Tetrahydrobiopterin increases myocardial blood flow in healthy volunteers: a double-blind, placebo-controlled study

OBJECTIVES

Tetrahydrobiopterin (BH4) is a regulatory cofactor for the activity of nitric oxide synthases. Vasodilating properties of BH4 have been reported in vitro and in vivo. The influence of BH4 on myocardial blood flow (MBF), however, is largely unknown. We therefore performed a double-blind, placebo-controlled study to investigate the effect of intravenous BH4 on MBF in healthy volunteers.

METHODS AND RESULTS

Resting MBF was assessed in 15 subjects receiving either intravenous BH4 (10 mg/kg) or placebo using positron emission tomography (PET) and [13N]ammonia. From a mean baseline MBF of 0.91 +/- 0.09 ml/min/g, MBF increased to 1.18 +/- 0.10 ml/min/g after BH4 (n = 10; p = 0.0042). In contrast, in the group receiving placebo mean MBF remained unchanged (non-significant decrease from 0.97 +/- 0.19 to 0.84 +/- 0.11 ml/min/g; n = 5; p = 0.36). Systemic haemodynamics and ECGs remained unaffected in both groups. BH4 was very well tolerated.

CONCLUSION

Systemically administered BH4 is safe and effectively increases resting MBF in healthy volunteers.

Tetrahydrobiopterin increases myocardial blood flow in healthy volunteers: a double-blind, placebo-controlled study

OBJECTIVES

Tetrahydrobiopterin (BH4) is a regulatory cofactor for the activity of nitric oxide synthases. Vasodilating properties of BH4 have been reported in vitro and in vivo. The influence of BH4 on myocardial blood flow (MBF), however, is largely unknown. We therefore performed a double-blind, placebo-controlled study to investigate the effect of intravenous BH4 on MBF in healthy volunteers.

METHODS AND RESULTS

Resting MBF was assessed in 15 subjects receiving either intravenous BH4 (10 mg/kg) or placebo using positron emission tomography (PET) and [13N]ammonia. From a mean baseline MBF of 0.91 +/- 0.09 ml/min/g, MBF increased to 1.18 +/- 0.10 ml/min/g after BH4 (n = 10; p = 0.0042). In contrast, in the group receiving placebo mean MBF remained unchanged (non-significant decrease from 0.97 +/- 0.19 to 0.84 +/- 0.11 ml/min/g; n = 5; p = 0.36). Systemic haemodynamics and ECGs remained unaffected in both groups. BH4 was very well tolerated.

CONCLUSION

Systemically administered BH4 is safe and effectively increases resting MBF in healthy volunteers.

Influence of D- and L-glucose on erythrocytes and blood viscosity

BACKGROUND

Elevated blood glucose levels are associated with substantial morbidity and mortality. The pathomechanism behind it is not well understood. The aim of the present study was to investigate the effect of glucose on blood rheology.

MATERIALS AND METHODS

Blood from healthy volunteers was incubated with various concentrations of D- and L-glucose for 1 h at 37 degrees C. Whole blood viscosity at haematocrit 45% was measured at high and low shear rate (94.5 and 0.1 s(-1)). Erythrocyte shape and volume were assessed. Haemoglobin solutions were incubated with D-glucose for up to 96 h and the viscosity was measured.

RESULTS

D-glucose dissolved in H2O and diluted with isotonic NaCl, added to whole blood (additional D-glucose concentrations 0-80 mM), led to a red cell swelling and an increase in blood viscosity at low shear rate (0.1 s(-1)). This process was reversible upon removal of D-glucose. L-glucose, which is not transported into the red cell by the D-glucose-specific transport protein GLUT-1, had no effect. When D-glucose was dissolved and diluted in autologous plasma, haematocrit and viscosity remained unaffected, but L-glucose decreased both values. Incubation of a haemoglobin solution with D-glucose at 37 degrees C led to a time-dependent increase in glycosylated haemoglobin (HbA1C) up to 8%, but left the viscosity unchanged.

CONCLUSION

Blood glucose tested in a wide range of concentrations did not affect blood viscosity and morphological or biophysical properties of erythrocytes.

