Angiostatic proteins and peptides

Angiogenesis, or the formation of new vasculature out of preexisting capillaries, is a sequence of events that is essential in the normal physiological processes of tissue growth and in a broad spectrum of pathologies. The diseases in which angiogenesis plays a key role are divided into diseases that are characterized by hypoxia/ ischemia and diseases that are dependent on neovascularization. The formerpathologies may benefit from therapeutic angiogenesis stimulation. This review concentrates on the different strategies to inhibit angiogenesis in diseases that are characterized by excessive angiogenesis, for example, cancer, arthritis, diabetic retinopathy, and inflammatory diseases. These diseases are dependent on the development of newvasculature, and hence, a large variety of different strategies to inhibit angiogenesis are underwayin laboratories throughout the world. At present, over250 angiogenesis inhibitors are described, and approximately half of them display activity in in vivo models. A large percentage of these molecules are natural, nonnatural, or synthetic so-called small molecules. Others are of protein origin, either endogenous or exogenous by nature. The authors highlight the current knowledge on the development of angiostatic proteins and peptides and their potential in the treatment of disease.     

Validation and reproducibility of computerised cell-viability analysis of tissue slices

Background

The identification of live cells using membrane integrity dyes has become a frequently used technique, especially with articular cartilage and chondrocytes in situ where tissue slices are used to assess cell recovery as a function of location. The development of a reproducible computerised method of cell evaluation would eliminate many variables associated with manual counting and significantly reduce the amount of time required to evaluate experimental results.

Methods

To validate a custom computerised counting program, intra-person and inter-person cell counts of nine human evaluators (three groups – unskilled, novice, and experienced) were compared with repeated pixel counts of the custom program on 15 digitised images (in triplicate) of chondrocytes in situ stained with fluorescent dyes.

Results

Results indicated increased reproducibility with increased experience within evaluators [Intraclass Correlation Coefficient (ICC) range = 0.67 (unskilled) to 0.99 (experienced)] and between evaluators [ICC = 0.47 (unskilled), 0.85 (novice), 0.93 (experienced)]. The computer program had perfect reproducibility (ICC = 1.0). There was a significant relationship between the average of the experienced evaluators results and the custom program results (ICC = 0.77).

Conclusions

This study demonstrated that increased experience in cell counting resulted in increased reproducibility both within and between human evaluators but confirmed that the computer program was the most reproducible. There was a good correlation between the intact cell recovery determined by the computer program and the experienced human evaluators. The results of this study showed that the computer counting program was a reproducible tool to evaluate intact cell recovery after use of membrane integrity dyes on chondrocytes in situ. This and the significant decrease in the time used to count the cells by the computer program advocate its use in future studies because it has significant advantages.

     

1,25-dihydroxycholecalciferol in renal osteodystrophy. Epiphysiolysis--anticonvulsant therapy

Three children with azotaemic renal osteodystrophy were treated with 1,25-dihydroxycholecalciferol (1,25(OH)2D3). All showed clinical, biochemical, and radiological improvement within 6 months of starting treatment. There were no complications. The dose of 1,25(OH)2D3 required was 0-5 microgram per day for 2 children aged 22 and 30 months, and 2 microgram per day for a 15-year-old boy. 2 of the patients were receiving phenobarbitone and phenytoin and in one of them prior treatment with dihydrotachysterol 0-5 mg daily and 6 microgram 1alpha-hydroxycholecalciferol (1alphaOHD3) daily had failed to induce improvement. In one patient, in whom serial iliac bone samples were available, 2 microgram 1,25(OH)2D3 resulted in histological improvement in previously severe osteomalacia. 1,25(OH)2D3 appears to be an effective and safe drug in the treatment of uraemic osteodystrophy.     

Peptic ulcer and gastric carcinoma: diagnosis with biphasic radiography compared with fiberoptic endoscopy

The diagnostic value of biphasic radiographic examination of the stomach and duodenum was compared with that of fiberoptic endoscopy in a prospective, blinded study of 385 patients with dyspepsia. This investigation was directed at gastric malignancies and peptic ulcers. Methodologically there is no absolute standard for a study of this kind because histologic examination is useful for detection of cancer but inadequate for ulcers. As an alternative, kappa indexes and the sensitivity and specificity, as derived by Hui and Walter, were calculated and compared. For the detection of gastric carcinoma, radiographic and endoscopic findings had almost perfect agreement beyond chance. For gastric ulcers, radiography and endoscopy had substantial agreement, which became perfect if small ulcers (less than 5 mm) were excluded. For duodenal ulcers, radiography had a lower sensitivity than endoscopy; this disagreement disappeared if small ulcers were excluded. Both methods have equal merit; choice of the initial diagnostic procedure will therefore depend on cost, discomfort to the patient, and risk of complications.     

