Growth on urea can trigger death and peroxidation of the cyanobacterium Synechococcus sp. strain PCC 7002

Laboratory conditions have been identified that cause the rapid death of cultures of cyanobacteria producing urease. Once the death phase had initiated in the stationary growth phase, cells were rapidly bleached of all pigmentation. Null mutations in the ureC gene, encoding the alpha subunit of urease, were constructed, and these mutants were no longer sensitive to growth in the presence of urea. High levels of peroxides, including lipid peroxides, were detected in the bleaching cells. Exogenously added polyunsaturated fatty acids triggered a similar death response. Vitamin E suppressed the formation of peroxides and delayed the onset of cell bleaching. The results suggest that these cyanobacterial cells undergo a metabolic imbalance that ultimately leads to oxidative stress and lipid peroxide formation. These observations may provide insights into the mechanism of sudden cyanobacterial bloom disappearance in nature.     

Traumatic brain injury in the developing rat: effects of maturation on Morris water maze acquisition

Previous work has demonstrated that postnatal and adult rats show different physiological responses to lateral fluid percussion (FP) brain injury. Compared to adult animals, the younger rats showed longer apnea and shorter unconsciousness, and sustained hypotension at all injury severities, with higher mortality following severe traumatic brain injury (TBI). To determine if these younger rats exhibit differential cognitive impairments, the Morris water maze (MWM) was used to compare the degree of spatial learning deficits between moderately injured postnatal day 17 (P17), P28, and adult rats, as well as their age-matched controls. Comparisons between shams of different ages showed a maturational time course for MWM acquisition, where adult rats learned the task 34-58% faster than younger age groups. Injured adults showed escape latency deficits throughout the entire training period, took 39% fewer direct paths to the platform during training, took 24% longer to reach criterion performance, and showed poor probe trial performance than adult shams. Injured P28s exhibited escape latency deficits during the first week, with 23% more trials to criterion and 24% fewer direct paths compared to P28 shams. In contrast, injured P17 rats showed no significant difference from age-matched controls in terms of escape latency, number of direct paths taken, or time to criterion performance. This work suggests that, upon surviving the insult, P17 injured rats show remarkable sparing compared to P28 and adult injured animals.     

Increased density of microtubule associated protein 2-immunoreactive neurons in the prefrontal white matter of schizophrenic subjects

Recent studies have suggested that schizophrenia may be related to prenatal disturbances in the cortical subplate, a transient but essential structure in the formation of cerebral cortical circuitry. Although most subplate neurons die during later development, some remain as the interstitial neurons of the adult white matter. In this study we used a monoclonal antibody against the cytoskeletal protein, microtubule associated protein-2 (MAP2), to quantify the density and distribution of labeled neurons in postmortem brain specimens containing the prefrontal white matter from five schizophrenic cases and matched controls. In both schizophrenics and matched controls, the density of white matter neurons decreased with increasing white matter depth. However, the mean density of MAP2-immunoreactive neurons was greater in the superficial white matter of the schizophrenic subjects compared to the matched controls. In contrast, no difference in the density of labeled neurons was seen in the deeper white matter. These findings are consistent with an abnormality in the development of the cortical subplate in at least some cases of schizophrenia.     

Delayed maturation of the interstitial cells of Cajal: a new diagnosis for transient neonatal pseudoobstruction. Report of two cases

BACKGROUND: Previous studies have suggested altered responses to repeat skin tests in the sites of IgE-mediated late-phase reactions (LPRs) induced within the previous 48 hours. To explore the possible modulation of LPRs in such rechallenge sites, we compared inflammatory responses in skin chambers induced over previous LPR and control sites. METHODS: Skin blisters were induced and unroofed in 12 human subjects over two sites of previous LPRs induced by intradermal injection of pollen antigens 24 hours or 48 hours earlier and two sites previously injected with buffer diluent (B). Skin chambers containing the same antigens were appended to one intradermal antigen site (called Ag/Ag) and one intradermal B site (B/Ag), and B-containing chambers were placed over antigen (Ag/B) and B (B/B) intradermal sites. Fluids were collected after the first and the second through fifth hours of challenge. RESULTS: In skin chamber challenges 24 hours after the intradermal injection, there was no significant difference after the first hours between the Ag/Ag or B/Ag sites in either histamine or tryptase levels; both were significantly higher than at Ag/B or B/B sites (p < 0.01). The same pattern of events was seen in fluids obtained from the second through fifth hours. The same pattern of findings was seen in examination of levels of the total leukocyte accumulation, total eosinophil accumulation, and frequency of activated (EG2+) eosinophils. Levels of lactoferrin, released from activated neutrophils, and eosinophil cationic protein, released from activated eosinophils, were also similar at Ag/Ag and B/Ag sites; both were significantly higher than at B/B sites, whereas levels at Ag/B sites were intermediate between those found at B/Ag and B/B sites. The pattern of events in skin chamber challenges 48 hours after intradermal injection was similar to that seen at 24 hours, except that levels of inflammatory mediators/cells in Ag/B sites were more intermediate between the B/Ag and B/B sites. CONCLUSION: There is no significant alteration of mediator or inflammatory cell responses after antigen rechallenge of previous LPR sites when compared with those found in antigen challenge of non-LPR sites.     

