Chromatin context-dependent regulation and epigenetic manipulation of prime editing

We set out to exhaustively characterize the impact of the cis-chromatin environment on prime editing, a precise genome engineering tool. Using a highly sensitive method for mapping the genomic locations of randomly integrated reporters, we discover massive position effects, exemplified by editing efficiencies ranging from ∼0% to 94% for an identical target site and edit. Position effects on prime editing efficiency are well predicted by chromatin marks, e.g., positively by H3K79me2 and negatively by H3K9me3. Next, we developed a multiplex perturbational framework to assess the interaction of trans-acting factors with the cis-chromatin environment on editing outcomes. Applying this framework to DNA repair factors, we identify HLTF as a context-dependent repressor of prime editing. Finally, several lines of evidence suggest that active transcriptional elongation enhances prime editing. Consistent with this, we show we can robustly decrease or increase the efficiency of prime editing by preceding it with CRISPR-mediated silencing or activation, respectively.

Induction and in silico staging of human gastruloids with neural tube, segmented somites & advanced cell types

Embryonic organoids are emerging as powerful models for studying early mammalian development. For example, stem cell-derived 'gastruloids' form elongating structures containing all three germ layers1-4. However, although elongated, human gastruloids do not morphologically resemble post-implantation embryos. Here we show that a specific, discontinuous regimen of retinoic acid (RA) robustly induces human gastruloids with embryo-like morphological structures, including a neural tube and segmented somites. Single cell RNA-seq (sc-RNA-seq) further reveals that these human 'RA-gastruloids' contain more advanced cell types than conventional gastruloids, including neural crest cells, renal progenitor cells, skeletal muscle cells, and, rarely, neural progenitor cells. We apply a new approach to computationally stage human RA-gastruloids relative to somite-resolved mouse embryos, early human embryos and other gastruloid models, and find that the developmental stage of human RA-gastruloids is comparable to that of E9.5 mouse embryos, although some cell types show greater or lesser progression. We chemically perturb WNT and BMP signaling in human RA-gastruloids and find that these signaling pathways regulate somite patterning and neural tube length, respectively, while genetic perturbation of the transcription factors PAX3 and TBX6 markedly compromises the formation of neural crest and somites/renal cells, respectively. Human RA-gastruloids complement other embryonic organoids in serving as a simple, robust and screenable model for decoding early human embryogenesis.

A single-cell time-lapse of mouse prenatal development from gastrula to birth

The house mouse (Mus musculus) is an exceptional model system, combining genetic tractability with close evolutionary affinity to humans1,2. Mouse gestation lasts only 3 weeks, during which the genome orchestrates the astonishing transformation of a single-cell zygote into a free-living pup composed of more than 500 million cells. Here, to establish a global framework for exploring mammalian development, we applied optimized single-cell combinatorial indexing3 to profile the transcriptional states of 12.4 million nuclei from 83 embryos, precisely staged at 2- to 6-hour intervals spanning late gastrulation (embryonic day 8) to birth (postnatal day 0). From these data, we annotate hundreds of cell types and explore the ontogenesis of the posterior embryo during somitogenesis and of kidney, mesenchyme, retina and early neurons. We leverage the temporal resolution and sampling depth of these whole-embryo snapshots, together with published data4-8 from earlier timepoints, to construct a rooted tree of cell-type relationships that spans the entirety of prenatal development, from zygote to birth. Throughout this tree, we systematically nominate genes encoding transcription factors and other proteins as candidate drivers of the in vivo differentiation of hundreds of cell types. Remarkably, the most marked temporal shifts in cell states are observed within one hour of birth and presumably underlie the massive physiological adaptations that must accompany the successful transition of a mammalian fetus to life outside the womb.

Chromatin context-dependent regulation and epigenetic manipulation of prime editing

Prime editing is a powerful means of introducing precise changes to specific locations in mammalian genomes. However, the widely varying efficiency of prime editing across target sites of interest has limited its adoption in the context of both basic research and clinical settings. Here, we set out to exhaustively characterize the impact of the cis- chromatin environment on prime editing efficiency. Using a newly developed and highly sensitive method for mapping the genomic locations of a randomly integrated "sensor", we identify specific epigenetic features that strongly correlate with the highly variable efficiency of prime editing across different genomic locations. Next, to assess the interaction of trans -acting factors with the cis -chromatin environment, we develop and apply a pooled genetic screening approach with which the impact of knocking down various DNA repair factors on prime editing efficiency can be stratified by cis -chromatin context. Finally, we demonstrate that we can dramatically modulate the efficiency of prime editing through epigenome editing, i.e. altering chromatin state in a locus-specific manner in order to increase or decrease the efficiency of prime editing at a target site. Looking forward, we envision that the insights and tools described here will broaden the range of both basic research and therapeutic contexts in which prime editing is useful.

A single-cell transcriptional timelapse of mouse embryonic development, from gastrula to pup

The house mouse, Mus musculus, is an exceptional model system, combining genetic tractability with close homology to human biology. Gestation in mouse development lasts just under three weeks, a period during which its genome orchestrates the astonishing transformation of a single cell zygote into a free-living pup composed of >500 million cells. Towards a global framework for exploring mammalian development, we applied single cell combinatorial indexing (sci-*) to profile the transcriptional states of 12.4 million nuclei from 83 precisely staged embryos spanning late gastrulation (embryonic day 8 or E8) to birth (postnatal day 0 or P0), with 2-hr temporal resolution during somitogenesis, 6-hr resolution through to birth, and 20-min resolution during the immediate postpartum period. From these data (E8 to P0), we annotate dozens of trajectories and hundreds of cell types and perform deeper analyses of the unfolding of the posterior embryo during somitogenesis as well as the ontogenesis of the kidney, mesenchyme, retina, and early neurons. Finally, we leverage the depth and temporal resolution of these whole embryo snapshots, together with other published data, to construct and curate a rooted tree of cell type relationships that spans mouse development from zygote to pup. Throughout this tree, we systematically nominate sets of transcription factors (TFs) and other genes as candidate drivers of the in vivo differentiation of hundreds of mammalian cell types. Remarkably, the most dramatic shifts in transcriptional state are observed in a restricted set of cell types in the hours immediately following birth, and presumably underlie the massive changes in physiology that must accompany the successful transition of a placental mammal to extrauterine life.

