Volume 7, Issue 1-2

The hypothesis that neopterin blood levels provide a reliable basis for the decision to use antibiotics was tested prospectively in 536 traumatised intensive care unit (ICU) patients. Where infection was suspected antibiotics were given either if deemed necessary (control group) or if neopterin levels were>40 nmol/L (study group). The number of patients with infections (24% vs. 29%), the number of infectious episodes per patient (3.1 vs. 4.8 ), the incidence of infections with Staphylococcus and Pseudomonas, and the treatment costs (minus 20%) were lower in the study group. Mean length of ICU stay and outcome remained unchanged. We conclude that it is beneficial to base the decision to use antibiotics in ICU patients with suspected infections on neopterin testing.

While cytokines are produced by various cells; T cells, B cells, NK cells, monocytes, vascular endothelial cells, neutrophils, and fibroblasts , neopterin is a substance of which production is limited to monocytes, B cells, kidney epithelial cells and vascular endothelial cells. Serum neopterin levels correlate well with the activation of circulating monocytes and reticuloendothelial system including vascular endothelial cells and macrophages in tissue. In the diagnosis of diseases and in the elucidation of their pathophysiology, neopterin determination appears to be a powerful and useful tool to assess the activation of monocyte-lineage cells.

Streptozotocin-induced diabetes resulted in the alteration of an overall hepatic folate metabolism In rats leading to an increased urinary excretion of folates, mainly of methyl formas.

A mouse liver eDNA library in λZAP was screened using a 627 bp portion of 32 p randomly labeled human dihydropteridine reductase (731 bp) cDNA and seven positive clones were obtained. Six of these clones were sequenced using T3 and T7 primers as well as five selected 18-mer oligonucleotides in a "primer walking" strategy. From the data a consensus sequence was obtained for the coding region, the 5 ' flanking region and the 3' flanking region up to the poly-A tail. Of the 720 nucleotides in the coding region of mouse dihydropteridine reductase only 89 were different from those in the human reductase and only 31 nucleotides were different from those in the rat reductase. The amino acid sequence of the mouse reductase on the other hand differed from that of the human reductase by 15 residues in addition to the three extra alanine residues at positions 4, 5 and 6 from the N terminus; and from the rat reductase by 6 residues, many of which were conservative changes. The rat enzyme differed from the human enzyme in 9 residues in addition to the three alanines. The similarity of the eDNA coding regions and the reductases produced were characteristic of, and essential for, a “house-keeping” enzyme. The DNA in the 5′ and 3′ flanking regions of the three cDNAs, on the other hand, were very dissimilar although the human DNA had diverged a lot more from the mouse DNA than the rat DNA. Initiation, termination and poly-A tail consensus sequence signals were identified in all three cDNAs. A vector was engineered that expressed mouse dihydropteridine reductase which had kinetic parameters (Km for q-6MeDHP 17.4µM, NADH 7.3µM and k 170 sec 1 and Km for natural q-6R-BH 2 8 .7µM, NADH 7.7µM and k 44.3 sec 1 ) similar to those for the natural mouse reductase (Km for q-6MeDHP 16.5 µM, NADH 16.0 µM and k 214 sec 1 ; and Km for natural q-6R-BH 2 4.7 µM, NADH 9 .1µM and k 81.9 sec 1 ) which was purified from mouse liver.

Incorporation of fatty acids into phospholipids has been investigated using samples of rat liver tissue homogenate (Krebs-Ringer-phosphate buffer, pH=7.4, containing 0.3% albumin, fatty acid mixture and glycerol). The addition of 7,8-dihydroneopterin and biopterin (5 and 30 pmol/g wet weight) to incubation medium induced a decrease of palmitic (7,8-dihydroneopterin) and stearic acid (7,8-dihydroneopterin, biopterin) and an increase of linolenic (7,8-dihydroneopterin) and arachidonic acid (7,8 - dihydroneopterin, biopterin) incorporation into phospholipids. Cholesterol content decreased but phospholipid content did not change in samples containing 7,8-dihydroneo-pterin or biopterin. No changes of fatty acid incorporation into phospholipids as well as of the content of cholesterol and phospholipids were observed in samples after addition of isoxanthopterin (5 and 30 pmoljg wet weight) to incubation medium for phospholipid biosynthesis in vitro . Despite the fact that 7,8-dihydroneopterin and biopterin have different oxidation states and some similar effects on phospholipid biosynthesis and cholesterol content have been observed in our study, we suggest that the oxidation state of pteridines is more important than the pterin-( 6 )-side chain in the deviations of fatty acid incorporation into phopholipids as well as in the regulation of cholesterol content in samples

Neurologic impairment In human immunodeficiency virus (HIV) infection may be related to metabolic factors in addition to a direct effect of HIV in the brain. An immune-enhanced tryptophan catabolism has been described in HIV infected patients that may contribute to neurologic/ psychiatric symptoms. In 41 HIV-infected patients we studied the serum and cerebrospinal fluid concentrations of interferon-γ, neopterin, tryptophan and kynurenine in comparison to determinations of neurologic and psychiatric abnormalities as measured by a mental test and computerized tomography. Serum concentrations of interferon-γ, neopterin, and kynurenine were increased, whereas tryptophan levels were de creased in patients. Similarly, cerebrospinal fluid concentrations of neopterin and kynurenine were increased in the majority of patients compared to normal values. Significant relations existed between serum neopterin, tryptophan and its degradation product kynurenine and neurologic parameters. In cerebrospinal fluid , concentrations of neopterin but not of the other parameters tested were related to the mental state of patients. Our study demonstrates that systemic immune activation and its influence on tryptophan metabolism are related to neurologic disease in HIV patients. Intrathecal alterations of tryptophan and kynurenine appear to be less important.