Embryo sectioning

Peripheral axotomy caused a decrease of Y1 mRNA in the small neurons and an increase in large neurons. These results suggested that the DRG Y1 receptor is mosdy a prejunctional receptor in primary afferent neurons and that it may play a role in the modulation of somatosensory information (Zhang et al., 1994). Low levels of Y1 mRNA have also been reported for rat splenic lymphocytes as documented by a partial cDNA clone, PCR and RNase protection (Petitto et al., 1994). A developmental study by in situ hybridization of whole rat embryo sections (Jazin et al., 1993) detected the earliest Y1 mRNA around day 14, both in diencephalon and spinal cord. 

A EXPERIMENTAL FIGURE 15-19 Maternally derived bicoid mRNA is localized to the anterior region of early Drosophila embryos. All embryos shown are positioned with anterior to the left and dorsal at the top. In this experiment, In situ hybridization with a radloactively labeled RNA probe specific for bicoid mRNA was performed on whole-embryo sections 2.5-3.5 hours after fertilization. 

Note that, when performing notochord ablations, the remarks on improving the visibility of the embryo (section 3.3.2.1) and reincubation of operated embryos (section 33.2.3) apply. 

We have utilized time-of-flight secondary ion mass spectrometry (ToF-SIMS) to image tissues by their secondary ions in deparaffinized mouse embryo sections. We have then differentiated these tissues based on differences in small molecules remaining after paraffin imbedding and fragments of the tissue proteins. These experiments serve as a preliminary study for further investigation of clinical FFPE samples from tumor and normal tissues. 

Embryo sections 1-11 are incubated at 40°C for overnight. Sections 1-10 on Si chips are then placed between clean glass slides that are pre-loaded in a glass slide holder (tee Note 4). 

Embryo section number 11 is deparaffinized and rehydrated by rinses in Clearene, 100, 95, 80% ethanol, and DI water. It is then stained with hematoxylin and eosin (H E) and dehydrated by rinses in 95 and 100% ethanol and Clearene. The slide with section number 11 is coverslipped using Per-mount and then observed under an optical microscope. An example of the optical image of an H E stained mouse embryo section is shown in Fig. 16.1a. The identified tissues in this section are used as a reference for the ToF-SIMS analysis. 

Mouse embryo section number 10 is selected for tissue imaging analysis. Load the sample into the ToF-SIMS instrument and pump down to 5x10 torr before analysis. 

Mouse embryo section number 10 is further analyzed with the same ToF-SIMS instrumental and data acquisition settings as the ones in tissue imaging analysis. Ten measurements are recorded for each of the six tissue types skull, rib, brain, spinal cord, heart, and liver, with each measurement covering a fresh, un-analyzed area. 

Each of the ten embryo sections is analyzed twice over a period of 1 month. The embryo sections are analyzed in a random order (see Note 13). To minimize instrument-induced variations, the instrument settings should remain unchanged throughout the whole experiment (fccNote 14). 

Never recycle or re-use Si substrates to avoid possible crosscontamination. The sliced embryo sections should be place at the center of the Si substrates with at least 1 mm margin... 

To avoid sample to sample variation indnced by the deparaffinization process, all embryo sections should be deparaffinized at a same time. Use fresh chemicals for all steps of deparaffinization and dehydration. 

Finally, there is evidence that constituents of technical DDT can have a feminizing effect on avian embryos (for further discussion, see Chapter 15, Section 15.6). Of... 

As stated in Section 2.1, there is a waiting period between the time of release of one bubble and the time of nucleation of the next at a given nucleation site. This is the period when the thermal boundary layer is reestablished and when the surface temperature of the heater is reheated to that required for nucleation of the next bubble. To predict the waiting period, Hsu and Graham (1961) proposed a model using an active nucleus cavity of radius rc which has just produced a bubble that eventually departs from the surface and has trapped some residual vapor or gas that serves as a nucleus for a new bubble. When heating the liquid, the temperature of the gas in the nucleus also increases. Thus the bubble embryo is not activated until the surrounding liquid is hotter than the bubble interior, which is at... 

Regulatory guidelines require that there be maternal toxicity at the highest dosage level in embryo-fetal developmental toxicity studies. It is important to avoid excessive toxicity in these studies since it is known that marked maternal toxicity can cause secondary developmental toxicity (see discussion in Section 8.4.3, Association between Developmental and Maternal Toxicity ). This secondary developmental toxicity is irrelevant to the assessment of the developmental hazard of the test agent and thus simply confounds the interpretation of the data. 

A cross-sectional view of a C. digitata seed is shown in a scanning electron micrograph (SEMT in Figure 1. The section was treated with hexane before being sputter-coated (12) and is morphologically identical to a similar view of C. pepo (12). The seed coat comprises the somewhat thin outer boundary of TRe section and the remainder is composed of two cotyledons separated by the first "true" leaves of the embryo. 

A burning issue is the ethics of obtaining pluripotent stem cells from embryos and fetuses. The US government has acted on this issue and declared that federal funds for stem cell research have to meet certain criteria. It requires that funding will only be provided to research with stem cells obtained before August 9, 2001, as a cut-off date to limit research to preexisting stem cells. Refer to Section 11.7 for an ethical debate on stem cells. 

As discussed in Section 4.7, stem cells have the potential to treat medical conditions beyond the scope that can be offered by drugs alone. However, there are many scientific and ethical hurdles to overcome. On the scientific front, stem cell research activities will intensify over the next decade. These challenges can broadly be divided into (1) determining how to develop stem cells into specific tissues and (2) implanting these tissues into the body without rejection by the recipient s immune system. On the ethical front, it is expected that there will be more debates on the ethical issues of stem cell research. Most scientists consent to therapeutic cloning (stem cell research) but not reproductive cloning. The ethical issue of stem cell research concerns harvesting cells from embryos that are a few days old. This action destroys the embryos. Some questions are ... 

From nucleation theory (see Section IX), one can estimate the expected rate of formation of critical-sized vapor embryos in a liquid as a function of temperature. This rate is a very strong function of temperature emd changes from a vanishingly low value a few degrees below the homogeneous nucleation temperature to a very large value at this temperature. 

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