In vitro growth inhibition of neoplastically transformed cells by non-transformed cells: requirement for gap junctional intercellular communication

We examined whether the inhibition of neoplastically transformed cell growth by co-cultured non-transformed cells involved gap junctional intercellular communication (GJIC). The growth of poorly communicating (approximately 25-35% dye-coupled cells), Ha-ras and neu oncogene-transformed WB-F344 rat liver epithelial cells was inhibited by co-culture with highly communicating (90-95% dye-coupling), non-transformed WB-F344 cells. Inhibition was dependent upon heterologous cell-cell contact and required that the non-transformed cells were GJIC competent. GJIC-deficient mutant WB-F344 cells did not suppress transformed cell growth. Restoration of mutant cell GJIC by transfection with rat connexin43 cDNA restored growth-inhibiting activity. These results clearly demonstrate a role for GJIC in the inhibition of transformed cell growth by non-transformed cells.

Restoring the apoptosis suppression response to IL-5 confers on erythroleukemic cells a phenotype of IL-5-dependent growth

We have established a human IL-5 (hIL-5) dependent cell line, JYTF-1, derived from TF-1 parental human erythroleukemic cells by long-term cultivation in the presence of hIL-5. The ED50 values of hIL-5 for both TF-1 and JYTF-1 cell lines remained similar. However, when cells were grown in an optimal concentration of IL-5, some TF-1 cells but not JYTF-1 cells died via apoptosis. Although the rates of DNA synthesis were similar for TF-1 and JYTF-1 cells grown in IL-5, [3-H]thymidine releasing of pulse-labeled DNA analysis indicated that the viable TF-1 cells in IL-5 were more apoptosis-prone than were JYTF-1 cells. Therefore, in the JYTF-1 variant, the ability to suppress apoptosis has apparently been restored. The following findings suggest that overexpression of the hIL-5 receptor alpha-chain may be responsible for restoring the apoptosis suppression ability of IL-5: 1) the growth of JYTF-1 cells remained cytokine-dependent; 2) the proliferation of JYTF-1 cells in IL-5 was not mediated by autocrine secretion; 3) JYTF-1 and TF-1 cells responded similarly to other cytokines such as human erythropoietin; 4) Northern blot analysis revealed that JYTF-1 cells expressed approximately eightfold more IL-5 receptor alpha-chain mRNA than did TF-1. To our knowledge, JYTF-1 represents the first example in which coupling of mitogenesis stimulation and apoptosis suppression from otherwise uncoupled parental cells confers a phenotype of IL-5-dependent growth.

Two types of normal human breast epithelial cells derived from reduction mammoplasty: phenotypic characterization and response to SV40 transfection

A culture method to grow two morphologically distinguishable normal human breast epithelial cell types derived from reduction mammoplasty has been developed. Type I cells were characterized by a more variable cell shape, smooth cell colony boundaries, the expression of epithelial membrane antigen (EMA) and keratin 18 and the non-expression of keratin 14 and alpha 6 integrin. In addition, the Type I cells were growth stimulated by fetal bovine serum (FBS) and were deficient in gap junctional intercellular communication (GJIC). In contrast, Type II cells were characterized by a uniform cell shape, expression of keratin 14 and alpha 6 integrin and the non-expression of EMA and keratin 18. In addition, Type II cells were growth inhibited by FBS and were proficient in GJIC. Type I cells can be induced by cholera toxin to change their morphology to a Type II cell morphology. Hence, Type I cells antigenically resemble luminal epithelial cells, while the Type II cells more closely resemble basal epithelial cells. Type I and Type II cells were transfected with SV40 DNA. Clones with extended lifespans were obtained from both Type I and Type II cells by SV40 transfection. Some (2/9) of the SV40-transfected Type I cell clones became immortal (> 100 cumulative population doubling level), whereas none (0/8) of the SV40-transfected Type II cell clones became immortal. The SV-40-transfected Type I and Type II cell-derived extended life clones and immortal cell lines phenotypically resembled their parental cells with respect to EMA, keratin 14 and keratin 18 expression and GJIC. Each (9/9) of the SV40 transfected Type I cell clones grew in soft agar; none (0/8) of the SV40-transfected Type II cell clones were capable of growing in soft agar. These results provide evidence that normal human breast epithelial cells, derived from reduction mammoplasty, can be separated into two morphologically and antigenically different cell types and that these two different cell types significantly differ in their response to an oncogenic (SV40) stimulus.

