Occurrence and Functions of PACAP in the Placenta

Pituitary adenylate cyclase activating polypeptide (PACAP) is an endogenous neuropeptide with a widespread distribution both in the nervous system and peripheral organs. The peptide is also present in the female gonadal system, indicating its role in reproductive functions. While a lot of data are known on PACAP-induced effects in oogenesis and in the regulation of gonadotropin secretion at pituitary level, its placental effects are somewhat neglected in spite of the documented implantation deficit in mice lacking endogenous PACAP. The aim of the present review is to give a brief summary on the occurrence and actions of PACAP and its receptors in the placenta. Radioimmunoassay (RIA) measurements revealed increased serum PACAP levels during the third trimester and several changes in placental PACAP content in obstetrical pathological conditions, further supporting the function of PACAP during pregnancy. Both the peptide and its receptors have been shown in different parts of the placenta and the umbilical cord. PACAP influences blood vessel and smooth muscle contractility of the uteroplacental unit and is involved in regulation of local hormone secretion. The effects of PACAP on trophoblast cells have been mainly studied in vitro. Effects of PACAP on cell survival, angiogenesis and invasion/proliferation have been described in different trophoblast cell lines. PACAP increases proliferation and decreases invasion in proliferative extravillous trophoblast cells, but not in primary trophoblast cells, where PACAP decreased the secretion of various angiogenic markers. PACAP pretreatment enhances survival of non-tumorous primary trophoblast cells exposed to oxidative stress, but it does not influence the cell death-inducing effects of methotrexate in proliferative extravillous cytotrophoblast cells. Interestingly, PACAP has pro-apoptotic effect in choriocarcinoma cells suggesting that the effect of PACAP depends on the type of trophoblast cells. These data strongly support that PACAP plays a role in normal and pathological pregnancies and our review provides an overview of currently available experimental data worth to be further investigated to elucidate the exact role of this peptide in the placenta

Nectar composition in 'Újfehértói fürtös' and 'Pándy 48' sour cherry cultivars

The knowledge of nectar composition in entomogamous fruits, including sour cherry cultivars, is of high importance, since pollinator insects have their own taste-preference, which can influence pollination, and hence fruit yield. The floral secretory product of several sour cherry cultivars was studied from 1997 to 2000, in order to determine the floral insect attraction of the cultivars. Here the nectar composition of two major cultivars, an autofertile ('Újfehértói fürtös') and an autosterile one ('Pándy 48'), will be presented. Samples were collected at the Research and Extension Centre for Fruitgrowing, Újfehértó, Hungary. Nectar was drained from the flowers with a microcapillary, following a 24-hour isolation. Sugar components of the floral secretory product were determined by thin layer chromatography, quantitative analysis was carried out by densitometry. When evaluating the results, air temperatures and precipitation data during sample taking were also taken into consideration. The nectar of both studied cultivars contains all three major sugar components: sucrose, glucose and fructose. In most seasons the total sugar concentration reached the apicultural threshold value (100 mg/ml). On the basis of the sucrose/(glucose+fructose) quotient the nectar of 'Újfehértói fürtös' belonged to the sucrose-rich group each year, like the majority of sour cherry cultivars, whereas the secretory product of 'Pándy 48' could be classified into the sucrose-dominant category in one of the seasons. The nectar sugar composition of 'Újfehértói fürtös' varied to a great extent according to the seasons, while the sugar components in the nectar of 'Pándy 48' were rather stable in the four seasons of study, their amounts changing to a small extent, effected by microclimatic factors

Composition of floral nectar and its seasonal variability in sour cherry cultivars

The sugar composition of floral nectar was studied in 17 sour cherry cultivars in Újfehértó in 1997-2000. All samples contained the three most frequent sugar components: glucose, fructose and sucrose, similarly to our previous data. The ranking of the floral nectar in sour cherry cultivars based on sucrose content was the following: 'Újfehértói fürtös' and 'Pándy 48' reached the threshold value of bee visitation in at least three seasons, and a significant amount of sucrose was detected in the flowers of 'Érdi jubileum AB' and 'Érdi bőtermő' as well. The above cultivars proved to be the most valuable in Újfehértó from the viewpoint of apiculture. According to the ranking based on fructose content, which considers human sensation of taste, the most favourable cultivars were 'Újfehértói fürtös', 'Meteor USA' and 'Korai pipacs'. Based on total sugar content the secretory products preferred by bees were those of 'Újfehértói fürtös' (in three seasons); 'Korai pipacs', 'Érdi nagygyümölcsű', 'Sárándi S/Gy', 'Debreceni bőtermő', 'Kántorjánosi 3', 'Montmorency' and 'Meteor USA' (in two seasons). The ratio of nectar sugars, based on the Baker-quotient, S/(G+F), was sucrose-dominant at least in one season in 'Érdi jubileum AB', 'Érdi nagygyümölcsű' and 'Pándy 48'; hexose-rich in 'Korai pipacs', 'Kántorjánosi 3' and 'Montmorency'; all other cultivars had a sucrose-rich nectar. The nectar of all studied sour cherry cultivars possessed a composition preferred by bees. The basis of bees' nectar preference is the ratio, quantity and concentration of nectar sugar components, which were influenced by the effects of season to a high degree, differing from data in literature. From the viewpoint of nectar composition and concentration the most favourable temperature was around 20 °C

