Association between coding variability in the LRP gene and the risk of late-onset Alzheimer’s disease

We have sequenced the entire (89 exons) open reading frame of the LRP gene in 12 cases of Alzheimer’s disease (AD) from Northern France. We have found no novel changes but confirm the occurrence of a polymorphism in exon 6 of the gene (A216V). This polymorphism is rare (2.8% of controls) and is in linkage equilibrium with previously reported polymorphisms. The V216 allele is negatively associated with the disease in a large case-controlled series. These data suggest that the LRP receptor may be involved in the pathobiology of AD, but the association that we report here cannot explain the previously reported genetic data implicating the LRP gene in AD. If the LRP gene is a major site of genetic variability leading to AD, there must be other biologically relevant variability in promoter or other regulatory elements of this large gene. Received: 28 December 1998 / Accepted: 1 March 1999     

The effects of cortisol and amino acids on the metabolic activity of rat skin stored in dimethyl sulfoxide buffer at −196 °C

Addition of amino acids to the DMSO buffer reduces the intracellular amino acid depletion of rat skin tissue frozen and stored at ?196 °C.Although prolonged exposure to DMSO progressively inhibits the [2-¹⁴C]glycine and l-[U-¹⁴C]leucine incorporation into the proteins, cortisol and amino acid additions to the buffer medium protect the protein-synthesizing activity. These factors also stimulate the incorporation of [6-³H]-thymidine into DNA. The stimulatory characteristics of cortisol and of amino acids separately are enhanced when both components are added together to the preserving buffer. These effects are noticeable in tissue only exposed to the DMSO buffer without freezing as well as in skin frozen and stored at ?196 °C and subsequently thawed at 40 °C.A stimulatory effect of cortisol and of a free amino acid, supplement to the medium on the α-amino-[1-¹⁴C]isobutyric acid uptake by the cells is only observed in skin exposed for a short period of time to the DMSO buffer, but it is not detectable after longer exposure and after freezing.     

Metabolic changes in ratskin stored in buffer medium at minus 3 degrees C

The incorporation of amino acids into the proteins of rat skin after storage in a buffer medium greatly depends on the animal's age, and on storage time.At —3 °C protein synthesizing activity is primarily impaired, accompanied by cell membrane damage, while DNA metabolism appears remarkably immune to preservation injury. The major injury to protein synthesis occurs during the first days and even hours of storage, followed by a longer period of storage where protein metabolism is reduced to a low level of activity. Addition of a mixture of amino acids to the medium protects and stimulates the subsequently tested amino acid incorporation into the proteins of rat skin.     

The Human Melanoma Side Population Displays Molecular and Functional Characteristics of Enriched Chemoresistance and Tumorigenesis

Melanoma remains the most lethal skin cancer, mainly because of high resistance to therapy. Side population (SP) cells are found in many types of cancer and are usually enriched in therapy-resistant as well as tumorigenic cells. Here, we identified a Hoechst dye-effluxing SP in a large series of human melanoma samples representing different progression phases. The SP size did not change with disease stage but was correlated with the prognostic “Breslow’s depth” in the primary (cutaneous) tumors. When injected into immunodeficient mice, the SP generated larger tumors than the bulk “main population” (MP) melanoma cells in two consecutive generations, and showed tumorigenic capacity at lower cell numbers than the MP. In addition, the SP reconstituted the heterogeneous composition of the human A375 melanoma cell line, and its clonogenic activity was 2.5-fold higher than that of the MP. Gene-expression analysis revealed upregulated expression in the melanoma SP (versus the MP) of genes associated with chemoresistance and anti-apoptosis. Consistent with these molecular characteristics, the SP increased in proportion when A375 cells were exposed to the melanoma standard chemotherapeutic agent dacarbazine, and to the aggravating condition of hypoxia. In addition, the SP showed enhanced expression of genes related to cell invasion and migration, as well as to putative (melanoma) cancer stem cells (CSC) including ABCB1 and JARID1B. ABCB1 immunoreactivity was detected in a number of tumor cells in human melanomas, and in particular in clusters at the invasive front of the primary tumors. Together, our findings support that the human melanoma SP is enriched in tumorigenic and chemoresistant capacity, considered key characteristics of CSC. The melanoma SP may therefore represent an interesting therapeutic target.     

