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K Huang

Publications and source records attributed to K Huang.

At least 109 records · Page 6Linked to original sources
PubMed1997

The yeast adaptor protein complex, AP-3, is essential for the efficient delivery of alkaline phosphatase by the alternate pathway to the vacuole.

A novel clathrin adaptor-like complex, adaptor protein (AP)-3, has recently been described in yeast and in animals. To gain insight into the role of yeast AP-3, a genetic strategy was devised to isolate gene products that are required in the absence of the AP-3 mu chain encoded by APM3. One gene identified by this synthetic lethal screen was VPS45. The Vps pathway defines the route that several proteins, including carboxypeptidase Y, take from the late Golgi to the vacuole. However, vacuolar alkaline phosphatase (ALP) is transported via an alternate, intracellular route. This suggested that the apm3-Delta vps45 synthetic phenotype could be caused by a block in both the alternate and the Vps pathways. Here we demonstrate that loss of function of the AP-3 complex results in slowed processing and missorting of ALP. ALP is no longer localized to the vacuole membrane by immunofluorescence, but is found in small punctate structures throughout the cell. This pattern is distinct from the Golgi marker Kex2p, which is unaffected in AP-3 mutants. We also show that in the apm3-Delta mutant some ALP is delivered to the vacuole by diversion into the Vps pathway. Class E vps mutants accumulate an exaggerated prevacuolar compartment containing membrane proteins on their way to the vacuole or destined for recycling to the Golgi. Surprisingly, in AP-3 class E vps double mutants these proteins reappear on the vacuole. We suggest that some AP-3-dependent cargo proteins that regulate late steps in Golgi to vacuole transport are diverted into the Vps pathway allowing completion of transfer to the vacuole in the class E vps mutant.

Alkaline Phosphatase↗
PubMed1997

A discussion about the DiFrancesco-Noble model.

An obvious defect in the DiFrancesco-Noble (DN) model was found, so methods to overcome this inadequacy are put forward. Based on these methods, different kinds of modified DN model can be obtained, and numerical results show that most of the dynamics of the DN model can be essentially preserved by these modified systems.

Animals↗
PubMed1997

Performance of a neural-network-based determination of amino acid class and secondary structure from 1H-15N NMR data.

A neural network which can determine both amino acid class and secondary structure using NMR data from 15N-labeled proteins is described. We have included nitrogen chemical shifts, 3JHNH alpha coupling constants, alpha-proton chemical shifts, and side-chain proton chemical shifts as input to a three-layer feed-forward network. The network was trained with 456 spin systems from several proteins containing various types of secondary structure, and tested on human ubiquitin, which has no sequence homology with any of the proteins in the training set. A very limited set of data, representative of those from a TOCSY-HSQC and HNHA experiment, was used. Nevertheless, in 60% of the spin systems the correct amino acid class was among the top two choices given by the network, while in 96% of the spin systems the secondary structure was correctly identified. The performance of this network clearly shows the potential of the neural network algorithm in the automation of NMR spectral analysis.

Amino Acids↗
PubMed1997

Are two interventions worse than none? Joint primary and secondary prevention of eating disorders in college females.

Prevention programs for eating disorders attempt to simultaneously prevent new cases from arising (primary prevention) and encourage students who already have symptoms to seek early treatment (secondary prevention), even though ideal strategies for these 2 types of prevention may be incompatible with each other. In the present study, an eating disorder prevention program was evaluated in a simple of female college freshmen. In the intervention, classmates who had recovered from eating disorders described their experiences and provided information about eating disorders. At follow-up, intervention participants had slightly more symptoms of eating disorders than did controls. The program may have been ineffective in preventing eating disorders because by reducing the stigma of these disorders (to encourage students with problems to seek help), the program may have inadvertently normalized them.

Adaptation, Psychological↗
PubMed1997

Alanyl aminopeptidase from human seminal plasma: purification, characterization, and immunohistochemical localization in the male genital tract.

