Ultrastructural changes in the cerebrovascular endothelium induced by a diet high in linoleic acid and deficient in vitamin E

A Review of Plasmodium coatneyi-Macaque Models of Severe Malaria

Malaria remains one of the most significant public health concerns in the world today. Approximately half the human population is at risk for infection, with children and pregnant women being most vulnerable. More than 90% of the total human malaria burden, which numbers in excess of 200 million annually, is due to Plasmodium falciparum. Lack of an effective vaccine and a dwindling stockpile of antimalarial drugs due to increased plasmodial resistance underscore the critical need for valid animal models. Plasmodium coatneyi was described in Southeast Asia 50 years ago. This plasmodium of nonhuman primates has been used sporadically as a model for severe malaria, as it mimics many of the pathophysiologic features of human disease. This review covers the reported macroscopic, microscopic, ultrastructural, and molecular pathology of P. coatneyi infection in macaques, specifically focusing on the rhesus macaque, as well as describing the critical needs still outstanding in the validation of this crucial model of human disease.

Protective effect of vitamin E on intraventricular haemorrhage in the newborn

Forty-four consecutively born babies of birth weights under 1751 g were randomly selected to receive a daily intramuscular injection of vitamin E (all-rac-alpha-tocopheryl acetate) from the day of birth (Day 0) until Day 3, or were allocated to a non-supplemented control group. Frequent ultrasound examinations of the brain were made during the first week of life and babies were classified as having 'no haemorrhage', 'subependymal haemorrhage (SEH) only' or 'intraventricular haemorrhage' (IVH). The incidence of SEH or IVH was similar in supplemented (42.9%) and control babies (43.5%). SEH or IVH was observed only in babies of less than 32 weeks gestation; when only babies under 32 weeks were considered, IVH was less common in those supplemented (18.8%) than in the controls (56.3%). Babies with IVH had lower median plasma vitamin E concentrations when compared with babies without any haemorrhage and compared with those with only SEH. Three supplemented babies suffered IVH and they were the three with the lowest plasma vitamin E concentrations among the babies supplemented with vitamin E from Day 0 to Day 3. We speculate that vitamin E protects endothelial cell membranes of capillaries in the subependymal layer of the brain against oxidative damage and disruption and thereby limits the magnitude of haemorrhage in the subependymal layer, and reduces the risk of extension into the ventricles.

Retinal vascular changes induced by the oxidative stress of alpha-tocopherol deficiency contrasted with diabetic microangiopathy

It has been proposed that oxidative tissue damage is involved in the development of diabetic angiopathies. To evaluate this hypothesis, experiments were conducted to identify the retinal vessel changes induced by the oxidative stress related to alpha-tocopherol deficiency and examine possible similarities with the lesions characteristic of diabetic retinopathy. Twenty-one-day-old male Fisher 344 albino rats were divided randomly to receive a basal, chemically defined diet either with (adequate group) or without (deficient group) alpha-tocopherol. After 6 and 8 months, some rats (n = 3 per group) were killed and the eyes removed. In order to evaluate cell integrity and localization of lipofuscin-specific autofluorescence by light and fluorescence microscopy, some of the retinas were prepared for cryostat-sections while others were digested by elastase to isolate intact retinal vasculatures. After 8 and 14 months, the central retina of one eye per rat (n = 6 to 8 per group) was examined by electron microscopy for retinal capillary basement membrane (RCBM) thickening and other ultrastructural changes. At 6 and 8 months, the deficient rats exhibited extensive shortening and disarray of rod outer segments (ROS), marked loss of photoreceptor cells, and pronounced increases in the numbers of granules with lipofuscin-specific autofluorescence in the retinal pigment epithelium (RPE) and retinal vessels. At 14 months, the ultrastructure revealed that the damage to ROS involved disruption of membranes and that the capillary lipofuscin was contained mainly within the endothelial cells. Membrane remnants were found in the lipofuscin granules of both the RPE and retinal vessels. In addition, there was an increase in RCBM thickness (98.7 +/- 2.6 nm vs. 86.9 +/- 2.9 nm). RCBM thickening was the only finding common with diabetic retinopathy, and the thickening was 13.6%, significantly less than that reported in diabetic rat models with 8 and 14 months durations (34% and 53.1%, respectively). Capillary lipofuscin accumulation, which was prominent in the deficient rats, is not notable in diabetes. Both the moderate RCBM thickening and marked lipofuscin accumulations seen in alpha-tocopherol-deficient rats were similar to changes occurring in the aging process, though more pronounced. The spectrum of microangiopathies characteristic of diabetic retinopathy did not develop in alpha-tocopherol-deficient rats. These findings suggest that oxidative damage, though probably involved, is unlikely to play a predominant role in the development of diabetic retinal microangiopathies.

