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Biomedical subjects

K Jordan

Publications and source records attributed to K Jordan.

At least 55 records · Page 3Linked to original sources

Effects of map orientation during learning on airport identification.

BACKGROUND: If an observer first learns to recognize an object in a specific orientation, a significant increase in processing time usually occurs when the object is subsequently seen in a different orientation; this phenomenon is called the "misorientation effect." The present study examines how quickly and how accurately human observers discriminate between airport maps that are viewed in orientations other than those in which they were initially learned. METHOD: Participants were trained to discriminate between two navigation maps that were seen in only one orientation; they subsequently were tested with maps and aerial photographs of the same airports that were presented in various orientations. RESULTS AND CONCLUSIONS: There were three principal findings: a) discriminative responses to maps of airports were most rapid when the maps were seen in the same orientation as that in which they were initially learned; b) a significant reduction in reaction time (RT) occurred with repeated presentations of the misoriented stimuli; and c) information learned from navigation maps was not sufficient for all observers to recognize aerial photographs of the same airports.

Adult↗

Discharge planning. Oiling the wheels.

A liaison nurse can ensure effective discharge planning, enhance the services provided and introduce quality improvements. Employing a liaison nurse in a children's private patient directorate has reduced the length of patient stay, and stopped wards being used for outpatient sessions for children receiving follow-up treatment. Ward nurses have more time to spend with inpatients, so that children and their families benefit from a more comprehensive service and continuity of care is improved.

Ambulatory Care↗

NHS reforms. Counting the costs.

Localism predominates in purchaser-provider relationships, with markets strictly limited in practice. Block contracting predominates, largely to enable purchasers to bring pressure to bear on providers' costs and outputs. The administrative costs of operating the purchaser-provider split have led to a clear growth in the overall administrative costs within the NHS. Locality commissioning may conflict with the need to reorganise clinical services.

Contract Services↗

Auditory event-related potentials in post- and prelingually deaf cochlear implant recipients.

The development of central auditory functions in cochlear implant (CI) patients was studied over six months of rehabilitation. Examinations were performed beginning with the first week after processor calibration, and in monthly follow-up sessions thereafter. The subjects were given a simple auditory perception task (detection of a 400 Hz and a 1450 Hz tone), as well as an oddball-paradigm (detection of one of the tones as a rare deviant). Auditory evoked potentials, reaction time and errors were recorded. Results from five patients, two postlingually deaf and three prelingually deaf CI recipients are shown. Generally, in the auditory evoked potentials of patients a shortening of N100 latency towards those of subjects with normal hearing was seen from month to month. However, in the prelingually deaf patients this effect was weaker and more variable over time. Three CI recipients showed a P300 component in the oddball-paradigm in correlation with their performance. Two prelingually deaf patients failed to show a P300 in the oddball-paradigm. For both components, the N100 and the P300 we found a larger spreading over the skull in the patients compared to a normal hearing person. The results show that from the very first days after initial processor fitting prelingually and postlingually deaf CI recipients may show cortical correlates of stimulus processing and discrimination. For some components of the auditory evoked potentials an initial temporal change but a maintained larger spreading over the skull was seen.

Cochlear Implantation↗

Islet amyloid and islet amyloid polypeptide in cynomolgus macaques (Macaca fascicularis): an animal model of human non-insulin-dependent diabetes mellitus.

To further characterize spontaneous diabetes mellitus in cynomolgus macaques (Macaca fascicularis) as a model for human non-insulin-dependent diabetes mellitus (NIDDM), we evaluated the morphologic characteristics of the endocrine pancreas of 4 diabetic and 12 age-matched nondiabetic cynomolgus macaques. In addition, the cDNA-predicted amino acid sequence for islet amyloid polypeptide (IAPP) of this species was determined. Islet amyloid deposits exhibiting typical congophilia and green birefringence were found in 4/4 diabetic animals and in 8/12 nondiabetics. Islet amyloid deposits were significantly more extensive in the diabetic macaques (P = 0.001), in which they occupied a mean of 60% of the islet area. In contrast, in the nondiabetic group the maximum islet area occupied by amyloid was 24% (group mean = 6.8%), with four animals having no detectable islet amyloid. Amyloid deposits consistently showed immunoreactivity for IAPP but not for insulin. Comparisons between group means for diabetic versus nondiabetic macaques showed significantly greater islet area (P = 0.01, 85,390 versus 36,540 microns 2) and significantly greater islet area fraction (P = 0.02, 0.065 versus 0.032) for the diabetic group. The cDNA-predicted amino acid sequence for cynomolgus IAPP was identical to that previously reported for pig-tail macaques (M. nemestrina) and had 92%, 86%, and 84% amino acid sequence identity with human, domestic cat, and murine IAPPs, respectively. These findings support the use of cynomolgus macaques as an animal model of human NIDDM.

