[Changes of femur minerals and serum BGP in hindlimb unloaded rats during convalescence]

Objective. To observe bone mass changes during convalescence after simulated weightlessness. Method. 7-week-old rats were tail-suspended for 21 d then reloaded for 7 d and 21 d to recover, and measured serum BGP. Result. Tail suspension of rats for 21 d caused significant decrease of serum BGP and phosphorus as well as femur minerals. Serum BGP and femur minerals were still lower than control levels, but serum contents of calcium, phosphorus and magnesium increased significantly after reloading for 7 d. Femur minerals and serum BGP, calcium, phosphorus and magnesium returned to control levels after reloading for 21 d. Conclusion. The deficit in femur mineral induced by hindlimb unloading in rats can be restored by return to normal weight bearing, BGP can be used to monitor the case of its recovery.

Discovery of High-Frequency Quasi-periodic Oscillations in the Black Hole Candidate XTE J1859+226

We report the discovery of quasi-periodic oscillations (QPOs) at roughly 187 and 150 Hz in the X-ray intensity of X-ray nova XTE J1859+226. The source was observed during a recent outburst with the Rossi X-Ray Timing Explorer. Besides these high-frequency QPOs, we have also detected QPOs (and sometimes their harmonics) at 6-7 Hz and significant broadband variability at low frequencies. These properties, as well as the observed hard X-ray spectrum, make XTE J1859+226 a black hole candidate (BHC). The detection of QPOs at two distinct frequencies greater, similar100 Hz in two observations separated by about 4 hr provide additional insights into the high-frequency QPO phenomenon in BHCs. The importance lies in the proposed interpretations, which invariably involve the effects of strong gravity near a black hole. We compare our results to those of other BHCs and discuss the impact of the observational data on the models in a global context.

2-amino-2-oxazolines as subtype selective alpha(2) adrenoceptor agonists

Cyclohexylamino oxazoline 1 (AGN 190837), an analogue of 2 (Bay a6781), is a potent alpha(2) adrenoceptor agonist. On the basis of a design generated by receptor-ligand modeling, a number of cyclohexyl and norbornyl analogues were synthesized wherein the propyl group of 1 was replaced by phenylalkyl subsituents. This resulted in compound 6 being an alpha(2c) selective agonist, as well as 7 and 9 being alpha(2a)/alpha(2c) selective.

On the Disappearance of Kilohertz Quasi-periodic Oscillations at a High Mass Accretion Rate in Low-Mass X-Ray Binaries

For all sources in which the phenomenon of kilohertz quasi-periodic oscillation (kHz QPO) is observed, the QPOs disappear abruptly when the inferred mass accretion rate exceeds a certain threshold. Although the threshold cannot at present be accurately determined (or even quantified) observationally, it is clearly higher for bright Z sources than for faint atoll sources. Here we propose that the observational manifestation of kHz QPOs requires direct interaction between the neutron star magnetosphere and the Keplerian accretion disk and that the cessation of kHz QPOs at a high accretion rate is due to the lack of such an interaction when the Keplerian disk terminates at the last stable orbit and yet the magnetosphere is pushed farther inward. The threshold is therefore dependent on the magnetic field strength-the stronger the magnetic field, the higher the threshold. This is certainly in agreement with the atoll/Z paradigm, but we argue that it is also generally true, even for individual sources within each (atoll or Z) category. For atoll sources, the kHz QPOs also seem to vanish at a low accretion rate. Perhaps the "disengagement" between the magnetosphere and the Keplerian disk also takes place under such circumstances because of, for instance, the presence of quasi-spherical advection-dominated accretion flow (ADAF) close to the neutron star. Unfortunately, in this case, the estimation of the accretion rate threshold would require a knowledge of the physical mechanisms that cause the disengagement. If the ADAF is responsible, the threshold is likely dependent on the magnetic field of the neutron star.

[Expressions of p21 and CD44v in human lung cancer and their significance.]

BACKGROUND

To investigate the clinical role of p21 and CD44v in primary lung cancer and their relationship with each other.

METHODS

p21 and CD44v expression in 29 frozen lung cancer and 10 corresponding non-cancer tissues were measured by flow cytometry (FCM) .

