High resolution analysis of DNA copy number variation using comparative genomic hybridization to microarrays

Gene dosage variations occur in many diseases. In cancer, deletions and copy number increases contribute to alterations in the expression of tumour-suppressor genes and oncogenes, respectively. Developmental abnormalities, such as Down, Prader Willi, Angelman and Cri du Chat syndromes, result from gain or loss of one copy of a chromosome or chromosomal region. Thus, detection and mapping of copy number abnormalities provide an approach for associating aberrations with disease phenotype and for localizing critical genes. Comparative genomic hybridization (CGH) was developed for genome-wide analysis of DNA sequence copy number in a single experiment. In CGH, differentially labelled total genomic DNA from a 'test' and a 'reference' cell population are cohybridized to normal metaphase chromosomes, using blocking DNA to suppress signals from repetitive sequences. The resulting ratio of the fluorescence intensities at a location on the 'cytogenetic map', provided by the chromosomes, is approximately proportional to the ratio of the copy numbers of the corresponding DNA sequences in the test and reference genomes. CGH has been broadly applied to human and mouse malignancies. The use of metaphase chromosomes, however, limits detection of events involving small regions (of less than 20 Mb) of the genome, resolution of closely spaced aberrations and linking ratio changes to genomic/genetic markers. Therefore, more laborious locus-by-locus techniques have been required for higher resolution studies. Hybridization to an array of mapped sequences instead of metaphase chromosomes could overcome the limitations of conventional CGH (ref. 6) if adequate performance could be achieved. Copy number would be related to the test/reference fluorescence ratio on the array targets, and genomic resolution could be determined by the map distance between the targets, or by the length of the cloned DNA segments. We describe here our implementation of array CGH. We demonstrate its ability to measure copy number with high precision in the human genome, and to analyse clinical specimens by obtaining new information on chromosome 20 aberrations in breast cancer.

Insulin-like growth factor I receptor primary structure: comparison with insulin receptor suggests structural determinants that define functional specificity

To identify structural characteristics of the closely related cell surface receptors for insulin and IGF-I that define their distinct physiological roles, we determined the complete primary structure of the human IGF-I receptor from cloned cDNA. The deduced sequence predicts a 1367 amino acid receptor precursor, including a 30-residue signal peptide, which is removed during translocation of the nascent polypeptide chain. The 1337 residue, unmodified proreceptor polypeptide has a predicted Mr of 151,869, which compares with the 180,000 Mr IGF-I receptor precursor. In analogy with the 152,784 Mr insulin receptor precursor, cleavage of the Arg-Lys-Arg-Arg sequence at position 707 of the IGF-I receptor precursor will generate alpha (80,423 Mr) and beta (70,866 Mr) subunits, which compare with approximately 135,000 Mr (alpha) and 90,000 Mr (beta) fully glycosylated subunits.

Growth hormone receptor and serum binding protein: purification, cloning and expression

A putative growth hormone receptor from rabbit liver and the growth hormone binding protein from rabbit serum have the same amino-terminal amino-acid sequence, indicating that the binding protein corresponds to the extracellular hormone-binding domain of the liver receptor. The complete amino-acid sequences derived from complementary DNA clones encoding the putative human and rabbit growth hormone receptors are not similar to other known proteins, demonstrating a new class of transmembrane receptors.

Racial residential segregation: a fundamental cause of racial disparities in health

Racial residential segregation is a fundamental cause of racial disparities in health. The physical separation of the races by enforced residence in certain areas is an institutional mechanism of racism that was designed to protect whites from social interaction with blacks. Despite the absence of supportive legal statutes, the degree of residential segregation remains extremely high for most African Americans in the United States. The authors review evidence that suggests that segregation is a primary cause of racial differences in socioeconomic status (SES) by determining access to education and employment opportunities. SES in turn remains a fundamental cause of racial differences in health. Segregation also creates conditions inimical to health in the social and physical environment. The authors conclude that effective efforts to eliminate racial disparities in health must seriously confront segregation and its pervasive consequences.

