Conformational studies of a synthetic cyclic decapeptide fragment of rat transforming growth factor-α

The solution conformation of a synthetic cyclic decapeptide [with sequence mimicking the third disulfide loop of rat transforming growth factor-α (rTGF-α)] in deuterated dimethyl sulfoxide was studied by 2D NMR. The determination of solution structures was based on NOE interproton distances, using a combination of distance geometry and simulated annealing protocols. The convergence of the selected structures was evident from the small atomic pairwise root-mean-square deviation values among them. Good agreement was noted between the experimental and simulated NOESY spectra, thereby reflecting the accuracy of the calculated solution structures. Analysis of the structures indicates that the residues Tyr5 and Arg9 exhibit similar side chain orientation as that in the corresponding disulfide loop of human transforming growth factor-α.     

Rat skeletal muscle metabolism in experimental heart failure: effects of physical training

Skeletal muscle metabolic abnormalities exist in chronic heart failure. The influence of physical training on muscle metabolism after myocardial infarction was studied in a rat model. ³¹P magnetic resonance spectroscopy and enzyme assays were performed in Wistar rats 12 weeks after coronary artery ligation. Infarcted rats were allocated randomly to either 6 weeks of training or non-training. Spectra were collected from the calf muscles during sciatic nerve stimulation at 2 Hz. Fibre typing and enzymatic assays were performed on the muscles of the contralateral non stimulated leg. Post-mortem rats were also divided into severe and moderate heart failure according to the lung weight per body weight. At 200 g twitch tension, phosphocreatine and pH were found to be significantly lower in the non-trained severe heart failure group compared with the other groups. Phosphocreatine recovery half-time was significantly longer in the non-trained group with severe heart failure and correlated with the citrate synthase activity in the muscle. The training did not induce a change in the enzyme activities in the infarcted animals with moderate heart failure but did correct the lower citrate synthase activity in the non-trained severe heart failure animals. This normalization of muscle metabolism was achieved by training without any change in calf muscle mass, making atrophy unlikely to be the sole cause of the metabolic changes in heart failure. Training in rats with severe heart failure can reverse the abnormalities of skeletal muscle metabolism, implicating decreased physical activity in the aetiology of these changes.     

SKIN LESIONS IN HIV-POSITIVE AND HIV-NEGATIVE PATIENTS IN SOUTH INDIA

Background. Various dermatologic conditions have been reported to occur with increased frequency in human immunodeficiency virus (HIV)-positive individuals, but there are only a few studies comparing the prevalences of skin diseases in HIV-positive patients with those in matched HIV-negative controls. Methods. Skin lesions in 129 HIV-positive patients and 258 HIV-negative controls were studied prospectively over an 18-month period from October 1991 to March 1993. Results. Oral Candida, tinea cruris, and ichthyosis were significantly more common in HIV-positive patients compared to controls. Several other dermatologic conditions were found only in the HIV-positive group. Conclusions. The pattern of skin lesions in Indian patients with HIV infection may be different from that in the West.     

The effect of iron deficiency on skeletal muscle metabolism of the rat

Using ³¹P magnetic resonance spectroscopy we compared skeletal muscle bioenergetics in Wistar rats made chronically anaemic by being fed a diet deficient in iron for 6 weeks with chronically iron deficient animals given a normal diet as well as 5 mg iron dextran at 2 or 7 days before experimentation. Spectra of the gastrocnemius muscle were taken at rest and during stimulation of the sciatic nerve at 2 Hz for 10 min. Relative concentrations of intracellular phosphate (Pi), phosphocreatine (PCr) and ATP were determined. Iron deficiency increased PCr breakdown and production of acid in stimulated skeletal muscle. Recovery of PCr and Pi concentrations after exercise was slow. These metabolic changes are consistent with either a reduction in supply of oxygen to the muscle cell or altered oxidative phosphorylation by the mitochondria. The latter may be mediated by defective function of iron-containing proteins crucial in oxidative phosphorylation and this is suggested both by the observation that treatment with iron, sufficient to correct the anaemia, does not completely reverse the metabolic changes and that there is a different time course for such metabolic improvements and the observed increase in haemoglobin concentration.     

