Updated evidence of the effectiveness and safety of transanal drainage tube for the prevention of anastomotic leakage after rectal low anterior resection: a systematic review and meta-analysis.

BACKGROUNDS: Anastomotic leakage (AL) represents a major complication after rectal low anterior resection (LAR). Transanal drainage tube (TDT) placement offers a potential strategy for AL prevention; however, its efficacy and safety remain contentious. METHODS: A systematic review and meta-analysis were used to evaluate the influence of TDT subsequent to LAR as part of the revision of the surgical site infection prevention guidelines of the Japanese Society of Surgical Infectious Diseases (PROSPERO registration; CRD42023476655). We searched each database, and included randomized controlled trials (RCTs) and observational studies (OBSs) comparing TDT and non-TDT outcomes. The main outcome was AL. Data were independently extracted by three authors and random-effects models were implemented. RESULTS: A total of three RCTs and 18 OBSs were included. RCTs reported no significant difference in AL rate between the TDT and non-TDT groups [relative risk (RR): 0.69, 95% confidence interval (CI) 0.42-1.15]. OBSs reported that TDT reduced AL risk [odds ratio (OR): 0.45, 95% CI 0.31-0.64]. In the subgroup excluding diverting stoma (DS), TDT significantly lowered the AL rate in RCTs (RR: 0.57, 95% CI 0.33-0.99) and OBSs (OR: 0.41, 95% CI 0.27-0.62). Reoperation rates were significantly lower in the TDT without DS groups in both RCTs (RR: 0.26, 95% CI 0.07-0.94) and OBSs (OR: 0.40, 95% CI 0.24-0.66). TDT groups exhibited a higher anastomotic bleeding rate only in RCTs (RR: 4.28, 95% CI 2.14-8.54), while shorter hospital stays were observed in RCTs [standard mean difference (SMD): -0.44, 95% CI -0.65 to -0.23] and OBSs (SMD: -0.54, 95% CI -0.97 to -0.11) compared with the non-TDT group. CONCLUSIONS: A universal TDT placement cannot be recommended for all rectal LAR patients. Some patients may benefit from TDT, such as patients without DS creation. Further investigation is necessary to identify the specific beneficiaries.

The effectiveness of fascial closure with antimicrobial-coated sutures in preventing incisional surgical site infections in gastrointestinal surgery: a systematic review and meta-analysis.

The aim of this study was to conduct a systematic review and meta-analysis of the efficacy of fascial closure using antimicrobial-sutures specifically for the prevention of surgical site infections (SSIs) in gastrointestinal surgery, as part of the revision of the SSI prevention guidelines of the Japanese Society of Surgical Infectious Diseases (JSSI). We searched CENTRAL, PubMed and ICHUSHI-Web in May 2023, and included randomized controlled trials (RCTs) comparing antimicrobial-coated and non-coated sutures for fascial closure in gastrointestinal surgery (PROSPERO No. CRD42023430377). Three authors independently screened the RCTs. We assessed the risk of bias and the GRADE criteria for the extracted data. The primary outcome was incisional SSI and the secondary outcomes were abdominal wall dehiscence and the length of postoperative hospital stay. This study was supported partially by the JSSI. A total of 10 RCTs and 5396 patients were included. The use of antimicrobial-coated sutures significantly lowered the risk of incisional SSIs compared with non-coated suture (risk ratio: 0.79, 95% confidence intervals: 0.64-0.98). In subgroup analyses, antimicrobial-coated sutures reduced the risk of SSIs for open surgeries, and when monofilament sutures were used. Antimicrobial-coated sutures did not reduce the incidence of abdominal wall dehiscence and the length of hospital stay compared with non-coated sutures. The certainty of the evidence was rated as moderate according to the GRADE criteria, because of risk of bias. In conclusion, the use of antimicrobial-coated sutures for fascial closure in gastrointestinal surgery is associated with a significantly lower risk of SSI than non-coated sutures.

Concurrent Hospice and Dialysis Care: Considerations for Implementation.

