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From Embryology

Lab 4 Online Assessment

  1. The allantois, identified in the placental cord, is continuous with what anatomical structure?
  2. Identify the 3 vascular shunts, and their location, in the embryonic circulation.
  3. Identify the Group project sub-section that you will be researching. (Add to project page and your individual assessment page)



Lab Attendance

--Z3290815 12:52, 28 July 2011 (EST)

--z3290815 11:05, 4 August 2011 (EST)

--z3290815 11:08, 11 August 2011 (EST)

--z3290815 11:01, 18 August 2011 (EST)

--z3290815 11:04, 25 August 2011 (EST)

--z3290815 11:03, 1 September 2011 (EST)

--z3290815 11:08, 15 September 2011 (EST)

Lab 1: Assessment

1. Identify the origin of In Vitro Fertilization and the 2010 nobel prize winner associated with this technique.

In Vitro Fertilization is one technique used in Assisted Reproduction Technology (ART) in which fertilization occurs outside of the body. In Vitro Fertilization is given its name from Latin origins; In Vitro meaning “in glass”. This is referring to the test tubes in which fertilization occurs, hence, the colloquial term for IVF babies are “test tube babies”. The first successful birth of an IVF baby was named Louise Brown born in the United Kingdom on the 25th of July, 1978. The development of In Vitro Fertilization and the successful birth of Louise Brown were by Robert G. Edwards. Consequently he received the Nobel Prize in Physiology or Medicine in 2010 for his developments. Although it wasn’t until 1978 when the first successful IVF human birth occurred, IVF can be dated as far back as the 1980’s by Walter Heape. He was a professor and physician and had conducted research on reproduction in multiple animal species and reported the first known case of embryo transplantation in a rabbit.

2. Identify a recent paper on fertilisation and describe its key findings.

The aim of this article[1] is to emphasize the advantages and the disadvantages of intracytoplasmic injection of sperm (ICSI) and how to maximise these potential benefits while minimising its complications. ICSI involves micromanipulation techniques involving the direct injection of spermatozoa into the oocyte.


Advantages:

  • ICSI helps males with severe infertility which cannot be amended through medicine or surgery the option to parent a genetically related child.
  • ICSI is used to alleviate severe male factor infertility due to the lack of sperm in the ejaculate due to severely impaired spermatogenesis.
  • Previously the primary treatment option for infertile men with obstructive azoospermia was vasovasostomy or vasoepididymostomy to reverse vasectomy.


Disadvantages:

  • There is increasing evidence of the involvement of genetic factors in male infertility and the potential risk of transmission of genetic disorders to the offspring.
  • A thorough genetic evaluation of the couple, classification of infertility and adequate counselling of the implications and associated risks prior to embarking on the procedure is necessary.

3. Identify 2 congenital anomalies.

A congenital anomaly is when there is something unusual or different at birth. This can be a minor anomaly whereby the anomaly has no serious medical or cosmetic concern or a major anomaly where there is a serious medical or cosmetic concern for example:

  • Atrial septal defect (ASD: form of congenital heart defect that enables blood flow between the left and right atria via the Interatrial septum.
  • Spina bifida: a developmental congenital disorder and neural tube defect caused by an incomplete closing of the embryonic neural tube.

Lab 2: Assessment

1. Identify the ZP protein that spermatozoa binds and how is this changed (altered) after fertilisation.

For fertilization to occur, the sperm must migrate through a layer of follicle cells and then bind to the egg coat called the zona pellucida. The crucial protein which allows the binding of a capacitated sperm to the zona pellucida is ZP3. As the binding is occurring, the sperm undergoes an acromosome reaction where exocytosis is released. This helps the sperm to maintain a tight binding to the zona pellucida while burrowing. Two mechanisms are in operation to block polyspermy from occurring (ensures that only one sperm fertilizes the egg); the primary block is the depolarization of the egg plasma membrane and the secondary block is provided by the egg cortical reaction.[2]

2. Identify a review and a research article related to your group topic.

Research Articles:

