Explaining the abundance of ants in lowland tropical rainforest canopies.
The extraordinary abundance of ants in tropical rainforest canopies has led to speculation that numerous arboreal ant taxa feed principally as "herbivores" of plant and insect exudates. Based on nitrogen (N) isotope ratios of plants, known herbivores, arthropod predators, and ants from Amazonia and Borneo, we find that many arboreal ant species obtain little N through predation and scavenging. Microsymbionts of ants and their hemipteran trophobionts might play key roles in the nutrition of taxa specializing on N-poor exudates. For plants, the combined costs of biotic defenses and herbivory by ants and tended Hemiptera are substantial, and forest losses to insect herbivores vastly exceed current estimates. (+info)
Biomechanics of ant adhesive pads: frictional forces are rate- and temperature-dependent.
Tarsal adhesive pads enable insects to hold on to smooth plant surfaces. Using a centrifuge technique, we tested whether a "wet adhesion" model of a thin film of liquid secreted between the pad and the surface can explain adhesive and frictional forces in Asian Weaver ants (Oecophylla smaragdina). When forces are acting parallel to the surface, pads in contact with the surface can slide smoothly. Force per unit pad contact area was strongly dependent on sliding velocity and temperature. Seemingly consistent with the effect of a thin liquid film in the contact zone, (1) frictional force linearly increased with sliding velocity, (2) the increment was greater at lower temperatures and (3) no temperature dependence was detected for low-rate perpendicular detachment forces. However, we observed a strong, temperature-independent static friction that was inconsistent with a fully lubricated contact. Static friction was too large to be explained by the contribution of other (sclerotized) body parts. Moreover, the rate-specific increase of shear stress strongly exceeded predictions derived from estimates of the adhesive liquid film's thickness and viscosity. Both lines of evidence indicate that the adhesive secretion alone is insufficient to explain the observed forces and that direct interaction of the soft pad cuticle with the surface ("rubber friction") is involved. (+info)
Tuberculosis peritonitis in Negara Brunei Darussalam.
INTRODUCTION: Tuberculosis peritonitis (TBP) is uncommon and symptoms can be non-specific. Local data are lacking and our aim is to review our local experience with TBP. MATERIALS AND METHODS: Between the period of 1996 to 2004, there were 10 [male: 6; mean age, 48 +/- 18.5 years (range, 26 to 73)] cases of histologically documented TBP. Comparisons were made with pulmonary tuberculosis (PTB) patients. RESULTS: The overall prevalence ranged from 0% to 1.01% of all TB infections. The median duration of symptoms before diagnosis was 2 months (range, 3 days to 24 months). Five patients (50%) had comorbid conditions and 3 patients (30%) had a history of positive contact. Presenting symptoms were abdominal distension (70%), abdominal pain (60%), fever (60%), anorexia (60%) and weight loss (40%). Two patients had pulmonary symptoms: cough/dyspnoea (n = 1) and cough (n = 1). Chest x-ray changes consistent with PTB were seen in 30%. TBP was diagnosed by laparoscopy (n = 6), laparotomy (n = 3) and blind peritoneal biopsy (n = 1). Adverse effects of TB drugs occurred in 80%, consisting of hepatitis (n = 4), nausea/vomiting (n = 2), rash (n = 1) and encephalopathy (n = 1). Haemoglobin (P = 0.026) and serum albumin levels (P = 0.002) were significantly lower in TBP patients. There was a significantly greater number of adverse effects (P <0.001). There were no significant differences between TBP and PTB with regard to age, non-specific symptoms (weight loss, anorexia and fever) and erythrocyte sedimentation rate. All were treated with standard regimes and there were no mortalities. CONCLUSIONS: TBP is uncommon in our population. TBP patients had significantly lower haemoglobin and serum albumin levels. They also experienced more adverse events during treatment. There were no differences in non-specific symptoms between TBP and PTB. (+info)
A preliminary study of dengue infection in Brunei.
The purpose of this study was to examine the extent of dengue infection in Brunei and to determine the predominant serotype circulating in the country. The study generated useful epidemiological data on dengue infection in Brunei. A total of 271 samples from patients suspected of having dengue infections were selected and analyzed. All patients were seen in clinics and hospitals in Brunei. The samples were collected from April 2005 to April 2006 and transported to the WHO Collaborating Centre for Arbovirus Reference and Research, University of Malaya, Malaysia. The following tests were used to achieve the objectives: in-house IgM-capture enzyme-linked immunosorbent assay, virus isolation in mosquito albopictus cell line (C6/36), and viral RNA detection and serotyping by reverse transcriptase-polymerase chain reaction (RT-PCR). The results show that 45 people were positive for dengue-specific IgM (27 males and 18 females), while RT-PCR detected dengue viral RNA in 12 patients, 3 identified as DEN-1 and 9 as DEN-2. Dengue virus was isolated from 6 patients using the C6/36 cell line; 3 were DEN-2 isolates and 3 were DEN-1 isolates. These data show that dengue virus is circulating in Brunei and the predominant infecting serotype for that period was DEN-2 followed by DEN-1. This study is the first to report the detection and isolation of dengue virus from Brunei using RT-PCR and culture in the C6/36 albopictus mosquito cell line. (+info)
Pattern of peritoneal permeability in continuous ambulatory peritoneal dialysis patients in Brunei.
