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PubMed1997

Novel modalities for appraising individual and coordinate pulsatile hormone secretion: the paradigm of luteinizing hormone and testosterone release in the aging male.

To quantify aging- and disease-associated alterations in the integrative and interactive components of a pulsatile neuroendocrine axis, novel biomathematical strategies are required. Here, I illustrate as an investigative paradigm otherwise subtle aging-dependent disturbances of the gonadotropin-releasing-hormone (GnRH)-luteinizing hormone (LH)-testosterone feedback axis in men, in whom strong age-related contrasts become evident via any of four strategies applied alone or in combination: (1) intensified blood sampling schedules to capture the temporal structure of episodic hormone (LH and testosterone) secretion; (2) deconvolution analysis as a technique to quantify underlying pituitary and gonadal hormone secretory rates from the observed plasma hormone concentration profiles; (3) approximate entropy as a scale- and model-independent measure of the serial regularity or orderliness of the hormone release process over time; and (4) cross-approximate entropy (cross-ApEn) to quantify joint asynchrony between two concurrent pulse trains without confounding by variable lag. These new methodologies are introduced and reviewed briefly, a stochastic differential equation feedback construct alluded to, and the resultant insights into distinct alterations of the aging male gonadotropic axis highlighted. In summary, the new experimental strategies of intensified venous sampling, multiparameter deconvolution analysis, approximate entropy, and cross-approximate entropy unveil new mechanisms underlying dynamic neuroendocrine-axis activity, as exemplified by aging-associated disruption of the human male reproductive axis.

Aging↗

PubMed2002

JAKs, STATs and Src kinases in hematopoiesis.

Hematopoiesis is the cumulative result of intricately regulated signal transduction cascades that are mediated by cytokines and their cognate receptors. Proper culmination of these diverse signaling pathways forms the basis for an orderly generation of different cell types and aberrations in these pathways is an underlying cause for diseases such as leukemias and other myeloproliferative and lymphoproliferative disorders. Over the past decade, downstream signal transduction events initiated upon cytokine/growth factor stimulation have been a major focus of basic and applied biomedical research. As a result, several key concepts have emerged allowing a better understanding of the complex signaling processes. A group of transcription factors, termed signal transducers and activators of transcription (STATs) appear to orchestrate the downstream events propagated by cytokine/growth factor interactions with their cognate receptors. Similarly, cytoplasmic Janus protein tyrosine kinases (JAKs) and Src family of kinases seem to play a critical role in diverse signal transduction pathways that govern cellular survival, proliferation, differentiation and apoptosis. Accumulating evidence suggests that STAT protein activation may be mediated by members of both JAK and Src family members following cytokine/growth factor stimulation. In addition, JAK kinases appear to be essential for the phosphorylation of the cytokine receptors which results in the creation of docking sites on the receptors for binding of SH2-containing proteins such as STATs, Src-kinases and other signaling intermediates. Cell and tissue-specificity of cytokine action appears to be determined by the nature of signal transduction pathways activated by cytokine/receptor interactions. The integration of these diverse signaling cues from active JAK kinases, members of the Src-family kinases and STAT proteins, leads to cell proliferation, cell survival and differentiation, the end-point of the cytokine/growth factor stimulus.

Animals↗

PubMed2003

Epi-fluorescence microscopic characterization of potential-induced changes in a DOPC monolayer on a Hg drop.