Massively parallel characterization of transcriptional regulatory elements in three diverse human cell types

The human genome contains millions of candidate cis-regulatory elements (CREs) with cell-type-specific activities that shape both health and myriad disease states. However, we lack a functional understanding of the sequence features that control the activity and cell-type-specific features of these CREs. Here, we used lentivirus-based massively parallel reporter assays (lentiMPRAs) to test the regulatory activity of over 680,000 sequences, representing a nearly comprehensive set of all annotated CREs among three cell types (HepG2, K562, and WTC11), finding 41.7% to be functional. By testing sequences in both orientations, we find promoters to have significant strand orientation effects. We also observe that their 200 nucleotide cores function as non-cell-type-specific 'on switches' providing similar expression levels to their associated gene. In contrast, enhancers have weaker orientation effects, but increased tissue-specific characteristics. Utilizing our lentiMPRA data, we develop sequence-based models to predict CRE function with high accuracy and delineate regulatory motifs. Testing an additional lentiMPRA library encompassing 60,000 CREs in all three cell types, we further identified factors that determine cell-type specificity. Collectively, our work provides an exhaustive catalog of functional CREs in three widely used cell lines, and showcases how large-scale functional measurements can be used to dissect regulatory grammar.

Optimized single-nucleus transcriptional profiling by combinatorial indexing

Single-cell combinatorial indexing RNA sequencing (sci-RNA-seq) is a powerful method for recovering gene expression data from an exponentially scalable number of individual cells or nuclei. However, sci-RNA-seq is a complex protocol that has historically exhibited variable performance on different tissues, as well as lower sensitivity than alternative methods. Here, we report a simplified, optimized version of the sci-RNA-seq protocol with three rounds of split-pool indexing that is faster, more robust and more sensitive and has a higher yield than the original protocol, with reagent costs on the order of 1 cent per cell or less. The total hands-on time from nuclei isolation to final library preparation takes 2-3 d, depending on the number of samples sharing the experiment. The improvements also allow RNA profiling from tissues rich in RNases like older mouse embryos or adult tissues that were problematic for the original method. We showcase the optimized protocol via whole-organism analysis of an E16.5 mouse embryo, profiling ~380,000 nuclei in a single experiment. Finally, we introduce a 'Tiny-Sci' protocol for experiments in which input material is very limited.

Embryo model completes gastrulation to neurulation and organogenesis

Embryonic stem (ES) cells can undergo many aspects of mammalian embryogenesis in vitro1-5, but their developmental potential is substantially extended by interactions with extraembryonic stem cells, including trophoblast stem (TS) cells, extraembryonic endoderm stem (XEN) cells and inducible XEN (iXEN) cells6-11. Here we assembled stem cell-derived embryos in vitro from mouse ES cells, TS cells and iXEN cells and showed that they recapitulate the development of whole natural mouse embryo in utero up to day 8.5 post-fertilization. Our embryo model displays headfolds with defined forebrain and midbrain regions and develops a beating heart-like structure, a trunk comprising a neural tube and somites, a tail bud containing neuromesodermal progenitors, a gut tube, and primordial germ cells. This complete embryo model develops within an extraembryonic yolk sac that initiates blood island development. Notably, we demonstrate that the neurulating embryo model assembled from Pax6-knockout ES cells aggregated with wild-type TS cells and iXEN cells recapitulates the ventral domain expansion of the neural tube that occurs in natural, ubiquitous Pax6-knockout embryos. Thus, these complete embryoids are a powerful in vitro model for dissecting the roles of diverse cell lineages and genes in development. Our results demonstrate the self-organization ability of ES cells and two types of extraembryonic stem cells to reconstitute mammalian development through and beyond gastrulation to neurulation and early organogenesis.

Results of genetic analysis of 11 341 participants enrolled in the My Life, Our Future hemophilia genotyping initiative in the United States

BACKGROUND

Hemophilia A (HA) and hemophilia B (HB) are rare inherited bleeding disorders. Although causative genetic variants are clinically relevant, in 2012 only 20% of US patients had been genotyped.

OBJECTIVES

My Life, Our Future (MLOF) was a multisector cross-sectional US initiative to improve our understanding of hemophilia through widespread genotyping.

METHODS

Subjects and potential genetic carriers were enrolled at US hemophilia treatment centers (HTCs). Bloodworks performed genotyping and returned results to providers. Clinical data were abstracted from the American Thrombosis and Hemostasis Network dataset. Community education was provided by the National Hemophilia Foundation.

RESULTS

From 2013 to 2017, 107 HTCs enrolled 11 341 subjects (68.8% male, 31.2% female) for testing for HA (n = 8976), HB (n = 2358), HA/HB (n = 3), and hemophilia not otherwise specified (n = 4). Variants were detected in most male patients (98.2%% HA, 98.1% HB). 1914 unique variants were found (1482 F8, 431 F9); 744 were novel (610 F8, 134 F9). Inhibitor data were available for 6986 subjects (5583 HA; 1403 HB). In severe HA, genotypes with the highest inhibitor rates were large deletions (77/80), complex intron 22 inversions (9/17), and no variant found (7/14). In severe HB, the highest rates were large deletions (24/42). Inhibitors were reported in 27.3% of Black versus 16.2% of White patients.

CONCLUSIONS

The findings of MLOF are reported, the largest hemophilia genotyping project performed to date. The results support the need for comprehensive genetic approaches in hemophilia. This effort has contributed significantly towards better understanding variation in the F8 and F9 genes in hemophilia and risks of inhibitor formation.

Systematic reconstruction of cellular trajectories across mouse embryogenesis

Mammalian embryogenesis is characterized by rapid cellular proliferation and diversification. Within a few weeks, a single-cell zygote gives rise to millions of cells expressing a panoply of molecular programs. Although intensively studied, a comprehensive delineation of the major cellular trajectories that comprise mammalian development in vivo remains elusive. Here, we set out to integrate several single-cell RNA-sequencing (scRNA-seq) datasets that collectively span mouse gastrulation and organogenesis, supplemented with new profiling of ~150,000 nuclei from approximately embryonic day 8.5 (E8.5) embryos staged in one-somite increments. Overall, we define cell states at each of 19 successive stages spanning E3.5 to E13.5 and heuristically connect them to their pseudoancestors and pseudodescendants. Although constructed through automated procedures, the resulting directed acyclic graph (TOME (trajectories of mammalian embryogenesis)) is largely consistent with our contemporary understanding of mammalian development. We leverage TOME to systematically nominate transcription factors (TFs) as candidate regulators of each cell type's specification, as well as 'cell-type homologs' across vertebrate evolution.

SwabExpress: An end-to-end protocol for extraction-free covid-19 testing

BACKGROUND

The urgent need for massively scaled clinical testing for SARS-CoV-2, along with global shortages of critical reagents and supplies, has necessitated development of streamlined laboratory testing protocols. Conventional nucleic acid testing for SARS-CoV-2 involves collection of a clinical specimen with a nasopharyngeal swab in transport medium, nucleic acid extraction, and quantitative reverse transcription PCR (RT-qPCR) (1). As testing has scaled across the world, the global supply chain has buckled, rendering testing reagents and materials scarce (2). To address shortages, we developed SwabExpress, an end-to-end protocol developed to employ mass produced anterior nares swabs and bypass the requirement for transport media and nucleic acid extraction.

