Prognostic impact of circumferential resection margin in esophageal cancer with or without neoadjuvant chemoradiotherapy.

The prognostic impact of circumferential resection margin (CRM) in surgically resected esophageal squamous cell carcinoma (ESCC) has been controversial. This investigation assessed the prognostic impact of CRM in surgically resected pathologic T3 ESCC patients with or without neoadjuvant chemoradiotherapy (nCRT). We reviewed consecutive p/yp T3 ESCC patients undergoing esophagectomy from two medical centers between January 2009 and December 2016. The cohort was divided into two groups: upfront esophagectomy (upfront surgery) and nCRT followed by esophagectomy (nCRT + surgery). CRM status was assessed and divided into CRM > 1 mm, 0 < CRM < 1 mm, and tumor at CRM. A total of 217 p/yp T3 ESCC patients undergoing esophagectomy (138 patients in the upfront surgery group and 79 in the nCRT + surgery group) were enrolled. In the upfront surgery group, patients with 0 < CRM < 1 mm showed equivalent overall survival to those with CRM > 1 mm (log-rank P = 0.817) and significantly outlived those with tumor at CRM (log-rank P < 0.001). However, in the nCRT + surgery group, CRM > 1 mm failed to show survival superiority to CRM between 0 and 1 mm or involved by cancer (log-rank P = 0.390). In conclusion, a negative CRM, even though being <1 mm, is adequate for pT3 ESCC patients undergoing upfront esophagectomy. In contrast, the CRM status is less prognostic in ypT3 ESCC patients undergoing nCRT followed by esophagectomy.

Patterns of recurrence after oesophagectomy and postoperative chemoradiotherapy versus surgery alone for oesophageal squamous cell carcinoma.

BACKGROUND: Patterns of recurrence after surgery with postoperative chemoradiotherapy (S-CCRT) or surgery alone in patients with oesophageal squamous cell carcinoma (SCC) may differ. This might influence the nature and timing of subsequent management strategies. METHODS: Patients with SCC who had undergone R0 resection were included. Propensity score matching was used to select matched groups. Survival and recurrence were compared by Kaplan-Meier analysis. Univariable and multivariable Cox regression analyses were used to identify prognostic factors for overall and disease-free survival. RESULTS: A total of 1390 patients were included, of whom 1000 had surgery alone and 390 underwent S-CCRT. Propensity score matching yielded 213 well balanced pairs. The 3-year overall survival rate and median survival time in the S-CCRT group were 0·50 and 36·5 (95 per cent c.i. 25·1 to 52·6) months respectively, compared with 0·38 and 22·8 (18·2 to 29·0) months in the surgery-alone group (P = 0·006). The 3-year disease-free survival rate and median disease-free survival time in the S-CCRT group were 0·46 and 30·6 (22·2 to 39·3) months respectively, compared with 0·36 and 17·6 (11·3 to 23·9) months in the surgery-alone group (P = 0·006). The 2-year freedom from locoregional recurrence rate was 0·87 and 0·77 in the S-CCRT and surgery-alone groups respectively (P = 0·003). In multivariable analysis, independent prognostic factors for disease-free survival included age over 56 years, pT3-4 category, pN category, poor differentiation, tumour length exceeding 4·0 cm, and receiving postoperative chemoradiotherapy (hazard ratio 0·62, 95 per cent c.i. 0·47 to 0·81; P < 0·001). CONCLUSION: Oesophagectomy with postoperative chemoradiotherapy was associated with longer survival and lower recurrence rates, especially at a locoregional level, compared with surgery alone.

Capsular serotypes and multilocus sequence types of bacteremic Klebsiella pneumoniae isolates associated with different types of infections.

