Morphology of rhinoceros platelets

Basic hematological information about rhinoceros species is limited. In this study, we have determined the platelet counts and described the platelet morphology of free-living white (Ceratotherium simum) and black (Diceros bicornis) rhinoceros using light and electron microscopy. The platelet counts of the two species were similar, but there were significant differences in platelet size as well as morphology between the species. The presence of large, nondiscoid platelet forms, resembling proplatelet or stress platelet forms, were observed in both, although not as often in the white rhinoceros as in the black rhinoceros.     

Critical Transitions in Early Embryonic Aortic Arch Patterning and Hemodynamics

Transformation from the bilaterally symmetric embryonic aortic arches to the mature great vessels is a complex morphogenetic process, requiring both vasculogenic and angiogenic mechanisms. Early aortic arch development occurs simultaneously with rapid changes in pulsatile blood flow, ventricular function, and downstream impedance in both invertebrate and vertebrate species. These dynamic biomechanical environmental landscapes provide critical epigenetic cues for vascular growth and remodeling. In our previous work, we examined hemodynamic loading and aortic arch growth in the chick embryo at Hamburger-Hamilton stages 18 and 24. We provided the first quantitative correlation between wall shear stress (WSS) and aortic arch diameter in the developing embryo, and observed that these two stages contained different aortic arch patterns with no inter-embryo variation. In the present study, we investigate these biomechanical events in the intermediate stage 21 to determine insights into this critical transition. We performed fluorescent dye microinjections to identify aortic arch patterns and measured diameters using both injection recordings and high-resolution optical coherence tomography. Flow and WSS were quantified with 3D computational fluid dynamics (CFD). Dye injections revealed that the transition in aortic arch pattern is not a uniform process and multiple configurations were documented at stage 21. CFD analysis showed that WSS is substantially elevated compared to both the previous (stage 18) and subsequent (stage 24) developmental time-points. These results demonstrate that acute increases in WSS are followed by a period of vascular remodeling to restore normative hemodynamic loading. Fluctuations in blood flow are one possible mechanism that impacts the timing of events such as aortic arch regression and generation, leading to the variable configurations at stage 21. Aortic arch variations noted during normal rapid vascular remodeling at stage 21 identify a temporal window of increased vulnerability to aberrant aortic arch morphogenesis with the potential for profound effects on subsequent cardiovascular morphogenesis.     

甘肃临夏盆地牙沟的哺乳动物化石及有关地层问题

记述了临夏盆地牙沟地点除巨犀以外的 8类哺乳动物化石 :Tsaganomysaltaicus、Mega lopterodonsp .、Schizotheriumordosium、Hyracodontidaegen.etsp .indet.、Ardyniaaltidentatasp .nov.、Ardyniasp .、Aprotodonlanzhouensis和Paraentelodoncf.P .macrognathus。新种Ardyniaalti dentata的主要特征是 :个体大 ,齿冠高 ;M2冠高大于冠长 ,“小刺”异常发育 ,后脊退缩 ;下臼齿下三角座变短 ,外中沟位于齿长的前 1 /3处。牙沟、椒子沟和毛沟底部地层中所发现的哺乳动物化石均产自同一层位 ,其时代为晚渐新世 ,而不是早中新世。含化石的地层属椒子沟组。李吉均等所建中庄组应予废除     

Comparison of whole mitochondrial genome sequences of northern and southern white rhinoceroses (<Emphasis Type="Italic">Ceratotherium simum</Emphasis>): the conservation consequences of species definitions

The probable extinction of the last confirmed population of northern white rhinoceros (Ceratotherium simum cottoni) in the world has ignited debate regarding its species status compared to the southern white rhinoceros (Ceratotherium simum simum). Previous studies, based on partial mitochondrial sequences, have reported conflicting results regarding the species status of the northern white rhinoceros. We use whole mitochondrial genomes obtained using Next Generation Sequencing of four northern white rhinoceros and three southern white rhinoceros using novel primers in three overlapping fragments. Phylogenetic relationships were constructed, using Maximum Likelihood, and recovered monophyletic clades for northern white rhinoceros and southern white rhinoceros. The divergence time between the two mitochondrial DNA lineages was estimated to be between 0.46 and 0.97 million years ago using Bayesian inferences. Since there are currently only three surviving northern white rhinoceros individuals these results put into sharp focus the ongoing debate regarding the methods of species definition, and in particular the consequences of such definitions in conservation management of endangered species and subspecies. We conclude that the designation of sub-species status is more applicable to northern and southern white rhinoceros.     

