Endotoxin impedes vasoconstriction in the spleen: role of endogenous interleukin-1 and sympathetic innervation.

Processes relevant for an appropriate immune response such as immune cell traffic and recirculation require a tight control of blood supply to lymphoid organs. Interactions between endogenous cytokines and sympathetic nerve fibers in lymphoid organs can contribute to this control. The results reported in this paper show that 1) administration of low doses of lipopolysaccharide (LPS), an endotoxin derived from gram-negative bacteria, causes an increase in splenic blood flow (SBF); 2) this increase is mediated by the production of endogenous interleukin-1 (IL-1); 3) the effect of LPS on SBF requires an intact splenic sympathetic innervation; 4) the LPS-induced increase in SBF is exerted at the postganglionic level; 5) the endotoxin inhibits the vasoconstriction induced by the in vivo stimulation of the splenic nerve but does not affect the vasoconstriction induced by norepinephrine (NE); and 6) although IL-1 and LPS stimulate general sympathetic activity as reflected by increased peripheral vascular resistance, they do not increase NE concentration in splenic dialysates. Together these in vivo results indicate that endogenous IL-1 affects blood supply to the spleen by inhibiting the sympathetic vasoconstrictor tonus at a postganglionic, prejunctional level. This effect is expected to be relevant for immune cell recirculation, homing, and traffic as well as antigen trapping in the spleen, an organ specialized in the control of these processes during immune responses.

Analysis of the p53 and MDM-2 gene in acute myeloid leukemia.

The MDM-2 (murine double minute 2) gene codes for a cellular protein that can bind to the p53 tumor suppressor gene product, thereby functioning as a negative regulator of p53. In order to define the role of the MDM-2 gene in the pathogenesis of human acute myeloid leukemia, the expression and the sequence of the MDM-2 gene were examined in samples of bone marrow and/or peripheral mononuclear cells of 38 patients by using immunostaining, polymerase chain reaction (PCR), single strand conformation polymorphism, and sequencing. Immunohistochemical staining detected a weak accumulation of the MDM-2 protein in AML patients of FAB classification M4 and M5. RT-PCR analysis revealed a heterogeneous expression pattern of MDM-2 mRNA in AML samples of different FAB classification. An increased level of MDM-2 mRNA expression was observed in 17 of 38 AML patients when compared to normal controls. No structural changes in a 488 bp region extending from nucleotide 890 to 1378 of the MDM-2 cDNA were detected using RT-SSCP and sequence analysis. In addition, heterogeneous expression of p53 transcripts was found with the highest p53 mRNA levels in AML M4 and M5. Interestingly, there seems to be a correlation between the relative ratios of p53 and MDM-2 mRNA levels in AML M4 and M5: in 15 of 23 cases high p53 mRNA expression was directly associated with high levels of MDM-2 transcripts. An exclusively intranuclear p53 immunostaining pattern was found in 10 of 16 (58%) AML FAB M4 and M5, whereas the remaining AML samples tested were negative for p53 (0/10). Using RT-SSCP analysis and direct sequencing of the RT-PCR amplification products of p53 exon 5-8, we observed that only 1 of 38 AML patients showed a point mutation in the p53 gene. This missense mutation occurred in the evolutionary highly conserved region of p53 at codon 255 (Ile to Phe). These data indicated that structural alterations of the p53 gene do not play an important role in the initiation and progression of AML. However, abrogation of p53 tumor suppressor function due to MDM-2 overexpression may be an alternative molecular mechanism by which a subset of AMLs may escape from p53-regulated growth control.

The effects of parasitism by Glyptapanteles liparidis (Braconidae: Hymenoptera) on the hemolymph and total body composition of gypsy moth larvae (Lymantria dispar, Lymantriidae: Lepldoptera).

The hemolymph and total body tissue composition (carbohydrates, lipids, proteins, and free amino acids) of gypsy moth larvae (Lymantria dispar, Lymantriidae:Lepidoptera) were analyzed and compared with the composition of larvae infected by their main parasitoid, Glyptapanteles liparidis (Braconidae:Hymenoptera). In the body tissue the concentrations of total lipids and total proteins decreased, whereas the glycogen concentration in the total body tissue was significantly elevated and exceeded the concentration of the nonparasitized larvae by a factor of approximately 3. Trehalose, glucose, and sorbitol were found in the hemolymph of both parasitized and nonparasitized larvae, but levels of all three carbohydrates were significantly reduced in parasitized individuals. The total lipid concentration was not altered due to parasitism. In the hemolymph the concentrations of total proteins nearly doubled in parasitized larvae, whereas the total free amino acid concentration was reduced; however, the levels of some single amino acids were reduced and those of others were elevated in the parasitized larvae. The polypeptide profile of the host hemolymph provided one parasitism-specific polypeptide at approximately 80 kDa. The results demonstrate that parasitization of gypsy moths by G. liparidis leads to significant alterations in levels of nearly all substance classes within the host's hemolymph and tissue.

Changes in protein content and free amino acid composition in metal-contaminated gypsy moth larvae (Lymantria dispar L., Lymantriidae, Lepidoptera).

Larvae of Lymantria dispar (Lymantriidae, Lepidoptera) were either reared on oak foliage or on an uncontaminated and metal-contaminated wheat germ diet from hatching to the end of experiment. Cd, Pb, Cu and Zn were separately applied, each at two concentrations in the range of no-observed-effect concentrations recently published for this species. Hemolymph was collected from day 3 fourth instar larvae, and total protein content and free amino acid composition were determined along with total body protein content (TBP) of the corresponding larvae. Clear diet-dependent differences were observed: total protein content of the larvae and of the hemolymph was higher in foliage-fed (281.2 micrograms/mg; 13.6 mg/ml) than in diet-fed control individuals (200.5 micrograms/mg; 10.5 mg/ml), whereas the opposite applied to the total free amino acid (TFAA) concentration (64.78 mM, 108.81 mM). Chronic exposure to Cd, Cu and Zn in the diet generally resulted in a decrease of total hemolymph protein but enhanced TFAA concentrations and TBP compared with artificial-diet-fed control group. Sixteen free amino acids were identified and quantitated by high-performance liquid chromatography. Concentrations of single amino acids and/or their relative abundance depended on the diet and the metal applied. For example, the concentration of histidine, the most abundant amino acid (40-53% of total amino acids), was lower in the oak-leaf-fed group (26.04 mM, 40.8% of total amino acids) than in the wheat germ control group (47.89 mM, 44%), but in most metal-contaminated specimens histidine increased significantly (56.58-69.78 mM, 46-53%). The phenylalanine concentration was not diet dependent but was the only amino acid elevated in all contaminated groups.

Effect of oxytetracycline and erythromycin on Syrian hamsters after intratracheal infection with Mycoplasma pneumoniae.

Male Syrian hamsters were infected intratracheally with Mycoplasma pneumoniae and treated here after for ten days with either OTC or erythromycin. The purpose of this study was to investigate whether there exists a relation between the persistence of M. pneumoniae in the lungs and the infection dose respectively the days passed after infection before starting treatment with antibiotics. The influence of antibiotic therapy on the immune response of the hamsters was also investigated.