Biomedical subjects

K Dong

Publications and source records attributed to K Dong.

At least 19 recordsLinked to original sources

PubMed2002

Novel sodium channel gene mutations in Blattella germanica reduce the sensitivity of expressed channels to deltamethrin.

Pyrethroid insecticides alter the normal gating of voltage-gated sodium channels in the nervous system. Three sodium channel mutations (E434K, C764R, L993F) were recently identified in pyrethroid resistant German cockroach populations. In this report, we show that the L993F mutation decreased sodium channel sensitivity to the pyrethroid, deltamethrin, by five-fold in Xenopus oocytes. In contrast, neither E434K nor C764R alone decreased channel sensitivity to deltamethrin. However, E434K or C764R combined with L993F reduced deltamethrin sensitivity by 100-fold. Furthermore, concomitant presence of all three mutations (KRF) reduced channel sensitivity to deltamethrin by 500-fold. None of the mutations significantly affected channel gating. However, sodium current amplitudes from the mutant sodium channel carrying either E434K or C764R alone were much reduced compared to those of the wild-type channel or the channel carrying the double or triple mutations (KF, RF and KRF). These results indicated that evolution of sodium channel insensitivity in the German cockroach is achieved by sequential selection of a primary mutation L993F and two secondary mutations E434K and C764R, and concomitant presence of all three mutations dramatically reduced sodium channel sensitivity to deltamethrin.

Animals↗

PubMed2001

Treatment with dehydroepiandrosterone sulfate increases NMDA receptors in hippocampus and cortex.

Our aim was to investigate if the memory-enhancing effects reported for dehydroepiandrosterone sulfate in rodents could be mediated through modulation of NMDA receptors. Using autoradiography we studied the effect of dehydroepiandrosterone sulfate, administered for 5 days (30 mg/kg, i.p. twice a day), on NMDA binding sites labelled with [3H]dizocilpine ([3H]MK801) in rat brain. Dehydroepiandrosterone sulfate treatment significantly increased the [3H]MK801 binding sites in hippocampal areas (field CA1, CA3, dentate gyrus lateral blade and medial blade) and in cortex layer IV as compared to the control group. These results demonstrate for the first time the ability of dehydroepiandrosterone sulfate to increase the number of NMDA binding sites in rat brain, an action that could be of interest for therapeutic application.

Animals↗

PubMed2001

An amino acid triplet in the NH2 terminus of rat ROMK1 determines interaction with SUR2B.

ATP-regulated (K(ATP)) channels are formed by an inward rectifier pore-forming subunit (Kir) and a sulfonylurea (glibenclamide)-binding protein, a member of the ATP binding cassette family (sulfonylurea receptor (SUR) or cystic fibrosis transmembrane conductance regulator). The latter is required to confer glibenclamide sensitivity to K(ATP) channels. In the mammalian kidney ROMK1-3 are components of K(ATP) channels that mediate K(+) secretion into urine. ROMK1 and ROMK3 splice variants share the core polypeptide of ROMK2 but also have distinct NH(2)-terminal extensions of 19 and 26 amino acids, respectively. The SUR2B is also expressed in rat kidney tubules and may combine with Kir.1 to form renal K(ATP) channels. Our previous studies showed that co-expression of ROMK2, but not ROMK1 or ROMK3, with rat SUR2B in oocytes generated glibenclamide-sensitive K(+) currents. These data suggest that the NH(2)-terminal extensions in both ROMK1 and ROMK3 block ROMK-SUR2B interaction. Seven amino acids in the NH(2)-terminal extensions of ROMK1 and ROMK3 are identical (amino acids 13-19 in ROMK1 and 20-26 in ROMK3) and may determine ROMK-SUR2B interaction. We constructed a series of hemagglutinin-tagged ROMK1 NH(2)-terminal deletion and substitution mutants and examined glibenclamide-sensitive K(+) currents in oocytes when co-expressed with SUR2B. These studies identified an amino acid triplet "IRA" within the conserved segment in the NH(2) terminus of ROMK1 and ROMK3 that blocks the ability of SUR2B to confer glibenclamide sensitivity to the expressed K(+) currents. The position of this triplet in the ROMK1 NH(2)-terminal extension is also important for the ROMK-SUR2B interactions. In vitro co-translation and immunoprecipitation studies with hemagglutinin-tagged ROMK mutants and SUR2B indicted that direct interaction between these two proteins is required for glibenclamide sensitivity of induced K(+) currents in oocytes. These results suggest that the IRA triplet in the NH(2)-terminal extensions of both ROMK1 and ROMK3 plays a key role in subunit assembly of the renal secretary K(ATP) channel.

