Stabilization of boron carbide via silicon doping

Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping.

Diagnostic performance of FDG PET or PET/CT in prosthetic infection after arthroplasty: a meta-analysis

AIM

The purpose of this study was to systematically review and perform a meta-analysis of published data regarding the diagnostic performance of positron emission tomography (PET) or PET/computed tomography (PET/CT) in prosthetic infection after arthroplasty.

METHODS

A comprehensive computer literature search of studies published through May 31, 2012 regarding PET or PET/CT in patients suspicious of prosthetic infection was performed in PubMed/MEDLINE, Embase and Scopus databases. Pooled sensitivity and specificity of PET or PET/CT in patients suspicious of prosthetic infection on a per prosthesis-based analysis were calculated. The area under the receiver-operating characteristic (ROC) curve was calculated to measure the accuracy of PET or PET/CT in patients with suspicious of prosthetic infection.

RESULTS

Fourteen studies comprising 838 prosthesis with suspicious of prosthetic infection after arthroplasty were included in this meta-analysis. The pooled sensitivity of PET or PET/CT in detecting prosthetic infection was 86% (95% confidence interval [CI] 82-90%) on a per prosthesis-based analysis. The pooled specificity of PET or PET/CT in detecting prosthetic infection was 86% (95% CI 83-89%) on a per prosthesis-based analysis. The area under the ROC curve was 0.93 on a per prosthesis-based analysis.

CONCLUSION

In patients suspicious of prosthetic infection, FDG PET or PET/CT demonstrated high sensitivity and specificity. FDG PET or PET/CT are accurate methods in this setting. Nevertheless, possible sources of false positive results and influcing factors should kept in mind.

Hypothyroidism and first-trimester spontaneous miscarriages

OBJECTIVE

To evaluate the association between hypothyroidism and first-trimester spontaneous miscarriages and to explain the mechanism.

MATERIALS AND METHODS

Patients admitted between October and May 2011 with threatened miscarriage in the first trimester were analyzed and levels of progesterone and thyroid hormones as T3, T4, and thyroid-stimulating hormone (TSH) were estimated. Once hypothyroidism was diagnosed, patients were treated with sodium levothyroxine (LT4) as substitution and outcomes were observed.

RESULTS

Measurement of progesterone was useful for predicting the outcome of threatened miscarriage The results showed that progesterone (P) = 14.74 ng/ml is selected as predictive value to judge whether the fetal treatment was successfully or not. When serum P value is above 14.74 ng/ml before treatment, it may favour a miscarriage, if the serum P value is below 14.74 ng/ml, miscarriage is unlikely; its sensitivity and specificity are high. The risk for miscarriage in patients diagnosed with hypothyroidism in which LT4 substitution was similar to the level observed in the controls, and P between the two groups had no distinct difference. The mechanism explaining the risk of miscarriage increased by thyroid disorders remains unclear, which needs advanced research.

CONCLUSION

Screening of thyroid disorders has important clinical significance in early pregnancy, and substitution of LT4 to those who are in the early pregnancy with hypothyroidism could reduce the risk of miscarriage.

P1-02-04: Estrogen Receptor beta Inhibits Breast Cancer EMT by Regulating the Expression of miR-200

Estrogen receptor beta (ERβ) mediates the effects of estrogens in a variety of human tissues and regulates cellular processes involved in initiation and progression of breast cancer such as cell proliferation and migration. Clinical studies produced contradictory data regarding the role for ERβ in prognosis of metastatic breast cancer and the molecular mechanism through which ERβ influences cell migration and invasion has not been fully elucidated. Here we show that induction of ERβ expression inhibits epithelial to mesenchymal transition (EMT) in metastatic breast cancer cells. This correlates with an ERβ-mediated induction in the expression of the epithelial marker E-cadherin and downregulation of its transcriptional repressors ZEB1 and SIP1. ERβ alters the expression of ZEB1 and SIP1 by inducing the expression of the miR-200a, miR200b and miR-429. Downregulation of these miRNAs in ERβ-expressing cells resulted in decreased cell-cell contact and decline of E-cadherin levels. In addition, ERβ was found to inhibit the invasiveness of metastatic breast cancer cells in a zebrafish xenotransplantation model. We are now examining breast cancer specimens derived from ductal carcinomas and metaplastic breast cancers to see whether ERβ levels decline in the mesenchymal regions and ERβ expression is correlated with epithelial markers. These data propose a crucial role for ERβ in the regulation of EMT and in prognosis of invasive and metastatic breast cancer.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-02-04.

