Transplacental micronucleus inducing ability of arecoline, a betel nut alkaloid, in mice

Arecoline, a major betel nut alkaloid, was tested for its effectiveness in inducing micronuclei in fetal mouse blood after transplacental exposure late in the gestation period. Positive results were obtained and a linear dose-response relationship was expressed when pregnant mice were treated with arecoline at dose levels of 20, 40 and 80 mg/kg and micronucleated polychromatic erythrocytes from fetal blood were subsequently analysed.     

Senescence of attached leaves: Regulation by developing pods

Analysis of total nitrogen, chlorophyll content, ribulose-1,5-bisphosphate carboxylase/oxygenase activity and net photosynthesis rate was carried out on the leaves that support the developing pods in pigeon pea [ Cajanus cajan (L.) Millsp. cv. Prabhat] at several stages during pod filling. A continuous loss in all the above-mentioned parameters was observed during the course of pod development. When no pods were allowed to develop by continuous flower removal treatment, there was a considerable delay in loss of all these metabolic parameters. Excision of pods after their mid-development resulted not only in no further loss, but also in a significant recovery both of total nitrogen and of other investigated characteristics.     

Analysis of sister chromatid exchanges in lymphocytes cultured from 71 healthy men

Sister chromatid exchanges (SCE) were analyzed in peripheral blood lymphocytes from a select group of 71 healthy men, 56 nonsmokers and 15 cigarette smokers. In addition to estimating baseline SCE, data were examined to seek relationships of SCE frequencies to age and smoking. The baseline value of 7.53 SCE per cell from the 56 nonsmokers was within the range (5.60 to 9.10 SCE/cell) reported for other human populations. No relationship was found between the mean SCE frequency per cell and age. However, a significant increase in the SCE mean value was observed in smokers as compared to nonsmokers. The results of this study are compared with those of other reports on SCE effects of age and smoking.Abbreviations BUdR 5-bromo,2-deoxyuridine - SCE sister chromatid exchange     

Evaluation of culture media for effects on cell cycle kinetics and incidence of chromosomal aberrations in human blood cells

Peripheral blood samples from 17 apparently healthy male volunteers were set up in duplicate cultures using three commercially available media: Eagle's MEM, RPMI 1640, and TC 199. BUdR (5-bromo,2-deoxyuridine) (10 micrograms/mL) was added to one of the cultures from each person in each medium after 24 h of culture initiation. All cultures were harvested at 72 h of incubation in the presence of colcemid. RPMI 1640 stimulated the highest mitotic activity in both BUdR-treated and untreated cultures. Higher numbers of first division metaphases corresponded with the higher frequency of chromosome-type aberrations in cultures with Eagle's MEM as compared with RPMI 1640 media. On the other hand, higher numbers of chromatid-type aberrations were present in cultures with TC 199 as compared with those with Eagle's MEM. When the chromosome- and chromatid-type aberration data were pooled to score total cytogenetic abnormalities, an influence of the medium was demonstrable. While cultures with Eagle's MEM and TC 199 had the greater number of first division cells, third of subsequent division cells were most prevalent in RPMI 1640 cultures. It is inferred that the length of the cell cycle, the mitotic index, and to some degree the incidence of spontaneous cytogenetic abnormalities are variable attributes of culture media.     

Analysis of cloned mRNA sequences encoding subfragment 2 and part of subfragment 1 of alpha- and beta-myosin heavy chains of rabbit heart

