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PubMed1995

Methods used by the United States National Institute for Occupational Safety and Health to monitor crystalline silica.

The National Institute for Occupational Safety and Health (NIOSH) in the United States has four methods for monitoring the concentration of crystalline silica dust. They all employ a cyclone for size-selective sampling in the field, but differ primarily in that the laboratory measurement is based on either infrared spectroscopy, X-ray diffraction, or colorimetry. The limits of detection for these methods are similar, but their accuracy is poor, particularly at low filter loadings near the current recommended exposure limit (50 mu g center dot m-3). Advances in analytical instrumentation have improved measurement precision. Correction techniques to account for X-ray absorption in samples loaded with nonsilica dust have eliminated one source of bias. Direct analysis on collection filters is a convenient technique that should decrease sample manipulation errors, but it has not been shown to improve precision or accuracy significantly.

Crystallization↗

PubMed1977

Collaborative study of an assay for progestational steroids in individual contraceptive tablets.

A single tablet assay method has been developed for determining norethindrone, norethynodrel, and norgestrel in commercial contraceptive tablets. The steroid is separated from the tablet constituents on a diatomaceous earth column, the chloroform eluate is reacted with isonicotinic acid hydrazide, and the steroid is determined by colorimetry. Norethynodrel is isomerized to a conjugated ketosteroid before the colorimetric determination. Fourteen laboratories collaboratively tested the method. The average recoveries in 3 brands of tablets were as follows: 102.6% for the sample labeled as containing 0.35 mg norethindrone/tablet, 99.4% for the 2.5 mg norethynodrel/tablet, and 98.2% for the 0.5 mg norgestrel/tablet. The assay method has been adopted as official first action.

Contraceptives, Oral, Combined↗

PubMed1996

Radiation effects on polypropylene for sterilization.

In order to improve the resistance of gamma-radiation sterilization of polypropylene (PP), the formulations of the additives such as antioxidants, crosslinking agent, and trans-stilbene oxide (StO) have been carried out. The irradiated PP and ethylene-propylene copolymer samples with control and additives were characterized by mechanical tester, colorimetry, and Fourier transform infrared spectroscopy with total attenuated reflectance mode (FTIR-ATR). Crosslinking agent and StO formulated PP showed remarkable radiation resistance and minimum discoloration. Also, radiation resistance of ethylene-propylene copolymers with 3% of ethylene contents was better than that of PP homopolymers in the case of no additives. The proposed mechanisms of radiation stabilization with additives are also discussed.

Antioxidants↗

PubMed1977

[Diagnosis of primary hyperlipoproteinemia in umbilical cord blood (author's transl)].

The aim of the present investigation was to assay the frequency of primary dyslipoproteinemia in a random sample of one hundred newborns and to describe the minimal methodical requirements for sound diagnosis. After comparison of different methods total lipids were determined by gravimetry, cholesterol and triglycerides by enzymatic methods, nonesterified fatty acids by direct colorimetry; phospholipids were estimated indirectly. All measurements were applied to umbilical cord sera and to lipoprotein fractions separated by selective precipitation. The diagnosis of hyperlipoproteinemia type IV, which is the most frequent one in adults, is highly afflicted with pitfalls in the postnatal period. A primary hyper-alpha-liproteinemia occured in one case and type II-hyperlipoproteinemia in two cases, one of the parents being involved in each case. For mass screening triglycerides should be assayed in serum and cholesterol in precipitated and resolubilized LDL-fraction, for which the minimal requirements are described.

Cholesterol↗

PubMed1977

Acid digestion, hydride evolution atomic absorption spectrophotometric method for determining arsenic and selenium in foods: collaborative study. tpart I.

The hydride evolution atomic absorption spectrophotometric (AAS) method for determining As and Se in foods developed and evaluated by the Food and Drug Administration and Agriculture Canada laboratories was subjected to collaborative study, Twenty-four laboratories provided results for As and 23 provided results for Se levels in 13 different samples consisting of tuna, swordfish, flounder, oyster, liver, flour, skim milk poweder, spinach, kale, and apple containing natural levels of As and Se in the ranges 0-15,000 and 0-4000 ng/g, respectively. Reference materials formed a substantial segment of samples, and a number of other laboratories using fluorometry, colorimetry, neutron activation, spark source mass spectrometry, and graphite furnace AAS provided confirmative reference values for the remaining samples. A variety of hydride generation instruments were used, ranging from commercially available devices to semiautomated and fully automated custom-made instruments. Although the accuracy of the method was fairly good, between-laboratory and between-determination (hydride evolution AAS measurement) precisions were not favorable. The main advantage of the hydride AAS method is the rapidity of the determinative step.

