Length Of Exposure Time Research Articles

Mitogenesis in human lymphocytes following brief exposure to hyperthermia

Whole blood obtained from normal human donors was incubated in vitro at temperatures ranging from 37°C to 51°C for 30 min. Immedlately following this incubation, whole blood cultures were established for assaying lymphocyte transformation in response to phytohemagglutinin (PHA) pokeweed mitogen (PWM) and concanavalin A (Con A). These cultures were maintained throughout the remainder of the experiment at 37°. Mitogenesis was minimally affected with pretreatment at 41°, significantly impaired at 43°, and totally abolished following brief exposure to temperatures in excess of 44°. In contrast, lymphocyte viability by trypan blue exclusion remained >99 % after a 30 min exposure to temperatures as high as 47° and was approximately 50% after 30 min at 53.5°. The length of exposure time (within the range of 30–120 min) became a critical variable at threshold temperatures at which impairment of mitogenesis was detectable with this assay system. This threshold temperature appears to pie within a very narrow range, similar to that in which tumor cell damage occurs. The necessity for accurate monitoring of both intratumor and core temperatures during treatment is apparent from these data. The response of heat-treated and control lymphocytes to optimal mitogen concentrations was compared to the response to sub-optimal (50% of optimal) concentrations. No differential effects of time (30, 60 min) and temperature (41°, 43°) were evident with the suboptimal concentrations.

Influence of hormone concentration and time factor on development of receptor memory in a unicellular ( Tetrahymena) model system

1. 1. Treatment of Tetrahymena pyriformis cells with diiodotyrosine (T 2) gave rise to a considerable, concentration-dependent increase of the growth rate within the range of 10 −15 and 10 −9 M, but did not influence it at the level of 10 −18 M. 2. 2. Re-exposure of the cells 1, 2 and 4 weeks later to the hormone concentrations originally used accounted for a marked increase of growth rate at all hormone levels tested, indicating that the extremely low concentration of 10 −18 M, which failed to stimulate growth on first exposure, did nevertheless give rise to hormonal imprinting, which caused the cells to “remember” the hormone, as judged from their increased responsiveness to it on re-exposure. 3. 3. The degree of growth response was concentration-dependent on both first and second exposure: higher levels of treatment gave rise to firmer imprinting, and to greater response on re-exposure. 4. 4. The length of exposure time proved to be more decisive than the level of treatment in respect of the development of hormonal imprinting. 5. 5. Short-term exposures up to 60 min, although they stimulated cell growth by direct effect, gave rise to lasting inhibition of cellular response to re-exposure(s) rather than to hormonal imprinting.

Three-dimensional observation of the radioactive concanavalin A receptors on the surface of human red blood corpuscles utilizing scanning electron microscope autoradiography.

Autoradiography combined with scanning electron microscopy (SEM-ARG) was applied to visualize the Con A receptor sites of human red blood corpuscles. Prepared erythrocytes on a glass slide were coated with emulsion by a dipping technique after evaporation by carbon under clean vacuum condition with a cooling trap of liquid nitrogen. Silver halide crystals in the emulsion were distritubed homogeneously on the surface of the erythrocytes. In these experiments, emulsion degelatinized by centrifugation seemed superior to normal emulsion. The remaining gelatin was removed by distilled water at 45°C after development.Electroconductive staining with tannic acid and osmium tetroxide was effective in obtaining good electron contrast and also in preventing artifacts due to the autoradiographic procedure. The number of developed silver grains on the surface of the red blood cells was proportional to the length of exposure time. After exposure for 8 weeks, the average number of grains was calculated to be 312.46±76.07 (3H-Con A-labeled specimen) or 372.58±106.05 (125I-Con A-labeled specimen) per single red blood corpuscle face. The SEM image of the grains was spherical or filamentous, so it was easy to distinguish the grains from the red blood cell surface. On the specimens labeled with 3H-or 125I-Con A, a large number of developed silver grains were distributed homogeneously on the surface of the red blood cells, but on the cells labeled with the same radioactive Con A containing α-metllyl-d-mannoside, there were almost no grains present on the surface. Therefore, the distribution of the developed silver grains probably represents Con A receptor sites.SEM-ARG seems to be a valuable method for the visualization of receptors on the cell surface, even though several problems still remain.

