An essential and highly selective protein import pathway encoded by nucleus-forming phage

Targeting proteins to specific subcellular destinations is essential in prokaryotes, eukaryotes, and the viruses that infect them. Chimalliviridae phages encapsulate their genomes in a nucleus-like replication compartment composed of the protein chimallin (ChmA) that excludes ribosomes and decouples transcription from translation. These phages selectively partition proteins between the phage nucleus and the bacterial cytoplasm. Currently, the genes and signals that govern selective protein import into the phage nucleus are unknown. Here, we identify two components of this protein import pathway: a species-specific surface-exposed region of a phage intranuclear protein required for nuclear entry and a conserved protein, PicA (Protein importer of chimalliviruses A), that facilitates cargo protein trafficking across the phage nuclear shell. We also identify a defective cargo protein that is targeted to PicA on the nuclear periphery but fails to enter the nucleus, providing insight into the mechanism of nuclear protein trafficking. Using CRISPRi-ART protein expression knockdown of PicA, we show that PicA is essential early in the chimallivirus replication cycle. Together, our results allow us to propose a multistep model for the Protein Import Chimallivirus pathway, where proteins are targeted to PicA by amino acids on their surface and then licensed by PicA for nuclear entry. The divergence in the selectivity of this pathway between closely related chimalliviruses implicates its role as a key player in the evolutionary arms race between competing phages and their hosts.

An essential and highly selective protein import pathway encoded by nucleus-forming phage

Targeting proteins to specific subcellular destinations is essential in prokaryotes, eukaryotes, and the viruses that infect them. Chimalliviridae phages encapsulate their genomes in a nucleus-like replication compartment composed of the protein chimallin (ChmA) that excludes ribosomes and decouples transcription from translation. These phages selectively partition proteins between the phage nucleus and the bacterial cytoplasm. Currently, the genes and signals that govern selective protein import into the phage nucleus are unknown. Here we identify two components of this novel protein import pathway: a species-specific surface-exposed region of a phage intranuclear protein required for nuclear entry and a conserved protein, PicA, that facilitates cargo protein trafficking across the phage nuclear shell. We also identify a defective cargo protein that is targeted to PicA on the nuclear periphery but fails to enter the nucleus, providing insight into the mechanism of nuclear protein trafficking. Using CRISPRi-ART protein expression knockdown of PicA, we show that PicA is essential early in the chimallivirus replication cycle. Together our results allow us to propose a multistep model for the Protein Import Chimallivirus (PIC) pathway, where proteins are targeted to PicA by amino acids on their surface, and then licensed by PicA for nuclear entry. The divergence in the selectivity of this pathway between closely-related chimalliviruses implicates its role as a key player in the evolutionary arms race between competing phages and their hosts.

Significance Statement

The phage nucleus is an enclosed replication compartment built by Chimalliviridae phages that, similar to the eukaryotic nucleus, separates transcription from translation and selectively imports certain proteins. This allows the phage to concentrate proteins required for DNA replication and transcription while excluding DNA-targeting host defense proteins. However, the mechanism of selective trafficking into the phage nucleus is currently unknown. Here we determine the region of a phage nuclear protein that targets it for nuclear import and identify a conserved, essential nuclear shell-associated protein that plays a key role in this process. This work provides the first mechanistic model of selective import into the phage nucleus.

Cellular arrangement impacts metabolic activity and antibiotic tolerance in Pseudomonas aeruginosa biofilms

Cells must access resources to survive, and the anatomy of multicellular structures influences this access. In diverse multicellular eukaryotes, resources are provided by internal conduits that allow substances to travel more readily through tissue than they would via diffusion. Microbes growing in multicellular structures, called biofilms, are also affected by differential access to resources and we hypothesized that this is influenced by the physical arrangement of the cells. In this study, we examined the microanatomy of biofilms formed by the pathogenic bacterium Pseudomonas aeruginosa and discovered that clonal cells form striations that are packed lengthwise across most of a mature biofilm's depth. We identified mutants, including those defective in pilus function and in O-antigen attachment, that show alterations to this lengthwise packing phenotype. Consistent with the notion that cellular arrangement affects access to resources within the biofilm, we found that while the wild type shows even distribution of tested substrates across depth, the mutants show accumulation of substrates at the biofilm boundaries. Furthermore, we found that altered cellular arrangement within biofilms affects the localization of metabolic activity, the survival of resident cells, and the susceptibility of subpopulations to antibiotic treatment. Our observations provide insight into cellular features that determine biofilm microanatomy, with consequences for physiological differentiation and drug sensitivity.

Jumbo phages are active against extensively drug-resistant eyedrop-associated Pseudomonas aeruginosa infections

Antibiotic-resistant bacteria present an emerging challenge to human health. Their prevalence has been increasing across the globe due in part to the liberal use of antibiotics that has pressured them to develop resistance. Those bacteria that acquire mobile genetic elements are especially concerning because those plasmids may be shared readily with other microbes that can then also become antibiotic resistant. Serious infections have recently been related to the contamination of preservative-free eyedrops with extensively drug-resistant (XDR) isolates of Pseudomonas aeruginosa, already resulting in three deaths. These drug-resistant isolates cannot be managed with most conventional antibiotics. We sought to identify alternatives to conventional antibiotics for the lysis of these XDR isolates and identified multiple bacteriophages (viruses that attack bacteria) that killed them efficiently. We found both jumbo phages (>200 kb in genome size) and non-jumbo phages that were active against these isolates, the former killing more efficiently. Jumbo phages effectively killed the three separate XDR P. aeruginosa isolates both on solid and liquid medium. Given the ongoing nature of the XDR P. aeruginosa eyedrop outbreak, the identification of phages active against them provides physicians with several novel potential alternatives for treatment.

A mobile intron facilitates interference competition between co-infecting viruses

Mobile introns containing homing endonucleases are widespread in nature and have long been assumed to be selfish elements that provide no benefit to the host organism. These genetic elements are common in viruses, but whether they confer a selective advantage is unclear. Here we studied a mobile intron in bacteriophage ΦPA3 and found its homing endonuclease gp210 contributes to viral competition by interfering with the virogenesis of co-infecting phage ΦKZ. We show that gp210 targets a specific sequence in its competitor ΦKZ, preventing the assembly of progeny viruses. This work reports the first demonstration of how a mobile intron can be deployed to engage in interference competition and provide a reproductive advantage. Given the ubiquity of introns, this selective advantage likely has widespread evolutionary implications in nature.

Sequential membrane- and protein-bound organelles compartmentalize genomes during phage infection

Eukaryotic viruses assemble compartments required for genome replication, but no such organelles are known to be essential for prokaryotic viruses. Bacteriophages of the family Chimalliviridae sequester their genomes within a phage-generated organelle, the phage nucleus, which is enclosed by a lattice of viral protein ChmA. Using the dRfxCas13d-based knockdown system CRISPRi-ART, we show that ChmA is essential for the E. coli phage Goslar life cycle. Without ChmA, infections are arrested at an early stage in which the injected phage genome is enclosed in a membrane-bound vesicle capable of gene expression but not DNA replication. Not only do we demonstrate that the phage nucleus is essential for genome replication, but we also show that the Chimalliviridae early phage infection (EPI) vesicle is a transcriptionally active, phage-generated organelle.

