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Biomedical subjects

D Harman

Publications and source records attributed to D Harman.

At least 37 records · Page 2Linked to original sources
PubMed1987

Oxygen radicals and human disease.

Toxic oxygen free radicals have been implicated as important pathologic mediators in many clinical disorders. We discuss the chemistry of oxygen radical production and the roles of iron and of various antioxidants as well as the diseases that have received active attention in oxy-radical research. Particular attention is focused on cigarette smoke oxidants, ischemia-reperfusion-induced radical production, carcinogenesis, and aging. Such research may well provide a firm foundation for therapeutic breakthroughs.

Aging↗
PubMed1986

The interrelationship between intraocular pressure and Honan Intraocular Pressure Reducer pressure.

The relationship between the pressure applied to the enucleated human eye using the Honan Intraocular Pressure Reducer (HIPR) and the peak intraocular pressure as a function of initial intraocular pressure has been examined. The peak intraocular pressure is linearly related to the applied HIPR pressure whether the latter is 30, 50, or 75 mm Hg. The slopes relating peak intraocular pressure to initial intraocular pressure at different HIPR settings are parallel. Use of the HIPR at settings greater than 30 mm Hg and an initial IOP of greater than 30 mm Hg could compromise ocular vascular perfusion.

Humans↗
PubMed1985

Out-patient letters: requirement and contents.

Twenty-five general practitioners were interviewed about the contents of out-patient letters. There was universal agreement on the need for the following information: diagnosis, abnormal physical findings, abnormal routine and non-routine test results, changes in treatment, comments on the patient's physical condition and disposal. The contents of 215 out-patient letters were analysed and the results compared with the GPs' views. There was little difference in the letters from medical and surgical clinics. Both were deficient to a limited extent in the reporting of abnormal test results, the reasons for, and significance of investigations, and in detailing the information given to patients.

Computers↗
PubMed1982

Nutritional implications of the free-radical theory of aging.

Aging is the progressive accumulation of changes with time associated with and/or responsible for the ever-increasing susceptibility to disease and death. These time-related changes are attributed to the aging process. This process may be due in part to free radical reactions, largely those involving oxygen, going on continuously throughout the cells and tissues. Dietary manipulations expected to lower the rate of production of free-radical reaction damage have been shown to 1) increase the life span of mice, rats, fruit flies, nematodes, and rotifers, as well as the life span of neurospora, 2) inhibit development of some forms of cancer, 3) enhance humoral and cell-mediated immune responses, and 4) slow development of amyloidosis and the autoimmune disorders of NZB mice. Free-radical reactions may also play a significant role in the deterioration of the cardiovascular and central nervous systems with age. It is reasonable to expect, on the basis of present data, that the healthy life span can be increased by five or more years by keeping body weight down, at a level compatible with a sense of well-being, while ingesting diets adequate in essential nutrients but designed to minimize random free-radical reactions in the body.

Aging↗
PubMed1981

The aging process.

Aging is the progressive accumulation of changes with time that are associated with or responsible for the ever-increasing susceptibility to disease and death which accompanies advancing age. These time-related changes are attributed to the aging process. The nature of the aging process has been the subject of considerable speculation. Accumulating evidence now indicates that the sum of the deleterious free radical reactions going on continuously throughout the cells and tissues constitutes the aging process or is a major contributor to it. In mammalian systems the free radical reactions are largely those involving oxygen. Dietary manipulations expected to lower the rate of production of free radical reaction damage have been shown (i) to increase the life span of mice, rats, fruit flies, nematodes, and rotifers, as well as the "life span" of neurospora; (ii) to inhibit development of some forms of cancer; (iii) to enhance humoral and cell-mediated immune responses; and (iv) to slow development of amyloidosis and the autoimmune disorders of NZB and NZB/NZW mice. In addition, studies strongly suggest that free radical reactions play a significant role in the deterioration of the cardiovascular and central nervous systems with age. The free radical theory of aging provides reasonable explanations for age-associated phenomena, including (i) the relationship of the average life spans of mammalian species to their basal metabolic rates, (ii) the clustering of degenerative diseases in the terminal part of the life span, (iii) the beneficial effect of food restriction on life span, (iv) the greater longevity of females, and (v) the increase in autoimmune manifestations with age. It is not unreasonable to expect on the basis of present data that the healthy life span can be increased by 5-10 or more years by keeping body weight down, at a level compatible with a sense of well-being, while ingesting diets adequate in essential nutrients but designed to minimize random free radical reactions in the body.

Aging↗
PubMed1977

Self-regulation of hemispheric asymmetry.

This study was performed to determine if individuals could demonstrate self-regulation of average EEG power of one hemisphere in comparison to the other. Temporal EEG was recorded from 8 males and 6 females. After a practice session, the subjects were instructed to increase or decrease the practice session, the subjects were instructed to increase or decrease the ratio of left to right temporal EEG. The subjects were given on-line feedback in the form of a graph presented via a computer display screen. The study demonstrated a significant ability of the subjects to change differentially the hemispheric power ratios upon instruction.

