Effect of heat shock on neuronal cultures: importance of protein synthesis and HSP72 induction for induced tolerance and survival

In this study the effects of 30 min heat-shock, ranging from 42 degrees C to 46 degrees C, on survival, protein synthesis and HSP72 expression were investigated in primary rat neuronal cultures. Heat-shock of 44 degrees C resulted in a complete, but transient inhibition of protein synthesis which recovered within 24 h. 46 degrees C heat-shock resulted in an irreversible inhibition of protein synthesis and complete neuronal loss within 24 h. Cycloheximide treatment of neuronal cultures resulted in aggravation of neuronal cell damage after heat-shock of 44 degrees C, indicating that the capacity for recovery of the overall protein synthesis is an important survival factor. In addition, the reduction of neuronal cell damage mediated by heat conditioning was abolished by cycloheximide treatment, indicating that the function of new proteins is important for induced thermotolerance. Induction of the strictly inducible member of the heat-shock protein 70kDa family, HSP72, was found in those few astrocytes which were contaminating the neuronal cell cultures, but not in neurons. These results indicate that newly synthesised proteins other than HSP72 are likely to mediate neuronal protection following heat shock in our experiments. These findings raise the possibility that induced tolerance may not necessarily be mediated by HSP72.

Bacterial filamentation of Yersinia pestis by beta-lactam antibiotics in experimentally infected mice

OBJECTIVE

To identify alternatives to streptomycin for treating pneumonic plague, we evaluated beta-lactam antibiotics to treat experimental pneumonic plague in mice.

METHODS

Mice were exposed to a lethal inhaled dose of Yersinia pestis and treated with beta-lactam antibiotics administered every 6 hours, starting 42 hours postexposure.

RESULTS

The mice died or were euthanized in extremis 3 days postexposure. We observed marked bacterial filamentation of Y pestis in the tissues of mice treated with ceftazidime (10/10 mice), aztreonam (9/10 mice), or ampicillin (1/10 mice), but not in the tissues of mice treated with cefotetan, cefazolin, ceftriaxone, or saline. There was no evidence of septation of the filamentous bacteria by light or electron microscopy. The filamentous bacteria were confirmed as Y pestis based on their reactivity with rabbit anti-Y pestis F1 serum.

CONCLUSIONS

Marked bacterial filamentation of Y pestis can be produced in vivo by certain beta-lactam antibiotics. This antibiotic-induced morphologic change is important because filamentous bacteria in clinical samples could possibly be confused with filamentous actinomycotic organisms.

Evidence of apoptosis in primary neuronal cultures after heat shock

We investigated the effects of 30-min heat shock on survival, DNA degradation, and nuclear morphology of primary rat cortical and hippocampal neurones. In cell cultures which were grown for 8 days in vitro (DIV), only a small portion of neurones showed apoptotic morphology after heat shock of 45 degrees C and typical DNA laddering was not detectable, despite the fact that nearly 50% of the neurones died within 24 h. The majority of the neurones presumably died by necrosis, as indicated by random DNA degradation. In neuronal cultures grown for 15 DIV, heat shock, however, resulted in DNA laddering, occurrence of apoptotic bodies and DNA strand breaks, typical of apoptosis. In these cultures, about 50% of the neurones showed apoptotic morphology following exposure to 45 degrees C in TUNEL and acridine orange staining, whereas glia were not affected in vitality. In addition we were interested whether the highly inducible member of the heat-shock protein family, HSP72, would be induced in apoptotic cells. Double staining for HSP72 and TUNEL revealed concomitant HSP72 induction and occurrence of DNA degradation only in very few neurones in 15-DIV cultures, which were growing adjacent to astrocytes. A clear association of the degenerative process and HSP72 expression, therefore, could not be established. These results demonstrate that environmental stress, such as heat shock, can induce apoptotic death in aged primary cultured neurones. The differentiation state and/or the presence of glial cell elements in the cultures appears to be an important factor for the occurrence of apoptotic features in cultured neurones.

Pathology of experimental Ebola virus infection in African green monkeys. Involvement of fibroblastic reticular cells

BACKGROUND

Ebola virus has been responsible for explosive lethal outbreaks of hemorrhagic fever in both humans and nonhuman primates. Previous studies showed a predilection of Ebola virus for cells of the mononuclear phagocyte system and endothelial cells.

OBJECTIVE

To examine the distribution of lesions and Ebola virus antigen in the tissues of six adult male African green monkeys (Cercopithecus aethiops) that died 6 to 7 days after intraperitoneal inoculation of Ebola-Zaire (Mayinga) virus.

