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In this paper, we report the functionalization of the surface of multiwalled carbon nanotubes (MWNTs) with Au dendrimer encapsulated nanoparticles (DENs). The results show that, when pristine MWNTs having hydrophobic surfaces are exposed to DENs, the dendrimers aggregate on the MWNT surface. However, when the MWNTs are oxidized in acid prior to exposure to DENs, well-dispersed submonolayer coverages of Au nanoparticles are observed on the MWNT surface. This suggests that acid-induced debundling of the nanotubes is an essential prerequisite for attachment of nearly monodisperse DENs. Electron microscopy and NMR spectroscopy confirm that the structures of the DENs and dendrimers are retained after immobilization on the surface of acid-functionalized MWNTs.

Numerous indices developed during the last 10 years to quantify the concept of trophic state turned out to be too ambiguous to be useful to lake managers. Based on empirical relationships between various water quality indicators, the most widely used indices use Secchi disk transparency, chlorophyll a concentration, and total phosphorus as a measure of lake trophic state. Indices based on data from north temperate lakes, however, are not directly applicable to Florida lakes. Many Florida lakes are known to be nitrogen rather than phosphorus limited. Florida lakes also commonly have macrophyte problems which are not accounted for by such indices. A series of indices based on Secchi disk transparency, chlorophyll a concentration, macrophyte abundance, total phosphorus concentration, and total nitrogen concentration were developed for Florida lakes. The Secchi disk index serves as a physical measure of trophic state. The public perceives water clarity as an important attribute of lakes, and Secchi disk transparency is a good measure of water clarity. The biological measures of trophic state are based on chlorophyll a concentration and macrophyte coverage. Chlorophyll a concentration is a good indicator of algal populations and macrophyte coverage is related to potential aquatic weed problems. Since phytoplankton and macrophytes compete for similar habitats, Florida's shallow lakes usually do not experience nuisance conditions of both these autotrophs simultaneously. The chemical measures of the trophic state are total phosphorus and total nitrogen concentrations. These elements are the principal nutrients limiting primary productivity in aquatic systems and therefore provide useful information on the nutritional status of lakes. When the lake is primarily phosphorus limited, based on the ratio of total nitrogen to total phosphorus concentration, the phosphorus trophic index is used. If the lake is nitrogen limited, based on the concentration ratio, the nitrogen index is used. Many Florida lakes are not limited by a single nutrient and are relatively well balanced. In this case an average of the nitrogen and phosphorus indices is used to determine the trophic status. The overall trophic state index for a Florida lake is determined by combining the appropriate values obtained from the physical, chemical, and biological indices. Over 570 lakes in the State were ranked by this method. The relative simplicity of the trophic index, combined with its accuracy and reliability, emphasizes its utility in statewide lake management.

A sensitive and specific radioimmunoassay for mitoxantrone in serum has been developed. The procedure allows direct measurement of mitoxantrone in unextracted serum samples, by using antisera from rabbits immunized with mitoxantrone-BSA antigen. Tritiated mitoxantrone of high specific radioactivity (ca. 15 Ci/mmol) was used as a radio-tracer ligand. The assay allows the detection of as little as 50 pg/ml and the quantitation of 75 pg/ml in 0.5 ml serum samples. Standard curves were linear in the concentration range of 75–2500 pg/ml, at antiserum dilutions of 1:15,000. The assay shows good reproducibility: coefficients of variation of 3–6% were obtained by analyzing five samples/concentration at 75, 100, 250, 500, and 1000 pg/ml. There was no cross reactivity with the major metabolite in human serum, having concentrations of up to 10,000 pg/ml. Serum samples collected at various time intervals from rats dosed intravenously with mitoxantrone (0.5 mg/kg), were analyzed for unchanged mitoxantrone by RIA. The drug concentrations decreased from 32 ng/ml at 0.5 h to 0.45 ng/ml by 24 h after dosing.

Thirty 4-month-old Shetland foals were fed pelleted rations that provided either (1) a calcium-phosphorus ratio of 2:1 (.9% calcium and .45% phosphorus) or (2) a calcium-phosphorus ratio of approximately 6:1 (2.5% calcium and .45% phosphorus) for a 4-year period. At the wider ratio the calcium intake was four to five times greater than the requirements suggested by Schryver and Hintz. However, dietary treatment had no effect on height, average weight gain or reproduction.Scalar selected radiograph projection areas and gamma ray absorption measurements suggest that treatment did affect bone growth. Subperiosteal appositional bone growth achievement was similar; however, the medullary region was relatively larger and the cortical bone area relatively smaller in ponies fed the high calcium diet. These differences in anatomical distribution of areas are accompanied by a decrease in the amount of bone mineral per unit of projection area of the cortex.

