Reasons for missed opportunities to screen and test for TB in healthcare facilities.

Missed opportunities for TB screening and/or passive testing in clinics continues to contribute to the number of missed cases. To understand reasons for these missed opportunities, we conducted focus group discussions with clinic-based nurses. Nurses described low indices of suspicion, prioritization of seemingly more urgent ailments and clinic operational challenges as barriers to TB screening and testing. To improve TB screening and testing in clinics, standard patients should be used to identify real-time factors that impact nurses' clinical decision-making and engage in real-time feedback and discussion with nurses to help optimize opportunities for TB screening and testing.

Les occasions manquées de dépistage de la TB et/ou de tests passifs dans les cliniques continuent de contribuer au nombre de cas manqués. Pour comprendre les raisons de ces occasions manquées, nous avons organisé des discussions de groupe avec des infirmières travaillant dans des cliniques. Les infirmières ont décrit les faibles indices de suspicion, la priorité accordée à des affections apparemment plus urgentes et les défis opérationnels des cliniques comme des obstacles au dépistage de la TB. Pour améliorer le dépistage et le test de la TB dans les cliniques, il faudrait utiliser des patients standard pour identifier les facteurs en temps réel qui influent sur la prise de décision clinique des infirmières et engager une rétroaction et une discussion en temps réel avec les infirmières pour aider à optimiser les occasions de dépistage et de test de la TB.

Regulation of tissue ingrowth into proteolytically degradable hydrogels.

Regulation of the rate of cell ingrowth into and within a matrix is desirable for efficient tissue regeneration. Polyethylene glycol hydrogels crosslinked with matrix metalloproteinase (MMP) susceptible peptide sequences permit cell-controlled invasion. In this study, hydrogels of the same stiffness polymerised using different ratios of a readily degradable MMP peptide sequence (PAN-MMP) and a MMP peptide with a limited degradation capacity (MMP-9) were assessed both in vitro and in vivo for cellular invasion. The degree of invasion into the various hydrogels was found to be tightly linked to the relative proportion of each peptide both in vitro and in vivo. Furthermore a good correlation between in vitro and in vivo ingrowth was observed. These findings demonstrate a highly tunable model for regulating cellular invasion which is readily translatable to in vivo models. This finding may allow for further optimisation of aspects of regenerative scaffolds such as tissue invasion, growth factor release and cellular encapsulation. STATEMENT OF SIGNIFICANCE: Degradable hydrogels are used in a wide range of tissue regeneration approaches. A particularly advantageous variant of these hydrogels is where due to peptide based crosslinking of the polymeric hydrogels, cell invasion rate is dependent on cellular enzymatic activity. This present study demonstrates a further refinement whereby both cellular and tissue invasion rates are finely regulated through the polymerisation of a hydrogel with varying combinations of enzymatically degradable peptides. Importantly this allows for invasion rates to be controlled without altering the biomechanical properties of the hydrogel such as stiffness. The latter can further influence cellular behaviour thus potentially interfering with the desired outcome.

Modification, crosslinking and reactive electrospinning of a thermoplastic medical polyurethane for vascular graft applications.

Thermoplastic polyurethanes are used in a variety of medical devices and experimental tissue engineering scaffolds. Despite advances in polymer composition to improve their stability, the correct balance between chemical and mechanical properties is not always achieved. A model compound (MC) simulating the structure of a widely used medical polyurethane (Pellethane) was synthesized and reacted with aliphatic and olefinic acyl chlorides to study the reaction site and conditions. After adopting the conditions to the olefinic modification of Pellethane, processing into flat sheets, and crosslinking by thermal initiation or ultraviolet radiation, mechanical properties were determined. The modified polyurethane was additionally electrospun under ultraviolet light to produce a crosslinked tubular vascular graft prototype. Model compound studies showed reaction at the carbamide nitrogen, and the modification of Pellethane with pentenoyl chloride could be accurately controlled to up to 20% (correlation: rho=0.99). Successful crosslinking was confirmed by insolubility of the materials. Initiator concentrations were optimized and the crosslink densities shown to increase with increasing modification. Crosslinking of Pellethane containing an increasing number of pentenoyl groups resulted in decreases (up to 42%, p<0.01) in the hysteresis and 44% in creep (p<0.05), and in a significant improvement in degradation resistance in vitro. Modified Pellethane was successfully electrospun into tubular grafts and crosslinked using UV irradiation during and after spinning to render them insoluble. Prototype grafts had sufficient burst pressure (>550 mm Hg), and compliances of 12.1+/-0.8 and 6.2+/-0.3%/100 mm Hg for uncrosslinked and crosslinked samples, respectively. It is concluded that the viscoelastic properties of a standard thermoplastic polyurethane can be improved by modification and subsequent crosslinking, and that the modified material may be electrospun and initiated to yield crosslinked scaffolds. Such materials hold promise for the production of vascular and other porous scaffolds, where decreased hysteresis and creep may be required to prevent aneurismal dilation.