57 NUCLEAR TRANSFER WITH RABBIT EMBRYONIC STEM CELLS: SERUM-STARVATION IMPROVES THE QUALITY OF CLONED EMBRYOS

Rabbit cloning by NT with somatic cells is so far a rather inefficient process. However, this technology is urgently required to generate rabbits with a humanized immune system as a source of human polyclonal antibodies. Embryonic stem cells (ESCs) have a number of advantages over somatic cells as tools for cell-mediated transgenesis including long periods of proliferation in vitro, higher frequency of homologous recombination between exogenous and chromosomal DNA, and less requirements for reprogramming (Rideout et al. 2000 Nat. Genet. 24, 109–110). To improve rabbit cloning we have derived and characterized 19 putative rabbit ESC lines and tested cells from 6 lines as donors for NT. First, we assessed in vitro development of NT embryos. Blastocyst rates varied in the range of 6–68% depending on the particular cell line and passage number, but the quality of the resultant embryos was worse compared to NT embryos derived from adult fibroblasts [hatched blastocysts: 13/214 (6%) v. 36/86 (42%), respectively]. Transfer of NT embryos derived from the ESC line showing the highest development to blastocysts into recipients resulted only in implantations (70%, 7/10) but not in offspring. Assuming that poor quality of NT embryos derived from ESCs could be due to the incompatibility between cell cycles of donor and recipient cells we used serum starvation to make ESCs more suitable for nuclear transfer. Serum starvation of one of the ESC lines (0.5% FCS for 3 days) greatly improved the quality of cloned embryos compared to those derived from non-starved cells of the same ESC line as indicated by the high proportions of hatched [38/151 (25%) v. 4/153 (3%)] and attached [25/151 (17%) v. 0%] to the surface of a culture dish blastocysts. Moreover, some of these blastocysts grew in vitro for 14–25 days. Our study provides evidence that the quality of NT embryos derived from ESCs can be significantly improved using serum starvation of donor cells suggesting possible effect of this treatment on the cell cycle synchronization. We are currently testing whether serum starvation of ESCs would also improve post-implantation development of rabbit NT embryos. This work is supported by Roche Diagnostic GmbH.

Design of annular photonic crystal slabs

We present the design of realistic annular photonic-crystal (APC) structures of finite thickness aiming to obtain a complete photonic bandgap (PBG). The APC is composed of dielectric rods and circular air holes in a triangular lattice such that each rod is centered within each hole. The optical and geometrical values of the structure are studied, and the interplay between various design parameters is highlighted. The coupled role of the inner-dielectric-rod radius, material types, and slab thickness is investigated. It is shown that the slab thickness is vital to obtain a complete photonic bandgap below the light line, and the specific value of the inner-dielectric-rod radius to sustain the maximum PBG if the hole radius is fixed at proper value is found.

102 RABBIT CLONING: HISTONE ACETYLATION STATUS OF DONOR CELLS AND CLONED EMBRYOS

Epigenetic status of the genome of a donor nucleus is likely to be associated with the developmental potential of cloned embryos produced by somatic cell nuclear transfer (SCNT). Prevention of epigenetic errors by manipulation of the epigenetic status of donor cells is expected to result in improvement of cloning efficiency. In this study, we transferred cultured rabbit cumulus cells (RCC) and fetal fibroblasts (RFF) from genetically marked rabbits (Ali/Bas) into metaphase II (MII) oocytes and analyzed the levels of histone H3K9 acetylation in donor cells and cloned embryos. We also assessed the correlation between the histone acetylation status of donor cells and cloned embryos and their developmental potential. To test whether alteration of the histone acetylation status affects development of cloned embryos, we treated donor cells with sodium butyrate (NaBu), a histone deacetylase inhibitor. Further, we tried to improve cloning efficiency by chimeric complementation of cloned embryos with one or two blastomeres from in vitro-fertilized or parthenogenetic embryos. Histone acetylation in donor cells and cloned embryos was detected by anti-acH3K9 antibody using Western immunoblot analysis or immunochemistry, respectively. Data were analyzed by chi-square (developmental rates) or Student-Newman-Keuls (histone acetylation) test. The levels of acetylated histone H3K9 were higher in RCCs than in RFFs (P < 0.05). Although the type of donor cells did not affect development to blastocyst, after transfer into recipients, RCC-cloned embryos induced a higher initial pregnancy rate as compared to RFF-cloned embryos (40% vs. 20%; P < 0.05). However, almost all pregnancies with either type of cloned embryos were lost by the middle of gestation and only one fully developed; a live RCC-derived rabbit was obtained. Treatment of RFFs with NaBu significantly (P < 0.05) increased the level of histone H3K9/14 acetylation and the proportion of nuclear transfer embryos developing to blastocyst (49% vs. 33% with non-treated RFF; P < 0.05). The distribution of signals for acH3K9 in either group of cloned embryos did not resemble that in in vivo-fertilized embryos, suggesting that reprogramming of this epigenetic mark is aberrant in cloned rabbit embryos and cannot be corrected by treatment of donor cells with NaBu. Aggregation of embryos cloned from NaBu-treated RFFs with blastomeres from in vivo-derived embryos improved development to blastocyst, but no cloned offspring were obtained. Two live cloned rabbits were produced from this donor cell type only after aggregation of cloned embryos with a parthenogenetic blastomere. Our study demonstrates that the levels of histone acetylation in donor cells and cloned embryos correlate with their developmental potential and can be a useful epigenetic mark to predict efficiency of SCNT rabbits. This work was supported by the Bayerische Forschungsstiftung and by Therapeutic Human Polyclonals, Inc.

