Infection dynamics of Centrocestus armatus cercariae (Digenea: Heterophyidae) to second intermediate fish hosts.

The infection dynamics of Centrocestus armatus cercariae with respect to second intermediate fish hosts were investigated using cercariae collected from naturally infected Semisulcospira libertina. Cercariae survival and infectivity were recorded at 2-hr intervals. Survival remained constant but decreased abruptly at 30 hr of age. An age-dependent model presented the best-fit curve for the survival data (r2 0.936), implying that cercariae tended to allocate resources equally among themselves and then died once those resources were depleted. Cercariae infectivity remained constant over the first 10 hr of life and then declined; an age-dependent model also provided a better fit (r2 = 0.956). The transmission rate of C. armatus cercariae to the fish host was relatively low near the time of emergence from the snail host but peaked at 85% after 1 hr and then maintained a plateau period until 5 hr of exposure to fish. The pattern of transmission was also investigated initially at varying densities of cercariae and then by maintaining a constant cercariae density but varying the total number. Results revealed that the pattern of transmission was frequency-dependent.

Histopathological study of canine optic nerve retina treated by organophosphate pesticide.

The fine structure of pathological changes was examined in the optic nerve and retina of beagle dogs after oral administration by capsule of the organophosphate pesticide ethylthiometon for 2 years. The optic nerve was invariably affected, and the number of myelinated axons markedly reduced. These were substituted for by delicate processes of astrocytes. Changes in the retina were mild and mainly seen in the peripapillary pigment epithelial cells and in the Müller cells of the peripheral retina. These histopathologic findings indicate that long-term administration of ethylthiometon involved both the optic nerce and selected portions of the retina.

Cataract in gyrate atrophy: clinical and morphologic studies.

The clinical appearance of the cataract in nine phakic patients with gyrate atrophy of the choroid and retina is described. The gross and microscopic examination of three cataractous lenses removed from patients 31 years to 47 years of age is reported. Clinically, the lens opacities appeared primarily along the confluence of the sutures posteriorly, interfering with vision because of their location in the visual axis. Histologically the region of the posterior sutures was filled with liquified and degenerated lens material typical of senile cataractous changes. By the second decade, cataract is a uniform finding in patients with gyrate atrophy and appears to be unique as compared with cataracts associated with other forms of retinal degeneration.

Membrane alterations during cataract development in the Nakano mouse lens.

The anterior cortical fiber cells of the 12-day-old Nakano mouse lens revealed an extremely large number of gap junctions, the appearance of which was identical to those of the normal lens. Although the number of gap junctions of the cells in the same area at 29 days was comparable to that seen at 12 days, the size of each junction became smaller with cataract formation. The junctions were almost absent in the anterior cortical cells in 7-month-old Nakano mice. Biochemical analysis revealed that the 26,000 MW polypeptide closely associated with the cell membrane was lower in amount in the membrane preparation of the 29-day Nakano mouse lens than in the 12-day lenses. With the membrane fractions of lenses from 90-day Nakano mice, the absence of a major 26,000 NW polypeptide component correlates with the decrease in gap junction structures. The alternations in the gap junctions and membrane associated polypeptides of the Nakano lens may be linked with the steps leading to cataract development.

Measures to control Toxocara egg contamination in sandpits of public parks.

We investigated measures to prevent Toxocara egg contamination of sandpits. Replacement of contaminated sand was not effective because 1-9 new fecal deposits per sandpit were found daily, with eggs reappearing in the sand 6-9 weeks after the replacement. When the sandpit was covered with a clear vinyl sheet, the temperature of the sand to a depth of 3 cm was 42 degrees C or more for 3 hr when the air temperature was higher than 30 degrees C. This procedure prevented contamination by fecal deposits and also resulted in the destruction of existing eggs because the sandpit was kept dry on rainy days. The method seemed safe and inexpensive. The effectiveness of a fence around a sandpit depended on user behavior, which could not be relied upon. Therefore, a practical method for the prevention of Toxocara egg contamination of sandpits is to cover the sandpit with a clear vinyl sheet at night and on rainy days.

Defecation habits of cats and dogs and contamination by Toxocara eggs in public park sandpits.

The defecation habits of cats and dogs in three sandpits in urban public parks were observed by camcorder. Cats were the main cause of fecal contamination of these sandpits. Most (80%) feline defecations occurred at night between 6:00 pm and 6:00 am. Each of the sandpits was used habitually as a defecation site by 4-24 cats, but these cats seemed to defecate elsewhere, as well. Fecal deposits within the sandpits were evenly distributed and did not tend to be concentrated in one area, suggesting that the cats avoided previously deposited feces when choosing a place to defecate. One sandpit was strongly contaminated and two were weakly contaminated with Toxocara eggs. Because sandpits are widely used as play areas for young children, effective sanitation measures should be implemented to prevent the contamination of sandpits by Toxocara eggs.

