Abruptio placentae during fetal myelomeningocele repair.

Myelomeningocele (MM) is a congenital neural tube defect with serious consequences, including hydrocephaly. An important hope for intrauterine repair is that hydrocephaly may be prevented by reversing the Arnold-Chiari malformation. Three medical centers in the United States are doing trials with this objective. We describe an intrauterine correction of MM in a Brazilian research center of fetal medicine, which resulted in abruptio placentae and fetal death, to illustrate factors that influence fetal-maternal risks during this surgical procedure.

Laparoscopic repair of pleural laceration produced during truncal vagotomy: case report.

A partial pneumothorax developed in a patient undergoing laparoscopic truncal vagotomy when a small pleural laceration was accidentally produced. Changes in oxygen saturation and PETCO2 were immediately detected by the anesthesiologist and measures were taken to maintain the patient's ventilatory stability. The pleural laceration was repaired laparoscopically, and the pneumothorax was corrected by ventilatory manipulation, avoiding the placement of a chest tube. The procedure was completed uneventfully. Literature about the causes of pneumothorax during laparoscopic procedures as well as preventive and therapy viewed.

Sleep and upper airway obstruction in children with achondroplasia.

OBJECTIVE: The features of achondroplasia, the most common form of dwarfism, includes short cranial base and midface hypoplasia; both abnormalities increased the risk of upper airway obstruction during sleep. The aim of our study was to evaluate sleep and respiratory function of children with achondroplasia and to differentiate central from obstructive apnea. We also wanted to correlate apneic events with foramen magnum stenosis. STUDY DESIGN: Sixteen children with achondroplasia (mean age, 4.7 years) were studied by noctumal polysomnography and brain computed tomography or magnetic resonance imaging. A comparison of sleep and respiratory findings was made between the study group and 25 children with adenotonsillar hypertrophy. RESULTS: The study revealed no significant difference between groups with respect to sleep architecture. We also found no relationship between apnea type and foramen magnum stenosis. Twelve children (75%) with achondroplasia had significant upper airway obstruction during sleep, with symptoms of continuous snoring and periods of brief obstructive apnea, hypopnea, or both. The mean apneahypopnea index (per hour of sleep) did not differ significantly between the two groups. However, the breathing rate during sleep was increased in children with achondroplasia. These findings indicate that the most important breathing disorder during sleep in children with achondroplasia is upper airway obstruction. CONCLUSION: We conclude that polysomnography with detailed scoring of breathing abnormalities is a useful tool in evaluating sleep-disordered breathing in children with achondroplasia.

Concentration dependence of the subunit association of oligomers and viruses and the modification of the latter by urea binding.

A theoretical model is presented that accounts for the facilitation of the pressure dissociation of R17 phage, and for the partial restoration of the concentration dependence of the dissociation, by the presence of subdenaturing concentrations of urea. As an indifferent osmolyte urea should promote the stability of the protein aggregates under pressure, and the decrease in pressure stability with urea concentration demonstrates that such indirect solvent effects are not significant for this case, and that the progressive destabilization is the result of direct protein-urea interactions. By acting as a "homogenizer" of the properties of the phage particles, urea addition converts the pressure-induced deterministic dissociation of the phage into a limited stochastic equilibrium. The model establishes the origin of the uniform progression from the stochastic equilibrium of dimers, to the temperature-dependent and partially concentration-dependent association of tetramers, to the fully deterministic equilibrium observed in many multimers and in the virus capsids.

Laparoscopic treatment of pancreatic serous cystadenoma.

A 69-year-old man with multiple medical pathology had a cystic neoplasm of the pancreas with obstructive symptoms and abdominal pain. Diagnosis and treatment were done by laparoscopy with total relief of symptoms. Sonograms every 3 months and a computed tomography scan performed 12 months after the procedure report no refilling of the cyst, and 18 months later the patient is free of symptoms. The last sonogram showed no changes. We consider laparoscopic diagnosis and treatment of serous cystadenoma of the pancreas to be a useful alternative in the management of this neoplasm.

Analysis of dissociation and unfolding of oligomeric proteins using a flat bed gel electrophoresis at high pressure.

