Terminal Bars Research Articles

A priest, a ghost and a recce walk into a bar… Masculinities in Ivan Vladislavić’s “The Terminal Bar”

Ivan Vladislavić’s short story “The Terminal Bar” has been neglected in criticism. This article reads the story as a critique of South Africa’s Border War (1966–1989), and of the society that formed in the background of that war, arguing that the eponymous bar serves as a microcosm of South Africa of the 1980s. Using recent scholarship on gender violence that confirms a link between ideology and normative masculinity, I demonstrate how the story’s presentation of the simultaneous existence of the violent and the quotidian recreates the profoundly uncomfortable atmosphere of normalized violence of 1980s South Africa. I call this “cognitive dissonance on a national scale.” I also investigate the masculinities represented in the story using the notion of the renounced feminine. In my reading, the story clearly shows that masculinities required and necessitated by the political dispensation of the time are detrimental to both the individual and to society at large. Lastly, I look into the presence and the function of a subtle female spectral presence that has escaped scholarly attention altogether, but that holds the key to the story’s central import.

Controls of sandstone architecture on hydrocarbon accumulation in a shallow-water delta from the Jurassic Shaximiao Formation of the western Sichuan Basin in China

The thin but widely distributed sandstones in the shallow-water deltas have the potential to hold large deposits of natural gas. The fluvial sand bodies formed from river channels with different sedimentary facies and sandstone architectures have remarkable heterogeneities. The results of this investigation suggest that the sandstone architectures of river channels have a significant impact on the hydrocarbon accumulation and production of sandstone reservoirs. Information regarding the sandstone origin and architecture of shallow-water deltas, especially of the fingered bar type, is still very limited. This investigation focused on the channel sandstones in the shallow-water delta of the Jurassic Shaximiao Formation on the eastern slope of the western Sichuan Basin in China. Based on data from cores and logs of sandstones, seven types of lithofacies and four sedimentary facies were identified. Sand-rich sedimentary facies, including distributary channels, mouth bars, and overbanks, have merged to form four types of compound sandbodies corresponding to the fourth-order architectural unit in the architectural classification. Four types of compound sand bodies were classified, including CS1 (variable distributary channel sand body), CS2 (diverting channel and residual overbank sand body), CS3 (diverting channel and residual mouth bar sand body), and CS4 (terminal channel and residual mouth bar sand body). Relatively good physical properties occur in the sandstone architectures of types CS3 and CS4, with an average porosity of 11.06% and an average permeability of 0.97 mD. Sandstone architectures from the Jurassic Shaximiao Formation of the study area were controlled by water depth and climate, tectonic subsidence, distance from provenance, erosion effect, and channel sinuosity and discharge. With strong lateral erosion, a shallow-water delta would have more sandstone architectures of types CS3 and CS4 in the high sinuosity of channels far from the provenance. Furthermore, sandstone architectures of types CS3 and CS4 are prone to form in connected channel sandbodies with relatively high contents of natural gas of approximately 4.48 × 104 m3/d. The results of this investigation are beneficial to improve the understanding of the characteristics of sandstone distributions in shallow-water deltas, especially in fingered bar types, and to guide oil and gas explorations in shallow-water delta systems.

Cytomorphologic clues for the diagnosis of fallopian tube prolapse in liquid-based vault samples with review of the literature.

