Ecological and habitat ranges of orchids in the northernmost regions of their distribution areas: A case study from Ural Mountains, Russia.

The Orchidaceae, which is one of the most interesting families of angiosperms, contains a large number of rare species. Despite their acknowledged importance, little attention has been paid to the study of orchids distributed in northern territories. In this study, we determined the syntaxonomical diversity and ecological parameters of orchid habitats in two of Europe's largest protected areas, the Pechoro-Ilychsky Reserve and the Yugyd Va National Park (northeastern European Russia), and then compared our findings to those in other parts of orchid distribution ranges. For this purpose, we studied 345 descriptions of plant communities (releves) containing species from Orchidaceae and defined habitat parameters using Ellenberg indicator values with the community weight mean approach, nonmetric multidimensional scaling (NMS), and relative niche width. We found that orchids were distributed in eight habitat types and 97 plant associations. The largest number of orchid species is found in forest communities. Half of the orchid species under study occur in the mires and rock habitats with open vegetation. Several orchids consistently occur in areas disturbed by human activity. In addition, our study indicates that the main drivers of orchid distribution across the vegetation types are light and soil nitrogen. Our analysis of the ecological parameters of orchid habitats indicates that some orchid species can be classified as habitat specialists that are confined to a relatively narrow ecological niche in the Urals (e.g., Goodyera repens, Cypripedium guttatum and Dactylorhiza maculata). Several other species (e.g. Neottia cordata and Dactylorhiza fuchsia) grow under diverse ecological parameters.

Grey wolf genomic history reveals a dual ancestry of dogs.

The grey wolf (Canis lupus) was the first species to give rise to a domestic population, and they remained widespread throughout the last Ice Age when many other large mammal species went extinct. Little is known, however, about the history and possible extinction of past wolf populations or when and where the wolf progenitors of the present-day dog lineage (Canis familiaris) lived1-8. Here we analysed 72 ancient wolf genomes spanning the last 100,000 years from Europe, Siberia and North America. We found that wolf populations were highly connected throughout the Late Pleistocene, with levels of differentiation an order of magnitude lower than they are today. This population connectivity allowed us to detect natural selection across the time series, including rapid fixation of mutations in the gene IFT88 40,000-30,000 years ago. We show that dogs are overall more closely related to ancient wolves from eastern Eurasia than to those from western Eurasia, suggesting a domestication process in the east. However, we also found that dogs in the Near East and Africa derive up to half of their ancestry from a distinct population related to modern southwest Eurasian wolves, reflecting either an independent domestication process or admixture from local wolves. None of the analysed ancient wolf genomes is a direct match for either of these dog ancestries, meaning that the exact progenitor populations remain to be located.

Occurrences of Threatened Species included in the Third Edition of the Red Data Book of the Komi Republic (Russia).

BACKGROUND: The purpose of the data paper was to introduce into scientific literature the results of scientific work carried out for the third edition of the 'Red Data Book of the Komi Republic'. The article reflects methodological approaches to the formation of a list of rare and in need of protection species and describes the corresponding datasets published in GBIF. NEW INFORMATION: Information about 7,187 occurrences of 438 rare species and infraspecies included in the third edition of the 'Red Data Book of the Komi Republic' have been published.

Ancient and modern genomes unravel the evolutionary history of the rhinoceros family.

Only five species of the once-diverse Rhinocerotidae remain, making the reconstruction of their evolutionary history a challenge to biologists since Darwin. We sequenced genomes from five rhinoceros species (three extinct and two living), which we compared to existing data from the remaining three living species and a range of outgroups. We identify an early divergence between extant African and Eurasian lineages, resolving a key debate regarding the phylogeny of extant rhinoceroses. This early Miocene (∼16 million years ago [mya]) split post-dates the land bridge formation between the Afro-Arabian and Eurasian landmasses. Our analyses also show that while rhinoceros genomes in general exhibit low levels of genome-wide diversity, heterozygosity is lowest and inbreeding is highest in the modern species. These results suggest that while low genetic diversity is a long-term feature of the family, it has been particularly exacerbated recently, likely reflecting recent anthropogenic-driven population declines.

Ancient horse genomes reveal the timing and extent of dispersals across the Bering Land Bridge.

