True Stem Research Articles

Gas-Lift Valve Performance Testing and Data Correlation

Summary This paper presents a method for analyzing data from gas-lift valve performance tests. This method relies on the ability to determine the true dynamic stem position of the valve during flowing conditions. The types of tests required to obtain the data needed by this analysis method are explained. The data analysis method is applicable to any pressure-operated gas-lift valve and yields predictions within 10% of actual flow rate.

Lymphoid differentiation of the hematopoietic stem cell that reconstitutes total erythropoiesis of a genetically anemic W/Wv mouse

We investigated whether the stem cell that reconstitutes total erythropoiesis of a WBB6F1-W/Wv mouse differentiates into lymphoid lineage. The electrophoretic pattern of hemoglobin was used as a marker of the reconstitution; 3-phosphoglycerate kinase (PGK), an X chromosome- linked enzyme was used as a tool for estimating clonality. We injected 10(5) bone marrow cells of 5-FU treated C57BL/6-Pgk-1b/Pgk-1a female mice, in which each stem cell had either A-type PGK or B-type PGK due to random inactivation of one of two X chromosomes, into genetically anemic (WB x C57BL/6)F1-W/Wv (hereafter WBB6F1-W/Wv) mice that contained only B-type PGK. The recipient WBB6F1-W/Wv mice, in which erythropoiesis was reconstituted with donor cells for a long term, were killed and the PGK patterns of bone marrows, thymus, lymph nodes, and Peyer's patches were examined. A considerable amount of A-type PGK was detected in the lymphoid organs of the WBB6F1-W/Wv mice in which erythrocytes showed only A-type PGK when killed. In contrast, A-type PGK was scarcely detectable in the lymphoid organs of the WBB6F1-W/Wv mice in which erythrocytes showed only B-type PGK when killed. The present results suggest that the hematopoietic stem cells estimated by the erythropoiesis reconstituting assay differentiate into lymphoid lineage and that the long-term erythropoiesis reconstitution assay is useful for detecting the true primitive hematopoietic stem cells.

Lymphoid Differentiation of the Hematopoietic Stem Cell That Reconstitutes Total Erythropoiesis of a Genetically Anemic W/WvMouse

We investigated whether the stem cell that reconstitutes total erythropoiesis of a WBB6F1-W/Wv mouse differentiates into lymphoid lineage. The electrophoretic pattern of hemoglobin was used as a marker of the reconstitution; 3-phosphoglycerate kinase (PGK), an X chromosome-linked enzyme was used as a tool for estimating clonality. We injected 10(5) bone marrow cells of 5-FU treated C57BL/6-Pgk-1b/Pgk-1a female mice, in which each stem cell had either A-type PGK or B-type PGK due to random inactivation of one of two X chromosomes, into genetically anemic (WB x C57BL/6)F1-W/Wv (hereafter WBB6F1-W/Wv) mice that contained only B-type PGK. The recipient WBB6F1-W/Wv mice, in which erythropoiesis was reconstituted with donor cells for a long term, were killed and the PGK patterns of bone marrows, thymus, lymph nodes, and Peyer's patches were examined. A considerable amount of A-type PGK was detected in the lymphoid organs of the WBB6F1-W/Wv mice in which erythrocytes showed only A-type PGK when killed. In contrast, A-type PGK was scarcely detectable in the lymphoid organs of the WBB6F1-W/Wv mice in which erythrocytes showed only B-type PGK when killed. The present results suggest that the hematopoietic stem cells estimated by the erythropoiesis reconstituting assay differentiate into lymphoid lineage and that the long-term erythropoiesis reconstitution assay is useful for detecting the true primitive hematopoietic stem cells.

In vivo dynamics of CD4-8- thymocytes. Proliferation, renewal and differentiation of different cell subsets studied by DNA biosynthetic labeling and surface antigen detection.