Ileoanal pouch function is related to postprandial pouch tone.

BACKGROUND: Functional impairments are frequently observed in patients with an ileoanal pouch. Meal ingestion increases pouch tone and motility. Little is known, however, about the influence of meal-stimulated pouch characteristics on pouch function. The aim was to characterize basal and postprandial pouch motor and sensory characteristics in relation to clinical pouch function in patients with an ileoanal pouch. METHODS: Nineteen patients with an ileoanal pouch, without faecal incontinence but with either a high stool frequency (n = 8) or an adequate stool frequency (n = 11), underwent pressure distension of the pouch, by which pouch compliance and sensitivity characteristics were assessed using an electronic barostat. A set pressure procedure was performed to assess the influence of a meal on pouch tone and motility. RESULTS: Mean(s.d.) compliance was 10(6) and 11(4) ml/mmHg in the groups with poor and adequate pouch function respectively (P not significant). Mean(s.d.) visual analogue scale scores (0-10 cm) for urge at the highest pressure of 28 mmHg were 2.3(1.0) versus 2.3(2.4) cm respectively (P not significant); those for pain were 0.8(1.0) versus 0.5(0.7) (P not significant). Postprandially mean(s.d.) pouch volume decreased by 70(24) per cent in the group with poor pouch function and 29(25) per cent in the group with adequate pouch function (P < 0.01). The frequency and amplitude of phasic pouch contractions increased significantly postprandially, but no differences in motility characteristics were observed between the two groups. CONCLUSION: In patients with uniform pouch design and follow-up after pouch construction, pouch compliance and sensitivity were no different between patients with normal and high stool frequency; however, postprandial pouch tone was increased significantly in patients with a high stool frequency.     

The tumour spectrum in hereditary non-polyposis colorectal cancer: a study of 24 kindreds in the Netherlands

The hereditary colonic cancer syndrome without polyposis, hereditary non-polyposis colorectal cancer (HNPCC), is usually divided into 2 main categories: hereditary site-specific colorectal cancer (Lynch syndrome I) and colorectal cancer in association with other forms of cancer (Lynch syndrome II). One problem associated with Lynch II is the uncertainty as to which types of cancer form part of the hereditary tumour spectrum. The present study was performed to obtain more information about the tumour spectrum of HNPCC. In the 24 HNPCC families studied, 104 patients had colorectal cancer (mean age at diagnosis: 46 years) and in 4 of the families this was the only type of cancer to occur. Sixty-five extra-colonic tumours were diagnosed in 20 families. Endometrial carcinoma was found in 16 patients belonging to 12 families. Cancer of the stomach occurred in 10 patients representing 5 families, and mainly in the older generations. Urinary-tract tumours were found in 8 patients from 4 families. Second primary tumours were diagnosed in 13 of the 16 patients with endometrial cancer, in 4 of the 10 patients with stomach cancer and in 7 of the 8 patients with a urinary-tract tumour. Many other types of carcinoma were found as well, but less frequently. In our families, the trait appears to be transmitted by patients with cancer of the stomach, endometrium or urinary tract, because some of their children have developed colorectal cancer. The findings suggest that, in these 24 HNPCC families, carcinomas of the endometrium, stomach and urinary tract belong to the hereditary tumour spectrum. Definite assignment of tumours to this spectrum will become possible only after a sensitive and specific biomarker becomes available. The screening programme should depend on which and how many extra-colonic tumours occur in a family.     

Digital imaging of the chest

During the past several years, image acquisition in nuclear medicine, computed tomography, ultrasonography, subtraction angiography, and magnetic resonance has been by digitization. Despite these advances, research in the development of digital imaging in conventional radiography has lagged behind. Although studies with a variety of digital techniques have been carried out on several fronts, we still do not possess a method that has captured the imagination of the majority of radiologists and other physicians to a point where it could replace conventional screen-film imaging. This article reviews the current status and general principles of the technology, focusing on the four digital radiographic techniques that have shown the greatest promise - film digitization, an image intensifier - based system, photostimulable phosphor plates, and a scanned projection system. The physical aspects of each of the four systems and the clinical results that have been reported to date, as well as the advantages and disadvantages of each system, are presented.     

