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Biomedical subjects

S Judge

Publications and source records attributed to S Judge.

9 recordsLinked to original sources
PubMed2003

Evaluation of a continuous glucose monitoring system in diabetic dogs.

The generation of a blood glucose curve is important for assessing the response to insulin therapy in diabetic dogs. Disadvantages of this technique include patient discomfort and the potential for missing transient hypo- or hyperglycaemic episodes. The aim of the current study was to evaluate a continuous glucose monitoring system (CGMS) for use in diabetic dogs. Interstitial fluid glucose concentrations were recorded in 10 diabetic dogs, every five minutes for up to 48 hours, using a subcutaneous sensor attached to the CGMS device. Blood glucose concentrations were measured simultaneously using a glucometer. The correlation between interstitial fluid and blood glucose values was 0.81 (P < 0.01). The largest discrepancies between the two sets of data were seen during the one- to three-hour period following feeding, suggesting that postprandial hyperglycaemia might not be reflected in the interstitial fluid. The authors conclude that the CGMS is a potentially valuable tool in the management of canine diabetic patients.

Animals↗
PubMed1999

Modulation of transmitter release from the locust forewing stretch receptor neuron by GABAergic interneurons activated via muscarinic receptors.

The role of muscarinic receptors in the down-regulation of acetylcholine (ACh) release from the locust forewing stretch receptor neuron (fSR) terminals has been investigated. Electrical stimulation of the fSR evokes monosynaptic excitatory postsynaptic potentials (EPSPs) in the first basalar motoneuron (BA1), produced mainly by the activation of postsynaptic nicotinic cholinergic receptors. The general muscarinic antagonists scopolamine (10(-6) M) and atropine (10(-8) to 10(-6) M) caused a reversible increase in the amplitude of electrically evoked EPSPs. However, scopolamine (10(-6) M) caused a slight depression in the amplitude of responses to ACh pressure-applied to the soma of BA1. These observations indicate that the EPSP amplitude enhancement is due to the blockade of muscarinic receptors on neurons presynaptic to BA1. The muscarinic receptors may be located on the fSR itself and act as autoreceptors, and/or they may be located on GABAergic interneurons which inhibit ACh release from the fSR. Electron microscopical immunocytochemistry has revealed that GABA-immunoreactive neurons make presynaptic inputs to the fSR. The GABA antagonist picrotoxin (10(-6) M) caused a reversible increase in the EPSP amplitude, which does not appear to be due to an increase in sensitivity of BA1 to ACh, as picrotoxin (10(-6) M) slightly decreased ACh responses recorded from BA1. Application of scopolamine (10(-6) M) to a preparation preincubated with picrotoxin did not cause the EPSP amplitude enhancement normally seen in control experiments; in fact, it caused a slight depression. This indicates that at least some of the presynaptic muscarinic receptors are located on GABAergic interneurons that modulate transmission at the fSR/BA1 synapse.

Acetylcholine↗
PubMed1999

GABA immunoreactivity in processes presynaptic to the locust wing stretch receptor neuron.

Studies on the locust Locusta migratoria (Leitch et al. [1998] Soc. Neurosci. Abstr. 624.10) suggest that gamma-aminobutyric acid (GABA)ergic interneurons, activated via muscarinic receptors, may be involved in modulation of transmitter release at synapses between the forewing stretch receptor (fSR) and wing depressor motoneurons. To help elucidate the role GABAergic interneurons may play in modulation of transmitter release from fSR terminals, the proportion and distribution of GABA-immunoreactive (GABA-IR) inputs to the fSR were analysed using double-labelling (horseradish peroxidase and GABA immunocytochemistry) and electron microscopy. Forty-three percent of synaptic inputs to the fSR were from GABA-IR profiles, the majority of which were located on lateral branches. The highest proportion (57%) of inputs to the fSR, however, were from non-IR processes containing either clear spherical vesicles or mixed clear and dense-cored vesicles. Outputs from the fSR to GABA-IR profiles were also found, although their number was relatively low (7%). Networks were identified in which both the fSR and its non-IR postsynaptic partner received input from the same GABA-IR neuron. Such an arrangement would allow both pre- and postsynaptic inhibition of fSR afferent outputs, for example at fSR/motoneuron synapses. These observations demonstrate that the fSR does receive presynaptic inputs from GABA-IR neurons, thus providing morphological support for pharmacological and electrophysiological findings that GABAergic neurons are involved in the presynaptic modulation of the fSR. Nevertheless, modulation at this synapse may be more intricate and involve other, as yet unidentified, neurotransmitters released from non GABA-IR presynaptic processes and also muscarinic receptors located on the fSR itself.