METHODS

Tissues were examined histologically, immunohistochemically, and ultrastructurally.

RESULTS

A major novel finding of this study was that fibroblastic reticular cells were immunohistochemically and ultrastructurally identified as targets of Ebola virus infection.

CONCLUSIONS

The role of Ebola virus-infected fibroblastic reticular cells in the pathogenesis of Ebola hemorrhagic fever warrants further investigation. This is especially important because of recent observations indicating that fibroblastic reticular cells, along with the reticular fibers they produce, maximize the efficiency of the immune response.

hDIP--a potential transcriptional regulator related to murine TSC-22 and Drosophila shortsighted (shs)--is expressed in a large number of human tissues

We have cloned a 420 bp cDNA from a human fetal brain cDNA library in lambda encoding the human homologue of a DSIP-immunoreactive leucine zipper protein (DIP) isolated from porcine brain. The derived human protein (hDIP) shares a significant sequence identity with parts of the murine TSC-22 and Drosophila shs, both proteins which are discussed as functioning as transcriptional regulators. A similar role of hDIP is partially confirmed by the results of an RT-PCR analysis, demonstrating the widespread distribution of the protein among different human tissues.

Neuroinvasion by simian immunodeficiency virus coincides with increased numbers of perivascular macrophages/microglia and intrathecal immune activation

During peak viremia and initial antibody response, rhesus macaques infected with pathogenic and nonpathogenic isolates of SIV show distinct differences in viral load and tissue distribution. Animals infected with pathogenic isolates of SIV invariably have virus in the CSF and brain parenchyma by two weeks postinoculation, whereas animals infected with nonpathogenic isolates do not. Mechanisms underlying neuroinvasion by SIV and HIV are unknown, but recruitment of latently infected mononuclear cells from the peripheral circulation (Trojan horse theory) is frequently proposed. Circulating monocytes, from which perivascular macrophage/microglia are derived, are a likely vehicle for cell-associated transport of virus across the blood-brain barrier. This transport and the kinetics of perivascular macrophage/microglial turnover in the CNS likely depend on endothelial and leukocyte adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1), which has previously been shown to be upregulated on cerebrovascular endothelium in SIV encephalitis. To investigate the role of peripheral monocyte recruitment into the perivascular macrophage/microglial cell pool at the time of initial viral neuroinvasion, we examined the temporal relationships among perivascular macrophage/microglia density, endothelial VCAM-1 expression and localization of viral nucleic acid in the CNS of macaques acutely infected with pathogenic and nonpathogenic molecular clones of SIV. The concentration of CSF quinolinic acid, a marker of intrathecal immune and macrophage activation, was examined concurrently. We found that significant increases in the density of perivascular macrophages/microglia coincided with viral neuroinvasion and marked elevations in CSF quinolinic acid. Furthermore, combined in situ hybridization and immunohistochemistry demonstrated that infected perivascular cells were macrophages/microglia. These findings provide evidence suggesting that neuroinvasion occurs through an influx of infected monocytes which take up residence in the CNS as perivascular macrophages/microglia. VCAM-1 expression, however, was not clearly correlated with these events, thus its contribution to initial viral neuroinvasion is unclear.

Dense granular bodies: a novel nucleoplasmic structure in hibernating dormice

Dense granular bodies (DGB) are particular structural constituents observed in cell nuclei of different tissues-liver, pancreas, brown adipose tissue, adrenal cortex-of hibernating dormice. They appear as strongly electron-dense clusters of closely packed granules, with thin fibrils spreading out at their periphery. DGB always occur in the nucleoplasm, sometimes making contact with other nuclear structural constituents typical of the hibernating state, such as coiled bodies, amorphous bodies and nucleoplasmic fibrils. DGB are present only during deep hibernation and rapidly disappear upon arousal from hibernation. Cytochemical and immunocytochemical analyses showed that DGB contain ribonucleoproteins and several nucleoplasmic RNA processing factors, suggesting that DGB can represent accumulation sites of splicing factors which are provided to splicing sites when normal metabolic activity is rapidly restored during arousal.

Rapid postmortem invasion of cecal mucosa of macaques by nonpathogenic Entamoeba chattoni

Although Entamoeba histolytica is the third leading parasitic cause of death in the world, most infections in humans are asymptomatic and restricted to the intestinal lumen. Entamoeba histolytica infections have also been reported in most species of captive nonhuman primates, with New World monkeys being particularly susceptible to fatal invasive amebiasis. In contrast, Old World monkeys appear to be resistant to the disease, although tissue invasion in asymptomatic monkeys has been reported. Our initial objectives were to determine the incidence, the predisposing factors, and the light microscopic and ultrastructural features of invasive amebiasis in Macaca mulatta (rhesus) and and M. fasicularis (cynomolgus) macaques. Our findings indicate that nonpathogenic E. chattoni in macaques can invade cecal mucosa rapidly (within 1 hr) after death. Therefore, the presence of invasive Entamoeba trophozoites in routinely collected necropsy materials should be interpreted with caution, particularly in cases where tissue fixation is delayed.