Development of some lepidopterous cotton pests as affected by exposure to sublethal levels of endotoxins of Bacillus thuringiensis for different periods

Three spore-δ-endotoxin preparations from Bacillus thuringiensis vars. kurstaki and entomocidus including a commercial biological insecticide, Thuricide, were studied with respect to their biological interactions with the lepidopterous cotton pests, Spodoptera littoralis, Spodoptera exigua, and Heliothis armigera. The biological effects of sublethal doses and the length of exposure time to low endotoxin concentrations were assessed during and after removal of toxin from the diet. Retardation in larval development, reduction in egg production of the moths, and fertility of the egg were observed together with significant reduction in pupal weight and appearance of deformities in both pupae and moth populations. The influence of exposure to sublethal toxin concentrations was also manifested in term of decreasing the adult emergence, fecundity reduction, and prolonging the generation period. In the exposed insects, the precentage of larvae that survived and succeeded to pupate increased with the decrease in the toxin concentration and with the decrease in exposure time. The reduction of the pupal weight significantly increased with the increase in either toxin concentration or the duration of exposure. The longevity of the moths was not affected by larval treatment and the data showed no clear correlation with the concentration and time of larval exposure to the toxin.

X‐Ray photoelectron spectroscopic study of the aqueous oxidation of stellite‐6 alloy

AbstractThe aqueous oxidation of the cobalt allow Stellite‐6 has been studied in pH 10 water 285°C, as a function of dissolved oxygen concentration and length of exposure time. The result surface films were analysed by X‐ray photoelectron spectroscopy (XPS) and other techniques. Using XPS, a quantitative measurement of the oxide and metallic surface components was obtained and depth‐concentration profiles were determined. The effect of gaseous oxidation on the surface composition was also studied, and from a comparison of the oxidation behaviour under aqueous and gas phase conditions, solid state and solution‐transport processes could be distinguished. The gas phase studies showed that cobalt ions diffuse preferentially to the outer surface. During aqueous oxidation, however, the surface composition is found to be depleted in cobalt; preferential dissolution of the cobalt component of the alloy is therefore occurring under these aqueous conditions.

The Effect of Physical Factors on the Colonization and Relocation Behavior of Immature Black Flies (Diptera: Simuliidae) 1

Water velocity, substrate placement and the length of exposure time influenced the number of Prosimulium mixtum/fuscum Syme and Davies and Cnephia dacotensis Dyar and Shannon larvae attaching to white ceramic tiles and clear plastic tapes in the field. P. mixtum/fuscum readily attached to either substrate whereas C. dacotensis demonstrated a preference for white ceramic tiles. In an artificial stream, both species preferred specific velocity ranges although they did not increase their relocation behavior when exposed to varying depths of 2 to 30 cm and temperatures of 2° to 30°C. P. mixtum/fuscum increased relocation behavior in the absence of light.

Change in risk factor and the development of chronic disease. A methodological illustration