Fallopian tube prolapse (FTP) is a rare complication of hysterectomy. The cytological features of the prolapsed fallopian tube in vault smears have been occasionally described in the literature. This was a retrospective study conducted to identify and describe the characteristic cytologic features of histopathologically confirmed cases of FTP in SurePath™ liquid-based preparations. Additionally, the literature documenting cytologic features of the prolapsed fallopian tube in vault smears was also reviewed. A total of four corresponding vault cytology samples of FTP cases, reported on histopathology, were available. On cytologic examination, these cases demonstrated strips and papillaroid clusters of columnar-shaped cells with mild nuclear enlargement, round to elongated nuclei, fine chromatin, inconspicuous nucleoli, and a moderate amount of wispy cytoplasm. Admixed inflammatory cells were also noted. Some of these cells demonstrated the presence of cilia and terminal bar toward the apical surface, indicative of tubal epithelium. The presence of three-dimensional papillaroid clusters lined by columnar cells as well as strips of similar cells with cilia and terminal bars at the apical surface and fine nuclear chromatin were the most consistent cytologic features in these cases. We conclude that a high index of clinical suspicion in post-hysterectomy cases with knowledge of the characteristic cytologic features can help in suggesting a diagnosis of tubal prolapse in vault samples.

Contrasting facies patterns between river-dominated and symmetrical wave-dominated delta deposits

ABSTRACT Process-physics-based, coupled hydrodynamic–morphodynamic delta models are constructed to understand preserved facies heterogeneities that can influence subsurface fluid flow. Two deltaic systems are compared that differ only in the presence of waves: one river dominated and the other strongly influenced by longshore currents. To understand an entire preserved deltaic succession, the growth of multiple laterally adjacent delta lobes is modeled to define delta axial to marginal facies trends through an entire regressive–transgressive depositional succession. The goal is to refine a facies model for symmetrical wave-dominated deltas (where littoral drift diverges from the delta lobe apex). Because many factors change depositional processes on deltas, the description of the river-dominated example is included to provide a direct reference case from which to define the impact of waves on preserved facies patterns. Both systems display strong facies trends from delta axis to margin that continued into inter-deltaic areas. River-dominated delta regression preserved a dendritic branching of compensationally stacked bodies. Transgression, initiated by sea-level rise, backfilled the main channel and deposited levees and splays on the submerging delta top. Wave-dominated deltas developed dual clinoforms: a shoreface clinoform built as littoral drift carried sediment away from the river month and onshore, and a subaqueous delta-front clinoform composed of sediment accumulated below wave base. Although littoral drift in both directions away from the delta axis stabilized the position of the river at the shoreline, distributary-channel avulsions and lateral migration of river flows across the subaqueous delta top produced heterogeneities in both sets of clinoform deposits. Separation of shoreface and subaqueous delta-front clinoforms across a subaqueous delta top eroded to wave base produced a discontinuity in progradational vertical successions that appeared gradual in some locations but abrupt in others. Littoral drift flows away from adjacent deltas converged in inter-deltaic areas, producing shallow water longshore bars cut by wave-return-flow channels with associated terminal mouth bars. Transgression initiated by sea-level rise initially led to vertical aggradation of wave-reworked sheet sands on the subaqueous delta top and then retreating shoreface barrier sands as the subaerial delta top flooded. Pseudo inter-well flow tests responded to local heterogeneities in the preserved deposits. As expected, abandoned channels in the river-dominated case defined shoreline-perpendicular preferential flow paths and wave-dominated delta deposits are more locally homogeneous, but scenarios for development of more pronounced shore-parallel heterogeneity patterns for wave-influenced deltas are discussed. The results highlight the need to consider the dual clinoform nature of wave-dominated delta deposition for facies prediction and subsurface interpretation.

Lophomonas blattarum - A blunder!

