Insulin influences astroglial morphology and glial fibrillary acidic protein (GFAP) expression in organotypic cultures

Variations in the levels and timing of exposure to insulin-related peptides influence the phenotypic appearance of astroglia present in organotypic cultures of the E17 mouse cerebellum as well as the expression of glial fibrillary acidic protein (GFAP) mRNA and its encoded protein. The morphology of GFAP-immunoreactive cells was influenced by the levels of insulin added in an age-specific manner. Fetal radial glia were selectively and significantly (P less than 0.001) increased by high (10 micrograms/ml) insulin levels, comprising the majority of the GFAP-positive cells seen. In contrast, there was an almost complete reversal of this pattern elicited by low (10 pg/ml) insulin levels, where GFAP-positive cells appeared undifferentiated and epithelioid (P less than 0.001). In newborn cultures, on the other hand, the morphological responses to both high and low levels of insulin were considerably attenuated and involved radial glia primarily, whose numbers were significantly increased by the high insulin levels. Exposure to high levels of insulin was accompanied by an increase in GFAP mRNA expression, as determined by non-isotopic (biotin) in situ hybridization histochemistry, and intense GFAP immunoreactivity, while low insulin levels elicited minimal expression of both message and protein product. In view of the critical interdependence of developing neurons and radial glia with respect to neuronal migration and the differentiation of neurons and astroglia, the responses observed suggest developmentally regulated mechanisms by which insulin-related peptides themselves may influence directly and indirectly both neuronal and astroglial differentiation.

Exact cleavage site of Alzheimer amyloid precursor in neuronal PC-12 cells

We have identified the secretory cleavage site in the Alzheimer amyloid precursor (APP) in a non-transfected neuronal cell line, using cyanogen bromide digests of APP purified from medium conditioned by PC-12 cells which were differentiated to a neuronal phenotype. The results obtained are most consistent with proteolysis of the Lys16-Leu17 bond in the beta amyloid peptide, followed by partial removal of Lys16 by a basic carboxypeptidase.

A research-oriented medical cost accounting system

Prospective research into factors affecting health care costs for individual patients requires a hybrid information management system with some features usually associated with a medical billing package and other features common to research databases. Furthermore, data collection for such a project must often be done in the field where a portable computer is most convenient. A software program is described which has been developed to address these disparate needs. It allows classification by study protocol assignment and provides multiple summary formats for the assessment of costs. For example, charges can be stratified by specialty, by category of service (pharmacy, room, surgery, respiratory therapy, etc.), by magnitude of expense ('big' vs 'little' ticket items) and so forth. The system design described may prove useful to other investigators studying variation in health care costs.

A possible mechanism of action of the neurotoxic agent iminodipropionitrile (IDPN): a selective aggregation of the medium and heavy neurofilament polypeptides (NF-M and NF-H)

Juvenile male rats treated acutely with the neurotoxic agent, iminodipropionitrile showed no changes in the levels of total neurofilament subunit mRNA or protein for up to 28 days. However, the drug promoted aggregation of the neurofilaments, both spontaneously upon isolation and in an in vitro reassembly assay. This observation correlated with a basic pI shift of the heavy neurofilament subunit, due to a yet to be identified modification. Because of the crucial involvement of this neurofilament subunit in axonal integrity, it is likely that iminodipropionitrile produces a major portion of its neurotoxicity through this mechanism.

Expression of the Alzheimer amyloid precursor in brain tissue and effects of NGF and EGF on its metabolism

Alzheimer's disease (AD) is the major cause of serious dementia and memory loss in several million elderly Americans. The most prominent lesions in the brains of these patients are the depositions of two types of abnormal filaments: the predominantly intraneuronal neurofibrillary tangles (NFT), which consist of paired helical filaments (PHF), and the extracellular amyloid fibers. These changes are characteristic of AD, and a final diagnosis of this disease is based on the presence of large numbers of these abnormal filamentous structures in the patient's brain. The amyloid fibers consist of a peptide subunit termed beta-protein or A4 peptide, which derives from a larger precursor protein. In this study we review the structural characteristics, regulation of expression, and metabolism of the Alzheimer amyloid precursor in brain tissue and cell cultures.

