Prolonged concurrent hypotension and low bispectral index ('double low') are associated with mortality, serious complications, and prolonged hospitalization after cardiac surgery.

BACKGROUND: Low bispectral index (BIS) and low mean arterial pressure (MAP) are associated with worse outcomes after surgery. We tested the hypothesis that a combination of these risk factors, a 'double low', is associated with death and major complications after cardiac surgery. METHODS: We used data from 8239 cardiac surgical patients from two US hospitals. The primary outcomes were 30-day mortality and a composite of in-hospital mortality and morbidity. We examined whether patients who had a case-averaged double low, defined as time-weighted average BIS and MAP (calculated over an entire case) below the sample mean but not in the reference group, had increased risk of the primary outcomes compared with patients whose BIS and/or MAP were at or higher than the sample mean. We also examined whether a prolonged cumulative duration of a concurrent double low (simultaneous low MAP and BIS) increased the risk of the primary outcomes. RESULTS: Case-averaged double low was not associated with increased risk of 30-day mortality {odds ratio [OR] 1.73 [95% confidence interval (CI) 0.94-3.18] vs reference; P =0.01} or the composite of in-hospital mortality and morbidity [OR 1.47 (95% CI 0.98-2.20); P =0.01] after correction for multiple outcomes. A prolonged concurrent double low was associated with 30-day mortality [OR 1.06 (95% CI 1.01-1.11) per 10-min increase; P =0.001] and the composite of in-hospital mortality and morbidity [OR 1.04 (95% CI 1.01-1.07), P =0.004]. CONCLUSIONS: A prolonged concurrent double low, but not a case-averaged double low, was associated with higher morbidity and mortality after cardiac surgery.

Intraoperative arterial blood pressure lability is associated with improved 30 day survival.

BACKGROUND: Arterial blood pressure lability, defined as rapid changes in arterial blood pressure, occurs commonly during anaesthesia. It is believed that hypertensive patients exhibit more lability during surgery and that lability is associated with poorer outcomes. Neither association has been rigorously tested. We hypothesized that hypertensive patients have more blood pressure lability and that increased lability is associated with increased 30 day mortality. METHODS: This was a retrospective single-centre study of surgical patients from July 2008 to December 2012. Intraoperative data were extracted from the electronic anaesthesia record. Lability was calculated as the modulus of the percentage change in mean arterial pressure between consecutive 5 min intervals. The number of episodes of lability >10% was tabulated. Multivariate logistic regression was performed to determine the association between lability and 30 day mortality using derivation and validation cohorts. RESULTS: Inclusion criteria were met by 52 919 subjects. Of the derivation cohort, 53% of subjects were hypertensive and 42% used an antihypertensive medication. The median number of episodes of lability >10% was 9 (interquartile range 5-14) per patient. Hypertensive subjects demonstrated more lability than normotensive patients, 10 (5-15) compared with 8 (5-12), P<0.0001. In subjects taking no antihypertensive medication, lability >10% was associated with decreased 30 day mortality, odds ratio (OR) per episode 0.95 [95% confidence interval (CI) 0.92-0.97], P<0.0001. This result was confirmed in the validation cohort, OR 0.96 (95% CI 0.93-0.99), P=0.01, and in hypertensive patients taking no antihypertensive medication, OR 0.96 (95% CI 0.93-0.99), P=0.002. Use of any antihypertensive medication class reduced this effect. CONCLUSIONS: Intraoperative arterial blood pressure lability occurs more often in hypertensive patients. Contrary to common belief, increased lability was associated with decreased 30 day mortality.

Low intraoperative tidal volume ventilation with minimal PEEP is associated with increased mortality.