METHODS

We evaluated anterior nares swabs, transported dry and eluted in low-TE buffer as a direct-to-RT-qPCR alternative to extraction-dependent viral transport media. We validated our protocol of using heat treatment for viral inactivation and added a proteinase K digestion step to reduce amplification interference. We tested this protocol across archived and prospectively collected swab specimens to fine-tune test performance.

RESULTS

After optimization, SwabExpress has a low limit of detection at 2-4 molecules/uL, 100% sensitivity, and 99.4% specificity when compared side-by-side with a traditional RT-qPCR protocol employing extraction. On real-world specimens, SwabExpress outperforms an automated extraction system while simultaneously reducing cost and hands-on time.

CONCLUSION

SwabExpress is a simplified workflow that facilitates scaled testing for COVID-19 without sacrificing test performance. It may serve as a template for the simplification of PCR-based clinical laboratory tests, particularly in times of critical shortages during pandemics.

SwabExpress: An end-to-end protocol for extraction-free COVID-19 testing

BACKGROUND

The urgent need for massively scaled clinical testing for SARS-CoV-2, along with global shortages of critical reagents and supplies, has necessitated development of streamlined laboratory testing protocols. Conventional nucleic acid testing for SARS-CoV-2 involves collection of a clinical specimen with a nasopharyngeal swab in transport medium, nucleic acid extraction, and quantitative reverse transcription PCR (RT-qPCR) (1). As testing has scaled across the world, the global supply chain has buckled, rendering testing reagents and materials scarce (2). To address shortages, we developed SwabExpress, an end-to-end protocol developed to employ mass produced anterior nares swabs and bypass the requirement for transport media and nucleic acid extraction.

METHODS

We evaluated anterior nares swabs, transported dry and eluted in low-TE buffer as a direct-to-RT-qPCR alternative to extraction-dependent viral transport media. We validated our protocol of using heat treatment for viral activation and added a proteinase K digestion step to reduce amplification interference. We tested this protocol across archived and prospectively collected swab specimens to fine-tune test performance.

RESULTS

After optimization, SwabExpress has a low limit of detection at 2-4 molecules/uL, 100% sensitivity, and 99.4% specificity when compared side-by-side with a traditional RT-qPCR protocol employing extraction. On real-world specimens, SwabExpress outperforms an automated extraction system while simultaneously reducing cost and hands-on time.

CONCLUSION

SwabExpress is a simplified workflow that facilitates scaled testing for COVID-19 without sacrificing test performance. It may serve as a template for the simplification of PCR-based clinical laboratory tests, particularly in times of critical shortages during pandemics.

Genome-wide strand asymmetry in massively parallel reporter activity favors genic strands

Massively parallel reporter assays (MPRAs) are useful tools to characterize regulatory elements in human genomes. An aspect of MPRAs that is not typically the focus of analysis is their intrinsic ability to differentiate activity levels for a given sequence element when placed in both of its possible orientations relative to the reporter construct. Here, we describe pervasive strand asymmetry of MPRA signals in data sets from multiple reporter configurations in both published and newly reported data. These effects are reproducible across different cell types and in different treatments within a cell type and are observed both within and outside of annotated regulatory elements. From elements in gene bodies, MPRA strand asymmetry favors the sense strand, suggesting that function related to endogenous transcription is driving the phenomenon. Similarly, we find that within Alu mobile element insertions, strand asymmetry favors the transcribed strand of the ancestral retrotransposon. The effect is consistent across the multiplicity of Alu elements in human genomes and is more pronounced in less diverged Alu elements. We find sequence features driving MPRA strand asymmetry and show its prediction from sequence alone. We see some evidence for RNA stabilization and transcriptional activation mechanisms and hypothesize that the effect is driven by natural selection favoring efficient transcription. Our results indicate that strand asymmetry is a pervasive and reproducible feature in MPRA data. More importantly, the fact that MPRA asymmetry favors naturally transcribed strands suggests that it stems from preserved biological functions that have a substantial, global impact on gene and genome evolution.

Caspase-8, association with Alzheimer's Disease and functional analysis of rare variants

The accumulation of amyloid beta (Aβ) peptide (Amyloid cascade hypothesis), an APP protein cleavage product, is a leading hypothesis in the etiology of Alzheimer's disease (AD). In order to identify additional AD risk genes, we performed targeted sequencing and rare variant burden association study for nine candidate genes involved in the amyloid metabolism in 1886 AD cases and 1700 controls. We identified a significant variant burden association for the gene encoding caspase-8, CASP8 (p = 8.6x10^-5). For two CASP8 variants, p.K148R and p.I298V, the association remained significant in a combined sample of 10,820 cases and 8,881 controls. For both variants we performed bioinformatics structural, expression and enzymatic activity studies and obtained evidence for loss of function effects. In addition to their role in amyloid processing, caspase-8 and its downstream effector caspase-3 are involved in synaptic plasticity, learning, memory and control of microglia pro-inflammatory activation and associated neurotoxicity, indicating additional mechanisms that might contribute to AD. As caspase inhibition has been proposed as a mechanism for AD treatment, our finding that AD-associated CASP8 variants reduce caspase function calls for caution and is an impetus for further studies on the role of caspases in AD and other neurodegenerative diseases.

Novel approach to genetic analysis and results in 3000 hemophilia patients enrolled in the My Life, Our Future initiative

Hemophilia A and B are rare, X-linked bleeding disorders. My Life, Our Future (MLOF) is a collaborative project established to genotype and study hemophilia. Patients were enrolled at US hemophilia treatment centers (HTCs). Genotyping was performed centrally using next-generation sequencing (NGS) with an approach that detected common F8 gene inversions simultaneously with F8 and F9 gene sequencing followed by confirmation using standard genotyping methods. Sixty-nine HTCs enrolled the first 3000 patients in under 3 years. Clinically reportable DNA variants were detected in 98.1% (2357/2401) of hemophilia A and 99.3% (595/599) of hemophilia B patients. Of the 924 unique variants found, 285 were novel. Predicted gene-disrupting variants were common in severe disease; missense variants predominated in mild-moderate disease. Novel DNA variants accounted for ∼30% of variants found and were detected continuously throughout the project, indicating that additional variation likely remains undiscovered. The NGS approach detected >1 reportable variants in 36 patients (10 females), a finding with potential clinical implications. NGS also detected incidental variants unlikely to cause disease, including 11 variants previously reported in hemophilia. Although these genes are thought to be conserved, our findings support caution in interpretation of new variants. In summary, MLOF has contributed significantly toward variant annotation in the F8 and F9 genes. In the near future, investigators will be able to access MLOF data and repository samples for research to advance our understanding of hemophilia.