RESULTS

In lung cancer , the expression rates of p21 and CD44v were 75. 9 % and 51. 7 % respectively. The two proteins showed much higher FI values and positive rates in lung cancer than those in non-cancer tissues ( P < 0. 01) . p21 alteration was independent from tumor size ,lymph node metastasis , TNM stage , differentiated grade and histological type. CD44v expression in stage II+III(83. 3 %) was much higher than that in stage I(29. 4 %) ( P < 0. 01) . As compared with lung cancer without lymph node metastasis (33. 3 %) , primary lung cancer with lymph node metastasis showed significantly higher expression rate of CD44v (81. 8 %) ( P < 0. 05) . Coexpression of p21 and CD44v had a distinct statistic significance ( P < 0. 01) .

CONCLUSIONS

Abnormality of p21 and CD44v may be involved in the carcinogenesis and development of lung neoplasms in coordination. Immunopositivity of CD44v may suggest a potential of high risk for lymph node metastasis in lung cancer.

[Expression of telomerase activity in human lung cancer.]

BACKGROUND

To investigate the expression of telomerase activity in lung cancer tissue and the correlation with the oncogenesis , progression and metastasis of lung cancer.

METHODS

Telomerase activity in specimens obtained by fiberbrochoscopy from 29 patients with suspected lung cancer was detected by polymerase chain reaction-ELISA.

RESULTS

The telomerase activity was positive in 18 cases of primary lung cancer and the positive rate was 81. 81 %(18/ 22) . Two of other seven specimens were positive for telomerase activity. Twelve lung cancer cases with lymph node metastasis showed positive expression , whereas only 6 of 10 cases without lymph node metastasis showed positive expression.

CONCLUSIONS

Telomerase activity may be useful both as a diagnostic marker to detect the existence of lung cancer and as a potential of high risk for lymph node metastasis.

[CD45-gating for flow cytometric immunophenotyping of leukemia]

OBJECTIVE

To establish a reliable and rapid multiparameter flow cytometric approach for leukemia immunophenotyping.

METHODS

Leukemia blast cells which exhibit a character of low CD45 expression and low side scatter density are easily recognized by "CD45-SSC gating", we measured 46 patients and 3 normal persons of immunophenotyping by this gating method as well as traditional forwardscatter-side scatter (FSC-SSC) gating method.

RESULTS

5 of 46 immunophenotypic results from "FSC-SSC gating" showed false diagnosis, which were corrected by "CD45-SSC gating". Further, immunophenotypic mapping of 46 different acute leukemia were obtained by "CD45-SSC gating" and three-color staining, The expression of related antigen could be readily observed.

CONCLUSIONS

"CD45-SSC gating" is a reliable and easy method to subclassify leukemia. Three-color staining, which is able to analyze the expression among two related antigens, not only be helpful in leukemia diagnosis but also contribute to study the occurrence, development and prognosis of diseases.

Phase Lag and Coherence Function of X-Ray Emission from Black Hole Candidate XTE J1550-564

We report the results from measuring the phase lag and coherence function of X-ray emission from black hole candidate XTE J1550-564. These temporal X-ray properties have been recognized to be increasingly important in providing important diagnostics of the dynamics of accretion flows around black holes. For XTE J1550-564, we found significant hard lag-the X-ray variability in high-energy bands lags behind that in low-energy bands-associated both with broadband variability and quasi-periodic oscillation (QPO). However, the situation is more complicated for the QPO: while hard lag was measured for the first harmonic of the signal, the fundamental component showed significant soft lag. Such behavior is remarkably similar to what was observed of microquasar GRS 1915+105. The phase lag evolved during the initial rising phase of the 1998 outburst. The magnitude of both the soft and hard lags of the QPO increases with X-ray flux, while the Fourier spectrum of the broadband lag varies significantly in shape. The coherence function is relatively high and roughly constant at low frequencies and begins to drop almost right after the first harmonic of the QPO. It is near unity at the beginning and decreases rapidly during the rising phase. Also observed is that the more widely separated the two energy bands are, the less the coherence function between the two. It is interesting that the coherence function increases significantly at the frequencies of the QPO and its harmonics. We discuss the implications of the results on the models proposed for black hole candidates.

