THE DISTRIBUTION OF PHENOTYPIC VARIANCE WITH INBREEDING

Fifty-two inbred populations of Drosophila melanogaster, each founded from a single pair, and a large number of control, outbred flies were measured for fitness and a set of six traits. A survey of the literature on the effects of inbreeding and population bottlenecks demonstrates that the commonly observed pattern of an apparent variance among characters and among species in changes of phenotypic variance may in fact be largely the result of sampling error, given the pattern of change that we demonstrate within a species for the same character. In our study, population bottlenecks on average decrease the amount of phenotypic variance for a suite of wing characteristics and size, but there is large and significant variation among lines in the amount of phenotypic variance. As a result, several lines increased in variance in spite of the average decrease. Interestingly, the changes in phenotypic variance for fitness are in sharp contrast to those seen for phenotypic variance for morphological traits. The amount of phenotypic variance for fitness varies highly significantly among lines but, on average, is increased by bottlenecks. The changes in phenotypic variance as a result of population bottlenecks are large enough to significantly affect the probability of peak shifts by the variance-induced peak shift model.     

ZONE BEHAVIOR OF ENZYMES : ILLUSTRATED BY THE EFFECT OF DISSOCIATION CONSTANT AND DILUTION ON THE SYSTEM CHOLINESTERASE-PHYSOSTIGMINE

1. The kinetics of the reversible combination of one enzyme center with one molecule of a substrate or inhibitor is treated as a true bimolecular instead of a pseudomonomolecular reaction. The general equations describing such a reaction are presented and analyzed algebraically and graphically. 2. A new term, "specific concentration," is introduced to denote the concentration of reactants in units equal to the dissociation constant. Its use makes the kinetic equations universally applicable to all reversible systems of the given type. 3. It is shown that such a system exhibits three "zones" of behavior. Each zone is characterized and shown to exhibit significant differences in the function relating the concentrations of the components of the system at equilibrium. The zone boundaries are rigorously defined in terms of the specific enzyme concentration, for the mathematical error tolerable with a given experimental accuracy; and approximate boundaries for practical use are proposed. 4. The classical treatment of enzyme kinetics is shown to be a limiting case valid only for low specific enzyme concentrations (zone A) and to be inapplicable in a number of systems whose dissociation constants are very small or whose molar enzyme concentrations are very great, and in which, therefore, the specific enzyme concentrations are large. See Table I for a summary of zone differences. 5. In an enzyme system containing substrate or inhibitor, dilution before determination of reaction velocities is shown to be a crucial operation, entailing large changes in the fraction of enzyme in the form of a complex. The changes in fractional activity or inhibition with dilution are shown to be a function of specific enzyme concentration, the dilution factor, and the fraction of enzyme initially in the form of complex. Equations are given permitting the calculation of the state of the system at any concentration. The errors introduced into physiological work by failure to take the dilution effect into account are pointed out. 6. Experimental data are presented showing that the system composed of serum cholinesterase and physostigmine behaves as predicted by the dilution effect equations. 7. Two other conclusions of practical pharmacological importance are drawn from the theory of zone behavior: (a) The finding that a biological response is a linear function of the dose of a drug does not necessarily mean that the reaction is irreversible, but only that if reversible, the reactant with which the drug combines has a high specific concentration. (b) If a tissue enzyme has a high specific concentration, all reversible inhibitors will be equally potent in combining with it, regardless of their relative potency in dilute systems; provided only that their dissociation constants are within certain broad limits. 8. It is shown how the type of analysis here applied to bimolecular reactions can be applied in toto to systems of the type E + nX ⇋ EX_n, where n molecules of substrate or inhibitor unite with one enzyme center. The zone boundaries and the magnitude of the dilution effect change with n, but the general characteristics of the zones are the same for all values of n. 9. Since the analysis is based only on mass law assumptions, it is applicable to any system that is formally analogous to the one here treated.     

CALCULATIONS OF BIOELECTRIC POTENTIALS : II. THE CONCENTRATION POTENTIAL OF KCl IN NITELLA

Cells of Nitella have been studied which behave differently from those described in earlier papers. They show unexpectedly large changes in P.D. with certain concentrations of KCl. This is due to the production of action currents (these are recorded at the spot where KCl is applied). A method is given for the separate evaluation of changes of P.D. due to partition coefficients and those due to mobilities. A new amplifier and an improved flowing contact are described.     