Modulation of Closed?State Inactivation in Kv2.1/Kv6.4 Heterotetramers as Mechanism for 4?AP Induced Potentiation

The voltage−gated K⁺ (Kv) channel subunits Kv2.1 and Kv2.2 are expressed in almost every tissue. The diversity of Kv2 current is increased by interacting with the electrically silent Kv (KvS) subunits Kv5−Kv6 and Kv8−Kv9, into functional heterotetrameric Kv2/KvS channels. These Kv2/KvS channels possess unique biophysical properties and display a more tissue-specific expression pattern, making them more desirable pharmacological and therapeutic targets. However, little is known about the pharmacological properties of these heterotetrameric complexes. We demonstrate that Kv5.1, Kv8.1 and Kv9.3 currents were inhibited differently by the channel blocker 4−aminopyridine (4−AP) compared to Kv2.1 homotetramers. In contrast, Kv6.4 currents were potentiated by 4−AP while displaying moderately increased affinities for the channel pore blockers quinidine and flecainide. We found that the 4−AP induced potentiation of Kv6.4 currents was caused by modulation of the Kv6.4−mediated closed−state inactivation: suppression by 4−AP of the Kv2.1/Kv6.4 closed−state inactivation recovered a population of Kv2.1/Kv6.4 channels that was inactivated at resting conditions, i.e. at a holding potential of −80 mV. This modulation also resulted in a slower initiation and faster recovery from closed−state inactivation. Using chimeric substitutions between Kv6.4 and Kv9.3 subunits, we demonstrated that the lower half of the S6 domain (S6c) plays a crucial role in the 4−AP induced potentiation. These results demonstrate that KvS subunits modify the pharmacological response of Kv2 subunits when assembled in heterotetramers and illustrate the potential of KvS subunits to provide unique pharmacological properties to the heterotetramers, as is the case for 4−AP on Kv2.1/Kv6.4 channels.     

Physical mapping of sequences homologous to an endogenous retrovirus LTR on human chromosome 19

The human genome contains multiple copies of sequences related to the HERV-K family of endogenous retroviruses, homologous to the B-type mouse mammary tumour virus. A DNA fragment closely resembling an HERV-K long tandem repeat (LTR) was detected in a library of hncDNA clones enriched for sequences from human chromosome 19. Sites showing homology to the sequence of this fragment have been identified on human chromosome 19 by hybridization to previously mapped chromosome 19 cosmids. Thus the distribution of LTR sequences on a specific human chromosome has been mapped for the first time. We estimate the total number of such sites on human chromosome 19 to be at least 110. Many of these sites are located in the vicinity of known genes. The precise localizations (to specific cosmids) of LTR-homologous sequences on chromosome 19 can serve as a reference source and will automatically provide further insight into LTR-gene relationships as new genes are mapped onto the chromosome.     

Changes in the Proteome of Poultry Muscle Tissue when Including Various Protein Supplements into Their Diet

Applied Biochemistry and Microbiology - It has been shown that when a fermented protein feed additive is added to the diet of broiler chickens, the presence of additional protein fragments was...     

Widespread and Functional RNA Circularization in Localized Prostate Cancer

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Metabolic changes in rat skin during preservation and storage in glycerol buffer at -196 degrees C.

The penetrating cryoprotective glycerol dissolved in different concentrations in buffer medium effectively protects skin tissue against freeze-thaw injury when progressively cooled to ?196 °C followed by a fast warming-up rate. Upon incubation of the tissue after storage, the incorporation of [2-¹⁴C]glycine into the proteins, of [6-³H]thymidine into DNA, and α-[1-¹⁴C]aminoisobutyric acid transport through the cell membrane are reduced compared to freshly incubated skin. An essential loss in metabolic activity occurs during exposure of the skin to the preserving buffer. Although the length of storage does not seem to affect the final viability, the actual freezing and thawing procedures are particularly damaging to tissue already injured by previous exposure to buffer containing cryoprotective agents.     

Renin-angiotensin-aldosterone system and oxidative stress in cardiovascular insulin resistance

Hypertension commonly occurs in conjunction with insulin resistance and other components of the cardiometabolic syndrome. Insulin resistance plays a significant role in the relationship between hypertension, Type 2 diabetes mellitus, chronic kidney disease, and cardiovascular disease. There is accumulating evidence that insulin resistance occurs in cardiovascular and renal tissue as well as in classical metabolic tissues (i.e., skeletal muscle, liver, and adipose tissue). Activation of the renin-angiotensin-aldosterone system and subsequent elevations in angiotensin II and aldosterone, as seen in cardiometabolic syndrome, contribute to altered insulin/IGF-1 signaling pathways and reactive oxygen species formation to induce endothelial dysfunction and cardiovascular disease. This review examines currently understood mechanisms underlying the development of resistance to the metabolic actions of insulin in cardiovascular as well as skeletal muscle tissue.