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Biomedical subjects

H Bergman

Publications and source records attributed to H Bergman.

At least 109 records · Page 6Linked to original sources
PubMed1992

Encoding of sound-source location and movement: activity of single neurons and interactions between adjacent neurons in the monkey auditory cortex.

1. Neuronal mechanisms for decoding sound azimuth and angular movement were studied by recordings of several single units in parallel in the core areas of the auditory cortex of the macaque monkey. The activity of 180 units was recorded during the presentation of moving and static sound stimuli. Both the activity of single units and the interactions between neighboring neurons in response to each stimulus were analyzed. 2. Sixty-two percent of the units showed significant modulation of their firing rates as a function of the stimulus azimuth. Contralateral stimuli were preferred by the majority (approximately 60%) of these neurons. Thirty-five percent of the units showed mild but statistically significant modulation of their firing rates, which was specifically attributed to the angular movement of the sound source. 3. Eighty-nine percent of the "movement-sensitive" units were also "azimuth sensitive." The sound source's azimuth determined the pattern of the response components (on, sustained, off), whereas the source's movement affected only the magnitude of these components, typically the sustained component. Most neurons for which the sustained response to static sounds was greater for contralateral than ipsilateral stimuli preferred moving sounds that were moving into the contralateral hemifield. 4. Cross-correlation analysis was carried out for 245 neuron pairs. Cross-correlograms were computed for each pair under all stimulus conditions to allow comparison of the neuronal interactions under the various conditions. The shapes of some correlograms (after subtraction of direct stimulus effects) were dependent on specific stimulus conditions, suggesting that the effective connectivity between these neurons depended on the location and/or movement of the sound stimuli. Furthermore, joint peristimulus time (JPST) analysis indicated that modifications of connectivity may be temporally related to the stimulus and may occur over short periods of time. These results could not have been predicted from analysis of the independent single-unit responses to the stimuli. 5. The data suggest that both firing rates and correlated activity between adjacent neurons in the auditory cortex encode sound location and movement.

Acoustic Stimulation↗
PubMed1991

Medical home care services for the housebound elderly.

In our health jurisdiction the proportion of elderly people is more than double the national average, and there is a severe shortage of both home care services and long-term care beds. To help the many elderly housebound people without primary medical care we initiated a medical services home care program. The goals were patient identification, clinical assessment, medical and social stabilization, matching of the housebound patient with a nearby family physician willing and able to provide home care and provision of a backup service to the physician for consultation and help in arranging admission to hospital if necessary. In the program's first 2 years 105 patients were enrolled; the average age was 78.9 years. More than 50% were widowed, single, separated or divorced, over 25% lived alone, and more than 40% had no children living in the city. In almost one-third of the cases there had never been a primary care physician, and in another third the physician refused to do home visits. Before becoming housebound 15% had been seeing only specialists. Each patient had an average of 3.2 active medical problems and was functionally quite dependent. Thirty-five of the patients were surveyed after 1 year: 24 (69%) were still at home, and only 1 (3%) was in a long-term care institution; 83% were satisfied with the care provided, and 79% felt secure that their health needs were being met. One-third of the patients or their families said that it was not easy to reach the physician when necessary. We recommend that programs similar to ours be set up in health jurisdictions with a high proportion of elderly people. To recruit and retain cooperative physicians hospital geriatric services must be willing to provide educational, consultative and administrative support.

Aged↗
PubMed1991

Appropriateness of patient transfer from a nursing home to an acute-care hospital: a study of emergency room visits and hospital admissions.

OBJECTIVE: To determine the appropriateness of transfers to acute care hospitals from a nursing home. DESIGN: Nursing home and hospital records of all the nursing home residents during the 3-year study period were reviewed retrospectively to determine: number and type of transfers; problems identified in the nursing home justifying the transfers; diagnoses made at the hospitals; length of hospital stays; outcome of hospital visits. SETTING: An 80-bed public nursing home. SUBJECTS: 112 residents in the nursing home over the 3-year study period. MAIN OUTCOME MEASURES: Based on the decision of the hospital physician, those transfers resulting in hospital admissions were considered appropriate. As well, transfers to the emergency room with return to the nursing home without hospital admission were also judged to be appropriate if the problems required diagnostic and therapeutic procedures not available in the nursing home. RESULTS: During the 3-year study period, 55 residents (49%) were transferred a total of 102 times. An average of 26% of patients were transferred each year. Direct admissions to acute hospitals accounted for 17% of the transfers, transfers to the emergency room with subsequent admission for 34%, and transfers to the emergency room with subsequent return to the nursing home without admission for 45%. Four percent of patients transferred died in the emergency room. On the basis of the outcome measure, 7% of all transfers could have been diagnosed and treated in the nursing home and were considered inappropriate. CONCLUSIONS: The majority of transfers from this nursing home to acute-care hospitals were appropriate.