Gender differences in health-related quality of life

In 1986 the life expectancy at birth was 71.3 years for males and 78.3 years for females--providing a 7-year advantage for women. Although women live longer, it has been reported that they paradoxically experience more physical and psychological illnesses. In this article, we estimate the expected well-years or quality-adjusted life years for men and women in the general population. The data were obtained in a random sample of 1,034 residents of San Diego. The well-life expectancy uses standard life expectancies with adjustments for quality of life. The well-life expectancy for men was 59.8 years; for women, it was 62.7 years. Thus, the quality adjustment had significantly more impact on women (15.6 years) than on men (11.5 years). Age-specific estimates of health-related quality of life suggested a male advantage before age 45 and a female advantage after age 45. The benefits of well-years of life as a public health statistic are discussed.

Differential brain expression of the Alzheimer's amyloid precursor protein

The expression of the Alzheimer amyloid protein precursor (AAPP) was examined in human, monkey, dog and rat brains. Two proteins, one identified as AAPP695 and the other as AAPP751, were immunoprecipitated from the in vitro translation of human, dog and rat brain polysomes. The AAPP751 to AAPP695 ratio was highest in human, intermediate in dog and lowest in rat brain polysomes. Human cerebral cortex contained higher levels of the AAPP751 mRNA than either dog or rat cortex. AAPP695 was detected in both cerebral cortex and cerebellum of all species examined. In contrast, AAPP751 was detected predominantly in the cortex of human, monkey and to a lesser extent dog brains while it was not detected in rat brain. These findings indicate that the amyloid precursors are differentially expressed in different mammalian brains and suggest that AAPP751 is mainly expressed in the brain regions involved in plaque formation.

Nerve and epidermal growth factors induce the release of the Alzheimer amyloid precursor from PC 12 cell cultures

Antisera against specific sites of the Alzheimer beta Amyloid protein precursor (beta APP) were used to study the effects of nerve and epidermal growth factors on the expression and processing of this protein in PC12 cell cultures. Two major beta APP proteins (140 and 105 kDa) both containing the Kunitz-protease inhibitor insert (KPI), were detected in cell extracts of naive PC12 cells. Treatment of these cultures with nerve growth factor (NGF) induced the release of two beta APP species 125 and 120 kDa, both of which contained the KPI domain and lacked the carboxy-terminal portion of the precursor. The released beta APP contained O-linked sugars. Only one of the released beta APP proteins bound to the lectin Concanavalin A indicating that they differ in their glycosylation. Epidermal growth factor (EGF) also induced the release of beta APP proteins into the culture medium with similar electrophoretic mobilities as those released by NGF.

Alzheimer's disease-associated reduction of polysomal mRNA translation

Polysomes from the frontal cortices of individuals who had histopathologically confirmed Alzheimer's disease were compared with polysomes from individuals who exhibited no neuropathological conditions. The cytosolic polysome yield from Alzheimer's disease frontal cortex was reduced 40% compared with that obtained from control frontal cortex. The translational activity per unit polysome of the Alzheimer's disease polysomes was only 50% of control in a reticulocyte lysate in vitro translation assay in which human polysomes do not undergo reinitiation. These differences exhibited brain region specificity in that polysomes isolated from Alzheimer's disease cerebellum were not different from control cerebellar polysomes. Thus, the disruptions are not due to a secondary and general response of the entire brain to the disease. These reductions were reflected by similar decreases in the translation of the mRNA for high molecular weight neurofilament polypeptide. Thus, the inhibition of polysomal mRNA translation is a mechanism by which gene expression is impaired in pathologically involved brain regions of individuals afflicted by Alzheimer's disease.

