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Biomedical subjects

D Caton

Publications and source records attributed to D Caton.

At least 19 recordsLinked to original sources
PubMed1990

Patterns of variation in progestin in pregnant sheep.

Patterns of variation in progestin concentrations were studied in pregnant sheep during the last half of gestation. In three sets of experiments, blood was drawn daily or every 4 h for 24 h or every 10 min for 8 h. Peripheral arterial concentration of progestin was examined for 'peaks' using the Pulsar program which identified peaks in daily samples and in samples collected every 10 min, though less often than in daily samples. Ovariectomy did not affect the frequency or character of the peaks. The data suggest that large variations in progestin concentrations occur during the last half of pregnancy. They are superimposed on a gradual increase in average concentration and last for 2 to 3 days.

Animals↗
PubMed1989

Cardiac output in women undergoing cesarean section with epidural or general anesthesia.

Cardiac output during cesarean section and for 24 hours after delivery was estimated by using a noninvasive ultrasonic Doppler technique and was compared between term pregnant patients who underwent either epidural or general anesthesia. Cardiac output peaked by 36.7% and 26.3% of baseline values at 15 and 30 minutes after delivery, respectively, with epidural anesthesia and by 28% and 17.2%, respectively, with general anesthesia. From 60 minutes to 24 hours after delivery, cardiac output in both groups remained elevated at preoperative levels. This study demonstrates a similar pattern of increase in cardiac output with epidural and general anesthesia and a return by 60 minutes to preoperative levels, which persisted for up to 24 hours after delivery. The applicability of this noninvasive technique can be extended in various circumstances during pregnancy, labor, delivery, and the postpartum period to further define cardiac output in pregnancy.

Anesthesia, Epidural↗
PubMed1989

Anesthetic management for obstetric hysterectomy: a multi-institutional study.

A prospectively designed review of all obstetric hysterectomies performed in five university hospitals between November 1, 1984 and October 31, 1987 has been performed. There were 41,107 deliveries and 46 obstetric hysterectomies, an incidence of 0.11%. Twenty-five hysterectomies were elective and 21 were emergent. The indication for 11 of the 21 emergency hysterectomies was placenta previa and/or accreta. Women in the emergency group had greater intraoperative blood loss, were more likely to have intraoperative hypotension, and were more likely to receive donor blood than women in the elective group (P less than 0.05). Twelve patients (eight from the elective group and four from the emergency group) received continuous epidural anesthesia, and none required intraoperative induction of general anesthesia. There was no evidence that epidural anesthesia significantly affected blood loss, crystalloid replacement, or requirement for transfusion in the elective group. Abnormal placentation now represents a major indication for emergency obstetric hysterectomy. Furthermore, significant hemorrhage is more likely with emergency obstetric hysterectomy than with elective hysterectomy. Finally, elective cesarean hysterectomy is not a contraindication to performance of continuous epidural anesthesia.

Adult↗
PubMed1988

Evidence that a decrease in opioid tone on proestrus changes the episodic pattern of luteinizing hormone (LH) secretion: implications in the preovulatory LH hypersecretion.

