scholarly journals RATIO OF PROCESSES OF CELL PROLIFERATION AND APOPTOSIS IN THE SKIN UNDER EXPOSURE TO HEAVY METAL SALTS AND CHELATORS OF ESSENTIAL METALS

2019 ◽  
Vol 96 (7) ◽  
pp. 690-694
Author(s):  
Tatyana V. Nikolaeva ◽  
V. S. Polyakova ◽  
N. P. Setko ◽  
L. G. Voronina
Keyword(s):  
Proliferative Activity ◽  
Lead Acetate ◽  
Zinc Sulfate ◽  
Nickel Sulfate ◽  
Iron Chelator ◽  
Proliferation Index ◽  
Sodium Dichromate ◽  
Proliferation And Apoptosis ◽  
Zinc Chelator ◽  
Apoptotic Activity

In the model experiment on C57BL /6 mice there were established features of the impact of heavy metals and chelators of essential metals on proliferation and apoptosis of epithelial skin cells (keratinocytes). For the execution of a study 40 test animals were divided into seven experimental and 1 control groups, each consisted of five animals. The proliferative and apoptotic activity of keratinocytes was determined by the immunohistochemical method and evaluated by calculating the proliferation index and the index of apoptosis in the cells of the surface epithelium and the epithelial cells of hair follicles in the late anagen stage. Comparative analysis of the proliferation index of the control group and experimental groups showed administration of zinc sulfate, sodium dichromate and zinc chelator (N, N, N`, N`-tetrakis (2-pyridylmethyl) ethylenediamine) to animals to give rise in a statistically significant increase in the proliferative activity of keratinocytes. The decline of proliferation index was detected in animals treated with lead acetate and copper chelator (ammonium tetrathiomolybdate). Introduction of an iron chelator (deferoxamine) had no effect on the proliferative activity of keratinocytes in experimental animals. Induction of apoptosis of epithelial cell was noted under the administration of nickel sulfate, sodium dichromate, lead acetate and zinc chelator (N, N, N`, N`-tetrakis (2-pyridylmethyl) ethylenediamine) to animals. In mice received deferoxamine zinc sulfate and apoptotic activity of keratinocytes has not changed. The use of cluster analysis allowed to classify substances administered to experimental animals, taking into account their simultaneous effect on the studied cellular processes. Lead acetate, iron chelator (deferoxamine) and copper chelator (ammonium tetrathiomolybdate) were shown to reduce the proliferative activity of keratinocytes and have little effect on apoptosis of the epithelial cells of the skin. Zinc sulfate, nickel sulfate, sodium dichromate and zinc chelator (N, N, N`, N`-tetrakis (2-pyridylmethyl) ethylenediamine) activate cell proliferation and induce apoptosis of keratinocytes.

scholarly journals STRUCTURAL-FUNCTIONAL REORGANIZATION OF SKIN AND ITS DERIVATIVES UNDER EXPERIMENTAL SUBACUTE OF INTOXICATION BY HEAVY METALS

2019 ◽  
Vol 96 (6) ◽  
pp. 593-596
Author(s):  
Tatyana V. Nikolaeva ◽  
V. S. Polyakova ◽  
N. P. Setko ◽  
L. G. Voronina
Keyword(s):  
Heavy Metals ◽  
Proliferative Activity ◽  
Lead Acetate ◽  
Dermal Papilla ◽  
Hair Follicles ◽  
The Body ◽  
Acetate Solution ◽  
Sodium Dichromate ◽  
Ki 67 ◽  
Nickel Chromium

There was executed an experimental study of the effect of salts of heavy metals (nickel, chromium, lead and zinc) entering the body by peroral route, on the morphology of the skin and its derivatives (hair follicles and sebaceous glands). The experiment was performed on C57BL / 6 mice with the use of the induction of hair follicle cycle by depilation. Under the subacute intoxication with salts of nickel, chromium and lead, there were revealed such signs of a dystrophic anagen as ectopia of granules of melanin in the dermal papilla and perifollicular tissue, enlarged channels of the hair. The duration of the anagen stage if compared with the control did not change. Under the intoxication with salts of nickel and lead there was revealed infiltration by mononuclear dermis and hypodermis. Lead acetate gave rise in the capillary congestion of the dermis, followed by diapedesis of erythrocytes and infiltration of the dermis by siderophages. In the course of the immunohistochemical study of the proliferative activity of keratinocytes of the skin integument derivatives with the use of antibodies to Ki-67, there was revealed a significant increase of proliferative activity of keratinocytes in comparison with the control under the use of a solution of zinc sulphate and sodium dichromate and its decrease with the use of lead acetate solution.