Velocity distribution along an elastic model of human arterial tree

An experimental investigation of an elastic model of the human arterial tree, has been performed for physiological type flow by pulsed Doppler ultrasonic velocimetry. The arterial tree model, fabricated in clear polyurethane, includes the aortic arch, with a Starr-Edwards ball valve mounted in the root of the aorta, the descending aorta and the iliac bifurcation. Our study showed that the velocity profile, a few centimeters beyond the valve, is skewed, with higher velocities towards the top and the inner wall (anatomically the posterior and left lateral wall). An inward shift of the maximum velocity and reverse flow are denoted along the inner wall of the aortic arch. The velocity profiles in the descending aorta are blunted. Downstream from the vertex of the iliac bifurcation, there is vorticity creation, but the branching effect is quickly damped by the pulsatility of the flow and the elasticity of the wall.     

Wall shear stress distribution in a model human aortic arch: assessment by an electrochemical technique

Wall shear stress (WSS) distribution in a human aortic arch model is studied using 130 cathode electrodes flush-mounted on the model walls. Flow visualizations are made in a transparent geometry model to identify the regions of fluid mechanical interests, e.g. regions of flow separation, eddy formation and flow stagnancy. The 130 electrodes are strategically positioned in the arch based on information obtained from the flow visualizations. The measured data indicate that the aortic arch may be categorized into eight regions: three along the inner wall of the arch (A,B,C); and five near the outer wall (D,E,F,G,H). (1) The regions of low WSS are distributed along the inner wall of the ascending aorta A; the inner wall of the descending aorta C; and the upstream inner wall of the innominate and the common carotid branchings F. (2) The high WSS regions are distributed along the outer wall of the arch E; and the inner wall in the arch opposite to the left subclavian branching B. (3) In certain regions, high and low WSS may be found next to each other (e.g. G and H) without a definable boundary in between; and (4) as the Reynolds number increases, the areas of low WSS decrease, while the high WSS areas increase with no obvious change in magnitude of the stress along the inner wall of the arch. At the branchings, the WSS distribution is not affected by the Reynolds number within the range of observations. The measured WSS distribution is compared with Rodkiewicz's map of early atherosclerotic lesions in the aortic arch of cholesterol fed rabbits.     

Pitx2c patterns anterior myocardium and aortic arch vessels and is required for local cell movement into atrioventricular cushions

Inactivation of the left-right asymmetry gene Pitx2 has been shown, in mice, to result in right isomerism with associated defects that are similar to that found in humans. We show that the Pitx2c isoform is expressed asymmetrically in a presumptive secondary heart field within the branchial arch and splanchnic mesoderm that contributes to the aortic sac and conotruncal myocardium. Pitx2c was expressed in left aortic sac mesothelium and in left splanchnic and branchial arch mesoderm near the junction of the aortic sac and branchial arch arteries. Mice with an isoform-specific deletion of Pitx2c had defects in asymmetric remodeling of the aortic arch vessels. Fatemapping studies using a Pitx2 cre recombinase knock-in allele showed that daughters of Pitx2-expressing cells populated the right and left ventricles, atrioventricular cushions and valves and pulmonary veins. In Pitx2 mutant embryos, descendents of Pitx2-expressing cells failed to contribute to the atrioventricular cushions and valves and the pulmonary vein, resulting in abnormal morphogenesis of these structures. Our data provide functional evidence that the presumptive secondary heart field, derived from branchial arch and splanchnic mesoderm, patterns the forming outflow tract and reveal a role for Pitx2c in aortic arch remodeling. Moreover, our findings suggest that a major function of the Pitx2-mediated left right asymmetry pathway is to pattern the aortic arches, outflow tract and atrioventricular valves and cushions.     

Note on rhinoceros thyroid gland constitution

In the absence of direct embryological information an estimation of rhinoceros thyroid gland constitution is essayed on the basis of indirect evidence provided by a study of 22 rhinoceros thyroid lobes, representing all available rhinoceros species. It is concluded that the rhinoceros thyroid gland comprises two embryonal elements, deriving from the thyro-glossal duct and from the 4th pharyngeal pouch, responsible respectively for its ventral and dorsal portions.     

