Synthesis of iodine-125 labeled 3-quinuclidinyl 4′-iodobenzilate

Iodine-125 labeled 3-quinuclidinyl 4′-iodobenzilate has been prepared via the reaction of the corresponding boronic acid with sodium [¹²⁵I]iodide in the presence of a mild oxidant.     

Alleviation of lindane induced toxicity in testis of Swiss mice (Mus musculus) by combined treatment with vitamin C, vitamin E and alpha-lipoic acid

Mitigation of lindane induced toxicity in testis of Swiss mice by combined treatment with vitamin C, vitamin E and alpha-lipoic acid has been evaluated. Male healthy mice (40), 8-10 weeks old were randomly selected and divided into 4 groups, control (C); lindane (L); antioxidant (A) and antioxidant plus lindane (A+L). Group C animals were administered only the vehicle (olive oil); in group L lindane was administered orally at a dose of 40 mg/kg body wt.; in group A combination of antioxidants at a dose of 125 mg/kg body wt.(vitamin C: 50 mg/kg body wt., vitamin E: 50 mg/kg body wt. and alpha-lipoic acid: 25 mg/kg body wt.) was administered orally; in group A+L both antioxidants (125 mg/kg body wt.) and lindane (40 mg/kg body wt.) were administered at their respective doses. In group A+L antioxidants were administered 1 h prior to lindane administration. All treatments were continuously given for 60 days. Histopathological changes due to lindane intoxication indicated shrunken and distorted seminiferous tubules, sparse Leydig cells and blood vessels and atrophy in the tissue. The testis weight also decreased significantly. Lindane treated group showed increased lipid peroxidation, whereas glutathione, glutathione peroxidase, superoxide dismutase, catalase and protein were significantly decreased compared to control. Lindane induced damage was minimized by administration of antioxidants. Results suggest that combined pretreatment with antioxidants can alleviate the damage caused to testis by lindane.     

Characterization of gonadotropin-releasing hormone (GnRH) binding sites in the pituitary and testis of the frog, Rana esculenta

Frog, Rana esculenta, pituitary and testis gonadotropin-releasing hormone (GnRH) receptors were characterized by using 125I-chicken IIGnRH (cIIGnRH) as radiolabeled ligand. At 4 C equilibrium binding of 125I-cIIGnRH to pituitary homogenates was achieved after 90 min of incubation; binding of 125I-cIIGnRH to testis membrane fractions reached its maximum at 60 min of incubation. Binding of the radioligand was a function of tissue concentration, with a positive correlation over the range 0.5-2 tissue equivalents per tube. One pituitary and one testis per tube were used as standard experimental condition. Incubation of the pituitary homogenate with increasing concentrations of 125I-cIIGnRH indicated saturable binding at radioligand concentrations of 1 nM and above while for the testis membrane preparation saturation was achieved using 5 nM 125I-cIIGnRH. The binding of 125I-cIIGnRH was found to be reversible after addition of the cold analog and the displacement curves could be resolved into one linear component for both tissues. Scatchard analysis suggested the presence of one class of binding sites for both pituitary and testis (Pituitary: Kd = 1.25 +/- 0.14 nM and Bmax = 8.55 +/- 2.72 fmol/mg protein; testis: Kd = 2.23 +/- 0.89 nM and Bmax = 26.48 +/- 7.39 fmol/mg protein). Buserelin displaced the labeled 125I-cIIGnRH with a lower IC50 as compared with cIIGnRH cold standard, while Arg-vasopressin (AVP) was completely ineffective, confirming the specificity of binding.     

Biological consequence of nuclear versus cytoplasmic decays of 125I: cysteamine as a radioprotector against Auger cascades in vivo

When the radionuclide 125I is localized in mouse testis as 125I-iododeoxyuridine (an analogue of thymidine) and incorporated into the DNA of spermatogonial cells, the cytocidal effects are as severe as those due to densely ionizing alpha particles. In contrast, 125I confined to the cytoplasm of these cells is much less radiotoxic, the efficacy being the same as for selective irradiation of the testis with sparsely ionizing external X rays. The biological effects, in both cases, are strongly mitigated upon pretreatment of the testes with very small amounts (0.75 microgram) of cysteamine, a radioprotector. These findings suggest an important role for such chemical agents in radiation protection and in understanding the mechanisms of radiation damage involving radionuclides incorporated in tissue.     

Two distinct subfractions in isolated Saccharomyces cerevisiae plasma membranes.

