Role of brain natriuretic peptide in cerebral vasospasm.

BACKGROUND: Brain natriuretic peptide (BNP) is a potent natriuretic factor responsible for hyponatremia observed in patients with SAH. Through its systemic effects (reduction of blood volume and blood pressure) BNP may augment cerebral blood flow reduction and ischemia secondary to vasospasm. The purpose of the present study was to evaluate the relationship between BNP plasma concentration during the first 12 days following SAH and the development of cerebral vasospasm (CVS). The authors propose a hypothesis for the role played by natriuretic peptides in the pathophysiology of cerebral vasospasm based on the present findings and review the literature. METHODS: Thirty eight patients with spontaneous SAH were prospectively included in the present study. BNP plasma concentrations were assessed at four different time periods following SAH (day 1-3, 4-6, 7-9, 10-12). TCD evidence of CVS was found in 26 patients (68.5%), fourteen patients (36.8%) had delayed ischemic neurological deficits (DIND). FINDINGS: Initial BNP plasma concentrations were significantly more elevated in patients who eventually did not develop DIND (95.07+/-107.65 pg/ml vs. 25.81+/-22.57 pg/ml, p=0.0053). However, in patients with DIND, the BNP plasma concentration increased by 3.69 ( p<0.05), 5.89 ( p<0.001) and 4.54 fold ( p<0.001) between days 1-3 to days 4-6, 7-9 and 10-12 respectively (day 1 was regarded as the day of hemorrhage). In patients without CVS or asymptomatic CVS the BNP plasma concentration decreased between days 1-3 to day 10-12. A similar trend in BNP plasma concentration was found in patients with severe SAH (Fisher's score 3-4) as compared with patients with non visible or moderate SAH (BNP concentration ratio day 7-9/1-3: 4.37 vs. 0.75, p=0.015; day 10-12/1-3: 3.37 vs. 0.3, p=0.0144). The trend in BNP plasma concentration between day 1-3 to day 7-9 was found to correlate with CVS severity with an average increase of 2.01, 3.8 and 5.44 fold for mild, moderate and severe VS respectively ( p<0.01, r=0.4174). INTERPRETATION: These results suggest that BNP secretion in SAH patients is closely related to the bleeding intensity and vasospasm severity as well as to development of DIND with a progressive and marked increase during the clinical course in patients who eventually develop cerebral ischemia. Taken together the local and systemic effects of BNP on CBF suggest that BNP might play a role in the pathophysiology of CVS through its systemic effects on blood pressure and plasma volume BNP leading to an aggravation of brain ischemia secondary to vasospasm.

Arbuscular mycorrhiza infection enhances the growth response of Lolium perenne to elevated atmospheric pCO(2).

Elevated atmospheric pCO(2) increases the C-availability for plants and thus leads to a comparable increase in plant biomass production and nutrient demand. Arbuscular mycorrhizal fungi (AMF) are considered to play an important role in the nutrient uptake of plants as well as to be a significant C-sink. Therefore, an increased colonization of plant roots by AMF is expected under elevated atmospheric pCO(2). To test these hypotheses, Lolium perenne L. plants were grown from seeds in a growth chamber in pots containing a silica sand/soil mixture for 9 weeks with and without inoculation with Glomus intraradices (Schenck and Smith). The growth response of plants at two different levels of N fertilization (1.5 or 4.5 mM) combined with ambient (35 Pa) and elevated atmospheric pCO(2) (60 Pa) was compared. The inoculation with G. intraradices, the elevated atmospheric pCO(2) and the high N fertilization treatment all led to an increased plant biomass production of 16%, 20% and 49%, respectively. AMF colonization and high N fertilization increased the plant growth response to elevated atmospheric pCO(2); the plant growth response to high N fertilization was also increased by AMF colonization. The root/shoot ratio was reduced by high N fertilization or elevated atmospheric pCO(2), but was not affected by AMF colonization. The unchanged specific leaf area indicated that if AMF colonization represented an increased C-sink, this was fully covered by the plant. Elevated atmospheric pCO(2) strongly increased AMF colonization (60%) while the high N fertilization had a slightly negative effect. AMF colonization neither improved the N nor P nutrition status, but led to an improved total P uptake. The results underline the importance of AMF for the response of grassland ecosystems to elevated atmospheric pCO(2).

Osteoporosis in murine systemic lupus erythematosus--a laboratory model.

