Fine structure and cytochemical evidence for the presence of polysaccharide surface coat of Dirofilaria immitis microfilariae

Cherian P. V., Stromberg B. E., Weiner D. J. and Soulsby E. J. L. 1980. Fine structure and cytochemical evidence for the presence of polysaccharide surface coat of Dirofilaria immitis microfilariae. International Journal for Parasitology10: 227–233. Cytochemical staining techniques were employed at the fine structural level using ruthenium red, ruthenium violet and Alcian blue-lanthanum nitrate to demonstrate the polysaccharide rich surface coat of Dirofilaria immitis microfilariae. The coat matrix present at the external surface of the cuticle of microfilariae stained densely with each of the polycationic dyes. The reaction products were restricted to the outer surface of the cuticle suggesting that the polycationic dyes did not penetrate the cuticle. The junctions of the cuticular annulations lacked surface coat matrix and reaction products which might be indicative of the absence of carbohydrate residues or the masking of reactive sugar molecules in these areas. The speciflcity of the reaction was indicated by the absence of reaction products in untreated organisms. These carbohydrate moieties probably represent glycoproteins as structural constituents of the parasite surface. Ultrastructural analysis of the surface of microfilariae is of signiflcance in elucidating both the molecular dynamics of the parasite surface and its immunological function in the host.     

Social grooming between squirrel monkeys and uakaris in a seminatural environment

Young squirrel monkeys (Saimiri sciureus) were reported grooming an adult female uakari (Cacajao calvus rubicundus) on four different occasions. Furthermore, the uakari was noted grooming two squirrel monkeys in separate instances. These observations took place in a seminatural rainforest (The Monkey Jungle; Goulds, Florida, U.S.A.) where provisions are provided. Some possible hypostheses tendered to account for this unusual behavior included (a) the unaverted interaction of food-seeking and fur-cleaning behavior, and (b) the compatibility of play-curiosity activities by squirrel monkeys with the uakaris' need for social contact.     

Survey of canine heartworm in the city of Recife, Pernambuco, Brazil.

Six hundred and eleven random-source dogs (338 male, 273 female) one year of age or older, from six sections of the city of Recife, Pernambuco, were examined antemortem for circulating microfilariae Dirofilaria immitis and Dipetalonema reconditum adult heartworm (D. immitis) antigen, and examined postmortem for adult heartworms. The prevalence of heartworm infection was 2.3% (14/611), as determined by necropsy for adult worms, and 1% (6/611) had circulating microfilariae of D. immitis; thus, 57.1% of the heartworm-infected dogs had occult infections. The results of serological testing indicated that 1.3% (8/611) of the dogs were positive for adult heartworm antigen. A total of 42 (6.9%) of the dogs had microfilariae of D. reconditum; 40 of these had only D. reconditum and two additional dogs had microfilariae of both species, D. immitis and D. reconditum.     

Brugia malayi: intravenous injection of microfilariae in ferrets as an experimental method for occult filariasis