Cell arrangement impacts metabolic activity and antibiotic tolerance in Pseudomonas aeruginosa biofilms

Cells must access resources to survive, and the anatomy of multicellular structures influences this access. In diverse multicellular eukaryotes, resources are provided by internal conduits that allow substances to travel more readily through tissue than they would via diffusion. Microbes growing in multicellular structures, called biofilms, are also affected by differential access to resources and we hypothesized that this is influenced by the physical arrangement of the cells. In this study, we examined the microanatomy of biofilms formed by the pathogenic bacterium Pseudomonas aeruginosa and discovered that clonal cells form striations that are packed lengthwise across most of a mature biofilm's depth. We identified mutants, including those defective in pilus function and in O-antigen attachment, that show alterations to this lengthwise packing phenotype. Consistent with the notion that cellular arrangement affects access to resources within the biofilm, we found that while the wild type shows even distribution of tested substrates across depth, the mutants show accumulation of substrates at the biofilm boundaries. Furthermore, we found that altered cellular arrangement within biofilms affects the localization of metabolic activity, the survival of resident cells, and the susceptibility of subpopulations to antibiotic treatment. Our observations provide insight into cellular features that determine biofilm microanatomy, with consequences for physiological differentiation and drug sensitivity.

IQGAP1 binds AMPK and is required for maximum AMPK activation

AMP-activated protein kinase (AMPK) is a fundamental component of a protein kinase cascade that is an energy sensor. AMPK maintains energy homeostasis in the cell by promoting catabolic and inhibiting anabolic pathways. Activation of AMPK requires phosphorylation by the liver kinase B1 or by the Ca²⁺/calmodulin-dependent protein kinase 2 (CaMKK2). The scaffold protein IQGAP1 regulates intracellular signaling pathways, such as the mitogen-activated protein kinase and AKT signaling cascades. Recent work implicates the participation of IQGAP1 in metabolic function, but the molecular mechanisms underlying these effects are poorly understood. Here, using several approaches including binding analysis with fusion proteins, siRNA-mediated gene silencing, RT-PCR, and knockout mice, we investigated whether IQGAP1 modulates AMPK signaling. In vitro analysis reveals that IQGAP1 binds directly to the α1 subunit of AMPK. In addition, we observed a direct interaction between IQGAP1 and CaMKK2, which is mediated by the IQ domain of IQGAP1. Both CaMKK2 and AMPK associate with IQGAP1 in cells. The ability of metformin and increased intracellular free Ca²⁺ concentrations to activate AMPK is reduced in cells lacking IQGAP1. Importantly, Ca²⁺-stimulated AMPK phosphorylation was rescued by re-expression of IQGAP1 in IQGAP1-null cell lines. Comparison of the fasting response in wild-type and IQGAP1-null mice revealed that transcriptional regulation of the gluconeogenesis genes PCK1 and G6PC and the fatty acid synthesis genes FASN and ACC1 is impaired in IQGAP1-null mice. Our data disclose a previously unidentified functional interaction between IQGAP1 and AMPK and suggest that IQGAP1 modulates AMPK signaling.

Endogenous IQGAP1 and IQGAP3 do not functionally interact with Ras

The Ras family of small GTPases modulates numerous essential processes. Activating Ras mutations result in hyper-activation of selected signaling cascades, which leads to human diseases. The high frequency of Ras mutations in human malignant neoplasms has led to Ras being a desirable chemotherapeutic target. The IQGAP family of scaffold proteins binds to and regulates multiple signaling molecules, including the Rho family GTPases Rac1 and Cdc42. There are conflicting data in the published literature regarding interactions between IQGAP and Ras proteins. Initial reports showed no binding, but subsequent studies claim associations of IQGAP1 and IQGAP3 with K-Ras and H-Ras, respectively. Therefore, we set out to resolve this controversy. Here we demonstrate that neither endogenous IQGAP1 nor endogenous IQGAP3 binds to the major Ras isoforms, namely H-, K-, and N-Ras. Importantly, Ras activation by epidermal growth factor is not altered when IQGAP1 or IQGAP3 proteins are depleted from cells. These data strongly suggest that IQGAP proteins are not functional interactors of H-, K-, or N-Ras and challenge the rationale for targeting the interaction of Ras with IQGAP for the development of therapeutic agents.

Paraffin Embedding and Thin Sectioning of Microbial Colony Biofilms for Microscopic Analysis

Sectioning via paraffin embedding is a broadly established technique in eukaryotic systems. Here we provide a method for the fixation, embedding, and sectioning of intact microbial colony biofilms using perfused paraffin wax. To adapt this method for use on colony biofilms, we developed techniques for maintaining each sample on its growth substrate and laminating it with an agar overlayer, and added lysine to the fixative solution. These optimizations improve sample retention and preservation of micromorphological features. Samples prepared in this manner are amenable to thin sectioning and imaging by light, fluorescence, and transmission electron microscopy. We have applied this technique to colony biofilms of Pseudomonas aeruginosa, Pseudomonas synxantha, Bacillus subtilis, and Vibrio cholerae. The high level of detail visible in samples generated by this method, combined with reporter strain engineering or the use of specific dyes, can provide exciting insights into the physiology and development of microbial communities.

IQGAP1 Binds to Yes-associated Protein (YAP) and Modulates Its Transcriptional Activity

During development, the Hippo signaling pathway regulates key physiological processes, such as control of organ size, regeneration, and stem cell biology. Yes-associated protein (YAP) is a major transcriptional co-activator of the Hippo pathway. The scaffold protein IQGAP1 interacts with more than 100 binding partners to integrate diverse signaling pathways. In this study, we report that IQGAP1 binds to YAP and modulates its activity. IQGAP1 and YAP co-immunoprecipitated from cells. In vitro analysis with pure proteins demonstrated a direct interaction between IQGAP1 and YAP. Analysis with multiple fragments of each protein showed that the interaction occurs via the IQ domain of IQGAP1 and the TEAD-binding domain of YAP. The interaction between IQGAP1 and YAP has functional effects. Knock-out of endogenous IQGAP1 significantly increased the formation of nuclear YAP-TEAD complexes. Transcription assays were performed with IQGAP1-null mouse embryonic fibroblasts and HEK293 cells with IQGAP1 knockdown by CRISPR/Cas9. Quantification demonstrated that YAP-TEAD-mediated transcription in cells lacking IQGAP1 was significantly greater than in control cells. These data reveal that IQGAP1 binds to YAP and modulates its co-transcriptional function, suggesting that IQGAP1 participates in Hippo signaling.

Modeling lesion counts in multiple sclerosis when patients have been selected for baseline activity

The number of new gadolinium-enhancing lesions discovered via magnetic resonance imaging is a well-established outcome for multiple sclerosis studies, especially Phase II Studies. Due to the high cost of magnetic resonance imaging scans, many investigators select participants for the presence of lesions. While this selection procedure is thought to improve the power of inferences, the effect of screening for baseline activity on parameter estimation and interval coverage has not yet been examined. The objective of this study was to investigate the performance of the negative binomial distribution for modeling lesion count data in multiple sclerosis when patients have been selected for activity on a baseline scan. We performed computer simulations to investigate the influence of the screening process on inferences made using a negative binomial model about treatment effects in two independent samples. We also demonstrate how the statistical properties of screening can be incorporated into trial design. We demonstrate that when the negative binomial distribution is used to model lesion counts, while screening for baseline activity improves point estimation, this practice also has the potential to decrease interval coverage and inflate the Type I error rate. For data that is to be modeled using a negative binomial distribution, screening for baseline activity can create a trade-off between cost effectiveness and a higher than desired false positive rate that must be carefully considered in planning Phase II trials.

