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Biomedical subjects

L F Cohen

Publications and source records attributed to L F Cohen.

32 records · Page 2Linked to original sources
PubMed1990

Career counseling practices in pediatric residency training programs.

Although there has been an emphasis on career satisfaction in pediatrics and on motivators that impact on resident career selection, little attention has been directed toward the career development process in pediatric residency training. This report summarizes the results of a survey conducted of 155 pediatric residency program directors about their counseling practices. Implications of the results and recommendations are discussed to improve this process.

Career Choice↗
PubMed1985

Phase I trial of mitoxantrone in children.

Mitoxantrone was administered as a single iv injection once every 3 weeks to 84 children with advanced acute leukemia and solid tumors in a phase I trial. Dose-limiting granulocytopenia occurred at dosages greater than 18 mg/m2 in children with solid tumors, while hospitalization for febrile episodes occurred in nine of 12 patients with acute leukemia receiving dosages greater than 24 mg/m2. Six children developed evidence of cardiac dysfunction, including three instances of congestive heart failure. No other significant toxicity was noted. Complete responses were seen in one child with neuroblastoma metastatic to bone, one with acute lymphoblastic leukemia, and four with acute nonlymphoblastic leukemia.

Acute Disease↗
PubMed1982

Cerebrospinal fluid levels of 2'-deoxycoformycin after systemic administration in monkeys.

2'-Deoxycoformycin (DCF) is an inhibitor of the enzyme adenosine deaminase (ADA) and has shown promise as an antileukemia agent. For the assessment of the extent to which systemically administered DCF crosses into the central nervous system (CNS), rhesus monkeys were given iv boluses of DCF. Simultaneous blood and cerebrospinal fluid (CSF) samples were assayed for DCF levels at times ranging from 10 minutes to 6 hours after the drug was given. Average peak CSF drug levels of 5.5 X 10(-8) M and 3 X 10(-7) M were reached 1 1/2 - 2 hours following injections of 0.25 and 1.0 mg DCF/kg, respectively. The ratio of peak CSF to simultaneous plasma levels was 1 to 10. Data obtained from a patient who had acute lymphocytic leukemia and who was given iv DCF were comparable. Drug levels achieved within the CSF following iv administration of 0.25 mg DCF/kg are similar to those previously demonstrated to inhibit ADA. These results may be important both for understanding DCF-related CNS toxicity and for designing combination chemotherapy with DCF.

Animals↗
PubMed1981

DNA crosslinking and cell survival in human lymphoid cells treated with 8-methoxypsoralen and long wavelength ultraviolet radiation.

8-Methoxypsoralen (8-MOP) when irradiated with long wavelength ultraviolet radiation (UV-A) inhibits DNA synthesis in lymphocytes in vitro and in vivo. 8-MOP binds reversibly to DNA in the dark; when exposed to UV-A, covalent monoadducts and cross-links are formed with the DNA. The present study correlates the cytotoxic effects of 8-MOP plus UV-A with DNA crosslinking. E-B virus transformed human lymphoblastoid cells were suspended in a colorless salt solution containing 8-MOP and exposed to UV-A from fluorescent lamps filtered to remove radiation below 320 nm (22.5 J/m2-sec). Cells were then returned to complete medium and assayed for survival (by daily counts of viable cells and by cloning in microtiter wells) and for DNA crosslinking by alkaline elution. 8-MOP alone or UV-A alone resulted in minimal to no alterations in survival or in DNA crosslinking. DNA crosslinking was found to be linearly dependent on 8-MOP concentration (in the range of 0.01-1.0 microgram/ml) for 3 different UV-A doses (3000-15 000 J/m2). The surviving fraction declined exponentially as a function of the relative number of DNA crosslinks. These results suggest that the cytotoxic effects of photoactivated 8-MOP in human lymphoblastoid cells may depend on DNA interstrand crosslinks.

Cells, Cultured↗
PubMed1980

Interstrand DNA crosslinking by 4,5'8-trimethylpsoralen plus monochromatic ultraviolet light. Studies by alkaline elution in mouse L1210 leukemia cells.

DNA crosslinking by 4,5',8-trimethylpsoralen plus monochromatic ultraviolet light of wavelength 365 nm was studied in mouse L1210 leukemia cells. DNA breaks and crosslinking were evaluated by alkaline elution of DNA from poly(vinyl chloride) filters. Trimethylpsoralen plus 365 nm light produced DNA crosslinks but not breaks. The kinetics of crosslinking were linear with respect to concentration and second-order with respect to light exposure time. The latter finding supports the proposed two photon mechanism for the formation of diadducts. In contrast to DNA crosslinking agents such as nitrogen mustard, nitrosoureas and platinums, trimethylpsoralen crosslinks were resistant to proteolytic digestion. Thus, trimethylpsoralen plus 365 nm light produced interstrand crosslinks, as proposed for a bifunctional agent binding to bases on opposite DNA strands.

Animals↗
PubMed1980

Cystic fibrosis and pregnancy. A national survey.

In a sruvey of 119 cystic fibrosis (CF) centres in the U.S.A. and Canada, information was obtained on 129 pregnancies in 100 patients with CF. 97 pregnancies were completed resulting in 86 viable infants, only one of whom had CF. This is close to the expected incidence and attests to the recessive nature of the transmission of CF, the commonest lethal genetic disorder of Caucasians. Shortened gestation and increased maternal and perinatal mortality were related to severe maternal pulmonary infection. Increased respiratory and cardiac work, and especially hypervolaemia, are hazards for pregnant women with CF, and when combined with advanced pulmonary disease may lead to increased perinatal complications. Maternal hypoxia and transplacental passage of antibiotics may affect the fetus; however, there were no congenital anomalies in this series in spite of frequent use of antibiotics by these mothers. Unless the clinical score is high, pregnancy should be avoided in CF patients.

