[9-cis retinoic acid induces apoptosis in HL-60 cells]

OBJECTIVE

To investigate the apoptosis of HL-60 cells induced by 9-cis retinoic acid (9-cis RA), and illustrate the possible molecular mechanism.

METHODS

Apoptosis was detected by morphological observation, DNA electrophoresis and flow cytometric cell cycle analysis. Bcl-2 expression was detected by flow cytometry.

RESULTS

9-cis RA initiated apoptosis of HL-60 cells after inducing them irreversibly commited to differentiation. Bcl-2 was downregulated during the differentiation and apoptosis process. 9-cis RA was more potent than all-trans retinoic acid (ATRA) did in inducing terminal differentiation associated apoptosis and in downregulation of Bcl-2 expression.

CONCLUSION

9-cis RA can induce apoptosis in HL-60 cells. Downregulation of Bcl-2 expression appears to play an important role in the apoptosis of the differentiated leukemic cells.

[Scale-up preparation of hydrophobic interaction chromatographic packing materials based on inorganic matrix]

Based on inorganic matrix controlled pore glass (CPG) and macro-pore silica sphere, by using polyethylene glycol (PEG 1000) as a ligand, a preparation method of hydrophobic interaction chromatographic (HIC) packing material was improved by adding a proper catalyst during the bonding process. The packing material can be synthesized in a scale-up batch, for example 150g for each batch, both for analytical and preparative columns. The retention of proteins, such as cytochrome C (Cyt-C), chymotrypsingen-A (Chy-A), lysozyme (Lys) and ribonuclease(Rnase), is increased with the increasing of (NH4)2SO4 concentration in the eluant 2.5 mol/L of salt concentration for the mobile phase was chosen by considering the separation efficiency and equipment life. After comparing the effect of pH for the retention of proteins it is found that the proteins are well separated at pH 7. The time of linear gradient elution program was optimized in considering the separation efficiency and speed. It is better to take 30 minutes of the gradient program for the separation. Six standard proteins can be well separated with the high-performance HIC column in the linear gradient elution program from 2.5 to 0 mol/L of (NH4)2SO4 in 50 mmol/L of phosphate buffer solution within 30 minutes. Cyt-C, Rnase, Lys and Chy-A can be separated by the HIC column based on CPG matrix. Six proteins, Cyt-C, Rnase, Lys, Chy-A, insulin(Ins) and lipase (Lip) can be well separated on the column based on silica matrix with gradient elution program. The recovery of trypsin detected with BAEE method is over 95% after purification with the HIC column.

[Somatostatin and its secretory cells in tumor surrounding mucosa in colorectal cancer patients and its significance]

The somatostatin (SS) levels in tumor surrounding mucosae were determined by RIA, and the SS secretory cells in these tissues were observed by immunocytochemistry in colorectal cancer patients. The mean SS level was higher in cancer-adjacent mucosa (CAM, 0-2 cm from the tumor) than in cancer-distant mucosa (CDM, about 5 cm from the tumor), and in CAM without atypical hyperplasia than in such mucosa with different grades of atypical hyperplasia (P < 0.01). In CAMs, there was a very significant negative correlation between the SS level and cell dysplasia (P < 0.01). The form and location of SS cells in all tumor surrounding mucosae were similar to the normal. Both the mean SS cell number and total positive degree were very significantly higher in CAM than CDM (P < 0.01). SS levels in CAMs were correlated positively with the SS cell numbers and the total positive degrees in CAM (P < 0.01). It is concluded that the elevation of SS level in CAM is mainly caused by the increase of SS cells, which secrete more SS. The change of SS in colorectal cancer surrounding mucosa may play an important role in inhibiting the development of CAM atypical hyperplasia or the tumor, and is a local defensive reaction in the body.

[Toxoplasmosis infection in pregnant women in Lanzhou]

OBJECTIVE

To investigate toxoplasmosis (TOX) infection in pregnant women.

METHODS

The blood samples from 1,250 pregnant women were tested by indirect hemaglutination (IHA) for TOX. 1,327 normal cases were included in control group.

RESULTS

The infection rate of TOX was 7.28% and 8.14% in the study and control group respectivity. There was no significant difference between the study group and control group (P > 0.05). There was no marked relationship between various age groups. (P > 0.05). No significant difference was noted in three gestational periods. Most pregnant women with of TOX infection were active and recent.

CONCLUSION

Pregnancy did not increase the chance of TOX infection.

