Subscribe

RSS Feed (xml)

Powered By

Skin Design:
Free Blogger Skins

Powered by Blogger

Thursday, August 7, 2008

article : The agriculture of Content

The Columbia Encyclopedia, Sixth Edition | Date: 2008

agriculture science and practice of producing crops and livestock from the natural resources of the earth. The primary aim of agriculture is to cause the land to produce more abundantly and at the same time to protect it from deterioration and misuse. The diverse branches of modern agriculture include agronomy , horticulture , economic entomology , animal husbandry , dairying , agricultural engineering, soil chemistry, and agricultural economics.

Early Agriculture

Early people depended for their survival on hunting, fishing, and food gathering. To this day, some groups still pursue this simple way of life, and others have continued as roving herders (see nomad ). However, as various groups of people undertook deliberate cultivation of wild plants and domestication of wild animals, agriculture came into being. Cultivation of crops—notably grains such as wheat, rice, corn, rye, barley, and millet—encouraged settlement of stable farm communities, some of which grew to be towns and city-states in various parts of the world. Early agricultural implements—the digging stick, the hoe , the scythe, and the plow —developed slowly over the centuries, each innovation (e.g., the introduction of iron) causing profound changes in human life. From early times, too, people created ingenious systems of irrigation to control water supply, especially in semiarid areas and regions of periodic rainfall, e.g., the Middle East, the American Southwest and Mexico, the Nile Valley, and S Asia.

Farming was often intimately associated with landholding (see tenure ) and therefore with political organization. Growth of large estates involved the use of slaves (see slavery ) and bound or semifree labor. In the Western Middle Ages the manorial system was the typical organization of more or less isolated units and determined the nature of the agricultural village. In Asia large holdings by the nobles, partly arising from feudalism (especially in China and Japan), produced a similar pattern.

The Rise of Commercial Agriculture

As the Middle Ages waned, increasing communications, the commercial revolution, and the rise of cities in Western Europe tended to turn agriculture away from subsistence farming toward the growing of crops for sale outside the community (commercial agriculture). In Britain the practice of inclosure allowed landlords to set aside plots of land, formerly subject to common rights, for intensive cropping or fenced pasturage, leading to efficient production of single crops.

In the 16th and 17th cent. horticulture was greatly developed and contributed to the so-called agricultural revolution. Exploration and intercontinental trade, as well as scientific investigation, led to the development of horticultural knowledge of various crops and the exchange of farming methods and products, such as the potato, which was introduced from America along with beans and corn (maize) and became almost as common in N Europe as rice is in SE Asia.

The appearance of mechanical devices such as the sugar mill and Eli Whitney's cotton gin helped to support the system of large plantations based on a single crop. The Industrial Revolution after the late 18th cent. swelled the population of towns and cities and increasingly forced agriculture into greater integration with general economic and financial patterns. In the American colonies the independent, more or less self-sufficient family farm became the norm in the North, while the plantation, using slave labor, was dominant (although not universal) in the South. The free farm pushed westward with the frontier.

Modern Agriculture

In the N and W United States the era of mechanized agriculture began with the invention of such farm machines as the reaper , the cultivator , the thresher, and the combine . Other revolutionary innovations, e.g., the tractor , continued to appear over the years, leading to a new type of large-scale agriculture. Modern science has also revolutionized food processing; refrigeration, for example, has made possible the large meatpacking plants and shipment and packaging of perishable foods. Urbanization has fostered the specialties of market gardening and truck farming . Harvesting operations (see harvester ) have been mechanized for almost every plant product grown. Breeding programs have developed highly specialized animal, plant, and poultry varieties, thus increasing production efficiency. The development of genetic engineering has given rise to genetically modified transgenic crops and, to a lesser degree, livestock that possess a gene from an unrelated species that confers a desired quality. Such modification allows livestock to be used as "factories" for the production of growth hormone and other substances (see pharming ). In the United States and other leading food-producing nations agricultural colleges and government agencies attempt to increase output by disseminating knowledge of improved agricultural practices, by the release of new plant and animal types, and by continuous intensive research into basic and applied scientific principles relating to agricultural production and economics.