The proliferative status of CD4-8- thymocyte subsets was determined by in vivo or in vitro labeling with bromodeoxyuridine (BrdUrd), a nonreutilized thymidine analogue detectable with a monoclonal antibody, simultaneously with relevant surface proteins. An actively cycling subset [J11d+, interleukin 2 receptor-positive (IL 2R+)] was defined, besides a relatively resting one (J11d-, Pgp1+, T cell receptor-positive). Continuous per os administration of BrdUrd showed that 85% only of CD4-8- thymocytes were labeled in 6 days confirming the existence of a relatively long-term resting subset. By contrast, CD4+8+ thymocytes were all labeled in 3-4 days. Observation of labeled CD4-8- cells after pulse labeling showed an immediate decrease of their absolute number per thymus, confirming their low autorenewal capacity. However, a small number of labeled cells which were hydroxyurea or colchicine resistant remained CD4-8- for several days and progressively acquired surface expression of IL 2R. IL 2R expression by cycling CD4-8- cells during thymus regeneration after antimitogenic drug treatment was rapid, but very transient. According to these results most CD4-8- thymocytes appear as largely engaged in a proliferation-dependent differentiative process, and do not behave as true stem cells. Consequently, this subset is principally renewed by thymic immigration of exogenously produced resting cells. However, a tenfold expansion of CD4-8- cells was found in the fetal and regenerating thymus, suggesting two proliferative phases during intrathymic CD4-8- cell maturation, the first one yielding to cell expansion and the second to cell differentiation. A tentative evaluation of daily cell immigration is proposed starting with the determination of the number of cells beginning DNA synthesis each day. A global model is finally discussed by confronting our kinetic results with the known reconstitution capacities of CD4-8- thymocyte subsets.

Prediction of induction and duration of complete remission in acute myelogenous leukemia: value of clonogenic cell properties.

The in vitro clonogenic assay in acute myelogenous leukemia (AML) has brought the possibility to study the proliferative and differentiating capacity of the clonogenic cells as well as their in vitro sensitivity to antileukemic drugs. Although these clonogenic cells do not represent the true leukemic stem cells, their properties of colony formation and in vitro self-renewal have been considered to reflect the characteristics of the leukemic proliferation and be correlated with the outcome of the disease [8].

Effect of grazing intensity in spring on pasture growth, composition and digestibility, and on milk production by dairy cows

Two 20-block farmlets, each of 6.5 ha, were rotationally grazed by milking cows in spring at stocking rates of 1.9 and 3.4 cows/ha to give a low (LGI) or high (HGI) grazing intensity. These grazing intensities were designed to simulate dairy farms with low or high levels of pasture conservation, and resulted in post-grazing residues of2.6 (LGI) and 1.7 (HGI) t/ha DM by late spring. Over summer, the 2 groups of cows continued to graze their respective areas, but spare cows were re-allocated between the groups so that stocking rates were the same at 1.7 cows/ha. The HGI cows produced 1 kg less milk fat (0.79 v. 0.81 kg/day.cow, P> 0.05) in spring (15 October-30 November), but produced significantly (P < 0.05) more milk fat (0.63 v. 0.59 kg/day.cow) and 1.3 kg milk protein (0.44 v. 0.42 kg/day.cow) in summer (1 December-1 February). Despite the higher grazing intensity in spring. there was no difference in intake of pasture or in digestibility of herbage selected by the cows in the two herds. In summer the HGI swards contained less dead herbage (P<0.05) but a similar quantity of green herbage compared with the LGI swards, and, compared with LGI cows, the HGI cows removed a higher proportion of this green herbage during grazing. Digestibility of the LGI swards was lower because of the higher content of dead herbage but cows in both groups rejected this dead material and selected a diet of similar digestibility. The presence of dead herbage in the LGI swards appeared to reduce animal production by reducing availability and intake of green herbage rather than by reducing the digestibility of the diet selected by the cows. The high grazing intensity increased daily net accumulation of grass leaf in spring (1 7 v. 6 kg/ha of DM, P< 0.05) but reduced that of true stem (-4 v. 28 kg/ha, P < 0.10) and of total herbage (43 v. 54 kg/ha, P<0.10). The HGI swards had higher ryegrass tiller densities in summer and higher (P<0.05) net accumulation rates of herbage in summer through to winter). Increased grazing intensity in spring above normally accepted levels increased pasture utilisation in spring and summer, and milk production in summer, and increased the quantity of spring herbage available for conservation.

