Matched study of three methods for palliation of malignant pyloroduodenal obstruction

BACKGROUND

The traditional management of pyloroduodenal obstruction is open gastrojejunostomy (OGJ). More recently laparoscopic gastrojejunostomy (LGJ) and endoscopic stenting (ES) have been introduced. The aim of this study was to evaluate the three approaches to the palliation of malignant pyloroduodenal obstruction.

METHODS

All patients who underwent surgery (open and laparoscopic) for malignant pyloroduodenal obstruction at Auckland City Hospital between 1989 and 2002 inclusive were identified from International Classification of Diseases (ICD) 10 codes and from the Otago Surgical Audit Database. Patients who had an endoscopic stent were identified from the Endoscribe database. A review of medical records was conducted and data recorded in a structured pro forma. There were 181 patients with malignant pyloroduodenal obstruction of whom 56 patients had OGJ, 14 had LGJ and 16 had ES. Patients in the LGJ and ES groups were matched with those who underwent OGJ with respect to American Society of Anesthesiologists (ASA) grade (I-V), age (within 10 years) and level of obstruction (pylorus, first part of duodenum D1, D2, D3 and D4). The primary outcomes compared between the groups were time to starting free oral fluids and light diet, length of stay and survival.

RESULTS

There were no significant differences in age, sex, ASA grade and level of obstruction between the matched OGJ (n=16), LGJ (n=14) and ES (n=16) groups. There was a significant reduction in time to starting free oral fluids and light diet, and length of stay after the procedure, in the ES group. Patients who underwent surgical palliation of the obstruction had significantly more complications than those who underwent stenting (P=0.016). There were no significant differences in requirement for biliary drainage either before or after the procedure between the three groups. Survival was shortest in the ES group.

CONCLUSION

This matched study showed significant advantages for ES compared with OGJ and LGJ in the palliation of malignant pyloroduodenal obstruction.

Skin Cancers in Organ Transplant Recipients

Long-term utilization of immunosuppression in organ transplant recipients (OTRs) leads to decreased immune-mediated tumor surveillance and development of malignant tumors. A delicate balance needs to be maintained in the intensity of immunosuppression to keep the risk of malignancy low without jeopardizing life-saving graft function. OTRs are prone to developing skin cancers that exhibit unique epidemiologic, pathophysiologic, and prognostic characteristics. In this review, we discuss the most commonly reported skin cancers in OTRs: squamous cell carcinoma (SCC), basal cell carcinoma (BCC), Kaposi sarcoma, Merkel cell carcinoma, and malignant melanoma (MM). Tumors in this high-risk population are aggressive and may respond poorly to standard therapies; however, new targeted therapies are promising. Checkpoint inhibitor antibodies have been used for treatment of cutaneous SCC, Merkel cell carcinoma, and MM; epidermal growth factor receptor inhibitors have been used for cutaneous SCC; hedgehog pathway inhibitors have been used for BCC; and BRAF and MEK inhibitors are being used increasingly in the management of MM. Guidelines for dermatologic screening are variable and primarily based on expert opinion. Prospective evidence-based trials by multidisciplinary groups are needed to better define surveillance schedules for pre- and posttransplant cutaneous malignancies.

Systematic review of oxidative stress associated with pneumoperitoneum

Background

There have been several reports of ischaemic complications after routine laparoscopy. The aim of this review was to investigate the relationship between this oxidative stress and pneumoperitoneum.

Methods

Medline, Medline in-process, The Cochrane Library, PubMed and EMBASE were searched for papers on oxidative stress and pneumoperitoneum, from 1947 to March 2008 with no language restriction or restriction on trial design. Papers that did not investigate pneumoperitoneum as a causative factor, or did not report outcome measures related to oxidative stress, were excluded.

