Biomedical subjects
J Conti
Publications and source records attributed to J Conti.
The pony as an animal model for vascular implants.
This study evaluated the pony as a potentially suitable model for vascular implant research. Healthy, conditioned ponies were randomly assigned to one of three groups: group I, carotid artery autografts (n = 6); group II, e-PTFE carotid interpositional grafts (n = 5); and group III, e-PTFE carotid interpositional grafts plus aspirin (10 mg/kg) and dipyridamole (3.5 mg/kg) drug administration. It was found that autografts remained patent longest (mean = 396.2 days; grafts were still patent at time of writing) followed by group III grafts (157.5 days), with group II grafts remaining patent for the shortest duration (61.1 days), (p less than 0.01). Patency was determined using two-dimensional real-time ultrasonography with Doppler velocimetry and/or arteriography. It was demonstrated that the pony's response to antithrombotic drugs was consistent and comparable to that in other animal models, both with respect to platelet function and affect on patency rate. The combination of the ease of surgical manipulation, drug administration, and platelet function testing, the comparable size of the pony and its heart and blood vessels to that of an adult human, the long life span of ponies, and the patency results of this study have demonstrated that the pony is a valuable animal model for vascular research.
Platelet function testing in the pony.
Platelet isolation techniques and platelet function were evaluated in 35 adult ponies. Platelet recovery from whole blood was consistent and the preparation of platelet rich plasma was facilitated by an enhanced erythrocyte sedimentation rate. All platelet samples aggregated in response to 10 microM ADP. However, concentrations of ADP as high as 100 microM did not elicit significant 14C-serotonin release. Collagen induced irreversible platelet aggregation and 14C-serotonin release in all samples. The threshold dose for collagen in most ponies was 1.5 micrograms. Arachidonic acid (500 microM) failed to induce irreversible platelet aggregation or 14C-serotonin release in any of the samples evaluated. Pony platelets were nonresponsive to epinephrine (5.5 microM).
An ionotropic phase transition in phosphatidylcholine: cation and anion cooperativity.
Evidence is presented for cooperative interaction between cations and anions specifically bound to dimyristoylphosphatidylcholine (DMPC). The cooperativity is with regard to an ion-induced (ionotropic) phase transition for the lipid and is signalled by a change in the luminescence from bound Tb3+. The intrinsic binding of Tb3+ to DMPC was determined from equilibrium dialysis experiments, using conventional methods to correct for electrostatic contributions. Preliminary results demonstrate great potential for infrared spectroscopy as a means to relate these Tb3+ luminescence studies to experiments involving less tractable cations. This work provides insight into the role of bound ions in modifying lateral phase behavior in phospholipid membranes.
Accuracy of PET RCBF measurements: effect of time shift between blood and brain radioactivity curves.
Analytic expressions were derived for estimating the error in PET RCBF measurements associated with the time lag between brain and blood radioactivity following bolus H2(15)O injection and during non-steady-state CO15O inhalation. This lag time reflects the physiological difference in arrival times of 15O activity at brain and radial arterial sampling site as well as the experimentally introduced resistance to flow offered by the arterial catheter/stopcock assembly. Multiple measurements of this time lag ranged between 1 and 10 s. For non-steady-state CO15O PET measurements, estimated errors in RCBF ranged from 0.02 to 30% for delays of 2-8 s and scan lengths of 30-180 s. In the range 20-100 ml min-1 per 100 g, variations in RCBF only marginally affected these errors. Errors increased with longer delays but decreased sharply with scan durations greater than 60 s. For 30-180 s scans, even larger errors are associated with the H2(15)O injection technique (peak blood activity at 10 s): 1-60% for delays of 2-8 s. A 'slow' bolus peaking at 20 s decreased the error by 40%. For the H2(15)O method it is essential to estimate the time shift to within 2 s if accurate flow measurements (error less than 5%) are to be obtained from 40-60 s scans.
Monitoring 5-hydroxytryptamine release in the brain of the freely moving unanaesthetized rat using in vivo voltammetry.
The possibility of using in vivo voltammetry to monitor 5-hydroxytryptamine (5-HT) release from brain tissue in freely moving unanaesthetized rats has been examined. A potential (+0.2 to +1.0 V) was applied to a micrographite electrode stereotaxically placed within a specific brain region and current changes following the oxidation of electroactive compounds in the vicinity of the electrode tip were recorded. Administration of p-chloroamphetamine (5 mg/kg) produced a large increase in current in the striatum and this could be prevented by pretreatment with p-chlorophenylalanine (150 mg/kg X 2) to deplete brain 5-HT or Fluoxetine (10 mg/kg) which prevents the uptake of p-chloroamphetamine by 5-HT neurones. Fluoxetine (10 mg/kg) caused a small but long lasting increase in current. Stimulation of the median raphe nucleus produced a marked and rapid rise in current in the hippocampus but a much smaller one in the striatum. This response could also be prevented by 24 h pretreatment with p-chlorophenylalanine (150 mg/kg). Seven days after p-chlorophenylalanine administration raphe stimulation again produced an increase in current. Rats under barbiturate anaesthesia showed no clear increase in current either after p-chloroamphetamine or raphe stimulation, indicating that barbiturates may affect neurotransmitter release. The results suggest that 5-HT release can be monitored in the freely moving unanaesthetized rat using in vivo voltammetry, and that a moderate decrease in brain 5-HT concentration leads to a substantial inhibition of drug or stimulation induced release of 5-HT.
The measurement of dopamine and 5-hydroxytryptamine release in CNS of freely moving unanaesthetised rats [proceedings].
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[Quantitative determination, characterization and stability of magnesium 5-methyltetrahydrofolate].
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[New method for quantitative determination, purity verification, and stability measure of calcium-leucovorin].
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