Lysosomal activity in enterocytes in the small intestine in piglets experimentally infected with Isospora suis

The lysosomal activity of enterocytes of the small intestine mucosa was investigated in gnotobiotic and conventional piglets experimentally infected on the first day after birth (DAB) by the oocysts of the coccidia Isospora suis. A method of the proof of beta-D-glucuronidase (EC.3.2.1.31.) activity was used to demonstrate lysosomes. The piglets were infected by different infection doses of oocysts (100,000 oocysts in gnotobiotic piglets and 200,000 oocysts in conventional piglets). In the gnotobiotic infected piglets the activity of beta-D-glucuronidase in enterocyte lysosomes was investigated in the period from day 3 to day 11 after infection (DAI) and in the infected conventional piglets in the period from day 2 to day 10 after infection. Comparing the control piglets, the group of gnotobiotic piglets at the age of 2-5 days and the group of conventional piglets at the age of 4-7 days, the higher activity of beta-D-glucuronidase was demonstrated in the lysosomes of intestinal mucosa enterocytes in the gnotobiotic control piglets (+5.30 of the average density value, Dx). In the infected gnotobiotic and conventional piglets the pattern of beta-D-glucuronidase activity was found to have three stages in the course of this infection. Two stages can be characterized by a great increase in the enzyme activity (DAI 3-9 in gnotobiotic piglets, DAI 2-3 and 7-9 in conventional piglets. The third stage, which is manifest mainly in the conventional infected piglets, is characterized by a marked decrease in the activity of beta-D-glucuronidase, reaching the level of control findings (DAI 10 and mainly 11 in gnotobiotic piglets. DAI 4-6 and 10 in conventional piglets). A topographical picture shows that the two stages of increase and the stage of beta-D-glucuronidase activity decrease occur in the whole small intestine without any predisposition defect of the enzyme in the different sections of the small intestine.     

Histochemistry of nucleoside phosphatases and phosphoglucomutase in the small intestine during coccidiosis in piglets]

The first day after birth, 22 conventional piglets were experimentally infected with the oocysts of the coccidia of I. suis (infection dose 200,000 oocysts). The activity of 5-nucleotidase (5-ribonucleotide phosphohydrolase, EC.3.1.3.5) and phosphoglucomutase (alpha-D-glucoso-1-phosphate phosphotransferase, EC.5.4.2.2) was densitometrically assessed in the mucosa of the small intestines of these piglets. Enzyme activities were studied in the infected piglets during the 2nd to 10th day after infection. The same histochemical examination was simultaneously performed in the intestinal mucosa of five control conventional piglets at an age of 2-14 days. 5-nucleotidase and phosphoglucomutase were found to have a high density in the mucosa of the small intestine of the control piglets: the high-density locations of these enzymes include, first of all, the supranuclear area of the absorption cells, the microvillous zone of enterocytes and the smooth muscle elements of lamina muscularis mucosae. The experimentally infected piglets showed a marked decline of the density of both enzymes during the infection. The deficit affected, for a transient period, the microvillous zone and the supranuclear region of enterocytes; the musculature of the mucous layer was affected permanently. The inactivity was more protracted in the case phosphoglutamase (especially 5 to 9 days after infection). The density of 5-nucleotidase showed a partial return to the normal already the 7th day after infection, with an interruption of resumption of activity on the 10th day. Resumption of enzyme activity in the lamina muscularis mucosae was not recorded during the infection. In the three locations under study, the density of none of the enzymes did reach parameters comparable with the controls at the end of the trial (10 days after infection).     

