bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of changes in colloid osmotic pressure on excretion of sodium by the ovine fetal kidney
Authors: Lumbers ER , Moore RS , Stevens AD
Published: October 2005

To find out if the gestation-dependent increase in fetal oncotic pressure is responsible for the gestation-dependent increase in the capacity of the fetal proximal tubule to reabsorb sodium, the effects on renal function of increases in oncotic pressure were studied in 8 volume-expanded chronically catheterized fetal sheep aged 128 +/- 3 (s.e.) days. Fetal extracellular volume was expanded by infusion of 65 +/- 10.8 (s.e.) mliter kg-1 estimated body weight of 0-15 M saline. This caused a decrease in fetal plasma protein concentrations (P < 0.01); fetal oncotic pressure decreased (P < 0.05). A diuresis and natriuresis occurred, which was due not to an increase in glomerular filtration rate but to a decrease in the fraction of the filtered sodium load reabsorbed by the proximal tubule (P < 0.05) and a decrease in the fraction of distally delivered sodium reabsorbed (P < 0.01). Fetal plasma protein concentrations were then increased to greater than control levels (P < 0.01) by infusion of maternal plasma (28 +/- 1.6 mliter kg-1); oncotic pressure was greater than after saline expansion (P < 0.05) and similar to control. The fraction of the filtered sodium load reabsorbed by the proximal tubule remained depressed (P < 0.01) relative to control, as did the fraction of distally delivered sodium that was reabsorbed (P < 0.01). Thus the natriuresis and diuresis continued. There was, however, a small effect of oncotic pressure on proximal fractional sodium reabsorption that was unmasked by multiple regression analysis. Obviously, this effect was not sufficient to override other effects of volume expansion on fetal proximal tubular function. Therefore, the reduction in fetal proximal fractional sodium reabsorption in volume expansion was not due solely to a fall in fetal oncotic pressure. Furthermore, since infusion of maternal plasma caused a rise in fetal plasma protein concentrations that was similar to the increase that would occur between 128 and 148 days gestation, it is unlikely that any gestation-dependent increase in proximal fractional sodium reabsorption is due solely to the increase in fetal plasma protein concentrations and hence oncotic pressure.
Physiological changes in antioxidant defences in fetal and neonatal rat liver
Authors: Gonzalez MM , Madrid R , Arahuetes RM
Published: October 2005

This study describes the physiological changes in the activities of the hepatic antioxidant enzymes superoxide dismutase isoenzymes (Cu/Zn-and Mn-superoxide dismutase) and catalase, in the glutathione content and in the lipid peroxidation levels in fetal (20 and 21 days of gestation) and neonatal rat liver (Days 1, 8, 15, and 22 post partum). The catalase and superoxide dismutase activities decreased before birth and increased after birth. The oxidized:reduced glutathione (GSSG:GSH) ratio declined before birth, but it increased between Days 1 and 15 post partum and then remained stable. Finally, newborn rat liver from the 1st day of life shows the highest susceptibility to lipid peroxidation. These results suggest that the changes in antioxidant defences could be related mainly to the beginning of diet intake after birth, which entails a higher hepatic metabolism rate, as well as a higher oxygen consumption.
Screening for Down syndrome in the first trimester
Authors: Powell KJ , Grudzinskas JG
Published: October 2005

Second-trimester maternal serum screening for Down syndrome is now well established, and permits detection of up to 70% of cases. The disadvantage of this sort of screening is that the timing of maternal blood sampling is relatively late (after 15 weeks). There is an accumulating body of evidence to suggest that in the first trimester concentrations of a number of pregnancy-associated proteins and hormones differ in chromosomally normal and abnormal pregnancies. A first-trimester maternal serum screening test for Down syndrome may therefore be possible. In addition, new methods of screening have recently been described based on ultrasound findings at 11 to 13 weeks of gestation. This review article presents a discussion of published data on the feasibility of first-trimester screening for Down syndrome.
Interrelationships between the renin angiotensin system and uteroplacental blood flow--a recent perspective
Authors: Binder ND , Laird MR , Faber JJ
Published: October 2005

In pregnancy, the maternal circulating renin-angiotensin system (RAS) and uteroplacental tissue RAS has been thought to support maternal placental flow by raising maternal arterial pressure or changing placental vascular resistance. Also, the placenta or uterus may alter maternal circulating RAS. Recent studies in the authors' laboratory using chronically catheterized rabbits are compared with previous studies on interactions between the RAS and uteroplacental flow. When uterine driving pressure was reduced either mechanically or after converting enzyme inhibition, maternal placental flow decreased in proportion to change in driving pressure; myoendometrial flow did not change. Angiotensin II (AII) infusion to increase pressure by 21 +/- 2 mm Hg decreased placental but not myoendometrial flow. Thus, there is no evidence that maternal placental flow is autoregulated or supported by a specific renin-angiotensin mechanism. Normally, there is no net uterine release or uptake of active plasma renin activity, AI, or AII, but there is a small net release of trypsin-activated plasma renin activity (tPRA), presumably prorenin. Distal aortic occluder inflation produced upper-body hypertension, and uterine release of tPRA increased. There was a significant uterine arteriovenous concentration difference for AII during AII infusion. These methods are adaptable for studying interactions between uteroplacental flow and other vasoactive agents.
Molecular approach to intrauterine growth retardation: an overview of recent data
Authors: Alsat E , Marcotty C , Gabriel R , Igout A , Frankenne F , Hennen G , Evain-Brion D
Published: October 2005