MIPgen: optimized modeling and design of molecular inversion probes for targeted resequencing

Molecular inversion probes (MIPs) enable cost-effective multiplex targeted gene resequencing in large cohorts. However, the design of individual MIPs is a critical parameter governing the performance of this technology with respect to capture uniformity and specificity. MIPgen is a user-friendly package that simplifies the process of designing custom MIP assays to arbitrary targets. New logistic and SVM-derived models enable in silico predictions of assay success, and assay redesign exhibits improved coverage uniformity relative to previous methods, which in turn improves the utility of MIPs for cost-effective targeted sequencing for candidate gene validation and for diagnostic sequencing in a clinical setting.

AVAILABILITY AND IMPLEMENTATION

MIPgen is implemented in C++. Source code and accompanying Python scripts are available at http://shendurelab.github.io/MIPGEN/.

The haplotype-resolved genome and epigenome of the aneuploid HeLa cancer cell line

The HeLa cell line was established in 1951 from cervical cancer cells taken from a patient, Henrietta Lacks, marking the first successful attempt to continually culture human-derived cells in vitro¹. HeLa’s robust growth and unrestricted distribution resulted in its broad adoption – both intentionally and through widespread cross-contamination² – and for the past sixty years it has served a role analogous to that of a model organism³. Its cumulative impact is illustrated by the fact that HeLa is named in >74,000 or ~0.3% of PubMed abstracts. The genomic architecture of HeLa remains largely unexplored beyond its karyotype⁴, in part because like many cancers, its extensive aneuploidy renders such analyses challenging. We performed haplotype-resolved whole genome sequencing⁵ of the HeLa CCL-2 strain, discovering point and indel variation, mapping copy-number and loss of heterozygosity (LOH), and phasing variants across full chromosome arms. We further investigated variation and copy-number profiles for HeLa S3 and eight additional strains. Surprisingly, HeLa is relatively stable with respect to point variation, accumulating few new mutations since early passaging. Haplotype resolution facilitated reconstruction of an amplified, highly rearranged region at chromosome 8q24.21 at which the HPV-18 viral genome integrated as the likely initial event underlying tumorigenesis. We combined these maps with RNA-Seq⁶ and ENCODE Project⁷ datasets to phase the HeLa epigenome, revealing strong, haplotype-specific activation of the proto-oncogene MYC by the integrated HPV-18 genome ~500 kilobases upstream, and permitting global analyses of the relationship between gene dosage and expression. These data provide an extensively phased, high-quality reference genome for past and future experiments relying on HeLa, and demonstrate the value of haplotype resolution for characterizing cancer genomes and epigenomes.

Multiplex targeted sequencing identifies recurrently mutated genes in autism spectrum disorders

Exome sequencing studies of autism spectrum disorders (ASDs) have identified many de novo mutations but few recurrently disrupted genes. We therefore developed a modified molecular inversion probe method enabling ultra-low-cost candidate gene resequencing in very large cohorts. To demonstrate the power of this approach, we captured and sequenced 44 candidate genes in 2446 ASD probands. We discovered 27 de novo events in 16 genes, 59% of which are predicted to truncate proteins or disrupt splicing. We estimate that recurrent disruptive mutations in six genes-CHD8, DYRK1A, GRIN2B, TBR1, PTEN, and TBL1XR1-may contribute to 1% of sporadic ASDs. Our data support associations between specific genes and reciprocal subphenotypes (CHD8-macrocephaly and DYRK1A-microcephaly) and replicate the importance of a β-catenin-chromatin-remodeling network to ASD etiology.

Naproxen and celecoxib do not prevent AD in early results from a randomized controlled trial

OBJECTIVE

To evaluate the efficacy and safety of naproxen and celecoxib for the primary prevention of Alzheimer disease (AD).

METHODS

Randomized, placebo-controlled, double-masked clinical trial conducted at six US dementia research clinics. Volunteers aged 70+ years, with cognitive screening scores above designated cut-offs and a family history of AD, were randomly assigned to celecoxib 200 mg BID, naproxen sodium 220 mg BID, or placebo. Enrollment began in early 2001. The main outcome measure was diagnosis of AD after randomization.

RESULTS

On December 17, 2004, treatments were suspended. Events while on treatment yielded hazard ratios vs placebo of 1.99 (95% CI 0.80 to 4.97; p = 0.14) for celecoxib and 2.35 (0.95 to 5.77; p = 0.06) for naproxen. Imperfect screening measures led to enrollment of 7 individuals with dementia and 46 others with milder cognitive syndromes. Their (prevalent) illness was detected at enrollment and diagnosed within 6 months following randomization. Secondary analyses that excluded the 7 cases of prevalent dementia showed increased hazard ratios for AD with both treatments. Neither treatment produced a notable effect on the incidence of milder cognitive syndromes.

CONCLUSIONS

These results do not support the hypothesis that celecoxib or naproxen prevent Alzheimer dementia, at least within the early years after initiation of treatment. Masked long-term follow-up of these participants will be essential.

Double-masked randomized trial comparing alternate combinations of intraoperative anesthesia and postoperative analgesia in abdominal aortic surgery

BACKGROUND

Improvement in patient outcome and reduced use of medical resources may result from using epidural anesthesia and analgesia as compared with general anesthesia and intravenous opioids, although the relative importance of intraoperative versus postoperative technique has not been studied. This prospective, double-masked, randomized clinical trial was designed to compare alternate combinations of intraoperative anesthesia and postoperative analgesia with respect to postoperative outcomes in patients undergoing surgery of the abdominal aorta.

METHODS

One hundred sixty-eight patients undergoing surgery of the abdominal aorta were randomly assigned to receive either thoracic epidural anesthesia combined with a light general anesthesia or general anesthesia alone intraoperatively and either intravenous or epidural patient-controlled analgesia postoperatively (four treatment groups). Patient-controlled analgesia was continued for at least 72 h. Protocols were used to standardize perioperative medical management and to preserve masking intraoperatively and postoperatively. A uniform surveillance strategy was used for the identification of prospectively defined postoperative complications. Outcome evaluation included postoperative hospital length of stay, direct medical costs, selected postoperative morbidities, and postoperative recovery milestones.

RESULTS

Length of stay and direct medical costs for patients surviving to discharge were similar among the four treatment groups. Postoperative outcomes were similar among the four treatment groups with respect to death, myocardial infarction, myocardial ischemia, reoperation, pneumonia, and renal failure. Epidural patient-controlled analgesia was associated with a significantly shorter time to extubation (P = 0.002). Times to intensive care unit discharge, ward admission, first bowel sounds, first flatus, tolerating clear liquids, tolerating regular diet, and independent ambulation were similar among the four treatment groups. Postoperative pain scores were also similar among the four treatment groups.