Histochemistry of selected peptidases in small intestine mucosa in piglets experimentally infected with Isospora suis

In the small intestine mucosa of 24 gnotobiotical piglets experimentally infected the first day post partum with oocysts of the coccidium Isospora suis, the activities of dipeptidylpeptidase IV (EC.3.4.14.5.; DAP IV) and gamma-glutamyl transferase (EC.2.3.2.2.; GGT) in the microvillous zone of enterocytes were evaluated by scanning densitometry. The tissue of the small intestine in piglets infected with a dose of 100,000 oocysts of the coccidia of I. suis was examined in the period from the first till the eleventh day post infection (DPI). In the control piglets at the age of 2-5 days it was found that most of the DAP IV activity was located in the microvillous zone of the enterocytes of the middle jejunum, rear jejunum and ileum. The DAP IV activity of duodenum mucosa was lower; as compared with the activity in the mucosa of the jejunum and ileum it reached 53-57%. In the case of GGT activity, the highest density values of the reaction product were recorded in the microvillous zone of enterocytes of the duodenum and the whole jejunum, the lowest in the ileum mucosa (86-89%) of the activity found in the duodenum and jejunum). During the experimental infection the infected piglets had a significant deficit of both peptidases, especially DAP IV (the whole studied period). The development of GGT activity was slightly different with the onset of the marked decline of the enzyme activity only on the fifth DPI. The lower GGT activity persisted till the eighth DPI. The density of the GGT reaction product began to return to the normal on the ninth to eleventh DPI. No predisposition in the location of the deficit was observed in the peptidases studied during the infection. The decline of the activity of both enzymes influenced also the mucosa of all studied parts of the small intenstine. The difference lay in the relevance of lowering of the density of reaction product of DAP IV and GGT on other DPI and in the different intensities of the return of the activity to the physiological normal.     

Densitometric analysis of aminopeptidase M activity in small intestine mucosa in piglets experimentally infected with Isospora suis

In gnotobiotical and conventional piglets infected a day post partum (DPP) with oocysts of the coccidium Isospora suis, densitometrical analysis of the activity of aminopeptidase M (EC.3.4.11.2; APM) was performed in the area of microvillous zone of the small intestine. Piglets were infected with different infection doses of oocysts (100,000 oocysts) in gnotobiotical piglets and 200,000 oocysts in conventional piglets). In infected gnotobiotical piglets, the APM activity was studied in the period from the 3rd to 11th day after infection (DAI) and in infected conventional piglets in the period of to the 2nd to 10th day after infection (DAI). Control piglets, in the group of the gnotobiotical animals at the age of 2 to 5 days in the group of the conventional animals at the age of 4 to 7 days, had different APM activity in the microvillous zone of the intestinal mucosa. It was stated that the microvillous zone of the intestinal mucosa gained higher values in control conventional piglets (+7.01 mean values of density). In infected gnotobiotical piglets the density fall of the reaction product of APM was demonstrated already on the third day with further marked reduction of APM density on the 4th day after infection in the whole small intestine with predominance of the persisting APM activity in ileum. Even despite the slight increase in the density of the reaction product of APM in the period from the 5th to 7th DAI (the highest increase in APM density on the 6th DAI), a further decrease of the activity was recorded again on the 8th and namely the 9th DAI in the whole small intestine (the lowest value of density was found in the rear jejunum), the ileum mucosa being affected, too. A slightly higher density of the reaction product of APM was found in the duodenum. On the 10th DAI the APM density started to change and on the 11th DAI in the duodenum and in the middle jejunum it even reached higher values in comparison with the control data. Some differences were proved in the infected conventional piglets in comparison with the development of the APM activity in the small intestine mucosa in the infected gnotobiotical piglets. On the 3rd and 4th DAI APM defect occurred in the whole small intestine, with APM density prevailing in the ileum mucosa (like in the group of infected gnotobiotical piglets). The second period of decrease in APM activity lasted for almost four days (6th to 9th DAI).(ABSTRACT TRUNCATED AT 400 WORDS)     

Activity of mucosubstances and the goblet cell count in the large intestine of piglets infected with the coccidium, Isospora suis