Consideration of the abnormal regulation of fetal growth leading to intrauterine growth retardation must take account of the fundamental differences between the regulation of growth before and after birth. The significance of endocrine regulators of growth differs greatly in utero. During the first trimester of pregnancy, embryonic growth might be controlled at the level of the individual organs by nutrient supply and by locally active growth factors. Later, fetal growth depends essentially upon materno-placental cooperation in delivering nutrients to the fetus. Therefore the major role of hormones in fetal growth is to mediate utilization of available substrate. Fetal growth seems to be regulated by fetal insulin, IGF-1 and certainly IGF-2, while growth hormone has only a secondary role to play. In late gestation, placental size and fetal growth rate are well correlated, pointing to a key role of the placenta in the regulation of fetal growth. It is therefore of importance to understand the molecular mechanisms involved in regulating placental development and endocrine functions. TGF alpha and EGF might play a major role as suggested by the modulation of their receptors with placental development, and by the specific alterations of epidermal growth factor receptors in intrauterine growth retardation. In addition, human placenta secretes specifically placental growth hormone. The concentration of placental growth hormone is significantly decreased in sera of pregnant women bearing a fetus with intrauterine growth retardation.
Chorangiosis and chorangioma in three cohorts of placentas from Nepal, Tibet, and Japan
Authors: Soma H , Watanabe Y , Hata T
Published: October 2005

It has been reported that both chorangiosis and chorangioma are increased in placentas at high altitudes. In this study, 1.14% of 2448 Japanese placentas obtained at 30-300 m had chorangiosis or chorangioma, compared with 3.24% of the Nepalese placentas (1300-3000 m) and 9.09% of the Tibetan samples (3800-4200 m). The incidence of both pathologies was significantly higher in the Himalayan groups than those of the Japanese group (P < 0.05). Obstetric complications of the 28 Japanese placentas with chorangiosis and chorangioma included Caesarean section 16 (57.1%), abruptio placentae 2 (7.14%), intrauterine growth retardation 3 (10.7%), intrauterine fetal death 4 (14.2%) and placenta praevia 4 (14.2%). Four infants (14.2%) had Apgar scores ranging from 0 to 3. Among 48 Himalayan placentas with chorangiosis and chorangioma, incidence of marked subchorionic fibrin was significantly higher (25%) than in the Japanese group (3.57%) (P < 0.05). The incidence of abnormal insertion of the cord was significantly higher (14.2%) in the Japanese group than in the Himalayan group (5%) (P < 0.05). There was no significant difference in the frequencies of intervillous thrombosis and infarction between the two groups. These findings suggest that the incidence of pathological change such as chorangiosis and chorangioma may be increased in placentas at Himalayan altitudes.
Ultrastructure of cellular components of human trophoblasts during early pregnancy
Authors: Jaggi M , Mehrotra PK , Maitra SC , Agarwal SL , Das K , Kamboj VP
Published: October 2005

Two cell types, the cyto- and syncytio-trophoblasts, were identified in human chorionic villi of 6-10 weeks' gestation. The intracellular organization of these cells was examined. Ultrathin sections of small pieces of chorionic villi revealed the presence of a multinucleate syncytiotrophoblastic layer, whose surface was covered with microvilli. The cytotrophoblasts, however, had a single large nucleus with a prominent nucleolus. An interesting feature of the basement membrane of these cells was the presence of aggregates of dark granules in samples of the earlier gestational age (6-8 weeks) and granular bodies having a dense outer ring and a translucent inner ring with a lucid central area in samples of 8-10 weeks' gestation. Both types of granules are mineralized and are assumed to perform a buffering role for maintaining the neutrality of the layer.
Activation of phospholipase D in cultured human amnion cells
Authors: Inamori K , Sagawa N , Hasegawa M , Itoh H , Yano J , Mori T
Published: October 2005

The regulation of phospholipase D (PLD) activity in the human amniotic membrane was examined using primary cultures of amnion cells. Cultured amnion cells were labelled with [3H]oleic acid, and PLD activity was determined as the amount of [3H]phosphatidylethanol (PEt) produced during incubation in the presence of 0.1% ethanol. PLD activity in cultured amnion cells was activated by addition of arginine vasopressin and oxytocin. PLD activity was also stimulated by treatment was arachidonic acid, the product of phospholipase A2 (PLA2), and phospholipase C (PLC). These results indicate that PLD in amnion cells is activated by substances present in amniotic fluid, and that cross-talk between phospholipases A2, C and D may occur in amnion cells.
Long-term cycling of surfactant films in Wilhelmy balance
Authors: Sun B , Curstedt T , Robertson B
Published: October 2005

Surface properties of porcine surfactant were observed during long-term cycling in Wilhelmy balance. Various amounts of surfactant were applied onto the surface as dry particles or droplets, or were suspended in the hypophase, and the films generated by this material were subjected to 50% cyclic compression at a rate of 1 cycle per min. Film spreading was faster from a droplet than from a particle of lyophilized surfactant, but the 'stable period' during which minimum surface tension of the compressed film remained below 5 mN/m was significantly longer for the dry material. For surfactant suspensions the period of film 'refinement', defined as the number of cycles required to reduce minimum surface tension to a level below 5 mN/m, was inversely correlated with the concentration of surfactant in the hypophase. Thirteen batches of porcine surfactant, used successfully in clinical trials for treatment of neonatal respiratory distress syndrome, were evaluated in the same system suspended in the hypophase at a concentration of 0.5 mg/ml. Films adsorbed from these batches had a median refinement period of 4 cycles, and a median stable period of 2160 cycles (36 h). In the same assay system, surfactant activity was inhibited in a dose-dependent manner by serum, fibrinogen, meconium, and bilirubin, but the specific inhibitory activity was significantly higher for bilirubin than for the other substances tested.
Effects of nitric oxide synthase inhibitors on the outcome of in vitro fertilization in the mouse
Authors: Herrero MB , Viggiano JM , Perez Martinez S , de Gimeno MF
Published: October 2005

