News and Views
Presswatch (Dr Vivek Chhabra)
How dynamite could help destroy prostate cancer
A chemical once used as a deadly explosive could be a powerful new treatment for prostate cancer. Patients who took part in a small clinical trial saw their levels of prostate–specific antigen (PSA), a chemical marker in the blood that increases when cancer is present, stabilize when small amounts of nitroglycerine seeped into the bloodstream. The latest trial, carried out at Queen’s University in Belfast, came about after researchers there performed laboratory tests that showed the explosive appeared to slow cancer growth. The results, published in the journal Urology, showed that within six months, PSA levels had stabilized in all but five of the 24 volunteers.
People with significant sleep apnea have much fewer nightmares (Dr G M Singh)
People with significant sleep apnea continue to dream, but they report fewer nightmares, said Dr. Jim Pagel, lead author of a study appearing in the Feb. 15 issue of the Journal of Clinical Sleep Medicine. There has been a question for a long time about the cognitive effects of sleep apnea. . . This is one of the first studies showing a clear cognitive change with sleep apnea and, surprisingly, it’s in a positive direction, he further added.
Antibiotics can actively make bacteria stronger
Current understanding of the way bacteria develop resistance has been challenged. The current thought that resistance is caused by a few bacteria, which by chance had the ability to resist the antibiotic, was initially challenged when it was found that the surviving bacteria were also then more resistant to other subsequent yet different antibiotics. A team at Harvard Medical School has found that some antibiotics actually induce mutations in bacteria. They do this by producing toxic free radicals which then result in mutations incorporated into bacterial DNA by the repair pathways. This process is greatest when drug levels are low and potentially
HIV and women
Nearly six in 10 women (58 percent) say they don’t get tested because they believe they are in a monogamous relationship.
Eye care snippets by Dr. Narendra Kumar (OptometryToday@gmail.com)
Lens Materials and coatings (Part 2)
Coatings: It’s surprising that ‘anti–reflection vs. UV–absorbing coatings is a commonly misunderstood area in ophthalmic dispensing. Let’s consider (a) visible and non–visible light, (b) effect of ultraviolet light, (c) anti–reflection coating, (d) mirror coating, and (e) UV–Protec dye, to understand the subject better.
Visible and non–visible light: Light varies considerably in wavelength; not all wavelengths cause an activation of photoreceptors. Not all light striking the eye is therefore visible. The actual range of wavelengths that reach the retina is between 380 and 1400 nm. It has been estimated that of these only those between 390 and 740 nm are visible. Light of wavelengths down to 300 nm could actually be seen if it were not absorbed by the anterior segment of the eye. And, when the crystalline lens is removed, objects illuminated with light down to 300 nm are reported to be visible. Most light of wavelengths less than 300 nm or greater than 250 nm is screened by the cornea, while light between almost 300 nm to 390 nm passes through the lens. The vitreous allows no light of wavelength longer than 1400 nm to reach the retina.
The effect of Ultraviolet light. Because the cornea absorbs (UV) light below 300 nm, excessive exposure to these UV wavelengths can result in inflammation of the cornea and conjunctiva. Exposure of the eye to large quantities of ultraviolet light between 300 and 400 nm can speed up or contribute to the formation of cataract.
Common sources of UV rays are sunlight at high altitudes, reflected sunlight from a surface such as water or snow, sun or other ultraviolet–type lamps, and welding. Even colour television screens and computer screens emit harmful UV–radiation. An aphakic, having had his crystalline lens removed, can no longer absorb light between 300 and 390 nm but allows it to fall on the retina. Outdoor workers, even on cloudy days, mountaineers, those indulging in water or snow games, users of UV–type lamps, sunbathers, welders, children sitting for long hours before colour television, and those working on computers, therefore, need a lens with UV–absorbing properties. Crown glass transmits 92% of the visible light striking its surface. The 8% not transmitted is lost through reflection. All UV light below 290 nm is absorbed by crown glass. Unfortunately, it is the UV between 290 and 390 nm that can be more disturbing.
Protection from bright sunlight is available through good–quality sunglasses. Normal transmission for sunglasses is generally between 15% and 30%. More than 30% transmission may not help the average wearer sufficiently in sunlight, while less than 15% may not be too dark for normal purposes. Plastic lenses offer greater versatility in tinting, since they may be dyed to almost any color, may be made as light or dark as desired by simply dipping in a solution of heated dye of the desired color, and may be bleached out and retinted again if a tint has proved unsatisfactory. Photochromic lens changes in its transmission when exposed to light, due to the activation of silver halide crystals within the glass by ultraviolet light of wavelengths between 300 and 400 nm, causing darkening of the whole lens.
Anti–reflection coating. An anti–reflection coating is a thin, clear layer of the coating film applied to the surface of a lens for the purpose of (i) reducing unwanted reflections from the lens surface and (ii) increasing the amount of light that actually passes through the lens to the eye. Reflections, including oncoming headlight annoyance at the time of night–driving, are reduced considerably by anti–reflection coatings. Another cosmetic, helpful aspect of AR–coating is reduction of the awareness of lenses.
