On the deep origin of the depressed rings on pearl surface illustrated from Polynesian Pinctada margaritifera (Linnaeus 1758)

Among the various defects that contribute to depreciate the commercial value of pearls, the occurrence of depressed rings is the most spectacular. Through a series of structural, physical and chemical characterizations of the pearl layer, this paper reveals that the origin and initial stages of these essentially superficial defects are to be found in the earliest stages of pearl formation. The disturbance in growth of the nacreous envelopes is the physical cause of the occurrence of these depressed areas. Attention is also drawn on the unexpected relationship between these large morphological alterations of the pearl surfaces and more punctual defects primarily well visible in the strongly coloured Polynesian pearls. An understanding of the actual origin of these very negative patterns opens the way to reduce their statistical occurrence by paying attention to the grafting practice.     

Non‐spherical pearl layers in the Polynesian ‘black‐lipped’ Pinctada margaritifera: The non‐nacreous deposits compared to microstructure of the shell growing edge

Cultivated pearls frequently exhibit morphological irregularities making obvious that mineral deposition was irregularly distributed onto nucleus surface. Taking advantage of experimental cultivations with short durations (from 10 days to few months), these irregular deposits predating occurrence of the nacre were investigated in Polynesian pearls by biochemical characterizations and a series of physical methods. Diversity in the resulting data suggests that various in‐depth alterations of the biomineralization mechanism may have occurred during the grafting process, leading to diversity in the biochemical pathways to nacreous deposition. This allows a precise discussion of current views about pearl formation. The “reversed shell theory” is formally disproved through point to point comparison with development of the shell growing edge. Similarity of pearl formation with “regeneration” or “shell repair” is also discussed, emphasizing the differences between these concepts.     

Heat stress effects on livestock: molecular,cellular and metabolic aspects,a review

Elevated ambient temperatures affect animal production and welfare. Animal's reduced production performances during heat stress were traditionally thought to result from the decreased feed intake. However, it has recently been shown that heat stress disturbs the steady state concentrations of free radicals, resulting in both cellular and mitochondrial oxidative damage. Indeed, heat stress reorganizes the use of the body resources including fat, protein and energy. Heat stress reduces the metabolic rates and alters post‐absorptive metabolism, regardless of the decreased feed intake. Consequently, growth, production, reproduction and health are not priorities any more in the metabolism of heat‐stressed animals. The drastic effects of heat stress depend on its duration and severity. This review clearly describes about biochemical, cellular and metabolic changes that occur during thermal stress in farm animals.     

Impacts of small hill dams on agricultural development of hilly land in the Jendouba region of northwestern Tunisia

We examine the shifting farming system around the small hill dams in northwestern Tunisia. A socio-economic questionnaire was given to a sample of farmers using water from eight representative small hill dams. Cluster analysis was used to establish farmer groups before and after creation of the reservoirs. Before the creation of hill dams, farmers were grouped into two clusters. Afterwards, three new farming systems emerged. The main differences between these groups are farm area, cropping system, irrigation practice, livestock type and number, and income. Following construction of the small hill dams farmers increased the extent of fruit tree cultivation, introduced irrigation practices, and augmented livestock herd size and production. Farmer income increased with the availability of water in the hill dam reservoirs.     

Anti‐diabetic effect of camel milk in alloxan‐induced diabetic dogs: a dose–response experiment

This study was conducted to evaluate the effect of camel milk in alloxan‐induced diabetic dogs and to follow this effect at three doses of milk. Firstly, three groups of dogs were used: two groups composed each of four diabetic dogs and receiving raw camel milk (treatment 1) or cow milk (treatment 2), and four healthy dogs getting raw camel milk (treatment 3) were used as control. Each animal was treated with 500 ml of milk daily. Secondly, we compared the effects of three amounts of camel milk: 100 ml, 250 ml and 500 ml to treat the diabetic dogs. After week 3, the dogs treated with camel milk showed a statistically significant decrease in blood glucose (from 10.88 ± 0.55 to 6.22 ± 0.5 mmol/l) and total protein concentrations (from 78.16 ± 2.61 g/l to 63.63 ± 4.43 g/l). For cholesterol levels, there was a decrease from week 2 (from 6.17 ± 0.5 mmol/l to 4.79 ± 0.5 mmol/l). There were no significant difference in blood glucose, cholesterol or total protein concentrations in dogs drinking 250 and 500 ml of camel milk. The dogs treated with 100 ml of camel milk did not show any significant decrease in blood glucose levels, and cholesterol and total protein concentrations. The investigation was not limited to the improvement in glycemic balance, lipids and proteins control in diabetic dogs getting camel milk, but we also noted a stability of this state after the dogs stopped to drink milk. This effect depended on the quantity of camel milk used to treat diabetic dogs.     

Ethephon elicits protection against Erysiphe necator in grapevine

The grapevine (Vitis vinifera) is susceptible to many pathogens such as Botrytis cinerea, Plasmopara viticola, Erysiphe necator, and Eutypa lata. Phytochemicals are used extensively in vineyards to reduce pathogen infections, but the appearance of pesticide-resistant pathogen strains and the need for environmental protection require the use of alternative strategies. The phytohormone ethylene is assumed to play a role in the development of disease resistance. In the present study, we have treated grapevine foliar cuttings (Cabernet Sauvignon) with ethylene-releasing ethephon. This resulted in an increase in the number of pathogenesis-related protein (CHIT4c, PIN, PGIP, and GLU) gene copies and in an enhancement of phytoalexin biosynthesis by inducing the PAL and STS genes that correlated with the accumulation of stilbenes (antimicrobial compounds). Moreover, ethephon treatment triggered the protection of grapevine detached leaves and grapevine foliar cuttings against Erysiphe necator, the causal agent of powdery mildew (64% and 70%, respectively). These studies emphasize the major role of ethylene in grapevine defense.