Hookworms dynamically respond to loss of Type 2 immune pressure.

The impact of the host immune environment on parasite transcription and fitness is currently unknown. It is widely held that hookworm infections have an immunomodulatory impact on the host, but whether the converse is true remains unclear. Immunity against adult-stage hookworms is largely mediated by Type 2 immune responses driven by the transcription factor Signal Transducer and Activator of Transcription 6 (STAT6). This study investigated whether serial passage of the rodent hookworm Nippostrongylus brasiliensis in STAT6-deficient mice (STAT6 KO) caused changes in parasites over time. After adaptation to STAT6 KO hosts, N. brasiliensis increased their reproductive output, feeding capacity, energy content, and body size. Using an improved N. brasiliensis genome, we found that these physiological changes corresponded with a dramatic shift in the transcriptional landscape, including increased expression of gene pathways associated with egg production, but a decrease in genes encoding neuropeptides, proteases, SCP/TAPS proteins, and transthyretin-like proteins; the latter three categories have been repeatedly observed in hookworm excreted/secreted proteins (ESPs) implicated in immunosuppression. Although transcriptional changes started to appear in the first generation of passage in STAT6 KO hosts for both immature and mature adult stages, downregulation of the genes putatively involved in immunosuppression was only observed after multiple generations in this immunodeficient environment. When STAT6 KO-adapted N. brasiliensis were reintroduced to a naive WT host after up to 26 generations, this progressive change in host-adaptation corresponded to increased production of inflammatory cytokines by the WT host. Surprisingly, however, this single exposure of STAT6 KO-adapted N. brasiliensis to WT hosts resulted in worms that were morphologically and transcriptionally indistinguishable from WT-adapted parasites. This work uncovers remarkable plasticity in the ability of hookworms to adapt to their hosts, which may present a general feature of parasitic nematodes.

Parasitic nematode fatty acid- and retinol-binding proteins compromise host immunity by interfering with host lipid signaling pathways.

Parasitic nematodes cause significant morbidity and mortality globally. Excretory/secretory products (ESPs) such as fatty acid- and retinol- binding proteins (FARs) are hypothesized to suppress host immunity during nematode infection, yet little is known about their interactions with host tissues. Leveraging the insect parasitic nematode, Steinernema carpocapsae, we describe here the first in vivo study demonstrating that FARs modulate animal immunity, causing an increase in susceptibility to bacterial co-infection. Moreover, we show that FARs dampen key components of the fly immune response including the phenoloxidase cascade and antimicrobial peptide (AMP) production. Our data also reveal that FARs deplete lipid signaling precursors in vivo as well as bind to these fatty acids in vitro, suggesting that FARs elicit their immunomodulatory effects by altering the availability of lipid signaling molecules necessary for an efficient immune response. Collectively, these data support a complex role for FARs in immunosuppression in animals and provide detailed mechanistic insight into parasitism in phylum Nematoda.

A Revised Adaptation of the Smart-Seq2 Protocol for Single-Nematode RNA-Seq.

The advancement of transcriptomic studies in plant parasitic nematodes will greatly benefit from the development of single-nematode RNA-seq methods. Since many plant parasitic nematodes are obligate parasites, it is often difficult to efficiently obtain sufficient amounts of nematodes for transcriptomic studies. Here we have adapted SMART-Seq2 for single-nematode RNA-seq requiring only an individual nematode for a sample replicate. This protocol provides a detailed step-by-step procedure of the RNA-seq workflow starting from lysis of the nematode to quantification of transcripts using a user-friendly online platform.

Differentiating between scavengers and entomopathogenic nematodes: Which is Oscheius chongmingensis?

Entomopathogenic nematodes (EPNs) continue to be explored for their potential usefulness in biological control and pest management programs. As more insect-associated species of nematodes are discovered and described, it is possible that scavengers and kleptoparasites may be mischaracterized as EPNs. If a nematode species is truly an entomopathogen it should display similar infectivity, as well as behaviors and preferences, to those of established EPN species, such as Steinernema carpocapsae. In this study we evaluated dauers of the putative EPN species Oscheius chongmingensis. We examined virulence, odor preferences as a measure of host-seeking behavior, and features of its bacterial symbiont Serratia nematodiphila. We determined that O. chongmingensis behaves more like a scavenger than an EPN. Not only did O. chongmingensis exhibit very poor pathogenicity in Galleria mellonella (wax moth larvae), it also displayed odor (host-seeking) preferences that are contrary to the well-known EPN S. carpocapsae. We also found that the bacterial symbiont of O. chongmingensis was antagonistic to S. carpocapsae; S. carpocapsae IJs were unable to develop when S. nematodiphila was a primary food source. We conclude that there is insufficient evidence to support the characterization of O. chongmingensis as an EPN; and based on the attributes of its preferences for already-infected or deceased hosts, suggest that this nematode is a scavenger, which may be on an evolutionary trajectory leading to an entomopathogenic lifestyle.

