Coordinated morphogenesis of epithelia during development of the Caenorhabditis elegans uterine-vulval connection

Development of the nematode egg-laying system requires the formation of a connection between the uterine lumen and the developing vulval lumen, thus allowing a passage for eggs and sperm. This relatively simple process serves as a model for certain aspects of organogenesis. Such a connection demands that cells in both tissues become specialized to participate in the connection, and that the specialized cells are brought in register. A single cell, the anchor cell, acts to induce and to organize specialization of the epidermal and uterine epithelia, and registrates these tissues. The inductions act via evolutionarily conserved intercellular signaling pathways. The anchor cell induces the vulva from ventral epithelial cells via the LIN-3 growth factor and LET-23 transmembrane tyrosine kinase. It then induces surrounding uterine intermediate precursors via the receptor LIN-12, a founding member of the Notch family of receptors. Both signaling pathways are used multiple times during development of Caenorhabditis elegans. The outcome of the signaling is context-dependent. Both inductions are reciprocated. After the anchor cell has induced the vulva, it stretches toward the induced vulval cells. After the anchor cell has induced specialized uterine intermediate precursor cells, it fuses with a subset of their progeny.     

Functional studies with a full-length P-glycoprotein cDNA encoded by the hamster pgp1 gene

Hamster cells grown in culture may, like human and mouse cells, develop multidrug resistance (MDR) when exposed to certain cytotoxic chemotherapeutic agents. Several phenotypic features that are characteristic of MDR have been described; these include (1) resistance to many structurally and functionally unrelated drugs that have different cellular targets and modes of action; (2) reversal of MDR by certain agents, including verapamil and cyclosporin A; and (3) reduced intracellular drug accumulation relative to that of drug-sensitive cells. In this report we show that the introduction and overexpression of the hamster pgp1 cDNA confers to otherwise drug-sensitive cells an MDR phenotype with these features. Moreover, pgp1 transfectants showed varying degrees of resistance to anthracycline analogues, indicating that structural analogues of commonly used anticancer agents are capable of circumventing drug resistance conferred by pgp.     

Haemostasis after partial hepatectomy using argon beam coagulation

The argon beam coagulator is a new device for haemostasis during and after surgery on parenchymatous organs. No data are available on its efficacy and tissue effect following hepatic resection. Blood loss, the time needed to achieve adequate haemostasis and histological findings after liver resection were assessed in 12 pigs using argon beam coagulation or suture ligation only, the mattress suture technique and tissue glue application. The treatment was randomly assigned to each of the four liver lobes in each pig. Median blood loss following argon beam coagulation was 13 (range 2-47) ml and after simple suture ligation 55 (range 2-260) ml (P < 0.02). The median time needed for adequate haemostasis following argon beam coagulation was 3 (range 2-7) min versus 14 (range 2-48) min in the control group (P < 0.005). There was no difference between argon beam coagulation and tissue glue, which were both superior to the use of mattress sutures. Argon beam coagulation resulted in less tissue damage than tissue glue or mattress suturing. The argon beam coagulator is an efficient device for achieving haemostasis following partial hepatectomy in the pig. It causes only a moderate tissue reaction.     

Accounting for the variation in collision kerma-to-terma ratio in polyenergetic photon beam convolution

In photon beam convolution, the distribution of energy deposition about a primary photon interaction site due to charged particles set in motion at that site is represented by the primary kernel. Energy deposited due to scattered photons, bremsstrahlung, and annihilation photons is represented by the scatter kernel. As the energy deposited in each kernel voxel is normalized to the energy imparted at the interaction site, it is known as a fractional energy distribution. In terma-based convolution, where kernels are normalized to total energy imparted at the interaction site and are convolved with the terma in the dose calculation process, the sum of fractional energies contained in the primary kernel is equal to the ratio of collision kerma (Kc) to terma (T) corresponding to the energy spectrum used to generate the kernel. Since the ratio of collision kerma to terma increases with depth as the beam hardens, the integral fractional energy in a primary kernel formed for the spectrum at the surface is less than the ratio Kc/T at depth. This causes primary dose to be increasingly underestimated with depth and scatter dose to be increasingly overestimated. Single polyenergetic convolution (using polyenergetic primary and scatter kernels formed using a polyenergetic primary photon spectrum) is thus not as rigorous as if a separate convolution is performed for each energy component. The ratio of true primary dose to single polyenergetic primary dose increases almost linearly with depth and is almost equal to the Kc/T ratio. Primary and scatter dose are calculated correctly if a single polyenergetic convolution is performed in terms of Kc (for primary) and T-Kc (for scatter), where the kernels are weighted sums of monoenergetic kernels normalized to Kc and T-Kc. With this method, it is ensured that total primary energy deposited due to primary photon interactions in a unit mass at a point is equal to Kc at that point.