ATP-Binding Cassette Transporters↗

PubMed2001

Alternative splicing of the BSC1 gene generates tissue-specific isoforms in the German cockroach.

Voltage-gated sodium channels are integral transmembrane proteins responsible for the rapidly-rising phase of action potentials in most excitable cells. In mammals, the functional diversity and wide distribution of sodium channel proteins in various tissues and cell types are achieved mainly by selective expression of many distinct sodium channel genes. In the model insect, Drosophila melanogaster, however, only one confirmed sodium channel gene, para, and one putative sodium channel gene, DSC1, are known. We cloned and sequenced a DSC1 ortholog, BSC1, from the German cockroach, Blattella germanica. We found that the BSC1 transcript was present in a wide range of tissues, including nerve cord, muscle, gut, fat body and ovary, whereas the para transcript was detected only in nerve cord and muscle. Moreover, different tissues contained distinct alternatively spliced variants of BSC1, and two muscle-specific spliced variants are predicted to encode truncated proteins with only the first two of the four homologous domains. Therefore, alternative splicing and expression of distinct splicing variants in functionally different tissues may be a major mechanism by which insects increase BSC1 channel diversity in neuronal and non-neuronal tissues.

Alternative Splicing↗

PubMed2000

Regulation of ROMK1 channels by protein-tyrosine kinase and -tyrosine phosphatase.

We have used the two-electrode voltage clamp technique and the patch clamp technique to investigate the regulation of ROMK1 channels by protein-tyrosine phosphatase (PTP) and protein-tyrosine kinase (PTK) in oocytes coexpressing ROMK1 and cSrc. Western blot analysis detected the presence of the endogenous PTP-1D isoform in the oocytes. Addition of phenylarsine oxide (PAO), an inhibitor of PTP, reversibly reduced K(+) current by 55% in oocytes coinjected with ROMK1 and cSrc. In contrast, PAO had no significant effect on K(+) current in oocytes injected with ROMK1 alone. Moreover, application of herbimycin A, an inhibitor of PTK, increased K(+) current by 120% and completely abolished the effect of PAO in oocytes coexpressing ROMK1 and cSrc. The effects of herbimycin A and PAO were absent in oocytes expressing the ROMK1 mutant R1Y337A in which the tyrosine residue at position 337 was mutated to alanine. However, addition of exogenous cSrc had no significant effect on the activity of ROMK1 channels in inside-out patches. Moreover, the effect of PAO was completely abolished by treatment of oocytes with 20% sucrose and 250 microg/ml concanavalin A, agents that inhibit the endocytosis of ROMK1 channels. Furthermore, the effect of herbimycin A is absent in the oocytes pretreated with either colchicine, an inhibitor of microtubules, or taxol, an agent that freezes microtubules. We conclude that PTP and PTK play an important role in regulating ROMK1 channels. Inhibiting PTP increases the internalization of ROMK1 channels, whereas blocking PTK stimulates the insertion of ROMK1 channels.

Alanine↗

PubMed2000

Novel point mutations in the German cockroach para sodium channel gene are associated with knockdown resistance (kdr) to pyrethroid insecticides.

