FeS2 nanosheets–luminol–O2 chemiluminescence method for determination of venlafaxine hydrochloride,imipramine hydrochloride,and cefazolin sodium

This study introduces a novel chemiluminescence (CL) approach utilizing FeS₂ nanosheets (NSs) catalyzed luminol–O₂ CL reaction for the measurement of three pharmaceuticals, namely venlafaxine hydrochloride (VFX), imipramine hydrochloride (IPM), and cefazolin sodium (CEF). The CL method involved the phenomenon of quenching induced by the pharmaceuticals in the CL reaction. To achieve the most quenching efficacy of the pharmaceuticals in the CL reaction, the concentrations of reactants comprising luminol, NaOH, and FeS₂ NSs were optimized accordingly. The calibration curves demonstrated exceptional linearity within the concentration range spanning from 4.00 × 10⁻⁷ to 1.00 × 10⁻³ mol L⁻¹, 1.00 × 10⁻⁷ to 1.00 × 10⁻⁴ mol L⁻¹, and 4.00 × 10⁻⁶ to 2.00 × 10⁻⁴ mol L⁻¹ with detection limits (3σ) of 3.54 × 10⁻⁷, 1.08 × 10⁻⁸, and 2.63 × 10⁻⁶ mol L⁻¹ for VFX, IPM, and CEF, respectively. This study synthesized FeS₂ NSs using a facile hydrothermal approach, and then the synthesized FeS₂ NSs were subjected to a comprehensive characterization using a range of spectroscopic methods. The proposed CL method was effective in measuring the aforementioned pharmaceuticals in pharmaceutical formulations as well as different water samples. The mechanism of the CL system has been elucidated.     

Determination of pioglitazone hydrochloride by flow injection chemiluminescence tris(2,2′-bipyridyl)ruthenium(II)–silver(III) complex system

A novel flow injection-chemiluminescence (FI–CL) approach is proposed for the assay of pioglitazone hydrochloride (PG-HCl) based on its enhancing influence on the tris(2,2′-bipyridyl)ruthenium(II)–silver(III) complex (Ru(bipy)₃²⁺-DPA) CL system in sulfuric acid medium. The possible CL reaction mechanism is discussed with CL and ultraviolet (UV) spectra. The optimum experimental conditions were found as: Ru(bipy)₃²⁺, 5.0 × 10⁻⁵ M; sulfuric acid, 1.0 × 10⁻³ M; diperiodatoargentate(III) (DPA), 1.0 × 10⁻⁴ M; potassium hydroxide, 1.0 × 10⁻³ M; flow rate 4.0 ml min⁻¹ for each flow stream and sample loop volume, 180 μl. The CL intensity of PG-HCl was linear in the range of 1.0 × 10⁻³ to 5.0 mg L⁻¹ (R² = 0.9998, n = 10) with limit of detection [LOD, signal-to-noise ratio (S/N) = 3] of 2.2 × 10⁻⁴ mg L⁻¹, limit of quantification (LOQ, S/N = 10) of 6.7 × 10⁻⁴ mg L⁻¹, relative standard deviation (RSD) of 1.0 to 3.3% and sampling rate of 106 h⁻¹. The methodology was satisfactorily used to quantify PG-HCl in pharmaceutical tablets with recoveries ranging from 93.17 to 102.77 and RSD from 1.9 to 2.8%.     

Histological and pharmacological investigations of the two symmetrically situated giant neurons,RPeNLN and LPeNLN,identified on the anterior surface of the pedal ganglia of an african giant snail (achatina fulica férussac)

