Candida albicans extracellular vesicles trigger type I IFN signalling via cGAS and STING

The host type I interferon (IFN) pathway is a major signature of inflammation induced by the human fungal pathogen, Candida albicans. However, the molecular mechanism for activating this pathway in the host defence against C. albicans remains unknown. Here we reveal that mice lacking cyclic GMP-AMP synthase (cGAS)-stimulator of IFN genes (STING) pathway components had improved survival following an intravenous challenge by C. albicans. Biofilm-associated C. albicans DNA packaged in extracellular vesicles triggers the cGAS-STING pathway as determined by induction of interferon-stimulated genes, IFNβ production, and phosphorylation of IFN regulatory factor 3 and TANK-binding kinase 1. Extracellular vesicle-induced activation of type I IFNs was independent of the Dectin-1/Card9 pathway and did not require toll-like receptor 9. Single nucleotide polymorphisms in cGAS and STING potently altered inflammatory cytokine production in human monocytes challenged by C. albicans. These studies provide insights into the early innate immune response induced by a clinically significant fungal pathogen.

Evaluation of Dose Requirements Using Weight-Based versus Non-Weight-Based Dosing of Norepinephrine to Achieve a Goal Mean Arterial Pressure in Patients with Septic Shock

No consensus exists regarding optimal dosing of norepinephrine in septic shock. We aimed to evaluate if weight-based dosing (WBD) lead to higher norepinephrine doses when achieving goal mean arterial pressure (MAP) than non-weight-based dosing (non-WBD). This was a retrospective cohort study conducted after standardization of norepinephrine dosing within a cardiopulmonary ICU. Patients received non-WBD prior to standardization (November 2018-October 2019) and WBD afterwards (November 2019-October 2020). The primary outcome was the norepinephrine dose needed to attain goal MAP. Secondary outcomes included time to goal MAP, duration of norepinephrine therapy, duration of mechanical ventilation, and treatment-related adverse effects. A total of 189 patients were included (WBD 97; non-WBD 92). There was a significantly lower norepinephrine dose at goal MAP (WBD 0.05, IQR 0.02, 0.07; non-WBD 0.07, IQR 0.05, 0.14; p < 0.005) and initial norepinephrine dose (WBD 0.02, IQR 0.01, 0.05; non-WBD 0.06, 0.04, 0.12; p < 0.005) in the WBD group. No difference was observed in achievement of goal MAP (WBD 73%; non-WBD 78%; p = 0.09) or time until goal MAP (WBD 18, IQR 0, 60; non-WBD 30, IQR 14, 60; p = 0.84). WBD may lead to lower norepinephrine doses. Both strategies achieved goal MAP with no significant difference in time to goal.

Spleen Tyrosine Kinase Is a Critical Regulator of Neutrophil Responses to Candida Species

Invasive fungal infections constitute a lethal threat, with patient mortality as high as 90%. The incidence of invasive fungal infections is increasing, especially in the setting of patients receiving immunomodulatory agents, chemotherapy, or immunosuppressive medications following solid-organ or bone marrow transplantation. In addition, inhibitors of spleen tyrosine kinase (Syk) have been recently developed for the treatment of patients with refractory autoimmune and hematologic indications. Neutrophils are the initial innate cellular responders to many types of pathogens, including invasive fungi. A central process governing neutrophil recognition of fungi is through lectin binding receptors, many of which rely on Syk for cellular activation. We previously demonstrated that Syk activation is essential for cellular activation, phagosomal maturation, and elimination of phagocytosed fungal pathogens in macrophages. Here, we used combined genetic and chemical inhibitor approaches to evaluate the importance of Syk in the response of neutrophils to Candida species. We took advantage of a Cas9-expressing neutrophil progenitor cell line to generate isogenic wild-type and Syk-deficient neutrophils. Syk-deficient neutrophils are unable to control the human pathogens Candida albicans, Candida glabrata, and Candida auris Neutrophil responses to Candida species, including the production of reactive oxygen species and of cytokines such as tumor necrosis factor alpha (TNF-α), the formation of neutrophil extracellular traps (NETs), phagocytosis, and neutrophil swarming, appear to be critically dependent on Syk. These results demonstrate an essential role for Syk in neutrophil responses to Candida species and raise concern for increased fungal infections with the development of Syk-modulating therapeutics.IMPORTANCE Neutrophils are recognized to represent significant immune cell mediators for the clearance and elimination of the human-pathogenic fungal pathogen Candida The sensing of fungi by innate cells is performed, in part, through lectin receptor recognition of cell wall components and downstream cellular activation by signaling components, including spleen tyrosine kinase (Syk). While the essential role of Syk in macrophages and dendritic cells is clear, there remains uncertainty with respect to its contribution in neutrophils. In this study, we demonstrated that Syk is critical for multiple cellular functions in neutrophils responding to major human-pathogenic Candida species. These data not only demonstrate the vital nature of Syk with respect to the control of fungi by neutrophils but also warn of the potential infectious complications arising from the recent clinical development of novel Syk inhibitors for hematologic and autoimmune disorders.

