Novel (Rp)-cAMPS analogs as tools for inhibition of cAMP-kinase in cell culture. Basal cAMP-kinase activity modulates interleukin-1 beta action

Novel (Rp)-cAMPS analogs differed widely in ability to antagonize cAMP activation of pure cAMP-dependent protein kinase I and II and to antagonize actions of cAMP on gene expression, shape change, apoptosis, DNA replication, and protein phosphorylation in intact cells. These differences were related to different abilities of the analogs to stabilize the holoenzyme form relative to the dissociated form of cAMP kinase type I and II. (Rp)-8-Br-cAMPS and (Rp)-8-Cl-cAMPS were the most potent cAMP antagonists for isolated type I kinase and for cells expressing mostly type I kinase, like IPC-81 leukemia cells, fibroblasts transfected with type I regulatory subunit (RI), and primary hepatocytes. It is proposed that (Rp)-8-Br-cAMPS or (Rp)-8-Cl-cAMPS should replace (Rp)-cAMPS as the first line cAMP antagonist, particularly for studies in cells expressing predominantly type I kinase. The phosphorylation of endogenous hepatocyte proteins was affected oppositely by (Rp)-8-Br-cAMPS and increased cAMP, indicating that (Rp)-8-Br-cAMPS inhibited basal cAMP-kinase activity. The inhibition of basal kinase activity was accompanied by enhanced DNA replication, an effect which could be reproduced by microinjected mutant cAMP-subresponsive RI. It is concluded that the basal cAMP-kinase activity exerts a tonic inhibition of hepatocyte replication. (Rp)-8-Br-cAMPS and microinjected RI also desensitized hepatocytes toward inhibition of DNA synthesis by interleukin-1 beta. This indicates that basal cAMP-kinase activity can have a permissive role for the action of another (interleukin-1 beta) signaling pathway.

Effects of CYP2D6 and SULT1A1 genotypes including SULT1A1 gene copy number on tamoxifen metabolism

BACKGROUND

Tamoxifen is hydroxylated by cytochrome P450 (CYP) 2D6 to the potent metabolites 4-hydroxytamoxifen (4OHtam) and 4-hydroxy-N-demethyltamoxifen (4OHNDtam), which are both conjugated by sulphotransferase (SULT)1A1. Clinical studies indicate that CYP2D6 and SULT1A1 genotypes are predictors for treatment response to tamoxifen. Therefore, we examined the relationship between CYP2D6 genotype, SULT1A1 genotype, SULT1A1 copy number and the pharmacokinetics of tamoxifen.

PATIENTS AND METHODS

The serum levels of tamoxifen and metabolites of 151 breast cancer patients were measured by high-pressure liquid chromatography-tandem mass spectrometry. The CYP2D6 and SULT1A1 polymorphisms and SULT1A1 copy number were determined by long PCR, PCR-based restriction fragment length polymorphism, DNA sequencing and fluorescence-based PCR.

RESULTS

The levels of 4OHtam, 4OHNDtam and N-demethyltamoxifen were associated with CYP2D6 predicted enzymatic activity (P < 0.05). The SULT1A1 genotype or copy number did not influence the levels of tamoxifen and its metabolites. However, the ratios of N-demethyltamoxifen/tamoxifen and N-dedimethyltamoxifen/N-demethyltamoxifen were related to SULT1A1 genotype.

CONCLUSION

CYP2D6 and SULT1A1 genotypes may partly explain the wide inter-individual variations in the serum levels of tamoxifen and its metabolites. We propose that therapeutic drug monitoring should be included in studies linking CYP2D6 and SULT1A1 genotypes to clinical outcome.

