Cell Pool Size Research Articles

Expansion of phospholipid pool size of rat intestinal villus cells during fat absorption.

The effect of fat absorption upon the phospholipid pool size of the intestinal mucosal cells was determined in rats receiving fatty emulsions as a bolus by stomach tube or as multiple meals in the form of fat-laden laboratory chow. The phospholipid content of the mucosal scrapings and of the isolated villus cells was determined 3 to 34 h after the meals and was compared with the phospholipid content of cells from similar animals receiving water alone or 10% sucrose in water. It was shown that continuously fed animals averaged 5-10% and single meal fed animals up to 40% higher phospholipid content in their mucosal cells than the corresponding controls, when compared per milligram cell protein. The expansion of the phospholipid pool involved all phospholipid classes and correlated well with the phospholipid composition of prechylomicrons and of microsomal membranes, which undergo a significant proliferation during fat absorption. The apparent lower expansion of the phospholipid pool in the continuously fed animals correlated with the lower triacylglycerol content of the lumen and of the cells at these times.

Analysis of flagellar size control using a mutant of Chlamydomonas reinhardtii with a variable number of flagella.

A mutant of Chlamydomonas reinhardtii with a variable number of flagella per cell has been used to investigate flagellar size control. The mutant and wild-type do not differ in cell size nor in flagellar length, yet the size of the intracellular pool of flagellar precursor protein can differ dramatically among individual mutant cells, with, for example, triflagellate cells having three times the pool of monoflagellate cells. Because cells of the same size, but with very different pool sizes, have flagella of identical length, it appears that the concentration of the unassembled flagellar precursor protein pool does not regulate flagellar length. The relation between cell size, pool size, and flagellar length has also been investigated for wild-type cells of different sizes and ploidies. Again, flagellar length appears to be maintained independent of pool size or concentration.

Evidence for structured variation in self-renewal capacity within long-term bone marrow cultures.

Bone marrow pluripotent stem cells (CFUs) demonstrate capacity for both proliferation and differentiation. The proliferative capacity of CFUs has been measured by serial transplantability and by the Rs, a measurement of CFU production in a single 14-day transfer. In the present study, the self-renewal capacity fo both adherent and nonadherent CFUs from long-term bone marrow cultures was measured. Culture conditions were established such that nonadherent cells were derived from the adherent cell layer. Both adherent and non-adherent cells produced spleen colonies, demonstrating that significant proliferative potential was present in both locations; however, at all times in culture, the CFUs within the adherent stromal cell layer had a significantly greater self-renewal capacity than did the nonadherent CFUs. During the initial establishment of the cultures, the self-renewal capacity of the adherent CFUs decreased as the total number of CFUs per flask increased. After 3 weeks in culture, the self-renewal potential of the adherent CFUs stabilized and was maintained. These results suggest two different mechanisms of stem cell proliferation. In order to increase the most primitive stem cell pool size, there was initial proliferation of early stem cells with a concomitant decrease in self renewal capacity. Once this pool was established, the self-renewal capacity of the adherent CFUs maintained for 13 weeks in culture suggests that CFU production and cell maintenance were achieved by clonal succession.

Cyclic Oscillation of Blood Neutrophils in a Patient With Multiple Myeloma

Abstract A patient with multiple myeloma developed periodic blood neutropenia (periodicity of 15–25 days) after 3 yr of intermittent treatment with cytotoxic agents. Peaks of serum colony-stimulating activity (CSA) level coincided with valleys of blood neutrophils. Fraction of marrow neutrophils in the multiplicative pool was high during blood neutrophil valleys and low during neutrophil peaks. In contrast, the maturation storage pool exhibited the reverse pattern. An increased fraction of marrow neutrophilic cells in the multiplicative pool was in active proliferation during a blood neutrophil valley and a decreased fraction during a blood neutrophil peak. These findings suggest that the marrow granulopoiesis was regulated through CSA. The defect causing the periodicity was probably related to the reduced number of neutrophils in the marrow maturation storage pool, which in turn may be related to a reduced and/or defective granulocytic stem cell pool size consequent to the long-term administration of cytotoxic drugs and/or infiltration of the marrow by myeloma cells.

Cyclic oscillation of blood neutrophils in a patient with multiple myeloma

A patient with multiple myeloma developed periodic blood neutropenia (periodicity of 15-25 days) after 3 yr of intermittent treatment with cytotoxic agents. Peaks of serum colony-stimulating activity (CSA) level coincided with valleys of blood neutrophils. Fraction of marrow neutrophils in the multiplicative pool was high during blood neutrophil valleys and low during neutrophil peaks. In contrast, the maturation storage pool exhibited the reverse pattern. An increased fraction of marrow neutrophilic cells in the multiplicative pool was in active proliferation during a blood neutrophil valley and a decreased fraction during a blood neutrophil peak. These findings suggest that the marrow granulopoiesis was regulated through CSA. The defect causing the periodicity was probably related to the reduced number of neutrophils in the marrow maturation storage pool, which in turn may be related to a reduced and/or defective granulocytic stem cell pool size consequent to the long-term administration of cytotoxic drugs and/or infiltration of the marrow by myeloma cells.