These changes have, of course, given new aspects to agricultural policies. In the United States and other developed nations, the family farm is disappearing, as industrialized farms, which are organized according to industrial management techniques, can more efficiently and economically adapt to new and ever-improving technology, specialization of crops, and the volatility of farm prices in a global economy. Niche farming, in which specialized crops are raised for a specialized market, e.g., heirloom tomatoes or exotic herbs sold to gourmet food shops and restaurants, revived or encouraged some smaller farms in the latter 20th and early 21st cents., but did little to stop the overall decrease in family farms. In Third World countries, where small farms, using rudimentary techniques, still predominate, the international market has had less effect on the internal economy and the supply of food.

Most of the governments of the world face their own type of farm problem, and the attempted solutions vary as much as does agriculture itself. The modern world includes areas where specialization and conservation have been highly refined, such as Denmark, as well as areas such as N Brazil and parts of Africa, where forest peoples still employ "slash-and-burn" agriculture—cutting down and burning trees, exhausting the ash-enriched soil, and then moving to a new area. In other regions, notably SE Asia, dense population and very small holdings necessitate intensive cultivation, using people and animals but few machines; here the yield is low in relation to energy expenditure. In many countries extensive government programs control the planning, financing, and regulation of agriculture. Agriculture is still the occupation of almost 50% of the world's population, but the numbers vary from less than 3% in industrialized countries to over 60% in Third World countries.

See also agricultural subsidies ; dry farming ; Granger movement ; Green Revolution ; ranch ; range .



See R. Jager, The Fate of Family Farming (2004).

Author not available, AGRICULTURE., The Columbia Encyclopedia, Sixth Edition 2008



The Columbia Encyclopedia, Sixth Edition. Copyright 2008 Columbia University Press

Read More......

Tuesday, August 5, 2008

article : Increasing access to antiretroviral drugs would drastically cut AIDS deaths in South Africa

More that 1.2 million deaths could be prevented in South Africa over the next five years by accelerating efforts to provide access to antiretroviral therapy (ART), according to a study released online today by the Journal of Infectious Diseases. Using a sophisticated mathematical model of HIV disease and treatment, a team of researchers led by Rochelle Walensky, MD, MPH of Massachusetts General Hospital (MGH) estimated the number of AIDS-related deaths in South Africa through 2012 under alternative ART scale-up assumptions.

The study results underscore the urgent need for Congress to reauthorize the U.S. President’s Emergency Plan for AIDS Relief (PEPFAR), which has supported the South African government’s effort to increase access to antiretroviral therapy, the researchers note. “If ART is not provided to all who need it, HIV mortality will be enormous,” says Walensky. “Deliberate, purposeful, and expedient scale-up will save millions of lives in South Africa alone.”

South Africa has one of the largest burdens of HIV infection in the world, with 5 to 6 million individuals and 19 percent of adults aged 15 to 49 infected. While government programs supported by PEPFAR and the Global Fund to Fight AIDS, Tuberculosis and Malaria have steadily increased access to antiretrovirals, at the end of 2006 only a third of individuals eligible for the therapy were receiving it.

In order to quantify the potential impact of various strategies for increasing access to ART, the research team projected the number of deaths under five scenarios – ranging from maintaining current access levels, through steady and moderate growth levels, to rapid growth and full access for all patients requiring treatment. Among other factors, calculations were based on the fact that the one-year survival rate for eligible patients who receive antiretroviral therapy is 94 percent, while only 55 percent of those not treated would be expected to survive one year.

Results showed that maintaining current treatment capacity would lead to 2.4 million AIDS-related deaths by 2012. Rapid scale-up, whereby everyone in need would have access by 2011, would reduce the projected number of deaths to 1.2 million during that time period, and immediate full access for all eligible patients would drop deaths to 800,000.

The researchers note that efforts to scale up treatment have resulted in a fivefold increase in access to ART in low and moderate-income countries. “Continued investments in antiretroviral treatment programs worldwide are a public health imperative; the potential loss of life without such support is simply unacceptable,” says Walensky, who is an associate professor of Medicine at Harvard Medical School.

Source : Massachusetts General Hospital


Read More......

article : Expansion of monocyte subset could serve as a biomarker for HIV progressions

An increase in the CD163+/CD16+ monocyte subset could be a biomarker for the progression of HIV disease, according to researchers at Temple University.

The researchers reported their findings, “CD163/CD16 Coexpression by Circulating Monocytes/Macrophages in HIV: Potential Biomarkers for HIV Infection and AIDS Progression,” in the March issue of AIDS Research and Human Retroviruses (www.liebertonline.com/aid).

