Do egg-laying crocodilian (Alligator mississippiensis) archosaurs form medullary bone?

It is beyond question that Mesozoic dinosaurs, like Aves and Crocodylia, are archosaurs. However, within the archosaurian clade, the origin and distribution of some major features are less clear, particularly with respect to reproductive physiology. Medullary bone, a highly mineralized, bony reproductive tissue present in the endosteal cavities of all extant egg-laying birds thus far examined, has recently been reported in Tyrannosaurus rex. Its presence or absence in extant crocodilians, therefore, may shed light on the timing of its evolutionary appearance. If medullary bone is present in all three taxa, it arose before the three lineages diverged. However, if medullary bone arose after this divergence, it may be present in both extinct dinosaurs and birds, or in birds only. If present in extinct dinosaurs and birds, but not crocodilians, it would indicate that it arose in the common ancestor of this clade, thus adding support to the closer phylogenetic relationship of dinosaurs and birds relative to crocodilians. Thus, the question of whether the crocodilian Alligator mississippiensis forms medullary bone during the production of eggs has important evolutionary significance. Our examination of long bones from several alligators (two alligators with eggs in the oviducts, one that had produced eggs in the past but was not currently in reproductive phase, an immature female and an adult male) shows no differences on the endosteal surfaces of the long bones, and no evidence of medullary bone, supporting the hypothesis that medullary bone first evolved in the dinosaur-bird line, after the divergence of crocodilians from this lineage.

Therapeutic constituents and actions of Rubus species.

Rubus species (family Rosaceae) have been cultivated for centuries for their fruits. These and other parts of the plants have been used traditionally for therapeutic purposes. This article highlights these and the potential they can offer. The constituents reported in the various species and those demonstrated to exhibit pharmacological properties have been reviewed. In the search for biologically active compounds, one of the most frequently documented species of the genus is the raspberry plant R. idaeus, the leaves of which have been used traditionally as a uterine relaxant and stimulant during confinement, for the treatment of diarrhoea and similar enteric disorders and as an astringent. Investigations of other Rubus species have been conducted in the last twenty-five years, and have shown possible application for a wide range of indications, including bacterial infections, anxiety, pain and inflammation.

Relaxant effects of parathyroid hormone and parathyroid hormone-related peptides on oviduct motility in birds and mammals: possible role of nitric oxide.

Parathyroid hormone (PTH) and PTH-related peptides (PTHrP) have previously been shown to modulate the contractile state of numerous types of smooth muscle. The effects of N-terminal PTH and PTHrP on spontaneous in vitro contractility of oviducal smooth muscle using tissues from egg-laying Japanese quail (10-15 h post ovulation), 4 and 9 days pregnant mouse uterus were investigated. Myometrial tissues from both species contracted vigorously for several hours, when incubated in organ baths in De Jalon's solution gassed with 5%CO2/95%O2. Contractions were enhanced in high (1.2-2.5 mM) compared with low (0.1-0.5 mM) calcium (Ca) containing media. Bovine PTH(1-34) (bPTH(1-34)), human PTH(1-34 amide) (hPTHrP(1-34) amide), and hPTHrP(1-40) caused similar concentration-related inhibition of contractions in media containing 1.2mM Ca over a range of 10(-9) to 10(-7)M, whereas C-terminal hPTHrP(107-139) was devoid of such activity. Responses to bPTH(1-34) in 4 and 9-day pregnant mouse tissues were similar but hPTHrP(1-40) showed substantial loss of activity in 9-day, compared with 4-day pregnant mouse tissues. Repeated exposure of mouse uterine tissue to the peptides resulted in desensitisation of responses. The EC50 responses of mouse tissues were inhibited by the PTH/PTHrP receptor antagonist, hPTHrP(7-34) amide. Responses to bPTH(1-34) were also inhibited by both non-selective and selective neuronal nitric oxide synthase (NOS) inhibitors N(omega)-nitro-L-arginine methyl ester (0.01-1mM) and 7-nitroindazole (0.01-10 microM), respectively. Both NOS inhibitors were more effective in inhibiting bPTH(1-34)-induced relaxation in the absence of L-arginine compared with in the presence of 1mM L-arginine (a NOS substrate) in the incubation media. It is concluded that relaxant responses to N-terminal PTH and PTHrP peptides are well conserved in oviducal and uterine tissues from avian and mammalian species. The results also suggest that NO may be responsible for mediating relaxant activities of these peptides in pregnant mouse uterine tissue.