The effect of three nitric oxide (NO) synthase inhibitors, L-NG-nitro-arginine (NO2Arg), NG-Nitro-L-arginine methyl ester (L-NAME) and aminoguanidine, on in vitro fertilization in the mouse was examined. Mouse epididymal spermatozoa were capacitated in a medium with or without NO synthase inhibitors. Oocytes were inseminated and the percentage of oocytes with two pronuclei was scored after an 8-h incubation. NO2Arg and L-NAME, but not aminoguanidine, inhibited fertilization. L-NAME inhibited fertilization in a dose-dependent manner, and its effects were stereospecific. The inhibitory effect was neutralized by L-arginine but not by D-arginine. Moreover, D-NAME did not inhibit fertilization. The results suggest that NO synthase activity (presumably of the constitutive type is necessary for spermatozoa to display their full fertilizing ability.
Specificity of a placental factor inhibiting breathing in fetal sheep
Authors: Alvaro RE , Rehan V , de Almeida V , Haider Z , Robertson M , Jansen A , Cates DB , Rigatto H
Published: October 2005

We have found previously that the infusion of a placental extract inhibits breathing induced by 100% O2 plus umbilical cord occlusion in the fetal sheep, suggesting that a placental factor is responsible for the inhibition of fetal breathing. To test whether this factor is specific to the placenta and whether it also inhibits spontaneous fetal breathing (occurring in the absence of cord occlusion), we administered extracts from the placenta, muscle and liver of the pregnant ewe, extracts of fetal liver, and Krebs solution to 16 chronically instrumented fetal sheep at 135 +/- 5 days of gestation. Infusions were made during low-voltage electrocortical activity, 5 to 15 min after a switch from high voltage, when breathing was well established. Within 90 s of the infusion of the placental extract in the carotid artery of the fetus, breathing decreased in 79% (33/42) of the experiments and was completely abolished in 71% (30/42) of them (P < 0.0001 compared with the other infusates). No apnoeas were observed with the Krebs solution (0/19) and the maternal muscle (0/20). Extracts of maternal and fetal liver abolished breathing in only 17% (4/23) and 21% (6/29) of the experiments respectively (NS compared with Krebs solution). There were no significant changes in blood gas tensions, pH, blood pressure and heart rate associated with the infusion of the extracts. The electrocortical activity (ECoG) switched from low to high voltage in 50% of the experiments using placental extract compared with 0% with Krebs solution and maternal muscle, and with 9% and 17% with maternal and fetal liver respectively (P < 0.005). Breathing output (integral of EMGdi x f) during and after the infusions significantly decreased only with the placental extract. These findings indicate the presence of a factor produced by the placenta which inhibits fetal breathing and may be responsible for the normal inhibition of breathing observed in fetal life.
Nitric oxide inhalation: effects on the ovine neonatal pulmonary and systemic circulations
Authors: DeMarco V , Skimming JW , Ellis TM , Cassin S
Published: October 2005

Others have shown that inhaled nitric oxide causes reversal of pulmonary hypertension in anaesthetized perinatal sheep. The present study examined haemodynamic responses to inhaled NO in the normal and constricted pulmonary circulation of unanaesthetized newborn lambs. Three experiments were conducted on each of 7 lambs. First, to determine a minimum concentration of NO which could reverse acute pulmonary hypertension caused by infusion of the thromboxame mimic U46619, the haemodynamic effects of 5 different doses of inhaled NO were examined. Second, the effects of inhaling 80 ppm NO during hypoxic pulmonary vasoconstriction were examined. Finally, to determine if tachyphalaxis occurs during NO inhalation, lambs were exposed to 80 ppm NO for 3 h during which time pulmonary arterial pressure was doubled by infusion of U46619. Breathing NO (80 ppm) caused a slight but significant decrease in pulmonary vascular resistance (PVR) in lambs with normal pulmonary arterial pressure (PAP). Nitric oxide, inhaled at concentrations between 10 and 80 ppm for 6 min (F1O2 = 0.60), caused decreases in PVR when PAP was elevated with U46619. Nitric oxide acted selectively on the pulmonary circulation, i.e. no changes occurred in systemic arterial pressure or any other measured variable. Breathing 80 ppm NO for 6 min reversed hypoxic pulmonary vasoconstriction. In the chronic exposure study, inhaling 80 ppm NO for 3 h completely reversed U46619-induced pulmonary hypertension. Although arterial methaemoglobin increased during the 3-h exposure to 80 ppm NO, there was no indication that this concentration of NO impairs oxygen loading. These data demonstrate that NO, at concentrations as low as 10 ppm, is a potent, rapid-action, and selective pulmonary vasodilator in unanaesthetized newborn lambs with elevated pulmonary tone. Furthermore, these data support the use of inhaled NO for treatment of infants with pulmonary hypertension.
A comparison of oocyte organelles in Monodelphis domestica with those of other marsupials and eutherians
Authors: Kress A
Published: October 2005