Fine mapping of 28S rRNA sites specifically cleaved in cells undergoing apoptosis

Bona fide apoptosis in rat and human leukemia cells, rat thymocytes, and bovine endothelial cells was accompanied by limited and specific cleavage of polysome-associated and monosome-associated 28S rRNA, with 18S rRNA being spared. Specific 28S rRNA cleavage was observed in all instances of apoptotic death accompanied by internucleosomal DNA fragmentation, with cleavage of 28S rRNA and of DNA being linked temporally. This indicates that 28S rRNA fragmentation may be as general a feature of apoptosis as internucleosomal DNA fragmentation and that concerted specific cleavage of intra- and extranuclear polynucleotides occurs in apoptosis. Apoptosis-associated cleavage sites were mapped to the 28S rRNA divergent domains D2, D6 (endothelial cells), and D8. The D2 cuts occurred in hairpin loop junctions considered to be buried in the intact ribosome, suggesting that this rRNA region becomes a target for RNase attack in apoptotic cells. D8 was cleaved in two exposed UU(U) sequences in bulge loops. Treatment with agents causing necrotic cell death or aging of cell lysates failed to produce any detectable limited D2 cleavage but did produce a more generalized cleavage in the D8 region. Of potential functional interest was the finding that the primary cuts in D2 exactly flanked a 0.3-kb hypervariable subdomain (D2c), allowing excision of the latter. The implication of hypervariable rRNA domains in apoptosis represents the first association of any functional process with these enigmatic parts of the ribosomes.

The nuclear receptors NUR77, NURR1 and NOR1 in obesity and during fat loss

BACKGROUND

Adipose tissue is critical for systemic metabolic health. Identifying key factors regulating adipose tissue function is a research priority. The NR4A subfamily of nuclear receptors (NRs) (NR4A1/NUR77, NR4A2/NURR1 and NR4A3/NOR1) has emerged as important proteins in different disease states and in the regulation of metabolic tissues, particularly in liver and muscle. However, the expression of the NR4A members in human adipose tissue has not previously been described, and their target genes are largely unknown.

OBJECTIVE

To determine whether the NR4As are differentially expressed in human adipose tissue in obesity, and identify potential NR4A target genes.

DESIGN

Prospective analysis of s.c. adipose tissue before and 1 year after fat loss, and during in vitro differentiation of primary human preadipocytes. Case-control comparison of omental (OM) adipose tissue.

SUBJECTS

A total of 13 extremely obese patients undergoing biliopancreatic diversion with duodenal switch for fat loss, 12 extremely obese patients undergoing laparoscopic sleeve gastrectomy and 37 lean individuals undergoing hernia repair or laparotomy were included in the study. Measurements were done by quantitative PCR gene expression analysis of the NR4A members and in silico promoter analysis based on microarray data.

RESULTS

There was a strong upregulation of the NR4As in extreme obesity and normalization after fat loss. The NR4As were expressed at the highest level in stromal-vascular fraction compared with adipocytes, but were downregulated in both fractions after fat loss. Their expression levels were also significantly higher in OM compared with s.c. adipocytes in obesity. The NR4As were downregulated during differentiation of primary human preadipocytes. Moreover, the NR4As were strongly induced within 30 min of tissue incubation. Finally, promoter analysis revealed potential NR4A target genes involved in stress response, immune response, development and other functions. Our data show altered adipose tissue expression of the NR4As in obesity, suggesting that these stress responsive nuclear receptors may modulate pathogenic potential in humans.

Identification and quantification of tamoxifen and four metabolites in serum by liquid chromatography-tandem mass spectrometry

We have developed a method for the determination of tamoxifen (tam) and its metabolites 4-hydroxytamoxifen (4OHtam), N-demethyltamoxifen (NDtam), N-dedimethyltamoxifen (NDDtam), tamoxifen-N-oxide (tamNox), and 4-hydroxy-N-demethyltamoxifen (4OHNDtam) in 50 microl human serum. Serum proteins were precipitated with acetonitrile. Deuterated-tamoxifen (D5 tam) was added as internal standard. Sample supernatant was injected into an on-line reversed-phase extraction column coupled with a C18 analytical column and analytes were detected by tandem mass spectrometry. The lower limits of quantification were 0.25 ng/mL for 4OHtam, NDtam and tam, 1.0 ng/mL for NDDtam and tamNox. Ranges of within- and between-day variation were 2.9-15.4% and 4.4-12.9%, respectively.

Nitric oxide in the oxygenator sweep gas reduces platelet activation during experimental perfusion

BACKGROUND

Hemorrhage is a major complication experienced in 10% to 35% of neonates treated with extracorporeal life support (ECLS). The increased bleeding tendency is partly due to an ECLS-induced thrombocytopenia and impaired platelet function. In the present study, we evaluated the effect of nitric oxide on the ECLS-induced platelet consumption and activation.

