A follow-up on quantitative and qualitative olfactory dysfunction and other symptoms in patients recovering from COVID-19 smell loss.

BACKGROUND: Sudden smell loss is a specific early symptom of COVID-19, which, prior to the emergence of Omicron, had estimated prevalence of ~40% to 75%. Chemosensory impairments affect physical and mental health, and dietary behavior. Thus, it is critical to understand the rate and time course of smell recovery. The aim of this cohort study was to characterize smell function and recovery up to 11 months post COVID-19 infection. METHODS: This longitudinal survey of individuals suffering COVID-19-related smell loss assessed disease symptoms and gustatory and olfactory function. Participants (n=12,313) who completed an initial survey (S1) about respiratory symptoms, chemosensory function and COVID-19 diagnosis between April and September 2020, were invited to complete a follow-up survey (S2). Between September 2020 and February 2021, 27.5% participants responded (n=3,386), with 1,468 being diagnosed with COVID-19 and suffering co-occurring smell and taste loss at the beginning of their illness. RESULTS: At follow-up (median time since COVID-19 onset ~200 days), ~60% of women and ~48% of men reported less than 80% of their pre-illness smell ability. Taste typically recovered faster than smell, and taste loss rarely persisted if smell recovered. Prevalence of parosmia and phantosmia was ~10% of participants in S1 and increased substantially in S2: ~47% for parosmia and ~25% for phantosmia. Persistent smell impairment was associated with more symptoms overall, suggesting it may be a key marker of long-COVID illness. The ability to smell during COVID-19 was rated slightly lower by those who did not eventually recover their pre-illness ability to smell at S2. CONCLUSIONS: While smell ability improves for many individuals who lost it during acute COVID-19, the prevalence of parosmia and phantosmia increases substantially over time. Olfactory dysfunction is associated with broader persistent symptoms of COVID-19, and may last for many months following acute COVID-19. Taste loss in the absence of smell loss is rare. Persistent qualitative smell symptoms are emerging as common long-term sequelae; more research into treatment options is strongly warranted given that even conservative estimates suggest millions of individuals may experience parosmia following COVID-19. Healthcare providers worldwide need to be prepared to treat post COVID-19 secondary effects on physical and mental health.

Effects of diethylnitrosamine on hepatic receptor binding and autophosphorylation of epidermal growth factor and insulin in rats.

Carcinogen-mediated alterations in hepatic membrane growth factor receptor activity were investigated with the use of the hepatocarcinogen diethylnitrosamine [(DENA) CAS: 55-18-5]. For the separate assessment of carcinogen-induced acute membrane receptor changes from changes associated with carcinogen-mediated alterations in growth, the receptor activity was measured both acutely after, and several months after, a single ip dose of DENA in male F344 rats. An acute dose-dependent decrease was observed in ligand binding and autophosphorylation of the epidermal growth factor (EGF) and insulin receptor. Binding decreased sharply by 36 hours and recovered by 30 days in Golgi fractions and more slowly in plasma membranes. Scatchard analysis revealed a decrease in receptor number but not affinity. Chronic DENA administration also decreased insulin and EGF binding. Hepatocellular carcinomas, induced by single DENA injections 1 year previously, had decreased EGF receptor binding and autophosphorylation compared to those seen in age-matched controls and also less extensive insulin receptor changes. Single DENA doses thus have two effects: an acute reversible receptor change and a delayed, apparently permanent change associated with altered growth.

Binding of epidermal growth factor and insulin and the autophosphorylation of their receptors in experimental primary hepatocellular carcinomas.

