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Biomedical subjects

H Gibbons

Publications and source records attributed to H Gibbons.

16 recordsLinked to original sources
PubMed2006

Unimpaired negative but enhanced positive priming in Parkinson's disease: evidence from an identity and a location priming task.

Mechanisms of selective attention are frequently reported to be impaired in Parkinson's disease (PD). Fundamental to selective attention is attending to relevant information and, concurrently, ignoring irrelevant information. Both processes can be assessed by positive priming (PP) and negative priming (NP) tasks, respectively. Unlike previous studies, in the present experiment, two separate identity- and location-based priming tasks were applied to 48 PD patients and 48 sex- and age-matched healthy controls. Results indicated that identity and location PP were reliably enhanced in PD patients compared to controls. Both groups showed significant location NP of almost identical magnitude but no identity NP. However, there was evidence for a positive functional relationship between severity of bradykinesia and identity NP. Furthermore, with increasing depression scores, location NP was enhanced in PD patients but not in controls. These findings suggest that disturbed selective attention associated with PD is due to changed mechanisms mediating attention to relevant information rather than due to mechanisms involved in inhibition of irrelevant information.

Aged↗
PubMed2002

Latent inhibition deficits in high-schizotypal normals: symptom-specific or anxiety-related?

Latent inhibition (LI) is the phenomenon in which subjects who have repeatedly experienced an irrelevant stimulus perform more poorly on a new learning task with that stimulus than with a novel stimulus, presumably because of a decline in stimulus-specific attention. The present article reviews the literature on LI deficits in high-schizotypal normal subjects and schizophrenic patients. Although LI-deficits have been thought to be specific to these groups, evidence is presented that the effects may be related to the anxiety components of high-schizotypality and related pathologies.

Anxiety↗
PubMed2000

c-Jun promotes neurite outgrowth and survival in PC12 cells.

We investigated the function of c-Jun in PC12 cells by transfecting them with a plasmid containing a c-Jun cDNA transcription cassette. Transfected cells expressed high levels of c-Jun mRNA and protein and demonstrated an increase in both AP-1 DNA binding and gene activation. The c-Jun over-expressing cells showed marked neurite outgrowth but no evidence of spontaneous cell death. In fact, c-Jun over-expressing cells were more resistant to okadaic acid-induced apoptosis. The process outgrowth was not indicative of a full neuronal differentiation response as the transfected PC12 cells did not display action potentials when examined with whole-cell patch-clamping. The phosphorylation of c-Jun on serine 73 appears to be important for this neurite sprouting effect as mutagenesis at this site reduced sprouting whereas a serine 63 mutant tended to increase sprouting. Thus, in PC12 cells c-Jun expression does not induce apoptosis, but rather functions as a neurite outgrowth and neuronal survival signal.

Action Potentials↗
PubMed2000

PU.1 expression in microglia.

The transcription factor PU.1 has a pivotal role in both the generation and function of macrophages. To determine whether PU.1 is also involved in microglial regulation, we investigated its expression following hypoxic-ischemia (HI) brain injury and in the BV-2 microglial cell line. We found that microglia constitutively expressed high levels of PU.1 protein in both their 'resting' and 'activated' states.

Animals↗
PubMed1999

Neurotrophic requirements of rat embryonic catecholaminergic neurons from the rostral ventrolateral medulla.

The factors that regulate the ontogeny and differentiation of C1 adrenergic neurons located in the rostral ventrolateral medulla (RVLM) are completely unknown. In the present study, we have investigated the effects of a number of neurotrophic factors on the survival of E18-19 rat C1 adrenergic neurons in culture. Immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) were used to study the expression of tyrosine hydroxylase (TH), an enzyme present in all catecholaminergic neurons, and of phenylethanolamine N-methyltransferase (PNMT), the final enzyme in the synthesis of adrenalin, as markers for the C1 RVLM neurons. Our results show that GDNF, CNTF BDNF, NT-3 and NT-4/5 increase the number of TH-immunoreactive neurons surviving in vitro. The effects of NGF, TGFbeta and bFGF were not significant. The E18-19 C1 neurons appeared to loose their ability to express PNMT in culture as examined with immunocytochemistry and RT-PCR, and none of the tested neurotrophic factors was able to sustain or induce this expression. Our results indicate that the adrenergic phenotype of C1 neurons, or the survival of these neurons, is determined by environmental factors other than the neurotrophic factors examined in this study.

Animals↗
PubMed1999

Effects of cyanide and hypoxia on membrane currents in neurones acutely dissociated from the rostral ventrolateral medulla of the rat.

