Muhamed Saric, MD, PhD, FACC, FASE
- Associate Director, Echocardiography Laboratory
- Associate Professor, New York University
- School of Medicine
- New York, New York
A blow on the side of the head may easily fracture the thin anterior part of the parietal bone impotence lab tests purchase malegra fxt plus 160 mg otc. The anterior branch of the middle meningeal artery commonly enters a bony canal in this region and is sectioned at the time of the fracture erectile dysfunction caused by heart medication generic 160mg malegra fxt plus free shipping. The resulting hemorrhage causes gradual accumulation of blood under high pressure outside the meningeal layer of the dura mater erectile dysfunction usmle buy 160 mg malegra fxt plus. The pressure is exerted on the underlying brain as the blood clot enlarges erectile dysfunction caffeine order malegra fxt plus 160mg line, and the symptoms of confusion and irritability become apparent. Pressure on the lower end of the motor area of the cerebral cortex (the right precentral gyrus) causes twitching of the facial muscles and,later,twitching of the left arm muscles. A detailed account of the various changes that occur in the skull in patients with an intracranial tumor is given on page 23. A patient suspected of having an intracranial tumor should not undergo a spinal tap. The withdrawal of cerebrospinal fluid may lead to a sudden displacement of the cerebral hemisphere through the opening in the tentorium cerebelli into the posterior cranial fossa or herniation of the medulla oblongata and cerebellum through the foramen magnum. The brain is floating in the cerebrospinal fluid within the skull, so a blow to the head or sudden deceleration leads to displacement of the brain. This may produce severe cerebral damage; stretching or distortion of the brainstem; avulsion of cranial nerves; and commonly, rupture of tethering cerebral veins. The spinal cord has (a) an outer covering of gray matter and an inner core of white matter. The following statements concern the cerebellum: (a) It lies within the middle cranial fossa. The following statements concern the cerebrum: (a) the cerebral hemispheres are separated by a fibrous septum called the tentorium cerebelli. The following statements concern the peripheral nervous system: (a) There are ten pairs of cranial nerves. The following statements concern the cerebrospinal fluid: (a) the cerebrospinal fluid in the central canal of the spinal cord is unable to enter the fourth ventricle. The following statements concern the vertebral levels and the spinal cord segmental levels: (a) the first lumbar vertebra lies opposite the L3-4 segments of the cord. Within an hour,she was found to have a large doughlike swelling over the right temporal region. A lateral radiograph of the skull showed a fracture line running downward and forward Answers and Explanations to Review Questions 31 across the anterior inferior angle of the right parietal bone. Select the most likely cause of the swelling over the right temporal region in this patient. Select the most likely cause of the muscular paralysis of the left side of the body in this patient. Radiologic examination of the lumbar region of the vertebral column revealed significant narrowing of the spinal canal caused by advanced osteoarthritis. Examination of the patient revealed weakness and some wasting of the muscles of the left leg. Radiologic examination showed that the osteoarthritic changes had spread to involve the boundaries of many of the lumbar intervertebral foramina. Anterior and posterior roots of a single spinal nerve are attached to a single spinal cord segment. The spinal cord has an outer covering of white matter and an inner core of gray matter. The cells in the posterior gray horn of the spinal cord are associated with sensory function (see p. The lower end of the medulla oblongata is directly continuous with the spinal cord in the foramen magnum. The medulla oblongata has a central canal in its lower part that is continuous with that of the spinal cord. The midbrain is completely surrounded with cerebrospinal fluid in the subarachnoid space (see p. The midbrain has a cavity called the cerebral aqueduct, which opens above into the third ventricle. The vermis is the name given to that part of the cerebellum joining the cerebellar hemispheres together (see p. The dentate nucleus is a mass of gray matter found in each cerebellar hemisphere (see p.
