Ancient Mammalian and Plant DNA from Late Quaternary Stalagmite Layers at Solkota Cave, Georgia.

Metagenomic analysis is a highly promising technique in paleogenetic research that allows analysis of the complete genomic make-up of a sample. This technique has successfully been employed to archaeological sediments, but possible leaching of DNA through the sequence limits interpretation. We applied this technique to the analysis of ancient DNA (aDNA) from Late Quaternary stalagmites from two caves in Western Georgia, Melouri Cave and Solkota. Stalagmites form closed systems, limiting the effect of leaching, and can be securely dated with U-series. The analyses of the sequence data from the Melouri Cave stalagmite revealed potential contamination and low preservation of DNA. However, the two Solkota stalagmites preserved ancient DNA molecules of mammals (bear, roe deer, bats) and plants (chestnut, hazelnut, flax). The aDNA bearing layers from one of the two Solkota stalagmites were dated to between ~84 ka and ~56 ka BP by U-series. The second Solkota stalagmite contained excessive detrital clay obstructing U-series dating, but it also contained bear bones with a minimum age of ~50 BP uncalibrated years and ancient DNA molecules. The preservation of authentic ancient DNA molecules in Late Quaternary speleothems opens up a new paleogenetic archive for archaeological, paleontological and paleoenvironmental research.

[Direct recording of the electrical activity of the sinoatrial node]. / Priamaia registratsiia élektricheskoi aktivnosti sinoatrial'nogo uzla.

The electrical activity of the sinoatrial node was recorded simultaneously from the epicardial and endocardial surfaces of the sinoatrial node in 73 dogs. The electrical activity of sinoatrial node had the form of a slow deflection and a rapid preatrial deflection, the duration of the former being 81 +/- 28 msec and reflecting slow propagation of excitation within the sinus node. Duration of the rapid preatrial deflection was 17 +/- 11 msec. It reflects the rapid propagation of the sinus impulse (probably, the rapid spread of the excitation in corona of the sinus node and invasion in crista terminals). The form and duration of the slow and rapid deflections changed under the influence of drugs.