A TR3/Nur77 Peptide-Based High-Throughput Fluorescence Polarization Screen for Small Molecule Bcl-B Inhibitors

Nuclear receptor TR3/Nur77/NR4A1 binds several antiapoptotic Bcl-2-family proteins (Bcl-B, Bcl-2, Bfl-1) in a non-BH3-dependent manner. A 9-amino-acid peptide derived from full-length TR3 with polyarginine tail (TR3-r8) recapitulates TR3's binding specificity, displaying high affinity for Bcl-B. TR3-r8 peptide was used to screen for small molecule Bcl-B inhibitors. A fluorescence polarization assay (FPA) employing fluorescein isothiocyanate (FITC)-labeled TR3-r8 peptide (FITC-TR3-r8) and Bcl-B protein was optimized, with nonfluorescent TR3-r8 serving to demonstrate reversible, competitive binding. Approximately 50,000 compounds were screened at 3.75 mg/L, yielding 145 reproducible hits with ≥50% FITC-TR3-r8 displacement (a confirmed hit rate of 0.29%). After dose-response analyses and counterscreening with an unrelated FITC-based FPA, 6 candidate compounds remained. Nuclear magnetic resonance (NMR) showed that 2 of these compounds bound Bcl-B, but not glutathione S-transferase (GST) control protein. One Bcl-B-binding compound was unable to displace FITClabeled BH3 peptides from Bcl-B, confirming a unique binding mechanism compared with traditional antagonists of antiapoptotic Bcl-2-family proteins. This compound bound Bcl-B with Kd1.94 ± 0.38 µM, as determined by isothermal titration calorimetry. Experiments using Bcl-B overexpressing HeLa cells demonstrated that this compound induced Bcl-B-dependent cell death. The current FPA represents a screen that can identify noncanonical inhibitors of Bcl-2-family proteins. ( Journal of Biomolecular Screening 2008:665-673)

High-dose CEB vs BEAM with autologous stem cell transplant in lymphoma

Between January 1996 and July 2002, 72 patients with non-Hodgkin's lymphoma or Hodgkin's disease underwent high-dose chemotherapy with autologous stem cell transplant conditioned with either cyclophosphamide, etoposide, carmustine (CEB) or carmustine, etoposide, cytarabine, melphalan (BEAM) at a single institution. In all, 52 patients received CEB and 20 patients received the BEAM regimen. Patient characteristics that were significantly different between the two groups are tumor grade and extranodal involvement (P = 0.0196, 0.0341, respectively). Regimen-related toxicities examined yielded only diarrhea occurring at a higher rate in the BEAM group (81 vs 51%, P = 0.0026), although cases were milder (92 vs 57%). Patients treated with CEB developed mucositis at a slightly higher rate (79%) than patients treated with BEAM (75%), but this difference did not reach statistical significance. However, the mucositis that occurred within the BEAM group was predominately mild (67%) in contrast to the predominance of moderate to severe cases in the CEB group (74%). In addition, patients treated with CEB required growth factor support for a longer time than patients treated with BEAM (P = 0.0399). Response rates were high in both groups, with trends favoring the BEAM group. Overall survival was higher after treatment with BEAM than with CEB (84 vs 60%).

Calcium Regulation of Exocytosis in PC12 Cells

The calcium (Ca(2+)) regulation of neurotransmitter release is poorly understood. Here we investigated several aspects of this process in PC12 cells. We first showed that osmotic shock by 1 m sucrose stimulated rapid release of neurotransmitters from intact PC12 cells, indicating that most of the vesicles were docked at the plasma membrane. Second, we further investigated the mechanism of rescue of botulinum neurotoxin E inhibition of release by recombinant SNAP-25 COOH-terminal coil, which is known to be required in the triggering stage. We confirmed here that Ca(2+) was required simultaneously with the SNAP-25 peptide, with no significant increase in release if either the peptide or Ca(2+) was present during the priming stage as well as the triggering, suggesting that SNARE (soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor) complex assembly was involved in the final Ca(2+)-triggered event. Using this rescue system, we also identified a series of acidic surface SNAP-25 residues that rescued better than wild-type when mutated, due to broadened Ca(2+) sensitivity, suggesting that this charged patch may interact electrostatically with a negative regulator of membrane fusion. Finally, we showed that the previously demonstrated stimulation of exocytosis in this system by calmodulin required calcium binding, since calmodulin mutants defective in Ca(2+)-binding were not able to enhance release.

