Temporal Effects of Bariatric Surgery on Adipokines, Inflammation and Oxidative Stress in Subjects with Impaired Glucose Homeostasis at 4 Years of Follow-up

Background

Previous studies have examined changes in plasma markers of inflammation and oxidative stress up to 24 months following bariatric surgery, but there is limited evidence on the long-term effects of bariatric surgery.

Objectives

To examine the effects of bariatric surgery on adipokines (adiponectin, leptin), inflammatory cytokines [C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-10(IL-10)] and global plasma measures of oxidative stress [thiobarbituric acid reactive substances (TBARS) and total antioxidant status (TAOS) 1 and 6 months, and 4 years post-surgery in subjects with obesity and impaired glucose regulation.

Methods

A prospective study comprising of 19 participants (13 females, mean age 50.4 ± 6.2 years, mean body mass index (BMI) 54 ± 14 kg/m², 17 type 2 diabetes) undergoing bariatric surgery (10 sleeve gastrectomy, 6 biliopancreatic diversion, 2 Roux-en-Y gastric bypass and 1 laparoscopic adjustable gastric banding). Serial measurements of the above markers were made pre-operatively, 1 and 6 months and 4 years post-operatively.

Results

Compared to pre-operative levels, significant decreases were seen 4 years post-operatively in CRP (11.4 vs 2.8 ng/mL, p < 0.001), IL-6 (8.0 vs 2.1 pg/mL, p < 0.001) and leptin (60.7 vs 32.1 pg/mL, p = 0.001). At 4 years, both fasting and 120 min TAOS significantly increased by 35% and 19% respectively. However, fasting and 120 min TBARS did not show any significant changes.

Conclusion

To our knowledge, no other studies have described changes in inflammation and oxidative stress at 4 years following bariatric surgery. This study contributes to the current literature supporting the longer-term beneficial effect of bariatric surgery on chronic inflammation and oxidative stress.

Effect of Laparoscopic Sleeve Gastrectomy on Static and Dynamic Measures of Glucose Homeostasis and Incretin Hormone Response 4-Years Post-Operatively

INTRODUCTION

There is limited literature available on the long-term effect of bariatric surgery especially laparoscopic sleeve gastrectomy (LSG) on the incretin hormone response.

AIM

Our primary aim was to investigate changes in glucose metabolism and incretin hormone responses in participants with impaired glucose regulation approximately 4 years after LSG. The secondary aim was to examine the long-term incretin hormone changes of biliopancreatic diversion (BPD).

METHOD

A non-randomised prospective study comprising of 10 participants undergoing LSG and 6 participants undergoing BPD. Serial measurements of glucose, insulin, C-peptide, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) were performed during an oral glucose tolerance test pre-operatively and 1 month, 6 months and at approximately 4-7 years post-operatively. Area under the curve (AUC) was examined at 60 and 120 min.

RESULTS

In the LSG group, a significant reduction in 2-h plasma glucose (2 h PG), HbA1c and HOMA-IR was observed at 4 years. Compared with pre-operative levels, significant increases in post-glucose GLP-1 secretion were observed at 1 and 6 months, but not maintained at 4 years. A linear increase was seen in post-glucose GIP response at 1 month and 6 months and 4 years. Within the BPD group, a reduction in HbA1c along with an increase GLP-1 response was observed at 7 years.

CONCLUSION

An increase in GLP-1 response was not preserved at 4 years, but a significant increase in GIP response was observed along with improved glycaemic control following LSG.

Closure of mesenteric defects during Roux-en-Y gastric bypass for obesity: A systematic review and meta-analysis protocol

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Roux-en-Y gastric bypass is an effective treatment for severe obesity and its comorbidities.

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Closure of mesenteric defects may reduce the overall incidence of internal herniation.

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Closure of mesenteric defects may also increase early small bowel obstruction and bleeding.

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This review is designed to establish the evidence for and against closure of mesenteric defects.

Introduction

Closure of mesenteric defects during laparoscopic Roux-en-Y gastric bypass surgery (RYGB) has not been fully established as standard operative practice. However, in recent years a body of evidence has emerged suggesting that non-closure of defects leads to increased rates of internal herniation and its potential consequences, including the need for reoperation, along with an associated morbidity and mortality risk. Within the emerging literature there has also been some evidence of a greater risk of 30-day complications in closure groups. This systematic review and meta-analysis aims to look at the existing evidence and provide guidance on whether closure of mesenteric defects should be standard operative practice.

Methods

The systematic review and meta-analysis has been registered a priori. A literature search will be performed interrogating the Medline and Embase databases via Ovid, and also the Cochrane Controlled Register of Trials (CENTRAL), to identify randomised and non-randomised studies reporting comparative outcomes following closure vs. non-closure of mesenteric defects during RYGB. The primary outcome will be reoperation for small bowel obstruction, and secondary outcomes will include internal herniation, jejuno-jejunal anastomosis narrowing or kinking, adhesions, complications (<30 days and >30 days after surgery), 30-day mortality, reoperation, and any other outcome deemed relevant and reported in more than one study.

Temporal Effect of Bariatric Surgery on Predicted 10-Year and Lifetime Cardiovascular Risk at 1 Month, 6 Months, and 5 Years Following Surgery: A Pilot Study

BACKGROUND AND AIMS

Cardiovascular (CV) risk equations are routinely used to predict risk in nonbariatric populations, but have not been studied in depth in patients undergoing bariatric surgery and specifically those with impaired glucose regulation. The aim of this pilot study was to investigate changes in the 10-year and lifetime predicted CV risk in subjects with impaired glucose regulation before, 1 month, 6 months, and 5 years after bariatric surgery.

METHOD AND RESULTS

A nonrandomized prospective study was conducted of 45 participants with impaired glucose regulation undergoing temporal assessments during follow-up. Body weight, body mass index (BMI), blood pressure, lipid profile, and HbA1c were recorded preoperatively, 1 month, 6 months, and 5 years postoperatively. Preoperative and postoperative predicted CV risk was calculated using the QRISK2, QRISK lifetime, and JBS3 calculators. Follow-up rates were 93%, 91%, and 71% at 1 month, 6 months, and 5 years, respectively. The sample had a mean age of 48.8 ± 7.0 years, a mean BMI of 53.9 ± 11.1 kg/m², and a mean HbA1c of 7.5% ± 1.7%. The predicted 10-year QRISK2 score decreased by 35%, 54%, and 24% at 1 month, 6 months, and 5 years, respectively (P < 0.001). The predicted lifetime risk also decreased with the greatest reduction (24.5% with QRISK lifetime and 26.7% with JBS3 lifetime score) observed at 5 years even though the subjects were 5 years older.

CONCLUSION

Bariatric surgery in patients with impaired glucose regulation is associated with a significant reduction in predicted 10-year and lifetime CV risk in a population that was 5 years older compared to baseline.

