Fabrication and characterization of microfluidic probes for convection enhanced drug delivery.

Convection enhanced drug delivery (CED) is a promising therapeutic method for treating diseases of the brain by enhancing the penetration of drugs. Most controlled release delivery methods rely on diffusion from a source to transport drugs throughout tissue. CED relies on direct infusion of drugs into tissue at a sufficiently high rate so that convective transport of drug is at least as important as diffusive transport. This work describes the fabrication and characterization of microfluidic probes for CED protocols and the role diffusion plays in determining penetration. Microfluidic channels were formed on silicon substrates by employing a sacrificial photoresist layer encased in a parylene structural layer. Flow in the microchannels was characterized by applying constant upstream pressures from 35 to 310 kPa, which resulted in flow rates of 0.5-4.5 microL/min. The devices were used to infuse Evans Blue and albumin in hydrogel brain phantoms. The results of these infusions were compared to a simple convection-diffusion model for infusions into porous media. In vivo infusions of albumin were performed in the gray matter of rats at upstream pressures of 35, 70, and 140 kPa. The microfabricated probes show reduced evidence of backflow along the device-tissue interface when compared with conventional needles used for CED.

The adsorption of Congo red and vacuum pump oil by rice hull ash.

Rice hull ash (RHA) of large surface area was obtained by acid wash and then calcination at 600 degrees C for 4 h. The white ash was then mixed with kaolin and starch to make pellet adsorbents with reasonable strength to be utilized in a packed column. Both ash and pellet samples showed good adsorption capacities toward the organic substances in wastewater. Furthermore, the surface nature of the white ash and pellet adsorbent could be modified through either hydration or esterification reactions. Corresponding changes in silanol concentrations were successfully correlated to changes in adsorption capacity toward either Congo red or vacuum pump oil molecules.

Effects of xanthan and galactomannan on the freeze/thaw properties of starch gels.

Three starches (maize, rice and wheat), and the two non-starch polysaccharides xanthan and locust bean gum galactomannan (LBG) were examined in gel and dough systems for texture and stability properties during freezing and low temperature storage. Xanthan and LBG were found to confer increased resistance to freeze/thaw cycling on rice starch gels but the non-starch polysaccharides had little effect on the performance of maize and wheat starch gels or on wheat dough.

Ecological Studies of Transformed Trichoderma harzianum Strain 1295-22 in the Rhizosphere and on the Phylloplane of Creeping Bentgrass.

ABSTRACT A beta-glucuronidase (GUS) reporter gene and a hygromycin B (hygB) phosphotransferase gene were integrated separately into the Trichoderma harzianum strain 1295-22 genome, using biolistic transformation. The mycelial growth and biocontrol ability of the transformed strains did not differ from that of the original strain. The transformed Gus(+)-kanamycin-resistant (Gus(+)Kan(R)) strains were used to monitor growth and interactions with Rhizoctonia solani on creeping bentgrass plants. The hygB-resistant (hygB(R)) strains were used to selectively recover strain 1295-22 from the rhizosphere soil and phylloplane of creeping bentgrass after spray applications. The population levels of two hygB(R) strains and the original strain were very similar for all treatments. All three strains persisted for the duration of the experiment (28 days) in both the rhizosphere soil and on leaves, although population levels declined somewhat over the course of the experiment in unautoclaved soils. In this study, the results demonstrated that hygB(R) strains remained dominant over time when assayed on Trichoderma-selective medium containing hygB. The hygB(R) strains were not displaced by strains that colonized untreated plants. Microscopic observation showed that the Gus(+)Kan(R) strains colonized the rhizoplane, seed coat, and phylloplane of creeping bentgrass. These results supported our earlier observation that strain 1295-22 was rhizosphere and phyllo-plane competent. Interactions between T. harzianum and R. solani were readily observed in situ and changed over time. Two types of reactions were found in these experiments. In the first type, sections of hyphae of R. solani near the hyphae of T. harzianum appeared damaged, and the pathogen appeared necrotic when viewed with a microscope. The second type, observed less frequently than the first type, was typical of myco-parasitism. The findings in this study provide new insight into the interactions between R. solani and T. harzianum, providing a basis for future research.

Improved Biocontrol Efficacy of Trichoderma harzianum 1295-22 for Foliar Phases of Turf Diseases by Use of Spray Applications.