Microfilaremia, immune responses, and pathology were compared in ferrets infected with 100 third-stage larvae of Brugia malayi (subperiodic strain) or injected intravenously with 10(6) microfilariae. Ferrets (Mustela putorius furo) inoculated with third-stage larvae typically became patent during the third month after infection, with a mean patency of 123 +/- 25 (SE) days. Ferrets injected intravenously with microfilariae exhibited a relatively constant microfilaremia for 3-4 weeks and usually cleared microfilariae before the fourth month. Ferrets that cleared microfilariae after intravenous injection of microfilariae or after infection with third-stage larvae failed to become patent or became amicrofilaremic within 3 weeks after a challenge intravenous injection of 10(6) microfilariae. Clearance of circulating microfilariae was associated with eosinophilia and serum antibody specific for the microfilarial sheath in ferrets injected with microfilariae and in most ferrets infected with third-stage larvae. Ferrets infected with third-stage larvae and necropsied after clearance of microfilariae had tissue inflammatory reactions to microfilariae characteristic of occult filariasis (tropical eosinophilia) in man; these ferrets exhibited immediate cutaneous hypersensitivity and circulating reaginic antibody to antigens of microfilariae. In ferrets necropsied following two intravenous injections of microfilariae, the majority of ferrets examined within 10 days after clearance of microfilariae had visible liver lesions to microfilariae identical to those of the ferrets infected with third-stage larvae; immediate cutaneous hypersensitivity and reaginic antibody were not consistently detected in ferrets injected with microfilariae. Sera from ferrets that had cleared circulating microfilariae were transferred passively into ferrets made microfilaremic by intravenous injection of microfilariae. Sera with microfilarial sheath-reactive IgG antibody titers (greater than or equal to 1:200) and microfilarial agglutination titers (greater than or equal to 1:40) rapidly cleared injected microfilariae (less than 24 hr); this serum also cleared or greatly reduced circulating microfilariae established by an infection with third-stage larvae; only the IgG-containing fraction of the sera was active in immune clearance. Sera that cleared microfilariae of B. malayi did not clear circulating microfilariae of Dirofilaria immitis or prevent recurrence of circulating microfilariae of B. malayi in ferrets infected with adult filariae.(ABSTRACT TRUNCATED AT 400 WORDS)     

Immunocytochemical and ultrastructural studies on Dipetalonema viteae (Filarioidea)

The antigenic properties of adult male and female of Dipetalonema viteae were studied by immunocytochemistry. Using antisera of the rodents Meriones unguiculatus and Mastomys natalensis infected with D. viteae, the binding of antibodies to sections of filariae embedded in Epon was assayed by the peroxidase-antiperoxidase (PAP) technique and by electron microscopy. The optimal staining intensity was obtained with an antiserum dilution of 1:5000. Control sera were obtained from sex and age matched uninfected animals. Female D. viteae showed maximal antigen-antibody reactions within the uterus: in the inner uterus wall, in the "nutrient channels" between the maturing eggs and the differentiating microfilariae, on the eggshells, in the cuticula of microfilariae and in the spermatheca on the cell membrane of the mature spermatozoa. Male filariae showed binding of antibodies in the vesicula seminalis: in the nucleus and the nuclear membrane of primary spermatocytes and on maturing spermatids. Less pronounced antigen-antibody reactions in the cuticula, muscle and intestine were observed in both sexes. The PAP-technique offers significant improvements in comparison with other techniques, e.g., immunofluorescence, used to detect antigens on filariae: the PAP-technique has an increased sensitivity with a concomitant reduction in nonspecific background and can be used for both light and electron microscopy; moreover, PAP-treated tissues can be stored indefinitely at room temperature.     

An ultrastructural study on the encapsulation of microfilariae of Brugia pahangi in the haemocoel of Anopheles quadrimaculatus

Chen C. C. and Laurence B. R. 1985. An ultrastructural study on the encapsulation of microfilariae of Brugia pahangi in the haemocoel of Anopheles quadrimaculatus. International Journal for Parasitology15: 421–428. The encapsulation of microfilariae of Brugia pahangi in the haemocoel of Anopheles quadrimaculatus was studied ultrastructurally. The microfilariae was first seen enclosed in an acellular electron dense capsule as early as 10 min after the engorgement of the mosquitoes from a cat parasitized by filariae. Two hours later, the mosquito plasmatocytes spread onto and around the humoral capsule. A completed capsule, which was seen at 24–48 h, was composed of an inner humoral layer and outer cellular layer. After 1 week, some electron dense haemocytes were seen attached to the outer surface of the cellular layer. These results suggested that the encapsulation of microfilariae in the haemocoel of mosquitoes combines both humoral and cellular reaction; humoral encapsulation occurs first and cellular encapsulation takes place later. The significance of combined reactions of humoral and cellular encapsulation in the mosquito-filarial system is discussed with reference to the encapsulation reaction of other insects.     

