Involvement of reactive oxygen intermediates in tumor necrosis factor alpha-dependent bacteriostasis of Mycobacterium avium

We studied the involvement of reactive oxygen intermediates and reactive nitrogen intermediates in the bacteriostasis of two Mycobacterium avium strains differing in virulence by resident peritoneal macrophages. We found that both the highly virulent strain (25291) and the low-virulence strain (1983) of M. avium induced superoxide production but inhibited nitrite production in vitro. This inhibition was due to the production of superoxide, a nitric oxide scavenger. The stimulation of superoxide production was two- to fivefold higher in strain 1983-infected than in strain 25291-infected resident peritoneal macrophages and was independent of contaminating T cells or NK cells. Superoxide secretion was dependent on the tumor necrosis factor (TNF) produced endogenously by the macrophages. This was also true when macrophages were isolated from infected mice. Addition of TNF to the infected resident peritoneal macrophages caused only a slight, albeit significant, increase in superoxide production by strain 25291-infected macrophages. Incubation of resident peritoneal macrophages with different scavengers of reactive oxygen intermediates showed that strain 1983 was susceptible to hydrogen peroxide produced by resident peritoneal macrophages. Strain 25291 was shown to decrease superoxide secretion inside heavily infected bone marrow-derived macrophages. This strain was also shown to be a better trigger for production of reactive oxygen intermediates than strain 1983. In summary, strain 1983 induced high levels of TNF synthesis that acted in an autocrine fashion to stimulate production of reactive oxygen intermediates by macrophages leading to growth restriction mediated by hydrogen peroxide. The highly virulent strain 25291 induced low levels of TNF synthesis, and therefore little reactive oxygen intermediate production, and could also inhibit superoxide production by the infected macrophages.

Reversion of phenotype of endothelial cells in brain tissue around glioblastomas

With the aim of studying the putative involvement of peritumoral microvessels in the formation of brain edema, small pieces of peritumoral brain tissue were removed from six patients with glioblastoma multiforme submitted to surgery. All patients had cerebral edema, as shown by preoperative C.T. and N.M.R. Control specimens were obtained from four patients undergoing ventriculo-peritoneal shunt. The tissue fragments were fixed in glutaraldehyde-osmium and embedded in Epon. In semi-thin sections observed under light microscopy peritumoral endothelial cells exhibited voluminous cytoplasm and nucleus. Under the electron microscope, capillary cells from glioblastoma patients differed from controls mainly by showing nuclei rich in euchromatin, cytoplasm rich in pinocytotic vesicles and with occasional fenestrations. All these morphological characteristics are compatible with a process of reversion of phenotype of capillaries around glioblastomas to that of periphery as well as an increase in permeability. Both events may be due to diffusion of a tumoral vascular permeability/endothelial growth factor. This peripheral vessel phenotype of peritumoral microvessels supports their participation in the formation of brain edema and may provide a new clue for therapeutic intervention: for example it fits quite well to the known increase in permeability by leukotrienes and decrease in permeability by corticosteroids in tumoral edema.

Tumour necrosis factor-alpha (TNF-alpha) in the host resistance to mycobacteria of distinct virulence

The relative virulence of different isolates of Mycobacterium avium has been linked to their capacity to trigger the secretion of TNF from the macrophages they infect. Smooth opaque (SmOp) variants of Myco. avium have been shown to trigger higher expression of TNF-alpha by macrophages in vitro than the smooth transparent (SmTr) variants. To analyse the role of TNF in resistance to infection by Myco. avium, we studied the infection by two different morphotypes of strain 2.151 of Myco. avium both in vitro and in vivo in the presence or absence of neutralizing antibodies to TNF. No effects were found in vitro regarding the growth of either isolate of Myco. avium. In vivo, only the virulent SmTr morphotype showed enhanced growth in the presence of the neutralizing antibodies. This enhancement occurred relatively late when priming for TNF secretion in vivo was evident. Among four isolates of Myco. avium, three virulent ones induced a marked priming for TNF release and one avirulent strain did not. Mycobacterium tuberculosis H37Ra, which is very active in inducing TNF release due to its lipoarabinomannan moiety, was used to compare with the previous results. The growth of H37Ra in macrophages was increased in vitro by the neutralization of TNF and neutralization of either TNF and/or interferon-gamma (IFN-gamma) enhanced the in vivo proliferation of this microbe in the spleen and liver of infected animals, whereas only the combination of both anti-TNF and anti-IFN-gamma enhanced bacterial proliferation in the lung. We conclude that resistance to the avirulent strains of Myco. avium did not involve TNF, but rather antimicrobial mechanisms expressed constitutively in the mononuclear phagocytes. In contrast, TNF plays an important role in the control of Myco. tuberculosis H37Ra infection.

Distribution patterns of the muscular branch of the median nerve in the thenar region

Studies on the distribution patterns of the muscular branch of the median nerve to the thenar muscles are scarce. Available accounts give only general descriptions. To establish the distribution pattern more precisely, we dissected 60 palmar regions from 30 cadavers of adult individuals, ranging in age from 23 to 77 y. The distribution pattern of the muscular branch was classified into 3 types. In 50% of subjects there were branches to the superficial head of flexor pollicis brevis (FPB), abductor pollicis brevis (APB) and opponens pollicis (OP) (type I). In 40% there were branches only to APB and OP (type II). In the remainder (type III) the muscular branch provided independent branches to APB, OP and FPB, to APB and OP, or to APB and FPB, after dividing precociously. Types I and II were further subdivided according to the site, direction and number of the individual branches.

