Evaluation of QSAR models for predicting mutagenicity: outcome of the Second Ames/QSAR international challenge project

Quantitative structure-activity relationship (QSAR) models are powerful in silico tools for predicting the mutagenicity of unstable compounds, impurities and metabolites that are difficult to examine using the Ames test. Ideally, Ames/QSAR models for regulatory use should demonstrate high sensitivity, low false-negative rate and wide coverage of chemical space. To promote superior model development, the Division of Genetics and Mutagenesis, National Institute of Health Sciences, Japan (DGM/NIHS), conducted the Second Ames/QSAR International Challenge Project (2020-2022) as a successor to the First Project (2014-2017), with 21 teams from 11 countries participating. The DGM/NIHS provided a curated training dataset of approximately 12,000 chemicals and a trial dataset of approximately 1,600 chemicals, and each participating team predicted the Ames mutagenicity of each trial chemical using various Ames/QSAR models. The DGM/NIHS then provided the Ames test results for trial chemicals to assist in model improvement. Although overall model performance on the Second Project was not superior to that on the First, models from the eight teams participating in both projects achieved higher sensitivity than models from teams participating in only the Second Project. Thus, these evaluations have facilitated the development of QSAR models.

CCX559 is a potent, orally-administered small molecule PD-L1 inhibitor that induces anti-tumor immunity

The interaction of PD-L1 with PD-1 is a major immune checkpoint that limits effector T cell function against cancer cells; monoclonal antibodies that block this pathway have been approved in multiple tumor indications. As a next generation therapy, small molecule inhibitors of PD-L1 have inherent drug properties that may be advantageous for certain patient populations compared to antibody therapies. In this report we present the pharmacology of the orally-available, small molecule PD-L1 inhibitor CCX559 for cancer immunotherapy. CCX559 potently and selectively inhibited PD-L1 binding to PD-1 and CD80 in vitro, and increased activation of primary human T cells in a T cell receptor-dependent fashion. Oral administration of CCX559 demonstrated anti-tumor activity similar to an anti-human PD-L1 antibody in two murine tumor models. Treatment of cells with CCX559 induced PD-L1 dimer formation and internalization, which prevented interaction with PD-1. Cell surface PD-L1 expression recovered in MC38 tumors upon CCX559 clearance post dosing. In a cynomolgus monkey pharmacodynamic study, CCX559 increased plasma levels of soluble PD-L1. These results support the clinical development of CCX559 for solid tumors; CCX559 is currently in a Phase 1, first in patient, multicenter, open-label, dose-escalation study (ACTRN12621001342808).

Measuring the impact of an educational intervention in rheumatoid arthritis: An open-label, randomized trial

Objectives

This study aims to determine whether patients with active rheumatoid arthritis (RA), either starting on or changing biological or targeted synthetic disease-modifying antirheumatic drugs (DMARDs), demonstrate better self-management safety skills three months after receiving a multidisciplinary educational intervention compared to patients receiving usual care.

Patients and methods

Between October 2015 and October 2018 , this open-label, randomized-controlled trial included a total of 107 RA patients (27 males, 80 females; mean age: 60.2±10.4 years; range, 54 to 71 years) who were on treatment or in whom treatment was changed with a biological or targeted synthetic DMARD. The patients were randomized into two groups: Group 1 (n=57) received additional intervention with educational DVD and one teleconference session and Group 2 (n=55) received usual care and were offered the intervention at three months. All patients underwent a final visit at six months. At each visit, the patients completed the BioSecure questionnaire measuring the self-care safety skills, a behavioral intention questionnaire, and the Beliefs about Medicines Questionnaire (BMQ).

Results

No significant difference was observed in the Biosecure score at three months between the two groups (p=0.08). After pooling the first three-month data in Group 1 and the last three-month data in Group 2, the mean score of the BioSecure questionnaire increased to 7.10±0.92 in the group receiving educational intervention (p<0.0001). This increase was maintained at six months in Group 2 (p=0.88). The rate of appropriate behavioral intention increased over time (76% at baseline and 85% at six months for both groups). There was no significant change in the BMQ (p=0.44 to 0.84).