• 1.1. Morphological and pharmacological investigations were made of two giant neurons, RPeNLN (right pedal nerve large neuron) and LPeNLN (left pedal nerve large neuron), situated symmetrically on the anterior surface of the pedal ganglia of an African giant snail (Achatina fulica Férussac).
• 2.]2. The two neurons (about 250–300 μm in diameter) were the largest ones identified in the ganglia of the snail species. The axonal pathways of the two neurons were symmetrical; of their four main axonal branches, the three main branches innervated the ipsilateral pedal nerves, whereas the last main branch projected to the contralateral pedal nerves.
• 3.]3. The pharmacological features of the two neurons were very similar. Both were inhibited markedly by dopamine [minimum effective concentrations (MECs): 3 × 10⁻⁶-10⁻⁵M], dl-octopamine (MECs: 2 × 10⁻⁶-2 × 10⁻⁵M), 5-hydroxytryptamine (MEC: 3 × 10⁻⁶M), GABA (MEC: 3 × 10⁻⁵ M), l-homocysteic acid (MECs: 3 × 10⁻⁵-10-10⁻⁴M) and erythro-β-hydroxy-l-ghitanuc acid (MEC: 3× 10⁻⁵M). Acetylcholine showed varied effects, either excitatory or inhibitory, on the two neurons examined. No substances were found to have any marked excitatory effects on the neurons.

     

Auxin Synthesis in Crown Gall Tumor Tissue: A Comparison of Three Putative Precursors

Axenic crown gall tumor callus (from Vinca rosea L.) which is known to synthesize its own auxin is able to convert exogenous ¹⁴C-indole or tryptamine to indoleacetic acid [5.4 and 10 × 10⁻⁶μmol × h⁻¹× (g fr wt)⁻¹ respectively], but little or no ³H-tryptophan is converted [less than 6.4 × 10⁻⁸×μmol × h⁻¹× (g fr wt)⁻¹].     

Effects of leucomyosuppressin on the excitation-concentration coupling of insect Leucophaea maderae visceral muscle

1. Leucomyosuppressin (LMS) inhibited neurally evoked contractions of the hindgut of the cockroach Leucophaea maderae. The threshold for this inhibition of LMS was in the range of 1 × 10⁻¹⁰ M.2. LMS caused a sharp reduction in both l-glutamate and proctolin induced contractions. Dose-response profiles of the effect of LMS (held constant at 10⁻⁸M) on variable amounts of proctolin showed an inhibitory effect at 10⁻⁹ M proctolin and below, but at 5 × 10⁻⁹ M proctolin and above, LMS caused no inhibition.3. Potassium (158 mM) depolarized hindguts treated with LMS (10⁻⁸ M) showed a marked reduction (76% ± 2.1) in the proctolin (10⁻⁸ M) response.4. When calcium depleted preparations were returned to normal calcium levels (2 mM) in the presence of proctolin (10 ⁻⁸ M) a contraction occurred that was 45% ± 4 of the maximum in normal saline solution. However, LMS (10⁻⁸ M) reduced this response to only 28% ± 2 of the maximum.5. Proctolin (10⁻⁸ M) induced contractions in the presence of the manganous ions (2mM) fell to 63% ± 4 of the maximum but on the addition of LMS (10⁻⁸M), such responses fell to only 16% ± 5 of the maximum.6. These results offer evidence for a non-synaptic site of action for LMS and a perturbation of key calcium dependent events in the excitation-contraction coupling sequence of visceral muscle by this peptide.     

Homological radiomics analysis for prognostic prediction in lung cancer patients

PurposeThis study explored a novel homological analysis method for prognostic prediction in lung cancer patients.Materials and methodsThe potential of homology-based radiomic features (HFs) was investigated by comparing HFs to conventional wavelet-based radiomic features (WFs) and combined radiomic features consisting of HFs and WFs (HWFs), using training (n = 135) and validation (n = 70) datasets, and Kaplan–Meier analysis. A total of 13,824 HFs were derived through homology-based texture analysis using Betti numbers, which represent the topologically invariant morphological characteristics of lung cancer. The prognostic potential of HFs was evaluated using statistically significant differences (p-values, log-rank test) to compare the survival curves of high- and low-risk patients. Those patients were stratified into high- and low-risk groups using the medians of the radiomic scores of signatures constructed with an elastic-net-regularized Cox proportional hazard model. Furthermore, deep learning (DL) based on AlexNet was utilized to compare HFs by stratifying patients into the two groups using a network that was pre-trained with over one million natural images from an ImageNet database.ResultsFor the training dataset, the p-values between the two survival curves were 6.7 × 10⁻⁶ (HF), 5.9 × 10⁻³ (WF), 7.4 × 10⁻⁶ (HWF), and 1.1 × 10⁻³ (DL). The p-values for the validation dataset were 3.4 × 10⁻⁵ (HF), 6.7 × 10⁻¹ (WF), 1.7 × 10⁻⁷ (HWF), and 1.2 × 10⁻¹ (DL).ConclusionThis study demonstrates the excellent potential of HFs for prognostic prediction in lung cancer patients.     

