Glass Funnel Research Articles

Ultrasound monitoring of fetal behaviour

HISTORICAL REVIEW Attempts at refining maternal perception of fetal activity by objective observation focused initially on the recording of cardiac activity. In the decades following Cremer’s first successful fetal electrocardiogram ( 1906) the technique was used essentially for the diagnosis of fetal life (Strassmann and Mussey, 1938; Southern, 1954). Later Southern ( 1957) and Hess and Hon ( 1960) attempted to recognise patterns of fetal heart rate recordings, obtained by electrodes placed on the mother’s abdomen and thigh, during labour which correlated with degrees of fetal distress. The use of Doppler ultrasound transducers on the mother’s abdomen to obtain prolonged recordings of the fetal heart rate pattern antepartum (Callagan et al., 1964; Bishop, 1966) allowed this assessment (and the possibility of appropriate intervention) to be brought into the antenatal period (Visser and Huisjes, 1977; Paul and Miller, 1978). Fetal body movements in utero were first recorded objectively with a kymograph by Ahlfeld ( 1905) using the displacement of an inverted glass funnel placed on the mother’s abdomen produced by the distortions of the maternal abdominal wall resulting from movement of the underlying fetus. Subsequently, various methods have been applied to record fetal activity using strain gauges (Sterman, 1967; Timor-Tritsch et al., 1976; Wood et al., 1977), electromagnetic devices (Sadovsky et al., 1973; Adler and Mahler, 1980) and piezoelectric sensors (Sadovsky et al., 1977). Ultrasonic recordings initially used A-mode signals, with reflections of the single ultrasound beam at different distances displayed as spikes on an oscilloscope. Fetal breathing movements could be effectively detected (Boddy and Robinson, 197 1) but more randomly moving fetal parts were difficult to identify with this method. The use of Bmode linear scans to produce a two-dimensional image of cross sections through the uterus was a major advance in demonstrating fetal anatomy (Kratochwil, 1967; Hofmann et al., 1967). A rapid succession of linear scans reproduced on a video screen in real-time allows comprehensive observations of fetal movement, amongst the earliest reports of which were by Hofmann and Hollinder ( 1968) and Reinold (1976). More recent advances in ultrasonic instrumentation include a B-scan phase-locked tracking system, which provides a fine resolution paper record of rhythmic movements of any portion of the fetus selected from a simultaneous conventional real-time picture (Adamson et al., 1980). The clinical significance of ultrasonic observation of musculoskeletal movements of the fetus has been appreciated in terms of establishing viability in early pregnancy (Hollander, 1979), of correlating them with our knowledge of the embryological development of the nervous system (Birnholz et al., 1978) and of using them as a parameter of fetal well being in later pregnancy (Manning et al., 1979).

Elimination of silica gel from gangliosides by using a reversed-phase column after preparative thin-layer chromatography.

A simple and effective procedure has been developed for eliminating silica gel from gangliosides after preparative thin-layer chromatography. Gangliosides were extracted from the scraped silica gel with chloroform-methanol-water 10:10:3 (by volume) and dried. The residue was suspended in 0.1 M NaCl and centrifuged. After filtration through a sintered glass funnel, the supernatant was applied to a reversed-phase column. The column was washed with 0.1 M NaCl, water, and methanol-water 1:1 (v/v). Gangliosides were eluted from the cartridge with methanol with yields of 92% and 90% in terms of dry weight and sialic acid content, respectively. Almost all of the silica gel contamination was eliminated from gangliosides by this procedure.

Mellowing and anisotropy induced by wetting of moulded soil samples

Disks of seven soils were prepared by moulding the soils at water contents in excess of their plastic limits and by drying. The disks were placed on edge on sintered glass funnels, were wetted from an arbitrary point on their circumference and were then dried isotropically. Disks that had been wetted were weaker than control disks that had not been wetted. For some soils there is a water potential, termed the critical mellowing potential, in excess of which little or no mellowing occurs. For three of the soils studied the mellowing occurred to different extents in different directions. Anisotropic mellowing was investigated as a function of the potential of the source of water causing wetting. Results from multiple wettings of disks indicate that anisotropic mellowing may lead to equilibrium states for a number of soil physical properties including structure and strength.

