1,251 research outputs found
Guidelines and recommendations for testing of Cx26 mutations and interpretation of results
No full textInvestigation of mitochondrial m.1555A>G aminoglycoside hearing loss
No full textThe mitochondrial DNA mutation, m.1555A>G, predisposes to severe hearing loss following aminoglycoside antibiotic exposure. The m.1555A>G mutation can also lead to hearing loss in the absence of antibiotic exposure termed non-syndromic m.1555A>G hearing loss. Two distinct concepts of mitochondrial dysfunction related to the m.1555A>G mutation have been postulated - mRNA misreading and 12S m⁶₂A rRNA methylation. Evidence from cell and animal models has indicated that m.1555A>G may make the 12S rRNA a better substrate for m⁶₂A methylation by the mitochondrial transcription factor B1 (TFB1M) enzyme, resulting in a higher ratio of methylated: unmethylated 12S rRNA transcripts in the mitochondrion, so called ‘hypermethylation’. Hypermethylation is thought to trigger a cascade of events, which results in mitochondrial dysfunction and hearing loss. Using a novel fluorescent method, suitable for paediatric patients, 12S m⁶₂A rRNA methylation was investigated in primary and non-primary cell-derived RNA samples from patients with m.1555A>G and controls. The data presented in this work indicates that previous findings may be an artefact of the experimental models used to study this hypothesis and 12S m⁶₂A rRNA methylation is unlikely to be a pathogenic mechanism. Aminoglycoside-induced reactive oxygen species (ROS) production is reported to play a key role in cochlear cell death. It is hypothesised that increased mitochondrial mRNA misreading disrupts oxidative phosphorylation, which leads to increased ROS. Using a multiplex flow cytometry-based method to measure mitochondrial superoxide, the response of cells from cases with m.1555A>G and controls to aminoglycoside treatment was examined. The data indicates that the control response to aminoglycoside treatment is variable. Exploring this variation will be crucial if the effects of antibiotic-induced changes in mitochondrial mRNA misreading are to be investigated and the cellular events that ensue to be targeted for treatment
Septicollarina zezinae Bitner, 2009, sp. nov.
No full textSepticollarina zezinae sp. nov. (Fig. 8; for a full systematic description see below) This is the first record of the genus Septicollarina from the New Caledonian region, including the Norfolk Ridge. The species was found on Jumeau East, Porthos and Zorro seamounts at a depth range of 670– 950 m. It occurs in the Fiji area (Bitner 2008) but, because of very limited material (one specimen), was at the time ascribed only to genus level. Two other species of Septicollarina ― S. hemiechinata Zezina, 1981 a from off Java and S. oceanica Zezina, 1990 from the Eastern Pacific ― are known from shallower water (240–485 m).Published as part of Bitner, Maria Aleksandra, 2009, Recent Brachiopoda from the Norfolk Ridge, New Caledonia, with description of four new species, pp. 1-39 in Zootaxa 2235 on page 14, DOI: 10.5281/zenodo.19039
Hearing in 44-45 year olds with m.1555A > G, a genetic mutation predisposing to aminoglycoside-induced deafness: a population based cohort study.