Application of the Phenomenex EZ:faasttrade mark amino acid analysis kit for rapid gas-chromatographic determination of concentrations of plasma tryptophan and its brain uptake competitors

The Phenomenex EZ:faast™ amino acid analysis kit is available for gas (GC) or liquid (LC) chromatographic analysis of amino acids (AA) using mass spectrometry (MS) and other GC detectors. We used it for rapid GC determination of plasma tryptophan, its brain uptake competitors (Val, Leu, Ile, Phe and Tyr) and many other amino acids. Based on solid-phase extraction, this fast method enables one person to process two plasma samples in 8–10 min and six samples in ∼15 min up to GC injection and a 7-min GC run per plasma sample. Using a Perkin-Elmer Clarus 500 GC, a Total Chrome software, a flame-ionisation detector (FID) and norvaline as internal standard, we used this method to analyse ∼1,000 plasma samples from normal subjects undergoing acute tryptophan depletion and loading tests. The limit of detection for most amino acids is 1 nmol/ml (1 μM) and in many cases less. With manual injection, coefficients of variation for the above six amino acids were 1.5–6.2% (intra-assay) and 3.8–9.7% (inter-assay). This simple, rapid and elegant method will be valuable to the amino acid analyst and researcher, as it can save much manpower time and meet urgent emergency requests and the demands of a high-throughput laboratory.

Multiple Spitz naevi: a report of both variants with clinical and histopathological correlation

Spitz naevi are usually solitary lesions. Multiple Spitz naevi are extremely rare and reported as widespread (disseminated) or grouped (agminated). We report two cases of multiple Spitz naevi and review their aetiology and treatment.

Upper airway obstruction as a result of massive subcutaneous emphysema following accidental removal of an intercostal drain

A case is described of extensive subcutaneous emphysema with rapid and life-threatening airway obstruction. The incident followed inadvertent removal of a chest drain in a patient with a persistent air leak from an iatrogenic pneumothorax. The pneumothorax had developed during pacemaker insertion.

The role of stratum corneum and dermal microvascular perfusion in penetration and tissue levels of water-soluble drugs investigated by microdialysis

BACKGROUND

Hydrophilic drugs are poorly absorbed when applied topically, due to low partitioning through the lipid matrix of the stratum corneum. Cutaneous blood flow rapidly clears the absorbed drug, which may result in low tissue levels. This is of importance for topically applied drugs whose site of action is within the epidermis or dermis. Dermal drug levels can be measured using cutaneous microdialysis, which is a means of continuously sampling substances from the dermal extracellular fluid.

OBJECTIVES

To measure the contribution of stratum corneum barrier and microvascular perfusion in determining dermal tissue levels of hydrophilic drugs (aciclovir and penciclovir) in vivo.

METHODS

Studies were performed using microdialysis of the volar surface of the forearm of healthy volunteers (n = 55) over a 5-h collection period. Stratum corneum was removed by tape stripping, and barrier disruption quantified by measurement of transepidermal water loss (TEWL); dermal microvascular perfusion was modulated by inclusion of noradrenaline in the microdialysis perfusate.

RESULTS

With intact skin and normal cutaneous blood flow the concentration of penciclovir recovered was below assay threshold (0.05 ng x mL(-1). With noradrenaline-induced local vasoconstriction, the area under the curve of drug absorbed through normal skin (+/- SEM) was 13.3 +/- 2.9 ng mL(-1) h(0-5) for penciclovir and 27.6 +/- 10.6 ng mL(-1) h(0-5) for aciclovir. Removal of the stratum corneum (to glistening) by tape stripping increased penciclovir absorption by 1300-fold and aciclovir absorption by 440-fold, confirming the stratum corneum as the major barrier to hydrophilic drug absorption. Sequential barrier disruption by tape stripping gave a close correlation between penciclovir concentration absorbed per hour and barrier disruption measured by TEWL (r2 = 0.9283). There was a 15.6-fold difference in the recovery of penciclovir through barrier-deficient skin with and without cutaneous blood flow. There was no relationship between fibre depth and amount of drug dialysed, which suggests free movement of antiviral drug on reaching the aqueous environment of the dermis.

CONCLUSIONS

This study defines for the first time the relationship between the degree of mechanical barrier impairment and drug absorption at the same anatomical site in humans, and the role of blood flow in drug clearance in vivo.

Study of five cell salvage machines in coronary artery surgery

We evaluated the effectiveness, ease of use and safety of five machines for blood salvage during coronary artery surgery. All were equally effective in concentrating red cells. We measured haemoglobin, packed cell volume, free haemoglobin, white cells, neutrophil elastase, platelets, thrombin-antithrombin complex (TAT), prothrombin activation peptide F1.2, fibrin degradation product (d-dimers), tissue plasminogen activator (tPA) and heparin in wound blood, in washed cell suspensions and in a unit of bank blood prepared for each patient. All machines were equally safe and easy to use and were equally effective in removing heparin and the physiological components measured. There were no adverse effects on patients. Clotting factors are severely depleted both in salvaged blood, even before washing, and in bank blood. Cell savers are a valuable adjunct to coronary artery surgery, but careful monitoring of coagulation is required when the volumes of either bank blood or salvaged blood are large.

Kidney dialysis-associated amyloidosis: a molecular role for copper in fiber formation

In the US alone, more than 250,000 people have impaired renal function that necessitates treatment by dialysis. A debilitating complication of long-term treatment is the deposition of beta2-microglobulin (beta2m) as amyloid fibers within the joint space. However, the intrinsic propensity of isolated beta2m protein to initiate in vitro fiber formation is negligible under conditions matched to the neutral pH and ionic conditions of serum. Here, we present evidence for a novel interaction between beta2m and Cu(2+) at a concentration within institutionally recommended limits for this metal ion in dialysate solution. Mass spectrometry, using electrospray ionization from native conditions, demonstrates that the binding of Cu(2+) is specific over Ca(2+) or Zn(2+). Despite maintaining a native-like conformation upon Cu(2+) binding, the folded protein is unusually destabilized against thermal and urea denaturation. We further demonstrate that destabilization by Cu(2+) uniquely promotes de novo fiber formation at 37 degrees C and neutral pH. Since the incidence of amyloidosis is dramatically reduced upon elimination of copper from dialysis membranes, our results provide a molecular understanding for dialysis-associated amyloid formation by beta2m.

Mitochondrial DNA content affects the fertilizability of human oocytes

Mitochondrial DNA content varies considerably in oocytes, even when collected from the same patient. In the present study, real-time quantitative polymerase chain reaction analysis of 113 unfertilized oocytes obtained from 43 patients revealed an average of 193,000 (range: 20,000 to 598,000) mitochondrial genomes per cell. We compared several groups of oocytes to investigate the relationship between mitochondrial DNA content and fertilizability. The average mitochondrial DNA copy number was significantly lower in cohorts suffering from fertilization failure compared to cohorts with a normal rate of fertilization. In addition, the mitochondrial copy number of oocytes from patients with fertilization failure due to unknown causes was significantly lower than that of oocytes from patients in which IVF failure was due mainly to a severe sperm defect. The lower mtDNA copy number could be due to defective cytoplasmic maturation of oocytes. We conclude that low mitochondrial DNA content, due to inadequate mitochondrial biogenesis or cytoplasmic maturation, may adversely affect oocyte fertilizability.