The Bering Land Bridge (BLB) last connected Eurasia and North America during the Late Pleistocene. Although the BLB would have enabled transfers of terrestrial biota in both directions, it also acted as an ecological filter whose permeability varied considerably over time. Here we explore the possible impacts of this ecological corridor on genetic diversity within, and connectivity among, populations of a once wide-ranging group, the caballine horses (Equus spp.). Using a panel of 187 mitochondrial and eight nuclear genomes recovered from present-day and extinct caballine horses sampled across the Holarctic, we found that Eurasian horse populations initially diverged from those in North America, their ancestral continent, around 1.0-0.8 million years ago. Subsequent to this split our mitochondrial DNA analysis identified two bidirectional long-range dispersals across the BLB ~875-625 and ~200-50 thousand years ago, during the Middle and Late Pleistocene. Whole genome analysis indicated low levels of gene flow between North American and Eurasian horse populations, which probably occurred as a result of these inferred dispersals. Nonetheless, mitochondrial and nuclear diversity of caballine horse populations retained strong phylogeographical structuring. Our results suggest that barriers to gene flow, currently unidentified but possibly related to habitat distribution across Beringia or ongoing evolutionary divergence, played an important role in shaping the early genetic history of caballine horses, including the ancestors of living horses within Equus ferus.

Origins and genetic legacy of prehistoric dogs.

Dogs were the first domestic animal, but little is known about their population history and to what extent it was linked to humans. We sequenced 27 ancient dog genomes and found that all dogs share a common ancestry distinct from present-day wolves, with limited gene flow from wolves since domestication but substantial dog-to-wolf gene flow. By 11,000 years ago, at least five major ancestry lineages had diversified, demonstrating a deep genetic history of dogs during the Paleolithic. Coanalysis with human genomes reveals aspects of dog population history that mirror humans, including Levant-related ancestry in Africa and early agricultural Europe. Other aspects differ, including the impacts of steppe pastoralist expansions in West and East Eurasia and a near-complete turnover of Neolithic European dog ancestry.

Pre-extinction Demographic Stability and Genomic Signatures of Adaptation in the Woolly Rhinoceros.

Ancient DNA has significantly improved our understanding of the evolution and population history of extinct megafauna. However, few studies have used complete ancient genomes to examine species responses to climate change prior to extinction. The woolly rhinoceros (Coelodonta antiquitatis) was a cold-adapted megaherbivore widely distributed across northern Eurasia during the Late Pleistocene and became extinct approximately 14 thousand years before present (ka BP). While humans and climate change have been proposed as potential causes of extinction [1-3], knowledge is limited on how the woolly rhinoceros was impacted by human arrival and climatic fluctuations [2]. Here, we use one complete nuclear genome and 14 mitogenomes to investigate the demographic history of woolly rhinoceros leading up to its extinction. Unlike other northern megafauna, the effective population size of woolly rhinoceros likely increased at 29.7 ka BP and subsequently remained stable until close to the species' extinction. Analysis of the nuclear genome from a ∼18.5-ka-old specimen did not indicate any increased inbreeding or reduced genetic diversity, suggesting that the population size remained steady for more than 13 ka following the arrival of humans [4]. The population contraction leading to extinction of the woolly rhinoceros may have thus been sudden and mostly driven by rapid warming in the Bølling-Allerød interstadial. Furthermore, we identify woolly rhinoceros-specific adaptations to arctic climate, similar to those of the woolly mammoth. This study highlights how species respond differently to climatic fluctuations and further illustrates the potential of palaeogenomics to study the evolutionary history of extinct species.

Early Pleistocene enamel proteome from Dmanisi resolves Stephanorhinus phylogeny.

The sequencing of ancient DNA has enabled the reconstruction of speciation, migration and admixture events for extinct taxa1. However, the irreversible post-mortem degradation2 of ancient DNA has so far limited its recovery-outside permafrost areas-to specimens that are not older than approximately 0.5 million years (Myr)3. By contrast, tandem mass spectrometry has enabled the sequencing of approximately 1.5-Myr-old collagen type I4, and suggested the presence of protein residues in fossils of the Cretaceous period5-although with limited phylogenetic use6. In the absence of molecular evidence, the speciation of several extinct species of the Early and Middle Pleistocene epoch remains contentious. Here we address the phylogenetic relationships of the Eurasian Rhinocerotidae of the Pleistocene epoch7-9, using the proteome of dental enamel from a Stephanorhinus tooth that is approximately 1.77-Myr old, recovered from the archaeological site of Dmanisi (South Caucasus, Georgia)10. Molecular phylogenetic analyses place this Stephanorhinus as a sister group to the clade formed by the woolly rhinoceros (Coelodonta antiquitatis) and Merck's rhinoceros (Stephanorhinus kirchbergensis). We show that Coelodonta evolved from an early Stephanorhinus lineage, and that this latter genus includes at least two distinct evolutionary lines. The genus Stephanorhinus is therefore currently paraphyletic, and its systematic revision is needed. We demonstrate that sequencing the proteome of Early Pleistocene dental enamel overcomes the limitations of phylogenetic inference based on ancient collagen or DNA. Our approach also provides additional information about the sex and taxonomic assignment of other specimens from Dmanisi. Our findings reveal that proteomic investigation of ancient dental enamel-which is the hardest tissue in vertebrates11, and is highly abundant in the fossil record-can push the reconstruction of molecular evolution further back into the Early Pleistocene epoch, beyond the currently known limits of ancient DNA preservation.