38 RABBIT NUCLEAR TRANSFER AND IN VIVO-FERTILIZED EMBRYOS FAIL TO EXPRESS A MOUSE Oct-4 PROMOTER-DRIVEN EGFP REPORTER GENE

Reprogramming of a donor cell genome during somatic cell nuclear transfer (SCNT) is largely dependent on appropriate expression of 'pluripotency'? genes, such as Oct-4 (POU5F1). Recently, we transfected bovine fetal fibroblasts with GOF18-ΔPE-EGFP, a reporter gene construct for the Oct-4 promoter and assessed the expression of Oct-4 after SCNT (Wuensch et al. 2006 Reprod. Fertil. Dev. 18, 144). Our previous study on DNA methylation reprogramming revealed that rabbit in vivo-fertilized and cloned embryos differ from bovine embryos in respect to this epigenetic modification (Shi et al. 2004 Biol. Reprod. 71, 340–347), suggesting differences in the mechanism of epigenetic reprogramming between these two species. In this study, we tested whether GOF18-ΔPE-EGFP could be used to monitor Oct-4 expression in rabbit cloned embryos. The reporter gene construct included the EGFP gene flanked by a 9-kb fragment of the murine Oct-4 upstream region with a deletion in the proximal enhancer (PE) and a 9-kb fragment containing the nontranscribed murine structural Oct-4 gene. The 21.2-kb fragment GOF18-DPE-EGFP was released from the vector backbone by NotI digestion and purified with QIAquickGel Extraction Kit (Qiagen, Hilden, Germany) after gel electrophoresis. Four stable transfected colonies of rabbit fetal fibroblasts (RFF), none of which exhibited green fluorescence, were used for SCNT. The resulting embryos were examined on Days 2–5 by fluorescence microscopy. To detect endogenous Oct-4 expression, in vivo-fertilized embryos were stained with anti-mouse Oct-3 antibody and then incubated with secondary Alexa 488-conjugated goat anti-mouse antibody. The most prominent endogenous Oct-4 expression was detected in in vivo-fertilized embryos at the morula and blastocyst stages. Depending on the donor cell line used for nuclear transfer, cleavage and blastocyst rates ranged from 56 to 97% and from 33 to 49%, respectively. When a total of 230 cloned embryos at the 2-to 16-cell stages and 93 cloned morulae and blastocycts were examined by fluorescence microscopy, none of the examined embryos exhibited fluorescence signals indicating the lack of Oct-4 promoter activity. Taking into account the fact that both cloned and in vivo-fertilized rabbit embryos have specific patterns of DNA methylation reprogramming, which are different from that of bovine embryos, we injected GOF18-ΔPE-EGFP gene constructs into pronuclei of in vivo-fertilized zygotes. None of the 74 injected embryos, which were examined at the 2-cell to blastocyst stages, showed fluorescence signals. Our results demonstrate that rabbit nuclear transfer and in vivo-fertilized embryos are unable to activate a mouse Oct-4 promoter-reporter construct. Potential reasons include incompatibilities between mouse Oct-4 promoter sequences and rabbit transcription factors as well as specific mechanisms of epigenetic reprogramming in the rabbit. This work was supported by the Bayerische Forschungsstiftung.

