Non-pathogenic bacteria elicit a differential cytokine response by intestinal epithelial cell/leucocyte co-cultures

BACKGROUND AND AIM

Intestinal epithelial cells (IEC) are thought to participate in the mucosal defence against bacteria and in the regulation of mucosal tissue homeostasis. Reactivity of IEC to bacterial signals may depend on interactions with immunocompetent cells. To address the question of whether non-pathogenic bacteria modify the immune response of the intestinal epithelium, we co-cultivated enterocyte-like CaCO-2 cells with human blood leucocytes in separate compartments of transwell cultures.

METHODS

CaCO-2/PBMC co-cultures were stimulated with non-pathogenic bacteria and enteropathogenic Escherichia coli. Expression of tumour necrosis factor alpha (TNF-alpha), interleukin (IL)-1beta, IL-8, monocyte chemoattracting protein 1 (MCP-1), and IL-10 was studied by enzyme linked immunosorbent assays (cytokine secretion) and by semiquantitative reverse transcription-polymerase chain reaction.

RESULTS

Challenge of CaCO-2 cells with non-pathogenic E coli and Lactobacillus sakei induced expression of IL-8, MCP-1, IL-1beta, and TNF-alpha mRNA in the presence of underlying leucocytes. Leucocyte sensitised CaCO-2 cells produced TNF-alpha and IL-1beta whereas IL-10 was exclusively secreted by human peripheral blood mononuclear cells. CaCO-2 cells alone remained hyporesponsive to the bacterial challenge. Lactobacillus johnsonii, an intestinal isolate, showed reduced potential to induce proinflammatory cytokines but increased transforming growth factor beta mRNA in leucocyte sensitised CaCO-2 cells. TNF-alpha was identified as one of the early mediators involved in cellular cross talk. In the presence of leucocytes, discriminative activation of CaCO-2 cells was observed between enteropathogenic E coli and non-pathogenic bacteria.

CONCLUSION

The differential recognition of non-pathogenic bacteria by CaCO-2 cells required the presence of underlying leucocytes. These results strengthen the hypothesis that bacterial signalling at the mucosal surface is dependent on a network of cellular interactions.

Folate deficiency in vitro induces uracil misincorporation and DNA hypomethylation and inhibits DNA excision repair in immortalized normal human colon epithelial cells

Epidemiological studies have indicated that folic acid protects against a variety of cancers, particularly cancer of the colorectum. Folate is essential for efficient DNA synthesis and repair. Moreover, folate can affect cellular S-adenosylmethionine levels, which regulate DNA methylation and control gene expression. We have investigated the mechanisms through which folate affects DNA stability in immortalized normal human colonocytes (HCEC). DNA strand breakage, uracil misincorporation, and DNA repair, in response to oxidative and alkylation damage, were determined in folate-sufficient and folate-deficient colonocytes by single cell gel electrophoresis. In addition, methyl incorporation into genomic DNA was measured using the bacterial enzyme Sss1 methylase. Cultured human colonocyte DNA contained endogenous strand breaks and uracil. Folate deficiency significantly increased strand breakage and uracil misincorporation in these cells. This negative effect on DNA stability was concentration dependent at levels usually found in human plasma (1-10 ng/ml). DNA methylation was decreased in HCEC grown in the absence of folate. Conversely, hypomethylation was not concentration dependent. Folate deficiency impaired the ability of HCEC to repair oxidative and alkylation damage. These results demonstrate that folic acid modulates DNA repair, DNA strand breakage, and uracil misincorporation in immortalized human colonocytes and that folate deficiency substantially decreases DNA stability in these cells.

Multidrug-resistant tuberculosis in patients without HIV infection

BACKGROUND

Investigations of outbreaks of multidrug-resistant tuberculosis have found low rates of treatment response and very high mortality, and they have mainly involved patients with advanced human immunodeficiency virus (HIV) infection. For patients without HIV infection, one study reported an overall rate of response to treatment of 56 percent, and the mortality from tuberculosis was 22 percent. We investigated treatment response and mortality rates in 26 HIV-negative patients in New York with multidrug-resistant tuberculosis.

