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M A Jackson

Publications and source records attributed to M A Jackson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Two circadian rhythms in the human electroencephalogram during wakefulness.

The influence of the circadian pacemaker and of the duration of time awake on the electroencephalogram (EEG) was investigated in 19 humans during approximately 40 h of sustained wakefulness. Two circadian rhythms in spectral power density were educed. The first rhythm was centered in the theta band (4.25-8.0 Hz) and exhibited a minimum approximately 1 h after the onset of melatonin secretion. The second rhythm was centered in the high-frequency alpha band (10.25-13.0 Hz) and exhibited a minimum close to the body temperature minimum. The latter rhythm showed a close temporal association with the rhythms in subjective alertness, plasma melatonin, and body temperature. In addition, increasing time awake was associated with an increase of power density in the 0.25- to 9.0-Hz and 13.25- to 20. 0-Hz ranges. It is concluded that the waking EEG undergoes changes that can be attributed to circadian and homeostatic (i.e., sleep-wake dependent) processes. The distinct circadian variations of EEG activity in the theta band and in the high-frequency alpha band may represent electrophysiological correlates of different aspects of the circadian rhythm in arousal.

Adult↗
PubMed1999

Occult hypoglycemia caused by hemodialysis.

BACKGROUND: Previous studies have ignored hypoglycemia in patients undergoing hemodialysis. The fall in plasma glucose may not have been considered to be clinically relevant because the patients were asymptomatic. The present study was designed to assess the effect of hemodialysis on plasma glucose, insulin, glucagon, cortisol and catecholamines in non diabetic patients. METHODS: 21 non diabetic patients with chronic renal failure were hemodialyzed using a glucose-free dialysis fluid. They did not take any medication prior to dialysis and were asked not to eat during the first hour on hemodialysis. Blood and dialysate fluid was sampled at regular intervals during the first hour of dialysis for analysis. RESULTS: Plasma glucose fell below 4.0 mmol/l (72 mg/dl) in 9 of the 21 patients, below 3.5 mmol/l (63 mg/dl) in 6 and below 3.0 mmol/l (54 mg/dl) in 3. The lowest recorded value was 2.1 mmol/l (38 mg/dl). The mode glucose loss in the waste dialysate fluid was 6 g/h. In the group of 9 patients whose plasma glucose fell below 4.0 mmol/l (72 mg/dl), no symptoms of hypoglycemia were shown but 4 of the 7 patients who felt very hungry and ate were in this group. When 7 patients from this group were subsequently dialysed with a dialysis fluid containing 5.5 mmol/l (100 mg/dl) glucose, their plasma glucose became stabilized within the fasting reference range. There were no significant hormonal changes during the dialysis or between euglycemic and hypoglycemic patients. CONCLUSIONS: Patients undergoing hemodialysis may become hypoglycemic and not be aware of it. There is no hormonal imbalance causing the hypoglycemia and the hormonal response to the hypoglycemia is blunted. Patients with an initial plasma glucose of 4.5 mmol/l (81 mg/dl) or less who are hemodialyzed and who do not eat during dialysis may be particularly at risk. They should be dialysed with a dialysis fluid containing at least 5.5 mmol/l (100 mg/dl) glucose.

Blood Glucose↗
PubMed1999

Short-term tests for defining mutagenic carcinogens.

The results of short-term tests for mutagenicity were first included in the IARC Monographs in the mid-1970s on the basis of the observation that most carcinogens are also mutagens, although not all mutagens are carcinogens. The experimental evidence at that time showed a strong correlation between mutagenicity and carcinogenicity and indicated that the short-term tests were useful for predicting carcinogenicity. Although the correlations have become weaker over the past 20 years, and with them the predictive value of short-term tests, such tests still provide vital information for identifying and understanding mechanisms involved in carcinogenicity. The results of short-term tests compiled in the US Environmental Protection Agency-IARC Genetic Activity Profile database over the past 12 years are summarized and reviewed here in relation to the classification of agents for carcinogenicity within the system used at IARC. The role of the information from short-term tests in making overall classifications of specific compounds in recent Monographs is discussed. The usefulness of data on three genetic end-points, gene mutation, chromosomal aberrations and aneuploidy, and the criteria for mutagenicity and lack of mutagenicity based on a 'defining set' of test results are examined. Recommendations are made for assessing chemicals on the basis of the strength of the evidence from short-term tests, and the implications of this approach for identifying putative mutational mechanisms of carcinogenicity are discussed.

