Profile of loiasis infection through clinical and laboratory diagnostics: the importance of biomarkers.

BACKGROUND: Detection of Loa loa microfilariae in peripheral blood is insensitive given only 30% of individuals are microfilaraemic while 70% are amicrofilaraemic with a variety of clinical signs. Biomarkers may improve the diagnosis of loiasis. METHODS: A total of 545 individuals exposed to L. loa were analysed using clinical data collected through a questionnaire (requesting information on eye worm, Calabar swelling, pruritis) and detection of microfilariae, immunoglobulin G4 (IgG4), DNA and antigens using microscopy, enzyme-linked immunosorbent assay (ELISA), quantitative polymerase chain reaction (qPCR) and Western blot, respectively. RESULTS: The results revealed that the rates of detection of L. loa microfilariae in the blood, of DNA by qPCR, of IgG4 by ELISA and of antigen by Western blot were 4.7%, 5.5%, 15.60% and 10.09%, respectively. CONCLUSIONS: This study showed that clinical signs based on a questionnaire are highly subjective. Therefore it is imperative to use IgG4 and DNA biomarkers as well as antigens detected by Western blot to identify individuals infected with L. loa.

Suppression of preneoplastic changes in the intestine of rats fed low levels of polyamines.

Administration for 7 days of an enteral diet that is naturally deficient in polyamines strikingly reduces the preneoplastic changes observed in the intestines of adult Wistar rats previously treated with the carcinogen 1,2-dimethylhydrazine. On the contrary, supplementing the enteral diet with spermidine favors preneoplastic development. The effects of the low-polyamine diet included a 40% decline in the putrescine content of the intestinal mucosa, a significant decrease in the turnover rate of the epithelial cells from the crypts to villus tip in the ileum, and a 2-fold reduction in the number of abnormal colonic crypts. The experimental data support the view that it might be of interest to control the dietary intake of polyamines in the clinical management of cancer patients.

Enteral supplementation with ornithine alpha ketoglutarate improves the early adaptive response to resection.

BACKGROUND: Polyamine synthesis or uptake, or both, might be an important event that initiates the adaptive hyperplasia seen in the intestinal remnant after partial small bowel resection. AIM: The ability of an enteral diet supplemented with the ornithine salt: ornithine alpha ketoglutarate (OKG), a precursor for polyamine synthesis, to modulate the adaptive response of the remnant ileum after jejunectomy was evaluated. METHODS: Adult Wistar rats underwent a resection of the proximal 50% of the small intestine. Controls underwent a single transection. The rats were fed intragastrically with a nutritive mixture supplemented either with casein hydrolysate or with OKG (1 g/kg). The isoenergetic and isonitrogeneous diets was given continuously for seven days. RESULTS: Villus and crypt hyperplasia was observed in the remnant ileum compared with transfected controls. OKG supplementation started after resection a further increase in villus height. After resection, OKG supplementation increased significantly the putrescine content and the amount of ornithine decarboxylase mRNA. A twofold to threefold increase of sucrase activity was measured in the resected animals compared with the transected rats. In contrast, the amount of sucrase mRNA was significantly lower in the ileum of the resected rats and OKG supplementation initiated a further drop in the amount of sucrase mRNA without pronounced changes in enzyme activity. CONCLUSIONS: The adaptive hypertrophy seen after resection can be accelerated by supplementing the diet with ornithine (OKG) a precursor of polyamine synthesis. In the remnant ileum, the reduced amount of sucrase mRNA, despite the increased level of sucrase activity, suggests a post-translational control of sucrase expression.

Premature expression of sucrase-isomaltase triggered by corticoid-dependent changes in polyamine metabolism.

A possible link between the corticoid-elicited premature expression of intestinal sucrase-isomaltase (SI) and endogenous changes in polyamine metabolism was investigated in preweaned rats. Starvation at postnatal day 12 caused a precocious expression of SI mRNA and activity. A rapid upsurge of serum corticosterone was observed during the first hour of isolation, occurring in parallel with a transient enhancement of ornithine decarboxylase (ODC) expression and followed by an increase in mucosal polyamine content. Administration of the antiglucocorticoid RU-38486 completely prevented the starvation-evoked stimulation of ODC. The treatment of the sucklings with RU-38486 or with alpha-difluoromethylornithine (DFMO), a specific inhibitor of ODC, dramatically reduced the amount of SI mRNA. When exogenous hydrocortisone (HC) was administered to 12-day-old sucklings nourished by their dam, an important accumulation of ODC mRNA was observed in the intestinal mucosa 4 h after treatment. Sucklings receiving HC and treated concomitantly with either RU-38486 or DFMO exhibited a reduced amount of ODC mRNA and a dramatic decline in both SI mRNA and activity. Altogether these data support the view that the premature induction of SI expression is dependent on changes in ODC expression and polyamine metabolism that can be elicited either by endogenous changes or by exogenously administered glucocorticoids.

