Submicroscopic structure of spermatozoa of a cyprinodontiform teleost,Jenynsia lineata

Summary A submicroscopical study of Jenynsia lineata spermatids and spermatozoa has been made. The formation of an axial nuclear cavity by folding is described. A sub-mitochondrial net with a very geometrical pattern has been found in the mid piece; to the author's knowledge this structure is not comparable to any other described up to now. Taxonomic importance of spermatozoa ultrastructural differences is stressed.This work was supported by a grant of the Consejo National de Investigaciones Científicas y Técnicas of Argentine. Dr. Narbaitz holds a research position and Dr. Dadone a fellowship in the same Institution.     

Related base sequences in the DNA of simple and complex organisms. III. Variability in the base sequence of the reduplicated genes for ribosomal RNA in the rabbit

A comparative study has been made of the arrangement of base sequences in the ribosomal RNA cistrons of Escherichia coliand rabbit DNA. This was accomplished by examination of the thermal stability profiles of DNA/RNA hybrids formed by the two types of ribosomal RNA under various conditions. The thermal stabilities of ribosomal RNA hybrids of rabbit origin are more dependent on the conditions of reaction during the formation and are always lower than those of E. coli RNA. It is concluded that the rabbit ribosomal RNA hybrids are formed mainly from mismatching between RNA molecules and DNA sites other than those from which they were transcribed. Thus, the cluster of ribosomal RNA cistrons in a mammalian DNA, representing a historical series of tandem duplications, exhibits intercistronic base sequence divergence. This research was supported by a research grant from the National Science Foundation (GB 6099) and a predoctoral traineeship (to R.L.M.) from the U.S. Public Health Service.     

Three hundred years of Taungya: A sustainable system of forestry in south China

Taungya is a system of forest management in which land is cleared and planted initially to food crops. Seedlings of desirable tree species are then planted on the same plot, leading in time to a harvestable stand of timber. Taungya is believed to have been developed by the British in Burma during the nineteenth century. Historical research indicates that successional systems of forest management which follow the pattern of taungya have been used for at least three centuries by ethnic minorities in and by the Han population. The resilience of these systems is associated with economic and social factors which have made the cultivation of trees an adaptive strategy of land use for the inhabitants of the highlands of southern China.Field Research in China for this paper was made possible by a grant from the Conservation and Research Foundation, New London, Connecticut.     

Karyological studies inCrocus V

Summary Karyological observations were made in fourteenCrocus including various Linnean species and garden varieties.C. biflorus Weldenii albus was an autotetraploid with five tetravalents,C. nudiflorus being also an autotetraploid having eleven tetravalents.The expenses of this study were partly defrayed by a grant from the Ministry of Education, to which I wish to express my cordial thanks.     

Mechanism involved in the response of granulated vesicles in the mouse pinealocyte to acute cold exposure

Summary Rudimentary cilia have been observed in muscle cells lining the tube feet of Ophioderma brevispinum (Ophiuroidea) and in muscle cells of the body wall and parapodial glands of Owenia fusiformis (Polychaeta). A diplosomal basal body is associated with each cilium. Striated rootlets are absent. This is the first report on rudimentary cilia in muscle cells of an echinoderm and an annelid.Supported by NSF grant #GB-42211 to R.M. Rieger. Costs of some photographic supplies were defrayed by a grant from Sigma Xi to S.L. Gardiner     

Electro-osmotic and biopotential measurements on phloem strands of Nymphoides

Summary Electroosmotic measurements on the excised vascular strand from the petiole of the water plant Nymphoides peltatum have been carried out, and the Onsager coefficients obtained. About 120 water moleculer per ion are carried electroosmotically when the strand is in 10^-4 M KCl, about 30 in 10^-1 M KCl. Potential measurements made on an intact and functioning petiole are discussed in the light of the pressure-flow and electroosmotic theories of translocation.This work has been made possible for one of us (D. S. Fensom) through the assistance of the National Research Council of Canada and a special grant from the Marjorie Young Bell Fund of Mount Allison University.     