Characterization of the potential-induced changes of a lipid-coated Hg-0.1 M KCl interface through electrochemical techniques and newly developed in situ fluorescence microscopy is described. Fluorescence of a fluorophore-containing dioleoyl phosphatidylcholine (DOPC) layer deposited from the gas-solution interface was observed to be dependent upon the potential of the Hg surface. The largest changes occurred for potentials where the lipid layer was desorbed: the lipid moved away from the electrode surface, reducing the efficiency of metal-mediated quenching of the excited state resulting in an increase in fluorescence. Electric potential-induced changes in the morphology of the adsorbed or desorbed DOPC lipid monolayer were observed optically for the first time using this technique. The observed potential-dependent fluorescence was compared to previous studies on an octadecanol-coated Au(111) electrode. Fluorescence microscopy was also used to characterize the fusion of DOPC liposomes with a previously adsorbed DOPC layer. Large changes in fluorescence were observed for the DOPC layer after fusion with liposomes. The fusion was accomplished via potential-created defects in the adsorbed DOPC monolayer through which the liposomes interact. The integration of the liposomes into the adsorbed monolayer results in a hybrid layer in which some lipid exists further from the electrode surface, resulting in a large increase in fluorescence. Possibilities for the creation of a biomimetic adsorbed hybrid lipid layer on Hg are also discussed.

Journal Article↗

PubMed2001

Implementation and evaluation of an undergraduate emergency medicine curriculum.

OBJECTIVE: To describe the implementation and evaluation of an undergraduate course in the first Australian academic emergency medicine unit. METHODS: A descriptive study of a course involving fifth year medical students at the University of Western Australia was undertaken. Teaching included self-directed case problem solving, small group tutorials, practical-skills teaching, clinical attachments and information handouts. Evaluation involved questionnaire scores and written feedback regarding life-support skills, tutorial teaching, course materials, clinical attachments and the course in general. Some groups of students underwent pre-course and post-course examinations. RESULTS: Subjective and objective testing showed that student knowledge significantly improved. Feedback was especially positive toward clinical attachments in emergency departments, practical skills tutorials and the case-based learning method. Students requested longer attachments to emergency departments, and more practical, case-based, interactive and bedside teaching. Problems encountered included inadequate time for teaching, vagueness about student roles and objectives, and dealing with death for the first time without adequate preparation. CONCLUSION: Undergraduate emergency medicine education should become an essential part of Australian and international undergraduate medical education. Emergency medicine is enjoyable and eminently suitable for problem-based, interactive and integrated teaching and improves confidence, clinical experience in emergencies, practical skills and teamwork. Improvements include more problem-based teaching, more practical skills sessions and better definition of student roles. These are general principles that can be applied to other undergraduate courses and to designers of other emergency medicine courses, both undergraduate and postgraduate.

Analysis of Variance↗

PubMed2003

Na+ stimulates binding of dopamine to the dopamine transporter in cells but not in cell-free preparations.

Although Na+ is crucial for the function of the dopamine (DA) transporter (DAT), its role in the substrate binding step has been questioned. To address this issue, we investigated the effect of Na+ on DA binding by measuring the potency of DA in inhibiting the binding of the cocaine analogue [3H]2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane (CFT) in intact cells expressing DAT in their plasma membranes and in membranes isolated from these cells. In cells, Na+ substantially enhanced the potency of DA in inhibiting CFT binding. This effect of Na+ was independent of buffer compositions and substitutes (sucrose vs. NMDG), more pronounced at 4 degrees C than 25 degrees C, and correlated with its stimulatory effect on DA uptake Km. Removing extracellular Na+ had little effect on intracellular concentrations of Na+ and K+, or on membrane potential. These data suggest that extracellular Na+ most likely acts at the transporter level to enhance the binding of external DA during the transport cycle. In contrast, in cell-free membrane preparations the Na+ stimulation was abolished without impairment of the potency of DA in inhibiting CFT binding, regardless of whether sucrose was used to maintain the buffer osmolarity. The difference in Na+ dependence for DA to inhibit CFT binding between plasma membranes of intact cells and isolated membranes raises the possibility that intracellular ion environment, alone or in combination with other cellular factors, plays a critical role in determining DA-DAT interaction and the integration of Na+ modulation in this interaction.

Binding, Competitive↗

PubMed2002

Docetaxel in ovarian cancer: phase III perspectives and future development.