In a group of conventional and gnotobiotic piglets experimentally infected with the Isospora suis coccidia the quantitative presence of acid and neutral mucous substances in the large intestine and the counts of goblet cells in the surface mucosa and in Lieberkühnis crypts (in the following text called just the crypts) were investigated. In conventional piglets infected with the dose of 200,000 oocysts of I. suis coccidia the lowest content of acid mucous substances was recorded from the eighth to tenth day after infection (DAI). A decrease in the activity of neutral mucous substances was somewhat slower. The lowest count of goblet cells was found on DAI 9, especially on the surface mucosa (4.89 to 4.91 goblet cells per 10 enterocytes). There was observed no difference in the piglets infected the first and fifth day after parturition (DAP). Gnotobiotic piglets infected with the dose of 100,000 oocysts of I. suis coccidia on DAP 1 showed the lowest content of mucous substances in the large intestine from the ninth to tenth day after infection. Unlike the conventional piglets, in gnotobiotic piglets there was recorded a decrease in the content of acid and neutral mucous substances. The gnotobiotic piglets had the lowest counts of goblet cells in the surface mucosa (10:4.57) and in the crypts (10:7.71) on DAI 9. As to the quantitative proportions, in the conventional and gnotobiotic piglets neutral mucous substances prevailed on the other days (DAI 3-7 and DAI 11), similarly like on DAI 8. The results of this investigation revealed a functional disease of the large intestine in conventional and gnotobiotic piglets infected experimentally with the Isospora suis coccidia.     

Alkaline phosphatase activity in goblet cells in the small intestine of piglets experimentally infected with the coccidium Isospora suis

Alkaline phosphatase activity (EC. 3.1.3.1.) in goblet cells was investigated in the small intestine of 16 gnotobiotic piglets infected one day after delivery (DAD) by different rates of oocysts of Isospora suis coccidia. At a high infection rate of I. suis (750,000) the goblet cells were found to be highly positive to alkaline phosphatase on day 3 to day 4 after infection (DAI). In piglets infected by a low infection rate of I. suis oocysts (100,000) the activity of alkaline phosphatase activity in goblet cells was proved on days 4 to 10 after infection. In the first group of piglets, the positive goblet cells prevailed in the middle region of jejunum, with the peak on 4th DAI. It the second group of piglets a marked increase in the alkaline phosphatase activity was recorded in the goblet cells in the posterior part of jejunum on days 4 to 5 after infection and on 10th DAI. No alkaline phosphatase activity in the goblet cells was demonstrated in the control gnotobiotic piglets at the age of two to seven days.     

Synthesis of nonspecific esterase in small intestine enterocytes during experimental coccidiosis in suckling pigs]

The activity of nonspecific esterase (EC. 3.1.1.1.) was evaluated in the small intestine mucosa of 21 conventional piglets infected on day 5 after parturition (DAP) with oocysts of the Eimeria debliecki coccidium (infection dose of 200,000 oocysts) for this evaluation a microdensitometric analysis at the level of enterocytes was used. The same examination was also performed in the small intestine mucosa of four control conventional piglets at the age of 2-5 days (Tab. I). The synthesis of nonspecific esterase in the experimentally infected piglets was followed on day 1 to day 10 after infection (DAI). The activity of nonspecific esterase in the small intestine mucosa was found to decrease in a direction from duodenum absorption cells (D mean 34.15) to caudal ones (Fig. 1); ileum enterocytes have the optical density of the enzyme by 8.2% lower (D mean 31.38). The deposition of nonspecific esterase is localized mainly in the supranuclear zone of enterocytes while in the para- and infranuclear zones of absorption cells its concentration is only minute. In the experimentally infected piglets a marked increase in the optical density of nonspecific esterase of enterocytes was observed as soon as on day 1 after infection when the enzyme concentration increased by 19.4% (Tab. II). The maximum increase in the activity of nonspecific esterase of absorption cells was recorded on DAI 9 when the enzyme D mean value was higher by 165% in comparison with the activity of nonspecific esterase demonstrated in the control piglets (Fig. 2, 3, 4). But at the end of experimental infection (DAI 10) the total density of nonspecific esterase of enterocytes decreased by 38.2%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Activity of selected dehydrogenases and monoamine oxidases in the small intestine of gnotobiotic piglets infected with the coccidium Isospora suis

