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Biomedical subjects

K Hicks

Publications and source records attributed to K Hicks.

At least 37 records · Page 2Linked to original sources
PubMed1996

Clinical evaluation of a microsample coagulation analyzer, and comparison with existing techniques.

A new microsample coagulation analyzer (Hemochron Jr.) has recently been developed which performs a modified activated clotting time (ACT+) and an aPTT by using different reagents. The Hemochron Jr. measures the clotting time of a 5-microliter whole-blood sample by an optical detector and extrapolates the results to the activated clotting time (ACT+) or the plasma-activated partial thromboplastin time by using a validated regression analysis. We compared 124 simultaneous ACT+ and Hemochron ACTs, and 53 paired Hemochron Jr. aPTTs and hospital laboratory aPTTs, in 44 patients during coronary intervention. The Hemochron Jr. aPTT closely correlated with the lab aPTT (r = .79, P < .0001), and the test results were available much more rapidly than the lab aPTT (3.5 +/- 1.1 vs. 56.3 +/- 25.5 min, P = 0.0029). A comparison of duplicate ACT+ measurements did not identify a significant difference in the means (292 +/- 115 sec vs. 293 +/- 112 sec, P = 0.72). The ACT+ closely correlated with the Hemochron ACTs (r = .85, P < .0001). At baseline, the mean ACT+ (175 +/- 43 sec) exceeded the Hemochron ACT (144 +/- 36 sec) by 22% (P < .001). After heparin administration, the mean ACT+ (378 +/- 74 sec) exceeded the Hemochron ACT (332 +/- 65) by 12% (P < .001). The Hemochron Jr. provides a fast and reproducible methodology for measuring ACT and aPTT, using a small blood volume. Further studies are required to determine the optimal anticoagulation range when using the Hemochron Jr. during or after interventional procedures.

Anticoagulants↗
PubMed1996

Comparison of fluorine-18-fluorodeoxyglucose and carbon-11-methionine PET in detection of malignant tumors.

UNLABELLED: Two commonly used tumor-seeking agents for PET are 2-deoxy-2-18F-fluoro-D-glucose (FDG) and L-methyl-11C-methionine (Met). This study compared FDG and Met in detecting residual or recurrent malignant tumors in the same patients. METHODS: Thirty-four lesions in 24 patients with clinically suspected recurrent or residual tumors were studied with PET using Met as well as FDG. FDG scans were conducted 1 hr after the completion of PET with Met. The color-coded superimposed images of standardized uptake values (SUVs) and transmission data were produced, and the peak SUVs in the lesions were then evaluated. Lesions above 2.5 SUV were interpreted as positive results for active tumor. RESULTS: The sensitivity of FDG-PET and Met-PET were 64.5% (20/31 lesions) and 61.3% (19/31 lesions), respectively. The mean SUV of FDG in residual or recurrent malignant tumors (n = 31) was significantly higher than that of Met but there was a significant correlation (r = 0.788, p < 0.01) between FDG and Met SUVs in all lesions (n = 34). CONCLUSION: PET using FDG and Met appear equally effective in detecting residual or recurrent malignant tumors although FDG uptakes were slightly higher than Met uptakes. Both showed a limited diagnostic sensitivity for small (< 1.5 cm) tumors.

Adult↗
PubMed1995

Traumatic isolated unilateral hypoglossal nerve palsy--case report and review of the literature.

Isolated unilateral hypoglossal nerve palsy may be caused by fracture through the occipital condyle. This is a rare but previously documented event, and can easily go undetected at time of injury, both clinically and radiographically. In addition, there is a potential for late presentation of the palsy. Such cases may present up to several months post injury, and an awareness of this unusual cause may assist the oral surgeon in establishing a diagnosis.

Adult↗
PubMed1994

A clinically practical method to acquire parametric images of unidirectional metabolic rates and blood spaces.

UNLABELLED: As SPECT imaging has become more quantitative with the advent of the attenuation correction, SPECT parametric imaging can become a reality if the data acquisition and the numeric reduction procedures can be simplified. METHODS: A method that is clinically practical for acquiring quantitative parametric images of unidirectional metabolic rate constants and apparent blood space is proposed. Its application to PET imaging with FDG was investigated. This procedure requires a short postinjection waiting period, three sequential imaging scans and one blood sample (1 ml) during each scan, obviating the requirements of continuous blood sampling, "assumed" rate constants (autoradiographic method) and difficult nonlinear regression computations. The effect of the early-phase blood input function is computed directly from the image. The clinical procedure is completed 1 hr after FDG injection. The computation time for generating 21 metabolic rate image slices and blood space slices is negligible (30 sec after image reconstruction). Preliminary human studies on brain, heart, liver and tumor were performed. RESULTS: The method was tested on seven normal subjects. The results showed that the rapidly changing early-phase blood input can be derived from the raw image and that the metabolic rate images of this method agreed with the results from the graphical analysis method, using continuous sampling, and with published data from three-compartment models. CONCLUSION: This study is clinically more practical and computationally simpler as a method to acquire parametric images of the metabolic rate constant, Ki, and the apparent blood space Vd for unidirectional tracers. Applying this simple quantitative parametric imaging method to routine clinical studies may improve the accuracy of routine clinical evaluations.

Blood↗
PubMed1993

Induction of heat shock hsp70 mRNA and HSP70 kDa protein in neurons in the 'penumbra' following focal cerebral ischemia in the rat.

