Mean Concentration Levels Research Articles

Reciprocal feedback regulation of kidney angiotensinogen and renin mRNA expressions by angiotensin II.

The present study asks whether angiotensin II (ANG II), a potent inhibitor of renal renin synthesis and release, regulates renal angiotensinogen synthesis. ANG II (or vehicle) was intravenously infused into male Sprague-Dawley rats for 3 days (vehicle or 100, 300, and 1,000 ng.kg-1 x min-1, n = 8/group), significantly increasing mean plasma ANG II concentrations and raising mean arterial blood pressure (MAP). ANG II dose dependently suppressed plasma renin concentration, kidney renin concentration, and renal renin mRNA levels. In contrast, ANG II infusion increased renal angiotensinogen mRNA levels stepwise to 122, 136 (P < 0.05), and 150% (P < 0.05) of control and also increased both liver mRNA levels (P < 0.05) and plasma angiotensinogen concentration (P < 0.05). Three days of angiotensin-converting enzyme inhibition (10 mg.kg-1 x day-1 quinapril in drinking water, n = 8) significantly decreased MAP (P < 0.05) and increased both mean plasma renin concentration (P < 0.05) and renal renin mRNA levels (P < 0.005). Plasma ANG II concentration tended to decrease (not significant), and neither renal nor hepatic angiotensinogen mRNA levels displayed significant difference. However, when data from ANG II-infused and quinapril-treated rats were analyzed together, correlation between plasma ANG II concentrations and renal angiotensinogen mRNA levels was highly significant (P < 0.005, r = 0.585). Thus plasma ANG II upregulates renal angiotensinogen gene expression and downregulates renal renin gene expression, a reciprocal feedback regulation that may have important physiological consequences.

Concentration levels and behavior of transuranium nuclides in Japanese coastal marine environment

The concentration of239,240Pu and241Am in different samples collected from the coastal marine environment of Ibaraki Prefecture, Japan facing the Pacific Ocean have been studied. Seawater samples have been collected since 1975 and sea-biota since 1981. The mean concentration levels of239,240Pu and241Am were 0.51, 0.20 for anchovy, 0.22, 0.11 for flounder, 4.9, 0.77 for brown algae, 2.0, 2.4 for shellfish, and 0.022, 0.0028 for seawater (in mBq/kl), respectively. The chronological change of239,240Pu in seawater was influence by fallout amounts. The activity ratio between the nuclides showed steady levels after two years from the end of atmospheric nuclear explosion tests. Activity levels and the ratios for each type of sample are briefly discussed.

Elevation of pineal melatonin secretion by electrical stimulation of the cervical sympathetic trunk in rabbits

The influence of electrical stimulation of the unilateral sympathetic trunk on the release patterns of plasma melatonin in the confluens sinuum of anesthetized rabbits was studied. Plasma melatonin exhibited an episodic release pattern, with pulses superimposed on a basal level. The mean concentration, mean maximum and minimum levels of plasma melatonin in the confluens sinuum were found to be significantly elevated when the sympathetic trunk was electrically stimulated. The frequency of pulse peaks of plasma melatonin sampled at 4-min intervals was not affected by electrical stimulation. Our results suggest that the diurnal rhythmic secretory pattern of pineal melatonin into the confluens sinuum of rabbits is regulated by the cervical sympathetic system.

PCB and PCQ concentrations in subcutaneous tissue from patients with PCB poisoning (yusho).

AbstractPolychlorinated biphenyl (PCB) and polychlorinated quaterphenyl (PCQ) concentrations in the blood and subcutaneous fat tissue from 11 patients with PCB poisoning (Yusho) and 10 controls were analyzed by electron captured gaschromatography. The mean concentration levels of blood PCB and PCQ and the CB% ratio were elevated in patients with Yusho. The PCB pattern was the A type in 5 cases and the B type in 6 others. The mean concentration level of PCB in subcutaneous fat tissue was 1579.45 ppb in the Yusho group, 3.9 times higher than that in the control group. The mean concentration level of PCQ was 206.65 ppb, 119 times higher than that in the control group. The mean value of CB% was 3.22 in the Yusho group and 0.66 in the control group. These results show that PCB and PCQ accumulate in the subcutaneous fat tissue of patients with PCB poisoning (Yusho), as late as 17 years after diagnosis of the disease. The PCB and PCQ concentration levels in the subcutaneous fat tissue appear to be useful in diagnosis and evaluation of prognosis in this disease. Investigations of the elimination of PCB and PCQ in subcutaneous tissues should be done.