Conclusion

The development of an educational DVD followed by a teleconference seem to improve self-care safety skills of the patients in practical situations.

Abstract 1274: CCX559 is a potent orally-administered small molecule PD-L1 inhibitor that induces anti-tumor immunity

Introduction: Cancer cells can escape tumor-specific T cell responses via engagement of inhibitory immune checkpoints. PD-L1/PD-1 interaction is one of the major checkpoints that limit effector T cell function against cancer cells, and monoclonal antibodies that block this interaction have been approved as therapies in multiple tumor indications. As a next generation therapy, small molecule inhibitors of PD-L1 potentially have advantageous properties compared to approved monoclonal antibodies, such as better penetration into solid tumors, reduced immunogenicity, lack of Fc-mediated side effects, convenience of oral administration, and lower cost of goods. We therefore embarked on an effort to identify and develop an orally available small molecule capable of targeting PD-L1/PD-1 interactions.

Methods: Inhibition of the PD-L1/PD-1 interaction was measured using a binding assay, followed by a cell culture system assessing PD-1 inhibition of T cell receptor (TCR) activation. Human T cell responses were assessed in vitro using the mixed lymphocyte reaction (MLR) assay, and a human peripheral blood mononuclear cell (PBMC)-mediated tumor cell killing assay. For in vivo studies CCX559 was dosed orally in a syngeneic tumor model and in a human tumor cell/PBMC co-implantation model in immune deficient mice.

Results: Using structural information and focused medicinal chemistry, we identified CCX559 as a potent inhibitor of PD-L1 interaction with PD-1. CCX559 prevented PD-L1/PD-1 inhibition of TCR signaling in a cell-based reporter assay, increased IFNγ secretion in allogeneic MLR assays, and increased tumor cell killing by human PBMCs. We demonstrated that CCX559 potentially employs multiple mechanisms to inhibit PD-L1, which are distinct from those published for human anti-PD-L1 antibodies. In murine tumor models, orally administered CCX559 reduced tumor growth similarly to a clinically-approved anti-human PD-L1 antibody.

Summary: CCX559 is a highly potent, small molecule PD-L1 inhibitor that can be orally administered. CCX559 enhanced primary human T cell activity in vitro and demonstrated anti-tumor efficacy in two murine tumor models. Based on its unique mechanism of PD-L1 inhibition, strong anti-tumor activity, desirable drug properties, and good safety profile, we plan to advance CCX559 into clinical development in the first half of 2021.

Citation Format: Chris Li, Marta Vilalta, Linda S. Ertl, Yu Wang, Yibin Zeng, Pingchen Fan, Christopher Lange, Darren McMurtrie, Ju Yang, Rebecca Lui, Ryan Scamp, Vicky Chhina, Alice Kumamoto, Ryan Ong, Ton Dang, Ashton Easterday, Niky Zhao, Shirley Liu, Rajinder Singh, Israel Charo, Kathleen Sullivan, Thomas J. Schall, Penglie Zhang. CCX559 is a potent orally-administered small molecule PD-L1 inhibitor that induces anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1274.

Abstract 5693: Anti-tumor effect of orally available small molecule PD-L1 inhibitors in a murine model of colon adenocarcinoma

Introduction: Antibody-based therapies targeting the Programmed cell Death-1/ Programmed Death-Ligand 1 (PD-1/PD-L1) immune checkpoint axis have achieved great success in cancer immunotherapy in recent years. As a next generation therapy, small molecule inhibitors of PD-1/PD-L1 offer the potential for increased tumor penetration, shorter half-life (to better manage immune related adverse events), and lower cost. We therefore embarked on an effort to identify and develop orally available small molecules capable of targeting PD-L1.

Methods: We designed and optimized a number of small molecule PD-L1 inhibitors which potently disrupted the interaction of PD-1 with PD-L1. Active compounds were first profiled by an ELISA assay measuring inhibition of the PD-1/PD-L1 interaction, followed by a functional cell-based reporter assay, mixed lymphocyte reaction (MLR) assay, and human peripheral blood mononuclear cell (PBMC)-mediated tumor cell killing assay. Targeted medicinal chemistry efforts were employed to improve potency and oral bioavailability, and candidate compounds were then evaluated in murine tumor models. Due to the specific reactivity of these compounds to human PD-L1 (but not murine PD-L1), a syngeneic tumor model with murine MC-38 colon tumor cells expressing human PD-L1 (MC38-hPD-L1 tumor model) was used.

