Percent Formaldehyde Research Articles

Protective role of (Bronco-T) against formaldehyde induced antioxidant, oxidative and histopathological changes in lung of male Wistar rats

The present study was sought to evaluate the oxidative, antioxidant status and histopathological changes by the acute chronic exposure of formaldehyde. Bronco-T a poly-herbal formulation treatment, changes the oxidative, antioxidant status and histopathology of rat lungs with antioxidant and regenerative property. In this experiment thirty adult male albino Wister rats were used for the study and subdivided in to five groups consist of 6 rats for each group. Group-I served as control and the other 4 groups such as II, III, IV and V are considered as experimental. The control and treatment rats are maintained for 21 days of experimental period. Experimental rats are exposed to 40 percent formaldehyde for 1 h treated with Bronco-T and salbutamol. In the present investigation, the formaldehyde exposed rats a series of free radical chain reactions were grimly provoked, the evaluation of antioxidant enzymes (SOD, CAT), other enzymes oxidative enzymes (G-6-PDH, SDH) and (ALT, ALAT and LDH) were measured. A clear assertive imbalance between oxidation and anti-oxidation status was critically observed, and oxidative stress was clearly exacerbated in lung tissue leading to altrations in architecture of lung histopathology. Oral gavage Bronco-T exhibits a beneficial action by bringing normal architecture in lung tissue of formaldehyde inhaled rats with antioxidant properties. Bronco-T treatment may be a suitable remedy for formalin occupational diseases.

Effect of formaldehyde antimicrobial feed additive on the immune competence of chickens experimentally infected with a known Newcastle disease virus strain

Thirty-seven percent (37%) formaldehyde- possessing antimicrobial activity has been used in various forms as a fumigant for mould control and as a feed additive for feed preservation. The study evaluated the effects of formaldehyde-treated poultry feed on the immune response of birds to Newcastle disease virus (NDV) infection with Kudu 113 strain. A total of 100 chicks were acquired from Zartech Hatchery, Ibadan, Nigeria. They were randomly appropriated into A, B, C and D experimental groups, with each group containing 25 birds. Group A chicks were vaccinated, fed treated feed and infected with ND virus while group B chicks were vaccinated, fed untreated feed and infected with ND virus. Chicks in group C were not vaccinated but fed treated feed and infected with ND virus whereas chicks in group D were not vaccinated, fed untreated feed and infected with ND virus. The data generated were analysed with analysis of variance (ANOVA). Formaldehyde-treated feed had no significant effect on the PCV, antibody response to NDV, organ index and feed intake but significantly affected the body weights of the birds. Formaldehyde, despite the antimicrobial activities, may not prevent infection of Newcastle disease virus infection, when used as a feed additive.

Quantification of buprenorphine and the metabolites of methadone and heroin in hair of patients in rehabilitation programs by GC–MS

Quantification of buprenorphine and the metabolites of methadone and heroin in hair of patients in rehabilitation programs by GC–MS

The Effect of Formaldehyde Vapour on the Lungs of Rabbits

Formaldehyde is an organic compound with the formula CH2O and it is the simplest aldehyde, with systematic name methanol. The aim of this investigation was to sensitize embalming laboratory users of the impending danger associated with overexposure to forty percent (40%) formaldehyde vapour (the active component of embalming fluid) on the lungs. Twenty adult male albino rats were used for this investigation. The animals were divided into five (A, B, C, D, and E) groups. Animals in group B, C, D and E were respectively exposed to forty percent( 40%) formaldehyde for ten(10), fifteen(15), twenty(20) and twenty five(25) days while animals in group A which serve as control group were not exposed to forty percent (40%) formaldehyde at all. At different stages of the experiment, the animals in each of the group were decapacitated and the thoracic cage cut open to expose the lungs. The lung tissue was processed for light microscopic investigation adopting the Haematoxylin and Eosin (H and E) staining procedure. The histopathological observation in this study showed that exposure to forty percent (40%) formaldehyde induced changes in the histology of the lungs. The observed changes were duration dependent. So forty percent (40%) formaldehyde may be able to have greater marked effect at a prolonged exposure. These findings suggests that forty percent (40%) formaldehyde vapour may be remarkably toxic on the rat lung tissue and advocate for precautionary measure for human handlers while handling this chemical especially in the histopathology unit for fixation and embalming purposes.