A core set of venom proteins is released by entomopathogenic nematodes in the genus Steinernema.

Parasitic helminths release molecular effectors into their hosts and these effectors can directly damage host tissue and modulate host immunity. Excreted/secreted proteins (ESPs) are one category of parasite molecular effectors that are critical to their success within the host. However, most studies of nematode ESPs rely on in vitro stimulation or culture conditions to collect the ESPs, operating under the assumption that in vitro conditions mimic actual in vivo infection. This assumption is rarely if ever validated. Entomopathogenic nematodes (EPNs) are lethal parasites of insects that produce and release toxins into their insect hosts and are a powerful model parasite system. We compared transcriptional profiles of individual Steinernema feltiae nematodes at different time points of activation under in vitro and in vivo conditions and found that some but not all time points during in vitro parasite activation have similar transcriptional profiles with nematodes from in vivo infections. These findings highlight the importance of experimental validation of ESP collection conditions. Additionally, we found that a suite of genes in the neuropeptide pathway were downregulated as nematodes activated and infection progressed in vivo, suggesting that these genes are involved in host-seeking behavior and are less important during active infection. We then characterized the ESPs of activated S. feltiae infective juveniles (IJs) using mass spectrometry and identified 266 proteins that are released by these nematodes. In comparing these ESPs with those previously identified in activated S. carpocapsae IJs, we identified a core set of 52 proteins that are conserved and present in the ESPs of activated IJs of both species. These core venom proteins include both tissue-damaging and immune-modulating proteins, suggesting that the ESPs of these parasites include both a core set of effectors as well as a specialized set, more adapted to the particular hosts they infect.

Sand crickets (Gryllus firmus) have low susceptibility to entomopathogenic nematodes and their pathogenic bacteria.

The entomopathogenic nematode, Steinernema scapterisci, a specialist parasite of crickets, has been successfully used to combat the southern mole cricket, Neoscapteriscus borellii, which is an invasive pest of turf grass. As an entomopathogenic nematode, S. scapterisci causes rapid death of the insects it infects and uses bacteria to facilitate its parasitism. However, our understanding of the relative contributions of the nematode, S. scapterisci, and its bacterial symbiont, Xenorhabdus innexi, to parasitism remains limited. Here we utilized the sand cricket, Gryllus firmus, as a model host to evaluate the contributions of the EPNs S. scapterisci and S. carpocapsae, as well as their symbiotic bacteria, X. innexi and X. nematophila, respectively, to the virulence of the nematode-bacterial complex. We found that G. firmus has reduced susceptibility to infection from both S. scapterisci and the closely related generalist parasite S. carpocapsae, but that S. scapterisci is much more virulent than S. carpocapsae. Further, we found that N. borellii has reduced susceptibility to X. nematophila, and that G. firmus has reduced susceptibility to X. nematophila, X. innexi, and Serratia marcescens, much more so than other insects that have been studied. We found that the reduced susceptibility of G. firmus to bacterial infection is dependent on development, with adults being less susceptible to infection than nymphs. Our data provide evidence that unlike other EPNs, the virulence of S. scapterisci to crickets is dependent on the nematode rather than the bacterial symbiont that it carries and we speculate that S. scapterisci may be evolving independence from X. innexi.

Host- and Helminth-Derived Endocannabinoids That Have Effects on Host Immunity Are Generated during Infection.