Background: Lophomonas blattarum is a parasite colonising gut of cockroaches. There are 136 case reports from immunocompromised patients and children suffering from respiratory tract infections. Here we report a case where broncho alveolar lavage fluid from a child showed structures which convincingly appeared like a flagellate parasite but was later confirmed to be ciliocytophthoria. Case Description: A 5 y old female child hailing from rural southern India came with complaints of cough, cold and abdominal pain since 6 m. In view of increased severity of symptoms, high grade fever and cavitatory lesions in the lung, the child was referred to our centre. We considered the differential diagnoses - Hydatid cyst, Tuberculosis, non infectious causes of lung cyst. Investigations showed Eosinophilia and raised ESR. CT scan of chest showed consolidation with cavities involving apical segment of right lower lobe, anterior segment of left upper lobe suggestive of infective etiology. Broncho alveolar lavage fluid was negative for acid fast bacilli and TB PCR. On wet mount examination, motile structures appearing to have tuft of flagella were seen. Modified Trichrome stain showed numerous inflammatory cells and pyriform shaped structures with tuft of flagella arranged irregularly at one pole. Inner structures were not appreciated very clearly and a presumptive diagnosis of the parasite Lophomonas blattarum was made. The patient was treated with metronidazole 7.5 mg/kg body weight for 10 d awaiting further results. Child improved symptomatically and discharged. Discussion: Since it was difficult to do the molecular tests, we sent the micrscopic photographs and videos to CDC Diagnostic Assistance team to help us solve the case. They confirmed it to be ciliocytophthoria. Bronchial epithelial cells are cylindrical with basal nuclei and a visible terminal bar just beneath the regularly arranged cilia at the other end. This was a learning experience for us to differenciate the cells from the parasite. We now routinely perform special stains on samples found to have motile structures like these. Conclusion: Lophomonas blattarum rarely causes human disease more often misdiagnosed because the movement of the flagellate parasite resembles the motion of detached ciliated bronchoepithelial cells when brochoalveolar lavage fluid is examined under the microscope.

Tail pattern variation in the Black Wheatear (Oenanthe leucura)

Delayed plumage maturation occurs in birds when subadult plumage is retained until after the first breeding season. We analysed data from 114 Black Wheatears (Oenanthe leucura), which were trapped during 2014–2016 in southeastern Spain, to explore whether biometric measurements, and more specifically tail pattern, differed among age and sex classes, and whether there was a relationship between tail pattern and delayed plumage maturation. Males and adults were heavier and had longer wings and tails than females and juveniles, respectively. Adult birds had longer terminal black tail bars than juveniles, which suggests a potential dominance-signalling function for the tail pattern. Further research is needed to investigate the relationship between these traits and sexual selection and dominance in Black Wheatear.

Identification criteria of the rare multi-flagellate Lophomonas blattarum: comparison of different staining techniques.

Bronchopulmonary lophomoniasis (BPL) is an emerging disease of potential importance. BPL is presented by non-specific clinical picture and is usually accompanied by immunosuppression. Culture of Lophomonas blattarum is difficult and its molecular diagnosis has not yet been developed. Therefore, microscopic examination of respiratory samples, e.g., bronchoalveolar lavage (BAL) or sputum, is the mainstay of BPL diagnosis. Creola bodies and ciliocytophthoria are two forms of bronchial cells which occur in chest diseases with non-specific clinical picture like that of BPL. Both forms could be misrecognized as multi-flagellates because of their motile cilia in the wet mounts and due to shape variability of L. blattarum in stained smears. The aim of the study is to compare different staining techniques for visualizing L. blattarum to improve the recognition and diagnosis of BPL, to distinguish respiratory epithelial cells from L. blattarum and to decide which stain is recommended in suspected cases of BPL. BAL samples from patients which contain L. blattarum, creola bodies, and ciliocytophthoria were collected then wet mounts were examined. The BAL samples were also stained by Papanicolaou (PAP), Giemsa, hematoxylin and eosin (H & E), trichrome, Gram, and Diff-Quik (DQ) stains. The different staining techniques were compared regarding the stain quality. In wet mounts, the ciliary movement was coordinate and synchronous while the flagellar movement was wavy and leaded to active swimming of L. blattarum. In stained slides, bronchial cells were characterized by the presence of basal nucleus and the terminal bar from which the cilia arise. Trichrome was the best stain in demonstration of cellular details of L. blattarum. H & E, PAP, and Giemsa stains showed good quality of stains. Gram and DQ stains showed only pale hues of L. blattarum. We recommended adding Wheatley's trichrome staining to the differential diagnosis workup of cases of non-specific chest infections, especially when BPL is suspected, to avoid overdiagnosis or underdiagnosis of it.

