Abstract. Earlier results from sectioned nuclei indicating that Schizosaccharomyces pombe does not develop a classical tripartite synaptonemal complex (SC) during meiotic prophase are confirmed by spreading of whole nuclei. The linear elements appearing during prophase I resemble the axial cores (SC precursors) of other organisms. The number of linear elements in haploid, diploid, and tetraploid strains is always higher than the chromosome number, implying that they are not formed continuously along the chromosomes. Time course experiments reveal that the elements appear after DNA replication and form networks and bundles. Later they separate and "~24 individual elements with a total length of 34/~m are observed before degradation and meiotic divisions. Parallel staining of DNA reveals changes in nuclear shape during meiotic prophase. Strains with a mei4 mutation are blocked at a late prophase stage. In serial sections we additionally observed a constant arrangement of the spindle pole body, the nucleolus, and the presumptive centromere cluster.Thus, S. pombe manages to recombine and segregate its chromosomes without SC. This might correlate with the absence of crossover interference. We propose a mechanism for chromosome pairing with initial recognition of the homologs at the centromeres and suggest functions of the linear elements in preparation of the chromosomes for meiosis I disjunction. With the spreading technique combined genetic, molecular, and cytological approaches become feasible in S. pombe.This provides an opportunity to study essential meiotic functions in the absence of SCs which may help to clari~ the significance of the SC and its components for meiotic chromosome structure and function. DJRING meiosis, DNA replication is followed by two rounds of nuclear divisions resulting in haploid gametes that are required for sexual reproduction of eukaryotes. The first meiotic division (reductional division) is preceded by a complex series of events that result in pairing of the homologous chromosomes and high levels of genetic recombination. These meisosis-specific events occur during prophase I and are required for segregation of the homologous chromosomes during the reductional division. After premeiotic DNA replication, proteinaceous filaments, called axial cores, form along each chromosome and connect the sister chromatids. The process of chromosome pairing culminates in the formation of a continuous synaptonemal complex (SC) t between the homologous chromosomes (for review, see Giroux, 1988). The SC is a tripartite structure consisting of two axial elements (or lateral elements) which are closely synapsed at a distance of ,ol00 nm and a central component which extends longitudinally between the two

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HindlII and 23 EcoRI clones were obtained. Southern blots revealed that complete and unrearranged segments were cloned with this approach, and restriction maps for five segments were obtained. Part of a 16.8 kbp segment was sequenced, found to be AT-rich (73%) and to contain six copies of a 17 bp repeated sequence. The development of the female reproductive tract in the course of pupal-adult development of the wasp was investigated and seen to be strictly correlated with the pigmentation pattern. By the use of a semiquantitative PCR, replication of viral DNA was observed to initiate at a specific stage of pupal-adult development.

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A modified 138 Xe washout technique was used to study changes in intrarenal hemodynamics during glycerol-induced acute renal failure in the rat. Within 10 minutes after glycerol injection, the flow fraction supplied to component 1 of the washout curve ("cortex A") decreases, reaching minimum values 24 hours afer glycerol (31% of control conditions). Seven days thereafter five of the rats, still uremic, showed cortical flow fractions less than 50% of control values. Nine others had recovered. Twenty-four hours after glycerol, renal blood flow was 27% and increased to 86% of control conditions in the recovered rats 7 days after glycerol. 85 Kr autoradiographs and silicone rubber casts of the renal vasculature demonstrated a severe cortical hypoperfusion at the height of oliguria that gradually disappeared in parallel with the functional recovery of the kidney. These observations, in good agreement with micropuncture data, suggest that oliguria and renal insufficiency in this experimental model are the result of a primary decrease in glomerular filtration rate due to an increased preglomerular resistance.