Chromosome movement during meiotic prophase in crane-fly spermatocytes: IV. Actin and the effects of cytochalasin D.
Cytochalasin D (CD) was applied to crane-fly spermatocytes at late diakinesis with the aim of perturbing actin structure and actin function, thereby testing the hypothesis that intranuclear chromosome movement during late diakinesis is actin-based. Isolated tests were incubated in a range of CD concentrations (2-100 microM) for 1 or 2 h. None of those treatments resulted in cessation of prophase movements in living cells. An immediate effect of 10-100 microM CD at late diakinesis was the formation of highly refractile, actin-containing cables within the nonchromosomal nucleoplasm. No such cables were observed in vehicle-treated control cells. CD treatments caused autosomal bivalents in unusually large numbers of spermatocytes to become aggregated into densely-packed clusters; for example, with 40 microM CD about 80% of late diakinesis spermatocytes had clustered autosomes, vs. about 25% clustering in untreated cells. We conclude from these data that the mechanism of chromosome positioning at the nuclear envelope is CD-sensitive. Rhodamine-conjugates of phalloidin and DNase I were used to assess the status of actin in untreated cells as well as the effect of CD on actin distribution. Differences in nucleoplasmic staining with phalloidin and DNase I conjugates suggest that nucleoplasm at late diakinesis contains actin in a nonfilamentous form.
Department of Biological Sciences, State University of New York at Buffalo 14260, USA. jrl@acsu.buffalo.edu
J R
JR
LaFountain
A J
AJ
Siegel
G K
GK
Rickards
D000199:Actins / Q000502:physiology; D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000235:genetics; D002875:Chromosomes / Q000187:drug effects / Q000502:physiology*; D015638:Cytochalasin D / Q000494:pharmacology; D004175:Diptera / Q000187:drug effects / Q000235:genetics*; D008297:Male; D008540:Meiosis; D008856:Microscopy, Fluorescence; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D011418:Prophase; D013090:Spermatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013737:Testis / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
D000199:Actins; D019384:Nucleic Acid Synthesis Inhibitors; D015638:Cytochalasin D