Effects of dietary selenium on differentiation, morphology and functions of spermatozoa of the house rat, Rattus rattus L.

Ingestion of 2 ppm and 4 ppm selenium in the diet by the house rat, Rattus rattus, for 5 weeks caused a dose-dependent reduction in its body weight, testicular and cauda epididymidis weights, concentration, motility and percentage of live spermatozoa with a simultaneous increase in the percentage of their abnormal forms. Compared to 1.39% abnormal spermatozoa in cauda epididymidis in untreated control rats, 3.89% and 24.64% abnormal spermatozoa were observed in rats with 2 ppm and 4 ppm dietary selenium respectively. Ingestion of 4 ppm selenium had no significant effect on abnormalities of the head and neck regions but abnormalities of the midpiece region and multiple abnormalities increased significantly. Analysis of the various stages of differentiation of spermatids in the testis has revealed that with 4 ppm dietary selenium, the abnormalities are induced mainly in the midpiece region of the flagellum which is a site of energy production.

Multi-choice food preference behaviour of the Indian mole rat Bandicota bengalensis.

Multi-choice food preference behaviour of the Indian mole rat Bandicota bengalensis has been studied with 4 and 8 foods consisting of cereals and a pulse in rat pens which had floor area of 143 x 94 cm and 143 x 94 plus 220 x 82 cm, respectively, and separate food and nest boxes. Nine combinations of three texture forms of 4 foods and one combination of 8 foods were tested. Significant differences were observed in the daily consumption of different foods irrespective of the daily clock-wise rotation in the location of the foods. The number of available foods, their taste and textural qualities were found to influence the feeding responses of B. bengalensis. In multi-choice feeding tests with 4 foods, small sized and less harder grains as of rice and millet were eaten more than those of maize and gram, while the maize flour was more preferred than the flour forms of other grains. Compared to other foods in any combination, rice in its whole (W), cracked (C) and flour (F) forms was generally eaten more than the W and C forms of maize and gram and F form of gram and millet. However, the 8 foods were eaten in the following order of preference: millet (W) > millet (C) > jowar (C) > wheat (C) > rice parmal (C) > rice basmati (C) > gram (C) > maize (C). The mole rat appeared to establish a particular order of preference of foods on the first day of feeding, and that was maintained on subsequent days by daily exploration and sampling of all foods. The particular patterns of food preference, as established in combinations of 4 foods and 8 foods, were not influenced significantly by the changes in location of foods among similar and familiar feeding sites of the rats.

Conditioned taste aversion in lesser bandicoot rat, Bandicota bengalensis.

The lesser bandicoot rat after ingesting a sublethal dose of 0.025% zinc phosphide, in preferred food millet (Pennisetum typhoides) grains, for 4 days, showed aversion for 5-6 days towards plain millet offered in choice with the less preferred sorghum (Sorghum vulgare) grains. The aversion response to nontoxic bait was stronger (aversion index greater than 0.7) for first 3-4 days in individual and for 1-2 days in paired rats. 100% or more shift in aversion index from pre-treatment to post-treatment periods indicated that the aversive and naive partners of the heterosexual and unisexual female pairs mutually influence the feeding preferences of each other as a result of which they showed aversion for first 2-3 days to the plain food in which poison was given to one of the partner earlier.

Morphological and histochemical observations on the vitelline cells of developing and adult Paramphistomum cervi (Trematoda: Digenea).

In 6 week-old Paramphistomum cervi, vitelline cells appear in the form of a few scattered cells, present below the body wall which divide mitotically to form vitelline follicles in 8 week-old worms. Small shell globules appear first in 10 week-old worms, the number and size of which continue to increase till the worm becomes adult. In the latter the vitelline follicles contain stem cells, immature, maturing and mature vitelline cells, which differ due to the distribution of shell globules as well as their histochemical nature. The shell globules are keratin in nature. The vitelline cells showed activities of various phosphatases but did not show the presence of any of the dehydrogenases studied.

Histochemical studies on eggshell formation in Paramphistomum cervi (Digenea: Paramphistomatidae).

