Strategies for Preventing Amplicon Contamination in Molecular Laboratory !

The Primer

The high sensitivity of the polymerase chain reaction (PCR)—theoretically with lower limits of detection as little as a single template molecule; practically, 10 to 100 copies for many assays as run—is one of its greatest strengths, but also its greatest weakness. As the method works through creating copies of its target, any positive sample can lead to large numbers of molecules which can in turn contaminate subsequent reactions and cause false positive results.

To get a sense of the scope of this, consider a successful “average” 25μl PCR somehow getting opened and spilled in the lab. This would contain on the order of 10^12 template copies (amplicons); in other words, if a thorough cleaning reduced this by a million fold, you’d still have a million amplicon copies “floating around,” each of which could contaminate a reaction. If you’re fortunate enough to have never experienced this first-hand, you can thank the widespread acceptance of real-time PCR methods, which do away with having to open reaction tubes post amplification, and perhaps gain an appreciation of why anyone who has been through the experience treats the risk as real and ever-present.

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Some Breast Cancers Fail to Respond to Treatments, Why?

Breast Cancer

Most breast cancers are estrogen receptor-positive, meaning that signals received from estrogen, a hormone, promote the growth of the tumors. To stop these cancers from spreading, estrogen inhibitors are usually prescribed. But what happens when tumors develop treatment resistance?

Studies suggest that "approximately 70 percent" of all the breast cancers are estrogen receptor-positive (ER-positive).

These types of cancer are typically treated with drugs — such as tamoxifen and fulvestrant — that either lower the levels of the hormone or inhibit the estrogen receptors to prevent the tumors from spreading. This is known as endocrine therapy.

However, around a third of the people treated with these drugs develop resistance to them, which negatively impacts their chances of survival. The mechanisms that underlie the tumors' resistance to therapy is not well understood and currently poses a major challenge.

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VITAMINS: The Micronutrients in Our Body !

Vitamins

The essential macronutrients are water, proteins, carbohydrates, fats, vitamins, and minerals.

In developed countries, vitamin deficiencies result mainly from poverty, food fads, drugs, or alcoholism. Vitamin toxicity (hypervitaminosis) usually results from taking megadoses of Vitamin A, D, B6, or niacin. In general, excess amounts of water-soluble vitamins are excreted via the Kidneys.

Vitamins may be Fat soluble (vitamins A, D, E, and K) or Water soluble (B vitamins and vitamin C). The B vitamins include biotin, Folate, niacin, pantothenic acid, riboflavin, thiamine, pyridoxine, and B12. After digestion and absorption, which circulatory system carries fat and fat-soluble vitamins?

“Vitamins are the essential nutrients that our body needs in small amounts. More specifically, an organic compound is defined as a vitamin when an organism requires it, but not synthesized by that organism in the required amounts (or at all). There are thirteen recognized vitamins.”

Vegans may develop vitamin B12 deficiency unless they consume yeast extracts or Asian style fermented foods. Strictly, vegetarian diets also tend to be low in calcium, iron, and zinc.

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Study Sheds Light on How High Cholesterol Causes Cancer !

Cholesterol

New research from the University of California, Los Angeles has found a previously unknown molecular mechanism involving cholesterol that may promote tumor growth in the intestines.

A report on the study — published in the journal Cell Stem Cell — reveals how increasing levels of cholesterol in mice increased proliferation of intestinal stem cells and made tumors grow faster.

One of the methods that the researchers used to increase the availability of cholesterol to intestinal cells in the mice was to feed them a high-cholesterol diet.

"We were excited to find," says senior author Peter Tontonoz, a professor of pathology and laboratory medicine, "that cholesterol influences the growth of stem cells in the intestines, which in turn accelerates the rate of tumor formation by more than 100-fold."

He and his colleagues believe that their findings could pave the way to new treatments for gastrointestinal diseases, such as colon cancer.

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Do Human Pheromones Exist? Are They The Real Deal?

Pheromones

Despite the prevalence of pheromone products on the market, substantial evidence that they can induce sexual attraction is lacking.

Search for “pheromones products” on the internet, and dozens of sprays and perfume additives will appear—many claiming to be able to increase your attractiveness to the opposite sex. Some companies, such as the Athena Institute, which, according to its founder, Winnifred Cutler, published its 108th consecutive ad in The Atlantic this month, assert that scientific studies back up their claims.