No full textBackground The mitochondrial DNA mutation m.1555A>G predisposes to permanent idiosyncratic aminoglycoside-induced deafness that is independent of dose. Research suggests that in some families, m.1555A>G may cause non-syndromic deafness, without aminoglycoside exposure, as well as reduced hearing thresholds with age (age-related hearing loss). Objectives To determine whether adults with m.1555A>G have impaired hearing, a factor that would inform the cost-benefit argument for genetic testing prior to aminoglycoside administration. Design Population-based cohort study. Setting UK. Participants Individuals from the British 1958 birth cohort. Measurements Hearing thresholds at 1 and 4 kHz at age 44-45 years; m.1555A>G genotyping. Results 19 of 7350 individuals successfully genotyped had the m.1555A>G mutation, giving a prevalence of 0.26% (95% CI 0.14% to 0.38%) or 1 in 385 (95% CI 1 in 714 to 1 in 263). There was no significant difference in hearing thresholds between those with and without the mutation. Single-nucleotide polymorphism analysis indicated that the mutation has arisen on a number of different mitochondrial haplogroups. Limitations No data were collected on aminoglycoside exposure. For three subjects, hearing thresholds could not be predicted because information required for modelling was missing. Conclusions In this cohort, hearing in those with m.1555A>G is not significantly different from the general population and appears to be preserved at least until 44-45 years of age. Unbiased ascertainment of mutation carriers provides no evidence that this mutation alone causes non-syndromic hearing impairment in the UK. The findings lend weight to arguments for genetic testing for this mutation prior to aminoglycoside administration, as hearing in susceptible individuals is expected to be preserved well into adult life. Since global use of aminoglycosides is likely to increase, development of a rapid test is a priority
Nipponithyris afra Cooper-Bitner & Logan 1973
No full textNipponithyris afra Cooper, 1973 (Fig. 1 H–R) 2016 Nipponithyris afra Cooper—Bitner & Logan, p. 28, fig. 16 (cum syn.). Material examined. DongSha 2014 cruise, stn CP 4130, 20°16’N, 116°08’E, depth 795–822 m, six specimens. Measurements. Maximum length 15.0 mm, width 12.7 mm, thickness 7.1 mm. Description. Shell of medium size, subpentagonal in outline, longer than wide, ventribiconvex with smooth surface and strongly unisulcate anterior commissure. Beak erect with weakly defined beak ridges. Foramen circular, mesothyrid to permesothyrid. Deltidial plates conjunct forming a visible symphytium. Shell posteriorly strongly thickened (Fig. 1 N– R). Ventral valve interior with short, thick teeth with swollen bases; delthyrial cavity narrow. Dorsal valve interior with massive inner socket ridges. Cardinal process prominent. Crura short. Descending branches slender becoming broad anteriorly. Septum short. Remarks. The specimens correspond well with those described as Nipponithyris afra. This species was first recorded by Cooper (1973a) from off Mozambique (see also Bitner & Logan 2016) and later recognized in the New Caledonian region (Laurin 1997). Nipponithyris afra differs from N. nipponensis Yabe & Hatai, 1934 that is found off the coasts of Japan in being rounder and in having a more strongly sulcate anterior commissure (Hatai 1940, Cooper 1973a).Published as part of Bitner, Maria Aleksandra & Romanin, Marco, 2017, Recent brachiopods from the South China Sea, NW Pacific, pp. 287-290 in Zootaxa 4306 (2) on page 289, DOI: 10.11646/zootaxa.4306.2.9, http://zenodo.org/record/84383
Aulites crosnieri Bitner, 2009, sp. nov.
No full textAulites crosnieri sp. nov. (Fig. 5; for a full systematic description see below) This rhynchonellide, closely related to Cryptopora, was represented by only three specimens from a single sample on Crypthelia seamount at 200– 291 m. The genus Aulites, originally monospecific, was previously known only from off the east, south and west coasts of Australia (Dall 1920; Richardson 1987). The present finding extends the geographical range of the genus about 1,500 km to the west.Published as part of Bitner, Maria Aleksandra, 2009, Recent Brachiopoda from the Norfolk Ridge, New Caledonia, with description of four new species, pp. 1-39 in Zootaxa 2235 on page 9, DOI: 10.5281/zenodo.19039
Annuloplatidia richeri Bitner, 2009, sp. nov.
No full textAnnuloplatidia richeri sp. nov. (Fig. 10; for a full systematic description see below) This is the first record of the genus Annuloplatidia from the New Caledonian region including the Norfolk Ridge, although the genus is known from the western Pacific (Zezina 1981 b), Atlantic and eastern Pacific (Atkins 1959; Bernard 1972; Lüter 2007). Annuloplatidia richeri was found only in sediment samples collected during Norfolk 1 cruise on 3 seamount cruises (Tables 1, 2). Its bathymetric range is 200–967 m (Fig. 14).Published as part of Bitner, Maria Aleksandra, 2009, Recent Brachiopoda from the Norfolk Ridge, New Caledonia, with description of four new species, pp. 1-39 in Zootaxa 2235 on page 16, DOI: 10.5281/zenodo.19039
Cryptopora norfolkensis Bitner, 2009, sp. nov.
No full textCryptopora norfolkensis sp. nov. (Fig. 4; for a full systematic description see below) The micromorphic brachiopod Cryptopora norfolkensis was found on five seamounts (Tables 1, 2), with a depth range of 200 to 980 m (Fig. 14). The genus Cryptopora has a worldwide distribution (Logan 2007) but this is the first record from the Norfolk Ridge. D’Hondt (1987) reported C. boettgeri Helmcke, 1940 from the New Caledonian slope but he had limited material and did not investigate internal structures, making it difficult to assess the reliability of his species assignment. The material collected during the Norfolk 1 and 2 cruises comprises more than 290 specimens, all found in loose sediment.Published as part of Bitner, Maria Aleksandra, 2009, Recent Brachiopoda from the Norfolk Ridge, New Caledonia, with description of four new species, pp. 1-39 in Zootaxa 2235 on page 8, DOI: 10.5281/zenodo.19039
Eucalathis daphneae Bitner & Logan 2016, n. sp.