DRY-ROT DISEASE OF THE POTATO

A laboratory method is described in which a modified hypodermic syringe is used to inoculate potato tubers with Fusarium caeruleum. This injection method gives consistent results and permits reliable assessments of factors such as varietal susceptibility.
The occurrence of arrested lesions is noted.
Suspensions of very high spore concentration or of spores already germinated did not greatly increase the amount of dry rot above that given by the standard too spores per inoculation, provided that spore germination was adequate.
The size of tuber and site of inoculation were found to have a considerable effect upon the results of inoculation experiments, large tubers being more susceptible than small ones and the heel end being more susceptible than the rose end. The necessity for uniformity of material used in inoculation experiments is emphasized.     

STUDIES ON PERMEABILITY OF MEMBRANES : V. THE DIFFUSION OF NON-ELECTROLYTES THROUGH THE DRIED COLLODION MEMBRANE.

A study has been made of the relative rates at which various organic non-electrolytes diffuse through the dried collodion membrane. It was found that acetone and urea pass through the membrane many times more rapidly than glycerine and that glycerine in its turn diffuses much faster than glucose. It was also demonstrated that the rate of diffusion varies directly with the difference in concentration between the solutions on the two sides of the membrane. It was shown that the presence of glycerine on the two sides of the membrane did not appreciably affect the rate of diffusion of acetone. In a study of the changes going on during the establishment of the stationary diffusion gradient with glucose experiments were described which strongly suggested that many of the membrane channels may gradually become clogged up with glucose molecules so that the diffusion rate decreases from day to day until the stationary gradient is finally reached. In explaining the various experimental data the conception of the collodion membrane as a sieve with pores approximating in smallness the size of individual molecules was utilized. The large differences in the diffusion rates between different substances were then referred to differences in molecular size, the relatively large molecules of glycerine and glucose being unable to pass through many of the smaller pores available for urea and acetone. From the data available it was possible to estimate that 98 per cent of the pore area distributed among holes large enough for the diffusion of acetone was unavailable for the passage of glycerine and that only 0.3 per cent of the pore area available for acetone could be utilized by glucose. In trying to correlate the ratio between the diffusion rates of two different substances with the characteristic concentration potential (Co P) given by the same membrane it was found (1) that with the acetone-glycerine ratio there is no correspondence (2) that with the acetone-glucose ratio a suggestive relation exists and (3) that with the glycerine-glucose ratio a definite correspondence can be shown, the higher ratios being obtained only with membranes giving high CO P values. A rational explanation for these facts was proposed.     

THE EFFECT OF CERTAIN SOIL TREATMENTS ON DIDYMELLA STEM ROT OF TOMATOES PART I. GLASSHOUSE EXPERIMENTS

When tomatoes were planted in steamed soil inoculated with spores of Didymella lycopersici Kleb., a large proportion became infected, but very few became infected in unsteamed soil similarly inoculated. In soil treated with formalin and subsequently inoculated the number of diseased plants was about half that in steamed soil. Reinfecting steamed soil with soil micro-organisms before inoculation with D. lycopersici reduced the amount of disease. Covering steamed soil with a layer of maiden loam filtered out a large proportion of D. lycopersici spores applied in water suspension and reduced the amount of disease. Addition of stable manure either before or after steaming did not affect the number of diseased plants. Steamed soil remained susceptible to infection by D. lycopersici for 4 months. D. lycopersici survived in a glasshouse soil over the winter, but the number of diseased plants was small. Cultivation may lessen the amount of disease by burying most of the infected surface layers of the soil. The peak of infection under glass occurred in May. The amount of disease and the yield were correlated, but with severe infection the yield varied with the time of infection and the distribution of diseased plants.     

