Seasonal changes in endocrine organs of the male common frog,Rana temporaria

Summary The annual cycle of the five morphological cell types in the pars distalis of the adenohypophysis of male common frogs,Rana temporaria, was studied in variously stained sections of the pituitary, collected at monthly intervals. All cell types showed a maximal development at the end of hibernation, a strong extrusion of secretory granules in the breeding season, and a more gradual release during later spring and early summer. A minimal development occurred in mid-summer, and a restoration followed in autumn and the hibernation period. During the phase of extrusion production was low, and vice-versa. These seasonal changes correspond with those of the testes and interrenal tissue of the same animals as well as with those of the thyroids and other endocrine tissues, and seems to be an important part of the biphasic annual life cycle of the species.The authors gratefully acknowledge the patient and skilful technical assistance of MissFemmy Brands. They thank Mr.H. van Kooten for making the photographs.     

Electron microscopical and histochemical observations on the relation between medio-dorsal bodies and neurosecretory cells in the basommatophoran snails Lymnaea stagnalis,Ancylus fluviatilis,Australorbis glabratus and Planorbarius corneus

Summary In Basommatophora medio-dorsal bodies (MDB) are closely attached to the cerebral ganglia, in which, just underneath the bodies, groups of Gomori-positive neurosecretory cells (MDC) occur. It has been suggested that the MDB-cerebral ganglion complex should be regarded as a neuro-endocrine association.In the present study the morphological relation between MDB and the ganglion is histochemically and ultrastructurally investigated in Lymnaea stagnalis, Ancylus fluviatilis, Australorbis glabratus and Planorbarius corneus.Histochemical tests showed the paraldehyde-fuchsin positive material of fibers in the MDB to be different from the neurosecretory material (NSM) in the MDC. At the ultrastructural level no penetration of nerve cell processes through the perineurium, separating the MDB from the ganglion, into the medulla of the MDB was observed. However, excepting for Lymnaea, the perineurium at these places shows particular differentiations. In the medulla of the MDB granule laden profiles (granule ø 700–900 Å) occur. They appeared to be processes of MDB cells.From these results it is concluded that the medulla of the MDB should not be regarded as a neurosecretory neuropile. Apparently, the MDB-cerebral ganglion complex is no neuroendocrine association. Probably the MDB is an endocrine organ. The small electron dense granules of the profiles in the medulla were also found in the MDB cell bodies. They are thought to represent a secretion product. The close morphological relation between MDB and cerebral ganglion may be connected with the origin of the MDB cells from perineural elements.     

Calorimetric measurement of free energy utilization by Nitrosomonas and Nitrobacter

Summary Calorimetric estimates of the utilization efficiency of the free-energy derived from substrate oxidation by cell suspensions of two nitrifying bacteria, Nitrosomonas and Nitrobacter, provided two ranges of values: 11 to 27% and 15 to 51%, respectively. About 15 to 30% of the utilized free-energy is used for driving endergonic reactions other than CO₂ fixation, probably the synthesis of polyphosphates.The molar heat of substrate oxidation does not seem to be influenced by the age of cells harvested during growth or by the length of the incubation period during which cells have been kept in a buffer suspension in a starved condition. The loss of respiratory activity measured either by oxygen uptake or heat evolution in the presence of the specific substrate, nitrite or ammonium, decreases according to kinetics which are influenced by the aerobiosis of the suspension. The viability of the starved cells decreases in a way which is similar to that of the respiratory activity. It seemed impossible to obtain cells which had lost their viability but kept the ability to oxidize their substrate.Two inhibitors of the respiratory chain, quinacrine and cyanide, are without effect on the molar heat of substrate oxidation and consequently on the free-energy utilization efficiency. 2.4 dinitrophenol did decrease the rate of heat evolution during substrate oxidation at concentrations at which the rate of oxygen uptake was not depressed, with the consequences that free-energy efficiency was apparently increased.     