A study was made of the effects of soil salinity, cotton leaf relative turgidity, and Cl content on reflectance and transmittance of radiation by single leaves. The relation of color film density to soil salinity, percentage ground cover, and cotton yield was also investigated. Reflectance from single leaves increased as soil salinity, leaf moisture deficit, and Cl content increased. Aerial photographs of field cotton on saline and nonsaline soils showed greater reflectance from cotton not affected by salt. (Kodak Ektachrome infrared aero film was used.) Multiple regression analyses indicated that under field conditions reflectance measured as film density was influenced by soil salinity and percentage ground cover. Since the same plant and soil factors that affect reflectance from the crop canopy also affect cotton yield, regression equations were calculated to express yield as a function of film density. The regression equations accounted for from 51 to 75% of the variation in yield.

A discussion of the bicolorimetric principle was first presented to this Society in November, 1921,1at which time we had the present work in mind. The method described below is essentially an adaptation of the colorimetric method of Cullen2for the determination of the PHof the blood plasma (or serum) to the bicolorimeter described by one of us.3As modified the final determination is carried out on 0.1 c.c. of plasma, and does not require more than 10 minutes after the blood has been obtained. The color comparison can be made with an accuracy of ± PH0.02.Blood is drawn without stasis in a narrow 5 c.c. Luer glass syringe containing sufficient mineral oil to fill any air spaces, and is at once delivered into a centrifuge tube of special design under oil. This tube is made of Pyrex glass and has at the bottom a bulb of 2 c.c. capacity (30 mm. in length with an internal diameter of 11 mm. and a neck of 4 mm.). Tubes with bulbs of 1 and 5 c.c. capacity have also been used, the latter being employed when a simultaneous estimation of the CO2content of the plasma is to be made. One drop of neutral 20 per cent. potassium oxalate is dried in the tube, after which three drops of mineral oil are added. In transferring the blood from the syringe to the centrifuge tube, the point of the needle is placed under the oil and sufficient blood delivered to bring the oil into the neck of the bulb. With the slight pressure exerted the blood readily takes up the oxalate and does not clot. The tube is centrifuged at moderate speed for about two minutes to separate the plasma.

Introduction:Delays in definitive management of critically ill patients are known to drive poor clinical outcomes. A scarcely studied time period in interfacility transfer is the time between initial patient presentation and the decision to transfer. This study seeks to identify patient, environmental and institutional characteristics associated with delays in decision to transfer critically ill patients by air ambulance to a tertiary care centre. Methods:Patients >18 years old who underwent emergent air ambulance interfacility transport to a tertiary care centre were included. Patient records were located in a provincial air ambulance database. The primary exposure variable was time from patient presentation to initial call to facilitate transfer. Patient, environmental and institutional characteristics were identified using stepwise variable selection at a significance of 0.1. These characteristics were then explored using quantile regression to identify significant factors associated with delay in transport initiation. Results:A total of 11231 patients were included in the analysis. There were 5009 females (44.60%) and 6222 males (55.4%). The median age of patients was 57. The median time to initiate the transfer was 3.05 hours. The variables identified with stepwise selection were gender, category of illness, heart rate, systolic blood pressure, Glasgow coma scale, vasopressor usage, blood product usage, time of day, and type of sending site. The following factors were significantly (p < 0.05) associated with an increase in time to initiate transfer compared to the reference category at the 90th centile of time: cardiac illness (+1.45h), gastrointestinal illness (+3.27h), respiratory illness (+4.90h), sepsis (+3.03h), vasopressors (+2.31h), and an evening hour of transport (+3.67h). The following factors were significantly (p < 0.05) associated with a decrease in time to initiate transfer compared to the reference category at the 90th centile of time: neurologic illness (-1.45h), obstetrical illness (-1.56h), trauma (-3.14h), GCS <8 (-0.98h), blood transfusion (-1.47h), and sending site being a community hospital >100 beds (-2.26h), <100 beds (-4.71h), or nursing station (-10.02h). Conclusion:Time to initiate transfer represents a significant window in a patient's transport journey. In looking at the predictors of early or late initiation of transfers, these findings provide education and quality improvement opportunities in decreasing time to definitive care in critically ill populations.