Alanyl aminopeptidase (AAP) was purified to homogeneity from human seminal plasma. The calculated molecular weight of the purified enzyme was approximately 137,000+/-5,000 from light scattering, 140,000 (main) and 137,000 (minor) from non-denatured PAGE and 153,000 from SDS-PAGE in the absence or presence of 2-mercaptoethanol (2-ME). These findings suggest that the enzyme is monomeric in form in human seminal plasma. The enzyme hydrolyzed several amino acid 4-methyl-coumaryl-7-amide (MCA) substrates. The order of Kcat/Km values of AAP at optimal pH (pH 7.5) was Ala- > Lys-Ala- > or = Met- > Leu- > Phe- > Arg- > or = Arg-Arg- > Lys- > Gly-MCAs. AAP was potently inhibited by bestatin, leuhistin, actinonin, amastatin, and 1,10-phenanthroline. These findings suggest that AAP is an aminopeptidase. We determined that the amino acid sequence of the first 22 residues of the enzyme was Ser1-Thr-Thr-Pro-Ser5-Ala-Ser-Ala-Thr-Thr10-Asn-Pro-Al a-Ser-Ala15-Thr-Thr-Leu-Asp-Gln20-Ser-Lys-. This sequence was completely coincident with that downstream of the transmembrane site of human intestinal alanyl aminopeptidase N (CD13). We also isolated cDNA encoding AAP from human prostate cDNA library, sequenced its structure, and confirmed human seminal plasma AAP to be identical with alanyl aminopeptidase N. We postulated that native human seminal plasma alanyl aminopeptidase is released into the seminal plasma after the specific site is cleaved by elastase or an elastase-like enzyme. The enzyme level in human seminal plasma determined by single radial immunodiffusion was 5.2+/-3.2 mg/100 ml (mean+/-SD, n=20) in individuals 20-47 years of age. AAP was immunohistochemically stained in the luminal site-cell membrane of epithelial cells in the prostatic gland and ductuli efferentes of the testis.

Adult↗
PubMed1997

Radioprotection of hematopoietic tissue by fibroblast growth factors in fractionated radiation experiments.

Acidic and basic fibroblast growth factors (FGF(1/2)) myeloprotect mice in single dose total body irradiation (TBI) experiments with a dose modification factor (DMF) of approximately 1.15. CFU-C assay suggests that one of the mechanisms is augmentation of the shoulder of the radiation dose response curve, and thus protection could be greater with fractionation. Four equal fractions of TBI were delivered to C3H/He mice at times 0 h, 8 h, 24 h, and 32 h. FGF(1/2) dose was 3 microg per i.v. injection given 24 and 4 hrs before the first radiation dose. FGF2 treated mice had a significant survival advantage over saline-treated mice with a DMF of 1.22 +/- 0.07 (p < 0.01). Adding a third dose of FGF2, had no additional benefit on LD(50/30) (dose of radiation lethal to 50% of animals measured at day 30) (DMF = 1.23 +/- 0.06, p < 0.01). FGF1 was not as effective with fractionation (DMF = 1.04 +/- 0.03). Increased survival in FGF2 treated mice was due to the a more rapid recovery of bone marrow hematopoietic cells and peripheral WBC, RBC and platelets. FGF2 may prove a useful treatment response modifier in clinical fractionated irradiation.

Animals↗
PubMed1997

[Experimental studies about effect of dexamethasone on diaphragm of normal rats].

The influence of dexamethasone on diaphragm function, its oxidative capacity, fiber cross-sectional areas, the content of glycogen and ultrastructural changes were determined in Wistar rats by receiving dexamethasone (2 mg/kg) muscle injection for two weeks. We noted dexamethasone treatment leads to significant atrophy of the mass of diaphragm, reduction of fiber cross-sectional areas (CSA) of type II a, II b fibers. Under high frequency (100 Hz) stimulation, the tention of the diaphragm muscle strips was decreased and diaphragm fatigue resistance (1/2 RT) was significantly improved. Histochemically, ATPase activity in type I and type II b fibers of the diaphragm was significantly reduced and a significant reduction of succinate dehydrogenase activity in the diaphragm was also observed, but increased glycogen was seen in the diaphragm. Ultrastructural changes including mitochondrial hyperplasia, swelling, myofibillae focus destructure were evident. It is concluded that steroid-induced myopathy may also involve the diaphragm.

Adenosine Triphosphatases↗
PubMed1997

[The long-term therapeutic results of chemotherapy combined with radiotherapy in advanced nasopharyngeal carcinoma].

OBJECTIVE: To evaluate the effect of chemothrapy combined with radiotherapy in advanced nasopharyngeal carcinoma (NPC). METHODS: From Dec. 1989 to Dec. 1990, 76 patients with locally advanced NPC (stage III or IV) were treated with 3 cycles of cisplatin [PDD, 20 mg.(m2)-1.day-1, i.v. on days 1-5] and 5-Fluorouracil (5-Fu, 700 mg.(m2)-1.day-1 by continuous i.v. infusion on days 1-5 followed shortly thereafter by radiotherapy. Eighty-six patients treated with radiotherapy alone in 1989 were taken as control. The methods and time/dose schedule of radiotherapy were similar in the two groups. RESULTS: The response rate to chemotherapy was 89.3% [complete response (CR) 18.4%]. The overall 5-year survival was 48.7% in the combined treatment group and 33.6% in the control group (P > 0.05). The 5-year survival in the combined treatment group was 44.1% and 39.5%, in patients with T2N3 and T2-4N3 and 21.6% and 20.4% in the control group, respectively (P < 0.05). CONCLUSION: This prospective study demonstrates that PDD/5-Fu chemotherapy followed by radiotherapy can improve 5-year survival in patients with T2-4N3 nasopharyngeal carcinoma.

