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Biomedical subjects

J G Phillips

Publications and source records attributed to J G Phillips.

At least 91 records · Page 5Linked to original sources
PubMed1993

Re-orientation of attention in Parkinson's disease: an extension to the vibrotactile modality.

Parkinson's disease (PD), a disorder of the dopaminergic nigro-striatal pathway, is associated with both motor and cognitive impairments, including perhaps the ability to focus attention. Disturbances of attentional processes were further examined in a series of vibrotactile choice reaction time (cRT) experiments involving biased probabilities of event occurrence, or valid/invalid precueing. Results of three experiments suggest that PD subjects, compared to controls, are less adept at maintaining attention in space. The performance of the PD subjects improved, however, when they were permitted to direct their gaze to one hand or the other, and when valid external precues were provided before each trial. Observed similarities between the cognitive and motor deficits of PD subjects support the notion that there is a close coupling between the mechanisms coordinating attention and movement.

Adult↗
PubMed1993

An evaluation of the role of internal cues in the pathogenesis of parkinsonian hypokinesia.

Our animal studies suggest that the basal ganglia provide an internal non-specific cue to trigger movement and imply that Parkinson's disease involves a deficiency in this cueing mechanism. Indeed parkinsonian patients typically rely upon external visual cues. To assess the effects of such non-specific cueing mechanisms on movement, we examined patients' utilization of a variety of auditory cues. Ten patients suffering from Parkinson's disease, and their matched controls, pressed buttons at a series of two-way choice points sequentially down a pathway, both when the latter remained illuminated throughout its length, and when it had to be followed from memory alone. In other experimental conditions, auditory cues were also provided, either contingent upon the previous response, at its initiation (a medium level of advance information) or at its completion (a low level of advance information), or as a series of regularly paced (non-contingent) auditory cues (from a metronome). In addition to error data, we recorded down time (DT, time to initiate each next response) and movement time (MT, time to execute each next response). However, both DT and MT measurements showed that parkinsonian patients were enormously disadvantaged by the absence of external cues. While contingent auditory cues were of some help, the performance of patients with Parkinson's disease was dramatically improved by the provision of non-contingent auditory information. Moreover, parkinsonian patients, unlike controls, were greatly affected by the length of individual sub-movements, especially in the absence of external cues. When the pathway to be followed remained illuminated, sub-movement length had little effect. We conclude that for well-learnt, predictable sequences the basal ganglia provide a non-specific internal cue that is necessary for switching between one movement and the next in a movement sequence, and also for development of preparatory activity for each sub-movement in the sequence.

Aged↗
PubMed1993

Canopy development and solar conversion efficiency in Acacia auriculiformis under drought stress.

A glasshouse experiment was performed with Acacia auriculiformis seedlings to investigate the effects of decreased soil water potential on phyllode extension, abscission and solar conversion efficiency, e. Six-month-old seedlings were subjected for 39 days to one of four treatments: well watered (soil water potential maintained above -0.5 MPa), moderately drought stressed (soil water potential maintained above -1.5 MPa), severely drought stressed (soil water potential maintained above -2.5 MPa) and well watered but pruned to maintain a leaf area approximating that of the severely drought-stressed treatment. Aboveground biomass accumulation decreased by 21% below that of the well-watered controls in the moderately drought-stressed seedlings and by 47% in the severely drought-stressed seedlings as a result of both decreased interception of solar radiation and lower e. Differences in phyllode extension rate, rather than in phyllode abscission, were primarily responsible for the differences in interception of solar radiation among treatments. Decreases in phyllode extension rate and water use occurred simultaneously in response to decreasing soil water potential. Specific leaf area decreased and water use efficiency increased in response to drought stress.

Journal Article↗
PubMed1993

Coding of movement direction and amplitude in Parkinson's disease: are they differentially impaired (or unimportant)?

A recent study suggested that the preparation of movement direction, but not amplitude, may be selectively impaired by Parkinson's disease (PD). The authors examined the reprogramming of direction only, amplitude only, and direction and amplitude together, and included a control condition in which neither parameter was reprogrammed. The findings suggested that neither direction nor amplitude coding was differentially impaired in PD. Thus the structures affected by PD may not be uniquely involved in specifying only the direction or the amplitude of future movements; these structures probably have more complex higher-level roles.

Aged↗
PubMed1992

Initiation and execution of movement sequences in those suffering from and at-risk of developing Huntington's disease.

Recent research has shown that Huntington's disease (HD) causes problems in the initiation and execution of movement (akinesia, bradykinesia): information which is useful in documenting the functional progression of the disease. The present experiment used a sequential movement task to characterize such impairments. Eighteen patients diagnosed as suffering from HD, and a similar number of matched At-Risk (AR) and Normal control subjects, performed sequential button pressing tasks, under varying amounts of visual advance information. Specific dimensions of motor control were examined (hand, direction). Movement initiation and in particular movement duration were useful indicators of the functional progression of the disease, and also detected anomalies of performance in some AR individuals. Impaired motor programming was indicated by patients' difficulty in initiating movements in the absence of external visual cues, and their problems in utilizing advance information to control movement. Patients had specific deficits in initiating movements with the nonpreferred hand, and directional movement asymmetries were accentuated. The results suggest that HD causes difficulties at three discrete levels: in utilizing advance information, in the initiation and in the spatial representation of movement.

