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Biomedical subjects

J Song

Publications and source records attributed to J Song.

At least 289 records · Page 16Linked to original sources
PubMed1996

Indications of a common folding pattern for VDAC channels from all sources.

Previous research on the mitochondrial channel VDAC from the yeast S. cerevisiae had identified protein strands forming the wall of VDAC's aqueous pore. Here we report the results of analyzing the primary sequences of VDAC from various sources to see if the transmembrane folding pattern identified from this yeast is conserved for VDAC of different species. We analyzed the primary sequences of VDAC from higher plants, fungi, invertebrates, and vertebrates and found that all have a very similar "beta-pattern" profile with 12-15 peaks indicating potential sided beta strands that are candidates for protein strands forming the wall of the aqueous pore. All these VDAC sequences can be put into the 13 transmembrane strand folding pattern previously identified for yeast VDAC. These folding patterns agree with available experimental data: both electrophysiological and protease digestion data. Although the primary sequences of VDAC from very diverse organisms show low homology, sequence similarity in the proposed corresponding 13 transmembrane strands is substantial. Competing proposals utilizing 16 transmembrane beta strands are in conflict with electrophysiological experimental observations and violate the constraints on such strands, such as no charged amino acids facing the phospholipid membrane and sufficient number of residues to span the membrane.

Amino Acid Sequence↗
PubMed1996

Direct determination of iron in ferritin using the polarographic catalytic current.

A new method for the determination of iron in ferritin using the polarographic catalytic current has been developed. Iron is released in NaOH and triethanolamine (TEA) solution and subsequently determined based on the polarographic catalytic wave in the presence of bromate with the peak potential of -1.0 V (vs.SCE). The 2.5-derivative peak height of iron is linearly proportional to its concentration in the range of 8.0 x 10(-8)-1.0 x 10(-6) g/ml with a correlation coefficient of 0.9991. The method has been applied to the determination of iron in human fetal liver and horse-spleen ferritin and the recovery is 95-112%.

Journal Article↗
PubMed1996

PhhR, a divergently transcribed activator of the phenylalanine hydroxylase gene cluster of Pseudomonas aeruginosa.

Pseudomonas aeruginosa was recently found to possess a cluster of structural genes encoding phenylalanine hydroxylase (PhhA), carbinolamine dehydratase (PhhB), and aromatic aminotransferase (PhhC). We now report the presence, in the flanking upstream region, of a divergently transcribed gene (phhR) encoding an activator protein. Inactivation of phhR markedly reduced expression of the structural genes. PhhR belongs to the large prokaryote family of sigma 54 enhancer-binding proteins, and activation of the phh operon by PhhR in P. aeruginosa required rpoN. The closest homologues of PhhR are the TyrR proteins from Escherichia coli and Haemophilus influenzae. E. coli TyrR is an unusual member of the homologue family in that the transcriptional units regulated by tyrR are driven by sigma 70 promoters. P. aeruginosa phhR was able to replace E. coli tyrR as a repressor of the aroF-tyrA operon (but not as an activator of mtr) in the heterologous E. coli system. Two regions that resemble E. coli TyrR boxes were identified in the intervening region between phhR and phhA. We propose that one or both boxes may be the target of PhhR acting as an autogenous repressor at a sigma 70 promoter in one direction. In the other direction, one or both boxes may be the upstream activator sequence targeted by PhhR to facilitate expression of the phh operon from a sigma 54 promoter. The phh operon was strongly induced in fructose- or glucose-based minimal medium by L-phenylalanine. Inactivation of phhR in P. aeruginosa abolished ability to utilize either L-phenylalanine or L-tyrosine as a sole source of carbon for growth.

Amino Acid Sequence↗
PubMed1996

Malaria control and fever management in Henan Province, China, 1992.

