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It is argued that photo-electrons emitted from trivalent atoms in a two-photon ionization process are totally polarized if the incident light is of total circular polarization and its wavelength matches the resonance condition for the transition between ground state (n2P12/) and the first excited state (n+1)2S12/. The estimated photoionization yield compares favourably with that of the analogous process in alkali atoms. Some of the most important conditions for a successful experiment are considered.

The effect of sound and vibration on the human fetus was studied in 46 patients. A significant alteration of the fetal heart rate and movement occurred following stimulation. Evidence was obtained that the response of the fetus was due to a direct fetal rather than an indirect maternal mechanism. The maternal administration of opiates diminished the effect of sound and vibration.

Calculations on electron impact excitation of the n=1 and n=2 states of hydrogenic ions have been made for atomic numbers Z ranging from 2 to 100 in a Coulomb-Born approximation in which Dirac wavefunctions are used instead of the more usual Schrodinger ones. All one-body relativistic effects are included, and of the two-body effects, mutual spin-orbit coupling but not magnetic or retardation effects. Relativistic effects are found to contribute 10% to the cross sections for most transitions at Z=25 and up to a factor of 6 at Z=100. The conservation of total spin is investigated and the spin-orbit interaction due to the nuclear potential found to be the most significant cause of changes in total spin except at very high incident electron energies.

Monopol is a bread wheat (Triticum aestivum L. em. Thell.) with medium winter-hardiness primarily adapted to the Annapolis Valley region of Nova Scotia. Breeder seed will be maintained by Firlbeck, West Germany and distributed in Canada through Minas Seed Cooperative Ltd.Key words: Wheat (winter), cultivar description

Possible allelopathic effects of decaying sweet potato plant residue on sweet potato [Ipomoea batatas (L.) Lam.] and cowpea [Vigna unquiculata (L.) Walp.] growth were assessed. Residue treatments consisted of factorial combinations of 2 sweet potato cultivars (‘Jewel’ or ‘Centennial’), 2 plant parts (vines or storage roots), and 2 methods of tissue preparation–dried, or frozen and then dried. Ground sweet potato residues were mixed with sand [2.7% residue (w/w)] and placed in pots. Dry weights of ‘Jewel’ sweet potato plant shoots 57 days after planting were reduced 32% and 74% by vine and storage root residues, respectively, while dry weights of ‘Centennial’ sweet potato plant shoots were reduced 18% and 73%, respectively. Dried vine tissue had no apparent inhibitory effect, but vines frozen prior to drying reduced fresh and dry weights of ‘Centennial’ shoots. Dry weights of ‘Brown crowder’ cowpea plant shoots were reduced 79% and 91% by sweet potato vine and storage root residues, respectively. Nodulation of cowpeas grown in residue-amended pots was negligible compared to plants grown in pure sand. Leachate pH from pots containing sweet potato root residue was 1.4 and 2 pH units lower than that from nonamended pots with both sweet potato cultivars and cowpeas, respectively.

Cross sections for electron-mercury scattering at incident electron energies from 0.1 to 1.4 eV have been calculated by numerical solution of the Dirac equation including exchange and a polarization potential but not coupling to inelastic channels. A resonance has been found in the p1/2 partial wave at about 0.2 eV which appears to correspond to the (6s26p1/2)2P1/2 ground state of Hg. This is probably the resonance observed experimentally by Burrow and Michejda (1975) at 0.63 eV.

Sweet potato [Ipomoea batatas (L.) Lam.] cv. Travis storage roots were bedded on 8 and 27 Mar. 1985 according to standard cultural practices. The following row cover and mulch treatments were tested for their effects on early transplant production: a) bare soil (control); b) black polyethylene mulch; c) nonwoven polyester row cover; d) slitted, clear polyethylene row cover; or e) slitted, white polyethylene row cover. All row cover and mulch treatments increased soil temperature (at a 5-cm depth) relative to the bare soil. Compared to black polyethylene mulch, slitted, clear polyethylene row covers increased soil temperatures, whereas soil temperature was reduced by slitted white polyethylene. Mulch and row covers increased weight and number of large transplants as compared to bare soil. The primary effect of row covers as compared to mulch was to increase the percentage of large (>15 cm long) transplants. The use of slitted, clear polyethylene and slitted, white polyethylene row covers appeared to reduce the incidence of sclerotial blight (Scleratium rolfsii) in plant beds. Row cover and mulch treatments did not alter yield of storage roots grown from transplants produced under the various bed treatments.