It has been recognized now for some time that the administration of salicylates and phenylcinchoninic acid (cinchophen) resulted in an increased excretion of uric acid in the urine. Quite recently it has been shown by Folin and Lyman,1and Fine and Chace,2in particular, that this action was accompanied by a marked drop in the uric acid content of the blood, and later the same was shown to be true of salicylates by Fine and Chace,3and Denis.4It has been assumed that these drugs induce an increased output of uric acid by endowing the renal cells with an increased power for eliminating uric acid. Fine and Chace5have pointed out that, in the last stages of interstitial nephritis cinchophen has little influence on the excretion of the uric acid, indicating that the renal cells can no longer be stimulated to increased activity.We have been endeavoring to obtain further light on the mechanism of the action of these drugs by experiments upon both man and animals. Setting aside cases of advanced interstitial nephritis where the action of cinchophen is comparatively slight, we have been struck by the fact that this drug and its methyl derivative show quite different ability to lower the blood uric acid in different individuals, the action being very pronounced in some cases and comparatively slight in others.In their experiments Folin and Lyman noted the interesting fact (in two cases) that cinchophen not only brings about a dimunition of the uric acid in the blood but also seems to lead to a dimunition of the nonprotein nitrogen and urea whenever these are present in the blood in unusual amounts. Unfortunately these two experiments were not followed by a control after period.

Cotton (Gossypium hirsutumL.) plants were grown hydroponically in a controlled environment. Sodium chloride was used to induce three osmotic stresses: low (0 atm), medium (6 atm), and high (12 atm). Leaves of approximately the same age were harvested 49 days after planting from five replications of each treatment, and their reflectance and transmittance spectra were obtained for the wavelength interval 500‐ to 2,500µ Osmotic stresses of 6 and 12 atm reduced reflectance and increased transmittance of near‐infrared light (750 ‐ 1,350 mµ) as compared with leaves from plants grown with low osmotic stress. Tissue sections from the same leaves were processed to provide transverse sections for histological examination; leaves from plants grown with 6 and 12 atm of osmotic stress exhibited a more compact cell arrangement than nonosmotically stressed leaves.

A density slicing system is used by experienced soil surveyors to interpret photographic tone patterns associated with soils of the Lake Dakota Plain area of north‐central South Dakota. The density slicing system color encodes the variation in optical density of film transparencies and measures the percent area of each color encoded density level. Field checking verified that the soil boundaries were more accurately located on the color encoded density maps than on the existing soil maps of the area.

Methods for the estimation of guanidine and its methyl derivatives have been subject to considerable criticism. A study of the color reaction for guanidines recently described by Marston1was undertaken in order to determine its biochemical applicability. Although Marston specifically states that his reagent will keep indefinitely, in our hands deterioration and precipitation invariably set in shortly after mixing the three ingredients, sodium nitroprusside, potassium ferrocyanide and sodium hydroxide.A reagent has been developed, which, although it contains the same ingredients as employed by Marston, has the advantage that it keeps well and gives within five minutes a full color development which does not fade or become turbid for more than an hour, thus allowing ample time for color comparison.The reagent we now employ is prepared as follows: 6 gm. sodium nitroprusside and 8.5 gm. potassium ferrocyanide are dissolved in water and made up to 100 cc. About 15 to 20 minutes before using, one volume of this solution is mixed with one volume of 10 per cent sodium hydroxide and two volumes of 3 per cent hydrogen peroxide. It has ken found convenient to add 1 cc. of the prepared reagent to 4 cc. of the unknown guanidine solution and compare in a colorimeter with standards similarly prepared. With this technique quantities of guanidine bases as small as 0.2 mg. may be estimated.Creatine and creatinine give a faint coloration with the reagent but do not interfere materially in the estimations. Uric acid and ammonia interfere by hindering the color devlelopment with the bases. Urea produces about one tenth of the color given by guanidine, a fact not mentioned by Marston. Methyl urea, β-methyl hydantoin, β-methyl liydantoic acid and glucose yield no color, while ethyl alcohol gives a very faint reaction.