Variant HeLa cells selected for their resistance to ouabain

The cardiac glycoside, ouabain, normally kills HeLa cells at concentrations of about 10⁻⁷ m or greater. By treating a population of HeLa cells with increasingly higher concentrations of the drug, a variant population was obtained of HeLa cells capable of growing in medium containing 10⁻⁴ M ouabain. Inhibition of volume regulation of cells subjected to hypotonic shock was used as a measure of inhibition of active transport of Na across the plasma membrane. In that way dose-response curves for the rapid effects of ouabain and other inhibitors of active Na transport were obtained with both the original, ouabain-sensitive (OS) and the variant, ouabain-resistant (OR) cells. Three other cardiac glycosides (digoxin, digitoxin and hellebrin) and two aglycones (digitoxigenin and strophanthidjn) were found to be equally as effective as ouabain in inhibiting volume regulation of the OS cells; the concentration which produced half-maximum inhibition, I(max/2), was about 6 × 10⁻⁷ M in each case. Similar inhibition of the OR population by ouabain was observed only when the concentration exceeded 10⁻⁴ m [I(max/2)∼2.5 × 10⁻⁴ m], and the other steroid compounds had no effect on the variant cells at the highest concentrations tested (∼2 × 10⁻⁵ m). OR and OS cells differed also in their sensitivities to the cardioactive erythrophleum alkaloid, coumingine; I(max/2) for OS and OR cells was 5 × 10⁻⁸ m and 6 × 10⁻⁷ M, respectively. These results, in addition to results of ouabain binding experiments and measurements of the rates of reversal of inhibition of volume regulation, suggest that a major reason for the differential sensitivities of the two phenotypes to these drugs is different affinities of their sodium pumps for inhibitors of active transport.     

Reevaluation of the rate constants for the reaction of hypochlorous acid (HOCl) with cysteine,methionine, and peptide derivatives using a new competition kinetic approach

Activated white cells use oxidants generated by the heme enzyme myeloperoxidase to kill invading pathogens. This enzyme utilizes H₂O₂ and Cl⁻, Br⁻, or SCN⁻ to generate the oxidants HOCl, HOBr, and HOSCN, respectively. Whereas controlled production of these species is vital in maintaining good health, their uncontrolled or inappropriate formation (as occurs at sites of inflammation) can cause host tissue damage that has been associated with multiple inflammatory pathologies including cardiovascular diseases and cancer. Previous studies have reported that sulfur-containing species are major targets for HOCl but as the reactions are fast the only physiologically relevant kinetic data available have been extrapolated from data measured at high pH (>10). In this study these values have been determined at pH 7.4 using a newly developed competition kinetic approach that employs a fluorescently tagged methionine derivative as the competitive substrate (k(HOCl + Fmoc-Met), 1.5×10⁸ M⁻¹ s⁻¹). This assay was validated using the known k(HOCl + NADH) value and has allowed revised k values for the reactions of HOCl with Cys, N-acetylcysteine, and glutathione to be determined as 3.6×10⁸, 2.9×10⁷, and 1.24×10⁸ M⁻¹ s⁻¹, respectively. Similar experiments with methionine derivatives yielded k values of 3.4×10⁷ M⁻¹ s⁻¹ for Met and 1.7×10⁸ M⁻¹ s⁻¹ for N-acetylmethionine. The k values determined here for the reaction of HOCl with thiols are up to 10-fold higher than those previously determined and further emphasize the critical importance of reactions of HOCl with thiol targets in biological systems.     