The Quality of Well-being Scale. Applications in AIDS, cystic fibrosis, and arthritis

The Quality of Well-being (QWB) Scale combines preference-weighted measures of symptoms and functioning to provide a numerical point in-time expression of well-being that ranges from zero (0) for death to 1.0 for asymptomatic optimum functioning. The QWB includes three scales of function: mobility, physical activity, and social activity. Each step of these scales is associated with preference weights. Preference adjustments for symptoms are also included. This paper describes how this general system was used to evaluate outcomes in three different clinical conditions: acquired immune deficiency syndrome (AIDS), cystic fibrosis, and arthritis. In one study, the QWB was administered to 31 patients participating in evaluation of azidothymidine (AZT) treatment for AIDS. The QWB system demonstrated substantial benefits of AZT treatment in comparison to placebo. In a second study, the QWB and a series of pulmonary function measures were administered to 44 patients with cystic fibrosis. The QWB was demonstrated to be significantly correlated with measures of pulmonary function, including FEV1 and maximal midexpiratory flow rate (MMEFR). In addition, there were significant associations between the QWB and measures of exercise tolerance. In the third study, the QWB and an arthritis-specific measure were administered to 83 arthritis patients before and after their treatment. The QWB was at least as capable of detecting clinical change in this population as was the disease-specific measure. For all three conditions, the QWB considered side effects and benefits of treatment in a common unit. Clinical trial data are cited to suggest that the QWB is a valuable outcome measure in arthritis treatment evaluation. We conclude that the QWB has substantial validity as a general health outcome measure and that the system can be used with different populations.

Using composite health status measures to assess the nation's health

Research in progress at the National Center for Health Statistics for evaluating the usefulness of composite measures of health status for assessing the nation's health is described. Three measures suitable for use in the general population, the Health Insurance Experiment-Functional Limitations (HIE-FL), the Health Utility Index (HUI), and the Quality of Well-being (QWB) scale, have been mapped to data collected in the 1980 National Health Interview Survey (NHIS). Analysis using current algorithms for making composite function status measures according to the QWB methods suggests that traditional single indicators of health tend to overestimate the level of health by about 10%. When symptoms and problems are added to the composite function score, the overestimate as measured by the single indicator is at least 50%. The authors are continuing to validate these algorithms, to develop similar ones for the HIE-FL and HUI, and to extend the analysis to data collected in 1977, 1979, and 1984. Current results indicate that to realize fully the benefits of composite measures, well-established, valid, and reliable measures of health-related quality of life should be included as part of the regular NHIS data collection procedures.

Efficacy of soft splints in reducing severe knee-flexion contractures

This study evaluated the effectiveness of soft splints made from polyurethane foam in reducing severe knee-flexion contractures of patients with cerebral palsy. The splints were applied nightly over a period of 10 months. Knee-flexion contractures were reduced by an average of 24 degrees in all patients. Younger patients generally presented with less severe initial contractures and had the greatest percentage of improvement. When used on a single limb when bilateral contractures were present, sympathetic reduction of the contracture occurred to varying degrees in the unsplinted limb. It is recommended that the splints be replaced regularly to maximize their effectiveness. The benefit-to-cost ratio is extremely high and their low cost makes soft splints feasible for use in developing countries and by low-income families.

A general health policy model: update and applications

This article describes the development of a General Health Policy Model that can be used for program evaluation, population monitoring, clinical research, and policy analysis. An important component of the model, the Quality of Well-being scale (QWB) combines preference-weighted measures of symptoms and functioning to provide a numerical point-in-time expression of well-being, ranging from 0 for death to 1.0 for asymptomatic optimum functioning. The level of wellness at particular points in time is governed by the prognosis (transition rates or probabilities) generated by the underlying disease or injury under different treatment (control) variables. Well-years result from integrating the level of wellness, or health-related quality of life, over the life expectancy. Several issues relevant to the application of the model are discussed. It is suggested that a quality of life measure need not have separate components for social and mental health. Social health has been difficult to define; social support may be a poor criterion for resource allocation; and some evidence suggests that aspects of mental health are captured by the general measure. Although it has been suggested that measures of child health should differ from those used for adults, we argue that a separate conceptualization of child health creates new problems for policy analysis. After offering several applications of the model for the evaluation of prevention programs, we conclude that many of the advantages of general measures have been overlooked and should be given serious consideration in future studies.