A year ago a simple technique of estimating the pH of urine was suggested,1in which application was made of the bicolorimeter and the phthalein dyes, phenol red, brom cresol purple and brom cresol green. At that time we concluded that as far as the matching of colors went, the method had a probable error of pH ± 0.02 to 0.04, but we realized that the factors of temperature and dilution must exert some influence on the true pH. Obviously one desires to know the pH of the undiluted urine at body temperature. During the past year we have been trying to ascertain how far colorimetric determinations on diluted urine at room temperature differ from electrometric determinations on undiluted urine at 38°. In connection with an acid-base balance study we felt that we should know just how far the present colorimetric determinations might deviate from the true pH values and if a correction factor might be applied which would hold for all urines.Since our preliminary report was made and the present study begun, Hastings, Sendroy and Robson2have reported a study of this question. They carry out their determinations at 38° diluting the urine 1-5. They state that the dilution error is the important error and amounts to about 0.1 pH, which must be subtracted from the colorimetric result. They believe that with this correction their results fall within 0.1 of the actual pH.In routine work it is quite troublesome to carry out colorimetric estimation at 38°. In the present study it has been found that the factor necessary to correct for the determination being made on the diluted urine at room temperature amounts to roughly 0.2 pH, about half of which is a temperature correction and half a dilution (salt and buffer) correction.

All human urines probably contain small amounts of sugar, as has quite recently been pointed out by both Cole1and Folin,2who have described tests for the detection of this small amount of sugar. It has been found possible to determine this reducing substance by precipitating the creatinine and uric acid, and probably other interfering substances with picric acid as suggested by Folin for his qualitative test, and then employing a technique similar to that introduced by Benedict and Lewis3for the estimation of the sugar of the blood.4It is presumed that the reduring substance in question is glucose, although this has been found difficult of positive proof. This question is being further investigated.The method is carried out as follows: About 2 grams of dry picric acid are added to 10 c.c. of urine in a test tube and the tube vigorously shaken. The tube is now stoppered and placed in an ice box at 0° C. After the tube has stood for an hour, it is again shaken and then allowed to stand over night in the ice box, after which the mixture is filtered through a small filter paper into a dry test tube. The filtrate now contains less than 0.1 mg. of creatinine per c.c, a quantity too small to invalidate the estimation of the sugar. If the urine has reacted negatively to Benedict's qualitative reagent, the filtrate is diluted 1-5 or 1-10 with saturated picric acid solution. If the qualitative test has shown a small amount of sugar, a greater dilution is made. The following rule may be followed: for 0.1 per cent. of sugar dilute 1-5, for 0.2 per cent. dilute 1-10, for 0.3 per cent. dilute 1-15, etc.

Within the last few years increasing attention has been given to studies concerning the changes in the concentration of a number of blood constituents during prenatal development. With the aid of such data it may be possible to add further information concerning the utilization of the various foodstuffs during the embryonic period. Further, it may be possible, by correlating the extent of functional development of the various organs of the embryo at a given age with such chemical blood data, to throw further light upon the influence of a given organ upon intermediary metabolism.The chick embryo was chosen as the experimental animal. The eggs were incubated under standard conditions and at the desired age the egg was carefully opened and sufficient blood for analysis was withdrawn from the vitelline artery or vein into a 1 cc. tuberculin syringe. Since satisfactory blood samples could not be obtained from embryos of less than 9 days incubation no analyses were attempted until that time. From this period on, however, the analyses were carried on through the entire incubation period and for several days after hatching.Table I presents the results of the average daily changes occurring in the several constituents of the blood during the course of ontogenetic development. The numbers in parentheses indicate the number of separate analyses from different embryos used to compute the average. From these results it is observed that the embryonic blood sugar is increased beginning with the 16th day of incubation. The increase in the uric acid concentration is observed much earlier in the developmental period. Similar increases are observed in the concentration of cholesterol and hemoglobin, and in red blood cell counts, with the exception of a definitely lowered level during the hatching period.