Association between the preoperative fasting and postprandial C-peptide AUC with resolution of type 2 diabetes 6 months following bariatric surgery

BACKGROUND AND AIMS

Bariatric surgery results in the remission of type 2 diabetes mellitus (T2DM) in morbidly obese subjects. The aim of the study was to investigate the predictive value of both static and dynamic measures of C-peptide in relation to T2DM resolution 6 months after bariatric surgery regardless of the operation type.

METHODS AND RESULTS

A non-randomized prospective study of 24 participants with T2DM undergoing bariatric surgery. Measurements of fasting and 2-hour plasma glucose, insulin, C-peptide and measures of insulin sensitivity were recorded temporally during an oral glucose tolerance test pre-operatively and 6 months post-operatively. A responder was defined with a fasting glucose <5.6 mmol/L and HbA1c <6.0% postoperatively. Within the sample there were 11 responders and 13 non-responders at 6 months. There was a significant difference in the duration of diabetes between the groups. Fasting C-peptide (P≤0.05) and 2-hour C-peptide (P≤0.05) were higher in responders compared to non-responders. Significantly higher C-peptide levels were observed preoperatively at all time points for responders, with significantly higher area under the curve (AUC0-60 and AUC0-120). Using the lower quartiles for C-peptide levels, both fasting C-peptide (>2.5 ng/mL [0.83 nmol/L]) and 2-hour C-peptide (>5.2 ng/mL [1.73 nmol/L]) had a sensitivity and negative predictive value of 100% to predict T2DM remission. Logistic regression showed that C-peptide, duration of diabetes and BMI were associated with response. The area under the ROC curve was 0.94 and a regression model predicted diabetes remission with a sensitivity of 85.7% and a specificity of 88.9%.

CONCLUSIONS

This study demonstrated that static (fasting) and dynamic (AUC, 2-hour) C-peptide measurements predict T2DM resolution 6 months following bariatric surgery. This work provides insight into C-peptide dynamics as a predictor of response to bariatric surgery.

Changes in markers of oxidative stress and DNA damage in human visceral adipose tissue from subjects with obesity and type 2 diabetes

AIMS

In the past 30 years, prevalence of obesity has almost trebled resulting in an increased incidence of type 2 diabetes mellitus and other co-morbidities. Visceral adipose tissue is believed to play a vital role, but underlying mechanisms remain unclear. Our aim was to investigate changes in markers of oxidative damage in human visceral adipose tissue to determine levels of oxidative burden that may be attributed to obesity and/or diabetes.

METHODS

Visceral adipose tissue samples from 61 subjects undergoing abdominal surgery grouped as lean, obese and obese with type 2 diabetes mellitus, were examined using 3 different markers of oxidative stress. Malondialdehyde (MDA) concentration was measured as a marker of lipid peroxidation, telomere length and Comet assay as markers of oxidative DNA damage.

RESULTS

No significant difference in MDA concentration, telomere length and DNA damage was observed between groups, although longer telomere lengths were seen in the obese with diabetes group compared to the obese group (P<0.05). Lower MDA concentration and longer telomere length were seen in subjects with diabetes compared to those without (P<0.05). DNA damage, analysed via Comet assay, was significantly lower in subjects with diabetes compared to those without (P<0.05).

CONCLUSION

A paradoxical decrease in oxidative stress and DNA damage was observed in samples from subjects with type 2 diabetes mellitus. Further work is required to investigate this further, however this phenomenon may be due to an up regulation of antioxidant defences in adipose tissue.

Changes in inflammatory markers after sleeve gastrectomy in patients with impaired glucose homeostasis and type 2 diabetes

BACKGROUND

Bariatric surgery is an effective treatment for morbid obesity. Obesity and type 2 diabetes are associated with chronic inflammation. There is lack of data examining the effects of sleeve gastrectomy (SG) on inflammatory biomarkers. Our aim was to study the effects of SG on specific cytokines associated with obesity including interleukin-6 (IL-6), interleukin-10 (IL-10), leptin, adiponectin, and C-reactive protein (CRP) preoperatively, 1 and 6 months after surgery.

METHODS

A nonrandomized prospective study comprising of 22 participants with impaired glucose homeostasis and type 2 diabetes undergoing SG (body mass index 50.1 kg/m(2), glycated hemoglobin [HbA1c] 53 mmol/mol). Serial measurements of IL-6, IL-10, leptin, adiponectin, and CRP were performed during oral glucose tolerance testing preoperatively, 1 and 6 months postoperatively.

RESULTS

We observed significant improvements at 1 and 6 months in leptin (P≤.001) and CRP (P = .003) after SG. We also observed a significant reduction in IL-6 at 6 months (P = .001). No statistically significant differences were observed for adiponectin and IL-10.

CONCLUSION

This study is the first to examine the detailed changes in the inflammatory cytokines after SG. Our study shows significant improvements in the inflammatory biomarkers after SG in patients with impaired glucose homeostasis and type 2 diabetes.

Does bariatric surgery adversely impact on diabetic retinopathy in persons with morbid obesity and type 2 diabetes? A pilot study

AIMS

To assess the incidence and progression of diabetic retinopathy (DR) 12 months post bariatric surgery in persons with morbid obesity and type 2 diabetes.

METHODS

A retrospective pilot analysis of electronic hospital records between 1998 and 2012.

RESULTS

40 of 148 subjects had pre- and post-surgery DR screening. Of those without DR pre-surgery 1.5% (n = 26) progressed to minimum background DR (BDR) post surgery. Those with minimum BDR (n = 9) pre-surgery revealed no progression, with 55.6% (n = 5) showing evidence of regression. One person with moderately severe BDR and two with pre-proliferative DR (PPDR) prior to surgery experienced progression. Two persons with PPDR prior to surgery remained under the hospital eye services and were therefore not eligible to be re-assessed by the screening service.

CONCLUSIONS

There was a low incidence of new DR and progression of DR in those either without evidence of retinopathy or with minimal BDR prior to surgery with some subjects showing evidence of regression. There was however a risk of progression of DR in those with moderate BDR or worse, and should therefore be monitored closely post-surgery.

Linking the antigen archive structure to pathogen fitness in African trypanosomes

Systems that generate antigenic variation enable pathogens to evade host immune responses and are intricately interwoven with major pathogen traits, such as host choice, growth, virulence and transmission. Although much is understood about antigen switching at the molecular level, little is known about the cross-scale links between these molecular processes and the larger-scale within and between host population dynamics that they must ultimately drive. Inspired by the antigenic variation system of African trypanosomes, we apply modelling approaches to our expanding understanding of the organization and expression of antigen repertoires, and explore links across these scales. We predict how pathogen population processes are determined by underlying molecular genetics and infer resulting selective pressures on important emergent repertoire traits.

