Approaches to reduce the glycemic response of gluten-free products: in vivo and in vitro studies.

This article aims to discuss the current approaches used to reduce the postprandial glycemic response (GR) of starchy gluten-free products (GFP) and to provide some further prospects. The GR is evaluated through in vivo trials to determine the glycemic index (GI) and the glycemic load (GL) of foods or using the in vitro starch digestibility method to predict the GI. The reviewed studies demonstrated that a reduction in the GR of GFP can be achieved by replacing traditionally used refined flours and starches with nutrient-dense alternative raw materials due to an increase in dietary fiber, resistant starch and protein contents, which can alter the rate of starch digestion, reduce the GI and dilute the amount of available carbohydrate; both the factors contribute to reduce the GL. The addition of viscous dietary fibers could also be a successful way to reduce the GR of GFP. Some studies have demonstrated the potential of germination of GF grains and sourdough fermentation in decreasing the GR of GF bread. Further studies could evaluate alternative GF flours, soluble fibers, resistant starch, and other formulation factors that may affect the GR of different types of GFP. New studies should be performed to test and optimize processing methods by considering the reduction of GR of GFP. Another key aspect for further investigation is the confirmation of the promising results obtained through in vitro assays by in vivo GI evaluation.

Recovery and upgrading bovine rumen protein by extrusion: effect of lipid content on protein disulphide cross-linking, solubility and molecular weight.

Bovine rumen protein with two levels of residual lipids (1.9% or 3.8%) was subjected to thermoplastic extrusion under different temperatures and moisture contents. Protein solubility in different buffers, disulphide cross-linking and molecular weight distribution were determined on the extrudates. After extrusion, samples with 1.9% residual lipids content had a higher concentration of protein insoluble by undetermined forces, irrespective of feed moisture and processing temperature used. Lipid content of 3.8% in the feed material resulted in more protein participating in the extrudate network through non-covalent interactions (hydrophobic and electrostatic) and disulphide bonds. A small dependency of the extrusion process on moisture and temperature and a marked dependency on lipid content, especially phospholipid, was observed, Electrophoresis under non-reducing conditions showed that protein extrusion with low feed moisture promoted high molecular breakdown inside the barrel, probably due to intense shear force, and further protein aggregation at the die end.

Cholesterol-lowering properties of whole cowpea seed and its protein isolate in hamsters.

Hypercholesterolemic hamsters were fed for 4 wk on diets rich in saturated fatty acids and cholesterol, differing only in protein source (20 %): casein (control group, HC), whole cowpea seed (HWS), and cowpea protein isolate (HPI). Hamsters fed on HWS and HPI presented significant reductions in plasma total cholesterol and non-HDL cholesterol. HPI and HC presented similar protein digestibility, which were significantly higher than that of HWS. Animals fed on HWS presented significantly higher levels of bile acids and cholesterol in feces than did the animals fed on casein or HPI diets. Histological analyses of the liver showed that HC diet resulted in steatosis widely distributed throughout the hepatic lobule, while HWS and HPI diets promoted reductions in liver steatosis. The effectiveness of HWS for modulating lipid metabolism was greater than that of HPI, as measured by plasma cholesterol reduction and liver steatosis.

Effects of processing methods on amaranth starch digestibility and predicted glycemic index.

Amaranth has attracted a great deal of interest in recent decades due to its valuable nutritional, functional, and agricultural characteristics. Amaranth seeds can be cooked, popped, roasted, flaked, or extruded for consumption. This study compared the in vitro starch digestibility of processed amaranth seeds to that of white bread. Raw seeds yielded rapidly digestible starch content (RDS) of 30.7% db and predicted glycemic index (pGI) of 87.2, the lowest among the studied products. Cooked, extruded, and popped amaranth seeds had starch digestibility similar to that of white bread (92.4, 91.2, and 101.3, respectively), while flaked and roasted seeds generated a slightly increased glycemic response (106.0 and 105.8, respectively). Cooking and extrusion did not alter the RDS contents of the seeds. No significant differences were observed among popped, flaked, and roasted RDS contents (38.0%, 46.3%, and 42.9%, respectively), which were all lower than RDS content of bread (51.1%). Amaranth seed is a high glycemic food most likely because of its small starch granule size, low resistant starch content (< 1%), and tendency to completely lose its crystalline and granular starch structure during those heat treatments.

