Features of the immune response to DNA in mice. I. Genetic control.
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The genetic control of the immune response to DNA was studied in various strains of mice F1 hybrids and corresponding back-crosses immunized with single stranded DNA complexed to methylated bovine serum albumin. Anti-DNA antibody response was measured by radioimmuno-logical technique. High responder, low responder, and intermediate responder strains were found and the ability to respond to DNA was characterized as a dominant genetic trait which is not linked to the major locus of histocompatibility. Studies in back-crosses suggested that this immune response is under multigenic control. High responder mice produce both anti-double stranded DNA and anti-single stranded DNA 7S and 19S antibodies, while low responder mice produce mainly anti-single stranded DNA 19S antibodies. (+info)
Activity in saline of phthalylated or succinylated derivatives of mycobacterial water-soluble adjuvant.
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A water-soluble fraction (WSA) of the cell wall can substitute for mycobacterial cells in Freund complete adjuvant. However, when WSA is administered in saline instead of in a water-in-oil emulsion, its adjuvant activity is very weak, and under certain experimental conditions it can even inhibit the humoral immune response. The data reported in the present study show that after treatment by phthalic or succinic anhydride the adjuvant activity of WSA was markedly changed, since high levels of circulating antibodies were produced when these derivatives were administered with an antigen in an aqueous medium. Moreover, the antigenic determinants of WSA were modified and acylated WSA had no tuberculin-like activity. (+info)
Drug-protein binding and blood-brain barrier permeability.
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The permeability surface area (PS) product, an index of permeability of the blood-brain barrier (BBB), was measured by using the in situ perfusion method. In the cerebral circulation, the fraction of drug that permeates into the brain through the BBB is not only the unbound fraction but also the fraction dissociated from the protein in the perfusate. The sum of these two fractions, the apparent exchangeable fraction, was estimated by fitting the parameters of the BBB permeability under the condition of varying BSA concentrations in the perfusate. The unbound fraction of drugs in a buffer containing 0.5 mM BSA was measured by using the ultrafiltration method in vitro, and the apparent exchangeable fraction was measured in vivo by using the intracarotid artery injection method. The apparent exchange fraction was 100% for S-8510, 96.5% for diazepam, 90.9% for caffeine, 38.3% for S-312-d, 33.1% for propranolol, and 6.68% for (+)-S-145 Na, and each of these was higher than the corresponding unbound fraction in vitro in all drugs. The apparent exchangeable fractions, for example, were 8 times higher for diazepam and 38 times for S-312-d than the unbound fractions in vitro. The apparent exchangeable fraction of drugs was also estimated from the parameters obtained with the perfusion method. Because drugs can be infused for an arbitrary length of time in the perfusion method, substances with low permeability can be measured. The apparent exchangeable fractions obtained with this method were almost the same as those obtained with the intracarotid artery injection method. (+info)
N,N'-Diacetyl-L-cystine-the disulfide dimer of N-acetylcysteine-is a potent modulator of contact sensitivity/delayed type hypersensitivity reactions in rodents.
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Oral N-acetyl-L-cysteine (NAC) is used clinically for treatment of chronic obstructive pulmonary disease. NAC is easily oxidized to its disulfide. We show here that N,N'-diacetyl-L-cystine (DiNAC) is a potent modulator of contact sensitivity (CS)/delayed type hypersensitivity (DTH) reactions in rodents. Oral treatment of BALB/c mice with 0.003 to 30 micromol/kg DiNAC leads to enhancement of a CS reaction to oxazolone; DiNAC is 100 to 1000 times more potent than NAC in this respect, indicating that it does not act as a prodrug of NAC. Structure-activity studies suggest that a stereochemically-defined disulfide element is needed for activity. The DiNAC-induced enhancement of the CS reaction is counteracted by simultaneous NAC-treatment; in contrast, the CS reaction is even more enhanced in animals treated with DiNAC together with the glutathione-depleting agent buthionine sulfoximine. These data suggest that DiNAC acts via redox processes. Immunohistochemically, ear specimens from oxazolone-sensitized and -challenged BALB/c mice treated with DiNAC display increased numbers of CD8(+) cells. DiNAC treatment augments the CS reaction also when fluorescein isothiocyanate is used as a sensitizer in BALB/c mice; this is a purported TH2 type of response. However, when dinitrofluorobenzene is used as a sensitizer, inducing a purported TH1 type of response, DiNAC treatment reduces the reaction. Treatment with DiNAC also reduces a DTH footpad-swelling reaction to methylated BSA. Collectively, these data indicate that DiNAC in vivo acts as a potent and effective immunomodulator that can either enhance or reduce the CS or DTH response depending on the experimental conditions. (+info)
Proteinuria induces tubular cell turnover: A potential mechanism for tubular atrophy.
