Functional comparison of the three isoforms of the Na+/Ca2+ exchanger (NCX1, NCX2, NCX3)

Three distinct mammalian Na+/Ca2+ exchangers have been cloned: NCX1, NCX2, and NCX3. We have undertaken a detailed functional comparison of these three exchangers. Each exchanger was stably expressed at high levels in the plasma membranes of BHK cells. Na+/Ca2+ exchange activity was assessed using three different complementary techniques: Na+ gradient-dependent 45Ca2+ uptake into intact cells, Na+ gradient-dependent 45Ca2+ uptake into membrane vesicles isolated from the transfected cells, and exchange currents measured using giant patches of excised cell membrane. Apparent affinities for the transported ions Na+ and Ca2+ were markedly similar for the three exchangers at both membrane surfaces. Likewise, generally similar responses to changes in pH, chymotrypsin treatment, and application of various inhibitors were obtained. Depletion of cellular ATP inhibited NCX1 and NCX2 but did not affect the activity of NCX3. Exchange activities of NCX1 and NCX3 were modestly increased by agents that activate protein kinases A and C. All exchangers were regulated by intracellular Ca2+. NCX1-induced exchange currents were especially large in excised patches and, like the native myocardial exchanger, were stimulated by ATP. Results may be influenced by our choice of expression system and specific splice variants, but, overall, the three exchangers appear to have very similar properties.

[Changes of carbohydrate metabolism in normal pregnancy and its relationship with placental lactogen concentrations]

OBJECTIVE

To observe the changes of glucose metabolism and its relationship with human placental lactogen (HPL) in normal pregnant women.

METHOD

94 normal pregnant women had their serum HPL concentration tested and had undergone a 75 g oral glucose tolerance tests (OGTT). Both serum insulin and glucose levels at different time intervals were determined, and the areas under curve (IAUC, GAUC) were caculated, also insulin resistance (IAI) was evaluated.

RESULTS

GAUC, IAUC, IAI and HPL are all significantly increased with advance of gestation (P < 0.05). Multiple correlation coefficient study demonstrated that HPL is significantly positively correlated with GAUC, IAUC and IAI(P < 0.001). But when IAUC and IAI were controlled, the relationship between HPL and GAUC was not found.

CONCLUSION

There are hyperinsulinemia and insulin resistance during pregnancy, and they are related to HPL. HPL is one of the factors that contributing to carbohydrate metabolism changes during pregnancy.

Ribulose-1,5-bisphosphate carboxylase/oxygenase activase deficiency delays senescence of ribulose-1,5-bisphosphate carboxylase/oxygenase but progressively impairs its catalysis during tobacco leaf development

Transgenic tobacco (Nicotiana tabacum L. cv W38) plants with an antisense gene directed against the mRNA of ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) activase grew more slowly than wild-type plants in a CO2-enriched atmosphere, but eventually attained the same height and number of leaves. Compared with the wild type, the anti-activase plants had reduced CO2 assimilation rates, normal contents of chlorophyll and soluble leaf protein, and much higher Rubisco contents, particularly in older leaves. Activase deficiency greatly delayed the usual developmental decline in Rubisco content seen in wild-type leaves. This effect was much less obvious in another transgenic tobacco with an antisense gene directed against chloroplast-located glyceraldehyde-3-phosphate dehydrogenase, which also had reduced photosynthetic rates and delayed development. Although Rubisco carbamylation was reduced in the anti-activase plants, the reduction was not sufficient to explain the reduced photosynthetic rate of older anti-activase leaves. Instead, up to a 10-fold reduction in the catalytic turnover rate of carbamylated Rubisco in vivo appeared to be the main cause. Slower catalytic turnover by carbamylated Rubisco was particularly obvious in high-CO2-grown leaves but was also detectable in air-grown leaves. Rubisco activity measured immediately after rapid extraction of anti-activase leaves was not much less than that predicted from its degree of carbamylation, ruling out slow release of an inhibitor from carbamylated sites as a major cause of the phenomenon. Nor could substrate scarcity or product inhibition account for the impairment. We conclude that activase must have a role in vivo, direct or indirect, in promoting the activity of carbamylated Rubisco in addition to its role in promoting carbamylation.