Results of non-relativistic and relativistic calculations of cross sections for elastic electron scattering from mercury at energies from 0.25 to 8 eV, both with and without inclusion of exchange effects, are presented. It is shown that the large differences between relativistic and non-relativistic results noticed by other authors is due to neglect of exchange.

Core temperature of fetal sheep was raised by perfusing warm water through a loop implanted into the abdomen, or into the stomach via the oesophagus. Raising fetal temperature by 0.8-2 degrees C was associated with an increase in amplitude and incidence of breathing movements, and an increase in the proportion of breathing movements that occurred during high voltage electrocortical (ECoG) activity. Fetal hyperthermia was maintained for 8 h, but the augmentation of breathing movements did not last for more than 2-3 h. The results indicate that changes of maternal temperature caused by hot weather, exercise, fever, and possibly diurnal changes of body temperature could alter the amplitude and pattern of fetal breathing movements.

We have isolated the human apolipoprotein (apo) A-IV gene from a cosmid library and determined its complete nucleotide sequence. The gene contains three exons of 162, 127, and 1180 nucleotides separated by two introns of 357 and 777 nucleotides. A sequence polymorphism has been identified in the 3' noncoding portion of the third exon. The human apoA-IV gene lacks an intron in the area encoding the 5' nontranslated region of its mRNA, which distinguishes it from all the other human apolipoprotein genes whose sequences are known. Comparison matrix analysis of the human apoA-IV gene sequence revealed evidence for an ancestral 11-nucleotide repeat unit that spans the third exon. These repeated sequences are much more highly conserved than those present in either rat apoA-IV or in any other human apolipoprotein. Optimal alignments of the 5' flanking regions of the rat and human apoA-IV genes disclosed multiple deletions in the rat sequence as well as a highly conserved region of 90 nucleotides (90% sequence identity) located within 170 nucleotides of the start site of transcription. The 5' flanking regions of the human and rat apoA-IV genes were ligated to the bacterial chloramphenicol acetyltransferase gene, then transfected into different cultured cells. The apoA-IV gene sequences elicited preferential expression of chloramphenicol acetyltransferase activity when introduced into intestinally derived Caco-2 cells and liver-derived Hep-G2 cells, consistent with the tissue specificity of the native gene. Analysis of deletion mutants of the human apoA-IV 5' flanking region indicated that regions from -293 to -233 and from -127 to -60 upstream of the transcription start site contain sequences required for maximum gene expression. These findings on the structure and expression of rat and human apoA-IV should prove useful in studying the control of the apoA-IV gene.

ALTHOUGH prostaglandins of the E and F series have been measured in amniotic fluid from several species1–3 their principal site of synthesis remains uncertain. In man, for example, the decidua4,5 foetal membranes6,7 and myometrium8 have all been shown to synthesise prostaglandins in vitro and each may contribute to the prostaglandin composition of amniotic fluid. The foetal lung and kidneys secrete considerable volumes of fluid into the amniotic sac9,10 and hence may also contribute to the prostaglandin content of amniotic fluid. The levels of prostaglandins in foetal tracheal fluid have been shown to be much lower than those in amniotic fluid11 and it was suggested that foetal urine is a more likely source of amniotic fluid prostaglandins. The foetal kidney is capable of synthesising prostaglandins12 and there is a growing body of evidence that prostaglandins are intimately involved in renal function13–15. We have, therefore, measured the concentrations of PGE, PGF and 13, 14-dihydro-15-keto-prostaglandin F (PGFM) in foetal urine during late pregnancy in sheep and have further determined the osmolality, Na+ and K+ concentrations of foetal urine and plasma. The concentrations of prostaglandins measured in foetal urine were similar to amniotic fluid levels but significantly greater than those previously reported in plasma and tracheal fluid suggesting that the kidney is a major source of amniotic fluid prostaglandins. The excretions of prostaglandins were related to the rate of urine flow; the excretions of PGF and PGFM were correlated with osmolar and solute-free water clearances and Na+ excretion, whereas excretion of PGE was related only to the clearance of solute-free water. Prostaglandins may thus contribute substantially to renal function and volume homeostasis in foetal life.

