Giants among Cnidaria: Large Nuclear Genomes and Rearranged Mitochondrial Genomes in Siphonophores

Siphonophores (Cnidaria: Hydrozoa) are abundant predators found throughout the ocean and are important constituents of the global zooplankton community. They range in length from a few centimeters to tens of meters. They are gelatinous, fragile, and difficult to collect, so many aspects of the biology of these roughly 200 species remain poorly understood. To survey siphonophore genome diversity, we performed Illumina sequencing of 32 species sampled broadly across the phylogeny. Sequencing depth was sufficient to estimate nuclear genome size from k-mer spectra in six specimens, ranging from 0.7 to 2.3 Gb, with heterozygosity estimates between 0.69% and 2.32%. Incremental k-mer counting indicates k-mer peaks can be absent with nearly 20× read coverage, suggesting minimum genome sizes range from 1.4 to 5.6 Gb in the 25 samples without peaks in the k-mer spectra. This work confirms most siphonophore nuclear genomes are large relative to the genomes of other cnidarians, but also identifies several with reduced size that are tractable targets for future siphonophore nuclear genome assembly projects. We also assembled complete mitochondrial genomes for 33 specimens from these new data, indicating a conserved gene order shared among nonsiphonophore hydrozoans, Cystonectae, and some Physonectae, revealing the ancestral mitochondrial gene order of siphonophores. Our results also suggest extensive rearrangement of mitochondrial genomes within other Physonectae and in Calycophorae. Though siphonophores comprise a small fraction of cnidarian species, this survey greatly expands our understanding of cnidarian genome diversity. This study further illustrates both the importance of deep phylogenetic sampling and the utility of k-mer-based genome skimming in understanding the genomic diversity of a clade.

An Opiliones-specific ultraconserved element probe set with a near-complete family-level phylogeny

Sequence capture of ultraconserved elements (UCEs) has transformed molecular systematics across many taxa, with arachnids being no exception. The probe set available for Arachnida has been repeatedly used across multiple arachnid lineages and taxonomic levels, however more specific probe sets for spiders have demonstrated that more UCEs can be recovered with higher probe specificity. In this study, we develop an Opiliones-specific UCE probe set targeting 1915 UCEs using a combination of probes designed from genomes and transcriptomes, as well as the most useful probes from the Arachnida probe set. We demonstrate the effectiveness of this probe set across Opiliones with the most complete family-level phylogeny made to date, including representatives from 61 of 63 currently described families. We also test UCE recovery from historical specimens with degraded DNA, examine population-level data sets, and assess "backwards compatibility" with samples hybridized with the Arachnida probe set. The resulting phylogenies - which include specimens hybridized using both the Opiliones and Arachnida probe sets, historical specimens, and transcriptomes - are largely congruent with previous multi-locus and phylogenomic analyses. The probe set is also "backwards compatible", increasing the number of loci obtained in samples previously hybridized with the Arachnida probe set, and shows high utility down to shallow population-level divergences. This probe set has the potential to further transform Opiliones molecular systematics, resolving many long-standing taxonomic issues plaguing this lineage.

Rampant loss of universal metazoan genes revealed by a chromosome-level genome assembly of the parasitic Nematomorpha

Parasites may manipulate host behavior to increase the odds of transmission or to reach the proper environment to complete their life cycle.1,2 Members of the phylum Nematomorpha (known as horsehair worms, hairworms, or Gordian worms) are large endoparasites that affect the behavior of their arthropod hosts. In terrestrial hosts, they cause erratic movements toward bodies of water,3,4,5,6 where the adult worm emerges from the host to find mates for reproduction. We present a chromosome-level genome assembly for the freshwater Acutogordius australiensis and a draft assembly for one of the few known marine species, Nectonema munidae. The assemblies span 201 Mbp and 213 Mbp in length (N50: 38 Mbp and 716 Kbp), respectively, and reveal four chromosomes in Acutogordius, which are largely rearranged compared to the inferred ancestral condition in animals. Both nematomorph genomes have a relatively low number of genes (11,114 and 8,717, respectively) and lack a high proportion (∼30%) of universal single-copy metazoan orthologs (BUSCO genes7). We demonstrate that missing genes are not an artifact of the assembly process, with the majority of missing orthologs being shared by the two independent assemblies. Missing BUSCOs are enriched for Gene Ontology (GO) terms associated with the organization of cilia and cell projections in other animals. We show that most cilium-related genes conserved across eukaryotes have been lost in Nematomorpha, providing a molecular basis for the suspected absence of ciliary structures in these animals.

Expanding on our knowledge of ecdysozoan genomes, a contiguous assembly of the meiofaunal priapulan Tubiluchus corallicola

Genomic data for priapulans are limited to a single species, restricting broad comparative analyses, and thorough interrogation of questions spanning phylogenomics, ecdysozoan physiology, and development. To help fill this void, we present here a high-quality priapulan genome for the meiofaunal species Tubiluchus corallicola. Our assembly combines Nanopore and Illumina sequencing technologies, and makes use of a whole genome amplification, to generate enough DNA to sequence this small meiofaunal species. We generated a moderately contiguous assembly (2547 scaffolds), with a high level of completeness (Metazoan BUSCOs n = 954, single copy complete = 89.6%, duplicated = 3.9%, fragmented = 3.5%, missing = 3.0%). We then screened the genome for homologs of the Halloween genes, key genes implicated in the ecdysis (moulting) pathway of arthropods, recovering a putative homolog of shadow. The presence of a shadow orthologue in two priapulan genomes suggests that the Halloween genes may not have evolved in a stepwise manner in Panarthropoda, as previously thought, but may have a deeper origin at the base of Ecdysozoa.

AB1384 CLINICAL SIGNIFICANCE OF DENSE FINE SPECKLED PATTERN ANA

Background

The clinical significance of Dense Fine Speckled (DFS) pattern Anti-nuclear antibodies (ANA) by indirect immunofluorescence method (IIF) is unclear and has been inversely associated with rheumatic disease 12.

Objectives

Our purpose was to determine associations between DFS pattern ANA and the disease categories of inflammatory arthritis, ANA associated rheumatic diseases (AARD), fibromyalgia/chronic pain syndrome/chronic fatigue syndrome and atopic disorder.