Results: The optimized PD-L1 inhibitors were highly potent in cell-based reporter assay, the MLR assay and PBMC-mediated tumor cell killing assays. These compounds also possess high oral bioavailability and desirable safety profiles. In the MC38-hPD-L1 tumor model, Lead compounds potently reduced tumor growth similarly to an anti-human PD-L1 antibody, which was used as a positive control for the experiments. The tumor microenvironment analysis by flow cytometry demonstrated that these compounds almost completely occupied human PD-L1 on the tumor cells in vivo, and thus could potently block the interaction of PD-1/PD-L1 and enhance the immune responses against tumor.

Summary: We have identified and advanced unique small molecule inhibitors of human PD-L1 by rational design and optimization. Molecules resulting from these efforts exhibited marked inhibition of the PD-1/PD-L1 interaction and signaling in vitro, and potent anti-tumor effects in an animal model.

Citation Format: Shijie "Chris" Li, Marta Vilalta, Linda S. Ertl, Yu Wang, Yibin Zeng, Pingchen Fan, Christopher Lange, Darren McMurtrie, Ju Yang, Rebecca Lui, Ryan Ong, Vicky Chhina, Alice Kumamoto, Simon Yau, Ton Dang, Ashton Easterday, Shirley Liu, Rajinder Singh, Israel Charo, Thomas J. Schall, Penglie Zhang. Anti-tumor effect of orally available small molecule PD-L1 inhibitors in a murine model of colon adenocarcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5693.

Abstract 1745: Inhibition of chemokine receptor 2 (CCR2) with a small molecule antagonist enhances the effectiveness of checkpoint inhibition by altering the tumor microenvironment in mouse colorectal tumors: Reducing tumor size and increasing long term survival

Mouse CT26 colorectal tumors are heavily infiltrated by tumor-specific CD8 T cells, but nevertheless grow rapidly in Balb/c mice. These tumors are partially responsive to anti-PD-1 (α-PD-1) monoclonal antibody therapy, which suggests that an active suppression of the tumor-specific cytotoxic T cells exists in the untreated tumor. As chemokine receptor 2 (CCR2) is expressed by a potentially suppressive leukocyte subset within these tumors (monocytic myeloid derived suppressor cells aka M-MDSCs), we aimed to test whether CCR2 blockade could enhance the anti-tumor effects of α-PD-1.

We have found that the therapeutic effects of α-PD-1 therapy are appreciably enhanced by specific blockade of CCR2 via a small molecule antagonist. This combined α-PD-1/CCR2i approach significantly decreases overall tumor size and increases the proportion of long-term survivors, with more than 50% of the mice (up to 73%) showing complete regression of a previously established tumor. The effects of this combined therapy are dependent on the presence of CD8+ T cells, as tumors do not respond to the therapy in CD8-depleted mice. The anti-CT26 tumor response is specific: long term survivors are resistant to re-inoculation with the CT26 tumor (even without further dosing of either drug) but are not resistant to the 4T1 breast tumor. CCR2 antagonism alters the tumor microenvironment by reducing the number of M-MDSC per gram of tumor (a CCR2hi population phenotypically defined as CD11b+/Ly6G-/Ly6Chi). Reduction in tumor size is inversely proportional to the ratio of CD8 T cells to M-MDSC.

These data are consistent with a hypothesis that CCR2 antagonism enhances α-PD-1 therapy by preventing M-MDSC from accumulating within the tumor, thus reducing their suppressive effects on cytotoxic T cells.

Citation Format: James J. Campbell, Christine Janson, Linda Ertl, Chris Li, Zhenhua Miao, Antoni Krasinski, Rebecca Lui, Venkat Mali, Jeffrey McMahon, Yibin Zheng, Yu Wang, Xiaoping Zang, Vicky Chhina, Marta Vilalta, Alice Kumamoto, Ton Dang, Shirley Liu, Simon Yao, Penglie Zhang, Thomas J. Schall, Rajinder Singh. Inhibition of chemokine receptor 2 (CCR2) with a small molecule antagonist enhances the effectiveness of checkpoint inhibition by altering the tumor microenvironment in mouse colorectal tumors: Reducing tumor size and increasing long term survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1745.