Earlier Onset of Hematopoietic Differentiation after Expansion of the Endogenous Stem Cell Pool

In previous studies of growth and differentiation of endogenous hematopoietic spleen colonies (E-CFU), the time of resumption of differentiation after irradiation was increasingly delayed, but the rate of growth of the E-CFU compartment was not affected as the radiation dose was increased. These results suggested that differentiation might not occur until a critical stem cell pool size was attained. To further study this question, mice were injected prior to irradiation with substances which increase the E-CFU compartment; foreign plasma and endotoxin. Mice were injected daily for 4 days with human plasma or once with S. typhosa endotoxin 1 day prior to exposure to 580, 670, 770, 860, or 960 rads, and killed 3 to 10 days after irradiation. Plasma injection hastened the resumption of erythropoiesis, as measured by increased iron uptake, by about 5 days and endotoxin injection by about 3 days. Spleen weight and colony counts also increased earlier in treated mice. For each increment of 100 rads the time of onset of erythropoiesis was delayed an average of 1.5 days. The data are in accord with the concept that onset of differentiation after irradiation is geared to stem cell pool size.

Enhancement and Retardation of Spontaneous Reticulum Cell Neoplasm Development in SJL/J Mice<xref ref-type="fn" rid="fn2">2</xref>

The enhancement or delay in the appearance of spontaneous reticulum cell neoplasms (RCN-B) in SJL/J mice was tested. Immunosuppressive treatment with antithymocyte serum and prolonged antigenic stimulation by repeated injections of sheep erythrocytes, leukemogenic cell-free centrifugates, and multichain synthetic polypeptides had no effect on the incidence or latency of spontaneous tumor appearance. Treatment with mineral oil or incomplete Freund adjuvant markedly enhanced tumor appearance (though the abundance of plasma cells induced by these treatments did not evoke the development of plasmacytomas, nor did it affect the incidence of serum paraproteinemia among mice with spontaneous tumors). Treatment with cortisone acetate, however, markedly retarded spontaneous tumor development. Tumors occurring early due to mineral oil and adjuvant treatment all had the characteristics of "RCN-B plasma cell type," and tumors occurring late due to cortisone treatment were all of the "RCN-B reticulum cell type." The possible involvement of the stem cell pool size in the enhancement or delay of spontaneous tumor development was discussed.

In vivomeasurements of the production rates of bacteria in the rumen

SummaryThe production rates of bacteria have been measured in the rumen of zebu calves and buffalo calves. The animals were fed green oat continuously at 2 h intervals. [35S]sodium sulphate was fed to the animals for 5 days at 2 h intervals by mixing in the feed. On the sixth day the radioactive feed was stopped and replaced by non-radioactive feed. The decline in the specific radioactivity of bacterial cells in the rumen as a function of time was taken for calculatingt/2. Simultaneously rumen volume was determined and pool size of bacterial cells was calculated in the rumen. A mathematical equation was applied to calculate the production rates of bacteria. The production rates of bacteria, on average, were 100·5 and 72·3 mg/min for buffalo calves and zebu calves, respectively.

Primordial cell pool size and lineage relationships of five human cell types.

Primordial cell pool size and lineage relationships of five human cell types.

An analysis of the spacing of aggregation centers in Polysphondylium pallidum

The primary purpose of this investigation was to determine whether or not a nonrandom distribution of sorocarps occurs in Polysphondylium pallidum, and to determine the factors that are instrumental in determining distribution. While a nonrandom distribution of centers does occur, the determining factor is probably not a substance present in the gaseous phase of the environment. There is a correlation between the density of sorocarps on the substrate and their spatial distribution. The clustered condition (sorocarps closer together than expected on the basis of chance) is associated with a high density of fruiting bodies, while a spaced distribution (sorocarps further apart than expected) is often found at low densities. Random distribution apparently can occur at almost any density. Center density depends upon the rate of center formation. This rate is markedly enhanced if the cells are in the stationary phase at the time of harvest and deposition, and are exposed to charcoal, mineral oil, or light. The latter factors are thought to remove or act upon a center suppressing substance in the environment. Cells taken from the logarithmic phase, incubated in the dark, and in the absence of charcoal and mineral oil show a reduced rate of center formation and a low center density. Three hypotheses are presented to account for the apparent relationship between the rate of center formation and center density, and the spatial distribution of centers: (1) A spacing substance surrounding the center may prohibit other centers from forming in the immediate area; (2) spacing may result from the removal of cells through aggregation in the area immediately surrounding the center; (3) spatial distribution may be determined by the action of acrasin. In all cases, the longer the interval between the appearance of one center and another, the greater the area controlled by the first center and the more spaced the distribution. The “acrasin” and “cell-depletion” hypotheses are favored for their equal acceptability as an explanation and because the postulation of an additional, unknown factor is not required. The dependence of sorocarp density and distribution upon cell pool size is considered. It is suggested that high cell number favors both randomization, by leaving enough cells after the first burst of aggregation to form secondary centers, and clustering, because aggregates that contain a large number of cells often split into closely associated secondary centers. Low cell number results in areas virtually free of myxamoebae surrounding newly formed centers, a condition which strongly favors a spaced distribution. The possible relationship between spacing in cellular slime aggregation and spacing in other developing, biological systems is considered.