scholarly journals Silver Antibacterial Synergism Activities with Eight Other Metal(loid)-Based Antimicrobials against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus

Antibiotics ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 853
Author(s):  
Ali Pormohammad ◽  
Raymond J. Turner
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Silver Nitrate ◽  
Zinc Sulfate ◽  
Nickel Sulfate ◽  
Luria Broth ◽  
Potassium Tellurite ◽  
Wound Fluid ◽  
E Coli

The present study surveys potential antibacterial synergism effects of silver nitrate with eight other metal or metalloid-based antimicrobials (MBAs), including silver nitrate, copper (II) sulfate, gallium (III) nitrate, nickel sulfate, hydrogen tetrachloroaurate (III) trihydrate (gold), aluminum sulfate, sodium selenite, potassium tellurite, and zinc sulfate. Bacteriostatic and bactericidal susceptibility testing explored antibacterial synergism potency of 5760 combinations of MBAs against three bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus) in three different media. Silver nitrate in combination with potassium tellurite, zinc sulfate, and tetrachloroaurate trihydrate had remarkable bactericidal and bacteriostatic synergism effects. Synergism properties of MBAs decreased effective antibacterial concentrations remarkably and bacterial cell count decreased by 8.72 log10 colony-forming units (CFU)/mL in E. coli, 9.8 log10 CFU/mL in S. aureus, and 12.3 log10 CFU/mL in P. aeruginosa, compared to each MBA alone. Furthermore, most of the MBA combinations inhibited the recovery of bacteria; for instance, the combination of silver nitrate–tetrachloroaurate against P. aeruginosa inhibited the recovery of bacteria, while three-fold higher concentration of silver nitrate and two-fold higher concentration of tetrachloroaurate were required for inhibition of recovery when used individually. Overall, higher synergism was typically obtained in simulated wound fluid (SWF) rather than laboratory media. Unexpectedly, the combination of A silver nitrate–potassium tellurite had antagonistic bacteriostatic effects in Luria broth (LB) media for all three strains, while the combination of silver nitrate–potassium tellurite had the highest bacteriostatic and bactericidal synergism in SWF. Here, we identify the most effective antibacterial MBAs formulated against each of the Gram-positive and Gram-negative pathogen indicator strains.

scholarly journals Effects of Watermelon Consumption on Cellular Proliferation, and Apoptosis in Rat Colon (P05-019-19)

2019 ◽  
Vol 3 (Supplement_1) ◽  
Author(s):  
Meseret Fesseha ◽  
Mee Young Hong
Keyword(s):  
Colon Cancer ◽  
Cell Proliferation ◽  
Cellular Proliferation ◽  
Dietary Intervention ◽  
Citrullus Lanatus ◽  
Proliferation Index ◽  
Cancer Center ◽  
Rat Colon ◽  
Proliferative Zone ◽  
Proliferation And Apoptosis

Abstract Objectives Colon Cancer is the second deadliest cancerous disease worldwide among men and women. It has been estimated that more than half of colon cancers may be preventable by dietary intervention. A disturbance of the homeostasis between cellular proliferation and apoptosis is associated with colon cancer development. Watermelon (Citrullus lanatus) is rich in L-citrulline, a precursor of L-arginine. It has been shown that L-arginine may have anti-inflammatory roles and serves as a substrate for synthesis of nitric oxide, which in turn exerts wide-ranging physiological effects including tumoricidal effects via modification of cell kinetics. Our research examined if colon cancer can be prevented with the supplementation of watermelon powder by lowering cellular proliferation but enhancing apoptosis. Methods In order to test the hypothesis, 21-days old 32 Sprague Dawley rats were allocated to three groups; control, L- arginine (0.36% L-arginine) and watermelon powder (0.5%, w/w). Carcinogen azoxymethane was injected at week 4 and 5, and colon tissues were harvested at 5 week after the 2nd carcinogen injection. Cell proliferation and apoptosis were enumerated using a quantitative immunohistochemical analysis of Ki-67 antibody and TUNEL assay, respectively. Results Cell proliferation was mainly located bottom of colonic crypt (P < 0.05). Apoptotic cells were mostly located in the upper part of crypt (P < 0.05). L-arginine and watermelon fed rats lowered cell proliferation index and proliferative zone (P < 0.05). However, no difference was found on apoptosis among the three groups. Conclusions These results suggest that watermelon powder supplementation may reduce the risk of colon cancer by reducing cell proliferation rather than alteration of apoptosis. Further study will follow to determine the mechanism of anti-proliferative effect of watermelon supplementation. Funding Sources National Watermelon Promotion Board; SDSU/UCSD Cancer Center Partnership Scholars Program.