Dependence of the interfacial behavior of beta-casein on phosphoserine residues.

The role of the phosphoserine residues on the dynamical and structural properties of beta-casein was studied by molecular dynamics of the protein in water/lipid interfacial regions. The initial protein structure adopted in the modeling was that proposed for bovine beta-casein A2, where the five phosphoserine residues, originally present in its primary structure, were partially or totally substituted by serine residues. The simulations revealed a dependence of the interfacial behavior of beta-casein on the phosphorylation grade. When only partially dephosphorylated, the protein showed a similar behavior as that observed for the original beta-casein reported in previous work. During dynamics, the protein migrated from the aqueous environment towards the lipid medium, and remained attached to the interface separating both media. Quite different was the dynamics of the totally dephosphorylated beta-casein, that did not perceive the interface and immersed incessantly into lipid medium. The results suggest that the phosphoserine residues appear to be, in fact, intrinsically related to the mechanisms of beta-casein emulsion stabilization.

Interaction of a type II myosin with biological membranes studied by 2H solid state NMR.

Deuterium nuclear magnetic resonance spectroscopy (2H NMR) has been employed to investigate the interaction of lung type II myosin protein with neutral bilayers containing dimyristoylphosphatidylcholine (DMPC) as the only constituent and mixed bilayers containing the negatively charged lipid dimyristoylphosphatidylglycerol (DMPG). DMPC was deuterated at its headgroup by substituting the four protons at the alpha- and beta-positions (DMPC-d4) and the nine protons at the gamma-position (DMPC-d9). DMPG was perdeuterated at its headgroup (DMPG-d5). No changes were observed in the quadrupole splittings or spin-lattice relaxation times for the deuterated DMPC headgroup segments when increasing amounts of myosin were added to liposomes, made exclusively of DMPC-d9 or of DMPC-d4. However, upon the insertion of the negatively charged lipid DMPG at 1:1 molar ratio into the DMPC bilayers, myosin was found to interact electrostatically with the liposomes, thereby affecting significantly both the quadrupole splittings and spin-lattice relaxation rates of the alpha-, beta-, and gamma-deuterons in labeled DMPC. Monitoring DMPG-d5 in mixed DMPC/DMPG bilayers revealed a direct electrostatic interaction of DMPG with the protein, where positively charged lysine residues located at the tail domain of myosin provide the necessary sites for the interaction to occur. When ATP and Mg2+ were complexed to the head domain of myosin, a reduced interaction with the negatively charged bilayers was observed. The results clearly indicate that a type II myosin can interact with membranes without the need for a specific hydrophobic domain or an anchor in the protein molecule, provided that negatively charged lipids are present in the bilayer.

Effect of electrical stimulation on post mortem biochemical characteristics and quality of Longissimus dorsi thoracis muscle from buffalo (Bubalus bubalis).

High voltage electrical stimulation (700 V, 1400 V peak, pulses 1 s on/1 s off, 60 Hz, 2 A) on buffalo carcasses resulted in a significantly more rapid pH fall in Longissimus dorsi thoracis muscle when compared to non stimulated controls (p < 0.01), during the first 24 h after slaughter. The IMP ATP ratio on the same period showed a much more rapid increase for the stimulated muscles (1.07 and 1.16 at times 1 and 2.5 hpost mortem vs control values of 0.77 and 0.83, respectively). Sensory and instrumental evaluation of texture of meat cooled by two distinct processes showed that tenderness at 24 hpost mortem was higher in the stimulated muscles compared to non-stimulated controls, irrespective of the cooling process adopted. High voltage stimulation significantly decreases cohesiveness, increases myofibril fragmentation; and SDS polyacrylamide gel electrophoresis of the myofibrillar proteins showed a weakening of Troponin T band during 6 days of ageing in non-stimulated control muscles, whereas electrical stimulation accelerated the process of ageing over 3 days. This is the first report on acceleration of conditioning in buffalo muscle and the conditions described here have a high potential for application in meat industry for buffalo slaughter.

Extrusion of food proteins.