[Clinical study on retarding aging effect of tongbu recipe to traditional Chinese medicine]

OBJECTIVE

To study the mechanism of Tongbu No. 1 (TB1, a prescription for reinforcing Kidney and Spleen, clearing up the bowel viscera to send Turbid downward and regulating Qi and blood) in retarding aging.

METHODS

A controlled, multiple indexes study was conducted in 56 old subjects randomized into 3 groups.

RESULTS

TB1 (containing ginseng leaf, cistanche, fleeceflower root, immature bitter orange, rhubarb, etc) could improve various symptoms of aging, and had the effect in regulating immune and endocrinal function, scavenging free radicals and adjusting coli flora. The effects of TB1 and TB2 (containing ginseng leaf, cistanche and fleeceflower root) were different significantly (P < 0.05, P < 0.01).

CONCLUSION

TB1 has a good comprehensive effect in retarding aging.

Metallothionein, neurotrophins and selegiline in providing neuroprotection in Parkinson's disease

The finding that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) elicits parkinsonism in human beings suggests that endogenous or xenobiotic neurotoxic compounds may be involved in the etiology of Parkinson's disease (PD). We have shown that cerebrospinal fluid (CSF) of newly diagnosed and drug untreated patients with PD contains a low molecular weight substance(s) which inhibits the growth and function of dopaminergic neurons in culture. In addition, selegiline in a dosage below the level that inhibits monoamine oxidase B (MAO-B), protects dopaminergic neurons in culture against toxic factor(s) present in the CSF of patients with PD, and the said effect is mediated via elaboration of brain-derived neurotrophic factor (BDNF). In view of the fact that 6-hydroxydopamine (6-OHDA) or MPTP causes parkinsonism by generating free radicals, and inducers of metallothionein (MT) isoforms avert the said neurotoxicity, we intended to learn whether MT isoforms were capable of scavenging free radicals. By employing electron spin resonance spectroscopy (ESR), we examined for the first time the free radical scavenging effects of MT-I and MT-II isoforms on four types of free radicals. Solutions of 0.15 mM of MT-I and 0.3 mM of MT-II scavenged the 1,1-diphenyl-2-picrylhydrazyl radicals completely. Furthermore, they were able to scavenge hydroxyl radicals generated in a Fenton reaction. Moreover, MT-I scavenged almost 90% of the superoxide generated by the hypoxanthine and xanthine oxidase system, while MT-II could only scavenge 40%. By using 2,2,6,6-tetramethyl-4-piperidone as a "spin-trap" for the reactive oxygen species (containing singlet oxygen, superoxide and hydroxyl radicals) generated by photosensitized oxidation of riboflavin, and measuring the relative signal intensities of the resulting stable nitroxide adduct, 2,2,6,6-tetramethyl-4-piperidone-1-oxyl, we observed that MT-II could scavenge 92%, while MT-I could completely scavenge all the reactive species generated. The results of this investigation are interpreted to suggest that selegiline by preventing the generation of free radicals, MT isoforms by scavenging free radicals, and neurotrophins by rescuing dopaminergic neurons are capable of attenuating oxidative stress and of providing neuro-protection in PD.

Modulation of nigrostriatal dopaminergic transmission by antisense oligodeoxynucleotide against brain-derived neurotrophic factor

Brain-derived neurotrophic factor (BDNF) promotes the differentiation and growth of developing dopamine (DA) neurons and supports the survival of mature DA cells in culture. However, the neurotrophic role of endogenous BDNF in the adult DA system in vivo has not been well established. To investigate the hypothesis that blockade of endogenous BDNF expression results in DA dysregulation, we used an 18-mer antisense oligodeoxynucleotide (ODN) targeted to the first ATG codon of the BDNF transcript. The biological activity of the antisense ODN was initially tested in vitro. In cultured dopaminergic MES 23.5 cells, antisense BDNF (20 microM) effectively reduced BDNF protein expression and cell survival. Furthermore, in primary embryonic mesencephalic cultures, antisense BDNF reduced the number of tyrosine hydroxylase positive neurons and inhibited [3H]DA uptake in a time- and dose-dependent manner. The specificity of the antisense molecule was confirmed by comparing its effects with those of a control ODN having the same base composition but in scrambled sequence. In rats, two days following an intranigral or intrastriatal injection of antisense BDNF (0.5 microg), we observed a two-fold and five-fold increase in nigral DA levels, respectively, but no change in striatal DA content. Seven days after an intrastriatal antisense BDNF injection, DA levels were elevated in the striatum apparently due to decreased DA turnover. These observations suggest that inhibition of endogenous BDNF expression tends to augment rather than inhibit nigrostriatal DA transmission. Thus, the biological effects of endogenous BDNF on the nigrostriatal DA system in the adult organism merits further investigation.

