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Biomedical subjects

M Trimble

Publications and source records attributed to M Trimble.

At least 19 recordsLinked to original sources
PubMed2002

Early vascular abnormalities and de novo nitrate tolerance in diabetes mellitus.

OBJECTIVE: The haemodynamic consequence of altered mechanical wall properties in diabetes can impair the compliance characteristics or pulsatile function of arteries before changes in calibre or peripheral resistance become evident. We studied the sensitivity of pulsatile and steady-state haemodynamic variables in identifying vascular abnormalities and assessing arterial responsiveness to glyceryl trinitrate (GTN) in patients with diabetes, free from clinical complications of the disease. METHODS: Radial artery pressure waveforms were recorded in 22 patients with diabetes and 22 age- and sex-matched control subjects, using a calibrated tonometer device. A computer-based assessment of the diastolic pressure decay was used to quantify changes in arterial waveform morphology in terms of pulsatile (arterial compliance) and steady-state (peripheral resistance) haemodynamics. Pressure pulse waveforms were recorded before and 3, 6 and 9 min after the administration of 300 micro g of GTN. RESULTS: Of the pulsatile and steady-state impedance parameters, only small artery compliance was significantly different in patients, 4.7 ml/mmHg (95% CI 3.8-5.8), compared with control subjects 7.1 ml/mmHg (95% CI 5.4-8.7); (p < 0.05). In response to GTN small artery compliance increased, and systemic vascular resistance decreased significantly in control subjects; (p < 0.05) but remained unchanged in patients with diabetes. CONCLUSIONS: Arterial waveform analysis proved more sensitive in detecting early vascular abnormalities and tracking the haemodynamic effects of GTN in patients with diabetes than changes in total peripheral resistance. The diminished responsiveness of the arterial vasculature to organic nitrates may have therapeutic implications for the treatment of cardiovascular disease in diabetes mellitus.

Adult↗
PubMed2002

Anomalies of cardiac venous drainage associated with abnormalities of cardiac conduction system.

The embryological development of the superior vena cava (SVC) is complex. If the left common cardinal vein fails to occlude it can, along with the left duct of Cuvier form a left SVC, which frequently drains into the coronary sinus. This may result in abnormalities in the anatomy of this structure. A persistent left SVC occurs in 0.5% of the normal population, and 3% to 4.3% of patients with congenital heart anomalies. The pacemaking tissue of the heart is derived from two sites near the progenitors of the superior vena cava. The right-sided site forms the sinoatrial node, the left-sided site is normally carried down to an area near the coronary sinus. Out of 300 patients with cardiac rhythm abnormalities, who have undergone electrophysiological studies (EPS), or permanent pacemaker insertion (PPI), we identified 12 patients with cardiac conduction abnormalities and anomalies of venous drainage. Anomalies of the coronary sinus may be associated with abnormalities of the conduction system of the heart. This may be due to the close proximity of the coronary sinus to the final position of the left-sided primitive pacemaking tissue. In our series of 300 patients, 4% had an associated left SVC, a similar incidence to that found in previous studies of congenital heart disease.

Adult↗
PubMed2001

Poetic talent unmasked by treatment of Parkinson's disease.

Parkinson's disease is typically characterised by loss of function and previous abilities, often accompanied by complications of treatment in later stages of the disease. We report on a patient who newly developed an artistic skill after starting treatment for Parkinson's disease. This case offers insight into the neurology of the artistic process as well as into the pathophysiology of psychiatric adverse reactions to the treatment of PD.

Antiparkinson Agents↗
PubMed2001

The last laugh.

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Journal Article↗
PubMed2001

A war on nerves.

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Journal Article↗
PubMed2001

Neurophysiological assessment of the feasibility and safety of neural tissue transplantation in patients with syringomyelia.