小鼠胚泡着床过程中子宫6—酮—PGF1α（6—KF）及TXB2含量的变化

本实验利用前列环素(Prostacyclin,简称PGI_2)及血栓素(Thromboxane A_2,简称TXA_2)的代谢产物6-KF及TXB_2的RIA技术,探讨了小鼠子宫在胚泡着床点及非着床部位上述二类PG_s的含量变化。实验表明,妊娠D_5胚泡着床部位及着床间区,6-KF的水平较高;而TXB_2含量较低变化也小。表明胚泡着床时,血管通透性增强与PGI_2升高密切相关。PGI_2与TXA_2比值的增高,使血管舒张,增强抗凝,有利于胚泡着床及营养供应。     

A PHASE RULE STUDY OF THE PROTEINS OF BLOOD SERUM: THE EFFECT OF CHANGES IN CERTAIN VARIABLES

Changes were studied in the standard solubility curve of fresh serum proteins by alterations in pH, temperature, concentration of protein, and nature of the salt used for precipitation. The principal factor affecting the precipitation of protein fractions was a change in temperature. In order to investigate the proteins in their original states low temperatures are necessary. Protein fraction A is altered by a change in pH and with the use of (NH₄)₂SO₄ as a precipitant, fraction B by a change in pH and temperature, and use of (NH₄)₂SO₄, C by a change in temperature and concentration of the protein, and D by a change in temperature and pH. The solubility of D is independent of the amount of protein in solution in high concentrations of salt.     

THE TEMPERATURE COEFFICIENT OF THE UREA DENATURATION OF EGG ALBUMIN

Evidence is brought forward to show that at concentrations of urea high enough to split the egg albumin molecule the solubility changes produced by urea are profoundly modified. The degree of precipitation after dialysis is the net result of two changes produced by the urea: the first, normally spoken of as denaturation, which makes the protein insoluble in dilute solution and the second, a splitting of the molecule which makes it soluble. These two reactions may proceed independently and simultaneously or the second reaction may follow the first, taking place in the denatured molecule only. In view of the decrease in the opalescence with time, the latter process is more probable. Both of these reactions have positive temperature coefficients, but as the concentration of urea increases the second reaction is more affected by increase in temperature than the first, and consequently the resulting opalescence decreases rather than increases with temperature. This accounts for and explains reports of negative temperature coefficients of denaturation, when denaturation is measured by the amount of insoluble material found on dilution. The occurrence of these two reactions, one leading to an increase and the other to a decrease in the amount of insoluble protein, should be taken into account when denaturation changes in egg albumin with urea are studied.     

STUDY OF THE EFFECT OF HYDROXYUREA ON THE ERYTHROPOIETIN-SENSITIVE CELLS

The response of polycythaemic mice to a standard dose of erythropoietin has been measured at various, time intervals after single or repeated injections of hydroxyurea. The results exclude S phase of the cell cycle as the period responsive to erythropoietin. They suggest the existence of feedback mechanisms within the cell cycle, operating at the G₁-S boundary and within the G₁ phase. Hydroxyurea given to polycythaemic mice at various time intervals after erythropoietin induced characteristic changes in the response. These changes can be explained if both gradual transit of differentiated cells into the DNA synthesis (S phase) and changes in amount of the erythropoietin sensitive cells caused by the feedback mechanisms operating in the cell cycle are considered.     

FOOD PREFERENCE AND THE EXTENT OF OVERLAP IN SOME INSECTIVOROUS BIRDS, WITH SPECIAL REFERENCE TO THE TYRANNIDAE

Analysis of published records of the food of flycatchers (Tyrannidae), swallows (Hirundinidae) and vireos (Vireonidae) of North America, and terns (Laridae) of the Pacific Ocean showed that size, rather than taxonomic, differences in food appear to be the most important ones for these birds. Although the distribution of insect sizes in nature approaches a two-parameter log-normal distribution, the distributions of the sizes of food items taken by birds show no significant differences from log-normal. Birds of a given feeding type (e.g. flycatchers) show a strong correlation of average prey size with bird body weight, and a significantly less strong correlation with bill characteristics, indicating that body size is a better predictor of prey size than any single bill character. The slopes and/or intercepts of regressions of food size against body weight are different for birds of different foraging type. Values of overlap in food preference are proportional to the similarity of the two species compared, expressed as the ratio of their weights. Because insect taxa differ in size and because the amount of overlap in taxonomic composition of foods is therefore very roughly proportional to the amount of overlap in size, taxonomic differences in food may merely reflect differences in size preferences. Values for overlap in food are greater than for most cases involving spatial niche parameters, indicating space is more easily divided than food, a conclusion supported by the relative rarity of large flycatchers.     