Methods

This retrospective study used data from patients tested for ANA by IIF between August 2017 to August 2019 at the University of Minnesota Medical Center. Comparisons between the diagnostic categories listed in objectives were made for patients with negative ANA, positive ANA (any pattern) and DFS pattern. Individual disease diagnoses belonging to the above categories were also analyzed. The inflammatory arthritis category included seropositive rheumatoid arthritis (RA), seronegative RA, RA with unknown serology, ankylosing spondylitis, and psoriatic arthritis. The disease category of AARD included systemic lupus erythematosus (SLE), systemic sclerosis, mixed connective tissue disease, idiopathic inflammatory myopathies, Sjogren’s syndrome (SS), and undifferentiated connective tissue disorder (UCTD). Atopic disorders included atopic dermatitis, allergic rhinitis, urticaria, and asthma. Frequency of Raynaud’s phenomenon (RP) was also calculated.

Results

13,845 patients with an ANA during the study period were identified. 9106 (65.8%) had negative ANA and 4739 (34.2%) had positive ANA by IIF (including all patterns). 640 (4.6%) had ANA positive DFS patterns. Relative risk (RR) was calculated for diagnostic categories and individual diseases. For patients with positive ANA and DFS pattern, the RR for diagnostic codes of inflammatory arthritis categories [1.35 (1.07- 1.71), p=0.02] was higher when compared to the frequency of codes in ANA negative. RR for AARD among patients with DFS pattern was also higher [1.78 (1.44- 2.2), p <0.001]. There was no significant difference in the frequency of diagnostic codes of chronic pain/fibromyalgia/chronic fatigue syndrome [1.02 (0.9- 1.2), p=0.84] atopic disorder [0.68 (0.4- 1.15), p=0.16] for DFS+ compared to the ANA group. The frequency of AARD diagnostic codes was lower for patients with DFS pattern [0.64 (0.52- 0.79), p<0.001] compared to ANA positive patients with all other patterns, consistent with published data. There was no significant difference of frequency of diagnostic codes for the rest of the disease categories when comparison was made between ANA positive DFS pattern and ANA positive with other patterns.

Individual disease diagnostic codes of RA were higher among DFS+ patients when compared to ANA- patients. The frequency of diagnostic codes of SLE, SS, UCTD, fibromyalgia, Raynaud’s phenomenon, and autoimmune thyroid disease was also higher among patients with DFS pattern compared to ANA- patients. The frequency of diagnostic codes of seropositive RA was lower among patients with DFS pattern compared to ANA+ with all other patterns. The frequency of diagnostic codes of SLE, SSc, UCTD, and chronic pain was also lower among DFS+ patients, compared to those with ANA of all other patterns, consistent with prior reports.

Conclusion

The frequency of diagnostic codes of RA, SS and Raynaud’s was higher among DFS pattern ANA compared to ANA negative group but was not significantly different from ANA positive with other patterns. This suggests that the presence of a DFS pattern should not be used to indiscriminately exclude the presence of a rheumatic disease.

References

[1]Mariz HA, Sato EI, Barbosa SH, Rodrigues SH, Dellavance A, Andrade LEC. Pattern on the antinuclear antibody-HEp-2 test is a critical parameter for discriminating antinuclear antibody-positive healthy individuals and patients with autoimmune rheumatic diseases. Arthritis Rheum. 2011;63(1):191-200. doi:10.1002/art.30084

[2]Watanabe A, Kodera M, Sugiura K, et al. Anti-DFS70 Antibodies in 597 Healthy Hospital Workers. ARTHRITIS Rheum. 2004;50(3):892-900. doi:10.1002/art.20096

Disclosure of Interests

None declared

Embryonic muscle splitting patterns reveal homologies of amniote forelimb muscles

Limb muscles are remarkably complex and evolutionarily labile. Although their anatomy is of great interest for studies of the evolution of form and function, their homologies among major amniote clades have remained obscure. Studies of adult musculature are inconclusive owing to the highly derived morphology of modern amniote limbs but correspondences become increasingly evident earlier in ontogeny. We followed the embryonic development of forelimb musculature in representatives of six major amniote clades and found, contrary to current consensus, that these early splitting patterns are highly conserved across Amniota. Muscle mass cleavage patterns and topology are highly conserved in reptiles including birds, irrespective of their skeletal modifications: the avian flight apparatus results from slight early topological modifications that are exaggerated during ontogeny. Therian mammals, while conservative in their cleavage patterns, depart drastically from the ancestral amniote musculoskeletal organization in terms of topology. These topological changes occur through extension, translocation and displacement of muscle groups later in development. Overall, the simplicity underlying the apparent complexity of forelimb muscle development allows us to resolve conflicting hypotheses about homology and to trace the history of each individual forelimb muscle throughout the amniote radiations.

Policy infrastructure and mechanism to Promote “Health by All” Movement for Overturning Obesity

Background

Obesity is a pressing pandemic. However, major policies have targeted individual responsibility and focused on “losing weight or lowering calories”. Such approach has limited effect and overlooks the hidden obesity.

Methods

Under auspices of NHRI Forum, Taiwan; the WAKE.TAIWAN Research Team analyzed the global trends of policies, strategies, and literatures to formulate guiding principles for a total solution. 1. Defining obesity should go beyond body weight and emphasize more on healthy body composition and muscle mass, etc. 2. Effective obesity control strategy should facilitate building healthy living environments, lifestyle, and culture for natural flow of healthy behaviors. 3. All sectorial leaders should be involved in engaging and promoting healthy lifestyle culture and environment.

Results

”Guidelines for Establishing a lifestyle and Culture of Healthy Body Build” has been published as a blueprint for policy reform and strategies development, which consists of three parts. Part I emphasizes the active roles, social responsibilities, influence, and opportunities confronted the leaders and experts in all sectors and how government may facilitate these societal engagements, “Healthy by All”. The crucial sectors should include academia, NGO/NPO, industry/business, workplaces, healthcare systems, educational sectors, media and press, etc. Part II details on community spatial planning and architectural designs for healthy lifestyles. Part III proposes governmental “Health in All” infrastructure and mechanism.

Conclusions

We anticipate that the Guideline may draw out expertise and volunteering in all sectors of the society and help guide the public to take initiative in building such a culture of healthy-body-build and achieving this goal in all aspects of daily life.

Key messages

Emphasize on healthy body composition rather than body weight. Propagate 'Health by all' movement to foster building 'healthy physique' culture.

Determining validity of the PALite and ODFS PACE activity logger for measuring step count in healthy adults

BACKGROUND

Determining adherence with orthoses is important for clinicians prescribing devices. Measuring orthotic use often relies on patient recall which has poor agreement with objective measures. Measuring step count whilst wearing an orthosis could help objectively quantifying adherence. The Odstock Drop Foot Stimulator (ODFS) Pace, used in foot drop, has an integral activity logger which provides data on step count. The PALite, an accelerometer, measures step count and can be fixed to an ankle foot orthoses (AFO). Both have the potential to provide objective measures of adherence; however, their validity for this purpose has not been determined.