Short report: possible Cryptosporidium muris infection in humans.

Oocysts of cryptosporidia whose morphology resembled that of Cryptosporidium muris were found in the stool of 2 healthy girls in Surabaya, Indonesia. The oocysts were predominantly oval and measured 7.75+/-0.17 x 5.55+/-0.13 microm (mean+/-SD). The number of oocysts excreted were more than 10(5) per gram of stool. The oocysts were well stained with fluorescein-conjugated monoclonal antibody to Cryptosporidium. The specimens from both girls containing the oocysts showed a positive result by the polymerase chain reaction (PCR) using primers specific for the genus Cryptosporidium, but a negative result by the PCR using primers specific for C. parvum. The 2 girls passed oocysts for 5 and 6 days, respectively. They did not complain of any symptoms during the passage of oocysts.

Prevalence of Cryptosporidium parvum infection and pattern of oocyst shedding in calves in Japan.

Cryptosporidium parvum infection and the pattern of oocyst shedding were observed in calves. A total of 480 fecal samples were collected from 30 calves (age, < or =30 days) over a period of 10 months from June 1998 to March 1999. A sucrose centrifugal flotation technique revealed 28/30 (93%) calves were passing Cryptosporidium oocysts. Oocyst shedding was first detected on the sixth day after birth, with 8% of the calves testing positive. This rate increased day by day and reached approximately 80% by day 15. Oocyst shedding varied from 1 to 13 days, with a mean of 7 days. Calves infected with C. parvum had a significantly higher rate of diarrhea (33%) than non-infected calves (8%) (P<0.05), suggesting C. parvum infection as the likely cause. The mean number of oocysts excreted by calves < or =30 days old was approximately 6x10(7) per gram of feces. These results indicated that one calf would excrete some 6x10(11) oocysts in the first month after birth, taking both the quantity of feces in a day and the period of excretion into consideration. Accordingly, it is clear that calves are important in the spread of cryptosporidiosis to calves and humans.

Differentiation of Toxocara canis and T. cati eggs by light and scanning electron microscopy.

In this study, we investigated the morphological identification of Toxocara canis and T. cati eggs on the basis of light and scanning electron microscopic (SEM) observations. T. canis and T. cati eggs used in this study were recovered from the uteri of respective gravid female worms. Measurement of egg size was not helpful in the differentiation of these species, because approximately 90% of eggs measured were of similar size. Using SEM, we were able to differentiate T. canis eggs from T. cati eggs based on their respective characteristic surface structures. Both species have subspherical eggs with markedly pitted surfaces like those of a golf ball, but the surface pitting in T. canis is more coarse than that in T. cati. In this study, however, these differences were not absolute, as 16% of T. canis and 29% of T. cati eggs showed surface pitting that was uncharacteristic of their species. Of the 16% of T. canis eggs that could not be differentiated by surface structure, 3% had pitting resembling T. cati, and the remaining 13% showed intermediate type surface pitting. Similarly, 5% of T. cati eggs resembled T. canis, and 25% of these were of intermediate type. Light microscopic observation yielded results similar to those of SEM, indicating that light microscopy is also a useful tool for the identification of Toxocara eggs.

Abrupt-onset diabetes mellitus in the elderly.

We present three elderly Japanese patients with abrupt onset of diabetes mellitus: a 61-year-old male with a complete defect of insulin secretion without insulin resistance, a 60-year-old male with an incomplete defect of insulin secretion associated with insulin resistance, and a 69-year-old female with a complete defect of insulin secretion and insulin resistance. The findings in these cases indicate the heterogeneity in insulin secretion and sensitivity of abrupt onset diabetes mellitus in the elderly. The changes in insulin secretion and sensitivity over time due to glucose toxicity may at least partially explain the heterogeneity.

Prevalence of antibody to Toxoplasma gondii in Hyogo Prefecture, Japan: comparison at a 10-year interval.

We have previously surveyed antibody to Toxoplasma gondii among Japanese populations. In this report, we studied the current situation of antibody prevalence and compared it with the situation approximately 10 years before. A total of 1,800 human serum samples were collected at the Central Laboratory of Kobe University Hospital from June through September, 1995, and were examined for Toxoplasma antibody using enzyme-linked immunosorbent assay. The overall prevalence was found to be 16.4% with similar seropositivities in males (16.8%) and females (15.9%). Prevalence of antibody increased with age, reaching 41.0% in males and 59.0% in females at 80 years or more. Comparison with data obtained at the same hospital in 1981 to 1982 indicated that seropositivities at 30-39 years significantly decreased in both males and females. A positivity currently obtained at a certain age group was similar to a positivity previously obtained at the corresponding age group (10 years younger), indicating that the previous age prevalence curve shifted to the current position. A serological survey among stray cats collected in Hyogo Prefecture in 1990-1991 indicated that 44 (19.0%) of 231 cats were positive for Toxoplasma antibody as determined by the latex agglutination test. These results suggested less transmission of Toxoplasma to humans in Hyogo Prefecture at least for the last 10 years comparing with the situation in the past, although the transmission cycle among cats was still active in nature.