CD82 controls CpG-dependent TLR9 signaling

The tetraspanin CD82 is a potent suppressor of tumor metastasis and regulates several processes including signal transduction, cell adhesion, motility, and aggregation. However, the mechanisms by which CD82 participates in innate immunity are unknown. We report that CD82 is a key regulator of TLR9 trafficking and signaling. TLR9 recognizes unmethylated cytosine-phosphate-guanine (CpG) motifs present in viral, bacterial, and fungal DNA. We demonstrate that TLR9 and CD82 associate in macrophages, which occurs in the endoplasmic reticulum (ER) and post-ER. Moreover, CD82 is essential for TLR9-dependent myddosome formation in response to CpG stimulation. Finally, CD82 modulates TLR9-dependent NF-κB nuclear translocation, which is critical for inflammatory cytokine production. To our knowledge, this is the first time a tetraspanin has been implicated as a key regulator of TLR signaling. Collectively, our study demonstrates that CD82 is a specific regulator of TLR9 signaling, which may be critical in cancer immunotherapy approaches and coordinating the innate immune response to pathogens.-Khan, N. S., Lukason, D. P., Feliu, M., Ward, R. A., Lord, A. K., Reedy, J. L., Ramirez-Ortiz, Z. G., Tam, J. M., Kasperkovitz, P. V., Negoro, P. E., Vyas, T. D., Xu, S., Brinkmann, M. M., Acharaya, M., Artavanis-Tsakonas, K., Frickel, E.-M., Becker, C. E., Dagher, Z., Kim, Y.-M., Latz, E., Ploegh, H. L., Mansour, M. K., Miranti, C. K., Levitz, S. M., Vyas, J. M. CD82 controls CpG-dependent TLR9 signaling.

Microfluidic Chip for Detection of Fungal Infections

Fungal infections can lead to severe clinical outcomes such as multiple organ failure and septic shock. Rapid detection of fungal infections allows clinicians to treat patients in a timely manner and improves clinical outcomes. Conventional detection methods include blood culture followed by plate culture and polymerase chain reaction. These methods are time-consuming and require expensive equipment, hence, they are not suitable for point-of-care and clinical settings. There is an unmet need to develop a rapid and inexpensive detection method for fungal infections such as candidemia. We developed an innovative immuno-based microfluidic device that can rapidly detect and capture Candida albicans from phosphate-buffered saline (PBS) and human whole blood. Our microchip technology showed an efficient capture of C. albicans in PBS with an efficiency of 61-78% at various concentrations ranging from 10 to 10⁵ colony-forming units per milliliter (cfu/mL). The presented microfluidic technology will be useful to screen for various pathogens at the point-of-care and clinical settings.

Tetraspanin CD82 Organizes Dectin-1 into Signaling Domains to Mediate Cellular Responses to Candida albicans

Tetraspanins are a family of proteins possessing four transmembrane domains that help in lateral organization of plasma membrane proteins. These proteins interact with each other as well as other receptors and signaling proteins, resulting in functional complexes called "tetraspanin microdomains." Tetraspanins, including CD82, play an essential role in the pathogenesis of fungal infections. Dectin-1, a receptor for the fungal cell wall carbohydrate β-1,3-glucan, is vital to host defense against fungal infections. The current study identifies a novel association between tetraspanin CD82 and Dectin-1 on the plasma membrane of Candida albicans-containing phagosomes independent of phagocytic ability. Deletion of CD82 in mice resulted in diminished fungicidal activity, increased C. albicans viability within macrophages, and decreased cytokine production (TNF-α, IL-1β) at both mRNA and protein level in macrophages. Additionally, CD82 organized Dectin-1 clustering in the phagocytic cup. Deletion of CD82 modulates Dectin-1 signaling, resulting in a reduction of Src and Syk phosphorylation and reactive oxygen species production. CD82 knockout mice were more susceptible to C. albicans as compared with wild-type mice. Furthermore, patient C. albicans-induced cytokine production was influenced by two human CD82 single nucleotide polymorphisms, whereas an additional CD82 single nucleotide polymorphism increased the risk for candidemia independent of cytokine production. Together, these data demonstrate that CD82 organizes the proper assembly of Dectin-1 signaling machinery in response to C. albicans.

Biguanides enhance antifungal activity against Candida glabrata

Candida spp. are the fourth leading cause of nosocomial blood stream infections in North America. Candida glabrata is the second most frequently isolated species, and rapid development of antifungal resistance has made treatment a challenge. In this study, we investigate the therapeutic potential of metformin, a biguanide with well-established action for diabetes, as an antifungal agent against C. glabrata. Both wild type and antifungal-resistant isolates of C. glabrata were subjected to biguanide and biguanide-antifungal combination treatment. Metformin, as well as other members of the biguanide family, were found to have antifungal activity against C. glabrata, with MIC₅₀ of 9.34 ± 0.16 mg/mL, 2.09 ± 0.04 mg/mL and 1.87 ± 0.05 mg/mL for metformin, phenformin and buformin, respectively. We demonstrate that biguanides enhance the activity of several antifungal drugs, including voriconazole, fluconazole, and amphotericin, but not micafungin. The biguanide-antifungal combinations allowed for additional antifungal effects, with fraction inhibition concentration indexes ranging from 0.5 to 1. Furthermore, metformin was able to lower antifungal MIC₅₀ in voriconazole and fluconazole-resistant clinical isolates of C. glabrata. We also observed growth reduction of C. glabrata with rapamycin and an FIC of 0.84 ± 0.09 when combined with metformin, suggesting biguanide action in C. glabrata may be related to inhibition of the mTOR complex. We conclude that the biguanide class has direct antifungal therapeutic potential and enhances the activity of select antifungals in the treatment of resistant C. glabrata isolates. These data support the further investigation of biguanides in the combination treatment of serious fungal infections.