PIK3CA is implicated as an oncogene in ovarian cancer

Ovarian cancer is the leading cause of death from gynecological malignancy and the fourth leading cause of cancer death among American women, yet little is known about its molecular aetiology. Studies using comparative genomic hybridization (CGH) have revealed several regions of recurrent, abnormal, DNA sequence copy number that may encode genes involved in the genesis or progression of the disease. One region at 3q26 found to be increased in copy number in approximately 40% of ovarian and others cancers contains PIK3CA, which encodes the p110alpha catalytic subunit of phosphatidylinositol 3-kinase (PI3-kinase). The association between PIK3CA copy number and PI3-kinase activity makes PIK3CA a candidate oncogene because a broad range of cancer-related functions have been associated with PI3-kinase mediated signalling. These include proliferation, glucose transport and catabolism, cell adhesion, apoptosis, RAS signalling and oncogenic transformation. In addition, downstream effectors of PI3-kinase, AKT1 and AKT2, have been found to be amplified or activated in human tumours, including ovarian cancer. We show here that PIK3CA is frequently increased in copy number in ovarian cancers, that the increased copy number is associated with increased PIK3CA transcription, p110alpha protein expression and PI3-kinase activity and that treatment with the PI3-kinase inhibitor LY294002 decreases proliferation and increases apoptosis. Our observations suggest PIK3CA is an oncogene that has an important role in ovarian cancer.

Identification of a gene encoding an acyl CoA:diacylglycerol acyltransferase, a key enzyme in triacylglycerol synthesis

Triacylglycerols are quantitatively the most important storage form of energy for eukaryotic cells. Acyl CoA:diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) catalyzes the terminal and only committed step in triacylglycerol synthesis, by using diacylglycerol and fatty acyl CoA as substrates. DGAT plays a fundamental role in the metabolism of cellular diacylglycerol and is important in higher eukaryotes for physiologic processes involving triacylglycerol metabolism such as intestinal fat absorption, lipoprotein assembly, adipose tissue formation, and lactation. DGAT is an integral membrane protein that has never been purified to homogeneity, nor has its gene been cloned. We identified an expressed sequence tag clone that shared regions of similarity with acyl CoA:cholesterol acyltransferase, an enzyme that also uses fatty acyl CoA as a substrate. Expression of a mouse cDNA for this expressed sequence tag in insect cells resulted in high levels of DGAT activity in cell membranes. No other acyltransferase activity was detected when a variety of substrates, including cholesterol, were used as acyl acceptors. The gene was expressed in all tissues examined; during differentiation of NIH 3T3-L1 cells into adipocytes, its expression increased markedly in parallel with increases in DGAT activity. The identification of this cDNA encoding a DGAT will greatly facilitate studies of cellular glycerolipid metabolism and its regulation.

The caregiver reaction assessment (CRA) for caregivers to persons with chronic physical and mental impairments

The development and testing of a multidimensional instrument to assess the reactions of family members caring for elderly persons with physical impairments, Alzheimer's disease, and cancer is reported. Forty items were administered to a sample of 377 caregivers of persons with physical impairments and Alzheimer's disease. Five dimensions of caregivers' reactions were identified through exploratory factor analysis. Using confirmatory factor analysis on an independent sample (N = 377), these dimensions were tested for factorial invariance across spouse and nonspouse caregivers and between caregivers of persons with cancer and those caring for persons with Alzheimer's disease. The subscales also had a high level of factorial invariance across a three-wave panel study (N = 185). The subscales appeared consistent with first order tests of construct validity.

Confidential inquiry into quality of care before admission to intensive care

OBJECTIVE

To examine the prevalence, nature, causes, and consequences of suboptimal care before admission to intensive care units, and to suggest possible solutions.

DESIGN

Prospective confidential inquiry on the basis of structured interviews and questionnaires.

SETTING

A large district general hospital and a teaching hospital.

SUBJECTS

A cohort of 100 consecutive adult emergency admissions, 50 in each centre.