A monocyte is a specific white blood cell, a part of the human body’s immune system that protects against blood-borne pathogens and moves quickly to sites of infection within the body’s tissues. As monocytes enter tissue, they undergo a series of changes to become macrophages.

The researchers were investigating alterations in this monocyte subset in patients with HIV infection. As part of this study, they examined a cohort of 18 patients from the Comprehensive HIV Program at Temple University Hospital, under the direction of Ellen Tedaldi, and seven individuals without HIV infection.

“At first, we were just looking at whether or not we saw alterations in this CD163+/CD16+ subset and whether it might be reflective of the amount of virus they have in circulation,” said Tracy Fischer-Smith, an associate scientist in Temple’s Neuroscience Department and the study’s lead author. “We did, indeed, find that patients with detectable virus had an increase of this monocyte subset that correlated with the amount of virus they had in their blood. We were surprised to find that patients with CD4+ T cell counts of less than 450 cells per microliter [200 or less per microliter is defined as AIDS], the increase of this monocyte subset correlates inversely with the number of T cells.”

Fischer-Smith said this finding suggests that as the monocyte cells are increasing, these patients are losing CD4+ T cells, which are critical for the maintenance of immunological competence.

“This may actually provide an earlier window into what is happening with HIV-infected patients where we might be able to see that immune impairment is taking place before we see a dramatic loss of CD4+ T cells,” she said.

“It looks like, based on these correlations, that this particular cell type may be involved in immune impairment and the progression of HIV,” said Jay Rappaport, professor of neuroscience and neurovirology, who oversaw the study. “Is it a good prognostic indicator" If you have a lot of these monocytes, does it mean you are going to progress into AIDS faster" “Right now, all we know is what the correlations are,” he said.

Rappaport added that he believes the CD163+/CD16+ monocyte subset is the first biomarker that correlates with viral load and CD4+ count. “The fact that it actually correlates with both, we think, might make it a key cell type in the pathogenesis of AIDS.” Fischer-Smith said the researchers plan to expand this study by following a cohort of patients longitudinally to see if their findings really can provide doctors with an early warning system and help to design better therapeutic strategies.

“When you are just looking at a single time-point, you don’t know how changes in this monocyte subset might occur over time, and how these changes might relate to the viral load and T cell number in individual patients,” she said. “That is why we want to investigate this further with a longitudinal study of HIV patients.”

Source : Temple University


Read More......

article : Clinical trial will test new HIV/AIDS vaccine

A phase 1 clinical trial to test a novel HIV/AIDS vaccine has begun at Brigham and Women’s Hospital (BWH). This new vaccine aims to overcome the problem of preexisting immunity to common vaccine vectors, which is thought to be a major problem in the developing world.

“This study will involve 48 healthy volunteers who will receive either two or three immunizations and who will be followed to assess the safety and immunogenicity of the vaccine,” explains Lindsey R. Baden, MD, Assistant Professor of Medicine at BWH and Harvard Medical School and Protocol Chair for the study.

The vaccine consists of a replication-incompetent, recombinant adenovirus serotype 26 (rAd26) vector encoding an HIV-1 envelope gene.

“The rAd26 vaccine vector was selected for its particularly low seroprevalence in human populations and for its potent immunogenicity and protective efficacy in preclinical studies,” explains Dan H. Barouch, MD, PhD, Associate Professor of Medicine at Beth Israel Deaconess Medical Center (BIDMC) and Harvard Medical School and Principal Investigator of the Integrated Preclinical/Clinical AIDS Vaccine Development (IPCAVD) program that developed the vaccine. This program is sponsored by the Division of AIDS, National Institute of Allergy and Infectious Diseases, National Institutes of Health.

Manufactured by the Dutch biotechnology company Crucell Holland BV, the rAd26 vaccine is the first HIV-1 vaccine candidate to emerge from the IPCAVD initiative, which brings together investigators from academia and industry in an effort to accelerate the development of promising HIV/AIDS vaccine candidates. The novel strategy used in developing this vaccine enables researchers to circumvent preexisting immunity to the adenovirus serotype 5, the virus responsible for the common cold, which has recently shown limitations as an HIV-1 vaccine vector.

