A new marker for mosaic analysis in Caenorhabditis elegans indicates a fusion between hyp6 and hyp7, two major components of the hypodermis

A fusion of the sur-5 protein to the green fluorescent protein containing a nuclear localization signal is demonstrated as a marker for genetic mosaic analysis in the nematode Caenorhabditis elegans. Because of an extensive accumulation of bright fluorescence in many nuclei, normal growth plates, each containing hundreds of worms, can be rapidly screened with a dissecting microscope for rare mosaic individuals. As the marker can also be used to detect transgenic worms, the construction of strains for mosaic analyses can be minimized. In the course of examining rare mosaic animals, an unexpected pattern of fluorescence was noticed for hyp6, a syncytial component of the hypodermis, which indicated that the marker may serve as a means of assessing cellular fusions during development. Immunofluorescent staining of adherens junctions confirmed a postembryonic fusion of hyp6 with hyp7, the major syncytium of the hypodermis.

Constitutive activation of opsin by mutation of methionine 257 on transmembrane helix 6

Rhodopsin is a member of the large family of G protein-coupled receptors (GPCR's). Constitutive activity of GPCR's, defined as ligand-independent signaling, has been recognized as an important feature of receptor function and has also been implicated in the molecular pathophysiology of a number of human diseases. Rhodopsin has evolved a unique mechanism to minimize receptor basal activity. The chromophore 11-cis-retinal, which acts as an inverse agonist in rhodopsin, is covalently bound to the receptor to ensure extremely low receptor signaling in the dark. In this study, we replaced Met257 in TM helix 6 of opsin with each of the remaining 19 amino acids. Only mutant opsin M257R failed to be expressed in COS-cell membranes. Each of the remaining 18 mutant opsins, with the exception of M257L, was significantly constitutively active. Two mutants in particular, M257Y and M257N, displayed very high levels of constitutive activity. In addition, the double-site mutants with substitutions of both Met257 and Glu113 in TM helix 3 tended to be much more constitutively active than the sums of the activities of the individual single-site mutants. Based on existing structural models of rhodopsin, we conclude that Met257 may form an important and specific interhelical interaction with a highly conserved NPXXY motif in TM helix 7, which stabilizes the inactive receptor conformation by preventing TM helix 6 movement in the absence of all-trans-retinal. Furthermore, we are able to show that the pharmacological properties of the large number (approximately 50) of mutant opsins that we have characterized to date support the two-state model of GPCR function. These results suggest that rhodopsin and other GPCR's share a common mechanism of receptor activation that involves specific changes in helix-helix interactions.

[Application of IHW2 purged bone marrow to autologous bone marrow transplantation in the treatment of acute myeloid leukemia]

OBJECTIVE

To observe the clinical effectiveness of IHW2 purged autologous bone marrow transplantation (ABMT) in the treatment of AML patients.

METHODS

Large volume of bone marrow was purged in vitro by IHW2 and then reinfused to patients for ABMT.

RESULTS

All of the three patients transplanted with IHW2 purged autologous bone marrow successfully reconstituted hemopoiesis. Two patients got continuous complete remission for 36+ and 34+ months, respectively. The karyotype of one of the two patient was 46,XY,del(16)(q22) before ABMT and changed to 46,XY in 2 months after transplantation. The third patient relapsed after ABMT 19 months.

CONCLUSION

The preliminary study suggests that IHW2 may have certain purging effect on leukemic cells and is safe for clinical application.

Homology-directed repair is a major double-strand break repair pathway in mammalian cells

Mammalian cells have been presumed to repair potentially lethal chromosomal double-strand breaks (DSBs) in large part by processes that do not require homology to the break site. This contrasts with Saccharomyces cerevisiae where the major DSB repair pathway is homologous recombination. Recently, it has been determined that DSBs in genomic DNA in mammalian cells can stimulate homologous recombination as much as 3 or 4 orders of magnitude, suggesting that homology-directed repair may play an important role in the repair of chromosomal breaks. To determine whether mammalian cells use recombinational repair at a significant level, we have analyzed the spectrum of repair events at a defined chromosomal break by using direct physical analysis of repair products. When an endonuclease-generated DSB is introduced into one of two direct repeats, homologous repair is found to account for 30-50% of observed repair events. Both noncrossover and deletional homologous repair products are detected, at approximately a 1:3 ratio. These results demonstrate the importance of homologous recombination in the repair of DSBs in mammalian cells. In the remaining observed repair events, DSBs are repaired by nonhomologous processes. The nonhomologous repair events generally result in small deletions or insertions at the break site, although a small fraction of events result in larger chromosomal rearrangements. Interestingly, in two insertions, GT repeats were integrated at one of the broken chromosome ends, suggesting that DSB repair can contribute to the spread of microsatellite sequences in mammalian genomes.

