Regulation of pro-inflammatory signalling networks by ubiquitin: identification of novel targets for anti-inflammatory drugs

Modification of cellular proteins with a small protein called ubiquitin has profound effects on their activities. Ubiquitin is covalently attached to lysine residues of acceptor proteins through the concerted action of E1 ubiquitin-activating enzyme, E2 ubiquitin-carrier proteins and E3 ligases. Mammalian cells contain a large number of E3 ligases, which determine the specificity of ubiquitination reactions. Recent studies have revealed that ubiquitination can be reversed by deubiquitinating enzymes that release ubiquitin monomers from modified proteins. Signalling networks that control inflammation are tightly regulated by a multitude of ubiquitination and deubiquitination reactions. This article begins by summarising current understanding of these pathways at a molecular level, and then focuses on the importance of ubiquitination and deubiquitination during the regulation of the pro-inflammatory transcription factor NF-κB. Finally, the potential for ubiquitin modifications to be targeted by novel classes of anti-inflammatory drugs is discussed.

Donor CD31 genotype and its association with acute graft-versus-host disease in HLA identical sibling stem cell transplantation

CD31 gene polymorphisms are implicated in the pathogenesis of graft-versus-host disease (GvHD) following haematopoietic stem cell transplantation (HST). We investigated the influence of CD31 genotype on the incidence of GvHD following HST from an human leukocyte antigen (HLA)-identical sibling donor. Donor and recipient CD31 codons 125, 563 and 670 DNA polymorphisms were determined in 85 cases of HLA identical sibling HST from two transplant centres. A correlation between CD31 genotype and acute GvHD was considered significant if observed in patients from both transplant centres independently. A strong correlation was identified between donor CD31 codon 125 genotype and the incidence of acute GvHD. Acute GvHD grades II-IV occurred in 27 of 46 (59%) recipients with a CD31 codon 125 leucine / valine heterozygous donor compared to nine of 39 (23%) recipients with a CD31 codon 125 homozygous donor (P=0.0019, relative-risk 2.45, 95% confidence interval 1.3-4.5). This correlation was significant in patients from both transplant centres (P=0.015 and P=0.019). We suggest that CD31 genotype may influence the function of donor-derived leukocytes and may be informative when there is a choice of comparable donors.

Zinc-finger protein A20, a regulator of inflammation and cell survival, has de-ubiquitinating activity

Ubiquitination regulates the stability and/or activity of numerous cellular proteins. The corollary is that de-ubiquitinating enzymes, which 'trim' polyubiquitin chains from specific substrate proteins, play key roles in controlling fundamental cellular activities. Ubiquitin is essential at several stages during the activation of NF-kappaB (nuclear factor kappaB), a central co-ordinator of inflammation and other immune processes. Ubiquitination is known to cause degradation of the inhibitory molecule IkappaBalpha (inhibitor of kappaB). In addition, activation of TRAF (tumour-necrosis-factor-receptor-associated factor) and IKKgamma (IkappaB kinase gamma)/NEMO (NF-kappaB essential modifier) signal adaptors relies on their modification with 'nonclassical' forms of polyubiquitin chains. Ubiquitin also plays a key role in determining cell fate by modulating the stability of numerous pro-apoptotic or anti-apoptotic proteins. The zinc-finger protein A20 has dual functions in inhibiting NF-kappaB activation and suppressing apoptosis. The molecular mechanisms of these anti-inflammatory and cytoprotective effects are unknown. Here we demonstrate that A20 is a de-ubiquitinating enzyme. It contains an N-terminal catalytic domain that belongs to the ovarian-tumour superfamily of cysteine proteases. A20 cleaved ubiquitin monomers from branched polyubiquitin chains linked through Lys48 or Lys63 and bound covalently to a thiol-group-reactive, ubiquitin-derived probe. Mutation of a conserved cysteine residue in the catalytic site (Cys103) abolished these activities. A20 did not have a global effect on ubiquitinated cellular proteins, which indicates that its activity is target-specific. The biological significance of the catalytic domain is unknown.

A novel type of deubiquitinating enzyme

A previous report from this laboratory described two novel proteins that have sequence similarity to A20, a negative regulator of NF-kappaB (Evans, P. C., Taylor, E. R., Coadwell, J., Heyninck, K., Beyaert, R., and Kilshaw, P. J. (2001) Biochem. J. 357, 617-623). One of these molecules, cellular zinc finger anti-NF-kappaB (Cezanne), a 100-kDa cytoplasmic protein, also suppressed NF-kappaB. Here we demonstrate that Cezanne is a novel deubiquitinating enzyme, distinct from the two known families of deubiquitinases, Types I and II. We show that Cezanne contains an N-terminal catalytic domain that belongs to the recently discovered ovarian tumor protein (OTU) superfamily, a group of proteins displaying structural similarity to cysteine proteases but having no previously described function. Recombinant Cezanne cleaved ubiquitin monomers from linear or branched synthetic ubiquitin chains and from ubiquitinated proteins. Mutation of a conserved cysteine residue in the catalytic site of the proteolytic domain caused Cezanne to co-precipitate polyubiquitinated cellular proteins. We also provide evidence for an additional ubiquitin binding site in the C-terminal part of the molecule. Our data provide the first demonstration of functional activity among OTU proteins.

Isolation and characterization of two novel A20-like proteins

The transcription factor nuclear factor kappa B (NF-kappa B) plays a pivotal role in inflammatory processes through induction of adhesion molecules and chemokines. The zinc finger molecule A20 is an important negative regulator of NF-kappa B. The mechanism utilized by A20 is not fully understood, but A20 has been shown to bind to tumour-necrosis-factor-receptor-associated factor (TRAF) molecules, which are necessary for pro-inflammatory cytokine signalling. We report two novel genes, Cezanne (cellular zinc finger anti-NF-kappa B) and TRABID (TRAF-binding domain), with sequence similarity to A20. Co-immunoprecipitation studies indicated that TRAF6 was able to interact with both Cezanne and TRABID. In contrast, reporter gene experiments revealed a specific ability of Cezanne to down-regulate NF-kappa B. It is likely, therefore, that Cezanne participates in the regulation of inflammatory processes.

Recipient HLA-DR3, tumour necrosis factor-alpha promoter allele-2 (tumour necrosis factor-2) and cytomegalovirus infection are interrelated risk factors for chronic rejection of liver grafts

BACKGROUND/AIMS

The tumour necrosis factor (TNF)-2 promoter allele, which elicits elevated expression of TNF-alpha, is in linkage disequilibrium with the extended haplotype HLA-A1-B8-DR3-DQ2. TNF-2 and HLA-DR3 have been implicated in renal and cardiac graft rejection and loss. Cytomegalovirus (CMV) infection has been associated with chronic allograft rejection. We examined the relationship between HLA-DR3, promoter allele TNF-2 and cytomegalovirus in relation to chronic rejection following liver transplantation.