Mirror coating. A mirror coating can be applied by a vacuum process to the front surface of the lens causing the lens to have the same properties as a two–way mirror. The observer, unable to see the wearer’s eyes, sees his own image reflected from the lens. The wearer is able to look through the lens normally. There is, of course, a reduction in the transmission of the lens because of the high percentage of light reflected. Mirror coatings are often used in combination with a tinted lens to provide more protection from intense sunlight. So, when there is a demand of a UV–dye coating and the optical practitioner provides AR–coating, instead, he not only is just not providing any answer to the blocking of UV–radiation affecting the ocular tissue but may actually also be increasing the UV–light transmission through the spectacles.
UV–Protec dye. The UV–Protec dye penetrates the lens surface. During the long heating process, the pores of the lens open up and the chemical is permanently enclosed. A treated lens absorbs 100% UV from 260 to 400 nm and the absorption does not weaken with time. Insertion in lens tint neutralizer does not affect absorption. The chemical comes in concentrated form. Three times water is added to the concentrate before using the dye (i.e. 750 ml water is added to 250 ml concentrate). Solution is heated to 96° C or 205° F. Cleaned CR–39 lenses are inserted only when temperature is reached. Lens is left in solution for 30 to 60 minutes. It is then removed from solution, allowed to cool off and residue washed off under hot water. Evaporated water is replaced, before next treatment, so that inserted lenses are completely covered by the solution. UV–Protec treated lens can be tinted, bleached and re–tinted, scratch–guard coated and AR coated. And is a viable UV–protection by means of tinted lenses for outdoor use and clear lenses for indoor use. (To be continued)
(To Read Part 1, see eMedinews dated 22.2.10)
3rd International Online Medical Conference (IOMC 2010)
Online Conference (including India participants)
Date: March 06–07, 2010
Quote of the Day
Prayer is a triumph, in whatever form. (Mirakel Reves)
Sulfonylurea increases pre-formed insulin and not insulin.
Public Forum (Press Release)
Natural foods and not supplements for preventing heart disease
One should consume seasonal and locally grown natural foods and vegetables grown at organic farms. Eat less, dinner lighter then the lunch, eat natural and eat in moderation are few of the mantras. Eating food supplements can be harmful.
Supplementation with beta carotene and vitamin E, either alone or in combination with each other or other antioxidant vitamins does not prevent heart disease.
High dose vitamin E supplementation (400 IU/day) may be associated with an increase in all–cause mortality.
Supplementation with vitamin C does not prevent second heart attack. Beta carotene supplementation may be dangerous and should be discouraged.
Vitamin E supplementation may be of benefit for only secondary prevention of heart patients with chronic renal failure who are undergoing hemodialysis.
The American Heart Association concluded that current data do not justify the use of antioxidant supplements for the prevention or treatment of cardiovascular disease risk.
The above recommendations apply to supplementation only. Diets high in natural antioxidants are associated with lower cardiovascular mortality.
Question of the day
What is the role of mesalazine in ulcerative colitis?
The mesalamine (mesalazine) group of drugs is formed by coating 5–aminosalicylic acid (5–ASA) with acrylic resins or by encapsulation in ethylcellulose microgranules. This results in drug delivery to the distal small bowel and colon.
The acrylic–base resin dissolves at a pH >6, while ethylcellulose serves as a semipermeable membrane allowing the release of 5–ASA, also in a pH–dependent fashion, as it traverses the small bowel.
Oral 5–ASA compounds, mesalamine is effective in inducing remissions in active ulcerative colitis.
The clinical response ranges from 50–71% (2–4 g/day). A trial found that 4.8 g/day of mesalamine were significantly more effective than 2.4 g/day at achieving overall improvement at six weeks (72 vs 59%) in patients with moderately active ulcerative colitis.
The mesalamine compounds are also prescribed at high doses to maintain remission in patients with Crohn’s disease when begun soon after surgical resection.
Because of the favorable safety profile many practitioners attempt treatment with aminosalicylates before treating with corticosteroids or immunosuppressants. Maintenance doses are similar to those used for ulcerative colitis.
eMedinewS Try this it Works
Schroeder KW, Tremaine WJ, Ilstrup DM. Coated oral 5–aminosalicylic acid therapy for mildly to moderately active ulcerative colitis. A randomized study. N Engl J Med 1987;317:1625.
Hanauer SB, Sandborn WJ, Kornbluth A, et al. Delayed–release oral mesalamine at 4.8 g/day (800 mg tablet) for the treatment of moderately active ulcerative colitis: The ASCEND II Trial. Am J Gastroenterol 2005;100:2478.
Support for walking
When patients with peripheral neuropathy have suboptimal visual input, they should use a cane. If a cane is used, the patient should have sufficient upper extremity strength to bear 20 - 25% of body weight on the cane; this can be checked with a bathroom spring scale in the office.
Dr Good Dr Bad
Situation: A borderline diabetic came for prescription.
Dr Bad: Start with lifestyle modifications.
Dr Good: Start with metformin and lifestyle interventions.
Lesson: As lifestyle interventions fail to achieve or maintain metabolic goals either due to failure to lose weight, weight regains, progressive disease, or a combination of factors for most individuals with type 2 diabetes, metformin therapy should be initiated concurrently with lifestyle intervention at diagnosis. It is recommended as the initial pharmacological therapy, in the absence of specific contraindications. (Source: Diabetes Care 2009;32(1):193–203.)