Signal model of noise in open-loop fiber-optic gyros

The characteristics of noise in fiber-optic gyros are analyzed quantitatively. Based on its physical characteristics and on autocorrelation function evidence, the noise is modeled as the addition of fractal Brownian motion (FBM) and Gaussian white noise (GWN). The value of self-similarlity parameter H in FBM and the intensity of GWN, sigma(w), in the model are robustly determined with an algorithm based on an orthonormal wavelet transform, which demonstrates well the coexistence of the long- and short-term correlation components of the gyro noise. Moreover, it is revealed that FBM dominates the gyro noise, whereas the GWN is minor.

Studies of the catabolic pathway of degradation of nitrobenzene by Pseudomonas pseudoalcaligenes JS45: removal of the amino group from 2-aminomuconic semialdehyde

Pseudomonas pseudoalcaligenes JS45 utilizes nitrobenzene as the sole source of nitrogen, carbon, and energy. Previous studies have shown that degradation of nitrobenzene involves the reduction of nitrobenzene to nitrosobenzene and hydroxylaminobenzene, followed by rearrangement to 2-aminophenol, which then undergoes meta ring cleavage to 2-aminomuconic semialdehyde. In the present paper, we report the enzymatic reactions responsible for the release of ammonia after ring cleavage. 2-Aminomuconic semialdehyde was oxidized to 2-aminomuconate in the presence of NAD by enzymes in crude extracts. 2-Aminomuconate was subsequently deaminated stoichiometrically to 4-oxalocrotonic acid. No cofactors are required for the deamination. Two enzymes, 2-aminomuconic semialdehyde dehydrogenase and a novel 2-aminomuconate deaminase, distinguished by partial purification of the crude extracts, catalyzed the two reactions. 4-Oxalocrotonic acid was further degraded to pyruvate and acetaldehyde. The key enzyme, 2-aminomuconate deaminase, catalyzed the hydrolytic deamination that released ammonia, which served as the nitrogen source for growth of the organism.

[Fermentation conditions of engineering strain utilizing starch for production of alkaline proteinase]

The highest activity of alkaline proteinase produced by Bacillus pumilus c172(pBX 96) transformant was 9,000 U/ml in shaking flask where corn meal and bean cake meal were carbon and nitrogen sources, respectively. The enzyme activity was raised under the conditions of initial pH 7.0, MgCl2 instead of MgSO4, and glucose (0.1%) in the substrate. The fermentation of c172(pBx 96) transformant was carried out with parameters of pH, reducing sugar, total sugar and enzyme activity.

Induction of tolerance to intrathecal butorphanol in rats

BACKGROUND

Butorphanol, an opioid agonist/antagonist, has been administered spinally and epidurally in humans for moderate to severe pain. However, unlike intrathecal (i.t.) morphine, virtually no information is available regarding butorphanol's ability to induce analgesic tolerance at the spinal cord level upon chronic i.t. administration.

METHODS

Continuous infusion of i.t. butorphanol was given via an osmotic minipump. Rats were randomly assigned to four groups (n = 7 each) to receive i.t. infusion (1 microliter/h) consisting of saline, or butorphanol (13, 26, or 52 nmol/h) for 96 h. Tail-flick (TF) latencies were measured during the period of i.t. infusion.

RESULTS

A dose-dependent antinociceptive effect, as measured by TF latency, was demonstrated in the groups receiving i.t. butorphanol as compared to the saline group. The overall antinociceptive effects calculated from the areas under the curve (AUC's) were 372 +/- 3.0, 394 +/- 7.5, and 433 +/- 20 for the 13, 26, and 52 nmol/h butorphanol-infused groups, respectively; the AUC's of the 26 and 52 nmol/h groups were significantly different from the AUC of 356 +/- 3.4 for the saline-infused group (p < 0.01, one way ANOVA; p < 0.05, post hoc Dunnett's test). The TF latencies of the 26 and 52 nmol/h groups were 3.77 +/- 0.05 and 3.73 +/- 0.03 s at the baseline (before the i.t. infusion), respectively; and gradually increased significantly (p < 0.01, two way repeated measure ANOVA; p < 0.05, post hoc Student-Newman-Keuls or SNK test) to the peak values of 4.31 +/- 0.14 and 4.90 +/- 0.28 s, respectively; then decreased significantly from the peaks (p < 0.05, post hoc SNK test) to the final values of 3.87 +/- 0.06 and 4.10 +/- 0.13 s at the end of the 96-h infusion, respectively. The TF values of the saline and the 13 nmol/h groups did not show statistically significant differences throughout the 96-h infusion period.