Electronic Roundwood Measurement and Connected Data Processing Computer as a Basic System for Automatic Log Yards

The electronic roundwood measurement supplies the basic data for the automated log yard. Elektronikbau Krippner & Kletzmaier have to date equipped over 120 sawmills with infra-red computer scanners or camera measurement systems. Depending on the thickness of the wood and the mode of application of the roundwood measuring systems, the sawmiller can choose between single or twin axis measuring systems and various resolutions (= degree of accuracy of measurement). The quality of an electronic roundwood measuring system is not only determined by the degree of accuracy of measurement, but also by factors such as sensitivity to external light, automatic error diagnosis, scanning speed, computer selection programme for the recognition of branch ends and true stem begin and stem end. By means of standardized interfaces data processing computers can be connected to the measuring systems.

The dynamics of the flavour precursors, the S‐alk(en)yl‐L‐cysteine sulphoxides, during leaf blade and scale development in the onion (Allium cepa)

This study was undertaken to determine the patterns of accumulation and loss of the flavour precursors. (+) S‐1‐propyl‐L‐cysteine sulphoxide, (+) trans‐S‐1‐propenyl‐L‐cysteine sulphoxide, and (+) S‐1‐methyl‐L‐cysteine sulphoxide, during the development and senescence of the leaf blades and scales of a brown onion (Allium cepa L. cv. Pukekohe Longkeeper).The levels of the flavour precursors were related to the ontogeny of the individual leaf blade and scale, and the ontogeny of the entire plant. Leaf blades which developed on a young or bulbing onion contained all 3 flavour precursors (total of about 50–70 mg leaf−1); but as each attached scale developed, the leaf blades lost their flavour precursors. All 3 flavour precursors increased in the developing scales and decreased in the senescing scales. Leaf blades which developed on an older, ripening onion contained, and then lost, only (+) S‐1‐propyl‐L‐cysteine sulphoxide, whilst the scales accumulated only (+) S‐1‐propyl‐L‐cysteine sulphoxide; (+) S‐1‐methyl‐L‐cysteine sulphoxide and (+) trans‐S‐1‐propenyl‐L‐cysteine sulphoxide were minimal. In the main scales of the onion, which did not senesce during ripening, there was a transition between these two patterns. These scales accumulated all 3 flavour precursors with (+) S‐1‐propyl‐L‐cysteine sulphoxide remaining constant at about 30 mg/scale; however there was a 10 fold loss of the other 2 flavour precursors (from 20 to about 2 mg/scale). The base plate (true stem) contained mainly (+) S‐1‐propyl‐L‐cysteine sulphoxide, which increased 5 fold in amount during bulbing. The other 2 flavour precursors were present at much lower levels.A recycling of flavour precursors is suggested, with the leaf blades supplying flavour precursors to scales, and in turn older senescing scales recycling their flavour precursors to developing younger scales.

Some consequences of imposing different continuous grazing pressures in the spring on sward morphology, herbage quality and the performance of young beef cattle

SUMMARYThe effects of different severities of continuous grazing imposed during the spring followed by a uniform continuous grazing management from midsummer onwards were examined in relation to sward morphology, herbage quality and the performance of young beef cattle in the years 1980 and 1981. The three grazing severities were based upon maintaining a constant sward height, namely 35 mm (severe), 50 mm (moderate) and 75 mm (lenient). From 1 June onwards a uniform grazing severity with a sward height of 60 mm was imposed. The grazing pressure on each paddock was adjusted by either adding or removing of cattle to maintain the target sward heights. When the grazing pressure was changed in June, the digestibility of both the herbage components on offer and the total herbage selected by the cattle was higher in the swards that had been severely grazed than that in the leniently grazed treatments. This appeared to be due to the combination of a higher proportion of younger, more digestible leaf laminae, less dead and less maturing true stem being present in the swards that had previously been severely grazed. Over the season as a whole, there was no significant difference between the grazing treatments in terms of individual animal performance or overall animal live-weight production per hectare.

How reliable are in vitro clonal cultures? Some comments based on hemopoietic cultures.

Clonal cultures in semisolid medium have proved invaluable in analyzing hemopoietic subpopulations and in detecting their specific growth regulators. However, they can be subject to certain deficiencies that an investigator must take care to exclude. These include inabilities of the particular culture system to detect the true stem cells under study or to allow self-generation of clonogenic cells or a full expression of their differentiation potential. Clonal cultures, like conventional cultures, can be subject to significant cell-cell interactions, complicating attempts to characterize the action of a test regulatory molecule. Culture data need to be supplemented by a variety of other data before they can be regarded as valid evidence that a regulatory molecule detected in vitro is likely to function in a similar manner in vivo.

