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Biomedical subjects

D Caton

Publications and source records attributed to D Caton.

At least 37 records · Page 2Linked to original sources
PubMed1984

Spectral analysis of fetal heart rate in sheep: the occurrence of respiratory sinus arrhythmia.

Respiratory sinus arrhythmia is a pattern of rhythmic variation in the heart rate that occurs at the frequency of respiration and is mediated principally by the vagus nerve. Spectral analysis can decompose the variance of a series of sequential measures into constituent frequencies to measure and verify whether there is respiratory sinus arrhythmia in utero in the fetal lamb. Recordings of heart period were obtained from electrodes implanted under fetal skin in six chronic preparations. Respiratory rate and heart period were recorded immediately after delivery and daily for the next 5 days. Respiratory sinus arrhythmia was clearly demonstrated in the neonatal lambs, and the same frequency of respiratory sinus arrhythmia was observed in the fetus and in the newborn lamb (0.8 to 0.1 Hz). There was a reproducible pattern of change in respiratory sinus arrhythmia from 27 days before delivery until term, with a decline in the amplitude of respiratory sinus arrhythmia 4 to 8 days before delivery. We conclude that respiratory sinus arrhythmia was demonstrated in fetal sheep and may serve as an indicator of the integrity of the central nervous system in the fetus and the neonate.

Animals↗
PubMed1984

Metkephamid-induced Flehmen in lambs.

When metkephamid, a systemically active analog of methionine enkephalin, was administered intracisternally to male or female prepubescent lambs as early as the first week of life, we observed a behavioral pattern akin to Flehmen, which is a well-characterized grimace displayed by mature ungulates during mating. This metkephamid-induced Flehmen was preceded by transient bradycardia and apnea followed by somnolence for approximately 1 hour, during which Flehmen was observed intermittently. Pretreatment with the specific opiate antagonist, naloxone, blocked this behavioral response. These observations indicate that endogenous opioid peptides may be involved in Flehmen.

Animals↗
PubMed1984

Relationship of 15-keto-13,14-dihydro-prostaglandin F2 alpha concentrations in peripheral plasma with local uterine production of F series prostaglandins and changes in uterine blood flow during the early postpartum period of cattle.

Cows were prepared for surgery, either within 12 h after parturition (Day 0, n = 3), on Day 1 (n = 1) or on Day 2 (n = 1) postpartum. The previously gravid uterine horn was exposed through a high lumbar laparotomy, and catheters inserted into an uterine branch of the ovarian vein (UBOV) and in the main uterine artery (UA) via a branch of the main uterine artery. A blood flow transducer (8-13 mm, internal diameter) was placed around the UA. Starting 12-24 h following surgery, simultaneous blood samples were collected from UBOV and UA at 15-min intervals for 1 or 2 h daily from Days 1 to 10 postpartum (mean = 5.3 days). Concurrently, uterine blood flow (UBF) was recorded daily for 6 h. Mean concentrations of prostaglandin F2 alpha (PGF2 alpha) and 15-keto-13, 14-dihydro-PGF2 alpha (PGFM) were higher (P less than 0.01) in UBOV than UA (4.64 +/- 0.6, n = 96 vs. 0.08 +/- 0.02 ng/ml, n = 92 and 5.67 +/- 0.41, n = 98 vs. 1.02 +/- 0.09, n = 94, ng/ml, respectively). Concentrations of PGF2 alpha and PGFM in the UBOV increased (P less than 0.1) on Days 2 and 3 and decreased (P less than 0.01) thereafter. Mean UBF (ml/min) decreased (P less than 0.01) from 3079 +/- 683 on Day 1 to 602 +/- 56 on Day 2 and was 413 +/- 55 on Day 5.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Adaptations to reduction of endometrial surface available for placental development in sheep.

On Day 5 of pregnancy, before the blastocyst migrates to the uterus, one uterine horn was ligated to restrict the trophoblast to the lumen ipsilateral to the corpus luteum. The numbers of placentomes (caruncles and cotyledons) were reduced by half, but neither at 120 nor at 140 days of pregnancy (term 147 days) did the weights of placentae and fetuses of treated ewes differ significantly from those of control ewes. Amongst uterus-ligated animals prepared for chronic study, the rate of uterine blood flow (electromagnetic flow transducer, ml/min) to the pregnant horn was higher than in control ewes, as was the concentration of progestagens in maternal peripheral blood. There may be a compensatory response that causes hypertrophy of placentomes and that increases blood flow to the uterine horn containing placental tissue.