In the small intestine of 16 gnotobiotic piglets infected a day post partum (DPP) by Isospora suis coccidia the activities were studied of selected dehydrogenases and monoaminoxidase (O2 oxidoreductase, MAOx, EC 1.4.3.4.). The following dehydrogenases were investigated: succinate dehydrogenase (SDH, EC 1.3.99.1.), glycerol-3-phosphate dehydrogenase (glycerol-3-phosphate:menadion oxidoreductase, GPOX, EC 1.1.99.5.) and tetrazolium oxidoreductase (NADH, ES 1.6.99.3.). The activities of NADH and GPOX were found to decrease, a decrease being somewhat milder in MAOx, at a high infection dose of I. suis oocysts (750,000 oocysts), in comparison with the control, already on the first day after infection (DAI). The SDH levels did not change. In piglets infected by a low infection dose of I. suis oocysts a double marked decrease (negative to slightly positive finding) was recorded in the period from the third to the eighth day after infection (DAI). A similar pattern with a longer time interval between the decreases was observed in GPOX (4th to 11th day after infection). The findings of SDH and MAOx activities were different. The SDH activity is maintained at the same level (++) for the whole period of investigation and there occurs a decrease (+) only on the 9th day after infection, persisting until 11 DAI. The MAOx activity and its change correspond to the SDH activity; the difference being that in the second group the starting level is high ( ) and on the eleventh day after infection it is low or medium (0-++), in comparison with the standard. This variability is discernible from 8th DAI.     

Histochemistry of acid phosphatase in small intestine mucosa in experimental coccidiosis in suckling piglets]

The activity of acid phosphatase (phosphohydrolase of orthophosphate monoesters; EC. 3.1.3.2) was evaluated densitometrically in the mucosa of duodenum, jejunum and ileum of 22 conventional piglets which were experimentally infected by oocysts of the coccidiae Isospora suis (infection dose of 200,000 oocysts) on day one after parturition (DAP). The activity of the studied hydrolase was investigated in the infected piglets during days two to ten after infection (DAI) in the intestinal mucosa (enterocytes) and in goblet cells. The density of the reaction product of acid phosphatase was simultaneously determined in the same mucosal cells of different sections of the small intestine in five control conventional piglets at the age of 2-14 days. In the small intestine mucosa of control piglets the activity of acid phosphatase was demonstrated to be located especially in the supranuclear zone of enterocytes. As for goblet cells, the reaction product of acid phosphatase is distributed in all zones (supra-, para-, infranuclear zones); the lowest density of this enzyme was found in the infranuclear zone. The activity of acid phosphatase is also localized in intestinal crypts: in their cells the enzyme concentration is decreasing from duodenum to caudal sections. Important changes were revealed, in comparison with the control data, in the development of the activity of acid phosphatase in the intestinal mucosa cells in the experimentally infected piglets. In the period of investigation (DAI 2-10) there were two stages of the development of the density of the enzyme reaction product. The first stage can be characterized by an increase, the other by a decrease in the level of acid phosphatase activity. Enterocytes are influenced in both stages, but the decrease in the density of the reaction product of acid phosphatase was observed only in absorption cells, and not in goblet cells. The increase in the activity of acid phosphatase occurs in the periods of DAI 4 and 9-10. Enzymatic deviations occur mainly in the absorption cells of the mucosa of duodenum and middle jejunum; in the cells of posterior jejunum and ileum an increase in the density of the reaction product of acid phosphatase was also demonstrated, but at the lower quantitative level (especially on DAI 4). The decrease in the activity of acid phosphatase has a protracted development and it takes place on DAI 5 to 8.(ABSTRACT TRUNCATED AT 400 WORDS)     

Dehydrogenase activity in small intestine mucosa in experimental coccidiosis in suckling pigs]