Evidence for the anti-hyperlipidaemic activity of the edible fungus Pleurotus ostreatus.

The effects are described of adding either the dried fruiting bodies of the oyster fungus Pleurotus ostreatus, or an ethanolic extract of it, to the diet of normal Wistar male rats and a strain with hereditary hypercholesterolaemia. Addition of the dry oyster fungus to the diet significantly increased, by more than two-fold, the triacylglycerol (TAG) level in the plasma of both groups of rats compared with their respective controls. In contrast, the ethanolic extract did not significantly change TAG levels. Values for total cholesterol and its high- and low-density lipoprotein fractions in the plasma, as well as the calculated atherogenic index, did not show any significant change. Levels of liver cholesterol were significantly lowered by the dried oyster fungus in both hypercholesterolaemic and normal groups of rats, and by the ethanolic extract in normal rats. A significantly increased phospholipid-to-cholesterol ratio in the aortas of both groups of rats, after the administration of either dried oyster fungus or the ethanolic extract of it, suggests a favourable anti-atherogenic effect for both.

Quantitative studies on the effect of prostacyclin on freshly isolated rat osteoclasts in culture.

Prostaglandins exert marked but transient inhibitory effects on bone resorption. The present study examines the effects of prostacyclin (0.15 to 25 microM) on the morphology of freshly disaggregated rat osteoclasts. An area descriptor, rho, represented changes in total cell spread area, and a motility descriptor, mu, represented overall changes in cell motility. The application of prostacyclin intercepted the trend of an increasing cell spread area with time and produced a transient reduction of rho, an R effect. Its magnitude depended upon concentration and was marked at 25 microM prostacyclin. The subsequent recovery (+0.8/min) of rho at this concentration resembled the persistent spreading seen in the absence of the agonist. There was also a sustained decrease in mu to approximately 60% of its pretreatment value (a Q effect) following the application of 25 microM prostacyclin. The extracellular application of 20 mM [Ca2+] produced a similarly transient cell retraction preceded by a rise of cytosolic [Ca2+], but without a corresponding decrease in mu. In contrast, prostacyclin did not elevate cytosolic [Ca2+], suggesting the triggering of an alternative transduction pathway. A fully reversible retraction together with incomplete quiescence may explain the transience characteristic of the antiresorptive action of prostacyclin.

Estimation of intracellular calcium activity in confluent monolayers of primary cultures of quail medullary bone osteoclasts.

The present study was concerned with an investigation of the relative utilities of the fluorescent indicators fura-2 and fluo-3 for spectrofluorimetric estimation of the intracellular calcium concentration ([Ca2+]i) in confluent osteoclast monolayers that had been isolated from medullary bone of quail hens and maintained in tissue culture for 6-8 days. Additionally, we have determined the effects of raised extracellular calcium ([Ca2+]o) and chicken calcitonin (CT) on [Ca2+]i in this preparation. Relative to fura-2, fluo-3 was poorly incorporated into the osteoclasts and had a high apparent equilibrium binding constant (Kd) for Ca2+ binding (809 nM). The osteoclasts were only weakly sensitive to the calcium ionophore, ionomycin. It is concluded that fura-2 is of greater utility than furo-3 in this preparation. In contrast to its lack of effect in freshly isolated cells, elevated [Ca2+]o up to 20 mM stimulated a concentration-dependent increase in [Ca2+]i in cultured osteoclasts, but CT was without effect. These findings further support the idea that quail osteoclasts are able to acquire a Ca2+ sensor or 'receptor' and thus to respond to [Ca2+]o in a similar manner to mammalian osteoclasts when they are removed from the bone microenvironment, but retain a refractoriness to CT under these conditions.