Aneuploidy↗
PubMed1998

Inhibition of genotoxic effects of mammalian germ cell mutagens.

Germ cell mutagens are among the most important chemicals for which chemopreventive agents should be sought and mechanistically defined. These mutagens may include environmental chemicals as well as drugs. In this investigation, the literature was reviewed for substances antimutagenic (or anticlastogenic) to compounds identified as mutagens in at least two germ cell studies. A complete matrix of test results was prepared to identify commonly tested pairs of germ cell mutagens and antimutagens. The categories of antimutagens most tested included vitamins, fatty acids, thiols, tannins and other phenolics. The most frequently studied mutagens were benzo[a]pyrene, cyclophosphamide, mitomycin C, and bleomycin. Based on the availability of the most relevant data, the analysis presented here focused on in vivo tests, specifically on bone marrow cytogenetics. The results indicated that antimutagens commonly found in the diet or endogenously in the body effectively antagonized the cytogenetic damage induced in the bone marrow by most of the germ cell mutagens studied to date. Bone marrow micronucleus and chromosomal aberration assays, which detect systemically active mutagens, may be predictive of similar mitigating effects in germ cells. Test results from antimutagenicity studies in germ cells, though limited, were comparable to the results from studies in the mouse bone marrow micronucleus test.

Animals↗
PubMed1997

Dynamics of the human EEG during prolonged wakefulness: evidence for frequency-specific circadian and homeostatic influences.

The electroencephalogram (EEG) of nine healthy individuals was recorded at half-hourly intervals during approximately 40 h of sustained wakefulness in a constant routine protocol. EEG power density in the 0.75-9.0 Hz range exhibited a global increasing trend, and a local trough in the evening, centered approximately 6 h prior to the temperature minimum. The former could be attributed to a wake-dependent influence, and the latter to a circadian influence. Power density in the 9.25-12.0 Hz band showed a circadian modulation, the trough coinciding with the minimum of the endogenous rhythm of body temperature, whereas a wake-dependent influence was not evident. Power density in the 12.25-25.0 Hz range exhibited a wake-dependent increase, whereas a circadian modulation was absent. It is concluded that the circadian pacemaker and the wake-dependent (i.e. homeostatic) process affect the waking EEG in a frequency-specific manner.

Adult↗
PubMed1997

Activity profiles of carcinogenicity data: application in hazard identification and risk assessment.

Animal cancer data play a primary role in human risk assessment due to the limited epidemiological data. The current database of test results from the NCI/NTP rodent bioassays provide valuable information concerning the carcinogenic potential of hundreds of environmental agents. An approach is presented to reduce and graphically display these data as activity profiles to allow visualization and assessment of tumor response trends across multiple parameters, e.g. species, sex, target site, and route of exposure. Spreadsheet graphics are used to construct the profiles organized on the multiple parameters of carcinogenicity in a format that enables comparative analysis among chemicals. Several example applications are described to illustrate the value of activity profiles in hazard identification and risk assessment. The NCI/NTP data used in developing this concept are from the Carcinogen Potency Database (CPDB) complied by Gold et al. (Environ. Health Perspect. 103 (Suppl. 8) (1995) 3-122). Computer links to the underlying details in the CPDB are maintained such that specific histopathologies at individual tumor sites, duration of the study, dose-response data, and notes related to diet, survival, treatments, and the authors evaluation are available to aid in the assessment process. The profiles display carcinogen potency based on the tumorigenic dose rate 50 (TD50), i.e. the chronic dose rate that would induce tumors in half of the test animals at the end of their standard lifespan adjusting for spontaneous tumors. The TD50 values provide an index for establishing a relative potency ranking of the chemicals for any specific parameter, such as species or target site. An example ranking of hepatocarcinogens is presented to illustrate relative potencies for chemical analogs. The rank order indicates that the degree and type of halogenation of alkanes has a direct bearing on the carcinogenic potency of these compounds.