While there have been several experiments examining the effects of compounds extracted from people’s armpits, much of the data on sex-related behaviors, The Scientist has found, go back more than a decade and were met then—and still now—with skepticism from pheromone researchers. “I am not compelled by any studies that are out there that say there is an active steroid component from the underarm that causes [sexual attraction],” says George Preti, an organic chemist at the Monell Chemical Senses Center in Philadelphia who conducted some of the early human pheromone trials.

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Cutaneous Leishmaniasis: Immune Responses in Protection and Pathogenesis.

Immunology

Cutaneous leishmaniasis is a major public health problem and causes a range of diseases from self-healing infections to chronic disfiguring disease. Currently, there is no vaccine for leishmaniasis, and drug therapy is often ineffective. Since the discovery of CD4+ T helper 1 (TH1) cells and TH2 cells 30 years ago, studies of cutaneous leishmaniasis in mice have answered basic immunological questions concerning the development and maintenance of CD4+ T cell subsets. However, new strategies for controlling the human disease have not been forthcoming. Nevertheless, advances in our knowledge of the cells that participate in protection against Leishmania infection and the cells that mediate increased pathology have highlighted new approaches for vaccine development and immunotherapy. In this Review, we discuss the early events associated with infection, the CD4+ T cells that mediate protective immunity and the pathological role that CD8+ T cells can have in cutaneous leishmaniasis.

Cutaneous leishmaniasis — which is caused by several protozoal parasites of the genus Leishmania — is endemic to South and Central America, Northern Africa, the Middle East and parts of Asia, and an estimated 1 million new cases arise each year. Of particular interest to immunologists is the wide range of clinical manifestations associated with this disease, which, similar to tuberculosis and leprosy, is dictated largely by the type and magnitude of the immune response of the host. As in most infections, the immune response to cutaneous leishmaniasis depends on many host factors, as well as on the differences between the infecting Leishmania spp. Experimental infections in mice also exhibit a spectrum of clinical presentations depending on the mouse strain and the infecting parasite species or strain used.

• Cutaneous leishmaniasis exhibits a wide spectrum of clinical presentations that is determined largely by the host immune response. The host immune response to infection is influenced both by host genetics and the Leishmania spp. and/or strain.
• The rapid recruitment of neutrophils and inflammatory monocytes following infection with Leishmania influences the course of disease. Neutrophils can have both protective and deleterious roles, whereas inflammatory monocytes kill Leishmania parasites and differentiate into monocyte-derived dendritic cells that promote the development of protective CD4+ T helper 1 (TH1) cells.
• Control of Leishmania infection depends on the production of interferon-γ by CD4+ TH1 cells, which leads to enhanced killing by macrophages due to the production of reactive oxygen species and nitric oxide.
• CD8+ T cells recruited to Leishmania lesions exhibit a cytolytic profile and lyse infected cells without killing the parasites, which leads to enhanced inflammation and increased severity of disease. Controlling these pathogenic CD8+ T cells, or the downstream mediators of inflammation that they induce, is a new approach to leishmaniasis immunotherapy.
• Infection with Leishmania generates several types of CD4+ T cells that mediate resistance to reinfection, including effector T cells, effector memory T cells, central memory T cells and tissue-resident memory T cells. There is currently no Leishmania vaccine, and a hurdle for vaccine development is that the most effective T cells are short-lived effector T cells; targeting longer lived central memory and tissue-resident memory T cells is an alternative approach.

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Kaplan MCAT Biology Review - Test Prep !

Exam Practice

MCAT Biology Review,

Test Prep for the MCAT Exam

KAPLAN pdf

Kaplan MCAT Biology Review, Test Prep pdf ebook

The MCAT is changing in 2015. With the addition of three semesters’ worth of material, more advanced critical thinking skills, a longer duration, and changes in Biology content, the new exam requires even more diligent prep with resources from Kaplan Test Prep.

Kaplan's MCAT Biology Review offers:

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Cancer Transcriptome Profiling at the Juncture of Clinical Translation !

Next-Generation Sequencing

Methodological breakthroughs over the past four decades have repeatedly revolutionized transcriptome profiling. Using RNA sequencing (RNA-seq), it has now become possible to sequence and quantify the transcriptional outputs of individual cells or thousands of samples. These transcriptomes provide a link between cellular phenotypes and their molecular underpinnings, such as mutations. In the context of cancer, this link represents an opportunity to dissect the complexity and heterogeneity of tumours and to discover new biomarkers or therapeutic strategies. Here, we review the rationale, methodology and translational impact of transcriptome profiling in cancer.