Genotoxic activity of methyl mercury chloride and dimethyl mercury in human lymphocytes

The genotoxicity of methyl mercury chloride (MMC, 0–25 × 10⁻⁶M) and dimethyl mercury (DMM, 0–434 × 10⁻⁶M) was evaluated by chromosome metaphase analysis in human lymphocytes treated in vitro for 24 h. Structural (CA) and numerical (AN) chromosomal aberrations were scored for the assessment of induced genotoxic effects, while the variation in mitotic index (MI) was considered a monitor for induced cellular toxicity. MMC induced CA and AN in a dose-related manner at doses exceeding 0.6 × 10⁻⁶M, and the proportion of cells with CA was constantly and significantly higher than that of cells with AN. DMM was able to induce both effects as well, although to a lesser extent than MMC, CA and AN being induced at doses exceeding 43.4 × 10⁻⁶M and 1.73 × 10⁻⁶M, respectively. MMC was 6-fold more effective in inducing CA than DMM at equivalent toxic doses. On the other hand, no significant difference was observed between the two compounds in inducing AN. Therefore MMC was much more c lastogenic than DMM, whereas mitotic spindle disturbances appeared to be almost equally induced by both compounds.     

Response of macrophyte litter decomposition in global blue carbon ecosystems to climate change

Blue carbon ecosystems (BCEs) are important nature-based solutions for climate change-mitigation. However, current debates question the reliability and contribution of BCEs under future climatic-scenarios. The answer to this question depends on ecosystem processes driving carbon-sequestration and -storage, such as primary production and decomposition, and their future rates. We performed a global meta-analysis on litter decomposition rate constants (k) in BCEs and predicted changes in carbon release from 309 studies. The relationships between k and climatic factors were examined by extracting remote-sensing data on air temperature, sea-surface temperature, and precipitation aligning to the decomposition time of each experiment. We constructed global numerical models of litter decomposition to forecast k and carbon release under different scenarios. The current k averages at 27 ± 3 × 10⁻² day⁻¹ for macroalgae were higher than for seagrasses (1.7 ± 0.2 × 10⁻² day⁻¹), mangroves (1.6 ± 0.1 × 10⁻² day⁻¹) and tidal marshes (5.9 ± 0.5 × 10⁻³ day⁻¹). Macrophyte k increased with both air temperature and precipitation in intertidal BCEs and with sea surface temperature for subtidal seagrasses. Above a temperature threshold for vascular plant litter at ~25°C and ~20°C for macroalgae, k drastically increased with increasing temperature. However, the direct effect of high temperatures on k are obscured by other factors in field experiments compared with laboratory experiments. We defined “fundamental” and “realized” temperature response to explain this effect. Based on relationships for realized temperature response, we predict that proportions of decomposed litter will increase by 0.9%–5% and 4.7%–28.8% by 2100 under low- (2°C) and high-warming conditions (4°C) compared to 2020, respectively. Net litter carbon sinks in BCEs will increase due to higher increase in litter C production than in decomposition by 2100 compared to 2020 under RCP 8.5. We highlight that BCEs will play an increasingly important role in future climate change-mitigation. Our findings can be leveraged for blue carbon accounting under future climate change scenarios.     

A novel LncRNA-based prognostic score reveals TP53-dependent subtype of lung adenocarcinoma with poor survival

The prognostic signatures play an essential role in the era of personalised therapy for cancer patients including lung adenocarcinoma (LUAD). Long noncoding RNA (LncRNA), a relatively novel class of RNA, has shown to play a crucial role in all the areas of cancer biology. Here, we developed and validated a robust LncRNA-based prognostic signature for LUAD patients using three different cohorts. In the discovery cohort, four LncRNAs were identified with 10% false discovery rate and a hazard ratio of >10 using univariate Cox regression analysis. A risk score, generated from the four LncRNAs’ expression, was found to be a significant predictor of survival in the discovery and validation cohort (p = 9.97 × 10 ⁻⁸ and 1.41 × 10 ⁻³, respectively). Further optimisation of four LncRNAs signature in the validation cohort, generated a three LncRNAs prognostic score (LPS), which was found to be an independent predictor of survival in both the cohorts ( p = 1.00 × 10 ⁻⁶ and 7.27 × 10 ⁻⁴, respectively). The LPS also significantly divided survival in clinically important subsets, including Stage I ( p = 9.00 × 10 ⁻⁴ and 4.40 × 10 ⁻², respectively), KRAS wild-type (WT), KRAS mutant ( p = 4.00 × 10 ⁻³ and 4.30 × 10 ⁻², respectively) and EGFR WT ( p = 2.00 × 10 ⁻⁴). In multivariate analysis LPS outperformed, eight previous prognosticators. Further, individual members of LPS showed a significant correlation with survival in microarray data sets. Mutation analysis showed that high-LPS patients have a higher mutation rate and inactivation of the TP53 pathway. In summary, we identified and validated a novel LncRNA signature LPS for LUAD.     