Arsenic↗

PubMed1996

[Determination of urea in milk by enzyme coupled electrode method].

An Enzyme coupled electrode method for the determination of urea content in milk was studied systematically. The linear range of the method, the detection limit, recovery and relative standard deviation are 2.1-2.1 x 10(3) micrograms/ml, 2 micrograms/ml, 95.3%-101.0% and 1.5%-3.9%, respectively. The reliability of the method was confirmed by comparison with colorimetry (0.2 < P < 0.05). Using this method, we determined the content of urea in seven milk samples from Chengdu. The values range from 152.2-288.5 micrograms/ml and agree with those reported by other authors. This method is simple, rapid, accurate and inexpensive.

Animals↗

PubMed1979

[Characteristics of human dental pulp cells in cell cultures].

The generation time and the division rate were measured with routine methods of cell culturing. The conditions contributing to the stagnation of growth were examined; the synchrony of the growth process was investigated. The biochemical composition of the cells was assessed via colorimetry and then compared with other cell systems. The cell culture examined may be used to test capping materials; only cells up through the eighth generation however should be utilized.

Adolescent↗

PubMed1996

[An experimental study of tumor necrosis factor (TNF) and interleukin-1 (IL-1) in aqueous humor after intraocular lens implantation].

OBJECTIVE: The tumor necrosis factor (TNF) and interleukin-1 (IL-1) levels in aqueous humor after intraocular lens (IOL) implantation were studied in rabbit eyes and their effects on post-operative anterior ocular inflammation were discussed. METHODS: 27 adult pigmented rabbits were divided into three groups: (1) Lens extraction and intraocular lens (IOL) implantation in the capsular bag. (2) Simple extracapsular lens extraction, and (3) normal control group without surgical intervention. Aqueous humor samples were aspirated on days 1, 3, 7 and 14 postoperatively. A modified double-antibody indirect sandwich ELISA was used to detect for the presence of TNF. MTT colorimetry was used to detect for the presence of IL-1. The data were analysed statistically. RESULTS: TNF and IL-1 levels in the aqueous humor were significantly higher (P < 0.05) at 1, 3, 7, and 14 days postoperatively in IOL implanted group than that in the control group, and TNF levels in aqueous humor at 3, 7 and 14 days postoperatively and IL-1 levels at 1 and 3 days postoperatively were significantly higher (P < 0.05) in IOL implanted group than that in simple extracapsular lens extraction group (P < 0.05). In the postoperative 7-14 days, the TNF and in the 3 to 14 days the IL-1 in the aqueous humor reached their maximum levels in IOL implantation group. CONCLUSIONS: It is reasonable to consider that the increases of TNF and IL-1 levels may play critical roles in the anterior ocular inflammation response after IOL implantation.

Animals↗

PubMed1998

Distribution of phenol in a fatal poisoning case determined by gas chromatography/mass spectrometry.

A victim who was presumed to have ingested waste fluid containing phenol of DNA extraction was found dead in his laboratory. The skin was partially chemically burned, with blisters as maps. No mechanical injuries were observed. The pathological findings of the liver and kidney were typical of those of acute substantial poisoning. Phenol concentrations in the blood, urine, stomach contents and organs were determined by gas chromatography/mass spectrometry. Phenol was distributed throughout the body. The concentration of free phenol in the blood was found to be 60 micrograms/mL, and in the urine it was 208 micrograms/mL. The phenol concentrations in the organs were found as follows: 106 micrograms/g in the brain; 116 micrograms/g in the lungs; 166 micrograms/g in the liver, and 874 micrograms/g in the kidney, respectively. Significantly high concentrations were observed in the kidney, urine, and liver. To the best of our knowledge, such an intoxication through this kind of ingestion has never been reported before. Distributions of phenol in fatal poisonings have been reported, but colorimetry was used as the analytical method and it cannot exclude the interference of other phenolic compounds.

Adult↗

PubMed1996

Inhibitory effect of suberogorgin on acetylcholinesterase.

AIM: To study the selection, reversibility, and kinetics of suberogorgin (Sub) on acetylcholinesterase (AChE). METHODS: The human plasma was used as butyrylcholinesterase (BuChE). The activity of ChE was determined with colorimetry. RESULTS: Sub obviously inhibited the AChE in vitro with pl50 4.03, 4.92, 3.82, and 4.67 in RBC membranes (of rat and human) and tissue extracts (of rat brain and earthworm dorsal muscle), respectively. No inhibition on BuChE was observed. The inhibition of Sub on AChE was far lower than that of physostigmine, but was close to that of galanthamine. Sub decreased the AChE activity to the lowest within 3 min after it was incubated with AChE. Centrifugalization washing reactivated the AChE which had been inhibited by Sub. The double-reciprocal plots of different concentrations of Sub on AChE showed parallel lines. CONCLUSION: Sub was a selective, reversible, and contra-competetive inhibitor of AChE at the binding site on the peripheral anion region of AChE.

