During the last decade, the GH axis has become the compelling focus of remarkably active and broad-ranging basic and clinical research. Molecular and genetic models, the discovery of human GHRH and its receptor, the cloning of the GHRP receptor, and the clinical availability of recombinant GH and IGF-I have allowed surprisingly rapid advances in our knowledge of the neuroregulation of the GH-IGF-I axis in many pathophysiological contexts. The complexity of the GHRH/somatostatin-GH-IGF-I axis thus commends itself to more formalized modeling (154, 155), since the multivalent feedback-control activities are difficult to assimilate fully on an intuitive scale. Understanding the dynamic neuroendocrine mechanisms that direct the pulsatile secretion of this fundamental growth-promoting and metabolic hormone remains a critical goal, the realization of which is challenged by the exponentially accumulating matrix of experimental and clinical data in this arena. To the above end, we review here the pathophysiology of the GHRH somatostatin-GH-IGF-I feedback axis consisting of corresponding key neurotransmitters, neuromodulators, and metabolic effectors, and their cloned receptors and signaling pathways. We propose that this system is best viewed as a multivalent feedback network that is exquisitely sensitive to an array of neuroregulators and environmental stressors and genetic restraints. Feedback and feedforward mechanisms acting within the intact somatotropic axis mediate homeostatic control throughout the human lifetime and are disrupted in disease. Novel effectors of the GH axis, such as GHRPs, also offer promise as investigative probes and possible therapeutic agents. Further understanding of the mechanisms of GH neuroregulation will likely allow development of progressively more specific molecular and clinical tools for the diagnosis and treatment of various conditions in which GH secretion is regulated abnormally. Thus, we predict that unexpected and enriching insights in the domain of the neuroendocrine pathophysiology of the GH axis are likely be achieved in the succeeding decades of basic and clinical research.

Pathophysiology of the neuroregulation of growth hormone secretion in experimental animals and the human

Electrophysiology of hypothalamic magnocellular neurones secreting oxytocin and vasopressin

Intramammary infections of dairy cows with Gram-positive bacteria such as Staphylococcus aureus (major cause of mastitis) have received a lot of attention because of their major economic impact on the dairy farm through production losses induced by an increase in somatic cell count. Management strategies, including greater awareness for efficient milking and hygienic measures, have limited the spread of Gram-positive bacteria and resulted in a significant decrease of proportion of S. aureus isolates and subclinical mastitis worldwide. Other organisms such as coliform subspecies and Streptococcus uberis, both environmental bacteria that cause clinical mastitis, have received less attention. Escherichia coli causes inflammation of the mammary gland in dairy cows around parturition and during early lactation with striking local and sometimes severe systemic clinical symptoms. This disease affects many high producing cows in dairy herds and may cause several cases of death per year in the most severe cases. It is well known that bacterial, cow and environmental factors are interdependent and influence mastitis susceptibility. Many studies, executed during the last decade, indicate that the severity of E. coli mastitis is mainly determined by cow factors rather than by E. coli pathogenicity. During E. coli mastitis, the host defense status is a cardinal factor determining the outcome of the disease. Today, we know that the neutrophil is a key factor in the cows' defense against intramammary infection with E. coli. Effective elimination of the pathogen by neutrophils is important for the resolution of infection and the outcome of E. coli mastitis. This review is a compilation of some major findings over the last 15 years concerning mainly host factors that modulate and influence neutrophil function and the mammary inflammatory reaction. The individual chapters address: virulence factors of E. coli strains, how neutrophils kill E. coli, connection between endotoxins, tumor necrosis factor-alpha and nitric oxide, severity classification of E. coli mastitis, lifespan of neutrophils, host factors that influence severity, tissue damage and production loss.

https://hal.archives-ouvertes.fr/hal-00902764/document

Severity of E. coli mastitis is mainly determined by cow factors

I. Introduction PROLACTIN (PRL) is one of the most versatile hormones of the pituitary gland in terms of biological actions. More than 100 different and distinct effects of the hormone have been documented (1), ranging from mammary development and initiation of lactation in mammals to osmoregulation in fishes, nesting behavior in birds, and growth and metamorphosis in amphibians. These are far in excess of the reported actions of all other adenohypophyseal hormones combined. But how does a single molecule evoke so many different responses? Studies in the last few years have shown that the hormone exists in several molecular forms, some arising from posttranslational modifications and others from genetically determined factors. Such findings have led to the suggestion that PRL is perhaps a prohormone, which is synthesized as a precursor molecule and then converted to different bioactive forms as it traverses the secretory pathway. The purpose of this review is to provide an account of the recent advances i...

Structural variants of prolactin: occurrence and physiological significance.