Effect of raised extracellular calcium on cell spread area in quail medullary bone osteoclasts.

The present study reports on the effects of extracellular calcium ([Ca2+]o) elevation and ionomycin on cell spread area of medullary bone osteoclasts freshly isolated from egg-laying Japanese quail. The responses were compared with those demonstrated in osteoclasts cultured for periods of 5-8 days and also to those previously demonstrated in neonatal rat osteoclasts. Freshly isolated medullary bone osteoclasts, unlike rat osteoclasts, were refractory to 20 mM [Ca2+]o, in that they showed no change in cell spread area. They did, however, show a modest (15%) reduction in cell spread area to ionomycin (7-50 microM), applied for 15-30 min. When medullary bone osteoclasts were precultured for 5-8 days, they exhibited a well-developed response to 20 mM [Ca2+]o with a 46% reduction in cell spread area. They also showed a similar reduction in cell spread area in response to ionomycin (4 microM). It is concluded that, unlike freshly isolated neonatal rat osteoclasts, those obtained from quail medullary bone appear refractory to inhibitory factors such as [Ca2+]o. However, when the avian cells are cultured for a few days they appear to recover their ability to respond to [Ca2+]o.

Osteoclasts from medullary bone of egg-laying Japanese quail do not express the putative calcium 'receptor'.

The present study reports the contrasting effects of extracellular calcium ([Ca2+]e) elevation on cytosolic free calcium levels ([Ca2+]i) of osteoclasts, freshly isolated either from medullary bone of the egg-laying Japanese quail or from rat cortical bone. [Ca2+]i was measured in single osteoclasts using the Ca(2+)-sensitive fluorochrome, Indo-1. We found that elevation of [Ca2+]e failed to induce a rise of [Ca2+]i in quail osteoclasts, whilst causing an elevation of [Ca2+]i in rat osteoclasts. The calcium ionophore, ionomycin, led to a sustained elevation of [Ca2+]i in both cell types. These findings suggest that osteoclasts isolated from egg-laying quail do not possess the calcium sensor or 'receptor' that appears to be vital for the survival and function of rat osteoclasts.

Parathyroid hormone-(1-34) peptide activates cyclic adenosine 3',5'-monophosphate in the human placenta.

Dually perfused human term placental lobules were exposed to forskolin, bovine parathyroid hormone (bPTH(1-34)) and human parathyroid hormone related-peptides, hPTHrP(1-34), hPTHrP(67-86)NH2 or PTHrP(107-138) for 15 min in the presence of 3-iso-butyl-1-methyl-xanthine (IBMX); control lobules were exposed to IBMX alone. Homogenates of these tissues were then assayed for cyclic adenosine 3',5'-monophosphate (cyclic AMP) and results normalized per mg of protein. Exposure to forskolin or bPTH(1-34) on both sides, and exposure to bPTH(1-34) at a concentration of 30 nM on the maternal side of the placenta or 120 nM on the fetal side of the placenta, significantly enhanced tissue cyclic AMP production compared with tissue exposed to IBMX alone. Exposure to hPTHrP(1-34), hPTHrP(67-86)NH2 and hPTHrP(107-138) at a concentration of 30 nM on both sides of the placenta had no significant effect upon tissue cyclic AMP production.

Inhibitor action on placental calcium transport.