Geographic pattern of genetic variation in Pinus resinosa: area of greatest diversity is not the origin of postglacial populations

Genetic diversity is low in natural populations of red pine, Pinus resinosa, a species that has a vast range across north-eastern North America. In this study, we examined 10 chloroplast microsatellite or simple sequence repeats (cpSSR) loci in 136 individuals from 10 widespread populations. Substantial variation for the cpSSR loci was observed in the study populations. The contrast with red pine's lack of variation for other types of loci is likely to be due to the higher mutation rates typical of SSR loci. The amount of variation is lower than that generally found for cpSSR loci in other pine species. In addition, the variation exhibits a striking geographical pattern. Most of the genetic diversity is among populations, with little within populations, indicating substantial isolation of and genetic drift within many populations in the southern half of the species distribution. The greatest diversity now occurs in the north-eastern part of New England, which is especially intriguing because this entire area was glaciated. Thus the centre of diversity cannot be the origin of postglacial populations, rather it is likely caused by admixture, most probably because of influences from two separate refugia. Furthermore, the pattern indicates that the spread of red pine since the last glaciation is rather more complex than usually described, and it likely includes more than one refugia, complex migration routes, and postglacial-retreat isolation and genetic drift among shrinking populations in regions of the present southern range.

[Reactivation of herpes virus infections by vaccination: evidence or coincidence?]

Varicella zoster and herpes simplex viruses cause latent infections by persisting in human cells. Reactivation has been associated with increasing age, immunosuppression, cancer, stress, fever, exposure to ultraviolet light, and tissue damage. Based on three cases reported to the Swiss Drug Monitoring Centre SANZ, we postulated previously that vaccinations may trigger reactivation of herpes virus infections due to vaccine-induced immunomodulation. In the meantime, 10 new cases of reactivated herpes virus infections soon after vaccinations have been reported. They involved 5 women and 5 men with an age range between 16 and 60. In only one case had a trauma preceded, otherwise healthy subjects with no known relevant comorbidity were vaccinated. The clustering of reports after publication points to a previous underreporting of similar cases. This may be explained by the fact that both vaccinations and reactivations of herpes virus infections are frequent, and a causal link is not suspected. However, these new cases do not prove causality, and extensive epidemiological or experimental studies are needed to elucidate the possible link between vaccination and reactivation of herpes virus infections.

Increased expression of mature cathepsin B in aging rat liver

Senescence has been proposed as an important safeguard against neoplasia. One of the hallmarks of cellular senescence in vitro as well as human aging in vivo is a reduced intracellular protein catabolism. The pathways affected and the mechanisms responsible for the decrease in overall protein turnover in aging cells are not well understood. Our aim was to determine whether or not expression of one of the major hepatic lysosomal cysteine peptidases, cathepsin B, changes during aging of Sprague-Dawley rats. Cathepsin B activity was assessed in whole rat liver homogenates, and was found to be increased fourfold (P< or =0.001) in aged livers compared with younger counterparts. This was paralleled by an at least a twofold increase in mature cathepsin B protein. Nonetheless, Northern blot analysis of total liver RNA revealed no change in steady-state levels of cathepsin B mRNAs. These findings seem to contradict the present dogma according to which aging tissues have a reduced intracellular capacity to catabolise proteins. We propose that our earlier observation of the accumulation of T-kininogen, a potent but reversible cysteine peptidase inhibitor, in aging rat liver may provide a plausible explanation for this discrepancy.

Modulation of the ERK pathway of signal transduction by cysteine proteinase inhibitors

Cell proliferation requires the coordinate synthesis and degradation of many proteins. In addition to the well-characterized involvement of the proteasome in the degradation of several cell cycle-regulated proteins, it has been established that cysteine proteinases are also involved in the control of cell proliferation, but their role is currently not understood. By using both synthetic cysteine proteinase inhibitors and overexpression of T-kininogen (T-KG), a physiologically relevant cysteine proteinase inhibitor, we show that inhibition of cysteine proteinases results in a severe inhibition of the ERK pathway of signal transduction. Mechanistically, this effect appears to be the result of stabilization of the ERK phosphatase MKP-1, which leads to an enhanced dephosphorylation (and hence inactivation) of ERK molecules. These results are specific to cysteine proteinase inhibitors and are not observed when either serine proteinases or the proteasome are inhibited. We hypothesize that inhibition of cysteine proteinases in vivo leads to a dysregulation of the ERK pathway, which results in an inability of the cell to transmit to the nucleus the signals generated by the presence of growth factors, thus resulting in loss of cell proliferation.