Restoring the apoptosis suppression response to IL-5 confers on erythroleukemic cells a phenotype of IL-5-dependent growth

We have established a human IL-5 (hIL-5) dependent cell line, JYTF-1, derived from TF-1 parental human erythroleukemic cells by long-term cultivation in the presence of hIL-5. The ED50 values of hIL-5 for both TF-1 and JYTF-1 cell lines remained similar. However, when cells were grown in an optimal concentration of IL-5, some TF-1 cells but not JYTF-1 cells died via apoptosis. Although the rates of DNA synthesis were similar for TF-1 and JYTF-1 cells grown in IL-5, [3-H]thymidine releasing of pulse-labeled DNA analysis indicated that the viable TF-1 cells in IL-5 were more apoptosis-prone than were JYTF-1 cells. Therefore, in the JYTF-1 variant, the ability to suppress apoptosis has apparently been restored. The following findings suggest that overexpression of the hIL-5 receptor alpha-chain may be responsible for restoring the apoptosis suppression ability of IL-5: 1) the growth of JYTF-1 cells remained cytokine-dependent; 2) the proliferation of JYTF-1 cells in IL-5 was not mediated by autocrine secretion; 3) JYTF-1 and TF-1 cells responded similarly to other cytokines such as human erythropoietin; 4) Northern blot analysis revealed that JYTF-1 cells expressed approximately eightfold more IL-5 receptor alpha-chain mRNA than did TF-1. To our knowledge, JYTF-1 represents the first example in which coupling of mitogenesis stimulation and apoptosis suppression from otherwise uncoupled parental cells confers a phenotype of IL-5-dependent growth.

The structural loop II of cobrotoxin is the main binding region for nAChR and epitope in the region is conformation-dependent

Modification of positively charged residues, Lys and Arg, in cobrotoxin revealed that Lys-27, Lys-47, Arg-28, Arg-30, Arg-33, and Arg-36 of cobrotoxin were essential for the lethality and binding activity to nicotinic acetylcholine receptor (nAChR). The antigenicity of cobrotoxin was drastically diminished when Lys-47, Arg-28, Arg-30, Arg-33, and Arg-36 were modified, while that of the Lys-27-modified derivative was not significantly changed. The CD spectra of cobrotoxin displayed similar patterns after modification of Lys-27, Lys-47, and Arg-28. These findings suggest that Lys-27, Lys-47, and Arg-28 residues may be related to the direct binding to nAChR, and that there is no involvement of Lys-27 in the antigenic determinants of cobrotoxin. Extending the modification to Arg-30, Arg-33, and Arg-36 caused progressive conformational changes of cobrotoxin and resulted in decreased binding activity to antibody and nAChR. This indicates that Arg-30, Arg-33, and Arg-36 may be of structural importance for maintaining the active conformation of cobrotoxin. These results, together with the facts that Tyr-25, Tyr-35, and Trp-29 of cobrotoxin are important in nAChR binding activity, but Trp-29 and Tyr-35 residues are not essential for the antigenicity, suggest that the structural loop II of cobrotoxin is the main binding region for nAChR and the epitope in that region is conformation-dependent.

Chemical modification of tryptophan residues in alpha-neurotoxins from Ophiophagus hannah (king cobra) venom

Two alpha-neurotoxins, Oh-4 and Oh-7, from the king cobra (Ophiophagus hannah) venom were subjected to Trp modification with 2-nitrophenylsulfenyl chloride (NPS-Cl). One major NPS derivative was isolated from the modified mixtures of Oh-4 and two from Oh-7 by HPLC. Amino acid analysis and sequence determination revealed that Trp-27 in Oh-4, and Trp-30 and Trp-26 and 30 in the two Oh-7 derivatives, were modified, respectively. Sulfenylation of Trp-27 in Oh-4 caused about 70% drop in lethal toxicity and nicotinic acetylcholine receptor-binding activity. Modification of Trp-30 in Oh-7 resulted in the decrease of lethal toxicity by 36% and binding activity by 61%. The activities were further lost when the conserved Trp-26 in Oh-7 was modified. Sulfenylation of the Trp residues did not significantly affect the secondary structure of the toxins as revealed by the CD spectra. These results indicate that the Trp residues in these two long alpha-neurotoxins may be involved in the receptor binding.