This paper reviews the current knowledge of oocyte cytology in marsupials, particularly Monodelphis domestica, and eutherian mammals. Some of the conspicuous features will be described and their function discussed. Despite many fundamental similarities between the oocytes of eutherian mammals and marsupials, some aspects are different (e.g. growth pattern, final size, timetable of cytoplasmic maturation and utilization of storage material during early cleavage stages), when most of the vesicles are extruded into the perivitelline space in marsupials.
Variation in ultrastructure of mucoid coat and shell membrane secretion of a dasyurid marsupial
Authors: Roberts CT , Breed WG
Published: October 2005

In the dasyurid marsupial Sminthopsis crassicaudata, the shell membrane of cleaving embryos has a compact granular structure but becomes fibrous around blastocysts. Polyclonal antibodies were raised against the extracellular coats, mucoid and shell membrane, of oocytes and early embryos. Immunogold cytochemistry resulted in labelling of secretory granules in the epithelia of both the ampulla and isthmus of the oviduct, although the secretory granules of these two regions differed in their ultrastructural appearance. Those in the ampulla were heterogeneous with areas of varying electron density, whereas those in the isthmus were electron dense and homogeneous. Shell membrane precursors were found in secretory granules in the epithelia of the uterotubal junction and endometrial glands and were electron lucent.
Effect of cooling and cryopreservation on sperm motility and morphology of several species of marsupial
Authors: Taggart DA , Leigh CM , Steele VR , Breed WG , Temple-Smith PD , Phelan J
Published: October 2005

The effects of long-term cooling and freezing on sperm motility are described for six marsupial species: the fat-tailed dunnart, koala, brushtail possum, long-footed potoroo, northern brown bandicoot and ring-tailed possum. The effects of up to eight days of cooling at 4 degrees C on the motility of dunnart spermatozoa and the effect of cryopreservation on spermatozoa of the other species were determined. The cryoprotectant used was a Tris-citrate-fructose-egg yolk-glycerol diluent. The percentage and rating of sperm motility, and sperm structure, as determined by light microscopy, were investigated. Sperm motility in the fat-tailed dunnart was retained for up to six days when cooled to 4 degrees C, suggesting that sperm from this species have some degree of tolerance to cold shock. After this time, however, the percentage of motile spermatozoa and their motility rating declined. In all species except the fat-tailed dunnart, reinitiation of motility following cryopreservation occurred across a range of glycerol concentrations (4-17%). Cryoprotectant containing 6% and/or 8% glycerol resulted in little change of motility rating or of the percentage of live sperm after thawing, although there was some decline in the percentage of motile sperm. The unusual structural and motility characteristics of dunnart spermatozoa may account for the lack of success of sperm cryopreservation in this species.
Patterns of hormone secretion throughout pregnancy in the one-humped camel (Camelus dromedarius)
Authors: Skidmore JA , Billah M , Allen WR
Published: October 2005

Peripheral serum samples were collected from 8 pregnant dromedary camels and hormone secretion patterns were examined at specific time intervals. Mean serum progesterone concentrations began to rise 3-4 days after ovulation and remained reasonably constant at 3-5 ng mL-1 for the first 90-100 days of gestation. Concentrations then showed a definite fall, but thereafter remained constant again at 2-4 ng mL-1 throughout the rest of pregnancy. In contrast, serum oestrogen concentrations showed pronounced fluctuations during the first 100 days of gestation. Mean oestradiol-17 beta concentrations increased at around Day 50 to about 100 pg mL-1 and then remained relatively constant from Day 90 to Day 300. Mean oestrone sulfate concentrations, however, showed two definite peaks in early gestation, each reaching about 10 ng mL-1, with the first peak occurring around Day 25 and the second peak around Day 75. Oestrogen production then remained fairly constant until around Day 300, after which concentrations of both oestrone sulfate and free oestradiol-17 beta rose steeply over the next 80 days to reach mean peak values of 46 ng ML-1 and 518.7 pg mL-1, respectively, at the time of parturition. Concentrations of 13,14 dihydro-15-keto prostaglandin F2 alpha (PGFM) remained low and reasonably steady at 100-200 pg mL-1 during the first 320 days of pregnancy; thereafter, PGFM concentrations rose steeply over the next 50 days, before an explosive further increase to a peak of 1900 +/- 141 pg mL-1 mean +/- sem on the day of calving. These results suggest that, as in the cow, a major change in steroid synthetic capability and/or enzyme content of the placenta may occur at around 80% (Day 300) of gestation in the pregnant camel.
Effects of calcium channel blockers on spontaneous electrical activity of freshly isolated three-day-old embryonic chick ventricle
Authors: Prakash P , Meera P , Tripathi O
Published: October 2005

