Blockade of Ca2+‐activated K+ channels in T cells: an option for the treatment of multiple sclerosis?

Voltage- and Ca(2+)-dependent K(+) channels in the membrane of both T and B lymphocytes are important for the cellular immune response. In the current issue of the European Journal of Immunology, Reich et al. demonstrate that selective blockade of the intermediate-conductance Ca(2+)-activated K(+) channel (the IK channel encoded by the KCNN4 gene) prevents cytokine production in the spinal chord and ameliorates the development of EAE caused by injection of myelin oligodendrocyte glycoprotein (MOG)(35-55) in mice. These data renew the focus on the IK channel as a potential target for the development of new immune-suppressant drugs for the treatment of autoimmune diseases.     

Bone tissue content of TGF-β2 changes with time in human heterotopic ossification after total hip arthroplasty

Transforming growth factor beta isoforms (TGF-β₁, TGF-β₂, and TGF-β₃) most likely play a role in bone physiology, but little is known about their relative importance in normal as well as in heterotopic bone. This study focused on possible differences in the localization and relative content of different TGF beta isoforms in heterotopic ossifications (HO) by comparing HOs, which have developed less than 17 months (immature HOs) with those developed 3–9 years (mature HOs). The HOs were harvested after total hip arthroplasty (THA) during revision surgery. The HO samples were decalcified, embedded in paraffin and sectioned. Azan staining was used to evaluate histological structure of the ossifications and immunohistochemical analysis was performed to estimate the localization of three TGF beta isoforms in the HOs. Comparison of different TGF beta isoforms in the immature and the mature ossifications showed that the content of TGF-β₂ was decreased by almost three times in the mature HO as compared to the immature HO (p = 0.0064). The proportions of other isoforms in HOs did not differ significantly. This study shows that the relative importance of TGF betas change with HO development.     

Pharmacokinetics and metabolism of the nitrogen mustard bioreductive drug 5-[N,N-bis(2-chloroethyl)amino]-2,4-dinitrobenzamide (SN 23862) and the corresponding aziridine (CB 1954) in KHT tumour-bearing mice

Purpose: To characterise the pharmacokinetics and metabolism in mice of 5-[N,N-bis(2-chloroethyl)amino]-2,4-dinitrobenzamide (SN 23862), the lead compound of a new class of bioreductive drugs in which a nitrogen mustard is activated by nitroreduction. Comparison is made with the corresponding aziridine derivative CB 1954. Methods: Male C₃H/HeN mice, bearing s.c. KHT tumours, received ³H-labelled SN 23862 or CB 1954 i.v. at 200 μmol/kg. Plasma, urine and tumour samples were assayed for total radioactivity, and for parent compounds by HPLC. Metabolites were identified by ¹H-NMR and mass spectrometry. Cytotoxicity of compounds against Chinese hamster AA8 cells was determined by growth inhibition assay. Results: The plasma pharmacokinetics of SN 23862 and CB 1954 were similar, with half-lives of 1.1 and 1.2 h, respectively. SN 23862 provided tumour/plasma ratios and absolute tumour AUC values almost two times higher than CB 1954. Despite this, SN 23862 was more extensively metabolised than CB 1954, the major route being sequential oxidative dechloroethylation of the nitrogen mustard moiety to the relatively non-toxic half mustard and 5-amine. The inferred chloroacetaldehyde co-product was 260 times more potent than SN 23862. A tetrahydroquinoxaline metabolite resulting from reduction of the 4-nitro group followed by intramolecular alkylation was weakly cytotoxic, while the more cytotoxic 2-amino derivative of SN 23862 was detected in trace amounts. CB 1954 was metabolised by analogous pathways, but the 4- and 2-amine nitroreduction products were the major metabolites while oxidative dealkylation was minor. Conclusion: The lesser propensity for SN 23862 to undergo nitroreduction in the host, relative to CB 1954, argues that dinitrobenzamide mustards may be preferable to the corresponding aziridines as bioreductive prodrugs for cancer treatment. However, the toxicological significance of oxidative metabolism of the bis(2-chloroethyl)amine moiety needs to be addressed. Received: 7 March 2000 / Accepted: 9 June 2000     

A murine model of congenital toxoplasmic retinochoroiditis

A histopathological study of toxoplasmic retinochoroiditis in 39 eyes of mice infected in utero with Toxoplasma gondii and sacrificed at 16 weeks post-partum showed a wide variation in the pattern of tissue destruction. The changes in individual eyes were graded from mild to severe; Toxoplasma cysts were present in the retina and optic nerve in each grade. In the least affected eyes, Toxoplasma cysts were rarely seen and the disease was limited to a low grade uveitis and retinal lymphocytic perivasculitis. In the more severely affected eyes, there was focal, sectorial or total retinal destruction with secondary degeneration in the lens. In some eyes inflammatory destruction of the outer retina was associated either with a paucity of cells, or with lymphocytic infiltration or with plasma cell infiltration; giant cell granulomatous reactions were rare. In the most severely affected eyes the retina was necrotic and calcified. The findings illustrate the complexity of toxoplasmic retinochoroiditis and suggest that autoimmunity may play a part in the disease process.     

Omiderm treatment of scalds in children

As a temporary dressing on scald wounds in children Omiderm was tried in 10 consecutive patients. Omiderm is a thin, transparent, hydrophilic polyurethane membrane, permeable to water and oxygen. It was applied on the wound when exudation was declining, about 4-10 hours postburn. The dressing formed a crust with the wound exudate and was removed when the wound had reepithelialized or at day 14 postburn before split skin grafting of the wound if the wound had not yet healed. The dressing had no advantages nor disadvantages compared to conventional exposure treatment with regard to healing time, rate of bacterial contamination, need for split skin grafting, quality of scars on spontaneously healed areas nor comfort to the patients.     

