Metabolism of Benzyladenine is Impaired in a Mutant of Arabidopsis thaliana Lacking Adenine Phosphoribosyltransferase Activity

Formation of the riboside-5′-monophosphate is a general feature of the metabolism of cytokinins in plants. As part of a study of the biological significance of the nucleotide form of cytokinins, we analyzed a mutant of Arabidopsis thaliana deficient in adenine phosphoribosyltransferase (APRT) activity for its ability to metabolize N⁶-benzyladenine (BA). Formation of N⁶-benzyladenosine-5′-monophosphate (BAMP) was assayed in vivo, by feeding tritiated BA to wild-type and mutant plantlets, and in crude plantlet extracts. Metabolites were separated by high performance liquid chromatography and quantitated by on-line liquid scintillation spectrometry. BA was rapidly absorbed by A. thaliana plantlets and primarily converted to BAMP and to BA 7- and 9-glucosides. BA was also rapidly absorbed by APRT-deficient plantlets, but its conversion to BAMP was strongly reduced. Formation of BAMP from N⁶-benzyladenosine was not affected in the mutant plantlets. In vitro conversion of BA to its nucleoside-5′-monophosphate was detected in crude extracts of wild-type plantlets, but not in extracts of APRT-deficient plantlets. Therefore, results of both assays indicate that APRT-deficient tissue does not convert BA to BAMP to a significant extent. Further, nondenaturing isoelectric focusing analysis of APRT activity in leaf extracts indicated that the enzyme activities which metabolize adenine and BA into their corresponding riboside-5′-monophosphate in extracts of wild-type plantlets have the same apparent isoelectric point. These activities were not detected in extracts prepared from APRT-deficient plantlets. Thus, these results demonstrate that APRT is the main enzyme which converts BA to its nucleotide form in young A. thaliana plants and that the ribophosphorylation of BA is not a prerequisite of its absorption by the plantlets.     

Two Apoplastic alpha-Amylases Are Induced in Tobacco by Virus Infection

α-Amylase activity (EC 3.2. 1.1) is greatly increased in leaves of tobacco (Nicotiana tabacum L. cv Samsun NN) infected with tobacco mosaic virus (TMV). The kinetics of enzyme induction during the hypersensitive reaction resemble those of other hydrolases known to be pathogenesis-related proteins of tobacco. Two α-amylases were purified from TMV-infected leaves and shown to have features in common with well-characterized pathogenesis-related proteins: they are acidic monomers that can be separated upon electrophoresis on basic native gels, and they are found in the apoplastic compartment of the cell. This extra-cellular localization was demonstrated by comparing the α-amylase partition between the intercellular wash fluid and the cell extract with that of proteins of known cellular compartmentalization. These data indicate an active secretion of both α-amylases produced in tobacco upon TMV infection.     

Eye muscles of the pike (Esox lucius) fiber types and their actomyosin ATPase and SDH activity

The eye muscles of the pike are organized in two distinct populations of fibers arranged in semicircular layers. The distal layer, consisting of small diameter muscle fibers, is mainly made up of type I and tonic (slow) fibers. The central and proximal (facing the eyeball) parts of the eye muscles are occupied by IIB and IIC (fast) fibers. As a main criterion for identification of muscle fiber types, the reaction for actomyosin ATPase activity has been used: metabolic characterization of these fibers has been carried out on the basis of SDH activity.     

Are antibodies responsible for a decreased superovulatory response in goats which have been treated repeatedly with porcine follicle-stimulating hormone?

Repeated administration of xenogenic gonadotropins in human or animal species may be responsible for antibody production and refractoriness. An experiment was conducted in which goats were treated with porcine FSH (p-FSH) at 6-week intervals for a period of 7 months. A sensitive radioimmunoassay (RIA) was used to detect antibodies to p-FSH in plasma samples taken at short-term intervals during a 7-month period. Antibodies appeared after the first injection, and levels increased following booster injections. A high correlation rate existed between antibody level and superovulatory response. Refractoriness in goats was associated with a high level of antibodies.     

Ovarian function and pregnancy rates in reindeer calves (Rangifer tarandus ) in Southern Norway

Reindeer calves (n = 632) were slaughtered in November/December (n = 476) or in January (n = 156). Dressed weights and amount of perirenal fat were recorded, and the reproductive organs were collected. A separate group of 130 reindeer calves were weighed at 7 months of age and were followed up with repeated weighings and pregnancy examinations up to 21 months. The onset of puberty and the pregnancy rate were significantly influenced by body weight and the amount of perirenal fat. Approximately 60 g of perirenal fat and 22 kg dressed weight were found at the lower limits for pregnancy. A total of 222 (35%) animals had reached puberty and 126 (20%) were pregnant when examined after slaughter. Animals which conceived during their first autumn showed only a moderate weight gain the following year, and the calf mortality rate in these animals was 47.4%. It was concluded that calf pregnancies are common among the reindeer of Southern Norway and that measures need to be taken to prevent them.     

