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Biomedical subjects

J M Davis

Publications and source records attributed to J M Davis.

At least 469 records · Page 26Linked to original sources
PubMed1986

Experimental lesions in rats corresponding to advanced human asbestosis.

Rats inhaling chrysotile asbestos developed a progressive interstitial fibrosis similar in most respects to human asbestosis. The earliest lesions were focal deposits of fibrous tissue in the walls of respiratory bronchioles and alveolar ducts. Later alveolar septa between adjacent bronchioles became progressively thickened to produce lesions with similarities to human honeycombing. The thickened septa between alveoli or "micro-honeycomb" spaces were mainly surfaced with cuboidal epithelial cells although some spaces lined by ciliated columnar epithelium were also found. Transmission electron microscopy of these advanced lesions showed that the cuboidal epithelial cells retained most of the characteristics of type 2 pneumocytes but that they frequently exhibited apical cytoplasmic blebs normally associated with the apocrine secretion of Clara cells. Columnar cells exhibited all stages from fully cilitated to cells with only an occasional cilium among the normal cell surface microvilli. Alveolar or micro-honeycomb spaces frequently contained clusters of pulmonary macrophages with their surface processes interdigitated but with no signs of fusion to giant cells. At more than 18 months after the end of dust inhalation these macrophages contained no chrysotile asbestos. The basement membranes beneath the epithelial layers of thickened septa were irregular and often convoluted as well as being much thicker than normal. Microscopic deposits of calcification were frequently found within the basement membrane material. Some thickened septa were relatively acellular, consisting mainly of masses of collagen fibrils but others were cellular and contained many macrophages, fibroblasts, plasma cells and mast cells. In these advanced lesions extremely little chrysotile asbestos was found and this was present in two sites only. Some chrysotile, always as individual fibrils and usually of short length, was present among collagen fibrils in areas of fibrosis and some was present within the thickened basement membranes.

Animals↗
PubMed1986

A primate model for the study of hallucinogens.

An animal model for studying the actions of hallucinogenic drugs using primate social colonies is presented. Although hallucinogens induce a number of behavioral changes in this paradigm, one emergent behavior, limb jerks, appears to be selectively induced by three classes of hallucinogens in doses which correlate with those reported to be hallucinogenic in humans. Several non-hallucinogenic congeners of hallucinogens failed to significantly elicit this response. Other behavioral changes induced by hallucinogens in monkeys such as ptosis and social withdrawal may be useful in studying aspects of hallucinogen intoxication other than hallucinations, or psychosis in general. Upon daily administration, tolerance developed to all hallucinogens tested except two, as is seen in humans. Moreover, cross-tolerance between hallucinogens could be demonstrated. Further experiments with the hallucinogen 5-methoxy N,N-dimethyltryptamine revealed that although certain individual behaviors could be antagonized by serotonin antagonists, dopamine antagonists, and physostigmine, no drug completely reversed the behavioral abnormalities induced by this hallucinogen. It is suggested that this paradigm, which offers an hallucinogen-induced behavior which correlates well with the human hallucinogen response and permits observation of a wide variety of other potentially relevant behaviors in primates, may be useful in developing and testing theories of hallucinogenic drug action. It may be especially valuable in view of the present difficulties of conducting hallucinogen research in humans.

Animals↗
PubMed1986

Path analysis of psychopharmacological data: catecholamine breakdown in man.

This article applies path analysis to the problem of characterizing metabolic alterations in catecholamine systems when only static or single measures of precursor and products are available. In this article, simulated data from kinetic models of norepinephrine metabolism were examined using path analysis. The method of path analysis, which is based on correlations between compartments and not actual flow, correctly identified operative and nonoperative metabolic pathways in simulated models. In addition, actual data from normal subjects as to the 24-hour urinary values for norepinephrine, normetanephrine, vanillylmandelic acid, and 3-methoxy-4-hydroxyphenylglycol were analyzed using path analysis. It was found that metabolic routes that are known to be incomplete did not fit these data, whereas the known metabolic pathways for norepinephrine were correctly identified using path analysis. These results suggest that path analysis may provide a useful tool in identifying normal and abnormal catecholamine metabolic pathways in experimental situations where only single values of precursor and products are available.

Humans↗
PubMed1986

Effects of the inhalation of dusts from calcium silicate insulation materials in laboratory rats.