Critical interplay between parasite differentiation, host immunity, and antigenic variation in trypanosome infections

Increasing availability of pathogen genomic data offers new opportunities to understand the fundamental mechanisms of immune evasion and pathogen population dynamics during chronic infection. Motivated by the growing knowledge on the antigenic variation system of the sleeping sickness parasite, the African trypanosome, we introduce a mechanistic framework for modeling within-host infection dynamics. Our analysis focuses first on a single parasitemia peak and then on the dynamics of multiple peaks that rely on stochastic switching between groups of parasite variants. A major feature of trypanosome infections is the interaction between variant-specific host immunity and density-dependent parasite differentiation to transmission life stages. In this study, we investigate how the interplay between these two types of control depends on the modular structure of the parasite antigenic archive. Our model shows that the degree of synchronization in stochastic variant emergence determines the relative dominance of general over specific control within a single peak. A requirement for multiple-peak dynamics is a critical switch rate between blocks of antigenic variants, which implies constraints on variant surface glycoprotein (VSG) archive genetic diversification. Our study illustrates the importance of quantifying the links between parasite genetics and within-host dynamics and provides insights into the evolution of trypanosomes.

Prognostic significance of endoscopic ultrasound-defined pleural, pericardial or peritoneal fluid in oesophageal cancer

BACKGROUND

Endoscopic ultrasound (EUS) is known to detect smaller effusion volumes than computerised tomography (CT), yet the outcomes for patients diagnosed with oesophageal carcinoma and EUS-defined pleural, pericardial or ascitic fluid effusions (EDFE) are unknown. The aim of this study was to determine the outcome of multidisciplinary stage directed treatment for such patients.

METHODS

Forty-nine (9.2%) out of a consecutive 527 patients diagnosed with oesophageal cancer from a single regional upper gastrointestinal (GI) cancer network were found to have evidence of EDFE undetected by CT. Thirty-nine (79.6%) patients had pleural effusions, eight (16.3%) pericardial effusions, and two (4.1%) ascites.

RESULTS

Twelve (24.4%) underwent surgery, 3 (6.1%) received neoadjuvant chemotherapy without subsequent surgery, 12 (24.5%) received definitive chemoradiotherapy (dCRT), and 22 (44.9%) received palliative treatment. Survival in patients with EDFE was significantly shorter (median and 2-year survival 15.6 months and 24%, respectively) when compared with patients without EDFE (26.7 months and 40%, respectively, p = 0.001), and was unrelated to EDFE type (p = 0.192). Two-year survival after oesophagectomy with or without neoadjuvant therapy was 45% in patients with EDFE compared with 42% in patients without EDFE (p = 0.668).

CONCLUSIONS

EDFE was an important adverse prognostic indicator, but patients deemed to have operable tumours should still be treated with radical intent.

What the genome sequence is revealing about trypanosome antigenic variation

African trypanosomes evade humoral immunity through antigenic variation, whereby they switch expression of the gene encoding their VSG (variant surface glycoprotein) coat. Switching proceeds by duplication of silent VSG genes into a transcriptionally active locus. The genome project has revealed that most of the silent archive consists of hundreds of subtelomeric VSG tandem arrays, and that most of these are not functional genes. Precedent suggests that they can contribute combinatorially to the formation of expressed, functional genes through segmental gene conversion. These findings from the genome project have major implications for evolution of the VSG archive and for transmission of the parasite in the field.

Prognostic significance of alarm symptoms in patients with gastric cancer

BACKGROUND

The aim of this study was to determine the incidence and spectrum of alarm symptoms in patients with newly diagnosed gastric cancer, and to examine the relationship between symptoms and outcome.

METHODS

Three hundred consecutive patients with gastric adenocarcinoma were studied prospectively. The outcomes of 40 patients (13.3 per cent) without alarm symptoms (21 men; median age 69 years) were compared with those of the 260 patients (86.7 per cent) with alarm symptoms (175 men; median age 72 years).

RESULTS

It was possible to perform an R0 gastrectomy more often in patients without alarm symptoms (21 patients; 52 per cent) than in those with alarm symptoms (71 patients; 27.3 per cent) (chi(2) = 10.35, 1 d.f., P = 0.001). The cumulative survival rate at 5 years was 38 per cent for patients without alarm symptoms versus 15.0 per cent for those with alarm symptoms (chi(2) = 10.18, 1 d.f., P = 0.001). In a multivariate analysis, distant metastasis (hazard ratio (HR) 2.73 (95 per cent confidence interval (c.i.) 2.04 to 3.66); P < 0.001), overall stage of cancer (HR 1.83 (95 per cent c.i. 1.53 to 2.19); P < 0.001) and persistent vomiting at diagnosis (HR 1.66 (95 per cent c.i. 1.26 to 2.18); P < 0.001) were independently associated with length of survival.

CONCLUSION

Alarm symptoms are absent in a significant minority of patients with gastric cancer at diagnosis; these patients stand a better chance of curative surgery and long-term survival than those with alarm symptoms.

The dynamics of antigenic variation and growth of African trypanosomes

Antigenic variation in African trypanosomes, which is a simple strategy for survival in the immune host, is rendered complex by its magnitude. For protection from nonspecific immunity and escape from specific immunity, each trypanosome is covered by a replaceable surface coat composed of the variant surface glycoprotein (VSG), which specifies the variable antigen type (VAT) of the trypanosome. Antigenic variation is the process by which the trypanosome switches from one coat to another. Here, David Barry and Michael Turner consider this phenomenon within the context of the course of trypanosome infection.

Prospective evaluation of nutritional status related to body mass indices and outcomes after modified D2 gastrectomy for carcinoma

AIMS

The aim of this study was to examine the perioperative nutritional status, body mass indices (BMI) and nutritional intakes of patients undergoing a modified D2 gastrectomy (preserving pancreas and spleen) for carcinoma to determine whether a relationship exists between the above and outcomes.

METHODS

Fifty consecutive patients [median age 71 years, 38 male] with gastric adenocarcinoma were studied prospectively.

RESULTS

Seven patients (14%) were obese (BMI > 30 kg/m2), 16 patients (32%) were overweight (BMI > 25 kg/m2), 21 patients (42%) were of normal weight (BMI 20-25 kg/m2), and six patients (12%) were underweight (BMI < 20 kg/m2). Operative morbidity was commoner in underweight patients (33%) when compared with overweight patients (17%, P = 0.391) and patients of normal weight (14%, P = 0.289). Fatal complications, however (two patients, 4%) were confined to overweight patients (P = 0.118). Preoperative serum albumin levels were significantly higher in overweight patients (43 g/dl) compared to underweight patients (34.5 g/dl; P = 0.003), though no correlation was found between patients' serum albumin levels and postoperative morbidity (r = -0.023, P = 0.877). Overweight patients were significantly less likely to achieve their protein requirements postoperatively than underweight patients (P = 0.037). Early enteral feeding contributed to 56% of the median energy requirements and 45% of the median protein requirements on the seventh postoperative day.