Search for Dark Matter Annihilations towards the Inner Galactic Halo from 10 Years of Observations with H.E.S.S

The inner region of the Milky Way halo harbors a large amount of dark matter (DM). Given its proximity, it is one of the most promising targets to look for DM. We report on a search for the annihilations of DM particles using γ-ray observations towards the inner 300 pc of the Milky Way, with the H.E.S.S. array of ground-based Cherenkov telescopes. The analysis is based on a 2D maximum likelihood method using Galactic Center (GC) data accumulated by H.E.S.S. over the last 10 years (2004-2014), and does not show any significant γ-ray signal above background. Assuming Einasto and Navarro-Frenk-White DM density profiles at the GC, we derive upper limits on the annihilation cross section ⟨σv⟩. These constraints are the strongest obtained so far in the TeV DM mass range and improve upon previous limits by a factor 5. For the Einasto profile, the constraints reach ⟨σv⟩ values of 6×10^{-26}  cm^{3} s^{-1} in the W^{+}W^{-} channel for a DM particle mass of 1.5 TeV, and 2×10^{-26}  cm^{3} s^{-1} in the τ^{+}τ^{-} channel for a 1 TeV mass. For the first time, ground-based γ-ray observations have reached sufficient sensitivity to probe ⟨σv⟩ values expected from the thermal relic density for TeV DM particles.

The DRAGO gamma camera

In this work, we present the results of the experimental characterization of the DRAGO (DRift detector Array-based Gamma camera for Oncology), a detection system developed for high-spatial resolution gamma-ray imaging. This camera is based on a monolithic array of 77 silicon drift detectors (SDDs), with a total active area of 6.7 cm(2), coupled to a single 5-mm-thick CsI(Tl) scintillator crystal. The use of an array of SDDs provides a high quantum efficiency for the detection of the scintillation light together with a very low electronics noise. A very compact detection module based on the use of integrated readout circuits was developed. The performances achieved in gamma-ray imaging using this camera are reported here. When imaging a 0.2 mm collimated (57)Co source (122 keV) over different points of the active area, a spatial resolution ranging from 0.25 to 0.5 mm was measured. The depth-of-interaction capability of the detector, thanks to the use of a Maximum Likelihood reconstruction algorithm, was also investigated by imaging a collimated beam tilted to an angle of 45 degrees with respect to the scintillator surface. Finally, the imager was characterized with in vivo measurements on mice, in a real preclinical environment.

Smoking and lung cancer in Harbin, northeast China

BACKGROUND

We studied the relationship between smoking and lung cancer risk in Harbin, Heilongjiang province, northeast China, an area with a very high baseline risk of lung cancer in both sexes, using data from a case-control study of lung cancer conducted between 1987 and 1990.

PATIENTS AND METHODS

Cases were 218 patients with incident, histologically confirmed lung cancer and controls were 436 patients admitted to the same hospital with non-neoplastic and non-lung diseases.

RESULTS

Compared with never-smokers, the multivariate odds ratio (OR) for current smokers was 3.47 [95% confidence interval (CI) 2.31--5.20], and for ex-smokers 1.53 (95% CI 0.81--2.87). Lung cancer risk increased by 20% (95% CI 14% to 28%) for an increment of 5 years in smoking duration, and by 29% (95% CI 15% to 45%) for an increment of five cigarettes per day. The OR for smokers reporting occupational exposure to selected known or likely lung carcinogens was 7.22, compared with non-smokers without occupational exposure.

CONCLUSIONS

This study further confirms that cigarette smoking is a strong determinant of lung cancer also in this high-risk area of northeast China.