Administration, Oral↗
PubMed1996

Fat content for nutritional labeling by supercritical fluid extraction and an on-line lipase catalyzed reaction.

A method using sequential supercritical fluid extraction (SFE) and enzymatic transesterification has been developed for the rapid determination of total nutritional fat content in meat samples. SFE conditions of 12.16 MPa and 50 degrees C were utilized to extract lipid species from the sample matrix. The enzymatic transesterification of the lipids by methanol was catalyzed by an immobilized lipase isolated from Candida antarctica. Conversion of the triglycerides to fatty acid methyl esters was monitored by supercritical fluid chromatography, while the fatty acid content of the extract was determined by capillary gas chromatography (GC). Total fat, saturated fat and monounsaturated fat contents were calculated from the GC data and compared to values from traditional extraction and lipid determination methods. Both off-line SFE and automated SFE followed by on-line GC analysis using two different instruments were utilized in this study. The enzymatic-based SFE method gave comparable results to the organic solvent extraction-based method followed by conventional BF3-catalyzed esterification.

Animals↗
PubMed1996

Genetic activity profiles of anticancer drugs.

The results from short-term tests for genetic and related effects, abstracted from the open literature for 36 anticancer drugs, are examined in this review. Data for 27 of these agents are available in the EPA/IARC Genetic Activity Profile (GAP) database. Data summaries, including data listings and activity profiles, are presented for nine anticancer drugs added to the GAP database for this analysis. Genetic toxicity data from the recent literature are included for the additional agents to provide a broader representation of the categories of drugs being evaluated. These categories, based on the chemical mode of action, are covalent and noncovalent DNA-binding drugs, topoisomerase II inhibitors, antimetabolites, mitotic spindle inhibitors, and drugs which affect endocrine function. The qualitative data for all 36 drugs are summarized in this report and findings are presented from pair-wise matching of genetic activity profiles, based on test results in common, for some chemical analogs. The significance of germ cell test results for some of these drugs and their implication in assessing risk of heritable genetic disease are discussed.

Animals↗
PubMed1996

Activity profiles of antimutagens: in vitro and in vivo data.

In this review, retinol, chlorophyllin, and N-acetylcysteine are examined and compared with regard to their antimutagenic activity against some promutagens and a group of direct-acting alkylating agents. The promutagens included aflatoxin B1, certain polycyclic aromatic hydrocarbons (e.g., benzo[a]pyrene), and certain heterocyclic amines (e.g., food pyrolysates). Results of antimutagenicity testing selected from data surveyed in the published literature are displayed graphically as activity profiles of antimutagens showing both the doses tested and the extent of inhibition or enhancement of mutagenic activity. All three antimutagens are discussed in terms of their putative mechanisms of action in vitro and in vivo with emphasis on the xenobiotic metabolizing enzyme systems.

Acetylcysteine↗
PubMed1996

Interpretation of short-term test data: implications for assessment of chemopreventive activity.

The same short-term tests that have been used extensively to identify mutagens and potential carcinogens are increasingly being used to identify antimutagens and potential anticarcinogens. It is not yet known whether the inhibition of carcinogen-induced mutation is a good indicator of anticarcinogenicity, as the available data on the inhibition of both carcinogenicity and mutagenicity In vivo are still quite incomplete. Furthermore, in vitro tests will detect only those compounds that show an effect that is demonstrable in vitro, such as direct inhibition of the metabolism of the carcinogen or inactivation of the carcinogen by direct reaction. Thus it is essential to confirm putative antimutagenic activity observed in vitro through the use of animal models. Indeed, the interpretation of antimutagenicity data from short-term tests must be subjected to all of the considerations that apply in the interpretation of mutagenicity test results. Moreover, the experimental variable of the antimutagens used must be considered in addition to the variables of the mutagens and short-term tests used. To analyse published results on antimutagens in short-term tests, we have developed the concept of activity profile listings and plots for antimutagens - an approach already used successfully for mutagenicity data. The activity profiles permit rapid visualization of considerable data and experimental parameters, including the inhibition as well as enhancement of mutagenic activity. Here we focus on the use of this methodology to interpret antimutagenicity data for retinol and chlorophyllin against several classes of mutagens in short-term tests.