Human term placental lobules were dually perfused with Krebs Ringer solution at 37 degrees C under open circuit conditions. Provided that perfusate Ca2+ concentrations were between 2.33 and 2.55 mM, there was a steady release of Ca2+ into the fetal circulation and uptake of Ca2+ from the maternal circulation. There was no significant calcium (Ca) protein binding in the perfusates. Addition of dinitrophenol altered the release of Ca2+ to an uptake on the fetal circuit and enhanced Ca2+ uptake on the maternal circuit. It also produced a release of potassium (K)+ and an uptake of Na+ on both sides of the placenta. Ouabain had no significant effect on Ca movements although it produced a marked release of K+ into the fetal perfusate. The effect of cooling on the fetal circuit was similar to that of dinitrophenol (DNP), although it did not produce significant changes in either Ca2+ or K+ movements on the maternal side of the lobule. Both DNP and cooling reduced the Ca concentration ratio between fetal and maternal outflows to unity. Replacement of Na+ by choline Ringer had only transient effect on the extraction of 45Ca from fetal perfusate. These observations indicate that a Ca2+/Na (sodium)+ exchanger does not make a major contribution to the transplacental movement of Ca2+ from mother to fetus and that this process is more probably associated with membrane-bound ATPases.

Calcitonin gene-related peptide promotes transient radiocalcium uptake into chick bone in vivo.

We have examined the in vivo effects in chicks of intravenously injected chicken (c-) and rat (r-) calcitonin gene-related peptides (CGRP) on uptake into bone of a simultaneously administered 45Ca label. Both peptides caused transient (10 min) increases in 45Ca uptake into a variety of bone types. In dose-response experiments at 10 min, CGRP doses of 0.26-1.04 nmol/100 g body wt were found to give maximal responses. These were well developed in chicks fasted for 22 h but absent in those which were continuously fed. This contrasts with the hypercalcaemic effect of CGRP which is apparent in fed rather than fasted chicks.

Effects of rat and chicken calcitonin gene-related peptides (CGRP) upon calcium metabolism in chicks.

In vivo effects of intravenously injected chicken(c-) and rat(r-) calcitonin gene related peptide (CGRP) upon plasma total (Cat), ionized (Cai) calcium, inorganic phosphate (Pi) and clearance of an acutely administered 45Ca label have been examined in chicks. Both peptides were hypercalcaemic in fasted chicks, unlike previously reported hypocalcaemic response in mammals. r-CGRP was hypercalcaemic at doses of both 0.26 and 1.31 nmol/100 g body wt, the lower dose produced a significant elevation of Cat one hour after injection into 12-h-fasted chicks, the upper dose had a similar effect at 20 min. Cai was also non-significantly elevated by r-CGRP. Pi was slightly increased by r-CGRP at both doses, 20 and 60 min after injection. c-CGRP produced a dose (0.26-4.17 nmol/100 g body wt) dependent elevation of Cat and Cai in 22-h-fasted chicks. A greater response was however seen in fed animals. Peak responses were observed 45 min after injection. c-CGRP (1.04 nmol/100 g body wt) caused a significant decline in plasma Pi (P less than 0.05) in fasted chicks. Pi was elevated in control fed animals compared with fasted controls. c-CGRP (1.04 nmol/100 g) did not effect plasma Pi in fed chicks. Whilst both peptides elevated plasma Ca, clearance of an acutely administered 45Ca label from plasma was greater in both r-CGRP treated 12-h-fasted chicks and c-CGRP treated 22-h-fasted chicks. In contrast, the rate of 45Ca clearance in fed chicks was not affected by c-CGRP treatment. The differential effects of these peptides upon plasma 45Ca clearance and other plasma parameters of Ca metabolism, suggest a complex mode of action of the peptide upon avian Ca homeostasis, possibly involving direct actions upon kidney and bone.

Kinetics of rapid 45Ca uptake into chick skeleton in vivo: effects of microwave fixation.