Helminths have coevolved with their hosts, resulting in the development of specialized host immune mechanisms and parasite-specific regulatory products. Identification of new pathways that regulate helminth infection could provide a better understanding of host-helminth interaction and may identify new therapeutic targets for helminth infection. Here we identify the endocannabinoid system as a new mechanism that influences host immunity to helminths. Endocannabinoids are lipid-derived signaling molecules that control important physiologic processes, such as feeding behavior and metabolism. Following murine infection with Nippostrongylus brasiliensis, an intestinal nematode with a life cycle similar to that of hookworms, we observed increased levels of endocannabinoids (2-arachidonoylglycerol [2-AG] or anandamide [AEA]) and the endocannabinoid-like molecule oleoylethanolamine (OEA) in infected lung and intestine. To investigate endocannabinoid function in helminth infection, we employed pharmacological inhibitors of cannabinoid subtype receptors 1 and 2 (CB1R and CB2R). Compared to findings for vehicle-treated mice, inhibition of CB1R but not CB2R resulted in increased N. brasiliensis worm burden and egg output, associated with significantly decreased expression of the T helper type 2 cytokine interleukin 5 (IL-5) in intestinal tissue and splenocyte cultures. Strikingly, bioinformatic analysis of genomic and transcriptome sequencing (RNA-seq) data sets identified putative genes encoding endocannabinoid biosynthetic and degradative enzymes in many parasitic nematodes. To test the novel hypothesis that helminth parasites produce their own endocannabinoids, we measured endocannabinoid levels in N. brasiliensis by mass spectrometry and quantitative PCR and found that N. brasiliensis parasites produced endocannabinoids, especially at the infectious larval stage. To our knowledge, this is the first report of helminth- and host-derived endocannabinoids that promote host immune responses and reduce parasite burden.

Hematopoietic cell-derived RELMα regulates hookworm immunity through effects on macrophages.

Resistin-like molecule α (RELMα) is a highly secreted protein in type 2 (Th2) cytokine-induced inflammation including helminth infection and allergy. In infection with Nippostrongylus brasiliensis (Nb), RELMα dampens Th2 inflammatory responses. RELMα is expressed by immune cells, and by epithelial cells (EC); however, the functional impact of immune versus EC-derived RELMα is unknown. We generated bone marrow (BM) chimeras that were RELMα deficient (RELMα-/- ) in BM or non BM cells and infected them with Nb. Non BM RELMα-/- chimeras had comparable inflammatory responses and parasite burdens to RELMα+/+ mice. In contrast, both RELMα-/- and BM RELMα-/- mice exhibited increased Nb-induced lung and intestinal inflammation, correlated with elevated Th2 cytokines and Nb killing. CD11c+ lung macrophages were the dominant BM-derived source of RELMα and can mediate Nb killing. Therefore, we employed a macrophage-worm co-culture system to investigate whether RELMα regulates macrophage-mediated Nb killing. Compared to RELMα+/+ macrophages, RELMα-/- macrophages exhibited increased binding to Nb and functionally impaired Nb development. Supplementation with recombinant RELMα partially reversed this phenotype. Gene expression analysis revealed that RELMα decreased cell adhesion and Fc receptor signaling pathways, which are associated with macrophage-mediated helminth killing. Collectively, these studies demonstrate that BM-derived RELMα is necessary and sufficient to dampen Nb immune responses, and identify that one mechanism of action of RELMα is through inhibiting macrophage recruitment and interaction with Nb. Our findings suggest that RELMα acts as an immune brake that provides mutually beneficial effects for the host and parasite by limiting tissue damage and delaying parasite expulsion.

Adapting the Smart-seq2 Protocol for Robust Single Worm RNA-seq.

Most nematodes are small worms that lack enough RNA for regular RNA-seq protocols without pooling hundred to thousand of individuals. We have adapted the Smart-seq2 protocol in order to sequence the transcriptome of an individual worm. While developed for individual Steinernema carpocapsae and Caenorhabditis elegans larvae as well as embryos, the protocol should be adaptable for other nematode species and small invertebrates. In addition, we describe how to analyze the RNA-seq results using the Galaxy online environment. We expect that this method will be useful for the studying gene expression variances of individual nematodes in wild type and mutant backgrounds.

Activated entomopathogenic nematode infective juveniles release lethal venom proteins.

Entomopathogenic nematodes (EPNs) are unique parasites due to their symbiosis with entomopathogenic bacteria and their ability to kill insect hosts quickly after infection. It is widely believed that EPNs rely on their bacterial partners for killing hosts. Here we disproved this theory by demonstrating that the in vitro activated infective juveniles (IJs) of Steinernema carpocapsae (a well-studied EPN species) release venom proteins that are lethal to several insects including Drosophila melanogaster. We confirmed that the in vitro activation is a good approximation of the in vivo process by comparing the transcriptomes of individual in vitro and in vivo activated IJs. We further analyzed the transcriptomes of non-activated and activated IJs and revealed a dramatic shift in gene expression during IJ activation. We also analyzed the venom proteome using mass spectrometry. Among the 472 venom proteins, proteases and protease inhibitors are especially abundant, and toxin-related proteins such as Shk domain-containing proteins and fatty acid- and retinol-binding proteins are also detected, which are potential candidates for suppressing the host immune system. Many of the venom proteins have conserved orthologs in vertebrate-parasitic nematodes and are differentially expressed during IJ activation, suggesting conserved functions in nematode parasitism. In summary, our findings strongly support a new model that S. carpocapsae and likely other Steinernema EPNs have a more active role in contributing to the pathogenicity of the nematode-bacterium complex than simply relying on their symbiotic bacteria. Furthermore, we propose that EPNs are a good model system for investigating vertebrate- and human-parasitic nematodes, especially regarding the function of excretory/secretory products.