A Discontinuous SNAP-25 C-terminal Coil Supports Exocytosis

Membrane fusion requires the formation of four-helical bundles comprised of the SNARE proteins syntaxin, vesicle-associated membrane protein (VAMP), and the synaptosomal-associated protein of 25 kDa (SNAP-25). Botulinum neurotoxin E cleaves the C-terminal coil of SNAP-25, inhibiting exocytosis of norepinephrine from permeabilized PC12 cells. Addition of a 26-mer peptide comprising the C terminus of SNAP-25 that is cleaved by the toxin restores exocytosis, demonstrating that continuity of the SNAP-25 C-terminal helix is not critical for its function. By contrast, vesicle-associated membrane protein peptides could not rescue botulinum neurotoxin D-treated cells, suggesting that helix continuity is critical for VAMP function. Much higher concentrations of the SNAP-25 C-terminal peptide are required for rescuing exocytosis (K(assembly) = approximately 460 microm) than for binding to other SNAREs in vitro (Kd < 5 microm). Each residue of the peptide was mutated to alanine to assess its functional importance. Whereas most mutants rescue exocytosis with lower efficiency than the wild type peptide, D186A rescues with higher efficiency, and kinetic analysis suggests this is because of higher affinity for the cellular binding site. This is consistent with Asp-186 contributing to negative regulation of the fusion process.

Model systems for investigating mucin gene expression in airway diseases

Overproduction of mucus and of mucin glycoproteins and goblet cell hyperplasia occurs in chronic obstructive airway diseases, including asthma and cystic fibrosis. Mucus overproduction results from alterations in several cellular processes, including altered regulation of airway mucin genes on exposure to environmental and infectious agents and to inflammatory mediators. Seven of the nine identified MUC genes (which encode the protein backbone of mucins) are normally expressed in human respiratory tract tissues. Several inflammatory mediators have now been shown to regulate expression of MUC2, MUC5AC, and MUC5B genes. Importantly, mucin gene expression can be regulated both transcriptionally and posttranscriptionally. Current information on airway mucin gene expression is summarized in this review along with an overview of airway epithelial model systems. In vitro model systems include airway epithelial carcinoma cell lines and primary normal human bronchial epithelial (NHBE) cells. In vivo systems include human respiratory tract tissues and rodent airways. Our laboratory has begun to investigate the role of cytokines on mucin gene expression in vitro and in vivo and on goblet cell metaplasia in vivo. Because cytokines can alter cell proliferation, we characterized the effect of interleukin (IL)-4 and IL-13 on the proliferation of NHBE cells and three human lung carcinoma cell lines--A549, NCI-H292, and Calu-3--that are frequently used for analyses of airway mucin gene expression. Both IL-4 and IL-13 had cell-specific effects. They increased proliferation moderately (1.2-3.0-fold) in NHBE and Calu-3 cells, but markedly inhibited proliferation of A549 cells in a dose-dependent manner. IL-4 increased proliferation of NCI-H292 cells moderately, although IL-13 had no significant effect. We also examined the role of IL-13 and IL-4 on MUC5AC messenger RNA (mRNA) expression in A549, Calu-3, and H292 cell lines and did not observe any significant effect. However, we recently showed an increase in Muc-5ac mRNA and protein expression in a murine model of ovalbumin-induced allergic asthma and in murine airways when IL-13 was delivered intranasally (Alimam, N.Z., et al. Am J. Respir. Cell Mol. Biol. 22:253--260). Thus, we speculate that IL-13 plays a role in the differentiation of murine airway epithelial cells into goblet cells, which then express Muc-5ac mRNA. A detailed analysis of the role of cytokines in airway cell differentiation and mucin gene expression both in vitro and in vivo is required to elucidate the roles of mucins in airway health and diseases. Identification of Muc-5ac as a major gene and gene product in goblet cell metaplasia should facilitate delineation of the molecular mechanisms underlying the induction and reversal of airway goblet cell metaplasia and goblet cell hyperplasia.

Sequential SNARE assembly underlies priming and triggering of exocytosis

Changes in SNARE conformations during MgATP-dependent priming of cracked PC12 cells were probed by their altered accessibility to various inhibitors. Dominant negative soluble syntaxin and, to a much lesser extent, VAMP coil domains inhibited exocytosis more efficiently after priming. Neurotoxins and an anti-SNAP25 antibody inhibited exocytosis less effectively after priming. We propose that SNAREs partially and reversibly assemble during priming, and that the syntaxin H3 domain is prevented from fully joining the complex until the arrival of the Ca2+ trigger. Furthermore, we find that mutation of hydrophobic residues of the SNAP25 C-terminal coil that contribute to SNARE core interactions affects the maximal rate of exocytosis, while mutation of charged residues on the surface of the complex affects the apparent affinity of the coil domain for the partially assembled complex.

