Cortical fibrils and secondary deposits in periderm of the hemichordate Rhabdopleura [Graptolithoidea]

Coenecia of extant hemichordates Rhabdopleura compacta and Rh. normani were investigated using SEM techniques. Cortical fibrils were detected in their fusellar tissue for the first time. The densely packed cortical fibrils form a characteristic band−like construction in fusellar collars, similar to some Ordovician rhabdopleurids. No traces of external secondary deposits are found in coenecia. Two types of internal secondary deposits in tubes are recognized: (1) membranous deposits, composed of numerous, tightly packed sheets, similar to the crustoid paracortex and pseudocortex; and (2) fibrillar deposits, devoid(?) of sheets and made of cortical fibrils, arranged in parallel and interpreted as equivalent to graptolite endocortex. There is no significant difference in either the shape or the dimensions of cortical fibrils found in Rhabdopleura and graptolites. The cortical fabric of both rhabdopleuran species studied is composed of long, straight and more or less wavy, unbranched fibrils arranged in parallel; their diameters vary from 220 to 570 µm. The study shows that there is no significant difference between extinct and extant Graptolithoidea (= Pterobranchia) in the histological and ultrastructural pattern of their primary and secondary deposits of the periderm. The nonfusellar periderm of the prosicula is pitted by many depressions similar to pits in the cortical tissue of graptolites

Graptolite-like fibril pattern in the fusellar tissue of Palaeozoic rhabdopleurid pterobranchs

The fusellar tissue of Palaeozoic rhabdopleurid pterobranchs has been studied using the SEM techniques. The fibrillar material of Ordovician Kystodendron ex gr. longicarpus and Rhabdopleurites primaevus exhibits a distinct dimorphism, comprising: (1) thinner, wavy and anastomosing/branching fusellar fibrils proper, producing a tight three-dimensional meshwork; and (2) long, more or less straight and unbranched cortical fibrils, sometimes beaded, and arranged in parallel. These fibrils are similar to the fusellar and cortical fibrils of graptolites, respectively. Until now, dimorphic fibrils and their arrangement within fusellar tissue were regarded as unique characters of the Graptolithina. In general, the fibrillar material of these fossils is partially preserved in the form of flaky material (new term) composed of flakes (new term). Flakes are interpreted as flattened structures originating from the fusion of several neighbouring tightly packed fibrils. A Permian rhabdopleurid, referred to as Diplohydra sp., reveals a fabric and pattern of fusellar tissue similar to that of both Ordovician rhabdopleurids but devoid (?) of cortical fibrils. The results presented here question views that: (1) substantial differences in fabric and pattern of fusellar tissue exist between fossil pterobranchs and graptolites; and (2) the ultrastructure of pterobranch periderm has remained unchanged at least since the Ordovician. The Palaeozoic rhabdopleurids investigated are closer ultrastructurally to graptolites than to contemporary pterobranchs. The pterobranchs and the graptolites should be treated as members of one class - the Graptolithoidea.Przeprowadzono badania ultrastrukturalne perydemy trzech paleozoicznych pióroskrzelnych (Pterobranchia) z rzędu Rhabdopleurida: ordowickich Kystodendron ex gr. longicarpus (Eisenack) i Rhabdopleurites primaevus Kozłowski, oraz permskiego Diplohydra sp. Wykazano, że tkanka fuzellarna form ordowickich składa się z tego samego tworzywa co u graptolitów oraz wykazuje typowy dla nich dymorfizm fibrylarny i układ przestrzenny: tworzą ją stosunkowo cienkie, rozgałęziające się, powyginane włókna fuzellarne oraz grube, często równolegle ułożone włókna kortykalne. Włókien kortykalnych nie stwierdzono u Diplohydra sp., która zachowała jednak typowo graptolitowy charakter włókien fuzellarnych. Między włóknami wszystkich zbadanych form występują struktury określone jako płatki (flakes), powstałe wskutek cementacji kilkunastu lub więcej sąsiadujących ze sobą włókien. Materiał perydermalny zbudowany z płatków (flaky material - nowy terrnin) obserwowany był uprzednio u graptolitów. Stwierdzony w badanym materiale dymorfizm fibrylarny był dotąd uważany za właściwy jedynie graptolitom, podczas gdy tkanka fuzellarna pióroskrzelnych, zarówno kopalnych jak i współczesnych miała być zbudowana wyłącznie z cienkich, nierozgałęziających się włókien. Uzyskane wyniki potwierdzają trafność koncepcji Beklemiszewa (1951) o traktowaniu współczesnych i kopalnych pióroskrzelnych jako przedstawicieli gromady Graptolithoidea

