Dorsal surface

The area postrema is a circumventricular brain region positioned on the dorsal surface of the medulla on the floor of the fourth ventricle. The blood-brain barrier and the cerebrospinal fluid-brain barrier are absent in this region and consequently many substances that do not pass across capillaries in other regions of the brain can do so in the area postrema. The chemoreceptor trigger zone (CTZ), located in the lateral area postrema is sensitive to blood-borne emetogens. Nerves from the CTZ connect with the vomiting centre. 

The cerebellum (Latin, little brain) is part of the hindbrain and is attached to the dorsal surface of the upper region of the brainstem. Although it constitutes only 10% of the total volume of the brain, it contains more than half of all its neurons. Its surface consists of a thin cortex of gray matter with extensive folding, a core of white matter, and three pairs of nuclei embedded within it. 

Epidural anesthesia is administered by injecting local anesthetic into the epidural space. Located outside the spinal cord on its dorsal surface, the epidural space contains fat and is highly vascular. Therefore, this form of anesthesia can be performed safely at any level of the spinal cord. Furthermore, a catheter may be placed into the epidural space, allowing for continuous infusions or repeated bolus administrations of anesthetic. 

Figure 5.1 shows that the dorsal surface of mane, both black and white, is covered with the usual scaly structures found in a large number of species of animal hair. No significant difference was observed between white and black mane. The cross section of mane (Fig. 5.2) reveals a network of tubular spaces inside the hair. Small grooves or pockets within the concave scales are distinguishable at a magnification of 5000X. 

Fig. 5.1 Cross section through mane (1000X) of white lion showing dorsal surface and net work... 

The typical test (illustrated in Figure 15.7) is performed using mice, normally female CBA mice 6-10 weeks of age. Female BALB/c and ICR mice have also been used. After animal receipt, they are typically acclimated to standard laboratory husbandry conditions for 7-10 days. The usual protocol will consist of at least two groups (vehicle control and test article treated) of five mice each. They are treated on the dorsal surface of both ears with 25 pi (on each ear) of test article solution for three consecutive days. Twenty-four to forty-eight hours after the last test article exposure, the animals are given a bolus (0.25 ml) dose of [3H]thymidine (20 pCi with a specific activity of 5.0-7.0 Ci/mmol) in phosphate buffered saline via a tail vein. Five hours after the injection, the animals are euthanized by C02 asphyxiation and the auricular lymph nodes removed. 

Treat dorsal surface of each ear with 25 pL on three consecutive days... 

Tongue (dorsal surface) Left lower incisor... 

Mechanisms that then restore the basal cytosolic [Ca2+] levels remain unclear. Besides a Ca2+-ATPase on the osteoclast dorsal surface relatively little is known of alternative or parallel methods for Ca2+ extrusion (Zaidi et al., 1993) although there is recent functional, evidence for a Na+/Ca2+ exchanger that, in analogy to the regulation of cytoplasmic [Ca2+] in cardiac muscle could be linked to the proton extrusion that is a primary determinant of the rate and extent of bone resorption (Moonga et al., 2001). 

The leaves of Erythroxylon coca, the divine plant of the Incas, contain a local anesthetic and a psychostimulant. Erythroxylaceae is a very small family, represented by two genera, the more important of which is Erythroxylon. They are mostly tropical shrubs with entire leaves and 5-merous flowers, and the fruit is a 1-seeded, reddish drupe resembling that of dogwood. The anatomy of the plants of this family closely resembles that of the Linaceae. Of special interest is the development of papillae on the dorsal surface of the leaves. This is found in most species of Erythroxylon. 

Step 5 Beetle larvae are transferred to the dorsal surface of female host bee, transported to the nest and develop on pollen provided by the bee. 

No lethality was reported among rabbits when a saline suspension of 5,000 mg 4-nitrophenol/kg was applied to the abraded dorsal surface for 24 hours (Monsanto 1983b). The animals were observed for 15 days. No treatment-related deaths were observed in rats treated dermally with doses between 50 and 250 mg/kg/day of 4-nitrophenol for 120 days (Angerhofer 1985). In mice, application of a 47 mg/kg/day dose of 2-nitrophenol or 4-nitrophenol to shaved skin for 12 weeks did not alter the survival rate (Boutwell and Bosch 1959). The NOAELs are recorded in Table 2-3. 

AVMs of the perimedullary fistula type are direct AV shunts that are located on the ventral or dorsal surface of the spinal cord or the conus medullaris, usually in the thoracolumbar area, occasionally thoracic, and rarely cervical. Their location thus is intradural, intra- or extramedullary. They are always supplied by spinal cord vessels, either by the anterior spinal artery (ventrally) or by a posterolateral artery (dorsally), depending on their location. They drain into spinal cord veins (Fig. 17.12). Drainage may even ascend up to the foramen magnum or into the posterior fossa. 

To measure the response of legs to noxious mechanical stimulus, a paw pressure test was applied to the dorsal surface of both hind paws using a device capable of progressively increasing the pressure at a rate of 15 g/s. The pressure at which the rat withdrew the paw from the device wad defined as the paw pressure threshold, and the mean of both paws was used for analysis. A cutoff pressure of400 g was used to prevent damage to the paws. 

DNOC is generally not irritating to the skin of animals. No signs of local irritation or evidence of systemic toxicity were observed after 1.8% DNOC as the sodium salt was applied daily to the depilated dorsal surface of 10 rats or 6 rabbits for 30 days (Ambrose 1942). However, slight skin irritation was observed only on the abdomen after DNOC was applied to both the abdomen and the ears of rabbits daily, for 1 -7 days or for 5 days/week for 4 weeks (Spencer et al. 1948). 

No changes in body weight were observed after 1.8% DNOC as the sodium salt was applied daily to the depilated dorsal surface of 10 rats or 6 rabbits for 30 days (Ambrose 1942). 

Q3 The parathyroid glands are four structures usually located on the dorsal surface of the thyroid gland, two on the right and two on the left. In most individuals the glands are embedded in thyroid gland tissue however, in some individuals, they are separate from the thyroid gland. 

Although these rhythmic contractions of the extensor>tibiae are initiated by spontaneous depolarizations in certain fibers within the muscle, they are regulated by a specific cell on the dorsal surface of the metathoracic ganglion. This cell is found in a cluster of neurosecretory cells called the dorsal unpaired median (DUM) neurons. Neuromuscular transmission and muscular contraction in the extensor-tibiae muscle is modulated by the biogenic amine octopamine and by the peptides, proctolin, and FMRFamide. 

Photo 27.9 Left hand, dorsal surface. (Berger et al., 1997. Reproduced with permission of the Health Physics Society.)... 

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