A conserved N-terminal sequence targets human DAP3 to mitochondria

Human DAP3 (death-associated protein-3) has been identified as an essential positive mediator of programmed cell death. Structure-function studies have shown previously the N-terminal extremity of the protein to be required in apoptosis induction. Analysis of human DAP3 gene structure predicted 13 exons and subsequent targeting prediction by two software packages (MITOPROT and TargetP) gave a high probability for mitochondrial targeting. The predicted N-terminal targeting structure was also found in the mouse, Drosophila, and C. elegans orthologues with a strong sequence homology between mouse and human. Secondary structure analyses identified alpha-helical structures typical of mitochondrial target peptides. To confirm experimentally this targeting we constructed a fusion protein with N-terminal human DAP3 upstream of enhanced green fluorescent protein (EGFP). Confocal analysis of transfected human fibroblasts clearly demonstrated EGFP localization exclusive to mitochondria. The positioning of this key apoptotic factor at the heart of the mitochondrial pathway provides exciting insight into its role in programmed cell death.

Alcohol-induced euphoria: exclusion of serotonin

During the first 30 min after acute ethanol consumption by three fasting normal male volunteers, no increase in circulating tryptophan availability to the brain occurred. On the contrary, a small decrease was observed, which became stronger subsequently. We conclude from this preliminary study that brain serotonin levels are not increased after alcohol intake by normal subjects and that, consequently, this indolylamine is unlikely to mediate the euphoric effects of alcohol.

Rat liver tryptophan pyrrolase activity and gene expression during alcohol withdrawal

Rat liver tryptophan (Trp) pyrrolase activity and gene expression were studied in relation to the alcohol-withdrawal syndrome (AWS). Both activity and gene expression were enhanced after withdrawal of ethanol-containing liquid diets and the time-course of these changes mirrored that of development and intensity of the behavioural disturbances of the AWS. By contrast, no correlation was observed between the AWS-induced behaviour and changes in activity of another hepatic glucocorticoid-inducible enzyme, tyrosine aminotransferase, and a negative correlation was noted between behaviour and the gene expression of this latter enzyme and also of that of the hepatic glucocorticoid receptor. We suggest that the metabolic consequences of activation of liver Trp pyrrolase during alcohol withdrawal may play a role in the behavioural features of the AWS.

Metastatic testicular cancer presenting as spinal cord compression: report of two cases

BACKGROUND

Testicular cancers are heterogenous neoplasms often found in young adults. They tend to metastasize to the chest, retroperitoneum, or neck, but rarely to the long bones or skeleton. However, they can cause neurologic compromise and should be considered in young male patients who present with symptoms of a spine lesion and no known primary cancer.

METHODS

Two patients presented with back pain and a rapid progression of lower extremity weakness. Both underwent radiographic workup and emergency surgery. Metastatic workup revealed testicular cancer and widespread metastases.

RESULTS

Both patients improved neurologically after surgery, but neither regained the ability to ambulate independently. They both underwent chemotherapy. One patient is alive at 1 year follow-up; the other died 9 months after surgery of widespread metastases.

CONCLUSIONS

Vertebral metastases from testicular tumors, although rare, should be considered in young men presenting with spinal cord compression. Work-up should include magnetic resonance imaging (MRI) of the spine and computed tomography (CT) of the chest, abdomen, and pelvis. Urgent intervention may be required, as these two cases show that loss of neurologic function can be rapid and permanent.

A compact monomeric intermediate identified by NMR in the denaturation of dimeric triose phosphate isomerase

The denaturation of triose phosphate isomerase (TIM) from Saccharomyces cerevisiae by guanidine hydrochlorids at pH 7.2 has been monitored by NMR spectroscopy in conjunction with optical spectroscopy. In the absence of denaturant, the hydrodynamic radius of 29.6(+/-0.25) A and the substantial chemical shift dispersion evident in the NMR spectrum are consistent with the highly structured dimeric native state of the protein. On the addition of 2. 2 M guanidine hydrochloride the effective hydrodynamic radius increases to 51.4(+/-0.43) A, consistent with that anticipated for the polypeptide chain in a highly unstructured random coil state. In 1.1 M guanidine hydrochloride, however, the effective hydrodynamic radius is 24.0(+/-0.25) A, a value substantially decreased relative to that of the native dimeric state but very close to that anticipated for a monomeric species with native-like compaction (23. 5 A). The lack of chemical shift dispersion indicates, however, that few tertiary interactions persist within this species. Far UV CD and intrinsic fluorescence measurements show that this compact intermediate retains significant secondary structure and that on average the fluorophores are partially excluded from solvent. Such a species could be important in the formation of dimeric TIM from its unfolded state.

Acute renal failure following cardiopulmonary bypass: a changing picture

OBJECTIVE

To assess the incidence of acute renal failure (ARF) developing perioperatively in adult patients requiring cardiopulmonary bypass surgery (CPB) and to make comparisons with data from the same institution published earlier.

DESIGN

Prospective, observational.

SETTING

Tertiary referral centre for cardiopulmonary medicine.

PATIENTS AND PARTICIPANTS

All patients admitted to the intensive care unit (ICU) who developed ARF perioperatively necessitating continuous veno-venous haemofiltration (CVVH) during the 24 months January 1997-December 1998.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Of 2337 adult patients undergoing cardiac surgery, 47 (2.0%) needed CVVH. Patients were excluded from analysis who underwent cardiac transplantation (n = 4), pericardial surgery (n = 3) or insertion of a left ventricular assist device (n = 1). Of the remaining 39, 21 patients died in ICU (53.8% mortality). Relatively more non-survivors suffered from diabetes, hypertension and preoperative renal dysfunction. A previous report from our Unit revealed that, in 1989-90, 2.7% of all patients undergoing CPB required CVVH with an in-hospital mortality of 83%. The current study population were older (65.3 vs 56.0 years in 1990), and more severely ill as evidenced by a higher percentage of patients requiring redo (30% vs 8.6% in 1990) and emergency (50% vs 25.7% in 1990) surgery.

CONCLUSIONS

The need for CVVH following CPB may be diminishing despite increased risk factors. ARF-associated mortality in these circumstances is falling.

Hypoxemia after coronary bypass surgery modeled by resistance to oxygen diffusion

OBJECTIVE

To evaluate a model describing postoperative hypoxemia after cardiac surgery by using two variables, i.e., shunt and resistance to oxygen diffusion (Rdff).

DESIGN

Estimation of these two variables in normal subjects and postoperative cardiac patients.

SETTING

The pulmonary function laboratory for the normal subjects and the intensive care unit for the cardiac patients.

PATIENTS/SUBJECTS

Nine postoperative cardiac patients and six healthy subjects.

INTERVENTIONS

Inspired oxygen fraction was varied in normal subjects and in cardiac patients 3-6 hrs after surgery. This variation occurred in four to seven steps to achieve arterial oxygen saturations in the range 0.90-1.00.

MEASUREMENTS AND MAIN RESULTS

Measurements were taken of arterial oxygen saturation, cardiac output, ventilation, and end-tidal gases at each inspired oxygen fraction. These measurements gave the following estimates for the normal subjects: shunt = 3.9+/-5.4% (mean +/- SD) and Rdiff = -5+/-16 torr/(L/min) [-0.7+/-2.2 kPa/(L/min)]; for the cardiac patients: shunt = 7.7+/-1.8% and Rdiff = 212+/-230 torr/(L/min) [28.2+/-30.6 kPa/(L/min)]. The increase in Rdiff (P = .01) was sufficient to explain the observed hypoxemia in these patients. The value for shunt was not significantly increased in the patients (p = .09). The two-variable model (shunt and Rdff) gave a better prediction of arterial oxygen saturation than a model with shunt as the only variable (p = .02).