METHODS

We obtained detailed data from seven teaching hospitals in New York City on patients with multidrug-resistant tuberculosis--defined as tuberculosis resistant at least to isoniazid and rifampin--who were HIV-negative on serologic testing. Lengths of times from diagnosis to the initiation of appropriate therapy and from the initiation of appropriate therapy to conversion to negative cultures were assessed. Therapeutic responses were evaluated by both microbiologic and clinical criteria.

RESULTS

Between March 1991 and September 1994, 26 HIV-negative patients were identified and treated. Of the 25 patients for whom adequate data were available for analysis, 24 (96 percent) had clinical responses; all 17 patients for whom data on microbiologic response were available had such a response. The median times from diagnosis to the initiation of appropriate therapy and from the initiation of therapy to culture conversion were 44 days (range, 0 to 181) and 69 days (range, 2 to 705), respectively. Side effects requiring the discontinuation of medication occurred in 4 of 23 patients (17 percent) who were treated with second-line antituberculosis medications. The median follow-up for the 23 patients who responded and who received appropriate therapy was 91 weeks (range, 41 to 225).

CONCLUSIONS

In this report from New York City, HIV-negative patients with multidrug-resistant tuberculosis, contrary to previous reports, responded well to appropriate chemotherapy, both clinically and microbiologically.

Activation of human peripheral blood mononuclear cells by nonpathogenic bacteria in vitro: evidence of NK cells as primary targets

The interaction of commensal bacteria with immunocompetent cells may occur in definite compartments of the mucosal immune system, as limited translocation through the epithelial barrier cannot be excluded. In this study the stimulation of human peripheral blood mononuclear cells and purified lymphocyte subsets by nonpathogenic gram-positive lactobacilli (Lactobacillus johnsonii and Lactobacillus sakei) and gram-negative Escherichia coli was investigated. The various bacterial strains induced a differential cytokine pattern. Whereas L. johnsonii and L. sakei strongly induced gamma interferon (IFN-gamma) and interleukin-12 (IL-12), E. coli and lipopolysaccharide (LPS) preferentially induced IL-10 after 16 h of stimulation. Expression of activation antigens CD69 and CD25 was observed on (CD3(-) CD56(+)) natural killer (NK) cells after stimulation of total human peripheral blood mononuclear cells. All bacteria mediated the proliferation of human peripheral blood mononuclear cells, and the strongest proliferative response was observed with L. johnsonii. Purified CD4(+), CD8(+), and CD19(+) lymphocyte subsets were not activated upon bacterial stimulation but showed normal response to a mitogenic stimulus. In contrast, purified NK cells upregulated the IL-2Ralpha chain (CD25) and underwent proliferation when stimulated by L. johnsonii. E. coli and LPS were less effective in inducing proliferation. Expression of CD25 or secretion of IFN-gamma from purified NK cells was significantly increased in the presence of bacterially primed macrophages, indicating that full activation required both bacterium- and cell contact-based signals derived from accessory cells.

Effects of parenteral lipid emulsions with different fatty acid composition on immune cell functions in vitro

BACKGROUND

Numerous studies suggest that immune function may be compromised by lipid emulsions rich in polyunsaturated fatty acids (PUFAs). In our study, we compared the effect of a new olive oil-based lipid emulsion (ClinOleic) containing a moderate level of PUFAs, with emulsions based on soybean oil (Intralipid or Ivelip), on immune functions of human cell in vitro.

METHODS

Peripheral white blood cells were collected from healthy volunteers. Lymphocyte proliferation was evaluated by [3H]-thymidine incorporation after stimulation with either phytohemagglutinin (PHA) or antibodies against T-cell specific antigens. Lymphocytes subsets and T-cell activation markers (CD25 and HLA-DR) were measured by flow cytometry. The release of cytokines (interleukin [IL]-2, IL-1beta, and tumor necrosis factor-alpha [TNF-alpha]) was measured by enzyme-linked immunosorbent assay (ELISA), after lymphocytes or monocytes/macrophages stimulation with PHA or lipopolysaccharide (LPS).