BACKGROUND: Anaesthetists have traditionally ventilated patients' lungs with tidal volumes (TVs) between 10 and 15 ml kg(-1) of ideal body weight (IBW), without the use of PEEP. Over the past decade, influenced by the results of the Acute Respiratory Distress Syndrome Network trial, many anaesthetists have begun using lower TVs during surgery. It is unclear whether the benefits of low TV ventilation can be extended into the perioperative period. METHODS: We reviewed the records of 29 343 patients who underwent general anaesthesia with mechanical ventilation between January 1, 2008 and December 31, 2011. We calculated TV kg(-1) IBW, PEEP, peak inspiratory pressure (PIP), and dynamic compliance. Cox regression analysis with propensity score matching was performed to examine the association between TV and 30-day mortality. RESULTS: Median TV was 8.6 [7.7-9.6] ml kg(-1) IBW with minimal PEEP [4.0 (2.2-5.0) cm H2O]. A significant reduction in TV occurred over the study period, from 9 ml kg(-1) IBW in 2008 to 8.3 ml kg(-1) IBW in 2011 (P=0.01). Low TV 6-8 ml kg(-1) IBW was associated with a significant increase in 30-day mortality vs TV 8-10 ml kg(-1) IBW: hazard ratio (HR) 1.6 [95% confidence interval (CI) [1.25-2.08], P=0.0002]. The association remained significant after matching: HR 1.63 [95% CI (1.22-2.18), P<0.001]. There was only a weak correlation between TV kg(-1) IBW and dynamic compliance (r=-0.006, P=0.31) and a weak-to-moderate correlation between TV kg(-1) IBW and PIP (r=0.32 P<0.0001). CONCLUSIONS: Use of low intraoperative TV with minimal PEEP is associated with an increased risk of 30-day mortality.

Dopamine D4 receptor, but not the ADHD-associated D4.7 variant, forms functional heteromers with the dopamine D2S receptor in the brain.

Polymorphic variants of the dopamine D(4) receptor have been consistently associated with attention-deficit hyperactivity disorder (ADHD). However, the functional significance of the risk polymorphism (variable number of tandem repeats in exon 3) is still unclear. Here, we show that whereas the most frequent 4-repeat (D(4.4)) and the 2-repeat (D(4.2)) variants form functional heteromers with the short isoform of the dopamine D(2) receptor (D(2S)), the 7-repeat risk allele (D(4.7)) does not. D(2) receptor activation in the D(2S)-D(4) receptor heteromer potentiates D(4) receptor-mediated MAPK signaling in transfected cells and in the striatum, which did not occur in cells expressing D(4.7) or in the striatum of knockin mutant mice carrying the 7 repeats of the human D(4.7) in the third intracellular loop of the D(4) receptor. In the striatum, D(4) receptors are localized in corticostriatal glutamatergic terminals, where they selectively modulate glutamatergic neurotransmission by interacting with D(2S) receptors. This interaction shows the same qualitative characteristics than the D(2S)-D(4) receptor heteromer-mediated mitogen-activated protein kinase (MAPK) signaling and D(2S) receptor activation potentiates D(4) receptor-mediated inhibition of striatal glutamate release. It is therefore postulated that dysfunctional D(2S)-D(4.7) heteromers may impair presynaptic dopaminergic control of corticostriatal glutamatergic neurotransmission and explain functional deficits associated with ADHD.

An embryonal carcinoma multiple phenotype locus maps to the proximal position of the mouse X chromosome.

A mutant embryonal carcinoma cell line, NR1-6, was established subsequent to retroviral insertion. The insertion was shown to be causative for a number of aberrant properties associated with the mutant cells. Analysis of >17 kb of the insertion site flanking region failed to reveal any homology between this locus and any reported sequence with the exception of one EST of unknown function and a few repetitive elements including B1 element and a CA dinucleotide repeat. CA repeats occur commonly in the mouse genome and usually show size variation. In this study, we mapped this multiphenotype locus using CA repeat polymorphism and Jackson Laboratory's interspecific backcross panels. The locus maps to the proximal end of the X chromosome between MGI offsets 1.5 and 4.5 and has been designated DXUalb1. There are several interesting candidate genes within this region. Analyses of their expression pattern may lead us to a better understanding of the molecular regulation of the variant mutant phenotypes.