The refined structure of human rhinovirus 16 at 2.15 A resolution: implications for the viral life cycle

BACKGROUND

Rhinoviruses belong to the picornavirus family and are small, icosahedral, non-enveloped viruses containing one positive RNA strand. Human rhinovirus 16 (HRV16) belongs to the major receptor group of rhinoviruses, for which the cellular receptor is intercellular adhesion molecule-1 (ICAM-1). In many rhinoviruses, one of the viral coat proteins (VP1) contains a hydrophobic pocket which is occupied by a fatty acid-like molecule, or so-called 'pocket factor'. Antiviral agents have been shown to bind to the hydrophobic pocket in VP1, replacing the pocket factor. The presence of the antiviral compound blocks uncoating of the virus and in some cases inhibits receptor attachment. A refined, high-resolution structure would be expected to provide further information on the nature of the pocket factor and other features previously not clearly identified.

RESULTS

The structure of native HRV16 has been refined to a resolution of 2.15 A. The hydrophobic pocket in VP1 is observed in two alternative conformations. In one of these, the pocket is filled by a pocket factor and the protein structure is similar to virus-antiviral compound complexes. In the other conformation, the hydrophobic pocket is collapsed and empty. RNA bases stack against both a tryptophan and a phenylalanine residue on the internal surface of the viral capsid. Site-directed mutagenesis of the tryptophan, which is conserved across the picornaviruses, to nonconservative residues results in non-viable virus. Five symmetry-related N termini of coat protein VP4 form a ten-stranded, antiparallel beta barrel around the base of the icosahedral fivefold axis. The N termini of VP1 are amphipathic alpha helices, which stack on the outside of this beta barrel. The N termini of VP1 and VP4 have not been observed previously in rhinovirus structures.

CONCLUSIONS

The observation of a partially occupied hydrophobic pocket in HRV16 forms a missing link between HRV14, which is always observed with no pocket factor in the native form, and rhinovirus 1A and other picornaviruses (e.g. poliovirus, coxsackievirus) which contain pocket factors. The pocket factor molecules probably regulate viral entry, uncoating and assembly. Picornavirus assembly is known to proceed via pentamers, therefore, the interaction of RNA with the conserved tryptophan residues across twofold axes between pentamers may play a role in picornavirus assembly. The positioning of a cation on the icosahedral fivefold axes and the structure of the N termini of VP4 and VP1 around these axes suggest a mechanism for the uncoating of rhinoviruses.

Enhanced DNA alkylation activities of Hoechst 33258 analogues designed for bioreductive activation

A series of analogues of Hoechst 33258, designed to be subject to bioreductive activation, were synthesized, and interactions between these compounds and pBR322 DNA were investigated. Compounds containing a quinone group reacted with DNA via two possible pathways in the presence of reductants NADH or NADPH: radical cleavage and DNA alkylation. The corresponding dimethoxy compounds, which are not subject to reduction, showed very weak DNA binding ability. The strength of alkylation reaction of the quinone derivatives is related to leaving group ability. Furthermore, the quinone compounds preferentially alkylate DNA at 5'-CG and TG sequences rather than at the AT sites preferred as binding sites of Hoechst 33258.

[The expression of IL-1 alpha gene in gingival tissue]

IL-1 is secreted by a variety of cells and plays an important role in the network of cytokines. In this study, the expression of IL-1 alpha in gingival tissue was determined with reverse transcription-polymerase chain reaction (RT-PCR). The PCR-product was confirmed by DNA sequencing. The results showed that IL-1 alpha transcription was detected in all 5 inflammatory gingival tissue samples, but it was not delected in the normal gingival tissue samples and in the samples after treatment. These findings suggested that IL-1 alpha may be a specific indicator of periodontal disease, and a potential mediator in pathogenesis of periodontitis.

Camptothecin and minor-groove binder hybrid molecules: synthesis, inhibition of topoisomerase I, and anticancer cytotoxicity in vitro