Aged↗
PubMed1991

Neural interactions in the frontal cortex of a behaving monkey: signs of dependence on stimulus context and behavioral state.

In order to gain an understanding of the processes taking place within and between neuronal assemblies, we made simultaneous recordings of spike trains from groups of up to 11 neurons in the frontal cortex of a rhesus monkey, that was trained to perform a sensorimotor behavioral task. We report here on preliminary results from correlation analysis of these neuronal activities, with special emphasis on signs of behaviorally induced modifications of neural interaction, possibly due to rapid modulations of discharge synchronization among the neurons. Our findings suggest that different functional groups of neurons may co-exist within each small volume of cortex, and that neurons may be dynamically recruited into such a group to fulfil a specific function.

Animals↗
PubMed1990

Reversal of experimental parkinsonism by lesions of the subthalamic nucleus.

Although it is known that Parkinson's disease results from a loss of dopaminergic neurons in the substantia nigra, the resulting alterations in activity in the basal ganglia responsible for parkinsonian motor deficits are still poorly characterized. Recently, increased activity in the subthalamic nucleus has been implicated in the motor abnormalities. To test this hypothesis, the effects of lesions of the subthalamic nucleus were evaluated in monkeys rendered parkinsonian by treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The lesions reduced all of the major motor disturbances in the contralateral limbs, including akinesia, rigidity, and tremor. This result supports the postulated role of excessive activity in the subthalamic nucleus in Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1990

Tetrahydroaminoacridine-lecithin combination treatment in patients with intermediate-stage Alzheimer's disease. Results of a Canadian double-blind, crossover, multicenter study.

We studied the efficacy and safety of oral tetrahydroaminoacridine (THA) combined with lecithin in 52 patients with Alzheimer's disease. The maximal tolerated dose of THA (up to 100 mg per day) was determined during an eight-week titration period, after which the tolerated dose of THA or placebo was given during two sequential randomized periods of treatment lasting eight weeks each. Highly purified lecithin (4.7 g per day) was administered during all phases of the study. Efficacy was expressed in terms of scores on the Mini-Mental State (MMS) test, the modified MMS test, the Hierarchic Dementia Scale, the Rapid Disability Rating Scale-II, and the behavioral scale of Reisberg et al. Safety was assessed by careful clinical monitoring as well as serial measurements of liver aminotransferases. Forty-six patients completed the titration period, and 39 completed the double-blind period, during which only the MMS score showed a small but significant increase (P less than 0.05) after four weeks of treatment with THA. Autonomic side effects of THA were common but mild. Reversible elevations of serum aspartate and alanine aminotransferase levels to three or more times the upper limit of normal occurred in 17 percent of patients; most of the patients affected were women. A liver biopsy performed in one patient showed resolving focal liver-cell necrosis. These studies fail to demonstrate a significant clinical benefit of THA given orally in a maximal dose of 100 mg per day over a period of eight weeks in combination with lecithin.

Administration, Oral↗
PubMed1990

Intraocular hypothalamic transplants containing histaminergic neurons: innervation of host iris and hippocampal cografts.

Hypothalamic tissue containing the tuberomammillary nucleus was dissected from fetuses of Embryonic Day 17 and inserted into the anterior chamber of the eye of young adult recipient rats. The growth of hypothalamic grafts was monitored through the translucent cornea and transplants were found to double in size over the 8 first weeks in oculo. After 4 weeks fetal hippocampal formation (Embryonic Day 18) was inserted into the eye chamber in half of the previously grafted animals and placed in contact with the first grafts. Double grafts were allowed to mature for up to 18 weeks before sacrifice. Recipient rats were anesthetized and superfused with carbodiimide and paraformaldehyde, after which transplants were removed, frozen, sectioned on a cryostat, and incubated with histamine antibodies. Immunohistochemical evaluations revealed a large number of histamine-positive nerve cell bodies with processes innervating the entire hypothalamic graft with a dense plexus of varicose fibers. Such histamine-positive fibers were also seen to invade the surrounding host iris in some cases with thick axon bundles as well as with single fibers. When hypothalamic transplants were combined with hippocampal grafts numerous histamine-immunoreactive fibers invaded the hippocampal tissue to form a plexus of varicose terminals throughout the cografts. After 4 weeks in oculo only a sparse histamine-positive innervation of hippocampal grafts was found, while 18-week-old double grafts contained a considerably larger amount of immunoreactive neurites.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Predictors and consequences of aggressive behavior by community-based dementia patients.