The activities of 3-beta-hydroxybutyrate dehydrogenase (EC. 1.1.1.30.; HBD) and isocitrate dehydrogenase (EC. 1.1.1.41; ICD) were evaluated microdensitometrically in the mucosa of duodenum, jejunum and ileum of 19 conventional piglets infected on the first day after parturition (DAP) with oocysts of Eimeria debliecki coccidium (infection dose of 200,000 oocysts). The two investigated enzymes are deposited in mitochondria which are dispersed in the supra-, para- and infranuclear region of absorption cells (Fig. 1). The synthesis of the two dehydrogenases was investigated in the small intestine mucosa in the period of 1st to 10th day after infection (DAI). The HBD and ICD activities were also followed in the small intestine of four control conventional piglets at the age of 2-5 days (Tab. I). The two dehydrogenases could be characterized by a topographic gradient; it means that their activity was increasing in the small intestine mucosa through duodenum in an aboral direction. The ICD activity is higher in the intestinal mucosa of healthy piglets (Figs. 2 and 3), where its topic concentration was more marked while the HBD activity is dispersed in enterocytes (Fig. 4). In infected piglets the density of the two enzymes was demonstrated to decrease already in the starting period of experimental infection, and it reaches the lowest values for the first time on DAI 5-6 (Fig. 5, Tab. II), then on DAIs 9 (HBD; Fig. 6, graph 11)) or 8 (ICD, Fig. 7 and 10). In the period of experimental infection no statistically significant predisposition to the hypoactivity of target dehydrogenases nor its marked shift were observed. Somewhat rapid resumption of synthesis was demonstrated as soon as on DAI 8 in ICD (Fig. 8); its activity on DAI 10 in the intestinal mucosa corresponded to the 93% activity of this dehydrogenase recorded in the small intestine of control piglets. The density of HBD to the same day (DAI 10) reached in the intestinal mucosa of infected piglets the values making only 44.7% of those demonstrated in the intestinal mucosa of the control group of animals.     

Density of selected enzymes in the goblet cells of the small intestine in piglets experimentally infected with the coccidium Isospora suis

The density of selected enzymes in the goblet cells of the mucous membrane of the small intestine was studied in a group of 12 gnotobiotic piglets experimentally infected with the coccidium Isospora suis one day after parturition (DPP), using the Vickers M-786 scanning and integrating microdensity meter. At an infecting dose of 100,000 oocysts of I. suis, the histochemistry of the goblet cells of the mucous membrane of the piglets changed significantly in the period of 4 to 10 days after infection (DPI). Increases occur in the density of non-specific esterase (EC. 3.1.1.1.) and acid phosphatase (EC. 3.13.2.). The density of acid and neutral muco-substances declines and the densities of alkaline phosphatase (EC. 3.1.3.1.) and aminopeptidase M (EC. 3.4.11.2) are significantly high. The goblet cells of the mid and posterior parts of jejunum are very similar in their histochemistry in the experimentally infected gnotobiotic piglets. In the duodenum and ileum the histochemical picture of the goblet cells shows no substantial difference from the data recorded in the goblet cells of the mucous membrane of the small intestine of the four control piglets at an age of two to seven days.     

Synthesis of glucose-6-phosphatase in small intestine mucosa during experimental coccidiosis in suckling piglets]

Glucoso-6-phosphatase activity (EC. 3.1.3.9.) was evaluated microdensitometrically in the small intestine mucosa of 19 conventional piglets infected with Eimeria debliecki coccidium oocysts (infection dose of 200,000 oocysts) on day 1 after delivery (DAD). The synthesis of the observed hydrolase was followed within days 1 to 10 after infection (DAI). The activity of the same enzyme was also determined in four control conventional piglets at the age of two to five days. The small intestine mucosa of healthy piglets was found to have relatively balanced glucoso-6-phosphatase concentrations in all observed sections (duodenum, middle and posterior jejunum and ileum). The topographic gradient failed to be demonstrated in control piglets. In piglets experimentally infected with E. debliecki coccidium the glucoso-6-phosphatase activity was decreasing during infection already since DAI 1. The enzyme hypoactivity was still lower in the following days and reached the minimum value at the end of the target period (DAI 10), when its value made only 33% of the concentration recorded in the intestine mucosa of control piglets. The topographic predisposition to the lower activity of glucoso-6-phosphatase was not found to be high. The only exception are DAI 6 and 7, when the lowest enzyme concentration was observed in the duodenum mucosa (52% on DAI 6; 54% on DAI 7). The activity of the observed enzyme was higher in the other sections of small intestine (57% on DAI 6; 62% on DAI 7).     