Fluorescent Tracking of Yeast Division Clarifies the Essential Role of Spleen Tyrosine Kinase in the Intracellular Control of Candida glabrata in Macrophages

Macrophages play a critical role in the elimination of fungal pathogens. They are sensed via cell surface pattern-recognition receptors and are phagocytosed into newly formed organelles called phagosomes. Phagosomes mature through the recruitment of proteins and lysosomes, resulting in addition of proteolytic enzymes and acidification of the microenvironment. Our earlier studies demonstrated an essential role of Dectin-1-dependent activation of spleen tyrosine kinase (Syk) in the maturation of fungal containing phagosomes. The absence of Syk activity interrupted phago-lysosomal fusion resulting in arrest at an early phagosome stage. In this study, we sought to define the contribution of Syk to the control of phagocytosed live Candida glabrata in primary macrophages. To accurately measure intracellular yeast division, we designed a carboxyfluorescein succinimidyl ester (CFSE) yeast division assay in which bright fluorescent parent cells give rise to dim daughter cells. The CFSE-labeling of C. glabrata did not affect the growth rate of the yeast. Following incubation with macrophages, internalized CFSE-labeled C. glabrata were retrieved by cellular lysis, tagged using ConA-647, and the amount of residual CFSE fluorescence was assessed by flow cytometry. C. glabrata remained undivided (CFSE bright) for up to 18 h in co-culture with primary macrophages. Treatment of macrophages with R406, a specific Syk inhibitor, resulted in loss of intracellular control of C. glabrata with initiation of division within 4 h. Delayed Syk inhibition after 8 h was less effective indicating that Syk is critically required at early stages of macrophage–fungal interaction. In conclusion, we demonstrate a new method of tracking division of C. glabrata using CFSE labeling. Our results suggest that early Syk activation is essential for macrophage control of phagocytosed C. glabrata.

Dectin-1 Controls TLR9 Trafficking to Phagosomes Containing β-1,3 Glucan

Dectin-1 and TLR9 play distinct roles in the recognition and induction of innate immune responses to Aspergillus fumigatus and Candida albicans. Dectin-1 is a receptor for the major fungal cell wall carbohydrate β-1,3 glucan that induces inflammatory cytokines and controls phagosomal maturation through spleen tyrosine kinase activation. TLR9 is an endosomal TLR that also modulates the inflammatory cytokine response to fungal pathogens. In this study, we demonstrate that β-1,3 glucan beads are sufficient to induce dynamic redistribution and accumulation of cleaved TLR9 to phagosomes. Trafficking of TLR9 to A. fumigatus and C. albicans phagosomes requires Dectin-1 recognition. Inhibition of phagosomal acidification blocks TLR9 accumulation on phagosomes containing β-1,3 glucan beads. Dectin-1-mediated spleen tyrosine kinase activation is required for TLR9 trafficking to β-1,3 glucan-, A. fumigatus-, and C. albicans-containing phagosomes. In addition, Dectin-1 regulates TLR9-dependent gene expression. Collectively, our study demonstrates that recognition of β-1,3 glucan by Dectin-1 triggers TLR9 trafficking to β-1,3 glucan-containing phagosomes, which may be critical in coordinating innate antifungal defense.

Dectin-1-dependent LC3 recruitment to phagosomes enhances fungicidal activity in macrophages

Autophagy has been postulated to play role in mammalian host defense against fungal pathogens, although the molecular details remain unclear. Here, we show that primary macrophages deficient in the autophagic factor LC3 demonstrate diminished fungicidal activity but increased cytokine production in response to Candida albicans stimulation. LC3 recruitment to fungal phagosomes requires activation of the fungal pattern receptor dectin-1. LC3 recruitment to the phagosome also requires Syk signaling but is independent of all activity by Toll-like receptors and does not require the presence of the adaptor protein Card9. We further demonstrate that reactive oxygen species generation by NADPH oxidase is required for LC3 recruitment to the fungal phagosome. These observations directly link LC3 to the inflammatory pathway against C. albicans in macrophages.