The responses to sympathetic stimulation of fetal sheep adrenal-demedullated or sympathectomised by infusion of guanethidine sulphate have been studied. Sympathetic responses in such denervated or sympathectomised fetuses was studied by intravenous infusion of adrenaline or noradrenaline at about 0.4 micrograms/min per kg. This infusion increased plasma concentration 100-200 fold and there was no significant difference between the control fetuses and those in the vasrious treatment groups. Catecholamine infusions at these rates normally have little effect upon fetal blood gas and pH values, but in adrenal-demedullated fetuses adrenaline infusion drepressed fetal arterial PO2 by 4-6 mmHg (P less than 0.05). The heart rate and blood pressure responses to catecholamine infusion in sympathectomised fetuses was, as expected, much increased. Similar observations were made on adrenal-demedullated fetuses, an unexpected finding, and this is taken to illustrate loss of the adrenal medulla is associated with enhanced responsiveness to adrenergic stimulation in peripheral tissues. The majority of the endocrine and metabolic responses, as reflected in fetal plasma concentrations of ACTH, cortisol, insulin, glucose, lactate and fatty acids, to catecholamine infusion were similarly much enhanced by adrenal-demedullation and chemical sympathectomy. Of particular note was a substantial increase in the responsiveness of the fetal adrenal, as reflected in plasma cortisol, to stimulation by ACTH, a change that usually induces labour, but not so in the present sheep. The results on increased sensitivity in adrenal-demedullated fetuses are discussed in relation to likely tissue mechanisms mediating the changes.

In fetal lambs after 115 days gestation breathing movements become episodic in association with electrocortical differentiation into predominantly high voltage slow or low voltage rapid activity, the latter characteristic of rapid eye movement sleep. Section of the brainstem at or above the colliculi dissociates fetal breathing from electrocortical activity. It is included that breathing is inhibited, towards the end of gestation, by a supracollicular mechanism during high voltage activity. After brainstem transection at the colliculi hypoxia no longer causes an arrest of fetal breathing, which often becomes more vigorous. The arrest of breathing in normal fetuses subjected to mild hypoxia is also attributed to a supracollicular mechanism. The pattern of fetal skeletal movements and of the spinal segmental reflexes is related to electrocortical activity near term; both are suppressed by hypoxia. The hypothesis is discussed of a central control centre, excited directly or indirectly by hypoxia, which inhibits fetal movements including breathing. Its possible location is considered.

It is now well known that neuronal development is dependent on a number of survival factors, and on certain growth factors that are specific for particular neuron types. Of these, nerve growth factor (NGF) is the best known, and the requirement of sensory, sympathetic and central cholinergic neurons for this substance for both development and maintenance has been described.

Polysynaptic reflex responses in the hind limb were obtained by stimulating the peroneal nerve in unanaesthetized lambs between 4 and 12 days from birth, before and after carotid denervation. In intact lambs isocapnic reduction of the Pa,O2 from 88 to 31 or to 23 mmHg caused an insignificant decrease in reflex amplitude. Denervation of the carotid bifurcations induced hypoventilation. When the Pa,O2 was then reduced to 22 mmHg the reflex amplitude fell by 77%. In carotid denervated lambs after complete transection of the spinal cord at T12-L1, reduction of the Pa,O2 to 23 mmHg did not alter the size of the reflex. The same result was observed after section of the dorsal part of the lateral funiculi. It is concluded that, in the young lamb a few days after birth, the afferent activity of the carotid chemoreceptors during hypoxia plays an important role in maintaining the excitability of motor reflexes. The possible mechanisms are discussed.

1. The electromyographic (e.m.g.) activity of the diaphragm and intercostal muscles has been recorded during breathing movements of unanaesthetized lambs in utero (109-135 days), and compared with the changes of tracheal pressure. 2. The diaphragm e.m.g. was irregular in size, shape and timing, with a variable rate of rise during inspiration, often with a flattening of integrated activity before the end of a breath and with little or no post-inspiratory activity. 3. The diaphragm e.m.g. gave the most reliable measurements of breath interval and incidence: in eucapnia mean TI was 0.45±0.02 (S.E. of mean) and TE was 0.74±0.05 sec, and 58-100% of the diaphragm bursts were associated with identifiable and appropriate changes of tracheal pressure. 4. During fetal hypercapnia, produced by increasing the maternal inspired CO2 in a single change or series of step changes, tracheal pressure amplitude and its rate of change during inspiration increased progressively over the Pa, CO2 range of 37-87 mmHg. 5. In eucapnia the area, amplitude and inspiratory slope of the integrated diaphragm e.m.g. were not always correlated with tracheal pressure amplitude, and in hypercapnia they increased only in the lower part of the Pa, CO2 range. Inspiratory intercostal activity increased progressively as the Pa, CO2 was raised. 6. The frequency histograms of variables derived from the tracheal pressure, diaphragm and intercostal e.m.g.s were skewed to the left in eucapnia but became normalized during hypercapnia. The rate and depth of breathing became regular. 7. The response to mild asphyxia was a combination of the responses to hypercapnia and hypoxia. 8. The interpretation of the tracheal pressure and diaphragm e.m.g. as measures of the `depth' of breathing and respiratory `drive' in the fetal lamb is discussed.