Trichoderma harzianum strain 1295-22 is an effective biocontrol agent for several fungal diseases. The efficacy of granule and spray applications of strain 1295-22 for control of Pythium root rot, brown patch, and dollar spot of creeping bentgrass was investigated. Spray applications of conidial suspensions (SA) of strain 1295-22 significantly reduced all three diseases of creeping bentgrass turf in both greenhouse and field experiments. Control was greatest when Triton X-100 at 0.1% was added to aqueous spray suspensions. When SA were applied weekly, the biocontrol treatments were equivalent to standard fungicides. Broadcast granule applications (GA) also significantly reduced foliar symptoms of Pythium root rot, dollar spot, and brown patch; turf quality also was enhanced. The populations of Trichoderma spp. in the root zone of a bentgrass putting green treated with SA or GA of strain 1295-22 increased 10- to 100-fold after treatment compared with untreated plots. However, strain 1295-22 was present at high levels on bentgrass leaves only following SA. Collectively, the results suggest that strain 1295-22 possesses both rhizosphere and phylloplane competence. The combination of broadcast applications of granules followed by spray applications of conidia reduced damage from both root and foliar diseases.

Intestinal parasites among the Southeast Asian laborers in Taiwan during 1993-1994.

BACKGROUND: A large number of foreign laborers are now working in Taiwan, the majority coming from Southeast Asia where parasitic infections are common. Since 1992, monitoring the intestinal parasitic infections of these foreigners has been carried out, particularly to prevent the introduction of some of the parasites into Taiwan. This paper reports results obtained during the year 1993-1994. METHODS: The merthiolate-iodine-formalin (MIF) concentration method was used to detect intestinal parasites; and the data were analyzed by chi 2-test. RESULTS: Among the 3,020 persons examined, 526 (17.4%) were infected and 14 kinds of parasites were identified; i.e. Ascaris lumbricoides, Trichuris trichiura, Strongyloides stercoralis, Enterobius vermicularis, hookworms, Taenia sp., Opisthorchis viverrini, Fasciolopsis buski, Schistosoma japonicum, an echinostome, Entamoeba histolytica. Entamoeba coli, Endolimax nana and Giardia lamblia. By nationality, those workers from Indonesia had the highest infection rate, at 32.3%; they were followed by the Filipinos (18.7%), the Thais (16.6%) and the Malaysians (8.0%). The three or four most prevalent parasites were T. Trichiura (21.8%), A. lumbricoides (5.6%) and hookworms (2.4%) for the Indonesians; T. Trichiura (9.1%), A. lumbricoides (3.7%), hookworms and E. histolytica (2.1% each) for the Filipinos; O. viverrini (8.4%), hookworms (3.3%) and E. histolytica (1.2%) for the Thais; T. trichiura (2.2%), A. lumbricoides and E. histolytica (1.8% each) and hookworms (1.4%) for the Malaysians. Among the 526 persons infected, 92.2% had 1 species, 7.2% had 2 species, 0.4% had 3 species and 0.2% had 4 species of parasites. CONCLUSIONS: The present result, a 17.4% infection rate, was significantly higher (p < 0.05) than the 12.3% obtained for the previous year (1992-1993). E. histolytica was found in 34 persons, 16 of whom were working as live-in housemaids. The epidemiological significance of some parasites is discussed here.

Pattern of emergence and the effects of temperature and light on the emergence and survival of heterophyid cercariae (Centrocestus formosanus and Haplorchis pumilio).

Production of the cercariae of Centrocestus formosanus and Haplorchis pumilio was not affected by a 10-day starvation of the snail host Melanoides tuberculata, and there was no circadian rhythm in the pattern of cercarial emergence. Daily average cercarial productions from each snail were 1,643 for C. formosanus and 689 for H. pumilio at 25 C and 500 lux illumination. The number of cercariae was moderately correlated with the size of snail host. The heaviest sheddings ever observed from 1 snail in 24 hr were 63,400 cercariae for C. formosanus and 3,470 cercariae for H. pumilio. The cercariae of C. formosanus could emerge in the dark, but the number was much less than in the light. In contrast, the cercariae of H. pumilio emerged equally well with or without light. Within the temperature range tested, the emergence of cercariae occurred at 15-35 C, but not at 10 C. Shedding of C. formosanus cercariae increased with the rise in ambient temperature, whereas the greatest shedding of H. pumilio cercariae occurred at 25 C. Life-span of the cercariae was temperature-dependent. The most favorable temperature for survival of C. formosanus was 15 C, at which some survived for 160 hr, and 20 C for H. pumilio, with the longest survival of 130 hr.

