Самый древний сохранившийся мозг
Три года назад в болотах Великобритании был найден прекрасно сохранившийся человеческий мозг возрастом примерно 2684 года. Недавно результаты его тщательного изучения были опубликованы в статье "Exceptional preservation of a prehistoric human brain from Heslington, Yorkshire, UK".
К сожалению, "прекрасно сохранился" мозг только по сравнению с мозгами его современников. Спасен он был случайно, когда владельцу мозга отрубили голову и сбросили ее в болото. Отсутствие кислорода и натуральная химическая фиксация позволили мозгу в целом сохраниться, но разрушение клеточной структуры все равно произошло. На будущее можно посоветовать использовать болота хотя бы в зоне вечной мерзлоты, а лучше в Антарктиде.
Самая интересная часть статьи:
"Изучение под микроскопом окрашенных срезов фрагментов мозга показало гомогенную аморфную субстанцию без клеточной или матричной структуры. Электронная микроскопия также не вскрыла клеточной структуры, хотя и были обнаружены следы разрушенных структур, напоминающих миелиновые оболочки нервных волокон. Эти результаты говорят о разрушении мозга путем стерильного автолиза."
Молекулярный анализ показал значительные изменения на молекулярном уровне, начиная от аномального состава аминокислот и заканчивая почти полным отсутствием фосфолипидов. Тем не менее с помощью методов протеомики удалось обнаружить два специфичных для мозга белка - липофилин и клаудин-11.
Я подозреваю, что с помощью поатомного сканирования с помощью нанороботов или послойной дизассембляции и дальнейшего анализа с помощью ИИ на суперкомпьютере можно было бы восстановить некоторую часть структуры на уровне достаточном для восстановления элементов нейронной сети мозга этого человека. Как известно, некоторые специалисты, такие как математик-нанотехнолог Ральф Меркль, придерживаются в этом отношении оптимистических взглядов.
Однако на практике более важным является возможность сохранения мозга с помощью крионики. Если даже природное сохранение (пусть даже и крайне редкое) мозга может обеспечить столь высокую сохранность на протяжении двух с половиной тысяч лет, то криосохранение практически гарантированно сохранит личность для оживления в будущем.
Под катом непереведенный фрагмент статьи про сохранность мозга. Полная статья тут. 4.4. Examination of the brain masses
CT of the cranium had revealed several fragments of brain loose inside and mixed with the denser sediment. The brain masses had recognisable sulci and gyri and many internal voids which are mainly post-mortem features (Fig. 4). CT could not differentiate between the brain cortex (grey matter) and underlying medulla (white matter). Subsequent MRI produced similarly useful images but did not elucidate this point.
Within the cranium, therewere five major brain masses and many millimetre-scale fragments of brain tissue. Following superficial cleaning of the masses, gross anatomical features such as well- defined sulci and gyri were clearly identifiable. The tissue was odourless, had a smooth surfacewith a resilient, tofu-like texture and wasmore pink/brown or tan in colour in daylight than had appeared when first viewed by electric light within the cranium, when it had appeared yellow (Fig. 9). The scale of the surface convolutions, taken with the overall volume of survivingmaterial, indicated that the brain had shrunken to perhaps 20% of the volume of a fresh brain (i.e. to about 250-300 ml). One of the largest masses, approximately 70 mm x 60 mm x 30 mm, also had an area of black membranous material, perhaps a fragment of the meninges (Fig. 9b). Where the masses had fractured, they had a soft, granular texture and were lighter in colour than the exterior surfaces (Fig. 9c). The expected distribution of white and grey matter could not be discerned macroscopically.
