PubMed Health⌕ Search

Biomedical subjects

T Lincoln

Publications and source records attributed to T Lincoln.

8 recordsLinked to original sources
PubMed1989

Chronic exercise training protects aged cardiac muscle against hypoxia.

To test the hypothesis that chronic exercise may improve tolerance to hypoxia in aged hearts, we compared cardiac function of exercised rats to that of their age-matched, nonexercised controls. Right ventricular papillary muscles were removed from young adult (9 mo) and old (24-26 mo) male Fischer 344 rats that were chronically exercised on a rodent treadmill and from their age-matched, nonexercised controls. During isometric contraction, hypoxia depressed contraction and relaxation in all muscles, but to a lesser extent in the exercised groups. A significant exercise effect was observed in the following variables: the maximum developed tension, the maximum rate of tension development, the maximum rate of tension decline, and the time required for the hypoxia to reduce maximum tension by 20%. The maximum rate of tension decline was more sensitive to hypoxia than was the maximum rate of tension development in all groups. Exercise also had an effect on the temperature dependence of cardiac performance during hypoxia. Thus, chronic exercise results in the preservation of both contraction and relaxation during hypoxia for aged as well as young adult hearts.

Aging↗
PubMed1986

Age-related differences in effect of exercise training on cardiac muscle function in rats.

To test the hypothesis that age may alter the effect of exercise training on myocardial function, we trained young adult (4-5 mo at study initiation) and old (21 mo at initiation) male Fischer 344 rats to run on a rodent treadmill 5 days/wk for 4.5 mo and compared their myocardial function with that of age-matched sedentary controls. Right ventricular papillary muscles were isolated from the young adult and aged animals and stimulated at the length at which developed isometric tension was maximal to contract isometrically at 12/min, bathed in oxygenated modified Krebs solution, and studied at 28 degrees, 32 degrees, 35 degrees, and 38 degrees C. In the absence of cardiac hypertrophy, exercise training significantly reversed the age-related prolongation of isometric contraction duration in the senescent rat (P less than 0.001). However, exercise training prolonged contraction duration in the young adult rat (P less than 0.05). The relaxation phase was more sensitive than the contraction phase to changes in temperature, especially in the aged rat (P less than 0.02). The ratio of developed tension to time-to-peak tension of the isometric twitch was not affected by exercise training. Because exercise training affects cardiac function in opposite directions from young adulthood to senescence, caution is advised in extrapolating results from exercise studies in young adult rats to populations of older animals.

Aging↗
PubMed1985

From micro to mainframe. A practical approach to perinatal data processing.

A new, practical approach to perinatal data processing for a large obstetric population is described. This was done with a microcomputer for data entry and a mainframe computer for data reduction. The Screen Oriented Data Access (SODA) program was used to generate the data entry form and to input data into the Apple II Plus computer. Data were stored on diskettes and transmitted through a modern and telephone line to the IBM 370/168 computer. The Statistical Analysis System (SAS) program was used for statistical analyses and report generations. This approach was found to be most practical, flexible, and economical.

Computers↗
PubMed1979

Childhood leukemia and lymphoma: correlation of clinical features with immunological and morphological studies.

Malignant cells from 49 children with lymphoid neoplasms other than Hodgkin disease were evaluated by surface marker and morphologic studies. We classified the patients into three groups: 36 patients (74%) with acute lymphocytic leukemia; 7 (14%) classified as convoluted lymphocytic lymphoma/leukemia; and 6 (12%) with small noncleaved follicular center cell lymphoma/leukemia. Diffuse marrow involvement was present at diagnosis in some patients in the latter two groups, but their clinical course was not characteristic of the patients with acute lymphocytic leukemia. Male predominance, poor prognosis, and high incidence of central nervous system disease characterized patients in the convoluted lymphocytic and follicular center cell lymphoma/leukemia groups. Clinical presentation in these two groups differed. Proliferations of convoluted lymphocytes were associated with mediastinal masses and proliferations of follicular center cells with intraabdominal tumors. The high incidence of CNS disease in children with neoplasms of convoluted lymphocytes and follicular center cells suggests that these processes have a predilection for the CNS and that patients with them may benefit from CNS prophylaxis.

Adolescent↗
PubMed1977

The brown dog tick Rhipicephalus sanguineus and the dog as experimental hosts of Ehrlichia canis.

Adult Rhipicephalus sanguineus ticks efficiently transmitted Ehrlichia canis to susceptible dogs for 155 days after detachment as engorged nymphs from a dog in the acute phase of ehrlichiosis. Adult ticks that had similarly engorged on a dog in the chronic phase of ehrlichiosis failed to transmit E canis to susceptible dogs. Infected but unfed adult ticks may be of greater importance than the chronically infected carrier dog as a natural reservoir of E canis.

Animals↗
PubMed1976

Computer simulation of leukemia therapy: combined pharmacokinetics, intracellular enzyme kinetics, and cell kinetics of the treatment of L1210 leukemia by cytosine arabinoside.

An integrated mathematic computer-based model of the pharmacokinetics, intracellular enzyme kinetics, and cell kinetics of the treatment of L1210 leukemia by cytosine arabinoside (ara-C) is described. The compartment model of Bischoff and Dedrick is extended to the intracellular level by inclusion of equations describing the phosphorylation, dephosphorylation, and deamination of ara-C with enzymatic feedback control. The activities of kinase, deaminase, and phosphatase are explicitly included in the models and are estimated from relevant data. Cell proliferation is described by a continuous-flow mathematic model in which cellular maturation and cell-to-cell variability in maturation rates are key variables. Cell proliferation is related to intracellular biochemistry through mathematic expressions which relate cell lethality and progression delay to the time course of intracellular ara-CTP. In vitro and in vivo experiments performed in a number of laboratories are compared by simulation. The most sensitive parameters in dose-response and cell-survival simulations are deoxycytidine kinase activity, ara-CTP half-life, renal clearance of ara-C, and cell-kinetic parameters for proliferation and cell killing. Progression delay is vital to the realistic simulation of divided-dose schedules. By comparative simulation we have identified areas of uncertainty which can be classified by a few additional measurements. The applications of simulations combining pharmacokinetic, biochemical, and cell-kinetic data in vitro and in vivo are discussed, exploring consistency among different measurements, and relating experimental protocols to clinical treatment.

Animals↗