The plasma membrane from Saccharomyces cerevisiae X2180-1A and a secretion-blocked mutant, secl (P. Novick and R. Schekman, Proc. Natl. Acad. Sci. U.S.A. 76:1858-1862, 1979) has been purified. Cell walls were digested by treatment with lyticase followed by concanavalin A coating of spheroplasts. alpha-Methylmannoside treatment after lysis, sonication at high salt concentration, and fractionation on a Renografin gradient resulted in two highly purified membrane fractions sedimenting at densities of 1.15 and 1.17 g/cm3. Yields determined by recovery of vanadate-sensitive ATPase activity were 11 to 18%, and those determined by recovery of the spheroplast surface label 125I were 17 to 29%. Iodinated cells have most of their label in sedimentable, nonspheroplast material. However, both membrane populations contain some 125I surface label and show ATPase activity with pH optima only at 5.5. The apparent Vmax of the plasma membrane ATPase equals 360 to 560 nmol of ATP hydrolyzed per min per mg of protein, with a Km for ATP of 0.7 mM. ATPase specific activity is not decreased in mutant plasma membrane. Analysis of 125I-labeled plasma membrane proteins by two-dimensional gel electrophoresis revealed seven major proteins on the plasma membrane surface.     

Loose binding of testicular mitochondrial ATPase to the inner membrane

Rat testis mitochondrial ATPase was not inhibited by oligomycin at pH 7.5. It was inhibited only at higher alkaline pH's, and showed a lower sensitivity both to oligomycin and N,N′-dicyclohexylcarbodiimide and a higher one to efrapeptin. In submitochondrial particles, testis ATPase was only slightly inhibited by oligomycin, ossamycin, and efrapeptin. The possibility of a loose binding of F₁ to the membrane was supported by its recovery from the supernatant of the submitochondrial particles. Furthermore, by electron microscopy, after hypoosmotic shock and negative staining of the mitochondrial preparations, most of the inner mitochondrial membranes showed only a few “knobs” or none at all. The capacity of the testis mitochondrial preparation to produce ATP was tested and compared to that from liver. ATP synthetase/ATPase activity ratio was $\text{30}\text{1}$ in liver mitochondria, whereas in the testis it was $\text{3}\text{1}$. In spite of this large difference, at least part of the testis ATPase must be firmly bound to the membrane, since it is able to form ATP. The rest seems to be loosely bound and its functional significance is still unknown.     

γ—Aminobutyric acid transporter （GAT1） overexpression in mouse affects the testicular morphology

γ-Aminobutyric acid and GABAergic receptors were previously reported to be distributed in reproductive systems besides CNS and predicted to participate in the modulation of testicular function.γ-Aminobutyric acid transporter was implicated to be involved in this process.However,the potential role of γ-aminobutyric transporter in testis has not been explored.In this study,we investigated the existence of mouse γ-aminobutyric acid transporter subtype I (mGAT1) in testis.Wild-type and transgenic mice,which overexpressing mGAT1 in a variety of tissues,especially in testis,were primarily studied to approach the profile of mGAT1 in testis.Mice with overexpressed mGAT1 develop normally but with reduced mass and size of testis as compared with wild-type.Testicular morphology of transgenic mice exhibited overt abnormalities including focal damage of the spermatogenic epithelium accompanied by capillaries proliferation and increased diameter of seminiferous tubules lumen.Reduced number of spermatids was also found in some seminiferous tubules.Our results clearly demonstrate the presence of GAT1 in mouse testis and imply that GAT1 is possibly involved in testicular function.     

Trypsin-induced changes in the orientation of latent ATPase in protoplast ghosts from Mycobacterium phlei.

Latent ATPase, located on the inner surface of protoplast ghosts of Mycobacterium phlei, was unmasked either by trypsin or an impermeable form of trypsin, ethylene maleic anhydride-trypsin. Density gradient experiments showed that the ghost preparations remained intact following trypsin treatment. Evidence was obtained that 125I-trypsin failed to penetrate the ghost membranes. Thus, attempts were made to determine whether the ATPase molecule in the ghost membranes is accessible from the outer surface. Treatment of protoplast ghosts and trypsin-treated ghosts with 125I by the lactoperoxidase method resulted in the labeling of ATPase only in the trypsin-treated ghost preparations. The antibody to latent ATPase inhibited ATPase activity in trypsin-treated ghosts. The changes in the fluorescence polarization of diphenyl hexatriene indicated that trypsin treatment of the ghost membranes resulted in an increase in membrane fluidity. These studies suggest that the latent ATPase moiety has undergone translocation to the outer surface or it became accessible to trypsin digestion from the outer surface of the membranes as a result of removal of some proteins covering ATPase molecule in the membranes.     

