Distilled-deionized Water Research Articles

Analysis of the survival of Venezuelan equine encephalomyelitis virus and possible viral simulants in liquid suspensions

To compare the inactivation rate of Venezuelan equine encephalomyelitis (VEE) virus in liquids to that of Sindbis virus (SV, another alphavirus) and to a bacteriophage (MS2) generally used as a viral simulant in the development of countermeasures in biodefense. Viruses were inoculated into liquids and viral titres were determined at various times postinoculation. The viruses were stable in distilled-deionized (dd) water at 4 degrees C during the 21 days of the study. The inactivation rates of VEE and SV in dd water at 21 and 30 degrees C were very similar (between 0.12 and 0.14 log(10) per day), while MS2 was three-fold slower. In tap water (chlorine content between 4 and 5 ppm) at 21 degrees C, VEE and SV were inactivated at twice the rate measured in dd water. The inactivation rates of VEE and SV were similar to each other and faster than MS2 in all liquids tested. VEE is likely to remain viable for many days after release into water, snow, or even chlorinated tap water. SV can be used to estimate the persistence of VEE in liquids, but using MS2 as a simulant would overestimate of the stability of VEE.

Dechlorination of Trichloroethylene (TCE) by Zero-Valent Iron

Dechlorination of TCE was done using zero-valent iron in two forms: powder and shavings. A simulated TCE solution of initial concentration 5 ppm was mixed with iron powder, finer than 100 mesh, in 120-mL serum bottles. The pH of the solution was varied at 5, 7 and 9; the amount of iron powder was at 10, 12.5 and 15 mg per mL of TCE solution; and the water used was distilled de-ionized water. On the other hand, 50 grams of iron shavings were used as materials packed in a glass column passed with simulated TCE solutions. Two thicknesses of the shavings were used (1 mm and 1.5 mm). The iron shavings were subjected to different preparations: pretreated with 0.1 M NaCl solution and untreated; and the water used was de-oxygenated, de-ionized distilled water. Samples taken at different intervals were analyzed for TCE and chloride ion concentrations. Results showed a decrease in the concentration of TCE, accompanied by the formation and increase in chloride ion concentration over time, thus confirming the dechlorination of TCE. Degradation was possible when the pH of the solution was 7 and below, while better dechlorination was observed with the thinnest iron shavings possible and with the said shavings subjected to pretreatment with the NaCl solution.

Simultaneous quantification of free triiodothyronine and free thyroxine by isotope dilution tandem mass spectrometry

Objectives: This study was designed to improve our previously developed tandem mass spectrometry (MS/MS) method for free thyroxine (FT4) by enhancing sensitivity and permitting simultaneous measurements of both free triidothyronine (FT3) and FT4 using a smaller plasma/serum sample. Design and methods: An API-5000 tandem mass spectrometer equipped with TurboIonSpray source and Shimadzu HPLC system was employed to perform the analysis using isotope dilution with deuterium labeled internal standard, T4- d 5. Four hundred microliters of human plasma/serum was filtered through a Centrifree YM-30 ultrafiltration device by centrifugation, and 450 μL of internal standard in methanol was then added to 150 μL of ultrafiltrate for deproteinization. After centrifugation, 500 μL of supernatant was diluted with 400 μL of distilled de-ionized water and a 650 μL aliquot was injected onto a C-18 column. After washing, the switching valve was activated and the analytes were eluted from the column with a water/methanol gradient into the MS/MS system. Quantification by multiple reaction-monitoring (MRM) analysis was performed in the negative mode. Results: The within-day and between-day coefficients of variation (CVs) were ≤ 9% for FT3 and ≤ 7% for FT4 at all concentrations tested. Accuracy ranged between 95% and 105%. The 2.5th–97.5th percentile for FT3 and FT4 was 0.09–0.4 ng/dL (1.4–6.2 pmol/L) and 0.8–2.1 ng/dL (10–26 pmol/L), respectively. The results correlated only moderately well with the immunoassays. Conclusions: We describe an improved simple, accurate and fast isotope dilution tandem mass spectrometry method for the simultaneous determination of FT3 and FT4 in human serum/plasma samples.