Results

A total of 73 relevant papers were identified: 36 animal studies, 21 human clinical trials, nine case reports, five review articles and two comments. Pneumoperitoneum causes a reduction in splanchnic blood flow, resulting in biochemical evidence of oxidative stress in a pressure- and time-dependent manner. There is evidence that the use of carbon dioxide for insufflation is contributory. Several measures proposed to minimize the oxidative stress have shown promise in animal studies, but few have been evaluated in the clinical setting.

Conclusion

There is an increasing body of evidence, mainly from animal studies, that pneumoperitoneum decreases splanchnic perfusion with resulting oxidative stress. It is now appropriate to investigate the clinical significance of pneumoperitoneum-associated oxidative stress.

Overexpression of Bcl-x(L) in beta-cells prevents cell death but impairs mitochondrial signal for insulin secretion

To study effects of Bcl-x(L) in the pancreatic beta-cell, two transgenic lines were produced using different forms of the rat insulin promoter. Bcl-x(L) expression in beta-cells was increased 2- to 3-fold in founder (Fd) 1 and over 10-fold in Fd 2 compared with littermate controls. After exposure to thapsigargin (10 microM for 48 h), losses of cell viability in islets of Fd 1 and Fd 2 Bcl-x(L) transgenic mice were significantly lower than in islets of wild-type mice. Unexpectedly, severe glucose intolerance was observed in Fd 2 but not Fd 1 Bcl-x(L) mice. Pancreatic insulin content and islet morphology were not different from control in either transgenic line. However, Fd 2 Bcl-x(L) islets had impaired insulin secretory and intracellular free Ca(2+) ([Ca(2+)](i)) responses to glucose and KCl. Furthermore, insulin and [Ca(2+)](i) responses to pyruvate methyl ester (PME) were similarly reduced as glucose in Fd 2 Bcl-x(L) islets. Consistent with a mitochondrial defect, glucose oxidation, but not glycolysis, was significantly lower in Fd 2 Bcl-x(L) islets than in wild-type islets. Glucose-, PME-, and alpha-ketoisocaproate-induced hyperpolarization of mitochondrial membrane potential, NAD(P)H, and ATP production were also significantly reduced in Fd 2 Bcl-x(L) islets. Thus, although Bcl-x(L) promotes beta-cell survival, high levels of expression of Bcl-x(L) result in reduced glucose-induced insulin secretion and hyperglycemia due to a defect in mitochondrial nutrient metabolism and signaling for insulin secretion.

Randomized, double-blind placebo-controlled trial of coenzyme Q10 in patients with acute myocardial infarction

The effects of oral treatment with coenzyme Q10 (120 mg/d) were compared for 28 days in 73 (intervention group A) and 71 (placebo group B) patients with acute myocardial infarction (AMI). After treatment, angina pectoris (9.5 vs. 28.1), total arrhythmias (9.5% vs. 25.3%), and poor left ventricular function (8.2% vs. 22.5%) were significantly (P < 0.05) reduced in the coenzyme Q group than placebo group. Total cardiac events, including cardiac deaths and nonfatal infarction, were also significantly reduced in the coenzyme Q10 group compared with the placebo group (15.0% vs. 30.9%, P < 0.02). The extent of cardiac disease, elevation in cardiac enzymes, and oxidative stress at entry to the study were comparable between the two groups. Lipid peroxides, diene conjugates, and malondialdehyde, which are indicators of oxidative stress, showed a greater reduction in the treatment group than in the placebo group. The antioxidants vitamin A, E, and C and beta-carotene, which were lower initially after AMI, increased more in the coenzyme Q10 group than in the placebo group. These findings suggest that coenzyme Q10 can provide rapid protective effects in patients with AMI if administered within 3 days of the onset of symptoms. More studies in a larger number of patients and long-term follow-up are needed to confirm our results.