Glyoxal-guanine DNA adducts: detection, stability and formation in vivo from nitrosamines

The glyoxal-deoxyguanosine adduct (gG) is formed from alpha-nitrosamino aldehydes and dG in vitro and in vivo from nitrosamines carrying the 2-hydroxyethyl side-chain as well as from N-nitrosomorpholine. The structures of all of the diastereomeric forms of both the cis and trans isomers of the adduct have been investigated by ab initio calculations and with nuclear magnetic resonance spectroscopy at 500 MHz. The preferred orientation of the OH groups is trans, but at equilibrium a small amount of the cis isomer was observed. The pH-independent equilibrium constant for the hydrolysis of the gG adduct is K = 1.36 x 10(-4) mol/L, and its rate of formation at pH 7.3 is k = 5.3 min-1 mol-1. In acid (pH 2), the hydrolysis of the nucleosidic linkage is nearly twice as rapid as the hydrolysis of gG to glyoxal and dG. We used a gG analogue to explore a number of reductive methods for derivatization of the adduct, but all of the processes either gave low yields or product mixtures which rendered them impractical for derivatizing the adduct in DNA. A 32P-postlabelling method for detection of the pH-sensitive gG adduct has been developed, which permitted detection of the adduct in the liver DNA of male Wistar rats after administration of selected nitrosamines. The levels of adducts found were: N-nitrosodiethanolamine > 2-hydroxyethylmethynitrosamine > N-nitrosomorpholine > 2-hydroxyethyethylnitrosamine. In separate experiments, N-nitrosodiethanolamine gave greater adduct levels than its metabolite 2-hydroxy-N-nitrosomorpholine. Mechanistic pathways for the generation of gG adducts in vitro and in vivo are discussed.

Three-layered atmospheric structure in accretion disks around stellar-mass black holes

Modeling of the x-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40 reveals a three-layered atmospheric structure in the inner region of their accretion disks. Above the cold and optically thick disk with a temperature of 0.2 to 0.5 kiloelectron volts, there is a warm layer with a temperature of 1.0 to 1.5 kiloelectron volts and an optical depth around 10. Sometimes there is also a much hotter, optically thin corona above the warm layer, with a temperature of 100 kiloelectron volts or higher and an optical depth around unity. The structural similarity between the accretion disks and the solar atmosphere suggests that similar physical processes may be operating in these different systems.

[Effects of tea on aberrant crypt foci and colorectal tumors in rats]

The present study was designed to investigate the chemopreventive effects of green tea and tea pigments (the main component of black tea) on 1,2-dimethylhydrazine (DMH)-induced rat colorectal carcinogenesis. Compared with the positive control group, green tea and tea pigments groups had less numbers of aberrant crypt foci (ACF) (P < 0.01) at the end of week 16. At the end of week 32, all rats in the positive control group developed colorectal tumors with an average of 2.6 tumors per rat, and a mean volume of 294.7 mm3 per tumor, while in the groups drinking green tea and tea pigments, the average numbers of colorectal tumors per rat were only 47.1% and 43.1% of controls respectively, and the mean tumor volume was inhibited by 77.1% and 68.1% respectively. It was concluded that tea pigments had a chemopreventive effect on colorectal tumor and ACF formation can be used as a useful intermediate end point to study chemopreventive effects on colorectal cancer.

[Establishment and biological characteristics of a novel erythroleukemia cell line (HIE1)]

OBJECTIVE

To establish a novel leukemia cell line and characterize its biological characteristics.

METHOD

The cell line was established by liquid cell culture. The genetic marker was analyzed by R-banding and reverse transcriptase-polymerase chain reaction (RT-PCR), cell morphology by microscopy, electron microscopy and histochemical staining, cell surface antigen by monoclonal antibody, hemoglobin by hyperomethemoglobin measurement and electrophoresis, erythroid differentiation by benzidine-staining, and monocyte-macrophage differentiation by cell morphology and phagocytosis.

RESULTS

A novel erythroleukemia cell line (HIE1), with original cell genetic marker (Ph chromosome, bcr/abl fusion gene rearrangement), was established from a CML patient in blast crisis, and has been passaged for over 60 generations. Myelomonocyte marker and hemoglycoprotein A were found on the cell surface. HIE1 cells contained hemoglobin, the same HbA and HbA(2) bands as in normal individuals were displayed by Hb electrophoresis. The benzidine positive HIE1 cells were induced after exposure to 3.6 x 10(-4) mmol/L Ara-C. When HIE1 cells were treated with 100 ng/ml PMA for 3 days, one third of the cells became spindle in shape, and 6.5% of the cells exert phagocytosis. The cells were classified into two types with Wright-staining: one showing light blue cytoplasm and a few of cells with basophilic granules, the other showing dark blue cytoplasm with vacuoles and pseudopods without granules. In addition, POX, SB, CE stains were negative, and AE, PAS, ACP stains positive. Colony formation of the cells was 37%, the cell doubling time was 22 - 24 hrs, and EB virus detection was positive.

