Diabetic-like retinopathy: early and late intervention therapies in galactose-fed rats

PURPOSE: To determine whether the diabetic-like thickening of retinal capillary basement membrane (RCBM) that develops in the galactose-fed rat model of diabetic ocular complications could be halted or ameliorated after 4 or 8 months of galactosemia by treatment with ARI-509, a potent new aldose reductase inhibitor (ARI), or by withdrawal of the galactose diet. METHODS: Weanling female Sprague-Dawley rats were randomized into eight groups and fed laboratory chow plus 50% starch, control group (CON); 50% D-galactose, galactose-fed group (GAL); 50% D-galactose with ARI-509 at 25 mg/kg or 10 mg/kg body wt per day, high-dose prevention group (HDP) and low-dose prevention group (LDP), respectively; 50% D-galactose for 4 or 8 months and then intervention by addition of ARI-509 (25 mg/kg body wt per day), 4-month intervention group (4IN) and 8-month intervention group (8IN), respectively; or 50% D-galactose for 4 or 8 months and then intervention by withdrawing galactose and replacing it with the 50% starch diet, 4-month galactose withdrawal group (4GW) and 8-month galactose withdrawal group (8GW), respectively. After 4, 8, 16, and 24 months of the experimental diets, the levels of carbohydrates in tissues and the extent of RCBM thickening in capillaries of the outer plexiform layer were determined in all groups. RESULTS: Retinal polyol was reduced by 95% in all ARI-treated groups and by 100% in the 4GW and 8GW groups after withdrawal of the galactose. The mean RCBM thickness increased rapidly in GAL rats, becoming almost two times greater (189 +/- 9.4 nm) than in CON rats (103 +/- 3.4 nm) by 24 months. Treatment with ARI-509 in high and low doses (HDP, LDP) initiated with the introduction of the galactose diet significantly prevented RCBM thickening at all time points (P < 0.05). In contrast, intervention by withdrawing galactose from the diet or by adding the high dose of ARI-509 had no significant effect (P < 0.05) on RCBM thickening until the 24-month time point (4IN, 166 +/- 10.3 nm; 8IN, 161 +/- 8.2 nm; 4GW, 136 +/- 5.1 nm; 8GW, 163 +/- 9.6 nm). CONCLUSIONS: Both early and late interventions decreased RCBM thickening compared with that in untreated GAL rats. The decreased thickening, however, was not evident until 16 to 20 months after the intervention. Because RCBM thickening is one of the earliest changes in diabetic and galactosemic retinopathy, the findings suggest that RCBM thickening and possibly subsequent retinal lesions are caused by early biochemical alterations induced by the galactose diet that are not readily reversed. The delayed response to therapy is consistent with that observed in the Diabetes Control and Complications Trial. The cumulative evidence indicates that intervention should begin as early after onset of diabetes as possible, and long follow-up periods should be used to evaluate efficacy.     

A phase II study of thioTEPA in children with recurrent solid tumor malignancies: a Children''s Cancer Group study

We report a murine leukemia cell variant (L1210/DDP), selected for cisplatin (DDP) resistance, to be cross-resistant to methotrexate (MTX). Cross-resistance of L1210 cells to DDP and MTX has been observed by others, and has also been recorded in P388 murine leukemia and SSC-25 human squamous carcinoma cells. We demonstrated that MTX resistance is not due to dihydrofolate reductase (DHFR) gene amplification, increased DHFR enzyme activity or decreased MTX binding to the target enzyme. Of the mechanisms commonly proposed for MTX resistance, only differences in transport were observed when comparing sensitive (L1210/0) and resistant (L1210/DDP) cells. Our results suggest that MTX resistance in L1210/DDP cells is due to altered methotrexate uptake.     

Anagrelide, a selective thrombocytopenic agent

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage and administration of anagrelide are reviewed. Anagrelide is a selective thrombocytopenic agent with FDA-approved labeling for the treatment of essential thrombocythemia. Clinical trials have shown that the drug may have a role in the treatment of other chronic myeloproliferative disorders, including polycythemia vera, chronic myeloid leukemia, and agnogenic myeloid metaplasia. The mechanism by which anagrelide reduces platelet count is not yet clear. The current hypothesis is that anagrelide affects the late (postmitotic) phases of megakaryocyte development. Anagrelide has a large volume of distribution and is extensively metabolized; less than 1% is recovered unchanged in the urine. Plasma half-life after a 0.5-mg dose is 1.3 hours. Anagrelide's efficacy and safety have been evaluated in open-label, noncomparative trials, in which the response rate was 60-93%. Adverse effects include headache, diarrhea, edema, palpitations, and abdominal pain. Patients with renal or hepatic dysfunction need to be closely monitored for signs of toxicity. The recommended starting dosage is 0.5 mg four times a day or 1 mg twice a day, with dosage adjustment to the lowest effective amount required to reduce and maintain platelet count below 600 x 10(9)/L. The wholesale acquisition price for 0.5-mg capsules is $350 per 100. Whether anagrelide will replace hydroxyurea as first-line therapy in some or all patients remains to be determined. Anagrelide is effective in the treatment of essential thrombocythemia and may have a role in the treatment of other myeloproliferative disorders.     