The effects of respirable dust from three commercially produced calcium silicate insulation materials were examined in laboratory rats by long-term inhalation and injection techniques. These calcium silicate products have been used as replacements for asbestos in the insulation of the engine rooms of ships, and the particle size distribution of the dust clouds generated for the experimental study closely matched those found in ships during the installation of this type of material. One year of exposure to a dust cloud of 10 mg/m3 of respirable dust had no discernible effect on the length of survival of treated animals compared to controls. No pulmonary lesions were found that appeared associated with the inhalation of calcium silicate per se, but one sample did contain significant amounts of quartz and this did produce a few small pulmonary nodules. While two small pulmonary neoplasms, one malignant and one benign, were found in dusted animals, neither was the cause of death, and the incidence was not significantly different from the control group where no tumors were found. One peritoneal mesothelioma was found in an animal from one of the inhalation groups, but this was considered to be a spontaneous tumor as none of over 100 animals injected intraperitoneally with 25 mg of calcium silicate developed these tumors. While the white blood cell count of dusted animals, compared to controls, was significantly raised in all treated groups at the end of the dusting period, these figures were within the published normal ranges for laboratory rats. It was concluded that the three tested calcium silicate products were harmless to the rats of this species at the doses tested.

Animals↗
PubMed1986

Effects of mild and moderate hearing impairments on language, educational, and psychosocial behavior of children.

An extensive psychoeducational evaluation was administered to 40 hearing-impaired children to investigate the effects of degree of hearing impairment, age, and other factors on intellectual, social, academic, and language behavior. Although children varied greatly in performance, hearing loss of any degree appeared to affect psychoeducational development adversely, leading to the conclusion that even minimal hearing loss places children at risk for language and learning problems.

Adolescent↗
PubMed1986

Endogenous lectins from cultured cells: subcellular localization of carbohydrate-binding protein 35 in 3T3 fibroblasts.

In previous studies, a lectin designated as carbohydrate-binding protein 35 (CBP35) has been isolated from cultured 3T3 fibroblasts. In the present study, rabbit antibodies directed against CBP35 were used to analyze the subcellular distribution of CBP35 in 3T3 cells. Several lines of evidence indicate that CBP35 is found externally exposed at the cell surface: immunofluorescent staining of live 3T3 cells; agglutination of suspension of 3T3 fibroblasts by specific antibodies; and isolation, by immunoaffinity chromatography, of a Mr 35,000 component from cells surface-labeled with 125I. In addition to the plasma membrane, CBP35 could also be found intracellularly, as revealed by immunofluorescence studies of fixed and permeabilized 3T3 cells. The staining pattern showed the presence of CBP35 on the nucleus and in the cytoplasm. These results are consistent with the finding that among several subcellular fractions, CBP35 can be found by immunoblotting procedures in the nuclear pellet, the soluble fraction, and the plasma membrane fraction of the postnuclear supernatant.

Cell Line↗
PubMed1986

In vitro assays for detecting carcinogenic mineral fibres: a comparison of two assays and the role of fibre size.

The activities of 13 carcinogenic fibrous dust samples were compared in two in vitro test systems using V79/4 and A549 cells. Eleven of the dusts had similar ranks in both assays but two samples had disparate results. The relationship between the fibre length and diameter distributions of 12 of the samples and their activity in each assay was examined. A significant association between fibre length and biological activity occurred in both assays. This relationship showed increasing strength of association with increasing fibre length. The only significant association between fibre diameter and activity in vitro was demonstrated with fibres greater than 0.2 micron in the A549 assay.

Carcinogens↗
PubMed1986

Consistent evidence for a biological subtype of depression characterized by low CSF monoamine levels.

Analysis of previously published CSF monoamine data has revealed statistical evidence for a biological subtype of depression, characterized by abnormally low CSF-5HIAA and CSF HVA. Using maximum likelihood gaussian mixture analysis we were able to resolve the empirical frequency distributions of both CSF HVA and CSF 5-HIAA into two component normal mixtures. Simultaneous analysis of both CSF 5-HIAA and CSF HVA revealed a two component bivariate normal mixture distribution in which 35% of the depressed patient sample were classified in the low subgroup. No evidence for mixture distributions was found in controls. Analysis of CSF MHPG revealed a single component normal distribution with virtually identical mean and variance in both patients and controls. These results are shown to be virtually identical to parallel analyses conducted on CSF monoamine data collected as part of the NIMH collaborative study on the psychobiology of depression study.

Depressive Disorder↗
PubMed1986

Apnoea and seizures.

We report two infants with near miss sudden infant death syndrome events exhibiting seizure disorders after caffeine treatment, suggesting there is an infant subgroup diagnosed as near miss sudden infant death syndrome who have apnoea possibly with seizures whose seizure threshold may be lowered by central nervous system stimulants like caffeine.

Apnea↗
PubMed1986

Urinary 3-methoxy-4-hydroxyphenylglycol in affective and schizophrenic patients. Behavior and symptom correlates.