Cytokine expression pattern in the genital tract of Chlamydia trachomatis positive infertile women - implication for T-cell responses

Human genital infection caused by Chlamydia trachomatis is thought to be immunologically mediated, resulting in local recruitment of lymphocyte subsets and inducing the production of cytokines. Little information is available about the role of lymphocyte recruitment and the regulation of cytokine production in the genital tract of C. trachomatis positive infertile women. We have evaluated the recruitment of lymphocyte subsets in the genital tract and production of Th1/Th2 cytokines in cervical secretions and laparoscopic specimens from the fallopian tubes of C. trachomatis positive infertile women (n = 17) and compared them with controls, viz. C. trachomatis negative infertile women (n = 20) using ELISA and flow cytometry. None of these patients were found to be infected either with Candida sps., bacterial vaginosis, Trichomonas vaginalis, Neisseria gonorrhoeae, Mycoplasma hominis or Ureaplasma urealyticum in the cervix. Flow cytometric analysis of cervical secretions in Chlamydia positive women revealed recruitment of both CD4 and CD8 lymphocytes to the genital tract was up-regulated and a variation in the production rates of different cytokines in cervical secretions and fallopian tube was observed. We found that the immune responses in cervical secretions were of Th0 type, since all the analysed cytokines, viz. IFN-gamma, TNF-alpha, IL-10 and IL-12 were up-regulated. As, both CD4 and CD8 cells contribute to the production of IFN-gamma and IL-10, these results suggest that along with CD4 cells, CD8 lymphocytes also may be important for local regulation of Th1/Th2 responses in the genital tract during C. trachomatis infection.

Injuries to the phrenic nerve resulting in diaphragmatic paralysis with special reference to stretch trauma

Traumatic interruption of the phrenic nerve causing diaphragmatic paralysis occurs much more commonly than realized. Patients present with symptoms referable to the respiratory, gastrointestinal, or cardiovascular systems as a result of anatomic displacement of the respective organ (eventration). Symptoms often occur shortly after the injury but may be delayed for many years; consequently, prolonged follow-up of these patients is essential. If patients are symptomatic after trauma, judicious observation is dictated, since many will experience gradual return of normal diaphragmatic function over the succeeding six to twelve months. In those who remain significantly symptomatic, thoracotomy and imbrication of the eventration is a simple and effective surgical procedure.

IKBKE is induced by STAT3 and tobacco carcinogen and determines chemosensitivity in non-small cell lung cancer

Serine/threonine kinase IKBKE is a newly identified oncogene; however, its regulation remains elusive. Here, we provide evidence that IKBKE is a downstream target of signal transducer and activator of transcription 3 (STAT3) and that tobacco components induce IKBKE expression through STAT3. Ectopic expression of constitutively active STAT3 increased IKBKE mRNA and protein levels, whereas inhibition of STAT3 reduced IKBKE expression. Furthermore, expression levels of IKBKE are significantly associated with STAT3 activation and tobacco use history in non-small cell lung cancer (NSCLC) patients examined. In addition, we show induction of IKBKE by two components of cigarette smoke, nicotine and nicotine-derived nitrosamine ketone (NNK). Upon exposure to nicotine or NNK, cells express high levels of IKBKE protein and mRNA, which are largely abrogated by inhibition of STAT3. Characterization of the IKBKE promoter revealed two STAT3-response elements. The IKBKE promoter directly bound to STAT3 and responded to nicotine and NNK stimulation. Notably, enforcing expression of IKBKE induces chemoresistance, whereas knockdown of IKBKE not only sensitizes NSCLC cells to chemotherapy but also abrogates STAT3- and nicotine-induced cell survival. These data indicate for the first time that IKBKE is a direct target of STAT3 and is induced by tobacco carcinogens through STAT3 pathway. In addition, our study also suggests that IKBKE is an important therapeutic target and could have a pivotal role in tobacco-associated lung carcinogenesis.

