Disequilibrium reaction pathways and the twin-mediated growth of tabular forsterite during contact metamorphism of quartz-bearing dolomite.

The forsterite zone of the Ubehebe Peak contact aureole, Death Valley, USA consists of an outer zone of tabular/jack-straw olivine and an inner zone of subequant polyhedral olivine. Subequant polyhedral forsterite crystals close to the intrusion are small and tabular forsterite crystals farther away are larger. To investigate the formation of the two morphologies, forsterite growth experiments were conducted in cold seal pressure vessels in the CaO-MgO-SiO2-CO2-H2O system. Forsterite precipitation follows a disequilibrium reaction pathway made of three reactions: [1] tabular forsterite growth from quartz and dolomite, [2] forsterite growth from tremolite dissolution, and [3] subequant polyhedral forsterite growth from tabular forsterite dissolution. Initially, quartz reacts with dolomite to simultaneously form twinned tabular forsterite and tremolite. As quartz reacts away, forsterite precipitation continues at a slower rate through tremolite dissolution. A second generation of forsterite then precipitates on top of some tabular forsterite but has different habit and tracht. Once all the tremolite reacts away, subequant polyhedral forsterite precipitation continues at an even slower rate through dissolution of tabular forsterite. The tabular morphology of jack-straw olivine is a consequence of twin-mediated unidirectional growth; the abundance of twins being due to rapid nucleation and growth at initially high reaction affinities. Twin junctions are preferential nucleation centers for steps, so faceted growth is enhanced on {100}. This phenomenon is the twin plane re-entrant effect. Subequant polyhedral forsterite in the Ubehebe Peak inner contact aureole recrystallized and ripened from tabular forsterite. In the outer contact aureole, conditions were not conducive to recrystallization and ripening so well-developed tabular forsterite persists.

Síndrome de carcinoma de células basales nevoides (Síndrome Gorlin): reporte de dos casos y revisión de la literatura / Nevoid basal-cell carcinoma syndrome (Gorlin Syndrome): report of two cases and review of the literature

RESUMEN El síndrome Gorlin (SG) es una condición genética, con patrón de herencia autosómico dominante, con penetrancia completa y expresividad variable, debida a mutaciones germinales en los genes PTCH1 o SUFU, los cuales son componentes de la vía molecular Sonic hedgehog. El SG se caracteriza por la presencia de múltiples carcinomas de células basales nevoides, quistes odontogénicos, calcificación de la hoz del cerebro y lesiones en sacabocado en palmas y plantas. Este es el primer reporte de casos en el Perú sobre pacientes con SG, que cuentan con evaluación y asesoría genética. Presentamos dos casos de SG que cumplen criterios clínicos del síndrome y una revisión de la literatura.

ABSTRACT Gorlin syndrome (GS) is a genetic disorder with an autosomal dominant inheritance pattern, with complete penetrance and variable expressivity. GS is caused by germline mutations in the genes PTCH1 or SUFU, which are components of the Sonic hedgehog molecular pathway. GS is characterized by the presence of multiple nevoid basal cell carcinomas, odontogenic cysts, calcification of the brain sickle, and lesions in the palms and soles. This study is the first to report cases in Peru of patients with GS who underwent genetic evaluation and counseling. We present two GS cases that meet the clinical criteria for the syndrome and review the literature

[Nevoid basal-cell carcinoma syndrome (Gorlin Syndrome): report of two cases and review of the literature]. / Síndrome de carcinoma de células basales nevoides (Síndrome Gorlin): reporte de dos casos y revisión de la literatura.

Gorlin syndrome (GS) is a genetic disorder with an autosomal dominant inheritance pattern, with complete penetrance and variable expressivity. GS is caused by germline mutations in the genes PTCH1 or SUFU, which are components of the Sonic hedgehog molecular pathway. GS is characterized by the presence of multiple nevoid basal cell carcinomas, odontogenic cysts, calcification of the brain sickle, and lesions in the palms and soles. This study is the first to report cases in Peru of patients with GS who underwent genetic evaluation and counseling. We present two GS cases that meet the clinical criteria for the syndrome and review the literature.

El síndrome Gorlin (SG) es una condición genética, con patrón de herencia autosómico dominante, con penetrancia completa y expresividad variable, debida a mutaciones germinales en los genes PTCH1 o SUFU, los cuales son componentes de la vía molecular Sonic hedgehog. El SG se caracteriza por la presencia de múltiples carcinomas de células basales nevoides, quistes odontogénicos, calcificación de la hoz del cerebro y lesiones en sacabocado en palmas y plantas. Este es el primer reporte de casos en el Perú sobre pacientes con SG, que cuentan con evaluación y asesoría genética. Presentamos dos casos de SG que cumplen criterios clínicos del síndrome y una revisión de la literatura.