The antimicrobial use of silver compounds pivots on the 100-year-old application of silver nitrate, silver foil, and silver sutures for the prevention and treatment of ocular, surgical, and dental infections. Ag+ kills pathogenic organisms at concentrations of < 50 ppm, and current/potential anti-infective applications include: acute burn coverings, catheter linings, water purification systems, hospital gowns, and caries prevention. To distill the current best evidence relative to caries, this systematic review asked: Will silver diamine fluoride (SDF) more effectively prevent caries than fluoride varnish? A five-database search, reference review, and hand search identified 99 human clinical trials in three languages published between 1966 and 2006. Dual review for controlled clinical trials with the patient as the unit of observation, and excluding cross-sectional, animal, in vitro studies, and opinions, identified 2 studies meeting the inclusion criteria. The trials indicated that SDF’s lowest prevented...

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Silver Diamine Fluoride: A Caries “Silver-Fluoride Bullet”

The interaction of cadmium and certain other metal ions with proteins and nucleic acids

Both histochemical and biochemical studies have been made on phosphatase activity in seven species of Monogenea (Entobdella hippoglossi, Calicotyle krbyeri, Polystoma integerrimum, Diplozoon paradoxum, Discocotyle sagittata, Diclidophora merlangi, and Octodactylus palmata) and eight species of Digenea (Haematoloechus medioplexus, Haplometra cylindracea, Opisthioglyphe ranae, Diplodiscus subclavatus, Gorgoderina vitelliloba, Gorgodera cygnoides, Fasciola hepatica, and Schistosoma mansoni). Results indicate that phosphatases are probably of widespread occurrence in the Trematoda but that differences exist between the two orders as to the nature and relative activity of the enzymes. In the Monogenea, alkaline phosphatase activity occurs over a fairly broad pH, with an optimum at pH 9 in vitro, and is predominantly found in the gut, the reproductive structures, and the walls of the excretory ducts. The Digenea possess both acid and alkaline phosphatases and show species differences in the relative activities of the two forms. In all cases pH optima for the enzymes, in vitro, were 4.5 to 5.0 and 9.0 to 9.5, respectively. Acid phosphatase activity is primarily localized in the microvilli of the gutt cells of all the Digenea, with the greatest activity in those species possessing an irregular and active surface to the gastrodermis. Species differences also occur in the distribution of acid and alkaline phosphatases associated with the reproductive complex, while the occurrence of alkaline phosphatase in the excretory system is common to all the species examined. Other reactive sites for phosphatases include the cuticle and subcuticular tissues, organs of attachment, and the pharyngeal gland cells in a number of species. The significance of phosphatase activity in the Trematoda is discussed in the light of its probable role in phosphorylated transfer mechanisms and carbohydrate metabolism. There are many reports of phosphatase activity in the Trematoda. In Fasciola hepatica, a fairly high degree of acid phosphatase activity has been recorded for tissue extracts (Pennoit de-Cooman and van Grembergen, 1942) and localized, histochemically, in the cuticle, subcuticular cells, and gastrodermis (Yamao and Saito, 1952; Tarazona Vilas, 1958; Saito, 1961). In addition, moderate activity for alkaline phosphatase has been found in the testes (Tarazona Vilas, 1958) and excretory duct walls (Reznik, 1963). The presence of both acid and alkaline phosphatases in F. hepatica has since been proved electrophoretically by Pantelouris (1966). Similarly, the enzymes have been reported in homogenates of Schistosoma mansoni, and again localized in the cuticle, gastrodermis, and reproductive structures (Dusanic, 1959; Robinson, 1961; Nimmo-Smith and Standen, 1963). Other species in which phosphatases have been demonstrated include Dicrocoelium lanceatum, Eurytrema sp. (Yamao, 1952a), Paragonimus westermani (Yamao, 1952b), Clonorchis sinensis (Ma, 1964), and Gastrothylax crumenifer (Goil, 1966). None of these reports include the MonogeReceived for publication 12 August 1966. * Present address: Department of Zoology, The Queen's University, Belfast, N. Ireland. nea, and for the most part they have not been comparative in nature. Because of this, and the fact that recent studies on nutrition in Trematoda (Halton and Jennings, 1965; Halton, 1967) have indicated distinct differences in phosphatase activity in the gut of the Monogenea and Digenea, both histochemical and biochemical studies have been made on phosphatase systems in a representative selection of trematodes. The investigation was primarily aimed at establishing the general pattern of phosphatase activity in the group, as well as noting species differences in the type of enzyme found. MATERIALS AND METHODS The trematodes studied were seven species of Monogenea: Entobdella hippoglossi, Calicotyle kroyeri (suborder Monopisthocotylea), Polystoma integerrimum, Diplozoon paradoxurn, Discocotyle sagittata, Diclidophora merlangi, and Octodactylus palmata (suborder Polyopisthocotylea); and eight species of Digenea: Haematoloechus medioplexus, Haplometra cylindracea, Diplodiscus subclavatus, Opisthioglyphe ranae, Gorgoderina vitelliloba, Gorgodera cygnoides, Fasciola hepatica, and Schistosoma mansoni. For details of the respective hosts and parasitic habitats see Halton and Jennings (1965) and Halton (1967). Specimens were collected alive from their hosts and after a brief wash in saline fixed for up to 8 hr at 4 C in 4% formaldehyde, phosphate-buffered to pH 7.0. Following fixation, the material was either transferred to 0.2M sucrose and frozen sec-

Studies on phosphatase activity in trematoda.