The use of finite element methods and genetic algorithms in search of an optimal fabric reinforced porous graft system.

The mechanics of arteries result from the properties of the soft tissue constituents and the interaction of the wall layers, predominantly media and adventitia. This concept was adopted in this study for the design of a tissue regenerative vascular graft. To achieve the desired structural properties of the graft, most importantly a diametric compliance of 6%/100 mmHg, finite element methods and genetic algorithms were used in an integrated approach to identify the mechanical properties of an adventitial fabric layer that were required to optimally complement an intimal/medial polyurethane layer with interconnected porosity of three different size classes. The models predicted a compliance of 16.0, 19.2, and 31.5%/100 mmHg for the non-reinforced grafts and 5.3, 5.5, and 6.0%/100 mmHg for the fabric-reinforced grafts. The latter, featuring fabrics manufactured according to the required non-linear mechanical characteristics numerically predicted, exhibited an in vitro compliance of 2.1 +/- 0.8, 3.0 +/- 2.4, and 4.0 +/- 0.7% /100 mmHg. The combination of finite element methods and genetic algorithms was shown to be able to successfully optimize the mechanical design of the composite graft. The method offers potential for the application to alternative concepts of modular vascular grafts and the incorporation of tissue ingrowth and biodegradation.

The selective modulation of endothelial cell mobility on RGD peptide containing surfaces by YIGSR peptides.

The ability of the biomimetic peptides YIGSR, PHSRN and RGD to selectively affect adhesion and migration of human microvascular endothelial cells (MVEC) and vascular smooth muscle cells (HVSMC) was evaluated. Cell mobility was quantified by time-lapse video microscopy of single cells migrating on peptide modified surfaces. Polyethylene glycol (PEG) hydrogels modified with YIGSR or PHSRN allowed only limited adhesion and no spreading of MVEC and HVSMC. However, when these peptides were individually combined with the strong cell binding peptide RGD in PEG hydrogels, the YIGSR peptide was found to selectively enhance the migration of MVEC by 25% over that of MVEC on RGD alone (p<0.05). No corresponding effect was observed for HVSMC. This suggests that the desired response of specific cell types to tissue engineering scaffolds could be optimized through a combinatory approach to the use of biomimetic peptides.

Diamine extension of glutaraldehyde crosslinks mitigates bioprosthetic aortic wall calcification in the sheep model.