Henan Province, which once had the highest malaria prevalence in China, had only 318 reported cases in 1992. Our purpose was to investigate this late 'consolidation phase' of malaria control in Henan with reference to malaria surveillance. We conducted a questionnaire survey of village doctors in Shang Shi Qiao Township during the transmission period of 1992. Of the 732 recorded fever cases, 16 were probable malaria cases by clinical and treatment response criteria, but only one received a full course of antimalarials. Of the 732 patients, 61% had fever every day, 37% went for treatment the first day, 52% waited 2-3 days and 10% waited longer. One hundred and twenty-eight patients took self-medication before seeing the doctor. Blood examination was carried out in 526 (71%) fever cases but only four were positive, all for Plasmodium vivax. Our findings highlight problems relating to patient behaviour and motivation of village doctors, malaria treatment, surveillance and microscopy, rural migration, economic development and malaria transmission. All need to be considered for reforming the malaria control strategy in Henan Province.

Adolescent↗
PubMed1996

Tracheoesophageal fistula in AIDS: stent versus primary repair.

Tracheoesophageal fistula arising secondary to Mycobacterium tuberculous infection in AIDS patients is extremely rare. We describe a case with a fistula lesion that initially failed to close using a four-drug antituberculosis regimen. The original lesion closed following placement of an esophageal stent. However, the stent migrated, causing an iatrogenic tracheoesophageal fistula that needed surgical repair. Tracheoesophageal fistula (TEF) is an uncommon clinical condition, most frequently arising as a sequelae to esophageal malignancy. Iatrogenic injury to the membraneous trachea secondary to cuffed endotracheal or tracheostomy tubes in the presence of an in-dwelling nasogastric tube and corrosive burns, accounts for most of the remainder of occurring fistulas. Infections such as candidiasis, syphilis, and tuberculosis are also known to cause this condition. We report stent migration with perforation and subsequent TEF formation in an HIV-positive patient who originally had stent placement for a tuberculous tracheoesophageal fistula.

AIDS-Related Opportunistic Infections↗
PubMed1996

Golgi dispersal during microtubule disruption: regeneration of Golgi stacks at peripheral endoplasmic reticulum exit sites.

Microtubule disruption has dramatic effects on the normal centrosomal localization of the Golgi complex, with Golgi elements remaining as competent functional units but undergoing a reversible "fragmentation" and dispersal throughout the cytoplasm. In this study we have analyzed this process using digital fluorescence image processing microscopy combined with biochemical and ultrastructural approaches. After microtubule depolymerization, Golgi membrane components were found to redistribute to a distinct number of peripheral sites that were not randomly distributed, but corresponded to sites of protein exit from the ER. Whereas Golgi enzymes redistributed gradually over several hours to these peripheral sites, ERGIC-53 (a protein which constitutively cycles between the ER and Golgi) redistributed rapidly (within 15 minutes) to these sites after first moving through the ER. Prior to this redistribution, Golgi enzyme processing of proteins exported from the ER was inhibited and only returned to normal levels after Golgi enzymes redistributed to peripheral ER exit sites where Golgi stacks were regenerated. Experiments examining the effects of microtubule disruption on the membrane pathways connecting the ER and Golgi suggested their potential role in the dispersal process. Whereas clustering of peripheral pre-Golgi elements into the centrosomal region failed to occur after microtubule disruption, Golgi-to-ER membrane recycling was only slightly inhibited. Moreover, conditions that impeded Golgi-to-ER recycling completely blocked Golgi fragmentation. Based on these findings we propose that a slow but constitutive flux of Golgi resident proteins through the same ER/Golgi cycling pathways as ERGIC-53 underlies Golgi Dispersal upon microtubule depolymerization. Both ERGIC-53 and Golgi proteins would accumulate at peripheral ER exit sites due to failure of membranes at these sites to cluster into the centrosomal region. Regeneration of Golgi stacks at these peripheral sites would re-establish secretory flow from the ER into the Golgi complex and result in Golgi dispersal.

Animals↗
PubMed1996

Sst2, a negative regulator of pheromone signaling in the yeast Saccharomyces cerevisiae: expression, localization, and genetic interaction and physical association with Gpa1 (the G-protein alpha subunit).