OBJECTIVE: Peritoneal permeability may be dissimilar in different populations. The present study identified the pattern of peritoneal permeability in continuous ambulatory dialysis (CAPD) patients treated at the Department of Renal Medicine, RIPAS Hospital, Brunei Darussalam. METHODS: Data were collected from patients on CAPD in 2001 (n = 65). Four children were excluded from the study. The remaining 61 patients underwent a 4-hour peritoneal equilibration test (PET) as prescribed by Twardowski et al. For those patients, adequacy of dialysis (Kt/V) was estimated. A retrospective analysis of the peritoneal membrane characteristics of those CAPD patients was also conducted. The membrane characteristics were compared with the urea clearance results. RESULTS: Of the 61 patients, 40 were non diabetic, and 21 (34.43%) were diabetic. More than half of our patients (55.74%) had membranes classified as high-average, followed by low-average (22.95%), high (18.03%), and low (3.28%). When the patient population was grouped separately into non diabetic and diabetic patients, peritoneal permeability differed between the groups (p = 0.000585). No relationship was observed between weekly Kt/V and transport characteristics in the group with diabetes (p = 0.219306), the group without diabetes (p = 0.74179), or the entire patient population (p = 0.376832) CONCLUSION: We conclude that peritoneal permeability among Bruneian CAPD patients is probably different from that among patients from other regions of Asia (more than half of our Bruneian patients had a peritoneal membrane classified as high average). We believe that the observed difference may be related to a difference in ethnicity. In general, patients with diabetes have a highly permeable membrane. Adequacy of dialysis had no correlation to PET results in our study. A larger prospective study is required to confirm our findings. (+info)
Medico-social problems in Bruneian dialysis patients.
OBJECTIVE: Our objective in the present study was to identify the medico-social problems in dialysis patients at the Department of Renal Medicine, RIPAS Hospital, Brunei Darussalam. PATIENTS AND METHODS: We retrospectively analyzed the social problems encountered by the patients in our dialysis program during the period January 2001 to June 2002. During that period, 285 patients were on hemodialysis (HD), and 65 patients were on continuous ambulatory peritoneal dialysis (CAPD). We made 302 referrals to the medical social unit. RESULTS: Of the 302 cases referred to the medical social unit, 35 (11.59%) were referred for welfare assistance from government or service clubs. Home assessments were conducted on 85 occasions (28.15%) during the study period. The HD section referred 18 (5.96%) patients to the medical social unit for assistance with employment- or work-related problems. The medical social unit also helped patients to settle medical bills (2 cases), acquire prosthetic equipment (9 cases), and obtain approval for housekeeping services applications (6 cases). Our medical social workers (MSWs) solved all 18 employment-related problems referred in HD cases. No cases were referred to the MSWs from the CAPD section for similar problems. It seems that employment-related problems are fewer in CAPD patients than in HD patients. However, long-term studies are required to confirm our findings. CONCLUSION: The MSWs helped to improve the quality of life in patients undergoing dialysis in Brunei. (+info)
Prevalence of active Helicobacter pylori infection among patients referred for endoscopy in Brunei Darussalam.
INTRODUCTION: The prevalence of Helicobacter pylori (H. pylori) infection has been reported to vary between and even within countries. We retrospectively assessed the prevalence among patients referred for endoscopy in our local setting. METHODS: 4,700 patients, who had endoscopy and H. pylori testing for the first time over a five-year period, were reviewed. RESULTS: The mean age was 45.4 +/- 17.1 years (male 51.1 percent), with racial breakdown similar to the national breakdown. The main indications for endoscopy were dyspepsia (59.6 percent), anaemia (12.6 percent), gastrointestinal bleeding (9.4 percent) and gastro-oesophageal reflux (7.6 percent). The overall prevalence of H. pylori was 26.9 percent, highest in the 30-39 years (30.3 percent) age group. This was higher in males compared to females (30.3 percent versus 23.3 percent, p-value is less than 0.001). Among the racial groups, the expatriate (35.3 percent, p-values are less than 0.001) and the indigenous (31.3 percent, p-values are less than 0.001) groups had significantly higher prevalence rates compared to the Malays (25.9 percent) and the Chinese (23.2 percent). Patients with dyspepsia had the highest prevalence (29.8 percent) compared to the other indications. In patients with peptic ulcer disease, the prevalence rate was 46.9 percent. Over the five-year period, there was a decline in prevalence from 32.3 percent to 25.6 percent. This trend was seen in the Malays and the Chinese, but not the indigenous and the expatriate groups. CONCLUSION: Similar to reported data from the regions, prevalence of H. pylori infection varies, with the Malays and the Chinese having the lowest prevalence rate. The prevalence among those with peptic ulcer disease was lower than reported. There was also a decline in the overall prevalence. (+info)
Longevity, lignin content and construction cost of the assimilatory organs of Nepenthes species.