Placental efficiency and adaptation: endocrine regulation

Size at birth is critical in determining life expectancy and is dependent primarily on the placental supply of nutrients. However, the fetus is not just a passive recipient of nutrients from the placenta. It exerts a significant acquisitive drive for nutrients, which acts through morphological and functional adaptations in the placenta, particularly when the genetically determined drive for fetal growth is compromised by adverse intrauterine conditions. These adaptations alter the efficiency with which the placenta supports fetal growth, which results in optimal growth for prevailing conditions in utero . This review examines placental efficiency as a means of altering fetal growth, the morphological and functional adaptations that influence placental efficiency and the endocrine regulation of these processes.     

Hypothalamic control of endocrine thermogenesis

Hypothalamic and ruminal cooling raised serum thyrotropin (TSH), adrenocorticotropin (ACTH), norepinephrine (NE), and glucose in conscious goats in 20 degree C ambient temperature. Cooling of the preoptic anterior hypothalamus (POAH) for 2 h initially evoked shivering and vasoconstriction, leading to 1.5 degree C rise in rectal temperature (Tr). Pituitary-thyroid activation by POAH cooling was shown by peak rises in TSH of 60% at 40 min, in triiodothyronine (T3) of 54% at 80 min, and in thyroxine (T4) of 40% at 140 min. At 60 min, ACTH and NE peaked at 57 and 65%, respectively. TSH, ACTH, and NE declined during the 2nd h of POAH cooling as Tr plateaued; when POAH cooling was stopped, these hormones fell below basal level as vasodilation and panting restored Tr to normal. In contrast to the core hyperthermia evoked by POAH cooling, ruminal intubation with O degree C water (1 liter/10 kg) led to general hypothermia, Tpoah and Tr falling 1.6 degree C at 40 min. Pituitary-thyroid responses were less but ACTH and NE more, compared with POAH cooling. TSH peaked at 37% at 20 min, T3 at 55% at 60 min, and T4 at 18% at 200 min. ACTH peaked at 250% at 30 min and NE at 120% at 20 min. Thermosensitive neurons in the POAH seem to mediate more sensitive and complete control over TSH than over ACTH, or NE release, whereas extrahypothalamic core thermosensitivity (e.g., brain stem, spinal cord, abdomen) may influence ACTH and NE more than TSH release.     

The relationship of preoperative distress to endocrine and subjective responses to surgery: Support for Janis' theory

To test Janis' theory that preoperative worry can improve postoperative recovery, endocrine and subjective responses were measured in 27 patients undergoing major abdominal surgery which entailed threat to their health or longevity. Questionnaires to assess emotional and somatic state were completed preoperatively and for 7 days postoperatively. Plasma cortisol, noradrenaline, adrenaline, and glucose were measured pre-, per-, and postoperatively. Preoperatively, noradrenaline correlated positively with pain and distress, and adrenaline negatively. Postoperatively, endocrine levels and distress were not clearly related. Nevertheless, preoperative pain negatively correlated with postoperative adrenaline and cortisol levels. This, and the negative correlation between preoperative distress and postoperative pain are consistent with Janis' theory. In addition, we found that the longer patients waited on the day of surgery, the greater were the cortisol, noradrenaline, and glucose responses.     

General theory of cell regulation

A general theory of cell regulation has been based on a previously described concept that both DNA chains of the chromatin may be expressed, and the protein products of this type of gene expression are also complementary to each other and can specifically interact with each other and with the nucleic acids which serve the code for them. The regulation of biological processes is directed by these specifically interacting molecules which are organized in Elementary Regulatory Units (ERU). The biological information in ERUs is persisting reversibly transformable (on the basis of protein and nucleic acid complementarity), buffered, and complementary information is in balance with each other. The information transfer by macromolecules in the ERUs follows the law of mass action. Biologically active “small” molecules (nucleotide phosphates, steroids, iodothyronins) interact with the ERUs and influence their steady states. The contact inhibition of the cells and the cooperative regulation of different cells and cell functions have been explained on the basis of the theoretically explained properties of the ERUs.     

Adrenomedullin and endocrine control of immune cells during pregnancy

The immunology of pregnancy is complex and incompletely understood. Aberrant immune activity in the decidua and in the placenta is believed to play a role in diseases of pregnancy, such as infertility, miscarriage, fetal growth restriction and preeclampsia. Here, we briefly review the endocrine control of uterine natural killer cell populations and their functions by the peptide hormone adrenomedullin. Studies in genetic animal models have revealed the critical importance of adrenomedullin dosage at the maternal-fetal interface, with cells from both the maternal and fetal compartments contributing to essential aspects underlying appropriate uterine receptivity, implantation and vascular remodeling of spiral arteries. These basic insights into the crosstalk between the endocrine and immune systems within the maternal- fetal interface may ultimately translate to a better understanding of the functions and consequences of dysregulated adrenomedullin levels in clinically complicated pregnancies.     

Nervous control of pancreatic endocrine secretion in pigs

The increases in the concentrations of insulin and pancreatic glucagon in portal venous and arterial plasma in response to electrical stimulation of the vagus nerves were studied in anesthetized splanchnicotomized young pigs. The responses were frequence dependent; threshold frequency was below 1 Hz and maximum response was reached at 8–12 Hz. With maximal stimulation responses of magnitudes comparable to the responses to maximal arginine (glucagon) and glucose stimulation (insulin) were observed. However, both the insulin and the glucagon response were critically dependent on the blood glucose concentration during the stimulation: the glucagon response was inversely correlated to blood glucose, whereas the insulin response was positively correlated to blood glucose at concentrations above 4.5 mmol · 1^-1. Below this glucose concentration there was no detectable insulin response and above 8.0 mmol ·^-1 no glucagon response to vagal stimulation. A stimulated secretion of glucagon as well as insulin was maintained for up to 30 min stimulation, but insulin secretion tended to decrease, whereas glucagon secretion tended to increase. Above blood glucose concentrations of 4 mmol · 1^-1, blood glucose concentrations increased slightly in response to vagal stimulation, whereas no change was noted during stimulations performed at lower blood glucose concentrations.     