THE MECHANISM OF DAYLENGTH PERCEPTION IN THE RED ALGA ACROSYMPHYTON PURPURIFERUM1

The red alga Acrosymphton purpuriferum (J. Ag.) Sjöst. (Dumontiaceae) is a short day plant in the formation of its tetrasporangia. Tetrasporogenesis was not inhibited by 1 h night-breaks when given at any time during the long (16 h) dark period (tested at 2 h intervals). However, tetrasporogenesis was inhibited when short (8 h) main photoperiods were extended beyond the critical daylength with supplementary light periods (8 h) at an irradiance below photosynthetic compensation. The threshold irradiance below photosynthetic compensation. The threshold irradiance for inhibition of tetrasporogenesis was far lower when supplementary light periods preceded the main photoperiod than when they followed it (< 0.05 μmol.m⁻². s⁻¹ vs. 3 μmol.m⁻².s⁻¹. The threshold level also depended on the irradiance given during the main photoperiod and was higher after a main photoperiod in bright light than after one in dim light (threshold at 3 μmol.m⁻².s⁻¹ after a main photoperiod at ca. 65 μmol.m⁻².s⁻¹ vs. threshold at <0.5 μmol.m⁻².s⁻¹ after a main photoperiod at ca. 35 μmol.m⁻².s⁻¹. The spectral dependence of the response was investigated in day-extensions (supplementary light period (8 h) after main photoperiod (8 h) at 48 μmol. m⁻².s⁻¹) with narrow band coloured light. Blue light (λ= 420 nm) was most effective, with 50% inhibition at a quantum-dose of 2.3 mmol.m⁻². However, yellow (λ= 563 nm) and red light (λ= 600 nm; λ= 670 nm) also caused some inhibition, with ca. 30% of the effectiveness of blue light. Only far-red light (λ= 710 nm; λ= 730 nm) was relatively ineffective with no significant inhibition of tetrasporogenesis at quantum-doses of up to 20 mmol. m⁻².     

Protein Metabolism in Cultured Plant Tissues

Rates of protein synthesis in normal callus tissues (either tight or loose morphological form), in crown gall callus tissues and in cultured pith cells were measured for both the lower surface cells (those in contact with the original growth medium) and upper surface cells (those never in contact with the growth medium until labeling). Cells of both surfaces of loose and crown gall callus and the upper-surface cells of tight callus had similar rates of protein synthesis, 29–31 mg of protein synthesized × (g protein)⁻¹× h⁻¹. The lower surface cells of tight callus had a 35% lower rate of synthesis, 20 mg × g⁻¹× h⁻¹. Pulse-chase experiments suggested that rates of protein degradation for all tissues were the same, 21–23 mg protein × (g protein)⁻¹× h⁻¹. Thus, there probably was no accumulation of protein in the lower surface cells of tight callus tissue, but the other tissues had rates of accumulation equaling 10 mg × (g protein)⁻¹× h⁻¹. Autoradiography and electron-microscopic examination of cells in tight callus labeled with ³H-leucine show that: (a) the lower-surface cells were more degenerate than cells within the callus or on the upper surface; and (b) the first few cell layers nearest the medium were preferentially labeled. Pulse-chase experiments were also used to quantitate the nonprecursor pool (defined as that tritium in the soluble amino acid pool that does not equilibrate with protein during a pulse-chase experiment). The nonprecursor pool increased linearly with time at the same rate as incorporation of ³H-leucine into protein. Furthermore, the nonprecursor pool copurified with leucine and was probably either D- or L-leucine.     