CONCLUSIONS

In cardiac patients requiring supplementary oxygen, the respiratory abnormality could, in our model, be best described by an increased Rdiff, not by an increased shunt value.

Predicting DSM-III-R disorders from the Youth Self-Report: analysis of data from a field study

OBJECTIVE

To predict DSM-III-R diagnoses from Youth Self-Report (YSR) scores.

METHOD

The Diagnostic Interview Schedule for Children Version 2.1c (DISC-2.1c) and YSR were administered to 289 homeless adolescents. Stepwise discriminant analysis identified YSR scales contributing to predictions of DSM-III-R disorders. Paper-and-pencil prediction rules based on YSR "borderline" or "clinical" scores were evaluated.

RESULTS

Statistically significant discriminant functions for disruptive disorders, depressive disorders, manic disorders, attention-deficit hyperactivity disorder, schizophrenia, and posttraumatic stress disorder, each based on a unique pair of YSR scales, produced overall hit rates of 0.66 to 0.90. Paper-and-pencil predictions produced comparable results. The weakest overall predictions were for the disruptive behaviors; the best rule ("IF Aggressive OR Delinquent is at least borderline THEN predict oppositional defiant disorder or conduct disorder") produced a 0.72 hit rate. The strongest overall predictions were for schizophrenia; the best prediction rule ("IF [Thought Problems AND Delinquent are at least borderline] AND [at least one is clinical] THEN predict schizophrenia") produced a 0.87 hlt rate.

CONCLUSIONS

While the success rates reported here are specific to this sample, it appears that the YSR has good ability to predict DSM-III-R diagnoses as determined by the DISC. Furthermore, it was demonstrated that categorical diagnoses can be treated as locations or cluster sectors in a multidimensional space.

Inhibition of rat liver tryptophan pyrrolase activity by fluoxetine

The present study has demonstrated the effectiveness of acute administration of fluoxetine to inhibit rat liver tryptophan pyrrolase activity. The maximum inhibition of basal liver tryptophan pyrrolase activity at 2 h after administration was observed with 1 mg/kg dose for the total enzyme and apoenzyme activities and that significant inhibition of these two activities was evident with a dose of the drug as small as 0.5 mg/kg. Serum free tryptophan concentrations were also increased using 10 mg/kg dose of fluoxetine. In view of the role of tryptophan depletion and thus 5-HT in pathophysiology of depression, it is strongly suggested that the inhibition of liver tryptophan pyrrolase activity may be a major mechanism of antidepressant action.

Tryptophan metabolism in alcoholism. Tryptophan but not excitatory amino acid availability to the brain is increased before the appearance of the alcohol-withdrawal syndrome in men

Tryptophan (Trp) metabolism and disposition and excitatory and other amino acid concentrations were determined in alcohol-dependent subjects in relation to the alcohol-withdrawal syndrome (AWS). Parameters were examined in 12 alcohol-dependent male subjects, undergoing elective upper digestive tract tumour resection, and 12 age-, gender-, and medication-matched controls on three occasions: pre-operatively, post-operatively, and immediately before (i.e. within 24 h of) the appearance of the AWS. No significant differences were observed between controls and alcoholic subjects on the first or second of these occasions. On the third occasion, within 24 h of the appearance of the AWS, alcoholics showed a dramatic elevation (117%) in free serum Trp concentration and a consequent increase (111%) in the ratio of [free Trp]/[competing amino acids], which is an accurate predictor of Trp entry into the brain. Increases were also observed on this third occasion in concentrations of total Trp (49%), cortisol (123%), and norharman (137%). Concentrations of glutamate, glycine, aspartate, serine, and taurine did not differ significantly within or between the control and alcohol-dependent groups of subjects on any of the three occasions. The possible significance of the Trp and related metabolic changes in relation to the behavioural features of the AWS is discussed.

Characterization of collapsed states in the early stages of the refolding of hen lysozyme

Early conformational states in the refolding of hen lysozyme from guanidine hydrochloride have been characterized by measuring both the fluorescence and the solvent exchange properties of tryptophan side chains. The indole proton occupancies indicate that at pH 5.5, 25 degrees C, half the protection against pulse labeling occurs in the dead time (4 ms) of the experiment, with the remaining protection developing with a time constant of 55 ms. Comparison of these data with the protection kinetics of backbone amides and with the fluorescence data provides evidence for hydrophobic collapse involving incorporation of tryptophan residues in a solvent-excluded state in advance of stable secondary structure formation. Analysis of the pH dependence of the indole hydrogen exchange protection is consistent with two or more structurally distinct collapsed states, and indicates that the generation of a correctly folded compact hydrophobic core is a key precursor to the formation of persistent native-like structure during refolding.

Tryptophan metabolism in male Sardinian alcohol-preferring (sP) and -non-preferring (sNP) rats

Parameters of tryptophan (Trp) and related metabolism were compared in male Sardinian alcohol-preferring (sP) and -non-preferring (sNP) rats. Liver Trp pyrrolase activity was 38-58% higher in sP than in sNP rats, and this was associated with a greater expression of the enzyme mRNA as measured by multiprobe oligonucleotide solution hybridization. Moderately (about 10-19%), but significantly, lower concentrations of free serum, total serum, and brain Trp were also observed in sP compared with sNP rats. Concentrations of whole brain 5-hydroxytryptamine (5-HT) and its major metabolite 5-hydroxyindol-3-yl-acetic acid (5-HIAA) were, however, 14-21% higher in sP rats. Serum corticosterone concentration was 18% higher in sP rats. We conclude that alcohol preference in Sardinian rats is associated with increased liver Trp pyrrolase activity and mRNA expression leading to a decrease in Trp availability to the brain. Although a simple serotonin deficiency could not be demonstrated in the whole brain, the possibility could not be ruled out that a deficiency may be present in discrete areas of the brain of the sP rat.

Reduced mortality in association with the acute respiratory distress syndrome (ARDS)

BACKGROUND

A study was undertaken to investigate possible reductions in mortality and/or changes in outcome predictive factors in patients with the acute respiratory distress syndrome (ARDS) managed in a single centre.

METHODS

The study was a prospective observational cohort study of two patient populations with ARDS. Group 1 comprised 41 patients enrolled between May 1990 and April 1993, and group 2 consisted of 78 patients enrolled between June 1993 and March 1997. The end points of the study were mortality and various factors predictive of death.

RESULTS

There was a marked reduction in mortality between groups 1 and 2 (66% versus 34%; relative risk 1.77; CI 1.23 to 2.55). There were no significant differences between the groups in terms of age (40.6 (3.3) versus 45.5 (2.2) years), APACHE score (14.5 (0.72) versus 13.6 (0.1)), lung injury score (2.95 (0.07) versus 2.8 (0.1)), incidence of multi-organ failure (29% versus 32%), incidence of sepsis (31% versus 39%), or PaO2/FIO2 (kPa) ratio (11.8 (0.67) versus 12.0 (0.6)). There was a significantly lower proportion of men in group 1 (51% versus 74%). The case mix of the two groups was closely matched: following elective surgery 48% versus 48%, trauma 17% versus 16%, primary lung injury 12% versus 24%. Patients in group 1 were supported using several ventilatory and other modes (volume preset, non-inverse ratio ventilation, n = 15; pressure controlled inverse ratio ventilation (PC-IRV), n = 11; ultra high frequency jet ventilation (UHFJV), n = 13; an intravascular oxygenation device (IVOX) and extracorporeal gas exchange (ECGE), n = 2). Within group 1 no significant difference in mortality was observed between the patients on volume controlled ventilation and the remainder. In group 2 all patients received PC-IRV (n = 78) but, in addition, some received other support techniques (UHFJV n = 4, ECGE n = 2). In group 1 only sepsis on admission (21% (survivors) versus 56% (non-survivors)) predicted death. In group 2 age of survivors and non-survivors (41.2 (2.6) versus 52.6 (3.5)), APACHE score (12.2 (0.6) versus 15.8 (0.9)), and PaO2/FIO2 (12.8 (0.86) versus 10.5 (0.72)) predicted survival, but not the incidence of sepsis or multi-organ failure.