scholarly journals IMMUNOPHENOTYPIC CHARACTERISTIC OF PROLIFERATION AND APOPTOSIS OF INTACT KERATINOCYTES IN SEPSIS

2020 ◽  
Vol 10 (2) ◽  
pp. 48-52
Author(s):  
Ye. Yu. Shapovalova ◽  
G. А. Demyashkin ◽  
M. Yu. Malanichrev ◽  
D. А. Pogasyan ◽  
V. I. Shchekin
Keyword(s):  
Systemic Inflammation ◽  
Caspase 3 ◽  
Mitotic Division ◽  
Multiple Organ ◽  
The Body ◽  
Sepsis Group ◽  
Ki 67 ◽  
Group I ◽  
Proliferation And Apoptosis ◽  
Apoptotic Activity

In response to infection by pathogenic microbes, a serious systemic inflammation occurs in the body, often lead- ing to death. Unbalanced systemic immune responses can lead to the accumulation of leukocytes, disseminated intravascular coagulation and microcirculatory dysfunction, followed by apoptosis and cell necrosis, as well as the development of multiple organ failure syndrome. The destruction of the barrier can apparently lead to a violation of the proliferation and apoptosis of keratinocytes. The aim of the study was to evaluate intracellular protein-regulators of the life cycle of keratinocytes of the intact epidermis in case of systemic inflammation. Material and methods. The study was performed on 40 archival paraffin blocks of skin fragments in two groups: group I (n = 30) - deceased patients with a diagnosis of severe bacterial sepsis; Group II (n = 10) – dead for reasons not related to an infectious disease (control). Immunohistochemical studies were performed according to a standard protocol using antibodies to Ki-67, caspase 3, Bcl-2 and p53. Results. In the cells of the epidermis of patients in the condition of systemic inflammation, the following expression of the studied markers is observed: caspase-3 – 39.4 ± 1.2%; p53 – 18.4 ± 0.7%; Ki-67 – 15.2 ± 4.1%; Bcl-2 – 4.2 ± 1.2%. Conclusion Under conditions of systemic inflammation in the epidermis, there is an imbalance in the proliferative- apoptotic activity of keratinocytes in the direction of reducing their mitotic division and activation of apoptosis, leading to cell death.

scholarly journals Influence of proinflamatory macrophages (M-1) on proliferative activity and PPAR-γ expression in neoplastic rat hepatocytes in vitro

2019 ◽  
Vol 75 (05) ◽  
pp. 6220-2019
Author(s):  
MARTA WÓJCIK ◽  
URSZULA KOSIOR-KORZECKA ◽  
MICHAŁ PLEWIK ◽  
RYSZARD BOBOWIEC
Keyword(s):  
Blood Cells ◽  
Proliferative Activity ◽  
Gradient Centrifugation ◽  
Liver Perfusion ◽  
Negative Relationship ◽  
Rat Hepatocytes ◽  
Neoplastic Cell ◽  
Proliferation Index ◽  
Ppar Γ

We sought to analyse the proliferative activity and PPARγ expression in neoplastic and non-neoplastic rat hepatocytes, exposed to immunologically trained macrophages M1 (Mf-M1). Ten-week-old female Wistar rats were divided into two groups: I - control (n=5) and II neoplstic (n=5). To induce HCC in the neoplastic group, genotoxic diethylnitrosamine (DEN) was administered after a partial hepatectomy (PH). Hepatocytes were isolated by liver perfusion method and the mononuclear blood cells were isolated using Lymphoprep density-gradient centrifugation. After differentiation, blood cells were treated with barley-derived β-glucan (BBG) (10 μg/ml). Adhered heaptocytes and Mf were cultured in 3D Quasi-Vivo System during 24 h. Then, hepatic proliferation and PPAR γ expression were analysed after 72 h and the 1st ,the 2nd and the 3rd week of incubation. The proliferation index of control hepatocytes ranged between 0.41±0.04 – 0.43±0.03 after 72 h and after the 3rd week of incubation respectively. Exposure of these cells to Mf resulted in marked increase of IP after the 1st, the 2nd and the 3rd week of incubation. When hepatocytes were influenced by proinflammatory Mf- M1, their proliferation was maintained at control stage. DEN-obtained hepatocytes, not influenced by macrophages, exhibit enhanced proliferation. When these cells where co-cultured with Mf-M1, marked (P≤0.05) inhibition of cell proliferation was observed. In such condition, a high negative relationship (r= -0.93) between proliferative activity of the hepatocytes and the PPARγ concentration was observed. We conclude that immunologically trained macrophages M1, are capable to activation of PPARγ in rat neoplastic hepatocytes derived from experimentally induced HCC. In turn intensified expression of PPARγ may inhibited proliferation of neoplastic cell in vitro.