IMPORTANCE: Hospice positively impacts care at the end of life for patients and their families. However, compared to the general Medicare population, patients on dialysis are half as likely to receive hospice. Concurrent hospice and dialysis care offers an opportunity to improve care for people living with end-stage kidney disease (ESKD). OBJECTIVE: We sought to (1) develop a conceptual model of the Program and (2) identify key components, resources, and considerations for further implementation. DESIGN: We conducted a template analysis of qualitative interviews and convened a community advisory panel (CAP) to get feedback on current concurrent care design and considerations for dissemination and implementation. PARTICIPANTS: Thirty-nine patients with late-stage chronic kidney disease (CKD), family caregivers, bereaved family caregivers, hospice clinicians, nephrology clinicians, administrators, and policy experts participated in interviews. A purposive subset of 19 interviewees composed the CAP. MAIN MEASURES: Qualitative feedback on concurrent care design refinements, implementation, and resources. KEY RESULTS: Participants identified four themes that define an effective model of concurrent hospice and dialysis: it requires (1) timely goals-of-care conversations and (2) an interdisciplinary approach; (3) clear guidelines ensure smooth transitions for patients and families; and (4) hospice payment policy must support concurrent care. CAP participants provided feedback on the phases of an effective model of concurrent hospice and dialysis, and resources, including written and interactive educational materials, communication tools, workflow processes, and order sets. CONCLUSIONS: We developed a conceptual model for concurrent hospice and dialysis care and a corresponding resource list. In addition to policy changes, clinical implementation and educational resources can facilitate scalable and equitable dissemination of concurrent care. Concurrent hospice and dialysis care must be systematically evaluated via a hybrid implementation-effectiveness trial that includes the resources outlined herein, based on our conceptual model of concurrent care delivery.

Highlights Regarding Host Predisposing Factors to Recurrent Vulvovaginal Candidiasis: Chronic Stress and Reduced Antioxidant Capacity.

We studied host factors that could predispose women to develop recurrent vulvovaginal candidiasis (RVVC), including glycemia, insulin resistance, chronic stress, antioxidant capacity, overall immune status, local inflammation and vaginal microbiota. The presence of yeasts in vaginal culture was screened in 277 women, with or without signs and symptoms of VVC and RVVC. The presence of an inflammatory process and microbiota were analyzed through vaginal bacterioscopy and cervical-vaginal cytology, respectively. Fasting-blood samples were collected by standard venipuncture for biochemical analyses. Flow cytometry was employed to obtain the T helper/T cytotoxic lymphocyte ratio, and insulin resistance was assessed by the HOMA index (HI). Yeasts were isolated from 71 (26%) women: 23 (32.4%) with a positive culture but without symptoms (COL), 22 (31%) in an acute episode (VVC), and 26 (36.6%) with RVVC. C. albicans was the main yeast isolated in all clinical profiles. The control group (negative culture) comprised 206 women. Diabetes mellitus and insulin resistance were more associated with the positive-culture groups (COL, VVC and RVVC) than with negative ones. The RVVC group showed lower mean levels of cortisol than the control group and lower antioxidant capacity than all other groups. The T Helper/T cytotoxic lymphocyte ratio was similar in all groups. The RVVC group showed a similar level of vaginal inflammation to the control group, and lower than in the COL and VVC groups. Only the CVV group showed a reduction in vaginal lactobacillus microbiota. Our data suggest that both chronic stress (decreased early-morning cortisol levels) and reduced antioxidant capacity can be host predisposing factors to RVVC.

Mutant TNF-alpha, mTNF-K90R, is a novel candidate adjuvant for a mucosal vaccine against HIV.

The development of a safe and effective mucosal vaccine adjuvant is a crucial step for the development of vaccines against human immunodeficiency virus type-1 (HIV). We have previously reported that a mutant tumor necrosis factor-alpha (TNF-alpha), mTNF-K90R, possessed strong mucosal vaccine adjuvant activities in mice. Here, we evaluated the potential of mTNF-K90R as a mucosal vaccine adjuvant for the induction of systemic and mucosal immune responses against HIV. Nasal immunization of BALB/c mice with 5 microg of an HIV gp120 env protein immunogen together with mTNF-K90R induced higher serum anti-HIV gp120 protein immunoglobulin G (IgG) responses than gp120 alone. Furthermore, mTNF-K90R induced anti-gp120 IgA responses in nasal as well as vaginal washes from immunized mice, although these were not administration sites. Again, responses with mTNF-K90R were higher than with gp120 alone. These results indicate that mTNF-K90R may be applicable as amucosal adjuvant for HIV vaccination to induce both systemic and mucosal immune responses.

Cotransduction of CCL27 gene can improve the efficacy and safety of IL-12 gene therapy for cancer.