This report examines and suggests solutions for the methodological problems usually encountered when the relationship between the rate of change in risk factors and the development of chronic disease is studied. The general pattern of changes in body mass index (BMI), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were compared between two groups: one including 525 subjects who developed ischemic heart disease (IHD) and/or stroke (CVA) over 26.5 yr of follow-up (IHD/CVA) and another group of 2877 subjects who remained free from these diseases during the same follow-up period (reference group). The longitudinal trends of these factors in classes of age, BMI, SBP and DBP at entry were found to be similar in both groups, and it was then concluded that comparisons could be made on parameters characterizing the elevation model of each factor; the attained level and the rate of change. It was also recognized that there were between-individual differences in the number of examinations, the length of exposure time and the time of exposure; and within-individual difference in the rate of change over different time periods. Furthermore, there was statistical artifact to be avoided. To consider and account for these problems, it was suggested that the cohort subjects be grouped retrospectively, and the rate of change in factors under study, be compared prospectively and separately in different time periods within classes classified according to the initial attained levels of all factors of interest. For simpler comparisons a frequency-adjustment method was also provided for summarizing the rates of change in time periods within each class. The data showed that IHD/CVA group not only had higher initial attained levels of age, BMI, SBP and DBP than the reference group, but also had larger subsequent rate of change in both SBP and DBP before the manifestation of IHD/CVA. The BMI rate of change did not show apparent difference between the two groups. These differences were compared and observed in classes classified according to age, BMI, SBP and DBP at entry. The differences on the rate of change in blood pressure were further supported by the findings that the incidence of ‘hypertension’ was higher, and among the ‘hypertensives’, the length of time to reach the status of ‘hypertension’ was shorter in the IHD/CVA group than in the reference group. Multiple logistic function analyses showed that the initial attained levels of age, BMI. SBP and DBP were all significantly, positively and independently associated with the risk of ‘hypertension’, and as a risk factor, the development of ‘hypertension’ after entry was closely related to the development of IHD/CVA, independent of the initial attained levels of age, BMI, SBP and DBP. Further evidence was presented to clarify the issue on the relationship between the attained level and the rate of change in blood pressure. It was concluded that the initial level and the rate of change in systolic blood pressure were two independent factors and they should be treated as such.

Stimulation by organic solvents and detergents of conversion of L‐sorbose to L‐sorbosone by Gluconobacter melanogenus IFO 3293

Treatment of Gluconobacter melanogenus IFO 3293 cells with benzene, carbon tetrachloride, cyclohexane, deoxycholate, toluene, or xylene stimulated their conversion of L-sorbose to L-sorbosone two- to threefold. The degree of stimulation depended upon the length of exposure time to the agent and the age of the G. melanogenus cells. A rapid decrease in viability of the cells and degradation of cell RNA was noted after treatment with the effective agents. The G. melanogenus cells were unable to absorb L-sorbose actively after toluene treatment.

Adsorption and activity of chitinase on kaolinite

Chitinase is adsorbed on kaolinite below the isoelectric point of the enzyme, pH 6.8. Maximum adsorption is reached below pH 4.6. The amount of chitinase adsorbed to kaolinite depends on the concentration and on the ratio of enzyme to kaolinite. Adsorption results in reduction of chitinase activity. the extent of which depends on the amount of kaolinite present, on pH, and on the length of exposure time. Upon sorption of chitinase on kaolinite the optimal pH for activity is increased from pH 4.7 to 5.7.

Effects of background adaptation, length of exposure time and hypophysectomy on the quantity of melanophore-stimulating substances in the hypothalamo-hypophyseal complex of Rana pipiens

The quantity of the individual melanophore-stimulating substances (MSS's) was determined in aqueous extracts of the pars intermedia (PI), pars distalis (PD), and hypothalamus (H) of frogs which were light (L) or dark (D) adapted (A) for 2 or 8 days. The quantity of two of the substances common to the PI and PD was greater in LA than in DA frogs. In fact, one of the MSS's of the PI was not detectable in DA frogs. With the exception of the MSS which was not detectable, more MSS was present in the PI at day 8 than at day 2 for both DA and LA frogs. One MSS of the PD increased in quantily by day 8 when the frogs were light adapted, but did not increase in quantity after 8 days of dark adaptation. The second MSS of the PD was greater in quantity at day 8 than at day 2 in both DA and LA frogs. In both the PI and PD, the third MSS did not vary with background or length of exposure. The quantity of the single MSS in the H was greater in DA than LA frogs. There was more MSS in the H at day 8 than at day 2 in DA frogs, but in LA frogs the quantity did not change with length of exposure, nor was the MSS depleted. Hypophysectomy of frogs DA for 8 days reduced the quantity of MSS in the H to a level not significantly different from the level in LA frogs after 8 days of exposure. In conclusion, two of three MSS's of the PI and of the PD fluctuated in response to changes in background coloration and to the length of background exposure. The reduction in H content of MSS after hypophysectomy of dark-adapted frogs indicates that the major portion of H MSS originates in the hypophysis.