Unlike the situation in mammals impotence nerve damage generic 160mg malegra fxt plus, sex determination in reptiles (and birds) is hormone-dependent erectile dysfunction medication for sale malegra fxt plus 160mg line. Estrogen can override temperature and induce ovarian differentiation even at masculinizing temperatures erectile dysfunction treatment herbal remedy order malegra fxt plus 160 mg. Similarly erectile dysfunction in diabetes mellitus pdf purchase 160 mg malegra fxt plus mastercard, injecting eggs with inhibitors of estrogen synthesis will produce male offspring, even if the eggs are incubated at temperatures that usually produce females (Dorizzi et al. Moreover, the sensitive time for the effects of estrogens and their inhibitors coincides with the time when sex determination usually occurs (Bull et al. It appears that the enzyme aromatase (which can convert testosterone into estrogen) is important in temperaturedependent sex determination. The estrogen synthesis inhibitors used in the experiments mentioned above worked by blocking the aromatase enzyme, showing that experimentally low aromatase conditions yield male offspring. The aromatase activity of Emys is very low at the male-promoting temperature of 25°C. At the female-promoting temperature of 30°C, aromatase activity increases dramatically during the critical period for sex determination (Desvages et al. Temperature-dependent aromatase activity is also seen in diamondback terrapins, and its inhibition masculinizes their gonads (Jeyasuria et al. One remarkable finding is that the injection of an aromatase inhibitor into the eggs of an all-female parthenogenetic species of lizards causes the formation of males (Wibbels and Crews 1994). It is not known whether the temperature sensitivity resides in the aromatase gene or protein itself or in other proteins that regulate it. One hypothesis is that the temperature is sensed by neurons in the central nervous system and transduced to the bipotential gonad by nerve fibers (see Lance 1997). This sex-determining gene is seen throughout the vertebrates, where its expression in gonads correlates extremely well with the production of testes. When two species of turtles were raised at female-promoting temperatures, Sox9 expression was down-regulated during the critical time for sex determination. However, in the bipotential gonads of those turtles raised at male-promoting temperatures, Sox9 expression was retained in the medullary sex cords destined to become Sertoli cells (Spotila et al. The evolutionary advantages and disadvantages of temperature-dependent sex determination are discussed in Chapter 21. This knowledge may have important consequences in environmental conservation efforts to protect endangered turtle species. Location-dependent sex determination in Bonellia and Crepidula As mentioned in Chapter 3, the sex of the echiuroid worm Bonellia depends on where a larva settles. If a Bonellia larva lands on the ocean floor, it develops into a 10-cm-long female. Therein it differentiates into a minute (1 3-mm-long) male that is essentially a spermproducing symbiont of the female (see Figure 3. Another example in which sex determination is affected by the location of the organism is the case of the slipper snail Crepidula fornicata. In this species, individuals pile up on top of one another to form a mound (Figure 17. This phase is followed by the degeneration of the male reproductive system and a period of lability. Similarly, the presence of large numbers of males will cause some of the males to become females. However, once an individual becomes female, it will not revert to being male (Coe 1936). More examples of context-dependent sex determination will be studied in Chapter 21. In some species, including most mammals and insects, sex is determined solely by chromosomes; in other species, sex is a matter of environmental conditions. We are finally beginning to understand the mechanisms by which this masterpiece is created. In mammals, primary sex determination (the determination of gonadal sex) is a function of the sex chromosomes. Germ cells enter the sex cords, but will not be released from the gonad until puberty.
A frequent association of cellular atypia and urothelial cell malignancies has also been reported in experimental animals and in many affected patients erectile dysfunction pill purchase malegra fxt plus 160mg. Because many affected patients have undergone kidney transplantation with immunosuppressive therapy erectile dysfunction drugs cost comparison order malegra fxt plus 160mg without a prescription, routine surveillance of urinary cytology is generally recommended in view of this association with urothelial malignancy erectile dysfunction commercials order malegra fxt plus 160 mg free shipping. A diagnostic test has not been developed for Balkan nephropathy erectile dysfunction exercise discount malegra fxt plus 160 mg free shipping, and there is not currently a specific treatment or preventive strategy for the disorder. Although the clinical course and affected populations for Balkan nephropathy and aristolochic acid nephropathy are quite distinct, the two entities share many similarities. Both diseases have been linked to aristolochic acid exposure, have predominant renal cortical pathology, and are associated with urothelial tumors. Studies have reported a wide range of tumor incidence, from 2% to 47%, in patients with Balkan nephropathy. These observations have further implicated aristolochic acid in the pathogenesis of Balkan nephropathy. Although interstitial disease, at times with noncaseating granuloma formation, is relatively common in sarcoidosis (15% to 30%), autopsy series indicate that it is unusual for the interstitial abnormalities to result in clinically significant kidney dysfunction. Moreover, it is unusual to observe interstitial disease in the absence of extrarenal involvement in sarcoidosis. Although most patients with impaired kidney function respond well to corticosteroid therapy, recovery of kidney function is frequently incomplete because of chronic interstitial inflammation and fibrosis. Presentation with hypercalcemia has been associated with more sustained response to corticosteroid therapy 1 year following therapy. It occurs most commonly along the confluence of the Danube River and has been reported almost exclusively in farmers. Although the disease etiology has not been elucidated, several environmental toxins (plant nephrotoxins, mycotoxins, trace metals, and aromatic hydrocarbons) have been explored. The tendency for clustering of cases in families has also suggested that genetic variables may play a role in disease susceptibility, and several recent studies suggest that disease is induced by chronic exposure to aristolochic acid in susceptible individuals. Because Aristolochia plants grow abundantly in agricultural areas, harvesting of crops such as wheat from contaminated fields could introduce aristolochic acid into the local food supply, exposing the population to the nephrotoxin. It is typically observed after the fourth decade of life and rarely affects patients younger