Protein extrusion has frustrated earlier predictions regarding its impact in the development of food products. The main reason for this disappointing performance has been its failure to yield fabricated food products with textural quality close enough to that of natural products at competitive prices. Texturized soya protein by extrusion is presently the only commercial success in this area, being incorporated into several convenience products, increasing their protein content and quality and conferring them some desirable sensory properties. Technological and scientific gaps in the extrusion texturization are still to be bridged if this technique is to be applied for upgrading unconventional protein. The precise mechanisms responsible for protein texturization through extrusion are still unclear. Proteins show a very wide range of extrusion behavior that is probably related to large differences in their association properties. New peptide bonds, formed by free amino and carboxylic groups of the protein, were postulated as being responsible for the cross-linking that takes place in protein extrusion. However, disulfide bonds and electrostatic and hydrophobic interactions are regarded presently as the texturization mechanism in this process. The recently suggested suspension (or filled "melt") model for biopolymer extrusion offered a new framework for testing extrusion of novel proteins. According to this view, the large differences between the association properties of proteins produce different types of aggregates. Some of them can be insoluble under extrusion conditions and act as a dispersed phase within the melt phase. The extrusion performance of a protein will thus depend on the amount of insoluble aggregate produced inside the extruder and on protein-protein interactions that occur after the superheated molten mass leaves it.

Correlation of renal organic anion and cation transport with blood pressure in SHR.

In 1974, we found that sera from SHR suppressed renal PAH transport (PSEBM 145:97, 1974). Since a "natriuretic factor" depresses PAH as well as Na transport, we proposed that "natriuretic factor" was elevated in SHR. Our current investigation amplifies the previous study. On a given day, one spontaneously hypertensive rat (SHR) and one rat from a normotensive strain [Wistar Kyoto (WKY) or Sprague-Dawley (SD]) were examined together. SHR sera compared to WKY/SD sera significantly depress PAH (organic anion) and TEA (organic cation) uptake by rat renal slices. The ability of SHR sera to depress uptake correlated significantly with the BP: the sera with the greatest depressive influence on renal PAH and TEA uptake came from the SHR with the highest BP (PAH r = 0.89, p less than 0.0001; TEA = r = 0.76, p less than 0.01). Subsequent separation of serum on Sephadex 25 localized the factor to the same fraction as "natriuretic hormone". A similar correlation was found between the ability of the fraction to depress the 2 transports and the height of the BP. The serum factor did not inhibit ATPase activity. In contrast to the serum effects, renal slices removed from SHR showed increased rather than decreased PAH and TEA transport which significantly correlated with the BP. The slices with the highest uptakes came from the SHR with the highest BP. The high uptake of organic ions by the SHR renal slices could be an adaptive response to the serum factor or vice versa. We postulate that a serum factor which depresses PAH and TEA transport and is not "ouabain-like" may play a role in the BP elevation of SHR.

Toxocariasis: sindrome de larva migrans, con especial referencia a cinco casos de localización ocular / Toxocariasis: larva migrans syndrome with special reference to five cases of ocular alocalization

Los autores presentan cinco casos de Toxocariasis ocular, cuatro de elllos con test de ELISA positivos con títulos variables entre 1/8 y 1/32. Tres niñas y dos varones con edades extremas entre los 8 y los 59 años de edad. Ninguno de los casos presentó previamente manifestaciones imputables a alguna localización del Síndrome de Larva Migrans Visceral. Todos coincidentemente presentaron su localización en el ojo izquierdo; con una evolución entre pocos meses a diez años. Tanto el Caso N§1, como el N§3 y el N§5 presentaron la forma clínica N§3 de la clasificación adoptada por Wilkinson y Col. (23). El Caso N§2 de nuestro casuística correspondería a la forma clínica N§2 del autor citado anteriormente; aunque casuística correspondería a la forma clínica N§2 del autor citado anteriormente; y el Caso N§4 podría equipararse al descripto por Gass (11) en 1978 como un Síndrome de Neuroretinitis Unilateral Subaguda Difusa, y que en 1983 demostró que el síndrome era causado por la larva del toxocara en forma directa o por su acción tóxica. Todos recibieron medicación con Thiobendazole entre 25 a 50 mg/Kg/día, asociado a prednisolona entre 40 a 60 mg/día. Un solo caso mostró intolerancia a la primera droga lo que abligó a suspender la medicación. Solo los casos N§1 y N§4 demostraron una mejoría evidente de la agudeza visual, en el último de ellos se sumó además la desaparición total de la sintomatología. En ninguno de los casos apareció leucocitosis; ni eosinofilia significativa (salvo en el caso N§1). Un solo paciente residía en el medio rural (Caso N§1) y otro en zonas periféricas de la ciudad (Caso N§3). Ccontacto evidente y franco con cachorros lo presentaron los casos N§1, N§2 y N§3. Casos N§4 y N§5 contacto ocasional con perros. Casos N§1 y N§3 antecedentes de geofagia