scholarly journals Retinoic Acid Sensitivity of Triple-Negative Breast-Cancer Cells Characterized by Constitutive Activation of the NOTCH1 Pathway: The Role of RARβ

2020 ◽  
Author(s):  
Gabriela Paroni ◽  
Adriana Zanetti ◽  
Maria Monica Barzago ◽  
Mami Kurosaki ◽  
Luca Guarrera ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Retinoic Acid ◽  
Rna Sequencing ◽  
Cell Lines ◽  
Triple Negative Breast Cancer ◽  
Proliferative Activity ◽  
Triple Negative ◽  
Proliferation Index ◽  
Constitutive Activation ◽  
Sequencing Studies

Abstract Background: All-trans retinoic-acid (ATRA) is a promising agent in the personalized treatment/chemo-prevention of breast-cancer. Triple-negative breast-cancer (TNBC) accounts for 15-20% of all mammary tumours and share common features such as a high proliferation index and a basal-like gene expression signature. In spite of this, TNBC is very heterogeneous and lacks effective therapeutic strategies.Methods: We profile eighteen TNBC breast-cancer cell-lines for their sensitivity to the anti-proliferative action of ATRA. In addition, we perform RNA-sequencing studies in two of the most sensitive cell-lines exposed to ATRA, a γ-secretase inhibitor and combinations thereof. Results: The only three TNBC cell-lines (HCC-1599, MB-157 and MDA-MB-157) endowed with ATRA-sensitivity are characterized by constitutive activation of the NOTCH1 γ-secretase product, N1ICD and we identify the associated genetic aberrations of the NOTCH1-gene. N1ICD expression renders HCC-1599, MB-157 and MDA-MB-157 cells sensitive not only to ATRA, but also to γ-secretase inhibitors, like DAPT [N-(N-(3,5-difluorophenacetyl)-L-alanyl)-S-phenylglycine-t-butyl-ester] and PF-03084014. The anti-proliferative action of ATRA and γ-secretase inhibitors is complementary, as combinations of ATRA and DAPT or PF-03084014 cause synergistic effects. This synergism is confirmed in mouse xenografts of HCC-1599 cells. RNA-sequencing studies performed in HCC-1599 and MB-157 cells exposed to ATRA and DAPT demonstrate that the two compounds act on common gene-sets, some of which belong to the NOTCH1 pathway. ATRA inhibits the growth of HCC-1599, MB-157 and MDA-MB-157 cells via RARα, which up-regulates several retinoid target-genes, including RARβ. RARβ induction is observed only in HCC-1599, MB-157 and MDA-MB-157 cells, as the other TNBC cell-lines lack ATRA-dependent stimulation of the retinoid-receptor. RARβ is a key determinant of ATRA anti-proliferative activity, as its silencing suppresses the effects exerted by the retinoid. Conclusions: We demonstrate that ATRA exerts a significant anti-tumor action in TNBC cells characterized by constitutive NOTCH1 activation. We show that ATRA enhances the anti-tumor activity of γ-secretase inhibitors in an additive/synergistic manner. We support the idea that ATRA anti-proliferative activity is mediated by the Retinoid-Acid-Receptor-β (RARβ). The present study represents the basis for the design of clinical trials on the efficacy of combinations between ATRA and γ-secretase inhibitors in the treatment of patients affected by a specific subtype of TNBC.

scholarly journals Optimized Conjugation of Fluvastatin to HIV-1 TAT Displays Enhanced Pro-Apoptotic Activity in HepG2 Cells