Chlamydia trachomatis and human papillomavirus infection in Indian women with sexually transmitted diseases and cervical precancerous and cancerous lesions

OBJECTIVES

Sexually transmitted diseases (STDs) and anogenital cancers are the major health problems in Indian women but no reliable estimate of the prevalence of either genital chlamydial infection or human papillomavirus (HPV) infection in STD patients is available. The aim of this study was to detect the frequency of Chlamydia trachomatis and the most prevalent high-risk HPV type 16 (HPV 16) infection in Indian women, with STDs and precancerous and cancerous lesions of the uterine cervix by polymerase chain reaction (PCR), and their comparison with those of conventional serology and antigen tests used for C. trachomatis detection.

METHODS

Endocervical swabs or scrapes were collected from 50 women with STDs and 30 normal healthy women attending the STD clinics of Smt. Sucheta Kripalani Hospital, New Delhi. Scraped cervical cell specimens were also collected from 50 women with precancerous and cancerous lesions of the uterine cervix. Detection of C. trachomatis and HPV was carried out by PCR using chlamydia and HPV genome-specific oligonucleotide primers. The detection of chlamydial antigen and IgG-specific antibodies was carried out by enzyme immunoassay (EIA) and serological enzyme-linked immunosorbent assay (ELISA), respectively.

RESULTS

A chlamydia plasmid-based PCR assay detected 50% (25 of 50) positivity of C. trachomatis in STD patients and HPV 16 DNA was found in 30% (15 of 50) of these cases which are significantly higher than those found in healthy controls. The PCR estimate of chlamydia was found to be higher than its reported frequency by tissue culture. The EIA could detect chlamydial antigen in only 13 cases (26%) while serological ELISA revealed evidence of chlamydia IgG-specific antibodies in 26 (52%) cases. Interestingly, in women with precancerous and cancerous lesions, the rate of HPV 16 infection was very high (52% and 72%, respectively), whereas the frequency of chlamydia infection was found to be 12-22% only. Occurrence of other sexually transmitted agents was also evaluated in the women.

CONCLUSIONS

This is the first PCR estimate of genital chlamydial (50%) and HPV 16 (30%) infection in STD patients and women with precancerous and cancerous lesions of the uterine cervix in India. The PCR method seems to be a good alternative to tissue culture.

Effect of treatment for Chlamydia trachomatis during pregnancy

OBJECTIVES

To screen and treat chlamydial infection in pregnant women in order to assess the effects of therapeutic intervention on the outcome of Chlamydia trachomatis-infected pregnancy.

METHODS

Enrolled in the study were 350 women in the first to third trimesters of pregnancy. Endocervical swabs were collected for C. trachomatis diagnosis by DFA and PCR. A few STD infections, viz.: Neisseria gonorrhoeae, Candida spp., bacterial vaginosis, Trichomonas vaginalis and Treponema pallidum were ruled out. After excluding 22 patients infected with other sexually transmitted infections, a cohort of 328 pregnant women comprised the study population. Anti-chlamydial treatment (viz.: oral therapy with erythromycin stearate, 500 mg 4 times daily for 7 days) was given to 17 women (group I) and their partners. Fifteen patients of group I were retested by DFA and PCR assay for C. trachomatis infection 2 weeks following therapy. Other Chlamydia-positive patients (n=42) who were lost to follow-up were classified as untreated positive cases (group II) while group III included C. trachomatis negative cases (n=269). Data on obstetric outcome were recorded in a total of 164 cases. Statistical comparison of the data were done using the chi(2)-test and means were compared using Student's t-test.

RESULTS

Among the 350 pregnant women enrolled initially for the study, C. trachomatis positivity was found to be 18.8% (n=66) in the endocervix by DFA and PCR assay. Co-infection with Candida spp., bacterial vaginosis, T. vaginalis and T. pallidum was 2.0%, 1.7%, 1.7% and 0.5%, respectively. None of the pregnant women was infected with N. gonorrhoeae. Pregnant women at an increased risk of chlamydial infection included those who had multiple births and were in second trimester of pregnancy. Fifteen patients of group I became Chlamydia-negative following treatment. Data on obstetric outcome were recorded in 11, 26 and 127 patients of groups I, II and III, respectively. The mean duration of gestation for premature deliveries was found to be significantly higher in group I in comparison with group II [35.5 vs. 33.1 weeks (P<0.05)], thereby showing an improved effect of treatment on pregnancy outcome. The mean of low birth weight births was higher in group I compared with group II (2200.0 vs. 2113.3 g), however, this was statistically non-significant. Stillbirths were significantly higher among group II in comparison with group III [11.5% vs. 4.7% (chi(2)=1.79; P<0.5)]. No stillbirths were recorded in patients who had taken anti-chlamydial treatment.