Toxocariasis: sindrome de larva migrans, con especial referencia a cinco casos de localización ocular / Toxocariasis: larva migrans syndrome with special reference to five cases of ocular alocalization

Los autores presentan cinco casos de Toxocariasis ocular, cuatro de elllos con test de ELISA positivos con títulos variables entre 1/8 y 1/32. Tres niñas y dos varones con edades extremas entre los 8 y los 59 años de edad. Ninguno de los casos presentó previamente manifestaciones imputables a alguna localización del Síndrome de Larva Migrans Visceral. Todos coincidentemente presentaron su localización en el ojo izquierdo; con una evolución entre pocos meses a diez años. Tanto el Caso Nº1, como el Nº3 y el Nº5 presentaron la forma clínica Nº3 de la clasificación adoptada por Wilkinson y Col. (23). El Caso Nº2 de nuestro casuística correspondería a la forma clínica Nº2 del autor citado anteriormente; aunque casuística correspondería a la forma clínica Nº2 del autor citado anteriormente; y el Caso Nº4 podría equipararse al descripto por Gass (11) en 1978 como un Síndrome de Neuroretinitis Unilateral Subaguda Difusa, y que en 1983 demostró que el síndrome era causado por la larva del toxocara en forma directa o por su acción tóxica. Todos recibieron medicación con Thiobendazole entre 25 a 50 mg/Kg/día, asociado a prednisolona entre 40 a 60 mg/día. Un solo caso mostró intolerancia a la primera droga lo que abligó a suspender la medicación. Solo los casos Nº1 y Nº4 demostraron una mejoría evidente de la agudeza visual, en el último de ellos se sumó además la desaparición total de la sintomatología. En ninguno de los casos apareció leucocitosis; ni eosinofilia significativa (salvo en el caso Nº1). Un solo paciente residía en el medio rural (Caso Nº1) y otro en zonas periféricas de la ciudad (Caso Nº3). Ccontacto evidente y franco con cachorros lo presentaron los casos Nº1, Nº2 y Nº3. Casos Nº4 y Nº5 contacto ocasional con perros. Casos Nº1 y Nº3 antecedentes de geofagia (AU)

Development of sugar-induced blood pressure elevation after uninephrectomy in a resistant rat strain.

Certain rat strains acutely increase blood pressure (BP) when given diets high in NaCl. Prior results showed that "salt-sensitive" rat strains, at least the ones studied, also increase BP in response to sugar loading. To examine this relationship further and learn more about the pathogenesis of sucrose-induced BP elevations, we examined the effects of unilateral nephrectomy (uninephrectomy) on sucrose-induced BP changes. The rationale is based upon the findings that renal mass removal sensitizes BP response to salt loading. Over 15 weeks, augmented sugar (sucrose) consumption by Long-Evans (LE) rats did not increase BP markedly compared to rats consuming a diet relatively low in sugar unless uninephrectomy was performed. The differences in BP caused by the high sugar diet in a uninephrectomized rat could not be explained adequately by alterations in catecholamine excretion, plasma renin activity, excesses in blood volume, or the other parameters examined. However, salt-induced hypertension has been attributed to the presence of circulating substances affecting ion transport. Among the dietary groups, there was a significant correlation between the ability of plasma to depress PAH and TEA renal slice uptake and the difference in BP. This is consistent with the presence of a circulating factor affecting cell transport that has its greatest activity in the high sugar-uninephrectomy group of LE rats. We conclude that reducing renal mass potentiates sugar-induced BP elevation similar to salt-induced BP elevation in a normally resistant rat strain, and the rise of BP may be caused by a circulating factor.

Blood pressure in unilaterally nephrectomized rabbits: a correlation with serum renotropic activity.