The feasibility and safety of a procedure involving fetal spinal cord tissue transplantation in patients with syringomyelia was assessed using a neurophysiological protocol designed to quantitate peripheral nerve function, spinal cord reflex excitability, and spinal cord conduction pathways essential for somatosensory evoked potentials. We report here data obtained before and for 18 months following the transplantation procedure performed on the first two patients in this study. The neurophysiological assessment protocols included measures of cortical and spinal cord evoked potentials, H-reflex excitability, and peripheral nerve conduction. Prior to the procedure, both patients had significant deficits on some of the neurophysiological measures, for example, lower extremity cortical evoked potentials. However, robust measures of intact pathways, such as upper extremity cortical evoked potentials, were also observed preoperatively in both patients. Thus, it was anticipated that conduction in these intact pathways could be at risk either from complications from the transplantation procedure and/or from continued expansion of the syrinx. Following the transplantation procedure, no negative changes were observed in any of the neurophysiological measures in either patient. In addition, patient 1 showed a decrease in the rate potentiation of tibial H-reflexes on the right side and an increase in the response probability of left tibial H-reflexes. The results of this postoperative longitudinal assessment provide a first-level demonstration of the safety of the intraspinal neural tissue transplantation procedure. However, the consideration of safety is currently limited to the grafting procedure itself, since the long-term fates of the donor tissue in these two patients remain to be shown more definitively.

Action Potentials↗
PubMed2000

Control strategies for initiation of human gait are influenced by accuracy constraints.

The accuracy of placement of swing limb heel-strike was used to determine strategies of motor control of the stance limb during gait initiation (GI). Subjects initiated gait as fast as possible with the swing limb heel-strike landing on either a small or large target. Stance limb ground reaction forces, electromyogram duration and temporal data for GI were measured. It was hypothesized that accuracy would affect movement speed and the rate of rise, or the slope, of the ground reaction forces that control GI. The slopes of the stance limb forces that coincide with swing limb toe-off remained invariant. However, the slopes of forces and peak forces related to swing limb heel-strike were significantly less for the small target. These initial data suggest that principles of upper extremity motor control may be generalized to the initiation of movement from upright stance.

Adult↗
PubMed2000

A functional neuroanatomy of tics in Tourette syndrome.

BACKGROUND: Tics are involuntary, brief, stereotyped motor and vocal behaviors often associated with irresistible urges. They are a defining symptom of the classic neuropsychiatric disorder, Tourette syndrome (TS), and constitute an example of disordered human volition. The neural correlates of tics are not well understood and have not been imaged selectively. METHODS: Event-related [(15)O]H(2)O positron emission tomography techniques combined with time-synchronized audio and videotaping were used to determine the duration of, frequency of, and radiotracer input during tics in each of 72 scans from 6 patients with TS. This permitted a voxel-by-voxel correlational analysis within Statistical Parametric Mapping of patterns of neural activity associated with the tics. RESULTS: Brain regions in which activity was significantly correlated with tic occurrence in the group included medial and lateral premotor cortices, anterior cingulate cortex, dorsolateral-rostral prefrontal cortex, inferior parietal cortex, putamen, and caudate, as well as primary motor cortex, the Broca's area, superior temporal gyrus, insula, and claustrum. In an individual patient with prominent coprolalia, such vocal tics were associated with activity in prerolandic and postrolandic language regions, insula, caudate, thalamus, and cerebellum, while activity in sensorimotor cortex was noted with motor tics. CONCLUSIONS: Aberrant activity in the interrelated sensorimotor, language, executive, and paralimbic circuits identified in this study may account for the initiation and execution of diverse motor and vocal behaviors that characterize tics in TS, as well as for the urges that often accompany them. Arch Gen Psychiatry. 2000;57:741-748

Adult↗
PubMed2000

Schizophrenia, temporal lobe epilepsy and psychosis: an in vivo magnetic resonance spectroscopy and imaging study of the hippocampus/amygdala complex.

BACKGROUND: We have used proton magnetic resonance imaging and spectroscopy to measure hippocampus/amygdala volumes and anterior hippocampal metabolite concentrations (N-acetyl aspartate (NAA), creatine/phosphocreatine and choline) in subjects with temporal lobe epilepsy (TLE), schizophrenia and in normal controls. METHOD: Four groups of right-handed patients were selected: 12 with TLE and psychosis (EP), 12 with TLE and no psychosis (ENP), 26 with schizophrenia, and 38 normal controls. Imaging and spectroscopy were performed with a 1.5T Signa GE scanner. RESULTS: The schizophrenia group showed a significant left-sided reduction in all metabolites. In the epilepsy groups NAA was reduced bilaterally. The NAA reduction in the EP group was greater than in the ENP group, especially on the left, although the result did not reach significance. Total hippocampus/amygdala volumes showed no significant differences in any of the groups when compared with normal controls. When compared with controls significant, specific regional volume reductions were present bilaterally in the EP group and in the left hippocampus/amygdala in schizophrenia. The regional volume reduction found in schizophrenia was also present in EP but not in ENP. CONCLUSION: Spectroscopic abnormalities were more pronounced in the epilepsy groups and were bilateral, and abnormalities in schizophrenia were left sided. Specific regional hippocampus/amygdala volume reductions were more marked in the EP group and were bilateral. Left-sided regional volume reduction identified in the dominant hemisphere of schizophrenics was also present in EP patients, but not in ENP, suggesting that this region in the left temporal lobe may be significant in the aetiology of psychosis. This is further supported by the predominantly left-sided NAA reduction in schizophrenia. High resolution morphometric studies may identify specific regions of the brain associated with the development of psychosis.