Anticancer efficacy of 3-(4-isopropyl) benzylidene-8-ethoxy, 6-methyl,chroman-4-one (SBL-060), a novel,dual, estrogen receptor-Akt kinase inhibitor in acute myeloid leukemia cells

Estrogen receptor (ER) α is expressed in a subset of patient-derived acute myeloid leukemia (AML) cells, whereas Akt is predominantly expressed in most types of AML. Targeting AML with dual inhibitors is a novel approach to combat the disease. Herein, we examined a novel small molecule, 3-(4-isopropyl) benzylidene-8-ethoxy,6- methyl, chroman-4-one (SBL-060), capable of targeting AML cells by inhibiting ERα and Akt kinase. The chemical properties of SBL-060 were identified by proton nuclear magnetic resonance (¹ H-NMR), ¹³C-NMR, and mass spectroscopy. In silico docking was performed using an automated protocol with AutoDock-VINA. THP-1 and HL-60 cell lines were differentiated using phorbol 12-myristate 13-acetate. ERα inhibition was assessed using ELISA. The MTT assay assessed cell viability. Flow cytometry was performed for cell cycle, apoptosis, and p-Akt analyses. Chemical analysis identified the compound as 3-(4-isopropyl) benzylidene-8-ethoxy,6-methyl, chroman-4-one, which showed high binding efficacy toward ER, with a ΔG_binding score of −7.4 kcal/mol. SBL-060 inhibited ERα, exhibiting IC₅₀ values of 448 and 374.3 nM in THP-1 and HL-60 cells, respectively. Regarding inhibited cell proliferation, GI₅₀ values of SBL-060 were 244.1 and 189.9 nM for THP-1 and HL-60 cells, respectively. In addition, a dose-dependent increase in sub G₀/G₁ phase cell cycle arrest and total apoptosis was observed after treatment with SBL-060 in both cell types. SBL-060 also dose-dependently increased the p-Akt-positive populations in both THP-1 and HL-60 cells. Our results indicate that SBL-060 has excellent efficacy against differentiated AML cell types by inhibiting ER and Akt kinase, warranting further preclinical evaluations.     

Changes in Late Potential Measurements as a Function of Decreasing Bandwidth

Bandwidth of Late Potentials Introduction: Limited bandwidth systems such as Holter recorders are being used to record cardiac late potentials. Standard late potential systems have a low-pass frequency of 300 Hz. This suggests that Holter tape systems may significantly distort the late potential measurements, when compared to standard late potential systems. Methods and Results: Signal-averaged recordings were obtained with an analog bandwidth of 0.05-300 Hz. Digital filters were then used to do high-pass filtering and low-pass filtering. All XYZ signal-averaged recordings were low-pass filtered at frequencies of 250, 150, 100, 75, 50, and 25 Hz using a second order Butterworth filter. A fourth order 40 Hz bidirectional high-pass filter was then applied to each set of recordings. The QRS duration (QRSd) was measured in the filtered vector magnitude. Thirty-eight syncope patients who had negative electrophysiologic studies for ventricular tachycardia, no prior infarction, normal ejection fractions (> 50%), and a QRSd <120 msec served as the negative late potential group. Thirty-seven patients with clinical ventricular tachycardia, a positive electrophysiologic study for ventricular tachycardia, and a QRSd>120 msec served as the positive late potential group. Conclusions: A statistically significant lengthening of the QRSd (P <0.05) was observed in the patients with late potentials between the 250 Hz and 25 Hz low-pass filter. There was a statistically significant shortening of the QRSd in the negative late potential patients between 250 Hz and 25 Hz, as well as between 250 Hz and 50 Hz, with P<0.05 in both cases. Thus, significant changes in late potentials are seen in limited bandwidth recordings that may limit the clinical usefulness of such systems.     

Use of the 3-nitro-2-pyridine sulfenyl protecting group to introduce Nε-branching at lysine during solid-phase peptide synthesis I. Application to the synthesis of a peptide template containing two addressable sites

TASPs (template-assembled synthetic peptides) are generated by the covalent attachment of linear peptides to a common peptide backbone, thus generating larger synthetic peptides/proteins with prefolded structure. In this work we present a strategy for the synthesis of a heterotemplate-assembled synthetic peptide containing two addressable sites. This orthogonal protection strategy would allow the selective introduction of different peptide chains via the ε-amino functions of template lysines being protected by either fluorenylmethoxycarbonyl (Fmoc) or 3-nitro-2-pyridine sulfenyl (Npys) groups. The N^α-Boc-N^ε-Npys-l -lysine required for solid-phase peptide synthesis (SPPS) is not readily available at a reasonable cost. To facilitate the more widespread use of this reagent we have compared the two published procedures for synthesizing this protected amino acid and evaluated the suitability of the products for SPPS. Two resin-bound peptides, a tripeptide Ac-G-K-Npys)-G-resin and an octapeptide template Ac-P₁-K₂-K₃-L₄-K_s-K₆-P₇-G₈-resin, were synthesized by SPPS. The ε-amino functions of lysines K₂ & K₆ and K₃ & K₅ of the octapeptide were protected by Fmoc and Npys groups, respectively. Secondly, these peptides were used to evaluate various reagents and reaction conditions for the deprotection of the ε-amino function of lysines bearing the N_ε-Npys protecting group. A procedure for the optimized selective and quantitative deprotection of the Npys group from the ε-amino function of lysine in a resin-bound peptide using 2-mercaptopyridine-N-oxide is described. © Munksgaard 1995.