The formation of the egg mass in the ootype, containing the oocyte, vitelline cells, numerous spermatozoa and Mehlis' gland secretion marks the beginning of eggshell formation. Mehlis' gland cells pour their lipoprotein secretion into the ootype; this secretion forms a thin template around the egg mass and upon this template the shell globules are deposited. Eggshell formation begins in the proximal uterus and is completed in the middle uterus. The eggshells are devoid of phenols and phenolase indicating that hardening is not by quinone tanning. The eggshells contain keratin and are stabilized by disulphide linkages.

The susceptibility of Rattus rattus and Bandicota bengalensis to a new anticoagulant rodenticide, flocoumafen.

The anticoagulant rodenticide flocoumafen was evaluated against Rattus rattus and Bandicota bengalensis. In no-choice 24 h feeding tests 100% mortality occurred at 0.00125% concentration of the poison in the bait in the case of B. bengalensis and at 0.00375% in R. rattus. Feeding of 0.0025% poison bait in 1-day, no-choice and 2-day choice tests resulted in 60% and 75% mortality of R. rattus, respectively, and 100% of B. bengalensis. The differences between the consumption of plain food in the pretreatment period and of poison bait in no-choice tests were non-significant, except in one case. The rodents consumed significantly more (P less than 0.01) poison bait than the plain alternative in the choice trials. Median period of survival and its 95% confidence limits of R. rattus and B. bengalensis, at the 100% mortality dose levels of the poison, were 6.3 (5.04-7.88) and 6.2 (4.92-7.81) days respectively.

Morphological and histochemical studies on the development of testis and spermatogenesis in the ruminal trematode of sheep, Paramphistomum cervi (Digenea: Paramphistomatidae).

Morphological and histochemical changes accompanying testicular development and spermatogenesis have been described in the ruminal trematode Paramphistomum cervi during the course of its infection in sheep. Small testes of 4-week-old worms contain a few primordial germ cells. Spermatogonial cells appear first in 6-week-old worms and increase in number by the 10th week when the testes become large and follicular. Mature spermatozoa appear in the testes of 16-week-old worms. General pattern of spermatogenesis is the same as described for other trematodes, i.e. a single spermatogonium gives rise to 32 spermatozoa. Cytophore is formed at secondary spermatogonial stage. Various spermatogenic stages contain proteins, glycogen and phospholipids, however, the amount of phospholipids decreases as the maturation proceeds. The mature spermatozoa stain strongly with PAS. The enucleated residual mass contains HgBB-positive proteins and lipid granules. The morphological and cytochemical changes occurring during various spermatogenic stages have been correlated with corresponding histoenzymological changes in the cytoplasm. Frequency of spermatogenesis has been worked out which indicates that the transformation of secondary spermatogonia into spermatids is relatively fast as compared to transformation of primary spermatogonia into secondary spermatogonia and stages of spermateleosis.

Evaluation of coumatetralyl against two predominant murid species.

Coumatetralyl was evaluated in the laboratory against Bandicota bengalensis and Rattus rattus. Feeding tests with 0.0375% coumatetralyl baits produced 100% mortality after a single day feeding period in B. bengalensis and after a 10-day period in R. rattus. The anticoagulant bait is less palatable in comparison to plain bait. In the case of R. rattus, LFP50 and LFP98 and their 95% confidence limits were 3.89 (2.62-5.77) days and 11.22 (6.1-20.65) days respectively. Median period of survival and its 95% confidence limits of B. bengalensis and R. rattus were 4.7 (3.85-5.7) days and 11.2 (9.33-13.44) days respectively.

Maturation of Paramphistomum cervi in sheep in India.

Histological studies of the trematode Paramphistomum cervi collected throughout the year from the rumen of sheep, revealed the occurrence of gravid worms from April to August and immature worms from September to March. The maturation of the gonads and the accessory sex glands i.e., the prostate-, Mehli's- and vitelline-gland began during the period March-April and showed functional peaks during the period July-August, which coincided with the availability of the intermediate host, Indoplanorbis exustus in nature. Maturation as well as the incidence of infection of P. cervi have also been discussed in relation to various ecological factors, i.e., rainfall and temperature.