CONCLUSIONS

Our findings suggest that routine screening and treatment of C. trachomatis infection in pregnant women, especially those in high risk groups, should be mandatory to reduce the adverse effects on obstetric outcome.

Influence of Podophyllum hexandrum on endogenous antioxidant defence system in mice: possible role in radioprotection

Podophyllum hexandrum, a Himalayan herb with known radioprotective and anti-tumour properties, was investigated for its mechanism of action. Glutathione S-transferase (GST), catalase, superoxide dismutase (SOD) activities and lipid peroxidation (LPx) were determined in the liver, jejunum and ileum at various time intervals, with and without the aqueous extract of P. hexandrum rhizome (200 mg/kg b.w. i.p.) in unirradiated and whole body irradiated (10 Gy,-2 h) male Swiss albino mice. Pre-irradiation treatment with P. hexandrum enhanced liver GST (P<0.01) and SOD (P<0.05) at 12 h post irradiation, the intestinal SOD (P<0.00005) at 84 h post irradiation was significantly elevated. However, no significant change was manifested in the catalase activity in the liver, at any of the post irradiation intervals (0, 12 and 84 h). The antioxidant defence with Podophyllum sp. treatment in mice can explain to some extent its protective action manifested in terms of survival against whole body lethal irradiation. However, some other possible mechanisms that may strengthen radioprotective action of the Podophyllum sp. extract need to be investigated further.

Deployment of membrane fusion protein domains during fusion

It is clear that both viral and intracellular membrane fusion proteins contain a minimal set of domains which must be deployed at the appropriate time during the fusion process. An account of these domains and their functions is given here for the four best-described fusion systems: influenza HA, sendai virus F1, HIV gp120/41 and the neuronal SNARE core composed of synaptobrevin (syn), syntaxin (stx) and the N- and C-termini of SNAP25 (sn25), together with the Ca(2+)binding protein synaptotagmin (syt). Membrane fusion begins with the binding of the virion or vesicle to the target membrane via receptors. The committed step in influenza HA- mediated fusion begins with an aggregate of HAs (at least eight) with some of their HA2 N-termini, a.k.a. fusion peptides, embedded into the viral bilayer (Bentz, 2000 a). The hypothesis presented in Bentz (2000 b) is that the conformational change of HA to the extended coiled coil extracts the fusion peptides from the viral bilayer. When this extraction occurs from the center of the site of restricted lipid flow, it exposes acyl chains and parts of the HA transmembrane domains to the aqueous media, i.e. a hydrophobic defect is formed. This is the 'transition state' of the committed step of fusion. It is stabilized by a 'dam' of HAs, which are inhibited from diffusing away by the rest of the HAs in the aggregate and because that would initially expose more acyl chains to water. Recruitment of lipids from the apposed target membrane can heal this hydrophobic defect, initiating lipid mixing and fusion. The HA transmembrane domains are required to be part of the hydrophobic defect, because the HA aggregate must be closely packed enough to restrict lipid flow. This hypothesis provides a simple and direct coupling between the energy released by the formation of the coiled coil to the energy needed to create and stabilize the high energy intermediates of fusion. Several of these essential domains have been described for the viral fusion proteins SV5 F1 and HIV gp120/41, and for the intracellular SNARE fusion system. By comparing these domains, we have constructed a minimal set which appears to be adequate to explain how the conformational changes can produce a successful fusion event, i.e. communication of aqueous compartments.

