The degree to which prevailing land tenure arrangements constrain agricultural productivity, and the sources of inefficiency associated with land tenure systems in sub-Saharan Africa are unresolved. Using a stochastic frontier production function, this paper examines the economic efficiency and the determinants of inefficiency of alternative land tenure arrangements in Ethiopia. The results show that sharecropping and borrowing are less technically efficient than owner-cultivation or fixed rentals due to restrictions imposed on them by landowners and the interactions of the land market with other imperfect and absent input markets. Thus, a policy to facilitate more efficient transactions of land between farmers and functioning of input markets are expected to reduce inefficiencies associated with these tenure systems.

Leptin is an adipose tissue-derived cytokine plays key roles in the regulation of food intake and energy expenditure. However, regulatory mechanisms of leptin gene expression are not fully elucidated in ruminants that utilize short-chain fatty acids (SCFA), known as volatile fatty acids, as principal energy sources. In this study, we determined effects of SCFA and long-chain fatty acids (LCFA) on leptin expression in bovine adipocytes. Bovine stromal vascular cells isolated from subcutaneous adipose tissue of Holstein cows were cultured to confluence and treated sequentially with dexamethasone and isobutylmethylxanthine for 2 days and insulin and troglitazone for 12 days to achieve full differentiation to adipocytes. The cells started to accumulate lipids 4 days after the onset of treatment, with increased mRNAs expression of leptin, as well as aP2, adiponectin, and PPAR-γ  Removal of fetal calf serum and reduction of glucose in the culture medium of differentiated adipocytes decreased leptin mRNA expression.Subsequent addition of acetate, butyrate, or propionate dose-dependently restored and rather increased leptin expression, while addition of LCFA suppressed it. The stimulatory effect of acetate was abolished by prior treatment of the cells with pertussis toxin and by addition of LCFA. Furthermore, cows fasted for 48h and fed thereafter, elaborate reduced and increased plasma leptin levels, respectively. Thus, these results suggest that plasma leptin levels in cows are inversely controlled at transcription by VFA and LCFA, and that the effects of SCFA possibly act through a G protein-coupled receptor for SCFA.

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The progression of diabetic nephropathy (DN) is accelerated by smoking. The current study investigated the ability of curcumin to protect the kidneys against damage from oxidative stress induced by diabetes mellitus (DM) and nicotine (NC). A total of 24 male Wistar rats were divided into four groups of six rats each. DM was induced by a single intraperitoneal injection of streptozotocin 60 mg/kg body weight. DM rats were treated with or without NC in the absence or presence of curcumin for 8 weeks. As compared with the controls, DM rats exhibited reduced serum levels of high density lipoprotein, superoxide dismutase and glutathione peroxidase, and decreased renal mRNA expression levels of synaptopodin, connexin 43 and erythropoietin (EPO), which were further suppressed by NC and restored to normal levels by curcumin treatment. Additionally, DM rats exhibited increases in their lipid profiles (cholesterol, triacylglycerol and phospholipids), oxidative markers (malondialdehyde, γ-glutamyltranspeptidase and nitric oxide), kidney function markers (urea and creatinine) and the mRNA expression levels of vimentin, desmin, SREBP-1, iNOS and TGF-β1. These effects were further enhanced by NC, but counteracted by curcumin treatment. Kidneys from DM rats displayed glomerular hypertrophy, sclerosis and tubulo-interstitial changes represented by tubular lipid deposition, interstitial mononuclear cell infiltration and fibroplasia. Pancreatic islets exhibited cellular vacuolation, morphological irregularity and damaged or reduced in size β-cells. These renal and pancreatic changes became more severe following NC treatment and were ameliorated by curcumin. Therefore, NC-induced DN progression may predominantly operate by increasing oxidative stress, reducing the levels of antioxidants, suppressing EPO levels, and causing perturbations to gap junction and podocyte structure. Curcumin may ameliorate the damaging effects of DM and NC on the kidney through normalization of the mRNA expression levels of several genes important in the progression of DN.

