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Biomedical subjects

J Summy-Long

Publications and source records attributed to J Summy-Long.

14 recordsLinked to original sources
PubMed1996

Induced abortion as an independent risk factor for breast cancer: a comprehensive review and meta-analysis.

STUDY OBJECTIVE: To ascertain, from the published reports to date, whether or not a significantly increased risk of breast cancer is specifically attributable to a history of induced abortion, independent of spontaneous abortion and age at first full term pregnancy (or first live birth); to establish the relative magnitude of such risk increase as may be found, and to ascertain and quantify such risk increases as may pertain to particular subpopulations of women exposed to induced abortion; in particular, nulliparous women and parous women exposed before compared with after the first full term pregnancy. INCLUDED STUDIES: The meta-analysis includes all 28 published reports which include specific data on induced abortion and breast cancer incidence. Since some study data are presented in more than one report, the 28 reports were determined to constitute 23 independent studies. Overall induced abortion odds ratios and odds ratios for the different subpopulations were calculated using an average weighted according to the inverse of the variance. An overall unweighted average was also computed for comparison. No quality criteria were imposed, but a narrative review of all included studies is presented for the reader's use in assessing the quality of individual studies. EXCLUDED STUDIES: All 33 published reports including data on abortion and breast cancer incidence but either pertaining only to spontaneous abortion or to abortion without specification as to whether it was induced or spontaneous. These studies are listed for the reader's information. RESULTS: The overall odds ratio (for any induced abortion exposure; n = 21 studies) was 1.3 (95% confidence interval of 1.2, 1.4). For comparison, the unweighted overall odds ratio was 1.4 (1.3,1.6). The odds ratio for nulliparous women was 1.3 (1.0,1.6), that for abortion before the first term pregnancy in parous women was 1.5 (1.2,1.8), and that for abortion after the first term pregnancy was 1.3 (1.1,1.5). CONCLUSIONS: The results support the inclusion of induced abortion among significant independent risk factors for breast cancer, regardless of parity or timing of abortion relative to the first term pregnancy. Although the increase in risk was relatively low, the high incidence of both breast cancer and induced abortion suggest a substantial impact of thousands of excess cases per year currently, and a potentially much greater impact in the next century, as the first cohort of women exposed to legal induced abortion continues to age.

Abortion, Induced↗
PubMed1994

An oxytocin receptor antagonist infused into the supraoptic nucleus attenuates intranuclear and peripheral release of oxytocin during suckling in conscious rats.

We tested the hypothesis that oxytocin (OXT) released within the supraoptic nucleus (SON) during suckling in lactating rats facilitates its own intranuclear release and thereby stimulates its secretion into blood during the milk ejection reflex. In the first study, to examine the positive feedback action of OXT released within the SON, microdialysates of the SON area were sampled before and during suckling. Either vehicle (1.0 microliter) or an OXT receptor antagonist (50 ng/microliters) was infused adjacent to the microdialysis probe into the SON area before suckling began. Compared to the corresponding presuckling values (100%), the OXT content in microdialysates sampled during the suckling period increased after vehicle treatment (to 501 +/- 174%; P < 0.01), whereas infusion of the OXT antagonist significantly (P < 0.05) attenuated the rise in the release of OXT during suckling (130 +/- 22.0%). In the second study, the influence of intranuclear OXT on release of OXT into the blood during suckling was examined. Compared to those in rats infused with vehicle into both SON before suckling started (100%), injection of the OXT antagonist decreased the concentration of OXT in plasma (to 32.1 +/- 5.50%; P < 0.05) and the milk transfer to the pups during the suckling period (to 30.2 +/- 13.3%; P < 0.01). Although the neuroendocrine response to suckling was attenuated in rats receiving the OXT antagonist, maternal behavior, assessed as the time at which six to eight pups began suckling and the time from the onset until the occurrence of the third milk ejection reflex, was unaffected. These findings provide evidence for a receptor-mediated positive feedback action of OXT on its own release within the SON during suckling. The amplification of intranuclear release of OXT is needed for the release of appropriate amounts of OXT into the bloodstream to stimulate milk transfer to the suckling pups.