CONCLUSIONS

In patients undergoing surgery of the abdominal aorta, thoracic epidural anesthesia combined with a light general anesthesia and followed by either intravenous or epidural patient-controlled analgesia, offers no major advantage or disadvantage when compared with general anesthesia alone followed by either intravenous or epidural patient-controlled analgesia.

Longitudinal observations on mutations conferring ganciclovir resistance in patients with acquired immunodeficiency syndrome and cytomegalovirus retinitis: The Cytomegalovirus and Viral Resistance Study Group Report Number 8

PURPOSE

Cytomegalovirus retinitis is the most common intraocular infection in patients with acquired immunodeficiency syndrome (AIDS). With prolonged suppressive anticytomegalovirus maintenance therapy, resistance occurs in over 25% of patients. We evaluated longitudinal changes in the cytomegalovirus genotype in patients with cytomegalovirus retinitis who developed ganciclovir resistance that was demonstrated in either the blood or urine.

METHODS

Patients with AIDS and previously untreated cytomegalovirus retinitis were followed prospectively for the occurrence of resistance while on treatment. Blood and urine specimens were obtained periodically for cytomegalovirus culture according to a predetermined schedule. Positive isolates were tested for phenotypic susceptibility and for mutations in the UL97 and UL54 genes.

RESULTS

A mutation conferring resistance to ganciclovir in either the UL97 or UL54 gene was detected in 18 patients. In general, patients with a genotypically resistant virus developed increasing phenotypic resistance over time. There was a suggestion that unless therapy was changed, UL97 mutations tended to persist. In seven of eight patients, the mutations identified in isolates from the blood and urine were identical. In selected patients, there was a suggestion that a mixed population of cytomegalovirus might be present. Progression of the retinitis in an involved eye (15 of 18), contralateral eye retinitis (10 of 11), and extraocular cytomegalovirus disease (5 of 18) occurred commonly among patients with resistant virus.

CONCLUSION

Resistance-conferring mutations in the cytomegalovirus genome emerge and may persist when the selective pressure for resistance is maintained. Some patients appear to harbor complex subpopulations of virus with different mutations and different levels of phenotypic resistance. Changes in therapy may result in a shift in virus population and changes in the cytomegalovirus genotype identified.

Two distinct domains within CIITA mediate self-association: involvement of the GTP-binding and leucine-rich repeat domains

CIITA is the master regulator of class II major histocompatibility complex gene expression. We present evidence that CIITA can self-associate via two domains: the C terminus (amino acids 700 to 1130) and the GTP-binding domain (amino acids 336 to 702). Heterotypic and homotypic interactions are observed between these two regions. Deletions within the GTP-binding domain that reduce GTP-binding and transactivation function also reduce self-association. In addition, two leucine residues in the C-terminal leucine-rich repeat region are critical for self-association as well as function. This study reveals for the first time a complex pattern of CIITA self-association. These interactions are discussed with regard to the apoptosis signaling proteins, Apaf-1 and Nod1, which share domain arrangements similar to those of CIITA.

Reliability, validity, and responsiveness of general and disease-specific quality of life measures in a clinical trial for cytomegalovirus retinitis

The objective of this study was to evaluate a questionnaire for assessing general and disease-specific quality of life among people with cytomegalovirus (CMV) retinitis. Cross-sectional and longitudinal analyses of data from 279 people enrolled in the CMV Retinitis Retreatment Trial were used. At baseline, Cronbach's alpha and multitrait analysis were used to assess internal consistency and discriminant construct validity for scales of general health, vision, and treatment impact. Associations of scales with clinical measures of health and vision were assessed at baseline with Pearson correlations and t tests, and over time with generalized estimating equations regression. Internal consistency coefficients ranged from .68 to.88. Criteria for discriminant validity were fulfilled for most scales; however, the general health perceptions and energy scales were highly correlated. Scales were moderately correlated with clinical measures at baseline. Over time, scale scores were associated with Karnofsky scores and clinical measures of CMV retinitis and vision. General and CMV retinitis-specific quality of life measures appear reliable, valid, and responsive.

Mutations conferring ganciclovir resistance in a cohort of patients with acquired immunodeficiency syndrome and cytomegalovirus retinitis

Cytomegalovirus (CMV) retinitis is among the most common opportunistic infections in patients with acquired immunodeficiency syndrome. In a prospective study of 210 patients with CMV retinitis, 26 were identified as having either a phenotypic or a genotypic ganciclovir-resistant isolate from either blood or urine cultures. For blood culture isolates with an IC(50) >6.0 microm for ganciclovir, the sensitivity and specificity for detecting a UL97 mutation were 95% and 98%, respectively, whereas for an IC(50) >8.0 microM they were 79% and 99%, respectively. Although there were trade-offs between the 2 thresholds for blood culture isolates, for urine culture isolates an IC(50) >8.0 microM appeared to be better at identifying genotypic resistance. UL97 mutations identified in both the blood and urine cultures of individual patients were identical in 87.5% of cases. High-level ganciclovir resistance (IC(50), >30 microM) typically, but not invariably, was associated with a mutation in both the UL97 and UL54 genes.

Risk factors for advancement of cytomegalovirus retinitis in patients with acquired immunodeficiency syndrome. Studies of Ocular Complications of AIDS Research Group

OBJECTIVE

To identify ocular and systemic factors that predict advancement of cytomegalovirus (CMV) retinitis during treatment.

METHODS

Patients with acquired immunodeficiency syndrome were enrolled in a multicenter clinical trial designed to evaluate foscarnet sodium and ganciclovir sodium as therapy for newly diagnosed CMV retinitis. Ocular characteristics at baseline and measurements of retinitis were assessed from fundus photographs by graders at a fundus photograph reading center. The following measures of advancement were assessed: (1) lesion border movement of at least 750 microm or development of a new lesion in involved eyes; (2) rate of increase in retinal area with CMV in involved eyes; and (3) development of retinitis in uninvolved eyes of patients with unilateral disease at baseline.

RESULTS

In eyes with retinitis, risk factors at baseline for advancement while receiving treatment included smaller area involved, active margins of retinitis, and posterior location. Risk factors for development of retinitis in uninvolved fellow eyes included blood and urine cultures positive for CMV and lower CD8(+) T-lymphocyte count.