Imaging by 3D laser scanning of the major fragments was successful, except for one fragment that, when turned over, dis- orted to the extent that the data sets could not be integrated. The mages reconstructed from the data allow the fragments to be viewed from all angles and brought together in different combi- nations to help identify the portions of the brain that have survived, without the risks associated with handling the fragments them- selves. The photographs can also be digitally added to the surface of he 3D reconstructions (Fig. 10) and the scan data could be used to produce replicas of the fragments using rapid phototyping tech- niques. Imaging by micro-CT was unsuccessful but it is hoped that more useful results may be obtained in the future if the results eported here, and subsequent analyses of composition, allow a more precise calibration of equipment to optimise the imaging. 4.5. Histological examination of the brain masses
Both toluidine blue and haematoxylineeosin staining of the brain sections showed a homogeneous, amorphous substance that had not retained any cellular or matrix structure. TEM also did not detect any surviving cellular structure although these images did show the presence of numerous morphologically-degraded struc- tures characteristic of the myelin sheath of nerve fibres (Fig. 11). A few bacterial spores could be recognised on TEM, but no other traces of putrefactive bacteria or fungi where evident. This obser- vation is more consistent with degradation by sterile autolysis than with putrefaction. SEM captured the spongy, granular nature of the fracture surface of the brain mass (Fig. 12) but added little to the understanding of the surviving histology. 4.6. Biomolecular analysis of the brain masses
It is only possible here to provide a summary of the initial results of the array of qualitative, quantitative and compositional techniques that have been applied to the brain. The C:N ratio of the tissues was 6.3 (n = 2) suggesting considerable retained nitrogen, more than double the nitrogen content of the least refractory soils, (soil C:N ratios range from13 to 40; e.g. Aitkenhead and McDowell, 2000). Degraded protein and indications of possible cyanobacterial colonisation were identified and the proportion of proteinaceous matter in the brainwas higher than in the sediments in and around the skull. Notably, however only 5% of the total tissue in the Heslington brain was detectable as hydrolysable amino acids whereas proteins represent more than a third of the dry weight of fresh brain tissue. The remaining nitrogen revealed by the C:N ratio remains unaccounted for in terms of protein. The amino acid profiles were all remarkably similar to each other and racemization levels were all lower than D/L 0.06 except for Asx (D/L 0.17). However when compared with a fresh brain the material was depleted in polar amino acids (Asx, Glx, Ser) and enriched in hydrophobic amino acids (Gly, Ala, Val, Phe, Leu, Ile). Two brain- specific proteins were unambiguously identified using proteomic techniques; myelin proteolipid protein (lipophilin) and claudin-11 (oligodendrocyte-specific protein). The three lipophilin peptide sequences matched are common to humans and a number of other mammals; the single claudin-11 peptide sequence detected is present in both humans and orang-utan. Aggregated structural brain-specific proteins have been isolated using highly sensitive in- house developed immunoassays (for review see Petzold, 2005).
Lipids constitute almost half the dry weight of fresh vertebrate brain tissue and roughly 25% of the total free cholesterol in thewhole body (McIlwain and Bachelard, 1985), however, very little unde- graded solvent-soluble brain lipid appears to have been preserved and this brain contains lower proportions of extractable lipids (0.8e1.1% wet weight compared with 17.1% for rat brain) than the sediments from the interior of the skull, the maxillary sinus and orbits. Significantly there is an almost complete absence of phos- pholipids and only a trace of cholesterol, but coprostanone (5b- cholestan-3-one), a well-known microbial alteration product of cholesterol, was detected along with fatty acids and other degrada- tion products of a wide range of lipids including hydroxyfatty acids, aldehydes, thiophenes and very low levels of sterols/stanones. This includes a series of 2-hydroxyfatty acids, identified as trimethylsilyl derivatives, with carbon numbers ranging from C22:0eC25:0 with the 2-hydroxyfatty acid of C24:0 predominating. The latter molecule is also known as cerebronic acid and is the major hydroxyfatty acid found in brain cerebrosides (Eng et al., 1965). The 2-hydroxy deriv- ative of C24:1 is also present in the lipid extract albeit in lower abundance compared to fresh brain tissue. Cerebrosides are present mainly in brainwhitematter, especially inmyelin (Siegel and Albers, 2006, 35). The same distribution of 2-hydroxy acids and sterols has been found in the brain tissue of GristhorpeMan (Melton et al., 2010; Heron, unpublished results) and in permafrost-preservedmammoth brains (Kreps et al., 1981).