The effects of four major types of organic Ca2+ channel blockers, verapamil, nifedipine, diltiazem and fendiline and of tetrodotoxin (TXX), a fast Na+ channel blocker, on the action potential (AP) of freshly isolated 3-day-old embryonic chick ventricle (3d ECV) were investigated to resolve the controversy about the ionic basis of upstroke. The APs were characterized by a maximum diastolic potential (MDP) of -60 mV, an overshoot (Eov) of 16 mV and a maximum upstroke velocity (+Vmax) of 42 V s-1. All four Ca2+ channel blockers (0.1-40 microM) and TTX (0.1-80 nM) produced a dose-dependent reduction in +Vmax and Eov. MDP was also reduced by Ca2+ channel blockers in a dose-dependent manner but was unaffected by TTX. A significant linear correlation between MDP and +Vmax was observed for verapamil (r = 0.99), nifedipine (r = 0.99), diltiazem (r = 0.96) and fendiline (r = 0.98). Surprisingly, all Ca2+ channel blockers produced a dose-dependent positive chronotropic effect leading to cessation of firing at high doses (20-40 microM). In preparations becoming quiescent with high doses of verapamil (20-40 microM), elevated extracellular concentrations of Ca2+ (up to 9.6 nM) and isoproterenol (0.5-40 microM) failed to restore spontaneous APs. Electrical stimulation also failed to elicit APs in preparations inhibited by verapamil, diltiazem and fendiline. The inhibition of +Vmax by TTX demonstrates that fast Na+ channels were involved in the upstroke of AP in 3d ECV. Voltage-dependent inactivation of fast Na+ channels during depolarization (reduction in MDP) by the Ca2+ channel blockers explains their inhibitory effect on +Vmax and indicates that L-type Ca2+ channels had no significant role in the upstroke. A positive chronotropic effect of the Ca2+ channel blockers further suggests that slow Ca2+ channels are not involved in automaticity in freshly isolated 3d ECV.
Protein sources affect follicular dynamics in ewes near the onset of the breeding season
Authors: Landau S , Houghton JA , Mawhinney JR , Inskeep EK
Published: October 2005

The influence of source of protein during the luteal phase before a synchronized oestrus on the dynamics of follicular development, observed daily by ultrasonography, was assessed in ewes that were beginning the sexual season. Iso-nitrogenous amounts of soybean meal (SBM) or of a corn-gluten meal-ground-corn grain mixture (CGM-GC), or an iso-energetic amount of ground-corn grain (GC), were fed from four days before to four days after treatment with prostaglandin F2 alpha (PGF2 alpha). Feeding with SBM was associated with a higher frequency of short luteal phases (P < 0.02). Dynamics of follicular population were studied in ewes that ovulated after normal cycles. More follicles > or = 2 mm in diameter were observed on the ovaries of ewes fed SBM four days before PGF2 alpha treatment (P < 0.02), but the highest number was seen in ewes fed CGM-GC at the time of injection of PGF2 alpha (P < 0.08). Ewes fed SBM had larger follicles at last detection and ovulated earlier after PGF2 alpha treatment than their counterparts fed other diets (P < 0.001). Ovulatory follicles developed over a greater range of days in ewes with twin ovulations compared with ewes with single ovulations (P < 0.08). Serum concentrations of insulin were increased after four days of feeding with CGM-GC (P < 0.01), but not with SBM or GC, and reached a peak at the time of oestrus. In summary: (1) the source of dietary protein during the late-luteal phase affected follicular maturation after PGF2 alpha treatment; (2) insulin and glucose may be involved in this response and may play a role in ovarian follicular activity; and (3) twin ovulations appeared to result from both reduced atresia and increased recruitment of follicles.
Regulation of mRNA encoding low density lipoprotein receptor and high density lipoprotein-binding protein in ovine corpora lutea
Authors: Tandeski TR , Juengel JL , Nett TM , Niswender GD
Published: October 2005

Three experiments were conducted to examine the regulation of steady-state concentrations of mRNA encoding ovine low density lipoprotein receptor (LDL-R) and high density lipoprotein-binding protein (HBP) in corpora lutea. In Experiment 1, corpora lutea were collected from ewes on Days 3, 6, 9, 12 and 15 (Day 0, oestrus) of the oestrous cycle. Enriched preparations of small and large steroidogenic luteal cells were also obtained on Days 6, 9, 12 and 15 of the oestrous cycle. In Experiment 2, 16 ewes were hypophysectomized on Day 5 of the oestrous cycle and received saline, luteinizing hormone (LH), growth hormone (GH) or a combination of LH+GH until collection of luteal tissue on Day 12 of the oestrous cycle. Corpora lutea were also collected from pituitary-intact control ewes on Day 5 and Day 12 of the oestrous cycle. In Experiment 3, 13 ewes on Day 11 or Day 12 of the oestrous cycle were administered prostaglandin F2 alpha (PGF2 alpha) and corpora lutea were collected 4 h, 12 h and 24 h later. Corpora lutea were also collected from 4 non-injected and 4 saline-injected (at 24 h) ewes. Results demonstrated that concentrations of mRNA encoding LDL-R did not differ throughout the oestrous cycle. Luteal tissue collected on Day 3 of the oestrous cycle had higher concentrations of mRNA encoding HBP than luteal tissue collected on any other day of the oestrous cycle. Hypophysectomy increased concentrations of mRNA encoding LDL-R but had no effect on concentrations of mRNA encoding HBP. Twelve hours following PGF2 alpha injection concentrations of mRNA encoding LDL-R were decreased but concentrations of mRNA encoding HBP were increased. Concentrations of both LDL-R and HBP mRNA were decreased 24 h following injection of PGF2 alpha. Thus, long-term positive and acute negative regulation of progesterone secretion from the corpus luteum by luteotrophic and luteolytic hormones was not mediated by changes in steady-state concentrations of mRNA encoding LDL-R or HBP.
Roles of growth factors in the development of bovine embryos fertilized in vitro and cultured singly in a defined medium
Authors: Lim JM , Hansel W
Published: October 2005