Predominance of Chlamydia trachomatis serovars associated with urogenital infections in females in New Delhi, India

Screening for Chlamydia trachomatis was done for 280 endocervical swab samples by PCR specific for endogenous plasmid. Age dependency was seen in symptomatic patients, with a high chlamydial prevalence rate (28%) found in younger women. Genotyping by restriction fragment length polymorphism analysis of omp1 PCR-positive samples showed serovars D, E, and F to be the most prevalent.

Modulatory potential of Spirulina fusiformis on carcinogen metabolizing enzymes in Swiss albino mice

The modulatory potential of Spirulina fusiformis was observed on the hepatic and extrahepatic carcinogen metabolizing enzymes in Swiss albino mice at a dose of 800 mg/kg b.w. given orally. A significant reduction in the hepatic cytochrome P-450 content was observed in the group treated with Spirulina in comparison with the control group. The hepatic glutathione S-transferase activity was induced significantly by Spirulina treatment. There was no change in the extrahepatic glutathione S-transferase activity after the animals were fed with Spirulina.

Systematic review and meta-analysis of cutting diathermy versus scalpel for skin incision

Background

Skin incisions have traditionally been made using a scalpel. Cutting diathermy, a more recent alternative, is thought to increase the risk of infection, impair healing and decrease cosmesis. Recent studies suggest otherwise, claiming that diathermy may offer potential advantages with respect to blood loss, incision time and postoperative pain. The aim of this meta-analysis was to compare skin incisions made by either scalpel or cutting diathermy.

Methods

A systematic literature search and review was performed for studies published from January 1980 until June 2011. Randomized clinical trials comparing scalpel and cutting diathermy for skin incisions of any operation were included. Primary outcomes included wound complication rate, blood loss, incision times and pain scores.

Results

Fourteen randomized trials met the criteria for inclusion in the meta-analysis, providing outcome data for a total of 2541 patients (1267 undergoing skin incision by cutting diathermy and 1274 by scalpel). The median length of follow-up across all studies was 6 weeks (range 4 days to 19 months). Compared with a scalpel incision, cutting diathermy resulted in significantly less blood loss (mean difference 0·72 ml/cm2; P &lt; 0·001) and shorter incision times (mean difference 36 s; P &lt; 0·001), with no differences in the wound complication rate (odds ratio 0·87; P = 0·29) or pain score at 24 h (mean difference 0·89; P = 0·05).

Conclusion

Skin incisions made by cutting diathermy are quicker and associated with less blood loss than those made by scalpel, and there are no differences in the rate of wound complications or postoperative pain.

Helicoverpa armigera baseline susceptibility to Bacillus thuringiensis Cry toxins and resistance management for Bt cotton in India

Transgenic cotton that produces insecticidal proteins from Bacillus thuringiensis (Bt), often referred to as Bt cotton, is widely grown in many countries. Bt cotton with a single cry1A gene and stacked also with cry2A gene has provided satisfactory protection against the damage by the lepidopteran bollworms, especially the cotton bollworm, Helicoverpa armigera (Hübner) which is considered as a key pest. The baseline susceptibility of the larvae of H. armigera to Cry1Ac and other toxins carried out in many countries has provided a basis for monitoring resistance. There is no evidence of development of field-level resistance in H. armigera leading to the failure of Bt cotton crop anywhere in the world, despite the fact that Bt cotton was grown on the largest ever area of 12.1 million hectares in 2006 and its cumulative cultivation over the last 11 years has surpassed the annual cotton area in the world. Nevertheless, the Bt resistance management has become a necessity to sustain Bt cotton and other transgenic crops in view of potential of the target insects to evolve Cry toxin resistance.