Application of atomic force microscopy in blood research

To find suitable solutions having lesser granules and keeping erythrocytes in normal shapes under atomic force microscopy (AFM). Eight kinds of solutions, 1% formaldehyde, PBS buffer (pH7.2), citrate buffer (pH 6.0), 0.9% NaCl, 5% dextrose, TAE, 1640 medium and 5% EDTA-K2, were selected from commonly used laboratory solutions, and venous blood from a healthy human volunteer was drawn and anticoagulated with EDTA-K2. Before scanned by AFM (NanoScopeIIIa SPM, Digital Instruments, Santa Barbara, CA), a kind of intermixture was deposited on freshly cleaved mica and then dried in the constant temperature cabinet (37 degrees). One percent formaldehyde, citrate buffer, 5% dextrose, TAE, were found to keep human erythrocytes in normal shape with few particles. Processed by these solutions, fine structures of human erythrocyte membrane were obtained. One percent formaldehyde, citrate buffer, 5% dextrose and TAE may be applied to dispose erythrocytes in AFM. The results may offer meaningful data for clinical diagnosis of blood by AFM.

Suprimento arterial do lobo torácico do timo em suínos da linhagem "Rezende"

Foram dissecados 30 exemplares de fetos de suínos da linhagem "Rezende", após injeção do sistema vascular arterial, via artéria aorta descendente torácica, com Neoprene látex "450" corado com pigmento específico e fixação em solução aquosa de formol a 10%, para a observação da origem, número e ordenação das artérias destinadas ao lobo torácico do timo. O antímero esquerdo foi irrigado por ramos diretos das artérias torácica interna esquerda (96,66%), cervical superficial esquerda (40,00%), torácica interna direita (26,66%), tronco braquiocefálico (20,00%), subclávia esquerda (10,00%), carótida comum esquerda (10,00%), vertebral esquerda (6,66%), cervical superficial direita (6,66%), tronco bicarotídico (6,66%), torácica externa direita (3,33%) e axilar esquerda (3,33%); ramos indiretos foram provenientes das artérias torácica interna esquerda (40,00%), cervical superficial esquerda (23,33%) e subclávia esquerda (3,33%). O antímero direito foi irrigado por ramos diretos, provenientes das artérias torácica interna direita (63,33%), cervical superficial direita (13,33%), carótida comum direita (6,66%), torácica externa direita (3,33%) e subclávia direita (3,33%); ramos indiretos foram originários das artérias torácica interna direita (20,00%), cervical superficial direita (10,00%), torácica externa direita (3,33%) e subclávia direita (3,33%). A massa tímica do antímero direito esteve presente em 43,33% dos casos, ausente em 30,00% e reduzida em 26,66%, sendo observado de 1 a 7 ramos penetrantes em seu parênquima. A massa tímica do antímero esquerdo foi encontrada em 100,00% das dissecações, recebendo de 2 a 9 ramos penetrantes.

Characterizing formaldehyde emission rates in a gross anatomy laboratory.

The evaporation of formaldehyde from cadavers in gross anatomy laboratories can produce high exposures among students and instructors. To understand the system that produces exposures and to plan for implementing control options, the generation of formaldehyde vapors must be characterized. A gross anatomy laboratory with 47 dissecting tables was studied during 15 lab sessions over a period of 16 weeks. Area concentrations were measured using National Institute of Occupational Safety and Health (NIOSH) method 3500. Average daily area concentrations in the laboratory ranged from 0.635 to 1.82 mg/m3. The ventilation was characterized on three separate days. The laboratory had a general ventilation rate of 9.8 air changes per hour. There was no local exhaust ventilation. The concentration measurements were used in a mass balance model along with ventilation rates to determine formaldehyde emission rates. The daily average formaldehyde emission rate from all sources in the laboratory ranged from 95.2-274 mg/min, with an average of 148 mg/min over the course of the study. This total emission rate was used along with the number of dissecting tables to develop an emission factor of 3.15 mg/min per table. The emission factor is a generalizable tool that can be used in laboratories of various sizes to predict emission rates and develop control strategies. This emission factor is applicable where the cadavers are prepared with similar embalming fluid consisting of approximately 10 percent formaldehyde.