Morphological and histochemical studies on the ovarian development and oogenesis in Paramphistomum cervi (Digenea: Paramphistomatidae).

The ovary in 4-week-old worms contains undifferentiated germ cells. The oogonial differentiation, together with the appearance of some PAS-positive material in the ooplasm occurs in the ovary of 8-week-old worms. The ovary of 16-week-old worms contains only oogonia and oocytes and no germ cells. In adult worms, the oocytes reach the pachytene stage and further development is arrested at this stage. Nucleolar fragmentation and subsequent transport of nuclei to the ooplasm have been observed. The ooplasm contains nutritive material rich in proteins, carbohydrates and lipids. Its amount varies with different stages of oogenesis. The localization of various phosphatases and dehydrogenases was studied during oogenesis and their functional significance was discussed.

Morphological and histochemical observations on the oocapt and oviducal transport of oocytes in paramphistomum cervi (Zeder, 1790) (Digenea: Trematoda).

The oocapt of Paramphistomum cervi has a narrow constriction followed by a wide lumen with a thickened wall and is surrounded by several unicellular flask-shaped gland cells opening into the lumen. The oocapt gland cells are filled with granules, the size and number of which vary in the body cells and its duct. Histochemical studies have shown that the oocapt gland cells secrete mainly mucoproteins but a few lipoprotein and phospholipid granules have also been observed. The passage of the oocyte through the lumen of the oocapt, appears to stimulate the oocapt gland cells to release their secretion which seems to be involved in transport of the oocyte through the oviduct.

Effects of carbon dioxide, temperature, pH and the number of worms on the in vitro survival, histology and histochemistry of Paramphistomum cervi (Paramphistomatidae: Digenea).

Survival of immature and mature stages of Paramphistomum cervi, collected from the intestine and the rumen of sheep has been studied in in vitro using Tyrode's, Hank's, Eagle's, Stephenson's saline and Hedon--Fleig media. Twenty-five ml quantities of carbon dioxide (CO2)-rich Hedon--Fleig solution at pH 6.7, at 37 degrees C supported the maximum survival of 5 worms of both immature and mature flukes for periods of 9 and 10 days, respectively. Alterations to the pH of the medium, the incubation temperature and the number of worms significantly affected the period of their in vitro survival. The tissues of immature and mature worms did not show any marked histological and histochemical change until 24 h of in vitro survival in Hedon--Fleig solution when the testes of adult worms started undergoing degeneration. There was a progressive depletion of stored lipids and carbohydrates in the parenchymatous tissue during the course of in vitro survival. After the second day of in vitro maintenance, the maturation of the worms' vitelline follicles was affected, and thereafter they started to degenerate. On Day 4, degeneration of some gastrodermal cells, and a ruptured body wall were observed in some worms. Though the degenerative changes in the tissues of worms appeared at 24 h and continued to increase during in vitro maintenance, the worms survived for 9-10 days.

Observations on the surface morphology of the ovarian balls of Moniliformis (Acanthocephala).

The surface morphology of fixed ovarian balls from female Moniliformis dubius, agd 12, 18, 26, 28, 42, 77, 105 and 118 days, has been examined by means of scanning electron microscopy. The appearance of the surface has been found to be variable between ovarian balls from worms of the same and different ages. Some parts of the surface are seen to possess micro-projections, cavities and ridges while other parts have the appearance of an irregular meshwork of fibres. Various protruding features have been observed to extend from the surfaces of the ovarian balls taken from the inseminated female worms. In most cases, the surfaces of the protruding features differ in appearance from the surrounding surfaces of the ovarian balls. Some of these features have been assumed to represent growing zygotes and developing eggs covered by the supporting syncytium of the ovarian ball. Single or several thread-like structures have been observed in association with the surfaces of ovarian balls taken from the inseminated female worms. At present, the thread-like structures are believed to be portions of spermatozoa. By means of light microscopy, preliminary observations have been made on what is considered to be the division process of ovarian balls taken from uninseminated and inseminated worms varying in age from 7 to 98 days.

The growth of Moniliformis (Acanthocephala) in rats fed on various monosaccharides and disaccharides.

