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Meiosis in Humans

Meiosis, the process by which sexually-reproducing organisms generate gametes (sex cells), is an essential precondition for the normal formation of the embryo. As sexually reproducing, diploid, multicellular eukaryotes, humans rely on meiosis to serve a number of important functions, including the promotion of genetic diversity and the creation of proper conditions for reproductive success.

Format: Articles

Subject: Processes, Reproduction

Golgi Staining Technique

The Golgi staining technique, also called the black reaction after the stain's color, was developed in the 1870s and 1880s in Italy to make brain cells (neurons) visible under the microscope. Camillo Golgi developed the technique while working with nervous tissue, which required Golgi to examine cell structure under the microscope. Golgi improved upon existing methods of staining, enabling scientists to view entire neurons for the first time and changing the way people discussed the development and composition of the brain's cells.

Format: Articles

Subject: Technologies, Processes

Mesenchyme

Mesenchyme is a type of animal tissue comprised of loose cells embedded in a mesh of proteins and fluid, called the extracellular matrix. The loose, fluid nature of mesenchyme allows its cells to migrate easily and play a crucial role in the origin and development of morphological structures during the embryonic and fetal stages of animal life. Mesenchyme directly gives rise to most of the body's connective tissues, from bones and cartilage to the lymphatic and circulatory systems.

Format: Articles

Subject: Processes

Somatic Cell Nuclear Transfer in Mammals (1938-2013)

In the second half of the
twentieth century, scientists learned how to clone organisms in some
species of mammals. Scientists have applied somatic cell nuclear transfer to clone human and
mammalian embryos as a means to produce stem cells for laboratory
and medical use. Somatic cell nuclear transfer (SCNT) is a technology applied in cloning, stem cell
research and regenerative medicine. Somatic cells are cells that
have gone through the differentiation process and are not germ
cells. Somatic cells donate their nuclei, which scientists

Format: Articles

Subject: Theories, Technologies, Processes

The Meselson-Stahl Experiment (1957–1958), by Matthew Meselson and Franklin Stahl

In an experiment later named for them, Matthew Stanley Meselson and Franklin William Stahl in the US demonstrated during the 1950s the semi-conservative replication of DNA, such that each daughter DNA molecule contains one new daughter subunit and one subunit conserved from the parental DNA molecule. The researchers conducted the experiment at California Institute of Technology (Caltech) in Pasadena, California, from October 1957 to January 1958.

Format: Articles

Subject: Processes, Experiments

The Process of Implantation of Embryos in Primates

Implantation is a process in which a developing embryo, moving as a blastocyst through a uterus, makes contact with the uterine wall and remains attached to it until birth. The lining of the uterus (endometrium) prepares for the developing blastocyst to attach to it via many internal changes. Without these changes implantation will not occur, and the embryo sloughs off during menstruation. Such implantation is unique to mammals, but not all mammals exhibit it.

Format: Articles

Subject: Processes

Biological Sex and Gender in the United States

In the United States, most people are assigned both a biological sex and gender at birth based on their chromosomes and reproductive organs. However, there is an important distinction between biological sex and gender. Biological sex, such as male, female, or intersex, commonly refers to physical characteristics. Gender refers to the socially constructed roles, behaviors, and actions people take on, usually in relation to expectations of masculinity or femininity. As of 2022, there is disagreement over the relation between sex and gender.

Format: Articles

Subject: Organizations, People, Processes, Ethics

“HPV in the Etiology of Human Cancer” (2006) by Nubia Muñoz, Xavier Castellsagué, Amy Berrington de González, and Lutz Gissmann

In 2006, the article “HPV in the Etiology of Human Cancer,” hereafter “HPV and Etiology,” by Nubia Muñoz, Xavier Castellsagué, Amy Berrington de González, and Lutz Gissmann, appeared as the first chapter in the twenty-fourth volume of the journal Vaccine. Muñoz and colleagues discuss the role of the Human Papillomavirus, or HPV, in uterine cervical cancers. The authors introduce the mechanisms of HPV infection that lead to genital and non-genital cancers, establishing a link between HPV and multiple human cancers.

Format: Articles

Subject: Disorders, Processes, Technologies

"The Role of Urethra in Female Orgasm" (1950), by Ernst Gräfenberg

In 1950, physician and researcher Ernst Gräfenberg published “The Role of Urethra in Female Orgasm,” in the International Journal of Sexology. The article was one of the first to mention the area in the anterior, or front, vaginal wall colloquially called the G-spot. In the article, Gräfenberg acknowledges that many females experience problems related to sexual satisfaction, and he argues that researchers and physicians of the time did not know enough information about the anatomical mechanisms and localization of the female orgasm to help them.

Format: Articles

Subject: Publications, Reproduction, Processes

“Female Ejaculation: A Case Study” (1981), by Frank Addiego, Edwin G. Belzer Jr., Jill Comolli, William Moger, John D. Perry, and Beverly Whipple

In 1981, Frank Addiego and colleagues published “Female Ejaculation: A Case Study” in The Journal of Sex Research. In the article, the authors find that female ejaculation, or the expulsion of fluid from a female’s urethra during or before orgasm, is a legitimate phenomenon that can occur when one stimulates an area in the vaginal wall that the team names the Gräfenberg-spot. According to the authors, at the time of publication, many individuals believed that if a female expelled fluid during orgasm, the fluid was urine and, thus, improper bladder control caused the expulsions.

Format: Articles

Subject: Publications, Processes, Reproduction

Luc Antoine Montagnier (1932-2022)

Luc Montagnier studied viruses, the immune system, and cancer in France during the second half of the twentieth century. In his early career, Montagnier studied how cancer-causing viruses replicate and infect host cells. He received the Nobel Prize in Physiology or Medicine in 2008 for his team’s discovery that a retrovirus, human immunodeficiency virus, or HIV, was the cause of acquired immunodeficiency syndrome, or AIDS. AIDS is a chronic condition that results from HIV infection and damages the immune system.

Format: Articles

Subject: People, Processes, Experiments

Sex Determination in Humans

In humans, sex determination is the process that determines the biological sex of an offspring and, as a result, the sexual characteristics that they will develop. Humans typically develop as either male or female, primarily depending on the combination of sex chromosomes that they inherit from their parents. The human sex chromosomes, called X and Y, are structures in human cells made up of tightly bound deoxyribonucleic acid, or DNA, and proteins.

Format: Articles

Subject: Processes, Processes

The Use of Morphine and Scopolamine to Induce Twilight Sleep

In 1907, researchers Bernhardt Kronig and Carl Gauss combined the drugs morphine and scopolamine to induce twilight sleep in women during childbirth. Physicians in the early twentieth century in Germany used twilight sleep, Dammerschlaf, to cause women to enter a state of consciousness in which they felt no pain and did not remember giving birth. Twilight sleep was associated with increased use of forceps during delivery, prolonged labor, and increased risk of infant suffocation.

Format: Articles

Subject: Processes

Pearl Luella Kendrick (1890–1980)

Pearl Luella Kendrick researched prevention for pertussis, commonly known as whooping cough, in Grand Rapids, Michigan, during the mid-1900s. Pertussis is a respiratory disease that mainly affects infants and young children. During the 1920s, pertussis was responsible for more deaths in children in the United States than any other disease. In the 1930s, Kendrick created one of the first pertussis vaccines that underwent large-scale clinical trials.

Format: Articles

Subject: People, Publications, Processes

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