CHEMICAL TREATMENT OF GROUND CORN TO LIMIT RUMINAL STARCH DIGESTION

Five trials were conducted to determine the effects of chemical treatment of ground corn on in vitro dry matter disappearance (IVDMD), in vivo nutrient utilization and ruminal starch digestion. Ground corn was treated with 0, 1, 2 or 3% (wt wt−1) formaldehyde, glyoxal, masonex, propionaldehyde or tannic acid. IVDMD of ground corn was inversely related (P < 0.01) to percent formaldehyde treatment level, while glyoxal, masonex, propionaldehyde and tannic acid were relatively ineffective in reducing IVDMD. Treatment of large batches of ground corn with 0, 0.5 or 1% (wt wt−1) formaldehyde also linearly reduced IVDMD (P < 0.01). Six abomasally fistulated wethers (average weight 95 kg) were used in a replicated 3 × 3 Latin square to determine the effects of 0, 1 or 2% (wt wt−1) formaldehyde treatment of ground corn on ruminal and total tract nutrient digestion. Ruminal dry matter (DM) digestion and total tract DM, organic matter (OM) and acid detergent fiber (ADF) digestion decreased linearly (P < 0.01) with increasing formaldehyde treatment levels. Ruminal starch digestion decreased 30% and 41.5% for 1 and 2% formaldehyde treatment, respectively, compared to untreated corn while total tract starch digestion was not affected (P > 0.05) by formaldehyde treatment level. Results of these trials are interpreted to suggest that formaldehyde treatment of ground corn reduced rumen microbial digestion of starch both in vitro and in vivo without reducing total tract starch digestion. Key words: Corn, starch digestion, formaldehyde, ruminants

The physical dimensions of the human neonatal cardiovascular system.

To establish a data base for studies which seek to model and simulate the human perinatal cardiovascular system, we dissected three stillborn, full-term infants and measured the length, internal diameter, and wall thickness of over 1000 blood vessel segments. Cumulatively, these segments represent the major and minor vessels of the systemic and pulmonary circulation at birth. Statistical analysis showed that the methods used to obtain these physical dimensions were highly consistent and that storage of tissue samples in 10 percent formaldehyde solution caused a linear shrinkage of approximately 6.3 percent. A topological code was developed to illustrate the network relationships of blood vessel segments. An example of data utilization based on the topological code is presented and discussed.

Protective immunity against Naegleria meningoencephalitis in mice

This study is to verify the protective ability against experimental Naegleria meningoencephalitis by immunization with Naegleria fowleri in mice. Naegleria fowleri, strain 0359, and Naegleria gruberi, strain EGB, were used in this study, and cultured in CGVS medium axenically. Inbred BALB/c mice, weighing about 20g, were immunized by three intraperitoneal injection of 1 x 10(6) N. fowleri trophozoites at the interval of one week. This N. fowleri trophozoites antigen was fixed with 5 percent formaldehyde. N. fowleri trophozoites from culture were homogenized with sonicator at 4 degrees C as monitored by phase contrast microscopy, and their membrane and cell content preparations were made for the immunization of mice. Their inoculation dose in volume was equivalent to the 1 x 10(6) trophozoites in each injection for immunization. And N. gruberi trophozoites, which was fixed with 5 percent formaldehyde, were also used for immunization. Mice were inoculated intranasally with 5 x 10(4) N. fowleri trophozoites in a 5 microliter suspension under anesthesia by as intraperitoneal injection of about l mg secobarbiturate. Nervousness, rotation or sluggish behaviour were observed in the mice which were infected with N. fowleri. Necrotic lesion was demonstrated in the anterior portion of brain, especially in the olfactory lobe. The inflammatory cell infiltration with numerous N. fowleri trophozoites was noticed. This pathological changes were more extensive in the control than in the experimental groups. Mice were dead due to experimental primary amoebic meningoencephalitis that developed between 8 days and 23 days after inoculation. Mortality rate of the mice was low in the immunized experimental group. Mean survival time, which is the survival duration of mice from the infection to death, was prolonged significantly in the immunized mice except in the mice immunized with N. fowleri membrane. Even in the mice immunized with N. gruberi, survival time was delayed. In summary, the effectiveness of immunization is demonstrated in terms of protective immunity against Naegleria meningoencephalitis in mice.