CONCLUSIONS

Lesion characteristics can be used to predict advancement of preexisting disease, whereas only systemic factors are associated with development of bilateral disease. These analyses describe retinitis activity before the introduction of potent antiretroviral therapies but provide an important reference point for patients in whom CMV retinitis develops after failure or intolerance of antiretroviral agents. Arch Ophthalmol. 2000;118:1196-1204

Combination gene therapy with CD86 and the MHC class II transactivator in the control of lung tumor growth

Early reports suggest that the costimulatory molecule CD86 (B7-2) has sporadic efficacy in tumor immunity, whereas changes in cancer immunity mediated by the MHC class II transactivator (CIITA) have not been extensively investigated. CIITA activates MHC class II expression in most cells; however, in the Line 1 lung carcinoma model system, CIITA activates MHC class I and well as class II. Here we show that CD86 is very effective in inducing a primary immune response against Line 1. Tumor cells expressing CD86 grew in only 50% of the mice injected with live cells, and those mice that developed tumors did so with significantly delayed kinetics. Furthermore, irradiated CD86-expressing Line 1 cells served as an effective tumor vaccine, demonstrating that CD86 is effective in inducing tumor immunity in the Line 1 system. These data suggest that if CIITA and CD86 cooperate, enhanced tumor immunity could be achieved. CIITA alone was mildly beneficial in slowing primary tumor growth but only when expressed at low levels. Clones expressing high levels of class II MHC grew as fast as or faster than parental tumor, and CIITA expression in a tumor vaccine assay lacked efficacy. When CIITA and CD86 were coexpressed, there was no cooperative immune protection from tumor growth. Cells that coexpress both genes also failed as a cancer vaccine, suggesting a negative role for CIITA in this lung carcinoma. These data suggest that human cancer vaccine trials utilizing CIITA gene therapy alone or in combination with CD86 should be approached with caution.

Major histocompatibility complex class II-transfected tumor cells present endogenous antigen and are potent inducers of tumor-specific immunity

We have developed an immunotherapy in which tumor cells transfected with syngeneic major histocompatibility complex (MHC) class II genes are cell-based vaccines for the treatment of established tumor and metastatic disease. If this strategy is to be used clinically, convenient methods for generating class II+ tumor cells are necessary. Interferon-gamma treatment or transduction of the class II transactivator (CIITA) gene induces class II expression but also up-regulates the class II-associated accessory molecules, invariant chain (Ii) and DM. To determine if interferon-gamma treatment and CIITA transduction are potential immunotherapies, we assessed the tumorigenicity of sarcoma cells expressing combinations of class II, Ii, and DM. Since we hypothesized that class II-transfected tumor cells not coexpressing Ii and DM present endogenously encoded tumor peptides, we have assessed the transfectants for antigen presentation activity to MHC class II-restricted antigen-specific CD4(+) T cells. Tumor challenge studies demonstrate that tumor cells expressing class II without coexpression of Ii or Ii plus DM are highly immunogenic and preferentially present endogenous antigens, while tumors coexpressing class II with Ii or Ii plus DM are not effective immunogens. Because tumor rejection correlates with expression of class II without coexpression of Ii and DM, the most efficacious vaccines will express MHC class II without coexpression of Ii and DM and will preferentially present endogenous antigen.

Expression of the murine CD21 gene is regulated by promoter and intronic sequences

Murine CD21 gene products are expressed primarily on the surface of B lymphocytes and follicular dendritic cells. To identify the genetic elements that control the tissue-specific expression of the CD21 gene, we analyzed, via transient transfections, the 5' proximal promoter region of the CD21 gene (1272 bp 5' of the initiating ATG). This region possessed strong promoter activity, but it was not tissue specific, in that T cell expression was equivalent to that of B cells. These data suggested that the anticipated tissue-specific control element(s) lies 3' of the initiating ATG. Analysis of a novel minigene construct that possessed both the 5' promoter region and a large region (9 kb) of the CD21 gene 3' of the initiating ATG demonstrated the expected tissue-specific expression. Further analysis using the luciferase reporter system indicated that such control elements reside in the first intron (5.5 kb in size), which separates the exons encoding the signal sequence and the first extracellular short consensus repeat domain of the mature protein. Further dissection of intron 1 demonstrated that the sequences controlling the tissue-specific expression of the murine CD21 gene are contained in the 5' 1.6-kb region of this intron. This 1.6-kb fragment was fractionated into an 800-bp sequence at the 5' end that showed very significant inhibitory activity in both B and T cells and a 3' 800-bp sequence that demonstrated moderate repression in T cells, but enhancer activity in B cells. These data suggest this region of the CD21 gene possesses a number of functionally distinct sites that positively and negatively regulate CD21 gene transcription.

Expression of the murine CD21 gene is regulated by promoter and intronic sequences

Murine CD21 gene products are expressed primarily on the surface of B lymphocytes and follicular dendritic cells. To identify the genetic elements that control the tissue-specific expression of the CD21 gene, we analyzed, via transient transfections, the 5' proximal promoter region of the CD21 gene (1272 bp 5' of the initiating ATG). This region possessed strong promoter activity, but it was not tissue specific, in that T cell expression was equivalent to that of B cells. These data suggested that the anticipated tissue-specific control element(s) lies 3' of the initiating ATG. Analysis of a novel minigene construct that possessed both the 5' promoter region and a large region (9 kb) of the CD21 gene 3' of the initiating ATG demonstrated the expected tissue-specific expression. Further analysis using the luciferase reporter system indicated that such control elements reside in the first intron (5.5 kb in size), which separates the exons encoding the signal sequence and the first extracellular short consensus repeat domain of the mature protein. Further dissection of intron 1 demonstrated that the sequences controlling the tissue-specific expression of the murine CD21 gene are contained in the 5' 1.6-kb region of this intron. This 1.6-kb fragment was fractionated into an 800-bp sequence at the 5' end that showed very significant inhibitory activity in both B and T cells and a 3' 800-bp sequence that demonstrated moderate repression in T cells, but enhancer activity in B cells. These data suggest this region of the CD21 gene possesses a number of functionally distinct sites that positively and negatively regulate CD21 gene transcription.

Induction of MHC class I expression by the MHC class II transactivator CIITA

Major histocompatibility complex (MHC) class I-deficient cell lines were used to demonstrate that the MHC class II transactivator (CIITA) can induce surface expression of MHC class I molecules. CIITA induces the promoter of MHC class I heavy chain genes. The site alpha DNA element is the target for CIITA-induced transactivation of class I. In addition, interferon-gamma (IFNgamma)-induced MHC class I expression also requires an intact site alpha. The G3A cell line, which is defective in CIITA induction, does not induce MHC class I antigen and promoter in response to IFNgamma. Trans-dominant-negative forms of CIITA reduce class I MHC promoter function and surface antigen expression. Collectively, these data argue that CIITA has a role in class I MHC gene induction.