THE EFFECT OF THE CONCENTRATION OF ENZYME ON THE RATE OF DIGESTION OF PROTEINS BY PEPSIN

1. In certain cases the rate of digestion of proteins by pepsin is not proportional to the total concentration of pepsin. 2. It is suggested that this is due to the fact that the enzyme in solution is in equilibrium with another substance (called peptone for convenience) and that the equilibrium is quantitatively expressed by the law of mass action, according to the following equation. See PDF for Equation It is assumed that only the uncombined pepsin affects the hydrolysis of the protein. 3. The hypothesis has been put in the form of a differential equation and found to agree quantitatively with the experimental results when the concentration of pepsin, peptone, or both is varied. 4. Pepsin inactivated with alkali enters the equilibrium to the same extent as active pepsin. 5. Under certain conditions (concentration of peptone large with respect to pepsin, and concentration of substrate relatively constant) the relative change in the amount of active pepsin is inversely proportional to the concentration of peptone and the equation simplifies to Schütz''s rule. 6. An integral equation is obtained which holds for the entire course of the digestion (except for the first few minutes) with varying enzyme concentration. This equation is identical in form with the one derived by Arrhenius for the action of ammonia on ethyl acetate. 7. It is pointed out that there are many analogies between the action of pepsin on albumin solutions and the action of toxins on an organism.     

Water Deficit and the Growth of Crop Seedlings: I. THE EFFECT OF RATE OF CHANGE OF SOIL WATER CONTENT ON KALE SEEDLINGS

Leaf growth of kale seedlings was compared over a range of soil-moisturecontents during a single drying cycle in a number of constantenvironments. With the particular soil and environments used,and when senescence effects were eliminated, relative leaf growth-ratewas a linear function of soil-moisture percentage in the rangeequivalent to pF 1.7 and 4.2. The relationship was independentof differences in the rate of change of soil moisture resultingfrom changes in atmospheric humidity or in the ratio of leafarea to amount of water in the soil mass. Nevertheless, smallchanges in the rate of water loss integrated over a period canhave relatively large effects on yield.     

THE SIGNIFICANCE OF CIRCADIAN BASED PHOTOSENSITIVITY IN THE HOUSE SPARROW PASSER DOMESTICUS

Adult male House Sparrows, wild caught in December and January, were held on daily seven-hour artificial photoperiods for 14 days beginning in late February, with the aviary lights arranged to switch-on at 07.00 hrs. A control sample was then killed and the remaining birds divided into groups which received six hours of light daily (beginning at 07.00 hrs) plus one further hour of light given at variable times from the dawn. A further group received 16 hours of light given continuously (16L-8D). Pooled plasma samples from these groups were assayed for luteinizing hormone (using a radio-immunoassay technique) and the histological condition of all testes was examined. Although all subjects received the same total amount of photostimulation only those given schedules simulating long days responded with testicular growth and spermatogenesis. It is argued that this was because light can only be effective if received during relatively restricted phases of a circadian-based rhythm; only during these phases is the neuroendocrine apparatus sensitised to photostimulation. Increase in size of the testis tubules and meiotic divisions of primary spermatocytes, leading to secondary spermatocyte production and increase in testis weight, were considered to be indicators of FSH activity. Using these criteria a curve of FSH activity could be drawn and be compared with the quantitative curve for LH levels obtained from the plasma assays (a comparable assay technique for FSH is not yet available). Although LH levels remained approximately the same in all groups, and this correlated with the histological and histochemical evidence, FSH activity was more pronounced in those groups given light flashes at increased intervals after the beginning of the dark period. Thus LH activity occurred in the absence of spermatogenetic development in those groups given “short-day” schedules. Birds kept on a 16L-8D regime contained less plasma LH than anticipated and the possible existence of inhibitory mechanisms is discussed. It is feasible that when much FSH secretion begins LH production declines, but this explanation is speculative. The temporal pattern of LH production was markedly different in Greenfinches (for which the experimental results are described elsewhere) than in the House Sparrows, and the discussion considers the reasons for these differences in terms of the ecological and ethological adaptations of the two species.     