Adult↗
PubMed1999

Principles underlying the organization of movement initiation from quiet stance.

The purpose of this study was to determine common principles underlying the programming of movement initiation from quiet stance. Subjects were asked to initiate gait, step over a ruler, or to step over a 10 cm high obstacle at a self-paced speed and as fast as possible. The independent variables were initiation condition (gait initiation, stepping over a ruler or obstacle) and initiation speed (self-paced and as fast as possible). The dependent measures for the stance limb only were the latency between postural soleus (S(1)) EMG inhibition and tibialis anterior (TA) EMG onset, the duration of both TA and soleus (S(2)) activity following TA, duration and slope, impulse, and peak forces of the anterior-posterior (Fx) ground reaction force. Selected timing events were also monitored. Analysis of variance was used to determine main and interaction effects. The following results were obtained. (1) The interval from the inhibition of S(1) postural activity to the onset of TA remained invariant between all conditions. (2) The duration of TA increased and S(2) decreased with an increase in speed of initiation. There was no difference in TA and S(2) duration between the initiation conditions. (3) Time to heel-off remained invariant for all conditions. (4) Prior to heel-off all force variables increased with initiation speed but were similar between initiation conditions. After heel-off force variables were different between speeds and conditions being greater for fast speed and stepping over the obstacle. Two conclusions may be drawn from this study. First, the results indicate that gait initiation consists of two, highly coordinated motor programs. Heel-off of the stance limb is the division between these two programs. Second, our findings also suggest that gait initiation and stepping are governed by the same motor programs.

Adult↗
PubMed1998

Effects of gabapentin on cognition and quality of life in patients with epilepsy.

The effect of gabapentin on cognition and quality of life (QoL) in patients with epilepsy was investigated using a controlled pre- and post-treatment design. Thirty patients with chronic epilepsy were administered a battery of cognitive tests and QoL measures at baseline (pre-treatment) and again following 1-2 months of treatment (post-treatment). All patients were receiving anticonvulsant medication at baseline. Following baseline assessment, 15 patients were started on gabapentin as add-on therapy (gabapentin group), and 15 patients remained on stable medication (control group). No between-group treatment effects were demonstrated on any of the mood measures. A significant between-group treatment effect was demonstrated on one cognitive measure, in favour of the gabapentin group. Results do not suggest any adverse short-term effects of gabapentin on cognition or QoL in patients with chronic epilepsy.

Acetates↗
PubMed1997

HMPAO SPET does not distinguish obsessive-compulsive and tic syndromes in families multiply affected with Gilles de la Tourette's syndrome.

BACKGROUND: Gilles de la Tourette's syndrome (GTS) is a familial neuropsychiatric disorder characterized by tics and obsessive-compulsive behaviours (OCB). Previous HMPAO SPET studies of subjects with GTS have shown hypoperfusion of striatal and frontal areas. Studies of patients with primary obsessive-compulsive disorder have shown, in contrast, hyperperfusion of similar areas. METHODS: Twenty subjects from five families affected by GTS, including individuals with OCB but no tics, were examined using HMPAO SPET. RESULTS: There were abnormalities of regional cerebral perfusion in individuals with GTS, OCB and tics. Hypoperfusion was in striatal, frontal and temporal areas. There was no hyperperfusion. CONCLUSIONS: Regional cerebral blood flow patterns in individuals with OCB in families affected by GTS are comparable to their relatives with GTS and differ from individuals with primary OCD in the absence of a family history of tic disorders.

Adolescent↗