Understanding the structural requirements of 4-anilidopiperidine analogues for biological activities at mu and delta opioid receptors

New 4-anilidopiperidine analogues in which the phenethyl group of fentanyl was replaced by several aromatic ring-contained amino acids (or acids) were synthesized to study the biological effect of the substituents on mu and delta opioid receptor interactions. These analogues showed broad (47 nM-76 microM) but selective (up to 17-fold) binding affinities at the mu opioid receptor over the delta opioid receptor, as predicted from the message-address concept.     

Hsp10 and Hsp60 suppress ubiquitination of insulin-like growth factor-1 receptor and augment insulin-like growth factor-1 receptor signaling in cardiac muscle: implications on decreased myocardial protection in diabetic cardiomyopathy

We have investigated the effects of two heat shock proteins, Hsp10 and Hsp60, on insulin-like growth factor-1 receptor (IGF-1R) signaling in cardiac muscle cells. Neonatal cardiomyocytes were transduced with Hsp10 or Hsp60 via adenoviral vector. Compared with the cells transduced with a control vector, overexpression of Hsp10 or Hsp60 increased the abundance of IGF-1R and IGF-1-stimulated receptor autophosphorylation. Thus, Hsp10 and Hsp60 overexpression increased the number of functioning receptors and amplified activation of IGF-1R signaling. IGF-1 stimulation of MEK, Erk, p90Rsk, and Akt were accordingly augmented. Transducing cardiomyocytes with antisense Hsp60 oligonucleotides reduced Hsp60 expression, decreased the abundance of IGF-1R, attenuated IGF-1R autophosphorylation, and suppressed the pro-survival action of IGF-1 in cardiomyocytes. Using cycloheximide to inhibit protein synthesis did not alter the effect of Hsp60 on IGF-1R signaling, and IGF-1R mRNA levels were not up-regulated by Hsp10 or Hsp60. Additional experiments showed that Hsp10 and Hsp60 suppressed polyubiquitination of IGF-1 receptor. These data indicate that Hsp10 and Hsp60 can modulate IGF-1R signaling through post-translational modification. In animal models of diabetes, diabetic myocardium is associated with decreased abundance of Hsp60, increased ubiquitination of IGF-1R, and lower level of IGF-1R protein. Declined myocardial protection is a major feature of diabetic cardiomyopathy. These data suggest that decreased Hsp60 expression and subsequent decline of IGF-1R signaling may be a fundamental mechanism underlying the development of diabetic cardiomyopathy.     

Overexpression of heat shock proteins differentially modulates protein kinase C expression in rat neonatal cardiomyocytes

Previous studies have suggested that protein kinase C (PKC) is involved in heat shock protein (Hsp)-mediated cardioprotection. Therefore, we wanted to determine whether overexpression of Hsps modulates PKC expression, which will give us further insight into understanding the mechanism by which Hsps and PKC interact to protect cells from stress-induced injury. Specifically, we overexpressed the inducible form of Hsp70 (Hsp70i) or Hsp90 in rat neonatal cardiomyocytes and evaluated PKCdelta or PKCepsilon expression by immunoblotting and immunofluorescent confocal microscopy. Western analysis showed that overexpression of Hsp70i or Hsp90 decreased PKCepsilon expression. However, overexpression of Hsp70i or Hsp90 did not modify PKCdelta expression over control levels. Overexpression of constitutively active PKCdelta or PKCepsilon increased Hsp70i expression over control levels. The data suggest that overexpression of Hsps differentially modulates expression of PKC isoforms in rat neonatal cardiomyocytes. Furthermore, PKC may directly play a role in Hsp-mediated cardioprotection by upregulating Hsp70i expression.     

Ionic events induced by epidermal growth factor. Evidence that hyperpolarization and stimulated cation influx play a role in the stimulation of cell growth.