Animals↗
PubMed1997

The locust DCMD, a movement-detecting neurone tightly tuned to collision trajectories

A Silicon Graphics computer was used to challenge the locust descending contralateral movement detector (DCMD) neurone with images of approaching objects. The DCMD gave its strongest response, measured as either total spike number or spike frequency, to objects approaching on a direct collision course. Deviation in either a horizontal or vertical direction from a direct collision course resulted in a reduced response. The decline in the DCMD response with increasing deviation from a collision course was used as a measure of the tightness of DCMD tuning for collision trajectories. Tuning was defined as the half-width of the response when it had fallen to half its maximum level. The response tuning, measured as averaged mean spike number versus deviation away from a collision course, had a half-width at half-maximum response of 2.4 &deg;&shy;3.0 &deg; for a deviation in the horizontal direction and 3.0 &deg; for a deviation in the vertical direction. Mean peak spike frequency showed an even sharper tuning, with a half-width at half-maximum response of 1.8 &deg; for deviations away from a collision course in the horizontal plane.

Journal Article↗
PubMed1995

The effect of streptozocin-induced diabetes on platelet aggregation as determined by impedance aggregometry and platelet secretion: a possible role for nitric oxide.

Previous studies from our laboratory showed that diabetes increases platelet aggregation in rats, but only in washed platelets. In the present study, we evaluated platelet aggregation coupled with adenosine triphosphate (ATP) release in normal and diabetic rats using a whole blood electrical aggregometer. Additionally, we investigated the role of endothelium-derived relaxing factor, or nitric oxide, in the platelet reactivity in diabetic rats. Rats were made diabetic using streptozocin, 55 mg/kg. After 1 month the rats were anesthetized, and arterial blood samples were collected directly into sodium citrate solution 3.8%. Platelet counts and mean platelet volumes were determined. Platelet aggregation, disaggregation, and ATP release in response to adenosine diphosphate (ADP), collagen, and arachidonic acid were measured. Platelet aggregation in response to ADP, collagen, and arachidonic acid was not different in diabetic rats when compared with that in controls. However, ATP release in response to ADP was significantly increased in diabetic rats. Platelets from diabetic animals were significantly larger than those of controls. Nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, decreased platelet aggregation in response to ADP in the normal animals, but not in the diabetic animals. However, arginine-induced nitric oxide production decreased platelet aggregation and enhanced the occurrence of disaggregation in platelets from both normal and diabetic rats. From these studies, we conclude that platelet aggregation in diabetic rats is not different using whole blood electrical aggregation, but platelet ATP secretion is significantly enhanced. Additionally, nitric oxide may modulate the platelet aggregation, disaggregation, and ATP secretory response. However, it does not appear to be a major factor in the altered aggregation responses in diabetic rats.

Adenosine Diphosphate↗
PubMed1977

Knife sharpening revolutionized.

A new application has been found for an adhesive-backed, nylon polishing cloth previously used chiefly in the metallurgic field. When adhered to the glass plate of an automatic microtome knife sharpener, the cloth provides a superior sharpening surface and eliminates the need for resurfacing the plate. We have found this new technique simple, inexpensive, and timesaving.

Histology↗