CONCLUSION

A novel erythroleukemia cell line with bcr/abl fusion gene and characteristics of myelomonocytic and erythroid cells was established.

Presenilin-1 forms complexes with the cadherin/catenin cell-cell adhesion system and is recruited to intercellular and synaptic contacts

In MDCK cells, presenilin-1 (PS1) accumulates at intercellular contacts where it colocalizes with components of the cadherin-based adherens junctions. PS1 fragments form complexes with E-cadherin, beta-catenin, and alpha-catenin, all components of adherens junctions. In confluent MDCK cells, PS1 forms complexes with cell surface E-cadherin; disruption of Ca(2+)-dependent cell-cell contacts reduces surface PS1 and the levels of PS1-E-cadherin complexes. PS1 overexpression in human kidney cells enhances cell-cell adhesion. Together, these data show that PS1 incorporates into the cadherin/catenin adhesion system and regulates cell-cell adhesion. PS1 concentrates at intercellular contacts in epithelial tissue; in brain, it forms complexes with both E- and N-cadherin and concentrates at synaptic adhesions. That PS1 is a constituent of the cadherin/catenin complex makes that complex a potential target for PS1 FAD mutations.

Shape-selective recognition of a model Okazaki fragment by geometrically-constrained bis-distamycins

Okazaki fragments represent interesting targets for the design of anticancer drugs because of their selective occurrence during DNA replication, a process often elevated in aggressive malignancies. Structural studies have indicated a bend occurs in the helical axis at the junction region (JR) that joins the DNA duplex region (DDR) and the RNA-DNA hybrid duplex region (HDR) of model Okazaki fragments. To identify a structural motif that provides a shape complementary to the Okazaki fragment minor groove, we have investigated the binding of geometrically-constrained bis-distamycins to a model Okazaki fragment, [OKA], with a sequence derived from the genome of simian virus 40 (SV40). Both the JR and the DDR of [OKA] contain consecutive A/T base pairs that could accommodate distamycin binding. Of the six bis-distamycins selected for analysis, the two with a para configuration of the distamycins on the benzene or pyridine scaffold bound [OKA] tightly (Kd approximately 10(-6) M from gel-shift assays; Kd approximately 10(-8) M from deltaT(M)) while the four with a meta orientation did not bind. The two mono-distamycins studied also did not bind [OKA]. Molecular modeling of the complex between the para bis-distamycin MT-9 and [OKA] revealed MT-9 adopted an S- shape complementary to the minor groove of the model Okazaki fragment.

[Preventive effect of vitamin K1 and calcium on osteoporosis in ovariectomized rat]

Ovariectomized female Wistar rats[(170 +/- 15) g] were treated with vitamin K1 or/and calcium for 6 months, in order to study the effect of vitamin K or/and calcium supplementation on the prevention of osteoporosis. Vitamin K1(90 mg/kg) or/and calcium(5 g/kg) were added to a semisynthetic basal diet (VK 50 micrograms/kg, Ca5 g/kg). The findings of the study were as follows: Vitamin K1 treatment led to a significant increase of bone mineral density of the femoral diaphysis and lumbar spine, and bone ash content of the proximal one third of the femur shaft. The results suggested that vitamin K1 could, to some extent, prevent the fast bone loss and the femoral fragility induced by ovariectomy. Regarding the parameters of bone metrology and biomechanics, the effect of vitamin K1 combined with calcium on the prevention of osteoporosis is better than that of vitamin K1 or calcium alone, and the treatments with VK and Ca had better effects on femur than lumbar spine. The present study indicates that for postmenopausal women, as a risk population of osteoporosis, to increase their dietary intake of vitamin K and calcium might be helpful.

[Changes of blood circulation, muscle and skeletal systems in 30 d tail-suspended [correction of tail-suspented] rats]

OBJECTIVE

To confirm the tail-suspended rat model for the study of countermeasures against weightlessness.

METHOD

The changes of blood circulation, muscle and skeletal systems in control group rats (n = 15) and 30 d tail-suspended rats (n = 15) were compared.

RESULT

Compared with the control group, the hemorrheology and erythrocyte deformability decreased significantly, muscle-fiber atrophy, muscle contraction function decreased, the type I muscle fibers transformed to the type II muscle fibers, bone-mineral content of L3 and load capacity of femur declined, bone metabolism changed in the suspended rats.

CONCLUSION

The tail-suspended rat is a suitable animal model for the study of countermeasures against weightlessness.