Knockdown resistance (kdr) to pyrethroid insecticides has been attributed to point mutations in the para sodium channel gene in more than a half dozen insect pest species. In this study, we identified two novel para mutations in five highly resistant kdr-type German cockroach strains. The two mutations, from glutamic acid (E434) to lysine (K434) and from cysteine (C764) to arginine (R764), respectively, are located in the first intracellular linker connecting domains I and II. E434K is located near the beginning of the linker (closest to domain I), whereas C764R is found toward the end of the linker (closest to domain II). Two additional mutations from aspartic acid (D58) to glycine (G58), and from proline (P1880) to leucine (L1888), respectively, were found in one of the resistant strains. The four mutations coexist with the previously identified leucine to phenylalanine (L993F) kdr mutation in IIS6, and are present only in the highly resistant individuals of a given strain. These findings suggest that these mutations might be responsible for high levels of knockdown resistance toward pyrethroid insecticides in the German cockroach.

Amino Acid Sequence↗

PubMed2000

Rat homolog of sulfonylurea receptor 2B determines glibenclamide sensitivity of ROMK2 in Xenopus laevis oocyte.

Recent studies showed that coexpression of Kir6.1 or Kir6.2 with the sulfonylurea receptor (SUR1, SUR2A, or SUR2B) reconstituted an inwardly rectifying, ATP-sensitive K(+) channel that was inhibited by glibenclamide (2, 15-17). Here we report the isolation of a rat homolog of mouse SUR2B (denoted rSUR2B) from a rat kidney cDNA library. The rSUR2B sequence contains a 4,635-bp open reading frame that encodes a 1,545-amino acid polypeptide, showing 67% shared identity with SUR1 (a pancreatic beta-cell isoform) and 98% with both SUR2A (a brain isoform) and SUR2B (a vascular smooth muscle isoform). Consistent with the predicted structures of other members of the ATP-binding cassette (ABC) superfamily, the sequence of rSUR2B contains 17 putative membrane-spanning segments. Also, predicted Walker A and B consensus binding motifs, present in other ABC members, are conserved in the rSUR2B sequence. RT-PCR revealed that rSUR2B is widely expressed in various rat tissues including brain, colon, heart, kidney, liver, skeletal muscle, and spleen. The intrarenal distribution of the rSUR2B transcript was investigated using RT-PCR and Southern blot of microdissected tubules. The rSUR2B transcript was detected in proximal tubule, cortical thick ascending limb, distal collecting tubule, cortical collecting duct, and outer medullary collecting duct, but not medullary thick ascending limb. This distal distribution overlaps with that of ROMK. Coexpression of rSUR2B with ROMK2 cRNA (in 1:10 ratio) in Xenopus laevis oocytes resulted in whole cell Ba(2+)-sensitive K(+) currents that were inhibited by glibenclamide (50% inhibition with 0.2 mM glibenclamide). In contrast, rSUR2B did not confer significant glibenclamide sensitivity to oocytes coinjected with ROMK1 or ROMK3. The interaction between ROMK2 and rSUR2B was further studied by coimmunoprecipitation of in vitro translated rSUR2B and ROMK2. In agreement with the functional data, the rSUR2B protein was coimmunoprecipitated with ROMK2 in the ROMK2-rSUR2B cotranslated samples. Our data demonstrate that ROMK2, but not ROMK1 and ROMK3, can interact with rSUR2B to confer a sulfonylurea-sensitive K(+) channel, implicating SUR proteins in forming and regulating renal ATP-sensitive K(+) channels. The ROMK isoform specificity of glibenclamide effects suggests that the NH(2) terminus of the ROMK protein mediates rSUR2B-ROMK2 interactions.

ATP-Binding Cassette Transporters↗

PubMed2000

Retrograde axonal transport impairment of large- and medium-sized retinal ganglion cells in diabetic rat.