Effect of sodium lactate under conditions of neutral pH on the release of calcium from the enamel surface in vitro.

The aim of the present investigation was to study the influence of complexing agents on the release of calcium from enamel surfaces under neutral pH conditions. Standardized enamel windows (Ø 4 mm) were prepared from human premolars and exposed to 25 ml batches of different sodium lactate solutions (0, 0.31, 0.62, 1.25, 2.5, 5 and 10%, pH 7.2) each solution containing 8 windows. From each batch 2-ml samples were taken after 1, 2, 4, 8, 16 and 32. The samples were analysed for Ca with the aid of atomic absorption spectroscopy. The Ca concentration in the solutions was found to increase significantly with the length of exposure time and with increasing sodium lactate concentration. The findings demonstrate a strong demineralizing effect of neutral solutions of sodium lactate which might be explained by the capacity to complex calcium; the kinetics of dissolution suggest a direct removal of calcium from apatite crystals.

Microanatomy alteration of gills and kidneys in freshwater mussel (Anodonta woodiana) due to cadmium exposure

Abstract. Fitriawan F, Sutarno, Sunarto. 2011. Microanatomy alteration of gills and kidneys in freshwater mussel (Anodonta woodiana) due to cadmium exposure. Nusantara Bioscience 3: 28-35. The purpose of this study was to determine the level of Cd accumulation in the gills and kidneys, to know the changes in microanatomic structure of A. woodiana after the various treatments of heavy metals. Completely randomized design pattern of 5 x 3 as used in this laboratory experiment. The amount of exposure of heavy metals Cd was (0 ppm, 0.5 ppm, 1 ppm, 5 ppm, 10 ppm), while the variation of length of exposure time to Cd were (7 days, 14 days, and 30 days). The parameters of Cd accumulation in the gills and kidney was analyzed by using AAS method, while abnormalities of gills and kidney were detected by microanatomy structure. Data collected were then analyzed using the analysis of variance (ANOVA) and continued with further test the DMRT. The results indicated that there is a significant effect in 475.3 > 0.000 and 60150.3 >0.000 with 5% significance level (P<0.05) of Cd treatment on gill and kidney microanatomy of A. woodiana. The changes in microanatomy structure of those organs are including edema, hyperplasia, fusion of lamella, necrosis, and atrophy.

On the Blue Light Inhibition of Sporulation in Helminthosporium oryzae

Experiments were carried out to understand the inhibition of sporulation of H. oryzae (isolate HA2) by the continuous light in examining the sensitive growth stage in inhibition of sporulation by the irradiation of blue light and the interaction between blue light and near-ultraviolet radiation (BLB).Sporulation of isolate HA2 is dependent upon the length of exposure time rather than the amount of dosage of BLB irradiation. The sporulation process of HA2 seems to be composed of three steps: (1) the initiation of conidiophore formation under BLB irradiation, (2) the maturation of conidiophore progress under darkness and suppressed by blue light and BLB irradiation, and (3) the conidium formation not suppressed by blue light. The blue light inhibits the maturation of conidiophore, and it is most effective when the fungus is exposed to blue light between 4 and 10hr after the termination of inductive BLB irradiation. A small amount of blue light exposure (1, 250erg/cm2/sec) for 10 minutes is enough to suppress the sporulation, when the light is given at the second step of the sporulation process. There seems to exist some interaction between blue light and BLB radiation. This is suggested by the fact that the inhibition of spo-rulation by blue light is counteracted by BLB irradiation.From these results, it is suggested that the inhibition of sporulation by the continuous exposure with BLB is due to the inhibiting action of short wave region of visible light contained in BLB radiation. The less sporulation of the dark period shorter than 8 hr in the alternation of light and dark or a steep decrease in sporulation under the day length longer than 14hr is able to be under stood from the result that the inhibition by blue light of sporulation is most prominent when the blue light is applied between 4 and 10hr after the termination of inductive BLB irradiation.