As a result of the recent experiments of Bollman, Mann and Magath1there is now little doubt that the liver plays the leading rôle in urea formation. Nevertheless very little is known concerning the mechanism of urea formation. To be sure we have long known from the experiments of Kossel and Dakin2that argininie may be split directly into urea and ornithine under the action of a specific enzyme, arginase, but relatively this accounts for only a small amount of the urea formed.We wish to record observations of autolysis experiments carried out some years ago3(1914) which we have recently confirmed and extended4. The original motive for initiating these experiments was the availability of a specific method for estimating urea (Marshall). We were able to show then that whereas urea formation took place in autolyzing liver tissue, no change in the concentration of urea occurred in muscle tissue similarly treated.Since our first experiments were carried out somewhat similar results have been obtained by several workers. Hoagland and Mansfield,5contrary to their expectations, obtainea entirely negative results in muscle autolyses. Fosse and Rouchelman,6employinlg the xanthydrol method, were able to demonstrate a six fold increase of urea in autolyzing liver tissue, a change which mas entirely inhibited by boiling the liver. Fosse7believes that the intermediate substance in urea formation is cyanic acid. McCance8has endeavored to ascertain the optimum conditions for urea formation in autolyses. He reports urea formation not only in liver but also in spleen.Data illustrating the results which were obtained in our earlier experiments are given in Table I. As will be noted there is no evidence of any urea formation in the muscle autolyses, but in the liver autolyses colncentration of the urea increased more than ten fold.

The present study was prompted by the findings of R. and S. Weissmann-Netter1who have made a series of observations on the carbon dioxide and the pH of the blood of patients with migraine. They found that the hydrogen ion concentration and the alkali reserve are normal in the periods of freedom from attacks but that a tendency to alkalosis develops 48 hours prior to an attack. They also reported that hyperventilation may result in an attack of migraine, probably through an excessive loss of carbon dioxide. As a result of the apparent success of controlling the migraine attacks by treatment with ketogenic diets,2it seemed desirable to reinvestigate the acid-base balance of the blood of individuals subject to migraine. To date 10 cases of migraine have been followed at intervals, the blood having been taken as early in the attack as possible, at the height of an attack, and immediately after cessation of the attack. It was found that the serum pH, CO2content, chloride and total base remained within normal limits, if one excepts 2 cases in which the pH was elevated slightly, due in all probability to the accompanying vomiting. It is probably of some significance that a fairly definite elevation of the blood cholesterol occurred in 50% of the cases.

When muscle tissue is allowed to autolyze, creatine is transformed to creatinine at a constant rate. The velocity of this reaction increases with a rise in temperature, although practically negligible at 0° C. The rate of formation at body temperature is nearly sufficient to account for the daily elimination of creatinine. The velocity of the reaction is increased by acids but not reduced by Henderson's neutral phosphate mixture. Added creatine experiences the same fate as the creatine originally present, while added creatinine inhibits the reaction, or if added in sufficient quantity causes it to proceed in the opposite direction. Pure solutions of creatine and creatinine experience the same transformations, although much more slowly. On the long standing of pure solutions there seems to be a slight loss in total creatinine (from both creatine and creatinine). This appears to be due in part to a transformation to urea. Whether or not these phenomena are vital factors in the formation of creatinine in the body, we are unprepared to say.To obtain further light on this point, experiments have been conducted on nephrectomized animals. The creatine and creatinine content of the various body tissues have been determined several days after a double nephrectomy. In certain of these experiments creatine and creatinine have been injected. Some what similar deductions may be drawn from our experiments in vivoto those in vitro;although there are certain differences between the two types of experiments, the significances of which are not as yet entirely clear to us.

In two cases of nephritis of the uremic type with high nonprotein nitrogen and urea, very high figures for both uric acid and creatinine have been observed. The increase in the concentration of these substances is best shown in tabular form. The figures are in mgm. per 100 c.c. of blood.The progressive increase in the various constituents as the condition approaches a fatal termination is well shown in Case 2. Attention is called to the possible etiological importance of the retention of creatinine on account of its containing the toxic guanidine group, also to the probable diagnostic and prognostic value of the determinations for uric acid and creatinine in this condition. The possible etiological bearing of the retention of creatinine is being considered from the standpoint of experimental nephritis.Estimations of total solids, total nitrogen, chlorides, sugar, and cholesterol have been made in all our cases in addition to the above determinations. In our earlier estimations of creatinine, Shaffer's suggestions for the estimation of creatinine in dilute solutions were followed, but recently we have employed Folin's new method which has been found very satisfactory.