CONCLUSION

BMI alone is a poor indicator of outcomes after modified D2 gastrectomy for carcinoma. The role of early enteral nutrition in patients undergoing gastrectomy for cancer deserves further evaluation.

Prognostic significance of acute presentation with emergency complications of gastric cancer

BACKGROUND

Although acute complications necessitating emergency hospital admission are well documented in patients with carcinoma of the colon, comparable data for patients with gastric carcinoma is thin. The aim of this study, therefore, was to examine the outcomes of patients presenting to hospital as acute admissions with emergency complications of previously undiagnosed gastric cancer.

METHODS

Three hundred consecutive patients with gastric adenocarcinoma were studied prospectively, and subdivided into two groups according to whether the patients were referred as acute emergencies ( n = 116) or as outpatients ( n = 184).

RESULTS

The commonest emergency complications were: abdominal pain (57%), vomiting (41%), gastrointestinal bleeding (37%), dysphagia (26%), and a palpable mass (18%). Stages of disease were significantly more advanced in patients presenting acutely (I : II : III : IV = 7 : 11 : 27 : 71) compared with patients referred via outpatients (20 : 23 : 50 : 91, Chi(2) = 3.955; DF, 1; P = 0.047). R0 gastrectomy was significantly less likely after acute presentation (23 patients; 20%) compared with patients referred via outpatients (70 patients; 38%; Chi(2) = 11.037; DF, 1; P = 0.001). Cumulative 5-year survival for patients referred acutely was 9%, compared with 22% after outpatient referral (Chi(2) = 9.11; DF, 1; P = 0.0025). Multivariate analysis revealed two factors to be significantly and independently associated with durations of survival: stage of disease (hazard ratio [HR], 1.742; 95% confidence interval [CI], 1.493-2.034; P = 0.0001) and presentation with acute complications (HR, 1.561; 95% CI, 1.151-2.117; P = 0.004).

CONCLUSION

Emergency complications of gastric cancer are a significant and independent prognostic marker of poor outcome.

Prospective comparison of D1 vs modified D2 gastrectomy for carcinoma

To compare the outcomes after D1 gastrectomy with those after modified D2 gastrectomy (preserving pancreas and spleen) performed by specialist surgeons for gastric cancer in a large UK NHS Trust. In all, 118 consecutive patients with gastric adenocarcinoma were referred by postcode, to undergo either a D1 gastrectomy (North Gwent (RJ), n=36, median age 76 years, 21 m) or a modified D2 gastrectomy (South Gwent (WL), n=82, 70 years, 57 m). Operative mortality in the two groups of patients was similar (D1 8.3% vs D2 7.3%, χ² 0.286, DF 1, P=0.593). Overall cumulative survival at 5 years was 32% after D1 gastrectomy compared to 59% after D2 gastrectomy (χ² 4.25, DF 1, P=0.0392). In patients with stage III cancers, survival was 8% after D1, compared with 33% after D2 gastrectomy (χ² 6.43, DF 1, P=0.0112). In a multivariate analysis, T stage (hazard ratio 2.339, 95% CI 1.683–2.995, P=0.01), N stage (hazard ratio 4.026, 95% CI 3.536–4.516, P=0.0001) and the extent of lymphadenectomy (hazard ratio 0.258, 95% CI –0.426–0.942, P=0.0001) were independently associated with durations of survival. In conclusion, modified D2 gastrectomy can improve survival four-fold for patients with stage III gastric cancer, without significantly increasing morbidity and mortality when compared with a D1 gastrectomy.

Laparoscopy significantly improves the perceived preoperative stage of gastric cancer

BACKGROUND

The aim of this study was to examine the accuracy of laparoscopy is staging patients with gastric cancer in comparison with preoperative computed tomography (CT) examination.

METHODS

One hundred patients out of a consecutive series of 258 patients with gastric adenocarcinoma underwent a preoperative staging CT followed by a staging laparoscopy. The strengths of the agreement between the CT stage, the laparoscopic stage, and the final histopathological stage were determined by the weighted Kappa statistic (Kw).

RESULTS

The strengths of agreement between the CT stage and the final histopathological stage were Kw = 0.336 (95% confidence interval [CI]; 0.172-0.5; P = 0.0001) for T stage and 0.378 (95% CI; 0.226-0.53; P = 0.0001) for M stage, compared with 0.455 (95% CI; 0.301-0.609; P = 0.0001) and 0.73 (95% CI; 0.596-0.864; P = 0.0001) for the laparoscopic T and M stages, respectively. Unsuspected metastases that were not detected by CT, were found in 21 patients at laparoscopy, all of whom had T3 or T4 locally advanced tumors evident on CT.

CONCLUSIONS

Preoperative laparoscopic staging of gastric cancer is indicated for potential surgical candidates with locally advanced disease in the absence of metastases on CT. The aim of this study was to examine the accuracy of laparoscopy in staging patients with gastric cancer in comparison with preoperative computed tomography (CT) examination.

Western body mass indices need not compromise outcomes after modified D2 gastrectomy for carcinoma

BACKGROUND

To determine the role of body mass index (BMI) in a Western population on outcomes after modified D2 gastrectomy (preserving pancreas and spleen where possible) for gastric cancer.

METHODS

Eighty-four consecutive patients undergoing an R0 modified D2 gastrectomy for gastric cancer were studied prospectively. Male patients with a BMI of greater than 24.7 kgm(-2) and female patients with a BMI of greater than 22.6 kgm(-2) were classified as overweight and compared with control patients with BMIs below these reference values.

RESULTS

Thirty-eight of the patients (45%) were classified as overweight. The median BMI of the overweight patients was 27.0 kgm(-2) (range, 22.7-34.7 kgm(-2); 27 males) compared with 21.2 kgm(-2) (range, 15.2-24.7 kgm(-2), 31 males) for control patients. Operative morbidity and mortality were 26% and 7.9% in overweight patients compared with 22% and 6.5% in control patients (morbidity, chi(2) = 0.240; df = 1; P = 0.624; mortality, chi(2) = 0.059; df = 1; P = 0.808). Cumulative survival at 5 years was 52% for overweight patients compared with 55% for control patients (chi(2) = 0.15; df = 1; P = 0.7002). In a multivariate analysis, the number of lymph node metastases (hazard ratio, 1.441; 95% confidence interval [CI], 1.159-1.723; P = 0.009) and splenectomy (hazard ratio, 12.111; 95% CI, 9.645-14.577; P = 0.043) were independently associated with the duration of survival.

CONCLUSION

High BMIs were not associated with increased operative risk, and longterm outcomes were similar in the two groups after modified D2 gastrectomy.

Open-access gastroscopy is associated with improved outcomes in gastric cancer

OBJECTIVE

To examine whether patients with gastric cancer diagnosed via open-access gastroscopy (OAG) differ in their outcomes compared with patients referred conventionally to outpatient clinics or as acute emergencies.

DESIGN AND SETTING

Prospective observational study in the gastroenterology and surgical units of a large district general hospital.