We have investigated uptake kinetics for 45Ca labels acutely administered as single intravenous injections into twelve-day-old chicks in vivo. Effects of microwave fixation on this process have also been studied. Rapid uptake of 45Ca was demonstrated into the skeleton with approximately 40% of injected label being found in the skeleton within the first 15 min. By 45 min tissue 45Ca levels had stabilized and showed little change during the following 90 min. Soft tissue isotope levels declined during the period from 3 to 135 min following injection. These data were obtained from animals in which tissue isotope levels were stabilized by fixation with microwaves at the point of killing by cervical dislocation. In animals where the microwave fixation step was omitted and tissues were dissected for counting at least 1 h after killing, 45Ca levels in both skeletal and soft tissues were 15-20% higher than in those from microwave groups during the period 3-15 min after injection. In a separate experiment, groups of chicks killed by cervical dislocation 3 min after isotope injection were fixed with microwaves at time intervals ranging from 0 to 45 min post-mortem. Isotope levels in femur increased with time and were significantly higher in groups in which fixation was carried out 12 and 45 min after death when compared with those fixed at the point of death. Data in calvarium reflected those in femur but were not statistically significant at the time intervals tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclic nucleotides and the rapid inhibitions of bone 45Ca uptake in response to bovine parathyroid hormone and 16,16-dimethyl prostaglandin E2 in chicks.

Intravenous injection of chicks with bovine parathyroid hormone (1-34) (3.3 micrograms/100 g body wt.) or 16,16-dimethyl PGE2 (5 micrograms/100 g body wt.) caused rapid (3 minute) net inhibition of 45Ca uptake into femur and calvarium. These agents also elevated bone adenosine 3',5'-cyclic monophosphate (cAMP) but not guanosine 3',5'-cyclic monophosphate (cGMP) levels at this time. Methylxanthine phosphodiesterase inhibitors (MXPI), caffeine, theophylline, and 3-isobutyl-1-methylxanthine (IBMX) (0.3-5 mg/100 g body wt.) similarly inhibited net 45Ca uptake into femur and to a lesser extent calvarium. Plasma 45Ca and total Ca levels were unaltered or showed a slight tendency to be increased over control values 3 minutes after injection. However, the effects of the non-MXPI, dibutyryl-cAMP (0.5-5 mg/100 g body wt.) on bone 45Ca uptake were negligible. Of the MXPI, only IBMX elevated total cAMP levels in chick bone at 3 minutes. These data implicate but do not confirm a mediatory role for cAMP in the rapid inhibitory actions of PTH and PGEs on bone net 45Ca uptake in chicks.

The transfer of zinc across the term dually perfused human placental lobule.

Net zinc transfer between fetal and maternal circulation has been described in the in vitro perfused lobule of the human term placenta. The transfer results in a 3 microM differential between fetal and maternal perfusates which is comparable to estimated values in vivo. Tissue zinc concentration is more than 10 times perfusate concentration and is correlated with zinc flux across the fetal borders of the lobule. Open-circuit studies on net transport of zinc, and upon flow of 65Zn relative to tritiated water (3H2O), indicate these fluxes depend upon the non-protein-bound (free) zinc gradient across the fetal-facing membranes. On the other hand movement across the maternal surface is not related to diffusion gradients of free zinc and is either independent of, or inversely related to, the level of tissue zinc. It is concluded that the uptake of zinc from the maternal perfusate may be coupled to metabolism, whereas its transfer to fetal circulation is linked to the level of free zinc in the tissue.

Effects of synthetic bovine parathyroid hormone (1-34) and its analogues on 45Ca uptake and adenylate cyclase activation in bone and plasma calcium levels in the chick.

We have previously demonstrated that intravenous injection of synthetic bovine parathyroid hormone (1-34) (bPTH(1-34)), but not necessarily bPTH(1-84), into chicks rapidly (3 min) inhibits skeletal uptake of an acute 45Ca label. In the present study hydrogen peroxide oxidation of bPTH(1-34) abolished this response and reduced its ability to activate adenylate cyclase in bone and kidney. Oxidised bPTH(1-34) did, however, exhibit the full hypercalcaemic activity of untreated hormone. In contrast, the analogue [Nle8, Nle18, Tyr34]-bPTH(1-34)amide reduced chick bone 45Ca uptake but failed to raise plasma Ca levels. Cyclic AMP formation in response to this analogue was also slight. Another analogue, [Nle8, Nle18, Tyr34]-bPTH(3-34)amide, failed to inhibit 45Ca uptake or stimulate cyclic AMP formation in chick bone. It was also without hypercalcaemic activity. These data suggest that the hypercalcaemic response to bPTH(1-34) in chicks is not merely a reflection of its inhibitory effect on bone 45Ca uptake. They also question the relevance of cyclic AMP in the former action. A model is proposed by which PTH could rapidly inhibit bone net 45Ca uptake by stimulating release and turnover of intracellular calcium stores in bone lining cells, thereby creating a gradient for Ca out of bone.