Human hematopoietic progenitor cells in long-term cultures express HLA-DR antigens and lack HLA-DQ antigens.

The expression of HLA-DR antigenic determinants on human hematopoietic progenitor cells (HPC) capable of differentiating into mature blood cells, as determined in semisolid cultures, has been demonstrated previously (3-7). Here, we investigated the expression of class II determinants on HPC responsible for the sustained proliferation of colony-forming units of granulocyte/macrophage (CFU-GM), of multilineage HPC (CFU-GEMM, granulocyte/erythrocyte/macrophage/megakaryocyte), and burst-forming units of erythroid cells (BFU-E) in liquid long-term cultures. Using both fluorescence-activated cell sorting and complement-dependent cytotoxicity assays, HLA-DR determinants could be identified on virtually all these HPC capable of proliferating in long-term cultures. Experiments in which the stromal layer had been irradiated provided evidence that the HPC themselves were truly HLA-DR+, and that the sustained proliferation of HPC was not due to activation of HLA-DR- residual HPC in the stromal layer by reinoculated HLA-DR+ accessory cells. Furthermore, it was shown that all HPC recognized in semisolid and liquid long-term cultures were HLA-DQ-. These results suggest that the human true pluripotential stem cell is HLA-DR+. These results open the possibility of studying class II-dependent regulation of hematopoiesis in liquid long-term cultures.

Concurrent Myelodysplasia and Lymphoproliferation: a Disorder of the True Pluripotential Stem Cell?

The lymphoproliferative disorders and the myelodysplastic syndromes are thought to result from the clonal expansion of a single abnormal precursor cell. Seven patients who were found to have concurrent myelodysplasia and lymphoproliferation are described. In all cases myelodysplasia and lymphoproliferation were diagnosed simultaneously or myelodysplasia preceded overt lymphoproliferation by a brief interval. Thus, myelodysplasia in these patients was not related to treatment given for a lymphoproliferative disorder. Stem cell theory is reviewed with special reference to evidence for an adult human stem cell common to both haemopoietic and lymphoid cell lines (CFU-L-M). The presence of concurrent myelodysplasia and lymphoproliferation in these seven patients may be the result of the clonal expansion of an abnormal pluripotential stem cell. It may be possible in some cases to achieve remission of the lymphoproliferative disorder with return of normal haematopoiesis if residual normal stem cells are present and repopulate the marrow following cytotoxic therapy.

Herbage losses from tiller pulling in a continuously grazed perennial ryegrass sward

AbstractTiller pulling was studied in a perennial ryegrass sward that was continuously grazed by cattle. The treatments included severe (sward height after grazing 25 mm), medium (50 mm) or lenient (75 mm) grazing from turn‐out in April to 1 June, followed by grazing to 50 mm in the remainder of the season. Tiller pulling was confined to the midsummer‐autumn period of the grazing season. The losses were most severe in swards that had been leniently grazed to a mean height of 75 mm during the spring and least severe in swards grazed to a height of 25 mm. The lenient grazing treatment allowed both the true stem development and aerial tillering whereas in the more tightly grazed swards true stem development was significantly less and aerial tillering was virtually absent. The pulled organic matter in the lenient treatment was equivalent to about 5·3% of the total harvested yield. In the severely grazed swards, pulling losses were equivalent to about 1·7% of the total harvested yield. A high rate of turnover of the pulled herbage was found in all the treatments with between 69 and 78% of the freshly pulled herbage disappearing within a week of being pulled. Tiller pulling was found to have no effect on either the subsequent autumn‐winter tiller density or yields of cuts taken in the following year.

The rate of water loss from cut grass of different species dried at 20°C

AbstractThe water loss from tall fescue cv. S170, perennial ryegrass cv. S24, Italian ryegrass cv. RvP and timothy cv. S352 when dried as a thin layer under controlled conditions at 20°C and r.h. 50% is described. Comparisons were made on six occasions between mid‐April and mid‐June. Tall fescue dried faster than the other species and the time to reach a water concentration of 0·2 g water per g dry matter varied little between the six harvests. In contrast, the drying time for the ryegrasses and timothy increased to maximal values in mid‐May and then fell. Drying time was dependent on the initial water concentration of the grass, the ratio of leaf to stem and on the amount of true stem exposed to the drying environment. The practical implications in relation to haymaking are discussed.