Use of a two-compartment model to assess the pharmacokinetics of human ethanol metabolism

The relationship between blood ethanol concentration and hepatic ethanol metabolism commonly is calculated using the Michaelis-Menten equation and a one-compartment model that assumes equality of blood and hepatic ethanol concentrations. However, at low blood concentrations, most of the ethanol arriving at the liver is metabolized, and hepatic ethanol concentrations may fall far below that of the entering blood. We have developed a two-compartment model of ethanol metabolism that accounts for the fall in ethanol concentration that may occur as blood traverses the liver and used this model to make predictions concerning ethanol metabolism at various blood ethanol concentrations. The two-compartment model predicts that near-complete saturation will occur more abruptly and at a lower blood concentration (approximately 3 mM) than is the case with the one-compartment model. Thus, the two-compartment model predicts a near-constant ethanol elimination rate for blood ethanol concentrations above 3 mM (as commonly observed in human subjects), whereas the one-compartment model predicts an increasing elimination rate over the range of concentrations observed in experimental studies. In agreement with observed data, the two-compartment model predicts that first-pass metabolism should be extremely sensitive to the rate of ethanol absorption. Application of this model to previously published data indicated that, when absorption was slowed via concomitant food ingestion, first-pass metabolism accounts for approximately 50% and 10% of ethanol dosages of 0.15 g/kg and 0.3 g/kg, respectively. When ingested without food, there is negligible first-pass metabolism of even very small ethanol dosages (0.15 g/kg). These findings suggest that first-pass metabolism is an unimportant determinant of the blood ethanol response to ingestion of potentially inebriating doses of ethanol.     

A G protein is involved in the angiotensin AT2 receptor inhibition of the T-type calcium current in non-differentiated NG108-15 cells

In non-differentiated NG108-15 cells, both angiotensin II (Ang II) (100 nM) and CGP 42112 (100 nM) decreased the T-type calcium current amplitude by 24 +/- 2% and 21 +/- 3%, respectively. cGMP is not a mediator of the Ang II effect, since loading of cells with 50 microM cGMP did not prevent the inhibitory effects of Ang II. The effects of Ang II involves a non-identified GTPase activity since incubation with GDP beta S (3 mM) completely reversed the inhibitory effect of Ang II while GTP gamma S mimicked its effect. However, Ang II binding was not affected by GTP gamma S, and the effect of Ang II was not modified in pertussis toxin-treated cells. The inhibitory effect of Ang II on the T-type Ca2+ current involves a phosphotyrosine phosphatase activity since sodium orthovanadate prevented the effects of Ang II, although microcystin-LR, a selective Ser/Thr phosphatase 1 and 2A inhibitor, did not modify the effect of Ang II. These results provide the first evidence of a modulation of membrane conductance by Ang II through the AT2 receptor and demonstrate the involvement of a phosphotyrosine phosphatase and a G protein in the AT2 transduction mechanism in NG108-15 cells. Moreover, our data suggest that phosphotyrosine phosphatase activation is proximal to receptor occupation, since sodium orthovanadate inhibits both GTPase activity and T-type current blockage induced by Ang II or CGP 42112, while GTP gamma S inhibition of the T-type calcium current is not impaired.     

1,4-Cyclohexanecarboxylates: potent and selective inhibitors of phosophodiesterase 4 for the treatment of asthma

Evaluation of a variety of PDE4 inhibitors in a series of cellular and in vivo assays suggested a strategy to improve the therapeutic index of PDE4 inhibitors by increasing their selectivity for the ability to inhibit PDE4 catalytic activity versus the ability to compete for high affinity [3H]rolipram-binding sites in the central nervous system. Use of this strategy led ultimately to the identification of cis-4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexane-1-carboxyl ic acid (1, SB 207499, Ariflo), a potent second-generation inhibitor of PDE4 with a decreased potential for side effects versus the archetypic first generation inhibitor, (R)-rolipram.     

Abdominal and thoracoabdominal aortic aneurysm

Most abdominal aortic aneurysms (AAA) and thoracoabdominal aortic aneurysms (TAAA) are asymptomatic and are found on physical exam or incidentally during radiological studies for other indications. These aneurysms are repaired primarily because their risk of rupture increases geometrically as the size exceeds 5 cm. The potential morbidity of intraoperative visceral and spinal ischemia involved with TAAA repair may be reduced with various adjunctive maneuvers.     

Anti-CD4 activity of normal human immunoglobulin G for therapeutic use. (Intravenous immunoglobulin, IVIg)

The effects of intravenously administered normal immunoglobulin G (IVIg) in autoimmune diseases are dependent on the ability of IVIg to interact with surface molecules of lymphocytes. In the present study, we demonstrate the presence of anti-CD4 activity in IVIg by showing the ability of IVIg to bind to CD4 and to inhibit CD4-dependent cellular functions. Binding of IVIg to recombinant soluble human CD4 was assessed by ELISA, immunoblotting and real time analysis of complex formation. Anti-CD4 antibodies isolated from IVIg by affinity-chromatography bound to human CD4+ T cells. These anti-CD4 antibodies inhibited proliferative responses in MLR and infection of CD4+ human T cells with HIV. These results indicate that IVIg contains antibodies reactive with human CD4 and that these anti-CD4 antibodies exhibit biological functions. The presence of anti-CD4 antibodies in IVIg may be relevant to the immunoregulatory effects of normal polyspecific immunoglobulin G.