than 20 years of age. Patients generally present with normal blood pressure and either normal or slightly reduced kidney size on ultrasonography. Circulating autoantibodies (anti-Ro and anti-La) are associated with Sjцgren syndrome, and they support the diagnosis. Kidney involvement has been reported in up to 67% of affected patients in some case series. The kidney lesion noted on biopsy consists predominantly of interstitial cellular infiltrates that invade and destroy renal tubules. With disease chronicity in Sjцgren syndrome, tubular atrophy and interstitial fibrosis are more apparent, and patients may exhibit biochemical disorders from tubular dysfunction. As with sarcoidosis treatment, patients typically respond to a course of corticosteroids. Brause M, Magnusson K, Degenhardt S, et al: Renal involvement in sarcoidosis-a report of 6 cases, Clin Nephrol 57:142-148, 2002. Evans M, Elinder C- G: Chronic renal failure from lead: myth or evidencebased fact? Sutherland Obstruction of the urinary tract can occur anywhere from the collecting duct to the urethral meatus. Microcrystals in the collecting duct, urinary calculi, tumors, and luminal strictures can block the normal flow of urine. Regardless of the cause, the ultimate effect is the same, an increase in the hydrostatic pressure of the collecting system, which is transmitted into Bowman space. The extent of kidney function loss and the damage to the physical structures of the collecting system varies depending on the duration and completeness of the obstruction. In an unobstructed kidney, when glomerular filtration is disrupted tubular functions collapse.
As described in Chapter 12 erectile dysfunction naturopathic treatment generic 160mg malegra fxt plus overnight delivery, neurons at the ventrolateral margin of the vertebrate neural tube become the motor neurons outcome erectile dysfunction without treatment cheap 160 mg malegra fxt plus overnight delivery, while different interneurons are derived from cells in the dorsal region of the tube erectile dysfunction pumps review order 160mg malegra fxt plus with visa. Ericson and colleagues (1996) have shown that two periods of Sonic hedgehog signaling are needed to specify the motor neurons: an early period wherein the cells of the ventrolateral margin are instructed to become ventral neurons erectile dysfunction korea cheap malegra fxt plus 160mg line, and a later period (which includes the S phase of its last cell division) that instructs a ventral neuron to become a motor neuron (rather than an interneuron). The first decision is probably regulated by the secretion of Sonic hedgehog from the notochord, while the latter decision is more likely regulated by Sonic hedgehog from the floor plate cells. Sonic hedgehog appears to specify motor neurons by inducing certain transcription factors at different concentrations (Ericson et al. If a cell is to become a neuron and, specifically, a motor neuron, will that motor neuron be one that innervates the thigh, the forelimb, or the tongue? The anterior-posterior specification of the neural tube is regulated primarily by the Hox genes from the hindbrain through the spinal cord, and by specific head genes (such as Otx) in the brain. As the younger cells migrate to the periphery, they must pass through neurons that differentiated earlier in development. As younger motor neurons migrate through the region of older motor neurons in the intermediate zone, they express new transcription factors as a result of a retinoic acid (or other retinoid) signal secreted by the early-born motor neurons (Sockanathan and Jessell 1998). These transcription factors are encoded by the Lim genes and are structurally related to those encoded by the Hox genes. As a result of their differing birthdays and migration patterns, motor neurons form three major groupings (Landmesser 1978; Hollyday 1980). The cell bodies of the motor neurons projecting to a single muscle are clustered in a longitudinal column called a "pool. The lateral and medial motor columns are subdivided along the mediolateral axis in a manner that correlates with the dorsal-ventral positions of their respective targets (Figure 13. The targets of these motor neurons are specified before their axons extend into the periphery. This was shown by Lance-Jones and Landmesser (1980), who reversed segments of the chick spinal cord so that the motor neurons were in new locations. The axons went to their original targets, not to the ones expected from their new positions (Figure 13. Pattern Generation in the Nervous System the functioning of the vertebrate brain depends not only on the differentiation and positioning of the neurons, but also on the specific connections these cells make among themselves and their peripheral targets. In some manner, nerves from a sensory organ such as the eye must connect to specific neurons in the brain that can interpret visual stimuli, and axons from the nervous system must cross large expanses of tissue before innervating their target tissue. How does the neuronal axon "know" to traverse numerous potential target cells to make its specific connection? This observation simplified, but did not solve, the problem of how neurons form appropriate patterns of interconnection. Harrison also noted, however, that axons must grow on a solid substrate, and he speculated that differences among embryonic surfaces might allow axons to travel in certain specified directions. The final connections would occur by complementary interactions on the target cell surface: That it must be a sort of a surface reaction between each kind of nerve fiber and the particular structure to be innervated seems clear from the fact that sensory and motor fibers, though running close together in the same bundle, nevertheless form proper peripheral connections, the one with the epidermis and the other with the muscle. The foregoing facts suggest that there may be a certain analogy here with the union of egg and sperm cell. Research on the specificity of neuronal connections has focused on two major systems: motor neurons, whose axons travel from the nerve to a specific muscle, and the optic system, wherein axons originating in the retina find their way back into the brain. In both cases, the specificity of axonal connections is seen to unfold in three steps (Goodman and Shatz 1993): Pathway selection, wherein the axons travel along a route that leads them to a particular region of the embryo. Target selection, wherein the axons, once they reach the correct area, recognize and bind to a set of cells with which they may form stable connections. Address selection, wherein the initial patterns are refined such that each axon binds to a small subset (sometimes only one) of its possible targets. The third process involves interactions between several active neurons and converts the overlapping projections into a finetuned pattern of connections. It has been known since the 1930s that motor axons can find their appropriate muscles even if the neuronal activity of the axons is blocked. Normal neuronal connections were made, even though no neuronal activity could occur.