Experimental chemical hepatocellular carcinomas that were induced in male F344 rats using three different regimens of limited exposure to the carcinogens 2-acetylaminofluorene or diethylnitrosamine were characterized by very low (as compared to peritumorous or normal tissues) binding of epidermal growth factor and decreased autophosphorylation of the epidermal growth factor receptors. Similar changes were also found in the insulin receptors. We suggest that the carcinogens 2-acetylaminofluorene and diethylnitrosamine cause an initial chemical effect on the great majority of cells. Most of them with time recover their receptor function, and only a small minority become truly initiated and retain these changed characteristics up to the tumor stage. The observed changes appear to be associated with the altered growth state induced by chemical carcinogens. Simultaneous changes observed in the two receptors raise the possibility of a common underlying mechanism.

Insulin and epidermal growth factor receptors in rat liver after administration of the hepatocarcinogen 2-acetylaminofluorene: ligand binding and autophosphorylation.

The livers of male F344 rats which were fed 0.02% 2-acetylaminofluorene (2-AAF) for two days or more had decreased binding of insulin and epidermal growth factor (EGF) to their hepatic receptors in microsomal and Golgi fractions. Hepatic receptors which were partially purified from carcinogen-fed rats by Triton X-100 solubilization and wheat germ agglutinin affinity column chromatography also had decreased binding activity compared to receptors from normal rats. Scatchard analysis indicated that the decrease in insulin receptor binding was due to decreased receptor number whereas the change in EGF receptor binding was attributed to decreased receptor affinity. Insulin receptor phosphokinase activity was also decreased in 2-AAF-fed rats and correlated with the decrease in receptor binding. EGF receptor phosphokinase activity was unchanged in 2-AAF-fed rats when stimulated with a high concentration (1 microM) of EGF but was decreased when stimulated with low concentrations (0.01-0.1 microM) of EGF. No EGF or insulin competing activity for receptor binding was found using acid-ethanol extracts of 2-AAF-altered liver. These results suggest that 2-AAF causes different alterations in the insulin and EGF receptors of the rat liver.

Chromium-associated 32P-labeling of proteins.

The incubation of proteins with chromium (Cr3+ or Cr6+) in the presence of 32P ([gamma-32P]ATP or H3(32)PO4) at room temperature for 10-30 min resulted in the labeling of these proteins with 32P. The 32P-labeled proteins could be separated by SDS-polyacrylamide gel electrophoresis and identified by exposure to X-ray film. The characteristics of this procedure included: the optimal chromium concentration was 100 microM; the minimum requirement of each protein was 1 microgram; the optimal pH value was between 6 and 8; metal ions such as V5+, Mn2+ and Fe3+ strongly inhibited the effect of chromium, whereas Ca2+ and Mg2+ had little effect. It was concluded that chromium binds to the proteins and forms a complex with 32P to achieve the 32P-labeling of the proteins. This technique can be applied for the rapid preparation of 32P labels on protein markers for gel electrophoresis and for the identification of unknown protein species.

Purification, partial characterization, and immunological relationships of multiple low molecular weight protease inhibitors of soybean.

Five protease inhibitors, I--V, in the molecular weight range 7000--8000 were purified from Tracy soybeans by ammonium sulfate precipitation, gel filtration on Sephadex G-100 and G-75, and column chromatography on DEAE-cellulose. In common with previously described trypsin inhibitors from legumes, I--V have a high content of half-cystine and lack tryptophan. By contrast with other legume inhibitors, inhibitor II contains 3 methionine residues. Isoelectric points range from 6.2 to 4.2 in order from inhibitor I to V. Molar ratios (inhibitor/enzyme) for 50% trypsin inhibition are I = 4.76, II = 1.32, III = 3.22, IV = 2.17, V = 0.97. Only V inhibit chymotrypsin significantly (molar ratio = 1.33 for 50% inhibition). The sequence of the first 16 N-terminal amino acid residued of inhibitor V is identical to that of the Bowman-Birk inhibitor; all other observations also indicate that inhibitor V and Bowman-Birk are identical. The first 20 N-terminal amino acid residues of inhibitor II show high homology to those of Bowman-Birk inhibitor, differing by 1 deletion and 5 substitutions. Immunological tests show that inhibitors I through IV are fully cross-reactive with each other but are distinct from inhibitor V.