SNARE-mediated membrane fusion

SNARE proteins have been proposed to mediate all intracellular membrane fusion events. There are over 30 SNARE family members in mammalian cells and each is found in a distinct subcellular compartment. It is likely that SNAREs encode aspects of membrane transport specificity but the mechanism by which this specificity is achieved remains controversial. Functional studies have provided exciting insights into how SNARE proteins interact with each other to generate the driving force needed to fuse lipid bilayers.

SNAREs contribute to the specificity of membrane fusion

Intracellular membrane fusion is mediated by the formation of a four-helix bundle comprised of SNARE proteins. Every cell expresses a large number of SNARE proteins that are localized to particular membrane compartments, suggesting that the fidelity of vesicle trafficking might in part be determined by specific SNARE pairing. However, the promiscuity of SNARE pairing in vitro suggests that the information for membrane compartment organization is not encoded in the inherent ability of SNAREs to form complexes. Here, we show that exocytosis of norepinephrine from PC12 cells is only inhibited or rescued by specific SNAREs. The data suggest that SNARE pairing does underlie vesicle trafficking fidelity, and that specific SNARE interactions with other proteins may facilitate the correct pairing.

Calmodulin and protein kinase C increase Ca(2+)-stimulated secretion by modulating membrane-attached exocytic machinery

The molecular mechanisms underlying the Ca(2+) regulation of hormone and neurotransmitter release are largely unknown. Using a reconstituted [(3)H]norepinephrine release assay in permeabilized PC12 cells, we found that essential proteins that support the triggering stage of Ca(2+)-stimulated exocytosis are enriched in an EGTA extract of brain membranes. Fractionation of this extract allowed purification of two factors that stimulate secretion in the absence of any other cytosolic proteins. These are calmodulin and protein kinase Calpha (PKCalpha). Their effects on secretion were confirmed using commercial and recombinant proteins. Calmodulin enhances secretion in the absence of ATP, whereas PKC requires ATP to increase secretion, suggesting that phosphorylation is involved in PKC- but not calmodulin-mediated stimulation. Both proteins modulate release events that occur in the triggering stage of exocytosis. The half-maximal increase was elicited by 3 nM PKC and 75 nM calmodulin. These results suggest that calmodulin and PKC increase Ca(2+)-activated exocytosis by directly modulating the membrane- or cytoskeleton-attached exocytic machinery downstream of Ca(2+) elevation.

SNARE complex formation is triggered by Ca2+ and drives membrane fusion

Neurotransmitter exocytosis, a process mediated by a core complex of syntaxin, SNAP-25, and VAMP (SNAREs), is inhibited by SNARE-cleaving neurotoxins. Botulinum neurotoxin E inhibition of norepinephrine release in permeabilized PC12 cells can be rescued by adding a 65 aa C-terminal fragment of SNAP-25 (S25-C). Mutations along the hydrophobic face of the S25-C helix result in SNARE complexes with different thermostabilities, and these mutants rescue exocytosis to different extents. Rescue depends on the continued presence of both S25-C and Ca2+ and correlates with complex formation. The data suggest that Ca2+ triggers S25-C binding to a low-affinity site, initiating trans-complex formation. Pairing of SNARE proteins on apposing membranes leads to bilayer fusion and results in a high-affinity cis-SNARE complex.

Syntaxin 13 mediates cycling of plasma membrane proteins via tubulovesicular recycling endosomes

Endocytosis-mediated recycling of plasma membrane is a critical vesicle trafficking step important in diverse biological processes. The membrane trafficking decisions and sorting events take place in a series of heterogeneous and highly dynamic organelles, the endosomes. Syntaxin 13, a recently discovered member of the syntaxin family, has been suggested to play a role in mediating endosomal trafficking. To better understand the function of syntaxin 13 we examined its intracellular distribution in nonpolarized cells. By confocal immunofluorescence and electron microscopy, syntaxin 13 is primarily found in tubular early and recycling endosomes, where it colocalizes with transferrin receptor. Additional labeling is also present in endosomal vacuoles, where it is often found in clathrin-coated membrane areas. Furthermore, anti-syntaxin 13 antibody inhibits transferrin receptor recycling in permeabilized PC12 cells. Immunoprecipitation of syntaxin 13 revealed that, in Triton X-100 extracts, syntaxin 13 is present in a complex(es) comprised of betaSNAP, VAMP 2/3, and SNAP-25. This complex(es) binds exogenously added alphaSNAP and NSF and dissociates in the presence of ATP, but not ATPgammaS. These results support a role for syntaxin 13 in membrane fusion events during the recycling of plasma membrane proteins.