The synthesis, characterization, inhibitory activity against topoisomerase I, and biological evaluation of a series of 14 camptothecin derivatives of polypyrrolecarboxamide (lexitropsin) conjugates of two structural classes: (A) camptothecin-NHCO-lexitropsin 44-51 and (B) camptothecin-CONH-lexitropsin 38-43 are described. All 16 compounds tested, 14 conjugates plus two functionalized camptothecin controls, inhibit topoisomerase I in the concentration range 1.12-16.6 microM that divide into three distinct categories based on activity. The most active enzyme inhibitors belong to structure class A with either cationic dimethylaminium or neutral amide end groups. Generally class B conjugates are less effective in inhibiting topoisomerase I. Cytotoxic potencies of the drugs was tested against four representative human tumor cell lines: SKOV3, SKLVB, HT29, and KB. All 16 drugs gave measurable IC50 values against the KB cell line and fell into two categories with IC50 values of 0.049-0.66 microM (largely structure class B) and 1.0-48 microM (largely class A). Thus the class B conjugates, while less potent against the enzyme, contain two of the most potent drugs, 38 and 39, against KB cell lines. In contrast, in the case of the cell lines SKOV3 and HT29 there was a general correlation between the better topoisomerase inhibitors and their cell cytotoxicities.

Cations in human rhinoviruses

All known crystal structures of rhinoviruses have some uninterpreted electron density on their fivefold axes at a distance of about 152 +/- 3 A from the viral center. This density had been assumed to be a Ca2+ ion, based on its shape, height, and the presence of Ca2+ ions in the crystallization solutions. Difference electron density maps between EGTA-soaked crystals of human rhinovirus 14 (HRV14), as well as HRV16, and their corresponding native structures show that this density is an EGTA-chelatable ion. Analysis of the coordination geometry indicates that the ions in HRV3, HRV14, and HRV1A could be Ca2+ and the ion in HRV16 might be Zn2+. These cations may play a role in regulation of rhinovirus stability, although the loss of the ion itself does not seem sufficient to lead to viral disassembly.

[A gas chromatographic method for determination of Butyraldehyde as a product of butanol biotransformation in rat liver]

Analysis of butyraldehyde obtained by the interaction of butanol with cytochrome P450 II E1 in rat liver microsomes prepared by centrifugation and with the NADPH added is described in this paper. The biotransformation rate of butanol into butyraldehyde can be used as an index for the assessment of the enzyme activity of cytochrome P450 II E1. A headspace gas chromatograghic method to determine the butyraldehyde has been developed. The detection limit and CV of this method for butyraldehyde in microsomes were 0.7 micromol/L and 8.1%-9.3% respectively. The recovery was 85.3%. The results show that this is a rapid and sensitive method with less interferences and fairly good precision. The method developed has made a reliable analytical methodological foundation for the assessment of the enzyme activity of cytochrome P450 II E1.

[GC-MS analysis of essential oils from the pericarps of Illicium majus Hook.f.et. Thoms. and I. micranthum Dunn]

The chemical constituents of essential oils from the pericarps of Illicium majus and I. micranthum were analyzed. Seventy-two compounds have been identified by GC-MS, of which safrole, linalool and limonene are higher in content.

A newly developed PCR assay of H. pylori in gastric biopsy, saliva, and feces. Evidence of high prevalence of H. pylori in saliva supports oral transmission

We have recently developed a new PCR assay for the detection of H. pylori. In this study, the polymerase chain reaction (PCR) assay was used to detect H. pylori in 88 gastric biopsy, 85 saliva, and 71 fecal specimens from 88 patients. H. pylori infection was confirmed in 71 of 88 patients by culture and/or histological stain of gastric biopsies. Serum IgG antibody to H. pylori was also measured and resulted in 97% sensitivity and 94% specificity. H. pylori DNA was detected by the PCR assay in gastric biopsy specimens from all 71 patients (100% sensitivity) with proven gastric H. pylori infection but not from 17 noninfected patients (100% specificity). In saliva specimens, H. pylori DNA was identified in 57 of the 68 patients (84%) with proven gastric H. pylori infection and in three of the 17 patients without gastric H. pylori infection. However, the PCR assay was only able to detect H. pylori DNA in the feces from 15 of 61 patients (25%) with proven gastric H. pylori infection and one of the 10 patients without gastric H. pylori infection. The results show that the PCR assay is reliable for detecting the presence of H. pylori in gastric biopsy and saliva specimens. The data indicate that H. pylori exists in a higher prevalence in saliva than feces and that the fecal-oral route may be an important means of transmission of this infection in developing countries but not as significant as previously suspected in the developed countries. It is likely that the oral-oral route is more prominent.