Previous reports suggested that some neurones located in the rostral ventrolateral medulla (RVL) can act as fast oxygen sensors which enhance the sympathetic activity and blood pressure independent of peripheral chemoreceptors. The aim of this study was to compare hypoxic responses of different subpopulations of RVL neurones to ascertain whether the hypoxic sensitivity is restricted to one group of these neurones. Whole-cell patch-clamp recordings were made from acutely dissociated neurones obtained from RVL of P13-P19 rats. Short-lasting hypoxia (1-2 min) was evoked by pressure injection of NaCN or lowering pO2. Cells projecting to the upper thoracic segments were retrogradely labelled with fluorescent beads. Catecholaminergic (CA) or non-catecholaminergic (non-CA) neurones were identified using single-cell reverse-transcription polymerase chain reaction (RT-PCR) or immunocytochemistry. Recordings were made from 38 neurones (26 spinally-projecting, 12 non-spinal) using Cs+/TEA or K+-containing pipettes. In most of the cells tested with slow depolarising ramp commands (78%; including spinally-projecting and non-spinal neurones, as well as CA and non-CA neurones), NaCN or hypoxia evoked a reversible increase of the sustained inward current. Extracellular application of 1 mM Co2+ or 25 nM TTX revealed three components of the hypoxia-sensitive inward current which resembled the persistent sodium (INaP), low threshold calcium (LVA Ca2+) and high threshold calcium (HVA Ca2+) currents. The NaCN or hypoxia induced increase of the current could also be observed during step commands. Recordings with K+-containing pipettes during similar depolarising ramps revealed, in addition, a reversible increase of IK in 78% of tested cells (in all four types of examined neurones). These results are consistent with the concepts that RVL neurones can act as a central oxygen sensor. However, in contrast to the previously published data demonstrating that in pentobarbital anaesthetised rats only the barosensitive and spinally projecting cells were affected by a short-lasting hypoxia, our findings obtained with dissociated RVL neurones indicate that sensitivity to hypoxia is widely distributed within this part of the medulla oblongata.

Animals↗
PubMed1999

Complications of phacoemulsification on the first postoperative day: can follow-up be safely changed?

PURPOSE: To establish the rate of complications detected on the first postoperative day and therefore the need for evaluation on that day. SETTING: Hinchingbrooke Hospital, Huntingdon, England. METHODS: Complications detected on the first day after phacoemulsification cataract surgery were retrospectively reviewed over 8 months. Ophthalmic nurse practitioners performed the 1 day postoperative examination and kept a log of patients seen, recording complications detected and whether referral to a physician was required. All patients had had routine phacoemulsification with intraocular lens implantation without anterior vitrectomy or trabeculectomy, as identified from the log book and cross-checked with operating theater records. Notes were reviewed if a complication or referral was recorded. Most cases were performed under local anesthesia as day cases using a temporal corneal approach. Sections were routinely left unsutured unless enlarged or closure was not satisfactory at the conclusion of surgery. RESULTS: The review yielded 392 patients. Six (1.53%) had intraocular pressure (> or = 30 mm Hg) requiring treatment, 1 (0.26%) had painless iris prolapse, 11 (2.81%) had corneal abrasions, and 7 (1.78%) were given a more intensive steroid regime. No cases of fibrinous uveitis were recorded. CONCLUSIONS: Potentially sight-threatening complications present on the first postoperative day, albeit infrequently. With our current practice and case mix, the need for this review persists. It is possible to reduce the demand on physician time by using appropriately trained nonmedical practitioners.

Adult↗
PubMed1998

Concept activation and coordination of activation procedure require two different networks.

In the present study, we used EEG-coherence analysis to assess general regional changes in neuronal activity related to semantic retrieval, testing the hypothesis that concept activation and coordination procedures are neurobiologically distinguishable. Four subjects had to decide whether or not a capital letter and a lower case letter have the identical name (e.g. Aa). This task requires two mental procedures: (i) the activation of concepts and (ii) their coordination, particularly when the interstimulus interval is shorter than the duration of concept activation. This memory retrieval of a concept appears to be subserved by two distinct networks: the left parietotemporal region for concept activation and the prefrontal region for coordination.

Adult↗
PubMed1991

Effects on vigilance performance and sleepiness of alcohol given in the early afternoon ('post lunch') vs. early evening.

There is a propensity for sleepiness in the early afternoon ('post-lunch dip'), that contrasts with the circadian peak of alertness in the evening. Alcohol has a soporific effect, and one might expect it to be more potent in the early afternoon than in the evening. This is a little explored area. Four, two or nil (English) units of alcohol (producing maximum blood alcohol concentrations [BACs] of approx. 70, 35 and less than 5 mg alcohol 100/ml blood respectively) were given with food to eight women, at 1300h or 1830h, in a double-blind randomized repeated-measures design. After this consumption, subjects underwent 1 h of vigilance testing. They rated themselves for sleepiness on a half-hourly basis. There were significant main effects for dose and for time of day with: reaction time, hits and sleepiness scores. There was also a significant dose x time of day interaction with: reaction time and hits. That is, two and four units of alcohol produced greater impairment in the afternoon compared with the corresponding evening values. Implications of these findings for driving behaviour are discussed (the maximum legal BAC for car drivers in the UK is 80 mg/100 ml blood).

Alcohol Drinking↗
PubMed1986

Air ambulance regulations: a model.

Prior attempts at establishing minimal federal air ambulance regulations and standards have been unsuccessful. However, reports of poor patient medical care during transport by some air ambulance services is now forcing many states to initiate air ambulance regulations. In 1984, the State of Utah Emergency Medical Services convened a special subcommittee to develop aeromedical regulations for the State of Utah. Using a three-level approach based upon the patient's requirements for basic, advanced, or specialized medical care and the urgency of transport, the subcommittee was able to derive medical categories necessary for the selection and utilization of air ambulance services. Minimum air ambulance regulations were then established for aircraft configuration, flight crew requirements, minimal equipment and medications, and the responsibilities of the medical director or designee for each of the three levels of medical care. We conclude that the application of a levels approach based upon the patient's medical requirements may be useful in assisting other states attempting to establish flexible but specific regulations directed at the safe transport of patients by aeromedical evacuation.

Aircraft↗