RESPONSES BY HECTOR'S DOLPHINS TO BOATS AND SWIMMERS IN PORPOISE BAY,NEW ZEALAND

Theodolite tracking (61 d; 251 h) was used to quantify dolphin reactions to boats and swimmers in the austral summers of 1995-1996 and 1996-1997. Dolphins were accompanied by swimmers (within 200 m) for 11.2% of the total observation time, whereas boats accounted for an additional 12.4%. Dolphins were not displaced by either of these activities. Swimmers caused only weak, non-significant effects, perhaps because dolphins could very easily avoid them. Reactions to the dolphin-watching boat were stronger. Analyses of relative orientation indicate that dolphins tended to approach the vessel in the initial stages of an encounter but became less interested as the encounter progressed. By 70 min into an encounter dolphins were either actively avoiding the boat or equivocal towards it, approaching significantly less often than would be expected by chance. Analyses of group dispersion indicate that dolphins were significantly more tightly bunched when a boat was in the bay.     

A study of the K+-site mutant of ascorbate peroxidase: mutations of protein residues on the proximal side of the heme cause changes in iron ligation on the distal side

A series of ferric and ferrous derivatives of wild-type ascorbate peroxidase (APX) and of an engineered K⁺-site mutant of APX that has had its potassium cation binding site removed have been examined by electronic absorption and magnetic circular dichroism (MCD) spectroscopy at 4??°C. Wild-type ferric APX has spectroscopic properties that are very similar to those of ferric cytochrome c peroxidase (CCP) and likely exists primarily as a five-coordinate high-spin heme ligated on the proximal side by a histidine at pH 7. There is also evidence for minority contributions from six-coordinate high- and low-spin species (histidine-water, histidine-hydroxide, and bis-histidine). The K⁺-site mutant of APX varies considerably in the electronic absorption and MCD spectra in both the ferric and ferrous states when compared with spectra of the wild-type APX. The electronic absorption and MCD spectra of the engineered K⁺-site APX mutant are essentially identical to those of cytochrome b ₅, a known bis-imidazole (histidine) ligated heme system. It therefore appears that the K⁺-site mutant of APX has undergone a conformational change to yield a bis-histidine coordination structure in both the ferric and ferrous oxidation states at neutral pH. This conformational change is the result of mutagenesis of the protein to remove the K⁺-binding site which is located ～8?Å from the peroxide binding pocket. Thus, mutations of protein residues on the proximal side of the heme cause changes in iron ligation on the distal side.     

Intestinal cholesterol absorption.

The strong association between intestinal cholesterol absorption and total plasma cholesterol level has renewed interest in the absorptive process and stimulated the generation of new animal models. Increasingly, new studies suggest that cholesterol absorption is genetically controlled and supports a protein-mediated mechanism for cholesterol uptake into the intestinal mucosal cell. Insights into potential mechanisms are predicted to lead to novel pharmacological approaches to inhibit cholesterol absorption.     

Evaluation of potential health effects of 10 kHz magnetic fields: A rodent reproductive study

New technology involving the use of high-frequency inductive power distribution (HID) has recently been developed for use in materials handling and personnel transfer. Sinusoidal magnetic fields at a frequency of 10 kHz with field intensities of approximately 0.2 mT are generated directly between the current-carrying coils of this equipment. Effects of 10 kHz magnetic fields on cell division, migration, and differentiation have never been previously investigated. To evaluate potential effects on these parameters, a rodent reproductive study was undertaken using Wistar rats. Exposures were at 0.095, 0.24, and 0.95 mT with a background exposure of 5–10 μT. Three sets of parental rats were exposed continuously for 20–23.5 h/day to the fields: maternal rats during gestation, paternal rats for at least 45 days prior to mating and maternal rats 1 month prior to mating. Exposure phases thus covered spermatogenesis, maturation of the ovum and ovulation, fertilization, implantation, embryogenesis, organogenesis, and maturation of the fetus immediately prior to parturition. In all experiments pregnancy outcome was assessed. These studies failed to demonstrate any reproductive toxicity resulting from maternal or fetal exposure during gestation or following paternal or maternal exposure for several weeks prior to mating. No quantitative or qualitative effects on spermatogenesis occurred after exposure, and no effects on the estrous cycle or ovulation could be demonstrably linked to the 10 kHz magnetic field exposure at 0.095, 0.25, or 0.95 mT. Where possible, parental clinical chemistry and hematology were also examined. As in mouse toxicology studies previously reported, minor differences were observed between control and treated groups. These were regarded as statistically, but not biologically, significant and could not categorically be attributed to magnetic field exposure. Bioelectromagnetics 19:162–171, 1998. © 1998 Wiley-Liss, Inc.     

Induction of phenazine biosynthesis in cultures of Pseudomonas aeruginosa by L-N-(3-oxohexanoyl) homoserine lactone

Abstract A range of Pseudomonas spp. and other Gram-negative bacteria were screened for induction of antimicrobial activity in response to the autoregulatory factor l - N -(3-oxohexanoyl)homoserine lactone. In one of these, P. aeruginosa ATCC 10145, the production of phenazine metabolites was shown to be inducible in a dose-dependent manner. The production of phenazine-1-carboxamide increased over 50-fold compared to control cultures when supplemented with 200 μg/ml of the autoregulator. In addition, the production of an unidentified polar antibacterial substance by this strain increased with autoregulator concentration.     