Both aging and chronic ethanol consumption have been correlated with reduced cardiac chronotropic and inotropic function. This study tested the hypothesis that aging potentiates the negative cardiac effects of chronic ethanol consumption. Using isolated tissue techniques we assessed baseline and maximum automaticity and tension development in atria from 4 groups of Fischer-344 rats (young normal, young ethanol, old normal, old ethanol). Baseline and maximum rate was depressed by aging and further depressed by chronic ethanol ingestion. Baseline and maximum tension was depressed only by aging plus chronic ethanol ingestion.

High environmental temperature is known to impair fetal growth and development. We now report long lasting changes in fetal breathing activity following the exposure of pregnant ewes to an ambient temperature of 43 degrees C for 8 h. In 16 trials in 10 ewes (119-138 days gestation) heat exposure increased maternal and fetal core temperatures 1.5-2.0 degrees C, and the hyperventilation by the ewe produced a fall in fetal PaCO2 from 53.5 +/- 1.3 to 34.8 +/- 5.3 mmHg (P less than 0.05). Fetal breathing movements decreased in incidence during the hyperthermia but remained episodic (present during low-voltage electrocortical activity) with occasional brief episodes of breathing at high rates (greater than 4 breaths/s). However, 1-2 h after the end of heating, when maternal and fetal core temperature and PaCO2 had returned to normal, fetal breathing movements became continuous, and were augmented 30-100% in amplitude. Fetal breathing movements occurred during both low- and high-voltage electrocortical activity. The results show that a heat load similar to that experienced by sheep in sub-tropical regions in the summer months cause prolonged changes in the central regulation of fetal breathing.

Extra-dural or cerebroventricular intracranial pressure was measured in 7 unanaesthetized fetal sheep (123-137 days gestation). Basal intracranial pressure was 6.7 +/- 1.7 mmHg, but there were many transient increases of pressure in association with spontaneous changes of amniotic pressure, fetal intrathoracic pressure, and particularly when the fetal nuchal muscles were active. These spontaneous increases of intracranial pressure were often associated with cessation of breathing movements and change of the electrocorticogram from low to high voltage activity. To test whether increased intracranial pressure influenced breathing movements and electrocortical activity, intracranial pressure was raised either by occluding the superior vena cava for 1 min with an implanted extravascular cuff, or by extra-dural injection of 0.3-1.0 ml of 0.9% NaCl. Increasing the intracranial pressure 5-15 mmHg by either method during low voltage electrocortical activity caused cessation of breathing movements, electro-ocular activity, and change of the electrocorticogram from low to high voltage in a significant proportion of trials. We propose that natural fluctuations of intracranial pressure caused by compression of the fetal body or skull, by body movements or by uterine activity, may cause changes in electrocortical activity and breathing movements.

Both cDNA and genomic clones encoding human apolipoprotein (apo-) A-IV have been isolated and characterized. Southern blot analyses of apo-A-IV gene-containing cosmids revealed that the apo-A-IV gene is linked to the apo-A-I and apo-C-III genes within a 20-kilobase span of chromosome 11 DNA. The apo-A-IV gene is located about 14 kilobases downstream from the apo-A-I gene in the same orientation, with the apo-C-III gene located between them in the opposite orientation. The nucleotide sequence of the corresponding human apo-A-IV mRNA was determined, and the derived amino acid sequence showed that mature plasma apo-A-IV contained 376 residues. Throughout most of its length, human apo-A-IV was found to contain multiple tandem 22-residue repeated segments having amphipathic, alpha-helical potential. Amino acid substitutions within these homologous segments were generally conservative in nature. A comparison of the sequences of human and rat apo-A-IV revealed a 79% identity of amino acid positions in the amino-terminal 60 residues and a 58% identity in the remainder of the sequences, with the human protein containing 5 extra residues near the carboxyl terminus. An examination of the distribution of apo-A-IV mRNA in different tissues of the rat, marmoset, and man showed that apo-A-IV mRNA was abundant in both the liver and small intestine of the rat, but abundant in both the liver and small intestine of the marmoset and man. It was expressed in only trace amounts in all other tissues that were examined. These findings on the structure and expression of apo-A-IV and the close linkage of its gene to those of apo-A-I and apo-C-III suggest a regulatory relationship between the three genes.

