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M Cook

Publications and source records attributed to M Cook.

At least 91 records · Page 5Linked to original sources
PubMed1995

MRI-based hippocampal volumetrics: data acquisition, normal ranges, and optimal protocol.

The process of producing magnetic resonance (MR) volume measurements can be divided into considerations of acquisition and postprocessing of the MR data. With careful attention to both of these, precise and reproducible measurements can be achieved. A statistical description of hippocampal measurements in normal volunteers must be available for comparison if volumetrics are employed either for clinical or research purposes. A wide range in "normal" hippocampal volume is present in the studies of normal young adults that have been reported to date. This variability is most probably due to interinstitutional differences in hippocampal boundary criteria, and in the software employed for counting pixels in a defined region of interest (ROI). Because the numeric output from the volume measurement procedure is highly technique-dependent, the statistical description of "normal" should be determined or calibrated at each institution wishing to use these techniques.

Adult↗
PubMed1995

Role of the cerebellar fastigial nucleus in the physiological regulation of cerebral blood flow.

Local cerebral blood flow (ICBF) was measured with [14C]iodoantipyrine in conscious, unrestrained rats during electrical stimulation of the fastigial nucleus (FN). Electrode position in the FN was determined by blood pressure (MABP) responses to stimulation under anesthesia. In nine rats in which MABP responses had been variable under anesthesia, bipolar stimulation (50 Hz, 0.5 ms, 1 s on/1 s off) with currents of 30-100 microA after recovery from anesthesia produced stereotypic behavior but little effect on MABP and ICBF. In seven other conscious rats currents could be raised to 75-200 microA without inducing seizures, resulting in sustained MABP elevations during the ICBF measurement and significantly increased ICBF in the sensory-motor (+45%), parietal (+31%), and frontal cortices (+56%) and the caudate-putamen (+27%) above control values (n = 9). Glucose utilization, measured with [14C]deoxyglucose, in rats similarly stimulated was significantly increased in six structures, including some of the above, indicating increases in ICBF due to metabolic activation. Unilateral or bilateral electrolytic lesions of the FN, placed 6-7 days before ICBF measurement, had negligible effects on resting ICBF and on autoregulation in conscious rats. These results fail to support a specific role for the FN in physiological regulation of cerebral blood flow in unanesthetized rats.

Anesthesia↗
PubMed1995

Lack of effects of inhibition of nitric oxide synthesis on local glucose utilization in the rat brain.

The effects of chronic treatment with NG-nitro-L-arginine methyl ester, a potent inhibitor of nitric oxide synthase activity, on local cerebral glucose utilization were examined in conscious rats. Intraperitoneal injections of 50 mg/kg of the nitroarginine twice daily for 4 days have been found to result in almost complete inhibition of nitric oxide synthase activity in brain. Local cerebral glucose utilization was determined by means of the quantitative autoradiographic [14C]deoxyglucose method in an experimental group (n = 7) of rats that were treated with the nitroarginine according to this schedule and in a normal control group (n = 7) treated similarly with saline. The rats were conscious but partially restrained during the determinations of local cerebral glucose utilization. The nitroarginine treatment raised mean arterial blood pressure statistically significantly to 147 +/- 3 mm Hg (mean +/- SEM) from a level of 120 +/- 5 mm Hg in the saline controls (p < 0.001 by grouped t test), but there were no statistically significant effects on glucose utilization in any of 39 brain structures examined. It is concluded that nitric oxide normally exerts no significant influence on energy metabolism in the rat brain.

Animals↗
PubMed1995

Panum's limiting case: double fusion, convergence error, or 'da Vinci stereopsis'.

Panum's limiting case--a perceived depth difference between two lines in one eye combined with only one in the other eye--has long been considered weak or reversible. In the last few years this has led to strong promotion of the view that Panum's case is not based on a stereoscopic process involving double fusion, that only one line is fused, with the depth of the other one attributable either to fixation disparity or to occlusion cues. This view is refuted in two ways. First it is shown that when the separation of the two lines, considered as a disparity, is within the range of 'patent stereopsis', depth is perceived with a precision and accuracy indistinguishable from regular stereopsis. The predictions of nonstereoscopic theories concerning the effects of fixation are not borne out at small disparities. Second, very compelling Panum versions of orientation and curvature disparity are introduced, which are difficult to account for except by a process of double fusion. Finally it is shown that at large disparities the depth in Panum's case deviates from prediction more frequently than does regular stereoscopic depth.

Convergence, Ocular↗
PubMed1995

Unintentional carbon monoxide poisoning in Colorado, 1986 through 1991.

Unintentional carbon monoxide poisonings were identified through death certificates, by hyperbaric chambers, and by laboratories required to report carboxyhemoglobin levels greater than 12%. From 1986 to 1991, 981 cases were reported, including 174 deaths. Deaths most often resulted from fire-related carbon monoxide intoxication (36.2%), followed by motor vehicle exhaust (34.5%), and furnaces (10.3%). Among nonfatal cases, furnaces were the leading source of carbon monoxide exposure (44.3%), followed by motor vehicle exhaust (22.8%). The importance of furnaces and other home heating devices in carbon monoxide intoxication may be underappreciated if only mortality data are examined. Surveillance of carbon monoxide-related morbidity is a useful adjunct to mortality surveillance in guiding prevention efforts.

Accidents↗
PubMed1995

Treatment of epilepsy.

Recently a number of new medications have become available for the treatment of epilepsy. In addition, advances in diagnostic facilities, particularly imaging, have improved dramatically in recent years. Patients with medically refractory epilepsy should be considered for the use of these drugs or for surgical therapy.