Observations on rhinoceros tongue morphology

The rhinoceros tongue is distinguished among perissodactyl organs by its sagittally divided intermolar eminence crowned by a dextral and a sinistral cluster of circumvallate papillae. These structures were originally noted in the Indian rhinoceros by Owen (1852) but have since remained unmentioned for this, or for any other rhinoceros form. They are here described for specimens of the Indian, African White and African Black rhinoceroses. The structural and functional nature of the intermolar eminence is established and this entity is distinguished from an hitherto unrecognized topographical component of the tongue, designated the pars elliptica linguae. The lingual morphology of the three rhinoceros forms is summarised and certain intergeneric differences are noted.     

Postcava structure in elephant and rhinoceros

The mammalian postcava is vulnerable to lumen diminution or collapse under sudden increase of intra-abdominal pressure. Against such collapse its dorsal wall receives an extrinsic protection from the abdominal parietes. Its ventral wall, however, develops an intrinsic protective mechanism in the form of a specialization of its histological architecture. This specialization is most readily noticeable in large-bodied mammals and details of it are given for four such forms, viz., Asiatic elephant ( Elephas ), Sumatran rhinoceros ( Didermocerus ), Black rhinoceros ( Diceros ) and White rhinoceros ( Ceratotheriurri ).     

Some properties of starch branching enzyme from indica rice endosperm (Oryza sativa L.)

Starch branching enzyme (α-1,4-glucan: α-1,4-glucan-6-glycosyl transferase; EC 2.4.1.18) catalyzes the formation of the α-1,6-bond in branched starch molecules such as amylopectin. Some characteristics of starch branching enzyme in rice endosperm (Oryza sativa L.) were determined because of the importance of starch structure for rice quality. Two or three peaks of starch branching enzyme activity were resolved by anion-exchange chromatography of extracts from high amylose rice. The properties of rice starch branching enzyme were similar to those found for the enzyme from other plant sources except for a much lower molecular weight. Rice branching enzyme had an apparent molecular weight of 40 000 as estimated by gel permeation chromatography. Multiple forms of starch branching enzyme could also be resolved in milled rice, suggesting that relationships between starch quality and characteristics of starch branching enzyme could be examined in the mature grain after harvest.     

FOOD PREFERENCES OF TWO BLACK RHINOCEROS POPULATIONS

Food preferences of two discrete black rhinoceros (Diceros bicornis L.) populations were studied in northern Tanzania from 1964–1966 Feeding rhinoceros were watched for a period of one hour, and the plants which they selected and rejected were identified, either as they were feeding or when they had moved on. A technique was used which provided an indication of the relative importance of certain plants in the diet. Observations were made in six different habitat types used by the rhinoceros during the wet and dry seasons. A total of 307 hours was spent actually watching feeding rhinoceros. During this period they were observed eating 191 plant species from 49 botanical families. In all habitat types rhinoceros consume a wide variety of the spectrum of plants available, but are highly selective for herbs and shrubs. At certain periods of the year stenophagous characteristics are apparent, and the species shows a marked preference for legumes. Grasses make up a small proportion of the diet.     

Cross-species chromosome painting in the Perissodactyla: delimitation of homologous regions in Burchell's zebra (Equus Burchellii) and the white (Ceratotherium Simum) and black rhinoceros (Diceros Bicornis)

Conserved chromosomal segments in the black rhinoceros, Diceros Bicornis (DBI, 2n = 84), and its African sister-species the white rhinoceros, Ceratotherium Simum (CSI, 2n = 82), were detected using Burchell's zebra (Equus Burchellii, EBU, 2n = 44) chromosome-specific painting probes supplemented by a subset of those developed for the horse (Equus Caballus, ECA, 2n = 64). In total 41 and 42 conserved autosomal segments were identified in C. Simum and D. Bicornis respectively. Only 21 rearrangements (20 fissions and 1 fusion) are necessary to convert the Burchell's zebra karyotype into that of the white rhinoceros. One fission distinguishes the D. Bicornis and C. Simum karyotypes which, excluding heterochromatic differences, are identical in all respects at this level of resolution. Most Burchell's zebra chromosomes correspond to two rhinoceros chromosomes although in four instances (EBU18, 19, 20 and 21) whole chromosome synteny has been retained among these species. In contrast, one rhinoceros chromosome (DBI1, CSI1) comprises two separate Burchell's zebra chromosomes (EBU11 and EBU17). In spite of the high diploid numbers of the two rhinoceros species their karyotypes are surprisingly conserved offering a glimpse of the putative ancestral perissodactyl condition and a broader understanding of genome organization in mammals.     