Effect of intestinal helminth infection on some nutritional parameters among rural villagers in Nepal.

We report the prevalence of intestinal helminthiasis and its impact on health of Nepalese in two different rural Village Development Committees (VDC) in Nepal. A total of 261 school children from Okharpauwa VDC in Nuwakot district (Central Region) and 242 inhabitants of Boya VDC in Bhojpur district (Eastern Region) in Nepal were included in this study. The overall prevalence in these two different districts were 57.5% and 55.4%, respectively. Altogether four types of helminths were detected. In both districts, Ascaris lumbricoides was the commonest helminth. Mixed helminth infection in both study areas accounted for less than 5.0%. All helminth infected subjects were treated with a single dose of albendazole. Heavy Trichuris trichiura infection needed a second dose. Blood hemoglobin and serum total protein level in school children in Okharpauwa VDC increased significantly after chemotherapy (P < 0.05). Eosinophil count (10.1%; SD 5.0325) returned to normal (4.8%; SD 4.6997). Helminth infection in Boya VDC was more common in children than in adults. Serum total protein, albumin, total cholesterol and triglycerides levels were not influenced by the presence or absence of helminths among the inhabitants of Boya VDC. In both districts, more than 80.0% of the household had no latrine. In Boya VDC, 94.0% of inhabitants interviewed were not aware of other intestinal parasite other than A. lumbricoides.

A human case of zoonotic onchocerciasis in Japan.

A 2-year-old girl living in southwestern Japan had a nodule of 2 months' duration on the left foot. A biopsy from the lesion showed transverse sections of a worm surrounded by granulomatous tissue. The worm was identified as an Onchocerca sp. from the morphological characteristics such as relatively thick cuticles, annular ridges on the cortical layer, and high somatic muscles. Positive serological tests using ELISA for Onchocerca gutturosa and Onchocerca volvulus supported the diagnosis. This was the first case of zoonotic Onchocerca infection detected in Japan. The clinicopathological aspects of zoonotic onchocerciasis of this case were discussed.

Orthograde axonal transport of optic nerve and injury--morphological study.

To investigate the effects of injury to the orthograde axonal transport in the optic nerve, horseradish peroxidase (HRP) was injected into the vitreous of the cat eye after various types of optic nerve injury, and the retina and optic nerve were examined with light and electron microscopes 8 hours after the injection. The optic nerve was sectioned in one eye at about 6 mm behind the eyeball and the optic nerve of the contralateral eye was used as the control. HRP reaction products were frequently observed within the retinal ganglion cells and their axons of the nerve fiber layer as well as in the retrolaminar optic nerve on the experimental side, and the findings were similar to those on the control side. The optic nerve was injured by cryocoagulation for 10 seconds or 30 seconds, and ischemic changes of various degrees were induced. Intracellular and intra-axonal HRP reaction products were markedly reduced at the retrolaminar portion, and the degree of reduction depended on the duration of cryocoagulation. The section of the optic nerve had, at least in the early stage, only minimal effects on the orthograde axonal transport, but the optic nerve injury accompanied by ischemic changes markedly blocked the axonal transport in both the inner part of the retina and the optic nerve.

Morphological study of age-related changes in mouse lens.

Age-related changes in the lenses of ddy strain mice, ranging from 4 to 24 months old, were studied histologically. The early change of aging lens was noted as a slight extension of fiber cells into the posterior capsule in the area behind the nuclear bow around 6 months of age. Those cell extensions formed villous projections reaching up to one half of the total capsule by 18 months of age. Another notable change was a decreasing cell population of the lens epithelium and the appearance of their nuclear inclusions. The latter contained rough endoplasmic reticulum, free ribosomes and filamentous matrix at the early stage and a mass of filamentous material at the later stage. This change was initiated by 12 months of age, and became profound with the increase of age. Moreover, the bow nuclei became markedly displaced posteriorly after 14 months of age. At about 18 months of age, when the pathological changes in both epithelial and bow regions became severe, the superficial cells in the posterior cortex showed swelling and atrophy, which soon led to the lens opacity due to accumulation of cell debris and fluid. These histopathological changes associated with aging appear to correspond to the incipient form of posterior subcapsular cataract which is detectable by clinical examinations.

Histopathological study of congenitally diabetic yellow KK mouse lens.