Adolescent↗
PubMed1996

Delayed maturation of CD4- CD8- Fc gamma RII/III+ T and natural killer cell precursors in Fc epsilon RI gamma transgenic mice.

Fc epsilon RI gamma (gamma) is a member of a group of related proteins (the zeta-family dimers) that function as signal-transducing components of both Fc receptors and the T cell antigen receptor (TCR). Analysis of gamma expression during fetal thymus ontogeny revealed that it is expressed in early thymocytes, before the initiation of clonotypic TCR-alpha and TCR-beta gene rearrangement but is down-regulated in most adult thymocytes. To explore a possible role for gamma in thymocyte development, we generated transgenic mice in which this protein was overexpressed at all stages of ontogeny. Overexpression of gamma inhibited the maturation of T cells as well as natural killer (NK) cells. The developmental effects were transgene dose related and correlated with markedly delayed maturation of fetal CD4-CD8- FcRII/III+ thymocytes, cells thought to include the progenitors of both T and NK cells. These results suggest that the zeta and gamma chains serve distinctive functions in thymocyte development and indicate that Fc receptor(s) may play an important role in regulating the differentiation of early progenitor cells within the thymus.

Animals↗
PubMed1996

Cloning and characterization of PTP-K1, a novel nonreceptor protein tyrosine phosphatase highly expressed in bone marrow.

A novel nonreceptor protein tyrosine phosphatase (PTP), PTP-K1, was identified using a consensus polymerase chain reaction-based approach. The full length cDNA encompasses an open reading frame of 1362 base pairs, predicting a protein of 453 amino acid residues with a molecular mass of 54 kDa. The PTP domain is located in the N-terminal portion of the molecule and shares approximately 50% amino acid identify with two other nonreceptor PTPs: PEP and PTP-PEST. PTP-K1 is preferentially expressed in mouse bone marrow with transcripts of 1.7 kb, 1.9 kb and 3.5 kb. The 1.7 kb transcript was also detected in kidney, lung and ovary. The PTP domain of PTP-K1 was expressed as a fusion protein in bacteria and had intrinsic PTP catalytic activity. Indirect immunofluorescence microscopy in COS-7 cells showed that PTP-K1 was localized to the cytoplasm. Ptp-k1 was mapped to mouse chromosome 1, and was closely linked to the interleukin-1 receptor gene. The high level expression of PTP-K1 mRNA in bone marrow suggests that PTP-K1 may be involved in signal transduction in growth and differentiation of hematopoietic cells.

Amino Acid Sequence↗
PubMed1996

Tumor growth and tumor radiosensitivity in mice given myeloprotective doses of fibroblast growth factors.

