Matrix Metalloproteinase-2 and Tissue Inhibitor of Metalloproteinase-1 in the Retinal Pigment Epithelium and Interphotoreceptor Matrix: Vectorial Secretion and Regulation

Matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs) play an essential role in both normal and pathological extracellular matrix degradation, and a TIMP has been associated with at least one type of retinal degeneration. We have studied expression of MMP-2 and TIMP-1 by zymography, immunocytochemistry, and immunoblotting in the retinal pigment epithelium (RPE) from normal, aged and diseased retinas. MMPs and TIMPs were found in the rat RPE, interphotoreceptor matrix (IPM), and in media conditioned by human and rat RPE in culture. In other polarized cells, MMPs and TIMP-2 are secreted vectorially towards the basal lamina. In the RPE, however, MMP-2 and TIMP-1 were secreted preferentially from the apical surface, the surface bordering the IPM. These findings provide new evidence that MMPs and TIMPs could play a role in the turnover of IPM components.Cell homogenates and conditioned media from RPE isolated from mutant Royal College of Surgeons (RCS) rats with inherited retinal dystrophy had similar amounts of MMP-2 and TIMP-1 as those from congenic control rats. The secretion of MMP-2 and TIMP-1 from RPE cell cultures isolated from young and aged human donors varied widely. However, with increasing cell passage number, secretion of MMPs and TIMPs from human RPE increased dramatically. Also, growing human RPE on bovine corneal endothelial cell-generated extracellular matrix instead of plastic reduced the secretion of both MMPs and TIMPs. These data suggest that the integrity of Bruch's membrane may serve to regulate RPE functions in MMP and TIMP secretion and that extracellular matrices contain signals that regulate MMP and TIMP synthesis and/or secretion by the RPE.     

Temporal stability of lipid responses to acute psychological stress in middle-aged men

The purpose of this study was to establish the temporal stability of lipid responses to acute psychological stress. Eighteen men were tested twice an average of 16.2 months apart in identical laboratory reactivity protocols. Total cholesterol, triglycerides, high- and low-density lipoprotein-cholesterol, plasma volume, heart rate, and blood pressure were assessed during rest, serial subtraction, and speech. After correction for changes in plasma volume, significant elevations were recorded for all variables during the speech task, but fewer variables showed changes during the serial subtraction task. Strong intersession associations were found when considering levels of the variables during baseline and stress (rs≥58). Correlations for the change scores ranged from .36 to .52 for the atherogenic lipids and from .39 to .87 for the cardiovascular variables. Little evidence was found for stability of plasma volume changes. There is moderate to high temporal stability of the atherogenic lipids when considering rest and stress levels and small to moderate temporal stability when considering change scores.     

Throat pain and pharyngeal packing: a controlled randomized double-blind comparison between gauze and tampons

In order to determine whether patients having pharyngeal packing experience more or less post-operative throat pain when tampons were used, 80 patients were randomized into two groups to receive either gauze or tampon pharyngeal packing. A third control group of 40 patients were intubated but did not have any throat packs. Post-operative throat pain was subjectively rated at both 6 hours and at 24 hours by an independent observer. Thirty-eight per cent of patients had moderate or severe throat pain in the gauze group, whilst in the tampon and control groups these amounted to only 15% and 1% respectively. A significantly higher proportion of patients also had a moderate or severe sore throat at 24 hours in the former group. Intubation alone resulted in a sore throat post-operatively in 50% of patients, but 85% of those had a mild sore throat only. No differences in pain ratings in any group could be shown between men or women or between age groupings. Endotracheal intubation often causes post-operative throat pain which is exacerbated by the use of pharyngeal packing. The results presented suggest that tampons are a safe, effective alternative to gauze and result in less severe post-operative throat pain.     

The Broiler Chicken as a Model for Immunotoxicity Assessment: 1. Standardization of in Vitro Immunological Assays

The Broiler Chicken as a Model for Immunotoxicity Assessment.1. Standardization of in Vitro Immunological Assays. BAECHER-STEPPAN,L., NAKAUE, H. S., MATSUMOTO, M., GAINER, J. H., AND KERKVLIET,N. I. (1989). Fundam. Appl. Toxicol. 12, 773–786. Thebroiler chicken was developed as an alternative animal modelto laboratory rodents for immunotoxico-logic assessment. Invivo treatment with 100–200 mg/kg cyclophosphamide (CY)was used as a known immunosuppressive treatment to standardizethe assay systems. Protocols for assessing specific immunologicalfunctions were developed in specific pathogen-free (SPF) broilersto measure lymphocyte blastogenesis to T-cell (concanavalinA and phytohemagglutinin) and B cell (Staphylococcus aureuscells) mitogens, delayed-type hypersensitivity (Dm) to tuberculin,natural killer (NK) cell cytotoxicity, plaque-forming cell (PFC)response to sheep red blood cells (SRBC), and serum antibodytiters to SRBC. CY was an effective immunosuppressant in thebroiler system for assessment of lymphocyte responsiveness tomitogenic stimulation, DTH reactivity, and the antibody responceto SRBC as assessed by PFC and serum antibody titers. NK cytotoxicitywas not altered on a cellular level following treatment withCY at a dose that preduced greater than 75% depletion of spleencellularity. However, under these conditions, it must bc assumedthat the capacity of CY-treated birds to mediate NK effectorfunctions would be reduced. These results demonstrate the applicabilityof the broiler chicken as an animal model for immunotoxicitytesting.     

Change in process: bringing about change in health care through action research

• ? A 2-year action-research project aiming to facilitate the management of change was carried out in a district general hospital.
• ? Hospital managers and senior ward nurses had very different views concerning the source of challenges and problems within the hospital organization.
• ? A case-study of nurses' experience of change at ward level was produced as part of the diagnostic phase of the action research.
• ? The results of the case-study indicated that general managers and professionals had different agendas for change hut that there is common ground between them.

     

Subchronic Inhalation Toxicity Studies with Hydrochlorofluorocarbon 123 (HCFC 123)

Hydrochlorofluorocarbon 123 (HCFC 123) is one of the chemicalsbeing considered as a replacement for the chlorofluorocarbons.Four subchronic inhalation toxicity studies from 1 to 3 monthsin duration have been conducted with HCFC 123. One study utilizedrats and dogs, while the others were limited to rats only. Theexposure levels have ranged from 300 ppm up to 20,000 ppm. Althoughthe studies were conducted over a 14-year period, the resultswere consistent. In all studies, increases in liver weightswere seen at 1000 ppm and above; additionally, one showed thiseffect at 500 ppm. Histopathological findings were minimal,consisting primarily of focal necrosis in the liver of the dogsat 10,000 ppm. Induction of peroxisomal activity, lowering ofserum cholesterol and triglyceride levels, and an increase inurinary fluoride levels were also seen. The 4-hr LC₅₀ in therat has been reported as 35,000 ppm. At 20,000 ppm for 6 hr,the total daily dose on a concentration times time basis isalmost equal to the LC₅₀ yet, in the 4-week study, with 20 exposuresat this level, there was no mortality or even marked signs oftoxicity. There appeared to be no evidence for cumulative toxicityfrom multiple exposures in these studies. Overall, HCFC 123appears to have a low level of toxicity by the inhalation route.