Photographic enclave. New York City and its inhabitants through camera lens

The title phrase “photographic enclave” expresses the condition of projects that tell about a city using a photographic medium. The article discusses three audiovisual works that use photos to portray New York and its inhabitants: Smoke by Wayne Wang and Paul Auster, Stefan Nadelman’s Terminal Bar, and the multimedia project One in 8 Million. The works represent a variety of film models (drama, documentary, interactive media), and their authors use the formal and cognitive aspects of photography in a different ways. The aim of the article is to analyze the function of photography for portraying urban communities and to see if this treatment was successful.

Desmoglein 2-mediated adhesion is required for intestinal epithelial barrier integrity

The integrity of intercellular junctions that form the "terminal bar" in intestinal epithelium is crucial for sealing the intestinal barrier. Whereas specific roles of tight and adherens junctions are well known, the contribution of desmosomal adhesion for maintaining the intestinal epithelial barrier has not been specifically addressed. For the present study, we generated a desmoglein 2 antibody directed against the extracellular domain (Dsg2 ED) to test whether impaired Dsg2-mediated adhesion affects intestinal epithelial barrier functions in vitro. This antibody was able to specifically block Dsg2 interaction in cell-free atomic-force microscopy experiments. For in vitro studies of the intestinal barrier we used Caco2 cells following differentiation into tight enterocyte-like epithelial monolayers. Application of Dsg2 ED to Caco2 monolayers resulted in increased cell dissociation compared with controls in a dispase-based enterocyte dissociation assay. Under similar conditions, Dsg2 antibody significantly decreased transepithelial electrical resistance and increased FITC-dextran flux, indicating that Dsg2 interaction is critically involved in the maintenance of epithelial intestinal barrier functions. As revealed by immunostaining, this was due to Dsg2 ED antibody-induced rupture of tight junctions because tight junction proteins claudins 1, 4, and 5, occludin, and tight junction-associated protein zonula occludens-1 were partially removed from cell borders by Dsg2 ED treatment. Similar results were obtained by application of a commercial monoclonal antibody directed against the ED of Dsg2. Antibody-induced effects were blocked by absorption experiments using Dsg2-Fc-coated beads. Our data indicate that Dsg2-mediated adhesion affects tight junction integrity and is required to maintain intestinal epithelial barrier properties.

Ciliated Adenocarcinoma of the Ovary With Evidence of Serous Differentiation: Report of a Case

A patient with bilateral ovarian adenocarcinomas composed predominantly of ciliated cells incidentally found at autopsy is reported. Although obviously malignant, a majority of the cells expressed well-differentiated cilia with terminal bar formation. In one of the masses, the neoplastic cells seemed to arise from a serous adenofibroma. The tumor was confined to the ovaries without evidence of metastatic spread. Although morphologically resembling an endometrioid-type neoplasm, immunohistochemical and molecular studies were more consistent with a serous phenotype, especially in light of its apparent origination from a serous adenofibroma. We agree with previous observations suggesting that although the neoplasm seems morphologically worrisome, it may actually portend a more benign clinical course.

La phalange distale du pouce d’ Orrorin tugenensis (Miocène supérieur du Kenya)

The lion's share of articles dealing with the thumb anatomy of Plio-Pleistocene hominids has focussed on the capacity to manipulate and manufacture tools, and has largely neglected the locomotor aspects. However, in these hominids, the forelimb was still employed in locomotion. Certain of the anatomical characters classically associated with manipulation and/or fabrication of tools are already present in the Late Miocene species Orrorin tugenensis as shown by the terminal thumb phalanx BAR 1901'01. This specimen reveals crucial information suggesting that thumb morphology is not exclusively related to such tool using and manufacturing activities but reflects in a frequently bipedal creature a deeper adaptation concerning the precision grip essential for climbing and balancing, different from that of apes.