METHODS

(i) Retrospective analysis of HLA-DR3 was performed in 307 liver transplant recipients and 283 donors. (ii) Prospective analysis of TNF-alpha promoter allele status, HLA-DR3 status and cytomegalovirus infection was assessed in 123 recipients.

RESULTS

(i) Retrospective analysis. Recipient HLA-DR3 (relative risk 1.9; 95% C.I. 1.01-3.58) was a risk factor for chronic rejection. (ii) Prospective analysis. Recipient HLA-DR3 was a risk factor for chronic rejection (relative risk 3.41; 95% C.I. 1.66-7.03) which was elevated further by superimposed CMV infection (relative risk 5.01; 95% C.I. 2-12.55). Recipient TNF-2 was associated with chronic rejection (relative risk 2.29; 95% C.I. 0.9-5.83) through linkage to HLA-DR3.

CONCLUSIONS

Recipient HLA-DR3, TNF-2 status and CMV infection were inter-related risk factors for chronic rejection of liver grafts.

Signaling through CD31 protects endothelial cells from apoptosis

Endothelial damage has been implicated in the pathogenesis of chronic rejection. Conversely, expression of protective genes [including A20, A1, bcl-xl, and hemoxygenase-1 (HO-1)] in the endothelium has been associated with long-term graft survival. Overexpression of protective genes in cultured endothelial cells confers protection from apoptosis and prevents expression of inflammatory molecules through inactivation of NF-kappaB. CD31 (PECAM-1) expressed at endothelial cell junctions is ligated by leukocytes during transendothelial migration. Our laboratory has recently shown that cross-linking CD31 using a monoclonal antibody (LCI-4) triggers signaling events in endothelial cells. In this study, we demonstrate that treatment with LCI-4 protected serum-starved endothelial cells from apoptosis. CD31 cross-linking also led to elevation of A20 and A1 mRNA levels and activation of the transcription factor Sp-1. In summary, signaling through CD31 on endothelial cells leads to protection from apoptosis in association with up-regulation of two protective molecules, A20 and A1.

Interleukin-13 protects endothelial cells from apoptosis and activation: association with the protective genes A20 and A1

BACKGROUND

Chronic rejection is the major obstacle to long-term survival of allografts and is associated with graft endothelial cell activation and apoptosis. Recent reports have found an association between graft survival, presence of Th2 cytokines, and expression by endothelial cells of cytoplasmic "protective" molecules that prevent apoptosis and down-regulate the inflammatory process.

METHODS

Cultured human umbilical vein endothelial cells (HUVEC) were used. Apoptotic cells were detected by staining with FITC-annexinV followed by flow cytometry. Expression of vascular cell adhesion molecule-1, E-selectin, and intercellular adhesion molecule-1 were also measured by flow cytometry. Transcripts were detected by reverse transcription-PCR and quantitation was achieved by co-amplification of competing, internal standard RNA.

RESULTS

We demonstrate that exposure of HUVEC to interleukin (IL)-13 for 72 hr afforded partial protection from apoptosis induced by tumor necrosis factor-alpha/cycloheximide or serum starvation. Pretreatment with IL-13 also modulated induction of E-selectin after acute exposure to tumor necrosis factor-alpha or IL-1alpha. Protection was associated with transcription of the genes A1 and A20. Prolonged treatment with IL-13 had minimal proinflammatory effects and did not induce expression of E-selectin or vascular cell adhesion molecule-1 or increase intercellular adhesion molecule-1 above basal levels.

CONCLUSIONS

Our data provide a possible explanation for the observed association between Th2 cytokines and expression of protective genes in the endothelium of long-surviving allografts and xenografts.

Cutting edge: persistent fetal microchimerism in T lymphocytes is associated with HLA-DQA1*0501: implications in autoimmunity

The host's MHC genotype plays a critical role in susceptibility to autoimmune diseases. We previously proposed that persistent fetal microchimerism from pregnancy contributes to the pathogenesis of autoimmune diseases such as scleroderma. In the current study, we investigated whether the specific host MHC genotype is associated with persistent microchimerism among T lymphocytes in women with scleroderma and in healthy women. Fetal microchimerism among T lymphocytes was strongly associated with HLA DQA1*0501 of the mother (odds ratio (OR) = 13.5, p = 0.007, p corrected (pc) = 0.06) and even more strongly with DQA1*0501 of the son (OR = infinity; p = 0. 00002, pc = 0.0002). This is the first description of an association between persistent fetal microchimerism in maternal T lymphocytes and specific HLA class II alleles. Although the association was observed in both healthy women and in women with scleroderma, the finding suggests an additional route by which HLA genes might contribute to susceptibility to autoimmune disease.

Effect of IGF-I on serine metabolism in fetal sheep

Acute infusion of IGF-I to the fetus has been shown to inhibit amino acid oxidation and appears to increase fetoplacental amino acid uptake. This study was designed to investigate further the effects of IGF-I on fetal amino acid metabolism. Radiolabeled serine was used to test the hypothesis that fetal IGF-I infusion enhances serine uptake into the fetus and/or placenta and inhibits serine oxidation. Eight fetal sheep were studied at 127 days of gestation before and during a 4-h infusion of IGF-I (50 microg/h per kg). During the infusion there was no change in uptake of serine or its oxidation by fetus or placenta. However, both uptake and oxidation of serine and glycine decreased in the fetal carcass. There was also a decrease in fetal blood serine and glycine concentrations which could indicate a decrease in protein breakdown, although reduced amino acid synthesis cannot be excluded. Thus IGF-I appeared to influence the distribution of these amino acids as oxidative substrates between different fetal tissues. In addition, fetal IGF-I infusion increased the conversion of serine to glycine which is likely to have increased the availability of one-carbon groups for biosynthesis. Our data provide further evidence that IGF-I plays a role in the regulation of fetoplacental amino acid metabolism.

An association between cytomegalovirus infection and chronic rejection after liver transplantation

BACKGROUND

Previous studies suggest a link between cytomegalovirus (CMV) infection and chronic rejection. Since these studies, more sophisticated diagnostic methods with high sensitivity and specificity for CMV have been developed and effective therapy/prophylaxis for CMV is now available. We sought CMV prospectively by polymerase chain reaction of serum and urine and by conventional methods in a group of 33 patients undergoing 57 transplants during 1993 or 1994, selected from a larger series. There were 13 grafts lost to chronic rejection. The remaining 44 grafts that did not develop chronic rejection served as controls and comprised 15 successful primary grafts, 15 second transplants, 8 third transplants, and 6 primary grafts that were lost for reasons other than chronic rejection.

