Plateau Phenomenon Research Articles

Sequential treatment of paget's disease with human calcitonin and dichloromethylene diphosphonate (CI 2MDP)

Dichloromethylene diphosphonate (CI 2MDP), a powerful inhibitor of bone resorption, was given (daily dose: 500 mg i.v. for 2 months and then 1600 mg p.o.) to five patients with Paget's disease after 8 months treatment with 50–100 MRC u/day of human calcitonin (CT). During treatment with CT plasma alkaline phosphatase (ALP) and urinary hydroxyproline (HOP) levels fell to about 60% of pretreatment values within the first 2 months in all the patients. CI 2MDP therapy resulted in a further drop of urinary HOP to 20% of baseline values, while serum ALP rose impressively during the first 2 weeks of therapy and then slowly fell to 25% of baseline values. We conclude that Cl 2MDP can induce a further biochemical response after the so-called plateau phenomenon to CT and that it may represent the therapy of choice for severe Paget's disease.

The oxygen uptake - work-output relationship of runners during graded cycling exercise: sprinters vs. endurance runners.

In order to study oxygen consumption (VO2) for a given work load at the exhaustive level of a graded cycling exercise in well-trained runners, a progressive cycle ergometer exercise test was performed on 9 sprinters and 12 endurance runners, all in good national standing; 12 sedentary men served as control subjects. The relationship between VO2 and work-output appeared to be linear in most of the subjects, but a plateau phenomenon was observed in two sprinters and two endurance runners. An upwards curvilinear increase in VO2 was noticed during the last two minutes of exercise in four endurance runners, but not in any of the sprinters. The four endurance runners with this unexpected increase in VO2 had a significantly higher (p < .01) "peak VO2" (mean = 75.3 ml.kg.-1.min.-1) than the rest of the endurance runners (mean = 55.1), and a significantly higher (p < .001) peak VO2 than the sprinters (mean = 46.0). It is concluded that the plateau phenomenon appears in runners during graded cycle ergometry, though rather seldom. It is less clear if the endurance runners showing the upwards curvilinear increase in VO2 possess a better aerobic performance capacity towards the end of progressive exercise. Nevertheless, the linear relationship between VO2 and work load does not appear to be the only one observed in runners during graded exercise.

Further resolution of adult chick hemoglobins by isoelectric focusing in polyacrylamide gel

Evidence is presented that adult chick hemoglobins exist in four types separable by isoelectric focusing on polyacrylamide gels instead of the two hemoglobin types previously resolved by other methods. These are hemoglobin A 1 (HbA 1), hemoglobin A 2 (HbA 2), hemoglobin D 1 (HbD 1), and hemoglobin D 2 (HbD 2). Their pI values are 7.53 ± 0.02, 7.37 ± 0.02, 6.92 ± 0.04 and 6.72 ± 0.05, respectively, constituting about 63, 14, 18 and 5% of the total hemoglobin from adult chick erythrocytes, respectively. HbA 1 and HbA 2 are identical in size, as determined on sodium dodecyl sulfate gels and similar in their amino acid composition and tryptic peptides. The molecular weights and amino acid composition of HbD 1 and HbD 2 are also identical although there are differences in their tryptic peptides. Experiments were done to show that the existence of four hemoglobin types is not due to genetic heterogeneity of the experimental animal, nor to artifacts of oxidation of carboxyhemoglobin to methemoglobin or of aggregation due to overloading or formation of multiple units of hemoglobin tetramers. Care was exercised to eliminate deamination and modification of side chain amino groups by using freshly prepared hemolysates and to minimize the “plateau phenomenon” peculiar to isoelectric focusing by controlling the duration of electrophoresis. The use of cyanmet form of (thus liganded) hemoglobin in this study reduced the chance of heterotetramer formation. Furthermore, consideration was given to possible anomalies caused by ampholytes. In the face of negative evidence for artifacts, it is concluded that adult chicken has more than the two hemoglobin types previously reported.

Thymidine labelling index as a criterion of aging in vitro.

