January 3, 2002
Chimerism of the Transplanted Heart
Eight male patients received cardiac transplants from female donors. In samples from these hearts, the investigators were able to detect Y chromosomes in about 10 percent of the myocytes, proving that they came from the male recipients. These results show that cells from the recipient are able to migrate into the donor heart and take up residence. Some of the Y-chromosome–positive cells were primitive and had the capacity to proliferate. The origin of the cells that migrated from the recipient to the transplanted heart is uncertain, but this study raises the possibility that primitive cells from the recipient may migrate to the donor heart and participate in the remodeling process.
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Risperidone versus Haloperidol to Prevent Relapses of Schizophrenia
Preventing relapse is an important goal in treating patients with schizophrenia or schizoaffective disorder. This study compared risperidone, a newer, atypical antipsychotic medication, and haloperidol, an older, conventional neuroleptic drug, for the prevention of relapse in clinically stable adult outpatients. Patients treated with risperidone had a lower risk of relapse. Patients with schizophrenia typically have a chronic course with frequent relapses and repeated hospitalizations. The findings of this study suggest that risperidone may be beneficial for some patients and should spur research on other new antipsychotic medications.
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Prothrombotic Coagulation Abnormalities Preceding the Hemolytic–Uremic Syndrome
This prospective study included 53 children with E. coli O157:H7 infections. The hemolytic–uremic syndrome developed in 16 of the children, who had coagulation abnormalities that preceded the onset of azotemia and thrombocytopenia. The abnormalities included increases in the concentrations of prothrombin fragment 1+2, tissue plasminogen activator antigen, and plasmin–antiplasmin complex. The hemolytic–uremic syndrome is a serious complication that develops in some children with E. coli O157:H7 infection, usually about one week after the onset of diarrhea. This study provides evidence that thrombin generation and inhibition of fibrinolysis precede the renal injury and may be the cause of it.
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The Interval between Pregnancies and the Risk of Preeclampsia
The risk of preeclampsia is lower in second than first pregnancies if the woman's partner is the same, but not if the partner is different. This study used data from a large birth registry in Norway to evaluate whether a longer interval between deliveries, rather than a change in partner, might explain this finding. The risk of preeclampsia in a second or third pregnancy correlated directly with the interval between deliveries and approximated the risk during a first pregnancy if 10 years or more had elapsed between pregnancies. These findings suggest that the reduction in the risk of preeclampsia associated with a previous pregnancy is transient. The increased risk that had previously been observed with a change of partner seems to be explained instead by a longer interval since the previous delivery.
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Clinical Practice: Screening for Colorectal Cancer
A healthy 50-year-old woman with no risk factors for colorectal cancer other than age comes in for an annual examination. Which screening test for colorectal cancer should be recommended? This article reviews various screening strategies for colorectal cancer, including three-sample fecal occult-blood testing, sigmoidoscopy, and colonoscopy.
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Mechanisms of Disease: Alpha1-Antitrypsin Deficiency — A Model for the Conformational Diseases
Alpha1-antitrypsin is a member of a family of protease inhibitors known as the serpins. Mutations in these molecules can lead to disease, not only because the biologic activity of the protease in tissue is increased, but also because the mutations result in misfolded (i.e., conformationally abnormal) protease molecules that accumulate in tissue. This review article summarizes the action of these protease inhibitors and how mutations lead to their accumulation in particular neurodegenerative disorders such as prion encephalopathies and Alzheimer's disease.
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