Concentrations of mercury, selenium and lead in blood samples from mothers and their newborn babies in four Greenlandic hunting districts

Earlier investigations carried out in Greenland have shown high exposure levels of mercury and lead to be present. The levels of mercury and lead are found not to be of immediate risk to adults, but both elements are able to pass the placental barrier and thereby influence foetal development. As the foetus must be regarded as most sensitive to environmental toxicants it was found necessary to carry out a follow-up investigation in order to elucidate foetal exposure. This investigation was started in the fall of 1981 and continued until the end of 1982. Samples of venous blood were collected from women giving birth, and the foetal exposure was evaluated on the basis of samples of cord blood. Samples were taken at the local hospitals in the four districts of Upernavik, Umanak, Scoresbysund, and Angmagssalik. In total, 98 sample pairs were collected: 14 from Upernavik, 36 from Umanak, 17 from Scoresbysund, and 31 from Angmagssalik. At the time of sampling a questionnaire was filled out with information on the age of the mother, length of pregnancy, weight of child, smoking and eating habits of the mother. All samples were analysed for mercury and lead contents. Furthermore, the selenium concentration was analysed, as in animal experiments this trace element has been shown to alleviate toxic effects of mercury and probably of lead, too. The high exposure level of mercury in Greenland was confirmed in this study, too. A close correlation was found between the blood of mothers and children. The children's blood contains more mercury than that of the mothers, approximately 80% more. The highest concentration seen in a newborn baby was 177 μg/1, which is close to values found to have caused mercury intoxication during the Minamata episode in Japan. Selenium concentrations were found to be correlated between mothers and children, but in a non-linear way. The concentration level was found to exceed that of mercury on a molar basis. This might constitute a protective effect, and explain that neither in Greenland nor in other places where marine food is an important part of the total diet, has mercury intoxication been found, except in cases such as the Minamata area in Japan, where a local mercury pollution was present. Still, the high concentration in babies must give rise to concern. No correlation was found between mercury and selenium concentrations on an individual basis, neither in mothers nor in children. This indicates that the two elements pass the placental barrier independent of each other. As seen in other investigations, lead was also shown to pass the placental barrier, and a significant correlation was found between the blood of mothers and of children, the mean concentration being approximately the same. The mean concentration level in mothers was a little lower than should have been expected from earlier investigations. This is probably due to the fact that the blood lead level decreases during pregnancy. As shown in earlier studies from Greenland, the blood lead level was found to be on the same level as that found in European industrial areas. The present information on heavy metal exposure in Greenlandic hunting districts should be subjected to a closer evaluation as regards the influence on the health condition in the Greenlandic population now and in the future. Such material will he highly relevant to the understanding of the significance of the global pollution by heavy metals.

Studies on anticancer treatment with an oily anticancer drug injected into the ligated feeding hepatic artery for liver cancer.

In six adult patients with nonresectable liver cancer, as well as in mature New Zealand white rabbits with implanted VX2 carcinoma in the liver, the artery feeding the hepatic lobe with the malignant lesion was ligated, and an oily contrast medium (Lipiodol Ultra-Fluid) was injected into the hepatoproximal lumen of the ligated artery of the liver with carcinoma. The oily contrast medium was detected in all the branches of the artery injected, and thereafter was found only in tumor tissue for 7 days experimentally and for 16 months clinically. Taking advantage of this phenomenon, the therapeutic effect of the injection of an oily anticancer drug (bleomycin oil suspension) into the hepatoproximal lumen of the ligated hepatic artery was investigated in rabbits with VX2 carcinoma of the liver. The mean concentration level of bleomycin in the tumor tissue was 2.4 +/- 0.4 microgram/g 1 week after the injection of bleomycin oil suspension (1.5 mg potency/kg) in three rabbits. However, its concentration level in nontumorous tissue of the liver was undetectably low in two rabbits, but 0.6 microgram/g in the third rabbit. The group of rabbits receiving an injection of bleomycin oil suspension into the ligated artery had a significantly longer mean survival time than those of the experimental group receiving an injection of saline solution of bleomycin into the ligated artery as well as the three other groups treated (P less than 0.02, N = 5 for each group). It may be concluded that an oily anticancer drug injected into the hepatoproximal lumen of the ligated hepatic artery can intensify the anticancer effects of a ligation of the hepatic artery for liver cancer.

Model experiments on the nature of air pollution transport near buildings

The paper describes wind tunnel experiments with rectangular blocks in uniform smooth and turbulent air flow to simulate the transport of windborne atmospheric pollutants near buildings. Dispersal is dominated by the flow in the areodynamic wakes of the blocks. Using light extinction apparatus, measurements were made of the time constant ( t d ) of the decay of the amount of smoke in the separation bubble following abrupt removal of the smoke source, and of the bubble length ( X). These quantities were expressed as H( Ut d / S, where U is the air velocity and S the block dimension) and X/ S respectively, found to be unique functions of the free-stream turbulence parameter, A( l f K 1/2 f / SU, where l f and k f are the length scale and kinetic energy respectively of the free-stream turbulence), for cubic blocks in the ranges l f / S ≲ 0.6 and k f 1/2/ U ≲, 0.15. Visual observation of tracer smoke indicated the onset of re-attachment of the separated flow on the top and side faces of the cubes at relatively low levels of free-stream turbulence, coinciding with sharply varying behaviour in H and X/ S. Measurements were also made of H and X/ S for square-faced blocks of various lengthwise aspect ratios, and for cubic blocks at various angles of incidence to the flow. From consideration of the turbulent transport of entities of an atmospheric pollutant across the boundary of the wake bubble behind a building, an expression is derived for the mean concentration level that can build up inside the bubble for a source of known strength and location. It contains the two terms H and X/ S which explicitly embody the complicated fluid mechanical properties of the near wake.