Charybdotoxin, a blocker of K+ channels, and the imidazole drug SC38249, a blocker of both voltage- and second messenger-operated Ca2+ channels, were employed in mouse NIH-3T3 fibroblasts overexpressing the epidermal growth factor (EGF) receptor 1) to characterize the ionic events activated by EGF; and 2) to establish the role of those events in cell growth. The [Ca2+]i response by EGF was little changed by charybdotoxin while the parallel hyperpolarization was inhibited in a dose-dependent manner. At high toxin concentrations (greater than 3 x 10(-8) M), the effect of EGF on membrane potential was turned into a persistent depolarization sustained by both Na+ and Ca2+. Pretreatment with 10 microM SC38249 induced only minor changes of the intracellular Ca2+ release by EGF (the process responsible for the initial phase of the [Ca2+]i and membrane potential responses) and blocked the persistent, second phase [Ca2+]i and the hyperpolarization responses, both dependent on Ca2+ influx, as well as the depolarization in the charybdotoxin-pretreated cells. Long term (up to 2-day) treatment with either charybdotoxin or SC38249 failed to affect the viability and growth of unstimulated EGFR-T17 cells. Moreover, in these cells, the ionic responses to EGF were restored after a 30-min incubation in fresh medium. In contrast, growth stimulated by EGF was inhibited, moderately (-20%) by charybdotoxin and markedly (-60%) by SC38249. These results indicate for the first time that both hyperpolarization and, especially, the persistent increase of [Ca2+]i sustained by Ca2+ influx play a role in the activity of EGF, ultimately cooperating with other intracellular events in mitogenesis.     

Winds at departure shape seasonal patterns of nocturnal bird migration over the North Sea

On their migratory journeys, terrestrial birds can come across large inhospitable areas with limited opportunities to rest and refuel. Flight over these areas poses a risk especially when wind conditions en route are adverse, in which case inhospitable areas can act as an ecological barrier for terrestrial migrants. Thus, within the east-Atlantic flyway, the North Sea can function as an ecological barrier. The main aim of this study was to shed light on seasonal patterns of bird migration in the southern North Sea and determine whether departure decisions on nights of intense migration were related to increased wind assistance. We measured migration characteristics with a radar that was located 18 km off the NW Dutch coast and used simulation models to infer potential departure locations of birds on nights with intense nocturnal bird migration. We calculated headings, track directions, airspeeds, groundspeeds on weak and intense migration nights in both seasons and compared speeds between seasons. Moreover, we tested if departure decisions on intense migration nights were associated with supportive winds. Our results reveal that on the intense migration nights in spring, the mean heading was towards E, and birds departed predominantly from the UK. On intense migration nights in autumn, the majority of birds departed from Denmark, Germany and north of the Netherlands with the mean heading towards SW. Prevailing winds from WSW at departure were supportive of a direct crossing of the North Sea in spring. However, in autumn winds were generally not supportive, which is why many birds exploited positive wind assistance which occurred on intense migration nights. This implies that the seasonal wind regimes over the North Sea alter its migratory dynamics which is reflected in headings, timing and intensity of migration.     

Avian influenza (H5N1) viruses isolated from humans in Asia in 2004 exhibit increased virulence in mammals

The spread of highly pathogenic avian influenza H5N1 viruses across Asia in 2003 and 2004 devastated domestic poultry populations and resulted in the largest and most lethal H5N1 virus outbreak in humans to date. To better understand the potential of H5N1 viruses isolated during this epizootic event to cause disease in mammals, we used the mouse and ferret models to evaluate the relative virulence of selected 2003 and 2004 H5N1 viruses representing multiple genetic and geographical groups and compared them to earlier H5N1 strains isolated from humans. Four of five human isolates tested were highly lethal for both mice and ferrets and exhibited a substantially greater level of virulence in ferrets than other H5N1 viruses isolated from humans since 1997. One human isolate and all four avian isolates tested were found to be of low virulence in either animal. The highly virulent viruses replicated to high titers in the mouse and ferret respiratory tracts and spread to multiple organs, including the brain. Rapid disease progression and high lethality rates in ferrets distinguished the highly virulent 2004 H5N1 viruses from the 1997 H5N1 viruses. A pair of viruses isolated from the same patient differed by eight amino acids, including a Lys/Glu disparity at 627 of PB2, previously identified as an H5N1 virulence factor in mice. The virus possessing Glu at 627 of PB2 exhibited only a modest decrease in virulence in mice and was highly virulent in ferrets, indicating that for this virus pair, the K627E PB2 difference did not have a prevailing effect on virulence in mice or ferrets. Our results demonstrate the general equivalence of mouse and ferret models for assessment of the virulence of 2003 and 2004 H5N1 viruses. However, the apparent enhancement of virulence of these viruses in humans in 2004 was better reflected in the ferret.     