Inhibition of gap junctional intercellular communication and malignant transformation of rat liver epithelial cells by neu oncogene

A retrovirus containing a neu oncogene was introduced into a Fischer F344 rat liver epithelial cell line (WB-F344) to study the effect of the expression of neu oncoprotein on gap junctional intercellular communication (GJIC), the ability to form colonies in soft agar and the ability to form tumors in rat liver by these cells. After viral infection, five different neu-transduced epithelial clones were randomly selected for further analysis. Southern blot analysis of HindIII-digested genomic DNA hybridized with a neu-specific probe indicated that the neu oncogene carried by the retrovirus was integrated into different chromosomal locations in the five different neu-transduced WB cell lines. Using the fluorescence recovery after photobleaching (FRAP) assay, we found that GJIC was significantly reduced in neu-transduced WB clones, compared with control virus-infected and parental WB cells. Western blot analysis of connexin 43 in the neu-transduced cell lines showed altered phosphorylation patterns compared with the normal WB-rat liver cell line. Confocal image analysis of the neu-transduced cells showed that the connexin 43 protein, as detected by fluorescent immunostaining, was localized in the cell nucleus. The neu-transduced WB cell lines also acquired the ability to grow in soft agar. Furthermore, cells from three of the five neu-transduced cell lines, when injected into the liver of Fischer F344 rats through the portal vein, were highly tumorigenic (multiple focal hepatic tumors developed within 2 weeks). Cells derived from the tumor were shown to be G-418 resistant, demonstrating that the tumor was derived from the injected WB-neu cells. The results of this study demonstrate that the expression of the neu oncogene is able to block GJIC and to induce tumorigenicity in the rat liver WB-F344 cell line.

Lupus in Chinese male: a retrospective study of 61 patients

BACKGROUND

Systemic lupus erythematosus (SLE) has traditionally been considered a disease of women, and is uncommon in men. In recent years, several large clinical series of male lupus patients have been reported. As no known data are available for lupus in males from Taiwan, a retrospective analysis of data from male lupus patients was done to determine whether these patients differed from other series of male or female SLE patients in the literature.

METHODS

Sixty-one male lupus patients, diagnosed and followed in Tri-Service General Hospital, between 1983 and 1993, were studied and their data analyzed, retrospectively.

RESULTS

The mean age of diagnosis was 30 +/- 17 (mean +/- SD, range: 13-81) years. The peak age of diagnosis was between 13 and 40 years. The mean duration of follow-up was 36 +/- 36 (range: 2-256) months. The 1-, 5- and 10-year survival rates were 84%, 76% and 75%, respectively. The frequency of clinical manifestations were renal disease, 75%; malar rash, 70%; arthritis, 60%; fever, 56%; photosensitivity, 48%; pleuritis, 39%; pericarditis, 31%; alopecia, 31%; mucosal ulcers, 29%; neuropsychiatric disease, 26%; discoid lupus, 21%; vasculitis, 15%; Raynaud's phenomenon, 10%; and lymphadenopathy, 2%. The frequency of abnormal laboratory findings were antinuclear antibodies (ANA), 95%; hypocomplementemia, 77%; antibodies to double-stranded DNA (anti-dsDNA), 57%; leukopenia, 44%; lupus erythematosus (LE) cells, 39%; anti-Ro, 39%; anti-Smith antibodies (anti-Sm), 19%; thrombocytopenia, 18%; rheumatoid factor, 17%; anti-ribonucleoprotein antibody (anti-RNP), 14%; autoimmune hemolytic anemia, 8%; false-positive venereal disease research laboratory test (VDRL), 6% and anti-La, 4%.

CONCLUSIONS

In a review of the 61 ethnic Chinese male lupus patients, a higher frequency of renal disease, malar rash and photosensitivity, but a lower frequency of arthritis and lymphadenopathy, compared to previous reports of Caucasians. There were no significant immunological differences from other series of male lupus, except a lower frequency of anti-dsDNA. In general, poor prognosis was noted for male lupus patients here.