MAIN OUTCOME MEASURES

Opinions of two external assessors on quality of care especially recognition, investigation, monitoring, and management of abnormalities of airway, breathing, and circulation, and oxygen therapy and monitoring.

RESULTS

Assessors agreed that 20 patients were well managed (group 1) and 54 patients received suboptimal care (group 2). Assessors disagreed on quality of management of 26 patients (group 3). The casemix and severity of illness, defined by the acute physiology and chronic health evaluation (APACHE II) score, were similar between centres and the three groups. In groups 1, 2, and 3 intensive care mortalities were 5 (25%), 26 (48%), and 6 (23%) respectively (P=0.04) (group 1 versus group 2, P=0.07). Hospital mortalities were 7 (35%), 30 (56%), and 8 (31%) (P=0.07) and standardised hospital mortality ratios (95% confidence intervals) were 1.23 (0.49 to 2.54), 1.4 (0.94 to 2.0), and 1.26 (0.54 to 2.48) respectively. Admission to intensive care was considered late in 37 (69%) patients in group 2. Overall, a minimum of 4.5% and a maximum of 41% of admissions were considered potentially avoidable. Suboptimal care contributed to morbidity or mortality in most instances. The main causes of suboptimal care were failure of organisation, lack of knowledge, failure to appreciate clinical urgency, lack of supervision, and failure to seek advice.

CONCLUSIONS

The management of airway, breathing, and circulation, and oxygen therapy and monitoring in severely ill patients before admission to intensive care units may frequently be suboptimal. Major consequences may include increased morbidity and mortality and requirement for intensive care. Possible solutions include improved teaching, establishment of medical emergency teams, and widespread debate on the structure and process of acute care.

A measurement of the cosmological mass density from clustering in the 2dF Galaxy Redshift Survey

The large-scale structure in the distribution of galaxies is thought to arise from the gravitational instability of small fluctuations in the initial density field of the Universe. A key test of this hypothesis is that forming superclusters of galaxies should generate a systematic infall of other galaxies. This would be evident in the pattern of recessional velocities, causing an anisotropy in the inferred spatial clustering of galaxies. Here we report a precise measurement of this clustering, using the redshifts of more than 141,000 galaxies from the two-degree-field (2dF) galaxy redshift survey. We determine the parameter beta = Omega0.6/b = 0.43 +/- 0.07, where Omega is the total mass-density parameter of the Universe and b is a measure of the 'bias' of the luminous galaxies in the survey. (Bias is the difference between the clustering of visible galaxies and of the total mass, most of which is dark.) Combined with the anisotropy of the cosmic microwave background, our results favour a low-density Universe with Omega approximately 0.3.

Quantitative mapping of amplicon structure by array CGH identifies CYP24 as a candidate oncogene

We show here that quantitative measurement of DNA copy number across amplified regions using array comparative genomic hybridization (CGH) may facilitate oncogene identification by providing precise information on the locations of both amplicon boundaries and amplification maxima. Using this analytical capability, we resolved two regions of amplification within an approximately 2-Mb region of recurrent aberration at 20q13.2 in breast cancer. The putative oncogene ZNF217 (ref. 5) mapped to one peak, and CYP24 (encoding vitamin D 24 hydroxylase), whose overexpression is likely to lead to abrogation of growth control mediated by vitamin D, mapped to the other.

Preferences for quality of life or survival expressed by patients with heart failure

BACKGROUND

As many patients with heart failure develop symptoms limiting daily life, newer therapies may be found to improve functional status without concomitant survival benefit. As some of these therapies may actually increase mortality, it is increasingly relevant to assess patients' preferences for survival vs improvement in symptoms.

METHODS

We enrolled 99 patients with advanced heart failure (ejection fraction 24 +/- 10, duration 6 +/- 5 years). Each patient completed time trade-off and standard gamble instruments, Minnesota Living with Heart Failure questionnaires and visual analog scales for dyspnea and overall health. Jugular venous pressure was assessed in all patients and peak oxygen consumption was measured during bicycle exercise in 60 patients.