Neonatal activity and state control differences among three squirrel monkey subspecies (Saimiri sciureus sciureus,S. boliviensis boliviensis,and S. boliviensis peruviensis)

Squirrel monkeys are a long-standing biomedical model, with multiple species and subspecies housed in research facilities. Few studies have examined the developmental differences between these subspecies, which may affect research outcomes. The primate neonatal neurobehavioral assessment was completed at 2 weeks of age with 279 dam-reared squirrel monkeys (188 Saimiri boliviensis boliviensis, 45 S. b. peruviensis, and 46 Saimiri. sciureus sciureus). Activity, orientation to stimuli, state control, and motor maturity scores, as well as startle responses and number of vocalizations were compared across subspecies and sex using factorial analysis of covariance (ANCOVAs) controlling for birthweight. There were no differences in orientation or motor maturity scores (p > .05) among the three subspecies or between sexes; however, there were significant subspecies differences in motor activity and state control scores. Of the three subspecies, S. s. sciureus has the lowest state control and activity scores (p < .05). They also had the most exaggerated startle response/aversion to a sudden loud noise, vocalized significantly less, and were less likely to resist restraint during the assessment (p < .05). The three subspecies of squirrel monkeys did not differ in motor development and attention to external stimuli but were significantly different in state control and activity levels. Overall S. s. sciureus were less active, agitated, irritable, and easier to console compared to S. b. boliviensis and S. b. peruviensis. This supports field research on socioecology which documented different social structure and behavior in wild populations of S. s. sciureus compared to S. b. boliviensis and S. b. peruviensis.     

Dipetalonema viteae: Effects of hypo- and hyperthermic stress on microfilaremia in the Mongolian jird, Meriones unguiculatus

The effects of thermal stress on the numbers of circulating microfilariae of the filariid parasite, Dipetalonema viteae, in its host, the Mongolian jird, Meriones unguiculatus, was determined. The microfilaremia of each animal was allowed to stabilize, and the effects of stress were measured from this level. The ambient temperature was raised or lowered in 5C increments and maintained at each increment for a 24-hr period. Deep core body temperature of the jirds was recorded by the use of telemetry transmitters placed in the abdominal cavity. The transmitter signals were recorded on a Dynograph recorder. Blood samples were drawn at 0, 12, and 24 hr exposure to each ambient temperature, and microfilariae counted. Microfilaremial levels were then compared to numbers circulating prior to thermal stress. Both hypothermia and hyperthermia in the jird resulted in increased numbers of microfilariae in the peripheral blood. It is speculated that these fluctuations are changes in the percentage of the total microfilarial pool, and represent fluctuations of larvae being driven out of tissue and deep circulatory channels.     

Susceptibility of squirrel monkey (Saimiri sciureus) to infection by mammalian schistosomes.

In a study of host-schistosome relationships, the squirrel monkey (Saimiri sciureus) was exposed to 500 cercariae of Schistosoma bovis (Kenya), S. intercalation (Cameroon), S. mattheei (South Africa), 2 strains of S. mansoni (Puerto Rico and South Africa), 2 strains of S. rodhaini (Uganda and Kenya), and Schistosomatium douthitti (North America). It is apparent that the squirrel monkey can be employed as an experimental host for a broad range of mammalian schistosomes. Based upon cercariae-adult worm ratios, it is a good host for S. intercalatum, S. mattheei, the Puerto Rico and South Africa strains of S. mansoni, and Schistosomatium, but only a fair host for S. bovis and the Uganda and Kenya strains of S. rodhaini. Individuality of host-parasite relationships is borne out by the great ranges recorded for egg deposits in different organs as well as by total body egg counts and eggs/worm pair.     

Protein composition of various developmental stages of dipetalonema viteae (Filarioidea)

The protein composition of various developmental stages of Dipetalonema viteae was analysed on polyacrylamide slab gels in the presence of sodium-dodecylsulphate. When the total proteins of adult male and female parasites, microfilariae, eggs, and third-stage larvae were compared, apparent qualitative similarities between mature and immature filariae were observed. However, several stage specific components were also identified.     

