Determination of protein, lipid, and mineral content of fish meat is necessary to ensure that it meets requirements for food regulations and commercial specifications. The objective of the present study was to determine the chemical composition ofOreochromis niloticus(L.), Nile tilapia, under three different ecosystems: (1) high pollution and high density ofEichhornia crassipes, that is, water hyacinth (Lake Chivero), (2) medium pollution and medium density of water hyacinth (Lake Manyame), and (3) low pollution and low density of water hyacinth (Lake Kariba). Dry matter, protein, lipids, and ash were evaluated by proximate analysis. Minerals were determined by atomic absorption spectrophotometry and pH was determined by a pH meter. Lake Kariba fish had the highest percentage of dry matter, protein, and ash. These qualities were correlated to low levels of pollutants and high oxygen content in the harvest waters. The phosphorus content of fish from Lake Chivero was very high, in tandem with phosphate levels in the harvest waters. In addition, water from Lake Chivero had an alkaline pH, high nitrate, and low oxygen content. The results suggest that effluent from sewage works and fertilizer industries caused pollution and proliferation of water hyacinth, contributing to pervasion of the chemical composition of fish.

The distribution of interstitial cells of Cajal (ICC), the probable pacemakers in gastrointestinal motility, was investigated using an antigenic marker of gastric ICC known as C-Kit. Antiserum raised against the general neuronal marker protein gene peptide 9.5 (PGP) as well as the nitrergic neuronal marker neuronal nitric oxide synthase (nNOS) were used to investigate the distribution of gastric nerves. Polyclonal goat anti-human C-Kit was reliable in labelling ICC in the stomach. Two classes of ICC were identified according to their distribution: ICC-MY distributed around the periphery of myenteric ganglia and ICC-IM in the circular and longitudinal muscle layers. The neuronal marker PGP was reliably consistent in revealing the density and distribution of the enteric nervous system. Density of nerve fibres was higher in circular smooth muscle than in longitudinal smooth muscle. From nNOS immunohistochemistry, it is evident that inhibitory (nitrergic) nerves constitute a substantial fraction of the enteric nervous system.

The aim of this study was to evaluate osmometry as a tool in quality analysis of milk. The osmolality of raw milk, sterilized milk, skimmed UHT (ultra-high temperaturetreated) milk, pasteurized milk, standardized UHT milk and fermented milk (Lactococcus lactis culture) was determined by freezing point osmometry. The relationship between osmolality and pH of fermented milk was further investigated during spontaneous fermentation of UHT milk at 37°C for 48 h. Average osmolality values (mean ± SD) were raw milk-290.2 ± 7.98, sterilized milk-290.2 ± 5.84, skimmed UHT milk-290.8±3.31, pasteurized milk-283.6±2.28, standardized UHT milk-281 ± 4.59 and fermented milk-466.0 ± 17.30 mOsmoles kg −1. For fresh milk samples, 88 % showed normal osmolality, 8 % were hypo-osmotic and 4 % hyper-osmotic. Fermentation studies revealed a high negative correlation between osmolality and pH, with a correlation coefficient of −97.49 %. Hypo-osmotic milk shows mixing of milk with water along the production chain. Hyper-osmotic milk indicates fermentation of milk at high ambient temperatures or with prolonged storage. It may also reveal adulteration of fresh milk with a soluble substance. Osmolality was highest for fermented milk owing to production of lactic acid during fermentation. This was confirmed by the high negative correlation between osmolality and pH of milk in fermentation studies. Hence the osmolality of fermented milks may be used as an index of the extent of fermentation.

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1. Occurrence of short chain fatty acids (SCFA) in anionic form limits their diffusion across the absorptive membrane. The present study sought to establish the mechanism of SCFA absorption in the ostrich. 2. Epithelial tissues were taken from the sacculated part of the colon and mounted in Ussing chambers in a bathing solution. The tissues were voltage-clamped and allowed to equilibrate to obtain a baseline short circuit current (Isc). 3. Propionate (23 mM) on the mucosal side increased the Isc. The SCFA-induced Isc was completely inhibited by anoxia, ouabain (1 to 2 mM), acetazolamide (0.5 mM) and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (0.1 mM) on the mucosal side. 4. These findings indicate that SCFA stimulate hydrogen ion secretion through an electrogenic H(+)-K(+)-ATPase, the source of hydrogen ions being carbonic anhydrase catalysed hydration of CO2. 5. Simultaneous activation of Cl(-)/HCO3(-) exchange prevents intracellular accumulation of bicarbonate ions. This system may provide hydrogen ions for protonation of SCFA anions and subsequent absorption by non-ionic diffusion.