U.S. cities try to stem gang violence CHICAGO, June 5 (UPI) -- U.S. cities are struggling to control criminal gangs that continue to grow even as violent crime has decreased in much of the nation, experts say. James "Buddy" Howell, a senior research associate at the National Gang Center, part of the U.S. Justice Department, said gangs have become so entrenched in some of the biggest U.S. cities that gang-related crime is largely unaffected by forces that have been reducing overall crime, USA Today reported. "There are some dynamics in gangs that just don't change and are transmitted across generations," Howell said. The turf battles, the internal struggles for control continue. In Chicago, where 10 people were killed over Memorial Day weekend, police said of 200 murders this year, about 80 percent were gang-related. The number of murders is up from 139 at the same time last year in Chicago, where gang membership is estimated at more than 100,000. "We're trying to get our arms around it," said Robert Tracy, Chicago's chief of crime control strategies. We're trying everything. Tracy points to changing gang structure in which young members of the city's 59 established gangs have splintered into more than 600 subgroups, each seeking to assert its authority. He says officials have tried strategies including intervening directly with gang leaders. In Houston, USA Today said, there are an estimated 200 gangs with 10,000 members. The number of homicides in Houston so far this year is up to 83 from 74 at the same time last year but lower than the 114 in the first five months of 2010. This year, about 20 percent of the killings have been linked to gang activity. In May, Harris County District Attorney Patricia Lykos, whose jurisdiction includes Houston, announced a $1.7 million anti-gang effort targeting what she called a network in which street gangs have joined forces with international groups, including drug cartels and organizations involved in human trafficking.