Isozyme Banding Patterns in Two Stands of Cetraria arenaria Kärnef.

Isozyme Banding Patterns in Two Stands of Cetraria arenaria Kärnef.

Isolation of Bloodstream Trypomastigotes of Trypanosoma cruzi by a Gradient of Metrizamide

Several methods have been used to isolate bloodstream forms (trypomastigotes) of trypanosomes from other blood components. Four of them have been widely applied: (1) defibrination of the blood by incubation in a medium containing calcium chloride and shaking with glass beads followed by passage of the parasites through a sintered glass funnel (Fulton and Spooner, 1957, Ann. Trop. Med. Parasitol. 51: 417-421); (2) defribination followed by low speed centrifugation in Krebs-buffered-glucose-saline layered on density gradients of sucrose (Williams and Cover, 1966, Trans. R. Soc. Trop. Med. Hyg. 60: 426-427; Jaffe et al., 1969, Exp. Parasitol. 25: 311-318); (3) separation using a gradient of N-methyl-3-5-diacetamide-2-4-6-triiodobenzoate and Ficoll (Budzko and Kierszenbaum, 1974, J. Parasitol. 60: 1037-1038); (4) separation using a DEAE-cellulose column (Lanham, 1968, Nature 218: 1273-1274; Lanham and Godfrey, 1970, Exp. Parasitol. 28: 521-534; Gutteridge et al., 1978, Parasitology 76: 159-176; Villalta and Leon, 1979, J. Parasitol. 65: 188-189). Electron microscopic observations made on Trypanosoma cruzi isolated by the first three methods indicate variable contamination with platelets (unpubl. observ.). The fourth method, which is being used routinely for isolation of Trypanosoma brucei, presents two problems. First, erythrocytes and bloodstream forms of T. cruzi have a similar surface charge (de Souza et al., 1977, J. Protozool. 24: 411-415). This problem was solved by a preliminary separation of the trypanosomes from the erythrocytes, using low speed centrifugation leaving the DEAE-cellulose column for separation of the trypanosomes from other blood components (Gutteridge et al., 1978, loc. cit.; Villalta and Leon, 1979, loc. cit.). Second, several lines of evidence indicate that passage of trypomastigotes of T. cruzi through DEAE-cellulose column may alter some properties of the parasite such as the transport of amino acids (Goldberg et al., 1976, J. Protozool. 23: 79-186), the surface charge (de Souza et al., 1977, loc. cit.), and infectivity to mice (Villalta and Leon, 1979, loc. cit.). In view of the problems pointed out above we decided to develop a method for separation of bloodstream trypomastigotes of T. cruzi by using a gradient of Metrizamide [2-(3acetoamido-5-N-methylacetamido-2-4-6-triiodobenzamido)-2-deoxy-D-glucose]. This substance has a molecular weight of 789, a density of 2.17 g/cm3, gives solutions of low viscosity and osmolality, dissolves readily in water or dilute solutions of salts, has no ionizable groups, and can be stored indefinitely at -20 C (Rickwood and Bimie, 1975, FEBS Lett. 50: 102-110). It has been applied to isolate several types of cells and subcellular particles. Blood (about 30 ml) obtained by bleeding mice through the retroorbital sinus (1-4.107 trypomastigotes/ml) was collected with medium 199 plus 3.8% sodium citrate as anticoagulant and centrifuged at 500 g for 5 min to pellet most of the erythrocytes, and left at 37 C for 30 min so that some pelleted trypomastigotes could move to the supernatant. The supernatant was centrifuged at 2,800 g for 30 min after which the pellet was resuspended in 3 ml of medium 199 plus 10% fetal bovine serum and left at 37 C for 5 min for aggregation of the platelets. In some experiments, adenosine diphosphate (final concentration of 1 mg/ml) was added slowly with occasional shaking in order to improve agglutination of the platelets. However, this step can be omitted. Pressing the platelet aggregate gently with a Pasteur pipette improved the liberation of some trypanosomes. The suspension containing the parasites plus aggregated platelets and other blood cells was layered on the top

Red cell filtration by paper filters.

