Interplay Between Cell Growth And Cell Cycle In Plants.

The growth of organs and whole plants depends on both cell growth and cell-cycle progression, but the interaction between both processes is poorly understood. In plants, the balance between growth and cell-cycle progression requires coordinated regulation of four different processes: macromolecular synthesis (cytoplasmic growth), turgor-driven cell-wall extension, mitotic cycle, and endocycle. Potential feedbacks between these processes include a cell-size checkpoint operating before DNA synthesis and a link between DNA contents and maximum cell size. In addition, key intercellular signals and growth regulatory genes appear to target at the same time cell-cycle and cell-growth functions. For example, auxin, gibberellin, and brassinosteroid all have parallel links to cell-cycle progression (through S-phase Cyclin D-CDK and the anaphase-promoting complex) and cell-wall functions (through cell-wall extensibility or microtubule dynamics). Another intercellular signal mediated by microtubule dynamics is the mechanical stress caused by growth of interconnected cells. Superimposed on developmental controls, sugar signalling through the TOR pathway has recently emerged as a central control point linking cytoplasmic growth, cell-cycle and cell-wall functions. Recent progress in quantitative imaging and computational modelling will facilitate analysis of the multiple interconnections between plant cell growth and cell cycle and ultimately will be required for the predictive manipulation of plant growth.

Fibrodysplasia ossificans progressiva: case report

Fibrodysplasia ossificans progressiva is a rare genetic disease characterized by widespread soft tissue ossification and congenital stigmata of the extremities. We report on a male child followed for ten years since the age of 3 years and 9 months, when the diagnosis was made. He was born with bilateral hypoplasic hallux valgus and ventricular septal defect, corrected by transsternal approach when 32 months old. Restriction of neck mobility followed and foci of ectopic ossification appeared. Four crises of disease exacerbation were treated with oral prednisone and/or other antiinflammatory drugs. Sodium etidronate 5 to 10 mg/kg/day was prescribed intermittently during about six years but was discontinued due to osteopenia. The disease course has been relentless, with severe movement restriction including the chest wall. A review showed few similar case reports in the Brazilian literature. We revisit the criteria for diagnosis and the essentials of management and treatment.

Cromomicose cerebral: registro de um caso

A case of brain abscess and meningitis due to pigmented fungi is reported. The patient was a 59-year-old white male, who had enjoyed excellent health until October 1977, when he developed headache, later accompanied by paresthesias and weakness in the left-sided extremities. These symptoms worsened progressively and in November of that year he had to quit his job. From February 1978 on he became inactive and anorexic. Intense continuous headache was associated with frequent episodes of vomiting. He gradually became tor-porous, and according to his relatives, suffered from visual and possibly auditory deficiency. On examination, he was malnourished and dehydrated, with decubitus ulcers. Temperature was 38,5°C. A left-sided spastic hemiplegia and prominent meningorradicular signs were noted. The CSF was examined six times between May 17th and June 1st and showed variable hypercytosis (143 to 4,437 leucocytes/ cu mm) with predominance of neutrophils (up tp 95%), low glucose and high protein concentrations. No microorganisms were identified. Electroencephalographic study disclosed a low background activity especially in left temporal areas. Despite supportive care and antibiotic therapy he lapsed into coma. Carotid angiography was normal on June 1st. He remained in deep coma until his death on June 6th, 1978. Necropsy was limited to the brain, which weighed 1,550 g after fixation and showed diffuse intense edema and hyperemia. On coronal sectioning an encapsulated abscess was found in the right basal ganglia, which also involved the internal capsule, and measured 1.5 cm in diameter. Microscopical examination disclosed large numbers of brownish fungi, appearing both as oval yeasts and as septate hyphae in the thick fibrous capsule and in the necrotic content of the abscess. The same organisms were demonstrated in moderate numbers in the leptomeninges of the medulla oblongata and , less frequently, of the hippo-campal region and cerebellum.