Studies of the rapid effects of parathyroid hormone and prostaglandins on 45Ca uptake into chick and rat bone in vivo.

The rapid effects of parathyroid hormones and a variety of prostaglandins on net uptake of 45Ca into the skeleton have been investigated in chicks and, in a limited parallel study, in immature rats. Intravenous injection of bovine (b) parathyroid hormone(1-34) (bPTH(1-34)) or 16,16-dimethyl prostaglandin E2 (16,16-dimethyl PGE2) in a 45Ca-labelled vehicle, combined with subsequent microwave fixation of tissue isotope levels, resulted in rapid (3-15 min) net inhibition of 45Ca uptake into endochondral bone (femur) in chicks (12 days old) and rats (4 weeks old). Use of 125I-labelled albumin and [14C]mannitol indicated that these responses were not a reflection of gross changes in tissue vascular or extracellular space. In rats, bPTH(1-84) also caused significant net inhibition of 45Ca uptake into femur at 10 min. Both bPTH(1-34) and 16,16-dimethyl PGE2 produced generally smaller decreases in 45Ca uptake into chick dermal bone (calvarium) at 3-15 min. In rat calvarium, however, these agents stimulated net uptake of 45Ca at these times. When microwave fixation was omitted, inhibitory responses were reduced or disappeared, while the stimulatory response in rat calvarium was enhanced. Responses to natural prostaglandins (PGE1, PGE2, PGF2 alpha and PGI2) in chicks at 3 min were similar but less marked than those to 16,16-dimethyl PGE2; 45Ca uptake into femur and, to a lesser extent in calvarium, being inhibited. In rats, PGE1, PGE2 and PGF2 alpha showed a tendency to decrease 45Ca uptake into femur while PGE1 and PGE2 both increased 45Ca uptake into calvarium.

Calcium transport across the isolated dually perfused human placental lobule.

1. Movements of 45Ca and 3H2O in maternal to fetal (M----F) and fetal to maternal (F----M) directions across the dually perfused isolated human placental lobule were measured under steady-state conditions. 2. M----F values of the clearances (CR) and extractions (ER) of 45Ca relative to 3H2O were 0.371 +/- 0.056 and 0.492 +/- 0.086 (mean +/- S.E. of mean) respectively. The corresponding values for F----M movements were 0.277 +/- 0.017 and 0.251 +/- 0.010 respectively. The F----M perfusion flow ratio (QF/QM) was 0.34 +/- 0.01 throughout. Comparison with previously published data indicated a significant degree of membrane limitation to Ca transfers. 3. There was evidence of a mismatch between tissues receiving a fetal and those receiving a maternal perfusion. 4. The relative extraction ER was markedly and reversibly enhanced when perfusate total Ca was reduced from 2.4 to 0.1 mM. The effect was present in both M----F and F----M transfers and provided evidence for carrier-mediated uptake of Ca on both aspects of the placental barrier. Small and transient decreases in the relative clearance CR were observed on changing from 2.4 to 0.1 mM-Ca in M----F and to a lesser extent F----M transfers while transient increases were seen on changing from 0.1 back to 2.4 mM-Ca. 5. Measurement of net changes in Ca levels in closed-circuit studies indicated a significant release of both ionized (Ca2+) and total (CaT) Ca into the fetal perfusate at total Ringer solution concentrations of 1.4, 1.9 and 2.4 mM-Ca. Release of Ca into the maternal circuit was also observed using 1.4 mM-Ca Ringer solution but when 1.9 and 2.4 mM-Ca Ringer solution was used a net uptake occurred. 6. These findings strongly suggest that mechanisms by which Ca is transferred from M----F circulations in vivo are at least partly preserved in the in vitro human placental preparation. They indicate that this preparation is suitable for the study of these mechanisms and their regulation by hormonal and other factors.

