Mitochondrial energy metabolism is regulated via nuclear-coded subunits of cytochrome c oxidase

A new mechanism on regulation of mitochondrial energy metabolism is proposed on the basis of reversible control of respiration by the intramitochondrial ATP/ADP ratio and slip of proton pumping (decreased H+/e- stoichiometry) in cytochrome c oxidase (COX) at high proton motive force delta p. cAMP-dependent phosphorylation of COX switches on and Ca2+-dependent dephosphorylation switches off the allosteric ATP-inhibition of COX (nucleotides bind to subunit IV). Control of respiration via phosphorylated COX by the ATP/ADP ratio keeps delta p (mainly delta psi(m)) low. Hormone induced Ca2+-dependent dephosphorylation results in loss of ATP-inhibition, increase of respiration and delta p with consequent slip in proton pumping. Slip in COX increases the free energy of reaction, resulting in increased rates of respiration, thermogenesis and ATP-synthesis. Increased delta psi(m) stimulates production of reactive oxygen species (ROS), mutations of mitochondrial DNA and accelerates aging. Slip of proton pumping without dephosphorylation and increase of delta p is found permanently in the liver-type isozyme of COX (subunit VIaL) and at high intramitochondrial ATP/ADP ratios in the heart-type isozyme (subunit VIaH). High substrate pressure (sigmoidal v/s kinetics), palmitate and 3,5-diiodothyronine (binding to subunit Va) increase also delta p, ROS production and slip but without dephosphorylation of COX.

Structure of the human serotonin 5-HT4 receptor gene and cloning of a novel 5-HT4 splice variant

Several variants of the serotonin 5-HT4 receptor are known to be produced by alternative splicing. To survey the existence and usage of exons in humans, we cloned the human 5-HT4 gene. Based on sequence analysis seven C-terminal variants (a-g) and one internal splice variant (h) were found. We concentrated in this study on the functional characterization of the novel splice variant h, which leads to the insertion of 14 amino acids into the second extracellular loop of the receptor. The h variant was cloned as a splice combination with the C-terminal b variant; therefore, we call this receptor 5-HT4(hb). This novel receptor variant was expressed transiently in COS-7 cells, and its pharmacological profile was compared with those of the previously cloned 5-HT4(a) and 5-HT4(b) isoforms, with the latter being the primary reference for the h variant. In competition binding experiments using reference 5-HT4 ligands, no significant differences were detected. However, the broadly used 5-HT4 antagonist GR113808 discriminated functionally among the receptor variants investigated. As expected, it was an antagonist on the 5-HT4(a) and 5-HT4(b) variant but showed partial agonistic activity on the 5-HT4(hb) variant. These data emphasize the importance of variations introduced by splicing for receptor pharmacology and may help in the understanding of conflicting results seen with 5-HT4 ligands in different model systems.

The allosteric ATP-inhibition of cytochrome c oxidase activity is reversibly switched on by cAMP-dependent phosphorylation

In previous studies the allosteric inhibition of cytochrome c oxidase at high intramitochondrial ATP/ADP-ratios via binding of the nucleotides to the matrix domain of subunit IV was demonstrated. Here we show that the allosteric ATP-inhibition of the isolated bovine heart enzyme is switched on by cAMP-dependent phosphorylation with protein kinase A of subunits II (and/or III) and Vb, and switched off by subsequent incubation with protein phosphatase 1. It is suggested that after cAMP-dependent phosphorylation of cytochrome c oxidase mitochondrial respiration is controlled by the ATP/ADP-ratio keeping the proton motive force Deltap low, and the efficiency of energy transduction high. After Ca(2+)-induced dephosphorylation this control is lost, accompanied by increase of Deltap, slip of proton pumping (decreased H(+)/e(-) stoichiometry), and increase of the rate of respiration and ATP-synthesis at a decreased efficiency of energy transduction.