Feeding and drinking habits of the black rhinoceros in Masai Mara Game Reserve

Feeding and drinking habits of the black rhinoceros (Diceros bicornis L.) population in Masai Mara Game Reserve, Kenya, were studied from May 1971 to August 1972. A total of 108 rhinoceros were recorded in the study area. Feeding rhinoceros were followed behind their feeding tracks until they stopped feeding (or changed to another activity) and the plants which they selected were identified. A technique was used which provided an indication of the relative importance of certain plants in the diet during May to September 1971 (wet-semi-dry), October 1971 to February 1972 (dry) and February to May 1972 (wet-semi-dry). A total of 240 h were spent actually watching feeding rhinoceros in thirteen distribution areas. During this period rhinoceros were observed eating seventy plant species from thirty botanical families. In all distribution areas rhinoceros were very selective for herbs and shrubs, and showed a marked preference for Solanum incanum, Dichrostachys cinerea and Acacia species. Rhinoceros were also observed to visit salt licks which contained sodium, magnesium, potassium and calcium. Two feeding peaks, one in morning and the other in the afternoon were recorded. Black rhinoceros drink water mainly at night. They spend most of the night time near the watering places for they were mostly located in the mornings walking to the feeding grounds.     

Reproductive behaviour of captive Sumatran rhinoceros (Dicerorhinus sumatrensis)

The Sumatran rhinoceros (Dicerorhinus sumatrensis) is on the verge of extinction in Malaysia. At the Sumatran rhinoceros Conservation Centre in Sungai Dusun, the reproductive behaviour of two female and two male rhinoceroses were studied for 8-10 months during attempts to breed them in captivity. Due to the paucity of scientific information on the reproductive biology of the Sumatran rhinoceros, this study was conducted to obtain information on the reproductive behaviour of this species. The male rhino was introduced to a female rhino in the morning for 1-2 h daily in order to observe for behavioural oestrus. Observations were made on the signs of oestrus and mating behaviour. Oestrus was determined by receptivity towards the male and lasted about 24 h. Common signs of oestrus were an increase in frequency of urine spraying, tail raising or swinging, anogenital and other contacts. Although the males exhibited mounting, the inability of the male to achieve intromission was poor. The study demonstrated that the pattern of courtship and copulation of the captive Sumatran rhinos were comparable with those of other rhino species, reported previously by other scientists and flehmen reflex was also exhibited by the male Sumatran rhinos. In a captive breeding programme, it is recommended that only an oestral female is introduced into a male enclosure due to the male solitary behaviour and to avoid serious injuries inflicted onto the females.     

New subspecies of Prosimulium macropyga korshunovi Patrusheva subsp. n. (Diptera, Simuliidae) from the Polar Urals]

A new subspecies, Prosimulium macropyga korshunovi Patr. subsp. n., from the Polar Urals differs from other forms of P. macropyga (Lundstr.) and allied species in having two dark longitudinal stripes on the dorsum and by the structure of genitalia in adult insects, by the number of setae in the great flabellum, by the structure of submentum and shape of the ventral incision in larvae and by the branching pattern of respiratory threads in pupa.     

兴安落叶松分枝格局的分形特征

对于树木分枝格局分形特征的定量描述,可以加深对树木生长过程的理解。本文采用分形几何学对兴安落叶松(Larix gmelini)的分枝格局进行研究,结果表明1)兴安落叶松分枝格局是一种分形结构,存在自相似性。2)兴安落叶松分枝格局的分形维数介于1.4~1.7之间,揭示了它的结构复杂性程度和占据生态空间、利用生态空间的能力。分形维数在树木光合作用及生长发育研究中是一个有用的参数。     

Conserving the African rhinoceros

The Southern African rhinoceros population has been dwindling through the years. A lot of effort has been put toward coming up with the most effective way of protecting the black and white rhinoceros population in the world yet still the animals remain endangered despite the enormous global efforts to protect the species. Such conservation efforts include; establishment of sanctuaries, wildlife farming, dehorning, trade and market controls, listing of species as endangered, use of biotechnology and biotelemetry. However useful, each of these methods has its own strengths and weaknesses relative to the success of rhinoceros conservation. It however has been noted in this review that dehorning is the most effective method as it involves removal of the horn hence extinguishing the need for poaching. Despite the high success rate it has also been noted that this requires a great deal of skill and finance hence limiting the application of this technique in developing nations. Sanctuaries provide an ideal breeding environment that is better than the wild and enhanced breeding accounted for a significant increase in rhinoceros population where it has been applied. It was however been conclude that a holistic conservation approach is required to conserve the African rhinoceros.