Physiological basis of host susceptibility of Florida mosquitoes to Dirofilaria immitis.

Young females of seven species of Florida mosquitoes were fed a meal of dog blood infected with Dirofilaria immitis to repletion to study the physiological mechanisms which control susceptibility and resistance in these mosquitoes. Various species of mosquitoes showed different grades of susceptibility. In all mosquitoes, microfilariae reached the midgut immediately after ingestion. Their movement from midgut to the specific host tissue—the Malpighian tubules—was either facilitated or inhibited depending on the presence or absence of anticoagulins in the salivary glands of these mosquitoes. In Anopheles quadrimaculatus, Aedes taeniorhynchus, and Aedes sollicitans, microfilariae move freely from the midgut to the Malpighian tubules, because of the presence of substantial amounts of anticoagulins in their salivary glands, and 30 to 60 mf/female developed normally to an infective stage. Very few microfilariae reached the tubules of Mansonia titillans as most of them were defaecated within a very short time after ingestion. In Aedes aegypti, Culex nigripalpus, and Culex pipiens quinquefasciatus movement of microfilariae from the midgut to the Malpighian tubules was obstructed by the coagulation of blood soon after ingestion. Coagulation of blood was followed by formation of oxyhaemoglobin crystals in C. nigripalpus and C. p. quinquefasciatus. It is suggested that secretions from symbiotic bacteria in the midgut of these mosquitoes lyse ingested red blood cells, and the released haemoglobin is oxidized to oxyhaemoglobin crystals which hinder the further movement of microfilariae and kill them.Microfilariae developed normally in A. quadrimaculatus, thus making them potentially the most susceptible mosquitoes, even though these mosquitoes did not survive to be effective potential vectors. A few microfilariae or their later developmental stages were melanized in the tubules of most A. sollicitans and A. taeniorhynchus, but the numbers of melanized stages were too few to affect the vectoring potentials of these species. In 20 per cent of A. sollicitans, 60 per cent of M. titillans, and ca. 80 per cent A. aegypti substantial numbers of the microfilariae after reaching the Malpighian tubules did not advance beyond the prelarval stage, and very few microfilariae developed successfully in the remaining mosquitoes. Very few microfilariae reached the Malpighian tubules of a small percentage of C. nigripalpus and C. p. quinquefasciatus and developed normally. The vectoring potentials of A. sollicitans, M. titillans, A. aegypti, and both Culex species were greatly hampered. These studies suggested that host-specificity of mosquitoes to D. immitis infection is controlled by the presence or absence of secondary physiological factors in their digestive tracts or in the Malpighian tubules.     

Oral transmission of Brugia pahangi and Dipetalonema viteae to adult and neonatal jirds

Sullivan J. J. and Chernin E. 1976. Oral transmission of Brugia pahangi and Dipetalonema viteae to adult and neonatal jirds. International Journal for Parasitology6: 75–78. Confirming previous studies, anaesthetized adult jirds became infected after oral doses of 100 infective larvae of B. pahangi; 4 of 5 jirds became microfilaria-positive and all 5 harbored adult worms. Among 7 unanaesthetized adult jirds similarly exposed, none developed microfilaraemia although 5 each harbored a few adult worms. In these unanaesthetized jirds, presumably, rapid passage of the inoculum through the mouth permitted fewer larvae to penetrate the mucosa, and the rest were probably killed in the stomach. Unanaesthetized 4-day old jirds proved highly and equally susceptible to oral or subcutaneous infection with B. pahangi as indicated by microfilaraemias and large worm-burdens. Direct and indirect evidence suggest that the baby's stomach and small intestine are not inimical to swallowed larvae, thus accounting for the relatively numerous mature worms in the peritoneal cavity. Third-stage larvae of D. viteae, readily infective subcutaneously, succeeded relatively infrequently in maturing when given orally to anaesthetized adult or to unanaesthetized baby jirds. Consistent oral infectivity may thus be a feature of filariae more closely related to B. pahangi.     