Distribution of fluorescently labeled alpha-actinin in living and fixed fibroblasts.

The distribution of flourescently labeled alpha-actinin after microinjection into fibroblasts has been determined in both living and fixed cells. We have found that the distribution of the injected tetramethylrhodamine isthiocyanate-labeled protein (TMRITC-alpha-actinin) in living cells, which is in ruffling membranes, actin microfilament bundles, and polygonal microfilament networks (Feramisco, 1979, Proc. Natl. Acad. Sci. U. S. A. 76:3967-3971), was virtually unaffected by the fixation (3.5 percent formaldehyde) and extraction (absolute acetone) used for the preparation of the cells for immunoflourescence. Also, these patterns were found to coincide with the alpha-actinin revealed by immunoflourescence. Also, these patterns were found to coincide with the alpha-actinin revealed by immunoflourescence. These findings offer, for the first time, evidence indicating the validity of the immunoflourescence technique in the localization of alpha-actinin in cultured cells. With the combination of the injection procedure and the immunoflourescence localization of endogenous structural proteins, it was determined that nearly all of the actin stress fibers were decorated in a periodic manner with the injected alpha-actinin. Endogenous tropomyosin in the injected cells was found to be distributed with a periodic pattern along the stress fibers that was antiperiodic to the pattern observed for the microinjected alpha-actinin. The tropomyosin antibody stained the polygonal microfilament networks and was excluded from the foci, whereas the microinjected alpha-actinin was incorporated into the foci of the networks. Thus, the microinjected fluorescent derivative of alpha-actinin appears to be incorporated into the functional pools of alpha-actinin within the living cell and to be utilized by the cell with fidelity.

Antimicrobial effectiveness in endodontic therapy using formocresol and two new alcoformol agents: Mechanical preparation during the second visit

Antimicrobial effectiveness of two alcoformol agents (AF 8.75 and AF 3.5) was studied in a clinical trial by means of bacteriologic examination of the root canals. After the initial culture was taken, one of the disinfectants was sealed in the pulp chamber for one week. At the second visit, the root canal was reamed and a second culture was taken. It was found that AF containing 3.5 percent formaldehyde is a satisfactory disinfectant for root canals of vital teeth. A concentration of 8.75 percent was needed for disinfection of teeth with necrotic pulps.

Analyse und Dokumentation der Arteriosklerose durch Röntgenkontrastdarstellung

Vessels as well as soft tissues can be contrasted in a solution of 10 percent formaldehyde and sodium iodate so that structural details can easily be identified by X-ray. Atheromatous plaques, ulcers and calcifications are demonstrable by comparing X-ray films of contrasted and uncontrasted vessels. This methods allow a quick investigation of vascular walls and of other tissues.

Activity of endonuclease S 1 in denaturing solvents: Dimethysulfoxide, dimethylformamide, formamide and formaldehyde

The endonuclease S 1 from Aspergillus oryzae is shown to be active in aqueous solutions of greater than 60 percent formamide, 50 percent dimethylsulfoxide, 30 percent dimethylformamide and in 2 percent formaldehyde. The melting profile of T7 DNA is determined by S 1 digestion in 50 percent formamide and is found to agree with the optical melting profile. The single-strand specificity of S 1 is retained in 50 percent formamide at 37°C, 3°C below the DNA melting temperature. S 1 is shown to be active at temperatures greater than 5°C above the DNA melting temperature in this solvent.