Congenital Hypomyelinating Neuropathy with Lethal Conduction Failure in Mice Carrying the Egr2 I268N Mutation[3]

  • Describes the engineering and characterisation of a mouse carrying the I268N mutation in Egr2.
  • The proper formation of myelin by Schwann cells requires a series of transcription factors including SOX10, SCIP/Oct6, Egr2, and Nab1/Nab2.
  • A loss of these transcription factors disrupts the myelination process, as does persistent overexpression.
  • This was observed in patients with recessively inherited Charcot–Marie–Tooth (CMT) disease type 4E, which is predicted to alter the ability of Egr2 to interact with the Nab transcriptional coregulatory proteins.
  • Charcot–Marie–Tooth disease (CMT) is a common inherited disorder of peripheral nerves characterized by progressive sensory loss and weakness beginning in the feet and legs, and later progressing to the hands
  • Mice homozygous for Egr2I268N developed a congenital hypomyelinating neuropathy similar to human counterparts.
  • Egr2I268N is expressed at normal levels in developing nerve but is unable to interact with Nab proteins or to properly activate transcription of target genes critical for proper peripheral myelin development.
  • Egr2I268N/I268N mutant mice maintain normal weight and have only mild tremor until 2 weeks after birth, at which point they rapidly develop worsening weakness and uniformly die within several days. Nerve electrophysiology revealed conduction block, and neuromuscular junctions showed marked

Congenital hypomyelinating neuropathy[4]

  • Describes the symptoms of two patients with congenital hypomyelinating neuropathy
  • Hypotonia = low muscle tone (amount of tension or resistance to movement in a muscle)
  • Areflexia = absence of neurologic reflexes such as the knee jerk
  • Distal muscle weakness
  • Atrophy = wasting of a part of the body
  • Exceedingly slow nerve conduction velocities
  • Usually leading to early death or severe disability.
  • It contains great images of the histology of the condition as well as the actual patients
  • It contains a detailed recount of sural nerve biopsies of the patients
  • It compares the symptoms of congenital hypomyelinating neuropathy in Trembler mice as they are very similar to human symptoms


Review Article:

Congenital hypomyelinating neuropathy: two patients with long-term follow-up[5]

  • Review of previously reported cases of congenital hypomyelinating neuropathy (CHN) aswell as two unrelated females with CHN
  • The first patient is now 9 years old and has showed continual improvement of motor function even though her follow up nerve conduction velocities remained unchanged
  • The second patient is now 5 years old and has also showed continual motor function improvement since her first visit even though her follow up nerve conduction velocities also remained unchanged

Differentially expressed RefSeq genes in human trisomy 21


Differentially expressed RefSeq genes in human trisomy 21.jpg


File:Differentially expressed RefSeq genes in human trisomy 21

Lab 3: Assessment

1. What is the maternal dietary requirement for late neural development?

Iodine[6] is an essential maternal dietary requirement for late neural development. Foetal thyroidogenes occurs by approximately the twelfth week of gestation and the foetal thyroid is capable of organifying iodine by approximately the 20th week of gestation. Before this time, maternal T4 is the only form of thyroid hormone that can traverse the placenta in small amounts. This must be adequate to meet the metabolic needs of the foetus.


Iodine deficiency remains the leading preventable cause of mental retardation worldwide.

Effects of Severe Iodine Deficiency:

  • Potential to cause both maternal and foetal hypothyroidism.
  • Poor obstetric outcomes including spontaneous abortion, prematurity, breech birth and stillbirth associated with adverse effects on the foetus including congenital anomalies, decreased intelligence, and neurological cretinism (which includes spasticity, deaf mutism, mental deficiency, and squint).
  • Linked to intellectual development in early childhood in the absence of overt mental retardation.
  • The IQ of iodine-sufficient children, on average, was 12.45 points higher.


Effects of Mild-to-Moderate Iodine Deficiency:

  • Less well understood than those of severe iodine deficiency but effects foetal neurodevelopment.
  • The infants with lower maternal fT4 had significantly lower psychomotor scores.
  • They found that lower maternal fT4 was associated with an increased risk of expressive language delay.
  • Significantly greater prevalence of attention deficit hyperactivity disorder (ADHD).
  • The IQ of iodine-sufficient children, on average, was 7 points higher.


