Unisex contraceptive tailed
Sperm go slow without a crucial protein.
The discovery of a protein that is crucial to sperm swimming in mice could lead to new male or female contraceptives or fertility treatments.
The protein forms a channel through the membrane of the sperm tail. It controls the inflow of calcium ions that trigger swimming.
All humans have the gene that encodes the channel, but it is switched on only in sperm cells. This would lessen the risk of side-effects from any channel-blocking contraceptive, for example.
“We think it’s going to be very useful for the development of male contraceptives,” says Dejian Ren of Harvard Medical School in Boston1.
Ren’s team created mutant mice lacking the ion channel; all were sterile. These animals’ sluggish sperm move at about one-third of normal speed. The sperm also lack their normal counterparts’ sense of direction.
Sperm without the channel are incapable of making a violent whiplash movement, called hypermotility. Sperm turn hypermotile inside a female – possibly in response to a chemical signal from her – just before fertilization.
This turn of speed seems to enable a sperm to burst into the egg. Mutant sperm are too feeble to do this; they can fertilize an egg only if its outer layer is removed.
“Calcium has long been known to be very important in sperm function, but the details have been very elusive,” says cell biologist David Garbers of the University of Texas Southwestern Medical Centre in Dallas. Much remains to be worked out about how the channel works, but the story so far is “all pretty cool”, he says.
Defective calcium channels might be a cause of human male sterility. The same could be true for other ion channels in sperm, says Susan Benoff of North Shore University Hospital in Manhasset, New York.
Benhoff is developing contraceptives that target calcium channels in the heads of sperm. “Most male contraceptives in the pipeline are based on hormonal methods,” she says. The effects of these may be hard to reverse: “Sperm count may not get back up to the usual level,” says Benhoff. Ion-channel blockers could avoid these pitfalls.
Worldwide, the market for oral contraceptives was worth almost US$4 billion last year. The demand for a male pill would be “phenomenal”, says Benoff. “Surveys show that men would be as willing as women to use oral contraception if it was convenient. I get phone calls every week from people wanting to take part in trials.”
Potential male contraceptives have been overhyped in the past, warns Paul Wassarman, who studies fertilization at Mount Sinai School of Medicine in New York City. “Everyone who’s able to prevent fertilization thinks they have a target for contraception. Whether it’s realistic or not remains to be seen.”
- Ren, D. et al. A sperm ion channel required for sperm motility and male fertility. Nature, 413, 603 – 609, (2001).
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Unisex contraceptive tailed Sperm kwenda polepole bila protini muhimu. Ugunduzi wa protini muhimu kwa ajili ya kuogelea kwa shahawa katika panya inaweza kuongoza kwa njia mpya za kuzuia mimba za kiume au za kike au matibabu ya uzazi. Protini hiyo hufanyiza mfereji kupitia utando wa mkia wa shahawa. Inadhibiti mtiririko wa ioni za kalsiamu ambazo huchochea kuogelea. Wanadamu wote wana chembe ya urithi inayotumia njia hiyo, lakini inaendeshwa tu katika chembe za shahawa. Hii ingepunguza hatari ya athari za upande kutoka kwa dawa yoyote ya kuzuia mimba, kwa mfano. "Tunafikiri itakuwa muhimu sana kwa maendeleo ya dawa za kuzuia mimba za kiume", anasema De Renjian wa Shule ya Matibabu ya Harvard huko Boston1. Timu ya Ren iliunda