[Study on the structures of poly (urea) urethane by FTIR and 1H NMR methods]

Using the FTIR and 1H NMR methods, the structures, relative ratio and inventory ratio of segmented poly (urea) urethanes which are synthesized with different extenders (1,4-butandiol, ethylene diamine and their mixtures)have been studied successfully and the ratationship between the branch ratio and inventory ratio has been determined.

The kinase suppressor of Ras (KSR) modulates growth factor and Ras signaling by uncoupling Elk-1 phosphorylation from MAP kinase activation

The Ras GTPase plays an essential role in many cellular signal transduction events. Activation of the mitogen activated protein (MAP) kinase is a primary consequence of Ras activation and plays a key role in mediating Ras signal transduction. A novel kinase, KSR, has recently been functionally isolated as a positive regulator of Ras signaling in Caenorhabditis elegans vulval induction and Drosophila photoreceptor differentiation. We have examined the effect of KSR on growth factor and Ras-induced MAP kinase signaling in mammalian cells. Surprisingly, we observed that KSR specifically blocks EGF and Ras-induced phosphorylation and activation of ternary complex factors (TCF), physiological substrates of MAP kinases, without affecting the activation of MAP kinase itself. A kinase-deficient mutant of KSR, KSR-RM, appears to function as a dominant interfering mutant which elevates phosphorylation of Elk-1, a member of the TCF family, and Elk-1-dependent transcription. The effect of KSR on Elk-1 was significantly decreased by inhibition of calcineurin, a putative Elk-1 phosphatase. These observations demonstrate that KSR is capable of uncoupling the MAP kinase activation from its target phosphorylation, and thus provide a novel mechanism for modulating the Ras-MAP kinase signaling pathway. This study provides the first evidence that signal output of MAP kinase cascades is subject to regulation at a level independent of MAP kinase activity.

Post-embryonic expression pattern of C. elegans let-60 ras reporter constructs

let-60 ras plays roles in the differentiation of several C. elegans tissues (Yochem, J., Sundaram, M., Han, M., 1997. Ras is required for a limited number of cell fates and not for general proliferation in Caenorhabditis elegans. Mol. Cell. Biol. 17, 2716-2722). To understand the transcriptional regulation of ras and to identify new functions for ras in development, we examined expression patterns of let-60::lacZ and let-60::GFP reporter constructs in C. elegans hermaphrodites. Fusion constructs were expressed in vulval precursor cells, sex myoblasts and in cell lineages of the somatic gonad, germline cells (GFP construct only), hypodermis, muscle and nervous system.

Role of the C9 methyl group in rhodopsin activation: characterization of mutant opsins with the artificial chromophore 11-cis-9-demethylretinal

Activation of the visual pigment rhodopsin involves both steric and electrostatic interactions between the chromophore and opsin within the retinal-binding site. Removal of the C9 methyl group of 11-cis-retinal inhibits light-dependent activation of the G protein, transducin, suggesting a direct steric contact. More recently, we have shown that steric interactions lead to receptor activation when Gly121 in the middle of transmembrane helix 3 is replaced by larger hydrophobic residues. In order to understand in more detail the role of the C9 methyl group of retinal in the structure and function of rhodopsin, we first studied the properties of recombinant 9-dm-Rho (opsin reconstituted with 11-cis-9-demethylretinal). The 9-dm-Rho pigment displayed a blue-shifted lambdamax, increased hydroxylamine reactivity, and decreased ability to activate transducin. These properties are consistent with the hypothesis that the C9 methyl group is a crucial structural anchor for the correct docking of the chromophore in its binding site. Next, we investigated the possible interaction between Gly121 of opsin and the C9 methyl group of retinal by characterizing recombinant pigments produced by combining mutant opsins (G121A, -V, -I, -L, and -W) with 11-cis-9-demethylretinal. Mutant opsins G121I, -L, and -W failed to bind the chromophore. However, the double mutant G121L/F261A bound 11-cis-9-demethylretinal to form a stable pigment with a lambdamax of 451 nm. When activity was assayed in membranes, the reduction in transducin activation by 9-dm-Rho caused by the lack of a C9 methyl group on the chromophore could be partially restored by replacing Gly121 with a bulky residue (leucine, isoleucine, or tryptophan). These results support a model of receptor activation that involves steric interaction between the C9 methyl group of the chromophore and the opsin in the vicinity of Gly121 on transmembrane helix 3.