In an earlier communication,1attention was called to the constancy in the content of muscle creatine for normal animals of a given species, though distinctive for different animals. It was further pointed out that during starvation in the rabbit, the percentage content of muscle creatine may show either an increase or a decrease, the latter depending in considerable part upon the rate and amount of creatine eliminated in the urine.These observations have been extended to rabbits which have been fed for varying periods upon carbohydrate—without fat or protein. Carbohydrate feeding greatly reduces the elimination of creatine in the urine, as previously observed, though the creatine content of the muscle does not materially differ from that found during a similar length of starvation. In other words, it may be markedly decreased during a long period of carbohydrate feeding. It seems probable that the action of the carbohydrate is simply one phase of the sparing action of carbohydrate on protein metabolism, in this case allowing sufficient time for the body to handle the creatine, i. e., to oxidize it, or change it to creatinine.That creatine when fed or injected does not reappear in the urine in the form of creatinine, except in traces, or in large amount unchanged, unless given in considerable quantity, has been as-certained by a number of investigators. The possibility that this creatine, which remains unaccounted for, is stored up in the muscle has not been adequately studied.has not been adequately studied. In four experiments on rabbits, the creatine content of the muscle, after repeated subcutaneous injections of creatine, has been found to be uniformly slightly above (4-7 per cent.) the normal amount. This would appear to indicate that a small atnount of the injected creatine was deposited in the muscles, though insufficient to account for the creatine not eliminated in the urine either unchanged or in the form of creatinine.

The question of the absorption of aluminum by the blood and its presence in other body tissues is one of considerable interest. A few figures have been reported for the dog, but they possess little value for the reason that the methods used were inadequate to estimate the very small amounts of aluminum found.Several very delicate color reactions for aluminum have recently been described. After considerable effort we have been able to utilize one of these reactions, that with aurin described by Hammett and Sottery,1for the estimation of small amounts of aluminum in biological material containing iron. Since the amounts of iron left by the ordinary means of separation give a color very similar to that of aluminum, it must be removed more completely. The presence of iron has, however, been utilized to advantage in carrying down aluminum in the first precipitation. For this reason it is necessary to add iron when it is absent.The method employed for blood is carried out briefly as follows: 5 cc. of blood are digested in a large Pyrex test tube over a micro burner with 2 cc. of sulfuric acid and 3 cc. of perchloric acid, until oxidation is complete. This requires less than 15 minutes.The digestion mixture is diluted with a little distilled water and transferred quantitatively with washing to a smaller Pyrex test tube, the volume being made up to about 15 cc. One cc. of saturated ammonium acetate is now added and the solution made alkaline with conc. ammonium hydroxide. The tube is placed in a vigorously boiling water bath until the excess of ammonia is expelled. The precipitate, which at first has tendency to rise, will settle out on shaking.

A delicate method of estimating invert activity (sucrase) would be of advantage in connection with a number of physiological problems. A substitution of one per cent. cane sugar for the one per cent. soluble starch or glycogen, employed by Myers and Killian,1in the estimation of the diastatic activity of the blood, furnishes a very delicate method for sucrase.The technic of the method is as follows: To 8 c.c. of water in a 50 c.c. centrifuge tube is added 1 c.c. of the extract to be examined, and the solution warmed to just 40° C. in a water bath with thermostat attachment. One c.c. of one per cent. cane sugar is now added and incubation carried out for 30 minutes. The solution is rapidly cooled in cold water and 0.5 to 1.0 gram of dry picric acid added, thoroughly mixed, centrifuged and filtered. The inverted sugar is now estimated colorimetrically in 3 c.c. portions as already described.1One must not let the sucrose stand for a long time in contact with the picric acid, owing to the hydrolytic action of the picric acid.2For this reason it might be of advantage to employ sodium picrate, as recently recommended by Benediet.3Utilizing the above method we have been unable to satisfactorily demonstrate sucrase in human blood or that of rabbits. With one per cent. yeast extract there was 60 per cent. inversion in one-half hour, i. e., 6 of the 10 mg. were inverted, while a one per cent. yeast extract in human blood gave a 54 per cent. inversion. With a 10 per cent. extract of the mucous membrane of rabbit's intestine figures of 13.2 and 12.8 per cent, were obtained. Controls were all negative.