Monitoring the temporal and spatial activation pattern of astrocytes in focal cerebral ischemia using in situ hybridization to GFAP mRNA: comparison with sgp-2 and hsp70 mRNA and the effect of glutamate receptor antagonists

We investigated the temporo-spatial expression of astrocyte glial fibrillary acidic protein (gfap) and sulfated glycoprotein 2 (sgp-2) mRNAs in comparison to 70-kDa heat shock protein (hsp70) mRNA by in situ hybridisation in rats subjected to permanent occlusion of the middle cerebral artery (MCA). Gfap mRNA started to increase in the cingulate cortex of the lesioned hemisphere 6 h after MCA occlusion and gradually spread over the lateral part of the ipsilateral cortex and the striatum from 12 h to 3 days, peaking at 3 days after MCA occlusion. Gfap mRNA also increased in the contralateral cingulate cortex and corpus callosum at 12 and 24 h. Hsp70 mRNA increased markedly in the ipsilateral cortex adjacent to the ischemic lesion, and slightly within the lesion area from 3 to 24 h and disappeared after 3 days. By 7 days, gfap and sgp-2 mRNAs were increased markedly in the peri-infarct area, and in the ipsilateral thalamus parallel with the delayed neuronal damage, whereas the widespread increase of gfap mRNA in the ipsilateral hemisphere declined. Post-occlusion treatment with the glutamate receptor antagonists MK-801 and NBQX slightly attenuate the induction of gfap but did not qualitatively affect the topical expression pattern. Within the cingulate cortex MK-801 treatment resulted in a significant decrease of the signal intensity at all survival times, reflecting most likely an attenuation of lesion-induced spreading depression like depolarization waves by MK-801. The area of hsp70 expression was reduced by both MK-801 and NBQX, most likely reflecting the decrease of the lesion area by both treatment regimens. Our study thus revealed an early and widespread increase of gfap mRNA in the non-ischemic area including the contralateral hemisphere starting between 3 and 6 h, and a delayed circumscribed expression in the peri-infarct border zone after 1 week. Comparison with the expression of hsp70 mRNA suggests that the absence of an early gfap mRNA induction in the peri-lesion zone reflects an impairment of astrocytic function which may be of importance for infarct growth during the early evolution of the pathological process.

Comparison of the pulmonary distribution and efficacy of antibodies given to mice by intratracheal instillation or aerosol inhalation

The respiratory tract is the portal of entry and target organ of many aerosolized toxins and infective agents, and there is increasing need for testing the efficacy of potential therapeutic agents delivered directly into the lungs. Intratracheal instillation and aerosol inhalation are the two methods most often used to introduce drugs, toxins, or infective agents into the respiratory tract of experimental animals. In this study we compared the distribution and efficacy of antibodies given to mice by aerosol inhalation or intratracheal instillation. We determined the pulmonary distribution of these antibodies by immunohistochemistry and observed the distribution and severity of pulmonary lesions that developed after exposure to aerosolized ricin. Although antibodies administered by either method prevented death, we found that instilled antibodies tended to concentrate around terminal airways and often failed to reach peripheral lung fields. Sometimes entire lung lobes were missed by the instillation route. Acute and chronic pulmonary lesions developed in the unprotected areas of instillation-treated lungs. In contrast, aerosolized antibodies covered all pulmonary surfaces and effectively prevented ricin-induced lesions throughout the lungs. Our findings suggest that the aerosol inhalation method may be preferable for evaluating the efficacy of therapeutic agents in the respiratory tract because of the failure of instilled agents to reach and protect peripheral alveoli.