Adult↗
PubMed1992

Programming of single movements in Parkinson's disease: comparison with Huntington's disease.

The preparation of individual finger movements was examined in Parkinson's disease (PD), in comparison with a similar study of Huntington's disease (HD). Motor programming was varied by increasing the amount of information available in advance of each movement. PD patients had particular difficulty when there was no cue light in advance of the movement, and when two upcoming movements were cued ahead of the current movement. Such difficulties suggest that PD patients may have difficulty in performing movements without sensory cuing, and in maintaining and organising a future sequence of movements. HD patients had been previously shown to have similar deficits. Commonalities in these once contrasted disorders probably arise from disruption of common mechanisms.

Adult↗
PubMed1992

Impairments of movement initiation and execution in unilateral neglect. Directional hypokinesia and bradykinesia.

Patients with unilateral neglect may exhibit slowness in the initiation of contralesionally directed movements in peripersonal space (directional hypokinesia). The present study used a sequential movement task to characterize any such impairment in a group of 24 patients with right hemisphere lesions, 18 of whom had left neglect. A further five patients with left hemisphere lesions, one of whom had right neglect, were also tested. We measured movement initiation and execution times for leftward and rightward movements in either hemispace and across the body midline. Most left neglect patients, particularly those with lesions involving posterior cortex, showed directional hypokinesia. Left neglect patients with anterior and/or subcortical lesions also showed directional bradykinesia, i.e. a slowing in the execution phase of contralesionally directed movements. This impairment occurred regardless of the spatial location of the apparatus and was exacerbated as patients moved closer to their neglected side. The patient with right neglect showed directional hypokinesia but not directional bradykinesia. Right hemisphere and left hemisphere lesion patients without neglect performed in a manner comparable to controls, who did not exhibit directional hypokinesia or directional bradykinesia. These results suggest that directional hypokinesia is associated with both left hemisphere and right hemisphere damage, but only in the context of unilateral neglect. Moreover, the site of hemispheric lesion may determine the temporal characteristics of movement impairments in neglect. Damage to posterior cortex produces deficits in detecting contralesional targets and initiating movements toward them, while damage to anterior or subcortical structures may disrupt the internal representation of an intended trajectory.

Adult↗
PubMed1992

Impairment in bilateral alternating movements in Parkinson's disease?

Although problems in bilateral simultaneous movements in Parkinson's disease (PD) are well known, such deficits have not been reported to be any more impaired than simultaneous movements within the same limb. This is surprising, since (a) the parallels between supplementary motor area (SMA) damage and PD are well documented and (b) the SMA seems to play a special role in bilateral motor control. Bilateral versus unilateral movements in PD were examined by using a task that compared alternating movements of fingers of the same hand with alternating movements of fingers of the opposite hands. PD patients showed particular problems in programming and transferring motor activity to fingers on the opposite side of the body, as opposed to switching motor activity between fingers on the same side of the body. These findings outline the relevance of SMA dysfunction to PD.

Aged↗
PubMed1991

Lack of ranitidine effects on cyclophosphamide bone marrow toxicity or metabolism: a placebo-controlled clinical trial.

We previously reported that cimetidine but not ranitidine significantly enhances cyclophosphamide-induced bone marrow toxic effects and the appearance of cyclophosphamide alkylating species in a murine leukemia mouse model, and we advised caution in the use of cimetidine with microsomally metabolized anticancer drugs. Both drugs have been used for the treatment of gastric complications of chemotherapy. Using a randomized, double-blind, crossover study design, we have now evaluated the potential interaction of ranitidine with cyclophosphamide in seven cancer patients, who received two courses of cyclophosphamide, one with ranitidine and one with placebo. Four patients received ranitidine in the first course, and three received placebo. Ranitidine or placebo was started 3 days before a single dose of cyclophosphamide and given for 17 consecutive days. Ranitidine or placebo was given orally (300 mg/d), and cyclophosphamide (600 mg/m2) was given intravenously with [3H]cyclophosphamide (1000 muCi). Cyclophosphamide treatment was repeated at 4 weeks plus or minus 4 days. Blood samples were collected at intervals from 5 minutes to 24 hours after cyclophosphamide treatment and analyzed by thin-layer chromatography and radioassay for the drug and its metabolites. On days 0, 7, 14, and 21 after cyclophosphamide administration, complete blood cell counts, white blood cell differential counts, platelet counts, and SMA-17 were determined. The differences in mean nadir white blood cell counts, granulocyte counts, hemoglobin levels, and hematocrit values during ranitidine versus placebo treatment were not statistically significant. In a statistical but not a clinical sense, mean nadir platelet counts were significantly lower with ranitidine. There was a statistically significant increase in area under the curve for drug concentration in plasma x time (AUC) with ranitidine as well as a statistically significant decrease in the total-body clearance rate of the cyclophosphamide molecule. However, the effect on AUC for the major oncolytic metabolites 4-hydroxycyclophosphamide and phosphoramide mustard was not statistically significant. The lack of toxicologic or metabolic interaction between ranitidine and cyclophosphamide suggests that ranitidine can be used safely with cyclophosphamide.