Adaptation, Physiological↗
PubMed1983

Relationships between maternal hormones and weight of newborn sheep.

Intact and ovariectomized mixed-breed sheep were studied in chronic experiments during the last weeks of pregnancy. Measurements were made of the rate of uterine blood flow (ml/min and ml X min-1 X kg-1, combined weight of fetus, uterus, and placenta) and of arterial and uterine venous concentrations of progestagens, estrone, and estradiol. The birth weight of the lamb was directly related to mean maternal concentrations of estrone and estradiol and to the rate of progestagen release by the uterus and its contents (ng X ml-1 X kg-1), calculated by taking the product of the rate of blood flow and the arteriovenous progestagen difference. Ovariectomy altered the relationship between birth weight and progestagen release. Data suggest that rates of progestagen release both by the fetoplacental unit and by the ovary are proportional to the birth weight of the lamb.

Animals↗
PubMed1983

Uterine blood flow in relation to endogenous hormones during estrous cycle and early pregnancy.

To evaluate the extent to which endogenous hormones in peripheral blood can account for uterine blood flow (UBF), rates of blood flow and concentrations of estrone (E1), estradiol (E2), and progesterone (P4) were measured simultaneously in four sheep during the estrous cycle and the first 3 wk of pregnancy. During the estrous cycle, UBF was inversely related to the concentration of P4 (P less than 0.01) and directly related to (E1 + E2)/P4 (P less than 0.01). There was no animal in which UBF was related to estrogen alone. No statistically significant relationship between endogenous hormones and UBF was detected in any ewe during the first 3 wk of pregnancy. Data support the idea that UBF varies during the estrous cycle in relation to peripheral concentrations of P4 and (E1 + E2)/P4 but leaves open the nature of the relationship in early pregnancy.

Animals↗
PubMed1983

Uterine blood flow: periodic fluctuations of its rate during pregnancy.

Daily measurements of the rate of uterine blood flow (ml/min) during the last half of pregnancy of four normal sheep reflected a 17-day cyclic fluctuation (range, 9.5-42 days) superimposed on a linear increase over time. The cyclic increase was not detected in two (of 7) intact ewes or in four pregnant ewes that had been ovariectomized. The cyclic pattern of increase may be related to ovarian activity.

Animals↗
PubMed1982

Androstenedione, dehydroepiandrosterone and testosterone in ovarian vein plasma and androstenedione in peripheral arterial plasma during the bovine oestrous cycle.

Catheters were placed in the carotid artery via a facial artery (n = 12) and in the ovarian vein (n = 12), and, in conjunction, electromagnetic flow meters were placed around the ovarian artery (n = 6) in cyclic beef cows. Androstenedione was quantitatively the highest and dehydroepiandrosterone the lowest of the ovarian androgens measured. Ovarian androgens were correlated positively with each other (P less than 0.05) but not with ovarian blood flow or day of the cycle. There was a trend for spikes of androgen release (ovarian vein concentration x ovarian blood flow) from the ovary to be greatest during the period of decreasing progesterone and CL regression. However, only with testosterone were spikes of release different (Days--13 to--9 less than Days -8 to -4; P less than 0.05; Day 0 = oestrus). The dynamic changes in ovarian androgens noted in this study were compatible with the concept of continuous follicular development and atresia throughout the oestrous cycle.

Androstenedione↗
PubMed1982

Ovarian function during the estrous cycle of the cow: ovarian blood flow and progesterone release rate.

