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Biomedical subjects

J D Miller

Publications and source records attributed to J D Miller.

At least 289 records · Page 16Linked to original sources
PubMed1987

Abnormal temporal lobe response in Alzheimer's disease during cognitive processing as measured by 11C-2-deoxy-D-glucose and PET.

Elderly controls and probable Alzheimer's disease patients underwent serial positron emission tomography (PET) studies during a baseline condition and while performing a verbal memory task. For the temporal lobes, all 7 Alzheimer patients demonstrated a relative shift in glucose metabolic rates to the right hemisphere during the memory condition relative to baseline, and 5 of 7 controls showed a shift to the left hemisphere. Baseline absolute regional metabolic rates replicate previous findings and were somewhat less useful than the memory challenge in differentiating patients from controls. These results indicate that a temporal lobe abnormality in Alzheimer's disease is related to memory performance.

Aged↗
PubMed1987

Supratentorial pressures. Part I: Differential intracranial pressures.

Dynamic supratentorial pressure changes may differentially alter tissue pressure and intraventricular fluid pressure. To evaluate these pressures, we used a floppy cuff intracerebral catheter and an intraventricular catheter in the cat and rhesus monkey. Baseline intraventricular pressures exceeded intracerebral pressure in both species. Intraventricular pressure was 3-4 mmHg in cats and 6-14 mmHg in monkeys, while the intracerebral pressure was in the range 0-4 mmHg in both. Saline injection into the spinal or cranial subarachnoid space resulted in a greater increase in ventricular fluid pressure, and the time for return to baseline was one and a half times longer in the intraventricular compartment. Jugular venous and abdominal compression resulted in a greater rise in the ventricular pressure than intracerebral pressure. Inflation of subdural balloons and intracerebral injection of silicone caused a differential pressure across the brain with the pressure being greatest in the ipsilateral hemisphere and lowest in the contralateral hemisphere. Rapidly evolving epidural masses produced varied results. We did not evaluate compensatory pressure changes in these animals. Those pressures that involve cerebrospinal fluid (CSF) dynamics alter intraventricular pressure more than tissue pressure. Alternatively, rapidly forming masses tend to increase tissue pressure near the mass more than intraventricular pressure.

Animals↗
PubMed1987

Supratentorial pressures. Part II: Intracerebral pulse waves.

Intracerebral pulse waves were recorded in cat and monkey while intracranial pressure (ICP) manipulations were performed. The intracerebral pulse waves appeared comparable to cerebrospinal fluid (CSF) pulsations. The wave forms were divided into multiple smaller waves, designated P1 to P4. The P1 component was primarily of arterial origin and was accentuated by increasing ICP unrelated to increased venous pressure, most commonly from a mass lesion. Bilateral carotid occlusion resulted in decreased amplitude of P1. Venous hypertension from jugular venous or sagittal sinus occlusion, on the other hand, accentuated waves P2 and P3 more than P1. This is consistent with a Starling resistor model of the cerebral venous system in which mass lesions may compress low-pressure veins and accentuate the arterial pressure-dependent P1 wave, whereas venous hypertension causes increased prominence of the later P2 and P3 waves.

Animals↗
PubMed1987

Use of connected discourse tracking to train functional speech skills.

The connected discourse tracking procedure was adopted for use as a production training task for profoundly hearing-impaired children. A clinician served as the receiver and 5 children with profound hearing losses each served as the sender for 16 tracking sessions. There were individual differences among the children in their ability to convey the connected discourse to the clinician over time. The increase in comprehension of each subject's speech during the last session relative to the amount of information understood during the first session ranged from 0 to 48%. Two independent observers were used during the first and last sessions to verify the tracking results obtained by the clinician (the primary receiver). There were differences in words tracked per minute among the three receivers with the primary clinician achieving higher tracking rates than the other two. The children learned how to use discourse strategies when they were not understood and they were highly motivated by the task. The results indicate that it is feasible to incorporate the procedure in a speech training program for hearing-impaired children.