Influence of electrical stimulation of locus coeruleus on the rat blood-brain barrier permeability to sodium fluorescein

The role of central adrenergic innervation of the brain capillaries is still a matter of discussion. The hypothesis that these nerves control the blood-brain barrier permeability was tested by electrically stimulating the locus coeruleus, the major central adrenergic nucleus, in the anaesthetized rat. Frequencies of 5, 15, and 30 Hz were used. A frequency dependent increase in blood-brain barrier permeability to sodium fluorescein was verified. Prior administration of the alpha-adrenoceptor antagonist phenoxybenzamine (10 mg/kg i.p., 24 h before electrical stimulation) totally blocked the effect of 15 Hz stimulation. The same dose of pindolol (a beta-adrenoceptor antagonist) given 1 h before electrical stimulation potentiated the effect of 5 Hz stimulation. Thus, blood-brain barrier permeability is increased, in a frequency dependent manner, by electrical stimulation of the locus coeruleus. The results obtained with phenoxybenzamine and pindolol suggest an opposite effect of alpha and beta-adrenoceptors on the control of sodium fluorescein transport through the blood-brain barrier.

Adrenergic influences on the control of blood-brain barrier permeability

The central adrenergic innervation of the cerebral microvessels may play a role in the control of blood-brain barrier permeability. To pursue the study of this hypothesis we investigated the effect of noradrenaline on both the permeability of the blood-brain barrier to sodium fluorescein and on the pinocytotic activity of cerebral endothelial cells in the rat. Noradrenaline, stereotactically injected in the right lateral cerebral ventricle, significantly increased the cerebral extraction ratio of sodium fluorescein in a dose-dependent way. The same effect was induced by phenylephrine. Prostaglandin F2 alpha had no significant effect on the passage of sodium fluorescein through the blood-brain barrier. The effect of noradrenaline (150 micrograms) on the cerebral extraction ratio of sodium fluorescein was totally blocked by phenoxybenzamine (25 mg/kg i.p., 24 h before noradrenaline). Noradrenaline (150 micrograms) significantly increased the pinocytotic activity of cerebral endothelial cells. Phenoxybenzamine (as above) reduced the effect of noradrenaline on pinocytosis. It is concluded that noradrenaline increases the blood-brain barrier's permeability to sodium fluorescein, most probably through an effect on alpha adrenoceptors. The increase induced in the blood-brain barrier's permeability by noradrenaline seems to be due, at least in part, to an increase in the pinocytotic activity of endothelial cells.

Effects of sympathetic denervation on liver fibroblasts: prevention by adenosine

1. The effect of chemical denervation with 6-hydroxydopamine (6-OHDA) upon portal tract fibroblasts of dogs and rabbits was studied. 2. Denervation led to a significant increase in the density of portal tract fibroblasts both in the dog and in the rabbit. 3. Mast cells, present in the dog but not in the rabbit liver, were also significantly increased by denervation. 4. Noradrenaline depletion induced by reserpine did not increase the density of fibroblasts in the liver portal spaces of the dog. Mast cell density, however, was actually decreased when compared with control. 5. Continuous i.v. infusions of adenosine (10 micrograms kg-1h-1) to dogs totally prevented the effects of 6-OHDA-induced denervation upon fibroblast and mast cell densities in the portal space connective tissue. 6. It is concluded that the sympathetic nervous system is exerting a repressive effect on liver fibroblasts, as was found to occur in various other mammalian tissues. Mast cells, which are known to be activated in various pathological processes of fibrosis, appear to share with fibroblasts a modulating effect from the sympathetic nervous system. 7. The results strongly support the hypothesis of adenosine being the sympathetic trophic factor involved in the control of fibroblasts in the connective tissue of dog liver. A similar role for adenosine had previously been found in the dog saphenous vein.

Amitriptyline-induced morphological alterations of the rat blood-brain barrier

Amitriptyline is known to increase the permeability of the blood-brain barrier but the morphological basis of this increase has not been studied. As catecholamines can influence pinocytosis in dog peripheral blood vessels, the effect of amitriptyline on the pinocytotic activity of blood brain microvessels was studied. Amitriptyline, 34 mg.kg-1 i.p., was injected to rats and the parietal cortex of control and treated animals was prepared for ultrastructural study. Pinocytotic vesicles in endothelial cells were quantified. Amitriptyline significantly increased the density of pinocytotic vesicles in capillary endothelial cells. No other morphological changes occurred after amitriptyline treatment. We conclude that the increase in blood-brain barrier permeability due to amitriptyline may be ascribed at least in part to an increase of pinocytotic activity in brain capillary endothelial cells.

Effects of denervation induced by 6-hydroxydopamine on cell nucleus activity of arterial and cardiac cells of the dog

1 Denervation was induced in dogs by 6-hydroxydopamine (6-OHDA) treatment. The effects of this on cell nucleus activity of smooth muscle cells and fibroblasts of the mesenteric artery (main trunk and jejunal branches) and of myocardial cells, fibroblasts and endothelial capillary cells of the heart were studied. 2 Changes in the nucleii or cell size measured with light microscopy morphometric techniques and frequency of nucleoli in myocardial cells were chosen as indices of cell nucleus activity state. 3 Noradrenaline depletion 5 days after initiation of 6-OHDA administration was much more marked in the heart (with a content of 10% of control values) than in the arterial vessels (with a content of 50% of control values). 4 Denervation by 6-OHDA led to an increase in the synthetic activity state of the cell nucleus in all cell types and tissues. 5 Plasma noradrenaline and adrenaline levels were strikingly increased by 6-OHDA treatment. 6 The results strongly support the hypothesis of a nuclear modulating effect of the sympathetic innervation upon the effector cells. The incapacity of high noradrenaline plasma levels to prevent the consequences of sympathetic denervation on the effector cells appears to indicate that in the sympathetic innervation there is a 'trophic factor' which is not identical with noradrenaline.