Adult↗
PubMed1991

Fate of unirradiated Salmonella in irradiated mechanically deboned chicken meat.

Mechanically deboned chicken meat was irradiated at 0, 1.25 and 2.50 kGy (Cesium 137) and inoculated with Salmonella dublin ATCC 15480, Salmonella enteritidis ATCC 9186 or Salmonella typhimurium ATCC 14028. Samples were then stored at 5 degrees C and 10 degrees C and were subjected to microbiological analysis directly after irradiation and inoculation (time 0), and after 24, 72, 120, 168 and 216 h of storage. Samples stored at 20 degrees C were examined at time 0 and after 6, 12 and 24 h of storage. Irradiation at 1.25 and 2.50 kGy caused an average reduction in bacterial levels of 2.23 and 3.44 logs, respectively. S. dublin, S. enteritidis and S. typhimurium showed very small, insignificant changes in numbers, during storage of meat for 9 days at 5 degrees C. The final populations of S. dublin and S. typhimurium in samples irradiated before inoculation and stored at 10 degrees C or 20 degrees C were greater than the equivalent populations in samples which had not been irradiated before inoculation. Reduction of indigenous microflora in mechanically deboned chicken meat by irradiation may create better conditions for the growth of salmonellae and may thus increase the risk of salmonellosis when accidental contamination and temperature abuse occur after a radiation treatment. Therefore, irradiated mechanically deboned chicken meat should be properly refrigerated and protected against contamination.

Aerobiosis↗
PubMed1991

A drape for temporomandibular joint surgery.

A method for draping in TMJ surgery including arthroscopy is presented using a urological drape. The advantage is that it allows movement of the mandible by the surgeon or assistant without their contamination by saliva.

Humans↗
PubMed1991

Reconstruction of the defect at the donor site of the temporalis muscle flap.

A method for the immediate correction of the defect created at the donor site of the temporalis muscle flap is described. It uses a performed acrylic prosthesis. A case is presented in which the prosthesis could have been used to good effect, and two cases are reported to show the successful use of this technique.

Acrylic Resins↗
PubMed1991

Laboratory biology of Ornithodoros (Alectorobius) puertoricensis (Acari: Argasidae).

The laboratory biology of Ornithodoros (Alectorobius) puertoricensis Fox was studied over a 2-yr period. Approximately 100-150 ticks were reared individually at each of four temperatures: 22, 27, 33, and 40 degrees C and 90-95% RH. The mean egg incubation periods at those temperatures were 20.3, 11.1, 7.3, and 6.1 d, respectively. The average larval feeding period was 5.8 +/- 1.5 d for 15,875 larvae that fed on guinea pigs. The development times for first to fourth nymphal instars were as follows: 11.7, 48.5, 75.1, and 92.1 d, respectively, at 22 degrees C; 5.8, 18.8, 38.0, and 36.0 d, respectively, at 27 degrees C; 4.2, 10.5, 14.9, and 38.1 d, respectively, at 33 degrees C; and 5.8, 10.7, 21.2, and 35.3 d, respectively, at 40 degrees C. Males usually eclosed after three or four molts, and females usually eclosed after four or five molts. Approximately 10% of all nymphs required more than one blood meal per instar at least once during development. Twenty pairs of adults were held at each of three temperatures (22, 27, and 33 degrees C) for a year to study reproductive behavior. The number of gonotrophic cycles per female per year was 6.9, 9.8, and 10.8 at 22, 27, and 33 degrees C, respectively. The mean duration of the gonotrophic cycle was 42.3 d at 22 degrees C, 25.5 d at 27 degrees C, and 20.5 d at 33 degrees C. Mean egg production per female per gonotrophic cycle was 151 at 22 degrees C, 117 at 27 degrees C, and 130 at 33 degrees C and was not affected by temperature. O. puertoricensis did not exhibit autogeny or parthenogenesis. Hyperparasitism was observed in immatures and adults.

Animals↗
PubMed1991

Movement disorders--limb movement and the basal ganglia.

The primary concern of this article is to review experimental methods that may lead to a better understanding of the functional role of the basal ganglia in the control of movement. Two models of basal ganglia impairment are considered: Parkinson's disease and Huntington's disease. The review focuses primarily on akinesia and bradykinesia because they are key abnormalities of basal ganglia dysfunction. In general, through electromyography and kinematic analysis of movement, it may be possible to characterize specific movement disorders. Specifically, if damage sustained by the central nervous system is traced to a certain structure, it may provide insight on the extent of involvement and functional role of that structure in the control of movement. Much of the data reviewed suggests that the basal ganglia may play a specific role in the initiation and regulation of force control.

Basal Ganglia↗