We have cloned CHS4, a gene that complements the resistance to Calcofluor of the Saccharomyces cerevisiae cal2 mutant. We show that CHS4 is allelic to the previously described SKT5 and CSD4 genes. CHS4 encodes a 696 amino acids protein with no potential transmembrane domain. chs4-null mutants are resistant to Calcofluor white and exhibit a considerable reduction in cell wall chitin and in chitin synthase III (CSIII) activity. Biochemical characterization of chitin synthase III from these null mutants indicates that the defect is due to a reduced V max of the enzyme. This defect can be overcome in vitro by trypsin treatment of the membrane preparations. Chs4p does not act as a transcriptional or translational regulator of CHS3, the gene coding for the catalytic subunit of CSIII activity, and we therefore propose that Chs4p would be an essential component of the CSIII complex, acting as a post-translational regulator of this activity. In addition to the chitin defect, the chs4 mutant shows a severe defect in mating.

Objectives To compare prospectively maternal acceptance of fetal and neonatal virtuopsy with that of conventional autopsy and to determine the confidence with which magnetic resonance (MR) virtuopsy can be used to diagnose normality/abnormality of various fetal anatomical structures. Methods

Chitin is a minor but essential component of the cell wall of Saccharomyces cerevisiae, with functions in septum formation in the vegetative life cycle and also in conjugation and spore cell-wall synthesis in the sexual cycle. Of the three chitin synthases present in yeast, chitin synthase III (CSIII) is responsible for the synthesis of most of the chitin found in the cell, including a chitin ring at early budding, chitin interspersed in the cell wall, and chitin laid down during the sexual cycle. We have tagged Chs3p, the putative catalytic subunit of CSIII, with the immunoreactive epitope of influenza virus hemagglutinin to follow expression of the protein. Little correlation was found between the levels of transcription and translation of Chs3p and in vivo function, supporting our previous conclusion that regulation of CSIII occurs at the posttranslational level. To identify possible regions of the protein involved in catalysis or regulation, mutations were generated in the QRRRW 'signature sequence' of chitin synthases. Arginine residue mutations in Chs3p, and in Chs1p and Chs2p, resulted in a loss of both function in vivo and enzymatic activity. Mutations in a serine residue adjacent to glutamine in Chs3p caused loss of function in vivo with a moderate decrease in CSIII activity, suggesting a regulatory role for the serine residue in chitin biosynthesis. Several truncations in the unique hydrophilic carboxy-terminal region of Chs3p identified a sequence of about 25 amino acids that is required for both function and in vitro activity. Since this region is not present in Chs1 or Chs2, it may be involved in the specific regulation of CSIII.Keywords : chitin synthase III; calcofluor resistance; morphogenesis; Saccharomyces cerevisiae.Chitin is a component of the yeast cell wall that, although only present in small amounts, is required for cell viability and has a major role in septum formation and cell division [1Ϫ3]. Three chitin synthases have been described in Saccharomyces cerevisiae, CSI, CSII and CSIII (see [1Ϫ3] for reviews), each with different functions. CSIII is responsible for synthesis of the chitin ring laid down at the base of an emerging bud; CSII is subsequently involved in the formation of the primary septum disk ; finally, CSI repairs damaged chitin during cell separation. Since CSIII also catalyzes the synthesis of chitin interspersed over all the cell wall and of that laid down during mating and sporulation, this enzyme is responsible for production of most of the chitin found in the cell [1].The different roles of chitin synthases require that each be regulated independently, so that it will execute its function at the required time and location in the cell. This regulation may take place during expression of the protein and/or posttranslationally. Some evidence of transcriptional regulation of the genes coding for the putative catalytic subunits of the three synthases (CHS1, CHS2 and CHS3) has been found [4]. However, further work showed that only CSII activity oscillates in the cell cycle...

• In cCMV, isolated periventricular T2-weighted signal hyperintensity has a good postnatal prognosis. • In cCMV, SNHL and neurological impairment can be predicted at 27 or 33 weeks. • In cCMV, fetal MR has a high NPV in predicting SNHL. • In cCMV, fetal MR has a high NPV in predicting neurological impairment.

Objective To compare the diagnostic accuracy of twodimensional (2D) ultrasound and three-dimensional (3D) computed tomography (CT) for the diagnosis of fetal skeletal anomalies. Methods

Post-mortem imaging combined with systematic organ biopsies is highly acceptable among all parents independent of their religion and the method used for organ biopsy.

Objectives To compare the diagnostic usefulness of highfield with low-field magnetic resonance imaging (MRI)and stereomicroscopic autopsy for examination of the heart in fetuses at or under 20 weeks' gestation. (95% CI,) and specificity 100. 0% (95% CI,. Eight fetuses out of 10 with congenital heart disease (CHD) were classified as having major CHD. Methods High-field MRI at 9.4 T was able to identify seven out of the eight cases of major CHD.Conclusion High-field MRI at 9.4 T seems to be an acceptable alternative approach to invasive stereomicroscopic autopsy for fetuses with CHD at or below 20 weeks' gestation.

This study showed no adverse effects of exposure to 1.5-T MR imaging in utero on neonatal hearing function or birth weight percentiles.