UCSF partnership to enrich science teaching for sixth graders in San Francisco's schools.

Increasing the diversity of students entering the health professions is a challenging goal for medical schools. One approach to this goal is to share the enthusiasm and energy of medical students with younger students, who may pursue medical education in the future. The MedTeach program, established in 1989 and coordinated by the Science & Health Education Partnership of the University of California, San Francisco (UCSF), does so by partnering volunteer medical students from UCSF with sixth-grade classes studying the human body. In 1997-98, around 350 sixth-graders in the San Francisco Schools benefitted from the program. Each team of medical student's visits its class ten to 12 times a year to present engaging, hands-on lessons on body systems and health. The medical students are also role models for the middle-school students. In addition, the diverse student population of San Francisco public schools provides a rich environment for the medical students to improve their communication and teaching skills.

Torso, a receptor tyrosine kinase required for embryonic pattern formation, shares substrates with the sevenless and EGF-R pathways in Drosophila.

The maternally expressed Drosophila gene torso (tor) is a receptor tyrosine kinase that, when activated, initiates a signal transduction cascade that is responsible for the proper differentiation of the terminal, nonsegmented regions of the embryo. l(1)pole hole, the Drosophila raf-1 serine-threonine kinase homolog, and corkscrew, a tyrosine phosphatase, have been shown previously to function in this signal transduction pathway. We have identified other products in this pathway by carrying out a mutagenesis screen for dominant suppressors of a tor gain-of-function allele. More than 40 mutations, some of which fall into seven complementation groups, have been characterized genetically. Two of these correspond to mutations in ras-1 and Son of sevenless (Sos), which also function in the sevenless and EGF receptor (Der) tyrosine kinase pathways. The phenotypes of several other Su(tor) mutations suggest that they also function in other receptor tyrosine kinase-activated pathways at different times during Drosophila development.

Spatial regulation of zerknüllt: a dorsal-ventral patterning gene in Drosophila.

zerknüllt (zen) is one of approximately 10 zygotically active genes that control the differentiation of the dorsal-ventral (D/V) pattern during early embryogenesis in Drosophila. Past genetic analyses suggest that maternal factors repress the expression of zen in ventral regions, thereby restricting zen products to dorsal and dorsal-lateral regions of precellular embryos. Subsequent interactions with other zygotic D/V regulatory genes refine the zen pattern, restricting expression to the dorsal-most ectoderm. Here we describe the use of zen promoter fusions and P-element transformation to identify cis elements that are responsible for the complex spatial pattern of zen expression. The zen promoter shows a two-tier organization: Distal sequences mediate its initial response to maternal factors, whereas proximal sequences are responsible for the refinement of the pattern in older embryos. The distal regulatory element has the property of a silencer (or anti-enhancer) element and can act over a distance to repress ventral expression of a heterologous promoter. Also, we discuss evidence that proximal promoter sequences interact with factors that may be modulated by a cell-cell communication pathway.

Transcripts encoded by a homoeo box gene are restricted to dorsal tissues of Drosophila embryos.

In Drosophila elaboration of positional identity along the anterior-posterior and dorsal-ventral embryonic body axes involves early zygotic gene functions that are expressed in response to maternal cues present in the unfertilized egg. Zygotic loci that are required for the specification of positional identity along the anterior-posterior body axis have been described in detail. Less is known about the zygotic loci responsible for differentiation of the dorsal-ventral pattern; however, several genes that might be involved have been identified. Zerknüllt (zen) is an example of a zygotic gene required for correct differentiation of dorsally derived embryonic tissues. On the basis of homoeo box cross homology, we have now isolated a gene, called S60, that derives from the zen region of the Antennapedia complex (ANT-C). Transcripts encoded by S60 transiently accumulate in the dorsal-most tissues of developing embryos. This pattern of expression suggests that S60 corresponds to zen. Since S60 contains a homoeo box, it is possible that differentiation of the anterior-posterior and dorsal-ventral embryonic patterns involves similar molecular mechanisms.

Cross-regulatory interactions among pair-rule genes in Drosophila.

The pair-rule genes of Drosophila are required for the subdivision of the developing embryo into a repeating series of homologous body segments. One of the pair-rule genes, even-skipped (eve), appears to be particularly important for the overall segmentation pattern since eve- embryos lack all segmental subdivisions in the middle body region. On the basis of homeo box cross-homology we have isolated a gene, S72, which probably corresponds to eve. In embryo tissue sections S72 transcripts show a periodic distribution pattern. The eve- phenotype appears to involve altered patterns of fushi tarazu and engrailed expression. These and other findings suggest that pair-rule gene expression might involve hierarchical cross-regulatory interactions.

Homeo box gene expression in anterior and posterior regions of the Drosophila embryo.

The homeo box is a 180-base-pair coding sequence that has been implicated in the control of Drosophila development. A common feature of the nine previously reported homeo box genes is their involvement in the establishment of the segmentation pattern of the embryo. In this report we describe the isolation and properties of two additional homeo box genes, F90-2 and S67. Transcripts encoded by the two genes are detected in embryonic tissues that derive from regions near the anterior and posterior poles of the embryo, which are outside the limits of expression of known homeotic genes. These results suggest that at least some homeo box genes specify positional identity along the anterior-posterior body axis that is independent of the process of segmentation.

Different humidification systems for high-frequency jet ventilation.

This study examined the effect of several different high-frequency jet ventilation (HFJV) humidification techniques on tracheobronchial mucosa. Six groups (2 in each group) of mongrel dogs, chronically instrumented, were cared for in an intensive care-like setting for data acquisition. Four groups received HFJV with different humidification systems during 72 h of continuous ventilation. Two groups served as controls (conventional ventilation with and without humidity). Although there was significant damage to tracheal mucosa during ventilation without humidification, there were no significant pathologic differences in bronchial mucosa between humidified and nonhumidified groups. Several techniques of HFJV humidification produced no pathologic evidence of mucosal damage and could be clinically useful.