Excitotoxic stimulation of brain microslices as an in vitro model of stroke.

Examining molecular mechanisms involved in neuropathological conditions, such as ischemic stroke, can be difficult when using whole animal systems. As such, primary or 'neuronal-like' cell culture systems are commonly utilized. While these systems are relatively easy to work with, and are useful model systems in which various functional outcomes (such as cell death) can be readily quantified, the examined outcomes and pathways in cultured immature neurons (such as excitotoxicity-mediated cell death pathways) are not necessarily the same as those observed in mature brain, or in intact tissue. Therefore, there is the need to develop models in which cellular mechanisms in mature neural tissue can be examined. We have developed an in vitro technique that can be used to investigate a variety of molecular pathways in intact nervous tissue. The technique described herein utilizes rat cortical tissue, but this technique can be adapted to use tissue from a variety of species (such as mouse, rabbit, guinea pig, and chicken) or brain regions (for example, hippocampus, striatum, etc.). Additionally, a variety of stimulations/treatments can be used (for example, excitotoxic, administration of inhibitors, etc.). In conclusion, the brain slice model described herein can be used to examine a variety of molecular mechanisms involved in excitotoxicity-mediated brain injury.

Maturational changes in the subunit composition of AMPA receptors and the functional consequences of their activation in chicken forebrain.

AMPA receptors play a critical role in synaptic plasticity and brain development. Here we show that Ca(2+) uptake in response to AMPA receptor activation decreases dramatically during maturation in chicken brain microslices without a change in tissue AMPA receptor content. We found that during maturation the relative concentration of GluR2 subunits increased, the concentration of the AMPA receptor-associated scaffold proteins SAP97 and GRIP decreased and that depolarization increased GluR1 phosphorylation at Ser831 in subcellular fractions enriched in postsynaptic densities at 2 weeks but not at 10 weeks. These changes are all consistent with a decreased Ca(2+) entry through AMPA receptor channels in response to receptor activation and may account for the changes in the functional properties of the receptor, which are thought to underlie, at least in part, the physiological changes that occur with maturation.

Assessment of personal qualities in selection of medical radiation science students.

UNLABELLED: It is increasingly acknowledged that, in addition to prior academic achievement, there is a need to seek evidence for the abilities and personal qualities of applicants to health professional programs at a university. The aim of this study was to determine the specific abilities and personal qualities required for excellence in practice in the relevant professional domains of medical radiation science (MRS). METHODS: A focus group, consisting of MRS academic staff, developed a questionnaire. The questionnaire was sent to senior MRS practitioners throughout Australia and 213 were returned for analysis. Respondents were asked to rate 40 specific abilities and qualities (referred to as "elements") on a 5-point scale. RESULTS: Two hundred thirteen completed questionnaires were returned, a 53% response rate. One hundred twelve respondents (52%) indicated they currently worked in diagnostic radiography (DR), 57 (27%) worked in radiation therapy (RT), and 44 (21%) worked in nuclear medicine (NM). The duration (mean +/- SD) of the respondents' professional practice in MRS was 14.5 +/- 10 y, with durations ranging from 1 to 43 y. Raw scores and mean scores were examined for any influence of the variable "Number of Years in Practice." DISCUSSION: No major differences were found between the ratings provided by the practitioners from the 3 different MRS professional domains of NM, RT, and DR. Factor analysis indicated the existence of 3 orthogonal factors in the questionnaire data: (a) treat others professionally and ethically, (b) engage with and be open to others, and (c) problem-solving ability. Qualitative analysis of the respondents' comments provided similar themes: (a) the need for professional competence (knowledge and abilities), (b) ethical behavior, (c) the need for a technology and a people orientation, and (d) MRS should be the first choice of MRS students and not a second choice to other professional degrees. CONCLUSION: Senior medical radiation scientists identified professionalism, ethical behavior, engagement with and openness to others, intrinsic specific motivation, and an orientation to people and technology as nonacademic qualities required for excellence in the practice of the professions embraced by MRS.

Angiotensin II causes calcium entry into bovine adrenal chromaffin cells via pathway(s) activated by depletion of intracellular calcium stores.

The characteristics and properties of the increase in cytosolic [Ca2+] that occurs in bovine adrenal medullary chromaffin cells on exposure to angiotensin 11 have been investigated. In fura-2 loaded cells exposure to a maximally effective concentration of angiotensin II (100 nM) caused a rapid, but transient increase in cytosolic [Ca2+] followed by a lower plateau that was sustained as long as external Ca2+ was present. In the absence of external Ca2+ only the initial brief transient was observed. In cells previously treated with thapsigargin in Ca2+-free medium to deplete the internal Ca2+ stores, angiotensin II caused no increase in cytosolic [Ca2+] when external Ca2+ was absent. Reintroduction of external Ca2+ to thapsigargin-treated, store-depleted cells caused a sustained increase in cytosolic [Ca2+] that was not further increased upon exposure to angiotensin II. Analysis of the data suggests that in bovine chromaffin cells angiotensin II causes Ca2+ entry via a pathway(s) activated as a consequence of internal store mobilization, and entry through this pathway(s) forms the majority of the sustained Ca2+ influx evoked by angiotensin II.

Ions, channels, and receptors.

In this section eight presenters focus on three distinct aspects of chromaffin cell biology: first, the properties of neuronal nicotinic receptors; second, the shaping of the Ca(2+) signals that underlie chromaffin cell function; and third, the properties and expression of cell surface transporter proteins. Together these studies provide considerable new insight into the complexity of the signaling mechanisms that regulate the functional activity of the cell.

In situ chelation of Ca(2+) in intracellular stores induces capacitative Ca(2+) entry in bovine adrenal chromaffin cells.

Reduction of intracellular Ca(2+) stores (by chelation with the EDTA structural analogue, TPEN) is itself a sufficient trigger of capacitative Ca(2+) entry. TPEN may be a useful tool in studies to investigate the mechanism of capacitative Ca(2+) entry, since potential confounders, such as changes in cytosolic Ca(2+) and second messenger levels, are obviated and the use of pharmacological modifiers of SERCA pumps and Ca(2+) release channels is avoided.