Dynamics of body mass index and visceral adiposity index in patients with rheumatoid arthritis treated with tofacitinib.

The increase in cardiovascular risk in patients with rheumatoid arthritis (RA) compared with the general population is due to the combined effect of traditional risk factors for cardiovascular diseases, metabolic disorders, systemic inflammation, and side effects of antirheumatic drugs. Tofacitinib (TOFA) is an oral reversible inhibitor of janus kinases for the treatment of RA with proven efficacy and good tolerability, but its effects on body weight and metabolic profile need to be clarified. We investigated the effects of TOFA on body mass index (BMI) and visceral adiposity index (VAI) in RA patients. Thirty-one consecutive patients with active RA and starting new treatment with TOFA were included in a prospective 1 year follow-up observational study of cardiovascular effects of TOFA treatment. Weight, height, waist circumference, BMI, blood pressure, lipid profile, fasting glucose and VAI were measured at baseline and 12 months of treatment. Median weight gain was 3 kg (4.2%) after 1 year of TOFA. 23 (74%) patients suffered from a weight gain, and 6 (26%) out of them from a weight increment of 10% or more. Patients with lower BMI (p = 0.024) and higher baseline DAS28 [ESR] (p = 0.017) have the risk of an increase in BMI > 5% during TOFA treatment in a multivariate analysis. A decrease in VAI after 12 months was recorded. Weight increment and improvement of VAI are frequent on TOFA treatment. BMI dynamics associated with higher disease activity at baseline and lower baseline BMI.

Metapodials of ancient bison (Bison priscus) of northeast Russia: "stress markers," sex and withers height.

A total of 175 metapodials (MP) of Pleistocene and early Holocene bison (Bison priscus Boj.) from the vast area of northeast Russia were studied. MP were attributed to males and females both visually and statistically. Data on the withers height of bison from northeast Russia are provided. Stress markers were recorded, including so-called "buttresses." With rare exceptions, stress markers were not of a pathological nature. The origin and development of the buttresses are age-related; their prevalence in bison females can be considered as the response to an increased load during pregnancy. Changes in the periosteum, found in males, are related to their greater activity. Buttresses are also well developed on metatarsals of the red deer and the elk; they are less developed in reindeer and not found in giant deer. A relationship among stress markers, locomotion and the environment is established. Possible peculiarities of the Rauchua River bison locomotion are discussed.

Dynamic of changes in coronary artery calcification in early rheumatoid arthritis patients over 18 months.

The coronary artery calcification (CAC) progression may be useful noninvasive predictor of future cardiovascular events (CVE). The progression rate of CAC in patients with early rheumatoid arthritis (RA) is poorly understood. To assess the dynamic of CAC scores in early RA patients for 18 months, 74 RA adult patients (ACR/EULAR criteria, 2010, duration ≤ 12 months, with moderate/high RA activity, without prior administration of disease-modifying anti-rheumatic drugs or glucocorticoids) were enrolled within the framework of the observational study: women 73%, median age 56 years, median RA duration 6 months, median DAS28[ESR] 5.4. Most of the patients had multiple Traditional Risk Factors (TRFs) of Cardiovascular Disease (CVD). All patients at baseline and after 18 months underwent 32-row scanning for CAC scoring. In patients younger than 45 years (n = 16) any CAC was not detected during 18 months. Among patients older than 45 years four new events of CAC were detected. Among patients older than 45 years with baseline CAC (n = 34) increase in CAC scores was detected in 82% cases. Among them, Δ Agatston Score exceeded the median annual Agatston Score progression predicted for the general population according to the Multi-Ethnic Study of Atherosclerosis (MESA) data in 57% of early RA patients. The significant increase of Agatston Score in accordance with Sevrukov's method was met in one patient with newly diagnosed CAC and among patients with baseline CAC-in 29%. The presence of CAC progression was associated with lower baseline total cholesterol (TC) level (p < 0.05). The extent of CAC progression associated with male gender and arterial hypertension (AH) (p < 0.05). Association between CAC dynamic and statin therapy, RA activity and cumulative inflammatory burden, response to anti-rheumatic therapy and the type of this therapy were not detected. Early RA patients older than 45 years have high incidence of CAC progression during 18 months. More than half of the early RA patients had the increase in AS which exceeded the median annual progression of Agatston Score in the MESA. The CAC progression was associated with male gender, AH and lower baseline TC level. We did not detect any association between CAC progression and statin therapy, RA activity and type of anti-rheumatic therapy.