Aspects of the course of infection, growth and reproductive activity of Moniliformis were studied in adult male and female rats fed on isoenergetic purified diets containing various sugars. When rats were infected and fed on experimental diets containing either 3% glucose or 3% galactose for 5 weeks, very little growth of worms and no signs of reproduction were observed. In contrast, Moniliformis grew well and showed many signs of normal reproduction when the rats were fed on diets containing either 3% fructose or 3% mannose. The ability of the worms to grow and reproduce was not lost by maintaining them first for 5 weeks in rats fed on diets containing 3% glucose and 3% galactose. When the diets of such rats were changed to ones containing 3% starch and 3% fructose, respectively, for a further 5 weeks, the worms grew and normal reproduction occurred. Similar experiments were carried out in which groups of infected rats were fed for 5 weeks on diets containing gradually increasing amounts of glucose (6-36%). It was not until the rats were fed on diets containing 24% glucose that the mean dry mass of the worms approached that of worms from rats fed on the diet containing 3% fructose; no host diet was found to be as effective a supporter of worm growth as 3% mannose. Under no circumstances, not even when the host's diet contained 36%, was galactose found to be a suitable sugar for supporting the growth and reproduction of Moniliformis. Results consistent with those recorded for worms from rats fed on the diets containing monosaccharides were obtained when infected rats were fed for 5 weeks on diets containing 3% of various disaccharides. Considerable growth and reproduction of Moniliformis occurred when sucrose was included in the host's diet, but not when lactose, maltose or trehalose was present. Several of these observations may be related to the fact that different sugars are absorbed at different rates from the intestinal tract. It is suggested that all of a given sugar, when present in the diet at a low concentration, may be removed rapidly from the anterior part of the small intestine with the result that none will be available to the parasites. Significant amounts, however, of those sugars that are absorbed more slowly may reach the region of the intestine in which the parasite normally lives.

Morphological and histochemical observations on the intestinal epithelium of Ascardia galli (Nematoda: Ascaridida).

The intestinal epithelium of Ascardia galli has been studied with various cytological and cytochemical techniques. It consists of large epithelial cells resting on a thick collagenous basal lamina. Their luminal surface is provided with microvilli. The intestinal cells store considerable amounts of glycogen and neutral lipids. Some intracellular granular inclusions, which stain for proteins, phospholipids and lipoproteins, are distributed throughout the cytoplasm. The brush border is composed of microvilli whereas the outer surface coat consists of saliva resistant PAS-positive material. The detailed histochemical analysis of surface material has revealed that it is composed of nonacetylated acid mucopolysaccharides rich in hyaluronic acid with carboxylate polyanions. The brush border shows intense activities of acid phosphatase and glucose-6-phosphatase, moderate of ATPase, and lipase, weak of 5'-nucleotidase. Acid phosphatase-positive intracellular structures are seen in the intestinal epithelium which form distinct aggregations.

Comparative histochemical observations on the excretory system of helminth parasites.

The excretory canals of Ascaridia galli (Nematoda) and the protonephridial ducts of Cotylophoron cotylophorum (Trematoda) and Raillietina cesticillus (Cestoda) have been studied with regard to the histochemical localization of lipids, carbohydrates and hydrolytic enzymes. Distinct excretory organs are absent in the acanthocephalan Centrorhynchus corvi. Triglycerides, phospholipids and lipoproteins are seen in association with the wall of excretory canals of A. galli and R. cesticillus, and phospholipids and lipoproteins at the corresponding site in C. cotylophorum. The physiological significance of lipids in association with excretion of substances has been discussed. Low molecular weight glycogen is present in the lumen of excretory canal of A. galli but not in other worms. The common feature of the excretory canals is the presence of enzyme activities of nonspecific alkaline phosphatase and Mg2+-dependent ATPase. Activity of acid phosphatase is seen only in the excretory canals of A. galli. Glucose-6-phosphatase is present in A. galli and C. cotylophorum and absent in R. cesticillus. Weak reaction of 5'-nucleotidase is present in the excretory canals of helminth species studied here. The role of these enzymes in transportation of substances across the wall of excretory canals and also in ionic regulation has been discussed in detail.