Internal transport and metabolism of cobalamin in Spirometra mansonoides (Cestoda) spargana

The anterior 2 mm of the sparganum of Spirometra mansonoides contained 35 to 48% of the total endogenous cobalamin (Cbl) with only 2 to 4% in the terminal 1 cm. [57Co]cobalamin taken up in the posterior region of spargana was transported directionally to the anterior region and concentrated there resulting in a uniform depletion of [57Co]Cbl along the remaining body length. The anterior 2 mm contained 24% of the sparganum's holo-MMCoAM activity with only 5% in the terminal 1 cm. When head and body preparations were chromatographed on Sephadex G-150 columns eluates from both regions exhibited single peaks of MMCoAM activity at an approximate molecular weight of 150,000 and two peaks of endogenous Cbl. The first Cbl peak cochromatographed with MMCoAM activity and the second Cbl peak eluted at the position of free Cbl. Spargana rapidly converted CN-[57Co]Cbl to hydroxocobalamin (OH-Cbl) and adenosylcobalamin (Ado-Cbl) in vitro. In the head region significant amounts of Ado-Cbl were present (25%) although OH-Cbl was the predominant form of Cbl (45%) after 264 hr in a Cbl-free medium. In the body Ado-Cbl was the predominant form of Cbl (44%) although significant amounts of OH-Cbl were present (27%) after 264 hr in a Cbl-free medium. No methylcobalamin (Me-Cbl) was detected, but an unidentified cobalamin-containing entity (Fraction 4) was present. Based on these results we propose that the sparganum takes up cobalamin, concentrates it in the anterior, "head" region, sequentially metabolizes it to the hydroxyl then the adenosyl forms, and that the adenosylated form is used in this region of high, anaerobic metabolism as an obligatory coenzyme for MMCoAM, in coordination with the differentiation of the sparganum to the adult cestode.     

Comparison of the uptake of vitamin B12 by Spirometra mansonoides and Hymenolepis diminuta and the functional groups of B12 analogs affecting uptake.

Uptake of 57Co-vitamin B12 (CN-Cbl) by spargana (larvae) of the pseudophyllidean tapeworm, Spirometra mansonoides, was affected by temperature, was saturable with respect to concentration of CN-Cbl in the medium, and was inhibited in the presence of several structural analogs of CN-Cbl. In uptake studies with various analogs it was found that chemical modifications which altered the benzimidazole moiety greatly reduced the ability of the worm to take up these analogs. Modifications in which the amide groups of the propionamide side chains were removed, resulting in carboxylic acid derivatives, showed greatly reduced transport properties. The C-13 epimer in which the e-proprionamide side chain is no longer on the benzimidazole side (lower) of the molecule but is inverted to a position on the upper side was freely taken up. The pharmacological implications of this last observation are discussed. Adult Hymenolepis diminuta did not take up CN-Cbl in vitro, which correlated with the finding that no CN-Cbl was detected in the worm by Ochromonas malhamensis assay.     

Insulin-like effects in the rat of the purified growth factor from Spirometra mansonoides plerocercoids

The acute effects of injections of the human growth hormone-like factor purified from plerocercoids of the tapeworm Spirometra mansonoides on carbohydrate, lipid, and protein metabolisms were determined in intact rats. Male rats were injected ip with saline, insulin, or various doses of partially purified PGF. The rats injected with insulin had significantly reduced serum glucose concentrations but no dose of PGF caused a change in serum glucose levels. Insulin and PGF stimulated [14C]glucose and [14C]leucine oxidation to 14CO2 in adipose tissue and muscle and increased incorporation of both [14C]glucose carbons into lipids and [14C]leucine into protein in fat and muscle. The responses to PGF were dose-dependent and persisted after 3 hr of incubation in vitro. Injections of naloxone prior to injecting PGF to block the stress response did not prevent the stimulation of insulin-like responses by PGF. Therefore, PGF has intrinsic insulin-like activities in normal male rats.     

