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Biomedical subjects

J Kahn

Publications and source records attributed to J Kahn.

At least 145 records · Page 8Linked to original sources
PubMed1983

The change in hypoxic and chronically hypoxic cell fraction in murine tumors treated with hyperthermia.

The effect of hyperthermia on the size of hypoxic and chronically hypoxic cell fractions in murine tumors was studied. The chronically hypoxic cell fraction was defined as a fraction of tumor cells which were not oxygenated under hyperbaric oxygen. Animals were C3Hf/Sed mice derived from our defined flora mouse colony. Tumors were FSa-II and MCa which were early generation isotransplants of a spontaneous fibrosarcoma and a mammary carcinoma, respectively. TCD50 (50% tumor control dose) or the radiation dose which yields a local tumor control in half the treated animals and TG (tumor growth) time or the time required for half the treated tumors to reach 1000 mm3 from the first treatment day were experimental end points. Hyperthermia was given by immersing animal feet into a water bath maintained at 43.5 +/- 0.1 degrees C. Animal tumors were irradiated with a 137Cs unit under hypoxic conditions, in air or under O2 30 psi. The hypoxic cell fraction increased immediately after hyperthermia in both MCa and FSa-II tumors. The chronically hypoxic cell fraction was, on the other hand, decreased following hyperthermia. The decrease was more substantial in the MCa than in FSa-II.

Animals↗
PubMed1983

The effect of step-down heating on murine normal and tumor tissues.

Cultured cells can be sensitized to low-temperature hyperthermia (below 43.0 degrees C) by a prior heat shock at a high temperature (above 43.0 degrees C) if the heat above 43.0 degrees C is immediately followed by the heat below 43.0 degrees C. This effect has been termed step-down heating (SDH). We have studied the effect of SDH on the response of murine tumor and normal tissues treated at 45.5 degrees C. Animal tumors were eighth-generation isotransplants of a spontaneous fibrosarcoma in C3Hf/Sed. mice. Tumor response was studied by TG (tumor growth) time assay, i.e., determination of the time required for half the treated tumors to reach 1000 mm3 from the first day of treatment. Normal tissue response was studied in the mouse foot. End point was the time to induction of a score 4.0 (loss of a toe) or greater reaction in half the treated animals, RD50. The SDH at 41.0 degrees C sensitized the response of tumor and normal tissues to 45.5 degrees C. The enhancement ratios were congruent to 1.7 for both tissues, indicating no differential sensitization between tumor and normal tissues. No sensitization was observed if the SDH was given immediately after a second dose of 45.5 degrees C given 6 hr to 5 days following the first dose of 10 min at 45.5 degrees C. The SDH appeared not to inhibit the development of thermal resistance as evidenced by no appreciable changes in the thermal resistance ratio.

Animals↗
PubMed1982

Transcutaneous electrical nerve stimulation for nonunited fractures; a clinical report.

Clinical observations were made to assess the value of standard transcutaneous electrical nerve stimulation apparatus for enhancement of osteogenesis. Pulse width and rate were adjusted to obtain maximum stimulation time. Electrode placements were selected dependent on the presence of plaster immobilization, accessibility of the fracture site, and anatomical limitations. In all cases, minimal current intensities were used because earlier studies stressed microamperage levels. Linear, crossed, and transverse electrode placement patterns were used. Standard equipment was used, including monophasic and biphasic units with single and dual channels. Three case reports were cited in which fractures had been nonunited for at least six months prior to study. The patients administered the stimulation daily at home, with rented units, for one month before reevaluation. Radiographic changes reported were fibrous bridging and early ossification activity. Interestingly, the patients reported decreases in pain even though electrode placements were not optimal for analgesic effects. This simple, safe, effective, and inexpensive technique for stimulating early osteogenesis with nonunited fractures is suggested as a routine procedure with all fractures.

Adult↗
PubMed1981

Metabolism of L-beta-lysine by a Pseudomonas. Purification and properties of a deacetylase-thiolesterase utilizing 4-acetamidobutyryl CoA and related compounds.

A deacetylase-thiolesterase that cleaves both the amide and thiolester bonds of 4-acetamidobutyryl CoA has been highly purified from extracts of Pseudomonas B4 grown in a medium containing L-beta-lysine (3,6-diaminohexanoate) as the main energy source. The enzyme has a molecular weight of about 275,000 and contains 8 apparently identical subunits of 36,500 daltons. Products of 4-acetamidobutyryl CoA degradation are stoichiometric amounts of CoASH and acetate, variable amounts of 4-aminobutyrate and its lactam, 2-pyrrolidinone, and a little 4-acetamidobutyrate. The relative yields of 4-aminobutyrate and 2-pyrrolidinone are determined by the enzyme level. At high enzyme levels the 4-aminobutyrate/pyrrolidinone ratio is about 2, whereas at low enzyme levels only pyrrolidinone is formed. Under the latter conditions, 4-aminobutyryl CoA accumulates transiently and is converted nonenzymatically to pyrrolidinone and CoASH. Since the enzyme does not form 4-aminobutyrate from synthetic or enzymatically formed 4-aminobutyryl CoA, we conclude that a 4-aminobutyryl CoA-enzyme complex is the actual precursor of 4-aminobutyrate, whereas free 4-aminobutyryl CoA is the precursor of pyrrolidinone. Several analogs of 4-acetamidobutyryl CoA containing different amino acid or amide moieties, and several simple acyl CoA compounds are utilized by the enzyme; 4-propionamidobutyryl CoA and 5-acetamidovaleryl CoA are most readily decomposed. Acetyl CoA is a very poor substrate. 3-Acetamidopropionyl CoA is first converted to acetate and beta-alanyl CoA and the latter compound is slowly hydrolyzed to beta-alanine and CoASH. Little deacetylase-thiolesterase is formed by bacteria grown in absence of beta-lysine, but another thiolesterase, lacking deacetylase activity, is produced. The deacetylase-thiolesterase catalyzes an essential step in the aerobic degradation of L-beta-lysine.