Neuronal degeneration and regeneration in the olfactory epithelium of pigeon following transection of the first cranial nerve

The pigeon olfactory nerve has been sectioned to explore the course of retrograde degeneration of the sensory neurons' perikarya, which are located in the olfactory neuroepithelium. Both light- and electron-microscopic observations have shown that from 3 to 8 days after axotomy the sensory neurons undergo retrograde, irreversible degeneration. Following disappearance of the mature neurons, the basal cells of the neuroepithelium actively divide and differentiate into mature olfactory sensory neurons. Consequently, the basal cells represent true stem cells of the olfactory sensory neurons. The olfactory mucosa regains a structural organization close to normal in a period of 30-50 days after axotomy. These observations indicate that, when the primary olfactory neurons degenerate as a consequence of the experimental section of their axons, restitutio ad integrum of the sensory olfactory connections can be reestablished by new elements which differentiate from basal cells of the olfactory neuroepithelium.20

Comparisons of the In Vitro Dry Matter Digestibility of Forage Oats Grown under Different Temperatures and Light Intensities

Two experiments were conducted with forage oats to find the effects of temperature and light intensity on in vitro dry matter digestibility (IVDMD). The IVDMD of the main shoot and its component leaves and stems, showed declines with the increase in temperature. The differences in the IVDMD of leaves were caused by the temperature effects on lignification, on the rate of leaf appearance, accordingly on the age of the leaves, and on the dry matter distribution pattern among leaf positions. Higher temperature seemed to increase slightly the rate of decline in IVDMD of a leaf with aging. Stem IVDMD was influenced by true stem formation and lignin deposition at higher temperatures. With the decrease in light intensity the IVDMD of the stem of the main shoot, and, as a result, of that of the whole main shoot and that of the whole top of a plant showed slight declines. CWC content was not affected very much, but nitrogen content increased and also ADF content slightly increased under lower light intensities. The positive effect of light intensity on IVDMD was partly concerned with its effect on ADF content and attributable to its effect on CWC digestibility.

The effect of interval between harvests and nitrogen application on the proportion and yield of crop fractions and on the digestibility and digestible yield and nitrogen content and yield of two perennial ryegrass varieties in the second harvest year

SummaryThe effect of six intervals between harvests and three levels of N application on the dry-matter yield of total herbage, the proportion and yield of green leaf, dead leaf, ‘stem’ and inflorescence of the sown species, the proportion and yield of unsown species, the digestibility and digestible yield and N content and yield was studied in S. 23 and S. 321 perennial ryegrass during a 30-week period in the second harvest year in a field experiment. In S. 23 the ‘stem’ was divided into true stem, leaf sheath, unemerged leaf and unemerged inflorescence.The results supported the main findings from the first harvest year (Wilmanet al.1976a, b).There was marked ingress of unsown species in the second harvest year with 3-, 4- and 5-week intervals in S. 321. The combination of 262–5 or 525 kg N/ha/year and 8- and particularly 10-week intervals over 2 years was too severe a treatment for the satisfactory survival of S. 23. With 525 kg N and 10-week intervals, S. 321 was equally badly affeoted.The application of 525 kg N/ha/year compared with nil reduced the proportion of green leaf in total herbage of the sown species by 11 percentage units, on average, and increased the proportion of ‘stem’ by 12 percentage units, in the second harvest year. The effect of N application on the proportion of crop fractions was found in both varieties and in all months of harvest. The effect was much greater than in the first harvest year. In S. 23 the application of 525 kg N compared with nil in the second harvest year increased the proportions of both true stem and leaf sheath (in total herbage of the sown species), true stem being the more important of the two, in this context, with the longer intervals and leaf sheath being the more important with the short intervals.Digestibility was not in general affected by N application despite the higher proportion of stem and leaf sheath and the lower proportion of green leaf blade resulting from N application. N did, however, tend to reduce digestibility at the harvests at which the proportion of stem was highest.Digestibility varied from one time of the year to another with a constant interval between harvests, but not as much as in the previous year. Lower digestibility of leafy crops in summer and autumn than in April and early May in both years may have been partly due to a higher proportion of dead material.Three periods were distinguished approximately in both years: May-June, July-August, and September-October. Only in the first of these periods was there a substantial increase in yield of digestible organic matter as a result of doubling the interval between harvests. Doubling the interval reduced digestibility in all three periods, but especially at harvests within the second period. Yield response to N was large in the first period, intermediate in the second, and low in the third. Apparent recovery of N was low and N content of herbage unduly high in the third period. N content of herbage was low with the long intervals between harvests at harvests in the first two periods. Applied N increased N content at these harvests and at all other times.