Enhanced transcription of the s-adenosylhomocysteine hydrolase gene precedes Epstein-Barr virus lytic gene activation in ganglioside-stimulated lymphoma cells

Stimulation of Epstein-Barr virus (EBV) genome-positive Burkitt lymphoma cells with the ganglioside IV3NeuAc-nLcOse4Cer leads to the induction of cell differentiation processes and activates the EBV lytic viral cycle. In cells of the Burkitt lymphoma line Raji differential expression of host cell genes was analysed in the early phase (150 min) post stimulation with the ganglioside to display the cell activities that precede the activation of the EBV lytic cycle using the differential display reverse transcription-polymerase chain reaction technique. Multiple fragment cDNAs derived from control cells and ganglioside-stimulated cells were amplified using random primers and displayed via polyacrylamide gel electrophoresis. The expression pattern of 8,400 bands was analysed. Eleven differentially expressed fragment cDNAs were reamplified and identified by nucleotide sequencing. Six of these could be identified as coding for proteins that may take part in virus reactivation and differentiation. The most striking finding was the induction of s-adenosylhomocysteine hydrolase (AHCY) expression. The cellular enzyme AHCY plays an important role in transmethylation reactions controlling the replication of several viruses. Thus. an involvement in EBV replication can be suggested.

Environmental and genetic risk factors and gene-environment interactions in the pathogenesis of chronic obstructive lung disease

Current understanding of the pathogenesis of chronic obstructive pulmonary disease (COPD), a source of substantial morbidity and mortality in the United States, suggests that chronic inflammation leads to the airways obstruction and parenchymal destruction that characterize this condition. Environmental factors, especially tobacco smoke exposure, are known to accelerate longitudinal decline of lung function, and there is substantial evidence that upregulation of inflammatory pathways plays a vital role in this process. Genetic regulation of both inflammatory responses and anti-inflammatory protective mechanisms likely underlies the heritability of COPD observed in family studies. In alpha-1 protease inhibitor deficiency, the only genetic disorder known to cause COPD, lack of inhibition of elastase activity, results in the parenchymal destruction of emphysema. Other genetic polymorphisms have been hypothesized to alter the risk of COPD but have not been established as causes of this condition. It is likely that multiple genetic factors interacting with each other and with a number of environmental agents will be found to result in the development of COPD.

Establishment and characterization of an arsenic-sensitive monoblastic leukaemia cell line (SigM5)

Few human monoblastic cell lines have been characterized to date. We have established the SigM5 cell line from a patient with acute monoblastic leukaemia (FAB M5a). Original leukaemic cells had a karyotype of 47,XY,+8, whereas the cell line showed a stemline clone of 81,XX,Y,Y,1,4,6,7,+8,+8,9,10,10,11,13,16,19[cp], with a minor sideline also present. Cytochemical staining was strongly positive with alpha-naphthylbutyrate acetate esterase, particulate positive with Sudan black and weakly positive for myeloperoxidase. Cells were positive for CD13, CD15, CD18, CD23, CD33, CD38, CD45, CD68 and myeloperoxidase. CD14 expression was 3-15%. SigM5 constitutively secreted interleukin (IL)-2, IL-8, IL-10, tumour necrosis factor (TNF)-alpha, ferritin, lysozyme, N-elastase and neopterin upon stimulation with interferon (IFN)-gamma. Cells expressed the proinflammatory mediator macrophage migration inhibitory factor (MIF). All NADPH oxidase subunits were constitutively present, but nitroblue tetrazolium reduction was only detectable upon activation with IFN-gamma. SigM5 monoblasts were sensitive to arsenic trioxide (As2O3) previously not described to induce apoptosis in monoblastic cells. Differing considerably in morphology, immunophenotype and sensitivity to arsenics from the widely used cell lines U937, HL-60 and THP-1, SigM5 is a new monoblastic cell line useful for studying leukaemogenesis, monocyte differentiation and tumour cell susceptibility to arsenic compounds.