PURPOSE: Several abnormalities in visual pathway functions in diabetic humans and animals have been reported. We demonstrated retrograde axonal transport impairment in retinal ganglion cells of streptozotocin-diabetic rats. METHODS: Diabetes was induced in male Wistar albino rats by intraperitoneal injection of streptozotocin. Three months after the induction of diabetes, fluoro-gold was injected into the dorsal lateral geniculate nucleus. Percentages of fluoro-gold-labeled large-, medium- and small-sized retinal ganglion cells per total population were calculated in wholemount retinas of diabetic and control rats. The same sections were stained with cresyl violet and each retinal ganglion cell type evaluated by light microscopy. RESULTS: Although a quantitative decrease in the population of each retinal ganglion cell type was not observed, mean percentages of fluoro-gold-labeled large- and medium-sized retinal ganglion cells per total population were significantly decreased in diabetic rats compared with controls. CONCLUSIONS: Our results suggest that diabetes affects the retrograde axonal transport in large- and medium-sized retinal ganglion cells despite the absence of morphological changes in the perikaryon and decrease in total cell population. Diabetes-induced impairment of retrograde axonal transport in large- and medium-sized retinal ganglion cells precede optic nerve involvement. However, this may merely be a consequence of metabolic changes in diabetic states.

Animals↗

PubMed1998

Retrograde double-labeling study of retinal ganglion cells from the ipsilateral vLGN and SC in the albino rat.

Retinal ganglion cells with branches to the ipsilateral ventral lateral geniculate nucleus (vLGN) and superior colliculus (SC) were studied by retrograde fluorescent double-labeling. Double-labeled cells were found in the ventral temporal crescent of the retina, with a few ipsilaterally projecting single-labeled cells scattered in this area. Single-labeled vLGN-projecting cells were found predominantly in the ventral-temporal crescent and to a lesser extent in the temporal and dorsotemporal octant. SC-projecting cells were present predominantly in the ventral-temporal crescent and to a lesser extent in the ventral and ventronasal octant. Our best animal model had 2200 ipsilaterally labeled cells. There were 451 (20.5%) double-labeled vLGN and SC-projecting cells, 561 (25.5%) single-labeled vLGN-projecting cells, and 1186 (53.9%) single-labeled SC-projecting cells.

Animals↗

PubMed1998

Comparing treatment intensities of tactile-thermal application.

The purpose of this study was to investigate the relationships of four intensities of tactile-thermal application (TTA) to changes in duration of stage transition (DST) and performance on a newly designed scale of penetration and aspiration by groups of patients made dysphagic by stroke. Patients were randomly assigned to receive 150, 300, 450, or 600 trials of TTA during each of 2 weeks. Data on the time required to provide such treatment, the actual number of trials clinicians were able to provide, and on the influence of the four intensities are provided. No single intensity emerged as the most therapeutic. It is suggested that subsequent studies with larger groups include intensities between 300 and 550.

Aged↗

PubMed1998

Alternating triple therapy for the treatment of intermediate grade and immunoblastic lymphoma.

BACKGROUND: CHOP is currently considered the gold standard of treatment for intermediate grade lymphomas. We designed a new regimen known as 'ATT' (alternating triple therapy) which uses three non-cross resistant combinations in alternating sequence for nine cycles. MATERIALS AND METHODS: This is a phase II clinical trial with comparison to CHOP/CMED historical controls using prognostic factors. The tumor score system was used to evaluate the results of this trial. Two hundred sixty-eight eligible patients who had one or more of the following adverse features: bulky disease, elevated LDH or > 1 extranodal site were analyzed. Outcome measures consist of survival and failure free survival. RESULTS: At a median follow-up of 32 months, there was no statistically significant difference in survival for those with favorable prognostic factors (tumor score < or = 2). However, there was a statistically significant difference in favor of ATT for those with unfavorable tumor scores. When we examined the failure-free survival of those with unfavorable tumor scores, we again observed a superiority for the ATT regimen over CHOP/CMED but the opposite was true for those with favorable tumor scores. We also found a statistically significant difference in favor of the ATT regimen when compared with CHOP/CMED for patients < or = 60 years old with a tumor score > or = 3, while no advantage was found for those > 60 years. CONCLUSIONS: ATT appears more effective but only for patients < 60 years old with unfavorable tumor scores. In those older than 60 years with favorable tumor score, CHOP/CMED appears superior. ATT might be an adequate regimen for young patients with poor prognostic features while CHOP/CMED might be a better choice for those with good prognosis irrespective of age. For those > 60 years with unfavorable tumor scores neither ATT or CHOP/CMED were adequate treatment. Because of the phase II nature of this study, these conclusions should be considered as hypotheses which require prospective testing.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1998

Alterations in retrograde axonal transport in optic nerve of type I and type II diabetic rats.