Hydrogen peroxide in basic media for whole blood sample dissolution for determination of its lead content by electrothermal atomization atomic absorption spectrometry

Hydrogen peroxide in basic media is proposed as a means for dissolving whole blood samples to be analyzed by electrothermal atomization atomic absorption spectrometry, ET AAS. Approximately 2 g of the whole blood sample were directly weighed in a 150 mL volumetric flask; 3 mL of a NaOH 0.2 mol L −1 solution, two drops of 1-octanol, as an antifoaming agent, and 1 mL of 30% volume hydrogen peroxide were added to the flask to promote oxidation. The solution was then manually shaken and after approximately three minutes of shaking, a clear solution, with no apparent suspended solids or greasy layers, was obtained. Distilled-deionized water was used to complete the volume. Ten μL of the resulting solution along with 10 μL of a solution containing 5000 mg L −1 of NH 4H 2PO 4 and 300 mg L −1 of Mg(NO 3) 2 as a modifier, were injected into transversely heated graphite tubes for lead determination. Both aqueous standards and standard addition calibration curves produced results not significantly different at a 95% confidence limit level. Accuracy of the measurements was assessed by analysis of the IAEA A-13 ( concentration of trace and minor elements in freeze dried animal blood) standard reference material containing 0.18 mg L −1 lead on a dry basis and by means of recovery tests. Analysis of the IAEA A-13 standard produced 0.17 ± 0.02 mg L −1 lead on a dry basis; recovery tests afforded values from 95 to 105%. Ten consecutive measurements of a 5 ppb lead solution gave a characteristic mass of 47.2 pg and a (3S) detection limit of 1.77 μg L −1 Pb. Results obtained from analysis of whole blood samples of volunteer donors covered a lead concentration range between 8 and 21 μg L −1 with a mean value of 11.9 ± 4.7 μg L −1.

Possible Application of Human c-Ha-ras Proto-Oncogene Transgenic Rats in a Medium-Term Bioassay Model for Carcinogens

With the aim of developing a medium-term assay for screening of environmental carcinogens, we exposed mammary carcinogen sensitive human c-Ha-ras proto-oncogene transgenic (Hras128) rats to various carcinogens, including compounds that do not normally induce mammary tumors. Seven-week-old Hras128 rats and wild-type littermates received administrations of 3-methylcholanthrene (3-MC), benzo[a]pyrene (B[a]P), anthracene, pyrene, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), dimethylarsinic acid (DMA), diethylnitrosamine (DEN) or azoxymethane (AOM) and were sacrificed at week 12 (females) (at week 10 for the 3-MC group) or week 20 (males). Female Hras128 rats receiving NNK, DEN, or DMA showed a significant increase in mammary tumor incidence and/or multiplicity compared to the respective values with olive oil or deionized distilled water (DDW) vehicles. In male Hras128 rats, a significant increase in mammary tumors was also observed in groups administered 3-MC, B[a]P, anthracene, IQ, and NNK. Mutations of transgenes were observed in codons 12 and/or 61 in the induced tumors by PCR-RFLP except in the DEN group in female and in the MeIQx group in male Hras128 rats. Thus various carcinogens, not necessarily limited to those normally targeting the breast, were found to induce mammary carcinomas in Hras128 rats, especially in females, pointing to potential use for medium-term screening.

Interferences contributed by leaching from filters on measurements of collective organic constituents

Membrane and glass fiber filters are widely used in laboratory water and wastewater analyses. During sample filtration, some filters release organic compounds, which may interfere with organic analyses. This research investigated the interferences due to organic leaching in the determinations of dissolved organic carbon (DOC), biodegradable dissolved organic carbon (BDOC), soluble biochemical oxygen demand (BOD), and soluble chemical oxygen demand (COD) and the appropriate cleaning method for the filters. Nineteen filters studied included 16 membrane filters and 3 glass fiber filters. A wide variation was observed on the amount and characteristics of organics leaching from the filters. Some filters showed no organic leaching while some others had very high organic leaching. Soaking the filters in deionized distilled water (DDW) resulted in more leachable organics from the filters compared with filtering DDW through them. Certain filters should be avoided for use in the above analyses and soaking in DDW is a more suitable cleaning method than discarding initial filtration volumes for most filters.