Sst2 is the prototype for the newly recognized RGS (for regulators of G-protein signaling) family. Cells lacking the pheromone-inducible SST2 gene product fail to resume growth after exposure to pheromone. Conversely, overproduction of Sst2 markedly enhanced the rate of recovery from pheromone-induced arrest in the long-term halo bioassay and detectably dampened signaling in a short-term assay of pheromone response (phosphorylation of Ste4, Gbeta subunit). When the GPA1 gene product (Galpha subunit) is absent, the pheromone response pathway is constitutively active and, consequently, growth ceases. Despite sustained induction of Sst2 (observed with specific anti-Sst2 antibodies), gpa1delta mutants remain growth arrested, indicating that the action of Sst2 requires the presence of Gpa1. The N-terminal domain (residues 3 to 307) of Sst2 (698 residues) has sequence similarity to the catalytic regions of bovine GTPase-activating protein and human neurofibromatosis tumor suppressor protein; segments in the C-terminal domain of Sst2 (between residues 417 and 685) are homologous to other RGS proteins. Both the N- and C-terminal domains were required for Sst2 function in vivo. Consistent with a role for Sst2 in binding to and affecting the activity of Gpa1, the majority of Sst2 was membrane associated and colocalized with Gpa1 at the plasma membrane, as judged by sucrose density gradient fractionation. Moreover, from cell extracts, Sst2 could be isolated in a complex with Gpa1 (expressed as a glutathione S-transferase fusion); this association withstood the detergent and salt conditions required for extraction of these proteins from cell membranes. Also, SST2+ cells expressing a GTPase-defective GPA1 mutant displayed an increased sensitivity to pheromone, whereas sst2 cells did not. These results demonstrate that Sst2 and Gpa1 interact physically and suggest that Sst2 is a direct negative regulator of Gpa1.

Amino Acid Sequence↗
PubMed1996

Estrogen regulates somatostatin receptor subtype 2 messenger ribonucleic acid expression in human breast cancer cells.

Somatostatin (SRIF) and its analogs exhibit antiproliferative effects that are mediated by SRIF receptors (sst) present in responsive normal and neoplastic tissue including breast cancer. However, information regarding regulation of sst gene expression in cancer cells and modulation of SRIF binding is limited. In the present study we have determined the pattern of sst subtype messenger RNA (mRNA) expression in human breast cancer cells. Furthermore, we investigated the effect of 17beta-Estradiol (E2) treatment on steady state levels of sst mRNA by solution hybridization/nuclease protection analysis and on SRIF binding to membranes of treated cells by receptor binding assay. sst2 mRNA was highly expressed in T47D, ZR75-1, and MDA MB231 cells. Transcripts for sst1 were also detected at very low levels in ZR75-1 cells, whereas sst5 mRNA was expressed at low levels in MCF-7 cells. No sst subtype was detected in MDA MB 435s cells. When the estrogen receptor (ER)(+) cell lines T47D and ZR75-1 were cultured in phenol red-free media plus CS-FCS, sst2 mRNA levels decreased by 60-80% compared with complete serum controls. Adding E2 restored sst2 mRNA levels to control in both cell lines. Moreover, the effect of E2 on sst2 gene expression in T47D and ZR75-1 cells was dose- and time-dependent. In contrast, neither culturing in phenol red-free media plus CS-FCS nor E2 influenced sst2 expression in the ER(-) cell line MDA MB231. E2-induced regulation of SRIF binding and sst2 mRNA expression occurred in a parallel manner in T47D cells but were dissociated in ZR75-1 cells. The pure antiestrogen ICI 182 780 inhibited E2-induced sst2 expression in both cell lines. The antiestrogen 4OH tamoxifen showed strong estrogen-like effects on sst2 mRNA expression in T47D cells, while acting as a potent antiestrogen in ZR75-1 cells. Thus, these data suggest that E2 regulates sst2 expression in human breast cancer cell lines through the ER. The human breast cancer cell lines provide a useful model to examine the molecular mechanisms involved in E2 regulation of sst2 expression.

Breast Neoplasms↗
PubMed1996

Foot type biomechanics. comparison of planus and rectus foot types.

The basic premise central to the diagnosis and treatment of most mechanogenic foot and ankle pathologies is that a given foot will display a characteristic function depending on the biomechanical alignment of the hindfoot and forefoot. However, the effects of foot type on an individual's ability to perform comfortable cadence locomotion have not been scientifically proven. Therefore, this study was conducted on 21 healthy, young subjects (10 subjects with planus foot type and 11 subjects with rectus foot type) to test whether different foot types yield distinguishable foot functions. New methods were developed to quantify biomechanical foot function during posture and comfortable cadence locomotion. The results of the study indicate that individuals with planus and rectus foot types show statistically significant differences in the biomechanical function of the foot.