Animals↗
PubMed1993

Hypothalamic and gastric myoelectrical responses during vection-induced nausea in healthy Chinese subjects.

The physiology of nausea, a uniquely human symptom, is poorly understood. The purpose of this study was to measure the temporal sequences of neurohormonal responses and gastric myoelectrical activity in healthy subjects during the rotation of an optokinetic drum that produced nausea and other symptoms of motion sickness. Plasma catecholamines, vasopressin, and cortisol were measured at baseline, during minutes 1-5, 6-10, and 11-15 of drum rotation, and after rotation stopped. Electrogastrograms were recorded throughout the study. Twelve subjects (80%) developed nausea and 4-9 cycles/min of gastric tachyarrhythmias; three subjects had no nausea and no gastric dysrhythmias. Tachyarrhythmias began 3.4 +/- 0.8 min after the onset of drum rotation, and nausea was reported, on average, 3 min later. During minutes 6-10 of drum rotation, vasopressin levels significantly increased in the subjects with nausea compared with subjects without nausea (P < 0.04). In the subjects with nausea, epinephrine and vasopressin increased significantly (P < 0.05) compared with baseline during minutes 6-10 and 11-15 of drum rotation. As nausea resolved during recovery, vasopressin decreased by 74%, whereas epinephrine increased 13%. We conclude that 1) in nauseated subjects, endogenous vasopressinergic and sympathetic circuits are activated before hypothalamic-pituitary-adrenal pathways, 2) plasma vasopressin levels correlate most closely with the temporal onset and resolution of nausea, and 3) peripheral gastric dysrhythmias may have a role in activating central vasopressinergic neurons.

Adult↗
PubMed1990

Vasopressin and oxytocin responses to illusory self-motion and nausea in man.

Vasopressin and oxytocin are nonapeptides secreted from the neurohypophysis; increases in vasopressin are associated with nausea and vomiting in some, but not all, species. Our aim was to determine whether plasma vasopressin and oxytocin levels were altered in healthy volunteers who did or did not develop nausea during vection, an optokinetic stimulus which produces the illusion of self-motion. Vection was produced by rotating a drum with an inner surface of black and white vertical stripes around the seated stationary subject. Gastric myoelectrical activity was recorded continuously throughout the experiment with electrodes positioned on the abdominal surface. Plasma samples were obtained before vection and after drum rotation stopped when nausea and tachygastria were present. Vasopressin and oxytocin were extracted from plasma and quantified by RIA. During vection six subjects reported nausea and developed gastric dysrhythmias; six other subjects had no nausea and remained in normal 3-cpm myoelectrical rhythms. Vasopressin and oxytocin values before vection were similar in each group of subjects. One minute after vection stopped, plasma vasopressin levels were significantly greater (P less than 0.05) in subjects experiencing nausea and tachygastrias (35.4 +/- 26.7 pmol/L) than in those without symptoms (2.7 +/- 0.47 pmol/L). Oxytocin levels were unchanged by either vection or nausea. It is concluded that 1) vasopressin, not oxytocin, neurons in the magnocellular-neurohypophyseal system are activated during vection-induced nausea and gastric dysrhythmias; and 2) illusory self-motion may be used safely to study the neuroendocrine responses to brain-gut interactions and nausea in man.

Adult↗
PubMed1975

Release of vasopressin by angiotensin II.

To test the hypothesis that angiotensin II releases antidiuretic hormone (ADH) after injection into ventricular cerebrospinal fluid, conscious adult male Sprague-Dawley rats with a lateral cerebroventricular cannula received an intraventricular injection of 0, 10, 50, or 100 ng angiotensin II. Trunk blood was collected 90 seconds later for radioimmunoassay of ADH. Plasma ADH, pg/ml (mean plus or minus S. E.), for the four dose levels were 2.8 plus or minus 0.7, 9.6 plus or minus 2.5, 22.6 plus or minus 5.6 and 25.0 plus or minus 5.0, respectively. The increases produced by angiotensin were statistically significant (p smaller than 0.05). Plasma ADH of the 10 ng group was intermediate between control and the two highest angiotensin doses (p smaller than 0.05), suggesting a dose-response relationship. These data provide direct evidence that angiotensin releases ADH by central mechanisms.

Angiotensin II↗