hamsters were inoculated intraperitoneally with Leishmania donovani. Testes were examined grossly and histologically by light and electron microscopy. Progressive testicular atrophy developed. Spermatogenic cells of the seminiferous tubules showed vacuolar degeneration and decreased in number leading to a total azoospermia in the final weeks of the pathological process. Lymphoplasmocytic infiltrates with macrophages containing leishmanias appeared in the intertubular space. Amyloid deposits in the intertubular space and tubular basement membrane were identified by optical and ultrastructural methods. It has been suggested that testicular amyloidosis may have a pathogenic mechanism related to a dysfunction of plasma cells and stimulation of the reticuloendothial system, due to the antigenic character of the parasite.