Jacques Balthazart – författare

In this fascinating book, Jacques Balthazart presents a simple description of the biological mechanisms that are involved in the determination of sexual orientation in animals and also presumably in humans. Using scientific studies published over the last few decades, he argues that sexual orientation, both homosexual and heterosexual, is under the control of embryonic endocrine and genetic phenomena in which there is little room for individual choice. The author begins with animal studies of the hormonal and neural mechanisms that control the so-called instinctive behaviors and analyzes how this animal work may potentially apply to humans. The book does not focus exclusively on homosexuality, however. Instead, the book acts as a broader guide to the biological basis of sexual orientation, and also discusses important gender differences that may influence sexual orientation. While firmly grounded in the scientific literature, this text is developed for a broader audience and will be of interest to psychologists, researchers, students, and anyone interested in the biological factors that determine our sexuality.

It is well known that the class of steroid hormones known as estrogens have powerful effects on organs related to reproduction such as the uterus and the breast. What is less well known is that estrogens also profoundly modulate brain function and behavior. Estrogens, such as estradiol, can occur in brain as the result of ovarian secretion of the hormone into the blood that then finds its way to the brain. In male vertebrates, the testes secrete androgens, such as testosterone, into the blood and this class of steroid hormones can be converted into estrogens in the brain via the action of the enzyme aromatase which is expressed in the male brain in many species. Finally estradiol can be synthesized de novo from cholesterol as it has been shown in a variety of species that all the enzymes required to synthesize estrogens are expressed in the brain. This book collects chapters by experts in the field that considers, how estradiol is synthesized in the brain and what its effects are on a variety of behaviors. Special attention is paid to the enzyme aromatase that is distributed in discrete regions of the brain and is highly regulated in a sex specific and seasonal specific manner. Recently it has become clear that estrogens can act in the brain at two very different time scales, one is rather long lasting (days to weeks) and involves the modulation of gene transcription by the hormone-receptor complex. A second mode of action is much quicker and involves the action of estrogens on cell membranes that can result in effects on second messenger systems and ultimately behavior within minutes. Thus this book highlights novel views of estrogen action that are still under-appreciated namely that estrogens have significant effects on the male brain and that they can act on two very different times scales. This volume will be of interest to both basic researchers and clinicians interested in the action of estrogens.

Research in biology and all basic sciences has undergone profound transformations in recent decades. We have seen the development of extremely sophisticated techniques, allowing us to study, in an objective manner, questions that were still considered science fiction at the end of the 20th century. All of this has allowed us to develop an in-depth knowledge of vast subjects, such as the biology of the brain, for example. Fifty Years of Evolution in Biological Research presents a panorama of these different technical advances. However, at the same time, there has been an increase in the number of constraints on researchers, a monetization of research and a correlative pressure to continually publish in more prestigious journals. This has resulted in a certain degradation of the quality of research activity. This book analyzes this evolution and proposes solutions.