Human rhinovirus 3 at 3.0 A resolution

BACKGROUND

The over 100 serotypes of human rhinoviruses (HRV) are major causative agents of the common cold in humans. These HRVs can be roughly divided into a major and minor group according to their cellular receptors. They can also be divided into two antiviral groups, A and B, based on their sensitivity to different capsid-binding antiviral compounds. The crystal structures of HRV14 and HRV16, major-receptor group rhinoviruses, as well as HRV1A, a minor-receptor group rhinovirus, were determined previously. Sequence comparisons had shown that HRV14 seemed to be an outlier among rhinoviruses. Furthermore, HRV14 was the only virus with no cellular 'pocket factor' in a hydrophobic pocket which is targeted by many capsid-binding antiviral compounds and is thought to regulate viral stability. HRV3, another major-receptor group virus, was chosen for study because it is one of a subset of serotypes that best represents the drug sensitivity of most rhinovirus serotypes. Both HRV3 and HRV14 belong to antiviral group A, while HRV16 and HRV1A belong to antiviral group B.

RESULTS

HRV3 was found to be very similar to HRV14 in sequence and structure. Like HRV14, crystallized HRV3 also has no bound pocket factor. The structure of HRV3 complexed with an antiviral compound, WIN56291, was also determined and found to be similar to the same antiviral compound complexed with HRV14.

CONCLUSIONS

The amino-acid sequence and structural similarity between HRV3 and HRV14 suggests that rhinoviruses in the same antiviral group have similar amino-acid sequences and structures. The similar amino-acid composition in the pocket region and the viral protein VP1 N termini in all known group B HRV sequences suggests that these viruses may all contain pocket factors and ordered N-terminal amphipathic helices in VP1. Both of these factors contribute to viral stability, which is consistent with the observations that group B rhinoviruses have a higher chance of successful transmission from one host to another and is a possible explanation for the observed higher pathogenicity of these rhinoviruses.

Effects of anti-peptide antibodies against the second extracellular loop of human M2 muscarinic acetylcholine receptors on transmembrane potentials and currents in guinea pig ventricular myocytes

The effects of anti-peptide antibodies against the second extracellular loop of human M2 muscarinic receptor on transmembrane potentials and currents in guinea pig single ventricular cells were analyzed using whole-cell patch clamp technique. These effects were compared with those of the muscarinic receptor agonists carbachol and acetylcholine. The antibodies shortened the action potential duration in a dose-dependent manner. By using a ramp or step rectangular pulse protocol, it was found that the antibodies increased the outward K+ current and decreased the inward basal ICa significantly. The reversal potential of both carbachol- and antibody-induced extra currents were close to -80 mV, being in proximity to the calculated Ek of -90 mV. A beta-adrenergic receptor agonist, isoprenaline, prolonged the action potential and increased the overshoot which could be inhibited by both antibody and carbachol. Isoprenaline increased inward ICa and outward Ik simultaneously. Both antibody and carbachol could significantly reduce the isoprenaline-stimulated ICa but not the isoprenaline-stimulated Ik. The antibody- or carbachol-induced outward K+ current and the depressant effects of antibody and carbachol on isoprenaline-stimulated ICa were partially antagonized by atropine. These results suggest that the anti-M2 muscarinic receptor antibodies display a stimulatory activity similar to muscarinic receptor agonist on the receptor-mediated electrophysiological events.

FliN is a major structural protein of the C-ring in the Salmonella typhimurium flagellar basal body

The Salmonella typhimurium FliN protein has been proposed to form a mutually interacting complex with FliG and FliM, the switch complex, that is required for flagellar morphogenesis and function. We have used affinity chromatography for purification of extended flagellar basal bodies sufficient for quantitative analysis of their protein composition. The belled, extended structure is predominantly comprised of the switch complex proteins; with FliN present in the most copies (111 +/- 13). This explains why single, missense fliN, fliG or fliM mutations, found in many non-motile strains, can alter the belled morphology. Cell lysates from these strains contained the wild-type complement of FliG, FliM and FliN; but the basal bodies lacked the outer, cytoplasmic(C)-ring of the bell and were separated by sedimentation from FliM and FliN. The amount of FliG present in basal bodies from wild-type and one such mutant, FliN100LP, was comparable. These data show that: (1) the mutations define a FliG and FliMFliN multiple contact interface important for motility. (2) FliG is responsible for the increased size of the membrane-embedded MS-ring complex of belled relative to acid-treated basal bodies. (3) FliN, together with FliM, account for most of the C-ring. As a major component of the C-ring, FliN is distinct from the other proteins implicated in axial flagellar protein export. Inner, cytoplasmic rod basal substructure, seen by negative-stain and quick-freeze replica electron microscopy, may gate such export. Lack of connectivity between the cytoplasmic rod and ring substructures places contacts between FliG and FliMFliN at the periphery of the basal body, proximal to the flagellar intramembrane ring particles. This topology is consistent with models where torque results from interaction of circumferential arrays of the switch complex proteins with the ring particles.