We previously have been able to show that fixation at increasing concentrations of glutaraldehyde (GA) leads to mitigated rather than facilitated tissue calcification. The purpose of the present study was to introduce additional crosslinks and provide evidence that crosslink density may be an underlying inhibitory principle. Entire aortic roots were chosen to verify the concept on the challenging aortic wall tissue. Porcine aortic roots were crosslinked with 0.2% GA, 3%GA, and 3% GA containing an interim step that introduced diamine bridges. Crosslink efficiency was determined on the basis of shrinkage temperature (SrT degrees ), resistance to protease digestion (RPD), residual amine analysis (RA), and tensile modulus (E(10)). Calcium levels, calcification patterns, and inflammation were assessed after 6 and 24 weeks of implantation in a sheep circulatory model. Crosslink efficiency in aortic wall tissue was moderately affected by increasing the fixative concentration from 0.2% GA to 3% GA (SrT degrees from 85.7 degrees +/- 0.3 degrees to 87.5 degrees +/- 0.3 degrees C, p < 0.002; RPD from 24.2 +/- 1.2 to 29.1 +/- 0.7%, p < 0.003; RA from 0.069 +/- 0.004 to 0.058 +/- 0.003 micromol/mg, p < 0.03, and E(10) from 1.9 +/- 0.11 to 2.94 +/- 0.34 MPa, p < 0.01), but it was distinctly enhanced when diamine bridges were introduced (SrT degrees from 87.5 degrees +/- 0.3 degrees to 93.4 degrees +/- 0.3 degrees C, p << 0.0001; RPD from 29.1 +/- 0.7 to 68.4 +/- 1.8%, p << 0.0001; and E(10) from 2.94 +/- 0.34 to 6.80 +/- 0.61 MPa, p < 0.0003). Aortic wall calcification was reduced significantly by increasing the GA concentration from 0.2 to 3% [37.8%, p = 0.076 (6 weeks) and 34.0%, p = 0.008 (24 weeks)] and further reduced by the introduction of additional diamine [84.0%, p = 0.006 (6 weeks) and 29.8%, p = 0.037 (24 weeks)]. The combined effect of increased GA concentration plus an interim diamine step on aortic wall tissue resulted in a 90% and 53.7% reduction of calcification after 6 weeks and 24 weeks, respectively. The correlation coefficients between calcification and SrT degrees, RDP, and E(10) was -0.9767, -0.9460, and -0.9740, respectively (6 weeks). The inflammatory host reaction regularly found in 0.2% fixed tissue was practically abolished through the introduction of diamine bridges. Our study demonstrated a distinct correlation between the mitigation of aortic wall calcification and three parameters used to assess crosslink density.

Glutaraldehyde detoxification in addition to enhanced amine cross-linking dramatically reduces bioprosthetic tissue calcification in the rat model.

BACKGROUND AND AIM OF THE STUDY: Enhanced fixation of bioprosthetic tissue by both increased concentrations of glutaraldehyde (GA) and the introduction of additional cross-links with L-lysine significantly reduces calcification. We have previously reported that prolonged exposure to high-volume amino-compounds under warm, acidic conditions leads to thorough, non-rebounding GA detoxification. The aim of the present study was to prove that removal of excess GA can amplify the benefits of enhanced GA cross-linking with regard to bioprosthetic tissue calcification. METHODS: Porcine ascending aortas and leaflet tissue, and bovine pericardium were immediately fixed using three GA concentrations (0.2%, 1.0%, 3.0% (v/v)) for seven days at 4 degrees C. Samples were allocated to nine groups. Groups I to III received no further treatment (one at each GA concentration); groups IV to IX underwent an additional L-lysine interim step (48 h/37 degrees C/0.1 M) two days before completion of standard seven-day GA fixation; and groups VII to IX were additionally treated with a GA extraction process using high-volume urazole solution (acetic acid buffer, pH 4.5, 37 degrees C, one week) followed by NaBH4 reduction (2 days, 37 degrees C). Samples were implanted subcutaneously in rats (six per group) for six weeks. Tissue calcium was measured by atomic absorption spectrophotometry and examined histologically after von Kossa staining. RESULTS: Calcification was reduced in all three tissue types by enhanced cross-linking and by extraction of excess GA. Increasing the GA concentration from 0.2% to 3.0% led to a reduction in calcification of 11.5% (p = 0.074; Student's t-test) in leaflets; 63.6% (p <0.0001) in pericardium; and 17.5% (p = 0.034) in aortic wall tissue. The introduction of additional cross-links with L-lysine resulted in a significant reduction of calcium in all tissues (maximally 42.5%, p = 0.0003 in leaflets; 79.3%, p = 0.005 in pericardium; and 49.6%, p <0.0001 in aortic wall; Student's t-test). Optimal reduction in calcification could be achieved with the combined effect of 3.0% GA fixation, L-lysine enhancement and urazole detoxification. When compared with 0.2% GA-fixed tissue, calcification could be reduced by 99.1% in leaflets, 95.9% in pericardium, and 90.8% in aortic wall tissue (p <0.0001 for all tissue types; Student's t-test). CONCLUSION: Removal of excess GA from fixed bioprosthetic tissue was capable of markedly improving the anti-calcific effect of enhanced GA cross-linking.

