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The Neuron Doctrine (1860-1895)

The neuron doctrine is a concept formed during the turn of the twentieth century that describes the properties of neurons, the specialized cells that compose the nervous system. The neuron doctrine was one of two major theories on the composition of the nervous system at the time. Advocates of the neuron doctrine claimed that the nervous system was composed of discrete cellular units. Proponents of the alternative reticular theory, on the other hand, argued that the entire nervous system was a continuous network of cells, without gaps or synapses between the cells.

Format: Articles

Subject: Theories

"Testing the Kin Selection Theory: Who Controls the Investments?" from The Ants (1990), by Bert Hölldobler and Edward O. Wilson

In “Testing the Kin Selection Theory: Who Controls the Investments?” Bert Hölldobler and Edward Osborne Wilson discussed the predictive power of kin selection theory, a theory about the evolution of social behaviors. As part of Hölldobler's and Wilson's 1990 book titled The Ants, Hölldobler and Wilson compared predictions about the reproductive practices of ants to data about the reproductive practices of ants. They showed that the data generally supported the expected behaviors proposed by kin selection theory.

Format: Articles

Subject: Publications, Theories

Sex-determining Region Y in Mammals

The Sex-determining Region Y (Sry in mammals but SRY in humans) is a gene found on Y chromosomes that leads to the development of male phenotypes, such as testes. The Sry gene, located on the short branch of the Y chromosome, initiates male embryonic development in the XY sex determination system. The Sry gene follows the central dogma of molecular biology; the DNA encoding the gene is transcribed into messenger RNA, which then produces a single Sry protein.

Format: Articles

Subject: Processes

"Male Development of Chromosomally Female Mice Transgenic for Sry gene" (1991), by Peter Koopman, et al.

Early 1990s research conducted by Peter Koopman, John Gubbay, Nigel Vivian, Peter Goodfellow, and Robin Lovell-Badge, showed that chromosomally female (XX) mice embryos can develop as male with the addition of a genetic fragment from the Y chromosome of male mice. The genetic fragment contained a segment of the mouse Sry gene, which is analogous to the human SRY gene. The researchers sought to identify Sry gene as the gene that produced the testis determining factor protein (Tdf protein in mice or TDF protein in humans), which initiates the formation of testis.

Format: Articles

Subject: Experiments

Clinica Para Madres (1934-1950)

The Clinica Para Madres (Mother’s Clinic) opened in Tucson, Arizona, in December of 1934 as the first birth control clinic in Arizona. After moving to Tucson, birth control activist Margaret Sanger, along with a group of local philanthropic women, founded the clinic to provide Arizona women with contraception. During the early 1900s in the US, contraception was illegal under the federal Comstock Act. Additionally, many viewed contraception and sex as obscene and not to be discussed in public or outside of marriage.

Format: Articles

Subject: Organizations, Reproduction, Outreach

Temperature-Dependent Sex Determination in Reptiles

The sex of a reptile embryo partly results from the production of sex hormones during development, and one process to produce those hormones depends on the temperature of the embryo's environment. The production of sex hormones can result solely from genetics or from genetics in combination with the influence of environmental factors. In genotypic sex determination, also called genetic or chromosomal sex determination, an organism's genes determine which hormones are produced.

Format: Articles

Subject: Experiments

Intraspecies Chimeras Produced in Laboratory Settings (1960-1975)

When cells-but not DNA-from two or more genetically distinct individuals combine to form a new individual, the result is called a chimera. Though chimeras occasionally occur in nature, scientists have produced chimeras in a laboratory setting since the 1960s. During the creation of a chimera, the DNA molecules do not exchange genetic material (recombine), unlike in sexual reproduction or in hybrid organisms, which result from genetic material exchanged between two different species. A chimera instead contains discrete cell populations with two unique sets of parental genes.

Format: Articles

Subject: Organisms, Processes

James Young Simpson (1811–1870)

James Young Simpson was one of the first obstetricians to administer anesthesia during childbirth in nineteenth century Scotland. Before his work in the 1800s, physicians had few ways to reduce the pain of childbirth. Simpson experimented with the use of ether and chloroform, both gaseous chemicals, to temporarily relieve pain. He found that those chemicals both successfully inhibited the pain women felt during childbirth and pain during other surgeries. Patients under the influence of chloroform fell asleep and were unaware of the intense pain of childbirth.