METHODS

Two identical in vitro ECLS circuits were primed with fresh, heparin-treated human blood and circulated for 24 hours. Nitric oxide (15, 40, or 77 ppm) was added to one of the oxygenators in each pair. Eight paired experiments were performed. Platelet count, plasma beta-thromboglobulin, platelet serotonin content, plasma nitrate, plasma cyclic guanosine monophosphate, and platelet membrane glycoprotein Ib were assayed before the start and at 0.5, 1, 3, 12, and 24 hours of perfusion.

RESULTS

Plasma nitrate and plasma cyclic guanosine monophosphate levels were significantly higher in the nitric oxide circuits than in the control circuits (p < 0.01). Higher platelet counts (p < 0.01) and lower beta-thromboglobulin levels (p < 0.01) were observed in the nitric oxide circuits compared with the control circuits. However, no significant differences in platelet serotonin content or platelet membrane glycoprotein Ib density were noted between the circuits.

CONCLUSIONS

Nitric oxide probably reduces platelet consumption and platelet activation during ECLS.

Cleaved intracellular plasminogen activator inhibitor 2 in human myeloleukaemia cells is a marker of apoptosis

The proteolytic modification of plasminogen activator inhibitor 2 (PAI-2) was studied during apoptosis in the human promyelocytic leukaemic NB4 cell line during treatment with the phosphatase inhibitors okadaic acid and calyculin A as well as the protein synthesis inhibitor cycloheximide. The apoptic type of cell death was ascertained by morphological and biochemical criteria. In cell homogenates PAI-2 was probed by [125I]urokinase plasminogen activator (uPA) and detected as a sodium dodecyl sulphate-stable M(r) 80,000 complex after reducing sodium dodecyl sulphate-polyacrylamide gel electrophoresis and autoradiography. During apoptosis a smaller (M(r) 70,000) uPA-PAI-2 complex was consistently detected. The modification was in the PAI-2 moiety, as the [125I]uPA tracer could be extracted in its intact form from the complex. Thus the cleaved PAI-2 isoform is a biochemical marker of apoptosis in the promyelocytic NB4 cell line. The modified PAI-2 isoform was also detected in homogenates made from purified human mononuclear leukaemic cells aspirated from the bone marrow of patients suffering from acute and chronic myeloid leukaemia.

Tamoxifen administration and metabolism in nude mice and nude rats

We investigated the kinetics of tamoxifen (tam) in immunodeficient mice and rats after oral treatment and compared drug and metabolite profile in nude rat serum and tissues after oral and subcutaneous (s.c.) routes of administration. The serum levels were compared to those observed in man. After oral dosing in mice, tam and the potent metabolite 4-hydroxytamoxifen (4-hydroxytam), were detectable in liver and lung tissue, but not in serum. The levels of 4-hydroxytam in these tissues were significantly higher than those of tam, a profile opposite to that observed in rat and man. In rats and man, the 4-hydroxytam/tam serum concentration ratios were 0.16 and 0.02, respectively. Compared to oral route, the s.c. pellets yielded only trace amounts of the demethylated derivatives of tam in rats. Thus, the kinetics of tam observed in the present study suggest that the nude rat may represent a preferable animal model in studying the pharmacokinetics of tam and that, the oral route yielded higher serum and tissue levels of tam and metabolites than equivalent s.c. pellet implants.

