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 ENDOCRINOLOGY: Leptin Serves Body as Energy Signal
An interventional study in men demonstrates that leptin controls some neuroendocrine hormones--including those involved in reproduction--during periods of starvation. The research, published in the May 1 Journal of Clinical Investigation, confirms in humans what many animal models and observational studies have pointed to: leptin is needed for normal reproductive function and may be responsible for many of the hormonal changes that occur in periods of low food intake. The study, led by Jean Chan (left) and Christos Mantzoros, also demonstrates important differences between leptin's effect in humans and in mouse models.
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 IMMUNOLOGY: A Mechanism Discovered for Antibody Deployment
In the case of infection or allergy, antibodies dispersed by activated B lymphocytes learn where to go and how to fight certain pathogens by genetic changes known as class switch recombination. Two studies from Frederick Alt's lab--in the April 17 Nature and the May Nature Immunology--and related work from other labs show the first detailed steps of how a crucial enzyme mutates the switch region, customizing the tail end of the antibody gene. The mechanism may contribute to the formation of some cancers.
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 PATHOLOGY: Tumor Suppressor Shows Another Way to Get Job Done
Chromosomal replication happens only once before a cell divides, otherwise the cell would be thrown into chaos with excess genetic material. To enforce this rule, the cell dispatches two proteins, cdk and geminin, to check the molecules that prepare the chromosomes to replicate. Anindya Dutta, Cyrus Vaziri, Sandeep Saxena (l to r), and their colleagues report in the April 25 Molecular Cell that they have discovered a third enforcer of the no rereplication rule--none other than the tumor suppressor p53. This role is another way that p53, which is inactivated or mutated in many tumors, puts a brake on cancer. The study suggests how much some cancer patients might benefit if p53 could be restored.
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Copyright 2003 by the President and Fellows of Harvard College
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