Transcription of dopamine D1A receptor mRNAs in rat heart

The existence of dopamine receptor subtypes in the heart has been suggested by pharmacological and biochemical techniques. So far, however, very little data is available as to the transcription of dopamine D1 subtype receptor genes in the heart. Therefore, in this study we employed reverse transcription-polymerase chain reaction (RT-PCR), which is a sensitive and highly specific method for identifying a low abundance mRNA in tissues, to determine if the D1A receptor gene was transcripted in the adult rat heart. Total RNA was isolated from the whole heart by the guanidium thiocyanate-CsCl method. Primers were based on the sequence of rat D1A cDNA cloned from the brain and corresponded to the third cytoplasmic loop of the receptor. A predicted size product (247bp) was evident from heart RNA. PCR performed in the absence of reverse transcriptase did not result in an amplification of the predicted product, indicating that these products were from cDNA and not from genomic DNA. The results demonstrate the existence of D1A receptor mRNA in the rat heart and that the D1A receptor in the heart are possibly identical to that from the brain. Since in this study the whole heart RNA was used, we cannot ascertain whether the mRNA comes from cardiac myocyte per se or from intermuscular coronary arterioles or from both.

Construction of an insecticidal baculovirus expressing insect-specific neurotoxin AaIT

Considering the factors which affect gene transcription, translation and the stability of mRNA, without changing the amino acid composition of the encoded polypeptide, AaIT gene encoding insect-specific neurotoxin was designed and synthesized according to bias in codon choice, overall G+C content and G+C content of bases at the third position in codons of polyhedrin genes of baculovirus and of plant genes as well. AaIT gene was fused behind a synthetic gp67 signal sequence and then recombined into the genome of Trichoplusia ni nuclear polyhedrosis virus (TnNPV) by transfer vector pSXIV VI+X3. The recombinant virus TnNPV-AaIT (occ+-gal-) was screened. The results of Southern blotting and SDS-PAGE demonstrated that AaIT gene had integrated into the genome of virus and expressed. Bioassays on the 3rd-instar Trichoplusia ni larvae showed that recombinant viruses TnNPV-AaIT could shorten the time of killing insect and improve the efficacy of killing agronomically important insects.

Expression of proliferating cell nuclear antigen in premalignant lesions of the larynx

PURPOSE

This study was performed to 1) evaluate the proliferative activity in premalignancies of the larynx by immunostaining for proliferating cell nuclear antigen (PCNA), 2) to examine the relationship between PCNA expression and histological diagnosis and 3) to evaluate clinical values of PCNA immunostaining.

MATERIALS AND METHODS

The percentage of PCNA-positive nuclei (PCNA index) and their highest location (PCNA grade) were evaluated in 44 specimens of premalignant lesions, 7 premalignant lesions near carcinomas, 9 normal epithelium, and 12 early invasive carcinomas of the larynx. Follow-up was conducted.

RESULTS

The mean of PCNA indices in premalignancies was significantly higher than in normal epithelium but lower than in early invasive carcinomas. PCNA index had no apparent correlation with the histological diagnosis, but in the same case, the higher degree of dysplasia showed higher PCNA index. PCNA grade showed significant correlation with the histological diagnosis. Cases with higher PCNA expression showed higher percentages of recurrence and cancerization. Premalignant lesions near carcinomas presented significantly high PCNA expression.

CONCLUSIONS

The proliferative activity in premalignancies of the larynx is higher than in normal epithelium and lower than in carcinomas. It differs from case to case, but in the same case the higher degree of dysplasia possesses higher proliferative activity. Dysplasia is associated with abnormal proliferation pattern. Special attention should be paid to those with abnormal proliferation patterns as well as high proliferative activity. PCNA immunostaining is of some referential value in predicting clinical outcome and guiding to make an early diagnosis of malignancy.

Insect-resistant tobacco plants expressing insect-specific neurotoxin AaIT

The recombinant plant expression vector pNGY-2 with designed and synthesized AaIT gene had been constructed. The AaIT gene was fused behind the sequence of TMV and inserted into expression vector under the control of two linked 35s promoters. The recombinant plasmid pNGY-2 was transferred into tobacco NC89 by agrobacterium-mediated transfer system. The GUS activity analysis and Southern blotting of regenerated plants indicated that AaIT gene had been integrated into tobacco genome. Insect bioassays showed that some transgenic plants had notable insect-resistant activity.