New Methodology for Computer-Aided Modelling of Biomolecular Structure and Dynamics 2. Local Deformations and Cycles

Abstract

A new methodology for the conformational modelling of biomolecular systems (1) is extended to local deformations of chain molecules and to flexible molecular rings. It is shown that these two cases may be reduced to considering an equivalent molecular model with a regular tree-like topology. A simple procedure is developed to analyze any flexible rings (the five- and six-membered suguar rings of carbohydrates and nucleic acids, in particular) and local deformation regions by energy minimization. Dynamic equations are also derived for such molecular systems. As a result, a unified approach is proposed for the efficient energy minimization and simulation of dynamic behavior of multimolecular systems having any set of variable internal coordinates, local deformation regions and cycles. Advantages and domains of applicability of the approach are discussed.     

ULTRASTRUCTURE OF OOSPORE GERMINATION IN PYTHIUM APHANIDERMATUM

Transmission electron microscopy was used in an examination of dormant and germinating oospores of Pythium aphanidermatum (Edson) Fitzp. Predominant cytoplasmic components of the dormant oospore were a single, centrally located globule and numerous storage bodies surrounding the globule. The lipid nature of the central globule and storage bodies was indicated by the examination of Br₂-treated and untreated, fixed specimens. Three layers of the oospore wall were distinguished. During the early stages of oospore germination, the central globule developed incurvatures and became partially surrounded by vacuoles. The thick middle layer of the wall showed a change in staining properties and became thin in the region of germ tube emergence. Germlings incubated on corn meal agar differed substantially from those incubated in nutrient broth during the later stages of germination. The role of vacuoles and vesicles in the utilization of storage reserves during germination is discussed.     

Meeting announcements

The levels of individual free and conjugated ecdysteroids and ecdysteroid acids, labeled from [¹⁴C]cholesterol, in five different age groups of male Manduca sexta during pupal-adult development were determined by HPLC. Eight free ecdysteroids, eight ecdysteroid phosphates, and two ecdysteroid acids were identified. Newly ecdysed pupae contained predominantly 3-epiecdysteroids in each of the free, conjugated, and acidic ecdysteroid fractions. The titer of each ecdysteroid fraction rose sharply by day 4, and this was particularly noteworthy with respect to free ecdysone and 3-epi-20-hydroxyecdysonoic acid. This stage demonstrated high degrees of ecdysone biosynthesis, oxidative catabolism, and phosphorylation. As development proceeded to day 16, total ecdysteroid titer remained constant; a decreasing free ecdysteroid titer was accompanieid by increasing titers of both conjugates and acids resulting from the metabolic processes of hydroxylation, oxidation, epimerization, and phosphorylation. The predominant metabolites throughout development were 3-epi-20-hydroxyecdysonoic acid and the phosphate conjugates of 3-epi-20-hydroxyecdysone and 3-epi-20,26-dihydroxyecdysone. The ultimate inactivation of the ecdysteroids of M. sexta during pupal-adult development is possibly mediated by two pairs of metabolically-linked processes, one leading to a 3-epiecdysteroid acid, and the other to 3-epiecdysteroid phosphates.