六盘山林区几种土地利用方式对土壤有机碳矿化影响的比较

 应用土壤培养法,比较分析了六盘山林区天然次生林（杂灌林、山杨（Populus davidanda）和辽东栎（Quercus liaotungensis）林）、农田、草地和人工林（13 a、18 a和25 a华北落叶松（Larix principis-rupprechtii））土壤在30℃和60%田间饱和含水量条件下培养180 d有机碳矿化速率的差异（以180 d累计释放的CO2-C计）。结果显示：农田和草地土壤碳矿化释放的CO2-C含量（180 d释放的gCO2-C·kg-1干土）分别比天然次生林低65%和23%,差异主要在0～40土层;人工林比农田和草地分别高155%和 17%,差异主要在0～70 cm土层。农田土壤碳矿化释放的CO2-C分配比例（即180 d释放CO2-C/土壤 C）比天然次生林平均低12%,草地比天然次生林平均高18%,差异主要在0～40 cm土层;人工林比农田平均高29%,草地比人工林平均高9%,差异主要在0～50 cm土层。不同土地利用方式土壤碳矿化释放的CO2-C含量的差异比其分配比例的差异大。土壤碳矿化释放的CO2-C含量和分配比例总体上都随土层加深而递减。分配比例随土层加深而递减的幅度方面,不同土地利用方式间的差异不大;含量随土层加深而递减的幅度方面,天然次生林和人工林比农田和草地中大;随土层递减的幅度方面,土壤碳矿化释放的CO2-C含量比其分配比例大。这主要由不同土地利用方式土壤碳输入和稳定性等差异所致。结果说明土壤碳矿化速率随天然次生林变成农田或草地而下降,随在农田或草地上造林而增加, 矿化速率变化幅度比分配比例的变化幅度大。另外,土地利用变化也使不同土层土壤碳矿化速率和分配比例差异改变,其中速率改变的幅度比分配比例改变的幅度大。     

THE EFFECT OF OXIDANTS AND REDUCTANTS UPON THE BIOELECTRIC POTENTIAL OF NITELLA

Nitella cells were exposed to various oxidants and reductants, to determine their effect upon the bioelectric potential. These included five systems, with an E_h range from +0.454 v. to –0.288 v., a total range of 0.742 v. When proper regard was given to buffering against acidity changes, and concentration changes of Na or K ions in the oxidized and reduced forms, no significant effect upon the bioelectric potential was found: 1. When an oxidant or reductant (K ferri- or ferrocyanide) was applied instead of an equivalent normality of an "indifferent" salt (KCl). 2. In changing from a given oxidant to its corresponding reductant (ferri- to ferrocyanide; oxidized to leuco-dye, etc.). 3. When a mixture of 2 dyes, (indophenol with positive E''₀, and safranin with negative E''₀) was oxidized and reduced, to give better poising at the extremes. It is conduded that the outer surface of this cell is not influenced by the state of oxidation or reduction of the systems employed; at least it does not respond with a manifest change of bioelectric potential to changes in oxidation-reduction intensity of the medium. The cells continued to show, however, at all times their usual response to concentration changes of KCl, NaCl, etc., and to electrical stimulation.     

THE COMBINATION OF ENZYME AND SUBSTRATE : I. A METHOD FOR THE QUANTITATIVE DETERMINATION OF PEPSIN. II. THE EFFECT OF THE HYDROGEN ION CONCENTRATION.

1. A quantitative method for the determination of pepsin is described depending on the change in conductivity of a digesting egg albumin solution. 2. The combination of pepsin with an insoluble substrate has been followed by this method. 3. The amount of pepsin removed from solution by a given weight of substrate is independent of the size of the particles of the substrate. 4. There is an optimum zone of hydrogen ion concentration for the combination of enzyme and substrate corresponding to the optimum for digestion. 5. It is suggested that the pepsin combines largely or entirely with the ionized protein.     

METABOLISM OF A TRYPTOPHAN LOAD IN THE HYPOTHALAMUS AND OTHER BRAIN REGIONS

Abstract— Results confirm previous findings that after injecting rats with 50mg/kg tryptophan the percentage increase of 5-hydroxytryptamine metabolism (as shown by 5-hydroxyindolylacetic acid changes) is particularly small in the hypothalamus. However, 15–30 min after tryptophan injection (when brain 5-hydroxytryptamine changes were maximal) percentage 5-hydroxytryptamine increases in the hypothalamus and in the rest of the brain were comparable. The small 5-hydroxyindolylacetic acid changes in the hypothalamus are consistent with a long 5-hydroxytryptamine turnover time therein as indicated by experiments using pargyline or probenecid and by the relatively small increases of 5-hydroxytryptamine after injecting tryptophan into tranylcypromine treated rats. When 5-hydroxytryptamine synthesis was partially inhibited by p -chlorophenylalanine and tryptophan was injected, there was a large percentage rise of hypothalamic 5-hydroxytryptamine but the concentration found in rats given neither drug was not attained and 5-hydroxyindolylacetic acid showed little change. Elsewhere in the brain 5-hydroxytryptamine attained concentrations comparable to those in rats given neither drug and 5-hydroxyindolylacetic acid rose considerably. Results are discussed in relation to the contributions made to brain 5-hydroxytryptamine turnover by functional and non-functional metabolism.     