C-peptide in NIDDM. Follow-up for 4-6 yr.

OBJECTIVE: To study whether fasting and 1-h postbreakfast C-peptide levels in NIDDM stabilize with time in individual patients. RESEARCH DESIGN AND METHODS: Within the period of 4-6 yr, 49 NIDDM patients had repeated tests of fasting and 1-h postprandial levels of plasma glucose and C-peptide with the aim of determining their individual qualitative patterns. Throughout the follow-up period, 13 patients were treated with insulin, 21 with oral sulfonylureas, and 15 were switched from oral drugs to insulin, with the tests done in both treatment periods. RESULTS: The group as a whole demonstrated no changes in mean fasting or postprandial C-peptide within 4-6 yr of observation, irrespective of the mode of therapy or its changes. Glycemic and C-peptide response to breakfast was qualitatively typical for each patient with the correlation between plasma glucose and C-peptide. However, the response was vastly different from patient to patient, and the cross-sectional data showed no correlation between postprandial changes in glycemia and C-peptide, nor between glycemic response to breakfast and fasting plasma glucose or C-peptide. In spite of high fasting glycemia, 25% of the patients showed remarkable tolerance to breakfast with only small increases in plasma glucose. In many other patients, however, in spite of similar increase in C-peptide, plasma glucose rose sharply after the meal. CONCLUSIONS: In our group, no deterioration of the insulin secretory function was observed within 4-6 yr of follow-up. Qualitative patterns of the glycemic and C-peptide responses to breakfast were typical for each patient but vastly different between patients. We see in NIDDM a syndrome with few common characteristics and recommend further work for its subclassification into forms with different pathogenesis.

Effects of enalapril and nitrendipine on the excretion of epidermal growth factor and albumin in hypertensive NIDDM patients.

OBJECTIVE: To compare the effect of the antihypertensive drugs nitrendipine and enalapril on the excretion of epidermal growth factor (EGF) and albumin in hypertensive non-insulin-dependent diabetes mellitus (NIDDM) subjects. RESEARCH DESIGN AND METHODS: After a 4-week washout period, mildly hypertensive (systolic blood pressure [sBP] > or = 140 mmHg and/or diastolic blood pressure [dBP] > or = 90 mmHg) NIDDM patients with albuminuria (15-200 micrograms/min) were randomized into an 8-month-long therapy with either nitrendipine (n = 11) or enalapril (n = 10). Blood pressure, EGF, and microalbumin excretion were measured at baseline and throughout the treatment period. RESULTS: A significant fall in sBP was noticed in the enalapril group and in dBP in the nitrendipine group. In the enalapril group, EGF excretion progressively increased from 188 to 214 nmol/mmol creatinine after 6 weeks and to 274 after 8 months of therapy (P = 0.03). There was a significant fall in albumin excretion while patients were on enalapril, but in the nitrendipine group, neither albuminuria nor EGF excretion changed significantly. There was no correlation of improved EGF excretion with a decrease in albuminuria or BP. CONCLUSIONS: The angiotensin-converting enzyme inhibitor enalapril has been effective in decreasing albumin and increasing EGF excretion. Measurement of urinary EGF may provide a new valuable index of renal function.

Effect of corticosterone on carbamylcholine-, leucine-, or calcium-induced insulin secretion by the isolated perfused rat pancreas.