Inhibition of acetylcholine release from mouse motor nerve by a P-type calcium channel blocker, omega-agatoxin IVA

1. The effects were studied of the central neurone P-type Ca2+ channel blockers, omega-agatoxin IVA, omega-conotoxin MVIIC (polypeptide toxins) and synthetic funnel-web spider polyamine toxin on acetylcholine release from mouse motor nerve. 2. omega-Agatoxin IVA decreased the quantal content of endplate potentials and blocked synaptic transmission in the nanomolar range in a reversible manner, whereas the other toxins depressed transmission in the hundred micromolar range. 3. The polyamine toxin, but not the polypeptide toxins, decreased the amplitude of the miniature endplate potential. The increase in the frequency of miniature endplate potentials evoked by high [K+], but not that evoked by alpha-latrotoxin, was effectively antagonized by omega-agatoxin IVA. 4. In the presence of omega-agatoxin IVA, high frequency nerve stimulation produced facilitation of endplate currents and tetanic contractions. 5. The results suggest that, under physiological conditions, the Ca2+ necessary for nerve action potential-evoked acetylcholine release is translocated via a subtype of the P-type Ca2+ channel sensitive to omega-agatoxin IVA.

beta-Eudesmol as an antidote for intoxication from organophosphorus anticholinesterase agents

beta-Eudesmol, a sesquiterpenol present in Chinese herbs, improved the tetanic contraction impaired by diisopropylfluorophosphate in isolated mouse diaphragm preparations by an inhibition of the regenerative acetylcholine release. The antagonism was enhanced when a small concentration of obidoxime was present. Neither enzyme reactivation nor curare-like action was evident. beta-Eudesmol (300 mg/kg, i.p.) elevated the LD50 of diisopropylfluorophosphate (s.c.) in control mice from 4.2 to 6.4 mg/kg and in mice pretreated with atropine from 7.8 to 10.6 mg/kg. In mice pretreated with atropine and obidoxime, beta-eudesmol showed a greater synergistic effect, increasing the LD50 from 281 to more than 800 mg/kg. beta-Eudesmol also markedly alleviated diisopropylfluorophosphate-induced muscle fasciculation, tremor and convulsion and prolonged the time to death. It is proposed that beta-eudesmol may be added to the standard antidotal regimen (atropine plus obidoxime) for treating organophosphate intoxication.

Activation of acyl-coenzyme A:cholesterol acyltransferase by cholesterol or by oxysterol in a cell-free system

Acyl-coenzyme A:cholesterol acyltransferase (ACAT) is an intracellular enzyme that catalyzes the conjugation of long chain fatty acid and cholesterol to form cholesteryl esters. It is an integral membrane protein located in the endoplasmic reticulum. Experiments performed in intact mammalian cells have shown that the rate of cholesteryl ester synthesis in intact cells, as well as the ACAT activity from cell extracts, are greatly activated by the addition of low density lipoprotein (LDL) or oxygenated sterols such as 25-hydroxycholesterol to the growth medium. However, the molecular mechanism(s) by which sterol(s) stimulate the ACAT activity remains to be elucidated. Recently, our laboratory reported the expression cloning of human ACAT cDNA (Chang, C. C. Y., Huh, H. Y., Cadigan, K. M., and Chang, T. Y. 1993) J. Biol. Chem. 268, 20747-20755). In the current study, we report the expression of human ACAT cDNA in insect Sf9 cells. Uninfected Sf9 cells do not express detectable ACAT-like activity. Infecting these cells with recombinant virus containing ACAT cDNA caused these cells to express high levels of ACAT protein and high levels of ACAT activity when assayed in vitro. The catalytic properties of ACAT expressed in these cells were found to be similar to those found in human tissue culture cells. The combination of high level of ACAT protein expression and the low level of cellular cholesterol content in the infected cells have provided us a novel opportunity to establish a simple cell-free system, whereby stimulation of ACAT by sterols can be readily demonstrated. Using this system, we have shown that cholesterol itself can serve as an ACAT activator in vitro, in addition to its role as an ACAT substrate. The current work provides the experimental basis to hypothesize that, inside mammalian cells, cholesterol itself may serve as a physiological regulator of ACAT.