Soluble CD40 ligand induces beta-chemokine production by macrophages and resistance to HIV-1 entry

CD40 ligand (CD40L) is a cell surface molecule of CD4(+)T cells that interacts with its receptor CD40 on antigen presenting cells to mediate thymus-dependent humoral immunity and inflammatory reactions. We report here that treating monocyte-derived macrophages (MDM) with a trimeric soluble form of CD40L (CD40LT) induced them to secrete high levels of the beta-chemokines RANTES, MIP-1alpha and MIP-1beta that are ligands for CCR5 and able to inhibit HIV-1 entry. CD40LT inhibited the entry of M-tropic HIV-1 reporter viruses. Furthermore, supernatants obtained from CD40LT-stimulated macrophages protected CEMx174-CCR5 cells from infection by HIV-1(JRFL)reporter virus. The inhibitory activity appeared to be due to beta-chemokines present in the supernatant, since pretreating them with a cocktail of antibodies to RANTES, MIP-1alpha and MIP-1beta neutralized the inhibitory activity of the supernatants. In addition, treating monocytes with CD40LT caused CCR5 and CD4 to be downregulated from the cell surface. In vivo, macrophages activated through CD40 could interfere with HIV replication.

GABAA-benzodiazepine receptors in the striatum are involved in the sedation produced by a moderate, but not an intoxicating ethanol dose in outbred Wistar rats

The role of the dorsal striatum in mediating the sedation produced by a moderate (0.75 g/kg) and an intoxicating (1.25 g/kg) EtOH dose was investigated in the open field by determining the capacity of direct intrastriatal injections of RY 008, a partial inverse agonist of the benzodiazepine (BDZ) receptor, to antagonize EtOH's effects. SR 95531, the competitive high-affinity GABAA antagonist was used as a reference compound. Intrastriatal RY 008 (50, 500 ng) and SR 95531 (50 ng) antagonized the sedation produced by the 0.75 g/kg EtOH dose. However, RY 008 did not alter the sedation produced by the 1.25 g/kg dose. RY 008 alone was without effect. RY 008 also failed to negatively modulate GABAergic function at alpha1beta2gamma2 or alpha6beta2gamma2 receptor subtypes expressed in Xenopus oocytes. Intrastriatal modulation of the moderate EtOH dose was site specific: no antagonism by RY 008 after intraaccumbens infusions was observed. The results suggest that central GABAA-BDZ receptors in the dorsal striatum play an important role in mediating the sedation produced by a moderate EtOH dose in the open field.

[Analysis of the chemical constituents of volatile oils of Metasequoia glyptostroboides leave]

The chemical constituents of volatile oils of Metasequoia glyptostroboides leave were analyzed by GC-MS-DS. 27 constituents were identified, alpha-pinene (70.65%) and caryophyllene (10.38%) of them are main components.

Analysis of human monoclonal antibodies elicited by vaccination with a Cryptococcus neoformans glucuronoxylomannan capsular polysaccharide vaccine

The Cryptococcus neoformans capsular polysaccharide glucuronoxylomannan (GXM) has been conjugated to tetanus toxoid (GXM-TT) as an investigational vaccine. GXM-TT elicits antibodies that are protective in C. neoformans-infected mice. In an effort to characterize the fine specificity and molecular structure of human GXM-TT-elicited antibodies, we generated two GXM monoclonal antibodies (MAbs) from peripheral blood lymphocytes of a volunteer GXM-TT recipient and studied serum GXM antibody idiotype expression in 10 additional vaccinees. The MAbs, 2E9 and 3B6, are the immunoglobulin M(lambda) isotype and bind capsular polysaccharides of C. neoformans serotypes other than the serotype A that was used for immunization. Neither antibody competes with murine GXM MAbs for antigen binding, suggesting that the human MAbs recognize a different epitope. The B-cell superantigen staphylococcal protein A binds both MAbs, and human immunodeficiency virus gp120 binds 2E9. MAb nucleic acid sequence analysis revealed that both antibodies use an identical V lambda 1a-J lambda genetic element with different, somatically mutated, members of the VH3 gene family and different DH and JH gene elements. The gene elements used by both MAbs occur in fetal B-lymphocyte repertoires, autoantibodies, and other polysaccharide antibodies. Post-GXM-TT vaccination GXM antibodies from 10 additional vaccinees expressed a shared idiotype defined by rabbit antiserum raised against MAb 2E9. Our data suggest that the human GXM antibody response is restricted and raise questions regarding the importance of specific variable-region elements and superantigens in the generation of human antibody responses to encapsulated pathogens.