Enhancement of fluoride release from glass ionomer cement following a coating of silver fluoride

This study investigated the extent to which a coating of 10% silver fluoride (AgF) on discs of glass jonomer cements (GIGs) would enhance the release of fluoride ion into eluting solutions at varying pH. Forty discs each of Fuji LX, Fuji VII and of Vitrebond were prepared in a plastic mould. Twenty discs of each material were coated for 30 seconds with a 10% solution of AgF. Five discs each of coated and uncoated material were placed individually in 4m1 of differing eluant solutions. The eluant solutions comprised deionized distilled water (DDW) and three separate acetate buffered solutions at pH 7, pH 5 and pH 3. After 30 minutes the discs were removed and placed in five vials containing 4m1 of the various solutions for a further 30 minutes. This was repeated for further intervals of time up to 216 hours, and all eluant solutions were stored. Fluoride concentrations in the eluant solutions were estimated using a fluoride specific electrode, with TISAB IV as a metal ion complexing and ionic concentration adjustment agent. Cumulative fluoride release patterns were determined from the incremental data. The coating of AgF greatly enhanced the level of fluoride ion release from all materials tested. Of the uncoated samples, Vitrehond released the greater concentrations of fluoride ion, followed by Fuji VII. However, cumulative levels of fluoride released from coated samples of the GICs almost matched those from coated Vitrebond. It was concluded that a coating of 10% AgF on GICs and a resin modified GIC greatly enhanced the concentration of fluoride released from these materials. This finding might be applied to improving protection against recurrent caries, particularly in high caries risk patients, and in the atraumatic restorative technique (ART) of restoration placement.

Influence of Ca 2+ in biological stimulating effects of AC magnetic fields on germination of bean seeds

This study reports an attempt to investigate the effects of AC magnetic field on the seed germination and seedling growth of beans, at different concentrations of CaCl 2, since Ca 2+ is an essential plant nutrient. Bean seeds were exposed to a combination of local geomagnetic field (DC field) and sinusoidal time-varying extremely low frequency (ELF) magnetic field (AC field) 28.3 Hz, 20 μT AC field tuned to the fundamental cyclotron resonance for calcium ions. . The application of AC field promoted the germination of bean seeds for all CaCl 2 concentrations. There was no significant change of average weight of the radicals for all concentrations of CaCl 2, whereas there was a significant increase of radicals’ length for deionized (DD) and distilled DD water and DD water+ Ca 10 mM.

After-cataract evaluation after using balanced salt solution, distilled deionized water, and 5-fluorouracil with a sealed-capsule irrigation device in the eyes of 4-week-old rabbits

To evaluate the Perfect Capsule sealed-capsule irrigation device (Milvella Pty., Ltd.) using 3 substances in young rabbit eyes. St. Erik's Eye Hospital, Stockholm, Sweden. Thirty 4-week-old rabbits had clear lens extraction in both eyes. In 1 randomly selected eye, the Perfect Capsule was applied and the lens capsule was irrigated for 5 minutes with 1 of 3 substances: balanced salt solution (BSS), distilled deionized water (DDW), or 5-fluorouracil (5-FU) 50 mg/mL. In the other eye, no sealed capsule irrigation was used. Forty days postoperatively, the animals were killed and the eyes fixed in formalin for histologic analysis. After-cataract was evaluated in 3 ways: clinically, from photographs, and histologically. Central posterior capsule thickness was evaluated using a microscope, camera, and computer. The Perfect Capsule sealed-capsule irrigation system could be used in all selected eyes. The vacuum to the anterior capsule was tight, and the system was sealed in all eyes. After-cataract developed in the BSS group and DDW group, but not in the 5-FU group. The 5-FU group had significantly less after-cataract than the other 2 groups (P<.05). There was no difference between the groups in capsule thickness. The Perfect Capsule sealed-capsule irrigation system could be used in small eyes. Distilled deionized water did not prevent after-cataract in rabbit eyes with highly proliferative cells, but 5-FU was effective in preventing after-cataract.

Effect of Sucrose on the Selection of Mutans Streptococci and Lactobacilli in Dental Biofilm Formedin situ

Microorganisms are selected in dental biofilm by the acidic environment created by sugar fermentation, but the effect of extracellular polysaccharide (EPS) on the counts of cariogenic bacteria is not clear. Dental biofilm was formed in situ for 13 days under exposure 8 times a day to distilled-deionized water, glucose + fructose or sucrose solutions. Mutans streptococci (MS) counts were not different among the groups, but lactobacilli (LB) were significantly higher in glucose + fructose and sucrose groups, without significant difference between them, irrespective of the higher insoluble EPS concentration in the sucrose biofilm matrix. The data suggest that exposure to sugar is more relevant for the predominance of LB in dental biofilm than for MS and that insoluble EPS does not change the counts of these microorganisms in the biofilm.