Transcriptomics is the large-scale study of RNA molecules by use of high-throughput techniques. It examines the abundance and makeup of a cell's transcriptome. In contrast to DNA, which is largely identical across all cells of an organism, the actively transcribed RNA is highly dynamic, reflecting the diversity of cell types, cellular states and regulatory mechanisms. Because a transcriptome profile can be regarded as a signature or snapshot of the underlying cell state, the experimental profiling of samples and specimens can provide insights into their unique biology.

Depending on the specific approach, transcriptomics can not only reveal the architecture of gene expression but also provide details on the structure, modification and variation of individual transcripts. Advances in transcriptome profiling, specifically the development of genome-wide methodologies targeting diverse RNA species, have enabled us to discover the seemingly endless complexity of RNA biology and to comprehensively annotate the human genome and other eukaryotic genomes. Arguably, transcriptomics is currently the most well-established modality and foundation of functional genomics, a field of study for which the goal is to synthesize large-scale data to understand the mechanisms that govern cellular and organismal phenotypes.

• RNA sequencing (RNA-seq) has the potential to bridge tumour genotypes (for example, mutations) and their phenotypic consequences (for example, cancer molecular subtypes).
• The field of transcriptomics has matured thanks to lockstep developments in experimental protocols, algorithms and databases.
• Methodological and algorithmic advances continue to enable clinical applications of transcriptome profiling.
• Detection of gene fusions is the most immediate application of RNA-seq.
• Gene expression signatures have demonstrated prognostic and predictive value.
• Transcriptome profiling will be essential for immuno-oncology.

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MCQ 12. 11 years old boy, restless all time, unable to concentrate in class, hardly ever in his seat, roams around the hall, difficulty in playing quietly.

MCQs

MCQ 12. An 11 years old boy is all the time so restless that the rest of the class is unable to concentrate. He is hardly ever in his seat and roams around the hall. He has difficulty in playing quietly.

What is the the most likely diagnosis?

a. Attention-deficit hyperactivity disorder 

b. Conduct disorder 

c. Depressive disorder 

d. Schizophrenia

Correct answer: Click here

Transcriptional Regulation by Mediator Complex

Gene Regulation

Alterations in the regulation of gene expression are frequently associated with developmental diseases or cancer. Transcription activation is a key phenomenon in the regulation of gene expression.

In all eukaryotes, mediator of RNA polymerase II transcription (Mediator), a large complex with modular organization, is generally required for transcription by RNA polymerase II, and it regulates various steps of this process. The main function of Mediator is to transduce signals from the transcription activators bound to enhancer regions to the transcription machinery, which is assembled at promoters as the preinitiation complex (PIC) to control transcription initiation.

Recent functional studies of Mediator with the use of structural biology approaches and functional genomics have revealed new insights into Mediator activity and its regulation during transcription initiation, including how Mediator is recruited to transcription regulatory regions and how it interacts and cooperates with PIC components to assist in PIC assembly.

Novel roles of Mediator in the control of gene expression have also been revealed by showing its connection to the nuclear pore and linking Mediator to the regulation of gene positioning in the nuclear space. Clear links between Mediator subunits and disease have also encouraged studies to explore targeting of this complex as a potential therapeutic approach in cancer and fungal infections.

Key points

• Recent structural advances based on improvements in electron microscopy methodology have enabled the generation of high-resolution structural models of the mediator of RNA polymerase II transcription (Mediator) complex and of the preinitiation complex (PIC) in the presence of Mediator.
• The module composition of Mediator changes between its recruitment to upstream regulatory regions (enhancers or upstream activating sequences where Mediator is bound to transcription factors) and its action on core promoters together with PIC components.
• The functional interplay between Mediator and general transcription factors in PIC assembly is closely related to chromatin architecture at promoter regions.
• Direct contact between Mediator and the nuclear pore-associated transcription-coupled export (TREX2) complex suggests that Mediator functions in gene positioning in the nuclear space.
• Mediator has been shown to function in the establishment of transcriptional memory, which also involves Mediator interactions with the nuclear pore.
• Potential therapeutic targeting and modulation of Mediator activity in cancers and in fungal infectious diseases emphasizes the importance of studies of Mediator mechanisms for improving human health.

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