CONCLUSIONS

In recent years a highly significant reduction in mortality associated with ARDS has been observed between two groups of patients well matched for disease severity and case mix. Changes in ICU organisation rather than specific interventions may account for this reduction, although different ventilatory and other management strategies used in the two groups may also be relevant.

No early effects of electroconvulsive therapy on tryptophan metabolism and disposition in endogenous depression

The possibility that a single electroconvulsive therapy (ECT) could increase tryptophan (Trp) availability to the brain for 5-hydroxytryptamine (5-HT, serotonin) synthesis was examined in 10 depressed patients before and during the 1st hour following an ECT and in 4 control (minor ear, nose, and throat surgical) subjects receiving similar premedication. Trp availability to the brain, expressed as the serum Trp: competing amino acid ratio, and related aspects of Trp disposition were not significantly altered by ECT any differently than from preoperative stress and premedication. We suggest that Trp availability to the brain and, hence, cerebral 5-HT synthesis are not altered in depressed patients early after a single ECT.

Hydrogen exchange properties of proteins in native and denatured states monitored by mass spectrometry and NMR

The extent of deuterium labeling of hen lysozyme, its three-disulfide derivative, and the homologous alpha-lactalbumins, has been measured by both mass spectrometry and NMR. Different conformational states of the proteins were produced by varying the solution conditions. Alternate protein conformers were found to contain different numbers of 2H atoms. Furthermore, measurement in the gas phase of the mass spectrometer or directly in solution by NMR gave consistent results. The unique ability of mass spectrometry to distinguish distributions of 2H atoms in protein molecules is exemplified using samples prepared to contain different populations of 2H-labeled protein. A comparison of the peak widths of bovine alpha-lactalbumin in alternate solution conformations but containing the same average number of 2H atoms showed dramatic differences due to different 2H distributions in the two protein conformers. Measurement of 2H distributions by ESI-MS enabled characterization of conformational averaging and structural heterogeneity. In addition, a time course for hydrogen exchange was examined and the variation in distributions of 2H atom compared with simulations for different hydrogen exchange models. The results clearly show that exchange from the native state of bovine alpha-lactalbumin at 15 degrees C is dominated by local unfolding events.

Leukotrienes are indicated as mediators of hyperoxia-inhibited alveolarization in newborn rats

We investigated the role of leukotrienes (LT) in hyperoxia-induced changes in lung parenchyma in neonatal rat pups. Rat pups were exposed to 21% O(2) (air) or >95% O(2) from days 4 to 14 after birth and were administered the 5-lipoxygenase (5-LO) inhibitor and LTD4 receptor antagonist Wy-50295, 5-LO-activating protein inhibitor MK-0591, or vehicle from days 3 to 14. All measurements were done on days 12-14. There was a significant (P < 0.05) increase in peptido-LT output from lung slices of animals exposed to O(2) compared with air-exposed animals. Both Wy-50295 and MK-0591 significantly lowered (P < 0.05) peptido-LT output in O(2)-exposed animals. The 6-ketoprostaglandin F(1alpha) output was increased similarly in both vehicle- and drug-treated O(2)-exposed animals. O(2) exposure also caused a significant increase in bronchoalveolar lavage fluid protein and extravascular lung water that could not be ameliorated by Wy-50295 or MK-0591. Hyperoxia-induced inhibition of alveolarization, indicated by a significantly (P < 0.05) lower parenchymal tissue density, specific internal surface area, and airspace perimeter-to-area ratio, and a significantly (P < 0.05) higher mean linear intercept and airspace unit volume than air-exposed animals, was prevented by both Wy-50295 and MK-0591. Although hyperoxia had no effect on septal thickness, Wy-50295 caused significant thickening in both air- and O(2)-exposed pups. Our studies provide evidence that hyperoxia-induced peptido-LT may mediate O(2)-induced inhibition of alveolarization and that this is not caused by an arachidonic acid shunt to cyclooxygenase.

Limitation of life support: frequency and practice in a London and a Cape Town intensive care unit

OBJECTIVES

To examine the frequency of limiting (withdrawing and withholding) therapy in the intensive care unit (ICU), the grounds for limiting therapy, the people involved in the decisions, the way the decisions are implemented and the patient outcome.

DESIGN

Prospective survey. Ethical approval was obtained.

SETTING

ICUs in tertiary centres in London and Cape Town.

PATIENTS

All patients who died or had life support limited.

INTERVENTIONS

Data collection only.

RESULTS

There were 65 deaths out of 945 ICU discharges in London and 45 deaths out of 354 ICU discharges in Cape Town. Therapy was limited in 81.5% and 86.7% respectively (p = 0.6) of patients who died. The mean ages of patients whose therapy was limited were 60.2 years and 51.9 years (p = 0.014) and mean APACHE II scores 18.5 and 22.6 (p = 0.19) respectively. The most common reason for limiting therapy in both centres was multiple organ failure. Both medical and nursing staff were involved in most decisions, which were only implemented once wide consensus had been reached and the families had accepted the situation. Inotropes, ventilation, blood products, and antibiotics were most commonly withdrawn. The mean time from admission to the decision to limit therapy was 11.2 days in London and 9.6 days in Cape Town. The times to outcome (death in all patients) were 13.2 h and 8.1 h respectively.

CONCLUSIONS

Withdrawal of therapy occurred commonly, most often because of multiple organ failure. Wide consensus was reached before a decision was made, and the time to death was generally short.

Definition and detection of alarms in critical care

Critical care medicine has developed enormously in complexity and even more so in cost over the past twenty years. There has been evidence of remarkable progress in improved outcomes from some conditions, particularly when severely ill patients are treated in well equipped and well managed intensive care units (ICU) which have clear directorship and comprehensive management guidelines and protocols (Zimmermann et al., Crit Care Med 1993; 21:1443-1451). Nevertheless, for some conditions such as severe acute respiratory failure and multiple organ failure, there is considerable debate as to whether there has been any improvement at all (Lee et al., Thorax 1994; 49:596-597. Artigas et al., Adult respiratory distress syndrome, Churchill Livingstone, Edinbugh, London, Madrid, Melbourne, New York, Tokyo, pp. 509-525). Developments in signal processing and monitoring and recording technology have resulted in a vast increase in the quantity of data that is available to clinicians trying to manage critically ill patients (Price, Bailliere's Clin Anaesthesiol 1987; 1:533-556) but there is little evidence that this apparent gain has lead to better clinical decisions or earlier warning of significant instability. One of the tasks of the European Union sponsored IMPROVE group was to attempt to identify significant downward trends in vital parameters sufficiently early to allow clinical intervention to be potent and effective and ultimately improve patient outcome from a wide range of life threatening conditions. The first stage of this task was to define examples of such life threatening deterioration and conduct a survey in representative intensive care units of the incidence of these conditions and the subsequent patient outcomes. This is a preliminary task, the next stage being the gathering of "real time' data from critically ill patients for 24-h sample periods to probe for deteriorating trends and to compile a comprehensive annotated data library of physiological data as a rich resource for future adaptations in signal processing technology and clinical decision support.

