PDE-5 is an enzyme found in trabecular smooth muscle. It catalyzes the degradation of cGMP, which results in an elevated cytosolic calcium concentration and smooth-muscle contraction (Fig. 2). PDE-5 inhibitors, therefore, block this biochemical pathway to promote erection. Eleven subtypes of PDEs have been described, with 30 isoenzymes mediating a variety of physiologic actions throughout the body.32 PDEs exhibit enormous functional diversity; at present, our understanding of PDE types 1 to 6 are considerably better than our understanding of PDE types 7 to 11.
Evidence of an immune-mediated, antitumor effect of PDE5 inhibition is further shown by tetramer analysis on splenocytes obtained from sildenafil-treated, CT26WT tumor- bearing mice, which revealed a higher number of CTLs specific for AH-1 (unpublished data), a CT26 tumor-associated antigen, as compared with their untreated counterparts (19). To confirm immune-mediated antitumor activity in the sildenafil-treated groups, we performed an in vivo cytotoxicity assay. BALB/c mice were injected with PBS (naive), vaccinated with -irradiated CT26WT or C26GM, or challenged with CT26WT or C26GM tumors on day 0. On day 12 (CT26WT) or day 5 (C26GM), all mice received carboxyfluorescein diacetate succinimidyl ester (CFSE)–labeled splenocytes pulsed with the MHC class I–restricted AH-1 peptide (CFSEhigh), admixed with CFSE-labeled splenocytes pulsed with the irrelevant hemagglutinin (HA)-peptide (CFSElow). In vivo T cell cytotoxicity was determined 40 h later (Fig. 2). These time points were chosen based on the kinetics of tumor outgrowth observed in Fig. 1 A and Fig. 1 B, respectively, when tumor size significantly differed between untreated and sildenafil-treated mice. As expected, an endogenous AH1-specific immune response was observed in the vaccinated mice as compared with their tumor-bearing counterparts. PDE5 inhibition in the vaccine-primed mice failed to augment antigen-specific CD8 responsiveness compared with no treatment. In contrast, tumor-bearing mice treated with sildenafil early after tumor challenge generated antigen-specific immunity that was significantly greater then that observed in their untreated counterparts and similar, or even superior, to that induced by vaccination. Collectively, this is the first indication that PDE5 inhibitors can modulate antitumor immunity. Because the sildenafil-mediated antitumor immune response does not completely eradicate tumors, tumor escape mechanisms may be associated with their outgrowth. To test this hypothesis, the parental CT26WT cell line, as well as the CT26 tumor removed on day 24 from sildenafil-treated mice (either AH-1 pulsed or unpulsed), and BALB/c splenocytes were incubated with either AH-1 peptide-primed (Fig. S1 C) or tumor-primed (Fig. S1 D) effector T cells. Although effector T cells recognized the parental CT26WT line and released IFN- in the assay, they failed to recognize the sildenafil-derived tumor. Its recognition, however, was restored by loading the sildenafil-derived tumor with the AH-1 peptide. (Fig. S1, C and D). These results suggest that the immune response in sildenafil-treated mice does not result in complete tumor eradication but rather in the selection of antigen-escape variants.
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The Latin term impotentia coeundi describes simple inability to insert the penis into the vagina. It is now mostly replaced by more precise terms. The study of erectile dysfunction within medicine is covered by andrology, a sub-field within urology.
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There are so many options that a man's quality of life should be considered strongly when weighing various procedures. In fact, a growing number of doctors say many prostate cancers are better off being left untreated.
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Following completion of this phase, the physician should be able to determine the medical status of the patient, to identify and characterize the type of dysfunction, and to determine the need for additional testing such as penile or pelvic blood flow studies, nocturnal penile tumescence testing, or other blood tests. The patient's needs, expectations, and priorities should be discussed in order to decide about further management or referral.
About 85 percent of women experience at least one premenstrual symptom every month, according to the American College of Obstetricians and Gynecologists. For most women PMS symptoms are mild, however about 20 to 30 percent of them suffer from moderate to severe symptoms.
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GORDON F. GREEN, CDR, MC, USNR
Hormone Imbalances
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Cardiovascular diseases: The most common cause of cardiovascular diseases in the United States is atherosclerosis, the narrowing and hardening of arteries that reduces blood flow. Atherosclerosis typically affects arteries throughout the body and is aggravated by hypertension, high blood cholesterol levels, cigarette smoking, and diabetes mellitus. When coronary arteries (arteries that supply blood to the heart muscle) are narrowed by atherosclerosis, heart attacks and angina occur. When cerebral arteries (arteries that supply blood to the brain) are narrowed by atherosclerosis, strokes occur. Similarly, when arteries to the penis and the pelvic organs are narrowed by atherosclerosis, insufficient blood is delivered to the penis to achieve an erection. There is a close correlation between the severity of atherosclerosis in the coronary arteries and erectile dysfunction. For example, men with more severe coronary artery atherosclerosis also tend to have more erectile dysfunction than men with mild or no coronary artery atherosclerosis. Some doctors suggest that men with new onset erectile dysfunction should be evaluated for silent coronary artery diseases (advanced coronary artery atherosclerosis that has not yet caused angina or heart attacks). For more information, please read the Heart Attack Prevention article.
bDivisione di Andrologia, Universita degli Studi di Pisa, Italia;
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Having trouble maintaining an erection from time to time isn't necessarily a cause for concern.
The hormonal birth control patch (brand name: Ortho Evra) uses estrogen and progestin to prevent pregnancy. It is applied to 1 of 4 places -- the buttocks, abdomen, upper torso or outer arm. The patch is used on a 4-week cycle. You put on a new patch once a week for 3 weeks. You don't use a patch during the 4th week and your period will start.
Erectile dysfunction can be defined as the inability to achieve or maintain a penile erection sufficient for satisfactory sexual performance.1 In the face of an aging population, decreasing social stigma associated with erectile dysfunction and an increasing availability of effective oral therapy for its treatment, the number of patients presenting with this complaint has increased dramatically. Current estimates describe 2–3 million Canadian men as having significant recurring erectile difficulties. Recent reports identifying a dramatic increase in rates of diabetes, increased longevity and higher quality-of-life expectations by "baby boomers" are all believed to be factors in a projected continued expansion of the patient population requesting medical help with sexual issues in the near future.2,3 Although historically erectile dysfunction was a problem identified and treated by urologists, today primary care physicians and other specialists write 80% of the prescriptions for sildenafil, the most popular drug used to treat the condition.4
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Nerve or spinal cord damage: Damage to the spinal cord and nerves in the pelvis can cause erectile dysfunction. Nerve damage can be due to disease, trauma, or surgical procedures. Examples include injury to the spinal cord from automobile accidents, injury to the pelvic nerves from prostate surgery, multiple sclerosis (a neurological disease with the potential to cause widespread damage to nerves), and long-term diabetes mellitus.
"There are several reasons ophthalmologists need to be acquainted with the pharmacologic profiles of PDE5 inhibitors and their potential side effects," the authors wrote "The frequency of erectile dysfunction, which is a form of peripheral vascular disease that impairs men's abilities to achieve and maintain an erection, increases dramatically with age and in the presence of cardiovascular risk factors. Therefore, many men who take PDE5 inhibitors to treat their erectile dysfunction will also be followed up by ophthalmologists for ocular disorders such as diabetic retinopathy, macular degeneration and ocular vascular disease."
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