Genetic control of morphogenetic variation in the sexcombs of drosophila melanogaster

The effect of the Y-chromosome on the sexcombs in the legs ofDrosophila melanogaster has been examined in four different genotypes, viz., Oregon R+,y, sx andPc-Scx. For this purpose, various Y-chromosome-fragments (Y^L and Y^S) and one or two XO conditions have been used.The results of this investigation show that both long (Y^L) and short (Y^S) arms of the Y-chromosome tend to increase the teeth number in the sexcomb of the first legs in all genotypes excepty. The XO-1 condition, derived by the loss of one X, appears to decrease it; the XO-2, resulting from the fertilization of an X-bearing ovum by a nullo-Y sperm, appears to show an increased teeth number or no effect at all. The effect of Y-fragments is least in the case ofy and maximum insx. The various Y-fragments used also show a parallel, though inversely related, effect on the production of intermediate bristles insx.These Y-fragments show an opposite effect on the sexcombs of the second and third legs of thePc-Scx genotype. Here the mean numbers of teeth are significantly reduced in all cases as compared to those in XY;Pc-Scx/++ genotype.The different Y-fragments behave differently in their effect on sexcomb pattern. It has been suggested that secondary modifiers may be present in association with different genotypes as well as in the Y, which are required to maintain a morphodynamic equilibrium in pattern formation.This investigation has been supported by a grant from Council of Scientific and Industrial Research to the first author, Scheme No. 38 (77)/65-GAU-II.     

Mathematical model of memory trace and forgetfulness

A mathematical model of a memory trace and forgetfulness is proposed here based on an improved version of our previous work (Harth et al., 1970; Anninos et al., 1970). Thus it was shown that the trace of a stimulus pattern presented to a subject decays with time due to the interference theory which assumes that competition among different associations leads to losses of retention. Such interference theory has been tested in this model by assuming that the retention of a first learned item followed by the learning of other successive tasks, depends on the inhibitory effect induced by them on the first item.This research has been supported by NIH grants NS-8012 and NS-8498, and NSP grant GB-30498. Computation assistance was provided by the Health Sciences Computing Facility, UCLA, sponsored by NIH Special Research Resources grant RR-3.     

The behaviour of the shoot apical meristem inChenopodium rubrum under conditions non-inductive for flowering

The results of different photoperiodic treatments preventing flowering and representing the control vegetative treatments in the studies of floral induction and differentiation were studied inChenopodium rubrum seedlings. A fully vegetative growth pattern of the meristem was maintained only in continuous light or after a photoperiodic treatment which consisted in a 15 min light break of the 8 h dark periods which themselves are a threshold for flowering inChenopodium. Light breaks applied to 10 h and longer dark periods did not prevent the changes resembling the early events of transition to flowering. Disappearance of zonal pattern, stimulation of apical growth, precocious initiation of leaf primordia and weakening of apical dominance have been observed. Flower formation did not follow. This work was supported by a grant from the Scientific Research Fund of SR Serbia.     

Chromosome studies on mosses from Austria,Czechoslovakia and other parts of Central Europe

Summary Reports are made on chromosomes in forty-six species from sixteen families of mosses. The plants were collected from all Austrian provinces, except the Tyrol and Vorarlberg, from Bohemia, Moravia, Slovakia, Bavaria, and also from Hungary and Italy. In addition to number or numbers of chromosomes reported for each species, observations are made on chromosome morphology, staining characteristics and behavior in meiosis or mitosis. The lowest numbers yet found are reported forDicranum fuscescens, n=8, andTimmia bavarica, n=8+1 m. For the latter species the study was made from mitotic configurations, and offers evidence that m-chromosomes may be normal members of the gametophytic set. These investigations reveal for the first time m-chromosomes inDicranoweisia cirrata, Pottia lanceolata, Timmia bavarica, Orthotrichum pumilum, Homalothecium lutescens, Brachythecium velutinum, Rhyncostegium murale, Rhyncostegiella pumila, andHypnum cupressiforme. Although the generaBartramia andPlagiopus previously have been characterized by different numbers of chromosomes, n=8 and n=7 respectively, plants ofPlagiopus oederi from Carinthia and Moravia were found, however, to have n=8. One species,Isopterygium seligeri, and one variety,Orthotrichum anomalum var.saxatile, have not been studied previously.Grateful acknowledgement is made to (1) the United States National Science Foundation for partial support of this investigation by a grant of research funds (NSF GB 6725) to Duke University, and (2) the Botanisches Institut der Universität Wien for laboratory space, equipment and use of the herbarium and library.     