Format: Articles

Subject: People

Impact of Air Pollution on Reproductive Health” (1999), by Radim Srám

In 1999, researcher Radim Srám, sometimes spelled Radim Šrám, published his article “Impact of Air Pollution on Reproductive Health” in the journal Environmental Health Perspectives. In the article, Srám analyzes the effects of exposure to air pollution, which can include harmful chemicals, on fetal growth and development. Srám discusses how industrialized countries such as the US and China have led to an increase in the global amount of respirable air pollutants.

Format: Articles

Subject: Publications

The China-US Study on the Prevention of Neural Tube Defects using Folic Acid (1999)

From 1993 to 1995 researchers led by Robert J. Berry from the US Centers for Disease Control headquartered in Atlanta, Georgia, and Zhu Li from Beijing Medical University in Beijing, China, conducted a collaborative study in China on the prevention of neural tube defects or NTDs using folic acid supplements. NTDs are birth defects in which openings in the spinal cord or the brain that occur during early development remain after birth. Neural-tube formation occurs in early pregnancy, often before a woman knows she is pregnant and therefore before she has begun taking prenatal vitamins.

Format: Articles

Subject: Experiments

Annie Dodge Wauneka (1910-1997)

Annie Dodge Wauneka, a member of the Navajo Tribal Council in Window Rock, Arizona, from 1951 to 1978, advocated for improved lifestyle, disease prevention, and access to medical knowledge in the Navajo Indian Reservation, later renamed the Navajo Nation. Wauneka served as chair of the Health and Welfare Committee of the Navajo Tribal Council and as a member of the US Surgeon General’s Advisory Committee on Indian Health. Wauneka advocated for initiatives aimed at promoting education, preventing tuberculosis, and reducing the infant mortality rate.

Format: Articles

Subject: People

Diprosopus (Craniofacial Duplication)

Diprosopus is a congenital defect also known as craniofacial duplication. The exact description of diprosopus refers to a fetus with a single trunk, normal limbs, and facial features that are duplicated to a certain degree. A less severe instance is when the nose is duplicated and the eyes are spaced far apart. In the most extreme instances, the entire face is duplicated, hence the name diprosopus, which is Greek for two-faced. Fetuses with diprosopus often also lack brains (anencephaly), have neural tube defects, or heart malformations.

Format: Articles

Subject: Disorders, Reproduction

Mitochondrial Diseases in Humans

Mitochondrial diseases in humans result when the small organelles called mitochondria, which exist in all human cells, fail to function normally. The mitochondria contain their own mitochondrial DNA (mtDNA) separate from the cell's nuclear DNA (nDNA). The main function of mitochondria is to produce energy for the cell. They also function in a diverse set of mechanisms such as calcium hemostasis, cell signaling, regulation of programmed cell death (apoptosis), and biosynthesis of heme proteins that carry oxygen.

Format: Articles

Subject: Disorders, Reproduction

Amniocentesis

Amniocentesis is a test used for prenatal diagnosis of inherited diseases, Rh incompatibility, neural tube defects, and lung maturity. Normally performed during the second trimester of a pregnancy, this invasive procedure allows the detection of health problems in the fetus as early as fifteen weeks gestation. Although amniocentesis does carry some significant risks, the medical community commonly accepts it as a safe and useful procedure.

Format: Articles

Subject: Technologies, Reproduction

"Gene Regulation for Higher Cells: A Theory" (1969), by Roy J. Britten and Eric H. Davidson

In 1969, Roy J. Britten and Eric H. Davidson published Gene Regulation for Higher Cells: A Theory, in Science. A Theory proposes a minimal model of gene regulation, in which various types of genes interact to control the differentiation of cells through differential gene expression. Britten worked at the Carnegie Institute of Washington in Washington, D.C., while Davidson worked at the California Institute of Technology in Pasadena, California. Their paper was an early theoretical and mechanistic description of gene regulation in higher organisms.

Format: Articles

Subject: Publications

Oral Glucose Tolerance Test for Gestational Diabetes

In the twentieth century, researchers developed the oral glucose tolerance test, or OGTT, as a method to diagnose different types of diabetes, a medical condition that causes blood sugar levels to become abnormally high. During the test, a healthcare provider measures a person’s blood sugar levels before and after the person consumes a predetermined amount of glucose solution. While not exclusively used for pregnant women, an OGTT may test for gestational diabetes which, according to the International Diabetes Federation, affected one in six pregnancies worldwide in 2019.