RESEARCH QUESTION

To determine the validity of the PALite and ODFS Pace activity logger in measuring total step count, by exploring their level of agreement.

METHODS

A convenience sample of sixteen healthy volunteers, aged 18-65, were recruited from Glasgow Caledonian University (GCU). Participants walked continuously for 5 min on a treadmill at three walking speeds; normal (1.3ms^-1), slow (0.4 ms^-1) and fast (1.7-2.0 ms^-1), wearing both the PALite and ODFS Pace. All walks were video recorded, viewed by 2 raters, and observed step count was determined by a click counter. Step count from both devices was validated against observed step count using video recording. The level of agreement between the three methods was established.

RESULTS

There was no significant difference between the 3 methods of measuring step count at any walking speed (normal, p = 0.913; slow, p = 0.938; fast, p = 0.566). Good levels of agreement for both devices with observed step count at all 3 walking speeds, with mean percentage differences being between -1.2 and 2.1 % (maximum upper and lower levels of agreement = 19.5 and -18.8 %) was detected.

SIGNIFICANCE

Clinicians could consider both devices to objectively measure step count with people who are prescribed foot drop orthoses, thus quantifying orthotic use.

Variation in landmarks for the rectum: an MRI study

AIM

This study aimed to assess the reliability of measurements and bony landmarks for the rectosigmoid junction on MRI.

METHOD

The staging MRI scans for 100 patients were reviewed. The junction of the mesorectum and mesocolon was used to identify the rectum and sigmoid. The performance of current metric measurements or bony landmarks was then compared against the actual anatomical bowel segment.

RESULTS

The mean distance of the sigmoid take-off from the anal verge was 12.6 cm (SD 1.8 cm, range 9.4-19.0 cm). At a cutoff of 12 cm, the anatomical bowel segment was found to be sigmoid colon rather than rectum in 35% of patients. At 15 and 16 cm the bowel segment was sigmoid in 84% and 96% of patients, respectively. At the sacral promontory and the third sacral segment, the bowel segment was sigmoid in 28% and 100% of patients, respectively.

CONCLUSION

Current definitions of the rectum that rely on arbitrary measurements or bony landmarks will not locate the correct point of transition between the rectum and sigmoid in the majority of patients. The sigmoid take-off offers an alternative, anatomically bespoke, landmark.

Structural dysconnectivity of key cognitive and emotional hubs in young people at high genetic risk for bipolar disorder

Emerging evidence suggests that psychiatric disorders are associated with disturbances in structural brain networks. Little is known, however, about brain networks in those at high risk (HR) of bipolar disorder (BD), with such disturbances carrying substantial predictive and etiological value. Whole-brain tractography was performed on diffusion-weighted images acquired from 84 unaffected HR individuals with at least one first-degree relative with BD, 38 young patients with BD and 96 matched controls (CNs) with no family history of mental illness. We studied structural connectivity differences between these groups, with a focus on highly connected hubs and networks involving emotional centres. HR participants showed lower structural connectivity in two lateralised sub-networks centred on bilateral inferior frontal gyri and left insular cortex, as well as increased connectivity in a right lateralised limbic sub-network compared with CN subjects. BD was associated with weaker connectivity in a small right-sided sub-network involving connections between fronto-temporal and temporal areas. Although these sub-networks preferentially involved structural hubs, the integrity of the highly connected structural backbone was preserved in both groups. Weaker structural brain networks involving key emotional centres occur in young people at genetic risk of BD and those with established BD. In contrast to other psychiatric disorders such as schizophrenia, the structural core of the brain remains intact, despite the local involvement of network hubs. These results add to our understanding of the neurobiological correlates of BD and provide predictions for outcomes in young people at high genetic risk for BD.

Ultra-low anterior resection with coloanal anastomosis for recurrent rectal prolapse in a young woman with colitis cystica profunda

This case demonstrates the successful treatment of a young female patient with colitis cystica profunda causing rectal prolapse, after primary treatment with a Delorme procedure had failed. An ultra-low anterior resection with a temporary defunctioning ileostomy was carried out with good postoperative results. This case illustrates the possibility of carrying out sphincter preserving surgery rather than an abdominoperineal resection in the treatment of this condition, which may be preferable for patients.

Gridless optical networking field trial: flexible spectrum switching, defragmentation and transport of 10G/40G/100G/555G over 620-km field fiber

We present results from the first gridless networking field trial with flexible spectrum switching nodes and 620 km of installed fibre links. Signals at 10G, 12.25G, 42.7G, DP-QPSK 40G, DP-QPSK 100G and 555G are generated, successfully transported and switched using flexible, custom spectrum allocation per channel. Spectrum defragmentation is demonstrated using integrated SOA-MZI wavelength converters. Results show error-free end-to-end performance (BER<1e-9) for the OOK channels and good pre-FEC BER performance with sufficient margin to FEC limit for the 40G and 100G coherent channels as well as for the 555G super-channel.

Experimental demonstration of gridless spectrum and time optical switching

An experimental demonstration of gridless spectrum and time switching is presented. We propose and demonstrate a bit-rate and modulation-format independent optical cross-connect architecture, based on gridless spectrum selective switch, 20-ms 3D-MEMS and 10-ns PLZT optical switches, that supports arbitrary spectrum allocation and transparent time multiplexing. The architecture is implemented in a four-node field-fiber-linked testbed to transport continuous RZ and NRZ data channels at 12.5, 42.7 and 170.8 Gb/s, and selectively groom sub-wavelength RZ channels at 42.7 Gb/s. We also showed that the architecture is dynamic and can be reconfigured to meet the routing requirements of the network traffic. Results show error-free operation with an end-to-end power penalty between 0.8 dB and 5 dB for all continuous and sub-wavelength channels.

The value of asthma camps for young people in Victoria, Australia

PURPOSE

This paper investigates the impact of the Asthma Foundation of Victoria's educational camp program on children's knowledge of asthma and its management, their feelings about asthma, and their attitudes toward physical and social activities. Parents' observations of changes in their child's behaviour and attitudes are also reported.