Adult↗
PubMed1996

Tamoxifen (estrogen antagonist) inhibits voltage-gated calcium current and contractility in vascular smooth muscle from rats.

Tamoxifen (Tx) has been used in breast cancer treatment and prophylaxis because of its antiestrogenic activity; however, Tx may also have beneficial cardiovascular effects and other actions mediated by mechanisms other than estrogen receptors. Previous studies showing interactions of Tx with Ca+(+)-channel blockers suggested that Tx may affect Ca++ channels, an hypothesis that was investigated using whole cell patch clamp techniques in vascular smooth muscle cells (cell line A7r5 and freshly dissociated cells) and by determining effects on contractions of isolated blood vessels. Tx reduced current through L-type Ca+2 channels, with an ID50 of 2 x 10(-6) M when applied by cumulative addition to A7r5 cells. With acute application, 10(-6) M Tx significantly reduced L-type current in A7r5 cells within 2 min to 88% of control (vehicle, 0.1% ethanol) in A7r5 cells, 67% of control in aortic vascular smooth muscle cells, and 60% of control in tail artery vascular smooth muscle cells. Tx also decreased the rate of inactivation of L-type current. Inhibition of T-type current by Tx was less than for L-type current but was significant at 10(-5) M Tx. Treatment of tail artery rings with Tx (10(-5) M, 15 min; 10(-6) M, 4 hr) reduced K+-elicited contractions. Since therapeutic concentrations of Tx during treatment may exceed 10(-6) M, these effects of Tx on vascular smooth muscle Ca++ channels and vessel contractions may have a role in the efficacy and side-effects of Tx treatment.

Animals↗
PubMed1996

Very low density lipoprotein and oxidized very low density lipoprotein induce monocyte chemotactic protein 1 in rabbit aortic smooth muscle cells.

OBJECTIVE: To understand whether very low density lipoprotein (VLDL) and oxidatively modified very low density lipoprotein (OX-VLDL) can stimulate vascular smooth muscle cells (SMCs) to express high level of monocyte chemotactic protein (MCP-1) mRNA. METHODS: LDL and VLDL were isolated from normal blood donors by density gradient ultracentrifugation and oxidatively modified by adding CuCl2 and incubation at 37 degrees C for 24 hours. Rabbit aortic SMCs were cultured by a substrate-attached explant method, and their total RNA was extracted by guanidinium isothiocyanate method. The expression of MCP-1 mRNA in SMCs was examined by dot blotting analysis using a probe of gamma-22P-end-labeled 35-mer oligonucleotide. RESULTS: Dot blotting analysis showed that cultured SMCs can express MCP-1 mRNA and the level of MCP-1 mRNA was increased significantly in SMCs after 24-hour coculture with VLDL (6-fold) and OX-VLDL (20-fold). CONCLUSIONS: VLDL and OX-VLDL both can induce MCP-1 mRNA expression in cultured rabbit aortic SMCs and the latter is more effective than the former.

Animals↗
PubMed1996

[Anti-herpes simplex virus action of combined therapy with cyclocytidine and ganciclovir].

OBJECTIVE: The study was designed to investigate the combined effect of cyclocytidine (CC) and ganciclovir (GCV) on herpes simplex virus-1 (HSV-1) in cell culture. METHODS: The 50% inhibition concentrations of HSV-1 plaque formation (IC50) of CC, GCV alone and in combination were determined by the inhibitory test of plaque formation. The combined anti-HSV-1 effect of CC and GCV was evaluated by a graphic method and fractional inhibitory concentration (FIC) indexes. RESULTS: IC50 of CC and GCV was 0.19 and 0.1 micrograms/ml, respectively. The combination of CC with GCV produced significantly synergistic activity against HSV-1 in cell culture. FIC indexes were all below 0.75. The combined therapy of CC and GCV can also decrease and delay the emergence of drug-resistant variants. CONCLUSION: These results suggest that this combined therapy of CC and GCV may be a potentially effective means in the management of patients with HSV-1 ocular infection.