The inhibitor peptide of the mitochondrial F1.F0-ATPase interacts with calmodulin and stimulates the calmodulin-dependent Ca2+-ATPase of erythrocytes

The binding of calmodulin to the mitochondrial F1.F0-ATPase has been studied. [125I]Iodoazidocalmodulin binds to the epsilon-subunit and to the endogeneous ATPase inhibitor peptide in a Ca2+-dependent reaction. The effect of the mitochondrial ATPase inhibitor peptide on the purified Ca2+-ATPase of erythrocytes has also been analyzed. The inhibitor peptide stimulates the ATPase when pre-incubated with the enzyme. The activation of the Ca2+-ATPase by calmodulin is not influenced by the inhibitor peptide, indicating that the two mechanisms of activation are different. These in vitro effects of the two regulatory proteins may reflect a common origin of the two ATPases considered and/or of the regulatory proteins.     

The changes of heavy metal and metallothionein distribution in testis induced by cadmium exposure

Cadmium (Cd) is known to cause various disorders in the testis, and metallothionein (MT) is known as a protein, which has a detoxification function for heavy metals. However, the changes of Fe, Cu, and Zn distribution in the testis induced by Cd exposure have not been well examined. Moreover, only a few studies have been reported on the localization of MT after Cd exposure. In this study, we have investigated the changes of Fe, Cu, and Zn distribution in Cd-exposed testis by a newly developed in air micro-Particle Induced X-ray Emission (PIXE) method. Also, we examined the distribution of MT expression in testis. In the testis of Cd-treated rats with significant increases of lipid peroxidation, the sertoli cell tight junction was damaged by Cd exposure, resulting from disintegration of the blood testis barrier (BTB). Evaluation by in air micro-PIXE method revealed that Cd and Fe distribution were increased in the interstitial tissues and seminiferous tubules. The histological findings indicated that the testicular tissue damage was advanced, which may have been caused by Fe flowing into seminiferous tubules followed by disintegration of the BTB. As a result, Fe was considered to enhance the tissue damage caused by Cd exposure. MT was detected in spermatogonia, spermatocytes, and Sertoli’s cells in the testis of Cd-treated rats, but was not detected in interstitial tissues. These results suggested that MT was induced by Cd in spermatogonia, spermatocytes, and Sertoli’s cells, and was involved in the resistance to tissue damage induced by Cd.     

Binding of 125I-labelled FSH in the mouse testis in vitro.

In-vivo testicular binding of highly purified pituitary FSH, labelled by a method which did not significantly affect biological potency, was hormone-specific, tissue-specific and dose-dependent. Hypophysectomy of mice was followed by a progressive increase in the amount of 125I-labelled FSH per unit weight of testis but not in the total amount of hormone taken up by the testis. Maximum binding occurred at 4 h in a membrane-containing fraction prepared by high-speed ultracentrifugation of testicular homogenate. This is considerably later than has been reported for testicular tissue incubated in vitro at 37 degrees C.     

Basolateral plasma membranes of intestinal epithelial cells. Identification by lactoperoxidase-catalysed iodination and isolation after density perturbation with digitonin.

Lactoperoxidase-catalysed iodination was used to label intestinal epithelial cell sheets with 125I. The iodination was carried out under conditions that allowed little penetration of lactoperoxidase into the cells and membrane-bound 125I therefore provided an effective marker for following plasma-membrane fragments through subcellular-fractionation procedures. 2. After homogenization and isopycnic zonal centrifugation through sucrose gradients two peaks of membrane-bound 125I were detected. One coincided with brush border enzymes such as alkaline phosphatase, disaccharidases and L-leucine B-naphthylamidase, whereas the other was coincident with the major peak of (Na++K+)-stimulated ATPase (adenosine triphosphatase), which has been thought to be concentrated in the basolateral plasma membranes of these cells. Neither peak of 125I reflected the distribution of any marker for an intracellular organelle. 3. A larger proportion of the (Na++K+)-stimulated ATPase, and thus of the basolateral plasma-membrane material, was found in a crude 'mitochondrial' fraction. It was not readiily separated from mitochondria by conventional techniques of subcellular fractionation. 4. Treatment of the 'mitochondrial' fraction with digitonin increased the density of basolateral plasma membrane but had little effect on mitochondrial density. A purified preparation of digitonin-loaded basolateral plasma membranes was isolated at a density of 1.20-1.22 by isopycnic centrifugation. 5. The enzymic composition of this preparation of basolateral plasma membranes is compared with previous preparations isolated from intestinal mucosal 'scrape' materials and from isolated cells.     