2-Methylvalerate formation in mitochondria ofAscaris suum and its relationship to anaerobic energy generation

Summary Anaerobic incubation of intactAscaris suum mitochondria with pyruvate and propionate results in the formation of acetate, 2-methylvalerate, and 2-methylpentenoate and involves a rotenone sensitive, electron-transport associated phosphorylation. Malate inhibits 2-methylvalerate formation in these incubations, apparently by dissipating reducing power necessary for 2-methylvalerate formation. Indeed, malonate, an inhibitor of NADH-dependent fumarate reduction, dramatically stimulates 2-methylvalerate formation in incubations containing malate/propionate and malate/pyruvate/propionate but not pyruvate/propionate. In addition, malonate stimulates both 2-methylbutyrate and 2-methylvalerate formation in incubations with malate alone. The results of the present study suggest that branched-chain fatty acid synthesis inA. suum mitochondria is energy linked and that the inability of isolated, intact mitochondria to form branched-chain fatty acids from malate, their presumed physiological substrate, may result from an imbalance in the initial malate dismutation.Abbreviations BFA branched-chain fatty acid - 2-MB 2-methylbutyrate - 2-MC 2-methylcrotonate - 2-MP 2-methylpentenoate - 2-MV 2-methylvalerate Supported in part by NIH grant No. AI 18427     

The larval eye of the aeolid nudibranch Trinchesia aurantia (Alder and Hancock)

Summary The larval eye of the aeolid nudibranch Trinchesia aurantia has been investigated at three different stages; in all, the eyes remain closely attached to, and in cellular contact with, the central ganglia. The larval eye is a simplified version of the adult eye in that, the eye and the constituent cells, nuclei, lens, microvilli and pigment granules are all smaller, and the interdigitation between the retinal cells is not developed. The absence of the small cells of the cornea and of the spherical vesicles in the cytoplasm of the sensory cells, is further evidence of the incomplete formation of the eye. The possible origin of the eye of Trinchesia is discussed and compared with that of other gastropods.I am very grateful for the help and guidance of my supervisor Dr. D. A. Dorsett throughout the preparation of this paper. I was sponsored by a grant from the N.E.R.C.     

Excitation parameters of the repetitive firing mechanism from a statistical evaluation of nerve impulse trains

Repetitive firing of single tonic neurones is modeled to include in detail both membrane excitation kinetics and electrotonic effects due to membrane non-uniformities in the impulse encoder region. The model is evaluated dynamically and compared with similar data obtained from the crayfish stretch receptor neuron. Two dynamic techniques utilizing small amplitude sinusoidal signals are employed. One technique is used to fix the values of two parameters which relate to the electrotonic control of membrane potential in the interspike interval and to the relaxation time of the K-conductance during repetitive firing. The other technique is employed as a consistency check. The dynamics are particularly sensitive to the K-channel relaxation time in the interspike interval.Research supported by NSF grant BNS 77-22532 and Public Health Service Grant EY 00293. Computer facilities were made available by a grant from the Air Force Office of Scientific Research (AFOSR-1221) and by the University of Minnesota Computer Center     

Ultrastructural study of the shell-repair membrane in the snail,Helix pomatia L.

Summary The shell-repair membrane of the snail, Helix pomatia, has been studied with the transmission electron microscope (TEM). The ultrastructure of the repair membrane, in the initial stages of calcification, revealed the presence of a fibrillar protein, proteoglycan granules, osmiophilic vesicles, and cytoplasmic dense bodies of different size and structure. The involvement of the cell constituents in the formation of calcifying centra and initial crystal formation is discussed. The amoebocytes present within the repair membrane appeared to be involved in three different functions: (1) phagocytosis, (2) release of granules, vesicles and dense bodies, and (3) secretion of a fibrillar protein. The possible lytic function of the amoebocytes is mentioned. The common features in the mineralizing process of the shell-repair membrane of the snail and the epiphyseal cartilage of the mammals were noted.This investigation was supported by a grant from the Swedish Natural Science Research Council, which is gratefully acknowledged. I am indebted to Miss Ch. Stensjö and Mrs. E. Hellmén for their technical assistance     

