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Biomedical subjects

L T Dunn

Publications and source records attributed to L T Dunn.

13 recordsLinked to original sources
PubMed1997

Secondary insults during the interhospital transfer of head-injured patients: an audit of transfers in the Mersey Region.

To assess the incidence of secondary insults and unidentified extracranial injuries a prospective audit of 50 head-injury transfers to a regional neurosurgical unit using a standardized assessment proforma was undertaken. There was wide variability in the quality of transfers. Six per cent of the group were hypoxic on arrival and 15 per cent were hypotensive. In the patients with multiple injuries, 29 per cent had inadequately diagnosed or managed injuries when they arrived. A comparison of this cohort of patients with previous studies is presented. As a result of the audit a set of transfer and referral guidelines have been drawn up and, following distribution of the guidelines to our referring hospitals, a further cohort of patients will be audited.

Adolescent↗
PubMed1995

Hemispherectomy for intractable seizures: a further modification and early experience.

Hemispherectomy is well recognized as an effective treatment for some types of intractable epilepsy, but the procedure is also known to be associated with significant late complications. A number of modifications to the original operation have been developed to try and minimize such late complications. These are reviewed and a further modification is described using a Zenoderm graft to isolate the hemispherectomy cavity from the remaining CSF pathways. We present our early experience with this new modification in seven patients with intractable epilepsy.

Adolescent↗
PubMed1995

Demonstration of neurovascular compression in trigeminal neuralgia with magnetic resonance imaging. Comparison with surgical findings in 52 consecutive operative cases.

Until recently, the inability to demonstrate neurovascular compression of the trigeminal nerve preoperatively resulted in surgery being offered only in cases of severe trigeminal neuralgia (TGN), frequently after a prolonged trial of medical treatment and following less invasive procedures, despite the fact that posterior fossa microvascular decompression gives long-term pain relief in 80% to 90% of cases. To assess whether vascular compression of the nerve could be demonstrated preoperatively, high definition magnetic resonance tomographic angiography (MRTA) was performed in 50 consecutive patients, five of whom had bilateral TGN, prior to posterior fossa surgery. The imaging results were compared with the operative findings in all patients, including two patients who underwent bilateral exploration. Vascular compression of the trigeminal nerve was identified in 42 of 45 patients with unilateral symptoms and on both sides in four patients with bilateral TGN. In the last patient with bilateral TGN, neurovascular compression was identified on one side, and on the other side the compressing superior cerebellar artery was separated from the nerve by a sponge placed during previous surgery. There was full agreement regarding the presence or absence of neurovascular compression demonstrated by MRTA in 50 of 52 explorations, but MRTA misclassified four vessels compressing the trigeminal nerve as arteries rather than veins. In two cases, there was disagreement between the surgical and MRTA findings. In the first of these cases, surgery revealed distortion of the nerve at the pons by a vein that MRTA had predicted to lie 6 mm remote from this point. In the second patient, venous compression was missed; however, this patient was investigated early in the series and did not have gadolinium-enhanced imaging. In nine cases, MRTA correctly identified neurovascular compression of the trigeminal nerve by two arteries. Moreover, MRTA successfully guided surgical reexploration in one patient in whom a compressing vessel was missed during earlier surgery and also prompted exploration of the posterior fossa in two patients with multiple sclerosis and one patient with Charcot-Marie-Tooth syndrome, in whom neurovascular compression was identified preoperatively. It is concluded that MRTA is an extremely sensitive and specific method for demonstrating vascular compression in TGN. As a result, open surgical procedures can be recommended with confidence, and microvascular decompression is now the treatment of choice for TGN at the authors' unit. They propose MRTA as the definitive investigation in such patients in whom surgery is contemplated.

Aged↗
PubMed1994

An immunotoxicity assessment of food flavouring ingredients.

A rapid screening protocol incorporating key elements of the US National Toxicology Program's immunotoxicity tier testing strategy was used to evaluate the effects of 35 commonly used food flavouring ingredients on humoral and cell-mediated immune responses. The test compounds were administered intragastrically on a daily basis for 5 days at three dose levels to female CD-1 or B6C3F1 mice, 6-8 wk old. A host resistance assay (Listeria monocytogenes bacterial challenge) was conducted to assess cell-mediated immunity. Humoral immunity was measured by the antibody plaque-forming cell (PFC) response to sheep erythrocytes. Body weights, lymphoid organ weights and spleen cellularity were also measured. Cyclophosphamide (80 mg/kg) served as an immunosuppressive positive control agent. The results indicated that the majority of the flavouring ingredients tested did not modulate the cell-mediated or humoral immune response. However, at very high dose levels, two of the materials tested, peppermint oil and citral dimethyl acetal, did increase mortality rate and reduce survival time in the host resistance assay. Neither of these materials significantly altered the PFC response. This rapid, economical screening battery for potential immunotoxicants proved to be a useful means of evaluating a large number of structurally diverse compounds and mixtures to prioritize them for more definitive testing.