Internal Consistency Analysis: a method for studying the accuracy of function assessment for health outcome and quality of life evaluation

Social, mental and physical function are major components of health outcomes and health related life quality, but the accuracy of function measurement is difficult to study rigorously. Internal Consistency Analysis (ICA) uses multiple sources of evidence from a survey interview to study the accuracy of a classification. It was developed to study function classifications for a general health outcome measure, the Quality of Well-being (QWB) scale. ICA is described and evidence of its utility in improving the classifications needed for the QWB is presented.

The interaction of calmodulin with human erythrocyte spectrin. Inhibition of protein 4.1-stimulated actin binding

The functional significance of calmodulin binding to human erythrocyte spectrin has been investigated under native conditions. Both native calmodulin and calmodulin derivatized with the photoactivable cross-linker methyl 4-azidobenzimidate (azidocalmodulin) have been used. When azidocalmodulin is photolyzed in the presence of erythrocyte ghosts, ghost extracts, or purified protein, it cross-links predominately to the beta subunit of erythrocyte spectrin. This cross-linking is calcium-dependent, requires photolysis, and is inhibited by 100 microM trifluoperazine or unlabeled calmodulin. Calmodulin labeled spectrin exhibits a specific and non-calcium-dependent inhibition of its ability to bind actin, even in the presence of protein 4.1. Its ability to self-associate or to bind spectrin-depleted membrane vesicles is unperturbed. Native calmodulin also inhibits protein 4.1-stimulated spectrin-actin binding, but unlike that of covalently bound calmodulin, inhibition by the uncross-linked calmodulin requires calcium. The degree of inhibition of spectrin-actin-4.1 binding induced by native calmodulin is significant since 109 microM calmodulin inhibits over 63% of the spectrin-actin binding induced by 4.5 microM protein 4.1. These results demonstrate a specific effect of calmodulin on erythroid spectrin function and suggest that calmodulin may influence the binding of protein 4.1 and actin to spectrin within the cytoskeleton.

Classifying function for health outcome and quality-of-life evaluation. Self- versus interviewer modes

Validity assessment and the underreporting of dysfunction have been major problems in health-related quality-of-life measurement, including collecting data for analysis by the General Health Policy Model, using the Quality of Well-being scale (QWB). This analysis compares the results of self- versus interviewer modes of measurement and short, direct-answer questions versus probing algorithms in the QWB. The comparisons are made in terms of 1) correlations; 2) aggregate frequencies; 3) individual subject classifications; and 4) the actual state, established using evidence from multiple sources. Despite extremely high correlations between QWB scores from the two modes (greater than 0.98), the lowest interviewer mode sensitivity (0.86) and predictive value dysfunctional (0.91) were substantially superior to the highest self-classification characteristics (0.66 and 0.73). In the populations studied, specificities and predictive values functional were equivalent (greater than 0.94) for the two modes. The probe pattern of the interviewer mode was also less susceptible to false reports of dysfunction. These results are consistent with the underreporting of dysfunction noted by several major investigations of health status measurement. The authors conclude that interviewer-administered instruments using question algorithms are necessary if health-related quality of life is to be measured with sufficient reliability and validity to evaluate major clinical trials and follow-up studies.