Calcification of coronary arteries in early rheumatoid arthritis prior to anti-rheumatic therapy.

Accelerated coronary atherosclerosis is common in patients with rheumatoid arthritis (RA). To examine coronary artery calcification (CAC) frequency and severity, its correlation with traditional risk factors (TRF) of cardiovascular diseases (CVD) and inflammatory markers in patients with early RA prior to anti-rheumatic therapy. RA adult patients (ACR/EULAR criteria, 2010, duration ≤ 12 months, without prior administration of disease-modifying anti-rheumatic drugs, glucocorticoids) underwent 32-row scanning for CAC scoring. Agatston, volume and mass calcium scores were calculated. Additionally, we used calculators on the website of the Multi-Ethnic Study of Atherosclerosis. 74 RA patients (women n = 54 (73%), median age 56 years, median RA duration 6 months) with moderate/high RA activity (median DAS28 [ESR] 5.4) were enrolled within the framework of the observational study. Most of the patients had multiple TRFs of CVD and subclinical organ damage. CAC has been detected in 34 (46%) early RA patients. Calcification severity was significantly higher in men and in patients with ischemic heart disease (IHD). In patients younger than 45 years (n = 16) CAC was not detected. Among patients older than 45 years (n = 58), the frequency of CAC was 59%: asymptomatic patients-n = 46 (48%), IHD patients-n = 12 (100%). Among asymptomatic patients the presence of CAC associated with a significantly higher frequency of arterial hypertension (1.6 fold) compared with cases without CAC. Coronary age in asymptomatic patients with CAC and IHD patients was significantly greater than their actual age. More than half of early RA patients older 45 years had CAC. The presence and severity of CAC correlated positively with TRFs, but not with lipid levels and RA activity.

Biomechanical rationale of coronary artery bypass grafting of multivessel disease.

The biomechanical model of human coronary arteries was modified for improving the quality of diagnosis and surgical treatment for coronary heart disease. The problem of hemodynamics in the left coronary artery with multivessel bed disease - 45% stenosis of the anterior descending branch and 75% stenosis of the circumflex branch - was particularly considered. Numerical simulation of the coronary arterial bypass of the main trunk was carried out to estimate the functional condition of the coronary arteries after restoring myocardial blood supply by surgery.

The PUFA-enriched fatty acid profiles of some frozen bison from the early Holocene found in the Siberian permafrost.

Knowledge concerning the availability of n-3 fatty acids for humans in prehistoric times is highly relevant in order to draw useful conclusions on the healthy dietary habits for present-day humans. To this end, we have analysed fat from several frozen bison found in the permafrost of Siberia (Russia). A total of 3 bison were included in this study, all them very close to the early Holocene (8,000; 8,200; and 9,300 years BP). All samples were analysed by gas-liquid chromatography-mass spectrometry (GLC-MS) and GLC flame-ionization detection (GLC-FID). Fat samples from two bison showed two well-differenced areas, i.e. brown and white, the latter being saturated fatty acid enriched, corresponding to an intermediate stage of adipocere formation, while the brown ones yielded α-linolenic acid in higher percentages than found in present-day bison. As demonstrated in this work, the subcutaneous fat of bison consumed by Mesolithic hunters contained amounts of n-3 fatty acids in higher quantities than those found in current bison; thus, the subcutaneous fat of bison could have contributed to meet today's recommended daily intake of essential fatty acids for good health in the Mesolithic to a greater extent than previously thought.

Extraocular muscle satellite cells are high performance myo-engines retaining efficient regenerative capacity in dystrophin deficiency.