Infective Juveniles of the Entomopathogenic Nematode Steinernema scapterisci Are Preferentially Activated by Cricket Tissue.

Entomopathogenic nematodes are a subgroup of insect-parasitic nematodes that are used in biological control as alternatives or supplements to chemical pesticides. Steinernema scapterisci is an unusual member of the entomopathogenic nematode guild for many reasons including that it is promiscuous in its association with bacteria, it can reproduce in the absence of its described bacterial symbiont, and it is known to have a narrow host range. It is a powerful comparative model within the species and could be used to elucidate parasite specialization. Here we describe a new method of efficiently producing large numbers of S. scapterisci infective juveniles (IJs) in house crickets and for quantifying parasitic activation of the IJs upon exposure to host tissue using morphological features. We found that parasite activation is a temporal process with more IJs activating over time. Furthermore, we found that activated IJs secrete a complex mixture of proteins and that S. scapterisci IJs preferentially activate upon exposure to cricket tissue, reaffirming the description of S. scapterisci as a cricket specialist.

Genomics of Entomopathogenic Nematodes and Implications for Pest Control.

Entomopathogenic nematodes (EPNs) have been used in biological control but improvement is needed to realize their full potential for broader application in agriculture. Some improvements have been gained through selective breeding and the isolation of additional species and populations. Having genomic sequences for at least six EPNs opens the possibility of genetic improvement, either by facilitating the selection of candidate genes for hypothesis-driven studies of gene-trait relations or by genomics-assisted breeding for desirable traits. However, the genomic data will be of limited use without a more mechanistic understanding of the genes underlying traits that are important for biological control. Additionally, molecular tools are required to fully translate the genomic resources into further functional studies and better biological control.

Proteomics and transcriptomics analyses of Arabidopsis floral buds uncover important functions of ARABIDOPSIS SKP1-LIKE1.

BACKGROUND: The ARABIDOPSIS SKP1-LIKE1 (ASK1) protein functions as a subunit of SKP1-CUL1-F-box (SCF) E3 ubiquitin ligases. Previous genetic studies showed that ASK1 plays important roles in Arabidopsis flower development and male meiosis. However, the molecular impact of ASK1-containing SCF E3 ubiquitin ligases (ASK1-E3s) on the floral proteome and transcriptome is unknown. RESULTS: Here we identified proteins that are potentially regulated by ASK1-E3s by comparing floral bud proteomes of wild-type and the ask1 mutant plants. More than 200 proteins were detected in the ask1 mutant but not in wild-type and >300 were detected at higher levels in the ask1 mutant than in wild-type, but their RNA levels were not significantly different between wild-type and ask1 floral buds as shown by transcriptomics analysis, suggesting that they are likely regulated at the protein level by ASK1-E3s. Integrated analyses of floral proteomics and transcriptomics of ask1 and wild-type uncovered several potential aspects of ASK1-E3 functions, including regulation of transcription regulators, kinases, peptidases, and ribosomal proteins, with implications on possible mechanisms of ASK1-E3 functions in floral development. CONCLUSIONS: Our results suggested that ASK1-E3s play important roles in Arabidopsis protein degradation during flower development. This study opens up new possibilities for further functional studies of these candidate E3 substrates.

Pollen S-locus F-box proteins of Petunia involved in S-RNase-based self-incompatibility are themselves subject to ubiquitin-mediated degradation.