The relations between urinary 3-methoxy-4-hydroxyphenylglycol, (MHPG) excretion, ward behavior in two environments (dayroom and gym), and symptomatology were examined in 58 psychiatric inpatients. In the total patient sample, idiosyncratic behaviors and body activity correlated positively with MHPG levels. Among depressed patients MHPG correlated negatively with eating lunch in the dayroom and positively with self-reported appetite loss, suggesting that appetite disturbance in major depression may be due to high norepinephrine turnover. The results support the utility of naturalistic observation instruments in exploring the relations between psychopathology and biological substrates.

Adolescent↗
PubMed1986

Sodium chloride, water and urea handling in the rat renal medulla: a computer simulation.

A dynamic rat renal medullary model was employed to study how independent control of excretion of various substances is achieved. Salt and water reabsorptive coupling was heterogeneous in the distal nephron. Diversion of filtrate to juxtamedullary nephrons retained salt with little effect on water or urea, a response enhanced by concomitant reduction in inner medullary blood flow. Urine concentration required high permeability and low flow in medullary blood vessels and active inner medullary salt transport. Collecting duct urea movement was closely coupled to that of water and urea recycling was enhanced by incorporation of nephrovascular bundles.

Animals↗
PubMed1986

Inductive plethysmography--a facilitated postural calibration technique for rapid and accurate tidal volume determination in low birth weight premature newborns.

Inductive plethysmography is a noninvasive method of measuring lung volumes in infants. This technique, however, has had very limited use in premature newborns because of the difficulty of calibrating the device with regard to the small tidal volumes (VT) in such infants. The present study describes a facilitated calibration of the inductive plethysmograph in low birth weight infants. The technique depends on generating significantly different compartmentalization of VT into rib cage and abdominal components by changing the infant's position from supine to upright. Linear regression analyses were performed to compare VT measurements made in 9 premature infants with the inductive plethysmograph and the pneumotachygraph; an overall Z-transformed correlation of 501 breath-to-breath comparisons yielded an r value of 0.80; the mean VT (pneumotachygraph) was 13.9 +/- 4.7 ml SD; the mean VT (inductive plethysmograph) was 14.3 +/- 5.1 ml SD. It is concluded that inductive plethysmography is an accurate method to measure VT in small premature infants. Moreover, the ease of the two-position technique for calibration of the device gives the inductive plethysmograph greater utility as a clinical and research tool for measuring lung volumes in premature infants.

Calibration↗
PubMed1986

Failure of urinary MHPG levels to predict treatment response in patients with unipolar depression.

The authors studied 64 depressed patients who were receiving a vanillylmandelic acid (VMA)-free diet and underwent a washout period (mean, 24 days) before treatment. During the washout period, a mean of 2.5 multiple 24-hour urinary 3-methoxy-4-hydroxyphenylglycol (MHPG) samples per patient were collected. Thirty-four patients were then treated with a "noradrenergic" antidepressant only (e.g., imipramine), and seven were treated with a "serotonergic" antidepressant only (e.g., amitriptyline). Twelve patients received combined drug treatment and 11 others spontaneously remitted. Response to treatment was rated on a clinical global evaluation scale from 1 (little or no response) to 7 (maximum response). No relationship was found between response to treatment, type of treatment, and the average pretreatment 24-hour urinary MHPG level. The authors thus failed to confirm the hypothesis that a low MHPG level predicts response to antidepressant treatment.

Adult↗
PubMed1986

Reconceptualizing assumptions about community mental health.

Beliefs that patients fall between the cracks in the transition from hospital to community services, that the aftercare population is shut out of community mental health agencies, and that services are duplicated to a high degree continue to be widely accepted. Using data from a study of a publicly funded mental health aftercare system in a major urban county, the authors reconceptualize these and similar assumptions about mental health aftercare. It appears that the primary focus of concern should be on the nature and quantity of the services being delivered rather than on increasing the proportion of patients connecting with them. Current services appear to be largely oriented toward helping the patient maintain a borderline existence in the community. Instead, much more emphasis is needed on meaningfully rehabilitating patients and reducing their chronic need for professional support.

Attitude↗
PubMed1986

The effects of alcohol abuse among the new chronically mentally ill.

In recent years, there has been a growing recognition of the high incidence of alcohol abuse among the new generation of chronically mentally ill. This article reports on a study that tracked a subgroup of the chronically mentally ill, those discharged from state psychiatric hospitals, through an entire community mental health aftercare system and its major auxiliary human service agencies. Those who were assessed by hospital discharge social workers as having a need for alcoholism services were found to be less likely to be referred for aftercare and to make contact with aftercare agencies post discharge; and for those with an alcoholism problem who do make contact, they generally received less service than those who did not have a need for alcoholism services. The professionals in both the mental health and alcoholism fields need to work together to better meet the needs of the chronically mentally ill with an alcohol problem.

Adult↗