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Biomedical subjects

M Larson

Publications and source records attributed to M Larson.

71 records · Page 4Linked to original sources
PubMed1983

Bumetanide inhibition of NaCl transport by Necturus gallbladder.

Salt transport by the Necturus gallbladder epithelium is the result of the coupled entry of NaCl into the cells across the apical membrane and the active transport of Na out of the cells across the basolateral membrane. The NaCl entry step was studied by measuring the rate of cell volume increase accompanying ouabain inhibition of the Na--K-ATPase in the basolateral membrane. When bumetanide, a diuretic analog of furosemide, was added to the mucosal bathing solution it reversibly blocked the entry of NaCl into the cells and abolished fluid transport. A dose-response relationship showed half-maximal inhibition of NaCl entry at a bumetanide concentration of 10(-9) M; complete inhibition of coupled NaCl movement occurred with as little as 10(-7) M bumetanide. Partial substitution of Na or Cl in the mucosal solution failed to demonstrate competition between bumetanide and either of the ions. The drug was also effective in blocking NaCl entry in the absence of ouabain; addition of the diuretic to the mucosal bathing solution resulted in prompt cell shrinkage and a decrease in intracellular NaCl. Cell volume decrease followed bumetanide addition to the mucosal bath because NaCl entry was blocked but active Na transport continued for several minutes until the intracellular Na transport pool was depleted.

Animals↗
PubMed1983

The influence of surgery and radiation therapy on patients with brain metastases.

The place for operation and for radiation therapy in the management of brain metastases is reviewed from the experience of 1895 patients treated in two studies of the Radiation Therapy Oncology Group. Operative removal may be of benefit to patients with solitary peripheral lesions in non-critical brain locations. Operation is also appropriate when the diagnosis is in doubt. Radiation therapy with appropriate steroid management is of benefit to patients with multiple metastases or where operative intervention is not reasonable. Short course low-dose treatment has been as beneficial as more aggressive prolonged radiation therapy.

Brain Neoplasms↗
PubMed1983

Hydraulic permeability of the peritubular and glomerular capillary membranes in the rat kidney.

The hydraulic conductivity of the peritubular capillary membrane was calculated from 1) single nephron fluid reabsorption and 2) net driving force, i.e. from hydrostatic and colloid osmotic pressures in renal interstitium and peritubular capillary blood, as determined by a micropuncture technique and with use of a computer-based model. Under control conditions the net driving force was estimated to be 15.4 mmHg and the hydraulic conductivity 1.04 nl/(min . mmHg) per 100 g rat. During extracellular volume expansion with 0.15 M saline, 4% and 10% of body weight, the net driving force decreased to 12.5 mmHg and 6.4 mmHg, respectively, whereas the conductivity increased to 1.85 and 3.14 nl/(min . mmHg) per 100 g rat. The reduction in net driving force was compensated by an increased hydraulic conductivity. In the glomeruli the net driving force for filtration increased from 14.2 mmHg under control conditions to 21.2 mmHg and 25.3 mmHg during saline expansion 4% and 10%, whereas the corresponding hydraulic conductivity de increased from 1.13 nl/(min . mmHg) per 100 g rat to 1.03 and 0.80 nl/(min . mmHg) per 100 g rat during the two expansions. During saline expansion the water permeability of the glomerular capillaries is decreased while that of the peritubular capillaries is increased. These changes in the water permeability will lead to retarded excretion of the excess fluid.

Animals↗
PubMed1982

A study of the use of the probability-of-being-in-response function as a summary of tumor response data.

The probability-of-being-in-response function (PBRF), proposed by Temkin (1978, Biometrics 34, 571-588) as a vehicle for analyzing transient response data, is examined using the simplified parametric model in which each of the failure processes is assumed to be exponential. Properties of the PBRF under these assumptions are discussed. It is demonstrated that the PBRF is a very complete summary of the data and has attractive properties for its intended use as a visual display. The model is extended to incorporate covariates, and it is demonstrated that the desired properties can be generalized under specific conditions for the covariates.

Antineoplastic Agents↗
PubMed1981

Equivalence of radiation schedules for the palliative treatment of brain metastases in patients with favorable prognosis.

Five whole-brain irradiation schedules ranging from 2000 rad in one week to 4000 rad in four weeks were evaluated in 1830 patients with cerebral metastases treated in two randomized studies by the Radiation Therapy Oncology Group. The duration of palliative effectiveness among those patients with favorable survival prognosis was investigated. Favorable subgroups were identified consisting of 123 ambulatory breast cancer patients with no soft tissue metastases, 373 ambulatory lung cancer patients with primary absent or no extracerebral metastases, and 65 ambulatory patients with other primaries and no extracerebral metastases. This group of 561 patients had a median survival of 28 weeks compared with 11 weeks for the remaining patients. Analyses of neurologic function control rates failed to show a significant benefit of higher doses. No advantage was demonstrated for treating brain metastases patients with favorable prognoses with more than one week of whole-brain irradiation.