Mechanisms of cytoskeletal regulation: functional and antigenic diversity in human erythrocyte and brain beta spectrin

A study of human erythrocyte and brain spectrin with particular emphasis on the beta subunits revealed a structural homology but functional dissimilarity between these two molecules. Six monoclonal antibodies raised to human erythrocyte beta spectrin identify three of the four proteolytically defined domains of erythrocyte beta spectrin. Five of these monoclonal antibodies cross-react with human brain spectrin. None of a previously identified set of alpha erythrocyte spectrin monoclonal antibodies [Yurchenco et al: J Biol Chem 257:9102, 1982] reacted with brain spectrin. A domain map generated by limited tryptic digestion shows that brain spectrin is composed of proteolytically resistant domains analogous to erythrocyte spectrin, but the brain protein is more basic. The binding of brain spectrin to erythrocyte ankyrin, both in solution and on erythrocyte IOVs, yielded an association constant approximately 100 time weaker than for erythrocyte spectrin. The binding of azido-calmodulin under native conditions was specific for the erythrocyte beta subunit but was not calcium dependent. In contrast, azido-calmodulin bound only to the alpha subunit of brain spectrin in a calcium-dependent manner. The similarity of structure but modified functional characteristics of the brain and erythrocyte beta spectrins suggest that these proteins serve different cellular roles.

Parasite screening and treatment among Indochinese refugees. Cost-benefit/utility and the General Health Policy Model

The General Health Policy Model and the Quality of Well-being scale are used to describe a "cost-benefit/utility" evaluation of a screening and treatment program for intestinal parasites among indochinese refugees in the United States. Cost-benefit/utility analysis subsumes conventional cost-effectiveness by explicitly adding social utility factors to the dollar dimension. Using actual data on parasite prevalence and program costs from one screening project and estimated figures for other factors, this article demonstrates calculation of the cost-benefit/utility outcome measure, dollars per well-year. Dollars per well-year for parasite screening are calculated for a number of examples. Further analysis and final conclusions on the worth of parasite screening and treatment programs await more reliable data for some terms of the developed model.

A poison education program for primary school

A program with which to teach children in grades 1 and 2 to identify poisons and hazard symbols, to learn where poisons should be stored and to recognize a poisoning and contact a poison control center in the event of a poisoning was developed. Each objective was taught in one 30-minute lesson by the children's school teachers. Evaluation of the approximately 400 children who received the program by pre- and post-tests demonstrated that they learned to identify poisons, to recognize hazard symbols and the telephone number of the local poison control center. The children were also asked to identify their source of knowledge about poisons and cited parents, television and school as their most important sources.

Comparison of Degradative Ability, Enzymatic Activity, and Palatability of Aquatic Hyphomycetes Grown on Leaf Litter

Stream fungi have the capacity to degrade leaf litter and, through their activities, to transform it into a more palatable food source for invertebrate detritivores. The objectives of the present study were to characterize various aspects of fungal modification of the leaf substrate and to examine the effects these changes have on leaf palatability to detritivores. Fungal species were grown on aspen leaves for two incubation times. Leaves were analyzed to determine the weight loss, the degree of softening of the leaf matrix, and the concentrations of ATP and nitrogen associated with leaves. The activities of a protease and 10 polysaccharide-degrading enzymes produced by each fungus were also determined. Most fungi caused similar changes in physicochemical characteristics of the leaves. All fungi exhibited the capability to depolymerize pectin, xylan, and cellulose. Differences among fungi were found in their capabilities to produce protease and certain glycosidases. Leaf palatability was assessed by offering leaves of all treatments to larvae of two caddisfly shredders ( Trichoptera ). Feeding preferences exhibited by the shredders were similar and indicated that they perceived distinct differences among fungi. Two fungal species were highly consumed, some moderately and others only slightly. No relationships were found between any of the fungal characteristics measured and detritivore feeding preferences. Apparently, interspecific differences among fungi other than parameters associated with biomass or degradation of structural polysaccharides influence fungal palatability to caddisfly detritivores.

"Counterintuitive" preferences in health-related quality-of-life measurement

The published preferences for scale steps in a health-related quality-of-life scale have been noted to be contrary to some prior assumptions about their rank ordering. The differences noted are actually statistically nonsignificant, and the observed ordering has a clear intuitive explanation. Several alternative explanations, including vagueness in the case descriptions, inaccuracy in the scaling method, the presence of interactions in the subjects' cognitive integration rules and chance inversions in the presence of the flat response surface characteristic of linear models, are all shown to be impossible or unlikely contributors to the empirical results. The implications of the "negative preferences" for other measurement approaches are discussed, as well as the role of separate attribute coefficients in health policy analyses.