DESIGN AND METHODS

This research was descriptive and applied. It used questionnaires atfour stages (directly pre- and post-camp, three-four months and ten-15 months post-camp) of an asthma education camp program to assess child asthma knowledge levels. At three months post-camp, parental observations of children's attitudes and behaviours were assessed using a questionnaire. Children's feelings toward asthma were also assessed using a questionnaire pre- and post-camp.

RESULTS

The children surveyed displayed a better knowledge of asthma and how to manage their condition immediately after the camp. This knowledge tended to return to pre-camp levels after ten months. The children also reported less anxiety and fear about their illness, a greater sense of wellbeing, and more confidence in participating in a whole range of physical and social activities. Many parents also noted positive changes in their children in terms of activities and asthma management at three months post-camp.

CLINICAL IMPLICATIONS

Although there were limitations to sustaining knowledge gained in the asthma camping program, the camping experience provided a benefit for children in terms of promoting their mental and social wellbeing. When readers consider modernising asthma education (e.g. shorter camps, education in everyday social settings such as schools), they need to consider retaining the key ingredients of the more traditional camping program that supports good asthma management, wellbeing and social participation.

Impaired humoral responses to subgenus D adenovirusenovirus infections in HIV-positive patients

HIV-positive patients are at increased risk of developing adenovirus infection, particularly of the gastrointestinal tract and with unusual subgenus D strains. To investigate humoral immunity to these strains of adenoviruses, the humoral immune response was examined in longitudinal samples of serum against isolates collected from a prospective study of HIV-positive patients with subgenus D adenovirus infection. Of 10 HIV-positive patients developing adenovirus infection, 3 had chronic infection (8->27 months) with one serotype, 3 had chronic infection (>/=10 months) with changing serotypes and 4 had acute and self-limiting adenovirus infection (<1 month). Fifty-one sera were tested, and samples collected before adenovirus infection were available in 8 patients. Neutralising assays were performed against the patient's own isolate (adenoviruses 9, 17, 19, 19/23, 19/37, 23, 26, 23/26, 43 and 46) and common circulating strains of adenovirus 1-5. Indirect immunofluorescence tests were carried out against the autologous isolate and complement-fixation tests were undertaken using a standard assay. Immunofluorescence test antibodies were detected (titre >/=160) in all patients, and present to high titre (>/=320) in 8/10 patients. Complement-fixing antibodies were not detected in significant titre. Of particular note, there was no significant neutralising antibody response to the patient's own isolate after acute infection. Neutralising antibody to adenovirus 3 (titre 20) was transiently detected in two patients. In the remaining patients neutralising antibody directed against adenoviruses 1-5 was not detected. Persistent carriage of subgenus D adenoviruses in HIV-positive patients is probably the result of failure of cell-mediated immune responses to clear primary infection. Nevertheless, there is marked impairment of B cell responses resulting in poor neutralising and complement-fixing antibody production even though immunofluorescence test determined antibodies are produced in high titre. These possibly reflect impairment of effective B cell priming mechanisms within the germinal centres of lymph nodes, or the polyclonal activation of B cells driven by HIV infection.

Cloning and analysis of the glucosyl transferase gene encoding type I antigen in Shigella flexneri

The O-antigen of most Shigella flexneri serotypes contains an identical tetrasaccharide repeating unit. Apart from serotype Y, the O-antigen is modified by addition of a glucosyl and/or O-acetyl residue to a specific position in the O-unit. In this study the glucosyl transferase gene from a serotype 1 a has been cloned and identified. The bacteriophage SfV integrase (int) gene was used to probe a S. flexneri Y53 (serotype 1 a) cosmid library and 18 unique clones were identified. Southern hybridisation of these clones indicated two unlinked regions of the chromosome contained the int homologue. When expressed in a live candidate vaccine strain of S. flexneri serotype Y (SFL124), clones with one region produced type I antigen, whereas clones containing the other region produced mainly type Y antigen. One of the cosmid clones positive for type I antigen by agglutination and Western blotting was selected for further study. Genes involved in O-antigen glucosyl modification were mapped on a 5.8 kb fragment and subclones were produced which fully or partially expressed the type I antigen, depending on the extent of the clone. Fully and partially expressing clones may be useful vaccine candidate strains for protection against disease caused by two serotypes of S. flexneri.

Pharmacology of montelukast sodium (Singulair), a potent and selective leukotriene D4 receptor antagonist

Montelukast sodium (Singulair), also known as MK-0476 (1-(((1(R)-(3-(2-(7-chloro-2-quinolinyl)-(E)-ethenyl)phenyl)(3-2-(1- hydroxy-1-methylethyl)phenyl)propyl)thio)methyl)cyclopropane) acetic acid sodium salt, is a potent and selective inhibitor of [3H]leukotriene D4 specific binding in guinea pig lung (Ki 0.18 +/- 0.03 nM), sheep lung (Ki 4 nM), and dimethylsulfoxide-differentiated U937 cell plasma membrane preparations (Ki 0.52 +/- 0.23 nM), but it was essentially inactive versus [3H]leukotriene C4 specific binding in dimethylsulfoxide-differentiated U937 cell membranes (IC50 10 microM) and [3H]leukotriene B4 specific binding in THP-1 cell membranes (IC50 40 microM). Montelukast also inhibited specific binding of [3H]leukotriene D4 to guinea pig lung in the presence of human serum albumin, human plasma, and squirrel monkey plasma with Ki values of 0.21 +/- 0.08, 0.19 +/- 0.02, and 0.26 +/- 0.02 nM, respectively. Functionally, montelukast antagonized contractions of guinea pig trachea induced by leukotriene D4 (pA2 value 9.3; slope 0.8). In contrast, montelukast (16 microM) failed to antagonize contractions of guinea pig trachea induced by leukotriene C4 (45 mM serine-borate), serotonin, acetylcholine, histamine, prostaglandin D2, or U-44069. Intravenous montelukast antagonized bronchoconstriction induced in anesthetized guinea pigs by i.v. leukotriene D4 but did not block bronchoconstriction to arachidonic acid, histamine, serotonin, or acetylcholine. Oral administration of montelukast blocked leukotriene D4 induced bronchoconstriction in conscious squirrel monkeys, ovalbumin-induced bronchoconstriction in conscious sensitized rats (ED50 0.03 +/- 0.001 mg/kg; 4 h pretreatment), and also ascaris-induced early and late phase bronchoconstriction in conscious squirrel monkeys (0.03-0.1 mg/kg; 4 h pretreatment). A continuous i.v. infusion of montelukast (8 micrograms.kg-1.min-1) resulted in a 70% decrease in the peak early response and a 75% reduction of the late response to ascaris aerosol in allergic conscious sheep. Montelukast, a potent and selective leukotriene D4 receptor antagonist with excellent in vivo activity is currently in clinical development for the treatment of asthma and related diseases.

