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Biomedical subjects

M Victor

Publications and source records attributed to M Victor.

At least 37 records · Page 2Linked to original sources
PubMed1983

Role of charge and hydrophobic interactions in the action of the bactericidal/permeability-increasing protein of neutrophils on gram-negative bacteria.

We have recently provided evidence suggesting that the action of purified cationic bactericidal/permeability-increasing protein (BPI) from neutrophils on susceptible gram-negative bacteria requires saturation binding to negatively charged surface sites (Weiss, J., S. Beckerdite-Quagliata, and P. Elsbach, 1980, J. Clin. Invest., 65: 619-628.)We now show that this charge interaction is necessary but not sufficient to produce the effects of BPI on the envelope and on viability. By altering the hydrophobic properties of the bacterial (outer) membrane, it is possible to separate saturation binding from the biological action of BPI, indicating that steps beyond surface binding are needed for the antibacterial action. Outer membrane properties were modified by (a) reducing temperature during BPI-Escherichia coli interaction; (b) growing E. coli at 42 degrees C to increase the saturated fatty acid content of membrane phospholipids; and/or (c) using smooth E. coli with a natively less fluid outer membrane. Hydrophobic interaction chromatography on phenyl-Sepharose and measurement of sensitivity to the hydrophobic antibiotic rifampicin were used to monitor the changes in hydrophobic properties of the bacterial outer membrane produced by these manipulations. Nearly all BPI can be removed from the bacterial surface by 80 mM MgCl(2) or by trypsin. At 37 degrees C, removal of BPI results in repair of the envelope alterations, but viability is irreversibly lost, even when Mg(2+) is added after only 15 s of exposure of the bacteria to BPI. However, under conditions of reduced outer membrane hydrophobicity, when saturation binding still occurs within 30 s, E. coli can be rescued by addition of Mg(2+) after up to 5-min exposure to BPI, indicating retardation of postbinding steps. We conclude that after initial binding BPI must enter into a hydrophobic interaction with the outer membrane in order to produce its antibacterial effects. These postbinding events reversibly mediate the membrane perturbations and irreversibly trigger the bactericidal action of BPI.

Animals↗
PubMed1983

Non-infantile neuronopathic Gaucher's disease: a clinicopathologic study.

Two siblings with Gaucher's disease developed a chronic, slowly progressive neurologic disorder in early adult life. Stimulus-sensitive myoclonus, generalized seizures, supranuclear gaze palsies, and cerebellar ataxia were the main clinical features. Autopsy disclosed perivascular Gaucher cells in the brain, and nerve cell loss and neuronophagia in the brainstem, cerebellum, and spinal cord. From these observations and the literature, there seem to be three clinically distinct neurologic syndromes in Gaucher's disease, depending on the age at which symptoms begin, but the neuropathologic changes are essentially the same in all of them. A modified classification of Gaucher's disease, based on these observations, is proposed.

Adult↗
PubMed1982

Sensitivity of K1-encapsulated Escherichia coli to killing by the bactericidal/permeability-increasing protein of rabbit and human neutrophils.

The presence of K1 capsular polysaccharides increases the resistance of Escherichia coli to killing by serum and phagocytosis by polymorphonuclear leukocytes (PMNs). To determine whether K1 capsule impedes the action of intracellular bactericidal systems of PMNs, we compared the sensitivity of several K1-encapsulated and non-encapsulated strains of E. coli to killing by the bactericidal/permeability-increasing protein (BPI) isolated from rabbit and human PMNs. BPI appears to be the principal bactericidal agent of PMNs toward E. coli and other gram-negative bacteria (Weiss et al., J. Clin. Invest. 69:959-970, 1982). The presence of K1 capsule was monitored by sensitivity to K1-specific bacteriophages. The non-encapsulated strains used represent both random bacteremic isolates and non-encapsulated derivatives of K1-encapsulated strains obtained by selection for resistance to K1-specific phages. We found little or no difference in the sensitivity of K1-encapsulated and non-encapsulated E. coli to killing by neutralized acid extracts of rabbit PMNs. Bacterial killing by these crude fractions can be attributed to the action of BPI because: (i) bacterial killing was blocked by immune (anti-BPI) immunoglobulin but not by preimmune immunoglobulin and (ii) comparison of the dose-response curves of bacterial killing by crude extracts and by purified BPI showed that the bactericidal activity of crude fractions corresponded closely to the BPI content. Human and rabbit BPIs exhibited similar bactericidal potency toward K1-encapsulated E. coli; i.e., <5 mug of either protein killed >90% of 2.5 x 10(7) bacteria. Thus, the potent bactericidal action of BPI toward E. coli is not impeded by K1 capsule, suggesting that the virulence of K1-encapsulated E. coli is a consequence of extracellular survival but not of resistance to intracellular killing.