The human physiome as an information environment.

Modern biology is rapidly laying the foundation necessary for integrated modeling of physiological processes in living organisms. The human physiome project attempts to model interactions between biochemicals, cellular organelles, cells, tissues, and organs within whole organisms. One of the first challenges that this project faces is the development of a database environment flexible enough to accommodate the diversity in structure and content of physiological data. This paper reviews the current state of database technology, presents our understanding of the physiome database problem, and proposes a preliminary strategy for addressing it.

t-complex-associated embryonic surface antigen homologous to mLAMP-1. I. Biochemical and molecular analyses.

Previously we described an embryonic cell surface glycoprotein, ESGp, associated with the t-embryonic lethal alleles of the mouse t complex. This antigen is expressed on the cell surface of both early mouse embryos and embryonal carcinoma (EC) cell lines. The antigen is localized to areas of cell-cell contact in EC lines and redistributes to the outer edges of the blastomeres during compaction, thereby indicating a potential role in embryonic cell-cell interaction. We now report that this t-complex-associated ESGp is homologous to the mouse lysosomal-associated membrane protein-1 (LAMP-1). Limited protein sequence analyses of the amino terminal and an internal peptide indicate considerable homology with the LAMP-1 protein. Biochemical parameters such as protein core size, sulfation and phosphorylation status, and resistance to proteolysis also demonstrate homology. While we detect only a single message with a mouse LAMP-1 cDNA probe via Northern blotting, Southern analyses indicate the existence of at least two homologous LAMP-1 genes. Additionally, we present evidence suggesting that ESGp/LAMP-1 serves as a substrate which may be differentially glycosylated by the activities of the gene products of the different t-lethal alleles.

t-complex-associated embryonic surface antigen homologous to mLAMP-1. II. Expression and distribution analyses.

We have previously demonstrated that a mouse t-complex-associated antigen (ESGp) is present on the cell surface, specifically at areas of cell-cell contact, of cleavage stage embryos and embryonal carcinoma cell lines. In the accompanying paper, we document isolation, purification, and partial sequencing of this molecule. Amino-terminal and internal peptide fragments are highly homologous to the mouse lysosomal-associated membrane protein-1 (mLAMP-1). We also demonstrate considerable similarity, though not necessarily identity, between these two antigens through both biochemical and molecular analyses. In this report we use immunological techniques to compare the expression and distribution of these antigens in various cell lines as well as mouse tissues and preimplantation stage embryos. The data presented indicate that there are: (1) different antigenic forms of the ESGp/ mLAMP-1 homologues and (2) changes in the molecular composition and expression of these forms during embryogenesis and differentiation. It is obvious from these studies that mLAMP-1 is not strictly a static molecule whose sole function is to protect the lumenal side of the lysosomal membrane but rather is a dynamic molecule of potential import in many other cellular and organismal functions.

Analysis of the factors involved in the retinoic acid-induced differentiation of a retinoid-hypersensitive embryonal carcinoma cell mutant.

Retinoic acid (RA) has been known to play an important role in cellular growth and differentiation as well as in vertebrate development. Many in vitro cell cultures also respond to RA by differentiating. Perhaps the most widely studied of these cultures are embryonal carcinoma (EC) cells. We have used an RA-hypersensitive EC cell mutant, created by retroviral insertion, to analyze the activity of the identifiable components in the RA response pathway. We have analyzed the mRNA expression patterns of the retinoic acid receptors (RARs) alpha, beta, and gamma, the retinoid X receptors (RXRs) alpha, beta, and gamma, and the cellular retinoic acid binding proteins (CRABPs) I and II. Our results indicate that CRABP I, RAR beta, and RAR gamma mRNAs are expressed differentially between parent and RA-hypersensitive mutant cells. All three messages are present at higher basal levels and at earlier times after RA addition in the mutant relative to parental cells. All other elements examined are equivalently expressed. Therefore analyses of the expression patterns of CRABPs, RARs, and RXRs in these RA-hypersensitive cells point to the probable importance of CRABP I, RAR beta, and RAR gamma in the RA induction pathway and also indicate that CRABP II and RXR gamma are not likely to be critical elements in the early differentiative response of cells to RA.