In the mid 1990s, the incorporation of paclitaxel into platinum-based therapy for ovarian cancer marked a significant advance in treatment. Future progress will probably involve reductions in toxicity, which may be achieved by combining the less neurotoxic agent docetaxel with carboplatin. In an international phase III study, 1,077 chemotherapy-naive patients with stage Ic-IV ovarian cancer were randomized to receive carboplatin targeted to an AUC of 5 plus either docetaxel 75 mg/m(2) or paclitaxel 75 mg/m(2) for six cycles. Patients treated with paclitaxel plus carboplatin experienced significantly greater neurotoxicity than those treated with docetaxel plus carboplatin. Docetaxel/carboplatin and paclitaxel/carboplatin produced similar rates of objective response (66% and 62%, respectively), and initial data on progression-free survival indicate that the two treatments appear very similar in efficacy. Thus, docetaxel may prove to be a valid alternative to paclitaxel as part of first-line therapy in ovarian cancer. Nevertheless, there remains considerable scope for improvements in treatment. There is the possibility of using existing drugs more effectively, perhaps by the use of sequential rather than concurrent regimens. This would allow the most active drugs to be used at full dose, increase tolerability, and avoid the possibility of negative drug interaction. The integration of molecularly targeted agents, such as those directed at epidermal growth factor receptors, into existing regimens is highly promising but will need to be explored in randomized trials of first-line therapy. Because the prime obstacle to successful treatment is the acquisition of drug resistance, understanding the underlying mechanisms is an important future priority. One candidate is mismatch repair deficiency; the interest here is that experimental resistance reversal is achievable with hypomethylating agents, raising the possibility of future clinical trials if the clinical relevance of this mechanism can be confirmed.

Antineoplastic Agents, Phytogenic↗

PubMed2006

Coactivator as a target gene specificity determinant for histone H3 lysine 4 methyltransferases.

Activating signal cointegrator-2 (ASC-2), a coactivator of multiple transcription factors that include retinoic acid receptor (RAR), associates with histone H3-K4 methyltranferases (H3K4MTs) MLL3 and MLL4 in mixed-lineage leukemia. Here, we show that mice expressing a SET domain mutant of MLL3 share phenotypes with isogenic ASC2+/- mice and that expression and H3-K4 trimethylation of RAR target gene RAR-beta2 are impaired in ASC-2-null mouse embryo fibroblasts (MEFs) or in MEFs expressing siRNAs against both MLL3 and MLL4. We also show that MLL3 and MLL4 are found in distinct ASC-2-containing complexes rather than in a common ASC-2 complex, and they are recruited to RAR-beta2 by ASC-2. In contrast, RAR-beta2 expression is intact in MEFs devoid of menin, a component of MLL1 and MLL2 H3K4MT complexes. These results suggest that ASC-2 confers target gene specificity to MLL3 and MLL4 H3K4MT complexes and that recruitment of H3K4MTs to their target genes generally involves interactions between integral components of H3K4MT complexes and transcription factors.

Animals↗

PubMed1991

Ferritin mRNA: interactions of iron regulatory element with translational regulator protein P-90 and the effect on base-paired flanking regions.

The ferritin iron regulatory element (IRE), a conserved sequence of 28 nucleotides in a hairpin loop, is a conserved mRNA-specific translational regulatory element; flanking the IRE are regions of varying sequence, which form 9-17 base pairs close to the 5' cap. P-90 is a ferritin mRNA-specific translation regulatory protein purified from animal liver and reticulocytes. To study the P-90-RNA interaction, protein nucleases (RNase S1 and T1) and chemical nucleases FeEDTA and/or 1,10-phenanthroline-Cu were used as probes of an oligonucleotide (n = 55), containing the IRE and flanking regions (FL), and natural ferritin mRNA. Footprints and "toeprints" showed that P-90 binding was confined to the stem and loop of the IRE itself. However, P-90 altered the structure of the flanking region by increasing base stacking or helicity (RNase V1 sensitivity). Comparison of the reactivity of the IRE and flanking regions in natural mRNA and the 55-mer showed that long-range interactions included protecting bulges, single-stranded, and stacked regions from protein nucleases as well as stabilizing the P-90-RNA interaction. Structural integration of the IRE with the base-paired flanking regions was indicated by common features of reactivity (periodic hypersensitivity to FeEDTA) and changes in the FL region caused by P-90. The increased secondary structure of the IRE flanking regions caused by P-90 binding to the IRE provides a likely mechanism for blocking initiation of ferritin mRNA translation, since the combined structure (IRE + FL) is so close (8-17 nucleotides) to the cap.