Characterization of specific binding sites for cysteinyl leukotrienes in sheep lung

Specific binding sites for [3H]leukotriene (LT)D4 and [3H]LTC4 have been identified in sheep lung parenchymal membranes. [3H] LTD4 specific binding was of high affinity (KD = 0.56 nM), saturable (Bmax = 43 fmol/mg of protein), stimulated by divalent cations and inhibited by nonhydrolyzable GTP analogs. LTs and LTD4-receptor antagonists competed for [3H]LTD4 specific binding with the rank order of potency predicted for the LTD4 receptor: LTD4 > ONO-1078 > ICI 204,219 > MK-571 > LTE4 > LTC4 > BAY u9773 >> LTB4. In contrast, [3H]LTC4 specific binding was of lower affinity (KD = 27 nM), abundant (Bmax = 87 pmol/mg of protein) and although stimulated by divalent cations was unaffected by GTP analogs. LTs and LTC4 analogs competed for [3H]LTC4 specific binding with the following rank order of potency: LTC2 > LTC3 > LTC4 > LTC5 >> N-methyl-LTC4 >> LTD4 approximately LTB4 approximately LTB4. [3H]LTD4 specific binding to sheep lung membranes has, therefore, the characteristics of being to a G-protein-coupled LTD4 receptor, whereas the profile of [3H]LTC4 specific binding strongly suggests that these sites are not LT-receptor related. Photolabeling of sheep lung membranes using [125I]azido-LTC4, a photoactivable LTC4 analog, resulted in the selective photolabeling of two polypeptides migrating at 30 kDa and 19 kDa. The selective photolabeling of the 19 kDa polypeptide could be modulated in an identical manner to [3H]LTC4 specific binding. This protein is, therefore, a candidate for being the principal [3H]LTC4 specific site in sheep lung membranes and has a comparable molecular mass to microsomal glutathione S-transferase, recently shown to be the predominant LTC4 binding protein in cellular membranes.

Detrusor hyperreflexia--are there two types?

The concept that elderly patients with urinary incontinence due to detrusor hyperreflexia can be divided into two groups with differing natural histories on the basis of the detrusor contractility found on cystometry is reassessed. Thirty patients shown to have hyperreflexia on urodynamic study for persistent urinary incontinence following a recent neurological lesion had their contractility measured by the suggested criteria of the residual urine following a hyperreflexic contraction and the rate of increase of detrusor pressure. The consistency of contractility on cystometry was also measured by repeating this three times on the same occasion. A spectrum of values for the post-contraction volumes and the rate of increase of detrusor pressure was found. On repetitive cystometry 11 out of 30 patients showed a variable post-contraction residual volume. While impaired contractility is common in detrusor hyperreflexia, the concept of two subgroups is not supported by these results. In some patients cystometric measures of contractility vary considerably on repeating the study on the same occasion.

The reflush effect--a prospective analysis of late perfusion

This prospective randomized trial examines the effect of a "reflush" with preservation solution immediately prior to renal allograft implantation, using hyperosmolar citrate (HOC, n = 10) or phosphate-buffered sucrose (PBS140, n = 10) versus no reflush (n = 10). All kidneys had been stored in HOC. The HOC reflush did not alter the postpreservation intra- or extracellular electrolyte milieu, whereas the PBS140 reflush resulted in an apparent overall loss of both sodium and potassium from the kidney (P < 0.0005). A small amount of calcium was released into the venous effluent in both reflush groups. A similar amount of lactic acid was released into the venous effluent of the two reflush groups, reflected by a lower pH (P < 0.0005), and there was a similar loss of lactate dehydrogenase and creatine phosphokinase. An analysis of procoagulant activity in the first urine produced was performed as a marker of reperfusion injury. The median value was higher in the No Reflush group at 457.5 units, compared with 263.0 and 209.0 units for the PBS140 and HOC Reflush groups, respectively (P = 0.06). Reflushing the kidneys reduced the postoperative dialysis requirement (from 40% to 15%), but by the end of the first posttransplant week there was no significant difference between the renal functional analyses of the three groups, and there was no difference at one year. The proposed mechanism for the early renal functional improvement is a reduction in the calcium paradox and free radical formation, by release of calcium and ATP breakdown products into the venous effluent prior to implantation.

Energy balance in healthy elderly women

There is a paucity of data on which to base estimates of the energy requirements of the elderly. In general, ageing appears to be associated with a reduction in energy requirement arising from a reduction in physical activity and loss of fat-free mass. The aim of the present study was to measure the total energy expenditure (TEE), basal metabolic rate (BMR), and energy expended on physical activity (calculated as TEE-BMR) in a group of healthy elderly women living in the community in Southampton. Mean rates of TEE (9.21 (SD 1.48) MJ/d) and energy expended on physical activity (4.12 (SD 1.19) MJ/d) were higher than those observed in some studies of younger adults in the UK, and higher than the factors used to estimate the average energy requirement for the elderly. The results suggest that an age-related reduction in energy requirement is not inevitable and support the hypothesis that the effects of ageing on physical activity, body composition, and hence energy requirements, are variable.

Pharmacology of the leukotriene antagonist verlukast: the (R)-enantiomer of MK-571

Verlukast (MK-679) (3-[(3-(2-(7-chloro-2-quinolinyl)-(E)-ethenyl)phenyl)[3-(dimethylamino)- 3- oxopropyl)thio)methyl)-thio)propionic acid) is a potent and selective inhibitor of [3H]leukotriene D4 binding in guinea-pig (IC50 = 3.1 +/- 0.5 nM) and human (IC50 = 8.0 +/- 3.0 nM) lung homogenates and dimethyl sulfoxide differentiated U937 cell membrane preparations (IC50 = 10.7 +/- 1.6 nM) but is essentially inactive versus [3H]leukotriene C4 binding in guinea-pig lung homogenates (IC50 values of 19 and 33 microM). Functionally, when tested at 60 nM, it antagonized contractions of guinea-pig trachea (GPT) induced by leukotriene C4, leukotriene D4, and leukotriene E4 (respective-log KB values of 8.6, 8.8, and 8.9) and contractions of human trachea (HT) induced by leukotriene D4 (-log KB value 8.3 +/- 0.2). In contrast, verlukast (20-200 nM) failed to antagonize contractions of GPT induced by leukotriene C4 in the presence of 45 mM L-serine borate. Intravenous (i.v.) and aerosol verlukast antagonized bronchoconstriction (BC) induced in anaesthetized guinea pigs by i.v. leukotriene D4 but did not block BC to arachidonic acid or histamine. Intraduodenal verlukast (0.25 mg/kg) antagonized leukotriene D4 (0.2 micrograms/kg) induced BC in guinea pigs. Oral and aerosol administration blocked leukotriene D4-induced BC in conscious squirrel monkeys. Orally administered compound also blocked ovalbumin-induced BC in conscious sensitized rats treated with methysergide (3 micrograms/kg). The pharmacological profile for verlukast is similar to that of the racemic compound, MK-571. Verlukast is currently in clinical development for the treatment of asthma and related diseases.

