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Swapping Germs: Bad for You and Dog

Dog owners and their pets may exchange harmful mouth bacteria that can cause gum disease and tooth decay in both humans and canines, according to a report in Archives of Oral Biology. Previous research has shown people can transmit oral bacteria to children through close daily contact. But few studies have looked at the bacteria exchanged between people and their pets.

About 5% of canines get dental caries, which includes tooth decay and cavities. But rates of periodontitis, an inflammatory mouth disease, in dogs have been reported to range from 50% to 70%.

Researchers late last year worked with dog owners in Japan to assess the prevalence of 10 bacteria that are associated with periodontitis in people. They also analyzed an oral microbe commonly found in dogs but not humans. Study participants were 81 members of 64 families that owned 66 dogs of various breeds and ages. Participants were divided into three groups: Most of the people had a high degree of contact with dogs while the others had little or no contact with dogs.

Analysis of dental plaque found all 10 of the human bacteria in dogs and humans. The most common—Tannerella forsythia, Porphyromonas gulae, and Campylobacter rectus—were detected in significantly higher levels in dogs than owners. As many as a quarter of the dogs and owners with close contact shared Eikenella corrodens bacteria. Periodontal bacteria were more prevalent in high-contact relationships and in older dogs.

P. gulae, rarely detected in humans, was found in 13 owners and their dogs, including two with low-contact relationships. This finding suggests bacteria can be transmitted from dogs to humans even with low contact, researchers said.

Caveat: Data about pre-existing periodontitis in dogs and owners wasn't available.

Visual clutter: A study of people with mild memory loss found they struggled to distinguish between similar-looking objects, suggesting memory and certain forms of perception may be linked in the brain, says a report in Hippocampus. Traditionally, the medial temporal lobe region of the brain has been thought to control long-term memory but not other cognitive functions. This study suggests that damage to a part of the medial temporal lobe called the perirhinal cortex affects both memory and perception.

A U.S.-Canadian research team administered a series of tests requiring complex perceptual processing, a key function of the perirhinal cortex region, to three groups of older adults. These included seven people with mild cognitive impairment, 10 at risk for such impairment and 19 healthy controls.

Subjects had to decide if pairs of objects shown on a screen were matched or not matched. In 88 trials, the objects resembled amoeba-like blobs with similar shapes, colors and patterned sections. In 88 other trials, the differences between the objects were more distinct, for example a pail paired with a chili pepper and a TV with a plant.

Compared with the control group, participants with mild cognitive impairment and those at risk for impairment had great difficulty distinguishing objects with similar visual features. Those participants' performance improved when they could discriminate between the objects' features more easily.

The researchers suggested that reducing visual clutter—for example, making buttons on a telephone of varying shapes and sizes—might make routine tasks easier for people with memory problems.

Caveat: As none of the subjects underwent MRI brain scans, the study couldn't identify the area of the perirhinal cortex involved in memory loss and impaired objection perception, researchers said.

Heart health: Cardiovascular risk factors, including body weight, cholesterol and arterial plaque, were significantly reduced in mice that were fed drinking water containing watermelon juice compared with controls, according to a study in the Journal of Nutritional Biochemistry. Previous research indicated that citrulline, a key compound in watermelons, may have blood-pressure lowering properties.

In this 13-week study, Purdue University scientists tested citrulline on mice genetically altered to develop high cholesterol. One group had unlimited access to drinking water containing 2% watermelon extract. Citrulline constituted 20% to 30% of the extract. Control mice received water without watermelon extract. Both groups ate a high-fat diet for 12 of the 13 weeks.

All mice gained about 1.8 grams per week for seven weeks after which weekly weight gain slowed to 1.1 grams in watermelon-extract mice compared with 1.6 grams in controls. Watermelon-extract mice also had significantly reduced cholesterol levels, body fat and aortic plaque, and significantly increased levels of interleukin-10, an anti-inflammatory compound, tests showed. No blood-pressure differences were recorded. Citrulline may decrease systemic inflammation associated with atherosclerosis, researchers said.

Caveat: The blood-pressure findings aren't explained in the findings, researchers said. Citrulline's effects on human cardiovascular health haven't been tested.

Pain culture: A study of U.S. and Dutch patients who had routine ankle surgery found that more Americans used strong narcotics for postoperative pain, but patients in both countries managed pain better with nonnarcotic drugs, according to a report in the journal Injury. Previous research found that anti-inflammatory drugs such as ibuprofen controlled pain more effectively than narcotics, or opioids, following cardiac and hip-replacement operations.

In this study, a U.S.-Dutch research team compared postoperative pain, pain-medication use and pain relief in 30 U.S. and 30 Dutch patients, ages 18 to 88, who underwent surgery for a fractured ankle from 2007 to 2009. Pain and pain relief were rated on the first day after surgery and when stitches were removed two weeks later. All medications used in and out of hospital were recorded.

On the first day after surgery, 100% of U.S. patients took opioid medications, mostly oxycodone, and 57% also took non-opioid drugs such as acetaminophen. Among Dutch patients, 67% used opioids, mostly tramadol, on the first postoperative day and 100% took non-opioid drugs, usually acetaminophen or paracetamol. At suture removal, 70% of U.S. patients took strong opioids and 13% of Dutch patients took weak opioids. Cultural differences may affect how patients perceive and cope with pain, researchers said.

Caveat: The influence of psychological factors on pain perception and tolerance wasn't assessed. In the U.S., tramadol wouldn't be considered in the same class of opioid medications as oxycodone, researchers said. The study was small and the findings may be relevant only in the Netherlands and U.S., they said.

Lymphedema: The removal of lymph nodes during breast-cancer surgery often leads to chronic swelling of the arm, a painful and disfiguring condition known as lymphedema. There is no cure for lymphedema but a report in the journal Angiogenesis suggests a naturally occurring protein, which is known for inducing inflammation, may form the foundation of an effective new treatment option.

A team of Southern California scientists conducted a series of experiments with interleukin-8 (IL-8), a protein that has been shown to stimulate the growth of new lymphatic vessels and nodes, a process called lymphangiogenesis. The vessel growth, however, occurs indirectly during inflammation, by activating immune cells to secrete factors that prompt lymphangiogenesis, they said.

To activate lymphangiogenesis directly, in the absence of inflammation, scientists created genetically modified mice that secreted a constant level of IL-8 in their skin. Lymphedema was induced in the modified mice and a normal control group by surgically obstructing lymphatic networks through the tail.

Postoperative swelling was initially similar in both groups but started to subside in modified mice after a week, whereas lymphedema was still prominent in controls at four weeks, results showed. Analysis of lymphatic vessels in the tails of both groups indicated vessel regeneration was more pronounced in modified mice. No signs of inflammation were detected.

Caveat: Interleukin-8 hasn't been tested in human studies of lymphedema.
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