We investigated the epidemiology of different serotypes of Klebsiella pneumoniae isolates causing bacteremic liver abscess (LA) using multilocus sequence typing (MLST). MLST and molecular typing were performed for 41 K1 (19 LA), 37 K2 (5 LA), and 33 non-K1/K2 (6 LA) isolates that were derived from a previous one-year K. pneumoniae bacteremia cohort. Capsular serotypes and rmpA of these isolates were determined by polymerase chain reaction (PCR) methods. Among the 41 K1 isolates, 39 were ST23 and the remaining two isolates were ST23 single-locus variant. There were 11 STs among K2 isolates. ST65 was the most common (n = 10), followed by ST86, ST373, and ST375. Only ST65 (n = 3), ST373 (n = 1), and ST375 (n = 1) caused LA, and ST65 was a three-locus variant of ST23. For non-K1/K2 isolates, the ST types varied widely. ST218 (K57) was the most common type (n = 6, 18 %), and it was a single-locus variant of ST23 and caused two cases of LA. The existences of rmpA among serotypes varied (100 % for K1, 89 % for K2, and 55 % for non-K1/K2). For isolates causing LA, all of them were positive for rmpA. For non-K1/K2 isolates causing infections other than LA, the positivity of rmpA ranged from 0 % (biliary tree infection) to 67 % (pneumonia). In this one-year cohort, all K1 isolates were ST23 or its single-locus variants, but the composition of ST types among K2 isolates was quite variable. ST23 and its one- (ST1005 and ST218) and three-locus (ST65) variants comprised 80 % of isolates causing LA.

Medical education in Vietnam.

BACKGROUND: Vietnam is one of the most populous countries in Southeast Asia, yet it displays an unsettling lack of doctors. AIMS: Medical education is an important factor contributing to this issue, yet little is known about the system currently in place in Vietnam. METHODS: Through an extensive literary search of medical schools' and Ministry of Health's data, we have examined the current medical education system in Vietnam. RESULTS: At present, there are 12 medical universities, and the general curriculum at each university follows a national framework but tends to vary from university to university. Medical training lasts either 4 or 6 years, with competitive graduates attending residency programs following graduation. While examinations are required to graduate, the lack of a national licensing exam makes it difficult to ensure that a nation-wide standard of quality exists, both at the medical universities themselves as well as amongst the doctors graduating from them. CONCLUSIONS: The development and institution of a national exam would introduce a standard of training throughout Vietnam's medical education system. Further, a substantial portion of a doctor's education is in subjects that are loosely related to medicine. When looking forward it will be important to evaluate whether or not these non-medical subjects detract from the quality of medical training.

Prognostic significance of hypoxia-inducible factor-1alpha, TWIST1 and Snail expression in resectable non-small cell lung cancer.

BACKGROUND: Metastasis is the most common cause of disease failure and mortality for non-small cell lung cancer (NSCLC) after surgical resection. Snail and TWIST1 are epithelial-mesenchymal transition (EMT) regulators which induce metastasis. Intratumoral hypoxia followed by stabilisation of hypoxia-inducible factor 1alpha (HIF-1alpha) promotes metastasis through regulation of certain EMT regulators. The aim of this study was to evaluate the prognostic value of HIF-1alpha, TWIST1 and Snail expression in patients with resectable NSCLC. METHODS: A retrospective analysis of 87 patients with resectable NSCLC from Taipei Veterans General Hospital between 2003 and 2004 was performed using immunohistochemistry to analyse HIF-1alpha, TWIST1 and Snail expression. The association between HIF-1alpha, TWIST1 and Snail expression and patients' overall and recurrence-free survivals was investigated. RESULTS: Overexpression of HIF-1alpha, TWIST1 or Snail was shown in 32.2%, 36.8% and 55.2% of primary tumours, respectively. Overexpression of HIF-1alpha, TWIST1 or Snail in primary NSCLCs was associated with a shorter overall survival (p = 0.005, p = 0.026, p = 0.009, respectively), and overexpression of HIF-1alpha was associated with a shorter recurrence-free survival (p = 0.016). We categorised the patients into four groups according to the positivity of HIF-1alpha/TWIST1/Snail to investigate the accumulated effects of these markers on survival. Co-expression of more than two markers was an independent prognostic indicator for both recurrence-free survival and overall survival (p = 0.004 and p<0.001, respectively, by multivariate Cox proportional hazards model). CONCLUSIONS: Co-expression of more than two markers from HIF-1alpha, TWIST1 and Snail is a significant prognostic predictor in patients with NSCLC.

Biostabilization assessment of MSW co-disposed with MSWI fly ash in anaerobic bioreactors.