A non-cannabinoid immunogen used to elicit antibodies with broad cross-reactivity to cannabinoid metabolites

A benzpyran derivative was linked to the lysines of bovine thyroglobulin (BTG) where 69% of the available lysines were modified. This derivative was designed to elicit antibodies that were directed towards the conserved epitopes of cannabinoid metabolites that appear in urine. Polyclonal antibodies from sheep and goats and murine monoclonal antibodies were generated using this immunogen. The cross-reactivity of the antibodies was compared with antibodies generated from the more traditional phenolic-linked or 9-linked immunogens. An ELISA assay was developed using delta 9-11-nor-9-carboxy-tetrahydrocannabinol (COOH-THC) to obtain a standard curve. The antibodies generated using the benzpyran immunogen showed an average of two to three times higher cross-reactivity towards 11-OH-delta 9-THC, 8 beta-OH-delta 9-THC, 8 alpha-OH-delta 9-THC, 11-OH-delta 8-THC, and 8 beta,11-di-OH-delta 9-THC than antibodies that were generated by traditional cannabinoid immunogens. The selectivity of the benzpyran-elicited antibodies was also compared with antibodies derived from traditional immunogens using clinical urine samples that were confirmed for cannabinoids by GC/MS. The total cross-reactive cannabinoid values obtained with the benzpyran-elicited antibodies were 49% higher than the values obtained using the traditional immunogen structures. The benzpyran immunogen-induced antibodies exhibited the same low cross-reactivity for non-structurally related compounds as antibodies derived from traditional immunogens. The novel benzpyran immunogen used in this study is the first non-cannabinoid immunogen used to generate cannabinoid-selective antibodies and demonstrates the usefulness of such a structure in developing broadly cross-reactive cannabinoid antibodies.

Association between corticosteroid use and vertebral fractures in older men with chronic obstructive pulmonary disease

Osteoporosis is a major complication of long-term corticosteroid administration, but the magnitude of the effect in patients with chronic obstructive pulmonary disease (COPD) is not well defined. In a cross-sectional study, we evaluated the association between steroid use and vertebral fractures in 312 men, 50 yr of age or older, with COPD. Subjects were evaluated according to their corticosteroid use: Never Steroid Users (NSU) (n = 117), Inhaled Steroid Users (ISU) (n = 70), and Systemic Steroid Users (SSU) (n = 125). The prevalence of one or more vertebral fractures was 48.7% in the NSU group, 57.1% in the ISU group, and 63.3% in the SSU group. Compared with NSU, SSU were two times as likely to have one or more vertebral fractures: age-adjusted odds ratio (OR) = 1.80; 95% CI, 1.08 to 3.07. This relationship was primarily due to a strong association between continuous systemic steroid use and vertebral fractures: age-adjusted OR = 2.36; 95% CI, 1.26 to 4.38. In addition, fractures in SSU were more likely to be multiple and more severe. A weaker relationship existed between inhaled steroid use and vertebral fractures: age-adjusted OR = 1.35; 95% CI, 0.77 to 2.56 compared with NSU. These data indicate that vertebral fractures are common in older men with COPD; the likelihood of these fractures is greatest in those men using continuous systemic steroids.

Cloning and expression of a human serotonin 5-HT4 receptor cDNA

Using a combination of library screening and nested PCR based on a partial human serotonin 5-HT4 receptor sequence, we have cloned the complete coding region for a human 5-HT4 receptor. The sequence shows extensive similarity to the published porcine 5-HT4A and rat 5-HT4L receptor cDNA; however, in comparison with the latter, we find an open reading frame corresponding to only 388 amino acids instead of 406 amino acids. This difference is due to a frame shift caused by an additional cytosine found in the human sequence after position 1,154. Moreover, we also found the same additional cytosine in the rat 5-HT4 sequence. We confirmed the occurrence of the sequence by examining this part of the sequence in genomic DNA of 10 human volunteers and in rat genomic DNA. Based on a part of the genomic 5-HT4 receptor sequence that was identified in the cloning process, there seem to be at least two possible splice sites in the coding region of the gene. The human 5-HT4 receptor, transiently expressed in COS-7 cells, showed radioligand binding properties similar to 5-HT4 receptors in guinea pig striatal tissue. [3H]GR 113808 revealed K(D) values of 0.15 +/- 0.01 nM for the human receptor and 0.3 +/- 0.1 nM in the guinea pig tissue. Binding constants were determined for four investigated 5-HT4 antagonists and three agonists, and appropriate binding inhibition constants were found in each case. Stimulation of transfected COS-7 cells with 5-HT4-specific agonists caused an increase in cyclic AMP levels.