The effects of section of the brain stem caudally (through the upper pons or mid-collicular) or rostrally (through the caudal hypothalamus or anterior commissure-suprachiasmatic nucleus) were studied in fetal lambs from 118 days gestation, after recovery in utero. In lambs sectioned caudally, breathing movements and electrocortical activity were dissociated. After some days recovery breathing tended to become continuous, with an abnormal prolongation of inspiratory time. Isocapnic hypoxia caused an increase in the rate and amplitude of breathing. After carotid denervation hypoxia still caused an increase in the amplitude of breathing. In lambs sectioned rostrally, there was also dissociation between breathing movements and electrocortical activity. Breathing remained episodic, with an incidence similar to that of intact fetal lambs. In two lambs after 10 days of recovery the breathing and electrocortical rhythms returned, from time to time, to their normal phasic relationship. Isocapnic hypoxia caused a diminution or arrest of breathing, as in intact lambs. The cardiovascular effects of transection were examined. Baroreflex sensitivity was normal in those lambs sectioned caudally and enhanced in those sectioned rostrally. It is concluded first that as a result of rostral section, independent episodic rhythms of fetal breathing and electrocortical activity can be dissociated. Secondly, moderate isocapnic hypoxia causes arrest of fetal breathing indirectly, requiring the integrity of a suprapontine mechanism. And thirdly, after caudal section of the brain stem, hypoxia causes enhancement of fetal breathing efforts, independently of the carotid chemoreceptors. Possible mechanisms are discussed.

Daily infusion of p-chlorophenylalanine (p-CPA) into unanesthetized fetal sheep for 3-6 days did not reduce brain 5-hydroxytryptamine (5-HT) concentrations or produce long-term changes in the pattern of electrocortical activity.

Fetal sheep were thyroidectomized at 80 days' gestation and reoperated at 118-122 days for insertion of vascular catheters. The effects of hypoxaemia and intravenous tyramine infusion on plasma catecholamine concentrations, blood pressure and heart rate were then determined in experiments at 125-135 days' gestation. Age matched intact fetuses were also studied. Thyroidectomy was associated with increased concentrations of noradrenaline, adrenaline and dopamine in some thoracic and abdominal organs, increased noradrenaline concentrations in the cerebellum, and decreased adrenaline concentrations in the hypothalamus, cervical spinal cord, and superior cervical and inferior mesenteric ganglia. Arterial pressure was significantly lower in the thyroidectomized fetuses (34.0 +/- 0.15 mmHg) than in intact fetuses (44.7 +/- 0.2 mmHg; p less than 0.001). In contrast, plasma noradrenaline concentrations were significantly higher in the thyroidectomized fetuses (2.04 +/- 0.25 ng/ml) compared to the intact fetuses (0.99 +/- 0.08 ng/ml; P less than 0.001). In the intact fetuses there was a significant increase in plasma noradrenaline concentration and blood pressure during hypoxaemia, and bradycardia at the onset of hypoxaemia. In contrast, in the thyroidectomized fetuses hypoxaemia did not cause significant change in plasma catecholamine concentrations, blood pressure or heart rate. Infusion of tyramine produced a 1.9-fold increase of plasma noradrenaline in thyroidectomized fetuses compared to a 9.2-fold increase in the intact fetuses (P less than 0.05). Tyramine infusion caused a similar proportional increase of blood pressure in both thyroidectomized and intact fetuses. Heart rate decreased during the tyramine-induced hypertension in the intact fetus, but increased in the thyroidectomized fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)

Fetal lambs were treated with a single dose of anti-mouse nerve growth factor (anti-NGF) at 80 days gestational age. The catecholamine content of tissues was determined at 135 days gestational age. There was a reduction of either norepinephrine, epinephrine, or both, in the thymus, thyroid, atrium (but not ventricle), lung, liver, kidney, and jejunum when compared with age-matched control fetuses. The spleen, ileum, colon, and the adrenal glands were not affected by anti-NGF. In treated fetuses there was a reduction in catecholamine content of the thalamus, hypothalamus, hippocampus, medulla, cerebellum, and cervical spinal cord. These results show that some tissues are sensitive to, and some are refractory to, the action of anti-NGF at 80 days gestation. Also the results suggest that NGF may play a role in the development of catecholamine-containing neurons within the central nervous system.