CONCLUSIONS

Therefore, continuous infusion of i.t. butorphanol at the rate of 26 and 52 nmol/h induced tolerance to tail-flick analgesia within 96 h.

[Tailed normal chromatographic peak expressed by plate model]

An equation for describing tailed normal chromatographic peak is derived based on the plate model. In terms of the de Moivre-Laplace theorem, which states that a binomial distribution can be approximated by the Gaussian distribution for large sample size, it is suggested that the concentration distribution along the distance downstream from the inlet of chromatographic column conforms to the Gaussian distribution function, but the concentration distribution with elution volume (or elution time) does not. The equation developed here, which is similar to the Gaussian distribution function, indicates that the normal chromatographic elution curve should be a tailing one. It is also shown that the symmetric Gaussian elution curve is an approximate solution of the plate model and can be obtained by the approximation of the equation here. The equation is proved to be congruent to the results of the diffusion model. Thus, the plate model and diffusion model are equivalent to each other in describing chromatographic process although different mechanism is based on.

[Cytological study of subretinal fluid]

OBJECTIVES

To determine the cellular components of subretinal fluid and the origin of cells participating in the proliferation in the membranous tissue of proliferative vitreoretinopathy (PVR).

METHODS

35 subretinal fluid samples were studied by cytology using autofluorescent and immunohistochemical assays.

RESULTS

There were a large quantity of retinal pigment epithelium (RPE) and small quantity of pigment epithelial cells originated from epithelial cells of ciliary body and iris, there were also various quantities of neuroretinal cells and macrophages. Neither T-lymphocytes nor B-lymphocytes were found in this group of samples.

CONCLUSIONS

RPE, pigment epithelial cells, neuroretinal cells and macrophages are in subretinal fluid and may participate in the formation and development of PVR in various degrees.

Vanadate activates membranous nonreceptor protein tyrosine kinase in rat adipocytes

The insulin-like effects of vanadate are independent of the insulin receptor and insulin receptor substrate 1 (IRS-1) phosphorylation. A cytosolic protein tyrosine kinase (CytPTK), sensitive to inhibition by nanomolar concentrations of staurosporine (concentration at which 50% inhibition occurs [IC50], 1-2 nmol/l), has been implicated in some (i.e., glucose oxidation, lipogenesis) but not all (i.e., hexose uptake, inhibition of lipolysis) of the insulin-like effects of vanadate. We report here the existence of another nonreceptor protein tyrosine kinase in rat adipocytes, located exclusively in the plasma membranes (MembPTK), which we suggest is associated with hexose uptake and the antilipolytic activity of vanadate. MembPTK is a nonglycoprotein with an estimated molecular weight of 55-60 kDa. In a cell-free experiment, vanadate activates MembPTK seven- to ninefold (median effective dose, 17 +/- 2 micromol/l). Vanadate-activated MembPTK is inhibited by staurosporine (IC50, 60 +/- 5 nmol/l). In intact adipocytes, staurosporine antagonized vanadate-induced hexose uptake (IC50, 6.0 +/- 0.3 micromol/l) and significantly reversed the antilipolytic effect of vanadate (IC50, 5.0 +/- 0.4 micromol/l). After vanadate treatment, a phosphorylated P55 protein is immunoprecipitated by antibodies to both phosphotyrosine and phosphatidylinositol (PI) 3-kinase. In conclusion, rat adipocytes contain an additional vanadate-activatable nonreceptor membranous protein tyrosine kinase that may participate in the effects of vanadate not carried out by CytPTK. We also suggest that after treatment with vanadate, MembPTK is activated by autophosphorylation and interacts with PI 3-kinase. This may explain how vanadate activates PI 3-kinase without involving receptor activation and IRS-1 phosphorylation.