Vasodilator agents modulate rat glomerular mesangial cell growth and collagen synthesis

Mesangial cell activation and extracellular matrix accumulation are hallmarks of many forms of glomerulonephropathy. We investigated the effect of several agents possessing vasodilating activities on rat mesangial cell growth and collagen synthesis. Using cell counting and a modified MTT assay, it was shown that dipyridamole, pentoxifylline, dicentrine, prazosin and doxazosin all caused a dose-dependent inhibition of serum-stimulated rat mesangial cell proliferation. Platelet-derived growth factor-induced cell proliferation was also inhibited by doxazosin and pentoxifylline. Dipyridamole and pentoxifylline inhibited collagen synthesis in confluent mesangial cells while dicentrine and doxazosin did not. The procollagen alpha 1 (I) mRNA expression was also decreased by dipyridamole and pentoxifylline. These results suggested that, in addition to dipyridamole, pentoxifylline and alpha 1-adrenoceptor blockers may have a potential to delay the progression of chronic glomerulopathy associated with mesangial proliferation.

Acquired immunodeficiency syndrome with CNS toxoplasmosis: a case report

Central nervous system (CNS) toxoplasmosis is an important infectious complication of acquired immunodeficiency syndrome (AIDS) which appears to result from reactivation of a previously acquired infection and requires prolonged treatment. A 31-year-old male presented in a drowsy mental state and with an unstable gait. Computerized tomographic (CT) scan and magnetic resonance imaging (MRI) showed multiple nodular lesions in the cerebrum and cerebellum; the seropositivity for the human immunodeficiency virus (HIV-1) and high serum IgG toxoplasma titers were also demonstrated. A presumptive diagnosis of CNS toxoplasmosis was based on neurological signs and neuroradiological findings. This was confirmed by improvement in both clinical and neuroradiological pictures during treatment with pyrimethamine and clindamycin. Four months later, however the patient died of intracranial hemorrhage and massive upper GI bleeding.

Heterogeneous chromosomal aberrations generate 3' truncations of the NFKB2/lyt-10 gene in lymphoid malignancies

The NFKB2(lyt-10) gene codes for a protein that is a member of the NK-kappa B/rel family of transcription factors containing a DNA-binding rel domain and a carboxy-terminal ankyrin-like domain. The NFKB2 gene represents a candidate proto-oncogene, since it has been found to be involved in a chromosomal translocation t(10;14)(q24;q32) in one case of B-cell lymphoma and in gene rearrangements in various types of lymphoid malignancies. To elucidate the structural and functional consequences of NFKB2 rearrangements, we report the molecular characterization of three novel rearranged NFKB2 genes in lymphoid tumors. In one case of multiple myeloma (MM), cloning and sequencing analysis of reciprocal breakpoint sites showed that they occurred within intron 15 of the NFKB2 gene and led to the complete deletion of the 3' portion of the gene coding for the ankyrin domain. Fluorescent in situ hybridization (FISH) analysis showed that the novel regions involved in the NFKB2 rearrangement originated from chromosome 7q34, thus implying the occurrence of a t(7;10)(q34;q24) reciprocal chromosomal translocation. In one case of T-cell cutaneous lymphoma (CTCL) and in one of B-cell chronic lymphocytic leukemia (B-CLL), NFKB2 rearrangements occurred, respectively, within exons 18 and 20 of the gene and involved recombinations with distinct regions of chromosome 10q24. Molecular analysis suggested that these rearrangements may occur as a consequence of small internal chromosomal deletions. In both of these cases, the rearrangements led to specific carboxy-terminal truncations of NFKB2 generating abnormal transcripts that coded for proteins lacking portions of the ankyrin domain. These proteins localize in the nucleus, suggesting their constitutive activation in vivo. Overall, our results indicate that NFKB2 rearrangements in lymphoid neoplasia may occur by heterogeneous mechanisms, including internal chromosomal deletion or chromosomal translocation. The common consequence of these rearrangements appears to be the deletion of 3' sequences of NFKB2 leading to the production of carboxy-truncated constitutively nuclear proteins that may be involved in tumorigenesis.

Urinary epidermal growth factor receptor-binding growth factors in patients with cancers of the digestive tract

To investigate whether the urinary excretion of epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) is increased in patients with cancer of the digestive tract, EGF and TGF-alpha were determined in 109 cancer patients and 40 healthy controls. Excluding EGF in hepatocellular carcinoma (HCC) and TGF-alpha in pancreatic cancer, both growth factors in each cancer group were significantly higher than in the control group. A receiver operating characteristic curve and likelihood ratio were applied to obtain the best diagnostic efficiency. Both EGF and TGF-alpha had high specificity (100%) in all cancer group. The high sensitivity of EGF in gastric cancer (100%) and metastatic liver cancer (93.3%), moderate sensitivity of TGF-alpha in metastatic liver cancer (86.6%), colon cancer (80.0%), and HCC (61.7%) suggested that they might be helpful in identifying these cancers. In conclusion, urinary excretion of EGF and TGF-alpha increased in most cancers of the digestive tract. They may be used as tumor markers.

