Washington, DC, USA. Human hormones regulate neuroendocrine activity. They can alter behavior and mood, and protect the brain from stress. They also contribute to brain aging and certain disease processes.

Understanding the underlying mechanisms involved, those that influence stress and the action of sex hormones, is an important activity in neuroscience. The neuroendocrine system links hormone secreton with behavior and experience.

"Neuroscientific proof of these differences can have profound impacts on everything from over-the-counter pharmaceuticals to government reimbursements for health care."

• Mothers with post-traumatic stress disorder (PTSD) may uniquely pass on biological risk factors to their offspring, according to work with the descendents of Holocaust survivors.
   
• Females appear to have a genetic predisposition toward reproducing the physiological reward produced by cocaine, suggesting sex chromosomes may influence habit formation.
   
• Females without a growth-factor gene can become more depressed than males.
   
• Estrogen can increase the possibility that females will start to take, and continue taking, cocaine.
   
• Stress can damage an area of the brain with a controlling effect on mood.

In three experiments with rats, Jill Becker, PhD, of the University of Michigan, found in each case that females showed an increased vulnerability to cocaine addiction.

In the study, a pool of 150 male and female rats of various predetermined hormone levels (some males were castrated, some females had their ovaries removed) were exposed to various combinations of estrogen, progesterone, or a peanut oil control.

Jane Taylor, PhD, of Yale University, studied cocaine's effects on the signaling pathway for protein kinase A (PKA), the enzyme that helps transfer dopamine-transmitting signals inside cells.

Working with the children of Holocaust survivors, Rachel Yehuda, PhD, at Mount Sinai Medical Center in New York City, studied biological risk factors by examining levels of the stress hormone cortisol.

Other findings indicate that stress may damage a region of the brain that regulates mood, adding to previous findings that had indicated damage in the hippocampus, which can regulate levels of cortisol. By identifying the biological changes that result from stress, researchers hope to pin down the ways stress can trigger depression in some people, and, in particular, how this may affect women, who show increased sensitivity to stress.

Tracy Bale, PhD, of the University of Pennsylvania, studied the effects of stress on male mice that were 3 months old, the equivalent of human adults. In particular, she focused on the role of corticotrophin-releasing factor (CRF), an important element in the brain's stress-response pathway. In one group of mice, a gene aiding the transmission of CRF was knocked out.

"We've shown that changes in gene expression in this area are probably vital to coping with stress, and the absence of such changes in the stress-sensitive mice may suggest potential sex differences linking heightened stress responsivity to disease."

Previous work has shown that anxiety and depression are more often diagnosed in females and that stress is a predisposing factor in the development of these mood disorders. Tara Perrot-Sinal, PhD, at Dalhousie University (Halifax, Canada), studied differences in stress responding between male and female rats using a number of models, including reactions to the natural stress of predator odor.

Chicago, IL, USA. Gender differences exist among surgeons who choose a surgical subspecialty, particularly when they evaluate the factors that may influence their career choice.

“Typically, surgery has been viewed as having an uncontrollable lifestyle with higher work hour demands. However, it is becoming evident through similar types of surveys that both men and women are placing a higher priority on personal and family time and seeking ways to shape their careers to accommodate these desires." So said Jaime H. McCord, MD, general surgery resident at the University of Wisconsin (Madison).

• interest in the field,
   
• intellectual appeal of field,
   
• an influential mentor, and
   
• clinical opportunities in that field.

• research exposure during residency (basic science, 38 percent versus 40 percent;
   
• clinical, 56 percent versus 61 percent, respectively; p>0.05);
   
• fellowship training (38 percent versus 69 percent, respectively; p=0.04); and
   
• academic practice setting (27 percent versus 46 percent, respectively; p=0.2).

Nashville, TN, USA. Intense beams of coherent light, called lasers, are increasingly popular for a variety of surgical procedures that can range from from cosmetic to brain surgery. However, there is a lot that scientists do not know about the ways in which laser light interacts with living tissue.

• Mid-infrared lasers with long wavelengths cut by burning. That is, they heat up the tissue to the point where the chemical bonds holding it together break down.
  
  Because they automatically cauterize the cuts that they make, infrared lasers are used frequently for surgery in areas where there is a lot of bleeding.
   
• Shorter wavelength lasers in the near-infrared, visible and ultraviolet range cut by an entirely different mechanism. They create a series of micro-explosions that break the molecules apart. During each laser pulse, high-intensity light at the laser focus creates an electrically-charged gas known as a plasma. At the end of each laser pulse, the plasma collapses and the energy released produces the micro-explosions.
  
  As a result, these lasers – particularly the ultraviolet ones – can cut more precisely and produce less collateral damage than mid-infrared lasers. That is why they are being used for eye surgery, delicate brain surgery and microsurgery.

“This is the first study that looks at the plasma dynamics of ultraviolet lasers in living tissue,” says Shane Hutson, assistant professor of physics at Vanderbilt University who conducted the research with post-doctoral student Xiaoyan Ma.

“The subject has been extensively studied in water and, because biological systems are overwhelmingly water by weight, you would expect it to behave in the same fashion. However, we found a surprising number of differences.”

Two sequences of confocal microscope images (the columns labeled a and b) show the effects of laser beams above the threshold energy level where they cut reliably and uniformly and at the threshold level where they cut erratically. The white circles are centered on micro-explosion sites and have radii equal to the explosion sizes. Credit: Shane Hutson.

Plasma and Cavitation Dynamics during Pulsed Laser Microsurgery in vivo. M. Shane Hutson and Xiaoyan Ma. Phys. Rev. Lett. 99, 158104 (2007). doi:10.1103/PhysRevLett.99.158104.

Stockholm, Sweden. Hysterectomy — a common operation involving the removal of the uterus — is the most common gynaecological abdominal operation in the world. It is normally performed as a cure for benign medical problems in order to improve life quality for the patients. However, the long-term effects are largely unknown.

A comment that accompanies the journal Article cited below shows how the findings contradict previous studies, and concludes there could be other reasons why the risk increases. — Ed.

"It's important that gynaecologists take this into account ahead of a hysterectomy, and the patients should themselves be aware of the greater risk the operation entails, particularly if they belong to a high-risk group," says Daniel Altman, gynaecologist and one of the researchers behind the study.