Schistosoma japonicum, zoophilic strain, in Oncomelania hupensis chiui and O. H. formosana: miracidial penetration and comparative histology.

Miracidial penetration and intramolluscan development of a zoophilic strain of Schistosoma japonicum were studied in the highly susceptible Oncomelania hupensis chiui and a highly resistant population of Oncomelania hupensis formosana. When exposed to 20 miracidia, an average of 3.6 miracidia penetrated O. h. chiui and 3.4 penetrated O. h. formosana. The distribution of sporocysts in the 2 snail subspecies was similar: 70.4% migrated to the cephalopedal sinus, 14.2% to the anterior viscera, and 3.1-4.9% to the posterior viscera, tentacle, mantle collar, and foot. In O. h. chiui only 1 out of 118 sporocysts degenerated and there was no host cellular response. In O. h. formosana, all the sporocysts survived for 12 hr, but by 5 days postinfection (DPI) all were dead and by 10 DPI they had disintegrated completely; the encapsulation was encountered in only 3 out of 78 sporocysts or 3 out of 23 snails, suggesting that it played a minor role in the defense against S. japonicum. All of the O. h. formosana snails of 10 and 15 DPI showed pronounced leukocytosis and elevated phagocytosis in the heart and increased cell debris in tissue spaces, which coincided with the disappearance of the parasites. It is suggested that these phenomena were provoked in response to degradation products released by the dead parasites.

Echinostoma macrorchis: life history, population dynamics of intramolluscan stages, and the first and second intermediate hosts.

Eggs of Echinostoma macrorchis were laid at the 1-cell stage and took 9 days (26-27 C) or 6 days (30 C) to hatch. The following accounts are based on studies undertaken at 24-26 C. Maximum survival of miracidia was 7 hr. Miracidia reached the ventricle of Gyraulus chinensis 15-20 hr after penetration and transformed into sporocysts. The earliest degeneration of sporocysts occurred 20 days postinfection (DPI), but some survived for 120 days. Mature mother rediac were first seen inside the sporocyst at 7 DPI, then were released to the ventricular cavity and migrated to other anatomical locations of the host. Among the germ balls present in a sporocyst, 1-3 developed concurrently to the mother redia stage. Young daughter rediae first appeared at 15 DPI and mature ones at 19 DPI. Snails of larger size produced more daughter rediae and cercariae than smaller ones. Initial shedding of cercariae from infected snails occurred between 25 and 48 DPI, with a mean of 34 DPI. The cercariae were phototactic and each snail shed a daily average of 34 cercariae. Gyraulus chinensis was proven to be the only snail capable of serving as the first intermediate host. Tadpoles of Rana latouchi and Bufo bufo, 9 species of gastropods, the bivalve Corbicula fluminea, and 1 unidentified planarian species served as experimental second intermediate hosts.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal helminths in Akaki town, with special emphasis on the epidemiology of Schistosoma mansoni.

Two thousand, three hundred and nine stool specimens from about 5% of the residents of Akaki were examined by Kato thick smear technique for helminthic infections. The prevalence of various parasites was as follows: Schistosoma mansoni, 1.5%; Ascaris lumbricoides, 40.7%; Trichuris trichiura, 27.5%, Enterobius vermicularis, 2.2%; Taenia saginata, 3.2%; and Hymenolepis nana, 0.6%. Infected Biomphalaria pfeifferi snails were collected from the Fanta Stream, and 12% of the residents along the stream were infected with S. mansoni with an arithmetic mean of 437 eggs per gram of faeces (e.p.g.) as compared to 250 e.p.g. average town-wide, indicating that there was active transmission of S. mansoni. The prevalence of S. mansoni infection was low. It is suggested that it would be easier and more cost effective if control measures were applied at this stage.

Schistosomiasis in the Gumara and Ribb irrigation project area, Ethiopia.