Clinical and electrophysiological examinations have yielded visual pathway function abnormalities in both humans and animal models with diabetes mellitus (DM). However, subclinical involvement of the optic nerve has not yet been fully investigated. In this study, we demonstrated the different impairments in retrograde axonal transport occurring in selective retinal ganglion cells (RGCs) of Type I and II diabetic rats. Rats were injected with streptozotocin (STZ) to induce Type I DM. The Otsuka Long-Evans Tokushima Fatty (OLETF) rats represented the Type II DM group. The STZ-induced (Type I) diabetic rats had low body weights and significant elevations in blood glucose levels compared with the age-matched control rats. On the contrary, the OLETF rats (Type II) had high body weights and significant elevations in blood glucose concentrations compared with the age-matched controls. Fluoro-Gold (FG) was injected into the bilateral dorsal lateral geniculate nucleus. Accumulation of FG in large and medium type RGCs in STZ-induced diabetic rats was significantly decreased compared with the controls. However, the accumulation of FG in RGCs of OLETF rats did not show a significant decrease compared with the controls. Our findings suggest that, within the time frame of study, retrograde axonal transport impairment of large and medium type RGCs in the STZ-induced (Type I DM) diabetic rats was greater than in the OLETF (Type II DM) diabetic rats. Impairment of retrograde axonal transport in Type I diabetes may precede or be a consequence of metabolic dysfunctions in the large and medium-sized RGCs eventually leading to optic nerve atrophy.

Animals↗

PubMed1998

[Retrocaval ureter].

OBJECTIVE: To improve the diagnosis of retrocaval ureter. METHOD: 20 cases of retrocaval ureter with an average age of 33.4 years were reported. The diagnosis of this disease depends on urography and retrograde ureterography. Operation was the principal treatment. Ureter orthopedics and reduction were performed in 19 cases of type 1 (low loop) except one case of type II (high loop). After removing 3 - 4 cm retrocaval ureter with pathological changes, we anastomosed the ureter without tension and regained its normal anatomic position. RESULT: B-ultrasound and excretory urography showed no stenosis and improvement of hydronephrosis. CONCLUSION: Ureter orthopedics and reduction are ideal for the treatment of retrocaval ureter.

Adolescent↗

PubMed1997

A single amino acid change in the para sodium channel protein is associated with knockdown-resistance (kdr) to pyrethroid insecticides in German cockroach.

Previous genetic and pharmacological studies suggest that knockdown-resistance (kdr) to pyrethroid insecticides likely results from a mutation(s) in the para sodium channel gene. In this study, para sodium channel genes from an insecticide-susceptible German cockroach strain, CSMA, and a kdr-type German cockroach strain, Ectiban-R, were cloned and sequenced. Comparison of the nucleotide sequences of paraCSMA and paraEctiban-R revealed two nucleotide differences at nt 1491 and nt 2979, respectively. Only the difference at nt 2979 (G in paraCSMA and C in paraEctiban-R) resulted in an amino acid change (Leu993 in CSMA and Phe993 in Ectiban-R). Leu993/Phe993 is located in the highly conserved membrane-spanning segment 6 of domain II (IIS6). Furthermore, reverse transcription-polymerase chain reaction (RT-PCR) sequence analysis using another two insecticide-susceptible and one kdr German cockroach strain, revealed that C2979 was specifically associated with kdr resistant strains, whereas only G2979 was present in all susceptible strains. These results suggest that a single amino acid change from Leu993 to Phe993 is responsible for the kdr-type resistance in German cockroach.

Amino Acid Sequence↗

PubMed1997

Genetic analysis of parasitism in the soybean cyst nematode Heterodera glycines.