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The current work was undertaken to settle the debate about the toxicity of artificial sweeteners (AS), particularly aspartame and saccharin. Twenty-five, 7-week-old male Wistar albino rats with an average body weight of 101 ± 4.8 g were divided into a control group and four experimental groups (n = 5 rats). The first and second experimental groups received daily doses equivalent to the acceptable daily intake (ADI) of aspartame (250 mg/Kg BW) and four-fold ADI of aspartame (1000 mg/Kg BW). The third and fourth experimental groups received daily doses equivalent to ADI of saccharin (25 mg/Kg BW) and four-fold ADI of saccharin (100 mg/Kg BW). The experimental groups received the corresponding sweetener dissolved in water by oral route for 8 weeks. The activities of enzymes relevant to liver functions and antioxidants were measured in the blood plasma. Histological studies were used for the evaluation of the changes in the hepatic tissues. The gene expression levels of the key oncogene (h-Ras) and the tumor suppressor gene (P27) were also evaluated. In addition to a significant reduction in the body weight, the AS-treated groups displayed elevated enzymes activities, lowered antioxidants values, and histological changes reflecting the hepatotoxic effect of aspartame and saccharin. Moreover, the overexpression of the key oncogene (h-Ras) and the downregulation of the tumor suppressor gene (P27) in all treated rat groups may indicate a potential risk of liver carcinogenesis, particularly on long-term exposure.

Retinol-binding protein 4 (RBP4) is a plasma protein involved in retinol transportation, and recent evidence in rodents suggests that RBP4 is also a metabolic regulator that modifies insulin sensitivity. To assess how RBP4 levels are regulated in ruminants, we determined the RBP4 concentrations in bovine plasma and milk using Western blot analysis. Plasma RBP4 levels in non-pregnant non-lactating (control) cows were around 45 mg/ml, which were sustained during 60-h fasting, but decreased significantly 4 h after lipopolysaccharide (LPS) administration. Basal plasma retinol concentration was around 30 mg/dl, but this decreased to approximately one-third and one-half of these values during fasting and 8 h after LPS challenge, respectively. Plasma RBP4 and retinol levels in cows 3-6 d before parturition were comparable to those of the controls. However, on the day of parturition both were significantly decreased and had returned to basal levels by two weeks after calving. Interestingly, RBP4 was clearly detected in colostrum (16 . 4±5 . 6 mg/ml) but was only faintly detected in milk from cows at 7 d and 15 d after calving. Retinol concentrations in colostrum were almost 10-fold higher than those in plasma, while those in milk were comparable to those in plasma. These results suggest that RBP4 and retinol levels are independently regulated under physiological and pathophysiological conditions and that RBP4, like retinol, is transferred from maternal stores to calves through colostrum.

ABSTRACT. Leptin is a protein synthesized and secreted primarily by adipose tissue. The blood leptin concentration is known to reflect body fat content in rodents, humans and dogs, and thereby is useful for quantitative assessment of obesity. In the present stud y, we produced recombinant feline leptin in Escherichia coli transfected with feline leptin cDNA we cloned previously. The recombinant feline leptin with a molecular weight of 16 kDa induced phosphorylation of the signal transducers and activators of transcription 3 (STAT3) protein in the cells expressing rat leptin receptor. The anti-feline leptin antibody raised in rabbits reacted well to feline a nd human leptin and less to rodents' leptin in Western blot analysis. Sandwich enzyme-linked immunosorbent assay (ELISA) was developed, using rabbit anti-feline leptin antibody and recombinant feline leptin as a standard. In this ELISA system, cross-reactivity to human, rat and mouse leptin was 30.7%, 69.5% and 66.6%, respectively. The plasma leptin levels of 24 healthy cats were in a range from 0.3 to 29.7 ng/ml with the mean ± SEM of 4.5 ± 1.3 ng/ml, being positively proportional to body fat content. These results indicate that our ELISA system may be useful for assessment of obesity in cats. KEY WORDS: ELISA, feline, leptin.