Transforming growth factor-beta expression by host cells is elicited locally by the filarial nematode Onchocerca volvulus in hyporeactive patients independently from Wolbachia

Transforming growth factor-beta (TGF-β) is a key cytokine in immune regulation, cell differentiation, development, wound healing, and tissue remodelling. It mediates immunosuppression in filarial infections facilitating parasite persistence, while attenuating immunopathology, which is induced by migrating microfilariae. Immunosuppression rises with parasite burden, but it remains unknown whether filariae elicit local release of immunosuppressive cytokines. Therefore, using immunohistology, we investigated the expression of stable, released latent TGF-β1 in subcutaneous nodules from highly infected, hyporeactive onchocerciasis patients, harbouring adult Onchocerca volvulus. Since many cell types produce TGF-β, we elucidated the cellular source, distribution and dependency on the worms’ sex, productivity and vitality. We found TGF-β1 to be abundantly expressed by T cells, plasma/B cells, macrophages, mast cells, fibrocytes, and vascular endothelial cells, particularly in onchocercomas with productive or previously productive females, damaged, dead and resorbed adult worms or microfilariae. We conclude TGF-β to be antigen induced by the filariae since expression was scarce around subcutaneous arthropods or cholesterol crystals in onchocercomas. Enhanced expression after ivermectin or endobacteria-depleting doxycycline treatment indicates induction to depend on filariae and not on Wolbachia endobacteria. TGF-β⁺ cells were reduced in HIV co-infection. This finding of local and sustained TGF-β induction by vital and dead filariae, untreated and after treatment, adds new aspects to immunomodulation by helminths.     

Differential habitat use byCebus apella andSaimiri sciureus in central surinam

Cebus apella, the black-capped or tufted capuchin, andSaimiri sciureus, the squirrel monkey, are frequently found in mixed species feeding and foraging groups throughout tropical South America and have been reported previously to show marked differences in techniques of insect foraging. Individuals of these taxa observed in central Surinam show numerous additional species-specific differences in other aspects of habitat utilization including gross dietary preferences, utilization of forest strata, locomotor behavior and arboreal support preferences.Cebus apella is more frugivorous, frequents the middle and lower levels of the main canopy, is predominantly quadrupedal and moves on medium-sized arboreal supports. By contrast, the smallerSaimiri sciureus is more insectivorous, frequents the lower strata of the forest, is more saltatory and moves on the smallest arboreal supports. Many of these differences in habitat use are interrelated and accord with patterns of habitat use seen in other primate taxa. The differences betweenCebus apella andSaimiri sciureus also accord with the types of behavioral differences frequently associated with differences in body size.     

Action at a distance: dependency sensitivity in a New World primate

Sensitivity to dependencies (correspondences between distant items) in sensory stimuli plays a crucial role in human music and language. Here, we show that squirrel monkeys (Saimiri sciureus) can detect abstract, non-adjacent dependencies in auditory stimuli. Monkeys discriminated between tone sequences containing a dependency and those lacking it, and generalized to previously unheard pitch classes and novel dependency distances. This constitutes the first pattern learning study where artificial stimuli were designed with the species'' communication system in mind. These results suggest that the ability to recognize dependencies represents a capability that had already evolved in humans’ last common ancestor with squirrel monkeys, and perhaps before.     