Genetic investigation of equine recurrent uveitis in Appaloosa horses

Equine recurrent uveitis (ERU) is characterized by intraocular inflammation that often leads to blindness in horses. Appaloosas are more likely than any other breed to develop insidious ERU, distinguished by low-grade chronic intraocular inflammation, suggesting a genetic predisposition. Appaloosas are known for their white coat spotting patterns caused by the leopard complex spotting allele (LP) and the modifier PATN1. A marker linked to LP on ECA1 and markers near MHC on ECA20 were previously associated with increased ERU risk. This study aims to further investigate these loci and identify additional genetic risk factors. A GWAS was performed using the Illumina Equine SNP70 BeadChip in 91 horses. Additive mixed model approaches were used to correct for relatedness. Although they do not reach a strict Bonferroni genome-wide significance threshold, two SNPs on ECA1 and one SNP each on ECA12 and ECA29 were among the highest ranking SNPs and thus warranted further analysis (P = 1.20 × 10⁻⁵, P = 5.91 × 10⁻⁶, P = 4.91 × 10⁻⁵, P = 6.46 × 10⁻⁵). In a second cohort (n = 98), only an association with the LP allele on ECA1 was replicated (P = 5.33 × 10⁻⁵). Modeling disease risk with LP, age and additional depigmentation factors (PATN1 genotype and extent of roaning) supports an additive role for LP and suggests an additive role for PATN1. Genotyping for LP and PATN1 may help predict ERU risk (AUC = 0.83). The functional role of LP and PATN1 in ERU development requires further investigation. Testing samples across breeds with leopard complex spotting patterns and a denser set of markers is warranted to further refine the genetic components of ERU.     

Protein kinase C β1 overexpression augments phorbol ester-induced increase in endothelial permeability

We studied the postulated involvement of the protein kinase C β₁ (PKCβ₁) isoform in the regulation of endothelial permeability using human dermal microvascular endothelial cell line (HMEC-1). We overexpressed the recombinant PKCβ₁ gene via retroviral-mediated transduction in these cells. PKCβ₁ gene transfer was stable, and PKCβ₁ protein production was persistent for at least 1 month posttransduction. Addition of 2 × 10⁻⁹ M and 2 × 10⁻⁸ M phorbol 12-myristate 13-acetate (PMA) to the control (nontransduced) HMEC-1 cells increased the transendothelial ¹²⁵I-albumin clearance rate (an index of endothelial permeability) from 2.5 ± 0.2 × 10⁻² μl/min to 5.4 ± 1.2 × 10⁻² μl/min and 16.8 ± 3.1 × 10⁻² μl/min, respectively. However, addition of 2 × 10⁻⁹ M PMA to PKCβ₁-overexpressing HMEC-1 cells produced a maximal increase in the transendothelial ¹²⁵I-albumin clearance rate of 15.9 ± 2.0 × 10⁻² μl/min. Challenge of these cells with 2 × 10 ⁻⁸ M PMA did not further augment the increase in permeability. Activation with PMA was associated with the translocation of the PKCβ₁ from the cytosol to the membrane. These data show that PKCβ₁ overexpression augments the increase in endothelial permeability in response to PKC activation, suggesting an important function for the PKCβ₁ isoform in the regulation of endothelial barrier. © 1996 Wiley-Liss, Inc.     

Pulse radiolytic study of α-tocopherol radical mechanisms in ethanolic solution

Pulse radiolytic studies of α-tocopherol (αTH) oxidation-reduction processes were carried out with low doses (5 Gy) of high-energy electrons in O₂₋, N₂₋, and air-saturated ethanolic solutions. Depending on the concentration of oxygen in solution, two different radicals, A· and B·, were observed. The first, A·, was obtained under N₂ and results from aTH reaction with solvated electron (k_aTH+csolv⁻ = 3.4 × 10⁸ mol⁻¹ liter s⁻¹) and with H₃C-ĊH-OH, (R·) (k_{aTH + R·} = 5 × 10⁵ mol⁻¹ liter s⁻¹). B·, observed under O₂, is produced by αTH reaction with RO₂ peroxyl radicals (k_aTH + RO₂^. = 9.5 × 10⁴ mol⁻¹ liter s⁻¹).     