Effects of suramin on in vitro growth of fresh human tumors

BACKGROUND

Suramin is a polysulfonated urea recently tested in clinical trials as an anticancer agent.

PURPOSE

To define tumor types for further clinical testing of suramin, we assessed the in vitro activity of suramin against fresh human tumor specimens.

METHODS

Inhibition of tumor colony formation (human tumor clonogenic assay [HTCA] method) and inhibition of tritiated thymidine incorporation (TTI method) were used as indicators of drug sensitivity.

RESULTS

With the use of the HTCA method, 80% or more of carcinomas of the colon, endometrium, kidney, lung (non-small-cell), and ovary as well as malignant melanoma and mesothelioma were sensitive to 200 micrograms/mL of suramin by continuous exposure. Suramin's antitumor activity was dose dependent, and it was less effective when tested at concentrations of 50 micrograms/mL or less. With the TTI method, the more slowly growing tumors (breast cancer, colon cancer, multiple myeloma, non-Hodgkin's lymphoma, prostate cancer, and sarcoma) appeared to be less sensitive to suramin. However, when the two assay methods were directly compared in melanoma and ovarian cancer specimens, individual tumors were generally more sensitive to suramin (greater inhibition relative to control) using the HTCA method, whereas the TTI method appeared to underestimate suramin's antitumor activity. There was no significant difference in the activity of suramin when tested in the presence of 10% versus 50% serum.

CONCLUSION

These results provide an experimental basis for clinical evaluations of suramin therapy in patients with colon, endometrial, kidney, non-small-cell lung, and ovarian cancers as well as malignant melanoma and mesothelioma.

Chronic right upper quadrant pain without gallstones: does HIDA scan predict outcome after cholecystectomy?

Patients with chronic right upper quadrant pain who do not have gallstones on ultrasound or cholecystography are often referred for surgery for presumed acalculous chronic cholecystitis. We followed 26 patients who had cholecystokinin (CCK) cholescintigraphy for evaluation of chronic right upper quadrant pain without demonstrable gallstones on ultrasound who underwent cholecystectomy so that it could be determined whether there was any relation between a low ejection fraction (EF), morphological features of chronic cholecystitis, and clinical outcome. Eighteen patients (69%) were considered therapeutic successes, whereas eight (31%) were failures after an average 2-yr follow-up. Both patient groups had significantly reduced EF: the successful group at 0.39 and the failures at 0.25. Thus, a low EF did not predict clinical outcome, since the failure group had an even lower EF than the success group. Seven gallbladders demonstrated chronic acalculous cholecystitis; the average EF of this group was 0.35. The remaining 19 gallbladders were normal, yet also had an EF of 0.35. Thus, decreased EF does not predict the histologic features of chronic cholecystitis without gallstones. The diagnostic value of cholescintigraphy in patients with acalculous right upper quadrant pain is low, probably because this entity represents a variety of processes, including inflammation, gallbladder dysmotility, and the irritable bowel syndrome.

Coexistence of mucinous cystadenoma of the ovary and ovarian sarcoidosis

A case of ovarian and systemic sarcoidosis with mucinous cystadenoma coexisting in the same ovary is described. This association has not been previously reported. The differentiation of systemic sarcoidosis from metastatic spread of ovarian cancer and from sarcoid-like reactions in regional lymph nodes of tumors is discussed.

Biological growth and spread modeled by systems of recursions. I. Mathematical theory

We study the asymptotic behavior of solutions to a system of recursions u in+1 = Qi[mu n], i = 1, ..., k. The vector operator Q has the origin theta and a positive vector beta as fixed points and is defined for vector-valued functions bounded between theta and gamma where gamma greater than or equal to beta. In addition, Q is order-preserving, commutes with translation, and is continuous in the topology of uniform convergence on compact subsets. Let theta less than or equal to pi much less than beta, and suppose that for all pi much less than alpha much less than beta, Q(n) alpha]----beta as n----infinity. If u0 much greater than pi on a sufficiently large ball and has bounded support, then un propagates with a speed c*(xi) in the direction of the unit vector xi as n----infinity. In certain cases, c*(xi) can be calculated explicitly. The results generalize those of a scalar equation studied by Weinberger.