A survey of intestinal schistosomiasis and vector snails was conducted in the Gumara and Ribb Irrigation project located on the eastern side of Lake Tana, northwest Ethiopia. Within the project area, stool specimens from 1273 people were examined by the thick smear method. The average infection rate for Schistosoma mansoni was 1.6%. Two localities, Addis Zemen and Yifag, located just outside the project area, were also examined, the former showing an S. mansoni prevalence of 34% (75/223) and the latter 18% (18/101) among school children. In Debre Tabor, the provincial capital 50 km away from the project site at an altitude of 2800 m., five S. mansoni cases were found among 111 school children, but they were considered to be imported cases. The possible establishment of intestinal schistosomiasis in the project area is discussed.

Helminth and snail survey in Harerge region of Ethiopia with special reference to schistosomiasis.

2300 persons from 25 communities in Harerge Administrative Region were examined for intestinal helminths. The overall prevalence rates were: Schistosoma mansoni 19.4%, Ascaris lumbricoides 13.4%, Trichuris trichiura 7.9%, and Taenia species 5.8%. Other parasites found in less than 3% included: Hymenolepis nana, Hymenolepis diminuta, Enterobius vermicularis, Strongyloides stercoralis and hookworms. Three age groups, 5-9, 10-14, and 15-19 years, had approximately similar prevalence (34.9-38.8%), but younger children had heavier egg loads (geometric mean egg output per gram of feces (EPG) of 347, 340 and 248, respectively). Boys had a higher prevalence of egg load than girls (42.4%, 395 EPG vs 26.5%, 277 EPG). Infection rates among Moslems were higher than Christians (45.5 vs 23.7%), but they had smaller egg output (333 vs 412 EPG). The frequency of light, moderate and heavy infections showed a normal distribution at 27, 46 and 27%. Biomphalaria pfeifferi was found to be infected with S. mansoni in Hirna (42/250), Esakly (6/80) and Genda Adem (20/200), the latter two in the Erer valley. Urine samples from 8 localities were negative for S. haematobium infection. The need for further study in several river valleys with agricultural potential is suggested.

Schistosomiasis in Ethiopia.

The literature on schistosomiasis in Ethiopia is reviewed with the objective of bringing together in one paper diverse sources which may not be available to those interested in schistosomiasis. Particular attention is given to the influence of altitude and climate, snail ecology and government economic programs on the distribution of schistosomiasis. Out of 365 communities studied between 1961 and 1986 for Schistosomiasis mansoni, cases were reported from 225 (62%), and in 85 (23%) the prevalence ranged from 10 to 92%. Most transmission sites and S. mansoni infections are in agricultural communities along streams between 1300 and 2000 m altitude infested with Biomphalaria pfeifferi, the major snail intermediate host. S. mansoni transmission above 2200 m and below 800 m is precluded in many parts of Ethiopia by low and high water temperatures, respectively. Schistosomiasis haematobium cases have been reported from 30 of the 54 communities studied, 17 of them with infection rates between 14 and 75%. Endemic S. haematobium appears to be confined in its distribution to lowlands below 800 m altitude. The highly focal distribution of S. haematobium transmission is largely due to the nonsusceptibility of most bulinine snails to the Ethiopian strain of the parasite and low water temperatures in the highlands. Water resources development, resettlement programs, refugee migration and other population movements may result in the spread of endemic S. mansoni. Lack of information on snail host/parasite relationships and the ecology of proven and suspected snail hosts does not permit predictions on the spread of endemic S. haematobium. Past and present schistosomiasis control programs in Ethiopia are reviewed and recommendations made for the national control program.

Susceptibility of new Taiwan foci of Oncomelania hupensis to geographic strains of Schistosoma japonicum.

Six new recently identified Taiwan Oncomelania hupensis foci were exposed to miracidia from the Changhua Taiwan zoophilic and Indonesian and Philippine anthropophilic strains of Schistosoma japonicum. All new foci were found susceptible to infection in varying degrees. In general the new foci were more susceptible to the Changhua zoophilic strain of S. japonicum than the anthropophilic strains; 17% exposed to the zoophilic strain shed cercariae while 9% and 7%, respectively, of those exposed to the Indonesian and Philippine human strains demonstrated infection. These snails along with O.h. chiui on Taiwan could possibly serve as intermediate host for human oriental schistosomiasis if the parasite was accidentally introduced onto Taiwan.

New Oncomelania hupensis foci on Taiwan.