Extraocular muscles (EOMs) are highly specialized skeletal muscles that originate from the head mesoderm and control eye movements. EOMs are uniquely spared in Duchenne muscular dystrophy and animal models of dystrophin deficiency. Specific traits of myogenic progenitors may be determinants of this preferential sparing, but very little is known about the myogenic cells in this muscle group. While satellite cells (SCs) have long been recognized as the main source of myogenic cells in adult muscle, most of the knowledge about these cells comes from the prototypic limb muscles. In this study, we show that EOMs, regardless of their distinctive Pax3-negative lineage origin, harbor SCs that share a common signature (Pax7(+), Ki67(-), Nestin-GFP(+), Myf5(nLacZ+), MyoD-positive lineage origin) with their limb and diaphragm somite-derived counterparts, but are remarkably endowed with a high proliferative potential as revealed in cell culture assays. Specifically, we demonstrate that in adult as well as in aging mice, EOM SCs possess a superior expansion capacity, contributing significantly more proliferating, differentiating and renewal progeny than their limb and diaphragm counterparts. These robust growth and renewal properties are maintained by EOM SCs isolated from dystrophin-null (mdx) mice, while SCs from muscles affected by dystrophin deficiency (i.e., limb and diaphragm) expand poorly in vitro. EOM SCs also retain higher performance in cell transplantation assays in which donor cells were engrafted into host mdx limb muscle. Collectively, our study provides a comprehensive picture of EOM myogenic progenitors, showing that while these cells share common hallmarks with the prototypic SCs in somite-derived muscles, they distinctively feature robust growth and renewal capacities that warrant the title of high performance myo-engines and promote consideration of their properties for developing new approaches in cell-based therapy to combat skeletal muscle wasting.

Hybrid coarse-grained/atomistic model of "chitosan + carbon nanostructures" composites.

We present a new hybrid molecular dynamics model of chitosan oligomers which is constructed specifically for studying chitosan + carbon nanostructures composites, their structure and mechanical properties. The model is derived for application within the modified molecular mechanics force field AMBER. Method of virtual sites mapping allowed to retain hexagonal rings of chitosan backbone. Mass and structural disposition of virtual atoms has been found as function of joined groups' atoms masses and coordinates. Geometrical parameters (e.g., bond length, valence angles, torsional angles and van der Waals distances) were found using semi-empirical methods. Parameters of interaction within the AMBER force field were estimated according to structural and energy characteristics of chitosan dimers and oligomers. Model has successfully passed multilevel verification based on comparison of its behaviour with atomistic chitosan within the same force field. It appeared that the model reproduces structural and energy characteristics of chitosan and its composites with carbon nanostructures. Moreover, it allows estimation of their mechanical properties. Dynamical characteristics of composite components are also well reproduced.

Effect of local and intravenous lidocaine on ongoing activity in injured afferent nerve fibers.

Lidocaine applied systemically or locally attenuates neuropathic pain in patients. Here we tested the hypothesis that ectopic activity in injured afferent A- or C-fibers is suppressed by lidocaine. In rats the sural nerve (skin nerve) or lateral gastrocnemius-soleus nerve (muscle nerve) was crushed. Four to 11 days after crush lesion afferent fibers were isolated from the lesioned nerves in bundles rostral to the injury site. Ongoing ectopic activity was recorded from 75 A-fibers (muscle N=43, skin N=32) and 69 C-fibers (muscle N=30, skin N=39). Most afferent fibers were functionally characterized by their responses to mechanical and thermal (mostly heat) stimuli applied at or distal to the nerve injury site. Low-threshold cold-sensitive cutaneous C-fibers were excluded from the analysis. Lidocaine was either applied to the nerve at or distal to the injury site in concentrations of 1 to 1000 µg/mL or injected i.v. in doses of 0.09 to 9 mg/kg (skin) or 0.047 to 4.7 mg/kg (muscle). Local application of lidocaine depressed ectopic activity in A- and C-fibers dose-dependently. Depression was weaker in C- than in A-fibers. Intravenous application of lidocaine depressed ongoing ectopic activity in A- and C-fibers dose-dependently. Responses to heat or mechanical stimulation of the injured nerve were not suppressed at the highest concentrations of lidocaine. The results support the hypothesis that decrease of neuropathic pain following local or systemic application of a local anesthetic is related to decrease of ectopic ongoing activity in injured afferent nerve fibers.