The C9 methyl group of retinal interacts with glycine-121 in rhodopsin

The visual pigment rhodopsin is a prototypical G protein-coupled receptor. These receptors have seven transmembrane helices and are activated by specific receptor-ligand interactions. Rhodopsin is unusual in that its retinal prosthetic group serves as an antagonist in the dark in the 11-cis conformation but is rapidly converted to an agonist on photochemical cis to trans isomerization. Receptor-ligand interactions in rhodopsin were studied in the light and dark by regenerating site-directed opsin mutants with synthetic retinal analogues. A progressive decrease in light-dependent transducin activity was observed when a mutant opsin with a replacement of Gly121 was regenerated with 11-cis-retinal analogues bearing progressively larger R groups (methyl, ethyl, propyl) at the C9 position of the polyene chain. A progressive decrease in light activity was also observed as a function of increasing size of the residue at position 121 for both the 11-cis-9-ethyl- and the 11-cis-9-propylretinal pigments. In contrast, a striking increase of receptor activity in the dark-i.e., without chromophore isomerization-was observed when the molecular volume at either position 121 of opsin or C9 of retinal was increased. The ability of bulky replacements at either position to hinder ligand incorporation and to activate rhodopsin in the dark suggests a direct interaction between these two sites. A molecular model of the retinal-binding site of rhodopsin is proposed that illustrates the specific interaction between Gly121 and the C9 methyl group of 11-cis-retinal. Steric interactions in this region of rhodopsin are consistent with the proposal that movement of transmembrane helices 3 and 6 is concomitant with receptor activation.

Application of liposomes for development of oral vaccines: study of in vitro stability of liposomes and antibody response to antigen associated with liposomes after oral immunization

In order to evaluate the usefulness of liposomes as oral vaccines, the stability of liposomes and serum IgA antibody response to antigen associated with liposomes after oral administration were examined. Liposomes composed of dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylserine (DPPS), and cholesterol (Chol) (1:1:2, molar ratio), distearoylphosphatidylcholine (DSPC) and Chol (7:2, molar ratio), and DSPC, DPPS, and Chol (7:3:2 or 1:1:2, molar ratio) were stable in acidic solution (pH 2.0), bile, and pancreatin solution, whereas liposomes composed of DPPC and Chol (7:2, molar ratio) and DPPC, DPPS, and Chol (7:3:2, molar ratio) were unstable in pH 2.0 and/or bile solutions. After the oral immunization of antigen (ganglioside GM1)-containing liposomes composed of DPPC, DPPS, and Chol (1:1:2, molar ratio) to mice, the serum IgA antibody responses against ganglioside GM1 were found. Furthermore, when monophosphoryl lipid A was incorporated into liposomes containing ganglioside GM1, further augmentation of IgA responses to ganglioside GM1 was observed. On the other hand, the oral administration with liposomes composed of DPPC, Chol, and ganglioside GM1 (unstable liposomes), ganglioside GM1 mixed with liposomes composed of DPPC, DPPS and Chol, and ganglioside GM1 alone was unable to induce any detectable anti-ganglioside GM1 IgA antibody responses. These results suggest that liposomes which showed the stability to acidic solution, bile, and pancreatin solution would serve effectively as an oral delivery vehicle for inducing mucosal immune responses.

