Pathogenic effect of enterotoxigenic Escherichia coli and Escherichia coli causing infantile diarrhoea.

Macroscopic, light and electron microscopic alterations in ligated rabbit intestinal loops challenged with five standard enterotoxigenic Escherichia coli (ETEC) and twenty-three enteropathogenic E. coli (EEC-I) strains, freshly isolated from infantile enteritis cases, were investigated. Only two O26 : K60 : H11 strains produced enterotoxin. Their living cultures, sterile filtrates of the fluid medium and ultrasonic lysates of the bacteria resulted in pronounced hypersecretion of the intestinal epithelium followed by fluid accumulation and loop dilatation. These two E. coli strains, similarly as the other loop-negative EEC-I strains, were able to penetrate into the intestinal epithelium. In contrast to the standard ETEC strains, the EEC-I bacteria, adhering to the brush border, intruded into the microvilli, multiplied on the outer epithelial cell membrane making close contact with it and, causing, shedding of microvilli, penetrated into enterocytes becoming enclosed in membrane-bound phagosome-like vacuoles, appeared in the lamina propria and elicited mild focal polymorphonuclear infiltration.     

Determination of Carboxylic Acids in Wines by Liquid Ion-Exclusion Chromatography

The chromatographic behavior of aromatic and aliphatic acids was studied using an ion-exclusive column. The conditions were determined under which the separation of the acids by single-column ion-exclusion chromatography with UV detection was the most selective and efficient. The method developed was employed for determining the content of carboxylic acids in wines.     

Dynamics of absorption of yellow fluorescent protein in intestine and reabsorption in kidney in rat postnatal ontogenesis

In experiments of the 5, 12 and 25-day old rat pups and adult rats in has been shown that after administration of yellow fluorescent protein (YFP) into stomach, its partial absorption in the non-degraded state in the small intestine takes place, with subsequent transport to kidney with blood flow and accumulation in cells of the proximal nephron segment. With age of rats, intensity of the intestinal YFP absorption decrease; the YFP accumulation in the kidney is more active in rats of the younger age groups than in adult animals. No accumulation of YFP in liver was revealed. The obtained data indicate an intensive absorption of YFP in the non-hydrolyzed form in the rat pup small intestine in early postnatal ontogenesis and an important role of kidney in protein metabolism and in proteolysis of exogenous proteins.     

Renal clearance of absorbed intact GFP in the frog and rat intestine

Intestine absorption of intact green fluorescent protein (GFP) and its following accumulation in the renal proximal tubule cells after its intragastric administration have been established by confocal microscopy in the rat and frog. Reabsorbed GFP was revealed in the endosomes and lysosomes of the proximal tubule cells by the methods of GFP photooxidation and immunofluorescent microscopy. The GFP intestine absorption rate and GFP accumulation in the kidney were significantly higher in the frog than in the rat. No specific fluorescence was revealed in the liver and colon cells after the GFP intragastric administration. The data obtained indicate the ability of the small intestine in the frog and rat to absorb intact proteins and an important role of the kidney in exogenous protein metabolism.     

Morpho-functional changes in small intestine epithelium of frog Rana temporaria during hibernation

Structure and function of small intestinal epithelium were studied in overwintering frogs Rana temporaria at various stages of hibernation. In the process of testing of absorption of arginine vasotocin (AVT) in experiments in vitro it is established that at the period of hibernation there is preserved the capability of the epithelium for absorption of this nonapeptide without hydrolysis. However, as compared with October-December, in January-February and later, a decrease of the AVT absorption takes place, which is the most pronounced in March-April. Changes in epithelial structures appear by the middle of winter and are progressing by spring. In April-May, as compared with the beginning of hibernation, the height of enterocytes, the length of microvilli, and the number of microvilli decrease by 33 %, 40 %, and 57 %, respectively. The absence of features of destruction indicates an adaptive character of the observed changes. Dynamics of the studied parameters indicates morphological plasticity of the small intestine epithelium of R. temporaria at the period of hibernation.     

Absorption of arginine-vasopressin and arginine-vasotocin in small intestine of the frog Rana temporaria

Experiments in vitro demonstrated a partial absorption of arginine-vasopressin (AVP) in the frog small intestine. Dynamics and efficiency of the nonapeptide absorption are studied with use of hydroosmotic method of recording of the osmotic permeability of the frog urinary bladder epithelium and immunoenzyme analysis. In the process of absorption there were preserved intactness of the hormone cyclic structure and its physiological activity, like in the case of the arginine-vasotocin (AVT) absorption. The AVP absorption increased at its administration into the gut with inhibitor of proteases. By methods of immunoelectron and immunofluorescent microscopy with use of polyclonal antibody to AVP, location of the label to the hormone was shown in the enterocyte cytoplasm. Thus, there was obtained a morphological evidence for the AVP absorption and transepithelial transfer in the frog small intestine. These data enlarge the concept of the poorly studied properties of the absorbing epithelium of the vertebrate intestine with respect to absorption of intact molecules of polypeptides.     

Tubular protein uptake pattern in the frog model (<Emphasis Type="Italic">Rana temporaria</Emphasis>): The effect of previous protein loading

The effect of increasing protein load on subsequent receptor-mediated protein uptake was studied in the kidney of the common frog Rana temporaria L. Results of in vivo experiments were analyzed in fixed kidney sections using fluorescent or confocal microscopy and immunohistochemistry. Lysozyme was used for daily tubular loading in short-term experiments. Reabsorption of yellow fluorescent protein (YFP) in the proximal tubule (PT) was tested 60 min after introduction into the dorsal lymphatic sac. YFP uptake decreased progressively with increasing duration of lysozyme preload from 2 to 4 days. Lysozyme loading and single protein injections did not change the morphological characteristics of frog glomeruli and PTs, as shown by light and electron microscopy and morphometric analysis. Cessation of loading led to a decrease in the amount of lysozyme accumulated in PT cells. Reduced YFP uptake gradually recovered after cessation of the 4-day load. Restoration of YFP reabsorption was accompanied by increasing expression of endocytic receptors, megalin and cubilin. Based on the data obtained, the frog model can be successfully used for studying both morphological and functional changes in the nephron caused by tubular or glomerular proteinuria and molecular mechanisms involved in the process of renal protein reabsorption.     

Erratum to: The original online version of the following articles was revised: the issue date is not January 2020, but January 2021

Journal of Evolutionary Biochemistry and Physiology - A Correction to this paper has been published: https://doi.org/10.1134/S0022093021020216     

Dynamics of absorption in gut and reabsorption in kidney of yellow fluorescent protein in rat postnatal ontogenesis

In experiments on rats aged 5, 12, and 25 days and on adult rats, absorption of yellow fluorescent protein (YFP) in small intestine was shown, with its subsequent entry to kidney with blood flow and accumulation in cells of the nephron proximal segment. With age, intensity of the YEP absorption in the gut decreased; the YEP accumulation in kidney was somewhat more active in the rat pups of younger age groups than in adult animals. No accumulation of YEP was revealed in liver. The obtained results indicate an intensive absorption in the rat pup small intestine in early postnatal ontogenesis and an important role of kidney in protein metabolism and proteolysis of alien proteins.