Stereospecific synthesis, assignment of absolute configuration, and biological activity of the enantiomers of 3-[[[3-[2-(7-chloroquinolin-2-yl)-(E)-ethenyl]phenyl] [[3-(dimethylamino)-3-oxopropyl]thio]methyl]thio]propionic acid, a potent and specific leukotriene D4 receptor antagonist

The enantiomers of the leukotriene D4 antagonist 3-[[[3-[2-(7-chloroquinolin-2-yl)-(E)-ethenyl]phenyl] [[3-(dimethylamino)-3-oxopropyl]thio]methyl]thio]propionic acid (L-660,711)(MK-571) have been prepared, their absolute stereochemistry has been assigned as S for (+)-1 and R for (-)-1 by X-ray analysis of a synthetic intermediate (5), and the biological activity of the enantiomers has been explored. Unexpectedly, the enantiomers are both comparably biologically active with (+)-1 slightly more intrinsically active at the LTD4 receptor in vitro.

The pharmacology of L-670,596, a potent and selective thromboxane/prostaglandin endoperoxide receptor antagonist

L-670,596 ((-)6,8-difluoro-9-rho-methylsulfonyl benzyl-1,2,3,4- tetrahydrocarbazol-1-yl-acetic acid) has been shown to be a potent receptor antagonist as evidenced by the inhibition of the binding of 125I-labeled PTA-OH to human platelets (IC50, 5.5 x 10(-9) M), inhibition of U-44069 induced aggregation of human platelet rich plasma (IC50, 1.1 x 10(-7) M), and competitive inhibition of contractions of the guinea pig tracheal chain induced by U-44069 (pA2,9.0). The compound was also active in vivo as shown by inhibition of arachidonic acid and U-44069 induced bronchoconstriction in the guinea pig (ED50 values, 0.04 and 0.03 mg/kg i.v., respectively), U44069 induced renal vasoconstriction in the pig (ED50, 0.02 mg/kg i.v.), and inhibition of ex vivo aggregation of rhesus monkey platelets to U-44069 (active 1-5 mg/kg p.o.). The selectivity of the compound was indicated by the failure to inhibit, first, ADP-induced human or primate platelet aggregation and, second, bronchoconstriction in the guinea pig in vivo and contraction of the guinea pig tracheal chain in vitro to a variety of agonists. It is concluded that L-670,596 is a potent, selective, orally active thromboxane A2/prostaglandin endoperoxide receptor antagonist.

Fractional conversion of thromboxane A2 and B2 to urinary 2,3-dinor-thromboxane B2 and 11-dehydrothromboxane B2 in the cynomolgus monkey

Following the intravenous administration of thromboxane (TX) B2, the stable hydration product of TXA2, to human and nonhuman primates the most abundant urinary metabolites are 2,3-dinor-TXB2 and 11-dehydro-TXB2. However, it is not known whether fractional conversion of TXB2 to its enzymatic metabolites is an accurate representation of TXA2 metabolism. Thus, we have compared the metabolic disposition of synthetic TXA2 and TXB2 via the beta-oxidation and 11-OH-dehydrogenase pathways in vivo in the monkey. TXA2 or TXB2 (20 ng/kg) was intravenously administered to four cynomolgus monkeys pretreated with aspirin in order to suppress endogenous TXA2 production. Urinary TXB2, 2,3-dinor-TXB2 and 11-dehydro-TXB2 were measured before, during and up to 24 h after thromboxane administration by means of reversed-phase high-performance liquid chromatography radioimmunoassay. Aspirin treatment suppressed urinary 2,3-dinor-TXB2 and 11-dehydro-TXB2 by approx. 75%. A similar fractional conversion of TXA2 and TXB2 into 2,3-dinor-TXB2 and 11-dehydro-TXB2 was found. These results suggest that TXA2 is hydrolyzed to TXB2 prior to enzymatic degradation and that metabolites of the latter represent reliable indices of TXA2 biosynthesis. Due to the variability in the conversion of thromboxanes into 2,3-dinor-TXB2 and 11-dehydro-TXB2, the measurement of both metabolites seems to represent a more reliable index of acute changes in TXA2 production.

The affinities of prostaglandin H2 and thromboxane A2 for their receptor are similar in washed human platelets

Both thromboxane A2 (TXA2) and its precursor prostaglandin H2 (PGH2) are labile and share a common receptor. The affinities of these two compounds for their putative common receptor are unknown. We compared the potencies of TXA2 and PGH2 to aggregate human platelets and bind to the TXA2/PGH2 receptor. TXA2 was more potent than PGH2 in initiating aggregation in platelet-rich plasma, EC50 of 66 +/- 15 nM and 2.5 +/- 1.3 microM, respectively. In washed platelets, however, PGH2 was more potent than TXA2 with EC50 values of 45 +/- 2 nM and 163 +/- 21 nM, respectively. The affinity of these two compounds in washed platelets was determined in radioligand competition binding assays employing [125I]-PTA-OH. The Kd values for PGH2 and TXA2 were 43 nM and 125 nM, respectively. The results demonstrate that the affinity of PGH2 for the platelet TXA2/PGH2 receptor is greater than previously thought. The data raise the possibility that PGH2 may significantly contribute to the responses attributed to TXA2 in vivo.