Dectin-1 activation controls maturation of β-1,3-glucan-containing phagosomes

Elimination of fungal pathogens by phagocytes requires phagosome maturation, a process that involves the recruitment and fusion of intracellular proteins. The role of Dectin-1, a β-1,3-glucan receptor, critical for fungal recognition and triggering of Th17 responses, to phagosomal maturation has not been defined. We show that GFP-Dectin-1 translocates to the fungal phagosome, but its signal decays after 2 h. Inhibition of acidification results in retention of GFP-Dectin-1 to phagosome membranes highlighting the requirement for an acidic pH. Following β-1,3-glucan recognition, GFP-Dectin-1 undergoes tyrosine phosphorylation by Src kinases with subsequent Syk activation. Our results demonstrate that Syk is activated independently of intraphagosomal pH. Inhibition of Src or Syk results in prolonged retention of GFP-Dectin-1 to the phagosome signifying a link between Syk and intraphagosomal pH. β-1,3-glucan phagosomes expressing a signaling incompetent Dectin-1 failed to mature as demonstrated by prolonged Dectin-1 retention, presence of Rab5B, failure to acquire LAMP-1 and inability to acidify. Phagosomes containing Candida albicans also require Dectin-1-dependent Syk activation for phagosomal maturation. Taken together, these results support a model where Dectin-1 not only controls internalization of β-1,3-glucan containing cargo and triggers proinflammatory cytokines, but also acts as a master regulator for subsequent phagolysosomal maturation through Syk activation.

A novel application for 222Rn emanation standards: radon-cryptophane host chemistry

In collaboration with the University of Pennsylvania, a (222)Rn emanation source was used for the determination of the binding affinity of radon to a cryptophane molecular host. This source was similar to a (222)Rn emanation standard that was developed and disseminated by the National Institute of Standards and Technology (NIST). The novel experimental design involved performing the reactions at femtomole levels, developing exacting gravimetric sampling methods and making precise (222)Rn assays by liquid scintillation counting. A cryptophane-radon association constant was determined, K(A)=(49,000±12,000) L mol(-1) at 293 K, which was the first measurement of radon binding to a molecular host.

Use of fungal derived polysaccharide-conjugated particles to probe Dectin-1 responses in innate immunity

The number of life-threatening fungal infections has risen in immunocompromised patients, and identification of the rules that govern an appropriate immune response is essential to develop better diagnostics and targeted therapeutics. The outer cell wall component on pathogenic fungi consists of β-1,3-glucan, and Dectin-1, a pattern recognition receptor present on the cell surface of innate immune cells, binds specifically to this carbohydrate. A barrier in understanding the exact immunological response to pathogen-derived carbohydrate epitopes is the presence of multiple types of carbohydrate moieties on fungal cell walls. To dissect the immunological mechanisms used to recognize pathogens, a system of "fungal like particles" was developed that consisted of polystyrene beads, which mimicked the three dimensional shape of the fungus, coated covalently with purified β-1,3-glucan derived from Saccharomyces cerevisiae. The morphology of the β-1,3-glucan layer was examined by immunofluorescence, flow cytometery, and immuno-transmission electron microscopy. The covalent linkages of the β-1,3-glucan to the polystyrene surface were stable after subjecting the beads to detergents. By pre-treating β-1,3-glucan beads with laminarinase, a specific β-1,3-gluconase, the reactivity of the anti-β-1,3-glucan antibody was abrogated in comparison to treatment with proteinase K indicating that the coating of these beads was predominantly β-1,3-glucan. TNF-α was also measured by stimulating bone-marrow derived macrophages with the β-1,3-glucan beads, and showed a dose dependent response compared to soluble β-glucan, insoluble β-1,3-glucan, uncoated beads, and soluble β-1,3-glucan mixed with uncoated beads. Finally, β-1,3-glucan beads were incubated with GFP-Dectin-1 expressing macrophages and imaged using confocal microscopy. β-1,3-beads were taken up within minutes and retained Dectin-1 recruitment to the phagosome as compared to uncoated beads. These data describe a unique fungal-like particle system that will permit immunologists to probe the critical steps in early recognition of pathogen-derived fungal carbohydrate antigens by innate immune cells.

Roles for the interleukin-4 receptor and associated JAK/STAT proteins in human articular chondrocyte mechanotransduction

OBJECTIVE

To identify functional interleukin-4 (IL4) receptor (IL4R) subtypes and associated Janus kinase/signal transducers and activators of transcription (JAK/STAT) molecules in human articular chondrocytes and assess the role of JAK/STAT proteins in chondrocyte mechanotransduction.

METHODS

Expression of IL4R subunits and associated molecules was assessed by immunohistochemistry and western blotting. Functional IL4R were identified by chemical crosslinking of IL4-stimulated chondrocytes and western blotting. JAK and STAT phosphorylation was assessed by western blotting.

RESULTS

Chondrocytes from normal and osteoarthritic (OA) cartilage express IL4Ralpha, gammac and IL13Ralpha1 subunits (components of the Type I and Type II IL4R). In the presence of IL4 only functional Type II IL4Rs were identified in normal or OA chondrocytes. With the exception of STAT2, no differences in JAK/STAT expression were detected between normal and OA cartilage. STAT2 was expressed in OA but not normal chondrocytes. Mechanical stimulation (MS) resulted in an IL4R-dependent increase in phosphorylated Tyk2 in normal chondrocytes, which could be abolished by IL1beta preincubation. No phosphorylation of STAT5 or STAT6 was detected in either normal or OA chondrocytes following mechanical stimulation (MS) IL4 stimulation resulted in a decrease in Tyk2 phosphorylation and an increase in phosphorylation of STAT6 in both normal and OA chondrocytes.