Adrenergic retinal neurons

Summary Adrenergic retinal neurons have been studied in cynomolgus monkeys, cats, rabbits, guinea-pigs, rats, and mice with the fluorescence technique of Falck and Hillarp. With some species variations, three adrenergic fibre layers have been observed: an outer adrenergic fibre layer (all species) at the border between the inner nuclear and inner plexiform layers, a middle adrenergic fibre layer (rabbits, guinea-pigs, rats, and mice) in the middle of the inner plexiform layer, and an inner adrenergic fibre layer (rabbits) at the border between the inner plexiform layer and the ganglion cell layer. Similarly, three kinds of adrenergic nerve cells have been found: a somewhat heterogenous group of outer adrenergic cells (all species) situated in the innermost cell rows of the inner nuclear layer, eremite cells (rabbits, guinea-pigs, rats, and mice) within the inner plexiform layer and alloganglionic cells (all species) with a position and appearance resembling some of the ordinary non-adrenergic cells of the ganglion cell layer. All the adrenergic cells are star-shaped with slender branching processes running to the different adrenergic layers.The research reported in this document has been sponsored by the Air Force Office of Scientific Research under grant AF EOAR 66-14 through the European Office of Aerospace Research (OAR), United States Air Force, by the United States Public Health Service (grant no. NB 05236-02), by the Swedish Medical Research Council (grant no. B 66-320), and by the Faculty of Medicine, University of Lund, Sweden.     

Actin acetylation in Drosophila tissue culture cells

In a permanent cell line derived from Drosophila embryos, cytoplasmic actin is produced as an unstable precursor, which is subsequently converted to a stable form. This conversion results in a reduction in isoelectric point, with no apparent change in molecular weight. The conversion involves an enzymatic acetylation, and results in an insensitivity to aminopeptidase digestion, suggesting N-terminal blockage. Both the acetylated and unacetylated actins can participate in the assembly of F-actin, but with different efficiencies.This work was supported by a grant from the NIH (GM 22866).     

On the fungitoxicity of some new thiocyanatopyrazole derivatives: Electron microscopical study in trichophyton mentagrophytes

Four thiocyanatopyrazole derivatives were synthesized and their fungistatic activity was demonstrated in vitro against a number of dermatophytic fungi. In Trichophyton mentagrophytes, the most active compound induced an unusual increase of the plasma membrane with production of intra and extracytoplasmic complexes, a deterioration of nuclear and mitochondrial membranes and a formation of autophagic-like vacuoles. Plasmolysis, accompanied by an almost complete disorganization of cytoplasmic structures, seemed to be the final event. A possible mechanism of action of the compounds was discussed.Investigation supported by a grant from Consiglio Nazionale delle Ricerche of Italy (Contract No. 7500536).     

Tutorial on large deviations for the binomial distribution

We present, in an easy to use form, the large deviation theory of the binomial distribution: how to approximate the probability ofk or more successes inn independent trials, each with success probabilityp, when the specified fraction of successes,a≡k/n, satisfies 0<p<a<1. Supported by NIH grant GM 36230 and NSF grant DMS 8601986. Supported by NIH grant GM 36230 and a grant from the System Development Foundation.     

A crustacean compound eye adapted for low light intensities (Isopoda)

Summary The optical performance of the apposition compound eye of the marine isopodCirolana borealis Lilljeborg (Crustacea) was investigated. The ommatidia comprise large lenses (diam. ca. 150 m), spherical crystalline cones and hypertrophied rhabdoms. The 7 rhabdomeres are fused distally and open proximally. We have designated this rhabdom type as semifused. Distal pigment cells screen neighbouring ommatidia, and a well developed reflecting pigment layer surrounds the rhabdom. The focal length was determined in situ and refractive index measurements, raytracings, and eye mappings were made. The focus was found to lie well below the distal rhabdom tip. A theoretical acceptance function was constructed and a 50% acceptance angle of 45 ° was estimated. The eye parameter (p, according to Snyder 1977) of different ommatidia was between 44 and 14. This together with the anatomy demonstrate an optimation to extremely low light intensities. TheCirolana eye provides an example where acuity is sacrificed for the eye to be able to see at the low light intensities of the inhabitat.The investigation has been supported by a grant from the Swedish Natural Science Research Council (grant no. 2760-103). Our thanks are due to the staff of the marine biological station in Espegrend (Norway). The skilled technical assistance of Miss Inger Norling, Mrs. Rita Wallen, and Miss Maria Walles is gratefully acknowledged. And finally, we would like to express our deep appreciation to Professor Rolf Elofsson for constructive discussions and for his interest and encouragement throughout the investigation.