Electroretinography in rats

Basic mechanisms of the rat ERG were reinvestigated with contemporary methods of recording and photic stimulation via an optic fiber system connected with a contact lens. Flash stimulation and background illuminance were performed with photometrically defined light stimuli. ERGs recorded in darkness, from dark adapted rats, were similar with those observed in earlier work in which light flashes of much longer duration had been used. Flash stimulation carried out under stepwise increased background illuminance gave new information on the characteristics of oscillatory potentials of the ERG. In general the present observations agreed with the notion that the rods of the rat retina are as sensitive as in man, whereas the cones are functionally less efficient with respect to light sensitivity and temporal resolution. Differences in function of the cones from rat to man have to be kept in mind when using the rat ERG as a model for risk assessment in safety studies.     

Comparison of Track XI fluorometric immunoassay with Bio-EnzaBead enzyme-linked immunosorbent assay for detection of serum antibody to mouse hepatitis virus.

The Track XI system (Microbiological Associates, Bethesda, Md.) was compared with the Bio-EnzaBead assay (Organon Teknika, Durham, N.C.) for the detection of antibody to mouse hepatitis virus (MHV). Strain A/J mice were inoculated intranasally with MHV type 3. Sera were collected at 1, 2, 4, and 9 weeks postinoculation and tested. Individual serum samples were retested twice by each method. The results suggested that the Track XI system was more sensitive and reliable than the Bio-EnzaBead assay in detecting antibody to MHV type 3 in individual serum samples from A/J mice.     

Mercury (II) alters mitochondrial activity of monocytes at sublethal doses via oxidative stress mechanisms

The perennial controversy about the safety of mercury in dental amalgams has adversely affected the availability and the quality of dental care. Chronic Hg(II) blood concentrations above 300 nM are known to alter function of the nervous system and the kidney. However, the effects of blood concentrations of 10 to 75 nM, far more common in the general population, are not clear and mechanisms of any effects are not known. The monocyte is an important potential target of Hg(II) because of its critical role in directing inflammatory and immune responses. In the current study we tested the hypothesis that concentrations of Hg(II) of 10 to 300 nM alter monocyte activity via a redox-dependent mechanism. Mitochondrial activity was used to establish inhibitory concentrations of Hg(II) following 6 to 72 h of exposures to THP1 human monocytic cells. Then subinhibitory concentrations were applied, and total glutathione levels and reactive oxygen species (ROS) were measured. Antioxidants [N-acetyl cysteine, (NAC); Na2SeO3, (Se)] and a pro-oxidant (tert-butylhydroquinone, tBHQ) were used to support the hypothesis that Hg(II) effects were redox-mediated. After 72 h of exposure, 20 microM of Hg(II) inhibited monocytic mitochondrial activity by 50%. NAC mitigated Hg(II)-induced mitochondrial suppression only at concentrations of greater than 10 microM, but Se had few effects on Hg-induced mitochondrial responses. tBHQ significantly enhanced mitochondrial suppression at higher Hg(II) concentrations. Hg(II) concentrations of 75 and 300 nM (0.075 and 0.30 microM, respectively) significantly increased total glutathione levels, and NAC mitigated these increases. Se plus Hg(II) significantly elevated Hg-induced total cellular glutathione levels. Increased ROS levels were not detected in monocytes exposed to mercury. Hg(II) acts in monocytic cells, at least in part, through redox-mediated mechanisms at concentrations below those commonly associated with chronic mercury toxicity, but commonly occurring in the blood of some dental patients.     

Long-term protective immune response elicited by vaccination with an expression genomic library of Toxoplasma gondii

Immunization of BALB/c mice with an expression genomic library of Toxoplasma gondii induces a Th1-type immune response, with recognition of several T. gondii proteins (21 to 117 kDa) and long-term protective immunity against a lethal challenge. These results support further investigations to achieve a multicomponent anti-T. gondii DNA vaccine.     

Diagnosis of acute myocardial infarction from sequential enzyme measurements obtained within 12 hours of admission to hospital.

A prospective study was made of sequential changes in serum creatine kinase (CK) and CK-MB isoenzyme activity within the 12 hours following admission to the coronary care unit on 65 patients with recent chest pain. CK determinations were performed in the laboratory or in the coronary care unit using a dry reagent strip analyser. Slope values for log CK/hour and log CK-MB/hour were calculated, used to confirm or exclude the diagnosis of myocardial infarction, and compared with diagnosis by conventional means. Compared with retrospective diagnosis using all available information, the CK slope had a sensitivity of 100% and a specificity of 94%. This compared with a sensitivity of 94% and specificity of 90% for diagnosis using upper reference limits alone. Determination of CK slope permits very rapid and accurate biochemical confirmation or exclusion of myocardial infarction and the possibility of performing the measurements on the coronary care unit. It additionally offers the prospect of major cost savings resulting from early discharge or transfer from the coronary care unit.     