Glutaraldehyde detoxification of aortic wall tissue: a promising perspective for emerging bioprosthetic valve concepts.

BACKGROUND AND AIMS OF THE STUDY: Due to its superb crosslinking activity, glutaraldehyde (GA) is still the most widely used fixative for bioprosthetic heart valves. At the same time, however, GA is also believed to be partly responsible for tissue calcification and the lack of surface re-endothelialization, both of which may contribute to valve degeneration. Although excess GA has previously been extracted from thin leaflet tissue, this treatment proved insufficient for the detoxification of thick aortic wall tissue of stentless valves or root prostheses. METHODS: In order to establish a detoxification procedure which thoroughly extracts biologically active GA from aortic wall tissue, we used a highly sensitive bioassay where endothelial cells were seeded onto glutaraldehyde-fixed aortic wall discs following various detoxification procedures. Absolute cell numbers and morphologic shape were correlated with shrinkage temperature and shrinkage extent of the tissue to determine the potential of the treatments to reverse crosslinks. To optimize treatment conditions, pH (3.2 versus 4.5), temperature (22 degrees C versus 37 degrees C) and incubation time (48 h versus one week) were varied. In order to identify an optimal detoxification agent, 12 different amino-reagents from four chemical groups were compared: low pKa aromatic amines, amino acids, low pKa N-heterocyclic compounds and amino sugars. RESULTS: Amino-reagent treatment required warm temperature (37 degrees C), prolonged reaction time (one week) and a pH of 4.5 to achieve long-term cell growth on glutaraldehyde-fixed aortic wall. All 12 amino-reagents were able to detoxify aortic tissue satisfactorily; and all mildly reversed crosslinks, although there were differences between candidates. When summarized data were ranked correlating cell growth and quality with shrinkage temperature and shrinkage extent, seven reagents had a rank sum above the overall mean value, and five below with statistically significant differences between candidates. The additional stabilization of the detoxification reaction through borohydride-reduction had no further effect on tissue biocompatibility and crosslinks. CONCLUSIONS: Efficient detoxification of thick aortic wall tissue is possible if a one-week incubation in an acetic acid buffer-based amino-reagent is carried out at 37 degrees C.

Gastric juice carcino-embryonic antigen estimation. A useful additional test in the diagnosis of gastric carcinoma?

There is a high incidence of gastric carcinoma in the coloured population of the Western Cape. Diagnostic tests other than barium meal examination or gastroscopy were investigated. In this study 50 patients were assessed and grouped according to the gastroscopic and histological findings. Twenty-five patients with gastric carcinoma and 25 with benign gastric ulcer and/or chronic atrophic gastritis and/or intestinal metaplasia were tabulated. The gastric juice and plasma carcino-embryonic antigen (CEA) levels were evaluated and compared in the two groups. The gastric juice CEA level was more useful than the plasma CEA level as an aid in diagnosing malignant gastric lesions. No correlation was evidence between CEA values and the extent of the gastric carcinoma and or histological typing. An elevated gastric juice CEA level was an additional aid in diagnosing gastric carcinoma. Markedly elevated values may also identify the high-risk patient who is prone to develop gastric carcinoma.

Gastric carcinoma at Tygerberg Hospital, 1979-1983. A retrospective study.

A retrospective study was carried out on patients with histologically proven gastric carcinoma diagnosed at the Gastro-intestinal Clinic, Tygerberg Hospital, over a 5-year period--1979-1983. Fifty per cent of patients were coloured men. The overall median age was 65 years but the coloured patients were significantly younger than the white. The main symptoms were loss of appetite and weight, abdominal pain and vomiting. The median duration of symptoms in all patients was 3 months. An abdominal mass, anaemia and obvious weight loss were the most important physical signs. A normocytic, normochromic anaemia, an elevated erythrocyte sedimentation rate, raised liver enzyme levels and hypo-albuminaemia were the most important laboratory findings. In 96% of the 149 patients gastroscopy yielded a positive diagnosis of gastric carcinoma and barium meal examination showed abnormalities in 87%. In the majority of cases the carcinoma was poorly differentiated.