Animals↗
PubMed1982

Killing of gram-negative bacteria by polymorphonuclear leukocytes: role of an O2-independent bactericidal system.

Previous studies have suggested that a cationic bactericidal/permeability-increasing protein (BPI) present in both rabbit and human polymorphonuclear leukocytes is the principal O2-independent bactericidal agent of these cells toward several strains of Escherichia coli and Salmonella typhimurium (1978. J. Biol. Chem. 253: 2664--2672; 1979. J. Biol. Chem. 254: 11000--11009). To further evaluate the possible role of this protein in the killing of gram-negative bacteria by polymorphonuclear leukocytes, we have measured the bactericidal activity of intact rabbit peritoneal exudate leukocytes under aerobic or anaerobic conditions and of intact human leukocytes from a patient with chronic granulomatous disease. Anaerobic conditions were created by flushing the cells under a nitrogen stream. Effective removal of oxygen was demonstrated by the inability of nitrogen-flushed leukocytes to mount a respiratory burst (measured as increased conversion of 1-[14C]glucose leads to 14CO2 or by superoxide production) during bacterial ingestion. At a bacteria/leukocyte ratio of 10:1, killing of gram-positive, BPI-resistant, Staphylococcus epidermidis is markedly impaired in the absence of oxygen (76.4 +/- 3.3% killing in room air, 29.2 +/- 8.2% killing in nitrogen). Essentially all increased bacterial survival is intracellular. In contrast, both a nonopsonized rough strain (MR-10) and an opsonized smooth strain (MS) of S. typhimurium 395 are killed equally well in room air and nitrogen. A maximum of 70--80 MR-10 and 30--40 MS are killed per leukocyte either in the presence or absence of oxygen. There is no intracellular bacterial survival in either condition indicating that intracellular O2-independent bactericidal system(s) of rabbit polymorphonuclear leukocytes can at least match the leukocyte's ingestive capacity. Whole homogenates and crude acid extracts manifest similar bactericidal capacity toward S. typhimurium 395. This activity can be accounted for by the BPI content of these cell fractions and is virtually eliminated by immune (anti-BPI), but not by preimmune goat IgG-rich fractions. Opsonization of smooth MS, required for bacterial killing by intact leukocytes, does not alter bacterial sensitivity to BPI in crude or purified form. Leukocytes of a patient with chronic granulomatous disease killed ingested S. typhimurium 396 MS nearly as well as did normal leukocytes. The bactericidal activity toward E. coli (J5) of crude acid extracts of the CGD and normal human leukocytes was virtually the same and was nearly completely inhibited by anti-BPI IgG-rich fractions, but not by preimmune IgG-rich fractions. These findings suggest that the killing of gram-negative bacteria such as S. typhimurium by intact polymorphonuclear leukocytes may also be attributed to the action of BPI.

Aerobiosis↗
PubMed1981

Heparin inhibits phagocytosis by polymorphonuclear leukocytes.

Phagocytosis of unopsonized Salmonella typhimurium 395, MR-10, opsonized Salmonella typhimurium 395 MS, and Staphylococcus epidermidis by rabbit polymorphonuclear leukocytes was inhibited by heparin at concentrations as low as 0.5 U/ml. Inhibition was dose dependent and nearly complete at 20 U/ml. Provided that heparin concentrations did not exceed 100 U/ml, inhibition could be largely reversed by washing. Heparin also reversibly inhibited the adherence of polymorphonuclear leukocytes to glass. In contrast, hexose monophosphate shunt activity of polymorphonuclear leukocytes stimulated by noningested S. typhimurium MR-10 or Streptococcus pyogenes B14 was not inhibited by heparin at concentrations as high as 100 U/ml.