Format: Articles

Subject: Technologies, Reproduction, Experiments

The March of Dimes Foundation

The March of Dimes Foundation, or the March of Dimes, is a non-profit organization headquartered in Arlington, Virginia, focused on the health of pregnant women and infants in the US. Former United States president Franklin Delano Roosevelt founded the March of Dimes, then called the National Foundation for Infantile Paralysis, in 1938 to address polio. Polio is a viral illness that infects the spinal cord and may lead to paralysis. Roosevelt contracted polio in 1921, which left him permanently paralyzed from the waist down.

Format: Articles

Subject: Organizations

The Whelan Method of Sex Selection

The Whelan Method of Sex Selection is a method for increasing a couple’s probability of conceiving an infant of the desired sex through timing intercourse. Elizabeth Whelan, a public health researcher, suggested that couples only have intercourse at specific times during the woman’s menstrual cycle based on whether they wanted a female or male infant. Whelan published her method in her book, Boy or Girl, in 1977.

Format: Articles

Subject: Technologies

Pregnancy Tests

Throughout history methods involving urine have been a popular way to test for pregnancy. Early ideas ranged from simply observing the color of a woman's urine to the notion that the urine of pregnant women contains special crystals or secretions. Indeed, pregnancy testing can be traced back to 1350 BCE in Ancient Egypt. A written document from the time describes a process in which a woman would urinate on wheat and barley seeds over several days and, depending on which plant grew, both the woman's pregnancy status and the sex of the fetus could be determined.

Format: Articles

Subject: Technologies, Reproduction

Alan Mathison Turing (1912-1954)

Alan Mathison Turing was a British mathematician and computer scientist who lived in the early twentieth century. Among important contributions in the field of mathematics, computer science, and philosophy, he developed a mathematical model of morphogenesis. This model describing biological growth became fundamental for research on the process of embryo development.

Format: Articles

Subject: People

Tissue Engineering

Tissue engineering is a field of regenerative medicine that integrates the knowledge of scientists, physicians, and engineers into the construction or reconstruction of human tissue. Practitioners of tissue engineering seek to repair, replace, maintain, and enhance the abilities of a specific tissue or organ by means of living cells. More often than not stem cells are the form of living cells used in this technology. Tissue engineering is one of the disciplines involved in translating knowledge of developmental biology into the clinical setting.

Format: Articles

Subject: Processes

George Richard Tiller (1941-2009)

George Richard Tiller, a doctor who performed abortions in Wichita, Kansas, was shot to death on 31 May 2009 by Scott Roeder. As the director of one of only a small number of clinics in the US that performed legal late-term abortions, Tiller was a target for anti-abortion activists. Though Tiller lived and worked in Kansas, his work agitated anti-abortion groups and fueled the controversy surrounding abortion at a national level. Tiller's life and death fueled the abortion debate in the US.

Format: Articles

Subject: People, Reproduction

The Discovery of The Dikika Baby Fossil as Evidence for Australopithecine Growth and Development

When scientists discovered a 3.3
million-year-old skeleton of a child of the human lineage (hominin) in
2000, in the village of Hadar, Ethiopia, they were able to study growth
and development of Australopithecus
afarensis, an extinct hominin species. The team of researchers,
led by Zeresenay Alemseged of the Max Planck Institute for Evolutionary
Anthropology in Leipzig, Germany, named the fossil DIK 1-1 and nicknamed
it Dikika baby after the Dikika research site. The Dikika fossil

Format: Articles

Subject: Theories

The Y-Chromosome in Animals

The Y-chromosome is one of a pair of chromosomes that determine the genetic sex of individuals in mammals, some insects, and some plants. In the nineteenth and twentieth centuries, the development of new microscopic and molecular techniques, including DNA sequencing, enabled scientists to confirm the hypothesis that chromosomes determine the sex of developing organisms. In an adult organism, the genes on the Y-chromosome help produce the male gamete, the sperm cell. Beginning in the 1980s, many studies of human populations used the Y-chromosome gene sequences to trace paternal lineages.

Format: Articles

Subject: Reproduction, Theories

Josef Warkany (1902–1992)

Josef Warkany studied the environmental causes of birth defects in the United States in the twentieth century. Warkany was one of the first researchers to show that factors in the environment could cause birth defects, and he helped to develop guidelines for the field of teratology, the study of birth defects. Prior to Warkany’s work, scientists struggled to explain if or how environmental agents could cause birth defects. Warkany demonstrated that a deficiency or excess of vitamin A in maternal nutrition could cause birth defects.

Format: Articles

Subject: People