RESULTS

Strong polarity of preference toward either survival or quality of life was expressed by 60% of patients. There was good correlation between time trade-off and standard gamble utility scores (r = 0.64), and between preference and functional class (r = 0.60). Higher jugular venous pressure and lower peak oxygen consumption were associated with poorer utility scores (p <.05). Higher dyspnea scores and worse Living with Heart Failure scores were also associated with preference to trade time or take risks for better health.

CONCLUSIONS

These findings suggest that heart failure patients express meaningful preferences about quality vs length of life. High jugular venous pressure, low peak oxygen consumption and poor Living with Heart Failure scores were related to low utility scores. These cannot be assumed, however, to predict the intensity of individual preference to trade nothing or virtually everything for better health.

Resident human hepatic lymphocytes are phenotypically different from circulating lymphocytes

BACKGROUND/AIMS

Murine and human studies have documented the existence of subpopulations of lymphocytes in particular tissues that differ phenotypically and functionally from those in peripheral blood and may mature locally. Since little is known about lymphocyte subpopulations in the normal human liver, we have analysed the surface phenotypes of lymphocytes isolated from liver specimens taken from 15 donors at the time of liver transplantation, and compared these with those of peripheral blood lymphocytes.

METHODS

Hepatic lymphocytes were prepared by mechanical dissociation and enzymatic digestion of liver tissue. The cells were stained with a panel of monoclonal antibodies (CD3, CD4, CD8, CD19, CD56, gammadeltaTCR, alphabetaTCR, CD8alpha-chain, CD8alphabeta dimer), and analysed by flow cytometry. In situ characterisation of hepatic lymphocytes was by haematoxylin and eosin staining of fixed liver sections and by immunohistochemical staining for common leukocyte antigen and CD3.

RESULTS

Significant numbers of hepatic T lymphocytes were localised to the portal tracts and parenchyma of normal liver specimens. Flow cytometry revealed that the CD4/CD8 ratio (1:3.5) was consistently reversed compared with that in peripheral blood (2:1). Other lymphocyte populations identified include double positive CD3+CD4+CD8+ cells which accounted for a mean of 5.5% (range 3-11.6%) of hepatic CD3+ cells compared with 1.3% in blood (range 0.7-3.6%; p < 0.007), and double negative CD3+ CD4-8- cells (14.5%; range 2.7-29% compared with 5.0%; range 2.1-10.8%, p < 0.02). Over 15% (range 6.8-34%) of all hepatic CD3+ cells expressed a gammadeltaTCR compared to 2.7% (range 0.9-4.7%) of CD3+ peripheral blood lymphocytes (p < 0.004) and almost 50% of these coexpressed CD8. The CD8 alpha-chain was expressed without the beta-chain (CD8alpha+beta-) by 15.4% (range 4-29.1%) of hepatic T cells, but this phenotype was undetectable among peripheral blood lymphocytes (p < 0.009). Cells expressing both the T cell marker CD3 and the natural killer cell marker CD56 constituted 31.6% (range 14-54%) of all hepatic CD3+ lymphocytes but were rarely present amongst peripheral blood lymphocytes (0-6%; p < 0.0001).

CONCLUSIONS

These data are the first to describe and quantify unconventional T lymphocyte subpopulations in the normal adult human liver which may have specialised functions in regional immune responses and which may differentiate locally. These findings have important implications for our understanding of hepatic immunoregulation and the pathogenic mechanisms involved in viral and immune-mediated liver disease and allograft rejection.

Positional cloning of ZNF217 and NABC1: genes amplified at 20q13.2 and overexpressed in breast carcinoma

We report here the molecular cloning of an approximately 1-Mb region of recurrent amplification at 20q13.2 in breast cancer and other tumors and the delineation of a 260-kb common region of amplification. Analysis of the 1-Mb region produced evidence for five genes, ZNF217, ZNF218, and NABC1, PIC1L (PIC1-like), CYP24, and a pseudogene CRP (Cyclophillin Related Pseudogene). ZNF217 and NABC1 emerged as strong candidate oncogenes and were characterized in detail. NABC1 is predicted to encode a 585-aa protein of unknown function and is overexpressed in most but not all breast cancer cell lines in which it was amplified. ZNF217 is centrally located in the 260-kb common region of amplification, transcribed in multiple normal tissues, and overexpressed in all cell lines and tumors in which it is amplified and in two in which it is not. ZNF217 is predicted to encode alternately spliced, Kruppel-like transcription factors of 1,062 and 1,108 aa, each having a DNA-binding domain (eight C2H2 zinc fingers) and a proline-rich transcription activation domain.