RESULTS

A significant dose-dependent inhibition of thymidine incorporation was observed with Intralipid and Ivelip (incorporation down to 39.9% of control, p < .001) whereas ClinOleic showed no inhibitory effect. Activation antigen expression on both CD4+ and CD8+ T-cells tended to decrease with Intralipid (CD25: -53.4% on CD4+ and -57.4% on CD8+; HLA-DR: -61.5% on CD4+ and -58.5% on CD8+) but not with ClinOleic (from -2.9% for CD25 on CD4+ to 16.7% for HLA-DR on CD4+). Intralipid decreased significantly IL-2 production (-39.0%, p < .05) whereas ClinOleic had little effect (-13.0%, NS). Intralipid and ClinOleic tended to inhibit to a similar extent the release of pro-inflammatory cytokines (TNF-alpha: -21.5% and -34.8%, IL-1beta: -45.1% and -40.3%; respectively).

CONCLUSIONS

Our results suggest that an olive oil-based lipid emulsion could modulate immune response selectively, maintaining protective immunity and reducing inflammatory response. Olive oil may offer an immunologically neutral alternative to soybean oil for use in parenteral lipid emulsions.

Penicillin resistance and other predictors of mortality in pneumococcal bacteremia in a population with high human immunodeficiency virus seroprevalence

Rates of invasive disease caused by penicillin-resistant pneumococci are rising. Previous reports have found no association between resistant pneumococci and increased mortality. To evaluate the impact of penicillin resistance and other variables on mortality, we retrospectively studied all cases of pneumococcal bacteremia identified by our microbiology laboratory from 1 January 1992 through 31 December 1996. There were 462 cases of pneumococcal bacteremia in 432 patients. The mean age was 35 years; 55% of the cases occurred in male patients, 58% were in black patients, and 40% were in Hispanic patients. One-half of the cases occurred in patients with documented human immunodeficiency virus (HIV) infection. Penicillin resistance was first noted in 1994 and increased yearly, accounting for 17% of 1996 isolates. Of all resistant isolates, 65% were resistant to penicillin at a high level. The overall mortality was 17%. On multivariate analysis, high-level penicillin resistance, older age, severe disease, multilobar infiltrates and/or effusion(s) on chest roentgenogram, and Hispanic ethnicity were independent predictors of mortality in pneumococcal bacteremia. In HIV-infected patients, a CD4 cell count below the median just missed statistical significance. This is the first report demonstrating penicillin resistance as an independent predictor of mortality among patients with pneumococcal bacteremia.

Pneumothorax in AIDS

OBJECTIVE

To determine risk factors for the development of pneumothorax in patients with the acquired immunodeficiency syndrome (AIDS).

DESIGN

Prospective cohort study.

SETTING

Tertiary care center.

PATIENTS

Of 1030 patients with AIDS who were followed at Memorial Sloan-Kettering Cancer Center between 1 January 1980 and 30 September 1989, 20 (2%) developed pneumothorax that was unrelated to trauma or a pulmonary procedure.

RESULTS

Of 20 patients with AIDS who presented with pneumothorax, 19 had compelling evidence of concurrent Pneumocystis carinii pneumonia. Using bivariate analysis, patients receiving aerosol pentamidine prophylaxis (relative risk, 17.6) and those with a history of P. carinii pneumonia (relative risk, 14.5) were more likely to develop pneumothorax. By Mantel-Haenszel stratified analysis, aerosol pentamidine use was a statistically significant risk factor independent of a history of P. carinii pneumonia. The pneumothorax-related mortality rate was 10% and there was considerable morbidity.

CONCLUSIONS

Patients with AIDS at the highest risk for developing pneumothorax are those with a history of P. carinii pneumonia who are receiving aerosol pentamidine prophylaxis but who nevertheless develop P. carinii pneumonia. The benefits of aerosol pentamidine prophylaxis in these patients far outweigh this risk. Pneumocystis carinii pneumonia should be considered as the most likely diagnosis in any patient with AIDS who develops a pneumothorax.

Improved outcomes for patients with multidrug-resistant tuberculosis

We conducted a retrospective study of patients with culture-confirmed multidrug-resistant tuberculosis (MDR-TB) at Bronx-Lebanon Hospital Center (South Bronx, NY) to determine what factors affected clinical and microbiological responses and survival. For the 38 patients with MDR-TB, reporting of first-line drug susceptibilities was relatively rapid (median time, 30 days). Thirty-four patients (89%) were infected with human immunodeficiency virus (HIV), and initial and overall response rates were 59% and 50%, respectively; the median survival was 315 days; and 50% of these patients died of tuberculosis. Bivariate analysis revealed that the following factors had a positive impact on response and survival: receiving > or = 2 consecutive weeks of appropriate therapy with at least two drugs to which the isolate was susceptible in vitro; starting appropriate therapy within 4 weeks of the diagnosis; and having tuberculosis that was limited to the lungs. Multivariate analysis revealed that the only variable associated with response was receipt of appropriate therapy for > or = 2 consecutive weeks. In contrast to findings in the published literature, our results indicate the outcome of MDR-TB can be improved, particularly for severely immunosuppressed HIV-infected patients. Rapid reporting of susceptibilities and prompt initiation and continuation of appropriate antituberculous therapy improved response and survival.