Chlorflurenol-methyl in soil: degradation, leaching, and effects on microbiological processes

Tests were conducted with the synthetic growth regulator chlorflurenol-methyl to investigate its rate of degradation in soil, leaching behavior, and possible side-effects on the soil microflora and on soil physiological processes. With two sandy soils (Ct = 1.0 and 2.58%) which were treated with 11.35 mg kg-1 chlorflurenol-methyl (congruent to 2.8 kg a.i. ha-1), over 90% of the compound disappeared within 4 to 8 days. The degradation products were 2-chloro-9-hydroxyfluorene-9-carboxylic acid and 2-chlorofluorenone, which undergo further decomposition. In leaching tests with three sandy soils (Ct = 0.69, 1.0 and 2.58%), chlorflurenol-methyl was not washed from the soil; however, with one soil (0.69% C), very small residues were observed in the effluent identified as 2-chlorofluorenone. In side-effects experiments with a parabrown (Ct = 1.26%) and a chernozem soil (Ct = 2.3%), which were treated with 1 and 10 mg kg-1 chlorflurenolmethyl, no persistent inhibition of anaerobic or aerobic nitrogen fixation (C2H2-reduction) was detected. Ammonification, nitrification, and mineralization of soluble starch were also not influenced. The mineralization of cellulose in compost soil (Ct = 13.59%) was temporarily delayed; however, this delay was later compensated for by a higher mineralization rate. The colonization density of fungi on soil particles and the numbers of bacteria, actinomycetes, and fungi were not negatively influenced. Chlorflurenol-methyl does not significantly influence these microbiological processes and populations in the soil.

Influence of selected pesticides on the microbial degradation of 14C-triallate and 14C-diallate in soil

Degradation in soil of [allyl-2-14C]triallate and [carbonyl-14C]diallate herbicides, as affected by other selected pesticides, was studied in an incubation system that allowed recovery of 95 to 100% of added 14C. The amount and sequence of pesticide additions simulated field use in the protection of wheat (triallate) and sugar beets (diallate). Neither the rate nor the pattern of triallate degradation in soil was influenced by the following sequence of formulated pesticides: dinoseb acetate, (bentazon + dichlorprop + 2,4,5-T), 2,4-D, (chlorcholinchloride + cholinchloride), tridemorph, and thiophanate. Similarly, diallate degradation was unaffected by pyrazon, dimethoate, and thiophanate. The effect of azinphosmethyl was unclear. In contrast, chlorpyrifos reduced diallate degradation by approximately 14% relative to the occurring in the insecticide's absence. This effect was caused by chlorpyrifos and not its formulation components. Chlorpyrifos was also found to partially inhibit degradation of triallate in soil. Inhibition of neither herbicide was considered to be of ecological significance. Triallate, diallate, and thiophanate were applied at 1 microgram/g; all others were at 2 microgram/g.

Measurement of bacterial and fungal contributions to respiration of selected agricultural and forest soils

A technique using selective inhibitors was used to estimate the relative contributions of bacterial and fungal populations to the respiration of six soils and one litter sample. The ratios of bacterial to fungal respiration in the four agricultural soils, given in percentage of the total microbial activity, ranged from 10/90 to 35/65, with the average ratio being about 30/70. In the forest soils, the ratios were 20/80 and 30/70, and in a beech litter sample, the ratio was 40/60. The fungi clearly dominated in all samples. The ratios were not found to be pH related. The difficulties which had previously limited the use of selective inhibitors for in situ soil ecological investigations, such as insufficient inhibitor specificity, inhibitor inactivation or degradation, and errors of measurement caused by elimination of competitor populations, were either resolved or methodologically avoided in the experiments. Inhibitor selectivity was demonstrated using both mixed and pure cultures of microorganisms from each soil. Through the use of experiments with short incubation periods (6-8 h), problems with population shifts and inhibitor degradation were eliminated.

