This paper demonstrates that the establishment and growth of the filarial nematode parasite, Litomosoides carinii, is reduced in pyridoxine-deficient cotton rats. Young cotton rats were assigned to one of three dietary: vitamin B6-deficient cotton rats (B6-AL) were fed a pyridoxine-free diet ad libitum; pair-fed controls (B6 + PF) were fed the same amount of pyridoxine-free diet as animals in the deficient group and given daily oral supplements of 100 micrograms pyridoxine; and pyridoxine-sufficient controls (B6 + AL) were fed the pyridoxine-free diet ad libitum and supplemented daily with 100 micrograms pyridoxine. Half of each group was infected with 50 L3 of L. carinii by subcutaneous injection 8 weeks after the start of the experimental feeding period. B6-deficient cotton rats ate less (P < 0.001) and gained less weight (P < 0.001) than B6-supplemented controls. The levels of microfilaraemia in deficient animals, measured weekly throughout the experiment by taking blood smears, was significantly lower than in supplemented animals (P < 0.001). The deficient rats became latent for L. carinii at 20 weeks post-infection, whereas there was patent microfilaraemia in rats in the other dietary groups until the end of the experiment. Smaller (P < 0.001) and fewer (P < 0.05) adult worms were recovered from the pleural and abdominal cavities of deficient animals than from either pair-fed or sufficient controls at autopsy 28 week post-infection.

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The beginning of functional luteolysis in cattle ranges from Days 16–19 (Day 0 = ovulation). During functional luteolysis, luteal size and blood flow decrease in heifers. The wide range of beginning of luteolysis and the low sensitivity of quick progesterone (P4) assays preclude targeting an individual for a specific period of luteolysis. The present study aimed to evaluate the changes in area and blood flow of corpus luteum (CL) during spontaneous luteolysis and test the hypothesis that a decrease in CL area (cm2) is more efficient in targeting the luteolytic period than using a specific day postovulation. Blood sampling and ultrasound scanning of CL were done every 12 h from Days 13–22 in dairy heifers (Holstein) and was used for a retrospective study (Experiment 1; n = 6 heifers). The P4 concentrations, maximum CL area, and the percentage of CL area with coloured signals of blood flow were centralized to 12-h sample when the end of luteolysis (P4 < 1 ng mL–1) was detected. The percentage decrease in CL area and blood flow between Day 13 and the 12-h sample before the end of luteolysis were calculated. In Experiment 2, a blood sampling and transrectal ultrasonography of CL were performed every 8 h starting on Day 14 to determine the beginning and end of functional luteolysis (n = 20 heifers). The hour of detection of luteolysis was defined as the scan at 8-h intervals when maximum CL area decreased by 25 or 12.5% on Day 14. Based on P4 concentrations, the preluteolytic, luteolytic, and postluteolytic periods in each heifer were identified. The area and blood flow were measured by a duplex B-mode and pulse-wave colour Doppler ultrasound instrument. In Experiment 1, the retrospective study indicated a 25% decrease in CL area and 65% decrease in blood flow 12 h before the end of functional luteolysis. In Experiment 2, the 25% and 12.5% CL area decrease from Day 14 occurred, respectively, on Days 18.1 ± 0.6 and 17.2 ± 0.5 postovulation. The hypothesis that a decrease in CL area is more efficient in targeting ongoing luteolysis than using a specific day postovulation was supported. This was indicated by the greater (P < 0.05) frequency of heifers detected in luteolytic period (12 of 20 heifers) using the criteria of a 12.5% decrease in CL area than using a specific day (Table 1). Using a day postovulation for obtaining heifers in the luteolytic phase was only 0 to 30% effective for targeting luteolysis. In conclusion, the technique of using an ultrasonic 12.5% reduction in CL area is a good tool to detect ongoing luteolysis and may be useful as an experimental design to study factors related to the luteolytic period in cattle. Table 1.Percentage values of heifers in preluteolytic, luteolytic, or postluteolytic periods according to a decrease in CL area criteria or a day postovulation Supported by grants from FAPESP (2012/04004-8 to GP).

Pyridoxine (vitamin B6) deficiency was induced in cotton rats which were then infected with the filarial parasite Litomosoides carinii. Embryogenesis was assessed microscopically in worms taken from pyridoxine deficient cotton rats and from various categories of control animals. Embryogenesis was retarded in worms from pyridoxine deficient hosts and more abnormal embryos were present in such worms than in those from control animals.

This paper demonstrates that the activities of glycogen phosphorylase (GP), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are reduced in adult worms of the filarial nematode Litomosoides carinii recovered from pyridoxine-deficient cotton rats when compared to worms recovered from pyridoxine-sufficient controls. GP, ALT and AST activities were determined in adult worms L. carinii recovered from cotton rat hosts over a 20-week experimental period. Activities of GP, ALT and AST in the parasite showed a direct correlation with the dietary pyridoxine intake of their host. Throughout the experiment, enzyme activities were significantly lower (P < 0.001) in worms from rats fed a pyridoxine-free diet ad libitum that in worms from rats fed either a stock colony diet, a pyridoxine-free diet ad libitum with daily supplementation of 100 micrograms pyridoxine or limited amounts of pyridoxine-free diet with daily supplementation of 100 micrograms pyridoxine. The lower than normal activity of GP, ALT, AST and other enzymes dependent on the biologically active derivative of pyridoxine, the coenzyme pyridoxal-5-phosphate (PLP), interferes with the protein, carbohydrate and lipid metabolism of L. carinii and may in part cause the reduced establishment, development and growth of the parasite in pyridoxine-deficient hosts.