Cyclic adenosine monophosphate acts synergistically with dexamethasone to inhibit the entrance of cultured adult rat hepatocytes into S-phase: with a note on the use of nucleolar and extranucleolar [3H]-thymidine labelling patterns to determine rapid changes in the rate of onset of DNA replication

Analogs of cyclic adenosine monophosphate (cAMP) (N6benzoyl cAMP and N6monobutyryl cAMP) as well as agents that increased the intracellular level of cAMP (glucagon and isobutylmethylxanthine) inhibited the EGF-stimulated DNA replication of adult rat hepatocytes in primary culture independently of cell density. This inhibition was strongly potentiated by the glucocorticoid dexamethasone. The effect of cAMP (and dexamethasone) was not due to toxicity, because the inhibition was reversible and the cell ultrastructure preserved. cAMP acted by decreasing the rate of transition from G1- to S-phase, the duration of G2- and S-phase of the hepatocyte cell cycle being unaffected. DNA replication started in the extranucleolar compartment of the nucleus and ended in the nucleolar compartment as described earlier for cells grown in the absence of cAMP (O.K. Vintermyr and S.O. Døskeland, J. Cell. Physiol., 1987, 132:12-21). The action of cAMP was very rapid: significant inhibition of the transition was noted 2 hr after the addition of glucagon/IBMX and half-maximal inhibition after 4 hours. The determination of extranucleolarly labelled nuclei in cells pulse-labelled with [3H]thymidine allowed precise analysis of rapid changes in the probability of transition from G1- to S-phase. The extranucleolar labelling index could also be determined in cells continuously exposed to [3H]thymidine.

Nuclear receptor co-activators and HER-2/neu are upregulated in breast cancer patients during neo-adjuvant treatment with aromatase inhibitors

BACKGROUND

Acquired resistance to endocrine therapy in breast cancer is poorly understood. Characterisation of the molecular response to aromatase inhibitors in breast cancer tissue may provide important information regarding development of oestrogen hypersensitivity.

METHODS

We examined the expression levels of nuclear receptor co-regulators, the orphan nuclear receptor liver receptor homologue-1 and HER-2/neu growth factor receptor using real-time RT-PCR before and after 13-16 weeks of primary medical treatment with the aromatase inhibitors anastrozole or letrozole.

RESULTS

mRNA expression of the steroid receptor co-activator 1 (SRC-1) and peroxisome-proliferator-activated receptor gamma co-activator-1alpha (PGC-1alpha) was correlated (P=0.002), and both co-activators increased during treatment in the patient group as a whole (P=0.008 and P=0.032, respectively), as well as in the subgroup of patients achieving an objective treatment response (P=0.002 and P=0.006). Although we recorded no significant change in SRC-3/amplified in breast cancer 1 level, the expression correlated positively to the change of SRC-1 (P=0.002). Notably, we recorded an increase in HER-2/neu levels during therapy in the total patient group (18 out of 26; P=0.016), but in particular among responders (15 out of 21; P=0.008).

CONCLUSION

Our results show an upregulation of co-activator mRNA and HER-2/neu during treatment with aromatase inhibitors. These mechanisms may represent an early adaption of the breast cancer cells to oestrogen deprivation in vivo.

Hepatocyte DNA replication is abolished by inhibitors selecting protein phosphatase 2A rather than phosphatase 1

Primary rat hepatocytes exposed to the phosphoprotein phosphatase (PP) inhibitors microcystin-LR and okadaic acid showed extensive surface protrusions and release of cell fragments, like cells in apoptosis. Microinjected microcystin fully reproduced these effects; the calculated intracellular concentration required for 50% effect being about 1 microM. The effects were counteracted by antagonists of calmodulin or of the multifunctional calmodulin-activated protein kinase II. The DNA replication of the epidermal growth factor-stimulated hepatocytes was nearly completely inhibited by okadaic acid at concentrations below those giving overt morphological effects. However, microcystin did not inhibit the DNA replication. Calmodulin antagonists counteracted the effect of okadaic acid on DNA replication. Microinjection of inhibitor-1 and inhibitor-2 (both directed against PP1) had no effect on DNA replication. Based on the known selectivity of okadaic acid for PP type 2A versus that of type 1, and the lack of such selectivity for microcystin, it is concluded that DNA replication is abolished by moderate inhibition of PP2A. Inhibition of PP1 did not impede DNA replication, suggesting that the two major liver phosphatases may have opposite roles in the regulation of hepatocyte DNA replication.