CONCLUSION

Chondrocytes from normal and OA cartilage signal through a Type II IL4R. This signalling is via a STAT6-independent pathway. Differences in IL4 signalling are likely due to crosstalk between integrin and cytokine signalling pathways, and not differences in IL4R expression.

Role of nucleic acid testing in cadaver organ donor screening: detection of hepatitis C virus RNA in seropositive and seronegative donors

Hepatitis C virus (HCV) transmission by both seropositive and seronegative cadaver organ donors has been documented, yet nucleic acid testing is not routinely used to identify active infection in these donors prior to transplantation. Between November 2001 and February 2004, we screened 1445 cadaver organ donors for anti-HCV antibodies with either HCV EIA-2.0 (Abbott Diagnostics, Chicago, IL, USA) and/or Ortho HCV Version 3.0 ELISA (Ortho-Clinical Diagnostics, Raritan, NJ, USA) and confirmed seropositive samples with Chiron RIBA3.0 SIA (Chiron Corporation, Emeryville, CA, USA). Samples with sufficient volume (n = 726) were tested by the VERSANT HCV [transcription-mediated amplification (TMA)] Qualitative assay (Bayer Healthcare LLC, Tarrytown, NY, USA) which can be performed in approximately 5 h. Those with detectable HCV RNA and sufficient volume were quantified by the VERSANT HCV 3.0 (bDNA) Assay (Bayer Healthcare LLC) and/or the HCV RNA TMA Quantitative Assay (n = 23) and genotyped (n = 57). Seventy-seven of 1445 (5.3%) donors were seropositive, reactive by either one or both anti-HCV assays. Fifty-two of 63 (82.5%) of the seropositive samples had detectable HCV RNA and were genotyped. Seventeen of these samples had quantifications ranging from 128,123 to >7,692,307 IU/mL. Six of 663 (0.9%) seronegative samples had detectable HCV RNA. Their quantifications ranged from <9.3 to 1,464,799 IU/mL, and five of these six were successfully genotyped. As HCV RNA was demonstrated in samples from both our seropositive and seronegative cadaver organ donors, we are now incorporating nucleic acid testing into our donor screening/diagnostic algorithm.

The natural substrate for nitric oxide synthase activity

There has been little evidence to indicate that arginine is the natural substrate for generating nitric oxide synthase (NOS) activity. It is now shown that carnosine, which is widely distributed in tissues, is likely to be the true substrate. In tissue sections it gives a stronger NOS reaction than does arginine.

Anti-oxidant, pro-oxidant properties of tannic acid and its binding to DNA

Tannic acid has numerous food and pharmacological applications. It is an additive in medicinal products, and is used as a flavouring agent and as an anti-oxidant in various foods and beverages. We have previously shown that tannic acid in the presence of Cu(II) causes DNA degradation through generation of reactive oxygen species. On the other hand, it exhibits antimutagenic and anticarcinogenic activities, and induces apoptosis in animal cells. It is known that most plant-derived polyphenolic anti-oxidants also act as pro-oxidants under certain conditions. In this paper, we compare the anti-oxidant and pro-oxidant properties of tannic acid and its structural component gallic acid. It is shown that tannic acid is the most efficient generator of the hydroxyl radical in the presence of Cu(II), as compared with gallic acid and its analogues syringic acid and pyrogallol. The anti-oxidant activity of tannic acid was studied by its effect on hydroxyl radical and singlet oxygen mediated cleavage of plasmid DNA. Again, tannic acid provided the maximum protection against cleavage, while gallic acid and its structural analogues were found to be non-inhibitory or partially inhibitory. The results suggest that the structural features of tannic acid that are important for its anti-oxidant action are also those that contribute to the generation of hydroxyl radicals in the presence of Cu(II). Restriction analysis of treated phage DNA and thermal melting profiles of calf thymus DNA indicated that tannic acid strongly binds to DNA. Indirect evidence indicates that modification of DNA bases may also occur.

Intimate examinations: use of chaperones in community-based family planning clinics

We examined women's preferences regarding the use of chaperones during intimate examinations by a female doctor or nurse in community-based family planning clinics. An anonymous questionnaire was completed before consultation and examination by 126 women attending five family planning clinics selected to cover a range of social and ethnic groups. The questionnaire explored women's views regarding intimate examinations by a woman and the presence of a chaperone. A clear majority (107 vs 19) of our community clinic users preferred to be alone with the woman doctor or nurse during an internal examination. There was no significant difference in preference or strength of feeling when analysed by age, ethnicity or previous experience.

Predominant expression of T helper 2 cytokines and altered expression of T helper 1 cytokines in long-term allograft survival induced by intrathymic immune modulation with donor class I major histocompatibility complex peptides

BACKGROUND

We have recently demonstrated that three synthetic peptides corresponding to the alpha-helices of the alpha1 and alpha2 domains of the donor class I RT1.Aa molecule served as efficient CD4+ T-cell epitopes for indirect recognition of this molecule during cardiac allograft rejection in the PVG.R8-toPVG.1U rat strain combination. These peptides induce long-term graft survival when injected into the thymus 7 days before transplantation under the cover of transient immunosuppression with anti-rat lymphocyte serum. In this study, we analyzed intragraft cytokine gene expression to test whether immune deviation to the T helper (Th) 2 response is associated with long-term allograft survival in this model.