Diethylstilbestrol attenuates antioxidant activities in testis from male mice

It has been reported that acute exposure to diethylstilbestrol (DES) induces apoptosis in the testis, and antioxidants play a role in preventing DES-induced tissue damage. In this study, the effect of chronic exposure to DES on the antioxidants was examined in the testis and liver. Eight-week old male ICR mice were treated subcutaneously with various doses of DES for 20 days. Morphologically apparent apoptotic changes, 4-hydroxy-2-nonenal-positive cells and TUNEL-positive DNA-fragmentation, were demonstrated in the testis, but were minimal in the liver. Activities of antioxidants such as glutathione (GSH) peroxidase and GSH S -transferase decreased in both the liver and testis. The activity of Mn-superoxide dismutase (SOD) decreased in the liver but increased in the testis. The activity of Cu, Zn-SOD decreased in the liver but was unchanged in the testis. On Western and Northern blots, gamma-glutamylcysteine synthetase ( γ-GCS), a rate limiting enzyme of GSH synthesis, was increased in the liver dependent on the dose of DES. However, the expression of γ-GCS was reduced in the testis. Since quinones, metabolites of DES, generate reactive oxygen species, which damage DNA, antioxidants are important to prevent the damage. The data suggest that antioxidant activities are impaired by DES, and the levels of GSH are related to DES-induced apoptosis in the testis.     

Diethylstilbestrol Attenuates Antioxidant Activities in Testis from Male Mice

It has been reported that acute exposure to diethylstilbestrol (DES) induces apoptosis in the testis, and antioxidants play a role in preventing DES-induced tissue damage. In this study, the effect of chronic exposure to DES on the antioxidants was examined in the testis and liver. Eight-week old male ICR mice were treated subcutaneously with various doses of DES for 20 days. Morphologically apparent apoptotic changes, 4-hydroxy-2-nonenal-positive cells and TUNEL-positive DNA-fragmentation, were demonstrated in the testis, but were minimal in the liver. Activities of antioxidants such as glutathione (GSH) peroxidase and GSH S -transferase decreased in both the liver and testis. The activity of Mn-superoxide dismutase (SOD) decreased in the liver but increased in the testis. The activity of Cu, Zn-SOD decreased in the liver but was unchanged in the testis. On Western and Northern blots, gamma-glutamylcysteine synthetase ( &#110 -GCS), a rate limiting enzyme of GSH synthesis, was increased in the liver dependent on the dose of DES. However, the expression of &#110 -GCS was reduced in the testis. Since quinones, metabolites of DES, generate reactive oxygen species, which damage DNA, antioxidants are important to prevent the damage. The data suggest that antioxidant activities are impaired by DES, and the levels of GSH are related to DES-induced apoptosis in the testis.     

Efficient mutation induction by 125I and 131I decays in DNA of human cells

To examine the role of radiation energy deposition in DNA on cellular effects, we investigated the ability of 125IdUrd and 131IdUrd to kill cells and induce mutations at the hprt locus. We employed human lymphoblastoid cells proficient (TK6) or deficient (SE30) in the ability to incorporate a thymidine analog into DNA by way of the thymidine kinase (TK) scavenger pathway. Iodine-125 releases a shower of low-energy Auger electrons upon decay which deposit most of their energy within 20 nm of the decay site, whereas 131I is a high-energy beta/gamma emitter that is generally considered to emit sparsely ionizing radiation. Although 125IdUrd incorporated into cellular DNA was very effective at producing toxic and mutagenic effects in TK6 cells, virtually no effect was seen in TK-deficient cells incubated with similar levels of 125IdUrd in the extracellular medium. In response to 131IdUrd treatment, 0.45 X 10(-6) mutants were induced per centigray dose deposited within the nucleus in TK-proficient cells, whereas few mutations were induced in TK-deficient cells at doses up to 38 cGy from 131I decays occurring in the medium. The differences in biological response between TK6 and SE30 cells cannot be explained by differential radiosensitivity or IdUrd sensitization of the cell lines involved. We conclude that both 125I and 131I decays occurring while incorporated into DNA are more effective at inducing cell killing and mutations in human cells than either nonincorporated decays or low-LET radiations. These results suggest that localized energy deposition is an important factor in producing biologically important damage by both of these isotopes, and that residual lesions following the decay of DNA-incorporated radioisotopes may contribute to the toxic and mutagenic effects observed in TK-proficient cells. Furthermore, they emphasize that certain beta/gamma-emitting isotopes such as 131I may be particularly hazardous when incorporated into DNA.     