Taxol-dependent transcriptional activation of IL-8 expression in a subset of human ovarian cancer

Taxol is important in the treatment of both primary and drug-resistant ovarian cancer. Although Taxol is known to stabilize microtubules and block cell mitosis, the effectiveness of this drug exceeds that of other antimitotic agents, suggesting it may have an additional mode of action. Stimulated by murine macrophage studies indicating cytokine induction by Taxol, we have investigated proinflammatory cytokine expression in a series of cell lines and recent explants of human ovarian cancer. Taxol induced secretion of interleukin (IL) 8 but not IL-6, IL-1alpha, or IL-1beta in 4 of 10 samples. Induction was dependent on transcriptional activation, and, in contrast to murine macrophage studies, was apparently independent of an active lipopolysaccharide signaling pathway. Confluent cultures secreted as much IL-8 as proliferating cells. Taxol did not induce IL-8 in breast carcinoma, endometrial stromal, or T-lymphocyte or monocyte cultures. We propose that the local expression of this chemokine in vivo may elicit a host response similar in effectiveness to that of cytokine gene therapy. These data are the first to suggest that a chemotherapeutic agent may have a direct effect on transcription of cytokine and/or growth factor genes in ovarian cancer, and that this effect may not be restricted to proliferating tumor cells.

Murine macrophages lack expression of the Cr2-145 (CR2) and Cr2-190 (CR1) gene products

Murine macrophages have been described as possessing complement receptors for C3b and iC3b. These binding activities have been assumed to be due to the presence of the CR1 and CR3 proteins, respectively. The mouse Cr2 gene produces two distinct gene products of approximately 190,000 relative molecular mass (M(r)) (Cr2-190) and 145,000 M(r) (Cr2-145). Because of the similarity in size to human complement receptors, the Cr2-190 protein has been dubbed murine CR1 while the murine Cr2-145 product has been termed murine CR2. In order to define the complement receptor genes expressed by murine macrophages, we investigated the expression patterns of Cr2-190, Cr2-145 and another mouse complement receptor, Crry, in three different mouse macrophage populations: bone marrow-derived macrophages, thioglycollate-elicited peritoneal macrophages and the macrophage cell line, J774. Neither of the Cr2 gene transcripts encoding the Cr2-145 and Cr2-190 proteins could be detected in these populations by RT-RPCR analysis although Crry transcripts were evident. Cr2-145 and Cr2s-190 proteins could not be detected on the surface of thioglycollate-elicited macrophages using a monoclonal antibody that recognizes both proteins. Thus, contrary to previously published data, murine macrophages do not possess the Cr2 gene products.

Functional identification of transcription control sequences of the mouse Crry gene

The mouse C receptor-related gene Crry is expressed by a wide variety of cells. Those sequences required for the transcriptional control of this gene were identified by deletion analysis of regions 5' of the initiating ATG. Fusion of Crry promoter sequences to the reporter gene CAT identified a region approximately 1,500 bp upstream of the transcriptional start site that enhanced transcription of this gene construct. Gel shift and methylation interference assays were performed, and a specific protein-DNA complex was identified within this region. These assays defined a 16-bp sequence 1,642 bp 5' of the initiating ATG that bound a protein in nuclear extracts prepared from all murine cell lines and tissues examined. The methylation interference assay indicated that the core region of the DNA sequence recognized by the protein was GGAA, the common core binding site for the ets family of proto-oncogenes. Oligonucleotides prepared from this sequence with the GGAA sequence did inhibit the DNA/protein complex formation, whereas those with a mutant GGAA sites did not. The minimal site identified by methylation interference was able to up-regulate transcription when placed downstream of a heterologous promoter, whereas the same sequence with an altered GGAA site could not. Thus, this site functions as an enhancer.

Functional identification of transcription control sequences of the mouse Crry gene

The mouse C receptor-related gene Crry is expressed by a wide variety of cells. Those sequences required for the transcriptional control of this gene were identified by deletion analysis of regions 5' of the initiating ATG. Fusion of Crry promoter sequences to the reporter gene CAT identified a region approximately 1,500 bp upstream of the transcriptional start site that enhanced transcription of this gene construct. Gel shift and methylation interference assays were performed, and a specific protein-DNA complex was identified within this region. These assays defined a 16-bp sequence 1,642 bp 5' of the initiating ATG that bound a protein in nuclear extracts prepared from all murine cell lines and tissues examined. The methylation interference assay indicated that the core region of the DNA sequence recognized by the protein was GGAA, the common core binding site for the ets family of proto-oncogenes. Oligonucleotides prepared from this sequence with the GGAA sequence did inhibit the DNA/protein complex formation, whereas those with a mutant GGAA sites did not. The minimal site identified by methylation interference was able to up-regulate transcription when placed downstream of a heterologous promoter, whereas the same sequence with an altered GGAA site could not. Thus, this site functions as an enhancer.

Identification of sites for distinct DNA binding proteins including Oct-1 and Oct-2 in the Cr2 gene

The murine Cr2 gene produces two distinct products in a variety of murine cell types. Both of these transcripts appear to initiate from the same position within the gene but vary from one another via an alternative splicing event within the coding exons. An analysis of those gene sequences that might control the cell specific expression of the Cr2 gene has identified a region of Cr2 5' of the transcription start site that is conserved in both the murine Cr2 and human CR2 genes. When this region was examined using the gel shift assay with nuclear extracts from cells expressing Cr2 (B cells) and those that do not (T cells and fibroblasts), at least four distinct proteins were identified that bound to at least three distinct sites. The DNA sequence recognized by two of these proteins is the octamer sequence recognized by a family of transcriptional regulators including the B cell specific Oct-2 protein. During an acute bacterial infection, the levels of Oct-2 and Cr2 mRNA are both depressed. This suggests that the Oct-2 protein directly controls the transcriptional activity of the Cr2 gene and that during such an infection, the levels of Ag receptors on B cells (Ig and complement receptors) are diminished.

Identification of sites for distinct DNA binding proteins including Oct-1 and Oct-2 in the Cr2 gene

The murine Cr2 gene produces two distinct products in a variety of murine cell types. Both of these transcripts appear to initiate from the same position within the gene but vary from one another via an alternative splicing event within the coding exons. An analysis of those gene sequences that might control the cell specific expression of the Cr2 gene has identified a region of Cr2 5' of the transcription start site that is conserved in both the murine Cr2 and human CR2 genes. When this region was examined using the gel shift assay with nuclear extracts from cells expressing Cr2 (B cells) and those that do not (T cells and fibroblasts), at least four distinct proteins were identified that bound to at least three distinct sites. The DNA sequence recognized by two of these proteins is the octamer sequence recognized by a family of transcriptional regulators including the B cell specific Oct-2 protein. During an acute bacterial infection, the levels of Oct-2 and Cr2 mRNA are both depressed. This suggests that the Oct-2 protein directly controls the transcriptional activity of the Cr2 gene and that during such an infection, the levels of Ag receptors on B cells (Ig and complement receptors) are diminished.