We have studied the LH secretion pattern evoked by diminution in the opioid tone produced by iv naloxone (NAL) infusion between 1100-1400 h on proestrus, the LH secretion pattern occurring spontaneously between 1430-1730 h on proestrus and the LH secretion pattern produced by exogenous LHRH administered either as a 10 ng/pulse at 20-, 30-, or 60-min intervals or infused continuously at a rate of 30 ng/h between 1200-1700 h in rats given pentobarbital at 1100 h on proestrus. Infusion of 0.5 ng NAL/h raised plasma NAL levels to 200-300 ng/ml and augmented LH secretion, as evident by increments in pulse amplitude and frequency discharge to one every 37.5 min from an average of one every 75 min in saline-infused control rats. A 4-fold increase in circulating NAL levels, produced by 2 mg/h NAL infusion, further augmented the frequency of LH episodes to 30-33 min and induced a surge-like LH secretion pattern which resembled that seen on the afternoon of proestrus. Further analysis of the secretory pattern of the preovulatory LH surge (n = 7) showed LH pulses of increased amplitude during the basal phase (n = 4), ascending phase (n = 2), and plateau and descending phases (n = 3); in two rats the LH rise was steep, and no LH pulses were identified. A LHRH pulse (10 ng/pulse) delivered at 20- or 30-min intervals or continuous infusion of LHRH at a rate of 30 ng/h produced LH surges, with peak levels reaching the range seen on the afternoon of proestrus. Further, despite the fact that 10 ng LHRH/pulse at 20-min intervals reproduced a proestrous-type LH surge, only 40% of the LHRH pulses were followed by identifiable LH pulses. Surprisingly, despite the observations that NAL evoked robust LH episodes, the basal pattern of FSH secretion in these rats was not altered. These findings show that a decrease in opioid tone on proestrus accelerates episodic LH discharge to the range that occurs after gonadectomy. A quantitative relationship between the degree of restraint on the opioid tone imposed by NAL and the magnitude of the LH response can be demonstrated. The evidence suggests that the preovulatory LH surge may occur in an episodic fashion and that it can be reproduced by LHRH delivered at a frequency rate of LH pulses seen in ovariectomized rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Cardiac output response to prostaglandin E2-induced abortion in the second trimester.

Maternal cardiac output changes were evaluated in 10 patients undergoing second-trimester abortion induced by prostaglandin E2 suppositories. The peak cardiac output increased by an average of 64.5% above preinduction values. This is similar to the percent increase described during oxytocin-induced labor at term. Inasmuch as resting cardiac output tends to be higher in midpregnancy than at term, absolute values during prostaglandin E2 induction were higher than those observed in laboring term patients.

Abortifacient Agents↗
PubMed1987

A comparison of d-tubocurarine pretreatment and no pretreatment in obstetric patients.

The effect of pretreatment with d-tubocurarine on the incidences of succinylcholine-induced fasciculations and post-operative muscle pain, and the time to onset of and 50% recovery from neuromuscular blockade were studied in 75 obstetric patients. Thirty women with term pregnancies undergoing general anesthesia for elective cesarean section or cesarean section indicated by cephalopelvic disproportion were randomly assigned to two groups. Group C-1 patients received 0.05 mg/kg of d-tubocurarine followed by 1.5 mg/kg of succinylcholine, and group C-2 patients received 1.5 mg/kg of succinylcholine, and group C-2 patients received 1 ml of normal saline followed by 1 mg/kg of succinylcholine. An investigator, unaware of the relaxant regimen used, judged severity of fasciculations and postoperative muscle pain and measured times to onset of and 50% recovery from neuromuscular blockade. This same study design was followed in a group of 30 women undergoing tubal ligation 1 day after vaginal delivery (groups T-1 and T-2). The incidence of both fasciculations and postoperative muscle pain was low and was not significantly different between pretreated and nonpretreated groups. Time to 100% twitch depression was also not significantly different between pretreated and nonpretreated groups. Time to 50% recovery from neuromuscular blockade was significantly longer in both nonpretreated groups (C-2 and T-2). An additional group of 15 patients undergoing general anesthesia for cesarean section using 0.7 mg/kg of succinylcholine without d-tubocurarine pretreatment was studied (group C-3). This smaller dose of succinylcholine produced onset and 50% recovery times similar to the group pretreated with d-tubocurarine (group C-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Uterine prostaglandin and blood flow responses to estradiol-17 beta in cyclic cattle.