[Genetic divergence of Cordyceps sinensis as estimated by random amplified polymorphic DNA analysis]

Random amplified polymorphic DNA(RAPD) has been used in analyzing 13 winter worm, summer grasses (Cordyceps sinensis [Berk.], Sacc.) from 5 areas in Qingzang plateau. For 19 arbitrary primers, each individual showed about 65 RAPD markers. The genetic distances among those 13 winter worm, summer grasses were correlated to their geographic distances. Molecular phylogenetic tree constructed by UPGMA and NJ suggested that 13 winter worm, summer grasses could be divided into 3 clusters: east cluster, north cluster and middle cluster, in consistence with their origins and genetic divergence among different clusters. Furthermore, our results implied that the RAPD markers of winter worm, summer grasses showed a geographic specificity and could be a better genetic marker in studying genetic diversity and phylogeny of winter worm, summer grasses.

[Effects of low concentration carbon monoxide on human physiological function]

Human volunteers were exposed to various low concentrations of carbon monoxide (CO) in a closed cabin. The results showed that 35 mg/m3 of CO caused slight subjective symptoms and reduction in contrast vision, operating efficiency and T-wave of ECG. At 80 mg/m3 and 115 mg/m3 the above changes were more severe and a rise in hearing threshold level was observed. It demonstrated that an inhibitory effect on the CNS and heart were caused by low concentrations of CO. According to the absorption curves for human exposed to CO, it is suggested that the sense effect level and vision effect level for CO are 7% COHb, and the hearing effect level is 9% COHb.

[Study on the contact allergen in 720 patients with dermatitis and eczema]

In order to investigate the causative factors of dermatitis and eczema, patch test was performed using the GB7804-87 standard allergens in 720 patients with dermatitis and eczema. There were 376 patients reacted to one or more allergens. The total positive reaction rate was 52.2%. Positive reactions were most frequently with cobaltsulphate (118 cases, 16.4%), potassium dichromate (115 cases, 16.0%), nickelchloride (108 cases, 15.0%) mercuric chloride (106 cases, 14.7%), Beihai detergent powder (63 cases, 8.8%), and p-phenylene diamine (50 cases, 6.9%). The positive rate was above 1% in 18 allergens. This study shows that the standard screening allergens are valuable in the investigation of the aetiology of the dermatitis and eczema.

Neuropilin-2, a novel member of the neuropilin family, is a high affinity receptor for the semaphorins Sema E and Sema IV but not Sema III

Semaphorins are a large family of secreted and transmembrane proteins, several of which are implicated in repulsive axon guidance. Neuropilin (neuropilin-1) was recently identified as a receptor for Collapsin-1/Semaphorin III/D (Sema III). We report the identification of a related protein, neuropilin-2, whose mRNA is expressed by developing neurons in a pattern largely, though not completely, nonoverlapping with that of neuropilin-1. Unlike neuropilin-1, which binds with high affinity to the three structurally related semaphorins Sema III, Sema E, and Sema IV, neuropilin-2 shows high affinity binding only to Sema E and Sema IV, not Sema III. These results identify neuropilins as a family of receptors (or components of receptors) for at least one semaphorin subfamily. They also suggest that the specificity of action of different members of this subfamily may be determined by the complement of neuropilins expressed by responsive cells.

Neuropilin is a receptor for the axonal chemorepellent Semaphorin III

Extending axons in the developing nervous system are guided to their targets through the coordinate actions of attractive and repulsive guidance cues. The semaphorin family of guidance cues comprises several members that can function as diffusible axonal chemorepellents. To begin to elucidate the mechanisms that mediate the repulsive actions of Collapsin-1/Semaphorin III/D (Sema III), we searched for Sema III-binding proteins in embryonic rat sensory neurons by expression cloning. We report that Sema III binds with high affinity to the transmembrane protein neuropilin, and that antibodies to neuropilin block the ability of Sema III to repel sensory axons and to induce collapse of their growth cones. These results provide evidence that neuropilin is a receptor or a component of a receptor complex that mediates the effects of Sema III on these axons.