Comparison of Rumen and Fecal Analysis to Describe Deer Diets

Rumen and fecal samples were collected simultaneously from mule deer (Odocoileus hemionus) and white-tailed deer (0. virginianus) in southeastern Arizona. Rumen samples were analyzed volumetrically and fecal samples microscopically to compare results obtained by the two techniques. Comparisons of the data acquired by these techniques show that results from microscopic fecal analysis are quite similar to those from volumetric rumen analysis. Fecal analysis appears to be a useful technique for studying deer diets in the arid Southwest. The utility of this technique for other areas and species is discussed as are sampling rates and suggestions for successful use of fecal analysis. J. WILDL. MANAGE. 38(3):535-540 The most commonly used procedure for studying food preferences of ungulates has been rumen analysis by volumetric (Dirschl 1962, Martinka 1968) or point analysis (Chamrad and Box 1964) methods. These methods of rumen analysis have been compared and evaluated on the basis of accuracy and time requirements by Robel and Watt (1970). When rumen samples must be collected from secretive and/or endangered species of ungulates, rumen analysis is not always a feasible technique. Consequently, biologists have often analyzed fecal samples microscopically for the remains of identifiable plant cuticles. Since every plant species has unique cuticle characteristics, and most plant cuticles are not digested in ruminant digestive processes, forage plants can be identified microscopically in fecal samples of grazing or browsing herbivores (Stewart 1965, 1967; Stewart and Stewart 1970; Adams 1957; Hercus 1960; Martin 1955). This technique has been used to study food habits of cottontail rabbits (Dusi 1949), waterbuck in Africa (Kiley 1966), pocket gophers (Myers and Vaughn 1964), many African game species (Stewart 1967, Stewart and Stewart 1970), and deer (Zyznar and Urness 1969). While using fecal analysis one must assume that the epidermis of each plant species survives digestion sufficiently to be identifiable in the feces (Stewart 1970). The validity of this assumption is questionable, and results from fecal analysis have not been compared with those of other techniques. The purpose of this research was to compare the results from rumen and fecal analysis when these samples are secured from individual deer simultaneously. Our results provide information on the usefulness of fecal analysis for studying deer diets in the Southwest. METHODS AND MATERIALS Simultaneous collections of rumen and fecal samples were obtained from 13 mule deer killed by hunters in the Dos Cabezas Mountains and from 9 white-tailed deer by special collections in the Santa Rita Mountains, southeastern Arizona. Samples from male mule deer were acquired in November during the 1970 and 1971 regular hunting seasons, and samples from female whitetailed deer were taken during the summer of 1970. Rumen samples were washed and preserved in a 10 percent formalin solution, 1 Present address: School of Forest Resources, Pennsylvania State University, University Park 16802. J. Wildl. Manage. 38 (3):1974 535 This content downloaded from 157.55.39.92 on Tue, 21 Jun 2016 05:28:25 UTC All use subject to http://about.jstor.org/terms 536 RUMEN AND FECAL ANALYSIS Anthony and Smith and fecal samples were preserved in formal acetic acid (85 parts-70 percent alcohol, 10 parts-40 percent formaldehyde, and 5 parts-glacial acetic acid) until they could be analyzed.