[Functional voice quality assessment in curative microsurgery of laryngeal malignancies. Postoperative voice rehabilitation based on the "laryngeal double valve function"]

According to Negus and Pressman the sphincter systems of the vocal folds and the ventricular folds form a respiratory "laryngeal double valve function". Correspondingly, we found a physiological phonation system of the glottis and a pathological-compensatory one of the supraglottis. They appear to be regulated through an automatic phonatory control system with the glottal phonatory function evidently acting as sensor level. In order to confirm this hypothesis, objective voice analyses with glottal-relevant parameters of 26 voice-rehabilitated patients after minimally invasive laser surgery of glottal carcinomas are presented and integrated into a "hoarseness diagram" with the coordinates roughness and breathiness. Using statistically deliminated acoustic dusters, our data show a qualitative hierarchy of different postoperative phonation mechanisms. They demonstrate the influence of the vibratory capacity of glottal and supraglottal structures on the quality of the vibratory closure. Both functional parameters evidently determine the resulting voice quality in the sense of our hypothesis.

Strong indication for a breast cancer susceptibility gene on chromosome 8p12-p22: linkage analysis in German breast cancer families

Chromosomal losses involving the short arm of chromosome 8 are frequent in a variety of tumor types, including breast cancer, suggesting the presence of one or more tumor suppressor genes in this region. Previous linkage analysis and studies of loss of heterozygosity (LOH) have suggested the presence of a putative third breast cancer susceptibility gene around D8S505 at 8p12-p22. We have performed linkage analysis in two German breast cancer families, showing negative lod scores with 17q and 13q markers, using seven adjacent microsatellite markers from 8p12-p22. Incorporating LOH data from tumors of the affected family members a maximum cumulative three-point lod score of 3.30 at theta = 0.00 was obtained with D8S137 and D8S131. Our findings considerably strengthen the evidence for a third breast cancer susceptibility locus (BRCA3) mapping to the short arm of human chromosome 8.

BRCA1 mutations and phenotype

More than 100 mutations have been described for the breast-cancer-susceptibility gene BRCA1. The paper describes phenotypical aspects of three selected mutations located at the beginning, in the middle, and at the end of the gene. A remarkable decrease of the age of diagnosis of the mammary carcinoma is observed with increasing length of the putative gene product, combined with greater severity of the disease.

Deletion mapping and linkage analysis provide strong indication for the involvement of the human chromosome region 8p12-p22 in breast carcinogenesis

We have identified a high frequency of loss of heterozygosity (LOH) on the human chromosome region 8p12-p22 in a panel of microdissected familial (86% LOH) and sporadic (74% LOH) breast tumours. The two most frequently deleted regions were defined around marker D8S133 and in a broader centromeric region bounded by markers D8S137 and D8S339. We cannot unequivocally characterize the 8p12-p22 loss as an early or a late event in breast carcinogenesis. In parallel, we have performed linkage analysis in four German breast cancer families. A location score greater than 13.67 corresponding to a LOD score of 2.97 at the marker D8S137 has been obtained. Our results considerably strengthen the evidence for a breast cancer susceptibility gene(s) located on the short arm of the chromosome region at 8p12-p22.

BRCA1 mutations in German breast-cancer families

We analyzed germline mutations of the BRCA1 gene in 20 German breast/ovarian-cancer families. BRCA1 mutations co-segregating with breast-cancer susceptibility were identified in 3 of these families. All mutations were found to generate a premature stop codon leading to the synthesis of truncated BRCA1 proteins of different length. Nine polymorphisms were detected in BRCA1, 4 of which have not been described previously. Analysis of familial tumors for LOH revealed that only the disease-related allele of BRCA1 was present.