Many flowering plants show self-incompatibility, an intra-specific reproductive barrier by which pistils reject self-pollen to prevent inbreeding and accept non-self pollen to promote out-crossing. In Petunia, the polymorphic S-locus determines self/non-self recognition. The locus contains a gene encoding an S-RNase, which controls pistil specificity, and multiple S-locus F-box (SLF) genes that collectively control pollen specificity. Each SLF is a component of an SCF (Skp1/Cullin/F-box) complex that is responsible for mediating degradation of non-self S-RNase(s), with which the SLF interacts, via the ubiquitin-26S proteasome pathway. A complete set of SLFs is required to detoxify all non-self S-RNases to allow cross-compatible pollination. Here, we show that SLF1 of Petunia inflata is itself subject to degradation via the ubiquitin-26S proteasome pathway, and identify an 18 amino acid sequence in the C-terminal region of S2 -SLF1 (SLF1 of S2 haplotype) that contains a degradation motif. Seven of the 18 amino acids are conserved among all 17 SLF proteins of S2 haplotype and S3 haplotype involved in pollen specificity, suggesting that all SLF proteins are probably subject to similar degradation. Deleting the 18 amino acid sequence from S2 -SLF1 stabilized the protein but abolished its function in self-incompatibility, suggesting that dynamic cycling of SLF proteins is an integral part of their function in self-incompatibility.

Regulation of the Arabidopsis anther transcriptome by DYT1 for pollen development.

Several genes encoding transcription factors have been shown to be essential for male fertility in plants, suggesting that transcriptional regulation is a major mechanism controlling anther development in Arabidopsis. DYSFUNCTIONAL TAPETUM 1 (DYT1), a putative bHLH transcription factor, plays a critical role in regulating tapetum function and pollen development. Here, we compare the transcriptomes of young anthers of wild-type and the dyt1 mutant, demonstrating that DYT1 is upstream of at least 22 genes encoding transcription factors and regulates the expression of a large number of genes, including genes involved in specific metabolic pathways. We also show that DYT1 can bind to DNA in a sequence-specific manner in vitro, and induction of DYT1 activity in vivo activated the expression of the downstream transcription factor genes MYB35 and MS1. We generated DYT1-SRDX transgenic plants whose fertility was dramatically reduced, implying that DYT1 probably acts as a transcriptional activator. Furthermore, we used yeast two-hybrid assays to show that DYT1 forms homodimers and heterodimers with other bHLH transcription factors. Our results demonstrate the important role of DYT1 in regulating anther transcriptome and function, and supporting normal pollen development.

Dual role of BKI1 and 14-3-3 s in brassinosteroid signaling to link receptor with transcription factors.

The plasma membrane-localized plant steroid hormone receptor, BRASSINOSTEROID INSENSITIVE 1 (BRI1), is quiescent in the absence of steroids, largely due to a negative regulator, BRI1 KINASE INHIBITOR 1 (BKI1). Here, we report that the steroid-induced, plasma membrane-dissociated and phosphorylated BKI1 also plays positive roles in BR signaling by interacting with a subset of 14-3-3 proteins. The cytosolic fraction of BKI1 carboxyl terminal region enhances BR signaling. Mutations of two serine residues in this region lead to reduced phosphorylation by the BRI1 kinase and constitutive plasma membrane localization. The 14-3-3 proteins can interact with the phosphorylated BKI1 through a motif that contains the two phosphorylation sites to release inhibition of BRI1 by BKI1. Meanwhile, the cytosolic BKI1 antagonizes the 14-3-3 s and enhances accumulation of BRI1 EMS SUPPRESSOR 1 (BES1)/BRASSINAZOLE RESISTANT 1 (BZR1) in the nucleus to regulate BR-responses.

[Diagnosis and treatments for recurrent malignant tumors involving the carotid artery].

OBJECTIVE: To study the diagnosis and treatment of the malignant tumor involving carotid artery. METHODS: A total of 23 cases of recurrent malignant tumors involving the carotid artery were included in this study. For the primary cancers, 8 of 23 cases were laryngeal carcinomas, 10 hypopharyngeal carcinomas, 2 thyroid carcinomas, 1 tonsil carcinoma, 1 parotid gland carcinoma, and 1 hypopharyngeal sarcoma with the invasion of cervical esophagus. Detailed evaluation on each case was performed before treatment. The relations of recurrent tumors with neck blood vessels were determined with enhanced CT/CTA. Of 23 cases with recurrent malignant tumors involving the carotid artery, 16 cases received surgery and 7 cases received the palliative treatment without operation. RESULTS: Seven patients with palliative treatments died of hemorrhage from the invaded neck blood vessels, systemic failure or pulmonary metastasis in six months. Of 16 cases with surgery, recurrent tumors were completely excised in 14 cases and there were residual tumor tissues on artery walls in 2 cases. Within 16 surgical cases, 2 cases died of neck hemorrhoea after one week because of infection, 2 cases died of lung metastasis 8 months later, 3 cases died of neck local recurrence 1 year later, 2 cases died of lung metastasis after 2 years, 1 case died of neck local recurrence 2 years later and 1 case died of a heart attack 2 years later. The rest 5 cases were alive. CONCLUSIONS: Enhancement CT/CTA can used in the evaluation for recurrent malignant tumors involving the carotid artery. Surgical treatments can be applied to some selected patients, which can improve the quality of life and survival time of the patients.