The frequency, nature, context, and caregivers' reactions to aggressive behavior in 213 dementia patients residing in the community was studied. Aggression was reported in 57.2% of the patients and in 10.6% of the caregivers. Predictors of patient aggression were greater frequency of behavior and memory problems, premorbid aggression, and a more troubled premorbid social relationship between patient and caregiver. Patient aggression predicted the decision to discontinue home care.

Aged↗
PubMed1989

Urea excretion as a strategy for survival in a fish living in a very alkaline environment.

Ammonia is toxic to all vertebrates. It can be converted to the less toxic urea, but this is a metabolically expensive process found only in terrestrial vertebrates that cannot readily excrete ammonia and marine fish that use urea as an osmotic filler. Freshwater fish mostly excrete ammonia with only a small quantity of urea. It seems the ornithine cycle for urea production has been suppressed in all freshwater teleosts except for some airbreathers which, when exposed to air, increase urea synthesis via the cycle. Here we show that the tilapia fish Oreochromis alcalicus grahami, the only fish living in Lake Magadi, an alkaline soda lake (pH = 9.6-10) in the Kenyan Rift Valley, excretes exclusively urea and has ornithine-urea cycle enzymes in its liver. A closely related species that lives in water at pH 7.1 lacks these enzymes and excretes mainly ammonia with small amounts of urea produced via uricolysis. It dies within 60 min when placed in water from Lake Magadi. We suggest that urea production via the ornithine-urea cycle permits O. a. grahami to survive the very alkaline conditions in Lake Magadi.

Acclimatization↗
PubMed1989

Ascertainment of informative Alzheimer disease families from the IMAGE Project registry for genetic linkage analysis studies.

Genetic linkage analysis requires the identification and documentation of large families with many affected members present, preferably in more than one generation. The IMAGE Project has been establishing a population-based Alzheimer disease (AD) registry in the Saguenay - Lac-Saint-Jean region of the Province of Quebec. The population of this region has a well-documented ancestry, with reliable genealogical records (since 1842) computerized by SOREP. We have recently begun to investigate the pedigrees of selected probands (definite, probable and possible) from the IMAGE registry in order to identify informative pedigrees for genetic linkage analysis. Interviews were carried out with close relatives of the probands (at least one informant per sibship) to identify secondary AD cases. The questionnaires used pertain to the accuracy of genealogical records, to family medical history and to a retrospective diagnosis of AD for people with cognitive deficits. By these means, we have documented a large extended pedigree in which a total of 15 individuals with cognitive deficits were ascertained over three generations. Of these cases, 7 are still living and there is autopsy confirmation in another one. Computer simulations using the program SIMLINK revealed that this is a potentially informative family for linkage analysis. Horizontal extension of the pedigree to second cousins of the proband is now being carried out. This will render the family IMAGE/1 even more informative in genetic linkage analysis studies.

Alzheimer Disease↗
PubMed1989

Progress report on the Canadian Multicentre Trial of tetrahydroaminoacridine with lecithin in Alzheimer's disease.

Since the discovery of a significant depletion of acetylcholine in discrete areas of the brain of patients affected by Alzheimer's disease, attempts at symptomatic therapy have concentrated on acetylcholine supplementation, an approach that is based upon the efficacy of dopaminergic supplementation therapy for Parkinson's disease. Choline, then lecithin, used orally, failed to improve symptoms but the hypothesis that long-term choline supplementation might stabilize the course of Alzheimer's disease remains to be tested. Nerve growth factor may also offer that possibility. Bethanechol administered intracerebroventricularly did not help when a fixed dose was used but individual titration of more selective muscarinic agonists may prove more effective. In this article we report that tetrahydroaminoacridine (THA), given together with highly concentrated lecithin, appears to bring improvement in cognition and in functional autonomy using the Mini Mental State and the Rapid Disability Rating Scale-2 respectively, without change in behavior as reflected by the Behave-AD. Double-blind cross-over studies are in progress to establish its efficacy. Improvement in study design and means of assessment of cognition, functional autonomy and behavior have been made possible by these drug trials.