Hypocaloric parenteral nutrition support in elderly obese patients

Hypocaloric nutritional support has been successfully used to achieve positive nitrogen balance in obese patients. However, advanced age is associated with changes in substrate metabolism. To evaluate the efficacy of this practice in elderly patients, we retrospectively reviewed 30 obese patients requiring parenteral nutrition support. Total caloric requirements (TCR) were calculated on the basis of the Harris-Benedict equation. Patients were given a minimum of 1.5 g/kg/day protein, 75 per cent of TCR when current body weight was >120 and < or =150 per cent of ideal body weight (IBW), and 60 per cent of TCR if current body weight was >150 per cent of IBW. The patients were divided into two groups: Group I (N = 18) patients were age <60 and Group II (N = 12) patients were > or =60 years of age. Only one of the Group I patients (143.2 +/- 25.7% IBW, received 18.2 +/- 3.7 kcal/kg/day and 1.6 +/- 0.4 g/kg/day protein), but five of the Group II patients (141.3 +/- 14.4% IBW, received 18.3 +/- 2.6 kcal/kg/day and 1.7 +/- 0.3 g/kg/day protein), had negative nitrogen balance (P = 0.025). Apparently, elderly obese patients have limited capacity to mobilize their fat stores as energy sources and may continue to undergo protein catabolism with hypocaloric high-protein nutrition support. Therefore, this form of nutritional support should be used with caution in elderly obese patients.

Influence of parathyroid hormone, calcitonin, 1,25(OH)2 cholecalciferol, calcium, and the calcium ionophore A23187 on erythrocyte morphology and blood viscosity

Parathyroid hormone and calcitonin, both endocrine modulators of calcium homeostasis, may influence blood rheology. Parathyroid hormone is known to reduce erythrocyte survival, leading to anemia. Calcitonin has been found to have some vascular effects. We have analyzed the Influence of parathyroid hormone (10(-7) to 10(-10) mol/L), calcitonin (10(-6) to 10(-12) mol/L), 1,25(OH)2 cholecalciferol (10(-7) to 10(-10) mol/L), additional calcium in plasma (+1 and 2 mmol/L), and the calcium lonophore A23187 (50 micromol/L) on erythrocyte morphology and blood viscosity at high shear rate (94 s(-1)) and low shear rate (0.1 s(-1)) in vitro. The loading of erythrocytes with calcium by the ionophore A23187 produced a marked echinocytic shape transformation, an increased blood viscosity at high shear rate caused by decreased deformability of these cells, and a decreased viscosity at low shear rate caused by decreased aggregation of echinocytes. In contrast, increasing plasma calcium concentrations, parathyroid hormone, calcitonin, and 1,25(OH)2 vitamin D3 had no effect on erythrocyte morphology and blood viscosity. We conclude that an increase in intraerythrocytic calcium leads to severe echinocytosis and altered blood viscosity. The endocrine modulators of calcium homeostasis--namely, parathyroid hormone, calcitonin, and 1,25(OH)2 vitamin D3--apparently do not influence intraerythrocytic calcium to a significant degree and have, therefore, no influence on cell morphology and blood viscosity.

An Experience of Peer Mentoring with Student Nurses: Enhancement of Personal and Professional Growth

This article discusses the importance of peer mentoring in nursing education. The current literature is reviewed and areas for further research are identified. Most specifically, the article explores the results of a recent research study conducted at Southern Cross University in Australia. The research investigated the relationship between personal and professional growth and peer mentoring with a group of women nurses. Seven nurses participated in this qualitative research project. Six of the participants were student nurses enrolled in an undergraduate nursing degree and the seventh participant was the degree program coordinator. The research was conducted over a 12-week period and was located in critical paradigm. The research methods used were reflective journaling and interviewing. The results indicated that the process of peer mentoring in nursing education demonstrated a strong relationship to personal and professional growth for all of the participants. Characteristics of the peer mentoring process such as shared learning, shared caring, reciprocity, commitment to each other's personal and professional growth, and friendship, are discussed.