Evidence of saturable uptake mechanisms at maternal and fetal sides of the perfused human placenta by rapid paired-tracer dilution: studies with calcium and choline.

Rapid uptake and efflux of 45Ca2+ and [3H]choline at the maternal and fetal interfaces of the syncytiotrophoblast in the dually-perfused human placenta was investigated by application of the single circulation paired-tracer dilution method (Yudilevich, Eaton, Short & Leichtweiss 1979). Cotyledons were perfused with Krebs-bicarbonate containing dextran (30 g/l; MW = 60-70,000) at 20 and 6 ml/min on maternal and fetal sides, respectively. The paired-tracer (test substrate and extracellular marker) technique consisted of an intra-arterial injection of a tracer bolus, followed by venous sampling over 5-6 min. There was a rapid (sec) uptake of 45Ca2+, followed by backflux (efflux into the ipsilateral circulation) which, over 5-6 min, was 59-100% on the fetal side. It was more variable but generally lower on the maternal interface. At 0.1 mM calcium, 45Ca2+ maximal uptake (Umax) was about 53% on the fetal side but on the maternal side it was variable and averaged 17%. At 2.4 mM calcium fetal side Umax was reduced to 40%. However, on the maternal side the effect was not consistent. Unidirectional influx (nmol/min per g) appeared to be not different on the two sides of the placenta. For [3H]choline (in choline-free perfusates) Umax was about 50% and 30% on fetal and maternal sides, respectively; tracer backflux was variable on the maternal side and averaged 50% on the fetal side. [3H]Choline uptake was highly inhibited by either 1.0 mM choline or the specific competitive inhibitor, hemicholinium-3 (0.1 mM). Specific transplacental transfer of 45Ca2+ (i.e. in excess of the extracellular marker) was not significant in either direction. For [3H]choline there was an apparent small excess (about 4%) preferential towards the fetal circulation. These findings in the human placenta are similar to those demonstrated previously in the guinea-pig placenta which suggested the existence of specific transport systems for choline and calcium on both sides of the syncytiotrophoblast.

A comparison of the effects of bovine parathyroid hormone 1-34 and methylated prostaglandin E2 analogues on plasma calcium and inorganic phosphate levels in immature chickens and rats.

The relative effects of bovine parathyroid hormone 1-34 (bPTH-(1-34] and prostaglandin (PG)E2 analogues, 16,16-dimethyl PGE2 and 11,16,16-trimethyl PGE2, on plasma calcium, inorganic phosphate (Pi), and osmolality in 12-day-old chickens were compared. bPTH-(1-34) and 16,16-dimethyl PGE2 were similarly tested for effects on plasma Ca and Pi in immature (3-week-old) rats. PGs administered iv in a saline vehicle (20 micrograms 16,16-dimethyl PGE2 or 125 micrograms 11,16,16-trimethyl PGE2/100 g body wt, respectively) produced significant hypercalcaemic effects in chicks compared with vehicle-injected controls at times ranging from 15 to 90 min, similar to those obtained with bPTH-(1-34) (3.3 micrograms/100 g body wt). The PGE2 analogues injected in chicks also produced significant increases in plasma Pi compared with controls at 15 and 45 min, while those treated with PTH showed smaller, nonsignificant plasma Pi responses. Little change in plasma osmolality was seen in chicks following injection with either bPTH-(1-34) or 16,16-dimethyl PGE2, although a small but significant increase in this parameter was seen in chicks treated with 11,16,16-trimethyl PGE2. Acute labelling of chicks with 32P incorporated into the 16,16-dimethyl PGE2 injection vehicle indicated a decreased exit of Pi from the blood as the mechanism underlying the PG-mediated hyperphosphataemic response. This type of response was not seen following bPTH-(1-34) injection in chicks.(ABSTRACT TRUNCATED AT 250 WORDS)