Bovine embryos at the 8- or 16-cell stage were cultured singly, or in groups (10-12 embryos), in the presence or absence of bovine oviduct epithelial cells (BOEC) in a defined medium which was used as a basic culture medium. A higher (P < 0.05) proportion of 8-cell embryos (48.3-50.8%) cultured singly developed beyond the 8-cell stage after the addition of platelet-derived growth factor (PDGF)-AB (1 ng mL-1) only, or with PDGF-AB + basic fibroblast growth factor (bFGF; 1 ng ml-1) + transforming growth factor (TGF)-beta 1 beta 2 (1 ng mL-1) than in basic medium alone (30.3%). In contrast, a significantly (P < 0.02) higher percentage (62.6-65.8%) of 16-cell embryos developed to the morula stage after the addition of TGF-beta 1 beta 2 only, or the addition of TGF-beta 1 beta 2 + bFGF + PDGF-AB than in basic medium alone (30.2%). These proportions were not significantly (P > 0.05) different from the proportions obtained when embryos were cultured in groups, but were significantly (P < 0.005) lower than the proportions obtained when embryos were cultured in groups on BOEC monolayers. Arachidonic acid (50 ng mL-1), beta-mercaptoethanol (10 microM) and glutathione (10-1000 microM) stimulated the development of 8-cell embryos in the presence of PDGF and TGF-beta 1 beta 2; blastocyst formation was observed for the first time in 8-cell embryos cultured singly in the presence of these embryotrophic substances (2.2-6.2%).
Postfire Growth of Pseudotsuga menziesii and Pinus contorta in the Northern Rocky Mountains, USA
Authors: Peterson DL , Arbaugh MJ , Pollock GH , Robinson LJ
Published: October 2005

Dendroecological methods were used to study the effects of wildfire on radial growth of Pseudotsuga mniiesii (Douglas-fir) and Pinus contorta (lodgepole pine) in the northern Rocky Mountains. Mean basal area increment during a 4-year postfire period declined relative to prefire growth in 75% of burned P. menziesii trees and 70% of P. contorta trees. Percent of crown volume scorched was the most important variable related to
postfire growth of P. menziesii, while basal scorch was slightly more important than crown scorch to postfire growth of P. contorta. Postfire growth always declined when crown scorch exceeded 50% in P. menziesii and 30% in P. contorta. None of the significant regression models had high predictive capability because of the large amount
of variance in the data. It is clear, however, that crown injury is critical to postfire survival and growth of P. menziesii, while basal injury is critical for the thin-barked species P. contorta.
A Meteorological Index of Forest Fire Hazard in Mediterranean France
Authors: Carrega P
Published: October 2005

The start and spread of a forest fire are strongly conditioned by the past and present meteorological situation. The interacting weather parameters determine a fire hazard which may be estimated using various indices. Among those used for the French Mediterranean region, the index 185, formulated by the author in 1985, and further successively improved (187,185/90), has proven to be very efficient.
Modelling Moisture Damping for Fire Spread in a Mixture of Live and Dead Fuels
Authors: Catchpole EA , Catchpole WR
Published: October 2005

A model, based on those of Rothermel(1972) and Wilson (1990), is developed for the effect of fuel moisture on fire spread rate in a fuel complex consisting of a mixture of live and dead fine fuel particles. Physical arguments lead to a modification of the heat sink term of Rothermel's model. A form of moisture damping is proposed which generalises that of Wilson. It uses one
extra parameter, which needs to be estimated from experimental burns in a mixture of live and dead fuels. The model is fitted to a series of experimental shrubland fires. The model fits this data better than does Rothermel's original model, but is not yet recommended for use by practitioners.
Heat-Induced Degradation Processes in Forest Soils
Authors: Soto B , Benito E , Diaz-Fierros F
Published: October 2005

Degradation by heating was studied in samples from the top 5 cm of six woolandHumic Cambisols under Ulex and Pinus pinaster stands in N.W. Spain. After heating to various temperatures, the samples were exposed for 30 minutes to simulated rain with an energy of 24.16 joul m-2 mm-1. Three kinds of degradation were observed: 1) loss of organic matter and water by volatilization ; 2) dry breakdown ; and 3) wet breakdown. The observed degradation processes correlated well with the differential thermal analysis data. Below 170°C, volatilization losses appeared, but there was no dry breakdown and resistance to wet breakdown increased slightly; between 170°C and 380–460°C, all three kinds of degradation increased greatly; and above 460°C, no further volatilization, non dry breakdown ocurred, and wet breakdown tended to decrease.
Burning California Chaparral - an Exploratory Study of Some Common Shrubs and Their Combustion Characteristics.
Authors: Weise DR , Ward DE , Paysen TE , Koonce AL
Published: October 2005

Prescribed fire is a tool used to manage
vegetation in southern California. The nature and quan
tity of gaseous and particulate emissions have not been
described for California chaparral. A study examining
carbon monoxide (CO), carbon dioxide (CO2), and par
ticulate matter emissions from fuel beds constructed from
common chaparral shrubs was initiated. Chamise
(Adenostoma fasciculatum), ceanothus (Ceanothus
crassifolius), manzanita (Arctostaphylos glandulosa), and
scrub oak (Quercus dumosa) fuel beds were burned in
December 1989, and March, May, and August, 1990. Gas
and particulate matter samples were collected from 45
fires. Emission factors for CO2 and particulate matter
were affected by species and month individually; month
and species interacted and affected CO emission factors.
Pearson's correlation coefficient and Kendall's tau indi
cated that emission factors for CO and particulate matter
were inversely related to combustion efficiency.
First Phases of Regeneration of Cistus Laurifolius and Cistus Ladanifer After Burning and Cutting in Experimental Plots
Authors: Alonso I , Luis E , Tarrega R
Published: October 2005