Immunological neutralization of cobrotoxin by its homologous precipitin and non-precipitin antibodies

Anti-cobrotoxin antibodies can be separated into precipitin and non-precipitin antibodies. The precipitin antibody possesses the same binding affinity to cobrotoxin as non-precipitin antibody, but the neutralizing capability of the latter is superior to that of the former in blocking cobrotoxin binding to nicotinic acetylcholine receptor (nAChR). After preincubation with antibodies, cobrotoxin completely lost its binding activity to nAChR. The dissociation of cobrotoxin-nAChR complex by the antibodies was low, and 60% of the complex formation appeared to be irreversible. These results indicate that the neutralization of cobrotoxin by the antibody may predominantly involve unbound, receptor-free cobrotoxin. The relationships of neutralization capacity and binding affinity as well as bond strength between cobrotoxin and its antibodies are incongruous. Different local conformational changes of a unique Trp in cobrotoxin on binding with the precipitin and non-precipitin antibodies seem to lead to different accessibility for fluorescence quenchers. Characterization of the binding domains by immunoprecipitation with the antibodies correlated with the quenching results. Thus, the binding topography of cobrotoxin may play an important role over the binding affinity and bond strength in neutralization by cobrotoxin antibody.

Facilitation of nicotinic receptor desensitization at mouse motor endplate by a receptor-operated Ca2+ channel blocker, SK&F 96365

When acetylcholinesterase was inhibited by neostigmine, SK&F 96365 (1-(beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl)-1H-imidazole hydrochloride) at 10 microM caused no effect on the amplitude of single endplate potentials (e.p.p.s) but shortened the decay time in mouse phrenic nerve-diaphragm preparations. However, SK&F 96365 inhibited high-frequency stimulation-evoked long-lasting depolarization of the endplate region and accelerated the run-down of trains of e.p.p.s which were eliminated within 1 s. After a train of stimulation, SK&F 96365 produced a post-tetanic depression of single e.p.p.s. The post-tetanic effect gradually dissipated with full restoration in 10-15 s. During a train of stimulation, SK&F 96365 also depressed miniature endplate potentials (m.e.p.p.s), which were restored after termination of stimuli in parallel with the recovery of e.p.p. The decay times of miniature endplate currents during recovery phases changed slightly. In control preparations not treated with neostigmine, however, SK&F 96365 did not alter the amplitude and decay time of m.e.p.p.s or e.p.p.s but accelerated the decay of succinylcholine-induced endplate depolarizations. The results suggest that SK&F 96365 facilitates nicotinic receptor desensitization in addition to blocking receptor-operated Ca2+ channels.

High-density multiplex detection of nucleic acid sequences: oligonucleotide ligation assay and sequence-coded separation

We describe a non-isotopic, semi-automated method for large-scale multiplex analysis of nucleic acid sequences, using the cystic fibrosis transmembrane regulator (CFTR) gene as an example. Products of a multiplex oligonucleotide ligation assay (OLA) are resolved electrophoretically from one another and from unligated probes under denaturing conditions with fluorescence detection. One ligation probe for each OLA target carries a fluorescent tag, while the other probe carries an oligomeric non-nucleotide mobility modifier. Each OLA product has a unique electrophoretic mobility determined by the ligated oligonucleotides and the mobility-modifier oligomer arbitrarily assigned (coded) to its target. The mobility range for practical mobility modifiers is much wider than the accessible range from unmodified ligated oligonucleotides of practical length. Each mobility modifier is built from phosphoramidite monomers in a stepwise manner on its associated oligonucleotide using an automated synthesizer. The resulting mobility modifiers lower the probe-target duplex Tm by less than 3 degrees C and retard probe-target annealing by less than 50%, with negligible effect on OLA yield and specificity. This method is especially useful for allelic discrimination in highly polymorphic genes such as CFTR.