The aim of this study was to assess the skeletal metabolism in a murine model of systemic lupus erythematosus (SLE). MRL/n and MRL/l mice (respectively representing a benign and a malignant form of the disease) were observed from 1.5 to 6.5 months of life. The monthly follow-up included: biochemical and histomorphometrical studies of the femoral bone, serum biochemistry, immunoglobulins and osteocalcin, and histological evaluation of the kidney tissue. The results showed a higher femoral weight (+11.5%), calcium (+4.4%) and protein bone content (+11.4%) and a significantly higher (+77%) phosphorus bone content in the MRL/n group; significantly lower (-48.9%) bone alkaline phosphatase enzymatic activity, lower bone alkaline/acid phosphatase enzymatic activities ratio (-40.8%) and lower (-38.4%) serum osteocalcin values in the MRL/l group (which might suggest reduced bone formation in these animals); markedly smaller trabecular bone volume (BV/TV) in the femoral head (-36.2%) and femoral neck (-39.8%), and smaller cortical and femoral areas in the mid-femoral shaft (-38.8% and -38.1% respectively) in the MRL/l group; higher serum immunoglobulins, increased serum blood urea nitrogen (BUN) and creatinine and a higher index of activity in the kidney histology in the MRL/l group, indicating increased activity of the disease in this substrain. The MRL mice, through their two substrains, may serve as a valuable laboratory animal model for study of the skeletal changes in SLE and of the influence of the disease activity on the skeletal metabolism.

Identification and characterization of trypanocides by functional expression of an adenosine transporter from Trypanosoma brucei in yeast.

The causative agents of sleeping sickness, Trypanosoma brucei rhodesiense and T. brucei gambiense, do not synthesize purines de novo but salvage purine bases and nucleosides from their hosts. We used yeast as an expression system for functional characterization of the trypanosomal adenosine transporter TbAT1. A selection of purine analogs and flavonoids were tested for their ability to interfere with adenosine transport, with the aims of identifying (a) trypanocidal TbAT1 substrates, and (b) inhibitors of trypanosomal purine transport. Cordycepin (3'-deoxyadenosine) was a TbAT1 substrate of high activity against T. brucei rhodesiense (IC50 0.2 nM). Inhibitors of mammalian nucleoside transport were not active, while the flavonol silibinin was a potent, noncompetitive inhibitor of TbAT1-mediated adenosine transport in yeast. Silibinin also inhibited melarsen-induced lysis of bloodstream form trypanosomes. IC50 values to T. brucei rhodesiense and to human carcinoma cells were 0.6 and 140 microM, respectively, indicating a good selectivity towards the parasites. Further studies are necessary to elucidate the effects of flavonoids on trypanosomal purine transport and their potential as trypanocides.

Novel quinone methides from Salacia kraussii with in vitro antimalarial activity.

Three novel quinone methides, i.e., 28-nor-isoiguesterin-17-carbaldehyde (1), 17-(methoxycarbonyl)-28-nor-isoiguesterin (2), and 28-hydroxyisoiguesterin (3), together with the known celastrol (5), pristimerin (6), and isoiguesterol (7), were isolated from the roots of Salacia kraussii (Celastraceae) by bioassay-guided fractionation. The structures of the compounds were determined by DEPT and 2D NMR techniques. The isolates showed antimalarial activity 30-50-fold greater than their cytotoxicity (in HT-29 cells) in vitro, and they showed an additive effect when combined with each other. In vivo, 2 was found to be inactive against blood stages of Plasmodium berghei in mice after oral and parenteral administration, and the compound was toxic with increasing concentrations.

The Alamar Blue assay to determine drug sensitivity of African trypanosomes (T.b. rhodesiense and T.b. gambiense) in vitro.

Alamar Blue, an indicator for metabolic cell function, was evaluated as a fluorescent and as a colorimetric dye in drug sensitivity assays for human pathogenic African trypanosomes, Trypanosoma brucei rhodesiense and T.b. gambiense. The experimental conditions were adjusted to find those where the relationship between trypanosome number and Alamar Blue signal was linear over the widest possible range. Fluorescent signals correlated to trypanosome numbers from 10(4) trypanosomes/ml (T.b. rhodesiense) and 10(5) trypanosomes/ml (T.b. gambiense) up to 2-3 x 10(6) trypanosomes/ml when trypanosomes were incubated for 2 h with 10% Alamar Blue. Trypanocidal activity of common drugs (melarsoprol, DFMO, suramin, pentamidine and diminazene aceturate) was determined employing this assay. The IC50 values obtained were comparable to those obtained with another fluorochrome, BCECF-AM. The Alamar Blue assay can be applied for drug screening, since it is simple, reproducible and economical. The assay can also be used in field sites with less equipped laboratories, because in addition to fluorometric endpoint determination, a colorimetric reading is possible.