Aged↗
PubMed1989

Neuronal activities related to higher brain functions--theoretical and experimental implications.

The activities of several single units (6-10) were recorded simultaneously in the auditory cortex and in frontal cortical areas of cats and monkeys. The response properties of the single units and the interaction between them were studied. It is shown that single units in both areas may participate in prolonged processes and be involved in more than one process. Adjacent neurons need not function in unison; while some neurons are activated, others may stay inactive. The interactions among adjacent neurons are weak, and can be modulated by sensory stimulation, and by arousal and behavioral states. These properties lead us to hypothesize that information is represented in the cortex by coactivation of sets of neurons rather than by independent modulation of the single-unit firing rate. A single unit may be a member of several representing sets. Thus, each neuron may participate in more than one function and each small cortical area may contain members of several functional sets. A mechanism for computing and transmitting information, based on converging-diverging links, between neuronal sets is described and tested by simulations and analysis of experimental data.

Animals↗
PubMed1989

Dependence on sedative-hypnotics: neuropsychological impairment, field dependence and clinical course in a 5-year follow-up study.

Despite some neuropsychological improvement in a group of 30 patients who had been hospitalized for primary abuse of sedatives or hypnotics 4-6 years earlier, the prevalence of intellectual impairment was still increased and about as high as before. As in alcoholic patients CAT scan of the brain showed an increased prevalence of dilatation of the ventricular system, but unlike alcoholics not of widened cortical sulci. Field dependence and visuo-spatial skills during treatment predicted abuse status at follow-up. Patients with improved drug habits had less pronounced withdrawal symptoms during treatment and a better social situation at follow-up than patients without improvement of drug habits. The results suggest that despite some neuropsychological improvement cerebral disorder diagnosed in patients abusing sedatives or hypnotics is often permanent through the years and that neuropsychological status is linked to long-term prognosis.

Adult↗
PubMed1989

Influence of improved drinking habits on brain atrophy and cognitive performance in alcoholic patients: a 5-year follow-up study.

In the period 1977-1979, a sample of consecutively admitted alcoholic in-patients was studied with CT scan of the brain and neuropsychological tests. A subsample of 52 patients met the following criteria: age less than 46 years, no history of severe head injury or focal signs of traumatic brain damage, and no history of liver disease, drug abuse, or long-lasting anticonvulsant therapy. However, 72% of the patients showed brain atrophy and 49% intellectual impairment as compared to 16% and 13%, respectively, in an age-matched sample of men from the general population. Five years later, after excluding patients with head trauma, serious alcoholic liver disease and drug abuse, 37 patients were reinvestigated. Sixteen patients were abstinent or had greatly improved drinking habits during the 5-year follow-up period and 21 were still drinking. Alcohol abstinence was found to be associated with a regress of cortical atrophy and central atrophy as assessed by the width of the 3rd ventricle. However, the recovery was not complete as compared with the prevalence of atrophy in the sample from the general population. Among the patients a significant improvement in one cognitive test and a trend to improvement in some other tests associated with improved drinking habits was observed. Regression of central atrophy as assessed by a decreased diameter of the 3rd ventricle was associated with improvement in the very same cognitive tests. The results suggest that both atrophy of the brain and cognitive ability can improve in alcoholics who give up drinking.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

A CASE-SAR study of mammalian hepatic azoreduction.

A group of 36 aryl azo dyes were examined for their ability to be reduced by rat liver microsomal azoreductase. This group of azo dyes featured a variety of substituents, including sulfonic acid, phenol, nitro, amide, and methyl functionalities on phenyl, alpha-naphthyl, and beta-naphthyl rings. Reduction rates for each dye were obtained using a spectrophotometric method and anaerobic incubation conditions. These rates ranged from 0 to 7.35 nmol dye reduced/min.mg protein. The reduction rates and dye structures provided the data for a CASE-SAR (computer automated structure evaluation-structure-activity relationship) fragment analysis, and three major structure fragments associated with the ability of this group of azo dyes to be reduced were identified. The three CASE fragments correctly label 92% of the azo dye structures as active or inactive and may be useful in future predictions of the ability of azo dyes to undergo reduction by rat liver azoreductase.

Animals↗