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Arterial or venous injury is especially likely to occur if the vessels enter a bony canal in this region erectile dysfunction instrumental buy malegra fxt plus 160 mg fast delivery. Bleeding occurs and strips the meningeal layer of dura from the internal surface of the skull impotence icd 9 code buy 160 mg malegra fxt plus otc. The intracranial pressure rises impotence type 1 diabetes purchase malegra fxt plus 160 mg otc,and the enlarging blood clot exerts local pressure on the underlying precentral gyrus (motor area) impotence gel cheap 160mg malegra fxt plus mastercard. Blood may also pass laterally through the fracture line to form a soft swelling on the side of the head. Subdural hemorrhage results from tearing of the superior cerebral veins where they enter the superior sagittal sinus. The cause is usually a blow to the front or back of the head, resulting in excessive anteroposterior displacement of the brain within the skull. This condition, which is much more common than middle meningeal hemorrhage, can be produced by a sudden minor blow. Once the vein is torn, blood under low pressure begins to accumulate in the potential space between the dura and the arachnoid. Acute and chronic forms of the clinical condition occur, depending on the speed of accumulation of fluid in the subdural space. For example, if the patient starts to vomit, the venous pressure will rise as the result of a rise in the intrathoracic pressure. Under these circumstances, the subdural blood clot will rapidly increase in size and produce acute symptoms. In the chronic form, over a course of several months, the small blood clot will attract fluid by osmosis, in which case a hemorrhagic cyst forms and gradually expands and produces pressure symptoms. The Shaken-Baby Syndrome Inflicted head injury is the most common cause of traumatic death in infancy. It is believed that sudden deceleration, which occurs when an infant is held by the arms or trunk and shaken or the head is forcefully struck against a hard surface, is responsible for the brain injuries. Biomechanical studies have shown that the rotation of the floating brain about its center of gravity causes diffuse brain injuries,including diffuse axonal injury and subdural hematoma. In shaken-baby syndrome,major rotational forces have to occur that clearly exceed those encountered in normal child play activities. Most cases of shaken-baby syndrome take place during the first year of life, and they are usually restricted to infants under 3 years of age. Common symptoms include lethargy, irritability, seizures, altered muscle tone, and symptoms indicating raised intracranial pressure,such as impaired consciousness,vomiting, breathing abnormalities, and apnea. In severe cases, the baby may be unresponsive, the fontanelles are bulging, and the child may have retinal hemorrhages. Autopsy findings commonly include localized subdural hemorrhage in the parietal-occipital region and subarachnoid blood, associated with massive cerebral swelling and widespread neuronal loss. Space-Occupying Lesions within the Skull Space-occupying or expanding lesions within the skull include tumor, hematoma, and abscess. Since the skull is a rigid container of fixed volume,these lesions will add to the normal bulk of the intracranial contents. An expanding lesion is first accommodated by the expulsion of cerebrospinal fluid from the cranial cavity. Later, the veins become compressed, interference with the circulation of blood and cerebrospinal fluid begins, and the intracranial pressure starts to rise. The venous congestion results in increased production and diminished absorption of cerebrospinal fluid, the volume of the cerebrospinal fluid begins to rise, and thus, a vicious circle is established. The position of the tumor within the brain may have a dramatic effect on the signs and symptoms. For example, a tumor that obstructs the outflow of cerebrospinal fluid or directly presses on the great veins will cause a rapid increase in intracranial pressure. The signs and symptoms that enable the physician to localize the lesion will depend on the interference with the brain function and the degree of destruction of the nervous tissue produced by the lesion. A spinal tap should not be performed in patients with suspected intracranial tumor.
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