The localisation and characterisation of insulin-like growth factor-I receptors and the investigation of melatonin receptors on the hair follicles of seasonal and non-seasonal fibre-producing goats

To define the hormonal influences that are directly involved in the hair follicle cycles of animals with differing patterns of fibre growth and moulting, we have investigated the possible presence of IGF-I and melatonin receptors on the dermis and hair follicles of cashmere and Angora goats, sampled in February. March and June, using quantitative in vitro autoradiography. The presence of IGF-I receptors in the dermis of both breeds of goat was determined using cryostat sections incubated with 50 pM 125I-labelled IGF-I in the presence or absence of 50 nM IGF-I. Sections of the growing tip of deep antlers concerning the cartilaginous zone, a tissue known to contain high concentrations of specific IGF-I receptors, were used as a positive control. As the production of antler velvet uniquely involves the generation of hair follicles de novo, the presence of IGF-I receptors in the velvet-producing region was also investigated. In both breeds of goat, specific 125I-IGF-I binding was localised over the inner and outer root sheath, the matrix, the germinal matrix, the dermal papilla and the sebaceous glands and satisfied the basic kinetic criteria considered to be representative of a specific IGF-I receptor. Analysis of saturation isotherms using a one-site binding model revealed dissociation constants (Kd) in the range 0.1-0.9 nM and theoretical maximal numbers of binding sites (Bmax) between 21.4 and 45.6 fmol/mg tissue. Kd and Bmax values derived from cashmere and Angora goats sampled at different times of the year did not differ significantly between breeds or sampling times. Specific 125I-IGF-I binding was also localised to the developing follicles on the deer antler dermis. The presence of melatonin receptors within the goat dermis was also investigated. Sections were incubated with 100 pM 2-[125I]iodomelatonin with or without 0.1 microM melatonin, along with sections of sheep pars tuberalis which are known to contain high levels of high-affinity melatonin receptors. No displaceable 2-[125I]iodomelatonin binding was found on any sections of the cashmere or Angora skin analysed. It is therefore concluded that melatonin receptors are not present on the hair follicles or associated structures. IGF-I receptors are present on the hair follicle and sebaceous gland and may be involved in the growth of both seasonally and non-seasonally produced fibre and in the development of antler velvet.

Prevention by cycloheximide of the audiogenic seizures and tryptophan metabolic disturbances of ethanol withdrawal in rats

Cycloheximide (20 mg/kg body wt, given intraperitoneally at-1 and 3 h after withdrawal of an ethanol-containing liquid diet) prevents the activation of liver tryptophan pyrrolase, the consequent inhibition of synthesis of brain 5-hydroxytryptamine, and the audiogenic seizures observed at 7 h after alcohol withdrawal. We suggest that a rapidly-turning-over protein mediates the alcohol withdrawal syndrome and discuss the possible role of liver tryptophan pyrrolase.

Effects of chronic administration and subsequent withdrawal of ethanol-containing liquid diet on rat liver tryptophan pyrrolase and tryptophan metabolism

An investigation of the effects of chronic administration of ethanol by the liquid diet procedure and its subsequent withdrawal on tryptophan (Trp) metabolism and disposition was performed in rats. Treatment with the control liquid diet caused an enhancement of liver Trp pyrrolase activity and mRNA abundance. These effects are not due to the starvation associated with this feeding procedure, because they occur in rats maintained on the liquid diet ad libitum. Chronic ethanol administration in the liquid diet did not further influence the above increased expression of Trp pyrrolase mRNA but caused inhibition of pyrrolase activity in competition with the effects of the diet. The control liquid diet decreased liver Trp concentration, but exerted no significant effects on other aspects of Trp disposition. The most striking and robust finding was a highly significant elevation in both Trp pyrrolase activity and mRNA expression at 7 h following discontinuation of ethanol availability, at which time there were demonstrable behavioural signs of ethanol withdrawal. The increase in Trp pyrrolase mRNA during alcohol withdrawal may be caused by corticosterone, whose circulating concentration was also increased. The changes in Trp pyrrolase activity during ethanol withdrawal were associated with significant alterations in Trp disposition including decreased brain Trp concentration and 5-hydroxytryptamine synthesis and turnover. These alterations may play a pivotal role in the behavioural manifestations of ethanol withdrawal including the hyperexcitement underlying audiogenic seizures. We suggest that rat Trp pyrrolase gene regulation may be an important biological determinant of the ethanol withdrawal syndrome and requires further study, and that the use of the liquid diet procedure in Trp metabolic studies requires inclusion of adequate controls and special attention to the effects of the liquid diet itself.

Defective transfer RNA-queuine modification in C3H10T1/2 murine fibroblasts transfected with oncogenic ras

tRNA isoacceptors for aspartic acid, asparagine, histidine, and tyrosine are modified in the anticodon wobble position with the deazaguanine analogue queuine. Queuine modification is defective in many tumors and transformed cell lines, and the extent of hypomodification correlates with staging and outcome in numerous human tumors. The molecular role of queuine modification in normal cells and the mechanisms of queuine hypomodification in tumors are unknown. We have characterized nontransformed C3H10T1/2 murine fibroblasts (C3H) and their ras-transfected counterparts (RasC4) with respect to the causes and effects of queuine hypomodification. RasC4 cells are hypomodified for queuine compared with C3H cells, despite increase tRNA-guanine ribosyltansferase activity. Excess exogenous queuine can cause repletion of tRNA queuine levels in RasC4 cells. Queuine modification of both C3H and RasC4 cells can be decreased by treatment with 7-methylguanine. This treatment does not affect growth in monolayer culture but enhances anchorage-independent growth of RasC4 cells greatly. These cell lines may be useful systems for the study of queuine function in normal cells and the causes and consequences of hypomodification for queuine in tumors.

Difficulties in predicting outcome in cardiac surgery patients

OBJECTIVE

To evaluate a novel combination of preoperative, intraoperative, and postoperative variables (including the Parsonnet, and the Acute Physiology and Chronic Health Evaluation II and III [APACHE II and III] scores) in cardiac surgery patients in order to predict hospital outcome, complications, and length of stay.

DESIGN

Prospective survey.

SETTING

Adult intensive care unit (ICU) at a tertiary care cardiothoracic surgery center.

PATIENTS

All cardiac surgery patients admitted to the ICU over a 1-yr period.

INTERVENTIONS

Medical history, Parsonnet score, intraoperative data (including bypass and ischemic times), APACHE II and III scores, complications, and outcome were collected for each patient.

MEASUREMENTS AND MAIN RESULTS

One thousand eight patients were entered into the study. The mean Parsonnet score was 7.8 (range 0 to 33), mean APACHE II score 11.8 (range 2 to 33), and mean APACHE III score 42.5 (range 9 to 132). ICU mortality rate was 2.7% and hospital mortality rate was 3.8%. The mean APACHE II predicted risk of dying was 5.31%, which gave a standardized mortality ratio of 0.71. The above scores were all statistically well correlated with hospital mortality. Further, a logistic regression model was developed for the probability of hospital death. This model (which included bypass time, need for inotropes, mean arterial pressure, urea, and Glasgow Coma Scale) had an area under the receiver operating characteristic curve of 0.87, while the Parsonnet score had an area of 0.82 and the APACHE II risk of dying had an area of 0.84.