Amino Acid Sequence↗

Quantitative imaging of iodine-124 with PET.

UNLABELLED: PET is potentially very useful for the accurate in vivo quantitation of time-varying biological distributions of radiolabeled antibodies over several days. The short half-lives of most commonly used positron-emitting nuclides make them unsuitable for this purpose. Iodine-124 is a positron emitter with a half-life of 4.2 days and appropriate chemical properties. It has not been widely used because of a complex decay scheme including several high energy gamma rays. However, measurements made under realistic conditions on several different PET scanners have shown that satisfactory imaging and quantitation can be achieved. METHODS: Whole-body and head-optimized scanners with different detectors (discrete BGO, block BGO and BaF2 time-of-flight), different septa and different correction schemes were used. Measurements of resolution, quantitative linearity and the ability to quantitatively image spheres of different sizes and activities in different background activities were made using phantoms. RESULTS: Compared with conventional PET nuclides, resolution and quantitation were only slightly degraded. Sphere detectability was also only slightly worse if imaging time was increased to compensate for the lower positron abundance. CONCLUSION: Quantitative imaging with 124I appears to be possible under realistic conditions with various PET scanners.

Half-Life↗

Assignment of islet amyloid polypeptide (IAPP) gene to feline chromosome B4 using the polymerase chain reaction technique on feline-rodent hybrid cell lines.

The most characteristic morphologic features of the pancreatic islets of human non-insulin-dependent diabetes mellitus (NIDDM, or type 2 diabetes mellitus) and of similar forms of diabetes in cats and macaques are the deposition of amyloid (islet amyloid) and the loss of beta cells. Islet amyloid is derived from islet amyloid polypeptide (IAPP), which is a normal secretory product of the beta cells. Therefore, knowledge of the IAPP gene is of potential importance in defining the pathogenesis of NIDDM. To identify the feline chromosome(s) on which the IAPP gene is located, we screened genomic DNA obtained from 38 feline-rodent hybrid cell lines that have a known feline chromosome content. Feline IAPP DNA was amplified and detected using the polymerase chain reaction technique. Discordancy analysis for each feline chromosome showed that chromosome B4 had the lowest discordancy (P < 0.0001). Feline chromosome B4 shows an extensive conserved syntenic relationship with human chromosome 12, on which the human IAPP gene is located. This study therefore extends and confirms the homology between human chromosome 12 and feline chromosome B4 and provides an additional genetic marker for feline chromosome B4.

Amyloid↗

Determination of nanogram levels of peptide drug in rabbit and human plasma using high-performance liquid chromatography coupled with electrospray ionization mass spectrometry.

High-performance liquid chromatography (HPLC) coupled to mass spectrometry (MS) using an electrospray ionization (ESI) interface provides a sensitive method for the quantitative analysis of peptide drugs in complex biological matrixes. ESI HPLC-MS was applied to the analysis of a pentapeptide drug (IRI-514) in rabbit and human plasma. Prior to analysis, the plasma samples were prepared using protein precipitation followed by solid-phase extraction. The lower limit of quantitation using selected ion monitoring was determined to be 2 ng/mL, when 8 mL of human plasma spiked with 1-40 ng/mL was extracted. Rabbit plasma (1 mL) samples spiked with 10-40,000 ng of authentic drug/mL gave a linear response when a deuterated peptide analog was employed as an internal standard. A commercial ESI interface was modified to permit higher flow rates (10-20 microL/min) to enter the mass spectrometer source. The revised interface provided a 10-fold increase in sensitivities and permitted the use of standard HPLC columns (2.0-mm i.d.) and HPLC instrumentation. ESI HPLC-MS analysis was automated to provide unattended, precise, and sensitive detection of small peptides in both human and rabbit plasma. Using this methodology, a toxicokinetic study of intravenously administered IRI-514 at three dose levels indicated that the area under the curve values were dose proportional.

Amino Acid Sequence↗

[Maximal and high-velocity power. A study in Swiss male and female national ski athletes].

An important quality aspect of a good alpine skier is his ability to produce torque at high angular velocities. Both the isokinetic dynamometer (Cybex 6000, open chain of movement) and a device to measure flight time in skill jumps (Ergo Jump, closed chain of movement) allow to identify subjects with outstanding capacities in explosive force production and possibly to measure changes after specific training protocols aiming at improving this important characteristics of alpine skiers.

Adult↗

[Quality assurance of nuclear medicine measuring systems: what do the new regulations say?].

