By David N. Leff
Editor's note: Science Scan is a round-up of recently published biotechnology-related research:
Eight baboons in Missouri have clarified the neuronal difference between Parkinson's disease (PD) and dystonia, a brain disorder that makes muscles contract and go into spasms.
Neuroscientists at Washington University, in St. Louis, injected the primates with a neurotoxin, MPTP, which induces symptoms of PD. At first, the animals started stretching and twisting their limbs — signs of dystonia — but only on one side of their body. The drug had been injected into the opposite side of their brains, via carotid artery. The dystonic symptoms lasted a few weeks, but when PD eventually took over, its tremors and slow, unstable movements persisted for many months.
During the dystonic phase, the researchers found 98 percent less dopamine in the animal brains' basal ganglia on the affected brain side than on the untreated, contralateral brain region. This pre-PD drop in dopamine was unexpected.
"It's well known that MPTP produces a substantial reduction of dopamine associated with parkinsonism," observed the project's principal scientist, Joel Perlmutter. The surprising feature here is that reduced dopamine levels also coincided with dystonic symptoms. Therefore," he observed, "additional factors must determine whether dystonia or PD results from a deficiency in dopamine function."
Perlmutter is senior author of a paper in the November 1997 issue of Neurology, titled: "MPTP induces dystonia and parkinsonism. Clues to the pathophysiology of dystonia."
Previous attempts to explain dystonia have arraigned overproduction of dopamine in the basal ganglia. "Our work," Perlmutter concluded, "reveals that this isn't the case."
Dystonia has been described as "Parkinson's disease from hell." Added to its agony is its insidious masquerading as common ailments, misdiagnosed as stiff neck, arthritis, tennis elbow, even psychiatric problems.
Dystonic muscle spasms can contort, even paralyze, the whole body or specific parts — eyelids, mouth, vocal cords, neck, hand. Current therapy is to inject affected muscles with a bacterial toxin that temporarily relaxes them. "If we could understand dystonia better," Perlmutter commented, "maybe we could find a better treatment. I'd much rather give patients a pill to cure dystonia than put a needle in the vocal cords or eye muscles to treat its symptoms."
Imported TB Menaces Last Surviving Isolated Indian Tribe In Amazon Rain Forest
In the Orinoco River basin rain forest of northern Brazil dwells a unique population, the Yanomami Indians. Numbering some 9,400 people, this tribe was isolated from contact with the mainstream of European-derived Brazilians until the 1960s.
Now a multinational medical mission reports the Yanomami have a strikingly high incidence and prevalence of pulmonary tuberculosis.
Of 625 individuals the TB task force examined clinically, 6.4 percent were actively infected with Mycobacterium tuberculosis, three years after receiving BCG anti-TB vaccination. This prevalence, they noted, "is 100-fold higher than that observed in the Amazonian State in general."
Over 70 percent of them had antibodies to bacterial antigens — relatively impotent against intracellular M. tuberculosis, but indicative of infection — as compared with only 14 percent of European-descended Brazilians.
The team's field report appears in the current Proceedings of the National Academy of Sciences, dated Nov. 25, 1997. Its title: "An epidemic of tuberculosis with a high rate of tuberculin anergy among a population previously unexposed to tuberculosis, the Yanomami Indians of the Brazilian Amazon."
In a scenario reminiscent of the diseases inflicted on immunologically naive native American populations by the Spanish conquistadores in the 1500s, a gold rush in the 1980s brought thousands of miners into Yanomami lands in the 1980s. The report observes that this invasion "introduced tuberculosis in the Yanomami population, as far as is known, for the first time."
Deploying a broad spectrum of modern molecular and genetic analyses, the teams evaluated blood cultures for drug resistance and assessed immunological profiles.
Its conclusion: "[T]he Yanomami are experiencing the beginning of an epidemic, which . . . in the absence of appropriate medical intervention, would be predicted to last for at least a century, and be devastating to this indigenous population." *