Lung epithelial cells and extracellular matrix components induce expression of Pneumocystis carinii STE20, a gene complementing the mating and pseudohyphal growth defects of STE20 mutant yeast

Pneumocystis carinii causes severe pneumonia in immunocompromised hosts. The binding of P. carinii to alveolar epithelial cells and extracellular matrix constituents such as fibronectin and vitronectin is a central feature of infection, which initiates proliferation of the organism. Herein, we demonstrate that P. carinii binding to lung cells specifically alters the gene expression of the organism, regulating fungal growth. Subtractive hybridization was performed to isolate P. carinii genes expressed following binding to mammalian extracellular matrix constituents. P. carinii STE20 (PCSTE20), a gene participating in mating and pseudohyphal growth of other fungi, was identified following adherence to the extracellular matrix constituents fibronectin, vitronectin, collagen, and lung epithelial cells. The expression of PCSTE20 and a related P. carinii mitogen-activated protein kinase (MAPK) kinase gene, also implicated in signaling of mating, were both specifically upregulated by binding to matrix protein. The expression of general cyclin-dependent kinases and other MAPKs not involved in mating pathways were not altered by organism binding. PCSTE20 expression was also strongly enhanced following organism attachment to A549 lung epithelial cells. When expressed in a Saccharomyces cerevisiae ste20Delta mutant, PCSTE20 suppressed defects in both mating and pseudohyphal growth. These findings are consistent with the observed proliferation and filopodial extension of Pneumocystis organisms adherent to the epithelium in the lungs of immunocompromised hosts. PCSTE20 expression appears to represent a significant component in the regulation of the life cycle of this intractable opportunistic pathogen.     

Regulation of glutathione by oxidative stress in bovine pulmonary artery endothelial cells

Glutathione plays important roles as an intracellular antioxidant and in the maintenance of cellular thiol-disulfide balance. In addition, glutathione may regulate cell growth signaling induced by oxidative stress. We previously reported that cellular glutathione is up-regulated by bleomycin in bovine pulmonary artery endothelial cells. The present study examined effects of hydrogen peroxide (H(2)O(2)) on cell growth and glutathione levels. Exogenous addition of H(2)O(2) induced biphasic effects on cell growth; 1 micro M was stimulatory and >10 micro M was inhibitory. However, both growth-promoting and inhibitory levels of H(2)O(2) increased cellular glutathione levels. Whereas 1 micro M H(2)O(2) moderately but significantly increased glutathione, 30 micro M caused a more substantial increase. Like bleomycin, both concentrations of H(2)O(2) activated DNA binding of antioxidant response element (ARE), a regulatory element in the promoter of the gamma-glutamylcysteine synthetase heavy chain subunit, a key regulator of glutathione synthesis. However, only high concentrations of H(2)O(2) activated p44/42 mitogen-activated protein (MAP) kinase. Thus, cellular glutathione is up-regulated by H(2)O(2), perhaps via activating ARE-binding factors in a mechanism independent of MAP kinase. H(2)O(2)-mediated increase in glutathione and activation of ARE binding may play important roles in growth and death of pulmonary artery endothelial cells.     

GATA6 mutations: Characterization of two novel patients and a comprehensive overview of the GATA6 genotypic and phenotypic spectrum

The first human mutations in GATA6 were described in a cohort of patients with persistent truncus arteriosus, and the phenotypic spectrum has expanded since then. This study underscores the broad phenotypic spectrum by presenting two patients with de novo GATA6 mutations, both exhibiting complex cardiac defects, pancreatic, and other abnormalities. Furthermore, we provided a detailed overview of all published human genetic variation in/near GATA6 published to date and the associated phenotypes (n = 78). We conclude that the most common phenotypes associated with a mutation in GATA6 were structural cardiac and pancreatic abnormalities, with a penetrance of 87 and 60%, respectively. Other common malformations were gallbladder agenesis, congenital diaphragmatic hernia, and neurocognitive abnormalities, mostly developmental delay. Fifty‐eight percent of the mutations were de novo, and these patients more often had an anomaly of intracardiac connections, an anomaly of the great arteries, and hypothyroidism, compared with those with inherited mutations. Functional studies mostly support loss‐of‐function as the pathophysiological mechanism. In conclusion, GATA6 mutations give a wide range of phenotypic defects, most frequently malformations of the heart and pancreas. This highlights the importance of detailed clinical evaluation of identified carriers to evaluate their full phenotypic spectrum.     

Chicken pox infection (varicella zoster virus) and acute monoarthritis: evidence against a direct viral mechanism.

A 9 year old boy developed acute monoarthritis of the left knee concurrent with the appearance of a varicella zoster virus (VZV) rash. Repeated VZV DNA hybridisation of the cells within the synovial fluid and synovial membrane failed to show any evidence of intracellular virus. Virus was isolated from synovial fluid 24 hours after the start of clinical infection but not later. These findings suggest that the mechanism of the arthritis is not due to viral replication inside the swollen joint.     

The functional organization of the intraparietal sulcus in humans and monkeys

In macaque monkeys, the posterior parietal cortex (PPC) is concerned with the integration of multimodal information for constructing a spatial representation of the external world (in relation to the macaque's body or parts thereof), and planning and executing object-centred movements. The areas within the intraparietal sulcus (IPS), in particular, serve as interfaces between the perceptive and motor systems for controlling arm and eye movements in space. We review here the latest evidence for the existence of the IPS areas AIP (anterior intraparietal area), VIP (ventral intraparietal area), MIP (medial intraparietal area), LIP (lateral intraparietal area) and CIP (caudal intraparietal area) in macaques, and discuss putative human equivalents as assessed with functional magnetic resonance imaging. The data suggest that anterior parts of the IPS comprising areas AIP and VIP are relatively well preserved across species. By contrast, posterior areas such as area LIP and CIP have been found more medially in humans, possibly reflecting differences in the evolution of the dorsal visual stream and the inferior parietal lobule. Despite interspecies differences in the precise functional anatomy of the IPS areas, the functional relevance of this sulcus for visuomotor tasks comprising target selections for arm and eye movements, object manipulation and visuospatial attention is similar in humans and macaques, as is also suggested by studies of neurological deficits (apraxia, neglect, Bálint's syndrome) resulting from lesions to this region.