CONCLUSIONS

Cardiac surgery remains a difficult area for outcome prediction. A combination of intraoperative and postoperative variables can improve predictive ability.

Decrease in circulating tryptophan availability to the brain after acute ethanol consumption by normal volunteers: implications for alcohol-induced aggressive behaviour and depression

Acute ethanol consumption by fasting male volunteers decreases circulating trytophan (Trp) concentration and availability to the brain as determined by the ratio of (Trp) to the sum of its five competitors ([Trp]/[CAA]ratio). These effects of alcohol are specific to Trp, because levels of the 5 competitors are not increased. The decrease in circulating (Trp) is not associated with altered binding to albumin and may therefore be due to enhancement of hepatic Trp pyrrolase activity. It is suggested that, under these conditions brain serotonin synthesis is likely to be impaired and that, as a consequence, a possible strong depletion of brain serotonin in susceptible individuals may induce aggressive behaviour after alcohol consumption. The possible implications of these findings in the relationship between alcohol and depression are also briefly discussed.

Expansion of mucin-reactive T-helper lymphocytes from patients with colorectal cancer

The ability to identify and expand effector cells with reactivity against tumor-associated antigens (TAA) is critical for effective adoptive cellular therapy. The purpose of this study was to assess lymph node lymphocytes sensitized in vivo to the shed TAA TAG-72 as a potential source of cells for adoptive cellular therapy. Lymph nodes containing microscopic tumor and/or shed TAG-72+ mucin were localized using radiolabeled CC49 monoclonal antibody and a gamma detector at the time of exploratory colorectal surgery. Lymph nodes containing microscopic tumor and shed mucin exhibited approximately 40-fold expansion in short-term (< 21 days) cultures with either IL-2 or IL-1 plus IL-2; the combination of IL-2/anti-CD3 monoclonal antibody (mAb) resulted in significantly higher expansion. Cultures generated with IL-2 alone favored the expansion of CD8+ and CD56+ cells, whereas addition of IL-1 or anti-CD3 mAb to IL-2 promoted outgrowth of CD4+ T-cells. The IL-2/anti-CD3 expanded cells exhibited low levels of cytolytic activity in vitro against autologous and allogeneic colon tumor targets. However, CD4+ cells expanded in IL-2/anti-CD3 retained the ability to proliferate in response to TAG-72 mucin-expressing autologous tumor as well as bovine submaxillary mucin (BSM) a soluble TAG-72+ mucin. In addition, CD4+ cells expressed mRNA for IL-2, IL-4, tumor necrosis factor-beta and IFNg, and retained the ability to secrete IL-2 after expansion. Thus, noncytolytic, cytokine-secreting, mucin-reactive T- cells can be expanded from lymph nodes of patients with colorectal cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Thioguanine-induced growth arrest in 6-mercaptopurine-resistant human leukemia cells

The thiopurines 6-thioguanine (6TG) and 6-mercaptopurine (6MP) are cytotoxic to proliferating cells by a mechanism involving incorporation into DNA via the purine salvage pathway, and resistance to these agents can be conferred by lack of the salvage pathway enzyme hypoxanthine-guanine phosphoribosyltransferase. However, human and murine hypoxanthine-guanine phosphoribosyltransferase-deficient leukemia cell lines have been shown to respond to 6TG by growth arrest and differentiation by a mechanism apparently not involving incorporation of 6TG into DNA. If so, leukemia cells resistant to 6MP should still respond to 6TG by growth arrest via an undescribed epigenetic mechanism. To test this, polyclonal 6MP-resistant variants were produced from three human leukemia cell lines, HL-60, U937, and CCRF-CEM. Treatment of both sensitive and resistant cells with 6TG induced growth arrest. The effect of 6TG in the 6MP-sensitive HL-60 and U937 cells was associated with significant loss of viability and DNA fragmentation. In contrast, the 6TG-treated 6MP-resistant cells exhibited a slower decline in viability and no DNA fragmentation. To identify the mechanism by which 6TG may induce growth arrest, tRNA was isolated from 6MP-resistant cells cultured for 48 h with 6TG. 6TG was found to be incorporated into tRNAs normally containing queuine in the anticodon wobble position. These studies may provide a basis for the development of new therapeutic regimens for the treatment of leukemia.

Adult respiratory distress syndrome: has there been a change in outcome predictive measures?

BACKGROUND

Studies suggest that the mortality in adults with acute respiratory distress (ARDS) has not changed over the past two decades, despite the introduction of new therapeutic techniques and sophisticated ventilatory support devices. Mortality and physiological variables that might predict outcome in patients with ARDS were therefore assessed.

METHODS

A retrospective survey was undertaken in 41 patients with ARDS.

RESULTS

Mortality was 66%. Only the presence of sepsis predicted death.

CONCLUSION

Mortality from ARDS is unchanged. Currently available severity scoring systems are not helpful in predicting outcome.

Transmission of hepatitis C by kidney transplantation--the risks

The use of cadaveric organ donors with positive serologic tests for hepatitis C (HCV) has caused considerable debate. We have reviewed the clinical course of 43 EIA1 HCV-negative recipients who received kidney transplants from EIA1 HCV-positive donors (Study). We have attempted to define the rate of HCV-RNA transmission and to determine the frequency of HCV disease transmission as determined by abnormalities in liver function tests. Viral transmission was assessed using serologic assays for HCV antibody formation (EIA1, EIA2, and Matrix--an automated multiple antigen immunoblot assay) and with PCR testing for the presence of HCV-RNA on recipient sera. Liver function was followed longitudinally in the Study patients and compared with a group of 103 kidney recipients of organs from EIA1 HCV-negative donors (Control). Of the Study patients, 56% became PCR-positive for HCV-RNA, suggesting the transmission of HCV-RNA from the HCV-positive donor. Interpretation of serologic tests for HCV was complex. Currently available first (EIA1) and second (EIA2) generation serologic assays were always negative. The multiple antigen immunoblots assay (Matrix) had a high positive predictive value (93%) for the presence of HCV-RNA transmission, but one-third of Matrix-negative Study patients were PCR-positive (sensitivity = 66%). Currently, only 38% of recipients have HCV-RNA, suggesting that the virus may have been cleared by one-third of Study recipients who had circulating virus. Traditional tests of liver function (ALT, AST, AP, and GGT) were of limited use in predicting HCV-RNA transmission. Average AST, AP, and GGT were similar in the two groups. Average ALT was increased (93 I/U and 47 I/U) in Study and Control patients, respectively, but this difference was not significant. Episodes of abnormal liver function (ALT 60-99 IU for > or = 14 days) occurred in 22% of Study and 10% of Control patients (P = NS) and lasted longer in Study compared with Control patients (301 vs. 138 days; P < 0.02). Hepatitis (ALT > or = 100 IU for > 14 days) occurred with an equal frequency (6.5%) in both groups. The presence of HCV-RNA did not predict episodes of abnormal liver function. Fulminant hepatitis or rapidly progressive cirrhosis did not occur in the recipients of organs from HCV-positive donors. These data demonstrate a high efficiency of transfer of HCV-RNA by kidney transplantation from an HCV-positive donor to an HCV-negative recipient. A majority of the patients have asymptomatic HCV infection.(ABSTRACT TRUNCATED AT 400 WORDS)