Using the isolated pancreas of male Sprague-Dawley rats, three different concentrations of glucose were tested in the perfusion medium: 4.0, 6.7, and 9.4 mM. The insulinotropic effects of several potent secretagogues were examined with and without a 10(-7)-M corticosterone-21-acetate (CS) background. When the perfusion medium contained 4.0 mM glucose, there was no insulin secretion in the basal state, but 10(-6)M carbamylcholine chloride, 5 mM L-leucine, and 5 mM calcium chloride elicited moderate but sharp responses of insulin output. When the secretagogues were superimposed on CS infusion, their stimulatory effects were abolished. When the perfusion medium contained 6.7 mM glucose, a steady insulin secretion was observed. A 4- to 5-fold stimulation of insulin release was elicited by carbamylcholine, leucine, and calcium. With CS in the perfusate, the secretagogues were ineffective. However, at a higher glucose level (9.4 mM), the stimulants could partially escape the inhibitory effects of CS. It is concluded that CS may play a role in the regulation of insulin output by directly modulating the activities of some potent secretagogues.

Binding of growth hormone to rat liver during experimental chemical hepatocarcinogenesis.

Male F-344 rats (180-200 g) received either a single injection of diethylnitrosamine (DEN) or continuous feeding with 2-acetylaminofluorene (AAF). DEN induced a decrease in the binding of human GH (hGH) to its hepatic Golgi receptors in a dose-dependent manner; the changes were due to a decrease in the number of hGH receptors without significant changes in their affinity. Thirty days after DEN, the binding of hGH returned to normal. After the administration of AAF, the binding of hGH increased owing to the greater number of binding sites, and this effect persisted for the 30-day period of the continuous AAF feeding. In three separate hepatocellular carcinomas, the hGH binding to the Golgi fraction of the tumors was only one quarter of the binding to the peritumorous tissues. We conclude that DEN and AAF, administered acutely for a short time, affect hepatic hGH receptors in a different way, but that hepatocellular carcinomas bind much less hGH than peritumorous or normal tissues. The results show that hepatocarcinogenesis encompasses changes in receptors belonging to different classes.

Insulin increases intracellular magnesium transport in human platelets.

Evidence suggests that magnesium (Mg) deficiency may play a key role in cardiovascular disease. In particular, Mg deficiency may lead to a potentiation of platelet aggregation. However, the factor(s) regulating intracellular-free Mg concentration ([Mg2+]i) in platelets is not known. We studied the effects of insulin on the changes of [Mg2+]i in human platelets. Preincubation of hirudinized platelet-rich plasma with insulin had a dose- and time-dependent effect on the increase of [Mg2+]i measured in Mag-fura-2-loaded cells with a fluorescence spectrophotometer. The maximal effect was achieved by incubation with 200 microU/mL insulin for 30 min. [Mg2+]i increased from the basal value of 266 +/- 23 mumol to 355 +/- 46 (SD, P < 0.001). In the presence of an antiinsulin receptor monoclonal antibody the effect of insulin was abolished suggesting that the Mg transport mechanism was an insulin-receptor mediated process. Furthermore, the insulin-stimulated Mg transport was inhibited by the addition of chelating agent ethylenediaminete-traacetate while the receptor binding was not altered. These findings suggest that insulin can translocate Mg from the extracellular space. Insulin alone had no effect on the changes of intracellular calcium (Ca) concentration using Ca-Fura-2 as a probe. In addition, glucose (5 mg/mL) was not effective in altering either the Mg or Ca concentration. Insulin (100 microU/mL) decreased thrombin-induced platelet aggregation (washed platelets resuspended in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-Tyrode buffer). Similarly, the production of the proaggregatory eicosanoids thromboxane B2 was inhibited by insulin from 16 +/- 1 ng/10(8) platelets to 13 +/- 2 (P < 0.05). The results suggest that insulin, through the interactions with its receptors may be a key factor regulating, Mg transport in human platelets.

Effect of extracellular magnesium on platelet activation and intracellular calcium mobilization.