Predictors of Ventricular Tachvcardia Inducibility in Programmed Electrical Stimulation and the Effectiveness of Serial Drug Testing: Polish Multicenter Study

WNUK-WOJNAR, A.M., ET AL.: Predictors of Ventricular Tachycardia Inducibility in Programmed Electrical Stimulation and Effectiveness of Serial Drug Testing: Polish Multicenter Study. In 100 patients with IHD and complex ventricular arrhythmias, programmed electrical stimulation was performed using up to three extrastimuli at sinus rhythm, and paced 100, 120, and 140 beats/min delivered from the RV apex, outflow tract or the LV with ventricular mapping to evaluate late potentials (LP) in 41 patients. Sustained monomorphic VT (SMVT) was provoked in 91% of 42 patients with a history of VT/VF, p < 0.001, all five patients had SMVT in 24-hour ECG, p < 0.005, and 91% of 21 patients with LV dyskinesis, p < 0.01. After depolarizations were found in 62% of 21 patients with a history of VT, in 58% of 31 patients with inducible VT, p < 0.01 and in five of six patients with LV dyskinesis. In patients with inducible VT, LP had a higher amplitude (105 ± 35 vs 60 ± 47 µV) and were more delayed (202 ± 96 vs 133 ± 75 msec) than in noninducible patients. In 17 patients, serial drug testing was performed after oral administration using mexilitene, disopyramide, chinidine, propafenone, sotalol, and amiodarone. If one drug was tested, the therapy efficacy was 25% if two drugs-60%, and if three drugs-75%. In eight patients, VT was inducible in all tests, but in only one of these patients chronic antiarrhythmic therapy was not effective. We conclude that the most important predictors of VT inducibility are a history of VT or 24-hour ECG, and LV dyskinesis. Serial drug testing is efficient only when many drugs are tested, but even if VT is inducible, it does not exclude the possibility of a good clinical outcome in chronic therapy.     

Naratriptan: biological profile in animal models relevant to migraine

The biological profile of naratriptan (N-methyl-3-(1-methyl-4-piperidinyl)-1H-indole-5-ethane-sulphona-mide), a novel 5HT_1B/1D receptor agonist, was investigated in a variety of experimental models of relevance to migraine. Naratriptan has high affinity for human recombinant 5HT_1B and 5HT_1D receptors (pKi = 8.70.03 and 8.30.1, respectively) and causes contractions of dog isolated basilar and middle cerebral artery (EC₅₀ values of 0.11 and 0.07 M, respectively). Naratriptan causes small contractions of human isolated coronary arteries (EC₅₀ value of 0.17 M; maximum contraction equivalent to 33% of 5HT maximum). In anaesthetized dogs, naratriptan causes selective vasoconstriction of the carotid arterial bed (CD₅₀ dose = 193 g kg⁻¹) and, in anaesthetized rats, naratriptan selectively inhibits neurogenic plasma protein extravasation in the dura (ID₅₀ = 4.1 g kg⁻¹). In a variety of antinociceptive tests, naratriptan has no effect even at high doses. In conscious rats and dogs, naratriptan has high oral bioavailability (71% and 95%, respectively). The data show that naratriptan is a selective agonist at 5HT_1B/1D receptors, with a pharmacological profile very similar to that of sumatriptan, albeit 2-3 fold more potent. These observations, coupled with high oral bioavailability in animals, suggest that naratriptan has the profile of an orally effective anti-migraine drug.     

Therapeutic approaches of angiogenesis inhibition: are we tackling the problem at the right level?

A growing body of evidence now demonstrates that inhibition of angiogenesis is a promising way for treatment of disease. Although the field of angiogenesis research is strongly linked to cancer biology, many other diseases were found to be dependent on angiogenesis as well, introducing a potential benefit from antiangiogenesis treatment. Recently, the first specific angiogenesis inhibitor was approved by the Food and Drug Administration for the treatment of colorectal cancer. Currently, several compounds with angiostatic activity are approved, and many are in late-stage clinical development. Most of these are indirect inhibitors, either clearing angiogenic growth factors from the circulation or blocking the signaling pathways activated by these growth factors. Although these compounds seem to represent an efficient strategy in cancer treatment, they possess an intrinsic threat to induce resistance. Therefore, it remains to be seen whether this strategy will be the most attractive in the future. Advancing insights into fundamental mechanisms will be necessary in the development of novel anticancer strategies based on inhibition of angiogenesis.