Municipal solid waste incinerator (MSWI) fly ash has been examined for possible use as landfill interim cover. For this aim, three anaerobic bioreactors, 1.2m high and 0.2m in diameter, were used to assess the co-digestion or co-disposal performance of MSW and MSWI fly ash. Two bioreactors contained ratios of 10 and 20 g fly ash per liter of MSW (or 0.2 and 0.4 g g(-1) VS, that is, 0.2 and 0.4 g fly ash per gram volatile solids (VS) of MSW). The remaining bioreactor was used as control, without fly ash addition. The results showed that gas production rate was enhanced by the appropriate addition of MSWI fly ash, with a rate of approximately 6.5l day(-1)kg(-1)VS at peak production in the ash-added bioreactors, compared to approximately 4l day(-1)kg(-1)VS in control. Conductivity, alkali metals and VS in leachate were higher in the fly ash-added bioreactors compared to control. The results show that MSW decomposition was maintained throughout at near-neutral pH and might be improved by release of alkali and trace metals from fly ash. Heavy metals exerted no inhibitory effect on MSW digestion in all three bioreactors. These phenomena indicate that proper amounts of MSWI fly ash, co-disposed or co-digested with MSW, could facilitate bacterial activity, digestion efficiency and gas production rates.

Two-layer method (UW solution/perfluorochemical plus O2) for lung preservation in rat lung transplantation.

A new preservation method using perfluorochemicals (PFC) with oxygen administered continuously was developed for lung preservation and compared with traditional cold preservation methods for rat lung transplantation. Male Sprague-Dawley rats underwent orthotopic left lung transplantations of grafts preserved in lactiated Ringers solution (LR), University of Wisconsin solution (UW), Celsior solution, or a two-layer (PFC plus O2) solution for 6 hours. One hour after reperfusion, the right pulmonary artery and bronchus were clamped and 5 minutes later we recorded peak airway pressure and PaO2 level. The isograft was excised for measurement of myeloperoxidase activity, wet-to-dry ratio, and histologic examination to evaluate isograft function. The mean peak airway pressure was 29.80+/-6.72 mm H2O in the LR group, 28.80+/-5.76 mm H2O in the UW group, 33.60+/-5.17 mm H2O in the Celsior group, and 32.40+/-2.60 in the two-layer group. The mean PaO2 level was 99.78+/-76.09 mm Hg in the LR group, 87.84+/-33.58 mm Hg in the UW group, 104.50+/-72.93 mm Hg in the Celsior group, and 62.08+/-31.34 mm Hg in PFC and UW solution plus O2 group (two layers). The mean net myeloperoxidase activity OD level was 0.110+/-0.104 in the LR group, 0.392+/-0.328 in the UW group, 0.351+/-0.620 in the Celsior group, and 0.532+/-0.616 in the two-layer group. The mean wet-to-dry ratio was 7.47+/-1.60 in the LR group, 6.56+/-0.62 in the UW group, 7.54+/-2.19 in the Celsior group, and 5.32+/-2.20 in the two-layer group. The differences between groups in these parameters were not significant. Upon histologic examination, more inflammatory cell aggregates were seen in the two-layer group, less in the LR and the Celsior groups. The function of the lung graft after 6 hours of storage was not better using this two-layer method for preservation than traditional preservation methods in rat lung transplantation. Histologic examination revealed more inflammatory cell aggregates in the lung graft preserved using a two-layer method.

Serglycin in tumor microenvironment promotes non-small cell lung cancer aggressiveness in a CD44-dependent manner.

Tumor microenvironment (TME) plays an active role in promoting tumor progression. To further understand the communication between TME and tumor cells, this study aimed at investigating the involvement of CD44, a type I cell surface receptor, in the crosstalk between tumor cells and TME. We have previously shown that chondroitin sulfate proteoglycan serglycin (SRGN), a CD44-interacting factor, was preferentially secreted by cancer-associated fibroblasts (CAFs) for promoting tumor growth in breast cancer patients. In this study, we show that SRGN is overexpressed in primary non-small cell lung cancers (NSCLCs), by both carcinoma and stromal cells. Using gain-of-function and loss-of-function approaches, we show that SRGN promotes NSCLC cell migration and invasion as well as colonization in the lung and liver in a CD44-dependent manner. SRGN induces lung cancer cell stemness, as demonstrated by its ability to enhance NSCLC cell sphere formation via Nanog induction, accompanied with increased chemoresistance and anoikis-resistance. SRGN promotes epithelial-mesenchymal transition by enhancing vimentin expression via CD44/NF-κB/claudin-1 (CLDN1) axis. In support, CLDN1 and SRGN expression are tightly linked together in primary NSCLC. Most importantly, increased expression of SRGN and/or CLDN1 predicts poor prognosis in primary lung adenocarcinomas. In summary, we demonstrate that SRGN secreted by tumor cells and stromal components in the TME promotes malignant phenotypes through interacting with tumor cell receptor CD44, suggesting that a combined therapy targeting both CD44 and its ligands in the TME may be an attractive approach for cancer therapy.