Pharmacological concentrations of arginine influence human whole blood viscosity independent of nitric oxide synthase activity in vitro

l-Arginine, the natural precursor of NO, is infused in patients to restore endothelial function. Concentrations up to 7.5 mM l-arginine have been measured after parenteral administration. We investigated whether such high concentrations of amino acids influence blood viscosity in vitro. Incubation of whole blood from healthy volunteers with l-arginine, d-arginine, which has no effect on stereospecific NO synthases (NOS), the NOS substrate L-AME, the NOS inhibitor L-NNA, the amino acids l-lysine and l-glutamic acid, and finally NaCl dose-dependently decreased (up to 30% at 10(-2) M) low shear viscosity, which is primarily determined by erythrocyte aggregation. In contrast, the lipophilic NOS inhibitor L-NAME had no effect on low shear viscosity. All molecules failed to influence high shear viscosity, which is primarily determined by red cell deformability, and the erythrocyte shape remained unaltered. We conclude that high concentrations amino acids may decrease blood viscosity at low shear rate independent of NOS activity. This effect may contribute to the improved blood flow after intravascular administration of l-arginine.

Impaired signal transduction in mitogen activated rat splenic lymphocytes during aging

Mitogen activated protein kinases (MAPK) are activated by a wide variety of signals leading to cell proliferation and differentiation in different cell types. With aging, there is a marked decrease in proliferation of T-lymphocytes in response to a variety of mitogens. Several age-related changes in the activation of MAPK pathways in T-lymphocytes activated via the T-cell receptor (TCR) have been described in different species. This way, some TCR proximal defects in tyrosine kinase activity have been delineated. In this study, we have used rat splenic lymphocytes to measure the effect of aging on the activation of two MAP kinase families: ERK and JNK. In order to bypass the receptor-proximal age-dependent defects previously described, we used phorbol ester (PMA) and Ca2+ ionophore (A23187) as co-mitogens. Our results demonstrate that splenic lymphocytes from old rats have a disturbance in the activation of the ERK and JNK MAPK signal transduction pathways, that are located downstream of the receptor-proximal events. At least part of the age-related defect leading to decreased ERK activity appears to be located upstream of ERK itself, since activation of MEK is also impaired. On the other hand, the observed defects in MAPK activation do result in decreased activation of downstream events, such as c-Jun phosphorylation. Thus, we conclude that aging of splenic lymphocytes results in a functional decline in signal transduction, and at least some of these defects are located downstream of the receptor-proximal events previously described by others. The impaired activity of these two MAP kinase pathways is likely to play a role in the diminished lymphoproliferation observed in old individuals.

The nitric oxide synthase cofactor tetrahydrobiopterin reduces allograft ischemia-reperfusion injury after lung transplantation

OBJECTIVE

Exogenous nitric oxide reduces ischemia-reperfusion injury after solid organ transplantation. Tetrahydrobiopterin, an essential cofactor for nitric oxide synthases, may restore impaired endothelium-dependent nitric oxide synthesis. We evaluated whether tetrahydrobiopterin administration to the recipient attenuates lung reperfusion injury after transplantation in swine.

METHODS

Unilateral left lung transplantation was performed in 15 weight-matched pigs (24-31 kg). Donor lungs were flushed with 1.5 L cold (1 degrees C) low-potassium-dextran solution and preserved for 20 hours. Group I animals served as controls. Group II and III animals were treated with a bolus of tetrahydrobiopterin (20 mg/kg). In addition, in group III a continuous infusion of tetrahydrobiopterin (10 mg/kg per hour over 5 hours) was given. One hour after reperfusion, the recipient right lung was occluded. Cyclic guanosine monophosphate levels were measured in the pulmonary venous and central venous blood. Extravascular lung water index, hemodynamic variables, lipid peroxidation, and neutrophil migration to the allograft were assessed.

RESULTS

In group III a significant reduction of extravascular lung water was noted in comparison with the controls (P =.0047). Lipid peroxidation in lung allograft tissue was significantly reduced in group II (P =.0021) and group III ( P =. 0077) in comparison with group I. Pulmonary venous levels of cyclic guanosine monophosphate increased up to 23 +/- 1 pmol/mL at 5 hours in group II and up to 40 +/- 1 pmol/mL in group III (group I, 4.1 +/- 0.5 pmol/mL [I vs III]; P <.001), whereas central venous levels of cyclic guanosine monophosphate were unchanged in all groups.

