DDT inhibition of Ca-Mg ATPase from peripheral nerves and muscles of lobster, Homarus americanus

Sensitivity of CaMg ATPase from axonic plasma membrane (APM) and sarcoplasmic reticulum (SR) of lobster, $\text{Homarus}\text{,}\text{americanus}$, to DDT was studied. The CaMg ATPase found in SR with the high Ca²⁺ affinity is sensitive to DDT while the portion of ATPase related to the low Ca²⁺ affinity site is not inhibited by DDT. Also, DDT is more inhibitory against the CaMg ATPase prepared from APM than the one obtained from SR. The relationship between inhibition of the CaMg ATPase by DDT in the axonic nerve membrane and $\text{in}\text{,}\text{vivo}$ poisoning symptoms of the nervous system is discussed.     

Effects of metabolic inhibitors on cell lethality and mutation induction in Chinese hamster cells. I. Inhibitors of de novo purine synthesis and a comparison with the effects of caffeine

The effect of pre- and posttreatment incubation of UV-irradiated and ethyl methanesulphonate (EMS) treated cells with non-toxic concentrations of inhibitors of de novo purine synthesis (dnPS) on expression of potentially lethal and premutational damage at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in V79 cells has been examined. The concentrations of inhibitors used were shown to profoundly perturb de novo DNA synthesis, by measurements of [¹⁴C]formate uptake, and cell cycle progression by flow cytofluorimetry. Postincubation in 6-methyl mercaptopurine ribonucleoside (MMPR) usually but not invariably potentiated the cytotoxic effects of UV and EMS but azaserine (AZS) and methotrexate (MTX) were without effect. No effects on mutant frequencies were observed on posttreatment with any of these agents. Caffeine produced the least effect on dnPS, but invariably potentiated lethal damage. This potentiation of lethal damage is not mediated by dnPS inhibition as has been suggested for Chinese hamster ovary (CHO) cells.     

Effects of aphidicolin on retrovirus DNA synthesis in vivo

Renaturation of $\text{Aequorea}$ green-fluorescent protein (A-GFP) was achieved for the first time following denaturation in guanidine-HCl or acid. Denaturation was accompanied by the concerted loss of visible fluorescence, alteration of absorption characteristics, and large negative deflection of CD signal in the far UV. Dialysis of a guanidine-denatured sample at pH 8 resulted in 64% renaturation (return to native absorption) and neutralization of an acid-denatured sample restored 90% of the native absorption. Renatured GFP is highly fluorescent and indistinguishable from native GFP with respect to the shape of excitation and emission spectra. Both native and denatured proteins exhibit resistance to trypsin hydrolysis and have identically broad pH and heat stability profiles, all of which suggest full renaturation.     

Convenient genotyping of six myostatin mutations causing double-muscling in cattle using a multiplex oligonucleotide ligation assay

We herein describe a procedure that allows for simultaneous genotyping of six loss-of-function mutations in the bovine myostatin gene associated with the double-muscling phenotype. The proposed method relies on a multiplex oligonucleotide ligation assay and detection of the fluorescently labelled products using automatic sequencers.     

Effect of the presence and location of corpus luteum on competence of bovine cumulus-oocyte complexes

This study aimed to determine the effect of presence of the corpus luteum (CL) and its influence on cumulus–oocyte complexes (COCs) obtained from the ipsilateral or contralateral ovary in bovine on the recovery and capacity of the oocytes to sustain mono-spermic fertilization, undergo preimplantation development, and develop to the blastocyst stage. Ovaries were collected at a local slaughterhouse and kept in pairs corresponding to the same animal. In the first experiment the variables evaluated were compared between cows with (CCL⁺) and without (CCL^-) CL, and for the second experiment, comparisons were made between ovaries with an ipsilateral (CL⁺), contralateral (CL⁻), and no (NCL). The recovery rate of COCs was higher in ovaries from CCL⁻ cows, and a higher proportion of grade 1 COCs were recovered from this group. A higher proportion of metaphase I oocytes at 7 h of maturation, and a higher rate of cleavage were observed in the CCL⁺ group; however, a higher proportion of embryos were obtained from the CCL⁻ group. Besides, COCs from the CL⁺ group had a lower proportion of grades 1 and 2 morphological qualities, lower rate of metaphase II oocytes at 22 h of maturation, and lower rate of formation of two pronuclei, whereas a higher proportion of unfertilized oocytes after in vitro fertilization. On the other hand, the COCs from the CL⁻ group displayed a lower proportion of oocytes with more than two pronuclei, higher cleavage rate, and higher final blastocyst production were obtained when compared to CL+. Thus, the effects of CL on the competence of bovine COCs are different depending on the anatomical proximity of their location in the animal, negatively affecting the quality of COCs located in the same ovary, but not having negative effects on the competence of COCs in the ovaries contralateral to their location.     

Specific lysis of GABAergic synaptosomes by an antiserum to glutamate decarboxylase

An antiserum to pure glutamate decarboxylase (GAD) when incubated with rat cortical synaptosomes in the presence of complement caused release of 33-53% of lactate dehydrogenase (LDH) and 22-41% of total GAD. In addition most of the gamma-aminobutyrate (GABA) present was released. Anti-GAD antiserum alone, or complement alone, were without action. The antiserum plus complement had no effect on noradrenaline or choline uptake, and did not release choline acetylase (ChAT). Anti-ChAT serum plus complement released 30-37% of ChAT and 10-13% of LDH. It prevented choline uptake. This serum did not produce GAD release or prevent GABA, choline or noradrenaline uptake. When cortical synaptosomes were exposed to both antisera plus complement, their actions were strictly additive. The data indicate specific lysis of GABAergic and cholinergic synaptosomal sub-populations.     

Regulation of Na/K/Cl cotransport in vascular smooth muscle cells

The regulation of Na/K/Cl cotransport was investigated in vascular smooth muscle cells. That a Na/K/Cl cotransport system exists was established by the finding that the ouabain insensitive K influx was sensitive to the "loop" diuretic bumetanide. Furthermore, bumetanide sensitive K influx was dependent upon the presence of both Na and Cl in the extracellular milieu. Bumetanide sensitive K influx was inhibited by agents which elevate cellular cyclic AMP levels, and to a lesser extent by agents which elevate cellular cyclic GMP levels. When serum, EGF or TPA was added, bumetanide sensitive K influx was enhanced. These results suggest that vascular smooth muscle cells have a ouabain insensitive, bumetanide sensitive Na/K/Cl cotransport system which is stimulated by serum, EGF or TPA and inhibited by cAMP or cGMP.