PARTICIPANTS

One hundred consecutive patients with gastric adenocarcinoma.

MAIN OUTCOME MEASURES

Data were collected prospectively and subdivided into two groups according to whether the patients were referred via the open-access route or the conventional route.

RESULTS

Diagnostic delay from onset of symptoms was shorter for patients referred via OAG compared with those referred conventionally. Stages of disease were significantly earlier in patients referred via OAG compared with patients referred conventionally. Potentially curative resection was significantly more likely following OAG than after conventional referral. Cumulative five-year survival for patients referred via OAG was 30% compared with 12% after conventional outpatient referral and 13% after acute referral. Multivariate analysis revealed three factors to be associated with survival: stage of disease, distant metastases and referral via the open-access route.

CONCLUSIONS

Gastric cancers presenting at OAG were diagnosed at an earlier stage than cancers diagnosed after conventional referral. This led to a higher proportion of potentially curative resections and better five-year survival.

D2 or not D2? The gastrectomy question

BACKGROUND

The best reported long-term survival following surgery for gastric cancer is from centers performing radical D2 gastrectomy. Yet comparative studies from European centers report higher rates of postoperative complications following D2 gastrectomy than after the less radical D1 gastrectomy, without any benefit in survival. We aimed to compare the outcome after modified D2 gastrectomy (preserving spleen and pancreas where possible), performed by specialist surgeons, with that after conventional D1 gastrectomy performed by general surgeons for gastric cancer in a large United Kingdom cancer unit.

METHODS

Two groups of patients were studied: a historical control group of 245 consecutive patients with gastric cancer, of whom 50 underwent a potentially curative D1 resection (median age, 69 years; 35 males) was compared with 200 consecutive patients, 72 of whom underwent a potentially curative D2 resection (median age, 71 years; 47 males).

RESULTS

Among the 122 patients judged to have curable cancers, patients who underwent a D2 gastrectomy had lower operative mortality (8.3% vs 12%; chi(2) = 0.48; P = 0.50) and experienced fewer complications (28% vs 36%; chi(2) = 0.93; P = 0.35) than patients who underwent a D1 gastrectomy. Cumulative survival at 5 years was 56% after D2 resections, compared with 11% after D1 resections ( P < 0.00001). In a multivariate analysis, only the stage of disease (stage I, hazard ratio [HR], 0.068; P = 0.0001; stage II, HR, 0.165; P = 0.001; stage III, HR, 0.428; P = 0.053) and the level of lymphadenectomy (HR, 0.383; P = 0.00001) were independently associated with the duration of survival.

CONCLUSION

Modified D2 gastrectomy without pancreatico-splenectomy, performed by specialist surgeons, can improve survival after R0 resections without increasing operative morbidity and mortality, when compared with D1 gastrectomy performed by general surgeons.

Why are parasite contingency genes often associated with telomeres?

Contingency genes are common in pathogenic microbes and enable, through pre-emptive mutational events, rapid, clonal switches in phenotype that are conducive to survival and proliferation in hosts. Antigenic variation, which is a highly successful survival strategy employed by eubacterial and eukaryotic pathogens, involves large repertoires of distinct contingency genes that are expressed differentially, enabling evasion of host acquired immunity. Most, but not all, antigenic variation systems make extensive use of subtelomeres. Study of model systems has shown that subtelomeres have unusual properties, including reversible silencing of genes mediated by proteins binding to the telomere, and engagement in ectopic recombination with other subtelomeres. There is a general theory that subtelomeric location confers a capacity for gene diversification through such recombination, although experimental evidence is that there is no increased mitotic recombination at such loci and that sequence homogenisation occurs. Possible benefits of subtelomeric location for pathogen contingency systems are reversible gene silencing, which could contribute to systems for gene switching and mutually exclusive expression, and ectopic recombination, leading to gene family diversification. We examine, in several antigenic variation systems, what possible benefits apply.

Surgical time and motion: the intermediate equivalent revisited

The relationship between operative time, the intermediate equivalent value (IEV) and the complexity of common general surgical operations was examined. Correlation was found between the BUPA schedule values for procedures categorized as intermediate and major, but complex major vascular reconstruction and oesophagogastric resection for cancer occupied significantly more theatre time than the four intermediate equivalents allocated by the Collins or BUPA schedule. Moreover, anaesthetic preparation time for complex major surgery in the latter surgical subspecialities contributed at least one further intermediate value. Re-evaluation of the ideal IEV weighting of all surgical operations including anaesthetic input from larger similar audits would allow more accurate audits of surgeons' work-load, and also facilitate transparent intensive management of operating theatre resource.

Special interest radiology improves the perceived preoperative stage of gastric cancer

AIM

The aim of this study was to compare the accuracy of spiral computed tomography (CT) performed by a specialist radiologist within a multi disciplinary team (MDT) framework with that of radiologists working outside of this framework.

MATERIALS AND METHODS

One hundred and ten patients [median age 70 (35-86)yr, 71m] underwent either a preoperative CT performed by the MDT specialist consultant radiologist (n=60) or a CT performed by one of 13 other consultant radiologists (n=50). The strength of the agreement between the CT stage and the histopathological stage was determined by the weighted Kappa statistic (Kw).

RESULTS

Sensitivity for T, N and M stage were 64%, 65% and 25% for MDT specialist CT, compared with 24%, 24% and 5% for control CT. Specificity for T, N and M stage were 68%, 59% and 95% for MDT specialist CT compared with 79%, 94% and 93% for control CT. Kw for T, N and M stage were 0.314, 0.350 and 0.255 for MDT specialist CT compared with 0.088, 0.102 and -0.019 for control CT. Unsuspected metastases were found in 12 patients staged by MDT specialist CT compared with 19 patients staged by control CT (Chi2=4.366, df=1,p =0.037).

CONCLUSION

Improved patient selection for surgery should maximize use of limited resource.