The prime role of plasma membrane cholesterol in the pathogenesis of immune evasion and clinical manifestations of falciparum malaria

The pathogenesis of falciparum malaria, with its immune evasion, mechanism of immune suppression and immunological inertia, the cause of its preferential incidence in children and pregnant mothers, and the pathological basis of clinical manifestations, are discussed from biochemical, biophysical and immunological perspectives. Sequestration and recrudescence are highlighted as the evolved means by which malaria parasites survive. These discussions are based on a novel hypothesis that changes in the lipid matrix fluidity of plasma membrane, through alterations of cholesterol and phospholipid content and variation in body temperature, significantly affect the membrane functions of cells. The pathogenesis of aggressive behavior in cerebral malaria is postulated to be different from that of coma, and complicated pregnancy in malaria is also discussed as a multifactorial condition wherein hypocholesterolemia, resulting from increased membrane biogenesis of multiplying parasites, is the common underlying factor.

Etiologic factors and pathologic alterations in selenium-vitamin E deficiency and excess in animals and humans

The etiology of selenium-vitamin E (Se-E) deficiency diseases may be complex. Many of the syndromes involve combined deficiency of selenium and vitamin E. Selenium moves into the animal and human food chain from soil and plants, which may contain inadequate amounts of the nutrient in many areas of the world. Vitamin E may be in low concentration in many animal feeds unless supplements are added. Some syndromes, such as steatitis in cats, result from an increased requirement of vitamin E in diets that contain large amounts of polyunsaturated fatty acids, and these diseases will only respond to vitamin E administration. Deficiency syndromes in animals owing to pure Se deficiency are infrequent and have been produced mainly by laboratory studies utilizing extreme deficiency conditions. Other factors that may affect the occurrence of these deficiency diseases are concurrent dietary deficiency of S-containing amino acids, bioavailability of different forms of dietary Se, intake of compounds that antagonize Se (e.g., silver salts), and exposure to various prooxidant substances (e.g., iron compounds, oxygen, ozone, and various drugs).

Cell-mediated immunity in protection and pathology of malaria

The stimulation of protective immunity against malaria is the goal of many research groups. But trials with antigens that stimulate antibodies have yet to fulfil these expectations, and it is increasingly recognized that non-antibody-mediated immunity is also important in immunity to malaria - especially through mediators such as gamma interferon, tumour necrosis factor and reactive forms of oxygen. However, the host can suffer if this type of immune response is too exuberant, and in this review, Ian Clark argues that much of what is recognized as clinical malaria is caused in this way. He suggests that only when discussed in these terms can malaria illness and pathology be seen as a coherent, predictable entity instead of a sea of unconnected surprises. Moreover, these ideas have important implications for vaccine development that, although requiring more basic work, must not be neglected.

