Chromosome variations inXenopsylla astia Rothschild, 1911 (Siphonaptera). A preliminary report

Summary 2 populations of rat fleas,Xenopsylla astia, collected from (A) Bombay and (B) Trivandrum, were found to differ in chromosome number as follows; (A) 2n=10 in both sexes; (B) 2n=18 (male) and 20 (female). Preliminary observations have further shown that the 2 populations differ in certain morphological characters and that their reciprocal hybrids are sterile in the male and partially sterile in the female sex.Acknowledgments. We wish to express our deepest gratitude to Dr Robert E. Lewis, Professor of Entomology, Iowa State University, USA, for confirming our identification of the 2 samples of rat fleas. We are indebted to Dr N.R. Prabhoo, Reader in Zoology, University of Kerala, Trivandrum, for his advice and helpful suggestions. We are also indebted to Prof. K.M. Alexander, for encouragement and providing facilities. Financial help of the University Grants Commission, India, to one of us (C.T.) is also gratefully acknowledged.     

Effect of dibutyryl cyclic AMP and analogs on the rate of contractions of myocytes in culture

Summary ²O,⁶N-butyryl, 3, 5-cyclic monophosphate (dibu cAMP) when added to fetal rat heart cells in culture inhibits myocyte contraction. This inhibition is 100, 84 and 51% complete when the dibu cAMP concentration used is 2, 0.2 and 0.02 mM, respectively. The potency of dibu cAMP derivatives in myocyte contraction inhibition follows the order, dibu cAMP> ⁶N-bu cAMP> ²O-bu cAMP=AMP>butyrate. The inhibition caused by the first three chemicals is greater than 70%.The author was a Moss Heart Fellow and acknowledges the technical assistance of Ms Martha Peet. This work was supported in part by the American Heart Association, National Science Foundation and American Cancer Society.     

Polyoxin fungicides: Demonstration of insecticidal activity due to inhibition of chitin synthesis

Summary Polyoxin A, a selective inhibitor of chitin synthetase, was found to be insecticidal when injected into the abdomen of grasshoppers nymphs, with an LD₅₀ of 1.26±0.20 g per insect. Symptomatology and the absence of any toxicity toward adult insects indicate that toxicity is due to interference with cuticle deposition.Acknowledgment. I thank Henry Bork for his expert technical assistance.     

An assessment of the effect of hormone and neurotransmitters on adenine and gluanine derivatives simultaneously in rat brain cortical slices

Summary A 2-dimensional thin-layer method has been developed for the separation on cellulose of adenine and guanine derivatives. Using incubated rat cerebral cortex slices it was shown that noradrenaline and acetylcholine stirnulated cAMP and cGMP production respectively but glutamate and -aminobutyric acid stimulated production of both cyclic nucleotides.     

Migration of lymphoid cells to the bone marrow of rat following eradication of cells in DNA synthesis and in mitosis

Summary Eradication of replicating bone marrow cells of rat by means of combined administration of single doses of hydroxyurea and vinblastin is followed within 9–10 h by an inflow of lymphoid cells of extramedullary origin in the range of 13,200,000/femur. The rat bone marrow with a high content of lymphoid cells was previously shown to be concentrated in stem cells. The factor(s) which convey the information of decrease of replicating marrow cells to extramedullary sites is at present unknown.Acknowledgment. This study was supported by a grant from the Chief Scientist Office, Ministry of Health, Israel.Hydroxyurea for this investigation was given as a gift by the Squibb Institute of Medical Research, Princeton, N.J. USA, to which the authors are indebted.     

Age-dependent response of lactate dehydrogenase of pituitary of rat to testosterone

Summary The effects of time and various doses of testosterone on the responsiveness of lactate dehydrogenase of pituitary of 7-, 38- and 78-week-old rats were studied. The activity of the enzyme increases in 78-week-old rats. Castration decreases the enzyme activity at all ages. Maximum increase in the enzyme activity is seen with 50 and 100 g of testosterone 4 h after administration of hormone to castrated rats. No further time and dose-dependent effect is observed. The magnitude of increase for the enzyme is higher at the age of 38 weeks and decreases in 78-week-old rats.To whom all correspondence should be addressed. The authors are grateful to Professor M.S. Kanungo, Biochemistry Laboratory, Department of Zoology, Banaras Hindu University for the suggestions and encouragement. K.V.G. thanks the PL-480 for a research fellowship.     

Degradation of ribosomal RNA from Escherichia coli by ribonuclease U2 and in vitro transcription of "RNA-fragments" into complementary DNA]

Under well defined conditions ribosomal RNAs purified from Escherichia coli can be degraded by ribonuclease U2 giving rise to RNA fragments of 60--70 nucleotides. In vitro, these fragments are efficiently transcribed into a complementary DNA by DNA polymerase RNA dependent, partially purified from extracts of E. coli. In vivo, "RNA-fragments-U2" inhibit the development of plant tumors.     

Variations au cours de la journée de l'incorporation in vivo de la leucine tritiée dans les protéines du cervelet et du cerveau du jeune rat normal et hypothyro?dien. Daily variations of the in vivo [3H] leucine incorporation into the cerebellar and cerebral proteins of the normal and hypothyroid young rat [(author's transl)

In the normal and hypothyroid 6-day-old rat, the specific radioactivity (RSA) and the relative RSA (ratio of the RSA to the [3H] lecine concentration of the acido soluble phase) of the cerebral and cerebellar proteins, changes during the day synchronally. They show a maximum at 15.00 h and a minimum at 0.300 h. At all stages studied, these values are significantly lower in the hyothyroid animals than in normal ones.     

Trichinella spiralis: acceleration and inhibition of cyst calcification in rats.

Daily administration of vitamin D3 (75,000 IU/kg b. wt) for 7 days accelerated Trichinella spiralis cyst calcification in rats with a 14-week-old infection. When disodium ethane-1-hydroxy-1, 1-diphosphonate (EHDP) was administered (50 mg/kg b. wt) from 2 days before until 2 days after vitamin D3 treatment, cyst calcification was inhibited. Thus, the ability to inhibit E. spiralis calcification has demonstrated for the first time.