L-641,953 (R-8-fluoro-dibenzo[b, f]thiepin-3-carboxylic acid-5-oxide): a novel thromboxane-prostaglandin endoperoxide antagonist

The effects of L-641,953 (R-8-fluoro-dibenzo[b, f]thiepin-3-carboxylic acid-5-oxide) have been studied on pulmonary and other smooth muscle preparations in vitro and in vivo. When studied in vitro on guinea-pig tracheal chains, L-641,933 produced significant shifts in the dose-response curves to the prostaglandin endoperoxide analogues, U-44069 (pA2 7.06) and U-46619 (pA2 7.14), and prostaglandin (PG) F2 alpha (pA2 6.33) had minimal activity against contractions induced by histamine (pA2 4.38), 5-hydroxytryptamine (pA2 4.63), and acetylcholine (pA2 4.56) and slightly enhanced relaxation induced by PGE2. When tested on the guinea-pig gall bladder strip in vitro, L-641,953 antagonized contractions induced by U-44069 (pA2 7.03) but was less active against those induced by PGF2 alpha (pA2 6.03), PGE1 (pA2 5.62), and histamine (pA2 4.84). When tested in vitro on the guinea-pig pulmonary artery, L-651-953 significantly antagonized contractions induced by U-44069 (pA2 7.04), U-46619 (pA2 7.14), and PGF2 alpha (pA2 7.16) but was less effective against contractions induced by histamine (pA2 4.19). Schild analysis indicated that L-641,953 was fully competitive against contractions of either the guinea-pig tracheal chain induced by U-46619 or the guinea-pig pulmonary artery induced by U-44069 and U-46619. When tested on human platelets in vitro L-641,953 inhibited aggregation induced by U-44069 (IC50 1.3 X 10(-6) M) but not ADP.(ABSTRACT TRUNCATED AT 250 WORDS)

Poly(ADP-ribosyl)ation of chromatin: kinetics of relaxation and its effect on chromatin solubility

We have studied the kinetics of relaxation of poly(ADP-ribosyl)ated polynucleosomes produced by endogenous enzyme activity by comparing the generation of hyper(ADP-ribosyl)ated histone H1 and its effect on the chromatin structure as revealed by electron microscopy. A correlation can be established between the appearance of histone H1 modified forms and the localized relaxation of the chromatin. We have also noticed, in parallel, that poly(ADP-ribosyl)ated chromatin showed increased solubility in the presence of Mg2+ and 0.2 M NaCl. Electron microscopic examination of the solubilized chromatin produced by poly(ADP-ribosyl)ation shows polynucleosomes exhibiting more relaxed conformation, whereas an increasing amount of hyper(ADP-ribosyl)ated histone H1 is found in the pellet, as shown by acid-urea-polyacrylamide electrophoretic separation of histone extracts.

beta-NADPHase- and TMPase-positive "snake-like tubules" in the exocrine pancreas: cytochemical and immunocytochemical studies

Using five different protocols, two enzymes, nicotinamide adenine dinucleotide phosphate phosphohydrolase (beta-NADPHase) and sodium trimetaphosphatase (TMPase), were localized in the acinar cell of rat pancreas by ultrastructural cytochemistry. The beta-NADPHase cytochemical localization was realized at pH 4.8 and pH 3.9. At pH 4.8, the beta-NADPHase activity was found in the Golgi intermediate saccules, lysosomes, gland lumen, and tubular structures, described as snake-like tubules (Beaudoin AR, Grondin G, Lord A: Eur J Cell Biol 33:275, 1984; Beaudoin AR, Grondin G, Lord A, Pelletier M: In Proc 42nd Ann Meeting Electron Microscopy Soc Am. San Francisco Press, CA, 1984). There was no detectable beta-NADPHase activity at pH 3.9. The TMPase cytochemistry was done at pH 3.9 according to Oliver (J Histochem Cytochem 28:78, 1980) and at pH 3.9 and 4.8 with the medium described by Berg (J Histochem Cytochem 8:92, 1960). TMPase localization varied according to the protocols. It was found in tubular structures described as "basal lysosomes," lysosomes, and zymogen granules, whereas Golgi saccules were generally negative. Our observations showed that the structures identified as "basal elongated lysosomes" and revealed by TMPase (Oliver C: J Histochem Cytochem 28:78, 1980; J Histochem Cytochem 31:1209, 1983) were morphologically similar to snake-like tubules (SLT) revealed by beta-NADPHase. Relationships between SLT and mitochondria as well as lysosomes and plasma membranes were observed. Using amylase-specific antibodies, it was also shown, by the protein A-gold immunocytochemical technique, that SLT do not contain amylase and, in fasting conditions, would not be involved in the transport of secretory proteins.

Leukotriene F4 and the release of arachidonic acid metabolites from perfused guinea pig lungs in vitro

Radioimmunoassay and bioassay techniques have been used to investigate the ability of leukotriene (LT)F4 to release products of arachidonic acid metabolism from guinea pig isolated lungs perfused via the pulmonary artery. Also, the abilities of LTC4, LTD4, LTE4 and LTF4 to contract guinea pig ileal smooth muscle (GPISM) was studied. Each of the LT's contracted GPISM. The rank order of potency was LTD4 greater than LTC4 greater than LTE4 much greater than LTF4 in a ratio of 1:7:170:280 respectively. Bioassay of pulmonary effluents indicated the passage of LTF4 through the lungs caused a contraction of rabbit aorta as well as an FPL-55712 sensitive contraction of GPISM. The contractions of rabbit aorta were inhibited by pretreatment of the lungs with Indomethacin but not with the thromboxane synthetase inhibitor Dazoxiben. Radioimmunoassay of the lung effluents indicated LTF4 to cause a 70-fold increase in thromboxane B2 (TXB2), 4-fold increase in prostaglandin (PG)E2 and a 16-fold increase in 6-keto PGF1 alpha levels. The LTF4-induced increments of these immunoreactive metabolites was inhibited by pretreatment of the lungs with Indomethacin. Pretreatment of lungs with Dazoxiben inhibited the LTF4-induced increment in TXB2 and enhanced the effluent levels of PGE2 24-fold (compared with untreated lungs). There were no detectable differences in either immunoreactive LTC4 or immunoreactive LTB4 levels. It is concluded LTF4 is a relatively weak agonist on GPISM and can induce the release of cyclooxygenase products of arachidonic acid metabolism from guinea pig perfused lung.