Reaction of Polyacrylamide with Commonly Used Additives

Letters to JPT Forum are limited to a maximum of 750 words, including 200 words for each table and illustration. Acceptable subjects include new engineering ideas, progress reports from the laboratory and field, and descriptions of unique equipment, processes or practices. Letters should be sent to the Editor. SPE reserves the right to edit material to eliminate commercialism on remarks of a questionable nature. In the past, several investigators have added formaldehyde as a bactericide to "pusher type" mobility control solutions. These investigators probably observed a decrease in resistance factor with time and attributed it to bacterial degradation. A more recent paper claims that formaldehyde acts as an effective paper claims that formaldehyde acts as an effective oxygen scavenger in polyacrylamide solutions. It states that low concentrations of HCHO are effective as a combination oxygen inhibitor and biocide, the oxygen inhibition being attributed solely to a reaction between HCHO and oxygen so that the latter is effectively removed from the system. The purpose of this note is to show that formaldehyde is a poor oxygen scavenger but that it probably reacts with the Pusher solution to form products that have properties quite different from the original proven Consequently, if formaldehyde is added to proven Consequently, if formaldehyde is added to a Pusher solution the behavior of the resulting system is not representative of the original polymer. This fact must be recognized if experimental results are to be interpreted intelligently. The following experiment clearly shows that a reaction occurs between formaldehyde and a typical Dow Chemical Co. Pusher. Two identical 500-ppm solutions of Pusher (700 type) were prepared in 2 percent NaCl. To one of them. 0.4 percent percent NaCl. To one of them. 0.4 percent formaldehyde (37 percent) was added immediately. After about 1 day of hydration at room temperature with intermittent slow stirring, the viscosity (Ostwald), the screen factor. and the pH were determined. These results are presented in the following table. Pusher Pusher (0.4% (no formaldehyde) formaldehyde) u(75deg. F), cp 1.90 1.92 Screen factor 12.40 12.70 pH 9.09 8.93 Each solution was also allowed to flow through a saturated, fine fritted glass filter disc (51, pore size) under a constant head, and the cumulative flow was measured as a function of time. The cumulative-flow vs time curves are shown in Fig. 1. where it can be seen that the solution containing formaldehyde completely plugged the fritted glass disc after the passage of about 19 cc. The other solution containing no formaldehyde propagated through the disc quite well. In other words, because of surface plugging the resistance factor exhibited by the polymer containing formaldehyde increased steadily from an initial value of 2.21 and eventually became infinite. The resistance factor of the polymer without formaldehyde was essentially constant (2.14 to 3.08) with throughput. It should be mentioned that both solutions were clear to the naked eye and no precipitate was apparent in the solution containing HCHO. Data for the same polymer solution containing only 0.1 percent polymer solution containing only 0.1 percent formaldehyde (therefore 370 ppm HCHO) are also shown in Fig. 1. The distinct curvature of the cumulative-flow vs time curve indicates a definite plugging action, but the effect is not nearly so plugging action, but the effect is not nearly so pronounced as in the case of the polymer containing pronounced as in the case of the polymer containing 0.4 percent HCHO. P. 1137

Early Results of Aortic Valve Homograft Replacement

The authors present the early results hi 50 cases of aortic valve homograft replacement. The homografts were sterilized and preserved in 4.0 percent formaldehyde solution buffered to a 5.6 pH, as proposed by Paneth. Aortic valve replacement only was performed in 34 cases, open mitral commisurotomy in 11 cases, and mitral valve replacement with a Starr-Edwards prosthesis in five cases. The immediate mortality was 4 percent and the late mortality was 6 percent The most important postoperative complications were myocardial infarction, transient atrioventricular block, acute bacterial endocarditis and the appearance of an aortic diastolic murmur of aortic insufficiency. The five deaths were caused by (1) cardiac arrest (2) myocardial infarction, (3) and (4) low cardiac output due to aortic incompetence, and (5) acute bacterial endocarditis.