Novel method for isolation of adult porcine pancreatic islets with two-stage digestion procedure

It is particularly difficult to isolate porcine islets (PI). Experience suggests that the success rate of porcine islet isolation (PII) is probably considerably influenced by the distension and digestion of the pancreas. In this study, we divided the digestion procedure into two stages and developed a new enzyme solution to improve both the distension and digestion procedures. As a result, we established a novel and stable method of large-scale adult porcine islet isolation (APII). The harvested pancreata of 2-year-old pigs weighing over 200 kg (n = 18) were distended by introducing our new enzyme solution gently and slowly through the pancreatic ducts. Two-stage digestion (cold, then warm) was then performed by first placing the distended pancreata on ice for 2 h to cause diffusion of the enzyme solution around the islets, and then by incubating the pancreata in a water bath at 37 degrees C for 45 min without shaking. The islets were purified by a COBE 2991 cell processor on dextran T70 discontinuous density gradients. Histological study was performed on porcine pancreata sampled after 0, 15, 30, and 45 min of the second stage, and stained with H&E stain. Next, islet equivalent was calculated. Static incubation study was performed by stimulating the islets with 3.3 and 16.7 mM glucose in Krebs' Ringer bicarbonate buffer (KRBB) solution at 37 degrees C for 1 h, and finally the insulin released was measured. The dilated acinar cells septa around the islets were observed at time 0. Destruction of the acinar cells around the islets by warm digestion was recognized at 15 and 30 min, and destroyed and separated acinar cells present around the islets at 45 min. During the entire course of the warm digestion, the islets remained intact. The number of isolated islets was 291,667 +/- 240,452 IEQ/pancreas (n = 14) and 3,294 +/- 2199 IEQ/g of pancreatic tissue. The purity of recovered porcine islets was over 90%. The concentration of the insulin secreted by 10,000 IEQ islets selected at random was 83.9 +/- 13.4 microU/dish/h in response to 3.3 mM glucose and 104.1 +/- 12.9 microU/dish/h in response to 16.7 mM glucose (n = 20). A success rate of approximately 80% was attained with APII. We demonstrated that this increase in the success rate was due to the improved distension and digestion provided by this method. This two-stage APII method with its new enzyme solution may facilitate the future use of porcine islets in clinical xenotransplantation trials.

[The Raman spectra of rubidium titanyl arsenate]

The Raman spectra of rubidium titanyl arsenate (RTA) single crystal with different geometric arrangements were obtained and compared with those of rubidium titanyl phosphate (RTP), potassium titanyl arsenate (KTA) and potassium titanyl phosphate (KTP) single crystals. The assignments of various vibration modes were made according to the experimental results. The strong Raman scattering intensity implies that RTA crystal possesses large nonlinear optical property and the strongest scattering is from the TiO6 octahedron. From the mode splitting of AsO4 tetrahedron, we conclude that the distortion of AsO4 in RTA is larger than that of PO4 in KTP.

No metal cofactor in orotidine 5'-monophosphate decarboxylase

Orotidine 5'-monophosphate decarboxylase (OMP decarboxylase, ODCase) is an important enzyme that catalyzes the final step of de novo pyrimidine nucleotide biosynthesis. The mechanism of this unique enzyme and whether metal ions play any role in catalysis have been topics of intense research interest. In this report, the role of Zn in ODCase was reexamined. Atomic absorption (AA) and X-ray absorption (XAS) spectroscopic studies did not detect zinc in active enzyme samples at high concentration. The XAS results also indicated the absence of other transition metal ions in ODCase.

Cisplatin-induced activation of mitogen-activated protein kinases in ovarian carcinoma cells: inhibition of extracellular signal-regulated kinase activity increases sensitivity to cisplatin

