But this approach is limited not only by the delay before female sexual maturity and the onset of first lactation, but also by the intermittent nature of lactation itself. Now, Francois Pothier and colleagues have created male transgenic mice that secrete human growth hormone into their ejaculate. They achieved this through the use of a DNA gene promoter sequence, P12, which is only active in male sex glands such as the seminal vesicle. By injecting fertilized mouse eggs with DNA encoding hGH linked up to the P12 DNA sequence, they showed that the hormone was secreted specifically into the semen of male animals. Gene expression analysis revealed that hGH was expressed in the seminal vesicle and the kidney, but in no other organs.
Experiments are currently under way to test the technique in boars.
Bioartificial blood vessels Many of the more than half a million patients who undergo heart bypasses in the United States every year do not have sufficient healthy arteries to donate for the operation. When implanted into the rabbit carotid artery, the tubes withstood suturing and lasted up to three months, with no signs of immunological rejection. In vitro experiments of explanted tubes in the presence of bradykinin, serotonin, norepinephrine, and potassium chloride also showed that the synthetic vessels contract in response to same chemical signals that spur normal arterial contractions. Boosting insect biocontrol Much in the same way that adjuvants are added to vaccines to potentiate immunogenicity, scientists have engineered transgenic rice plants with a factor that boosts the effectiveness of a biopesticide against caterpillars. In this issue, a team of Japanese researchers, headed by Tosihiko Hukuhara, show that the rice pest armyworm is much more susceptible to NPV when feeding on transgenic rice plants containing the virus-enhancing factor.