Six new areas for Oncomelania hupensis were found on Taiwan: three in Nan-tou, and 1 each in Chia-i, Hua-lien and Tai-tung counties. Most of the new habitats, unlike previously known areas, are not in alluvial plains, but are at higher elevations. The Nan-shan-chi colony in Nan-tou county is located at the altitude of 740 m, which is the highest of all known Oncomelania localities on the island. Oncomelania has now been found in 9 out of 15 counties on Taiwan. Shell features of the newly-discovered snails resemble those of Oncomelania hupensis formosana but further study will be required for final subspecies designation. Nearly 60,000 oncomelanids from both old and new localities were examined for schistosome infection with negative results.

Observations on the host-parasite relations between Echinostoma revolutum and lymnaeid snails.

Echinostoma revolutum from Taiwan was studied in lymneid snails at 29 +/- 0.5 degrees C. Given 3-5 miracidia, 95% of Lymnaea ollula and 40% of Lymnaea swinhoei became positive; the prepatent periods were 18 and 25 days, respectively. The following are based on the observations in Lymnaea ollula: The time required for miracidial penetration was about one hour. The sporocysts developed only in the ventricle of the snail but mother rediae developed in the heart and other organs. Mature daughter rediae were not found in the heart cavity. The sporocysts reached the ventricle within 3 days. Mother rediae were released after 6 days and daughter rediae after 8 days. Given 5 miracidia, 1-3 sporocysts reached the heart and 2-20 mother rediae were found per snail. The number of mature daughter rediae was usually 100-200 although more than a thousand may develop in a snail. The sporocysts and mother rediae attained maximal size 9 days postinfection and started degeneration 13 days postinfection. Daughter rediae were largest at the beginning of cercarial emergence and decreased in size thereafter. Simultaneous production of daughter rediae and cercariae by the mother redia was seen only once in this snail mature cercariae were obtained in 10 days postinfection. The cercariae emerged from a small area of mantle collar near the posterior corner of shell aperture. They were negatively phototactic and positively geotactic. An estimation showed that each snail shed about 350 cercariae a day. The cercariae reached the pericardial cavity of snail in one hour via the renal orifice and metacercariae were seen 4-5 hours after exposure. The infectivity of cercariae at various times after shedding, as expressed by cyst recovery rates, were: 51.6%, O-hr old; 76.1%, 2-hr; 68% 4-hr; 32%, 6-hr; 3%, 8 and 10-hr. Cyst recovery rates were not different within the dosage of 50-500 cercariae per snail. Most metacercariae recovered 1-2 days after cercarial exposure were viable; only 5 among 6,533 cysts were dead.

Studies on Schistosoma bovis in Ethiopia.

Schistosoma bovis occurs in at least seven of the 14 rovinces of Ethiopia. Results of faecal and snail surveys in three foci are reported. Adwa. One collection showed that nine out of 26 bulinids were infected with S. bovis. The snail host was a tetraploid form of Bulinus (n = 36). The examination of 200 specimens of cattle faces revealed no S. bovis eggs, which was attributed to poor technique or light infection. Gewani. The snail host was Bulinus abyssinicus, which was also infected with S. haematobium, the combined infection rate being 60%. S. bovis eggs were seen in 1-5% (3/197) of specimens of cattle faeces. Lake Awassa. Among 715 bulinids(a mixture of diploid (n = 18) and tetraploid (n = 36) forms), 22 were infected with S. bovis. Infected snails all belonged to the tetraploid form. Infection in cattle faeces was 5-5%(11/200). The Fasciola infection rates in these three areas were 29%, 78% and 60% respectively. Susceptibility of laboratory and wild animals to the Gewani and Lake Awassa strains of S. bovis was investigated. Combined results show that there are at least five species of wild rodents in Ethiopia which are susceptible to S. bovis: Arvicanthis niloticus, Praomys albipes, Rattus rattus, Mastomys coucha and Lophuromys flavopunctatus, in addition to hamsters, white mice, rabbits and guinea pigs. Immature female worms resembling S. bovis were recovered from a goat and a sheep exposed to a mixture of S. bovis and S. haematobium cercariae shed by naturally infected snails. Using the same mixture of cercariae, a Gelada baboon (Theropithecus gelada) could be infected by both schistosomes, but a dog was completely refractory. ABSCESS. Some of these inconclusive results are thought to be due to a unisexual infection. The Gewani strain of SEWANI STRAIN OF S. bovis had a wider range of snail hosts than the Adwa and Awassa strains, covering the tropicus, truncatus and africanus groups of Bulinus. The Adwa and Awassa strains could infect only members of the truncatus group.