Cytokine release during long-term extracorporeal circulation in an experimental model

The objective of this study was to determine the degree of leukocyte activation, as measured by cytokine release, in circulating blood during experimental extracorporeal circulation. Complete in vitro extracorporeal membrane oxygenation (ECMO) circuits were used, and 9 experiments were performed. Whole blood stored at 37 degrees C was used as the control. Blood samples were withdrawn before the start of perfusion and at 24 h of perfusion. Statistically significant releases of interleukin (IL)-1beta, IL-8, and IL-1 receptor antagonist were observed in the perfusion circuits compared to both the control blood and baseline values. Also, increases in plasma tumor necrosis factor (TNF)alpha and IL-6 were seen after 24 h of perfusion although these changes did not reach statistical significance. These results indicate that extracorporeal circulation induced leukocyte activation and cytokine release. These reactions might, as an additional trauma, deteriorate the situation in an already severely ill patient. A search for methods to counteract this untoward activation seems warranted.

A child with a t(11;19)(q14-21;p12) in a pulmonary mucoepidermoid carcinoma

We report on a mucoepidermoid carcinoma (MEC) of the lung in a 6-year-old girl with a t(11;19)(q14-21;p12) as the sole karyotypic abnormality. An apparently identical t(11;19) has been reported previously in a MEC originating from the major and minor salivary glands. Our findings indicate that the t(11;19) is intimately associated with the mucoepidermoid phenotype and may be used as a diagnostic marker for this tumour type.

Extracorporeal membrane oxygenation as a bridge to definitive tracheal surgery in children

Extracorporeal membrane oxygenation was used as a bridge for three infants with complicated long segment congenital tracheal stenosis to tracheal homograft transplantation with cadaveric tracheal homograft and for one child, with an extensive traumatic tracheal laceration caused by aspiration of a sharp foreign body, to definitive tracheal repair. In all four cases mechanical ventilation was impossible and death almost certain without extracorporeal membrane oxygenation.

Okadaic acid, cAMP, and selected nutrients inhibit hepatocyte proliferation at different stages in G1: modulation of the cAMP effect by phosphatase inhibitors and nutrients

The protein phosphatase inhibitor okadaic acid (> 100 nM) caused an abrupt and complete cessation of primary rat hepatocyte cell cycle progression at the restriction point in late G1. A decline in the G1/S transition rate was observed in response to elevated cAMP, excess selected nutrients, and okadaic acid (< 100 nM). Excess nutrients (40 mM glucose +/- 5 mM dihydroxyacetone) acted by imposing an incomplete block in early G1. The cAMP action was potentiated by the phosphatase inhibitor microcystin, which in itself did not affect DNA replication. This suggests that cAMP acted by phosphorylating substrate(s) that is dephosphorylated by a microcystin-sensitive phosphatase. The additive effects of submaximal concentrations of okadaic acid and cAMP analogs indicated that okadaic acid and cAMP acted via different pathways. In conclusion, okadaic acid, cAMP, and excess nutrients, acting through distinct pathways, inhibited hepatocytes in different parts of the G1 phase.

Weight cycling promotes fat gain and altered clock gene expression in adipose tissue in C57BL/6J mice

Repeated attempts to lose weight by temporary dieting may result in weight cycling, eventually further gain of body fat, and possible metabolic adaptation. We tested this with a controlled experiment in C57BL/6J mice subjected to four weight cycles (WC), continuous hypercaloric feeding (HF), or low-fat feeding (LF). To search for genes involved in an adaptive mechanism to former weight cycling and avoid acute effects of the last cycle, the last hypercaloric feeding period was prolonged by an additional 2 wk before euthanization. Total energy intake was identical in WC and HF. However, compared with HF, the WC mice gained significantly more total body mass and fat mass and showed increased levels of circulating leptin and lipids in liver. Both the HF and WC groups showed increased adipocyte size and insulin resistance. Despite these effects, we also observed an interesting maintenance of circulating adiponectin and free fatty acid levels after WC, whereas changes in these parameters were observed in HF mice. Global gene expression was analyzed by microarrays. Weight-cycled mice were characterized by a downregulation of several clock genes (Dbp, Tef, Per1, Per2, Per3, and Nr1d2) in adipose tissues, which was confirmed by quantitative PCR. In 3T3-L1 cells, we found reduced expression of Dbp and Tef early in adipogenic differentiation, which was mediated via cAMP-dependent signaling. Our data suggest that clock genes in adipose tissue may play a role in metabolic adaptation to weight cycling.