Animals↗

PubMed1999

Interaction between RGS7 and polycystin.

Regulators of G protein signaling (RGS) proteins accelerate the intrinsic GTPase activity of certain Galpha subunits and thereby modulate a number of G protein-dependent signaling cascades. Currently, little is known about the regulation of RGS proteins themselves. We identified a short-lived RGS protein, RGS7, that is rapidly degraded through the proteasome pathway. The degradation of RGS7 is inhibited by interaction with a C-terminal domain of polycystin, the protein encoded by PKD1, a gene involved in autosomal-dominant polycystic kidney disease. Furthermore, membranous expression of C-terminal polycystin relocalized RGS7. Our results indicate that rapid degradation and interaction with integral membrane proteins are potential means of regulating RGS proteins.

Amino Acid Sequence↗

PubMed1996

A kinase anchor protein 75 targets regulatory (RII) subunits of cAMP-dependent protein kinase II to the cortical actin cytoskeleton in non-neuronal cells.

Neuronal A kinase anchor protein (AKAP) homologs, such as AKAPs 75 and 150, tether cAMP-dependent protein kinase II (PKAII) isoforms to the postsynaptic cytoskeleton, thereby creating target sites for cAMP action. These AKAPs, which bind regulatory subunits (RIIs) of PKAII, are also expressed in certain non-neuronal cells. Non-neuronal cell lines that stably express wild type and mutant AKAP75 transgenes were generated to investigate the extraneuronal function of AKAPs. In non-neuronal cells, AKAP75 accumulates selectively in the actin-rich, cortical cytoskeleton in close proximity with the plasma membrane. AKAP75 efficiently sequesters cytoplasmic RIIalpha and RIIbeta (PKAII isoforms) and translocates these polypeptides to the cell cortex. Two structural modules in AKAP75, T1 (residues 27-48), and T2 (residues 77-100), are essential for targeting AKAP75.RII complexes to the cortical cytoskeleton. Deletions or amino acid substitutions in T1 and/or T2 result in the dispersion of both AKAP75 and RII subunits throughout the cytoplasm. AKAP75 is co-localized with F-actin and fodrin in the cortical cytoskeleton. Incubation of cells with 5 microM cytochalasin D disrupts actin filaments and dissociates actin from the cell cortex. In contrast, the bulk of AKAP75 and fodrin remain associated with the cortical region of cytochalasin D-treated cells. Thus, targeting of AKAP75 does not depend upon direct binding with F-actin. Rather, AKAP75 (like fodrin) may be associated with a multiprotein complex that interacts with integral plasma membrane proteins.

A Kinase Anchor Proteins↗

PubMed1997

Sorting determinants in the transmembrane domain of p24 proteins.

Members of the p24 family of putative cargo receptors are proposed to contain retrograde and anterograde trafficking signals in their cytoplasmic domain to facilitate coat protein binding and cycling in the secretory pathway. We have analyzed the role of the transmembrane domain (TMD) of a p24 protein isolated from COPI-coated intra-Golgi transport vesicles. CD8-p24 chimeras were transiently expressed in COS7 cells and analyzed by immunofluorescence and pulse-chase experiments. The localization and transit of the wild-type chimera from the endoplasmic reticulum (ER) through the Golgi complex involved a glutamic acid residue and a conserved glutamine in the TMD. The TMD glutamic acid mediated the localization of the chimeras to the ER in the absence of the conserved glutamine. Efficient ER exit required the TMD glutamine and was further facilitated by a pair of phenylalanine residues in the cytoplasmic tail. TMD residues of p24 proteins may mediate the interaction with integral membrane proteins of the vesicle budding machinery to ensure p24 packaging into transport vesicles.