Acyl Coenzyme A↗
PubMed1981

Aneuploidy in cultured human lymphocytes: II. A comparison between senescence and dementia.

A study has been made of aneuploidy in the cultured lymphocytes of senile dements (46 females and 8 males), arteriosclerotic dements (10 females and 8 males) and normal geriatric controls (55 females and 18 males). Contrary to previous reports of senile dements having a higher degree of hypodiploidy (chromosome loss) than age-matched controls, there were no significant differences between any of the diagnostic groups. The association between individual subjects' age and hypodiploidy is positive, though not significant, with a high degree of individual variation. The reasons for the discrepancies between this and previous studies are discussed as are possible future lines of research in this field.

Aged↗
PubMed1981

The Paris Cardiovascular Risk Factor Prevention Trial. Effects of two years of intervention in a population of young men.

The Paris Cardiovascular Risk Factor Prevention Trial was designed to determine whether individualised intervention could induce a reduction in the coronary risk factor levels in young men. Three thousand three hundred and thirty-six men aged 25 to 35, working in the 160 sections of a large Parisian administration, were examined. The section were randomly allocated to a control and an intervention group. Advice concerning diet, cigarette smoking, and physical activity was provided repeatedly to the subjects in the intervention group. Two years after the first intervention, the first 1292 subjects who entered the study, whether from the intervention or the control group, were recalled; 86% of the intervention group and 84% of the control group responded. The changes in weight, blood pressure, and cigarette smoking in the intervention group, corrected for changes in the control group, were respectively -0.4 kg (p = 0.06), -1.4 mm Hg (p less than 0.05), and -1.2 cigarettes (p less than 0.01). There was no difference between the two groups in serum cholesterol change. Most of these results concerning young men are in agreement with recently reported results of community intervention programmes in middle-aged men.

Adult↗
PubMed1980

Aneuploidy in cultured human lymphocytes: I. Age and sex differences.

The chromosomes of the lymphocytes of 208 subjects have been analysed in order to determine the relationship between age, sex and aneuploidy. The subjects consisted of 111 females and 34 males all over 65 years and 31 females and 32 males aged between 18 and 32 years. The degree of hypodiploidy (chromosome loss) differs significantly between the elderly and young subjects of each sex and between the aged males and females. Hyperdiploidy differs significantly only between the old and the young females. Giemsa banding shows that, in elderly females, increased hypodiploidy is especially due to the loss of an X-chromosome. The possible mechanisms accounting for these results are discussed.

Adolescent↗
PubMed1980

Ironstrene (ferric sodium edetate) treatment of anaemic infants.

This study deals with haemoglobin (Hb) measurements of healthy 1-year-old children in one district in central Norway. The aim was to study the Hb levels, to treat any children having iron deficiency anaemia (Hb less than or equal to 10.8 g/100 ml), and to evaluate the effect of sodium iron edetate after 4 weeks of treatment, with a follow-up after 1 year. A total of 141 children were examined, of whom 40 had Hb less than or equal to 10.8 g/100 ml (28.4%). The study showed that the Hb levels in healthy 1-year-olds have a normal distribution. Thirty-four children with Hb less than or equal to 10.8 g/100 ml were treated for 4 weeks with sodium iron edetate (six drop-outs). The study showed a significant increase in Hb levels immediately after the treatment period as well as 4 weeks later. Hb decreases significantly immediately after ceasing treatment and continues to do so during the control period of 1 year. The Hb levels probably increase to a maximum 2 weeks after the treatment period.

Anemia, Hypochromic↗
PubMed1978

[Operative trauma of the common bile duct. Report of eight cases (author's transl)].

The authors report eight cases of operative trauma to the common bile duct; seven patients were sent up for reoperation often during the late stages following an attempt at immediate or secondary repair. Emphasis was placed on the interest of extensive resection of the stenosis and wide and high opening of the common bile duct for construction of the bilio-jejunal anastomosis, and furthermore the late risk of onset of portal hypertension requiring portacaval anastomosis, finally the possible degradation of the good initial results requiring difficult reoperations.

Adult↗