Over 40 years ago, Grollman reported that unilateral nephrectomy (UN) in rabbits precipitated hypertension and suggested that liberation of a pressor substance by an ischemic or damaged kidney could not be causative. Because others were unable to corroborate that UN in rabbits led to increased blood pressure (BP), we followed 7 rabbits after UN and 4 rabbits after a sham operation. At 7-10 days postoperatively, BP increased from the baseline average of 83 to an average of 97 mm Hg in the UN rabbits (p less than 0.01). In contrast, BP did not change significantly after sham operation. Measurements of blood chemistries, serum insulin levels and digoxin-like substances showed no significant changes after UN which would explain the BP rise, but plasma renin activity (PRA) rose from 11.4 to 30.3 ng/ml/h, (p less than 0.05). However, similar elevations occurred in sham-operated rabbits that showed no significant change in BP, i.e. 10.6-26.2 ng/ml/h. Measurement of serum renotropic activity after UN, but not after sham operation, also showed a significant elevation above baseline 97.6% (p less than 0.001). The renotropic activity 7-10 days after UN unlike PRA correlated significantly with the changes in BP (r = 0.87, p less than 0.001). We conclude that BP rises after UN in rabbits, confirming Grollman's findings. The correlative rise in BP and serum renotropic activity may play an important role in the BP elevation after UN.

Long-term effects of excess sucrose ingestion on three strains of rats.

We placed groups of spontaneously hypertensive rats (SHR), Wistar-Kyoto rats (WKY) and a local strain of normotensive Wistar rats on 5 different diets. Our baseline diet (I) derived a near equal number of calories from sucrose, proteins and fats, ie, 1/3 of total calories was provided by each macronutrient. Two other diets (II,III) derived the majority of calories from sucrose with less calories from proteins or fats respectively. The last two diets (IV,V) were relatively low in sucrose with a higher percentage of the total calories from proteins or fats respectively. The rats were assigned to the special diets at 3 months of age. They have now been ingesting these diets a total of 12 months. In SHR, the diets highest in sucrose calories (II,III), in contrast to diets I,IV and V, were associated with a markedly increased blood pressure (BP) at 3 months. The difference of approximately 20 to 30 mm Hg has held over 12 months. In contrast, the normotensive Wistar rats consuming diets II and III showed significant differences in BP (approximately 10 mm Hg) only after 12 months. The response of WKY was intermediate. Some clearcut elevation of BP, although not statistically significant, in WKY consuming diets II and III was present by 3 months. This difference became greater with time (20 mm Hg at 12 months). Consistent changes in body weights between the rats on the different diets were lacking. We conclude that excess ingestion of sucrose can cause chronic elevations in BP, the pattern of which varies among rat strains.

Excess sucrose and glucose ingestion acutely elevate blood pressure in spontaneously hypertensive rats.

Spontaneously hypertensive rats (SHR) were fed 6 different diets. The baseline diet (I) derived equal calories from sucrose, proteins, and fats. Three other diets (II, III, VI) derived the majority of calories from refined CHO, sucrose or glucose, with decreases in calories from proteins or fats. The last two diets (IV, V) were relatively low in sucrose with a higher percentage of the total calories from proteins and fats, respectively. From 3 to 15 weeks on the diets, the highest average BP was in rats consuming high concentrations of sucrose or glucose (II, III, VI). Urinary excretory rates of norepinephrine (NE) at 5, 10 and 15 weeks and epinephrine at 5 and 10 weeks were significantly elevated in rats ingesting diets high in refined CHO, and NE positively correlated with blood pressure (BP) at 5 and 10 weeks of the study. At the end of the study, serum insulin levels were not different, but plasma renin and serum glucagon levels were lower in SHR consuming the diets with high CHO concentrations. We conclude that equally elevated BP are seen with relatively high intakes of either sucrose or glucose, whether the balance of calories is derived from lessening fat or protein. This is secondary, at least in part, to alterations in NE metabolism.

Effect of sodium and potassium ingestion on renal growth in rats.

To determine whether differences in dietary Na and K intake influence renal growth and compensatory renal growth following unilateral nephrectomy (uni), rats were given 2 diets for 2 weeks which differed only in Na-K concentrations. Diet 1 (High Na, Low K) contained 1.0% Na, 0.36% K and diet 2 (Low Na, High K) contained 0.05% Na, 2.0% K. Half of the rats consuming diets 1 and 2 for 1 week received uni and the other half of sham operation (sham). The rats were followed for another week while consuming the experimental diets. Uni and sham rats on diet 1 showed significant increase in blood pressure (BP) (136 +/- 4 v 126 +/- 3 mm Hg, P less than .05). Uni itself did not alter blood pressure. Body weight and heart rate were unchanged by diet or operation. Kidney weight, renal RNA, protein, RNA/DNA, and protein/DNA increased significantly after uni but the differences were not affected by diet. Serum blood urea nitrogen (BUN) and creatinine were not markedly different among any group of rats suggesting no major renal damage. We conclude that dietary changes of Na-K which cause no obvious renal damage even though BP is elevated moderately do not influence renal growth or compensatory renal growth. Based on RNA, DNA and protein metabolism, the form of growth (hypertrophy or hyperplasia) is also not influenced by renal electrolyte handling.