Ornithosis in Somerset. Experience in the South Somerset clinical area 1964-71

During an 8-year period, seventy patients were found, by complement fixation testing, to have had ornithosis. A clinical analysis was made of forty-seven who fulfilled strict diagnostic criteria; thirty-three had been referred to a chest clinic, fourteen had been hospitalized. A non-specific, febrile, myalgic illness with respiratory symptoms was the usual clinical syndrome; cough was a prominent, often dramatic, symptom. Pulmonary crepitations, variable radiographic changes, and a normal white blood cell count were found to be useful diagnostic features. Ornithosis sometimes masqueraded as major chest disease, and could be debilitating. Careful retrospective interrogation revealed significant bird contacts in the majority of patients. Treatment with a tetracycline was of possible clinical benefit.

Method for Simultaneous Measurement of Radioactive and Inactive CO 2 Evolved from Soil Samples During Incubation with Labeled Substrates

An apparatus is described which allows the simultaneous, continuous, and highly sensitive analysis of inactive and radioactive CO 2 evolved from 14 C-supplemented soils or other materials. The apparatus consists of a control unit, a commercially available conductometric CO 2 analyzer, and fraction collector. A number of model experiments were conducted to demonstrate the potentials of the apparatus. These included analysis of the time course of priming action, when 14 C-glucose was added to soil, separation of CO 2 respiration peaks caused by simultaneous degradation of radioactive and inactive soil supplements, and study of the effects of a fungicide, Benomyl, on degradation of 14 C-labeled glucose. In the last experiment, partial degradation of the fungicide could also be followed.

Effects of various soil fungi and insecticides on the capacity of Mucor alternans to degrade DDT

Pure cultures of the fungus Mucor alternans, isolated from DDT-contaminated soils, were able to degrade DDT to water-soluble metabolites. After the addition of fungal spores to DDT-contaminated soils, however, the insecticide-degrading capacity of the fungus was no longer evident. Since under field conditions many species of fungi are simultaneously exposed to mixed residues of pesticidal chemicals, the effects of various species of soil fungi and of various insecticides on DDT degradation by M. alternans were investigated. Experiments were conducted to study the effect of nine fungal species, their stale cell-free media, and various insecticides and related compounds on the capacity of M. alternans to degrade 14C-DDT to water-soluble metabolites. It was found that several pure fungal cultures or some cell-free media, in which mycelia had grown, could also degrade the insecticide. In most cases, however, addition of one of the various fungi to 14C-DDT-treated M. alternans cultures resulted in a total depression of the appearance of water-soluble metabolites in the media. This was due to an accumulation of the metabolites in the mycelium of the other fungus or in an inhibition of metabolite formation. Addition of stale media from various fungi to 14C-DDT-treated M. alternans cultures had various effects on fungal growth and on the capacity of the fungus to degrade the insecticide. Among the insecticides and related compounds tested only lindane, parathion, and Dyfonate caused a reduction in DDT degradation by M. alternans, without severely reducing its vegetative growth.

Effect of nutritional factors on DDT-degradation by Mucor alternans

The effects of nutritional factors on the capacity of Mucor alternans to degrade 14C-DDT in shake cultures were investigated. Fungal spores did not grow in media that contained DDT as the sole carbon source, but they remained viable over a 2-month period and developed into a mycelium, once glucose had been added. The degradation of DDT by the fungus was not related to the mycelial mass. The quantity of water-soluble metabolites produced from DDT was, to some extent, dependent on the insecticide concentration, but largely on the carbon and nitrogen sources in the culture media. Largest quantities of the metabolites were formed with glucose and ammonium nitrate. The concentration of glucose affected this metabolism quantitatively. With the exception of ribose, growth on other sugars resulted in a decrease in the production of DDT-metabolites, which was most noticeable when maltose was used. No qualitative differences in the metabolites were observed. When ammonium nitrate was replaced with other nitrogen sources, the production of water-soluble metabolites was substantially reduced (35 to 75%) and qualitative differences in the appearance of metabolites were also observed.