THE EFFECTS OF HYDROGEN ION CONCENTRATION UPON THE METAMORPHIC PATTERN OF THYROXIN- AND IODINE-TREATED TADPOLES

1. It has been shown quantitatively that the degree of response of the hind limbs of tadpoles to the action of thyroxin is dependent upon the lengths of the limbs at the beginning of treatment. 2. Both the potency of the inducing substance and the rate of penetration of the substance into the animal might be involved in the effects of hydrogen ion concentration on induced development. 3. Changes in hydrogen ion concentration affect the inducing power of thyroxin and iodine differently. With thyroxin, it is the rate of penetration of the molecule which determines the amount of growth, but with iodine it is the chemical form in which the substance has entered the animal which is of prime importance. 4. The hydrogen ion concentration of thyroxin solutions does not affect their potency when they are injected into tadpoles. 5. Change in hydrogen ion concentration of the environment does not affect the potency of thyroxin injected into tadpoles. 6. When thyroxin is administered in the environmental solution its effects, as measured by increase in hind limb length are greater at higher than at lower hydrogen ion concentrations in the range tested. 7. Since the potency of thyroxin is unaffected by change in hydrogen ion concentration when the thyroxin solution is injected, the above fact (point 6) seems explicable only on the basis of differences in the rate of penetration of thyroxin into the animals at the different hydrogen ion concentrations. 8. These differences in penetration of the thyroxin at different hydrogen ion concentrations may be the result of a differential effect of hydrogen ion concentration upon the rate of metabolism of the animal. The metabolic rate is significantly greater when the tadpoles are kept in solutions of higher hydrogen ion concentration than when they are kept in solutions of low hydrogen ion concentration. It is postulated that the rate of metabolism, since it controls the rate of intake of the environmental fluid and therefore of dissolved thyroxin, also controls the amount of thyroxin-induced development. 9. Change in hydrogen ion concentration of iodine solutions affects their potency when injected into tadpoles. A peak of effectiveness is reached at about the neutral point, with a lowered efficiency as the hydrogen ion concentration is either increased or decreased from this point. 10. Change in hydrogen ion concentration of the environment affects the potency of iodine injected into tadpoles. The effect is similar to that noted in point 9. 11. The hydrogen ion concentration of the environment seems to affect the chemical nature of the iodine in solution in the environment. If this is so, it is possible that the differences in the metamorphic effects of iodine at different hydrogen ion concentrations are dependent upon the chemical form of iodine present. 12. The effect of hydrogen ion concentration on normal development is similar to that on thyroxin-induced development; an effect on the rate of metabolism of the animal causes increased growth in more acid solutions.     

DEVELOPMENT OF EYE COLORS IN DROSOPHILA: SOME PROPERTIES OF THE HORMONES CONCERNED

The substance inducing the production of pigment in the eyes of vermilion brown mutants of Drosophila melanogaster has been shown to be a relatively stable chemical entity possessing true hormone-like activity. A simple method for obtaining hormone solutions has been developed involving extraction of dried wild type Drosophila pupae with ethyl alcohol and water. A logarithmic proportionality has been found to exist between the amount of hormone and the induced eye color. This relationship provides a simple method for the quantitative determination of hormone concentration in given extracts. Larvae and pupae of D. melanogaster contain an intracellular enzyme which inactivates the hormone in the presence of molecular oxygen. The hormone is not oxidized under ordinary conditions with either molecular oxygen or hydrogen peroxide. The hormone has been found to be an amphoteric compound with both acidic and basic groups and with a molecular weight between 400 and 600. The solubility and precipitation reactions of the hormone suggest its amino acid-like nature. However, the instability to heat, acid, and alkali, and its rather restricted occurrence indicate a rather complex specific structure.