Influence of oat bran on sucrose-induced blood pressure elevations in SHR.

To determine whether oat fiber influences BP, we gave spontaneously hypertensive rats (SHR) a diet high in sucrose and low in protein (calories: sucrose 52%, protein 15%, fat 33%) or a diet low in sucrose and high in protein (calories: sucrose 13%, protein 52%, fat 35%). The amount of fat in these particular diets has not been shown to influence BP, so we modified the 2 diets by replacing fat with oat bran (10% w/w). Accordingly, we examined 4 groups of 5 rats consuming different diets: high sucrose, high sucrose + oat bran, low sucrose, and low sucrose + oat bran. Not unexpectedly, SHR consuming the diet high in sucrose had a significantly higher BP after 2 weeks than those consuming the diet low in sucrose. The significant difference in BP continued over the next 3 weeks. At the end of 6 week duration of study, we found the following BP: SHR ingesting the high sucrose diet, 217 mm Hg +/- 5 (SEM) vs SHR consuming the low sucrose diet, 187 mm Hg +/- 4 (SEM) p less than .0001]. SHR eating the low sucrose diet and consuming supplemental bran showed no significant change in BP after 6 weeks compared to SHR eating the basic diet alone, 188 mm Hg +/- 6 (SEM); however, 5 SHR consuming the high sucrose diet with added oat bran showed a significantly lower BP 200 mm Hg +/- 2 (SEM) than SHR ingesting the basic high sucrose diet devoid of oat bran [p less than .01]. We conclude that addition of oat bran to the diet can ameliorate sucrose-induced BP elevations in SHR.

Lung proteins: effect of defatting with several solvents and extrusion cooking on some functional properties.

Dried lung defatted with several solvents was texturized by extrusion cooking. The emulsifying capacity, water absorption capacity, and protein solubility, at different pH and MgCl(2) concentrations, of this material were determined prior to the after extrusion, as well as the texture profile analysis of the rehydrated extrudates. Solubility profile and emulsifying capacity of the lung proteins varied in relation to the solvent used in their defatting while the water absorption capacity was not affected. The extrusion of these materials promoted a higher solubilization of the protein fraction. The texture parameters of the extrudates studied and the solvent used to defat this material are related, indicating that the lipid-protein complex, left after solvent extraction, may play an important role in the texturization processof lung proteins.

Presence of a serum vasoconstrictive factor following unilateral nephrectomy.

Experimental hypertension is often associated with decreased renal mass and/or impediments to normal renal compensatory growth. This has led to the hypothesis that the renal growth factor (renotropin) is also a vasoconstrictor responsible for elevated blood pressure. Unilateral nephrectomy (uni) is the most popular mechanism to investigate compensatory renal growth. Accordingly, we examined the vasoconstrictive potential of rat sera following uni in order to compare it with serum renotropic activity. Compared to sham-operated (sham) rat sera, uni sera obtained at 24 hours after operation, a point in time when renotropic activity is highest, stimulated the constriction of isolated rat aortic rings significantly more than sham sera, and in a dose-dependent fashion. By paired analysis, the differences in constriction between uni and sham sera were significant at all doses examined. Unlike those obtained at 24 hours, uni sera did not show this response 48 hours, 1 week and 2 weeks after operation, simulating the temporal course of renotropin found in sera after uni. The uni serum factor was not influenced by dialysis suggesting that its molecular weight exceeds 6,000 daltons and that the vasoconstrictive response was not due to electrolyte differences between uni and sham sera. Vasoconstrictive activity was retained after serum passage through Affi-gel blue to remove albumin and after serum was heated in boiling water for 5 minutes. We conclude that a heat resistant serum vasoconstrictive factor with a molecular weight greater than 6,000 daltons arises shortly after uni but disappears once the remaining kidney begins to undergo a physiological compensatory growth response.