A study of the demographic characteristics of domestic tourists

"A sample survey was conducted [in China]: more than 6,000 questionnaires were submitted and retrieved from domestic tourists in Shanghai, Xi'ian, Huangshan, and Huashan in order to provide data for demographic analysis of the special fluid population of tourists. The paper looks at the relationship between tourists' gender, age, income, occupation, education, and family structure, as well as their tourist activity, selection of destinations, shopping, and other tourist behaviors."

FliG and FliM distribution in the Salmonella typhimurium cell and flagellar basal bodies

Salmonella typhimurium FliG and FliM are two of three proteins known to be necessary for flagellar morphogenesis as well as energization and switching of flagellar rotation. We have determined FliG and FliM levels in cellular fractions and in extended flagellar basal bodies, using antibodies raised against the purified proteins. Both proteins were found predominantly in the detergent-solubilized particulate fraction containing flagellar structures. Basal flagellar fragments could be separated from partially constructed basal bodies by gel filtration chromatography. FliG and FliM were present in an approximately equimolar ration in all gel-filtered fractions. FliG and FliM copy numbers, estimated relative to that of the hook protein from the early fractions containing long, basal, flagellar fragments, were (means +/- standard errors) 41 +/- 10 and 37 +/- 13 per flagellum, respectively. Extended structures were present in the earliest identifiable basal bodies. Immunoelectron microscopy and immunoblot gel analysis suggested that the FliG and, to a less certain degree, the FliM contents of these structures were the same as those for the complete basal bodies. These facts are consistent with the postulate that FliG and FliM affect flagellar morphogenesis as part of the extended basal structure, formation of which is necessary for assembly of more-distal components of the flagellum. The determined stoichiometries will provide important constraints to modelling energization and switching of flagellar rotation.

Apoptosis and c-jun induction by cisplatin in a human melanoma cell line and a drug-resistant daughter cell line

Cisplatin resistance was developed in the human melanoma cell line RPMI8322 by repeated short-term exposures to cisplatin. The most resistant daughter cell line, RPMI8322/CDDP-300, was 4-fold resistant to cisplatin, and partially cross-resistant to carboplatin, melphalan and UV, but not to BCNU. RPMI8322/CDDP-300 cells showed less apoptosis after cisplatin than the parental cells. The cisplatin resistance was not paralleled by a similar reduction in cellular cisplatin accumulation or DNA cross-links in RPMI8322/CDDP-300 cells, and these cells exhibited no increase in cellular glutathione or in mRNA encoding the DNA excision repair protein ERCC1 and XPB. Induction of c-jun mRNA by cisplatin was considerably lower in RPMI8322/CDDP-300 cells than in RPMI8322 cells, consistent with the possibility that c-jun induction may be involved in a pathway that triggers apoptosis after exposure to DNA damaging agents. However, c-jun induction is not necessary for apoptosis, since cisplatin also induced apoptosis in A14 rat embryo fibroblasts, cells in which the c-jun gene is deleted.

Structural effects of mutations in Salmonella typhimurium flagellar switch complex

Mutations in Salmonella typhimurium fliG, fliM and fliN give rise either to non-flagellate, non-motile or non-chemotactic mutant bacteria. The FliG, FliM and FliN proteins form part of recently characterized extended flagellar basal structures, and have been postulated to form a mutually interacting structural complex. We have examined basal body preparations from non-motile or non-chemotactic fliG, fliM and fliN mutant strains by electron microscopy and immunoblot gel analysis. Most flagellar preparations isolated from the non-motile mutants lacked FliM, but contained FliG. The basal bodies lacked the belled morphology characteristic of the wild-type structures, but had protrusions which could be labelled with anti-FliG. Non-motile mutant preparations severely depleted of FliG but containing FliM were also obtained. These preparations contained extended, belled flagellar structures that were labelled with anti-FliM. Thus, FliM is part of the shell of the extended structures responsible for the belled morphology, while FliG may be part of the inner substructure. The extended basal structures from a FliG temperature-sensitive mutant strain rapidly lost FliM, as well as FliG, upon a shift to a non-permissive temperature, implying interaction between the FliG- and FliM-containing substructures. In dramatic contrast to non-motile mutants, extended basal structures isolated from non-chemotactic mutants were indistinguishable from wild-type structures. This difference may reflect the energetics of the different protein-protein interactions operative during torque generation and the switching of rotation sense.