Topics 18 - 22

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BIOL 370 – Developmental Biology

Compressed Final Lecture

Postembryonic Development

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BIOL 370 – Developmental Biology

Topic #18

Due to time constraints, I have decided to compress our final topics into a smaller format for presentation during our last lecture.

I am starting at the point where I left off in lecture last, and have already completed my discussion of many topics in Topic 18.

Regeneration of a salamander forelimb

Effects of vitamin A (a retinoid) on regenerating salamander limbs

Retinoic acid appears to help in regeneration in a variety of ways. The limbs of these salamanders had a more rapid regeneration when the growing regions were bathed in this vitamin a derivative.

Proximalization of blastema respecification by retinoic acid

Organisms must effect a compromise between the energy allocated to reproduction and growth and the energy allocated to the maintenance and repair of bodily tissues

Life span and the aging phenotype

The children in (B) have a condition called Hutchinson-Gilford Progeria. This is a genetic condition characterized by the dramatic, rapid appearance of aging beginning in childhood. Affected children typically look normal at birth and in early infancy, but then grow more slowly than other children and do not gain weight at the expected rate.

Survival curves for the U.S. population for the periods 1900–1902, 1949–1951, and 1999–2001

The Germ Line: Additional Concepts

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BIOL 370 – Developmental Biology

Topic #19

In addition to creating their own body tissues, an animal must also develop what are called germ cells. These cells will provide the material and instructions for the next generation of that organism.

In most of the organisms we have studied, there is a clear separation of germ cells from body (somatic) cells, but in some organisms the demarcation is not so obvious (from class…. the fern and the flatworm are examples).

In those groups that have a separate germ and somatic region, we can see two different methods of specification:

•Autonomous germ cell specification (fruit flies for example)

•Induced germ cell specification (mammals for example)

Photomicrograph of a section through a mouse teratocarcinoma, showing numerous differentiated cell types

A teratocarcinoma refers to a germ cell tumor that is a mixture of teratoma with embryonal carcinoma. This is a kind of mixed germ cell tumor.

Teratomas have been reported to contain hair, teeth, bone and, very rarely, more complex organs or processes such as eyes, torso, hands, feet, or other limbs.

Growth of oocytes in the frog

The number of germ cells in the human ovary changes over the life span

Medical Aspects of Developmental Biology:Birth Defects, Endocrine Disruptors, & Cancer

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BIOL 370 – Developmental Biology

Topic #20

Fate of 20 hypothetical human eggs in the United States and western Europe

100%

84%

69%

42%

35%

31%

Down syndrome

Down’s Syndrome is a mixture of various, albeit similar forms. The most common form is more specifically called Trisomy 21 Disorder. The CDC estimates that about one of every ~700 babies born in the United States each year is born with Trisomy 21 Disorder.

Mosaic and relational pleiotropy

In this example, the gene’s product is needed for both tissues to develop normally.

In this example, the gene’s product is needed for one tissue, but another product from the initial tissue is requited to guide normal development in a second tissue.

Weeks of gestation and sensitivity of embryonic organs to teratogens

Fetal Alcohol Syndrome - a pattern of mental and physical defects that can develop in a fetus in association with high levels of alcohol consumption during pregnancy. Alcohol crosses the placental barrier and can stunt fetal growth or weight, create distinctive facial stigmata, damage neurons and brain structures, which can result in psychological or behavioral problems, and cause other physical damage. The main effect of FAS is permanent central nervous system damage, especially to the brain.

Comparison of a brain from an infant with fetal alcohol syndrome (FAS) with a brain from a normal infant

Alcohol-induced craniofacial and brain abnormalities in mice

Genital anomalies can occur in women exposed to DES in utero

DES - Diethylstilbestrol is a synthetic estrogen first synthesized in 1938.

•It is now classified as an endocrine disruptor.

•From ~1940 to 1970, DES was sometimes perscribed to pregnant women to reduce the risk of pregnancy complications and loss.

•Public awareness grew when in 1971, DES was shown to cause a rare vaginal tumor in girls and women who had been exposed to this drug in utero.

Bisphenol A (BPA) – chemical used in some plastics and epoxy resins. First used in 1957, BPA-laden plastic is clear, tough, yet flexible. Plastic of this sort is used to make a variety of common consumer goods (for example, baby and water bottles, sports equipment, and CDs and DVDs) and lining water pipes.

Bisphenol A causes meiotic defects in maturing mouse oocytes

In these images, mouse oocytes are shown. (A) is showing normal meiosis associated with normal maturation. (B) is showing abnormal meiosis caused by BPA exposure. The result in the organism is decreased or absent fertility or abnormal chromosomal numbers in the eggs (aneuploidy).

Bisphenol A induces mammary lesions in mice

In more and more studies, BPA is being tied to increased instances of breast cancer.

Developmental estrogen syndrome is manifest in climbing rates of breast cancer and testicular dysgenesis

The unfortunately growing rate of exposures to environmental estrogens (endocrine disrupting compounds) has been associated with a variety of reproductive and associated systems abnormalities.

Seminiferous tubules from the testes of (A) a control rat and (B) a rat whose grandfather was born from a mother injected with vinclozolin

Vinclozolin is a fungicide used to control a variety of plant diseases including blights, rots and molds agriculturally. It is also used on turf on golf courses. It has been implicated in reproductive system issues as well as can be seen in (B) below.

Effects of estrogen implants on different strains of mice

Ecological Development: Biotic, Abiotic, and Symbiotic Regulation of Development

(Chapter 18 9th Edition; Chapter 19 10th edition)

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BIOL 370 – Developmental Biology

Topic #21

Figure 18.1 Developmental plasticity in insects

Figure 18.3 The presence or absence of horns determines the male reproductive strategy in some dung beetle species

Figure 18.4 Maternal diet can affect phenotype

End.

Developmental Mechanisms of Evolutionary Change

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BIOL 370 – Developmental Biology

Topic #22

Figure 19.9 Correlation between beak shape and the expression of Bmp4 in Darwin’s finches

Figure 19.10 Correlation between beak length and the amount of calmodulin (CaM) gene expression in Darwin’s finches

Figure 19.11 Role of BMP4 and calmodulin (CaM) in beak evolution in Darwin’s finches

Allometry is the study of the relationship of body size to shape,

anatomy , physiology and finally behaviour, first outlined by Otto Snell in 1892, D'Arcy Thompson in 1917 and Julian Huxley in 1932.

Figure 19.12 Allometric growth in the whale head

Figure 19.23 Mice with mutations in the leptin genes are genetically obese

End.

Developmental Mechanisms of Xenoplastic Specialization in Extra Terra Modalities

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BIOL 370 – Developmental Biology

Topic #23

Correlation between eyestalk shape and body configuration in green aliens (Viridis peregrinus)

Please notice how the eyestalk shape as well as the surprise effect have influenced the development of green alien (Viridis peregrinus) morphology.

Proceed to the next slide…

Suggestions to help in planning for the final examination in BIOL 370

The Biology 370 Final Examination is cumulative. That said, however, the focus is that roughly ½ of the exam is based upon “big picture, key concepts” associated with the first three exams. You will be provided a fairly comprehensive review sheet to help you in preparing for this comprehensive portion.

Follow the review sheet as a guide as you prepare for the comprehensive portion.

The other half of the exam is organized over the topics covered since exam #3 and follow the same sort of format and question styles as you have experienced in past exams.

I thank you for having been a part of BIOL 370 – Developmental Biology. I greatly enjoy teaching this course, and I am working hard to try to make it better each semester.