The first phases of regeneration of two Cistus species (Cistus laurifolius and Cistus ladanfer) are compared in experimental plots that were subjected to different treatments: cutting and burning. In both treatments the parameters used were: seedling number, height and cover. Differences between their rowth are discussed and compared with that of Erica australis subsp. aragonensis, that can resprout vegetatively.
Influence of Heat on Seed Germination of Cistus Laurifolius and Cistus Ladanifer
Authors: Valbuena L , Tarrega R , Luis E
Published: October 2005

The influence of high temperatures on germination of Cistus laurifolius and Cistus ladanifer seeds was analyzed. Seeds were subjected to different temperatures for different times, afterwards they were sowed in plastic petri dishes and monitored for germinated seeds over two months.The germination rate observed in Cistus ldanifer was greater than in Cistus laurifolius. In both species, heat increased germination percentages. For Cistus laurifolius higher temperatures or longer exposure times were needed. Germination percentages of Cistus ladanifer were lower when heat exposure time was 15 minutes.It must be emphasized that germination occurred when seeds were not treated, while seeds exposed to 150�C for 5 minutes or more did not germinate.
Atmospheric Simulations of Extreme Surface Heating Episodes on Simple Hills
Authors: Heilman WE
Published: October 2005

A two-dimensional nonhydrostatic atmospheric model was used to simulate the circulation patterns (wind and vorticity) and turbulence energy fields associated with lines of extreme surface heating on simple two-dimensional hills. Heating-line locations and ambient
crossflow conditions were varied to qualitatively determine the impact of terrain geometry on the development
of buoyancy-induced horizontal roll vortices and their
turbulence structures. The model simulations indicate
that the type of induced circulation that develops near a
line of extreme surface heating on a simple hill is very
dependent on the location of the heating line. Heating
lines located on the crests of simple hills produced symmetric horizontal roll vortices with large values of turbulent kinetic energy. Symmetric vortices did not develop
over heating lines located on the slopes of the hills. The
introduction ofa light ambientcrossflowradically changed
the circulation and turbulence structures. Simulated
vorticity and turbulence energy values over a heating line
located on the windward slope were very different than
those observed over heating lines located on the crest or
leeward slope. A low-level vortex developed just downwind of the windward-slope heating line when a light
ambient crossflow was introduced, and this vortex became stronger as the steepness of the hill was increased.
Although field dataare not available toconfirm the model
results, the simulations suggest that terrain effects play an
important role in the development and destruction of
vortices near lines of extreme surface heating, especially
when a light ambient crossflow is introduced. These
effects have implications for fire-fighter safety in actual
wildland fire episodes.
Fire and Nutrient Cycling in Seral Grasslands of Cherrapunji in North-Eastern India
Authors: Ram SC , Ramakrishnan PS
Published: October 2005

Nutrient cycling under four grassland types of Charrapunji, one of the wettest spots of the world in north-eastern India, representing varied stages of arrested succession arising out of fire events was studied. More frequent fire reduced elemental quantities in the aboveground biomass than in the belowground parts. Under frequent burning, nutrient contents in the soil declined sharply and reached very low levels characteristic of highly desertified sites. Grasslands subjected to frequent fire had higher elemental turnover rates in the vegetation but lower rates in the soil. Under extreme desertification, the annual turnover rates for elements in the impoverished grassland was generally low. It is concluded that the initial perturbation impact on the forest ecosystem resulting in these arrested seral grasslands under exceptionally high rainfall is further exaggerated by fire effects on nutrient cycling properties.
Moisture Diffusivity in Forest Fuels
Authors: Viney NR
Published: October 2005

Abstract. Apracticalmeans of quanmingthe diffusivities
of forest fuels from fielddata is presented. The mathematics of this method is explored for four fuel shapes: a litter
layer, a hardwood leaf, a twig and a square fuel moisture
analogue stick, which are represented geometrically by a
semi-infinite solid, a slab, a cylinder and a square prism,
respectively. Theresults are presented graphically. Analyses of two published sets of field data indicate defusivities
of 4.1 x 10-12m2 s-1 and 1.3 x 10-10m2 s-1 for Eucalyptus
leaves and twigs, respectively, and 2.9 x 10-9m2 s-1 for a
lodgepole pine litter layer.
Early Vegetative Response to Wildfire in a Table Mountain-Pitch Pine Forest
Authors: Groeschl DA , Johnson JE , Smith DW
Published: October 2005

Abstract. This study was established to measure vegetation in a mid-elevation Pinus pungens Larnb.- Pinus rigida
Mill. (table mountain pine-pitch pine) forest following
wildfire in the Shenandoah National Park, Virginia.
Vegetation in the overstory, shrub, and regeneration
strata were monitored one and two growing seasons
following a July, 1988 wildfire.
High severity burn areas were impacted greater in
terms of stand composition, structure, and diversity than
areas of low severity. Two years after fire occurrence,
overstory basal area mortality was nearly 98 percent in
areas of high severity, and only 26 percent in areas of low
severity. The live, residual overstory basal area in the
areas of low fire severity did not differ significantly from
adjacent unburned areas until the second year due to
delayed mortality following fire injury.
Wildfire resulted in the mortality of nearly all shrub
stratum species; however, the most significant changes in
species importance values and diversity were detected in
high severity areas. Unlike the overstory and shrub strata,
species diversity of the regeneration stratum increased
following wildfire. This increase was attributed to the
invasion of early colonizer species and the germination of
Pinus pungens and Pinus rigida seedlings following fire.
Although changes or shifts in species importance and
diversity occurred in the overstory and shrub strata, these
shifts are likely temporary as stems from previous species
grow into these size classes. The exclusion of fire from
Pinus pungens-Pinus rigida pine forests may be a greater
cause for concern than fire occurrence.
A Fire Perimeter Expansion Algorithm-Based on Huygens Wavelet Propagation
Authors: Knight I , Coleman J
Published: October 2005