Interactions between the microbiota and the intestinal mucosa

The intestinal microflora can be considered as a postnatally aquired organ composed of a large diversity of bacterial cells that can perform different functions for the host. This organ is highly exposed to environmental influences and thus modulated in its composition and functions by external factors, such as nutrition. Specific components of the intestinal microflora, including lactobacilli and bifidobacteria, have been associated with beneficial effects on the host, such as promotion of gut maturation and integrity, antagonisms against pathogens and immune modulation. In addition, the microflora seem to play a significant role in the maintenance of intestinal immune homeostasis and prevention of inflammation. At the present time, the contribution of intestinal epithlial cell in the first line of defence against pathogenic bacteria and microbial antigens has been recognized, in contrast, the interactions of intestinal epithelial cells with commensal bacteria are less understood. The present work summarizes the increasing scientific attention for mechanisms of the innate immune response of the host to different components of the autochthonous microflora and suggests a potential role for selected probiotic bacteria in the regulation of intestinal inflammation.

An inhibitory role of the phosphatidylinositol 3-kinase-signaling pathway in vascular endothelial growth factor-induced tissue factor expression

Vascular endothelial growth factor (VEGF) is not only essential for vasculogenesis and angiogenesis but is also capable of inducing tissue factor, the prime initiator of coagulation, in endothelial cells. In this study we have analyzed the VEGF-elicited pathways involved in the induction of tissue factor in human umbilical cord vein endothelial cells. Using specific low molecular weight inhibitors we could demonstrate a crucial role of the p38 and Erk-1/2 mitogen-activated protein (MAP) kinases. In contrast, treatment with wortmannin or LY294002, inhibitors of phosphatidylinositol 3 (PI3)-kinase, resulted in a strong enhancement of the VEGF-induced tissue factor production, indicating a negative regulatory role of the PI3-kinase on tissue factor-inducing pathways. Accordingly, transduction with constitutively active Akt led to a reduction of VEGF-induced tissue factor production. Western blot analyses using antibodies specific for phosphorylated p38 showed an enhanced activation of this MAP kinase in human umbilical cord vein endothelial cells when stimulated with VEGF in the presence of wortmannin in comparison to either agent alone. Thus, the negative regulation of the PI3-kinase pathway on endothelial tissue factor activity can be explained at least in part by a suppression of this MAP kinase-signaling pathway. This is the first demonstration of a reciprocal relationship between procoagulant activity and the PI3-kinase-Akt signaling pathway, and it reveals a novel mechanism by which tissue factor expression can be controlled in endothelial cells.

Therapy of alcohol withdrawal syndrome in intensive care unit patients following trauma: results of a prospective, randomized trial

OBJECTIVES

To assess the effect of three different alcohol withdrawal therapy regimens in traumatized chronic alcoholic patients with respect to the duration of mechanical ventilation and the frequency of pneumonia and cardiac disorders during their intensive care unit (ICU) stay.

DESIGN

A prospective, randomized, blinded, controlled clinical trial.

SETTING

A university hospital ICU.

PATIENTS

Multiple-injured alcohol-dependent patients (n=180) transferred to the ICU after admission to the emergency room and operative management. A total of 180 patients were included in the study; however, 21 patients were excluded from the study after assignment.

INTERVENTIONS

Patients who developed actual alcohol withdrawal syndrome were randomized to one of the following treatment regimens: flunitrazepam/clonidine (n=54); chlormethiazole/haloperidol (n=50); or flunitrazepam/haloperidol (n=55). The need for administration of medication was determined, using a validated measure of the severity of alcohol withdrawal (Revised Clinical Institute Withdrawal Assessment for Alcohol Scale).