Gap junctions and growth control in liver regeneration and in isolated rat hepatocytes

The hepatocytes in the mature normal liver are tightly coupled through gap junctions, except during compensatory hyperplasia (regeneration) after partial hepatectomy when the gap junctions become down-regulated. The significance of this down-regulation has been a long-standing enigma. The present study of hepatocytes in primary culture and in the regenerating liver aimed at defining the relationship, if any, between hepatocyte gap junctional communication and proliferation. Gap junctional down-regulation in the regenerating liver appeared to be a specific phenomenon because desmosomes and the surface contact area between neighboring hepatocytes remained constant. All agents and conditions (dexamethasone in vivo; dexamethasone, cyclic adenosine monophosphate, serum, and high cell density in vitro) delaying gap junctional down-regulation also increased the lag before the cells reached competence to enter S phase. This raised the possibility that hepatocyte DNA replication was inhibited through preservation of gap junctions. However, we disproved this assumption by showing that the DNA replication (more specifically the G1/S transition rate constant) was inhibited even in hepatocytes completely devoid of gap junctional communication. The teleological advantage of linking gap junctional down-regulation to hepatocyte G1 progression therefore may not be to trigger DNA replication but to ensure that proliferating hepatocytes and hepatocytes responsible for liver-specific metabolic functions maintain separate pools of metabolites and signaling molecules.

Transcriptional regulation of the bovine CYP17 gene by cAMP

The transcription of steroid hydroxylase genes is controlled by ACTH and cAMP in the adrenal cortex. In most instances the regulation appears to rely on transcription factors traditionally not associated with cAMP-dependent gene expression. For the non-traditional factors it remains necessary to elucidate the coupling of increases in intracellular cAMP and cAMP-dependent protein kinase (PKA) activity to the function of these proteins. The bovine CYP17 gene, which encodes the steroid 17 alpha-hydroxylase, contains two discrete DNA elements within its promoter and upstream region (CRS1 and CRS2) that individually can confer cAMP responsiveness. The CRS1 element is a target for PKA signalling and for negative regulation via the protein kinase C signal transduction pathway. The homeodomain protein Pbx1 enhances CRS1-dependent transcription, but additional CRS1-binding proteins remain to be identified. Furthermore it is not known how PKA regulates the activity of Pbx1 or its possible binding partners. Closer to the promoter, the nuclear orphan receptors SF-1 and COUP-TF have overlapping binding sites in CRS2 and they bind in a mutually exclusive manner with very similar affinities; 8 and 10 nM, respectively. SF-1 stimulates whereas COUP-TF inhibits transcription from the bovine CYP17 promoter. Together, the data suggest that cAMP-dependent control of the amounts of the activator SF-1 vs. the repressor COUP-TF could influence CRS2-dependent transcription. In addition, PKA may influence the phosphorylation of SF-1, thus increasing its activity. In vitro, PKA will elicit phosphorylation of SF-1. However, although SF-1 can be immunoprecipitated from adrenocortical cells as a phosphroprotein, we have not been able to show cAMP-dependent increase in net phosphorylation in intact cells. More careful examination of individual phosphorylation sites in SF-1 may still reveal hormone- and cAMP-induced phosphorylation of SF-1.

The effect of albumin priming solution on platelet activation during experimental long-term perfusion

The objective of this study was to evaluate the effect of albumin priming on platelet consumption and activation during long-term perfusion. Two identical in vitro extracorporeal membrane oxygenation circuits were used; one was primed with Ringer's solution containing human serum albumin, the other with Ringer's solution only. Fresh heparinized human blood was pooled, divided between the two systems and circulated for 24 h at 37 degrees C. Platelet count, plasma concentration of betathromboglobulin (BTG), platelet membrane density of glycoprotein (GP) Ib and of GPIIb/IIIa were assayed before the start and at 0.5, 1, 3, 12 and 24 h of perfusion. In total, seven experiments were performed. We found that during the first hour of perfusion, slightly higher platelet counts (p = 0.058) and lower BTG values (p = 0.0005) were observed in the circuits primed with albumin, compared to the control circuits. No statistically significant differences were observed for the platelet membrane expression of GPIb and GPIIb/IIIa. We conclude that albumin priming appears to transiently prevent platelet consumption and activation during long-term perfusion.