Adolescent↗
PubMed1987

Etiology and clinical course of missed spine fractures.

A prospective study was designed to document course and outcome. Two hundred fifty-three patients with 274 spinal injuries were reviewed at the time of injury and discharge from hospital, as well as at 1, 2, and 5 years postinjury. Thirty-eight of these patients were identified who had been misdiagnosed at the initial assessment. Fracture location, cause of injury, neurologic deficit, and delay in diagnosis were all documented: 22.9% of cervical injuries, and 4.9% of the thoracolumbar injuries had a delayed diagnosis ranging from less than 1 day to 36 days. The causes of delayed diagnosis were: 1) failure to take X-rays, 2) fractures missed on X-ray, and 3) failure of patients to seek medical attention. Associated factors such as intoxication of the patient, multiple injuries, level of consciousness, or two levels of spinal injury contributed to the delayed diagnosis of these injuries. Certain "at-risk" populations for missed spinal injuries have been identified. In spite of delays in diagnosis, progression of an established neurologic deficit did not appear to occur in our study. However, the development of secondary deficits was significant in the delayed diagnosis group.

Accidents, Traffic↗
PubMed1987

The role of tactile aids in providing information about acoustic stimuli.

Devices that convert sound patterns into patterns of vibrotactile stimulation have been shown in laboratory and clinical studies to enable persons to appreciate many aspects of the acoustic environment, and thus are of potential benefit to deaf persons. In the present article, a framework is outlined for describing normal listening situations as a hierarchy of tasks requiring increasingly complex analysis of the acoustic waveform, including sound detection, environmental sound identification, syllable rhythm and stress categorization, phoneme and word identification, and comprehension of connected speech. The types of benefits provided by tactile aids in each of these tasks are exemplified using data from studies of single-channel commercially available devices and multichannel tactile vocoders in our own and other laboratories. The discussion of these data addresses such issues as the features of the acoustic environment that can or should be transmitted through a tactile aid, the differences in the information transmitted by commercially available versus experimental laboratory devices, the comparison of tactile aids and cochlear implants, and the technical problems that remain to be overcome in the design and evaluation of improved vibrotactile aids.

Acoustic Stimulation↗
PubMed1987

Rapid and pervasive occupation of fallen mangrove leaves by a marine zoosporic fungus.

Samples of leaves of red mangrove (Rhizophora mangle) were incubated on an agar medium selective for pythiaceous oomycetes. Leaves on trees above the water did not contain oomycetes. Marine oomycetes, principally Phytophthora vesicula, had colonized leaves within 2 h of leaf submergence, probably finding them by chemotaxis. The frequency of occurrence of P. vesicula in submerged leaves reached 100% within 30 h of submergence. By 43 h most, if not all, parts of leaves were occupied, and surface treatment with a biocide indicated that leaves were occupied internally. Frequencies of P. vesicula remained near 100% through about 2 weeks of submergence and then declined to about 60% in older (>/=4 weeks) leaves. Leaves of white mangrove (Laguncularia racemosa) were also extensively occupied by P. vesicula after falling into the water column, but decaying leaves of turtlegrass (Thalassia testudinum) were not colonized by oomycetes. Ergosterol analysis indicated that the standing crop of living, non-oomycete (ergosterol-containing) fungal mass in submerged red-mangrove leaves did not rise above that which had been present in senescent leaves on the tree; decaying turtlegrass leaves had an ergosterol content that was only about 2% of the maximum concentration detected for red-mangrove leaves. These results suggest that oomycetes are the predominant mycelial eucaryotic saprotrophs of mangrove leaves that fall into the water column and that for turtlegrass leaves which live, die, and decompose under submerged conditions, mycelial eucaryotes make no substantial contribution to decomposition.

Journal Article↗
PubMed1987

Changes in the cerebrospinal fluid pulse wave spectrum associated with raised intracranial pressure.