To model the spread of the perimeter of a wildfire, the perimeter can be regarded as a continuous curve, or more simply as a discrete number of points, which approximate the curve. Each point on the perimeter can be regarded as a point source which expands as a small ellipse. The parameters of each ellipse depend on the local fuel type, slope and meteorological conditions and the time step. According to Huygens' principle, the envelope of these ellipses describes the new perimeter. With discontinuous terrain and fuel, the perimeter may become complex, developing concavities and surrounding areas of low rate of spread. An algorithm which defines this envelope has been developed as part of the National Bushfire Model (a real-time computer application for personal computers).
A Numerical Fire Simulation-Model
Authors: Wallace G
Published: October 2005

An extension of the simple ellipse model of a vegetation fire is presented. This facilitates numerical implementation, and can therefore incorporate irregular topographical features and temporal changes in burning conditions. The model has been encoded into an interactive PC program which gives a visual simulation of the spread of a fire on a graphics screen. The model has considerable potential for fire management.
Modeling Tree Mortality Following Wildfire in Pinus ponderosa Forests in the Central Sierra-Nevada of California
Authors: Regelbrugge JC , Conard SG
Published: October 2005

We modeled tree mortality occurring two years following wildfire in Pinus ponderosa forests using data from 1275 trees in 25 stands burned during the 1987 Stanislaus Complex fires. We used logistic regression analysis to develop models relating the probability of wildfire-induced mortality with tree size and fire severity for Pinus ponderosa, Calocedrus decurrens, Quercus chrysolepis, and Q. kelloggii. One set of models predicts mortality probability as a function of DBH and height of stem-bark char, a second set of models uses relative char height (height of stem-bark char as a proportion of tree height) as the predictor. Probability of mortality increased with increasing height of stem-bark char and decreased with increasing tree DBH and height. Analysis of receiver operating characteristic (ROC) curves indicated that both sets of models perform well for all species, with 83 to 96 percent concordance between predicted probabilities and observed outcomes. The models can be used to predict die probability of post-wildfire mortality of four tree species common in Pinus ponderosa forests in the central Sierra Nevada of California.
Modeling Wildland Fire Containment With Uncertain Flame Length and Fireline Width
Authors: Mees R , Strauss D , Chase R
Published: October 2005

We describe a mathematical model for the probability that a fireline succeeds in containing a fire. The probability increases as the fireline width increases, and also as the fire's flame length decreases. More interestingly, uncertainties in width and flame length affect the computed containment probabilities, and can thus indirectly affect the optimum allocation of fire-fighting resources. Uncertainty about the fireline width that will be produced can often affect containment chances as much as uncertainty in flame length.
Interactions Between Plant Ash Leachates and Soil
Authors: Soto B , Diaz-Fierros F
Published: October 2005

We studied a) leaching of Ulex, Pinus and Eucalyptus ashes; b) leaching from the surface layer (0 - 5 cm) of 6 types of soil subjected to thermal shock at a range of temperatures equivalent to those reached in a wildfire (25-degrees-C to 700-degrees-C); and c) leaching of Ulex, Pinus and Eucalyptus ashes through a subsurface soil layer not subjected to thermal shock. Element release from plant ashes and heat-treated soils was highly dependent on the solubility of the principal chemical forms in which that element occurred. The monovalent cations Na and K, largely present as chlorides and carbonates, were mobilized much more rapidly than the divalent cations Ca and Mg, largely present as oxides and carbonates. Element release from heat-treated soil was also dependent on shock temperature. The monovalent cations were extensively mobilized following shocks at less than 380-degrees-C, and the divalent cations following higher-temperature shocks. These differences appear to be related to element volatilization and mineralization of organic matter. The subsurface soil not subjected to thermal shock showed a tendency to retain the elements released from plant ashes and from heat-treated surface soil. The subsurface layers may also release hydrogen ions and organic matter, as a result of cation exchange and dissolution processes respectively.
Fire Regime of the Okefenokee Swamp and Its Relation to Hydrological and Climatic Conditions
Authors: Yin ZY
Published: October 2005

A fire record of the Okefenokee Swamp National Wildlife Refuge during the period 1938-1989 was examined in this study. Frequency analysis indicated that fires with burnt area 50% or more of the swamp area have return periods longer than 100 years, much longer than the previously assumed 20-25 year return period. Results of statistical analysis showed that fire activity is significantly related to die water level of the Okefenokee Swamp. Based on this relationship, a potential fire size can be estimated for a given water level. It seemed difficult to prove the link between the fire activity in the Okefenokee Swamp and the El Nino/Southern Oscillation (ENSO) events. However, further analysis revealed that the hydrological condition of the swamp is significantly related to the ENSO events. During the warm events, the Okefenokee Swamp area is wetter than normal; during the cold events, the area is drier than normal, and major fires tend to occur. The investigation of the fire regime may help achieve a better understanding of the effect of fires on the dynamics of this large complex ecosystem. The results are also useful for the refuge managers, especially in the mid- to long-term planning of fire management practices.