An alpha-helical minimal binding domain within the H3 domain of syntaxin is required for SNAP-25 binding

The interaction between the proteins syntaxin 1A and SNAP-25 is a key step in synaptic vesicle docking and fusion. To define the SNAP-25 binding domain on syntaxin, we have prepared peptides that span the syntaxin H3 domain (residues 191-266), the region previously shown to be important for binding to SNAP-25, and then determined the affinities of these peptides for binding to SNAP-25. A minimal binding domain was identified within a region of 32 amino acids (residues 189-220). Its affinity for SNAP-25 is substantially enhanced by C-terminal extension (residues 221-266). Circular dichroism revealed the presence of substantial alpha-helicity in the H3 domain and in the 32-mer minimal binding domain, but not in H3 peptides that do not bind to SNAP-25. At temperatures that denature the alpha-helix of the minimal binding domain peptide, SNAP-25 binding is lost. Selected mutations in evolutionarily conserved residues of the amphiphilic alpha-helix within the minimal binding domain (e.g., residues 205 and 209) greatly reduce the affinity for SNAP-25 but have no major effect on secondary structure, suggesting that these residues may interact directly with SNAP-25. The H3 domain peptide and the minimal binding domain peptide inhibit norepinephrine release from PC12 cells. These results suggest that specific amino acid residues in the H3 domain, positioned by the underlying alpha-helical structure, are important for its binding to SNAP-25 and support the notion that this interaction is important for presynaptic vesicular exocytosis.

Hrs-2 is an ATPase implicated in calcium-regulated secretion

Associations between proteins present on neurotransmitter-containing vesicles and on the presynaptic membrane are thought to underlie docking and fusion of synaptic vesicles with the plasma membrane, which are obligate steps in regulated neurotransmission. SNAP-25 resides on the plasma membrane and interacts with syntaxin (a plasma membrane t-SNARE) and VAMP (a vesicle v-SNARE) to form a core protein complex thought to be an intermediate in a biochemical pathway that is essential for vesicular transport. We have now characterized a protein, Hrs-2, that interacts with SNAP-25. The binding of Hrs-2 to SNAP-25 is inhibited by calcium in the physiological concentration range that supports synaptic transmission. Furthermore, Hrs-2 binds and hydrolyses nucleoside triphosphates with kinetics that suggest that ATP is the physiological substrate for this enzyme. Hrs-2 is expressed throughout the brain and is present in nerve terminals. Moreover, recombinant Hrs-2 inhibits calcium-triggered 3H-noradrenaline release from permeabilized PC12 cells. Our results suggest a role for Hrs-2 in regulating secretory processes through calcium- and nucleotide-dependent modulation of vesicle-trafficking protein complexes.

Intrathecal morphine for neuropathic pain in a pregnant cancer patient

Although they have been documented, opioid treatments in obstetrics are mostly limited to methadone maintenance treatment in pregnant addicts or analgesia/anesthesia for labor. A literature search revealed no previous studies describing analgesic techniques for relief of severe cancer pain in pregnant patients. As response to morphine is dose-dependent, its conventional use can be problematic in pregnant women suffering from severe cancer pain because it is important to prevent opioid intoxication of the fetus. Furthermore, long-term exposure to morphine may result in physical dependence on the drug by the fetus, causing acute withdrawal syndrome and growth retardation after delivery. We report our experience in treating a 35-year-old pregnant female, in her 32nd gestational week, suffering from neuropathic pain due to advanced ovarian cancer. Using a microcatheter technique, we administered small doses of morphine intrathecally and successfully controlled the pain before delivery without complications in the mother and fetus. Treatment options of systemic vs spinal and epidural vs intrathecal opioids under such unique circumstances are discussed.