Captive breeding of squirrel monkeys,Saimiri sciureus and Saimiri boliviensis: The problem of hybrid groups

The electrophoretic variability of blood proteins coding for up to 32 genetic loci was analyzed in 108 squirrel monkeys (Saimiri sciureus, Saimiri boliviensis, hybrids) from two captive colonies. Twelve polymorphic loci with 31 alleles are reported. The biallelic Ada* locus, G-statistics and Hardy-Weinberg genotype equilibria are useful for recognizing hybrids between S. sciureus and S. boliviensis. Backcrosses in hybrid stocks and gene flow in a natural hybrid belt, however, complicate the taxonomic diagnosis of captive specimens: S. sciureus phenotypes imported from Peru possessed the allele Ada*132, which generally characterizes S. boliviensis (or species hybrids). The complex taxonomy of Saimiri spp. Requires careful planning of captive breeding. We suggest a genetic analysis of the founder individuals before their inclusion in the European studbook population and to breed S. sciureus from Guyana separately from Peruvian imports, because the latter bear a greater risk of being taxonomically heterogeneous. Zoo Biol 17:95–109, 1998. © 1998 Wiley-Liss, Inc.     

Synthesis,crystal structure and biological activity of novel analogues of tricyclic drugs

A series of fourteen novel, eight-membered lactam- and dilactam-based analogues of tricyclic drugs were obtained in a simple one-pot procedure. Crystal structures of two compounds were determined by single-crystal X-ray diffraction analysis and their selected structural features were discussed and compared with those of imipramine and dibenzepine. Affinity of developed molecules for histamine receptor H₁, serotonin receptors 5-HT_1A, 5-HT_2A, 5-HT₆, 5-HT₇, serotonin transporter (SERT) and dopamine receptor D₂ was determined. The commercial drug dibenzepine was also checked on these molecular targets, as its mechanism of action is largely unknown. Two derivatives of 11,12-dihydrodibenzo[b,f]azocin-6(5H)-one (7,8) and two of dibenzo[b,f]azocin-6(5H)-one (9,10) were found to be active toward the H₁ receptor in sub-micromolar concentrations.     

In vitro activity of levamisole on the infective larvae, microfilariae and adult worms of Breinlia Sergenti

In vitro activity of levamisole on the infective larvae, microfilariae and adult worms of Breinlia sergenti. International Journal for Parasitology4: 207–210. Levamisole shows in vitro activity against the infective larvae, microfilariae and adult worms of Breinlia sergenti. The polygraph studies using the adult worms indicate that levamisole causes an increase in the muscle tone; this action being dose related. The adult worms are more sensitive to the drug than the infective larvae and microfilariae. In vitro, levamisole is more potent compared with diethylcarbamazine against all the three stages of B. sergenti.     

Competition and Facilitation in the Capuchin–Squirrel Monkey Relationship

In Guyana, the range of the brown capuchin, Cebus apella, meets the range of its congener, the wedge‐capped capuchin, C. olivaceus, with the two species exhibiting a mutually exclusive patchy distribution. Squirrel monkeys, Saimiri sciureus, and C. apella form ubiquitous interspecific associations, but the reason remains debatable. With a large biogeographic field study, we tested the degree to which the distribution and abundance of Cebus and S. sciureus is determined by habitat type, fruit availability, and geography (i.e., determinants of the fundamental niche) relative to interspecific interactions, such as competition and facilitation (i.e., the realized niche). We used the competition between the two capuchin monkeys as a natural experiment that subjected S. sciureus to C. apella and C. olivaceus ‘treatments’. Using spatial regression models and principal components analysis, we found that S. sciureus was associated with seasonally flooded forests, and was correlated with fruit abundance and diversity (fundamental niche), but was also correlated with C. apella density even when accounting for habitat and fruit availability (realized niche). Saimiri sciureus density was unrelated to C. olivaceus density. Cebus apella was associated with a variety of forest types, but particularly included disturbed and edge habitats such as logged forests, seasonally flooded forests, and upland savanna, in addition to mature forest. Cebus apella was also positively correlated with S. sciureus density and negatively correlated with the density of C. olivaceus. In contrast, C. olivaceus avoided riparian areas and was associated with mixed‐height forests on sloped mountainous terrain. In sum, interspecific interactions such as competition between species of Cebus and facilitation between C. apella and S. sciureus were as important as habitat and fruit availability in determining the distribution and abundance of these primates.