MEASUREMENTS AND MAIN RESULTS

The duration of mechanical ventilation and major intercurrent complications, such as pneumonia, sepsis, cardiac disorders, bleeding disorders, and death, were documented. Patients did not differ significantly between groups regarding age, Revised Trauma and Injury Severity Score and Acute Physiology and Chronic Health Evaluation II score on admission. In all except four patients in the flunitrazepam/clonidine group, who continued to hallucinate, the Revised Clinical Institute Withdrawal Assessment for Alcohol Scale decreased to <20 after initiation of therapy. ICU stay did not significantly differ between groups (p=.1669). However, mechanical ventilation was significantly prolonged in the chlormethiazole/haloperidol group (p=.0315) due to an increased frequency of pneumonia (p=.0414). Cardiac complications were significantly (p=.0047) increased in the flunitrazepam/clonidine group.

CONCLUSIONS

There was some advantage in the flunitrazepam/clonidine regimen with respect to pneumonia and the necessity for mechanical ventilation. However, four (7%) patients had to be excluded from the study due to ongoing hallucinations during therapy. Also, cardiac complications were increased in this group. Thus, flunitrazepam/haloperidol should be preferred in patients with cardiac or pulmonary risk. Further studies are required to determine which therapy should be considered.

Enterococcus faecium SF68 enhances the immune response to Giardia intestinalis in mice

We studied the ability of the probiotic organism Enterococcus faecium SF68 to antagonize Giardia intestinalis infection in mice. Oral feeding of E. faecium strain SF68 starting 7 d before inoculation with Giardia trophozoites significantly increased the production of specific anti-Giardia intestinal IgA and blood IgG. This humoral response was mirrored at the cellular level by an increased percentage of CD4(+) T cells in the Peyer's patches and in the spleens of SF68-fed mice. The improvement of specific immune responses in probiotic-fed mice was associated with a diminution in the number of active trophozoites in the small intestine as well as decreased shedding of fecal Giardia antigens (GSA65 protein). The ability of SF68 to stimulate the immune system at both mucosal and systemic levels highlights mechanisms by which this probiotic might antagonize pathogens in vivo. Taken together, the data demonstrate the strong potential of strain SF68 to prevent protozoa from causing intestinal infections.

Intercurrent complications in chronic alcoholic men admitted to the intensive care unit following trauma

OBJECTIVE

A chronic alcoholic group following trauma was investigated to determine whether their ICU stay was longer than that of a non-alcoholic group and whether their intercurrent complication rate was increased.

DESIGN

Prospective study.

SETTING

An intensive care unit.

PATIENTS

A total of 102 polytraumatized patients were transferred to the ICU after admission to the emergency room and after surgical treatment. Of these patients 69 were chronic alcoholics and 33 were allocated to the non-alcoholic group. The chronic-alcoholic group. met the DSM-III-R and ICD-10 criteria for alcohol dependence or chronic alcohol abuse/harmful use. The daily ethanol intake in these patients was > or = 60 g. Diagnostic indicators included an alcoholism-related questionnaire (CAGE), conventional laboratory markers and carbohydrate-deficient transferrin.

MEASUREMENT AND RESULTS

Major intercurrent complications such as alcohol withdrawal syndrome (AWS), pneumonia, cardiac complications and bleeding disorders were documented and defined according to internationally accepted criteria. Patients did not differ significantly between groups regarding age, TRISS and APACHE score on admission. The rate of major intercurrent complications was 196% in the chronic alcoholic vs 70% in the non-alcoholic group (p = 0.0001). Because of the increased intercurrent complication rate, the ICU stay was significantly prolonged in the chronic-alcoholic group by a median period of 9 days.

CONCLUSIONS

Chronic alcoholics are reported to have an increased risk of morbidity and mortality. However, to our knowledge, nothing is known about the morbidity and mortality of chronic alcoholics in intensive care units following trauma. Since chronic alcoholics in the ICU develop more major complications with a significantly prolonged ICU stay following trauma than non-alcoholics, it seems reasonable to intensify research to identify chronic alcoholics and to prevent alcohol-related complications.