["Pinch-off sign" and spontaneous fracture of an implanted central venous catheter: report of a case]

Percutaneous subclavian implantation of an indwelling central venous catheter is an easy technique and provides convenient venous access for long-term intravenous therapy. Although rarely reported, spontaneous fracture of the catheter is an ominous complication which requires a prompt diagnosis and urgent treatment. We present a case of "pinch-off sign" resulting in a spontaneous fracture of an indwelling central venous catheter. A 49-year-old female breast cancer patient was admitted and Port-A-Cath was implanted for chemotherapy. Immediately after the implantation, fluid infusion and blood withdrawal was smooth until clinical "pinch-off sign" developed 3 weeks later. Chest X ray revealed no abnormal findings. Extravasation of antineoplastic drugs was noted 113 days after operation. Fracture of the indwelling catheter was found at the clavicle-rib junction. The fractured fragment was removed with a transvenous snare under fluoroscope. There was no hemodynamic derangement during the peri-operative period. Microscopy studies suggested that intermittent pressure on the catheter between the clavicle and the first rib may be responsible. The catheter wore on the medial side ue to a tearing and scissoring effect associated with free shoulder joint movement exerted additional forces on this wearing point which led to catheter fracture. The relationship between the spontaneous catheter fracture and "pinch-off sign" is reviewed. Our suggestions are: (1) By avoiding the traditional cannulation of the median subclavian vein, the lateral subclavian vein, infraclavicular axillary vein or internal jugular vein should be better routes for implantation. (2) Chest X ray (anterior-posterior and lateral view) should be examined routinely 3 weeks after the operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous succinylcholine infusion and phase II block in short surgical procedures

The study was designed to observe continuous succinylcholine infusion and phase II block in short surgical procedures (duration < 90 min). The characteristics of neuromuscular blockade produced by continuous succinylcholine infusion were observed in 15 adult patients anesthetized with nitrous-oxide-isoflurane (0.7% end tidal concentration) and fentanyl, and were compared with the single-dose technique (n = 13) in recovery time. Ulnar nerve was stimulated supramaximally with repeated train-of-four (interval = 10 sec, frequency = 2 Hz) via surface electrodes at the wrist using an electromyographic monitor (Datex, Relaxograph, Finland). The infusion rate was adjusted to maintain the height of the first twitch (T1) in each train of four at 5-10% of control twitch height. The mean duration of infusion was 50.74 +/- 18.06 minutes. The steady state infusion rate required to maintain 90% to 95% twitch depression was 83.5 +/- 21.4 micrograms/kg/min. Five patients developed phase II block (T4/T1 < 0.5) designated as IB. The other ten did not develop phase II block as IA. Recovery times (T1 = 10.50%, 10-100%) between IA and IB were not statistically significantly different. The recovery time of train-of-four fade (T1 = 10% to T1 = 100% and train of four > 75%) was 5.73 +/- 0.43 minutes. However, recovery times between continuous infusion group and single dose group were significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the combined effects of atropine and neostigmine with atropine and edrophonium on the occurrence of postoperative nausea and vomiting

To investigate the effects of different types of anticholinesterase on the incidence of the postoperative nausea and vomiting, 100 ASA class I-II adult premenopausal female patients undergoing elective lower abdominal surgery were randomized into two groups. In both groups, anesthesia was induced with thiopental and fentanyl and 50% nitrous oxide and 0.5-1.5% of isoflurane were used for anesthetic maintenance with succinylcholine 1 approximately 1.5 mg/kg for intubation and atracurium 0.3 mg/kg/hr for maintenance of muscle relaxation. Patients received reversal agents for neuromuscular blockade after operation when the evoked train-of-four (TOF) count returned to four visual responses. A mixture of atropine 8 micrograms/kg and edrophonium 0.75 mg/kg was given to the first group of patients while atropine 15 micrograms/kg and neostigmine 40 micrograms/kg was given to another group of patients. All the patients were observed for the occurrence of nausea or vomiting for 2 hours after the operation in the recovery room. The incidence of nausea was not statistically significantly different in both groups (20% in neostigmine group and 26% in edrophonium group). The occurrence of vomiting was also similar in both groups (8% in neostigmine group and 6% in edrophonium group). We concluded that there were no difference in the incidence of postoperative nausea or vomiting with the use of either neostigmine or edrophonium with atropine for antagonizing neuromuscular blockade after the lower abdominal surgery.