Induction of hsp70 heat shock protein (HSP70) and hsp70 mRNA was examined using adjacent sections in the same rat brain following permanent middle cerebral artery (MCA) occlusions, hsp70 mRNA was induced within 4 h of MCA occlusion and persisted for at least 24 h. Cellular resolution autoradiographs suggested that hsp70 mRNA was induced primarily in neurons in the periphery of ischemia both outside and inside of the infarction, with small amounts of hsp70 mRNA being induced in the core of the infarction. HSP70 protein was localized in neurons outside the infarction and in endothelial cells within the infarction at 24 h but not at 4 h following permanent MCA occlusions. It is proposed that the penumbra, one of the areas that can be rescued by pharmacological agents, can be defined anatomically as the volume of tissue outside the area of infarction in which HSP70 protein is expressed primarily in neurons.

Animals↗
PubMed1991

Proventriculotomy to relieve foreign body impaction in ostriches.

A study was conducted to identify the clinical signs associated with impaction of the proventriculus in ostriches, to identify diagnostic aids, and to develop a surgical procedure for management of the disorder. Clinical signs indicating the need for surgical intervention included chronic inappetance, a change in fecal consistency or production, dehydration, weight loss, and failure to respond to laxatives. Diagnosis of impacted proventriculus was by abdominal radiography and external palpation. Impactions were caused by sand and rocks (5 ostriches), hay and sand (1 ostrich), and leaves (1 ostrich). After surgery, 5 of the ostriches were clinically normal within (mean) 1 week. One ostrich failed to regain a normal appetite until 2 weeks after surgery, and one juvenile ostrich died after surgery. Of the 6 ostriches that survived, 1 died 1 week after discharge from the hospital. The remaining birds survived without redevelopment of impaction.

Abdominal Muscles↗
PubMed1991

Conduction in bullfrog atrial strands: simulations of the role of disc and extracellular resistance.

A number of fundamental properties of intercellular conduction in simulated cylindrical strands of cardiac tissue are examined. The paper is based on recent biophysical information describing the transmembrane ionic currents in bullfrog atrial cells as well as anatomical data on the structures (gap junctions) responsible for the coupling between cells in that tissue. A mathematical model of the single bullfrog atrial cell based on suction microelectrode single-cell voltage clamp data is employed, as well as a modified version of the well-known model of Heppner and Plonsey, to characterized the resistive connections between adjacent cells in a cardiac strand. In addition, the simulated cellular strand is assumed to be encased in a cylindrical, resistive endothelial sheath, thus forming an idealized atrial trabeculum; the trabeculum is immersed in an extensive volume conductor. It is possible to simulate both uniform and discontinuous conduction in this atrial strand model by appropriately changing the resistance of the intercalated discs that occur at cell boundaries. The conduction velocity achieved in the normal or control case is within the range of conduction velocities that have been measured for bullfrog atrial trabeculae using optical methods. Extracellular resistance is shown to have a significant effect on both conduction velocity and the critical value of disc resistance at which discontinuous conduction first occurs. Since the atrial cell model employed in this study is based on experimental data and can accurately simulate the atrial action potential, the transmembrane ionic currents generated by the model are capable of providing detailed information concerning the mechanisms of intercellular current spread, particularly in the region of the intercalated disc.

Animals↗
PubMed1991

c-fos mRNA, Fos, and Fos-related antigen induction by hypertonic saline and stress.

The induction of c-fos mRNA was assessed using Northern blots and in situ hybridization in adult rats administered hypertonic saline (HS) and isotonic saline (IS). HS induced c-fos mRNA in magnocellular paraventricular nucleus (PVNm), parvocellular paraventricular nucleus (PVNp), supraoptic nucleus (SON), and lamina terminalis (LMT). This occurred within 5 min, peaked at 30-60 min, and disappeared by 180 min. Fos protein, detected using a specific monoclonal antibody, was maximal at 1-2 hr and disappeared 4-8 hr after HS administration. This confirms observations showing that the c-fos gene response is transient even in the presence of a continuing stimulus. In contrast, Fos-like immunoreactivity (FLI), detected using two polyclonal antisera, was observed in PVNm, PVNp, SON, and LMT for 1-24 hr during continuous osmotic stimulation. Moreover, FLI was observable in these structures for 7 d in rats administered HS and allowed to drink water ad libitum beginning 24 hr later. At times greater than 8 hr, FLI presumably represents Fos-related antigens (FRA), proteins immunologically and functionally related to Fos, whose expression is much more prolonged than authentic Fos following the osmotic stimulus. In addition to induction of c-fos expression in regions specifically involved in osmotic regulation, HS injections also induced c-fos in many other forebrain regions. In order to assess the induction of c-fos mRNA due to the "stress" of the injections, rats injected with isotonic saline were compared to uninjected controls. Isotonic saline injections induced c-fos mRNA in the PVNp, anterior hypothalamus, suprachiasmatic nucleus, cingulate gyrus, neocortex, ventral lateral septal nucleus, piriform cortex, hippocampal pyramidal and dentate granule neurons, paraventricular and intralaminar thalamic nuclei, bed nuclei of stria terminalis, cortical and medial amygdaloid nuclei, and other structures. In accord with other work, we interpret this pattern of c-fos expression to result from the stress of handling and injections. Since Fos and FRA probably bind to the promoters of target genes and regulate their expression, they likely mediate biochemical changes in the cells activated by the osmotic and stressful stimuli. Whereas the Fos signal is transient, FRA may act on target genes for the duration of the stimulus or longer.

Animals↗