The frequency spectrum of the cerebrospinal fluid (CSF) pulse and the amplitude transfer function between arterial and CSF pressures were measured from the cisterna magna of anesthetized, artificially ventilated cats when the intracranial pressure (ICP) was raised by saline infusion. The spectrum of CSF pulsation was composed of a fundamental and three higher harmonic waves. The amplitude and the amplitude transfer function of each spectral component revealed significant positive correlation with ICP and negative correlation with cerebral perfusion pressure (CPP). Both the amplitude and the transfer function of the fundamental CSF pulse wave showed an exponential correlation with ICP and CPP. A distortion factor of the CSF pulse wave, a measure of its difference from a simple sine wave, was calculated from the spectral components. This showed that distortion of the CSF pulse wave was rapidly and progressively reduced as the ICP rose to 50 mm Hg and then was reduced less thereafter.

Animals↗
PubMed1987

Correction factors for gravimetric measurement of peritumoural oedema in man.

The water content of samples of normal and oedematous brain in lobectomy specimens from 16 patients with cerebral tumours has been measured by gravimetry and by wet and dry weighing. Uncorrected gravimetry underestimated the water content of oedematous peritumoural cortex by a mean of 1.17%, and of oedematous peritumoural white matter by a mean of 2.52%. Gravimetric correction equations calculated theoretically and from an animal model of serum infusion white matter oedema overestimate peritumoural white matter oedema in man, and empirical gravimetric error correction factors for oedematous peritumoural human white matter and cortex have therefore been derived. These enable gravimetry to be used to accurately determine peritumoural oedema in man.

Adult↗
PubMed1987

Experimental cerebral and plasma pharmacokinetic studies of TCNU: implications for brain tumour chemotherapy.

This study of the pharmacokinetics of TCNU, a new nitrosourea, in the rodent has shown that TCNU concentrations in the plasma (ng/ml) and brain (ng/g) are equivalent from 15 min to 4 hours after drug administration. The absolute levels of TCNU obtained with a dose of 100 mg TCNU/kg bodyweight were at most time points, three to four times those obtained with dosage of 25 mg TCNU/kg. The profile of rodent plasma TCNU levels following drug administration is similar to that recorded in humans, with peak TCNU concentrations occurring around 45 min. Since TCNU crosses an intact blood brain barrier (BBB), and clinical Phase I trials have shown it to possess potent antitumour properties. It may be a useful agent in the management of primary and secondary cerebral neoplasia.

Animals↗
PubMed1987

Horse riding and head injury: admissions to a regional head injury unit.

A retrospective survey has been carried out of 59 patients who suffered head injury related to horse riding out of 7172 cases of head and spinal injury admitted to a regional head injury unit in the 5-year period 1980-85. Most (85%) were female, against the usual 80% male predominance of head injury, 56 were minor injuries and 3 severe, of whom 2 died. Skull fracture was present in 10 patients (17%) of whom at least 5 had been wearing headgear at impact, and scalp trauma was noted in 22 (37%) with a predominance of occipital injuries. All the severely injured cases had an occipital skull fracture. One fifth of the patients suffered additional significant injuries. While most patients (90%) made a good recovery, 2 remained moderately and one severely disabled. Horse riding posed a significant risk of head injury to the population of riders, mainly young women. This survey suggests that the wearing of amateur riding headgear does not adequately protect the rider from scalp and skull injury, particularly in the occipital region.

Adolescent↗
PubMed1987

Motorcycling and head injury: admissions to a regional head injury unit.

In a 5-year period during which 7,178 patients with head injury were admitted to a regional head injury unit, 191 motorcyclists (2.7%) were admitted with head injuries of which 76% were classified as minor, 6% as moderate and 18% as severe (in coma). Two thirds of the patients were aged 20 years or less. Eighty-two riders (43%) had some form of facial or scalp trauma and 37 (19%) sustained skull fracture. Intracranial haematomas requiring surgical evacuation were detected in 3 of the minor head injuries (2%), 2 of the moderate injuries (17%) and 11 of the severely head injured patients (32%). Twenty-nine of the 34 severely injured patients were managed using artificial ventilation and intracranial pressure monitoring. The remaining patients died before these measures could be instituted. Overall mortality was 7%, but deaths were restricted to the severely head injured, among whom there were 13 fatalities. Head injuries associated with motorcycle riding include an unduly high proportion of severe cases and occur in a young population, often within a short time of starting to ride a motorcycle. Protective headgear was virtually always worn (94%); to reduce morbidity further, increased training and supervision during the first 6 months of motorcycle ownership should be emphasized.