Acetylcholinesterase↗

PubMed1996

Effects of suberogorgin and its derivates on learning and memory in mice.

AIM: To study the relationship between the effects of suberogorgin (Sub) and its derivates on memory and their anti-acetylcholinesterase (AChE) actions. METHODS: The step-down latency (SDL) and the escape latency (EL) of mice were determined at the same time in a passive avoidance task after Sub, N-suberogorgamide-N-N-dicyclohexyl urea (Sub-DU), or N-cyclohexyl suberogorgamide (N-CS) was injected i.p. The AChE activities in brain hemogenates were determined with colorimetry. RESULTS: Sub 1.9, Sub-DU 3.0, or physostigmine (Phys) 0.15 mg.kg-1 obviously lengthened the SDL by 195%, 271%, and 210%, and shortened the EL by 56%, 61%, and 33%, and the two formers inhibited the brain AChE activities by 17% and 19%, respectively in aging (3-4 months) mice. These actions were decreased in a dose-dependent manner when Sub or Sub-DU was increased to 2.9-4.3 or 4.5-6.7 mg.kg-1 respectively. Sub 1.9, Sub-DU 2.0, and Phys 0.15 mg.kg-1 also lengthened the SDL by 187%, 209%, and 152%, and shortened the EL by 52%, 62%, and 57%, respectively in aged (12-14 months) mice. Sub 1.3-1.9, Sub-DU 0.9-2.0, or Phys 0.15 mg.kg-1 reversed the cycloheximide- or scopolamine-induced disruptions of memory retention. No obvious effect of N-CS on the acquisition of memory and the AChE activity in mice was observed. CONCLUSION: The improvements of Sub and Sub-DU on memory were chiefly related to their anti-AChE actions.

Acetylcholinesterase↗

PubMedDate not supplied

[Antioxidative effect of N2-mercaptopropionylglycine (N2 MPG) in experimental acute pancreatitis].

The N2-Mercaptopropionylglycine (N2-MPG) is a potent antioxidant by inhibiting the abnormal production of xantina-oxidase. The aim of this research is to analyze the antioxidant capacity of this tiol compound by offering some protection to pancreatic tissue in the acute pancreatitis (AP). The induction of AP was obtained through two methods: a) supramaximal dose of cerulein; b) infusion of 2.5% sodium taurocholate into the biliopancreatic duct of the rat. Thirty-six male Wistar rats (220-270 g) were divided into four groups. AP with cerulein (Two parenteral doses of 20 micrograms/kg; one hour interval): in two groups: GI: nineteen rats previously treated with N2-MPG (100 mg/kg) ten minutes before AP. GII (control): seventeen animals which received saline 0.9%. AP with taurocholate (0.5 ml into the main biliopancreatic duct): in other two groups: GIII: eleven rats previously treated with N2-MPG (100 mg/kg) ten minutes before AP. GIV (control): fifteen animals which received saline 0.9%. The albumin leakage into the cell interstice as an inflammatory parameter was measured through Evans-Blue (EB) colorimetry, that links totally with serum albumin after injection into the pancreatic tissue, immediately before induction of AP. The rats were sacrificed one hour after. Water tissue content was also measured. There was a relevant reduction of EB leakage in GI (344 +/- 27 micrograms/gtissue) when compared to GII (729 +/- 84 micrograms/gtissue), p < 0.01, and in GIII (386 +/- 52 micrograms/gtissue) when compared to GIV (543 +/- 53 micrograms/gtissue), p < 0.05. There was no difference in tissue water content between GI (88.2 +/- 0.6%) and GII (87.4 +/- 0.9%), but certainly between GIII (77.7 +/- 2.1%) and GIV (82.8 +/- 1.2%), p < 0.05. The amilase levels didn't show any difference among the four groups. These results suggest that the use of the antioxidant N2-MPG offers a protective action, at least in rats, reducing the severity of AP induced by supramaximal dose of cerulein, and even in a more severe AP such as produced by sodium taurocholate at 2.5%, although apparently not interfering with its pathogenesis. It also strengthens the actual participation of free radicals of oxygen in the physiopathology of acute pancreatitis.

Acute Disease↗

PubMed1964