RESULTS

The combination donor CMV antibody negative with recipient antibody positive and the duration of CMV infection >30 days were associated with an increased relative risk of chronic rejection. In contrast, the presence of CMV infection alone, symptomatic CMV infection, the detection of CMV by PCR of serum or urine, and the peak/cumulative viral load were not predictive. CMV infection occurred earlier in those undergoing a second transplant for chronic rejection than for those undergoing a second transplant for other reasons. In addition, a human leukocyte antigen B mismatch was associated with prolonged CMV infection.

CONCLUSION

These data are consistent with the hypothesis that prolonged subclinical cytomegalovirus infection is associated with an increased risk of chronic rejection.

Cytomegalovirus infection of bile duct epithelial cells, hepatic artery and portal venous endothelium in relation to chronic rejection of liver grafts

BACKGROUND/AIM

Chronic rejection is an important cause of graft loss following liver transplantation. A number of risk factors for chronic rejection have been identified previously, albeit inconsistently. These include cytomegalovirus infection detected by a number of different techniques, including immunohistochemical staining and in situ hybridisation of liver grafts. However, tissue-based techniques for the detection of CMV have not been applied to grafts lost to conditions other than chronic rejection. The purpose of this study was to investigate the relationship between the presence of cytomegalovirus infection detected by in situ hybridisation and immunohistochemistry with respect to graft outcome, the presence of cytomegalovirus infection detected by other techniques and in addition, the type of infected cell.

METHODS

The 29 patients studied included 15 patients who lost their primary liver graft to chronic rejection in 8 cases, to hepatic artery thrombosis in 4 cases and to causes other than chronic rejection or hepatic artery thrombosis in 3 further cases. In each case, sections containing septal or large ducts and vessels were selected (usually blocks) since these may be more representative. Needle biopsies from 14 further patients who ultimately achieved satisfactory graft function served as control tissue. Of these, ten had evidence of cytomegalovirus infection at the time of study by serum/urine PCR, DEAFF testing or seroconversion, while 4 patients had no evidence of cytomegalovirus infection according to these techniques.

RESULTS

Cytomegalovirus infection was detected in the liver of 12 of the 29 patients. These included 8/15 grafts lost, which comprised 3/8 with chronic rejection, 2/3 with hepatic artery thrombosis and 3/4 with grafts lost to other causes, as well as 4/14 who retained grafts. CMV was detected most commonly in association with symptomatic infection and notably was detected only by in situ hybridisation in two cases. Predominant cell types that contained cytomegalovirus were hepatocytes and mononuclear cells. However, bile duct epithelial cells, hepatic artery endothelial cells and portal venous endothelial cells also contained cytomegalovirus in some cases.

CONCLUSIONS

These data support previous studies that cytomegalovirus infection is detectable in patients with chronic rejection and are consistent with the theory that CMV is involved in chronic rejection. However, cytomegalovirus infection was detected in explanted grafts lost to conditions other than chronic rejection, and the association may not be causal but a consequence of graft injury.

Comparison of three PCR techniques for detecting cytomegalovirus (CMV) DNA in serum, detection of early antigen fluorescent foci and culture for the diagnosis of CMV infection

Three PCR assays were developed for detection of cytomegalovirus (CMV) DNA in serum and were evaluated with samples from organ transplant recipients. The Qiamp Blood Kit was efficient for extraction of DNA from sera. Single-round PCR of a 293-bp region of CMV DNA was sensitive and highly specific for CMV targets and was more sensitive than detection of early antigen fluorescent foci (DEAFF) testing or isolation of CMV from buffy coat by cell culture. The results of a significant proportion of buffy coat samples were not interpretable because of toxicity in conventional culture or DEAFF tests. A non-competitive quantitative PCR test and semi-quantitative PCR test for the detection of CMV DNA in serum yielded comparable results for samples taken serially from three bone marrow transplant recipients. Single-round PCR was superior to conventional techniques for the diagnosis of CMV infection, was simple to perform and was completed rapidly. The semi-quantitative technique has added advantages where quantification is important.

Alpha-galactosyl-mediated activation of porcine endothelial cells: studies on CD31 and VE-cadherin in adhesion and signaling

BACKGROUND

Ligation of alpha-galactosyl epitopes on endothelial cells by naturally occurring human antibodies causes hyperacute rejection in porcine-to-human xenotransplantation. The alpha-galactosyl-specific lectin Bandeiraea simplicifolia isolectin B4 (IB4) has been reported to trigger endothelial "gap" formation and tyrosine phosphorylation of an unidentified 130-kDa protein. We have studied two 130-kDa junctional adhesion molecules, CD31 and VE-cadherin, in porcine aortic endothelial cells (PAECs) during IB4-mediated activation. The cellular distribution of these molecules, their susceptibility to tyrosine phosphorylation, and their capacity to bind IB4 or natural human antibodies have been determined.

METHODS

Porcine CD31 and VE-cadherin were cloned. Recombinant proteins and monoclonal antibodies were prepared. The distribution and phosphorylation of CD31 and VE-cadherin in confluent PAECs activated with IB4 or human serum were studied by confocal microscopy and Western blotting, respectively.

RESULTS

IB4 caused rapid redistribution of CD31 and VE-cadherin away from cell junctions and tyrosine-phosphorylation of CD31 but not VE-cadherin. A monoclonal antibody to CD31 also triggered tyrosine phosphorylation of this molecule, but brief exposure of PAECs to normal human serum did not. Tyrosine-phosphorylated CD31 complexed with SHP2 and other unidentified phosphoproteins. Both IB4 and natural human antibodies bound to porcine CD31 but not to VE-cadherin. Cell adhesion tests showed that porcine and human CD31 are functionally incompatible.

CONCLUSIONS

Endothelial cell retraction during IB4-mediated activation of PAECs is associated with rapid loss of CD31 and VE-cadherin from cell junctions. CD31 becomes strongly tyrosine-phosphorylated and forms a cell signaling complex, which may have a significant role in the response of the xenograft vascular endothelium.