A method for the assessment of red cell filterability with paper filters is described. Two milliliters of a washed red cell suspension with a hematocrit of 50% was filtered through a filter paper cone in a glass funnel and the filtration half-time (FT1/2) was measured. The filter papers were calibrated by previous measurement of the filtration time for the suspending solution, the calibration time (CT). A linear correlation between CT and FT1/2 was found for individual red cell suspensions (p less than 0.001) as well as for a normal population (p less than 0.001). Consequently, the index FT1/2/CT should represent a more reproducible parameter than FT1/2 and experimentally this appears to be the case. In fact, elimination of erratic values in a normal population was realized. Furthermore, discrimination between normal and abnormal values was improved and the coefficient of variation of single measurements passed from 28.4 to 9.4%. The reproducibility and reliability of this extremely simple method are therefore decisively enhanced without complication of the procedure.

Insecticides for Cat Flea Control, 1978

Abstract Adult fleas were maintained on laboratory cats (4) housed in individual metal cages with metal mesh floors. The cages were tapered below the mesh and were fitted with a 1 -gal glass Jar into which flea eggs dropped from each cat and were collected. Larvae were reared in 1-qt jars on a pulverized mixture of dry dog chow, dried beef blood, and brewers yeast (10:1.5:1) mixed with equal parts of fine grain sand and sawdust. After 7 days, pupae were separated daily from the larval medium with a No. 16 screen. A glass funnel fitted with 16 mesh screen fastened to a Jar lid was used to separate adults and pupae. Adult fleas 2-5 days old were exposed to treated 78 cm2 plush nylon carpet discs. Liquid insecticides were applied with a B&G compression sprayer equipped with a Sprayer Systems multijet nozzle set to deliver a fine mist from 1-2 ft. Aerosol was sprayed to visible dampness. The Al applied was determined by immediately weighing filter paper sprayed simultaneously with the carpet (ca 0.10 mg/cm2 per 1% spray). Each treated disc was allowed to dry for ca 24 hr. Discs were placed, treated surface up, at the bottom of leucite cylinders (10.0 cm i.d. x 38.1 cm). Replicates (n = 3) of 30-120 fleas were placed onto the treated carpet discs and allowed to remain on the discs 4 hours. The discs were subsequently removed from the cylinder with long forceps and placed on a pedestal in a covered enamel pan containing ca 2 cm of water. Live fleas jumped off the carpet into the water and were counted. Dead fleas on the carpet were counted. Control mortality was corrected by Abbott’s Formula.

Effects of internal free calcium upon the sodium and calcium channels in the tunicate egg analysed by the internal perfusion technique.

1. The unfertilized egg of the tunicate, Halocynthia roretzi, was intracellularly perfused with various solutions. 2. The perfusion apparatus consisted of lower and upper compartments which were connected by a small glass funnel. A denuded egg cell without chorion was dropped into the funnel and brought into close contact with the glass wall of the funnel. The membrane of the egg faced to the lower compartment was ruptured by a slight difference of hydrostatic pressure and the inside of the egg was perfused with the internal solution flowing through the lower compartment. The current across the upper membrane was analysed by voltage-clamp technique. 3. The egg cell in contact with 400 mM-Na external solution and perfused intracellularly with 400 mM-Na for 30 min showed a relatively low Na reversal potential, +6 mV, in comparison with +60 mV in the intact egg in standard artificial sea water. The exchange efficiency was monitored by observing the shift of Na reversal potential during perfusion with high Na internal perfusate. 4. The internal perfusate containing F- ions stabilized the egg membrane and kept the excitability for 1--2 hr during the intracellular perfusion. With the internal F- perfusate the intracellular cationic content was changed to 400 mM-Na, K, Rb or Cs (external solution of 400 mM-Na) and permeability ratios of the egg Na channel were estimated as PNa:PK:PRb:PCs=1.0:0.14:0.05:0.04. The internal F- perfusate abolished Ca current which was consistently observed in the intact egg, while the internal Cl- perfusate kept both Na and Ca current as in the intact egg. However with the internal Cl- perfusate the egg cell could not be kept in good condition more than 20-30 min. 6. The effects of intracellular free Ca ions upon the egg Na and Ca channels were analysed by using Ca ion-buffered internal Cl- and high Na perfusate. The results showed that internal Ca ions above 10(-6) reduced the Ca current and enhanced the Na current at the same time. In the range between 10(-5) and 10(-4) M the Ca current became half of the control obtained with zero free Ca perfusate while the Na conductance at the zero current level doubled. The internal Ca ions above one mM seemed to abolish the Ca current and to reduce the Na current as well. The reciprocal effect of intracellular Ca ions upon the egg Na and Ca channels was demonstrated in the concentration range from 10(-6) to 10(-3) M.