The effects of recombinant bovine interferon-alpha on fertility in ewes

Recombinant bovine interferon-alpha(I)1 (rBolFN-alpha) may be useful for enhancing fertility in sheep because it has extensive sequence homology with ovine trophoblast protein-1. To test the effectiveness of rBolFN-alpha, several experiments were performed in which bred females were given intramuscular injections of rBolFN-alpha around the time of maintenance of the corpus luteum. Treatment with rBolFN-alpha enhanced the fertility of ewes that were bred via natural service or embryo transfer of whole or demi-embryos. Interferon treatment was successful in enhancing lambing rate if injections were given twice daily from Days 11 to 18, 12 to 14, 12 to 15 or 12 to 16. Overall, the lambing rate for ewes bred via natural service was 94/126 (74.6%) for control ewes and 101/126 (80.2%) for rBolFN-alpha treated ewes. Litter size was not affected by treatment. Interferon treatment was not successful in increasing the lambing rate if given as a single injection on Day 12 or as a series of once-daily injections from Days 11 to 16. These results demonstrate that rBolFN-alpha can increase the lambing rate in ewes.     

Determination of ovulation time in bitches based on teasing, vaginal cytology, and elisa for progesterone

The estrous cycle of 16 mature mongrel female dogs was monitored to evaluate the accuracy of teasing, vaginal cytology and quantitative ELISA progesterone assay to determine ovulation. The dogs were presented to male, and blood samples and vaginal swabs were taken daily during proestrus and estrus. Selected serum samples collected during estrus were assayed for endogenous LH by radioimmunoassay (RIA). Plasma samples collected during proestrus and estrus were assayed for progesterone with a commercially avialable ELISA kit. Ovulation was considered to take place 48 h after the preovulatory LH peak. Vaginal cytology smears were stained with Wright's stain and evaluated for the percentage of superficial squamous cells. Day 1 of diestrus (Day 1) was defined as a drop of 20% or more in the total number of superficial cells. Two standard curves (linear and best fitted curves) commonly used with ELISA were compared together and with the RIA progesterone assay. Ovulation was estimated to occur when progesterone concentration was 4.9 +/- 1.0ng/ml (mean +/- SD, n = 15), with a range of 3.4 to 6.6 ng/ml. Based on vaginal cytology, ovulation took place 6.9 +/- 1.6 d (n = 15) after 80% of the squamous cells were superficial and 6.8 +/- 1.4 d (n = 16) before Day 1. Ovulation took place 2.1 +/- 3.9 d (n=11) after the first day of standing estrus and 8.8 +/- 1.5 d (n = 10) before the last day of receptivity. The two standard curves were found parallel to each other and to the RIA progesterone assay. Based on the results of the present study, ELISA progesterone assay and determination of the first day of estrus by vaginal cytology are reliable methods for predicting ovulation, whereas the last day of receptivity as determined by teasing and Day 1 as determined by vaginal cytology are reliable methods to retrospectively estimate ovulation time.     

The use of the probit model to predict pregnancy status of buffalo based on physio-chemical properties of estrual mucus

Improper timing of artificial insemination with respect to ovulation is one of the major factors hampering the conception rate in buffalo. The present study was an attempt to relate physio-chemical changes in estrual mucus to subsequent pregnancy status in order to find their optimal values for determining the time for artificial insemination (AI). Serum estradiol, total protein and dry matter contents of estrual mucus were evaluated to predict the subsequent pregnancy in 36 buffalo during October 1988 to February 1989. Serum estradiol was determined by radioimmunoassay (RIA); spinnbarkeit, dry matter and total protein were determined by standard methods. Multivariate probit analyses were carried out to relate these variables to subsequent pregnancy status. Elasticity and protein concentration were significantly related to prediction probability of pregnancy status, and they predicted the pregnancy status 86% of the times correctly (P < 0.05). The probability of pregnant animals being correctly classified was 0.76, whereas the corresponding value for non-pregnant animals was 0.95. The present study demonstrated the possibility of using such a statistical model on mucus characteristics for determining proper AI time for better conception rates in Nili-Ravi water buffalo.     

Population genetics of freshwater snails

Freshwater snails have attracted the attention of biologists for a long time, because they are intermediate hosts of schistosomes, agents of bilharziases. However, population-genetic studies of freshwater snails have been undertaken only during the past decade, covering topics such as the relative roles of genetic drift and gene flow in subdivided populations and the roles of extinction and recolonization events in determining population structure. Other studies in freshwater snails have investigated the maintenance of sex and the evolution of selling, widening a debate restricted mainly to plant populations. The possible role of parasites in freshwater-snail population genetics has also been investigated.     

Morbidity, due to schistosomiasis mansoni, and its control in Subsaharan Africa

The measuring and monitoring of morbidity are essential components of schistosomiasis control programmes. Bruno Gryseels and Anton Polderman assess the objectives, difficulties and importance of morbidity control of schistosomiasis mansoni in subsaharan Africa.