For logarithmically growing cultures of the human diploid cell lines WI-38 and WI-26, there is an exponential increase in the fraction of cells not incorporating [3H]dT under conditions of continuous labelling. Thymidine uptake, phosphorylation and incorporation into DNA can be correlated with cell proliferation. In addition, determination of the labelling index is reproducible within relatively broad limits of thymidine concentrations and specific activity. The plateauing phenomenon of the curve expressing percent-labelled nuclei versus time, which occurs in populations with less than 100% cycling cells, is largely due to radiation damage to the cells. The results of these studies provide insight into the population dynamics of aging fibroblast-like cell cultures. More importantly, however, the measurement of labelling index as described can be used as a reproducible and quantitative measure of the age of the diploid cell culture.

Radiation-Induced Mixed-Disulfide Formation from Cystamine and Aliphatic Disulfides in Aqueous Solution

Solutions containing cystamine and dithiodiglycollic acid give, upon x-irradiation, the mixed-disulfide aminoethyldithioacetic acid. Yields increase with disulfide concentration, reach G values of 100 at 50 mM disulfide concentrations in air-saturated solutions, and undoubtedly reflect the occurrence of chain reactions. Radiolytic yields in deaerated solutions are double those in aerated solutions. A plateau phenomenon is observed; at a fixed cystamine concentration, mixed disulfide yields increase with increasing dithiodiglycollate concentration up to a certain point but do not increase significantly thereafter. This behavior indicates that dithiodiglycollate is much more reactive than cystamine in the chain-propagating step. Mixtures of cystamine with methyl and ethyl disulfides behave similarly. The reactive intermediate is unlikely to be a common species such as thiyl radical produced by interaction of both hydroxyl radicals and electrons with disulfide. Rather, two distinct species such as the disu...

The Effect of Carbon Dioxide Concentration of Atomospheric on Growth of Leaf Beet with Various Plant Densities

Dry matter production and plant density relationships of leaf beet plants were examined under a range of carbon dioxide concentrations from 0.03% to 0.6% CO2. Leaf beet plants (Beta vulgaris L, var. flavascens D. C.) were raised in gravel culture beds in polythin growth chambers from June 11 to July 10, 1965. The carbon dioxide concentrations in four chambers employed in this experiment were 0.03, 0.07, 0.15 and 0.6%, respectively. The each bed in the chambers was partitioned into four sections and the leaf beet plant with the height of 6 cm were transplanted in these sections at the densities of 50, 125, 292 and 500plants/m2, respectively.As can be seen in Fig. 1, the dry weight per unit area increased throughout the range of plant density values applied, although the initial increase is more rapid. The increase rate of the dry weight is larger for the chambers with high CO2 concentrations than for the chamber with usual CO2 concentration, indicating that the dry weight for the chamber with usual CO2 concentration is approximately constant in the range of plant densities over 200plants/m2 and LAI 6. On the other hand, the dry weight for the chamber with CO2 concentration of 0.6% did not show any saturating values throughout the range of plant density values applied.The value of absorptivity of incoming solar radiation of the plant canopy was measured for respective plots. The absorptivity decreases throughout the range of plant density values applied, although the initial decrease is more rapid (see Fig. 2.). In the range of plant density over 200plants/m2, no difference in the absorptivities was found among the chambers.The above results suggest that a principal cause for the plateau phenomenon in photosynthesis is not the limitation of absorption of incoming solar radiation by plant canopy, but the limitation of the supply of carbon dioxide from the atmosphere and soil to plant communities. This proposition is applicable to plant communities with foliage over LAI 6 under summer conditions in Japan.

Comparative levels and types of microbial contamination detected in industrial clean rooms.

The primary objective of this study was to determine quantitatively and qualitatively the predominant types of microbial contamination occurring in conventional and laminar flow clean rooms. One horizontal laminar flow, three conventional industrial clean rooms, and three open factory areas were selected for microbiological tests. The results showed that as the environment and personnel of a clean room were controlled in a more positive manner with respect to the reduction of particulate contamination, the levels of airborne and surface microbial contaminants were reduced accordingly. The chief sources of microbial contamination were associated with the density and activity of clean room personnel. In addition, the majority of microorganisms isolated from the intramural air by air samplers were those indigenous to humans. Studies on the fallout and accumulation of airborne microorganisms on stainless-steel surfaces showed that, although there were no significant differences in the levels of microbial contamination among the conventional clean rooms, the type of microorganism detected on stainless-steel surfaces was consistently and significantly different. In addition, the "plateau phenomenon" occurred in all environments studied. It was concluded that the stainless-steel strip method for detecting microbial accumulation on surfaces is efficient and sensitive in ultra-clean environments and is the most reliable and practical method for monitoring microbial contamination in future class 100 clean rooms to be used for the assembly of spacecraft which will be sterilized.