The ratio of enterocytes and goblet cells in the mucosa of the small intestine in experimental infection of piglets with the coccidium Isospora suis

The proportions of cup-shaped cells and enterocytes were studied in piglets infected the first and fifth day after birth with 200,000 oocysts of Isospora suis. The greatest imbalance was found in the ratio of the cells of the intestinal mucous membrane in the region of middle and lower jejunum (ratio of 10:1.75)--this was recorded the third to fourth day after infection when the ratio made 10:0.62, whereas in the control animals it was 10:5.7. On the eighth to ninth day after infection the number of cup-shaped cells began to increase, the ratio reaching the values of 10:2.62. Even the 13th day after infection the ratio remained far from normal (10:2.50).     

Pathogenesis of experimental combined infections with Isospora suis and rotavirus in conventional and gnotobiotic piglets

51 gnotobiotic and 63 conventional, one-, or two-days-old piglets were divided into five groups and infected orally either with Isospora suis or rotavirus alone, or with both agents simultaneously or successively with alternative sequences and various intervals. 15 gnotobiotic and 10 conventional piglets served as controls. The development of small intestinal lesions after infection with I. suis was biphasic. The dominant alteration resulting from rotavirus infection was villus atrophy, considerably more pronounced and extensive in gnotobiotic than in conventional piglets. Synergistic action of I. suis and rotavirus was manifested both clinically, and morphologically. This action culminated at the time of the actual, or presumed development of merogony of I. suis, i.e. on DPI 3 to 5. The action develops only if the intestinal epithelium is damaged functionally and morphologically by a preceding rotavirus infection. It is concluded that the synergistic action is based on a competition of rotavirus and I. suis for mature, enzymatically active absorptive cells.     

Morphometric analysis of the activity of alkaline phosphatase in the small intestine of piglets infected with the coccidium Isospora suis

Gnotobiotical one-day-old piglets were infected with 100,000 Isospora suis coccidia oocysts, and were immediately killed. In piglets killed on the 3rd to 11th day after infection (DAI), the morphometric analysis of alkaline phosphatase activity was performed in the area of the microvillus zone of small intestine. In the control 2-7 days old animals, the small intestine was not equally supplied with alkaline phosphatase. In duodenum the activity reached 88.37 per cent of the active length of absorbent surface (% LAac), in the middle jejunum 95.98 per cent LAac, in the dorsal jejunum 78.63% LAac and the ileum 90.55 % LAac. The width of the active area was more balanced and ranged from 5.003 microM in the ileum to 6.129 microM in the dorsal jejunum. In infected gnotobiotical piglets the lowest activity was found out on the 3rd to 4th DAI, with a greater decline on the 9th day after infection. The range from 25.99 to 40.50 per cent LAac with minimum in the duodenum and maximum in the ileum was observed on the 3rd DAI. In the middle and dorsal ileum the activity was nearly equal (28.34 and 27.69 per cent LAac). nI the dorsal jejunum a moderate increasing was up to 47.13% LAac on the 4th DAI, with the exception of the ileum, where the activity of alkaline phosphatase decreased to 24.96% LAac. On the 9th DAI the activity of alkaline phosphatase was nearly equal in the whole small intestine (from 55.70 to 60.01% LAac) with the maximum in the middle jejunum. In the width of the reaction product a direct dependence on the total activity of alkaline phosphatase was evident only in the segment of the middle and dorsal jejunum and ileum, but merely on the period of the 3rd to 4th DAI. The lowest values were measured in the middle jejunum (0.982 micron on the 3rd DAI and 0.709 micron on the 4th DAI). No dependence was observed between the total activity and the reaction product in the middle jejunum (0.982 micron on the 3rd DAI and 0.709 micron on the 4th DAI), there was no general stabilisation of the activity of alkaline phosphatase.     