Growth and development of Pleurogenoides orientalis (Srivastava, 1934) (Trematoda: Lecithodendriidae) in the intermediate and definitive hosts

Two phases with an intervening brief lag-phase are recognized during the growth of the metacercaria of Pleurogenoides orientalis in the intermediate host (nymphs of Tramea limbata), the first phase being characterized by rapid growth and organogeny and the second phase by limited growth and development. The phases of growth and development of the metacercaria are correlated with various events in the cyst-forming process. The growth of the adult fluke in the definitive host (Rana cyanophlyctis) is characterized by a short initial lag-phase followed by a rapid phase during which there is rapid growth. Comparison of allometric growth parameters of various organs of the metacercaria and of the adult revealed definite allometric shifts. The validity of various species included in the genus Pleurogenoides is examined in the light of observations made on intraspecific variation in P. orientalis.     

Seasonal dynamics of the acanthocephalan Pomphorhynchm laevis (Müller, 1776) in its intermediate and preferred definitive hosts

No seasonal cycle was found in either the prevalence or the intensity of natural Pomphorhynchus laevis infections in Leuciscus cephalus . There was a slight seasonal change in female maturity distribution but only irregular fluctuations in the size structure of the adult parasite population throughout the year. Cystacanths were available in all seasons. Rates of parasite growth, maturation and mortality, but not establishment, increased with water temperature (or factors indirectly associated with elevated water temperature) in laboratory-infected Salmo gairdneri . Increased rates of parasite growth and maturation mask any marked shifts in the size and maturity structure of the adult parasite population which might otherwise be due to the higher turnover of adult parasites in the summer months.     

Modification of carbohydrate compositions of 31/36 kDa proteins of plerocercoids (sparganum) of Spirometra mansoni grown in different intermediate hosts

We purified specific 31/36 kDa antigenic molecules from sparganum in different intermediate hosts (snakes and mice) and analyzed their monosaccharide compositions. Compositional analysis showed that glucose and mannose concentrations were 2-3 fold higher in the 31/36 kDa molecule purified from snakes than those from mice. This result implies that antigenic glycoproteins of sparganum from snakes might be modified in mammalian sparganosis with respect to their carbohydrate composition.     

Seasonal transmission ofRaphidascaris acus (Nematoda), a parasite of freshwater fishes,in definitive and intermediate hosts

Synopsis The seasonal transmission ofRaphidascaris acus was studied in two small lakes on Manitoulin Island, Ontario. Dragonfly nymphs and caddisfly larvae, acting as paratenic hosts, contained second-stage larvae. Several fishes, including percids and cyprinids, were intermediate hosts with second, third, and fourth-stage larvae in the liver. Yellow perch,Perca flavescens, was the most important of these. Intensities were up to 928 and increased with length and age of the perch; prevalence was 100%. Abundance ofR. acus tended to be higher in females but was not related to condition of the perch. Second-stage larvae were acquired from invertebrates in summer and developed to the fourth stage by November. They became surrounded by fibrous capsules during the next summer but remained alive for at least another year. The longevity of larvae in the intermediate host may ensure survival of the parasite through periods of low host abundance after winterkill. Northern pike,Esox lucius, was the definitive host. Abundance ofR. acus tended to be greater in larger pike but was not related to sex or condition of the fish. The parasite was acquired in late fall. Prevalence was 100% and mean intensities were over 200 in winter and spring, declining to 64–100% and less than 15, respectively, in summer. Mature worms were present from early spring through summer. Seasonality of infection in the definitive host is not attributable to seasonal availability of larvae in perch. Instead it may be controlled by timing of predation on perch and rate of development and longevity of the parasite. Transmission to pike apparently continues in summer. Low intensity may result from low recruitment rate and rapid turnover of the parasite population.     