Comments on Bartolino et al. (2011): limits of cumulative relative frequency distribution curves for hotspot identification

The recent paper by Bartolino et al. (Popul Ecol 53:351–359, 2011) presents a new method to objectively select hotspots using cumulative relative frequency distribution (CRFD) curves. This method is presented as being independent from the selection of any threshold and, therefore, less arbitrary than traditional approaches. We argue that this method, albeit mathematically sound, is based on likewise arbitrary decisions regarding threshold selection. Specifically, the use of the CRFD curve approach requires the occurrence of two criteria for the method to be applied correctly: the selection of a 45° tangent to the curve, and the need to consider the highest relative value of the study parameter corresponding to a 45° slope tangent to the curve. Using two case studies (dealing with species richness and abundance of a particular species), we demonstrate that these two criteria are really unrelated to the underlying causes that shape the spatial pattern of the phenomena under study, but rather related to sampling design and spatial scale; hence, one could likewise use different but valid criteria. Consequently, the CRFD curve approach is based on the selection of a pre-defined threshold that has little, if any, ecological justification, and that heavily influences the final hotspot selection. Therefore, we conclude that the CRFD curve approach itself is not necessarily better and more objective than any of the global methods typically used for hotspot identification. Indeed, mathematical and/or statistical approaches should not be viewed as a panacea to solve conservation problems, but rather used in combination with biological, practical, economic and social considerations.     

Novel nonclassical inhibitors of glycinamide ribonucleotide formyltransferase: 10-Formyl and 10-hydroxymethyl derivatives of 5,8,10-trideazapteroic acid

Several new 10-formyl and 10-hydroxymethyl derivatives of 5,8,10-trideazapteroic acid have been synthesized by a novel and convenient enamine alkylation procedure. Two of these compounds (10a and 10b) were shown to be very powerful inhibitors of L. casei (10a, IC₅₀ = 8 × 10⁻⁶ M ; 10b, IC₅₀ = 7 × 10⁻⁶ M ) and recombinant mouse (10a, IC₅₀ = 3.4 × 10⁻⁵ M ; 10b, IC₅₀ = 2.8 × 10⁻⁵ M ) glycinamide ribonucleotide formyltransferase (GARFT). These IC₅₀ values are comparable to the classical GARFT inhibitor (6R)-DDATHF (IC₅₀, L. casei 2.3 × 10⁻⁶M ; recombinant mouse 2.3 × 10⁻⁵ M ) under identical assay conditions. For both compounds, the inhibition of L. casei GARFT increased with time of incubation, but not markedly with the recombinant mouse enzyme. Due to their potential ability to interfere with purine biosynthesis and to penetrate microbial cells the new nonclassical GARFT inhibitors reported here may be useful for the treatment of infections caused by microorganisms that are sensitive and resistant to conventional antimicrobial agents.     

Effects of VA-045, a novel apovincaminic acid derivative,on isolated blood vessels: Cerebroarterial selectivity

We investigated the effects of VA-045, an apovincaminic acid derivative, on isolated blood vessels. VA-045 (10⁻⁷−10⁻⁵M) and vinpocetine (10⁻⁷−10⁻⁵M) inhibited the 64 mM KCl-induced and 10⁻⁶M norepinephrine (NE)-induced contraction of rat aortic strips. VA-045 (10⁻⁷−10⁻⁴M) and vinpocetine (10⁻⁷−10⁻⁴M) inhibited the activity of cyclic AMP and cyclic GMP phosphodiesterase in porcine coronary artery. VA-045 (3×10⁻⁹−3×10⁻⁶M) relaxed the 64 mM KCl-induced contraction of the canine basilar artery without affecting the peripheral arteries. These results indicate that VA-045 selectively dilates canine cerebral artery, and that it may be a useful agent for the treatment of cerebrovascular diseases such as stroke.