Exposure of Tribolium confusum to thio-TEPA, and its effect upon development of Hymenolepis diminuta cysticercoids

Flour beetles, Tribolium confusum, were exposed to concentrations of thio-TEPA equivalent to 10, 20, 40, and 80 mg/sq ft for either 1, 2, or 3 hours. The exposures were made at varying times over a 3-week period from 6 days before the beetles were infected with the eggs of Hymenolepis diminuta, to 15 days after the beetles were infected. When the cysticercoids are more than 6 days old, exposure of the vectors to thio-TEPA has no significant effect on their development, irrespective of both the strength and length of time of exposure. The mortality of cysticercoids up to 3 days old is high and depends on the strength of thio-TEPA and the age of the cysticercoids. Exposure of the beetles 72 hours or more before infection resulted in no significant decrease in the number of cysticercoids developing. Exposure 48 hours or less before infection resulted in a highly significant ( p < 0.001) reduction in the number of cysticercoids which developed. There is a 5-day period corresponding to 2 days prior to infection until 3 days after infection, during which exposure of the vectors to thio-TEPA causes up to 100% mortality of the cysticercoids. Within this period there is some evidence that the strength of the thio-TEPA deposit is also significant. Irrespective of length of exposure time or strength of chemosterilant deposit, those cysticercoids that managed to develop were also capable of establishing themselves in the definitive host and of reaching maturity.

The effects of exposure time in immediate recall on abnormal and questionnaire criteria of personality.

The present investigation deals with the effects of two lengths of exposure time in neurotic and schizophrenic subjects, and with the relations between these effects and measures of extraversion, neuroticism and rigidity. A consideration of previous work, discussed in the following paragraphs, led to three main predictions concerning varying exposure times.

NOISE-INDUCED HEARING LOSS

<h3>INTRODUCTION</h3> HEARING loss resulting from exposure to noise has received considerable attention in otologic literature.¹In recent years, this type of hearing loss has assumed increased importance, partly because of its position in theories of audition but principally, perhaps, because industry is coming to realize its occurrence in those members of the labor force who function in a noisy environment. There is a mass of evidence indicating that workers who spend sufficient time in sufficiently high noise levels are exposed to the possibility of incurring an irreversible hearing loss. The length of exposure time and the intensity level of the noise above which loss is imminent are not known within exact limits, nor can the probable severity of hearing loss under given conditions of exposure be predicted on the basis of present knowledge. There appear to be large differences in individual susceptibility to noise-induced hearing loss, such that it is

Studies on Chromium: I. The Quantitative Determination of Chromium in Human Tumors

A preliminary note with regard to our finding of chromium in certain human tumors was published in 1932 (1) and a detailed description of the new technic for the determination of transmittancy was given in a recent communication (2). The present paper deals with the application of this method to the quantitative determination of chromium in certain human tumors. In the above mentioned note it was pointed out that chromium could be determined in the presence of iron from transmission values at wavelengths between 5040 A and 5800 A. In order to choose the most suitable spectrum lines for use in determining transmission values in this region, microphotometer (Moll type A) record was made of a tungsten spark spectrogram. The air lines 5045 A and 5710.7 A gave records that were sharp and sufficiently distant from neighboring lines to be satisfactory for this purpose. A series of spectrograms was made using various slit widths. An investigation of the microphotometer records of the lines mentioned led to the choice of 0.05 mm. slit width as being the most desirable. The length of exposure time was determined from the characteristic curve to the Wratten M plates used. Fifteen seconds was found to be the longest exposure time that produced density values falling on the straight line portion of the curve, and this was accordingly chosen as the standard time.