Factors influencing time to sputum conversion among patients with smear-positive pulmonary tuberculosis

For hospitalized patients with smear-positive pulmonary or laryngeal tuberculosis, the Centers for Disease Control and Prevention recommends that three consecutive sputum samples be negative for acid-fast bacilli (AFB) before respiratory isolation is discontinued. Limited data are available to predict the length of time to obtain three negative sputum smears and cultures and to determine factors associated with a prolonged interval before sputum smear and culture conversion, especially among patients infected with human immunodeficiency virus (HIV). For 100 consecutive patients with smear-positive pulmonary tuberculosis, the mean and median numbers of days from the initiation of appropriate therapy to the first of three consecutive negative smears were calculated, and associated risk factors were determined. The mean number of days before the first of three consecutive negative sputum smears was 33 days; the median was 23 days. On stepwise multiple regression analysis, cavitary disease, numerous AFB on the initial smear, and no prior history of tuberculosis were the factors independently associated with an increased number of days for both smear and culture conversion. HIV does not prolong the period of infectiousness.

Memory after silent stroke: hippocampus and infarcts both matter

OBJECTIVE

Memory decline commonly occurs among elderly individuals. This observation is often attributed to early neurodegenerative changes in the hippocampus and related brain regions. However, the contribution of vascular lesions, such as brain infarcts, to hippocampal integrity and age-associated memory decline remains unclear.

METHODS

We studied 658 elderly participants without dementia from a prospective, community-based study on aging and dementia who received high-resolution structural MRI. Cortical and subcortical infarcts were identified, and hippocampal and relative brain volumes were calculated following standard protocols. Summary scores reflecting performance on tasks of memory, language, processing speed, and visuospatial function were derived from a comprehensive neuropsychological battery. We used multiple regression analyses to relate cortical and subcortical infarcts, hippocampal and relative brain volume, to measures of cognitive performance in domains of memory, language, processing speed, and visuospatial ability.

RESULTS

Presence of brain infarcts was associated with a smaller hippocampus. Smaller hippocampus volume was associated with poorer memory specifically. Brain infarcts were associated with poorer memory and cognitive performance in all other domains, which was independent of hippocampus volume.

CONCLUSIONS

Both hippocampal volume and brain infarcts independently contribute to memory performance in elderly individuals without dementia. Given that age-associated neurodegenerative conditions, such as Alzheimer disease, are defined primarily by impairment in memory, these findings have clinical implications for prevention and for identification of pathogenic factors associated with disease symptomatology.

Randomised double-blind placebo-controlled study of the effect of Lactobacillus paracasei NCC 2461 on skin reactivity

In recent decades, the prevalence of subjects with reactive skin has considerably increased in industrialised countries. 50% of women and 30% of men report cutaneous discomfort classified under reactive/sensitive skin. Several topical approaches have been proposed, in particular through improvement of galenic forms or protection of epidermal surface. We propose to act differently, deeply from inside the body via an innovative nutritional approach. To this purpose, Lactobacillus paracasei NCC 2461 (ST11) was selected because of its specific beneficial skin properties discovered in in vitro studies, i.e. diminution of neurogenic inflammation and promotion of the recovery of skin barrier function. We designed a randomised double-blind placebo-controlled clinical study with a two-month supplementation in two female treatment groups (n=32 per group). A capsaicin test was performed to monitor the time course of skin sensitivity. Moreover, transepidermal water loss was assessed to analyse the rate of skin barrier function recovery; dryness of the leg and roughness of the cheeks was investigated by a dermatologist as well as by self-assessment. The results of the present clinical trial show that oral supplementation with the probiotic decreases skin sensitivity and increases the rate of barrier function recovery. Thus, the data provide evidence that daily intake of ST11 could improve reactive skin condition.

ATP hydrolysis by initiation factor 4A is required for translation initiation in Saccharomyces cerevisiae

Saccharomyces cerevisiae translation initiation factor eIF-4A, an RNA helicase of the Asp-Glu-Ala-Asp (DEAD) box protein family, was mutated in the putative ATP binding site and expressed in Escherichia coli. Mutant proteins with alanine at position 66 replaced by glycine [eIF-4A(A66G)] or valine [eIF-4A(A66V)] were purified from Escherichia coli extracts and analyzed in vitro for activity in ATP crosslinking, ATP hydrolysis, RNA helicase, and translation assays. The results show that in vitro ATP hydrolysis activity, RNA helicase activity, and translation activity of eIF-4A correlate with in vivo activity of the factor. Whereas eIF-4A(A66G) showed wild-type activity in all assays, eIF-4A(A66V) was active in ATP crosslinking but inactive in ATP hydrolysis and RNA helicase assays. In vitro translation was supported by wild-type eIF-4A and eIF-4A(A66G) but not by eIF-4A(A66V). The results show that, for their translation, the majority of mRNAs from Saccharomyces cerevisiae including an mRNA with the initiator AUG positioned 8 nucleotides downstream of the cap structure require eIF-4A that is able to hydrolyze ATP.