Discovery of Pterobranchia [Graptolithoidea] in the Permian

The fossil remains of a hemichordate exoskeleton, recognized as fragments of the stolons and their cyst−like swellings connected with the fusellar zooidal tubes, were derived by chemical isolations from Late Permian (Kazanian) mudstones of the Svalis Dome (central Barents Sea, Norway). These fossils, referred to as Diplohydra szaniawskii sp. nov., are the first undoubted representatives of the class Graptolithoidea found in Permian deposits. The genus Diplohydra Kozłowski, 1959, known previously only from the Ordovician and originally established as a thecate hydroid taxon, is reinterpreted as an aberrant member of the order Rhabdopleuroidea. This strange hemichordate, characterized by fusellar tubes distinctly narrower than stolon−like tubes and their swellings, reveals a certain degree of dimorphism in the stolon system. D. szaniawskii sp. nov. also displays some peculiar morphological features common to the Ordovician rhabdopleuroid genus Rhabdopleurites Kozłowski and the stolonoid genus Stolonodendrum Kozłowski

The world`s oldest crustoid graptolites from the Upper Tremadocian of Poland

The Crustoidea are an order of sessile basic graptolites that are morphologically intermediate between the extant genus Rhabdopleura (Rhabdopleuroidea) and the extinct sessile order—the Dendroidea (Kozłowski 1962, 1966; Bulman 1970; Urbanek 1986). So far these rather poorly known graptolites of significant phylogenetic importance have been reported from the upper Arenigian or lower Llanvirnian (Kozłowski 1962) to the upper Ludlow (Mierzejewski 1977). Isolated fragments of the graptolite stolon system were chemically extracted from upper Tremadocian chert nodules from Wysoczki (Holy Cross Mountains, central Poland) and examined with SEM. Because of the characteristic trifurcation and fine annulation of the stolons they are recognized as remnants of the crustoid graptolites. This discovery extends the stratigraphic distribution of the crustoid graptolites and explains the enigmatic presence of graptoblasts in the upper Tremadocian beds of Wysoczki

How to assess kidney function in oncology patients

Assessment of kidney function in oncology patients is a fundamental factor in profiling the survival risk, determining the appropriate dose of chemotherapeutic drugs, and defining a patient eligibility for clinical trials with novel agents. Both overestimation and underestimation of kidney function may affect the treatment efficacy and outcomes. Overestimation may lead to overdosing or inappropriate agent selection and the corresponding toxicity, whereas underestimation may be responsible for underdosing or inappropriate agent exclusion and subsequent treatment failure. This is of utmost importance in patients with cancer. Evaluation of kidney function is not only limited to the estimation of glomerular filtration rate or creatinine clearance. An accurate assessment of kidney function is advisable to reduce variability in decision making and ultimately the therapeutic outcomes of toxicity and clinical benefit. Therefore, additional studies are needed to investigate the validity of currently used formulas estimating kidney function in this population as well as their applicability to traditional chemotherapy, novel targeted therapies, and immunotherapies. Because of rapid discovery and development of new cancer agents, a reliable and comprehensive manner to screen for potential nephrotoxicity is critically important. As kidney function not only is limited to glomerular filtration rate changes but also involves tubular and even vascular dysfunction, urinalysis and kidney imaging studies should also be considered before therapeutic decisions are taken. However, several questions remain regarding these new technologies such as kidney-on-a-chip systems for the assessment of kidney function and injury, particularly in oncology, and it has yet to be implemented in clinical practice