Electrophoretic and cytological evidence for heterogeneity of pancreatic acinar cell responsiveness to carbachol, caerulein and secretin

Incubation of rat pancreatic lobules for 90 min with optimal concentrations of caerulein, carbachol or secretin caused the release of about 30% of the amylase content. Combination of secretin with carbachol or caerulein increased the amylase output to about 40%. With secretin, as with carbachol or caerulein, heterogeneity of cellular responsiveness was observed, some acini being partially or completely depleted of their zymogen granules, whereas others appeared to be resting. When secretin was combined with carbachol or caerulein, granule depletion, originally confined to small groups of neighbouring acini, spread to form large areas of degranulated cells, sometimes comprising a whole section of a lobule. In dispersed acini, under the same conditions, carbachol caused the release of about 60% of the amylase content, and secretin 40%. When both secretagogues were combined, a significant increase to 78% was observed. Under these conditions, there was some important cellular damage, as indicated by the release of 20% of the amylase content and between 6 and 12% of lactate dehydrogenase into the media, in the absence of stimulus. These results were corroborated by cytological observations. On the basis of their secretory response two groups of acini can be distinguished, those that respond to carbachol, caerulein or secretin and those that respond to the combination of secretin with carbachol or caerulein. Electrophoretic patterns of secretory proteins released by lobules stimulated by these different types of secretagogues were essentially similar. The pattern was quite different, however, in the absence of a stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)

Secretagogues cause a preferential discharge of large size granules in rat pancreas

We have compared the diameters of zymogen granules in the exocrine pancreas of fasted or stimulated rats. The average granule diameter was 0.73 microns +/- 0.18 SD (sample size, 1460) in fasted animals and significantly reduced to 0.68 microns +/- 0.17 SD (sample size, 860) after 120 min and two intraperitoneal injections of urecholine. Reduction of granule size was attributable to the preferential discharge of large size granules. The range between first and third quartiles of the distribution curve was identical in the two groups at 0.24 microns. There was no significant increase in the proportion of granules smaller than 0.40 microns after urecholine stimulation. A third group of animals was "hyperstimulated" by an infusion of a mixture of caerulein, secretin, and urecholine. After 210 min, the average granule diameter was reduced to 0.43 microns +/- 0.14 SD (sample size, 786). The range between first and third quartiles of the distribution curve was 0.16 microns. In this group, 43.5% of the granules was smaller than 0.40 microns. Granule size reduction was accompanied by the appearance of numerous pleiomorphic condensing vacuoles. The present results strongly support the views that secretagogues cause the preferential release of large size granules and favor the formation of small size granules.

Bronchoconstriction induced by N-formyl-methionyl-leucyl-phenylalanine in the guinea pig; involvement of arachidonic acid metabolites

The chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (F-met-leu-phe) was shown to be a potent myotropic agent on the guinea-pig parenchymal strip (IC50, 2 X 10(-7)M). The response was unaffected by the histamine (H1) antagonist, mepyramine, but in the presence of the cyclooxygenase inhibitor, indomethacin, the dose response curve was shifted to the left (IC50, 4 X 10(-8)M) and the maximal response reduced. Injection of F-met-leu-phe into perfused guinea pig lungs resulted in the release of leukotriene-like activity which was detected by superfusion over guinea-pig ileum preparations in the presence and absence of FPL-55712. Intravenous injection of F-met-leu-phe to spontaneously breathing anaesthetized guinea pigs resulted in transient increases in pulmonary resistance and blood pressure and decreases in dynamic compliance and heart rate. The pulmonary parameters were significantly inhibited by BW 755C, indomethacin, FPL-55712 and a contractile prostanoid antagonist, L-640,035. These results demonstrate that F-met-leu-phe is a potent bronchoconstrictor in the guinea pig and that the peptide may induce these changes through the generation of products of the cyclooxygenase and lipoxygenase pathways of arachidonic acid metabolism.

Cytological effects of ionophore-induced stimulation on the exocrine pancreas of the rat

Rat-pancreas lobules were incubated with the ionophore A-23187 in the presence of Ca2+. After 90 min, some of the acini were partially or almost completely depleted of their zymogen granules while others had the appearance of resting acini. With few exceptions, the cells of a given acinus were degranulated to a comparable level. Slight dispersion of the zymogen granules was noticed in cells incubated in a Ca2+-free medium containing EGTA with or without A-23187. In the presence of Ca2+ the secretory response obtained with the ionophore was comparable to that observed with 10(-5)M urecholine. The results obtained provide cytological evidence that the secretory response is only partially determined at the membrane-receptor level and that other mechanisms intervene between cytosol Ca2+ increase and exocytosis.

Ultrastructural localization of nicotinamide adenine dinucleotide phosphatase (NADPase) activity in the exocrine pancreas of rat: identification of a novel structure

NADPase activity has been localized in the exocrine pancreas of rat, by cytochemistry according to the procedure of Smith as modified by Clermont et al. With NADP or NADPH as substrate, an intense reaction was detected in one or two intermediary saccules of the Golgi stack. Reaction product was also present in lysosomes, dense bodies and the gland lumen. It was absent from condensing vacuoles and zymogen granules. A very intense reaction was found over a "snake-like" structure not previously reported. These are elongated tubules located in basal and central portions of the acinar cell where they are frequently seen close to the Golgi stack or the basolateral cell surface.

Correlation between endogenous nucleosomal hyper(ADP-ribosyl)ation of histone H1 and the induction of chromatin relaxation

The effect of poly(ADP-ribose) synthesis on chromatin structure was investigated by velocity sedimentation and electron microscopy. We demonstrate that locally relaxed regions can be generated within polynucleosome chains by the activity of their intrinsic poly(ADP-ribose)polymerase. This relaxation phenomenon is also shown to be NAD dependent and to be correlated with the formation of hyper(ADP-ribosyl)ated forms of histone H1. Evidence is also presented which suggests that hyper(ADP-ribosyl)ated histone H1 is neither released from the relaxed chromatin, nor does it seem to participate in polynucleosomal aggregation.

Chloroquine stabilizes hepatic glucocorticoid receptors

Chloroquine (an antiarthritic, antimalarial, lysosomotropic amine) was found to significantly stabilize rat unbound hepatic glucocorticoid receptors in vitro for 2 h at 25 degrees C. Chloroquine stabilization was concentration dependent with statistically significant protection at 0.3 mM concentration and optimal effectiveness at approximately 3 mM. KC1 (0.3 M) induced unbound receptor inactivation at low temperature was also markedly reduced in the presence of 3 mM chloroquine. In addition, steroid prebound complexes were significantly stabilized at 4 degrees C and 25 degrees C by 3 mM chloroquine. Unlike molybdate (perhaps the most commonly used glucocorticoid receptor stabilizing reagent), chloroquine did not alter the sedimentation of glucocorticoid-receptor complexes in sucrose-density gradients. These results suggest that chloroquine may have useful application in glucocorticoid receptor quantitation, characterization and purification and may have interesting implications into the biological and pharmacological effects of chloroquine.