Anticarcinogenic Agents↗
PubMed1995

Seasonal respiratory viral infections. Impact on infants with chronic lung disease following discharge from the neonatal intensive care unit.

OBJECTIVE: To determine the frequency and severity of acute respiratory infections in infants with bronchopulmonary dysplasia following discharge from the neonatal intensive care unit. DESIGN: A prospective cohort study of 30 oxygen-dependent children who were younger than 2 years (mean age, 9.8 months; range, 3 to 24 months) were studied from September 1990 through April 1991. MEASUREMENTS/RESULTS: During the study, 101 (90.2%) of 112 visits for illness were prompted by new or worsening respiratory symptoms. Diagnoses included upper respiratory tract infection (30.4%), otitis media (26.0%), pneumonia (11.1%), acute exacerbation of bronchopulmonary dysplasia (10.4%), reactive airway disease (9.6%), and bronchiolitis (5.9%). Among these children, an increase in the fraction of inspired oxygen was necessary during 43% of visits. Ten children were hospitalized on 25 occasions for a mean of 37.6 hospital days per child (range, 1 to 107 days), and mean length of stay for each hospitalization was 15 days (median, 6 days). Five children were admitted to the pediatric intensive care unit. Respiratory viruses isolated included respiratory syncytial virus (n = 7), parainfluenza 3 virus (n = 3), and adenovirus (n = 2). No isolates of influenza A or B were detected. Anthropometrics at study entry and study end were converted to z scores as descriptors of weight for age, height for age, and weight for height. Growth improved during the 8 months of the study; however, overall, the children were leaner at study end than at study entry. CONCLUSIONS: In children with bronchopulmonary dysplasia, respiratory viral infections led to significant morbidity, which included long and frequent hospitalizations during the peak of the respiratory viral season. Although weight and linear growth increased throughout the study, patients were leaner at study conclusion than at study entry.

Bronchopulmonary Dysplasia↗
PubMed1995

Abdominal wall haematoma mimicking visceral injury: the role of CT scanning.

Four patients are presented who were thought to have sustained visceral injury following blunt abdominal trauma. However, CT demonstrated abdominal wall haematomata and allowed nonoperative management. Similarity between the clinical findings in visceral injury and abdominal wall haematoma can lead to diagnostic difficulty. The cases illustrate the need to consider abdominal wall haematoma as a possible diagnosis in patients with blunt abdominal trauma. The place of CT in making this diagnosis is highlighted.

Abdominal Injuries↗
PubMed1995

Immunohistochemical localization of transforming growth factor-beta 1 in Kaposi's sarcoma.

Immunohistochemical localization of transforming growth factor beta 1 (TGF-beta 1) was studied in Kaposi's sarcoma (KS) tissues obtained from autopsy and biopsy materials of patients with and without acquired immunodeficiency syndrome (AIDS) or human immunodeficiency virus (HIV) infection. There was no difference in the localization and distribution of TGF-beta 1 in KS tissues regardless of the HIV-1 status of the patients. Rabbit polyclonal antibodies to synthetic peptides, corresponding to the first 30 amino acids of mature TGF-beta 1, anti-LC(1-30), and anti-CC(1-30), were used for localization of intracellular and extracellular TGF-beta 1. An antibody to a peptide corresponding to amino acids 266 to 278 of the TGF-beta 1 precursor sequence anti-Pre(266 to 278) was used to detect the TGF-beta 1 precursor and the latency-associated peptide. Intracellular mature TGF-beta 1 was demonstrated in mononuclear cells, presumably macrophages, within KS tumors but not in spindle-shaped KS cells. Extracellular mature TGF-beta 1 was localized in the basement membranes of blood vessels and fibrous capsules of KS tumors. Intracellular reactivity to anti-Pre was localized in vascular smooth muscle cells and pericytes within the tumor, in variable proportions of spindle-shaped KS cells, and also in macrophage-like cells. These cells appear to be the production sites of TGF-beta 1, which may exert paracrine as well as autocrine proliferative effects.

Acquired Immunodeficiency Syndrome↗