Effects of antimalarials and protease inhibitors on plasmodial hemozoin production

Malarial hemozoin may play an important role as a target for antimalarial drugs and in disease pathogenesis. A new assay for hemozoin was developed in which the hemozoin was separated from cells by filtration. Trophozoites have substantially more hemozoin than rings, but there are relatively small differences between chloroquine-sensitive and chloroquine-resistant strains. The effects of hemozoin content of chloroquine and artemisinin, two antimalarial drugs, and E64 and Pepstatin A, two protease inhibitors, were measured. At concentrations at which hypoxanthine incorporation was unaffected, the hemozoin content of rings was decreased by E64, but not by the other three compounds. Artemisinin and Pepstatin A also had little effect on the hemozoin content of trophozoites. Chloroquine and E64 inhibited trophozoite hemozoin formation, but inhibited hypoxanthine uptake to a similar or greater extent. When either rings or trophozoites were exposed to several higher concentrations of chloroquine, hemozoin content was diminished, but significantly less than hypoxanthine uptake. Various concentrations of E64, in contrast, inhibited hemozoin production by both rings and trophozoites significantly more than hypoxanthine incorporation, suggesting that hemozoin production may be directly affected by E64.

Functional involvement of Lys-6 in the enzymatic activity of phospholipase A2 from Bungarus multicinctus (Taiwan banded krait) snake venom

Phospholipase A2 (PLA2) from Bungarus multicinctus snake venom was subjected to Lys modification with 4-chloro-3,5-dinitrobenzoate and trinitrobenzene sulfonic acid, and one major carboxydinitrophenylated (CDNP) PLA2 and two trinitrophenylated (TNP) derivatives (TNP-1 and TNP-2) were separated by high-performance liquid chromatography. The results of amino acid analysis and sequence determination revealed that CDNP-PLA2 and TNP-1 contained one modified Lys residue at position 6, and both Lys-6 and Lys-62 were modified in TNP-2. It seemed that the Lys-6 was more accessible to modified reagents than other Lys residues in PLA2. Modification of Lys-6 caused a 94% drop in enzymatic activity as observed with CDNP-PLA2 and TNP-1. Alternatively, the enzyme modified on both Lys-6 and Lys-62 retained little PLA2 activity. Either carboxydinitrophenylation or trinitrophenylation did not significantly affect the secondary structure of the enzyme molecule as revealed by the CD spectra, and Ca2+ binding and antigenicity of Lys-6-modified PLA2 were unaffected. Conversion of nitro groups to amino groups resulted in a partial restoration of enzymatic activity of CDNP-PLA2 to 32% of that of PLA2. It reflected that the positively charged side chain of Lys-6 might play an exclusive role in PLA2 activity. The TNP derivatives could be regenerated with hydrazine hydrochloride. The biological activity of the regenerated PLA2 is almost the same as that of native PLA2. These results suggest that the intact Lys-6 is essential for the enzymatic activity of PLA2, and that incorporation of a bulky CDNP or TNP group on Lys-6 might give rise to the distortion of the interaction between substrate and the enzyme molecule, and the active conformation of PLA2.

Energy transfer from tryptophan residues of proteins to 8-anilinonaphthalene-1-sulfonate

The binding of the apolar fluorescent dye 8-anilinonaphthalene-1-sulfonate (ANS) to bovine serum albumin (BSA), phospholipase A2 (PLA2), ovalbumin, lysozyme, cobrotoxin and N-acetyltryptophanamide was used to assess the factors affecting the efficiency of energy transfer from Trp residues to the ANS molecule. We found that the efficiency of energy transfer from Trp residues to ANS was associated with the ability of proteins to enhance the ANS fluorescence. At the same molar concentration of protein, BSA enhanced ANS fluorescence most among these proteins; its Trp fluorescence was drastically quenched by the addition of ANS. Fluorescence enhancement of ANS in PLA2-ANS complex increased upon addition of Ca2+ or change of the buffer to acidic pH, resulting in a higher efficiency of energy transfer from Trp residues to ANS. There was limited ANS fluorescence enhancement with ovalbumin, lysozyme, cobrotoxin, and N-acetyltryptophanamide and a less efficient quenching in Trp fluorescence. The capabilities of proteins for binding with ANS correlated with the decrease in their Trp fluorescence being quenching by ANS. However, the microenvironment surrounding Trp residues of proteins did not affect the energy transfer. Based on these results, the factors that affected the energy transfer from Trp residues to ANS are discussed.