The Lipid Composition of a Species of Alternaria of the “Alternaria Alternata Group”

(1973). The Lipid Composition of a Species of Alternaria of the “Alternaria Alternata Group”. Mycologia: Vol. 65, No. 4, pp. 958-963.

Unusual film‐forming properties of aromatic heterocyclic ladder polymers

AbstractA new method of obtaining films of aromatic heterocyclic ladder polymers has been found which circumvents casting from high‐boiling acidic solvents. The BBL ladder polymer has been formed into tough, durable films by collecting suspensions of the polymer obtained from acid reprecipitations upon a fritted glass funnel. After drying, the polymer can be removed as film, with thickness dependent upon the amount of material used. Such a film has a tensile strength of 9,600 lb/in.2 as compared to a tensile strength of 16,000 lb/in.2 obtained from the same polymer when cast from methanesulfonic acid solution.

Pollen release by diploid and tetraploid sugar‐beet plants

SUMMARYPollen released during three summers at Broom's Barn, Suffolk, by diploid and tetraploid multigerm sugar‐beet plants was caught by automatic volumetric spore traps and by glass funnels situated in the crop. Tetraploids produced on average 66% as much pollen as diploids, their pollen grains were larger and they needed drier air to release pollen, the concentration of which increased more slowly early in the day and was particularly small on dull, damp days. Pollen catches from diploids and tetraploids decreased at a similar rate with increasing distance from the pollinators. The germination of fruits harvested from male‐sterile plants among the pollinators was consistently less with a tetraploid than with a diploid pollinator, but was not affected by distance of the male‐sterile plants from either pollinator.

Purification of trypsin by affinity chromatography on ovomucoid-sepharose resin

One of the major problems in enzymology is the difficulty in purifying enzymes. The purification is usually done through multiple steps which takes a long time and results in low yields. The usefulness of affinity chromatography in overcoming these difficulties was demonstrated by Fritz et al. [l] . They cross-linked trypsin, cw-chymotrypsin and kallikrein to copolymer of ethylenemaleic acid (EMA), an insoluble carrier introduced by Levin et al. [2] , and used the insoluble enzymes to isolate the corresponding natural inhibitors of these proteases. In later study, Fritz et al. [3 ] fractionated kallikrein and plasmin by chromatography on resin of kallikrein inhibitor crosslinked to EMA. Cuatreccasas et al. [4] cross-linked synthetic inhibitors of several enzymes to the uncharged insoluble carrier Sepharose according to the method of AxCn et al. [5] and used the synthetic inhibitor-Sepharose resins to purify several enzymes by single step of affinity chromatography. Chicken ovomucoid is an egg white protein which is capable of inhibiting bovine trypsin [6] . In this study the method of affinity chromatography was adapted to purification of trypsin by use of chicken ovomucoidSepharose resin. Eighty-five ml of Sepharose 2B (Pharmacia) were activated with CNBr according to Cuatrecases et al. [4] and were coupled to 200 mg chicken ovomucoid (Worthington Biochemical Corp.). The coupling was done by stirring for 24 hr at room temperature the activated Sepharose and the ovomucoid in 250 ml of 0.10 M NaHC03, pH 8.5. After coupling, the ovomucoidSepharose was washed on sintered glass funnel with the following: six times each with 250 ml of 0.10 M NaHCO,, pH 8.5; H20; 0.20 M KCI-HCI,