A dose-dependent effect of magnesium on the inhibition of platelet aggregation and release of ATP from dense granules was observed in human platelets (in whole blood, platelet-rich plasma, or washed platelets) against various aggregation agents (ADP, U46619, collagen, or thrombin). The synthesis and release of the proaggregatory cyclooxygenase (CO) and lipoxygenase (LO) products, thromboxane A2 (TXA2) and 12-hydroxyeicosatetraenoic acid (12-HETE), respectively, in platelets were also inhibited by Mg in a dose-dependent manner (IC50 4 to 6 mmol/L). These Mg-mediated activities were further enhanced when platelets were preincubated with insulin (100 microU/mL). The effect of extracellular Mg on the change of intracellular calcium concentration ([Ca2+]i) was assessed using Fura-2/AM loaded cells in the presence or absence of extracellular Ca. Thrombin-stimulated influx of Ca ions decreased from 194 +/- 30 nmol/L to 156 +/- 21 nmol/L in the presence of 5 mmol/L Mg and to 111 +/- 16 nmol/L in 10 mmol/L Mg. However, the intracellular Ca release (as determined in the presence of 5 mmol/L EGTA) was not affected by Mg. The intracellular Ca-dependent protein kinase C and myosin light chain kinase activities on the phosphorylation of endogenous p47 and p20 proteins studied after 2 min of thrombin addition decreased only 10 to 25% in the presence of 5 to 10 mmol/L Mg. Similar results were obtained when EGTA was added prior to the initiation of protein phosphorylation. We conclude that Mg can dose dependently inhibit a wide variety of agonists on platelet aggregation. Furthermore, insulin can potentiate the inhibitory effects of Mg on platelet activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Infusion of epidermal growth factor in mice: organ distribution and urinary excretion.

Anesthetized mice were infused into the tail vein with 7.5% mannitol in saline (0.1 ml/min for 60 min) alone or with EGF at 0.5 microgram/min. Urine was collected every 10 min starting 20 min after the beginning of the infusion and ending 20 min after its termination. EGF concentration in the serum of mice infused with EGF increased from the baseline level of 0.6 +/- 0.4 to 70.7 +/- 16.0 ng/ml at 80 min. Total excretion of EGF for 80 min was 117 +/- 49 ng with mannitol alone and 1916 +/- 420 ng (6.4% of the EGF infused) after mannitol with EGF. Serum and urine EGF was indistinguishable from the native mouse EGF by its radioimmunoassay and HPLC characteristics. Intact labeled EGF was also found in urine when mice were infused with 125I-EGF (1 x 10(6) cpm/ml) in mannitol. After 5 min infusion with 125I-EGF (6 x 10(6) cpm/ml in saline), more than 80% of the label was found in the liver and kidneys and more than 90% of it was intact EGF. However, 30 min after infusion more than 95% of the labeled EGF was degraded. We conclude that at least part of the urinary EGF in mice originates in blood and that liver and kidneys are the main organs of EGF degradation.

Trauma, especially of the submandibular glands, causes release of epidermal growth factor into bloodstream in mice.

Submandibular glands in mice were traumatized by handling and then removed. Immunoreactive epidermal growth factor (EGF) in serum increased after 5 min and continued to increase, reaching at 1 h a peak of 50-fold normal in males and twice normal in females. If after traumatization the glands were repositioned with their blood supply intact, maximal increase of serum EGF at 1 h was 190-fold control values in males and 2-fold in females. In male mice, incision of abdominal wall skin led to a 15-fold increase of EGF in the serum; this rise was absent 3 days after sialoadenoectomy. After traumatization, repositioned submandibular glands lost 80% of their EGF; after the abdominal wall incision, only 30%. Following removal of submandibular glands, decrease of EGF level in serum was very slow: to 60% of the initial value after 3 days and to 40% after 10 days. By the HPLC characteristics, immunoreactive EGF in control serum and at its peak were indistinguishable. Urinary excretion of EGF was significantly elevated only when its serum level was 190-fold normal. We conclude that traumatized submandibular glands discharge into circulation a large part of their stored EGF. A similar but much less pronounced process takes place after abdominal skin incision. The presence of EGF in serum after its slow decline in sialoadenoectomized mice shows that a fraction of circulating EGF may recirculate prolonging its apparent half-life.

