Evaluation of hepatic changes and local and systemic immune responses in goats immunized with recombinant Peroxiredoxin (Prx) and challenged with Fasciola hepatica

Protection against Fasciola hepatica in goats immunized with Peroxiredoxin (Prx) was assessed. The experimental trial consisted of three groups of seven animals: group 1 were unimmunized and uninfected, group 2 were immunized with adjuvant only and group 3 were immunized with recombinant Prx in adjuvant (immunized and infected). Immunization with Prx in Quil A adjuvant, group 3, induced a reduction in fluke burden of 33.04% when compared to adjuvant control, group 2, although this difference was not significant. The hepatic gross and microscopical morphometric study revealed lower damage in the Prx-immunized compared to group 2 (p

An investigation of clustered radiation-induced lesions in DNA

Recent track structure modelling studies indicate that radiation induced damage to DNA consists of a spectrum of different lesions of varying complexity. There is considerable evidence to suggest that, in repair-proficient systems, it is only the small proportion of more complex forms that is responsible for most of the biological effect. The complex lesions induced consist initially of clustered radical sites and a knowledge of their special chemistry is important in modelling how they react to form the more stable products that are processed by the repair systems. However, much of the current understanding of the chemical stage of radiation has developed from single-radical systems and there is a need to translate this to the more complex reactions that are likely to occur at the important multiple radical sites. With low LET radiation, DNA dsb may derive either from single-radical attack that damages both strands by a transfer mechanism, or from pairs of radical sites induced in close proximity, with one or more radical on each strand. With high LET radiation, modelling studies indicate that there is an increased probability of dsb arising from sites with more than two radical centres, leading to a greater frequency of more complex types of break. The spectrum of these lesions depends on the overall outcome of consecutive physical and chemical processes. The initial pattern of radical damage is determined by the energy depositions on and around the DNA, according to the type of radiation. This pattern is then modified by scavengers that inhibit the formation of radicals on the DNA, and by agents that either chemically repair (e.g. thiols) or fix (e.g. oxygen) a large fraction of these radicals. The reaction kinetics associated with clustered radical sites will differ from those of single sites: (1) because of the opportunities for interactions between the radicals themselves; and (2) because certain endpoints, e.g. a dsb, may require a combination of the products of two or more radicals. Fast response techniques using pulsed low and high LET irradiation have been established to measure the reactions of radical sites on pBR322 plasmid DNA with oxygen and thiols with a view to obtaining information about cluster size. This paper describes experimental approaches to explore the role of the chemical stage of the radiation effect in relation to lesion complexity.

Vitamin B-6 deficiency in rats reduces hepatic serine hydroxymethyltransferase and cystathionine beta-synthase activities and rates of in vivo protein turnover, homocysteine remethylation and transsulfuration

Vitamin B-6 deficiency causes mild elevation in plasma homocysteine, but the mechanism has not been clearly established. Serine is a substrate in one-carbon metabolism and in the transsulfuration pathway of homocysteine catabolism, and pyridoxal phosphate (PLP) plays a key role as coenzyme for serine hydroxymethyltransferase (SHMT) and enzymes of transsulfuration. In this study we used [H-2(3)]serine as a primary tracer to examine the remethylation pathway in adequately nourished and vitamin B-6-deficient rats pi and 0.1 mg pyridoxine (PN)/kg diet]. [H-2(3)]Leucine and [1-C-13]methionine were also used to examine turnover of protein and methionine pools, respectively, All tracers were injected intraperitoneally as a bolus dose, and then rats were killed (n = 4/time point) after 30, 60 and 120 min. Rats fed the low-PN diet had significantly lower growth and plasma and liver PLP concentrations, reduced liver SHMT activity, greater plasma and liver total homocysteine concentration, and reduced liver S-adenosylmethionine concentration. Hepatic and whole body protein turnover were reduced in vitamin B-6-deficient rats as evidenced by greater isotopic enrichment of [H-2(3)]leucine. Hepatic [H-2(2)]methionine production from [H-2(3)]serine via cytosolic SHMT and the remethylation pathway was reduced by 80.6% in vitamin B-6 deficiency. The deficiency did not significantly reduce hepatic cystathionine-beta-synthase activity, and in vivo hepatic transsulfuration flux shown by production of [H-2(3)]cysteine from the [H-2(3)]serine increased over twofold. In contrast, plasma appearance of [H-2(3)]cysteine was decreased by 89% in vitamin B-6 deficiency. The rate of hepatic homocysteine production shown by the ratio of [1-C-13]homocysteine/[1-C-13]methionine areas under enrichment vs. time curves was not affected by vitamin B-6 deficiency. Overall, these results indicate that vitamin B-6 deficiency substantially affects one-carbon metabolism by impairing both methyl group production for homocysteine remethylation and flux through whole-body transsulfuration.

Microvascular lesions of diabetic retinopathy: clues towards understanding pathogenesis?

Retinopathy is a major complication of diabetes mellitus and this condition remains a leading cause of blindness in the working population of developed countries. As diabetic retinopathy progresses a range of neuroglial and microvascular abnormalities develop although it remains unclear how these pathologies relate to each other and their net contribution to retinal damage. From a haemodynamic perspective, evidence suggests that there is an early reduction in retinal perfusion before the onset of diabetic retinopathy followed by a gradual increase in blood flow as the complication progresses. The functional reduction in retinal blood flow observed during early diabetic retinopathy may be additive or synergistic to pro-inflammatory changes, leucostasis and vaso-occlusion and thus be intimately linked to the progressive ischaemic hypoxia and increased blood flow associated with later stages of the disease. In the current review a unifying framework is presented that explains how arteriolar dysfunction and haemodynamic changes may contribute to late stage microvascular pathology and vision loss in human diabetic retinopathy.

A proposed mechanism for chlorpromazine jaundice--defective hepatic sulphoxidation combined with rapid hydroxylation

On the basis of previous experimental studies we postulated that individuals who were phenotypically good hydroxylators but poor sulphoxidisers would be susceptible to chlorpromazine jaundice. Sulphoxidation capacity was assessed in 12 subjects with a history of chlorpromazine jaundice, using S-carboxymethyl-L-cysteine as an in vivo probe. Following an oral dose of 750 mg, unchanged compound and sulphoxide metabolites were measured in urine. All 12 subjects (100%) were shown to be poor sulphoxidisers compared to 22% of normal controls (P less than 0.001) and 23.8% of liver disease controls (P less than 0.001). No subjects with a history of chlorpromazine jaundice had an impaired hydroxylation capacity as assessed by recovery of 4-hydroxydebrisoquine in urine following oral debrisoquine. The results support the hypothesis and demonstrate an inherent metabolic basis of susceptibility to chlorpromazine jaundice.