Lenses of Yellow KK mice with marked obesity and diabetic symptoms were examined by light and electron microscopy. At 2 months of age, the entire lens appeared normal. At 4 months, however, epithelial cells sometimes had become necrotic and showed intranuclear inclusions. At 6 months, the anterior cortical fibers were swollen. At 8 months, the number of intranuclear inclusions of the epithelial cells had increased, and the posterior cortex contained densely stained cells among the fibers, with swollen cytoplasm. At 10 months, these cells had become atrophic. At 12 months, the lens cells in the posterior sutural area showed marked swelling, and the suture was almost separated. This animal model showed a slow progressive cataract in the superficial cortical zone which is similar to the diabetic cataract in human eyes.

Lens reconstruction after mature cataract in SCR rat.

PURPOSE: To conduct a long-term observation study of SCR rats that had developed a mature cataract at 11 weeks of age at 3-month intervals until the rats were 12 months old. METHODS: Lenses of 15 rats were examined with both light and electron microscopes. RESULTS: At 12 weeks, opacity was observed in the perinuclear zone and the cortical intermediate layer. Liquefaction of the posterior subcapsular area and regression of cortical superficial fibers were also observed at this stage. Epithelial cells at the anterior polar area were multilayered. At 12 months, the lens recovered as a result of the regenerated lens fibers in the intermediate layer and the cortical superficial layer, although the opacity remained in the perinuclear zone. The multilayered cellular structure in the center of the epithelium returned to its original monolayer form. However, the equatorial epithelial cells became vacuolated and swollen with age, showing regression from the bow region. CONCLUSIONS: These results suggest that the decrease of opacity in SCR rats is merely a temporary phenomenon that reflects the differentiating and metabolizing functions of the epithelial cells. With initiation of epithelial regression, the regeneration of the lens fibers ceased, suggesting that further decrease in opacity was no longer possible.

Morphological study of age-related changes in Fischer rat lens.

The authors conducted a morphological investigation of age-related changes in the lens of male Fischer rats at 6, 12, 18 and 24 months of age. At 6 months, there were no abnormalities of particular note other than slight swelling of the subcapsular fibers. Moreover, other than a slight decrease in the density of epithelial cells and slightly more extensive fiber swelling, there were no remarkable changes seen in the lens at 12 months. At 18 months of age, posterior invasion by the processes of the cortical lens fibers toward the lens capsule and slight swelling of the anterior cortical fibers were seen in addition to the above-mentioned changes. By 24 months of age, these changes had become more noticeable, with further reduction in the density of epithelial cells, swelling and degeneration of both anterior and posterior fibers and extension of the thin processes of the equatorial fibers toward the capsule. However, the bow configuration at the equator appeared almost normal. These findings indicate that the age-related changes in the Fischer rat lens occurred in the epithelial cells and superficial layer of the cortical fibers, subsequently leading to the loss of clarity in the lens.

Lens development and crystallin distribution of the early onset hereditary cataract in the UPL rat.

The Upjohn Pharmaceuticals Limited (UPL) rat is a new dominant hereditary cataract model with two types of cataract formation, early onset (E-type) and late onset (L-type). In the UPL E-type rat cataracts have formed by the time the eyes open. The E-type rat also develops microphthalmos and buphthalmos. In this study, histological observations of cataract development in the E-type rats were performed during the period of fetal development, at birth and at 1, 3 and 62 weeks of age. In addition, the distribution of alpha- and gamma-crystallins in the developing lens was determined using anti-crystallin antisera. Abnormal elongation of the lens fibers was first observed on the 13th day of gestation. Stratification of lens epithelial cells was present on the 19th day of gestation and this change became more severe with age. There was no alteration in alpha- and gamma-crystallin expression during the fetal period. The continuity between the lens epithelial cells and lens fibers was lost at 3 weeks of age and it was assumed that differentiation of lens epithelial cells had ceased. These findings suggested that development of the UPL rat E-type cataract was related to an early abnormality in lens cell differentiation not involving crystallin expression.

Soil contamination and infections by soil-transmitted helminths in an endemic village in southern Thailand.

The aim of this study was to test the association between soil contamination and infection of the household members by soil-transmitted helminths in dry and rainy seasons. A lake-side community in southern Thailand with a population of 2,340 was studied twice, in the dry season and rainy season of 1995. Fifty households were randomly selected. Soil samples near the latrine, in the yard, at the foot-washing area and under the trees were taken and analysed for presence of helminthic eggs. All members of the selected household were interviewed and stool samples obtained. Age-adjusted odds ratios of presence of Ascaris and Trichuris eggs in the household soil for ascariasis and trichuriasis were 10.5 (95% CI 1.5-77.1) and 5.5 (95% CI 2.4-12.7) in dry season and 10.4 (95% CI 2.5-43.8) and 8.3 (95% CI 3.4-20.0) in rainy season. The levels of hookworm eggs detected in the soil were too low to test the association. Soil analysis for eggs of Ascaris and Trichuris may be used to predict infections among the household members but not that for hookworm.