The methods which are in use at present for the colorimetric estimation of cholesterol in blood are either time-consuming or of questionable accuracy. In connection with a study of the blood lipoids in obesity, it seemed necessary to investigate further the question of a suitable cholesterol method. For some time now we have employed a procedure which is comparatively simple and we believe to be very satisfactory.The method consists essentially in mixing one C.C. of whole blood, plasma or serum with 4-5 grams of plaster of Paris, drying, and extracting the powder directly with chloroform in a special extraction apparatus. The plaster of Paris is emptied into a small paper extraction shell (4 cm. long) and this inserted in a short test tube (2.5 × 6 cm.) in the bottom and sides of which are a number of small holes. This is now attached to a large cork on a small reflux condenser and the tube and cork inserted in the neck of a 150 C.C. extraction flask containing about 20-25 c.c. of chloroform. Extraction is continued for 30 minutes on an electric hot plate, the chloroform made up to some suitable volume, such as 20 c.c., filtered if necessary, and colorimetric estimation carried out with the aid of the Liebermann-Burchard reaction, according to the the technique of Grigaut and of Autenrieth and Funk. Brown colors do not develop as with the Bloor method. An aqueous solution of naphthol green B, which is permanent, is used as standard.Since the cholesterol esters give the color reaction, as pointed out by Bloor, saponification is unnecessary. With this method perfect duplicates and quantitative recoveries of added cholesterol and cholesterol esters may be had.

Review: new results since last review in 2005; 116 refs.

The procedure introduced by Lewis and Benedict,1for the estimation of the sugar of the blood, is utilized in the estimation of its diastatic activity. Two 2 c.c. samples of oxalated blood are taken, and to one of these is added 1 c.c. of 1 per cent. soluble starch solution. Both tubes are now made up to 10 c.c. and incubated at 40° C. for 15 minutes. About 0.5 gram of dry picric acid is now added and the mixture stirred. When the proteins are precipitated, the tubes are centrifuged and the supernatant fluid filtered. The sugar in three cubic centimeter portions of the filtrates is now estimated according to the technique described by Myers and Bailey.2Correction is made for the sugar originally present in the blood (with the aid of the control) and for the slight reducing action of the soluble starch. The results are recorded in terms of the percentage of the soluble starch (10 mg.) transformed to reducing sugars (calculated as glucose) by the 2 c.c. of blood employed. It is believed that under the above conditions, the possible error of glycolysis is a negligible one.The diastatic activity of the blood, according to this method, appears to vary from 15 to 2j in a variety of miscellaneous conditions in the human subject, while in diabetes, figures from 30 to 70 have been observed. The possible significance of these observations we are not prepared to discuss at the present time.

Comparative analyses of blood and spinal fluid were carried out in 15 cases. These patients were suffering from nephritis of various stages of severity, and gave chemical blood pictures varying from practically normal to the excessive retention of uremia. The concentration of urea in the spinal fluid averaged 88 per cent. of that in the blood; the concentration of creatinine, 46 per cent.; of creatine, 22 per cent.; and of uric acid, 5 per cent. of the respective concentrations in the blood. If these differences in concentrations may be regarded as representing the relative permeability of the cells separating the blood and spinal fluid, one notes that the extent of passage into the spinal fluid is greatest for urea, less for creatinine, still less for creatine and least for uric acid. It is of interest to note that this represents also the order of their solubility in water, and, in part, the relative ease with which these substances appear to be eliminated by the kidney.It may be further observed that the sugar concentrations of the spinal fluid in these fifteen cases averaged 57 per cent. as much as that of the blood.

Typical cases of gout show, as a rule, blood uric acid values from 2 to 5 times the normal. The amounts of urea and creatinine are normal or in the case of urea, only slightly above normal. Many early cases of nephritis, especially of the interstitial type, give blood pictures which differ little from those of gout. The uric acid findings are quite as high and the urea content varies from only slightly above to more than double the normal amount. The creatinine is only slightly increased. As the condition of cases of this type becomes more severe, the retention of urea increases, until we have high values for urea as well as for uric acid. If improvement takes place the concentration of urea gradually falls until the picture is that of the preceding group. If, on the other hand, the case goes on to a fatal termination, the retention of uric acid and urea is followed by that of creatinine, the concentration of which may reach twenty times the normal. Here the phthalein output is practically zero.From the foregoing it would appear that as the permeability of the kidney is lowered it becomes evident in the blood, first, by an increase in the uric acid, second, by that of urea and lastly, by that of creatinine. That this should be the case seems quite plausible when we consider the ease of excretion of these constituents, as determined from a comparative nitrogen partition of normal urine and blood. Uric acid nitrogen forms 2 per cent. of the non-protein nitrogen of both urine and blood, urea nitrogen about 85 per cent. in urine but 50 per cent. in blood and creatinine nitrogen 5 per cent. in urine but only 2 per cent. in blood.