Adult↗
PubMed1977

Free radical theory of aging: effect of age, sex and dietary precursors on rat-brain docosahexanoic acid.

Increasing the peroxidizability of dietary fat has an adverse effect on the function of the central nervous system (CNS) in the rat. This effect may be influenced by the level of docosahexanoic acid, a highly unsaturated fatty acid, selectively concentrated in the phospholipids of brain membranes. This study was aimed at determining the influence of age, sex, and the nature of a dietary lipid supplement - linolenic acid (18:3w3), docosahexanoic acid (22:6w3), or the same amount of 22:6w3 in the form of menhaden oil triglycerides - on the rate of increase in the percentage of 22:6w3 in the whole-brain fatty acids of rats between the ages of 1 and 12 months. The dietary lipid supplements were reflected in linear increases in the brain 22:6w3 of female rats throughout the study. Between 6 and 12 months of age, the rate of incorporation of dietary 22:6w3 and its precursors into the brain 22:6w3 of male rats dropped. At 12 months it was about half that for females in the case of 22:6w3 and menhaden oil, and about zero for 18:3w3. It is suggested that dietary 22:6w3 and its precursors may modify CNS function by altering membrane function and peroxidizability through changes in the concentration of 22:6w3 in membrane phospholipids.

Age Factors↗
PubMed1976

The clinical gerontologist.

A major objective now and in the future should be that of maximizing health and well-being during our essentially fixed span of life. It is proposed that this objective be delegated to a new field of medicine, perhaps to be known as clinical gerontology--a combination of preventive medicine and geriatrics.

Forecasting↗
PubMed1976

Free radical theory of aging: inhibition of amyloidosis in mice by antioxidants; possible mechanism.

The antioxidants, alpha-tocopherol acetate and a quinolone derivative (Santoquin), inhibited the development of amyloidosis when added to the diet of casein-injected C3HeB/FeJ male mice. Santoquin, and to a lesser extent butylated hydroxytoluene (BHT), also depressed the appearance of a plasma protein fraction in these mice; the effect of alpha-tocopherol was not determined. Consideration of the current knowledge of amyloid, in the light of these antioxidant studies, prompted the following hypothesis. Amyloidosis is largely the result of an enhanced rate of oxidative degradation of a connective-tissue glycoprotein(s) coupled with oxidative/enzymatic changes in the plasma, both of the tissue-derived substances and of immunoglobulins, to form the amyloid fibril protein subunits (AL and AA) which subsequently aggreagate to form the amyloid fibrils.

Aging↗
PubMed1976

Free radical theory of aging: effect of dietary fat on central nervous system function.

Free radical reactions have been implicated in aging. A rise in the level of random free radical reactions in a biologic system might have a greater effect on the central nervous system (CNS) than elsewhere, partly because of the presence of glial cells and the unique connections between neurons. To evaluate this possibility, some animal experiments were conducted. The initial experiment involved old male Sprague-Dawley rats fed (since shortly after weaning) with semisynthetic diets characterized by fat differing in amount or degree of unsaturation. The number of errors made in a Hebb-Williams maze was determined and found to be higher as the amount or degree of unsaturation of the fat was increased. Likewise rats aged 6 and 9 months, fed semisynthetic diets containing 20 percent by weight of lard, oleinate, or safflower oil +alpha-tocopherol performed significantly better in a discrimination learning situation (Skinner box) than did rats fed a diet containing 20 percent by weight of safflower oil. The diets employed in these studies did not have a significant effect on the mortality rates. These results are compatible with the possibility that enhancing the level of lipid peroxidation has an adverse effect on the CNS, out of proportion to the effect on the body as a whole, as measured by the mortality rate.

Aging↗
PubMed1975

Rat brain fatty acid composition: effect of dietary fat and age.

The polyunsaturated fatty acid composition of human brain changes, as well as progressively decreases, with age. To determine if whole brain rat lipid shows similar changes with age, rats born to mothers fed semi-synthetic diets were raised on the same diet as their mothers for varying periods prior to sacrifice. Whole brain lipid composition was determined for female offspring, fed diets containing 20% w (by weight) of either lard or safflower oil, from age 6 days to 730 days. The percentage of 20:4omega6 and 22:6omega6 decreased with age; as in man these changes were compensated for largely by increases in 18:1omega9. In contrast, 22:6omega3 rose gradually from 6 to 730 days of age. Varying the degree of unsaturation and/or the amount of dietary fat, with the exception of lard, did not influence the fatty acid composition of whole brain lipid or of the two major phospholipids, phosphatidyl ethanolamine (PE) and phosphatidyl choline (PC). Lard was found to contain trace amounts of 22:5omega3; this acid was avidly retained in the brain accompanied by corresponding decreases in 22:5omega6. The functional significance of the observed age-related brain lipid changes is unknown; it is likely that the lipid changes are in some way related to the deterioration of the central nervous system with time.

Aging↗