Effect of nitric oxide gas on platelets during open heart operations

BACKGROUND

The increased bleeding tendency observed after cardiopulmonary bypass is caused in part by thrombocytopenia and impaired platelet function induced by the procedure. Previous in vitro studies have shown that nitric oxide (NO) added to the oxygenator sweep gas reduces platelet activation during experimental perfusion. We evaluated the effect of 40 ppm of NO, added to the oxygenator sweep gas, on platelet consumption and activation in patients undergoing cardiopulmonary bypass.

METHODS

Twenty patients scheduled to undergo cardiopulmonary bypass were randomized to either the control or the NO arm of the study. Their platelet count, plasma beta-thromboglobulin level, platelet membrane glycoprotein Ib and IIb/IIIa levels, adenosine diphosphate-induced platelet aggregation, plasma nitrate level, and plasma hemoglobin were assayed before, during, and after cardiopulmonary bypass.

RESULTS

After operation, slightly higher platelet counts were observed in the NO-treated patients than in the control patients, which might indicate a lower degree of platelet adhesion to the artificial surfaces of the extracorporeal circuit. However, this difference did not reach statistical significance. In addition, a difference in platelet membrane expression of glycoprotein Ib was seen between the NO and control groups after operation; the platelets of the control patients had significantly higher glycoprotein Ib expression than those of the NO-treated patients. The results of platelet aggregometry indicated preserved platelet function in both the NO-treated and control patients. The blood methemoglobin levels also were low in both groups.

CONCLUSIONS

Nitric oxide might reduce the platelet consumption encountered during cardiopulmonary bypass without having any adverse effect on platelet function, as reflected by the preserved aggregation response seen in our patients. However, the best route of NO administration and the optimum dose remain to be established.

Metabolic substrates, muscle fibre composition and fibre size in late walking and normal children

In 10 children with delayed walking, muscle specimens were obtained by needle biopsy from the vastus lateralis muscle for determination of ATP, creatine phosphate (CP), glycogen and lactate concentration, as well as fibre composition and fibre size. The values obtained are compared with corresponding results for a control group of 25 children aged 2 months--11 years. Details of the control series are given and its validity as a reference group is discussed. Six children (group I) who showed minor gross motor delay but otherwise normal development at follow-up were found to have lowered ATP, CP and glycogen concentrations, compared to 4 children (group II) who had general developmental delay, and to the control group. The children in group I were shown to have smaller fibre size and a greater difference between type 1 and 2 fibres than the children in group II and in the control group. No differences in the concentrations of metabolic substrates or the morphometric values could be detected between group II and the control group.

Blood Platelet Activation and Membrane Glycoprotein Changes during Extracorporeal Life Support (Ecls). In Vitro Studies

The aim of this study was to evaluate an in vitro model for investigation of platelet function parameters in an extracorporeal system. Two different perfusion pumps were compared, a roller pump (Polystan) and a centrifugal pump (Biomedicus). A continuous increase in glycoprotein (GP)1b-negative platelets was observed in both circuits. A marked increase of plasma β-thromboglobulin thromboglobulin concentration and a decrease of the intracellular pool of serotonin was observed, indicating a marked release of alpha as well as of dense granules. The plasma concentration of glycocalicin increased in parallel with a reduced platelet surface expression of GP1b, suggesting that the loss of GP1b is caused by proteolysis rather than by a downregulation of this receptor protein. It is concluded that ECLS results in a pronounced platelet degranulation and causes changes of important membrane receptors which might explain some of the bleeding problems observed in patients treated with ECLS. No significant difference was noted between the roller pump and the centrifugal pump. Trial of strategies, e.g. protease inhibitors and nitric oxide to revert this untoward effect of ECLS are highly warranted.