Evaluation of Copper Speciation and Water Quality Factors That Affect Aqueous Copper Tasting Response

This study determined taste thresholds for copper as its speciation was varied among free cupric ion, complexed cupric ion, and precipitated cupric particles. The impact of copper chemistry on taste is important as copper is added to many beverages and can be present in drinking water as a natural mineral or due to corrosion of copper plumbing. A one-of-five test was used to define thresholds with solutions containing 0.025-8 mg/l Cu (from copper sulfate) in distilled or mineralized water of varying pH. The mineralized water was designed to mimic the composition of a typical tap water. Group thresholds for copper in either distilled-deionized water or mineralized water were not significantly different and ranged from 0.4 to 0.8 mg/l Cu. A difference from control test was used to assess the impact of soluble and particulate copper on taste. Soluble copper species, including free cupric ion and complexed copper species, were readily tasted, while particulate copper was poorly tasted.

Effects of blanching and soaking on some physical characteristics of grass pea (&lt;i&gt;Lathyrus sativus&lt;/i&gt;)

Lathyrus sativus , containing a lathyritic principle, called β-ODAP (β-N-Oxalyl-L- α, β-diaminopropionic acid), is widely grown and consumed in Ethiopia. It is a hardy crop grown under various agro-ecological situations. The major drawback in the use of the legume is the fact that the seeds, in common with other legumes, are not easily rehydrated, are difficult to cook, the seed coat is difficult to remove and long cooking time is required by traditional processing methods for tenderization. In this study, the effect of processing methods like blanching, soaking and cooking on water absorption, leached solids, swelling power, cooking time and sensory qualities of grass pea seeds were investigated. The soaking solutions used were mixed with salt solution, wood ash solution and double distilled de-ionized water. Blanching significantly (p Keywords : blanching, cooking, Lathyrus sativus , soaking African Journal of Food, Agriculture, Nutrition and Development Vol. 6(1) 2006

Continuous chemiluminescence determination of formaldehyde in air based on Trautz–Schorigin reaction

A new continuous method for the determination of formaldehyde in air is described. A cylindrical wet effluent diffusion denuder is used for the collection of formaldehyde from air into a thin film of absorption liquid (distilled-deionized water). Formaldehyde in the denuder concentrate is on-line detected employing a chemiluminescence flow method based on a reaction of formaldehyde and gallic acid with hydrogen peroxide in an alkaline solution. The collection efficiency of formaldehyde is quantitative at the air flow rate of 0.5 L min −1 (absorption liquid flow rate of 336 μL min −1). The limit of detection (S/N = 3) is 0.60 μg m −3 HCHO (0.49 ppb). The calibration graph is linear up to 300 μg m −3 HCHO (244 ppb). The relative standard deviations of chemiluminescence method for 1 × 10 −6 and 5 × 10 −6 M HCHO are 2.87% and 1.49%, respectively. Acetaldehyde interferes negligible, other compounds do not interfere. The method was employed for formaldehyde measurement in ambient air. The comparison measurement illustrates the good agreement of results obtained by proposed method with those obtained by reference fluorimetric method.

Absorption spectra of liquid water and aqueous buffers between 0.3 and 3.72THz

We have developed a terahertz absorption spectrometer suitable for strongly absorbing liquids such as water, and have precisely measured the absorption spectrum of water between 0.3 and 3.72 THz (10-124 cm(-1)). We have also examined the absorption spectra of aqueous 50 mM potassium phosphate buffers at pH 3 and 8, and find that they do not differ significantly from pure distilled de-ionized water.