Induction of alkane-oxidizing andα-olefin-epoxidizing enzymes by a non-hydrocarbon in aPseudomonas

A strain ofPseudomonas aeruginosa could be induced to oxidizen-paraffins and to epoxidize-olefins by treating peptone-grown cells with 1,6-hexanediol or by growing them on this substrate. Of some related alcohols and acids investigated, only a few showed weak inducing capacities.Shell Research N.V.     

Chromosomes of Syrphidae

In this report the karyotypes of 54 species of the tribe Milesiini and of four species of the tribe Myoleptini are described in detail with illustrations and idiograms. These species belong in the genera Lejota, Myolepta, Blera, Calliprobola, Criorhina, Hadromyia, Milesia, Somula, Sphecomyia, Spilomyia, Syritta, Temnostoma, Tropidia and Xylota. Six species have 2n = 8 chromosomes, 35 have 2n = 10 (including Xylota nemorum which has about 20 extra microchromosomes in some specimens), 15 have 2n = 12, one has 2n = 14, and Somula decora has 2n = 10 large chromosomes plus about eight microchromosomes. The mean total complement length (TCL) for 347 complements analysed in these tribes was 53.7 but there is great variation between TCL's of complements analysed even from a single fly. Karyotypes of species of Myolepta in the Myoleptini resemble in certain respects those of species of Tropidia in the Milesiini. Our observations support Currran's transfer of Lejota cyanea to the Milesiini. The 2n = 12 karyotypes of species of Blera, Criorhina, Lejota, Milesia, and to a lesser extent Sphecomyia, have some features in common. Spilomyia species have rather distinct 2n = 10 karyotypes. Certain species in Calliprobola, Syritta and Hadromyia are karyologically similar to some species of the genus Xylota in which species studied fall into fairly distinct karyological groups. These observations provide clear evidence of the accumulation of karyotypic variations in the origin of species in these two tribes.     

CONSTANCY OF DNA CONTENT IN ADRENAL MEDULLA NUCLEI OF COLD-TREATED RATS

Reports of changes in DNA content of certain types of cells following exposure to conditions of stress has led to the suggestion that two kinds of DNA may be present. One is genetic DNA, and the other is called "metabolic" DNA. In a further attempt to investigate the possibility of this phenomenon, determinations of DNA content were made on Feulgen-stained nuclei of adrenal glands and kidneys in cold-treated rats. Feulgen-stained nuclei were measured by two-wavelength microspectrophotometry. Particular attention was given to the handling of the smears in hydrolysis and staining. Mean values of Feulgen-DNA contents in a total of 720 nuclei demonstrated (a) a constancy of DNA content within 2% in individual nuclei both in adrenal medulla and kidney cortex, (b) no more than an average of 2% difference in DNA content between control and experimental nuclei, and (c) no more than an average of 1.5% difference in DNA content between normal kidney cortex nuclei and normal adrenal medulla nuclei. These results confirm the view that the more precise the measurement, the more accurately the constancy rule is obeyed. Moreover, there is no support for the concept of a metabolic DNA in the rat adrenal medulla.     

Some observations on variegation inDrosophila

Attempts to modify experimentally the variegated phenotypes of the mutantsz inDrosophila melanogaster andw ^m2 inD. hydei, were largely unsuccessful. Transplanted eyes ofz were found to be more intensely pigmented, but this effect was not influenced by treatment of the imaginal disks or by the host's genotype. Inw ^m2, increased pigmentation was observed after treatment with 5-bromo-uracil.Thew ^m2 phenotype is strongly modified by supernumerary Y chromosomes. One Y shifts the eye colour from yellow to brown, two Y's, to dark red. In the Malpighian tubules, two Y's have a similarly strong effect, but one Y a slight effect only. Malpighian tubules ofw ^m2 larvae were used for a quantitative analysis of mottling. An average clonal cluster size of 1.1 was found. This indicates that the state of pigmentation is determined around the last cell division in the embryo.     

Notes on chromosome behaviour in the spermatogenesis of the damselflyEnallagma cyathigerum (Charp.) (Odonata: Coenagrionidae)

The chromosome number in the damselflyEnallagma cyathigerum (Charp.) is 2n =27, 2n =28, n =14 (13). The sex determining mechanism is XX-XO, the X segregates postreductionally in the male.