Neonatal surgery for coarctation of the aorta. The Gothenburg experience

Thirty-four neonates (weights 0.97-4.47 kg) were operated on for coarctation of the aorta. They included five premature infants with birth weight less than or equal to 2.1 kg. All 34 were symptomatic, 31 severely so. Coarctation was "simple" in 12 cases and "complex" in 22; 12 with ventricular septal defect and 10 with more complex malformations. The mean age at operation was 11 days. Subclavian flap aortoplasty was used in 27 cases, a lusoric artery in two, and combined end-to-end anastomosis and flap repair in five. The main pulmonary artery was banded in 13 of the 22 complex coarctation syndromes. Absorbable suture was used in the last 22 cases. There was one early postoperative death. Serious ischaemic complications (bowel or limb gangrene) arose in four patients who were in severe heart failure preoperatively. During follow-up averaging 1.9 years there were two recurrences of coarctation. Resection with end-to-end anastomosis combined with subclavian flap aortoplasty when there is bulging ductal tissue or long, narrow isthmus and use of absorbable vascular suture may further lower the incidence of recurrent coarctation.

Influence of hemofiltration on plasma cytokine levels and platelet activation during extra corporeal membrane oxygenation

OBJECTIVE

Extra corporeal circulation of human blood is used daily in lifesaving procedures such as open-heart surgery and extracorporeal membrane oxygenation (ECMO). But extracorporeal circulation also induces activation of various cascade reactions in the blood. The objective of this study was to evaluate the effects of hemofiltration on cytokine release and removal as well as on platelet activation and consumption.

MATERIAL AND METHODS

Two complete ECMO systems, each of them holding a hollow fiber oxygenator, a bladder box, PVC tubing and a roller pump were perfused for 24 h with fresh, heparinized human blood. A hemofilter was added to one of the paired systems. Blood samples were collected from both circuits before start, and at 0.5, 1, 3, 12 and 24 h of perfusion. A total of 8 paired experiments was performed.

RESULTS

The plasma concentration of interleukin (IL)1beta, IL-6 and IL-8, as well as of IL-1 receptor antagonist (IL-1ra) increased over time in both systems, but consistently lower levels were observed in the filter circuits compared to the controls. Only minor parts of these cytokines could be assayed in the ultrafiltrate. No significant difference in platelet count and platelet membrane expression of glycoprotein Ib was observed between the circuits.

CONCLUSIONS

By adding a hemofilter to the ECMO circuit, it is possible to reduce the plasma concentration of interleukins without significantly affecting platelet activation and consumption.

Vitamin B6 status and interferon-γ-mediated immune activation in primary hyperparathyroidism

OBJECTIVES

Primary hyperparathyroidism (PHPT) has been associated with low-grade inflammation and elevated risk of cardiovascular disease (CVD). In inflammatory conditions, interferon-γ (IFN-γ) activity is enhanced and a decreased circulating concentration of vitamin B6 is often observed. Such changes in IFN-γ activity or vitamin B6 levels have been associated with increased incidence of CVD. The aim of the study was to investigate systemic markers of IFN-γ-mediated immune activation, such as neopterin, the kynurenine-to-tryptophan ratio (KTR) and kynurenine pathway metabolites, as well as B6 vitamers in patients with PHPT.

DESIGN/SUBJECTS

A total of 57 patients with PHPT and a control group of 20 healthy blood donors were included in this study. PHPT patients who responded positively to parathyroidectomy were followed for 6 months. Forty-three patients participated in the longitudinal study in which blood samples were taken at inclusion and 1, 3 and 6 months after surgery.

RESULTS

Plasma concentrations of the B6 vitamers pyridoxal 5'-phosphate (PLP) (P = 0.007) and pyridoxal (P = 0.013) were significantly lower in the patient group compared to healthy control subjects. An increase in the KTR indicated that the kynurenine pathway of tryptophan metabolism was altered in PHPT patients (P = 0.015). During the initial 6 months after surgery, levels of PLP (P < 0.001) and anthranilic acid (P < 0.001) increased significantly, whereas neopterin decreased (P = 0.018).

CONCLUSIONS

The results of this study demonstrate altered levels of vitamin B6 and the KTR in PHPT patients, both of which may reflect cellular immune activation. These abnormalities should be considered in relation to the increased risk of CVD previously observed in patients with PHPT.