Robert E. Kemm

A Blended Approach to Active Learning in a Physiology Laboratory-Based Subject Facilitated by an e-Learning Component

Learning via online activities (e-learning) was introduced to facilitate existing face-to-face teaching to encourage more effective student preparation and then informed participation in an undergraduate physiology laboratory-based course. Active learning was encouraged by hypothesis formation and predictions prior to classes, with opportunities for students to amend their e-learning submissions after classes. Automatic or tutor feedback was provided on student submissions. Evaluation of the course was conducted via student questionnaires, individual student interviews, and analysis of student marks in examinations and of the e-learning component. Student feedback on this entire subject in the university-wide quality of teaching survey was very high by University of Melbourne standards and most encouraging for the first implementation of such a curriculum modification. Results from further detailed surveys of student interactions and engagement and correlation analysis between student responses were also very supportive of the effectiveness of the course. There were no significant differences between examination marks in the new course with e-learning and the previous year without e-learning. However, there was a significant correlation between assessment of student e-learning work and their final examination mark. Correlation analysis between various survey responses helped interpret results and strengthened arguments for e-learning and suggested future improvements for student use of e-learning. This mode of e-learning used to support face-to-face learning activities in the laboratory can be adapted for other disciplines and may assist students in developing a greater appreciation and a deeper approach for learning from their practical class experiences.

Intracellular responses of olfactory bulb granule cells to stimulating the horizontal diagonal band nucleus

The effects of centrifugal afferents on membrane potentials of identified granule cell layer using evoked field potential profiles, and trans-synaptic activation via antidromic stimulation of output cell axon collaterals. Intracellular recordings maintained for 4-30 min showed complex spontaneous spike discharges and allowed characterization of the cells input resistance, and on some occasions its morphology following intracellular injection of Lucifer Yellow. Stimulation in the nucleus of the horizontal limb of the diagonal band, but not surrounding regions, produced hyperpolarizing responses in 13 of 27 cells in the granule cell layer; four of these were morphologically identified as granule cells of two types, in five the responses had reversal potentials more negative than the resting potential, and six were identified as granule cells by monosynaptic activation from output axon collaterals. A different set of three cells in the granule cell layer responded with depolarization. The results are consistent with the inhibition of tonic activity of granule cells by the nucleus of the horizontal limb of the diagonal band, leading to disinhibition of mitral and tufted cells via dendrodendritic synapses of granule cells on mitral/tufted cell secondary dendrites.

Effect of stimulating the nucleus of the horizontal limb of the diagonal band on single unit activity in the olfactory bulb

The effects of centrifugal afferents on single unit discharge in the main olfactory bulb were studied in anaesthetized rats. Recording with extracellular micropipettes revealed spontaneous firing in all bulb layers. Units were located to different laminae using evoked field-potential profiles and histological verification. Output neurons were identified by antidromic response to stimulation of the lateral olfactory tract. Single- or brief multiple-pulse stimulation in the nucleus of the horizontal limb of the diagonal band, but not in adjacent regions, facilitated 17 out of 27 mitral cells with no effect on 10, but inhibited 21 out of 33 granule cell layer units with no effect on 12. Of 13 presumed tufted cells, six were facilitated and the rest unaffected. In contrast, stimulation of olfactory cortex inhibited mitral cells and facilitated most granule layer cells. The results are consistent with an inhibition of tonic granule cell discharge by the horizontal diagonal band nucleus, with resultant disinhibition of mitral cells via the dendrodendritic synapses of granule cells on mitral cell secondary dendrites.

Whole-cell K+ currents in identified olfactory bulb output neurones of rats.

1. Voltage‐gated whole‐cell K+ currents have been investigated in olfactory bulb (OB) output (mitral/tufted) neurones from neonatal rats, which were retrogradely labelled by rhodamine or Fast Blue and identified after enzymatic dissociation. Forty‐five per cent of labelled neurones exhibited either phasic or non‐phasic spontaneous firing in cell‐attached configuration. 2. Four outward K+ currents have been identified in all such identified OB output neurones. They are the transient (IA), the delayed rectifier (IDK), and two Ca(2+)‐dependent (IK(Ca)) currents. No inward rectifier was detected. 3. The IA was activated at around ‐45 mV and reached its peak within 3‐10 ms. The decay phase could be described by single exponential distribution with the time constant of 45.2 +/‐ 3.8 ms at depolarizations 10‐60 mV from a holding potential of ‐70 mV. Its activation and steady‐state inactivation processes could be fitted with Boltzmann equations yielding half‐maximal activation potentials of 7.6 +/‐ 0.4 and ‐47.4 +/‐ 0.2 mV, respectively. It was sensitive to block by 4‐AP (1 mM) and by Zn2+ (1 mM). 4. The IDK was activated at potentials more positive than ‐30 mV, with half‐maximal activation at 21 mV. It was sustained during 1 s test pulses without apparent decay. It was blocked by TEA at a concentration of 20 mM. About 8% of the sustained current, in 11/24 cells tested, was found to resist block by a combination of all pharmacological agents tested. 5. Apamin at 100 nM blocked a TEA‐insensitive component which accounted for about 23% of the maximal sustained currents. Iberiotoxin (IbTX), which has been found to block maxi K+ currents more selectively than does charybdotoxin, reversibly blocked Ca(2+)‐activated K+ current, with a half‐maximal dose of about 100 nM in 8/13 OB output neurones tested. This accounted for 20% of the maximal sustained K+ current. The effect of IbTX was not observed in the presence of 20 mM external TEA. 6. Direct evidence is provided in this study regarding kinetic and pharmacological properties of four types of outward K+ channels in OB output neurones.

Olfactory bulb output neurons excited from a basal forebrain magnocellular nucleus

We present intracellular data which demonstrates a unique facilitatory centrifugal influence on the output cells of the olfactory bulb; the source being the lateral component of the nucleus of the horizontal limb of the diagonal band (HDB), part of the basal forebrain magnocellular complex. Damage to this facilitatory HDB influence may explain the loss of olfactory sensitivity seen early in Alzheimers disease in which pathological changes occur in the basal forebrain.

P-GLYCOPROTEIN EXPRESSION IN CLASSICAL MULTI-DRUG RESISTANT LEUKAEMIA CELLS DOES NOT CORRELATE WITH ENHANCED CHLORIDE CHANNEL ACTIVITY

1. P‐glycoprotein (Pgp) is an ATP‐dependent drug efflux pump responsible for classical multi‐drug resistance (MDR).