Biological growth and spread modeled by systems of recursions. II. Biological theory

The mathematical theory developed in Part I is applied to a selection-migration model in population genetics with sex-linked locus and to the host-vector or venereal disease epidemic model. In both models, a constant c*(xi) is found for each unit vector xi. The mathematical results imply that under certain initial conditions, the frequency of the advantageous gene in the male and female gametic outputs or the epidemic will spread at a speed c*(xi) in the direction xi as time goes to infinity. Time is measured in discrete nonoverlapping generations. In most cases, we can find a formula for c*(xi).

Esophagogastric anastomosis performed with a stapler: the occurrence of leakage and stricture

The circular stapler has lowered the leakage rate of an esophageal anastomosis to a level hitherto achieved by only a few surgeons performing hand anastomosis on selected patients with carcinoma of the esophagus. However, the esophageal anastomosis performed with a stapler is also associated with a high stricture rate. Our prospective study was conducted to determine the leakage rate and the incidence of stricture after esophagogastric anastomosis was performed with a stapler, the relationship of stricture to the size of the stapler, and the risk of stricture in relation to time. In a group of 174 patients with carcinoma of the thoracic esophagus, resection was performed, and a one-stage esophagogastric anastomosis was constructed. There were 33 hand anastomoses, 64 anastomoses with an EEA stapler (U.S. Surgical Corp., Norwalk, Conn.), and 77 anastomoses with an ILS stapler (Ethicon Ltd., Edinburgh, U.K.). The anastomotic leakage rate was 3.4% (6/174); 3% with the hand technique and 3.5% with the stapler technique (4.7% for the EEA and 2.6% for the ILS). After leakages and hospital deaths were excluded, 133 discharged patients were evaluated for the occurrence of anastomotic strictures. Only those who complained of dysphagia were investigated. The incidence of stricture for hand anastomosis was 8.7%-EEA 20% and ILS 10%; the overall incidence of anastomoses with a stapler was 14.5%. The true incidence would probably be higher if all patients were assessed by endoscopic or radiologic examination after operation. All three sizes of EEA staplers had a high incidence of stricture. For the ILS stapler the 25 mm size had the highest stricture rate (28.6%) of all groups, but for the 29 and 33 mm sizes, the incidences were 5.3% and 0%, respectively. Actuarial analysis showed an increasing risk of stricture with a reduction in the size of stapler used and was 32.5% and 35%, respectively, for the ILS 25 mm and EEA 25 mm staplers at 131/2 months. The risk of stricture occurrence was highest in the first 4 months. Treatment by bougienage was satisfactory. In conclusion, esophagogastric anastomosis performed with a stapler is a very safe procedure with respect to leakage but is associated with a high risk of stricture, except when the largest ILS staplers are used. However, dilatation readily overcomes the stricture occurrence and adequately compensates for the reduced leakage rate and its attendant serious consequences.

Postoperative flexible choledochoscopy for residual primary intrahepatic stones

Postoperative flexible choledochoscopy was carried out in 103 patients with residual biliary calculi. Forty-one patients had residual stones in the common duct, and 63 patients had residual stones in the intrahepatic ducts with or without stones in the common duct. The majority of the intrahepatic stones were primary stones. Postoperative choledochoscopy was very effective in removing residual common duct stones (95% removed, no morbidity). For intrahepatic stones, removal was more difficult and was associated with a higher morbidity (11.2%). Stone extraction through the stenotic intrahepatic ducts was made possible by the balloon dilatation of the ducts. Repeated endoscopic access to the biliary system was made easier by the construction of a hepatico-cutaneous-jejunostomy, which also provides a route to the biliary tree for future stone removal if stone reformation occurs. Complimented by these procedures, postoperative choledochoscopy was successful in removing the residual intrahepatic stones in 82.3% of the patients. At a median follow-up of 17 months, the majority of the patients who had all the stones removed as well as those who had stones left behind were symptom free.