雏鸡感染柔嫩艾美耳球虫后脂质过氧化物的变化

为了探讨柔嫩艾美耳球虫 (E.tenella)对感染雏鸡的损伤机制 ,本试验给 10日龄海兰白公雏鸡口服柔嫩艾美耳球虫孢子化卵囊 8× 10 4个 /只 ,在感染后 2、4、6、7、9、12、16和 2 1d分别各取 5只雏鸡剖检 ,取盲肠并采血 ,观察盲肠病理组织学变化 ,测定盲肠组织及血清中的丙二醛 (MDA )、超氧化物歧化酶 (SOD)、谷胱甘肽过氧化物酶 (GSH- Px)的水平。结果表明 ,雏鸡在感染 E.tenella后 2～ 4d,盲肠开始出现损伤 ,同时 SOD和 GSH- Px活性也开始下降 ;感染后 4～ 7d,盲肠粘膜上皮和肠腺上皮细胞大量变性、坏死崩解 ,发生严重损伤时 ,盲肠及血清中 MDA含量显著增加 ,并持续到 9d,同时 SOD和 GSH- Px活性也显著下降 ;感染 9d后 ,损伤的盲肠组织及 MDA、SOD和 GSH- Px水平逐渐恢复 ,至 2 1d基本达到正常     

Role of acquired immunity and natural age resistance on course of Isospora suis coccidiosis in nursing piglets.

Thirty-two piglets from three litters were experimentally inoculated with 200000 sporulated oocysts of Isospora suis at 3 days of age and/or rechallenged at 19 days of age or primary inoculated at 19 days of age, to compare the role of acquired immunity and natural age resistance on the course of coccidiosis. Twelve piglets were not inoculated and served as a control. Following challenge, the signs of coccidiosis characterised by clinical symptoms, oocysts shedding and weekly weights were similar to those which occurred in piglets primary inoculated at 19 days of age. This comparison suggests that maturation of non-specific components of the immune system plays a more important role in the resistance of neonatal piglets to I. suis infection than specific immune mechanisms.     

Lesions of gnotobiotic calves experimentally infected with a calicivirus-like (Newbury) agent

Fourteen gnotobiotic calves were killed 0.5 to ten days after infection with Newbury agent SRV-1 and the changes in small intestinal structure and function were assessed, qualitatively and quantitatively, by light microscopy, scanning and transmission electron microscopy, enzymology and xylose absorption. The first enterocytes detected as infected by immunoperoxidase were those on the sides of villi at the base. Subsequently exfoliation of degenerate enterocytes resulted in stunted villi; mucosal beta-galactosidase activity fell and there was xylose malabsorption. Small intestinal damage, first detected at 12 hours after infection but almost repaired by ten days, was restricted to the anterior half of the small intestine. In the distal small intestine, where no virus-induced damage occurred, villi lengthened--possibly due to increased mitosis of crypt cells stimulated by enteroglucagon release.     

仔猪等孢球虫与等孢球虫病研究进展

仔猪等孢球虫病是由猪等孢球虫寄生在哺乳期及新近断奶仔猪小肠上皮细胞所引起的一种寄生性原虫病，呈世界性分布，给养猪场造成严重的经济损失。本文对猪等孢球虫病的病原分类、虫体形态和生活史、致病性、流行病学特点、临床症状、病理变化、诊断、防治等方面的目前研究状况进行了综述，为猪等孢球虫病的有效防制提供参考。     

Alkaline phosphatase activity levels during infection with the coccidia Isospora suis in piglets

The activity of alkaline phosphatase (EC 3.1.3.1.) was studied in the small intestines of piglets infected with the coccidia Isospora suis on the first and fifth day of age. Alkaline phosphatase activity is reduced significantly the third to fourth day after infection (DAI) throughout the small intestine in piglets infected on the fifth day of age. Similar results were obtained in the piglets killed the eighth to tenth DAI which had also been infected on the fifth day of their age. Piglets infected the first day of age and killed on the 8th to 13th DAI exhibited no larger differences from the above-mentioned groups, but alkaline phosphatase activity was distributed more regularly all over the surface of the villi. The normal values, comparable with the controls, were not obtained within 13 days after infection (piglet age 14 days).