The effect of interval between harvests and nitrogen application on the proportion and yield of crop fractions in four ryegrass varieties in the first harvest year

SUMMARYThe effect of six intervals between harvests and three levels of N application on the proportion and yield of green leaf, dead leaf, ‘stem’ and inflorescence was studied in four ryegrass (Lolium) varieties during a 30-week period in the first harvest year in a field experiment. In one variety, S.23, the ‘stem’ was divided into true stem, leaf sheath, unemerged leaf and unemerged inflorescence.There was a bigger yield of ‘stem’ and a bigger total herbage yield response to doubling the interval between harvests in S.321 and S.22 than in S.23 and S.24.In the absence, but not generally in the presence, of applied N, S.321 outyielded the other varieties. S.24 was particularly responsive to applied N, especially in terms of green leaf yield.There was a large positive effect on yield of doubling the interval (from 3, 4 or 5 weeks to 6, 8 or 10 weeks respectively) during the main period of stem development. During the subsequent period, however, doubling the interval produced very little extra yield of total herbage and reduced green leaf yield substantially.The percentage increase in yield due to the application of N progressively decreased as the interval was increased.Maximum net production of green leaf was obtained by harvesting every 4 or 5 weeks for most of the season, extending to 6 weeks at the end. Harvesting every 3 weeks, by comparison, resulted in a slightly lower annual green leaf yield, but with a distinctly higher proportion of green leaf in the crop.Applied N generally had little effect on the proportion of crop fractions, but reduced the proportion of green leaf and increased that of' stem' in S.23 and S.24 at the August and September harvests.

Interrelations in the growth and development of Lolium. I. Some effects of vernalization on growth and development

The responses of Lolium rigidum Gaud. and L. perenne L. to low temperature seed vernalization were determined by comparing the growth and development of vernalized and unvernalized plants raised in the field and in a controlled environment cabinet. Vernalization did not appear to influence growth in the vegetative phase, but usually induced earlier heading and a greater proportion of reproductive tillers. Comparisons of vernalized (reproductive) and unvernalized (vegetative) plants show increased reproductive development to be associated with higher growth rates, lower tillering, and greater weight per tiller. High growth rates during the reproductive phase are considered to be due to the ability of reproductive tillers to grow more rapidly than vegetative tillers through the growth of true stem functioning as a "sink" for assimilate. Generalized growth curves for vernalized and unvernalized ryegrass grown under long days are presented and discussed.

EVIDENCE OF CIRCUMNUTATIONAL GROWTH MOVEMENTS OF RHIZOMES OF POA PRATENSIS L. THAT AID IN SOIL PENETRATION

The growth of rhizomes of Poa pratensis L. through dense soil was studied by means of an apparatus consisting of a short, pivoted, balance arm having, at one end, a cone into which a rhizome tip was guided, and at the other end, an inclined mirror onto which a collimated light beam was directed, the reflection being projected onto the distant wall of a darkened room.At 1000 × magnification a circular, clockwise, 24 hour rotation of the rhizome tip was observed. The actual diameter of revolution was between 0.5 and 3.0 mm.At 1000 × magnification a minor, circular, clockwise, revolution of 1 to 2 hours period, superimposed on the major revolution was determined. The actual diameter of revolution was between 0.001 and 0.010 mm.The major and minor revolutions were circumnutational movement rather than torsional twisting. The region of both movements was the ultimate 2 to 3 cm of the rhizome. Both the ultimate cataphyll and the true rhizome stem were involved.These rotational movements undoubtedly aid the rhizome in penetration of the soil.