Aerosolized specific antibody protects mice from lung injury associated with aerosolized ricin exposure

Parenteral vaccination with ricin toxoid, although protective against death after a lethal aerosol ricin challenge, only partially protects against lung lesions. Therefore, we tested whether passive protection with aerosolized specific anti-ricin IgG (goat polyclonal, affinity-purified) could protect against both lethality and lung lesions in unvaccinated mice. Healthy CD-l mice were administered antibody (Ab) by small particle aerosol. Group 1 received non-specific control Ab (2160 mg/min/m3), and groups 2 and 3 received anti-ricin IgG (960 and 3280 mg/min/m3, respectively). Each group was challenged with a lethal dose of aerosolized ricin 1 hr after Ab exposure. All group 1 (control Ab) mice developed diffuse airway epithelial necrosis, with severe interstitial edema and inflammation involving all lung lobes, and died 48-96 hr post-challenge (PC). In contrast, in groups 2 and 3 at 24 hr PC, lung lesions were absent to very mild although there was rare epithelial necrosis in the upper airways in both groups. By 48 hr PC, necrosis of the tracheal epithelium and peritracheal inflammation were noted in some group 3 mice only. By 4 days PC, lungs and airways did not differ from cage controls in most group 2 and 3 mice. Weight gain in group 2 and 3 mice paralleled that of control mice. At 14 days PC, lungs were no different in controls than in group 3 mice. However, two non-survivors in group 3 had obstructions due to proximal airway epithelial damage. All group 2 mice survived, although a mild lymphoplasmacytic perivasculitis was present at 14 days PC which was not noted in the group 3 mice.

Cyclin D1 messenger RNA is induced in microglia rather than neurons following transient forebrain ischaemia

Following 30 min of forebrain ischaemia in the rat, delayed neuronal death occurs in the CA1 sector of the hippocampus within two to three days, whereas neurons in other selectively vulnerable regions, such as the dorsolateral striatum, die within 6-12 h. In this study, we investigated cyclin D1 expression, which codes for a regulatory protein in cell cycle regulation, but it is also induced in sympathetic neurons undergoing programmed cell death. Cyclin D1 messenger RNA could not be detected by in situ hybridization techniques in brains of control rats, but was found at one and two days after ischaemia in regions of the dorsolateral striatum with neuronal degeneration. DNA fragmentation in this region, identified by the terminal transferase biotinylated-UTP nick end labelling (TUNEL) procedure, was observed from 6 h after ischaemia onward. In the hippocampus, increased levels of cyclin D1 messenger RNA were found at two and three days after ischaemia in the striatum pyramidale of the CA1 sector. This expression was associated with the occurrence of neuronal damage and TUNEL-stained neurons. By seven days cyclin D1 messenger RNA was found in hardly any brain structure. There was no temporospatial overlap of cyclin D1 expression with the expression of the immediate-early genes c-fos, c-jun, and mkp-1, a result which is clearly distinct from findings in sympathetic ganglion neurons undergoing programmed cell death. These results do not suggest a role for cyclin D1 in neuronal cell death following transient forebrain ischaemia. The similarity of the cyclin D1 expression profile with that of the microglia-specific CR3 complement receptor beta-subunit messenger RNA, and the results of combined in situ hybridization and microglia-specific immunohistochemistry suggest that microglia are the source of cyclin D1 messenger RNA in the postischaemic brain. Since cyclin D1 codes for a critical regulatory protein for progression of the G0 to G1 phase in the cell cycle and we did not observe prominent occurrence of DNA fragmentation in microglial cells in the hippocampus at time points when cyclin D1 messenger RNA was found, we suggest that cyclin D1 induction is involved in the onset of microglial cell proliferation.

Expression of variants of the major surface glycoprotein of Pneumocystis carinii

Previously, we have shown that a multicopy family of related but unique genes encodes the major surface glycoprotein (MSG) of Pneumocystis carinii. To examine whether different members of this gene family are expressed by P. carinii, antisera were prepared against peptides whose sequences were determined from the deduced amino acid sequences of variants of rat-derived MSG. Immunohistochemical staining of serial sections of rat lungs of infected animals showed that at least three variants of MSG were expressed in an individual lobe, that there was a focal expression of these variants within the lung, and that the relative numbers of these foci were different. Indirect immunofluorescent staining of purified P. carinii organisms using these antisera revealed that at least three variants of MSG were present in organisms isolated from an individual rat and that both cysts and trophozoites reacted with each antiserum. A substantial difference in the fraction of organisms reacting with a specific antipeptide antiserum was seen when comparing organisms isolated from rats raised in a single colony over a period of two years as well as organisms isolated at one time point from rats raised in different colonies. This demonstration of antigenic variation in P. carinii supports the hypothesis that P. carinii utilizes such variation for evading host defense mechanisms.

Lethal experimental infection of rhesus monkeys with Ebola-Zaire (Mayinga) virus by the oral and conjunctival route of exposure

OBJECTIVE

The source of infection or mode of transmission of Ebola virus to human index cases of Ebola fever has not been established. Field observations in outbreaks of Ebola fever indicate that secondary transmission of Ebola virus is linked to improper needle hygiene, direct contact with infected tissue or fluid samples, and close contact with infected patients. While it is presumed that the virus infects through either breaks in the skin or contact with mucous membranes, the only two routes of exposure that have been experimentally validated are parenteral inoculation and aerosol inhalation. Epidemiologic evidence suggests that aerosol exposure is not an important means of virus transmission in natural outbreaks of human Ebola fever; this study was designed to verify that Ebola virus could be effectively transmitted by oral or conjunctival exposure in nonhuman primates.