Physiology of the male reproductive system: endocrine, paracrine and autocrine regulation

This presentation reviews the male reproductive system, concentrating on newer advances in our knowledge of its physiology, biochemistry, and regulation, and introduces the topic of male reproductive toxicology. GnRH is the hypothalamic peptide responsible for the stimulation of LH and FSH release from the pituitary. It is synthesized as a pro-hormone, processed in the hypothalamus and released into the portal system in a pulsatile fashion. The timing of these pulses is critical to the release of LH and FSH into the general circulation. While LH and FSH are the main trophic hormones for the testis, we now realize the importance of not only endocrine control, but also of paracrine and autocrine regulation. Specifically, the local control of Leydig cells, Sertoli cells, and germ cells appears to be modulated by numerous growth factors and local regulators arising from within the testis. This point is emphasized both during a discussion of the interaction of the various cell types in the testis and during a discussion of spermatogenesis, where techniques which show stage-specific secretions are highlighted. Newest advances in the mechanism of action of steroidal and peptide hormones are also emphasized with special reference to the possible interaction between toxicants and endocrine control of the reproductive system. This update of the reproductive system "sets the stage" for an in-depth examination of the site and mechanism of action of reproductive toxicants.     

Decision theory applied to image quality control in radiology

Background  

The present work aims at the application of the decision theory to radiological image quality control (QC) in diagnostic routine. The main problem addressed in the framework of decision theory is to accept or reject a film lot of a radiology service. The probability of each decision of a determined set of variables was obtained from the selected films.     

Thermoregulation as a switchboard of autonomic nervous and endocrine control.

Analyzing the multiple effectors of autonomic temperature regulation has, sometimes unexpectedly, provided insights into the characteristics according to which the non-thermoregulatory functions of these effectors are controlled. This article reviews the sympathetic control of cardiovascular and immune functions, hormonal control of energy balance and neurohormonal control of salt and fluid balance inasmuch as they are challenged by competing demands of thermoregulatory requirements. These interactions are taken as examples for the analytical power of the experimental conception to challenge non-thermoregulatory control systems with thermoregulatory activation, and vice versa. Animal models carrying spontaneous or intentionally produced gene defects and molecular and histochemical techniques of gene identification and neuronal tracing are becoming increasingly important. They are applied, in connection with physiological studies exploiting mutual interactions of autonomic control systems, with the aim to elucidate the cytoarchitecture of neuronal circuits by which specific autonomic regulatory activities are controlled.     

Negative endocrine control system for inflammation in rats

Inflammatory processes may be suppressed by endogenous mechanisms such as release of adrenocorticosteroid hormones through stimulation of the hypothalamus-pituitary-adrenal axis. In the present study, the relationship between the temporal development of carrageenan-induced edema in the hindlimb of the rat and release in plasma of the principal endogenous adrenocorticosteroid of the rat corticosterone was investigated. Suplantar injection of carrageenan produced a biphasic increase in basal plasma corticosterone levels that was not attributed to diurnal variation. The plasma level of corticosterone increased rapidly after injection of carrageenan and peaked 12-fold at 20 min. This first phase increase was attributed to the stress of the injection since it was mimicked by subplantar injection of saline. The second phase of corticosterone relase was gradual and peaked 12-fold 7hr after injection of carrageenan. The second phase was not elicited by subplantar injection of saline. When the hypothalamus-pituitary-adrenal axis is impaired via hypophysectomy, carrageenan-induced edema is more intense and lasts longer than in control rats. The results demonstrate that adrenocorticosteroid hormones are released as a result of the stress of injection and by the inflammatory response. Release of adrenocorticosteroids acts as a feedback mechanism to suppress the inflammatory response.The reader is directed to two excellent, complimentary, pertinent journal articles which have appeared since this article was submitted for publication: E. M. Sternberg, J. M. Hill, G. P. Chrousos, T. Kamilaris, S. J. Listwak, P. W. Gold and R. L. Wilder,Inflammatory Mediator-induced hypothalamic-pituitary-adrenal axis activation is defective in streptococcal cell wall arthritis-susceptible Lewis rats. Proc. Natl. Acad. Sci.86, 2374–2378 (1989) and E. M. Sternberg, W. S. Young, R. Bernardini, A. E. Calogers, G. P. Chrousos, P. W. Gold and R. L. Wilder, A central nervous system defect in biosynthesis of corticotropin-releasing hormone is associated with susceptibility to streptococcal cell wall-induced arthritis in Lewis rats. Proc. Natl. Acad. Sci.86, 4771–4775 (1989).     

Application of robotics to prosthetic control

Multiaxis robotic and prosthetic systems have a number of common characteristics such that control techniques for robots may sometimes be adapted for prosthetic devices. One characteristic that is particularly important for these systems is that good performance over a wide range of motion and loads is difficult since it is dependent upon complex time-varying, nonlinear dynamics. This paper gives an example of the complexity of the dynamics for a two degree-of-freedom, double-inverted pendulum which has been used as a model for study of biped locomotion. Two different methods called the “inverse plant” and State Space Memory, now being considered for robotic mechanisms, are then presented which base the control on the dynamics of the system and may have application for prosthetic devices.