[Surgical treatment in pulmonary tuberculosis with sputum long-term Mycobacterium tuberculosis positive]

OBJECTIVE

To evaluate the importance of surgical treatment in pulmonary tuberculosis with sputum long-term Mycobacterium tuberculosis positive.

METHOD

Sixty-five patients with pulmonary tuberculosis who failed antituberculosis chemotherapy received lung resection or thoracoplasty.

RESULT

Sputum negative conversion was found in sixty-three patients without recurrence during 1-3 year follow-up, while sputum positive conversion was found only in one case during the period of follow-up. Among all the patients, one died of respiratory failure after the operation, three complicated with empyema and recovered from operating again.

CONCLUSION

Surgical operation is still important for treating pulmonary tuberculosis patients with sputum long-term Mycobacterium tuberculosis positive.

Properties of early photolysis intermediates of rhodopsin are affected by glycine 121 and phenylalanine 261

Glycine 121 in transmembrane (TM) helix 3 and phenylalanine 261 in TM helix 6 of bovine rhodopsin have been shown to be critical residues for creating an appropriate chromophore binding pocket for 11-cis-retinal [Han, M., Lin, S. W., Smith, S. O., and Sakmar, T. P. (1996) J. Biol. Chem. 271, 32330-32336; Han, M., Lin, S. W., Minkova, M., Smith, S. O., and Sakmar, T. P. (1996) J. Biol. Chem. 271, 32337-32342]. To further explore structure-function relationships in the vicinity of receptor helices 3 and 6, time-resolved absorption difference spectra of rhodopsin mutants G121A, G121V, and G121L/F261A were obtained at 20 degrees C. Data were collected from 30 ns to 690 ms after laser photolysis with 7 ns pulses (lambdamax = 477 nm) and analyzed using a global exponential fitting procedure after singular value decomposition (SVD). For each mutant, the decay of its bathorhodopsin photoproduct (batho) into an equilibrium with its blue-shifted intermediate (bsi) was too fast to resolve (<20 ns). The reaction scheme found for the mutants G121A and G121L/F261A was batho/bsi --> lumirhodopsin (lumi) --> metarhodopsin I (MI) --> metarhodopsin II (MII). For G121V, an additional early 380 nm absorber, with a back-reaction to lumi, had to be included in the above scheme. For the three Gly121 mutants, the main pathway to reach the active MII state is via lumi and MI. This is in contrast to rhodopsin where the main pathway in detergent samples is via lumi and an early 380 nm absorber, MI380. From the accelerated batho decay present in all three mutants, we conclude that Gly121 is likely to participate in the earliest chromophore-protein interactions. In addition, bsi decay is further accelerated in mutant G121L/F261A, suggesting that Phe261 is an essential determinant of the protein processes involved in bsi decay.

Partial agonist activity of 11-cis-retinal in rhodopsin mutants

Rhodopsin, the photoreceptor molecule of the vertebrate rod cell, is a G protein-coupled receptor. Rhodopsin consists of the opsin apoprotein and its 11-cis-retinal chromophore, which is covalently bound to a specific lysine residue by a stable protonated Schiff base linkage. Rhodopsin activation occurs when light causes photoisomerization of the 11-cis chromophore to its all-trans form. The all-trans chromophore is the receptor agonist. The 11-cis-retinylidene chromophore is analogous pharmacologically to a potent inverse agonist of the receptor. We report here that replacement of a highly conserved glycine residue (Gly121) causes 11-cis-retinal to become a pharmacologic partial agonist. Although the mutant apoproteins do not display constitutive activity, they are active in the dark when bound to an 11-cis-retinylidene chromophore, or to a "locked" chromophore analogue, Ret-7. The degree of partial agonism is directly related to the size of the amino acid replacement at position 121, and it can be reversed by a specific second-site replacement of Phe261. Thus, mutation of Gly121 in rhodopsin causes 11-cis-retinal to act as a partial agonist rather than an inverse agonist, allowing the mutant pigment to activate transducin in the dark.

[Relationship between human parvovirus B19 infection and spontaneous abortion]

OBJECTIVE

To determine whether there is a relationship between parvovirus B19 infection and spontaneous abortion.