Adult↗
PubMed1994

The kinetics of facilitated diffusion followed by enzymatic conversion of the substrate.

The uptake of a substrate that is transported into the cell by facilitated diffusion and subsequently converted in a series of enzymatic reactions, measured as a function of the external concentration, does not usually show the rectangular hyperbolic function characteristic of Michaelis-Menten kinetics. Instead, a seemingly biphasic curve is observed, consisting of Michaelis-Menten kinetics at low concentrations and no further uptake at higher levels. By combining the equations for facilitated diffusion and an enzymatic reaction, we have derived an equation that describes the overall rate of uptake and metabolism of a substrate that is transported across the plasma membrane by facilitated diffusion. Modelling based on this equation simulated the kinetics found experimentally, as long as the kinetic parameters of the carrier were chosen to render it asymmetric. The overall rate was influenced by the kinetics of both reactions over a wide range of concentrations, confirming the principles of the 'Control Analysis' theory in an independent manner.

Biological Transport↗
PubMed1994

The limited (needle biopsy) autopsy and the acquired immunodeficiency syndrome.

It is often uncertain whether deaths that occur during active treatment for complications of AIDS result from diagnostic or therapeutic failure. Accurate diagnosis of infections is particularly important, and has relevance not only for the patient but also to partners, relatives, hospital staff and other patients. In the absence of adequate physical facilities and in view of the lack of success in obtaining formal autopsies in patients dying with AIDS, a limited autopsy protocol was devised for routine application at our hospital, beginning in 1989. The major aim of this protocol was to enable the safe collection of diagnostic material from patients who died despite active therapy, to ascertain unrecognized conditions and confirm existing diagnoses. We present findings from the first 16 limited autopsies which resulted in 12 additional diagnoses and a revision of the principal cause of death in 7 cases.

AIDS-Related Opportunistic Infections↗
PubMed1994

Neurilemoma. A case report.

In this article, a case report of a patient presenting with "burning pain in the ball of her right foot" is detailed. Topics discussed include the diagnosis, surgical excision, and histopathology.

Aged↗
PubMed1993

Assessment of blood lead levels in children living in a historic mining and smelting community.

Lead poisoning in childhood is an important public health problem, and thus, it is important to determine how children are exposed to lead. In 1987, the authors conducted an exposure assessment and blood lead screening for children aged 6-71 months living in Leadville, Colorado. High levels of lead had been found in the soil as a result of both past mining and smelting activities and natural mineralization. Blood was collected from each child for lead analysis, and behavioral characteristics were identified through an interview with a parent or guardian. Three sources of exposure to lead were associated with blood lead levels: lead in a core sample taken from the backyard of the family's home, lead brought home on the clothes of a miner, and lead from soldering in the home. Two pathways of exposure were associated with blood lead levels: the child swallowing things other than food, and taking food or a bottle outside to play. Multivariate regression using these variables found effect modification by age. For children aged 6-36 months, only sources of exposure were independent predictors of blood lead levels, while in children aged 37-71 months, a pathway of exposure in addition to sources of exposure independently predicted blood lead levels.

Child↗
PubMed1993

Correction processes in early reaching: reaches by infants to prismatically displaced targets.

A comparison was made between trajectories of reaches to visual targets by 6-months-old infants, with and without lateral prismatic displacement. In the No Prism condition, the major element of the movement veered towards the target, confirming the results of Mathew and Cook (1990). In the Prism condition, the prism did not affect hand position or movement direction at the beginning of the major element, but a lateral displacement was evident by the end of the element. This is taken as evidence that shifts in trajectory during the element were not due to visual guidance. It is suggested instead that these shifts may reflect correction based upon somatic feedback about position in relation to the visually specified goal of the movement. Evidence that the hand approached the virtual target supports the suggestion that any visual guidance was confined to the approach phase of the reach. Nevertheless, it appears that visual guidance was operating at this stage, since movement direction was displaced away from the virtual target and towards the real target.

Attention↗
PubMed1993

Mechanisms involved in the observational conditioning of fear.

Three experiments support the hypothesis that mechanisms involved in observational conditioning (OC) of fear are similar to those of direct classical conditioning and involve the organism attempting to detect the causal structure of its environment. Experiment 1, a correlational analysis, shows that model monkeys' fear behaviors on snake trials (unconditioned stimulus [US]) were highly correlated with observer monkeys' fear (unconditioned response) while watching the models' fear. In Experiment 2, all observers showed distress while watching the model's fear during Session 1 of OC, but only observers who could see the snake to which the model was reacting continued to show fear during subsequent OC sessions, suggesting that the model's fear is an easily habituable US. In Experiment 3, observers acquired significant fear of snakes after 1 OC session, indicating that the continued fear of those Experiment 2 observers that could see the snake may reflect their own acquired fear of snakes.

Animals↗
PubMed1993

Detection of DNA in ancient skeletal remains using DNA flow cytometry.

Cortical bone samples were removed from individual burials from Tomb Dk31 in the Dakhleh Oasis, Egypt. The tissue was disaggregated, stained with the DNA specific fluorescent dye DAPI and analyzed using the flow cytometer. DNA flow cytometry measures the cellular DNA content and this is correlated with modal chromosome content. When DNA is present in skeletal remains further investigations such as extracting, amplifying and sequencing may then be carried out. The method offers a relatively rapid and inexpensive means of pinpointing samples of skeletal DNA that can be further analyzed.

Adult↗
PubMed1992

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Educational Measurement↗