Release of different fractions of epidermal growth factor from human platelets in vitro: preferential release of 140 kDa fraction.

Platelet-rich plasma in acidic-citrate-dextrose anticoagulant was kept for 5 days in an oxygen-permeable bag at 22 degrees C in an incubator/rotator. Platelet count remained stable throughout the experiment. On days 0, 3 and 5, aliquots were removed; platelets were isolated by centrifugation at 22 degrees C, 1500 g for 20 min, reconstituted to the original volume with PBS buffer, and the contents of alpha-granules were released by repeated freezing and thawing. Epidermal growth factor (EGF) and beta-thromboglobulin (beta-TG) in the platelet-poor plasma and platelet lysates were determined by radioimmunoassays. Results indicated that in platelet-free plasma, both total EGF and beta-TG increased 3-5-fold after 5 days; this amount represented 10-20% of the factors stored in the platelets. Correspondingly, the EGF and beta-TG contents of the platelet lysates exhibited accompanying decreases. HPLC fractionation showed that the main EGF fraction which progressively decreased in the lysates and increased in plasma had a molecular mass of 140 kDa. The contents of the 67 kDa and 6 kDa fractions did not change substantially. We conclude that under these conditions, the 140 kDa fraction was released preferentially. In view of these and previous experiments, it seems likely that different organs contribute to plasma EGF fractions.

Excretion of epidermal growth factor (EGF) in diabetes.

Excretion of epidermal growth factor (EGF) is decreased in renal failure. We assayed it in diabetes mellitus in an attempt to relate it to clinical parameters, esp. those of diabetic nephropathy. EGF excretion declined with age but in all age groups of diabetic patients was below the first percentile for controls. In 26 control and 34 prepubertal diabetic children excretion was correspondingly 1126 +/- 442 and 932 +/- 489 pmol/mmol creatinine (P = 0.087); in 26 control and 42 diabetic adolescents below age 18, 778 +/- 222 and 676 +/- 335 (P = 0.023) and in 81 control and 83 diabetic adults, 371 +/- 153 and 235 +/- 140 (P less than 0.0001). Decreased excretion of EGF was seen in some patients without any diabetic complications. Excretion of EGF was independently and inversely correlated with age and duration of diabetes but not with type of diabetes, treatment, body built, C-peptide, plasma glucose, glycohemoglobin or retinopathy. A positive correlation was seen with creatinine clearance and a negative correlation, with albuminuria, but the strongest and the only independent correlation found by stepwise multiple variable selection was with serum creatinine (r -0.711, P less than 0.0001). EGF excretion was not elevated in patients with hyperfiltration. We conclude that EGF excretion is abnormal in many patients with diabetes and that this abnormality reflects a kidney function different from glomerular filtration or glomerular permeability.

Epidermal growth factor in serum, urine, submandibular glands and kidneys of diabetic mice.