Interleukin-12 (IL-12) is a potent antitumoral cytokine, but high doses are toxic. Herein, we demonstrate that combinational transduction of IL-12 and CC-chemokine ligand-27 (CCL27) genes into pre-existing murine OV-HM ovarian carcinoma and Meth-A fibrosarcoma, by using RGD fiber-mutant adenoviral vectors, could induce tumor regression and relieve systemic side effects more effectively than either treatment alone. The antitumor activity of the IL-12 and CCL27 combination treatment was T-cell-dependent, and development of long-term specific immunity was confirmed in rechallenge experiments. Immunohistochemical analysis of tumors transduced with CCL27 gene alone or cotransduced with IL-12 and CCL27 genes showed significant increases in numbers of infiltrating CD3(+) T cells, which included both CD4(+) and CD8(+) cells. Additionally, cotransduction with IL-12 and CCL27 genes could more efficiently activate tumor-infiltrating immune cells than transduction with CCL27 alone, as determined by the frequency of perforin-positive cells and expression levels of IFN-gamma. Furthermore, mice treated with the IL-12 and CCL27 combination compared with those treated with IL-12 alone showed milder pathological changes, for example, lymphocyte infiltration and extramedullary hematopoiesis, in lung, liver and spleen. Our data provide evidence that combinational in vivo transduction with IL-12 and CCL27 genes is a promising approach for the development of cancer immunogene therapy that can simultaneously recruit and activate tumor-infiltrating immune cells.

Optimization of anti-tumor necrosis factor-alpha single chain Fv displayed on phages for creation of functional antibodies.

In this study, we converted the immunoglobulin-type anti-human tumor necrosis factor-alpha (TNF-alpha) monoclonal antibody (Mab) to a scFv-type antibody in order to assess its basic properties. The immunoglobulin VH and VL genes were isolated from the hybridoma that produced an anti-TNF-alpha neutralizing Mab, and they were then linked together to create scFvs of the VL-VH or VH-VL-form. The binding affinity to TNF-a was retained in both scFvs. Interestingly, the VL-VH-type scFv effectively inhibited the TNF-alpha-mediated cytotoxicity, while this neutralization activity was dramatically decreased in the VH-VL-type scFv. These results suggest that the VL-VH-type scFv is a suitable template to create improved versions of the anti-TNF-alpha antibody using a phage display system, and they also show that the structural format must be taken into account in manufacturing scFvs.

Augmentation of the migratory ability of DC-based vaccine into regional lymph nodes by efficient CCR7 gene transduction.

Although dendritic cell (DC)-based immunotherapy is considered a promising approach for cancer treatment, a large quantity of DC vaccine is required for effective sensitization/activation of immune cells because of the poor migratory ability of administered DCs into regional lymphoid tissue. In this study, we created a DC vaccine sufficiently transduced with CC chemokine receptor-7 gene (CCR7/DCs) by applying RGD fiber-mutant adenovirus vector (AdRGD), and investigated its immunological characteristics and therapeutic efficacy. CCR7/DCs acquired strong chemotactic activity for CC chemokine ligand-21 (CCL21) and exhibited an immunophenotype similar to mature DCs but not immature DCs with regard to major histocompatibility complex/costimulatory molecule-expression levels and allogenic T cell proliferation-stimulating ability, while maintaining inherent endocytotic activity. Importantly, CCR7/DCs injected intradermally into mice could accumulate in draining lymph nodes about 5.5-fold more efficiently than control AdRGD-applied DCs. Reflecting these properties of CCR7/DCs, DC vaccine genetically engineered to simultaneously express endogenous antigen and CCR7 could elicit more effective antigen-specific immune response in vivo using a lower dosage than DC vaccine transduced with antigen alone. Therefore, the application of CCR7/DCs having positive migratory ability to lymphoid tissues may contribute to reduction of efforts and costs associated with DC vaccine preparation by considerably reducing the DC vaccine dosage needed to achieve effective treatment by DC-based immunotherapy.

High gene expression of the mutant adenovirus vector, both in vitro and in vivo, with the insertion of integrin-targeting peptide into the fiber.

In the present study, a first-generation adenovirus (Ad) vector was modified with the RGD peptide inserted into the fiber. The insertion of an integrin-targeting sequence into the Ad vector notably enhanced the luciferase expression in the Coxsackie virus and Adenovirus Receptor-deficient A2058 and B16BL6 melanoma cells. The results of an in vivo study with tumor-bearing mice also showed that Ad-RGD-Luc had enhanced gene expression in many organs and in the B16BL6 tumor compared to that induced by a conventional Ad vector after intravenous injection.