[Swallowing and laryngeal function preserving in surgical treatment of the head and neck tumors involving the tongue root].

OBJECTIVE: To investigate the surgical technique which could preserve the swallowing and laryngeal function effectively in the malignant head and neck tumors involving the tongue root. METHODS: From January 2003 to December 2008, 31 cases of malignant head and neck tumors involving the tongue base had been treated in this hospital were retrospectively analyzed. There were 27 males and 4 females in which 9 cases of primary malignant tumor were from the base of tongue; 3 cases were from the tonsil, 11 cases were from supraglottic laryngeal carcinoma and 8 cases were from hypopharyngeal carcinoma. Preserved the lingual artery of the reserved side and the normal tissue of the root of tongue according to the clinical anatomy of lingual artery during the operation. If preoperative CT had indicated that bilateral lingual arteries were involved, total glossectomy should have been done. The epiglottis, vocal cords and the ventricular band of larynx was preserved as much as possible for the mechanisms of laryngeal function. RESULTS: In this group, residual tongue necrosis did not occurred. One case with total glossectomy didn't remove the trachea cannula. Five had total laryngectomy. The other 25 cases decannulated from 14th days to 90th days postoperatively. The time of oral feeding was started from 10th days to 31st days postoperatively. Two cases with hypopharyngeal carcinoma developed fistula, which were cured by dressing change. Two with root of tongue cancer and 1 with tonsil cancer had postoperative infection and healed in 2 weeks. The median follow-up time was 36 months, and the Kaplan-Meier 3-years and 5-years survival rates were 79.5% and 69.6% respectively. CONCLUSIONS: In the surgical treatments of the malignant head and neck tumors involving the base of tongue, the excisions and reconstructions of the primary tumor and the involved tongue base according to the clinical anatomy of lingual artery and the protection mechanisms of laryngeal function during the operation was one of the most effective technique to preserve the swallowing and laryngeal function.

[Anatomical landmarks of skull base and safety of the skull base surgery].

OBJECTIVE: In order to improve the safety of skull base surgery and to completely resect the skull base tumors, the anatomical landmarks of skull base were studied. METHODS: 29 cases of skull base surgery were performed between 1992 and 2002, and their clinical data were retrospectively analysed. The anatomical landmarks of cranial base, such as comb, pterygoid process, spine of temporal bone, styloid process, and internal caroid artery, were analysed in preoperative diagnosis and operative treatment of various kinds of skull base tumors. RESULTS: In the early stages, because of lacking the knowledge of anatomical landmarks of the skull base, the surgery lasted longer, part of skull base tumors remained and operative blood lose was much more than that in later stage. In the later stage, no operative death and severe complications were found in 26 cases which underwent various kinds of skull base surgery. The survival rates at 3 and 5 years were 72.2% and 35.7% respectively for malignant tumors. CONCLUSIONS: Comb, pterygoid process, spine of temporal bone, styloid process, internal caroid artery and their adjacent structures were important anatomical landmarks for operative treatment of anterior, middle and lateral cranial base tumors. It was important to know the anatomical landmarks to ensure the safety of the skull base surgery.

[The surgical treatment of cancer in the base of tongue].

OBJECTIVE: To seek for a better approach for the resection of carcinoma of the base of tongue. METHOD: From 1991 to 2000, all 21 cases of tongue base carcinoma had been removed by transhyoid pharyngotomy(11 cases), mandibulectomy(7 cases) and step-liked mandibulotomy (3 cases). RESULT: Three patients with step-liked mandibulotomy had speech disorder and dysphagy. The rest had satisfactory speech and swallowing functions. During followed-up of 2-5 years, 2 cases lost follow-up, 18 cases were alive at 2 years, 13 cases were alive at 3 years, 5 cases 5 years. CONCLUSION: Transhyoid pharyngotomy provides good exposure to resect those tumors that involve the base of tongue, epiglottis, hypopharynx and larynx.