Outcome of mobile ear surgery for chronic otitis media in remote areas.

OBJECTIVES: The Inuit of Greenland, Canada and Alaska suffer from chronic otitis media (COM). In Greenland these patients used to be referred to Denmark for ear surgery. This was expensive and unsatisfactory, and the results were poor. A mobile ear surgery project was developed. DESIGN: The study is longitudinal and prospective with follow-up. SUBJECTS AND METHODS: The 274 patients were selected according to severity of COM and hearing loss. Only air conduction (AC) audiometry was obtained. Median age was 27 years and 55% were females. RESULTS: Closure rates at three weeks, one year, and two years were 67 percent, 72 percent, and 76 percent, respectively. Median AC pure tone average improvement was 15 dB and 12 dB after one year and two years, and 73 percent and 67 percent were satisfied. Outcome was associated with quality of the surgical skills (P < 0.002). We found marked spontaneous fluctuations between the follow-ups. CONCLUSION: The results of mobile ear surgery in Greenland are acceptable. Mobile ear surgery may be implemented in areas with limited access to health care, eg, in developing countries.     

Oxygen dependence and extravascular transport of hypoxia-activated prodrugs: comparison of the dinitrobenzamide mustard PR-104A and tirapazamine

PURPOSE: To compare oxygen dependence and tissue transport properties of a new hypoxia-activated prodrug, PR-104A, with tirapazamine, and to evaluate the implications for antitumor activity when combined with radiotherapy. METHODS AND MATERIALS: Oxygen dependence of cytotoxicity was measured by clonogenic assay in SiHa cell suspensions. Tissue transport parameters were determined using SiHa multicellular layers. Spatially resolved pharmacokinetic (PK) and pharmacodynamic (PD) models were developed to predict cell killing in SiHa tumors and tested by clonogenic assay 18 h after treatment with the corresponding phosphate ester, PR-104. RESULTS: The K-value (oxygen concentration to halve cytotoxic potency) of PR-104A was 0.126 +/- 0.021 microM (10-fold lower than tirapazamine at 1.30 +/- 0.28 microM). The diffusion coefficient of PR-104A in multicellular layers (4.42 +/- 0.15 x 10(-7) cm2 s(-1)) was lower than that of tirapazamine (1.30 +/- 0.05 x 10(-6) cm2 s(-1)) but PK modeling predicted better penetration to hypoxic cells in tumors because of its slower metabolism. The tirapazamine PK/PD model successfully predicted the measured activity in combination with single-dose radiation against SiHa tumors, and the PR-104A model underpredicted the activity, which was greater for PR-104 than for tirapazamine (at equivalent host toxicity) both with radiation and as a single agent. CONCLUSION: PR-104/PR-104A has different PK/PD properties from tirapazamine and superior activity with single-dose radiotherapy against SiHa xenografts. We have inferred that PR-104A is better able to kill cells at intermediate partial pressure of oxygen in tumors than implied by the PK/PD model, most likely because of a bystander effect resulting from diffusion of its activated metabolites from severely hypoxic zones.     

Soft-tissue procedures for the exposed knee arthroplasty: 18 cases followed for 7 (1-17) years

Reconstructive surgery was performed in 18 knee arthroplasties because of wound-healing problems or skin necrosis. The procedure, after debridement, included myocutaneous, muscle flap, and split-skin grafts. Revision was necessary in 6 cases. After 1-17 years, 6 patients had died, 2 had had a low femur amputation, and 5 had had an arthrodesis. Five patients had retained the prosthesis, although 3 of them had considerable pain and poor mobility; only 2 patients were tolerably painfree and had acceptable mobility. Patients with an exposed knee endoprosthesis should be referred to centers with special competence in plastic reconstructive surgery.     

Adrenergic effects on adrenocortical cortisol response to incremental exercise to exhaustion

This study evaluated the influence of adrenergic factors on the cortisol response to maximal exercise in endurance-trained men. This was achieved by testing healthy young men during exercise while varying both the condition of β-adrenergic blockage and the presence of a well-controlled simulated competitive environment to simulate activity of the sympatho-adrenal systems. Subjects (n = 10) performed maximal exercise (running) to exhaustion on a treadmill during four conditions: (1) placebo non-competitive [PNon] (2) after administration of 80 mg propranolol non-competitive [βNon] (3) in a simulated competition after a placebo intake [PCom], and (4) in a simulated competition after propranolol intake [βCom]. Blood samples were obtained before (pre-) and 3 min after (post-) exercise and assayed for cortisol (C). The data were analyzed with a multi-factorial repeated measures ANCOVA procedure. Statistical analysis revealed a significant three-way interaction for the drug versus competition versus sampling time effects (P < 0.05). Post-hoc tests revealed that the pre-exercise cortisol values did not differ significantly among the conditions. Cortisol did increase from pre- to post-exercise in all experimental conditions (P < 0.01), and the magnitudes of increase in the PCom, βNon and βCom conditions were greater than that of the PNon condition. Furthermore, the cortisol increases for both β-blockage conditions post-exercise (βNon, βCom) did not differ from one another (P > 0.05). The findings suggest β-adrenergic blockage and competitive conditions enhance the exercise cortisol response. In combination, however, these conditions do not act in an additive fashion. This suggests that perhaps there may be two separate influences or mechanisms (i.e., excitatory, inhibitory) on the adrenergic control of adrenocortical function, or a sympathetic compensation for β-blockage during exhaustive maximal exercise. Furthermore, the data suggests a possible “ceiling” on the hypothalamic-pituitary-adrenal axis response to exercise in endurance-trained men.