Administration of crushed extended-release pentoxifylline tablets: bioavailability and adverse effects

The pharmacokinetics of crushed and intact pentoxifylline tablets were compared, and the frequency of adverse effects was evaluated. Intact 400-mg extended-release pentoxifylline tablets, crushed 400-mg tablets, intact 600-mg tablets, and crushed 600-mg tablets were given sequentially to 10 healthy male volunteers. Blood samples were collected at time 0, at 30-minute intervals for the first three hours, and at 4, 6, 8, 12, and 24 hours after the dose and analyzed by capillary gas chromatography for pentoxifylline and three major metabolites. The bioavailability of the crushed tablets relative to the intact tablets was 156% for the 400-mg strength and 137% for the 600-mg strength. The area under the plasma drug concentration-time curve from 0 to 24 hours (AUC0-24) for the 400-mg tablets (crushed and intact) differed significantly from that for the 600-mg tablets; there was no significant difference between intact 400-mg and intact 600-mg tablets or crushed 400-mg and crushed 600-mg tablets. The maximum plasma drug concentration (Cmax) was significantly greater and the time to maximum concentration (t(max)) significantly shorter for crushed tablets than intact tablets. The 400-mg crushed tablet caused mild nausea in three subjects. The 600-mg crushed tablet caused both moderate nausea and dizziness in seven subjects and diaphoresis, headache, and vomiting in one subject each. Cmax was higher and tmax shorter when pentoxifylline tablets were administered crushed rather than intact, and the increase in maximum plasma concentrations appeared to cause dose-related adverse effects; crushing the tablets did not decrease the relative bioavailability.

Microchimerism of maternal origin persists into adult life

Recent studies indicate that fetal cells persist in maternal blood for decades after pregnancy. Maternal cells are known to engraft and persist in infants with immunodeficiency, but whether maternal cells persist long-term in immunocompetent offspring has not specifically been investigated. We developed sensitive human leukocyte antigen-specific (HLA-specific) PCR assays and targeted nonshared maternal HLA genes to test for persistent maternal microchimerism in subjects with scleroderma and in healthy normal subjects. Nonshared maternal-specific DNA was found in 6 of 9 scleroderma patients. In situ hybridization with double labeling for X and Y chromosome-specific sequences revealed female cells in peripheral blood samples from 2 male scleroderma patients. HLA-specific PCR also frequently revealed persistent maternal microchimerism in healthy control subjects. The mean age of all subjects with maternal microchimerism was 28 years (range: 9-49 years). With few exceptions, mothers of subjects with persistent maternal microchimerism were HLA incompatible with subjects for class I and class II alleles. These results clearly indicate that HLA-disparate maternal cells can persist in immunocompetent offspring well into adult life. The biological significance of maternal microchimerism and whether it might contribute to autoimmune disease requires further investigation.

Long-term fetal microchimerism in peripheral blood mononuclear cell subsets in healthy women and women with scleroderma

Fetal CD34(+) CD38(+) cells have recently been found to persist in maternal peripheral blood for many years after pregnancy. CD34(+) CD38(+) cells are progenitor cells that can differentiate into mature immune-competent cells. We asked whether long-term fetal microchimerism occurs in T lymphocyte, B lymphocyte, monocyte, and natural-killer cell populations of previously pregnant women. We targeted women with sons and used polymerase chain reaction for a Y-chromosome-specific sequence to test DNA extracted from peripheral blood mononuclear cells (PBMC) and from CD3, CD19, CD14, and CD56/16 sorted subsets. We also asked whether persistent microchimerism might contribute to subsequent autoimmune disease in the mother and included women with the autoimmune disease scleroderma. Scleroderma has a peak incidence in women after childbearing years and has clinical similarities to chronic graft-versus-host disease that occurs after allogeneic hematopoietic stem-cell transplantation, known to involve chimerism. Sixty-eight parous women were studied for male DNA in PBMC and 20 for PBMC subsets. Microchimerism was found in PBMC from 33% (16 of 48) of healthy women and 60% (12 of 20) women with scleroderma, P =.046. Microchimerism was found in some women in CD3, CD19, CD14, and CD56/16 subsets including up to 38 years after pregnancy. Microchimerism in PBMC subsets was not appreciably more frequent in scleroderma patients than in healthy controls. Overall, microchimerism was found in CD3, CD19, and CD14 subsets in approximately one third of women and in CD56/16 in one half of women. HLA typing of mothers and sons indicated that HLA compatibility was not a requirement for persistent microchimerism in PBMC subsets. Fetal microchimerism in the face of HLA disparity implies that specific maternal immunoregulatory pathways exist that permit persistence but prevent effector function of these cells in normal women. Although microchimerism in PBMC was more frequent in women with scleroderma than healthy controls additional studies will be necessary to determine whether microchimerism plays a role in the pathogenesis of this or other autoimmune diseases.

Qualitative and semiquantitative polymerase chain reaction testing for cytomegalovirus DNA in serum allows prediction of CMV related disease in liver transplant recipients

AIM

To identify cytomegalovirus (CMV) infection in liver transplant recipients by polymerase chain reaction (PCR) techniques and to separate the cases in which CMV related disease will occur, for whom treatment is indicated, from those in whom infection will remain innocuous.

METHODS

The combination of qualitative and semiquantitative PCR of serum and urine was assessed to determine whether these assays can identify those at risk of CMV related disease and compared their performance with conventional approaches to diagnosis.

RESULTS

Qualitative PCR of serum had superior specificity, sensitivity, and positive and negative predictive values compared with urine DEAFF (detection of early antigen fluorescent foci) and PCR of urine. All episodes of CMV related disease were associated with the presence of CMV DNA by PCR in serum or urine; CMV was detected before clinical onset in 70% and 60% of cases, respectively. The period over which CMV DNA could be detected was not correlated with CMV related disease. Both peak viral load and cumulative viral load estimated using a semiquantitative PCR method on serum samples positive by the qualitative method could be used to distinguish asymptomatic infection from CMV related disease with 100% specificity and sensitivity. In contrast semiquantitative PCR of urine was of little value.

CONCLUSIONS

An approach based on PCR testing with a combination of qualitative and subsequently semiquantitative serum samples would improve the diagnosis of CMV infection and aid identification of those patients at risk of CMV related disease, allowing treatment to be targeted specifically.

