Biology subjects

Wibbelt, G.

Publications and source records attributed to Wibbelt, G..

3 recordsLinked to original sources

bioRxiv2024

Eye features and retinal photoreceptors of the nocturnal aardvark (Orycteropus afer, Tubulidentata)

The nocturnal aardvark Orycteropus afer is the only extant species in the mammalian order Tubulidentata. Previous studies have claimed that it has an all-rod retina. In the retina of one aardvark, we found rod densities ranging from 124,000/mm2 in peripheral retina to 214,000/mm2 in central retina; the retina of another aardvark had 182,000 - 245,000 rods/mm2. This is moderate in comparison to other nocturnal mammals. With opsin immunolabelling we found that the aardvark also has a small population of cone photoreceptors. Cone densities ranged from 300 to 1,300/mm2 in one animal, and from 1,100 to 1,600/mm2 in the other animal, with large local variations and no large central-peripheral density gradient. Overall, cones comprised 0.25-0.9% of the photoreceptors. Both typical mammalian cone opsins, longwave-sensitive (L) and shortwave-sensitive (S), were present. However, there was colocalization of the two opsins in many cones across the retina (35 - 96% dual pigment cones). Pure L cones and S cones formed smaller populations. This probably results in poor colour discrimination. Thyroid hormones, important regulators of cone opsin expression, showed normal blood serum levels. The relatively low rod density and hence a relatively thin retina may be related to the fact that the aardvark retina is avascular and its oxygen and nutrient supply have to come from the choriocapillaris by diffusion. In contrast to some previous studies, we found that the aardvark eye has a reflective tapetum lucidum with features of a choroidal tapetum fibrosum, in front of which the retinal pigment epithelium is unpigmented. The discussion considers these findings from a comparative perspective.

zoology↗

bioRxiv2019

Intravital multi-modal flux analysis reveals the transport mechanism of bile acids through hepatic microconduits

Small-molecule flux in tissue-microdomains is essential for organ function, but knowledge of this process is scant due to the lack of suitable methods. We developed two independent techniques that allow the quantification of advection (flow) and diffusion in individual bile canaliculi and in interlobular bile ducts of intact livers in living mice, namely Fluorescence Loss After Photoactivation (FLAP) and Intravital Arbitrary Region Image Correlation Spectroscopy (IVARICS). The results challenge the prevailing ‘mechano-osmotic’ theory of canalicular bile flow. After active transport across hepatocyte membranes bile acids are transported in the canaliculi primarily by diffusion. Only in the interlobular ducts, diffusion is augmented by regulatable advection. Photoactivation of fluorescein bis-(5-carboxymethoxy-2-nitrobenzyl)-ether (CMNB-caged fluorescein) in entire lobules demonstrated the establishment of diffusive gradients in the bile canalicular network and the sink function of interlobular ducts. In contrast to the bile canalicular network, vectorial transport was detected and quantified in the mesh of interlobular bile ducts. In conclusion, the liver consists of a diffusion dominated canalicular domain, where hepatocytes secrete small molecules and generate a concentration gradient and a flow-augmented ductular domain, where regulated water influx creates unidirectional advection that augments the diffusive flux.One Sentence Summary/Keywords Bile flux proceeds by diffusion in canaliculi, augmented by advection in ducts.Competing Interest StatementThe authors have declared no competing interest.View Full Text

physiology↗

bioRxiv2019

Eimeria falciformis BayerHaberkorn1970 and novel wild derived isolates from house mice: differences in parasite lifecycle, pathogenicity and host immune reactions

Species of Eimeria (Apicomplexa:Coccidia) differ in the timing of lifecycle progression and resulting infections vary in host immune reactions and pathology they induce. Eimeria infections in house mice are used as models for basic immunology and the most commonly used isolates have been passaged in laboratory mice for over 50 years. We questioned in how far such isolates are still representative for infections in natural systems.\n\nIn the current study, we address this question by comparing the \"laboratory isolate\" E. falciformis BayerHaberkorn1970 with a novel, wild derived isolate E. falciformis Brandenburg88, and contrast this with another novel wild derived isolate, E. ferrisi Brandenburg64. We compare parasite lifecycle progression. We relate this to immune cell infiltration at the site of infection (in the caecum) and cytokine gene expression in the spleen as a measure of host immune response. We assess host weight loss as a measure of pathogenicity.\n\nA species-specific slower parasite lifecyle progression and higher pathogenicity are observed for E. falciformis vs. E. ferrisi. Host cytokines, in contrast, are expressed at significantly higher level in the spleen of mice infected with the E. falciformis laboratory isolate than in both wild derived isolates, irrespective of the species. Differences in histopathology are observable between all three isolates: The E. falciformis BayerHaberkorn1970 laboratory isolate induces the strongest inflammation and cellular infiltration (with lymphocytes, plasma cells and eosinophilic granulocytes) followed by the wild derived E. falciformis Brandenburg88 isolate. E. ferrisi Brandenburg64 is inducing milder histological changes than both E. falciformis isolates.\n\nIt can be speculated that the serial passaging of E. falciformis BayerHaberkorn1970 has resulted in evolutionary divergence rendering this isolate more virulent in NMRI mice. Caution is needed when findings from experimental infection with laboratory strains should be integrated with observations in natural systems.\n\nHighlightsO_LIE. ferrisi has a shorter pre-patency than wild-derived and laboratory isolates of E. falciformis.\nC_LIO_LIE. ferrisi is less virulent than both E. falciformis isolates and the timing of maximal oocyst shedding relative to host weight loss differs.\nC_LIO_LIThe laboratory strain of E. falciformis induces stronger cytokine expression in the spleen than both wild derived strains of E. falciformis and E. ferrisi.\nC_LIO_LIThe laboratory strain of E. falciformis induces stronger tissue infiltration of immune cells than the wild-derived strain. E. ferrisi infections are associated with the lowest infiltration.\nC_LI

microbiology↗