The relationship between the amplitude of electrically evoked responses from nerves of a hindlimb and electrocortical activity has been determined in fetal sheep from 105-141 days gestation. Stimulation of the common sciatic, tibial or peroneal nerves and recording from the two nerves not stimulated revealed an early (4.5 ms) and late (18.6 ms) evoked neural response, probably reflex. These responses were reduced or absent in low voltage compared with high voltage electrocortical activity after 125 days gestation. Spontaneous gastrocnemius activity was more frequent during high voltage activity. The electrocorticogram was undifferentiated before 115 days, and the evoked responses in peripheral nerves were largest when breathing and eye movements were present. After electrocortical differentiation the responses were enhanced when brief episodes of augmented eye and breathing movements occurred during the transition between high and low voltage activity. The possibility that this indicates arousal or wakefulness in utero is discussed.

A procedure in fetal sheep for causing peripheral sympathectomy by regular intravascular guanethidine sulphate administration and for causing adrenal demedullation by intragland injection of acid formalin is reported. Demedullation substantially removed adrenaline from the fetal circulation, but has a small effect only on noradrenaline. Plasma noradrenaline levels were depressed by 50% when demedullated fetuses were also subject to peripheral sympathectomy by guanethidine sulphate treatment. This provides some evidence that the paraganglia in the sheep fetus contributes to resting plasma catecholamines. Furthermore the ability of adrenal demedullation to increase markedly this pool of extra-adrenal chromaffin tissue indicates that in the fetus adrenal activity regulates the growth of these para-aortic bodies. In response to sympathectomy plasma vasopressin concentrations rose substantially, whilst adrenal demedullation caused a small rise. Demedullation and sympathectomy depressed fetal plasma glucose and elevated plasma cortisol. In both sympathectomised and adrenal demedullated fetuses resting heart rate and blood pressure was not depressed. However in those with a depleted peripheral nervous system periods of cardiovascular instability were apparent after 2-3 days of treatment with guanethidine sulphate. Hence there were regular episodes where fetal blood pressure and heart rate fell sharply followed 60-90s later by very large increases in blood pressure sustained for up to 10 min and associated with substantial production of plasma vasopressin and catecholamines. These results show that fine cardiovascular control in the fetus requires an intact sympathetic system as the endocrine system is too slow responding to effectively maintain reflex vascular control.

A technique for implanting and maintaining catheters in both utero-ovarian veins (UOV) of intact, conscious sheep has been developed. Both UOV catheters remained patent for more than 2 weeks in 72.7% of animals. In non-pregnant ewes, large pulses of PGF2α were observed in UOV plasma collected on days 13 to 16 of the cycle (frequency 1.3 ± 0.2/12 h; pulse height range 1.0–26.9 ng/ml). In contrast, on days 13 to 16 of gestation, significantly (P < 0.001) fewer pulses of PGF2α (frequency 0.42 ± 0.2/12 h) were observed in both UOVs of pregnant ewes, which were significantly (P < 0.001) smaller in amplitude (pulse height range 1.4–4.9 ng/ml). The maintenance of the corpus luteum (CL) during early pregnancy may therefore directly result from a decreased uterine PGF2α release. During the luteal phase (day 4–12), the PO2 of UOV blood draining an ovary containing a CL (UOV/CL) was significantly higher than blood in the contralateral UOV (P 2 of UOV/CL blood had decreased and was not significantly different to that observed in the contralateral UOV (P >0.1). On day 17, the PO2 of blood in both UOVs was elevated significantly compared to levels observed on the two preceding and the two following days (P < 0.001). We consider that the higher PO2 in UOV/CL blood resulted from a very high luteal blood flow, and that the decrease on days 15 and 16 of the cycle resulted from a decline in luteal blood flow during luteolysis. The subsequent increase in PO2 of blood from both UOVs on day 17 was considered to result from an increased uterine blood flow.