A controlled trial of intramuscular lidocaine in the prevention of premature ventricular contractions associated with acute myocardial infarction

Intramuscular lidocaine administration is known to produce blood concentration levels considered to be therapeutic for prevention of premature ventricular contractions. This double blind study was designed to study the effect of intramuscular lidocaine in the prevention of PVC's in acute myocardial infarction. Forty-six patients with confirmed acute myocardial infarction, without congestive heart failure, shock, or major arrhythmias were admitted to the trial. Twenty-one patients received 4.5 mg. per kilogram of intramuscular lidocaine and 25 patients received placebo in the deltoid muscle within 14 hours of the onset of symptoms. Rhythm strips of 2 minutes' duration, blood pressure, heart rate, and blood specimens for blood concentration levels were obtained prior to and 5, 10, 15, 30, 60, 90, and 120 minutes after injection. The mean blood concentration level of lidocaine was 1.81 +/- 0.22 mug per milliliter at 5 minutes, reached a maximum of 2.18 +/- 0.22 mug per milliliter at 10 minutes, and was still 0.81 +/- 0.05 at 120 minutes. Analysis of rhythm strips revealed that only three of 21 patients (14 per cent) in the intramuscular lidocaine group developed at least one PVC as compared to 13 of 25 (52 per cent) in the placebo group (p less than 0.0005). No significant toxic effects were noted. This study suggests that intramuscular lidocaine may significantly reduce potentially fatal arrhythmias in early phases of acute myocardial infarction.

The variations in the concentrations of airborne particulate matter with wind direction and wind speed in Denmark

Abstract A statistical investigation of the connection between wind direction and wind speed and concentrations of airborne particulate matter at different places in Denmark is briefly described. The results show that the mean concentration levels over the whole country are highest in case of southerly to southeasterly winds. In general, the mean concentrations are decreasing with increasing wind speed for most wind directions, but in southeasterly winds the mean concentrations are higher for high wind speeds than for low wind speeds.

Experimental Model Techniques for the Investigation of the Dispersion of Chimney Plumes

The use of wind tunnels for the study of flue-gas dispersion, the scaling criteria appropriate to the modelling of the motion of buoyant plumes in turbulent boundary layers, and an experimental technique for measuring mean concentration levels are presented and discussed. Two examples of wind-tunnel experiments are used to demonstrate the techniques and to illustrate the implications of the scaling criteria. Both experiments were performed at ***1 300 scale in a simulated neutrally stable atmospheric boundary layer. Finally, the present limitations of wind-tunnel studies are considered and possible future developments are discussed.

Collaborative Study of the Determination of Propylene Glycol, Glycerol, and Triethylene Glycol in Tobacco

Abstract Collaborative study was carried out on a method for determination of propylene glycol, glycerol, and triethylene glycol in tobacco. The method involves gas chromatography of the methanolic extract of tobacco on a 42 × 3/16″ column packed with 5% Carbo wax 20M-terephthalic acid on 60-80 mesh 1:1 Diatoport S-Chromosorb 101 mixed support. 1,3-Butylene glycol is used as an internal standard. The oven temperature is programmed from 90 to 240°C at 15°/min. Results for propylene glycol and glycerol gave coefficients of variation &amp;lt;10%. Results for triethylene glycol in cut tobacco at mean concentration levels of 0.95 and 1.30% gave coefficients of variation of 9.24 and 6.93%, respectively. At a mean concentration level of 0.54% triethylene glycol, the coefficient of variation was 20.8%. The method has been adopted as official first action.

Interphase transfer in stationary two-phase media

A variational procedure is applied to obtain upper bounds on and estimates of interphase transfer rates in random two-phase media. Results are expressed in terms of the void-size distribution as introduced by Scheidegger, the void size at a point being defined as the minimum distance of that point from the interface between the phases. Specific cases discussed are, first, the diffusion controlled adsorption, at the interface, of a solute present in one phase; here the bounds obtained are on the rate of decay of the mean solute concentration in the limit of long times. The second case is that of diffusion controlled adsorption at the interface balanced by a uniform and constant generation of solute throughout one phase; bounds and estimates are obtained for the ratio of the rate of generation to the mean concentration level maintained at the steady state. In addition, the transfer of solute between two phases with identical properties is treated. If the solute is initially distributed uniformly over one phase and absent from the other, it is possible to derive an exact expression for the fraction of total solute present in either phase as a function of time. The geometry of the interface enters into this expression in the form of the probability S(ρ) that two randomly placed points a distance ρ apart will both fall within the phase which originally contains the solute.