Quantitative analysis of simple lipid classes by thin-layer chromatography

1. 1. A quantitative thin-layer Chromatographie procedure for the analysis of simple lipid classes (‘neutral lipids’) is described. They were separated by two-step development on silica gel thin-layer chromatoplates. In the first step the solvent diisopropyl ether-acetic acid (96:4, v/v) was used and in the second step, petroleum ether-diethyl ether-acetic acid (90:10:1, v/v/v). 2. 2. After separation, lipid bands were detected by Rhodamine 6G spray, the silica gel with adhered lipids was scraped off and the lipids were eluted. Triglycerides, diglycerides, free fatty acids and hydrocarbons were eluted with diethyl ether, whereas monoglycerides, free cholesterol and cholesteryl esters were eluted by chloroform-methanol (4:1, v/v). The eluates were filtered through sintered glass (‘fine’ porosity) funnels. 3. 3. The eluted lipids were analyzed in the following ways: quantity of triglycerides, diglycerides, monoglycerides and hydrocarbons were determined by quantitative infrared spectrophotometry; free fatty acids by titration; and cholesteryl esters and cholesterol by a standard chemical procedure. 4. 4. The average recovery of individual lipid classes was in the range 98.9–102.0%. 5. 5. Applicability of the procedure for quantitative analyses of tissue lipids is demonstrated on lipid extracted from rat livers.

Nitrodan in Feeds

Abstract The anthelmintic, nitrodan, 3-methyl-5(p-nitrophenyl-azo) rhodanine, is extracted from the feed with dimethyl for mamide: ethanol (1 + 1). The intensely absorbing purple solution formed is separated from the residue by suction filtration through a sintered glass funnel. The filtrate is transferred to a volumetric flask, a small amount of NaOH is added, and the solution is brought to volume, Absorbance is measured at 575 mμ, and the amount of nitrodan present is calculated from a standard curve of known concentrations.

The Gallocyanin-Chrome Alum Stain; Influence of Methods of Preparation on Its Activity and Separation of Active Staining Compound

A dye, which is probably a cationic chelate, has been separated from a gallocyanin-chrome alum staining solution and prepared in the dry form. This dye is apparently the major staining compound. To prepare the chelate or dye, dissolve 150 mg of gallocyanin and 15 gm of chrome alum in 100 ml of distilled water and boil for 10-20 min, cool, filter, wash the precipitate with sufficient distilled water to restore the volume of the filtrate to 100 ml, then add concentrated NH4OH until the pH is raised to 8-8.5. Filter, with suction, through a medium porosity fritted glass funnel. Wash with 100-200 ml of anhydrous ethyl ether and air dry the precipitate. This ratio of chrome alum to gallocyanin and the 10-20 min boiling time are optimal for preparation of the staining solution, which may be used either for staining or for separation of the chelate in its dry form. From the dried chelate, the staining solution is prepared as a 3% solution in1 N H2SO4 and a staining time of 16-24 hr is required. No differentiatio...

Fertility of Turkey Eggs as Related to Method of Collecting and Aeration of Semen

BURROWS and Quinn (1937) described a method of semen collection from the domestic fowl and turkey. The literature was reviewed by them as well as by Parker (1942), Kamar (1958) and lake (1962). Research reporting comparison of equipment for collecting semen for artificial insemination of turkeys is not available. Burrows and Quinn (1937) used a small glass funnel for semen collection while Rooney (1950) and Lorenz et al. (1959) described a vacuum or aspirator bottle method.Bajpai and Brown (1963) noted fertility was not affected when turkey semen was exposed to temperatures of 10°, 15°, 20° and 25°C. and used immediately for inseminating. The fertilizing capacity of turkey spermatozoa was found to be reduced when held in temperatures ranging from 10° to 15°C. for more than one or two hours according to Harper (1955), Carter et al. (1957) and McCartney et al. (1959).The role of aeration of semen…

PREPARATION OF RAT GROWTH HORMONE.