The United States Institute of Medicine’s recommended daily allowance for iodine is 220mcg during pregnancy and 290mcg during lactation [20].

2. Upload a picture relating to you group project.

Hippocampal Formation.jpg

Figure 1: Hippocampal formation.[7]

Images of the hippocampal formation at the level of the lateral geniculate body from (A) patient 1 and (C) patient 3 show abnormal expansion of CA1 by increased numbers of pyramidal neurons. These are compared with the more usual hippocampal microarchitecture that shows a thinner linear band of neurons in CA1, as seen in (B) a 62-year-old male control. Haematoxylin and eosin, original magnification ×10; scale bar = 1 mm. Arrow indicates bulge/expansion composed of increased numbers of pyramidal cells in (A) patient 1 and (C) patient 3.

Copyright: This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

File: Hippocampal_Formation

Lab 4: Assessment

1. The allantois, identified in the placental cord, is continuous with what anatomical structure?

The allantois is an endodermal evagination of the developing hindgut which collects liquid waste and exchange gases used by the embryo. Therefore the allantois is connected to the fetal bladder via the urachus.

2. Identify the 3 vascular shunts, and their location, in the embryonic circulation.

  • Ductus arteriosus: is a shunt connecting the pulmonary artery to the aortic arch which allows most of the blood from the right ventricle to bypass the foetus's fluid-filled lungs.
  • Ductus venosus: shunts the blood flow of the umbilical vein directly to the inferior vena cava. To allow oxygenated blood from the placenta to bypass the liver.
  • Foramen ovale: allows highly oxygenated blood to communicate between the left and right atrium.

3. Identify the Group project sub-section that you will be researching.

  • History
  • Epidemiology

Lab 5: Assessment

1. Which side (L/R) is most common for diaphragmatic hernia and why?

90% of foetal diaphragmatic hernias are found on the left side of the diaphragm. Depending on how large the hole is, the intestines, spleen, liver and/or stomach may move up into the chest cavity causing the lungs to develop poorly.

Lab 6: Assessment

1. What week of development do the palatal shelves fuse?

The primary palate fuses in the human embryo between week 6 and 7. The secondary palate fuses in week 9 of embryological development which requires the growth of the palatal shelves.

2. What early animal model helped elucidate the neural crest origin and migration of neural crest cells?

Both the chicken model and quail-chick chimeras were used as early animal models which helped explain the neural crest origin and migration of neural crest cells. Chicken embryo sequencing can show the migration of Dii-labelled neural crest cells towards the brachial arches and Nicole Le Douarin pioneered the quail-chick in the 1980’s as a way to study the migration path and final destination of transplanted neural crest cells.

3. What abnormality results from neural crest not migrating into the cardiac outflow tract?

If neural crests do not migrate to the cardiac outflow tract, than due to the reduction in number of cells added to the myocardium of the distal outflow tract, there will be a subsequent shortening of this tract. The shortened outflow tract leads to an altered cardiac looping. This malalignment of the outflow tract is seen as a dextroposed aorta which in babies, is classified as the congenital abnormality Tetralogy of Fallot[8].

Lab 7: Assessment

Lab 8: Assessment

Lab 9: Assessment

Lab 10: Assessment

Lab 11: Assessment

Lab 12: Assessment

References

  1. <pubmed>21716935</pubmed>
  2. B. Alberts, A. Johnson, J. Lewis, et al. Fertilization. Molecular Biology of the Cell. 4th edition. http://www.ncbi.nlm.nih.gov/books/NBK26843/
  3. <pubmed>19244508</pubmed>
  4. <pubmed>10207934</pubmed>
  5. <pubmed>4087003</pubmed>
  6. <pubmed>21765996</pubmed>
  7. <pubmed>21303513</pubmed>
  8. http://circ.ahajournals.org/content/106/4/504.full.pdf