Optimisation of the polymerase chain reaction and dot-blot hybridisation for detecting cytomegalovirus DNA in urine: comparison with detection of early antigen fluorescent foci and culture

Rapid, sensitive and specific assays are required for the diagnosis of CMV infection following transplantation. We describe our experience in developing assays for detecting CMV in urine. Conventional preparation of probes cloned after amplification in E. coli led to contamination with E. coli nucleic acids; these hybridised to E. coli DNA present in urine and produced false positive results. Two CMV probes (Hind III and gL) hybridised to human DNA despite high stringency; these probes were thus unsuitable for detecting viral nucleic acids in clinical samples. A PCR derived probe from the immediate early gene of CMV detected dot-blotted CMV DNA specifically. Optimal preparation of urine for detection of CMV DNA was as follows; four freeze/thaw cycles and ultracentrifugation before in vitro proteinase K/SDS treatment, phenol:chloroform extraction, heat denaturation and direct application onto a nylon membrane. However, dot-blot hybridisation was a poor test for CMV in urine; it had low sensitivity and specificity compared with virus isolation and DEAFF. Single round PCR of a 293 bp region of CMV DNA was sensitive and specific to CMV targets. However, undiluted urine contained PCR inhibitors that could only be partly removed by using PEG precipitation. PCR of CMV DNA from urine was specific but was insensitive compared to conventional culture and DEAFF. A significant proportion of urine samples were toxic in conventional culture and DEAFF tests but, PCR of CMV DNA from urine is insensitive and despite its specificity is unlikely to be advantageous in clinical practice even when DEAFF or culture prove unreliable.

Fetal growth and placental function

Fetal growth is largely determined by the availability of nutrients to the fetus. The fetus is at the end of a supply line that ensures delivery of nutrients from the maternal/uterine circulation to the fetus via the placenta. However, this supply line can not be regarded as a linear relationship. Maternal undernutrition will not only reduce global nutrient availability but will also influence the maternal and fetal somatotrophic axis. Both endocrine systems react in a very similar way to limited substrate supply. The hormones of the fetal somatotrophic axis, and in particular insulin-like growth factor (IGF)-1, are important regulators of fetal growth. Placental function is pivotal to materno-fetal nutrient and metabolite transfer. Placental function in turn, is heavily influenced by the maternal and fetal growth hormone (GH)-IGF-1 system. The placenta itself is also an active endocrine organ and it produces a large number of hormones including GH and IGF-1 as well their corresponding receptors. Thus the placenta can no longer be considered merely a passive conduit for fetal nutrition. Rather, it is actively involved in the integration of nutritional and endocrine signals from the maternal and fetal somatotrophic axes.

Microchimerism and HLA-compatible relationships of pregnancy in scleroderma

BACKGROUND

Fetal cells can be found in the maternal circulation in most pregnancies. Fetal progenitor cells have been found to persist in the circulation of women many years after childbirth. We tested the hypothesis that microchimerism is involved in the pathogenesis of scleroderma. Scleroderma is of interest because of a strong female predilection, an increased incidence in the years after childbearing, and clinical similarities between scleroderma and chronic graft-versus-host disease after allogeneic bone-marrow transplantation. We also investigated whether HLA-compatibility of a child was associated with later development of scleroderma in the mother.

METHODS

We enrolled 40 women who had previously given birth to at least one son--16 healthy controls, 17 scleroderma patients, and seven healthy sisters of patients. We used quantitative PCR to amplify a Y-chromosome-specific sequence in whole peripheral blood from these women. Also 32 controls with 58 children, and 21 scleroderma patients with 47 children were HLA genotyped.

FINDINGS

The mean number of male cell DNA equivalents among controls was 0.38 cells per 16 mL whole blood (median 0 [range 0-2]) and 11.1 (6.0 [0-61]) among scleroderma patients (p = 0.0007). Controls' youngest sons were born a mean of 15.4 years previously, and scleroderma patients' sons 18.5 years previously. Some scleroderma patients had concentrations of male DNA higher than those found in most pregnant women. HLA-class II compatibility of a child from the mother's perspective was more common among scleroderma patients than among controls, but was not essential for persistence of male DNA in maternal peripheral blood.

INTERPRETATION

Low concentrations of male DNA can be detected in healthy women decades after the birth of a son. Microchimerism in scleroderma patients could be secondary to the underlying disease. However, the finding that HLA class II compatibility of a child was more common for scleroderma patients than for controls, supports the possibility that microchimerism may be involved in the pathogenesis of scleroderma.

Maternal growth hormone treatment increases placental diffusion capacity but not fetal or placental growth in sheep

We tested the hypothesis that chronic maternal GH administration would increase fetal substrate supply, increase maternal and fetal insulin-like growth factor I (IGF-I) concentrations, and therefore enhance growth in the late gestation fetal sheep. Eleven ewes received bovine GH 0.1 mg/kg twice daily for 10 days, whereas 10 control ewes received saline. GH treatment increased placental capacity for simple diffusion (P < 0.01), with a trend toward an increase in placental capacity for facilitated diffusion (P = 0.07). GH treatment also lowered maternal and fetal blood urea concentrations, and there was a trend toward increased fetal protein oxidation (P = 0.07). Maternal but not fetal IGF-I and insulin concentrations increased. Fetal and placental growth were not altered by GH treatment. Maternal and fetal metabolic status was significantly affected by maternal food intake. We conclude that maternal GH treatment increases placental transport capacity, but that anabolic effects in the mother may limit fetal substrate supply and therefore prevent an increase in fetal growth.

The effects of ovine placental lactogen infusion on metabolites, insulin-like growth factors and binding proteins in the fetal sheep

It has been suggested, but not shown, that in the fetus placental lactogen (PL) may affect the regulation of the IGFs and fetal metabolism. To examine the effects of PL on the circulating concentrations of the IGFs, IGF-binding proteins (IGFBPs), glucose, free fatty acids (FFAs) and amino nitrogen (AN), we infused late gestation sheep fetuses with recombinant ovine PL (roPL). Five chronically-catheterised sheep fetuses were infused intravenously with three 24 h infusions of saline, roPL (100 micrograms bolus then 500 micrograms over 24 h) and then saline again. Fetal roPL infusion increased plasma oPL from 0.4 +/- 0.1 to 3.3 +/- 0.5 nM (mean +/- S.E.M.; P < 0.05; factorial analysis of variance and Scheffé's test). Fetal plasma IGF-I, IGF-II, insulin, FFAs and blood glucose were unaffected by the roPL infusion. Fetal plasma IGFBP-3, as measured by Western ligand blotting, decreased by 30% during fetal roPL infusion while other fetal plasma IGFBPs were unaffected. Fetal roPL infusion decreased fetal blood AN from 7.3 +/- 0.5 to 6.6 +/- 0.2 mM (P < 0.05). Maternal plasma IGF-I, IGF-II, IGFBPs, insulin, FFAs, blood glucose and AN were unaffected by the fetal roPL infusion. Saline infusion had no effect on any parameter. The data suggest that PL is not a significant determinant of plasma IGFs in the late gestation sheep fetus although there may be an indirect effect via alterations in levels of IGFBP-3. The effect of fetal roPL infusion on fetal blood AN concentrations may suggest some role for PL in the regulation of fetal amino acid metabolism.