CONCLUSION

Tetrahydrobiopterin administration during lung allograft reperfusion may reduce posttransplantation lung edema and oxygen-derived free radical injury in the graft. This effect is mediated by local enhancement of the nitric oxide/cyclic guanosine monophosphate pathway.

A membrane-located glycosphingolipid of monocyte/granulocyte lineage cells induces growth arrest and triggers the lytic viral cycle in Epstein-Barr virus genome-positive Burkitt lymphoma lines

Gangliosides are known to influence cell growth and differentiation. The neolacto series ganglioside IV3NeuAc-nLc4 (2-->3-sialosylparagloboside) is present in members of the monocyte/granulocyte lineage, but is not found in cells that belong to the lymphocyte lineage. In this study we demonstrated that IV3NeuAc-nLc4 inhibits the proliferation of Epstein-Barr virus (EBV) genome-positive Burkitt lymphoma cells of the lines Raji and P3HR-1K. IV3NeuAc-nLc4-induced growth inhibition is associated with an increase in G0/G1 phase cells and a reduced expression of CD21 and HLA-DR antigens on Raji cells. These data suggest that IV3NeuAc-nLc4 may affect differentiation of lymphoma cells. Additionally, the increased expression of viral mRNA species which are characteristic for the lytic viral cycle in the non-producer line Raji and the enhanced release of virions from the producer line P3HR-1K demonstrate that IV3NeuAc-nLc4 activates the replication of EBV. Growth inhibition and termination of the viral latency suggest that IV3NeuAc-nLc4 present in monocyte/granulocyte lineage cells may be an effector of the natural defense against EBV persistency and transformation.

Mosquito cathepsin B-like protease involved in embryonic degradation of vitellin is produced as a latent extraovarian precursor

Here we report identification of a novel member of the thiol protease superfamily in the yellow fever mosquito, Aedes aegypti. It is synthesized and secreted as a latent proenzyme in a sex-, stage-, and tissue-specific manner by the fat body, an insect metabolic tissue, of female mosquitoes during vitellogenesis in response to blood feeding. The secreted, hemolymph form of the enzyme is a large molecule, likely a hexamer, consisting of 44-kDa subunits. The deduced amino acid sequence of this 44-kDa precursor shares high similarity with cathepsin B but not with other mammalian cathepsins. We have named this mosquito enzyme vitellogenic cathepsin B (VCB). VCB decreases to 42 kDa after internalization by oocytes. In mature yolk bodies, VCB is located in the matrix surrounding the crystalline yolk protein, vitellin. At the onset of embryogenesis, VCB is further processed to 33 kDa. The embryo extract containing the 33-kDa VCB is active toward benzoyloxycarbonyl-Arg-Arg-para-nitroanilide, a cathepsin B-specific substrate, and degrades vitellogenin, the vitellin precursor. Both of these enzymatic activities are prevented by trans-epoxysuccinyl-L-leucylamido-(4-guanidino)butane (E-64), a thiol protease inhibitor. Furthermore, addition of the anti-VCB antibody to the embryonic extract prevented cleavage of vitellogenin, strongly indicating that the activated VCB is involved in embryonic degradation of vitellin.

Primary pleomorphic adenoma of the external auditory canal diagnosed by fine needle aspiration cytology. A case report

BACKGROUND

Pleomorphic adenoma (PA) arising in the external auditory canal (EAC) is a very rare neoplasm, thought to be derived from ceruminous glands.

CASE

A 43-year-old male presented with a slowly growing mass in the right EAC. Clinical and radiologic examinations showed a well-circumscribed tumor limited to the EAC, without a connection to the parotid gland. Fine needle aspiration cytology (FNAC) revealed the typical cytologic findings of PA. The diagnosis was confirmed by histologic examination.

CONCLUSION

This case illustrates that together with clinical and radiologic findings, primary PA of the EAC can confidently be diagnosed by FNAC.