Tumor-suppressive activities by chemokines introduced into OV-HM cells using fiber-mutant adenovirus vectors.

In this study, fiber-mutant adenovirus vectors encoding chemokines, Ad-RGD-mCCL17, Ad-RGD-mCCL21 and Ad-RGD-mCCL22 were constructed. The insertion of integrin-targeting RGD sequence into fiber knob of adenovirus vectors notably enhanced the infection efficiency into tumor cells. Among three chemokine-encoding vectors evaluated, Ad-RGD-mCCL22 showed significant tumor-suppressive activity via transduction into OV-HM cells.

Dendritic cells transduced with gp100 gene by RGD fiber-mutant adenovirus vectors are highly efficacious in generating anti-B16BL6 melanoma immunity in mice.

Dendritic cells (DCs) are the most potent professional antigen-presenting cells for the initiation of antigen-specific immune responses, and antigen-loaded DCs have been regarded as promising vaccines in cancer immunotherapy. We previously demonstrated that RGD fiber-mutant adenovirus vector (AdRGD) could attain highly efficient gene transduction into human and murine DCs. The aim of the present study is to demonstrate the predominance of ex vivo genetic DC manipulation using AdRGD in improving the efficacy of DC-based immunotherapy targeting gp100, a melanoma-associated antigen (MAA). Vaccination with murine bone marrow-derived DCs transduced with AdRGD encoding gp100 (AdRGD-gp100/mBM-DCs) dramatically improved resistance to B16BL6 melanoma challenge and pulmonary metastasis as compared with immunization with conventional Ad-gp100-transduced mBM-DCs. The improvement in antimelanoma effects upon immunization with AdRGD-gp100/mBM-DCs correlated with enhanced cytotoxic activities of natural killer (NK) cells and B16BL6-specific cytotoxic T lymphocytes (CTLs). Furthermore, in vivo depletion analysis demonstrated that CD8(+) CTLs and NK cells were the predominant effector cells responsible for the anti-B16BL6 immunity induced by vaccination with AdRGD-gp100/mBM-DCs, and that helper function of CD4(+) T cells was necessary for sufficiently eliciting effector activity. These findings clearly revealed that highly efficient MAA gene transduction to DCs by AdRGD could greatly improve the efficacy of DC-based immunotherapy against melanoma.

An investigation of adverse effects caused by the injection of high-dose TNFalpha-expressing adenovirus vector into established murine melanoma.

We previously reported that RGD fiber-mutant adenovirus vector carrying human TNFalpha cDNA (AdRGD-TNFalpha) could more effectively induce mouse B16 BL6 melanoma regression than conventional Ad-TNFalpha on intratumoral injection at less than 10(9) vector particles (VP). Although mice treated with either Ad type at 10(10) VP showed remarkable tumor regression due to hemolytic necrosis, severe adverse effects including extreme reduction in body weight were also induced by Ad treatment. Here, we attempted to elucidate the cause of the adverse effects to optimize the application of AdRGD-TNFalpha. More than 99% of systemically administered Ad accumulated in the liver, and the rate of Ad leakage into systemic circulation from the B16 BL6 tumors injected with AdRGD or conventional Ad at 10(10) VP was about 1% of the administered VP. Although the leaked Ad did not directly induce hepatotoxicity or body weight reduction, excessive TNFalpha produced in the tumors leaked into the blood at high concentrations and caused systemic inflammation, tissue denaturation, and body weight reduction in mice injected intratumorally with AdRGD-TNFalpha or Ad-TNFalpha at 10(10) VP. Our results demonstrated that an exact AdRGD-TNFalpha dosage must be determined to prevent TNFalpha leakage from tumors into systemic circulation, thereby enabling safe application of AdRGD-TNFalpha to clinical melanoma gene therapy in the future.

Therapy of rat tracheal carcinoma IC-12 in SCID mice: vascular targeting with [213Bi]-MAb TES-23.