Brain Neoplasms↗
PubMed1981

Influence of renal nerve activity on arteriolar resistance, ultrafiltration dynamics and fluid reabsorption.

In anaesthetized 300 g rats, the influence of sympathetic nerve activity on the renal hemodynamics, glomerular filtration and fluid reabsorption was studied with direct stimulation at frequencies of 2 Hz and 5 Hz. The single nephron plasma flow at control conditions was 164 nl/min decreasing to 138 nl/min during 2 Hz and 68 nl/min during 5 Hz, reaching complete glomerular ischemia at about 10 Hz. At 2 Hz, the pressure drop over the two arterioles remained essentially unchanged, indicating an equal response to sympathetic discharge. At higher frequencies the afferent tone showed a more marked increase. The glomerular ultrafiltration decreased in parallel to the blood flow. The filtration fraction remained thereby constant at about 0.33. The fractional proximal fluid reabsorption up to the puncture site in early distal tubules showed a clear increase; the Tf/P-Inulin increasing from 6.0 to 7.1 and 7.2 for 2 Hz and 5 Hz, respectively. The absolute reabsorption decreased, however, and indeed not far from the decrement in glomerular filtration. It is concluded that sympathetic nerve activity acts in the direction of fluid conservation, by reducing the glomerular filtration and increasing the fractional reabsorption. The hemodynamic effects will play the dominant role even at 2 Hz stimulation.

Adrenergic Fibers↗
PubMed1981

Ovarian failure in long-term survivors of childhood malignancy.

The frequency and causes of ovarian failure among 182 long-term survivors of childhood cancer were examined. Twenty-two patients (12%) had ovarian failure. Ovarian failure was found in 17 of 25 patients (68%) who had both ovaries within abdominal radiotherapy fields, in five of 35 patients (14%) whose ovaries were at the edge of the treatment field, and in none of 122 patients with one or both ovaries outside of an abdominal treatment field (p < 10(-4)). The odds for ovarian failure in patients with both ovaries in the field are 19.7 higher than those for other irradiated patients (95% confidence interval, 5.3 to 72.8). Covariate and multivariate analyses of tumor type, age at diagnosis, duration of follow-up, abdominal tumor surgery, abdominal radiotherapy, number of chemotherapeutic agents administered, and cumulative doses of several drugs revealed that the location of the ovaries relative to radiation treatment fields was the only risk factor for subsequent ovarian failure.

Abdominal Neoplasms↗
PubMed1981

Functional characteristics of the renal interstitium.

The renal interstitial space analyzed as "inulin space" comprises about 13% in the rat. The Starling forces of this compartment are governed by the balance between tubular and capillary fluid transport and also by the leakage of plasma proteins from the blood side. Protein transport will occur in a large-pore system in the peritubular capillary membrane. During control antidiuresis, the interstitial hydrostatic pressure is 2-4 mmHg. The colloid osmotic pressure shows a larger variability but is generally about 5 mmHg. During conditions of depressed capillary reabsorption but unchanged tubular reabsorption, as in saline expansion, the interstitial hydrostatic pressure rises 3-4 times, whereas the colloid osmotic pressure will show a steep fall resulting from the increased fluid entry and unchanged protein transport. The interstitial volume increases only slightly, since it is compressed by the expanding tubules. The influence of interstitial physical forces on tubular transport remains unclear, mainly due to the inaccessibility of the lateral interspaces to direct measurement of relevant parameters.

Albumins↗
PubMedDate not supplied

Pre- and post-operative counseling for laryngectomees and their spouses: an update.

This survey was developed to determine if pre-operative counseling services have improved since the 1978 Keith, Linebaugh, and Cox study. The questions were aimed to obtain information on the quality and quantity of support services available to laryngectomees and their spouses. Questions addressed the type, amount, and content of information received. In addition, questions regarding post-operative counseling services for laryngectomees and spouses of laryngectomees also were included. Results indicated that 21% of the laryngectomees were not aware that laryngectomy surgery would result in loss of voice. In addition, not all speech rehabilitation options were explained to the patients. Pre- and post-operative counseling services for laryngectomees continue to be inadequate. It appears that little change has been made to improve this situation.

Aged↗