Animals↗
PubMed1994

Anticonvulsant and antibiotic prophylaxis in head injury.

The evidence for and against the prophylactic use of anticonvulsants and antibiotics in head injury is reviewed. There is a lack of blinded placebo-controlled trials in this area. On balance there is no compelling evidence to support the use of either anticonvulsant or antibiotic prophylaxis in head injury, with the possible exception of antibiotic prophylaxis in compound depressed skull fractures and penetrating brain injuries.

Animals↗
PubMed1988

Double dissociations of the effects of amygdala and insular cortex lesions on conditioned taste aversion, passive avoidance, and neophobia in the rat using the excitotoxin ibotenic acid.

The results in this article show that although electrolytic amygdala lesions disrupt learning of a conditioned taste aversion (CTA), ibotenic acid-induced, axon-sparing lesions of the amygdala do not. However, ibotenic acid lesions of the insular cortex do disrupt learning of a CTA. Electrolytic, but not ibotenic acid lesions of the amygdala, interrupt axons running between the insular (gustatory) cortex and the brain stem/hypothalamus. It is the destruction of these projections which appear to underly CTA deficits after amygdala lesions. Other results revealed that ibotenic acid lesions of the insular cortex attenuated the reaction to the novel taste of saccharin in a familiar environment but failed to affect the ingestion of a novel food in a novel environment or passive avoidance learning. Conversely, ibotenic acid lesions of the amygdala did not affect the reaction to novel saccharin in a familiar environment but did impair both the reaction to novel food in a novel environment and passive avoidance learning. We conclude that the insular cortex is involved in reactions to the novelty and associative salience exclusively of taste stimuli, whereas the amygdala is probably more concerned with the reaction to more general aspects of novelty in the environment and in fear-motivated behavior.

Amygdala↗
PubMed1987

The effects of lesions to noradrenergic projections from the locus coeruleus and lateral tegmental cell groups on conditioned taste aversion in the rat.

Lesions of the coeruleo-cortical noradrenergic projections caused marked cortical noradrenaline depletions but were not associated with deficits in the acquisition or extinction of a conditioned taste aversion (CTA). Lesions of lateral tegmental noradrenergic projections resulted in marked hypothalamic noradrenaline depletions, enhanced neophobia to the novel taste of saccharin, unimpaired acquisition but prolonged extinction of the CTA. However, when animals with lateral tegmental noradrenergic lesions received extensive preconditioning exposure to saccharin, acquisition of the CTA was attenuated and extinction was more rapid than in controls. Alterations in CTA learning and extinction following lesions of the lateral tegmental noradrenergic system appear to reflect alterations in the way that animals with lesions react toward the hedonic aspects of taste-related stimuli rather than alterations in associational or attentional mechanisms.

Animals↗
PubMed1986

A comparison of two different methods for the measurement of drinking in the rat.

Drinkometers based on two different principles are described and compared. A capacitative design relied on the detection of a very small current through the animal as a means of recording contacts between the animal's tongue and the drinking spout. A photocell-based design relied on a beam across the front of the drinking spout being broken by the animal's tongue as a record of access to the spout. Both types of device were found to give a picture of the animal's behaviour similar to that obtained by a measure of the volume of fluid ingested. However the devices using a photocell were found to be less prone to error than the capacitative devices.

Animals↗
PubMed1983

Changes in body weight and food-related behaviour induced by destruction of the ventral or dorsal noradrenergic bundle in the rat.

Three experiments contrasted the effects of 6-hydroxydopamine-induced lesions of the ventral noradrenergic and dorsal noradrenergic projections, predominantly to hypothalamus and cortex, respectively, upon body weight changes and food-related behaviour in the rat. In general, ventral noradrenergic bundle lesions enhanced weight gain and these effects were exaggerated by the provision of palatable cheese to the standard chow diet. In contrast, lesions of the dorsal noradrenergic bundle produced minor changes in body weight. Associated with the effects of ventral noradrenergic bundle lesions were hyperphagia, enhanced suppression of intake of food adulterated with quinine, (at high concentration), a small attenuation of food neophobia, and enhanced acquisition, but not performance, of the eating response to tail-pinch stimulation. These ventral noradrenergic bundle lesions failed to alter basal activity levels, amphetamine anorexia or the diurnal pattern of eating or activity. In contrast, lesions of the dorsal noradrenergic bundle did not produce either hyperphagia or enhanced rejection of food adulterated with quinine. However, there was a strong attenuation of food neophobia and a retarded acquisition (but unimpaired performance) of eating in response to tail-pinch stimulation. The results are discussed in connection with previous studies of ventral and dorsal noradrenergic bundle lesions, with the effects of ventromedial hypothalamic lesions and with the underlying behavioural and physiological processes that mediate these contrasting effects of different neuroanatomical patterns of central noradrenaline depletion.

Animals↗