Passage Of Serum Proteins Research Articles

Influence of casein on flux and passage of serum proteins during microfiltration using polymeric spiral-wound membranes at 50°C

Raw milk (approximately 1,800kg) was separated at 4°C, pasteurized (at 72°C for 16s), and split into 2 batches. One batch (620kg) was microfiltered (MF) using pilot-scale ceramic uniform transmembrane pressure Membralox membranes (model EP1940GL0.1μA, 0.1-μm alumina; Pall Corp., East Hills, NY) to produce retentate and permeate. The permeate from the MF uniform transmembrane pressure was casein-free skim milk (CFSM). The CFSM was MF using polymeric spiral-wound (SW) membranes (model FG7838-OS0x-S, 0.3 μm; Parker-Hannifin Corp., Process Advanced Filtration Division, Tell City, IN) at a concentration factor of 3× and temperature of 50°C. Following the processing of CFSM, the second batch of skim milk (1,105kg) was processed using the same polymeric membranes to determine how casein content in the feed material for MF with polymeric membranes affects the performance of the system. There was little resistance to passage of milk serum proteins (SP) through a 0.3-μm polyvinylidene fluoride (PVDF) SW membrane at 50°C and no detectable increase in hydraulic resistance of the membrane when processing CFSM. Therefore, milk SP contributed little, if any, to fouling of the PVDF membrane. In contrast, when processing skim milk containing a normal concentration of casein, the flux was much lower than when processing CFSM (17.2 vs. 80.2kg/m2 per hour, respectively) and the removal of SP from skim milk with a single-pass 3× bleed-and-feed MF system was also much lower than from CFSM (35.2 vs. 59.5% removal, respectively). Thus, when processing skim milk with a PVDF SW membrane, casein was the major protein foulant that increased hydraulic resistance and reduced passage of SP through the membrane.

Permeability of Basement Membranes to Macromolecules

ConclusionsBasement membranes are important structures within many tissues, and for at least some tissues, the ability of the basement membranes to restrict the passage of macromolecules is important for function. We have concentrated on the renal glomerular and tubular basement membranes because they have been studied more than others, but the basement membranes of capillaries may be important in many different organs (65). In the renal glomerulus, the GBM certainly plays an important role in restricting the passage of serum proteins into the forming urine; however, some data are conflicting, and the relative roles of cells and the GBM are not yet defined. In the renal proximal tubule, the TBM may play a part in the process of epithelial transport of fluid, and the example that we have given shows the importance of considering the dynamics of the in vivo situation in assessing the role of the basement membrane. Describing the permeability properties of basement membrane will require more work in vitro, a...

Mucin and protein release in the rabbit jejunum: Effects of bethanechol and vagal nerve stimulation

The role of the vagus nerve and cholinergic mechanisms in the control of rabbit jejunal mucin and protein release was investigated in vivo. In anesthetized animals, a 10-cm segment of the jejunum was cannulated and perfused with saline. Perfusate was collected and analyzed for mucin (by immunoassay) and protein. Bilateral cervical vagotomy had no effect on basal mucin or protein output, suggesting that the vagus nerve does not exert a tonic control on jejunal macromolecule secretion. Electrical stimulation of the vagi did not alter mucin release, even in the presence of muscarinic cholinergic (scopolamine) or adrenergic (propranolol and phentolamine) blockade. In contrast, protein output increased significantly after vagal stimulation, an effect inhibited by scopolamine. In both vagotomized and vagally intact rabbits, the cholinergic agonist bethanechol (200 μg/kg intraperitoneally) induced a scopolamine-sensitive increase in both mucin and protein output. Predominantly serum proteins were released into intestinal perfusates after vagal or cholinergic stimulation. It is concluded that the extrinsic vagus nerve does not regulate rabbit jejunal mucin secretion in vivo and that cholinergic control of intestinal goblet cells is implemented entirely by the intrinsic enteric nervous system. In addition, cholinergic or vagal stimulation increases intestinal vascular and epithelial permeability, resulting in the passage of serum proteins into the lumen, possibly by opening tight junctions and paracellular pathways.

Thyroid albumin originates from blood.

Iodoalbumin has been found in the goiter of Dutch goats with a thyroglobulin synthesis defect. Immunohistochemical studies showed that in the goiter the percentage of follicles containing albumin was higher than that in normal thyroid glands. In the albumin-containing follicles of normal and goitrous glands, transferrin and immunoglobulin G could be found. Also, between the epithelial cells, serum proteins were detected. These results indicate intercellular passage of serum proteins. After in vivo labeling with 125I, goiter slices were incubated with [3H] leucine. Purified 125I-containing albumin did not contain [3H]leucine, while thyroglobulin antigens were double labeled. Cyanogen bromide treatment of albumin out of the goiter and of serum albumin gave comparable cleavage patterns, indicating that no great differences in amino acid composition, especially methionine, exist. In total RNA from goiter, no albumin mRNA could be detected after blotting and hybridization with goat albumin cDNA. Also, the polymerase chain reaction method with albumin DNA primers was unable to detect any albumin mRNA in normal and goitrous glands of goats. From these results we conclude that "thyralbumin" originates from blood and is not synthesized by the thyroid gland.

Studies on iron metabolism: I. Evidence of gastrointestinal dysfunction in infants withiron deficiency anemia: A preliminary report

<h2>Summary</h2> A preliminary study of a group of infantswith iron deficiency anemia has revealed evidence of occult gastrointestinal bleeding, precipitins to cow's milk, and the passage of serum proteins into gastric juice. These findings are strong evidence of gastrointestinal dysfunction. Guaiac-positive stools were found in 40per cent of the iron-deficient infants tested. Precipitins to cow's milk were found in 75 to 80 per cent of the iron-deficient subjects who were taking this food prior to diagnosis. This is regarded as an abnormal finding. Serum proteins in the fasting gastric juice were demonstrated in 12/13 of anemic subjects and in 2/12 of control subjects by means of agar diffusion techniques. Semiquantitative estimates of serum albumin, and gamma globulin in the gastric juice suggest a pathologic loss of these proteins in at least some anemic subjects. These findings suggest the existence of at least 2 forms of iron deficiency anemia in infants; two forms, that is, which are etiologically distinct. The first of these has been termed "primary iron deficiency"; the second is believed to depend on primary sensitization to cow's milk. Mechanisms have been proposed to explain the possible interrelationships of the causative factors in each group.