MATERIALS AND METHODS

Adult rhesus monkeys (Macaca mulatta) were exposed to Ebola-Zaire (Mayinga) virus orally (N=4), conjunctivally (N=4), or by intramuscular inoculation (N=1, virus-positive control).

RESULTS

Four of four monkeys exposed by the conjunctival route, three of four monkeys exposed by the oral route, and the intramuscularly inoculated positive control monkey (one of one) were successfully infected with Ebola-Zaire (Mayinga). Seven monkeys died of Ebola fever between days 7 and 8 postexposure. One monkey was given aggressive supportive therapy and a platelet transfusion; it lived until day 12 postexposure.

CONCLUSIONS

Findings in this study experimentally confirm that Ebola virus can be effectively transmitted via the oral or conjunctival route of exposure in nonhuman primates.

Venezuelan equine encephalitis in BALB/c mice: kinetic analysis of central nervous system infection following aerosol or subcutaneous inoculation

OBJECTIVE

To investigate the routes of entry of Venezuelan equine encephalitis (VEE) virus into the brain, we infected BALB/c mice with a virulent strain (V3000) by aerosol or subcutaneous inoculation.

METHODS

Immunohistochemistry and in situ hybridization methods were used to detect VEE virus in tissues taken at daily intervals postinfection.

RESULTS

In both groups, virus in the brain first appeared in olfactory regions. Aerosol exposure caused early massive infection of olfactory epithelium, which developed into bilaterally symmetrical infection of the olfactory nerves, olfactory bulbs, and lateral olfactory tracts by day 2 postinfection. After subcutaneous inoculation, VEE in the brain also appeared first in olfactory regions, but was not detected until day 3 postinfection. By day 4 postinfection, VEE viral infection had spread throughout the brain in both groups. Vascular endothelium and the choroid plexus remained uninfected during the entire study.

CONCLUSIONS

Our findings suggest that VEE virus, whether given by aerosol or subcutaneously, first enters the brain through the olfactory tract.

Molecular correlates of delayed neuronal death following transient forebrain ischemia in the rat

Following transient forebrain ischemia selective and delayed neuronal degeneration occurs in the CA1 sector of the hippocampus. It is presently unclear whether this cell death is related to programmed cell death (PCD), which occurs in neurons during development of the CNS. Recently, the expression of various genes, such as c-fos, c-jun mkp-1, cyclin D1, and hsp70 was found to be associated with PCD in model systems. We and others have described that these genes are also upregulated in the hippocampus following ischemia. Most notably, c-fos, c-jun, and hsp70 are expressed specifically in CA1 neurons at survival times shortly preceding cell degeneration in rat models of global ischemia. In addition, the gene products could be detected by immunohistochemical methods, despite a general impairment of protein synthesis. These finding are especially relevant, since recent report suggests a functional role for Fos family proteins and c-jun in PCD in neurons of the superior cervical ganglion. These results could be indicative for the occurrence of a PCD-related program in CA1 neurons ad corroborate several other lines of evidences, such as occurrence of DNA fragmentation. Clearly, further studies are necessary to elucidate the functional role of the gene inductions following ischemia in vivo.

Prognostic significance of molecular biological and immunohistological parameters in gastrointestinal carcinomas

Histological type, malignancy grade, and tumor stage are among the most important parameters predicting outcome in cancer patients. Making use of immunocytochemistry as well as polymerase chain reaction-based techniques the demonstration of micrometastatic tumor spread, for example, into bone marrow, lymph nodes, and peritoneal cavity, is a new staging parameter of prognostic significance. In contrast, the prognostic value of different proliferation markers such as Ki67 (Mib 1), PCNA, and AgNOR has not yet been unequivocally established. A series of genetic change has been described in the development of cancer. In general, these changes seem to be of predictive value within defined tumor stages and it might be helpful to determine several genetic lesions within one tumor. Very recently a new mechanism of carcinogenesis closely related to the hereditary nonpolyposis cancer syndrome (HNPCC) was detected. Due to mutations in mismatch repair genes (hMSH 2, hMLH1, hPMS1,2) instabilities in simple repetitive genomic sequences occur, which are the genetic hallmark of most HNPCC tumors. This opens a new field to cancer prevention.