Polyvinyl Alcohol-Fixative-Adhesive for Small Helminths and Protozoa

Following the method of Brooke and Goldman (1949), the author was able to fix, mount and stain small helminths and parasitic protozoa of fish in polyvinyl alcohol-fixative smears. However, because there was much granular material in the PVA-Schaudin's mixture, AFA fixative was substituted for the Schaudin's. The PVA went into solution readily using this fixative. The solution was accomplished by adding 5 grams Elvanol #71-301 to 62 ml. of water, heating to 950 C. until dissolved and adding 5 ml. of acetic acid, 112 ml. of glycerine, 10 ml. of formaldehyde, and 30 ml. of 95 percent alcohol. Protozoa were placed on a slide in a drop of water; 2 drops of PVA-AFA were added and the mixture spread over approximately one-half of the slide. The slide was dried two days at room temperature or overnight in the 550 C. oven. This mixture appeared to fix Trichodina, Myxosoma spores, Oxytricha, and Paramecium as well as the PVA-Schaudin's mixture. After drying, the slides were stained, dehydrated and mounted as ordinary smears. In no instance did the smears come off. As Brooke and Goldman (1949) noted, the slides can be re-dried at any stage before dehydration prior to mounting. As many live cercariae as could be collected in a drop were placed on a slide and two drops of the PVA-AFA mixture added. This was spread out and allowed to dry as for protozoa. Cercariae of Posthodiplostomum m. minimum and Crassiphiala bulboglossa were fixed in a slightly contracted state but were satisfactory for staining. The slides were stained and mounted with very little loss of material. Previously fixed cercariae can be handled in the same manner. Those fixed in hot 5-10 percent formaldehyde and then attached to the slide with PVA should yield excellent specimens. Small metacercariae and nematodes that are so easily lost during handling were fixed in a small Petri dish or beaker of hot 10 percent neutralized formaldehyde, transferred to a slide in a drop of fixative, and one drop of PVA-AFA was added. Slides were dried, stained, and mounted as before. The metacercariae of Uvulifer, Crassiphiala, Diplostomulum, Ornithodiplostomum, and the small nematode, Rhabdochona, were easily handled by this method. Hot AFA fixative caused the worms to stick to the container and they were damaged in removal. However, hot formaldehyde alone did not cause them to stick but did prevent extreme contraction. Small helminths can be fixed directly in the PVAAFA solution on a slide, but they contract as they do in arty cold fixation. Attempts to anesthetize the worms in 0.4 percent chloretone previous to mounting in the PVA-AFA solution also resulted in contracted speci-

Formaldehyde Curing of Zein Fibers

Conditions necessary for the rapid formaldehyde curing of zein fibers were investigated and a continuous two-stage curing process was developed. The first stage (precuring) consists of a mild cure to introduce approximately 0.75 percent formaldehyde into the fiber and produces, after stretching, a fine-diameter fiber of exceptional strength and elasticity. The second stage (post-curing) consists of a strong cure to introduce about 3.0 percent additional formaldehyde into the stretched fiber to stabilize its length. Formaldehyde is bound under both alkaline and acid conditions, but it is only under acid conditions that any curing occurs. Ammonium salts act as catalysts for the reaction in the pH range 0 to 4 and the resulting fibers are stable to boiling in mild alkali. When cured under highly acidic conditions (below pH 0), the fibers are stable to both acid and alkaline boiling.

A Photoelectric Nephelometer

A nephelometer is described that does not require a precision optical system or an electronic amplifier. It is sensitive enough to measure the growth of E. coli from a starting concentration of approximately 2×106 bacteria per ml. The readings are reliable from 107 to 109 bacteria per ml. A graph of the photo-current caused by the scattered light versus the number of E. coli per ml is given. The E. coli culture is a saturated 24-hr. nutrient broth culture in the lag phase. The bacteria were killed with 1 percent formaldehyde. In this range of bacterial concentrations the scattered light is nearly proportional to the number of scattering centers. The instrument is well adapted to the study of growth curves of bacterial cultures and the lysis phenomena that occur when the organisms are attacked by bacteriophages. A horizontal beam of light passes through the vertical test tube containing the specimen. The light scattered downward is measured with a barrier layer photo-cell. The horizontal incident light produces a photo-current of 2.4×10−3 ampere. The light scattered by a specimen whose titer is 5×107 E. coli (growing exponentially) per ml produces a photo-current of 1.2×10−5 ampere. In this case the scattered light reaching the photo-cell is 1/200 of the incident light.