No full textEucalathis daphneae n. sp. (Fig. 10 E-O; Table 9) TYPE MATERIAL. — North-West Madagascar. MIRIKY, stn DW 3234, holotype (MNHN IB-2013-61; Fig. 10 F-J). — Same data, stn DW 3196, paratypes (MNHN IB-2013-62, 63; Fig. 10E, K-O). TYPE LOCALITY. — Madagascar, MIRIKY, stn DW 3234, 13°27'S, 47°55'E, 187- 247 m. DIAGNOSIS. — Eucalathis with single, broad, rounded costae nearly smooth in anterior half, and incomplete loop. MATERIAL EXAMINED. — North-West Madagascar. MIRIKY, stn DW 3196, 8 bivalved specimens. — Stn DW 3234, 2 bivalved specimens, 1 ventral valve, 1 dorsal valve. DEPTH RANGE. — 187-249 m DESCRIPTION Shell small (maximum observed length 5.9 mm), ventribiconvex, widely subtriangular in outline. Shell surface covered with 10-12 strong, single, rounded costae. Costae weakly beaded posteriorly, nearly smooth in anterior half except where crossed by elevated growth lines; intercostal spaces wide. Anterior commissure rectimarginate. Hinge line slightly curved. Beak low, suberect. Foramen large, subcircular, mesothyrid; deltidial plates small, triangular (Fig. 10E, G). Ventral valve interior with small teeth; pedicle collar wide. Dorsal valve interior with massive inner socket ridges extending beyond margin. Cardinal process distinct. Crura long, slender; crural processes short, can be slightly incurved. Loop short with an incomplete transverse band (Fig. 10 I-O). Low, short median ridge visible on inner dorsal valve. Inner margin of both valves crenulated. REMARKS In size, outline and ornamentation the new species described here is most similar to Eucalathis rotundata. In the strong costation E. daphneae n. sp. also resembles E. rugosa Cooper, 1973, differing in size and outline, as well as in the character of costae. E. rugosa possesses beaded, strongly tuberculate ribs (Cooper 1973c; Laurin 1997; Bitner 2008, 2009, 2010); in E. daphneae ribs are nearly smooth. However, the species described by Cooper (1973c, 1981a) have a typical loop for the genus, whereas in all specimens collected in North-West Madagascar the loop has an incomplete transverse band. Among Recent representatives of chlidonophorids only in the species Melvicalathis macroctena (Zezina, 1981) may the loop be incomplete (Zezina 1981b; Lee et al. 2008), however, it possesses broad, triangular in cross-section costae with smooth ridges without any tubercles, differing greatly from E. daphneae. In the fossil chlidonophorids an incomplete loop is observed only in the Eocene-Oligocene genus Orthothyris Cooper, 1955 (see Bitner & Müller 2015).Published as part of Bitner, Maria Aleksandra & Logan, Alan, 2016, Recent Brachiopoda from the Mozambique-Madagascar area, western Indian Ocean, pp. 5-41 in Zoosystema 38 (1) on page 18, DOI: 10.5252/z2016n1a1, http://zenodo.org/record/457814
Annuloplatidia richeri Bitner, 2009, sp. nov.
No full textAnnuloplatidia richeri sp. nov. (Fig. 10; for a full systematic description see below) This is the first record of the genus Annuloplatidia from the New Caledonian region including the Norfolk Ridge, although the genus is known from the western Pacific (Zezina 1981 b), Atlantic and eastern Pacific (Atkins 1959; Bernard 1972; Lüter 2007). Annuloplatidia richeri was found only in sediment samples collected during Norfolk 1 cruise on 3 seamount cruises (Tables 1, 2). Its bathymetric range is 200–967 m (Fig. 14).Published as part of Bitner, Maria Aleksandra, 2009, Recent Brachiopoda from the Norfolk Ridge, New Caledonia, with description of four new species, pp. 1-39 in Zootaxa 2235 on page 16, DOI: 10.5281/zenodo.19039
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