Stable interaction between G-actin and neurofilament light subunit in dopaminergic neurons

Excessive accumulation of neurofilaments in the cell bodies and proximal axons of motor neurons is a major pathological hallmark of motor neuron diseases. In this communication we provide evidence that the neurofilament light subunit (68 kDa) and G-actin are capable of forming a stable interaction. Cytochalasin B, a cytoskeleton disrupting agent that interrupts actin-based microfilaments, caused aggregation of neurofilaments in cultured mesencephalic dopaminergic neurons, suggesting a possible interaction between neurofilaments and actin; which was tested further by using crosslinking reaction and affinity chromatography techniques. In the cross-linking experiment, G-actin interacted with individual neurofilament subunits and covalently cross-linked with disuccinimidyl suberate, a homobifunctional cross-linking reagent. Furthermore, G-actin was extensively cross-linked to the light neurofilament subunit with this reagent. The other two neurofilament subunits showed no cross-linking to G-actin. Moreover, neurofilament subunits were retained on a G-actin coupled affinity column and were eluted from this column by increasing salt concentration. All three neurofilament subunits became bound to the G-actin affinity column. However, a portion of the 160 and 200 kDa neurofilament subunits did not bind to the column, and the remainder of these two subunits eluted prior to the 68 kDa subunit, suggesting that the light subunit exhibited the highest affinity for G-actin. Moreover, neurofilaments demonstrated little or no binding to F-actin coupled affinity columns. The phosphorylation of neurofilament proteins with protein kinase C reduced its cross-linking to G-actin. The results of these studies are interpreted to suggest that the interaction between neurofilaments and actin, regulated by neurofilament phosphorylation, may play a role in maintaining the structure and hence the function of dopaminergic neurons in culture.

Selegiline protects dopaminergic neurons in culture from toxic factor(s) present in the cerebrospinal fluid of patients with Parkinson's disease

The cerebrospinal fluid (CSF) of patients with Parkinson's disease (PD) contains substance(s) that inhibit the growth and functions of dopaminergic neurons. Further, selegiline, a monoamine oxidase B (MAO) inhibitor (0.125-0.250 microM) enhanced the number of tyrosine hydroxylase (TH)-positive neurons, augmented the high affinity uptake of dopamine (DA), and averted the neurotoxic effects of CSF of PD patients on rat mesencephalic neurons in culture. The neuroprotective effects of selegiline may be related either to its ability to inhibit MAO B, preventing the generation of free radicals, or to neuronal rescue property due to unknown mechanisms.

Expression and regulation of brain metallothionein

Many, but not all, zinc-containing neurons in the brain are a subclass of the glutamatergic neurons, and they are found predominantly in the telencephalon. These neurons store zinc in their presynaptic terminals and release it by a calcium-dependent mechanism. These "vesicular" pools of zinc are viewed as endogenous modulators of ligand- and voltage-gated ion channels. Metallothioneins (MTs) are low molecular weight zinc-binding proteins consisting of 25-30% cysteine, with no aromatic amino acids or disulfide bonds. The areas of the brain containing high contents of zinc such as the retina, the pineal gland, and the hippocampus synthesize unique isoforms of MT on a continuous basis. The four MT isoforms are thought to provide the neurons and glial elements with mechanisms to distribute, donate, and sequester zinc at presynaptic terminals; or buffer the excess zinc at synaptic junctions. In this cause, glutathione disulfide may participate in releasing zinc from MT. A similar nucleotide and amino acid sequence has made it difficult to obtain cDNA probes and antibodies capable of distinguishing indisputably among MT isoforms. MT-I and MT-II isoforms are found in the brain and in the peripheral tissues; MT-III isoform, possessing an additional seven amino acids, is expressed mostly in the brain and to a very minute extent in the intestine and pancreas; whereas MT-IV isoform is found in tissues containing stratified squamous epithelial cells. Since MTs are expressed in neurons that sequester zinc in their synaptic vesicles, the regulation of the expression of MT isoforms is extremely important in terms of maintaining the steady-state level of zinc and controlling redox potentials. The concentration of zinc has been shown to be altered in an extensive number of disorders of the central nervous system, including alcoholism. Alzheimer-type dementia, amyotrophic lateral sclerosis, Down's syndrome, epilepsy, Friedreich's ataxia, Guillaine-Barré syndrome, hepatic encephalopathy, multiple sclerosis, Parkinson's disease, Pick's disease, retinitis pigmentosa, retinal dystrophy, schizophrenia, and Wernicke-Korsakoff syndrome. The status of MT isoforms and other low molecular weight zinc-binding proteins in these conditions, diseases, disorders, or syndromes is being delineated at this time. Since several of these disorders, such as amyotrophic lateral sclerosis, are associated with oxidative stress, and since MT is able to prevent the formation of free radicals, it is believed that cytokine-induced induction of MT provides a long-lasting protection to avert oxidative damage.

