AZFb deletions predict the absence of spermatozoa with testicular sperm extraction

Abstract
Genetic abnormalities, including partial deletions of the Y-chromosome, are commonly detectable in men with non-obstructive azoospermia (NOA). NOA can be treated using testicular sperm extraction (TESE) with intracytoplasmic sperm injection (ICSI).

Tokens are making news now as an innovative method of crowdfunding, especially for the start-ups which start as small, aiming big. Tokens can be very easily created without any expert guidance or paid service through self-operating platforms such as Ethereum. Tokens based on Ethereum blockchain use ERC20 as the technical system for the smart contracts, ERC stands for Ethereum Request for Comment and the request was assigned the number 20.

More about ERC20

ERC20 was proposed in the year 2015 by Fabian Vogelstellar. This system consists of a well-defined set of protocols or common rules to be followed by token created through Ethereum platform so that they become cohesively joined within the large Ethereum pool. The rules mainly revolve around the methods for transferring tokens between two or more addresses and for accessing the data related to these tokens.

Examples of ERC20 tokens

EOS, Qash, Bankex, Bancor etc.

The main purpose of ERC20 is to generalize token generation so that the investors or public who intend to create them can conveniently do the same as well the interaction between tokens so created can be accurately predicted.  The developers can use these rules to program the functioning of newly created tokens.

ERC20 also defines the two different signals taken by each token and to which other token is tailored to. By achieving this kind of harmony, all the token within the Ethereum pool behave in a similar fashion at comparable situations and can be stored in the same wallets.

The six functions stand for the total supply of tokens, getting the account balance of an owner using the address, transfer a specific amount of tokens to the given address, transfer the specified amount of tokens from the address of the source account, approve the withdrawal of an amount by the permitted spender and give the balance of the account available for withdrawal.

You can compare the utility of this system to the MS office document saved as a 2003-2007 format. It is compatible with both the versions and if we want to make any modification, it can be easily done without tweaking the format of the document. When token developers like Bitcoin Loophole and many more release a new set of tokens, if they are compliant with ERC20 rules, additional modifications can be simply added to them and no need to redo.

ERC20 is still growing from the inputs of experts and experienced developers, troubleshooting the existing drawbacks and adding more appeal as the digital currency market is growing in appeal.

Recent studies have shown that the presence of deletions involving the AZFc region do not appear to affect the chance of retrieving spermatozoa or have a significant impact on fertilization or pregnancy rates with ICSI. We investigated the effect of Y-chromosome partial deletions on the chance of sperm retrieval with TESE. Eighty attempts at sperm retrieval were performed using TESE on men who were previously evaluated for Y-chromosome partial deletions. Y-chromosome analysis was performed using a polymerase chain reaction (PCR)-based technique with 35 sequence-tagged-sites. Of the 80 men, nine (11%) had partial Y-chromosome deletions detected. Two azoospermic men with AZFc deletions had successful sperm retrieval, ICSI and a subsequent clinical pregnancy. Seven men had deletions involving the AZFb region (three men had isolated AZFb deletions, one had AZFa, AZFb and AZFc deleted, and three had AZFb and AZFc deleted). None of the seven men had spermatozoa extracted by TESE, a result that is significantly different from the overall 64% (47/73) sperm retrieval rate achieved at our centre (P = 0.001). Two men with AZFb deletions had cells consistent with round spermatids identified and injected into oocytes without effecting any normal fertilizations. Although preliminary, these results suggest that the presence of an AZFb deletion is a significantly adverse prognostic finding for TESE. Men with AZFb deletions should be apprised of these results before attempting TESE-ICSI. Alternatives such as donor insemination or adoption should be considered or therapy delayed until improved results with round spermatid injections are likely.

PMID: 9804236
[Indexed for MEDLINE]