panya waliobadilika-badilika ambao hawakuwa na njia ya ioni; wote walikuwa wasio na uzazi. Mimea hiyo ya kiume ya wanyama hao husonga kwa kasi ya theluthi moja ya ile ya kawaida. Pia, shahawa hizo hazina uwezo wa kujua mahali zinapopaswa kwenda. Mazao ya shahawa yasiyo na mfereji huo hayawezi kufanya mwendo mkali wa kupigwa na mjeledi, unaoitwa hypermotility. Sperm inageuka kuwa yenye mwendo wa juu ndani ya mwanamke - labda kwa kujibu ishara ya kemikali kutoka kwake - kabla tu ya kuzaliana. Inaonekana kwamba mwendo huo wa kasi hufanya chembe ya uzazi iingie ndani ya yai. Sperm ya mutant ni dhaifu sana kufanya hivyo; wanaweza kuzalisha yai tu ikiwa tabaka lake la nje limeondolewa. "Kalsiamu imekuwa ikijulikana kwa muda mrefu kuwa muhimu sana katika kazi ya shahawa, lakini maelezo yamekuwa magumu sana", anasema mwanabiolojia wa seli David Garbers wa Chuo Kikuu cha Texas Southwestern Medical Center huko Dallas. Mengi bado ni kazi nje kuhusu jinsi kituo kazi, lakini hadithi hadi sasa ni <unk>all pretty baridi<unk>, anasema. Vituo vyenye kasoro vya kalsiamu vinaweza kusababisha utasa wa wanaume. "Hiyo inaweza kuwa kweli kwa njia nyingine za ion katika shahawa, ""anasema Susan Benoff wa Hospitali ya Chuo Kikuu cha North Shore huko Manhasset, New York." Benhoff anatengeneza dawa za kuzuia mimba zinazolenga njia za kalsiamu katika vichwa vya shahawa. "Vitu vingi vya kuzuia mimba vya kiume vinavyopatikana vinategemea mbinu za homoni", anasema. Huenda ikawa vigumu kurekebisha athari za mambo hayo: "Huenda idadi ya shahawa isiweze kurudi kwenye kiwango cha kawaida", asema Benhoff. Dawa za kuzuia njia za ioni zinaweza kuepuka matatizo hayo. Kwa mujibu wa ripoti hiyo, soko la dawa za kuzuia mimba za mdomo duniani kote liliongezeka kwa asilimia zaidi ya asilimia moja mwaka jana. Benoff anasema kwamba mahitaji ya dawa ya kulevya ya wanaume yangekuwa "ya ajabu". <unk> Uchunguzi unaonyesha kwamba wanaume wangekuwa tayari kama wanawake kutumia njia za kuzuia mimba za mdomo ikiwa ingekuwa rahisi. "Wakati wa utafiti huo, Paul Wasserman, ambaye anafanya utafiti wa uzazi katika Chuo cha Tiba cha Mount Sinai huko New York, alisema: ""Kuna uwezekano mkubwa kwamba dawa za kuzuia mimba za kiume zimetumiwa sana katika siku za nyuma." <unk>Kila mtu anayeweza kuzuia uzazi anafikiri ana lengo la kuzuia mimba. Je, ni ya kweli au la bado itaonekana. - Ren, D. et al. Mfereji wa ioni ya shahawa unaohitajika kwa ajili ya mwendo wa shahawa na uzazi wa kiume. Nature, 413, 603 <unk> 609 (2001). Habari zote za hivi karibuni kutoka kwa jamii: Afya na Tiba Eneo hili la somo linajumuisha utafiti na masomo katika uwanja wa dawa ya binadamu. Miongoni mwa orodha pana ya mada zilizofunikwa hapa ni anesthesiology, anatomy, upasuaji, urithi wa binadamu, usafi na dawa ya mazingira, dawa ya ndani, neurology, pharmacology, physiology, urology na dawa ya meno. Ugunduzi wa virusi vya magonjwa kwa haraka na kwa usahihi zaidi kwa kuyeyuka DNA: Njia mpya ya uchambuzi inaweza kugundua virusi vya magonjwa katika sampuli za damu kwa haraka na kwa usahihi zaidi kuliko tamaduni za damu, ambazo ni hali ya sasa ya sanaa kwa utambuzi wa maambukizo. Pembe nyeusi iliyo katikati ya Mfereji wa Maziwa inafanana na mpira wa miguu Watafiti wamefunua kuwa kasi ya mzunguko wa shimo nyeusi inaweza kutoa "mshtuko wenye nguvu sana" kwa vitu vinavyozunguka. Shimo jeusi kubwa zaidi katika nyota ya Milky Way linaonekana kuwa na uwezo wa kugundua chanzo cha viumbe vilivyopo duniani, na timu ya watafiti imesoma viumbe vilivyopo duniani na kugundua chanzo cha viumbe hivyo. Ili kujifunza juu ya viumbe wa kwanza kwenye sayari yetu, watafiti wanapaswa kuchambua miamba ya...