“The rAd26 vector does not regularly occur in the human population and human antibodies to this vector are rare,” explains Jaap Goudsmit, Chief Scientific Officer at Crucell. “The rAd26 vector therefore is efficacious in eliciting good T and B cell responses.”

AIDS remains one of the world’s most devastating health problems, with an estimated 33.2 million people living with HIV/AIDS and 2.5 million new infections reported in 2007 alone.

Source : Beth Israel Deaconess Medical Center


Read More......

article : Leading HIV researchers to collaborate on vaccine development

Two global research organizations dedicated to designing a vaccine against HIV – the International AIDS Vaccine Initiative (IAVI), and the Center for HIV/AIDS Vaccine Immunology (CHAVI) – have signed an agreement to work together to address major biological questions that have slowed development of a safe, effective and affordable AIDS vaccine.

“Solving the HIV vaccine puzzle is a scientific challenge that can only be solved through fundamental and applied research, collaboration and transparency. The work that will be done by IAVI, CHAVI and their networks of partners will rapidly enhance our understanding of HIV and help lay the groundwork for new vaccine approaches,” says Dr. Barton Haynes, CHAVI director and professor of medicine at Duke University Medical Center.

There are approximately 33 million people around the world living with HIV, the virus that causes AIDS. Scientists have tested multiple vaccine candidates in early phase trials, but only two have been fully tested in efficacy trials and neither has been found effective in preventing HIV infection or lowering the viral load in patients who subsequently encountered HIV and became infected.

“We are committed to the discovery of an effective vaccine, particularly for regions hardest hit by the epidemic,” says Dr. Wayne Koff, senior vice president of research and development at IAVI. “We are hoping that the synergy of shared investigation will yield insight into novel solutions that will advance AIDS vaccine discovery.”

The shared CHAVI/IAVI research mission will focus on four key areas that will help inform the design of new and improved vaccine candidates:

  • Identification and full-length genetic sequencing of newly transmitted viruses
  • Clarifying the impact of human genetics on the control of HIV infection
  • Collaborative immunological studies that could shed light on why some people who are exposed to HIV do not develop AIDS
  • Development of standardized methods to sample tissues from mucosal surfaces in the body, where HIV initially establishes infection.

Investigators supported by both organizations are especially interested in further understanding what happens in the very earliest post-infection stage of HIV infection, especially within the body’s T cells, a class of white blood cells that normally fight off foreign invaders like bacteria and viruses. One of the goals of this work will be to identify any genetic variations linked to the strength of the immune response at the site of initial infection. CHAVI and IAVI hope that by sharing samples, reagents, databases and laboratories and by launching parallel studies, they will be able to speed up discoveries about this critical phase of the disease.

Each partner to the agreement will contribute unique resources. For example, CHAVI supports high-throughput sequencing technology that can reveal tiny mutations in the ever-changing virus, but which require large numbers of HIV samples in order to identify variations that are meaningful. Through its network of clinical research centers and immunological laboratories around the world, IAVI and its partners have developed a number of tests to evaluate human immune responses to HIV and to potential vaccine candidates, information that can help researchers refine and improve any candidate that shows promise. By pooling technologies, protocols and access to samples, the IAVI/CHAVI collaboration aims to extract maximum information to help accelerate the development of a safe and effective AIDS vaccine.

“As an African clinical investigator and the leader of the scientific steering committee that oversees the IAVI-supported study of acute HIV infection, I am pleased to be collaborating with IAVI and CHAVI. It is critical to investigate the influence of genetic diversity of HIV as well as the variety of human immune responses to HIV among populations that are hardest hit by the epidemic,” said Dr. Pontiano Kaleebu, assistant director and a Principal Investigator at the Uganda Virus Research Institute.

“Now, more than ever, we need to understand the complexities of HIV and the genes that control the human immune response to it,” says Dr. Alan Bernstein, recently appointed as the first executive director of the Global HIV/AIDS Vaccine Enterprise. The Enterprise was established to accelerate development of a safe and effective HIV vaccine through encouraging collaboration within the HIV vaccine research field. “This new collaboration holds great promise in accelerating our basic understanding of HIV and will form the necessary underpinnings needed to develop a vaccine,” Bernstein added.

Source : Duke University Medical Center


Read More......

Search by Google

Custom Search
 

Search Engine Optimization - AddMe

Enter your email address:

Delivered by FeedBurner