WE have devised a simple method for the preparation of rat growth hormone from fresh frozen anterior pituitary glands. The hormone preparation was obtained in high yield and showed good biological activity while being essentially free of contamination by other pituitary hormones. Disk electrophoresis on polyacrylamide gels indicated the hormone to be relatively homogeneous. In a typical experiment 300 rat pituitary glands were homogenized for 1 min in 4 ml. of ice cold 0.3 M potassium chloride using a glass homogenizer with a ‘Teflon’ pestle. The homogenate was adjusted to pH 5.5 and stirred for 20 min at 5° C and afterwards centrifuged for 10 min at 14,000 r.p.m. The resultant supernatant was brought to an ethanol concentration of 30 per cent at −20° C and immediately centrifuged at 14,000 r.p.m. for 5 min. Additional growth hormone (10–12 mg) was recovered by extracting the residue in 0.3 M potassium chloride at pH 10. However, inconsistent biological activity has been obtained with the material so extracted. The ethanol supernatant was then dialysed, lyophilized and when assayed was found to contain the gonadotropic hormones. The ethanol precipitate was taken up in 1 ml. of tris-hydrochloric acid buffer, pH 8.6 (0.2 M tris, 0.05 M hydrochloric acid), and dialysed against four 500 ml. changes of this same buffer for a period of 4 h at 5° C. The dialysed solution was applied to a block of ‘Pevikon C-870’ (92 cm × 5 cm × 0.5 cm) equilibrated with tris-hydrochloric acid buffer, pH 8.6. A current of 400 V and 80 m.amp was applied for 18 h. After the completion of electrophoresis, the ‘Pevikon’ block was divided into 2-cm segments and each individual fraction was eluted with three 5-ml. portions of buffer using small sintered glass funnels and suction. ‘Pevikon’ particles, which passed through the filter, were removed by centrifugation. The equipment as well as the procedure used for zone electrophoresis was similar to that described by Muller-Eberhard1. The effluent diagram of a typical zone electrophoresis is shown in Fig. 1. Protein concentration was estimated by measuring absorption at 280 mµ The effluent portions were concentrated by partial lyophilization and combined into Fractions A, B and C after analysing individual eluates by disk electrophoresis. Each of the combined fractions was lyophilized and then desalted by gel-filtration on ‘Sephadex G-25’. Fraction A was found to contain from 20–25 mg of rat growth hormone. Fraction B (10–12 mg protein) contained some growth hormone, but was also found to be contaminated with Fraction C. This latter fraction, yielding 8–10 mg of protein, demonstrated no growth hormone activity. Zone electrophoresis of Fraction B resulted in the recovery of an additional quantity (5–7 mg) of rat growth hormone. Zone electrophoresis studies have also been carried out at pH 10 (carbonate Γ/2 = 0.1) with no improvement in resolution. It was noticed that additional electrophoretic components were formed on exposure to pH 10 as compared with the electrophoretic pattern which resulted from isolation at pH 8.6. The yield and biological profile of rat growth hormone (Fraction A] is summarized in Table 1. Of particular interest is the absence of significant prolactin activity.

Synergistic Renal Effects of DCI and Cortisone in Mice Poisoned with Bacterial Endotoxin.