METHODS

105 embryo tissues from spontaneous abortions of unknown cause during 1994-1995 were studied using nested polymerase chain reaction (PCR) assay for parvovirus B19 DNA. As controls 40 fetal tissues were also examined. Among which, 20 were collected from induced abortions, and the others were stillbirths. The positive specimens underwent further study for TORCH infections.

RESULTS

26 (24.5%) were B19 DNA positive in the case group and 2 (5.0%) in the control group. The difference was significant (P < 0.05). Among 26 positive specimens, 5 had cytomegalovirus (CMV) infection as well as 2 had both CMV and herpes simplex virus (RSV) infections.

CONCLUSIONS

Parvovirus B19 infection may be an important pathogen for spontaneous abortion, and it is suggested to investigate parvovirus B19 infection among pregnant women in China.

[Studies on expansion ex vivo of murine bone marrow cells and its hematopoietic reconstitution capacity]

OBJECTIVE

To investigate the effects of stem cell factor (SCF) in combination with interleukin-1 (IL-1) or/and interleukin-3 (IL-3) on ex vivo expansion of 5FU treated bone marrow cells and hematopoietic recovery in lethally irradiated mice transplanted with the expanded cells.

METHODS

5FU treated bone marrow cells (d3-5FU-BMC) were cultured in a cytokines-containing medium, and the net increments of CFU-GM and high proliferative potential colony forming cell (HPP-CFC) were evaluated.

RESULTS

CFU-GM increased by 33.7 +/- 18.1- or 18.1 +/- 6.3- fold, and HPP-CFC by 17.8 +/- 10.5- or 12.7 +/- 9.1- fold, respectively, in cultures containing SCF with IL- or IL-3, as compared with that in control; while SCF alone had little effect. Compared with fresh d3-5FU-BMC, transplantation of the expanded bone marrow cells accelerated the recovery of recipients' peripheral blood cell counts by 1 approximately 3 days and increased the survival rate of the transplanted animals (d3-5FU-BMC group 50% vs expansion group 8U approximately 100%).

CONCLUSION

SCF in combination with IL-1 or IL-3 synergetically ex vivo expands hematopoietic cells. Transplantation of the expanded bone marrow cells accelerates the recipient's hematopoietic reconstitution.

The steric trigger in rhodopsin activation

Rhodopsin is the seven transmembrane helix receptor responsible for dim light vision in vertebrate rod cells. The protein has structural homology with the other G protein-coupled receptors, which suggests that the tertiary structures and activation mechanisms are likely to be similar. However, rhodopsin is unique in several respects. The most striking is the fact that the receptor "ligand", 11-cis retinal, is covalently bound to the protein and is converted from an "antagonist" to an "agonist" upon absorption of light. NMR studies of rhodopsin and its primary photoproduct, bathorhodopsin, have generated structural constraints that enabled docking of the 11-cis and all-trans retinal chromophores into a low-resolution model of the protein proposed by Baldwin. These studies also suggest a mechanism for how retinal isomerization leads to rhodopsin activation. More recently, mutagenesis studies have extended these results by showing how the selectivity of the retinal-binding site can be modified to favor the all-trans over the 11-cis isomer. The structural constraints produced from these studies, when placed in the context of a high-resolution model of the protein, provide a coherent picture of the activation mechanism, which we show involves a direct steric interaction between the retinal chromophore and transmembrane helix 3 in the region of Gly121.

[Effects of IFN-alpha on the expressions of perforin and granzymes in IL-2 activated lymphocytes]

OBJECTIVE

To study the effect of IFN-alpha on the expressions of perforin and granzymes in IL-2-activated-lymphocytes.

METHODS

NK and LAK activities were assayed by 4 hour standard 51Cr release test, the activity of perforin was detected by hemolysis method, expression of granzyme B was measured by ABC immunohistological method, expression of granzyme A was measured by BLT method.

RESULTS

IFN-alpha significantly augmented the activities of NK and LAK in IL-2 activated peripheral blood lymphocytes (PBL) after 1 day culture. Perforin activity in lymphocytes was increased after 1 day exposure to IL-2 or IFN-alpha, and was enhanced when exposed to the combination of IL-2 and IFN-alpha. After 3 day culture, the perforin activity remained high in lymphocytes activated by IL-2 alone or in combination with IFN-alpha, while declined to control level in IFN-alpha exposed group. IL-2 and IFN-alpha alone or in combination had no effect on expression of granzyme A and B.