METHODS

Intragraft cytokine gene expression was analyzed using a competitive reverse transcription polymerase chain reaction method we developed for this study. Cytokine gene expression was quantified in control allografts (n=5) with acute rejection and allografts from intrathymically manipulated recipients with acute rejection (n=5), delayed rejection (n=7), or no rejection (n=8).

RESULTS

Long-surviving allografts expressed high levels of interleukin (IL)-4, IL-10, transforming growth factor (TGF)-beta, interferon (IFN)-gamma, and undetectable levels of IL-2. Allografts that were rejected in a delayed fashion expressed mostly IL-2, IFN-gamma, and TGF-beta with low or undetectable levels of IL-4 and IL-10. Acutely rejected allografts from unmanipulated controls or peptide-manipulated recipients expressed high levels of IL-2, IFN-gamma, TGF-beta and undetectable levels of IL-4 or IL-10. All allografts also expressed T-cell receptor Cbeta gene, providing evidence for the presence of T-cell infiltrates in the grafts.

CONCLUSIONS

These observations demonstrate that acute graft rejection in this model is associated with the expression of Th1 cytokines, IL-2, and IFN-gamma, whereas long-term survival is associated with predominant expression of Th2 cytokines, IL-4, and IL-10. The expression of IFN-gamma in long-surviving allografts in the absence of IL-2 provides evidence for altered activation of the Th1 response in this intrathymic immune modulation model.

Structural features of tannic acid important for DNA degradation in the presence of Cu(II)

Tannic acid has numerous food and pharmacological applications. It is an additive in medicinal products and is used as a flavouring agent and as an antioxidant in various foods and beverages. However, there are reports of its mutagenicity and carcinogenicity in bacterial and animal test systems. Tannic acid and its structural monomer gallic acid are also capable of inducing apoptosis in animal cells. We have earlier shown that tannic acid in the presence of Cu(II) causes DNA degradation through generation of reactive oxygen species such as hydroxyl radicals. In order to understand the chemical basis of the various biological properties of tannic acid we have studied the structure-activity relationship between tannic acid and gallic acid using the DNA cleavage assay. Results in the present paper indicate that gallic acid is considerably more active than tannic acid. However, if two of the three hydroxyl groups of gallic acid are methylated (syringic acid) the DNA degrading capacity declines sharply. Further, decarboxylation of gallic acid (pyrogallol) leads to enhancement of its activity. In conclusion, the results indicate that the DNA cleavage activity of tannic acid is due to its digalloyl moeity and that free hydroxyl groups are essential for cleavage.

Increased arachidonic acid induced platelet chemiluminescence indicates cyclooxygenase overactivity in schizophrenic subjects

Platelets were found to emit a burst of chemiluminescence during incubation with arachidonic or linoleic acid. This chemiluminescence response may indicate activation of the enzyme prostaglandin synthase in the arachidonate-induced platelet chemiluminescence as it is inhibited by aspirin. Stimulation of platelets with arachidonic acid and linoleic acid induced a concentration dependent chemiluminescence response. Platelets from drug naive schizophrenic subjects showed significantly increased arachidonic acid metabolism compared to control subjects. No significant difference was observed between schizophrenic and control subjects in the chemiluminescence response to linoleic acid. In schizophrenic subjects treated with neuroleptic drugs the overactive arachidonic acid response was normalized. Linoleic acid chemiluminescence response was unaffected by neuroleptic treatment. Hyperactive cyclooxygenase activity may reflect a similar condition in the brain and implicates prostaglandin pathway abnormalities in the pathogenesis of schizophrenia.

Hypothalamic hypertensive factor: an inhibitor of nitric oxide synthase activity

Human and rat plasma and rat hypothalamus contain a cytochemically detectable substance, the concentration of which rises with an increase in salt intake. The plasma concentration of this material is also raised in essential hypertension and in the spontaneously hypertensive rat (SHR), the Milan hypertensive rat, and the reduced renal mass (RRM) hypertensive rat. In the normal rat, the greatest concentration is found in the hypothalamus of the SHR and the RRM hypertensive rat. The physicochemical characteristics of this cytochemically detectable hypothalamic hypertensive factor (HHF), including chromatographic behavior and molecular weight range, suggest that it may share features common to a substituted guanidine that is present in established nitric oxide synthase (NOS) inhibitors. It was therefore decided to determine the effect on NOS activity of the HHF obtained from mature SHR. The ability of HHF to inhibit NOS activity was studied on (1) NOS extracted from bovine aorta, rat brain, and human platelets by measuring the conversion of radiolabeled L-arginine to L-citrulline and (2) rat liver NOS measured indirectly with a cytochemical technique based on the stimulation of soluble guanylate cyclase activity in hepatocytes by NO. HHF showed a biphasic inhibitory action on platelet NOS activity that was greater with HHF obtained from SHR than from Wistar-Kyoto rats. HHF also had a biphasic inhibitory effect on hepatocyte NOS activity that was more potent when obtained from SHR. It is proposed that the increase in HHF, a novel form of NOS inhibitor that is elevated in SHR, may be involved in the rise in arterial pressure.