Inhibition of experimental liver metastasis by combined treatment with tamoxifen and interferon

The demonstration of estrogen receptors (ERs) in the liver has established it as a hormonally responsive organ. Estrogens have been imputed to have a role in the development of benign and malignant liver tumors. The detection of ERs in samples of normal liver tissue and in hepatocellular carcinomas suggested a treatment strategy with anti-hormonal drugs, i.e. tamoxifen, as used clinically for the treatment of breast cancer. The objective of this study was to test the effect of tamoxifen and tamoxifen in combination with other agents [5-fluorouracil (5-FU) and interferon (IFN)] against experimental liver metastases of human colorectal tumor cells xenografted into nude mice. A human colorectal tumor cell line, LoVo, was injected into the spleens of nude mice. This produces liver metastases in virtually 100% of the mice in 6-8 weeks. One week before tumor cell implantation, all mice were ovariectomized. Treatment was started 3 days after the intrasplenic injections. This consisted of 5 mg tamoxifen pellets (60-day release) implanted s.c., 5-FU given i.p. once a week for 4 weeks on a 46 mg/kg basis and IFN given s.c., daily for 4 weeks, 3 x 10(5) units/injection. The effect of tamoxifen alone on liver metastases was not significantly different from untreated controls. Tamoxifen in combination with IFN and 5-FU, however, resulted in 50-67% inhibition of liver metastases, as compared with the controls. The effectiveness of the treatment was in the order: tamoxifen + IFN > tamoxifen + 5-FU + IFN > tamoxifen + 5-FU. Thus, IFN may be useful as a potentiating agent in combination with tamoxifen for the treatment of estrogen-dependent tumors.

Linkage analysis in German breast cancer families with early onset of the disease, using highly polymorphic markers from the chromosome 17q11-q24 region

Linkage analysis in German breast cancer families with early onset of the disease by using six markers on chromosome 17q11-q24 has been carried out. In the region between markers D17S250 and GH, three markers showed positive LOD scores at an estimated distance of zero. Evidence for linkage is greatest for D17S250, with a LOD score of 2.42.

Recombinant human antibodies: linkage of an Fab fragment from a combinatorial library to an Fc fragment for expression in mammalian cell culture

The combinatorial phage library approach to immunoglobulin repertoire cloning recently made it possible to isolate gene fragments encoding human immunoglobulin G1 Fabs binding with high affinity to specific antigens. Here we describe the construction of genes encoding whole human anti-tetanus toxoid antibodies based on one of these gene fragments and the efficient expression of these constructs by co-transfection of separate heavy and light chain vectors into a Chinese hamster ovary cell line constitutively expressing a viral transactivator protein. This system will be generally useful for the rapid analysis of recombinant antibodies derived from combinatorial libraries.

[Results of the surgical treatment of mandibular body fractures during the growth period]

8 patients, aged between 9 and 13 years, had undergone surgery for fractures of the mandibular body. Miniplates were used for fragment fixation. No growth disorders or anomalies in tooth eruption were observed during a follow-up period of up to 9 years.

Synthesis and secretion of hirudin by Streptomyces lividans

To examine the secretory production of heterologous proteins by Streptomyces lividans, we fused the DNA encoding the signal peptide of the alpha-amylase inhibitor tendamistat, derived from S. tendae with a synthetic gene encoding the thrombin inhibitor hirudin. The analysis of secretion by immunoblots revealed an efficient translocation of hirudin through the membrane, with no detectable immunoreaction among the cellular proteins. The secreted hirudin was stable in the shaking culture for about 6 days. A comparison of the hirudin secreted by S. lividans and recombinant reference hirudin from yeast by immunoblots and thrombin inhibition assays shows that hirudin from Streptomyces has a lower specific activity, which may be due to a different aminoterminal sequence or to inexact processing of the precursor.