In fetal sheep acute hypoxia causes a decreased incidence of breathing movements and motor activity, and the excitability of polysynaptic reflexes in the hindlimbs is depressed. To determine whether this inhibitory effect extends to other areas in the fetal CNS, we have studied the effect of hypoxia on two reflexes with cranial pathways. The digastric (jaw opening) reflex was elicited by stimulation of the dental nerve through a pair of stainless steel electrodes implanted into the mandible (4 fetuses). The thyroarytenoid muscle of the larynx was reflexly activated by stimulation of the superior laryngeal nerve by a cuff electrode (4 fetuses). Low level stimulation at 1.5-2 X threshold was repeated at approximately 2 min intervals for 3-4 h; the stimulation did not alter the pattern of electrocortical activity, breathing movements, or cause arousal. The amplitude of the digastric reflex was greatest during low voltage electrocortical activity; conversely, the amplitude of the thyroarytenoid reflex was greatest during high voltage electrocortical activity. Isocapnic hypoxia lasting 30-60 min (16 trials), in which the PaO2 was reduced to 12-14 mmHg, did not reduce the amplitude of either reflex. The reduction of thyroarytenoid reflex amplitude which normally occurred during low voltage electrocortical activity was not present during hypoxia. These experiments show that the inhibitory effects of hypoxia on spinal reflexes, breathing movements and motor activity do not include these cranial pathways.

Fetal breathing movements are discontinuous and are inhibited by neural mechanisms associated with the development of non-rapid eye movement sleep. Sudden reduction of arterial PO2 also reduces the incidence of breathing movements in the fetus. Recent work which is directed towards identifying the control pathways and neurotransmitters involved in these effects is discussed. The possibility that breathing may also be inhibited in certain situations after birth is addressed, particularly in relation to the ability of hypoxaemia to produce behavioural arousal in the normal newborn infant, but not in fetal life.

Comparative egg maturation was observed between fertile eggs laid by unirradiated females, by unirradiated females mated with irradiated males, by irradiated females mated with normal males, and by virgin unirradiated females. Haploid eggs turn yellow and dry by the fifth day. Eggs from irradiated parents develop more slowly than normal eggs. Most embryos from parents irradiated as P generation adults at 16.8 kilorads for males and 12.0 kR for females die early in embryonic development. A description of egg development is included.

Fetal and maternal temperatures were measured during labor and cesarean section by means of thermistor probes. In 5 patients during cesarean section, the temperature profile between mother and fetus was plotted. Very small differences in temperature between the fetal surface, amniotic fluid, and placenta were found in contrast to large differences (0.45° C.) between fetal and maternal structures. Temperatures monitored continuously during labor in 27 patients showed that fetal scalp and amniotic fluid temperatures were significantly more variable than maternal vaginal or rectal temperatures, and a correlation was found between changes in fetal temperature and fetal heart rate. In the light of this and other data, the pathways of heat loss for the fetus have been discussed with particular reference to the placenta.

Prostaglandins (PG) E and F, and 13,14-dihydro-15-keto-prostaglandin F (PGFM) were measured in plasma collected from the umbilical artery and vein, the maternal carotid artery, and the utero-ovarian vein of pregnant sheep between 116 and 139 days of gestation. PGE levels were greater than PGF levels in the umbilical artery and vein and the maternal carotid artery, but not in the utero-ovarian vein. PGFM exceeded PGF in samples from all vessels. There was a significant vein-to-artery concentration difference for PGF and PGFM, but not for PGE, in the umbilical circulation. Utero-ovarian concentrations of all 3 PGs generally exceeded their concentrations in the maternal caroitd artery.

Vuka is a utility grade, medium-hard, red winter wheat (Triticum aestivum L. em. Thell.) with high yield and medium winterhardiness in Atlantic Canada, but primarily adapted to the Annapolis Valley of Nova Scotia. Breeder seed will be maintained at Hohenheim University, West Germany. Seed release of Vuka in Canada is through Minas Seed Co-operative Ltd., Nova Scotia.Key words: Wheat (winter), cultivar description

Concentration of endogenous ethylene was higher in Ag+-treated cuttings of sweet potato (Ipomoea batatas Lam.) than in the control or in cuttings subjected to 48°C for 2 minutes. When leaf tissue was dipped in 0, 125, 250, or 500 mg/liter Ag+, endogenous ethylene was increased by the 250 and 500 mg/liter treatments. When equal concentrations of NO3– were applied to cuttings as KNO3, Ca(N)O3)2, or AgNO3, only AgNO3 increased the endogenous ethylene content.