Mutations of the forkhead/winged-helix gene, FKHL7, in patients with Axenfeld-Rieger anomaly

Genetic linkage, genome mismatch scanning, and analysis of patients with alterations of chromosome 6 have indicated that a major locus for development of the anterior segment of the eye, IRID1, is located at 6p25. Abnormalities of this locus lead to glaucoma. FKHL7 (also called "FREAC3"), a member of the forkhead/winged-helix transcription-factor family, has also been mapped to 6p25. DNA sequencing of FKHL7 in five IRID1 families and 16 sporadic patients with anterior-segment defects revealed three mutations: a 10-bp deletion predicted to cause a frameshift and premature protein truncation prior to the FKHL7 forkhead DNA-binding domain, as well as two missense mutations of conserved amino acids within the FKHL7 forkhead domain. Mf1, the murine homologue of FKHL7, is expressed in the developing brain, skeletal system, and eye, consistent with FKHL7 having a role in ocular development. However, mutational screening and genetic-linkage analyses excluded FKHL7 from underlying the anterior-segment disorders in two IRID1 families with linkage to 6p25. Our findings demonstrate that, although mutations of FKHL7 result in anterior-segment defects and glaucoma in some patients, it is probable that at least one more locus involved in the regulation of eye development is also located at 6p25.

Metallic Biomaterials: Current Challenges and Opportunities

Metallic biomaterials are engineered systems designed to provide internal support to biological tissues and they are being used largely in joint replacements, dental implants, orthopaedic fixations and stents. Higher biomaterial usage is associated with an increased incidence of implant-related complications due to poor implant integration, inflammation, mechanical instability, necrosis and infections, and associated prolonged patient care, pain and loss of function. In this review, we will briefly explore major representatives of metallic biomaterials along with the key existing and emerging strategies for surface and bulk modification used to improve biointegration, mechanical strength and flexibility of biometals, and discuss their compatibility with the concept of 3D printing.

High-level vancomycin-resistant enterococci causing hospital infections

Nosocomial infection or colonization due to enterococci with high-level resistance to vancomycin (minimal inhibitory concentrations [MICs] between 64 and greater than 2000 mg/L) has occurred in 41 patients with renal disease. These vancomycin-resistant enterococci were cultured from many sources including blood. All but one strain contained one or more plasmids ranging in molecular weight from 1.0 to 40 Megadaltons (MDa). Vancomycin resistance was transferable by conjugation to a susceptible recipient strain of Enterococcus faecalis but this was not always associated with plasmid DNA. The emergence of transferable high-level vancomycin resistance in enterococci causing significant clinical infections is of particular importance since vancomycin is widely regarded as a reserve drug for the management of infections with multi-resistant Gram-positive organisms.

Genome scanning with array CGH delineates regional alterations in mouse islet carcinomas