The adrenergic blocking agent DCI or 3,4-dichloroisoproterenol provided a measure of protection against bacterial endotoxin when given subcutaneously to mice by McLean and Berry(1). Cortisone had been found to protect mice from these lipopolysaccharides by Berry et al.(2,3) and the handling of nitrogenous waste products was implicated(4). In the present work the influence of DCI on nitrogen excretion and its interaction with cortisone has been investigated. Methods. Male CF1 mice were used in this study. Saline blanks were given subcutaneously as were the doses of DCI 10 mg/kg and cortisone acetate 5 mg/mouse. Difco crystalline lipopolysaccharide from E. coli (Code 0.27:B8, Control 118023) was the endotoxin used. An approximate LD50 of 0.3 mg/mouse was injected intraperitoneally. The DCI dose was given twice; 5 hours before and 1 hour before the endotoxin. The cortisone doses were given in the same way. The average weight of the mice used in these experiments was about 23 g. The micro-Kjel-dahl procedure was used for determination of urinary nitrogen and blood non-protein nitrogen (NPN). Urine was collected under toluene in conical centrifuge tubes. Pairs of mice were restrained by small stainless steel screens over glass funnels. The animals were without food and water throughout the collection period, which was 17 hours (5 P.M.-10 A.M.). For determination of NPN one volume of blood (about 1 cc) was mixed with 2 volumes of 10% trichloroacetic acid, centrifuged at 3000 RPM for 3 minutes and then filtered. One cc of the filtrate was combined with 0.5 cc 36N H2SO4. Results. Three separate experiments were conducted, each with 6 values per group. Two sets of values were combined to give the data presented in Fig. 1 and the final experiment, carried out some months later than the others, confirmed the earlier findings.

Electrolyte balances following total body x-irradiation.

One of the prominent features of irradiation sickness is the attendant upset of salt and water metabolism. Depending upon the species, this may be manifested in the forms of vomiting, diarrhea, and diuresis. An exact determination of the changes in electrolyte balance following total body x-irradiation is, therefore, of interest.Methods. Twenty 250 g male white rats (Rolfsmeyer Co., Madison, Wisconsin) were placed in metabolism cages over siliconized glass funnels, and allowed free access to distilled water and a diet containing 60% sucrose, 18% lactalbumin, 16.9% Crisco, 4% modified Wesson salt mixture (minus its Na+, K+, and Cl), 1% liver extract (Wilson Co., liver fraction D. Lot 41863), 0.1% choline hydrochloride, with supplements of thiamine, pyridoxine, riboflavin and calcium pantothenate. Roughly 5% of the Na+, K+, and Cl intake was furnished by the diet; coming largely from the liver extract. The remainder of the sodium and potassium chlorides was administered daily by intraperitoneal injection. In the control period the average total electrolyte intake was 1.55 meq of sodium. 2.37 meq of potassium, and 2.54 meq of chloride per 48-hour period. Under these conditions the electrolyte intake was largely independent of the level of food intake. Each 48 hours, the food intake and body weight were recorded, and the excreta were removed for analysis. The excreta were collected quantitatively in barium hydroxide solution, evaporated to dryness, and ashed at 500°C for 12 hours. Sodium and potassium determinations were made on food, injection solutions, and excreta, with a flame photometer attachment to the Beckman DU Spectrophotometer. Chlorides were determined on the same samples by the Volhard method.

Carious-like lesions of enamel produced in the artificial mouth

For the work described in this report, freshly extracted teeth were mounted in plastic boxes and the surfaces were photographed at a magnification of about 8×. The mounted teeth were placed in cylindrical glass funnels and a bacteriologic medium was allowed to flow dropwise over the individual teeth. The teeth were inoculated at weekly intervals by soaking for thirty minutes in a sample of pooled saliva. Usually at regular intervals, the teeth were examined at a magnification of 30× and photographed when necessary. Under these conditions, lesions of the enamel have been produced which are very similar in appearance and position to natural carious lesions. By the use of bilaterally identical teeth, it has been shown that tooth surfaces brushed twice daily remain fairly sound for long periods, whereas unbrushed or roughened areas soften rapidly. Typical regions of attack of brushed teeth are developmental pits and grooves, particularly on the occlusal surfaces, proximal surfaces, and cervical areas near the cementoenamel junction. The mode of attack is quite different when a strictly decalcifying medium is used without bacterial development. Individual teeth exhibit considerable difference in resistance to enamel attack. Apparently deciduous and unerupted teeth are much less resistant than old erupted teeth. Enamel attack has been observed only when glucose is present in the media, and when streptococci, lactobacilli, or both have developed. In the absence of glucose, the tooth surfaces remain intact for long periods. Dentine is decalcified under these conditions, but usually the structure is retained. Some instances of dentine destruction have been noted; in current investigations the conditions necessary for dentine destruction are under active investigation.