Screening of antinutrients in leaves, fruit pulp and seeds of Gishta (Annona spp.) of Ethiopia, North East Africa

<div><p><em>Graviola or Gishta (Annona spp. of Ethiopia) are generally useful for human consumption were analysed for the presence of potentially harmful chemicals (antinutrients) and for their toxicity. The purpose of the study was to determine whether the Graviola or Gishta (Annona spp. of Ethiopia) leaves, fruit pulp and seed extracts were safe for human consumption. Chemical analysis showed that none of tested parts contained cyanogenic glycosides, however all the three tested plant materials contained oxalic acid in high concentrations and also contained negligible amounts of phytic acid, saponins and alkaloids. Tested plant samples also found to inhibit trypsin activity. These chemical analyses were carried out in duplicate.</em></p></div>

Fetuin: its enigmatic property of growth promotion

A variety of cell types in culture respond to fetuin, a glycoprotein from fetal bovine serum, which is often an important supplement to many serum-free media. Bovine fetuin preparation has been shown to inhibit trypsin activity and promote cellular attachment, growth, and differentiation in many different culture systems. In addition, fetuin associates with various growth factors or growth-promoting substances. However, whether the growth-promoting activity of fetuin preparation is due to fetuin per se or to its minor contaminant(s) has been a long-standing puzzle. The present review surveys the literature concerning this enigmatic property of fetuin and summarizes three possibilities: 1) fetuin itself is active, although the majority of studies do not support this; 2) various contaminants of fetuin preparations, including potentially unidentified ones, are responsible for the activity, a possibility supported by numerous reports; and 3) one of the fetuin subspecies, one of its contaminants, or a combination of both of these is responsible for growth of a specific cell type. In addition, the basic physicochemical properties and other biological functions of fetuin have also been presented.

Proteins but not amino acids, carbohydrates, or fats stimulate cholecystokinin secretion in the rat

Because of prior difficulties in measuring plasma cholecystokinin (CCK) levels, it has not been established which components of food stimulate CCK secretion in rats. In the present study, we used a sensitive and specific bioassay for measuring plasma CCK and determined the effects of proteins, protein hydrolysates, amino acids, fats, starch, and glucose on CCK secretion in this species. Intact proteins were the only stimulants of CCK release. Solutions of 18% casein and 0.2% soybean trypsin inhibitor caused prompt increases in plasma CCK levels from 0.5 +/- 0.2 to 7.9 +/- 1.9 and 8.0 +/- 2.0 pM, respectively, within 5 min of orogastric administration. The proteins lactalbumin and bovine serum albumin caused smaller elevations in circulating CCK. In contrast, hydrolysates of casein and lactalbumin and the amino acids L-phenylalanine and L-tryptophan did not stimulate CCK release. In addition, plasma CCK levels did not increase with the feeding of fat, starch, or glucose. The ability of proteins to stimulate CCK secretion paralleled their ability to inhibit trypsin activity in vitro. Furthermore, the plasma CCK response to casein was completely abolished by the simultaneous administration of trypsin. These studies indicate that proteins are the major food stimulants of CCK release in the rat and that the effects of proteins are related to inhibition of intraluminal protease activity.

MODIFICATION OF THE GELATIN SUBSTRATE PROCEDURE FOR DEMONSTRATION OF ACROSOMAL PROTEOLYTIC ACTIVITY

In situ proteolytic activity in the heads of sperm of seven mammalian species has been demonstrated using autoradiographic film as a gelatin substrate. The film is first exposed and processed and then coated with the sperm sample. Proteolytic activity is monitored by following the appearance of "halos," which are areas of gelatin digestion and are found to surround the heads of reacting sperm. The proteolytic factor appears to be released from the acrosome and may be the protease with trypsin-like activity that has been found associated with the acrosome in biochemical studies. l-Chloro-3-tosylamido-7-amino-2-heptanone and diisopropyl fluorophosphate, both of which inhibit trypsin activity, apparently interact with a substance released from the acrosome but do not interfere with the formation of halos. Sperm treated with trichloroacetic acid, urea or formalin do not form halos.