Behavior and DNA synthesis of the nuclei produced after meiosis in Paramecium caudatum.

Haploid micronuclei produced by meiosis in Paramecium caudatum are destined either to survive or to degenerate depending upon their position in the cytoplasm. The behavior of the four meiotic division products in living cells and their DNA synthesis patterns were examined to determine whether there were differences between nuclei destined to survive and those destined for degeneration. Some prospective degenerating nuclei divided, as did the surviving nuclei, but then became pycnotic immediately after division. This indicates that division and pycnosis are not alternative nuclear fates, but are independent processes. Microspectrophotometric measurements of DNA content showed that each meiotic product had 1 C amount of DNA at the second meiotic telophase and then increased the amount to 2 C linearly with time after the telophase. The time course of the DNA synthesis in the prospective degenerating nuclei was not different from that in the surviving ones. These results suggest that the determination of survival or degeneration of meiotic products is a process independent of division and DNA replication. But spindles and daughter nuclei of prospective degenerating nuclei showed some morphological differences from those of surviving ones. Furthermore, the degenerating nuclei became indistinct and small at the beginning of the degeneration, whereas this change was not observed in the surviving ones. Most of the surviving nuclei were surrounded by a clear region of the cytoplasm before their division. These morphological differences between the prospective surviving and degenerating nuclei may be related to their eventual outcomes.

Mechanism of injury and anatomic injury as criteria for prehospital trauma triage.

Prehospital trauma triage should permit accurate identification and transport of patients with critical injuries to trauma centers without overloading these centers with patients having minor injuries. In most trauma systems a combination of physiologic criteria (Trauma Score [TS]), mechanisms of injury (MOI), and anatomic injury (AI) are used as prehospital trauma triage criteria. The purpose of our study was to assess the predictive value of specific MOI and AI in detecting critically injured trauma victims (Injury Severity Score [ISS] of more than 15) and determine the best combination of TS, MOI, and AI that produced the lowest percentage of undertriage and overtriage. Previous studies have examined only patients triaged to trauma centers; our study included all trauma patients regardless of destination. A total of 1,473 trauma patients was evaluated and transported by the emergency medical services system and studied prospectively during a nine-week period. Prehospital TS, specific MOI and AI, and final disposition and diagnosis were determined on all patients. The ISS was calculated on all hospital admissions. A total of 97 patients had an ISS of more than 15. Three hundred forty-one (23%) had one of the specific MOI studied; 102 (6.9%) had one of the specific AI studied. Four hundred twelve patients (28%) had at least one of the study MOI or AI.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracellular positional control of survival or degeneration of nuclei during conjugation in Paramecium caudatum.

The survival or degeneration of nuclei produced after meiosis in Paramecium caudatum depends upon their position in the cytoplasm. The surviving nucleus lies in the paroral region, which is the region around the cytostome. In this study, this was confirmed by quantitative measurements of the location of surviving nuclei in both stained and living conjugating cells. Observation of nuclear behaviour in living cells shows that there is an active mechanism for localizing one of the four meiotic products into the paroral region after the second meiotic division. When this mechanism is inhibited by vinblastine, none of the four nuclei gets into the paroral region and all of them become pycnotic, before degenerating. The results show that migration into the paroral region is essential for survival of the nucleus and that microtubules are involved in this nuclear migration.