Three-dimensional adaptive optics ultrahigh-resolution optical coherence tomography using a liquid crystal spatial light modulator

A liquid crystal programmable phase modulator (PPM) is used as correcting device in an adaptive optics system for three-dimensional ultrahigh-resolution optical coherence tomography (UHR OCT). The feasibility of the PPM to correct high order aberrations even when using polychromatic light is studied, showing potential for future clinical use. Volumetric UHR OCT of the living retina, obtained with up 25,000 A-scans/s and high resolution enables visualization of retinal features that might correspond to groups of terminal bars of photoreceptors at the external limiting membrane.

Primary Extraneural Myxopapillary Ependymoma of the Broad Ligament

Primary extraneural ependymomas are rare tumors that arise in ectopic sites, including pulmonary, sacrococcygeal region, ovarian, and paraovarian tissues. Four such ependymomas reported in the literature involve the paraovarian tissues, including 2 broad ligament ependymomas. Here we describe a myxopapillary ependymoma of the broad ligament in a 22-year-old woman, which may be the first tumor of this type to be reported in this location. Cytology, histology, cytochemistry, immunohistochemistry, and flow cytometry ploidy analysis are studied and described. Identification of perivascular ependymal rosettes, ependymal canals, vimentin and glial fibrillary acidic protein immunoreactivity, cytochemical staining of blepharoplasts or terminal bars by phosphotungstic acid hematoxylin, and presence of multiple foci of myxoid degeneration among the ependymal rosettes characterized a myxopapillary ependymoma.

Three New Pupfish Species, Cyprinodon (Teleostei, Cyprinodontidae), from Chihuahua, México, and Arizona, USA

Three new species of Cyprinodon (Teleostei, Cyprinodontidae) are described, each long recognized as distinct. Cyprinodon pisteri occupies a variety of systems and habitats in the Lago de Guzmán complex basin in northern Chihuahua, México. It is distinguished by its dusky to black dorsal fin and narrow or inconspicuous terminal bar on the caudal fin in mature males. Cyprinodon albivelis is distributed largely in relatively high elevation sites in the upper Río Papígochic (Río Yaqui basin), with a single occurrence in the Río Santa María basin. It is distinguished most notably by the striking white dorsal and anal fins displayed by breeding males. Cyprinodon arcuatus is a distinctive form most similar to Cyprinodon macularius and Cyprinodon eremus and is restricted to the upper Santa Cruz River basin in southern Arizona and Northern Sonora. It is distinguished in having a sharply convex dorsal body profile form the head to dorsal fin origin and in lacking yellow or orange pigmentation on the part of nuptial males. Extensive and careless human alterations to this system drove C. arcuatus to extinction, with the last natural population perishing in Monkey Spring (Santa Cruz County, Arizona), devoured by introduced sport fish. Where appropriate, biogeography and conservation issues are discussed with regard to these species.

Geomorphology, facies architecture, and high-resolution, non-marine sequence stratigraphy in avulsion deposits, Cumberland Marshes, Saskatchewan