Measurements of the acid-binding capacity of ingredients used in pig diets

Some feed ingredients bind more acid in the stomach than others and for this reason may be best omitted from pig starter foods if gastric acidity is to be promoted. The objective of this study was to measure the acid-binding capacity (ABC) of ingredients commonly used in pig starter foods. Ingredients were categorised as follows: (i) milk products (n = 6), (ii) cereals (n = 10), (iii) root and pulp products (n = 5), (iv) vegetable proteins (n = 11), (v) meat and fish meal (n = 2), (vi) medication (n = 3), (vii) amino acids (n = 4), (viii) minerals (n = 16), (ix) acid salts (n = 4), (x) acids (n = 10). A 0.5 g sample of food was suspended in 50 ml distilled de-ionised water with continuous stirring. This suspension was titrated with 0.1 mol/L HCl or 0.1 mol/L NaOH so that approximately 10 additions of titrant was required to reach pH 3.0. The pH readings after each addition were recorded following equilibration for three minutes. ABC was calculated as the amount of acid in milliequivalents (meq) required to lower the pH of 1 kg food to (a) pH 4.0 (ABC-4) and (b) pH 3.0 (ABC-3). Categories of food had significantly different (P < 0.01) ABC values. Mean ABC-4 and ABC-3 values of the ten categories were: (i) 623 (s.d. 367.0) and 936 (s.d. 460.2), (ii) 142 (s.d. 79.2) and 324 (s.d. 146.4), (iii) 368 (s.d. 65.3) and 804 (s.d. 126.7), (iv) 381 (s.d. 186.1) and 746 (s.d. 227.0), (v) 749 (s.d. 211.6) and 1508 (s.d. 360.8), (vi) 120 (s.d. 95.6) and 261 (s.d. 163.2), (vii) 177 (s.d. 60.7) and 1078 (s.d. 359.0), (viii) 5064 (s.d. 5525.1) and 7051 (s.d. 5911.6), (ix) 5057 (s.d. 1336.6) and 8945 (s.d. 2654.1) and (x) -5883 (s.d. 4220.5) and -2591 (s.d. 2245.4) meq HCl per kg, respectively. Within category, ABC-3 and ABC- 4 values were highly correlated: R2 values of 0.80 and greater for food categories i, iv, v, vi, vii and viii. The correlation between predicted and observed ABC values of 34 mixed diets was 0.83 for ABC-4 and 0.71 for ABC-3. It was concluded that complete diets with low ABC values may be formulated through careful selection of ingredients. The final pH to which ABC is measured should matter little as ABC-3 and ABC-4 are highly correlated.

Comparison of Stress Corrosion Cracking and Corrosion Fatigue (Anodized and Non-Anodized Grade 4 CP Ti)

Abstract In light of the possible effects of anodization on stress corrosion cracking (SCC) and corrosion fatigue (CF) of CP titanium, a research project has been completed recently in our laboratories to evaluate and compare SCC and CF of anodized versus non-anodized samples from a single lot of Grade 4 CPTi. Initial evaluation of alloy composition, microstructure, Vickers microhardness, and mechanical properties including the tensile and yield strength, % elongation and reduction of area was performed. After these tests ensured the material met the standards of ASTM Standard Specification for Unalloyed Titanium for Surgical Implant Applications (F 67), samples were prepared using low stress grinding techniques. Samples were divided into two groups, and the non-anodized SCC and CF testing was initiated. The surface of the second group of samples was anodized by Synthes to provide a green/gold surface consistent with standard production processing and then tested using the identical methodology as used for the non-anodized samples. Results of the slow strain rate SCC testing on both smooth and notched anodized and non-anodized samples in both distilled de-ionized water and Ringers solution at 37°C showed no effect of anodization. Results of corrosion fatigue testing indicated that, while there was no effect of anodization on corrosion fatigue, there was a significant effect of the notch on the fatigue characteristics regardless of the two different surface conditions.

Two SUR1-specific Histidine Residues Mandatory for Zinc-induced Activation of the Rat KATP Channel

Zinc at micromolar concentrations hyperpolarizes rat pancreatic beta-cells and brain nerve terminals by activating ATP-sensitive potassium channels (KATP). The molecular determinants of this effect were analyzed using insulinoma cell lines and cells transfected with either wild type or mutated KATP subunits. Zinc activated KATP in cells co-expressing rat Kir6.2 and SUR1 subunits, as in insulinoma cell lines. In contrast, zinc exerted an inhibitory action on SUR2A-containing cells. Therefore, SUR1 expression is required for the activating action of zinc, which also depended on extracellular pH and was blocked by diethyl pyrocarbonate, suggesting histidine involvement. The five SUR1-specific extracellular histidine residues were submitted to site-directed mutagenesis. Of them, two histidines (His-326 and His-332) were found to be critical for the activation of KATP by zinc, as confirmed by the double mutation H326A/H332A. In conclusion, zinc activates KATP by binding itself to extracellular His-326 and His-332 of the SUR1 subunit. Thereby zinc could exert a negative control on cell excitability and secretion process of pancreatic beta-and alpha-cells. In fact, we have recently shown that such a mechanism occurs in hippocampal mossy fibers, a brain region characterized, like the pancreas, by an important accumulation of zinc and a high density of SUR1-containing KATP.