A genetic analysis of parasitic ability in the soybean cyst nematode Heterodera glycines was performed. To identify and characterize genes involved in parasitism, we developed three highly inbred H. glycines lines, OP20, OP25 and OP50, for use as parents for controlled crosses. Through these crosses, we have identified genes in the inbred parents that control reproduction of the nematode on hosts that carry resistance genes. These genes, designated as ror-* for reproduction on a resistant host, segregate in a normal Mendelian fashion as independent loci. Host range tests of F1 generation progeny indicated that at least one parasitism gene in both the OP20 and OP50 lines for host PI 88788 was dominant. Parasitism genes in OP50 for hosts "Peking" and PI 90763 are recessive. Two types of single female descent populations, a single backcrossed BC1F2-derived and a double backcrossed BC2F1-derived, were established on the susceptible soybean cultivar "Lee 68." Host range tests for parasitism in these lines demonstrated the presence of two independent genes in OP50, one for host PI 88788 designated ror-1 and one for host PI 90763 designated ror-2. OP20 carries two independent genes for parasitism on PI 88788, designated as alleles kr3 and kr4.

Animals↗

PubMed1997

[Hyperosmotic glucose and antibiotics induce production of plasminogen activator inhibitor and expression of TGF beta mRNA by rat peritoneal mesothelial cells].

To investigate the mechanism of fibrosis in peritoneal dialysis, we observed the effects of the hyperosmotic glucose and antibiotics such as gentamicin and cefazolin on rat peritoneal mesothelial cells with cell culture, fibrin-plate lyzing and Northern blotting analysis method. The peritoneal mesothelial cells may express PAI-1 mRNA. The expression of PAI-1 mRNA in peritoneal mesothelial cells and activities of PAI in the supernatants were enhanced by 11.2 mmol/L glucose, gentamicin and cefazolin at 12 hr. By 24 hr, the activity of PAI-1 also increased in the supernatants with 11.2 mmol/L glucose. The expression of PAI-1 mRNA and production of PAI activities by the peritoneal mesothelial cells were increased by gentamicin, and the TGF-beta mRNA increased in the peritoneal mesothelial cells was induced by 11.2 mmol/L glucose, gentamicin and cefazolin. The results suggested that 11.2 mmol/L glucose, gentamicin and cefazolin may increase the expressions or productions of PAI and TGF-beta in peritoneal mesothelial cells. So by perosmotic glucose, cefazolin and gentamicin promote the peritoneal fibrosis in patients with CAPD.

Animals↗

PubMed1997

The termination of optic nerve fibers in the albino mouse.

To establish the terminal sites of the optic nerve fibers in the albino mouse, the immunohistochemical method using cholera toxin, subunit B (CTB), as well as three kinds of selective silver impregnation methods for degenerating nerve fibers were used. Termination was confirmed in the following nuclei: bilateral dorsal nuclei of the lateral geniculate body (LGB), ventral nuclei of LGB, preoptic areas, posterolateral nuclei, superior colliculi, suprachiasmatic nuclei, medial terminal nuclei of the accessory optic tract (AOT), and dorsal terminal nuclei of AOT. The percentage of the optic nerve fibers crossing at the optic chiasm was estimated at 90 to 95. Fibers from the unilateral retina were observed to terminate more in the contralateral nucleus. With regard to the suprachiasmatic nucleus, however, the terminations were observed to be distributed evenly and bilaterally.

Animals↗

PubMed1996

Fluoro-Green and Fluoro-Red: two new fluorescent retrograde tracers with a number of unique properties.

As a means of improving nerve tract-tracing in the peripheral and central nervous systems we experimented with two (retrograde) fluorescent emulsions, which we have tentatively named Fluoro-Green (FGr) and Fluoro-Red (FRe), and which we believe possess the following seven advantages: (1) they show little diffusion beyond the injection site; (2) their excitation/emission characteristics allow their use in double-tracing experiments; (3) they do not 'leak' from labeled cells; (4) their fluorescence is presented as large granules in the cytoplasm and its processes; (5) the fluorescence lasts for a sufficiently long time to permit repeated observation; (6) they may be used in combination with a wide variety of other neuroanatomical tracing methods; (7) they are economical, non-toxic and easy to utilize.

Animals↗