Maternal insulin-like growth factor-I infusion alters feto-placental carbohydrate and protein metabolism in pregnant sheep

Insulin-like growth factor-I (IGF-I) in the maternal circulation may have a role in the regulation of placental function and fetal growth, but its mechanisms of action are not known. We studied the effects of maternal IGF-I infusion (30 micrograms/kg.h for 4 h) in eight chronically catheterized pregnant sheep. IGF-I infusion caused an increase in fetal blood glucose concentrations, but no change in placental or fetal glucose uptake. Maternal plasma insulin concentrations fell. Placental lactate production increased by 56%, with most of this lactate taken up by the fetus. Maternal and fetal blood amino nitrogen concentrations fell, but fetal protein oxidation was unchanged. IGF-I infusion did not change feto-placental oxygenation, placental blood flow, or placental transfer by simple or facilitated diffusion. The metabolic effects of maternal IGF-I infusion in part oppose those of fetal IGF-I. We hypothesize that the balance of maternal and fetal IGF-I concentrations contributes to the regulation of substrate distribution between mother, placenta and fetus, and may thus mediate the nutritional regulation of fetal growth.

Insulin-like growth factor 1 alters feto-placental protein and carbohydrate metabolism in fetal sheep

Insulin-like growth factor 1 (IGF-1) is an anabolic hormone in postnatal life and may be an important endocrine regulator of fetal growth. However, its effects on fetal metabolism in vivo have not previously been determined. We studied the effect of 50 micrograms/h.kg IGF-1 infusion in 12 chronically catheterized fetal sheep. Fetal blood amino nitrogen concentrations fell 10% and maternal 7%, consistent with a rise in feto-placental amino acid uptake. Fetal amino acid oxidation, measured by fetal urea production fell by 30% (44.4 +/- 10.5 to 30.9 +/- 8.0 mumol/min). Fetal and maternal blood glucose concentrations both fell by 0.1 mM, consistent with increased feto-placental glucose uptake. Placental lactate production fell 30% (114 +/- 15 to 78 +/- 11 mumol/min), as did fetal and uterine lactate uptake. There was no change in umbilical or uterine blood flows, nor in placental transfer by simple or facilitated diffusion. We conclude that IGF-1 has anabolic effects on feto-placental protein and carbohydrate metabolism. Circulating IGF-1 may in part mediate the regulation of fetal growth in response to fetal nutrient supply.

Glucose but not a mixed amino acid infusion regulates plasma insulin-like growth factor-I concentrations in fetal sheep

The influence of fetal glucose and amino acid supply on the regulation of fetal plasma IGF-I levels was investigated in fetuses from starved ewes. Paired maternal and fetal blood samples were taken during an initial 2-d control period, after 48 h of maternal starvation, during a 24-h fetal infusion of glucose (n = 6) or an amino acid mixture (Synthamin 17, n = 5) with continued starvation, and after 48 h of maternal refeeding. After 48 h of starvation, maternal and fetal plasma IGF-I, insulin, and blood glucose fell significantly in both groups compared with control values (IGF-I for glucose group: maternal, -18.53 +/- 6.60; fetal, -5.23 +/- 1.81 nmol/L; amino acid group: maternal, -18.2 +/- 6.97, fetal, -5.12 +/- 1.61 nmol/L; both p < 0.05). Fetal glucose but not mixed amino acid infusion raised fetal plasma IGF-I, insulin, and blood glucose to near control values (glucose group fetal IGF-I, -1.77 +/- 1.98; amino acid group, -5.93 +/- 2.22 nmol/L; both p < 0.05). Maternal plasma IGF-I remained depressed during glucose infusion (-16.33 +/- 8.32 nmol/L), but continued to fall in the amino acid group (-21.41 +/- 8.20 nmol/L, p < 0.05). After 48 h of maternal refeeding, all values had returned to near control values for both groups (glucose group IGF-I: maternal, -5.2 +/- 3.86; fetal, 0.01 +/- 2.2; nmol/L; amino acid group: maternal, -11.66 +/- 3.2; fetal, -0.70 +/- 2.61 nmol/L). We conclude that in the ovine fetus glucose may have a more important role than amino acids in the regulation of fetal plasma IGF-I.

Solid-phase separation of 14C-labelled urea and aminoisobutyric acid for membrane transport studies

A sorbent extraction method has been developed for separating 14C-labelled urea and aminoisobutyric acid (AIB) in blood. The use of commercial solid-phase extraction cartridges containing aminopropyl-bonded silica provided a convenient and rapid separation of urea and AIB with better than 92% recovery of each and less than 5% cross-contamination. This allows these compounds, together with [3H]methylglucose, to be used as marker compounds for investigating three aspects of membrane transport. The facility to separate any two of the three compounds permits their simultaneous measurement, greatly increasing the amount of data obtainable from each in vivo preparation.

A colorimetric assay for amino nitrogen in small volumes of blood: reaction with beta-naphthoquinone sulfonate

An assay has been developed for the colorimetric estimation of total amino acids in small volumes (100 microliters) of whole blood. The procedure utilizes the reaction of amino nitrogen with beta-naphthoquinone sulfonate. It represents a substantial improvement on previously published methods by decreasing reagent volumes and accurately specifying and maintaining pH conditions for the reaction itself (9.2-9.4) and for removal of excess reagent prior to measurement of the resulting complex (2.2-2.4). Ammonia is the only compound shown to significantly interfere with the assay but this is not a problem at physiological concentrations.

The nutritional regulation of circulating placental lactogen in fetal sheep

Maternal and fetal plasma ovine placental lactogen (oPL), insulin, and IGF-I levels were measured in response to the starvation and refeeding of pregnant sheep on two defined planes of nutrition. Chronically catheterized pregnant ewes were placed on either a high plane (n = 5) or low plane (n = 5) of nutrition at least 1 wk before the experiment. At 125 to 135 d gestation, the ewes were starved for 72 h and then an i.v. infusion of 10% glucose was administered over 4 h, followed by refeeding at the designated nutritional plane. Plasma oPL levels of fetuses whose mothers had been on a high plane of nutrition were significantly higher during starvation (p less than 0.05) than those of fetuses whose mothers had been on a low plane (high + 0.54 +/- 0.17 and low -0.02 +/- 0.17 nmol/L from mean control levels). Intravenous glucose infusion to the ewes at the end of starvation caused a marked rise in fetal plasma oPL levels in both groups (increments of 2.61 +/- 1.4 nmol/L in the high group and 2.81 +/- 1.16 nmol/L in the low group). Maternal oPL levels did not differ significantly between the two nutritional groups during starvation and did not change during glucose infusion. Fetal and maternal plasma IGF-I levels both fell during starvation. Maternal IGF-I levels fell faster in the high group (-17.9 +/- 4.5 at 24 h versus -4.7 +/- 7.2 nmol/L in the low group), but the groups were not different at the end of starvation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of beta-hydroxybutyrate infusion on hind limb metabolism in fetal sheep

OBJECTIVES

This study investigated the effects of high ketone levels on fetal carcass metabolism. Specifically, we aimed to determine whether beta-hydroxybutyrate was taken up by fetal muscle and whether lactate production by the fetal hind limb contributed to the raised circulating lactate levels seen in high ketone states.