Cytokines and costimulatory molecules as genetic adjuvants

DNA vectors expressing an antigen derived from a pathogen or a cancerous cell have been shown, after inoculation into experimental animals, to trigger de novo synthesis of foreign proteins, which induce an immune response. This immune response can be modulated by coinoculation of vectors encoding either cytokines or costimulatory molecules. A variety of cytokines such as granulocyte/macrophage colony-stimulating factor (GM-CSF), IL-2, IL-4, IL-12 and IFN-gamma, as well as the costimulatory molecule B7.1, have been tested to date for their ability to amplify the immune response to genetic vaccines. Although the results obtained thus far clearly show that coadministration of vectors expressing immunomodulatory molecules, such as cytokines, may increase the efficacy of genetic vaccines, this approach is currently considered unsuitable for use in human patients due to the potential side effects of persistent cytokine expression.

[Microsatellite instability in nephroblastoma and its relationship to clinicopathological variables]

OBJECTIVE

To study the relationship between microsatellite instability (MSI) and clinicopathological variables in nephroblastoma.

METHODS

2 microsatellite repeat sequences AR (chromosome X), UT762(chromosome 21) were examined in normal and tumor pairs from 50 nephroblastoma patients by PCR and denatured polyacrylamide gel electrophoresis.

RESULTS

The MSI positive for AR and UT loci were 14/50 and 10/50 respectively in nephroblastoma. MSI positive for both AR and UT occurred in 2 cases. According to NTWS-III categorization, stage I & II belong to early stage and stage III & IV belong to late stage, the MSI for this series were 16/38 and 6/12 for early and late stages. According to the NWTI-II categorization, the MSI of this series for favorable and non-favorable histology were 71% and 33% respectively.

CONCLUSIONS

Analysis of MSI may have some significance in discriminating the malignant status of nephroblastoma.

Role of protein-protein interactions in the function of replication protein A (RPA): RPA modulates the activity of DNA polymerase alpha by multiple mechanisms

Replication Protein A (RPA) from human cells is a stable complex of 70-, 32-, and 14-kDa subunits that is required for multiple processes in DNA metabolism. RPA binds with high affinity to single-stranded DNA and interacts with multiple proteins, including proteins required for the initiation of SV40 DNA replication, DNA polymerase alpha and SV40 large T antigen. We have used a series of mutant derivatives of RPA to map the regions of RPA required for specific protein-protein interactions and have examined the roles of these interactions in DNA replication. T antigen, DNA polymerase alpha and the activation domain of VP16 all have overlapping sites of interaction in the N-terminal half (residues 1-327) of the 70-kDa subunit of RPA. In addition, the interaction site for DNA polymerase alpha is composed of two functionally distinct regions, one (residues 1- approximately 170) which stimulates polymerase activity and a second (residues approximately 170-327) which increases polymerase processivity. In the latter, both the direct protein-protein interaction and ssDNA-binding activities of RPA were needed for RPA to modulate polymerase processivity. We also found that SV40 T antigen inhibited the ability of RPA to increase processivity of DNA polymerase alpha, suggesting that this activity of RPA may be important for elongation but not during the initiation of DNA replication. DNA polymerase alpha, but not T antigen also interacted with the 32- and/or 14-kDa subunits of RPA, but these interactions did not seem to effect polymerase activity.

The effect of interferon-gamma on genetic immunization

The effect of co-inoculation of a plasmid vector expressing the rabies virus glycoprotein and an additional vector encoding mouse interferon (IFN)-gamma on the development of an antigen specific B and T helper cell response was tested upon intramuscular inoculation of mice. The effect of IFN-gamma was dependent on the promoter driving expression of the viral antigen. The immune responses to antigen-expressing vector carrying a viral promoter such as the SV40 early promoter or the major histocompatibility (MHC) class I promoter were reduced in presence of IFN-gamma while the B and T helper cell response to a vector expressing the antigen under the control of the MHC class II promoter was not affected by this cytokine.