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BACKGROUND: Proteinuria and tubular atrophy have both been closely linked with progressive renal failure. We hypothesized that apoptosis may be induced by tubular cell exposure to heavy proteinuria, potentially leading to tubular atrophy. Apoptosis was studied in a rat model of "pure" proteinuria, which does not induce renal impairment, namely protein-overload proteinuria. METHODS: Adult female Lewis rats underwent intraperitoneal injection of 2 g of bovine serum albumin (BSA, N = 16) or sham saline injections (controls, N = 8) daily for seven days. Apoptosis was assessed at day 7 in tissue sections using in situ end labeling (ISEL) and electron microscopy. ISEL-positive nuclei (apoptotic particles) were counted in blinded fashion using image analysis with NIH Image. Cell proliferation was assessed by detection of mRNA for histone by in situ hybridization, followed by counting of positive cells using NIH Image. RESULTS: Animals injected with saline showed very low levels of apoptosis on image analysis. BSA-injected rats had heavy proteinuria and showed both cortical and medullary apoptosis on ISEL. This was predominantly seen in the tubules and, to a lesser extent, in the interstitial compartment. Overall, the animals injected with BSA showed a significant 30-fold increase in the number of cortical apoptotic particles. Electron microscopy of tubular cells in a BSA-injected animal showed a progression of ultrastructural changes consistent with tubular cell apoptosis. The BSA-injected animals also displayed a significant increase in proximal tubular cell proliferation. This increased proliferation was less marked than the degree of apoptosis. CONCLUSION: Protein-overload proteinuria in rats induces tubular cell apoptosis. This effect is only partially balanced by proliferation and potentially provides a direct mechanism whereby heavy proteinuria can induce tubular atrophy and progressive renal failure. (+info)
Resolution of fluorescence correlation measurements.
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The resolution limit of fluorescence correlation spectroscopy for two-component solutions is investigated theoretically and experimentally. The autocorrelation function for two different particles in solution were computed, statistical noise was added, and the resulting curve was fitted with a least squares fit. These simulations show that the ability to distinguish between two different molecular species in solution depends strongly on the number of photons detected from each particle, their difference in size, and the concentration of each component in solution. To distinguish two components, their diffusion times must differ by at least a factor of 1.6 for comparable quantum yields and a high fluorescence signal. Experiments were conducted with Rhodamine 6G and Rhodamine-labeled bovine serum albumin. The experimental results support the simulations. In addition, they show that even with a high fluorescence signal but significantly different quantum yields, the diffusion times must differ by a factor much bigger than 1.6 to distinguish the two components. Depending on the quantum yields and the difference in size, there exists a concentration threshold for the less abundant component below which it is not possible to determine with statistical means alone that two particles are in solution. (+info)
Acute troglitazone action in isolated perfused rat liver.
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1. The thiazolidinedione compound, troglitazone, enhances insulin action and reduces plasma glucose concentrations when administered chronically to type 2 diabetic patients. 2. To analyse to what extent thiazolidinediones interfere with liver function, we examined the acute actions of troglitazone (0.61 and 3.15 microM) on hepatic glucose and lactate fluxes, bile secretion, and portal pressure under basal, insulin- and/or glucagon-stimulated conditions in isolated perfused rat livers. 3. During BSA-free perfusion, high dose troglitazone increased basal (P < 0.01), but inhibited glucagon-stimulated incremental glucose production by approximately 75% (10.0 +/- 2.5 vs control: 40.0 +/- 7.2 micromol g liver(-1), P < 0.01). In parallel, incremental lactate release rose approximately 6 fold (13.1 +/- 5.9 vs control: 2.2 +/- 0.8 mmol g liver(-1), P < 0.05), while bile secretion declined by approximately 67% [0.23 +/- 0.02 vs control: 0.70 +/- 0.05 mg g liver(-1) min(-1)), P < 0.001]. Low dose troglitazone infusion did not enhance the inhibitory effect of insulin on glucagon-stimulated glucose production, but rapidly increased lactate release (P < 0.0005) and portal venous pressure (+0.17 +/- 0.07 vs +0.54 +/- 0.07 cm buffer height, P < 0.0001). 4. These results indicate that troglitazone exerts both insulin-like and non-insulin-like hepatic effects, which are blunted by addition of albumin, possibly due to troglitazone binding. (+info)
Stabilization of L-ascorbic acid by superoxide dismutase and catalase.
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The effects of superoxide dismutase (SOD) and catalase on the autoxidation rate of L-ascorbic acid (ASA) in the absence of metal ion catalysts were examined. The stabilization of ASA by SOD was confirmed, and the enzyme activity of SOD, which scavenges the superoxide anion formed during the autoxidation of ASA, contributed strongly to this stabilization. The stabilization of ASA by catalase was observed for the first time; however, the specific enzyme ability of catalase would not have been involved in the stabilization of ASA. Such proteins as bovine serum albumin (BSA) and ovalbumin also inhibited the autoxidation of ASA, therefore it seems that non-specific interaction between ASA and such proteins as catalase and BSA might stabilize ASA and that the non-enzymatic superoxide anion scavenging ability of proteins might be involved. (+info)