Animals↗
PubMed1980

Optic atrophy in experimental vitamin B12 deficiency in monkeys.

The clinical findings and pathological changes of the visual pathway of vitamin B12 deficient monkeys have been described. The cellular morphology and counts of the peripheral blood and bone marrow remained normal during the study (nine deficient, three controls: one still alive in each group). Visual impairment was noted in all seven of the deficient animals that were evaluated by clinical observations. Ophthalmoscopic examination disclosed optic atrophy in six of the seven deficient monkeys. Degeneration of the visual pathway was demonstrated by pathological examination in eight of the deficient group of nine (one is still alive). Loss of ganglion cells was noted in the maculae of two of three deficient animals with completed studies. In the three control animals there were neither visual disturbances nor ophthalmoscopic changes and in two animals autopsies disclosed no lesions in the visual pathways. The third animal is still alive and well.

Animals↗
PubMed1979

Pontine and extrapontine myelinolysis.

No coherent theory has been advanced to explain either the particular localization of the myelinolytic lesions of central pontine myelinolysis or their pathogenesis. However, several lines of evidence support the generalization that the centre of the basis pontis has a special susceptibility to a metabolic fault. The constancy of localization of the lesion and its bilateral symmetry are the very attributes that characterize other metabolic (nutritional) disorders, such as the assymmetrical degeneragion of the papillomacular bundles within the optic nerves and tracts in deficiency amblyopia and the specific affection of the paraventricular regions in the Wernicke-Korsakoff syndrome. And clinically, the frequent occurrence of central pontine myelinolysis in a setting of severe metabolic derangement, particularly of the serum sodium, points in the same direction.

Adult↗
PubMed1978

An ultrastructural study of subacute combined degeneration of the spinal cord in vitamin B12-deficient rhesus monkeys.

Prolonged deprivation of vitamin B12 in rhesus monkeys produced changes in the central nervous system that were indistinguishable topographically and histologically from those of human subacute combined degeneration. Ultrastructural studies of early lesions of the spinal cord disclosed a degeneration of myelin characterized by separation of myelin lamellae and formation of intramyelinic vacuoles, leading eventually to complete destruction of myelin sheaths. At a later stage, there was degeneration and loss of axons, and marked gliosis. The theories of pathogenesis of subacute combined degeneration are reviewed in the light of these observations.

Animals↗
PubMed1978

Hypertensive encephalopathy: a clinicopathologic study of 20 cases.

The clinical and pathologic findings in 20 patients with hypertensive encephalopathy were reviewed. The dominant central nervous system (CNS) symptoms were altered state of consciousness and severe headache. Nausea, vomiting, and visual disturbances were less common. Seizures and focal signs were infrequent. The changes seen were invariably accompanied both by the characteristic ophthalmoscopic alterations of malignant hypertension and by uremia. The neuropathologic changes consisted of severe vascular alterations (fibrinoid necrosis of arterioles, thrombosis of arterioles and capillaries), and of parenchymal lesions (microinfarcts, petechial hemorrhages) secondary to the vascular lesions. The vascular changes were not confined to the brain but were diffuse, affecting the eyes, kidneys, and other organs. In the CNS the brainstem was most severely affected. Cerebral edema was not observed, even in those patients who had increased cerebrospinal fluid pressure and papilledema.

Adult↗
PubMed1976

Neuropathology of experimental vitamin B12 deficiency in monkeys.

We have produced severe vitamin B12 deficiency in rhesus monkeys by feeding them a defined experimental diet under controlled conditions. Five years after institution of the deficient diet, the morphology and counts of peripheral blood and bone marrow are normal. Gross visual impairment appeared in five of the monkeys between 33 and 45 months after the institution of the vitamin B12 deficient diet. Subsequently, in three of the visually impaired animals, a gradually progressive spastic paralysis of their hind limbs developed. Autopsies of six deficient animals showed degeneration of the peripheral visual pathway in all and of white matter in the spinal cord in four. Degeneration of several cranial nerve roots was found in four monkeys and a mild diffuse degeneration of cerebral white matter in four. The lesions in all affected parts of the central nervous system were bilaterally symmetrical and were indistinguishable from those due to B12 deficiency in the human. No abnormalities were found in one B12 supplemented control animal.

Animals↗