Retinoic acid-induced differentiation of a nontumorigenic embryonal carcinoma cell mutant created through retroviral insertion.

A mutant embryonal carcinoma cell line, NR1-6, was created through retroviral insertion. We have previously reported that due to a single insertional event the mutant cell line is altered in regard to both its morphology and its tumorigenic capacity. We now report that this same cell line is also aberrant in its differentiative potential following exposure to the morphogen retinoic acid (RA). Unlike the parental NR1-0 cells, the NR1-6 cells apparently do not respond to RA by elaborating primitive endodermal derivatives in monolayer culture but rather appear morphologically to differentiate into mesodermal cells. This hypothesis is substantiated by the observation that RA treatment induces the transcription of both Endo A and B mRNA in parental but not mutant cells. No differences have been observed in the transcription of other RA sensitive markers such as c-myc, tissue plasminogen activator, collagen type IV, and laminin. In addition, the mutant cells are quantitatively much more sensitive to RA induction than are the parental cells, achieving full differentiation within 72 h of treatment with 10(-10) M RA. The parental cells, in contrast, will only differentiate at concentrations of 10(-5) or 10(-6) M RA, following 5 to 7 days of treatment. A spontaneous revertant cell line, which was isolated from an NR1-6 population and lacks the retroviral insert, is identical to the parental population in all parameters. Therefore, these data indicate that, in this case at least, a single genetic locus is involved in regulating both the qualitative and quantitative response of EC cells to RA-induced differentiation, as well as their morphology and tumorigenic potential.

Characterization of a developmentally regulated mouse embryonic antigen.

A mammalian embryonic cell surface glycoprotein (ESGp), whose expression and biochemical structure seem to be developmentally regulated, has been isolated and characterized. The molecule expressed in two cell through morula stage mouse embryos has a molecular weight, by electrophoretic analyses, of 90 kDa. At the blastocyst stage, however, the molecule migrates as a broad, heterogeneous band ranging from 90 to 110 kDa. Evidence obtained from studies of embryonal carcinoma (EC) cells indicates that this band is actually a composite of three distinct molecules (molecular weight 90, 95, and 105 to 110 kDa), each of which is synthesized uniquely by one of the different cell types of the blastocyst: the embryonic ectoderm and visceral and parietal endoderms, respectively. A survey of various mouse tissues and cell lines has revealed that undifferentiated cells express the low molecular weight form (90 kDa) characteristic of embryonic ectoderm, whereas differentiated cells and adult tissues express the high molecular weight form (110 kDa) characteristic of parietal endoderm. Only the EC visceral endoderm cell analogues have been shown to express the intermediate molecule (95 kDa). In embryos, the antigen is uniformly distributed over the cell surface during early cleavage stages (two to eight cell); just before compaction, however, it seems to redistribute and becomes polarized at the outside exposed edges of blastomeres. In cultured EC cells, ESGp is found only in areas of cell-to-cell contact; free-standing surfaces of cells are negative for expression. It is possible, therefore, that ESGp may be involved in the intercellular adhesion of both EC cells and compacting embryos.

Analysis of a nontumorigenic embryonal carcinoma cell line.

Embryonal carcinoma (EC) cells have proven to be of particular value in studies of both oncogenesis and mammalian development as well as in evaluating the relationship between these two phenomena. We have infected EC cells with a retrovirus in an effort to obtain by insertional mutagenesis cell lines defective in either differentiative or oncogenic potentials. One such cell line, identified originally by its unique morphological phenotype, is abnormal with respect to both parameters. These cells do not differentiate along typical EC cell lineages, possibly having lost their ability to elaborate endodermal derivatives. They do, however, retain certain cell surface markers characteristic of EC cells and lose these markers after exposure to retinoic acid. Most significantly, they also fail to form tumors in vivo in syngeneic mice, although they grow as well as the parental cells in vitro. Southern blot analysis indicates that this variant cell line has a single viral insert and the original cell was probably hemizygous for the insertion site, suggesting that a single gene may regulate both the tumorigenic and differentiative capacities of the cell.