Species diversity and distribution of schistosome intermediate snail hosts in The Gambia

There is a need for recent information on intermediate snail hosts of schistosomes in The Gambia; the previous studies were conducted over three decades ago. This study assessed the incidence, species diversity, distribution and infection status of schistosome intermediate snail hosts in the country. Malacological surveys were conducted in all 5 regions of The Gambia: Central River Region (CRR), Upper River Region (URR), Western Region (WR), Lower River Region (LRR) and North Bank Region (NBR). Sampling of snails was undertaken at 114 sites that included permanent water bodies such as streams (bolongs), rice fields, irrigation canals and swamps; and temporal (seasonal) laterite pools. Ecological and physicochemical factors of sites were recorded. Snails were identified morphologically and screened for schistosome infections using molecular techniques. Freshwater snails were found at more than 50% (60/114) of sites sampled. While three species of Bulinus were collected, no Biomphalaria snails were found in any of the sites sampled. Of the total 2877 Bulinus snails collected, 75.9% were identified as Bulinus senegalensis, 20.9% as Bulinus forskalii and 3.2% as Bulinus truncatus. Seasonal pools produced the largest number of snails, and CRR was the region with the largest number of snails. Bulinus senegalensis was found more in seasonal pools as opposed to permanent sites, where B. forskalii and B. truncatus were observed to thrive. Bulinus snails were more common in seasonal sites where aquatic vegetation was present. In permanent sites, the abundance of snails increased with increase in water temperature and decrease in water pH. Bulinus senegalensis was found infected with both S. haematobium and S. bovis, while B. forskalii and B. truncatus had only S. bovis infection. While the human parasite S. haematobium was restricted to just four sites, the livestock parasite S. bovis had a much more widespread geographical distribution across both CRR and URR. This new information on the distribution of intermediate snail hosts of schistosomes in The Gambia will be vital for the national schistosomiasis control initiative.     

Transmammary infection of paratenic and definitive hosts with Alaria marcianae (trematoda) mesocercariae

Transmammary infection with Alaria marcianae mesocercariae was demonstrated using mice as model, paratenic hosts. Prenatal transmission was ruled out because neonates removed immediately postpartum from infected dams were never infected. Mesocercarial distribution in virgin females and in females examined immediately postpartum showed no marked preference for the mammary glands. In contrast, infection of neonates that were allowed to suckle on infected dams was absolute, and the number of mesocercariae in the mammary glands of postparturient dams that suckled their young was increased significantly. These experimental observations were coupled with other observations on paratenic hosts to outline the pathways open to mesocercariae in gravid hosts. The term amphiparatenic host is coined for those host species that are paratenic hosts as adults, but as juveniles can serve as definitive hosts.     

Szidatia joyeuxi (Trematoda: Cyathocytylidae): morphological and tegumental changes during growth in the definitive host

The morphological changes of Szidatia joyeuxi (Trematoda: Cyathocotylidae) during its development in the definitive host were studied. Four stages were selected: 24- and 48-hour-old juveniles and 3- and 6-month-old adults. The body underwent a real metamorphosis in its general organization and tegumental ultrastructure. It became bipartite with a linguiform and spinous forebody and a subcylindrical and aspinous hindbody. The tegumental spines became multi-pointed almost immediately after the definitive host was infected. The high degree of complexity of the parasite was reached six months later. These changes, as well as their functional aspects, are discussed and compared with other trematodes. The interpretation that the multi-pointed spines serve to abrade the host's tissues, thus permitting extra-corporeal digestion, is supported.     

Notch signaling regulates growth and differentiation in the mammalian lens

The Notch signal transduction pathway regulates the decision to proliferate versus differentiate. Although there are a myriad of mouse models for the Notch pathway, surprisingly little is known about how these genes regulate early eye development, particularly in the anterior lens. We employed both gain-of-function and loss-of-function approaches to determine the role of Notch signaling in lens development. Here we analyzed mice containing conditional deletion of the Notch effector Rbpj or overexpression of the activated Notch1 intracellular domain during lens formation. We demonstrate distinct functions for Notch signaling in progenitor cell growth, fiber cell differentiation and maintenance of the transition zone. In particular, Notch signaling controls the timing of primary fiber cell differentiation and is essential for secondary fiber cell differentiation. Either gain or loss of Notch signaling leads to formation of a dysgenic lens, which in loss-of-function mice undergoes a profound postnatal degeneration. Our data suggest both Cyclin D1 and Cyclin D2, and the p27^Kip1 cyclin-dependent kinase inhibitor act downstream of Notch signaling, and define multiple critical functions for this pathway during lens development.