RESUMO
INTRODUCTION: Fibrocartilaginous embolism and spinal cord infarction may resemble transverse myelitis with antecedent minor trauma (sporting activity or minor falls) or with hyperacute (<12-hour) presentation. METHODS: Diagnostic criteria for fibrocartilaginous embolism and spinal cord infarction were applied to a 10-year (2007-2016) cohort of children aged 1 month to 16 years with transverse myelitis and clinical, laboratory, neuroimaging, and outcome data compared between those with and without antecedent minor trauma. RESULTS: Thirty-two children of median age 8.9 (range 2.7-15.8) years were included; 19 (59%) were female. Falls at home, school, or play (6 children, 60%), swimming (2, 20%), physical education (1, 10%), and caning (1, 10%) were antecedent events in 10 (31%) children. Six (19%) had hyperacute presentations. One patient met spinal cord infarction criteria; none had fibrocartilaginous embolism. Children with transverse myelitis and antecedent minor trauma had single, short spinal cord lesions (median 3 vertebral bodies) but without a specific neuroimaging lesion pattern. None had intervertebral disc abnormalities or brain involvement and were negative for myelin oligodendrocyte and aquaporin 4 antibodies. Twenty-five (86%) of 29 had cerebrospinal fluid inflammation, and 30 (94%) received immunotherapy. Thirty (97%) were followed for a median of 3.6 (0.1-10.2) years, with good outcome (modified Rankin Scale score 0-1) in the majority (80%). Four (75%) with hyperacute presentation had a good outcome (modified Rankin Scale score 0-1), but the patient with spinal cord infarction was the most disabled (modified Rankin Scale score 4). CONCLUSION: Minor trauma or hyperacute presentations does not always indicate fibrocartilaginous embolism or spinal cord infarction. Children with minor trauma preceding transverse myelitis have a distinct clinicoradiologic syndrome, with good outcome following immunotherapy.
Assuntos
Imageamento por Ressonância Magnética/métodos , Mielite Transversa/diagnóstico por imagem , Traumatismos da Medula Espinal/diagnóstico por imagem , Adolescente , Criança , Pré-Escolar , Diagnóstico Diferencial , Feminino , Humanos , Masculino , SingapuraRESUMO
The catalytic subunit of human telomerase, hTERT, actively elongates the 3' end of the telomere in most cancer cells. The hTERT promoter, which contains many guanine-rich stretches on the same DNA strand, exhibits an exceptional potential for G-quadruplex formation. Here we show that one particular G-rich sequence in this region coexists in two G-quadruplex conformations in potassium solution: a (3 + 1) and a parallel-stranded G-quadruplexes. We present the NMR solution structures of both conformations, each comprising several robust structural elements, among which include the (3 + 1) and all-parallel G-tetrad cores, single-residue double-chain-reversal loops, and a capping A.T base pair. A combination of NMR and CD techniques, complemented with sequence modifications and variations of experimental condition, allowed us to better understand the coexistence of the two G-quadruplex conformations in equilibrium and how different structural elements conspire to favor a particular form.