Cisplatin treatment activates multiple signal transduction pathways, which can lead to several cellular responses including cell cycle arrest, DNA repair, survival, or apoptosis. We investigated the response of the mitogen-activated protein kinases, extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun-N-terminal kinase 1 (JNK1), and p38, to cisplatin treatment in the ovarian carcinoma cell line SK-OV-3. Cisplatin caused a late and prolonged induction in a dose-dependent manner of both ERK1/2 and JNK1 activity. ERK1/2 and JNK1 activities continued to increase in magnitude up to 24 h following initiation of cisplatin treatment. In contrast, cisplatin treatment had no effect on p38 activity. Transplatin failed to induce either ERK1/2 or JNK1 at 24 h, which suggests that the activation of these kinases was dependent on cisplatin-specific DNA damage. Treatment with cycloheximide resulted in inhibition of cisplatin-induced ERK1/2 activation, demonstrating that ERK1/2 activity induced by cisplatin was dependent on de novo protein synthesis. Furthermore, inhibition of cisplatin-induced ERK1/2 activity by PD 98059 caused enhanced cisplatin cytotoxicity. Similar enhanced cytotoxic effects of cisplatin were also observed following treatment with PD 98059 in the ovarian carcinoma cell line UCI 101. These observations indicate that ERK1/2 activation induced by cisplatin partially protects cells from cisplatin cytotoxicity. Continued investigation into the mechanism by which the ERK pathway and other signal transduction pathways modulate the response to cisplatin may be helpful in the development of new strategies for improving the therapeutic use of platinum drugs.

[Serum levels of soluble intercellular adhesion molecule 1 in malignant lymphoproliferative disorders]

OBJECTIVE

To investigate the correlation of serum levels of soluble intercellular adhesion molecule 1 (sICAM-1) with clinical situation and treatment outcome in lymphoproliferative disorders.

METHODS

Serum sICAM-1 levels were measured by immunoenzymatic assay.

RESULTS

Pre-treatment serum sICAM-1 levels were above normal in 41% (9/22) of multiple myeloma (MM), 53% (17/32) of non-Hodgkin's lymphoma (NHL) and 63% (12/19) of acute lymphocytic leukemia (ALL) patients. Serum sICAM-1 levels in MM were positively correlated with Bataille stages, but were not related to Durie stage. Meanwhile, sICAM-1 levels in NHL were associated with the category of pathology, Ann Arbor stage and B symptom, but were not related to serum LDH levels. sICAM-1 levels were significantly higher in ALL patients complicated with central nervous system leukemia (CNSL) than in those without CNSL. Patients with elevated serum sICAM-1 levels had poorer treatment outcomes. Serum sICAM-1 levels were returned to normal at remission.

CONCLUSION

Measurement of serum sICAM-1 levels in lymphoproliferative disorders patients is helpful for judging the clinical status and treatment outcome.

Nitroreductase-mediated cell ablation is very rapid and mediated by a p53-independent apoptotic pathway

Nitroreductase (NTR)-mediated selective cell ablation using the prodrug CB1954 has been achieved in vivo by targeting the nitroreductase gene to the luminal cells of the mammary gland in transgenic mice. We report that the cell ablation occurs very rapidly, starting as early as 7 h after administration of the prodrug. By cross-breeding the BLG-NTR transgenic mice to a p53-deficient mouse strain, we have generated BLG-NTR transgenic mice on a p53 null background and tested NTR-mediated cell ablation in these mice. The transgenic mice lacking a functional p53 gene showed cell ablation at a similar level compared with p53 wild-type transgenic mice, showing that functional p53 is not required for CB1954-NTR mediated cell death. These results provide further support for using this system in anti-cancer therapy.

A novel follicle-cell-dependent dominant female sterile allele, StarKojak, alters receptor tyrosine kinase signaling in Drosophila

We describe a new dominant allele, StarKojak, that alters receptor tyrosine kinase signaling in the follicle cells and in the eyes in Drosophila. We isolated StarKojak in a screen for follicle-cell-dependent dominant female sterile mutations. We show that StarKojak and revertants of StarKojak do not complement Star loss-of-function mutations. We propose that StarKojak is a novel type of allele of Star that has both dominant gain-of-function phenotypes early in development and dominant loss-of-function phenotypes later in development. Star encodes a putative transmembrane protein that has previously been shown to be a critical component of the epidermal growth factor receptor tyrosine kinase signaling pathway. Early in oogenesis, Star mRNA expression is higher in StarKojak egg chambers than in wild-type egg chambers, consistent with its gain-of-function phenotype. Later in oogenesis, Star mRNA expression is lower in StarKojak follicle cells than in wild-type follicle cells, consistent with its loss-of-function phenotype. By genetically analyzing StarKojak and its revertants, we present evidence that Star is involved in anterior-posterior axis formation both in the female germline cells and in the somatic follicle cells. We also demonstrate that at least part of the dominant female sterile phenotype of StarKojak is restricted to the posterior-pole follicle cells. We propose that Star functions by processing pro-Gurken to mature Gurken, which is thereby released in the region between the oocyte and the follicle cells and binds to the epidermal growth factor receptor in the follicle cells.