Normal cyclic dairy cattle (n = 7) underwent a midventral laparotomy on day 17 of the estrous cycle and were fitted, ipsilateral to the CL, with: an electromagnetic flow transducer around the uterine artery (UA; n = 5); catheters within the ovarian vein (OV; n = 7) via a uterine branch of the ovarian vein, uterine branch of the ovarian artery (UBOA; n = 5) and facial artery (FA; n = 7). On day 18, blood samples were collected at 30 min intervals for 1 h prior to injection of estradiol-17 beta (E2; 3 mg) and 12 h post-E2. Uterine blood flow (UBF) was monitored continuously and plasma samples analyzed for PGF2 alpha and PGFM. Exact locations of catheters in reproductive tracts were verified post-slaughter. Data were analyzed by method of least squares analysis of variance. Uterine blood flow (ml/min) increased above pre-E2 flow rates within 30 min post-E2 injection, peaked between 2.5 to 3.5 h and declined between 4 to 8.5 h. A small secondary rise in UBF occurred between 9 and 12 h. Regression analysis for concentrations (pg/ml) of PGF2 alpha and PGFM in the OV (i.e., [OV]-[FA]) demonstrate a similar response as PGFM concentration in the FA in that all increased at approximately 3 h, peaked between 5 and 7 h and returned to near baseline levels by 9 to 10 h post-E2. Facial artery PGFM concentrations were positively correlated with uterine production of PGF2 alpha (r = .66) and PGFM (r = .30), whereas FA PGF2 alpha concentrations were not. In three of five cows, a difference in PGF2 alpha was detected between UBOA and FA (UBOA greater than FA); supportive of a local countercurrent exchange between the uterine venous drainage and the ovarian artery.

Animals↗
PubMed1986

Endogenous hormones and regulation of uterine blood flow during pregnancy.

Fourteen pregnant sheep were prepared for measurements of blood flow through a major uterine artery (UBF) and of arterial concentrations of estrone, estradiol, and progestagen. Five of the animals were ovariectomized. Measurements were made daily (n = 12) or every 4 h for 24 h (n = 4). Statistically significant (P less than 0.01) correlation coefficients were detected between UBF and hormone, either alone or in combination; the closest and most consistent associations were those in which estrogen and progestagen concentrations were summed or multiplied. Ewes with higher hormonal concentrations were those that had the higher rates of UBF. Correlation coefficients were statistically significant more often among ovariectomized animals. No associations were detected within one animal that delivered a growth-retarded fetus nor from any of the 24-h data. Estrogens and progestagen accounted for as much as 25% of the daily variation of UBF among and within sheep during the last half of pregnancy.

Animals↗
PubMed1985

The secularization of pain.

After Morton's demonstration in the Ether Dome of the Massachusetts General Hospital, anesthesia for surgery was accepted around the world at a speed unusually fast for any medical or scientific innovation. However, the concept of surgical anesthesia had been rejected on four occasions during the preceding 40 years. The rapid acceptance of anesthesia in 1846 appears to have had a political and social basis as well as medical. Two factors are particularly important. First was a change in the perception of disease and pain; both lost religious connotations and became biologic phenomena as part of a process of secularization that affected all aspects of Western society. Second was the growth of a sense of well-being and progress, which imbued patients and physicians alike with confidence in their ability to control natural processes. During the last half century, pain has remained secular, but the confidence in both progress and the ability to control nature may have diminished.

Anesthesia↗
PubMed1985

Characteristics of prostaglandin F measurements in the ovarian circulation during the oestrous cycle and early pregnancy in the cow.

Holstein or crossbred beef cows were anaesthetized on Days 15 to 17 after oestrus; the ovarian artery (OA), ovarian (utero-ovarian) vein (OV) and a peripheral artery (PA), were catheterized for chronic blood sampling. Beginning on the day after surgery, 6 sequential blood samples were collected every 30-40 min twice daily from 8 cyclic and 6 pregnant cows during Days 16-20: 818 blood samples (including 216 OA and PA concurrent arterial pairs) were collected. Overall least squares means for PGF concentrations (pg/ml) in the OV, OA and PA of cyclic cows were 562, 228 and 106, respectively. A significant (P less than 0.01) OA-PA difference (122 pg/ml) suggests that a local transfer system, between uterine venous effluent and ovarian arterial affluent, is functional in the cow. A transfer efficiency of about 1% was estimated. In cyclic cows differences in OA-PA concentrations of PGF were minimal on Days 16-18 and increased to about 160 pg/ml during luteal regression (Days 19-20). In pregnant cows a biphasic OA-PA pattern of difference in PGF between days was detected, with a peak on Day 18 (136 pg/ml) which was not apparent on Days 19-20. Amplitude of PGF spikes in the OA was significantly higher in cyclic (725 pg/ml) than in pregnant cows (397 pg/ml). We suggest that pregnancy suppresses PGF delivery to the ovarian circulation, resulting in maintenance of the corpus luteum in pregnant cows.

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↗