Physician Scientist Training in the United States: A Survey of the Current Literature.

The declining number of physician scientists is an alarming issue. A systematic review of all existing programs described in the literature was performed, so as to highlight which programs may serve as the best models for the training of successful physician scientists. Multiple databases were searched, and 1,294 articles related to physician scientist training were identified. Preference was given to studies that looked at number of confirmed publications and/or research grants as primary outcomes. Thirteen programs were identified in nine studies. Eighty-three percent of Medical Scientist Training Program (MSTP) graduates, 77% of Clinician Investigator Training Program (CI) graduates, and only 16% of Medical Fellows Program graduates entered a career in academics. Seventy-eight percent of MSTP graduates succeeded in obtaining National Institute of Health (NIH) grants, while only 15% of Mayo Clinic National Research Service Award-T32 graduates obtained NIH grants. MSTP physician scientists who graduated in 1990 had 13.5 ± 12.5 publications, while MSTP physician scientists who graduated in 1975 had 51.2 ± 38.3 publications. Additionally, graduates from the Mayo Clinic's MD-PhD Program, the CI Program, and the NSRA Program had 18.2 ± 20.1, 26.5 ± 24.5, and 17.9 ± 26.3 publications, respectively. MSTP is a successful model for the training of physician scientists in the United States, but training at the postgraduate level also shows promising outcomes. An increase in the number of positions available for training at the postgraduate level should be considered.

Differential accumulations of 4,977 bp deletion in mitochondrial DNA of various tissues in human ageing.

Several types of deletions in mitochondrial DNA (mtDNA) have been recently identified in various tissues of old humans. In order to determine whether there are differences in the incidence and proportion of deleted mtDNAs in different tissues during human ageing, we examined the 4,977 bp deletion in mtDNA of various tissues from subjects of different ages. Total DNA was extracted from each of the biopsied tissues and was serially diluted by two-fold with distilled water. A 533 bp DNA fragment was amplified by PCR from total mtDNA using a pair of primers L3304-3323 and H3817-3836, and another 524 bp PCR product was amplified from 4,977 bp deleted mtDNA by identical conditions using another pair of primers L8150-8166 and H13631-13650. The maximum dilution fold of each sample that still allowed the ethidium bromide-stained PCR product (533 bp or 524 bp) in the agarose gel to be visible under UV light illumination was taken as the relative abundance of the mtDNA (wild-type or mutant) in the original sample. By this method, we were able to determine the proportion of deleted mtDNA in human tissues. We found that the 4,977 bp deletion started to appear in the second and third decades of life in human muscle and liver tissues. But the deletion was not detectable in the testis until the age of 60 years. Moreover, the proportion of deleted mtDNA varied greatly in different tissues. Among the tissues examined, muscle was found to harbor higher proportion of deleted mtDNA than the other tissues. The average proportion of the 4,977 bp deleted mtDNA of the muscle from subjects over 70 years old was approximately 0.06%, and that of the liver and the testis was 0.0076% and 0.05%, respectively. These findings suggest that the frequency and proportion of the deleted mtDNA in human tissues increase with age and that the mtDNA deletions occur more frequently and abundantly in high energy-demanding tissues during the ageing process of the human.

Different spontaneous breathing trials in patients with atrial fibrillation.

INTRODUCTION: Weaning from mechanical ventilation is one of the most important and challenging problems for most intensive care unit (ICU) patients. Spontaneous breathing trial (SBT) is the most common method used to evaluate patients' ability to breathe by themselves and plays an important role in decision making for weaning. The aim of our study was to investigate the effect of different methods of SBT in respiratory care unit (RCU) patients with atrial fibrillation (AF) on weaning outcome. METHODS: We retrospectively analyzed different methods of SBT in patients with and without AF. We enrolled RCU patients who required mechanical ventilation and had undergone transthoracic echocardiography from January 2011 to January 2012. RESULTS: There was a higher SBT passing rate among AF patients who received pressure support ventilation (PSV) trial than in those who received T-piece trail (92.5% vs. 73.1%, p=0.041). The weaning rates between these two groups were not significantly different (83.8% vs. 94.7%, p=0.403). Total ventilator days were longer in T-piece group than in PSV group (median 40.0, IQR: 18.2-125.1 days vs. 33.0, IQR: 29.6-51.0 days respectively, p=0.580), but this difference was not statistically significant. These results were not found in patients without AF. CONCLUSIONS: The use of PSV trial might be considered first instead of T-piece trial for SBT when AF patients were ready to wean.