New specifications for quality control of nuclear medical instrumentation are given in the German "Richtlinie Strahlenschutz in der Medizin", published in 1993. These specifications include the corresponding DIN-Normen, the German standards. In both papers the description of the various test procedures is given in a very abbreviated form, so that many of the people having to perform these test procedures are more or less puzzled. This paper will provide for a better understanding of what is meant and will also give many useful hints in performing the test procedures. A discussion of the necessary test phantoms and auxiliary devices completes this paper.

Germany↗

Major difference in the hepatocarcinogenicity and DNA adduct forming ability between toremifene and tamoxifen in female Crl:CD(BR) rats.

The hepatoproliferative effects of 2 antiestrogens, tamoxifen and toremifene, were compared in a sequential 15-month study in which 2 doses of each compound were administered by daily gavage to female Sprague-Dawley rats for up to 12 months. The doses were 11.3 and 22.6 mg/kg for tamoxifen and 12 and 24 mg/kg for toremifene. There were scheduled sacrifices at 3, 6, 12, and 15 months, the latter including a 3-month recovery period from the 12th through the 14th month. In the chronic toxicity study, tamoxifen at 22.6 mg/kg produced 100% incidence of hepatocellular carcinoma at the 12- and 15-month sacrifice intervals and 67% and 71% incidences at the 11.3-mg/kg dose. Sequential observations showed an increased incidence of glutathione S-transferase-positive foci of hepatocellular alteration by 3 months with tamoxifen in the absence of hepatotoxicity, with the first liver carcinoma appearing by 6 months of treatment. Unscheduled deaths occurring beyond 7.5 months in the tamoxifen treated groups were due in almost all cases to liver cancer. In striking contrast, toremifene did not produce any hepatoproliferative effects at 12- and 24-mg/kg dose levels, nor in a pilot study at 48 mg/kg. The 24-mg/kg dose of toremifene exerted an inhibiting effect on foci of hepatocellular alteration in rat liver detectable by glutathione S-transferase immunohistochemistry at 3 months and by conventional histology at 12 months. An antiproliferative effect was also evident in mammary gland and anterior pituitary where both toremifene and tamoxifen suppressed tumor incidence in comparison to the control group. The ability of these drugs to modify rat liver DNA after p.o. administration was investigated using the 32P-postlabeling assay. Administration of tamoxifen at 45 mg/kg for 7 days produced liver DNA nucleoside modifications represented by 7 spots on the autoradiogram. Unlike tamoxifen, toremifene did not produce any modified bases in rat liver DNA detectable by the 32P-postlabeling technique. The dose levels of tamoxifen that are strongly hepatocarcinogenic in the rat are compared with doses used in humans in various applications. Taking internal drug exposure into account, we conclude that the margin of safety for use of tamoxifen as an endocrine prophylactic agent for healthy, but breast cancer prone, women is questionable.

Adenoma↗

Effects of the nootropic AWD 52-39 on the blood-brain transfer of leucine, choline and glucose in rats after 14-d exposure to ethanol.

The transport of the neutral amino acid L-leucine as well as of choline and D-glucose across the blood-brain barrier (BBB) of male Wistar rats was studied after 14-day exposure to ethanol and treatment with the nootropic drug AWD 52-39 (1). After ethanol exposure the half-saturation constant (Km) and the maximum velocity of transport (Vmax) declined in the majority of the investigated brain regions. Also, the treatment elicited a regionally different increase of the permeability-surface area (PS) product of choline (between 10% and 33%) and glucose (between 12% and 27%). The changes in the blood-brain transfer of the three compounds were diminished or prevented by additional application of 1. The cerebral blood flow was increased by the exposure to ethanol by maximally 44%. After additional administration of 1 the changes were reversed and the blood flow reached control values. In addition, the activity of the enzyme acetylcholine esterase was determined in the striatum and the hippocampus. After ethanol exposure the enzyme activity declined by 32%. It was less diminished after treatment with 1. The latter effects let assume that the changes of the BBB permeability elicited by ethanol and 1 are related to alterations of brain metabolism.

Acetylcholinesterase↗

Spatial resolution in SPECT: influence of measurement set-up and reconstruction parameters.

The ability of a tomographic system to detect small lesions and to assess them quantitatively is affected by several performance parameters, among them spatial resolution in the transverse slice and in the axial direction. This study was done to determine reconstructed resolution under clinical conditions for various parameters, i.e. radius of rotation, radial position within the transverse field of view, and amount of smoothing in the reconstruction process (various reconstruction filters and a Metz prefilter). The axial resolution is independent of the reconstruction filter but depends on the prefilter, the radius of rotation (ROR), and the source position. The transaxial resolution is dependent on the reconstruction filter, the prefilter, the ROR, and the source position. The reconstructed resolution and the system resolution were compared and differences between both are discussed.

Humans↗