BACKGROUND: Radiation at doses high enough to cure cancer also frequently destroys normal tissue. Development of agents that protect normal tissue without also protecting diseased tissue has been difficult. In vivo radioprotection of bone marrow by acidic and basic fibroblast growth factors (FGF1 and FGF2, respectively) has recently been demonstrated after whole-body irradiation of C3H/HeN mice. PURPOSE: Our purpose was to determine whether myeloprotective doses of those growth factors also protect malignant tumors. METHODS: First, we investigated the effects of exogenous FGF1 or FGF2 (FGF1/2) administration (treatment group receiving two intravenous injections of 3 micrograms FGF1/2 per mouse 24 hours and 4 hours before local irradiation of right hind leg and control group receiving two intravenous injections of 0.1 mL of saline) on growth and radiosensitivity of three transplantable murine tumors (one squamous cell carcinoma [SCC-VII] and two sarcomas [KHT and Rif-1]), all of which were grown in C3H/HeN mice. We then evaluated the effect of FGF1/2 on tumor cell proliferation, cell cycle distribution, and pulmonary metastatic frequency in the mice. Specifically, survival studies were performed in mice treated with 0, 6, 6.5, 7.5, 8.5, 9, or 10 Gy whole-body irradiation with or without FGF2 (n = 250). Rif-1 (n = 40), KHT (n = 40), and SCC-VII (n = 40) tumors were implanted in the hind leg of mice, and mice were treated with FGF2 or saline when their tumor-bearing thighs were 9 mm in diameter. In separate experiments (treatment group receiving two injections of 3 micrograms each of FGF2 [6 micrograms total] either intravenously or intratumorally 24 hours and 4 hours before local tumor irradiation and control group receiving 0.1 mL saline), tumor growth was followed, and mice were killed to count lung metastases and measure tumor proliferating cell nuclear antigen (PCNA) and bromodeoxyuridine labeling at various times thereafter (three to eight mice per group). Tumor growth curves of untreated and irradiated tumors were determined with and without intravenous or intratumoral FGF1/2 in SCC-VII tumors (n = 120). Radiation doses to the tumor-bearing leg were 15 and 30 Gy for SCC-VII, 30 Gy for Rif-1, and 15 Gy for KHT. From each experiment, the mean (+/- 1 standard error) was calculated from data obtained from three to 20 mice. Statistical tests used included two-tailed Student's t test, the chi-squared test, and Fisher's exact test. All P values represent two-tailed tests of statistical significance. RESULTS: There was no statistically significant difference in tumor growth rate between FGF2-treated and saline-treated mice when FGF2 was administered intravenously at doses and schedules found to be optimally myeloprotective in whole-body irradiation experiments. Intravenous administration of FGF2 did not induce lung metastases, and it did not augment the S-phase fraction of tumor cells. Likewise, there was no evidence of enhanced cell proliferation as measured by PCNA-labeling index. Intratumoral injection of FGF1/2 did increase the size of SCC-VII tumors (P < .05 [Student's t test] at 3 days after treatment); however, the radiation response after intratumoral injection of growth factor was not compromised. CONCLUSION: Low intravenous doses of FGF1 or FGF2 appear to protect bone marrow from the toxic effects of radiation without increasing the rates of tumor growth or metastases or decreasing the radiosensitivity of tumors.

Animals↗
PubMed1996

Detection of monoclonal microsatellite alterations in atypical breast hyperplasia.

Atypical hyperplastic (AH) breast lesions are currently classified and treated as benign proliferative disorders, but their presence is associated with a four- to fivefold increased risk of developing breast cancer. Currently, it is not known if an AH lesion is a marker of increased risk, or is itself a premalignant lesion. To investigate this question, we used a series of 15 microsatellite loci to analyze 15 separate AH lesions microdissected from the archived pathology specimens of subjects with no coincident or previous breast malignancy. We found that a significant subset (6/15, or 40%) of these AH lesions demonstrated evidence of monoclonal microsatellite alterations, both length variation and allele loss. These monoclonal alterations suggest that the AH lesion has already undergone genetic changes conferring a growth advantage. Thus, these AH lesions may actually be early neoplasms. We also noted that monoclonality characterized AH lesions in younger as compared with older women (44 vs. 59 yrs, P < 0.05) and that a subset of monoclonal lesions (4/6) demonstrated microsatellite alterations at more than one locus, suggesting that an undetermined type of genetic instability may play a role early in the development of abnormal breast proliferations. These findings contribute to our understanding of the pathogenesis of AH lesions and may have implications regarding their relationship to breast tumors.

Adult↗
PubMed1996

Dipeptidyl peptidase II from porcine seminal plasma: purification, characterization, and its homology to granzymes, cytotoxic cell proteinases (CCP 1-4).

Dipeptidyl peptidase II (DPP II) was purified to homogeneity from porcine seminal plasma by polyacrylamide gel electrophoresis (PAGE). The molecular weight of the purified enzyme was calculated to be approx. 185,000 and 200,000 on Superdex 200 column chromatography and non-denatured PAGE, respectively, and to be 58,000 and 61,000 on SDS-PAGE in the absence and presence of beta-mercaptoethanol (beta-ME), respectively. These findings suggested that the enzyme is composed of three identical subunits. The enzyme rapidly hydrolyzed the substrates Lys-Ala-MCA and Gly-Pro-MCA at acidic pH. The Km and V(max) values of DPP II at optimal pH (pH 6.0) were 1330 microM and 2.9 mumol/mg per min for Gly-Pro-MCA, and 360 microM and 1.43 mumol/mg per min for Lys-Ala-MCA, respectively. It was strongly inhibited by diisopropylphosphofluoride (DFP), and moderately by 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF). These findings suggest that DPP II is a serine peptidase. Furthermore, the enzyme activity was also strongly inhibited by copper ions. The amino-acid sequence of the first 41 residues of the enzyme was determined as Ala1-Ser-Pro-Pro-Glu-Pro-Gly-Phe-Arg- Glu10-Val-Tyr-Phe-Glu-Gln-Leu-Leu-Asp-His-Phe20-Asn-Phe-Glu- Arg-Phe- Gly-Lys-Lys-Thr-Phe30-Arg-Gln-Arg-Phe-Leu-Val-Ser-Asp-Lys-Phe40 -Trp. This sequence showed homology (11.6-30.2%) to the N-terminal amino-acid sequences of cytotoxic cell proteinases (CCP 1-4), granzymes. Other properties of DPP II including pH optimum, pH stability, and heat stability were characterized.