Antigenic variation in trypanosomes: enhanced phenotypic variation in a eukaryotic parasite

African trypanosomes are unicellular, eukaryotic parasites that live extracellularly in a wide range of mammals, including humans. They have a surface coat, composed of variant surface glycoprotein (VSG), which probably is essential and acts as a defence against general innate immunity and against acquired immunity directed at invariant surface antigens. In effect, the VSG is the only antigen that the host can target, and each trypanosome expresses only one VSG. To counter specific antibodies against the VSG, trypanosomes periodically undergo antigenic variation, the change to expression of another VSG. Antigenic variation belongs to the general survival strategy of enhanced phenotypic variation, where a subset of 'contingency' genes of viruses, bacteria and parasites hypermutate, allowing rapid adaptation to hostile or changing environments. A fundamental feature of antigenic variation is its link with the population dynamics of trypanosomes within the single host. Antigenic variants appear hierarchically within the mammalian host, with a mixture of order and randomness. The underlying mechanisms of this are not understood, although differential VSG gene activation may play a prominent part. Trypanosome antigenic variation has evolved a second arm in which the infective metacyclic population in the tsetse fly expresses a defined mixture of VSGs, although again each trypanosome expresses a single VSG. Differential VSG expression enhances transmission to new hosts, in the case of bloodstream trypanosomes by prolonging infection, and in the metacyclic population by generating diversity that may counter existing partial immunity in reservoir hosts. Antigenic variation employs a huge repertoire of VSG genes. Only one is expressed at a time in bloodstream trypanosomes, as a result of transcription being restricted to a set of about 20 bloodstream expression sites (BESs), which are at chromosome telomeres. Only one BES is active at a time, probably through transcriptional elongation being inhibited in the silent BESs. Although transcriptional switching between BESs can effect a VSG switch, the most prolific switch route involves homologous recombination of deoxyribonucleic acid, usually by the copying of a silent gene into a BES. Hierarchical expression of VSGs may be dictated in part by the different types of locus occupied by VSG genes. The VSG genes expressed in the metacyclic population also occupy telomeric sites, which appear to be derived from BESs but have a simpler structure. Their differential expression is achieved by random transcriptional activation; the detailed story requires direct study of the metacyclic stage itself. Available evidence suggests that the VSG originated as a surface receptor, and it can be proposed that a number of selective events have contributed to the evolution of the complex, multisystem phenomenon that antigenic variation has become.

An update on antigenic variation in African trypanosomes

African trypanosomes can spend a long time in the blood of their mammalian host, where they are exposed to the immune system and are thought to take advantage of it to modulate their own numbers. Their major immunogenic protein is the variant surface glycoprotein (VSG), the gene for which must be in one of the 20--40 specialized telomeric expression sites in order to be transcribed. Trypanosomes escape antibody-mediated destruction through periodic changes of the expressed VSG gene from a repertoire of approximately 1000. How do trypanosomes exclusively express only one VSG and how do they switch between them?

Oesophagogastric cancer and surgical subspecialisation: how much work?

The aim of this study was to assess the volume of work generated by one consultant (out of a surgical unit of seven) managing all the upper gastrointestinal malignancy in a district general hospital serving a population of 480,000. A 3-year period was prospectively audited and the volume of out-patient and in-patient workload assessed with particular reference to resource management and levels of surgical staffing. Oesophagogastric cancer accounted for a mean of 61 new cases per year, representing 5.3% of new patient referrals. Assuming that a complex major operation for an oesophagogastric cancer equates to four intermediate equivalent values (IEVs), then this translated to a mean operative workload of 186 IEVs per year, representing 16.7% of the total elective operative workload of 1140 IEVs per year. Thus, all the oesophagogastric cancer was managed by a single firm as a speciality in a district general hospital over this 3-year period, though a relatively small proportion of new patients with oesophagogastric cancer translated into a significantly greater burden on the resources of consultant manpower and operating theatre time.

Characterisation of the loci encoding the glutamic acid and alanine rich protein of Trypanosoma congolense

We have characterised the organisation of genes encoding the glutamate and alanine rich protein (GARP) surface coat of the procyclic and epimastigote stages of Trypanosoma congolense in the tsetse fly. The GARP genes are arranged at two, possibly physically linked, loci, one of which exhibits allelic variation. One locus contains a single GARP gene, whilst both alleles of the other have a large tandem array of polycistronically transcribed GARP genes. Sequence analysis has revealed that there are very few coding differences between different GARP genes. A sequence related to the Trypanosoma brucei expression site associated gene 4 (encoding a transmembrane protein with a cytoplasmic adenylate cyclase domain) has been identified within a region at the downstream flank of one locus. There is no evidence that, within the single trypanosome, GARP genes are as diverse as the procyclin genes that encode a corresponding coat in T. brucei.

A role for RAD51 and homologous recombination in Trypanosoma brucei antigenic variation

Antigenic variation is an immune evasion strategy used by African trypanosomes, in which the parasites periodically switch the expression of VSG genes that encode their protective variant surface glycoprotein coat. Two main routes exist for VSG switching: changing the transcriptional status between an active and an inactive copy of the site of VSG expression, called the bloodstream VSG expression site, or recombination reactions that move silent VSGs or VSG copies into the actively transcribed expression site. Nothing is known about the proteins that control and catalyze these switching reactions. This study describes the cloning of a trypanosome gene encoding RAD51, an enzyme involved in DNA break repair and genetic exchange, and analysis of the role of the enzyme in antigenic variation. Trypanosomes genetically inactivated in the RAD51 gene were shown to be viable, and had phenotypes consistent with lacking functional expression of an enzyme of homologous recombination. The mutants had an impaired ability to undergo VSG switching, and it appeared that both recombinational and transcriptional switching reactions were down-regulated, indicating that RAD51 either catalyzes or regulates antigenic variation. Switching events were still detectable, however, so it appears that trypanosome factors other than RAD51 can also provide for antigenic variation.

Identification of promoter elements of parasite nematode genes in transgenic Caenorhabditis elegans

Transformation of the free-living nematode Caenorhabditis elegans with promoter/reporter gene constructs is a very powerful technique to examine and dissect gene regulatory mechanisms. No such transformation system is available for parasitic nematode species. We have exploited C. elegans as a heterologous transformation system to examine activity and specificity of parasitic nematode gene promoters. Using three different parasite promoter/lac Z reporter constructs strict tissue-specific expression is observed. Upstream sequences of the Haemonchus contortus gut pepsinogen gene pep-1 and cysteine protease gene AC-2 direct expression exclusively in gut cells, while promoter sequence of the Ostertagia circumcincta cuticular collagen gene colost-1 directs hypodermal-specific expression. Mutation analysis indicates that AC-2 promoter function is dependent on a GATA-like motif close to the translation start site, similar to our findings with the C. elegans cpr-1 cysteine protease gene. While the spatial expression of these parasite promoters in C. elegans correlates with their expression in the parasite, the exact timing of expression does not. This suggests that regulatory mechanisms influencing the timing of expression may have evolved more rapidly than those controlling spatial expression of structural genes.