Levels of epidermal growth factor (EGF) in serum were significantly decreased in streptozotocin (STZ)-diabetic mice (446 +/- 168 pg/ml after 1 week and 423 +/- 52 after 4 weeks vs 766 +/- 162 pg/ml in controls, P.002 and less than .001. respectively) and in genetically diabetic ob/ob mice (455 +/- 285 vs 962 +/- 453 pg/ml in nondiabetic ob/+ controls, P.043). The urinary excretion of EGF was significantly increased in STZ mice (104 +/- 53 vs 51 +/- 23 ng/h, P.013) but unchanged in ob/ob mice (33 +/- 9 vs 45 +/- 16 ng/h, P.134). However, when expressed per mg creatinine it was decreased in both cases: in STZ mice to 680 +/- 250 ng/mg at 1 week and 684 +/- 211 at 4 weeks vs 1250 +/- 303 ng/mg in controls (P less than .01); and in the ob/ob mice to 552 +/- 117 vs 1237 +/- 300 ng/mg in ob/+ controls (P less than .01). EGF content of the submandibular glands of STZ mice remained unchanged at 1 week (13.1 +/- 2.9 vs 11.0 +/- 1.8 micrograms/mg protein, P.170) but dropped by 4 weeks (4.7 +/- 1.2 micrograms/mg, P less than .001); in the ob/ob mice it was less than 20% that of controls (2.1 +/- 0.8 vs 12.2 +/- 3.6 micrograms/mg protein). In kidneys, the EGF content was not altered in either ob/ob (524 +/- 50 vs 571 +/- 33 pg/mg protein) or STZ mice (652 +/- 183 vs 665 +/- 80 pg/mg). The preproEGF mRNA level in STZ-treated mice was reduced after 4 weeks in submandibular glands but not in kidneys. The results show that diabetes affects EGF production, utilization and/or excretion in mice and that kidneys are spared from suppression of EGF synthesis that is pronounced in the submandibular glands.

In vitro effects of ethanolamine on insulin secretion.

The effects of ethanolamine on insulin secretion by the perfused rat pancreas were examined. During the second phase of glucose-induced insulin secretion 5-minute perfusions of ethanolamine at final concentrations of 0.1, 1 and 10 mM inhibited insulin release in a dose-related manner. When given throughout the experiment the highest dose of ethanolamine markedly suppressed both phases of glucose-induced insulin release. The inhibitory effect of ethanolamine was blunted in the presence of phentolamine. It is concluded that ethanolamine inhibits glucose-induced insulin secretion by the perfused rat pancreas and that alpha-adrenergic receptors play a role in its actions on insulin output.

Epidermal growth factor excretion and receptor binding in diabetic rats.

Urinary epidermal growth factor (EGF) excretion was calculated as ng EGF per mg creatinine and ng EGF per 24 hr. It was increased 4-9 fold in rats with genetic (BB) or streptozotocin-induced diabetes. It decreased to 2-3 fold control values in insulin-treated animals. In contrast, EGF concentration in serum was lower in diabetic than in control rats (360 +/- 72 vs 524 +/- 150 pg/ml, P .086); EGF level in plasma was unchanged (319 +/- 67 vs 313 +/- 96 pg/ml). In diabetic rats EGF content was increased in submaxillary glands (1018 +/- 259 vs 738 +/- 122 pg/mg protein, P .060) but unchanged in the kidneys (70 +/- 18 vs 65 +/- 6 pg/mg protein in controls). EGF binding to the liver microsomes in diabetic rats was decreased by 30-40% and was not restored by insulin therapy. Binding to the kidneys also showed a tendency to decrease in diabetic animals. The EGF excretion and receptor binding were normal in obese normoglycemic Zucker fa/fa rats. We suggest that hyperglycemia and/or glucosuria may affect EGF synthesis and/or excretion in the kidneys and EGF synthesis or accumulation in the megakaryocytes. The mechanism of decreased EGF receptor binding remains to be clarified.

Insulin-like activity of chromium-binding fractions from brewer's yeast.

51CrCl3 was added to the incubation medium of Saccharomyces cerevisiae for up to 48 hr. After repeated freezing and thawing, lysing in 9 M urea with 1% NP-40 detergent, and dialysis against water, the lower molecular weight (Mr less than 3500) dialysate was retained on a SE53 cationic exchange column, eluted with 0.25 M NH4OH and fractionated on a Bio-gel P-2 column. The insulin-like biological activity of the fractions was measured by the 14C-glucose oxidation in isolated rat adipocytes. The biological activity that was found in two of nine fractions did not correspond to their chromium content. Moreover, identical findings were obtained when chromium was added not to the live yeast but to the yeast extract, which showed that its binding was a chemical process not requiring cellular activity. No fraction demonstrated insulin-potentiating activity on rat adipocytes.