Carcinomas that develop in the pancreatic islets of transgenic mice expressing the SV40 T-antigens (Tag) under transcriptional control of the rat insulin II promoter (RIP) progress through well-characterized stages that are similar to aspects of human tumor progression, including hyperplastic growth, increased angiogenesis and reduced apoptosis. The latter two stages have been associated with recurrent loss of heterozygosity (LOH) and reduced genome copy number on chromosomes 9 (LOH9) and 16 (LOH16), aberrations which we believe contribute to these phenotypes. Earlier analyses localized LOH9 to approximately 3 Mb and LOH16 to approximately 30 Mb (both syntenic with human 3q21-q25) but were limited by low throughput and a lack of informative polymorphic markers. Here we show that comparative genomic hybridization to DNA microarrays (array CGH) overcomes these limitations by allowing efficient, genome-wide analyses of relative genome copy number. The CGH arrays used in these experiments carried BACs distributed at 2-20-MB intervals across the mouse genome and at higher density in regions of interest. Using array CGH, we further narrowed the loci for LOH9 and LOH16 and defined new or previously unappreciated recurrent regions of copy-number decrease on chromosomes 6, 8 and 14 (syntenic with human chromosomes 12p11-p13, 16q24.3 and 13q11-q32, respectively) and regions of copy-number increase on chromosomes 2 and 4 (syntenic to human chromosomes 20q13.2 and 1p32-p36, respectively). Our analyses of human genome sequences syntenic to these regions suggest that CYP24, PFDN4, STMN1, CDKN1B, PPP2R3 and FSTL1 are candidate oncogenes or tumor-suppressor genes. We also show that irradiation and genetic background influence the spectrum of aberrations present in these tumors.

GW170817: Measurements of Neutron Star Radii and Equation of State

On 17 August 2017, the LIGO and Virgo observatories made the first direct detection of gravitational waves from the coalescence of a neutron star binary system. The detection of this gravitational-wave signal, GW170817, offers a novel opportunity to directly probe the properties of matter at the extreme conditions found in the interior of these stars. The initial, minimal-assumption analysis of the LIGO and Virgo data placed constraints on the tidal effects of the coalescing bodies, which were then translated to constraints on neutron star radii. Here, we expand upon previous analyses by working under the hypothesis that both bodies were neutron stars that are described by the same equation of state and have spins within the range observed in Galactic binary neutron stars. Our analysis employs two methods: the use of equation-of-state-insensitive relations between various macroscopic properties of the neutron stars and the use of an efficient parametrization of the defining function p(ρ) of the equation of state itself. From the LIGO and Virgo data alone and the first method, we measure the two neutron star radii as R_{1}=10.8_{-1.7}^{+2.0}  km for the heavier star and R_{2}=10.7_{-1.5}^{+2.1}  km for the lighter star at the 90% credible level. If we additionally require that the equation of state supports neutron stars with masses larger than 1.97  M_{⊙} as required from electromagnetic observations and employ the equation-of-state parametrization, we further constrain R_{1}=11.9_{-1.4}^{+1.4}  km and R_{2}=11.9_{-1.4}^{+1.4}  km at the 90% credible level. Finally, we obtain constraints on p(ρ) at supranuclear densities, with pressure at twice nuclear saturation density measured at 3.5_{-1.7}^{+2.7}×10^{34}  dyn cm^{-2} at the 90% level.

Zf9, a Kruppel-like transcription factor up-regulated in vivo during early hepatic fibrosis

Wound repair in the liver induces altered gene expression in stellate cells (resident mesenchymal cells) in a process known as "activation." A zinc finger transcription factor cDNA, zf9, was cloned from rat stellate cells activated in vivo. Zf9 expression and biosynthesis are increased markedly in activated cells in vivo compared with cells from normal rats ("quiescent" cells). The factor is localized to the nucleus and the perinuclear zone in activated but not quiescent cells. Zf9 mRNA also is expressed widely in nonhepatic adult rat tissues and the fetal liver. The zf9 nucleotide sequence predicts a member of the Kruppel-like family with a unique N-terminal domain rich in serine-proline clusters and leucines. The human zf9 gene maps to chromosome 10P near the telomere. Zf9 binds specifically to a DNA oligonucleotide containing a GC box motif. The N-terminal domain of Zf9 (amino acids 1-201) is transactivating in the chimeric GAL4 hybrid system. In Drosophila schneider cells, full length Zf9 transactivates a reporter construct driven by the SV40 promoter/enhancer, which contains several GC boxes. A physiologic role for Zf9 is suggested by its transactivation of a collagen alpha1(I) promoter reporter. Transactivation of collagen alpha1(I) by Zf9 is context-dependent, occurring strongly in stellate cells, modestly in Hep G2 cells, and not at all in D. schneider cells. Our results suggest that Zf9 may be an important signal in hepatic stellate cell activation after liver injury.