[Double pylorus and pyloroduodenal fistulas: two case reports and discussion]. / Dubbele pilorus en piloroduodenale fistels. Twee gevalbeskrywings met bespreking.

Congenital double pylorus is extremely rare; only 2 cases have been found in the English and French literature. Acquired double pylorus occurs more often; up to 1982, 66 cases had been reported. During 6 810 consecutive barium meal examinations over a period of 2 years, we diagnosed the condition in 5 patients. Two came to operation, at which the diagnosis was confirmed. These 2 cases are described. Acquired double pylorus is in reality a short pyloroduodenal fistula situated next to the pylorus, usually on the lesser curvature side. In the majority of cases it results from a pyloric ulcer penetrating into the duodenum. In a minority of cases the primary lesion is a duodenal ulcer penetrating into the pyloric area. Cases initially present with peptic ulcer symptoms. With the formation of the fistula, symptoms may disappear. Some authorities consider this to indicate spontaneous cure of the ulcer, thus obviating the need for further medical or surgical treatment. In the present 2 cases there was no remission of symptoms. None of the cases has been associated with malignant disease. It is thought that the condition may be recognized more often in future.

Folate levels in patients with ulcerative colitis receiving sulphasalazine.

The question of folate deficiency in patients receiving sulphasalazine is still controversial. A random sample of patients with ulcerative colitis receiving sulphasalazine were studied to determine the clinical significance of the inhibition of folic acid absorption by the drug. No significant lowering of folate levels could be determined.

A comparison of 4-week peptic ulcer healing rates following treatment with antacids and ranitidine.

Eighty-eight patients with endoscopically proven gastric and duodenal ulceration were treated with ranitidine ( Zantac ; Glaxo) or an antacid preparation containing aluminium hydroxide and magnesium trisilicate ( Gelusil ; Warner) over a 4-week period to assess healing. Clinical, haematological and biochemical assessment and endoscopy were performed at the beginning and at the end of this period. Of the duodenal ulcers, 74% healed on ranitidine therapy and 63% on Gelusil . This difference was not statistically significant (chi 2(1) = 0,55). Of the gastric ulcers 58% healed on ranitidine therapy and 35% on Gelusil , but this difference did not reach statistical significance (chi 2(1) = 1,79). There was no significant difference between the two therapies with regard to symptomatic relief in the duodenal ulcer group, but ranitidine produced significantly better results in the gastric ulcer group. No side-effects were noted in either group.

Enzymatic analysis of gastric microbiopsy specimens. An aid in the differential diagnosis between peptic ulcers and gastric carcinoma?

Microgastric biopsies were obtained from 20 patients with clinical, radiologic, and endoscopic features of gastric neoplasms. Biopsy specimens were taken from both macroscopically normal gastric mucosa (confirmed histology), and from the lesion. In 16 patients, various stages of adenocarcinoma were confirmed. Repeated biopsy examinations, ruled out malignancy in the four remaining patients, in which a final diagnosis of healing ulcers was established. Homogenates were prepared from the biopsy specimens, and subsequently assayed individually for acid- and alkaline phosphatase and acid proteases. Significant variances (P less than 0.05), were demonstrated for acid protease activities when tumor homogenate levels were compared; firstly with normal mucosa and secondly with ulcer homogenate levels. Biopsy hydrolase determinations may be valuable in providing important additional information not obtained from histologic examinations.

The association between ulcerative colitis and chronic liver disease at Tygerberg Hospital.

Twenty consecutive patients with ulcerative colitis were evaluated at the Gastro-intestinal Clinic, Tygerberg Hospital, with special reference to the biochemical tests and histological findings in the liver. Abnormal liver function tests warrant a liver biopsy, since the underlying liver disease influences the subsequent prognosis and treatment.

Chronic organophosphate poisoning.

Prolonged exposure to organophosphates in low concentrations caused diarrhoea in 38 students, lecturers and other personnel at an agricultural college. The symptoms of those affected, plasma pseudocholinesterase levels, topography of the orchards and vegetable gardens, the various insecticides and quantities used, and the exposure due to prevailing winds have been studied. We conclude that safety and precautionary measures must be strictly enforced.