Secretory synthesis of human interleukin-2 by Streptomyces lividans

To study the ability of Streptomyces lividans to produce heterologous proteins by secretion, we directly fused DNA encoding the leader peptide of the alpha-amylase inhibitor, tendamistat, produced by Streptomyces tendae, with DNA encoding the mature part of interleukin-2 (IL-2). Such cloned fusion constructs are translated in S. lividans, in spite of the quite different codon usage. The active Il-2 is secreted into the culture broth, though the amounts are much less than that of the alpha-amylase inhibitor. The presence of IL-2 in the supernatants could be demonstrated both by an activity assay and by immunoblotting. In addition to the secreted form, three different species of Il-2 antibody immunoreactive proteins, with different Mrs, are either present in the cells or attached to the cells. This indicates that inefficient processing and translocation of the precursor is a major reason for the low activities found in the supernatant.

Contrast echocardiography: a method to visualize changes in regional myocardial perfusion in the dog model for CABG surgery

The ability of contrast echocardiography to assess regional myocardial perfusion during cardiopulmonary bypass in a dog model for coronary artery bypass surgery was evaluated. Sonicated Renograffin-76 microbubbles (meglumin diatrigoate and sodium diatrigoate) were injected into an aortic root proximal to an aortic occlusion clamp root while dogs were on cardiopulmonary bypass, with the heart arrested in diastole. Echocardiographic contrast-enhanced regions of myocardial perfusion were easily visualized. Differences in contrast-enhanced myocardial regions depended on coronary artery occlusion or patency. The contrast-enhanced images of myocardial perfusion showed that, for a given myocardial segment of the supplying vessel, the presence or absence of contrast effect reliably predicted vessel occlusion or patency (P less than .01). In the future contrast echocardiography may allow the direct assessment of regional myocardial perfusion in the operating room.

Effects of warm and cold ischemia on mitochondrial functions in brain, liver and kidney

The purpose of this work was to study the effects of warm (37 degrees C) and cold (4 degrees C) ischemia on different mitochondrial functions in rat brain, liver and kidney. After 10 to 60 minutes of ischemia at 37 degrees C the energy coupled respiration as well as the ADP-induced malate-aspartate shuttle activity in brain and liver mitochondria or the rate of mitochondrial ATP synthesis in kidney were significantly decreased. However, the respiratory rates and the shuttle activity in the absence of ADP remained unchanged. These data suggest that ischemia primarily affects electron transport in the respiratory chain rather than the hydrogen shuttle and the energy coupling system. When the temperature during the indicated ischemic periods was decreased to 4 degrees C, in brain and liver no significant alterations of these mitochondrial functions were found in comparison with the non-ischemic controls. When rat kidneys were stored for 36 hours at 4 degrees C according to Collins mimicking transplantation conditions, the mitochondrial respiration and ATP synthesis were only slightly decreased. It therefore appears that hypothermia can prevent effectively mitochondrial dysfunction due to ischemia.

Effects of excess thymidylate on thymidylate low-requiring strains of Saccharomyces cerevisiae: high mutagenicity and absence of DNA strand breaks

dTMP exposure concentrations of 0.1 mM or higher are genotoxic in exponentially growing cells of thymidylate low-requiring mutants of Saccharomyces cerevisiae. Mutagenicity of excess dTMP is highest in an exposure concentration 10-fold of that needed for external supplementation of endogenously blocked thymidylate synthesis. Still higher dTMP concentrations are primarily cytotoxic. The canavanine forward-mutation system shows excess dTMP to be as potent a mutagen as irradiation by ultraviolet light. Mutagenicity of excess dTMP, however, differs from that of direct DNA-attacking mutagens in that it is highest in the absence of significant toxicity. Alkaline sucrose gradient centrifugation shows that excess dTMP does not induce significant numbers of DNA single- or double-strand breaks, while conditions of thymidylate deprivation lead to DNA-strand breaks and thymineless death.