Adolescent↗
PubMed1980

Acute tumor lysis syndrome. A review of 37 patients with Burkitt's lymphoma.

Renal and metabolic complications of tumor lysis during 46 episodes of remission induction chemotherapy were reviewed in 37 patients with American Burkitt's lymphoma. Azotemia occurred in 14 patients, preceding chemotherapy in eight. All of these patients had abdominal tumors. Pretreatment azotemia was associated with elevated lactic dehydrogenase (LDH) and uric acid levels, and sometimes extrinsic ureteral obstruction by tumor. Two patients required dialysis for uric acid nephropathy before chemotherapy was initiated. Following chemotherapy, major complications of tumor lysis (hyperuricemia, hyperkalemia and hyperphosphatemia) were associated with very large tumors, high LDH levels and inadequate urinary output. In patients undergoing diuresis and receiving allopurinol, hyperkalemia or hyperuricemia developed infrequently unless concomitant renal failure ensued. Hyperphosphatemia, which occurred only after chemotherapy, developed in 10 of 32 (31 per cent) nonazotemic and in all azotemic patients. Hemodialysis was required in three post-treatment patients for control of azotemia, hyperuricemia, hyperphosphatemia and/or hyperkalemia. Because of the potential for renal failure caused by precipitation of phosphate, severe hyperphosphatemia is an additional criterion for dialysis in patients with acute tumor lysis syndrome.

Adolescent↗
PubMed1978

Clinical estimation of liver span in infants and children.

The liver span in 350 infants and children was determined by percussion of the upper and lower borders in the midclavicular line. Mean liver span was found to be related to age curvilinearly and ranged from a minimum of 1.9 cm at 1 week of age to a maximum of 7.7 cm in males and 6.3 cm in females at 20 years of age. In children with normal growth patterns, age and sex were found to be the major factors influencing liver size. Though height and weight also correlated with liver span, these variables did not add substantially to the correlation using age and sex alone. The presence of minor systemic illnesses, eg, otitis and gastroenteritis, did not affect liver span. The expected normal values for liver span at different ages for male and female children have been established and provide the basis for comparison during routine physical examination.

Adolescent↗
PubMed1977

The syndrome of inappropriate antidiuretic hormone secretion as a cause of hyponatremia in cystic fibrosis.

The syndrome of inappropriate secretion of antidiuretic hormone was observed in two patients with cystic fibrosis during acute exacerbation of chronic pulmonary disease. It was diagnosed by the accepted clinical and laboratory criteria and confirmed in one case by values for immunoreactive vasopressin that were inappropriately high for plasma osmolality. The severe hyponatremia was corrected by fluid restriction, alone or combined with intravenous treatment with diuretic and hypertonic saline solution. In addition, there was simultaneous therapy of the pulmonary disease. SIADH thus must be added to salt loss as a cause of hyponatremia in CF, and may be more common than realized in patients with CF and severe pulmonary disease.

Adult↗
PubMed1976

Fluctuations of unbound whole blood polyamine levels during the menstrual cycle.

Perchloric acid-extractable whole blood spermidine and spermine concentrations were determined over a 4-week period in three men, four women, and one ovariectomized woman. Individual male spermidine/spermine ratios showed little fluctuation and similar values were obtained for each of the three males studied. Male spermidine and spermine concentrations, although stable for each male, varied from one subject to the next. Individual female spermidine/spermine ratios, as well as individual concentrations, fluctuated substantially when compared to those valued obtained for males; female ratios appear to rise and fall as a function of the menstrual cycle. The spermidine/spermine ratios obtained from a normal female receiving oral contraceptive, as well as those from an ovariectomized female, were characteristic of values obtained form men. It is suggested that a sex-related hormone(s) influences sperimidine and spermine concentrations in females.

Adult↗
PubMed1976

Distribution of spermidine and spermine in blood from cystic fibrosis patients and control subjects.

Previous studies have shown an abnormality of the spermidine-to-spermine (Spd/Spm) ratio in whole blood of cystic fibrosis homo-and heterozygotes. To investigate Spd and Spm distribution amoung blood components as a possible cause of the abnormality, blood was fractionated using Rabinowitz's glass bead technique and Boyum's Ficoll-Hypaque method. Free (unconjugated) polyamines were extracted with perchloric acid and quantitated on an amino acid analyzer. In controls, mean +/- SEM concentrations in nmoles/10(9) cells of Spd and Spm, respectively, were 1.02 +/- 0.08 and 0.894 +/- 0.28 for erythrocytes; 126 +/- 31 and 357 +/- 105 for lymphocytes; 36 +/- 16 and 240 +/- 33 for granulocytes; and less than 0.5 and less than 0.5 nmoles/ml for plasma. When converted to the concentration in whole blood, it was found that greater than 90% of Spd and over 70% of Spm was associated with erythrocytes. While the higher cellular concentration in leukocytes was not unexpected, the fact that Spd and Spm in whole blood were primarily associated with erythrocytes was a new finding. Comparison with controls revealed that the Spd/Spm ratio in both whole blood and erythrocytes was significantly higher in the group of cystic fibrosis patients.

Cell Fractionation↗