In previous work, we have demonstrated that vascular targeting of [213Bi], an alpha-emitter, to lung blood vessels could efficiently destroy tumour colonies growing in the lung. In order to expand this approach to treatment of tumours growing in other sites, we employed the monoclonal antibody (MAb) TES-23, which reacts with CD44H, preferentially expressed on new blood vessels in tumours. Biodistribution studies of N-succinimidyl [125I] 3-iodobenzoate (SIB)-radiolabelled MAb TES-23 in ICR-severe combined immunodeficient (SCID) mice bearing subcutaneous (s.c.) and intramuscular (i.m.) IC-12 tumours, demonstrated efficient tumour uptake. At 24 h, accumulation in small tumours was 45%ID/g for s.c. tumours, and 58%ID/g for i.m. tumours and in large tumours it was 25%ID/g for s.c. tumours and 17%ID/g for i.m. tumours. Micro-autoradiography data confirmed that radiolabel accumulated in or near tumour blood vessels. Normal tissues had very low levels of radioactivity. Treatment of mice bearing small IC-12 tumours with [213Bi] MAb TES-23 retarded tumour growth relative to animals treated with cold MAb TES-23. Biodistribution and therapy experiments were also performed in BALB/c mice bearing both s.c. and i.m. syngeneic, lung carcinoma (line 498) tumours. [I(125)] SIB MAb TES-23 accumulated efficiently in both s.c. and i.m. tumours (14%ID/g and 15%ID/g, respectively, at 4 h); however, no therapeutic effect of [213Bi] MAb TES-23 treatment could be demonstrated in this model system. The data demonstrate that the timing of vascularisation of the tumours and the delivery kinetics of MAb relative to the half-life of the therapeutic radionuclide are critical for effective therapy.

Availability of lobe-selective bronchial blockade for video-assisted thoracic surgery: an initial experience with three cases.

BACKGROUND: Stable oxygenation and sufficient collapse of the lung are essential for video-assisted thoracic surgery (VATS). We performed the lobe-selective lung collapse technique with VATS for patients who had deteriorated lung function. METHODS AND RESULTS: CASE 1: A 75-year-old man who had undergone thoracoplasty showed spontaneous pneumothoraces in the contralateral side. Bullae were stapled successfully under complete isolation and collapse of diseased lobe. CASE 2: A 57-year-old woman who had undergone left lower lobectomy for lung cancer presented with another lung cancer in the right lower lobe. The right lower lobe bronchus was closed selectively, and basal segmentectomy was performed. CASE 3: A 60-year-old woman who had lost left lung function presented with right-side spontaneous pneumothoraces. The right upper lobe was collapsed selectively, and bullectomy was performed. CONCLUSION: Lobe-selective bronchial blockade may be beneficial when VATS is performed for selected patients with deteriorated lung function.

Identification of homologous biologically active sites on the N-terminal domain of laminin alpha chains.

Laminin, a multifunctional glycoprotein of the basement membrane, consists of three different subunits, alpha, beta, and gamma chains. To date, five different alpha chains have been identified. N-terminal domain VI in the alpha1 chain has various biological activities. Here we screened biologically active sequences on domain VI of the laminin alpha2, alpha3, and alpha5 chains using a large number of overlapping peptides. HT-1080 human fibrosarcoma cell attachment to the peptides was evaluated using peptide-coated plastic plates and peptide-conjugated Sepharose beads. We identified four cell adhesive sequences from laminin alpha2 chain domain VI, two sequences from the alpha3 chain, and two sequences from the laminin alpha5 chain. Sequences homologous to A13 (RQVFQVAYIIIKA, alpha1 chain 121-133) on all the alpha chains (FQIAYVIVKA, alpha2 chain 130-139; GQLFHVAYILIKF, alpha3 chain 96-108; FHVAYVLIKA, alpha5 chain 74-83) showed strong cell attachment activity. A5-16 (LENGEIVVSLVNGR, alpha5 chain 147-160) showed the strongest cell attachment activity in the plate assay, and the homologous peptide in the alpha3 chain promoted similar strong cell attachment activity. A5-16 and its homologous peptide in the alpha2 chain promoted moderate cell attachment, while the homologous peptide to A5-16 in the alpha1 chain did not show activity. A2-7 (SPSIKNGVEYHYV, alpha2 chain 108-120) showed cell attachment activity only in the plate assay, but homologous sequences in the alpha1, alpha3, and alpha5 chains did not promote activity. A2-7 promoted endothelial cell sprouting from aortic rings in vitro and melanoma colonization to murine lungs in vivo. However, none of the homologous peptides of A2-7 promoted experimental pulmonary metastasis by B16-BL6 melanoma cells. These results indicate that there are chain-specific active sites in domain VI of the laminin alpha chains, some of which contain conserved activities.

