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Biomedical subjects

J Henderson

Publications and source records attributed to J Henderson.

259 records · Page 15Linked to original sources
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Selective abolition of the NMDA component of long-term potentiation in mice lacking mGluR5.

The mechanisms underlying the differential expression of long-term potentiation (LTP) by AMPA and NMDA receptors, are unknown, but could involve G-protein-linked metabotropic glutamate receptors. To investigate this hypothesis we created mutant mice that expressed no metabotropic glutamate receptor 5 (mGluR5), but showed normal development. In an earlier study of these mice we analyzed field-excitatory postsynaptic potential (fEPSPs) in CA1 region of the hippocampus and found a small decrease; possibly arising from changes in the NMDAR-mediated component of synaptic transmission. In the present study we used whole-cell patch clamp recordings of evoked excitatory postsynaptic currents (EPSCs) in CA1 pyramidal neurons to identify the AMPAR- and NMDAR-mediated components of LTP. Recordings from control mice following tetanus, or agonist application (IS, 3R-1-amino-cyclopentane 1,3-dicarboxylic acid) (ACPD), revealed equal enhancement of the AMPA and NMDA receptor-mediated components. In contrast, CA1 neurons from mGluR5-deficient mice showed a complete loss of the NMDA-receptor-mediated component of LTP (LTP(NMDA)), but normal LTP of the AMPA-receptor-mediated component (LTP(AMPA)). This selective loss of LTP(NMDA) was seen in three different genotypic backgrounds and was apparent at all holding potentials (-70 mV to +20 mV). Furthermore, the LTP(NMDA) deficit in mGluR5 mutant mice could be rescued by stimulating protein kinase C (PKC) with 4beta-phorbol-12,13-dibutyrate (PDBu). These results suggest that PKC may couple the postsynaptic mGluR5 to the NMDA-receptor potentiation during LTP, and that this signaling mechanism is distinct from LTP(AMPA). Differential enhancement of AMPAR and NMDA receptors by mGluR5 also supports a postsynaptic locus for LTP.

Animals↗
PubMedDate not supplied

Evacuation.

What happens to your patients when a forest fire burning out of control threatens your community and forces a major evacuation? This summer, nurses in Salmon Arm found they had a lot of support from their colleagues in the region.

British Columbia↗
PubMedDate not supplied

Effects of proximal and distal muscles' groups contraction and mental stress on the amplitude and frequency of physiological finger tremor. An accelerometric study.

Physiological finger tremor was assessed by two-dimensional solid accelerometry in 40 healthy normal subjects at rest (R) with the hand hanging over the armrest of a chair, in posture (P) with the arm rested on the armrest but the hand extended from the wrist, and finally adding proximal muscles contraction in extension (E) with the arm extended in front of the patient, each time with and without mental stress. The mean amplitude for physiological tremor, about 30 microns, was almost doubled by hand extension and increased by 4 to 5-fold by arm extension with further increase by mental stress in each position, which gives a good estimation of the contribution of proximal and distal muscles into the amplitude of physiological tremor. There was no significant effect of age between 20 and 60 years on tremor amplitude, but mean tremor frequency decreased significantly between 40 to 60 years. Mental stress increased amplitude but decreased tremor frequency of both across all position, possibly by increasing the synchronization of motor unit firing and by modifying the gain of the motoneurones and the stretch reflex as shown by electrophysiological studies.

Adult↗
PubMedDate not supplied

Daily diving pattern of Korean and Japanese breath-hold divers (ama).

Daily diving patterns and thoracic skin and sea-water temperatures were recorded during the entire work shift of Korean female unassisted (cachido) and Japanese male unassisted and partly assisted (funado) divers using Underwater Physiological Data Loggers developed in Buffalo and Japan. All 3 groups of divers were studied during the summer of 1989 and 1990. Additional studies were conducted during the winter of 1991 on Korean female divers who, unlike Japanese divers, dive all year round. The water temperature of the diving grounds in summer was 24 degrees C in both Korea and Japan, and 10 degrees C during winter in Korea. Both Korean female and Japanese male cachido divers made 113-138 dives a day and stayed in the water a total of 170-200 min.day-1, of which only 52-63 min were spent diving submerged, and the remaining time at the water surface. These diving patterns were not different between female and male cachido divers. Compared with Japanese male divers, Korean female divers dived to a shallower depth (3.7 vs. 6.9 m) with shorter dive time (29 vs. 37 s) and shorter bottom time (14 vs. 18 s). Velocities of descent (0.72 vs. 0.47 m.s-1) and ascent (0.77 vs. 0.56 m.s-1) were also slower in female divers than in male divers. The diving pattern of Korean female divers was similar in both summer and winter. Although all cachido divers wore wet suits and thus were protected from severe cold stress, thoracic skin temperature decreased during a work shift by 7 degrees C in winter (vs. 1 degree C in summer) in Korean divers. Compared with Japanese male cachido divers, Japanese male funado divers stayed in the diving ground (including time in the boat) longer (201 vs. 305 min.day-1) but performed only 23 dives per day. The average diving depth (9.7 m), duration (69 s), and bottom time for each dive (45 s), however, were significantly greater in funados. The velocity of vertical descent (1.0 m.s-1) was also significantly greater in funados because they descend with a weight (8-12 kg). The rate of ascent was not different.

Body Temperature↗