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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
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↗
PubMed1989

Basic fibroblast-like growth factor is present in the conditioned medium of simian sarcoma virus transformed NRK cells.

The conditioned medium of Simian sarcoma virus (SSV)-transformed NRK cells contains at least two activities that down regulate the epidermal growth factor receptor. To identify these activities, we analyzed the medium for the presence of factors both related to and distinct from the v-sis oncogene product. Fractionation of the conditioned medium from SSV-transformed NRK cells by chromatography on heparin-Sepharose yielded two active fractions capable of inhibiting EGF binding. The first component, which eluted at 0.8 M NaCl, is able to induce autophosphorylation of the platelet-derived growth factor (PDGF) receptor, is a mitogen for Swiss 3T3 cells and corresponds to the PDGF B chain product of the v-sis oncogene. The second component requires 2 M NaCl for elution, is mitogenic for Swiss 3T3 cells and inhibits high affinity EGF binding through a protein kinase C-independent pathway, all properties of basic FGF. These results suggest that the conditioned medium of v-sis-transformed cells contains at least two factors that can act in an autocrine capacity, one derived from v-sis and one corresponding to basic FGF.

Animals↗
PubMed1989

Basic and acidic fibroblast growth factors modulate the epidermal growth factor receptor by a protein kinase C-independent pathway.

Human acidic and basic fibroblast growth factors (aFGF and bFGF) inhibit epidermal growth factor (EGF) receptor binding in mouse Swiss 3T3 cells. Scatchard analysis indicates that aFGF and bFGF cause a decrease in the high affinity EGF receptor population, similar to that observed for activators of protein kinase C such as phorbol esters, platelet-derived growth factor (PDGF) and bombesin. However, unlike phorbol esters, aFGF and bFGF inhibit EGF binding in protein kinase C-deficient cells. The time course and dose response of inhibition of EGF binding by both aFGF and bFGF are very similar, with an ID50 of approximately 0.10 ng/ml. In contrast to bombesin but like PDGF, neither aFGF nor bFGF act on the EGF receptor through a pertussis toxin-sensitive G protein. These results indicate that both acidic and basic FGF depress high affinity EGF binding in Swiss 3T3 cells with similar potency through a protein kinase C/Gi-independent pathway.

Animals↗