Rewritable remote encoding and decoding of miniature multi-bit magnetic tags for high-throughput biological analysis.

We have investigated a new magnetic labelling technology for high-throughput biomolecular identification and DNA sequencing. Planar multi-bit magnetic tags comprising a magnetic barcode formed by an ensemble of micron-sized thin film ferromagnetic Co bars and a 15 x 15 micron Au square for immobilization of probe molecules have been designed and fabricated. We show that by using a globally applied magnetic field and magneto-optical Kerr microscopy the magnetic elements in the multi-bit magnetic tags can be addressed individually and encoded/decoded remotely. The power of the approach is the read/write technique, which allows modest globally applied magnetic fields to write almost unlimited numbers of codes to populations of tags rather than individuals. The magnetic nature of the technology also lends itself naturally to fast, remote decoding and the ability to rewrite tags if needed. We demonstrate the critical steps needed to show the feasibility of this technology, including fabrication, remote writing and reading, and successful functionalization of the tags as verified by fluorescence detection. This approach is ideal for encoding information on tags in microfluidic flow or suspension, in order to label oligonucleotides during split-and-mix synthesis, and for combinatorial library-based high-throughput multiplexed bioassays.

Results of the in vitro fertilization programme at Tygerberg Hospital, phases II and III.

Phases II and III of the human in vitro fertilization programme at Tygerberg Hospital are presented. In phase II, 42 laparoscopies were performed and oocytes were obtained from 76% of the follicles aspirated, but with a fertilization rate of only 37%. The viable pregnancy rate per embryo transfer was 4%. Important changes took place in the programme, which led to a fertilization rate of 77% in phase III. Of the 78 patients subjected to laparoscopy, 65 (83%) reached the embryo transfer stage, resulting in a clinical pregnancy rate per embryo transfer of 23%, and with a 19% pregnancy rate per laparoscopy. The changes, methods and results of phases II and III are discussed.

Results of phase I of the in vitro fertilization and embryo transfer programme at Tygerberg Hospital.

Phase I (3 June - 31 October 1983) of the in vitro fertilization (IVF) programme at Tygerberg Hospital is outlined in this article. This programme led to the birth of the first IVF baby in South Africa after fertilization and embryo transfer (ET) took place at this institution. The baby was born on 29 April 1984; a second baby was born on 20 June 1984. During phase I 24 laparoscopies were performed; 32 oocytes were obtained from 56 follicles, of which 62,5% were fertilized. Eleven ETs were performed, which led to 3 pregnancies. An ongoing pregnancy rate of 18% per ET and a pregnancy rate of 12,5% per laparoscopy were achieved.

[A comparative study of the white cell pipette method and the Makler counting chamber method of counting spermatozoa]. / 'n Vergelykende studie van die Witselpipet- en Makler-telkamermetodes vir die tel van spermatosoa.

A new method for counting spermatozoa was introduced by Makler. This method was compared with the white blood cell pipette method and the results revealed high precision and accuracy (difference of means = 5,9%). Makler's method, which is very simple to perform, has the advantage that rapid and reliable sperm counts can be done. Therefore, the Makler counting chamber can be used with confidence in the performance of semen analysis by any doctor or in any laboratory.