Sugar composition of floral nectar in sour cherry cultivars

The composition of floral nectar in sour cherry cultivars studied in 1997 at Újfehértó was in agreement with our previous data, the three most frequent sugar components being glucose, fructose and sucrose. Nectar secreted at night is generally more diluted than nectar produced during the day. None of the nectar samples produced at night reached the threshold value (100 mg/ml) of bee visitation. In the majority of cultivars the difference in concentration between night and day nectar is not too high, but in two cultivars, 'Korai pipacs' and ‘Újfehértói fürtös’ the difference is quite significant. Most sucrose was found in the nectar of cvs. 'Érdi jubileum' and ‘Újfehértói fürtös’, but a high amount of sucrose was measured also in the flowers of 'Korai pipacs' and 'Meteor USA'. Nectar concentration varies from opening of the flower to petal fall to a smaller or greater degree, depending on the given cultivar. From the 9 sour cherry cultivars studied ‘Újfehértói fürtös’ and Tandy 48' had the most attractive nectar for bees. There was no correlation between nectar composition and free fertilisation. On the basis of nectar composition the majority of the sour cherry cultivars studied can be classified into the sucrose-rich category; only one cultivar, 'Érdi jubileum' had a sucrose-dominant secretory product. The composition of nectar in the studied sour cherry cultivars is preferred by bees. &nbsp

Floral biological investigations of apple cultivars in relation to fire blight

Floral activity was studied in two apple cultivars: an Erwinia-tolerant (Treedorn') and a sensitive one (`Sampion'). Since more types of protogyny occur in apples, the period of stigma activity is different. Papillae of the exposed stigma in flowers of 'Freedom' function longer (usually more than a week) than in the delayed homogamous `Sampion'. Despite of this, cv. 'Freedom' is tolerant to Erwinia amylovora (Burr.) Winslow et al., suggesting no relationship between the floral biological type (including the exposure and longevity of stigma) and the infection by E. amylovora. According to SEM micrographs, nectary stomata in `Freedom' are already open in the flower bud, where nectar secretion starts and continues until the senescence of the stigma. However, the long period of nectar secretion does not create optimal conditions for bacterial growth, since nectar production is scant in the flowers of 'Freedom'. The surface of the nectary, its nectar-retaining capacity, and the amount and concentration of nectar may influence the susceptibility of apple cultivars. It is manifested well by the smooth nectary surface with nectary stomata rising slightly above the epidermis in flowers of cv. 'Freedom', contrasting the wrinkled, striate nectary surface with slightly sunken stomata in the flowers of 'Sampion'

Floral nectar production and composition in quince cultivars and its apicultural significance

The sugar composition of the floral nectar was studied in 22 mainly Hungarian local quince cultivars in 2004. The material for investigation was taken from the quince genebank of the Research and Extension Centre for Fruitgrowing, Újfehértó, Hungary. The three main sugar components of the nectar were glucose, fructose and sucrose. Sucrose was present in the greatest amount in the nectar of all investigated quince cultivars. Glucose which is the least sweet among the three main nectar sugars for bees was present in the least amount. The nectar of most cultivars contained more fructose than glucose. The amount of the total nectar sugars was the lowest in cv. 'Pear-shaped Noszvaji' and the highest in cv. 'Kúti'. According to the Baker-quotient (S/F+G), the majority of the quince cultivars belonged to the sucrose dominant category. However, the cultivars 'Mezőkövesdi', 'Apple-shaped Dunabogdány' and 'Váli' had sucrose-rich nectar. The concentration of floral secretory product in all cultivars reached the threshold of bee visitation. The nectar refraction was lower at the end of bloom than in full bloom while flowers contained more nectar at the previous stage. The above results are important from the viewpoint of pollination biology, apiculture and defence against fire blight