Tissue cages for study of experimental streptococcal infection in rabbits. I. Production of erythrogenic toxins in vivo

Tissue cages implanted subcutaneously were used to infect rabbits with erythrogenic toxin (ET) producing streptococci. The in-vivo production of ET was followed during the infection by immunoprecipitation analyses of the tissue cage fluid (TCF). ET types A and C were mainly detected during the first week of infection, but, as late as 4 weeks after the inoculation, ET was occasionally found in TCF. The nonspecific mitogenic activity of ET on human lymphocytes was also used as a biological marker to recognize ET in TCF. Mitogenic activity was detected in 90% of samples during the first week. In order to characterize the mitogenic material released by growing streptococci, TCF was electrofocused in polyacrylamide gel. The eluates of sliced gels were checked for mitogenic activity and compared with a purified ET preparation containing ET types A and C. It could be verified that ET type A was produced under in-vivo conditions by strains NY-5 and SF130, while ET type C was produced by strain T18. Differences between production of toxins in vitro and in vivo might be of significance for the understanding of the pathogenetic mechanisms in streptococcal infection.     

Hürthle cell and mitochondrion-rich papillary carcinomas of the thyroid gland: an ultrastructural and immunocytochemical study

Of 52 consecutive papillary carcinomas of the thyroid, the following cases were included in this study: one Hürthle cell papillary carcinoma, one papillary carcinoma with foci of Hürthle cells, and 10 cases of papillary carcinoma with abundant mitochondria (volumetric density of mitochondria greater than or equal to 20%). All cases were studied by light microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and immunocytochemistry. Our results showed that papillary carcinomas mainly or exclusively composed of Hürthle cells are very rare; that Hürthle cell papillary carcinomas of the thyroid share the biologic characteristics and blend insidiously with the so-called mitochondrion-rich papillary carcinomas; that TEM and SEM can provide useful evidence for achieving the differential diagnosis between Hürthle cell and so-called mitochondrion-rich papillary carcinomas; and that immunocytochemical studies are useless in the aforementioned differential diagnosis.     

Hormone-sensitive lipase in skeletal muscle: regulatory mechanisms

AIM: The enzymatic regulation of intramuscular triacylglycerol (TG) breakdown has until recently not been well understood. Our aim was to elucidate the role of hormone-sensitive lipase (HSL), which controls TG breakdown in adipose tissue. METHODS: Isolated rat muscle as well as exercising humans were studied. RESULTS: The presence of HSL was demonstrated in all muscle fibre types by Western blotting of muscle fibres isolated by collagenase treatment or after freeze-drying. The content of HSL varies between fibre types, being higher in oxidative than in glycolytic fibres. Analysed under conditions optimal for HSL, neutral lipase activity in muscle can be stimulated by adrenaline as well as by contractions. These increases are abolished by presence of anti-HSL antibody during analysis. Moreover, immunoprecipitation with affinity-purified anti-HSL antibody causes similar reductions in muscle HSL protein concentration and in measured neutral lipase responses to contractions. The immunoreactive HSL in muscle is stimulated by adrenaline via beta-adrenergic activation of protein kinase A (PKA). From findings in adipocytes it is likely that PKA phosphorylates HSL at residues Ser563, Ser659 and Ser660. Contraction probably also enhances muscle-HSL activity by phosphorylation, because the contraction-induced increase in HSL activity is increased by the protein phosphatase inhibitor okadaic acid and reversed by alkaline phosphatase. A novel signalling pathway in muscle by which HSL activity may be stimulated by protein kinase C (PKC) via extracellular signal regulated kinase (ERK) has been demonstrated. In contrast to previous findings in adipocytes, in muscle activation of ERK is not necessary for stimulation of HSL by adrenaline. However, contraction-induced HSL activation is mediated by PKC, at least partly via the ERK pathway. In fat cells ERK is known to phosphorylate HSL at Ser600. So, phosphorylation of different sites may explain that in muscle the effects of contractions and adrenaline on HSL activity are partially additive. In line with the view that the two stimuli act by different mechanisms, training increases the contraction-mediated, but diminishes the adrenaline mediated HSL activation in muscle. CONCLUSION: The existence and regulation of HSL in skeletal muscle indicate a role of HSL in muscle TG metabolism.     

Characterization of cell lines derived from hamster tumors induced with the BK virus

Summary Some of the properties of three continuous cell lines derived from BK virus-induced hamster tumors were examined. The cell lines hadin vitro growth characteristics of transformed cells. Morphologically most of the cells were fibroblastic, but multinucleated giant cells were also common. Ultrastructurally all three cell lines displayed the usual features of cells grownin vitro. Marked variation in the nuclear size and shape as well as prominent nucleoli were characteristic to these cells. No viruses or virus-like particles were found. Virus isolation attempts by fusing the cells with Vero cells were negative, and no virion antigen was detected in these cells by immunofluorescence. T antigen similar to that of other papovaviruses was found in the cells. This antigen stained with sera from a number of hamsters carrying transplanted BK virus-induced tumors, and also with SV 40 T antisera. The antigen disappeared after 30 minutes at 56° C. Cytogenetic analyses showed that the three cell lines were heteroploid with subtetraploid numbers of chromosomes. Chromosome abnormalities were also seen. All three cell lines induced sarcomatous tumors in adult hamsters after subcutaneous inoculation.With 4 Figures     