Inverse relationship between body mass index and mortality in older nursing home residents: a meta-analysis of 19,538 elderly subjects.

Body mass index (BMI) and mortality in old adults from the general population have been related in a U-shaped or J-shaped curve. However, limited information is available for elderly nursing home populations, particularly about specific cause of death. A systematic PubMed/EMBASE/CINAHL/SCOPUS search until 31 May 2014 without language restrictions was conducted. As no published study reported mortality in standard BMI groups (<18.5, 18.5-24.9, 25-29.9, ≥30 kg/m(2)), the most adjusted hazard ratios (HRs) according to a pre-defined list of covariates were obtained from authors and pooled by random-effect model across each BMI category. Out of 342 hits, 20 studies including 19,538 older nursing home residents with 5,223 deaths during a median of 2 years of follow-up were meta-analysed. Compared with normal weight, all-cause mortality HRs were 1.41 (95% CI = 1.26-1.58) for underweight, 0.85 (95% CI = 0.73-0.99) for overweight and 0.74 (95% CI = 0.57-0.96) for obesity. Underweight was a risk factor for higher mortality caused by infections (HR = 1.65 [95% CI = 1.13-2.40]). RR results corroborated primary HR results, with additionally lower infection-related mortality in overweight and obese than in normal-weight individuals. Like in the general population, underweight is a risk factor for mortality in old nursing home residents. However, uniquely, not only overweight but also obesity is protective, which has relevant nutritional goal implications in this population/setting.

Ageing-associated tandem duplications in the D-loop of mitochondrial DNA of human muscle.

Using PCR techniques, we detected a approximately 260 bp (type I) and a approximately 200 bp (type II) tandem duplications in the mtDNA of muscle biopsies from aged individuals. Only one 70-year-old subject was found to harbour the type I and 28 out of 58 subjects had type II duplication. About 90% of the subjects harbouring the duplicated mtDNAs also had the 4,977 bp deletion. Moreover, the incidence and quantity of the type II duplication were found to increase with age. The proportion of the type II duplicated mtDNA in the muscle of a 71-year-old subject was 3.1% while that of a 55-year-old individual was only 0.78%. We suggest that the tandem duplications occur alone or with mtDNA deletions in human tissues in an age-dependent manner, and thereby cause synergistic deleterious effects on mitochondrial respiratory functions in human ageing.

Evidence of possible carcinogenesis during conformational changes in bladder mucosa induced by bladder outlet obstruction.

Fourier transform infrared spectroscopy with attenuated total reflectance technique was applied to determine the mucosa on the surface of the rabbit urinary bladder wall before and after obstruction. Several abnormal spectra related to the hydrogen bonding in nucleic acids of protein, previously found in the colon malignant tissues, appeared in the infrared spectra of the obstructed bladder mucosa, which could not be found in normal bladder mucosa. Urinary bladder outlet obstruction seemed to induce carcinogenesis in the obstructed bladder mucosa by forming several infrared spectral abnormalities.

New imidazoles as probes of the active site topology and potent inhibitors of beta-glucosidase.

Series of 4-arylimidazoles, omega-N-acylhistamines and 4-(omega-phenylalkyl)imidazoles were synthesized in order to probe the active site topology of sweet almond beta-glucosidase. These imidazole derivatives were shown to be very powerful competitive inhibitors. Among the 20 tested compounds, omega-N-benzoylhistamine and 4-(3'-phenylpropyl)imidazole are the most potent inhibitors of the enzyme, with pH-independent Ki values of 0.06 and 0.07 microM, respectively. The inhibition of 4-(omega-phenylalkyl)imidazoles exhibited an interesting trend as to Ki values: 4-phenylimidazole (6.6 microM)>4-benzylimidazole (1.4 microM)>4-(2'-phenylethyl)imidazole (0.82 microM)>4-(3'-phenylpropyl)imidazole (0.07 microM)<4-(4'-phenylbutyl)imidazole (0.13 microM)<4-(5'-phenylpentyl)imidazole (0.3 microM). This revealed that the imidazole and aryl binding sites (which result from favorable interactions within the corresponding glycone and aglycone binding subsites) are separated by the optimal distance equivalent to the length of a -CH2-CH2-CH2- group. Substitutions of the phenyl moieties of 4-phenylimidazole and 4-benzoylhistamine result in weaker inhibition. These classes of imidazoles are particularly powerful inhibitors of sweet almond beta-glucosidase.