Dissection and Mounting of Drosophila Pupal Eye Discs

The Drosophila melanogaster eye disc is a powerful system that can be used to study many different biological processes. It contains approximately 800 separate eye units, termed ommatidia¹. Each ommatidium contains eight neuronal photoreceptors that develop from undifferentiated cells following the passage of the morphogenetic furrow in the third larval instar². Following the sequential differentiation of the photoreceptors, non-neuronal cells develop, including cone and pigment cells, along with mechanosensory bristle cells³. Final differentiation processes, including the structured arrangement of all the ommatidial cell types, programmed cell death of undifferentiated cell types and rhodopsin expression, occurs through the pupal phase^4-7. This technique focuses on manipulating the pupal eye disc, providing insight and instruction on how to dissect the eye disc during the pupal phase, which is inherently more difficult to perform than the commonly dissected third instar eye disc. This technique also provides details on immunostaining to allow the visualization of various proteins and other cell components.     

Resolution of 4-amino-cyclopentanecarboxylic acid methyl esters using hydrolytic enzymes.

A number of esterases (EC 3.1.1.1) and lipases (EC 3.1.1.3) of microbial and mammalian origin were screened for the ability to resolve racemic 4-amino-cyclopentanecarboxylic acid methyl ester derivatives as potential intermediates in the production of carbocyclic nucleosides. Surprisingly, functionalization of the remote amino group had a profound effect on both the rate and enantioselectivity of hydrolysis of the methyl ester. 4-(Benzoylamino)-2-cyclopentenecarboxylic acid, methyl ester (V) with pig liver esterase gave the highest enantioselectivity. The residual ester, which was of the correct absolute stereochemistry [(+) 1S, 4R] for carbocyclic nucleoside synthesis, could be obtained in high optical purity. Optimization of pH, solvent type, and concentration improved the enantioselectivity of the process by a further twofold.     

GENDER-RELATED DIFFERENCES IN GAS EXCHANGE ARE NOT RELATED TO HOST QUALITY IN THE XYLEM-TAPPING MISTLETOE,PHORADENDRON JUNIPERINUM (VISCACEAE)

Male and female individuals of dioecious species often differ in morphology, physiology, growth, and habitat distribution. Where habitat distribution differences have been demonstrated, female plants generally occupy those habitats with greater resource availability (“rich” habitats). Gender-specific habitat preferences are often presumed to be a consequence of greater resource requirements, per gamete, of female reproduction. Previous work has shown that Phoradendron juniperinum, a xylem-tapping dioecious mistletoe that parasitizes Juniperus species in western North America, displays the opposite pattern: males are relatively more numerous than females in richer sites (i.e., branches with relatively high light and low evaporative demand within the host tree). We report here differences in host (“site”) quality and gas-exchange properties between the sexes. To minimize environmental variation, all measurements were made on sunlit foliage between 9:00 a.m. and 2:00 p.m. Males had significantly higher photosynthetic rates (4.0 [SE = 0.2] μmol m^-2 sec^-1) than either females (2.9 [0.3] μmol m^-2 sec^-1) or nonreproductive individuals (3.0 [0.2] μmol m-² sec^-1). Female photosynthetic rates were not statistically different from those of nonreproductive individuals. No concomitant differences in stomatal conductance were observed. Gas exchange data were independently confirmed by significant differences in carbon isotope ratio (δ¹³C). Gender-related differences were not related to host quality as measured by foliar N, foliar δ¹³C, or water potential of the host tree. The fate of the additional photosynthate in males is unknown, but we discuss the possibility that carbon costs of reproduction in males have been underestimated in past work.     

Cysteine (C)-X-C Receptor 4 Undergoes Transportin 1-Dependent Nuclear Localization and Remains Functional at the Nucleus of Metastatic Prostate Cancer Cells

The G-protein coupled receptor (GPCR), Cysteine (C)-X-C Receptor 4 (CXCR4), plays an important role in prostate cancer metastasis. CXCR4 is generally regarded as a plasma membrane receptor where it transmits signals that support transformation, progression and eventual metastasis. Due to the central role of CXCR4 in tumorigenesis, therapeutics approaches such as antagonist and monoclonal antibodies have focused on receptors that exist on the plasma membrane. An emerging concept for G-protein coupled receptors is that they may localize to and associate with the nucleus where they retain function and mediate nuclear signaling. Herein, we demonstrate that CXCR4 associated with the nucleus of malignant prostate cancer tissues. Likewise, expression of CXCR4 was detected in nuclear fractions among several prostate cancer cell lines, compared to normal prostate epithelial cells. Our studies identified a nuclear pool of CXCR4 and we defined a nuclear transport pathway for CXCR4. We reveal a putative nuclear localization sequence (NLS), ‘RPRK’, within CXCR4 that contributed to nuclear localization. Additionally, nuclear CXCR4 interacted with Transportinβ1 and Transportinβ1-binding to CXCR4 promoted its nuclear translocation. Importantly, G_αi immunoprecipitation and calcium mobilization studies indicated that nuclear CXCR4 was functional and participated in G-protein signaling, revealing that the nuclear pool of CXCR4 retained function. Given the suggestion that functional, nuclear CXCR4 may be a mechanism underlying prostate cancer recurrence, increased metastatic ability and poorer prognosis after tumors have been treated with therapy that targets plasma membrane CXCR4, these studies addresses a novel mechanism of nuclear signaling for CXCR4, a novel mechanism of clinical targeting, and demonstrate an active nuclear pool that provides important new information to illuminate what has been primarily clinical reports of nuclear CXCR4.