The effects of parasitism by five species of larval Digenea on the digestive gland cells of Littorina saxatilis (Olivi) subsp. tenebrosa (Montagu) were investigated by comparing histochemically stained cells in healthy, starved and parasitized animals.Two distinct effects were apparent: (a) The germinal sacs compress the walls of the digestive gland tubules and block the lumen. Since food cannot pass this block, digestive gland cells behind undergo starvation autolysis. (b) In digestive gland tubules not cut off from their food supply, glucose, glycogen, glycoproteins and lipid food storage globules are reduced and there is a compensatory increase in the number of food vacuoles in the digestive cells; an increase in glucose but a decrease in glycogen in the visceral haemocoel; and an increase in the number of secretory cells, perhaps in order to eliminate the parasite's excretory products from the visceral haemocoel.

The effects of parasitism by larval Digenea on the digestive gland of the intertidal prosobranch, Littorina saxatilis (Olivi) subsp. tenebrosa (Montagu).

Hemoglobins of parasitic animals.

Fat metabolism in trematode parasites.

Biochemical studies on the non-specific phosphomonoesterases of Fasciola hepatica have shown the presence of acid phosphomonoesterase active at pH 4·6 and two forms of alkaline phosphomonoesterases active at pH 7·6 and pH 9·6 respectively. Histochemical studies have located acid phosphomonoesterase in the walls of the intestinal caeca and to a lesser extent in the tegument. Alkaline phosphomonoesterase was found to occur mainly in the excretory ducts and to a lesser degree in the uterine wall. Glycogen was mainly concentrated in the yolk glands, parenchyma, mature eggs and the non-muscular regions of both oral and ventral suckers.Dr A. J. Probert takes pleasure in recording the support of the British Council and the Indian University Grants Commission to enable him to study in India.

Biochemical and histochemical studies on the non-specific phosphomonoesterases of Fasciola gigantica Cobbold 1855.

1. Introduct ion Following the classical exper iments of W:EI~LA:ND (1901, 1904) on the metabol ism of he lmin th parasites, considerable work has been done on this subject in recent years. The accumula ted l i terature, an indirect measure of the interes t shown by world workers ill this b ranch of science, has been reviewed by McCoY (1935), vo~ B~A~D (1938), YON BRAXD and JAHN (1942), SMrTH (1947), HOBSO~ (1948), BVEDING (1949), and vo~ B~AND (1952). While the metabolic behaviour of cestodes and nematodes has received considerable a t tent ion , l i t t le work appears to have been done on the metabol isnl of t rematodes ; and whatever has been done relates to the metabolic behaviour of Fasciola hepatica, probably due to its larger size. In F. hepatica, FLUtCY and LEEB (1926) found 3.1 parts of glycogen per 100 parts of fresh weight of tissue or 15 par ts of glycogen per 100 parts of d ry weight of tissue, while WEI~LA~D and vo~ BRA~D (1926) in the same species found 3.7% ot glycogen on f. w. basis or 21% of glycogen on d. w. basis. I n anothel t rematode Schistosoma mansoni, BUEDI:NG and KOLETSKY (1950) estimated 14 to 29% of glycogen of the d ry ma t t e r in the males and 3 to 5% of t ha t in females. They also concluded tha t the glycogen content of the older males was greater t han in the younger specimens. The present paper deals with the studies conducted on the carbohydrate metabol ism of two t rematodes namely, Paramphistomum explanatum and Gastrothylax crumeni/er.

Carbohydrate metabolism in trematode parasites.

Dete rmina t ions of oxygen consumpt ion have been repor ted for a number of endoparasi tes , specially cestodes and nematodes among the parasi t ic helminths , a l though not much work appears to have been done on t rematodes . Studies using the Warbu rg technique have been repor ted for the adul t stages of Fasciola hepatica ( H ~ i S C H 1932, v a n G~MBEl~GnN 1949), Paramphistomum cervi (LAzARvS 1950), Schistosoma mansoni (BuEDI~G 1950), and Gynaecotyla adunca [HUNT]~R and VER~ERG 1955 (I a. I I ) ] . I n the present s tudy two t r ema tode parasi tes were selected namely , Paramphistomum expganatum and Gastrothylax crumeni/er of ruminan t s which were v e r y easi ly avai lable in abundance.

Rate of oxygen consumption in trematode parasites.

Studies on aspartate aminotransferase (GOT) and l-alanine aminotransferase (GPT) of Paramphistomum explanatum have shown that GPT activity has more than twice the activity of GOT. The effect of some —SH reagents like cadmium, mercury, silver and iodoacetamide revealed that both enzymes were inhibited except that GOT was insensitive to cadmium ions. GPT was found to be much more sensitive to —SH reagents than GOT. There was unusual reaction to the two thiols used, cysteine and mercaptoethanol. Cysteine inhibited both the enzymes and mercaptoethanol activated GPT and inhibited GOT. Thiols in combination with iodoacetamide showed that the strong inhibitory effect of cysteine on both enzymes was reduced by iodoacetamide, but with mercaptoethanol the inhibitory effect on GOT was greater than when either of them was used alone, while on GPT the effect of either counteracted each other. EDTA activated both enzymes and partially protected mercury inhibition of both enzymes and silver inhibition of GOT only. It provided no protection against silver inhibition of GPT but complete protection of GPT against total inhibition by cadmium ions.

Madan M. Goil

Papers

Fat metabolism in trematode parasites.

Biochemical and histochemical studies on the non-specific phosphomonoesterases of Fasciola gigantica Cobbold 1855.

Carbohydrate metabolism in trematode parasites.

Rate of oxygen consumption in trematode parasites.

Effect of some--SH and other reagents on aspartate aminotransferase and L-alanine aminotransferase of Paramphistomum explanatum Fischoeder, 1901.