Cerebrospinal fluid of Parkinson's disease patients inhibits the growth and function of dopaminergic neurons in culture

We report the possible existence of an inhibitory factor in the CSF of Parkinson's disease patients that inhibits the function and growth of dopaminergic neurons in rat mesencephalic culture. After 40 hours' exposure to the < 10 kd fraction of CSF from PD patients, the high-affinity dopamine uptake was 66% of that of cultures exposed to CSF from controls. However, the number of dopaminergic neurons remained unchanged at this time. After 90 hours' exposure to the < 10 kd fraction of CSF from PD patients, the number of dopaminergic neurons decreased to 10% of that in cultures exposed to CSF from controls, and the size of the remaining dopaminergic neurons in the culture became smaller. This inhibitory factor did not affect the growth of other types of neurons. The chemical nature of this inhibitory factor is under investigation.

Distribution of zinc metallothionein I mRNA in rat brain using in situ hybridization

Metallothionein (MT) isoforms I and II were first identified and characterized in our laboratories in several regions of brain, in hippocampal neurons in primary culture, and in retinoblastoma and neuroblastoma cell lines. In this study, by having employed the MT-I cDNA as a probe, we sought to gain additional insight about the function of MT by discerning the regional distribution of its mRNA. Northern blot analyses of brain mRNA revealed that the administration of zinc enhanced dramatically MT-I mRNA (570 bp). The in situ hybridization study revealed that MT-I mRNA was located in several areas of brain, with the highest concentrations found in the cerebellum, hippocampus, and ventricles. The results of these studies are interpreted to suggest that zinc enhances the synthesis of MT mRNA and MT in turn may participate in zinc associated functions in neurons.

Cloning of the gene for glutamate decarboxylase and its expression during conidiation in Neurospora crassa

Neurospora crassa glutamate decarboxylase (GAD) is produced during conidiation and stored in dormant conidia. Polyclonal antibody was generated to GAD that had been purified to homogeneity. The anti-GAD antibody was specific for N. crassa GAD and inhibited GAD activity. The level of GAD protein decreased during conidial germination, indicating that GAD was degraded during this phase of development. The anti-GAD antibody was used to isolate a cDNA clone of GAD from a lambda ZAP cDNA expression library. Escherichia coli containing a plasmid with the cDNA insert produced GAD activity. The cDNA clone contained a 2.6 kbp insert and hybridized to a 2.6 kb mRNA species from conidiating cultures of N. crassa. GAD mRNA was not present in vegetative hyphae. In conidiating cultures, GAD mRNA was first detected when conidia began to appear. The level of GAD mRNA increased as conidiation progressed. This is the first example of the cloning of an enzyme that is regulated at the level of mRNA during the asexual developmental cycle of N. crassa.

Purification and characterization of metallothionein and its activation of pyridoxal phosphokinase in trout (Salmo gairdneri) brain

1. Brain metallothionein was isolated and purified for the first time from rainbow trout. 2. Brain metallothionein exhibited an elution volume (Ve/Vo) of 2.0, had a molecular weight of 6762 Daltons, and contained a zinc content of 9 micrograms/mg protein. 3. Brain pyridoxal phosphokinase was isolated and assayed for the first time in rainbow trout. 4. Zinc (0.20 microM) or zinc metallothionein (6-30 microM) stimulated the activity of brain pyridoxal kinase in a linear fashion. 5. The results of these studies are interpreted to suggest that in trout brain zinc metallothionein may participate in metabolism of vitamin B6 and formation of pyridoxal phosphate, the active coenzyme.