Accidents, Traffic↗
PubMed1987

The response of suprachiasmatic neurons of the rat hypothalamus to photic and nicotinic stimuli.

Single neurons in the suprachiasmatic nucleus (SCN) and surrounding hypothalamic nuclei of the rat were characterized functionally and pharmacologically. Photically responsive neurons of the SCN typically exhibited a similar response to intravenous nicotine. The response to nicotine was antagonized by the nicotinic blocker, mecamylamine. Nicotinic blockade either eliminated or even reversed the sign of the photic response during subsequent photic stimulation. This constellation of results was not seen in neurons of adjacent hypothalamic regions.

Action Potentials↗
PubMed1987

Development and preliminary evaluation of an earmold sound-to-tactile aid for the hearing-impaired.

A binaural earmold sound-to-tactile aid was constructed by inserting a vibrating element into a Lucite earmold. The earmold could be vibrated at either 80 Hz (when incoming acoustic signals were below 2000 Hz), at 300 Hz (when incoming acoustic signals were above 2000 Hz), or both (when incoming acoustic signals were broadband). Subjects were fitted with one of these bimodal vibrating earmolds in each ear. Normal-hearing and hearing-impaired subjects were tested in three tasks: sound localization, environmental sound identification, and syllable rhythm and stress. The device provided some benefit to performance, although the amounts of improvement varied across tasks and subjects. Possible modifications in device design, and potential combinations of auditory and tactile input via earmold systems, are discussed.

Adult↗
PubMed1987

Qualities and locations of stimuli and responses affecting discrimination learning of chinchillas (Chinchilla laniger) and pigeons (Columba livia).

Chinchillas and pigeons were used as subjects in separate experiments to study interactions among stimulus and response characteristics in discrimination learning. Both the stimuli and the responses could differ with respect to their "quality" and their "location." Bright versus dim lights and upper versus lower lights served as the stimulus qualities and stimulus locations for the chinchillas, respectively. Red versus green lights and upper versus lower lights served as the stimulus qualities and stimulus locations for the pigeons, respectively. Respond versus no-respond and respond-left versus respond-right served as the response qualities and response locations, for both species, respectively. In both experiments, response-quality performance was superior when the discriminative stimuli differed in quality than when they differed in location, whereas response-location performance was superior when the discriminative stimuli differed in location than when they differed in quality. These results were interpreted within the framework provided by a general law of learning, that is, the "quality-location hypothesis."

Animals↗
PubMed1987

Sex hormone receptors in intracranial tumours and normal brain.

Fifty-four intracranial neoplasms (29 meningiomas, 16 gliomas, seven acoustic neuromas and two cerebral metastases) and nine specimens of normal brain were evaluated for specific progesterone and oestrogen receptor proteins using a dextran-coated charcoal assay and Scatchard plot analysis. Sixteen meningiomas (55%) were progesterone receptor (PgR) positive (median 52; mean 120; range 10-486 fmol mg-1 cytosol protein), whilst all were oestrogen receptor negative (ER-). Two (28%) of the acoustic neuromas contained small amounts of PgR protein, but all seven were ER-. None of the gliomas, cerebral metastases or specimens of normal brain contained ER or PgR protein. Analysis of PgR status and clinicopathological data suggest that there is no predictive correlation between PgR status and the patients age, sex, reproductive status, tumour histology or tumour behaviour. These results again suggest that in meningiomas PgR proteins are not modulated by oestrogens acting through ER. This finding may explain the failure of antioestrogen therapy to influence the growth of meningiomas. The significance of PgR protein in intracranial meningiomas is discussed with respect to tumour heterogeneity and implications for research with gene probes.

Adult↗