Ultrastructural quantitation of atubular and hypertrophic glomeruli in rats with lithium-induced chronic nephropathy

Summary The very heterogeneous population of glomeruli in rats with lithium-induced chronic nephropathy which includes small glomeruli without connection to a proximal tubule (atubular glomeruli) and large hypertropic glomeruli with connection to a normal proximal tubule, was studied at the ultrastructural level, using stereological methods. After 8 weeks of lithium treatment followed by 8 weeks without lithium the hypertrophic glomeruli showed no changes in their relative ultrastructural composition, including normal mesangium, basement membrane-like material and peripheral basement membrane. The absolute quantities of each component were, however, increased due to the increased volume of the glomeruli. The atubular glomeruli had increased volume fractions of mesangium, peripheral basement membrane, basement membrane-like material and epithelium, whereas the absolute quantities were decreased due to the decreased volume. The thickness of the basement membrane was within normal limits in the group of hypertrophic glomeruli but increased by 31% above controls in the group of atubular glomeruli. Both groups of glomeruli in lithium-treated animals showed normal mean foot process width, but with a slightly abnormal distribution. The atubular glomeruli showed a disproportionate large decrease in peripheral filtration surface and capillary length, compared with the reduction in glomerular volume, whereas the hypertrophic glomeruli showed changes in proportion with the increased volume.     

Neutrophil-mediated antibody-dependent cellular cytotoxicity against erythrocytes. Mechanisms of target cell destruction

Human neutrophils were cytotoxic to IgG coated ox erythrocytes as determined by a 51Cr release assay. Target cell phagocytosis was found to take place during the cytotoxic reaction, suggesting that cytolysis occurs as a post-phagocytic event. Studies, performed with neutrophils from patients with chronic granulomatous disease, demonstrated that these cells had an impaired cytotoxic activity, despite their ability to normally ingest target cells. Thus the cytotoxicity of human neutrophils against sensitized ox erythrocytes depends mainly on oxidative mechanisms. Oxygen radical scavengers failed to prevent the target cell lysis, possibly because of their inability to gain access into the killing sites. However, when cytotoxicity was carried out in presence of latex particles, pre-incubated with oxygen radical scavengers, a significant inhibition of target cell lysis by superoxide dismutase and cytochrome c was obtained. As well, in these experimental conditions, catalase had no effect. Furthermore, cytotoxicity was unaffected by hemeprotein inhibitors, cyanide and azide. Together, these results indicate that superoxide anion plays a key role in the neutrophil-mediated cytotoxicity against ox erythrocytes, whereas hydrogen peroxide alone or in combination with myeloperoxidase is unoperative under the experimental conditions employed.     

Plasma cystine concentration and redox state in aging and physical exercise

Because redox-regulated signalling pathways are often modulated by the thiol/disulfide redox state (REDST), changes in plasma REDST may possibly account for pathological processes. We, therefore, investigated the mechanisms that account for changes in the plasma REDST as derived in first approximation from the cystine and acid soluble thiol (mainly cysteine) concentrations. Elderly subjects (studies A) and younger subjects after intensive physical exercise (IPE) (study B) i.e. subjects in conditions typically associated with decreased insulin responsiveness, showed, on the average, an increase in the plasma total free amino acid (TAA) concentration to approximately 3000 microM, including an increase in cystine but no increase in the thiol concentration if compared with controls. The REDST was decreased accordingly. A study on the postabsorptive amino acid exchange rates across the lower extremities (study C) indicated that a TAA level > or =2800 microM supports a balanced net protein synthesis even under conditions of weak insulin stimulation, suggesting that high TAA levels may prevent the release of cysteine into the blood in the postabsorptive state. Collectively, these studies indicate that the age-related oxidative shift in plasma REDST may result from the decrease in amino acid clearance capacity and may be aggravated by excessive physical exercise.     

Electrodermal Responsivity in Young Hypotensive and Hypertensive Men

Electrodermal responses were recorded during the presentation of 16 moderately intense (1000 Hz, 90dB) tones in three groups of young men: borderline hypertensives (138/79 mmHg), normotensives (112/65 mmHg), and hypotensives (104/63 mmHg). Electrodermal response habituation was measured as a decline in response over trials, number of trials to a response criterion of three successive nonresponses, and number of inversions of response amplitude (larger responses following smaller responses) in the stimulus sequence. Habituation was fastest in hypotensives. Nonspecific electrodermal responses at rest and during tone presentations were most frequent in borderline hypertensives, least frequent in the hypotensive group, with the normotensive group falling in between. There were no significant differences in electrodermal level. The rapid habituation rate in hypotensives is discussed in terms of cursory information processing associated with impulsive behaviour. The higher nonspecific electrodermal activity in borderline hypertensives is interpreted to indicate increased sympathetic nervous system activity.