Abstract This paper demonstrates field relationships between landforms, facies, and high-resolution sequences in avulsion deposits. It defines the building blocks of a prograding avulsion sequence from a high-resolution sequence stratigraphy perspective, proposes concepts in non-marine sequence stratigraphy and flood basin evolution, and defines the continental equivalent to a parasequence. The geomorphic features investigated include a distributary channel and its levee, the Stage I crevasse splay of Smith et al. (Sedimentology, vol. 36 (1989) 1), and the local backswamp. Levees and splays have been poorly studied in the past, and three-dimensional (3D) studies are rare. In this study, stratigraphy is defined from the finest scale upward and facies are mapped in 3D. Genetically related successions are identified by defining a hierarchy of bounding surfaces. The genesis, architecture, geometry, and connectivity of facies are explored in 3D. The approach used here reveals that avulsion deposits are comparable in process, landform, facies, bounding surfaces, and scale to interdistributary bayfill, i.e. delta lobe deposits. Even a simple Stage I splay is a complex landform, composed of several geomorphic components, several facies and many depositional events. As in bayfill, an alluvial ridge forms as the feeder crevasse and its levees advance basinward through their own distributary mouth bar deposits to form a Stage I splay. This produces a shoestring-shaped concentration of disconnected sandbodies that is flanked by wings of heterolithic strata, that join beneath the terminal mouth bar. The proposed results challenge current paradigms. Defining a crevasse splay as a discrete sandbody potentially ignores 70% of the landform's volume. An individual sandbody is likely only a small part of a crevasse splay complex. The thickest sandbody is a terminal, channel associated feature, not a sheet that thins in the direction of propagation. The three stage model of splay evolution proposed by Smith et al. (Sedimentology, vol. 36 (1989) 1) is revised to include facies and geometries consistent with a bayfill model. By analogy with delta lobes, the avulsion sequence is a parasequence, provided that its definition is modified to be independent from sea level. In non-marine settings, facies contacts at the tops of regional peats, coals, and paleosols are analogous to marine flooding surfaces. A parasequence is redefined here as a relatively conformable succession of genetically related strata or landforms that is bounded by regional flooding surfaces or their correlative surfaces. This broader definition incorporates the concept of landscape evolution between regional flooding surfaces in a variety of depositional settings. With respect to landscape evolution, accommodation space has three spatial dimensions — vertical (x), lateral (y), and down-the-basin (z). A flood basin fills in as landforms vertically (x) and laterally accrete (y), and prograde down-the-basin (z). Vertical aggradation is limited by the elevation of maximum flood stage (local base level). Differential tectonism and geomorphology control the slope of the flood basin floor and the direction of landscape evolution. These processes produce parasequences that include inclined stratal surfaces and oriented, stacked macroforms (clinoforms) that show the magnitude and direction of landscape evolution.

Immunocytochemical distribution of the c-H-ras protein in nasal polyps: localization to the terminal bars

Objective: This study was performed to investigate the role of proto-oncogene products, c-H-ras and c-erbB-2, in the pathophysiology of nasal polyps. Methods: An immunocytochemical investigation of the expression of proto-oncogene products of c-H-ras and c-erbB-2 was performed on 16 nasal polyps and 15 nasal mucosa specimens. Results: The c-H-ras protein was found to be localized to the terminal bars of apical cells of the epithelium in 11 of 16 nasal polyps and in seven of 15 nasal mucosa. Localized staining at the terminal bars for the c-H-ras protein was significantly more frequently observed in glandular-cystic type than in edematous type nasal polyps. Such localized staining was significantly more frequently seen in polyp specimens with invaginated epithelia than in those with no invaginated epithelium. Our findings confirmed that the c-erbB-2 protein was mainly localized to the plasma membrane in all samples. Conclusion: These results suggest that the c-H-ras protein localized to the terminal bars plays an important role in the pathophysiology of glandular-cystic type nasal polyps and that it may be related to invagination of nasal polyp epithelium.

A Modification of Mayer's Tannic Acid-Ferric Chloride Staining Method for Demonstrating Cellular Membranous Systems for Light Microscopy

To observe cellular membranous systems under a light microscope, we modified Mayer's tannic acid-ferric chloride stain method by adding a treatment with hematoxylin after the original procedure. We used the modified tannic acid-ferric chloride (MTA-Fe) stain method to examine kidneys, liver, heart, trachea, epididymides and other organs of rats and dogs. The MTA-Fe stain clearly demonstrated the basement membrane, brush border, basolateral invaginations and cell processes in the kidneys which enabled easy differentiation of the S1 and S3 segments of proximal convoluted tubules. Our technique also demonstrated hepatic cell membranes and bile canaliculi in the liver, cross striations and longitudinal traveling of myofibrils in the heart, cilia of the epithelial cells in the trachea, and stereocilia and terminal bars in the epididymis. The MTA-Fe stain is a convenient method to visualize cellular membranous systems even for light microscopy. The stain has the advantages of using no toxic materials, simple and easy technique, little variation of staining results, and little fading for several months after staining.