Relative Pool Size of Potentially Competent Antibody-Forming Cells of Primed and Nonprimed Spleen Cells Grown in in Vivo Culture

Summary Spleen cells from primed and nonprimed donors were cultured in lethally irradiated, isologous recipients and the relative pool size of PC cells was determined at varying intervals for 13 days under various experimental conditions. The results showed that the pool size of PC cells decreased to a minimum during the first 5 days after culture of nonprimed spleen cells. This decrease in pool size can be circumvented almost completely by the combined treatment of reduced radiation exposure to recipients and bone marrow therapy. It can be accentuated by exposing these cells to a noncross-reacting antigen when spleen cells are known to be proliferating and differentiating into terminal blood cells maximally. In contrast, the pool size of PC cells from primed donors neither increased nor decreased significantly during this period of observation and, furthermore, was not affected by these treatments. These results indicate that there exist, in accordance with the unidirectional flow model, at least two sequential compartments of PC cells, PC1 and PC2. Cells in the former compartment can be considered to be multipotent—capable of differentiating along several paths depending upon the stimuli—and those in the latter unipotent and therefore insensitive to hematopoietins and unrelated antigenic stimuli.

RESISTANCE TO 6-MERCAPTOPURINE: I. BIOCHEMICAL DIFFERENCES BETWEEN THE EHRLICH ASCITES CARCINOMA AND A 6-MERCAPTOPURINE-RESISTANT SUBLINE

A 6-mercaptopurine (6-MP)-resistant subline of the Ehrlich ascites carcinoma developed in this laboratory has been reported previously to lack the ability to synthesize thioinosinate, a characteristic believed to be related to mercaptopurine resistance. A comparison was made of various aspects of purine nucleotide metabolism in cells of the parent tumor line and the resistant subline in order to detect differences which, if they existed, might account for resistance to 6-MP.The synthesis of adenylate or of inosinate from adenine-8-C14was found to take place at similar rates in the two cell types under conditions in which adenylate renewal was independent of adenine-8-C14concentration. Both cell types synthesized adenylate and inosinate at comparable rates from hypoxanthine-8-C14and had equivalent adenylate deaminase activities. The size of the pool of inosinate in the tumor cells was measured by the isotope dilution method and that of the Ehrlich cells was found to be 1.6 times the pool size of the resistant cells. The conversion of guanine-8-C14to guanylate took place at similar rates in both tumors.In general, no differences in purine nucleotide metabolism were revealed which were obviously related to resistance or to the characteristic inability of the resistant subline to synthesize thioinosinate. This inability did not appear to be due to an inadequacy of the phosphoribosylpyrophosphate resources of the resistant cell, since the rates of purine nucleotide synthesis were similar in the two cell types. In Part II it is shown that extracts of the 6-MP-resistant cells catalyzed the synthesis of thioinosinate. It was concluded that the failure of intact resistant cells to synthesize thioinosinate was due to failure of 6-MP to enter the cell.

RESISTANCE TO 6-MERCAPTOPURINE: I. BIOCHEMICAL DIFFERENCES BETWEEN THE EHRLICH ASCITES CARCINOMA AND A 6-MERCAPTOPURINE-RESISTANT SUBLINE

A 6-mercaptopurine (6-MP)-resistant subline of the Ehrlich ascites carcinoma developed in this laboratory has been reported previously to lack the ability to synthesize thioinosinate, a characteristic believed to be related to mercaptopurine resistance. A comparison was made of various aspects of purine nucleotide metabolism in cells of the parent tumor line and the resistant subline in order to detect differences which, if they existed, might account for resistance to 6-MP.The synthesis of adenylate or of inosinate from adenine-8-C14was found to take place at similar rates in the two cell types under conditions in which adenylate renewal was independent of adenine-8-C14concentration. Both cell types synthesized adenylate and inosinate at comparable rates from hypoxanthine-8-C14and had equivalent adenylate deaminase activities. The size of the pool of inosinate in the tumor cells was measured by the isotope dilution method and that of the Ehrlich cells was found to be 1.6 times the pool size of the resistant cells. The conversion of guanine-8-C14to guanylate took place at similar rates in both tumors.In general, no differences in purine nucleotide metabolism were revealed which were obviously related to resistance or to the characteristic inability of the resistant subline to synthesize thioinosinate. This inability did not appear to be due to an inadequacy of the phosphoribosylpyrophosphate resources of the resistant cell, since the rates of purine nucleotide synthesis were similar in the two cell types. In Part II it is shown that extracts of the 6-MP-resistant cells catalyzed the synthesis of thioinosinate. It was concluded that the failure of intact resistant cells to synthesize thioinosinate was due to failure of 6-MP to enter the cell.