Pattern of interleukins in minimal-change nephrotic syndrome of childhood

Assays of interleukin-1 (IL-1) and IL-2 were done in supernatants from phytohaemagglutinin-activated lymphocyte cultures from 10 children suffering from minimal-change nephrotic syndrome (MCNS) to assess their role in the aetiopathogenesis of this disorder. Increased levels of IL-1 and IL-2 had been found in supernatants from patients having MCNS compared with controls, suggesting a significant role of these cytokines in the immunopathogenesis of proteinuria in this syndrome.

Retrospective cohort analysis of neoadjuvant treatment and survival in resectable and borderline resectable pancreatic ductal adenocarcinoma in a high volume referral centre

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease. Neoadjuvant therapy (NA) with chemotherapy (NAC) and radiotherapy (RT) prior to surgery provides promise. In the absence of prospective data, well annotated clinical data from high-volume units may provide pilot data for randomised trials.

METHODS

Medical records from a tertiary hospital in Sydney, Australia, were analysed to identify all patients with resectable or borderline resectable PDAC. Data regarding treatment, toxicity and survival were collected.

RESULTS

Between January 1 2010 and April 1 2016, 220 sequential patients were treated: 87 with NA and 133 with upfront operation (UO). Forty-three NA patients (52%) and 5 UO patients (4%) were borderline resectable at diagnosis. Twenty-four borderline patients received NA RT, 22 sequential to NAC. The median overall survival (OS) in the NA group was 25.9 months (mo); 95% CI (21.1-43.0 mo) compared to 26.9 mo (19.7, 32.7) in the UO; HR 0.89; log-ranked p-value = 0.58. Sixty-nine NA patients (79%) were resected, mOS was 29.2 mo (22.27, not reached (NR)). Twenty-two NA (31%) versus 22 UO (17%) were node negative at operation (N0). In those managed with NAC/RT the mOS was 29.0 mo (17.3, NR). There were no post-operative deaths with NA within 90-days and three in the UO arm.

DISCUSSION

This is a hypothesis generating retrospective review of a selected real-world population in a high-throughput unit. Treatment with NA was well tolerated. The long observed survival in this group may be explained by lymph node sterilisation by NA, and the achievement of R0 resection in a greater proportion of patients.

Comprehensive kinetic analysis of influenza hemagglutinin-mediated membrane fusion: role of sialate binding

The data of Danieli et al. (J. Cell Biol. 133:559-569, 1996) and Blumenthal et al. (J. Cell Biol. 135:63-71, 1996) for fusion between hemagglutinin (HA)-expressing cells and fluorescently labeled erythrocytes has been analyzed using a recently published comprehensive mass action kinetic model for HA-mediated fusion. This model includes the measurable steps in the fusion process, i.e., first pore formation, lipid mixing, and content mixing of aqueous fluorescent markers. It contains two core parameters of the fusion site architecture. The first is the minimum number of aggregated HAs needed to sustain subsequent fusion intermediates. The second is the minimal number of those HAs within the fusogenic aggregate that must undergo a slow "essential" conformational change needed to initiate bilayer destabilization. Because the kinetic model has several parameters, each data set was exhaustively fitted to obtain all best fits. Although each of the data sets required particular parameter ranges for best fits, a consensus subset of these parameter ranges could fit all of the data. Thus, this comprehensive model subsumes the available mass action kinetic data for the fusion of HA-expressing cells with erythrocytes, despite the differences in assays and experimental design, which necessitated transforming fluorescence dequenching intensities to equivalent cumulative waiting time distributions. We find that HAs bound to sialates on glycophorin can participate in fusion as members of the fusogenic aggregate, but they cannot undergo the essential conformational change that initiates bilayer destabilization, thus solving a long-standing debate. Also, the similarity in rate constants for lipid mixing and content mixing found here for HA-mediated fusion and by Lee and Lentz (Proc. Natl. Acad. Sci. U.S.A. 95:9274-9279, 1998) for PEG-induced fusion of phosphatidylcholine liposomes supports the idea that subsequent to stable fusion pore formation, the evolution of fusion intermediates is determined more by the lipids than by the proteins.