Spironolactone metabolism: steady-state serum levels of the sulfur-containing metabolites

Metabolism of spironolactone in man is extensive and complex. For many years the dethioacetylated metabolite, canrenone, was assumed to be the major metabolite. However, recent studies using specific high performance liquid chromatography (HPLC) have demonstrated the presence of spironolactone and the sulfur-containing metabolites 7 alpha-thiomethylspirolactone (IV) and 6 beta-hydroxy-7 alpha-thiomethylspirolactone (V), in addition to canrenone, in the serum after a single oral dose of spironolactone. The importance of spironolactone and metabolites IV and V relative to canrenone at steady state remains unknown and was the subject of the present investigation. Twelve healthy males received 100 mg spironolactone, once daily, for 15 days. Repeated blood samples were taken on days 1, 8 and 15 for estimation of spironolactone and its metabolites. Peak serum levels [mean (SD)] of spironolactone, canrenone, and sulfur-containing metabolites IV and V were 72 (45), 155 (43), 359 (106) and 101 (26) ng/ml, respectively on day 1 and 80 (20), 181 (39), 391 (118) and 125 (24) ng/ml, respectively on day 15. The AUC (0-24) values of these compounds on day 15 were 231 (50), 2173 (312), 2804 (777) and 1727 (367) ng.hr/ml, respectively and the post-steady state elimination half-life (t1/2) values were 1.4 (0.5), 16.5 (6.3), 13.8 (6.4), and 15.0 (4.0) hours, respectively. It was concluded that unmetabolized spironolactone is present in the serum and that the sulfur-containing metabolite IV rather than canrenone is the major metabolite in serum following single or repeated doses of spironolactone.

Building a relational database for a physician document index

We show how three existing medical knowledge bases: Medical Subject Headings (MeSH), Standardized Nomenclature of Medicine (SNOMED) and Current Medical Information and Technology (CMIT) are mapped into a relational data model and stored on an Apollo workstation and an Intelligent Database Machine. Since two of these knowledge bases have been used in the indexing of medical literature and patient records, they can be useful not only as direct views on the organization of medical concepts but also as tools for the retrieval of documents. In order that the concepts from one knowledge base can be connected to those of the other knowledge base, a method has been developed for the semi-automatic merging of MeSH, SNOMED and CMIT. This method takes advantage of the relational model and the synonyms that are given in SNOMED and CMIT, in order to recommend concepts to be merged. An expert interacts with the system to accept or reject the recommendations of the computer. The method would apply equally well to other knowledge bases and is particularly well-suited for knowledge bases that contain tens of thousands of concepts.

A repeated dose pharmacokinetic study of a new hypnotic agent, zopiclone (Imovane)

Eleven volunteers were dosed once daily for 14 days with zopiclone (7.5 mg/day). The peak plasma zopiclone concentration (65 ng/ml) occurred at 1.4 h after dosing and thereafter declined by a biexponential process, with half-lives of 2.0 and 6.5 h, to 3 ng/ml by 24 h after dosing. Repeated once daily dosing did not markedly alter the peak plasma zopiclone concentration or the pharmacokinetic parameters of absorption or elimination.

Comparison of occult blood loss caused by pirazolac and diclofenac sodium: a double-blind crossover study

A study was carried out in 10 healthy subjects to compare the faecal blood loss caused by pirazolac, a new non-steroidal anti-inflammatory drug, and diclofenac sodium, using chromium51-labelled red blood cells. After 1 week on placebo, subjects received at random either 200 mg pirazolac 3-times daily or 50 mg diclofenac sodium 3-times daily for 7 days. They were then crossed over to the alternative medication for a further 7 days, preceded and followed by 1 week on placebo. Stool samples were collected and bulked for each day and total blood loss over 14 days (7 days on treatment and 7 days immediately after) was calculated for each period. The results showed that both drugs caused a greater blood loss than that measured in the placebo run-in period, and diclofenac sodium caused significantly greater blood loss than did pirazolac. Three subjects reported gastro-intestinal side-effects during diclofenac sodium treatment but there were no reports of any side-effects whilst subjects were receiving pirazolac.

Comparative bioavailability of two furosemide formulations in humans

Twelve healthy male volunteers participated in a balanced crossover comparison of a brand-name and generic furosemide formulations. Each treatment was given as a single 40-mg tablet following an overnight fast. Furosemide concentrations in plasma and urine were determined up to 24 h after treatment; urine output and urinary sodium excretion were also measured. In comparison with the brand-name tablets, generic furosemide was significantly less bioavailable. Using a 95% confidence interval approach, generic furosemide gave up to 66% lower maximum furosemide plasma levels, up to 52% less area under the plasma level curve to infinite time, and up to 37% less urinary recovery of furosemide. Comparison of the effect of the two treatments was a less sensitive measurement of bioequivalence. Confidence intervals for differences in urinary output and sodium excretion over the period of maximum effect (0-4 h) were, however, asymmetrical, and pharmacodynamic differences between treatments were significant at the 10% level.

Trazodone--a new assay procedure and some pharmacokinetic parameters

1 A simple and specific procedure is described for the determination of the new anti-depressant trazodone in human plasma utilising reverse-phase HPLC which is sensitive to 20 ng ml-1. 2 Following oral administration of single 50 mg doses of two formulations of trazodone on separate occasions to healthy fasted volunteers, the peak plasma concentration, time to peak concentration, area under the curve, elimination rate constant and half-life were determined. 3 The two formulations are closely similar and they are considered to have comparable bioavailability.

Gas-liquid chromatography of methylpentynol carbamate and its metabolite 3-methylpentyne-3,4-diol

Procedures are described for the determination of methylpentynol carbamate in serum, either by injection into the chromatograph of diluted serum or extraction of the drug into chloroform and injection of an aliquot of the concentrated organic phase; a 4% CDMS column is used. Similar assays for measuring the metabolite 3-methylpentyne-3,4-diol in urine are reported. The methods have been used for measuring methylpentynol carbamate and its metabolite in samples from rats and dogs.

The kinetics of elimination of salicylic acid and the formation of gentisic acid

1. A method for the estimation of gentisic acid in urine has been devised which is based on thin-layer chromatography and fluorimetry.2. In man the urinary excretion of gentisic acid accounted for 0.6% of a 0.32 g dose of aspirin and 1.1% of a 1.28 g dose. The increase in the percentage of the dose excreted as gentisic acid provides further evidence that the elimination of salicylic acid cannot be entirely described by first order kinetics.3. Equations are presented which describe the amount of gentisic acid formed from various doses of salicylic acid in a model system, when elimination proceeds partly by simultaneous first order and zero order kinetics. The close agreement of the experimental and theoretical results indicates that the model provides an acceptable interpretation of salicylic acid elimination in man.