Amino Acid Sequence↗

PubMed1998

Phosphatidylinositol 3-kinase is involved in the induction of macrophage growth by oxidized low density lipoprotein.

Early atherosclerotic lesions are characterized by the presence of cholesterol-rich, macrophage-derived foam cells. It has recently been shown that macrophage proliferation occurs during the development of early lesions and that oxidized low density lipoprotein (LDL) stimulates macrophage growth. Possible mechanisms for this induction of macrophage growth include potentiation of mitogenic signal transduction by a component of oxidized LDL following internalization and degradation, interaction with integral plasma membrane proteins coupled to signaling pathways, or direct or indirect activation of growth factor receptors on the cell surface (e.g. GM-CSF receptor) through an autocrine/paracrine mechanism. The present study was undertaken to characterize some of the early intracellular signaling events by which oxidized LDL mediates macrophage cell growth. Extensively oxidized LDL increased protein-tyrosine phosphorylation and caused a 2-fold increase in phosphatidylinositol (PI) 3-kinase activity in phorbol ester-pretreated THP-1 cells (a human monocyte-like cell line). Similar concentrations of native LDL had no effect. Oxidized LDL also stimulated growth of resident mouse peritoneal macrophages, and this effect was reduced by 40-50% in cells treated with PI 3-kinase inhibitors (100 nM wortmannin or 20 microM LY294002). These results suggest that PI 3-kinase mediates part of the mitogenic effect of oxidized LDL, but parallel pathways involving other receptors and signal transduction pathways are likely also involved.

Androstadienes↗

PubMed2002

The COOH terminus of GATE-16, an intra-Golgi transport modulator, is cleaved by the human cysteine protease HsApg4A.

Docking of a vesicle at the appropriate target membrane involves an interaction between integral membrane proteins located on the vesicle (v-SNAREs) and those located on the target membrane (t-SNAREs). GATE-16 (Golgi-associated ATPase enhancer of 16 kDa) was shown to modulate the activity of SNAREs in the Golgi apparatus and is therefore an essential component of intra-Golgi transport and post-mitotic Golgi re-assembly. GATE-16 contains a ubiquitin fold subdomain, which is terminated at the carboxyl end by an additional amino acid after a conserved glycine residue. In the present study we tested whether the COOH terminus of GATE-16 undergoes post-translational cleavage by a protease which exposes the glycine 116 residue. We describe the isolation and characterization of HsApg4A as a human protease of GATE-16. We show that GATE-16 undergoes COOH-terminal cleavage both in vivo and in vitro, only when the conserved glycine 116 is present. We then utilize an in vitro assay to show that pure HsApg4A is sufficient to cleave GATE-16. The characterization of this protease may give new insights into the mechanism of action of GATE-16 and its other family members.

Adaptor Proteins, Signal Transducing↗

PubMed2002

The immune-enhancing effects of dietary fibres and prebiotics.

The gastrointestinal tract is subjected to enormous and continual foreign antigenic stimuli from food and microbes. This organ must integrate complex interactions among diet, external pathogens, and local immunological and non-immunological processes. It is critical that protective immune responses are made to potential pathogens, while hypersensitivity reactions to dietary antigens are minimised. There is increasing evidence that fermentable dietary fibres and the newly described prebiotics can modulate various properties of the immune system, including those of the gut-associated lymphoid tissues (GALT). This paper reviews evidence for the immune-enhancing effects of dietary fibres. Changes in the intestinal microflora that occur with the consumption of prebiotic fibres may potentially mediate immune changes via: the direct contact of lactic acid bacteria or bacterial products (cell wall or cytoplasmic components) with immune cells in the intestine; the production of short-chain fatty acids from fibre fermentation; or by changes in mucin production. Although further work is needed to better define the changes, mechanisms for immunomodulation, and the ultimate impact on immune health, there is convincing preliminary data to suggest that the consumption of prebiotics can modulate immune parameters in GALT, secondary lymphoid tissues and peripheral circulation. Future protocols on the physiological impact of consuming prebiotics should be designed to include assessments of the gut microflora, gut physiology and the function and composition of the various regions of GALT.