A structural and transcription pattern for variant surface glycoprotein gene expression sites used in metacyclic stage Trypanosoma brucei

African trypanosomes first express the variant surface glycoprotein (VSG) at the metacyclic stage in the tsetse fly vector, in preparation for transfer into the mammal. Metacyclic (M)VSGs comprise a specific VSG repertoire subset and their expression is regulated differently from that of bloodstream VSGs, involving exclusively transcriptional regulation during the life cycle. To identify basic structural and functional features that may be common to MVSG telomeric transcription units, we have characterized the anatomy and transcription of the telomere containing the ILTat 1.61 MVSG gene. This telomere contains pseudogenes of the ESAG1 and ESAG9 families found in bloodstream VSG transcription units. The 1.61 MVSG occupies a monocistronic transcription unit and is transcriptionally controlled through the life cycle. The 1.61, and also the 1.22, MVSG transcription initiation site sequences resemble eukaryotic initiator elements. Sequence comparison reveals that four out of five characterized MVSG expression sites have a conserved region 2.0-4.7 kb long upstream of the MVSG. In some cases, this region contains not only the transcription initiation site that we have observed to be active in fly-transmitted trypanosomes but also, upstream, another sequence, described elsewhere as a 'putative promoter' for the MVAT set of M/VSGs (Nagoshi YL, Alarcon CM, Donelson JE. A monocistronic transcript for a trypanosome variant surface glycoprotein, Mol Biochem Parasitol 1995;72:33-45). In fly-transmitted trypanosomes, the latter element is transcriptionally silent. Our analysis of the structure of MVSG telomeres suggests that metacyclic expression sites arose from bloodstream expression sites.

Predominance of duplicative VSG gene conversion in antigenic variation in African trypanosomes

A number of mechanisms have been described by which African trypanosomes undergo the genetic switches that differentially activate their variant surface glycoprotein genes (VSGs) and bring about antigenic variation. These mechanisms have been observed mainly in trypanosome lines adapted, by rapid syringe passaging, to laboratory conditions. Such "monomorphic" lines, which routinely yield only the proliferative bloodstream form and do not develop through their life cycle, have VSG switch rates up to 4 or 5 orders of magnitude lower than those of nonadapted lines. We have proposed that nonadapted, or pleomorphic, trypanosomes normally have an active VSG switch mechanism, involving gene duplication, that is depressed, or from which a component is absent, in monomorphic lines. We have characterized 88 trypanosome clones from the first two relapse peaks of a single rabbit infection with pleomorphic trypanosomes and shown that they represent 11 different variable antigen types (VATs). The pattern of appearance in the first relapse peak was generally reproducible in three more rabbit infections. Nine of these VATs had activated VSGs by gene duplication, the tenth possibly also had done so, and only one had activated a VSG by the transcriptional switch mechanism that predominates in monomorphic lines. At least 10 of the donor genes have telomeric silent copies, and many reside on minichromosomes. It appears that trypanosome antigenic variation is dominated by one, relatively highly active, mechanism rather than by the plethora of pathways described before.

ELT-3: A Caenorhabditis elegans GATA factor expressed in the embryonic epidermis during morphogenesis

We have identified a gene encoding a new member of the Caenorhabditis elegans GATA transcription factor family, elt-3. The predicted ELT-3 polypeptide contains a single GATA-type zinc finger (C-X2-C-X17-C-X2-C) along with a conserved adjacent basic region. elt-3 mRNA is present in all stages of C. elegans development but is most abundant in embryos. Reporter gene analysis and antibody staining show that elt-3 is first expressed in the dorsal and ventral hypodermal cells, and in hypodermal cells of the head and tail, immediately after the final embryonic cell division that gives rise to these cells. No expression is seen in the lateral hypodermal (seam) cells. elt-3 expression is maintained at a constant level in the epidermis until the 2(1/2)-fold stage of development, after which reporter gene expression declines to a low level and endogenous protein can no longer be detected by specific antibody. A second phase of elt-3 expression in cells immediately anterior and posterior to the gut begins in pretzel-stage embryos. elt-1 and lin-26 are two genes known to be important in specification and maintenance of hypodermal cell fates. We have found that elt-1 is required for the formation of most, but not all, elt-3-expressing cells. In contrast, lin-26 function does not appear necessary for elt-3 expression. Finally, we have characterised the candidate homologue of elt-3 in the nematode Caenorhabditis briggsae. Many features of the elt-3 genomic and transcript structure are conserved between the two species, suggesting that elt-3 is likely to perform an evolutionarily significant function during development.

A trypanosome metacyclic VSG gene promoter with two functionally distinct, life cycle stage-specific activities

In the mammalian bloodstream, African trypanosomes express the variant surface glycoprotein (VSG), continual switching of which allows evasion of the host immune response. Bloodstream VSG genes are transcribed from polycistronic bloodstream expression sites with promoters which are located 45-60 kb upstream. These promoters are not exclusively stage-regulated, being active in the insect midgut stage where VSG is not expressed. However, the metacyclic VSG (M-VSG) genes, a small subset activated when VSG synthesis begins in the metacyclic stage in the tsetse fly salivary glands, are transcriptionally activated specifically in that stage from promoters <3 kb upstream. Using deletion mapping and transient transfection, we show that the entire 1.22 M-VSG gene promoter region (171 bp) is required for full activity in metacyclic-derived trypanosomes. However, a subsidiary, bloodstream stage-specific activity is present in its 5' half which directs transcription initiation very close to the initiation site used in metacyclic-derived trypanosomes. Our results imply that the M-VSG gene promoter is longer and more complex than other VSG gene promoters.

VSG gene control and infectivity strategy of metacyclic stage Trypanosoma brucei

As the metacyclic trypanosome stage develops in the tsetse fly salivary glands, it initiates expression of variant surface glycoproteins (VSGs) and does so by each cell activating, at random, one from a small subset of metacyclic VSG (M-VSG) genes. Whereas differential activation of individual VSG genes in the bloodstream occurs as a function of time, to evade waves of antibody, it is believed that the aim in the metacyclic stage is simultaneously to generate population diversity. M-VSG genes are activated in their telomeric loci and belong to monocistronic transcription units, unlike all other known trypanosome protein-coding genes, which appear to be transcribed polycistronically. The promoters of these metacyclic expression sites (M-ESs) have the unique property, in this organism, of being switched on and off in a life-cycle stage specific pattern. We have found that the 1.22 M-ES promoter is regulated according to life cycle stage, differential control being exerted through different elements of the promoter and under the influence of its genomic locus. We have characterized in detail the telomeres containing the 1.22 and 1.61 M-ESs. Upstream of the M-ES is a possibly haploid, non-transcribed region with some degenerate sequences homologous with expression site associated genes (ESAGs) that occur in bloodstream VSG expression sites. Further upstream (respectively, 22 and 13 kb upstream of the 1.22 and 1.61 VSG genes) are alpha-amanitin sensitive transcription units that may be polycistrons and are transcribed in all examined life cycle stages. They contain a number of genes. The differences between metacyclic and bloodstream ESs may have important consequences for life cycle regulation, genetic stability, phenotype complexity and adaptability of the metacyclic stage as it infects different host species.