Amino Acid Sequence↗
PubMed1996

Effects of tetrandrine on cardiac noradrenaline release evoked by electrical stimulation.

The effects of tetrandrine (TD) on endogenous cardiac noradrenaline (NA) release evoked by electrical stimulation were investigated in perfused guinea pig hearts. The overflow of cardiac NA and its intraneuronal metabolite 3,4-dihydroxyphenylethyleneglycol (DOPEG) were determined by high pressure liquid chromatography (HPLC). In the presence of TD, the release of NA evoked by either nerve ganglion-stimulation or cardiac field-stimulation was significantly reduced (P < 0.01). The overflow of DOPEG was markedly enhanced (P < 0.01). TD inhibited cardiac endogenous NA release resulting from activation of the sympathetic nerve terminals within the myocardium, and increased the release of DOPEG, indicating that TD could result in a loss of NA from storage vesicles or activate monoamine oxidase in axoplasma, which could be detected by markedly increased DOPEG release. These effects of TD may be associated with its property of calcium antagonist.

Alkaloids↗
PubMed1996

Saccharomyces cerevisiae G1 cyclins differ in their intrinsic functional specificities.

The three budding yeast CLN genes appear to be functionally redundant for cell cycle Start: any single CLN gene is sufficient to promote Start, while the cln1 cln2 cln3 triple mutant is Start defective and inviable. Both quantitative and apparently qualitative differences between CLN genes have been reported, but available data do not in general allow distinction between qualitative functional differences as opposed to simply quantitative differences in expression or function. To determine if there are intrinsic qualitative differences between Cln proteins, we compared CLN2, CLN3, and crippled (but still partially active) CLN2 genes in a range of assays that differentiate genetically between CLN2 and CLN3. The results suggest that different potencies of Cln2, Cln3, and Cln2 mutants in functional assays cannot be accounted for by a simple quantitative model for their action, since Cln3 is at least as active as Cln2 and much more active than the Cln2 mutants in driving Swi4/Swi6 cell cycle box (SCB)-regulated transcription and cell cycle initiation in cln1 cln2 cln3 bck2 strains, but Cln3 has little or no activity in other assays in which Cln2 and the Cln2 mutants function. Differences in Cln protein abundance are unlikely to account for these results. Cln3-associated kinase is therefore likely to have an intrinsic in vivo substrate specificity distinct from that of Cln2-associated kinase, despite their functional redundancy. Consistent with the idea that Cln3 may be the primary transcriptional activator of CLN1, CLN2, and other genes, the activation of CLN2 transcription was found to be sensitive to the gene dosage of CLN3 but not to the gene dosage of CLN2.

Cell Cycle↗
PubMed1996

Purification and characterization of sulochrin oxidase from Penicillium frequentans.

Sulochrin oxidase, an enzyme catalyzing regio- and stereospecific phenol oxidative coupling reaction to form (+)-bisdechlorogeodin from sulochrin, was isolated from Penicillium frequentans CMI 96659. By chromatographies on DEAE-cellulose, hydroxyapatite, Phenyl-Sepharose, Mono P, Mono Q, and HPLC gel filtration columns, sulochrin oxidase was purified to apparent homogeneity. The purified enzyme had a molecular weight of 230 K as estimated by gel filtration and 110 K as estimated by sodium dodecylsulfate-polyacrylamide gel electrophoresis under denaturing conditions, suggesting that the active enzyme was a homodimer. The enzyme showed pI 4.0 and an optimum pH of 6. The enzyme activity was strongly inhibited by the copper-chelating reagent, diethyldithiocarbamate, and did not recover its full activity even after removing the inhibitor by dialysis. However, enzyme activity was fully restored by the addition of Cu2+. Thus, sulochrin oxidase is considered to be a copper protein. The enzyme showed high substrate specificity for benzophenone compounds such as sulochrin and dihydrogeodin.

Alcohol Oxidoreductases↗