STUDY DESIGN

Hind limb metabolism was studied in 10 chronically catheterized fetal sheep. Substrate/oxygen quotients were measured before and after 2 hour infusions of beta-hydroxybutyrate and compared with the Wilcoxon signed-rank test.

RESULTS

beta-Hydroxybutyrate was taken up by hind limb tissues in large amounts (butyrate/oxygen quotient = 1.02 +/- 0.40). Lactate was produced by the hind limb (lactate/oxygen quotient = -0.96 +/- 0.52) in amounts almost equivalent to glucose uptake (glucose/oxygen quotient = 1.32 +/- 0.29). Hind limb oxygen consumption increased 35% and fetal arterial oxygen content fell 16%.

CONCLUSION

beta-Hydroxybutyrate may be consumed by the fetal carcass in amounts sufficient to entirely substitute for glucose. Glucose may then be released as lactate for metabolism elsewhere. Ketones may be important fetal substrates during maternal starvation.

beta-Hydroxybutyrate is an alternative substrate for the fetal sheep brain

Brain uptake of substrates other than glucose has been demonstrated in vivo in postnatal but not fetal life. In this study, brain uptake of potential alternative substrates beta-hydroxybutyrate and lactate was studied during 2 h substrate infusions in 10 chronically-catheterised fetal sheep at 135-141 days gestation. beta-hydroxybutyrate appeared to be taken up by the brain of 5 fetuses with spontaneously low arterial blood glucose concentrations, and produced by the brains of the 5 with higher glucose concentrations. Brain butyrate/oxygen quotients at the end of the infusions were directly related to fetal arterial blood glucose concentrations (r2 = 0.72, P less than 0.01. Brain butyrate/oxygen quotients were not related to the arterial beta-hydroxybutyrate concentrations at the beginning or end of the infusions. No brain uptake of lactate was demonstrated. This study suggests for the first time that the fetal brain in vivo may take up substrates other than glucose. The near term fetal sheep brain appears to take up beta-hydroxybutyrate only when arterial butyrate concentrations are high and glucose is low.

Quantitation of the antitumour agent N-[2-(dimethylamino)ethyl]acridine-4-carboxamide in plasma by high-performance liquid chromatography

N-[2-(Dimethylamino)ethyl]acridine-4-carboxamide is a new experimental antitumour agent which has excellent in vivo activity against the Lewis lung tumour in mice. A reversed-phase high-performance liquid chromatographic method is described for the measurement of this agent in plasma. The internal standard was N-[2-(diethylamino)ethyl]acridine-4-carboxamide. The compounds of interest were extracted from plasma (0.2 ml) with acetonitrile and further purified on C18 solid-phase extraction Bond Elut columns. After elution with acetonitrile-ammonium acetate buffer and evaporation, the final separation was carried out on a C18 muBondapak column with fluorimetric detection. Over the plasma concentration range 100-5000 nM, the intra- and inter-assay coefficients of variation were less than 4.1 and 7.7%, respectively. The accuracy of the method varied from 97 to 105% of the theoretical values. The lowest concentration which could be measured with acceptable accuracy (+/- 10%) and precision (coefficient of variation less than 10%) was 10 nM. The method was sufficiently sensitive to allow pharmacokinetic analyses of 30 mumol/kg doses for more than six half-lives (t1/2) in rabbits (t1/2 = 4) and mice (t1/2 = 1.3 h).

Disposition of amsacrine and its analogue 9-([2-methoxy-4-[(methylsulfonyl)amino]phenyl]amino)-N,5-dimethyl-4- acridinecarboxamide (CI-921) in plasma, liver, and Lewis lung tumors in mice

9-([2-Methoxy-4-[(methylsulfonyl)amino]phenyl]amino)-N,5-dimethyl-4- acridinecarboxamide (CI-921), an analogue of the clinical antileukemia drug amsacrine with improved solid tumor activity in mice, is currently being evaluated in patients. In order to determine whether CI-921 possesses any advantages over amsacrine in terms of tissue delivery, the pharmacokinetics of amsacrine and CI-921 were determined following i.v. injection in male B6D2F1 mice. Plasma kinetics in normal mice were measured following administration of 14.4, 28.9, and 57.7 mumol/kg. The kinetics in s.c. Lewis lung tumors, and in plasma and livers of normal and tumor-bearing mice were measured following administration of 57.7 mumol/kg. CI-921 and amsacrine were quantitated by high-performance liquid chromatography after extraction from plasma and from liver and tumor homogenates. In experiments with appropriate 3H-labeled compounds, both total and covalently bound radioactivity (determined after precipitation and washing with acetonitrile) were measured in plasma and in liver homogenates. Over this dose range, nonlinear kinetics were observed in plasma for unchanged CI-921 and amsacrine, and a reasonable fit was obtained with Michaelis-Menten kinetics to a one-compartment model for CI-921 (Km 3.7 mumol/liter; Vmax 18 mumol/h/kg; V ss 3.3 liter/kg) and a two-compartment model for amsacrine (Km 3.6 mumol/liter; Vmax 76 mumol/h/kg; Vss 4.8 liter/kg). The area under the concentration-time curve (AUC) for plasma following a dose of 57.7 mumol/kg was 31 mumol.h/liter for CI-921 and 6.3 mumol.h/liter for amsacrine. However, equilibrium dialysis measurements indicated high plasma protein binding with free drug fractions for CI-921 and amsacrine of 0.63 and 6.7%, respectively. In the liver, unchanged drug concentrations and total radioactivity for both compounds were approximately 10-fold those in plasma, and the tissue half-life of CI-921 was approximately 4-fold longer for CI-921 than for amsacrine. Plasma and liver kinetics in mice with s.c. Lewis lung tumors were similar to those in normal mice. Tumor half-lives of unchanged CI-921 and amsacrine were 3.9 and 2.7 h, respectively, considerably longer than those for plasma (1.2 and 0.30 h respectively) or liver (1.2 and 0.28 h, respectively). Tumor AUC values for CI-921 and amsacrine were 68 and 37 mumol.h/liter, respectively, as compared to the calculated AUC values for free drug in plasma of 0.19 and 0.42 mumol.h/liter, respectively. It is concluded that the uptake into tumors from the plasma free drug fraction is more efficient for CI-921 than for amsacrine.