Expression and role in growth regulation of tumour necrosis factor receptors p55 and p75 in acute myeloblastic leukaemia cells.

Tumour necrosis factor (TNF)-alpha exerts multiple effects on human acute myeloblastic leukaemia (AML) cells in vitro, including (1) synergistic stimulation of proliferation with interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF); (2) inhibition of granulocyte-CSF (G-CSF) and stem cell factor (SCF)-induced growth; (3) suppression of multiplication of clonogenic leukaemic cells; (4) induction of autocrine growth. Recently, two distinct TNF receptors (TNF-Rs), TNF-Rp55 and TNF-Rp75, have been identified. In this study we show that both receptors are expressed on freshly isolated AML blasts, with p75 being the predominant TNF-receptor type. This study investigates the roles of these two receptors in TNF-alpha-driven growth regulation of AML blasts in vitro. Using a receptor-specific antibody, it is shown that both receptor types participate in TNF-alpha-mediated stimulation of GM-CSF/IL-3-induced proliferation and in TNF-alpha-induced autocrine growth. In contrast, the TNF-alpha-triggered growth inhibition (antiproliferation) and the potent suppression of G-CSF- and SCF-induced proliferation exclusively result from activation of TNF-Rp55. Taken together, these results suggest that the proliferative effects of TNF-alpha on AML blasts are mediated through both p55 and p75 TNF receptors, whereas the TNF-alpha-signalled growth inhibition is exclusively transduced via TNF-Rp55.

Respective effects of soluble interleukin-1 receptor and tumour necrosis factor receptor on IL-1 and TNF-alpha-induced DNA synthesis of common acute lymphoblastic leukaemia blasts in vitro.

This study investigates the capacity of human recombinant interleukin-1 alpha (IL-1 alpha), IL-1 beta and tumour necrosis factor-alpha (TNF-alpha) to induce DNA synthesis of highly purified blasts from nine adult common acute lymphoblastic leukaemias (cALL) in 7 d liquid culture. IL-1 alpha, IL-1 beta and TNF-alpha stimulated 3H-TdR uptake in leukaemic blasts in a dose-dependent fashion. The IL-1-induced DNA synthesis of cALL cells could not be prevented by the addition of neutralizing antibodies against IL-3, GM-CSF, IL-6 or TNF-alpha. Similarly, the TNF-alpha-stimulated 3H-TdR incorporation of leukaemic blasts was not affected by the addition of antibodies towards IL-1 alpha, IL-1 beta, IL-3, GM-CSF or IL-6. These observations suggest that IL-1 as well as TNF-alpha stimulated growth could not be attributed to the endogenous production of factors, corresponding to the antibodies used in these experiments. Both IL-1 as well as TNF-alpha mediate their action through interaction with specific cell surface receptors. Recently two distinct types of IL-1 receptors (IL-1-Rs), IL-1R(p80) and IL-1-R(p65), as well as two distinct types of TNF-receptors (TNF-Rs), TNF-R (p55) and TNF-R (p75) have been identified. Both types of TNF-Rs exist also in soluble forms (sTNF-Rs), while soluble IL-1-Rs (sIL-1-Rs) have not yet been found naturally. In this study we show that sIL-1-R as well as sTNF-R modulate the effects of their corresponding cytokine in a dose-dependent bimodal fashion; at lower concentrations they augmented while at higher concentrations they inhibited the cytokine-stimulated DNA synthesis of cALL blasts in vitro. It may therefore be concluded from this study that soluble receptors for both IL-1 and TNF, at least in vitro, are functional and interfere with their corresponding cytokine bioactivity.

Cyclic nucleotide levels in human breast cancer and in rat mammary tissues during tumor development.

The levels of cyclic adenosine 3':5'-monophosphate (cAMP) and cyclic guanosine 3':5'-monophosphate (cGMP) were studied in dimethylbenz(a)anthracene (DMBA)-induced mammary tumors of Sprague-Dawley rats and in human breast cancer. In the rat carcinomas, these levels were significantly lower than in non-malignant tissues when calculated on the basis of DNA content, but higher (cAMP) or equal (cGMP) when calculated on the basis of weight. In human breast cancer the cyclic nucleotide levels were higher than in non-malignant tissues according to both methods of calculation. No correlation was found in human carcinomas between the cyclic nucleotide levels and mitotic index, nuclear grade, tumor size, or lymph node involvement. The rat tumors were subclassified according to state of differentiation, mitotic index, and state of development. Not all the sub-groups had cAMP levels different from normal values. Differences in cAMP levels between the sub-groups could not be correlated with tumor growth rates and/or mitotic index. Thus, cyclic nucleotides may not be useful in prognosis of breast cancer.