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T Whitfield

Publications and source records attributed to T Whitfield.

5 recordsLinked to original sources
PubMed2003

Vanadogermanate cluster anions.

Three novel vanadogermanate cluster anions have been synthesized by hydrothermal reactions. The cluster anions are derived from the (V(18)O(42)) Keggin cluster shell by substitution of V=O(2+) "caps" by Ge(2)O(OH)(2)(4+) species. In Cs(8)[Ge(4)V(16)O(42)(OH)(4)].4.7H(2)O, 1, (monoclinic, space group C2/c (No. 15), Z = 8, a = 44.513(2) A, b = 12.7632(7) A, c = 22.923(1) A, beta = 101.376(1) degrees ) and (pipH(2))(4)(pipH)(4)[Ge(8)V(14)O(50).(H(2)O)] (pip = C(4)N(2)H(10)), 2 (tetragonal, space group P4(2)/nnm (No. 134), Z = 2, a = 14.9950(7) A, c = 18.408(1) A), two and four VO(2+) caps are replaced, respectively, and each cluster anion encapsulates a water molecule. In K(5)H(8)Ge(8)V(12)SO(52).10H(2)O, 3, (tetragonal, space group I4/m (No. 87), Z = 2, a = 15.573(1) A, c = 10.963(1) A), four VO(2+) caps are replaced by Ge(2)O(OH)(2)(4+) species, and an additional two are omitted. The cluster ion in 3 contains a sulfate anion disordered over two positions. The cluster anions are analogous to the vanadoarsenate anions [V(18)(-)(n)()As(2)(n)()O(42)(X)](m)(-) (X = SO(3), SO(4), Cl; n = 3, 4) previously reported.

Journal Article↗
PubMed1997

Intercellular signals and cell-fate choices in the developing inner ear: origins of global and of fine-grained pattern.

The major regions of the inner ear begin to be distinguishable by their patterns of gene expression very early, before the otocyst has closed. Later, individual cells within a neurogenic or sensory patch become committed to specific pathways of differentiation. Insights gained from homologies with invertebrates and from studies of tissues other than the ear, combined with discoveries from screens for mutations affecting development in the zebrafish, are beginning to reveal the genes and signalling mechanisms that control these cell-fate choices in the developing inner ear.

Journal Article↗
PubMed1993

XLPOU-60, a Xenopus POU-domain mRNA, is oocyte-specific from very early stages of oogenesis, and localised to presumptive mesoderm and ectoderm in the blastula.

POU-domain proteins are a large family of transcriptional regulatory proteins, related to the homeodomain proteins, many of which are implicated in the control of gene expression during early development. We describe here the isolation of a cDNA encoding a Xenopus POU-domain protein, XLPOU-60. The predicted protein sequence of this cDNA is most closely related to the mouse germ line-specific transcription factor Oct-3/4. The XLPOU-60 gene is specifically expressed in oocytes of newly metamorphosed frogs, from the earliest stages at which transcription is known to occur. The mRNA is concentrated in the animal half of fully grown oocytes and is inherited maternally by the embryo, where it remains localised to animal cap and marginal zone cells of the blastula. Transcripts decline abruptly to a low level during gastrulation, but remain detectable throughout larval stages. However, unlike Oct-3/4, the transcript is not detectable in primordial germ cells, and XLPOU-60 is therefore probably not the functional homologue of the murine gene. We suggest that XLPOU-60 is one of the earliest genes to be transcribed in oocyte development, and that the XLPOU-60 protein may therefore be involved in initiating oocyte-specific patterns of transcription. Localisation of the transcript in the embryo may indicate that XLPOU-60 is also required for the initiation of mesoderm- and ectoderm-specific patterns of transcription in the embryo.

Amino Acid Sequence↗
PubMedDate not supplied

Hair cells without supporting cells: further studies in the ear of the zebrafish mind bomb mutant.

Each sensory hair cell in the ear is normally surrounded by supporting cells, which separate it from the next hair cell. In the mind bomb mutant, as a result of a failure of lateral inhibition, cells that would normally become supporting cells differentiate as hair cells instead, creating sensory patches that consist of hair cells only. This provides a unique opportunity to pinpoint the functions for which supporting cells are required in normal hair cell development. We find that hair cells in the mutant develop an essentially normal cytoskeleton, with a correctly structured hair bundle and well-defined planar polarity, and form apical junctional complexes with one another in standard epithelial fashion. They fail, however, to form a basal lamina or to adhere properly to the adjacent non-sensory epithelial cells, which overgrow them. The hair cells are eventually expelled from the ear epithelium into the underlying mesenchyme, losing their hair bundles in the process. It is not clear whether they undergo apoptosis: many cells staining strongly with the TUNEL procedure are seen but do not appear apoptotic by other criteria. Supporting cells, therefore, are needed to hold hair cells in the otic epithelium and, perhaps, to keep them alive, but are not needed for the construction of normal hair bundles or to give the hair bundles a predictable polarity. Moreover, supporting cells are not absolutely required as a source of materials for otoliths, which, though small and deformed, still develop in their absence.

Animals↗