Activity of a trypanosome metacyclic variant surface glycoprotein gene promoter is dependent upon life cycle stage and chromosomal context

African trypanosomes evade the mammalian host immune response by antigenic variation, the continual switching of their variant surface glycoprotein (VSG) coat. VSG is first expressed at the metacyclic stage in the tsetse fly as a preadaptation to life in the mammalian bloodstream. In the metacyclic stage, a specific subset (<28; 1 to 2%) of VSG genes, located at the telomeres of the largest trypanosome chromosomes, are activated by a system very different from that used for bloodstream VSG genes. Previously we showed that a metacyclic VSG (M-VSG) gene promoter was subject to life cycle stage-specific control of transcription initiation, a situation unique in Kinetoplastida, where all other genes are regulated, at least partly, posttranscriptionally (S. V. Graham and J. D. Barry, Mol. Cell. Biol. 15:5945-5956, 1985). However, while nuclear run-on analysis had shown that the ILTat 1.22 M-VSG gene promoter was transcriptionally silent in bloodstream trypanosomes, it was highly active when tested in bloodstream-form transient transfection. Reasoning that chromosomal context may contribute to repression of M-VSG gene expression, here we have integrated the 1.22 promoter, linked to a chloramphenicol acetyltransferase (CAT) reporter gene, back into its endogenous telomere or into a chromosomal internal position, the nontranscribed spacer region of ribosomal DNA, in both bloodstream and procyclic trypanosomes. Northern blot analysis and CAT activity assays show that in the bloodstream, the promoter is transcriptionally inactive at the telomere but highly active at the chromosome-internal position. In contrast, it is inactive in both locations in procyclic trypanosomes. Both promoter sequence and chromosomal location are implicated in life cycle stage-specific transcriptional regulation of M-VSG gene expression.

Viral infections of nonhuman primates

Approximately 53,000 serologic tests and viral isolation studies were performed on 1,700 nonhuman primate specimens for evidence of past and/or current viral infection. Information, other than the requested test, generally was not provided with the specimen. This lack of information does not permit any attempt at interpretation of results. Requested testing included a large number of diverse viral agents in approximately 40 primate species. The resulting data are in keeping with those of previous studies and offer an insight into the needs of colony management, as well as some general information on the overall frequency of infection with the indicated viruses. Inasmuch as the results represent testing of single specimens, they are not to be construed as "diagnostic," and simply indicate past infection as represented by the presence of antibody in the test animal. Viral isolation results are listed, and the number of positive results versus the number of animals tested emphasizes the limitations of the procedure. Investigations such as these continue to assist in the maintenance of healthy nonhuman primate colonies. This information also supports continued use of nonhuman primates for research in human viral infections and may be helpful in terms of animal selection for use in xenotransplants.

The relative significance of mechanisms of antigenic variation in African trypanosomes

The large number of genes involved in antigenic variation in African trypanosomes has been the focus of a wide literature that describes an almost bewildering array of mechanisms for their differential activation. To the outsider searching for an underlying strategy for antigenic variation, this can appear as a rather disordered and confusing picture. Here, David Barry argues that an understanding of which mechanisms are significant, which ones are primarily inconsequential and which ones perhaps even arise from overdependence on laboratory models, might be achieved by turning attention to trypanosomes that have not undergone adaptation in laboratory conditions. Application of such an approach has led to a proposal for a main mechanism for antigenic variation.

cis regulatory requirements for hypodermal cell-specific expression of the Caenorhabditis elegans cuticle collagen gene dpy-7

The Caenorhabditis elegans cuticle collagens are encoded by a multigene family of between 50 and 100 members and are the major component of the nematode cuticular exoskeleton. They are synthesized in the hypodermis prior to secretion and incorporation into the cuticle and exhibit complex patterns of spatial and temporal expression. We have investigated the cis regulatory requirements for tissue- and stage-specific expression of the cuticle collagen gene dpy-7 and have identified a compact regulatory element which is sufficient to specify hypodermal cell reporter gene expression. This element appears to be a true tissue-specific promoter element, since it encompasses the dpy-7 transcription initiation sites and functions in an orientation-dependent manner. We have also shown, by interspecies transformation experiments, that the dpy-7 cis regulatory elements are functionally conserved between C. elegans and C. briggsae, and comparative sequence analysis supports the importance of the regulatory sequence that we have identified by reporter gene analysis. All of our data suggest that the spatial expression of the dpy-7 cuticle collagen gene is established essentially by a small tissue-specific promoter element and does not require upstream activator or repressor elements. In addition, we have found the DPY-7 polypeptide is very highly conserved between the two species and that the C. briggsae polypeptide can function appropriately within the C. elegans cuticle. This finding suggests a remarkably high level of conservation of individual cuticle components, and their interactions, between these two nematode species.

Polysomal, procyclin mRNAs accumulate in bloodstream forms of monomorphic and pleomorphic trypanosomes treated with protein synthesis inhibitors

The major surface antigen of insect stage (procyclic and epimastigote form) Trypanosoma brucei is termed procyclin or procyclic acidic repetitive protein (PARP). Procyclin/PARP is not expressed in bloodstream form parasites, which are coated instead with the variant surface glycoprotein (VSG). Although procyclin/PARP protein is not present and the mRNA is barely detectable, procyclin/PARP genes are transcribed at this life cycle stage. We examined the mechanism for down-regulation of procyclin/PARP expression in bloodstream trypanosomes by using protein synthesis inhibitors to effect accumulation of procyclin/PARP transcripts. We show that the accumulation is not due to increased transcription of procyclin/PARP genes. Further, transcripts which accumulate under these conditions are of mature size, polyadenylated and polysome-associated indicating that normally, in bloodstream trypanosomes, down-regulation of procyclin/PARP expression is exerted either during transcript processing or at the level of mRNA stability. A comparison of the inhibitor-induced accumulation of procyclin/PARP transcripts in bloodstream forms of monomorphic and pleomorphic cell lines of trypanosome stock EATRO 795 shows that accumulation occurs with similar kinetics in both cell lines.

Cuticular collagen genes from the parasitic nematode Ostertagia circumcincta

The nematode cuticle is a multifunctional structure whose roles include exoskeleton and barrier between the animal and its environment. It is an extracellular matrix which consists predominantly of small collagen-like proteins. For those species studied, these cuticular collagens are encoded by a multigene family. In the free living nematode Caenorhabditis elegans, this family has approximately 100 members. Our data indicate a gene family of similar size in the parasitic nematode Ostertagia circumcincta. We have characterised a pair of tandemly duplicated collagen genes from O. circumcincta, colost-1 and colost-2, which we believe to be the direct homologues of col-12 and col-13, a tandemly duplicated pair previously identified in C. elegans. The interspecies comparison of these homologues indicates regions of extreme conservation. We conclude that the gene duplication event that resulted in the creation of col-12 and col-13 in C. elegans is most likely the same duplication that generated colost-1 and colost-2 in O. circumcincta, and thus this particular gene duplication precedes the divergence of the two species. These two nematode species are deeply diverged, O. circumcincta belonging to the order Strongylata and C. elegans to Rhabditata. The ability to identify direct homologues of individual cuticular collagen genes between deeply diverged species provides a powerful method for determining regions of structural importance in these small collagens. Characteristics that are conserved between homologues in divergent species, but not conserved with other members of the multigene family within one species, must relate to the specific function of that particular cuticular collagen.