Comparative Levels and Types of Microbial Contamination Detected in Industrial Clean Rooms

The primary objective of this study was to determine quantitatively and qualitatively the predominant types of microbial contamination occurring in conventional and laminar flow clean rooms. One horizontal laminar flow, three conventional industrial clean rooms, and three open factory areas were selected for microbiological tests. The results showed that as the environment and personnel of a clean room were controlled in a more positive manner with respect to the reduction of particulate contamination, the levels of airborne and surface microbial contaminants were reduced accordingly. The chief sources of microbial contamination were associated with the density and activity of clean room personnel. In addition, the majority of microorganisms isolated from the intramural air by air samplers were those indigenous to humans. Studies on the fallout and accumulation of airborne microorganisms on stainless-steel surfaces showed that, although there were no significant differences in the levels of microbial contamination among the conventional clean rooms, the type of microorganism detected on stainless-steel surfaces was consistently and significantly different. In addition, the "plateau phenomenon" occurred in all environments studied. It was concluded that the stainless-steel strip method for detecting microbial accumulation on surfaces is efficient and sensitive in ultra-clean environments and is the most reliable and practical method for monitoring microbial contamination in future class 100 clean rooms to be used for the assembly of spacecraft which will be sterilized.

The relation of population heterogeneity to the plateau phenomenon in radiation doso-response curves.

The relation of population heterogeneity to the plateau phenomenon in radiation doso-response curves.

Quantitative studies of prostatic secretion. III. Simultaneous measurement of size and secretion of the canine prostate and the interaction of androgenic and estrogenic substances thereon.

The prostate of the dog was relocated permanently in the perineum where its size could be measured and correlated with the output of prostatic secretion during many months. The secretion of a submaxillary gland obtained through a fistula was utilized as an internal biologic standard of the effects of pilocarpine, the secretory stimulus employed, because the amount and route of administration of the alkaloid are critical factors in inducing secretion. Prostatic secretion was found to be profoundly affected by androgenic and estrogenic compounds, in contrast to salivation. The curves of the secretory response of the prostate and submaxillary glands to pilocarpine proved to be similar and a mathematical formula has been constructed to represent them. When testosterone propionate was administered in increasing quantities for periods of weeks at each level, the volume of the prostate increased in a series of flattened curves. This volume, under the conditions mentioned, was found to stand in a simple arithmetic relationship to the amount of testosterone propionate administered. Moderate quantities of testosterone propionate masked the effects of small amounts of stilbestrol on the prostate. The reverse was also true and the critical amounts of these compounds were defined. The amounts of stilbestrol were determined which lowered the quantity of prostatic secretion resulting from the simultaneous administration of moderate amounts of testosterone propionate in castrate dogs, the result being a level and flat secretory curve which was maintained for many weeks. We designate this effect the plateau phenomenon. When this amount of estrogen was continued, and the dosage of testosterone propionate greatly augmented, the prostatic secretion did not increase in volume. Very slight increases above the critical amount of stilbestrol, however, caused the secretory curve to fall to new and still lower levels though the secretion was never completely suppressed. The acid phosphatase content of the prostatic secretion in the regions of secretory plateaus was similar to that of castrate dogs injected with androgen alone. The plateau phenomenon is due to simultaneous physiologic action of androgenic and estrogenic compounds on the prostatic cells. The depression of prostatic secretion resulting in the plateau phenomenon is due to both functional and structural changes in the prostatic epithelium. They are best explained on the assumption that differences in steroid threshold exist in groups of cells within the prostate, those of the anterior rim of the gland being least susceptible to estrogenic activity.