Immunohistochemical localization of beta-1,4-galactosyltransferase in human pancreatic tissues.

beta-1,4-Galactosyltransferase (GalTase) is the glycosyltransferase in the Golgi apparatus that transfers galactose from UDP-galactose to terminal N-acetylglucosamine residues in glycoconjugates with formation of a beta-1,4 linkage. Neoplasms undergo various changes in the carbohydrate moieties of their glycoconjugates. This process also indicates the possibility of changes in glycosyltransferases themselves. Therefore, we compared the binding pattern of a monoclonal antibody (MAb8628) against GalTase in both normal and neoplastic exocrine pancreatic tissues. Ten normal and 11 neoplastic human exocrine pancreatic tissues obtained from surgery were used. Frozen sections were incubated with this antibody. Supranuclear regions and terminal bars of normal duct cells and acinar cells revealed positive staining for GalTase at the light microscopic level. Centroacinar cells revealed positive staining in their perinuclear region. Neoplastic cells were also stained in their supranuclear regions and terminal bars. Supranuclear regions were well developed in neoplastic cells and intensely stained compared with those in normal cells. The supranuclear regions and the terminal bars corresponded to the trans cisternae of the Golgi apparatus and the junctional complex (i.e., tight junction and adherens junction), respectively, seen at the electron microscopic level. Pancreatic neoplastic changes thus led to an increase in the expression of GalTase in the Golgi apparatus, the increase of which may have an important effect on the intercellular adhesion and communication among pancreatic epithelial cells. Measurement of this enzyme is useful for diagnosis of exocrine pancreatic neoplastic changes from normal tissues.

Structural Repairs to Fire-Damaged Guastavino Tile Vaults at Grand Central Terminal's Oyster Bar

Structural Repairs to Fire-Damaged Guastavino Tile Vaults at Grand Central Terminal's Oyster Bar

Retinal pigment epithelium and photoreceptor maturation in a wallaby, the quokka.

Cell generation and the early stages of maturation of the retinal pigment epithelium (RPE) and photoreceptors were examined in a marsupial, the quokka, Setonix brachyurus. Results are presented for animals aged up to postnatal day (P)250. RPE cell generation was studied by analysis of cell number from wholemounted retinae and by tritiated thymidine (3HThy) autoradiography in sectioned material. For 3HThy autoradiography, quokkas aged P1-P200 were injected with 3HThy and killed either 6-20 hours later (pulse-kill) or at P100 or P250 (pulse-leave). The extent of pigmentation of the RPE sheet was examined from sections of embryonic and early postnatal stages. Retinae from animals aged P5 to P160 were also examined at the electron microscope. By P100, RPE cell number is within the range found in adults. New RPE cells are generated in a peripheral band which moves outwards as cells leave the cell cycle in more central locations. RPE cells thus complete their last cell division in a centre-to-periphery wave centred about the optic nerve head. At any given retinal location, RPE cells complete their last cell division earlier than the overlying layers of the neural retina. Cells of the RPE rapidly develop a mature morphology. For example, melanin granules are observed at P5 and Verhoeff's membrane (the terminal bar complex) is evident by P25. By contrast, photoreceptor development in this species is protracted; cone inner segments are observed by P40, whilst the first rod inner segments are observed at P60. Despite being generated earlier, morphological maturation of the cones appears retarded and prolonged compared with that of the rods. The last stages of RPE cell maturation occur late in development, in synchrony with the generation of rods.