Members of the olfactory receptor gene family are contained in large blocks of DNA duplicated polymorphically near the ends of human chromosomes

We have identified three new members of the olfactory receptor (OR) gene family within a large segment of DNA that is duplicated with high similarity near many human telomeres. This segment is present at 3q, 15q, and 19p in each of 45 unrelated humans sampled from various populations. Additional copies are present polymorphically at 11 other subtelomeric locations. The frequency with which the block is present at some locations varies among populations. While humans carry seven to 11 copies of the OR-containing block, it is located in chimpanzee and gorilla predominantly at a single site, which is not orthologous to any of the locations in the human genome. The observation that sequences flanking the OR-containing segment are duplicated on larger and different sets of chromosomes than the OR block itself demonstrates that the segment is part of a much larger, complex patchwork of subtelomeric duplications. The population analyses and structural results suggest the types of processes that have shaped these regions during evolution. From its sequence, one of the OR genes in this duplicated block appears to be potentially functional. Our findings raise the possibility that functional diversity in the OR family is generated in part through duplications and inter-chromosomal rearrangements of the DNA near human telomeres.

Comparison of propofol and midazolam for sedation in critically ill patients

101 critically ill patients admitted to five intensive-care units were allocated randomly to receive a continuous intravenous infusion of either propofol or midazolam for sedation for up to 24 h. In addition, morphine was given to provide analgesia. The mean duration of infusion was 20.2 h (range 3.0-24.5) in the propofol group and 21.3 h (4.0-47.0) in the midazolam group and infusion rates were 1.77 mg/kg/h (range 0.40-5.00) and 0.10 mg/kg/h (0.01-0.26), respectively. The infusion rates were adjusted as necessary, and the desired level of sedation was achieved easily in most patients in both groups. There were slight falls in arterial pressure, but there were no significant differences between the groups. Heart rate was lower in patients who received propofol. Some small changes occurred in biochemical and haematological variables in both groups, but they were not clinically significant. There was no indication that either drug substantially impaired adrenal steroidogenesis. When the infusion was discontinued, there was less variability in recovery of consciousness in patients who had received propofol. In a subgroup of patients, weaning from mechanical ventilation was achieved significantly faster after discontinuation of propofol than of midazolam. Propofol proved to be a satisfactory agent for sedation of these critically ill patients and compared favourably with midazolam.

Natural T cells in the human liver: cytotoxic lymphocytes with dual T cell and natural killer cell phenotype and function are phenotypically heterogenous and include Valpha24-JalphaQ and gammadelta T cell receptor bearing cells

The adult liver contains lymphocytes with a unique phenotypic distribution compared to blood and other organs. We have characterized a human lymphocyte population that exhibits dual T cell and natural killer (NK) cell phenotype and function, denoted natural T (NT) cells, in nine normal adult liver specimens. Flow cytometry revealed that up to 55% (mean 27%) of hepatic (but <6% of peripheral) CD3+ lymphocytes expressed CD56, CD161 and/or one or more of the killer inhibitory receptors (KIR) p58.1, p58.2, p70 and CD94. NK function was attributed to the CD3+CD56+ cells by the demonstration that hepatic, but not peripheral, CD3+ lymphocytes could be induced to lyse NK-sensitive K562 target cells, while CD56- cells from both compartments could not. Three color flow cytometric analysis of fresh hepatic cells indicated that CD3+CD56+ NT cells can be either CD8+, CD4+ or CD4 CD8-, they express alphabeta or gammadelta T cell receptors (TCR) and CD161 and KIRs, but rarely CD16. Hepatic NT cells predominantly express the mature/activated CD45RO and CD56dim phenotypes. Analysis of mRNA production by isolated NT cells indicated a preferential usage of the invariant CD1-restricted Valpha24-JalphaQ TCR. The presence of such large numbers of chronically activated NT cells provides compelling evidence that the liver has unique immunoregulatory functions.