1 Compound Eyes and the World of Vision Research.- 2 Autrum's Impact on Compound Eye Research in Insects.- 3 Optics and Evolution of the Compound Eye.- 4 Photoreceptor Optics, Theory and Practice.- 5 Variations in the Structure and Design of Compound Eyes.- 6 Visual Pigments of Compound Eyes - Structure, Photochemistry, and Regeneration.- 7 Distribution of Insect Visual Chromophores: Functional and Phylogenetic Aspects.- 8 Pigments in Compound Eyes.- 9 Phototransduction in Limulus Ventral Photoreceptors: Roles of Calcium and Inositol Trisphosphate.- 10 The Retina-Lamina Pathway in Insects, Particularly Diptera, Viewed from an Evolutionary Perspective.- 11 Coding Efficiency and Design in Visual Processing.- 12 Neurotransmitters in Compound Eyes.- 13 Circadian Rhythms in the Invertebrate Retina.- 14 Color Vision in Honey Bees: Phenomena and Physiological Mechanisms.- 15 Polarization Sensitivity in Compound Eyes.- 16 Beneath the Compound Eye: Neuroanatomical Analysis and Physiological Correlates in the Study of Insect Vision.- 17 Directionally Selective Motion Detection by Insect Neurons.- 18 Neural Mechanisms of Visual Course Control in Insects.- 19 Size and Distance Perception in Compound Eyes.

Facets of Vision

The purpose of these studies was to determine the effect of suckling on the plasma oxytocin (OT) concentration profile in conscious primiparous rats during midlactation. Comparisons were made with pla

Comparison of plasma profiles of oxytocin and prolactin following suckling in the rat.

The ability of various exteroceptive stimuli to inhibit milk ejection and the suckling-induced release of prolactin was tested in lactating rats on postpartum day 7. Milk ejection was assessed by weighing the milk in the pups’ stomachs at the conclusion of suckling; prolactin was assayed with the intradermal pigeon crop-sac method. The odor of oil of peppermint, intermittent bright light, or intermittent low intensity sounds, including personnel conversation, each significantly reduced the amount of milk obtained by the pups in 30 min of suckling following 8 hr of nonsuckling. The odor of an oily solution of chlorophyll was ineffective. The subcutaneous injection of 40 mU oxytocin concomitant with the inhibiting stimuli restored milk yields to normal values in each instance. This suggests that the stimuli employed affect milk ejection through a central inhibition of oxytocin release. The exteroceptive stimuli which inhibited milk ejection failed in the same rats to alter the extent of the reduction in the...

Effect of auditory, olfactory and optic stimuli upon milk ejection and suckling-induced release of prolactin in lactating rats.

Effect of suckling upon the secretion and release of prolactin from the pituitary of the lactating rat.

A 50-70% depletion in the anterior pituitary concentration of PRL occurred within 5 min of electrical stimulation of a single abdominal mammary nerve of urethane-anesthetized lactating rats previously nonsuckled for 6-8 h The stimulus parameters were: 1-msec pulses, 10-20/sec at 5-30 V applied 5 sec on and 10 sec off The anterior pituitary concentration of PRL remained low for another 15-30 min after depletion, then repleted to prestimulus levels by the 90th min The same pattern of depletion-repletion occurred when mammary nerve stimulation was applied for 5 min as when it was applied for 180 min In other experiments, plasma PRL concentration rose swiftly and attained a maximal level, 4- to 5-fold in Wistar rats and 8- to 10-fold in Holtzman rats, above basal concentrations within 10-15 min of mammary nerve stimulation The maximal level was sustained throughout the time the nerve was stimulated and for 45 min after the stimulation was stopped, ie the sustained secretion of PRL into the plasma occurred at the same time that depleted PRL was repleting Ligation of both adrenals or iv injection of the beta-adrenergic blocker, propranolol, before stimulation of the nerve had no effect upon the plasma PRL profile in response to mammary nerve stimulation These data indicate that mammary nerve stimulation mimics that of suckling upon depletion, repletion, and the release of PRL into the circulation and add further support to the hypothesis that these phases are independent processes

Flavio Mena

Papers

Comparison of plasma profiles of oxytocin and prolactin following suckling in the rat.

Effect of auditory, olfactory and optic stimuli upon milk ejection and suckling-induced release of prolactin in lactating rats.

Effect of suckling upon the secretion and release of prolactin from the pituitary of the lactating rat.

Effect of Electrical Stimulation of Mammary Nerve upon Pituitary and Plasma Prolactin Concentrations in Anesthetized Lactating Rats

Circadian variations of hormonal content in the nervous system of the crayfish.