2020 ◽  
Vol 21 (11) ◽  
pp. 4138
Author(s):  
Lamya H. Al-Wahaibi ◽  
Muneera S. M. Al-Saleem ◽  
Osama A. A. Ahmed ◽  
Usama A. Fahmy ◽  
Nabil A. Alhakamy ◽  
...  
Keyword(s):  
Zeta Potential ◽  
Hepg2 Cells ◽  
Proliferative Activity ◽  
Annexin V ◽  
Immunodeficiency Virus ◽  
Late Apoptosis ◽  
Apoptotic Activity ◽  
Apoptotic Effects ◽  
Hiv 1

Accumulating evidence indicates that statins reduce the risk of different cancers and inhibit the proliferation of liver cancer cells. This study aims to explore whether the electrostatic conjugation of optimized fluvastatin (FLV) to human immunodeficiency virus type 1 (HIV-1) trans-activator transcription peptide (TAT) would enhance the anti-proliferative activity against HepG2 cells. FLV–TAT conjugation was optimized to achieve the lowest size with highest zeta potential. Nine formulae were constructed, using a factorial design with three factors—FLV concentration, TAT concentration, and pH of the medium—while the responses were zeta potential and size. The optimized formula showed a particle size of 199.24 nm and 29.14 mV zeta potential. Data indicates that conjugation of FLV to TAT (optimized formula) significantly enhances anti-proliferative activity and uptake by HepG2 cells when compared to raw FLV. Flow cytometry showed significant accumulation of cells in the pre-G phase, which highlights higher apoptotic activity. Annexin V staining indicated a significant increase in total cell death in early and late apoptosis. This was confirmed by significantly elevated caspase 3 in cells exposed to FLV–TAT preparation. In conclusion, the FLV–TAT optimized formula exhibited improved anti-proliferative action against HepG2. This is partially attributed to the enhanced apoptotic effects and cellular uptake of FLV.

scholarly journals Encapsulation of Lovastatin in Zein Nanoparticles Exhibits Enhanced Apoptotic Activity in HepG2 Cells

2019 ◽  
Vol 20 (22) ◽  
pp. 5788 ◽  
Author(s):  
Nabil A. Alhakamy ◽  
Osama A.A. Ahmed ◽  
Hibah M. Aldawsari ◽  
Mohammad Y. Alfaifi ◽  
Basma G. Eid ◽  
...  
Keyword(s):  
Hepg2 Cells ◽  
Proliferative Activity ◽  
Caspase 3 ◽  
Annexin V ◽  
Entrapment Efficiency ◽  
Positive Staining ◽  
Cell Accumulation ◽  
A Cell ◽  
Apoptotic Activity ◽  
Zn Nanoparticles

Research on statins highlights their potent cytotoxicity against cancer cells and their potential for cancer prevention. The aim of the current study was to examine whether loading lovastatin (LVS) in zein (ZN) nanoparticles (NPs) would potentiate the anti-proliferative effects of LVS and enhance its proliferation-inhibiting activity in HepG2 cells. LVS-ZN NPs were prepared and showed excellent characteristics, with respect to their particle size, zeta potential, diffusion, and entrapment efficiency. In addition, they showed the most potent anti-proliferative activity against HepG2 cells. ZN alone showed an observable anti-proliferative that was significantly higher than that of raw LVS. Furthermore, LVS uptake by HepG2 cells was greatly enhanced by the formulation in ZN. A cell cycle analysis indicated that LVS induced a significant cell accumulation in the G2/M and pre-G phases. In this regard, the LVS–ZN NPs exhibited the highest potency. The accumulation in the pre-G phase indicated an enhanced pro-apoptotic activity of the prepared formula. The cells incubated with the LVS-ZN NPs showed the highest percentage of cells with annexin-V positive staining. In addition, the same incubations showed the highest content of caspase-3 enzyme in comparison to raw LVS or ZN. Thus, the loading of LVS in ZN nanoparticles enhances its anti-proliferative activity against HepG2 cells, which is attributed, at least partly, to the enhanced cellular uptake and the induction of apoptosis.