Mechano- and thermosensitivity of injured muscle afferents.

Injury of limb nerves leading to neuropathic pain mostly affects deep somatic nerves including muscle nerves. Here, we investigated the functional properties of injured afferent fibers innervating the lateral gastrocnemius-soleus muscle 4-13 h [time period (TP) I] and 4-7 days (TP II) after nerve crush in anesthetized rats using neurophysiological recordings from either the sciatic nerve (165 A-, 137 C-fibers) or the dorsal root L(5) (43 A-, 28 C-fibers). Ongoing activity and responses to mechanical or thermal stimulation of the injury site of the nerve were studied quantitatively. Of the electrically identified A- and C-fibers, 5 and 38% exhibited ectopic activity, respectively, in TP I and 51 and 61%, respectively, in TP II. Thus all afferent fibers in an injured muscle nerve developed ectopic activity since ∼ 50% of the fibers in a muscle nerve are somatomotor or sympathetic postganglionic. Ongoing activity was present in 50% of the afferent A-fibers (TP II) and in 53-56% of the afferent C-fibers (TP I and II). In TP II, mechanical, cold, and heat sensitivity were present in 91, 63, and 52% of the afferent A-fibers and in 50, 40, and 66% of the afferent C-fibers. The cold and heat activation thresholds were 5-27 and 35-48°C, respectively, covering the noxious and innocuous range. Most afferent fibers showed combinations of these sensitivities. Mechano- and cold sensitivity had a significantly higher representation in A- than in C-fibers, but heat sensitivity had a significantly higher representation in C- than in A-fibers. These functional differences between A- and C-fibers applied to large- as well as small-diameter A-fibers. Comparing the functional properties of injured muscle A- and C-afferents with those of injured cutaneous A- and C-afferents shows that both populations of injured afferent neurons behave differently in several aspects.

Meiosis errors in over 20,000 oocytes studied in the practice of preimplantation aneuploidy testing.

This study presents the world's largest series of over 20,000 oocytes tested for aneuploidies, involving chromosomes 13,16, 18, 21 and 22, providing the data on the rates and types of aneuploidies and their origin. Almost every second oocyte (46.8%) is abnormal, with predominance of extra chromatid errors predicting predominance of trisomies (53%) over monosomies (26%) in the resulting embryos (2:1), which is opposite to monosomy predominance observed in embryo testing. Of the detected anomalies in oocytes, 40% are complex, so testing for a few most prevalent chromosome errors may allow detection of the majority of abnormal embryos. Chromosome 21 and 22 errors are more prevalent, while two different patterns of error origin were observed for different chromosomes: chromosome 16 and 22 errors originate predominantly from meiosis II, compared with chromosome 13, 18 and 21 errors originating from meiosis I. This provides the first evidence for the differences in the aneuploid embryo survival depending on the meiotic origin. Considering the problem of mosaicism, which is the major limitation of the cleavage-stage testing, the direct oocyte aneuploidy testing by polar body analysis may be of obvious practical value in improving accuracy and reliability of avoiding aneuploid embryos for transfer.

Stable isotope ((13)C/(12)C and (15)N/(14)N) composition of the woolly rhinoceros Coelodonta antiquitatis horn suggests seasonal changes in the diet.

The extinct woolly rhinoceros Coelodonta antiquitatis is a prominent member of the Mammuthus-Coelodonta faunal complex, but its biology is poorly known, partly because very few specimens with well-preserved soft tissues have been discovered to date. However, the permafrost-preserved horns of the woolly rhinoceros are recording structures which contain isotopic records of the diet, environmental conditions and physiological status of the animal during most of its life. In this study we report the first data on the pattern of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) isotopic composition along the nasal horn of woolly rhinoceros. We found systematic variations in δ(13)C and δ(15)N values associated with morphologically expressed transverse banding of the horn. The comparative analysis of isotopic variation in keratinous tissues of extant and extinct herbivores suggests that the oscillation in isotopic composition of the horn was induced by seasonal changes in the diet. Although the compiled evidence is in part contradictory, we suggest that more positive δ(13)C and δ(15)N values associated with dark-colored and less dense zones of the horn indicate a summer diet. More dense and light-colored zones of the horn have lower δ(13)C and δ(15)N values possibly indicating a larger proportion of woody and shrub vegetation in the winter diet. The validity of these conclusions has to be proven in further investigations, but our data underline the potential of isotopic analysis for studies on diet and habitat use by extinct members of Pleistocene fauna.