Elevated endogenous nitric oxide synthase inhibitor in schizophrenic plasma may reflect abnormalities in brain nitric oxide production

Cellular origins of methylarginines are not precisely known but the presence of free methyl and dimethylarginines in the brain were reported. We have investigated the circulating concentrations of asymmetrical dimethylarginine NG,NG-dimethylarginine (ADMA), NG,NG-dimethylarginine (SDMA), nitrate and nitrite levels in drug naive first episode schizophrenic patients and matched control subjects. Three of those patients were treated with neurolepties for 3 months. Plasma ADMA levels increased significantly but nitrate levels were significantly low compared to control subjects. Drug treatment apparently lowered ADMA levels and increased nitrate levels in plasma. Methylation of arginine to methylarginines may have an important role in regulating signal transduction through the nitric oxide system in the brain, and suggest novel therapeutic targets.

Pediatric emergency physician interpretation of plain radiographs: Is routine review by a radiologist necessary and cost-effective?

STUDY OBJECTIVE

To determine the concordance rate of plain radiograph interpretations by pediatric emergency physicians and pediatric radiologists, to evaluate the effect of incorrect radiologic diagnosis on patient management, and to evaluate the necessity and cost-effectiveness of routine follow-up review of all plain radiographs by a radiologist.

METHODS

We assembled a prospective series of all patients who presented to the emergency department of an urban tertiary care children's hospital and underwent plain radiography between October 1 and October 31, 1994. Pediatric emergency physicians documented their interpretations. Within 24 hours, films were reviewed by a pediatric radiologist. The two interpretations were classified as concordant or discordant and were further assessed for medical significance and subsequent change in management.

RESULTS

During the study period, 707 radiographic examinations were performed: chest, 56%; skeletal excluding spine, 20.1%; abdomen, 11.9%; sinus, 4.2%; spine, 3.6%; and other, 4%. The accuracy or concordance rate was 90.2% (638 of 707) for pediatric emergency physician interpretations; clinical management was unchanged in 96.9% (685 of 707) of the cases. Of the 69 discordant interpretations, 48 were clinically significant, with 22 requiring changes in management. They included 9 false-negative interpretations by pediatric emergency physicians: (5 fractures, 2 cases of pneumonia, 1 case of sinusitis, 1 case of cardiomegaly); 10 false-positive interpretations by pediatric emergency physicians (5 fractures, 4 cases of pneumonia, 1 case of sinusitis), and 3 false-positive interpretations by radiologists (1 case of C-2 spine subluxation, 1 retropharyngeal abscess, and 1 case of necrotizing enterocolitis). No adverse outcomes resulted from these misinterpretations. Routine review of all plain radiographs by a radiologist represents an estimated $210,000 annual cost to the patients and payers.

CONCLUSION

Radiograph interpretations by pediatric emergency physicians were generally accurate, and no adverse outcomes occurred as a result of misinterpretation. Clinical assessment probably assisted these physicians in interpreting the radiographs of high-risk patients. Judicious consultation with a radiologist during the initial presentation of a high-risk patient, when deemed warranted by the pediatric emergency physician, will help the emergency physician deliver high-quality, cost-effective health care. Given the overall clinical accuracy rate of radiograph interpretations by the pediatric emergency physicians and the cost of routine review of all plain radiographs in the ED by a radiologist, routine review versus selective specialty consultation must be further evaluated.

Elevated platelet calcium mobilization and nitric oxide synthase activity may reflect abnormalities in schizophrenic brain

Schizophrenia has a diverse nature of clinical symptoms and a number of hypotheses have been suggested to explain its aetiological basis. In this study we have examined two aspects of membrane function, receptor-activated calcium mobilization and calcium activated nitric oxide synthase activity in schizophrenic subjects. Thrombin induces mobilization of calcium ions from intracellular stores. The platelet response of drug naive schizophrenics was found to be significantly increased over a range of thrombin concentrations (0.01 to 0.60 U/ml) compared to control subjects. Possible involvement of nitric oxide (NO) in the aetiology of schizophrenia was investigated. NO has been functionally linked to both dopaminergic and glutamatergic systems both of which are strongly implicated in the biochemical pathology of schizophrenia. Nitric oxide synthase (NOS) activity was determined in platelets of controls, schizophrenic and panic disorder subjects. Enzyme activity was found to be significantly higher in platelets of drug naive schizophrenic subjects compared to controls, drug treated schizophrenics and panic disorder subjects. It is suggested that there is an imbalance of the calcium-induced L-arginine- nitric oxide pathway in platelets of schizophrenic subjects which may be modified by neuroleptic treatment. This imbalance may be mirrored in the central nervous system in particular at the NMDA receptor. It is possible that such a disturbance in the L-arginine-nitric oxide pathway may have pathological implications in the aetiology of schizophrenia.

