Temporal Effects of Sleeve Gastrectomy on Glucose-Insulin Homeostasis and Incretin Hormone Response at 1 and 6 Months.

BACKGROUND: Bariatric surgery is an effective treatment for morbid obesity and glycaemic dysfunction. OBJECTIVES: The aim of the work was to examine both the static and dynamic changes of glucose-insulin homeostasis and incretin hormone response following sleeve gastrectomy (SG) in a sample of 55 participants preoperatively and 1 month and 6 months postoperatively. The focus was on a sample of patients with impaired glucose tolerance and type 2 diabetes (T2D). SETTING: Morriston Hospital, UK. METHODS: Prospective study comprising of 55 participants with impaired glucose homeostasis and T2D undergoing SG (mean body mass index [BMI] 50.4 kg/m2, mean glycated haemoglobin [A1C] 7.4%). Serial measurements of glucose, insulin, C-peptide, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic hormone (GIP) were performed during oral glucose tolerance testing preoperatively and 1 and 6 months postoperatively. Areas under the curve (AUC) were examined at 30, 60, and 120 min. RESULTS: We observed significant improvements in measures of obesity, as well as static and dynamic measures of glucose, insulin, C-peptide and HOMA. Furthermore, significant increases in GLP-1 response as early as 6 months postoperatively were also seen. CONCLUSIONS: To our knowledge, no study has examined the detailed dynamic changes in glucose and insulin homeostasis in this number of participants undergoing SG in relation to incretin hormones GIP and GLP-1. This current study supports the role of SG for the treatment of obesity-related glucose dysregulation.

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.

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.

Mitigation of pain during intravenous catheter placement using a topical skin coolant in the emergency department.

OBJECTIVE: Although intravenous (i.v.) line placement is a common procedure in the emergency department (ED), it is an uncomfortable experience for many patients. Topical analgesic agents are rarely used because they have long onsets of action and thereby cause unacceptable treatment delays. Cryoanaesthesia, the use of cooling agents to reduce pain, has been recognised for many years as a potential pain management strategy. The purpose of this study was to determine whether an instantaneous topical skin coolant spray reduces patient's pain during i.v. cannulation and represents a feasible alternative for cutaneous analgesia in the ED setting. METHODS: We conducted an unblinded, randomised, controlled study, in a convenience sample of ED patients. Utilising a random number generator to assign patients to the control or study group, patients over the age of 18 years who required i.v. cannulation as part of their evaluation were enrolled at two tertiary care hospitals. In both groups, i.v. lines were placed in accordance with accepted clinical standards of practice, with the single addition of the coolant spray delivered to the i.v. site before needle insertion in the study group. All study participants answered questionnaires before and after i.v. placement and rated pain during procedure on a 100 mm visual analogue scale. RESULTS: Of the 92 patients enrolled in the study, 47 (51.1%) were randomised to the study group and received the anaesthetic spray, and 45 (48.9%) were randomised to the control group and had their i.v. placed in a standard method. 66 patients were female (71.8%) and 26 (28.2%) were males. The mean pain score in the study group was 27 mm (95% confidence interval (CI) 19.9 to 34.1 mm) and 28 mm (95% CI 20.4 to 35.6 m) in the control group (p = 0.934). Subgroup analysis of female and male patients did not show significance. CONCLUSIONS: Our study failed to detect a difference in pain perception resulting from the pre-procedural application of a skin coolant associated with i.v. placement in the ED setting.

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.

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%, chi2 0.286, DF 1, P=0.593). Overall cumulative survival at 5 years was 32% after D1 gastrectomy compared to 59% after D2 gastrectomy (chi2 4.25, DF 1, P=0.0392). In patients with stage III cancers, survival was 8% after D1, compared with 33% after D2 gastrectomy (chi2 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.

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.

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.

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 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.

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.