Basal/Myoepithelial Cells in Chronic Sinusitis, Respiratory Epithelial Adenomatoid Hamartoma, Inverted Papilloma, and Intestinal-Type and Nonintestinal-Type Sinonasal Adenocarcinoma: An Immunohistochemical Study

2007 ◽  
Vol 131 (4) ◽  
pp. 530-537 ◽  
Author(s):  
John A. Ozolek ◽  
E. Leon Barnes ◽  
Jennifer L. Hunt
Keyword(s):  
Proliferative Activity ◽  
Chronic Sinusitis ◽  
S100 Protein ◽  
Myoepithelial Cells ◽  
Inverted Papilloma ◽  
Proliferation Index ◽  
Ki 67 ◽  
Respiratory Epithelial Adenomatoid Hamartoma ◽  
Sinonasal Adenocarcinoma ◽  
Respiratory Epithelial

Abstract Context.—The pathogenesis of respiratory epithelial adenomatoid hamartoma (REAH) and inverted papilloma (IP) is poorly understood, especially compared with sinonasal adenocarcinoma (SNAC). One feature of malignant glandular lesions is loss of the basal/myoepithelial layer. The immunophenotype of the basal/myoepithelial layer has not been fully examined in benign glandular lesions of the sinonasal tract. Objective.—To examine benign and malignant glandular lesions in the sinonasal tract for the immunophenotype of basal/myoepithelial cells, proliferation index, and cytokeratin and intestinal differentiation profiles. Design.—Sinonasal adenocarcinoma (intestinal-type adenocarcinoma [ITAC] and nonintestinal type adenocarcinoma [non-ITAC]), REAH, IP, and chronic sinusitis (CS) were stained for cytokeratin (CK) 7, CK20, 34βE12, CDX-2, p63, Ki-67, smooth muscle actin (SMA), S100 protein, and calponin. Results.—Basal/myoepithelial cells in CS and REAH were positive for p63 and 34βE12 but negative for SMA, S100 protein, and calponin. Proliferative activity was localized to the compartment containing p63-positive cells. Inverted papilloma demonstrated broad areas staining for p63 and 34βE12, with intermediate proliferative activity in these areas. Sinonasal adenocarcinoma had the highest Ki-67 labeling index, and p63-positive SNACs had higher proliferation indices than p63-negative SNACs. REAH, IP, CS, and most SNACs expressed CK7. Only SNAC expressed CK20. Sixty percent of morphologic ITACs expressed CDX-2. Conclusions.—Basal/myoepithelial cells in CS and REAH should be considered basal and not myoepithelial cells. In benign lesions, proliferative activity is limited to the compartments with p63 staining. In SNAC and IP, p63 expression correlates with proliferation index. REAH, IP, and CS share similar immunoprofiles (CK7+, CK20−, and CDX-2−), contrasting with SNAC (CK7+, CK20+/−, CDX-2−/+).

scholarly journals Anomalous Liesegang stratifications produced by the action of light

1921 ◽  
Vol 99 (701) ◽  
pp. 496-502 ◽  
Keyword(s):  
Lead Acetate ◽  
A Priori ◽  
Potassium Chromate ◽  
Lead Chromate ◽  
Sodium Dichromate ◽  
Agar Gel ◽  
Unknown Quantity ◽  
Low Concentrations ◽  
Normal Specimen ◽  
Quantitative Treatment

The investigation to be described in the present paper was originally begun with the intention of studying the Liesegang phenomenon under conditions more strictly defined than have been observed hitherto, and more particularly with definite volume ratios of the reacting solutions. In all the experiments recorded in the literature the amount of solution placed on a given, or unknown, quantity of gel has been arbitrary and is generally not even stated. A quantitative treatment of the phenomenon is impossible a priori as long as this ratio is unknown, and would probably become simplest if one, or both, volumes were made—practically—infinite. In the course of the preliminary studies for such experiments an extremely striking anomaly, not observed so far, was discovered, which appears to deserve being put on record before the main investigation is completed. The reaction chosen for this work was the formation of lead chromate in agar gel by the interaction of lead acetate (dissolved in the gel) with potassium or sodium dichromate, or with potassium chromate. This reaction, in very low concentrations, produces extremely fine and numerous stratifications, which were first obtained by L. J. de Whalley; the low concentrations and the cheapness of the ingredients also made it eminently suitable for work involving the use of large volumes. Soon after its discovery the reaction was employed by the author and the results discussed in their bearing on some controversial points, in the paper quoted above. A normal specimen is illustrated in fig. 1 (Plate 8); in this, as in all other specimens photographed, the excess of soluble dichromate present in the gel has been removed by prolonged diffusion, so as to show the lead chromate strata as distinctly as possible.

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