Potent activation of nitric oxide synthase by garlic: a basis for its therapeutic applications

Garlic (Allium sativum L.) is thought to have a variety of therapeutic applications including inhibition of platelet aggregation. Many of the therapeutic actions of garlic parallel the physiological effects of nitric oxide and may be explained by its ability to increase nitric oxide synthase activity intracellularly. Our studies showed that both water and alcoholic extracts of garlic are very potent inhibitors of platelet aggregation induced by epinephrine and ADP. Similar dilutions of garlic extract also activated nitric oxide synthase activity in isolated platelets in vitro. The same extract was also very effective in activating nitric oxide synthase activity in placental villous tissue. The addition of garlic extracts increased nitric oxide synthase activity in a dose-dependent manner. Nitrite levels in the supernatants of incubated placental villous tissue were similarly increased. Activation of calcium-dependent nitric oxide synthase and the subsequent production of nitric oxide is probably the most novel mechanism yet claimed by which garlic can exert its therapeutic properties.

Neonatal resuscitation

All emergency departments should be adequately equipped and well prepared to handle a newborn delivery and resuscitation. It is important to remember that most neonates will respond to drying, warming, positioning, suctioning, and tactile stimulation and that overzealous and invasive resuscitation is not only unwarranted in most cases, but substantially increases the risk of iatrogenic complications. After the initial management, further therapy is based on assessment of respirations, heart rate, and skin and mucous membrane color. An algorithm outlining neonatal resuscitation is presented in Figure 6.

Smooth-pursuit initiation in the presence of a textured background in monkey

Smooth pursuit eye movements in the monkey were studied by measuring the average eye acceleration in the first 100 msec of the ocular response to suddenly moving constant velocity discrete visual targets. The tracking target's motion was initiated on or eccentric to the fovea against a very dimly lit homogeneous background or an illuminated, highly textured, large-field background. The effect of the textured background was always to reduce the initial eye acceleration as compared to that present in the homogeneous background case. Movement of the background in the opposite direction to target spot movement also reduced the initial eye acceleration. In contrast, steady-state tracking measured several hundred msec after the onset of pursuit under the same conditions was only marginally reduced by the presence of the textured background.

Sensory transduction and neuronal transmission as related to ultrastructure and encoding of information in different labyrinthine receptor systems of vertebrates

Mechano-electric transduction and neuronal transmission were studied in sensory systems ascending from and descending to single receptor cells of the labyrinth organs in submammalian vertebrates. The animals were young crocodiles (Caiman crocodilus), geckos (Gekko gecko, Tarentola mauritanica), and turtles (Pseudemys scripta elegans, Chinemys reevesii). Intracellular receptor potentials from the apical region of the hair cell (or from the ciliary surface) were recorded in the ampullar, macular, and papillar sensory cells. These single-cell responses are, within limits, proportional to stimulus amplitude, frequency, or phase and are bidirectional in that they show depolarization by kinociliopetal stereociliar displacement and hyperpolarization by kinociliofugal displacement. Synaptic potentials (presynaptic from the basal region of the hair cell, postsynaptic from the contacting nerve endings) were recorded in the utricular, saccular, and lagenar neuroepithelia with electron-optic localization of the in situ fixed microelectrode tip. As local excitatory or inhibitory processes, respectively, they follow the stimulus and receptor potential with latency and with nonlinear distortion. Action potentials (spikes), as synchronized by the excitatory synaptic potentials, were recorded from single nerve fibers or bipolar cells, related to ampullar, macular, or papillar receptor units. Unit responses and synaptic potentials were recorded from the first, second, and following centripetal and central neurons of the ascending systems, or from neurons of the descending systems in the brain stem or from centrifugal neurons. Such records were achieved during adequate mechanical or acoustical stimulation of the different receptor systems, with additional electrical stimulation, uni- or bilaterally. Thus, the influence of centripetal-centrifugal bilateral interaction on the receptor functions was measured, as inhibition or disinhibition, respectively. The input-output relations of these sequential stages of information transfer were plotted as histograms of different types, as characteristic curves, power spectra, or by correlation operations, with or without feedback, from the different systemic levels.U

Functions of different receptor systems in the reptilian labyrinth

Different biopotentials, following a mechanical stimulus, were recorded from single hair cells of the reptilian labyrinth, with electronoptically circumscript localizations: 1. From the apical cell pole, the receptor potential, intracellular or from the ciliary surface, within the physiological range proportional to stimulus amplitude, frequency or phase, without delay, and with no real threshold of mechanosensitivity, as measured by ciliary displacement amplitude or velocity. 2. From the synaptic zone, in the basal region of the hair cell, or from contacting nerve endings, the synaptic potentials, local excitatory or inhibitory processes, respectively, with measurable latencies and with non-linear distortion. 3. From the (dendritic) endings of the first afferent neuron (or neurons), spike-shaped action potentials, synchronized by the (excitatory) synaptic potentials. Characteristic curves were plotted as a quantitative representation of the mechano-electric input-output relations of the different types of hair cells. For proceeding morphological and physiological system analysis, the comparison of the different submammalian inner-ear receptor systems gives us some new possibility of a closer correlation between ultrastructure and function.