Dietary Fiber↗

PubMed2002

Learning outcomes and instructional objectives: is there a difference?

Learning outcomes are broad statements of what is achieved and assessed at the end of a course of study. The concept of learning outcomes and outcome-based education is high on today's education agenda. The idea has features in common with the move to instructional objectives which became fashionable in the 1960s, but which never had the impact on education practice that it merited. Five important differences between learning outcomes and instructional objectives can be recognized: (1) Learning outcomes, if set out appropriately, are intuitive and user friendly. They can be used easily in curriculum planning, in teaching and learning and in assessment. (2) Learning outcomes are broad statements and are usually designed round a framework of 8-12 higher order outcomes. (3) The outcomes recognize the authentic interaction and integration in clinical practice of knowledge, skills and attitudes and the artificiality of separating these. (4) Learning outcomes represent what is achieved and assessed at the end of a course of study and not only the aspirations or what is intended to be achieved. (5) A design-down approach encourages ownership of the outcomes by teachers and students.

Clinical Competence↗

PubMedDate not supplied

Women and depression.

As Western society increases in complexity and becomes more reliant on technology, women who thrive as integrators in interactional modes will face new dilemmas. Many women will view these changes as challenges, but for many other women, who view these changes as threats, the response will be depression. We lay a foundation to an understanding of depression in women, evaluating the current concept of depression and pointing out its limitations. We then review the traditional theories of women's increased vulnerability to depressive disorders, which have failed to explain adequately this phenomenon. A more recent theory of women's depression, based on the self-in-relation theory of women's development, is offered as an alternative.

Depressive Disorder↗

PubMedDate not supplied

The interrupted career group: a preliminary report.

This paper reports on the Interrupted Career Group, a therapy group for individuals whose professional and personal lives have drastically changed due to psychiatric illness and whose attempts to resume a career or other meaningful activities have been unsuccessful. Thirty-two persons with interrupted careers were asked to specify and pursue a vocational, educational, or volunteer track that integrated previous skills and activities with their present life situation and psychiatric limitations. They were also encouraged to discuss feelings of envy, shame, inferiority, rage, and humiliation associated with their interruption or activated in their new pursuits. Twenty-two of the participants effected change by utilizing the group to discuss feelings and efforts connected to resuming an integrated track. Such changes were seen equally in vocational/educational/volunteer activities and emotional functioning, or more in emotional functioning than in vocational/educational/volunteer activities. Ten participants did not show change; they were too psychiatrically disabled, lacked adequate motivation, or were unable to process affects related to actual pursuit of changes and integration. An interactive group process focusing on feelings of shame, envy, rage, inferiority, and humiliation related to experiences of an interrupted career can contribute to improved emotional and vocational functioning.

Adult↗

PubMed2005

Clinical anti-aging hormetic strategies.

Hormesis is a term describing the beneficial effects of mild and repeated stimulation or stress, which ultimately bolsters defences against deleterious processes. Although hormetic influences are clearly encountered at the cellular and molecular level, little is known about the effects of hormesis at a clinical level. This paper examines the suggestion that mild stimulation or appropriately timed challenges may be used clinically in order to influence the impact of age-related disease and dysfunction. Examples of stimulation or challenges that may exhibit hormetic effects include dietary restriction, physical and mental exercise, and even social and spiritual stimulation. Dietary restriction places the organism under nutritional stress, stimulating several biochemical repair pathways that may counteract certain age-related changes. Physical and mental challenges, if appropriately timed and sufficiently varied, are directed at increasing the complexity and integration of interacting muscular, cardiovascular, and neural stimuli. Social and spiritual stimulation aimed at reversing age-related loss of dynamical complexity acts upon even higher levels to ensure a reduced risk of social problems in aging.

Aging↗