The influence of genetic background and the homologous chromosome 17 on t-haplotype transmission ratio distortion in mice.

Transmission ratio distortion is a characteristic of complete t-haplotypes, such that heterozygous males preferentially transmit the t-haplotype bearing chromosome 17 to the majority of their progeny. At least two genes contained within the t-haplotype have been identified as being required for such high transmission ratios. In this study we examine the effects of the genetic background and the chromosome homologous to the t-haplotype on transmission ratio distortion. We use two different congenic lines: BTBRTF/Nev.Ttf/t12, in which the t12 haplotype has a transmission ratio of 52%, and C3H/DiSn.Ttf/t12, in which the t12 haplotype has a transmission ratio of 99%. By intercrossing these two strains to produce reciprocal F1 and F2 generations, we have isolated the effects of the homologous chromosome 17 from the effects of the genetic background. We demonstrate that both the homologous chromosome and the genetic background have profound effects on t-haplotype transmission ratio distortion. Furthermore, it is evident that the t-haplotype transmission ratio behaves as a quantitative character rather than an intrinsic property of t-haplotypes.

DNA topoisomerase I and II activities during cell proliferation and the cell cycle in cultured mouse embryo fibroblast (C3H 10T1/2) cells.

We have used C3H 10T1/2 cells to examine the regulation of topoisomerase activities during cell proliferation and the cell cycle. The specific activity of topoisomerase I was about 4-fold greater in proliferating (log phase) cells than in non-proliferating (confluent) cells. In synchronized cells, the bulk of the increased activity occurred during or just prior to S phase, depending upon the method of synchronization. A smaller increase in activity also occurred during G1 phase. The increase in activity during S phase was not altered by a hydroxyurea block at the G1/S phase boundary indicating that it is not directly coupled to DNA synthesis and is not the result of topoisomerase I gene dosage. The increase was inhibited by blocking cells at mid-G1 phase using isoleucine deprivation. Thus, the increase in activity during S phase is dependent on events occurring during mid- to late G1 phase. In contrast to the changes in topoisomerase I levels, the specific activity of topoisomerase II showed no detectable difference in proliferating vs non-proliferating cells. In addition, no detectable difference in topoisomerase II specific activity was seen in G1, S and M phases of the cell cycle. The differences in the activity profiles of the topoisomerases I and II during the cell cycle suggest that the two activities are regulated independently and may be required for different functions.

Expression of a glucose-regulated cell surface protein in early mouse embryos.

A 100,000-Da glucose-regulated surface protein (100K-GRP) has previously been isolated from the cell surface and culture medium of human fibroblasts. A rabbit antiserum directed against this protein reacts with the cell surface of both human and murine cultured cells and with a broad spectrum of mammalian tissues. It is shown, via indirect immunofluorescence, that this protein is also present on cells of the developing mouse embryo and can be detected as early as the 4-cell stage. The 8-cell embryo and morula show positive surface labeling; the inner cell masses of both the pre- and postimplantation blastocysts are also positive but the trophectoderm is not. At the 6-day egg cylinder stage, the embryonic and extra-embryonic ectoderm label intensely with the antiserum and visceral endoderm shows faint labeling. No labeling can be detected on parietal endoderm or on the trophoblastic giant cells invading the uterine decidua. However, the internal cells of the ectoplacental cone exhibit bright fluorescence. The same pattern is observed on 7- to 8.5-day embryos, except that at this stage no label is associated with the visceral endoderm. In addition, mesodermal cells emerging from the primitive streak are also labeled.