Impact on human health of Salmonella spp. on pork in The Netherlands and the anticipated effects of some currently proposed control strategies

Cell-cell and cell-extracellular matrix interactions are fundamental processes involved in cell migration and tissue remodeling. Both the cyclic regeneration of the human endometrium during the menstrual cycle as well as the process of embryo implantation involve such dynamic interactions. It has become quite clear that integrin adhesion molecules expressed on the surface of cells play critical roles in the transmission of signals from the extracellular milieu to the cells. It is these signals that presumably regulate the behavior of these cells during major morphogenetic processes. In recent years, work in human endometrium and trophoblasts has uncovered both the regulated and constitutive expression of integrin subunits and their extracellular matrix ligands in these tissues. In addition, attempts have been made to correlate pathological states related to either infertility or abnormal pregnancy to the aberrant expression of several of these integrins. The purpose of the present review is to describe briefly our present state of knowledge of the expression of integrins in human endometrium and trophoblasts and provide the reader with the necessary background needed to understand, at the cellular and molecular levels, processes in reproduction such as embryo implantation.     

Overexpression of human superoxide dismutase inhibits oxidation of low-density lipoprotein by endothelial cells

Oxidation of LDL in the subendothelial space has been proposed to play a key role in atherosclerosis. Endothelial cells produce superoxide anions (O2.-) and oxidize LDL in vitro; however, the role of O2.- in endothelial cell-induced LDL oxidation is unclear. Incubation of human LDL (200 microg/mL) with bovine aortic endothelial cells (BAECs) for 18 hours resulted in a 4-fold increase in LDL oxidation compared with cell-free incubation (22.5+/-1.1 versus 6.3+/-0.2 [mean+/-SEM] nmol malondialdehyde/mg LDL protein, respectively; P<0.05). Under similar conditions, incubation of LDL with porcine aortic endothelial cells resulted in a 5-fold increase in LDL oxidation. Inclusion of exogenous copper/zinc superoxide dismutase (Cu/ZnSOD, 100 microg/mL) in the medium reduced BAEC-induced LDL oxidation by 79%. To determine whether the intracellular SOD content can have a similar protective effect, BAECs were infected with adenoviral vectors containing cDNA for human Cu/ZnSOD (AdCu/ZnSOD) or manganese SOD (AdMnSOD). Adenoviral infection increased the content and activity of either Cu/ZnSOD or MnSOD in the cells and reduced cellular O2.- release by two thirds. When cells infected with AdCu/ZnSOD or AdMnSOD were incubated with LDL, formation of malondialdehyde was decreased by 77% and 32%, respectively. Two other indices of LDL oxidation, formation of conjugated dienes and increased LDL electrophoretic mobility, were similarly reduced by SOD transduction. These data suggest that production of O2.- contributes to endothelial cell-induced oxidation of LDL in vitro. Furthermore, adenovirus-mediated transfer of cDNA for human SOD, particularly Cu/ZnSOD, effectively reduces oxidation of LDL by endothelial cells.     

Transgenic DNA integrated into the oat genome is frequently interspersed by host DNA

Integration of transgenic DNA into the plant genome was investigated in 13 transgenic oat (Avena sativa L.) lines produced using microprojectile bombardment with one or two cotransformed plasmids. In all transformation events, the transgenic DNA integrated into the plant genome consisted of intact transgene copies that were accompanied by multiple, rearranged, and/or truncated transgene fragments. All fragments of transgenic DNA cosegregated, indicating that they were integrated at single gene loci. Analysis of the structure of the transgenic loci indicated that the transgenic DNA was interspersed by the host genomic DNA. The number of insertions of transgenic DNA within the transgene loci varied from 2 to 12 among the 13 lines. Restriction endonucleases that do not cleave the introduced plasmids produced restriction fragments ranging from 3.6 to about 60 kb in length hybridizing to a probe comprising the introduced plasmids. Although the size of the interspersing host DNA within the transgene locus is unknown, the sizes of the transgene-hybridizing restriction fragments indicated that the entire transgene locus must be at least from 35-280 kb. The observation that all transgenic lines analyzed exhibited genomic interspersion of multiple clustered transgenes suggests a predominating integration mechanism. We propose that transgene integration at multiple clustered DNA replication forks could account for the observed interspersion of transgenic DNA with host genomic DNA within transgenic loci.