Two cardiac myosin heavy chain cDNA clones, pMHC alpha 252 and pMHC beta 174, were constructed using rabbit ventricular mRNA isolated from adult thyrotoxic and normal hearts, respectively. The complete DNA sequences of the 2.2- and 1.4-kilobase inserts of pMHC beta 174 and pMHC alpha 252, respectively, were obtained. The 736 amino acids specified by pMHC beta 174 begin 439 (1.3 kilobases) residues from the heavy chain NH2 terminus and include a 400-amino acid segment of subfragment 1 and the entire subfragment 2 region. Clone pMHC alpha 252 encodes 465 amino acids encompassing all of subfragment 2 and a portion of light meromyosin. Comparison of these two clones revealed extensive sequence overlap which included 1107 nucleotides specifying a 369-amino acid segment corresponding to subfragment 2. Within this region 78 (7%) base and 32 (8.7%) amino acid mismatches were noted. These differences were clustered within discrete regions, with the subfragment 1/subfragment 2 junctional region being particularly divergent. Structural differences between pMHC alpha 252 and pMHC beta 174 indicate that these two clones represent two similar but distinct myosin heavy chain genes whose expression is responsible for ventricular myosin heavy chain isoforms alpha and beta, respectively. The derived amino acid sequences of both clones exhibit extensive homology (greater than 81%) with sequences obtained by direct analysis of adult rabbit skeletal muscle myosin heavy chain protein. The sequences corresponding to the subfragment 2 region are consistent with an alpha-helical conformation with a characteristic 7-residue periodicity in the linear distribution of nonpolar amino acids. Conversely, subfragment 1 sequences specified by pMHC beta 174 suggest a folded highly irregular structure.     

Inhibition of ADP-induced platelet aggregation by reduced factor Xa

Treatment of blood coagulation factor Xa with insolubilized hexyl-agarose derivative of prostaglandin E1 (PGE1) results in the generation of two sulfhydryl groups in the protein molecule. The reduced factor Xa was found to be a potent inhibitor of platelet aggregation and thromboxane A2 synthesis induced by ADP. In contrast to the inhibition of thromboxane formation, the reduced factor Xa had no effect on the formation of PGE2 indicating that thromboxane synthetase might be selectively inhibited by the reduced factor Xa. Incubation with oxidized glutathione reversed the inhibitory activity of factor Xa previously exposed to the insolubilized hormone. Soluble PGE1 also reduces factor Xa, but more slowly than the insolubilized PGE1. PGE1 also exhibits reducing ability as tested with redox dyes. Reduction of factor Xa by dithiothreitol also transformed the coagulation factor into an inhibitor of platelet aggregation and thromboxane A2 formation. These experiments indicate that reduction of factor Xa leads to a reversible alteration of the molecule which inhibits platelet aggregation induced by ADP. This effect of reduced factor Xa is probably mediated through the inhibition of thromboxane A2 synthesis.     

Effect of 3-phenylindole on lipophilic ion and carrier-mediated ion transport across bilayer lipid membranes

The physical effects of 3-phenylindole, an antimicrobial compound which interacts with phospholipids, on ion transport across phosphatidylcholine-cholesterol bilayers have been investigated using three lipophilic ions and one ion-carrier complex. It was found that 3-phenylindole increased membrane electrical conductance of positively charged membrane probes and decreased electrical conductance of negatively charged probes. The enhancement of conductance detected by nonactin-K+ complex and tetraphenylarsonium+ was several orders of magnitude, whereas the suppression of conductance due to tetraphenylborate- and dipicrylamine- was less than a factor of ten. Presence of 3-phenylindole in aqueous phase slightly decreased adsorption of tetraphenylborate- and dipicrylamine- at the membrane surface. From the voltage dependence of the steady-state conductance it was shown that 3-phenylindole induced kinetic limitation of membrane transport of potassium mediated by nonactin. No such limitation was found in the case of tetraphenylarsonium+ transport. These results are shown to be consistent with the present concept of ion diffusion in membranes and the assumption that 3-phenylindole decreases the electric potential in the membrane interior. The asymmetry of the effect of 3-phenylindole on the magnitude of conductance changes for positively and negatively charged membrane permeable ions is also discussed as a reflection of the discreteness of both the absorbed 3-phenylindole and lipid dipoles.     

Haematological studies on the prewintering and wintering frog, Rana esculenta

1. A study of the haematology of the frog Rana esculenta including erythrocyte count (RBC), haemoglobin content (Hb), haematocrit (HCT), mean cell volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC) and erythrocyte size as a function of prewinter and winter was made. 2. The RBC count and Hb were significantly higher in contrast to MCV and MCH values during prewinter in both sexes. 3. The surface area to volume ratio was higher in prewinter whereas the length to width ratio (eccentricity) of the cytosome and nucleus was significantly higher during winter in both sexes. 4. Sexual differences in the erythrocyte count, Hb content and the surface area to volume ratio were also observed. 5. The physiological significance of these observations are reported for Rana esculenta.