If you need affordable high-performance microscopes and related instruments for your lab, business or school Microscope Showroom has exactly what you're looking for no matter what industry you're in. We have teamed up with ebay so that we can provide the most extensive and diverse selection of competitively priced new and used precision Vickers microscopes and microscope accessories that any site offers. From industrial microscopes including digital microscopes, video inspection systems, stereoscopes, and inspection microscopes to scientific microscopes such as electron microscopes and confocal light microscopes, Microscope Showroom is the only name you need to remember for great deals on microscopes from the industry's top equipment providers like Vickers. Microscope Showroom specializes in just one thing - precision medical, laboratory, industrial and educational microscopes. Let Vickers put their vast expertise to work for you with an affordably priced microscope from our vast selection of Vickers instruments. All types of operations and usages for microscopic instrumentation including industrial, scientific, biological, medical, electronic, metallurgical and educational applications can be effectively handled with Vickers's innovative and well-engineered microscopes and accessories. It is suggested, therefore, that chromosomes at maximum preleptotene condensation cannot enter a meiotic sequence without first undergoing a within-chromosomal reorganization of their chromatin, and that preleptotene chromosome decondensation stage represents such a reorganization.Vickers is one of the industry's top providers of full-featured and ultra-precision industrial, medical and scientific microscopes. Two parallel threads (chromatids) are visible in chromosomes at preleptotene condensation stage while, in chromosomes at leptotene, invariably only a single thread is seen. It is concluded that preleptotene chromosome condensation stage has no effect on normal meiotic chromosome pairing behaviour and probably has no significant function. In 'Black Beauty', however, the control regulating the initiation of meiosis apparently is effective later in the cell cycle and acts only after p.m.cs have entered mitotic prophase. In normal Lilium genotypes meiosis is initiated by p.m.cs at G2 of premeiotic interphase. It is suggested, therefore, that preleptotene condensation and decondensation represent a true mitotic reversion in which metaphase and anaphase are omitted. Similarly, the appearance and behaviour of chromosomes at preleptotene decondensation is indistinguishable from that normally seen at mitotic telophase. The appearance and behaviour of chromosomes at preleptotene condensation stage is the same as that displayed by chromosomes at mitotic prophase. The nature and possible significance of preleptotene chromosome condensation and decondensation are discussed. Thereafter chromosomes underwent decondensation and elongation and eventually passed into leptotene without first entering any other stage. At this stage the appearance of the chromosomes was indistinguishable from that of late prophase or prometaphase chromosomes at mitosis. At maximum chromosome contraction the diploid chromosome number (2n = 24) could often be counted, but no evidence of association of chromosomes was seen. All the p.m.cs within an anther loculus underwent preleptotene chromosome condensation stage with a degree of synchrony not less than that found at early first meiotic prophase. 'Black Beauty' p.m.cs entered preleptotene chromosome condensation stage from G2 of premeiotic interphase having completed DNA synthesis. A brief illustrated description is given of the appearance of p.m.cs at various stages of preleptotene chromosome condensation in both methylene blue stained anther sections, and in Feulgen stained anther squashes. chromosomes during preleptotene condensation and decondensation was essentially the same as that described by Walters (1970, 1972) for the corresponding stages in Lilium longiflorum cv. Moreover, the preleptotene condensation and decondensation stage was apparently shorter in e.m.cs (about 0.7 days) than in p.m.cs. However, the maximum degree of chromosome contraction at the preleptotene condensation stage was much greater in p.m.cs than in e.m.cs. Preleptotene chromosome condensation and contraction also occurred in embryo sac mother cells (e.m.cs) of 'Black Beauty'. The duration of this period was estimated to be about 1.16 days in pollen mother cells (p.m.cs) of plants grown at 20 degrees C. A period of chromosome condensation followed by decondensation occurs between premeiotic interphase and leptotene in Lilium hybrid cv.