The effect of cimetidine, phenobarbitone and buthionine sulphoximine on the disposition of N-5-dimethyl-9-[(2-methoxy-4-methyl-sulphonylamino)phenylamino]- 4-acridinecarboxamide (CI-921) in the rabbit

N-5-dimethyl-9-[(2-methoxy-4-methylsulphonyl-amino)phenylamino]-4- acridinecarboxamide (CI-921) is an amsacrine analogue currently undergoing phase II clinical trials as an antitumor drug. Significant alterations in the plasma clearance (CL) of amsacrine have been demonstrated in rabbits after pretreatment with cimetidine (CT), phenobarbitone (PB) and buthionine sulphoximine (BSO). In the present study, the influence of these agents on the disposition of CI-921 was investigated in rabbits. After a short infusion of CI-921 (12.7 mumol/kg), blood (8 x 3 ml) was collected up to 12 h and the total plasma concentration of CI-921 determined by HPLC. Model-independent pharmacokinetic parameters were compared by Student's paired t-test. CT pretreatment significantly (P = 0.011) increased the AUC (mean, 21%; range, 3%-43%) and significantly (P = 0.019) decreased the CL (mean, 17%; range, 4%-30%). The induction effect of PB pretreatment was not confirmed with CI-921. No significant reduction in AUC or increase in CL was apparent. BSO pretreatment caused a small but significant (P = 0.049) increase in AUC (mean, 20.5%; range, 4%-59%) but had no effect on CL. Although more modest changes in kinetic parameters were observed with CI-921 than with amsacrine, these results suggested the involvement of the hepatic mixed-function oxidase system but not PB-inducible cytochrome P-450 isozymes in the elimination of CI-921 in the rabbit. As with amsacrine, a reduction in hepatic glutathione (GSH) concentrations in the body also appeared to have a modest effect on the disposition of CI-921.

The clinical pharmacokinetics of N-5-dimethyl-9-[(2-methoxy-4-methyl-sulfonylamino)phenylamino]-4 -acridinecarboxamide (CI-921) in a phase 1 trial

The pharmacokinetics of CI-921 were studied after 65 infusions over a 20-fold dose range (13-270 mg/m2 per day) in 16 patients during a phase 1 trial. CI-921 was given by a 15 min infusion on three consecutive days. Plasma samples were collected after the first and third infusions, and urine, at 6 h intervals throughout the 3 days. CI-921 concentrations were measured by an HPLC method. Maximum plasma concentrations ranged from 3-86 mumol/l. The plasma concentration-time disposition curves were mainly biphasic over the 24-h postinfusion period. There was no significant difference by the paired t-test between the Cmax, AUC, CL, Vss, MRT, t1/2 alpha, or t1/2 beta calculated for the first and third infusions. The means (range) of model-independent pharmacokinetic parameters were: CL, 158 (94-290) ml/h per kg; Vss, 319 (219-614) ml/kg; MRT, 2.1 (1.1-3.5) h; t1/2 alpha, 0.5 (0.2-1.1) h; and t1/2 beta, 2.6 (1.1-5.0) h. There was a strong linear correlation between the dose and the AUC and Cmax, suggesting linear kinetics over this dose range. A very small amount (less than 1%) of the total dose was excreted as unchanged CI-921 in the urine, mostly in the 12-h postinfusion period.

Thiolytic cleavage and binding of the antitumour agent CI-921 in blood

The antitumour agent 9-[[2-methoxy-4-[methylsulphonylamino]-phenyl]amino]-N,5-dimethyl- 4-acridinecarboxamide (CI-921; NSC 343499) is currently undergoing clinical evaluation. The plasma disposition of this compound together with its ability to bind to plasma proteins has been investigated in the mouse. Five minutes after intravenous administration of [acridinyl-G-3H]-CI-921 (57.7 mol/kg) to male BDF1 mice, plasma samples were taken and precipitated with acetonitrile. 17% of the total plasma radioactivity was found to be bound to plasma proteins, increasing to 31% by 30 min. To ascertain the mechanism of binding, [acridinyl-G-3H]-CI-921 was incubated at 37 degrees C in mouse blood or plasma and the radioactivity analysed after precipitation with acetonitrile. CI-921 and the cleavage product 4-amino-3-methoxy-methanesulphonanilide (MSA) were detected in the acetonitrile supernatants by HPLC using electrochemical and ultraviolet detection. After incubation for 1 h with blood, extensive association of radioactivity (80% of total) with plasma proteins, together with a rapid decrease in CI-921 concentration and a concomitant increase in MSA concentration, was observed. In blood samples from mice given CI-921, low concentrations (1 to 2 mumol/l) of MSA were detected up to 1 h after injection. The results suggest that in vivo at least part of the covalent binding in blood arises from the nucleophilic attack by protein thiols at the C-9 position of the acridine ring resulting in covalent protein adducts and release of MSA.

Dose-dependent pharmacokinetics of N-5-dimethyl-9-[(2-methoxy-4-methylsulphonylamino)phenylamino]- 4-acridinecarboxamide (CI-921) in rabbits

N-5-dimethyl-9-[(2-methoxy-4-methylsulphonylamino)phenylamino]-4- acridinecarboxamide (CI-921), which is an analogue of amsacrine, has entered phase I clinical trials as an antitumour drug. The plasma pharmacokinetics of CI-921 has been studied in six rabbits after short i.v. infusions of 6.35, 12.7 and 25.4 mumol/kg. Total plasma concentrations of CI-921 were determined by a high-performance liquid chromatography method for up to 12 h post infusion. Comparison of pharmacokinetic parameters for each rabbit by within-subject analysis of variance indicated that with a four-fold increase in the dose from 6.35 to 25.4 mumol/kg there was a 44% increase in the area under the concentration-time curve normalised to dose (P less than 0.001) and a 43% increase in the elimination half-life (P less than 0.005), and a 30% decrease in the total plasma clearance (P less than 0.001). Dose had no effect on the end of infusion concentration normalised to dose, or on the steady-state volume of distribution. These results indicate that CI-921 experiences dose-dependent elimination kinetics in the rabbit.

Rubella susceptibility in Navajo women

Rubella susceptibility among Navajo women equals that in other parts of the country. Even though crowded conditions exist in the homes, communicable disease is more prevalent than in other areas, and many children attend boarding schools. The present immunization policy is discussed and an alternative plan of immunization is presented as recently recommended by the Navajo Area Indian Health service committee on rubella.