Efficient antigen gene transduction using Arg-Gly-Asp fiber-mutant adenovirus vectors can potentiate antitumor vaccine efficacy and maturation of murine dendritic cells.

Dendritic cells (DCs), the most effective antigen-presenting cells, are being studied as adjuvants or antigen delivery vehicles for eliciting T-cell-mediated antitumor immunity. Gene delivery to DCs provides an intracellular source of antigen for efficient and persistent loading to MHC class I molecules capable of activating CD8(+) CTLs, which play a central role in antitumor immunity. We previously reported that the fiber-mutant adenovirus vector (Ad) harboring the Arg-Gly-Asp (RGD) sequence in the HI loop of its fiber knob could more efficiently transduce the LacZ gene into both murine DC lines and normal human DCs than conventional Ad. In the present study, we compared immunological properties and vaccine efficacy of DC2.4 cells, an immature murine DC line, transduced with an ovalbumin (OVA) gene by fiber-mutant Ad (Ad-RGD-OVA) or conventional Ad (Ad-OVA). Ad-RGD-OVA-infected DC2.4 cells could more efficiently present OVA peptides via MHC class I molecules in a vector particle-dependent manner and induce OVA-specific CTL response by vaccination than Ad-OVA-infected DC2.4 cells. This result was correlated with the efficiency of gene transduction into DC2.4 cells by both types of Ad. Moreover, vaccination with Ad-RGD-OVA-infected DC2.4 cells could achieve an equal or greater antitumor effect against challenge with E.G7-OVA tumor cells with lower doses of Ad on infection or fewer cells for immunization than the vaccination procedure using Ad-OVA-infected DC2.4 cells. In addition, the maturation of DC2.4 cells was promoted by efficient expression of the antigen gene by the Arg-Gly-Asp fiber-mutant Ad. Flow cytometric analysis indicated enhanced expression of MHC class I and II molecules as well as CD80, CD86, CD40, and CD54, and reverse transcription-PCR analysis revealed increased levels of interleukin 12 p40 mRNA. However, infection by Ad-OVA or Ad that did not contain the cDNA of interest (Ad-Null and Ad-RGD-Null) contributed little to phenotypical changes in DC2.4 cells. On the basis of these results, we propose that DC manipulation using the Arg-Gly-Asp fiber-mutant Ad system could advance the development of more effective vaccines and allow for more convenient administration of DC-based gene immunotherapy.

Pharmacotherapy by intracellular delivery of drugs using fusogenic liposomes: application to vaccine development.

We prepared fusogenic liposomes by fusing conventional liposomes with an ultra-violet inactivated Sendai virus. Fusogenic liposomes can deliver encapsulated contents into the cytoplasm directly in a Sendai virus fusion-dependent manner. Based on the high delivery rates into the cytoplasm, we originally planned to apply the fusogenic liposomes to cancer chemotherapy and gene therapy. We have recently also examined the use of fusogenic liposomes as an antigen delivery vehicle. In terms of vaccine development, cytoplasmic delivery is crucial for the induction of the cytotoxic T lymphocyte (CTL) responses that play a pivotal role against infectious diseases and cancer. In this context, our recent studies suggested that fusogenic liposomes could deliver encapsulated antigens into the cytoplasm and induce MHC class I-restricted, antigen-specific CTL responses. In addition, fusogenic liposomes are also effective as a mucosal vaccine carrier. In this review, we present the feasibility of fusogenic liposomes as a versatile and effective antigen delivery system.

Co-production of microcystins and aeruginopeptins by natural cyanobacterial bloom.

The relationship between Microcystis composition and the production of microcystins and nontoxic peptides in bloom cells, which was regularly collected in Lake Suwa, Japan, in the summer season from 1991 to 1994, was investigated. In order to determine the structures of the nontoxic peptides, we collected large amounts of bloom materials from the same lake on July 23, 1991, and isolated three nontoxic peptides. They were named as aeruginopeptins 917S-A, -B, and -C, and their structures were mainly determined by a mass spectrometry/mass spectrometry (MS/MS) technique as 19-membered cyclic depsipeptides possessing the Ahp (3-amino-6-hydroxy-2-piperidone) moiety. An analysis of the microcystins and aeruginopeptins in the collected blood cells and their Microcystis composition suggested that the M. aeruginosa large cell size produces both microcystins and aeruginopeptins, and the production of both compounds is genetically closely related.