CONCLUSION

IFN-alpha enhances the cytotoxicity of lymphocytes activated by IL-2. The mechanism might be that IFN-alpha upregulates the perforin expression.

Ras is required for a limited number of cell fates and not for general proliferation in Caenorhabditis elegans

Experiments with mammalian tissue culture cells have implicated the small GTPase Ras in the control of cellular proliferation. Evidence is presented here that this is not the case for a living animal, the nematode Caenorhabditis elegans: proliferation late in embryogenesis and throughout the four larval stages is not noticeably affected in animals lacking Ras in various parts of their cell lineages. Instead, genetic mosaic analysis of the let-60 gene suggests that Ras is required only, at least later in development (a maternal effect cannot be excluded), for establishment of a few temporally and spatially distinct cell fates. Only one of these, the duct cell fate, appears to be essential for viability.

[An approach to the binocular vision of traumatic cataract after intraocular lens implantation]

OBJECTIVE

To explore the recovery of binocular vision and stereoacuity of monocular cataract extraction after posterior chamber intraocular lens (IOL) implantation.

METHODS

After extraction of traumatic cataract, primary or secondary posterior chamber IOL implantation was performed on 36 cases. The naked vision, corrected vision and binocular dioptric state were observed pre- and post-operatively. Synoptophore, Bogolini striated glasses, barred reading and Tiemus stereoscopic vision picture were applied.

RESULTS

The visual acuities of 36 cases were significantly improved postoperatively, the corrected visual acuities of 24 cases (66.7%) were over 4.95 and 30 cases were over 4.8 after three months. The binocular and stereoscopic vision of 21 cases was recovered well.

CONCLUSION

IOL implantation should be performed early after extraction of monocular cataract in order to improve the recovery and development of binocular vision and stereoacuity, particularly in children.

The natural history and treatment of adrenal myelolipoma

PURPOSE

We determined the natural history and clarified the treatment of adrenal myelolipoma.

MATERIALS AND METHODS

A retrospective review of medical records and radiographic imaging studies of 20 patients diagnosed with adrenal myelolipoma was performed.

RESULTS

Of 20 patients 4 presented with abdominal pain and 1 had Cushing's syndrome. The remaining tumors were discovered incidentally. Four patients underwent surgery because of abdominal pain in 2, adrenal hyperfunction (Cushing's syndrome) in 1 and a tumor 10.5 cm. in largest dimension in 1. Of 15 patients (16 adrenal myelolipomas) followed without surgical intervention for an average of 3.2 years (range 0.3 to 10.8) 13 remained asymptomatic and 2 experienced persistent, vague abdominal discomfort. One patient was lost to followup. A total of 13 tumors from 12 patients was serially imaged, with tumor size increasing in 6, decreasing in 2 and remaining unchanged in 5.

CONCLUSIONS

These data suggest that the majority of adrenal myelolipomas can be treated conservatively. While tumors can become enlarged, they also exhibit variable growth, and size and growth rate do not necessarily correlate with symptoms. Computerized tomography can be used for diagnosis.

[Effect of bone marrow transplantation conditioning regimen on thyroid and adrenocortical functions in patients with blood diseases]

OBJECTIVE

In order to investigate the life quality of patients with hematological diseases after bone marrow transplantation (BMT).

METHODS

Pituitary-thyroid and adrenocortical function were de tected in 29 patients with hematological diseases before and after BMT.

RESULTS

All patients had normal thyroid and adrenocortical functions before BMT. As compared with pre-BMT,the median serum TSH levels were significantly increased at 3, 6, 12 (P<0.01), 24-60 (P<0.05) months post-BMT. The adrenocortical function had no change in all patients, and thyroid dysfunction were found in 6 of 24 patients detected at a median time of 6 month post-BMT. Five of the 6 thyroid dysfuntion patients developed hypothyroidism, and one hyperthyroidism.

CONCLUSION

There was little effect of conditioning regimen on adrenocortical function, while thyroid dysfunction was common after BMT. Long term follow up on thyroid function in patients after BMT is necessary.