Effect of pH on non-enzymatic browning reaction during γ-irradiation processing using sugar and sugar–glycine solutions

Effects of pH on the non-enzymatic browning reaction caused by γ-irradiation processing were investigated. The brown colour development of irradiated sugar–glycine solutions was greater in a buffer system than in deionized distilled water (DDW) with higher pH. Although browning of irradiated sugar solution without glycine was highly increased was in alkaline buffer, no browning was developed in DDW. The maximum browning of the solutions of sugar and sugar–glycine were observed at pH 10 and pH 8, respectively. The browning intensity was in the following order: sucrose ⩾ fructose > glucose. Non-constant pH was observed in DDW (dropped pH between 1.58 and 2.03 units); however, the use of buffers was partially effective in keeping pH constant (pH dropped between 0.03 and 0.56 units). When the irradiated solutions of sugar with and without glycine were analyzed using reverse phase high performance liquid chromatography with diode-array detection (HPLC-DAD), three peaks were separated at 3.37 ± 0.04, 4.60 ± 0.02, and 2.53 ± 0.26 min, and the λ max values of these peaks were the range 259–288 nm. The sum of the areas of these peaks at 260 nm increased with increasing pH. The results of this study indicated that conditions of the system, such as pH and media, can influence the non-enzymatic browning reaction during γ-irradiation.

Effect of copolymer and additive concentrations on the behaviors of mesoporous tungsten oxide

Nanostructured tungsten oxide films exhibit a series of interesting behaviors due to their excellent properties of photochromic reaction and gas sensing. Mesoporous films with a large surface area are desirable to improve their performance. The main purpose of this study is to elucidate the effects of the copolymer and additive concentrations on the microstructure of the mesoporous tungsten oxide prepared by a sol–gel method. The typical calcined tungsten oxide samples synthesized by L62 and P123 exhibit a Brunauer–Emmett–Teller (BET) surface area of 156 and 138 m 2/g, respectively. The pore size of 4–10 nm in the sample increases with increasing copolymer concentration. For different additive conditions synthesized by a triblock copolymer, HCl or distilled deionized water (DDW) additive could further promote the BET surface area of mesoporous tungsten oxide than an additive of NaOH, which can be attributed to the stabilization of the micellization in acid media. The sol–gel tungsten oxide involving the use of nonionic triblock copolymer as the templates with disorder pores exhibits outstanding sensitivity in photochromic and gas-sensing properties. Mesoporous tungsten oxide powder synthesized by triblock copolymer exhibits a high transmittance with an indirect E G of 3.73 eV. Gas-sensing measurement reveals excellent recovery and sensitivity under low gas concentration, low operation temperature for mesoporous tungsten oxide film and a sensitivity of 25 as exposed to 20 ppm NO gas at 40 °C.

PKC isoforms were reduced by lead in the developing rat brain

A plethora of protein kinase C (PKC) isoforms play important roles in regulating synaptic plasticity and neurotransmitter release. Even though, most PKC isoforms are involved in Pb-induced neuronal toxicity, its mechanism is still unclear. The current study addresses the effect of Pb on PKC isoforms in different regions of the developing rat brain. Sprague–Dawley (SD) pregnant rats were exposed to 0.1% Pb as lead acetate dissolved in distilled deionized water (DDW) from gestation day 6 through 21 postnatal day (PND). Control rats were allowed to drink DDW. Pups were sacrificed on PND 1, 5, 10 and 45. Rat brain was immediately excised and separated into the brain stem (BS), the cerebellum (CB), the hippocampus (HC) and the frontal cortex (FC). The Pb level in different regions of the brain was determined using an analytical graphite tube atomizer (Varian). Typical PKC (α, β, γ), novel PKC (ɛ) and atypical PKC (μ) in the above brain regions were enriched by immunoprecipitation and later were assayed by Western blotting. The total, calcium-dependent and -independent PKC activities were determined by the radioactivity of total γ-32P transferred to histone. The results indicated that on PND 1, Pb reduced the PKC-γ protein in HC and FC, whereas on PND 5 the proteins of PKC isoforms (α, β, γ, ɛ, μ) in HC and FC were significantly reduced. These reductions in PKC proteins were higher in membrane fractions than in cytosolic fractions. On PND 10, Pb reduced all PKC isoforms. However, on PND 45, Pb had no significant effect on all PKC isoforms except ɛ. Pb inhibited the total PKC activity by 70% on PND 1 and 5, the bulk of these PKC activities were calcium-dependent. The results suggest that during early stages of the rat brain development, Pb exposure decreased PKC activities and also reduced PKC isoforms including PKC-γ and ɛ which are reported to have roles in the memory formation and long-term potentiation (LTP).