Dissemination and proliferation of Salmonella typhimurium in genetically resistant and susceptible mice.

Genetically resistant A/J and CBA mice were inoculated intraperitoneally with either 10(3) or 10(4) organisms of a virulent strain of Salmonella typhimurium; susceptible C57BL/6J and BALB/c mice were inoculated with either 10(2) or 10(3) organisms. Except with the smaller dose in resistant mice, fatal infection ensued. Bacteraemia occurred within 1 h after inoculation, except that it was not detectable during the first 6 h in the susceptible mice inoculated with 10(2) organisms. From day 2, the circulating bacterial population continued to increase in all infected mice, except that it remained under control in the resistant mice inoculated with the lower dose (10(3) organisms). The pathogen proliferated logarithmically in the liver from day 2, and a bacterial count of c. 10(8) cfu/g of tissue was reached when the animals died at 5-7 days; again, the resistant mice inoculated with 10(3) organisms were an exception in which the hepatic bacterial population was kept under control and the mice survived.

Protective immunity induced in mice by detoxified salmonella lipopolysaccharide.

C3H/HeNMTV mice were immunised intraperitoneally (i.p.) with lipopolysaccharide (LPS) or detoxified LPS (D-LPS) derived from Salmonella typhimurium strain SR-11. In both cases, effective protection was achieved against a challenge dose of greater than 2 x 10(2) LD50 of the same organism given by i.p. injection. However, by comparison with LPS, approximately 6- to 10-fold more of D-LPS by weight was needed to protect mice to an equivalent degree. Histopathological studies showed that the initial lesions in infected mice protected with either LPS or D-LPS were composed of self-limiting abscesses which transformed into granulomas as the animals recovered. It is suggested that D-LPS may be modified to become a highly effective, non-toxic salmonella vaccine.

Electronmicroscopy studies on the bactericidal action of inflammatory leukocytes in murine salmonellosis.

Inbred female C3H mice were given 2 X 10(7) cfu virulent Salmonella typhimurium by intraperitoneal injection. Peritoneal washings were harvested between 3 h and 72 h after infection and examined by electronmicroscopy. There was evidence of intracellular killing by polymorphs and macrophages. The degeneration of intracellular salmonellae was seen initially as enlarging central electron-lucent areas in the cytoplasm and peripheral condensation of cytoplasmic granules, followed by disruption of the bacterial envelope and disintegration of cellular structure. Alternatively, the initial injury appeared as an irregular and discontinuous bacterial envelope with compression of the bacterium and diffuse condensation of cytoplasmic granules. It was also evident that virulent salmonellae multiplied extracellularly in the peritoneal cavity of the infected mice.

Electronmicroscopy studies on the opsonic role of antiserum and the subsequent destruction of Salmonellae within murine inflammatory leukocytes.

Inbred female C3H mice were given, by intraperitoneal injection, 4 X 10(7) virulent Salmonella typhimurium organisms opsonised with specific antiserum. Peritoneal washings were obtained between 1.5 and 24 h after injection and examined by electronmicroscopy. Opsonised salmonellae were ingested rapidly by peritoneal exudate cells and were digested rapidly. The presence of antibody facilitated the phagocytic efficiency of the host cells. Destruction of ingested bacteria appeared to be an innate capacity of the host phagocytes independent of the presence of antibody.

Intracellular destruction of salmonellae in genetically resistant mice.

Virulent Salmonella typhimurium, 2000 LD50, were injected intraperitoneally into inbred male A/J mice, genetically resistant to salmonella infection. Peritoneal exudate cells were harvested between 5 and 54 h after infection and examined by electronmicroscopy. Polymorphs were seen ingesting as well as digesting the pathogens as early as 5 h after infection. Macrophages were equally active in destroying the phagocytosed organisms throughout this period. In the meantime, the proliferation of salmonellae appeared to occur extracellularly in the peritoneal cavity as evidenced by their division.