Analyses of surface membrane carbohydrates in parasitic flagellates of the order kinetoplastida using lectins

Crithidia fasciculata, Leishmania donovani, Leishmania major, Leishmania mexicana amazonensis, Leishmania tropica, Leishmania tarentolae, Trypanosoma sp. from Formosan bats (Tb), Trypanosoma lewisi, Trypanosoma musculi, and different strains of Trypanosoma cruzi (Tc) were cultivated at 27 degrees C in a liquid culture medium. Flagellates harvested from log phase culture were analyzed for their lectin agglutinating characteristics with concanavalin A (Con A), Peanut agglutinin, Ricinus communis agglutinin 120, soybean agglutinin (SBA), Ulex europeus agglutinin (UEA) and wheat germ agglutinin (WGA). Results indicated that all these flagellates might have D-galactose and methyl- alpha-D-manopyranoside on their surface. The presence of L-Fucose, which complexes specifically with UEA, could not be demonstrated on the surface of these flagellates. Results from quantitative comparison of surface molecules of Tb and the Tulahuen strain of Tc suggested that Tb may have more WGA-binding molecules while Tc may have more ConA-binding molecules. Pretreatment of the flagellates with 0.05% trypsin at 37 degrees C for 30 minutes caused some reduction of agglutination titers. Cell agglutination with lectins was completely inhibited or reversed in the presence of the specific lectin-binding monosaccharides.

Evidence of the non-infectivity of herpes simplex viral particles in Trichomonas vaginalis

Fan et al., employing an indirect immunofluorescent antibody (IFA) technique, reported the presence of herpes simplex virus type 2 (HSV-2) in Trichomonas vaginalis. However, using the same method, we found that the protozoa showed autofluorescence immediately after acetone fixation. In order to demonstrate the non-infectivity of HSV-2 in T. vaginalis, several other methods were performed in this study. Trichomonads were experimentally incubated together with HSV-2 and examined after immunofluorescent staining procedures. Organisms without any contact with HSV-2 were used as control. Results obtained from both vital stained and methanol-fixed organisms failed to show any fluorescence. Data from DNA fluorochrome staining, immunoblot, electron microscopy and viral titer assay were in accordance with the results of the IFA method. No obvious difference between the freshly isolated and the long term-cultured organisms could be detected by these methods. All strains of T. vaginalis investigated by this study failed to show the presence of intracellular HSV-2.

Studies on growth and distribution of Angiostrongylus cantonensis larvae in Ampullarium canaliculatus

The intramolluscan development of Angiostrongylus cantonensis larvae in Ampullarium canaliculatus, a fresh-water migrant snail which multiplies in tremendous rate in Taiwan, was followed for 28 consecutive days in this study. The snails were infected with first stage larvae of A. cantonensis and groups of three snails were sacrificed daily to study various larval stages in different organs. A. cantonensis larvae were found in all snails examined. During the first four days, they were obtained only from the digestive tract. Mouth is thus suggested as the primary route of natural infection. The first molt was observed on the fifth day of infection, and the second molt, the 12th day. Molting occurred in almost all kinds of organs examined. Studies on tissue tropism showed that the predilection site of A. cantonensis in this freshwater snail was headfoot region. Relatively few larvae were found in visceral organs including liver, heart, and ovary. Most parasites, 62.1%, recovered on the 28th day of infection were third-stage larvae.

Multiple loop purification method for selective cultivation of Pentatrichomonas hominis

It is always troublesome having protozoan cultures contaminated with other organisms in the laboratory. The method described here produces high efficiencies of purification for fast moving flagellate protozoa. A human strain Pentatrichomonas hominis was employed in the study to examine the effects of multiple loop tubes on the purification of flagellates. Trichomonads were harvested from a trypticase yeast extract iron-serum-33 (TYI-S-33) medium, adjusted to 2 X 10(5) organisms/ml, and mixed with an equal volume of 2 X 10(6) organisms/ml of bacteria. The isolation was performed at 37 degrees C in TYI-S-33 medium containing a suitable amount of antibiotics (1000 U/ml of penicillin, 1000 micrograms/ml of streptomycin, and 4 micrograms/ml of fungizone). Four days later, 10(6) organisms/ml of protozoa, free of bacteria, were observed at the other end of the single loop and the double loop tubes. About the same amount of flagellates could be found at the other end of the triple loop tube six days after incubation. The traditional U-shaped tubes were used as controls and 10(5) cells/ml of flagellates were recovered in the presence of bacteria two days after incubation. An axenic culture of P. hominis was successfully isolated from the feces of a Formosan rock-monkey, Macaca cyclopsis, by this method. Purified trichomonads were recovered from a double loop purification tube five days after incubation.