A set of human putative lymphocyte G0/G1 switch genes includes genes homologous to rodent cytokine and zinc finger protein-encoding genes

Lymphocyte G0/G1 switch genes (G0S genes) are potential oncogenes and may regulate, be regulated by, or be coordinately regulated with, latent lymphotropic viruses. To identify these genes, a cDNA library was prepared from blood mononuclear cells that had been cultured for 2 hr with a T-cell mitogen (lectin) and cycloheximide. Eight differentially hybridizing recombinants were characterized by RNA and DNA blotting and sequencing. One cDNA (G0S7) corresponded to the oncogene c-fos. Another cDNA (G0S19) was homologous (70%) to a cDNA encoding a murine inhibitor of stem cell proliferation (the cytokine MIP1 alpha) and, less closely, to other members of the "small inducible" secreted protein-encoding gene family. Whereas cDNA hybridization to genomic DNA blots indicated a small subfamily of G0S19 genes, simple patterns of bands indicated that most cDNAs, including G0S30 cDNA, corresponded to single-copy genes. The 3' noncoding sequence of G0S30 cDNA was homologous (87-89%) to the 3' noncoding sequences of certain rodent genes (NGFI-A, Krox24, EGR1) that encode zinc finger proteins (putative transcriptional regulators). This degree of evolutionary conservation suggests an important function for the 3' noncoding region. The 3' noncoding regions of some cDNAs contained the TTATTTAT (mRNA destabilization) element. The corresponding RNAs each formed doublets in agarose gels. Previous studies of c-fos RNA from HeLa cells indicate that this is due to cycloheximide-dependent stabilization of poly(A) tails. Our results reveal the power of cycloheximide enrichment in isolating what would appear to be significant low-abundance mRNAs.

Caspase activity plays an essential role in long-term memory

Activation of intracellular second messenger cascades has been linked to learning and memory in various organisms. Identification of down-stream targets of these second messengers that play a role in learning and memory is an active area of research. Recently, it has been reported that increases in intracellular calcium can activate a cysteine-dependent aspartate-directed protease (caspase) cascade in mice. Using an antibody that selectively recognizes activated caspase-3, we detected the presence of this enzyme in hippocampal neurons. Inhibition of caspase activity in the hippocampus blocked long-term, but not short-term, spatial memory. These results suggest that a caspase-mediated cellular event(s) in hippocampal neurons is critical for long-term spatial memory storage.

Relationship between human immunodeficiency virus infection and salmonellosis in 20- to 59-year-old residents of New York City

Among 20- to 59-year-old residents of New York City who have septicemia, gastroenteritis, urinary tract infection, and multiple site infections due to Salmonella, those listed in the New York City AIDS Registry were highly overrepresented. Among the patients listed in the registry, males outnumbered females by 4:1 (septicemia), 9:1 (multiple site infections), 5.6:1 (gastroenteritis), and 2.5:1 (urinary tract infection); among patients not listed, males outnumbered females by 2.7:1 (septicemia), 3:1 (multiple site infections), 1.2:1 (gastroenteritis), and 1.6:1 (urinary tract infection). These results strongly suggest that most nonlisted males with septicemia and multiple site infections, and a minority with gastroenteritis and urinary tract infection, were human immunodeficiency virus (HIV)-positive. Among individuals who were HIV-positive, or likely to be so, Salmonella enteritidis was more competent in causing septicemia and less competent in causing gastroenteritis than was Salmonella typhimurium; among HIV-negative individuals, the reverse was true. The different capacities for infection with and invasiveness of S. enteritidis, S. typhimurium, and other Salmonella serotypes in HIV-positive and HIV-negative individuals and the use of HIV testing for Salmonella-infected individuals are discussed.