Rapid determination of benzalkonium chloride in pharmaceutical preparations with flow injection liquid-liquid extraction

Benzalkonium chloride was assayed by on-line extraction of the benzalkonium ion with picrate to chloroform. The absorbance of picrate was measured. The extractions were performed with a home-made flow injection extraction unit. Calibration curves (1.5-180 x 10(-4)% w/v) were straight lines (r = 0.9993) and the relative standard deviation of a series of injections was less than or equal to 2%. Pharmaceutical benzalkonium preparations, containing xylometazoline, timolol, phenylephrine or carbachol could also be assayed. The method was compared with a modified HPLC assay.     

Differential immune response of congenic mice to ultraviolet-treated major histocompatibility complex class II-incompatible skin grafts

The influence of ultraviolet (UVB) irradiation on the survival of H-2 class II-disparate skin grafts was studied in congenic mouse strains. Isolated skin was UVB irradiated in vitro at a dose of 40 mJ/cm2 from both sides to remove Ia immunogenicity. Immediately after irradiation the skin was transplanted onto the flank of allogeneic mice. When B10.AQR grafts were transplanted onto B10.T(6R) recipients, a significant prolongation of the survival time was observed, while 50% of the UVB-treated grafts were not rejected at all. However, in the opposite direction--i.e., B10.T(6R) grafts onto B10.AQR recipients, no significant prolongation of the survival was observed. To test whether this effect was due to a difference in susceptibility of the donor skin to UVB irradiation or to a different immune response in the recipients, (B10.T(6R) x B10.AQR) grafts were transplanted onto the parent strains. Similar results were obtained, in that UVB-treated grafts did not show a prolonged survival in B10.AQR recipients, whereas a significant prolongation (50% of the grafts survived more than 100 days) was observed in B10.T(6R) recipients. UVB-treated (B10.T(6R) x B10.AQR)F1 grafts were also transplanted onto (B10.T(6R) x C57B1/10)F1, (B10.AQR x C57B1/10)F1, (B10.T(6R) x Balb/c)F1 and (B10.AQR x Balb/c)F1 recipients--but in none of these combinations was a prolonged survival time observed. These data suggest that, in contrast to all in vitro experiments, the abrogation of the immune response by UVB treatment of the stimulator cells is, in vivo, not a general phenomenon. The genetic constitution of the responder mice seems to play an important role in determining whether or not an immune response takes place.     

Rupture of the posterior tibial tendon: CT and surgical findings

Computed tomography (CT) was performed in 42 patients with 49 clinically suspected tears of the posterior tibial tendon. Twenty-eight of the 49 suspected tears were subsequently surgically explored and repaired. Three patterns of tendon abnormalities were recognized on CT scans: type I-intact, hypertrophied, heterogeneous tendon; type II-attenuated tendon; and type III-absence of a portion of a tendon. Types I and II correlated with partial rupture seen during surgery, and type III correlated with complete rupture of the tendon. CT findings were accurate in 96% of the patients who underwent surgery. In four cases (14%), tendon rupture was seen on CT scans, but the extent of the injury was underestimated and the rupture was misclassified. Reactive periostitis of the distal tibia was seen in 71% of diseased tendons and may represent an important factor in the diagnosis of tendon rupture.     

Incidence of skin cancer after renal transplantation in The Netherlands

The incidence of squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) was analyzed separately in all 764 patients who received a renal allograft between 1966 and 1988 at the Leiden University Hospital. The mean follow-up period was 8.7 posttransplant years (range 1-21 years). During this time period 176 skin cancers were diagnosed in 47 patients. The overall risk to develop a first tumor increased from 10% after 10 years to 40% after 20 years of graft survival. The overall incidence of SCC was 250 times higher and that of BCC 10 times higher when compared with the general Dutch population. Moreover the localization of SCCs and BCCs differed considerably. Solar radiation is thought to be an important risk factor for the development of skin cancer. However, the occurrence of skin cancer in long-term graft survivors forms also a major problem in a country with a higher geographical latitude and a moderate amount of sun-exposure, such as the Netherlands.