[A four-box multi-function testing system of pharmacology reaction]

The organism position matrix method, a new method of testing pharmacology reaction is proposed. On the basis of the method, we have developed a four-box multi-function testing system which can test the spontaneous activity, analgesic effect, and learning and memory ability of 1 to 4 mice in three dimensions respectively. Four quantitative parameters, the total distance, the movement intensity, the vertical number and the jumping number are put forward to describe the spontaneous activity. The starting time of continuous jumping and the jumping number are used to describe the analgesic effect. The time from the electrical shock to escape onto a safety platform and the number of the electrical shock are used to describe the learning and memory ability. The system has the characteristics of good repeatability, high efficiency, quantitative and automatic control.

Expression of an Epstein-Barr-virus receptor and Epstein-Barr-virus-dependent transformation of human nasopharyngeal epithelial cells

The human herpes virus Epstein-Barr (EBV) is clearly associated with African Burkitt's lymphoma and the undifferentiated form of nasopharyngeal carcinoma (NPC). EBV has been implicated in other types of lymphoma, as well as in some human breast cancers. However, its route of entry into epithelial cells is incompletely understood. We report here evidence that there is no gene alteration in the SCR 1 and 2 exons of EBVR/CR2 in human embryonic nasopharyngeal epithelial (HENE) cells and NPC cells and that SCR 1 and 2 mRNA could be detected in HENE cells, different differentiated NPC cell lines and well-differentiated NPC biopsies. None of 15 cases of poorly differentiated NPC cryosections has SCR 1 and 2 mRNA. We also provide evidence that transformation of HENE cells results from exposure to infectious EBV and that transformation is dependent on the presence of phorbol ester. These data suggest that expression of SCR 1 and 2 of EBVR/CR2 may be associated with replication of EBV and support the notion of direct infection and transformation of human nasopharyngeal epithelial cells destined to evolve into the carcinoma by EBV through EBVR/CR2.

[mRNA expression of metastasis-suppressor gene nm23 in carcinoma of buccal mucosa. II. Quantitative reverse transcription PCR amplification]

The nm23 gene is a conspicuous metastasis-suppressor gene. The authors detected both nm23-H1 and nm23-H2 mRNA levels in 47 tissues samples of patients with carcinoma of buccal mucosa (CBM) by quantitative reverse transcription PCR amplification. The results showed that expression levels of both nm23-H1 and nm23-H2 mRNA varied in normal buccal mucosa, leukoplakia, adjacent nontumorous mucosa, submandibular gland, CBM and lymph nodes with or without metastasis. The nm23-H1 mRNA expression levels in CBM with lymph nodes metastases were lower than those in CBM without metastases (P < 0.05), while no significance of nm23-H2 mRNA expression levels was found between CBM with and CBM without metastasis (P > 0.05). The results were comparative to those of Northern blotting of the same cases. The authors concluded that, as also in the study of Northern blotting, the expression of nm23-H1 mRNA significantly correlated inversely with lymph node metastasis in CBM, while the expression of nm23-H2 mRNA not. Q-RT-PCR was a useful method to detect the mRNA levels of nm23 gene in buccal carcinoma.

Isolation of human complexes proficient in nucleotide excision repair

More than 20 polypeptides are required for the process of nucleotide excision repair (NER) in both human and yeast cells. This pathway of excision repair has most often been viewed as an ordered multi-step process involving steps of damage recognition, incision/excision and finally repair DNA synthesis. Here we present evidence for the existence of a complex of human NER proteins pre-assembled in the absence of damaged DNA. This multi-protein complex was initially isolated from HeLa cell extracts by affinity chromatography on a matrix containing the damage recognition protein XPA. Subsequent co-immunoprecipitation and gel filtration experiments demonstrated that a significant portion of the human NER proteins was present in the form of a high molecular weight complex and that these complexes, or repairosomes, were capable of performing all steps of NER in vitro . Consistent with studies indicating that DNA polymerasesdeltaandstraightepsiloncan both function in NER, these two polymerases are found in these repairosome complexes.