Precocious and reversible expression of sucrase-isomaltase unrelated to intestinal cell turnover.

The effect of starvation and refeeding on the developmental pattern of intestinal sucrase-isomaltase (SI) was analyzed in preweaned rats. Starvation at postnatal day 12 caused a precocious expression of SI activity and mRNA. Alkaline phosphatase activity was slightly reduced, and no significant change was observed for aminopeptidase and lactase activities. Immunostaining showed that SI molecules appear in cells at the base of the villus. Sucrase expression was further increased by prolonged food deprivation, whereas enzyme activity as well as the amount of SI mRNA dropped to reach the low level found in control sucklings when 48 h-starved pups were refed by returning them to their dams. During the refeeding period, the enterocytes that were committed to produce SI by starvation continued to express the enzyme while migrating up the villi. However, the new epithelial cells arising from the crypts no longer synthesized the disaccharidase. The starvation-evoked appearance of SI was preceded by a transient burst of expression of the protooncogene c-fos, an event that may be correlated to the ontogenic rise of c-fos mRNA observed before weaning. However, in contrast to the normal weaning condition, SI induction by starvation occurred without obvious increase of epithelial cell proliferation and turnover. During the starvation and refeeding period, patterns of sucrase activity and SI mRNA paralleled the serum level of glucocorticoids.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidermal growth factor and the maturation of intestinal sucrase in suckling rats.

The regulatory effect of epidermal growth factor (EGF) on the postnatal maturation of sucrase was investigated in the small intestine of suckling and weanling rats. Administration of EGF (0.5 micrograms.g body wt-1.day-1) to suckling rats caused a slight precocious induction of sucrase expression. In weanling rats EGF markedly stimulated sucrase activity; however, at both ages, the effect of hydrocortisone was more potent. When the glucocorticoid antagonist RU-38486 was administered to sucklings, the precocious induction of sucrase activity by hydrocortisone was inhibited by 80%. However, RU-38486 or adrenalectomy did not prevent the inductive effect of EGF, indicating that EGF acts in a glucocorticoid-independent manner. EGF also potentiated the effect of hydrocortisone and dietary sucrose on the precocious induction of sucrase activity in the sucklings. At weaning, administration of an antiserum specific to rat EGF significantly decreased sucrase activity. This study shows the involvement of EGF in the postnatal maturation of intestinal sucrase in the rat.

Improved purification of rat intestinal lactase.

A rapid and improved method to obtain purified lactase from rat intestine is described. The purification procedure involved only two chromatographic steps. The degree of purification was far above (500 fold) the values reached with classical methods. Rabbit antisera raised to the purified lactase were characterized using conventional immunological techniques. The specificity of the lactase antibodies was confirmed by the lack of interference on maltase, aminopeptidase and alkaline phosphatase activities measured after papain extraction of the membrane proteins.

Modulation by thyroxine of the amount of lactase protein in the jejunum of adult rats.

Adult rats starved for 48 h received a daily injection of thyroxine over a 3-day period before they were killed. When compared to nourished animals, starvation provoked a 4- to 5-fold increase in immunoreactive lactase protein, which paralleled a similar stimulation of lactase activity in the brush border membranes of the proximal jejunum. Exogenous thyroxine completely inhibited the starvation-induced increase in immunoreactive lactase protein in both the intracellular and the brush border membranes.

Stimulation of lactase synthesis induced by starvation in the jejunum of adult rat.

The effects of actinomycin D and of cycloheximide administration have been investigated on the enzyme activities of the jejunal brush border membrane in adult rats after a 48-hour period of starvation. The modifications in the protein and enzyme patterns of the brush border membrane and the incorporation of radiolabelled amino acid in the protein band corresponding to lactase have been studied in the nourished and in the starved animal. The results show that actinomycin D administration did not modify the stimulation of lactase activity caused by starvation whereas cycloheximide completely inhibited this process. The stimulation of lactase activity, in the starved animal, is related to a quantitative increase of the corresponding protein band and with enhanced incorporation of L-[3H]valine in this protein band after separation of brush border proteins by gel electrophoresis. It is concluded that the stimulation of lactase activity observed during starvation is the consequence of de novo synthesis of lactase molecules and that this process is regulated at a translational level. A general hypothesis is proposed in order to clear up partly the mechanism involved in the stimulation of lactase activity by food deprivation in the adult rat.

Lactase activity is under hormonal control in the intestine of adult rat.

In the adult rat, starvation during 48 hours led to a three fold increase of lactase specific activity in the intestinal brush border membranes. Thyroxine injection during the three days before death (0.5 micrograms/g daily) inhibited the stimulation of lactase activity induced by starvation without modifying sucrase activity whereas hydrocortisone injections (25 micrograms/g daily) or thyroidectomy did not modify the stimulatory effect of starvation on lactase activity. These results suggests a specific hormonal control of intestinal lactase activity in the rat.