Pathophysiology of severe falciparum malaria in man

The term severe falciparum malaria implies an infection with manifestations and complications which are potentially fatal in man, the natural host for this parasite. Much that has been written on the pathophysiology of animal malarias is of doubtful relevance to the understanding of the mechanism ofPlasmodium falciparuminfection in man. The clinical picture of severeP. falciparuminfection differs in several respects from severe animal malarias, even those of non-human primates. Cerebral dysfunction is the most common severe manifestation of falciparum malaria in man. Coma develops suddenly after a generalized convulsion or gradually towards the end of the first week of illness. There are signs of a symmetrical upper motor neurone lesion and brain-stem dysfunction, but only about 5% of survivors show persisting neurological deficit after 2 or 3 days of unconsciousness. The mortality of cerebral malaria depends on how it is defined and on the predominant age group and other factors. In patients with proved acuteP. falciparuminfection with unrousable coma, in whom other causes of encephalopathy have been excluded, the mortality is between 15 and 50% despite treatment with antimalarial drugs (Warrell, Looareesuwan, Warrell, Kasemsarn, Intaraprasert, Bunnag & Harinasuta, 1982).

Vitamin E concentrations in the brains and some selected peripheral tissues of selenium-deficient and vitamin E-deficient mice

Weanling male CD-l mice were fed control, vitamin E-deficient or selenium-deficient diets for periods of 12 to 20 weeks. alpha-Tocopherol concentrations in plasma, liver, and testes, as well as in three specific areas in the brain (cerebral hemisphere, cerebellum, and medulla plus pons) were determined by high performance liquid chromatography. Significant concentrations of alpha-tocopherol were found in all brain samples from vitamin E-deficient animals long after the peripheral tissues were depleted, indicating that brain is more resistant to vitamin E deficiency than peripheral tissues. Cerebellar concentrations of alpha-tocopherol were consistently lower than those of cerebral hemisphere and medulla-pons. Furthermore, the cerebellar alpha-tocopherol concentration sustained a larger decline than the other two brain areas within 6 weeks of vitamin E deficiency treatment. These and other data suggest that cerebellum may be more susceptible to damage from vitamin E deficiency than other parts of the brain. Selenium deficiency did not affect brain alpha-tocopherol concentrations during the 12 weeks of the study.

Protective effect of vitamin E (DL-alpha-tocopherol) against intraventricular haemorrhage in premature babies

Forty four babies, of less than 32 weeks' gestation, were either randomly given 25 mg/kg vitamin E (DL-alpha-tocopherol acetate) intramuscularly after birth (day 0) and on days 1, 2, and 3 or served as controls. Frequent real time ultrasound examinations of the brain were made in each baby during the first week and less frequently thereafter. In babies under 32 weeks' gestation the incidence of intraventricular haemorrhage was lower in supplemented babies (18.8%) compared with the controls (56.3%). On days 0, 1, 2, and 3 median plasma vitamin E concentrations in babies without haemorrhage and in those with subependymal haemorrhage only were similar. Babies with intraventricular haemorrhage had lower median concentrations on day 1 (p less than 0.002) and day 2 (p less than 0.05) compared with those with subependymal haemorrhage and lower concentrations on day 0 (p less than 0.02) and day 1 (p less than 0.05) compared with those without haemorrhage. These findings suggest that in premature babies vitamin E, an antioxidant, protects endothelial cell membranes from oxidative damage and disruption and limits the magnitude of haemorrhage and its spread from the subependyma into the ventricles.

Toxicity of free fatty acids for cultured rat heart muscle and endothelioid cells. II. Unsaturated long-chain fatty acids

Oleic (C18:1), linoleic (C18:2), linolenic (C18:3) and arachidonic (C20:4) acids were compared for their toxic effects upon cultured rat heart muscle and endothelioid cells. The free fatty acids (FFA) were bound to albumin (6:1) and tested at concentrations from 5 x 10(-5)M to 5 x 10(-4)M. Reduction of cell viability (51Cr release) and in situ mitochondrial and lysosomal labilization were used as indices of injury. Oleic acids was non-toxic at all times and concentrations tested while linoleic acid increased cell death only in muscle cells after 32 h. Arachidonic acid, by contrast, demonstrated significant toxicity as early as 2 h while both linolenic and arachidonic acids produced major injury at longer durations. A detergent effect was excluded as the injury mechanism because of marked differences in the toxicities of the individual FFA. The similarity in the effects of linolenic and arachidonic acids would appear to exclude prostaglandins as responsible toxic products.