A slab gel electrophoresis apparatus with the ability to operate over a pressure range of 10(-3) to 2 kbar is described. The system presented here is an improvement of a previous apparatus (A. A. Paladini, J. L. Silva, and G. Weber, Anal. Biochem. 161, 358-364, 1987). It consists of a flat bed gel, with a significantly enlarged buffer reservoir, which eliminates the requirement of high concentrations of running buffers, and at the same time allows shorter runs, leading to enhanced resolution and reproducibility. The application of the method to the dissociation of the tetramer glycogen phosphorylase a as a function of hydrostatic pressure is described. The flat geometry of the apparatus allows for the first time the analysis of the stability of oligomers and their constituent subunits to chemical denaturation by urea gradient electrophoresis gels at high pressure. Dimeric hexokinase shows a reversible cooperative unfolding transition with a midpoint at 3.8 M urea. In contrast, the monomers unfold at very low urea concentration (< 1.0 M). The observed differences in stability validates oligomerization as an important stabilizing element of the protein structure.

Reversible pressure dissociation of R17 bacteriophage. The physical individuality of virus particles.

In the absence of urea, pressures up to 2.5 kbar promote only 10% dissociation of the whole particles of R17 bacteriophage. In the presence of concentrations of urea between 1.0 and 5.0 M, pressure promotes complete, reversible dissociation of the virus particles. At the lower urea concentrations reversible dissociation of R17 virus particles shows no dependence on protein concentration indicating a high degree of heterogeneity of the particles, but higher urea concentrations, 2.5 to 5.0 M, result in progressive restoration of the protein concentration dependence of the pressure dissociation. At still higher urea concentrations, 5.0 to 8.0 M, irreversible dissociation of virus takes place at atmospheric pressure. In contrast, the dissociation of the isolated dimers of the capsid protein was dependent on protein concentration to the extent predicted for a stochastic equilibrium, and dimers were much less stable than the whole virus both to dissociation by pressure or urea. In contradistinction, the reversible whole-virus dissociation observed at urea concentrations below 2.5 M appears to be a typical deterministic equilibrium, without appreciable dynamic exchange between whole particle and subunits during the lengthy experiments. The experiments demonstrate that the "thermodynamic individuality" of the virus particles arises in conformational differences in the assembled viruses, and that there is a direct relation between the stability of the particles and their heterogeneity.

Pressure and low temperature effects on the fluorescence emission spectra and lifetimes of the photosynthetic components of cyanobacteria.

The effects of hydrostatic pressure on the excited state reactions of the photosynthetic system of cyanobacteria were studied with the use of stationary and dynamic fluorescence spectroscopy. When the cells were excited with blue light (442 nm), hydrostatic pressure promoted a large increase in the fluorescence emission of the phycobilisomes (PBS). When PBS were excited at 565 nm, the shoulder originating from photosystem II (PSII) emission (F685) disappeared under 2.4 kbar compression, suggesting suppression of the energy transfer from PBS to PSII. At atmospheric pressure, the excited state decay was complex due to energy transfer processes, and the best fit to the data consisted of a broad Lorentzian distribution of short lifetimes. At 2.4 kbar, the decay data changed to a narrower distribution of longer lifetimes, confirming the pressure-induced suppression of the energy transfer between the PBS and PSII. When the cells were excited with blue light, the decay at atmospheric pressure was even more complex and the best fit to the data consisted of a two-component Lorentzian distribution of short lifetimes. Under compression, the broad distribution of lifetimes spanning the region 100-1,000 ps disappeared and gave rise to the appearance of a narrow distribution characteristic of the PBS centered at 1.2 ns. The emission of photosystem I underwent 2.2-fold increase at 2.4 kbar and room temperature. A decrease in temperature from 20 to -10 degrees C at 2.4 kbar promoted a further increase in the fluorescence emission from photosystem I to a level comparable with that obtained at temperatures below 120 degrees K and atmospheric pressure. On the other hand, when the temperature was decreased under pressure, the PBS emission diminished to very low value at blue or green excitation, suggesting the disassembly into the phycobiliprotein subunits.

Myxozyma neotropica sp. nov. (Candidaceae)--a new yeast species from Costa Rica.

Two strains of an undescribed, soil-borne species of the genus Myxozyma were recovered. They differ from other accepted species of this genus in their carbon assimilation pattern, mol% G+C and low extent of DNA complementary. A description of the new species, Myxozyma neotropica, and a key to the species accepted in the genus are given.