Ancitabine↗
PubMed1996

Calcium dependence of indolactam-mediated contractions in resistance vessels.

The protein kinase C activator, (-)-indolactam, has been shown to enhance reactivity of arterioles by a mechanism not requiring an increase in intracellular Ca++ (Ca++i). The aim of this study was to characterize the Ca++ requirement for indolactam-induced contraction of resistance vessels. Studies were performed in small mesenteric arteries (diameter, 260 +/- microm), using intact segments or after permeabilization with alpha-toxin (500 U/ml). Additional studies were preformed using isolated smooth muscle cells to allow electrophysiological assessment of the effect of indolactam on voltage-gated Ca++ entry. Intact and permeabilized vessel segments showed dose-dependent constriction to indolactam. Studies of Fura 2-loaded vessels and permeabilized segments maintained at low Ca++i, showed that the constriction occurred without an overt increase in Ca++i. That Ca++ was required was evident by near maximal relaxation after the removal of Ca++. Patch clamp studies indicated that indolactam potentiated voltage-gated Ca++ entry; however, nifedipine (0.5 microM) and La (0.2 or 1 mM) were relatively ineffective in reversing the contraction, indicating that voltage-gated Ca++ entry was not an absolute requirement. In intact vessel segments, the myosin light chain (MLC) kinase inhibitors, ML-7 and ML-9, reversed the indolactam contraction, suggesting the requirement of the MLC chain phosphorylation pathway. Furthermore, indolactam caused by a significant increase in MLC phosphorylation in permeabilized vessels, despite clamping of Ca++i at pCa 7.0. The data are consistent with the suggestion that the protein kinase C activator, indolactam, acts to modulate the Ca++ sensitivity of the smooth muscle contractile process such that higher than expected levels of MLC phosphorylation exist for a given level of Ca++i.

Animals↗
PubMed1996

The role of fibroblast growth factors in early Xenopus development.

In recent years we and others have been attempting to identify the molecular nature of the inducing signals in early Xenopus development. We have found that most members of the fibroblast growth factor (FGF) family are biologically active as mesoderm-inducing factors when applied to ectoderm from blastulae. In addition to this, they will support continued expression of the pan-mesodermal transcription factor Xbra in the mesoderm of gastrula stage embryos. We have studied the expression pattern of four types of FGF in early embryos. Two types (FGF-2 and FGF-9) are expressed maternally and are thus present at the time of natural mesoderm induction. The expression of two other types (FGF-3 and FGF-4) is activated in the newly formed mesoderm of the gastrula. If the activity of the FGF family is inhibited by overexpression of a dominant-negative FGF receptor, there is a reduction in mesoderm formation, there are abnormalities arising from an inhibition of normal gastrulation movements and there is a defect in formation of the posterior parts. We believe that the mesoderm formation and cell movement effects are attributable to loss of Xbra expression, and the posterior defects to lack of posterior HOX gene activity. Overexpression of eFGF gives rise to a posteriorized phenotype, in which posterior HOX genes are expressed in a more anterior position. We conclude that the FGF system has multiple functions in early development, including mesoderm formation, gastrulation movements and anteroposterior patterning.

Animals↗
PubMed1996

Field trials of combined use of two species of mermithid nematodes to control Anopheles and Culex breeding in China.

The field tests of combined use of Romanomermis yunanensis 2000-3000 larvae per sq m and Romanomermis sp 1000-2000 larvae per sq m in rice fields. Ponds and streams in four cities of China, resulted in 60.8-95.5% parasitism in Culex tritaeniorhynchus, Cx. quinquefasciatus, Anopheles sinensis and An. anthropophagus. This successful use of two species of Romanomermis together not only curb mosquito nuisance it also controls the major vectors of malaria, filariasis and encephalitis B in China.

Animals↗
PubMed1996

[Pharmacological action of siwei shaoyao decoction].

The Siwei Shaoyao Decoction possesses a marked effect on the alleviation of trigeminal neuralgia in rats caused by penicillin G potassium injection. As shown from the hot-plate test, it also has an obvious analgesic effect on mice. To some extent, the decoction has a significant anti-inflammatory effect on the acute edema in hind paws of rats and the effect is believed to be related to the reduction of capillary permeability.

Animals↗