To study the function of the corpus luteum (CL) through its major secretory product, progesterone (P4), catheters were inserted into the carotid artery (via the facial artery) and the ovarian vein (n = 12), and electromagnetic flow transducers were placed around the ovarian artery in cycling Angus and Hereford cows (n = 6). Blood samples were taken four times daily (at 0600, 1200, 1800 and 2400 h) and ovarian blood flow (OBF) was monitored for 60 min immediately after each blood sampling. After chromatography, P4 was measured by radioimmunoassay. The P4 concentrations in the ovarian vein (OP4) were correlated with day of the estrous cycle (r = .25; P less than .05) and were higher during the morning hours (P less than .05). Arterial progesterone (SP4) was correlated to OP4 (r = .24; P less than .05) and day of the cycle (r = .35; P less than .05). The OBF changed among days (P less than .05). The highest rates were noted during luteal maturation (23 ml/min; SE = .09) and the lowest were noted with the demise of the CL (SP4 less than 1 ng/ml) and approach of estrus (8 ml/min; SE = .07). The OBF was correlated with SP4 (r = .24; P less than .05), although no within-day trends were noted. Exogenous estrone (6 mg) administered via jugular vein decreased OBF within 30 to 45 min, but similar injections of P4 (up to 100 mg) had no effect. Progesterone release (P4R) from the ovary [(OP4 - SP4) x OBF] was higher in the morning hours (P less than .05). The P4 concentration (OP4, SP4) and release (P4R) exhibited wide variations among and within days. The changes in OP4 and P4R were both good indicators of CL development, maturation and regression, as associated with SP4 changes. Oxygen (O2) and carbon dioxide (CO2) concentrations monitored in the carotid artery and ovarian vein indicated that the ovary with the CL was not limited in O2 availability or CO2 removal during periods of low blood flow or high secretion of P4.

Animals↗
PubMed1980

Correlation of rate of uterine blood flow and plasma steroid concentrations at parturition in sheep.

Blood flow transducers were placed around one uterine artery per ewe and observations of the rate of blood flow through this artery and the peripheral plasma concentrations of free, unconjugated oestrone, oestradiol and progestagens were made at intervals of 1-3 days during the last 2-3 weeks of pregnancy and at hourly intervals after spontaneous delivery at term. Rates of uterine blood flow decreased on average by 50% or more within the first hours of parturition and patterns of change in blood flow varied considerably among the animals. Spontaneous daily (pre partum) and hourly (post partum) changes in uterine blood flow were significantly correlated (P < 0.01) with the product of the concentrations of progestagens and of total free oestrogens (oestrone and oestradiol) and with the product of progestagens and oestradiol in peripheral blood.

Animals↗
PubMed1979

O2 delivery to the pregnant uterus: its relationship to O2 consumption.

Normal sheep were studied at intervals of 3-5 days during the last weeks of pregnancy in order to evaluate variability in rate of O2 consumption (QO2) of the uterus in relation to several variables involved in delivery of O2 to the organ. Among-animal differences of uterine QO2 were statistically significant and directly related to birthweight of the lamb. Among-animal differences of uterine blood flow (UBF) and uterine arteriovenous O2 content difference [C(a-v)O2] also were statistically significant, though neither was related to birthweight, presumably since they tended to vary inversely with one another. In a given ewe relative magnitude of UBF and of C(a-v)O2 was related to maternal arterial O2 content (CaO2), day of pregnancy, and whether the animal carried singlets or twins. Variability in QO2 was most closely related to UBF, although its relations to C(a-v)O2 and CaO2 were significant also. These data suggest there are systematic relationships among variables involved in the delivery of O2 to the uterus of pregnant sheep.

Animals↗
PubMed1979

Method for obtaining ovine uterine secretions from unilaterally pregnant ewes.

Development of the ovine conceptus was confined to the uterine horn ipsilateral to the corpus luteum (CL) by placing a ligature around that uterine horn at a point near the uterine body on day 5 of pregnancy. On day 140 of gestation, seven of 10 ewes were still pregnant and from 21 to 815 ml of uterine fluid (488 +/- 94 ml, X +/- SEM) were collected from the nongravid uterine horn. Total recoverable protein (X +/- SEM) was 13.4 +/- 3.4 grams. Polyacrylamide gel electrophoresis of the reduced proteins in presence of sodium dodecyl sulfate indicated that protein composition of uterine fluid was distinct from that of colostrum, serum, amniotic fluid, and allantoic fluid, and revealed the presence of two major polypeptides with molecular weights of about 57,000 and 58,500, respectively, plus numerous other minor components. Gel filtration on columns of Sephadex G-200 and Sepharose CL-6B suggested that these polypeptides formed a series of aggregates of high molecular weight when kept under nonreducing conditions. Glucose (.18 +/- .03 mg/ml), but not fructose, was present in uterine fluid. In addition, high levels of prostaglandin F (451.4 +/- 83.3 ng/ml) were present.

Allantois↗