125I]azidosalicylyl melittin binding domains: evidence for a polypeptide receptor on the gastric (H+ + K+)ATPase

We have previously shown that melittin, a bee venom peptide, potently inhibited the catalytic and transport functions of rabbit gastric (H+ + K+)ATPase. A radioactive photoaffinity analog of melittin, ([125I]azidosalicylyl melittin), labeled the (H+ + K+)ATPase. These results suggested that melittin exerted inhibitory effects through direct interaction with the (H+ + K+)ATPase. In this study we attempt to define the melittin-binding domain of the (H+ + K+)ATPase using conformation-dependent proteolytic fragmentation of [125I]azidosalicylyl melittin-labeled hog gastric (H+ + K+)ATPase. In the presence of KCl (E2 form) the 95,000-Da [125I]-azidosalicylyl melittin-labeled (H+ + K+)ATPase was cleaved by trypsin to a 40,000-Da NH2-terminal tryptic fragment and a 56,000-Da COOH-terminal fragment through cleavage at Arg 454 of the (H+ + K+)ATPase. The 40,000-Da fragment was labeled by [125I]-azidosalicylyl melittin. The 56,000-Da fragment was not labeled. When unmodified (H+ + K+)ATPase was trypsinized in the presence of KCl, and the fragments were then reacted with [125I]azidosalicylyl melittin, similar tryptic fragmentation results were obtained. In the absence of KCl (E1 form), the 56,000- and 40,000-Da fragments did not accumulate. Chymotryptic hydrolysis of [125I]azidosalicylyl melittin-labeled (H+ + K+)-ATPase was very slow in the presence of KCl (E2 form). In the absence of KCl (E1 form), chymotryptic hydrolysis was more rapid, with accumulation of a major 42,000-Da fragment which was radiolabeled. The melittin-binding region on the (H+ + K+)ATPase is N-terminal to Arg 454 of the (H+ + K+)ATPase. This region is known to contain the aspartyl phosphate residue (Asp 385), the site of phosphoenzyme formation on the (H+ + K+)ATPase. Melittin is also known to bind to calmodulin and other proteins. Another known calmodulin-binding peptide with a different sequence but similar structure, Trp-3, (Leu-Lys-Trp-Lys-Lys-Leu-Leu-Lys-Leu-Leu-Lys-Lys-Leu-Leu-Lys-Leu-Gly) also inhibited the (H+ + K+)ATPase and label incorporation by [125I]azidosalicylyl melittin. These Trp-3 results suggested that the (H+ + K+)ATPase contains a peptide-binding domain which is similar to the peptide-binding domains found on other melittin-binding proteins.     

Amplification of oncogenes and integrated SV40 sequences in mammalian cells by the decay of incorporated iodine-125

Iodine-125, in the form of 5-[125I]iododeoxyuridine (I-UdR), was incorporated into the DNA of SV40 transformed Chinese hamster embryo cells. Disintegration of the 125I led to increased cell killing with increasing dose as measured by the colony-forming ability of single cells. The D37 (the dose at which 37% of the cells survive) amounts to 95 decays per cell, corresponding to 0.66 Gy. Variations in the copy number of specific DNA sequences was measured by using dispersed cell blotting with sensitive DNA hybridizations. A 13-fold amplification of the viral DNA sequences (SV40) and a twofold amplification of two cellular oncogenes of the ras-family (Ki-ras and Ha-ras) were found. Other cellular genes, like the alpha-actin gene, were not amplified, and no variation in gene copy number was detected after incubation of cells with cold I-UdR. We suggest the observed gene amplifications are induced by the densely ionizing radiation emitted by the decay of the incorporated 125I atoms.     

The inhibitor peptide of the mitochondrial F1 · F0-ATPase interacts with calmodulin and stimulates the calmodulin-dependent Ca2+-ATPase of erythrocytes

The binding of calmodulin to the mitochondrial F₁ · F₀-ATPase has been studied. [^125I]Iodoazidocalmodulin binds to the ε-subunit and to the endogeneous ATPase inhibitor peptide in a Ca²⁺-dependent reaction. The effect of the mitochondrial ATPase inhibitor peptide on the purified Ca²⁺-ATPase of erythrocytes has also been analyzed. The inhibitor peptide stimulates the ATPase when pre-incubated with the enzyme. The activation of the Ca²⁺-ATPase by calmodulin is not influenced by the inhibitor peptide, indicating that the two mechanisms of activation are different. These in vitro effects of the two regulatory proteins may reflect a common origin of the two ATPases considered and/or of the regulatory proteins.